title: Usefulness of histological analysis for predicting the presence of microorganisms at the time of reimplantation after hip resection arthroplasty for the treatment of infection.
abstract: BACKGROUND
  Appropriate interpretation of a frozen section has a relatively high specificity and sensitivity for the diagnosis of infection when septic loosening of a prosthesis is suspected. However, its usefulness for predicting the presence of microorganisms at the time of reimplantation after hip resection arthroplasty for the treatment of infection is not well defined. The aim of the present study was to evaluate the usefulness of histological analysis in this situation.
  
  
  METHODS
  From January 2002 to February 2006, a total of twenty-one patients underwent reimplantation after hip resection arthroplasty for the treatment of infection. Histological studies and cultures of specimens of periprosthetic tissue that had been obtained at the time of reimplantation were retrospectively reviewed. The results of culture were considered positive when the same microorganism was isolated in at least two samples. Two histological criteria were used to diagnose infection: (1) Criterion A (the Feldman criterion), defined as the presence of at least five neutrophils per high-power field (x400) in at least five separate microscopic fields and (2) Criterion B (the Athanasou criterion), defined as the presence of at least one neutrophil per high-power field (x400), on average, after examination of ten microscopic fields. The sensitivity, specificity, positive predictive value, and negative predictive value of each of these criteria were calculated with use of microbiological results as the gold standard for defining infection.
  
  
  RESULTS
  Seven of the twenty-one patients had a positive result on culture, and the most common microorganism was coagulase-negative staphylococcus. The sensitivity, specificity, positive predictive value, and negative predictive value of frozen-section analysis were 28.5%, 100%, 100%, and 73.6%, respectively, according to the Feldman criterion and 71.4%, 64.2%, 50%, and 81.8%, respectively, according to the Athanasou criterion. The numbers of lymphocytes and plasma cells did not help in the diagnosis of infection. Fibrosis was more common in patients without an infection.
  
  
  CONCLUSIONS
  The probability of infection is high when at least five neutrophils per high-power field are found in the periprosthetic tissue, but it is not possible to rule out infection when the number of neutrophils is less than five.
  
  
  METHODS
  Diagnostic Level I.
authors.affiliation: Department of Orthopaedics and Traumatology, Hospital Clinic, University of Barcelona, C/Villarroel 170, 08036 Barcelona, Spain. gbori@clinic.ub.es
authors.forename: Guillem
authors.initials: G
authors.lastname: Bori
authors.forename: Alex
authors.initials: A
authors.lastname: Soriano
authors.forename: Sebastián
authors.initials: S
authors.lastname: García
authors.forename: Carme
authors.initials: C
authors.lastname: Mallofré
authors.forename: Josep
authors.initials: J
authors.lastname: Riba
authors.forename: Josep
authors.initials: J
authors.lastname: Mensa
mesh_terms: D000368:Aged; D019644:Arthroplasty, Replacement, Hip; D005260:Female; D005355:Fibrosis; D005629:Frozen Sections; D006801:Humans; D008297:Male; D008875:Middle Aged; D011475:Prosthesis Failure; D016459:Prosthesis-Related Infections / Q000382:microbiology / Q000473:pathology* / Q000601:surgery*; D012092:Replantation; D012680:Sensitivity and Specificity