Use of cost-effectiveness analysis to evaluate new technologies in orthopaedics. The case of alternative bearing surfaces in total hip arthroplasty.

Background: Alternative bearing surfaces offer the potential to reduce wear and improve implant longevity following total hip arthroplasty. However, these technologies are associated with higher costs, the potential for unintended consequences, and uncertain benefits in terms of long-term survival of the implants. The purpose of this study was to evaluate the cost-effectiveness of the use of alternative bearings in total hip arthroplasty.

Methods: A decision-analysis model was constructed to estimate the cost-effectiveness of the use of alternative bearings for patients undergoing total hip arthroplasty. Model inputs, including costs, clinical outcome probabilities, and health utility values, were derived from a review of the literature. Sensitivity analyses were performed to evaluate the impact of patient age at the time of surgery, implant costs, and reductions in revision rates on the cost-effectiveness of alternate bearing surfaces.

Results: In a population of fifty-year-old patients, use of an alternative bearing with an incremental cost of 2000 dollars would be cost-saving over the individual's lifetime if it were associated with at least a 19% reduction in the twenty-year implant failure rate when compared with the failure rate for a conventional bearing. In a population of patients over the age of sixty-three years, the same implant would be associated with higher lifetime costs than would a conventional bearing, regardless of the presumed reduction in the revision rate. Conversely, an alternative bearing that adds only 500 dollars to the cost of a conventional total hip arthroplasty could be cost-saving in a population of patients over the age of sixty-five years, even if it were associated with only a modest reduction in the revision rate. In a population of patients over the age of seventy-five years, no alternative bearing would be associated with lifetime cost-savings, regardless of the cost or the presumed reduction in the revision rate.

Conclusions: The cost-effectiveness of alternative bearings is highly dependent on the age of the patient at the time of surgery, the cost of the implant, and the associated reduction in the probability of revision relative to that associated with conventional bearings. Our findings provide a quantitative rationale for requiring greater evidence of effectiveness in reducing the probability of implant failure when more costly alternative bearings are being considered, particularly for older patients.