Current evaluation of hydraulics to replace the cable force transmission system for body-powered upper-limb prostheses

Present body-powered upper-limb prostheses use a cable control system employing World War II aircraft technology to transmit force from the body to the prosthesis for operation. The cable and associated hardware are located outside the prosthesis. Because individuals with arm amputations want prostheses that are natural looking with a smooth, soft outer surface, a design and development project was undertaken to replace the cable system with hydraulics located inside the prosthesis. Three different hydraulic transmission systems were built for evaluation, and other possibilities were explored. Results indicate that a hydraulic force transmission system remains an unmet challenge as a practical replacement for the cable system. The author was unable to develop a hydraulic system that meets the necessary dynamic requirements and is acceptable in size and appearance.     

Biomechanical evaluation of two types of short-stemmed hip prostheses compared to the trust plate prosthesis by three-dimensional measurement of micromotions

Background

Stemless and short-stemmed hip prostheses have been developed to preserve femoral bone stock. While all these prostheses claim a more or less physiological load transfer, clinical long-term results are only available for the stemless thrust plate prosthesis. In this study, the in vitro primary stability of the thrust plate prosthesis was compared to two types of short-stemmed prostheses. In addition to the well-established Mayo prosthesis, the modular Metha prosthesis was tested using cone adapters with 130° and 140° neck-shaft-angles.

Methods

The prostheses were implanted in composite femurs and loaded dynamically (300–1700 N). Three-dimensional micromotions at the bone-prosthesis interface were measured. In addition, the three-dimensional deformations at the surface of the composite femur were measured to gain data on the strain distribution.

Findings

For all tested prostheses, the micromotions did not exceed 150 μm, the critical value for osteointegration. The thrust plate prosthesis revealed similar motions as the short-stemmed prostheses. The short-stemmed prosthesis with the 130° cone tended to have the highest micromotions of all tested short-stemmed prostheses. The thrust plate prosthesis revealed the lowest alteration of bone surface deformation after implantation.

Interpretation

The comparably low micromotions of the thrust plate prosthesis and the short-stemmed prostheses should be conducive to osseous integration. The higher alteration of load transmission after implantation reveals a higher risk of stress shielding for the short-stemmed prostheses.     

The in-vivo effects of an intramedullary implant evoking a constant radial stress to bone. An animal study in the tibia of the goat

Initial stability is essential for successful bone ingrowth into non-cemented prostheses. An entire new concept to increase the initial stability directly after implantation of intramedullary stems was developed (the tension rod prosthesis). The concept is based on a tension rod made out of memory metal that pulls a proximal stem of a prosthesis towards a distal anchor with a constant force. The stress generated along the long axis of the bone produces a radial stress around the prosthesis in the proximal femur. The main goal of this design is to increase the primary stability of the prosthesis during the ingrowth phase and to prevent stress shielding and bone resorption, as realized by the radial force applied to the proximal endosteum of the bone. To assess the efficacy of this concept and to collect data for the anchor design, an implant was developed for implantation into the tibia of the goat. Analyses of push-out strength and bone reactions were performed postoperatively. After 48 weeks the push-out strength of this implant was increased and the histological evaluation showed almost complete osseousintegration. Histomorphometrical analysis showed pronounced, permanent periosteal reactions, located around the anchor of the implant, which generates the radial stress. These first results showed that the bone can withstand the radial stress provoked by the anchor of the tension rod. It is concluded that the concept of a tension rod prosthesis is viable.     

Does having a computerized prosthetic knee influence cognitive performance during amputee walking?

OBJECTIVE: To compare objective cognitive performance and perception of cognitive burden during walking tasks using 2 different prosthetic knees: a computerized hydraulic knee (Otto Bock C-leg) and a noncomputerized hydraulic knee (Ossur Mauch SNS). DESIGN: Two-group crossover trial, with participants randomly assigned to order of prosthesis. Participants completed assessments under 2 conditions, a self-selected speed walk and a controlled speed walk, on 2 separate occasions (precrossover, postcrossover). SETTING: Veterans Health Administration hospital. PARTICIPANTS: Eight transfemoral amputees. INTERVENTION: Computerized versus noncomputerized prosthetic knee. MAIN OUTCOME MEASURES: Objective cognitive performance measures included verbal fluency (Controlled Oral Word Association Test, Category Test), attention and working memory (serial subtraction), and walking speed during cognitive tasks. Measures of perceived cognitive burden included subjective attentional requirements of walking and cognitive tasks and subjective general cognitive burden of prosthesis. RESULTS: There were no significant differences in objective cognitive performance on any task between prostheses, nor did walking speed vary by prosthesis during the free-speed walk. Participants reported that walking required less attention while wearing the C-leg and that the C-leg was less of a cognitive burden than the noncomputerized prosthesis. CONCLUSIONS: In nondemanding walking conditions with experienced amputees, participants reported that the more costly C-leg required less cognitive attention than the noncomputerized knee. However, this subjective experience did not translate to improved performance on neuropsychologic screening instruments or on walking speed. Noncomputerized prostheses may be adequate for a majority of amputees, and further research is needed to identify particular groups of amputees (ie, new amputees, amputees with complex physical or cognitive demands) who may benefit from computerized prostheses.     

基于迭代学习控制智能下肢假肢研制:实现了对健肢步速的跟随

背景:传统下肢假肢通过手动方式将气压或者液压膝关节阻尼器调整到一种比较适宜的状态,行走状态改变时膝关节阻尼不能随之改变,假肢跟随性差,步速变化范围小.智能下肢假肢能够根据人体运动信息调整膝关节阻尼力,从而达到更加接近正常步态的效果.开发国内智能下肢假肢对提高国内残疾人生活质量有着重要的现实意义.目的:研制能够实现步速跟随功能的智能下肢假肢.方法:智能下肢假肢机械部分采用带固定式气缸阻尼器的四连杆机构,由四连杆后臂下轴的转动角度得出步行速度,依照迭代学习算法得出的知识库确定该步行速度下的针阀开度,通过永磁式直线步进电机作为执行器驱动针阀来控制缓冲气缸腔室间气道有效截面积来调整假肢摆动速度.结果与结论:实验结果显示,采用电位计作为检测手段不但能够获得步行速度,而且能够区分支撑期和摆动期.在不同速度下,智能下肢假肢膝关节最大摆动角度变化小于13°.提示智能下肢假肢能够识别步行速度,并根据步行速度调整膝关节摆动速度,实现了对健肢步行速度的跟随,为进一步的研究奠定了实验基础.     

Fixed and mobile-bearing total ankle prostheses: Effect on tibial bone strain

BackgroundTotal ankle replacement is associated to a high revision rate. To improve implant survival, the potential advantage of prostheses with fixed bearing compared to mobile bearing is unclear. The objective of this study was to test the hypothesis that fixed and mobile bearing prostheses are associated with different biomechanical quantities typically associated to implant failure.MethodsWith a validated finite element model, we compared three cases: a prosthesis with a fixed bearing, a prosthesis with a mobile bearing in a centered position, and a prosthesis with mobile bearing in an eccentric position. Both prostheses were obtained from the same manufacturer. They were tested on seven tibias with maximum axial compression force during walking. We tested the hypothesis that there was a difference of bone strain, bone-implant interfacial stress, and bone support between the three cases. We also evaluated, for the three cases, the correlations between bone support, bone strain and bone-implant interfacial stress.FindingsThere were no statistically significant differences between the three cases. Overall, bone support was mainly trabecular, and less effective in the posterior side. Bone strain and bone-implant interfacial stress were strongly correlated to bone support.InterpretationsEven if slight differences are observed between fixed and mobile bearing, it is not enough to put forward the superiority of one of these implants regarding their reaction to axial compression. When associated to the published clinical results, our study provides no argument to warn surgeons against the use of two-components fixed bearing implants.     

Prosthetic loading during kneeling of persons with transfemoral amputation

Observations in the field of lower limb prosthetic rehabilitation have shown that several transfemoral prostheses show signs of wear on some components of the knee unit. This is thought to be a result of severe loading developed during activities associated with kneeling. Some prostheses may have failed due to repetitive action of such loading. In order to determine the nature and magnitude of the loads developed during kneeling by persons with transfemoral amputation, and to investigate the influence of various prosthetic parameters, an analysis of the results of 162 tests in prosthetic knee hyperflexion was undertaken. The services of four males with amputation were enlisted. The measurements involved simultaneous use of two Kistler force platforms, a six-channel strain gauge transducer mounted on the prosthetic shank, and a data acquisition system. The critical loads for this configuration were found to be the shear force on the knee hinge, the shear force imposed by the knee chassis on the shin, and the bending moment tending to hyperflex the knee. These loads ranged from 0.6 to 6.2 kN, 0.9 to 6.7 kN, and from 18.3 to 155.7 Nm, respectively. To achieve a comfortable kneeling position, some prostheses permit foot rotation about the pylon axis of 90 infinity to allow the shank to be approximately parallel to the ground. Tests were also conducted with the prostheses in this configuration and the most influential prosthetic parameter was found to be the external rotation of the foot (toe-out angle). During kneeling, it was found that the loading was dependent upon the position of the torso relative to the prosthesis, but loads were much higher than those developed during level walking.     

Migration and cyclic motion of a new short-stemmed hip prosthesis--a biomechanical in vitro study

BACKGROUND: Uncemented, short-stemmed hip prostheses have been developed to reduce the risk of stress shielding and to preserve femural bone stock. The long-term success of these implants is yet uncertain. Prerequisite for osseointegration is sufficient primary stability. In this study the cyclic motion and migration patterns of a new short-stemmed hip implant were compared with those for two clinically successful shaft prostheses. METHODS: The prostheses were implanted in paired fresh human femura and loaded dynamically (gait cycle) with increasing load (max 2,100 N) up to 15,000 cycles. Relative displacements between prosthesis and bone were recorded using a 3D-video analysis system. FINDINGS: The short stem displayed a biphasic migration pattern with stabilisation at maximum load. Initial migration was predominantly into varus and was greater than that for the shaft prostheses. Failure occurred in cases of poor bone quality and malpositioning. Cyclic motion of the short prosthesis was less than that for the shaft prostheses. Surface finish showed no effect. System stiffness for the new stem was lower than for the shaft prostheses. INTERPRETATION: The new stem tended to migrate initially more than the shaft prostheses, but stabilised when cortical contact was achieved or the cancellous bone was compacted sufficiently. Bone quality and correct positioning were important factors for the short stem. The lower cyclic motion of the new stem should be favourable for bony ingrowth. The lower system bending stiffness with the new implant indicated a more physiological loading of the bone and should thereby reduce the effects of stress shielding.     

Comparison of electromyography and force as interfaces for prosthetic control

The ease with which persons with upper-limb amputations can control their powered prostheses is largely determined by the efficacy of the user command interface. One needs to understand the abilities of the human operator regarding the different available options. Electromyography (EMG) is widely used to control powered upper-limb prostheses. It is an indirect estimator of muscle force and may be expected to limit the control capabilities of the prosthesis user. This study compared EMG control with force control, an interface that is used in everyday interactions with the environment. We used both methods to perform a position-tracking task. Direct-position control of the wrist provided an upper bound for human-operator capabilities. The results demonstrated that an EMG control interface is as effective as force control for the position-tracking task. We also examined the effects of gain and tracking frequency on EMG control to explore the limits of this control interface. We found that information transmission rates for myoelectric control were best at higher tracking frequencies than at the frequencies previously reported for position control. The results may be useful for the design of prostheses and prosthetic controllers.     

Comparison of myoelectric and conventional prostheses for adolescent amputees

We questioned whether myoelectric prostheses were a reasonable alternative to conventional prostheses for adolescents with unilateral, congenital, below-elbow amputations in respect to fit, function, cosmesis, and cost. Ten patients were studied. Each received a physical, functional, and psychosocial evaluation prior to prosthetic fitting. The physical evaluation included myopotential, residual limb length and circumference, active range of motion, terminal device grasp force, and mechanical range. The functional evaluation consisted of a questionnaire of 38 bimanual activities. The psychosocial evaluation included an assessment of both the patient and the family. Following prosthesis fabrication, each patient received 10 days of training, a 3-month checkup, and a 6-month reevaluation. Wearing patterns, perception of cosmesis, change in physical attributes of the residual limb, and functional performance were documented. Results indicate that for these subjects myoelectric prostheses with a hand were an acceptable alternative to conventional prostheses with a hook.     

Colorimetric analysis of silicone cosmetic prostheses for upper-limb amputees

Every year the Italian National Insurance Institute of Accidents on Work (INAIL) Prosthesis Centre manufactures more than 300 silicone cosmetic upper-limb prostheses that are aesthetically similar to patients' missing limbs; however, the prostheses have the following drawbacks: subjectivity in color choice, high production costs, and long time frames for patient tests and prosthesis production. In an attempt to minimize these factors, we performed a study to test various systems that automatically detect the color of human skin. Such a system would allow us to reproduce a patient's exact skin color for silicone cosmetic prostheses. We analyzed the color identification systems available on the market and assessed the possibility of introducing such a system into the production cycle of the prostheses. We found that because of intrinsic factors of the materials, automatic color detection for prosthesis production is complex. Therefore, any of the systems we tested will require further development for full satisfaction of the needs of prostheses manufacturers.     

Biomechanical risk factors for knee osteoarthritis when using passive and powered ankle–foot prostheses

BackgroundGait compensations following transtibial amputation negatively affect sound limb loading and increase the risk of knee osteoarthritis. Push-off assistance provided by new powered prostheses may decrease the demands on the sound limb. However, their effects in a young population in the early stages of prosthetic use are still unknown. The purpose of this study was to compare limb loading between 1. passive and powered ankle–foot prostheses, 2. sound and amputated limbs, and 3. individuals with amputations in the relatively early stages of prosthetic use and controls.MethodsTen young, active individuals with unilateral transtibial amputation and 10 controls underwent biomechanical gait analysis at three speeds. The peak external knee flexor and adductor moments, adductor moment's angular impulse, peak vertical ground reaction force and loading rate were calculated. Repeated measures ANOVAs compared between limbs, prostheses, and groups.FindingsThe powered prosthesis did not decrease the sound limb's peak adduction moment or its impulse, but did decrease the external flexor moment, peak vertical force and loading rate as speed increased. The powered prosthesis decreased the loading rate from controls. The sound limb did not display a significantly greater risk for knee osteoarthritis than the intact limb or than controls in either device.InterpretationIn the early stages of prosthetic use, young individuals with transtibial amputation display few biomechanical risk factors for knee osteoarthritis development. However, a powered ankle–foot prosthesis still offers some benefits and may be used prophylactically to mitigate potential increases of these variables with continued prosthetic use over time.     

Biomechanics of walking with silicone prosthesis after midtarsal (Chopart) disarticulation

Background

Currently accepted understanding is that silicone foot prostheses have little influence on biomechanics of walking; however clinical observations suggest several beneficial effects. The objective of this study was to characterize biomechanics of gait in a group of subjects with disarticulation through the talonavicular (T-N) and calcaneocuboid (C-C) (midtarsal) joints wearing two different prosthetic solutions: silicone prostheses and conventional prostheses.

Methods

Four subjects that underwent Chopart partial foot amputation were included in the study. Silicone prosthesis was custom manufactured for each individual subject. Instrumented gait analysis was performed in each subject in four experimental conditions: barefooted, barefooted and wearing silicon prosthesis, wearing footwear with conventional prosthesis and wearing footwear with silicon prosthesis. Comparisons and statistical analysis were made between both barefooted conditions and both foot-wearing conditions.

Findings

Our results show that silicone prosthesis without reinforced sole increases gait velocity, improves generation of ankle plantarflexion moment throughout the stance phase and enables greater power generation at push-off. The most important changes, however, occur in the frontal plane, where improved hip adduction angles and higher hip abduction moment in the stance enable more normal pelvic movement and consequently also less trunk inclination toward amputated side.

Interpretation

We conclude that silicone prostheses are not solely for cosmetic reasons but may be also biomechanically superior over other prosthetic solutions, especially for walking barefoot.     

赝复体辅助术后近距离放射治疗对颌骨恶性肿瘤的作用

目的探讨赝复体辅助术后近距离放疗治疗颌骨恶性肿瘤的应用价值。 方法分析2012年5月至2017年9月在徐州市中心医院口腔科就诊的31例晚期颌骨恶性肿瘤病例,近距离放疗前均接受过颌骨部分或全部切除术,将颌骨CT扫描数据导入近距离放疗三维治疗计划系统,进行赝复体布源器计算机辅助设计及制作,通过肿瘤体积变化情况及患者自我评估等指标评价临床治疗效果,应用Kaplan-Meier分析法进行生存分析。 结果31例患者治疗总有效率达到87.1%,2年无进展生存率和总生存率分别为71.2%和78.3%。赝复体固位稳定性良好,患者自我评价全优,随访过程未发生严重的不良反应。 结论赝复体修复技术可以有效修复手术导致的颌骨组织缺损,并辅助近距离放疗防治恶性肿瘤的复发和转移。     

A self-contained, mechanomyography-driven externally powered prosthesis

The measurement of the low-frequency (5-50 Hz) "sounds" or vibrations produced by contracting muscles is termed mechanomyography (MMG). As a control signal for powered prostheses, MMG offers several advantages over conventional myoelectric control, including, nonspecific sensor placement, distal signal measurement, robustness to changing skin impedance, and reduced sensor costs. The objectives of this study were to demonstrate 2-function prosthesis control based on a triplet of distally recorded, normalized root mean square MMG signals and to identify necessary future research toward full clinical implementation of MMG signals in upper-limb externally powered prostheses. A novel self-contained MMG-driven prosthesis for below-elbow amputees was designed, implemented, and preliminarily tested on 2 subjects. This prosthesis was composed of specialized software and hardware modules that emulate a 2-site electromyography sensing system. Although the use of MMG signals for prosthesis control has been shown previously, we report, for the first time, successful control within a self-contained unit in unconstrained environments. Specifically, essential requirements for practical use, such as standardized sensor attachment, basic noise elimination, and miniaturization of the system, have been achieved. Both subjects were able to voluntarily open and close the prosthesis hand with no significant delays from intention to action (approximately 120 ms). Quantitative analyses revealed 88% and 71% control accuracy for subjects 1 and 2, respectively.     

State of the art of prosthesis simulators for the upper limb: A narrative review

BackgroundResearch into prosthesis training and design puts a burden on the small population of people with upper-limb absence who can participate in these studies. One solution is to use a prosthetic hand simulator, which allows for attaching a hand prosthesis to an intact limb. However, whether the results of prosthesis simulator studies can be translated to people with upper-limb absence using a hand prosthesis is unclear.ObjectiveTo review the literature on prosthetic hand simulators, provide an overview of current designs, and highlight the differences and similarities between prosthesis simulators and traditional prostheses.MethodsA Boolean combination of keywords was used to search 3 electronic databases: PubMed, Scopus and Web of Science. Relevant articles in English were selected.ResultsIn total, 52 papers were included in the review, and an overview of the state of the art was presented. We identified the key differences between prosthesis simulators and traditional prostheses as the position of the terminal device and the available degrees of freedom of the arm and (prosthetic) wrist.ConclusionsThis paper provides an overview of prosthesis simulator designs over the past 27 years and an overview of the similarities and differences between prosthesis simulators and prostheses. The literature does not provide enough evidence to establish whether the results obtained from simulator studies could be translated to prostheses. A recommendation for future simulator design is to constrain pro- and supination of the forearm of anatomically intact participants and add a prosthetic wrist that can pro- and supinate. Additional research is required to find the ideal terminal device position for a prosthesis simulator with respect to the person's hand.     

The effect of the orientation of the radial head on the kinematics of the ulnohumeral joint and force transmission through the radiocapitellar joint

Background. The treatment of radial head fractures that are not amenable to an open reduction and internal fixation, remains to be a difficult issue. A potential problem with prosthetic replacement of the radial head is the shape of current radial head prostheses. The purpose of this study was to determine the effect of the shape of the radial head on kinematics and load transfer of the elbow. Methods. Kinematics of the elbow and radiocapitellar force transmission were measured in 6 fresh frozen upper extremities. The effect of radial head shape was tested by rotating the head 90 degrees , with a custom-made 'native' radial head prosthesis. 3-D spatial orientation of the ulna showed an average difference in ulnohumeral laxity, between the nominal and 90 degrees conditions, of 0.1 degrees throughout the arc of motion with neutral forearm rotation (maximum: 2 degrees ). Findings. We found an average difference in ulnar axial rotation, of 0.1 degrees (maximum: 1.9 degrees ). No differences showed statistical significance. Radiohumeral joint force was measured and maximally showed a 32 times increase of force in the altered shape conditions. Interpretation. Our results show that the kinematics of the elbow was not affected by altering the shape of the radial head, but it did adversely affect the forces in the radiohumeral joint. This could possibly generate degenerative changes in the elbow.     

Updating upper extremity temporary prosthesis: thermoplastics.

Since 1989 amputees with upper-extremity burns have been fitted with a temporary prosthesis fabricated from low-temperature thermoplastic. Before 1989 conventional temporary prostheses were fabricated with plaster. The use of the thermoplastic material has produced a lightweight, cost-effective, modular system. No patients exhibited skin breakdown with the thermoplastic material. It appears that thermoplastics may be the next major breakthrough in terms of a design for a temporary upper-extremity prosthesis.     

Selection of biological prosthesis for abdominal wall repair on the basis of in vitro biocompatibility determination

Research on prostheses for repairing abdominal wall defects has progressed through past decades for developing an ideal prosthesis. The study was designed to compare different extracellular matrix (ECM) derived biological prostheses as alternate to conventional synthetic polymeric prostheses for the repair of full thickness abdominal wall defects. Five biological scaffolds derived from bovine diaphragm, bovine aorta, bovine gall bladder, porcine gall bladder, and rabbit skin were prepared and screened for their in vitro biocompatibility. Decellularized ECMs were subjected to various biocompatibility analyses, namely, water absorption potential, matrix degradation analysis, biomechanical testing, and cytocompatibility analysis. Though the rabbit skin displayed maximum biomechanical strength, due to its rapid degradation, it failed to fulfill the criteria of an ideal prosthesis. ECMs derived from bovine diaphragm and aorta were found to be superior than others based upon hydration and matrix degradation analysis, with best scores for bovine diaphragm followed by bovine aorta. The bovine diaphragm and aorta also displayed sufficient biomechanical strength, with diaphragm being the second highest (next to rabbit skin), in biomechanical strength followed by aorta. None of the biological prosthesis revealed any cytotoxicity. Thus, bovine diaphragm and aorta derived ECM fulfill the necessary criteria for their use as biological prosthesis. Because these prostheses are biocompatible, apart from their low cost, ease of availability, and simple preparation, they present a potential alternative to synthetic prosthesis for repair of abdominal wall defects, especially in veterinary patients.