TABLE I

Inclusion and Exclusion Criteria*

Inclusion CriteriaExclusion Criteria
Patients
  • • Patients with cervical myelopathy secondary to OPLL

  • • Treated surgically and followed postoperatively

  • • Age, >18 yr

  • • Patients with other forms of degenerative cervical myelopathy, traumatic spinal cord injury, thoracic or lumbar myelopathy, tumor, infection, radiculopathy only, or other nondegenerative myelopathies

  • • Patients undergoing revision surgery

Prognostic factors
  • • OPLL-related factors

  • • Occupying ratio

  • • Thickness

  • • Shape (hill, plateau, mushroom-shaped)

  • • Type (segmental, continuous, mixed, localized)

  • • K-line status (+)/(–)

  • • No. of ossified levels

  • • Clinical factors (age, duration of symptoms, baseline severity score, signs, symptoms, comorbidities, smoking status, sex, body mass index)

  • • Non-OPLL-related imaging factors (signal changes on T1 or T2-weighted MRI scans, transverse area, anteroposterior diameter, cervical alignment, range of motion)

  • • Surgical factors (surgical approach, technique, no. of operated segments, no. of stages, fusion, operative duration, estimated blood loss)

Outcome
  • • Quality-of-life outcomes

  • • Neck Disability Index, SF-36

  • • Functional outcomes

  • • mJOA or JOA score, Nurick classification

  • • Return to work

  • • Progression of OPLL

  • • Surgical complications

  • • Heterotopic ossification

  • • Radiographic outcomes

  • • Neurological examination or subjective improvement of symptoms

Study design
  • • Cohort studies designed to evaluate prognostic factors

  • • Must report p values or odds ratios

  • • Studies that did not distinguish between patients with CSM and OPLL

  • • Review articles

  • • Opinions

  • • Studies with <15 patients

  • • Animal or biomechanical studies

  • * mJOA = modified Japanese Orthopaedic Association, CSM = cervical spondylotic myelopathy.