European Effort Seeks to Enhance Upper-Extremity FES
by JoJo Platt, contributing editor and James Cavuoto, editor
October 2022 issue
The market for treating upper-extremity paralysis caused by cervical level spinal cord injury has been a difficult one for neurotechnology vendors to crack. In the early 2000s, an Ohio company called NeuroControl developed an implanted hand-grasp stimulator called Freehand that restored hand function to hundreds of quadriplegics before that company closed its doors, largely for financial reasons.
Since that time, other vendors, such as Bioness (now Bioventus) have offered noninvasive functional electrical stimulation systems that have not met with wide success in part because of the difficulty in donning and doffing the wearable devices. And the Cleveland FES Center has continued to improve its experimental upper-extremity system while offering continued support for the Freehand users stranded after NeuroControl’s demise. But a newer European effort from several research institutions and commercial firms may help move this product category forward
An interdisciplinary team at Montpellier, including researchers from the institute INRIA, surgeons from the clinic St. Jean Orthosud, clinicians from the USSAP Rehabilitation Center and biotechnology engineers from the company Neurinnov, have joined forces towards this end. Members of the team have been using CorTec’s multi-contact spiral epineural cuff electrodes for epineural stimulation for years. Using these electrodes to stimulate the medial and the radial nerves in the arm, they have already shown that functional hand movements could be elicited, including useful grip types for everyday life, such as the “key grip,” the “power grip,” and the “hook grip.” This preliminary work, however, was done in anesthetized patients.
The logical next step was to attempt a similar feat in awake patients, who got the electrodes implanted for a limited period of time (28 days). In a research paper published in Nature, the authors presented their successes. In two tetraplegic patients, the neurostimulation could induce functional and powerful grasping movements, which remained consistent and stable over the whole duration of implantation. What’s more, the patients learned to produce the movements themselves, using an intuitive interface controlled by residual voluntary movements of their shoulder or head. In an movie, the authors showed one of the subject performing meaningful actions with this setup, such as picking up food from a plate and feeding himself.
Despite this success, a few drawbacks still need to be considered: First, the patients’ hands had to be supported by splints to maintain the wrist at a functional extended position. Second, the stimulation settings and the interface had to be individually designed and adjusted for each patient. Third, and most importantly, the setup was using percutaneous cables. A fully implantable solution without any skin breach will be needed to arrive at an assistive system that is suitable for everyday life. Given the swift progress in implantable technologies, however, provided, for example, by CorTec and other companies in the sector, finding a solution for this seems only a matter of time.
Jörn Rickert, CorTec’s chief strategic and scientific officer, spoke with NBR about the company’s cuff electrodes. “The combination of the soft and flexible silicone that we use together with platinum, with a very good biocompatibility and long-term stability, are excellent,” he said. “That, in combination with the laser structured manufacturing, helps us produce thinner and softer electrodes with a higher resolution of contacts than can be done by our competitors present on the market today. We also have a patented opening mechanism, which is a very simple way to put the electrodes on the nerve.
These efforts to improve upper-extremity FES stand in contrast to and may well complement efforts at Onward and several research institutions in Europe and North America pursuing epidural or spinal column stimulation to restore hand and arm function. And advances in robotic exoskeletons offer a third technology that could individually or in concert restore meaningful function to people with tetraplegia.