Introduction: Cervical total disc replacement (TDR) was developed to treat neck pain and neurological sequelae associated with cervical spondylosis, while preserving motion. While ACDF has been the standard of care, a recent randomized controlled trial (RCT)1 suggested similar outcomes for two-level disease. However, the quality of life benefit in this population, afforded by both TDR 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 was derived from LDR’s RCT1. Included patients (n=330) had degenerative disc disease with radiculopathy/myeloradiculopathy at two contiguous levels from C3-C7 that was unresponsive to conservative treatment. Using linear regression, we constructed health states based on the stratification of clinical outcomes used in the RCT, namely, neck disability index (NDI) and visual analog scale (VAS). Data from SF-12 questionnaires2, completed pre-operatively and at each follow-up visit, were then transformed into utilities using the validated SF-6D mapping algorithm3. These were then compared to the previously derived health states. SAS v.9.3 was used for the analyses.
Results: A strong correlation (R2=0.6864, P<0.0001) was found between NDI and VAS. We constructed five distinct health states by projecting established NDI intervals onto the VAS scale. The distributions of SF-6D utility scores illustrated a clear trend with improvement in overall quality of life for all patients when comparing mean utility pre-op and at 24-months post-op (mean utility improvement =0.206, 95%CI: 0.187-0.225, P<0.0001). The mean utility value was then calculated for each health state, again highlighting a clear association between health states and utility.
Conclusions: To our knowledge, this is the first instance where distinct utility values have been derived for validated health states related to cervical spine disease. There is substantial potential for these to become baseline indices for future cost-utility analyses in similar populations.
Patient Care: The research has the potential to improve patient care by specifically addressing preference-based utility values (quality of life) when evaluating surgical intervention and technology. These utility values for the 5 defined health states for cervical spine disease will be used in future cost-utility analyses. The potential for these results to affect policy in a meaningful way (i.e., approve or disapprove insurance reimbursement for artificial discs in the appropriate populations) may have significant impact.
Learning Objectives: By the conclusion of this session, participants should be able to: 1) Describe the importance of developing baseline utility indices, 2) Discuss, in small groups, the potential for future cost-utility analyses with respect to cervical spondylosis, 3) Identify effective treatment options for cervical spine disease and refer to ongoing research in the area of artificial discs
References: 1. Davis RJ et al., Cervical total disc replacement with Mobi-C® Cervical Artificial Disc versus anterior discectomy and fusion for the treatment of two-level symptomatic degenerative disc disease: a prospective, randomized, controlled multicenter clinical trial. JNS Spine. (Revision submitted)
2. Gandek B. et al., Cross-validation of item selection and scoring for the SF-12 Health Survey in nine countries: results from the IQOLA Project. International Quality of Life Assessment. J Clin Epidemiol. 1998 Nov;51(11):1171-8
3. Brazier J. et al., The estimation of a preference-based measure of health from the SF-36. J Health Econ. 2002 Mar;21(2):271-92