The Role of BMI in Hip Fracture Surgery.

Introduction: Obesity is an oft-cited cause of surgical morbidity and many institutions require extensive supplementary screening for obese patients prior to surgical intervention. However, in the elderly patients, obesity has been described as a protective factor. This article set out to examine the effect of body mass index (BMI) on outcomes and morbidity after hip fracture surgery.

Methods: The National Surgical Quality Improvement Program database was queried for all patients undergoing 1 of 4 surgical procedures to manage hip fracture between 2008 and 2012. Patient demographics, BMI, and known factors that lead to poor surgical outcomes were included as putative predictors for complications that included infectious, cardiac, pulmonary, renal, and neurovascular events. Using χ2 tests, 30-day postoperative complication rates were compared between 4 patient groups stratified by BMI as low weight (BMI < 20), normal (BMI = 20-30), obese (BMI = 30-40), and morbidly obese (BMI > 40).

Results: A total of 15 108 patients underwent surgery for hip fracture over the examined 5-year period. Of these, 18% were low weight (BMI < 20), 67% were normal weight (BMI = 20-30), 13% were obese (BMI = 30-40), and 2% were morbidly obese (BMI > 40). The low-weight and morbidly obese patients had both the highest mortality rates and the lowest superficial infection rates. There was a significant increase in blood transfusion rates that decreased linearly with increasing BMI. Deep surgical site infection and renal failure increased linearly with increasing BMI, however, these outcomes were confounded by comorbidities.

Conclusion: This study demonstrates that patients at either extreme of the BMI spectrum, rather than solely the obese, are at greatest risk of major adverse events following hip fracture surgery. This runs contrary to the notion that obese hip fracture patients automatically require additional preoperative screening and perioperative services, as currently implemented in many institutions.