Assessing Risk of Iatrogenic Peroneal Nerve Injury in All-Inside Lateral Meniscal Repair Between Standard Vs. Arthroscopic MRI.

BACKGROUND: Various studies have examined the risk of peroneal nerve injury with use of standard magnetic resonance imaging (MRI) of the knee. However, the position of the knee during standard MRI is different from that during an actual arthroscopic lateral meniscal repair. The purpose of the present study was to evaluate and compare the risk of peroneal nerve injury during simulated all-inside lateral meniscal repairs on the basis of MRI scans made with the knee in both positions.

METHODS: With use of axial MRI scans made with the knee in the standard position (i.e., in 30° of flexion) and in the actual position used during arthroscopic lateral meniscal repair (i.e., in a figure-of-4 position), direct lines were drawn to simulate the passage of a straight all-inside meniscal repair device from the anteromedial and anterolateral portals to the medial and lateral borders of the popliteus tendon. The distance from the closest passage of each line to the peroneal nerve was measured. If a line touched or passed through the peroneal nerve, a risk of iatrogenic injury was noted and a new line was drawn from the same portal to the outer border of the peroneal nerve. The danger area was measured from the first line to the new line along the joint capsule.

RESULTS: In 28 Thai patients, the shortest distances from each line to the peroneal nerve were significantly shorter on the MRI scans made with the knee in the standard position than on those made with the knee in the arthroscopic position (p < 0.05 for all). All danger areas on the MRI scans that were made with the knee in the arthroscopic position were included within the danger areas on the scans that were made with the knee in the standard position.

CONCLUSIONS: Standard MRI scans of the knee can be used to determine the risk of peroneal nerve injury at the time of arthroscopic lateral meniscal repair, although the risks are slightly overestimated.

LEVEL OF EVIDENCE: Diagnostic Level III. See Instructions for Authors for a complete description of levels of evidence.