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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.

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). 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.

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.

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.

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.

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.

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.

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.

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.

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.

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

Phantom limb sensation refers to the perception of a variety of physical feelings in a part of the body that has been removed. Although this is generally associated with limb amputation, phantom sensations have also been reported in women following mastectomy and in certain spinal cord injuries. Phantom limb sensations can include an “awareness” of the missing limb in its usual position or a sense that the affected limb is an unusual size (either too large or too small), is moving, is in an unusual position, is wrapped in cotton, or is wet. Phantom pain, or phantom limb pain, is a subtype of phantom limb sensation in which these perceptions are perceived as noxious. Although there are numerous historical examples of phantom limb pain, the term itself is generally credited to the U.S. Army physician Silas Weir Mitchell, who in 1872 described that “thousands of spirit limbs were haunting as many good soldiers, every now and then tormenting them.” Keywords: health psychology; pain; phantom pain; somatoform disorder

Most people who have suffered amputations feel the missing limb for some considerable time, as though it were still present: this is the socalled phantom limb feeling. Its origin is as yet unexplained. In the case of amputations in peace-time it often lasts for only a few days or weeks, whereas, when amputations are carried out under war-time conditions, the feeling of the phantom limb, or the hallucinatory feeling of pain, may last from the moment of the amputation onwards, [...]

Due to their opposing movement the swinging arms are considered not to have a major contribution to the overall motion of running. However, missing one upper extremity limb can lead to significant asymmetries. In the present study it was investigated what influence weighted cuffs, which are added to the missing limb, have on the ground reaction forces in running of an elite unilateral upper extremity amputee athlete. One elite athlete (PB 400m: 0:48.45, PB 800m:1:50.92) currently classified as T47 by the International Paralympic Committee due to missing his right forearm participated in this study. The subject had to perform several runs on a 100m Tartan track with a velocity of 8 m/s (high race speed) without and with wearing two differently weighted cuffs (0.5 kg and 1 kg) applied to the elbow of the impaired limb. Ground reaction forces (GRFs) were captured using four floor- level mounted Kistler force plates, mean vertical and horizontal GRFs were calculated over 100% of stance phase duration and statistical data was evaluated for maximum and minimum values. Patterns of vertical GRFs did not differ dramatically whereas the maximum vertical force revealed a highly significant and significant difference between left and right foot when running with heavy or no additional weight respectively. Overall results showed only singular differences for different weight conditions, but several statistically significant differences between left and right foot were found independent from weight conditions.

Admiral Lord Horatio Nelson lost an arm at the battle of Tenerife in 1797. He wrote to a friend that he could still sense his missing arm and that he took this as evidence for the existence of his eternal soul. Whatever one may think of his conclusion, one wishes that patients could adopt this 18th century attitude of acceptance and curiosity. Unfortunately for many, their lives become dominated by some sensory aspect of their missing limb. In Charles Dickens’ Our Mutual Friend, a street-hawker of sheet music has had a leg amputated. He regularly and obsessionally visits a shop where his leg is for sale in a glass jar.

Following limb loss, patients usually continue having sensations on their missing limbs as if they were still present. Significant amount of such sensations are painful and referred as Phantom Limb Pain (PLP). Previous research has shown that providing the patient with the visual feedback of a limb at the place of the missing one in Virtual Reality (VR) can reduce PLP. In this paper we introduce a model to coordinate the arms allowing the exercising of a much broader range of reach tasks for alleviating the PLP more efficiently. Our Two-Arm Coordination Model (TACM) synthesizes the missing limb pose from the instantaneous variations of the intact opposite limb for a given reach task. Moreover, we propose a setup that makes use of a virtual mirror to enhance the full-body awareness of the patient in the virtual space.

Transtibial (TT) amputations, or below-knee amputations, are among the most frequently performed major limb removals. To replace the missing limb, numerous prosthetic devices were developed. A study of the state-of-the-art in TT prostheses shows that none of the commercially available devices are capable of mimicking an able-bodied ankle-foot complex. Still on a research level, some powered prosthetic devices have the potential to improve amputee walking experience, but still need heavy and bulky actuators to provide the necessary power of propulsion. With the AMP-Foot 2.0, the authors propose a new concept for an energy efficient, powered transtibial prosthesis. Its design enables the use of a low power actuator which stores energy in springs during the complete stance phase that can be released at push-off. Thanks to this, the size and weight of the actuator can be decreased considerably while the ankle still provides the full power necessary for forward propulsion. A prototype of the AMP-Foot 2.0 has been built and experiments with a transfemural amputee were conducted. The captured data is presented and analyzed throughout this article

Following amputation, individuals ubiquitously report experiencing lingering sensations of their missing limb. While phantom sensations can be innocuous, they are often manifested as painful. Phantom limb pain (PLP) is notorious for being difficult to monitor and treat. A major challenge in PLP management is the difficulty in assessing PLP symptoms, given the physical absence of the affected body part. Here, we offer a means of quantifying chronic PLP by harnessing the known ability of amputees to voluntarily move their phantom limbs. Upper-limb amputees suffering from chronic PLP performed a simple finger-tapping task with their phantom hand. We confirm that amputees suffering from worse chronic PLP had worse motor control over their phantom hand. We further demonstrate that task performance was consistent over weeks and did not relate to transient PLP or non-painful phantom sensations. Finally, we explore the neural basis of these behavioural correlates of PLP. Using neuroimaging, we reveal that slower phantom hand movements were coupled with stronger activity in the primary sensorimotor phantom hand cortex, previously shown to associate with chronic PLP. By demonstrating a specific link between phantom hand motor control and chronic PLP, our findings open up new avenues for PLP management and improvement of existing PLP treatments.

Lower limb prosthetic technology has greatly advanced in the last decade, but there are still many challenges that need to be tackled to allow amputees to walk efficiently and safely on many different terrain conditions. Neuro-mechanical modelling and online simulations combined with somatosensory feedback, has the potential to address this challenge. By virtually reconstructing the missing limb together with the associated somatosensory feedback, this approach could enable amputees to potentially perceive the bionic legs as extensions of their bodies. A prosthesis equipped with such biologically inspired closed-loop control could duplicate the mechanics of walking far more accurately than conventional solutions. The project SimBionics aims to explore these opportunities and advance the state-of-the-art in lower limb prosthesis control.