Prospective, multicenter clinical trial comparing M6-C compressible six degrees of freedom cervical disc with anterior cervical discectomy and fusion for the treatment of single level degenerative cervical radiculopathy: Two- year results of an FDA investigational device exemption study.

BACKGROUND CONTEXT Various designs of total disc replacement (TDR) devices have been compared to ACDF with favorable outcomes in FDA-approved investigational device exemption (IDE) trials. The design of M6-C with a compressible viscoelastic nuclear core and an annular structure is substantially different than prior designs and has previously demonstrated favorable kinematics and clinical outcomes in small case series. PURPOSE To evaluate the safety and effectiveness of the novel M6-C compressible artificial cervical disc compared with anterior cervical discectomy and fusion (ACDF) for subjects with single level degenerative cervical radiculopathy. STUDY DESIGN/SETTING Prospective, multicenter, concurrently- and historically-controlled, FDA-approved investigational device exemption (IDE) clinical trial. PATIENT SAMPLE Subjects with one-level symptomatic degenerative cervical radiculopathy were enrolled and assigned to receive M6-C or ACDF. OUTCOME MEASURES Pain and function (NDI, VAS), quality of life (SF-36), safety, neurological and radiographic assessments of motion (both flexion extension and lateral bending) were performed. The primary clinical endpoint was composite clinical success (CCS) at 24 months. METHODS Using propensity score subclassification to control for selection bias, 160 M6-C subjects were compared to a matched subset of 189 ACDF controls (46 concurrent and 143 historical controls). RESULTS Both ACDF AND M6-C subjects reported significant improvements in patient reported outcomes at all time points over baseline. Overall SF-36 Physical Component Score and neck and arm pain scores were significantly improved for M6-C as compared to ACDF treatment. CCS and mean NDI improvements were similar between M6-C and ACDF. Correspondingly, there were significantly fewer subjects that utilized pain medication or opioids following M6-C treatment at 24 months relative to baseline. Range of motion was maintained in subjects treated with M6-C. Subsequent surgical interventions, dysphagia rates, and serious adverse events were comparable between groups. CONCLUSIONS M6-C treatment demonstrated both safety and effectiveness for the treatment of degenerative cervical radiculopathy. Treatment with M6-C demonstrated non-inferiority for the primary endpoint, indicating a similar ability to achieve Composite Clinical Success (CCS) at 24 months. However, for the secondary endpoints, M6-C subjects demonstrated significantly improved pain and function compared to ACDF subjects, while maintaining range of motion, improving quality of life and decreasing analgesic and opioid usage at 2 years postoperatively relative to baseline.