Sensitivity to temporal parameters of intraneural tactile sensory feedback

BACKGROUND

Recent studies have shown that neural stimulation can be used to provide artificial sensory feedback to amputees eliciting sensations referred on the amputated hand. The temporal properties of the neural stimulation modulate aspects of evoked sensations that can be exploited in a bidirectional hand prosthesis.

METHODS

We previously collected evidence that the derivative of the amplitude of the stimulation (intra-digit temporal dynamics) allows subjects to recognize object compliance and that the time delay among stimuli injected through electrodes implanted in different nerves (inter-digit temporal distance) allows to recognize object shapes. Nevertheless, a detailed characterization of the subjects' sensitivity to variations of intra-digit temporal dynamic and inter-digit temporal distance of the intraneural tactile feedback has not been executed. An exhaustive understanding of the overall potentials and limits of intraneural stimulation to deliver sensory feedback is of paramount importance to bring this approach closer and closer to the natural situation. To this aim, here we asked two trans-radial amputees to identify stimuli with different temporal characteristics delivered to the same active site (intra-digit temporal Dynamic Recognition (DR)) or between two active sites (inter-digit Temporal distance Recognition (TR)). Finally, we compared the results achieved for (simulated) TR with conceptually similar experiments with real objects with one subject.

RESULTS

We found that the subjects were able to identify stimuli with temporal differences (perceptual thresholds) larger than 0.25 s for DR and larger than 0.125 s for TR, respectively. Moreover, we also found no statistically significant differences when the subjects were asked to identify three objects during simulated 'open-loop' TR experiments or real 'closed-loop' tests while controlling robotic hand.

CONCLUSIONS

This study is a new step towards a more detailed analysis of the overall potentials and limits of intraneural sensory feedback. A full characterization is necessary to develop more advanced prostheses capable of restoring all lost functions and of being perceived more as a natural limb by users.

Estimated forces and moments experienced by osseointegrated endoprostheses for lower extremity amputees

BACKGROUND

Percutaneous osseointegrated (OI) docking of prosthetic limbs returns loading directly to the residual bone of individuals with amputations. Lower limb diaphyseal biomechanics have not been studied during the wide range of daily activities performed by individuals with lower extremity amputations; therefore, little is known about the loads experienced at the bone-endoprosthetic interface of a percutaneous OI device.

RESEARCH QUESTION

Does residual limb length and/or gender influence loading magnitudes in the diaphysis of the femur or tibia during daily activities?

METHODS

This observational study used motion capture data from 40 non-amputee volunteers performing nine activities ranging from low to high demand, to virtually simulate residual limbs of amputees. To simulate diaphyseal bone loading in individuals with lower limb amputations, virtual joints were defined during post-processing at 25, 50, and 75 % of residual limb length of both the femur and the tibia, representing six clinically relevant residual limb lengths for OI device placement. Peak axial distractive and compressive forces, torsional moments, and bending moments were calculated for each activity. Comparisons were made between genders and between different levels of the simulated residual limb.

RESULTS

For simulated above and below knee amputations, short residual limbs showed the highest average bending, torsion, and axial distractive loads, while axial compressive loads were highest for long residual limbs. Absolute maxima for all subjects showed this same trend, except in below knee torsion, where 75 % residual tibia length showed the maximum. The highest demand activities yielding peaks in all directions were cutting with right leg planted, jump, run, and fall.

SIGNIFICANCE

Overall, individuals with shorter residual limbs experienced higher diaphyseal forces. This should be taken into consideration during surgical implantation of percutaneous OI devices where residual limb length can potentially be shortened, and during rehabilitation of percutaneous OI patients.

User-relevant factors determining prosthesis choice in persons with major unilateral upper limb defects: A meta-synthesis of qualitative literature and focus group results

OBJECTIVE

Considering the high rejection rates of upper limb prostheses, it is important to determine which prosthesis fits best the needs of each user. The introduction of the multi-grip prostheses hands (MHP), which have functional advantages but are also more expensive, has made prosthesis selection even harder. Therefore, we aimed to identify user opinions on factors determining prosthesis choice of persons with major unilateral upper limb defects in order to facilitate a more optimal fit between user and prosthesis.

METHODS

A qualitative meta-synthesis using a 'best-fit framework' approach was performed by searching five databases (PROSPERO registration number: CRD42019126973). Studies were considered eligible if they contained qualitative content about adults with major unilateral upper limb defects experienced in using commercially available upper limb prostheses and focused on upper limb prosthesis users' opinions. Results of the meta-synthesis were validated with end-users (n = 11) in a focus group.

RESULTS

Out of 6247 articles, 19 studies were included. An overview of six main themes ('physical', 'activities and participation', 'mental', 'social', 'rehabilitation, cost and prosthetist services' and 'prosthesis related factors') containing 86 subthemes that could affect prosthesis choice was created. Of these subthemes, 19 were added by the focus group. Important subthemes were 'work/school', 'functionality' and 'reactions from public'. Opinions of MHP-users were scarce. MHPs were experienced as more dexterous and life-like but also as less robust and difficult to control.

CONCLUSION

The huge number of factors that could determine upper limb prosthesis choice explains that preferences vary greatly. The created overview can be of great value to identify preferences and facilitate user-involvement in the selection process. Ultimately, this may contribute to a more successful match between user and prosthesis, resulting in a decrease of abandonment and increase of cost-effectiveness.

Online Reinforcement Learning Control for the Personalization of a Robotic Knee Prosthesis

Robotic prostheses deliver greater function than passive prostheses, but we face the challenge of tuning a large number of control parameters in order to personalize the device for individual amputee users. This problem is not easily solved by traditional control designs or the latest robotic technology. Reinforcement learning (RL) is naturally appealing. The recent, unprecedented success of AlphaZero demonstrated RL as a feasible, large-scale problem solver. However, the prosthesis-tuning problem is associated with several unaddressed issues such as that it does not have a known and stable model, the continuous states and controls of the problem may result in a curse of dimensionality, and the human-prosthesis system is constantly subject to measurement noise, environmental change and human-body-caused variations. In this paper, we demonstrated the feasibility of direct heuristic dynamic programming, an approximate dynamic programming (ADP) approach, to automatically tune the 12 robotic knee prosthesis parameters to meet individual human users' needs. We tested the ADP-tuner on two subjects (one able-bodied subject and one amputee subject) walking at a fixed speed on a treadmill. The ADP-tuner learned to reach target gait kinematics in an average of 300 gait cycles or 10 min of walking. We observed improved ADP tuning performance when we transferred a previously learned ADP controller to a new learning session with the same subject. To the best of our knowledge, our approach to personalize robotic prostheses is the first implementation of online ADP learning control to a clinical problem involving human subjects.

The future of upper extremity rehabilitation robotics: research and practice

The loss of upper limb motor function can have a devastating effect on people's lives. To restore upper limb control and functionality, researchers and clinicians have developed interfaces to interact directly with the human body's motor system. In this invited review, we aim to provide details on the peripheral nerve interfaces and brain-machine interfaces that have been developed in the past 30 years for upper extremity control, and we highlight the challenges that still remain to transition the technology into the clinical market. The findings show that peripheral nerve interfaces and brain-machine interfaces have many similar characteristics that enable them to be concurrently developed. Decoding neural information from both interfaces may lead to novel physiological models that may one day fully restore upper limb motor function for a growing patient population.

Prediction of gait intention from pre-movement EEG signals: a feasibility study

BACKGROUND

Prediction of Gait intention from pre-movement Electroencephalography (EEG) signals is a vital step in developing a real-time Brain-computer Interface (BCI) for a proper neuro-rehabilitation system. In that respect, this paper investigates the feasibility of a fully predictive methodology to detect the intention to start and stop a gait cycle by utilizing EEG signals obtained before the event occurrence.

METHODS

An eight-channel, custom-made, EEG system with electrodes placed around the sensorimotor cortex was used to acquire EEG data from six healthy subjects and two amputees. A discrete wavelet transform-based method was employed to capture event related information in alpha and beta bands in the time-frequency domain. The Hjorth parameters, namely activity, mobility, and complexity, were extracted as features while a two-sample unpaired Wilcoxon test was used to get rid of redundant features for better classification accuracy. The feature set thus obtained was then used to classify between 'walk vs. stop' and 'rest vs. start' classes using support vector machine (SVM) classifier with RBF kernel in a ten-fold cross-validation scheme.

RESULTS

Using a fully predictive intention detection system, 76.41±4.47% accuracy, 72.85±7.48% sensitivity, and 79.93±5.50% specificity were achieved for 'rest vs. start' classification. While for 'walk vs. stop' classification, the obtained mean accuracy, sensitivity, and specificity were 74.12±4.12%, 70.24±6.45%, and 77.78±7.01% respectively. Overall average True Positive Rate achieved by this methodology was 72.06±8.27% with 1.45 False Positives/min.

CONCLUSION

Extensive simulations and resulting classification results show that it is possible to achieve statistically similar intention detection accuracy using either only pre-movement EEG features or trans-movement EEG features. The classifier performance shows the potential of the proposed methodology to predict human movement intention exclusively from the pre-movement EEG signal to be applied in real-life prosthetic and neuro-rehabilitation systems.

The Utility of the 2-Minute Walk Test as a Measure of Mobility in People With Lower Limb Amputation

OBJECTIVES

To establish reference values for the 2-minute walk test (2-MWT) distance and gait speed in people with a lower limb amputation (LLA) who are prosthetic ambulators. Also, to describe the differences in distance and gait speed between sexes, causes of amputation, levels of amputation, health risk classification, functional levels, and age groups.

DESIGN

Cross-sectional study.

SETTING

National meeting for people with lower limb amputation.

PARTICIPANTS

A convenience sample of unilateral people (N=101; 47 men, 54 women; mean age ± SD, 50.9±14.3 y) with an LLA; 48 had a transtibial amputation and 53 had a transfemoral amputation. Participants were classified as either limited community ambulators, community ambulators, or those who exceed basic ambulation skills (K2, n=7; K3, n=70; K4, n=24).

INTERVENTION

Not applicable.

MAIN OUTCOME MEASURE

2-MWT performance (ie, distance and gait speed).

RESULTS

The mean ± SD 2-MWT distance and gait speed for the entire sample was 143.8±37.5 meters (range, 49-259 m) and 72.1±18.8 meters per minute (range, 25-130 m/min), respectively. Men walked farther (distance: men, 154.2±34.2 m; women, 134.4±38.1 m) and faster (gait speed: men, 77.3±17.1 m/min; women, 67.4±19.1 m/min) than women (P<.05). The mean ± SD 2-MWT distance for K4, K3, and K2 level participants was 177.9±31.1 meters, 138.4±28.5 meters, and 81.7±26.9 meters, respectively. Functional level K4 participants performed better than K3 participants (P<.05), and K3 participants performed better than K2 participants (P<.05). People with transtibial amputation walked farther than those with transfemoral amputation (152.9±43.0 m vs 135.6±43.0 m) (P<.05). The distance and speed ambulated by those participants classified in the very high health risk group was worse than those categorized as being at an increased high health risk group (P<.05) and the no increase health risk group (P<.05). The performance of participants older than 70 years old was inferior to the performance of all younger age groups.

CONCLUSIONS

Reference values for the 2-MWT distance and gait speed were established in people with LLA who are prosthetic ambulators. Significant differences in the 2-MWT performance were found between sexes, causes of amputation, levels of amputation, health risk classification, functional levels, and age groups.

Differences in muscle synergies between healthy subjects and transfemoral amputees during normal transient-state walking speed

BACKGROUND

Lower limb amputation is a major public health issue globally, and its prevalence is increasing significantly around the world. Previous studies on lower limb amputees showed analogous complexity implemented by the neurological system which does not depend on the level of amputation.

RESEARCH QUESTION

What are the differences in muscle synergies between healthy subjects (HS) and transfemoral amputees (TFA) during self-selected normal transient-state walking speed?

METHODS

thirteen male HS and eleven male TFA participated in this study. Surface electromyography (sEMG) data were collected from HS dominant leg and TFA intact limb. Concatenated non-negative matrix factorization (CNMF) was used to extract muscle synergy components synergy vectors (S) and activation coefficient profiles (C). Correlation between a pair of synergy vectors from HS and TFA was analyzed by means of the coefficient of determination (R²). Statistical parametric mapping (SPM) was used to compare the temporal components of the muscle synergies between groups.

RESULTS

the highest correlation was perceived in synergy 2 (S2) and 3 (S3) and the lowest in synergy 1 (S1) and 4 (S4) between HS and TFA. Statistically significant differences were observed in all of the activation coefficients, particularly during the stance phase. Significant lag in the activation coefficient of S2 (due mainly to activated plantarflexors) resulted in a statistically larger portion of the gait cycle (GC) in stance phase in TFA.

SIGNIFICANCE

Understanding the activation patterns of lower limb amputees' muscles that control their intact leg (IL) and prosthetic leg (PL) joints could lead to greater knowledge of neuromuscular compensation strategies in amputees. Studying the low-dimensional muscle synergy patterns in the lower limbs can further this understanding. The findings in this study could contribute to improving gait rehabilitation of lower limb amputees and development of the new generation of prostheses.

Kinematic analysis of motor learning in upper limb body-powered bypass prosthesis training

Motor learning and compensatory movement are important aspects of prosthesis training yet relatively little quantitative evidence supports our current understanding of how motor control and compensation develop in the novel body-powered prosthesis user. The goal of this study is to assess these aspects of prosthesis training through functional, kinematic, and kinetic analyses using a within-subject paradigm compared across two training time points. The joints evaluated include the left and right shoulders, torso, and right elbow. Six abled-bodied subjects (age 27 ± 3) using a body-powered bypass prosthesis completed the Jebsen-Taylor Hand Function Test and the targeted Box and Blocks Test after five training sessions and again after ten sessions. Significant differences in movement parameters included reduced times to complete tasks, reduced normalized jerk for most joints and tasks, and more variable changes in efficiency and compensation parameters for individual tasks and joints measured as range of motion, maximum angle, and average moment. Normalized jerk, joint specific path length, range of motion, maximum angle, and average moment are presented for the first time in this unique training context and for this specific device type. These findings quantitatively describe numerous aspects of motor learning and control in able-bodied subjects that may be useful in guiding future rehabilitation and training of body-powered prosthesis users.

Impedance Control Strategies for Enhancing Sloped and Level Walking Capabilities for Individuals with Transfemoral Amputation Using a Powered Multi-Joint Prosthesis

INTRODUCTION

Powered prostheses are a promising new technology that may help people with lower-limb loss improve their ability to perform locomotion tasks. Developing active prostheses requires robust design methodologies and intelligent controllers to appropriately provide assistance to the user for varied tasks in different environments. The purpose of this study was to validate an impedance control strategy for a powered knee and ankle prosthesis using an embedded sensor suite of encoders and a six-axis load cell that would aid an individual in performing common locomotion tasks, such as level walking and ascending/descending slopes.

MATERIALS AND METHODS

Three amputees walked on a treadmill and four amputees walked on a ramp circuit to test whether a dual powered knee and ankle prosthesis could generate appropriate device joint kinematics across users.

RESULTS

Investigators found that tuning 2-3 subject-specific parameters per ambulation mode was necessary to render individualized assistance. Furthermore, the kinematic profiles demonstrate invariance to walking speeds ranging from 0.63 to 1.07 m/s and incline/decline angles ranging from 7.8° to 14°.

CONCLUSION

This work presents a strategy that requires minimal tuning for a powered knee & ankle prosthesis that scales across a nominal range of both walking speeds and ramp slopes.

Knee joint biomechanics in transtibial amputees in gait, cycling, and elliptical training

Transtibial amputees may experience decreased quality of life due to increased risk of knee joint osteoarthritis (OA). No prior studies have compared knee joint biomechanics for the same group of transtibial amputees in gait, cycling, and elliptical training. Thus, the goal of this study was to identify preferred exercises for transtibial amputees in the context of reducing risk of knee OA. The hypotheses were: 1) knee biomechanics would differ due to participant status (amputee, control), exercise, and leg type (intact, residual) and 2) gait kinematic parameters would differ due to participant status and leg type. Ten unilateral transtibial amputee and ten control participants performed exercises while kinematic and kinetic data were collected. Two-factor repeated measures analysis of variance with post-hoc Tukey tests and non-parametric equivalents were performed to determine significance. Maximum knee compressive force, extension torque, and abduction torque were lowest in cycling and highest in gait regardless of participant type. Amputee maximum knee extension torque was higher in the intact vs. residual knee in gait. Amputee maximum knee flexion angle was higher in the residual vs. intact knee in gait and elliptical. Gait midstance knee flexion angle timing was asymmetrical for amputees and knee angle was lower in the amputee residual vs. control non-dominant knees. The results suggest that cycling, and likely other non-weight bearing exercises, may be preferred exercises for amputees due to significant reductions in biomechanical asymmetries and joint loads.

Osseointegrated Prosthetic Implants for People With Lower-Limb Amputation: A Health Technology Assessment

BACKGROUND

Osseointegrated prosthetic implants are biocompatible metal devices that are inserted into the residual bone to integrate with the bone and attach to the external prosthesis, eliminating the need for socket prostheses and the problems that may accompany their use. We conducted a health technology assessment of osseointegrated prosthetic implants, compared with conventional socket prostheses, for people with lower-limb amputation who experience chronic problems with their prosthetic socket, leading to prosthesis intolerance and reduced mobility. Our analysis included an evaluation of effectiveness, safety, cost-effectiveness, the budget impact of publicly funding osseointegrated prosthetic implants, and patient preferences and values.

METHODS

We performed a systematic literature search of the clinical evidence on the safety and effectiveness of the latest iterations of three implant systems: the Osseointegrated Prostheses for the Rehabilitation of Amputees (OPRA) Implant System, the Endo-Exo-Femur-Prosthesis, and the Osseointegration Group of Australia-Osseointegration Prosthetic Limb (OGAP-OPL). We assessed the risk of bias of individual studies and determined the quality of the body of evidence according to the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) Working Group criteria. We performed a systematic economic literature search and conducted a cost-utility analysis with a lifetime horizon from a public payer perspective. We also analyzed the net budget impact of publicly funding osseointegrated prosthetic implants in Ontario. To contextualize the potential value of osseointegrated prosthetic implants, we spoke with people with lower-limb amputations.

RESULTS

We included nine studies in the clinical evidence review. All studies included patients with above-the-knee amputation who underwent two-stage surgery and mostly had short-term follow-up. With osseointegrated prosthetic implants, scores for functional outcomes improved significantly as measured by 6-Minute Walk Test (6MWT), Timed Up and Go (TUG) test, and Questionnaire for Persons with a Transfemoral Amputation (Q-TFA). The scores for quality of life measured by SF-36 showed significant improvement in the physical component summary but a nonsignificant decline for the mental component summary. The most frequently seen adverse event was superficial infection, occurring in about half of patients in some studies. Deep or bone infection was a serious adverse event, with variable rates among the studies depending on the length of follow-up. The treatment of deep or bone infection required long-term antibiotic use, surgical debridement, revision surgery, and implant extraction in some cases. Other adverse events included femoral bone fracture, implant breakage, issues with extramedullary parts that required replacement, and implant removal. Our assessment of the quality of the clinical evidence according to the GRADE criteria found low certainty in terms of improvement in functional outcomes, low certainty for quality of life, and high certainty of an increase in adverse events; all findings compared receiving an osseointegrated prosthetic implant with not receiving an osseointegrated prosthetic implant.In our economic model, osseointegrated prosthetic implants were found to be more effective and more expensive than having people remain users of an uncomfortable socket prosthesis. Our best estimate of the incremental cost-effectiveness ratio (ICER) for osseointegration, compared with an uncomfortable socket, was $94,987 per quality-adjusted life-year (QALY) gained. The probability of osseointegration being cost-effective was 54.2% at a willingness-to-pay value of $100,000 per QALY gained. The annual net budget impact of publicly funding osseointegrated prosthetic implants in Ontario over the next 5 years, for a small population of eligible candidates, would range from $1.5 million in year 1 to $0.6 million in year 5, for a 5-year total of $5.3 million.We interviewed 13 people with a lower-limb amputation; nine had experience with both a conventional socket prosthesis and an osseointegrated prosthetic implant, three had experience with a conventional socket prosthesis only, and one had only recently undergone amputation and had not yet chosen a prosthesis. People who had received an osseointegrated prosthetic implant said they had better mobility and quality of life than before receiving this implant but had concerns about the ongoing risk of infection and potential for problems with implant maintenance. People using a conventional socket prosthesis said cost was the only factor preventing them from undergoing an osseointegration procedure.

CONCLUSIONS

In the studies included in the clinical evidence review, most people who received osseointegrated prosthetic implants were followed for only a few years. Studies showed that functional outcomes and physical ability improved with osseointegrated prosthetic implants (GRADE: Low), but there was uncertainty about the impact of these implants on people's emotional health (GRADE: Low). Osseointegrated prosthetic implants can lead to serious adverse events such as bone infection and bone fracture in some patients, which may require additional surgeries (GRADE: High). The reference case of the primary economic evaluation represented a conservative estimate of cost-effectiveness and found osseointegration may be cost-effective, but there is a large degree of uncertainty given parameter uncertainty and the need to use proxy costs. Scenario analyses explored potential variations in approaches to modelling and parameter selection. Qualitative interviews with people with a lower-limb amputation and caregivers underscored the challenges of conventional socket prostheses, but cost remains an important barrier to pursuing osseointegrated prosthetic implantation.

Clinical evaluation of the refined clothespin relocation test: A pilot study

BACKGROUND

The refined clothespin relocation test is a test used to evaluate the performance of a prosthesis user by analysing the compensatory motions and time to complete a grasping and placement exercise. The test has been studied previously with a motion capture laboratory and has now been adapted for a clinical setting. A comparison of prosthesis user to an able-bodied group is needed to determine efficacy as an assessment tool.

OBJECTIVE

To modify the previous refined clothespin relocation test and assess whether it can distinguish between able-bodied and prosthesis users.

STUDY DESIGN

Comparative analysis.

METHODS

Forty-two able-bodied subjects and three prosthesis users completed the adapted refined clothespin relocation test protocol. Average refined clothespin relocation test scores describing the degree of compensatory movements and the time to complete the protocol were compared using a Mann-Whitney U-test.

RESULTS

A significant difference was found in the refined clothespin relocation test score between the able-bodied (Md = 65.32, n = 42) and prosthesis users (Md = 23.07, n = 3) with a medium effect size (p < 0.001, r = 0.43).

CONCLUSION

Prosthesis users demonstrated larger compensations and longer completion times, as reflected in the refined clothespin relocation test final score. The refined clothespin relocation test has the potential to be a useful clinical tool to assess user performance on a functional task.

CLINICAL RELEVANCE

This preliminary study demonstrates that the adapted protocol can distinguish between the two groups based on refined clothespin relocation test score. A future multi-centre study is required using multiple raters and comparing it with the existing outcome measures to validate the refined clothespin relocation test and determine inter-rater reliability.

Effects of extended powered knee prosthesis stance time via visual feedback on gait symmetry of individuals with unilateral amputation: a preliminary study

BACKGROUND

Establishing gait symmetry is a major aim of amputee rehabilitation and may be more attainable with powered prostheses. Though, based on previous work, we postulate that users transfer a previously-learned motor pattern across devices, limiting the functionality of more advanced prostheses. The objective of this study was to preliminarily investigate the effect of increased stance time via visual feedback on amputees' gait symmetry using powered and passive knee prostheses.

METHODS

Five individuals with transfemoral amputation or knee disarticulation walked at their self-selected speed on a treadmill. Visual feedback was used to promote an increase in the amputated-limb stance time. Individuals were fit with a commercially-available powered prosthesis by a certified prosthetist and practiced walking during a prior visit. The same protocol was completed with a passive knee and powered knee prosthesis on separate days. We used repeated-measures, two-way ANOVA (alpha = 0.05) to test for significant effects of the feedback and device factors. Our main outcome measures were stance time asymmetry, peak anterior-posterior ground reaction forces, and peak anterior propulsion asymmetry.

RESULTS

Increasing the amputated-limb stance time via visual feedback significantly improved the stance time symmetry (p = 0.012) and peak propulsion symmetry (p = 0.036) of individuals walking with both prostheses. With the powered knee prosthesis, the highest feedback target elicited 36% improvement in stance time symmetry, 22% increase in prosthesis-side peak propulsion, and 47% improvement in peak propulsion symmetry compared to a no feedback condition. The changes with feedback were not different with the passive prosthesis, and the main effects of device/ prosthesis type were not statistically different. However, subject by device interactions were significant, indicating individuals did not respond consistently with each device (e.g. prosthesis-side propulsion remained comparable to or was greater with the powered versus passive prosthesis for different subjects). Overall, prosthesis-side peak propulsion averaged across conditions was 31% greater with the powered prosthesis and peak propulsion asymmetry improved by 48% with the powered prosthesis.

CONCLUSIONS

Increasing prosthesis-side stance time via visual feedback favorably improved individuals' temporal and propulsive symmetry. The powered prosthesis commonly enabled greater propulsion, but individuals adapted to each device with varying behavior, requiring further investigation.

Comparison of the Functional Outcomes of Lower Limb Amputees with or without End-Stage Renal Disease

BACKGROUND

The potential for full rehabilitation following amputation among end-stage renal disease patients is poor.

OBJECTIVES

To evaluate the functional outcomes and survival among amputees treated with hemodialysis at the end of the rehabilitation procedure.

METHODS

We recruited 46 patients after lower limb amputation. Of these individuals, 19 (41.3%) were treated with dialysis and 27 (58.7%) were non-dialysis-dependent patients (NDDP). Both groups were divided into three sub-groups according to their independence with regard to activities of daily living (ADL) and their ability to walk with prostheses.

RESULTS

The survival of lower limb amputees treated with dialysis was shorter compared to NDDP. Survival after amputation among the NDDP who were fully or partially independent in ADL and with regard to mobility, was longer compared to the non-mobile amputees as with the patients treated with dialysis.

CONCLUSIONS

Survival was significantly longer in lower limb amputees NDDP and shorter in patients who did not achieve a certain level of functioning.

Potential Application of Virtual Reality for Interface Customisation (and Pre-training) of Amputee Patients as Preparation for Prosthetic Use

Virtual Reality has been used to great effect in the field of retraining and strengthening neural pathways in victims of serious brain injury and stroke.Meanwhile, VR visualisation of missing limbs in amputees has been used to great effect not only in the treatment of "phantom limb syndrome" but in helping amputees restore muscle tone in remaining limb sections and torso prior to fitting these areas for prosthetics.The natural next step, combining elements of both approaches, is the potential application of virtual reality to actively train the patient for using these prostheses prior to them being fitted, and furthermore adjusting and customising the prosthetic itself to the emergent needs of the patient whilst using the VR training.This raises fascinating new applications not only for virtual reality itself, but for the numerous peripheral technologies which have risen around VR. These technologies include force feedback, "haptic" sensory simulation and monitoring of muscle strength, position and movement ranges.This chapter aims to assess the capabilities of these technologies, both now and in the future.By reviewing the work of two key studies in this area this chapter aims to bring together the necessary skills and establish the collaborative crossovers (and existing precedents) which would be required to develop this application of VR in the future.

Upper Limb Prosthesis Control for High-Level Amputees via Myoelectric Recognition of Leg Gestures

Recognition of motion intent via surface electromyography (EMG) has become increasingly practical for prosthesis control, but lacking residual muscle sites remains a major obstacle to its use by high-level amputees. Currently, there are few approaches to upper limb prosthesis control for individuals with amputations proximal to the elbow, all of which suffer from one or more of three primary problems: invasiveness, the need for intensive training, and lacking functionality. Using surface EMG sensors placed on the lower leg and a natural mapping between degrees of freedom of the leg and the arm, we tested a noninvasive control approach by which high-level amputees could control prosthetic elbow, wrist, and hand movements with minimal training. In this paper, we used able-bodied subjects to facilitate a direct comparison between control using intact arm and leg muscles. First, we found that foot gestures could be classified offline using time domain features and linear discriminant analysis with accuracy comparable to an equivalent system for recognizing arm movements. Second, we used the target achievement control test to evaluate real-time control performance in three and four degrees of freedom. After approximately 20 min of training, subjects tended to perform the task as well with the leg as with intact arm muscles, and performance overall was comparable to other control methods.

Optimal integration of intraneural somatosensory feedback with visual information: a single-case study

Providing somatosensory feedback to amputees is a long-standing objective in prosthesis research. Recently, implantable neural interfaces have yielded promising results in this direction. There is now considerable evidence that the nervous system integrates redundant signals optimally, weighting each signal according to its reliability. One question of interest is whether artificial sensory feedback is combined with other sensory information in a natural manner. In this single-case study, we show that an amputee with a bidirectional prosthesis integrated artificial somatosensory feedback and blurred visual information in a statistically optimal fashion when estimating the size of a hand-held object. The patient controlled the opening and closing of the prosthetic hand through surface electromyography, and received intraneural stimulation proportional to the object's size in the ulnar nerve when closing the robotic hand on the object. The intraneural stimulation elicited a vibration sensation in the phantom hand that substituted the missing haptic feedback. This result indicates that sensory substitution based on intraneural feedback can be integrated with visual feedback and make way for a promising method to investigate multimodal integration processes.

Functional performance and safety of bone-anchored prostheses in persons with a transfemoral or transtibial amputation: a prospective one-year follow-up cohort study

OBJECTIVES:

(1) To compare level of function, activity, health-related quality of life (HRQoL) and satisfaction in persons with a lower extremity amputation before surgery and 6- and 12-months after implantation of an osseointegration implant and (2) to report adverse events.

DESIGN:

Prospective cohort study.

SETTING:

University medical centre.

SUBJECTS:

A total of 40 consecutive persons (median age: 56 years) who received a transfemoral (31) or transtibial (9) osseointegration implant, between April 2014 and March 2016.

INTERVENTION:

Osseointegration implant surgery followed by a predefined rehabilitation programme.

MAIN MEASURES:

Hip abductor strength, prosthetic use, back pain frequency, postoperative pain, mobility level (Timed-Up and Go (TUG) and wheelchair-boundedness), walking ability (6 minute walking test (6MWT) and walking distance in daily life), HRQoL, satisfaction regarding the prosthesis, and adverse events.

RESULTS:

Strength, prosthetic use, walking distance, HRQoL, and satisfaction level increased significantly at 6- and 12-month follow-up compared to baseline ( P ⩽ 0.002). The TUG showed no change at 6-month follow-up ( P = 0.420) but improved significantly at 12-month follow-up compared to baseline ( P = 0.005). Wheelchair-boundedness decreased from 12/40 participants at baseline to 0 at follow-ups. The 6MWT ( P ⩾ 0.038) and back pain ( P ⩾ 0.437) did not change over time. Stump pain was present in 28/39 and 22/40 of the participants at 6-and 12-month follow-up, respectively. The major adverse events were managed successfully and included three dual-cone breakages and four bone fractures. An uneventful course was completed by 19/31 transfemoral and 4/9 transtibial bone-anchored prostheses users.

CONCLUSION:

Bone-anchored prostheses lead to improved performance and appear to be safe, so they might be considered for persons with socket-related problems.

Towards functional restoration for persons with limb amputation: A dual-stage implementation of regenerative agonist-antagonist myoneural interfaces

While amputation has traditionally been viewed as a failure of therapy, recent developments in amputation surgery and neural interfacing demonstrate improved functionality and bidirectional communication with prosthetic devices. The agonist antagonist myoneural interface (AMI) is one such bi-directional neural communication model comprised of two muscles, an agonist and an antagonist, surgically connected in series within the amputated residuum such that contraction of one muscle stretches the other. By preserving agonist-antagonist muscle dynamics, the AMI allows proprioceptive signals from mechanoreceptors within both muscles to be communicated to the central nervous system. Preliminary human evidence suggests that AMIs have the capacity to provide high fidelity control of a prosthetic device, force feedback, and natural proprioception. However, AMIs have been implemented only in planned amputations and require healthy distal tissues, whereas the majority of amputations occur in patients who do not have healthy distal tissues. Through the use of a dual-stage surgical procedure which leverages existent tissues, this study proposes a revision model for implementation of the AMI in patients who are undergoing traumatic amputation or have already undergone a standard amputation. This paper validates the resulting AMI's physiology, revealing robust viability and mechanical and electrophysiological function. We demonstrate the presence of H-waves in regenerative grafts, indicating the incorporation of the AMI into physiological reflexive loops.

A pilot study towards long-term thermal comfort research for lower-limb prosthesis wearers

BACKGROUND:

Thermal discomfort among lower-limb prosthesis wearers is prevalent with social and medical consequences.

OBJECTIVES:

This study aimed to verify the feasibility of out-of-laboratory thermal comfort studies.

STUDY DESIGN:

Repeated measures pilot study.

METHODS:

Thermistors were placed on participants' residual limbs during two experimental phases. In phase 1, mean limb temperature was calculated over a controlled 55-min rest-exercise-rest protocol. In phase 2, participants conducted activities of their choosing wherever they wanted away from the lab, while limb temperature data were collected. Descriptive statistics and statistical differences between phases are presented.

RESULTS:

Five male amputees participated with an average age ±standard deviation of 30 ± 9 years. In phase 1, mean limb temperature change ranged between 1.6°C and 3.7°C. In phase 2, mean limb temperature change ranged between 1.8°C and 5.1°C. Limb temperature was significantly higher in out-of-lab studies (+1.9°C, p = 0.043) compared to in-lab studies.

CONCLUSION:

Independent multiple-hour temperature studies are shown to be feasible. Results also indicate that out-of-lab residual limb temperature can be significantly higher than in-lab temperatures.

CLINICAL RELEVANCE

Thermal discomfort and sweating may lead to skin conditions and reduce quality of life among prosthesis wearers. Out-of-lab, long-term temperature studies are needed to comprehensively characterize thermal discomfort to create preventive solutions.

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.