Intertunnel relationship in combined anterior cruciate ligament and posterolateral corner reconstruction : an in vivo 3D anatomical study

Abstract

Combined anterior cruciate ligament (ACL) and posterolateral ligament complex (PLC) injuries are relatively common, and crowded tunneling of the lateral femur condyle area is required in combined ACL and PLC reconstruction. Therefore, tunnel convergence during surgery could occur. However, available studies on this topic are limited. This study sought to elucidate the ranges of angles and distances of lateral collateral ligament (LCL) and popliteus tendon (PT) femoral tunnels that do not violate ACL tunnels during combined ACL and PLC reconstruction and to provide practical guidelines for this operation. Knee computed tomography images were taken from 14 subjects at 0, 45, 90, and 120°, and three-dimensional anatomical knee models were created using customized software. At 120°, a coin was attached to the anteromedial (AM) portal area. Single- and double-bundle ACL tunneling using the transtibial method for AM bundles and the AM portal method for posterolateral bundles were performed. Femur model cutting was performed at the following angles relative to the transepicondylar axis (TEA) on the horizontal plane from the LCL and PT insertion: posterior 20 (−20°) and 10° (−10°), 0°, and anterior 10 and 20°. The safe angles and distances that did not violate the ACL tunnel or intercondylar notch were determined in the proximal (superior) and distal (inferior) directions.Generally, the ranges of safe angles increased as the LCL and PT femoral tunnel was positioned in the posterior to anterior direction. When the LCL and PT tunnel was positioned anteriorly to the TEA (10 and 20°), the ranges of safe angles exceeded 40°; however, when the tunnel was positioned posteriorly (−10 and −20°), collision with the intercondylar notch or ACL tunnel occurred. Distances that made tunneling possible at the margin of the safe angle were approximately 35 mm for the

LCL and 30 mm for the PT. Collision usually occurred with the AM bundle tunnel. However, convergence with the PL bundle occurred rarely. We found that LCL and PT femoral tunnels should be directed anteriorly rather than posteriorly on the axial plane. Considering the relationship between LCL and PT tunnels and fixation strength, we believe that tunneling would be safe when the LCL and PT are positioned at an angle of approximately anterosuperior 10°. We admit that there would be differences between the results of our simulation study and those of actual operations. However, our results would help to reduce the incidence of tunnel collisions in actual combined ACL and PLC reconstructions. We believe that our results are meaningful not only in providing practical safe ranges but also in attracting attention to collisions when we perform combined ligament reconstruction surgeries.