Instrument Adjusting
a.k.a. Mechanically-assisted Adjustments

This section was compiled by Frank M. Painter, D.C.
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The Technique page contains articles about chiropractic techniques, as well as links to various named-technique websites.

The About Chiropractic Adjusting Page
A Chiro.Org article collection

Review a variety of articles about chiropractic adjusting (aka spinal manipulation).

Chiropractic Subluxation and Neurology Articles
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This page contains a wide variety of articles about the Subluxation Complex, and it's impact on the nervous system and health.

Spine Adjusting Instrument (Impulse®) Attenuates Nociception and Modulates Oxidative
Stress Markers in the Spinal Cord and Sciatic Nerve of a Rat Model of Neuropathic Pain

Pain Medicine 2021 (May 16); pnab167 [Epub]

ISMT significantly increased mechanical threshold and withdrawal latency after CCI. In the spinal cord, ISMT prevented the increase of pro-oxidative superoxide anion generation and hydrogen peroxide levels. Lipid hydroperoxide levels both in the spinal cord and in the sciatic nerve were attenuated by ISMT. Total antioxidant capacity increased in the spinal cord and sciatic nerve of CCI rats with and without ISMT. CCI and ISMT did not significantly change the total thiol content of the spinal cord.   Our findings suggest reduced oxidative stress in the spinal cord and/or nerve may be an important mechanism underlying a therapeutic effect of SMT to manage NP non-pharmacologically.

Characteristics of Paraspinal Muscle Spindle Response to Mechanically Assisted
Spinal Manipulation: A Preliminary Report

J Manipulative Physiol Ther. 2017 (Jun 17) [Epub] ~ FULL TEXT

Short duration (<10 ms) MAM thrusts decrease muscle spindle discharge with a majority of afferents requiring prolonged periods (>6 seconds) to return to baseline MF activity. Physiological consequences and clinical relevance of described MAM mechanoreceptor responses will require additional investigation.

Manual and Instrument Applied Cervical Manipulation for Mechanical Neck Pain:
A Randomized Controlled Trial

J Manipulative Physiol Ther. 2016 (Jun);   35 (5):   319–329 ~ FULL TEXT

This study demonstrates that a single cervical manipulation is capable of producing immediate and short-term benefits for mechanical neck pain (MNP). The study also demonstrates that not all manipulative techniques have the same effect and that the differences may be mediated by neurological or biomechanical factors inherent to each technique.

Neural Response During a Mechanically Assisted Spinal Manipulation
in an Animal Model: A Pilot Study

J Nov Physiother Phys Rehabil. 2015 (Sep);   2 (2):   20–27 ~ FULL TEXT

This pilot study demonstrates feasibility of recording in vivo muscle spindle response during spinal manipulation using clinical mechanically-assisted spinal manipulation devices. It also demonstrates that extremely short duration manipulative thrusts (<5ms) of equivalent forces to that delivered to the human cervical spine can have an immediate and/or perhaps a prolonged effect (> 40s) on paraspinal muscle spindle discharge. While the clinical relevance of how mechanoreceptor stimulation or inhibition related to spinal manipulation modulates central nervous system activity remains to be clarified, determining how various mechanoreceptors respond during and following spinal manipulative thrusts in a clinically relevant fashion is an important step toward achieving this goal.

Craniocervical Chiropractic Procedures -
A Précis of Upper Cervical Chiropractic

J Can Chiropr Assoc 2015 (Jun);   59 (2):   173–192 ~ FULL TEXT

Presented here is a narrative review of upper cervical procedures intended to facilitate understanding and to increase knowledge of upper cervical chiropractic care. Safety, efficacy, common misconceptions, and research are discussed, allowing practitioners, chiropractic students, and the general public to make informed decisions regarding utilization and referrals for this distinctive type of chiropractic care.

Three-dimensional Vertebral Motions Produced by Mechanical
Force Spinal Manipulation

J Manipulative Physiol Ther 2006 (Jul);   29 (6):   425–436 ~ FULL TEXT

Larger-magnitude, 3D intersegmental displacement and acceleration responses were observed for spinal manipulative thrusts delivered with Impulse at most force settings and always at the high force setting. Our results indicate that the force-time characteristics of impulsive-type adjusting instruments significantly affects spinal motion and suggests that instruments can and should be tuned to provide optimal force delivery.

Increased Multiaxial Lumbar Motion Responses During Multiple-Impulse
Mechanical Force Manually Assisted Spinal Manipulation

Chiropractic & Osteopathy 2006 (Apr 6);   14 (1):   6 ~ FULL TEXT

Knowledge of the vertebral motion responses produced by impulse-type, instrument-based adjusting instruments provide biomechanical benchmarks that support the clinical rationale for patient treatment. Our results indicate that impulse-type adjusting instruments that deliver multiple impulse SMTs significantly increase multi-axial spinal motion.
There are more articles like this at our About Chiropractic Adjusting Page

The Efficiency of Multiple Impulse Therapy
for Musculoskeletal Complaints

J Manipulative Physiol Ther 2006 (Feb);   29 (2):   162 ~ FULL TEXT

Response of patients in the study sample to multiple impulse therapy for symptoms of low back and neck pain appeared to be considerably faster than that obtained in 3 recent studies
There are more articles like this at our Chiropractic Technique Page

Pilot Study of Patient Response to Multiple
Impulse Therapy for Musculoskeletal Complaints

J Manipulative Physiol Ther 2006 (Jan);   29 (1):   51 ~ FULL TEXT

Patients expressed improvement in symptoms after the first visit (average improvement in subjective pain rating scale of 41%). Patient symptoms improved between the first and second visits for 70% of patients (average improvement in subjective pain scale for all patients was 58%). The majority of patients achieved complete resolution of symptoms between the third and fourth visits. Maximum benefit for patients across all symptoms required an average of 4.2 visits. The half-life for response to multiple impulse therapy for all symptoms was 17 to 26 days. The half-life for response to multiple impulse therapy using the PulStarFRAS for low back pain was 9 to 16 days.

Comparison of Mechanical Force of Manually Assisted
Chiropractic Adjusting Instruments

J Manipulative Physiol Ther 2005 (Jul);   28 (6):   414–422 ~ FULL TEXT

The minimum-to-maximum force excursion settings for the spring-loaded mechanical adjusting instruments produced similar minimum-to-maximum peak forces that were not appreciably different for most excursion settings. The electromechanical adjusting instruments produced short duration ( approximately 2–4 ms), with more linear minimum-to-maximum peak forces. The force-time profile of the electromechanical devices resulted in a more uniform and greater energy dynamic frequency response in comparison to the spring-loaded mechanical adjusting instruments.

A Review of the Literature Pertaining to the Efficacy, Safety, Educational
Requirements, Uses and Usage of Mechanical Adjusting Devices

Journal of Canadian Chiropractic Assoc 2004 (Mar);   48 (1–2):   74–88, 152–161 ~ FULL TEXT

Part I     and     Part II   (Adobe Acrobat files)
Over the past decade, mechanical adjusting devices (MADs) were a major source of debate within the Chiropractor's Association of Saskatchewan (CAS). Since Saskatchewan was the only jurisdiction in North America to prohibit the use of MADs, the CAS established a committee in 2001 to review the literature on MADs. The committee evaluated the literature on the efficacy, safety, and uses of moving stylus instruments within chiropractic practice, and the educational requirements for chiropractic practice.

Biomechanical and Neurophysiological Responses to Spinal Manipulation in Patients
With Lumbar Radiculopathy

J Manipulative Physiol Ther. 2004 (Jan);   27 (1):   1–15 ~ FULL TEXT

Because spinal manipulation (SM) is a mechanical intervention, it is inherently logical to assume that its mechanisms of therapeutic benefit may lie in the mechanical properties of the applied force (mechanical mechanisms), the body's response to such force (mechanical or physiologic mechanisms), or a combination of these and other factors. Basic science research, including biomechanical and neurophysiological investigations of the body's response to SM, therefore, should assist researchers, educators, and clinicians to understand the mechanisms of SM, to more fully develop SM techniques, to better train clinicians, and ultimately attempt to minimize risks while achieving better results with patients.

Neuromechanical Characterization Of In Vivo Lumbar Spinal Manipulation.
Part II. Neurophysiological Response

J Manipulative Physiol Ther. 2003 (Nov);   26 (9):   579–591 ~ FULL TEXT

Spinal manipulative thrusts resulted in positive electromyographic (EMG) and compound action potential (CAP) responses that were typically characterized by a single voltage potential change lasting several milliseconds in duration. However, multiple EMG and CAP discharges were observed in numerous cases. The temporal relationship between the initiation of the mechanical thrust and the neurophysiologic response to internal and external spinal manipulative therapy (SMT) thrusts ranged from 2.4 to 18.1 ms and 2.4 to 28.6 ms for EMG and CAP responses, respectively. Neurophysiologic responses varied substantially between patients. Vertebral motions and resulting spinal nerve root and neuromuscular reflex responses appear to be temporally related to the applied force during SMT. These findings suggest that intersegmental motions produced by spinal manipulation may play a prominent role in eliciting physiologic responses.

PulStar Differential Compliance Spinal Instrument:
A Randomized Interexaminer and Intraexaminer Reliability Study

J Manipulative Physiol Ther 2003 (Oct);   26 (8):   493–501 ~ FULL TEXT

The PulStar mechanical adjusting device set to analysis mode appears to have good to excellent reliability when used by either an experienced or a novice (but trained) examiner. In addition, as a measure for resistance to a light thrust or spinal compliance, reliability was similarly good to excellent between the 2 doctors using the PulStar instrument.

The Minimum Energy Hypothesis:
A Unified Model of Fixation Resolution

J Manipulative Physiol Ther 2002 (Feb);   25 (2):   105–110 ~ FULL TEXT

A unified theory of manipulative effectiveness is proposed that integrates the fixation and sensory tonus models of manipulation. The theory is based on the fact that the spine will assume a position of minimum internal energy when mechanical equilibrium is achieved. By using a simple mathematical model, it is shown that the fixation model and the sensory tonus models are 2 different aspects of the same theoretical construct. The Minimum Energy Hypothesis predicts that the spine will seek an optimal minimum energy configuration if the constraints preventing it from doing so are removed. Constraints are hypothesized to be joint fixations caused by inflammation in and about the spine and its sequella, muscle spasm, fibroadipose and scar tissue, and ultimately, degeneration. It is further hypothesized that the use of a computerized mechanical manipulative device may resolve such fixations, an example of which is radiographically demonstrable cervical hypolordosis.

Differential Compliance Instrument in the Treatment of
Infantile Colic: A Report of Two Cases

J Manipulative Physiol Ther 2002 (Jan);   25 (1):   58–62 ~ FULL TEXT

A PulStar Function Recording and Analysis System (PulStar FRAS, Sense Technology, Inc, Pittsburgh, Penn) device was used to administer light impulses (approximately 1.7 joules, which produced a 3 to 4 lb force) at each segmental level throughout the dorsal spine, with probe tips spaced 2 cm apart straddling the spinous processes. Crying was reduced by 50% after a single session of instrumental adjusting in a 6–week old girl and after 4 sessions in a 9–week old boy, according to colic diaries kept by the mothers. Average hours of uninterrupted daily sleep increased from 3.5 to 6.5 hours after a single session.

Chiropractic Treatment of Postsurgical Neck Syndrome with
Mechanical Force, Manually Assisted Short-lever Spinal Adjustments

J Manipulative Physiol Ther 2001 (Nov);   24 (9):   589–595 ~ FULL TEXT

The patient was treated with conservative instrumental chiropractic manipulation, consisting of mechanical force, manually assisted short-lever spinal adjustments rendered with an Activator Adjusting Instrument (AAI) II. She comfortably tolerated the treatment and responded favorably to this therapy. All chronic symptoms had resolved within 30 days of instituting the chiropractic instrumental adjustments with an AAI. More interestingly, longitudinal examination over the next 2 years showed that the patient experienced no residual effects or further recurrences of her previous chronic problem after her initial course of chiropractic care.

A Pilot Randomized Clinical Trial on the Relative Effect of Instrumental
(MFMA) Versus Manual (HVLA) Manipulation in the Treatment
of Cervical Spine Dysfunction

J Manipulative Physiol Ther 2001 (May);   24 (4):   260–271 ~ FULL TEXT

The objective range of motion measures showed statistically significant changes in the Instrument=adjusted (MFMA) group for left and right rotation and left and right lateral flexion from initial consultation to final consultations and for right rotation and right lateral flexion from initial consultation to 1–month follow-up. The HVLA group showed only the change in left rotation from initial to final consultations and from initial consultation to 1–month follow-up to be statistically significant.

Mechanical Force Spinal Manipulation Increases Trunk Muscle Strength
Assessed By Electromyography: A Comparative Clinical Trial

J Manipulative Physiol Ther. 2000 (Nov);   23 (9):   585–595 ~ FULL TEXT

The results of this preliminary clinical trial demonstrated that MFMA SMT results in a significant increase in sEMG erector spinae isometric MVC muscle output. These findings indicate that altered muscle function may be a potential short-term therapeutic effect of MFMA SMT, and they form a basis for a randomized, controlled clinical trial to further investigate acute and long-term changes in low back function.

Neurophysiologic Response to Intraoperative Lumbosacral Spinal Manipulation
J Manipulative Physiol Ther. 2000 (Sep);   23 (7):   447–457 ~ FULL TEXT

During the active trials, mixed-nerve root action potentials were observed in response to both internal and external spinal manipulative thrusts. Differences in the amplitude and discharge frequency were noted in response to varying segmental contact points and force vectors, and similarities were noted for internally and externally applied spinal manipulative thrusts. Amplitudes of mixed-nerve root action potentials ranged from 200 to 2600 mV for internal thrusts and 800 to 3500 mV for external thrusts.

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