OBJECTIVES: The cost of treating fractures has a significant impact on Medicare expenditures, totalling in the billions of dollars annually. The expected cost of treatment for electrical and ultrasound bone stimulators in the concomitant conservative treatment of stable nonunion fractures was assessed to identify the least costly stimulator. METHODS: Treatment pathways for five different bone stimulators--Exogen®, Physio-Stim®Lite, OL1000 Bone Growth Stimulator, OrthoPak®, and EBI Bone Healing System®--were modelled using a decision tree (TreeAge Data v3.0.13). Treatment failures were assumed to require surgery. Probabilities of treatment success came from published literature, manufacturers’ data, and patient registry data. Cost data came from published literature and Durable Medical Equipment Regional Carriers (DMERCs). For each stimulator, the expected cost of treating a nonunion fracture was calculated by folding back the decision tree. One-way sensitivity analyses were performed by varying all probabilities by ±0.20 and all costs by ±50%. A Monte Carlo simulation was conducted to determine the optimal bone stimulator for a hypothetical cohort of 10,000 patients. The analysis was undertaken from the perspective of United States Centers for Medicare and Medicaid Services. RESULTS: Exogen® had the lowest expected cost ($6610), followed by Physio-Stim®Lite ($8714). Sensitivity analyses demonstrated expected costs were sensitive to the probability of success: Exogen® would have the lowest expected cost if its probability of success were at least 0.745, while OL1000 would have the lowest expected cost if its probability of success were at least 0.84. The Monte Carlo simulation showed that Exogen® was the optimal stimulator for 85% of patients, Physio-Stim®Lite for 14%, and EBI Bone Healing System® for 1%. CONCLUSION: Exogen® was the least costly bone stimulator for conservatively treated nonunion fractures. Public insurers should consider the cost benefits of expanding coverage for Exogen® to include concomitant conservative treatment of stable non-union fractures.