Table 1 Primary and secondary outcome parameters

Primary outcome parameter

Neck Disability Index at five years’ follow-up

Secondary outcome parameters

Core Outcome Measures Index

Individual patient success at 12, 24, 36, 48 and 60 month defined as:

  ● Improvement of at least 17 in the Neck Disability Index (100 points) compared with baseline (adjustable according to results from own minimal clinically important change results for Neck Disability Index).

  ● Pain relief, as defined by ≥20 mm improvement on 100 mm visual analog for arm/shoulder pain

  ● Global outcome (1 or 2 on five-category Likert scale)

  ● No opiates or opiate derivatives because of neck or arm pain

  ● Absence of symptomatic device failure and re-operations at the index level

Pain relief, as defined by ≥20 mm improvement on 100 mm visual analog scale for neck pain and arm or shoulder pain

Changes in physical and mental health defined as improvement of 15% in the overall score as captured by the Short Form-12 (SF-12) version 2 questionnaire (Brazier 2005)

Modified Japanese Orthopedic Association score and Nurick score

Adjacent level degeneration:

  ● By evidence of instability, defined as sagittal plane translation >3.5 mm (20% of vertebral body anterior-posterior diameter) or sagittal plane rotation of >20° based on standing flexion or extension X-rays

  ● By evidence of disc degeneration (Miyazaki grade ≥ IV) or osteochondrosis (Modic change type I) on magnetic resonance imaging

  ● Radiographic classification (Walraevens 0 to 3)

  ● By occurrence of operation because of adjacent level disease

Quantitative sensory testing

Segmental lordosis and overall cervical sagittal alignment

Operative time

Length of hospital stay

Pain medication usage (including epidural injections and nerve block injections)

Return to work

Worker’s compensation

Direct and indirect societal costs