Substantial clinical benefit for Neck Disability Index revisited: establishing the goal for treatment?

Purpose: It is difficult for clinicians to inform patients about the success rate of a treatment as a cervical anterior discectomy procedure. Ideally, a proportion of good outcome as rated by patients is known. Patient-reported outcome measurements are helpful. The purpose is to relate the difference in Neck Disability Index (NDI) after a cervical anterior discectomy procedure for single level cervical degenerative disc disease with the patients' rating of their actual clinical situation after long-term follow-up to define the substantial clinical benefit (SCB).

Methods: After completion of the NDI, patients who were surgically treated for cervical single level degenerative disease were asked to complete a five-item Likert scale to rate their clinical situation. After dichotomisation of the outcome in good versus less than good, a cut-off value was defined by determining the value of the difference of NDI with the highest specificity and sensitivity. Funding was not obtained.

Results: SCB for NDI after surgery for cervical single level degenerative disease should be set at ten with area under the curve (AUC) of 0.71 for sensitivity as well specificity.

Conclusions: The goal for each treatment is a good outcome. While comparing treatments for cervical degenerative disc disease only those with an SCB of ten will be relevant for the patient, as patients who achieved this difference in NDI rated their actual situation at long-term follow-up as good.