Summary

Medial opening wedge high tibial osteotomy affects more than just the knee: A study looking at changes in the knee, hip and ankle joints during gait.

Abstract

Introduction

The primary goal of medial opening wedge High Tibial Osteotomy (HTO) is to reduce loads on the medial tibiofemoral compartment, in order to provide pain relief, improve knee function and delay a more invasive total knee arthroplasty. HTO has excellent clinical, radiological, survivorship and gait-analysis outcomes (Lieshout et al. 2019; Niinimaki et al. 2012; Lau et al. 2021). Much literature exists on the effect of HTO on knee biomechanics during gait (Liu et al. 2021). Notwithstanding, little is known about the effect of HTO on the adjacent ankle and hip joint angles, moments, and compressive forces during gait. This study aimed to assess the motions and loads in the knee, hip and ankle joints during gait pre- and post- HTO. We hypothesized that HTO induces changes in gait biomechanics not only at the knee, but also at the hip and ankle joints.

Methods

Surgical planning was based on the weightbearing line intersecting Fujisawa’s point, and executed using computer navigation, with locking plate fixation and allograft bone. Intraoperative navigation ensured agreement between planned and achieved alignment. Biomechanical and radiological data, including long leg alignment x-rays was collected pre- and post- HTO. Full-body motion, lower-limb ground reaction force and muscle electromyographic data were recorded simultaneously when the operated leg was in contact with the ground (i.e. stance phase). Knee injury and osteoarthritis outcome score (KOOS) were also collected.

Results

Data from 25 simultaneous patients undergoing HTO was collected. Hip-knee-ankle angle (HKA) as planned went from varus 7°±3.8° to valgus 2.4°±1.6°; p<0.05. MPTA went from 84.4°±2.8° pre-operatively to 93.1°±2.3°; (p<0.05). JLO changed from 173.7°±2.9° at pre HTO to 182.0°±3.9° at post HTO (p<0.05). The patients walked at similar walking speed of 1.1±0.13m/s2 versus post, 1.1±0.15m/s2;p>0.05). They walked with a wider step width after surgery (p<0.05). Pre-operatively patients walked with abnormally increased flexion of the hip, knee and ankle joints (consistent with knee osteoarthritis gait biomechanics). Post-operatively, patients walked with less flexion at these joints (p<0.05), and with a more adducted hip, abducted knee and inverted ankle motion (p<0.05); no radiological change was observed at these joint spaces and no patient reported symptoms in these joints. Joint compressive reaction forces at the three joints were reduced after HTO (p<0.05). KOOS scores significantly improved after HTO (pre, 46.9±17.7 versus post, 72.1±17.9; p<0.05).

Discussion

This study demonstrated that HTO achieved excellent clinical outcomes with improved knee function and pain score after coronal realignment of the lower-limb to around 2.4 degrees valgus. In support of our hypothesis, we determined that HTO affected joint motion and loads across all 3 joints (p<0.05). Post HTO, the hip and ankle joints compensated to be more adducted and inverted, respectively (p<0.05). The compressive joint loads were reduced (p<0.05) and patients walked with a more normal gait pattern. This study suggests that HTO has beneficial effects beyond improving knee pain and function, and has potential benefits also for ankle and hip joints, and for global lower limb function.