Regional differences in body mass index with effect on one-year outcome scores in patients undergoing total hip arthroplasty

Introduction Obesity is known to influence surgical risk in total hip replacement (THR), with increased Body Mass Index (BMI) leading to elevated risk of complications and poorer outcome scores. Using a multinational trial data of a single implant, we assess the impact of BMI and regional variations on Harris Hip scores (HHS). Method We assessed BMI in 11 regional centres and associations with HHS at one year. Data were collected from 744 patients prospectively from 11 centres in the UK, Germany, Switzerland, Austria, New Zealand and Netherlands as part of a multicentre outcome trial. All Arthroplasties used RM Pressfit vitamys components (Mathys, Switzerland). Demographic, operative data and HHS were analysed with General Linear Model Anova, Minitab 16 (Minitab Inc, Pennsylvania). Results 744 patients were included with mean age 70.0yrs (30.5–93.1, SD 10yrs) with 58.3% female distribution. Mean BMI was 27.7 (16.7–47.1 SD 4.7). The most frequent approach was Posterior in 48.5% cases, Anterior 18.1%, Anterolateral 16.9% and Lateral 15.7%. The study included patients from Austria 6.4%, Germany 20.2%, Netherlands 34.6%, NZ 6.9%, Switzerland 24.2% and UK 39.5%. The greatest proportion of high risk BMI >40 were performed in the UK 4.4% and NZ 5.9% with Germany and the Netherlands operating on high BMI patients 30) patients at 39%. The greatest proportion of BMI Higher BMI was associated with improvements in HHS (p=0.043). Age and Approach had no influence on outcome scores. Discussion Higher BMI positively correlates with a greater improvement in Harris Hip score showing that obese patients benefit more from THR. No differences were observed with age, approach or gender. Conclusion Although higher risk, this study shows obese patients benefit more from THR.