# Radiographic medial posterior tibial slope ≥16° predicts multiple revisions after anterior cruciate ligament reconstruction

## TL;DR

A higher radiographic medial posterior tibial slope of 16° or more is linked to a greater risk of needing multiple ACL surgery revisions.

## Contribution

Identifies a specific radiographic threshold (≥16°) for medial posterior tibial slope that predicts multiple ACLR revisions.

## Key findings

- Radiographic medial PTS was significantly higher in patients with multiple revisions (12.5° vs. 11.2°).
- A medial PTS ≥16° was associated with a 3.10-fold increased risk of multiple revisions.
- MRI-based PTS measurements did not show significant differences between groups.

## Abstract

An increased posterior tibial slope (PTS) has been implicated as a risk factor for anterior cruciate ligament (ACL) graft failure. This matched case–control study aimed to compare radiographic and magnetic resonance imaging (MRI)‐based PTS measurements between patients undergoing multiple revision anterior cruciate ligament reconstruction (ACLR) and those with successful primary ACLR and to identify thresholds predictive of high revision risk.

In this matched case–control study, 156 patients were analysed: 78 patients undergoing multiple revision ACLR and 78 patients with successful primary ACLR. Medial PTS was measured on radiographs, while medial, lateral and PTS difference (PTS asymmetry) were measured on MRI. Group differences were assessed using independent t tests and χ
2 tests. Receiver operating characteristic (ROC) analysis identified optimal thresholds, and logistic regression quantified odds ratios (ORs) for multiple revisions per 1° increase in radiographic medial PTS, adjusting for body mass index (BMI), sex, side, height and weight.

Radiographic medial PTS was significantly higher in the multiple‐revision group (12.5 ± 3.5° vs. 11.2 ± 3.0°, p = 0.016). ROC analysis identified an optimal medial PTS cutoff of 13° (area under the curve = 0.58, sensitivity = 0.49, specificity = 0.65), but only a PTS ≥ 16° was significantly associated with increased multiple revision risk (OR = 3.10, 95% confidence interval [CI]: 1.14–8.40; p = 0.037; specificity = 0.91; positive predictive value [PPV] = 0.70). MRI‐based medial and lateral PTSs, as well as PTS asymmetry, did not differ significantly between groups. Univariate logistic regression demonstrated a 10% increase in odds per 1° increase in radiographic PTS (OR = 1.10, 95% CI: 1.00–1.22, p = 0.049), remaining significant after adjustment for BMI, sex, side, height and weight (adjusted OR = 1.11, 95% CI: 1.01–1.23, p = 0.034). Radiographic medial PTS correlated moderately with MRI‐based medial PTS (r = 0.49, p < 0.001), but not with lateral PTS (p: n.s.).

Radiographic medial PTS showed the strongest differentiation between successful primary ACLR and multiple‐revision ACLR. A PTS ≥ 16° identifies patients at significantly higher risk of multiple revisions, whereas MRI‐based medial PTS, lateral PTS and PTS asymmetry provide no additional discriminatory value. Radiographic medial PTS appears practical for preoperative risk stratification, whereas MRI‐based measures do not show similar utility.

Level III.