Abstract
Background
This study aimed to investigate the effect of body mass index (BMI) on functional outcome following hip preservation surgery using the U.K. Non-Arthroplasty Hip Registry (NAHR).
Methods
Data on adult patients who underwent hip arthroscopy or periacetabular osteotomy (PAO) between January 2012 and December 2018 was extracted from the UK Non-Arthroplasty Hip Registry dataset allowing a minimum of 12 months follow-up. Data is collected via an online clinician and patient portal. Outcomes comprised EuroQol-5 Dimensions (EQ-5D) index and the International Hip Outcome Tool 12 (iHOT-12), preoperatively and at 6 and 12 months
Results
A total of 6,666 patients were identified with BMI data available in 52%, comprising 3,220 arthroscopies and 277 PAO. Patients were divided into WHO groups: <25kg/m2 (n=1,745 (49.8%)), 25–30kg/m2 (n=1,199 (34.2%)), and ≥30kg/m2 (n=562 (16.0%)). Patients with higher BMI tended to be older. Pre-operative, 6 and 12-month follow-up were available for 91%, 49% and 45% of cases respectively. Higher BMI was associated with significantly poorer baseline, 6- and 12-month outcomes (12-month mean iHOT-12 score: <25kg/m2 = 62.3 (95%CI 60.4 to 64.3), 25–30kg/m2 = 57.3 (95%CI 55.0 to 59.7), ≥30kg/m2 = 54.7 (95%CI 51.1 to 58.2)). However, all groups saw similar and statistically significant improvement in pre- vs post-op scores (mean 12-month iHOT-12 gain: <25kg/m2 = +27.1 (95%CI 25.1 to 29.0), 25–30kg/m2 = +26.5 (95%CI 24.0 to 29.0), ≥30kg/m2 = +26.8 (95%CI 23.2 to 30.4), between-group p = 0.9). EQ-5D outcomes followed the same trend. Modelling for age, sex and procedure we found no significant difference in 12-month iHOT-12 gain between BMI groups.
Conclusion
Whilst obese patients started from, and achieved lower post-operative raw functional scores, all BMI groups saw similar and significant degrees of improvement in functional outcome post-operatively. Obesity should not be considered a contraindication to hip preservation surgery.
