Quantification of muscle-derived signal interference during monopolar needle electromyography of a peripheral nerve interface in the rat hind limb

Regenerative Peripheral Nerve Interfaces Effectively Prevent Neuroma Formation After Sciatic Nerve Transection in Rats

Objective

The disordered growth of nerve stumps after amputation leading to the formation of neuromas is an important cause of postoperative pain in amputees. This severely affects the patients' quality of life. Regenerative peripheral nerve interfaces (RPNIs) are an emerging method for neuroma prevention, but its postoperative nerve growth and pathological changes are yet to be studied.

Methods

The rat sciatic nerve transection model was used to study the effectiveness of RPNI in this experiment. The RPNI (experimental) group (n = 11) underwent RPNI implantation after sciatic nerve transection, while the control group (n = 11) only underwent sciatic nerve transection. Autotomy behavior, ultrasonography, and histopathology were observed for 2 months postoperatively.

Results

Compared to the control group, the incidence and size of the neuromas formed and the incidence and extent of autotomy were significantly reduced in the RPNI group. The axon density in the stump and degree of stump fibrosis were also significantly reduced in the RPNI group.

Conclusion

RPNI effectively prevented the formation of neuromas.

The Need to Work Arm in Arm: Calling for Collaboration in Delivering Neuroprosthetic Limb Replacements

Over the last few decades there has been a push to enhance the use of advanced prosthetics within the fields of biomedical engineering, neuroscience, and surgery. Through the development of peripheral neural interfaces and invasive electrodes, an individual's own nervous system can be used to control a prosthesis. With novel improvements in neural recording and signal decoding, this intimate communication has paved the way for bidirectional and intuitive control of prostheses. While various collaborations between engineers and surgeons have led to considerable success with motor control and pain management, it has been significantly more challenging to restore sensation. Many of the existing peripheral neural interfaces have demonstrated success in one of these modalities; however, none are currently able to fully restore limb function. Though this is in part due to the complexity of the human somatosensory system and stability of bioelectronics, the fragmentary and as-yet uncoordinated nature of the neuroprosthetic industry further complicates this advancement. In this review, we provide a comprehensive overview of the current field of neuroprosthetics and explore potential strategies to address its unique challenges. These include exploration of electrodes, surgical techniques, control methods, and prosthetic technology. Additionally, we propose a new approach to optimizing prosthetic limb function and facilitating clinical application by capitalizing on available resources. It is incumbent upon academia and industry to encourage collaboration and utilization of different peripheral neural interfaces in combination with each other to create versatile limbs that not only improve function but quality of life. Despite the rapidly evolving technology, if the field continues to work in divided "silos," we will delay achieving the critical, valuable outcome: creating a prosthetic limb that is right for the patient and positively affects their life.

Surgical Algorithm for Neuroma Management: A Changing Treatment Paradigm

Successful treatment of the painful neuroma is a particular challenge to the nerve surgeon. Historically, symptomatic neuromas have primarily been treated with excision and implantation techniques, which are inherently passive and do not address the terminal end of the nerve. Over the past decade, the surgical management of neuromas has undergone a paradigm shift synchronous with the development of contemporary techniques aiming to satisfy the nerve end. In this article, we describe the important features of surgical treatment, including the approach to diagnosis with consideration of neuroma type and the decision of partial versus complete neuroma excision. A comprehensive list of the available surgical techniques for management following neuroma excision is presented, the choice of which is often predicated upon the availability of the terminal nerve end for reconstruction. Techniques for neuroma reconstruction in the presence of an intact terminal nerve end include hollow tube reconstruction and auto- or allograft nerve reconstruction. Techniques for neuroma management in the absence of an intact or identifiable terminal nerve end include submuscular or interosseous implantation, centro-central neurorrhaphy, relocation nerve grafting, nerve cap placement, use of regenerative peripheral nerve interface, "end-to-side" neurorrhaphy, and targeted muscle reinnervation. These techniques can be further categorized into passive/ablative and active/reconstructive modalities. The nerve surgeon must be aware of available treatment options and should carefully choose the most appropriate intervention for each patient. Comparative studies are lacking and will be necessary in the future to determine the relative effectiveness of each technique.

Surgical Algorithm for Neuroma Management: A Changing Treatment Paradigm

Successful treatment of the painful neuroma is a particular challenge to the nerve surgeon. Historically, symptomatic neuromas have primarily been treated with excision and implantation techniques, which are inherently passive and do not address the terminal end of the nerve. Over the past decade, the surgical management of neuromas has undergone a paradigm shift synchronous with the development of contemporary techniques aiming to satisfy the nerve end. In this article, we describe the important features of surgical treatment, including the approach to diagnosis with consideration of neuroma type and the decision of partial versus complete neuroma excision. A comprehensive list of the available surgical techniques for management following neuroma excision is presented, the choice of which is often predicated upon the availability of the terminal nerve end for reconstruction. Techniques for neuroma reconstruction in the presence of an intact terminal nerve end include hollow tube reconstruction and auto- or allograft nerve reconstruction. Techniques for neuroma management in the absence of an intact or identifiable terminal nerve end include submuscular or interosseous implantation, centro-central neurorrhaphy, relocation nerve grafting, nerve cap placement, use of regenerative peripheral nerve interface, “end-to-side” neurorrhaphy, and targeted muscle reinnervation. These techniques can be further categorized into passive/ablative and active/reconstructive modalities. The nerve surgeon must be aware of available treatment options and should carefully choose the most appropriate intervention for each patient. Comparative studies are lacking and will be necessary in the future to determine the relative effectiveness of each technique.

Adjacent regenerative peripheral nerve interfaces produce phase-antagonist signals during voluntary walking in rats

Background

Regenerative Peripheral Nerve Interfaces (RPNIs) are neurotized muscle grafts intended to produce electromyographic signals suitable for motorized prosthesis control. Two RPNIs producing independent agonist/antagonist signals are required for each control axis; however, it is unknown whether signals from adjacent RPNIs are independent. The purpose of this work was to determine signaling characteristics from two adjacent RPNIs, the first neurotized by a foot dorsi-flexor nerve and the second neurotized by a foot plantar-flexor nerve in a rodent model.

Methods

Two Control group rats had electrodes implanted onto the soleus (tibial nerve) and extensor digitorum longus (peroneal nerve) muscles in the left hind limb. Two Dual-RPNI group rats had two separate muscles grafted to the left thigh and each implanted with electrodes: the extensor digitorum longus was neurotized with a transected fascicle from the tibial nerve, and the tibialis anterior was implanted with a transected peroneal nerve. Four months post-surgery, rats walked on a treadmill, were videographed, and electromyographic signals were recorded. Amplitude and periodicity of all signals relative to gait period were quantified. To facilitate comparisons across groups, electromyographic signals were expressed as a percent of total stepping cycle activity for each stance and swing gait phase. Independence between peroneal and tibial nerve activations were assessed by statistical comparisons between groups during stance and swing.

Results

Electromyographic activity for Control and Dual-RPNI rats displayed alternating activation patterns coinciding with stance and swing. Significant signal amplitude differences between the peroneal and tibial nerves were found in both the Control and Dual-RPNI groups. Non-inferiority tests performed on Dual-RPNI group signal confidence intervals showed that activation was equivalent to the Control group in all but the peroneal RPNI construct during stance. The similar electromyographic activity obtained for Control and RPNI suggests the latter constructs activate independently during both stance and swing, and contain minimal crosstalk.

Conclusions

In-vivo myoelectric RPNI activity encodes neural activation patterns associated with gait. Adjacent RPNIs neurotized with agonist/antagonist nerves display activity amplitudes similar to Control during voluntary walking. The distinct and expected activation patterns indicate the RPNI may provide independent signaling in humans, suitable for motorized prosthesis control.

The Evolution of Neuroprosthetic Interfaces

The ideal neuroprosthetic interface permits high-quality neural recording and stimulation of the nervous system while reliably providing clinical benefits over chronic periods. Although current technologies have made notable strides in this direction, significant improvements must be made to better achieve these design goals and satisfy clinical needs. This article provides an overview of the state of neuroprosthetic interfaces, starting with the design and placement of these interfaces before exploring the stimulation and recording platforms yielded from contemporary research. Finally, we outline emerging research trends in an effort to explore the potential next generation of neuroprosthetic interfaces.