Even though the hand comprises only 1% of our body weight, about 30% of our central nervous systems (CNS) capacity is related to its control. The loss of a hand thus presents not only the loss of the most important tool allowing us to interact with our environment, but also leaves a dramatic sensory-motor deficit that challenges our CNS. Reconstruction of hand function is therefore not only an essential part of restoring body integrity and functional wholeness but also closes the loop of our neural circuits diminishing phantom sensation and neural pain. If biology fails to restore meaningful function, today we can resort to complex mechatronic replacement that have functional capabilities that in some respects even outperform biological alternatives, such as hand transplantation. As with replantation and transplantations, the challenge of bionic replacement is connecting the target with the CNS to achieve natural and intuitive control. In recent years, we have developed a number of strategies to improve neural interfacing, signal extraction, interpretation and stable mechanical attachment that are important parts of our current research. This work gives an overview of recent advances in bionic reconstruction, surgical refinements over technological interfacing, skeletal fixation, and modern rehabilitation tools that allow quick integration of prosthetic replacement. K E Y W O R D Sbionic reconstruction, hybrid fitting, interface, osseointegration, prostheses, rehabilitation, targeted muscle reinnervation 110 | AMAN et Al. meets the supreme principle to reconstruct "like with like" best, as it offers a hand of flesh and blood with immediate, intuitive proprioceptive motor control, sensory feedback, and a sense of ownership that at this time cannot be achieved by any prosthetic device.Aside from bionic reconstruction with myoelectric prostheses, controlled by at least 2 electromyography (EMG) signals from remnant stump muscles, also passive, bodypowered devices are used in prosthetic reconstruction. Passive prostheses range from stable or adjustable cosmetic hands, with silicone cover and natural appearance, to prosthetic tools, which are mainly hooks or grasping devices. 5 Socalled body-powered prostheses can perform simple grasping tasks by external cables attached to the prosthetic arm, driven by body movement. This serves as an assistant hand to the dominant hand, but it is obviously not capable of performing different grasps or hand movements.

SummaryBackgroundNerve transfers are a powerful tool in extremity reconstruction, but the neurophysiological effects have not been adequately investigated. As 81 % of nerve injuries and most nerve transfers occur in the upper extremity with its own neurophysiological properties, the standard rat hindlimb model may not be optimal in this paradigm. Here we present an experimental rat forelimb model to investigate nerve transfers.MethodsIn ten male Sprague-Dawley rats, the ulnar nerve was transferred to the motor branch of long head of the biceps. Sham surgery was performed in five animals (exposure/closure). After 12 weeks of regeneration, muscle force and Bertelli test were performed and evaluated.ResultsThe nerve transfer successfully reinnervated the long head of the biceps in all animals, as indicated by muscle force and behavioral outcome. No aberrant reinnervation occurred from the original motor source. Muscle force was 2,68 N ± 0.35 for the nerve transfer group and 2,85 N ± 0.39 for the sham group, which was not statically different (p = 0.436). The procedure led to minor functional deficits due to the loss of ulnar nerve function; this, however, could not be quantified with any of the presented measures.ConclusionThe above-described rat model demonstrated a constant anatomy, suitable for nerve transfers that are accessible to standard neuromuscular analyses and behavioral testing. This model allows the study of both neurophysiologic properties and cognitive motor function after nerve transfers in the upper extremity.

OBJECTIVEOver the last decade, a number of authors have investigated the utility of different biological and synthetic matrices as alternatives to conventional nerve grafts. However, the autologous nerve graft remains the gold standard, even though it often involves using a pure sensory nerve to reconstruct a mixed or even a pure motor nerve. Furthermore, limited donor sites often necessitate a significant mismatch of needed nerve tissue, especially for large proximal nerve defects such as brachial plexus lesions. Here, the authors present a new technique that overcomes these problems: the fascicular shift procedure (FSP). A fascicular group of the nerve distal to the injury is harvested in a sufficient length to bridge the nerve defect.METHODSThe method of fascicular shifting was tested at the sciatic nerve in 45 Lewis rats. In the experimental group, a 15-mm nerve defect was created and reconstructed with a fascicular group that was harvested directly distal to the gap. This group was compared with 1 negative control group (defect without reconstruction) and 3 positive control groups (sensory, motor, and mixed graft). After 12 weeks of nerve regeneration, outcome was evaluated using retrograde labeling, histomorphometric analysis, and muscle force analysis.RESULTSAll reconstructed groups showed successful regeneration with various levels of function. The negative control group showed minimal force measurements that were of no functional value. The fascicular shift provided sufficient guidance to overcome nerve defects, had higher (p < 0.1) motor neuron counts (1958.75 ± 657.21) than the sensory graft (1263.50 ± 538.90), and was equal to motor grafts (1490.43 ± 794.80) and mixed grafts (1720.00 ± 866.421). This tendency of improved motor regeneration was confirmed in all analyses. The mixed graft group was compared with the experimental group to investigate the influence of the potential damage induced by the fascicular shift distal to the repair site. However, none of the analyses revealed an impairment of nerve regeneration for both the tibial and common peroneal index muscles.CONCLUSIONSThis study demonstrates that harvesting a transplant from the nerve segment distal to the injury site offers a mixed graft without causing additional donor-site morbidity. These grafts perform statistically better than a standard sensory graft in terms of motor recovery. The fascicular shift presents a novel method to reconstruct large proximal nerve defects, making it immensely attractive in brachial plexus reconstruction.

Introduction: Man-machine interfacing remains the main challenge for accurate and reliable control of bionic prostheses. Implantable electrodes in nerves and muscles may overcome some of the limitations by significantly increasing the interface's reliability and bandwidth. Before human application, experimental preclinical testing is essential to assess chronic in-vivo biocompatibility and functionality. Here, we analyze available animal models, their costs and ethical challenges in special regards to simulating a potentially life-long application in a short period of time and in non-biped animals. Methods:We performed a literature analysis following the PRISMA guidelines including all animal models used to record neural or muscular activity via implantable electrodes, evaluating animal models, group size, duration, origin of publication as well as type of interface. Furthermore, behavioral, ethical, and economic considerations of these models were analyzed. Additionally, we discuss experience and surgical approaches with rat, sheep, and primate models and an approach for international standardized testing. Results:Overall, 343 studies matched the search terms, dominantly originating from the US (55%) and Europe (34%), using mainly small animal models (rat: 40%). Electrode placement was dominantly neural (77%) compared to muscular (23%). Large animal models had a mean duration of 135 ± 87.2 days, with a mean of 5.3 ± 3.4 animals per trial. Small animal models had a mean duration of 85 ± 11.2 days, with a mean of 12.4 ± 1.7 animals.Discussion: Only 37% animal models were by definition chronic tests (>3 months) and thus potentially provide information on long-term performance. Costs for large animals were up to 45 times higher than small animals. However, costs are relatively small compared to complication costs in human long-term applications. Overall, we believe a combination of small animals for preliminary primary electrode testing and large animals to investigate long-term biocompatibility, impedance, and tissue regeneration parameters provides sufficient data to ensure long-term human applications.

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