Summary

The delta length of the whole leg and the leg length discrepancy decreased after MCWDFO, whereas they were significantly increased after LOWDFO. Although postoperative femoral length changed depending on each surgery, the straightening effect of the alignment correction minimized the change in overall leg length, resulting in the initial leg length being maintained.

Abstract

Purpose

To compare the radiological and clinical outcomes of medial closed wedge distal femoral osteotomy (MCWDFO) and lateral open wedge distal femoral osteotomy (LOWDFO), specifically to evaluate leg length discrepancy (LLD) in each technique. It was hypothesized that MCWDFO would result in a reduced leg length in comparison to LOWDFO.

Methods

This study included patients who underwent MCWDFO or LOWDFO at a single institution between 2014 and 2022 with a minimum follow-up of 1 year. Radiological assessment included hip-knee-ankle angle, lateral distal femoral angle, medial proximal tibial angle, length of the whole leg and femur, and LLD, which was compared to the contralateral side. The postoperative HKA target was 180°. The intended corrective angle for all cases was calculated using the reversed Miniaci et al. method. The difference between the pre- and postoperative values for each parameter is expressed as a delta. The postoperative assumed LLD based on wedge height, the postoperative assumed LLD based on the femur, and the straightening effect on the overall leg length were calculated by finding the total sum of the preoperative LLD and either the gap distance or delta length of the femur, or by subtracting the postoperative assumed femoral LLD from the postoperative LLD, respectively. Radiological and clinical outcomes were statistically evaluated using the Simple Knee Value (SKV) for each procedure. Statistical comparisons between the MCWDFO and LOWDFO groups were made using the paired or unpaired t-test for parametric data, the Mann-Whitney U test for non-parametric variables, and the Chi-squared test for categorical outcomes, with the significant level set at or below 0.05.

Results

A total of 52 patients, consisting of 26 patients in the MCWDFO group and 26 patients in the LOWDFO group, were included in the study. There were no significant differences between the two groups with respect to demographic data except for follow-up period and radiological parameters of bony geometries. Although the delta length of the femur decreased by 2.7 ± 0.6 mm postoperatively in the MCWDFO group and increased by 2.7 ± 0.4 mm in the LOWDFO group, the delta length of the whole leg decreased by 0.5 ± 3.8 mm in the MCWDFO group and increased by 1.7 ± 2.6 mm postoperatively in the LOWDFO group (p<0.001). The straightening effect on overall leg length was significantly greater for the MCWDFO group than for the LOWDFO group (2.0 ± 4.1 mm vs -1.1 ± 2.5 mm, p>0.001). In addition, there was no significant difference in clinical outcomes using SKV between the two groups (p=0.691).

Conclusions

The delta of total leg length and LLD decreased significantly after MCWDFO, but increased significantly after LOWDFO. Although postoperative femoral length changed depending on each surgery, the straightening effect of the alignment correction minimized the change in overall leg length, resulting in the maintenance of the original leg length.