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

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.