Design of novel test rig for prosthetic finger distal interphalangeal and phalanx strengths

Testing is one of the most significant phases of any engineering process, the last process followed by conceptualization, designing, and fabricating. If the testing outcomes are not genealogy sensible measurables, then eventually it calls for a redesign overhaul. Existing testing equipment to analyze the load and failures are conventional digital universal testing machines with minimum jigs and fixtures. In addition, the existing fixtures cannot be adapted to the anatomy of a human finger. Consequently, the present work explores the best possible design of a jig for testing the naturally articulated movement of a human finger (prosthetic wear-on). Furthermore, the present jig design checks a wide range of parameters such as freedom of motion, a path along with curvature, load, failures, and intermittent positions of applied load, which is adaptable to existing universal testing machines available for broader applications.

Quantification of finger grasps during activities of daily life using convolutional neural networks: A pilot study

Quantifying finger kinematics can improve the authors' understanding of finger function and facilitate the design of efficient prosthetic devices while also identifying movement disorders and assessing the impact of rehabilitation interventions. Here, the authors present a study that quantifies grasps depicted in taxonomies during selected Activities of Daily Living (ADL). A single participant held a series of standard objects using specific grasps which were used to train Convolutional Neural Networks (CNN) for each of the four fingers individually. The experiment also recorded hand manipulation of objects during ADL. Each set of ADL finger kinematic data was tested using the trained CNN, which identified and quantified the grasps required to accomplish each task. Certain grasps appeared more often depending on the finger studied, meaning that even though there are physiological interdependencies, fingers have a certain degree of autonomy in performing dexterity tasks. The identified and most frequent grasps agreed with the previously reported findings, but also highlighted that an individual might have specific dexterity needs which may vary with profession and age. The proposed method can be used to identify and quantify key grasps for finger/hand prostheses, to provide a more efficient solution that is practical in their day-to-day tasks.

Working with partial hand prostheses: An investigation into experiences of clinicians

BACKGROUND

Individuals living with partial hand absence often face challenges in performing everyday tasks and fully participating in society. Prosthetic devices offer a range of benefits, including improved functionality or cosmesis. However, partial hand devices can be rejected by users. In addition, there is a lack of evidence that establishes methods or factors influencing the clinical prescription of prosthetics specifically designed for this population.

OBJECTIVES

The objectives of the investigation were to gain understanding of who is prescribing partial hand prosthetics and the factors which influence device selection.

STUDY DESIGN

A 36-item anonymous online survey was designed on Qualtrics and distributed to clinicians. The survey contained multiple-choice, Likert-type, closed, and open-ended questions.

METHODS

Quantitative and qualitative analyses were performed on Qualtrics and Microsoft Excel.

RESULTS

Thirty-seven clinicians from various occupations participated. The majority agreed that outcome measures are useful for assessing partial hand prosthetics but suggested room for improvement. Although clinicians use various outcome measurement tools, there is a lack of tools specifically tailored to this population. Factors such as existing function, occupation, and hobbies were identified as important when selecting prosthetic devices for users. Funding influenced the range of partial hand devices available for prescription.

CONCLUSIONS

The prescription process involves multiple stakeholders. Various factors, including funding and user satisfaction, must be considered in the decision-making process. There is a lack of specific outcome measures recommended for evaluating prosthetics in this population. However, providing loaner units before final prescription yields positive outcomes.

Restoring natural upper limb movement through a wrist prosthetic module for partial hand amputees

BACKGROUND

Most partial hand amputees experience limited wrist movement. The limited rotational wrist movement deteriorates natural upper limb system related to hand use and the usability of the prosthetic hand, which may cause secondary damage to the musculoskeletal system due to overuse of the upper limb affected by repetitive compensatory movement patterns. Nevertheless, partial hand prosthetics, in common, have only been proposed without rotational wrist movement because patients have various hand shapes, and a prosthetic hand should be attached to a narrow space.

METHODS

We hypothesized that partial hand amputees, when using a prosthetic hand with a wrist rotation module, would achieve natural upper limb movement muscle synergy and motion analysis comparable to a control group. To validate the proposed prototype design with the wrist rotation module and verify our hypothesis, we compared a control group with partial hand amputees wearing hand prostheses, both with and without the wrist rotation module prototype. The study contained muscle synergy analysis through non-negative matrix factorization (NMF) using surface electromyography (sEMG) and motion analyses employing a motion capture system during the reach-to-grasp task. Additionally, we assessed the usability of the prototype design for partial hand amputees using the Jebsen-Taylor hand function test (JHFT).

RESULTS

The results showed that the number of muscle synergies identified through NMF remained consistent at 3 for both the control group and amputees using a hand prosthesis with a wrist rotation module. In the motion analysis, a statistically significant difference was observed between the control group and the prosthetic hand without the wrist rotation module, indicating the presence of compensatory movements when utilizing a prosthetic hand lacking this module. Furthermore, among the amputees, the JHFT demonstrated a greater improvement in total score when using the prosthetic hand equipped with a wrist rotation module compared to the prosthetic hand without this module.

CONCLUSION

In conclusion, integrating a wrist rotation module in prosthetic hand designs for partial hand amputees restores natural upper limb movement patterns, reduces compensatory movements, and prevent the secondary musculoskeletal. This highlights the importance of this module in enhancing overall functionality and quality of life.

Hand Surgeons' Understanding of Partial Hand Prostheses: Results of a National Survey Study

PURPOSE

Partial hand amputations are devastating injuries that often negatively affect individuals and communities. Partial hand prostheses can mitigate the burdens of living with an amputation, especially when reconstruction alone cannot restore form or function. However, hand surgeons may be unfamiliar with these newer devices because the prosthetic field is rapidly progressing.

METHODS

An electronic survey was distributed to hand surgeon members of the American Association for Hand Surgery with the intent of assessing surgeons' familiarity with partial hand prosthetic devices and their clinical applications. Survey items used Likert 5-point scales, rank order, multiple-choice, and yes/no question formats. Responses were compared by training background (orthopedic or plastic surgery) and by years of experience (≤10 years in practice or >10 years in practice).

RESULTS

Overall, hand surgeons are unfamiliar with modern partial hand prosthetic devices. Most of the cohort denied working within a multidisciplinary hand team (76.2%) or consulting with a prosthetist prior to revisional surgeries (71.4%). Restoring gross motor function and reducing pain were important outcomes to the cohort (4.42 and 4.17, respectively). Plastic trained hand surgeons were more likely to list toe-to-hand transfers as treatment options for multilevel digital amputations (P = .03) and transmetacarpal amputations (P = .02). Senior hand surgeons were more likely to suggest no treatment for partial thumb amputations (P = .02).

CONCLUSIONS

Expanding surgeon knowledge and encouraging collaboration within a multidisciplinary team may enhance amputee care.

Satisfaction of individuals with partial-hand amputations after they were fitted with cosmetic silicone prostheses

BACKGROUND

Partial-hand amputations are the most common level of upper-limb amputations which can lead to cosmetic and functional problems. Partial-hand amputations can be acquired or congenital. Cosmetic silicone prostheses are used in the management of partial-hand amputation; however, a literature review shows that most of the studies are on the fabrication of prosthesis, and data remain deficient on the satisfaction of users with silicone prostheses.

OBJECTIVES

To assess the satisfaction of individuals after they were fitted with cosmetic silicone prostheses for partial-hand amputations.

STUDY DESIGN

Cross-sectional study.

METHODS

Fifty-four participants with partial-hand amputations and who received cosmetic silicone prostheses participated in the survey using the validated Arabic version of the Client Satisfaction with Device (CSD-Ar).

RESULTS

Nearly half of the participants were using their silicone prosthesis daily. Most of the patients reported satisfaction with durability and donning, whereas most of the patients were dissatisfied with comfort. The mean of CSD-Ar total score was 16.8 ± 4.7 of 32. The CSD-Ar total score was significantly associated with the side of amputation ( p -value = 0.014) and usage of prosthesis ( p -value < 0.001).

CONCLUSION

The satisfaction of individuals with partial-hand amputations can be enhanced by fitting them with cosmetic silicone prostheses. However, these prostheses should meet certain criteria including fitting, weight, comfort, donning, appearance, durability, skin abrasion and irritation, and pain. Individuals' expectations and concerns should be considered as well.

The Starfish Procedure for Independent Digital Control of a Myoelectric Prosthesis

Management of partial hand amputations is a notable clinical challenge. Historically, myoelectric prostheses have not allowed for independent digital control, resulting in unsatisfactory function and high rejection rates among upper extremity amputees. The Starfish Procedure was developed for patients who sustained loss of multiple digits through the level of the base of the proximal phalanx or distal metacarpal. The procedure involves the pedicled transfer of 1 or more dorsal interosseous muscles to a subcutaneous location. This allows for a myoelectric sensor to capture the signals generated by these transferred muscles, thereby enabling intuitive, independent, digital prosthetic flexion and extension. In this article, we detail the relevant anatomy, indications, and technique for performing the Starfish Procedure. Given our patients' promising outcomes to date, we hope this technique paper will encourage upper extremity surgeons of all training backgrounds to perform this relatively straightforward procedure, thereby allowing patients with life-altering finger amputations to regain meaningful function by enhancing control of digital prostheses.

Current and emerging prostheses for partial hand amputation: A narrative review

Partial hand amputation can have a tremendous range of impact and functional loss on a person's life. One solution to improve function and address some of the problems that partial hand amputees face is to fit them with a prosthesis. Partial hand prosthetic devices range in a wide spectrum in both function and aesthetics. At this time, there is no one, perfect prosthetic device that can replace what is lost. Many individuals with partial hand amputation require more than one prosthetic device. In this review article, we explored and compared several prosthetic options that have been investigated and marketed by researchers and companies. Some of these options include passive, body-powered, activity-specific, and externally-powered prostheses. Lastly, we described our experiences with partial hand prostheses at Walter Reed National Military Medical Center.

Conceptualization of an Anthropomorphic Replacement Hand with a Sensory Feedback System

In this paper, a concept for an anthropomorphic replacement hand cast with silicone with an integrated sensory feedback system is presented. In order to construct the personalized replacement hand, a 3D scan of a healthy hand was used to create a 3D-printed mold using computer-aided design (CAD). To allow for movement of the index and middle fingers, a motorized orthosis was used. Information about the applied force for grasping and the degree of flexion of the fingers is registered using two pressure sensors and one bending sensor in each movable finger. To integrate the sensors and additional cavities for increased flexibility, the fingers were cast in three parts, separately from the rest of the hand. A silicone adhesive (Silpuran 4200) was examined to combine the individual parts afterwards. For this, tests with different geometries were carried out. Furthermore, different test series for the secure integration of the sensors were performed, including measurements of the registered information of the sensors. Based on these findings, skin-toned individual fingers and a replacement hand with integrated sensors were created. Using Silpuran 4200, it was possible to integrate the needed cavities and to place the sensors securely into the hand while retaining full flexion using a motorized orthosis. The measurements during different loadings and while grasping various objects proved that it is possible to realize such a sensory feedback system in a replacement hand. As a result, it can be stated that the cost-effective realization of a personalized, anthropomorphic replacement hand with an integrated sensory feedback system is possible using 3D scanning and 3D printing. By integrating smaller sensors, the risk of damaging the sensors through movement could be decreased.

[Update on prosthesis for partial hand and finger amputations]

Partial hand and finger amputations are relatively rare but devastating due to the consequences they provoque. In addition, they are more likely than lower limb amputations in car accidents, work accidents and by certain weapons of war. Men are going to have a much higher risk of traumatic amputation than women, with a rate 6.6 times higher. Fitting can be a complex process and a challenge for professionals. For this reason, it is important to know all the options available on the market that can meet the needs of patients, from cosmetic to myoelectric prostheses. Fitting requires the coordinated activity of a multiassistant clinical work team, the center of the team being the person who has suffered the amputation, who must have all the information possible to be able to actively participate in decision-making.

Osseointegrated Metallic Implants for Finger Amputees: A Review of the Literature

Digital trauma amputations and digital agenesis strongly affect the functionality and aesthetic appearance of the hand. Autologous reconstruction is the gold standard of treatment. Unfortunately, microsurgical options and transplantation procedures are not possible for patients who present contraindications or refuse to undergo transplantation from the toe (e.g. toe‐to‐thumb transplantation). To address these issues, osseointegrated finger prostheses are a promising alternative. The functional assessments registered during follow‐up confirmed the promising outcomes of osseointegrated prostheses in the treatment of hand finger amputees. This review outlines (a) a detailed analysis of osseointegrated finger metallic components of the implants, (b) the surgical procedures suggested in the literature, and (c) the functional assessments and promising outcomes that demonstrate the potential of these medical osseointegrated devices in the treatment of finger amputees.

Design of Bionic Prosthetic Fingers Using 3D Topology Optimization

Compliant mechanisms are frequently used in the design of prosthetic fingers since their monolithic structure and flexible movement are quite similar to the biological human fingers. However, the design of compliant prosthetic fingers is not easy, as the conventional rigid-link-based mechanism theory cannot be directly applied. In this paper, we introduce a 3D topology optimization based design framework to simplify the synthesis process of bionic compliant prosthetic fingers. The proposed framework is implemented in the software MATLAB and the realized fingers can be quickly fabricated using selective laser sintering (SLS) technology. To illustrate the design process of the proposed framework, a design example was presented. The bending performance of the realized finger was successfully verified by the FEM-based simulation and the payload test. In future work, the optimized fingers have the potential to be integrated into prosthetic hands to realize sophisticated grasping movements.

Starfish Procedure

For those patients with partial hand level amputation who would benefit from myoelectric prosthetic digits for enhanced prehensile function, the Starfish Procedure provides muscle transfers, which allow for the generation of intuitively controlled electromyographic signals for individual digital control with minimal myoelectric cross-talk. Thoughtful preoperative planning allows for creation of multiple sources of high-quality myoelectric signal in a single operation, which does not require microsurgery, providing for wide applicability to hand surgeons of all backgrounds.

Fascicle-Specific Targeting of Longitudinal Intrafascicular Electrodes for Motor and Sensory Restoration in Upper-Limb Amputees

Multichannel longitudinal intrafascicular electrode (LIFE) interfaces provide optimized balance of invasiveness and stability for chronic sensory stimulation and motor recording/decoding of peripheral nerve signals. Using a fascicle-specific targeting (FAST)-LIFE approach, where electrodes are individually placed within discrete sensory- and motor-related fascicular subdivisions of the residual ulnar and/or median nerves in an amputated upper limb, FAST-LIFE interfacing can provide discernment of motor intent for individual digit control of a robotic hand, and restoration of touch- and movement-related sensory feedback. The authors describe their findings from clinical studies performed with 6 human amputee trials using FAST-LIFE interfacing of the residual upper limb.

Pattern of upper limb amputation associated with lower limb amputation: the UK military experience from Iraq and Afghanistan

INTRODUCTION

The conflicts in Iraq and Afghanistan resulted in large numbers of personnel sustaining extremity injuries. In the context of polytrauma, partial hand amputation is often unrecorded. The aim of this work was to quantify the burden of upper limb (UL) amputation at any level occurring concurrently with a major (ankle and proximal) lower limb (LL) amputation. Knowledge of this cohort could aid in prosthetic modification to further improve quality of life outcomes in a population with dexterity loss.

METHOD

A trauma database search was undertaken for all UK military LL amputees from the conflicts in Iraq and Afghanistan. A manual search method was employed to identify from the major LL amputees those who had a concurrent UL amputation at any level (including isolated finger amputation). Demographics, level of amputation, and injury profile data were recorded.

RESULTS

Sixty-eight individuals were identified; the most prevalent population was bilateral LL with a unilateral UL amputation (60%). Most UL amputations were partial hand (75%). The was no statistically significant difference between left or right side (p=0.13). On the left side, correlation was found between amputation of the thumb and third digit (rho=0.34; p=0.005) not seen on the right.

CONCLUSION

We have determined the rate of UL amputation at any level, in combination with LL amputation as a result of blast injury. Knowledge of these combinations enables further research to support anecdotal evidence that there is a need for tailored prosthetics in the context of potential dexterity loss making donning and doffing problematic.

Selection of EMG Sensors Based on Motion Coordinated Analysis

The intelligent prosthesis driven by electromyography (EMG) signal provides a solution for the movement of the disabled. The proper position of EMG sensors can improve the prosthesis's motion recognition ability. To exert the amputee's action-oriented ability and the prosthesis' control ability, the EMG spatial distribution and internal connection of the prosthetic wearer is analyzed in three kinds of movement conditions: appropriate angle, excessive angle, and angle too small. Firstly, the correlation characteristics between the EMG channels are analyzed by mutual information to construct a muscle functional network. Secondly, the network's features of different movement conditions are analyzed by calculating the characteristic of nodes and evaluating the importance of nodes. Finally, the convergent cross-mapping method is applied to construct a directed network, and the critical muscle groups which can reflect the user's movement intention are determined. Experiment shows that this method can accurately determine the EMG location and simplify the distribution of EMG sensors inside the prosthetic socket. The network characteristics of key muscle groups can distinguish different movements effectively and provide a new strategy for decoding the relationship between limb nerve control and body movement.

Restoring Form and Function to the Partial Hand Amputee: Prosthetic Options from the Fingertip to the Palm

Partial hand amputations are the most common upper extremity amputations and affect individuals across a spectrum of socioeconomic and geographic backgrounds. Prosthetic devices can provide straightforward solutions to the devastating aesthetic, functional, psychological, and social deficits caused by these injuries. However, because of the recent development of multiple partial hand prosthetic devices, many hand providers remain unaware of their applicability in practice. This article highlights the various classes of partial hand prostheses currently available, including passive functional, body-powered, and externally powered options. Familiarity with these partial hand prostheses will better enable providers to care for partial hand amputees.

Temporal Asynchrony but Not Total Energy Nor Duration Improves the Judgment of Numerosity in Electrotactile Stimulation

Stroke patients suffer from impairments of both motor and somatosensory functions. The functional recovery of upper extremities is one of the primary goals of rehabilitation programs. Additional somatosensory deficits limit sensorimotor function and significantly affect its recovery after the neuromotor injury. Sensory substitution systems, providing tactile feedback, might facilitate manipulation capability, and improve patient's dexterity during grasping movements. As a first step toward this aim, we evaluated the ability of healthy subjects in exploiting electrotactile feedback on the shoulder to determine the number of perceived stimuli in numerosity judgment tasks. During the experiment, we compared four different stimulation patterns (two simultaneous: short and long, intermittent and sequential) differing in total duration, total energy, or temporal synchrony. The experiment confirmed that the subject ability to enumerate electrotactile stimuli decreased with increasing the number of active electrodes. Furthermore, we found that, in electrotactile stimulation, the temporal coding schemes, and not total energy or duration modulated the accuracy in numerosity judgment. More precisely, the sequential condition resulted in significantly better numerosity discrimination than intermittent and simultaneous stimulation. These findings, together with the fact that the shoulder appeared to be a feasible stimulation site to communicate tactile information via electrotactile feedback, can serve as a guide to deliver tactile feedback to proximal areas in stroke survivors who lack sensory integrity in distal areas of their affected arm, but retain motor skills.

Affordable passive 3D-printed prosthesis for persons with partial hand amputation

BACKGROUND AND AIM

Partial hand amputations are common in developing countries and have a negative impact on patients and their families' quality of life. The uniqueness of each partial hand amputation, coupled with the relatively high costs of prostheses, makes it challenging to provide suitable prosthetic solutions in developing countries. Current solutions often have long lead times and require a high level of expertise to produce. The aim of this study was to design and develop an affordable patient-specific partial hand prosthesis for developing countries.

TECHNIQUE

The prosthesis was designed for a patient with transmetacarpal amputation (i.e. three amputated fingers and partial palm). The final design was passive, controlled by the contralateral hand, and utilized the advanced flexibility properties of thermoplastic polyurethane in a glove-like design that costs approximately 20 USD to fabricate. Quantitative and qualitative tests were conducted to assess performance of the device after the patient used the final design. A qualitative assessment was performed to gather the patient's feedback following a series of tests of grasp taxonomy. A quantitative assessment was performed through a grasp and lift test to measure the prosthesis' maximum load capacity.

DISCUSSION

This study showed that the prosthesis enhanced the patient's manual handling capabilities, mainly in the form of grasp stability. The prosthesis was light weight and could be donned and doffed by the patient independently. Limitations include the need to use the contralateral hand to achieve grasping and low grasp strength.

CLINICAL RELEVANCE

Persons with partial hand amputation in developing countries lack access to affordable functional prostheses, hindering their ability to participate in the community. 3D-printed prostheses can provide a low-cost solution that is adaptable to different amputation configurations.

Adaptive, Tendon-Driven, Affordable Prostheses for Partial Hand Amputations: On Body-Powered and Motor Driven Implementations

Adaptive, tendon-driven and affordable prosthetic devices have received an increased interest over the last decades. Prosthetic devices range from body-powered solutions to fully actuated systems. Despite the significant progress in the field, most existing solutions are expensive, heavy, and bulky, or they cannot be used for partial hand amputations. In this paper, we focus on the development of adaptive, tendon-driven, glove-based, affordable prostheses for partial hand amputations and we propose two compact and lightweight devices (a body powered and a motor driven version). The efficiency of the devices is experimentally validated and their performance is evaluated using two different types of tests: i) grasping tests that involve different everyday objects and ii) tests that assess the force exertion capabilities of the proposed prostheses.

Fluidic Haptic Interface for Mechano-Tactile Feedback

Notable advancements have been achieved in providing amputees with sensation through invasive and non-invasive haptic feedback systems such as mechano-, vibro-, electro-tactile and hybrid systems. Purely mechanical-driven feedback approaches, however, have been little explored. In this paper, we now created a haptic feedback system that does not require any external power source (such as batteries) or other electronic components (see Fig. 1 ). The system is low-cost, lightweight, adaptable and robust against external impact (such as water). Hence, it will be sustainable in many aspects. We have made use of latest multi-material 3D printing technology (Stratasys Objet500 Connex3) being able to fabricate a soft sensor and a mechano-tactile feedback actuator made of a rubber (TangoBlack Plus) and plastic (VeroClear) material. When forces are applied to the fingertip sensor, fluidic pressure inside the system acts on the membrane of the feedback actuator resulting in mechano-tactile sensation. Our [Formula: see text] feedback actuator is able to transmit a force range between 0.2 N (the median touch threshold) and 2.1 N (the maximum force transmitted by the feedback actuator at a 3 mm indentation) corresponding to force range exerted to the fingertip sensor of 1.2-18.49 N.

Quantitative functional evaluation of a 3D-printed silicone-embedded prosthesis for partial hand amputation: A case report

STUDY DESIGN

A male patient with partial hand amputation of his nondominant hand, with only stumps of the proximal phalanx of the first and fifth finger, was evaluated. The performance of using two alternative 3D printed silicone-embedded personalized prostheses was evaluated using the quantitative Jebsen Hand Function Test.

INTRODUCTION

Custom design and fabrication of 3D printed prostheses appears to be a good technique for improving the clinical treatment of patients with partial hand amputations. Despite its importance the literature shows an absence of studies reporting on quantitative functional evaluations of 3D printed hand prostheses.

PURPOSE OF THE STUDY

We aim at producing the first quantitative assessment of the impact of using 3D printed silicone-embedded prostheses that can be fabricated and customized within the clinical environment.

METHODS

Alginate molds and computed tomographic scans were taken from the patient's hand. Each candidate prosthesis was modeled in Computer Aided Design software and then fabricated using a combination of 3D printed parts and silicone-embedded components.

DISCUSSION

Incorporating the patient's feedback during the design loop was very important for obtaining a good aid on his work activities. Although the explored patient-centered design process still requires a multidisciplinary team, functional benefits are large.

CONCLUSION(S)

Quantitative data demonstrates better hand performance when using 3D printed silicone-embedded prosthesis vs not using any aid. The patient accomplished complex tasks such as driving a nail and opening plastic bags. This was impossible without the aid of produced prosthesis.

Electro-cutaneous stimulation on the palm elicits referred sensations on intact but not on amputated digits

OBJECTIVE

Grasping and manipulation control critically depends on tactile feedback. Without this feedback, the ability for fine control of a prosthesis is limited in upper limb amputees. Early studies have shown that non-invasive electro-cutaneous stimulation (ES) can induce referred sensations that are spread to a wider and/or more distant area, with respect to the electrodes. Building on this, we sought to exploit this effect to provide somatotopically matched sensory feedback to people with partial hand (digital) amputations.

APPROACH

For the first time, this work investigated the possibility of inducing referred sensations in the digits by activating the palmar nerves. Specifically, we electrically stimulated 18 sites on the palm of non-amputees to evaluate the effects of sites and stimulation parameters on modality, magnitude, and location of the evoked sensations. We performed similar tests with partial hand amputees by testing those sites that had most consistently elicited referred sensations in non-amputees.

MAIN RESULTS

We demonstrated referred sensations in non-amputees from all stimulation sites in one form or another. Specifically, the stimulation of 16 of the 18 sites gave rise to reliable referred sensations. Amputees experienced referred sensations to unimpaired digits, just like non-amputees, but we were unable to evoke referred sensations in their missing digits: none of them reported sensations that extended beyond the tip of the stump.

SIGNIFICANCE

The possibility of eliciting referred sensations on the digits may be exploited in haptic systems for providing touch sensations without obstructing the fingertips or their movements. The study also suggests that the phenomenon of referred sensations through ES may not be exploited for partial hand prostheses, and it invites researchers to explore alternative approaches. Finally, the results seem to confirm previous studies suggesting that the stumps in partial hand amputees partially acquire the role of the missing fingertips, physiologically and cognitively.

A narrative review: current upper limb prosthetic options and design

Purpose: This review was conducted to provide an overview of current literature as it relates to upper limb difference, available componentry, and prosthetic options and design. Emerging technologies combined with an increased awareness of the limb difference community have contributed to recent advancements in upper extremity prosthetics.Methods: A search of five major clinical databases utilizing keywords relating to upper limb prostheses, componenty and limb difference levels resulted in over 1200 articles. These articles were subjected to inclusion and exclusion criteria in order to identify current peer reviewed research relevant to this topic.Results: Fifty-five applicable articles and sources of standards were reviewed based on the inclusion and exclusion criteria, presenting five general options for prosthetic intervention. This information was assimilated and categorized in this article, which provides an overview of the aforementioned options.Conclusion: While a noteworthy amount of research focuses on technological advancements, the five options for prosthetic intervention are inherently represented in the current literature. For individuals with upper limb difference, as well as their care team, successful rehabilitation hinges on awareness of new components, the functional efficacy of these components, and the evolved techniques used in prosthetic design and fabrication. It is noted that the rapid evolution of upper limb prosthetics consistently outpaces research and publication of information.Implications for rehabilitationTo provide an overview of prosthetic design considerations and options to help create a more informed rehabilitation team, leading to improved outcomes in prescription and management of upper limb prosthetics.To bring awareness of current research in the field of upper limb prosthetics in order to provoke further exploration of the efficacy of prosthetic options and design considerations.

Regressing grasping using force myography: an exploratory study

BACKGROUND

Partial hand amputation forms more than 90% of all upper limb amputations. This amputation has a notable effect on the amputee's life. To improve the quality of life for partial hand amputees different prosthesis options, including externally-powered prosthesis, have been investigated. The focus of this work is to explore force myography (FMG) as a technique for regressing grasping movement accompanied by wrist position variations. This study can lay the groundwork for a future investigation of FMG as a technique for controlling externally-powered prostheses continuously.

METHODS

Ten able-bodied participants performed three hand movements while their wrist was fixed in one of six predefined positions. The angle between Thumb and Index finger ([Formula: see text]), and Thumb and Middle finger ([Formula: see text]) were calculated as measures of grasping movements. Two approaches were examined for estimating each angle: (i) one regression model, trained on data from all wrist positions and hand movements; (ii) a classifier that identified the wrist position followed by a separate regression model for each wrist position. The possibility of training the system using a limited number of wrist positions and testing it on all positions was also investigated.

RESULTS

The first approach had a correlation of determination ([Formula: see text]) of 0.871 for [Formula: see text] and [Formula: see text]. Using the second approach [Formula: see text] and [Formula: see text] were obtained. The first approach is over two times faster than the second approach while having similar performance; thus the first approach was selected to investigate the effect of the wrist position variations. Training with 6 or 5 wrist positions yielded results which were not statistically significant. A statistically significant decrease in performance resulted when less than five wrist positions were used for training.

CONCLUSIONS

The results indicate the potential of FMG to regress grasping movement, accompanied by wrist position variations, with a regression model for each angle. Also, it is necessary to include more than one wrist position in the training phase.

The S-Finger: A Synergetic Externally Powered Digit With Tactile Sensing and Feedback

Partial hand amputation is by far the most common type of amputation worldwide. Nevertheless, regardless of their potential clinical and socioeconomic impact, battery-powered partial hand prostheses, namely, powered digits, have modestly progressed so far, and very few clinical solutions are available today. Here, we present a mechanical architecture, an alternative to state-of-the-art solutions, which exploits a high efficiency, non-back drivable mechanical transmission based on a face-gear pair and a miniaturized clutch. We took inspiration from the synergetic prehension approach proposed by Childress for whole hand amputation. The finger was equipped with a myoelectric controller and a tactile sensor able to provide users with discrete event sensory feedback. Measured speed (90°/s) and force (6.5 N) of the newly dubbed S-Finger proved comparable with those of clinically available prostheses. The design demonstrated to be compact and rugged enough to undergo a clinical viability test with two partial hand amputees, fitted with custom three-fingered research prostheses using the S-Finger. The subjects successfully completed several dexterity tests and gave relevant feedback for the development of a second-generation device. These results contribute to the increasing research endeavors in the field of partial hand amputation.

Wrist-Powered Partial Hand Prosthesis Using a Continuum Whiffle Tree Mechanism: A Case Study

Among the advances in upper extremity prostheses in the past decades, only a small portion of the results were obtained for partial hand prostheses, possibly due to the highly diverse partial hand presentations and limited space for component integration. In an attempt to address these challenges, this paper presents the design, construction, installation, and experimental characterization of a wrist-powered partial hand prosthesis developed in Shanghai Jiao Tong University (hereafter referred to as the JTP hand), customized for a specific amputee. The JTP hand possesses: 1) a continuum whiffle tree mechanism to allow adaptive grasping; 2) a force-magnifying partial gear pair to enhance the power of the grip; and 3) a phalange-embedded disengageable ratchet to enable or disable backdrivability. Various grasps and gestures were formed using the JTP hand. The obtained results suggest that the proposed design might be a viable option for patients with transmetacarpal amputation.

A cosmetic prosthetic digit with bioinspired embedded touch feedback

Partial hand amputation is the most frequent amputation level worldwide, accounting for approximately 90% of all upper limb amputations. Passive cosmetic prostheses represent one of the possible choices for its treatment, probably the most affordable one. However, these devices restore very limited motor function and subtle sensory feedback. The latter is an important component for restoring the body schema. In this work we present a simple yet potentially effective and low cost cosmetic digital prosthesis that embeds touch feedback; we dubbed this DESC-finger. It delivers short-lasting vibrotactile bursts when it makes and breaks contact with the environment, based on the Discrete Event-driven Sensory feedback Control (DESC) policy. One prototype was developed and used by one amputee at home, for two months. The effectiveness of the device was experimentally assessed by means of an interview and a virtual eggs test, which showed, albeit preliminarily, that time discrete feedback can improve the motor control of a partial hand prosthesis in daily life conditions. Besides targeting people that already use cosmetic digits, the DESC-finger targets those that do not use them complaining for loss of sensibility. The production costs and manufacturing process makes the DESC-finger suitable for exploitation in high- and low-income countries.