Table 1.

Definition of Overall Success. All of the following were required for a patient's outcome to be considered an Overall Success (Reprinted with permission from Gornet MF, Burkus JK, Shaffrey ME, Argires PJ, Nian H, Harrell FE: Cervical disc arthroplasty with PRESTIGE LP disc versus anterior cervical discectomy and fusion: a prospective, multicenter investigational device exemption study. J Neurosurg Spine. 2015 Jul 31:1-16. [Epub ahead of print] PMID: 26230424.²²).

Variables	Definition
Neck Disability Index (NDI) Success	≥15-point improvement postoperatively compared to preoperative score
Neurological Status Success	Maintenance or improvement in postoperative neurological status (motor function, sensory function, and reflexes) compared to preoperative condition
Functional Spinal Unit (Disc Height) Success	Functional spinal unit anterior or posterior measurement height declined by no more than 2 mm vs. the 6-week postoperative assessment
No serious adverse event classified as implant or implant/surgical procedure associated	Serious AE = Grade 3 or Grade 4 per World Health Organization criteria (typically, resulting in ER visit or hospitalization)
No secondary surgical procedure classified as a “failure”	Supplemental fixation, removal or revision = treatment failure. Reoperation or other surgical procedure ≠ treatment failure

AE = adverse event, ER = emergency room.