title: Early return to surgery for evacuation of a postoperative hematoma after primary total knee arthroplasty.
abstract: BACKGROUND
  Development of a postoperative hematoma is a reported complication after primary total knee arthroplasty. However, little is known about the clinical outcomes in patients who require surgical evacuation of an acute hematoma. The purpose of this study was to determine the incidence, risk factors, and long-term sequelae of postoperative hematomas requiring surgical evacuation.
  
  
  METHODS
  From 1981 to 2004, 17,784 primary total knee arthroplasties were performed at our institution. Forty-two patients (forty-two knees) returned to the operating room within thirty days of the index arthroplasty for evacuation of a postoperative hematoma. A case-control study, with forty-two patients matched one-to-one with forty-two control subjects, was performed to attempt to identify risk factors for the development of postoperative hematoma requiring surgical evacuation.
  
  
  RESULTS
  The rate of return to surgery within thirty days for evacuation of a postoperative hematoma was 0.24% (95% confidence interval, 0.17% to 0.32%). For patients undergoing postoperative hematoma evacuation, the two-year cumulative probabilities of undergoing subsequent major surgery (component resection, muscle flap coverage, or amputation) or having a deep infection develop were 12.3% (95% confidence interval, 1.6% to 22.4%) and 10.5% (95% confidence interval, 0.2% to 20.2%), respectively. In contrast, for knees without early hematoma evacuation, the two-year cumulative probabilities were 0.6% (95% confidence interval, 0.5% to 0.7%) and 0.8% (95% confidence interval, 0.6% to 0.9%), respectively (p < 0.001 for both outcomes). A history of a bleeding disorder was identified as having a significant association with the development of a hematoma requiring surgical evacuation (p = 0.046).
  
  
  CONCLUSIONS
  Patients who return to the operating room within thirty days after the index total knee arthroplasty for evacuation of a postoperative hematoma are at significantly increased risk for the development of deep infection and/or undergoing subsequent major surgery. These results support all efforts to minimize the risk of postoperative hematoma formation.
authors.affiliation: Mayo Clinic, 200 First Street S.W., Rochester, MN 55905, USA.
authors.forename: Daniel D
authors.initials: DD
authors.lastname: Galat
authors.forename: Scott C
authors.initials: SC
authors.lastname: McGovern
authors.forename: Arlen D
authors.initials: AD
authors.lastname: Hanssen
authors.forename: Dirk R
authors.initials: DR
authors.lastname: Larson
authors.forename: Jeffrey R
authors.initials: JR
authors.lastname: Harrington
authors.forename: Henry D
authors.initials: HD
authors.lastname: Clarke
mesh_terms: D000368:Aged; D019645:Arthroplasty, Replacement, Knee; D005260:Female; D006406:Hematoma / Q000209:etiology / Q000601:surgery*; D006801:Humans; D007239:Infections / Q000209:etiology; D008297:Male; D011183:Postoperative Complications; D012086:Reoperation; D012307:Risk Factors; D016896:Treatment Outcome