Septic sacroiliitis.

Two cases of septic sacroiliac (SI) joint arthritis are presented to illustrate the difficulty of diagnosing and treating this uncommon osteoarticular infection. The patients presented are a 68-year-old woman with septic sacroiliitis caused by Streptococcus agalactiae and a 20-year-old man with Salmonella infantis infection involving the SI joint. The recent literature is reviewed and compared with previously published series. Of the 177 cases we reviewed, 47 (27%) occurred in pediatric patients. The mean age was 20 years. Only six patients (3%) were older than 60 years of age. Magnetic resonance imaging (MRI) is most useful for defining extent of infection, osteomyelitis, and abscess formation in the SI joint. Computed tomography (CT) is valuable for defining the extent of bone involvement and for guidance of percutaneous needle arthrocentesis. Other imaging modalities are useful primarily in the initial evaluation of patients with a nonspecific presentation. Four to six weeks of intravenous (i.v.) antibiotic therapy is recommended. Indications for surgical intervention include abscess formation, osteomyelitis, sequestrum of necrotic bone, and failure to respond to i.v. antibiotic therapy.