Oval Tunnel Shows Better Rotational Stability Than Round Tunnel in Anatomical Single-Bundle Anterior Cruciate Ligament Reconstruction: Biomechanical Study in a Porcine Model

Abstract

Background To compare knee laxity between the conventional round tunnel and oval tunnel techniques in primary anterior cruciate ligament (ACL) reconstruction in a porcine knee model. Methods Twenty porcine knees were used for evaluating laxity in terms of anterior translation and anterolateral rotation. The study determined porcine knee kinematics on the Instron instruments under simulated Lachman (89 N anterior tibial load) at 15°, 30°, and 60° of flexion and a simulated pivot shift test (89 N anterior tibial load, 10 Nm valgus, and 4 Nm internal tibial torque) at 30° of flexion. Kinematics were recorded for intact (n = 10), ACL-deficient (n = 10), and conventional round (n = 10) or oval tunnel (n = 10) techniques. All measurements were repeated twice, and the average was used for comparison. Results Under the Lachman test, the conventional round tunnel and oval tunnel both showed significantly larger anterior tibial translation (ATT) at 30° and 60° compared to the intact knee ( p < 0.05), but smaller ATT compared to the ACL-deficient knees ( p < 0.05). However, there were no differences in ATT between the conventional round tunnel and oval tunnel techniques ( p > 0.05). Under simulated pivot shift at 30° flexion, there was a significant difference between the conventional round tunnel and oval tunnel techniques (round vs. oval: 4.27 ± 0.87 mm vs. 3.52 ± 0.49 mm, p = 0.028). Conclusions Both conventional round tunnel and oval tunnel techniques reduced ATT compared to ACL-deficient knees but failed to restore normal knee stability. However, the oval tunnel technique showed better rotational stability at 30° than the round tunnel technique. These findings suggest that the oval tunnel technique would be a reasonable option in anatomical single-bundle ACL reconstruction.