Pathoanatomy of lumbar disc herniation as demonstrated by computed tomography/discography.

Computed tomography/discography was performed in 378 patients (403 discs) with lumbar disc herniation receiving intradiscal therapy. The grade of disc degeneration defined by the Dallas discogram description correlated closely with age. The most common herniation routes ran through the central portion of the posterior aspect of the disc (48.9%), through the paracentral portion (18.6%) and through the entire central portion (9.7%), with these directions parallel to the sagittal plane. However, the intraforaminal and extraforaminal routes (4.2%) passed obliquely to the sagittal plane. The development of these herniation routes has been well explained by the findings of earlier histopathologic and biomechanical studies. Computed tomography/discography was very useful in observing the detailed features of HNP such as the range, site of maximum protrusion and protrusion size.