Clinical and epidemiological differences between implant-associated and implant-free orthopaedic infections

Although there have been many publications regarding the risk factors for implant-associated orthopaedic infections, none have investigated how clinical presentations and epidemiology may differ between infections with and without osteosynthetic material. We pooled clinical data from several databases of adult patients with orthopaedic infections hospitalized at Geneva University Hospitals from January 2004 to December 2014. Among 2740 episodes of orthopaedic infections, 76% were implant-free osteoarticular or soft tissue infections. Among the 665 (24% of the total episodes) infections that involved osteosynthetic material, 319 (49%) were total joint arthroplasties, 143 single plates, and 50 single nails. The remainders were mixed implant infections, pins, wires, screws, cerclages or spondylodeses. The implant-associated, compared to the implant-free, infections were significantly more frequently associated with female sex, older age, bacteraemia and skin commensal infections, e.g. coagulase-negative staphylococci, corynebacteria or propionibacteria. In contrast, implant-associated infections were significantly less frequently associated with immune suppression, abscess formation, infections due to Staphylococcus aureus or streptococci, polymicrobial pathogens and foot infections. The serum CRP levels at admission were similar (median 82 vs. 75 mg/L). Compared to implant-free infections, implant-associated orthopaedic infections are more likely monomicrobial, bacteraemic and due to skin commensals. They involve more often female and older patients, but are less often associated with immune suppression, abscess formation and foot infections.