STUDY DESIGN::
Retrospective 1-year cost-utility analysis.

OBJECTIVE::
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.

SUMMARY OF BACKGROUND DATA::
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.

METHODS::
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 (PLIF/TLIF)), and Cohort 4 (Decompression with instrumented PLF and PLIF/TLIF). 1-year postoperative health outcomes were assessed based on Visual Analogue Scale (VAS), Pain Disability Questionnaire (PDQ), and EuroQol 5 Dimensions (EQ-5D) 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.

RESULTS::
Compared with preoperative health states, EQ-5D QALY scores improved for all cohorts (P< 0.01). The one-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 one-year ICERs relative to Cohort 1 were: Cohort 2 (Dominated), Cohort 3 ($1,060,549/QALY gained), and Cohort 4 ($830,047/QALY gained).

CONCLUSION::
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, while 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.