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Prosthetic joint infection (PJI) is a serious complication that may occur after total joint arthroplasty (TJA). In addition, PJI has a devastating impact on the patient's quality of life. Therefore, it is imperative to increase our knowledge of PJI prevention, diagnosis, and treatment.

Prevention of PJI through effective strategies must be taken to avoid this catastrophic complication. Diagnosing PJI is a major challenge, with no gold standard diagnostic criteria. Although there are several diagnostic algorithms available, these are not sufficiently accurate and require continuous evaluation and improvement. Treating PJI is complex and includes a combination of surgical intervention and long-term antibiotic treatment. In this thesis we investigated whether various preventive, diagnostic, and treatment methods could improve the outcome after PJI.

We found that patients suffering from superficial surgical site infection (SSSI) after primary hip or knee arthroplasty had a high risk of progression to PJI. Patient-related factors such as age, high American Society of Anesthesiologists (ASA) classification, and obesity were associated with a high prevalence of SSSI. High ASA classification seems to be a crucial factor in progressing from SSSI to PJI.

On PJI diagnostics, our studies revealed that the measurement of alpha-defensin levels in synovial fluid play a role in the diagnostic algorithm of PJI. The diagnostic accuracy of the alpha-defensin lateral flow test is inferior to the immunoassay test. However, the rapid availability of the lateral flow test result gives this method a place in ruling in a suspected PJI intraoperatively. In preoperative diagnostics identifying causative bacteria is essential in planning the optimal treatment regime. 

We found that debridement antibiotics and implant retention, as the surgical choice in patients suffering from early PJI caused by Staphylococci, has a higher rate of failure if the causative Staphylococci is resistant to rifampicin. Oral antibiotic alternatives to intravenously administered antibiotics are highly valued for lowering the risks of intravenous administration and reducing longer hospital stays. Our results provide evidence that linezolid is a useful alternative with manageable and reversible adverse events (AEs) in patients with PJI caused by coagulase-negative staphylococci.

In conclusion, arthroplasty surgery can provide a pain-free life for many patients if complications such as PJI can be avoided. This thesis argues that the best treatment outcome after arthroplasty surgery involves optimising the patient, applying accurate PJI diagnostic tools with no or low risk for the patient, and having available treatment options that closely follow established guidelines.