Cost-utility of lumbar decompression with or without fusion for patients with symptomatic degenerative lumbar spondylolisthesis

Background context: The most common surgical treatment of symptomatic degenerative lumbar spondylolisthesis (DLS) is decompression and instrumented fusion. However, contemporary, midline-sparing, microdecompressive techniques have shown good results for selected patients with stable Grade 1 DLS. Growing concerns over the rising cost and rates of spinal fusion warrant both clinical and economic comparative effectiveness research in this common spinal diagnosis.

Purpose: To determine the relative cost-utility of decompression with and without concomitant instrumented fusion for selected patients with DLS.

Study design/setting: Comparative cost-effectiveness study.

Patient sample: Probabilities and utilities were estimated from an observational cohort study and the current literature. Costing information was obtained from our institution (microcase costing data/patient) and the literature. Probabilities considered were perioperative and general mortality, probability of clinical improvement and clinical worsening, and reoperation.

Outcome measures: The primary outcome was the incremental cost/utility ratio (ICUR) expressed as the differential cost per relative gain in quality-adjusted life-year (QALY).

Methods: A Markov model with 10-year follow-up was developed. The analyses were carried out from the hospital's perspective. Sensitivity analysis was used to test the robustness of the model.

Results: The cost-utility of decompression with fusion and decompression alone at 10 years postintervention was $3,281/QALY and $1,040/QALY, respectively. Compared with decompression alone, decompression plus instrumented fusion was associated with an improvement in quality of life at a cost of $185,878 per QALY in the base-case analysis. The ICUR was invariant to changes in clinical effectiveness of decompression alone, percentage of inpatient decompressions, and varying cost or QALY discounting rates. The ICUR was sensitive to change in QALY and cost structure changes.

Conclusions: For a select subgroup of patients with DLS (leg-dominant pain with a stable Grade 1 spondylolisthesis), decompression without fusion is significantly more cost effective than instrumented fusion and provides an opportunity for increased service delivery and/or cost savings for this growing population.