Aim. Aseptic loosening is the leading cause of revision of total hip arthroplasty (THA). It is well recognized that an occult infection is the underlying cause of some aseptic revisions. Intraoperative cultures are central to the diagnosis of prosthetic joint infection (PJI). However, the diagnostic and prognostic value of unexpected positive intraoperative cultures remains unclear. The aim was to study whether first-time aseptic revision of a total hip arthroplasty with unexpected bacterial growth in cultures of intraoperatively taken biopsies have an increased risk of secondary revision due to all causes and increased risk of PJI revision, specifically. Method. Cases reported as first-time aseptic loosening revisions to the Danish Hip Arthroplasty Register (DHR) performed during January 1. st. , 2010, to May 15. th. , 2016, were included. DHR data were merged with the Danish Microbiology Database, which contains data from all intraoperatively obtained cultures in Denmark. Included first-time revisions were grouped based on the number of positive cultures growing the same bacteria genus: ≥2, 1 and 0 cultures. Revisions were followed until secondary revision, death, or end of follow-up period after one year. Relative risk for secondary revision due to all causes and PJI was estimated. Results. We included 2,305 first-time aseptic revisions. Unexpected growth was found in 282 (12%) of which 170 (60%) cases showed growth of the same bacteria in only one culture. Coagulase-negative staphylococcus accounted for 121 (71%). Secondary revision was performed in 163 (7%) cases, with PJI being the indication for revision in 43 (26%) cases. The relative risk of secondary revision was significantly higher for cases of one positive culture growing the same bacteria compared to culture negative cases, both for revision due to all causes; 1.73 (95%CI 1.07; 2.80) and PJI exclusively; 2.63 (1.16; 5.96). Cases of 2 or more biopsies culturing the same bacteria had a relative risk of all cause revision of 1.52 (0.82; 2.80). Conclusions. First-time aseptic loosening THA revisions with unexpected growth in only one biopsy culture had an increased risk of secondary revision, both due to all causes and PJI. Our findings indicate that some cases of unexpected growth of bacteria should likely be regarded as clinically significant and not sample contamination, underlining the need for more awareness and better strategies when treating patients with unexpected positive intraoperative cultures. The improved diagnosis of occult PJI in clinically aseptic THA is of great importance for future care of this large and growing patient group

Purpose: Deep infections of the operative bed are rare but serious complications of first-intention total hip arthroplasty. Data from French series are scarce. We present a study of incidence, characteristic features and potential risk factors using a consecutive series of 790 implants performed during first-intention procedures in the same university hospital. Material and methods: All patients who underwent first-intention surgery from November 1995 to May 1999 were included. We collected demographic, clinical, and therapeutic data. Deep infection was defined as bacteriological demonstration of the infectious agent from at least two intra-operative specimens during the revision procedure. Patient follow-up ranged from one month to four years. Univariate analysis was used to search for potential risk factors. The chi-square and Fischer exact tests were applied. Results: Overall incidence was 1.77 deep infections for 100 operations (95%IC 0.84–2.7). Mean time to development ranged from 14 days to 32 months. Eleven infections were recognised within the first year and three after one year. Two risk factors were identified: absence of systemic antibiotic prophylaxis (relative risk = 4.74, p=0.03), and drainage discharge after 48 hr (relative risk = 3.62, p=0.02). Other variables associated with infection with a relative risk greater than 2 were obesity, corticosteroid therapy, and haematoma or postoperative wound healing problem. Conclusion: The incidence found in this series is slightly higher than generally described in other countries. This study has incited us to revisit our protocols for preoperative skin preparation and to establish a systemic antibiotic prophylaxis