The Association Between Tibial Slope and Revision Anterior Cruciate Ligament Reconstruction in Patients ≤21 Years Old: A Matched Case-Control Study Including 317 Revisions

Background: There is evidence that tibial slope may play a role in revision risk after anterior cruciate ligament reconstruction (ACLR); however, prior studies are inconsistent. Purpose: To determine (1) whether there is a difference in lateral tibial posterior slope (LTPS) or medial tibial posterior slope (MTPS) between patients undergoing revised ACLR and those not requiring revision and (2) whether the medial-to-lateral slope difference is different between these 2 groups. Study Design: Case-control study; Level of evidence, 3. Methods: We conducted a matched case-control study (2006-2015). Cases were patients aged <= 21 years who underwent revision surgery after primary unilateral ACLR; controls were patients aged <= 21 years without revision who were identified from the same source population. Controls were matched to cases by age, sex, body mass index, race, graft type, femoral fixation device, and post-ACLR follow-up time. Tibial slope measurements were made by a single blinded reviewer using magnetic resonance imaging. The Wilcoxon signed rank test and McNemar test were used for continuous and categorical variables, respectively. Results: No difference was observed between revised and nonrevised ACLR groups for LTPS (median: 6 degrees vs 6 degrees, P = .973) or MTPS (median: 4 degrees vs 5 degrees, P = .281). Furthermore, no difference was found for medial-to-lateral slope difference (median: -1 vs -1, P = .289). A greater proportion of patients with revised ACLR had an LTPS >= 12 degrees (7.6% vs 3.8%) and >= 13 degrees (4.7% vs 1.3%); however, this was not statistically significant after accounting for multiple testing. Conclusion: We failed to observe an association between revision ACLR surgery and LTPS, MTPS, or medial-to-lateral slope difference. However, there was a greater proportion of patients in the revision ACLR group with an LTPS >= 12 degrees, suggesting that a minority of patients who have more extreme values of LTPS have a higher revision risk after primary ACLR. A future cohort study evaluating the angle that best differentiates patients at highest risk for revision is needed.