Periprosthetic Joint Infections. Clinical and Epidemiological Aspects

Sammanfattning: Periprostheteic joint infection (PJI) is a rare complication of arthroplasty with severe consequences for the affected patients. PJI most often necessitates additional surgery and prolonged courses of antibiotic treatment, leading to worse functional results and increased societal costs. Evaluating treatment of PJI as well as preventive efforts are essential to increase our understanding of PJI and to enable improved approaches in the future.In this thesis four studies covering different aspects of PJI are included. PJIs caused by streptococci and enterococci were investigated in papers I and II, respectively. Patients in Skåne with growth of either streptococci or enterococci in sterile cultures from prosthetic joints were included and data from the medical records were reviewed retrospectively. The aim was to describe the affected populations, surgical and antimicrobial treatments and treatment outcome. Paper I showed that streptococcal PJIs were often acute hematogenous infections treated with surgical debridement. Successful outcome was achieved in 89% of cases. Paper II showed that enterococcal PJI were often early postoperative infections in elderly fragile patients, where enterococci were found as a part of a polymicrobial flora. Overall cure was reached in 67% of cases. However, when complete cure, defined as preservation of a functional joint and eradication of infection, was the treament intention, this was achieved in 80% of cases. In paper III the effect of a national infection control programme on the incidence of PJI after primary total knee arthroplasty (TKA) was evaluated. Through matching of 45,438 primary TKAs from the Swedish Knee Arthroplasty Register to the Swedish Prescribed Drug Register, 2505 TKAs were identified as having received ≥28 days of continuous antibiotic treatment within 2 years of TKA. Subsequent review of medical records identified 644 PJIs, giving a cumulative 2 year incidence of 1.45%. PJI incidence rates were similar during both time-periods. In paper IV mortality of patients with PJI after primary TKA was compared to patients without PJI using data aquired in paper III and mortality data from the tax agency. Results showed a significantly increased mortality for PJI patients in both short- and long-term. This thesis shows that patients with streptococcal PJI have a relatively good prognosis. Patients with enterococcal PJI, on the other hand, are challanging to cure. However, the results do suggest acceptable success rates for a subset of enterococcal PJI-patients where complete cure is a viable option. Further, this thesis shows that incidence rates of PJI were similar before and after a national project to reduce infection rates. The lack of effect of the prevention programme, however, remains to be explained. Patients undergoing primary TKA with PJI have a higher mortality rate than non-infected patients. This effect remains long-term, indicating that mortality is not related to PJI alone, perhaps reflecting a general frailty in the PJI population.