Summary

Anterior tibial subluxation on MRI in cases of complete ACL rupture was significantly associated with male sex, MRI performed more than 3 months post-injury, and meniscal injuries.

Abstract

Introduction

Static anterior tibial subluxation (ATS) following anterior cruciate ligament (ACL) injury highlights the altered relationship between the tibia and femur in patients with ACL insufficiency. Several factors, including injuries to secondary stabilizers, bony morphological variations, and the time elapsed between injury and magnetic resonance imaging (MRI), have been investigated as potential risk factors for increased ATS. Recent literature indicates that patients with significant preoperative ATS experience markedly reduced knee stability following ACL reconstruction, leading to poorer clinical outcomes compared to those with minimal or no preoperative ATS.

Purpose

To assess the correlation between the interval from injury to MRI, demographic factors, tibial slope, and associated injuries with the degree of ATS on MRI in patients with complete ACL ruptures.

Methods

A cohort of 558 consecutive patients treated for ACL injuries was identified from an institutional registry. Anterior tibial subluxation of the medial and lateral compartments relative to the femoral condyles was measured on preoperative MRI. Meniscal tears, chondral defects, tibial slope, and injuries to the anterolateral ligament (ALL) were also evaluated on MRI. Chronic ACL injury was defined as more than 3 months between injury and MRI. Linear regression analysis was performed for each variable to evaluate its association with ATS.

Results

The mean lateral ATS was 8.26 ± 3.8 mm, and the mean medial ATS was 3.68 ± 2.33 mm. The mean age of the cohort was 31 ± 9.57 years, with 82% being male. Among the patients, 50% had a meniscal injury, 20% had cartilage damage, and 25% had an ALL injury. Chronic ACL injury was present in 20% of cases. Lateral ATS was significantly greater in chronic ACL injuries (9.2 ± 8.4 mm vs. 8 ± 3.7 mm; p = 0.002) and in male patients (8.4 ± 3.8 mm vs. 7.4 ± 3.9 mm; p = 0.024). Meniscal injuries were associated with a significantly higher lateral ATS (0.84 mm, 95% CI 0.09-1.58 for the medial meniscus and 1.72 mm, 95% CI 1.72-2.28 for the lateral meniscus). Age showed a statistically significant but clinically minimal association, with subluxation increasing by an average of 0.42 mm (95% CI 0.08, 0.75) per decade. While lateral tibial slope was not significantly associated with ATS, the medial tibial slope demonstrated a significant association of 0.15 mm (95% CI 0.04, 0.26), independent of sex and age. No significant association was found between ALL injury and lateral ATS (p = 0.56).

Conclusion

Anterior tibial subluxation on MRI in cases of complete ACL rupture was significantly associated with male sex, MRI performed more than 3 months post-injury, and meniscal injuries.

Level of Evidence: IV, retrospective cohort study.