INFECTION OF THE SPINE (SPONDYLITIS)
Infection of the vertebral column in infants and children is much less common than osteomyelitis of the pelvis or long bones. Only about 2% of pediatric osteomyelitis cases involve the vertebrae. In children, the 10 to 15 year age group is most commonly affected. The vertebral infection typically occurs by way of hematogenous inoculation (arterial or venous). Other potential mechanisms include penetrating trauma, iatrogenic introduction of organisms (e.g., lumbar puncture or spinal surgery), and spread from a paravertebral abscess. Spread of infection from the vertebral column can lead to paravertebral cellulitis, meningitis, spinal epidural abscess, or psoas abscess. In decreasing order of frequency, the locations of vertebral osteomyelitis are lumbar, thoracic, and cervical.1,2
Most instances of vertebral osteomyelitis likely involve an arterial septic microembolus that lodges in a metaphyseal artery of the subchondral portion of the vertebral body. The subchondral portions of the vertebral bodies are metaphyseal equivalents. The microembolus deposits organisms at the site and causes a small septic infarct of the bone, which is apparently an important component of the pathophysiology of vertebral osteomyelitis. The extensive subchondral intraosseous anastomoses that are present in the vertebral bodies of infants and young children are relatively protective against infarction. This is an important factor in the lower frequency of vertebral osteomyelitis in young children as compared to adolescents and adults.
The most commonly isolated organism in children with vertebral osteomyelitis is Staphylococcus aureus. Other bacteria that can infect the spine include Streptococcus species, Kingella kingae, E. coli, Pseudomonas (common with intravenous drug abusers), Salmonella, and Klebsiella. The spine is a relatively common skeletal site for tuberculosis. Vertebral osteomyelitis and epidural abscess can occur in children with cat scratch disease. The clinical manifestations of vertebral osteomyelitis partly relate to the virulence of the organism and the host response. The clinical spectrum ranges from an acute febrile presentation to an indolent course with nonspecific back pain. Blood cultures are positive in some patients; image guided percutaneous aspiration is useful for others.3–5
Radiographs are often normal early in the course of vertebral osteomyelitis, when the infection is confined to the subchondral zone of the vertebral body. The initial radiographic finding often consists of intervertebral disc space narrowing, apparently due to the release of proteolytic enzymes that destroy the disc. The margins of the vertebral endplates are usually indistinct at this point. Frank destruction of subchondral bone typically becomes evident within 1 to 2 weeks after the onset of infection. These osseous changes tend to be most prominent in the anterior two-thirds of the vertebral body.
With progression of the infection, radiographic findings of vertebral body infection include bony endplate destruction, cortical permeation, and blurring of the disc space margins. There may be loss of height of the involved vertebral body. Prominence of the paravertebral soft tissues is often ...