[Clinical effect of cervical artificial disc replacement on two-segment cervical spondylosis]

To investigate the clinical effect of cervical artificial disc replacement (CADR) on two-segment cervical spondylosis and to research its influences on the range of motion (ROM) of the diseased segments and the adjacent superior and inferior segments.

From September 2004 to February 2007, 7 cases with cervical spondylosis at C4,5 and C5,6 were treated with CADR using Bryan artificial disc prosthesis, including 4 males and 3 females aged 30-45 years old (average 38.5 years old). All the patients had cervicodynia in various degrees, pain and numbness of limbs and decreased muscle strength, including 3 cases of cervical spondylotic radiculopathy, 3 of cervical spondylotic myelopathy and 1 of mixed cervical spondylosis. The course of disease was 12-54 months (average 27 months). Preoperatively, X-ray films revealed the intervertebral space of C4,5 and C5,6 was narrowed and the cervical curve became straight, CT or MRI showed the intervertebral disk hernia of C4,5 and C5,6, and the hyperostosis of vertebral margin compressed nerve root or spinal cord. All the patients had no response to the preoperatively conservative treatment. JOA score and ROM of the diseased segments and the adjacent superior and inferior segments were compared before and after operation.

All the patients survived the perioperative period, without hoarse voice, muscle spasm, dysphagia and cervicodynia. X-ray films showed the implanted prosthesis was well located, the height of intervertebral space was normal, and no prosthesis loosening, prosthesis migration and infection occurred 12 months after operation. All the 7 cases were followed up for 12-41 months (average 26.7 months). Cervicodynia and limbs' pain and numbness disappeared, and muscle strength was improved obviously. The JOA score before and during the follow-up period was (8.35 +/- 1.27) and (14.65 +/- 1.61) points, respectively, indicating there was a significant difference (P < 0.05). For the ROM of C4,5 and C5,6, it was (8.38 +/- 0.48) degrees and (9.16 +/- 0.54) degrees before operation, respectively, and it increased to (11.15 +/- 0.65) degrees and (12.75 +/- 0.73) degrees after operation, respectively, showing there was a significant difference (P < 0.05). The ROM at C3,4 and C6,7 before operation was (9.71 +/- 0.76) degrees and (12.39 +/- 0.58) degrees, respectively, while it was improved to (10.26 +/- 0.47) degrees and (13.67 +/- 0.71) degrees after operation, respectively, indicating there were no significant differences between before and after operation (P > 0.05).

The application of Bryan Disc CADR for two-segment cervical spondylosis has satisfying therapeutic effects, can improve the ROM of diseased segments obviously, and has minor influences on the ROM of adjacent superior and inferior segment.