J Manipulative Physiol Ther 2005 (Sep);28 (7): 493–501
Kirstin A. Shearar, MTech, Christopher J. Colloca, DC, Horace L. White, MChiro, BEd
Chiropractic Department, Durban Institute of Technology, Durban, South Africa
OBJECTIVE: To investigate the effect of instrument-delivered compared with traditional manual-delivered thrust chiropractic adjustments in the treatment of sacroiliac joint syndrome.
METHODS: Prospective, randomized, comparative clinical trial. Sixty patients with sacroiliac syndrome were randomized into two groups of 30 subjects. Each subject received 4 chiropractic adjustments over a 2-week period and was evaluated at 1-week follow-up. One group received side-posture, high-velocity, low-amplitude chiropractic adjustments; the other group received mechanical-force, manually-assisted chiropractic adjustments using an Activator Adjusting Instrument (Activator Methods International, Ltd, Phoenix, Ariz).
RESULTS: No significant differences between groups were noted at the initial consultation for any of the outcome variables. Statistically significant improvements were observed in both groups from the first to third, third to fifth, and first to fifth consultations for improvements (P < .001) in mean numerical pain rating scale 101 (group 1, 49.1-23.4; group 2, 48.9-22.5), revised Oswestry Low Back Pain Disability Questionnaire (group 1, 37.4-18.5; group 2, 36.6-15.1), orthopedic rating score (group 1, 7.6-0.6; group 2, 7.5-0.8), and algometry measures (group 1, 4.8-6.5; group 2, 5.0-6.8) for first to last visit for both groups.
CONCLUSIONS: The results indicate that a short regimen of either mechanical-force, manually-assisted or high-velocity, low-amplitude chiropractic adjustments were associated with a beneficial effect of a reduction in pain and disability in patients diagnosed with sacroiliac joint syndrome. Neither mechanical-force, manually-assisted nor high-velocity, low-amplitude adjustments were found to be more effective than the other in the treatment of this patient population.
From the Full-Text Article:
The results of this study showed that chiropractic care including both HVLA and MFMA-type chiropractic adjustments were associated with a positive effect in the treatment of SIJ syndrome in this patient population. Because group 1 did not exhibit a greater effect over group 2 in either subjective (self-perceived pain and disability) or objective (ORS, pain pressure threshold) findings as hypothesized, this study found that both chiropractic adjustment regimens had an equal effect in the treatment of SIJ syndrome. The improvement in LBP symptoms, combined with improvement in objective clinical findings in both groups, is consistent with anecdotal claims of efficacy among clinicians using these forms of chiropractic adjustments in patients with SIJ syndrome. This is the first study to compare different forms of chiropractic adjustment/spinal manipulation in the management and treatment of patients with SIJ syndrome.
Because this study did not include a control group, these results cannot be taken as proof supporting the clinical efficacy of chiropractic adjustment for SIJ syndrome; however, the positive trends observed suggest the call for a well-designed randomized controlled clinical trial in a similar patient population. Noteworthy was that patients included in the study had LBP for at least a 2-week duration at the time of initial consultation with a total of more than 4 weeks of LBP in the preceding year. The significant improvements in subjective and objective findings of SIJ syndrome associated with chiropractic treatment over a relatively brief treatment regimen (4 visits over 2 weeks with 1-week follow-up) are encouraging for the conservative treatment of this disorder.
Because this study did not include a control group, the natural history of SIJ syndrome was not investigated. The natural progression of sacroiliac syndrome would be best observed in a group receiving placebo treatment (sham manipulation), as used in other studies. [40, 41] Thus, implementing a control and sham group would also allow a greater understanding of the true clinical benefits of these manipulative procedures. In addition, blinding the examiner to the patient's clinical findings could have also eliminated observer bias. Larger group sample sizes would also increase the validity of the study and minimize the possibility of a type II error. Long-term follow-up consultations would also assist in the understanding of the efficacy and cost-effectiveness of chiropractic treatment of SIJ syndrome. Furthermore, individualizing the treatment regimen, as opposed to our standardized treatment protocol of two visits per week, may have produced different results.
Other limitations in the current study deserve discussion. Most noteworthy, perhaps, is the controversial nature of SIJ syndrome itself. Histologic examination of human SIJs has revealed nerve fibers compatible with a broad repertoire of sensory receptors including nociceptive afferents. [42-43] This innervation pattern may provide explanations for various patterns of local, pseudoradicular, and referred pain in afflictions of the SIJ that have been confirmed with direct SIJ capsular stimulation. [44-46] A reduction in pain in patients treated for presumptive SIJ pain by injection of an anesthetic into the SIJ has also been shown, validating its status as a pain generator. 
Although the SIJ has been shown to be a pain generator, confirming an SIJ syndrome diagnosis in the absence of SIJ block (arthrogram) is limited, thus presenting another limitation to the current study. Several noninvasive clinical methods such as the orthopedic tests as used in the current study have been found not to be reproducible [6, 48] and, thus, should not be used alone by practitioners to provide reliable information concerning where to direct a manipulative procedure in patients with chronic mechanical LBP.  However, recent work has shown a strong correlation between 3 or more positive SIJ pain provocation tests (as used in the current study) and positive SIJ injection.  Because the current study did not confirm the SIJ as the pain generator via SIJ block, it is possible that false-positive and false-negative clinical indicators for differential diagnosis of SIJ syndrome were present in our patient population. Such misdiagnosis may have affected our results. Although it would be advantageous to have confirmation of the SIJ as the primary pain generator via arthrogram, we believe that the invasiveness of this procedure would have affected our subject recruitment. Future studies, however, should include diagnostic SIJ block to confirm the SIJ syndrome diagnosis.
Experimental stimulation of the SIJ has been further found to cause neuromuscular responses in the gluteus maximus, quadratus lumborum, and multifidus muscles.  Such muscular activation assists in providing control of locomotion and body posture and provides stability of the SIJ and lumbar spine.  Thus, sensitization of SIJ nociceptive afferents not only contributes to mechanical LBP, but also further plays a role in SIJ biomechanics via reflexogenic activation of the trunk and gluteal muscles. [50-51] This acts to restrict SIJ motion and promotes a subsequent SIJ inflammatory response, which most probably contributes to the presented positive subjective and objective findings in this patient population. Indeed, other studies have reported alterations in spinal motion in chronic LBP subjects.  Detecting alterations in SIJ biomechanics by qualitative means, such as palpation, has its limitations and is likely to have contributed to examiner error in the current study. Kinematic studies of SIJ motion have varied but similarly agree on the small amount of motion occurring at the joint, between 0.5° and 6° of rotation and 0.7 to 3 mm of translation. [53-57] This small amount of movement is difficult to differentiate clinically [58-60] and, thus, could have contributed to examiner error in the decision making of type of SIJ fixation and the subsequent direction to apply the chiropractic adjustment, consequently also affecting our results.
In this study, confirmation of the SIJ syndrome diagnosis was made through correlation of patient history and physical examination findings including both the orthopedic and algometry findings. The application of the pressure of the algometer can be therapeutic. However, algometry measures have been shown to be stable across treatment days, [38, 61] and inasmuch, we do not believe that the pressure applied during the algometry examinations contributed to the subjective and objective improvements observed in the study population. The pain pressure threshold on the symptomatic side was lowered on the side of SIJ syndrome from algometry measures in both groups (Fig 4). Algometry has been found to be a valid and reliable measure of pain pressure threshold. [36-37] It is likely that the chiropractic adjustment, as delivered in this study, was delivered on the true symptomatic side. It is also possible that anatomic positioning error existed in the test-retest conditions of the algometry protocol that also may have contributed to error in the algometry results. Until strict validated clinical measures are established as diagnostic criteria SIJ syndrome, the validity and, ultimately, the efficacy of the treatments for this condition will continue to be questioned.
In general, the benefits of chiropractic adjustment or spinal manipulation involve biomechanical and neurophysiologic mechanisms. These mechanisms include restoring joint play to dysfunctional joints through releasing entrapped synovial folds or plica, relaxing hypertonic muscles, and disrupting articular or periarticular adhesions.  Beneficial effects of chiropractic adjustments/spinal manipulation have been thought to be associated with mechanosensitive afferent stimulation and presynaptic inhibition of nociceptive afferent transmission in the modulation of pain, [63-64] inhibition of hypertonic muscles, [11, 65, 66] and improved functional ability. [62, 67, 68] Although improvements in SIJ function have been reported after SIJ manipulation,  manipulation has not been found to change the position of the SIJ.  It is likely that SIJ manipulation acts indirectly on the supporting musculature, improving the global function of the region.
Several studies have presented physiological or functional outcomes resulting from SIJ manipulation. Suter et a [l9, 10] found that SIJ manipulation caused a reduction in lower extremity muscle inhibition in patients suffering SIJ dysfunction and knee and anterior thigh complaints. Electromyographic reflex responses have been found to be elicited via both HVLA11 and MFMA12 manipulation of the SIJ. Murphy et al  reported decreased Hoffman reflex responses indicative of a decrease in motor neuron excitability after HVLA SIJ manipulation in clinically relevant patients with LBP. Herzog et al  found that HVLA SIJ manipulation was superior to a back school regimen on gait symmetry for patients with SIJ pain. Similarly, Cibulka et al  noted improved innominate bone tilt after HVLA SIJ manipulation in patients with SIJ dysfunction. Few clinical outcome studies, however, have evaluated the effectiveness of HVLA or MFMA SIJ manipulation. In a case series of 10 subjects diagnosed with chronic SIJ syndrome, Osterbauer et al  reported decreases in pain, disability, and pain pressure threshold initially and at 1-year follow-up in patients undergoing MFMA chiropractic treatment. In contrast to the findings of Herzog et al,  Osterbauer et al  found no effect on gait symmetry or postural sway in their patients receiving chiropractic (MFMA) treatment.
Despite its limitations, this study is one of few studies investigating conservative treatments of SIJ syndrome and the first study to compare different chiropractic techniques in its management. Noteworthy are the findings of the current study in contrast to the beliefs of an expert panel assembled to evaluate the efficacy of different chiropractic techniques in the treatment of LBP. In a recent report, Gatterman et al  rated HVLA manipulation as more efficacious than MFMA manipulation in the treatment of low back conditions, which included SIJ dysfunction in concordance with the available evidence and their expert opinions. On the contrary, the results of the current study showed no difference in subjective or objective outcomes with either HVLA or MFMA treatments in this population of patients with SIJ syndrome. In this regard, this study adds to the sparse body of literature on efficacy of conservative treatments for mechanical LBP involving SIJ syndrome and forms the basis for a more rigorous investigation using chiropractic adjustments/spinal manipulation.
The results of this trial indicate that a relatively short regimen (4 visits) of MFMA or HVLA chiropractic adjustments were associated with beneficial effects of reduction in pain and disability in patients diagnosed with SIJ syndrome. Neither MFMA nor HVLA adjustments were found to be more effective than the other in the treatment of this patient population. Acknowledging and overcoming the limitations of this study will allow for designing further research contributing to a greater understanding of the clinical benefits of chiropractic adjustments/spinal manipulation in patients with SIJ syndrome.