Benefits of the Cybathlon 2020 experience for a prosthetic hand user: a case study on the Hannes system.

BACKGROUND: Cybathlon championship aims at promoting the development of prosthetic and assistive devices capable to meet users' needs. This paper describes and analyses possible exploitation outcomes of our team's (REHAB TECH) experience into the Powered Arm Prosthesis Race of the Cybathlon 2020 Global Edition, with the novel prosthetic system Hannes. In detail, we present our analysis on a concurrent evaluation conducted to verify if the Cybathlon training and competition positively influenced pilot's performance and human-technology integration with Hannes, with respect to a non-runner Hannes user. METHODS: Two transradial amputees were recruited as pilots (Pilot 1 and Pilot 2) for the Cybathlon competition and were given the polyarticulated myoelectric prosthetic hand Hannes. Due to COVID-19 emergency, only Pilot 1 was trained for the race. However, both pilots kept Hannes for Home Use for seven weeks. Before this period, they both participated to the evaluation of functionality, embodiment, and user experience (UX) related to Hannes, which they repeated at the end of the Home Use and right after the competition. We analysed Pilot 1's training and race outcomes, as well as changes in the concurrent evaluation, and compared these results with Pilot 2's ones. RESULTS: The Cybathlon training gradually improved Pilot 1's performances, leading to the sixth place with a single error in task 5. In the parallel evaluation, both pilots had an overall improvement over time, whereas Pilot 2 experienced a deterioration of embodiment. In detail, Pilot 1, who followed the training and raced the Cybathlon, improved in greater way. CONCLUSION: Hannes demonstrated to be a valuable competitor and to perform grasps with human-like behaviors. The higher improvements of Pilot 1, who actively participated in the Cybathlon, in terms of functionality, embodiment and UX, may depend on his training and engagement in the effort of achieving a successful user-prosthesis interaction during the competition. Tasks based on Cybathlon's ones could improve the training phase of a prosthetic user, stimulating dexterity, prosthetic integration, and user perception towards the prosthesis. Likewise, timed races or competitions could facilitate and accelerate the learning phase, improving the efficiency and efficacy of the process.

User experiences of digital prostheses in daily functioning in people with an amputation of thumb or finger.

STUDY DESIGN": Qualitative research design using interpretative phenomenological analysis (IPA) to interpret users' experiences with digital prostheses. BACKGROUND: Digital prostheses are rarely used, and little is known about the experiences of traumatic finger amputees with digital prostheses. When advising patients regarding digital prostheses, it is crucial for professionals to understand users experiences of wearing a digital prosthesis and the meaning attached to wearing a digital prosthesis. PURPOSE OF STUDY: The aim of this study was to explore and understand users experiences of wearing a digital prostheses in daily functioning. METHODS: Individual semi-structured interviews were conducted, recorded, and transcribed. The written interview texts were analysed following Interpretative phenomenological analysis guidelines. RESULTS: Four participants were interviewed. They experienced the prostheses as valuable additions to their daily functioning. Three different themes relating to wearing and using digital prostheses emerged from in-depth analysis of the data: How the prosthesis supporting them regaining a 'grip' on life, reduced overload on unaffected side and restored body image. CONCLUSIONS: This study provides a deeper understanding of the experiences of people with digital amputations who use prostheses. Most importantly, that a prosthesis is of crucial importance for participants to be able to act independently and autonomously as well as to participate in family, work and social environments. This insight will help practitioners when considering, with clients the most appropriate digital prosthesis to meet their goals.

Comparison of vibrotactile and joint-torque feedback in a myoelectric upper-limb prosthesis.

BACKGROUND: Despite the technological advancements in myoelectric prostheses, body-powered prostheses remain a popular choice for amputees, in part due to the natural sensory advantage they provide. Research on haptic feedback in myoelectric prostheses has delivered mixed results. Furthermore, there is limited research comparing various haptic feedback modalities in myoelectric prostheses. In this paper, we present a comparison of the feedback intrinsically present in body-powered prostheses (joint-torque feedback) to a commonly proposed feedback modality for myoelectric prostheses (vibrotactile feedback). In so doing, we seek to understand whether the advantages of kinesthetic feedback present in body-powered prostheses translate to myoelectric prostheses, and whether there are differences between kinesthetic and cutaneous feedback in prosthetic applications. METHODS: We developed an experimental testbed that features a cable-driven, voluntary-closing 1-DoF prosthesis, a capstan-driven elbow exoskeleton, and a vibrotactile actuation unit. The system can present grip force to users as either a flexion moment about the elbow or vibration on the wrist. To provide an equal comparison of joint-torque and vibrotactile feedback, a stimulus intensity matching scheme was utilized. Non-amputee participants (n=12) were asked to discriminate objects of varying stiffness with the prosthesis in three conditions: no haptic feedback, vibrotactile feedback, and joint-torque feedback. RESULTS: Results indicate that haptic feedback increased discrimination accuracy over no haptic feedback, but the difference between joint-torque feedback and vibrotactile feedback was not significant. In addition, our results highlight nuanced differences in performance depending on the objects' stiffness, and suggest that participants likely pay less attention to incidental cues with the addition of haptic feedback. CONCLUSION: Even when haptic feedback is not modality matched to the task, such as in the case of vibrotactile feedback, performance with a myoelectric prosthesis can improve significantly. This implies it is possible to achieve the same benefits with vibrotactile feedback, which is cheaper and easier to implement than other forms of feedback.

Evaluation of EMG pattern recognition for upper limb prosthesis control: a case study in comparison with direct myoelectric control.

BACKGROUND: Although electromyogram (EMG) pattern recognition (PR) for multifunctional upper limb prosthesis control has been reported for decades, the clinical benefits have rarely been examined. The study purposes were to: 1) compare self-report and performance outcomes of a transradial amputee immediately after training and one week after training of direct myoelectric control and EMG pattern recognition (PR) for a two-degree-of-freedom (DOF) prosthesis, and 2) examine the change in outcomes one week after pattern recognition training and the rate of skill acquisition in two subjects with transradial amputations. METHODS: In this cross-over study, participants were randomized to receive either PR control or direct control (DC) training of a 2 DOF myoelectric prosthesis first. Participants were 2 persons with traumatic transradial (TR) amputations who were 1 DOF myoelectric users. Outcomes, including measures of dexterity with and without cognitive load, activity performance, self-reported function, and prosthetic satisfaction were administered immediately and 1 week after training. Speed of skill acquisition was assessed hourly. One subject completed training under both PR control and DC conditions. Both subjects completed PR training and testing. Outcomes of test metrics were analyzed descriptively. RESULTS: Comparison of the two control strategies in one subject who completed training in both conditions showed better scores in 2 (18%) dexterity measures, 1 (50%) dexterity measure with cognitive load, and 1 (50%) self-report functional measure using DC, as compared to PR. Scores of all other metrics were comparable. Both subjects showed decline in dexterity after training. Findings related to rate of skill acquisition varied considerably by subject. CONCLUSIONS: Outcomes of PR and DC for operating a 2-DOF prosthesis in a single subject cross-over study were similar for 74% of metrics, and favored DC in 26% of metrics. The two subjects who completed PR training showed decline in dexterity one week after training ended. Findings related to rate of skill acquisition varied considerably by subject. This study, despite its small sample size, highlights a need for additional research quantifying the functional and clinical benefits of PR control for upper limb prostheses.

A comparative study of virtual hand prosthesis control using an inductive tongue control system.

This study compares the time required to activate a grasp or function of a hand prosthesis when using an electromyogram (EMG) based control scheme and when using a control scheme combining EMG and control signals from an inductive tongue control system (ITCS). Using a cross-over study design, 10 able-bodied subjects used a computer model of a hand and completed simulated grasping exercises. The time required to activate grasps was recorded and analyzed for both control schemes. End session mean activation times (ATs; seconds) for the EMG control scheme grasps 1 -5 were 0.80, 1.51, 1.95, 2.93, and 3.42; for the ITCS control scheme grasps 1 ‒5 they were 1.19, 1.89, 1.75, 2.26, and 1.80. Mean AT for grasps 1 and 2 was statistically significant in favor of the EMG control scheme (p = 0.030; p = 0.004). For grasp 3 no statistical significance occurred, and for grasps 4 and 5 there was a statistical significance in favour of the ITCS control scheme (p = 0.048; p = 0.004). Based on the amount of training and the achieved level of performance, it is concluded that the proposed ITCS control scheme can be used as a means of enhancing prosthesis control.

Implementing social and affective touch to enhance user experience in human-robot interaction.

In this paper, we discuss the potential contribution of affective touch to the user experience and robot performance in human-robot interaction, with an in-depth look into upper-limb prosthesis use as a well-suited example. Research on providing haptic feedback in human-robot interaction has worked to relay discriminative information during functional activities of daily living, like grasping a cup of tea. However, this approach neglects to recognize the affective information our bodies give and receive during social activities of daily living, like shaking hands. The discussion covers the emotional dimensions of affective touch and its role in conveying distinct emotions. In this work, we provide a human needs-centered approach to human-robot interaction design and argue for an equal emphasis to be placed on providing affective haptic feedback channels to meet the social tactile needs and interactions of human agents. We suggest incorporating affective touch to enhance user experience when interacting with and through semi-autonomous systems such as prosthetic limbs, particularly in fostering trust. Real-time analysis of trust as a dynamic phenomenon can pave the way towards adaptive shared autonomy strategies and consequently enhance the acceptance of prosthetic limbs. Here we highlight certain feasibility considerations, emphasizing practical designs and multi-sensory approaches for the effective implementation of affective touch interfaces.

Evidencing the effectiveness of upper limb prostheses: a multi-stakeholder perspective on study requirements.

The provision of upper limb prosthetic devices through the National Health Services (NHS) within the United Kingdom is driven by national policies. NHS England have recently published a new policy to provide multi-grip myoelectric hands. The policy highlighted that there was limited evidence to support its deployment and it will be reviewed should new information arise. The clear identification of the evidence gap provides an opportunity for the academic research community to conduct studies that will inform future iterations of this and other upper limb prosthetic related policies. This paper presents a summary of findings and recommendations based on two multi-stakeholder workshops held in June 2022 and July 2022, which explored the design requirements for policy-driven research studies. The workshops involved people from a broad range of stakeholder groups: policy, academia, NHS clinical and management, industry, and a person with upper limb absence. The workshop discussions focused on the research questions that NHS England identified in the policy evidence review: (1) Clinical Effectiveness; (2) Cost Effectiveness; (3) Safety; and (4) Patient Subgroups. The recommendations based on stakeholder discussions included the need to gather qualitative and quantitative research evidence, use goal-based outcome measures, and conduct longitudinal studies. Future research studies also need to address the complexities of conducting national and international policy-driven research, such as clinical resource capacity and participant involvement.

Towards User-Centred Prosthetics Research Beyond the Laboratory.

The purpose of this study was to explore a range of perspectives on how academic research and clinical assessment of upper-limb prosthetics could happen in environments outside of laboratories and clinics, such as within peoples' homes. Two co-creation workshops were held, which included people who use upper limb prosthetic devices (hereafter called users), clinicians, academics, a policy stakeholder, and a representative from the upper-limb prosthetics industry (hereafter called professionals). The discussions during the workshops indicate that research and clinical assessment conducted remotely from a laboratory or clinic could inform future solutions that address user needs. Users were open to the idea of sharing sensor and contextual data from within their homes to external laboratories during research studies. However, this was dependent upon several considerations, such as choice and control over data collection. Regarding clinical assessment, users had reservations of how data may be used to inform future prosthetic prescriptions whilst, clinicians were concerned with resource implications and capacity to process user data. The paper presents findings of the discussions shared by participants during both workshops. The paper concludes with a conjecture that collecting sensor and contextual data from users within their home environment will contribute towards literature within the field, and potentially inform future care policies for upper limb prosthetics. The involvement of users during such studies will be critical and can be enabled via a co-creation approach. In the short term, this may be achieved through academic research studies, which may in the long term inform a framework for clinical in-home trials and clinical remote assessment.

Prosthetic management of unilateral transradial amputation and limb deficiency: Consensus clinical standards of care.

INTRODUCTION: Upper limb research is currently lacking detailed clinical guidance on the provision of unilateral transradial prostheses. Clinical practice guidelines are meant to serve as assistance for the decision-making process, and Delphi surveys have been used with increasing frequency within orthotics and prosthetics to create these guidelines for clinical practice. METHODS: A three round Delphi survey was used to gain consensus on clinical statements regarding unilateral transradial prostheses. RESULTS: We achieved consensus (> 80% agreement) on a total of 40 statements by surveying 22 experts on upper limb prosthetics over three rounds of surveys. Response rate ranged from 81.8-86.4% with a total of 55 total statements under consideration throughout the duration of the survey. The 40 passing statements were arranged into nine guidelines for provision of prosthetic care in this population. CONCLUSIONS: The Delphi technique allowed for the creation of a set of clinical practice guidelines for the unilateral transradial patient in the absence of conclusive empirical evidence.

Co-creation and User Perspectives for Upper Limb Prosthetics.

People who either use an upper limb prosthesis and/or have used services provided by a prosthetic rehabilitation centre, experience limitations of currently available prosthetic devices. Collaboration between academia and a broad range of stakeholders, can lead to the development of solutions that address peoples' needs. By doing so, the rate of prosthetic device abandonment can decrease. Co-creation is an approach that can enable collaboration of this nature to occur throughout the research process. We present findings of a co-creation project that gained user perspectives from a user survey, and a subsequent workshop involving: people who use an upper limb prosthesis and/or have experienced care services (users), academics, industry experts, charity executives, and clinicians. The survey invited users to prioritise six themes, which academia, clinicians, and industry should focus on over the next decade. The prioritisation of the themes concluded in the following order, with the first as the most important: function, psychology, aesthetics, clinical service, collaboration, and media. Within five multi-stakeholder groups, the workshop participants discussed challenges and collaborative opportunities for each theme. Workshop groups prioritised the themes based on their discussions, to highlight opportunities for further development. Two groups chose function, one group chose clinical service, one group chose collaboration, and another group chose media. The identified opportunities are presented within the context of the prioritised themes, including the importance of transparent information flow between all stakeholders; user involvement throughout research studies; and routes to informing healthcare policy through collaboration. As the field of upper limb prosthetics moves toward in-home research, we present co-creation as an approach that can facilitate user involvement throughout the duration of such studies.

Interaction in Assistive Robotics: A Radical Constructivist Design Framework.

Despite decades of research, muscle-based control of assistive devices (myocontrol) is still unreliable; for instance upper-limb prostheses, each year more and more dexterous and human-like, still provide hardly enough functionality to justify their cost and the effort required to use them. In order to try and close this gap, we propose to shift the goal of myocontrol from guessing intended movements to creating new circular reactions in the constructivist sense defined by Piaget. To this aim, the myocontrol system must be able to acquire new knowledge and forget past one, and knowledge acquisition/forgetting must happen on demand, requested either by the user or by the system itself. We propose a unifying framework based upon Radical Constructivism for the design of such a myocontrol system, including its user interface and user-device interaction strategy.

Channel-hopping during surface electrical neurostimulation elicits selective, comfortable, distally referred sensations.

Objective.Lack of sensation from a hand or prosthesis can result in substantial functional deficits. Surface electrical stimulation of the peripheral nerves is a promising non-invasive approach to restore lost sensory function. However, the utility of standard surface stimulation methods has been hampered by localized discomfort caused by unintended activation of afferents near the electrodes and limited ability to specifically target underlying neural tissue. The objectives of this work were to develop and evaluate a novel channel-hopping interleaved pulse scheduling (CHIPS) strategy for surface stimulation that is designed to activate deep nerves while reducing activation of fibers near the electrodes.Approach.The median nerve of able-bodied subjects was activated by up to two surface stimulating electrode pairs placed around their right wrist. Subjects received biphasic current pulses either from one electrode pair at a time (single-channel), or interleaved between two electrode pairs (multi-channel). Percept thresholds were characterized for five pulse durations under each approach, and psychophysical questionnaires were used to interrogate the perceived modality, quality and location of evoked sensations.Main results.Stimulation with CHIPS elicited enhanced tactile percepts that were distally referred, while avoiding the distracting sensations and discomfort associated with localized charge densities. These effects were reduced after introduction of large delays between interleaved pulses.Significance.These findings demonstrate that our pulse scheduling strategy can selectively elicit referred sensations that are comfortable, thus overcoming the primary limitations of standard surface stimulation methods. Implementation of this strategy with an array of spatially distributed electrodes may allow for rapid and effective stimulation fitting. The ability to elicit comfortable and referred tactile percepts may enable the use of this neurostimulation strategy to provide meaningful and intuitive feedback from a prosthesis, enhance tactile feedback after sensory loss secondary to nerve damage, and deliver non-invasive stimulation therapies to treat various pain conditions.

A custom, functional and lifelike passive prosthetic hand for infants and small toddlers: Clinical note.

BACKGROUND AND AIM: For infants and small toddlers with congenital upper limb deficiencies, terminal devices mainly provide either cosmesis or functionality. We report a clinical note about fitting a child with a low-cost passive hand targeting both functionality and cosmesis. TECHNIQUE: An elastomeric, alloy-wire-reinforced hand was fabricated using additive manufacturing to allow independent positioning of the digits. A clinical pilot in-home evaluation was conducted on a child with upper limb loss. DISCUSSION: The fabricated hand met the functional requirements but required a cover for cosmesis due to a poor surface finish associated with the fabrication technique. The participant child was comfortable using the prosthesis for various tasks. The parents were satisfied with the hand's function and cosmesis when covered with a cosmetic glove. This work demonstrated a new design and process that may in the future improve the utilization of prosthetic hands to promote early prosthesis use and a child's development. CLINICAL RELEVANCE: Early prosthesis use is important for infants and toddlers. Additive manufacturing may enable the fabrication of custom passive prosthetic hands that provide both cosmesis and functionality.

Fabrication and application of an adjustable myoelectric transhumeral prosthetic socket.

BACKGROUND AND AIM: Although upper limb myoelectric prostheses can offer improved functionality and dexterity over body-powered systems, abandonment rates remain high. User dissatisfaction in comfort and control are among the top contributors. The design of the prosthetic socket must be comfortable, while maintaining contact of control electrodes with the residual limb throughout the day. We present a myoelectric socket design that provides user-adjustable compression over electrode control sites to promote consistent control, while maintaining comfort and fit. TECHNIQUE: A cable tensioning system was threaded through a series of paneled windows in the socket wall over electrode sites. Adjusting tension provided tuning of electrode contact. DISCUSSION: A case study of a single transhumeral prosthetic user with a follow-up interview 11 months post delivery suggests that our adjustable design has the potential to address control and comfort challenges, critical factors in myoelectric prosthetic use, and abandonment. CLINICAL RELEVANCE: Achieving consistent electrode contact with muscle control sites in traditional rigid sockets is a critical challenge for myoelectric prostheses. We present a unique solution via user-adjustable electrode contacts built into the socket.

Clinical evaluation of the refined clothespin relocation test: A pilot study.

BACKGROUND: The refined clothespin relocation test is a test used to evaluate the performance of a prosthesis user by analysing the compensatory motions and time to complete a grasping and placement exercise. The test has been studied previously with a motion capture laboratory and has now been adapted for a clinical setting. A comparison of prosthesis user to an able-bodied group is needed to determine efficacy as an assessment tool. OBJECTIVE: To modify the previous refined clothespin relocation test and assess whether it can distinguish between able-bodied and prosthesis users. STUDY DESIGN: Comparative analysis. METHODS: Forty-two able-bodied subjects and three prosthesis users completed the adapted refined clothespin relocation test protocol. Average refined clothespin relocation test scores describing the degree of compensatory movements and the time to complete the protocol were compared using a Mann-Whitney U-test. RESULTS: A significant difference was found in the refined clothespin relocation test score between the able-bodied (Md = 65.32, n = 42) and prosthesis users (Md = 23.07, n = 3) with a medium effect size (p < 0.001, r = 0.43). CONCLUSION: Prosthesis users demonstrated larger compensations and longer completion times, as reflected in the refined clothespin relocation test final score. The refined clothespin relocation test has the potential to be a useful clinical tool to assess user performance on a functional task. CLINICAL RELEVANCE: This preliminary study demonstrates that the adapted protocol can distinguish between the two groups based on refined clothespin relocation test score. A future multi-centre study is required using multiple raters and comparing it with the existing outcome measures to validate the refined clothespin relocation test and determine inter-rater reliability.

Remote fitting procedures for upper limb 3d printed prostheses.

BACKGROUND: The objective of the current investigation was twofold: i) describe a remote fitting procedure for upper limb 3D printed prostheses and ii) assess patient satisfaction and comfort with 3D printed prostheses fitted remotely. METHODS: A qualitative study using content and score analysis to describe patient satisfaction after remote prosthetic fitting. Research participants reported QUEST and OPUS scores that allow for perceived rating of general aspects and functionality of upper limb prostheses. RESULTS: Six children (three girls & boys, 6-16 years of age) and 2 adult males (25 and 59 years of age) with congenital (n = 7) and acquired (n = 1) upper limb loss participated in this study. Highest device satisfaction items of the QUEST include weight (4.50 ± 0.76), safety (4.38 ± 0.52), and ease of use (4.13 ± 0.64). Functional tasks of the OPUS observe that prosthesis donning and doffing (1.5 ± 0.84) and drinking from a paper cup (1.75 ± 0.89) were the easiest functional tasks. CONCLUSION: The presented methodology for remote fitting of 3D printed upper-limb prostheses exhibits significant potential for rapid fabrication of functional prostheses to developing countries due to increased availability of digital devices in rural areas.

Conception, design, and fabrication of novel cost-effective partial-hand prosthetic devices for a quadrilateral individual with limb loss.

BACKGROUND AND AIM: The author designed customized upper-limb prosthetic devices for a 22-year-old man with quadrilateral limb loss. The devices were created to meet his functional requirements, while remaining cost-effective. What made this solution unique was that it utilized low-cost items that were easily sourced and maintained. TECHNIQUE: Devices with polypropylene sockets, wooden positional fingers from an artist's wooden hand and a metal extension plate were conceptualized and manufactured. The patient gave written consent to the publication of information and photographs in this report. DISCUSSION: The devices allowed the individual to complete tasks he desired to be able to perform independently, which included using a computer mouse, aided by the devices. The devices utilized were low-cost and easily accessible materials, such as polypropylene and wood, to cater to financial constraints. The final design had positional fingers and an extension plate to restore surface area for grip, support, and opposition to enable the execution of daily tasks of living. CLINICAL RELEVANCE: A cost-effective method of fabricating partial-hand devices with easily accessible materials is described. The resulting devices were successful at restoring the upper-limb surface area for improved grip, support, and opposition for performance of daily tasks.

Biomechanical analysis of users of multi-articulating externally powered prostheses with and without their device.

BACKGROUND: Loss of the hand results in significant functional deficits and requires adaptation of movement patterns which may result in overuse injuries. An externally powered prosthesis may improve function of the affected limb and reduce the overreliance on the intact side; however, little research has been done in this area. OBJECTIVE: Investigate changes in upper limb function and kinematics in individuals with partial-hand amputations performing a functional assessment by comparing results with and without a multi-articulating hand prosthesis. STUDY DESIGN: Cross-sectional. METHODS: Three-dimensional kinematics of four- and five-digit limb loss participants were collected as they performed the Southampton Hand Assessment Procedure with and without a prothesis. RESULTS: Ten males completed the protocol: five with four-digit loss (thumb intact) and five with five-digit loss. Significantly larger joint motions were seen without the prosthesis than with for all participants, which may be an indicator of higher risk for overuse injury. Significant improvement was seen in Southampton Hand Assessment Procedure scores in the five-digit limb loss participants using the prosthesis compared with not using the device (p < 0.05 for 6/7 Southampton Hand Assessment Procedure score categories). CONCLUSION: The prosthesis reduced functional deficits and decreased joint range of motion in individuals with partial hand loss. Results showed reduced compensatory motions throughout the upper limb and torso which may reduce the risk of overuse injury. CLINICAL RELEVANCE: Results of this study indicate that externally powered partial hand prostheses can be effective in improving function and reducing compensation in individuals with partial hand loss.

Spike detection: The first step towards an ENG-based neuroprosheses.

BACKGROUND: Being able to control an upper limb prosthesis by means of the signals recorded from the peripheral nerves is not a trivial task. New generations of neural electrodes are able to record this information but the quality of the signal can make difficult the extraction of the useful information. Several techniques have been adopted both for central and peripheral acquisitions in order to remove the noise and/or enhance the electrical activity generated by the brain or carried by the nerves. NEW METHODS: In this review, common spike detection algorithms have been tested on both real and simulated recordings to verify which is the best choice to be applied in a neuroprosthetics context. In particular, the moving average algorithm (MAA), the non-linear energy operator (NEO) and the wavelet denoising (WD) have been implemented and their performance have been tested by means of the number of the detected real positives (RPs) and false positives (FPs). RESULTS: MAA outperforms the other techniques because it is capable of detecting a high amount of RPs and, compared to NEO, with a reduced number of FPs. COMPARISON WITH EXISTING METHODS: MAA needs only the information of the duration of the action potential while the NEO and the WD require the frequency and/or the shape of the action potentials. CONCLUSIONS: NEO and WD are algorithms requiring information about the signal, not a priori known. MAA, then, seems most suitable for online applications.

Fatigue-free operation of most body-powered prostheses not feasible for majority of users with trans-radial deficiency.

BACKGROUND: Body-powered prostheses require cable operation forces between 33 and 131 N. The accepted upper limit for fatigue-free long-duration operation is 20% of a users' maximum cable operation force. However, no information is available on users' maximum force. OBJECTIVES: To quantify users' maximum cable operation force and to relate this to the fatigue-free force range for the use of body-powered prostheses. STUDY DESIGN: Experimental trial. METHODS: In total, 23 subjects with trans-radial deficiencies used a bypass prosthesis to exert maximum cable force three times during 3 s and reported discomfort or pain on a body map. Additionally, subjects' anthropometric measures were taken to relate to maximum force. RESULTS: Subjects generated forces ranging from 87 to 538 N. Of the 23 subjects, 12 generated insufficient maximum cable force to operate 8 of the 10 body-powered prostheses fatigue free. Discomfort or pain did not correlate with the magnitude of maximum force achieved by the subjects. Nine subjects indicated discomfort or pain. No relationships between anthropometry and maximal forces were found except for maximum cable forces and the affected upper-arm circumference for females. CONCLUSION: For a majority of subjects, the maximal cable force was lower than acceptable for fatigue-free prosthesis use. Discomfort or pain occurred in ~40% of the subjects, suggesting a suboptimal force transmission mechanism. Clinical relevance The physical strength of users determines whether a body-powered prosthesis is suitable for comfortable, fatigue-free long-duration use on a daily basis. High cable operation forces can provoke discomfort and pain for some users, mainly in the armpit. Prediction of the users' strength by anthropometric measures might assist the choice of a suitable prosthesis.