A quantitative histologic comparison: ACL degeneration in the osteoarthritic knee

Abstract

Newer prosthetic total knee arthroplasty (TKA) designs as well as unicondylar TKAs spare the anterior cruciate ligament (ACL). Although success of these procedures requires near normal ACL function, little has been written about the histologic features or the arthritic ACL. This study was designed to histologically evaluate the ACL for microscopic evidence of degeneration. Nineteen ACLs were harvested from 16 different patients who underwent TKA as a result of severe osteoarthritis. Control ligaments were obtained from bone bank donors (N = 14), patients with above-knee amputations (N = 5), and cadaveric formalin-preserved knees (N = 6). Orientation was maintained for each ACL. Degenerative parameters included loose, fibrous connective tissue and myxoid and cystic occurrences, and the presence of chondroid metaplasia or calcium phosphate crystals were evaluated and scored. Forty-seven percent of the osteoarthritic group had moderate/marked degeneration, whereas no control specimen showed such changes. Seventy-two percent of the controls were considered normal, compared with only 26% of the osteoarthritic group. Both of these findings were statistically significant (P<.001). Statistical analysis revealed no gender bias either within or between groups. In the control group, no statistical difference was found between patients older than age 65 and those younger than 65. In the osteoarthritic group, however, 70% of patients younger than 65 demonstrated moderate/marked changes compared with only 22% of those older than 65 (P<.05). There also was no difference demonstrated between the 4 focal sections of the ligaments that were examined.