Cost-effectiveness analysis of unicompartmental knee arthroplasty as an alternative to total knee arthroplasty for unicompartmental osteoarthritis.

BACKGROUND The purpose of this study was to compare the cost-effectiveness of unicompartmental knee arthroplasty as an alternative to total knee arthroplasty in patients with degenerative arthritis limited to either the medial or lateral compartment. METHODS A decision model was created for the treatment of end-stage unicompartmental knee arthritis. A literature review was used to identify possible outcomes and their probabilities following treatment with either unicompartmental or total knee arthroplasty. Each outcome was weighted for quality of life with use of a utility factor, and effectiveness was expressed in units of quality-adjusted life years. Gross costs were estimated from Medicare reimbursement data for the relevant Current Procedural Terminology and Diagnosis-Related Group codes. RESULTS Sensitivity analysis demonstrated that the cost-effectiveness of unicompartmental knee arthroplasty is dependent on the assumption that its durability and functional outcomes approach those of total knee arthroplasty. Specifically, it is necessary for the survival of unicompartmental implants to be within three to four years of the assumed survival of total knee implants for unicompartmental arthroplasty to remain a cost-effective alternative. Under these assumptions, the use of unicompartmental arthroplasty is a cost-effective choice as it results in incremental gains in effectiveness at a cost of less than US dollars 50,000 (in 1998 United States dollars) per quality-adjusted life year gained. CONCLUSIONS This study supports unicompartmental knee arthroplasty as a cost-effective alternative for the treatment of unicompartmental arthritis when the durability and function of a unicompartmental replacement are assumed to be similar to those of a primary total knee replacement. This suggests that, with appropriate patient selection, the currently available literature supports unicompartmental arthroplasty as a cost-effective alternative to total knee arthroplasty. LEVEL OF EVIDENCE Economic and decision analysis, Level II.