The Kenevo microprocessor-controlled prosthetic knee compared with non-microprocessor-controlled knees in individuals older than 65 years in Sweden: A cost-effectiveness and budget-impact analysis

Abstract

Background: Growing evidence suggests that individuals with transfemoral amputation or knee disarticulation using a prosthesis equipped with a microprocessor-controlled knee (MPK) benefit from enhanced mobility and safety, including less falls. In elderly individuals, high mortality rates are assumed to reduce the expected useful life of MPKs, and this raises concerns regarding their economic effectiveness.

Objective: To investigate the cost-effectiveness and budget impact of the Kenevo/MPK (Ottobock, Germany) compared with non-microprocessor-controlled knees (NMPKs) in people older than 65 years at the time of transfemoral amputation/knee disarticulation, from a Swedish payer's perspective.

Methods: A decision-analytic model was developed to conduct the economic analysis of the Kenevo/MPK. Model parameters were derived from Swedish databases and published literature. Univariate and probabilistic sensitivity analyses were performed to explore parameter uncertainty.

Results: Compared with NMPKs, the Kenevo/MPK reduced the frequency of hospitalizations by 137 per 1,000 person years while the frequency of fatal falls was reduced by 19 per 1,000 person-years in the simulation. Over a 25-year time horizon, the incremental cost-effectiveness ratio was EUR11,369 per quality-adjusted life year. The probability of the MPK being cost-effective at a threshold of EUR40,000 per quality-adjusted life year was 99%. The 5-year budget impact model predicted an increase in payer expenditure of EUR1.76 million if all new patients received a Kenevo/MPK, and 50% of current NMPK users switched to the MPK.

Conclusions: Results of the modeling suggest that the Kenevo/MPK is likely to be cost-effective for elderly individuals, primarily because of a reduction in falls.

Figure 1.

Structure of the decision-analytic model.

Figure 2.

Cost-effectiveness results in the six subgroups. Green or blue bars show the base-case results for the six subgroups. The black lines represent the 2.5% and 97.5% quantiles of the Monte Carlo simulation.

Figure 3.

Cumulated budget impact over time. Additional costs for the statutory health insurance, occurring from Kenevo fittings instead of non–microprocessor-controlled knees. The values include both, individuals using prostheses with diabetes mellitus/peripheral vascular disease and individuals with other etiologies. The blue lines show the 2.5% and 97.5% quantiles of the Monte Carlo simulation. The budget impact over 5 years (2020–2024) amounts to EUR1.70 million (EUR0.75-EUR2.41 million).

Figure 4.

Contribution of subgroups to the total budget impact.

Figure 5.

Budget impact of Kenevo for different penetration rates. Budget impact over 5 years for different penetration rates. In penetration rates, a distinction was made between patients with transfemoral amputation/knee disarticulation before 2020 and fitted with a non–microprocessor-controlled knees and patients who were fitted with prostheses for the first time from 2020. In the former, it was assumed that a prosthesis revision would allow the patient to switch from a non–microprocessor-controlled knees to a Kenevo.

Figure 6.

Results of the probabilistic sensitivity analysis: scatterplot. The green dots each show the results of one iteration of the Monte Carlo simulation. The larger blue point shows the average quality-adjusted life years gained and the average additional costs of the Kenevo compared with non–microprocessor-controlled knees. The incremental cost-effectiveness ratio (ICER)—additional costs per quality-adjusted life year gained—is shown by the blue lines. The solid lines show the average ICER and the dashed lines the 2.5% and 97.5% quantiles.

Figure 7.

Results of the probabilistic sensitivity analysis: cost-effectiveness acceptability curve. The green and blue lines show the cost-effectiveness probabilities of the Kenevo microprocessor-controlled knee or the non–microprocessor-controlled knees for given willingness-to-pay thresholds per quality-adjusted life year gained. The black dashed lines mark the cost-effectiveness probabilities of the Kenevo MPK for the Swedish thresholds of EUR8,00 and EUR40,000 per quality-adjusted life year gained. The probabilities are the proportion of Monte Carlo interactions with an incremental cost-effectiveness ratio below the given threshold.

Figure 8.

Results of univariate and multivariate sensitivity analyses: incremental cost-effectiveness ratio.

Figure 9.

Results of univariate and multivariate sensitivity analyses: budget impact.