Use of the Ottawa knee rule: a cost minimization study

Abstract

Purpose: To determine whether adoption of the Ottawa knee rule will decrease the cost of evaluating adult patients with acute blunt knee trauma compared with not using the rule. Materials and methods: A decision tree was constructed with two arms, one that included explicit use of the Ottawa knee rule and another that did not include adoption of the Ottawa knee rule. Probability estimates for the model were obtained from an internally generated data set, while cost estimates were obtained from hospital charges, Medicare reimbursement rates, and Department of Labor statistics. A societal perspective was adopted. Results: The baseline analysis indicated that adoption of the Ottawa knee rule results in an average savings per patient of US$3. Cost savings increase as the cost of radiography increases. However, under certain conditions, adoption of the Ottawa knee rule may result in increased costs, especially if the sensitivity of the rule drops below .94. Conclusions: Under most conditions, adoption of the Ottawa knee rule results in modest cost savings compared with not using the rule. Individual institutions may wish to determine whether their practice environment (fracture prevalence, cost of radiography, patient waiting time, etc.) is conducive to significant cost savings before formally adopting the knee rule.