Amputee Subjects Research Articles

Dynamic Balance Control (DBC) in lower leg amputee subjects; contribution of the regulatory activity of the prosthesis side

BackgroundRegaining effective postural control after lower limb amputation requires complex adaptation strategies in both the prosthesis side and the non-amputated side. The objective in this study is to determine the individual contribution of the ankle torques generated by both legs in balance control during dynamic conditions. MethodsSubjects (6 transfemoral and 8 transtibial amputees) stood on a force platform mounted on a motion platform and were instructed to stand quietly. The experiment consisted of 1 static and 3 perturbation trials of 90s duration each. The perturbation trials consisted of continuous randomized sinusoidal platform movements of different amplitude in the sagittal plane. Weight distribution during the static and dynamic perturbation trials was calculated by dividing the average vertical force below the prosthesis foot by the sum of forces below both feet. The Dynamic Balance Control represents the ratio between the stabilizing mechanism of the prosthetic leg and the stabilizing mechanism of the non-amputated leg. The stabilizing mechanism is calculated from the corrective ankle torque in response to sway. The relationship between the prosthetic ankle stiffness and the performance during the platform perturbations was calculated. FindingsAll patients showed a (non-significant) weight bearing asymmetry in favor of the non-amputated leg. The Dynamic Balance Control ratio showed that the contribution of both legs to balance control was even more asymmetrical. Moreover, the actual balance contribution of each leg was not tightly coupled to weight bearing in each leg, as was the case in healthy controls. There was a significant positive correlation between the prosthetic ankle stiffness and the Dynamic Balance Control. InterpretationThe Dynamic Balance Control provides, in addition to weight distribution, information to what extent the stabilizing mechanism of the corrective ankle torque of both legs contributes to balance control. Knowledge of the stiffness properties may optimize the prescription process of prosthetic foot in lower leg amputee subjects in relation to standing stability.

Object Discrimination With an Artificial Hand Using Electrical Stimulation of Peripheral Tactile and Proprioceptive Pathways With Intrafascicular Electrodes

Trans-radial amputee subjects were implanted with intrafascicular electrodes in the stumps of the median and ulnar nerves. Electrical stimulation through these electrodes was used to provide sensations of touch and finger position referred to the amputated hand. Two subjects were asked to identify different objects as to size and stiffness by manipulating them with a myo-electric hand without visual or auditory cues. Both subjects were provided with information about contact force with the objects via tactile sensations referred to their phantom hands. One subject, who was provided with information about finger position in the prosthetic hand via a different tactile sensation referred to his phantom hand, was unable to correctly identify the objects. The other subject, who received information about finger position via a proprioceptive sensation referred to his phantom hand, correctly identified the objects at a level statistically significantly above chance performance.

Standing Stability Enhancement With an Intelligent Powered Transfemoral Prosthesis

The authors have developed a ground-adaptive standing controller for a powered knee and ankle prosthesis which is intended to enhance the standing stability of transfemoral amputees. The finite-state-based controller includes a ground-searching phase, a slope estimation phase, and a joint impedance modulation phase, which together enable the prosthesis to quickly conform to the ground and provide stabilizing assistance to the user. In order to assess the efficacy of the ground-adaptive standing controller, the control approach was implemented on a powered knee and ankle prosthesis, and experimental data were collected on an amputee subject for a variety of standing conditions. Results indicate that the controller can estimate the ground slope within ±1° over a range of ±15°, and that it can provide appropriate joint impedances for standing on slopes within this range.

A Decision-Based Velocity Ramp for Minimizing the Effect of Misclassifications During Real-Time Pattern Recognition Control

Real-time pattern recognition control is frequently affected by misclassifications. This study investigated the use of a decision-based velocity ramp that attenuated movement speed after a change in classifier decision. The goal was to improve prosthesis positioning by minimizing the effect of unintended movements. Non-amputee and amputee subjects controlled a prosthesis in real-time using pattern recognition. While performing a target achievement test in a virtual environment, subjects had a significantly higher completion rate (p < 0.05) and a more direct path (p < 0.05) to the target with the velocity ramp than without it. Using a physical prosthesis, subjects stacked a greater average number of 1 cubes (p < 0.05) in three minutes with the velocity ramp than without it (76% more blocks for non-amputees; 89% more blocks for amputees). Real-time control using the velocity ramp also showed significant performance improvements above using majority vote. Eighty-three percent of subjects preferred to control the prosthesis using the velocity ramp. These results suggest that using a decision-based velocity ramp with pattern recognition may improve user performance. Since the velocity ramp is a post-processing step, it has the potential to be used with a variety of classifiers for many applications.

Surface electromyographic activity of five residual limb muscles recorded during isometric contraction in transfemoral amputees with osseointegrated prostheses

Background Femoral osseointegrated implants represent a new development in amputee rehabilitation, eliminating socket pressure discomfort, improving hip range of movement and facilitating prosthetic limb attachment. A clinical aspect that has not previously been reported on is the function of muscles in the residuum with implications concerning energy expenditure, hip-hiking and viability of the electrogram as a myoprocessor. Typically, amputees fitted with osseointegrated fixation have shorter residuums and weaker attachment of cleaved muscles. Function of muscle can be assessed by surface electromyography through changes in amplitude and median frequency of the signal. Methods Five male transfemoral amputees with osseointegrated fixations participated together with a control group comprised of ten adult males. Electrodes recorded surface electromyographic activity of five residual limb muscles or left lower limb muscles of control subjects. Isometric contractions were performed against resistance. The increase in mean rectified amplitude from resting to maximally contracting was calculated and median frequencies estimated. Findings The amputees were unable to maintain a maximum voluntary contraction of constant amplitude. Amplitude increase was lowest for rectus femoris and adductor magnus. The median frequency of adductor magnus was significantly greater ( P = 0.02) for the amputees than intact subjects and there was a significant difference ( P < 0.01) between gluteus maximus and adductor magnus for amputee subjects. Interpretation High electromyographic amplitude variability suggests that using residuum muscles singly as a myoprocessor might be challenging. Adductor magnus displayed a different sEMG profile compared to intact subjects indicating decreased function and neuromuscular changes. Further work into optimal muscle anchorage is required to ensure maximal mechanical performance.

Effects of elevated vacuum on in-socket residual limb fluid volume: Case study results using bioimpedance analysis

Bioimpedance analysis was used to measure the residual limb fluid volume of seven transtibial amputee subjects using elevated vacuum sockets and nonelevated vacuum sockets. Fluid volume changes were assessed during sessions with the subjects sitting, standing, and walking. In general, fluid volume losses during 3 or 5 min walks and losses over the course of the 30 min test session were less for elevated vacuum than for suction. Numerous variables, including the time of day that data were collected, soft tissue consistency, socket-to-limb size and shape differences, and subject health, may have affected the results and had an equivalent or greater effect on limb fluid volume compared with elevated vacuum. Researchers should well consider these variables in the study design of future investigations on the effects of elevated vacuum on residual limb volume.

Upslope Walking With a Powered Knee and Ankle Prosthesis: Initial Results With an Amputee Subject

This paper extends a previously developed level- ground walking control methodology to enable an above knee amputee to walk up slopes using a powered knee and ankle prosthesis. Experimental results corresponding to walking on level ground and two different slope angles (5 (°) and 10 (°)) with the powered prosthesis using the control method are compared to walking under the same conditions with a passive prosthesis. The data indicate that the powered prosthesis with the upslope walking controller is able to reproduce several kinematic characteristics of healthy upslope walking that the passive prosthesis does not (such as knee flexion after heel strike and a powered ankle plantarflexion during push-off). Finally, results are shown that demonstrate the ability of the prosthesis to generate a slope estimate, which is in turn utilized to adapt the underlying control parameters to the corresponding slope.

Muscle Activation Patterns of the Forearm: High-Density Electromyography Data of Normally Limbed and Transradial Amputee Subjects

In Brief For many years, myoelectric prostheses have been accepted by upper limb amputees. Multifunction pattern recognition has been used successfully to develop myoelectric-controlled limbs; however, much of this research has used normally limbed subjects as they are capable of producing distinguishable muscle activation patterns for different movements. Surprisingly, there has been limited research using clinical populations to test advanced devices and control systems. One reason for the lack of studies with amputees is the limited data regarding their ability to produce repeatable muscle activation patterns. Although it would be expected that these patterns would differ between amputees and normally limbed individuals, it is worthwhile to determine whether amputees can produce repeatable muscle patterns. Therefore, the purpose of this study was to look for distinct and repeatable muscle activation patterns (required for pattern recognition myoelectric control) using amputee subjects. A high-density electromyography system was used to investigate muscle activation patterns during wrist and hand motions. Subjects performed repetitions of different movements, so that intertrial and intermovement electromyography activity comparison could be completed within subject. Topographical (energy maps), classification accuracies, and a separability index were used to determine the discriminate power of the movements performed. It was found that amputee subjects are able to elicit distinct and repeatable patterns for at least a subset of the movements, suggesting promise for amputee control of multifunction myoelectric prostheses. This study aimed to determine if transradial amputees could produce distinct and repeatable muscle activation patterns required for successful pattern recognition myoelectric control. These preliminary results are promising and indicate there is a future for multifunction pattern recognition based control systems in the clinical setting. The results from this work support the hypothesis that amputee subjects are able to elicit distinct and reproducible patterns for a subset of movements.

Volitional Control of a Prosthetic Knee Using Surface Electromyography

This paper presents a method for providing volitional control of a powered knee prosthesis during nonweight-bearing activity such as sitting. The method utilizes an impedance framework, such that the joint can be programmed with a given stiffness and damping that reflects the nominal impedance properties of an intact joint. Volitional movement of the knee joint is commanded via the stiffness set-point angle of the joint impedance, which is commanded by the user as a function of the measured surface electromyogram (EMG) from the hamstring and quadriceps muscles of the residual limb. Rather than using the respective EMG measurements from these muscles to directly command the flexion or extension set point of the knee, the presented approach utilizes a combination of quadratic discriminant analysis and principal component analysis to align the user's intent to flex or extend the knee joint with the pattern of measured EMG. The approach was implemented on three transfemoral amputees, and their ability to control knee movement was characterized by a set of knee joint trajectory tracking tasks. Each amputee subject also performed the same set of trajectory tracking tasks with his sound side (intact) knee joint. The average root mean square trajectory tracking errors of the prosthetic knee employing the EMG-based volitional control and the intact knee of the three subjects were 6.2° and 5.2°, respectively.

Biomechanical Differences between Two Exoprosthetic Hip Joint Systems during Level Walking

Previous studies have shown low end-user acceptance of a hip disarticulation style prosthesis and that the limitations of such prostheses, including poor gait pattern, socket discomfort, weight of the prosthesis, loss of mobility, instability and high energy consumption are a contributing factor. This study was initiated to determine if a new style of prosthetic hip joint could help to overcome some of the limitations concerning the gait pattern. The present study analyzed the gait pattern of six hip disarticulation amputee subjects. The objective was to compare two different prosthetic hip joints, both from Otto Bock HealthCare: The new Helix(3D) and the 7E7, which is based on the Canadian model proposed by McLaurin (1954). Kinematics and kinetics were recorded by an optoelectronic camera system with six CCD cameras and two force plates. During weight acceptance, the Helix(3D) extends considerably slower and reaches full extension later than the 7E7. The increased range of pelvic tilt observed with hip disarticulation amputees is significantly reduced (by 5 ± 3 degrees) when using the Helix(3D) Hip Joint. In addition, this system showed increased stance phase knee joint flexion as well as increased maximum swing phase knee flexion angles compared to the 7E7. These motion analysis results show that the Helix(3D) Hip Joint can reduce gait abnormalities compared to the uniplanar design of the 7E7 hip joint.

Strength asymmetry and osteoarthritis risk factors in unilateral trans-tibial, amputee gait

Persons with a unilateral, trans-tibial amputation have an increased risk of developing osteoarthritis (OA) in the knee of their intact limb. Between-side strength discrepancies observed in individuals with an amputation may indicate overuse of the intact limb and increased osteoarthritis risk; however, the relationship between lower extremity strength and gait mechanics has not been addressed in previous literature. It was hypothesized that amputee subjects’ strength and gait would be more asymmetrical than controls, and that strength asymmetry would positively correlate with gait variable asymmetry and intact side gait variables associated with osteoarthritis risk. Eight persons with unilateral, trans-tibial amputation and eight able-bodied control subjects participated. Three gait variables related to osteoarthritis risk (knee external adduction moment, knee adduction moment load rate, and vertical ground reaction force load rate) were measured bilaterally, along with three strength measures (hip abductors, knee extensors, and knee flexors). Four of the six variables were more asymmetrical in the amputee group than the control group ( p < 0.05 and/or effect size greater than 0.70). Knee extension strength asymmetry was significantly related to knee adduction moment load rate asymmetry (rho = 0.714), and knee flexion strength asymmetry was moderately related to the vertical ground reaction force on the intact limb (rho = 0.643). Results suggest that strength asymmetry in unilateral trans-tibial amputees has a moderate relationship with osteoarthritis risk, and may be a useful way to assess gait ability and the need for rehabilitation in this population.

Mechanical hyperesthesia and cold perception hypoesthesia in distal residual limbs of amputees

In this prospective study, we report that the distal residual limbs (DRL) of amputee subjects are hyperesthetic/allodynic for pressure pain thresholds (large fibers) and hypoesthetic for cold perception threshold (small fibers) in comparison with the contralateral unaffected extremities. We prospectively assessed twenty-two subjects (18 with pain, 4 without) with a unilateral upper or lower limb amputation. We utilized the Fischer algometer to compare pressure pain thresholds (PPT) and the Medoc peltier type device to compare thermal perception thresholds. The Wilcoxon Signed Rank Test was used to analyze the affected limb versus the unaffected limb of these psychophysical tests. Our results revealed decreased perceptual threshold values for pressure pain threshold(p <0.016) and an elevated threshold for cold perception (p<0.017) There were no significant difference in thresholds for cold pain or hot perception or pain. There were no differences detected between subjects with and without pain. These results suggest a possible peripheral pathological processes in superficial tissue of the residual limb, such as a differential dying back phenomena of small (cold perception) or peripheral sensitization of large fiber output; or a central phenomena such as sensitization or disinhibition.

Rebuttal from Weyand and Bundle

POINT:COUNTERPOINTArtificial limbs do/do not make artificially fast running speeds possibleRebuttal from Weyand and BundlePublished Online:01 Apr 2010https://doi.org/10.1152/japplphysiol.01238.2009bMoreSectionsPDF (38 KB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat We agree that minimum leg repositioning, or swing times, and mass-specific ground reaction forces are critical determinants of sprint running performance.Swing times: biologically normal or artificially brief?Our conclusion that the bilateral artificial limb swing time (0.284 s) measured at top speed (10) is artificially brief is based on the well-established practice of evaluating single observations vs. a comparison sample population's mean and variance with a threshold of >3.0 standard deviations (SD) for identifying outliers (7). In comparison to an intact-limb reference population (9) of 33 active, treadmill-tested subjects [mean (SD) = 0.373 (0.026) s]; four performance-matched track athletes (10) during treadmill running [0.359 (0.019) s]; and 22 male, world-class, 100-m sprinters (6, 8) in competition [0.330 (0.014) s]; the double-artificial-limb value is −3.4, −4.0, and −3.3 SD units below these three respective means. It is also 15.7% shorter than the mean of the five former 100-m world-record holders (0.337 s) in the competition sample.Even in comparison to individuals with the most extreme gait adaptations for speed in recorded human history, the double-artificial-limb value is not simply an outlier; it is quite literally off the biological charts.Our colleagues recently published (4) conclusion that the double-artificial-limb value is not artificially brief is not supported by the data we have published with them (10) or the valid data from field (6, 8) and laboratory (9, 10) settings analyzed above. Instead, television footage of Olympic races acquired for entertainment purposes is cited (4). Low shutter speeds, frame rates (30 Hz), wide fields of view, and force-video offsets (9) make television-estimated swing times highly uncertain. For example, the swing time of the one Olympian purportedly more brief (0.274 ± 0.004 s; Ref. 4) than the double-amputee value, is actually 16.2% greater (0.318, 0.318, and 0.320 s) when measured using research-quality, high-speed, motion-capture techniques (6).Reduced force requirements for speed.Given that the stride-averaged vertical force must equal the body's weight, lesser ground support forces at the same speeds should not be interpreted as a limb strength deficiency, but here (Fig. 1) represent the inevitable physical consequence (3) of ground contact times lengthened, and aerial times shortened by artificially compliant and lightweight (2) lower limbs. Our double amputee subject “bounces” on his compliant lower limbs while holding his upper biological limbs relatively straight (2; Fig. 1, inset). More erect limb posture (1) and reduced ground force requirements co-reduce the muscular forces required to attain the same sprint running speeds to less than one-half of intact limb levels.REFERENCES1. Biewener AA , Farley CF , Temanar T , Roberts J. Mechanical advantage during walking and running: implications for energetic cost. J Appl Physiol 95: 1955–1962, 1998.Google Scholar2. Bruggeman GP , Arampatzis A , Emrich F , Potthast W. Biomechanics of double tanstibial amputee sprinting using dedicated sprint prostheses. Sports Technol 4–5: 220–227, 2009.Crossref | Google Scholar3. Cutnell JD , Johnson JW. Physics, 6th edition. New Jersey: John Wiley and Sons, 2004.Google Scholar4. Grabowski AM , McGowan CP , McDermott WJ , Beale MT , Kram R , Herr HM. Running-specific prosthesis limit ground-force during sprinting. Biol Lett; doi:10.1098/rsbl.2009.0729.Google Scholar5. Kram R , Grabowski A , McGowan C , Brown MB , Herr H. Counterpoint: Artificial limbs do not make artificially fast running speeds possible. J Appl Physiol; doi:10.1152/japplphysiol.01238.2009.ISI | Google Scholar6. Mann R. The Mechanics of Sprinting and Hurdling. Las Vegas: Compusport, 2004, p. 2006–2008.Google Scholar7. Mendenhall RJ , Beaver RJ , Beaver BM. Introduction to Probability and Statistics, 13th edition. Belmont, CA: Thomson Brooks/Cole, 2006.Google Scholar8. Moravec P , Ruzicka J , Susanka P , Dostal E , Kodejs M , Nosek M. The 1987 International Athletic Foundation/IAAF Scientific Project Report: Time analysis of the 100 metres events at the II. World Championships in Athletics. New Studies Athletics 3: 61–96, 1988.Google Scholar9. Weyand PG , Sternlight DB , Bellizzi MJ , Wright S. Faster top running speeds are achieved with greater ground forces not more rapid leg movements. J Appl Physiol 81: 1991–1999, 2000.Link | ISI | Google Scholar10. Weyand PG , Bundle MW , McGowan CP , Grabowski A , Brown MB , Kram R , Herr H. The fastest runner on artificial limbs: different limbs similar function? J Appl Physiol 107: 903–911, 2009.Link | ISI | Google Scholar Download PDF Previous Back to Top Next FiguresReferencesRelatedInformation More from this issue > Volume 108Issue 4April 2010Pages 1014-1014 Copyright & PermissionsCopyright © 2010 the American Physiological Societyhttps://doi.org/10.1152/japplphysiol.01238.2009bHistory Published online 1 April 2010 Published in print 1 April 2010 Metrics

Design and Fabrication of a Passive-Function, Cylindrical Grasp Terminal Device

To assist upper extremity amputees with achieving stable grasps of cylindrical tools, this article describes the development and testing of a prosthetic device for recreational kayak paddling. Initial development included participation of a non-amputee expert kayakist. Subsequent testing of the device used a pseudo-prosthesis for testing on a non-amputee subject, followed by qualitative feedback on the device from a unilateral transradial amputee. The device was evaluated by exploring whether subjects could independently don the terminal device, apply the paddle and use it in a pool and on a river. A semi-hinged, two hemi-cylinder sleeve was designed to be fitted onto a kayak paddle. The terminal device's frame, a second (larger) semi-hinged two hemi-cylinder sleeve, attached the device to the prosthesis. This second sleeve had internal edges that prevent lateral shifting. This component allowed smooth paddle rotation while preventing lateral shift and maintaining grasp. The non-amputee subject was successful at donning the pseudo-prosthesis and paddling. Similarly, the amputee subject was also able to don the prosthesis and paddle using the device. The design reported here is a viable option for fabricating a cylindrical grasp, passive function terminal device for kayaking. It is adaptable to other cylindrical grasp functions such as lifting an exercise weight.

Clinical Utility of In-Socket Residual Limb Volume Change Measurement

Bioimpedance analysis was used to measure conductive tissue extracellular fluid (ECF) volume changes in the residual limbs of four unilateral transtibial amputee subjects during standing and walking conditions. Results showed that all residual limbs experienced ECF volume decreases during 5 min standing intervals. During 5 min of walking immediately after a standing interval, the residual limbs of healthy subjects increased in ECF volume while those of diseased subjects, one with peripheral vascular disease and another with cardiovascular insufficiency and a high-salt intake, decreased. One subject demonstrated less absolute value ECF volume change during standing and walking at 12 months post-surgical revision compared with at six months. Presentation of bioimpedance data to patients improved compliance to practitioner recommendations and patient understanding. Results were useful towards clinical assessment, patient education, and decision-making about treatment.

Preliminary Evaluations of a Self-Contained Anthropomorphic Transfemoral Prosthesis.

This paper presents a self-contained powered knee and ankle prosthesis, intended to enhance the mobility of transfemoral amputees. A finite-state based impedance control approach, previously developed by the authors, is used for the control of the prosthesis during walking and standing. Experiments on an amputee subject for level treadmill and overground walking are described. Knee and ankle joint angle, torque, and power data taken during walking experiments at various speeds demonstrate the ability of the prosthesis to provide a functional gait that is representative of normal gait biomechanics. Measurements from the battery during level overground walking indicate that the self-contained device can provide more than 4500 strides, or 9 km, of walking at a speed of 5.1 km/h between battery charges.

Multiclass Real-Time Intent Recognition of a Powered Lower Limb Prosthesis

This paper describes a control architecture and intent recognition approach for the real-time supervisory control of a powered lower limb prosthesis. The approach infers user intent to stand, sit, or walk, by recognizing patterns in prosthesis sensor data in real time, without the need for instrumentation of the sound-side leg. Specifically, the intent recognizer utilizes time-based features extracted from frames of prosthesis signals, which are subsequently reduced to a lower dimensionality (for computational efficiency). These data are initially used to train intent models, which classify the patterns as standing, sitting, or walking. The trained models are subsequently used to infer the user's intent in real time. In addition to describing the generalized control approach, this paper describes the implementation of this approach on a single unilateral transfemoral amputee subject and demonstrates via experiments the effectiveness of the approach. In the real-time supervisory control experiments, the intent recognizer identified all 90 activity-mode transitions, switching the underlying middle-level controllers without any perceivable delay by the user. The intent recognizer also identified six activity-mode transitions, which were not intended by the user. Due to the intentional overlapping functionality of the middle-level controllers, the incorrect classifications neither caused problems in functionality, nor were perceived by the user.

Examination of Force Discrimination in Human Upper Limb Amputees With Reinnervated Limb Sensation Following Peripheral Nerve Transfer

Artificial limbs allow amputees to manipulate objects, but the loss of a limb severs the sensory link between a subject and objects they touch. A novel surgical technique we term targeted reinnervation (TR) allows severed cutaneous nerves to reinnervate skin on a different portion of the body. This technique provides a physiologically appropriate portal to the sensory pathways of the missing limb through the reinnervated skin. This study quantified the ability of three amputee subjects who had undergone TR surgery on the chest (two subjects) and upper arm (one subject) to discriminate changes in graded force on their reinnervated skin over a range of 1-4 N using a stochastic staircase approach. These values were compared to those from sites on their intact contralateral skin and index fingers, and from the chests and index fingers of a control population (n = 10) . Weber's ratio (WR) was used to examine the subjects' abilities to discriminate between a baseline force and subsequent forces of different magnitudes. WRs of 0.22, 0.25, and 0.12 were measured on the reinnervated skin of the three TR subjects, whereas WRs of 0.25, 0.23, and 0.12 were measured on their contralateral skin. TR subjects did not have substantially different WRs on their reinnervated versus their contralateral normal side and did not appear to exhibit a trend towards impaired sensation. No significant difference was found between the WR of the chest and index finger of the control subjects, which ranged between 0.09 and 0.21. WR of reinnervated skin for TR subjects were within the 95% confidence interval of the control group. These data suggest that subjects with targeted reinnervation have unimpaired ability to discriminate gradations in force.

The fastest runner on artificial legs: different limbs, similar function?

The recent competitive successes of a bilateral, transtibial amputee sprint runner who races with modern running prostheses has triggered an international controversy regarding the relative function provided by his artificial limbs. Here, we conducted three tests of functional similarity between this amputee sprinter and competitive male runners with intact limbs: the metabolic cost of running, sprinting endurance, and running mechanics. Metabolic and mechanical data, respectively, were acquired via indirect calorimetry and ground reaction force measurements during constant-speed, level treadmill running. First, we found that the mean gross metabolic cost of transport of our amputee sprint subject (174.9 ml O(2)*kg(-1)*km(-1); speeds: 2.5-4.1 m/s) was only 3.8% lower than mean values for intact-limb elite distance runners and 6.7% lower than for subelite distance runners but 17% lower than for intact-limb 400-m specialists [210.6 (SD 13.2) ml O(2)*kg(-1)*km(-1)]. Second, the speeds that our amputee sprinter maintained for six all-out, constant-speed trials to failure (speeds: 6.6-10.8 m/s; durations: 2-90 s) were within 2.2 (SD 0.6)% of those predicted for intact-limb sprinters. Third, at sprinting speeds of 8.0, 9.0, and 10.0 m/s, our amputee subject had longer foot-ground contact times [+14.7 (SD 4.2)%], shorter aerial [-26.4 (SD 9.9)%] and swing times [-15.2 (SD 6.9)%], and lower stance-averaged vertical forces [-19.3 (SD 3.1)%] than intact-limb sprinters [top speeds = 10.8 vs. 10.8 (SD 0.6) m/s]. We conclude that running on modern, lower-limb sprinting prostheses appears to be physiologically similar but mechanically different from running with intact limbs.

Self-Contained Powered Knee and Ankle Prosthesis: Initial Evaluation on a Transfemoral Amputee.

This paper presents an overview of the design and control of a fully self-contained prosthesis, which is intended to improve the mobility of transfemoral amputees. A finite-state based impedance control approach, previously developed by the authors, is used for the control of the prosthesis during walking and standing. The prosthesis was tested on an unilateral amputee subject for over-ground walking. Prosthesis sensor data (joint angles and torques) acquired during level ground walking experiments at a self-selected cadence demonstrates the ability of the device to provide a functional gait similar to normal gait biomechanics. Battery measurements during level ground walking experiments show that the self-contained device provides over 4,500 strides (9.0 km of walking at a speed of 5.1 km/h) between battery charges.