Analytical approach:
A discrete-event simulation (DES) was used to assess the costs and outcomes of the interventions. DES modelling allows the individual history of a patient to be captured and evaluated. The time horizon was the lifetime of the patient. The authors reported that a health system perspective was adopted.
Effectiveness data:
The clinical and effectiveness data were from published studies and national registries. The main effectiveness parameters were the time to failure and the failure rates of joint replacements due to short-term causes. This evidence was from revision rates over seven years reported in the Australian National Joint Replacement Registry.
Monetary benefit and utility valuations:
The disability weights were derived from the Burden of Disease study to quantify the impact of osteoarthritis on quality of life. Quality of life estimates, obtained using questionnaires like the European Quality of life (EQ-5D) questionnaire and the Short Form (SF)-36 Health Survey, were converted into disability weights.
Measure of benefit:
Disability-adjusted life-years (DALYs) averted were the measure of benefit, and future benefits were discounted at an annual rate of 3%.
Cost data:
The costs included surgery (primary replacements and revisions), complications, offset costs (future costs that were offset as a result of the interventions), unrelated health care costs incurred in extended life-years after receiving joint replacements, and patient out-of-pocket costs (including time for travel, waiting, pre-surgery visits, operation, and recuperation). The costs of surgery were from Australian diagnosis-related group information. The patient’s out-of-pocket costs, offset costs, and unrelated health care costs were from published studies. The price year was 2003 and future costs were discounted at an annual rate of 3%. All costs were reported in Australian dollars (AUD).
Analysis of uncertainty:
Uncertainty distributions were allocated to all the model parameters, and 2,000 Monte Carlo simulations were conducted. One-way sensitivity analyses evaluated the impact of excluding time costs, offset costs, and unrelated health care costs.