Ultrasound imaging of the intervertebral disc.

STUDY DESIGN In vitro ultrasound imaging of dog intervertebral discs was performed. OBJECTIVE To determine the reliability of ultrasound imaging in the detection of structural changes associated with disc pathology. SUMMARY OF BACKGROUND DATA Little work has been done to evaluate the potential applications of ultrasound in the imaging of intervertebral discs. Initial in vitro studies, however, have indicated that ultrasound imaging is capable of producing images of the disc that contain a high degree of structural information. METHODS Explanted lumbosacral discs from 13 nonchondrodystrophic dogs, mean age 5 years and 8 months, were stripped of all surrounding tissues and scanned using ultrasound before being sectioned and photographed. The ultrasound images were graded according to criteria chosen to reflect progressive stages of disc degeneration, allowing correlation with the grading scale used to assess the photographic images of the discs. Grades assigned to each disc were compared using Cronbach's alpha to determine the reliability of the images obtained using ultrasound. RESULTS The results for the anterior anulus fibrosus produced an alpha value of 0.924; those for the nucleus pulposus produced a value of 0.821; whereas those for the posterior anulus fibrosus produced a value of 0.882. Where the grade given to the ultrasound image did not match those given in visual assessment, the disparity was never greater than one grade. Ultrasound images of several discs demonstrated echo patterns that matched, in both location and appearance, real structural defects identifiable on the sectioned discs. CONCLUSIONS Ultrasound images of intervertebral discs relate well to their pathologic condition. In addition, ultrasound is able to locate specific pathologic defects.