Three-dimensional simulation of wall impingement and graft bending in anatomical double-bundle ACL reconstruction using weight-bearing upright multi-detector CT

Purpose: Graft-notch impingement and large graft bending angle (GBA) in anterior cruciate ligament reconstruction (ACLR) carry a risk of graft failure and subsequent poor postoperative outcomes. Most studies have analyzed the impingement rate and GBA using computed tomography (CT) in the supine position, but not in the standing condition. This study aimed to assess the graft impingement and GBA using upright multi-detector CT (MDCT). Methods: We analyzed 43 knee joints of 23 healthy volunteers (women, n = 13; men, n = 10) in a single-leg standing position using an upright 320-detector-row CT. We defined the putative position of the graft tunnel in three-dimensional models and assessed the impingement rate and GBA of both the anteromedial (AMB) and posterolateral bundles (PLB). Result: The impingement rate for the AMB with a 6-mm graft diameter (81.4 %) was significantly higher than that for the PLB (0.7 %; P < 0.001). The modified AMB tunnel position, which connects the midpoint between the traditional AM and PL tunnel apertures of the femur to the most medial point within the tibial AM footprint, reduced the impingement rate by 14.0 % (P < 0.001). The impingement rate of the modified AMB with a 10-mm graft diameter (32.6 %) was significantly lower than that of the traditional AMB with a 6-mm graft diameter (81.4 %; P < 0.001). The GBA of the modified AMB was significantly smaller than that of the traditional AMB (P < 0.001). Conclusion: This study indicated high graft-notch impingement rates and large GBA for traditional AMB in the standing position, highlighting potential biomechanical challenges associated with traditional double-bundle ACLR configurations.