Summary

Patients with isolated ACL injuries had similar medial and lateral posterior tibial slopes when compared to those with concomitant ligamentous injuries.

Abstract

Introduction

Increased tibial slope is a known risk factor for isolated anterior cruciate ligament rupture. However, existing studies have not reviewed the relationship between posterior tibial slope and multi-ligamentous knee injuries. Our study aims to determine if posterior tibial slope is associated with the incidence of multi-ligamentous knee injuries which involve more than just the anterior cruciate ligament.

Methodology

We recruited patients who underwent anterior cruciate ligament reconstruction, with or without other ligamentous reconstruction, in a single tertiary institution. All pre-operative magnetic resonance imaging scans of the involved knee were reviewed. The patients were divided into two groups: Anterior cruciate ligament injury only (ACL) and anterior cruciate ligament injury with other concomitant ligamentous injuries (ACL-plus), which included injuries to the medial collateral ligament, lateral collateral ligament, posterior cruciate ligament, or posterolateral corner. Medial and lateral posterior tibial slope for each knee were measured on available magnetic resonance imaging scans. We compared both groups in terms of demographic data, as well as the degrees of medial and lateral posterior tibial slope. Student’s t-test was used to compare continuous variables whilst Pearson’s chi-squared test was used to compare categorical variables. Intra-observer and inter-observer reliability were calculated using intra-class correlation coefficients using Cronbach’s alpha.

Results

192 patients who had magnetic resonance imaging scans performed for a suspected anterior cruciate ligament injury, with or without other ligamentous injuries, were included. There were 96 patients in the ACL group and 96 patients in the ACL-plus group. There was no difference in terms of gender, ethnicity, and body mass index, as illustrated in Table 1. Patients in the ACL-plus group were older (26.5 years vs 29.7 years; p=0.024). As shown in Table 2, mean lateral posterior tibial slope was similar between groups but mean medial posterior tibial slope was higher in patients in the ACL group (5.29 degrees vs 4.29 degrees; p=0.044). Interobserver reliability (Cronbach’s alpha) was 0.875 (95% CI, 0.833-0.905) for lateral posterior tibial slope and 0.831 (95% CI, 0.775-0.873) for medial posterior tibial slope.

Discussion And Conclusion

Patients in the ACL plus group were older by an average of 3.2 years but this is unlikely to be clinically significant as ACL injuries most commonly occurs between the ages 14 to 35. In our study, patients who suffered from ACL-plus injuries did not appear to have clinically significant differences in both medial and lateral PTS as compared to those with isolated ACL injuries. Future research could be done to investigate other predisposing factors for ACL-plus injuries.