The Effect of Femoral Tunnel Position on Graft Forces during Inlay Posterior Cruciate Ligament Reconstruction

Abstract

Background The femoral tunnel may be positioned centrally or eccentrically within the posterior cruciate ligament footprint during a single-bundle posterior cruciate ligament reconstruction. Hypothesis After reconstruction, graft forces are significantly different from those of the native posterior cruciate ligament and are affected by the position of the femoral tunnel. Study Design Controlled laboratory study. Methods The resultant force in the native posterior cruciate ligament was measured in nine cadaveric knees as the knee was flexed from —5° to 120° of flexion. Posterior cruciate ligament reconstruction was performed with the femoral side of the graft positioned centrally and then offset 5 mm eccentric to the central position. Results Mean graft forces were not significantly different between eccentric and central tunnel positions during passive knee extension between 120° and 0° of flexion; at 5° of hyperextension, the eccentric position generated significantly lower graft forces. For both reconstruction techniques, mean graft forces were significantly higher than those for the native posterior cruciate ligament beyond approximately 90° of flexion, for 5 N·m internal and external tibial torque; 5 N·m varus and valgus moment. Conclusions Graft force reductions achieved with the eccentric femoral position appear to be relatively small compared with the forces expected during rehabilitation and activities of daily living. Clinical Relevance After posterior cruciate ligament graft reconstruction, rehabilitation activities that load the knee at high degrees of flexion should be avoided to limit excessive forces on the maturing graft.