ABSTRACT
STUDY DESIGN: Retrospective radiographic review. OBJECTIVE: To investigate the effects of cervical disc herniation on kinematics at adjacent vertebral motion segments. SUMMARY OF BACKGROUND DATA: Kinetic magnetic resonance imaging (kMRI) is an alternative method to conventional MRI, which allows evaluation of the cervical spine in a more physiologic, weight-bearing position, and acquisition of images in flexion, extension, and neutral alignment. kMRI has previously been used to evaluate the effects of disc degeneration on cervical kinematics. METHODS: A total of 407 patients with neck pain without prior history of surgery were evaluated using kMRI. Translational motion, angular variation, and disc height were measured at each segment from C2-C3 through C7-T1. Other factors including the degree of disc degeneration, age, gender, and vertebral segment location were analyzed in order to determine any predisposing risk factors for segmental instability adjacent to disc herniations. RESULTS: Spinal levels above the disc herniation exhibited, on average, a 7.2% decrease in translational motion per mm of disc herniation (P = 0.0113), without significant change in angular motion. Levels below the herniation demonstrated a 5.2% decrease in angular motion per mm of disc herniation (P = 0.0236) without significant change in translational motion. The degree of disc degeneration had no significant effect on adjacent level motion. Disc herniation had no significant impact on disc height at adjacent levels, although disc degeneration correlated with decreased disc height above and increased disc height below. CONCLUSION: Although disc height, translational motion, and angular variation are significantly affected at the level of a disc herniation, no significant changes are apparent in adjacent segments. Our results indicate that herniated discs have no effect on ROM at adjacent levels regardless of the degree of disc degeneration or the size of disc herniation, suggesting that the natural progression of disc degeneration and adjacent segment disease may be separate, unrelated processes within the cervical spine.
