Poor nutritional status is a preventable condition frequently associated with low body mass index (BMI). The purpose of this study is to comparatively analyze low (≤19 kg/m2) and normal (19-24.9 kg/m2) BMI cohorts, examining if a correlation between BMI, postoperative outcomes, and resource utilization exists.
Discharge data from the 2006-2012 National Inpatient Sample were used for this study. A total of 3550 total hip arthroplasty (THA) and 1315 total knee arthroplasty (TKA) patient samples were divided into 2 cohorts, underweight (≤19 kg/m2) and normal BMI (19-24.9 kg/m2). Using the Elixhauser Comorbidity Index, all cohorts were matched for 27 comorbidities. In-hospital postoperative outcomes and resource utilization among the cohorts was then comparatively analyzed. Multivariate analyses and chi-squared tests were generated using SAS software. Significance was assigned at P < .05.
Underweight patients undergoing THA were at higher risk of developing postoperative anemia and sustaining cardiac complications. In addition, underweight patients had a decreased risk of developing postoperative infection. Resource utilization in terms of length of stay and hospital charge were all higher in the underweight THA cohort. Similarly, in the underweight TKA cohort, a greater risk for the development of hematoma/seroma and postoperative anemia was observed. Underweight TKA patients incurred higher hospital charge and were more likely to be discharged to skilled nursing facilities.
Our results indicate that low-BMI patients were more likely to have postoperative complications and greater resource utilization. This serves a purpose in allowing orthopedic surgeons to better predict patient outcomes and improve treatment pathways designed toward helping various patient demographics.