Slope-Reducing Osteotomy of the Tibia

Posterior tibial slope >12° is a significant contributor to ACL reconstruction failure. Increased slope alters the biomechanical forces across the knee resulting in greater anterior tibial translation. This increases the forces sustained by the ACL graft and heightens the risk failure and of concomitant intraarticular injury. Posterior tibial slope may be calculated with separate medial and lateral tibial plateau measurements or by taking an average of the two. The slope frequently varies between medial and lateral sides of the same extremity, and researchers are uncertain which side most places patients at increased risk for rerupture. Measurement of posterior tibial slope may be accomplished on either radiographs or advanced imaging. CT and MRI afford the ability to measure the medial and lateral slopes independently. A lack of uniform method for calculating posterior tibial slope makes comparing these measurements across the literature difficult. An anterior closing-wedge osteotomy should correct the slope to between 3° and 10°. Generally, about 1 mm of anterior cortex resection yields 1 degree of correction. Supratubercle and transtubercle osteotomies are both effective. These may be performed with a revision ACL reconstruction as a one-stage procedure or the ACL may be reconstructed as a second stage after the osteotomy has healed. Published outcomes show good to excellent outcome measures with a significant beneficial effect on rerupture rate. The most common complications include DVT, stiffness, and hematoma though surgeons should be aware of the potential for neurovascular injury and compartment syndrome.