Overweight patients benefit from high tibial osteotomy to the same extent as patients with normal weights but show inferior mid-term results

PURPOSE: The purpose of this prospective study was to analyze the impact of obesity on the clinical and radiological outcomes 6 years after open-wedge high tibial osteotomy (HTO). METHODS: A total of 120 prospectively recorded patients with medial compartment osteoarthritis underwent open-wedge HTO between 2008 and 2011. The study cohort was frequently examined over a minimum of a 6-year follow-up. The cohort was divided into three groups according to body mass index (BMI): normal weight patients (BMI < 25 kg/m(2)), pre-obese patients (BMI 25–30 kg/m(2)) and obese patients (BMI > 30 kg/m(2)). Clinical and functional outcomes (Oxford Knee Score, Hospital for Special Surgery Score, Lequesne Score, Tegner Activity Scale), subjective health-related quality of life (SF-36), change in mechanical limb alignment (mTFA) as well as conversion to unicompartmental or total knee arthroplasty (TKA) were evaluated. To compare clinical scoring between the groups, univariate variance analysis was applied. Changes in outcome variables over time were analyzed with dependent t tests. RESULTS: From 120 patients, 85 were followed-up over a 6.7-year period on average (6–11.8 years) after HTO. The mean BMI was 28.6 ± 4.6 kg/m(2). Each group showed a significant pre- to postoperative increase in all recorded scores (p < 0.05). In absolute terms, both mental and clinical scores of overweight patients did not reach the peak values of the normal weighted population during the period of observation. There was a conversion to TKA in 10.5% after an average of 50.1 ± 25.0 months following surgery. A total of five complications occurred without significant differences (BMI < 25: n = 1, BMI 25–30: n = 2, BMI > 30: n = 2; n.s.). There was a mean pre- to postoperative (six weeks after surgery) correction difference of 6.9° ± 3.2° (mTFA) with higher loss of correction over time in overweight patients. CONCLUSION: In terms of clinical outcome and health-related quality of life, overweight patients may receive a benefit from open-wedge HTO to the same extent as patients with normal weights and show similar complication rates. However, they have inferior preoperative clinical and functional results and mid-term results after open-wedge HTO compared to patients with normal weights. LEVEL OF EVIDENCE: Level III.