Four patients underwent targeted sensory reinnervation (TSR), a surgical technique in which a defined skin area is first selectively denervated and then surgically reinnervated by another sensory nerve. In our case, either the area of the lateral femoral cutaneous nerve or the saphenous nerve was reinnervated by the sural nerve. Patients were then fitted with a special prosthetic device capable of transferring the sense of pressure from the sole of the prosthesis to the newly wired skin area. Pain reduction after TSR was highly significant in all patients. In three patients, permanent pain medication could even be discontinued, in one patient the pain medication has been significantly reduced. Two of the four patients were completely pain-free after the surgical intervention. Surgical rewiring of existing sensory nerves by TSR can provide the brain with new afferent signals seeming to originate from the missing limb. These signals help to reduce phantom limb pain and to restore a more normal body image. In combination with special prosthetic devices, the amputee can be provided with sensory feedback from the prosthesis, thus improving gait and balance.

Unilateral lower limb amputations usually present with asymmetric interlimb gait patterns, in the long term leading to secondary physical conditions and carrying the risk of low physical activity and impairment of general health. To assess prosthetic fittings and rehabilitation measures, reference values for asymmetries as well as the most significant gait parameters are required. Kinetic gait data of 865 patients with unilateral lower limb amputations (hip and knee disarticulations, transfemoral, transtibial and foot amputations) and 216 able-bodied participants were quantitatively assessed by instrumented gait analyses. Characteristic spatiotemporal (stance time, walking speed, step length and width) and ground reaction force parameters (weight-acceptance and push-off peak) were contrasted to normal gait. All spatiotemporal and ground reaction force parameters differed significantly from normal gait with the largest differences in transfemoral amputations. These also differed between amputation levels and showed age-dependencies. The stance time and push-off peak difference were identified as the most discriminative parameters with the highest diagnostic specificity and sensitivity. The present results mark the first step to establishing universal reference values for gait parameters by means of which the quality and suitability of a prosthetic fitting and the rehabilitation progress can be assessed, and are generalizable for all adults with unilateral lower limb amputations in terms of level walking.

Focal vibration therapy seeks to restore the physiological function of tissues and the nervous system. Recommendations for vibration settings, e.g., that could improve residual limb health and prosthesis acceptance in people with amputation, are pending. To establish a physiological connection between focal vibration settings, clinical outcomes, and molecular and neuronal mechanisms, we combined the literature on focal vibration therapy, vibrotactile feedback, mechanosensitive Piezo ion channels, touch, proprioception, neuromodulation, and the recovery of blood vessels and nerves. In summary, intermittent focal vibration increases endothelial shear stress when applied superficially to blood vessels and tissues and triggers Piezo1 signaling, supporting the repair and formation of blood vessels and nerves. Conversely, stimulating Piezo1 in peripheral axon growth cones could reduce the growth of painful neuromas. Vibrotactile feedback also creates sensory inputs to the motor cortex, predominantly through Piezo2-related channels, and modulates sensory signals in the dorsal horn and ascending arousal system. Thus, sensory feedback supports physiological recovery from maladaptations and can alleviate phantom pain and promote body awareness and physical activity. We recommend focal vibration of phantom limb maps with frequencies from ~60–120 Hz and amplitudes up to 1 mm to positively affect motor control, locomotion, pain, nerves, and blood vessels while avoiding adverse effects.

Background/Objectives: Tactile gnosis derives from the interplay between the hand’s tactile input and the memory systems of the brain. It is the prerequisite for complex hand functions. Impaired sensation leads to profound disability. Various invasive and non-invasive sensory substitution strategies for providing feedback from prostheses have been unsuccessful when translated to clinical practice, since they fail to match the feeling to genuine sensation of the somatosensory cortex. Methods: Herein, we describe a novel surgical technique for upper-limb-targeted sensory reinnervation (ulTSR) and report how single digital nerves selectively reinnervate the forearm skin and restore the spatial sensory capacity of single digits of the amputated hand in a case series of seven patients. We explore the interplay of the redirected residual digital nerves and the interpretation of sensory perception after reinnervation of the forearm skin in the somatosensory cortex by evaluating sensory nerve action potentials (SNAPs), somatosensory evoked potentials (SEPs), and amputation-associated pain qualities. Results: Digital nerves were rerouted and reliably reinnervated the forearm skin after hand amputation, leading to somatotopy and limb maps of the thumb and four individual fingers. SNAPs were obtained from the donor digital nerves after stimulating the recipient sensory nerves of the forearm. Matching SEPs were obtained after electrocutaneous stimulation of the reinnervated skin areas of the forearm where the thumb, index, and little fingers are perceived. Pain incidence was significantly reduced or even fully resolved. Conclusions: We propose that ulTSR can lead to higher acceptance of prosthetic hands and substantially reduce the incidence of phantom limb and neuroma pain. In addition, the spatial restoration of lost-hand sensing and the somatotopic reinnervation of the forearm skin may serve as a machine interface, allowing for genuine sensation and embodiment of the prosthetic hand without the need for complex neural coding adjustments.

Background and Objectives: After major upper-limb amputation, people face challenges due to losing tactile information and gripping function in their hands. While vision can confirm the success of an action, relying on it diverts attention from other sensations and tasks. This case report presents a 30-year-old man with traumatic, complete vision loss and transradial left forearm amputation. It emphasizes the importance of restoring tactile abilities when visual compensation is impossible. Materials and Methods: A prototype tactile feedback add-on system was developed, consisting of a sensor glove and upper arm cuff with related vibration actuators. Results: We found a 66% improvement in the Box and Blocks test and an overall functional score increase from 30% to 43% in the Southampton Hand Assessment Procedure with feedback. Qualitative improvements in bimanual activities, ergonomics, and reduced reliance on the unaffected hand were observed. Incorporating the tactile feedback system improved the precision of grasping and the utility of the myoelectric hand prosthesis, freeing the unaffected hand for other tasks. Conclusions: This case demonstrated improvements in prosthetic hand utility achieved by restoring peripheral sensitivity while excluding the possibility of visual compensation. Restoring tactile information from the hand and fingers could benefit individuals with impaired vision and somatosensation, improving acceptance, embodiment, social integration, and pain management.

Inpatient gait analysis is an essential part of rehabilitation for foot amputees and includes the ground contact time (GCT) difference of both legs as an essential component. Doctors communicate improvement advice to patients regarding their gait pattern based on a few steps taken at the doctor’s visit. A wearable sensor system, called Suralis, consisting of an inertial measurement unit (IMU) and a pressure measuring sock, including algorithms calculating GCT, is presented. Two data acquisitions were conducted to implement and validate initial contact (IC) and toe-off (TO) event detection algorithms as the basis for the GCT difference determination for able-bodied and prosthesis wearers. The results of the algorithms show a median GCT error of −51.7 ms (IMU) and 14.7 ms (sensor sock) compared to the ground truth and thus represent a suitable possibility for wearable gait analysis. The wearable system presented, therefore, enables a continuous feedback system for patients and, above all, a remote diagnosis of spatio-temporal aspects of gait behaviour based on reliable data collected in everyday life.