Increased Incidence of Sacroiliac Joint Infection At a Children's Hospital

Background: Pyogenic sacroiliitis (PSI) is an uncommon type of osteoarticular infection. A study is undertaken to confirm an observed increase in incidence of PSI at our pediatric institution and to evaluate any associations with increasing incidence of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) infection and other factors. Methods: All inpatients with osteoarticular infection were identified from the periods of 1992 to 1996 and 2004 to 2007. Patients with surgical site infection, immunologic deficits, decubiti, or other predisposing factors were excluded. Demographic, microbiologic, and clinical factors were analyzed for comparison. Results: Overall 362 cases were included: 205 with osteomyelitis alone and 157 with pyarthrosis, of which 15 were PSI cases. The incidence of PSI increased from the periods of 1992 to 1996 and 2004 to 2007 (0.8 vs. 2.8 cases/y, P=0.03), along with osteomyelitis at pelvic and spinal sites (ie, axial sites; 1.6 vs. 5.0 cases/y; P=0.03), whereas the incidence of osteoarticular infection at other sites remained stable. CA-MRSA was isolated in 1 (6.7%) PSI case. In the second time period, CA-MRSA did not form a higher proportion of S. aureus isolates at sacroiliac or other axial sites (CA-MRSA: 17% of S. aureus in PSI and axial osteomyelitis vs. 45% of S. aureus at nonaxial sites, P=0.08). Patients were older in the second time period (4.5 y vs. 7 y; P<0.0001), and patients with PSI (10.5 y) and axial osteomyelitis (8.5 y) were older than those with osteoarticular infection at other sites (5.3 y; P<0.0001). Conclusions: The emergence of CA-MRSA does not explain the increasing incidence of PSI. The incidence of PSI and osteomyelitis involving the axial skeleton are increasing, predominantly in older patients. These trends should be prospectively investigated. Level of Evidence: III, Prognostic Study.