• Rikke Soegaard, Cody E Bünger, Terkel Christiansen, Kristian Høy, Søren P Eiskjaer, and Finn B Christensen.
• Orthopaedic Research Laboratory, University Hospital of Aarhus, Aarhus, Denmark. rikke.sogaard@ki.au.dk
• Spine. 2007 Oct 15;32(22):2405-14.

Study DesignCost-utility evaluation of a randomized, controlled trial with a 4- to 8-year follow-up.ObjectiveTo investigate the incremental cost per quality-adjusted-life-year (QALY) when comparing circumferential fusion to posterolateral fusion in a long-term, societal perspective.Summary Of Background DataThe cost-effectiveness of circumferential fusion in a long-term perspective is uncertain but nonetheless highly relevant as the ISSLS prize winner 2006 in clinical studies reported the effect of circumferential fusion superior to the effect of posterolateral fusion. A recent trial found no significant difference between posterolateral and circumferential fusion reporting cost-effectiveness from a 2-year viewpoint.MethodsA total of 146 patients were randomized to posterolateral or circumferential fusion and followed 4 to 8 years after surgery. The mean age of the cohort was 46 years (range, 20-65 years); 61% were females, 49% were smokers, 30% had primary diagnosis of isthmic spondylolisthesis, 35% had disc degeneration and no previous surgery, and 35% had disc degeneration and previous surgery. Eighty-two percent of patients have had symptoms for more than 2 years and 50% were out of the labor market due to sickness. The EQ-5D instrument was applied for the measurement of health-related quality of life and costs (2004 U.S. dollars) were measured in a full-scale societal perspective. Productivity costs were valued by the Friction Cost method, and both costs and effects were discounted. Arithmetic means and 95% bias-corrected, bootstrapped confidence intervals were reported. Nonparametric statistics were used for tests of statistical significance. Comprehensive sensitivity analysis was conducted and reported using cost-effectiveness acceptability curves.ResultsThe circumferential group demonstrated clinical superiority over the posterolateral fusion group in functional outcome (P < 0.01), fusion rate (P < 0.04), and number of reoperations (P < 0.01) among others. Cost-utility analysis demonstrated circumferential fusion dominant over posterolateral fusion, that is, for each QALY gained performing circumferential fusion, the incremental saving was estimated at U.S. $49,306 (95% confidence interval, $27,183-$2,735,712). Results proved to be strong to various sensitivity analyses; only a differentiated underestimation of patients' need for postoperative household help against the circumferential approach could alter the dominance; however, still the probability of cost-effectiveness was >0.85 given a threshold for willingness to pay of U.S. $50,000 per QALY.ConclusionCircumferential fusion is dominant over instrumented posterolateral fusion, that is, both being significantly cheaper and significantly better in a long-term, societal perspective.

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