Anaerobic septic arthritis.

During a 3 1/2 year period anaerobic septic arthritis was diagnosed in 43 patients (46 joints). The hip and knee accounted for 83% of the infected joints. Anaerobic infections complicated elective musculoskeletal surgery in 23 patients, including 21 with total joint arthroplasties. An additional 12 patients developed septic arthritis following surgical treatment of traumatic injuries of an extremity. Gram-positive cocci were the anaerobes most commonly found in these two groups of surgical patients, accounting for 64% of the isolates; Peptococcus magnus was the most common organism. In contrast, gram-negative bacilli (especially Bacteroides fragilis) comprised 63% of the anaerobes isolated from eight patients with chronic debilitating diseases who had not had prior surgery. Only anaerobes were recovered from approximately half of all the patients with septic arthritis while mixed aerobic-anaerobic cultures accounted for the remainder. Adequate treatment required aggressive surgery and prolonged (minimum of three weeks) antimicrobial therapy. Infected total joint arthroplasties had to be removed. Loss of joint function occurred in six patients with posttraumatic infections when surgery was delayed or antimicrobials were inadequate. Outcome was poorest in the patients with chronic debilitating diseases, four of whom died.