Infection following orthopaedic implants and bone surgery.

Forty-seven patients were investigated for early or late postoperative infections of orthopaedic implants and/or bone. A total of 88 isolates were recovered (64 aerobes and 24 anaerobes). Pseudomonas aeruginosa and Staphylococcus epidermidis were the most common causative agents. Anaerobic bacteria were isolated from 16 (34%) patients; 50% of patients with late-onset infection and 10.5% with early-onset infection. In 6 (12.8%) patients, infection was with anaerobic organisms alone. All these patients had retained an extramedullary internal fixation device. Anaerobic microorganisms appear to play a significant role in the pathogenesis of late-onset postoperative infection, especially where there is an extramedullary internal fixation device.