Identification of Asymptomatic Prosthetic Joint Infection: Microbiologic and Operative Treatment Outcomes.

Background: This prospective study investigated the role of mechanical and biological factors in aseptic implant loosening or presumed silent prosthetic joint infection (PJI).

Methods: Thirty-seven patients were investigated. Microbiologic and molecular methods were used to detect bacteria on the surface of the failed implants removed during revision arthroplasty. Histopathologic analysis was performed. The influence of body mass index (BMI) and various co-morbidities on implant failure also was determined.

Results: The results of sonicated fluid cultures were positive for bacteria in 29.7% and the results of intra-operative tissue and joint liquid cultures in 18.9% and 16.2%, respectively. Molecular detection with 16S rRNA sequencing revealed a large variety of bacteria. The most frequent organism was coagulase-negative Staphylococcus (CNS). The outcomes of histopathologic tests of peri-prosthetic tissue showed evidence of the infection type in all culture-positive joints and in 41.4% of the cases with negative culture results. Overweight status or obesity was present in 82.8% of the culture-negative patients.

Conclusions: The results of this study proved the presence of micro-organisms on the surface of implants in both aseptic and presumed PJI cases. Inclusion of the sonication procedure in the diagnostic algorithm increased the ability to identify the pathogen. The results of our study suggest the co-existing roles of BMI and the time to implant loosening as well as biological agents in causing prosthesis loosening.