A four-year prospective study on microbial ecology of explanted prosthetic hips in 52 patients with "aseptic" prosthetic joint loosening.

The bacteriology of explanted prosthetic hips and surrounding soft tissue was studied in 52 patients undergoing surgical revision for joint loosening. In a prospective four-year study, positive bacterial cultures were recorded in 34 (76%) patients. Coagulase-negative staphylococci were the predominant isolates, and 11 patients (33%) had more than three organisms isolated, 7 (20%) had two only, and 11 (33%) had one species. Among the 23 patients from whom specimens from all 11 predetermined anatomic sites were cultured, the highest frequency of positive cultures (52% and 47%) came from the shaft and capsular tissue, respectively. Organisms were less frequently recovered from the cement and acetabulum (13% and 4%, respectively). Using molecular typing in eight patients with paired isolates of the same species, clonal identity was found in four. An additional patient underwent a second revision for loosening 17 months after the first revision and the same clone of Staphylococcus epidermidis was isolated on both occasions.