Clinical and microbial features of prosthetic joint infection.

A one-year experience with prosthetic joint infection, in which 63 cases were identified, is reviewed. Thirty cases (48 percent) were early infections, in the first postoperative year, and 33 cases (52 percent) were late, occurring more than one year after implantation. Pain was the predominant symptom, but clinical clues suggesting infection were frequently absent, with fever in 43 percent and leukocytosis in only 10 percent. The radiographic appearance was more frequently abnormal in late infections (67 versus 37 percent, p less than 0.02). Staphylococci were predominant organisms, constituting 59 percent of prosthetic joint infections, and S. epidermidis was the predominant species in both early and later infections. Of the hematogenous infections, 11 of 13 occurred in the group with late infections; these were mostly nonstaphylococcal . Antigenic proteins of S. epidermidis were characterized by gel electrophoresis, but no infection-specific antigens could be identified when patient serum was compared with normal samples. Precipitating antibodies to the extracellular proteins of S. epidermidis were present in 50 percent of patients with S. epidermidis prosthetic joint infections, 27 percent of patients with nonstaphylococcal infections, 20 percent of patients with S. aureus infections, and 11 percent of normal subjects. In view of the increasing importance of prosthetic joint infection, further study of the pathogenesis of the infection and the host immune response is warranted.