Significance of tangential views in lumbar discography

In 64 patients with 69 herniated lumbar discs, craniocaudal or caudocranial tangential views were made in addition to conventional posteroanterior (PA) and lateral views in lumbar discography. Tangential views more clearly demonstrated details of annular tears and herniated discs in comparison with conventional views. The advantages of tangential views are as follows: precise demonstration of position, width, and shape of the hernial opening (main annular tear); precise demonstration of position and shape of the herniated mass; and a topographic display of disc degeneration. Dermal radiation absorbed during tangential views is less than that of computerized tomographic (CT) scans of discography. In addition, tangential views can be readily made at any hospital. The disadvantages of tangential views are that the X-ray tube direction must be chosen for each individual depending on whether there is a cranially or caudally migrated disc herniation; there is a tendency toward decreased sharpness of the exposure, especially when there are advanced degenerative discs; and, absorbed doses of gonadal radiation are higher during caudocranial tangential views than during CT discography in women.