Using locking plates in opening-wedge high tibial osteotomy (OWHTO) via a medial opening theoretically allows early weight-bearing without need for bone or bone-substitute grafting. It incurs a risk of non-consolidation in case of large correction (>10°), although rates and risk factors of non-union are not known. The present retrospective study compared OWHTO with correction <10° versus >10°, with a view to determining: (1) complications rates (non-union) according to degree of correction, and (2) risk factors for such complications.

OWHTO with correction greater than 10° without graft shows normal consolidation and allows early weight-bearing.

Forty-one patients treated by OWHTO for medial osteoarthritis of the knee between January 2101 and November 2015 were included in a retrospective study. HKA angle was assessed by long-leg axis radiographs, preoperatively and at 3 months. Clinical and radiological follow-up at 6 weeks, 3 months and 6 months assessed consolidation in terms of >40% filling of the osteotomy site. Partial (contact) weight-bearing was allowed from the first postoperative day, with full weight-bearing at 6 weeks.

Mean patient age was 59±5 years. Mean body-mass index (BMI) was 30.3±5.2; 17 patients (41.5%) had BMI >30. Mean initial HKA angle was 173.5°±3° (range, 167–178°) and mean correction was 10.7°±2.7° (range, 5–15°). There were 27 corrections of 10° or more, and 14 less than 10°. At 3 months, mean HKA was 182.9°±2.5° (range, 178–187°). Twelve cases showed lateral tibial cortex fracture after opening. Thirty-six patients (87.8%) showed consolidation, at a mean 5±3 months. Five patients showed osteotomy site non-union; in all these cases, the lateral cortex was broken initially (P=0.003); all had BMI >30 (mean, 37.2±3.8; P<0.03); none were smokers. On univariate analysis, lateral tibial cortex fracture (OR=10; 95% CI, (1.59–196.30)), BMI >30 (OR=1.18; 95% CI, (1.03–1.41)) and correction ≥10° (OR=10.50; 95% CI, (2.49–53.86)) were associated with delayed consolidation. On multivariate analysis, only degree of osteotomy was significantly associated with delayed consolidation (OR=11.51; 95% CI, (2.13–95.74)).

Obesity and initial lateral cortex fracture appeared as risk factors for non-consolidation of OWHTO with large correction. Systematic bone or bone-substitute grafting may therefore be considered in this population in case of >10° correction.

IV, prospective cohort study.