Summary

Lateral location of the tibial tunnel increases the lateral meniscal extrusion after single bundle ACL reconstruction

Abstract

Introduction

The anterior lateral meniscal root (ALMR) has a role in functionally stabilising the lateral meniscus. The tibial footprint of the anterior cruciate ligament (ACL) overlaps with the ALMR and there is a possibility that reaming of the tibial tunnel damages the ALMR attachment. The aim of this study is to investigate the relationship between the location of the tibial tunnel and presence of the lateral meniscal extrusion (LME) after anatomical single bundle ACL reconstruction.

Methods

A prospectively collected database, including demographics, clinical factors and associated intraoperative findings for 153 patients undergoing primary anatomical ACL reconstruction between October 2014 and July 2016, was investigated. Out of 153 cases, 55 cases (15-58 years old) had no meniscal injuries at surgery and were included in this study. Tibial plateau length (TPL), width (TPW), the LME and tibial tunnel location were evaluated from post-operative high-resolution MRI, performed using a previously published validated protocol. The distance in medial lateral (MLD) and anterior posterior (APD) directions from the tip of the medial tibial eminence were measured, and the location of the tibial tunnel was shown by MLD percentage (%MLD; MLD/TPW×100) and APD percentage (%APD; APD/TPL×100). Correlations between magnetic resonance imaging (MRI)-based LME percentage (%LME; LME/TPW×100) and tibial tunnel location were evaluated.

Results

A positive correlation was observed between %LME and %MLD (r=0.450; p<0.001). Applying receiver operating characteristic analysis, we determined that a cutoff value of 4 %MLD gave an 80.0% sensitivity to %LME with a specificity of 72.5%. The mean %LME was 1.50 for %MLD >4, compared to 0.29 for %MLD <4 (p<0.001). There was no significant correlation between %LME and clinical outcomes at one year follow up.

Conclusion

Lateral location of the tibial tunnel has been shown to correlate with increased risk of lateral meniscal extrusion after single bundle ACL reconstruction using hamstring autograft. This has implications for surgical technique in ACL reconstruction, with particular reference to careful consideration of graft size and tunnel location, in order to avoid damage to the anterior horn of the lateral meniscus.