The Influence of Femoral Technique for Graft Placement on Anterior Cruciate Ligament Reconstruction Using a Skeletally Immature Canine Model With a Rapidly Growing Physis

Purpose: The purpose of this study was to evaluate 3 different femoral techniques of anterior cruciate ligament (ACL) reconstruction using a skeletally immature canine model. Methods: A soft-tissue autograft ACL reconstruction was performed in 25 ten-week-old canines via a central transphyseal tibial tunnel and 1 of 3 femoral techniques: epiphyseal, over the top, or transphyseal. The contralateral hind limbs served as controls. The canines were killed at 16 weeks postoperatively and evaluated by gross inspection, plain radiographs, photography, magnetic resonance imaging, and histomorphometry. Results: There were no significant differences in femoral longitudinal growth; however, tibial growth was significantly greater on the experimental side relative to controls (P = .001). Angular and rotational deformities were noted on the femoral side but not on the tibial side. The epiphyseal technique resulted in less angular deformity and most closely maintained the anatomic position of the ACL graft with growth; however, this technique exhibited increased femoral rotational deformity. All techniques exhibited a high rate of graft failure. Magnetic resonance imaging revealed chondral and subchondral injuries to the lateral femoral condyle, most frequently in the epiphyseal group. Conclusions: From the results of our study, we cannot advocate any single femoral reconstructive technique. An epiphyseal femoral technique may reduce the risk of angular deformity and allow a more optimal femoral graft position after growth as opposed to transphyseal and over-the-top techniques. However, the epiphyseal technique may possess an increased risk for rotational deformity, physeal injury, and articular surface injury. Metaphyseal fixation of ACL grafts traversing rapidly growing physes may be responsible for the observed abnormalities in graft integrity, femoral graft position, and femoral angulation and rotation. Clinical Relevance: ACL reconstruction in the skeletally immature individual is complicated by the presence of active physeal and epiphyseal cartilage surrounding the growing knee, the pathophysiologic consequences of injury to these developing structures, and the final effect on the anatomy and function of the graft, bone, and articular surface. Animal models can provide insight and direction as we develop and evaluate our treatment methods for this clinical problem, but these animal models have anatomic and physiologic differences that limit direct comparison to humans.