title: Relationship between the degree of osteolysis and cultures obtained by sonication of the prostheses in patients with aseptic loosening of a hip or knee arthroplasty.
abstract: BACKGROUND
  The pathogenesis of prosthesis loosening is not well understood. The aim of our study was to sonicate components of joint prostheses removed due to aseptic loosening, culture the sonicate fluid, and to correlate these results with the degree of radiological osteolysis.
  
  
  METHODS
  From January 2008 to June 2009 all consecutive patients who underwent a revision of hip or knee prosthesis due to aseptic loosening were included in the study. Aseptic loosening was established when the patient had radiological signs of loosening without symptoms or signs of infection. The diagnosis was confirmed when histology was negative, and ≥ 5 out of 6 standard cultures of periprosthetic tissue were negative. Bone lysis was measured according to the Paprosky or Engh classifications without knowing the result of sonication cultures. Removed components were placed in sterile bags and immediately transported to the microbiology laboratory and sonicated. Sonicate fluid was cultured and the results were correlated with the degree of bone lysis. The proportion of components with positive sonication culture according to the bone lysis classification was compared using χ(2) test.
  
  
  RESULTS
  A total of 52 patients were included and 123 components were sonicated. In 30 patients at least 1 sonicated component was positive (57.7%) and 44 out of 123 (35.8%) components were positive. The proportion of positive sonication cultures was significantly higher in the group of components with a higher degree of bone lysis of 3 (76.5%) than in those with lower degrees (33.9% for 1 and 24% for 2) (χ(2) test, p = 0.0004).
  
  
  CONCLUSIONS
  Sonication cultures were positive in 57% of patients who underwent revision arthroplasty for aseptic loosening. The percentage of positive sonication cultures was significantly higher in patients with severe osteolysis.
  
  
  METHODS
  level I of Prognostic Studies-Investigating the Effect of a Patient Characteristic on the Outcome of Disease.
authors.affiliation: Department of Microbiology, Hospital Clínic of Barcelona, Barcelona, Spain.
authors.forename: Josep M
authors.initials: JM
authors.lastname: Sierra
authors.forename: Sebastián
authors.initials: S
authors.lastname: García
authors.forename: Juan C
authors.initials: JC
authors.lastname: Martínez-Pastor
authors.forename: Xavier
authors.initials: X
authors.lastname: Tomás
authors.forename: Xavier
authors.initials: X
authors.lastname: Gallart
authors.forename: Jordi
authors.initials: J
authors.lastname: Vila
authors.forename: Guillem
authors.initials: G
authors.lastname: Bori
authors.forename: Francisco
authors.initials: F
authors.lastname: Maculé
authors.forename: Josep
authors.initials: J
authors.lastname: Mensa
authors.forename: Josep
authors.initials: J
authors.lastname: Riba
authors.forename: Alex
authors.initials: A
authors.lastname: Soriano
mesh_terms: D000368:Aged; D019644:Arthroplasty, Replacement, Hip; D019645:Arthroplasty, Replacement, Knee; D016009:Chi-Square Distribution; D015897:Comorbidity; D020878:Device Removal; D005260:Female; D006622:Hip Prosthesis / Q000382:microbiology*; D006801:Humans; D007720:Knee Prosthesis / Q000382:microbiology*; D008297:Male; D010014:Osteolysis / Q000000981:diagnostic imaging / Q000382:microbiology*; D011475:Prosthesis Failure / Q000209:etiology*; D016459:Prosthesis-Related Infections / Q000000981:diagnostic imaging / Q000382:microbiology*; D011859:Radiography; D012086:Reoperation; D012307:Risk Factors; D013010:Sonication