Cost-Utility Analysis of Instrumented Fusion Versus Decompression Alone for Grade I L4-L5 Spondylolisthesis at 1-Year Follow-up: A Pilot Study.

Abstract

Retrospective 1-year cost-utility analysis. To determine the cost-effectiveness of decompression with and without instrumented fusion for patients with grade I degenerative L4-L5 spondylolisthesis at 1-year follow-up. Despite its benefits to health outcomes, lumbar fusion is associated with substantial costs. This study analyzed the cost-effectiveness of instrumented fusion for grade I L4-L5 spondylolisthesis at 1-year follow-up. Four cohorts of 25 patients with grade I L4-L5 degenerative spondylolisthesis were analyzed: cohort 1 (decompression), cohort 2 (decompression with instrumented posterolateral fusion (PLF), cohort 3 (decompression with instrumented posterior lumbar interbody fusion/transforaminal lumbar interbody fusion), and cohort 4 (decompression with instrumented PLF and posterior lumbar interbody fusion/transforaminal lumbar interbody fusion). One-year postoperative health outcomes were assessed based on Visual Analogue Scale, Pain Disability Questionnaire, and EuroQol 5 Dimensions questionnaires. Direct medical costs were estimated using Medicare national payment amounts and indirect costs were based on patient missed work days. Postoperative 1-year cost/utility ratios and incremental cost-effectiveness ratios (ICERs) were calculated. Cost-effectiveness was assessed using a threshold of $100,000/QALY gained. Compared with preoperative health states, EuroQol 5 Dimensions QALY scores improved for all cohorts (P<0.01). The 1-year cost-utility ratio for cohort 1 was significantly lower ($56,610/QALY gained; P<0.01) than that for cohorts 2 ($116,991/QALY gained), 3 ($109,740/QALY gained), and 4 ($107,546/QALY gained). The 1-year ICERs relative to cohort 1 were: cohort 2 (dominated), cohort 3 ($1,060,549/QALY gained), and cohort 4 ($830,047/QALY gained). Decompression without fusion is cost-effective for patients with grade I L4-L5 spondylolisthesis. Decompression with fusion is not cost effective in a 1-year timeframe for these patients based on the threshold. Accordingly, although fusion is beneficial for improving health outcomes in patients with spondylolisthesis, it is not cost-effective when analyzing a 1-year timeframe based on the threshold. The durability of these results must be analyzed with longer term cost-utility analysis studies.