Chapter 120. Osteomyelitis (Part 2)

Vertebral OsteomyelitisThe vertebrae are the most common sites of hematogenous osteomyelitis in adults. Organisms reach the well-perfused vertebral body via spinal arteries and quickly spread from the end plate into the disk space and then to the adjacent vertebral body. Sources of bacteremia include the urinary tract (especially among men over age 50), dental abscesses, soft tissue infections, and contaminated IV lines, but the source of bacteremia is not evident in more than half of patients. Diabetes mellitus requiring insulin injection, a recent invasive medical procedure, hemodialysis, and injection drug use carry an increased risk of spinal infection. Many...
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Chapter 120. Osteomyelitis (Part 2) Chapter 120. Osteomyelitis (Part 2) Vertebral Osteomyelitis The vertebrae are the most common sites of hematogenous osteomyelitis inadults. Organisms reach the well-perfused vertebral body via spinal arteries andquickly spread from the end plate into the disk space and then to the adjacentvertebral body. Sources of bacteremia include the urinary tract (especially amongmen over age 50), dental abscesses, soft tissue infections, and contaminated IVlines, but the source of bacteremia is not evident in more than half of patients.Diabetes mellitus requiring insulin injection, a recent invasive medical procedure,hemodialysis, and injection drug use carry an increased risk of spinal infection.Many patients have a history of degenerative joint disease involving the spine, andsome report an episode of trauma preceding the onset of infection. Penetratinginjuries and surgical procedures involving the spine may cause nonhematogenousvertebral osteomyelitis or infection localized to a disk. Most patients with vertebral osteomyelitis report neck or back pain; patientsmay describe atypical pain in the chest, the abdomen, or an extremity that is due toirritation of nerve roots. Symptoms are localized to the lumbar spine more oftenthan to the thoracic spine (>50% vs. 35% of cases) or the cervical spine inpyogenic infections, but the thoracic spine is involved most commonly intuberculous spondylitis (Potts disease). More than 50% of patients experience asubacute illness in which a vague, dull pain gradually intensifies over 2–3 months.Fever is usually low-grade or absent, but some patients recall having had anepisode of fever and chills prior to or at the onset of pain. An acute presentationwith high fever and toxicity is less common and suggests ongoing bacteremia.Percussion over the involved vertebra elicits tenderness, and physical examinationmay reveal spasm of the paraspinal muscles and limitation of motion. Laboratory findings at the time of presentation include a normal ormodestly elevated white blood cell count, anemia, and, almost invariably, anincreased erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP)level. Blood cultures are positive only 20–50% of the time. By the time the patient seeks medical attention, plain radiographs oftenshow irregular erosions in the end plates of adjacent vertebral bodies andnarrowing of the intervening disk space. This radiographic pattern is virtuallydiagnostic of bacterial infection because tumors and other diseases of the spinerarely cross the disk space. CT or MRI may demonstrate epidural, paraspinal,retropharyngeal, mediastinal, retroperitoneal, or psoas abscesses that originate inthe spine. A spinal epidural abscess may evolve suddenly or over several weeks; theclassic clinical presentation is spinal pain progressing to radicular pain and/orweakness. Irreversible paralysis may result from failure to recognize epiduralabscess before the development of neurologic deficits. MRI is the best procedurefor detection of epidural abscess and should be performed in all cases of vertebralosteomyelitis accompanied by subjective weakness or objective neurologicabnormalities. Microbiology More than 95% of cases of hematogenous osteomyelitis are caused by asingle organism, with Staphylococcus aureus accounting for 50% of cases. Othercommon pathogens in children are group A streptococci and, during the neonatalperiod, group B streptococci and Escherichia coli. In adults, vertebralosteomyelitis is caused by E. coli and other enteric bacilli in ~25% of cases. S.aureus, Pseudomonas aeruginosa, Serratia, and Candida albicans infections areassociated with injection drug use and may involve the sacroiliac, sternoclavicular,or pubic joints as well as the spine. Salmonella spp. and S. aureus are the majorcauses of long-bone osteomyelitis complicating sickle cell anemia and otherhemoglobinopathies. Tuberculosis and brucellosis affect the spine more often thanother bones. Other common sites of tuberculous osteomyelitis include the smallbones of the hands and feet, the metaphyses of long bones, the ribs, and thesternum. Unusual causes of hematogenous osteomyelitis include disseminatedhistoplasmosis, coccidioidomycosis, and blastomycosis in endemic areas.Immunocompromised persons may rarely develop osteomyelitis due to atypicalmycobacteria, Bartonella henselae, or opportunistic fungi. Hematogenousosteomyelitis with Mycobacterium bovis has been reported followingintravesicular instillation of bacille Calmette-Guérin (BCG) for cancer of thebladder. The etiology of chronic relapsing multifocal osteomyelitis, aninflammatory condition of children that is characterized ...