Intra-individual biomechanical effects of a non-microprocessor-controlled stance-yielding prosthetic knee during ramp descent in persons with unilateral transfemoral amputation

BACKGROUND:

A stance-yielding mechanism for prosthetic knees may reduce lower limb loading during specific activities, but quantitative data are insufficient.

OBJECTIVES:

To clarify the biomechanical effect of a non-microprocessor-controlled stance-yielding mechanism on ramp descent for individuals with unilateral transfemoral amputation.

STUDY DESIGN:

Intra-subject intervention study.

METHODS:

Seven individuals with unilateral transfemoral amputation underwent three-dimensional motion analysis of ramp descent with and without activating a stance-yielding mechanism. Regarding early-stance internal joint moment and ground reaction force, whole-group and subgroup analyses stratified by stance prosthetic knee flexion were performed to verify differences in prosthetic side and contralateral limb loading between conditions.

RESULTS:

Whole-group analysis revealed significant reduction in early-stance prosthetic knee extension moment with stance-yielding mechanism activation. Changes in prosthetic side hip extension moment and contralateral limb loading were inconsistent between conditions. Subjects with prosthetic stance knee flexion walked slower with a smaller stride and greater increase in aft ground reaction force and ankle dorsiflexion moment when stance-yielding was activated.

CONCLUSION:

Stance-yielding mechanism has a biomechanical potential to decrease excessive knee hyperextension. However, prosthetic side stance knee flexion induced by the stance-yielding mechanism might not necessarily reduce the mechanical load on residual hip or contralateral lower limb joints.

CLINICAL RELEVANCE

This study showed individual variability in the possibility of reducing the load on the remaining lower limb when using a non-microprocessor-controlled stance-yielding knee. This suggests that individualized prosthetic management and monitoring the activities of individuals wearing a stance-yielding prosthetic knee are crucial to maximize the benefits of stance-yielding prosthetic knees.

Artificial tactile and proprioceptive feedback improves performance and confidence on object identification tasks

Somatosensory feedback of the hand is essential for object identification. Without somatosensory feedback, individuals cannot reliably determine the size or compliance of an object. Electrical nerve stimulation can restore localized tactile and proprioceptive feedback with intensity discrimination capability similar to natural sensation. We hypothesized that adding artificial somatosensation improves object recognition accuracy when using a prosthesis. To test this hypothesis, we provided different forms of sensory feedback–tactile, proprioceptive, or both–to two subjects with upper limb loss. The subjects were asked to identify the size or mechanical compliance of different foam blocks placed in the prosthetic hand while visually and audibly blinded. During trials, we did not inform the subjects of their performance, but did ask them about their confidence in correctly identifying objects. Finally, we recorded applied pressures during object interaction. Subjects were free to use any strategy they chose to examine the objects. Object identification was most accurate with both tactile and proprioceptive feedback. The relative importance of each type of feedback, however, depended on object characteristics and task. Sensory feedback increased subject confidence and was directly correlated with accuracy. Subjects applied less pressure to the objects when they had tactile pressure feedback. Artificial somatosensory feedback improves object recognition and the relative importance of tactile versus proprioceptive feedback depends on the test set. We believe this test battery provides an effective means to assess the impact of sensory restoration and the relative contribution of different forms of feedback (tactile vs. kinesthetic) within the neurorehabilitation field.

Behavior-Change Intervention Targeting Physical Function, Walking, and Disability After Dysvascular Amputation: A Randomized Controlled Pilot Trial

OBJECTIVE

To determine preliminary efficacy of a home-based behavior-change intervention designed to promote exercise, walking activity, and disease self-management.

DESIGN

A single-blind, randomized controlled pilot trial.

SETTING

One Veterans Administration and 2 regional medical centers.

PARTICIPANTS

A total of 38 participants randomized to behavior-change intervention (n=19) or attention control (CTL; n=19) group.

INTERVENTIONS

Weekly 30-minute telephone sessions for 12 weeks with intervention group sessions focused on health behavior change and CTL group sessions focused on health status monitoring.

MAIN OUTCOME MEASURES

Physical function, walking activity (steps/d averaged over 10d), and disability were measured at baseline, 12 weeks (intervention end), and 24 weeks after baseline with the Timed Up and Go (TUG) test as the primary outcome measure.

RESULTS

The TUG test was not changed from baseline in either group and was not different between groups after 12 or 24 weeks. Several exploratory outcomes were assessed, including daily step count, which increased 1135 steps per day in the intervention group compared to 144 steps per day in the CTL group after 12 weeks (P=.03). Only the intervention group had within-group increase in steps per day from baseline to 12 (P<.001) and 24 (P=.03) weeks and spent significantly less time in sedentary activity (4.8% decrease) than the CTL group (0.2% decrease) at 24 weeks (P=.04). There were no other between-group differences in physical function or disability change over time.

CONCLUSION

The behavior-change intervention demonstrates promise for increasing walking activity for people with dysvascular transtibial amputation (TTA). The efficacy of implementing such intervention in the scope of conventional TTA rehabilitation should be further studied.

Pre-operative rehabilitation for dysvascular lower-limb amputee patients: A focus group study involving medical professionals

Background

Major lower-limb amputation (LLA) predisposes patients post-operatively to a significant decline in daily-life functioning. The physical condition of amputee patients prior to surgery is significantly deteriorated due to chronic peripheral vascular disease (PVD) and diabetes, which accounts for the majority of LLAs in the adult population. A common strategy called pre-rehabilitation has been used in multiple patient populations to prepare the patient for undergoing a surgical event and to improve post-operative patient outcomes. Pre-rehabilitation might enhance the outcome of dysvascular LLA patients and reduce the high post-operative mortality rates. However, experience of experts with pre-rehabilitation and feasibility of a pre-rehabilitation program in this group remains unknown.

Objective

To investigate the experiences of medical professionals and researchers in the field of LLA with the use of pre-rehabilitation in general and in particular PVD patients. Additionally, the study examines their opinions regarding need for and feasibility of a pre-rehabilitation program for dysvascular patients at risk for an LLA.

Methods

Two explorative focus group discussions were organized with in total 16 experts in the field of treatment and research of LLA. Transcribed data were coded using the Atlas.ti software package. Thematic analysis with inductive approach was opted to arrange and interpret codes.

Results

The experiences of the experts with pre-rehabilitation in dysvascular patients were scarce. The experts described dysvascular patients at risk for an LLA as a difficult group for pre-rehabilitation due to short time window prior to surgery, older age, multiple co-morbidities and lack of motivation for behavioral change. The experts concluded that a pre-rehabilitation program should focus on patients who have sufficient time in advance before the amputation for pre-rehabilitation and who are motivated to participate.

Conclusion

Although in general the effects of pre-rehabilitation are promising, pre-operative rehabilitation in dysvascular patients at risk for an LLA seems not feasible. Future research could focus on a better monitoring of dysvascular patients and the development of pre-rehabilitation in subgroups of younger dysvascular LLA patients.

A New Modeling Method to Characterize the Stance Control Function of Prosthetic Knee Joints

OBJECTIVE

Biomechanical models can inform design and optimization of prosthetic devices by connecting empirically derived biomechanical data to device design parameters. A new method is presented to characterize the function of prosthetic stance control under mobility conditions associated with activities of daily living. The method is based on a model of the gait modes corresponding to finite stance control states.

METHODS

Empirical data from amputee and simulated gait were acquired using a custom-built wearable instrument and input into the model.

RESULTS

The modeling approach was shown to be robust, responsive, and capable of accurate characterization of controller function under diverse locomotor and prosthetic setup conditions.

CONCLUSION

Future work is focused on the development of a fully self-contained wearable system, to facilitate collection of large datasets across a variety of user demographics, controller designs, and activities of daily living.

SIGNIFICANCE

The method offers predictive capability, which can assist in the virtual testing of new designs or modifications.

Smart Data-Driven Optimization of Powered Prosthetic Ankles Using Surface Electromyography

The advent of powered prosthetic ankles provided more balance and optimal energy expenditure to lower amputee gait. However, these types of systems require an extensive setup where the parameters of the ankle, such as the amount of positive power and the stiffness of the ankle, need to be setup. Currently, calibrations are performed by experts, who base the inputs on subjective observations and experience. In this study, a novel evidence-based tuning method was presented using multi-channel electromyogram data from the residual limb, and a model for muscle activity was built. Tuning using this model requires an exhaustive search over all the possible combinations of parameters, leading to computationally inefficient system. Various data-driven optimization methods were investigated and a modified Nelder⁻Mead algorithm using a Latin Hypercube Sampling method was introduced to tune the powered prosthetic. The results of the modified Nelder⁻Mead optimization were compared to the Exhaustive search, Genetic Algorithm, and conventional Nelder⁻Mead method, and the results showed the feasibility of using the presented method, to objectively calibrate the parameters in a time-efficient way using biological evidence.

Residual limb fluid volume change and volume accommodation: Relationships to activity and self-report outcomes in people with trans-tibial amputation

BACKGROUND

Fluctuations in limb volume degrade prosthesis fit and require users to accommodate changes using management strategies, such as donning and doffing prosthetic socks.

OBJECTIVES

To examine how activities and self-report outcomes relate to daily changes in residual limb fluid volume and volume accommodation.

STUDY DESIGN

Standardized, two-part laboratory protocol with an interim observational period.

METHODS

Participants were classified as "accommodators" or "non-accommodators," based on self-report prosthetic sock use. Participants' residual limb fluid volume change was measured using a custom bioimpedance analyzer and a standardized in-laboratory activity protocol. Self-report health outcomes were assessed with the Socket Comfort Score and Prosthesis Evaluation Questionnaire. Activity was monitored while participants left the laboratory for at least 3 h. They then returned to repeat the bioimpedance test protocol.

RESULTS

Twenty-nine people were enrolled. Morning-to-afternoon percent limb fluid volume change per hour was not strongly correlated to percent time weight-bearing or to self-report outcomes. As a group, non-accommodators ( n = 15) spent more time with their prosthesis doffed and reported better outcomes than accommodators.

CONCLUSION

Factors other than time weight-bearing may contribute to morning-to-afternoon limb fluid volume changes and reported satisfaction with the prosthesis among trans-tibial prosthesis users. Temporary doffing may be a more effective and satisfying accommodation method than sock addition. Clinical relevance Practitioners should be mindful that daily limb fluid volume change and prosthesis satisfaction are not dictated exclusively by activity. Temporarily doffing the prosthesis may slow daily limb fluid volume loss and should be investigated as an alternative strategy to sock addition.

A clinical survey about commercial games in lower limb prosthetic rehabilitation

BACKGROUND

Despite the popularity of commercial games in lower limb prosthetic rehabilitation, data about their prevalence of use as well as therapists' perspectives about these games are still lacking.

OBJECTIVES

To learn about the prevalence of use of commercial games in lower limb prosthetic rehabilitation and therapists' perspectives about these games.

STUDY DESIGN

Cross-sectional.

METHODS

An online survey was sent to physical and occupational therapists across prosthetic rehabilitation facilities in Canada. The survey had questions about the use of commercial games and therapists' perspectives.

RESULTS

Data were collected from 82 therapists. Overall, 46.3% (38/82) reported that they use commercial games; of those, 94.7% (36/38) used the Nintendo Wii Fit. The most reported perceived benefits were the Wii Fit helping to improve weight shifting ( n = 76/82, 92.7%) and balance ( n = 75/82, 91.5%), and being motivating and complementing traditional therapy ( n = 75/82, 91.5%). The most reported perceived barriers/challenges were lack of time and familiarity with the games ( n = 58/82, 70.7%).

CONCLUSION

Commercial games, particularly the Wii Fit, are commonly used in lower prosthetic rehabilitation in Canada. Most of the queried therapists view the Wii Fit positively. Knowledge translation activities and developing standard treatment protocols would be helpful in minimizing the barriers identified in this study. Clinical relevance The Wii Fit is prevalent in lower limb prosthetic rehabilitation in Canada and it is viewed positively by therapists as having the potential to improve balance and weight bearing, making rehabilitation more motivating, and complementing traditional therapy. Future studies should investigate the efficacy of the Wii Fit in prosthetic rehabilitation.

Two ways to improve myoelectric control for a transhumeral amputee after targeted muscle reinnervation: a case study

BACKGROUND

Myoelectric control of multifunctional prostheses is challenging for individuals with high-level amputations due to insufficient surface electromyography (sEMG) signals. A surgical technique called targeted muscle reinnervation (TMR) has achieved impressive improvements in myoelectric control by providing more sEMG control signals. In this case, some channels of sEMG signals are coupled after TMR, which limits the performance of conventional amplitude-based control for upper-limb prostheses.

METHODS

In this paper, two different ways (training and algorithms) were attempted to solve the problem in a transhumeral amputee after TMR. Firstly, effect of rehabilitation training on generating independent sEMG signals was investigated. The results indicated that some sEMG signals recorded were still coupled over the targeted muscles after rehabilitation training for about two months. Secondly, pattern recognition (PR) algorithm was then applied to classify the sEMG signals. In the second way, to further improve the real-time performance of prosthetic control, a post-processing method named as mean absolute value-based (MAV-based) threshold switches was utilized.

RESULTS

Using the improved algorithms, substantial improvement was shown in a subset of the modified Action Research Arm Test (ARAT). Compared with common PR control without post-processing method, the total scores increased more than 18% with majority vote and more than 58% with MAV-based threshold switches. The amputee was able to finish all the tasks within the allotted time with the standard MAV-based threshold switches. Subjectively the amputee preferred the PR control with MAV-based threshold switches and reported it to be more accurate and much smoother both in experiment and practical use.

CONCLUSIONS

Although the sEMG signals were still coupled after rehabilitation training on the TMR patient, the online performance of the prosthetic operation was improved through application of PR control with combination of the MAV-based threshold switches.

TRIAL REGISTRATION

Retrospectively registered http://www.chictr.org.cn/showproj.aspx?proj=22058 .

Grasp specific and user friendly interface design for myoelectric hand prostheses

This paper presents the design and characterisation of a hand prosthesis and its user interface, focusing on performing the most commonly used grasps in activities of daily living (ADLs). Since the operation of a multi-articulated powered hand prosthesis is difficult to learn and master, there is a significant rate of abandonment by amputees in preference for simpler devices. In choosing so, amputees chose to live with fewer features in their prosthesis that would more reliably perform the basic operations. In this paper, we look simultaneously at a hand prosthesis design method that aims for a small number of grasps, a low complexity user interface and an alternative method to the current use of EMG as a preshape selection method through the use of a simple button; to enable amputees to get to and execute the intended hand movements intuitively, quickly and reliably. An experiment is reported at the end of the paper comparing the speed and accuracy with which able-bodied naive subjects are able to select the intended preshapes through the use of a simplified EMG method and a simple button. It is shown that the button was significantly superior in the speed of successful task completion and marginally superior in accuracy (success of first attempt).

Analyzing at-home prosthesis use in unilateral upper-limb amputees to inform treatment & device design

New upper limb prosthetic devices are continuously being developed by a variety of industrial, academic, and hobbyist groups. Yet, little research has evaluated the long term use of currently available prostheses in daily life activities, beyond laboratory or survey studies. We seek to objectively measure how experienced unilateral upper limb prosthesis-users employ their prosthetic devices and unaffected limb for manipulation during everyday activities. In particular, our goal is to create a method for evaluating all types of amputee manipulation, including non-prehensile actions beyond conventional grasp functions, as well as to examine the relative use of both limbs in unilateral and bilateral cases. This study employs a head-mounted video camera to record participant's hands and arms as they complete unstructured domestic tasks within their own homes. A new 'Unilateral Prosthesis-User Manipulation Taxonomy' is presented based observations from 10 hours of recorded videos. The taxonomy addresses manipulation actions of the intact hand, prostheses, bilateral activities, and environmental feature-use (aiïordances). Our preliminary results involved tagging 23 minute segments of the full videos from 3 amputee participants using the taxonomy. This resulted in over 2,300 tag instances. Observations included that non-prehensile interactions outnumbered prehensile interactions in the affected limb for users with more distal amputation that allowed arm mobility.

Upper-limb prosthetic control using wearable multichannel mechanomyography

In this paper we introduce a robust multi-channel wearable sensor system for capturing user intent to control robotic hands. The interface is based on a fusion of inertial measurement and mechanomyography (MMG), which measures the vibrations of muscle fibres during motion. MMG is immune to issues such as sweat, skin impedance, and the need for a reference signal that is common to electromyography (EMG). The main contributions of this work are: 1) the hardware design of a fused inertial and MMG measurement system that can be worn on the arm, 2) a unified algorithm for detection, segmentation, and classification of muscle movement corresponding to hand gestures, and 3) experiments demonstrating the real-time control of a commercial prosthetic hand (Bebionic Version 2). Results show recognition of seven gestures, achieving an offline classification accuracy of 83.5% performed on five healthy subjects and one transradial amputee. The gesture recognition was then tested in real time on subsets of two and five gestures, with an average accuracy of 93.3% and 62.2% respectively. To our knowledge this is the first applied MMG based control system for practical prosthetic control.

Human mimetic forearm mechanism towards bionic arm

The paper presents a mechanical forearm mechanism to extend the pronation and supination (P/S) movement of the trans-radial amputee when he/she is able to conduct the P/S motion partially with his/her remaining forearm. The P/S motions of the existing prostheses and robotic arms developed till now are completely different from those of the human. When we are to develop the robotic prostheses for the amputees, two important issues should be considered such as cosmetic issue to look like normal arm and motion harmony issue between robotic prosthesis and the amputated living arm. Most prostheses do not realize the human-like P/S motion, but the simple rotational motion at the wrist by using the electric motor. In this paper, the well-known spatial four-bar mechanism is adopted in order to mimic human P/S motion as if the person does, because it is one of the best candidates to describe actual human forearm movement. To obtain the design parameters of the mechanism, first, 3D data of the amputated arm as well as the opposite side non-amputated arm are captured by using MRI (Magnetic Resonance Imaging) and 3D scanner. The design parameters such as link lengths, joint locations, and volumetric shape are determined from the measured data. Second, mathematical analysis is performed to simulate one degree-of-freedom P/S motion realized from the spatial four-bar mechanism, and the simulation results are suggested to confirm whether or not it acts like the relative movement between human ulnar and radius bones. Finally the effectiveness of the proposed mechanism is verified through two ADL (activities of daily living) tests.

Wrist-Powered Partial Hand Prosthesis Using a Continuum Whiffle Tree Mechanism: A Case Study

Among the advances in upper extremity prostheses in the past decades, only a small portion of the results were obtained for partial hand prostheses, possibly due to the highly diverse partial hand presentations and limited space for component integration. In an attempt to address these challenges, this paper presents the design, construction, installation, and experimental characterization of a wrist-powered partial hand prosthesis developed in Shanghai Jiao Tong University (hereafter referred to as the JTP hand), customized for a specific amputee. The JTP hand possesses: 1) a continuum whiffle tree mechanism to allow adaptive grasping; 2) a force-magnifying partial gear pair to enhance the power of the grip; and 3) a phalange-embedded disengageable ratchet to enable or disable backdrivability. Various grasps and gestures were formed using the JTP hand. The obtained results suggest that the proposed design might be a viable option for patients with transmetacarpal amputation.

Evaluation of Performance-Based Outcome Measures for the Upper Limb: A Comprehensive Narrative Review

Objective performance-based outcome measures (OMs) have the potential to provide unbiased and reproducible assessments of limb function. However, very few of these performance-based OMs have been validated for upper limb (UL) prosthesis users. OMs validated in other clinical populations (eg, neurologic or musculoskeletal conditions) could be used to fill gaps in existing performance-based OMs for UL amputees. Additionally, a joint review might reveal consistent gaps across multiple clinical populations. Therefore, the objective of this review was to systematically characterize prominent measures used in both sets of clinical populations with regard to (1) location of task performance around the body, (2) possible grips employed, (3) bilateral versus unilateral task participation, and (4) details of scoring mechanisms. A systematic literature search was conducted in EMBASE, Medline, and Cumulative Index to Nursing and Allied Health electronic databases for variations of the following terms: stroke, musculoskeletal dysfunction, amputation, prosthesis, upper limb, outcome, assessments. Articles were included if they described performance-based OMs developed for disabilities of the UL. Results show most tasks were performed with 1 hand in the space directly in front of the participant. The tip, tripod, and cylindrical grips were most commonly used for the specific tasks. Few measures assessed sensation and movement quality. Overall, several limitations in OMs were identified. The solution to these limitations may be to modify and validate existing measures originally developed for other clinical populations as first steps to more aptly measure prosthesis use while more complete assessments for UL prosthesis users are being developed.

LEVEL OF EVIDENCE

Level III.

Identifying classifier input signals to predict a cross-slope during transtibial amputee walking

Advanced prosthetic foot designs often incorporate mechanisms that adapt to terrain changes in real-time to improve mobility. Early identification of terrain (e.g., cross-slopes) is critical to appropriate adaptation. This study suggests that a simple classifier based on linear discriminant analysis can accurately predict a cross-slope encountered (0°, -15°, 15°) using measurements from the residual limb, primarily from the prosthesis itself. The classifier was trained and tested offline using motion capture and in-pylon sensor data collected during walking trials in mid-swing and early stance. Residual limb kinematics, especially measurements from the foot, shank and ankle, successfully predicted the cross-slope terrain with high accuracy (99%). Although accuracy decreased when predictions were made for test data instead of the training data, the accuracy was still relatively high for one input signal set (>89%) and moderate for three others (>71%). This suggests that classifiers can be designed and generalized to be effective for new conditions and/or subjects. While measurements of shank acceleration and angular velocity from only in-pylon sensors were insufficient to accurately predict the cross-slope terrain, the addition of foot and ankle kinematics from motion capture data allowed accurate terrain prediction. Inversion angular velocity and foot vertical velocity were particularly useful. As in-pylon sensor data and shank kinematics from motion capture appeared interchangeable, combining foot and ankle kinematics from prosthesis-mounted sensors with shank kinematics from in-pylon sensors may provide enough information to accurately predict the terrain.

The experiences of people with diabetes-related lower limb amputation at the Komfo Anokye Teaching Hospital (KATH) in Ghana

OBJECTIVE

Lower limb amputation not only causes major disfigurement, but renders people less mobile and at risk of loss of independence. Yet with appropriate rehabilitation, many people can learn to walk or function again and live high quality lives. This study sought to explore the experiences of patients with diabetes-related lower limb amputation at the Komfo Anokye Teaching Hospital. An exploratory study design was adopted using a qualitative approach and a purposive sampling to select 10 participants for the study. A semi-structured interview guide was used with an in-depth face-to-face interview. The interview was tape-recorded with an audio recorder while notes were taken in addition to the audio recording.

RESULTS

There were varying degrees of experiences ranging from physical as well as psychological and economic challenges. Amputees had to cope with playing entirely new roles after the amputation. They also experienced some economic challenges which were as a result of their inability to work. Some of the amputees consoled themselves with the fact that, despite their condition, they were better than other people. Others believed that whatever happened was Gods doing and nothing could be done about it. This self-consolation and the belief in God helped them to cope.

Sockets for Limb Prostheses: A Review of Existing Technologies and Open Challenges

In the prosthetics field, one of the most important bottlenecks is still the human-machine interface, namely the socket. Indeed, a large number of amputees still rejects prostheses or points out a low satisfaction level, due to a sub-optimal interaction between the socket and the residual limb tissues. The aim of this paper is to describe the main parameters (displacements, stress, volume fluctuations and temperature) affecting the stump-socket interface and reducing the comfort/stability of limb prostheses. In this review, a classification of the different socket types proposed in the literature is reported, together with an analysis of advantages and disadvantages of the different solutions, from multiple viewpoints. The paper then describes the technological solutions available to face an altered distribution of stresses on the residual limb tissues, volume fluctuations affecting the stump overtime and temperature variations affecting the residual tissues within the socket. The open challenges in this research field are highlighted and the possible future routes are discussed, towards the ambitious objective of achieving an advanced socket able to self-adapt in real-time to the complex interplay of factors affecting the stump, during both static and dynamic tasks.

The effects of prosthetic foot stiffness on transtibial amputee walking mechanics and balance control during turning

BACKGROUND

Little evidence exists regarding how prosthesis design characteristics affect performance in tasks that challenge mediolateral balance such as turning. This study assesses the influence of prosthetic foot stiffness on amputee walking mechanics and balance control during a continuous turning task.

METHODS

Three-dimensional kinematic and kinetic data were collected from eight unilateral transtibial amputees as they walked overground at self-selected speed clockwise and counterclockwise around a 1-meter circle and along a straight line. Subjects performed the walking tasks wearing three different ankle-foot prostheses that spanned a range of sagittal- and coronal-plane stiffness levels.

FINDINGS

A decrease in stiffness increased residual ankle dorsiflexion (10-13°), caused smaller adaptations (<5°) in proximal joint angles, decreased residual and increased intact limb body support, increased residual limb propulsion and increased intact limb braking for all tasks. While changes in sagittal-plane joint work due to decreased stiffness were generally consistent across tasks, effects on coronal-plane hip work were task-dependent. When the residual limb was on the inside of the turn and during straight-line walking, coronal-plane hip work increased and coronal-plane peak-to-peak range of whole-body angular momentum decreased with decreased stiffness.

INTERPRETATION

Changes in sagittal-plane kinematics and kinetics were similar to those previously observed in straight-line walking. Mediolateral balance improved with decreased stiffness, but adaptations in coronal-plane angles, work and ground reaction force impulses were less systematic than those in sagittal-plane measures. Effects of stiffness varied with the residual limb inside versus outside the turn, which suggests that actively adjusting stiffness to turn direction may be beneficial.

Comparison of six electromyography acquisition setups on hand movement classification tasks

Hand prostheses controlled by surface electromyography are promising due to the non-invasive approach and the control capabilities offered by machine learning. Nevertheless, dexterous prostheses are still scarcely spread due to control difficulties, low robustness and often prohibitive costs. Several sEMG acquisition setups are now available, ranging in terms of costs between a few hundred and several thousand dollars. The objective of this paper is the relative comparison of six acquisition setups on an identical hand movement classification task, in order to help the researchers to choose the proper acquisition setup for their requirements. The acquisition setups are based on four different sEMG electrodes (including Otto Bock, Delsys Trigno, Cometa Wave + Dormo ECG and two Thalmic Myo armbands) and they were used to record more than 50 hand movements from intact subjects with a standardized acquisition protocol. The relative performance of the six sEMG acquisition setups is compared on 41 identical hand movements with a standardized feature extraction and data analysis pipeline aimed at performing hand movement classification. Comparable classification results are obtained with three acquisition setups including the Delsys Trigno, the Cometa Wave and the affordable setup composed of two Myo armbands. The results suggest that practical sEMG tests can be performed even when costs are relevant (e.g. in small laboratories, developing countries or use by children). All the presented datasets can be used for offline tests and their quality can easily be compared as the data sets are publicly available.

When to biomechanically examine a lower-limb amputee: A systematic review of accommodation times

BACKGROUND

Hundreds of investigations examining biomechanical outcomes of various prostheses have been completed, but one question remains unanswered: how much time should an amputee be given to accommodate to a new prosthesis prior to biomechanical testing?

OBJECTIVE

To examine the literature for accommodation time given during biomechanical investigations to determine whether consensus exists.

STUDY DESIGN

Systematic review.

METHODS

A systematic search was completed on 7 January 2016 using PubMed and Scopus.

RESULTS

The search resulted in 156 investigations. Twenty-eight studies did not provide an accommodation or were unclear (e.g. provided a "break in period"), 5 studies tested their participants more than once, 25 tested only once and on the same day participants received a new prosthesis (median (range): above-knee: 60 (10-300) min; below-knee: 18 (5-300) min), and 98 tested once and gave a minimum of 1 day for accommodation (hip: 77 (60-180) days; above-knee: 42 (1-540) days; below-knee: 21 (1-475) days).

CONCLUSION

The lack of research specifically examining accommodation and the high variability in this review's results indicates that it remains undecided how much accommodation is necessary. There is a need for longitudinal biomechanical investigations to determine how outcomes change as amputees accommodate to a new prosthesis. Clinical relevance The results of this review indicate that little research has been done regarding lower-limb amputees accommodating to a new prosthesis. Improper accommodation could lead to increased variability in results, results that are not reflective of long-term use, and could cause clinicians to make inappropriate decisions regarding a prosthesis.

The use of a direct manufacturing prosthetic socket system in a rural community in South Africa: A pilot study and lessons for future research

BACKGROUND

Challenges exist with the provision of appropriate mobility assistive devices in rural areas. The use of the direct manufacturing prosthetic socket system is a possible solution to these challenges.

OBJECTIVES

The objective of this study was to test and explore the clients' perspectives with the application of this device.

STUDY DESIGN

Within a mixed-methods approach, a longitudinal sequential explanatory design was applied.

METHODS

The Orthotic and Prosthetic User's Survey was administered to explore the use of the direct manufacturing prosthetic socket system in terms of function, health-related quality of life and client satisfaction. A conveniently selected sample of 21 individuals who suffered a unilateral trans-tibial amputation was included. Data were collected at 1, 3 and 6 months post fitting, and two focus group discussions were also administered.

RESULTS

Of the 21 participants recruited, 11 returned for follow up. Although participants reported favourably about the prosthesis, their scores were generally worse than the norms with regard to function and quality of life. Participants highlighted the need for improvement in the cosmetic appearance of the prosthesis.

CONCLUSION

The direct manufacturing prosthetic socket system could be considered as an alternative technique of socket manufacturing for individuals living in rural areas due to the shorter manufacture time and promising initial results, but further research on this topic with a bigger sample is recommended. Clinical relevance The direct manufacturing prosthetic socket system may be considered as an alternative to the traditional prosthetic socket manufacturing technique used in South Africa. As this device requires only one visit and therefore decreased travel by the patients to the hospitals, it could be applicable to more amputees who cannot return to hospital post discharge.

A lightweight robotic ankle prosthesis with non-backdrivable cam-based transmission

Below-knee level amputation significantly impacts the ability of an individual to ambulate. Transtibial amputees are typically prescribed energetically passive ankle-foot prostheses that behave as a spring or controlled damper, and therefore cannot fully replace the function of the missing limb. More recently, fully-powered devices have been proposed to more closely match the power generation ability of intact limbs. However, these fully-powered devices are significantly heavier than passive devices, thus increasing the stress on the socket-residual limb interface. An alternative solution consists of using a motorized mechanism to actively reposition the foot during non-weight-bearing phases. By using this approach, the Össur© PROPRIO FOOT® showed promising outcomes such as improved gait energetics at self-selected speed, symmetry, and comfort. However, this device cannot be used by many transtibial amputees due to large build height (180 mm). Moreover, its weight has been shown critical for socket suspension. To address these limitations, we propose a novel non-backdrivable cam-based transmission. Based on this novel transmission, we developed a compact, lightweight ankle foot prosthesis. Bench-top testing and preliminary experiments with an able-bodied subject show that the proposed design can actively reposition the foot in swing as necessary to increase foot clearance, while adapting the ankle position to the ground inclination in stance.

Across-user adaptation for a powered lower limb prosthesis

Pattern recognition algorithms have been used to control powered lower limb prostheses because they are capable of identifying the intent of the amputee user and therefore can provide a method for seamlessly transitioning between the different locomotion modes of the prosthesis. However, one major limitation of current algorithms is that they require subject-specific data from the individual user. These data are difficult and time-consuming to collect and consequently these algorithms do not generalize well across users. We have developed an adaptive pattern recognition algorithm that automatically learns new subject-specific data acquired from a novel user during ambulation. We tested this adaptive algorithm with one transfemoral amputee subject walking on a powered knee-ankle prosthesis. Before adaptation, the algorithm, which was initially trained with data from two other transfemoral amputee subjects, made critical errors that prevented continuous ambulation. With adaptation, error rates dropped from 4.21% before adaptation to 1.25% after adaptation, and allowed the novel amputee user to complete all mode transitions. This study demonstrates that adaptation can decrease error rates over time and can allow pattern recognition algorithms to generalize to novel users.

Longitudinal high-density EMG classification: Case study in a glenohumeral TMR subject

Targeted muscle reinnervation (TMR) represents a breakthrough interface for prosthetic control in high-level upper-limb amputees. However, clinically, it is still limited to the direct motion-wise control restricted by the number of reinnervation sites. Pattern recognition may overcome this limitation. Previous studies on EMG classification in TMR patients experienced with myocontrol have shown greater accuracy when using high-density (HD) recordings compared to conventional single-channel derivations. This case study investigates the potential of HD-EMG classification longitudinally over a period of 17 months post-surgery in a glenohumeral amputee. Five experimental sessions, separated by approximately 3 months, were performed. They were timed during a standard rehabilitation protocol that included intensive physio- and occupational therapy, myosignal training, and routine use of the final myoprosthesis. The EMG signals recorded by HD-EMG grids were classified into 12 classes. The first sign of EMG activity was observed in the second experimental session. The classification accuracy over 12 classes was 76% in the third session and ∼95% in the last two sessions. When using training and testing sets that were acquired with a 1-h time interval in between, a much lower accuracy (32%, Session 4) was obtained, which improved upon prosthesis usage (Session 5, 67%). The results document the improvement in EMG classification accuracy throughout the TMR-rehabilitation process.