Analytical approach:
The analysis was based on a decision tree, with a time horizon of 90 months. The authors stated that the perspective of the third-party payer was adopted.
Effectiveness data:
A literature review was carried out in the MEDLINE database, using wide search criteria, to identify studies in which the two strategies were directly compared. Published reviews were also screened. No clinical trials were found; four head-to-head comparison studies were used. From these studies, 229 patients for surgery and 155 for conservative treatment were analysed, with a mean follow-up of 89 months for surgery and 90 months for conservative treatment. The proportions of patients at various levels of physical activity after the interventions were key inputs for the model.
Monetary benefit and utility valuations:
The utility values were estimated from the responses of 25 orthopaedic surgeons to a questionnaire that included the Health Utilities Index (HUI3). Values were estimated for several patient profiles based on their level of physical activity.
Measure of benefit:
Quality-adjusted life-years (QALYs) were the summary benefit measure.
Cost data:
The economic analysis included the costs of surgical reconstruction, conservative treatment, and any long-term complications after anterior cruciate ligament rupture (meniscal lesions or osteoarthritis). The cost data were from patients at a university hospital in Zurich, Switzerland, or from expert opinion. All costs were converted from Swiss francs to US $.
Analysis of uncertainty:
A probabilistic sensitivity analysis was carried out, using Monte Carlo simulation, to assess how robust the model outcomes were to variations in the utility values. A worst-case scenario, excluding complications, such as meniscal lesions and osteoarthritis, was considered.