The effect of oblique femoral tunnel placement on rotational constraint of the knee reconstructed using patellar tendon autografts

Purpose: Despite the high long-term success rates of anterior cruciate ligament (ACL) reconstructions, 8% of patients undergoing this primary procedure have recurrent disability and graft failure. Nonanatomic tunnel positioning (primarily of the femoral tunnel) accounts for most of all technical failures. We hypothesized that reconstructions that closely recreate the oblique femoral attachment of the ACL would result in more normal knee rotational stability than more vertical reconstruction. The purpose of this study was to determine whether obliquity of the femoral tunnel in the coronal (frontal) plane has an effect on rotational constraint after ACL reconstruction, as measured by anterior tibial translation, external rotation, and internal rotation. Type of Study: Ex vivo biomechanical study. Methods: Ten matched pairs of fresh-frozen cadaver knees were alternately assigned to a standard or an oblique tunnel position reconstruction. Each knee was tested at 30degrees and 90degrees of flexion on a materials testing machine in ACL-intact, ACL-sectioned, and ACL-reconstructed states. A 100-N load was applied at a rate of 10 N/second, and anterior tibial translation was measured. Then 6.5 Nm of torque were applied, and external tibial rotation and internal tibial rotation were measured. The effects of tunnel placement and ligament condition were analyzed with a repeated measures analysis of variance. Significance was set at P less than or equal to .05 (Tukey's test). Results: At 30degrees of flexion, internal tibial rotation in oblique reconstruction was restored to intact values and was significantly less than the internal tibial rotation values in standard reconstruction. Internal tibial rotation in standard reconstruction was significantly greater than intact values. No significant differences were found between standard and oblique tunnel reconstructions and the respective intact values for the remaining internal tibial rotation and all external tibial rotation tests, regardless of flexion angle. Conclusions: In our biomechanical model, ACL reconstructions using oblique femoral tunnels restored normal knee kinematics.