Improved detection of infection in hip replacements

Abstract

Our aim was to determine if the detection rate of infection of total hip replacements could be improved by examining the removed prostheses. Immediate transfer of prostheses to an anaerobic atmosphere, followed by mild ultrasonication to dislodge adherent bacteria, resulted in the culture of quantifiable numbers of bacteria, from 26 of the 120 implants examined. The same bacterial species were cultured by routine microbiological techniques from only five corresponding tissue samples. Tissue removed from 18 of the culture-positive implants was suitable for quantitative tissue pathology and inflammatory cells were present in all samples. Furthermore, inflammatory cells were present in 87% of tissue samples taken from patients whose implants were culture-negative. This suggests that these implants may have been infected by bacteria which were not isolated by the techniques of culture used.The increased detection of bacteria from prostheses by culture has improved postoperative antibiotic therapy and should reduce the need for further revision.

Propionibacterium acnes Types I and II Represent Phylogenetically Distinct Groups

“…Previously, by adopting strict anaerobic protocols and including a mild ultrasonication step to remove adherent bacteria growing as a biofilm, we isolated P. acnes as frequently as Staphylococcus spp. from implants and associated tissue of patients undergoing revision hip surgery (33,34). In this study, analysis of P. acnes isolates recovered directly from prosthetic hip implants revealed approximately equal numbers of type I and II strains, while isolates from associated bone and tissue samples were predominantly of type I. Isolates recovered from patients with acne and dental infections, and skin isolates from surgical incision sites, were also found to be predominantly type I.…”

“…While the opportunistic pathogenic potential of coagulase-negative staphylococci (CoNS), such as Staphylococcus epidermidis, is well recognized, the importance of P. acnes may still be overlooked (13), despite the fact that it produces more kinds of putative virulence determinants than CoNS (5,38). This fact is illustrated by recent studies in which P. acnes was recovered as frequently as CoNS from the prosthetic hips of patients undergoing revision arthroplasty (33,34).…”

“…We now report that the phenotypic differences observed by antibody labeling reflect deeper differences at the gene level, and we propose that types I and II represent phylogenetically distinct cluster groups. (33,34). A total of 18 skin isolates were obtained from spinal operation incision sites after homogenization of skin samples as previously described (33,34).…”

“…(33,34). A total of 18 skin isolates were obtained from spinal operation incision sites after homogenization of skin samples as previously described (33,34). In addition, a further 19 P. acnes isolates from tissue samples associated with failed prosthetic hips, as well as isolates recovered from patients with acne (n ϭ 22) and dental (n ϭ 8) infections, were kind gifts.…”

Adherent Endotoxin on Orthopedic Wear Particles Stimulates Cytokine Production and Osteoclast Differentiation

“…In this regard, a large number of microbiological studies have documented the presence of bacteria on the surface of many orthopedic implants in the absence of any signs of clinical infection. (27)(28)(29)(30)(31)(32)(33)(34)(35)(36) More sensitive polymerase chain reactionand immunofluorescence-based techniques indicate that these microbiological studies have likely underestimated the incidence of bacteria in aseptic loosening. (37,38) The potential importance of subclinical levels of bacteria is emphasized by a Norwegian study of over 10,000 total hip replacements showing that inclusion of antibiotics in the bone cement used for fixation of the implant reduced the frequency of aseptic loosening by approximately 50%.…”