Restoration of sensorimotor function after amputation has remained challenging because of the lack of human-machine interfaces that provide reliable control, feedback, and attachment. Here, we present the clinical implementation of a transradial neuromusculoskeletal prosthesis—a bionic hand connected directly to the user’s nervous and skeletal systems. In one person with unilateral below-elbow amputation, titanium implants were placed intramedullary in the radius and ulna bones, and electromuscular constructs were created surgically by transferring the severed nerves to free muscle grafts. The native muscles, free muscle grafts, and ulnar nerve were implanted with electrodes. Percutaneous extensions from the titanium implants provided direct skeletal attachment and bidirectional communication between the implanted electrodes and a prosthetic hand. Operation of the bionic hand in daily life resulted in improved prosthetic function, reduced postamputation, and increased quality of life. Sensations elicited via direct neural stimulation were consistently perceived on the phantom hand throughout the study. To date, the patient continues using the prosthesis in daily life. The functionality of conventional artificial limbs is hindered by discomfort and limited and unreliable control. Neuromusculoskeletal interfaces can overcome these hurdles and provide the means for the everyday use of a prosthesis with reliable neural control fixated into the skeleton.

Remnant muscles in the residual limb after amputation are the most common source of control signals for prosthetic hands, because myoelectric signals can be generated by the user at will. However, for individuals with amputation higher up the arm, such as an above-elbow (transhumeral) amputation, insufficient muscles remain to generate myoelectric signals to enable control of the lost arm and hand joints, thus making intuitive control of wrist and finger prosthetic joints unattainable. We show that severed nerves can be divided along their fascicles and redistributed to concurrently innervate different types of muscle targets, particularly native denervated muscles and nonvascularized free muscle grafts. We engineered these neuromuscular constructs with implanted electrodes that were accessible via a permanent osseointegrated interface, allowing for bidirectional communication with the prosthesis while also providing direct skeletal attachment. We found that the transferred nerves effectively innervated their new targets as shown by a gradual increase in myoelectric signal strength. This allowed for individual flexion and extension of all five fingers of a prosthetic hand by a patient with a transhumeral amputation. Improved prosthetic function in tasks representative of daily life was also observed. This proof-of-concept study indicates that motor neural commands can be increased by creating electro-neuromuscular constructs using distributed nerve transfers to different muscle targets with implanted electrodes, enabling improved control of a limb prosthesis.

Background: Painful conditions such as residual limb pain (RLP) and phantom limb pain (PLP) can manifest after amputation. The mechanisms underlying such postamputation pains are diverse and should be addressed accordingly. Different surgical treatment methods have shown potential for alleviating RLP due to neuroma formation — commonly known as neuroma pain — and to a lesser degree PLP. Two reconstructive surgical interventions, namely targeted muscle reinnervation (TMR) and regenerative peripheral nerve interface (RPNI), are gaining popularity in postamputation pain treatment with promising results. However, these two methods have not been directly compared in a randomised controlled trial (RCT). Here, we present a study protocol for an international, double-blind, RCT to assess the effectiveness of TMR, RPNI, and a non-reconstructive procedure called neuroma transposition (active control) in alleviating RLP, neuroma pain, and PLP. Methods: One hundred ten upper and lower limb amputees suffering from RLP will be recruited and assigned randomly to one of the surgical interventions (TMR, RPNI, or neuroma transposition) in an equal allocation ratio. Complete evaluations will be performed during a baseline period prior to the surgical intervention, and follow-ups will be conducted in short term (1, 3, 6, and 12 months post-surgery) and in long term (2 and 4 years post-surgery). After the 12-month follow-up, the study will be unblinded for the evaluator and the participants. If the participant is unsatisfied with the outcome of the treatment at that time, further treatment including one of the other procedures will be discussed in consultation with the clinical investigator at that site. Discussion: A double-blind RCT is necessary for the establishment of evidence-based procedures, hence the motivation for this work. In addition, studies on pain are challenging due to the subjectivity of the experience and the lack of objective evaluation methods. Here, we mitigate this problem by including different pain evaluation methods known to have clinical relevance. We plan to analyse the primary variable, mean change in NRS (0–10) between baseline and the 12-month follow-up, using the intention-to-treat (ITT) approach to minimise bias and keep the advantage of randomisation. The secondary outcomes will be analysed on both ITT and per-protocol (PP). An adherence protocol (PP population) analysis will be used for estimating a more realistic effect of treatment. Trial registration: ClinicalTrials.gov NCT05009394.

The profunda femoris artery perforator (PAP) flap has been recently popularized as an alternative option for microsurgical reconstruction. The use of PAP flap has never been reported and described for reconstruction of the upper extremities, in particular the forearm. The purpose of this case report is to describe a case suggesting the PAP flap as a further reconstructive option in the upper limb. A 16-year-old girl who sustained a traumatic injury to her right dominant forearm resulting in subtotal circumferential tissue loss following a road traffic accident was referred to the authors' department 2 years post-trauma. The disabling fibrotic sequelae on her volar forearm (15 x 10 cm) resulted in a nonfunctional hand. She was unable to perform any active movement of her wrist or digits. Passive movements in the finger joints were preserved. Following debridement and reconstruction of nerves and tendons, soft tissues were resurfaced with a PAP flap. The transverse skin paddle, 12 x 7 cm, was placed distally with the adipofascial portion positioned proximally above the muscle bellies and anastomoses site. A small raw area (4 x 3 cm) was covered with an acellular dermal matrix (ADM). The postoperative course was uneventful. At 9 months postoperatively, the patient demonstrated active flexion and extension of the fingers with independent function. The patient reported satisfaction with the flap donor site and forearm resurfacing. The PAP flap can be a further option for areas requiring soft tissue coverage in patients refusing visible scars. This flap had both the advantage of reducing the morbidity and visibility of the donor site, as well as the ability to resurface a large recipient site with soft and pliable tissue, covering exposed nerves and tendons.

Phantom limb experiences, including phantom limb sensations (PLS) and phantom limb pain (PLP), are common after limb amputation or deafferentation, with PLP significantly impacting quality of life. However, the mechanisms underlying PLP remain unclear, complicating treatment development. Investigating phantom phenomena has been proposed to gain insights into the mechanisms behind the insurgence of PLS and PLP, potentially informing new therapeutic approaches. However, small, heterogeneous samples and a lack of objective pain metrics often limit research on individuals with limb loss. Here, we investigate whether phantom experiences, similar to those reported after amputation, also occur in individuals with intact limbs following a brachial plexus nerve block, excluding the brain from afferent and efferent signals. To investigate the phenomenon, we conducted a multifaceted phenomenological study involving 14 individuals undergoing elective hand or arm surgery under brachial plexus nerve block. Participants were asked to report on the presence of phantom experiences and describe them in terms of vividness, quality, position, telescoping, movements, and pain. Assessments occurred at four-time points: before surgery, during surgery, after surgery, and at home. These findings were then compared to observations in the amputation population. 93 % of the participants reported PLS 20-40 min following brachial plexus anesthesia. The most frequently reported qualities of PLS were tingling, heaviness, and warmth. Commonly reported experiences after limb loss, such as distorted limb position, telescoping, and execution of phantom limb movements, were also reported by the participants after the deafferentation. Notably, participants experiencing distorted limb positions did not find them painful or uncomfortable. PLP was reported by only one participant. This study demonstrates that individuals with temporary sensorimotor deafferentation via brachial plexus nerve block experience many phantom phenomena similar to those reported by individuals with limb loss. This suggests that brachial plexus nerve block is a promising model for studying PLP and a potential test bed for its treatment.