Chronic Evaluation Of Nerves Transposed Into Bone With An Osseointegrated Neural Interface For Prosthetic Control
Aaron M. Dingle, PhD1; Jared P Ness, MS2; Joseph Novello, MS2; Weifeng Zeng, MD3; Brett Nemke, BS4; Yan Lu, MD2; Mark D Markel, DVM, PhD2; Aaron J Suminski, PhD2; Justin C. Williams, PhD5; Samuel O. Poore, MD, PhD6
1Plastic and Reconstructive Surgery, University of Wisconsin - Madison, Madison, WI, 2University of Wisconsin, Madison, Madison, WI, 3University of Wisconsin - Madison, Division of Plastic and Reconstructive Surgery, Madison, WI, 4University Wisconsin, Madison, WI, 5University of Wisconsin - Madison, Madison, WI, 6University of Madison, Madison, WI
Introduction: The ability to evoke sensory perception through advanced prostheses represents a key component to providing amputees with unabated functionality of a replacement limb. A peripheral nerve interface is a connection between the peripheral nervous system and the electronic components of the prostheses that allows bidirectional signaling to actuate the prostheses. The transposition of nerves into bone has been used clinically to treat the painful sequela associated with amputation neuroma; however, little is known about the state of the nerve transposed into bone beyond the successful treatment of pain. The Osseointegrated Neural Interface (ONI) represents a novel approach to peripheral nerve interfacing, utilizing the medullary cavity of amputated long bones to house and protect the amputated nerve and the delicate electrode interface. The ONI has been designed to explore the physiological capacity of nerves transposed into bone over time for bi-directional neural prosthetic control.
Materials and Methods: Transfemoral amputation was performed on New Zealand white rabbits. Briefly, the sciatic nerve was isolated and severed above the point of trifurcation. The femur was amputated at the midpoint and the nerve passed through a corticotomy. The terminal end of the nerve was sutured into a bipolar cuff electrode, and pressed back into the medullary canal. A second bi-polar cuff electrode was secured proximal to the corticotomy in order to stimulate and record efferent and afferent signals between the proximal and distal electrodes respectively. Both electrodes were connected to independent printed circuit boards (PCBs), which were intern secured to a stainless steel screw. The stainless steel screw served as both the osseointegrated and percutaneous portion of the ONI device. The muscle and skin were closed over the femur. Animals underwent electrophysiological recordings of compound nerve action potentials (CNAPs) at weeks 3, 5, 8 and 12 weeks under anesthesia, as well as terminal recordings of somatosensory evoked potentials (SSEPs) at week 12.
Results: Bidirectional signaling was achieved through an ONI, as demonstrated by the ability to record both afferent and efferent CNAPs. Furthermore, physiological function of nerves transposed into bone improve over time, indicated by achieving higher peak amplitudes from lower stimulation over time. The ability to record afferent SSEPs generated from an ONI demonstrates the ability to write sensory information through the ONI.
Conclusions: Nerves transposed into bone remain physiologically viable, and function improves over time. The ONI is capable of chronic bidirectional neural interfacing, including writing sensory information to the brain.
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