Is obesity a risk factor for extended length of stay and readmission after total hip arthroplasty?

Background: The burden of hospital length of stay and readmission rates for total hip arthroplasty patients has been scrutinized as a source of potentially preventable cost. Attempts to determine and minimize the risks for increased length of stay and readmission rates have focused on patients' comorbidities, particularly obesity. While many studies have demonstrated obesity's connection with total hip arthroplasty complications, there is conflicting data on obesity's effect on length of stay and readmission rates. The purpose of this case-control study was to determine if obesity was independently associated with greater odds of increased length of stay and readmission rates when compared with other comorbidities. Methods: A total of 1,433 surgeries performed in 1,265 patients from our institution (622 males, 811 females) were studied. Readmissions were defined as any cause re-hospitalization within 90 days. Analysis of variables was used to determine which patient demographics and comorbidities were associated with body mass index. Odds ratios for risk of readmission and increased length of stay (>= 5 days) were calculated for each body mass index category and possible confounders. Multivariable logistic regression with backward elimination was used to examine body mass index >= 40 and >= 50 as independent risk factors after adjusting for the possible confounders. All tests with a P value <0.05 were considered statistically significant. Results: The following patient factors were associated with increased body mass index: younger age, black race, hypertension, diabetes mellitus, mental illness, chronic obstructive pulmonary disease, and coronary artery disease, length of stay. Obesity did not confer an increased odds of extended length of stay at any level and only conferred independently increased odds of readmission at body mass index >= 50, although the sample size was small for that group (n=11), while several comorbidities including asthma, coronary artery disease, congestive heart failure, peripheral vascular disease, chronic obstructive pulmonary disorder, and mental illness were all associated with both increased odds of extended length of stay and readmission. Hypertension was associated with increased odds of readmission only and diabetes was associated with increased odds of extended length of stay only. Conclusions: When compared with the other comorbidities examined in this study, obesity was not independently associated with a significantly increased odds of the adverse outcomes extended length of stay and readmission below a body mass index of 50. This suggests that more effort should be spent on optimizing these other comorbidities prior to total hip arthroplasty rather than on lowering body mass index.