Posterior tibial tunnel placement to avoid anterior cruciate ligament graft impingement by the intercondylar roof. An in vitro and in vivo study.

Recent recommendations to "customize" tibial tunnel placement based on the slope of the intercondylar roof and the amount knee hyperextension were derived from a series of cases with graft impingement by the intercondylar roof. We believe that this impingement is caused by anterior placement of the graft and not by variations of notch anatomy among individual patients. In Phase 1 of this study, we drilled tibial tunnels in the posteromedial aspect of the anterior cruciate ligament "footprint" after the ligament was excised in cadaveric knees. We then passed an impingement rod into the back of the knee joint. Lateral radiographs with the knee in hyperextension were taken of each specimen, and the distance between the superior border of the rod and intercondylar roof was measured. In Phase 2, we prospectively obtained lateral hyperextension radiographs of 75 consecutive knees with anterior cruciate ligament reconstructions and evaluated them for graft impingement based on recently published guidelines. In Phase 1, we found no cases of impingement and an average roof clearance of 8.3 mm. In Phase 2, we noted no cases of severe impingement, 3 cases of moderate impingement (4%), and 72 cases (96%) with no impingement. We conclude that posteromedial tibial tunnel placement alone is adequate to avoid graft impingement in almost all patients. Individualized tibial tunnel placement with specialized tibial guidance systems is not necessary.