Perspectives on the comparative benefits of body-powered and myoelectric upper limb prostheses.

BACKGROUND: Patient access to body-powered and myoelectric upper limb prostheses in the United States is often restricted by a healthcare system that prioritizes prosthesis prescription based on cost and perceived value. Although this system operates on an underlying assumption that design differences between these prostheses leads to relative advantages and disadvantages of each device, there is limited empirical evidence to support this view. MAIN TEXT: This commentary article will review a series of studies conducted by our research team with the goal of differentiating how prosthesis design might impact user performance on a variety of interrelated domains. Our central hypothesis is that the design and actuation method of body-powered and myoelectric prostheses might affect users' ability to access sensory feedback and account for device properties when planning movements. Accordingly, other domains that depend on these abilities may also be affected. While our work demonstrated some differences in availability of sensory feedback based on prosthesis design, this did not result in consistent differences in prosthesis embodiment, movement accuracy, movement quality, and overall kinematic patterns. CONCLUSION: Collectively, our findings suggest that performance may not necessarily depend on prosthesis design, allowing users to be successful with either device type depending on the circumstances. Prescription practices should rely more on individual needs and preferences than cost or prosthesis design. However, we acknowledge that there remains a dearth of evidence to inform decision-making and that an expanded research focus in this area will be beneficial.

Surveying the interest of individuals with upper limb loss in novel prosthetic control techniques.

BACKGROUND: Novel techniques for the control of upper limb prostheses may allow users to operate more complex prostheses than those that are currently available. Because many of these techniques are surgically invasive, it is important to understand whether individuals with upper limb loss would accept the associated risks in order to use a prosthesis. METHODS: An online survey of individuals with upper limb loss was conducted. Participants read descriptions of four prosthetic control techniques. One technique was noninvasive (myoelectric) and three were invasive (targeted muscle reinnervation, peripheral nerve interfaces, cortical interfaces). Participants rated how likely they were to try each technique if it offered each of six different functional features. They also rated their general interest in each of the six features. A two-way repeated measures analysis of variance with Greenhouse-Geisser corrections was used to examine the effect of the technique type and feature on participants' interest in each technique. RESULTS: Responses from 104 individuals were analyzed. Many participants were interested in trying the techniques - 83 % responded positively toward myoelectric control, 63 % toward targeted muscle reinnervation, 68 % toward peripheral nerve interfaces, and 39 % toward cortical interfaces. Common concerns about myoelectric control were weight, cost, durability, and difficulty of use, while the most common concern about the invasive techniques was surgical risk. Participants expressed greatest interest in basic prosthesis features (e.g., opening and closing the hand slowly), as opposed to advanced features like fine motor control and touch sensation. CONCLUSIONS: The results of these investigations may be used to inform the development of future prosthetic technologies that are appealing to individuals with upper limb loss.

A Comparison of Approaches for Segmenting the Reaching and Targeting Motion Primitives in Functional Upper Extremity Reaching Tasks.

There is growing interest in the kinematic analysis of human functional upper extremity movement (FUEM) for applications such as health monitoring and rehabilitation. Deconstructing functional movements into activities, actions, and primitives is a necessary procedure for many of these kinematic analyses. Advances in machine learning have led to progress in human activity and action recognition. However, their utility for analyzing the FUEM primitives of reaching and targeting during reach-to-grasp and reach-to-point tasks remains limited. Domain experts use a variety of methods for segmenting the reaching and targeting motion primitives, such as kinematic thresholds, with no consensus on what methods are best to use. Additionally, current studies are small enough that segmentation results can be manually inspected for correctness. As interest in FUEM kinematic analysis expands, such as in the clinic, the amount of data needing segmentation will likely exceed the capacity of existing segmentation workflows used in research laboratories, requiring new methods and workflows for making segmentation less cumbersome. This paper investigates five reaching and targeting motion primitive segmentation methods in two different domains (haptics simulation and real world) and how to evaluate these methods. This work finds that most of the segmentation methods evaluated perform reasonably well given current limitations in our ability to evaluate segmentation results. Furthermore, we propose a method to automatically identify potentially incorrect segmentation results for further review by the human evaluator. Clinical impact: This work supports efforts to automate aspects of processing upper extremity kinematic data used to evaluate reaching and grasping, which will be necessary for more widespread usage in clinical settings.

Computer-assisted approaches for measuring, segmenting, and analyzing functional upper extremity movement: a narrative review of the current state, limitations, and future directions.

The analysis of functional upper extremity (UE) movement kinematics has implications across domains such as rehabilitation and evaluating job-related skills. Using movement kinematics to quantify movement quality and skill is a promising area of research but is currently not being used widely due to issues associated with cost and the need for further methodological validation. Recent developments by computationally-oriented research communities have resulted in potentially useful methods for evaluating UE function that may make kinematic analyses easier to perform, generally more accessible, and provide more objective information about movement quality, the importance of which has been highlighted during the COVID-19 pandemic. This narrative review provides an interdisciplinary perspective on the current state of computer-assisted methods for analyzing UE kinematics with a specific focus on how to make kinematic analyses more accessible to domain experts. We find that a variety of methods exist to more easily measure and segment functional UE movement, with a subset of those methods being validated for specific applications. Future directions include developing more robust methods for measurement and segmentation, validating these methods in conjunction with proposed kinematic outcome measures, and studying how to integrate kinematic analyses into domain expert workflows in a way that improves outcomes.

A comparison of compensatory movements between body-powered and myoelectric prosthesis users during activities of daily living.

BACKGROUND: People with upper limb absence use compensatory movements to accommodate lack of motion in the prosthetic hand. The purpose of this study was to determine if the type of prosthesis used (i.e. body-powered or myoelectric) affects compensatory movements during activities of daily living. METHODS: Twelve transradial body-powered and/or myoelectric prosthesis users performed up to six unimanual and bimanual activities of daily living. Trunk range of motion and peak upper limb angles for each task were compared between prostheses. FINDINGS: Compensatory movement generally did not differ based on prosthesis type. However, body-powered users had increased trunk lateral lean compared to myoelectric users during a deodorant application task (P = 0.025). Body-powered users also had increased trunk axial rotation (P = 0.048) and decreased shoulder elevation (P = 0.046) when transferring a box between shelves. Compensatory movements were not systematically correlated with duration of prosthesis ownership, socket comfort, or terminal device type. INTERPRETATION: A prosthesis user's compensatory movements may depend on other factors beyond whether the prosthesis terminal device is actuated through body-powered or myoelectric mechanisms. Further exploration of the factors that influence joint kinematics in prosthesis users may inform future prosthesis prescription practices and help patients become successful users.

First Demonstration of Functional Task Performance Using a Sonomyographic Prosthesis: A Case Study.

Ultrasound-based sensing of muscle deformation, known as sonomyography, has shown promise for accurately classifying the intended hand grasps of individuals with upper limb loss in offline settings. Building upon this previous work, we present the first demonstration of real-time prosthetic hand control using sonomyography to perform functional tasks. An individual with congenital bilateral limb absence was fitted with sockets containing a low-profile ultrasound transducer placed over forearm muscle tissue in the residual limbs. A classifier was trained using linear discriminant analysis to recognize ultrasound images of muscle contractions for three discrete hand configurations (rest, tripod grasp, index finger point) under a variety of arm positions designed to cover the reachable workspace. A prosthetic hand mounted to the socket was then controlled using this classifier. Using this real-time sonomyographic control, the participant was able to complete three functional tasks that required selecting different hand grasps in order to grasp and move one-inch wooden blocks over a broad range of arm positions. Additionally, these tests were successfully repeated without retraining the classifier across 3 hours of prosthesis use and following simulated donning and doffing of the socket. This study supports the feasibility of using sonomyography to control upper limb prostheses in real-world applications.

Differences in quality of movements made with body-powered and myoelectric prostheses during activities of daily living.

BACKGROUND: Upper limb prostheses likely do not enable movements having the same kinematic characteristics as anatomical limbs. The quality of movements made using body-powered and myoelectric prostheses may further differ based on the availability of sensory feedback and method of terminal device actuation. The purpose of this work was to compare the quality of movements made with body-powered and myoelectric prostheses during activities of daily living. METHODS: Nine transradial body-powered and/or myoelectric prosthesis users and nine controls without limb loss performed six activities of daily living. Movement quality, defined as duration, straightness, and smoothness, for the reaching and manipulation phases was compared between prostheses, as well as prostheses and anatomical limbs. FINDINGS: The quality of reaching movements were generally similar between prostheses. However, movements with body-powered prostheses were slower (P = 0.007) and less smooth (P < 0.001) when reaching to a deodorant stick and movements with myoelectric prostheses were slower when reaching to place a pin on a corkboard (P = 0.023). Movements with myoelectric prostheses were slower (P ≤ 0.021) and less smooth (P ≤ 0.012) than those with body-powered prostheses during object manipulation, but these differences were not present for all tasks. Movements with prostheses were slower, more curved, and less smooth compared to those with anatomical limbs. INTERPRETATION: Differences in the quality of movements made with body-powered and myoelectric prostheses primarily occur during object manipulation, rather than reaching. These differences do not exist for all tasks, suggesting that neither prosthesis type offers an absolute advantage in terms of movement quality.

Recommendations for the Successful Implementation of Upper Limb Prosthetic Technology.

Despite the numerous prosthetic hand designs that are commercially available, people with upper limb loss still frequently report dissatisfaction and abandonment. Over the past decade there have been numerous advances in prosthetic design, control, sensation, and device attachment. Each offers the potential to enhance function and satisfaction, but most come at high costs and involve surgical risks. Here, we discuss potential barriers and solutions to promote the widespread use of novel prosthetic technology. With appropriate reimbursement, multidisciplinary care teams, device-specific rehabilitation, and patient and clinician education, such technology has the potential to revolutionize the field and improve patient outcomes.

Differential experiences of embodiment between body-powered and myoelectric prosthesis users.

Prosthesis embodiment, the perception of a prosthesis as part of one's body, may be an important component of functional recovery for individuals with upper limb absence. This work determined whether embodiment differs between body-powered and myoelectric prosthesis users. In a sample of nine individuals with transradial limb absence, embodiment was quantified using a survey regarding prosthesis ownership and agency. The extent to which the prosthesis affected the body schema, the representation of the body's dimensions, was assessed using limb length estimation. Because body-powered prostheses offer proprioceptive feedback that myoelectric prostheses do not, it was hypothesized that both measures would reveal stronger embodiment of body-powered prostheses. However, our results did not show differences across the two prosthesis designs. Instead, body schema was influenced by several patient-specific characteristics, including the cause of limb absence (acquired or congenital) and hours of daily prosthesis wear. These results indicate that regular prosthesis wear and embodiment are connected, regardless of the actual prosthesis design. Identifying whether embodiment is a direct consequence of regular prosthesis use would offer insight on how individuals with limb absence could modify their behavior to more fully embody their prosthesis.

Reliability of upper limb movement quality metrics during everyday tasks.

BACKGROUND: Quantitative assessments of an individual's functional status commonly involve the use of movement quality metrics. RESEARCH QUESTION: The purpose of this work was to quantify the reliability of movement quality metrics in healthy adults during a variety of unconstrained activities of daily living (ADLs). METHODS: Nineteen participants performed six ADLs (lifting a laundry basket, applying deodorant, turning a doorknob, placing a pill in a pillbox, placing a pushpin in a bulletin board, and drinking water from a glass) during two separate sessions. The ADLs were divided into reaching and object manipulation phases. Movement quality for each phase was assessed using three measures of smoothness (log dimensionless jerk, spectral arc length, and number of submovements) and one measure of straightness (index of curvature). Within- and between-session reliability was quantified using intraclass correlation coefficients (ICCs) and minimum detectable changes in measured units and as a percentage of their mean value (MDC%). RESULTS: Reliability was generally lower within-session than between-session and for object manipulation tasks compared to reaching tasks. The ICCs exceeded 0.75 for 5% of the within-session metrics and 73% of the between-session metrics. The average MDC% was 35% for the within-session metrics and 20% for the between-session metrics. Reliability was similar for most metrics when averaged across the tasks, but the number of submovements consistently indicated much lower reliability. SIGNIFICANCE: Unconstrained ADLs can reliably be used to assess movement quality in functional settings that mimic real-world challenges. However, the specific movement quality metrics used in the assessment should be chosen carefully since some metrics perform dissimilarly when applied to the same data. In particular, it may be advisable to use the number of submovements in combination with other metrics, if it is to be used at all.

Reliability of upper limb and trunk joint angles in healthy adults during activities of daily living.

Assessments of upper limb performance should require participants to perform tasks that challenge the limits of their ability. In order to select appropriate tasks, it is important to know which joints are used to perform the movement and how reliably those movements can be measured. The purpose of this work was to quantify the reliability of upper limb and trunk joint angles in healthy adults during common activities of daily living (ADLs). Nineteen participants performed six ADLs with the right arm (applying deodorant, turning a doorknob, answering a desk telephone, placing a pushpin in a bulletin board, wiping a plate with a towel, and pouring water from a pitcher) during two separate sessions. Within- and between-session reliability was quantified using intraclass correlation coefficients (ICCs) and minimum detectable change values (MDCs). Reliability was generally better within-session than between-session. The ICCs exceeded 0.75 for 88% of the joint angles and exceeded 0.90 for 32% of the angles. All MDCs were less than 25° and 61% were also less than 10°. The MDCs represented a larger percent of the average angles for the trunk (61%) and wrist (62%) compared to the shoulder (18%) and elbow (26%). Although these results show that most angles can be measured reliably for these six ADLs, reliability varied considerably between joints. It is therefore important to select tasks for assessing of upper limb performance based on which specific joints need to be evaluated.

Factors associated with interest in novel interfaces for upper limb prosthesis control.

BACKGROUND: Surgically invasive interfaces for upper limb prosthesis control may allow users to operate advanced, multi-articulated devices. Given the potential medical risks of these invasive interfaces, it is important to understand what factors influence an individual's decision to try one. METHODS: We conducted an anonymous online survey of individuals with upper limb loss. A total of 232 participants provided personal information (such as age, amputation level, etc.) and rated how likely they would be to try noninvasive (myoelectric) and invasive (targeted muscle reinnervation, peripheral nerve interfaces, cortical interfaces) interfaces for prosthesis control. Bivariate relationships between interest in each interface and 16 personal descriptors were examined. Significant variables from the bivariate analyses were then entered into multiple logistic regression models to predict interest in each interface. RESULTS: While many of the bivariate relationships were significant, only a few variables remained significant in the regression models. The regression models showed that participants were more likely to be interested in all interfaces if they had unilateral limb loss (p ≤ 0.001, odds ratio ≥ 2.799). Participants were more likely to be interested in the three invasive interfaces if they were younger (p < 0.001, odds ratio ≤ 0.959) and had acquired limb loss (p ≤ 0.012, odds ratio ≥ 3.287). Participants who used a myoelectric device were more likely to be interested in myoelectric control than those who did not (p = 0.003, odds ratio = 24.958). CONCLUSIONS: Novel prosthesis control interfaces may be accepted most readily by individuals who are young, have unilateral limb loss, and/or have acquired limb loss However, this analysis did not include all possible factors that may have influenced participant's opinions on the interfaces, so additional exploration is warranted.