Highlights
- •Substantial Clinical Benefit links meaningful change to surgical intervention.
- •Neck Disability Index is a viable metric for evaluating cervical myelopathy.
- •Patient derived outcome measures are time sensitive.
- •Patient derived outcome measures should be calibrated for follow-up time.
Abstract
Patient-reported outcome measures are increasingly used to access pain, disability,
physical function, and mental status to quantify effectiveness of surgical intervention
in cervical myelopathy, yet each score has little meaning without established thresholds
linked to clinical benefit. We set out to develop thresholds for substantial clinical
benefit (SCB) in patients undergoing surgery for cervical myelopathy and to evaluate
the effect of length of follow-up on SCB thresholds.
Thirty-five patients undergoing spinal surgery for progressive cervical myelopathy
were tracked from 2005 to 2015. Observations were categorized into three groups: short-term,
intermediate, and long-term, corresponding to average follow-up intervals of 3.8,
9.2, and 29.0 months. SCB thresholds were calculated for neck visual analog score
(VAS), Neck Disability Index (NDI), Short Form-12 physical (PCS), SF-12 mental component
scores (MCS), and modified Japanese Orthopedic Association score (mJOA) using receiver
operating curve analysis with a 5-level patient satisfaction index as the anchor.
SCB thresholds for each outcome measure were obtained with a range of areas under
the curve indicating varying degrees of discriminatory ability, reported with increasing
length of follow-up. NDI and PCS were most discriminatory of SCB at any time period.
Stratification of thresholds by length of time revealed a significant effect of follow-up
time with NDI but not PCS.
NDI and PCS thresholds have significantly strong discriminatory value in identifying
patients receiving substantial clinical benefit with regard to cervical myelopathy.
When NDI is used to predict outcome, choosing thresholds calibrated for follow-up
time is recommended to maximize predictive power.
Abbreviations:
AUC (area under the curve), CDM (cervical degenerative myelopathy), CI (confidence interval), IT (intermediate follow-up), LT (long-term follow-up), MCID (minimal clinically important difference), MCS (mental component score), mJOA (modified Japanese Orthopedic Association score), NDI (Neck Disability Index), PCS (physical component score), PROM (patient-reported outcome measures), PSI (patient satisfaction index), ROC (receiver operating curve), SCB (substantial clinical benefit), ST (short-term follow-up), VAS (visual analog scale)Keywords
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Article info
Publication history
Published online: January 16, 2019
Accepted:
December 12,
2018
Received:
March 29,
2018
Identification
Copyright
© 2018 Published by Elsevier Ltd.
