Survival and Risk Factor Analysis of Medial Open Wedge High Tibial Osteotomy for Unicompartment Knee Osteoarthritis

Abstract

The purpose of this retrospective study was to evaluate the survival rates and analyze the factors that affect survival rate after primary treatment with medial open wedge high tibial osteotomy (MOWHTO) for medial unicompartmental knee osteoarthritis. Clinical evaluation using Knee Society Score (KSS) and Western Ontario and McMaster Universities Osteoarthritis Index score and radiographic evaluation, including mechanical axis, were done before and after surgery. The main failure criteria for survival included the conversion to total knee arthroplasty or KSS of <60 points. Furthermore, risk factors that affected the survival after MOWHTO were analyzed. Three hundred thirty-nine knees were included after a minimum of 5years' follow-up. Their mean age was 56years, and mean follow-up duration was 9.6years. The mean KSS and Western Ontario and McMaster Universities Osteoarthritis Index scores were significantly improved after surgery (87.3 and 18.5 points at 5years and 81.7 and 23.6 points at 10years). The mean hip-knee-ankle (HKA) angle was corrected from 7.2° varus to 3.4° valgus 1year after surgery, which was maintained until 10years after surgery (2.9° valgus at 5years and 2.3° valgus at 10years, P > .05). Using Kaplan-Meier survival estimates, the probability of survival for MOWHTO was 96.8% at 5years, 87.1% at 10years, and 85.3% at 13years. The multivariate regression analysis revealed that age ≥65years (hazard ratio [HR]= 2.34, P= .046), medial compartment cartilage damage International Cartilage Repair Society grade ≥4 (HR= 2.46, I= .045), lateral compartment cartilage damage International Cartilage Repair Society grade≥2 (HR= 3.38, P= .006), postoperative HKA angle <0° (HR= 4.69, P < .001) were associated with failure. MOWHTO seems to be a good treatment option for young and active patients with medial knee osteoarthrosis and varus alignment, with acceptable survival rates and satisfactory outcomes. Age ≥65years, grade 4 cartilage damage in medial compartment, grade ≥2 cartilage damage in lateral compartment, and undercorrection of HKA angle appear to be significant risk factors associated with failure. Level IV: retrospective case series.