The ALPS classification: Predicting ACL graft failure based on deviation from mean posterior tibial slope-A systematic review and meta-analysis.

Abstract

To quantify the association between posterior tibial slope (PTS) and anterior cruciate ligament (ACL) graft failure using meta-analysis. This study introduces the anatomic-lateral-posterior slope (ALPS) classification as a simple, clinically oriented, slope-based risk stratification tool. Embase, MEDLINE, Scopus and Cochrane were searched from inception through 30 August 2024 for studies comparing PTS in ACL graft failure versus control knees. Random-effects models synthesized mean differences (MDs) and adjusted odds ratios (aORs). Studies reporting slope-category data were mapped to ALPS risk bands based on standard deviations from the failure-group mean slope. Subgroup analyses and meta-regression examined imaging modality and measurement technique. Twenty-four studies (6335 knees; 1597 failures) were included. Lateral PTS was associated with higher graft-failure risk per 1° increase (aOR = 1.15; 95% confidence interval: 1.06-1.23). Failure incidence rose across ALPS categories (9% green; 16%-23% blue; 41% red and 50% black). Medial PTS differences were smaller and not consistently predictive. Heterogeneity was substantial. Time to re-injury was an independent determinant; other moderators were collinear. Increased PTS-particularly lateral slope-is associated with ACL graft failure. The ALPS classification offers a pragmatic way to communicate slope-related risk; however, given non-significant aORs in some analyses and an anomalous signal in one 'low-risk' subgroup, its predictive capability should be viewed as preliminary pending prospective validation. Level III.