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

• Published in: Clinical orthopaedics and related research 2022-06, Vol.480 (6), p.1191-1204
• Main Authors: Gstoettner, Clemens, Festin, Christopher, Prahm, Cosima, Bergmeister, Konstantin D., Salminger, Stefan, Sturma, Agnes, Hofer, Christian, Russold, Michael F., Howard, Charla L., McDonnall, Daniel, Farina, Dario, Aszmann, Oskar C.
• Format: Article
• Language: English
• Subjects: Amputation; Animal models; Animals; Artificial Limbs; Basic Research; Biocompatibility; Cadaver; Cadavers; Dogs; Elbow; Electrodes; Electrodes, Implanted; Electromyography; Feasibility Studies; Foreign bodies; Humans; Inflammation; Interfaces; Medical innovations; Motor task performance; Muscles; Patients; Polyethylene; Prostheses; Rabbits; Reinnervation; Sheep; Shoulder; Surgery; Telemetry; Transplants & implants
• ISSN: 0009-921X; 1528-1132
• DOI: 10.1097/CORR.0000000000002135

Currently used prosthetic solutions in upper extremity amputation have limited functionality, owing to low information transfer rates of neuromuscular interfacing. Although surgical innovations have expanded the functional potential of the residual limb, available interfaces are inefficacious in translating this potential into improved prosthetic control. There is currently no implantable solution for functional interfacing in extremity amputation which offers long-term stability, high information transfer rates, and is applicable for all levels of limb loss. In this study, we presented a novel neuromuscular implant, the the Myoelectric Implantable Recording Array (MIRA). To our knowledge, it is the first fully implantable system for prosthetic interfacing with a large channel count, comprising 32 intramuscular electrodes. The purpose of this study was to evaluate the MIRA in terms of biocompatibility, functionality, and feasibility of implantation to lay the foundations for clinical application. This was achieved through small- and large-animal studies as well as test surgeries in a human cadaver. We evaluated the biocompatibility of the system's intramuscular electromyography (EMG) leads in a rabbit model. Ten leads as well as 10 pieces of a biologically inert control material were implanted into the paravertebral muscles of four animals. After a 3-month implantation, tissue samples were taken and histopathological assessment performed. The probes were scored according to a protocol for the assessment of the foreign body response, with primary endpoints being inflammation score, tissue response score, and capsule thickness in µm. In a second study, chronic functionality of the full system was evaluated in large animals. The MIRA was implanted into the shoulder region of six dogs and three sheep, with intramuscular leads distributed across agonist and antagonist muscles of shoulder flexion. During the observation period, regular EMG measurements were performed. The implants were removed after 5 to 6 months except for one animal, which retained the implant for prolonged observation. Primary endpoints of the large-animal study were mechanical stability, telemetric capability, and EMG signal quality. A final study involved the development of test surgeries in a fresh human cadaver, with the goal to determine feasibility to implant relevant target muscles for prosthetic control at all levels of major upper limb amputation. Evaluation of the foreign body react