Frequency of Multifocal Disease and Pyogenic Arthritis of the Hip in Infants with Osteoarticular Infection in Three Neonatal Intensive Care Units

Objective To describe the clinical features of osteoarticular infection in infants cared for in neonatal intensive care units (NICUs) and to assess the presence of multifocal infection. Study design Retrospective medical record review with structured data abstraction of infants with osteomyelitis or pyogenic arthritis or both in NICUs at 3 children's hospitals over a 29-year period. Results Of the 45 cases identified, 87% occurred in prematurely born infants, with a median gestational age of 27.4 weeks (IQR, 26, 31 weeks). Median postnatal age at diagnosis of infection was 33 days (IQR, 20, 50 days). Osteomyelitis was present without joint involvement in 53% and with joint involvement in 44% of cases. Methicillin-susceptible Staphylococcus aureus (71%) was the predominant pathogen, despite prevalent methicillin-resistant S aureus in community-associated infections. More than 1 bone was infected in 34% of cases. The femur (in 50% of patients) was the most frequently involved bone and the hip (in 20% of patients) was the most frequently involved joint. Bacteremia persisted for 4 or more days in 54% of patients with a positive blood culture despite active antimicrobial therapy. Conclusions Among infants with osteoarticular infection in NICUs, multifocal disease is common and frequently is unsuspected. Search for additional sites of infection including the hip is warranted following the diagnosis of osteoarticular infection at a single site. Involvement of contiguous joints should be suspected in cases of osteomyelitis; conversely the presence of pyogenic arthritis usually indicates extant osteomyelitis in a contiguous bone.