CORR Insights®: Feasibility of a Wireless Implantable Multi-electrode System for High-bandwidth Prosthetic Interfacing: Animal and Cadaver Study

摘要

Where Are We Now? Amputation has an incidence of about 1.5 per 1000 people and is performed because of trauma, peripheral vascular disease, tumor, infection, and congenital anomalies [10]. The use of an external device to replace the missing part of the body has come a long way from primitive cosmetic prostheses to advanced implants with seamless human–machine integration [2]. This is important in patients with upper limb amputation, considering the high incidence of prosthesis abandonment owing to unsatisfactory functional results and poor quality of life [9]. Myoelectric prostheses are one of the main solutions to achieve functional recovery after upper limb amputation; they have biological signals measured through electrodes (internal wire or needle electrodes, implanted electrodes, or surface electrodes) and are used to control movement of the prosthesis. The basic concept of implanted myoelectric devices for recording intramuscular EMG signals has been widely reported for more than 20 years in patients with spinal cord injury [6-8]. The use of an implanted multi-channel myoelectric device may improve signal source recording and limit noise, but there is a major concern of long-term biocompatibility [4]. A myoelectric prosthesis uses electrodes to measure action potential and control the external device through muscle electricity. The term “crosstalk” defines the interaction between the muscles and the prosthesis control system. The ideal myoelectric control can be achieved by combining multiple EMG signals recorded independently and concurrently from specific muscles with the functions or multiple degrees of freedom to be controlled. Several implantable myoelectric systems for signal detection and prosthesis control are in development. Previous implantable systems relied on an existing telemetry architecture that required a large inductive field to be maintained through a cross-section of the whole limb, facilitated by a large coil that encloses the residual limb. Recently, there have been fascinating advances in myoelectric control, such as the decoding of motor neuron spike trains directly extracted from multi channel EMG [5]. The current study [3] is a clinically oriented paper presenting a new solution to man–machine interface. The authors [3] reported a well-tailored study on the myoelectric implantable recording array system, confirming the implant has full biocompatibility, continued functionality, and mechanical stability after long-term in vivo testing. This study should be considered the beginning of a “proof of concept,” and could lead to examinations of functional differences achieved by increasing the number of electrode sites from five or six to 32. Researchers could use these results to increase the number of movements that can be studied, improving prosthesis control and use at all levels of major upper limb amputation [11]. Based on these discoveries, and considering that patients learn from the actions of the machine and change their behavior for the best results, patient learning could be achieved with prerecorded or actual signals through online or real-life experimentation, allowing external prostheses to function more realistically and accurately. Where Do We Need To Go? The paper by Gstoettner et al. [3] raises important questions. Most important among them: What is the appropriate biotechnological interface between the dense neuromuscular data of the biologic signal recording and prosthesis control, and what can be done to alleviate this bottleneck to improve functional outcomes in patients with external prostheses after upper limb amputation? Decoding information transmitted from the brain to the muscles or directly from activated muscles using EMGs is a complicated task. Surgeons are directly involved, maintaining the function of active muscles or through surgical transfer of residual nerves to alternative muscles where surface EMG signals can be recorded (targeted muscle reinnervation). However,