Effect of tibial tunnel position on stability of the knee after anterior cruciate ligament reconstruction: is the tibial tunnel position most important?

Abstract

Background: Minimal attention has been directed toward tibial tunnel position and the native tibial anterior cruciate ligament (ACL) footprint.

Purpose: To evaluate the effect of tibial tunnel position on restoration of knee kinematics and stability after ACL reconstruction.

Study design: Controlled laboratory study.

Methods: Ten paired cadaveric knees were subjected to biomechanical testing (standardized Lachman and mechanized pivot-shift examination). With each maneuver, a computer-assisted navigation system recorded the 3-dimensional motion path of a tracked point at the center of the tibia, medial tibial plateau, and lateral tibial plateau. The testing protocol consisted of evaluation in the intact state and after complete ACL transection, after ACL transection with bilateral meniscectomy, and after ACL reconstruction using 3 tibial tunnel positions--over the top (OTT), anterior footprint (AT), and posterior footprint (PT)--with a standard femoral socket placed in the center of the femoral footprint. Repeated-measures analysis of variance with a post hoc Tukey test compared measured translations with each condition.

Results: A significant difference in anterior translation was seen with Lachman examination between the ACL-deficient condition and both the OTT and AT reconstructions, but no significant difference was observed between the ACL-deficient and PT reconstruction. The OTT and AT constructs were significantly better in limiting anterior translation of the lateral compartment compared with the PT ACL reconstruction during a pivot-shift maneuver in the ACL- and meniscal-deficient knee. However, anteriorizing the tibial position was accompanied by a correspondingly greater risk and magnitude of graft impingement in extension.

Clinical relevance: The OTT and anterior tibial tunnel positions better control the Lachman and the pivot shift compared with an ACL graft placed in the posterior aspect of the tibial footprint. However, an anterior tibial tunnel position must be balanced against an increased risk and magnitude of graft impingement in extension.