Quantification of cavitation and gapping of lumbar zygapophyseal joints during spinal manipulative therapy

Abstract

Objectives: 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.

Methods: This was a randomized, controlled, mechanistic clinical trial with blinding. Forty healthy participants (18-30 years old) without a history of low-back pain participated. Seven accelerometers were affixed to the skin overlying the spinous processes of L1 to L5 and the S1 and S2 sacral tubercles. Two additional accelerometers were positioned 3 cm left and right lateral to the L4/L5 interspinous space. Participants 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 = upside for both groups); gapping (gapping difference) was determined by the difference between pre- and postintervention magnetic resonance imaging scan joint space measurements. Results of mean gapping differences were compared.

Results: Upside SMT and SPP joints gapped more than downside joints (0.69 vs -0.17 mm, P < .0001). Spinal manipulative therapy upside joints gapped more than SPP upside joints (0.75 vs 0.52 mm, P = .03). Spinal manipulative therapy upside joints gapped more in men than in women (1.01 vs 0.49 mm, P < .002). Overall, joints that cavitated gapped more than those that did not (0.56 vs 0.22 mm, P = .01). No relationship was found between the occurrence of cavitation and gapping with upside joints alone (P = .43).

Conclusions: Zygapophyseal joints receiving chiropractic SMT gapped more than those receiving SPP alone; Z joints of men gapped more than those of women, and cavitation indicated that a joint had gapped but not how much a joint had gapped.

Figure 1

Subjects were first MRI scanned in the neutral supine position (A). Nine accelerometers were placed on each subject and the output from them was collected for a period of fours seconds during spinal manipulative therapy (Group 1) or side-posture positioning (Group 2)(B; inset shows one of the 1.0 cm³ accelerometers). After recordings were completed, the accelerometers were removed and a second MRI scan was taken in the side-posture position (C).

Figure 2

Pre- (A) and post-spinal manipulation (SMT) (B) horizontal plane (axial) MRI scans of a side-posture SMT subject (Group 1) demonstrating gapping of the left (L) L5/S1 zygapophyseal (Z) joint (left side = up-side during SMT). Notice that the central width (thickness) of the left post-SMT Z joint space (lateral edge of joint indicated by arrow in B) is wider than the left pre-SMT Z joint space (arrow in A).The central anterior to posterior (AP) distance between the superior and inferior articular processes of the Z joints was measured (2A, inset) for the left and right L3/L4, L4/L5, and L5/S1 Z joints from each subject’s first and second MRI scans. Fig. 2B has been rotated counter clockwise 20 degrees for orientation similar to 2A.

Figure 3

Mean gapping difference of spinal manipulation (SMT) vs. no-SMT zygapophyseal (Z) joints. Z joints that received SMT (up-side, Group 1) had a greater gapping difference than controls (no-SMT, up-side Group 2).

Figure 4

Mean gapping difference of female vs. male zygapophyseal (Z) joints. Z joints of males receiving spinal manipulation (SMT) (up-side, Group 1) gapped significantly more than the same joints of females.

Figure 5

Mean gapping difference of zygapophyseal (Z) joints that cavitated vs. those that did not cavitate. Z joints that cavitated gapped more than those that did not.