Prevalence: 2–10% of all cases of osteomyelitis

Cause:

1. Direct penetrating trauma (most common) following surgical removal of nucleus pulposus
2. Hematogenous: associated with urinary tract infections / following genitourinary surgery / instrumentation; diabetes mellitus; drug abuse

Pathophysiology: infection begins in low-flow end-vascular arcades adjacent to subchondral plate

Organism: Staphylococcus aureus, Salmonella

Peak age: 5^th–7^th decade

• pain in back, neck, chest, abdomen, flank, hip
• neurologic deficit; positive blood / urine culture
• fever (most common presenting symptom), leukocytosis
• increased erythrocyte sedimentation rate

Location: vertebral body, intervertebral disk, posterior elements (20%)

• disk space narrowing (earliest radiographic sign)
• demineralization of adjacent vertebral endplates
• bulging of paraspinal lines

MR (90% accuracy = method of choice):

• hypointense decreased marrow signal on T1WI
• iso- / hyperintense marrow signal on T2WI
• hyperintense signal on STIR sequence

CEMR:

• enhancing foci in bone marrow + disk space

NUC (time-intensive combined bone-gallium scan):

• tracer uptake in adjacent portions of two vertebral bodies
• PET-CT (comparable to gallium imaging)

Cx: secondary infection of intervertebral disk (frequent)

Rx:>4 weeks course of IV antibiotics

DDx: diskitis