The multi-grip and standard myoelectric hand prosthesis compared: does the multi-grip hand live up to its promise?

BACKGROUND: Multi-grip myoelectric hand prostheses (MHPs), with five movable and jointed fingers, have been developed to increase functionality. However, literature comparing MHPs with standard myoelectric hand prostheses (SHPs) is limited and inconclusive. To establish whether MHPs increase functionality, we compared MHPs with SHPs on all categories of the International Classification of Functioning, Disability, and Health-model (ICF-model). METHODS: MHP users (N = 14, 64.3% male, mean age = 48.6 years) performed physical measurements (i.e., Refined Clothespin Relocation Test (RCRT), Tray-test, Box and Blocks Test, Southampton Hand Assessment Procedure) with their MHP and an SHP to compare the joint angle coordination and functionality related to the ICF-categories 'Body Function' and 'Activities' (within-group comparisons). SHP users (N = 19, 68.4% male, mean age = 58.1 years) and MHP users completed questionnaires/scales (i.e., Orthotics and Prosthetics Users' Survey-The Upper Extremity Functional Status Survey /OPUS-UEFS, Trinity Amputation and Prosthesis Experience Scales for upper extremity/TAPES-Upper, Research and Development-36/RAND-36, EQ-5D-5L, visual analogue scale/VAS, the Dutch version of the Quebec User Evaluation of Satisfaction with assistive technology/D-Quest, patient-reported outcome measure to assess the preferred usage features of upper limb prostheses/PUF-ULP) to compare user experiences and quality of life in the ICF-categories 'Activities', 'Participation', and 'Environmental Factors' (between-group comparisons). RESULTS: 'Body Function' and 'Activities': nearly all users of MHPs had similar joint angle coordination patterns with an MHP as when they used an SHP. The RCRT in the upward direction was performed slower in the MHP condition compared to the SHP condition. No other differences in functionality were found. 'Participation': MHP users had a lower EQ-5D-5L utility score; experienced more pain or limitations due to pain (i.e., measured with the RAND-36). 'Environmental Factors': MHPs scored better than SHPs on the VAS-item holding/shaking hands. The SHP scored better than the MHP on five VAS-items (i.e., noise, grip force, vulnerability, putting clothes on, physical effort to control) and the PUF-ULP. CONCLUSION: MHPs did not show relevant differences in outcomes compared to SHPs on any of the ICF-categories. This underlines the importance of carefully considering whether the MHP is the most suitable option for an individual taking into account the additional costs of MHPs.

Simultaneous assessment and training of an upper-limb amputee using incremental machine-learning-based myocontrol: a single-case experimental design.

BACKGROUND: Machine-learning-based myocontrol of prosthetic devices suffers from a high rate of abandonment due to dissatisfaction with the training procedure and with the reliability of day-to-day control. Incremental myocontrol is a promising approach as it allows on-demand updating of the system, thus enforcing continuous interaction with the user. Nevertheless, a long-term study assessing the efficacy of incremental myocontrol is still missing, partially due to the lack of an adequate tool to do so. In this work we close this gap and report about a person with upper-limb absence who learned to control a dexterous hand prosthesis using incremental myocontrol through a novel functional assessment protocol called SATMC (Simultaneous Assessment and Training of Myoelectric Control). METHODS: The participant was fitted with a custom-made prosthetic setup with a controller based on Ridge Regression with Random Fourier Features (RR-RFF), a non-linear, incremental machine learning method, used to build and progressively update the myocontrol system. During a 13-month user study, the participant performed increasingly complex daily-living tasks, requiring fine bimanual coordination and manipulation with a multi-fingered hand prosthesis, in a realistic laboratory setup. The SATMC was used both to compose the tasks and continually assess the participant's progress. Patient satisfaction was measured using Visual Analog Scales. RESULTS: Over the course of the study, the participant progressively improved his performance both objectively, e.g., the time required to complete each task became shorter, and subjectively, meaning that his satisfaction improved. The SATMC actively supported the improvement of the participant by progressively increasing the difficulty of the tasks in a structured way. In combination with the incremental RR-RFF allowing for small adjustments when required, the participant was capable of reliably using four actions of the prosthetic hand to perform all required tasks at the end of the study. CONCLUSIONS: Incremental myocontrol enabled an upper-limb amputee to reliably control a dexterous hand prosthesis while providing a subjectively satisfactory experience. The SATMC can be an effective tool to this aim.

Transfer of mode switching performance: from training to upper-limb prosthesis use.

BACKGROUND: Current myoelectric prostheses are multi-articulated and offer multiple modes. Switching between modes is often done through pre-defined myosignals, so-called triggers, of which the training hardly is studied. We evaluated if switching skills trained without using a prosthesis transfer to actual prosthesis use and whether the available feedback during training influences this transfer. Furthermore we examined which clinically relevant performance measures and which myosignal features were adapted during training. METHODS: Two experimental groups and one control group participated in a five day pre-test-post-test design study. Both experimental groups used their myosignals to perform a task. One group performed a serious game without seeing their myosignals, the second group was presented their myosignal on a screen. The control group played the serious game using the touchpad of the laptop. Each training session lasted 15 min. The pre- and post-test were identical for all groups and consisted of performing a task with an actual prosthesis, where switches had to be produced to change grip mode to relocate clothespins. Both clinically relevant performance measures and myosignal features were analysed. RESULTS: 10 participants trained using the serious game, 10 participants trained with the visual myosignal and 8 the control task. All participants were unimpaired. Both experimental groups showed significant transfer of skill from training to prosthesis use, the control group did not. The degree of transfer did not differ between the two training groups. Clinically relevant measure 'accuracy' and feature of the myosignals 'variation in phasing' changed during training. CONCLUSIONS: Training switching skills appeared to be successful. The skills trained in the game transferred to performance in a functional task. Learning switching skills is independent of the type of feedback used during training. Outcome measures hardly changed during training and further research is needed to explain this. It should be noted that five training sessions did not result in a level of performance needed for actual prosthesis use. Trial registration The study was approved by the local ethics committee (ECB 2014.02.28_1) and was included in the Dutch trial registry (NTR5876).

User training for machine learning controlled upper limb prostheses: a serious game approach.

BACKGROUND: Upper limb prosthetics with multiple degrees of freedom (DoFs) are still mostly operated through the clinical standard Direct Control scheme. Machine learning control, on the other hand, allows controlling multiple DoFs although it requires separable and consistent electromyogram (EMG) patterns. Whereas user training can improve EMG pattern quality, conventional training methods might limit user potential. Training with serious games might lead to higher quality EMG patterns and better functional outcomes. In this explorative study we compare outcomes of serious game training with conventional training, and machine learning control with the users' own one DoF prosthesis. METHODS: Participants with upper limb absence participated in 7 training sessions where they learned to control a 3 DoF prosthesis with two grips which was fitted. Participants received either game training or conventional training. Conventional training was based on coaching, as described in the literature. Game-based training was conducted using two games that trained EMG pattern separability and functional use. Both groups also trained functional use with the prosthesis donned. The prosthesis system was controlled using a neural network regressor. Outcome measures were EMG metrics, number of DoFs used, the spherical subset of the Southampton Hand Assessment Procedure and the Clothespin Relocation Test. RESULTS: Eight participants were recruited and four completed the study. Training did not lead to consistent improvements in EMG pattern quality or functional use, but some participants improved in some metrics. No differences were observed between the groups. Participants achieved consistently better results using their own prosthesis than the machine-learning controlled prosthesis used in this study. CONCLUSION: Our explorative study showed in a small group of participants that serious game training seems to achieve similar results as conventional training. No consistent improvements were found in either group in terms of EMG metrics or functional use, which might be due to insufficient training. This study highlights the need for more research in user training for machine learning controlled prosthetics. In addition, this study contributes with more data comparing machine learning controlled prosthetics with Direct Controlled prosthetics.

Flexibility in joint coordination remains unaffected by force and balance demands in young and old adults during simple sit-to-stand tasks.

PURPOSE: We examined the possibility that old adults use flexibility in joint coordination as a compensatory mechanism for the age-related decline in muscle strength when performing the sit-to-stand (STS) task repeatedly under high force and balance demands. METHOD: Young (n = 14, 22.4 ± 2.1) and old (n = 12, 70 ± 3.2) healthy adults performed repeated STSs under high and low force and balance demands. The balance demand was manipulated by reducing the base of support and the force demand by increasing body weight with a weight vest. Uncontrolled manifold analysis was used to quantify age differences in motor flexibility. RESULTS: While there were age-typical differences in kinematic STS strategies, flexibility in joint coordination was independent of age and task difficulty during repeated STSs. DISCUSSION: That simple manipulations of force and balance demands did not affect flexibility in joint coordination in old and young adults suggests that motor flexibility acts as a compensatory mechanism only at the limits of available muscle strength and balance abilities during STS movements. Intervention studies should identify how changes in specific neuromuscular functions affect flexibility in joint coordination during activities of daily living such as STS.

Fixed muscle synergies and their potential to improve the intuitive control of myoelectric assistive technology for upper extremities.

BACKGROUND: Users of myoelectric controlled assistive technology (AT) for upper extremities experience difficulties in controlling this technology in daily life, partly because the control is non-intuitive. Making the control of myoelectric AT intuitive may resolve the experienced difficulties. The present paper was inspired by the suggestion that intuitive control may be achieved if the control of myoelectric AT is based on neuromotor control principles. A significant approach within neurocomputational motor control suggests that myosignals are produced via a limited number of fixed muscle synergies. To effectively employ this approach in myoelectric AT, it is required that a limited number of muscle synergies is systematically exploited, also when muscles are used differently as required in controlling myoelectric AT. Therefore, the present study examined the systematic exploitation of muscle synergies when muscles were used differently to complete point-to-point movements with and without a rod. METHODS: Healthy participants made multidirectional point-to-point movements with different end-effectors, i.e. with the index finger and with rods of different lengths. Myosignals were collected from 22 muscles in the arm, trunk, and back, and subsequently partitioned into muscle synergies per end-effector and for a pooled dataset including all end-effectors. The exploitation of these muscle synergies was assessed by evaluating the similarity of structure and explanatory ability of myosignals of per end-effector muscle synergies and the contribution of pooled muscle synergies across end-effectors. RESULTS: Per end-effector, 3-5 muscle synergies could explain 73.8-81.1% of myosignal variation, whereas 6-8 muscle synergies from the pooled dataset also captured this amount of myosignal variation. Subsequent analyses showed that gradually different muscle synergies-extracted from separate end-effectors-were exploited across end-effectors. In line with this result, the order of contribution of muscle synergies extracted from the pooled dataset gradually reversed across end-effectors. CONCLUSION: A limited number of muscle synergies was systematically exploited in the examined set of movements, indicating a potential for the fixed muscle synergy approach to improve the intuitive control of myoelectric AT. Given the gradual change in muscle synergy exploitation across end-effectors, future research should examine whether this potential can be extended to a larger range of movements and tasks.

Development and reliability of the rating of compensatory movements in upper limb prosthesis wearers during work-related tasks.

STUDY DESIGN: Reliability study. INTRODUCTION: Quantifying compensatory movements during work-related tasks may help to prevent musculoskeletal complaints in individuals with upper limb absence. PURPOSE OF THE STUDY: (1) To develop a qualitative scoring system for rating compensatory shoulder and trunk movements in upper limb prosthesis wearers during the performance of functional capacity evaluation tests adjusted for use by 1-handed individuals (functional capacity evaluation-one handed [FCE-OH]); (2) to examine the interrater and intrarater reliability of the scoring system; and (3) to assess its feasibility. METHODS: Movement patterns of 12 videotaped upper limb prosthesis wearers and 20 controls were analyzed. Compensatory movements were defined for each FCE-OH test, and a scoring system was developed, pilot tested, and adjusted. During reliability testing, 18 raters (12 FCE experts and 6 physiotherapists/gait analysts) scored videotapes of upper limb prosthesis wearers performing 4 FCE-OH tests 2 times (2 weeks apart). Agreement was expressed in % and kappa value. Feasibility (focus area's "acceptability", "demand," and "implementation") was determined by using a questionnaire. RESULTS: After 2 rounds of pilot testing and adjusting, reliability of a third version was tested. The interrater reliability for the first and second rating sessions were к = 0.54 (confidence interval [CI]: 0.52-0.57) and к = 0.64 (CI: 0.61-0.66), respectively. The intrarater reliability was к = 0.77 (CI: 0.72-0.82). The feasibility was good but could be improved by a training program. DISCUSSION: It seems possible to identify compensatory movements in upper limb prosthesis wearers during the performance of FCE-OH tests reliably by observation using the developed observational scoring system. CONCLUSIONS: Interrater reliability was satisfactory in most instances; intrarater reliability was good. Feasibility was established.

The development of consistency and flexibility in manual pointing during middle childhood.

Goal-directed actions become truly functional and skilled when they are consistent yet flexible. In manual pointing, end-effector consistency is characterized by the end position of the index fingertip, whereas flexibility in movement execution is captured by the use of abundant arm-joint configurations not affecting the index finger end position. Because adults have been shown to exploit their system's flexibility in challenging conditions, we wondered whether during middle childhood children are already able to exploit motor flexibility when demanded by the situation. We had children aged 5-10 years and adults perform pointing movements in a nonchallenging and challenging condition. Results showed that end-effector errors and flexibility in movement execution decreased with age. Importantly, only the 9-10-year-olds and adults showed increased flexibility in the challenging condition. Thus, while consistency increases and flexibility decreases during mid-childhood development, from the age of nine children appear able to employ more flexibility with increasing task demands.

Old adults preserve motor flexibility during rapid reaching.

PURPOSE: Our ability to flexibly coordinate the available degrees of freedom allows us to perform activities of daily living under various task constraints. Healthy old adults exhibit subclinical peripheral and central nervous system dysfunctions, possibly compromising the flexibility in inter-joint coordination during voluntary movements and the ability to adapt to varying task constraints. METHOD: We examined how healthy old (75.4 ± 5.2 years, n = 14) compared with young adults (24.3 ± 2 years, n = 15) make use of the available motor flexibility to adapt to physical and dexterity constraints during a rapid goal-directed reaching task. We manipulated physical and dexterity demands by changing, respectively, external resistance and target size. Motor flexibility was quantified by an uncontrolled manifold (UCM) analysis. RESULTS: We found that healthy young and old adults employ similar motor flexibility as quantified by the ratio between goal equivalent and non-goal equivalent variability (V Ratio) and were similarly able to adapt to increases in physical and dexterity demands during goal-directed rapid reaching (V Ratio: p = .092; young: 0.548 ± 0.113; old: 0.264 ± 0.117). Age affected end-effector kinematics. Motor flexibility and end-effector kinematics did not correlate. CONCLUSION: The data challenge the prevailing view that old age affects movement capabilities in general and provide specific evidence that healthy old adults preserve motor flexibility during a reaching task. Future studies applying UCM analysis should examine if experimental set-ups limit movement exploration, leaving possible age differences undetected.

The Southampton Hand Assessment Procedure revisited: A transparent linear scoring system, applied to data of experienced prosthetic users.

STUDY DESIGN: Cross-sectional. INTRODUCTION: Southampton Hand Assessment Procedure (SHAP) provides function scores for hand grips (prehensile patterns) and an overall score, the index of function (IOF). The underlying equations of SHAP are not publicly available, which induces opacity. Furthermore, SHAP has been scarcely tested in prosthetic users. METHODS: Issues with SHAP-IOF are discussed; an alternative scoring system, that is, linear index of function (LIF) and a weighted version (W-LIF) are presented. In LIF, task times are transformed linearly, relative to SHAP norms, and are computed into LIF-prehensile patterns (LIFPP). LIF and IOF were compared using data of 27 experienced prosthetic users. RESULTS: High correlation and agreement between LIF and IOF was found: LIFPP vs IOFPP ranged from r = 0.880 to r = 0.988, and W-LIF vs IOF had a correlation coefficient of r = 0.984. DISCUSSION: SHAP data of prosthetic users are valuable benchmarks for health care professionals. LIF calculations are a good and cost free alternative for IOF scores. CONCLUSION(S): Measurements with LIF and IOF may be considered similar, but LIF is transparent and easier to use than IOF. LEVEL OF EVIDENCE: Clinical measurement and cross-sectional.

Intermanual Transfer Effects in Below-Elbow Myoelectric Prosthesis Users.

OBJECTIVES: To determine intermanual transfer effects in patients with a below-elbow amputation using a myoelectric prosthesis and to establish whether laterality affects these effects. DESIGN: Case-control. SETTING: A standardized setting in a rehabilitation clinic. PARTICIPANTS: A convenience sample (N=44) of experienced myoelectric prosthesis users (n=22) and matched controls (n=22). Controls were matched on sex, age (±5y), and hand dominance. INTERVENTIONS: Both the experienced group and the control group performed several tasks using a prosthesis simulator attached to their nonaffected arm. MAIN OUTCOME MEASURES: Movement time, force control, Box and Block test (BBT) scores, and duration of hand opening. RESULTS: Movement times of myoelectric prosthesis users were shorter, and these users had significantly higher BBT scores and shorter hand opening durations than those of controls. No intermanual transfer effects on force control and no laterality effects were found. CONCLUSIONS: Intermanual transfer effects were present in experienced myoelectric prosthesis users with a below-elbow amputation, independent of laterality. These findings support the clinical relevance of intermanual transfer training, which may facilitate persons with an upper limb amputation to start training directly after the amputation.

Upper Limb Absence: Predictors of Work Participation and Work Productivity.

OBJECTIVES: To analyze work participation, work productivity, contributing factors, and physical work demands of individuals with upper limb absence (ULA). DESIGN: Cross-sectional study: postal survey (response rate, 45%). SETTING: Twelve rehabilitation centers and orthopedic workshops. PARTICIPANTS: Individuals (n=207) with unilateral transverse upper limb reduction deficiency (RD) or acquired amputation (AA), at or proximal to the carpal level, between the ages of 18 and 65 years, and a convenience sample of control subjects (n=90) matched on age and sex. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Employment status, self-reported work productivity measured with the Quality-Quantity method, and self-reported upper extremity work demands measured with the Upper Extremity Work Demands scale. RESULTS: Seventy-four percent of the individuals with RD and 57% of the individuals with AA were employed (vs 82% of the control group and 66% of the general population). Male sex, younger age, a medium or higher level of education, prosthesis use, and good general health were predictors of work participation. Work productivity was similar to that of the control group. Higher work productivity was inversely related to musculoskeletal complaint-related pain. When having predominantly mentally demanding work, individuals with ULA perceived higher upper extremity work demands compared with controls. CONCLUSIONS: Work participation of individuals with RD was slightly higher compared with that of the general population, whereas employment rates of individuals with AA were slightly lower. Furthermore, work productivity did not differ between individuals with RD, AA, and controls.

Musculoskeletal Complaints in Transverse Upper Limb Reduction Deficiency and Amputation in The Netherlands: Prevalence, Predictors, and Effect on Health.

OBJECTIVE: (1) To determine the prevalence of musculoskeletal complaints (MSCs) in individuals with upper limb absence in The Netherlands, (2) to assess the health status of individuals with upper limb absence in general and in relation to the presence of MSCs, and (3) to explore the predictors of development of MSCs and MSC-related disability in this population. DESIGN: Cross-sectional study: national survey. SETTING: Twelve rehabilitation centers and orthopedic workshops. PARTICIPANTS: Individuals (n=263; mean age, 50.7±16.7y; 60% men) ≥18 years old, with transverse upper limb reduction deficiency (42%) or amputation (58%) at or proximal to the carpal level (response, 45%) and 108 individuals without upper limb reduction deficiency or amputation (n=108; mean age, 50.6±15.7y; 65% men) (N=371). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Point and year prevalence of MSCs, MSC-related disability (Pain Disability Index), and general health perception and mental health (RAND-36 subscales). RESULTS: Point and year prevalence of MSCs were almost twice as high in individuals with upper limb absence (57% and 65%, respectively) compared with individuals without upper limb absence (27% and 34%, respectively) and were most often located in the nonaffected limb and upper back/neck. MSCs were associated with decreased general health perception and mental health and higher perceived upper extremity work demands. Prosthesis use was not related to presence of MSCs. Clinically relevant predictors of MSCs were middle age, being divorced/widowed, and lower mental health. Individuals with upper limb absence experienced more MSC-related disability than individuals without upper limb absence. Higher age, more pain, lower general and mental health, and not using a prosthesis were related to higher disability. CONCLUSIONS: Presence of MSCs is a frequent problem in individuals with upper limb absence and is associated with decreased general and mental health. Mental health and physical work demands should be taken into account when assessing such a patient. Clinicians should note that MSC-related disability increases with age.

Learning to use a body-powered prosthesis: changes in functionality and kinematics.

BACKGROUND: Little is known about action-perception learning processes underlying prosthetic skills in body-powered prosthesis users. Body-powered prostheses are controlled through a harness connected by a cable that might provide for limited proprioceptive feedback. This study aims to test transfer of training basic tasks to functional tasks and to describe the changes over time in kinematics of basic tasks of novice body-powered prosthesis users. METHODS: Thirty able-bodied participants and 17 controls participated in the study, using a body-powered prosthetic simulator. Participants in the training group were divided over four groups and practiced during a 2-week-period either direct grasping, indirect grasping, fixation, or a combination of these tasks. Deformable objects with different compliances had to be manipulated while kinematic variables and grip force control were assessed. Functional performance was measured with the Southampton Hand Assessment Procedure (SHAP) prior to and after the training sessions, and after 2 weeks and 3 months retention. The control group only performed the SHAP tests. RESULTS: All four training groups and the control group improved on the SHAP, also after a period of non-use. Type of training had a small but significant influence on the improvements of the SHAP score. On a kinematic level movement times decreased and hook closing velocities increased over time. The indirect grasping group showed significantly shorter plateau times than the other training groups. Grip force control only improved a little over training. CONCLUSIONS: Training action-perception couplings of body-powered prosthesis in basic tasks transferred to functional tasks and this lasted after a period of non-use. During training movement times decreased and the indirect grasping group showed advantages. It is advisable to start body-powered training with indirect grasping tasks but also to practice hook-object orientations.

Preliminary study of the Southampton Hand Assessment Procedure for Children and its reliability.

BACKGROUND: The Southampton Hand Assessment Procedure (SHAP) is currently used in the adult population for evaluating the functionality of impaired or prosthetic hands. The SHAP cannot be used for children because of the relatively larger size of the objects used to perform SHAP tasks and unknown clinimetric properties. The aims of this study were to adapt the SHAP for use in children (SHAP-C), to determine norm values for the SHAP-C, and to analyze the reliability of the SHAP-C. METHODS: The SHAP-C was adapted based on the SHAP protocol. Some objects were downsized, and the timing of tasks was performed by the rater instead of the participant. Intra- and inter-rater reliability were assessed in 24 children (5 [0.54] y/o) with unimpaired hands. The repeatability coefficients (RCs) were calculated. An RC ≤ 75% of the mean SHAP-C task values was considered good reliability. RESULTS: Participants were able to perform all SHAP-C tasks. The means of the SHAP-C tasks ranged from 0.75 to 1.21 seconds for abstract objects and from 0.64-19.13 seconds for activities of daily living. The RCs of a single assessor did not exceed 75% in 17/26 SHAP-C tasks, displaying a relatively good intra-rater reliability, whereas the RCs for the inter-rater reliability exceeded 75% in 22/26 SHAP-C tasks, thus displaying poor reliability. CONCLUSION: In this first study that adjusted the SHAP for pediatric use, we found that all SHAP-C objects and tasks could be performed by children. The intra-rater reliability was better than the inter-rater reliability. Although the SHAP-C appears to be a promising instrument, the protocol requires further modifications to provide reliable measurements in children.

Changes in performance over time while learning to use a myoelectric prosthesis.

BACKGROUND: Training increases the functional use of an upper limb prosthesis, but little is known about how people learn to use their prosthesis. The aim of this study was to describe the changes in performance with an upper limb myoelectric prosthesis during practice. The results provide a basis to develop an evidence-based training program. METHODS: Thirty-one able-bodied participants took part in an experiment as well as thirty-one age- and gender-matched controls. Participants in the experimental condition, randomly assigned to one of four groups, practiced with a myoelectric simulator for five sessions in a two-weeks period. Group 1 practiced direct grasping, Group 2 practiced indirect grasping, Group 3 practiced fixating, and Group 4 practiced a combination of all three tasks. The Southampton Hand Assessment Procedure (SHAP) was assessed in a pretest, posttest, and two retention tests. Participants in the control condition performed SHAP two times, two weeks apart with no practice in between. Compressible objects were used in the grasping tasks. Changes in end-point kinematics, joint angles, and grip force control, the latter measured by magnitude of object compression, were examined. RESULTS: The experimental groups improved more on SHAP than the control group. Interestingly, the fixation group improved comparable to the other training groups on the SHAP. Improvement in global position of the prosthesis leveled off after three practice sessions, whereas learning to control grip force required more time. The indirect grasping group had the smallest object compression in the beginning and this did not change over time, whereas the direct grasping and the combination group had a decrease in compression over time. Moreover, the indirect grasping group had the smallest grasping time that did not vary over object rigidity, while for the other two groups the grasping time decreased with an increase in object rigidity. CONCLUSIONS: A training program should spend more time on learning fine control aspects of the prosthetic hand during rehabilitation. Moreover, training should start with the indirect grasping task that has the best performance, which is probably due to the higher amount of useful information available from the sound hand.

Effects of IMU sensor-to-segment calibration on clinical 3D elbow joint angles estimation.

Introduction: Inertial Measurement Units (IMU) require a sensor-to-segment calibration procedure in order to compute anatomically accurate joint angles and, thereby, be employed in healthcare and rehabilitation. Research literature proposes several algorithms to address this issue. However, determining an optimal calibration procedure is challenging due to the large number of variables that affect elbow joint angle accuracy, including 3D joint axis, movement performed, complex anatomy, and notable skin artefacts. Therefore, this paper aims to compare three types of calibration techniques against an optical motion capture reference system during several movement tasks to provide recommendations on the most suitable calibration for the elbow joint. Methods: Thirteen healthy subjects were instrumented with IMU sensors and optical marker clusters. Each participant performed a series of static poses and movements to calibrate the instruments and, subsequently, performed single-plane and multi-joint tasks. The metrics used to evaluate joint angle accuracy are Range of Motion (ROM) error, Root Mean Squared Error (RMSE), and offset. We performed a three-way RM ANOVA to evaluate the effect of joint axis and movement task on three calibration techniques: N-Pose (NP), Functional Calibration (FC) and Manual Alignment (MA). Results: Despite small effect sizes in ROM Error, NP displayed the least precision among calibrations due to interquartile ranges as large as 24.6°. RMSE showed significant differences among calibrations and a large effect size where MA performed best (RMSE = 6.3°) and was comparable with FC (RMSE = 7.2°). Offset showed a large effect size in the calibration*axes interaction where FC and MA performed similarly. Conclusion: Therefore, we recommend MA as the preferred calibration method for the elbow joint due to its simplicity and ease of use. Alternatively, FC can be a valid option when the wearer is unable to hold a predetermined posture.

Assessing the effectiveness of serious game training designed to assist in upper limb prothesis rehabilitation.

Introduction: Controlling a myoelectric upper limb prosthesis is difficult, therefore training is required. Since training with serious games showed promising results, the current paper focuses on game design and its effectivity for transfer between in-game skill to actual prosthesis use for proportional control of hand opening and control of switching between grips. We also examined training duration and individual differences. Method: Thirty-six participants were randomly assigned to one of three groups: a task-specific serious game training group, a non-task-specific serious game training group and a control group. Each group performed a pre-test, mid-test and a post-test with five training sessions between each test moment. Test sessions assessed proportional control using the Cylinder test, a test designed to measure scaling of hand aperture during grabbing actions, and the combined use of proportional and switch control using the Clothespin Relocation Test, part of the Southampton Hand Assessment Procedure and Tray Test. Switch control was assessed during training by measuring amplitude difference and phasing of co-contraction triggers. Results: Differences between groups over test sessions were observed for proportional control tasks, however there was lack of structure in these findings. Maximum aperture changed with test moment and some participants adjusted maximum aperture for smaller objects. For proportional and switch control tasks no differences between groups were observed. The effect of test moment suggests a testing effect. For learning switch control, an overall improvement across groups was found in phasing of the co-contraction peaks. Importantly, individual differences were found in all analyses. Conclusion: As improvements over test sessions were found, but no relevant differences between groups were revealed, we conclude that transfer effects from game training to actual prosthesis use did not take place. Task specificity nor training duration had effects on outcomes. Our results imply testing effects instead of transfer effects, in which individual differences played a significant role. How transfer from serious game training in upper limb prosthesis use can be enhanced, needs further attention.

Sensibility of the stump in adults with an acquired major upper extremity amputation.

OBJECTIVES: To compare the sensibility of the stump in adults with an acquired major upper extremity amputation with the sensibility of the unaffected side and with the corresponding body parts of healthy controls, as well as to relate the sensibility of the stump to daily functioning. DESIGN: A survey with matched controls. SETTING: A tertiary referral center. PARTICIPANTS: A referred sample of patients (n=30) with an acquired upper extremity amputation, at least 1 year after amputation, and control subjects (n=30) matched for age, sex, and hand dominance were evaluated. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Three different modalities of sensibility were measured: (1) touch-pressure sensibility, tested using Semmes-Weinstein monofilaments; (2) stereognosis, detected using the Shape and Texture Identification test; and (3) kinesthesia. Daily functioning was assessed using the Upper Extremity Functional Status Module of the Orthotics and Prosthetics Users' Survey. RESULTS: The mean time ± SD since amputation was 20±17.8 years. Twenty patients used a prosthesis. The stump sensibility was similar to that of unaffected hands and tended to be less than that of unaffected arms (P=.08). The patients using a prosthesis had significantly poorer touch-pressure sensibility in the stump compared with the nonusers (P=.04). However, touch-pressure sensibility and stereognosis were worse in the patients than in controls (P<.001 and P=.03, respectively). Two patients were able to identify shapes using their stump. Kinesthesia of the shoulders and elbows did not differ between the affected and unaffected side. Moreover, daily functioning was not related to sensibility. CONCLUSIONS: The touch-pressure sensibility in the stumps of patients using prostheses was poorer than the sensibility in nonusers, and remarkably, the unaffected extremities of the amputees were less sensitive than the extremities of the controls.

On the psychological origins of tool use.

The ubiquity of tool use in human life has generated multiple lines of scientific and philosophical investigation to understand the development and expression of humans' engagement with tools and its relation to other dimensions of human experience. However, existing literature on tool use faces several epistemological challenges in which the same set of questions generate many different answers. At least four critical questions can be identified, which are intimately intertwined-(1) What constitutes tool use? (2) What psychological processes underlie tool use in humans and nonhuman animals? (3) Which of these psychological processes are exclusive to tool use? (4) Which psychological processes involved in tool use are exclusive to Homo sapiens? To help advance a multidisciplinary scientific understanding of tool use, six author groups representing different academic disciplines (e.g., anthropology, psychology, neuroscience) and different theoretical perspectives respond to each of these questions, and then point to the direction of future work on tool use. We find that while there are marked differences among the responses of the respective author groups to each question, there is a surprising degree of agreement about many essential concepts and questions. We believe that this interdisciplinary and intertheoretical discussion will foster a more comprehensive understanding of tool use than any one of these perspectives (or any one of these author groups) would (or could) on their own.