Aim

Prosthetic Joint Infection (PJI) remains one of the leading cause for revision arthroplasty.^1,2 Early recognition and appropriate initial treatment of early PJI with debridement, antibiotics and implant retention (DAIR) can eradicate infection on first attempt and prevent implant failure. We evaluated the outcome after one year of patients who were treated for an early PJI after primary total knee arthroplasty (TKA) or total hip arthroplasty (THA) with DAIR. Furthermore, we determined preoperative infection markers, microbiology, and treatment factors related to treatment failure after DAIR procedure.

Aims

Positive cultures are not uncommon in cases of revision total knee and hip arthroplasty (TKA and THA) for presumed aseptic causes. The purpose of this study was to assess the incidence of positive intra-operative cultures in presumed aseptic revision of TKA and THA, and to determine whether the presence of intra-operative positive cultures results in inferior survival in such cases.

Aim

Despite a preoperative workup with no evidence to suspect a prosthetic joint infection (PJI) before revision surgery, routinely obtained intraoperative cultures still can be unexpectedly positive. The purpose of this study was (1) to assess the incidence of unexpected positive intraoperative cultures in presumed aseptic knee and hip revisions and (2) to determine whether a difference exists between the infection-free implant survival rate of patients with and without unexpected positive intraoperative cultures.

Background: Proprionibacterium acnes (P. acnes) is a skin commensal which is often interpreted as a contaminant when found in cultures of surgical specimens. However, recent reports suggest that P. acnes can be identified as the causative micro-organism of infection. Furthermore P. acnes infections occur more often after shoulder surgery than after surgery of the lower extremities or spine. The aim of this study was to identify how frequent P. acnes was responsible for infection after orthopaedic surgery of the shoulder, lower extremity and spine in a single centre.

Patients and Methods: Inclusion criteria were the occurrence of infection after surgery of the shoulder, lower extremity (hip and knee), or spine in a 100-bed orthopaedic hospital. The inclusion period was between January 2000 and May 2008. Infection was defined when two or more cultures were positive with the same microorganism in the presence of clinical signs and symptoms. The first goal was to identify the incidence of infection due to P. acnes amongst all infections. The secondary outcome was the incidence of infection versus contamination amongst all cases with positive cultures for P. acnes. Both outcomes were compared for surgery of the shoulder, lower extremity and spine.

Results: A total of 3703 surgeries of the shoulder were performed, compared to 19906 lower extremity- and 5687 spine surgeries. The incidence of infection after surgery of the shoulder was 1.4% (52 cases; prosthesis [n=23], fractures [n=5], soft tissue surgery [n=16] and others [n=8]). After surgery of the lower extremity and spine this was 2.8% (548 cases) and 3.1% (177 cases), respectively. The incidence of infection due to P. acnes after shoulder surgery (23%) was significantly greater then after surgery of the lower extremity (1.3%; p < 0.001) or spine (0%; p < 0.001). Furthermore, in cases where P. acnes was cultured after surgery of the shoulder it was more often identified as the causative pathogen of infection than when P. acnes was cultured after surgery of the lower extremity or spine (71% vs 22%; p < 0.05 and 71% vs 0%; p < 0.01).

Conclusion: The low virulent P. acnes can cause orthopaedic surgical infections and should not be regarded a priori as a contaminant in cultures. This is especially true for shoulder surgery, where P. acnes infections occur frequently and significantly more often than in surgery of other joints.