2017 ISAKOS Biennial Congress ePoster #1511

 

Discrepancy of Alignment in Different Weight Bearing Conditions Before and After High Tibial Osteotomy

Byung-Hoon Lee, MD, PhD, Incheon KOREA, REPUBLIC OF
Joon Ho Wang, MD, PhD, Seoul KOREA, REPUBLIC OF

Samsung Medical Center / Kang-Dong Sacred Heart Hospital, Seoul, KOREA, REPUBLIC OF

FDA Status Cleared

Summary

There is the discrepancy of alignment in different weight bearing conditions before and after HTO.

Abstract

Introduction

Medial opening wedge high tibial osteotomy (HTO) is an established procedure for medial compartment osteoarthritis of the knee. However, the ideal correction angle in preoperative planning has not yet been defined, and how to achieve a desired realigned mechanical axis angle is a critical concern. Correlation of peak knee adduction moment to Mechanical axis angle (MA) may also play a factor as assessed from supine, single-limb (SL) and double-limb (DL) stance radiographs. Measurement of MA in a SL stance has been proposed as a functional measure of malalignment suitable for planning HTO. A SL standing pose is thought to be most representative of the dynamic knee joint loading experienced during walking. This study aims to evaluate the differences in the amount of varus malalignment and valgus (over) correction in relation to three different weight bearing conditions from whole leg AP radiographs (single-limb (SL) stance, double- limb (DL) stance, supine position) before and after high tibial osteotomy (HTO), and to evaluate which alignment parameters affect the changes for patients in three different weight bearing conditions.

Methods

A total of 40 consecutive patients (43 knees) with varus osteoarthritis underwent navigation assisted open wedge HTO. MA was measured before and after surgery from hip-to-ankle radiographs taken with patients in three different weight bearing conditions. To find significant factors that affect the alignment differences, several variables including patient demographics, soft tissue laxity, pelvic obliquity, and ground mechanical axis deviation of tibia (calculated by the angle between two lines, tibial anatomical axis and weight-bearing line) were evaluated.

Results

Preoperatively, mean MA measured on SL stance radiographs was significantly more varus than on DL stance (10.1° ± 2.4° and 8.0° ± 2.6°, respectively, p < 0.001), which was significantly more varus than on supine position (6.6° ± 2.6°, p < 0.001). Meanwhile, in patients with postoperatively valgus corrected knee, MA did not show the same pattern of change as with preoperative varus knee. Mean MA measured on DL stance radiographs was more valgus than in supine position (-3.0o ± 2.4o and -2.6o ± 3.1o, p = 0.455), while mean MA on SL stance radiographs (-2.0o ± 2.1o) was significantly lesser valgus than on DL stance (p = 0.002). The ground mechanical axis deviation of tibia showed a significant correlation with MA difference between SL and DL stance radiographs before (ß = -0.341, p = 0.045) and after surgery (ß = -0.536, p = 0.001).

Conclusion

In preoperative varus knee, the mean MA on SL stance was changed to more varus than on DL stance, which changed to lesser valgus in postoperative valgus knee. The understanding in discrepancy of alignment in different weight bearing conditions before and after HTO should be considered for the appropriate realignment of the limb.