Development and validation of the coffee task: a novel functional assessment for prosthetic grip selection.

BACKGROUND: Lack of standardized assessments that explicitly quantify performance during prosthetic grip selection poses difficulty determining whether efforts to improve the design of multi-grip hands and their control approaches are successful. In this study, we developed and validated a novel assessment of multi-grip prosthetic performance: The Coffee Task. METHODS: Individuals without limb loss completed the Box and Block Test and two versions of the Coffee Task - Continuous and Segmented - with a myoelectric prosthetic emulator. On different days, participants selected prosthetic grips using pattern recognition and trigger control. Outcomes of the Continuous and Segmented Coffee Task were completion time and number of errors, respectively. Two independent raters assessed outcomes of the Coffee Task using video recordings to determine inter-rater reliability. Known-group validity was assessed by comparing outcomes with the emulator to those with an intact limb. Convergent validity was assessed through the correlation of the Coffee Task outcomes and those of the Box and Blocks Test. Responsiveness to changes with practice and control approach were assessed using the standardized response mean (SRM). RESULTS: Inter-rater reliability was high for both versions of the Coffee Task (Intra-class coefficient > 0.981). Coffee Task outcomes were moderately correlated with the Box and Blocks outcomes (|r| ≥ 0.412, p ≤ 0.007). Participants completed the Coffee Task faster with their intact limb than with the emulator (p < 0.001). Both versions of the Coffee Task were responsive to changes with training (SRM ≥ 0.81) but not control approach (SRM ≤ 0.12). CONCLUSIONS: The Coffee Task is reliable, has good known-group and convergent validity, and is responsive to changes due to practice. Future work should assess whether the Coffee Task is feasible and reliable for people with upper limb loss who use multi-grip prostheses.

Electrical Stimulation of Regenerative Peripheral Nerve Interfaces (RPNIs) Induces Referred Sensations in People With Upper Limb Loss.

Individuals with upper limb loss lack sensation of the missing hand, which can negatively impact their daily function. Several groups have attempted to restore this sensation through electrical stimulation of residual nerves. The purpose of this study was to explore the utility of regenerative peripheral nerve interfaces (RPNIs) in eliciting referred sensation. In four participants with upper limb loss, we characterized the quality and location of sensation elicited through electrical stimulation of RPNIs over time. We also measured functional stimulation ranges (sensory perception and discomfort thresholds), sensitivity to changes in stimulation amplitude, and ability to differentiate objects of different stiffness and sizes. Over a period of up to 54 months, stimulation of RPNIs elicited sensations that were consistent in quality (e.g. tingling, kinesthesia) and were perceived in the missing hand and forearm. The location of elicited sensation was partially-stable to stable in 13 of 14 RPNIs. For 5 of 7 RPNIs tested, participants demonstrated a sensitivity to changes in stimulation amplitude, with an average just noticeable difference of 45 nC. In a case study, one participant was provided RPNI stimulation proportional to prosthetic grip force. She identified four objects of different sizes and stiffness with 56% accuracy with stimulation alone and 100% accuracy when stimulation was combined with visual feedback of hand position. Collectively, these experiments suggest that RPNIs have the potential to be used in future bi-directional prosthetic systems.

Long-term upper-extremity prosthetic control using regenerative peripheral nerve interfaces and implanted EMG electrodes.

Objective.Extracting signals directly from the motor system poses challenges in obtaining both high amplitude and sustainable signals for upper-limb neuroprosthetic control. To translate neural interfaces into the clinical space, these interfaces must provide consistent signals and prosthetic performance.Approach.Previously, we have demonstrated that the Regenerative Peripheral Nerve Interface (RPNI) is a biologically stable, bioamplifier of efferent motor action potentials. Here, we assessed the signal reliability from electrodes surgically implanted in RPNIs and residual innervated muscles in humans for long-term prosthetic control.Main results.RPNI signal quality, measured as signal-to-noise ratio, remained greater than 15 for up to 276 and 1054 d in participant 1 (P1), and participant 2 (P2), respectively. Electromyography from both RPNIs and residual muscles was used to decode finger and grasp movements. Though signal amplitude varied between sessions, P2 maintained real-time prosthetic performance above 94% accuracy for 604 d without recalibration. Additionally, P2 completed a real-world multi-sequence coffee task with 99% accuracy for 611 d without recalibration.Significance.This study demonstrates the potential of RPNIs and implanted EMG electrodes as a long-term interface for enhanced prosthetic control.

Transtibial prosthetic alignment has small effects on whole-body angular momentum during functional tasks.

Due to the loss of ankle function, many people with a transtibial amputation (TTA) have difficulty maintaining balance during functional tasks. Prosthetic alignment may affect how people with TTA maintain balance as it affects ground reaction forces (GRFs) and centers of pressure. We quantified the effect of prosthetic alignment on dynamic balance during several functional tasks. Ten people with TTA and 10 controls without TTA completed tasks including walking and transitioning from a chair. Participants with TTA completed all tasks with their prescribed alignment and six shifted alignments, including ±10 mm anterior/posterior, medial/lateral, and ±20 mm in the vertical direction. For each task, we quantified dynamic balance as the range of whole-body angular momentum (H→WB) and quantified trunk range of motion (ROM) and peak GRFs. Compared to controls, participants with TTA using their prescribed alignment had a greater range of H→WB in the sagittal plane during walking, in all planes during sit-to-stand, and in the transverse plane during stand-to-sit. These results were associated with GRF and trunk ROM differences between participant groups. Alignment only affected the range of H→WB in the frontal plane during walking. The larger range for the tall alignment coincided with a greater difference in vertical GRF between intact and amputated legs compared to other alignments. Our findings suggest that people with TTA can adapt to small, translational, alignment changes to maintain similar levels of dynamic balance during chair transitions. Future work should investigate alignment changes during other tasks and in lower functioning individuals.

Comparison of five different methodologies for evaluating ankle-foot orthosis stiffness.

BACKGROUND: The mechanical properties of an ankle-foot orthosis (AFO) play an important role in the gait mechanics of the end user. However, testing methodologies for evaluating these mechanical properties are not standardized. The purpose of this study was to compare five different evaluation frameworks to assess AFO stiffness. METHOD: The same 13 carbon composite AFOs were tested with five different methods. Four previously reported custom test fixtures (the BRUCE, KST, SMApp, and EMPIRE) rotated an AFO into dorsiflexion about a defined axis in the sagittal plane. The fifth method involved quasi-static deflection of AFOs into dorsiflexion by hanging weights (HW) from the footplate. AFO rotational stiffness was calculated as the linear fit of the AFO resistive torque and angular deflection. Differences between methods were assessed using descriptive statistics and a repeated measures Friedman with post-hoc Bonferroni-Holm adjusted Wilcoxon signed-rank tests. RESULTS: There were significant differences in measured AFO stiffnesses between test methods. Specifically, the BRUCE and HW methods measured lower stiffness than both the EMPIRE and the KST. Stiffnesses measured by the SMApp were not significantly different than any test method. Stiffnesses were lowest in the HW method, where motion was not constrained to a single plane. The median difference in absolute AFO stiffness across methods was 1.03 Nm/deg with a range of [0.40 to 2.35] Nm/deg. The median relative percent difference, measured as the range of measured stiffness from the five methods over the average measured stiffness was 62% [range 13% to 156%]. When the HW method was excluded, the four previously reported test fixtures produced a median difference in absolute AFO stiffness of 0.52 [range 0.38 to 2.17] Nm/deg with a relative percent difference between the methods of 27% [range 13% to 89%]. CONCLUSIONS: This study demonstrates the importance of developing mechanical testing standards, similar to those that exist for lower limb prosthetics. Lacking standardization, differences in methodology can result in large differences in measured stiffness, particularly for different constraints on motion. Non-uniform measurement practices may limit the clinical utility of AFO stiffness as a metric in AFO prescription and future research.

Upper limb prostheses: bridging the sensory gap.

Replacing human hand function with prostheses goes far beyond only recreating muscle movement with feedforward motor control. Natural sensory feedback is pivotal for fine dexterous control and finding both engineering and surgical solutions to replace this complex biological function is imperative to achieve prosthetic hand function that matches the human hand. This review outlines the nature of the problems underlying sensory restitution, the engineering methods that attempt to address this deficit and the surgical techniques that have been developed to integrate advanced neural interfaces with biological systems. Currently, there is no single solution to restore sensory feedback. Rather, encouraging animal models and early human studies have demonstrated that some elements of sensation can be restored to improve prosthetic control. However, these techniques are limited to highly specialized institutions and much further work is required to reproduce the results achieved, with the goal of increasing availability of advanced closed loop prostheses that allow sensory feedback to inform more precise feedforward control movements and increase functionality.

Use of regenerative peripheral nerve interfaces and intramuscular electrodes to improve prosthetic grasp selection: a case study.

Objective.Advanced myoelectric hands enable users to select from multiple functional grasps. Current methods for controlling these hands are unintuitive and require frequent recalibration. This case study assessed the performance of tasks involving grasp selection, object interaction, and dynamic postural changes using intramuscular electrodes with regenerative peripheral nerve interfaces (RPNIs) and residual muscles.Approach.One female with unilateral transradial amputation participated in a series of experiments to compare the performance of grasp selection controllers with RPNIs and intramuscular control signals with controllers using surface electrodes. These experiments included a virtual grasp-matching task with and without a concurrent cognitive task and physical tasks with a prosthesis including standardized functional assessments and a functional assessment where the individual made a cup of coffee ('Coffee Task') that required grasp transitions.Main results.In the virtual environment, the participant was able to select between four functional grasps with higher accuracy using the RPNI controller (92.5%) compared to surface controllers (81.9%). With the concurrent cognitive task, performance of the virtual task was more consistent with RPNI controllers (reduced accuracy by 1.1%) compared to with surface controllers (4.8%). When RPNI signals were excluded from the controller with intramuscular electromyography (i.e. residual muscles only), grasp selection accuracy decreased by up to 24%. The participant completed the Coffee Task with 11.7% longer completion time with the surface controller than with the RPNI controller. She also completed the Coffee Task with 11 fewer transition errors out of a maximum of 25 total errors when using the RPNI controller compared to surface controller.Significance.The use of RPNI signals in concert with residual muscles and intramuscular electrodes can improve grasp selection accuracy in both virtual and physical environments. This approach yielded consistent performance without recalibration needs while reducing cognitive load associated with pattern recognition for myoelectric control (clinical trial registration number NCT03260400).

Temporal and spatial goal-directed reaching in upper limb prosthesis users.

Understanding the fundamental characteristics of prosthetic movement control is imperative in improving prosthesis design and training. This study quantified how using an upper limb prosthesis affected performance during goal-directed reaching tasks. Nine prosthesis users with unilateral transradial limb absence and nine healthy controls completed a series of goal-directed reaching movements with different goals: one spatial and three temporal with different goal frequencies. We quantified end-point accuracy, smoothness, and peak speed for the spatial task and temporal accuracy, horizontal distance, and speed for the temporal task. For the temporal task, we also used a goal-equivalent manifold (GEM) approach to decompose variability in movement distance and speed into those perpendicular and tangential to the GEM. Detrended fluctuation analysis (DFA) quantified the temporal persistence of each time series. For the spatial task, movements made with prostheses were less smooth, had larger end-point errors, and had slower peak speed compared to those with control limbs (p < 0.041). For the temporal task, movements made with prostheses and intact limbs of prosthesis users and control limbs were similar in distance and speed and had similar timing errors (p > 0.138). Timing errors, distance, speed, and GEM deviations were corrected similarly between prosthetic limbs and control limbs (p > 0.091). The mean and variability of distance, speed, and perpendicular deviations decreased with increased goal frequency (p < 0.001). Our results suggest that prosthesis users have a sufficient internal model to successfully complete ballistic movements but are unable to accurately complete movements requiring substantial feedback.

Characterizing sensory thresholds and intensity sensitivity of Regenerative Peripheral Nerve Interfaces: A Case Study.

Current prosthetic limbs offer little to no sensory feedback. Developments in peripheral nerve interfaces provide opportunities to restore some level of tactile feedback that is referred to the prosthetic limb. One such method is a Regenerative Peripheral Nerve Interface (RPNI), composed of a muscle graft wrapped around a free nerve ending. Here, we characterize perception and discomfort thresholds, as well as sensitivity to stimulation through two-alternative forced choice discrimination tasks. One person with transradial amputation who had one RPNI constructed from the median nerve and two constructed from the ulnar nerve participated. Average perception thresholds across all RPNIs were between 950 and 1120 nC with variance of less than 350 nC over a 36-month period. Discomfort thresholds were from 3880 nC to 9770 nC across all RPNIs. The just noticeable difference for the Median RPNI was 520 nC, larger than either the Ulnar-1 or Ulnar-2 RPNIs (210 nC, 470 nC, respectively). We also calculated Weber fractions to compare sensitivity between different RPNIs and relate our results to previous studies. Weber fractions for each of the Median, Ulnar-1, and Ulnar-2 RPNIs were 0.134, 0.088, 0.087, respectively. This work is the first to quantify the functional stimulation range and sensitivity of RPNIs in a human participant. Future work will focus on characterizing RPNI sensation in additional individuals to determine if these findings are generalizable to the amputee population.

Artificial referred sensation in upper and lower limb prosthesis users: a systematic review.

Objective.Electrical stimulation can induce sensation in the phantom limb of individuals with amputation. It is difficult to generalize existing findings as there are many approaches to delivering stimulation and to assessing the characteristics and benefits of sensation. Therefore, the goal of this systematic review was to explore the stimulation parameters that effectively elicited referred sensation, the qualities of elicited sensation, and how the utility of referred sensation was assessed.Approach.We searched PubMed, Web of Science, and Engineering Village through January of 2022 to identify relevant papers. We included papers which electrically induced referred sensation in individuals with limb loss and excluded papers that did not contain stimulation parameters or outcome measures pertaining to stimulation. We extracted information on participant demographics, stimulation approaches, and participant outcomes.Main results.After applying exclusion criteria, 49 papers were included covering nine stimulation methods. Amplitude was the most commonly adjusted parameter (n= 25), followed by frequency (n= 22), and pulse width (n= 15). Of the 63 reports of sensation quality, most reported feelings of pressure (n= 52), paresthesia (n= 48), or vibration (n= 40) while less than half (n= 29) reported a sense of position or movement. Most papers evaluated the functional benefits of sensation (n= 33) using force matching or object identification tasks, while fewer papers quantified subjective measures (n= 16) such as pain or embodiment. Only 15 studies (36%) observed percept intensity, quality, or location over multiple sessions.Significance.Most studies that measured functional performance demonstrated some benefit to providing participants with sensory feedback. However, few studies could experimentally manipulate sensation location or quality. Direct comparisons between studies were limited by variability in methodologies and outcome measures. As such, we offer recommendations to aid in more standardized reporting for future research.

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.

Restoration of Proprioceptive and Cutaneous Sensation Using Regenerative Peripheral Nerve Interfaces in Humans with Upper Limb Amputations.

SUMMARY: Without meaningful and intuitive sensory feedback, even the most advanced prosthetic limbs remain insensate and impose an enormous cognitive burden during use. The regenerative peripheral nerve interface can serve as a novel bidirectional motor and sensory neuroprosthetic interface. In previous human studies, regenerative peripheral nerve interfaces demonstrated stable high-amplitude motor electromyography signals with excellent signal-to-noise ratio for prosthetic control. In addition, they can treat and prevent postamputation pain by mitigating neuroma formation. In this study, the authors investigated whether electrical stimulation applied to regenerative peripheral nerve interfaces could produce appreciable proprioceptive and/or tactile sensations in two participants with upper limb amputations. Stimulation of the interfaces resulted in both participants reporting proprioceptive sensations in the phantom hand. Specifically, stimulation of participant 1's median nerve regenerative peripheral nerve interface activated a flexion sensation in the thumb or index finger, whereas stimulation of the ulnar nerve interface evoked a flexion sensation of the ring or small finger. Likewise, stimulation of one of participant 2's ulnar nerve interfaces produced a sensation of flexion at the ring finger distal interphalangeal joint. In addition, stimulation of participant 2's other ulnar nerve interface and the median nerve interface resulted in perceived cutaneous sensations that corresponded to each nerve's respective dermatome. These results suggest that regenerative peripheral nerve interfaces have the potential to restore proprioceptive and cutaneous sensory feedback that could significantly improve prosthesis use and embodiment.

Surgically Implanted Electrodes Enable Real-Time Finger and Grasp Pattern Recognition for Prosthetic Hands.

Currently available prosthetic hands are capable of actuating anywhere from five to 30 degrees of freedom (DOF). However, grasp control of these devices remains unintuitive and cumbersome. To address this issue, we propose directly extracting finger commands from the neuromuscular system. Two persons with transradial amputations had bipolar electrodes implanted into regenerative peripheral nerve interfaces (RPNIs) and residual innervated muscles. The implanted electrodes recorded local electromyography with large signal amplitudes. In a series of single-day experiments, participants used a high speed movement classifier to control a virtual prosthetic hand in real-time. Both participants transitioned between 10 pseudo-randomly cued individual finger and wrist postures with an average success rate of 94.7% and trial latency of 255 ms. When the set was reduced to five grasp postures, metrics improved to 100% success and 135 ms trial latency. Performance remained stable across untrained static arm positions while supporting the weight of the prosthesis. Participants also used the high speed classifier to switch between robotic prosthetic grips and complete a functional performance assessment. These results demonstrate that pattern recognition systems can use intramuscular electrodes and RPNIs for fast and accurate prosthetic grasp control.

Getting a Grip on the Impact of Incidental Feedback From Body-Powered and Myoelectric Prostheses.

Sensory feedback from body-powered and myoelectric prostheses are limited, but in different ways. Currently, there are no empirical studies on how incidental feedback differs between body-powered and myoelectric prostheses, or how these differences impact grasping. Thus, the purpose of this study was to quantify differences in grasping performance between body-powered and myoelectric prosthesis users when presented with different forms of feedback. Nine adults with upper limb loss and nine without (acting as controls) completed two tasks in a virtual environment. In the first task, participants used visual, vibration, or force feedback to assist in matching target grasp apertures. In the second task, participants used either visual or force feedback to identify the stiffness of a virtual object. Participants using either prosthesis type improved their accuracy and reduced their variability compared to the no feedback condition when provided with any form of feedback (p < 0.001). However, participants using body-powered prostheses were significantly more accurate and less variable at matching grasp apertures than those using myoelectric prostheses across all feedback conditions. When identifying stiffness, body-powered prosthesis users were more accurate using force feedback (64% compared to myoelectric users' 39%) while myoelectric users were more accurate using visual feedback (65% compared to body-powered users' 53%). This study supports previous findings that body-powered prosthesis users receive limited force and proprioceptive feedback, while myoelectric prosthesis users receive almost no force or proprioceptive feedback from their device. This work can inform future supplemental feedback that enhances rather than reproduces existing incidental feedback.

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.

The effect of powered ankle prostheses on muscle activity during walking.

Individuals with transtibial amputation (TTA) walk with greater muscle activity and metabolic costs than non-amputees. Powered prostheses aim to address these deficits by replicating the active function of the biological ankle. The purpose of this study was to determine if people with TTA alter muscle activity when walking with a powered prosthesis, and if this change relates to changes in metabolic costs. Ten individuals with TTA and 10 non-amputees walked on a treadmill while we measured metabolic cost and muscle activity from 16 lower limb muscles. Participants with TTA walked with their prescribed unpowered prosthesis and a commercial powered prosthesis (BiOM T2, Bedford, MA, USA), in random order. The integrated EMG across the gait cycle was greater with the powered prosthesis for the intact limb gluteus medius (p = 0.002) and residual limb vastus medialis (p = 0.013). There were several non-significant, moderate-to-strong correlations between changes in muscle activity and changes in metabolic cost between prostheses (p > 0.0504). Decreased muscle activity in the residual limb gluteus medius correlated with lower metabolic cost (r = 0.543). In contrast, lower metabolic cost was correlated with increased residual limb rectus femoris activity (r = -0.627) and increased co-contractions in the residual limb thigh muscles in terminal stance (r = -0.585) and late swing (r = -0.754). Overall, there were no consistent changes in muscle activity in response to the powered prosthesis. The correlations suggest that individuals who can effectively stabilize their residual limb during stance are more likely to benefit metabolically.

The ins and outs of dynamic balance during 90-degree turns in people with a unilateral transtibial amputation.

The ability to maintain balance when turning is essential to functional and independent living. Due to the lack of neuromuscular ankle control on the prosthetic side in people with a transtibial amputation (TTA), turning is likely more challenging. The purpose of this study was to quantify how people with TTA maintain dynamic balance during 90-degree turns made with the prosthesis on the inside and outside of the turn compared to people without amputation. Eight participants with TTA and eight age-, height-, and sex- matched non-amputee controls performed left and right 90-degree step turns at a self-selected speed. The primary outcomes were range of whole-body angular momentum and positive and negative contributions of six segment groups (head/trunk, pelvis, arms, and legs) to whole-body angular momentum during the continuation stride. Participants with TTA had greater range of frontal- and sagittal-plane whole-body angular momentum when turning with the prosthesis on the inside compared controls. They also had a greater range of whole-body angular momentum in all planes of motion when turning with the prosthesis on the inside compared to outside of the turn. The contributions for the head/trunk and inside and outside legs differed between groups and turns, suggesting altered interactions between segment momenta to compensate for the reduced contribution of the amputated leg. This study provides insight into possible training paradigms to reduce the high incidence of turn related falls in people with TTA and, potentially, ways to alter prosthetic function to promote balance control.

The effect of rotational speed on ankle-foot orthosis properties.

Ankle-foot orthoses (AFOs) are devices that support ankle motion. An AFO's sagittal plane rotational stiffness can affect gait kinematics. Because AFOs are often made from viscoelastic materials, their properties may vary at different walking speeds. The influence of rotational speed on AFO properties has not been thoroughly investigated. Therefore, the purpose of this study was to determine the impact of rotational speed on AFO stiffness about the ankle. We tested a sample of one thermoplastic off-the-shelf AFO and two 3-D printed carbon fiber enforced nylon AFOs. Each AFO's dynamic resistance torque was measured as it was flexed at five speeds (5-100 °/s) using a custom-built measurement apparatus. We compared loading stiffness, neutral angle, and energy dissipation parameters for each AFO across speeds. Parameter values were generally greater at higher speeds. These effects were statistically significant for all AFOs (p≤0.002). However, differences in AFO stiffness and neutral angle across speeds were quite small (<0.6 Nm/° and <2.2 °). Changes in the thermoplastic AFO's stiffness were lower than the minimum detectable difference. Energy dissipation, as indicated by hysteresis area, increased by up to 6.3 J (about 250%) at the highest speed. This demonstrates that AFO flexion speed can influence the properties of different AFOs over the range typically achieved in human walking. Future work should assess whether the observed small variations of stiffness and neutral angle have a clinically meaningful impact on user performance, as well as explore effects of angular speed on a variety of AFO materials and designs.

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.

The influence of powered prostheses on user perspectives, metabolics, and activity: a randomized crossover trial.

BACKGROUND: Powered prosthetic ankles provide battery-powered mechanical push-off, with the aim of reducing the metabolic demands of walking for people with transtibial amputations. The efficacy of powered ankles has been shown in active, high functioning individuals with transtibial amputation, but is less clear in other populations. Additionally, it is unclear how use of a powered prosthesis influences everyday physical activity and mobility. METHODS: Individuals with unilateral transtibial amputations participated in a randomized clinical trial comparing their prescribed, unpowered prosthesis and the BiOM powered prosthesis. Participants' metabolic costs and self-selected walking speeds were measured in the laboratory and daily step count, daily steps away from home, and walking speed were measured over two weeks of at-home prosthesis use. Participants also rated their perception of mobility and quality of life and provided free-form feedback. Dependent measures were compared between prostheses and the relationships between metabolic cost, perception of mobility, and characteristics of walking in daily life were explored using Pearson's correlations. RESULTS: Twelve people were randomly allocated to the powered prosthesis first (n = 7) or unpowered prosthesis first (n = 5) and ten completed the full study. There were no differences in metabolic costs (p = 0.585), daily step count (p = 0.995), walking speed in-lab (p = 0.145) and in daily life (p = 0.226), or perception of mobility between prostheses (p ≥ 0.058). Changes varied across participants, however. There were several medium-sized effects for device comparisons. With the powered prosthesis, participants had increased self-reported ambulation (g = 0.682) and decreased frustration (g = 0.506). CONCLUSIONS: There were no universal benefits of the powered prosthesis on function in the lab or home environment. However, the effects were subject-specific, with some reporting preference for power and improved mobility, and some increasing their activity and decreasing their metabolic effort. Additionally, self-reported preferences did not often correlate with objective measures of function. This highlights the need for future clinical research to include both perception and objective measures to better inform prosthetic prescription. TRIAL REGISTRATION: https://clinicaltrials.gov , #NCT02828982. Registered 12 July 2016, https://clinicaltrials.gov/ct2/show/NCT02828982.