The acute structural changes of loaded articular cartilage following meniscectomy or ACL-transection

Objective: Meniscectomy and anterior cruciate ligament (ACL) rupture have b een identified as precursors of osteoarthrosis (OA) in clinical reviews and animal experiments. In this study, the acute effects of these injuries on articular cartilage matrix deformation, preserved in a loaded state using a cryopreservation technique, were studied by scanning electron microscopy ( SEM). Method: Whole knee joints from adult White New Zealand rabbits (N=87) were loaded ex vivo, using a simulated quadriceps pull under static and cyclic l oading conditions, following medial meniscectomy or transection of the ACL. Specimens were plunge-frozen while under load, or following a recovery per iod, and prepared for SEM by cryofixation. Using SEM and photographic image s, the medial tibial plateau cartilage was assessed both qualitatively and quantitatively. Results: After meniscectomy, significantly increased bending and crimping o f radial collagen fibers occurred with static loading. Compared to intact k nees, the area of tibial cartilage showing an indentation was increased by 80% (P<0.05), the articular cartilage thickness was significantly more redu ced when under load (for high force long duration static loading, intact jo ints had 53%+/-3 reduction in cartilage thickness compared to 39%+/-4 after meniscectomy, P<0.05), and it took nearly twice as long for the cartilage thickness to recover following loading. These post-meniscectomy differences were either not present or were minimal when the joint was allowed to exte nd when loaded. ACL-transection slightly increased collagen deformation in the deeper zones, but only with cyclic loading. Conclusion: The findings indicate that, with static loading, significantly increased deformation of articular cartilage collagen structure can occur f ollowing meniscectomy, but is minimized by joint motion. This increased def ormation may be relevant to the etiology and progression of joint degenerat ion. (C) 2000 OsteoArthritis Research Society international.