Introduction: Degenerative Cervical Myelopathy (DCM) is the most common cause of non‐traumatic spinal cord impairment in adults. Surgery has been shown to improve neurological symptoms and functional status, but it is costly. As healthcare sustainability concerns rise, the value of care has come to the forefront of policy decision‐making. Evidence for both health related quality of life outcomes and costs are needed to inform medical policies. The aim of this analysis is to determine if surgery for DCM is cost effective and to provide an estimate of the lifetime incremental cost utility of the intervention.
Methods: All patients undergoing surgery for DCM at a Canadian tertiary care center between 2005 and 2011, who were enrolled in either the AOSpine CSM‐North America or CSM‐International studies were included. Health utility was measured at baseline and then 6, 12 and 24‐months following surgery using the Short Form‐6D (SF‐6D) health utility score. Costs were calculated on a patient level, from the hospital budgetary expenditures over the 24‐month follow‐up period. All costs were obtained from a micro‐cost database and reported in Canadian dollars; inflated to January 2015 values. Quality adjusted life year (QALY) gain was estimated as an area under the curve with a linear interpolation. Lifetime incremental cost utility ratios (ICUR) for surgery were estimated using a Markov state transition model (Figure 1). Sensitivity to structural uncertainly arising from lifetime extrapolation and the single arm cohort design of the study was assessed by constructing supplementary constrained models. Deterministic and probabilistic sensitivity analyses were used to account for parameter uncertainty. All QALY gains and costs were discounted at 3% per annum.
Results: The analysis included 171 patients; follow‐up at 2‐years was 96.5%. Mean age was 58.2 ± 12.0 years and baseline health utility was 0.56 ± 0.14. Average QALY gained over the 24‐month following surgery was 0.14 (95% CI: 0.11–0.17, p < 0.001). The average 2‐year cost of treatment was $19,218 ± 12,404. Cost associated with the surgery accounted for two‐thirds (65.7%) of the total costs. The remainder of the costs were for pre‐surgical preparation, post‐surgical recovery and re‐operations. Three patients required a re‐operation over the 2‐year follow‐up period, and accounted for 1.85% of the total costs. The estimated lifetime ICUR of surgical intervention was $11,496.02 / QALY gained (Figure 2A), with 97.9% of model estimates (Figure 2B and 2C) meeting the criteria to be considered ‘very cost effective’ ($54,000 CAD). Model structure sensitivity assessments revealed ICUR estimates that remained within the ‘very cost effective’ threshold, suggesting the findings are robust to the estimations of the lifetime model.
Conclusion: Our study suggests that surgery for DCM is associated with significant and clinically meaningful improvements in quality of life and is cost effective.