The effects of modified posterior tibial slope on anterior cruciate ligament strain and knee kinematics: a human cadaveric study.

Increases to the posterior tibial slope can lead to an anterior shift in tibial resting position. However, the effect of this shift on anterior cruciate ligament (ACL) strain has not been investigated sufficiently. This study examined the relationship between increased tibial slope and ACL strain, as well as the subsequent kinematics of the tibiofemoral joint. We hypothesized increases in slope would shift the tibia anterior relative to the femur and increase ACL strain. Anterior cruciate ligament strain measurements and tibiofemoral kinematics were compared for 5 intact and experimental knees subject to anterior opening wedge osteotomy. Combinations of both compressive and AP loading were applied. As slope increased, the resting position of the tibia shifted anteriorly, external tibial rotation increased, and tibial translation remained unchanged. Contrary to our hypothesis, ACL strain decreased. The clinical implication of these findings is that alterations to the posterior tibial slope should not increase strain in the ACL.