Running-specific prostheses reduce lower-limb muscle activity compared to daily-use prostheses in people with unilateral transtibial amputations

People with unilateral transtibial amputation (TTA) have biomechanical differences between the amputated and intact legs and compared to people without TTA during running. Additional biomechanical differences emerge between running with running-specific (RSPs) and daily-use prostheses (DUPs), but the associated underlying muscle activity is unclear. We collected surface electromyography from the biceps femoris long head, rectus femoris, vastus lateralis, and gastrocnemius as well as body kinematics and ground reaction forces in six people with and six people without TTA. We compared stance phase muscle activity and peak activation timing in people with and without TTA and between people using RSPs compared to DUPs during running at 3.5 m/s. Peak amputated leg hamstring activity occurred 34% (RSP) and 31% (DUP) earlier in stance phase compared to the intact leg. Peak amputated leg rectus femoris activity of people wearing DUPs occurred 8% and 9% later in stance phase than the intact leg of people wearing DUPs and amputated leg of people wearing RSPs, respectively. People with TTA had 45% (DUP) and 61% (RSP) smaller peak amputated leg knee extension moments compared to people without TTA, consistent with observations of quadriceps muscle activity. Using RSPs decreased overall muscle activity compared to DUPs.

Upper extremity prosthetic selection influences loading of transhumeral osseointegrated systems

Percutaneous osseointegrated (OI) implants are increasingly viable as an alternative to socket suspension of prosthetic limbs. Upper extremity prostheses have also become more complex to better replicate hand and arm function and attempt to recreate pre-amputation functional levels. With more functionality comes heavier devices that put more stress on the bone-implant interface, which could be an issue for implant stability. This study quantified transhumeral loading at defined amputation levels using four simulated prosthetic limb-types: (1) body powered hook, (2) myoelectric hook, (3) myoelectric hand, and (4) advanced prosthetic limb. Computational models were constructed to replicate the weight distribution of each prosthesis type, then applied to motion capture data collected during Advanced Activities of Daily Living (AADLs). For activities that did not include a handheld weight, the body powered prosthesis bending moments were 13–33% (range of means for each activity across amputation levels) of the intact arm moments (reference 100%), torsional moments were 12–15%, and axial pullout forces were 30–40% of the intact case (p≤0.001). The myoelectric hook and hand bending moments were 60–99%, torsional moments were 44–97%, and axial pullout forces were 62–101% of the intact case. The advanced prosthesis bending moments were 177–201%, torsional moments were 164–326%, and axial pullout forces were 133–185% of the intact case (p≤0.001). The addition of a handheld weight for briefcase carry and jug lift activities reduced the overall impact of the prosthetic model itself, where the body powered forces and moments were much closer to those of the intact model, and more complex prostheses further increased forces and moments beyond the intact arm levels. These results reveal a ranked order in loading magnitude according to complexity of the prosthetic device, and highlight the importance of considering the patient’s desired terminal device when planning post-operative percutaneous OI rehabilitation and training.

A Biomechatronic EPP upper-limb prosthesis controller and its performance comparison to other topologies

Historically, Classic Extended Physiological Proprioception (EPP) as an upper-limb prosthesis control topology has been outperforming functionally all other topologies of the past. A novel Biomechatronic EPP controller has been designed to overcome shortcomings of the classic EPP control topology, and has been hypothesized to be functionally equivalent to the classic EPP topology. Using the dSpace realtime hardware platform and other mechanical and electronic components, the following were developed in the lab: (a) A Biomechatronic EPP controller, (b) a classic EPP controller, (c) an "unconnected" controller and (d) an EMG controller. All four topologies were tested in the lab using the target experiments methodology. Initial results of one subject show that performance of (a) is superior or comparable to (b) and superior to (c) and (d).

Transplants for non-lethal conditions: a case against hand transplantation in minors

Human allografts for life-threatening organ failure have been demonstrated to be lifesaving and are now considered to be standard of care for many conditions. Transplantation of non-vital anatomic body parts has also been accomplished. Hand transplantation after limb loss in adults has been shown to offer some promising benefits in both functional and psychological measures in preliminary studies. It has been suggested to expand eligibility criteria to include minors, with one such operation having already been performed. With this in mind, we examine the current state of hand transplantation research in the context of available alternatives. We examine the ethics of carrying out these operations in minors, including under the protections of clinical research. We argue that children should not be considered for this surgery due to the substantial risks of immunosuppressive medication, the likelihood that the graft will need to be replaced during the patient's lifetime and the lack of significant compensatory advantages over modern prosthetics.

Evaluation of NU-FlexSIV Socket Performance for Military Service Members with Transfemoral Amputation

Ischial containment sockets are the current standard of care for military service members with transfemoral amputation. However, they fit intimately with the ischium, which may limit hip motion and contribute to proximal socket discomfort, a common complaint among prosthesis users. Subischial sockets, such as the newly described Northwestern University Flexible Subischial Vacuum (NU-FlexSIV) Socket technique, do not interact with the ischium, potentially increasing hip motion and improving comfort.

PURPOSE

To transfer the NU-FlexSIV Socket technique to military prosthetists and evaluate performance among military service members with transfemoral amputation.

STUDY DESIGN

case series.

METHODS

Four of the 11 enrolled subjects completed the study protocol comparing the NU-FlexSIV Socket to the ischial containment socket. Gait kinematics (over ground and on stairs), physical performance measures (Four-Square Step Test, T-test of Agility, and an obstacle course), limb-socket motion, and socket comfort were assessed after accommodation time in each socket.

RESULTS

While wearing the NU-FlexSIV Socket, sagittal plane hip motion generally increased while coronal plane trunk motion and walking speed remained largely unaffected during over ground walking. During stair ascent, sagittal plane hip motion increased while wearing the NU-FlexSIV Socket, with minimal changes in walking speed for all subjects. Pre- and post-walking fluoroscopy measures suggest fit of the NU-FlexSIV Socket was less affected by activity. Most subjects reported that the NU-FlexSIV Socket was more comfortable for sitting but some found it less comfortable for walking and running. Performance measure results were mixed. Although attempts were made to consistently implement the NU-FlexSIV Socket technique, some challenges were experienced.

CONCLUSIONS

The NU-FlexSIV Socket provided greater hip motion across a variety of tasks without adversely affecting other movement mechanics but did not consistently improve socket comfort. Variability in the liners and socket materials used may have contributed to variability in results. Overall, the design was a viable alternative to traditional ischial containment sockets for some individuals with transfemoral amputation.

Robo-Psychophysics: Extracting Behaviorally Relevant Features from the Output of Sensors on a Prosthetic Finger

Efforts are underway to restore sensorimotor function in amputees and tetraplegic patients using anthropomorphic robotic hands. For this approach to be clinically viable, sensory signals from the hand must be relayed back to the patient. To convey tactile feedback necessary for object manipulation, behaviorally relevant information must be extracted in real time from the output of sensors on the prosthesis. In the present study, we recorded the sensor output from a state-of-the-art bionic finger during the presentation of different tactile stimuli, including punctate indentations and scanned textures. Furthermore, the parameters of stimulus delivery (location, speed, direction, indentation depth, and surface texture) were systematically varied. We developed simple decoders to extract behaviorally relevant variables from the sensor output and assessed the degree to which these algorithms could reliably extract these different types of sensory information across different conditions of stimulus delivery. We then compared the performance of the decoders to that of humans in analogous psychophysical experiments. We show that straightforward decoders can extract behaviorally relevant features accurately from the sensor output and most of them outperform humans.

Spatial asymmetry in tactile sensor skin deformation aids perception of edge orientation during haptic exploration

Upper-limb amputees rely primarily on visual feedback when using their prostheses to interact with others or objects in their environment. A constant reliance upon visual feedback can be mentally exhausting and does not suffice for many activities when line-of-sight is unavailable. Upper-limb amputees could greatly benefit from the ability to perceive edges, one of the most salient features of 3D shape, through touch alone. We present an approach for estimating edge orientation with respect to an artificial fingertip through haptic exploration using a multimodal tactile sensor on a robot hand. Key parameters from the tactile signals for each of four exploratory procedures were used as inputs to a support vector regression model. Edge orientation angles ranging from -90 to 90 degrees were estimated with an 85-input model having an R (2) of 0.99 and RMS error of 5.08 degrees. Electrode impedance signals provided the most useful inputs by encoding spatially asymmetric skin deformation across the entire fingertip. Interestingly, sensor regions that were not in direct contact with the stimulus provided particularly useful information. Methods described here could pave the way for semi-autonomous capabilities in prosthetic or robotic hands during haptic exploration, especially when visual feedback is unavailable.

HyVE-hybrid vibro-electrotactile stimulation-is an efficient approach to multi-channel sensory feedback

An important reason for the abandonment of commercial actuated hand prostheses by the users is the lack of sensory feedback. Wearable afferent interfaces capable of providing electro- or vibro-tactile stimulation have high potential to restore the missing tactile and/or proprioceptive information to the user. By definition, these devices can elicit single modality (i.e., either vibrotactile or electrotactile) substitute sensations. In a recent research we have presented a novel approach comprising hybrid vibro-electrotactile (HyVE) combined stimulation, in order to provide multimodal sensory feedback. An important advantage of this approach is in the size of the design: the HyVE interface is much more compact than two separated single-modality interfaces, since electro- and vibro-tactile stimulators are placed one on top of the other. The HyVE approach has been previously tested in healthy subjects and has shown to provide a range of hybrid stimuli that could be properly discriminated. However, this approach has never been assessed as a method to provide multi-channel stimuli, i.e., stimuli from a variety of stimulators, mapping information from a multitude of sensors on a prosthesis. In this study, the ability of ten healthy subjects to discriminate stimuli and patterns of stimuli from four different five-channel interfaces applied on their forearms was evaluated. We showed that multiple HyVE units could be used to provide multi-channel sensory information with equivalent performance (∼95 percent for single stimuli and ∼80 percent for pattern) to single modality interfaces (vibro- or electro-tactile) larger in size and with better performance than vibrotactile interfaces (i.e., 73 percent for single stimuli and 69 percent for pattern) with the same size. These results are promising in relation to the current availability of multi-functional prostheses with multiple sensors.

Exploring teleimpedance and tactile feedback for intuitive control of the Pisa/IIT SoftHand

This paper proposes a teleimpedance controller with tactile feedback for more intuitive control of the Pisa/IIT SoftHand. With the aim to realize a robust, efficient and low-cost hand prosthesis design, the SoftHand is developed based on the motor control principle of synergies, through which the immense complexity of the hand is simplified into distinct motor patterns. Due to the built-in flexibility of the hand joints, as the SoftHand grasps, it follows a synergistic path while allowing grasping of objects of various shapes using only a single motor. The DC motor of the hand incorporates a novel teleimpedance control in which the user's postural and stiffness synergy references are tracked in real-time. In addition, for intuitive control of the hand, two tactile interfaces are developed. The first interface (mechanotactile) exploits a disturbance observer which estimates the interaction forces in contact with the grasped object. Estimated interaction forces are then converted and applied to the upper arm of the user via a custom made pressure cuff. The second interface employs vibrotactile feedback based on surface irregularities and acceleration signals and is used to provide the user with information about the surface properties of the object as well as detection of object slippage while grasping. Grasp robustness and intuitiveness of hand control were evaluated in two sets of experiments. Results suggest that incorporating the aforementioned haptic feedback strategies, together with user-driven compliance of the hand, facilitate execution of safe and stable grasps, while suggesting that a low-cost, robust hand employing hardware-based synergies might be a good alternative to traditional myoelectric prostheses.

Use of the Delphi Technique for developing national clinical guidelines for prescription of lower-limb prostheses

The aim of this project was the development of evidence- and consensus-based clinical practice guidelines for lower-limb prosthesis prescription for achieving transparency and consensus among clinicians, manufacturers, and insurance companies. This article describes a modified Delphi Technique, which is based on different methods of collecting evidence, and its role in the development of national clinical guidelines for prosthesis prescription. We used a multimethod approach to develop guidelines for the clinical practice of prosthesis prescription for lower-limb amputees. The Delphi Technique was central in the process, and the panel was made up of experts from three key disciplines on a national level. Our approach involved various methods: a systematic review, a survey of national clinical practice on prosthesis prescription, and interviews with experts. These activities resulted in 45 postulates about prosthesis prescription. The views of the national expert panel were then presented at a consensus development conference. The participants in the Delphi Technique sessions reached a consensus on 37 of the postulates on prosthesis prescription for lower-limb amputees. The postulates were categorized according to amputation level and partitioned into different domains. The total process resulted in the development of draft clinical guidelines comprising guidance for prescribing prostheses for the lower limb. The scope and applicability of these guidelines will have to be measured and evaluated in future work.

Prosthetic rehabilitation of persons with lower limb amputations due to tumour

The retrospective study was to analyse some characteristics of patients with lower limb amputations due to tumour, as well as the prosthetic rehabilitation. From 2000 to 2004, we observed 46 patients (25 men and 21 women) who were admitted prosthetic rehabilitation after a lower limb amputation due to tumours. We examined their medical documentation and recorded their general clinical status paying a special attention to the local status of the stump. The average age of patients was 51 +/- 17.11 years. Osteosarcoma was the most frequent cause in 26%. The trans-femoral amputation was in 50% and the knee disarticulation was in 8.7%. The average duration of prosthetic rehabilitation was 35 +/- 7.94 days. The average daily use of the prosthesis was 5.5 h. At the time of admission for rehabilitation, 10.9% of patients were using wheelchairs, 8.7% were using walkers and 80.4% were using two crutches to assist their walking abilities, whereas at the time of discharge 89.1% of patients used two crutches and 4.4% used one crutch for assistance, while 6.5% were able to walk unassisted. The adequate prosthetic rehabilitation in patients with lower limb amputations due to tumour is important preconditions for reintegration into the family and community.

Fatigue test of low-cost flexible-shank monolimb trans-tibial prosthesis

Monolimb refers to a kind of trans-tibial prostheses with the socket and shank moulded into one piece of thermoplastic material. If properly designed, the shank of a monolimb can deflect which may compensate for the lost ankle plantarflexion and dorsiflexion to some extent. However, provision of shank flexibility is usually accompanied by reduced structural strength of the entire prosthesis. In the recent work using finite element analysis and the Taguchi method, the dimensions of the shank for the monolimb were derived which aimed at giving high shank flexibility and reasonable strength to resist static load. Yet, fatigue testing has not been performed. Fatigue failure may happen when a relatively low level of load is applied repeatedly. This study aimed to document the fatigue life of two flexible-shank monolimbs, by applying cyclic force of 800 N at the forefoot region for 500,000 cycles. Results showed that the design of the foot bolt adaptor played an important role in the structural integrity of the monolimb. One monolimb completed the fatigue test of 500,000 cycles without visual material yield, but with 3.8 degrees change in dorsiflexion angle when the load was removed.

Quality benchmark for trans-tibial prostheses in low-income countries

Based on four series of patients (N=141) participating in clinical field testing of prosthetic feet and all provided with trans-tibial prostheses in accordance with the polypropylene component and assembly system developed by the International Committee of the Red Cross (ICRC) a series of quality benchmarks was developed and tested against historical data. The patient compliance demands were set for walking >1 km at 90 +/- 10%, non-users at 5 +/- 5%, discomfort at 10 +/- 10%, pain at 10 +/- 10%, and patient satisfaction at 90 +/- 10%. The technical performance demands were set for good socket fit at 60 +/- 10%, misalignment at 15 +/- 10%, insufficient craftsmanship at 10 +/- 10%, and requirements for socket change at 10 +/- 10%.

A picture of amputees and the prosthetic situation in Haiti

PURPOSE

The purpose of this study is to present the situation of Haitian amputees and to outline some of the major barriers in Haiti that prevent people from receiving prosthetic treatment.

METHOD

Interviews were conducted with amputees throughout Haiti using a 42-question questionnaire. Additionally, interviews were conducted with traditional healers, health care workers, and leaders of handicap associations. Each interview was manuscripted and the data were subsequently coded and analysed in the USA.

RESULTS

There are three full-time prosthetic shops and two part-time prosthetic shops in Haiti, all of which are severely limited in the scope of services they are able to provide amputees due to insufficient supplies and inadequately trained personnel. Only 25% of the 164 amputees interviewed had ever had a prosthetic limb. Typically prosthetic treatment is inaccessible and unaffordable for amputees, which prevents many from seeking treatment. The most common cause of amputation in Haiti is infection, followed by motor vehicle accidents.

CONCLUSION

There must be additional cooperation between Haitian patients, doctors, traditional healers, prosthetists, and government officials in order to provide more adequate prosthetic care. Prosthetic treatment in Haiti can be successful with cooperation of different entities, proper rehabilitation therapy, adequately trained personnel, and development of culturally appropriate limbs.

Measurement of the consistency of patellar-tendon-bearing cast rectification

The quality of fit of a trans-tibial patellar-tendon-bearing (PTB) socket may be influenced by consistency in casting, rectification or alignment. This paper quantifies, for the first time, the variations in the rectified casts between two experienced prosthetists and the variation between the rectified casts of each individual prosthetist. Prosthetists A and B observed the hand casting of a typical trans-tibial amputee. Each prosthetist was supplied with 5 previously measured duplicated plaster models. The two prosthetists rectified the supplied plaster models based on their own interpretation of basic rectification guidelines. Both prosthetists operated in isolation. The re-measured rectified plaster model data was compared with the unrectified data. The extent of rectification at each of 1800 locations per plaster model was calculated. In zones of major rectification, the mean difference between prosthetists was quantified as 2mm and the standard deviation (SD) about that mean was +/- 1mm for each prosthetist. The co-ordinates of the apex of the fibular head for the 10 modified casts indicated that the maximum variation was in the axial direction with a SD of 4.3mm for prosthetist A and a SD of 2.8mm for prosthetist B. The lengths of the 5 plaster models rectified by prosthetist A indicated a SD of 0.2mm whereas the lengths of the 5 plaster models rectified by prosthetist B indicated a SD of 2.9mm.

Reliability of the two-minute walk test in individuals with transtibial amputation

OBJECTIVE

To determine inter- and intrarater reliability of the two-minute walk test (2MWT) in individuals with transtibial amputation.

DESIGN

Prospective; test-retest method by a pair of trained physical therapists.

SETTING

Two regional amputee rehabilitation centers in Canada.

PARTICIPANTS

Thirty-three subjects (23 men, 10 women; mean age +/- standard error, 63.6+/-2.0y) with transtibial amputation; 6 in outpatient rehabilitation, 27 in inpatient rehabilitation. The most common primary diagnoses were peripheral vascular disease (n=15) and diabetes (n=11).

INTERVENTIONS

Each subject performed a total of four 2MWTs, 1 test for each rater, on 2 consecutive days at approximately the same time of day. Subjects were given at least a 20-minute rest between tests. The order of raters was randomized on the first day and reversed for the next day. The walk tests were performed in the same enclosed corridors with the same starting point for all tests. The subjects were familiar with the test or were given 1 or more practice tests at least 1 day before testing. Subjects were allowed to walk with a mobility aid of their choice. Raters used a digital stopwatch to time the tests and a calibrated wheel with a counter to measure the distance walked in meters. The raters were blinded to each other's scores.

MAIN OUTCOME MEASURE

Distance walked in 2 minutes (in meters).

RESULTS

Within-rater reliability was high (intraclass correlation coefficient [ICC],.90-.96). Between rater reliability was also high (ICC.98-.99). Analysis of variance (ANOVA) showed a significant effect for day of test (P<.001) in the inpatient group but no effect for therapist (P=.098) or for interaction of day and therapist (P=.710). Similarly, in the outpatient group, ANOVA showed a significant effect for day (P=.013) but no effect for therapist (P=.259) or interaction of day and therapist (P=.923).

CONCLUSION

Although the 2MWT showed evidence of inter- and intrarater reliability in individuals with unilateral below-knee amputation, the distance walked in 2 minutes continued to improve over time. This improvement was not solely the result of a training and learning effect.

Neuroprostheses for grasping

In recent years a number of neuroprostheses have been developed and used to assist stroke and spinal cord injured subjects to restore or improve grasping function. These neuroprostheses clearly demonstrated that the targeted group of subjects can significantly benefit from this technology and that functional electrical stimulation (FES) is a viable method for restoring or improving grasping function. In this article the FES technology is briefly explained and some of the better known neuroprostheses for grasping are discussed. Furthermore, a typical population of subjects that can benefit from this technology is indicated as well as the methodology to select and train these subjects to apply the neuroprosthesis in daily living activities. This article also provides a brief summary of the achieved results with the existing neuroprostheses for grasping and discusses some of the challenges this technology is currently facing.

Lower extremity prosthetic mobility: a comparison of 3 self-report scales

OBJECTIVE

To assess and compare the reliability and validity of the Houghton Scale, the Prosthetic Profile of the Amputee Locomotor Capabilities Index (PPA-LCI), and the Prosthetic Evaluation Questionnaire (PEQ) mobility subscale, 3 disease-specific self-report measures of functional mobility for lower extremity prosthetic mobility.

DESIGN

Four-week test-retest: 1 sample for reliability analyses, 1 sample for validity analyses.

SETTING

University-affiliated outpatient amputee clinic, in Ontario, Canada.

PARTICIPANTS

Two outpatient amputee samples (sample 1 [n = 55], for reliability analysis; sample 2 [n = 329], for validity analysis).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Test-retest of reliability and convergent validity of the 3 scales. Convergent validity and discriminative ability were also assessed after setting a priori hypotheses for 2 scales of walking performance, balance confidence, and other indicators of ambulatory ability.

RESULTS

The reliability of the PPA-LCI (intraclass correlation coefficient [ICC] = .88) was slightly higher than the Houghton Scale (ICC = .85) and the PEQ mobility subscale (ICC = .77). The PPA-LCI was prone to high ceiling effects (40%) that would limit its ability to detect improvement. Evidence for convergent validity, when compared with the 2-Minute Walk Test, Timed Up and Go, and the Activity-Specific Balance Confidence Scale, was supported as hypothesized in all the scales. Each of the scales was able to discriminate between different groups for amputation cause, walking distance, mobility device use, and automatism, with each having varying strength related to relative precision. The Houghton Scale was the only scale able to distinguish between amputation levels.

CONCLUSIONS

Reliability and validity of all the scales are acceptable for group level comparison. None of the scales had clearly superior psychometric properties compared with the others. Further research is required to assess responsiveness.

Checklist for evaluating a transtibial prosthesis

A thorough initial evaluation and ongoing follow-up are critical to an amputee's success with his or her prosthesis. A checklist is presented as a guide for the rehabilitation team to perform a clinical evaluation of a transtibial prosthesis. This evaluation is a tool to standardize the assessment process and to improve patient care.

[Significance of static prosthesis alignment for standing and walking of patients with lower limb amputation]

The influence of three alignment parameters of a transtibial prosthesis (sagittal foot position, plantar flexion, mediolateral foot position) on the load and motion of the lower extremity joints was investigated in 13 unilateral transtibial amputees. The aim was to determine whether a correlation exists between static prosthetic alignment and gait pattern that would allow an optimal biomechanical prosthetic alignment. The gait pattern was measured using kinematic, kinetic, and electromyographic methods. Statics was defined using the alignment apparatus L.A.S.A.R. Posture. The electromyogram of the m. vastus lateralis and m. biceps femoris was recorded on both sides. The motion of joints is described by joint angles. External joint moments define the mechanical loads. Alignment has almost no influence on muscle activity and joint mechanics of the contralateral leg. In contrast, prosthetic alignment affects clearly and systematically the load and motion of the knee joint during the stance phase on the ipsilateral side. The sagittal foot position influences the maximal flexion angle in the stance phase. The plantar flexion of the foot affects the temporal structure of knee motion. The mediolateral foot position causes correspondingly different varus and valgus moments acting on the knee. Swing phase motion does not depend on prosthetic alignment. The iEMG of the m. vastus lateralis is reduced. Innervation characteristics of the m. biceps femoris on the prosthetically fitted leg has completely changed. The ischiocrural muscles take over the neuromuscular action of the m. gastrocnemius to compensate for the external knee extension moment during the second part of the stance phase. Prosthetic statics determines if the knee joint is physiologically stressed in a standing posture and during walking. Statics will be correct if the anatomical knee axis of the standing amputee is located about 15 mm posterior to the load line in the sagittal plane. In the frontal plane, the load line touches the lateral patella border and strikes the middle of the foot about 5 cm anterior to the adapter. During walking, attention should be paid to performance of knee flexion in the stance phase.

The design of a finger wear simulator and preliminary results

A dual-cycle finger wear simulator has been designed, manufactured and commissioned. The simulator interspersed dynamic flexion-extension motion under light load with a heavier static 'pinch' load to a test prosthesis immersed in a lubricant heated to 37 degrees C. A validation test was undertaken on a size 2 Swanson prosthesis, leading to prosthesis failure in less than 1 million cycles. A second test was carried out on a Durham metacarpophalangeal prosthesis. After 4.8 million cycles a total wear factor for the joint of 0.60 x 10(-6) mm3/N m was calculated, with no cracks or damage visible. Both test results compare well with earlier tests undertaken on the Stokoe finger wear simulator.

Assessment of the non-linear behaviour of plastic ankle foot orthoses by the finite element method

The stiffness characteristics of plastic ankle foot orthoses (AFOs) are studied through finite element modelling and stress analysis. Particular attention is given to the modelling and prediction of non-linear AFO behaviour, which has been frequently observed in previous experimental studies but not fully addressed analytically. Both large deformation effects and material non-linearity are included in the formulation and their individual influence on results assessed. The finite element program is subsequently applied to the simulation of a series of tests designed to investigate the relation between AFO trimline location and stiffness for moderate and large rotations. Through careful consideration and identification of key modelling parameters, the developed finite element solution proves to be a reliable and effective alternative means of assessing variations of a typical plastic AFO design so that particular patient requirements could be met, in the long term.

A pilot study comparing the cognitive demand of walking for transfemoral amputees using the Intelligent Prosthesis with that using conventionally damped knees

OBJECTIVE

To compare the cognitive demand of walking when using a conventional prosthesis with that using a microprocessor-controlled prosthesis.

DESIGN

Ten unilateral transfemoral amputees wearing conventional pneumatic swing phase control (conventional prosthesis) prostheses walked on a treadmill which enforced a pattern of constantly varying speeds. The subjects simultaneously performed a simple or a complex distracting task. Following a period of accustomization, the subjects performed the same test wearing a prosthesis with microprocessor control of swing phase damping (the Intelligent Prosthesis).

OUTCOME MEASURES

The three-dimensional trajectory (sway) of a retroreflective marker attached to the forehead was measured by a video-based motion analysis system, and used as a measure of gait quality. The ratio of the sway for the complex task over the simple task (the 'automation index') was used as a measure of the degree of automation of gait.

RESULTS

No significant differences were found in the automation index between the two devices. However, the total sway for the conventional prosthesis was significantly higher. Sway during the complex distracting task was significantly higher than during the simple task.

CONCLUSIONS

The microprocessor-controlled prosthesis was not found to be less cognitively demanding than a conventional prosthesis.

Simulated feedforward neural network coordination of hand grasp and wrist angle in a neuroprosthesis

This study presents a possible solution of the general problem of coordinating muscle stimulation in a neuroprosthesis when multiarticular muscles introduce mechanical coupling between joints. In a hand-grasp neuroprosthesis, extrinsic hand muscles cross the wrist joint and introduce large wrist flexion moments during grasp. In order to control hand grasp and wrist angle independently, a controller must take the mechanical coupling into account. In simulation, we investigated the use of artificial neural networks to coordinate hand and wrist muscle stimulation. The networks were trained with data that is easily obtained experimentally. Feedforward control showed excellent hand and wrist coordination when the properties of the system were fixed and there were known external loads. Predictable disturbances (e.g., gravity acting on the hand) can be compensated by sensing arm orientation. However, since wrist angle is sensitive to unpredictable disturbances (e.g., fatigue or object weight), voluntary intervention or feedback control may be required to reduce residual errors.

Custom design in lower limb prosthetics for athletic activity

In summary, the prosthetist is the best source of information with regard to the fast-changing lower extremity prosthetics technology for sports. The needs and desires of the amputee should be outlined and balanced with the cost of the desired components and design. In many cases, one carefully designed prosthesis can serve in dual roles for everyday ambulation and certain athletic activities. In other cases, the amputee is limited severely by a prosthesis that is not designed for a specific activity. Using a prosthesis for activities that it was not designed to accommodate can cause physical injury to the amputee as well as structural failure of the device. A properly designed and fitted prosthesis can open a whole new world of activity to the amputee and helps him or her to reach the desired a vocational goals.

Computer automated design and computer automated manufacture

The introduction of computer aided design and computer aided manufacturing into the field of prosthetics and orthotics did not arrive without concern. Many prosthetists feared that the computer would provide other allied health practitioners who had little or no experience in prosthetics the ability to fit and manage amputees. Technicians in the field felt their jobs may be jeopardized by automated fabrication techniques. This has not turned out to be the case. Prosthetists who use CAD-CAM techniques are finding they have more time for patient care and clinical assessment. CAD-CAM is another tool for them to provide better care for the patients/clients they serve. One of the factors that deterred the acceptance of CAD-CAM techniques in its early stages was that of cost. It took a significant investment in software and hardware for the prosthetists to begin to use the new systems. This new technique was not reimbursed by insurance coverage. Practitioners did not have enough information about this new technique to make a sound decision on their investment of time and money. Ironically, it is the need to hold health care costs down that may prove to be the catalyst for the increased use of CAD-CAM in the field. Providing orthoses and prostheses to patients who require them is a very labor intensive process. Practitioners are looking for better, faster, and more economical ways in which to provide their services under the pressure of managed care. CAD-CAM may be the answer. The author foresees shape sensing departments in hospitals where patients would be sent to be digitized, similar to someone going for radiograph or ultrasound. Afterwards, an orthosis or prosthesis could be provided from a central fabrication facility at a remote site, most likely on the same day. Not long ago, highly skilled practitioners with extensive technical ability would custom make almost every orthosis. One now practices in an atmosphere where off-the-shelf orthoses are the standard. This reduced fabrication time, but compromised the accuracy of the fit of a custom made orthosis. Computer aided design and manufacturing has the ability to combine the accuracy of custom made with the speed and labor savings of off-the-shelf systems. This would be a substantial benefit to patients, practitioners, and third party payors as well. The field may run full circle and return to custom made systems at off-the-shelf costs. As scientific knowledge base increases and computer aided design improves, one still needs the interface between the design methodology and the patient. That interface is the prosthetist/orthotist. The clinician and the clients they serve have a lot to gain from further research in this field. If one does not lose focus on how one can improve prostheses and orthoses for the consumer, one can expect great things from the methodology of CAD-CAM. There is no question that computerization is here and will continue to influence the fields of prosthetics and orthotics.

Biomechanical evaluation of a prototype foot/ankle prosthesis

In this paper, we report on our pilot evaluation of a prototype foot/ankle prosthesis. This prototype has been designed and fabricated with the intention of providing decreased ankle joint stiffness during the middle portion of the stance phase of gait, and increased (i.e., more normal) knee range of motion during stance. Our evaluation involved fitting the existing prototype foot/ankle prosthesis, as well as a traditional solid ankle cushioned heel (SACH) foot, to an otherwise healthy volunteer with a below-knee (BK) amputation. We measured this individual's lower extremity joint kinematics and kinetics during walking using a video motion analysis system and force platform. These measurements permitted direct comparison of prosthetic ankle joint stiffness and involved side knee joint motion, as well as prosthetic ankle joint moment and power.

Clinical evaluation of a new, above-elbow, body-powered prosthetic arm: a final report

The AdVAntage Arm is an above-elbow (AE) body-powered arm designed to improve upon, and overcome, some of the major limitations of conventional prostheses. It is the result of research and development (R&D) accomplished at the Center for Engineering Design (CED), University of Utah and Sarcos Research Corporation (SRC), Salt Lake City, UT. The AdVAntage Arm was developed to provide the following main features: lightweight, independent elbow and terminal device (TD) control, and a cable recovery system for full TD actuation at any elbow position. The Department of Veterans Affairs (VA) Rehab R&D Service's Technology Transfer Section (TTS), with collaboration from the VA National Prosthetic and Sensory Aids Service (PSAS), managed a multi-center clinical evaluation of the precommercial AdVAntage Arm (the Arm). The purpose was to objectively assess and affirm the Arm's functional advantages, reliability, clinical application, and commercial readiness. Eleven VA prosthetic services served as evaluation sites with a total of 16 subjects with amputation (14 unilateral and 2 bilateral). Fifteen prosthetists provided their comments. Overall, the results demonstrated that the Arm could be fit for use by persons with transhumeral, and even with forequarter, amputation. Once the learning curve was overcome, the majority of subjects reported that the Arm offered several functional advantages over their conventional prosthesis. Its overall light weight, separation of elbow and TD function, and cable recovery system allowed opening and closure of the TD at any elbow position; resulting in a more fluid manner of use and allowing subjects to perform more activities from waist level and above (especially in the outstretched and overhead positions). At the conclusion of clinical trials, 10 subjects elected to keep the Arm for continued use. The manufacturer is committed to the commercial marketing and technical support of the arm. Based upon the clinical findings, the AdVAntage Arm was recommended for commercial production and availability, upon prescription, to appropriate veteran beneficiaries.

The design and development of a gloveless endoskeletal prosthetic hand

Current prosthetic hands, although functional, have the potential of being improved significantly. We report here the design and development of a novel prosthetic hand that is lighter in weight, less expensive, and more functional than current hands. The new prosthesis features an endoskeleton embedded in self-skinning foam that provides a realistic look and feel and obviates the need for a separate cosmetic glove. The voluntary-closing mechanism offers variable grip strength. Placement of joints at three locations (metacarpophalangeal and proximal and distal interphalangeal) within each of four fingers affords realistic finger movement. High-strength synthetic cable attached to the distal phalanx of each finger is used to effect flexion. A multiposition passive thumb provides both precision and power grips. The new prosthesis can securely grasp objects with various shapes and sizes. Compared to current hands, weight has been reduced by approximately 50%, and cable excursion required for full finger flexion by more than 50%. The new endoskeletal prosthesis requires approximately 12-24% less force input to grasp a variety of everyday objects, largely due to its adaptive grip. Production cost estimates reveal the new prosthesis to be significantly less expensive than current prosthetic hands.

Using practice led design research to develop an articulated mechanical analogy of the human hand

Contemporary prostheses have developed from small iterations on moderately successful archetypes. This has resulted in modern designs that can either be termed cosmetic or functional, with neither attribute being fully satisfied. A new strategy is needed to develop a generation of upper-limb prostheses that will integrate both cosmetic and functional requirements in a single device. It is hypothesized that design principles applicable to a new generation of prostheses will result from exploring close analogies to the human upper limb. A method of practice led design research has been adopted to explore appropriate analogies, using the production of physical models to elucidate the design problem to the design team and other interested parties. This method uses a consciously iterative approach whereby criticisms and lessons learnt in the development of early models are embodied in subsequent models. This paper describes the first iterative cycle. It includes a critical review of the devices currently available and a study of mechanical analogies to original anatomy which form two of the inputs to the development of a skeletal model hand. It details the lessons learnt from this study and concludes on the wider application of practice led design research in medical engineering.

Prosthesis satisfaction outcome measurement in pediatric limb deficiency

OBJECTIVE

To describe the development and initial psychometric properties of a new outcome measure to assess satisfaction with prosthesis in children with limb deficiencies.

DESIGN

Parents of children with limb deficiency were surveyed during routine outpatient clinic visits.

SETTING

Two outpatient pediatric clinics.

PARTICIPANTS

Ninety-seven parents of children with limb deficiency aged 1 to 17 years.

MAIN OUTCOME MEASURE

The newly developed Child Amputee Prosthetics Project-Prosthesis Satisfaction Inventory (CAPP-PSI).

RESULTS

Internal consistency reliability is high. Zero-order correlations with prosthesis wear/use patterns and with parent ratings of prosthesis appearance provide support for the construct validity of the CAPP-PSI.

CONCLUSION

The CAPP-PSI is a promising, brief, parent-administered inventory for the assessment of prosthesis satisfaction in children with limb deficiency. It may be useful in future research for predicting prosthesis wear and use patterns in this population.

Stride analysis after proximal tibial replacement

Ten patients who had undergone primary intraarticular proximal tibial replacement between April 1985 and December 1994, and had a minimum of 2 years of followup, were available for stride analysis. Mean age, time since intraarticular proximal tibial replacement, height, and weight were 23.8 years, 6.5 years, 167 cm, and 63 kg, respectively. A volunteer control group of five male patients who had undergone above knee amputation was obtained from the local community. The mean age, time since above knee amputation, height, and weight were 43.6 years, 24.1 years, 165 cm, and 70 kg, respectively. Stride analysis was performed over the central 6-m portion of a 10-m walkway at a self selected, comfortable pace. Gait velocity, stride length, cadence, and stance time symmetry were measured. Velocity after intraarticular proximal tibial replacement versus above knee amputation was 79.2 +/- 7.6 m per minute versus 71.4 +/- 5.4 m per minute. Cadence after intraarticular proximal tibial replacement versus above knee amputation was 112.4 +/- 10.6 steps per minute versus 110.1 +/- 2.4 steps per minute. There were no significant differences between stride length (1.41 +/- 0.13 m versus 1.43 +/- 0.12 m) and stance time symmetry (0.90 +/- 0.07 versus 0.87 +/- 0.11) for intraarticular proximal tibial replacement versus above knee amputation. The results suggest that endoprosthetic reconstruction resulted in a gait comparable with that after above knee amputation with an external prosthesis.

Mechanism and computer simulation of a new robot hand for potential use as an artificial hand

A prosthetic hand is essential to provide rehabilitation for individuals who lose a hand. A prosthetic hand serves two purposes: cosmetic and functional. In this paper, a prototype of the artificial hand with an emphasis on the functionality purpose is presented. A new mechanism, the NTU-Hand (NTU-Hand, patent number 107115, Taiwan, R.O.C.), which has 5 fingers with 17 degrees of freedom, has been designed and fabricated in our laboratory. Due to the special design of the mechanism, the hand has an uncoupled configuration in which each finger and joint are all individually driven. The size of the hand is almost the same as a human hand. All actuators, mechanical parts, and sensors are on the hand. The compact design makes it feasible to adapt the hand to the injured wrist. A computer simulation with three-dimensional graphics was also built to evaluate the manipulative range of the artificial hand. From the results of this simulation, the relationship between the hand and the grasped object in a specific viewpoint can be obtained.

Orthotic variants

When patients present with problems for which existing devices are not adequate, research is stimulated. However, new methods and devices must improve on the older versions and should not result in variation that is less effective than the original versions. Variants less effective than the originals will be discussed with illustrative examples. Orthoses, prostheses, and pressure-reduction techniques for the diabetic foot will be considered.

Outcome of fitting an ICEROSS prosthesis: views of trans-tibial amputees

A report of the outcome of fitting ICEROSS prostheses to trans-tibial amputees from a subregional amputee rehabilitation centre is presented. This work has mainly concentrated on obtaining patients' own views to judge advantages and disadvantages of ICEROSS compared to their previous patellar-tendon-bearing (PTB) prostheses. Sixty-nine patients were entered for this study, but the results of the study are based on 54 patients who responded. Fifteen patients (27.7%) had rejected their ICEROSS prosthesis at the time of the study. Provision of ICEROSS prostheses did not improve indoor and outdoor walking abilities in terms of distance or use of other walking aids, nor were they more comfortable to wear. An increase in sweating in the first 3 months of wearing ICEROSS was significant, but settled afterwards. The amputees considered that the rate of stump skin breakdown with ICEROSS compared to their PTB prostheses was significantly less. Walking up and down stairs was more comfortable and in general overall rating of ICEROSS prostheses they were scored significantly higher by the amputees themselves. It is concluded that appropriate patient selection is vital and in certain cases ICEROSS will provide considerable benefits to the amputees.

A comparison of energy expenditure by a high level trans-femoral amputee using the Intelligent Prosthesis and conventionally damped prosthetic limbs

Comparisons were made between the Intelligent Prosthesis (IP), Mauch and pneumatic swing phase control damping systems on the same prosthesis worn by a high level trans-femoral amputee. Speeds self selected by corridor walking (4.4-5.5 kmh-1) proved not to be sustainable for treadmill walking. Comfortable speeds were attained when the subject walked on a treadmill at 2.0, 2.6 and 3.2 kmh-1 in two tests for each prosthesis type. Oxygen uptake (VO2), cadence and heart rate were measured over 5 minute walks interspersed with rest periods. Spearman's correlation was used to test for differences between prosthesis types at each speed. At the two slower speeds no significant difference was found, but at the higher speed of 3.2 kmh-1, the IP was associated with a significantly lower VO2 (p < 0.05). A two way analysis of variance with replication (ANOVA) demonstrated a significant difference between VO2 for different limb types (p = 0.015). A square law function was fitted to the mean VO2 for each prosthesis type by the method of least squares regression. ANOVA demonstrated a significant difference between velocity coefficients for the different prosthesis types (p < 0.05). Cadence was almost constant during the period of each walk, varying by 1 step min-1 at most. However the test-retest differences in cadence were considerable. It is concluded that there was little difference in energy expenditure between prosthesis types at slower speeds, but at higher speeds (==> 3.2km h-1) the IP gave a lower oxygen uptake by about 10%.

Is body powered operation of upper limb prostheses feasible for young limb deficient children?

The investigators measured efficiencies of body powered prehensors and cable control components of prostheses available for young children. Results indicated that the cable control systems and hook type prehensors have moderate to high efficiencies, but children's body powered hands have very low efficiencies. Measures of arm and shoulder strength of 3-5 year-old limb deficient children, both on the limb deficient and sound sides, were less than that reported in the sound sides, were less than that reported in the literature for normal children. The findings were examined in relation to children's strength available compared with prosthesis strength requirements. The comparison demonstrates a way to establish measurable efficiency targets for new prehensor designs. The article includes detailed findings on children's strength, and findings on efficiencies of the prehensors and cable control systems of children's upper limb prosthses. Sample calculations may be useful to future designers of body powered prehensors for young children. A more efficient body powered hand is especially needed. Preliminary calculations indicate that the use of currently available children's voluntary opening (VO), body powered hands is not feasible, given the low strength of young limb deficient children and the low efficiencies of the VO hands. The use of voluntary closing (VC) hands may be feasible but remains to be tested.

The Peter Principle in orthopedics

Original orthopedic devices that were developed, tested, and found useful, were subsequently modified and seemingly "improved" to a point of diminished usefulness--a manifestation of the Peter Principle applied to orthopedics. The authors describe seven examples: (1) the talar-tilt inversion apparatus; (2) the patellar-tendon-bearing, below-knee amputation prosthesis; (3) the patellar-tendon-bearing orthosis; (4) the Veterans Administration Prosthetic Center's lumbosacral orthosis; (5) the partial-foot prosthesis; (6) the ankle-foot orthosis; and (7) the occipito-zygomatic cervical orthosis.

Fatigue testing of energy storing prosthetic feet

This paper describes a simple approach to the fatigue testing of prosthetic feet. A fatigue testing machine for prosthetic feet was designed as part of the programme to develop an energy storing prosthetic foot (ESPF). The fatigue tester does not simulate the loading pattern on the foot during normal walking. However, cyclic vertical loads are applied to the heel and forefoot during heel-strike and toe-off respectively, for 500,000 cycles. The maximum load applied was chosen to be 1.5 times that applied by the bodyweight of the amputee and the test frequency was chosen to be 2 Hz to shorten the test duration. Four prosthetic feet were tested: two Lambda feet (a newly developed ESPF), a Kingsley SACH foot and a Proteor SACH foot. It was found that the Lambda feet have very good fatigue properties. The Kingsley SACH foot performed better than the Proteor model, with no signs of wear at the heel. The results obtained using the simple approach was found to be comparable to the results from more complex fatigue machines which simulate the load pattern during normal walking. This suggests that simple load simulating machines, which are less costly and require less maintenance, are useful substitutes in studying the fatigue properties of prosthetic feet.

Clinical evaluation of trans-tibial prosthesis sockets: a comparison between CAD CAM and conventionally produced sockets

This study is an evaluation, from the patient's point of view, of CAD CAM prosthesis sockets compared with conventional sockets. Twenty-two trans-tibial amputees were divided into two groups. One group was provided with a CAD CAM (CAPOD) socket, the other with a conventionally made one. After one month the groups were evaluated with regard to subjective experience, the judgement of a prosthetist and a physiotherapist, social variables and objective gait parameters. Then the groups switched over to the other type of socket, and after another month a new evaluation was performed. The study design was a single-blind study. In total 175 variables were evaluated. No difference was found between the two types of socket, except for a lower number of terry cloth stockings used in the CAD CAM socket. As the standard of conventional prosthetics in Sweden is considered to be high, the results were considered as satisfactory. The quality of the CAD CAM sockets was at least at the same level as conventionally made ones.

Comparison of gait using a Multiflex foot versus a Quantum foot in knee disarticulation amputees

The subjective responses and gait patterns of unilateral knee disarticulation amputees wearing prostheses fitted first with the Multiflex foot and then with the Quantum foot were studied. Nine amputees were included in the trial. A questionnaire asked the amputees about their preference for one of the feet. Gait analysis was performed measuring temporal parameters and goniometry of hips, knees and ankles in the sagittal and frontal planes. There was a slight preference for the Quantum foot. Preference seemed not to be related to physical characteristics of the amputees nor to gait parameters. There were no differences in gait as far as the temporal factors were concerned. The main differences in the range of motion of the joints were in the frontal plane: the eversion-inversion movement of the ankle and the adduction-abduction movement of the hip. During walking at comfortable speed with the Multiflex foot the ankle and hip range of motion averaged 2.1 and 3.1 degrees respectively, less than during walking with the Quantum foot.

Lightweight prostheses for bilateral below-elbow amputees

In view of the anticipated activity of the patient and working environment, lightweight prostheses were designed for an adult female, bilateral below-elbow (BE) amputee at NIRTAR to provide the greatest degree of function. The prostheses were fabricated using lightweight materials and new techniques. Depending on the stump length there were two different types of lightweight prostheses designed and successfully used, (1) an endoskeletal BE prosthesis and (2) an exoskeletal BE prosthesis. After periodic follow-up and evaluation the function of the prostheses was found to be most satisfactory. By reducing the weight considerably compared to other available alternatives, it is more likely that the amputee will make use of the prostheses to efficiently perform various activities. The new prosthesis designs may counteract the high rejection rate of old conventional ones and the principle may be applied to the fabrication of all BE prostheses.

The CAT-CAM socket and quadrilateral socket: a comparison of energy cost during ambulation

Twenty unilateral trans-femoral amputees fitted with either the Contoured Adducted Trochanteric-Controlled Alignment Method (CAT-CAM) socket (n = 10) or the quadrilateral (QUAD) socket (n = 10), and a "non-amputee" control group (n = 10) participated in the study. Subjects meeting the following criteria were studied: healthy males between the ages of 18 and 55 years, amputation due to non-vascular pathology, an unaffected sound limb, at least six months use of the test prosthesis, and a minimal stump length of 15 cm. Subjects ambulated in two randomized trials separated by 20 minutes of rest at 2 assigned speeds: a pace reflecting normal walking speed (97 m/min = 2.5 mph) or a slower speed (48.5 m/min = 1.25 mph). Heart rate (HR) and Oxygen uptake (VO2) measured during steady state walking were analyzed via two-way ANOVA. Differences among means were further analyzed using Tukey post hoc and simple effects tests. Significant differences were observed between the control group and CAT-CAM subjects with respect to VO2 (p < 0.05) and HR (p < 0.01) at the slower speed. The control group and subjects using the QUAD socket also differed with respect to VO2 (p < 0.01) and HR (p < 0.01) at the slower pace. Faster pace required more energy expenditure (p < 0.01) and produced higher HR (p < 0.01) than slower speeds. At faster pace, a significantly higher energy expenditure in the QUAD than the CAT-CAM group was observed (p < 0.01). It is concluded that ambulating at normal pace using the CAT-CAM socket design uses less energy than when using a QUAD socket design.