Predictors for Unfavorable Early Outcomes in Elective Total Hip Arthroplasty: Does Extreme Body Mass Index Matter?

BACKGROUND: Studies of previous cohorts have demonstrated a controversial association between extreme body mass index (BMI) and complication rates following total hip arthroplasty (THA). The purpose of this study was to compare 30-day perioperative complications in underweight (BMI <18.50 kg/m(2)), normal-weight (BMI 18.50–24.99 kg/m(2)), overweight (BMI 25.00–29.99 kg/m(2)), class I obesity (BMI 30.00–34.99 kg/m(2)), and morbidly obese (BMI ≥35.00 kg/m(2)) groups. METHODS: We performed a cohort study including patients who underwent unilateral primary THA by a single surgeon between January 2010 and December 2015 at our institution. We assessed 30-day complications, operation time, operative blood loss, and length of hospital stay. RESULTS: We identified 1565 primary THAs that were performed in patients with varying BMI levels. Compared with the normal-weight patients, the morbidly obese group had a higher 30-day complication rate (8.9% vs. 2.4%), longer operative time (79 minutes vs. 70 minutes), and more blood loss (376 mL vs. 302 mL). Underweight patients did not present any 30-day complications, and there were no differences among underweight and normal-weight patients regarding complication rates, operative time, or blood loss. The mean length of hospital stay was comparable among the different BMI groups. In the multivariate regression model, higher BMI was not associated with a higher risk of 30-day complications. Independent risk factors for 30-day complications were advanced age, prolonged operative time, and cardiovascular comorbidities. CONCLUSION: Although increased operative time, blood loss, and perioperative complications were seen in the morbidly obese patients, BMI alone was not an independent risk factor for a higher 30-day complication rate. Therefore, our data suggest clinicians should make elderly patients aware of increased 30-day complications before the procedure, particularly those with cardiovascular comorbidities. Withholding THA solely on the basis of BMI is not justified.