25 - Spinal Infections

Summary

VERTEBRAL OSTEOMYELITIS

Introduction

Pyogenic infections of the spine are most frequently caused by hematogenous spread. Other possible mechanisms are direct inoculation and local extension from a contiguous infection. Involved structures may include the vertebral body, intervertebral disk, spinal canal, or surrounding soft tissues. Because it is an uncommon disease, diagnosis of vertebral body osteomyelitis is often delayed, and late diagnosis may result in collapse of the vertebral body, kyphosis, and spinal instability that can lead to neurologic compromise.

Epidemiology

Vertebral osteomyelitis usually occurs in men older than 50 years of age, though increasing incidence has been noted in younger patients who are injection drug users. The spine is involved in 2% to 4% of all cases of osteomyelitis with the lumbar region most frequently involved. Gram-positive organisms are responsible for the majority of cases, with Staphylococcus aureus reported as the causative organism in greater than 50% of cases. Vertebral infection by Escherichia coli and Proteus has been associated with preceding urinary tract infection, and infection by Pseudomonas has been reported in injection drug users. Diabetes mellitus or penetrating trauma may increase susceptibility to anaerobic infection. Patients with sickle cell anemia are at risk for Salmonella osteomyelitis. Staphylococcus epidermidis and Streptococcus viridans cause infections characterized by an indolent course.