The role of the meniscus in the anterior-posterior stability of the loaded anterior cruciate-deficient knee. Effects of partial versus total excision.
The effects of progressive removal of the menisci on the anterior-posterior force-versus-displacement response of the anterior cruciate-deficient knee were studied in fresh cadaver specimens at 20 degrees of flexion without and with tibial-femoral contact force (joint load). In the absence of joint load, removal of the medial meniscus increased total anterior-posterior laxity measured at 200 newtons of applied tibial force by 10 per cent, and subsequent lateral meniscectomy produced an additional 10 per cent increase. When a bucket-handle tear of the medial meniscus was removed, the application of joint load caused the tibia to displace (subluxate) forward on the femur, thereby changing the balance condition of the knee. Subsequent removal of the remainder of the medial meniscus and complete lateral meniscectomy both produced additional smaller anterior tibial subluxations. Changes in total anterior-posterior laxity due to progressive meniscectomy in the loaded knee were dependent on both the amount of applied anterior-posterior force and the level of compressive force. At 200 newtons of anterior-posterior tibial force, increases in laxity in the loaded knee due to progressive meniscal removal were not significantly different than those recorded in the unloaded condition. At applied forces of fifty newtons or less, the laxities for loaded specimens were always significantly less than those for unloaded specimens at comparable stages of meniscal removal. Bilateral meniscectomy had no significant effect on the posterior response curve, as posterior tibial translation was effectively checked by the intact posterior cruciate ligament.(ABSTRACT TRUNCATED AT 250 WORDS)