The effects of postoperative joint immobilization on articular cartilage degeneration following meniscectomy.

Bilateral medial meniscectomy was performed in 12 mature greyhounds. One knee joint of half the group was immobilized by a Kirschner splint for a period of 5 weeks immediately following meniscectomy, after which the device was removed and the animals were allowed free movement for a further 21 weeks before sacrifice. Three greyhounds served as controls. While the collagen levels of articular cartilage from the femoral condyles and tibial plateaus of meniscectomized animals were the same as that of controls, differences were found for proteoglycan (PG) content and extractability using nondissociative conditions (0.5 M guanidinium hydrochloride (GuHCl) but not dissociative conditions (4.0 M GuHCl). With nondissociative conditions, twice as much PG was extracted from medial femoral condyle of meniscectomized animals encouraged to bear weight on joints immediately after surgery compared to that from controls or animals in whom joints were immobilized after surgery. Proteoglycans from medial tibial plateau cartilage of the free contralateral joints of the immobilized group were more readily extracted using 0.5 M GuHCl and also showed a statistically significant depression of uronic acid levels relative to both controls and tissues of other surfaces. The data suggest that postoperative management of meniscectomy in the human may be more important than has hitherto been recognized.