Public Health Nutrition

Research Paper

Impact of body mass on hospital resource use in total hip arthroplasty

John A Batsisa1 c1, James M Naessensa2, Mark T Keegana3, Amy E Wagiea2, Paul M Huddlestona4 and Jeanne M Huddlestona2a5

a1 Section of General Internal Medicine, Department of Medicine, Dartmouth-Hitchcock Medical Center, 1 Medical Center Drive, Lebanon, NH 03756, USA

a2 Division of Health Care Policy and Research, Mayo Clinic College of Medicine, Rochester, MN, USA

a3 Department of Anesthesia, Mayo Clinic College of Medicine, Rochester, MN, USA

a4 Department of Orthopedic Surgery, Mayo Clinic College of Medicine, Rochester, MN, USA

a5 Division of Hospital Medicine, Department of Medicine, Mayo Clinic College of Medicine, Rochester, MN, USA


Objective To determine the impact of BMI on post-operative outcomes and resource utilization following elective total hip arthroplasty (THA).

Design A retrospective cohort analysis on all primary elective THA patients between 1996 and 2004. Primary outcomes investigated using regression analyses included length of stay (LOS) and costs (US dollars).

Setting Mayo Clinic Rochester, a tertiary care centre.

Subjects Patients were stratified by pre-operative BMI as normal (18·5–24·9 kg/m2), overweight (25·0–29·9 kg/m2), obese (30·0–34·9 kg/m2) and morbidly obese (≥35·0 kg/m2). Of 5642 patients, 1362 (24·1 %) patients had a normal BMI, 2146 (38·0 %) were overweight, 1342 (23·8 %) were obese and 792 (14·0 %) were morbidly obese.

Results Adjusted LOS was similar among normal (4·99 d), overweight (5·00 d), obese (5·02 d) and morbidly obese (5·17 d) patients (P = 0·20). Adjusted overall episode costs were no different (P = 0·23) between the groups of normal ($17 211), overweight ($17 462), obese ($17 195) and morbidly obese ($17 655) patients. Overall operative and anaesthesia costs were higher in the morbidly obese group ($5688) than in normal ($5553), overweight ($5549) and obese ($5593) patients (P = 0·03). Operating room costs were higher in morbidly obese patients ($3418) than in normal ($3276), overweight ($3291) and obese ($3340) patients (P < 0·001). Post-operative costs were no different (P = 0·30). Blood bank costs differed (P = 0·002) and were lower in the morbidly obese group ($180) compared with the other patient groups (P < 0·05). Other differences in costs were not significant. Morbidly obese patients were more likely to be transferred to a nursing home (24·1 %) than normal (18·4 %), overweight (17·9 %) or obese (16·0 %) patients (P = 0·001 each). There were no differences in the composite endpoint of 30 d mortality, re-admissions, re-operations or intensive care unit utilization.

Conclusions BMI in patients undergoing primary elective THA did not impact LOS or overall institutional acute care costs, despite higher operative costs in morbidly obese patients. Obesity does not increase resource utilization for elective THA.

(Received July 16 2008)

(Accepted January 07 2009)


c1 Corresponding author: Email