Summary

This study evaluates the risk and danger zones of iatrogenic posterior neurovascular injury and saphenous nerve injury in arthroscopic medial meniscal repair using MRI in the arthroscopic medial meniscal repair position with valgus force and joint fluid dilatation. The surgeon can use the results from this study to decrease a chance of iatrogenic neurovascular injury.

Abstract

Background

Arthroscopic medial meniscus repair carries a risk of iatrogenic neurovascular injury, potentially leading to significant morbidity. Previous studies have attempted to determine the risk of iatrogenic injury for this procedure using standard knee magnetic resonance imagings (MRIs); however, this method may not accurately reflect the actual risk because the knee position in standard knee MRIs is different from the actual arthroscopic medial meniscal repair position. Additionally, previous studies used some anatomical landmarks which are not applicable intraoperatively because they are not visible during arthroscopy and are not reproducible. Therefore, it would be advantageous to evaluate the risk of iatrogenic neurovascular injury using knee images in the actual arthroscopic medial meniscus repair position, with slight knee flexion, valgus force, and joint dilation which would be more precise in defining the risk and danger zones of iatrogenic neurovascular injury to decrease the risk of neurovascular injury.

Objective

This study aimed to identify the risk and danger zones of neurovascular injury in arthroscopic medial meniscus repair using MRIs simulating the actual arthroscopic medial meniscus repair position with slight knee flexion, valgus force, and joint fluid dilation.

Methods

We utilized axial MRI images taken in the actual arthroscopic medial meniscus repair position. Anteromedial and accessory anteromedial portals were simulated at the medial border and 10 mm from the medial border of the patellar tendon, respectively, with anterolateral and accessory anterolateral portals simulated at the lateral border and 10 mm from the border of the patellar tendon, respectively. A straight line was drawn from each portal to the medial border of the posterior medial meniscal root (pMMR). If a line passed through or touched the posterior neurovascular structure, a risk of iatrogenic injury was recorded. Second and third lines were drawn from the same portals to the inner and outer edges of the saphenous nerve, respectively. The distance from the first to the second and the first to the third lines were measured along the posterior border of the medial meniscus. The "danger zones" were defined as the distances between the second and third lines.

Results

We analyzed axial MRI images from 28 adult patients. There was a risk of iatrogenic posterior neurovascular injury when repairing through the anteromedial and accessory anteromedial portals with incidences of 8% and 43%, respectively. The danger zones of posterior neurovascular injury when repairing through the anteromedial and accessory anteromedial portals were from the medial border of the pMMR to 3.2 mm and 2.9 mm beyond the medial border of the pMMR, respectively. There was a risk of saphenous nerve injury when repairing through all portals with danger zones in repairing through the anterolateral, anteromedial and accessory anteromedial portals of 15.2 to 20.3 mm, 28.1 to 32.7 mm and 31.5 to 36 mm from the medial border of the pMMR, respectively.

Conclusion

There was a risk of injury to the posterior neurovascular bundle and saphenous nerve during medial meniscus repair. The surgeon can use the danger zones delineated in this study to minimize the risk of iatrogenic neurovascular injury.