General Session: Cervical Motion Preservation

Presented by: F. Phillips - View Audio/Video Presentation (Members Only)


F. Phillips(1), R. Sasso(2), D. Coric(3), R. Guyer(4), A. Sama(5), F. Cammisa(5), S. Blumenthal(4), T. Albert(5), J. Zigler(4)

(1) Midwest Orthopaedics at Rush University, Chicago, IL, United States
(2) Indiana Spine Group, Carmel, IN, United States
(3) Carolina Neurosurgery & Spine Associates, Charlotte, NC, United States
(4) Texas Back Institute, Plano, TX, United States
(5) Hospital for Special Surgery, New York, NY, United States


Introduction: Clinical outcomes for a number of 1st generation ball-and-socket design cervical total disc replacements (TDRs) have been previously reported. The M6-C TDR (Spinal Kinetics, Sunnyvale, CA) is an advanced generation artificial disc designed to replicate the anatomic, physiologic, and biomechanical characteristics of the native disc. The unique design of the M6-C enables the disc to have all six degrees of freedom including axial compression with independent angular motions in flexion-extension, lateral bending and axial rotation, allowing independent translations along the three anatomic axes. The purpose of this analysis is to evaluate the one-year clinical and radiographic results associated with the use of the M6-C TDR in five investigational centers.

Methods: This is a prospective, multi-center, FDA approved IDE study of patients with cervical radiculopathy who had not improved with at least 6 weeks conservative care and were implanted with the M6-C TDR at one cervical level from C3 - C7. Patients were enrolled according to designated entry criteria including NDI score of ≥ 30%, neck or arm pain VAS ≥ 4, with exclusions consistent with prior FDA IDE studies. The study cohort was derived from 5 investigational sites. Patient evaluation included the Neck Disability Index (NDI), Neck and Arm Visual Analogue Scales (VAS), neurological assessment, and radiographic confirmation of radiculopathy. A/P, lateral, F/E and lateral-bending x-rays were obtained for both quantitative and qualitative assessment using validated, computer-assisted methods (QMA®: Medical Metrics, Inc., Houston, TX).

Results: Eighty-three (83) patients are included in this analysis. Forty-three (52%) patients were males. The mean age at the time of surgery was 44 years. Surgery was performed at the C5-C6 and C6-C7 levels in 90% of the patients. Mean blood loss was 31 cc, and surgical time (skin-to-skin) was 83 minutes. Ninety-eight percent of patients had their PLL released at surgery. Mean hospital stay was 0.5 days. Baseline mean NDI was 55.4 and at one year follow-up was significantly decreased to 10.8 (p< 0.001). There was a significant reduction in VAS neck pain from 7.3 preoperative to 1.3 at one year (p< 0.001). Mean predominant preoperative arm VAS pain was 7.1 and improved to 0.7 at one year (p< 0.001). Radiographically there were no radiolucencies or migrations. There were no cases of revision, removal, or supplemental fixation. One patient experienced caudal subsidence. Mean index level ROM was maintained from 7.8 degrees preoperative to 7.9 degrees at one year. Index level lordosis was improved to 7.1 degrees at one year vs. 1.8 degrees at baseline. Mean left-right bending ROM was 5.8 degrees preoperative and 7.2 degrees at one year. .

Conclusion: The results from this one-year follow-up of patients implanted with the M6-C indicate clinical effectiveness as evidenced by excellent clinical and radiographic outcomes. Prior biomechanical studies have confirmed the kinematic advantages of the M6-C over 1st generation TDR designs. The excellent clinical and radiographic results and low reoperation rates seen with the M6-C will hopefully stimulate comparative clinical trials.