Regenerative Peripheral Nerve Interfaces for Prevention and Management of Neuromas

Neuroma Analysis in Humans: Standardizing Sample Collection and Documentation

INTRODUCTION

The biology of symptomatic neuromas is poorly understood, particularly the factors causing pain in human neuromas. Pain presence varies among and within individuals, with some having painful and nonpainful neuromas. To bridge these knowledge gaps, our group developed a protocol for assessing neuroma pain and collecting tissue for molecular analysis. This manuscript outlines our workflow and challenges and aims to inspire other centers to share their experiences with these tissues.

METHODS

For every included patient and collected nerve or bone tissue specimens, we perform a detailed chart review and a multifaceted analysis of pain and pain perception immediately before surgery. We collect patient-reported outcome measures (PROMs) on pain, function, and mental well-being outcomes at preoperative assessment and at the 6-month follow-up postoperatively. Before surgery, the patient is assessed once again to obtain an immediate preoperative pain status and identify potential differences in pain intensity of different neuromas. Intraoperatively, specimens are obtained and their gross anatomical features are recorded, after which they are stored in paraformaldehyde or frozen for later sample analyses. Postoperatively, patients are contacted to obtain additional postoperative PROMs.

RESULTS

A total of 220 specimens of nerve tissue have been successfully obtained from 83 limbs, comprising 95 specimens of neuromas and 125 specimens of nerves located proximal to the neuromas or from controls.

CONCLUSIONS

Our approach outlines the methods combining specimen collection and examination, including both macroscopic and molecular biological features, with PROMs, encompassing physical and psychological aspects, along with clinical metadata obtained through clinical teams and chart review.

Biology and pathophysiology of symptomatic neuromas

ABSTRACT

Neuromas are a substantial cause of morbidity and reduction in quality of life. This is not only caused by a disruption in motor and sensory function from the underlying nerve injury but also by the debilitating effects of neuropathic pain resulting from symptomatic neuromas. A wide range of surgical and therapeutic modalities have been introduced to mitigate this pain. Nevertheless, no single treatment option has been successful in completely resolving the associated constellation of symptoms. While certain novel surgical techniques have shown promising results in reducing neuroma-derived and phantom limb pain, their effectiveness and the exact mechanism behind their pain-relieving capacities have not yet been defined. Furthermore, surgery has inherent risks, may not be suitable for many patients, and may yet still fail to relieve pain. Therefore, there remains a great clinical need for additional therapeutic modalities to further improve treatment for patients with devastating injuries that lead to symptomatic neuromas. However, the molecular mechanisms and genetic contributions behind the regulatory programs that drive neuroma formation-as well as the resulting neuropathic pain-remain incompletely understood. Here, we review the histopathological features of symptomatic neuromas, our current understanding of the mechanisms that favor neuroma formation, and the putative contributory signals and regulatory programs that facilitate somatic pain, including neurotrophic factors, neuroinflammatory peptides, cytokines, along with transient receptor potential, and ionotropic channels that suggest possible approaches and innovations to identify novel clinical therapeutics.

Pain and Functional Outcomes following Targeted Muscle Reinnervation: A Systematic Review

BACKGROUND

It is estimated that by 2050, a total of 3.6 million patients will be living with an amputation in the United States. The objective of this systematic review is to evaluate the effect of targeted muscle reinnervation (TMR) on pain and physical functioning in amputees.

METHODS

A literature search was performed on PubMed, Embase, and MEDLINE up to November 28, 2021. Clinical studies assessing the outcomes of TMR (pain, prosthesis control, life quality, limb function, and disability) were included.

RESULTS

Thirty-nine articles were included. The total number of patients who underwent TMR was 449, and 716 were controls. Mean follow-up was 25 months. A total of 309 (66%) lower-limb and 159 (34%) upper-limb amputations took place in the TMR group, the most common being below-knee amputations (39%). The control group included a total of 557 (84%) lower-limb and 108 (16%) upper-limb amputations; the greatest proportion being below-knee amputations in this group as well (54%). Trauma was the most common indication for amputation. Phantom limb pain scores were lower by 10.2 points for intensity ( P = 0.01), 4.67 points for behavior ( P = 0.01), and 8.9 points for interference ( P = 0.09). Similarly, residual limb pain measures were lower for cases for intensity, behavior, and interference, but they failed to reach significance. Neuroma symptoms occurred less frequently, and functional and prosthesis control outcomes improved following TMR.

CONCLUSION

The literature evidence suggests that TMR is a promising therapy for improving pain, prosthesis use, and functional outcomes after limb amputation.

Regenerative Peripheral Nerve Interface Surgery for the Management of Chronic Posttraumatic Neuropathic Pain

Chronic pain resulting from peripheral nerve injury remains a common issue in the United States and affects 7 to 10% of the population. Regenerative Peripheral Nerve Interface (RPNI) surgery is an innovative surgical procedure designed to treat posttraumatic neuropathic pain, particularly when a symptomatic neuroma is present on clinical exam. RPNI surgery involves implantation of a transected peripheral nerve into an autologous free muscle graft to provide denervated targets to regenerating axons. RPNI surgery has been found in animal and human studies to be highly effective in addressing postamputation pain. While most studies have reported its uses in the amputation patient population for the treatment of neuroma and phantom limb pain, RPNI surgery has recently been used to address refractory headache, postmastectomy pain, and painful donor sites from the harvest of neurotized flaps. This review summarizes the current understanding of RPNI surgery for the treatment of chronic neuropathic pain.

Primary Targeted Muscle Reinnervation in Above-Knee Amputations in Patients with Unsalvageable Limbs from Limb-Threatening Ischemia or Infection

BACKGROUND

 Amputees frequently suffer from chronic pain in both their residual limbs (RLP) and phantom limbs (PLP) following their amputation. Targeted muscle reinnervation (TMR) is a nerve transfer technique that has been demonstrated to improve pain secondarily and at time of amputation. The goal of this study is to report on the efficacy of primary TMR at time of above-knee level amputations in the setting of limb-threatening ischemia or infection.

METHODS

 This is a retrospective review of a single-surgeon experience with TMR in patients undergoing through- or above-knee level amputations from January 2018 to June 2021. Patient charts were reviewed for the comorbidities in the Charlson Comorbidity Index. Postoperative notes were assayed for presence and absence of RLP and PLP, overall pain severity, chronic narcotic use, ambulatory status, and complications. A control group of patients undergoing lower limb amputation who did not receive TMR from January 2014 to December 2017 was used for comparison.

RESULTS

 Forty-one patients with through- or above-knee level amputations and primary TMR were included in this study. The tibial and common peroneal nerves were transferred in all cases to motor branches to the gastrocnemius, semimembranosus, semitendinosus, and biceps femoris. Fifty-eight patients with through- or above-knee level amputations without TMR were included for comparison. The TMR group had significantly less overall pain (41.5 vs. 67.2%, p = 0.01), RLP (26.8 vs. 44.8%, p = 0.04), and PLP (19.5 vs. 43.1%, p = 0.02). There were no significant differences in complication rates.

CONCLUSION

 TMR can safely and effectively be performed at time of a through- and above-knee level amputation and improves pain outcomes.

Phantom Limb Pain and Painful Neuroma After Dysvascular Lower-Extremity Amputation: A Systematic Review and Meta-Analysis

BACKGROUND

Phantom limb pain (PLP) and symptomatic neuroma can be debilitating and significantly impact the quality of life of amputees. However, the prevalence of PLP and symptomatic neuromas in patients following dysvascular lower limb amputation (LLA) has not been reliably established. This systematic review and meta-analysis evaluates the prevalence and incidence of phantom limb pain and symptomatic neuroma after dysvascular LLA.

METHODS

Four databases (Embase, MEDLINE, Cochrane Central, and Web of Science) were searched on October 5th, 2022. Prospective or retrospective observational cohort studies or cross-sectional studies reporting either the prevalence or incidence of phantom limb pain and/or symptomatic neuroma following dysvascular LLA were identified. Two reviewers independently conducted the screening, data extraction, and the risk of bias assessment according to the PRISMA guidelines. To estimate the prevalence of phantom limb pain, a meta-analysis using a random effects model was performed.

RESULTS

Twelve articles were included in the quantitative analysis, including 1924 amputees. A meta-analysis demonstrated that 69% of patients after dysvascular LLA experience phantom limb pain (95% CI 53-86%). The reported pain intensity on a scale from 0-10 in LLA patients ranged between 2.3 ± 1.4 and 5.5 ± .7. A single study reported an incidence of symptomatic neuroma following dysvascular LLA of 5%.

CONCLUSIONS

This meta-analysis demonstrates the high prevalence of phantom limb pain after dysvascular LLA. Given the often prolonged and disabling nature of neuropathic pain and the difficulties managing it, more consideration needs to be given to strategies to prevent it at the time of amputation.

Regenerative Peripheral Nerve Interfaces (RPNIs) in Animal Models and Their Applications: A Systematic Review

Regenerative Peripheral Nerve Interfaces (RPNIs) encompass neurotized muscle grafts employed for the purpose of amplifying peripheral nerve electrical signaling. The aim of this investigation was to undertake an analysis of the extant literature concerning animal models utilized in the context of RPNIs. A systematic review of the literature of RPNI techniques in animal models was performed in line with the PRISMA statement using the MEDLINE/PubMed and Embase databases from January 1970 to September 2023. Within the compilation of one hundred and four articles employing the RPNI technique, a subset of thirty-five were conducted using animal models across six distinct institutions. The majority (91%) of these studies were performed on murine models, while the remaining (9%) were conducted employing macaque models. The most frequently employed anatomical components in the construction of the RPNIs were the common peroneal nerve and the extensor digitorum longus (EDL) muscle. Through various histological techniques, robust neoangiogenesis and axonal regeneration were evidenced. Functionally, the RPNIs demonstrated the capability to discern, record, and amplify action potentials, a competence that exhibited commendable long-term stability. Different RPNI animal models have been replicated across different studies. Histological, neurophysiological, and functional analyses are summarized to be used in future studies.

Sexually Dimorphic Pattern of Pain Mitigation Following Prophylactic Regenerative Peripheral Nerve Interface (RPNI) in a Rat Neuroma Model

BACKGROUND

Treating neuroma pain is a clinical challenge. Identification of sex-specific nociceptive pathways allows a more individualized pain management. The Regenerative Peripheral Nerve Interface (RPNI) consists of a neurotized autologous free muscle using a severed peripheral nerve to provide physiological targets for the regenerating axons.

OBJECTIVE

To evaluate prophylactic RPNI to prevent neuroma pain in male and female rats.

METHODS

F344 rats of each sex were assigned to neuroma, prophylactic RPNI, or sham groups. Neuromas and RPNIs were created in both male and female rats. Weekly pain assessments including neuroma site pain and mechanical, cold, and thermal allodynia were performed for 8 weeks. Immunohistochemistry was used to evaluate macrophage infiltration and microglial expansion in the corresponding dorsal root ganglia and spinal cord segments.

RESULTS

Prophylactic RPNI prevented neuroma pain in both sexes; however, female rats displayed delayed pain attenuation when compared with males. Cold allodynia and thermal allodynia were attenuated exclusively in males. Macrophage infiltration was mitigated in males, whereas females showed a reduced number of spinal cord microglia.

CONCLUSION

Prophylactic RPNI can prevent neuroma site pain in both sexes. However, attenuation of both cold allodynia and thermal allodynia occurred in males exclusively, potentially because of their sexually dimorphic effect on pathological changes of the central nervous system.

A Direct Comparison of Targeted Muscle Reinnervation and Regenerative Peripheral Nerve Interfaces to Prevent Neuroma Pain

BACKGROUND AND OBJECTIVES

Targeted muscle reinnervation (TMR) and regenerative peripheral nerve interface (RPNI) surgeries manage neuroma pain; however, there remains considerable discord regarding the best treatment strategy. We provide a direct comparison of TMR and RPNI surgery using a rodent model for the treatment of neuroma pain.

METHODS

The tibial nerve of 36 Fischer rats was transected and secured to the dermis to promote neuroma formation. Pain was assessed using mechanical stimulation at the neuroma site (direct pain) and von Frey analysis at the footpad (to assess tactile allodynia from collateral innervation). Once painful neuromas were detected 6 weeks later, animals were randomized to experimental groups: (a) TMR to the motor branch to biceps femoris, (b) RPNI with an extensor digitorum longus graft, (c) neuroma excision, and (d) neuroma in situ. The TMR/RPNIs were harvested to confirm muscle reinnervation, and the sensory ganglia and nerves were harvested to assess markers of regeneration, pain, and inflammation.

RESULTS

Ten weeks post-TMR/RPNI surgery, animals had decreased pain scores compared with controls ( P < .001) and they both demonstrated neuromuscular junction reinnervation. Compared with neuroma controls, immunohistochemistry showed that sensory neuronal cell bodies of TMR and RPNI showed a decrease in regeneration markers phosphorylated cyclic AMP receptor binding protein and activation transcription factor 3 and pain markers transient receptor potential vanilloid 1 and neuropeptide Y ( P < .05). The nerve and dorsal root ganglion maintained elevated Iba-1 expression in all cohorts.

CONCLUSION

RPNI and TMR improved pain scores after neuroma resection suggesting both may be clinically feasible techniques for improving outcomes for patients with nerve injuries or those undergoing amputation.

Regenerative peripheral nerve interface reduces the incidence of neuroma in the lower limbs after amputation: a retrospective study based on ultrasound

BACKGROUND

Amputees suffer from symptomatic neuroma and phantom limb pain. Regenerative peripheral nerve interface (RPNI) has recently been regarded as an effective method to prevent neuroma after amputation. However, the verifications of RPNI efficacy are mostly based on subjective evaluation, lacking objective approaches. This study aims to unveil the effect of RPNI on preventing neuroma formation and provide evidence supporting the efficacy of RPNI based on ultrasound.

METHODS

Amputees of lower limb at Peking University People's Hospital from July 2020 to March 2022 were analyzed retrospectively. The clinical data collected consisted of general information, pathology of primary disease, history of limb-salvage treatment, amputation level of nerve, pain scales such as the Numerical Rating Scale (NRS) and the Manchester Foot Pain and Disability Index (MFPDI). Three months after amputation, the transverse diameter, anteroposterior diameter, and cross-sectional area of neuromas in stump nerves at the end of residual limbs were measured using ultrasound and compared to adjacent normal nerves.

RESULTS

Fourteen patients were enrolled in the study, including 7 in the traditional amputation group (TA group) and 7 in the RPNI group. There was no significant difference in basic information and amputation sites between the two groups. The NRS and MFPDI scores of patients in RPNI group were significantly lower than those in TA group, and decreased with the follow-up time increasing, indicating that RPNI could reduce symptomatic neuroma pain. The comparison of preoperative ultrasound and postoperative pathology showed ultrasound could reflect the size of neuroma in vivo. Independent-sample t tests indicated that the ratios of anteroposterior diameter, transverse diameter and area of the cross section of both the neuroma and adjacent normal nerve obtained via ultrasound were significantly reduced in the RPNI group.

CONCLUSION

This study suggested that RPNI can effectively prevent the formation of symptomatic neuroma after amputation using ultrasound.

Design trends in actuated lower-limb prosthetic systems: a narrative review

INTRODUCTION

Actuated lower limb prostheses, including powered (active) and semi-active (quasi-passive) joints, are endowed with controllable power and/or impedance, which can be advantageous to limb impairment individuals by improving locomotion mechanics and reducing the overall metabolic cost of ambulation. However, an increasing number of commercial and research-focused options have made navigating this field a daunting task for users, researchers, clinicians, and professionals.

AREAS COVERED

The present paper provides an overview of the latest trends and developments in the field of actuated lower-limb prostheses and corresponding technologies. Following a gentle summary of essential gait features, we introduce and compare various actuated prosthetic solutions in academia and the market designed to provide assistance at different levels of impairments. Correspondingly, we offer insights into the latest developments of sockets and suspension systems, before finally discussing the established and emerging trends in surgical approaches aimed at improving prosthetic experience through enhanced physical and neural interfaces.

EXPERT OPINION

The ongoing challenges and future research opportunities in the field are summarized for exploring potential avenues for development of next generation of actuated lower limb prostheses. In our opinions, a closer multidisciplinary integration can be found in the field of actuated lower-limb prostheses in the future.

Regenerative Peripheral Nerve Interface Surgery: Anatomic and Technical Guide

Regenerative peripheral nerve interface (RPNI) surgery has been demonstrated to be an effective tool as an interface for neuroprosthetics. Additionally, it has been shown to be a reproducible and reliable strategy for the active treatment and for prevention of neuromas. The purpose of this article is to provide a comprehensive review of RPNI surgery to demonstrate its simplicity and empower reconstructive surgeons to add this to their armamentarium. This article discusses the basic science of neuroma formation and prevention, as well as the theory of RPNI. An anatomic review and discussion of surgical technique for each level of amputation and considerations for other etiologies of traumatic neuromas are included. Lastly, the authors discuss the future of RPNI surgery and compare this with other active techniques for the treatment of neuromas.

Surgical treatments for postamputation pain: study protocol for an international, double-blind, randomised controlled trial

BACKGROUND

Painful conditions such as residual limb pain (RLP) and phantom limb pain (PLP) can manifest after amputation. The mechanisms underlying such postamputation pains are diverse and should be addressed accordingly. Different surgical treatment methods have shown potential for alleviating RLP due to neuroma formation - commonly known as neuroma pain - and to a lesser degree PLP. Two reconstructive surgical interventions, namely targeted muscle reinnervation (TMR) and regenerative peripheral nerve interface (RPNI), are gaining popularity in postamputation pain treatment with promising results. However, these two methods have not been directly compared in a randomised controlled trial (RCT). Here, we present a study protocol for an international, double-blind, RCT to assess the effectiveness of TMR, RPNI, and a non-reconstructive procedure called neuroma transposition (active control) in alleviating RLP, neuroma pain, and PLP.

METHODS

One hundred ten upper and lower limb amputees suffering from RLP will be recruited and assigned randomly to one of the surgical interventions (TMR, RPNI, or neuroma transposition) in an equal allocation ratio. Complete evaluations will be performed during a baseline period prior to the surgical intervention, and follow-ups will be conducted in short term (1, 3, 6, and 12 months post-surgery) and in long term (2 and 4 years post-surgery). After the 12-month follow-up, the study will be unblinded for the evaluator and the participants. If the participant is unsatisfied with the outcome of the treatment at that time, further treatment including one of the other procedures will be discussed in consultation with the clinical investigator at that site.

DISCUSSION

A double-blind RCT is necessary for the establishment of evidence-based procedures, hence the motivation for this work. In addition, studies on pain are challenging due to the subjectivity of the experience and the lack of objective evaluation methods. Here, we mitigate this problem by including different pain evaluation methods known to have clinical relevance. We plan to analyse the primary variable, mean change in NRS (0-10) between baseline and the 12-month follow-up, using the intention-to-treat (ITT) approach to minimise bias and keep the advantage of randomisation. The secondary outcomes will be analysed on both ITT and per-protocol (PP). An adherence protocol (PP population) analysis will be used for estimating a more realistic effect of treatment.

TRIAL REGISTRATION

ClincialTrials.gov NCT05009394.

Neuroma Treatment With the Acellular Nerve Allograft Reconstruction Technique

Treatment of a painful neuroma is a challenging problem for both the patient and the providers. Current surgical treatment options typically include excision of the neuroma and stump relation. However, with both treatment options, patients have high rates of persistent pain and rates of neuroma recurrence. We describe two patients with neuromas treated with our acellular nerve allograft reconstruction technique. This technique involves the excision of the neuroma and bridging the proximal nerve end to the surrounding tissue with an acellular nerve allograft. Both patients had immediate resolution of their neuropathic pain that was maintained at their final follow-up. Acellular nerve allograft reconstruction is a promising treatment option for the treatment of painful neuromas.

Update on Upper Limb Neuroma Management

Painful terminal neuromas in the upper limb due to nerve injury are common. Neuroma symptoms include a sharp and burning sensation, cold intolerance, dysesthesia, pain, numbness, and paresthesia. These symptoms could have a negative impact on the functional ability of the patient and quality of life. In addition, Prostheses use might be abandoned by amputees due to neuroma-induced pain. Many clinicians face challenges while managing neuromas. Contemporary "active" methods like regenerative peripheral nerve interface (RPNI), targeted muscle reinnervation (TMR), and processed nerve allograft repair (PNA) are replacing the conventional "passive" approaches such as excision, transposition, and implantation techniques. RPNI involves inducing axonal sprouting by transplanting the free end of a peripheral nerve into a free muscle graft. TMR includes reassigning the role of the peripheral nerve by the transfer of the distal end of a pure sensory or a mixed peripheral nerve to a motor nerve of a nearby muscle segment. To give the peripheral nerve a pathway to re-innervate its target tissue, PNA entails implanting a sterile extracellular matrix prepared from decellularized and regenerated human nerve tissue with preserved epineurium and fascicles. Of these, RPNI and TMR appear to hold a promising treatment for nerve-ending neuromas and prevent their relapse. In contrast, PNA may reduce neuroma pain and allow meaningful nerve repair. The aim of this article is to provide an overview of the newer approaches of TMR, RPNI, and PNA and discuss their implications, surgical techniques, and reported consequences.

Factors influencing perceived function in the upper limb prosthesis user population

BACKGROUND

Patient-reported outcomes (PROs) can be used to evaluate perceived capacity of an individual in executing tasks in a natural environment with their prosthetic device. According to the World Health Organization International Classification of Health, Functioning, and Disability (ICF) models, there may be specific factors of a person, factors of assistive prosthetic technology, or factors related to the health condition or body function that affect their functioning and disability. However, an understanding of factors affecting an upper limb prosthesis user's perception of their ability to execute tasks in a natural environment is not well established.

OBJECTIVE

To use the ICF model to identify which health condition-related, body function, environmental, and personal factors influence activity as measured by perceived function in the upper limb prosthesis user population.

DESIGN

Quantitative clinical descriptive study.

SETTING

Clinical offices within outpatient private practice (removed for blinding).

PARTICIPANTS

A sample of 101 participants with upper limb amputation who use a prosthetic device and were undergoing a prosthesis fitting process.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

PROs on pain with/without a prosthesis, satisfaction, and perceived function derived from the Comprehensive Arm Prosthesis and Rehabilitation Outcomes Questionnaire.

RESULTS

Model coefficients indicate that with a unit increase in satisfaction (p < .001) and pain (p = .031) scores (with higher pain scores signifying less pain), the mean of perceived function increases by 0.66 and 0.47 units, respectively. Conversely, for individuals with elbow disarticulation, transhumeral, shoulder disarticulation, and interscapulothoracic amputations, the mean of perceived function decreases by 22.02 units (p = .006).

CONCLUSIONS

Based on our sample, perceived function is significantly associated with satisfaction, pain, and amputation level. These findings could potentially help to inform initial clinical approach and targeted outcomes for patients based on these factors.

Traumatic injury to peripheral nerves

This article reviews the epidemiology, classification, localization, prognosis, and mechanisms of recovery of traumatic peripheral nerve injuries (PNIs). Electrodiagnostic (EDx) assessments are critical components of treating patients with PNIs. In particular, motor and sensory nerve conduction studies, needle electromyography, and other electrophysiological methods are useful for localizing peripheral nerve injuries, detecting and quantifying the degree of axon loss, and contributing toward treatment decisions as well as prognostication. It is critical that EDx medical consultants are aware of the timing of these changes as well as limitations in interpretations. Mechanisms of recovery may include recovery from conduction block, muscle fiber hypertrophy, distal axonal sprouting, and axon regrowth from the site of injury. Motor recovery generally reaches a plateau at 18 to 24 months postinjury. When patients have complete or severe nerve injuries they should be referred to surgical colleagues early after injury, as outcomes are best when nerve transfers are performed within the first 3 to 6 months after onset.

Traumatic peripheral nerve injuries: diagnosis and management

PURPOSE OF REVIEW

To review advances in the diagnostic evaluation and management of traumatic peripheral nerve injuries.

RECENT FINDINGS

Serial multimodal assessment of peripheral nerve injuries facilitates assessment of spontaneous axonal regeneration and selection of appropriate patients for early surgical intervention. Novel surgical and rehabilitative approaches have been developed to complement established strategies, particularly in the area of nerve grafting, targeted rehabilitation strategies and interventions to promote nerve regeneration. However, several management challenges remain, including incomplete reinnervation, traumatic neuroma development, maladaptive central remodeling and management of fatigue, which compromise functional recovery.

SUMMARY

Innovative approaches to the assessment and treatment of peripheral nerve injuries hold promise in improving the degree of functional recovery; however, this remains a complex and evolving area.

Peripheral Neurectomy With Customized Nerve Reconstruction for Periorbital Neuropathic Pain: Initial Experience and Clinical Outcomes

PURPOSE

To describe a novel, minimally invasive surgical technique to treat severe, intractable periorbital neuropathic pain.

METHODS

A retrospective analysis of patients with severe, treatment-refractory periorbital pain who underwent transection of affected sensory trigeminal branches with nerve repair was performed. Collected data included etiology and duration of neuropathic pain, comorbidities, prior treatment history, surgical technique including site of transected sensory nerves and type of nerve repair, preoperative and postoperative pain scores as well as follow-up duration. Differences between preoperative and postoperative values were analyzed by the Wilcoxon signed-rank test.

RESULTS

A total of 5 patients with severe periorbital neuropathic pain underwent transection of affected supraorbital, supratrochlear, infratrochlear, infraorbital, zygomaticotemporal, and zygomaticofacial nerves with customized nerve reconstruction. All 5 had improvement of periorbital pain after surgery, with 3 (60%) noting complete resolution of pain and 2 (40%) experiencing partial pain relief over a median follow-up period of 9 months (interquartile range [IQR], 6-19 months). Of the 3 patients who had complete resolution of pain, all reported continued pain relief. Median McGill pain scores significantly decreased from 8.4 (IQR, 8.2-10.0) preoperatively to 0.0 (IQR, 0.0-4.8; p < 0.001) postoperatively. All patients reported satisfaction with the surgical procedure and stated that they would undergo the procedure again if given the option. One patient with history of postherpetic neuralgia (PHN) had reactivation of herpes zoster at postoperative month 3, which was self-limited, without worsening of her neuropathic pain. Another patient with PHN required a staged procedure to achieve complete pain relief.

CONCLUSION

Peripheral neurectomy with customized reconstruction of involved sensory nerves can successfully reduce and even eradicate periorbital neuropathic pain that was previously recalcitrant to combination pharmacotherapy and prior neurolysis procedures.

Surgically Implanted Electrodes Enable Real-Time Finger and Grasp Pattern Recognition for Prosthetic Hands

Currently available prosthetic hands are capable of actuating anywhere from five to 30 degrees of freedom (DOF). However, grasp control of these devices remains unintuitive and cumbersome. To address this issue, we propose directly extracting finger commands from the neuromuscular system. Two persons with transradial amputations had bipolar electrodes implanted into regenerative peripheral nerve interfaces (RPNIs) and residual innervated muscles. The implanted electrodes recorded local electromyography with large signal amplitudes. In a series of single-day experiments, participants used a high speed movement classifier to control a virtual prosthetic hand in real-time. Both participants transitioned between 10 pseudo-randomly cued individual finger and wrist postures with an average success rate of 94.7% and trial latency of 255 ms. When the set was reduced to five grasp postures, metrics improved to 100% success and 135 ms trial latency. Performance remained stable across untrained static arm positions while supporting the weight of the prosthesis. Participants also used the high speed classifier to switch between robotic prosthetic grips and complete a functional performance assessment. These results demonstrate that pattern recognition systems can use intramuscular electrodes and RPNIs for fast and accurate prosthetic grasp control.

Contemporary Approaches to Peripheral Nerve Surgery

“State of the Art” Learning Objectives: This manuscript serves to provide the reader with a general overview of the contemporary approaches to peripheral nerve reconstruction as the field has undergone considerable advancement over the last 3 decades. The learning objectives are as follows: To provide the reader with a brief history of peripheral nerve surgery and some of the landmark developments that allow for current peripheral nerve care practices. To outline the considerations and management options for the care of patients with brachial plexopathy, spinal cord injury, and lower extremity peripheral nerve injury. Highlight contemporary surgical techniques to address terminal neuroma and phantom limb pain. Review progressive and future procedures in peripheral nerve care, such as supercharge end-to-side nerve transfers. Discuss rehabilitation techniques for peripheral nerve care.

Target Receptors of Regenerating Nerves: Neuroma Formation and Current Treatment Options

Neuromas form as a result of disorganized sensory axonal regeneration following nerve injury. Painful neuromas lead to poor quality of life for patients and place a burden on healthcare systems. Modern surgical interventions for neuromas entail guided regeneration of sensory nerve fibers into muscle tissue leading to muscle innervation and neuroma treatment or prevention. However, it is unclear how innervating denervated muscle targets prevents painful neuroma formation, as little is known about the fate of sensory fibers, and more specifically pain fiber, as they regenerate into muscle. Golgi tendon organs and muscle spindles have been proposed as possible receptor targets for the regenerating sensory fibers; however, these receptors are not typically innervated by pain fibers, as these free nerve endings do not synapse on receptors. The mechanisms by which pain fibers are signaled to cease regeneration therefore remain unknown. In this article, we review the physiology underlying nerve regeneration, the guiding molecular signals, and the target receptor specificity of regenerating sensory axons as it pertains to the development and prevention of painful neuroma formation while highlighting gaps in literature. We discuss management options for painful neuromas and the current supporting evidence for the various interventions.

Surgical Approaches for Prevention of Neuroma at Time of Peripheral Nerve Injury

Painful neuroma is a frequent sequela of peripheral nerve injury which can result in pain and decreased quality of life for the patient, often necessitating surgical intervention. End neuromas are benign neural tumors that commonly form after nerve transection, when axons from the proximal nerve stump regenerate in a disorganized manner in an attempt to recreate nerve continuity. Inflammation and collagen remodeling leads to a bulbous end neuroma which can become symptomatic and result in decreased quality of life. This review covers surgical prophylaxis of end neuroma formation at time of injury, rather than treatment of existing neuroma and prevention of recurrence. The current accepted methods to prevent end neuroma formation at time of injury include different mechanisms to inhibit the regenerative response or provide a conduit for organized regrowth, with mixed results. Approaches include proximal nerve stump capping, nerve implantation into bone, muscle and vein, various pharmacologic methods to inhibit axonal growth, and mechanisms to guide axonal growth after injury. This article reviews historical treatments that aimed to prevent end neuroma formation as well as current and experimental treatments, and seeks to provide a concise, comprehensive resource for current and future therapies aimed at preventing neuroma formation.

Pilot feasibility study of a simple regenerative peripheral nerve interface designed to diminish cutaneous dysesthesia after supraclavicular operations

Supraclavicular operations can be associated with postoperative cutaneous dysesthesia and hypersensitivity. Regenerative peripheral nerve interfaces, created by attaching the proximal end of a divided peripheral nerve into a viable muscle target, can promote neurite regrowth and neuromuscular connections to help suppress painful nerve hyperactivity. During 40 consecutive operations for neurogenic thoracic outlet syndrome, we demonstrated that division of at least one of the superficial supraclavicular cutaneous sensory nerve branches was necessary in 98% of cases. We subsequently developed a novel regenerative peripheral nerve interface for supraclavicular operations using the adjacent omohyoid muscle and have described the technical steps involved in this procedure.

Restoration of Proprioceptive and Cutaneous Sensation Using Regenerative Peripheral Nerve Interfaces in Humans with Upper Limb Amputations

SUMMARY

Without meaningful and intuitive sensory feedback, even the most advanced prosthetic limbs remain insensate and impose an enormous cognitive burden during use. The regenerative peripheral nerve interface can serve as a novel bidirectional motor and sensory neuroprosthetic interface. In previous human studies, regenerative peripheral nerve interfaces demonstrated stable high-amplitude motor electromyography signals with excellent signal-to-noise ratio for prosthetic control. In addition, they can treat and prevent postamputation pain by mitigating neuroma formation. In this study, the authors investigated whether electrical stimulation applied to regenerative peripheral nerve interfaces could produce appreciable proprioceptive and/or tactile sensations in two participants with upper limb amputations. Stimulation of the interfaces resulted in both participants reporting proprioceptive sensations in the phantom hand. Specifically, stimulation of participant 1's median nerve regenerative peripheral nerve interface activated a flexion sensation in the thumb or index finger, whereas stimulation of the ulnar nerve interface evoked a flexion sensation of the ring or small finger. Likewise, stimulation of one of participant 2's ulnar nerve interfaces produced a sensation of flexion at the ring finger distal interphalangeal joint. In addition, stimulation of participant 2's other ulnar nerve interface and the median nerve interface resulted in perceived cutaneous sensations that corresponded to each nerve's respective dermatome. These results suggest that regenerative peripheral nerve interfaces have the potential to restore proprioceptive and cutaneous sensory feedback that could significantly improve prosthesis use and embodiment.

Effective Treatment of Chronic Mastectomy Pain with Intercostal Sensory Neurectomy

SUMMARY

Chronic postmastectomy pain affects up to 40 percent of patients and leads to diminished quality of life and increased risk of opioid dependence. The cause of this pain is incompletely understood; however, one hypothesis is that direct injury to cutaneous intercostal nerves at the time of mastectomy and/or reconstruction leads to chronic pain. As a result, proximal neurectomy of the involved sensory nerve(s) has been suggested to be effective for these patients. The purpose of this study was to determine whether chronic pain in postmastectomy patients can be diagnosed reliably in an office setting and pain reduced by intercostal sensory neurectomy. The authors performed a retrospective review of seven patients with a history of breast surgery and chronic pain who underwent intercostal neurectomy combined with muscle or dermal wrapping of the proximal end of the resected nerve. All patients were diagnosed by history and physical examination, and suspected nerves were further identified with local anesthetic nerve blocks. An average of 3.14 neurectomies were performed per patient (range, one to six). There was a significant reduction in visual analogue scale pain scores following surgery, from 9 preoperatively to 1 postoperatively (p = 0.02). Eighty-six percent of patients were pain-free or "considerably improved" at their latest follow-up appointment (average, 6.14 months). It is concluded that intercostal sensory nerve injury at the time of mastectomy and/or reconstruction can lead to chronic mastectomy pain, which can be easily diagnosed and effectively treated with intercostal neurectomy.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, IV.

Prophylactic Regenerative Peripheral Nerve Interfaces in Elective Lower Limb Amputations

Regenerative peripheral nerve interface (RPNI) is a relatively new surgical technique to manage neuromas and phantom pain after limb amputation. This study evaluates prophylactic RPNI efficacy in managing post-amputation pain and neuroma formation in amputees compared with patients in which lower limb amputation was performed without this procedure. We included 28 patients who underwent above the knee amputation (AKA) or below the knee amputation (BKA) for severe soft tissue infection from July 2019 till December 2020. All patients had insulin-dependent diabetes. The patients were divided into two groups, 14 patients with primary RPNI and 14 patients without. We analyzed the demographic data, level of amputation, number of RPNIs, operative time, postoperative complications and functional outcome on the defined follow up period. The mean patient age was 68.6 years (range 49-85), 19 (67.9 %) male and 9 (32.1 %) female patients. In this study 11 (39.3 %) AKA and 17 (60.7 %) BKA were performed. Overall, 37 RPNIs were made. The mean follow-up period was 49 weeks. PROMIS T-score decreased by 15.9 points in favor for the patients with RPNI. The VAS score showed that, in the RPNI group, all 14 patients were without pain compared to the group of patients without RPNI, where the 11 (78.6 %) patients described their pain as severe. Patients with RPNI used prosthesis significantly more (p < 0.005). Data showed significant reduction in pain and high patient satisfaction after amputation with RPNIs. This technique is oriented as to prevent neuroma formation with RPNI surgery, performed at the time of amputation. RPNI surgery did not provoke complications or significant lengthening of operative time and it should be furthermore exploited as a surgical technique.

Clinical Basis for Creating an Osseointegrated Neural Interface

As technology continues to improve within the neuroprosthetic landscape, there has been a paradigm shift in the approach to amputation and surgical implementation of haptic neural prosthesis for limb restoration. The Osseointegrated Neural Interface (ONI) is a proposed solution involving the transposition of terminal nerves into the medullary canal of long bones. This design combines concepts of neuroma formation and prevention with osseointegration to provide a stable environment for conduction of neural signals for sophisticated prosthetic control. While this concept has previously been explored in animal models, it has yet to be explored in humans. This anatomic study used three upper limb and three lower limb cadavers to assess the clinical feasibility of creating an ONI in humans. Anatomical measurement of the major peripheral nerves- circumference, length, and depth- were performed as they are critical for electrode design and rerouting of the nerves into the long bones. CT imaging was used for morphologic bone evaluation and virtual implantation of two osseointegrated implants were performed to assess the amount of residual medullary space available for housing the neural interfacing hardware. Use of a small stem osseointegrated implant was found to reduce bone removal and provide more intramedullary space than a traditional implant; however, the higher the amputation site, the less medullary space was available regardless of implant type. Thus the stability of the endoprosthesis must be maximized while still maintaining enough residual space for the interface components. The results from this study provide an anatomic basis required for establishing a clinically applicable ONI in humans. They may serve as a guide for surgical implementation of an osseointegrated endoprosthesis with intramedullary electrodes for prosthetic control.

Peripheral Nerve Management in Extremity Amputations

The effective management of peripheral nerves in amputation surgery is critical to optimizing patient outcomes. Nerve-related pain after amputation is common, maybe a source of dissatisfaction and functional impairment, and should be considered in all amputees presenting with pain and dysfunction. While traction neurectomy or transposition has long been the standard of care, both regenerative peripheral nerve interface (RPNI) and targeted muscle reinnervation (TMR) have emerged as promising techniques to improve neuroma-related and phantom pain. A multi-disciplinary and multi-modal approach is essential for the optimal management of amputees both acutely and in the delayed or chronic setting.

Digital Nerve Management and Neuroma Prevention in Hand Amputations

BACKGROUND

Hand and digit amputations represent a relatively common injury affecting an active patient population. Neuroma formation following amputation at the level of the digital nerve can cause significant disability and lead to revision surgery. One method for managing digital nerves in primary and revision partial hand amputations is to perform interdigital end-to-end nerve coaptations to prevent neuroma formation.

METHODS

All patients with an amputation at the level of the common or proper digital nerves that had appropriate follow-up at our institution from 2010 to 2020 were included. Common or proper digital nerves were managed with either traction neurectomy or digital end-to-end neurorrhaphy. The primary outcome was the development of a neuroma. Secondary outcomes included revision surgery, complications, and visual analog pain scores.

RESULTS

A total of 289 nerves in 54 patients underwent hand or digital amputation in the study period. Thirteen hands with 78 nerves (27%) underwent direct end-to-end coaptation with a postoperative neuroma incidence of 12.8% compared with 22.7% in the 211 nerves that did not have a coaptation performed. Significantly fewer patients reported persistent pain if an end-to-end coaptation was performed (0% vs. 11.8%, P < .01). The prevalence of depression and workers compensation status was significantly higher in in patients with symptomatic neuromas than in patients without symptomatic neuromas (P < .01).

CONCLUSIONS

Digital nerve end-to-end neurorrhaphy is a method for neuroma prevention in partial hand amputations that results in decreased residual hand pain without increase complications. Depression and worker's compensations status were significantly associated with symptomatic neuroma formation.

Indications and outcomes of palliative major amputation in patients with metastatic cancer

BACKGROUND

Patients with stage IV cancer often experience diminished quality of life and pain. Although palliative amputation (PA) can reduce pain, it is infrequently performed because of the morbidity associated with amputation and the limited life expectancy in this population. Here, we describe the indications for PA in patients with stage IV carcinoma or sarcoma and discuss their clinical courses and outcomes. We hypothesized that PA would be associated with reduced pain and improved quality of life in these patients.

METHODS

We retrospectively reviewed medical records of all patients who underwent major amputation (proximal to the ankle or wrist) for metastatic sarcoma or carcinoma from January 1995 to April 2021. We excluded patients who underwent amputation for indications other than palliation. Cox proportional hazards regression analysis was used to determine factors associated with survival after PA.

RESULTS

Twenty-six patients underwent PA (11 for carcinoma, 15 for sarcoma). The most common indications for PA were pain (all patients) and fungating tumor (16 patients). PA was the initial surgery in 7 patients. Forequarter amputations were the most common procedure (6 patients). All patients reported reduced pain after PA, with the mean (±standard deviation) visual analog pain score (on a 10-point scale) decreasing from 5.7 ± 2.9 preoperatively to 0.43 ± 1.3 postoperatively (p < 0.001). The mean preoperative ECOG score was 1.9 ± 0.2 compared with 1.3 ± 0.1 postoperatively (p < 0.001). Fourteen patients were fitted for prostheses (6 upper extremity, 8 lower extremity). Two patients had local recurrence, both within 6 months after PA. The mean survival time after PA was 13 ± 12 months, and mean follow-up was 28 ± 29 months. Mean survival time after PA was not significantly different between patients with sarcoma (11 ± 11 months) versus carcinoma (15 ± 14 months) (p = 0.51). Adjuvant chemotherapy was positively associated with survival; no other factors were associated with survival.

CONCLUSIONS

PA was associated with significantly reduced pain in all patients with stage IV cancer. PA should be considered for those with intractable pain, fungating tumors, or symptoms that diminish quality of life.

LEVEL OF EVIDENCE

Level III.

A consecutive series of targeted muscle reinnervation (TMR) cases for relief of neuroma and phantom limb pain: UK perspective

BACKGROUND

Studies have suggested that targeted muscle reinnervation (TMR) can improve symptoms of neuroma pain (NP) and phantom limb pain (PLP) in patients.

OBJECTIVES

Our primary objective was to measure changes in NP and PLP levels following TMR surgery at 4-time points (baseline, 3, 6- and 12-months postoperatively). Secondary aims included identification of the character and rate of any surgical complications and patients' satisfaction with TMR.

METHODS

A retrospective review of outcomes of 36 patients who underwent TMR surgery to treat intractable NP and/or PLP after major amputation of an upper (UL) or lower limb (LL) at a single centre in London, UK over 7 years. The surgical techniques, complications, and satisfaction with TMR are described.

RESULTS

Forty TMR procedures were performed on 36 patients. Thirty patients had complete data for NP and PLP levels at all pre-defined time points. Significant improvements (p<0.01) in both types of pain were observed for both upper and LL amputees. However, there were varying patterns of recovery. For example, UL amputees experienced worsening of PLP in the first few months post-operatively whereas surgical complications were more common in LL cases. Patients were overwhelmingly satisfied with the improvements in their symptoms (90%).

CONCLUSIONS

TMR surgery appeared to relieve both NP and PLP although the retrospective nature of this study limits the strength of this conclusion. However, complication rates were high, and it is crucial for surgeons and patients to fully understand the course and outcomes of this novel surgery prior to undertaking treatment.

"Decreasing Postamputation Pain with the Regenerative Peripheral Nerve Interface (RPNI)"

Over 185,000 limb amputations are performed in the United States annually, many of which are due to the sequelae of peripheral vascular disease. Symptomatic neuromas remain a significant source of postamputation morbidity and contribute to both phantom limb (PLP) and residual limb pain (RLP). While many interventions have been proposed for the treatment of symptomatic neuromas, conventional methods lead to a high incidence of neuroma recurrence. Furthermore, these existing methods do not facilitate an ability to properly interface with myoelectric prosthetic devices. The Regenerative Peripheral Nerve Interface (RPNI) was developed to overcome these limitations. The RPNI consists of an autologous free muscle graft secured around the end of a transected nerve. The muscle graft provides regenerating axons with end organs to reinnervate, thereby preventing neuroma formation. We have shown that this simple, reproducible, and safe surgical technique successfully treats and prevents neuroma formation in major limb amputations. In this paper, we describe RPNI surgery in the setting of major limb amputation and highlight the promising results of RPNIs in our animal and clinical studies.

Regenerative Peripheral Nerve Interfaces for Advanced Control of Upper Extremity Prosthetic Devices

The quest to find the ideal prosthetic device interface that enables intuitive control has motivated several recent innovations. Although current prosthetic device control strategies have advanced the field of neuroprosthetic control, they are limited in their ability to generate reliable, stable, and specific signals to replicate the complex movements of the upper extremity. The regenerative peripheral nerve interface (RPNI) is a promising solution to enhance prosthetic device control. This article describes the development of RPNIs and summarizes its successful use in the control of advanced prosthetic devices in patients with upper extremity amputations.

Brain-Machine Interfaces: Lessons for Prosthetic Hand Control

Brain-machine interfaces (BMI) are being developed to restore upper limb function for persons with spinal cord injury or other motor degenerative conditions. BMI and implantable sensors for myoelectric prostheses directly extract information from the central or peripheral nervous system to provide users with high fidelity control of their prosthetic device. Control algorithms have been highly transferable between the 2 technologies but also face common issues. In this review of the current state of the art in each field, the authors point out similarities and differences between the 2 technologies that may guide the implementation of common solutions to these challenges.

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.

Prevalence of residual limb pain and symptomatic neuromas after lower extremity amputation: a systematic review and meta-analysis

ABSTRACT

Residual limb pain (RLP) is associated with (partial) extremity amputations and is defined as pain felt in the remaining part of the amputated limb. A common cause of RLP is neuroma formation after nerve transections. Neuromas can be very painful and severely debilitating pathologies, preventing prosthetic use, reducing quality of life, and requiring medication. Residual limb pain and symptomatic neuromas are often not properly recognized by physicians explaining the varying prevalence in the literature. This systematic review and meta-analysis aim to provide a comprehensive overview of published literature on the prevalence of RLP and symptomatic neuroma after lower extremity amputation. Studies reporting the prevalence of RLP and symptomatic neuroma pain in patients who have had a lower extremity amputation published between 2000 and 2020 were identified in PubMed and Embase. Random-effects meta-analyses of proportions were performed to quantify the prevalence of RLP and symptomatic neuroma. Subgroups were identified and analysed. For RLP, the pooled prevalence was 59% (95% CI: 51-67). For symptomatic neuromas, the pooled prevalence was 15% (95% CI: 7-28). Residual limb pain subgroup analysis showed statistically significant higher prevalence in patients aged >50 years, follow-up >2 years, and in studies using a self-administered questionnaire for data collection. The prevalence of RLP and symptomatic neuroma in patients who have had a lower extremity amputation is 59% and 15%, respectively. Knowledge of their high prevalence may result in better awareness among physicians, in turn providing timely and adequate management.

Surgical Treatment of Abdominal Wall Neuromas

Neuromas are an under-recognized contributor to chronic abdominal pain. Other than after mesh inguinal hernia repair, surgical management of painful abdominal wall neuromas has not been well established in the literature.

Targeted Muscle Reinnervation to Expendable Motor Nerves for the Treatment of Refractory Symptomatic Neuromas in Nonamputees

Symptomatic neuromas can cause debilitating pain, significantly impairing patients’ quality of life. There are numerous medical and surgical options for management. Targeted muscle reinnervation (TMR) is a nerve transfer procedure that is now commonly used to prevent or treat symptomatic neuromas or phantom limb pain in amputees. There are a few reports in the current literature about performing TMR in the nonamputee, but no cohort studies to date that report pain outcomes. This study evaluates TMR to treat symptomatic neuromas in nonamputee patients. This is a retrospective cohort study of all patients with symptomatic neuromas treated with TMR over a 1-year period from January 1,2019, to January 1, 2020, at MedStar Georgetown University Hospital. The neuromas are excised to healthy nerve fascicles, and a redundant donor motor fascicle is selected for nerve transfer. Patients were asked in clinic or via telephone about their preoperative and postoperative pain, function, and quality of life, and postoperative clinic notes were reviewed for complications and motor deficits. Fifteen patients were included in this study. Patients had symptomatic neuromas involving the upper extremity, lower extremity, and trunk. Pain frequency decreased from 6.7 times per week to 3.9 (P < 0.01) and from 9.1 times per day to 5.1 (P < 0.01). Pain severity decreased from an average of 7.9/10 to 4.3/10 (P < 0.01). Overall physical function increased from 3.7/10 to 5.8/10 (P = 0.01), and overall quality of life increased from 4.9/10 to 7.0/10 (P < 0.01). No patients had demonstrable weakness of the motor function of the donor nerve. Targeted muscle reinnervation is a viable surgical option for the treatment of symptomatic neuromas, particularly in those patients who have previously failed prior neuroma excisions.

Neurotized free VRAM used to create myoelectric signals in a muscle-depleted area for targeted muscle reinnervation for intuitive prosthesis control: A case report

Targeted muscle reinnervation enables native muscles to send electromyographic signals to myoelectric receptors, which drive movements in a prosthesis. This system requires voluntary contracture of muscles for sequential control of powered prosthetic joints. This report describes a surgical solution for cases where the chest wall is depleted of muscle targets. A 13-year-old boy with left forequarter amputation and pectoralis major resection as a result of extended necrotizing facilities 8 years prior received a neurotized free Vertical Rectus Abdominus Mycocutaneous (VRAM) flap (28 × 10 cm) designed to produce myoelectric signals, reduce pain, and provide stability for prosthetic fitting. Five intercostal nerves from the VRAM were coapted to portions of the brachial plexus to create a myoelectric interface for targeted muscle reinnervation. The postoperative course was uneventful. At 39 months of follow-up, the patient gained control of the transferred VRAM and was able to operate a custom-fitted myoelectric prosthesis together with contraction of the ipsilateral infraspinatus muscle. The neurotized VRAM transfer created a neural interface in an area with depleted neuromuscular targets while decreasing pain and adding tissue bulk for proper prosthesis fitting. Such a surgical strategy may have applications in other areas of the body.

Nerve injury and repair in a ketogenic milieu: A systematic review of traumatic injuries to the spinal cord and peripheral nervous tissue

Dietary interventions such as intermittent fasting and the ketogenic diet have demonstrated neuroprotective effects in various models of neurological insult. However, there has been a lack of evaluation of these interventions from a surgical perspective despite their potential to augment reparative processes that occur following nerve injury. Thus, we sought to analyze the effects of these dietary regimens on nerve regeneration and repair by critical appraisal of the literature. Following PRISMA guidelines, a systematic review was performed to identify studies published between 1950 and 2020 that examined the impact of either the ketogenic diet or intermittent fasting on traumatic injuries to the spinal cord or peripheral nerves. Study characteristics and outcomes were analyzed for each included article. A total of 1,890 articles were reviewed, of which 11 studies met inclusion criteria. Each of these articles was then assessed based on a variety of qualitative parameters, including type of injury, diet composition, timing, duration, and outcome. In total, seven articles examined the ketogenic diet, while four examined intermittent fasting. Only three studies examined peripheral nerves. Neuroprotective effects manifested as either improved histological or functional benefits in most of the included studies. Overall, we conclude that intermittent fasting and the ketogenic diet may promote neuroprotection and facilitate the regeneration and repair of nerve fibers following injury; however, lack of consistency between the studies in terms of animal models, diet compositions, and timing of dietary interventions preclude synthesis of their outcomes as a whole.

Investigation of Parameters Influencing Tubular-Shaped Chitosan-Hydroxyapatite Layer Electrodeposition

Tubular-shaped layer electrodeposition from chitosan-hydroxyapatite colloidal solutions has found application in the field of regeneration or replacement of cylindrical tissues and organs, especially peripheral nerve tissue regeneration. Nevertheless, the quantitative and qualitative characterisation of this phenomenon has not been described. In this work, the colloidal systems are subjected to the action of an electric current initiated at different voltages. Parameters of the electrodeposition process (i.e., total charge exchanged, gas volume, and deposit thickness) are monitored over time. Deposit structures are investigated by scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR). The value of voltage influences structural characteristics but not thickness of deposit for the process lasting at least 20 min. The calculated number of exchanged electrons for studied conditions suggests that the mechanism of deposit formation is governed not only by water electrolysis but also interactions between formed hydroxide ions and calcium ions coordinated by chitosan chains.

Surgically Implanted Electrodes Enable Real-Time Finger and Grasp Pattern Recognition for Prosthetic Hands

Currently available prosthetic hands are capable of actuating anywhere from five to 30 degrees of freedom (DOF). However, grasp control of these devices remains unintuitive and cumbersome. To address this issue, we propose directly extracting finger commands from the neuromuscular system via electrodes implanted in residual innervated muscles and regenerative peripheral nerve interfaces (RPNIs). Two persons with transradial amputations had RPNIs created by suturing autologous free muscle grafts to their transected median, ulnar, and dorsal radial sensory nerves. Bipolar electrodes were surgically implanted into their ulnar and median RPNIs and into their residual innervated muscles. The implanted electrodes recorded local electromyography (EMG) with Signal-to-Noise Ratios ranging from 23 to 350 measured across various movements. In a series of single-day experiments, participants used a high speed pattern recognition system to control a virtual prosthetic hand in real-time. Both participants were able to transition between 10 pseudo-randomly cued individual finger and wrist postures in the virtual environment with an average online accuracy of 86.5% and latency of 255 ms. When the set was reduced to five grasp postures, average metrics improved to 97.9% online accuracy and 135 ms latency. Virtual task performance remained stable across untrained static arm positions while supporting the weight of the prosthesis. Participants also used the high speed classifier to switch between robotic prosthetic grips and complete a functional performance assessment. These results demonstrate that pattern recognition systems can use the high-quality EMG afforded by intramuscular electrodes and RPNIs to provide users with fast and accurate grasp control.

SUMMARY

Surgically implanted electrodes recorded finger-specific electromyography enabling reliable finger and grasp control of an upper limb prosthesis.