Advances in upper extremity prosthetics

The Role of Fascial Tissue Layer in Electric Signal Transmission from the Forearm Musculature to the Cutaneous Layer as a Possibility for Increased Signal Strength in Myoelectric Forearm Exoprosthesis Development

Myoelectric exoprostheses serve to aid in the everyday activities of patients with forearm or hand amputations. While electrical signals are known key factors controlling exoprosthesis, little is known about how we can improve their transmission strength from the forearm muscles as to obtain better sEMG. The purpose of this study is to evaluate the role of the forearm fascial layer in transmitting myoelectrical current. We examined the sEMG signals in three individual muscles, each from six healthy forearms (Group 1) and six amputation stumps (Group 2), along with their complete biometric characteristics. Following the tests, one patient underwent a circumferential osteoneuromuscular stump revision surgery (CONM) that also involved partial removal of fascia and subcutaneous fat in the amputation stump, with re-testing after complete healing. In group 1, we obtained a stronger sEMG signal than in Group 2. In the CONM case, after surgery, the patient’s data suggest that the removal of fascia, alongside the fibrotic and subcutaneous fat tissue, generates a stronger sEMG signal. Therefore, a reduction in the fascial layer, especially if accompanied by a reduction of the subcutaneous fat layer may prove significant for improving the strength of sEMG signals used in the control of modern exoprosthetics.

Adaptable Poly-Articulated Bionic Hands EnhanceBoth Performance and User's Perception in Bilateral Amputation: A Case Study

This article evaluates and compares the performance and perception of prosthetic devices based on different design principles, a traditional rigid gripper and an adaptable poly-articulated hand, in a pre- and post-training protocol with an individual with bilateral amputation. As a representative of the first class, we use commercial hands (Ottobock's MyoHand VariPlus Speed), which is a widely adopted model by prosthesis users worldwide. We compare these with two SoftHand Pro hands, which are experimental prototypes exhibiting 19 articulations actuated by one single motor, and are inspired by human hand motor control models. Results show that the individual with bilateral amputation, who was a non-expert myoelectric user, achieved better performance with adaptive poly-articulated hands. Furthermore, the acceptation, satisfaction and perceived functionality of the user were considerably higher for the SoftHand Pro. An observational analysis of the patient's behaviour by experienced therapists suggests that adaptable poly-articulated hands reduced compensatory movements and cognitive load. Using soft technologies may be especially advantageous for individuals with bilateral amputation, who present a very limited residual mobility and can largely benefit from the active use of their artificial arms in everyday life.

The Role of Amputation and Myoelectric Prosthetic Fitting in Patients with Traumatic Brachial Plexus Injuries

BACKGROUND

A cohort of patients with traumatic brachial plexus injuries (BPIs) underwent elective amputation following unsuccessful surgical reconstruction or delayed presentation. The results of amputation with and without a myoelectric prosthesis (MEP) using nonintuitive controls were compared. We sought to determine the benefits of amputation, and whether fitting with an MEP was feasible and functional.

METHODS

We conducted a retrospective review of patients with BPI who underwent elective upper-extremity amputation at a single institution. Medical records were reviewed for demographics, injury and reconstruction details, amputation characteristics, outcomes, and complications. Prosthesis use and MEP function were assessed. The minimum follow-up for clinical outcomes was 12 months.

RESULTS

Thirty-two patients with BPI and an average follow-up of 53 months underwent elective amputation between June 2000 and June 2020. Among the cases were 18 transhumeral amputations, 12 transradial amputations, and 2 wrist disarticulations. There were 29 pan-plexus injuries, 1 partial C5-sparing pan-plexus injury, 1 lower-trunk with lateral cord injury, and 1 lower-trunk injury. Amputation occurred, on average, at 48.9 months following BPI and 36.5 months following final reconstruction. Ten patients were fitted for an MEP with electromyographic signal control from muscles not normally associated with the intended function (nonintuitive control). Average visual analog scale pain scores decreased post-amputation: from 4.8 pre-amputation to 3.3 for the MEP group and from 5.4 to 4.4 for the non-MEP group. Average scores on the Disabilities of the Arm, Shoulder and Hand questionnaire decreased post-amputation, but not significantly: from 35 to 30 for the MEP group and from 43 to 40 for the non-MEP group. Patients were more likely to be employed following amputation than they were before amputation. No patient expressed regret about undergoing amputation. All patients in the MEP group reported regular use of their prosthesis compared with 29% of patients with a traditional prosthesis. All patients in the MEP group demonstrated functional terminal grasp/release that they considered useful.

CONCLUSIONS

Amputation is an effective treatment for select patients with BPI for whom surgical reconstruction is unsuccessful. Patients who underwent amputation reported decreased mechanical pain, increased employment rates, and a high rate of satisfaction following surgery. In amputees with sufficient nonintuitive electromyographic signals, MEPs allow for terminal grasp/release and are associated with high rates of prosthesis use.

LEVEL OF EVIDENCE

Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Mechanical Design Optimization of Prosthetic Hand's Fingers: Novel Solutions towards Weight Reduction

From the mechanical function of grabbing objects to the emotional aspect of gesturing, the functionality of human hands is fundamental for both physical and social survival. Therefore, the loss of one or both hands represents a devastating issue, exacerbated by long rehabilitation times and psychological treatments. Prosthetic arms represent an effective solution to provide concrete functional and esthetical support. However, commercial hand prostheses still lack an optimal combination of light weight, durability, adequate cosmetic appearance, and affordability. Among these aspects, the priority for upper-limb prosthesis users is weight, a key parameter that influences both the portability and the functionality of the system. The purpose of this work is to optimize the design of the MyHand prosthesis, by redesigning both the proximal and distal finger and thumb in light of finding an optimal balance between weight reduction and adequate stiffness. Starting from elastic–plastic numerical models and experimental tests on obsolete components, analyzed under the worst loading condition, five different design solutions are suggested. An iterative topology optimization process locates the regions where material removal is permitted. From these results, 2 mm geometrical patterns on the top surface of the hand prosthesis appear as the most prominent, preventing object intrusion.

Comparison between rigid and soft poly-articulated prosthetic hands in non-expert myo-electric users shows advantages of soft robotics

Notwithstanding the advancement of modern bionic hands and the large variety of prosthetic hands in the market, commercial devices still present limited acceptance and percentage of daily use. While commercial prostheses present rigid mechanical structures, emerging trends in the design of robotic hands are moving towards soft technologies. Although this approach is inspired by nature and could be promising for prosthetic applications, there is scant literature concerning its benefits for end-users and in real-life scenarios. In this work, we evaluate and assess the role and the benefits of soft robotic technologies in the field of prosthetics. We propose a thorough comparison between rigid and soft characteristics of two poly-articulated hands in 5 non-expert myo-electric prosthesis users in pre- and post-therapeutic training conditions. The protocol includes two standard functional assessments, three surveys for user-perception, and three customized tests to evaluate the sense of embodiment. Results highlight that rigid hands provide a more precise grasp, while soft properties show higher functionalities thanks to their adaptability to different requirements, intuitive use and more natural execution of activities of daily living. This comprehensive evaluation suggests that softness could also promote a quick integration of the system in non-expert users.

Cost Analyses of Prosthetic Devices: A Systematic Review

OBJECTIVE

To synthesize extant literature on the cost-effectiveness of prosthetic interventions and explore applicability to low- and middle-income country (LMIC) settings.

DATA SOURCES

A systematic literature review using subject headings including "prosthetics," "amputation," and "cost analysis" was performed with PubMed, Embase, and Web of Science search engines, yielding 1194 articles. An additional 22 articles were identified via backward citation searching for 1144 total after duplicate removal. The search was last run in May of 2019.

STUDY SELECTION

Studies were included if they conducted an economic analysis of an upper or lower extremity prosthetic device. Studies were excluded if (1) full text was unavailable in English; (2) study was a systematic review or meta-analysis; or (3) study did not have a prosthetic comparison group. Using DistillerSR software, 2 authors independently conducted title and abstract screening. One author conducted full-text screening. The proportion of initially identified studies that met final inclusion criteria was 1% (12 of 1144).

DATA EXTRACTION

Data were dually extracted by 2 authors and reviewed by 3 additional authors.

DATA SYNTHESIS

All included studies (N=12) examined lower extremity amputations comparing advanced technology. No studies were conducted in LMICs. Comparable data between studies demonstrated (1) the cost-effectiveness of microprocessor- over nonmicroprocessor-controlled knees for transfemoral amputation in high-income settings; (2) equivocal findings regarding osseointegrated vs socket-suspended prostheses; and (3) increased cost for ICEX and modular socket systems over patellar tendon-bearing socket systems with no functional improvement.

CONCLUSIONS

There are few prosthetic cost analyses in the literature. Additional analyses are needed to determine the direct and indirect costs associated with prosthetic acquisition, fitting, and maintenance; the costs of amputee rehabilitation; and long-term economic and quality-of-life benefits. Such studies may guide future prosthetic and rehabilitative care, especially in resource-austere settings where prosthetic needs are greatest.

Cross limb vessel transfer for salvage of the extremity with irreparable artery injury

PURPOSE

Complex injuries of the extremity can be very challenging to treat. In the setting of soft tissue infection and vascular defect, arterial reconstructions are at high risk of failure. Historically, there have not been good options to successfully salvage limbs with these serious injuries. We describe our experience of utilizing a cross limb vessel transfer to salvage the limb.

METHODS

Patients were identified retrospectively with complex vascular injuries of the extremity and wound infection, who were treated with a cross limb vessel transfer. Once the infection has successfully been cleared, flow-through flap transfer was performed for definitive reconstruction of the arterial injury. Data collated included patient demographics, injury and operation details, and post-operative outcomes including blood supply of the limb, wound infection and complications.

RESULTS

Between April 2014 and January 2017, 3 patients with an average age of 21 years (range, 16-29) were admitted. The median length of hospital stay was 62 days (range, 26-122). The average number of operation was 7.3 times (range, 6-10). Two patients' upper limb had survived with limited movement, relatively minor donor site morbidity and confirmed flow through the vessel reconstruction using CTA, while one patient had lower limb amputation due to severe infection and prolonged ischemia time.

CONCLUSIONS

This series of patients demonstrates that cross limb vessel transfer is an invaluable technique to salvage the limb in patients with complex vascular injury and wound infection. However, for lower limb with prolonged ischemia time and severe infection, limb salvage is not recommended.

Measuring intrinsic hand strength in healthy adults: The accuracy intrarater and inter-rater reliability of the Rotterdam Intrinsic Hand Myometer

STUDY DESIGN

Clinical measurement study.

INTRODUCTION

Measuring the isometric strength generated during isolated hand joint motions is a challenging feat. The Rotterdam Intrinsic Hand Myometer (RIHM; med.engineers, Rotterdam, Netherlands) permits measurement of isolated movements of the hand. To date, there is limited evidence on the inter-rater reliability and limited adult normative data of RIHM. Given that multiple raters, often with varying degrees of experience, are needed to collect normative data, inter-rater reliability testing and a comparison of novice and experienced raters are needed.

PURPOSES OF THE STUDY

The purposes of this study were to test the accuracy, intrarater reliability, and inter-rater reliability of the RIHM in healthy-handed adults.

METHODS

RIHM accuracy was tested through use of precision class F weights. Adults 18 years or older without upper limb dysfunction were recruited. Each participant was tested by 4 raters, 3 occupational therapy graduate students, and an experienced certified hand therapist, through use of a calibrated RIHM. Five strength measures were tested bilaterally (ie, thumb carpometacarpal palmar abduction, index finger metacarpophalangeal [MP] abduction, index finger MP flexion, thumb MP flexion, and small finger MP abduction) 3 times per a standardized protocol. Statistical methods were used to test accuracy, inter-rater reliability, and intrarater/response stability.

RESULTS

The accuracy of RIHM device error was 5% or less. Reliability testing included the participation of 19 women and 10 men (n = 29). All raters were in excellent agreement across all muscles (intraclass correlation coefficient, ≥0.81). Low standard error of measurement values of ≤8.3 N (1.9 lb) across raters were found. The response stability and/or intrarater reliability of the novice and certified hand therapist raters were not statistically different.

DISCUSSION

The RIHM has an acceptable instrument error; the RIHM and its standardized procedure have excellent inter-rater reliability and response stability when testing those without hand limitations; and the response stability and/or intrarater reliability of expert and novice raters were consistent.

CONCLUSIONS

The use of the RIHM is justified when multiple raters of varying expertise collect normative data or conduct cohort studies on persons with healthy hands. Future research is warranted.

LEVEL OF EVIDENCE

Not applicable.

Influence of Digitalization on the Tasks of Employees with Disabilities in Germany (1979–2006)

The deployment of technology in the workplace is increasingly replacing routine tasks and creating more non-routine tasks. In this article, we investigate the influence of computer technology on tasks carried out by employees with disabilities compared to employees without disabilities. We assume significant differences between both groups and stronger substitutive and complementary effects of computer technology in the case of a higher degree of disability. We use four waves of the German BIBB-IAB (BIBB: Federal Institute for Vocational Education and Training- IAB: Institute of Employment Research) and BIBB-BauA (BIBB: Federal Institute for Vocational Education and Training- BauA: German Federal Institute for Occupational Safety and Health Employment surveys (1976–2006) to investigate the development of tasks and the influence of computer technology carried out by employees with disabilities compared to employees without disabilities. The results show a development of tasks carried out by employees with disabilities that is very similar to that of employees without disabilities. In line with the assumptions of the task-based approach, we find that computer technology in the workplace has a complementary effect on routine tasks and a substitutive effect on non-routine tasks carried out by employees with disabilities. Against our theoretical assumptions, we find no systematic differences in the effects of computer technology on the tasks of employees with and without a disability. Moreover, we do not find systematic differences with regard to the degree of disability.

Peromelia - congenital transverse deficiency of the upper limb: a literature review and current prosthetic treatment

Peromelia or congenital transverse deficiency describes a truncation of the upper limb below various limb levels. Recommendations regarding treatment vary and are mainly based on expert opinions. This paper summarizes the current literature regarding the aetiology, pathogenesis and specifically treatment algorithms for children with peromelia. We performed a non-systematic review of the current literature from MEDLINE/PubMed to obtain comprehensive up-to-date information about peromelia, focusing on current recommendations for the treatment of peromelia (e.g. prosthetic fitting, external stump lengthening). The current literature lacks clear evidence as to whether prosthetic treatment is superior to prosthetic non-usage. However, based on the available studies, children with transradial or transhumeral peromelia should preferably be fitted with passive/cosmetic prostheses at the age between six and 24 months, followed by active/myoelectric devices at the age of 2.5 to four years. It remains controversial whether early myoelectric prosthetic fitting can reduce prosthesis rejection times; however, cognitive readiness and the ability to absolve a guided training programme are seen as important prerequisites for myoelectric fitting. Children with very short stumps may benefit from stump lengthening using external fixators and prosthetic modification. The treatment of children with peromelia generally requires a guided, multidisciplinary team approach. A training programme is essential to optimize individuals' performance in the execution of activities of daily living and decrease rejection risks whenever a myoelectric device is prescribed. Myoelectric fitting should preferably be commenced at no later than four years of age. However, long-term reports on the benefits of prosthetic treatment are still pending.

Mechanical Design and Assessment of a Low-Cost 7-DOF Prosthetic Arm for Shoulder Disarticulation

This work presents the design of a low-cost prosthetic device for shoulder disarticulation. A proper design of the mechanisms has been addressed to obtain a prototype that presents 7 degrees of freedom. Shoulder movement is achieved by means of a spherical parallel manipulator, elbow movement is performed by a six-bar mechanism, and the wrist movement is implemented by a spherical parallel manipulator. A set of dynamic simulations was performed in order to assess the functionality of the design. The prototype was built using 3D printing techniques and implementing low-cost actuators. An experimental evaluation was carried out to characterize this device. The result of this work is a prototype that weighs 1350 g that is able to perform movements related to activities of daily living.

Targeted Muscle Reinnervation for Transradial Amputation: Description of Operative Technique

Targeted muscle reinnervation (TMR) is a revolutionary surgical technique that, together with advances in upper extremity prostheses and advanced neuromuscular pattern recognition, allows intuitive and coordinated control in multiple planes of motion for shoulder disarticulation and transhumeral amputees. TMR also may provide improvement in neuroma-related pain and may represent an opportunity for sensory reinnervation as advances in prostheses and haptic feedback progress. Although most commonly utilized following shoulder disarticulation and transhumeral amputations, TMR techniques also represent an exciting opportunity for improvement in integrated prosthesis control and neuroma-related pain improvement in patients with transradial amputations. As there are no detailed descriptions of this technique in the literature to date, we provide our surgical technique for TMR in transradial amputations.

Differences in myoelectric and body-powered upper-limb prostheses: Systematic literature review

The choice of a myoelectric or body-powered upper-limb prosthesis can be determined using factors including control, function, feedback, cosmesis, and rejection. Although body-powered and myoelectric control strategies offer unique functions, many prosthesis users must choose one. A systematic review was conducted to determine differences between myoelectric and body-powered prostheses to inform evidence-based clinical practice regarding prescription of these devices and training of users. A search of 9 databases identified 462 unique publications. Ultimately, 31 of them were included and 11 empirical evidence statements were developed. Conflicting evidence has been found in terms of the relative functional performance of body-powered and myoelectric prostheses. Body-powered prostheses have been shown to have advantages in durability, training time, frequency of adjustment, maintenance, and feedback; however, they could still benefit from improvements of control. Myoelectric prostheses have been shown to improve cosmesis and phantom-limb pain and are more accepted for light=intensity work. Currently, evidence is insufficient to conclude that either system provides a significant general advantage. Prosthetic selection should be based on a patient's individual needs and include personal preferences, prosthetic experience, and functional needs. This work demonstrates that there is a lack of empirical evidence regarding functional differences in upper-limb prostheses.

Restoring motor control and sensory feedback in people with upper extremity amputations using arrays of 96 microelectrodes implanted in the median and ulnar nerves

OBJECTIVE

An important goal of neuroprosthetic research is to establish bidirectional communication between the user and new prosthetic limbs that are capable of controlling >20 different movements. One strategy for achieving this goal is to interface the prosthetic limb directly with efferent and afferent fibres in the peripheral nervous system using an array of intrafascicular microelectrodes. This approach would provide access to a large number of independent neural pathways for controlling high degree-of-freedom prosthetic limbs, as well as evoking multiple-complex sensory percepts.

APPROACH

Utah Slanted Electrode Arrays (USEAs, 96 recording/stimulating electrodes) were implanted for 30 days into the median (Subject 1-M, 31 years post-amputation) or ulnar (Subject 2-U, 1.5 years post-amputation) nerves of two amputees. Neural activity was recorded during intended movements of the subject's phantom fingers and a linear Kalman filter was used to decode the neural data. Microelectrode stimulation of varying amplitudes and frequencies was delivered via single or multiple electrodes to investigate the number, size and quality of sensory percepts that could be evoked. Device performance over time was assessed by measuring: electrode impedances, signal-to-noise ratios (SNRs), stimulation thresholds, number and stability of evoked percepts.

MAIN RESULTS

The subjects were able to proportionally, control individual fingers of a virtual robotic hand, with 13 different movements decoded offline (r = 0.48) and two movements decoded online. Electrical stimulation across one USEA evoked >80 sensory percepts. Varying the stimulation parameters modulated percept quality. Devices remained intrafascicularly implanted for the duration of the study with no significant changes in the SNRs or percept thresholds.

SIGNIFICANCE

This study demonstrated that an array of 96 microelectrodes can be implanted into the human peripheral nervous system for up to 1 month durations. Such an array could provide intuitive control of a virtual prosthetic hand with broad sensory feedback.

Hand-in-hand advances in biomedical engineering and sensorimotor restoration

BACKGROUND

Living in a multisensory world entails the continuous sensory processing of environmental information in order to enact appropriate motor routines. The interaction between our body and our brain is the crucial factor for achieving such sensorimotor integration ability. Several clinical conditions dramatically affect the constant body-brain exchange, but the latest developments in biomedical engineering provide promising solutions for overcoming this communication breakdown.

NEW METHOD

The ultimate technological developments succeeded in transforming neuronal electrical activity into computational input for robotic devices, giving birth to the era of the so-called brain-machine interfaces. Combining rehabilitation robotics and experimental neuroscience the rise of brain-machine interfaces into clinical protocols provided the technological solution for bypassing the neural disconnection and restore sensorimotor function.

RESULTS

Based on these advances, the recovery of sensorimotor functionality is progressively becoming a concrete reality. However, despite the success of several recent techniques, some open issues still need to be addressed.

COMPARISON WITH EXISTING METHOD(S)

Typical interventions for sensorimotor deficits include pharmaceutical treatments and manual/robotic assistance in passive movements. These procedures achieve symptoms relief but their applicability to more severe disconnection pathologies is limited (e.g. spinal cord injury or amputation).

CONCLUSIONS

Here we review how state-of-the-art solutions in biomedical engineering are continuously increasing expectances in sensorimotor rehabilitation, as well as the current challenges especially with regards to the translation of the signals from brain-machine interfaces into sensory feedback and the incorporation of brain-machine interfaces into daily activities.

Regenerative Engineering and Bionic Limbs

Amputations of the upper extremity are severely debilitating, current treatments support very basic limb movement, and patients undergo extensive physiotherapy and psychological counselling. There is no prosthesis that allows the amputees near-normal function. With increasing number of amputees due to injuries sustained in accidents, natural calamities and international conflicts, there is a growing requirement for novel strategies and new discoveries. Advances have been made in technological, material and in prosthesis integration where researchers are now exploring artificial prosthesis that integrate with the residual tissues and function based on signal impulses received from the residual nerves. Efforts are focused on challenging experts in different disciplines to integrate ideas and technologies to allow for the regeneration of injured tissues, recording on tissue signals and feed-back to facilitate responsive movements and gradations of muscle force. A fully functional replacement and regenerative or integrated prosthesis will rely on interface of biological process with robotic systems to allow individual control of movement such as at the elbow, forearm, digits and thumb in the upper extremity. Regenerative engineering focused on the regeneration of complex tissue and organ systems will be realized by the cross-fertilization of advances over the past thirty years in the fields of tissue engineering, nanotechnology, stem cell science, and developmental biology. The convergence of toolboxes crated within each discipline will allow interdisciplinary teams from engineering, science, and medicine to realize new strategies, mergers of disparate technologies, such as biophysics, smart bionics, and the healing power of the mind. Tackling the clinical challenges, interfacing the biological process with bionic technologies, engineering biological control of the electronic systems, and feed-back will be the important goals in regenerative engineering over the next two decades.