Tunnel Convergence in Combined Anterior Cruciate Ligament and Posterolateral Corner Reconstruction

Purpose: To examine the geometric relationship between tunnels created in the lateral femoral condyle in reconstruction of the anterior cruciate ligament (ACL) and the posterolateral structures. Methods: The geometric relationship between a standard ACL tunnel and 11 lateral femoral tunnel variations in synthetic femur specimens was examined. Tunnel collision frequency and tunnel separation were measured radiographically. Subsequent evaluation was performed on 7 paired cadaveric specimens (14 knees) to access the efficacy of 2 configurations. Results: Phase I—Tunnel collision frequency was 0% and 58% for 25-mm and 30-mm tunnel depths, respectively. Axial angles greater than 40° and coronal angles ≥20° resulted in unsafe configurations. The safest position for lateral tunnel placement was straight lateral approach (0° in the coronal plane) with increased axial plane orientation (hand dropped toward the floor 40°). The safe zone for lateral tunnel configuration was determined to be between [0,0] and [0,40] ([coronal, axial]). Phase II—Control group ([0,0]) collision frequencies were 43% and 86% for the 25-mm 30-mm tunnels, respectively. Experimental group ([0,40]) collision frequencies were 29% and 43% for the 25-mm and 30-mm tunnel, respectively. In femoral condyles measuring <35 mm, collision rates were 100% versus 0% in the control group ([0,0]) versus the experimental group ([0,40]). In specimens where no collision was seen, tunnel separation distance was 4.5 ± 4.4 mm and 5.8 ± 2.2 mm for the control and experimental groups, respectively (P = .39). Conclusions: Tunnel collision occurred often. Tunnel collision is dependent on femoral condyle geometry, tunnel depth, and tunnel configuration. To minimize the potential for tunnel collision, the surgeon should maintain a neutral alignment in the coronal plane, limit lateral tunnel depth to ≤25 mm, and direct the lateral tunnel anteriorly in the axial plane to a maximum of 40°. Clinical Relevance: This study describes guidelines for tunnel placement to prevent tunnel collision when performing combined ACL and posterolateral corner reconstruction.