We evaluated nonreversed vein grafts in above-knee bypasses for chronic critical limb ischemia in a retrospective study with intention-to-treat analysis in patients who underwent above-knee bypass grafting. During a 4-year period, 51 patients (men, 32; women, 19; mean age 66 years) with 53 critically ischemic lower extremities underwent above-knee femoropopliteal bypass grafting. The follow-up evaluation consisted of clinical examination, assessment of the ankle- brachial systolic blood pressure index, and, whenever necessary, duplex scanning. Three ( 5.7%) deaths occurred within 30 days, two from myocardial infarction and one from an undetermined cause. The 2-year cumulative success rate was 82.5 +/- 9.6% for primary patency, 84.6 +/- 8.9% for secondary patency, 90.1 +/- 7.3% for tertiary patency, 86.9 +/- 7.6% for limb salvage, 77.7 +/- 8.4% for survival, 68.0 +/- 11.1% for composite patency, and 68.4 +/- 9.3% for amputation- free survival; the corresponding estimates for vein grafts alone were 86.6 +/- 9.2%, 88.9 +/- 8.6%, 89.0 +/- 8.5%, 88.1 +/- 8.1%, 81.1 +/- 9.1, 76.8 +/- 11.1%, and 72.6 +/- 10.2%. Three prosthetic grafts failed and were replaced with an arm vein graft. Nonreversed vein bypass grafts in above- knee revascularization of critically ischemic limbs are justified.
OBJECTIVE: The authors report on their 20-year experience with 120 patients with infected extracavitary prosthetic arterial grafts (95 polytetraflouroethylene, 25 Dacron). Throughout this experience, an effort was made, when appropriate, to salvage all or a portion of these infected grafts. METHODS: When patients had arterial bleeding (20 cases) or systemic sepsis (6 cases), immediate graft excision was performed. When the infected graft was occluded (43 cases), subtotal graft excision was performed, leaving an oversewn 2- to 3-mm graft remnant to maintain patency of the artery. Complete graft preservation was attempted in 51 cases in which the graft was patent, the patient was not septic, and the anastomoses were intact. Aggressive operative wound debridement was repeated, as necessary, to achieve wound healing. The preferred method of revascularization, when necessary, included secondary bypasses tunneled through uninfected (often lateral) routes. Follow-up averaged 3 years (range, 1 month-20 years). RESULTS: This strategy resulted in a hospital mortality of 12% (14/120) and a hospital amputation rate in survivors of 13% (14/106 threatened limbs). Of the surviving patients treated by complete graft preservation, the hospital amputation rate was only 4% (2/45) and long-term complete graft preservation was successful in 71% (32/45) of cases. Partial graft preservation also proved successful in 85% (35/41) of surviving patients who had occluded grafts. Successful complete graft preservation was as likely when gram-negative or gram-positive bacteria were cultured from the wound...
Better fit and function of prosthetic limbs is promoted when section and closure is done with attention to the prospective use of the stump as a pad for seating the limb. Preservation of tissue, fixing muscles to bone under physiologic tension, and making sure that bone ends are well covered with tissue are important to the comfort and usefulness of the limb that is to be fitted to the stump. Immediate application of a plaster-cast to form a total-contact socket for seating a temporary prosthetic limb, then early standing, weight-bearing and walking aid in healing and in shaping the stump to the permanent prosthetic socket it will ultimately occupy.
In five experiments, we investigated the effects of visual exposure to a real hand, a rubber hand, or a wooden block on reaching movements made with the unseen left hand behind a parasagittal mirror. Participants reached from one of four starting positions, corresponding to four levels of conflict between the proprioceptively- and visually-specified position of the reaching hand. Reaching movements were affected most by exposure to the real hand, intermediately by the rubber hand, and least of all by the wooden block. When the posture and/or movement of the visible hand was incompatible with that of the reaching hand, the effect on reaching was reduced. A ‘rubber hand illusion’ questionnaire revealed that illusions of ownership of the rubber hand were not strongly correlated with reaching performance. This research suggests that proprioception recalibrates following visual exposure to prosthetic hands, and that this recalibration is independent of the rubber hand illusion.
Existing prosthetic limbs do not provide amputees with cutaneous feedback. Tactile feedback is essential to intuitive control of a prosthetic limb and it is now clear that the sense of body self-identification is also linked to cutaneous touch. Here we have created an artificial sense of touch for a prosthetic limb by coupling a pressure sensor on the hand through a robotic stimulator to surgically redirected cutaneous sensory nerves (targeted reinnervation) that once served the lost limb. We hypothesize that providing physiologically relevant cutaneous touch feedback may help an amputee incorporate an artificial limb into his or her self image. To investigate this we used a robotic touch interface coupled with a prosthetic limb and tested it with two targeted reinnervation amputees in a series of experiments fashioned after the Rubber Hand Illusion. Results from both subjective (self-reported) and objective (physiological) measures of embodiment (questionnaires, psychophysical temporal order judgements and residual limb temperature measurements) indicate that returning physiologically appropriate cutaneous feedback from a prosthetic limb drives a perceptual shift towards embodiment of the device for these amputees. Measurements provide evidence that the illusion created is vivid. We suggest that this may help amputees to more effectively incorporate an artificial limb into their self image...
Although the survival rates of warfighters in recent conflicts are among the highest in military history, those who have sustained proximal limb amputations, may pose additional rehabilitation concerns. In some of these cases, traditional prosthetic limbs may not provide adequate function for returning to an active lifestyle. Osseointegration has emerged as a potential prosthetic alternative for those with limited residual limb length. Using this technology, direct skeletal attachment occurs between a transcutaneous osseointegrated implant (TOI) and the host bone, thereby eliminating the need for a socket. While reports from the first 100 patients with a TOI have been promising, some rehabilitation regimens require 12–18 months of restricted weight bearing to prevent overloading at the bone implant-interface. Electrically induced osseointegration has been proposed as an option for expediting periprosthetic fixation and preliminary studies have demonstrated the feasibility of adapting the TOI into a functional cathode. To assure safe and effective electrical fields that are conducive for osseoinduction and osseointegration, we have developed multiscale modeling approaches to simulate the expected electric metrics at the bone-implant interface. We have used computed tomography scans and volume segmentation tools to create anatomically accurate models that clearly distinguish tissue parameters and serve as the basis for finite element analysis. This translational computational biological process has supported biomedical electrode design...
Individuals with transtibial amputation (TTA) have a high incidence of falls during walking. Environmental factors, such as uneven ground, often play a contributing role in these falls. The purpose of this study was to quantify the adaptations TTA made when walking on a destabilizing loose rock surface. In this study, 13 young TTA walked over a rock surface and level ground level ground at four controlled speeds. Subjects successfully traversed the rock surface by adopting a conservative gait characterized by shorter and wider steps. They also took shorter steps with their prosthetic limbs and exhibited greater variability in foot placement when stepping onto their intact limb. Between-limb differences in step length and width variability increased at faster walking speeds. TTA increased hip and knee flexion during initial stance, which contributed lowering the whole-body center of mass. TTA also increased hip and knee flexion during swing, enabling them to significantly increase their toe clearance on the rock surface compared to level ground. Toe clearance on the prosthetic side was aided by increased ipsilateral hip flexion. The results suggest that TTA were able to adapt their gait to overcome the challenge imposed by the rock surface. These adaptations were asymmetric and initiated proximally.
Chestek, Cynthia A.; Gilja, Vikash; Nuyujukian, Paul; Foster, Justin D.; Fan, Joline M.; Kaufman, Matthew T.; Churchland, Mark M.; Rivera-Alvidrez, Zuley; Cunningham, John P.; Ryu, Stephen I.; Shenoy, Krishna V.
Cortically-controlled prosthetic systems aim to help disabled patients by translating neural signals from the brain into control signals for guiding prosthetic devices. Recent reports have demonstrated reasonably high levels of performance and control of computer cursors and prosthetic limbs, but to achieve true clinical viability the long-term operation of these systems must be better understood. In particular, the quality and stability of the electrically-recorded neural signals requires further characterization. Here, we quantify action potential changes and offline neural decoder performance over 382 days of recording from 4 intracortical arrays in 3 animals. Action potential amplitude decreased by 2.4% per month on average over the course of 9.4, 10.4, and 31.7 months in 3 animals. During most time periods, decoder performance was not well correlated with action potential amplitude (p > 0.05 for 3 of 4 arrays). In two arrays from one animal, action potential amplitude declined by an average of 37% over the first 2 months after implant. However, when using simple threshold crossing events rather than well isolated action potentials, no corresponding performance loss was observed during this time using an offline decoder. One of these arrays was effectively used for online prosthetic experiments over the following year. Substantial short-term variations in waveforms were quantified using a wireless system for contiguous recording in one animal...
Uneven walking surfaces pose challenges to balance, especially in individuals with lower extremity amputation. The purpose of this study was to determine if lateral stability of persons with unilateral transtibial amputation (TTA) is compromised when walking on a loose rock surface. Thirteen TTA and 15 healthy controls walked over level ground and over a loose rock surface at four controlled speeds. Dependent measures, including medial-lateral center of mass (COM) motion, step width variability, lateral arm swing velocity, and mean and variability of the minimum margins of stability (MOSmin), were compared between subject groups and across conditions. TTA had greater average MOSmin than Control subjects (p = 0.018). TTA exhibited decreased MOSmin on their prosthetic limbs compared to their intact limbs (p = 0.036), while Control subjects did not exhibit side to side differences. Both groups increased MOSmin with increasing walking speed (p ≤ 0.001). There was no difference in the average MOSmin between walking surfaces (p = 0.724). However, the variability of MOSmin was greater on the rocks compared to level ground. Both subject groups increased step width, step width variability, COM range of motion and peak COM velocity when walking on the rock surface. TTA exhibited greater variability of both step width and MOSmin...
Carbon fiber running-specific prostheses (RSPs) have allowed individuals with lower extremity amputation (ILEA) to participate in running. It has been established that as running speed increases, leg stiffness (Kleg) remains constant while vertical stiffness (Kvert) increases in able-bodied runners. The Kvert further depends on a combination of the torsional stiffnesses of the joints (joint stiffness; Kjoint) and the touchdown joint angles. Thus, an increased understanding of spring-like leg function and stiffness regulation in ILEA runners using RSPs is expected to aid in prosthetic design and rehabilitation strategies. The aim of this study was to investigate stiffness regulation to various overground running speeds in ILEA wearing RSPs. Eight ILEA performed overground running at a range of running speeds. Kleg, Kvert and Kjoint were calculated from kinetic and kinematic data in both intact and prosthetic limbs. Kleg and Kvert in both limbs remained constant when running speed increased, while intact limbs in ILEA running with RSPs have a higher Kleg and Kvert than residual limbs. There were no significant differences in Kankle, Kknee and touchdown knee angle between the legs at all running speeds. Hip joints in both legs did not demonstrate spring-like function; however...
Carbon fiber running-specific prostheses (RSPs) have allowed individuals with lower extremity amputation (ILEA) to actively participate in sporting activities including competitive sports. In spite of this positive trait, the RSPs have not been thoroughly evaluated regarding potential injury risks due to abnormal loading during running. Vertical impact peak (VIP) and average loading rate (VALR) of the vertical ground reaction force (vGRF) have been associated with running injuries in able-bodied runners but not for ILEA. The purpose of this study was to investigate vGRF loading in ILEA runners using RSPs across a range of running speeds. Eight ILEA with unilateral transtibial amputations and eight control subjects performed overground running at three speeds (2.5, 3.0, and 3.5 m/s). From vGRF, we determined VIP and VALR, which was defined as the change in force divided by the time of the interval between 20 and 80% of the VIP.We observed that VIP and VALR increased in both ILEA and control limbs with an increase in running speed. Further, the VIP and VALR in ILEA intact limbs were significantly greater than ILEA prosthetic limbs and control subject limbs for this range of running speeds. These results suggest that 1) loading variables increase with running speed not only in able-bodied runners...
One of the most exciting and compelling areas of research and development is building brain-machine interfaces (BMIs) for controlling prosthetic limbs. Prosthetic limb technology is advancing rapidly, and the Johns Hopkins University/Applied Physics Lab (JHU/APL) Modular Prosthetic Limb (MPL) permits actuation with 17 degrees of freedom in 26 articulating joints. There are many signals from the brain that can be leveraged, including the spiking rates of neurons in the cortex, electrocorticographic (ECoG) signals from the surface of the cortex, and electroencephalographic (EEG) signals from the scalp. Unlike microelectrodes which record spikes, ECoG does not penetrate the cortex and also has higher spatial specificity, signal-to-noise ratio, and bandwidth than EEG signals. We have implemented an ECoG-based system for controlling the MPL in the Johns Hopkins Hospital Epilepsy Monitoring Unit, where patients are implanted with ECoG electrode grids for clinical seizure mapping and asked to perform various recorded finger or grasp movements. We have shown that low frequency local motor potentials and ECoG power in the high gamma frequency (70–150 Hz) range correlates well with grasping parameters and they stand out as good candidate features for closed-loop control of the MPL.
The purpose of this research was to investigate the influence of sock addition and sock removal on residual limb fluid volume in people using prosthetic limbs. We used bioimpedance analysis to measure residual limb extracellular fluid volume on 28 transtibial amputee subjects during 30-minute test sessions. Upon addition of a 1-ply polyester sock, residual limb fluid volume changes ranged from −4.0% to 0.8% (mean −0.9% (s.d.=1.3%)) of the initial limb fluid volume. Changes for sock removal ranged from −1.2% to 2.8% (mean 0.5% (s.d.=0.8%)). Subjects who reduced in fluid volume with both addition and removal of a sock and subjects with high positive ratios between the fluid volume loss upon sock addition and the gain upon sock removal (high Add/Remove(AR) ratios) tended to have arterial disease, were obese and smokers. Subjects with low positive AR ratios, subjects who increased in fluid volume both with sock addition and removal, and a single subject who increased in fluid volume with sock addition and decreased with sock removal tended to be non-smokers and either healthy individuals without complications or individuals without arterial problems. Results are relevant towards anticipating limb volume changes during prosthetic fitting and towards the design of adjustable-socket technologies.
A device using radio frequency identification technology (RFID) was developed to continuously monitor sock use on people using prosthetic limbs. RFID tags were placed on prosthetic socks worn by subjects with transtibial limb loss, and a high-frequency (HF) RFID reader and antenna were placed in a portable unit mounted to the outside of the prosthetic socket. Bench testing showed the device to have a maximum read range between 5.6 cm and 12.7 cm, depending on the RFID tag used. Testing in a laboratory setting on three participants with transtibial amputation showed that the device correctly monitored sock presence during sitting, standing, and walking activity when one or two socks were worn but was less reliable when more socks were used. Accurate detection was sensitive to orientation of the tag relative to the reader, presence of carbon fiber in the prosthetic socket, pistoning of the limb in the socket, and overlap among the tags. Use of ultra high frequency (UHF) RFID may overcome these limitations. With improvements, the technology may prove useful to practitioners prescribing volume accommodation strategies for patients by providing information about sock use between clinical visits, including timing and consistency of daily sock ply changes.
Developing World Prosthetics NGO has been in contact with the Jaipur Foot Organization in order to create a human powered vacuum pump for a new technique in prosthetic fitment. The new technique would provide mobility to fitment camps due to the non-reliance of an electrical grid. The design however would need to meet the demands of third-world conditions and heavy, continuous usage. This thesis seeks to explore a variety of mechanisms in order to meet the required specifications of the JFO and the new technique.; by Philip Thomas Garcia.; Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2008.; Includes bibliographical references (leaf 19).
Introduction: Transtibial amputation is one of the lower limb amputations more often performed. Objective: The aim of this study was to compare, using 3D gait analysis, gait deviations of patients with transtibial amputation, previously trained, using KBM and vacum prosthetic fittings. Methodology: Transtibial amputees that used Kondylen Bettung Münster (KBM) and vacuum prosthetic fitting waived by the Sistema Único de Saúde (SUS) were evaluated. The final sample consisted of 12 participants in the "KBM" group and 5 in the "vacuum" group. They all underwent a physical examination, which consisted of goniometry, muscle strength testing and anthropometric data. They also performed three-dimensional (3D) gait analysis. For this, they were vested with reflexive markers on anatomical and prosthetic corresponding landmarkers according to the Helen Hayes and walked across a 10-m walk-way at their self-selected speed. The capture system consisted of 6 cameras Hawk and the Cortex software version 22.214.171.1248 for capturing and editing the trials, both from Motion Analysis Corporation. The Gait Profile Scores (GPS), Gait Variable Score (GVS) and temporal-spatial parameters performed the comparison between the two groups. In addition, we tested the correlation between GPS and GVS and between GPS and temporal-spatial parameters. Results: The two groups had significantly lower gait speed...
The greater metabolic demand during the gait of people with a transfemoral amputation limits their autonomy and walking velocity. Major modifications of the kinematic and kinetic patterns of transfemoral amputee gait quantified using gait analysis may explain their greater energy cost. Donelan et al. proposed a method called the individual limb method to explore the relationships between the gait biomechanics and metabolic cost. In the present study, we applied this method to quantify mechanical work performed by the affected and intact limbs of transfemoral amputees. We compared a cohort of six active unilateral transfemoral amputees to a control group of six asymptomatic subjects.
Compared to the control group, we found that there was significantly less mechanical work produced by the affected leg and significantly more work performed by the unaffected leg during the step-to-step transition. We also found that this mechanical work increased with walking velocity; the increase was less pronounced for the affected leg and substantial for the unaffected leg. Finally, we observed that the lesser work produced by the affected leg was linked to the increase in the hip flexion moment during the late stance phase, which is necessary for initiating knee flexion in the affected leg. It
is possible to quantify the mechanical work performed during gait by people with a transfemoral amputation...
Targeted reinnervation is a new neural-machine interface that has been developed to help improve the function of new-generation prosthetic limbs. Targeted reinnervation is a surgical procedure that takes the nerves that once innervated a severed limb and redirects them to proximal muscle and skin sites. The sensory afferents of the redirected nerves reinnervate the skin overlying the transfer site. This creates a sensory expression of the missing limb in the amputee's reinnervated skin. When these individuals are touched on this reinnervated skin they feel as though they are being touched on their missing limb. Targeted reinnervation takes nerves that once served the hand, a skin region of high functional importance, and redirects them to less functionally relevant skin areas adjacent to the amputation site. In an effort to better understand the sensory capacity of the reinnervated target skin following this procedure, we examined grating orientation thresholds and point localization thresholds on two amputees who had undergone the targeted reinnervation surgery. Grating orientation thresholds and point localization thresholds were also measured on the contralateral normal skin of the targeted reinnervation amputees and on analogous sites in able-bodied controls. Grating orientation thresholds for the reinnervated skin of the targeted reinnervation amputees were found to be similar to normal ranges for both the amputees’ contralateral skin and also for the control population. Point localization thresholds for these amputees were found to be lower for their reinnervated skin than for their contralateral skin. Reinnervated point localization thresholds values were also lower in comparison to homologous chest sites on the control population. Mechanisms appear to be in place to maximize re-established touch input in targeted reinnervation amputees. It seems that sound sensory function is provided to the denervated skin of the residual limb when connected to afferent pathways once serving highly functionally relevant regions of the brain. This suggests that tactile interface devices could be used to give a physiologically appropriate sense of touch to a prosthetic limb...
The issues of research required in the field of bio medical engineering and
externally-powered prostheses are attracting attention of regulatory bodies and
the common people in various parts of the globe. Today, 90 percent of
prostheses used are conventional body powered cable-controlled ones which are
very uncomfortable to the amputees as fairly large amount of forces and
excursions have to be generated by the amputee. Additionally, its amount of
rotation is limited. Alternatively, prosthetic limbs driven using electrical
motors might deliver added functionality and improved control, accompanied by
better cosmesis, however,it could be bulky and costly. Presently existing
proposals usually require fewer bodily response and need additional upkeep than
the cable operated prosthetic limbs. Due to the motives mentioned, proposal for
mechanization of body-powered prostheses, with ease of maintenance and cost in
mind, is presented in this paper. The prosthetic upper limb which is being
automated is for Transhumeral type of amputees that is amputated from above
elbow. The study consists of two main portions: one is lifting mechanism of the
limb and the other is gripping mechanism for the hand using switch controls,
which is the most cost effective and optimized solution...
Many clinically available, upper-extremity prosthetic limbs provide myoelectric control of a single device, such as a hand, elbow, or wrist. Most commonly, these systems yield control information from myoelectric signal (MES) amplitude  or rate of change of MES . Such systems have been beneficial; however, prosthetic users would no doubt find enhanced functionality and usability if they could reliably control more than a single function (or device). Seeking to address this issue, extensive work has gone into developing schemes that provide multifunction myoelectric classification with very high accuracy . However, for all continuous multifunction MES classifiers, no matter how accurate and repeatable, there exists no defined threshold (classification accuracy) of acceptability. This is due, in large part, to the limited availability of prosthetic devices housing multiple electromechanical functions.
Described in this paper is a recently developed MES control software tool that incorporates state-of-the-art multifunction control and a multifunction, real-time virtual limb. Twelve subjects have performed a virtual clothes pin functional test  yielding results that relate classification accuracy and multifunction device usability. Preliminary results indicate no strong relationship between accuracy and usability scores as determined by this tool.