Pediatric Hospital Medicine

43 CHAPTER

Bone and Joint Infections

Jennifer Kaczmarek and Jennifer Scavone

OSTEOMYELITIS ■ INTRODUCTION

Acute hematogenous osteomyelitis (AHO) is the most common type of pediatric bone and joint infection. Pathogenic invasion and prolif eration within the bone matrix typically occur through hematogenous spread, by direct inoculation (penetrating or surgical trauma), or by contiguous spread from a local infection of adjacent structures (eg, chronic soft tissue ulcer). 1-3 ■ EPIDEMIOLOGY AND RISK FACTORS In children under the age of 13, AHO occurs annually in 1 out of 5,000 children in the United States and in 1 out of 1,000 to 20,000 children worldwide. 1 Children are more susceptible to bone infections given the highly vascular structure of their rapidly growing and developing long bone metaphyses. The femur is the most common site of AHO, followed by the tibia and humerus. Males are more frequently affected than females. 1,2,4 The most common causative pathogens identified in pediatric bone and joint infections are summarized in Table 43.1. Staphylococcus au reus (both methicillin-susceptible [MSSA] and methicillin-resistant [MRSA] species) is the primary causative organism across all age groups. 3 Risk factors for the acquisition of community-acquired MRSA include frequent antibiotic treatment, skin trauma, crowded environ ments, and sharing of contaminated items. 5 In addition, Salmonella species may cause bone and joint infections in children with sickle cell disease and related hemoglobinopathies. 3 ■ CLINICAL MANIFESTATIONS AND DIAGNOSTIC STUDIES Initial illness history and physical exam findings can be highly vari able and nonspecific in AHO. Symptoms typically present over 5 to 7 days and up to 25% will not have associated fever. The most common

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