A Retrospective Review of Radiographic and Clinical Findings from the M6 Cervical Prosthesis

Study Design: Retrospective clinical study. Purpose: To evaluate clinical results of the M6 cervical prosthesis. Overview of Literature: Cervical disk prostheses have been developed to preserve motion and reduce degeneration in adjacent segments in degenerative disk diseases. Methods: A retrospective evaluation was performed on 43 patients who received the M6 cervical disk prosthesis between 2012 and 2016. Standard and dynamic radiographs, computed tomography, and magnetic resonance imaging were used to evaluate all the patients preoperatively and postoperatively. The Neck Disability Index (NDI) and Visual Analog Scale (VAS) scores were examined in evaluating the clinical and functional results of patients with collapsed disk herniation who had received the M6 cervical prosthesis and to evaluate whether the core structure of the prosthesis protects motion. Results: The mean follow-up period was 34.12 +/- 6.70 months. Radiologically, the preoperative cervical segment ROM was measured as a mean of 5.77 degrees +/- 2.19 degrees preoperatively and 8.49 degrees +/- 2.37 degrees at the inal postoperative follow-up examination. In the patients with a preoperative disk height of <4 mm, the segmental ROM increased from 4.53 degrees +/- 2.79 degrees preoperatively to 7.2 degrees +/- 3.18 degrees postoperatively. In the patients with a preoperative disk height of >4 mm, the cervical segment ROM increased from 6.4 degrees +/- 1.45 degrees preoperatively to 8.6 degrees +/- 2.02 degrees at the inal postoperative follow-up examination. The NDI scores reduced from 53.86 +/- 9.77 preoperatively to 22.69 +/- 7.26 postoperatively and the VAS scores reduced from 8.74 +/- 0.58 to 1.88 +/- 1.14. During follow-up in any patient, no collapse of the levels at which surgery was performed was observed. No heterotopic ossiication or implant failure was recorded in any patient during the follow-up period. Conclusions: The M6 new-generation cervical disk prosthesis had few complications. No heterotopic ossiication was observed in any patient, and lexion-extension ROM was maintained in all the patients, indicating the M6 prosthesis as a promising alternative.