437 - M6-C Artificial Cervical Disc 24 Month Follow up: Clinical and Radiogr...

General Session: Arthroplasty - Hall F

Presented by: R. Sasso


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

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


Introduction: Artificial cervical disc designs continue to evolve. The purpose of this study is to evaluate the two-year clinical and radiographic results of the M6-C Artificial Cervical Disc (Spinal Kinetics, Sunnyvale, CA), a next generation six-degree of freedom cervical disc, designed to replicate the anatomic, physiologic and biomechanical characteristics of the natural cervical disc, for the treatment of single-level cervical radiculopathy at five investigational sites participating in a FDA approved IDE Study. The M6-C's novel design incorporates a compressible nucleus within a multi-layer fiber annulus allowing for a controlled range of motion and natural kinematics in all planes of motion.

Methods: The five investigational centers participated in a prospective, multi-center, FDA IDE study of patients with cervical radiculopathy who had not improved with at least 6-weeks of non-surgical care. Specific inclusion and exclusion criteria were used to determine eligibility for participation in the study (preoperative NDI ≥ 30%, neck or arm pain ≥ VAS 4 out of 10 cm, no previous anterior cervical spine surgery, etc.). 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 patients were treated with the arthroplasty device with a mean age of 44 years, BMI of 27 and a mean length of symptoms prior to surgery of 24 months. Surgery was performed at C5-6 or C6-7 levels in 90% of the patients. Mean surgical time (incision-to-skin closure) was 83 minutes with an average blood loss of 31cc. Mean hospital stay was 0.5 days. Mean preoperative NDI was 55.4 which significantly decreased to 11.3 (p< 0.001) at two-years. There was a significant reduction in VAS neck pain from 7.3 preoperative to 1.3 (p< 0.001) at the two year follow up. Mean predominant preoperative arm VAS pain was 7.2 which improved to 0.5 (p< 0.001) at two-years. Index level lordosis improved to 7.1 degrees at one year vs. 1.8 degrees at baseline and mean index level ROM increased slightly from 7.8 degrees preoperative to 8.1 at two years. Radiographically, there were no migrations and one mild radiolucency. One removal due to suspected infection and 3 incidences of subsidence were reported. There were no serious adverse events deemed to be device related in this cohort as adjudicated by an independent panel of surgeons.

Conclusions: The two-year clinical outcomes from five investigational centers suggests that the device performs as intended both clinically and radiographically for the treatment of symptomatic cervical radiculopathy. Prior biomechanical studies have confirmed the kinematic advantages and long-term stability of the M6-C over first generation TDR designs. In this cohort there were no incidents of device mechanical failure and no findings of device migration throughout the follow-up. Additional follow-up of the population at these five centers and in the overall study will further elucidate safety & effectiveness outcomes as well as the potential kinematic benefits offered by this next generation cervical disc replacement.