Cost-Effectiveness of Weight-Bearing Computed Tomography in Diagnosing Syndesmotic Instability

CATEGORY: Ankle; Sports; Other INTRODUCTION/PURPOSE: To optimize clinical outcomes, accurate diagnosis and treatment of syndesmotic instability is critical, but subtle instability can be challenging to identify. Weightbearing computed tomography (WBCT) has proved to be a reliable tool for diagnosing syndesmotic instability under physiologic load. We aimed to examine the cost-effectiveness of WBCT with radiographs and/or conventional CT for the diagnosis of syndesmotic instability from a patient perspective. METHODS: A decision tree model was constructed to examine the cost-effectiveness of WBCT versus conventional CT (NWB CT) versus weightbearing (WB) radiographs versus non-weightbearing (NWB) radiographs (base case) as initial imaging with additional possible imaging for1268 patients with suspected syndesmotic instability. Patient's clinical and radiological notes were evaluated until the diagnosis of syndesmotic instability was established. The decision tree's probabilities, durations, and image counts were based on patient data. The main outcomes were 1) total imaging costs needed before syndesmotic instability was diagnosed, 2) quality-adjusted life-years (QALYs), 3) incremental cost-effectiveness ratios (ICERs), and 4) overall radiation dose prior to diagnosis. Imaging costs and radiation dose were derived from National Medicare reimbursement rates and the American College of Radiology, respectively. An incremental cost-effectiveness ratio threshold of $50,000 per quality-adjusted life years was used to evaluate cost-effectiveness. In addition, one-way and two-way sensitivity analyses were performed to determine the robustness of our findings. RESULTS: WBCT resulted in 0.057 additional QALY gained per week compared with NWB radiographs, indicating WBCT to be more effective than NWB radiographs. Costs for WBCT imaging were $38.71 higher than NWB radiographs for an ICER of $38,563.96/QALY. Applying a commonly used threshold of $50,000 per QALY, the patient's willingness-to-pay for the amount of quality-adjusted life-year gained from using WBCT as an initial imaging modality was $54.41, suggesting WBCT first imaging strategy was a cost-effective intervention. In our study, the cost of WBCT imaging was $157.35. Sensitivity analyses demonstrated that WBCT was more cost effective than NWB radiographs up to a cost of $173.05. Additionally, initial WBCT resulted in lower overall radiation dosage (6.4 uSv) compared to the use of the other three imaging modalities as initial imaging strategy (initial NWB radiographs - 12.41 uSv; initial WB radiographs - 8.30 uSv, NWB CT first - 25 uSv). CONCLUSION: WBCT leads to higher QALYs compared to other diagnostic imaging modalities, resulting in improved outcomes for patients by eliminating redundant imaging.