Summary

In this study we investigated the relationship between each screw and peroneal nerve with the 2 different placements of the locking plate in medial opening-wedge high tibial osteotomy in order to elucidated the risk of peroneal nerve injury.

Abstract

Introduction

Recently, a new method of medial opening-wedge HTO (MOWHTO) using a locking plate has increasingly been recognized and accepted as a treatment option for medial compartment osteoarthritis or osteonecrosis of the knee. Nerve injury is one of the complication of MOWHTO on account of screw interference. Therefore, it is recommended that the most distal screw should not be fixed bi-cortically in order to avoid peroneal nerve injury. However, no study so far has examined the risk of nerve injury in MOWHTO. Thus, we undertook this study to elucidate the relationship between the locking screws and peroneal nerve in MOWHTO.

Material And Methods

Ten cadaveric knees with normal anatomy were prepared for this study. First, the common peroneal nerve (CPN) was identified at the branch from the sciatic nerve. Secondly, the CPN was carefully exposed to the distal part while maintaining the relation to the proximal fibula intact. The branch of the deep peroneal nerve (DPN) and superficial peroneal nerve (SPN) were also identified and exposed to the distal. After exposing the nerve, MOWHTO was performed and locking plate was temporarily fixated with 2.4mm diameter kirschner wires (K-wire). The distance between each K-wire and the DPN (Dn), as well as the distance from the tibial cortex at the measurement point (Dt), were measured using a caliper. The two types of plate placement, the most anterior and the most posterior, were evaluated. The data were compared using paired t-test in order to examine the effect of plate placement. Significance was set at <.05.

Results

The results (Dt / Dn) at each screw hole (mean ± SE (mm)) were as follows. Plate anterior : hole A (9.0 ± 2.7 / 8.6 ± 2.7) , hole B (10.1 ± 2.3 / 4.5 ± 2.0) , hole C (10.5 ± 1.8 / 2.0 ± 1.1 ), hole 1 (23.2 ± 6.7 / 8.8 ± 1.8) , hole 2 (18.2 ± 1.8 / 4.1 ± 0.9), hole 3 (15.0 ± 1.2 / 2.4 ± 0.8) , hole 4 (14.2 ± 1.5 / 1.0 ± 0.4) ; Plate posterior : hole A (5.4 ± 1.8 / 19.9 ± 2.2) , hole B (5.6 ± 1.9 / 14.3 ± 2.2) , hole C (5.0 ± 2.1 / 9.4 ± 1.6 ), hole 1 (24.8 ± 2.5 / 3.1 ± 1.8) , hole 2 (18.6 ± 1.5 / 1.5 ± 0.7), hole 3 (15.0 ± 1.4 / 2.0 ± 1.2) , hole 4 (11.6 ± 1.2 / 1.3 ± 0.6) respectively.

Discussion

The most important findings in this study were that in either plate placement, screw 2.3.4 was directed toward the DPN (within 3mm). Furthermore, although screw directions were altered by the plate placement, distances from the K-wire to DPN did not significantly change. Therefore, the surgeon should be extremely careful not to perforate the opposite cortex when drilling the screw holes A to C and not to over penetrate the drill on the opposite side of the tibial cortex when drilling the screw holes 1 to 4.