LAUSR

Background: Acute native septic arthritis is a joint-threatening emergency. To date, however, no gold-standard treatment nor joint-specific treatment algorithms exist. We aimed to evaluate the etiologies, bacterial spectrum, treatments, and surgical outcomes of septic arthritis of the shoulder and knee. Methods: Seventy-one patients with septic arthritis of either the knee (n = 42) or the shoulder (n = 29) were followed over a mean period of 40 months (26-65). Data were collected according to the performed surgical procedure and pathway as well as the cause of infection, bacterial spectrum, and the Gächter classification. The prospective clinical examination included the Knee Society Score (KSS) or Constant Score (CS; shoulder group), pre- and post-operative pain, and return to previous activity. Results: Septic arthritis was caused primarily by post-interventional or post-traumatic conditions in the knee group and by hematogenous infection in the shoulder group. Staphylococcus aureus and S. epidermidis were most common, whereas Propionibacerium. were seen only in shoulder infections. Remission rates were 95% in the knee versus 90% in the shoulder group, whereas the mortality rate in the shoulder group was 10% (no one died in the knee group). While most knee infections could be managed with an arthroscopic approach, all shoulder infections necessitated an open approach. The mean KSS was 87.3 (49-100); the mean CS was 66.6 (37-95). Fifty percent of patients in the shoulder group versus 71% in the knee group reached their previous level of activity. Conclusion: The knee group exhibited post-interventional etiology, in line with high-virulence microbes and a high success rate with arthroscopic restoration. Septic shoulder arthritis showed hematogenous scattering, low-virulent microbes, and multiple interventions with a final open approach was always required. In contrast to the knee, in septic arthritis of the shoulder, a significant reduction in function has to be expected.