Clinical and microbiological findings in prosthetic joint replacement due to aseptic loosening.

OBJECTIVES: A role for microorganisms in aseptic prosthetic loosening (AL) is postulated. We analyse the microbiological and clinical findings of patients with suspected AL, and compare them with patients with chronic prosthetic joint infection (PJI).

METHODS: Prospective study (2011-2012) of patients with presumed AL. Evaluation of tissue samples (≥5; TS) at the time of surgery and sonication fluid (SF) of prosthesis.

RESULTS: According to positive culture in TS/SF, 89 patients were divided into: Group1: (≥2 positive-TS; n = 12); Group2: single positive-TS and concordant SF (n = 10); Group3: one positive or non-concordant TS or SF (n = 38); and Group4: cultures negative (n = 29). Positive-SF was always concordant with TS in Group 1 (75%); it was positive in 74% in Group 3. Median months (prosthesis-age: implantation to revision arthroplasty) for PJI and Group 1-4 was 21, 46, 65, 63 and 81, respectively (P < 0.001); they also had a different dynamic trend in prosthesis failure (P < 0.001).

CONCLUSIONS: Several patients with suspected AL are misdiagnosed PJI. Results from SF correlated well with TS in Group 1, led us to consider single positive-TS as significant (Group 2) and to suggest that microorganisms were on the prosthesis (Group 3). We observed a correlation between microbiology and prosthesis-age, which supports that early loosening is more often caused by hidden PJI than late loosening.