Session V - Pelvis
Fri., 10/8/04 Spine & Pelvis, Paper #27, 4:42 pm
Body Mass Index (BMI): A Predictor of Perioperative Complications after Operative Treatment of Acetabular Fractures in the Obese
Purpose: The epidemic rise in the rate of obesity in the United States is an increasingly recognized major public health issue. Morbidly obese patients have been reported to have a higher incidence of complications after blunt trauma. The purpose of this study was to determine whether body mass index (BMI) could be used as a predictor for early complications after the operative treatment of acetabular fractures in the obese patient.
Methods: A retrospective review was performed of the records of 169 consecutive patients with operatively treated acetabular fractures. The 126 male and 43 female patients (average age, 41 years) that comprised the subject group were divided into subgroups on the basis of body mass index (BMI) as follows: 47 normal (BMI 25 kg/m2), 47 overweight (BMI = 26 to 29 kg/m2), 55 obese (BMI = 30 to 39 kg/m2) and 20 morbidly obese (BMI 40 kg/m2). Intraoperative outcomes measured included positioning time (PT), estimated blood loss (EBL), and operating time (OR). Postoperative outcomes included length of hospital stay (LOS) and the following adverse events: infection, nerve palsy, deep venous thrombosis (DVT), pulmonary embolus (PE), and heterotopic ossification (HO). Multivariate general linear models were used to test for the relationship between BMI as a continuous measure and perioperative outcomes while controlling for potential intervening variables. Variables that were controlled for included age, sex, fracture type, injury severity score, and surgical approach. For calculation of odds ratios, continuous measures (PT, EBL, OR, LOS) were re-categorized as dichotomous measures by using the median values of the normal weight (BMI 25 kg/m2) subgroup as a cut point. Pearson chi square tests with exact significance were used to compare the incidence of perioperative outcomes by BMI category.
Results: With BMI measured as a continuous variable, significant relationships were identified for positioning time (P <0.001), estimated blood loss (P <0.001), operating time (P <0.001), length of hospital stay (P = 0.005), and incidence of wound infection (P = 0.001). The incidence of HO (P = 0.32), nerve palsy (P = 0.43), and PE (P = 0.20) were not significantly related to BMI. Odds ratio analysis revealed that obese subjects (BMI 30) were 3.5 times more likely to require more than 43 minutes for patient positioning (95% CI, 1.8 to 7.1, P <0.001); 2.1 times more likely to have an EBL >750 cc (95% CI, 1.1 to 4.0, P = 0.03); 2.4 times more likely to have an operative time >4 hours (95% CI, 1.2 to 4.5, P = 0.01); 2.6 times more likely to develop a DVT (95% CI, 1.1 to 5.8, P = 0.03) and 16 times more likely to develop a wound infection (95% CI, 2.0 to 127, P = 0.001).
Discussion/Conclusions: Obesity is gaining increasing recognition as a major public health concern and contributor to complications after blunt trauma. The results of this study demonstrate that obese patients undergoing operative fixation of acetabular fractures are more likely to have longer surgical procedures with a greater blood loss and a higher incidence of complications than a similar cohort of patients whose weight is within normal limits. The BMI is predictive, as incremental increases in this measure were associated with an increased rate of perioperative complications.