Long-term outcomes and predictors of failure after medial opening-wedge high tibial osteotomy: a 138-knee cohort with up to 10-year follow-up.

Abstract

To quantify 10-year survivorship after medial opening-wedge high tibial osteotomy (MOWHTO) and identify modifiable predictors of conversion to total knee arthroplasty (TKA), focusing on joint-line obliquity (JLO), obesity and smoking. Single-centre retrospective cohort of 138 MOWHTOs (2007-2022) with Ahlbäck I-II medial osteoarthritis, correctable varus and ≥24-month follow-up. Long-leg radiographs measured alignment, JLO (tibial plateau angle relative to floor) and medial proximal tibial angle (MPTA; pre-/post-operative). TKA conversion. Kaplan-Meier estimated survivorship; multivariable Cox with proportional-hazards checks and Fine-Gray competing-risk analyses were used. A sensitivity model added post-operative JLO and deviation from planned hip-knee-ankle (HKA) alignment; a complementary model evaluated post-operative MPTA >95°. Mean age 46.9 years; mean follow-up 83.4 months. Twelve of 138 knees (8.7 %) underwent TKA; survivorship was 98.5 % at 2 years, 90.4 % at 5 years and 79.7 % at 10 years. Independent predictors of conversion were age (HR 1.09/year), BMI ≥30 (HR 1.12), smoking (HR 2.85) and pre-operative JLO >5° (HR 1.32) (all p < 0.05). Post-operative MPTA >95° was not significant. Findings were consistent in competing-risk analyses. Complications occurred in 13.0 % (hinge fracture 5.1 %, delayed/non-union 3.6 %, infection 4.3 %). WOMAC improved from 45.8 to 22.1 (p < 0.001); all KOOS domains improved (p < 0.001); satisfaction 86.2 %. MOWHTO achieved ∼80 % 10-year TKA-free survivorship with durable functional gains. Older age, obesity, smoking and increased pre-operative JLO predicted earlier conversion; post-operative MPTA >95° was not significant. Considering MPTA thresholds alongside pre-operative JLO may help avoid excessive obliquity and optimise longevity. Level IV (retrospective cohort/case series).