Wide stance gait style compliments high tibial osteotomy in reducing knee joint loading

Purpose: The external knee adduction moment (KAM) has been studied as a surrogate measure of medial compartment load. A high KAM has been associated with medial knee osteoarthritis (OA) disease progression. Additionally, the knee adduction angular impulse (KAAI) has been studied as a dynamic representation of medial knee load. Methods to offload the medial compartment include gait adaptation and surgical re-alignment. This study aims to identify differences in medial knee joint loading parameters between wide stance gait (WS) and high tibial osteotomy (HTO). These treatments aim to offload the medial compartment with dynamic or anatomical compensation of varus knee deformity respectively. This study aims to identify if any benefit in reducing KAM can be attained with WS after HTO.

Methods: This was a controlled cohort study. Healthy volunteers participated as control participants and were compared to a patient cohort who underwent HTO. Healthy volunteers were recruited, with no current knee symptoms and no previous knee surgery. Patients were diagnosed with medial compartment knee OA based on history, clinical examination and plain radiographs for disease severity. Varus deformity was confirmed on full leg weightbearing radiographs. The study was part of ongoing research associated with the Arthritis Research UK, Biomechanics and Bioengineering Centre.

Three-dimensional motion analysis and ground reaction forces (GRF) was performed on 17 patients with medial compartment knee OA and varus deformity prior to undergoing HTO, 12 patients were assessed approximately 12 months post-operatively, and results compared to 12 healthy controls.

Participants walked along the walkway at self-selected speeds. Participants performed 6 walking trials with satisfactory force plate strikes with their natural step width. A verbal and visual demonstration of WS was provided and participants were then asked to walk with their feet wider apart compared to their normal gait feet width, to a comfortable distance. The feet width achieved was within the boundaries of what would be achievable and tolerated by patients in clinical practice.

Data was processed using Visual 3D to compute kinetic and kinematic data, where a bespoke model and analysis pipeline was applied to each participants’ static measurement and dynamic trials.Metrics were calculated from individual trials, and then averaged across the six walking trials for each participant, for WS and natural gait. Student's t-test was performed to compare means from two groups. Analysis of variance (ANOVA) testing was performed where there were more than two groups, in which case post hoc tests were performed to identify significant differences between the groups. These were performed using SPSS v25.0. Assumptions of normality were confirmed, and a P value of 0.05 or less was considered a statistically significant result.

Results: Table 1 outlines the group demographics and Table 2 outlines results for stance width, gait speed, first and second KAM, KAAI, peak knee flexion moment and peak knee flexion angle.

Pre-HTO, patients had a significantly higher first and second peak KAM, and KAAI, compared to healthy controls irrespective of gait style. Wide stance gait did not significantly reduce first peak KAM or KAAI, compared to pre-HTO NG. Pre-HTO, patients had a significantly less peak knee flexion angle compared with the healthy cohort, with WS having a significantly less peak flexion angle than pre-HTO NG.

Post-HTO patients had a significantly lower first and second peak KAM, and KAAI, compared to pre-HTO patients irrespective of gait style. Additionally, with WS gait, frontal plane loading parameters were significantly reduced further compared to post-HTO NG. Post-HTO, patients had a significantly lower peak knee flexion moment compared to pre-HTO NG. However, with WS, peak knee flexion moment significantly increased compared to post-HTO NG. Post-HTO, patients walked with a significantly increased peak knee flexion angle compared with pre-HTO. However, with WS peak knee flexion angle significantly reduced from post-HTO NG.