Underweight Body Mass Index Is Associated With Increased In-Hospital Complications and Length of Stay After Revision Total Joint Arthroplasty

J Am Acad Orthop Surg. 2022 Oct 15;30(20):984-991. doi: 10.5435/JAAOS-D-22-00214. Epub 2022 Jul 11.


Introduction: The purpose of this study was to assess the impact of underweight status on in-hospital postoperative outcomes and complications after revision total joint arthroplasty (rTJA) of the hip and knee.

Methods: Data from the National Inpatient Sample were used to identify all patients undergoing rTJA in the United States between 2006 and 2015. Patients were divided into two groups based on a concomitant diagnosis of underweight body mass index and a control normal weight group. Propensity score analysis was performed to determine whether underweight body mass index was a risk factor for in-hospital postoperative complications and resource utilization.

Results: A total of 865,993 rTJAs were analyzed. Within the study cohort, 2,272 patients were classified as underweight, whereas 863,721 were classified as a normal weight control group. Underweight patients had significantly higher rates of several comorbidities compared with the control cohort. Underweight patients had significantly higher rates of any complication (49.98% versus 33.68%, P = 0.0004) than normal weight patients. Underweight patients also had significantly greater length of stay compared with normal weight patients (6.50 versus 4.87 days, P < 0.0001).

Conclusion: Underweight patients have notably higher rates of any complication and longer length of stay after rTJA than those who are not underweight. These results have important implications in preoperative patient discussions and perioperative management. Standardized preoperative protocols should be developed and instituted to improve outcomes in this patient cohort.

MeSH terms

  • Arthroplasty, Replacement, Hip* / adverse effects
  • Arthroplasty, Replacement, Knee* / adverse effects
  • Body Mass Index
  • Hospitals
  • Humans
  • Length of Stay
  • Postoperative Complications / epidemiology
  • Postoperative Complications / etiology
  • Retrospective Studies
  • Risk Factors
  • United States