Magnetic resonance imaging zygapophyseal joint space changes (gapping) in low back pain patients following spinal manipulation and side-posture positioning: a randomized controlled mechanisms trial with blinding.

OBJECTIVE: The purpose of this study was to quantify lumbar zygapophyseal (Z) joint space separation (gapping) in low back pain (LBP) subjects after spinal manipulative therapy (SMT) or side-posture positioning (SPP). METHODS: This was a controlled mechanisms trial with randomization and blinding. Acute LBP subjects (N = 112; four n = 28 magnetic resonance imaging [MRI] protocol groups) had 2 MRI appointments (initial enrollment and after 2 weeks of chiropractic treatment, receiving 2 MRI scans of the L4/L5 and L5/S1 Z joints at each MRI appointment. After the first MRI scan of each appointment, subjects were randomized (initial enrollment appointment) or assigned (after 2 weeks of chiropractic treatment appointment) into SPP (nonmanipulation), SMT (manipulation), or control MRI protocol groups. After SPP or SMT, a second MRI was taken. The central anterior-posterior joint space was measured. Difference between most painful side anterior-posterior measurements taken postintervention and preintervention was the Z joint "gapping difference." Gapping differences were compared (analysis of variance) among protocol groups. Secondary measures of pain (visual analog scale, verbal numeric pain rating scale) and function (Bournemouth questionnaire) were assessed. RESULTS: Gapping differences were significant at the first (adjusted, P = .009; SPP, 0.66 ± 0.48 mm; SMT, 0.23 ± 0.86; control, 0.18 ± 0.71) and second (adjusted, P = .0005; SPP, 0.65 ± 0.92 mm; SMT, 0.89 ± 0.71; control, 0.35 ± 0.32) MRI appointments. Verbal numeric pain rating scale differences were significant at first MRI appointment (P = .04) with SMT showing the greatest improvement. Visual analog scale and Bournemouth questionnaire improved after 2 weeks of care in all groups (both P < .0001). CONCLUSIONS: Side-posture positioning showed greatest gapping at baseline. After 2 weeks, SMT resulted in greatest gapping. Side-posture positioning appeared to have additive therapeutic benefit to SMT.

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

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.

Distribution of cavitations as identified with accelerometry during lumbar spinal manipulation.

OBJECTIVE: This project determined the location and distribution of cavitations (producing vibrations and audible sounds) in the lumbar zygapophyseal (Z) joints that were targeted by spinal manipulative therapy (SMT). METHODS: This randomized, controlled, clinical study assessed 40 healthy subjects (20 men, 20 women) 18 to 30 years of age who were block randomized into SMT (group 1, n = 30) or side-posture positioning only (group 2; control, n = 10) groups. Nine accelerometers were placed on each patient (7 on spinous processes/sacral tubercles of L1-S2 and 2 placed 3 cm left and right lateral to the L4/L5 interspinous space). Accelerometer recordings were made during side-posture positioning (groups 1 and 2) and SMT (group 1 only). The SMT was delivered by a chiropractic physician with 19 years of practice experience and included 2 high-velocity, low-amplitude thrusts delivered in rapid succession. Comparisons using χ(2) or McNemar test were made between number of joints cavitating from group 1 vs group 2, upside (contact side for SMT) vs downside, and Z joints within the target area (L3/L4, L4L5, L5/S1) vs outside the target area (L1/L2, L2/L3, sacroiliac). RESULTS: Fifty-six cavitations were recorded from 46 joints of 40 subjects. Eight joints cavitated more than once. Group 1 joints cavitated more than group 2 joints (P < .0001), upside joints cavitated more than downside joints (P < .0001), and joints inside the target area cavitated more than those outside the target area (P < .01). CONCLUSIONS: Most cavitations (93.5%) occurred on the upside of SMT subjects in segments within the target area (71.7%). As expected, SMT subjects cavitated more frequently than did subjects with side-posture positioning only (96.7% vs 30%). Multiple cavitations from the same Z joints had not been previously reported.

Reliability of zygapophysial joint space measurements made from magnetic resonance imaging scans of acute low back pain subjects: comparison of 2 statistical methods.

OBJECTIVE: This purpose of this study was to assess the reliability of measurements made of the zygapophysial (Z) joint space from the magnetic resonance imaging scans of subjects with acute low back pain using new equipment and 2 different methods of statistical analysis. If found to be reliable, the methods of Z joint measurement can be applied to scans taken before and after spinal manipulation in a larger study of acute low back pain subjects. METHODS: Three observers measured the central anterior-to-posterior distance of the left and right L4/L5 and L5/S1 Z joint space from 5 subject scans (20 digitizer measurements, rounded to 0.1 mm) on 2 separate occasions separated by 4 weeks. Observers were blinded to each other and their previous work. Intra- and interobserver reliability was calculated by means of intraclass correlation coefficients and also by mean differences using the methods of Bland and Altman (1986). A mean difference of less than +/-0.4 mm was considered clinically acceptable. RESULTS: Intraclass correlation coefficients showed intraobserver reliabilities of 0.95 (95% confidence interval, 0.87-0.98), 0.83 (0.62-0.92), and 0.92 (0.83-0.96) for each of the 3 observers and interobserver reliabilities of 0.90 (0.82-0.95), 0.79 (0.61-0.90), and 0.84 (0.75-0.90) for the first and second measurements and overall reliability, respectively. The mean difference between the first and second measurements was -0.04 mm (+/-1.96 SD = -0.37 to 0.29), 0.23 (-0.48 to 0.94), 0.25 (-0.24 to 0.75), and 0.15 (-0.44 to 0.74) for each of the 3 observers and the overall agreement, respectively. CONCLUSIONS: Both statistical methods were found to be useful and complementary and showed the measurements to be highly reliable.