Lateral Tibial Slope is Increased with Patients with Early Graft Failure Following ACL Reconstruction

OBJECTIVES: To determine the relationship between lateral tibial slope and probability of early graft failure in patients who have undergone anterior cruciate ligament (ACL) reconstruction. METHODS: Fifty-eight patients were initially identified who experienced graft failure following primary ACL reconstruction and were revised between 1989 and 2009. Exclusion criteria were: clinical follow-up of less than four years, graft failure occurring greater than two years from primary surgery, skeletal immaturity, deep infection, lack of availability of preoperative MRI imaging, and history of previous trauma to the proximal tibia. This left 35 cases of early (within 2 years) failure of primary ACL reconstruction. These cases were matched to 35 controls that had undergone ACL reconstruction with a minimum of 4 years of clinical follow-up and no evidence of graft failure. Patients were matched by age, gender, date of primary surgery, and graft type. Lateral tibial slope was then determined on MRI imaging in blinded fashion. RESULTS: All 35 cases failed within 2 years of primary ACL reconstruction. Mean time to failure in this group was 1 year (range 0.6-1.4 years). Mean follow-up of the matched control group was 6.9 years (range 4.0-13.9 years). Mean lateral tibial slope in the early ACL failure group was found to be 8.4 degrees, which was significantly larger than the control group at 6.5 degrees (p=0.02). The odds ratio for failure considering a 2 degree increase in tibial slope was 1.5 (95% CI 1.02-2.2), and continued to increase to 2.2 (95% CI 1.1-4.6) and 3.3 (95% CI 1.1-10) with 4 degree and 6 degree increases in tibial slope, respectively (Fig 1). No significant association was identified between graft type and primary ACL reconstruction failure. CONCLUSION: Increased lateral tibial slope is associated with an increased risk for early ACL graft failure, regardless of graft type. Orthopaedic surgeons should consider measuring lateral tibial slope as part of the preoperative assessment of ACL-injured patients.