Abstract
Background
Both from experimental studies and the large arthroplasty registries there is evidence that bacteria are more often involved in implant loosening then is currently reported. To further elucidate this potential problem, the current study investigated the hypothesis that many total hip arthroplasty revisions, classified as aseptic, are in fact low-grade infections missed with routine diagnostics.
Methods
In 7 Dutch hospitals, 176 patients with the preoperative diagnosis of aseptic loosening of their total hip arthroplasty were enrolled. From each patient, the preoperative history was obtained. During surgery, between 14 and 20 tissue samples were obtained for routine culture, pathology analysis and broad range 16S rRNA PCR with reverse line blot hybridization (PCR-RLB). Samples were taken from the (neo-) capsule and acetabular and femoral interface tissue. Cultures were performed locally according to similar protocols. One specialized pathologist, blinded for all other results, analyzed all pathology samples. The PCR-RLB analysis was performed centrally, using a technique previously validated for orthopedic use. Patients were classified as not infected, suspect for infection or infected, according to strict, predefined criteria. Each patient had a follow-up visit after 1 year.
Results
Seven patients were classified as infected, of whom 4 were not identified by routine culture. In these patients, positive PCR-RLB results were supported by pathology analyses suspect for infection as well. An additional 15 patients were suspect for infection as well. The microorganisms identified were low virulent bacteria, like coagulase negative staphylococci and Proprionibacterium acnes, in most cases. Twenty of these 22 patients received a cemented prosthesis, fixated with antibiotic-loaded bone cement. All patients received prophylactic systemic antibiotics, after obtaining the tissue samples. Seven of the 22 patients reported complaints one year post-surgery, only one showing signs of early loosening. However, in none of the patients additional surgery was performed.
Discussion
Although percentages were not as high as previously reported in literature, between 4 and 13 percent of patients with the preoperative diagnosis of aseptic loosening were infected. However, as thorough debridement was performed during surgery and prophylactic antibiotics were used, it did not have many clinical consequences, as most patients performed well at the 1-year follow-up. Whether it has implications for long-term implant survival remains to be seen.
