Posterior Tibial Offset Ratio (PTOR) Is Associated With Revision After Hamstring-Autograft Anterior Cruciate Ligament Reconstruction: A Matched Case-Control Study

Abstract

Background: Graft failure after primary anterior cruciate ligament (ACL) reconstruction remains clinically important. This study evaluated the posterior tibial offset ratio (PTOR), defined as posterior plateau distance (PPD) divided by anterior plateau distance (APD) on a true lateral radiograph, as a complementary descriptor of sagittal tibial plateau morphology and compared it with posterior tibial slope (PTS). Hypothesis: Higher PTOR would be associated with revision after hamstring-autograft ACL reconstruction and this association would persist after accounting for PTS and total plateau length. Study Design: Case-control study; Level of evidence, 3.Methods: This retrospective matched case-control study included primary ACL reconstructions performed between January 2012 and December 2022 at a tertiary referral center. Revision cases (n = 67) were matched 1:1 to no-revision controls (n = 67) by age, sex, and available follow-up duration using a custom algorithm; all controls had at least 24 months of follow-up. Standardized semiflexed true lateral radiographs were analyzed. Receiver operating characteristic curve thresholds were exploratory and derived by the Youden index. Results: PTOR was higher in revision cases than controls (0.72 +/- 0.23 vs 0.46 +/- 0.13; P < .001), as was PTS (14.0 degrees +/- 3.4 degrees vs 11.2 degrees +/- 3.0 degrees; P < .001). PTOR showed a higher exploratory area under the curve than PTS (0.852 [95% CI, 0.790-0.915] vs 0.733 [95% CI, 0.648-0.819]); exploratory thresholds were 0.568 for PTOR and 12.0 degrees for PTS. In matched conditional logistic regression using standardized continuous predictors, PTOR remained associated with revision after adjustment for PTS and total plateau length (odds ratio [OR] per 1 SD, 22.65; 95% CI, 3.58-143.41; P = .001), as did PTS (OR, 3.82; 95% CI, 1.32-11.05; P = .013); total plateau length was not associated with revision. Conclusion: PTOR is a reproducible, complementary radiographic marker associated with revision after hamstring-autograft ACL reconstruction. PTOR should be interpreted within the PTS/sagittal tibial morphology paradigm, not as a stand-alone indication for osseous correction. Proposed thresholds are exploratory and require external validation.