The Effect of Tunnel Placement on Bone-Tendon Healing in Anterior Cruciate Ligament Reconstruction in a Goat Model

Background: Misplacement of the bone tunnels is one of the main causes of graft failure of anterior cruciate ligament surgery. Hypothesis: Anatomic tunnel placement in anterior cruciate ligament surgery reconstruction will lead to improved outcomes, including biological ingrowth and biomechanical properties, when compared with nonanatomic tunnel placement. Study Design: Controlled laboratory study. Methods: Anterior cruciate ligament surgery reconstructions were performed on 3 different groups of goats (1 anatomic tunnel placement group and 2 different nonanatomic tunnel placement groups, with 10 goats in each group). For each group of 10 knees, 3 knees were used for histologic evaluation (bone tunnel enlargement, number of osteoclasts at the bone tendon interface, and revascularization of the graft) and 7 knees were used for biomechanical testing (anterior tibial translation, in situ force, cross-sectional area, and ultimate failure load). Animals were sacrificed at 12 weeks after surgery. Results: The anatomic tunnel placement group showed less tunnel enlargement on the tibial side, fewer osteoclasts on both the tibial and femoral sides, and more vascularity in the femoral side when compared with the 2 nonanatomic reconstruction groups. Biomechanically, the anatomic tunnel placement group demonstrated less anterior tibial translation and greater in situ force than both nonanatomic tunnel placement groups. Conclusion: Anatomic tunnel placement leads to superior biological healing and biomechanical properties compared with nonanatomic placement at 12 weeks after anterior cruciate ligament surgery reconstruction in a goat model. Clinical Relevance: The findings of this study demonstrate the importance of anatomic tunnel placement in anterior cruciate ligament surgery reconstruction.