Medial opening-wedge high tibial osteotomy with dynamic axial external fixation in varus knee osteoarthritis: a prospective case series

Abstract

Varus malalignment in medial compartment osteoarthritis increases load transmission through the diseased compartment, accelerating symptomatic and structural degeneration. High tibial osteotomy remains a joint-preserving option in carefully selected younger and active patients, and dynamic axial external fixation permits gradual, controlled correction while avoiding retained internal implants. This prospective case series included 10 patients (8 women and 2 men) aged 35-55 years with symptomatic medial compartment osteoarthritis and varus deformity. All patients underwent medial opening-wedge high tibial osteotomy below the tibial tuberosity, stabilized with a dynamic axial external fixator. Gradual correction was initiated on postoperative day 7 at approximately 1 mm/day, typically through four incremental adjustments of 0.25 mm every 6 hours, and patients were mobilized early with walker support. Clinical outcomes were assessed using the visual analog scale for pain, the knee injury and Osteoarthritis Outcome Score pain and function subscales, and the Oxford knee score, with a minimum follow-up of 12 months. The mean correction achieved was 8-10 degrees of valgus, with radiological union occurring within 8-12 weeks. The mean VAS pain score improved from 6.8±0.9 preoperatively to 1.6±0.7 at 12 months; KOOS pain improved from 54.2±6.1 to 82.4±5.8, KOOS function from 51.6±5.4 to 79.7±6.2, and the Oxford knee score from 19.4±3.2 to 39.6±3.5. No pin-tract infection, fixation failure, loss of correction, or neurovascular injury was observed. One patient sustained a lateral cortex fracture classified as Takeuchi type II, without compromise to eventual union or need for conversion to alternative fixation. This case series describes an initial experience with dynamic axial external fixator-assisted high tibial osteotomy, demonstrating controlled correction, radiological union within the observed period, and a limited complication profile in this selected cohort; larger studies with longer follow-up and complete patient-level radiographic data are warranted.