Opening-wedge high tibial osteotomy without bone grafting in severe varus osteoarthritic knee. Rate and risk factors of non-union in 41 cases

Introduction: 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 degrees), although rates and risk factors of non-union are not known. The present retrospective study compared OWHTO with correction <10 degrees versus >10 degrees, with a view to determining: (1) complications rates (non-union) according to degree of correction, and (2) risk factors for such complications. Hypothesis: OWHTO with correction greater than 10 degrees without graft shows normal consolidation and allows early weight-bearing. Material and method: 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. Results: 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 degrees +/- 3 degrees (range, 167-178 degrees) and mean correction was 10.7 degrees +/- 2.7 degrees (range, 5-15 degrees). There were 27 corrections of 10 degrees or more, and 14 less than 10 degrees. At 3 months, mean HKA was 182.9 degrees +/- 2.5 degrees (range, 178-187 degrees). 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 (A= 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 degrees (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)). Discussion/conclusion: Obesity and initial lateral cortex fracture appeared as risk factors for nonconsolidation of OWHTO with large correction. Systematic bone or bone-substitute grafting may therefore be considered in this population in case of >10 degrees correction. (C) 2018 Elsevier Masson SAS. All rights reserved.