Do the potential benefits of metal-on-metal hip resurfacing justify the increased cost and risk of complications?

Abstract

Background: Metal-on-metal hip resurfacing arthroplasty (MoM HRA) may offer potential advantages over total hip arthroplasty (THA) for certain patients with advanced osteoarthritis of the hip. However, the cost effectiveness of MoM HRA compared with THA is unclear.

Questions/purposes: The purpose of this study was to compare the clinical effectiveness and cost-effectiveness of MoM HRA to THA.

Methods: A Markov decision model was constructed to compare the quality-adjusted life-years (QALYs) and costs associated with HRA versus THA from the healthcare system perspective over a 30-year time horizon. We performed sensitivity analyses to evaluate the impact of patient characteristics, clinical outcome probabilities, quality of life and costs on the discounted incremental costs, incremental clinical effectiveness, and the incremental cost-effectiveness ratio (ICER) of HRA compared to THA.

Results: MoM HRA was associated with modest improvements in QALYs at a small incremental cost, and had an ICER less than $50,000 per QALY gained for men younger than 65 and for women younger than 55. MoM HRA and THA failure rates, device costs, and the difference in quality of life after conversion from HRA to THA compared to primary THA had the largest impact on costs and quality of life.

Conclusions: MoM HRA could be clinically advantageous and cost-effective in younger men and women. Further research on the comparative effectiveness of MoM HRA versus THA should include assessments of the quality of life and resource use in addition to the clinical outcomes associated with both procedures.

Level of evidence: Level I, economic and decision analysis. See Guidelines for Authors for a complete description of levels of evidence.

Fig. 1A–B

(A) A Markov decision tree compares the clinical outcomes for MoM HRA and THA patients. MoM THA and primary THA are represented as Markov nodes (“M”). The branches are the Markov states. Conversion from HRA to THA is analogous to first major revision in the primary THA alternative. The [+] indicates there are subsequent events in each state. (B) The detailed outcomes in the post-conversion from HRA to THA branch are shown.

Fig. 2

One-way sensitivity analyses of ICER to probabilities of clinical outcomes, costs, and QoL are shown. The width of each bar indicates the range of the ICER as each independent variable changes over its range. The upper value for the ICER is over $7,627,147 at the upper value of the annual probability of HRA failure (0.0225). The graph shows that the factors that have the greatest impact on the model results are the probability of HRA failure, cost of HRA and primary THA, probability of primary THA failure, probability of operative death from HRA and primary THA, and quality of life after conversion of HRA to THA.

Fig. 3

A graph shows a one-way sensitivity analysis to difference in QoL after conversion from HRA to THA compared to primary THA by gender and age strata. The ICER increased rapidly with small differences in the quality of life after conversion of HRA to THA compared to primary THA for men age less than age 55, men age 55 to 64, and women less than age 55. Men, age 55 to 64 had a more favorable (lower) ICER with much smaller change in ICER as the difference in quality of life after conversion from HRA to THA increased.

Fig. 4

The graph shows a one-way sensitivity analysis to incremental cost of HRA compared to THA by gender and age strata. For both men and women, there is a linear relationship of the ICER to the incremental costs of MoM HRA implants. MoM HRA would be cost saving (ICER intercept = 0) if the incremental cost of MoM HRA were less than $313 for men less than age 55 years, less than $711 for men age 55 to 64 years, and less than $175 for men aged 65 to 74 years. For women in each age stratum, the costs of the MoM HRA treatment strategy are higher than the costs of the THA at every value of incremental cost of the MoM HRA implant compared to THA and there is no cost-saving threshold. In women less than age 55, the ICER of MoM HRA is less sensitive to the incremental cost of the HRA implants compared to THA, due to the higher probability of HRA failure in women than in men.

Fig. 5A–D

These graphs show two-way sensitivity analyses of incremental cost of HRA compared to primary THA and difference in QoL after conversion from HRA to THA compared to primary THA for (A) men younger than 55 years, (B) men aged 65 to 74 years, (C) women younger than 55 years, and (D) women aged 65 to 74 years. The graph area shows the combination of the incremental cost of HRA and difference between QoL after conversion from HRA to THA and primary THA where MoM HRA (black) or primary THA (white) is optimal based on net monetary benefits analysis with a willingness to pay threshold of $50,000 per QALY. In general, over a wide range of values for the QoL reduction after conversion from HRA to THA and the incremental cost of HRA conversion, MoM HRA was more favorable compared to THA for men than for women (Fig. 5A versus 5C and Fig. 5B versus 5D) and for younger patients (age less than 55) compared to older patients (age 65 or older) (Fig. 5A versus 5B, and Fig. 5C versus 5D).

Fig. 6

An acceptability curve from the probabilistic sensitivity analysis shows the probability that ICER is below a particular willingness to pay threshold based on the simulation using 10,000 samples for each gender and age stratum. The probability (confidence) that the ICER was less than or equal to $100,000 per QALY gained was only 63% for men less than age 55, 75% for men ages 55–64, and 68% for women less than age 55. The probabilities were lower for the remaining three strata. The uncertainty illustrated by these acceptability curves indicates that variation in costs of HRA, failure rates of HRA and THA, and quality of life difference after conversion of HRA to THA have a large impact on the comparative clinical and cost-effectiveness of MoM HRA.