Septic arthritis is a rapidly destructive joint disease, leading to irreversible damage of the cartilage, bone and surrounding soft tissue. Therefore, this infection requires rapid diagnosis and appropriate treatment. The diagnosis is challenging due to false-negative joint fluid cultures, delay until positive microbiology and overlap with other aseptic joint disorders. Invasive and antimicrobial treatment is not standardized and widely depends on the treating physician (surgeon or internist). The optimal management of septic arthritis is not defined and requires systematic evaluation of different approaches; especially that post-interventional septic arthritis is expected to rise and may involve other pathogens than observed in hematogenous septic arthritis.
In our retrospective study, data from 101 cases of septic arthritis in adults at a single university institution were analyzed. Septic arthritis was defined either by positive synovial fluid culture or by clinical findings PLUS positive blood culture or abnormal synovial fluid leukocyte count PLUS exclusion of other causes. A single joint was affected in most cases (95%). The knee joint was most commonly involved (49%), followed by ankle (13%), wrist (10%), hip (9%) and other joints (18%). Most cases of septic arthritis (74%) occurred by bloodstream seeding (i.e. hematogenous route) and 26% occurred after joint manipulation (i.e. post-interventional route). Among the hematogenous septic arthritis, 27 patients were active intravenous drug users. The post-interventional septic arthritis occurred after joint surgery (minimal-invasive arthroscopy in 11 patients and open joint surgery in 11 patients) or joint puncture (with steroid injection in 4 patients and without injection in 3 patients). Since the numbers of joint interventions is increasing in the aging population, the number of septic joint complication is expected to rise as well. The clinical presentation of septic arthritis is not exclusive; therefore, laboratory tests are needed. In our study, synovial fluid culture positive in 79% and the results were available only after a delay of several days. Gram stain of synovial fluid (direct microscopic visualization) was more rapid, but was positive in only 38%. Synovial fluid leukocyte count was >20 x 109/l in 68% cases and 90% neutrophils in 62% cases. Blood cultures were positive in 40% of cases. Staphylococcus aureus was the most prevalent isolated organism found in 51 episodes, followed by Streptococcus species in 18 episodes. In 9 cases no causing organism was isolated. In 8 episodes (8%), crystals (4 uric and 4 pyrophosphate crystals) were concomitantly found in synovial fluid, which was higher than reported in the literature and does not exclude septic arthritis.
All patients were treated with antimicrobial treatment for a median of 36 days. Invasive treatment was performed in 80% of the patients. In patients admitted to medical ward (n = 39) versus surgical ward (n = 55), needle aspiration was performed in 14 versus 4 episodes (p = 0.001, OR 7.14), arthroscopic lavage in 6 versus 42 episodes (p = 0.0001, OR 17.76) and no invasive treatment in 14 versus 4 episodes (p = 0.001, OR 7.14). In conclusion, patient treatment largely depends on involved physician specialty.
This work demonstrates that septic arthritis remains a medical problem with unresolved questions concerning the optimal diagnosis and treatment. In future, studies should address how to diagnose septic arthritis faster and standardize the treatment concepts. Interdisciplinary, prospective, multicenter studies are needed to address open questions in microbiology, antimicrobial treatment and surgical approach.