Impingement following anterior cruciate ligament reconstruction: comparing the direct versus indirect femoral tunnel position

During anterior cruciate ligament (ACL) reconstruction, authors have suggested inserting the femoral tunnel at the biomechanically relevant direct fibres, but this higher position can cause more impingement. Therefore, we aimed to assess ACL graft impingement at the femoral notch for ACL reconstruction at both the direct and indirect tunnel positions. A virtual model was created for twelve cadaveric knees with computed tomography scanning in which a virtual graft was placed at direct and indirect tunnel positions of the anteromedial bundle (AM), posterolateral bundle (PL) or centre of the both bundles (C). In these six tunnel positions, the volume (mm(3)) and mid-point location of impingement (A degrees) were measured at different flexion angles. Generally, more impingement was seen with the indirect position compared with the direct position although this was only significant at 90A degrees of flexion for the AM position (97 +/- 28 vs. 76 +/- 20 mm(3), respectively; p = 0.046). The direct tunnel position impinged higher at the notch, whereas the indirect position impinged more towards the lateral wall, but this was only significant at 90A degrees of flexion for the AM (24 +/- 5A degrees vs. 34 +/- 4A degrees, respectively; p < 0.001) and C position (34 +/- 5A degrees vs. 42 +/- 5A degrees, respectively; p = 0.003). In this cadaveric study, the direct tunnel position did not cause more impingement than the indirect tunnel position. Based on these results, graft impingement is not a limitation to reconstruct the femoral tunnel at the insertion of the biomechanically more relevant direct fibres.