Christensen, Joshua J.

Background: The lateral tibial posterior slope (LTPS) has been reported in multiple studies to correlate with an increased risk for native anterior cruciate ligament (ACL) tearing. To date, no study has examined the effect of an increased LTPS as measured on magnetic resonance imaging (MRI) on the likelihood of ACL graft failure. Hypothesis: An increased LTPS as measured on MRI would correlate with an increased risk for ACL graft failure. Study Design: Case-control study; Level of evidence, 3. Methods: Fifty-eight patients were initially identified who experienced graft failure after primary ACL reconstruction and underwent revision between 1998 and 2009. Exclusion criteria were clinical follow-up of less than 4 years, graft failure occurring greater than 2 years after primary surgery, skeletal immaturity, deep infection, lack of available preoperative MRI, and history of trauma to the proximal tibia. This left 35 patients with early (within 2 years) failure of primary ACL reconstruction. These patients were matched to 35 control participants who 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, sex, date of primary surgery, and graft type. The LTPS was then determined on MRI in a blinded fashion. Results: The mean time to failure in patients in the study group was 1 year (range, 0.6-1.4 years). The mean follow-up of those in the matched control group was 6.9 years (range, 4.0-13.9 years). The mean LTPS in the early ACL failure group was found to be 8.4°, which was significantly larger than that in the control group at 6.5° ( P = .012). The odds ratio for graft failure considering a 2° increase in the LTPS was 1.6 (95% CI, 1.1-2.2) and continued to increase to 2.4 (95% CI, 1.2-5.0) and 3.8 (95% CI, 1.3-11.3) with 4° and 6° increases in the LTPS, respectively. No significant association was identified between graft type and graft failure. Conclusion: An increased LTPS is associated with an increased risk for early ACL graft failure, regardless of graft type. Orthopaedic surgeons should consider measuring the LTPS as part of the preoperative assessment of ACL-injured patients.

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.