Objectives To describe the clinical characteristics, treatment and outcome of patients diagnosed with pyogenic septic arthritis.

Methods Design: retrospective (1984-2012). Location: University hospital. Referial area: 800,000 inhabitants. The medical records of patients with pyogenic arthritis were reviewed. Inclusion criteria: isolation of bacteria in joint fluid or blood. Patients with soft tissue infection, prosthetic, fungal and mycobacterial septic arthritis were excluded.

Results One hundred one patients were selected: 66 males and 35 females. Mean age: 54.5 ± 21.2 years. The following risk factors were identified: alcoholism (24), cirrhosis (12), diabetes mellitus (18), chronic renal failure (17), neutropenia (6), immunosuppression (10), HIV (10), AIDS (5), parenteral drug addiction (12), cancer (6), RA (4) and microcrystalline arthritis (17). Seventeen patients had undergone joint manipulation prior to the onset of the infection: 9 arthrocentesis with corticosteroids injection, 6 arthrocentesis and 2 arthroscopies. The pattern of join involvement was monoarticular in 72 patients (71.3%): knee 38 (36.8%), and shoulder and ankle 8 (8%) respectively. Polyarticular involvement was found in 29 patients (28.7%). Fifty nine patients 58.4% had fever. Cellulitis was observed in 17 cases (17%). The mean time between onset of symptoms and diagnosis was 7.9 ± 8.2 days. Mean hospital stay was 30.4 ± 28 days. Blood cultures were positive in 40 cases (39.7%) and in 85% of them the same microorganism was isolated in joint fluid. Septic arthritis was caused by gram positive in 79%, gram negative 19% and 2% were polymicrobial. The most common were: S. aureus methicillin sensitive (45), S. aureus methicillin resistant (MRSA in 5 cases since 2008), S. agalactiae (6), S. pyogenes (3), S. pneumoniae (9), E.Coli (9), P.aeuriginosa (3), Enterobacter cloacae (2) and Salmonella (2). Acute phase reactants were increased: ESR: 89.5 ± 29.6 mm/1sth and C-reactive protein 162 ± 122 mg/dl. The mean leukocyte count of joint fluid was 65,602 ± 62477/mm³. Synovial glucose was decreased in 50% of patients. Mean duration of intravenous antibiotic therapy: 3 weeks. Thirty-four patients (33.6%) required surgical treatment. Three patients required a second arthrotomy. Complications were: septic shock (20), pneumonia (6), reflex sympathetic dystrophy (2), osteonecrosis (2), endocarditis (3), respiratory distress (1). Most of the cases evolved favorably. Fifteen cases resulted in death (15%): 8 cases had monoarticular involvement and 7, polyarticular involvement. The causative organisms were: S. Aureus (10 cases), MRSA (3 cases), Pneumococcal (1 case) and polymicrobial (1 case of S.aureus more E.Coli).

Conclusions S. aureus is the most common pathogen isolated. Furthermore MARSA is an emerging microorganism. Hematogenous spread and polyarticular involvement are poor prognostic factors. Prolonged antibiotic therapy and surgical debridement are essential for proper healing.

Disclosure of Interest None Declared