Distribution of Cavitations Study Title: Distribution of cavitations as identified with accelerometry during lumbar spinal manipulation Authors: Cramer GD, Ross JK, Raju PK et al. Publication Information: Journal of Manipulative & Physiological Therapeutics 2011; 34: 572-583. BACKGROUND INFORMATION Most of us utilize spinal manipulative therapy (SMT) every day to help our patients and treat a variety of ailments. We, and our patients, normally want to hear the “pop” (or cavitation)! During an adjustment, theory suggests that facet joint surfaces are gapped, creating an intra-articular vacuum that draws gas into the joint space (out of the joint fluid?), producing vibrations in addition to the “pop.” This noise, combined with the gapping of one or multiple facet joints is thought to directly relate to the clinical effects of SMT in numerous ways. Whether through the breakup of connective tissue adhesions within the joint, stimulation of afferent nerve fibres in the joint capsule or surrounding musculature, or a neurological or immunological reflex, it is thought that joint gapping and cavitation can both result in clinical and measurable effects.1,2 In fact, joint gapping and cavitation have been so neatly intertwined that cavitation is often considered to be a sign that the joint has achieved end-range motion and that the manipulation was, in fact, successful. Several studies have been conducted examining the general relationship between cavitation and clinical outcome3,4 and a recent study investigated the relationship between joint gapping and cavitation.5 However, none has examined the specific levels from which these cavitations originate (most only ask clinicians to indicate that a cavitation was heard during treatment). Interestingly, many of us assume that we know which specific levels cavitate when we deliver an adjustment, despite the lack of credible laboratory research to support this assertion. In fact, there is some evidence to suggest that we are not as accurate as we think!6 As research on SMT evolves, it can help us clarify historical theory and our understanding of the mechanisms behind what we do. There is currently a need for more research exploring the mechanisms and consequences of cavitation during SMT, particularly in the lumbar spine. This study utilized accelerometry with the aim of determining the location and distribution of cavitations in the lumbar spine during side posture positioning and lumbar SMT in healthy subjects. The authors hypothesized that upside lumbar facets would cavitate more frequently than downside joints, and that joints within the treatment target region would cavitate more frequently than those outside the region. CONCLUSIONS AND PRACTICAL APPLICATIONS The results of this study strike many Dcs as predictable, but just because we believe something to be true doesn’t mean we should not investigate and validate! The study results do point to the fact that, at least in healthy younger subjects, more cavitations occur on the upside (contact side) and typically occur in the targeted region during side-posture lumbar manipulation. As mentioned in the introduction, this is one of the first studies to investigate the specific location and origin of cavitations in the lumbar spine during SMT. Further research is needed on clinical populations in other age ranges, and these results cannot be extrapolated to the cervical or thoracic regions. Readers should also keep in mind that this study did not evaluate the association between the cavitations recorded and joint gapping at those specific levels (these authors have investigated this in other work5), or the relation between cavitation and clinical outcomes. To see this review in full, including study methods and results, strengths and weaknesses, and additional references, please visit “Current Issue” at www.canadianchiropractor.ca. Dr. Shawn Thistle is the founder and president of Research Review Service Inc., an online, subscriptionbased service designed to help busy practitioners to integrate current, relevant scientific evidence into their practice. Shawn graduated from CMCC and holds an Honours Degree in Kinesiology from McMaster University. He also holds a certificate in Contemporary Medical Acupuncture from McMaster University, and is a Certified Active Release Techniques (ART®) Provider. For more information about the Research Review Service, visit www.researchreviewservice.com.