Abstract
PURPOSE: The aim of this study was to compare initial joint kinematics and tissue forces following complete transphyseal, partial transphyseal and physeal-sparing anterior cruciate ligament (ACL) reconstruction (ACLR) in an early adolescent porcine model. METHODS: Eighteen early adolescent porcine knees were tested using a six-degree-of-freedom robotic testing system at 40° and 60° of flexion. An 80 N anterior-posterior (AP) force, 120 N compression force and 4 N m varus-valgus torque were applied to the tibia in intact, ACL transected and ACLR states. Complete transphyseal, partial transphyseal, and physeal-sparing surgical techniques were performed (n = 6 legs/technique). Kinematics under applied loads were recorded to assess joint stability and compared across each state. Individual tissue forces were calculated using the principle of superposition. For comparisons between surgical techniques, both joint stability and tissue forces were normalized to intact control data from the same joints. RESULTS: At 40° of flexion, the increase in AP tibial translation following physeal-sparing ACLR was 3.8 mm smaller than the complete transphyseal (p = 0.02). Under anterior tibial loading, the anterior force taken by the reconstructed ACL graft significantly decreased similarly following reconstruction by each technique, which shifted to the medial collateral ligament (MCL). The increase in anterior MCL forces following complete transphyseal reconstruction was 283% higher than that after physeal-sparing reconstruction (p = 0.04). Under valgus torque, the change in compression force in the lateral meniscus following physeal-sparing reconstruction was 82% smaller than that after partial transphyseal reconstruction (p = 0.02). At 60° of flexion, the average increase in ATT under compression following partial transphyseal and physeal-sparing reconstruction was 5.0 and 6.9 mm smaller than following complete transphyseal reconstruction (p ≤ 0.001 for each). CONCLUSION: In early adolescent porcine joints, the physeal-sparing technique led to better initial joint stability with less anterior force shifted to the MCL compared to the complete transphyseal technique.