The kinematics of anterior cervical discectomy and fusion versus artificial cervical disc: A pilot study

OBJECTIVE: Anterior cervical discectomy and fusion (ACDF) for the management of cervical spondylosis may contribute to further degenerative changes at adjacent levels secondary to abnormal spinal motion. Insertion of a Bryan Cervical Disc (AD) (Medtronic Sofamor Danek, Memphis, TN) may prevent this accelerated degeneration. This retrospective study compares the in vivo x-ray cervical spine kinematics in patients with ACDF and AD. METHODS: Ten patients with single-level AD were matched to 10 patients with single-level ACDF based on age and sex. Lateral neutral, flexion and extension cervical x-rays were obtained preoperatively and at regular intervals up to 24 months postoperatively. Kinematic parameters, including range of motion, anteroposterior translation, and disc height, were assessed for all cervical functional spinal units using quantitative motion analysis software. Changes in these parameters were compared between matched patients from both groups using paired Student's t tests. RESULTS: The range of motion at the operated level was greater in the AD group compared with the ACDF group at early (6.9 versus 0.89 degrees, P < 0.01) and late (8.4 versus 0.53 degrees, P < 0.01) follow-up evaluations. Translation was greater at the operated level in patients with AD at late follow-up (6.8 versus 0.8%, P < 0.03) evaluation. No significant between-group kinematic differences were seen at adjacent levels. CONCLUSION: Patients with AD and those with ACDF demonstrated similar in vivo adjacent level kinematics within the first 24 months after anterior cervical decompression.