Individual success is defined as at least a 15 point improvement in Neck Disability Index (NDI) Score at 120 months compared with baseline, maintenance or improvement in neurologic status at 120 months compared with baseline, no additional surgical procedure at the index level within 120 months, and the absence of a serious adverse event classified as implant-associated or implant/surgical procedure-associated within 120 months. A subject must meet each criterion to be considered an overall study success.
NDI scale is reported in a range from 0 - 100, with 0 consistent with best ability to function and 100 with worst ability to function.