EFFECT OF DEGENERATION OF THE INTERVERTEBRAL-DISK ON THE PROCESS OF DIFFUSION

PURPOSE: To test the hypothesis that diffusion of contrast medium into the intervertebral disk is affected by the integrity of the nucleus p ulposus and annulus fibrosus. METHODS: In canine intervertebral disks, defects were made in the annulus fibrosus and nuclear material was re moved from the disk with a nucleotome. MR imaging was performed with i ntravenous contrast medium at 15, 30, 60, and 90 days after the proced ure. The diffusion of contrast medium in the intervertebral disk was s tudied by visual inspection and by measuring changes in signal intensi ty. The intervertebral disk were classified at each MR study as normal or abnormal on the basis of the signal intensity on T2-weighted image s. RESULTS: In untreated disks after intravenous injection of contrast medium, a band of increased signal intensity was observed near the en dplates that became wider with time and approached the center of the d isk. In six of the 12 treated disks, the band of increased signal inte nsity was visibly diminished or less discrete compared with that in th e control disks. Weeks later, these treated disks showed diminished si gnal intensity an T2-weighted images and bulging of the annulus fibros us. CONCLUSIONS: Intervertebral disks with defects in the annulus fibr osus and reduced cartilage content were characterized by abnormal diff usion of contrast medium into the disk, and changes characteristic of early disk degeneration were detected subsequently.