The purpose of this study was to use previously validated methods to quantify and relate 2 phenomena associated with chiropractic spinal manipulative therapy (SMT): 1) cavitation and 2) the simultaneous gapping (separation) of the lumbar zygapophyseal (Z) joint spaces.
This was a randomized, controlled, mechanistic clinical trial with blinding. Forty healthy subjects (18 to 30 years of age) without a history of low back pain participated. Seven accelerometers were affixed to the skin overlying the spinous processes of L1-L5 and the S1 and S2 sacral tubercles. Two additional accelerometers were positioned 3 cm left and right lateral to the L4/L5 inter-spinous space. Subjects were randomized into: Group 1–side-posture SMT (n=30) or Group 2–side-posture positioning (SPP, n=10). Cavitations were determined by accelerometer recordings during SMT and SPP (left-side=up-side for both groups); gapping (gapping difference) was determined by the difference between pre- and post-intervention MRI joint space measurements. Results of mean gapping differences were compared.
Up-side SMT and SPP joints gapped more than down-side joints (0.69 vs. −0.17mm, p<0.0001). SMT up-side joints gapped more than SPP up-side joints (0.75 vs. 0.52mm, p=0.03). SMT up-side joints gapped more in males than females (1.01 vs. 0.49mm, p<0.002). Overall, joints that cavitated gapped more than those that did not (0.56vs. 0.22mm, p=0.01). No relationship was found between the occurrence of cavitation and gapping with up-side joints alone (p=0.43).
Z joints receiving chiropractic SMT gapped more than those receiving side-posture positioning alone, Z joints of males gapped more than those of females, and cavitation indicated that a joint had gapped, but not how much a joint had gapped.
Keywords: spinal manipulation, zygapophyseal joints, facet joints, cavitation, chiropractic