Upper limb activity in myoelectric prosthesis users is biased towards the intact limb and appears unrelated to goal-directed task performance

Studies of the effectiveness of prosthetic hands involve assessing user performance on functional tasks in the lab/clinic, sometimes combined with self-report of real-world use. In this paper we compare real-world upper limb activity between a group of 20 myoelectric prosthesis users and 20 anatomically intact adults. Activity was measured from wrist-worn accelerometers over a 7-day period. The temporal patterns in upper limb activity are presented and the balance of activity between the two limbs quantified. We also evaluated the prosthesis users’ performance on a goal-directed task, characterised using measures including task success rate, completion time, gaze behaviour patterns, and kinematics (e.g. variability and patterns in hand aperture). Prosthesis users were heavily reliant on their intact limb during everyday life, in contrast to anatomically intact adults who demonstrated similar reliance on both upper limbs. There was no significant correlation between the amount of time a prosthesis was worn and reliance on the intact limb, and there was no significant correlation between either of these measures and any of the assessed kinematic and gaze-related measures of performance. We found participants who had been prescribed a prosthesis for longer to demonstrate more symmetry in their overall upper limb activity, although this was not reflected in the symmetry of unilateral limb use. With the exception of previously published case studies, this is the first report of real world upper limb activity in myoelectric prosthesis users and confirms the widely held belief that users are heavily reliant on their intact limb

Refined clothespin relocation test and assessment of motion

Background: Advancements in upper limb prosthesis design have focused on providing increased degrees of freedom for the end effector through multiple articulations of a prosthetic hand, wrist and elbow. Measuring improvement in patient function with these devices requires development of appropriate assessment tools. Objectives: This study presents a refined clothespin relocation test for measuring performance and assessing compensatory motion between able-bodied subjects and subjects with upper limb impairments. Study Design: Comparative analysis Methods: Trunk and head motions of 13 able-bodied subjects who performed the refined clothespin relocation test were compared to the motion of a transradial prosthesis user with a single degree of freedom hand. Results: There were observable differences between the prosthesis user and the able-bodied group. The assessment used provided a clear indication of the differences in motion through analysis of compensatory motion. Conclusion: The refined clothespin relocation test provides additional benefits over the standard clothespin assessment and makes identification of compensatory motions easily identifiable to the researcher. While this paper establishes the method for the new assessment, further validation will need to be performed with more users

The role of order of practice in learning to handle an upper-limb prosthesis

OBJECTIVE: To determine which order of presentation of practice tasks had the highest effect on using an upper-limb prosthetic simulator. DESIGN: A cohort analytic study. SETTING: University laboratory. PARTICIPANTS: Healthy, able-bodied participants (N=72) randomly assigned to 1 of 8 groups, each composed of 9 men and 9 women. INTERVENTIONS: Participants (n=36) used a myoelectric simulator, and participants (n=36) used a body-powered simulator. On day 1, participants performed 3 tasks in the acquisition phase. On day 2, participants performed a retention test and a transfer test. For each simulator, there were 4 groups of participants: group 1 practiced random and was tested random, group 2 practiced random and was tested blocked, group 3 practiced blocked and was tested random, and group 4 practiced blocked and was tested blocked. MAIN OUTCOME MEASURES: Initiation time, the time from the starting signal until the beginning of the movement, and movement time, the time from the beginning until the end of the movement. RESULTS: Movement times got faster during acquisition (P<.001). The blocked group had faster movement times (P=.009), and learning in this group extended over the complete acquisition phase (P<.001). However, this advantage disappeared in the retention and transfer tests. Compared with a myoelectric simulator, movements with the body-powered simulator were faster in acquisition (P=.004) and transfer test (P=.034). CONCLUSIONS: Performance in daily life with a prosthesis is indifferent to the structure in which the training is set up. However, practicing in a blocked fashion leads to faster performance; in novice trainees, it might be suggested to practice part of the training tasks in blocks

Learning to control opening and closing a myoelectric hand

Bouwsema H, van der Sluis CK, Bongers RM. Learning to control opening and closing a myoelectric hand. OBJECTIVE: To compare 3 different types of myoelectric signal training. DESIGN: A cohort analytic study. SETTING: University laboratory. PARTICIPANTS: Able-bodied right-handed participants (N=34) randomly assigned to 1 of 3 groups. INTERVENTIONS: Participants trained hand opening and closing on 3 consecutive days. One group trained with a virtual myoelectric hand presented on a computer screen, 1 group trained with an isolated prosthetic hand, and 1 group trained with a prosthetic simulator. One half of the participants trained with their dominant side, and the other half trained with their nondominant side. Before and after the training period, a test was administered to determine the improvement in skill. Participants were asked to open and close the hand on 3 different velocities at command. MAIN OUTCOME MEASURES: Peak velocity, mean velocity, and number of peaks in the myoelectric signal of hand opening and closing. RESULTS: No differences were found for the different types of training; all participants learned to control the myoelectric hand. However, differences in learning abilities were revealed. After learning, a subgroup of the participants could produce clearly distinct myoelectric signals, which resulted in the ability to open and close the hand at 3 different speeds, whereas others could not produce distinct myoelectric signals. CONCLUSIONS: Acquired control of a myoelectric hand is irrespective of the type of training. Prosthetic users may differ in learning capacity; this should be taken into account when choosing the appropriate type of control for each patient

Movement characteristics of upper extremity prostheses during basic goal-directed tasks

Background: After an upper limb amputation a prosthesis is often used to restore the functionality. However, the frequency of prostheses use is generally low. Movement kinematics of prostheses use might suggest origins of this low use. The aim of this study was to reveal movement patterns of prostheses during basic goal-directed actions in upper limb prosthetic users and to compare this with existing knowledge of able-bodied performance during these actions. Methods: Movements from six users of upper extremity prostheses were analyzed, three participants with a hybrid upper arm prosthesis, and three participants with a myoelectric forearm prosthesis. Two grasping tasks and a reciprocal pointing task were investigated during a single lab session. Analyses were carried out on the kinematics of the tasks. Findings: When grasping, movements with both prostheses showed asymmetric velocity profiles of the reach and had a plateau in the aperture profiles. Reach and grasp were decoupled. Kinematics with the prostheses differed in that the use of upper arm prostheses required more time to execute the movements, while the movements were less smooth, more asymmetric, and showed more decoupling between reach and grasp. The pointing task showed for both prostheses less harmonic movements with higher task difficulty. Interpretation: Characterizing prosthetic movement patterns revealed specific features of prosthetic performance. Developments in technology and rehabilitation should focus on these issues to improve prosthetic use, in particular on improving motor characteristics and the control of the elbow, and learning to coordinate the reach and the grasp component in prehension. (C) 2010 Elsevier Ltd. All rights reserved

Bernstein's levels of construction of movements applied to upper limb prosthetics

This article addresses the neuromotor control processes underlying the use of an upper limb prosthesis. Knowledge of these processes is used to make recommendations as to how prostheses and prosthesis training should develop to advance the functionality of upper limb prostheses. Obviously, modern-day prostheses are not optimally integrated in neuromotor functioning. The current article frames the problems underlying the handling of upper limb prosthetic devices in the hierarchical levels of construction of movement as proposed by Bernstein (1996). It follows that 1) postural disturbances resulting from prosthetic use should be considered in training and in the development of prosthetic devices, 2) training should take into account that new synergies have to be learned, 3) the feedback about the state of the prosthesis should improve, and 4) the alteration between different grip patterns should be made easy and fast. We observed that many of the current innovations in the prosthetics field are in line with the aim to integrate the prosthesis in sensory-motor functioning.</p

Bernstein’s levels of construction of movements applied to upper limb prosthetics

This article addresses the neuromotor control processes underlying the use of an upper limb prosthesis. Knowledge of these processes is used to make recommendations as to how prostheses and prosthesis training should develop to advance the functionality of upper limb prostheses. Obviously, modern-day prostheses are not optimally integrated in neuromotor functioning. The current article frames the problems underlying the handling of upper limb prosthetic devices in the hierarchical levels of construction of movement as proposed by Bernstein (1996). It follows that 1) postural disturbances resulting from prosthetic use should be considered in training and in the development of prosthetic devices, 2) training should take into account that new synergies have to be learned, 3) the feedback about the state of the prosthesis should improve, and 4) the alteration between different grip patterns should be made easy and fast. We observed that many of the current innovations in the prosthetics field are in line with the aim to integrate the prosthesis in sensory-motor functionin

Determining skill level in myoelectric prosthesis use with multiple outcome measures

To obtain more insight into how the skill level of an upper-limb myoelectric prosthesis user is composed, the current study aimed to (1) portray prosthetic handling at different levels of description, (2) relate results of the clinical level to kinematic measures, and (3) identify specific parameters in these measures that characterize the skill level of a prosthesis user. Six experienced transradial myoelectric prosthesis users performed a clinical test (Southampton Hand Assessment Procedure [SHAP]) and two grasping tasks. Kinematic measures were end point kinematics, joint angles, grasp force control, and gaze behavior. The results of the clinical and kinematic measures were in broad agreement with each other. Participants who scored higher on the SHAP showed overall better perfoiluance on the kinematic measures. They had smaller movement times, had better grip force control, and needed less visual attention on the hand. The results showed that time was a key parameter in prosthesis use and should be one of the main focus aspects of rehabilitation. The insights from this study are useful in rehabilitation practice because they allow therapists to specifically focus on certain parameters that may result in a higher level of skill for the prosthesis user