This project determined the location and distribution of cavitations (audible sounds producing vibrations) in the lumbar zygapophyseal (Z) joints that were targeted by spinal manipulative therapy (SMT).
This randomized, controlled, clinical study assessed 40 healthy subjects (20 male, 20 female), 18–30 years of age, that 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 SPs/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 chi-square or McNemar’s test were made between number of joints cavitating from: Group 1 vs. Group 2, up-side (contact side for SMT) vs. down-side, and Z joints within the target area (L3/L4, L4L5, L5/S1) vs. outside the target area (L1/L2, L2/L3, sacroiliac).
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<0.0001), up-side joints cavitated more than down-side joints (p<0.0001), and joints inside the target area cavitated more than those outside the target area (p<0.01).
Most cavitations (93.5%) occurred on the up-side of SMT subjects in segments within the target area (71.7%). As expected, SMT subjects cavitated more frequently than side-posture positioning only subjects (96.7% vs. 30%). Multiple cavitations from the same Z joints had not been previously reported.