Compensatory mechanisms for proximal & distal joint alignment & gait in varus knee osteoarthritis treated with high tibial osteotomy: A systematic review

Background Varus deformity is common in medial compartment knee osteoarthritis (OA). This malalignment in the coronal plane is compensated for by static and dynamic adjustments in the position of the adjacent joints, principally in the hindfoot & ankle. This condition can be treated in selected patients by high tibial osteotomy (HTO), stabilised with a fixed angle plate or circular frame, which may reverse this compensation. The aim of this systematic review is to determine the evidence available for such compensatory mechanisms with the main objectives being to improve deformity planning and optimise patient outcomes. Method A systematic review with meta-analysis was designed using the PRISMA template to meet the research aims & objectives. Results A total of 1006 patients (1020 knees), combined mean age 54.5 years, female:male ratio of 0.9:1 were extracted from 19 included studies. The methodologies of the majority of studies were at high risk of bias according to the Newcastle-Ottawa Scale demonstrating significant heterogeneity. The combined mean change in the HKA axis was 7.7°; MPTA 7.4°; TT, 0.21°; TI 4.56° & AJLO 4° valgus. Preoperative hindfoot valgus compensation reverts towards neutral post-HTO. There is limited evidence available for a direct relationship between static alignment and dynamic gait parameters. Conclusions An inverse relationship between ankle and hindfoot alignment in varus deformity of the knee forms the basis of this compensation theory. In cases with a stiff hindfoot which may not revert postoperatively, the reconstructive orthopaedic surgeon may consider angulation with translation HTO, in order to optimise joint alignment and minimise transference of symptoms to the foot and ankle.