The spine is critical for normal human function, providing structure, support, and protection of the spinal cord and spinal nerves. Given the wide range of pathologic conditions that can affect the spine, recognition of normal anatomy and variants, differentiation from abnormal anatomy, and diagnosis of different pathologic conditions are the goals of spine imaging.
It is assumed that the reader is already familiar with basic spine anatomy learned early in medical school. With such a foundation, this chapter on the imaging appearance of the spine will serve to solidify and perhaps even enhance this knowledge base.
The purpose of this chapter is to review the different techniques employed in spine imaging, to emphasize normal anatomy as depicted with these techniques, and to highlight the appearance of certain common lesions. Relative advantages and disadvantages of the various imaging modalities are reviewed within the context of an overall imaging strategy. It is not intended that the reader will be an accomplished spine radiologist after reading this chapter. Rather, it is hoped that the reader will gain basic familiarity with normal imaging anatomy and the appearance of certain types of abnormalities, as well as a sense of which test might be the best to order for a given clinical circumstance.
Prior to the advent of computed tomography (CT) in the 1970s, spine imaging consisted primarily of plain-film radiography and an adjunct test, myelography, to be discussed later. Spine imaging was revolutionized by CT, and, subsequently, magnetic resonance (MR) imaging, which for the first time allowed direct acquisition of axial, sagittal, and coronal (multiplanar) images, allowing for better spatial and contrast resolution. Not until the era of CT could the spinal cord be visualized and evaluated. These imaging modalities have so changed the face of diagnosis and treatment of spine pathology that virtually no neurosurgeon today would undertake spine surgery without first obtaining a CT and/or MR imaging study.
This section reviews the major modalities currently employed to image the spine. The highly specialized technique of spinal arteriography, which is used principally to detect vascular malformations, is beyond the scope of this review. Nuclear medicine scanning also is not discussed, because it is seldom used as a primary diagnostic study in the evaluation of spine disease (though spinal metastases are frequently diagnosed with whole-body isotope bone scanning).
Plain films are conventional radiographs, which are commonly referred to as x-rays. They may be obtained in a frontal projection—anteroposterior (AP) or posteroanterior (PA); the difference is insignificant in the spine—a lateral projection (side view), or an oblique projection (Figures 13-1, 13-2, and 13-3). Plain films are most useful for the visualization of bony structures. Soft-tissue structures (everything but bone) are largely radiolucent and cannot be seen clearly on plain films unless abnormal density such as calcification is present. Although plain films depict bone anatomy quite well, certain structures ...