LAUSR

Objectives: There is evidence the slope of the tibial plateau may play a role in need for revision following ACL reconstruction (ACLR), however, previous studies are limited by small sample sizes, radiographic measurement, single surgeon experience, lateral tibial posterior slope (LTPS) only, or a lack of confounder adjustment. Further, the role of the medial posterior tibial slope (MTPS) on revision risk has yet to be evaluated. We sought to (1) determine the relationship of revision status following ACLR and LTPS, (2) determine the relationship of revision status and MTPS, and (3) determine the relationship of revision status and the difference between MTPS and LTPS. Methods: We conducted a nested case-control study of 317 matched pairs using an integrated U.S. healthcare system’s ACLR registry (2006- 2014). Cases were defined as patients who underwent a revision following primary unilateral ACLR; controls were defined from the same cohort as non-revised patients during the same time frame. Controls were matched to cases according to age, gender, body mass index, race, graft type, femoral fixation device, and follow-up time. Magnetic resonance imaging (MRI) images were used by a single blinded reviewer to measure tibial slopes. Wilcoxon signed rank test was applied to compare the slopes between revised and non-revised groups continuously and McNemar test to compare slopes of ≥12° between groups. Results: No difference was observed between revised and non-revised patients in LTPS (mean: 6.1 vs. 6.1, p=0.972) or MTPS (mean: 4.6 vs. 4.9, p=0.281) measurement. When comparing revised ACLR to non-revised ACLR, a greater proportion of revised ACLR had a LTPS of ≥12° (7.6% vs. 3.8%, P=0.034), while no difference was found in the proportion of ACLR with a MTPS ≥12° (1.6% vs. 2.5%, P=0.405). No difference was found when evaluating the medial-to-lateral slope difference (-1.5 vs. -1.2, p=0.289). Conclusion: In our nested case-control study of over 300 revised ACLR patients matched to non-revised patients, we did not find an association between the slope of the lateral and medial tibial plateaus and revision. Figure 2. Distribution of the lateral tibial posterior slope (LTPS) for 317 revision and 317 non-revision ACLR. Lateral tibial posterior slope (LTPS) and medial tibial posterior slope (MTPS) results for 317 revised and 317 non-revised anterior cruciate ligament reconstruction patients. Revision Patients No Revision Patients P LTPS  Degree, mean (SD) 6.1 (3.5) 6.1 (3.1) 0.973  Slope ≥12°, % 7.6 3.8 0.034 MTPS  Degree, mean (SD) 4.7 (3.1) 4.9 (3.0) 0.281  Slope ≥12°, % 1.6 2.5 0.405 Slope difference = Medial - Lateral, mean (SD) -1.5 (2.7) -1.2 (2.9) 0.289  LTPS and MTPS comparisons  Lateral < Medial, % 20.2 25.9 0.096  Lateral = Medial, % 15.1 13.9 0.731  Lateral > Medial, % 64.7 60.3 0.261