The socio-economic impact of robotic prosthetics: the Hannes hand case study
This study assesses the socio-economic impact of Hannes using the SROI framework, which quantifies the benefits generated for a wide range of stakeholders. These include, first and foremost, patients, as well as caregivers, orthopedists, orthopedic workshops, local health authorities (ASL), and institutions such as INAIL. By analyzing the outcomes and changes associated with the use of the Hannes device, the study evaluates both tangible and intangible benefits, such as improved quality of life for patients and reduced healthcare costs, providing an estimate of the broader social value generated for each stakeholder group.
Table 3 offers a comprehensive overview of each stakeholder, detailing their specific outcomes. It also identifies the most suitable indicators for impact evaluation, their quantification, and the estimated economic value or financial proxies used to monetize both tangible and intangible outcomes. The total monetary impact incorporates deadweight percentages, which measure changes that would have occurred without the Hannes device. In this study, deadweight percentages were calculated using the questionnaires referenced in the previous paragraph to identify patients who would have achieved similar outcomes with their regular prostheses.
The study identified nine outcomes: six for patients (primary beneficiaries), one for caregivers, and two for broader stakeholders, including healthcare professionals and supporting institutions.
Patients, the main beneficiaries
Outcomes, indicators, and quantification
Patient outcomes were defined based on users’ expectations regarding the capabilities that myoelectric prostheses should guarantee, and their potential implications1,16,49. The first two outcomes presented in Table 3 concern functionality, specifically the performance of the device and the participants’ ability to carry out daily activities. These are followed by social outcomes, related to patients’ job reintegration and broader social participation. Last outcomes relate to psychosocial dimensions: by enabling more natural gestures and postures, myoelectric prostheses can improve users’ appearance50, facilitate social interactions, and contribute to higher self-esteem. Furthermore, thanks to advanced functionality and anthropomorphic design, advanced prostheses can foster a sense of embodiment51,52,53, meaning that users increasingly perceive the prosthesis as part of their body rather than as an external tool.
After identifying the outcomes, it is essential to quantify the number of participants in the clinical trial who have experienced them.
For certain outcomes, a synthetic index was already available. Specifically, for the outcome “Restore over 80% of the functionality of a real hand”, we utilized the synthetic index from the SHAP functional test. The SHAP functional test evaluates hand functionality through 12 abstract object tasks and 14 ADLs. The time taken to complete each task, measured in seconds, is entered into a web-based scoring tool, which calculates an overall score called the Index of Function (IoF), providing a comprehensive measure of hand performance.
For the embodiment outcome, a single indicator was used, derived from item 15 of the ad hoc questionnaire specifically designed for the project. This questionnaire item, “I felt as if the robotic hand was part of me, incorporated into my person rather than as a tool”, was rated on a 1-5 Likert scale, where 1 indicates strong disagreement and 5 indicates strong agreement, effectively assessing the patient’s sense of embodiment.
For the remaining outcomes, various elementary indicators were derived from different items included in the questionnaires administered to patients during the clinical trial. The selection of these items for each outcome was carried out in collaboration with the Hannes development team and the clinical trial designers. As detailed in the Materials and methods section, when multiple indicators were used to measure a single outcome, normalization was applied to ensure comparability across different scales. Indicator polarity was also adjusted so that higher values consistently represented more favorable outcomes.
Given that the selection of indicators involves an element of subjectivity, empirical criteria were applied to ensure objectivity. In particular, we employed two statistical methods – item–scale correlation and Cronbach’s alpha – to verify that all selected items were appropriately aligned with the intended construct and demonstrated satisfactory internal consistency.
This approach was applied to all outcomes defined by multiple elementary indicators, specifically: “Possibility of performing ADLs and improved functional independence”, “Job reintegration”, “Social reintegration and reduction of social isolation”, “Increased self-esteem”, and “Offer with higher quality standards”. Table 4 summarizes the number of indicators and Cronbach’s alpha for each outcome, with all values exceeding the reliability threshold of 0.7.
Following the selection of elementary indicators, a synthetic index was constructed for each outcome by averaging the normalized values of the indicators. Thresholds for achieving each outcome, derived from the response scales, are presented in Table 5.
For the first outcome, “Restore over 80% of the functionality of a real hand”, the threshold was derived from the literature on the Southampton Hand Assessment Procedure (SHAP). SHAP indicates that non-disabled hands typically achieve an Index of Function (IoF) score of 95–100%. Therefore, a threshold of 0.76 was selected, representing 80% of the lower end of this range (0.80 * 0.95 = 0.76).
A threshold of 0.75 was established for “Possibility of performing ADLs and improved functional independence”, “Job reintegration”, “Social reintegration and reduction of social isolation”, and “Embodiment” outcomes. The elementary indicators for these outcomes used five-point response scales (0, 0.25, 0.5, 0.75, and 1) after normalization.
For “Increased self-esteem” a threshold of 1 was used, reflecting the uniformly high scores reported by all patients for both Hannes and their regular prosthesis.
The “Offer with higher quality standards” outcome used a threshold of 0.7, considering its diverse item scales: three-point (0, 0.5, 1), five-point (0, 0.25, 0.5, 0.75, 1), and a ten-point scale for overall patient satisfaction.
The number of patients experiencing each outcome was determined by counting those exceeding the respective threshold. To ensure a conservative and credible analysis, we also considered counterfactuals, such as patients who would likely have experienced similar benefits using their regular prostheses, by applying deadweight percentages. Attribution and displacement coefficients were not considered necessary in this context, as the effects can be directly attributed to the project due to the strict eligibility and inclusion criteria applied to the clinical trial participants, and no substitution effects are expected.
The results emerging from the clinical trial, presented in Table 3, illustrate that Hannes improved participants’ ability to perform daily activities, thereby fostering greater independence. This result is consistent with the findings of Laffranchi et al.20 and Semprini et al.54. Socially, the device contributed to job reintegration, helping patients overcome isolation and engage in community or recreational activities, such as sports. Additionally, Hannes improved users’ perceived appearance and social engagement, which in turn elevated self-esteem. The sense of embodiment, reported by many participants, can be attributed to the advanced human-like design and grasping behavior of the prosthesis55.
Monetary valuation approach
Different financial proxies, particularly for intangible outcomes, were initially explored to approximate social value, as direct measurement is often infeasible56.
The financial proxy of the first outcome, which aimed to restore at least 80% of natural hand functionality, was based on INAIL compensation awarded to workers who experience a loss of psychophysical integrity resulting from a workplace accident or occupational disease, as defined in Article 13 of Legislative Decree No. 38/2000. Because INAIL assigns a 70–80% disability rating for forearm in the middle third or complete hand loss, compensation was calculated at 75%. In addition to the subject’s permanent disability percentage, the calculation considers age (using the sample average of 49), job classification (“industry”), annual salary (€27,000, based on 2023 ISTAT data), and number of dependents (two, representing a spouse and child, based on 2021 ISTAT data, which indicated an average of 1.25 children per woman).
The financial proxy for the second outcome, focusing on the ability to perform ADLs and increased independence, was derived from the cost savings associated with hiring a caregiver. The annual caregiver cost was calculated using a minimum wage of €9 per hour, assuming 24 hours per week (see Pinelli et al.,57).
For job reintegration, the proxy used was the monthly INPS allowance granted to individuals with a recognized partial reduction in work capacity, falling below the legal income thresholds. This allowance, paid by INPS for 13 months annually, amounts to €313.97 in 2023.
To monetize the outcome related to patients’ social reintegration, such as returning to recreational or sports activities, we adopted a proxy based on the annual cost of membership in a team sport club. This approach is grounded in the idea that participation in such activities reflects a concrete form of social engagement and inclusion. This financial proxy has already been used in literature, specifically in a study by Bellucci et al.58, in which the authors adopted an annual cost of team sports membership (€576, ISTAT 2016), which we have adjusted for inflation to €683.71.
To determine a financial proxy for embodiment, literature on prosthesis abandonment was consulted. High abandonment rate in upper-limb prosthesis users59,60,61 is influenced by various factors, including individual characteristics, level of amputation59, type of prosthesis62, and the adequacy of training. Social and psychological factors also play a crucial role, especially in how well users can integrate the device into their body image and seamlessly incorporate it into their daily lives. The difficulty in achieving this integration may lead to abandonment of the device63. Several studies—such as those conducted by Biddiss et al.59, Smail et al.60, and Salminger et al.61—identify key reasons for prosthesis abandonment, which can be grouped into three main categories: (1) lack of comfort (e.g., excessive weight or temperature), (2) limited functionality (e.g., inadequate control or sensory feedback), and (3) poor aesthetics. Since embodiment is facilitated when a prosthesis successfully fulfills a dual role, supporting both appearance and functional performance64, we argue that increased embodiment reduces the likelihood of abandonment. Therefore, the cost savings from avoided prosthesis replacement represent a suitable financial proxy for this outcome. The monetary value was determined by multiplying the cost of a high-technology prosthesis by the observed rejection rate of 12.5%. This rate reflects the proportion of patients who reached a 0.75 embodiment threshold with the Hannes prosthesis but did not achieve this threshold with their regularly used prosthesis. The INAIL price list sets the cost of replacing a failed prosthesis with a more advanced model, such as the Michelangelo hand (Ottobock), at €26,473.30.
Finally, the significant boost in self-esteem experienced by Hannes users was financially valued using the average cost of ten counseling sessions designed to improve self-confidence and self-esteem.
This SROI analysis, based on data from the clinical trial (which directly involved only patients), represents an initial assessment of the project’s social impact. While limited by the available data, it identifies other relevant stakeholders and estimates their potential outcomes and social impact.
Additional stakeholders—outcomes, indicators, quantification and monetary valuation approach
Caregivers are a key stakeholder group. Hannes significantly enhances the autonomy of limb-difference subjects20,54, thereby reducing their need for assistance with essential activities such as cleaning or meal preparation. To estimate the potential reduction in caregiver burden, we relied on the outcome “Possibility of performing ADLs and improved functional independence”. In this context, 8 out of 11 patients achieved the target value of 0.75, indicating increased independence. These eight patients were assumed to no longer require caregiver support, allowing corresponding cost savings to be calculated. The time commitment of professional and non-professional caregivers was assessed using Italy’s average gross hourly wage (€14.5, ISTAT) and caregiver workload estimates based on Law 104, which provides for 3 days of paid leave per month. The enhanced ability of users to perform activities of daily living (ADLs) generated benefits for both patients and caregivers. For patients, the benefit is greater independence, and the proxy is measured as the estimated annual cost of hiring a caregiver. For caregivers, the proxy captures the value of time saved or stress reduced, estimated using the cost of informal or professional care. Consequently, we employed the same indicator to measure two distinct outcomes with separate financial proxies. This approach is consistent with the SROI methodology, which allows the same event to generate different outcomes for different stakeholders, provided that stakeholders are clearly distinguished, and proxies reflect their unique perspectives.
Other stakeholders include orthopedists, orthopedic workshops, local health authorities (ASL), and INAIL. Adopting Hannes could improve the quality standards of their services while enhancing market attractiveness and reputation. Although IIT, as a private foundation, cannot directly market products, Hannes has CE certification, complying with Directive 93/42/EEC and EU safety standards, making it a valuable offering for these stakeholders.
For the “Offer with higher quality standards” outcome, we used the mean score from patient questionnaires that assessed the quality of the Hannes device. Eight of eleven patients scored above the 0.7 threshold. The monetary value was estimated by calculating the cost savings from the price difference of similar offers. Specifically, the comparison was made with the best-in-class Michelangelo prosthesis (€42,000).
The increased facility attractiveness and reputation were assessed by considering the savings in advertising costs resulting from media exposure. Using the number of press articles mentioning Hannes (536, per IIT’s communication office) as an indicator, the monetary value was derived using a cost-per-article from the online price list of journalists’ tariff (refer to the following online document: Journalists’ Tariff).
The final key stakeholders are IIT and INAIL. As project funders and implementers, IIT and INAIL played a pivotal role in developing and deploying Hannes. Additionally, they clearly understand the changes experienced by both direct and indirect beneficiaries.
Based on actual costs incurred for small series production (11 units), the average production cost per prosthesis was €13,500. More precisely, these costs include expenses for the purchase of mechanical and electronic components, as well as accessory and commercial parts related to the wrist and hand, in addition to labor costs. With 11 prostheses produced for the clinical trial, the total investment amounted to €148,500.
We can assume that with larger-scale production, the costs of the various prosthetic components would decrease, thereby potentially increasing the SROI value.
Impact calculation
Table 3 shows that Hannes generates almost €461,500.00 in social value for various stakeholders against an initial investment of €148,500.00, yielding an SROI ratio of 3.11:1 for the first year. This ratio was calculated by comparing the monetary value of social benefits with project costs, using a conservative approach to avoid overestimation. The results confirm a significant social return on investment.
The INAIL center estimates the lifespan of a myoelectric prosthesis for upper limb amputations at five years (Annex No. 4 to Resolution 92009). Short-term outcomes, such as those related to orthopedists, workshops, the healthcare system, and INAIL, are assigned a one-year duration. Outcomes directly related to Hannes used, with medium-to-long-term effects, are assigned a five-year duration. Because some outcomes extend beyond a single year, it was crucial to set a drop-off to account for diminishing impacts over time. An annual drop-off rate of 5% was chosen by the IIT development team to account for possible wear and tear, even though they expect the prosthesis to maintain stable performance throughout its 5-year lifespan. Moreover, despite its limited service life, the prosthesis is supported by ongoing maintenance, warranty, and assistance, further ensuring sustained functionality. This rate is considered conservative because certain social benefits – such as improved user skills, increased autonomy, and enhanced performance – may grow over time as users become more experienced and confident with the prosthesis. This decision is also supported by evidence from the clinical study, which showed consistently high levels of use and user engagement with the Hannes prosthesis.
If the time horizon under consideration exceeds one year, SROI requires the application of a discount rate to account for the time value of money. This rate facilitates the comparison of costs and benefits across different periods. Determining an appropriate discount rate requires consideration of several factors, including prevailing market interest rates, project-specific risks, and broader economic expectations. It is worth noting that the discount rate is subject to variability depending on the specific context and sector. To provide a realistic estimate, we adopted a discount rate of 4.25%, based on the coupon rate of low-risk investments, exemplified by BTPs (Buoni del Tesoro Poliennali).
Table 6 reports the values of the impact calculation for each year. Starting from the second year, all impacts were adjusted by applying an annual drop-off rate of 5% to account for the potential reduction in outcomes over time. Furthermore, the Present Value for each year was calculated by dividing the sum of all impacts in t by \((1+r)^t\), where r is the discount rate (4.25%) and t is the corresponding year. Over five years, the total cumulative impact value reaches €1,297,318.75 with an SROI ratio of 8.74. This underscores Hannes’ value in delivering direct benefits to patient well-being and indirect benefits to other stakeholders.
To estimate the counterfactual scenario, we calculated the deadweight among current myoelectric prosthesis users. Deadweight represents the proportion of outcomes that would have been achieved with existing prostheses, independent of Hannes. This calculation is based on a comparison of pre- and post-Hannes questionnaire data. Expanding the comparison to include upper-limb amputees not using myoelectric prostheses reduces deadweight to 0%, resulting in an SROI of 4.61:1. Considering the full project period, the SROI increases to 12.58:1. This demonstrates that Hannes’ benefits grow over time, confirming its substantial long-term impact.
As noted, SROI reliability can be influenced by subjective choices in selecting indicators and assigning financial proxies. To mitigate the subjectivity in indicator selection, we employed an empirical approach, using item-scale correlation and Cronbach’s alpha coefficient to ensure that indicators accurately measured the same underlying or latent construct.
Sensitivity analyses were performed by testing different financial proxies for the same outcome. Specifically, we calculated the SROI for all conceivable combinations of these financial proxies, thereby defining a range within which the index may vary. The analysis, based on the lowest and highest values for each financial proxy, showed that the SROI remained consistently positive, ranging from 2.92 to 3.20 for the first year and from 7.94 to 9.14 over five years, demonstrating the robustness and stability of the results. The SROI ratio of 8.74 reflects a balanced and cautious approach, aligning with SROI principles and ensuring a scientifically effective representation of the project’s social and economic impact. Further sensitivity analysis was conducted by adjusting thresholds used to determine the number of individuals experiencing a particular outcome. The sensitivity analysis revealed that, despite variations in threshold values of up to \(\pm 5\%\), the SROI estimates consistently remained positive and relatively close to the reference scenario values, thereby confirming the robustness and reliability of the findings. The results of these sensitivity analyses are detailed in Appendix B of the online Supplementary material.
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