Summary

Several anatomical parameters were changed between the legs closed standing and legs spread standing positions.

Abstract

Purpose

Coronal whole-leg radiographs are generally used in the preoperative planning for high tibial osteotomy (HTO). Although determining the correction angle and gap are essential for HTO using weight-bearing coronal whole-leg radiographs, the effect of standing position on anatomical parameters have not been clarified.The purpose of this study was to assess the differences in lower limb global alignment and anatomical parameters of coronal whole-leg radiographs, according to different weight-bearing standing positions.

Methods

Digital radiographs were obtained from 176 patients (60 males and 116 females) with Kellgren-Lawrence (KL) grade I, II, or III varus knee osteoarthritis or another knee disorders such as meniscus injury and anterior cruciate ligament injury. The patients were divided into four groups according to severity (KL-0, KL-I, KL-II, and KL-III). Patients with flexion contractures or those unable to stand with full weight-bearing were excluded. This investigation was conducted as case series with no comparison group. Full weight-bearing coronal whole-leg radiographs with the patella centred on the femoral condyle were taken for all subjects. Each patient was assessed in two standing positions: legs closed and legs spread. In the legs closed standing position, the subjects were indicated to firmly close their feet together. On the other hand, radiographs in the legs spread standing position were taken naturally, with feet shoulder width apart. The examinations were performed in a random order. The mechanical distal femoral angle (mLDFA), medial proximal tibial angle (MPTA), femorotibial angle (FTA), joint line convergence angle (JLCA), percentage weight bearing line (%WBL), and hip-knee-ankle angle (HKAA) were measured. Means and standard deviations were determined for each measured anatomical parameter. The demographic data of the four groups were statistically analysed using one-way analysis of variance and the chi-square test. The Student’s t test was used to compare the two standing positions. A P value < 0.05 indicated a statistically significant difference. A priori power analysis showed that a minimum of 23 subjects in each group was required to detect differences with a power of 0.8 and an alpha of 0.05. The intraobserver ICC for mLDFA, MPTA, FTA, JLCA, %WBL, and HKAA was 0.943, 0.878, 0.996, 0.564, 0.997, and 0.998, respectively. The interobserver ICC for mLDFA, MPTA, FTA, JLCA, %WBL, HKAA was 0.923, 0.871, 0.997, 0.581, 0.997, and 0.995, respectively.

Results

The MPTAs of legs closed standing and legs spread standing were 84.9 ± 2.6° and 85.1 ± 2.4° in KL-0, 84.7 ± 2.0° and 84.9 ± 2.1° in KL-I, and 85.0 ± 2.43° and 85.4 ± 2.4° in KL-II, respectively. There were statistically significant differences in the MPTA between the two standing positions in KL-0, KL-I, and KL-II. In contrast, the %WBL and HKAA did not change regardless of the standing position. In the KL-III group, no statistical significance was observed for any of the anatomical parameters.

Conclusion

Several anatomical parameters were changed between the legs closed standing and legs spread standing positions. It was suggested that the standing position should be taken into consideration in the planning for HTO.