Objective 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). Methods 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). 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<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). Conclusions 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.

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 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. Results 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). Conclusions 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.

Objective This feasibility study used novel accelerometry (vibration) and microphone (sound) methods to assess crepitus originating from the lumbar spine before and after side-posture spinal manipulation (SMT). Methods This study included 5 healthy and 5 low back pain (LBP) subjects. Nine accelerometers and 1 specialized directional microphone were applied to the lumbar region, allowing assessment of crepitus. Each subject underwent full lumbar ranges of motion (ROM), bilateral lumbar SMT, and repeated full ROM. Following full ROMs the subjects received side-posture lumbar SMT on both sides by a licensed doctor of chiropractic. Accelerometer and microphone recordings were made during all pre- and post-SMT ROMs. Primary outcome was a descriptive report of crepitus prevalence (average number of crepitus events/subject). Subjects were also divided into 3 age groups for comparisons (18–25, 26–45, and 46–65 years). Results Overall, crepitus prevalence decreased pre-post SMT (average pre= 1.4 crepitus/subject vs. post= 0.9). Prevalence progressively increased from the youngest to oldest age groups (pre-SMT= 0.0, 1.67, and 2.0, respectively; and post-SMT= 0.5, 0.83, and 1.5). Prevalence was higher in LBP subjects compared to healthy (pre-SMT-LBP= 2.0, vs. pre-SMT-healthy= 0.8; post-SMT-LBP= 1.0 vs. post-SMT-healthy= 0.8), even though healthy subjects were older than LBP subjects (40.8 years vs. 27.8 years); accounting for age: pre-SMT-LBP= 2.0 vs. pre-SMT-healthy= 0.0; post-SMT-LBP= 1.0 vs. post-SMT-healthy= 0.3. Conclusions Our findings showed that a larger study is feasible. Other findings included that crepitus prevalence increased with age, was higher in LBP than healthy subjects, and overall decreased following SMT. This study showed that crepitus assessment using accelerometers has the potential of being an outcome measure/biomarker for assessing spinal joint (facet/Z joint) function during movement and the effects of LBP treatments (eg, SMT) on Z joint function.

A previous study of 40 subjects undergoing spinal manipulative therapy (SMT) assessed cavitation measured by accelerometry and L3/L4 – L5/S1 zygapophysial (Z) joint space separation (gapping) measured from MRI scans. An unexpected (and previously unreported) finding was that 6 joints cavitated multiple times.MethodsWe performed an IRB‐approved comparative study (n=18) assessing morphometric analysis of multiple‐cavitating (MC), single‐cavitating (SC), and non‐cavitating (NC) Z joints (joints matched for segmental level, side, and gender). The medial, central, and lateral aspects of the Z joint spaces were measured from pre‐SMT MRI scans. Group comparisons using the Kruskal‐Wallis Test were made for the measurements from the 3 locations and the total of the 3 measurements (total measurement = TM, the primary outcome).ResultsTM and medial joint space were smaller/narrower for the MC group (TM, p=0.008; medial, p=0.04). No differences were found for the central and lateral joint spaces (central, p=0.18; lateral, p=0.29).ConclusionsMultiple cavitations during SMT may be related to the “close packed” nature of a joint in the neutral position (particularly the medial aspect of the joint). These findings provide information about the characteristics of Z joints cavitating during SMT. Funding: NIH/NCCAM Grant # 3R01AT000123‐06S2.

Novel methods assessed and localized zygapophyseal (Z) joint audible sounds (crepitus and cavitations) during normal lumbar motion and side‐posture spinal manipulation (SMT).MethodsFive healthy subjects ages 21–65 years had 9 accelerometers and one specialized directional microphone (with modifications) applied to their lumbar region in a previously developed pattern that allowed specific localization of joint sounds. Each subject underwent full lumbar ranges of motion (ROM), lumbar SMT (left side = up‐side), and repeated full ROM; all while recordings were made from the accelerometers and microphone. Accelerometer and microphone data were assessed for cavitations and crepitus.ResultsVibration and acoustic methods were successfully implemented and provided complementary information that identified cavitations, crepitus, and verified artifacts. Ten cavitations and 1 crepitus were recorded from 7 joints (all left side). Three instances of multiple joint cavitations were identified [2 from 2 joints (L L1/L2 and L L3/L4) and 3 from 1 joint (L L1/L2)]. Some recordings identified a cavitation when inaudible to subject and clinician.ConclusionsAccelerometers and microphone provided unique and complementary information. Assessing accelerometer and acoustic data could help deepen understanding of spinal mechanics and SMT. Funding: NIH/NCCAM Grant # 3R01AT000123‐06S2.