Zygapophyseal Joint Adhesions After Induced Hypomobility

ObjectiveAdhesions (ADH) have been previously identified in many hypomobile joints, but not in the zygapophyseal (Z) joints of the spine. The objective of this study was to determine if connective tissue ADH developed in lumbar Z joints after induced intervertebral hypomobility (segmental fixation).MethodsUsing an established rat model, 3 contiguous segments (L4, L5, L6) were fixed with specially engineered, surgically implanted, vertebral fixation devices. Z joints of experimental rats (17 rats, 64 Z joints) with 4, 8, 12, or 16 weeks of induced hypomobility were compared with Z joints of age-matched control rats (23 rats, 86 Z joints). Tissue was prepared for brightfield microscopy, examined, and photomicrographed. A standardized grading system identified small, medium, and large ADH and the average numbers of each per joint were calculated.ResultsConnective tissue ADH were characterized and their location within Z joints described. Small and medium ADH were found in rats from all study groups. However, large ADH were found only in rats with 8, 12, or 16 weeks of experimentally induced intervertebral hypomobility. Significant differences among study groups were found for small (P < .003), medium (P < .000), and large (P < .000) ADH. The average number of medium and large ADH per joint increased with the length of experimentally induced hypomobility in rats with 8 and 16 weeks of induced hypomobility.ConclusionsWe conclude that hypomobility results in time-dependent ADH development within the Z joints. Such ADH development may have relevance to spinal manipulation, which could theoretically break up Z joint intra-articular ADHs.