A Novel Quality-of-Life Utility Index in Patients With Multilevel Cervical Degenerative Disc Disease Comparison of Anterior Cervical Discectomy and Fusion With Total Disc Replacement

Study Design. Decision analysis from prior randomized controlled trial (RCT) data. Objective. To describe the importance of developing baseline utility indices while identifying effective treatment options for cervical spine disease. Summary of Background Data. Cervical total disc replacement (CTDR) was developed to treat cervical spondylosis while preserving motion. Although anterior cervical discectomy and fusion (ACDF) has been the standard of care, a recent RCT suggested similar outcomes for 2-level disease. The quality-of-life benefit afforded by both CTDR and ACDF has never been fully elucidated. The purpose of our investigation was to better define the changes in utility and perceived value for patients undergoing these procedures. Methods. Data were derived from LDR's RCT comparing CTDR and ACDF for 2-level cervical disc disease. Using linear regression, we constructed health states on the basis of the stratification of clinical outcomes used in the RCT, namely, neck disability index and visual analogue scale. Data from SF-12 questionnaires, completed preoperatively and at each follow-up visit, were transformed into utilities using the SF-6D mapping algorithm. SAS v.9.3 was used for the analyses. Results. A strong correlation (R-2 = 0.6864, P < 0.0001) was found between neck disability index and visual analogue scale. We constructed 5 distinct health states by projecting neck disability index intervals onto visual analogue scale. A poorer health state was associated with a lower mean utility value whereas a higher health state was associated with a higher mean utility value (P < 0.0001). The difference in preoperative utility between 2-level ACDF and CTDR was not significant (P = 0.1982), and yet, the difference in the postoperative utility between the cohorts was significant (P < 0.05) at every time point collected from 6 to 60 months. Conclusion. This is the first instance in which distinct utility values have been derived for validated health states related to cervical spine disease. There is substantial potential for these to become baseline future indices for cost-utility analyses in similar populations. Level of Evidence: 1