Increased Tibial Slope and Decreased Medial Proximal Tibial Angle Negatively Affect ACL Graft Maturation: Objective Evidence on When to Add a Lateral Extra-Articular Augmentation Procedure to a Soft Tissue Anterior Cruciate Ligament Reconstruction.

Abstract

Recent anterior cruciate ligament (ACL) research focuses on risk factors for ACL graft failure and techniques and augmentations to limit failure. One of the most recognized risk factors is sagittal malalignment in the form of high posterior tibial slope (PTS), especially PTS ≥ 12°, which leads to increased force through the ACL and ACL graft. To reduce the risk associated with increased PTS, lateral augmentation techniques, typically either a lateral extra-articular tenodesis (LET) or an anterolateral ligament reconstruction (ALLR), improve clinical outcomes, and the authors preferred graft choice, particularly in such cases, is bone-patellar tendon-bone autograft (BTB). Furthermore, in revision cases, there exists a strong argument to perform a slope reducing osteotomy to correct bony malalignment which could lead to ACL graft failure. Slope reducing osteotomies are reported to significantly decrease anterior tibial translation and forces on the ACL graft Coronal malalignment is also a risk factor for ACL failure, (although not as extensively studied as sagittal alignment). Both varus and valgus alignment of the knee can lead to increased forces through the ACL or ACL graft compared to knees in neutral alignment, and workup requires proper lateral and long leg anteroposterior radiographs to determine sagittal and coronal alignment and guide treatment algorithms. Recent research shows that decreased medial proximal tibial angle of the knee (increasing varus alignment of the tibia) may delay graft maturation. However, there is yet to be a consensus about what exactly contributes to ACL graft failure in the coronal plane and what is the best treatment option, especially in the primary setting when an osteotomy is not indicated. Again, we recommend BTB autograft as our preferred graft choice unless contraindicated by skeletal immaturity.