Bone and joint infections may occur at any age but are more common in children than adults. Optimal management requires early diagnosis and aggressive initial treatment to prevent disabling sequelae. This is best achieved with care provided by a multidisciplinary team of pediatricians and orthopedic surgeons experienced in the specific issues encountered in care of growing children. Soft tissue infections in children, generally less difficult to diagnose and treat than skeletal infections, remain important because of their greater frequency of occurrence and the need for antibiotic therapy, occasionally in conjunction with hospitalization and surgery.
ACUTE HEMATOGENOUS OSTEOMYELITIS
PATHOGENESIS AND EPIDEMIOLOGY
The majority of bone infections in children are of hematogenous origin. The vascular anatomy of long bones in children underlies the predilection for localization of blood-borne bacteria. In children, unlike young infants, the blood supply of the epiphysis is separate from the metaphysis. The nutrient artery to the metaphysis empties into a system of venous sinusoids in which sluggish flow presumably facilitates deposition of bacteria. During the cellulitic phase of acute osteomyelitis, infection originates on the venous side of the system and then spreads to the nutrient artery, causing thrombosis of the nutrient artery. The resultant ischemia prevents host defense mechanisms from reaching the area and allows bacterial proliferation. Formation of an abscess can then occur, which can rupture into the subperiosteal space with subsequent elevation of the periosteum, which is loosely adherent in children. If infection is uncontrolled, purulent material may extend up and down the diaphysis and circumferentially around the bone (Fig. 229-1). In areas in which the metaphysis is intra-articular, such as the hip and shoulder, the intraosseous abscess may rupture into the joint, resulting in septic arthritis. In young infants, blood vessels connect the metaphysis and epiphysis, and rupture of pus into the adjacent joint space is more common.
Magnetic resonance imaging scan axial view demonstrating an extensive subperiosteal abscess (arrow) surrounding the cortex of the fibula secondary to Staphylococcus aureus.
Thrombosis of blood vessels and elevation of the periosteum deprive the bone of its blood supply, resulting in necrosis, which can be extensive without early surgical drainage. Left untreated, granulation tissue forms around the dead bone, which separates from live bone and becomes a sequestrum. New bone growing around the dead bone is called an involucrum. Sinus tract formation occurs in the involucrum allowing pus to escape and eventually form sinus tracts through the skin. The involucrum is mechanically weak and may become the site of pathologic fractures.
Acute hematogenous osteomyelitis (AHO) is one of the most common and important invasive bacterial infections affecting children. The incidence ranges from 2 to 13 per 100,000 in developed countries, but is considerably higher (up to 200/100,000) in ...