Early Radiological Analysis of Cervical Arthroplasty with Bryan and Mobi-C Cervical Disc Prosthesis

ABSTRACT

OBJECTIVE: We investigated whether there are any different results in the overall sagittal alignment, neutral functional spine unit (FSU) angle and segmental FSU ROM (range of motion) angle from the patients undergone by cervical arthroplasty with two kinds of artificial cervical disc prostheses, Bryan and Mobi-C cervical disc. METHODS: Twenty eight patients underwent anterior cervical discectomy and implantation of artificial cervical disc prosthesis; Eighteen of them underwent operation with Bryan and the rest of them with Mobi-C cervical disc prosthesis. These patients consist of fourteen females and fourteen males with mean age 46.9 years old and 9.4 months mean follow-up period. There were 4 cases of C 4-5, 18 cases of C 5-6 and 6 cases of C 6-7 level. We measured overall sagittal alignment, neutral FSU angle and segmental FSU ROM angle using lateral radiographs preoperatively and postoperatively. The clinical outcome was evaluated by neck disability index(NDI). RESULT: The average angle of overall sagittal alignments was changed from -17.45degrees preoperatively to -14.21degrees postoperatively in Bryan cervical disc group. It decreased 3.24degrees in cervical lordosis. However, in Mobi-C cervical disc group, the average angle of overall sagittal alignments was changed from -10.33degrees preoperatively to -16.89degrees postoperatively. It increased 6.56degrees in cervical lordosis. The averages of neutral FSU angles were -1.14degrees preoperatively and -3.26degrees postoperatively in Bryan cervical disc group, and were -0.93degrees preoperatively and -9.7degrees postoperatively in Mobi-C cervical disc group. The averages of segmental FSU ROM angles were 11.18degrees preoperatively and 10.61degrees postoperatively in Bryan cervical disc group, and was 8.31degrees preoperatively and 13.6degrees postoperatively in Mobi-C cervical disc group. NDIs were 24.0 preoperatively and 5.9 postoperatively in Bryan cervical disc group, and 24.7 preoperatively and 8.7 postoperatively in Mobi-C cervical disc group. CONCLUSION: Postoperative cervical lordosis and segmental FSU ROM angle were increased in Mobi-C cervical disc group (p<0.05). To preserve segmental motion and avoid adjacent segment degeneration is to the focus in cervical arthroplasty. To preserve cervical lordosis after operation is physiologic than postoperative cervical kyphosis. It remains controversial whether cervical kyphosis influences clinical outcome after anterior cervical operation. The results of this study show that the technical and mechanical improvement of Bryan cervical disc prosthesis may be considered.