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The desire for functional replacement of a missing hand is an ancient one. Historically, humans have replaced a missing limb with a prosthesis for cosmetic, vocational, or personal autonomy reasons. The hand is a powerful tool, and its loss causes severe physical and often mental debilitation. Technological advancements have allowed the development of increasingly effective artificial hands, which can improve the quality of life of people who suffered a hand amputation. Here, we review the state of the art of robotic prosthetic hands (RPHs), with particular attention to the potential and current limits of their main building blocks: the hand itself, approaches to decoding voluntary commands and controlling the hand, and systems and methods for providing sensory feedback to the user. We also briefly describe existing approaches to characterizing the performance of subjects using RPHs for grasping tasks and provide perspectives on the future of different components and the overall field of RPH development.

Background Electrical stimulation of residual afferent nerve fibers can evoke sensations from a missing limb after amputation, and bionic arms endowed with artificial sensory feedback have been shown to confer functional and psychological benefits. Here we explore the extent to which artificial sensations can be discriminated based on location, quality, and intensity. Methods We implanted Utah Slanted Electrode Arrays (USEAs) in the arm nerves of three transradial amputees and delivered electrical stimulation via different electrodes and frequencies to produce sensations on the missing hand with various locations, qualities, and intensities. Participants performed blind discrimination trials to discriminate among these artificial sensations. Results Participants successfully discriminated cutaneous and proprioceptive sensations ranging in location, quality and intensity. Performance was significantly greater than chance for all discrimination tasks, including discrimination among up to ten different cutaneous location-intensity combinations (15/30 successes, p p p p p Conclusion Electrode location, stimulation frequency, and stimulation pattern can be modulated to evoke functionally discriminable sensations with a range of locations, qualities, and intensities. This rich source of artificial sensory feedback may enhance functional performance and embodiment of bionic arms endowed with a sense of touch.

An ideal prosthesis should perform as well as or better than the missing limb it was designed to replace. Although this ideal is currently unattainable, recent advances in design have significantly improved the function of prosthetic devices. For the lower extremity, both passive prostheses (which provide no added power) and active prostheses (which add propulsive power) aim to emulate the dynamic function of the ankle joint, whose adaptive, time-varying resistance to applied forces is essential for walking and running. Passive prostheses fail to normalize energetics because they lack variable ankle impedance that is actively controlled within each gait cycle. By contrast, robotic prostheses can normalize energetics for some users under some conditions. However, the problem of adaptive and versatile control remains a significant issue. Current prosthesis-control algorithms fail to adapt to changes in gait required for walking on level ground at different speeds or on ramps and stairs. A new paradigm of ‘muscle as a tunable material’ versus ‘muscle as a motor’ offers insights into the adaptability and versatility of biological muscles, which may provide inspiration for prosthesis design and control. In this new paradigm, neural activation tunes muscle stiffness and damping, adapting the response to applied forces rather than instructing the timing and amplitude of muscle force. A mechanistic understanding of muscle function is incomplete and would benefit from collaboration between biologists and engineers. An improved understanding of the adaptability of muscle may yield better models as well as inspiration for developing prostheses that equal or surpass the functional capabilities of biological limbs across a wide range of conditions.

Phantom limb pain (PLP) is a chronic neuropathic pain condition of a missing limb following amputation. Pain management is multi-modal, including various non-pharmacological therapies. The purpose of this scoping review was to investigate the evidence surrounding current non-pharmacological treatment modalities for PLP and provide insight into their clinical feasibility.A systematic search was conducted using four databases (Medline, Embase, PsychInfo, and CINAHL) following the PRISMA-ScR method. Results from papers meeting the inclusion criteria were charted to summarize findings, demographics, and use of neuroimaging.A total of 3387 papers were identified, and full texts of 142 eligible papers were assessed. Eleven treatment modalities for PLP were identified with varying levels of evidence. Overall, there were 25 RCTs, 58 case reports, and 59 a combination of pilot, quasi-experimental, observational, and other study designs.Currently, the evidence surrounding most treatment modalities is limited and only a fraction of studies are supported by strong evidence. The findings of this review demonstrated a clear need to conduct more rigorous research with diverse study designs to better understand which modalities provide the most benefit and to incorporate neuroimaging to better determine the neural correlates of PLP and mechanisms of various treatments.Implications for RehabilitationPhantom limb pain (PLP) is a prevalent and debilitating condition following amputation and health care professionals should incorporate an evidence-based pain management protocol into their rehabilitation program.There exist a number of different non-pharmacological therapies to address PLP, however the scientific rigor and levels of evidence vary across modalities.Prescription of interventions for PLP should consider individual patient differences, accessibility to the patient, and quite possibly, a multi-modal approach, particularly for those who also experience residual limb pain.Imagery-based therapies provide the highest level of current evidence based on robust and large randomized control trials, are readily accessible, and are thus most recommended for relief of PLP.

Many individuals who undergo limb amputation experience persistent phantom limb pain (PLP), but the underlying mechanisms of PLP are unknown. The traditional hypothesis was that PLP resulted from maladaptive plasticity in sensorimotor cortex that degrades the neural representation of the missing limb. However, a recent study of individuals with upper limb amputations has shown that PLP is correlated with aberrant electromyographic (EMG) activity in residual muscles, posited to reflect a retargeting of efferent projections from a preserved representation of a missing limb. Here, we assessed EMG activity in a residual thigh muscle (vastus lateralis, VL) in patients with transfemoral amputations during cyclical movements of a phantom foot. VL activity on the amputated side was compared to that recorded on patients' intact side while they moved both the phantom and intact feet synchronously. VL activity in the patient group was also compared to a sample of control participants with no amputation. We show that phantom foot movement is associated with greater VL activity in the amputated leg than that seen in the intact leg as well as that exhibited by controls. The magnitude of residual VL activity was also positively related to ratings of PLP. These results show that phantom limb movement is associated with aberrant activity in a residual muscle after lower-limb amputation and provide evidence of a positive relationship between this activity and phantom limb pain.NEW & NOTEWORTHY This study is the first to assess residual muscle activity during movement of a phantom limb in individuals with lower limb amputations. We find that phantom foot movement is associated with aberrant recruitment of a residual thigh muscle and that this aberrant activity is related to phantom limb pain.

To fully replace the missing limb, a myoelectric prosthesis needs to provide a bidirectional communication between user's brain and its bionic limb. And indeed, modern prosthetic hands are advanced mechatronic systems that approach the design and capabilities of biological hands both morphologically (size, shape, and weight) and functionally (degrees of freedom). In addition, these hands are controlled intuitively by mapping muscles' activations to prosthesis functions using direct control or pattern classification. However, commercial systems do not yet provide somatosensory feedback to their users. In this chapter, we provide an overview of the methods and techniques that can be used to stimulate the sensory motor structures of an amputee subject in order to restore the missing sensations. We then discuss the prosthesis variables that are most often transmitted through the stimulation as well as the encoding schemes that can be used to map those variables to stimulation parameters. The contradictory evidence about the impact of feedback on the prosthesis performance is presented next, illustrating that designing, implementing, and assessing effective feedback interfaces is indeed a challenging task. Finally, the chapter ends with discussion and recommendation for further research that will hopefully lead to a successful solution for closed-loop prosthesis control.

The Mexican Axolotl is able to regenerate missing limb structures in any position along the limb axis throughout its life and serves as an excellent model to understand the basic mechanisms of endogenous regeneration. How the new pattern of the regenerating axolotl limb is established has not been completely resolved. An accumulating body of evidence indicates that pattern formation occurs in a hierarchical fashion, which consists of two different types of positional communications. The first type (Type 1) of communication occurs between connective tissue cells, which retain memory of their original pattern information and use this memory to generate the pattern of the regenerate. The second type (Type 2) of communication occurs from connective tissue cells to other cell types in the regenerate, which don’t retain positional memory themselves and arrange themselves according to these positional cues. Previous studies suggest that molecules within the extracellular matrix (ECM) participate in pattern formation in developing and regenerating limbs. However, it is unclear whether these molecules play a role in Type 1 or Type 2 positional communications. Utilizing the Accessory Limb Model, a regenerative assay, and transcriptomic analyses in regenerates that have been reprogrammed by treatment with Retinoic Acid, our data indicates that the ECM likely facilities Type-2 positional communications during limb regeneration.

A student with a physical disability successfully completes the first 2 years of a baccalaureate in nursing degree program and is preparing to enter the clinical phase of his education. The student was born without a right forearm but has learned to compensate for the disability. The faculty are concerned that he will not be able to perform all required nursing skills or cannot practice safely in the clinical setting. The student is also concerned about how he will be viewed by both students and faculty.

The lower-limb robotic prostheses can provide assistance for amputees’ daily activities by restoring the biomechanical functions of missing limb(s). To set proper control strategies and develop the corresponding controller for robotic prosthesis, a prosthesis user’s intent must be acquired in time, which is still a major challenge and has attracted intensive attentions. This work focuses on the robotic prosthesis user’s locomotion intent recognition based on the noninvasive sensing methods from the recognition task perspective (locomotion mode recognition, gait event detection, and continuous gait phase estimation) and reviews the state-of-the-art intent recognition techniques in a lower-limb prosthesis scope. The current research status, including recognition approach, progress, challenges, and future prospects in the human’s intent recognition, has been reviewed. In particular for the recognition approach, the paper analyzes the recent studies and discusses the role of each element in locomotion intent recognition. This work summarizes the existing research results and problems and contributes a general framework for the intent recognition based on lower-limb prosthesis.

Following amputation, almost two-thirds of amputees experience unpleasant to painful sensations in the area of the missing limb. Whereas the mechanism of phantom limb pain (PLP) remains unknown, it has been shown that maladaptive cortical plasticity plays a major role in PLP. Transcutaneous electrical nerve stimulation (TENS) generating sensory input is believed to be beneficial for PLP relief. TENS effect may be caused by possible reversing reorganization at the cortical level that can be evaluated by changes in the excitability of the corticospinal (CS) pathway. Excitability changes are dependent on the chosen stimulation patterns and parameters. The aim of this study was to investigate the effect of two TENS patterns on the excitability of the CS tract among healthy subjects. We compared a non-modulated TENS as a conventional pattern with pulse width modulated TENS pattern. Motor evoked potentials (MEPs) from APB muscles of stimulated arm (TENS-APB) and contralateral arm (Control-APB) were recorded. We applied single TMS pulses on two subjects for each TENS pattern. The results showed that both patterns increase the CS excitability, while the effects of the conventional TENS is stronger. However, the amplitude of MEPs from control-APB after TENS delivery remained almost the same.Clinical Relevance- The primary results revealed changes in the activity of CS pathway for both patterns. A future study on a larger population is needed to provide strong evidence on the changes in CS excitability. The evaluation part with more factors such as changes in intracortical inhibition (ICI) may be beneficial to find an optimal modulated TENS pattern to enhance pain alleviation process in PLP.

Many individuals who undergo limb amputation experience persistent phantom limb pain (PLP). The underlying mechanism of PLP is unknown, but the phenomenon has been associated with reorganization in sensorimotor cortex following amputation. The traditional view is that cortical reorganization degrades the missing limb’s representation. However, recent work suggests that an amputated limb’s cortical representation remains intact and that reorganization reflects a retargeting of efferent projections to residual muscles proximal to the amputation site. Evidence of retargeting has only been shown in individuals with upper limb amputations, and the relationship of retargeting to PLP is controversial. This study assessed retargeting and its relationship to PLP in 10 individuals with lower limb amputations. We recorded electromyographic (EMG) activity in a residual thigh muscle (vastus lateralis, VL) in patients with above-knee amputations during cyclical movements of the foot. VL activity on the amputated side was compared to that recorded on patients’ intact side while they moved their phantom and intact feet, respectively. VL activity in the patient group was also compared to VL activity from a sample of 9 control participants with no amputation. We show that phantom foot movement is associated with greater VL activity in the amputated leg than that seen in the intact leg as well as that exhibited by controls. The magnitude of residual VL activity was also positively related to ratings of PLP. These results provide the first support for retargeting in lower limb amputees and suggest that retargeting is related to the experience of phantom pain.New and NoteworthyPrevious work has only examined retargeting in upper limb amputees. This study provides evidence for retargeting in lower limb amputees and suggests that retargeting is related to phantom limb pain.

Previous prostheses for replacing a missing limb following amputation must be worn externally on the body. This limits the extent to which prostheses could physically interface with biological tissues, such as muscles, to enhance functional recovery. The objectives of our study were to (1) test the feasibility of implanting a limb prosthesis, or endoprosthesis, entirely within living skin at the distal end of a residual limb, and (2) identify effective surgical and post-surgical care approaches for implanting endoprostheses in a rabbit model of hindlimb amputation. We iteratively designed, fabricated, and implanted unjointed endoprosthesis prototypes in six New Zealand White rabbits following amputation. In the first three rabbits, the skin failed to heal due to dehiscence along the sutured incision. The skin of the final three subsequent rabbits successfully healed over the endoprotheses. Factors that contributed to successful outcomes included modifying the surgical incision to preserve vasculature; increasing the radii size on the endoprostheses to reduce skin stress; collecting radiographs pre-surgery to match the bone pin size to the medullary canal size; and ensuring post-operative bandage integrity. These results will support future work to test jointed endoprostheses that can be attached to muscles.

A prosthesis is an artificial replacement for any or all parts of the lower or upper extremities, it is a device that is designed to replace, as much as possible, the function or appearance of a missing limb or body part.There are so many types of prosthetic feet open today. Some are expected for unprecedented errands, for instance, walking, moving, cycling, hitting the fairway, swimming, snow skiing or running. Many are waterproof and made of lightweight materials, for instance, plastic, metal blends and carbon-fiber composites. Prosthetic feet can be basic (unmoving), clarified (moving in no less than one orientation), or component response (securing and returning essentialness when walking, giving a sentiment “pushing off,” much like the human foot). However there are sure issues which are not totally handled by the presently accessible prosthesis for which the strolling design remains firmly aggravated. Practical prosthetics can be comprehensively classified into two camps: body-fueled and remotely controlled prosthetics. Body-controlled prosthetics utilize links and tackles strapped to the person to mechanically move the fake appendage through muscle, shoulder, and arm development. While they are profoundly strong, they regularly yield a characteristic appearance for direct usefulness. Too, however the client encounters coordinate control and input through its mechanical operation, the procedure can be exhausting. Externally-powered artificial prosthesis are an attempt to solve this physical exertion. In this paper we have presented a lower leg foot prosthesis outline that is fit for humanlike lower leg elements while as yet coordinating the shape and mass of the missing original limb. After the designing the strength analysis has been done on the prosthesis using ANSYS and the results of the same are compared to the actual load distribution on knee of a non-amputed person.

Myoelectric devices are controlled by electromyographic signals generated by contraction of residual muscles, which thus serve as biological amplifiers of neural control signals. Although nerves severed by amputation continue to carry motor control information intended for the missing limb, loss of muscle effectors due to amputation prevents access to this important control information. Targeted Muscle Reinnervation (TMR) was developed as a novel strategy to improve control of myoelectric upper limb prostheses. Severed motor nerves are surgically transferred to the motor points of denervated target muscles, which, after reinnervation, contract in response to neural control signals for the missing limb. TMR creates additional control sites, eliminating the need to switch the prosthesis between different control modes. In addition, contraction of target muscles, and operation of the prosthesis, occurs in reponse to attempts to move the missing limb, making control easier and more intuitive. TMR has been performed extensively in individuals with high-level upper limb amputations and has been shown to improve functional prosthesis control. The benefits of TMR are being studied in individuals with transradial amputations and lower limb amputations. TMR is also being investigated in an ongoing clinical trial as a method to prevent or treat painful amputation neuromas.

Limb ischemia is acute, chronic, or acute on chronic, and the prevalence of the latter is rising with the presence of an increasing aging population. When occlusion to the flow of blood is sudden, it results in acute limb ischemia, the early diagnosis of which is vital for the salvage of the limb. In chronic ischemia, the occlusion is progressive, and diagnosis can alter the quality of life for a patient, besides limb salvage. Dark skin tones are more common in Africa, India, Asia, and the Middle East. Diagnosis of limb ischemia is missed in this subset because the classical “pallor” described in Caucasians is not seen. It is seen as shades of duskiness, like the purplish hue on an aubergine – also known as Badinjal, Eggplant, or Brinjal. This article explains why there is a color discrepancy and a need for healthcare professionals to be aware, hence improving limb salvage.

Orthopedic technologies encompass all devices applied externally to the user's body to substitute a missing limb (prosthesis) or to replace a missing function (orthosis). Metals, wood, leather, fabrics, thermoplastics, thermosetting composites, foamed plastics, and elastomers are the principle materials mostly used in current orthopedic industry. Due to the fabrication ability of customized sophisticated devices, 3D printing has the potential to facilitate the design of the orthopedic devices. The final choice for material selection will rely on the local availability of materials, technical expertise of orthotist/prosthetist, and expected function for individual patient. The interplay of materials science and processing techniques will reveal new insights, and therefore consistent development and enhancement of materials guarantees the achievements of forthcoming expectations in orthotic and prosthetics industry.

The hand and arm are exceptionally dexterous, exquisitely sensitive, and proficient in performing tasks and functions. Given the invaluable functions of the upper extremity in daily life, replacement of a missing limb through prosthetic substitution is challenging. Prosthetic and rehabilitation needs of injured Service members from recent military conflicts have brought upper extremity amputation to the forefront, which has led to an increase in attention and resource allocation. This article provides an overview of the care of the upper extremity amputee including surgical considerations, prosthetic design and fitting, and preprosthetic and post-prosthetic rehabilitation considerations.

Nearly everyone who undergoes the sudden loss of a limb will continue to feel the presence of and experience sensations in the missing limb for at least some time after the loss. This "phantom limb" phenomenon has been known for centuries, but remains poorly understood. Most work on phantom limb phenomena focuses on the phantom sensations, especially pain, that seem to emanate from the missing limb. This work tends to focus on the role of the body image in maintaining the sense of the phantom. A minority of work in the field distinguishes the body image from body schema, and offers an important corrective to the literature by outlining the unique contribution of the latter to generating and maintaining phantom limb phenomena. Here I review this literature, and motivate a further distinction between a motor body schema and a somatosensory body schema, which allows me to develop a novel hypothesis about the specific contributions of each to the experience of a phantom limb.

Following amputation, most amputees still report feeling the missing limb and often describe these feelings as excruciatingly painful. Phantom limb sensations (PLS) are useful while controlling a prosthesis; however, phantom limb pain (PLP) is a debilitating condition that drastically hinders quality of life. Although such experiences have been reported since the early 16th century, the etiology remains unknown. Debate continues regarding the roles of the central and peripheral nervous systems. Currently, the most posited mechanistic theories rely on neuronal network reorganization; however, greater consideration should be given to the role of the dorsal root ganglion within the peripheral nervous system. This Review provides an overview of the proposed mechanistic theories as well as an overview of various treatments for PLP.

The human powers of regeneration are limited: Broken bones knit, wounds heal, and large parts of the liver can regenerate, but that9s about it. But the axolotl—a large salamander also called the Mexican walking fish—can replace an entire missing limb or even its tail, which means regrowing the spinal cord, backbone, and muscles. About 30 research teams are probing how those and other salamanders do it. In the axolotl, they9ve found, various tissues work together to detect limb loss and coordinate regrowth by reactivating the same genetic circuits that guided the formation of those structures during embryonic development, causing generalist stem cells to specialize. The ultimate hope: One day, we9ll be able to coax injured humans to execute similar repairs.

The axolotl is one of the few tetrapods that are capable of regenerating complicated biological structures, such as complete limbs, throughout adulthood. Upon injury the axolotl generates a population of regeneration-competent limb progenitor cells known as the blastema, which will grow, establish pattern, and differentiate into the missing limb structures. In this review we focus on the crucial early events that occur during wound healing, the neural-epithelial interactions that drive the formation of the early blastema, and how these mechanisms differ from those of other species that have restricted regenerative potential, such as humans. We also discuss how the presence of cells from the different axes of the limb is required for the continued growth and establishment of pattern in the blastema as described in the polar coordinate model, and how this positional information is reprogrammed in blastema cells during regeneration. Multiple cell types from the mature limb stump contribute to the blastema at different stages of regeneration, and we discuss the contribution of these types to the regenerate with reference to whether they are "pattern-forming" or "pattern-following" cells. Lastly, we explain how an engineering approach will help resolve unanswered questions in limb regeneration, with the goal of translating these concepts to developing better human regenerative therapies.

BackgroundThis systematic review aimed to summarise and critically appraise the evidence for the effect of bodily illusions on corticomotoneuronal excitability.MethodsFive databases were searched, with two independent reviewers completing study inclusion, risk of bias, transcranial magnetic stimulation (TMS) reporting quality, and data extraction. Included studies evaluated the effect of an illusion that altered perception of the body (and/or its movement) on excitability of motor circuitry in healthy, adult, human participants. Studies were required to: use TMS to measure excitability and/or inhibition; report quantitative outcomes (e.g., motor evoked potentials); compare the illusion to a control or active comparison condition; evaluate that an illusion had occurred (e.g., measured illusion strength/presence).ResultsOf 2,257 studies identified, 11 studies (14 experiments) were included, evaluating kinaesthetic illusions (n = 5), a rubber hand illusion (RHI) paradigm (n = 5), and a missing limb illusion (n = 1). Kinaesthetic illusions (induced via vision/tendon vibration) increased corticomotoneuronal excitability. Conflicting effects were found for traditional, visuotactile RHIs of a static hand. However, embodying a hand and then observing it move ("self-action") resulted in decreased corticomotoneuronal excitability and increased silent period duration (a measure of Gamma-Aminobutynic acid [GABA]B-mediated intracortical inhibition in motor cortex), with the opposite occurring (increased excitability, decreased inhibition) when the fake hand was not embodied prior to observing movement ("other-action"). Visuomotor illusions manipulating agency had conflicting results, but in the lower risk study, illusory agency over movement resulted in a relative decrease in corticomotoneuronal excitability. Last, an illusion of a missing limb reduced corticomotoneuronal excitability.ConclusionWhile evidence for the effect of bodily illusions on corticomotoneuronal excitability was limited (only 14 experiments) and had a high risk of bias, kinaesthetic illusions and illusions of embodying a hand (and seeing it move), had consistent effects. Future investigations into the role of embodiment and the illusion strength on corticomotoneuronal excitability and inhibition are warranted.

In this study, we hypothesized that haptic feedback would enhance grip force control of surface electromyography (sEMG)-controlled prosthetic hands for targeted reinnervation (TR) amputees. A new miniature haptic device, a tactor, that can deliver touch, pressure, shear, and temperature sensation, allows modality-matching haptic feedback. TR surgery that creates sensory regions on the patient's skin that refer to the surface of the missing limb allows somatotopic-matching haptic feedback. This paper evaluates the hypothesis via an sEMG-controlled virtual prosthetic arm operated by TR amputees under diverse haptic feedback conditions. The results indicate that the grip force control is significantly enhanced via the haptic feedback. However, the simultaneous display of two haptic channels (pressure and shear) does not enhance, but instead degrades, grip force control.

Commercial transfemoral prostheses remain limited to energetically passive devices. Intelligent prostheses still do not replace the power generation capabilities of the missing limb. Active Transfemoral Prosthesis is designed to compensate the movements of transfemoral amputees. Base on the function and principle of huaman lower limb, Active transfemoral prosthesis is designed. Virtual prototype of active transfemoral prosthesis 3D model is built through Solidworks. A dynamical system is used to generate a position trajectory to control a linear motor replacing the missing joint. Hopf oscillator is used to construct a central pattern generator (CPG), which makes up the dynamical system.

PEOPLE WHO lose a limb to war, accident, or disease can choose from a remarkable array of prosthetic replacements, including legs specialized for cyclists and sprinters or arms with hands that can grasp and manipulate playing cards and paring knives. Bioengineers continue to refine prosthetic limbs, but they still can’t replicate the entire constellation of capabilities provided by flesh and blood. So a few determined scientists are pursuing a different solution: They are seeking the recipe for regrowing a missing limb. The ability to assemble a biological limb cell by cell in a lab requires so much detailed knowledge and such advanced technical capabilities that it may be a century off, according to biologist Michael Levin, who directs the Tufts Center for Regenerative & Developmental Biology at Tufts University. “But asking the host organism to build a limb is a much more achievable goal,” he says. After all, the body already knows how to ...

Up to 80% of people who suffer an amputation experience phantom pain from the missing limb. With increasing numbers of dogs and cats undergoing amputation, Lyn Forster is studying the effects of amputation on feline patients at the RVC.

We present evidence that the most commonly found deformities in wild-caught amphibians, those featuring missing limbs and missing limb segments, may be the result of selective predation. Here we report that predatory dragonfly nymphs can severely injure and even fully amputate developing hind limbs of anuran tadpoles. Developmental responses of the injured/amputated tadpole limbs range from complete regeneration to no regeneration, with intermediate conditions represented by various idiosyncratic limb deformities, depending mainly on the developmental stage of the tadpole at the time of injury/amputation. These findings were reinforced by experimental amputations of anuran tadpole hind limbs that resulted in similar deformities. Our studies suggest that selective predation by dragonfly nymphs and other aquatic predators may play a significant role in the most common kinds of limb deformities found in natural populations of amphibians.

Phantom limb sensations may be linked to motor activities in the deafferented cortices of amputees, with artificial visual feedback of an amputated limb leading to enhanced phantom sensations. The present study was designed to verify if cortical motor activity related to an amputated limb can be triggered by visual input using an objective behavioral measure and with a neurophysiological correlate. Trauma amputees and normally limbed subjects showed superior performance in a mirror-drawing task when the mirror was placed sagittally (giving visual feedback of the amputated/inactive limb) compared with when it was placed frontally. Measurement of lateralized movement-related brain potentials showed that, under the lateral mirror condition, contralateral motor activity of the viewed hand was observed in both normal subjects and trauma amputees. In contrast, this activity was not observed in subjects with congenital limb absence. These findings suggest that, in traumatic amputees, motor enhancement due to visualization of the movements of the missing limb reflects the effectiveness of motor commands to the missing limb, strengthening the hypothesis of the functional survival of deafferented cortical motor areas.

At moderate to fast walking speeds, the human ankle provides net positive work at high-mechanical-power output to propel the body upward and forward during the stance period. On the contrary, conventional ankle-foot prostheses exhibit a passive-elastic response during stance, and consequently, cannot provide net work. Clinical studies indicate that transtibial amputees using conventional prostheses have higher gait metabolic rates than normal. Researchers believe that the main cause for these higher rates is due to the inability of conventional prostheses to provide sufficient positive power at terminal stance in the trailing leg to limit heel strike losses of the adjacent leading leg. In this investigation, we evaluate the hypothesis that a powered ankle-foot prosthesis, capable of providing human-like ankle work and power during stance, can decrease the metabolic cost of transport (COT) compared to a conventional passive-elastic prosthesis. To test the hypothesis, a powered prosthesis is built that comprises a unidirectional spring, configured in parallel with a force-controllable actuator with series elasticity. The prosthesis is shown to deliver the high mechanical power and net positive work observed in normal human walking. The rate of oxygen consumption and carbon dioxide production is measured as a determinant of metabolic rate on three unilateral transtibial amputees walking at self-selected speeds. We find that the powered prosthesis decreases the amputee's metabolic COT on average by 14% compared to the conventional passive-elastic prostheses evaluated (Flex-Foot Ceterusreg and Freedom Innovations Sierra), even though the powered system is over twofold heavier than the conventional devices. These results highlight the clinical importance of prosthetic interventions that closely mimic the mass distribution, kinetics, and kinematics of the missing limb.

In this article I consider instances in visual culture in which artists and filmmakers aestheticize women with damaged, missing or anomalous limbs. I focus upon Joel Peter Witkin’s photomontage Las Meninas (1987), Peter Greenaway’s film “A Zed and Two Noughts” (1985), Alison Lapper Pregnant a statue by Marc Quinn, Mathew Barney’s film “Cremaster” (2002), David Cronenberg’s “Crash” (1996), Luis Buñuel’s “Tristana” (1970) and David Lynch’s short film “The Amputee” (1973). I argue that although the artists and filmmakers reveal, rather than disguise the damaged, anomalous or missing limb(s) of the women, thus valorising their particular embodiment, these women are paradoxically still portrayed as deviant and monstrous.

Target motor reinnervation can produce additional myoelectric control signals for improved powered prosthesis control. This reinnervation allows simultaneous operation of multiple functions in an externally powered prosthesis with physiologically appropriate pathways, and it provides more intuitive control than is possible with conventional myoelectric prostheses. Target sensory reinnervation has the potential to provide the sensory feed-back to the amputee that feels like it is in the missing limb. This concept has great potential for improving the function of people with upper limb amputations, especially for high-level amputations, in which the disability is greatest. It is hoped that future research will develop the technique further and build synergistically with other exciting research areas.

Background Lower-limb amputation causes the individual a huge functional impairment due to the lack of adequate sensory perception from the missing limb. The development of an augmenting sensory feedback device able to restore some of the missing information from the amputated limb may improve embodiment, control and acceptability of the prosthesis. Findings In this work we transferred the Rubber Hand Illusion paradigm to the lower limb. We investigated the possibility of promoting body ownership of a fake foot, in a series of experiments fashioned after the RHI using matched or mismatched (vibrotactile) stimulation. The results, collected from 19 healthy subjects, demonstrated that it is possible to elicit the perception of possessing a rubber foot when modality-matched stimulations are provided synchronously on the biological foot and to the corresponding rubber foot areas. Results also proved that it is possible to enhance the illusion even with modality-mismatched stimulation, even though illusion was lower than in case of modality-matched stimulation. Conclusions We demonstrated the possibility of promoting a Rubber Foot Illusion with both matched and mismatched stimulation.

Primates with long-standing therapeutic amputations of a limb at a young age were used to investigate the possibility that deefferented motor nerves sprout to new muscle targets. Injections of anatomical tracers into the muscles proximal to the amputated stump labeled a larger extent of motoneurons than matched injections on the intact side or in normal animals, including motoneurons that would normally supply only the missing limb muscles. Although the total numbers of distal limb motoneurons remained normal, some distal limb motoneurons on the amputated side were smaller in size and simpler in form. These results suggest that deprived motoneurons survive and retain function by reinnervating new muscle targets. The sprouted motor efferents may account for some of the reorganization of primary motor cortex that follows long-standing amputation.

A body-image disturbance observed in most patients who undergo amputation of a limb is the perception of having the missing limb. The phenomenon is known as ‘phantom limb’. Despite a vast clinical literature on painless and painful phantom limb sensations, little is known about their origin. In fact, the precise mechanism responsible for the generation of these phantom feelings has not yet been determined. However, there have been a number of attempts to explain, within a theoretical framework, the origin of phantom limb sensations and related phenomena. This paper reviews some of the most tenable explanations, along with the work completed on this issue to date. With regard to painful phantom limb sensations and their management, a number of treatment techniques, employed by neuroscientists with varying degrees of success, are presented here.

Little is known about whether and how multimodal representations of the body (BRs) and of the space around the body (Peripersonal Space, PPS) adapt to amputation and prosthesis implantation. In order to investigate this issue, we tested BR in a group of upper limb amputees by means of a tactile distance perception task and PPS by means of an audio-tactile interaction task. Subjects performed the tasks with stimulation either on the healthy limb or the stump of the amputated limb, while wearing or not wearing their prosthesis. When patients performed the tasks on the amputated limb, without the prosthesis, the perception of arm length shrank, with a concurrent shift of PPS boundaries towards the stump. Conversely, wearing the prosthesis increased the perceived length of the stump and extended the PPS boundaries so as to include the prosthetic hand, such that the prosthesis partially replaced the missing limb.

The moment transferred at the residual limb socket interface of transtibial amputees can be a limiting factor of the comfort and activity level of lower limb amputees. The high pressures seen can be a significant source of pain, as well as result in deep tissue damage. The compensation of the sound limbs causes an asymmetrical gait which can be a contributor of early onset osteoarthritis in the sound limbs. It has been shown that the moment transferred with conventional passive prostheses can be lowered in magnitude by aligning the tibia with ground reaction forces, but this limits the effectiveness of the device. With recent powered prosthetics designed to mimic the missing limb, power can be injected into the gait cycle, but can also be limited by this pressure threshold. This paper shows the results of calculations that suggest that altering the prosthetic ankle mechanism can reduce the socket interface moments by as much as 50%. This supports the development of an active non-anthropomorphic ankle prosthesis which reduces socket interface moments while still injecting substantial power levels into the gait cycle.

Limb regeneration is a phenomenon occurring only in some urodeles. The process seems to be initiated by the dedifferentiation of the terminally differentiated cells. These cells differentiate, subsequently, to the tissues that comprise the limb, thus reconstructing the pattern of the missing limb part. In this paper we review and present evidence that certain cell types of the limb have the capacity to differentiate to different cell types than their original one by cellular metaplasia. This switch is called transdifferentiation. The focus of this review is the process of dedifferentiation which is the necessary prerequisite for differentiation, and the possible mechanisms involved.

While dreaming amputees often experience a normal body image and the phantom limb may not be present. However, dreaming experiences in amputees have mainly been collected by questionnaires. We analysed the dream reports of amputated patients with phantom limb collected after awakening from REM sleep during overnight videopolysomnography (VPSG). Six amputated patients underwent overnight VPSG study. Patients were awakened during REM sleep and asked to report their dreams. Three patients were able to deliver an account of a dream. In all dreaming recalls, patients reported that the amputated limbs were intact and completely functional and they no longer experienced phantom limb sensations. Phantom limb experiences, that during wake result from a conflict between a pre-existing body scheme and the sensory information on the missing limb, were suppressed during sleep in our patients in favour of the image of an intact body accessed during dream.

Above-knee amputation significantly reduces the amputee’s mobility and physical condition that can be built up through training or other sports activities. Alpine skiing is one of them. This paper deals with an above-knee prosthesis, which provides better kinematics of the leg structure. Imitating the kinematics of the human body, we looked for the kinematics of a system that comes closest to imitating natural movement and replace the missing limb to the highest possible degree. Based on the analysis of human leg kinematics and entire human mass system dynamics, a prototype for a special multi-axis prosthetic knee was developed. Measurements of leg movement during skiing were performed, which served as a basis for the concept. The concept was verified by kinematics, dynamics and strength analysis, and a complete geometric model was made. The concept was then verified on a working prototype, tested on a ski slope.

The experimental study of amphibian limb regeneration spans most of the 20th century and the first decade of the 21st century. We first review the major questions investigated over this time span: (1) the origin of regeneration blastema cells, the mechanism of tissue breakdown that liberates cells from their tissue organization to participate in blastema formation, (3) the mechanism of dedifferentiation of these cells, (4) how the blastema grows, (5) how the blastema is patterned to restore the missing limb structures, and (6) why adult anurans, birds and mammals do not have the regenerative powers of urodele salamanders. We then look forward in a perspective to discuss the many unanswered questions raised by investigations of the past century, what new approaches can be taken to answer them, and what the prospects are for translation of basic research on limb regeneration into clinical means to regenerate human appendages.

The brain often reorganizes itself after damage to some of its sensory inputs, amputation of a forearm for instance. Work involving both microelectrode recording and stimulation of an area of the brain known as the somatosensory thalamus, on people with and without amputations, shows that brain reorganization can take different courses — but that, in amputees who suffer from phantom sensations from the missing limb, such reorganization has not resulted in the respecification of neural function.

Publisher Summary This chapter describes postamputation pain, clinical characteristics, underlying mechanisms, treatment possibilities, and possible preventive measures. It reviews phantom phenomena that are experienced by almost all patients in the first weeks or months after limb amputation. Most patients feel that the missing limb is still present, and some may have vivid sensations of shape, length, posture, and movement. Such nonpainful phantom sensations rarely pose any clinical problem, but 60–80% of all amputees also have painful sensations located to the missing limb. Stump pain is another consequence of trauma or surgery, but in most patients the pain subsides within a few weeks. However, some patients develop chronic pain located to the stump. There are only few documented treatments available for the treatment of established stump and phantom pain. Further studies are needed to determine the role of peripheral and central mechanisms in postamputation pain to find better types of treatment. It is probably not possible to prevent phantom pain by a perioperative epidural blockade.

The following brief report describes the experiences of a hand and arm amputee following the administration of the Harvard Group Scale of Hypnotic Susceptibility, Form A (HGSHS:A) of Shor and Orne, 1962. The participant passed two of the three motor items involving his missing limb. This report discusses the results of a postsession interview regarding our participant's experiences during hypnosis and briefly discusses phantom limb sensations in general.

Neuroprosthetics![Figure][1] Prosthetic hand holds cherry tomato CREDITS: (TOP TO BOTTOM) V. ALTOUNIAN/ SCIENCE ; RUSSELL LEE/RUSSELL LEE PHOTO A major challenge for amputees—even those who wear prosthetic limbs—is the loss of sensation from the missing limb. Tan et al. placed a simple electronic cuff around nerves in the upper arm of two amputees to activate the neural pathways responsible for hand sensations. The amputees could then perceive multiple natural sensations in their prosthetic hands and perform fine motor tasks such as picking up soft fruit and pulling the stalks out of cherries. Sci. Transl. Med. 6 , 257ra138 (2014). [1]: pending:yes

Studies of phantom limb in cases of congenital (aplasic) absence of limb have provided inadequate evidence concerning the innate neurological substrate responsible for the phantom. In this study we review evidence from ultrasonic and behavioral studies of hand-mouth coordination in utero and in early infancy, neurobiological studies in primates, and studies of neural reorganization following amputation. We suggest two complementary hypotheses to explain aplasic phantoms. First, aplasic phantoms are based on the existence of specific neural circuitry associated with innate motor schemas, such as the neural matrix responsible for early hand-mouth coordination. Second, aplasic phantoms are modified by mechanisms that involve a reorganization of neural representations of the missing limb within a complex network involving both cortical and subcortical structures.

The most popular explanation for phantom limb pain involves maladaptive reorganization of the sensorimotor cortex, where the loss of sensory input results in altered limb representation. However, a new neuroimaging study shows that phantom pain involves intact cortical representation and that pain intensity is inversely correlated with connectivity in the primary sensorimotor cortex. Phantom pain was also associated with greater activity and structural integrity in the phantom area. Together, these findings indicate that phantom pain is associated with preserved rather than disrupted representation of the missing limb.

The control of robotic prostheses based on pattern recognition algorithms is a widely studied subject that has shown promising results in acute experiments. The long-term implementation of this technology, however, has not yet been achieved due to practical issues that can be mainly attributed to the use of surface electrodes and their highly environmental dependency. This paper describes several implantable electrodes and discusses them as a solution for the natural control of artificial limbs. In this context “natural” is defined as producing control over limb movement analogous to that of an intact physiological system. This includes coordinated and simultaneous movements of different degrees of freedom. It also implies that the input signals must come from nerves or muscles that were originally meant to produce the intended movement and that feedback is perceived as originating in the missing limb without requiring burdensome levels of concentration. After scrutinizing different electrode designs and their clinical implementation, we concluded that the epimysial and cuff electrodes are currently promising candidates to achieving a long-term stable and natural control of robotic prosthetics, provided that communication from the electrodes to the outside of the body is guaranteed.