Association Between Posterior Tibial Slope and Graft Survival in High-Risk Anterior Cruciate Ligament Reconstruction With Lateral Extra-articular Tenodesis

Abstract

Background:

Posterior tibial slope (PTS) is a well-established anatomic risk factor for anterior cruciate ligament (ACL) graft failure. Lateral extra-articular tenodesis (LET) is increasingly used as an adjunctive procedure in high-risk patients to reduce rerupture rates; however, how its protective effect varies across the continuum of slope values remains insufficiently characterized.

Purpose:

To determine how PTS modifies the protective effect of LET in high-risk patients and to evaluate the influence of PTS on graft failure across different risk profiles.

Study Design:

Cohort study; Level of evidence, 3.

Methods:

A retrospective cohort of 585 patients who underwent primary ACL reconstruction (ACLR) with hamstring tendon autografts between 2014 and 2017 was analyzed at a minimum follow-up of 6 years. Patients were nonrandomly allocated according to predefined clinical risk criteria into a low-risk group (isolated ACLR) and a high-risk group (ACLR + LET). A graft rerupture was defined clinically and confirmed by imaging. Multivariable logistic regression was used to assess the association between PTS and graft failure. Restricted cubic spline regression was also used to explore nonlinear relationships and identify slope ranges associated with low and high failure probabilities.

Results:

PTS independently predicted a graft rerupture in both groups, with a stronger effect in the high-risk group (adjusted odds ratio, 1.63; P = .005) compared with the low-risk group (adjusted odds ratio, 1.21; P = .029). The relationship between PTS and graft failure was nonlinear. In the high-risk group, the lowest failure probabilities were observed within a PTS range of 5° to 9°, below which the risk of failure plateaued. In contrast, PTS values exceeding 11° to 12° were associated with high failure probabilities in both groups.

Conclusion:

PTS was independently associated with graft failure in both groups. Although LET was associated with lower failure probabilities within a moderate slope range, increasing PTS values were linked to a progressively higher risk of reruptures in both groups. The association between a steeper slope and failure observed in the ACLR with LET group suggests that an elevated PTS may attenuate the relative protective effect of LET.