title: Leukocytosis is common after total hip and knee arthroplasty.
abstract: BACKGROUND
  Postoperative infection is a potentially devastating complication after THA and TKA. In the early postoperative period, clinicians often find nonspecific indicators of infection. Although leukocytosis may be a sign of a developing infection in the early postoperative period, it may also be part of a normal surgical response. QUESTIONS AND PURPOSES: We determined (1) the natural history of white blood cell values after primary THA and TKA, (2) factors associated with early postoperative leukocytosis, and (3) the predictive value of white blood cell count for early postoperative periprosthetic joint infection.
  
  
  METHODS
  Using our institutional database, we identified all THA and TKA cases between January 2000 and December 2008. We determined the incidence of leukocytosis and characterized the natural history of postoperative white blood cell counts. We then investigated potential indicators of postoperative leukocytosis, including development of early periprosthetic infection.
  
  
  RESULTS
  The average postoperative white blood cell count increased to approximately 3 × 10(6) cells/μL over the first 2 postoperative days and then declined to a level slightly higher than the preoperative level by Postoperative Day 4. The incidence of postoperative leukocytosis for all patients was 38%. Factors associated with postoperative leukocytosis included TKA, bilateral procedures, older age, and higher modified Charlson Comorbidity Index. The sensitivity and specificity of white blood cell count for diagnosing early periprosthetic infection were 79% and 46%, respectively.
  
  
  CONCLUSIONS
  Postoperative leukocytosis is common after THA and TKA and represents a normal physiologic response to surgery. In the absence of abnormal clinical signs and symptoms, postoperative leukocytosis may not warrant further workup for infection.
  
  
  METHODS
  Level III, diagnostic study. See Guidelines for Authors for a complete description of levels of evidence.
authors: The Rothman Institute of Orthopaedics at Thomas Jefferson University Hospital, 925 Chestnut Street, 5th Floor, Philadelphia, PA 19107, USA.
authors: Gregory K
authors: GK
authors: Deirmengian
authors: Benjamin
authors: B
authors: Zmistowski
authors: Christina
authors: C
authors: Jacovides
authors: Joseph
authors: J
authors: O'Neil
authors: Javad
authors: J
authors: Parvizi
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects*; D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects*; D002648:Child; D015897:Comorbidity; D016208:Databases, Factual; D005260:Female; D006801:Humans; D007958:Leukocyte Count; D007964:Leukocytosis / Q000175:diagnosis* / Q000453:epidemiology / Q000209:etiology; D008297:Male; D008875:Middle Aged; D010414:Pennsylvania / Q000453:epidemiology; D011183:Postoperative Complications; D011237:Predictive Value of Tests; D016459:Prosthesis-Related Infections / Q000097:blood / Q000175:diagnosis* / Q000453:epidemiology; D055815:Young Adult