Two-year cost-effectiveness analysis of alternate-level instrumentation in open-door cervical laminoplasty: secondary analysis of a randomized controlled trial.

BACKGROUND CONTEXT: The optimal number of fixation levels in cervical open-door laminoplasty remains controversial. A recent randomized controlled trial (RCT) demonstrated that alternate-level instrumentation (skip-fixation) achieved non-inferior improvement in the Japanese Orthopaedic Association (JOA) score compared with instrumentation at every level (all-fixation). Skip-fixation requires instrumentation at approximately half of the laminar levels and may therefore theoretically reduce implant-related costs. However, the economic impact of fixation strategy has not been formally evaluated. PURPOSE: To evaluate the cost-effectiveness of skip-fixation compared with all-fixation using two-year direct medical costs and health-related quality-of-life (HRQoL) data within the Japanese public health insurance system. STUDY DESIGN/SETTING: A secondary cost-effectiveness analysis conducted alongside a prospective, multicenter randomized controlled trial at four hospitals in Japan. PATIENT SAMPLE: Patients aged ≥60 years who underwent C3-C6 open-door cervical laminoplasty for degenerative cervical myelopathy in a multicenter randomized controlled trial. OUTCOME MEASURES: Two-year cumulative direct medical costs, including surgery-related inpatient costs, postoperative outpatient costs, and costs associated with complications or reoperations, were evaluated from the payer's perspective. HRQoL was measured using the EQ-5D-5L at baseline and at 3, 12, and 24 months postoperatively, and quality-adjusted life-years (QALYs) were calculated. METHODS: Incremental net monetary benefit (INMB) was calculated at a willingness-to-pay (WTP) threshold of JPY 5,000,000 (USD 45,900) per QALY. Uncertainty was assessed using 10,000 bootstrap replications to generate cost-effectiveness planes and acceptability curves. RESULTS: A total of 129 patients with complete two-year cost and utility data were analyzed (66 skip-fixation; 63 all-fixation). No statistically significant difference in two-year QALYs was observed between groups (ΔQALY = 0.035; 95% CI, -0.083 to 0.152). Mean two-year total direct medical costs were lower in the skip-fixation group (ΔCost = USD -1,460; 95% CI, -2,834 to -173). At the WTP threshold of USD 45,900, the mean INMB was USD 3,061 (95% CI, -2,481 to 8,569). The probability that skip-fixation was cost-effective was 86.3%. Scenario analyses demonstrated greater economic advantage when higher-cost plate fixation was assumed. CONCLUSIONS: Skip-fixation was cost-effective compared with all-fixation in cervical open-door laminoplasty over a two-year period. This economic advantage was more pronounced when high-cost implants were used.