Abstract
Objective. The implantation of intraneural electrodes in amputees has been observed to be effective in providing subjects with sensory feedback. However, this implantation is challenging and time consuming. Surgeons must be especially trained to execute the implantation. Therefore, we aimed at developing a novel peripheral intraneural electrode and insertion mechanism, which could drastically reduce the overall implantation time while achieving a high neural selectivity. Approach. A new insertion method based on hollow microneedles was developed to realize the prompt and effective simultaneous implantation of up to 14 active sites in a transversal manner. Each needle guided two Pt/Ir microwires through the nervous tissue. After the insertion, the microneedles were released, leaving behind the microwires. Each microwire had one active site, which was coated with poly-3,4-ethylenedioxythiophene (PEDOT) to enhance the electrochemical properties. The active sites were characterized by evaluating the impedance, charge storage capacity, and maximum injectable charge. Twelve quick to implant peripheral intraneural electrodes (Q-PINEs) were implanted in four pig sciatic nerves to evaluate the implantation time and neural selectivity. We compared the stimulation of the sciatic nerve with that of its branches. Main results. The average surgical access time was 23 min. The insertion time for 12 electrodes was 6.7 min (std. ±1.6 min). The overall implantation time was reduced by 40.3 min compared to the previously reported values. The Q-PINE system demonstrated a satisfactory performance during in vitro and in vivo characterization. The electrochemical results showed that the PEDOT coating successfully increased the electrochemical parameters of the active sites. Significance. With an average impedance of 1.7 kΩ, a maximum charge level of 76.2 nC could be achieved per active site. EMG recruitment curves showed that 46% of the active sites exhibited selective stimulation of four out of six muscles. The histological analysis indicated that the microwires successfully penetrated the nerve and single fascicles.
Highlights
Several groups have used intraneural electrodes to deliver electrical current to peripheral nerves to restore sensory feedback or record neural signals
Two different surgeons implanted the transversally intrafascicular multichannel electrode (TIME), and the findings indicated that the transversal insertion time of thin film electrodes depends significantly on the surgeons’ training
Implantation procedure Four 14 active sites (ASs) quick to implant peripheral intraneural electrode (Q-PINE), and eight 10 AS Q-PINEs were implanted in four pigs to evaluate the implantation time and neural selectivity
Summary
Several groups have used intraneural electrodes to deliver electrical current to peripheral nerves to restore sensory feedback or record neural signals. The transversally intrafascicular multichannel electrode (TIME), developed by (Boretius et al 2010), allowed the restoration of sensory feedback for up to six months in upper limb (Petrini et al 2019b; Raspopovic et al 2014), and lower limb amputees (Petrini et al 2019c). In 2011, with current delivered intraneurally using a longitudinal intrafascicular electrode (LIFE), two blindfolded participants could distinguish objects (Horch et al 2011). In 2017, Utah slanted electrode arrays (USEAs) were intraneurally inserted in the nerves of two participants to control a virtual robotic hand and induce cutaneous sensations on the phantom hand of the participants. Epineural electrodes have demonstrated notable success in upper and lower limb amputees. The FINE, implanted around the median and ulnar nerve, could provide sensory feedback for up to one year (Tan et al 2014)
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