Infections of the Spine: A Review of Clinical and Imaging Findings

Vikram K. Sundaram, MD; Amish Doshi, MD

Disclosures

Appl Radiol. 2016;45(8):10-20. 

In This Article

Vertebral Body Vascular Anatomy

The anatomy of the adult vertebral body vascular network is important in understanding the typical patterns of infection within the spinal column. The arterial supply to each vertebral body consists of paired segmental arteries that arise, depending on the location, from the vertebral arteries, the aorta, or the iliac arteries. The segmental arteries run in the equatorial plane around their respective vertebral body, and along their course toward the transverse processes, and give off multiple extraosseous anastomotic channels. Arising within a vertebral body from each segmental artery are paired metaphyseal arteries and a single nutrient artery, both of which have end vessels at the superior and inferior endplates of each vertebral body. The metaphyseal arteries also supply an intermetaphyseal anastomotic arterial network that spans multiple vertebral body levels (Figure 1).[1]

Figure 1.

Sagittal and coronal drawings represent the point at which intercostal and lumbar arteries (LA) become segmental arteries that pass through the neural foramina, course beneath the posterior longitudinal ligament, and enter the basivertebral foramen as the nutrient artery (NA). Each segmental artery also gives rise to paired metaphyseal anastomosing arteries (MA) that parallel their course along the metaphyses. The segmental artery joins each MA by about 10–15 primary periosteal arteries (PPA). Adjacent MA interlink via approximately 20 intermetaphyseal artery anastomoses (MAN). The anterolateral equatorial artery (ALEA) and periosteal arteries (PA) are also depicted. (Adapted from Ratcliffe J. F. The arterial anatomy of the adult human lumbar vertebral body: A microarteriographic study. J. Anat., 1980;131 (Pt 1):77.)

In childhood, this arterial network extends to the level of the intervertebral disc and provides a rich capillary network that are considered to be end-vessels and are typically the final location for septic emboli. In adults, however, the rich capillary network regresses and the arterial end-vessels terminate at the superior and inferior endplates of the vertebral bodies, resulting in a different typical initial location for spinal infection compared to pediatric patients.

The multiple extraosseous and intermetaphaseal anastomotic channels imply that an infection can span multiple and sometimes non-contiguous vertebral bodies. In addition, the avascularity of the adult intervertebral discs suggests that these parts of the spinal column would be involved in the infection at a chronic or advanced stage, and only in organisms with the appropriate proteolytic activity to gain access to the disc space.

The venous supply can also provide a channel for potential infection. Valveless veins exit the vertebral body at the dorsal nutrient foramen and drain into an extradural venous plexus that in turn drains into the paravertebral venous plexus of Batson. The venous route allows for retrograde spread of infection from abdominal and pelvic organs, such as in urinary tract infection. It also tends to be the preferred route of fungal infections and tuberculosis.[2]

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