Association of obesity with thromboembolic complications after hip fracture surgery: a tertiary center retrospective cohort study (HipCLOTS)

BACKGROUND: Patients undergoing hip fracture surgery are at an increased risk of thromboembolic complications, but the impact of obesity on the outcomes remains poorly understood. We aimed to investigate arterial and venous thromboembolic complications following hip fracture surgery and their association with body mass index (BMI). MATERIALS AND METHODS: In this retrospective cohort study at a tertiary referral center, patients aged ≥60 years who underwent hip fracture surgery between 2010 and 2020 were categorized by BMI (underweight, normal weight, overweight, and obese). The primary outcome was the occurrence of thromboembolic complications within 90 days post-surgery. The secondary outcomes included systemic complications and all-cause mortality within a year. Regression analysis was performed to assess BMI's association with outcomes, considering the competing risk of death. RESULTS: Out of the 1853 patients, 214 (11.5%) experienced 90-day thromboembolic complications. Myocardial infarction was most prevalent in individuals in the underweight category (7.4%; n = 20), followed by those with obesity (6.4%; n = 13). Deep venous thrombosis and pulmonary embolism occurred most frequently in individuals with overweight (7.4%; n = 33), whereas ischemic stroke was more common in patients with obesity (2.5%; n = 5). In adjusted competing risk analyses, individuals with overweight and obesity had a higher 90-day thromboembolic risk than those with normal BMI, with sub-hazard ratios of 1.80 (95% CI: 1.04-3.10; P = 0.04) and 2.39 (95% CI: 1.28-4.49; P = 0.006), respectively. Compared to individuals with a normal BMI, those in the underweight category had higher odds (OR: 1.6; 95% CI: 1.2-2.3; P = 0.002), while those with obesity had lower odds (OR: 0.5; 95% CI 0.3-0.8; P = 0.005) of 1-year mortality. CONCLUSIONS: BMI is significantly associated with 90-day thromboembolic complications and 1-year mortality following hip fracture surgery. This highlights the need for prolonged thromboprophylaxis and regular follow-up in this patient group.