TABLE II

Demographics and Characteristics of Prognostic Studies Involving Multivariate Analysis*

StudySample and CharacteristicsNon-OPLL Factors AssessedOPLL Factors AssessedMain Outcome Measure
Chen et al.21 (2014)
  • • OPLL (n = 133)

  • • Male: 63.2%

  • • Mean age (range): 56.8 ± 6.4 yr (27 to 78 yr)

  • • Surgery: anterior corpectomy with fusion

  • • Follow-up: 3, 6, and 12 mo

  • • Age

  • • Sex

  • • Preoperative JOA score

  • • Duration of symptoms

  • • Smoking status

  • • Diabetes

  • • Levels of corpectomies

  • • Signal change on T2-weighted MRI

  • • Occupying ratio

  • • Dural ossification

  • • Postoperative JOA score

Choi et al.22 (2005)
  • • OPLL (n = 47)

  • • Male: 76.6%

  • • Mean age: 54.7 ± 8.0 yr

  • • Surgery: anterior corpectomy with fibular allograft fusion

  • • Follow-up: 16 mo

  • • Age

  • • Sex

  • • Preoperative Nurick grade

  • • Duration of symptoms

  • • Duration of follow-up

  • • Snake-eye appearance

  • • Diabetes

  • • Pavlov ratio

  • • Occupying ratio§

  • • Type of OPLL#

  • • Double-layer sign

  • • Nurick grade

    • ○ Good outcome: increase of at least 1 Nurick grade

    • ○ Poor outcome: no change or decrease in Nurick grade

Iwasaki et al.23 (2002)
  • • OPLL (n = 64)

  • • Male: 67.19%

  • • Mean age (range): 56.0 yr (42 to 78 yr)

  • • Surgery: laminoplasty

  • • Follow-up: 10 yr

  • • Age

  • • Preoperative JOA score

  • • Type of OPLL#

  • • Occupying ratio

  • • Space available for the spinal cord

  • • Postoperative JOA score

Iwasaki et al.7 (2007)
  • • OPLL (n = 66)

  • • Male: 77.27%

  • • Mean age (range): 57.0 yr (41 to 75 yr)

  • • Surgery: laminoplasty

  • • Mean follow-up (range): 10.2 yr (5 to 20 yr)

  • • Age

  • • Preoperative JOA score

  • • Sagittal alignment

  • • Shape of ossification (plateau or hill-shaped)

  • • Occupying ratio**

  • • Space available for the spinal cord

  • • Postoperative JOA score and recovery rate at time of latest follow-up

  • • Maximum postoperative JOA score and recovery rate

Kim et al.24 (2015)
  • • OPLL (n = 71)

  • • Male: 71.83%

  • • Mean age (range): 57.3 yr (35 to 76 yr)

  • • Surgery: anterior decompression and fusion

  • • Mean follow-up (range): 48 mo (12 to 68 mo)

  • • Age

  • • Sex

  • • Preoperative JOA score

  • • Diabetes

  • • Smoking status

  • • BMI

  • • Signal intensity grade

  • • Sagittal alignment

  • • Shape of ossification (plateau or hill-shaped)

  • • Occupying ratio**

  • • Type of OPLL#

Ogawa et al.25 (2005)
  • • OPLL (n = 57)

  • • Male: 78.95%

  • • Mean age (range): 58 yr (40 to 77 yr)

  • • Surgery: laminoplasty

  • • Median follow-up (range): 10 yr (7 to 18 yr)

  • • Segmental OPLL

  • • Postoperative JOA score

  • • Change in JOA score

  • • Upper-extremity and trunk scores

  • • Lower-extremity and bladder scores

Uchida et al.26 (2005)
  • • OPLL (n = 58)

  • • Male: 67.24%

  • • Surgery: anterior decompression with fusion or laminoplasty

  • • Mean follow-up (range): 8.3 yr (1.0 to 12.8 yr)

  • • Age

  • • Sex

  • • Duration of symptoms

  • • Preoperative JOA score

  • • Crandall and Batzdorff type

  • • Surgical procedure

  • • Rate of cord flattening

  • • Signal change on T2-weighted MRI

  • • Grade of SCEP

  • • Occupying ratio**

  • • Type of OPLL#

  • • Postoperative JOA score

  • * JOA = Japanese Orthopaedic Association score, BMI = body mass index, SCEP = spinal cord evoked potentials.

  • Evaluated on axial CT scan.

  • The Hida double-layer sign was investigated to indicate dural ossification.

  • § (Area of OPLL/area of the spinal canal) × 100%; evaluated on axial CT scan.

  • # Continuous, segmental, mixed, or circumscribed/localized.

  • ** Evaluated on lateral radiographs or CT scans.

  • †† Recovery rate = (postoperative JOA score − preoperative JOA score)/(17 − preoperative JOA score) × 100%.