What is The
Chiropractic Subluxation?

This section is compiled by Frank M. Painter, D.C.
Send all comments or additions to:   Frankp@chiro.org

If there are terms in these articles you don't understand, you can get a definition from the Merriam Webster Medical Dictionary.   If you want information about a specific disease, you can access the Merck Manual.   Search PubMed for more abstracts on this topic.

Jump to:	Definition of Subluxation	Subluxation Anatomy	Subluxation Degeneration
	Subluxation Neurology	The Effects of Adjusting	Evolution of the Theory

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The definition of subluxation, as adopted by the American Chiropractic Association and the Association of Chiropractic Colleges is:

“A subluxation is a complex of functional and/or structural and/or pathological articular changes that compromise neural integrity, and may influence organ system function and general health.”

The 5 Component Vertebral Subluxation Complex Model   [ 3,   4,   7,   8 ]

According to Kent: [1]   Dishman [2]   and Lantz [3,   4]   developed and popularized the five component model of the “vertebral subluxation complex” attributed to Faye. [5]   However, the model was presented in a text by Flesia [6] dated 1982, while the Faye's notes bear a 1983 date.   The original model has five components:

1. Kinesiopathology — spinal pathomechanics, including alignment and motion irregularities, involving:

   • Hypomobility, segmental blockade, fixation:   Abnormal restriction of joint motion, OR
     

   • Hypermobility:   Abnormal increase in joint motion.
     

   • Compensation reaction:   Long term hypomobility causes the joint above the hypomobile area and occasionally the joint below to become hypermobile.
     

   • Loss of joint play:   The loss of normal vertical "joint slack/play" so that the joint becomes hypomobile on the vertical plane.
     

   • Loss of central axis of motion:   The loss of normal "Joint Slack/play" so that the joint becomes hypomobile on the rotational joint plane.
     

   • Positional dyskinesia, dynamic misalignment:   Joint misalignment throughout the entire range of motion of the involved joint.

   
   

2. Neuropathophysiology, Neuropathology — compressed or facilitated nerve tissue, involving:

   • Compressive lesion, the pinched nerve, neurological hypoactivity:   The literature indicates that of the neurological damage induced by spinal kinesiopathologic changes, about 10-15% results in a compressive profile.
     

   • Facilitative lesion, the facilitative segment, neurological irritation, neurological hyperactivity:   The literature indicates that, of the neurological damage induced by spinal kinesiopathologic changes, about 85-90% results in a facilitated profile.
     

   • Articular neuropathy,   the hyaline cartilage pads in the diarthrodial spinal joints as well as the local articular ligamentous support tissue are seriously stressed during an acute episode of the vertebral subluxation complex and more so in long term uncorrected vertebral subluxation complex episodes. This causes, in addition to the histopathologically induced pathoanatomical changes due to long term uncorrected vertebral subluxation complex, significant damage to the balance and proprioceptive nerve endings (the Type I Mechano receptors, Type II & III Articular Receptors and Type IV Nociceptive 'Pain' Receptors) in the articular surfaces and the capsular ligaments so that "Noxious" nerve impulses are fired off afferently back to the spinal balance center in the cerebellum, the proprioceptor center in the cerebral cortex and in the Limbic 'joint pain' regions of the cerebral cortex. Surprisingly, the spinal cord stores facilitated data also, causing reflexogenic activity from the involved joint.

   
   

3. Myopathology — muscle spasm, muscle weakness/ atrophy involving:

   There are parallel changes in the organ depots, of course. However, this is dealt with broadly under component #5. Myopathology is listed as a separate major component of the vertebral subluxation complex simply because myopathology is more readily testable and recognizable at the office level than are organ depot changes. The myopathological phenomenon associated with the vertebral subluxation complex are identical with myopathology induced by nerve damage due to other causes than spinal kinesiopathology. These changes can be referenced in many text books dealing with basic clinical pathology, clinical neuropathology and sports injuries.
   
   A.   From the compressive lesion:
   

   1. Neurological hypoactivity
      

   2. Hypotonus
      

   3. Atrophy
      

   4. Fibrosis (To varying degrees). The current literature points out that fibrosis in muscle tissue begins within one week of the original injury and becomes permanent within a few weeks. Krusen's Handbook of Physical Medicine and Rehabilitation, 1982, edited by Kottke, Stillwell, and Lehman. ISBN 07216-5501-7, chapter 18, pg. 391," Adhesion Formation." Experimental Models of Osteoarthritis: The Role of Immobilization, T. Videman, Clinical Biomechanics, 2:223-229, 1987, and the various papers by Videman there referenced. Managing Low Back Pain, 1st Ed. 1983, 2nd Ed. 1988; edited by W. H. Kirkaldy-Willis. 1st Ed. ISBN 0-443-08189-1 2nd Ed. ISBN 0-443-085358 Patholgenesis of Low Back Pain: Clinical Applications by Kirkaldy-Willis, MD, "Pathophysiology: Overview, Myofascial Cycle." These reports explain the progressive nature of fibrotic muscle degeneration, therefore leading to permanent spinal biomechanical aberrant function. Since, fibrosis begins within the first week after injury, and becomes irreversible shortly after that the basis for appropriate intervention within the three types of chiropractic care must be rethought.

   
   B.   From the facilitative lesion:

   1. Neurological hyperactivity
      

   2. Hypertonus
      

   3. Spasm
      

   4. Fibrosis (see above)

   
   C. From articular neuropathy

   1. "Erroneous" adaptation responses
      

   2. Adaptive spasm and weakness
      

   3. Resulting fibrous tissue (see above)

   
   

4. Histopathology — inflammation, edema and swelling of tissue, usually local to the traumatized area, involving:

   Basically, histopathology is to be considered as the entire range of the inflammato.ryprocess. Uncorrected, this leads to fibrotic degeneration. In some cases this degenerative process leads to calcific salt deposition within the fibrous lattice. The literature presents three phases of fibrotic/ calcific ligamentous degeneration.

Phase 1 -   The original sprain.

Phase 2 -   The beginnings of fibrosis.

Phase 3 -   Complete fibrosis. Complete fibroses and the beginnings of fibrosis are not reversible, leading to permanent spinal biomechanical impairment. Bone degeneration is considered under component #5.




5. Pathophysiology, Pathology, Biochemical Changes — pathophysiologic and pathoanatomical changes due to the previous four components usually seen locally as degeneration, fibrous tissue and/or erosion local and peripherally as a loss of global homeostasis.

A.   Local to the spine:



1. Bone degeneration-   Bone and soft tissue degeneration is an inevitable consequence of uncorrected spinal trauma (micro or macro) and to a degree, a result of a shifting postural alignment to gravity.
   
   

2. Bone regeneration-   A normal physiologic phenomenon. Bone regeneration alters architectural outlines of bone when the involved bone tissue becomes chronically out of alignment with gravity. This can be seen on spinal x-rays and is usually confused with the spinal degenerative process.

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Lantz   [5]   has since revised and expanded the “vertebral subluxation complex” model to include nine components:

The 9 Component Vertebral Subluxation Complex Model

1. Kinesiology
   
2. Neurology
   
3. Myology
   
4. Connective Tissue Physiology
   
5. Angiology
   
6. Inflammatory Response
   
7. Anatomy
   
8. Physiology
   
9. Biochemistry

He summarizes his objectives for expanding the model:   [5]

“The VSC allows for every aspect of chiropractic clinical management to be integrated into a single conceptual model, a sort of ‘unified field theory’ of chiropractic...Each component can, in turn, be described in terms of precise details of anatomic, physiologic, and biochemical alterations inherent in subluxation degeneration and parallel changes involved in normalization of structure and function through adjustive procedures.”

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The remainder of this page contains the collected articles written about the subluxation complex, including the degenerative changes that occur after a joint becomes fixated, the neurologic consequences following this fixation, the improvements that occur following chiropractic care, and a series of articles that discuss the evolving development of subluxation theories.


REFERENCES:

1. Models of Vertebral Subluxation: A Review
   Journal of Vertebral Subluxation Research 1996;   1 (1):   1-6
   
   

2. Review of the Literature Supporting a Scientific Basis
   for the Chiropractic Subluxation Complex
   J Manipulative Physiol Ther 1985 (Sep);   8 (3) Sep:   163–174
   
   

3. The Vertebral Subluxation Complex PART 1:
   An Introduction to the Model and Kinesiological Component
   Chiropractic Research Journal 1989;   1 (3):   23-36
   
   

4. The Vertebral Subluxation Complex PART 2:
   The Neuropathological and Myopathological Components
   Chiropractic Research Journal 1990;   1 (4):   19-38
   
   

5. The Subluxation Complex.   In: Gatterman MI,ed.
   Foundations of Chiropractic Subluxation.   St. Louis, MO: Mosby, 1995
   
   

6. Renaissance:   A Psychoepistemological Basis for the New Renaissance Intellectual.
   Renaissance International, Colorado Springs, CO, 1982
   
   

7. The Vertebral Subluxation Complex:
   An Integrative Perspective
   ICA International Review of Chiropractic 1992 (Mar): 25-27
   
   

8. Immobilization Degeneration and the Fixation
   Hypothesis of Chiropractic Subluxation
   Chiro Res J 1988;   1 (1) Spring:   21–46

Basic Science Research Related to Chiropractic Spinal Adjusting: The State of the Art and Recommendations Revisited FROM:   J Manipulative Physiol Ther. 2006 (Nov);   29 (9):   726–761 Anatomical Research The topic of anatomical research will be divided into studies that relate specifically to spinal manipulation/adjusting (SM) (“Studies Related to SM”) and those that add detail to the understanding of the spine (“Studies Adding to the Knowledge Base of the Spine”). Studies Related to SM Gapping of the zygapophysial joints Dysfunction of the spine that is treated by chiropractors has been described as the vertebral subluxation complex. This complex, as described by Lantz [2] and Rosner, [3] has several components. These components include myologic, connective, vascular, neurologic, and lymphatic tissue involvement. Many hypothesize that a fundamental component of the vertebral subluxation complex is the development of adhesions in the zygapophysial joints (Z joints) after hypomobility of these structures. [4-6] Spinal adjusting of the lumbar region is thought to separate the articular surfaces of the Z joints. [7-9] This “gapping” is theoretically the action that “breaks up” adhesions. Elimination of adhesions would allow the Z joints to become more mobile, thus helping the motion segment (2 adjacent vertebrae and the ligamentous structures connecting them) to reestablish a physiologic range of motion (ROM). [5] Although the idea that gapping the Z joints would occur during a SM and that this action would break up adhesions seems logical to those who have performed these procedures, no anatomical or physiologic evidence existed [1] to show that gapping of the Z joints actually occurred, or that adhesions in the Z joints could potentially be broken until relatively recently. [10, 11] Cramer et al [10, 11] found that in healthy volunteers, the lumbar Z joints did gap during both side-posture positioning and during chiropractic adjusting and the joints gapped significantly more during the latter procedure. However, no reports have been published by any group regarding gapping of the Z joints in the low back pain population. Degeneration of the z joints after hypomobility Paris [12] has reportedly identified adhesions in the Z joints after hypomobility. More recently, degenerative changes have been identified in the Z joints of rats after induced hypomobility. [13] See the section on Animal Models for further details. Advances in magnetic resonance imaging relevant to the spine and spinal adjusting Functional magnetic resonance imaging (MRI) evaluation of the spinal cord maps MRI signal changes following a specific stimulus designed to change neural activity. This procedure may become fundamental in the future workup of spinal cord injury [14] and may provide intriguing possibilities to the assessment of the spinal cord following procedures such as spinal adjusting. Diffusion and perfusion MRI provides information related to the structure and function of tissue at a microscopic level and will play a more prominent role in future neurovascular imaging. [15] As MRI at the molecular level becomes possible, opportunities for advances in research (and clinical practice) increase. [16] Research is also being done involving morphometry of the spine by means of MRI. [17] Morphometric measurements allow for an increased ability to study the structures influenced by chiropractic adjusting. [11, 17] Of related interest is that direct oblique cervical MRI provides more accurate assessment of all of the borders of the cervical intervertebral foramens (IVFs) than standard sagittal MRI. [11] Studies Adding to the Knowledge Base of the Spine Zygapophysial joints Between 15% and 40% of chronic low back pain is related to the Z joints. [18] The Z joint capsule receives a significant sensory innervation, [19, 20] much of which is probably related to nociception, that is, signaling potential or real tissue damage. The medial branches of the posterior primary divisions innervating a Z joint terminate as 1 of 3 types of sensory receptors: free nerve endings (nociceptive), complex unencapsulated nerve endings, and encapsulated nerve endings. The free nerve endings are associated with nociception. The ultrastructure of these receptors has been described. [20, 21] The Z joint capsules throughout the vertebral column are thought to do little to limit motion. [22] However, the capsules probably help to stabilize the Z joints during motions. [23] The gross and microscopic anatomy of the Z joint capsules has been described in detail. [23, 24] See the sections on Biomechanics and Somatic Nervous System for further details of current research related to the Z joints and spinal adjusting. Ligaments of the spine Nerve tracing techniques indicate that stretching of spinal ligaments results in “a barrage of sensory feedback from several spinal cord levels on both sides of the spinal cord.” [25] The sensory information has been found to ascend to many higher (cortical) centers. Such findings provide provocative evidence that the spinal ligaments, along with the Z joint capsules, and the small muscles of the spine (interspinales, intertransversarii, and transversospinalis muscles) play an important role in mechanisms related to spinal proprioception (joint position sense) and may play a role in the neural activity related to spinal adjusting. [26] Recent work has also been done assessing the structure of spinal ligaments. The attachment sites and dimensions of the anterior and posterior longitudinal ligaments [27, 28] and the innervation and gross and light microscopic structure of the ligamenta flava [29, 30] and iliolumbar ligaments [31] have been studied in detail. The long posterior sacroiliac ligament may be important in transmitting loads from the lower extremity to the spine. [32] The strongest fibers course from the posterior superior iliac spine to the sacrotuberous ligament, and many important structures attach to this band, including the aponeurotic attachments of the common origin of the erector spinae muscle. The ligament is tensed during counternutation of the sacrum and slackened during nutation. [32] These findings are considered to be important by those involved with the study of the “kinetic chain concept” of load transmission from the lower extremity to the spine. The intervertebral disk and intervertebral disk degeneration Many relevant studies on the biology of the intervertebral disks (IVDs) have been completed in recent years. Disk degeneration is characterized by loss of fluid pressure, disruption or breakdown of collagen and proteoglycans, and sclerosis of the cartilaginous end plate and the adjacent subchondral bone. All of these hallmark signs of IVD degeneration can also occur as part of the normal aging process of the IVD. For these reasons, disk degeneration and normal aging of the disk are frequently discussed interchangeably, [33, 34] although the biochemical processes may be distinct. The IVD seems to age differently from other tissues, probably because of its lack of a blood supply, and the degenerative process may begin as early as 20 years of age (earlier in some cases). [33] In fact, certain teenagers may experience back pain because of IVD degeneration. [35] There is an extremely wide variation in aging and degeneration of the IVD. Some individuals in their 70s have disks of equivalent health to some in their 30s. The aging and degenerative stages of the IVD from prenatal development through the ninth decade of life have been worked out in considerable detail at the gross and light microscopic levels. [34-40] Calcification of the IVD during the aging process is much more common than was once thought, being found in 58.3% of subjects at autopsy. Such calcification is “significantly underestimated” by conventional radiography. [41] Several conditions promote or even possibly initiate disk degeneration. These include traumatic Schmorl's node formation, advanced aortic atherosclerosis, [42] and possibly, nicotine consumption. [43] The biochemistry of IVD degeneration is also being elucidated. In this regard, extruded nucleus pulposus has been found to spontaneously produce increased amounts of many chemokines that not only initiate a series of events that decrease the size of the IVD bulge but also result in IVD degeneration. [26, 35, 44-47] Intervertebral disk protrusion The normal mechanics of the IVD continue to be investigated. [33, 48-51] In addition, the mechanisms involved in IVD protrusion and failure have been studied in detail [35, 39, 52-62], as well as the effects of changing intradiscal pressure. [63, 64, 65] In addition, a set of terms to be used when describing bulging of the IVD was established by the International Society for the Study of the Lumbar Spine. [66] This terminology included disk bulge, protrusion (tearing of some inner layers of the anulus fibrosus with the nucleus extending into the radial tear), extrusion (tearing of all layers of the anulus fibrosus allowing nuclear material to enter the vertebral canal), and sequestration (a piece of extruded nucleus breaks off of the host IVD). Much recent research related to IVD protrusion in the cervical and lumbar regions (protrusion in the thoracic region has not been studied as extensively) has found that IVD protrusion is a very dynamic process and that after approximately 1 to 3 weeks, IVD protrusion will usually begin a 2-month to 1-year process of resolution, resulting in significant resorption and, from a patient's standpoint (ie, pain), often complete remission of signs and symptoms. [33, 67-69] In fact, histologic evidence of resorption of sequestered nuclei pulposi has been found, [70. 71], and shrinkage of protruded nuclei pulposi has been seen on both computed tomography and MRI. [72] This provides hope to patients with protruded IVDs and for those using conservative methods to treat this condition. Adenovirus-mediated transfer of genes and the resultant production of therapeutic growth factors are being investigated as a means to further study the biology of the IVD and the potential for treatment of disk degeneration [73]; however, the low vascularity of the adult IVD may preclude the effective use of gene therapy in IVD disease. [34] Two published studies have shown that the inhibition of tumor necrosis factor–a (TNF-a) (extruded nucleus pulposus contains high levels of TNF-a) by a monoclonal antibody (Remicade [infliximab], Centocor, Inc., Horsham, Pa) is successful in alleviating sciatica. [74, 75] Finally, the mechanisms of radicular pain continue to be studied. [41, 76-78] Innervation of IVDs The significant innervation of the IVDs continues to be investigated in detail. [79-82] Degenerated disks have been found to receive increased innervation by sensory fibers conducting nociception. [83] The added innervation seems to be stimulated by Schwann cells of the nerves innervating the outer aspect of the anulus fibrosus. [84] Consequently, injured or degenerated disks are likely to be more sensitive to pain than normal disks. Unique characteristics of the cervical IVDs The cervical IVDs have been found to differ significantly from the lumbar disks. Rather than being made up of many lamellae, the anulus fibrosus of each cervical disk is composed of a single, crescent-shaped piece of fibrocartilage that is thick anteriorly and becomes very narrow laterally and posteriorly. [85] Range of motion studies Noteworthy studies measuring both the ranges of motion in various regions of the spine (eg, cervical region) and the motions between individual vertebrae continue. The latter activity has led to studies attempting to better understand the concept of coupled motions in the spine. Finally, significant findings related specifically to motions in the sacroiliac joints have also been published in recent years. These findings are summarized next. Although ROMs (eg, cervical ROMs) can be measured reliably, [86] measurements made on different days of the same individual can vary considerably. [87] Coupled motion (eg, rotation of vertebrae during lateral flexion) of spinal segments continues to be actively studied. Current investigators are finding that: (1) these motion patterns are very complex; (2) all spinal motions are coupled motions; and (3) coupling differs from 1 motion segment to the next. Furthermore, consensus has not been reached on many of these motion patterns. [88] The full ROM of the sacroiliac joint is not expressed until the extremes of hip motion are reached, moving an average of 7.5° (range, 3°-17°) in the sagittal plane during full flexion and extension of the hips. [89] Motions as high as 22° to 36° have been reported in preteen and early teenage children. [90] Contraction of the left and right transversus abdominis muscles increases stiffness of the sacroiliac joint, thus potentially reducing sprains of the ligaments that protect it. [91] Morphometric studies Morphometry means “measurement of an organism or its parts.” The past decade has seen many morphometric studies of various spinal structures. These studies allow for more accurate biomechanical and computer modeling (finite element analysis) studies to be performed and also allow for more accurate patient treatment protocols (surgical and manipulative) to be designed. Table 1 shows many of the morphometric studies performed since 1995, the region of the spine investigated, and the specific anatomical structure analyzed. Certain anatomical findings can best be discussed with each spinal region. The following sections describe anatomical findings of particular significance in the cervical, thoracic, lumbar, and sacroiliac regions. Each of the topics discussed is related to an active area of research. Anatomical Findings of Clinical Significance by Spinal Region: Cervical Region Connective tissue attachments to the spinal dura mater Connective tissue attachments to the posterior aspect of the spinal dura arising from the foramen magnum, posterior arch of C1, the spinous process of C2, [114] the rectus capitis posterior minor muscle, [115-117] the ligamentum nuchae, [118, 119] and the ligamenta flava between C1-C2 and C6-C7 [120, 121] have been described. These attachments may hold the dura mater posteriorly during cervical extension (to prevent buckling of the dura mater into the spinal cord) and flexion (to prevent the dura from moving forward and compressing the cord). Some authors have speculated that increased tension of the cervical paraspinal muscles may traction the connection between the rectus capitis posterior minor muscle and the dura, leading to headaches secondary to dural tension. [122] Others have proposed that tearing of these connective tissue attachments during the flexion component of flexion-extension (whiplash) type of injuries or other trauma to the cervical region could lead to buckling of the dura mater into the cervical segments of the spinal cord. Such dural buckling could conceivably result in the chronic neck pain, headaches, disorders of balance, and signs and symptoms of cervical myelopathy experienced by some patients who have had trauma to the cervical region. [118] The experimental work of Shinomiya et al [120, 121] lends support to these theories. In addition, homologous attachments in the lumbar region, called meningovertebral ligaments, have been shown to traction the dura mater and the related nerve roots after IVD protrusion. Vertebral artery The structure of the vertebral artery continues to be studied. The tortuosity of the vertebral artery can occasionally increase with severe, multilevel IVD degeneration. [123] Haynes et al [124] found that usually, there is no compression or stenosis of the vertebral artery with atlantoaxial rotation. Li et al [125] found that extreme extension and extension with rotation resulted in decreased flow in both vertebral arteries. Licht et al [126] found a decrease in flow in the vertebral artery contralateral to rotation and, for the first time, documented an increase in flow on the ipsilateral side of rotation. Mitchell et al [118] found a decrease in flow through both the left and right vertebral arteries (more in the contralateral vessel) with maximal rotation, especially in those arteries with underlying pathology (eg, atherosclerosis). Therefore, maximal rotation and extension seem to decrease flow through the vertebral arteries, but submaximal rotation seems to have less of an effect. E.   Anatomical Findings of Clinical Significance by Spinal Region: Thoracic Region Idiopathic Scoliosis The cause of idiopathic scoliosis remains unknown, but it is thought to be the result of many factors. A genetic component [127, 128] to the disorder is likely with secondary factors that include a decrease in melatonin production [129-131] and a related increase in circulating levels of the hormone calmodulin. [128] Changes in skeletal muscle, [132] connective tissue [46, 47] bone density, rib distortion, [128] decreased height of the posterior vertebral arch, [133] asymmetry of the neurocentral synchondrosis, [134] and the relatively common finding (up to 26%) of syrinx formation and other neuroanatomical abnormalities in the spinal cord [135, 136] are probably the result of the altered biomechanics of the spine and spinal cord that occur with spinal curvatures. [128] In addition, increasing evidence exists supporting the theory that the primary disorder (probably related to genetic influences) is the involvement of high (cortical) brain centers involved in processing vestibular information. [137-139] An interesting study by D'Attilio et al [140] may indicate that there could be more than 1 subpopulation of patients with idiopathic scoliosis. These investigators showed that the alignment of the spinal column may be strongly influenced by dental occlusion and temporomandibular joint disturbance. These investigators reported that all 15 rats in an experimental group with an induced malocclusion developed thoracolumbar scoliosis within 1 week after the intervention. The scoliotic curvature was then completely resolved in 83% of these rats 1 week after correction of the malocclusion. None of the 15 untreated control rats in their study developed scoliosis. They suggested that an anatomical and functional relationship between the stomatognathic apparatus and the spinal column could explain their observations. They noted the presence of convergent sensory inputs to the craniocervical cord from stomatognathic and cervical spine structures and posited that a consequential tilt of the first cervical vertebra (C1) could affect the alignment of adjacent vertebrae, destabilizing the vertical alignment of the spine. Anatomical Findings of Clinical Significance by Spinal Region: Lumbar Region Many of the findings described previously in the section entitled “Intervertebral Disk” were related to the lumbar IVDs and will not be repeated here. Lumbar intervertebral foramina Transforaminal ligaments of the IVF can be identified on MRI, with a positive predictive value of 86.7%. [141] These ligaments are present in approximately 60.0% of lumbar IVFs (66.7% of L5-S1 IVFs) [141] and have been implicated as both a cause of low back pain and nerve root entrapment. [142-146] These structures can be quite sturdy (especially at the L5-S1 region) and can calcify. [147] They have been found to decrease the dimensions of the compartment transmitting the anterior primary division of the spinal nerve by 31.5%. [148] Limiting the size of the compartment in this way may, at times, contribute to the incidence of neurologic symptoms in the region, especially after trauma or secondary to degenerative arthritic changes in the region of the IVF. [148] Anatomical Findings of Clinical Significance by Spinal Region: Sacroiliac Joints Acquired accessory sacroiliac joints frequently (19.1%) form within the posterior (fibrous) portion of the joint. These accessory joints are more common in obese and older individuals and are also associated with other signs of degeneration and periodic low back pain. [149] Recommendations Continue to investigate the effects of spinal adjusting on the tissues of the spine and other organ systems (see section on Autonomic Nervous System) in various disease states (eg, gapping studies of the Z joints). Continue to evaluate the causes of hypomobility of vertebral segments in the general population, under what conditions such hypomobility is maintained, and continue to characterize the changes of the tissues of the spine after hypomobility (and possibly hypermobility) when normal activity is reestablished (ie, normal forces to the spine are reestablished) and also after spinal adjusting is added in an attempt to help reestablish normal forces and movement to hypomobile tissues. A combination of human and animal studies will be needed to achieve this recommendation. Evaluate the effects of spinal manipulative procedures on pain of radicular origin and on radiating pain. Further evaluation at the basic science level of the issue of vertebral and basilar artery iatrogenic pathology is warranted. Conduct descriptive studies to clarify regional differences (ie, between the cervical, thoracic, and lumbar regions) in the anatomy of the vertebral column and related spinal tissues. Conduct studies evaluating the normal development of all spinal tissues from embryogenesis through the mid 20s. Conduct studies further evaluating the aging spine (fourth through ninth decades). All of the recommendations above should be carried out in both human and animal studies at the gross (imaging and postmortem studies), light microscopic (biopsy specimens, eg, those obtained during surgery, cadaveric studies), and electron microscopic (biopsy specimens and postmortem studies) levels.

   Spinal Anatomy 101
           This page reviews the anatomy of vertebrae, describes the function of the “Spinal Motion Unit”, and clarifys which tissues suffer degenerative changes from the subluxation complex.

   Surgical Model of a Chronic Subluxation in Rabbits
           J Manipulative Physiol Ther. 1988 (Oct);   11 (5):   366–372
           Critically needed in chiropractic research is an animal model of a subluxation that will allow experimental study. Previous attempts in this, as well as other, laboratories have been only minimally successful. We report here the development of a straightforward surgical method of producing a misalignment of the thoracic spine in rabbits, one that appears to be satisfactory for further study.

Basic Science Research Related to Chiropractic Spinal Adjusting: The State of the Art and Recommendations Revisited FROM:   J Manipulative Physiol Ther. 2006 (Nov);   29 (9):   726–761 Measures of Pathologic States An intriguing question has begun to be answered relating to whether changes in intersegmental stiffness can be discerned using clinically available tools. Colloca et al [175] measured intersegmental impedance (dynamic stiffness) of lumbar vertebrae and correlated it with characteristics of vertebral height and IVD height measured from plain film radiographs. They found that there was a correlation between decreased disk height at L5-S1 and increased dynamic stiffness at the same segment. These findings were analogous to those of Kaigle et al [176] who, using a porcine model, also observed increased spine dynamic stiffness associated with degenerated disks, compared with normal controls. Using ultrasound indentation, another noninvasive approach, Kawchuk et al [177] also found that IVD degeneration in a porcine model resulted in decreased indentation for the same applied load. This is an analogous metric as spine stiffness. The use of ultrasound indentation in this animal model had high sensitivity (75.0%), specificity (83.3%), and accuracy (77.1%), compared with other approaches (arthroscopy, MRI, and plain film radiography). Two biomechanics studies have been performed to examine the effects of fixation (ie, a hypomobile subluxation) of the lumbar spine. Cramer et al [13] used a rat model of fixation in the lumbar spine by externally fixating the spinous processes of L4-L6 for up to 8 weeks. A principal finding due to the fixation was the development of osteophytes and degenerative articular changes of the facet joints within a few weeks. Reversal of some of the degeneration was observed for joints that were fixated for a short term (~1 week), but after 4 weeks, no reversal was observed. Little et al [178] simulated a hypomobile subluxation in intact, cadaveric human lumbar spine specimens by screwing a plate into the left anterior aspect of the L4 and L5 vertebral bodies. During physiologic motions of the fixated spine specimens for flexion, extension, and lateral bending, the motions at L4-5 were significantly decreased, whereas below and above that level, intersegmental motions were significantly increased. Correspondingly, the plane strains of the facet joint capsules were significantly decreased and increased at and above/below the site of fixation, respectively. Experimental Models to Study Somatic Inputs from the Paraspinal Tissues Since publication of the original white paper, 2 experimental animal models have been developed that facilitate study of the relationship between spinal biomechanics and neurophysiology in general and of SM specifically: a cervical spine model developed by Bolton and Holland [211] and a lumbar spine model developed by Pickar. [212] Additional animal models also relevant to chiropractic spinal adjusting are presented in the section on Animal Models later in this paper. The experimental preparations enable application of controlled mechanical loads to individual vertebra and, at the same time, provide access to the dorsal roots for recording neural activity from paraspinal tissues affected by the mechanical load. The discharge properties of primary afferents with receptive fields in paraspinal tissues and the effects of these sensory inputs on somatomotor, somatovisceral, and central neural processing can be determined. The preparations use a servo-driven motor to control the displacement of or force applied to the spinous process. Recently, a large animal model (goat) has been used to determine how strains in the facet capsule affect neural input from the capsule. [213] This model needs additional work to determine whether the capsule is sufficiently preloaded to enable accurate determination of strain and to confirm that identified neurons can be distinguished in the multiunit recordings. The preparations described in this section provide the opportunity to conduct neurophysiologic studies not possible in humans. With information obtained from these animal models, hypotheses can be formulated and then tested noninvasively in humans. Animal Models The remarkable scientific progress in both industry and medicine over the last 100 years has been responsible, in large part, to a transition from observational to experimental research. [305, 306] Human clinical studies contributed greatly to this progress, but animal studies have permitted investigators to perform experimental interventions that were not possible in human studies, and allowed a wider range of study designs. In addition, statistical power is easier to obtain in animal studies because large numbers of animals can be evaluated at relatively low costs, and animal study groups can be genetically homogeneous. Moreover, research animals are often bred to have genetic predispositions to illnesses that mimic those of humans, such as asthma, [307] cancer, [308] diabetes mellitus, [309] and hypertension. [310] These important features, and the ability to strictly control potentially confounding influences, make animal research an essential tool for today's health care researchers. Consequently, the need for animal models in chiropractic research has been acknowledged in each of the major reviews of scientific progress in chiropractic. [1, 311, 312] Despite this, some still question how we can learn anything about people from studying animals. The basis for this concern lies in the obvious anatomical and physiologic differences between humans and animals. Animal studies are generally used to examine fundamental mechanisms that are common to both humans and nonhuman species. In addition, as noted above, many human diseases can be mimicked in animal models. Consequently, animal research provides information about fundamental mechanisms common to both humans and animals, and often suggests new hypotheses for evaluation in subsequent human studies. The discovery of insulin provides an excellent example. It was also one of the most dramatic events in the history of health care research. [313] Animal studies showed that the pancreas was a critical organ in the development of diabetes mellitus. Additional work produced an extract of the pancreas that reduced hyperglycemia and glycosuria in animals that had been previously rendered diabetic by removal of the pancreas. After further extensive evaluation with laboratory animals, the purified extract was deemed ready for human tests. In the first human trial, a 14-year-old boy with severe diabetes received an intramuscular injection of the “purified” pancreatic extract but failed to show clinical improvement and developed a sterile abscess at the injection site. [314] However, on the strength of the previous animal studies, work continued to further purify the pancreatic extract, and additional human studies were conducted. These new human studies, using the purified extract, showed a tremendous clinical improvement in all subjects. [314] Therefore, animal studies revealed the critical role of insulin in diabetes, provided a source of the hormone for subsequent study, and showed the potential of insulin as a therapeutic agent. All of these events were necessary before human clinical trials of insulin could begin. In 1923, the Nobel Prize for Physiology or Medicine was awarded to Banting and Macleod, recognizing that the discovery of insulin had [315] “conferred the greatest benefit on mankind.” The current era of chiropractic experimental research began after the first federally funded workshop to examine SM, The Research Status of Spinal Manipulative Therapy, in 1975. [311] At the conclusion of this historical conference, it was widely acknowledged that little basic or clinical research data were available to evaluate the claims of clinicians using SM. Immediately after the first Research Agenda Conference in 1996, a white paper was published on the status of basic science research in chiropractic, "Basic Science Research in Chiropractic: The State of the Art and Recommendations for a Research Agenda". [1] A contemporary review by Vernon was cited in which 18 animal studies examined spine subluxation (1 historical monograph, 4 abstracts, and 13 articles). [316] A recent review by Henderson, Animal Models in the Study of Subluxation and Manipulation: 1964 to 2004, presents synopses of 34 animal studies (5 abstracts and 29 articles) published within the past 40 years. [317] In this review, studies were included if they specifically examined subluxation, the osteopathic lesion (somatic dysfunction), or SM. Studies examining subluxation or somatic dysfunction were grouped under the general term subluxation studies. These studies used animals to model either subluxation (31 studies) or SM (3 studies). The 31 subluxation studies examined either “full-mimic models” that attempted to induce spine fixation in intact animals (14 studies) or “component models” that emulated specific mechanical or chemical components attributed to spine subluxation (17 studies). The 3 SM studies used either manual (1 study) or instrumental interventions (2 studies). Subluxation Mimic Models Only 1 subluxation mimic model has been introduced since the 1996 Research Agenda Conference. This model, the external link model, combines surgically implanted spinous attachment units and an external link system to produce reversible, mechanical fixation of 3 adjacent lumbar segments (L4, L5, and L6) in the rat. [13] Cramer et al [13] used the external link model to examine degenerative changes after spine fixation. They observed stiffness and Z joint changes that developed within weeks after experimental fixation of a spine segment. Both the occurrence (number of involved segments) and severity (0-3 scale, least to most severe) of degenerative changes were recorded. These investigators reported significant differences in Z joint degeneration between fixed segments and nonfixed segments within the same animal. In addition, the occurrence and severity of articular degeneration and osteophyte formation on Z joints in rats with fixated vertebrae was significantly greater than similar degenerative changes, on comparable segments, in never-linked control rats. This subluxation mimic study provided strong evidence that decreased vertebral motion (vertebral fixation) produced degenerative changes in the Z joint that were greater for longer periods of fixation. Generally, these degenerative changes continued to progress after removal of the fixating links. However, the data also suggested that time thresholds exist, before which removal of the experimental fixation (links) may spontaneously reduce or reverse the fixation-induced degenerative changes. These time thresholds appeared to be earlier for facet surface degeneration (occurring between 1 and 4 weeks of fixation time) and later for osteophytic degeneration (occurring between 4 and 8 weeks of fixation time). In addition, facet degeneration was observed to occur earlier than osteophyte formation. The existence of these time thresholds is intriguing, and may have clinical significance. However, the authors warned that there is no known basis for projecting rat time frames to human subjects. Further work with this model and subsequent human studies are required to expand our understanding of these issues.

   The Chiropractic and Degenerative Joint Disease Page
           This page contains many articles that explain the relationship between spinal subluxations and degenerative joint disease.

   Radiologic Manifestations of Spinal Subluxations
           Basic Chiropractic Procedural Manual ~ Chapter 16
           By Richard C. Schafer, D.C., FICC and the ACAPress
           This chapter describes the radiologic signs that may be expected when spinal subluxations are demonstrable by radiography. Through the years, there have been several concepts within the chiropractic profession about what actually constitutes a subluxation. Each has had its rationale (anatomical, neurologic, or kinematic), and each has had certain validity contributing to our understanding of this complex phenomenon.

The following series of articles by Chuck Henderson, DC, PhD (Palmer Center for Chiropractic Research) and Gregory D. Cramer, DC, PhD (Department of Research, National University of Health Sciences) discuss the adhesions and degenerative changes that occur in zygapophyseal (Z) joints when a segment is subluxated. Zygapophyseal Joint Adhesions After Induced Hypomobility J Manipulative Physiol Ther. 2010 (Sep);   33 (7):   508–518 Experimentally induced segmental hypomobility (fixation) of the lumbar Z joints resulted in time dependent intra-articular ADH formation. The ADH were found in approximately equal numbers in the left and right Z joints and were most prevalent in the peripheral regions of the joint from medial to lateral and cephalad to caudal. These findings are consistent with the hypothesis that hypomobility results in time-dependent degenerative changes and ADH development of the Z joints. Introducing the External Link Model for Studying Spine Fixation and Misalignment: Current Procedures, Costs, and Failure Rates J Manipulative Physiol Ther 2009 (May);   32 (4):   294–302 The great promise of basic chiropractic “subluxation” research is that it will clarify for clinical researchers the mechanisms by which spine fixation or malposition may cause harm and show or suggest effective therapeutic remedies. Answers are needed to pressing and fundamental questions such as: Does chiropractic subluxation actually occur? If so, does chiropractic spinal subluxation significantly threaten a patient's health? Are there features that will allow researchers and clinicians to determine its accurate and precise location as well as its specific nature? Can spinal manipulative therapy prevent, stop the progression, or reverse adverse health effects related to chiropractic subluxation? Are there “time windows” that might influence the outcome of treatment? When these questions are answered, clinicians will be able to more objectively match the unique features of a patient's presentation to the diversity of chiropractic techniques, treatment frequency, number of visits, and treatment duration. Introducing the External Link Model for Studying Spine Fixation and Misalignment: Part 2, Biomechanical Features J Manipulative Physiol Ther 2007 (May);   30 (4):   279–294 This study suggests that the external link model can be a valuable tool for studying the effects of spine fixation and misalignment, 2 cardinal features of what has been historically described as the chiropractic subluxation. Significant residual stiffness and misalignment remained after the links were removed. The progressive course of this lesion is consistent with subluxation theory and clinical chiropractic experience.. Introducing the External Link Model for Studying Spine Fixation and Misalignment: Part 1— Need, Rationale, and Applications J Manipulative Physiol Ther 2007 (Mar);   30 (3):   239–245 This is the first article in a series introducing a new animal model, the External Link Model that we propose will allow researchers to produce and study spine lesions with the cardinal biomechanical features of the chiropractic subluxation: fixation (hypomobility) and misalignment. After the first federally subsidized scientific workshop on spinal manipulation, The Research Status of Spinal Manipulative Therapy (1975), [9] General Chairman Murray Goldstein commented, “The lack of a relevant and reproducible animal model may be one important obstacle to clarification of these issues. …Thus, subluxation remains a hypothesis yet to be evaluated experimentally.” Unfortunately, this ‘important obstacle’ remained in place for more than a quarter century following this conference. Degenerative Changes Following Spinal Fixation in a Small Animal Model J Manipulative Physiol Ther 2004 (Mar);   27 (3):   141-154 Fixed segments had more degenerative changes than nonfixed segments for all Z joint parameters (ANOVA, P <.0001). Osteophyte formation and ASD were directly dependent on duration of fixation. These findings indicate that fixation (hypomobility) results in time-dependent degenerative changes of the zygapophysial joints. You may also enjoy reviewing the FCER-funded research project that led to the publication of this article. Articular Cartilage Surface Changes Following Immobilization of the Rat Knee Joint. A Semiquantitative Scanning Electron-microscopic Study Acta Anat (Basel). 1996;   157 (1):   27–40 Normal articular cartilage surfaces are not flat and smooth, but are contoured with various degrees of roughness. We applied the articular surface classification system developed by Jurvelin to evaluate contour and surface quality changes in rat patellae after varying periods of knee joint immobilization. Numerous studies have demonstrated that joint immobilization induces degenerative changes in articular cartilage. We found a correlation between the duration of immobilization and changes in the measured area of contour and surface quality subclasses.

   The Immobilization Degeneration & the Fixation Hypothesis
of Chiropractic Subluxation
Chiropractic Research Journal 1988;   1 (1):   21-46 ~ FULL TEXT
The literature was reviewed concerning the effects of joint immobilization on the degeneration of articular and periarticular connective tissue. Every connective tissue component of an articulation is affected by immobilization, and each major component is discussed individually; these include the articular cartilage, synovium, articular capsule, periarticular ligaments, subchondral bone, the intervertebral disc and the meninges. Particular emphasis was placed on changes in the biochemical constituents of connective tissue, collagen, proteoglycans and hyaluronic acid, and the relation of these changes to alterations in the functional and biomechanical properties of the tissues. T hus an attempt is made here to establish a molecular basis for the theory and practice of chiropractic.


   Surgical Model of a Chronic Subluxation in Rabbits
           J Manipulative Physiol Ther. 1988 (Oct);   11 (5):   366–372
           Critically needed in chiropractic research is an animal model of a subluxation that will allow experimental study. Previous attempts in this, as well as other, laboratories have been only minimally successful. We report here the development of a straightforward surgical method of producing a misalignment of the thoracic spine in rabbits, one that appears to be satisfactory for further study.

Basic Science Research Related to Chiropractic Spinal Adjusting: The State of the Art and Recommendations Revisited FROM:   J Manipulative Physiol Ther. 2006 (Nov);   29 (9):   726–761 Somatic Nervous System Knowledge of and research directions for understanding the effects of chiropractic spinal adjusting on the somatic nervous system needs, as its basis, an understanding of neurophysiology as it relates to structure and function of the vertebral column. Thus, 2 areas are presented in this portion of the white paper. The first area beginning immediately below represents a substantial portion of our knowledge base for understanding the neurophysiologic properties of paraspinal tissues. The second area beginning with the section on Effects of SMs on Muscle and Muscle Spindles reviews how neural elements of the vertebral column and their organization are affected by SM. Information is included that predates the 1997 white paper when it was not included in that article. Experimental Models to Study Somatic Inputs from the Paraspinal Tissues Since publication of the original white paper, 2 experimental animal models have been developed that facilitate study of the relationship between spinal biomechanics and neurophysiology in general and of SM specifically: a cervical spine model developed by Bolton and Holland [211] and a lumbar spine model developed by Pickar. [212] Additional animal models also relevant to chiropractic spinal adjusting are presented in the section on Animal Models later in this paper. The experimental preparations enable application of controlled mechanical loads to individual vertebra and, at the same time, provide access to the dorsal roots for recording neural activity from paraspinal tissues affected by the mechanical load. The discharge properties of primary afferents with receptive fields in paraspinal tissues and the effects of these sensory inputs on somatomotor, somatovisceral, and central neural processing can be determined. The preparations use a servo-driven motor to control the displacement of or force applied to the spinous process. Recently, a large animal model (goat) has been used to determine how strains in the facet capsule affect neural input from the capsule. [213] This model needs additional work to determine whether the capsule is sufficiently preloaded to enable accurate determination of strain and to confirm that identified neurons can be distinguished in the multiunit recordings. The preparations described in this section provide the opportunity to conduct neurophysiologic studies not possible in humans. With information obtained from these animal models, hypotheses can be formulated and then tested noninvasively in humans. Sensory Input from Group I and II Afferents (Proprioceptive Afferents) Group I and II afferents are primary sensory neurons that convey information to the central nervous system from muscle spindles, Golgi tendon organs, and other low threshold mechanoreceptors such as Ruffini endings and Pacinian corpuscles. These afferents conduct action potentials rapidly (>35 m/s) due to their large diameters and heavy myelination. The structure and function of muscle spindles in the vertebral column have some unique aspects compared with those in the appendicular skeleton. Studies in animal models have described muscle spindles in the hind limb as single receptors located both deep in the muscle belly and close to the musculotendinous junction. [214-217] Spindle densities range from 5 to 45 spindles per gram of hindlimb muscle weight. [218] In the cervical spine of the human [219] and cat, [220, 221] however, muscle spindles are rarely seen as single entities, and their densities are greater than in peripheral musculature. In the cat, Richmond and Abrahams [220] describe cervical spindle complexes wherein 2 to 6 spindles are in close contact with each other or share capsules and/or intrafusal fibers. Spindle density can be 2 to 8 times higher (47-107 spindles per gram) in superficial cervical muscles [220] and 10 to 25 times higher (137-460 spindles per gram) in deep cervical muscles [221] than in hindlimb muscles. These differences in spindle densities between axial neck muscles and appendicular muscles appears similar in the humans. [222] In the lumbar spine of the cat, Carlson [223] identified muscle spindles in the longissimus, iliocostalis, sacrocaudalis, intertransversarii, multifidus, and interspinalis muscles, but quantification and morphological description of the spindles were not performed. Similarly, muscle spindles have been identified in the medial, intermediate, and lateral portions of the lumbar erector spinae in the human fetus. [224] Carlson [223] also noted that spindle density appeared higher in the central compared with peripheral portions of the longissimus. The high spindle density in the cervical and lumbar muscles is consistent with the high percentage of slow twitch fibers found in muscles of these 2 regions. [220, 223] The reflex organization of sensory input from paraspinal muscles spindles also has some unique aspects compared with that of the appendicular skeleton. A well-recognized concept related to the cat hindlimb is that the monosynaptic stretch reflex is elicited by excitation of muscle spindles. Afferents from each muscle spindle synapse upon a-motoneurons to that same muscle (homonymous a-motoneurons). [225-227] This stretch reflex arc uses a single excitatory synapse to homonymous a-motoneurons. [226, 228] The afferent arm of the reflex is comprised primarily of group Ia and possibly group II afferents. [227, 229] Each group Ia afferent from a given hindlimb muscle makes functional, monosynaptic connections with 50% to 100% of the homonymous a-motoneurons. [230, 231] Thus, stimulation of a group Ia afferent from a specific hindlimb muscle evokes a monosynaptic excitatory postsynaptic potential in all a-motoneurons to the same muscle. [232, 233] In contrast, in the cervical spine, the monosynaptic reflex connections to homonymous a-motoneurons are weaker. Excitatory postsynaptic potentials are smaller in amplitude, and group Ia afferents make functional connections with only 10% of the homonymous a-motoneurons. [234, 235] This probably contributes to the absence or weakness of monosynaptic reflexes in cervical muscle. [236] In the lumbar spine of the cat, stretch reflexes can be elicited from the longissimus muscle but not from the iliocostalis muscle. Conduction delays suggest that the reflex arc is not monosynaptic [237] unlike that in the hindlimb. [226, 228] The presence of monosynaptic stretch reflexes from the deeper lumbar muscles has not been determined. In humans, indirect evidence for the presence of muscle spindles and muscle spindle reflexes in lumbar paraspinal muscles was obtained by measuring evoked cerebral potentials in response to vibration of the lumbar paraspinal muscles, [238] which relatively selectively stimulates muscle spindles. [239] Muscle spindles, along with Golgi tendon organs, comprise a proprioceptive feedback system, which contributes to the sense of movement and position. [240-242] Abnormal sensory input from muscle spindles elicits limb lengthening illusions. [240, 243] When a vibrating mechanical stimulus (100 Hz) is applied to the Achilles tendon of a person standing erect with eyes closed, primary endings in the muscle spindle are excited. Because they monitor change in muscle length, the increased neural discharge signals to the central nervous system that the calf muscles are stretched or lengthened more than they actually are. Spindles increase their static firing rate by ~4 to 5 Hz per millimeter of muscle lengthening. [215] Because calf muscles normally lengthen as the body leans forward, the proprioceptive feedback error arising from the vibratory stimulus elicits a postural compensation in the form of backward sway. This movement compensates for the illusory forward flexion at the ankle. Recently, Wise et al [244] showed that spindles in muscles surrounding the elbow are sufficiently sensitive to signal 0.05° to 0.15° changes in elbow rotation. Thus, it seems reasonable to suppose that paravertebral muscle spindles can signal extremely small positional changes or movement of the vertebra to which their parent muscle is attached and, thus, contribute to control of intervertebral motions that might minimize or prevent noxious spinal loading. Recent findings in humans suggest that proprioceptive input from paravertebral muscle spindles is important for normal reflex activity and repositioning of the lumbar spine. For example, tapping the erector spinae muscles normally elicits short latency paravertebral EMG activity. However, vibration of the lumbar paravertebral muscles, which increases background spindle discharge, inhibits this reflex response. [245] Additional evidence indicates that proprioceptive input from spindles in the lumbar paravertebral muscles is necessary to accurately position the pelvis and lumbosacral spine. Although healthy individuals can accurately reposition their lumbosacral spine, their repositioning ability is impaired when muscle spindle discharge is increased by applying vibration to the lumbar paravertebral muscles. [246, 247] The correct position is consistently undershot because of the misperception of vertebral position. Interestingly, lumbosacral repositioning ability is impaired in individuals with a history of low back pain, but is improved in the presence of vibration, unlike normal individuals. [247] Proprioceptive input can alter muscle force directly via its effect on a-motoneuron excitability and indirectly via its effect on the excitability of segmental and suprasegmental interneurons. Even small changes in paraspinal muscle forces are thought to have a large impact on a motion segment's biomechanical behavior and stability. [248] For example, in vitro experiments accompanied by a modeling approach, which incorporated graded activity of 1 lumbar paraspinal muscle, showed an increase in vertebral stabilization as determined by decreases in the intersegmental neutral zone and ROM. Similarly, very small increases in lumbar paraspinal muscle activity at L2-L4 (1-3% of maximal voluntary contraction) were sufficient to restore segmental stability to the lumbar spine even under strenuous loading conditions. [249] More complex modeling that incorporates force vectors from 5 paraspinal muscles suggests that neuromuscular [250] mechanisms controlling multifidus muscle activity alone could functionally impact a lumbar motion segment especially during flexion-extension and axial rotation. A recent study suggests the presence of a previously unrecognized phenomenon in the lumbar multifidus and longissimus muscles that could affect proprioceptive mechanisms controlling paraspinal muscle function. [251] Changes in intersegmental positions in the lumbar spine that elongated the paraspinal muscles for 10 seconds desensitized paraspinal muscle spindles to subsequent vertebral movement when compared with intersegmental positions that shortened the paraspinal muscles. The findings suggested that either voluntary static postures or involuntary intervertebral positions, which are maintained for short durations, could elicit proprioceptive feedback errors and alter paraspinal muscle force. The spine may be particularly susceptible to this phenomenon because intersegmental positions are not under voluntary control, and a vertebra's spatial position is not uniquely determined at low loads. [252] Sensory Input from Group III and IV Afferents Group III and IV afferents from deep tissue (labeled as A-d and C-fibers, respectively, when from skin) are primary sensory neurons with mechanically, chemically, or thermally sensitive receptive endings. Some endings are sensitive to only a single modality; others are polymodal. Group III and IV mechanoreceptive endings can have high or low thresholds to mechanical stimuli. Those group III and IV endings that respond in a graded fashion to any stimulus that threatens or actually inflicts injury are called “nociceptors.” Group III and IV afferents conduct their action potentials slowly (=30 m/s) because of their small diameters and light myelination (group III) or lack of myelination (group IV). Deep tissues of the low back are innervated by afferent endings responsive to both mechanical and chemical stimuli. [253-259] For example, Cavanaugh et al [253] recorded multiunit activity from group III and IV afferents from the medial branch of the dorsal rami from deep connective tissue after removing lower back muscles in the rat. Gentle probing of the facet capsule, as well as forceful pulling on the supraspinous ligament, elicited a slowly adapting discharge from these afferent nerves. In a systematic study of 57 unmyelinated afferents from the tail and lumbar region of the rat, Bove and Light [259] found mechanonociceptive endings in muscle bellies, tendon, subcutaneous tissue, and neurovascular bundles. Up to a third of the afferents had receptive endings in more than 1 tissue. No receptive fields were found in the facet joint capsule. Pickar and McLain [258] recorded single-unit activity from group III and group IV afferents in the intact lumbar spine of cats during movement of the L5-6 facet joint. Most afferents, including 7 with receptive fields in or near the facet joint capsule, responded in a graded fashion to the direction of a nonnoxious load applied to the joint. Yamashita et al [256] found that only 20% of group III afferents in and around the lumbar facet joint had high mechanical thresholds (>8.5 g), as determined with von Frey–like hairs. This latter finding contrasts with afferents studied in the cervical spine where almost all group III afferents studied had high mechanical thresholds. [260] In addition, Bolton and Holland [211] found silent afferents innervating the cervical facet joints, which were only activated by firm, potentially noxious prodding of their receptive fields. Most unmyelinated mechanonociceptive afferents are also sensitive to chemical stimulation by capsaicin, but only 50% were sensitive to the inflammatory agent bradykinin. [259] Group III and IV receptive endings in and around the lumbar facet joint can be both activated and sensitized by chemical stimuli. Substance P increases their resting discharge by 80% and decreases their von Frey thresholds by -30%. [256] Similarly, carrageenan-induced inflammation increases the resting discharge of group III, group IV, and some group II afferents innervating the lumbar muscles and facet joints and sensitizes their receptive endings to mechanical stimuli. [257] The inflammation also activates previously silent group III and IV afferents. [257] In the cervical spine, group III afferents with a resting discharge were insensitive to the inflammatory mediator bradykinin, [260] but previously silent small-diameter afferents were activated by bradykinin. [211] These neural responses to inflammation likely underlie the findings that mustard oil induced inflammation elicits muscle activity in the neck. Mustard oil intensely activates high-threshold C-fibers (group IV afferents). [261] When very small volumes (20 µL) were injected into deep cervical paraspinal tissues, EMG activity was increased in a wide variety of upper cervical muscles including digastric, masseter, trapezius, and rectus capitis posterior. [262] Because the volume was small and its spread to the neighboring tissues was limited, the effects were likely mediated by a reflex. The large number of muscles affected by inflammation of cervical paraspinal muscles may relate to the hyperconvergence, described by Gillette et al [263] (see next paragraph), and to the communication between segmental paraspinal tissues via intersegmental connections within the spinal cord, reported by the laboratory of Pickar. [264] Dorsal horn neurons in the spinal cord with receptive fields in the lumbar paraspinal tissues, including paraspinal muscles and facet joints, receive more convergent input from group III and IV afferents than is true for dorsal horn neurons with receptive fields in the limbs. [263] In these electrophysiologic studies, Gillette et al [263] found that wide dynamic range and nociceptive specific neurons in the superficial dorsal horn of the L4-5 spinal segments shared receptive fields with deep and superficial tissues of the lumbar spine, the hip, and proximal leg. This type of input was termed hyperconvergent. Axonal tracing studies revealed that small diameter primary afferents from multifidus muscle and facet joints produce substantial bilateral labeling in laminae I, II, and III, as well as in the deeper laminae V-VIII and X. [265] Many of these laminae are involved in nociceptive processing and also project to autonomic centers. Axons Inside or Outside the IVF Adhesions, fixations, or discal herniation may produce an ectopic source of neural activity. Bove et al [266] inflamed the axons of mechanically sensitive group II, III, and IV afferents that innervate both superficial and deep structures. The inflammation led to increased spontaneous activity and/or increased mechanical sensitivity of only the group III and IV axons innervating deeper structures. Increasing evidence shows that the mechanical and chemical consequences of a herniated disk can affect neural tissue within the IVF. Dorsal roots and dorsal root ganglia (DRG) are more susceptible to the effects of mechanical compression than are axons of peripheral nerves because impaired or altered function is produced at substantially lower pressures. [267, 268] Applying as little as 10 mm Hg of pressure to the dorsal root reduces by 20% to 30% the nutritional transport to peripheral axons. [269] Recently, a mean pressure of 53 mm Hg (range, 7-256 mm Hg) was measured between a herniated disk and the nerve root in 34 humans undergoing surgery for lumbar disk herniation. [78] Song et al [270] inserted small pins into the IVF to model a space-reducing lesion in an animal model. Although pressures in the IVF were not measured, this lesion produced mechanical hyperalgesia in the hindlimb and increased the excitability of dorsal root ganglion cells. The application of nucleus pulposus to a lumbar nerve root increases spontaneous nerve activity and increases the mechanical sensitivity of dorsal root ganglion cells. [271] In addition, nucleus pulposus applied to a lumbar nerve root produces mechanical hyperalgesia, [272] causes swelling in and decreases blood flow to the DRG, and decreases blood flow to the lower leg. [273] Moderate doses of phospholipase A2, an inflammatory mediator associated with disk herniation, also increases the mechanical sensitivity of dorsal roots, produces long-lasting discharges, and increases the discharge of previously silent dorsal root ganglion cells. [41, 274] As mentioned in the previous section, extruded nucleus pulposus contains high levels of TNF-a, and 2 studies have shown that the inhibition of TNF-a by a monoclonal antibody (Remicade) is successful in alleviating sciatica. [74, 75] It should be noted that several case studies [201, 275, 276] and randomized clinical studies [277, 278] show that patients with herniated intervertebral disk, who received SM, gained clinical improvement. Effects of SMs on Muscle and Muscle Spindles Spinal manipulation induces somatomotor changes, that is, changes in muscle activity, apparently because of sensory input from the somatic nervous system. In asymptomatic patients, Herzog's group [279, 280] showed that PA spinal manipulative treatments applied to the cervical, thoracic, lumbar, and sacroiliac regions increased paraspinal EMG activity in a pattern related to the region of the spine that was manipulated. The EMG response latencies occur within 50 to 200 milliseconds after initiation of the manipulative thrust. Similarly, SM using an Activator-adjusting instrument applied to a transverse process elicited paraspinal EMG activity at the same segmental level but within 2 to 3 milliseconds. [281] This is surprisingly fast for a reflex response. Colloca and Keller [282] confirmed these latter findings in symptomatic patients with low back pain and, in addition, reported that the increased EMG activity, while beginning within 2 to 3 milliseconds of the manipulation, reached its peak within 50 to 100 milliseconds. Paraspinal EMG responses were greatest in magnitude when the manipulation was delivered close to the electrode site, and interestingly, the more chronic the low back pain, the less the EMG response. The EMG electrodes were not placed relative to any physical finding in the low back such as palpable muscle tension, as perceived by the practitioner or tissue tenderness as experienced by the patient. Spinal manipulation's effect on paraspinal muscle activity is not exclusively excitatory. In 1 symptomatic patient with spontaneous muscle activity in the thoracic spine, Herzog's group [280] observed reduced paraspinal EMG activity within 1 second after a thoracic SM. In a case series study, DeVocht et al [283] collected surface EMG activity from 16 participants in 2 chiropractic offices. Electrodes were placed over 2 sites exhibiting paraspinal muscle tension determined by manual palpation. Spinal manipulation was administered to 8 participants using Activator protocol. The other 8 were treated using Diversified protocol. EMG activity was decreased after treatment by both methods by at least 25% at 24 of the 31 EMG recording sites. The effects of SM on paraspinal EMG activity may also be associated with increases in muscle strength. Suter et al [284] studied symptomatic patients with sacroiliac joint dysfunction, anterior knee pain, and evidence of motor inhibition to knee extensor muscles. A side posture SM applied to the sacroiliac joint significantly decreased the inhibition of the knee extensors on the side of the body to which the manipulation was applied. Similarly, Keller and Colloca [285] found that erector spinae isometric strength (assessed using EMG) was increased after spinal compared with sham manipulation. A series of studies have addressed how SM affects central processing of somatomotor information. Spinal manipulation can increase the excitability of motor pathways in the central nervous system and depress the inflow of sensory information from muscle spindles to these motor pathways. This may, in part, account for the disparate clinical findings described above. In asymptomatic patients, Dishman et al [286] showed that SM increased central motor excitability. EMG activity from gastrocnemius muscle, evoked by direct activation of descending corticospinal tracts using transcranial magnetic stimulation, was larger after lumbar SM compared with simply positioning the patient but not applying the manipulation. However, SM can also depress the H-reflex. Manipulation applied to the sacroiliac joint in a PA direction decreased the magnitude of the tibial nerve H-reflex for up to 15 minutes in asymptomatic humans. [287] Similarly, side-posture lumbar manipulation of L5-S1 joint inhibited the H-reflex from the tibial nerve. [288] Mobilization alone but not massage also inhibited the tibial nerve H-reflex, but the effect of manipulation tended to be greater. [288, 289] After manipulation alone, the inhibition lasted for approximately 20 seconds but lasted up to 1 minute when the SM was preceded by spinal mobilization. Similarly, SM delivered to the cervical region depressed the median nerve H-reflex. [290] The magnitude of the response from the lumbar manipulation was greater than the response from the cervical manipulation, suggesting that central processing of sensory inputs from a SM is different in the neck and the low back. [290] The depression of the H-reflex does not appear to be a global response. Instead, it appears specific to the region of the spine manipulated because cervical manipulation did not affect the tibial nerve H-reflex. [291] Patient positioning, which flexes the lumbar spine before the manipulation, may augment the inhibition of tibial nerve the H-reflex. [292] A possible mechanism contributing to SM's inhibitory effects on the H-reflex and on spontaneous paraspinal EMG activity is suggested by recent experiments. Sensory input from tissues of the facet joint elicited by SM might reflexively decrease paraspinal muscle activity. Indahl et al [293] elicited reflex longissimus and multifidus EMG activity by electrically stimulating the intervertebral disk in a porcine preparation. Stretching the facet joint by injecting 1 mL of physiologic saline abolished the EMG activity. Haldeman's group [238, 294] has shown that SM can also affect higher centers in the brain. Using magnetic stimulation, Zhu et al [294] stimulated lumbar paraspinal muscles and recorded the evoked cerebral potentials. Stimulation of paraspinal muscle spindles using vibration reduced the magnitude of the cerebral potentials. Similarly, muscle spasm in human patients reduced the magnitude of the paraspinal muscle evoked cerebral potentials. Spinal manipulation reversed these effects, reducing muscle spasm and restoring the magnitude of the evoked cerebral potentials. [294] There is reason to believe that stretching the facet joint capsule and surrounding tissues likely occurs during SM, although this has received little study. [165] Furthermore, there may be reason to believe that the mechanically sensitive primary afferents could be stimulated beyond the short duration of an SM. Using MRI scans in human subjects, Cramer et al [10, 11] showed that a side-posture SM accompanied by cavitation gaps the facet joints. The synovial space of the lumbar facet joints increased in width an average of 2.2 mm in subjects who were positioned in side posture and received a side posture spinal adjustment. By comparison, the joint space widened by only 1.5 mm (a difference of 0.7 mm) in subjects who were positioned in side posture but did not receive a manipulation. The MRI scan was performed immediately after manipulation and lasted 20 minutes. Although not studied directly, it seems likely, based upon data from the laboratory of Khalsa, [165] that joint separations of these magnitudes are sufficient to load the facet joint tissues. If so, this raises the possibility that tissues surrounding the facet joint could be stretched for periods longer than the duration of the manipulation itself. Sensory input from tissues surrounding the facet joint that is graded with direction of facet movement [258] could elicit reflex muscle responses similar to those measured by Indahl et al. [293] Direct evidence from 1 of the experimental models described at the outset of this section [212] shows that the impulse load of an SM activates a variety of low-threshold mechanoreceptors in paraspinal muscles and that abrupt changes occur in the discharge from their parent afferent neurons [251, 295] as the speed of delivery approaches that used in clinical practice. [296-299] Pickar and Wheeler [251] recorded afferent activity from muscle spindle and Golgi tendon organ afferents having receptive fields in the lumbar multifidus and longissimus muscles while applying a spinal manipulative-like load to a lumbar vertebra. Muscle spindle afferents from lumbar multifidus and longissimus muscles were stimulated more by the impulse of an SM than by the load preparatory to the impulse (200% compared with 30%). Another type of low-threshold mechanoreceptor, a presumed Pacinian corpuscle, uniquely responded to the impulse of a manipulative-like load, that is, it did not respond to loads with a slower force-time profile. When an SM's duration was varied between 25 and 800 milliseconds, durations shorter than 400 milliseconds produced abrupt increases in discharge rates from 6 low-threshold mechanoreceptive afferents innervating the lumbar multifidus and longissimus muscles. [295] An increase in loading magnitude did not appear to systematically affect the discharge from these 6 low-threshold mechanoreceptors. Interestingly, Gillette et al [263, 265] showed that both weak and strong mechanical stimuli applied to paraspinal tissues can suppress spinal cord neurons that receive noxious input from the low back. In an anesthetized human patient undergoing an L4-L5 laminectomy, SM of the lumbosacral region evoked multiunit activity from the intact S1 nerve root. [300] This neural discharge measured in a clinical setting may be analogous, at least in part, to the discharge of low-threshold mechanoreceptors measured in an animal model. Effects of SMs on Pain or Pain Processing Numerous studies suggest that SM alters central processing of noxious stimuli because pain tolerance or pain threshold levels can increase after manipulation. In patients with low back pain, Glover et al [301] examined areas of lumbar skin that were painful to a pinprick. Fifteen minutes after SM of the lumbar region, the size of the area from which the pinpricks evoked pain was reduced, compared with the control group receiving detuned short wave therapy. Terrett and Vernon [302] quantified the reduction in pain sensitivity after SM using graded, electrical stimulation of cutaneous paraspinal tissues. A blinded observer assessed the minimal current necessary to evoke pain (pain threshold) and the maximal tolerable current that evoked pain (pain tolerance) in subjects with tender regions of the thoracic spine. Spinal manipulation significantly increased pain tolerance levels 1.5-fold within 30 seconds. Over the next 9.5 minutes, tolerance levels progressively increased up to 2.4-fold. In a case study, Vernon [303] assessed pressure/pain thresholds before and after SM using a handheld pressure algometer. The threshold measurement indicated the amount of pressure at which the perception of pressure changed to the perception of pain. The algometer was applied to 6 tender points in the neck region. The participant identified his own specific tender points. Spinal manipulation increased pressure-pain thresholds and decreased pain sensitivity by approximately 45% on average. In an effort to extend the findings in this case study, Cote et al [304] focused on chronic mechanical low back pain. A pressure algometer was applied to 3 sites in the lumbar region. The sites were standardized myofascial trigger points associated with low back pain. Unlike Vernon's earlier case study, these trigger points were not necessarily clinically relevant, that is, they were not identified as tender by participants, nor were they necessarily the most sensitive points for each individual. Unlike Vernon's case study, no changes in pressure-pain thresholds were observed. Recommendations and Action Steps “Nearly all proposed theories to explain the effects and mechanisms of action of SM have failed to withstand intense scientific scrutiny” (from the original white paper, Brennan et al [1]). This statement from the original white paper does not adequately express the state of chiropractic science. It seems more accurate to say that nearly all the proposed theories to explain the effects and mechanisms of action of SM have not been fully tested. Spinal manipulation is a biomechanical input generally delivered at high velocity. The question of how a short-lasting biomechanical input can presumably have long-lasting changes on a person's health needs answering. Research should seek to determine if SM produces long-term effects on biomechanics and/or neurophysiology. Determine the discharge characteristics (ie, the pattern or frequency of action potentials) of primary sensory neurons innervating the vertebral column in response to high-velocity loading. Determine how these patterns of activity affect the signaling properties of neurons in the central nervous system, for example, do they produce long-lasting changes. Determine if SM produces long-lasting changes in spinal biomechanics, which would presumably produce long-lasting changes in sensory input. Determine if SM produces long-lasting changes in neuromuscular control of paraspinal muscles, possibly comparing the use of fine wire electrodes with surface EMG or scanning EMG. Determine if paraspinal tissues have any unique physiology, compared with appendicular tissues, by comparing, for example, reflex changes initiated from sensory receptors in appendicular tissues with reflex responses initiated from sensory receptors in axial tissues. Identify objective changes in the vertebral column that lead one to think that SM is needed. Use new technologies to determine changes in intersegmental stiffness. Determine if hyperalgesia is associated with the manipulable lesion. Determine whether the manipulable lesion is inflamed and, conversely, if inflammation of spinal and paraspinal tissues can cause the manipulable lesion. General Recommendations.   A seed recommendation in the 1997 white paper (Brennan et al [1]) was to “concentrate basic science research at one lead chiropractic college and provide sufficient support personnel to conduct needed studies.” Acting on this recommendation in some way is sorely needed. A critical mass of chiropractic-oriented scientists able to easily interact and develop new ideas is critically important to drive chiropractic science. Basic and clinically-oriented basic scientists are scattered almost individually at chiropractic colleges and are isolated. This is in sharp contrast to the traditional university setting where a wide variety of fields are represented and allow for not only interdisciplinary collaborations but provide opportunities for informed discussion leading to inspiration and the writing and submission of research grants. Consideration should be given to the relative merits of developing basic science infrastructure at chiropractic colleges either in contrast to or in addition to establishing a small cadre of chiropractic scientists within a traditional university setting containing established infrastructure in terms of space, equipment and collaborative potential with established scientists from multiple disciplines.

   Neuroconceptual Models of Chiropractic
           Chapter 5 from: Basic Principles of Chiropractic Neuroscience
           By Richard C. Schafer, D.C., FICC and the ACAPress
           The structural spinal fault, the associated nerve involvement, and the ensuing functional alterations comprise classic chiropractic subluxation concepts. In contrast, limited concepts of spinal biomechanical faults, modes of possible nerve involvement, and etiologic rationales of functional changes promote narrow viewpoints, disciplines, and therapeutic approaches, as well as foster empiricism and dogma. Awareness of the varied concepts of structural lesions, neuroinsults, and the causes of abnormal functional changes promotes wider perspective for intuitive practices, multifaceted observations, and fewer practices with reliance on empiricism that is dictated by dogmatic frameworks.


   What is Different About Spinal Pain?
           Chiropractic & Manual Therapies 2012 (Jul 5);   20 (1):   22 ~ FULL TEXT
           This thesis addressed the question "what is different about spine pain?"   Neuroanatomic and neurophysiologic findings from studies in the last twenty years provide preliminary support for the thesis that deep spine pain is different from deep pain arising from peripheral limb structures.


   Cerebral Perfusion in Patients with Chronic Neck
and Upper Back Pain: Preliminary Observations
J Manipulative Physiol Ther. 2012 (Feb);   35 (2):   76–85
RESULTS:   Group 1 (mild) consisted of 14 patients. Cerebral perfusion measured by SPECT was normal in all 8 brain regions. Group 2 (moderate) consisted of 16 patients. In this group, a decrease in cerebral perfusion was observed (range, 20%-35%), predominantly in the parietal and frontal zones. Group 3 (severe) consisted of 15 patients. In this group, the decrease in cerebral perfusion observed was from 30% to 45%, again predominantly in the parietal and frontal zones. A significant difference was found between NDI groups ("moderate" and "severe" showed significantly greater hypoperfusion than "mild"). Total blockage score correlated with SPECT scores at r = 0.47, P = .001. In a multivariate analysis, NDI scores contributed 39% of the variance of SPECT scores.


   Cerebral Metabolic Changes in Men
After Chiropractic Spinal Manipulation for Neck Pain
Altern Ther Health Med. 2011 (Nov);   17 (6):   12–17
Research on chiropractic spinal manipulation (CSM) has been conducted extensively worldwide, and its efficacy on musculoskeletal symptoms has been well documented. Previous studies have documented potential relationships between spinal dysfunction and the autonomic nervous system and that chiropractic treatment affects the autonomic nervous system. The authors hypothesized that CSM might induce metabolic changes in brain regions associated with autonomic nervous system functions as assessed with positron emission tomography (PET). PET is a nuclear medicine imaging technique that allows quantification of cellular and molecular processes in humans such as cerebral glucose metabolism which is thought to reflect regional neuronal activities.


   Spinal Motor Neuronal Degeneration After Knee Joint
Immobilization in the Guinea Pig
J Manipulative Physiol Ther. 2010 (Jun);   33 (5):   328–337
After various periods of knee joint immobilization, a variety of features of motor neuronal degeneration were observed. Specific characteristics included gradual increases in the expressions of neuronal nitric oxide synthase and ultrastructural changes in affected motor neurons including reduction of cell organelles, indentation of the nuclear envelop, and small compact clumps of chromatin in the nuclei. We conclude that motor neuronal degeneration in the spinal cord and axons in this study was the result of knee joint immobilization. Increases in motor neuronal nitric oxide-mediated oxidative stress level after reduction of target tissue activity may contribute to the mechanism for degenerative changes in the motor neurons in adult spinal cord of the guinea pig.


   Exploring the Neuromodulatory Effects of the Vertebral Subluxation
and Chiropractic Care
Chiropractic Journal of Australia 2010 (Mar); 40 (1): 37–44 ~ FULL TEXT
Over the past 15 years our research group has been conducting a variety of experiments aimed at testing out the theory that adjusting subluxations improves central nervous system functioning and overall expression of health and well being. To do this the theory was first formulated into a model (Figure 2) that could be scientifically tested with a programme of research studies. This model became the basis for the lead author’s PhD research, [5] and continues to be a foundational premise that our research group is attempting to elucidate with our work. The model was constructed using early chiropractic research data and a thorough review of the neurophysiology scientific literature.


   Immobilization Induces Changes in Presynaptic Control
of Group Ia Afferents in Healthy Humans
J Physiol. 2008 (Sep 1);   586 (Pt 17):   4121–4135
Although the present study involved limb immobilization in able-bodied subjects, the findings may also be of clinical relevance. This is especially the case in relation to neurological disorders leading to physical inactivity. It is noteworthy that the findings of increased H-reflexes, decreased GABAergic presynaptic inhibition and decreased post-activation depression following immobilization to some extent matches the findings of previous studies in spastic patients and it is worth considering the effects of reduced physical activity in itself. As mentioned previously, it is possible that the decreased presynaptic inhibition and post-activation depression observed in patients with cerebral or spinal lesions may at least in part be a consequence of the disuse of motoneurons and Ia afferents.


   Preliminary Morphological Evidence That Vertebral Hypomobility
Induces Synaptic Plasticity in the Spinal Cord
J Manipulative Physiol Ther. 2007 (Jun);   30 (5):   336–342
These preliminary data suggest that chronic vertebral hypomobility (fixation) at L4 through L6 in the rat affects synaptic density and morphology in the superficial dorsal horn of the L2 spinal cord level. Morphological parameters that appear to be affected include synaptic curvature, type of postsynaptic profile, and perforations of the PSD. Additional more definitive studies are warranted, and the biologic significance of these finding should be investigated.


   Does Facet Joint Inflammation Induce Radiculopathy? An Investigation
Using a Rat Model of Lumbar Facet Joint Inflammation
Spine (Phila Pa 1976) 2007 (Feb 15);   32 (4):   406–412
The association between lumbar facet joint inflammation and radiculopathy was investigated using behavioral, histologic, and immunohistochemical testing in rats. Both mechanical and chemical factors have been identified as important for inducing radiculopathy. In lumbar spondylosis, facet joint osteophytes may contribute to nerve root compression, which may induce radiculopathy. Furthermore, inflammation may occur in the facet joint, as in other synovial joints. Inflamed synovium may thus release inflammatory cytokines and induce nerve root injury with subsequent radiculopathy. (In this study) when inflammation was induced in a facet joint, inflammatory reactions spread to nerve roots, and leg symptoms were induced by chemical factors. This work supports yet another aspect of the Vertebral Subluxation Complex hypothesis.


   Chiropractic Subluxation Assessment:
What the Research Tells Us
J Canadian Chiropractic Assoc 2002;   46 (4):   215–220 ~ FULL TEXT
When you speak of subluxation, the first description that often jumps to mind is the traditional misalignment, occlusion of a foramen, pressure on a nerve and interference (MOPI) model proposed by B.J. Palmer. [1] In fact there are several modern models currently in use as well. Some are conceptual models, such as the Vertebral Subluxation Complex model of Faye and Lantz, [2 which proposes as many as nine components interacting in a complex.


   Neurophysiological Effects of Spinal Manipulation
           Spine Journal 2002 (Sep);   2 (5):   357–671
           Biomechanical changes caused by spinal manipulation are thought to have physiological consequences by means of their effects on the inflow of sensory information to the central nervous system. Muscle spindle afferents and Golgi tendon organ afferents are stimulated by spinal manipulation. Smaller-diameter sensory nerve fibers are likely activated, although this has not been demonstrated directly. Mechanical and chemical changes in the intervertebral foramen caused by a herniated intervertebral disc can affect the dorsal roots and dorsal root ganglia, but it is not known if spinal manipulation directly affects these changes.


   Effect of Chiropractic Treatment on the Endocrine and Immune System
in Asthmatic Patients
Proceedings of the 2002 International Conference on Spinal Manipulation
The broad aims of this FCER funded study is to determine whether stress is a factor in the pathophysiology of asthma and to determine if chiropractic management of asthmatics can alleviate stress induced asthma. More specifically for this meeting, our study aims to determine whether chiropractic treatment has beneficial effects on the endocrine system through measurement of salivary cortisol and on the immune system via salivary IgA determination. You can review other articles on this topic at the Chiropractic and Asthma Page.


   The Functional Spinal Lesion:
An Evidence-Based Model of Subluxation
Topics In Clinical Chiropractic 2001 (Dec);   8 (1):   16–28 ~ FULL TEXT
The buckling model builds on clinical observations and supplements them with both direct and indirect biomechanical evidence. This model does not preconceive or proscribe any source of symptoms, but is able to accommodate the multifaceted clinical presentations of patients who respond favorably to manipulation/adjustment. It also can sustain a variety of hypothetical and evidence-based challenges. These findings offer an opportunity to reconceptualize and refine theoretical models of the spinal lesion into a platform for scientific, clinical, and political advancement of the profession.


   The Effects of Mild Compression on Spinal Nerve Roots with Implications for Models of Vertebral Subluxation and the Clinical Effects of Chiropractic Adjustment
J Vertebral Subluxation Research 2001 (May);   4 (2):   1–13
There is evidence of nerve compression at the level of the intervertebral foramen (IVF) occurring anywhere from 15.4% to 78% of levels inspected. Most of the spines inspected were already prescreened to eliminate those that were definitely known to have nerve compression problems. Pressures as little as 10 mm Hg can alter the nerve root and dorsal root ganglion’s abilities to function normally. In the normal range of motion the pressures generated in the IVF may exceed 30 mm Hg. When considering the concept of a joint fixated in a diminished sphere of its normal range of motion in conjunction with the mild pressure increases, it becomes apparent that nerve function can be significantly altered.


   Response of Muscle Proprioceptors to Spinal Manipulative-like Loads
in the Anesthetized Cat
J Manipulative Physiol Ther. 2001 (Jan);   24 (1):   2–11
The data suggest that the high-velocity, short-duration load delivered during the impulse of a spinal manipulation can stimulate muscle spindles and Golgi tendon organs more than the preload. The physiologically relevant portion of the manipulation may relate to its ability to increase as well as decrease the discharge of muscle proprioceptors. In addition, the preload, even in the absence of the impulse, can change the discharge of paraspinal muscle spindles. Loading of the vertebral column during a sham manipulation may affect the discharge of paraspinal proprioceptors.


   The Reflex Effects of Subluxation: The Autonomic Nervous System
           J Manipulative Physiol Ther 2000 (Feb);   23 (2):   104-106
           There is no shortage of theories to explain the role of subluxation in disease and the effect of adjustment in relieving symptoms. The autonomic nervous system has often been invoked in constructing mechanisms to account for the effects of spinal dysfunction; recent investigations justify the attention that has been focused on this component of the nervous system. Recent neuroscience research supports a neurophysiologie rationale for the concept that aberrant stimulation of spinal or paraspinal structures may lead to segmentally organized reflex responses of the autonomic nervous system, which in turn may alter visceral function.


   The Somatosensory System of the Neck and its Effects
on the Central Nervous System
J Manipulative Physiol Ther. 1998 (Oct);   21 (8):   553–563
Studies involving human and nonhuman vertebrates have provided considerable information about the anatomy of the sensory receptors located in the neck and about where information from these receptors is relayed in the spinal cord and brain. Physiological experiments involving electrical and natural stimulation of the head and neck regions have identified a role for some of these receptors in neck-evoked reflexes. It is clear that in addition to signaling nociception, the somatosensory system of the neck may influence the motor control of the neck, eyes, limbs, respiratory muscles and possibly the activity of some preganglionic sympathetic nerves.


   Dysafferentation:   A Novel Term to Describe the Neuropathophysiological Effects of Joint Complex Dysfunction. A Look at Likely Mechanisms of Symptom Generation
J Manipulative Physiol Ther 1998 (May);   21 (4):   267-280 ~ FULL TEXT
Since the founding of the chiropractic profession, very few efforts have been made to thoroughly explain the mechanism(s) by which joint complex dysfunction generates symptoms. Save for a few papers, only vague and physiologically inconsistent descriptions have been offered. The purpose of this article is to propose a precise and physiologically sound mechanism by which symptoms may be generated by joint complex dysfunction. This thought provoking FULL TEXT article was released exclusively to Chiro.Org by National College of Chiropractic and JMPT. You may also enjoy this response from another chiropractic researcher.


   Somatic Dysfunction and the Phenomenon of Visceral Disease Simulation: A Probable Explanation for the Apparent Effectiveness of Somatic Therapy in Patients Presumed to be Suffering from True Visceral Disease
J Manipulative Physiol Ther 1995 (Jul-Aug);   18 (6):   379–397
The proper differential diagnosis of somatic vs. visceral dysfunction represents a challenge for both the medical and chiropractic physician. The afferent convergence mechanisms, which can create signs and symptoms that are virtually indistinguishable with respect to their somatic vs. visceral etiologies, need to be appreciated by all portal-of-entry health care providers, to insure timely referral of patients to the health specialist appropriate to their condition. Furthermore, it is not unreasonable that this somatic visceral-disease mimicry could very well account for the "cures" of presumed organ disease that have been observed over the years in response to various somatic therapies (e.g., spinal manipulation, acupuncture, Rolfing, Qi Gong, etc.) and may represent a common phenomenon that has led to "holistic" health care claims on the part of such clinical disciplines.

Four Articles Which Describe the Relationship Between the Upper Cervical Spine and Headaches and Chronic Head Pain Thanks to Rick Hallgren! 1.  Atrophy of Suboccipital Muscles in Chronic Pain Patients We have observed previously unreported muscle atrophy in the rectus capitis posterior minor (RCPMI) muscles of a group of chronic pain patients. We hypothesize that chronic pain, in this select group of patients, is a consequence of tramua that occurs to the C1 dorsal ramus during whiplash. 2.  Magnetic Resonance Imaging of the Upper Cervical Spine We are currently using MRI to investigate the functional integrity of the upper cervical spine. We started out looking for hypertonic muscles in a population of patients who were suffering from chronic head and neck pain. My first task was to collect MRI data and to identify suboccipital muscles within the MR images. So I brought together a physician and an anatomy professor to see if they could help me out. Their comments were classic. The anatomy professor said, "The reason you can't find those muscles is because they are not there." The physician immediately responded by saying, "No wonder these patients don't get any better." I had been using images that were collected from a chronic pain patient, and it was apparent that the rectus capitis posterior minor muscles were missing. When we looked at images from a control subject it was very easy to locate these muscles. At that point, the focus of our research switched from looking for hypertonic muscles to comparing muscle density between the control group and the chronic pain group. 3.  Anatomic Relation Between the Rectus Capitis Posterior Minor Muscle and the Spinal Dura Mater We observed that the PAO membrane was securely fixed to the surface of the dural tube by multitudinous fine connective tissue fibers. There was no real interlaminar space between these two structures and they appeared to function as a single entity. The influence of the RCPMI muscle on the dura mater was artificially produced in the hemisected specimen. Artificially functioning the muscle produced obvious movement of the spinal dura between the occiput and the atlas, and resultant fluid movement was observed to the level of the pons and cerebellum. 4.  Visualization of the Muscle-Dural Bridge in the Visible Human Female Data Set SPINE Journal 1995;   20 (23):   2484-2486 It has been speculated that the function of the muscle dural bridge may be to prevent folding of the dura mater during hyperextension of the neck. Also, clinical evidence suggests that the muscle dural bridge may play an important role the pathogenesis of the cervicogenic headaches.

   The Neurophysiological Evaluation of the Subluxation Complex:
Documenting the Neurological Component with Somatosensory Evoked Potentials
Chiropractic Research Journal 1994;   3 (1) ~ FULL TEXT
The results seen in this study indicate highly significant changes for the pre vs post adjustment SSEP tests. The mean latencies decreased after chiropractic adjustment in each of the nerves tested. This would seem to indicate that the upper cervical subluxation does cause neurological compromise in nerves forming both the brachial and lumbo-sacral plexuses. The removal of the subluxation by chiropractic adjustment results in improved conduction of the neural impulses as demonstrated on the post-adjustment tests. The improvements that were observed are similar to the changes seen when neurological compromise is relieved by surgical procedures to decompress or stabilize the spine.



   Subluxation and the Nervous System
           Dynamic Chiropractic ~ February 12, 2004 ~ FULL TEXT
           The important point to appreciate now is that the subluxation complex will alter the firing of spinal tissue nociceptors and mechanoreceptors, and this will lead to various symptoms that we often encounter in the clinical setting that respond to chiropractic care. So, when we think about subluxation, the subluxation complex, or joint dysfunction, we need to think about receptors and afferent fibers.


   How Does Subluxation Affect the Nervous System?
           Dynamic Chiropractic ~ October 7, 1996,
In 1976, Drs. Vert Mooney and James Robertson set out to confirm the earlier research on referred pain and discussed their findings in a well-known paper, "The Facet Syndrome."3 Their attention was directed toward the facet joints rather than spinal muscles and ligaments. The subjects in this study included five normal individuals and 15 patients with low back pain. To make a semi-long story short, Mooney and Robertson discovered that, indeed, injecting hypertonic saline into facet joints resulted in local and referred pain. They also discovered that, "slightly increasing the volume of injection would consistently increase the amount of pain radiation."


   Nociception, Mechanoreception and Proprioception:
What's the Difference and What Do They Have to Do with Subluxation?
Dynamic Chiropractic ~ November 18, 1994
Nociception is the process by which nociceptive receptors receive tissue damaging stimuli that is then carried into the CNS by nociceptive axons (A-delta and C fibers). Potential outcomes of nociceptive input to the cord include pain, autonomic symptoms, vasoconstriction and muscle spasm. Nociceptive input to the cord appears to be the driving force behind the pathogenesis of subluxation (see Figure A). We must remember that nociception and pain are two completely different animals. However, a devastating consequence of both pain and nociceptive stimulation of the hypothalamus, is the release of cortisol by the adrenal glands. Over time, elevated levels of cortisol will promote glucose intolerance, inhibit collagen formation, increase protein breakdown, inhibit secretory IgA output, and inhibit white blood cell function. Clearly, the clinical importance of pain and nociception should not be minimized.


   Nociception and Subluxation
           Dynamic Chiropractic ~ September 23, 1994 ~ FULL TEXT
           When discussing subluxation with our patients, the great majority of DCs still describe it in terms of a bone-out-of-place that pinches or chokes nerves. There are two major problems with this explanation: It is inaccurate because subluxations rarely, if ever, pinch or choke nerves. Secondly, by repeating this erroneous explanation again and again, DCs eventually come to believe it. Repetitive exposure to information embeds in the mind.

Basic Science Research Related to Chiropractic Spinal Adjusting: The State of the Art and Recommendations Revisited FROM:   J Manipulative Physiol Ther. 2006 (Nov);   29 (9):   726–761 Biomechanics Biomechanics is the study of the effects of loads applied to biologic cells, tissues or systems. Biomechanics has its origins from Galileo's studies of mechanics in general and his creation of the term mechanics as a subtitle of his book "Two New Sciences" (1638) to refer to force, displacement, and strength of materials. Arguably, the “father of biomechanics” is Giovanni Alfonso Borelli, who published in "De Motu Animalium" (1681) the principles of muscle movements based on statics and dynamics. However, the word “biology” and its concept as the study of living organisms did not occur until 1802 when the German naturalist, Gottfried Reinhold Treviranus, published his first volume "Biologie; oder die Philosophie der lebenden Natur". To rigorously understand SM and its effects requires an understanding of the principles of biomechanics. Manipulation Forces Since the publication of the first white paper in 1997, there have been several important studies that have further clarified the loads that are applied during SM, and especially during high-velocity, low-amplitude (HVLA) SM. Triano and Shultz [150] measured the total force that was transmitted through the body during a side-lying lumbar or lumbosacral HVLA SM. The transmitted forces were similar to the applied forces for their temporal history, but the transmitted forces and moments were shown to vary substantially based on patient positioning. Herzog et al [151] measured the force distribution during thoracic HVLA SM and concluded that there was an important distinction between the total and effective applied forces, with the latter being much smaller than the total applied force. They found that the total peak force was being applied over a mean contact area of 34.8 cm2, but for the thoracic spine, the physiologic contact area of the transverse processes was only 0.25 cm2 (less than 1/100 of the total contact region). Hence, most of the total peak force was being applied to soft tissues (eg, skin, muscle, and fat), and only a small portion (~5 N) was being applied to the transverse process. A similar finding was reported by Kirstukas and Backman, [152] who reported that the “intense contact area” was on the order of 10 cm2 during thoracic HVLA SM. Clearly, the effective applied force during HVLA SM in general will vary based on the contact area of the manipulator's hand and the aspect of the vertebra, but in general, the effective force will be less, and sometimes substantially so, than the applied force. The 3-dimensional force applied during HVLA SM of the cervical, thoracic, and sacroiliac regions has now been measured. [153] The 3-dimensional data showed that forces in plane with the back (ie, Fx and Fy or shearing forces) always occurred during the SM, which was dominated by the normal (ie, Fz or perpendicular) applied force. The shearing forces were considerable in magnitude, ranging from a low mean of 15% (at T4-5) to a high of 29% (at sacroiliac) of the peak Fz force. As has been previously reported by others, [154] there was a consistent drop in the preload force magnitude just before the impulse portion of the HVLA SM, which is speculated to be due to a “countermovement” affect. The role of sex in developing force magnitude has been investigated. [155] The only previous report that compared male and female manipulators found no significant differences during HVLA SM using a patient simulator. [156] Forand et al [155] used an experienced matched group (range, 1-24.5 year of experience) of female and male chiropractors (14 per group) and found that there were no significant differences between sexes in thoracic HVLA SM forces. The one exception was that, in the lower thoracic spine, men applied significantly greater preload than did women. Another type of SM is mobilization or low-velocity low-amplitude SM, which is commonly used by physical therapists as well as other health professionals, including chiropractors. The general approach is to apply an increasing force over 5 to 10 seconds to determine the “end feel,” and then so calibrated, to apply a slow oscillation (~1 Hz for 10 seconds) about a mean graded force (I-IV arbitrary scale), which is less than the end feel. [157] Using an instrumented mobilization table, it was found that there was considerable variation in the force magnitudes used by experienced therapists for end feel, as well as grades I-IV mobilizations of L3 vertebra in healthy subjects. [157] When comparing treatment of younger vs older healthy subjects, it was found that, although mean forces were similar, smaller amplitudes and higher frequency of oscillations were used with older patients. [158] In a study of patients with nonspecific low back pain, there was considerable variation in the magnitudes of forces used, but the variation was strongly influenced not by the patient's severity of complaint but by the physical therapist's training. [159] Effects of External Loading on Vertebral Displacements Our understanding of the kinematics of SM has been increased by 2 different types of investigations. First, Keller et al [160-162], have published 2 studies using mechanical force, manually assisted, short-lever SM (ie, Activator [Activator Methods International, Phoenix, Ariz] or very HVLA [VHVLA]) in vivo on patients undergoing lumbar surgery. Using forces ranging from 30 N (lowest setting) to 150 N (maximum setting) on the adjusting instrument, the vertebra where the force was applied had peak displacements of approximately 0.5 mm occurring within 10 milliseconds. Intersegmental displacements occurred of similar magnitudes but with large oscillations lasting 2 to 3 times longer (ie, 20-30 milliseconds), but all oscillations appeared to have damped out within 100 milliseconds. In a second in vivo study, they found that the vertebral displacements due to the Activator instrument were slightly larger (mean, ~0.62 mm) and did not vary significantly, depending on whether the instrument was positioned over the spinous process or facet joint (left or right). [163] 0 Second, using intact cadaveric human lumbar spine specimens, Ianuzzi and Khalsa [164] simulated lumbar HVLA SM while measuring vertebra kinematics and facet joint capsule strain. During simulated HVLA SM, the applied loads were within the range measured during in vivo HVLA SM. Vertebral translations occurred primarily in the direction of the applied load and were similar in magnitude (on order of 1-2 mm) regardless of manipulation site. Vertebral rotations (on order of 1°-3°) and facet joint capsule strain magnitudes (on order of 5%) during simulated HVLA SM were within the range that occurred during physiologic motions. [165] At a given facet joint capsule, distal manipulations induced capsule strains similar in magnitude to those that occurred when the manipulation was applied proximally. The mobility of lumbar vertebrae in healthy volunteers during mobilization has been assessed using dynamic MRI. Powers et al [166] found that applying a 10-second grade IV posterior to anterior (PA) mobilization (~100 N force) at the spinous process of a lumbar vertebra produced an extension of the vertebra ranging from a mean of 1.2° at L2 to 3.0° at L5. Using plain film radiographs, Lee and Evans [167] found similar displacements for a 150 N PA mobilization at L4. Kulig et al, [168] also using dynamic MRI, found that applying a PA mobilization induced intersegmental motion in all lumbar vertebrae, caudal and cranial, to the site of applied force. This is consistent with the findings of Ianuzzi and Khalsa [164] who also found that simulated HVLA SM at a single vertebra induced motion in all other lumbar vertebrae. Thus, it is not possible to move only a single vertebrae with SM (high or low velocity) because the spine is a linked and coupled structure. Other effects HVLA SM is commonly associated with a “cracking” sound, which has previously been shown to be associated with a cavitation phenomenon in the facet joints. [169, 170] In healthy volunteers, Ross et al [171] found that single HVLA SM were typically associated with multiple cavitations (ranging from 2 to 6), which were from nearby vertebrae. This was consistent with the findings of Beffa and Mathews, [172] who found no significant relationship between the location of the cavitation and HVLA SM of the L5 or sacroiliac joint in asymptomatic volunteers. There is some question as to whether HVLA SM can actually induce motion into the sacroiliac joint, as Tullberg et al, [173] using stereo radiography, were unable to measure any significant motion of the sacrum relative to the ilium after a combination of HVLA and mobilization SM in patients with “subluxated” sacroiliac joints. Furthermore, Flynn et al [174] found no association between an “audible pop” and improvement in ROM, pain, or disability in patients with nonradicular low back pain. Measures of Pathologic States An intriguing question has begun to be answered relating to whether changes in intersegmental stiffness can be discerned using clinically available tools. Colloca et al [175] measured intersegmental impedance (dynamic stiffness) of lumbar vertebrae and correlated it with characteristics of vertebral height and IVD height measured from plain film radiographs. They found that there was a correlation between decreased disk height at L5-S1 and increased dynamic stiffness at the same segment. These findings were analogous to those of Kaigle et al [176] who, using a porcine model, also observed increased spine dynamic stiffness associated with degenerated disks, compared with normal controls. Using ultrasound indentation, another noninvasive approach, Kawchuk et al [177] also found that IVD degeneration in a porcine model resulted in decreased indentation for the same applied load. This is an analogous metric as spine stiffness. The use of ultrasound indentation in this animal model had high sensitivity (75.0%), specificity (83.3%), and accuracy (77.1%), compared with other approaches (arthroscopy, MRI, and plain film radiography). Two biomechanics studies have been performed to examine the effects of fixation (ie, a hypomobile subluxation) of the lumbar spine. Cramer et al [13] used a rat model of fixation in the lumbar spine by externally fixating the spinous processes of L4-L6 for up to 8 weeks. A principal finding due to the fixation was the development of osteophytes and degenerative articular changes of the facet joints within a few weeks. Reversal of some of the degeneration was observed for joints that were fixated for a short term (~1 week), but after 4 weeks, no reversal was observed. Little et al [178] simulated a hypomobile subluxation in intact, cadaveric human lumbar spine specimens by screwing a plate into the left anterior aspect of the L4 and L5 vertebral bodies. During physiologic motions of the fixated spine specimens for flexion, extension, and lateral bending, the motions at L4-5 were significantly decreased, whereas below and above that level, intersegmental motions were significantly increased. Correspondingly, the plane strains of the facet joint capsules were significantly decreased and increased at and above/below the site of fixation, respectively. Diagnostic tools or outcome measures The principal biomechanical “tool” still used by most chiropractors is palpation. As such, there has been a continued investigation into factors that change what is felt during palpation. Humans are relatively good at discriminating different magnitudes of stiffness for purely “elastic” materials. [179] However, the human spine responds as a viscoelastic system, in which the speed of force application changes the apparent stiffness. Nicholson et al [180] have shown that the relatively poor ability of clinicians to accurately estimate spine stiffness magnitudes is likely due to a 50% poorer ability to discriminate viscous components of viscoelastic systems. Latimer et al [181] found that therapists used different forces to discern spine stiffness and, hence, had different internal perceptual scales. By training therapists to use a calibrated stiffness instrument, discrimination of PA stiffness in the spine can be done with relatively high interexaminer reliability. [182] Furthermore, objective instruments have been developed that can reliably measure PA spine stiffness. [183] Perhaps, the most important aspect of using palpation to detect subluxations (ie, a “manipulable lesion”) is standardization of training. [184] When examiners are trained in a standardized fashion, they are able to obtain relatively high interexaminer reliability (? = 0.68) for detecting cervical fixations. Stiffness of the spine is influenced by many factors. If the ribcage is constrained, then the stiffness measured at T12-L4 can be significantly increased. [185] Change in orientation of an applied load to the spinous process can have small yet significant changes in objectively measured stiffness. [186] Furthermore, because the spine is a viscoelastic system, there will be a preconditioning effect when applying loads, such that after preconditioning the spine with standard mobilization SM, there will be no measurable change in stiffness. [187] There has also begun to be a growing appreciation for the natural (and normal) variability in spine stiffness as assessed by standard ROM tests during a physical examination. Christensen and Nilsson [87] found that in asymptomatic volunteers during a 3-week period, there was an intrinsic variability in ROM of the cervical spine of ± 20°, ± 14°, and ± 12° for flexion/extension, lateral bending, and rotation, respectively. In contrast, repositioning the head to the neutral position, which is related to proprioception, is done with relatively high fidelity over the same period. [188] Asymptomatic volunteers were able to reachieve the neutral zero position of their heads with a mean difference of 2.7°, 1.0°, and 0.7° for the sagittal, horizontal, and frontal planes, respectively. Using a case study approach, Lehman and McGill [189] observed that a single HVLA SM session in the lumbar spine caused notable changes in biomechanical factors associated with a complex task (ie, a golf swing in an experienced golfer who had chronic low back pain). In addition to changes in vertebral kinematics, they observed decreased electromyographic (EMG) responses of the associated lumbar muscles. In a subsequent study, Lehman and McGill [190] found that lumbar HVLA SM in patients with low back pain resulted in variable changes in lumbar ROM and associated muscle EMG. The largest changes were associated with patients with the greatest reported pain. In a review of the available literature. Lehman [191] reported that, currently, the best way to discriminate between normal and low back patient groups was using biomechanical tests that assessed “higher-order kinematics during complex movement tasks.” Simpler end ROM tests had poor predictive ability. Another commonly performed clinical test is measuring leg lengths, especially in the prone position. Using a special designed table to minimize friction and allow independent loading of each leg, Jansen and Cooperstein [192] determined that the prone leg length test was reliable for detecting non–weight-bearing asymmetry in leg lengths. Nguyen et al [193] found that there was reasonable concordance (? = 0.6) in determining whether a short leg was present using the Activator protocol. Cooperstein et al [194] found that it was possible to detect a leg length difference of 1.9 mm but recommended that only differences of greater than 3.7 mm should have confidence associated with them. Mathematical and Computational Models One of the signs of maturity of any field is the ability to produce predictive models. In spine biomechanics, most models are computationally based and either use finite element approaches [195] or optimization with minimization of an objective function. Analytical approaches have also been performed, which include a linear elastic model of a lumbar motion segment. [196] This model successfully predicted loads born by various ligaments under physiologic loads. Solinger [197] created a model that predicted the dynamic response of L2-L3 to impulsive loads on the order of those used in VHVLA SM. Using a lumped parameter approach, Keller and Colloca [198] created an analytical model that predicted the frequency dependent response of the human lumbar spine to PA forces applied to the spinous processes, as is done during low velocity and low amplitude (ie, mobilization), HVLA, and VHVLA (ie, Activator). An alternative approach was adopted by Dulhunty [199] who modeled force transmission in the cervical spine to predict whether parallel forces or concurrent forces are the optimization function. A relatively new approach in spine modeling, especially in the lumbar spine, is to incorporate what are called “follower loads” for muscles. The issue is that the ex vivo (cadaveric) intact lumbar spine will buckle under compressive loads of ~100 N, whereas in vivo, the lumbar spine easily supports compressive loads of ~1000 N (ie, 10 times greater). Patwardhan et al [200] found that by modeling muscle activation so that their loads followed the tangent of the lumbar lordosis, their model would approximate the in vivo condition. A couple of new comprehensive models have been advanced to explain how the spine becomes subluxated in the first place and how SM can restore it to “normal.” Triano [201, 202] has advocated a mechanical model based on the concept of intersegmental buckling, which was based on original observations by Wilder et al [203, 204] and fluoroscopic recordings of a buckling event in a weightlifter by Cholewicki et al [205] and Cholewicki and McGill. [206] Essentially, this model proposes that there is a balance point between each pair of vertebrae that under certain loading conditions can suddenly shift, which then results in increased tissue strain of associated soft tissues (eg, facet joint capsule). The increased tissue strain can result in small tears and associated biologic inflammatory response. Evans et al [207] have proposed an optimization model where the spine system is biased toward minimizing the mechanical energy associated with loading the spine. Their model is described for the case of linear elasticity, although they claim it is also apropos of nonlinear elasticity. As with any theory (or model), the value of these new theories is really found in their predictive ability and how well their predictions are validated by experimental data. So far, neither of these theories has been tested to any degree. Instrumented Manipulation Passive devices have been used for many decades to treat patients with back disorders. Recently, a simple distraction device, Rola Stretcher (Unique Relief, Inc, Davenport, Iowa), designed to be used at home without supervision, was tested to determine whether it showed any lengthening of the spine subsequent to its use. Devocht et al [208] tested 12 asymptomatic adults and found a significant increase in sitting height after 10 minutes of lying supine on the device. They concluded that it at least temporarily lengthened the spine, presumably by increasing the intervertebral disk height. In addition to the activator adjusting tool, which has had increasing amounts of scientific study, [160-163] the PulStar computer-assisted, differential compliance spinal instrument has been developed, and a few studies on it have appeared. [209, 210] This latter device also applies an impulse load (up to ~150 N), although the duration of the impulse has not been characterized in articles available in the indexed peer-reviewed literature. The device also incorporates a sensor to measure the compliance of the material that it loads, and hence, the compliance of the paraspinal region can be assessed as well as loaded with the same device. A case study has reported that the instrument was used to treat the spines of infants having colic. [210] F.   Recommendations and Action Steps Determine (quantify) the biomechanical basis of the subluxation. Determine the parameters that dictate whether a given vertebra should be manipulated. Determine the parameters that will guide the optimal approach to administering the manipulation. Determine the effects of manipulation on tissues of the spine. Which ligaments (including facet joint capsule) sustain the largest strains due to SM The influence of the vector direction of a given type of SM on ligament strains Measure the effects of SM on change in tissue characteristics (eg, ligament modulus of elasticity) and cellular response to SM. Quantify the biomechanical safety of SM in fracture, disk lesions, ligament strains, muscle, and tendon strains. Develop comprehensive models of the spine that predict how it responds to physiologic and SM loads. Determine the biomechanical parameters of SM that dominate the neurophysiologic beneficial effects of SM.

   Biomechancial Quantification of Pathologic Manipulable Spinal Lesions:
An In Vivo Ovine Model of Spondylolysis and Intervertebral Disc Degeneration
J Manipulative Physiol Ther 2012 (Jun);   35 (5):   354–366
Using a previously validated ovine lumbar degenerative disc lesion model and a novel ovine spondylolysis lesion model, surgically induced spinal lesions were prospectively tracked histologically and radiologically through a 6-month follow-up. Objective evidence of an increase in dynamic spinal stiffness, as well as reductions in vertebral displacements occurring in response to SM, were observed in the spondylolysis and disc degeneration groups compared with their age-matched and exposure level controls. Histologic evidence of pathology consistent with an alteration of spinal stiffness accompanied by alterations in the neuromuscular system provides novel insights into quantifying manipulable spinal lesions as well as a means to biomechanically assess SMT outcomes.


   Cerebral Perfusion in Patients with Chronic Neck
and Upper Back Pain: Preliminary Observations
J Manipulative Physiol Ther. 2012 (Feb);   35 (2):   76–85
RESULTS:   Group 1 (mild) consisted of 14 patients. Cerebral perfusion measured by SPECT was normal in all 8 brain regions. Group 2 (moderate) consisted of 16 patients. In this group, a decrease in cerebral perfusion was observed (range, 20%-35%), predominantly in the parietal and frontal zones. Group 3 (severe) consisted of 15 patients. In this group, the decrease in cerebral perfusion observed was from 30% to 45%, again predominantly in the parietal and frontal zones. A significant difference was found between NDI groups ("moderate" and "severe" showed significantly greater hypoperfusion than "mild"). Total blockage score correlated with SPECT scores at r = 0.47, P = .001. In a multivariate analysis, NDI scores contributed 39% of the variance of SPECT scores.


   Cerebral Metabolic Changes in Men
After Chiropractic Spinal Manipulation for Neck Pain
Altern Ther Health Med. 2011 (Nov);   17 (6):   12–17
Research on chiropractic spinal manipulation (CSM) has been conducted extensively worldwide, and its efficacy on musculoskeletal symptoms has been well documented. Previous studies have documented potential relationships between spinal dysfunction and the autonomic nervous system and that chiropractic treatment affects the autonomic nervous system. The authors hypothesized that CSM might induce metabolic changes in brain regions associated with autonomic nervous system functions as assessed with positron emission tomography (PET). PET is a nuclear medicine imaging technique that allows quantification of cellular and molecular processes in humans such as cerebral glucose metabolism which is thought to reflect regional neuronal activities.


   Self-reported Nonmusculoskeletal Responses to Chiropractic Intervention:
A Multination Survey
J Manipulative Physiol Ther 2005 (Jun);   28 (5):   294–302
Positive reactions were reported by 2% to 10% of all patients and by 3% to 27% of those who reported to have such problems. Most common were improved breathing (27%), digestion (26%), and circulation (21%).


   Effect of Chiropractic Treatment on the Endocrine and Immune System
in Asthmatic Patients
Proceedings of the 2002 International Conference on Spinal Manipulation
The broad aims of this FCER funded study is to determine whether stress is a factor in the pathophysiology of asthma and to determine if chiropractic management of asthmatics can alleviate stress induced asthma. More specifically for this meeting, our study aims to determine whether chiropractic treatment has beneficial effects on the endocrine system through measurement of salivary cortisol and on the immune system via salivary IgA determination. You can review other articles on this topic at the Chiropractic and Asthma Page.


   Chronic Pediatric Asthma and Chiropractic Spinal Manipulation:
A Prospective Clinical Series and Randomized Clinical Pilot Study
J Manipulative Physiol Ther 2001 (Jul);   24 (6):   369-377
After 3 months of combining chiropractic SMT with optimal medical management for pediatric asthma, the children rated their quality of life substantially higher and their asthma severity substantially lower. These improvements were maintained at the 1-year follow-up assessment.


   Epilepsy and Seizure Disorders: A Review of Literature Relative to
Chiropractic Care of Children
J Manipulative Physiol Ther 2001 ( Mar);   24 (3):   199-205
Chiropractic care may represent a nonpharmaceutical health care approach for pediatric epileptic patients. Current anecdotal evidence suggests that correction of upper cervical vertebral subluxation complex might be most beneficial. It is suggested that chiropractic care be further investigated regarding its role in the overall health care management of pediatric epileptic patients.


   The Short–Term Effect of Spinal Manipulation in the Treatment of
Infantile Colic: A Randomized Controlled Clinical Trial with a Blinded Observer
J Manipulative Physiol Ther 1999 (Oct);   22 (8):   517–522
By trial days 4 to 7, hours of crying were reduced by 1 hour in the dimethicone group compared with 2.4 hours in the manipulation group (P = .04). On days 8 through 11, crying was reduced by 1 hour for the dimethicone group, whereas crying in the manipulation group was reduced by 2.7 hours (P = .004). From trial day 5 onward the manipulation group did significantly better that the dimethicone group. The authors then conclude: Spinal manipulation is effective in relieving infantile colic. You may also enjoy FCER's review of this article.

   The Research Agenda Conference (RAC IV): Chiropractic Theory in Research:
Subluxation Theory Finally Gets the Attention It Deserves
Robert Mootz, D.C.
Theories are designed to explain observable phenomena. In actuality, the "subluxation model" that postulates a relationship between body structure, physiological function and health is an inherently viable one. The precise biomechanical, neurophysiological and/or psychosocial mechanisms that may or may not come into play remain to be elucidated through research. As more becomes known, chiropractic models should rightly be refined to better explain clinical observations. Well-developed theories help pose research questions and study designs that do a better job at finding out information that can improve our practices and benefit the patients we are here to serve.


   The Basis for Spinal Manipulation:
Chiropractic Perspective of Indications and Theory
J Electromyogr Kinesiol. 2012 (Apr 16) [Epub ahead of print]
It is reasonable to think that patients responding to spinal manipulation (SM), a mechanically based therapy, would have mechanical derangement of the spine as a critical causal component in the mechanism of their condition. Consequently, SM practitioners routinely assess intervertebral motion, and treat patients on the basis of those assessments. In chiropractic practice, the vertebral subluxation has been the historical raison d'etre for SM. Vertebral subluxation is a biomechanical spine derangement thought to produce clinically significant effects by disturbing neurological function. This paper reviews the putative mechanical features of the subluxation and three theories that form the foundation for much of chiropractic practice. It concludes with discussion of subluxation as an indicator for SM therapy, particularly from the perspective that subluxation may be one contributory cause of ill-health within a "web of causation".


   Historical Overview and Update on Subluxation Theories
           Journal of Chiropractic Humanities 2010 (Dec);   17 (1):   22–32 ~ FULL TEXT
           This article presents a personal view of the historical evolution of theories of subluxation in the chiropractic profession. Two major themes emerge from this review: those related to the mechanical behavior of the spine and those related to the neurologic implications of these mechanical issues. Chiropractic subluxation theory is one of the few health-related theories whereby these mechanical and neurologic theories have been unified into a comprehensive theory of disorder of spinal function. For this disorder, doctors of chiropractic have used the term subluxation. These theories, and their unification in the “subluxation concept,” have undergone evolution in the profession's history. The “subluxation concept” currently faces challenges, which are briefly reviewed in this article. The only way forward is to strengthen our efforts to investigate the “subluxation concept” with high-quality scientific studies including animal models and human clinical studies.


   Subluxation – Historical Perspectives
           Chiropractic Journal of Australia 2009 (Dec);   39 (4):   151–164 ~ FULL TEXT
           The notion that by changing the word subluxation to another term we will somehow change the clinical, political, and philosophical connotations of the concept central to chiropractic practice is simply not rational. Changing the term used for the articular lesion treated by chiropractors (subluxation) does not eradicate the clinical, political, and philosophical issues that surround the construct; it obviously evades the issues. [30]


   Subluxation – Historical Perspectives Part II
           Chiropractic Journal of Australia 2009 (Dec);   39 (4):   143–150 ~ FULL TEXT
           Subluxation is a term that has been used by the chiropractic profession since its early days. The term, meaning less than a luxation, has been used for millennia, similarly so has manipulation been the preferred intervention to overcome this problem. This paper reviews some of the early uses of subluxation and manipulation identifying highlights, to help the reader appreciate that subluxation and manipulation, both spinal and general, are as old as civilisation itself.


   General Causes and Potential Effects of the Subluxation Complex
           Chapter 6 from: Basic Principles of Chiropractic Neuroscience
           By Richard C. Schafer, D.C., FICC and the ACAPress
           Until the last 2 decades, most evidence about the success of chiropractic adjustments on the correction of vertebral subluxations and their related functional disturbances was empiric. The gap between controlled research documentation and frequent clinical observation still exists, but it has greatly narrowed in recent years. The greatest concern today is not is it effective but why is it effective and why is it effective in some cases but not in others that appear almost identical? Added to these can be the questions: what causes the positive effects in a specific body area that result from spinal adjustments that cannot be explained on an anatomical basis and what causes the indirect, far-reaching, diverse improvement in function so often witnessed?


   Basic Spinal Subluxation Considerations
           Chapter 19 from: Chiropractic Management of Sports and Recreational Injuries
           By Richard C. Schafer, D.C., FICC and the ACAPress
           The concept that an "off centered" vertebral or pelvic segment parallels a unique effect upon the neuromuscular bed which may be the cause of, aggravation of, or "triggering" of certain syndromes is a major contribution to the field of functional pathology and clinical biology by the chiropractic profession. This section discusses the basic biomechanics and effects of vertebral subluxations as related to the management of sports-related and recreational injuries.


   Evaluating Functional Integrity With Vertebral Subluxation Assessment
           Todays Chiropractic 2002 (Jan);   31 (1):   41–45 ~ FULL TEXT
           Practicing chiropractors are faced with the challenge of determining when to adjust. Trying to apply examination procedures, such as medical orthopedic tests, which do not indicate the presence or correction of vertebral subluxations, has frustrated many doctors. The concept of nerve interference is often challenging to patients. Their confusion is compounded when the chiropractor claims to subluxation-based, but bases care on the presence or absence of symptoms.


   The Functional Spinal Lesion:
An Evidence-Based Model of Subluxation
Topics In Clinical Chiropractic 2001 (Dec);   8 (1):   16–28 ~ FULL TEXT
The buckling model builds on clinical observations and supplements them with both direct and indirect biomechanical evidence. This model does not preconceive or proscribe any source of symptoms, but is able to accommodate the multifaceted clinical presentations of patients who respond favorably to manipulation/adjustment. It also can sustain a variety of hypothetical and evidence-based challenges. These findings offer an opportunity to reconceptualize and refine theoretical models of the spinal lesion into a platform for scientific, clinical, and political advancement of the profession.

A Series of Subluxation Articles By Meridel I. Gatterman, MA, DC, MEd Thanks to Dynamic Chiropractic!    The Vertebral Subluxation Syndrome    Is the Spinal Subluxation a Risk Factor?    Separated by a Common Language:        Its Time to Develop Chiropractic Nomenclature

   The Subluxation Complex
           Journal of Chiropractic Humanities 1999; 9 (1) ~ FULL TEXT
          This 4 page Adobe Acrobat (35 KB) article, by Leonard J. Faye, D.C. states “The concept of the subluxation complex was always intended as simply a heuristic device, a convention. The idea was to get the future chiropractors to think more complexly about a complex problem. It forced the integration of a much wider areas of information and knowledge”.


   Models of Vertebral Subluxation: A Review
           Journal of Vertebral Subluxation Research 1996;   1 (1):   1-6 ~ FULL TEXT
           Enjoy this Adobe Acrobat (59 KB) file from the first issue of JVSR, a review of clinical models of the vertebral subluxation, including neurobiological mechanisms. Models reviewed include the subluxation complex model, subluxation degeneration, nerve compression, dysafferentation, the neurodystrophic model and segmental facilitation. Clinical models, including the segmental, postural, and tonal approaches are discussed.


   A Review of the Evolution of Chiropractic Concepts of Subluxation
              Topics in Clincial Chiropractic 1995:   2 (2):   1-10 ~ FULL TEXT
             This particular review traces the evolution of the subluxation concept within the context of the chiropractic profession. There is a growing body of evidence, from both within and outside the discipline, that supports many of chiropractic's basic concepts. Evidence regarding the contribution of spinal joint derangement to a number of significant health problems becomes more compelling as more is learned. The role of manual procedures, especially as performed by chiropractors, becomes more prominent each year. A new environment without the overt ostracism of political medicine and a burgeoning research enterprise within chiropractic academia and practice are helping to poise the profession for greater contributions to the health care of society as chiropractic enters its next century.

A Series of Subluxation Articles By Joseph M. Flesia, Jr., D.C. Thanks to the ICA!    The Vertebral Subluxation Complex: An Integrative Perspective        ICA Int Rev Chiro 1992 (Mar):   25-27    The Vertebral Subluxation Complex Part II: An Outline        ICA Int Rev Chiro 1992 (Oct):   19-23    The Vertebral Subluxation Complex Part III: Pathogenesis        ICA Int Rev Chiro 1992 (Oct):   45-47    The Vertebral Subluxation Complex Part IV: Pathogenesis (Continued)        ICA Int Rev Chiro 1993 (Mar):   37-41

   A Consensus Approach to Subluxation Based Chiropractic:
Phase 1 Questionnaire Results
Chiropractic Research Journal 1994; 3 (4) ~ FULL TEXT
Consensus methods have been employed by health care provider groups in an effort to standardize the management of various clinical problems. [1] Such techniques are generally developed within the conceptual framework of the allopathic paradigm. Specifically, diagnostic and/or treatment strategies are developed for specific diseases or clinical syndromes. Critics of the consensus method have suggested that developing formalized standards of practice leads to the practice of "cookbook medicine." It is feared that the unique circumstances of the patient, the condition of the patient, and the clinical insights of the attending doctor are subservient to the standards promulgated in the "cookbook."


   The Vertebral Subluxation Complex Part 1:
         An Introduction to the Model and Kinesiological Component
           Chiropractic Research Journal 1989;   1 (3):   23-36 ~ FULL TEXT
           The concept of subluxation has been a cornerstone of the theory and practice of chiropractic since its founding by D. D. Palmer (1) in 1895. It is one of the most controversial concepts in health care today, and finds its supporters and critics both within and outside the chiropractic profession. The original concept of the subluxation was that of a slightly misaligned vertebra, not sufficient to be qualified as a true luxation or dislocation but substantial enough to impinge on the segmental nerves associated with it (1). While this original concept requires some modification in light of current research findings, there has been a wealth of knowledge accumulated in the past two decades that supports the concept of vertebral subluxations as a real entity (2- 9). It must be stressed that from the contemporary, scientific chiropractic point of view, the subluxation is a dynamic process, involving several tissue levels and integrative components.


   The Vertebral Subluxation Complex Part 2:
         The Neuropathological and Myopathological Components
           Chiropractic Research Journal 1990;   1 (4):   19-38 ~ FULL TEXT
           The neurological component of the Vertebral Subluxation Complex (VSC) is, for many, the cornerstone of chiropractic theory.(1) For those who see beyond the application of chiropractic and other manipulative procedures as merely a means of relieving head ache and low back pain, the nervous system is the mediator of vitality and health to the individual organs and tissues(2). Today, more than ever before, basic scientific and medical research supports this fundamental concept of chiropractic.(3-7). In chiropractic clinical practice, the prominence of the nervous system is unquestionable.


   Review of the Literature Supporting a Scientific Basis
for the Chiropractic Subluxation Complex
J Manipulative Physiol Ther 1985 (Sep);   8 (3) Sep:   163–174 ~ FULL TEXT
A review of the literature reveals strong evidence for both the mechanical model of disease production (structural) and the neurobiological model (functional). Outdated models which attempt to describe a scientific basis for chiropractic theory are inadequate and indeed harmful to the progress and acceptance of chiropractic.

   Dump Subluxation? Give Me a Break!
          The front-page headline of the September issue (volume 13, no. 12) of the Chiropractic Journal reads "Research Conference Urges Profession to Dump Subluxation." Well, I'm here to tell you that nothing even remotely of the kind happened, and I still find it hard to understand why one person, Matthew McCoy, chose to spin the story so inaccurately, especially after (silently) sitting through only one morning of an extensive three-day meeting at my invitation (and Palmer's expense). A responsible journalist who didn't hear the whole story would have checked not only his facts, but his context as well.

Vertebral Subluxation Research Conference

   Eleventh Annual Vertebral Subluxation Research Conference
         October 11-12, 2003 in Spartanburg, SC


   Tenth Annual Vertebral Subluxation Research Conference
         December 7-8, 2002 in Hayward, CA


   Ninth Annual Vertebral Subluxation Research Conference
         October 13-14, 2001 in Spartanburg, SC


   Eighth Annual Vertebral Subluxation Research Conference
         October 7-8, 2000 in Spartanburg, SC


   Seventh Annual Subluxation Conference
         October 9-10, 1999 in Spartanburg, SC


   Sixth Annual National Subluxation Conference
         October 10-11, 1998 in Atlantic City, NJ

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Since 3-06-1997

Updated 4-03-2013