Summary

This study aimed to evaluate the clinical outcomes of anatomic ACLR based on the degree of postoperative ATS.

Abstract

Background

Anterior tibial subluxation (ATS) in extension following an anterior cruciate ligament (ACL) injury indicates a forward shift of the tibia relative to the femur. Recent studies have shown that this subluxation can sometimes be irreductible, meaning that ACL reconstruction (ACLR) may not fully restore the normal tibiofemoral alignment. The persistence of this subluxation and high anterior translation values after ACLR have been associated to poor knee stability and unfavorable clinical outcomes. Additionally, these factors have been proposed as risk factors for graft rerupture.

Objective

This study aimed to evaluate the clinical outcomes of anatomic ACLR based on the degree of postoperative ATS. We hypothesized that the excessive postoperative lateral ATS (>10 mm) would be associated with inferior clinical outcomes.

Methods

A total of 221 consecutive patients who underwent primary ACLR with a minimum follow-up of two years were included. ATS of the lateral and medial compartments in extension, relative to the femoral condyles, were measured on preoperative and postoperative MRI. Based on lateral ATS in postoperative MRI, the population was divided into three groups: Group 1 (<6mm), Group 2 (6 – 10mm), Group 3 (>10mm). Demographic variables, time from injury to surgery and associated cartilage, meniscus, or anterolateral ligament injuries were evaluated. Time to return to sports and sports level were evaluated using the Tegner scale. Additionally, the Lysholm score and IKDC were assessed preoperatively and at the final follow-up visit.

Results

Although the mean difference in lateral ATS between preoperative and postoperative MRI was 0.69mm (p<0.01), 62% (n=137) of cases had ≥6mm lateral ATS on postoperative MRI. Multivariate logistic regression analysis identified preoperative lateral ATS as the only factor significantly associated with fixed ATS. The average time to return to sports was 10 months, with no significant differences between groups (p=0.056). 97% of patients returned to sports, and 69% returned to their pre-injury level, with no significant differences between groups (p=0.781, p=0.127). Multivariate analysis revealed that meniscal injury was associated with a lower sports level (OR 0.4, 95% CI 0.19 - 0.82). The average clinical scores (IKDC and Lysholm) were 86 and 89, respectively, with no differences between groups (p=0.2, p=0.71). However, multivariate analysis showed that patients with lateral ATS greater than 10mm on postoperative MRI had significantly worse clinical outcomes compared to those with less than 6 mm. The overall failure rate was 7%, with no statistical difference between groups (p=0.13).

Conclusion

Anatomic ACLR did not fully restore the tibiofemoral relationship, as a high percentage of patients (62%) had ≥6mm of postoperative ATS. The extent of postoperative subluxation was not a determining factor for subjective scales, return to sports, or reruptures following ACL reconstruction. However, patients with lateral ATS greater than 10mm had significantly worse clinical outcomes at two years follow-up.

Cross-sectional study; Level of evidence: 3