Effects of notchplasty and femoral tunnel position on excursion patterns of an anterior cruciate ligament graft

Purpose: Errors in femoral tunnel placement in anterior cruciate ligament (ACL) reconstruction can cause excessive length changes in the graft during knee flexion and extension, resulting in graft elongation during the postoperative period. To improve the accuracy of tunnel placement and to avoid graft impingement, a notchplasty is commonly performed. The purpose of this study was to determine the effects of varying the position of the femoral tunnel and of performing a 2-mm notchplasty of the lateral femoral condyle and roof of the intercondylar notch on excursion patterns of a bone-patellar tendon-bone graft. Type of Study: Biomechanical cadaveric study. Methods: A cylindrical cap of bone, containing the tibial insertion of the ACL, was mechanically isolated in 15 fresh-frozen cadaveric specimens using a coring cutter. The bone cap was attached to an electronic isometer that recorded displacement of the bone cap relative to the tibia as the knee was taken through a 90degrees range of motion. After native ACL testing, the proximal end of a 10-mm. bone-patella tendon-bone graft was fixed within femoral tunnels drilled at the 10, 11, and 12-o'clock (or 2-, 1-, and 12-o'clock) positions within the notch. The distal end of the graft was attached to the isometer. Testing was then completed at each tunnel position before and after notchplasty. Results: Before notchplasty, mean graft excursions at the 10- or 2-, 11- or 1-, and 12-o'clock tunnels were not significantly different from the excursions of the native ACL or each other. After a 2-mm notchplasty, mean graft excursions at the 3 tunnel locations were not sigificantly different from each other but were greater than mean graft excursions before notchplasty. After notchplasty, all grafts tightened during knee flexion. Conclusions: Although errors in placement along the arc of the intercondylar notch did not significantly affect graft excursion patterns, the apparent graft tightening with knee flexion that was observed for all, 3 tunnel positions after notchplasty suggests that graft forces would increase with knee flexion over this range. This would indicate that as little amount of bone as possible should be removed from the posterior portion of the intercondylar notch in ACL reconstruction.