Incidence of Nerve Injury After Extremity Trauma in the United States

Extracellular vesicle-derived MicroRNAs as potential therapies for spinal cord and peripheral nerve injuries

Complete nerve regeneration is limited in current therapeutic approaches for spinal cord injuries (SCIs) and peripheral nerve injuries (PNIs). Extracellular vesicles (EVs) and microRNAs (miRNAs) play a pivotal role in intercellular communication by transporting various biomolecules, including miRNAs, to the recipient cells. Thus, they are promising targets for novel neural regeneration drugs. This comprehensive study examined the roles of EV-derived miRNAs in facilitating neural rejuvenation after SCI and PNI. It also explored the mechanisms by which they augment neuroprotection and promote cell viability. It also discusses their translational potential for treating nerve injury and evaluates their potential impact on advancements in nerve resurrection and prospective research in regenerative medicine. The findings may provide effective treatments and improve outcomes, as well as contribute to addressing the direction for the next studies, for the pathologies of SCI and PNI.

Extensive Periosteal Injury During Fracture Induces Long-Term Pain in Mice

Bone fractures pose a significant public health challenge, often necessitating surgical interventions to facilitate bone healing and functional recovery. Sensory nerve fibers innervate various compartments of the bone tissue, with the periosteum exhibiting the most extensive innervation that is susceptible to injury during trauma. Despite its importance, the effect of injured periosteum on fracture pain remains unknown. This study examines the impact of extensive periosteal injury on fracture pain by using a mouse model. Periosteal injury is induced by mechanical resection during unilateral transverse fracture and compared to transverse fractures with no periosteal injury. Our results demonstrate that extensive periosteal injury induces severe and long-term pain, as assessed by von Frey and dynamic weight bearing measurements, for up to 12 weeks postfracture. Immunofluorescence staining revealed an increase in local neurofilament heavy polypeptide (NF200 +) nerve innervation and an elevated number of calcitonin gene-related peptide (CGRP +) expressing neurons in the dorsal root ganglion (DRG). Additionally, flow cytometric analyses revealed increased presence of myeloid immune cells in the DRG. Furthermore, bone healing in fractures with extensive periosteal injury exhibited reduced callus size at all time points as assessed by Faxitron X-ray imaging. This study describes a previously unknown effect of extensive periosteal injury in exacerbating fracture pain and establishes a potential model to study long-term orthopedic fracture pain.

Pilot Study: A Multicenter, Prospective Study Demonstrating Safety, Usability, and Feasibility of Perioperative 1-hour Electrical Stimulation Therapy for Enhancing Peripheral Nerve Regeneration

Background

Electrical stimulation (ES) applied for 1 hour following surgical intervention enhances axonal regeneration and functional outcomes. Clinical implementation, however, has been hindered due to the lack of appropriately designed stimulators.

Methods

This multicenter, prospective, open-label study aimed to demonstrate the safety and device feasibility of a novel, single-use stimulator for implementing perioperative ES therapy in a variety of upper extremity surgical procedures. Patients undergoing surgical intervention for upper extremity nerve injury, neuropathy, or lesions were included. An investigational version of a novel therapeutic peripheral nerve stimulator was used to deliver 1-hour ES therapy perioperatively. Safety was assessed by the cumulation of adverse events. Patient tolerance to ES therapy was obtained during the treatment, and pain was also assessed at the first postoperative visit. Device usability questionnaires were completed by the study surgeons.

Results

A total of 25 patients were enrolled. There were no related adverse events or adverse device effects. Implementation of the device took less than 5 minutes in the operating room in most cases. Bipolar stimulation was preferred, with a mean ± SD stimulus level of 2.2 ± 0.7 mA, and therapy was well tolerated. The mean first postoperative pain score was 1.2 out of 10. Surgeons indicated that perioperative implementation of the therapeutic peripheral nerve stimulator was easy and did not cause major disruptions to the clinical workflow.

Conclusions

Perioperative application of 1-hour ES therapy is a feasible, safe, and promising approach to enhancing peripheral nerve regeneration as an adjunct to surgical intervention.

Assessment, management, and rehabilitation of traumatic peripheral nerve injuries for non-surgeons

Electrodiagnostic evaluation is often requested for persons with peripheral nerve injuries and plays an important role in their diagnosis, prognosis, and management. Peripheral nerve injuries are common and can have devastating effects on patients' physical, psychological, and socioeconomic well-being; alongside surgeons, electrodiagnostic medicine specialists serve a central function in ensuring patients receive optimal treatment for these injuries. Surgical intervention-nerve grafting, nerve transfers, and tendon transfers-often plays a critical role in the management of these injuries and the restoration of patients' function. Increasingly, nerve transfers are becoming the standard of care for some types of peripheral nerve injury due to two significant advantages: first, they shorten the time to reinnervation of denervated muscles; and second, they confer greater specificity in directing motor and sensory axons toward their respective targets. As the indications for, and use of, nerve transfers expand, so too does the role of the electrodiagnostic medicine specialist in establishing or confirming the diagnosis, determining the injury's prognosis, recommending treatment, aiding in surgical planning, and supporting rehabilitation. Having a working knowledge of nerve and/or tendon transfer options allows the electrodiagnostic medicine specialist to not only arrive at the diagnosis and prognosticate, but also to clarify which nerves and/or muscles might be suitable donors, such as confirming whether the branch to supinator could be a nerve transfer donor to restore distal posterior interosseous nerve function. Moreover, post-operative testing can determine if nerve transfer reinnervation is occurring and progress patients' rehabilitation and/or direct surgeons to consider tendon transfers.

Mechanisms of muscle repair after peripheral nerve injury by electrical stimulation combined with blood flow restriction training

This review elucidates the impact of electrical stimulation (ES) and blood flow restriction (BFR) training on muscle function. ES induces a transformation in muscle fibers type by rearranging myosin heavy chain isoform patterns. Additionally, it influences muscle protein synthesis and degradation through specific signaling pathways such as protein kinase B/mechanistic target of rapamycin (Akt/mTOR), as well as via autophagy and the ubiquitin-proteasome system, thereby effectively maintaining muscle mass. BFR, on the other hand, restricts muscle blood flow, leading to metabolic products accumulation and localized hypoxia, which not only promotes the recruitment of fast-twitch fibers but also activates the mTOR signaling pathway, enhancing muscle protein synthesis. The combination of ES and BFR synergistically facilitates muscle protein synthesis through the mTOR pathway, thereby accelerating the recovery of muscle function following peripheral nerve injury.

Combat-related peripheral nerve injuries

Active-duty service members (ADSM) and military Veterans represent a population with increased occupational risk for nerve injuries sustained both during training operations and wartime. Mechanisms of war-related nerve injuries have evolved over time, from the musket ball-related traumas described by S.W. Mitchell to complex blast injuries and toxic exposures sustained during Middle East conflicts in the 21st century. Commonly encountered nerve injury etiologies in this population currently include compression, direct trauma, nutritional deficits, traumatic limb amputation, toxic chemical exposures, or blast-related injuries. Expeditious identification and comprehensive, interdisciplinary treatment of combat-associated neuropathies, as well as prevention of these injuries whenever possible is critical to reduce chronic morbidity and disability for service members and to maintain a well-prepared military. However, diagnosis of a combat-associated nerve injury may be particularly challenging due to comorbid battlefield injuries or delayed presentation of neuropathy from military toxic exposures. Advances in imaging for nerve injury, including MRI and ultrasound, provide useful tools to compliment EMG in establishing a diagnosis of combat-associated nerve injury, particularly in the setting of anatomic disruption or edema. Surgical techniques can improve pain control or restoration of function. In all cases, comprehensive interdisciplinary rehabilitation provides the best framework for optimization of recovery. Further work is needed to prevent combat-associated nerve injuries and promote nerve recovery following injury.

Modern Medical Rehabilitation Methods for Patients with Peripheral Nerve and Brachial Plexus Injuries (Review)

Peripheral nerve and brachial plexus injuries represent one of the most serious medical challenges due to the high frequency of disabling consequences. Medical rehabilitation for such injuries is critically important as it ensures the most complete functional recovery for patients. The aim of this review is to summarize and interpret the data on medical rehabilitation methods, as well as to assess the effectiveness of rehabilitation strategies and techniques for restoring upper limb functions after peripheral nerve and brachial plexus injuries. Information is provided on the theoretical foundations of functional recovery following peripheral nerve and nerve plexus injuries, as well as on factors that may hinder the full functional recovery of patients. There are discussed rehabilitation strategies and methods aimed at accelerating nerve fiber regeneration, preventing complications, correcting cortical plasticity, restoring patients' functional capabilities, and improving their quality of life. Special attention is given to pain management, electrical stimulation, sensory deficit correction, and physical therapy in the postoperative period. Rehabilitation modalities and the medical rehabilitation duration are highly individualized and depend on numerous factors that determine the rehabilitation interventions direction. However, a significant number of rehabilitation methods have a low evidence base: many scientific studies are based on small samples, do not consider the heterogeneous nature of injuries, and do not evaluate longterm outcomes. Further research is needed to assess the effectiveness of both individual rehabilitation techniques and comprehensive rehabilitation programs that facilitate the recovery of motor activity in patients with peripheral nerve and brachial plexus injuries.

Clinical evaluation of a novel disposable neurostimulator used to accelerate regeneration of injured peripheral nerves in the hand

BACKGROUND

Preclinical and early clinical evidence demonstrates that electrical stimulation (ES) applied for one hour following surgical nerve intervention enhances axonal regeneration and functional outcomes. Wide clinical implementation however, has been hindered by a lack of suitably designed stimulators. The aim of this pilot study was to investigate sensory recovery, safety, tolerability, and RCT feasibility for the use of a novel single-use stimulator to deliver ES therapy in an acute nerve transection cohort.

METHODS

Patients with complete transection of a proper digital nerve were included in the trial. An investigational version of PeriPulseTM was used with intraoperative electrode implantation and 1-hour ES therapy delivered postoperatively. Patient tolerance was assessed during stimulation and visual-analogue pain scores were collected at the first post-operative visit. At 3- and 6-months post-op, sensory recovery and quality of life were assessed using 2-point discrimination, monofilament tests, and the Disability of Arm, Shoulder, and Hand (DASH) questionnaire, respectively.

RESULTS

A total of 10 patients were enrolled. Intraoperative electrode placement did not impact operating room time, taking less than 5 minutes to implement. There were no related adverse events. Participants reported tolerable stimulation during ES therapy with no reports of pain. At the first post-operative visit patients had a mean visual-analogue pain score of 0.6 (range 0 - 1.9). Pressure threshold detection significantly improved between baseline, 3 months and 6 months. A greater proportion of ES treated patients (87.5%) had improved hand pressure thresholds (diminished light touch or diminished protective sensation) at 6 months compared to a historical comparator group. DASH scores improved over the timeline. Participants treated with ES therapy experienced minimal postoperative functional disability.

CONCLUSIONS

The use of the PeriPulseTM prototype for the delivery of perioperative ES therapy was safe, well-tolerated, and usable. Sensory recovery was demonstrated and a larger RCT is feasible.

TRIAL REGISTRATION

 NCT04732936; 2021 - 01 - 29.

Harnessing Polyethylene Glycol 3350 for Enhanced Peripheral Nerve Repair: A Path to Accelerated Recovery

Background and Objectives: Peripheral nerve injuries often result in significant functional impairment, and complete recovery remains challenging despite surgical interventions. Polyethylene glycol (PEG) has shown promise in nerve repair by facilitating axonal fusion and inhibiting Wallerian degeneration. This study investigates the biochemical, histopathological, and electrophysiological effects of PEG 3350 in a sciatic nerve injury model. Materials and Methods: Thirty adult male Wistar rats were divided into three groups: a control group, a surgery and saline group, and a surgery and PEG 3350 treatment group. Sciatic nerve transection was performed, and PEG 3350 was administered intraperitoneally for 12 weeks. Electromyography (EMG) and the inclined plane test assessed functional recovery. Sciatic nerve tissues were analyzed histologically and biochemically, including nerve growth factor (NGF), heat shock protein 70 (HSP-70), and malondialdehyde (MDA) levels. Results: PEG 3350 significantly improved electrophysiological parameters, reducing compound muscle action potential (CMAP) latency and increasing CMAP amplitude compared to the saline group (p < 0.05). Functional recovery, assessed by the inclined plane test, showed a significant improvement in the PEG-treated group (p < 0.01). Biochemical analysis revealed increased NGF and HSP-70 levels, suggesting enhanced neuroprotection and regeneration. Histopathological analysis demonstrated reduced fibrosis and increased axonal density in the PEG group compared to controls. PEG 3350 enhances nerve regeneration by improving electrophysiological function, promoting axonal repair, and increasing neurotrophic factor expression. Conclusions: These findings suggest PEG as a potential adjunct therapy for peripheral nerve injuries. Future research should explore the optimal administration protocols and combined therapeutic strategies for maximizing recovery.

Peripheral nerve ultrasound: a survival guide for the practicing radiologist with updates

Peripheral nerve injuries negatively impact patients' quality of life and healthcare resources. This review discusses using high-resolution neurosonography (HRNUS) for mapping peripheral nerves and detecting pathologic lesions. It emphasizes the importance of HRNUS in diagnosing nerve disorders and briefs the widely accepted schemes for peripheral nerve injury classification. It also highlights the non-intrusive, flexible, patient-friendly, and cost-effective nature of HRNUS, making it a valuable tool in managing nerve disorders. The authors recommend the use of HRNUS to enable precise diagnoses, prevent permanent disabilities, and contribute to the efficient utilization of healthcare resources.

Indications and Outcomes of Nerve Reconstructions After Resection of Extremity Tumors: A Systematic Review

Objective: Peripheral nerve injuries resulting from tumor resection are unusual, but occasionally unavoidable. It can result in serious morbidity in motor deficits, sensory deficits, and even chronic pain. Nerve reconstruction after tumor resection is possible and seems to have positive recovery outcomes. However, nerve reconstructions are rarely performed and clear outcomes of nerve reconstructions after tumor resection are missing. This review aims to create an overview of the indications and outcomes in these patients. Methods: A systematic review was performed in May 2024 in PubMed and Embase databases according to the PRISMA guidelines. Search terms related to "tumor" and "nerve reconstruction" were used. Studies evaluating nerve reconstructions (nerve graft, transfer or coaptation) after tumor resection were included. Tumors not located in the extremities were excluded. A qualitative synthesis was performed on all studies. Where possible, motor, and sensory grades were recalculated according to the Medical Research Council (MRC)-scale. Results: Fifty-nine articles were included for quality synthesis after full-text screening. A total of 90 patients were described of which 44 after resection of malignant tumors. Most patients improved in motor and sensory function after nerve reconstruction. In both benign and malignant tumors, 77% demonstrated functional recovery on the MRC scale of ≥3. Most of the patients, >80%, recovered to a protective sensation of S2 or higher. Conclusion: Nerve reconstruction after tumor resection can help recover both sensory and motor function and may avoid chronic nerve pain. Nerve reconstructions should therefore be considered in tumor surgery.

Motor nerve transfers for reconstruction of traumatic upper extremity nerve injuries - a scoping review

Peripheral nerve injuries to the radial, median, and ulnar nerves have been traditionally treated via direct repair or interposition nerve grafts. Late presentation or failed functional restoration may be salvaged with tendons transfers. Nerve transfers may be deployed either as an adjunct to a proximal reconstruction or as a primary reconstructive strategy, and these techniques are being increasingly adopted as the published evidence matures. The advantages of nerve transfers include shorter reinnervation distances, restoration of original muscle action, and maintenance of independent muscle function. Tendon transfers are reliable, not dependent on time, and the functional use of the limb is often achieved quickly,. Hybrid combinations that combine nerve and tendon transfers can also be used to maximize the recovery potential. This scoping review aimed to provide an overview of nerve transfer possibilities after peripheral nerve injuries and guide management decisions for clinicians treating patients with upper limb paralysis from peripheral nerve injuries.

Comparison of Photochemically Sealed Commercial Biomembranes for Nerve Regeneration

Peripheral nerve injuries affect 13-23 per 100,000 people annually in the U.S. and often result in motor and sensory deficits. Microsurgical suture repair (SR) is the standard treatment but is technically challenging and associated with complications. Photochemical tissue bonding (PTB), which uses light and a photoactivated dye to bond collagenous tissues, offers a promising alternative. We compared PTB with commercially available collagen membranes for SR and PTB using cryopreserved human amnion (HAM) in a rat sciatic nerve transection model. In total, 75 Lewis rats underwent nerve repair with one of five methods: SR, PTB-HAM, PTB with commercial collagenous membranes (human amnion monolayer (AML), human amnion-chorion-amnion trilayer (ATL), or swine intestinal submucosa (SIS)). Functional recovery was assessed with walking tracks and the Static Sciatic Index (SSI) at days 30, 60, 90, and 120; histological evaluations at days 30 and 120 examined inflammation, axon density, and fascicle structure. No significant differences in SSI scores were found between groups, though PTB-AML and PTB-SIS improved over time. Histology showed inflammation at day 30 that decreased by day 120. Histomorphometry revealed similar axon regeneration across groups. These results suggest that PTB with commercial membranes is a viable alternative to SR.

The Potential Role of Adipose-Derived Stem Cells in Regeneration of Peripheral Nerves

Peripheral nerve injuries are common complications in surgical and dental practices, often resulting in functional deficiencies and reduced quality of life. Current treatment choices, such as autografts, have limitations, including donor site morbidity and suboptimal outcomes. Adipose-derived stem cells (ADSCs) have shown assuring regenerative potential due to their accessibility, ease of harvesting and propagation, and multipotent properties. This review investigates the therapeutic potential of ADSCs in peripheral nerve regeneration, focusing on their use in bioengineered nerve conduits and supportive microenvironments. The analysis is constructed on published case reports, organized reviews, and clinical trials from Phase I to Phase III that investigate ADSCs in managing nerve injuries, emphasizing both peripheral and orofacial applications. The findings highlight the advantages of ADSCs in promoting nerve regeneration, including their secretion of angiogenic and neurotrophic factors, support for cellular persistence, and supplementing scaffold-based tissue repair. The regenerative capabilities of ADSCs in peripheral nerve injuries offer a novel approach to augmenting nerve repair and functional recovery. The accessibility of adipose tissue and the minimally invasive nature of ADSC harvesting further encourage its prospective application as an autologous cell source in regenerative medicine. Future research is needed to ascertain standardized protocols and optimize clinical outcomes, paving the way for ADSCs to become a mainstay in nerve regeneration.

Protocol to Develop a Core Outcomes Set for Peripheral Nerve Injury

Background: Advances in treatment philosophies and microsurgical techniques for peripheral nerve injuries (PNI) have led to improved outcomes. However, lack of standardisation in the evaluation of clinical outcomes after PNI treatment precludes the ability to compare reconstruction methods, such as nerve transfer, nerve grafting, free functioning muscle transfers and tendon transfers. To this end, our goal is to work collaboratively to establish a core outcome set to evaluate outcomes after PNI. Methods: The protocol for this arc of work, delineated in this manuscript, consists of two phases: (1) conducting a systematic review of how outcomes are currently reported following PNI and (2) a Delphi process to gain consensus on the measures to include in the core outcome set for PNI. In the Delphi process, two online rounds will be used to gather consensus on the importance of each outcome measure. A final round will be conducted in person to discuss and resolve measures for which there is not yet consensus and to finalise the core outcomes set. Conclusions: Through this process, a common standard for reporting outcomes after PNI will be created, facilitating collaboration and future research.

Consumer Products Nerve Injuries Among Patients Products Presenting to United States Emergency Departments Between 2012 and 2021: A Nationwide Cohort

Introduction

Nerve injuries and resultant pain are common causes of emergency department (ED) visits in the United States. Injuries often occur either due to activity (ie sports related injury) or due to consumer products such as stairs or bedframes. We investigated the incidence of consumer product-related nerve injuries (CPNIs) in patients who presented to the ED in the United States.

Materials and Methods

The National Electronic Injury Surveillance System was queried to identify patients presenting to US EDs between 2012 and 2021 with CPNIs. The cohort was categorized by age: 1) 0-17-year-olds, 2) 18-64-year-olds, 3) and 65+ year-olds. The primary outcomes were the type of injury and the location of injury.

Results

A total of 14,410 CPNIs were reported. There was an increase in yearly CPNIs (β = 4763, (95% confidence interval 1940-7586); P = 0.004). The majority (11,547/14,410, 80.1%) of injuries were among adults. Elderly females encountered more CPNIs than males (52.5% vs 47.8%, P = 0.002). Stairs were most involved in nerve injuries among adults (8.21%) and children (3.96%) whereas beds or bedframe injuries were most frequent (12.0%) among the elderly. Sciatica was the most common diagnosis (≥60%) followed by radiculopathy (≥20%) in adults >18 years of age. Among adults aged 18 to 29, the upper trunk, lower arm, and wrist was more frequently involved, while these areas were less commonly involved in adults aged 40 to 49. Compared to adults, the pediatric and elderly patients presented with more traumatic spinal cord injuries.

Conclusion

Sciatica, radiculopathy, and traumatic spinal cord injury were the most common diagnoses following CPNIs. Children and the elderly tended to present with more severe CPNIs than the general adult population. Further investigations exploring interventions to lower the burden of CPNIs, improve consumer product safety, and reduce potentially chronic and debilitating injuries are necessary.

Using Transcranial Magnetic Nerve Stimulation to Differentiate Motor and Sensory Fascicles in a Mixed Nerve: Experimental Rat Study

BACKGROUND

 Accurately matching the correct fascicles in a ruptured mixed nerve is critical for functional recovery. This study investigates the use of transcranial magnetic stimulation (TMS) to differentiate motor and sensory fascicles in a mixed nerve.

METHODS

 In all 40 rats, the median nerve in the left upper arm was evenly split into three segments. The rats were separated into two groups. In Group A (20 rats), the segment with the highest amplitude during TMS was selected as the motor neurotizer and transferred to the musculocutaneous nerve. In Group B (20 rats), only the medial one-third segment was selected and transferred without using TMS. The results were compared using grooming tests, nerve electrophysiological studies, muscle tetanus contraction force measurements, muscle weight, and axon counts at 16 weeks.

RESULTS

 The grooming test showed that Group A performed significantly better than Group B at 12 and 16 weeks postoperatively. Tetanic muscle contraction force measurements also revealed that Group A had significantly better outcomes than Group B. However, electrophysiological testing, muscle weight, and axon counts showed no significant differences between the two groups.

CONCLUSION

 This study suggests that TMS can be used to distinguish motor fascicles from sensory fascicles in a mixed nerve. It is desirable to apply this technique intraoperatively to differentiate motor and sensory fascicles for appropriate nerve matching and to select the motor fascicles as a motor neurotizer for functioning free muscle innervation in human mixed nerve injury.

Polyethylene Glycol-Mediated Axonal Fusion Promotes Early Sensory Recovery after Digital Nerve Injury: A Randomized Clinical Trial

BACKGROUND

Peripheral nerve repair is limited by Wallerian degeneration coupled with the slow and inconsistent rates of nerve regrowth. In more proximal injuries, delayed nerve regeneration can cause debilitating muscle atrophy. Topical application of polyethylene glycol (PEG) during neurorrhaphy facilitates the fusion of severed axonal membranes, immediately restoring action potentials across the coaptation site. In preclinical animal models, PEG fusion resulted in remarkable early functional recovery.

METHODS

This is the first randomized clinical trial comparing functional outcomes between PEG fusion and standard neurorrhaphy. Participants with digital nerve transections were followed up at 2 weeks, 1 month, and 3 months postoperatively. The primary outcome was assessed using the Medical Research Council Classification (MRCC) rating for sensory recovery at each time point. Semmes-Weinstein monofilaments and static 2-point discrimination determined MRCC ratings. Postoperative quality of life was measured using the Michigan Hand Outcomes Questionnaire.

RESULTS

Forty-eight transected digital nerves (25 control and 23 PEG) across 22 patients were analyzed. PEG-fused nerves demonstrated significantly higher MRCC scores at 2 weeks (OR, 16.95; 95% CI, 1.79 to 160.38; P = 0.008) and 1 month (OR, 13.40; 95% CI, 1.64 to 109.77; P = 0.009). Participants in the PEG cohort also had significantly higher average Michigan Hand Outcomes Questionnaire scores at 2 weeks (Hodge g , 1.28; 95% CI, 0.23 to 2.30; P = 0.0163) and 1 month (Hodge g , 1.02; 95% CI, 0.04 to 1.99; P = 0.049). No participants had adverse events related to the study drug.

CONCLUSION

PEG fusion promotes early sensory recovery and improved patient well-being following peripheral nerve repair of digital nerves.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, II.

Testosterone Promotes Nerve Tethering and Acellular Biomaterial Perineural Fibrosis in a Rat Wound Repair Model

Objective: Nerve scarring after traumatic or iatrogenic exposure can lead to impaired function and pain. Nerve-adjacent biomaterials promoting a regenerative tissue response may help reduce perineural fibrosis. Our prior work suggests that testosterone may promote fibrotic skin scarring, but it is unknown how testosterone alters nerve fibrosis or shifts the response to biomaterials. Approach: Sterilized Lewis rats received either testosterone cypionate (+T) or placebo (-T) biweekly. Fifteen days later, wounds were created over the sciatic nerve and covered with an acellular matrix (AM) or closed via primary closure (PC). At day 42, force gauge testing measured the force required to mobilize the nerve, and wound tissue was analyzed. Results: Nerve mobilization force was greater in +T versus -T wounds (p < 0.01). Nerves tore before gliding in 60% of +T versus 6% of -T rats. Epidermal gap (p < 0.01), scar width (p < 0.01), and cross-sectional scar tissue area (p = 0.02) were greater in +T versus -T rats. +T versus -T rats expressed less Col-3 (p = 0.02) and CD68 (p = 0.02). Nerve mobilization force trended nonsignificantly higher for PC versus AM wounds and for +T versus -T wounds within the AM cohort. Innovation: Testosterone increases nerve tethering in the wound healing milieu, altering repair and immune cell balances. Conclusion: Testosterone significantly increases the force required to mobilize nerves in wound beds and elevates histological markers of scarring, suggesting that testosterone-induced inflammation may increase perineural adhesion. Testosterone may reduce the potential anti-tethering protective effect of AM. Androgen receptor antagonism may represent a therapeutic target to reduce scar-related nerve morbidity.

Insights Into the Epidemiology of Peripheral Nerve Injuries in the United States: Systematic Review

BACKGROUND

Peripheral nerve injuries (PNI) range from mild neurapraxia to severe transection, leading to significant morbidity. Despite their impact, the societal implications of PNI in the United States are not well understood. This study aims to systematically review the literature on PNI epidemiology in the United States. We hypothesize that this review will reveal significant gaps in the understanding of PNI incidence, demographics, and economic impact.

METHODS

Following Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, we queried the literature for studies on PNI that reported at least one of the following: incidence rates, demographics, affected nerve distribution, injury mechanisms, surgical intervention rates, and associated direct costs. Exclusion criteria included non-English publications, abstracts, conference proceedings, reviews, or editorials, studies published before 2000, non-US studies, or studies focusing solely on digital nerves or plexus injuries.

RESULTS

Fifteen studies met the inclusion criteria. Data indicate a higher incidence of upper extremity nerve injuries compared with lower extremity injuries. The literature lacks comprehensive reporting on surgical intervention rates, with no recent data since 2013. There is a notable absence of nationwide epidemiological data on PNI mechanisms and recent cost data, with most information over a decade old and primarily focused on inpatient costs, neglecting outpatient visits, physical therapy, and medication expenses.

CONCLUSION

The epidemiological data on PNI are limited and outdated, highlighting the need for further research. Future studies should focus on recent trends in PNI incidence, injury mechanisms, and financial burden, including comprehensive reporting on surgical interventions, to inform strategies aimed at improving patient outcomes and health care resource allocation.

Design and In Vivo Testing of an Anatomic 3D-Printed Peripheral Nerve Conduit in a Rat Sciatic Nerve Model

Background: Three-dimensional (3D) printer technology has seen a surge in use in medicine, particularly in orthopedics. A recent area of research is its use in peripheral nerve repair, which often requires a graft or conduit to bridge segmental defects. Currently, nerve gaps are bridged using autografts, allografts, or synthetic conduits. Purpose: We sought to improve upon the current design of simple hollow, cylindrical conduits that often result in poor nerve regeneration. Previous attempts were made at reducing axonal dispersion with the use of multichanneled conduits. To our knowledge, none has attempted to mimic and test the anatomical topography of the nerve. Methods: Using serial histology sections, 3D reconstruction software, and computer-aided design, a scaffold was created based on the fascicular topography of a rat sciatic nerve. A 3D printer produced both cylindrical conduits and topography-based scaffolds. These were implanted in 12 Lewis rats: 6 rats with the topographical scaffold and 6 rats with the cylindrical conduit. Each rodent's uninjured contralateral limb was used as a control for comparison of functional and histologic outcomes. Walking track analysis was performed, and the Sciatic Functional Index (SFI) was calculated with the Image J software. After 6 weeks, rats were sacrificed and analyses performed on the regenerated nerve tissue. Primary outcomes measured included nerve (fiber) density, nerve fiber width, total number of nerve fibers, G-ratio (ratio of axon width to total fiber width), and percent debris. Secondary outcomes measured included electrophysiology studies of electromyography (EMG) latency and EMG amplitude and isometric force output by the gastrocnemius and tibialis anterior. Results: There were no differences observed between the cylindrical conduit and topographical scaffold in terms of histological outcomes, muscle force, EMG, or SFI. Conclusion: This study of regeneration of the sciatic nerve in a rat model suggests the feasibility of 3D-printed topographical scaffolds. More research is required to quantify the functional outcomes of this technology for peripheral nerve regeneration.

Mesenchymal stromal cell therapies for traumatic neurological injuries

Improved treatment options are urgently needed for neurological injuries resulting from trauma or iatrogenic events causing long-term disabilities that severely impact patients' quality of life. In vitro and animal studies have provided promising proof-of-concept examples of regenerative therapies using mesenchymal stromal cells (MSC) for a wide range of pathological conditions. Over the previous decade, various MSC-based therapies have been investigated in clinical trials to treat traumatic neurological injuries. However, while the safety and feasibility of MSC treatments has been established, the patient outcomes in these studies have not demonstrated significant success in the translation of MSC regenerative therapy for the treatment of human brain and spinal cord injuries. Herein, we have reviewed the literature and ongoing registered trials on the application of MSC for the treatment of traumatic brain injury, traumatic spinal cord injury, and peripheral nerve injury. We have focused on the shortcomings and technological hurdles that must be overcome to further advance clinical research to phase 3 trials, and we discuss recent advancements that represent potential solutions to these obstacles to progress.

Assessing tissue mechanical properties: Development of a custom-made tensile device and application on rodents sciatic nerves

The development of biomaterials such as synthetic scaffolds for peripheral nerve regeneration requires a precise knowledge of the mechanical properties of the nerve in physiological-like conditions. Mechanical properties (Young's modulus, maximum stress and strain at break) for peripheral nerves are scarce and large discrepancies are observed in between reports. This is due in part to the absence of a robust testing device for nerves. To overcome this limitation, a custom-made tensile device (CMTD) has been built. To evaluate its reproducibility and accuracy, the imposed speed and distance over measured speed and distance was performed, followed by a validation using poly(dimethylsiloxane) (PDMS), a commercial polymer with established mechanical properties. Finally, the mechanical characterization of rodents (mice and rats) sciatic nerves using the CMTD was performed. Mouse and rat sciatic nerves Young's modulus were 4.57 ± 2.04 and 19.2 ± 0.86 MPa respectively. Maximum stress was 1.26 ± 0.56 MPa for mice and 3.81 ± 1.84 MPa for rats. Strain at break was 53 ± 17% for mice and 32 ± 12% for rats. The number of axons per sciatic nerve was found to be twice higher for rats. Statistical analysis of the measured mechanical properties revealed no sex-related trends, for both mice and rats (except for mouse maximum stress with p=0.03). Histological evaluation of rat sciatic nerve corroborated these findings. By developing a robust CMTD to establish the key mechanical properties (Young's modulus, maximum stress and strain at break) values for rodents sciatic nerves, our work represent an essential step toward the development of better synthetic scaffolds for peripheral nerve regeneration.

Skeletal muscle reprogramming enhances reinnervation after peripheral nerve injury

Peripheral Nerve Injuries (PNI) affect more than 20 million Americans and severely impact quality of life by causing long-term disability. PNI is characterized by nerve degeneration distal to the site of nerve injury resulting in long periods of skeletal muscle denervation. During this period, muscle fibers atrophy and frequently become incapable of "accepting" innervation because of the slow speed of axon regeneration post injury. We hypothesize that reprogramming the skeletal muscle to an embryonic-like state may preserve its reinnervation capability following PNI. To this end, we generate a mouse model in which NANOG, a pluripotency-associated transcription factor is expressed locally upon delivery of doxycycline (Dox) in a polymeric vehicle. NANOG expression in the muscle upregulates the percentage of Pax7+ nuclei and expression of eMYHC along with other genes that are involved in muscle development. In a sciatic nerve transection model, NANOG expression leads to upregulation of key genes associated with myogenesis, neurogenesis and neuromuscular junction (NMJ) formation. Further, NANOG mice demonstrate extensive overlap between synaptic vesicles and NMJ acetylcholine receptors (AChRs) indicating restored innervation. Indeed, NANOG mice show greater improvement in motor function as compared to wild-type (WT) animals, as evidenced by improved toe-spread reflex, EMG responses and isometric force production. In conclusion, we demonstrate that reprogramming muscle can be an effective strategy to improve reinnervation and functional outcomes after PNI.

Epidemiology and regional variance of traumatic peripheral nerve injuries in Sweden: A 15-year observational study

INTRODUCTION

Traumatic peripheral nerve injuries pose significant challenges to healthcare systems and individuals, affecting sensory function, causing neuropathic pain, and impairing quality of life. Despite their impact, comprehensive studies on the epidemiology and regional variance of these injuries are scarce. Understanding the incidence, trends, and anatomical distribution of such injuries is essential for targeted interventions and resource allocation.

METHODS

This observational study utilized register-based data from the Swedish National Patient Register covering the period from 2008 to 2022. Incidence rates, trends, and anatomical distribution of traumatic peripheral nerve injuries were analyzed using descriptive statistics, Poisson regression modeling, and regional comparisons.

RESULTS

Higher incidences of peripheral nerve injuries were observed among men compared to women across all age groups. The hand and wrist were the most commonly affected sites. Regional variations in incidence rates were evident, with some regions consistently exhibiting higher rates compared to others. Notably, a decreasing trend in injuries was observed over the study period.

CONCLUSION

This study underscores the importance of targeted interventions and preventive strategies, considering sex, age, and regional disparities. Further research incorporating individual patient-level data is warranted to enhance our understanding and inform tailored interventions to reduce the burden of these injuries.

Improving outcomes in traumatic peripheral nerve injuries to the upper extremity

Peripheral nerve lesions of the upper extremity are common and are associated with devastating limitations for the patient. Rapid and accurate diagnosis of the lesion by electroneurography, neurosonography, or even MR neurography is important for treatment planning. There are different therapeutic approaches, which may show individual differences depending on the injured nerve. If a primary nerve repair is not possible, several strategies exist to bridge the gap. These may include autologous nerve grafts, bioartificial nerve conduits, or acellular nerve allografts. Tendon and nerve transfers are also of major importance in the treatment of nerve lesions in particular with long regeneration distances. As a secondary reconstruction, in addition to tendon transfers, there is also the option for free functional muscle transfer. In amputations, the prevention of neuroma is of great importance, for which different strategies exist, such as target muscle reinnervation, regenerative peripheral nerve interface, or neurotized flaps. In this article, we give an overview of the latest methods for the therapy of peripheral nerve lesions.

Electrospun PCL Nerve Wrap Coated with Graphene Oxide Supports Axonal Growth in a Rat Sciatic Nerve Injury Model

Background/Objectives: Peripheral nerve injuries (PNIs) are a debilitating problem, resulting in diminished quality of life due to the continued presence of both chronic and acute pain. The current standard of practice for the repair of PNIs larger than 10 mm is the use of autologous nerve grafts. Autologous nerve grafts have limitations that often result in outcomes that are not sufficient to remove motor and sensory impairments. Bio-mimetic nanocomposite scaffolds combined with mesenchymal stem cells (MSCs) represent a promising approach for PNIs. In this study, we investigated the potential of an electrospun wrap of polycaprolactone (PCL) + graphene oxide (GO), with and without xenogeneic human adipose tissue-derived MSCs (hADMSCs) to use as a platform for neural tissue engineering. Methods: We evaluated, in vitro and in vivo, the potential of the nerve wrap in providing support for axonal growth. To establish the rat sciatic nerve defect model, a 10 mm long limiting defect was created in the rat sciatic nerve of 18 Lewis rats. Rats treated with the nanocomposites were compared with autograft-treated defects. Gait, histological, and muscle analyses were performed after sacrifice at 12 weeks post-surgery. Results: Our findings demonstrate that hADMSCs had the potential to transdifferentiate into neural lineage and that the nanocomposite successfully delivered hADMSCs to the injury site. Histologically, we show that the PCL + GO nanocomposite with hADMSCs is comparable to the autologous nerve graft, to support and guide axonal growth. Conclusions: The novel PCL + GO nerve wrap and hADMSCs used in this study provide a foundation on which to build upon and generate future strategies for PNI repair.

Diffusion Tensor Imaging: Techniques and Applications for Peripheral Nerve Injury

ABSTRACT

Peripheral nerve injuries (PNIs) represent a complex clinical challenge, necessitating precise diagnostic approaches for optimal management. Traditional diagnostic methods often fall short in accurately assessing nerve recovery as these methods rely on the completion of nerve reinnervation, which can prolong a patient's treatment. Diffusion tensor imaging (DTI), a noninvasive magnetic resonance imaging (MRI) technique, has emerged as a promising tool in this context. DTI offers unique advantages including the ability to quantify nerve recovery and provide in vivo visualizations of neuronal architecture. Therefore, this review aims to examine and outline DTI techniques and its utility in detecting distal nerve regeneration in both preclinical and clinical settings for peripheral nerve injury.

The Role of Tissue Engineering and Three-Dimensional-Filled Conduits in Bridging Nerve Gaps: A Review of Recent Advancements

Tissue-engineered nerve guidance conduits (NGCs) are an area of research interest and investment. Currently, two separate three-dimensional, filled NGCs have Food and Drug Administration approval in the management of nerve gaps up to 3 cm in length, with more on the horizon. Future NGC options will leverage increasingly intricate designs to mimic the natural biology and architecture of native nerve tissue. To enhance the development of next-generation NGCs, experimental protocols and models should be standardized. For the NGCs currently on the market, more clinical data and randomized comparative studies are needed.

The Physiologic Basis of Molecular Therapeutics for Peripheral Nerve Injury: A Primer

Peripheral nerve injuries affect a significant number of patients who experience trauma affecting the hand and upper extremity. Improving unsatisfactory outcomes from repair of these injuries remains a clinical challenge despite advancements in microsurgical repair. Imperfections of the nerve regeneration process, including imprecise reinnervation, distal axon degradation, and muscular atrophy, complicate the repair process. However, the capacity for peripheral nerves to regenerate offers an avenue for therapeutic advancement. Regeneration is a temporally and spatially dynamic process coordinated by Schwann cells and neurons among other cell types. Neurotrophic factors are a primary means of controlling cell growth and differentiation in the repair setting. Sustained axon survival and regrowth and consequently functional outcomes of nerve repair in animal models are improved by the administration of neurotrophic factors, including glial cell-derived neurotrophic factor, nerve growth factor, sterile alpha and TIR motif containing 1, and erythropoietin. Targeted and sustained delivery of neurotrophic factors through gelatin-based nerve conduits, multiluminal conduits, and hydrogels have been shown to enhance the innate roles of these factors to promote expedient and accurate peripheral nerve regeneration in animal models. These delivery methods may help address the practical limitations to clinical use of neurotrophic factors, including systemic side effects and the need for carefully timed, precisely localized release schedules. In addition, tacrolimus has also improved peripheral nerve regrowth in animal models and has recently shown promise in addressing human disease. Ultimately, this realm of adjunct pharmacotherapies provides ample promise to improve patient outcomes and advance the field of peripheral nerve repair.

Development of Biomaterials for Addressing Upper Extremity Peripheral Nerve Gaps

Peripheral nerve injuries within the upper extremities can lead to impaired function and reduced quality of life. Although autografts have traditionally served as the primary therapeutic approach to bridge nerve gaps, these present challenges related to donor site morbidity. This review delves into the realm of biomaterials tailored for addressing nerve gaps. Biomaterials, whether natural or synthetically derived, offer the potential not only to act as scaffolds for nerve regeneration but also to be enhanced with growth factors and agents that promote nerve recovery. The historical progression of these biomaterials as well as their current applications, advantages, inherent challenges, and future impact in the arena of regenerative medicine are discussed. By providing a comprehensive overview, we aim to shed light on the transformative potential of biomaterials in peripheral nerve repair and the path toward refining their efficacy in clinical settings.

Isoflurane conditioning improves functional outcomes after peripheral nerve injury in a sciatic cut repair murine model

Introduction

Anesthetic conditioning has been shown to provide neuroprotection in several neurological disorders. Whether anesthetic conditioning provides protection against peripheral nerve injuries remains unknown. The aim of our current study is to investigate the impact of isoflurane conditioning on the functional outcomes after peripheral nerve injury (PNI) in a rodent sciatic nerve injury model.

Methods

Adult male Lewis rats underwent sciatic nerve cut and repair and exposed to none (Group 1, sham), single isoflurane exposure (Group 2), three-time isoflurane exposure (Group 3), and six-time isoflurane exposure (Group 4). Isoflurane conditioning was established by administration of 2% isoflurane for 1 hour, beginning 1-hour post sciatic nerve cut and repair. Groups 3 and 4 were exposed to isoflurane for 1 hour, 3 and 6 consecutive days respectively. Functional outcomes assessed included compound muscle action potential (CMAP), evoked muscle force (tetanic and specific tetanic force), wet muscle mass, and axonal counting.

Results

We observed an increase in axons, myelin width and a decrease in G-ratio in the isoflurane conditioning groups (3- and 6-days). This correlated with a significant improvement in tetanic and specific tetanic forces, observed in both groups 3 and 4.

Discussion

Isoflurane conditioning (3- and 6-day groups) resulted in improvement in functional outcomes at 12 weeks post peripheral nerve injury and repair in a murine model. Future experiments should be focused on identifying the therapeutic window of isoflurane conditioning and exploring the underlying molecular mechanisms responsible for isoflurane conditioning induced neuroprotection in PNI.

Advances in Exosome-Based Therapies for the Repair of Peripheral Nerve Injuries

Peripheral nerve injuries (PNIs) are the term used to describe injuries that occur to the nerve fibers of the peripheral nervous system (PNS). Such injuries may be caused by trauma, infection, or aberrant immunological response. Although the peripheral nervous system has a limited capacity for self-repair, in cases of severe damage, this process is either interrupted entirely or is only partially completed. The evaluation of variables that promote the repair of peripheral nerves has consistently been a focal point. Exosomes are a subtype of extracellular vesicles that originate from cellular sources and possess abundant proteins, lipids, and nucleic acids, play a critical role in facilitating intercellular communication. Due to their modifiable composition, they possess exceptional capabilities as carriers for therapeutic compounds, including but not limited to mRNAs or microRNAs. Exosome-based therapies have gained significant attention in the treatment of several nervous system diseases due to their advantageous properties, such as low toxicity, high stability, and limited immune system activation. The objective of this review article is to provide an overview of exosome-based treatments that have been developed in recent years for a range of PNIs, including nerve trauma, diabetic neuropathy, amyotrophic lateral sclerosis (ALS), glaucoma, and Guillain-Barre syndrome (GBS). It was concluded that exosomes could provide favorable results in the improvement of peripheral PNIs by facilitating the transfer of regenerative factors. The development of bioengineered exosome therapy for PNIs should be given more attention to enhance the efficacy of exosome treatment for PNIs.

Growth Factors to Enhance Nerve Regeneration: Approaching Clinical Translation

Following nerve injury, growth factors (GFs) are transiently upregulated in injured neurons, proliferating Schwann cells, and denervated muscle and skin. They act on these same cells and tissues to promote nerve regeneration and end-organ reinnervation. Consequently, much attention has been focused on developing GF-based therapeutics. A major barrier to clinical translation of GFs is their short half-life. To provide sustained GF treatment to the affected nerve, muscle, and skin in a safe and practical manner, engineered drug delivery systems are needed. This review highlights recent advancements in GF-based therapeutics and discusses the remaining hurdles for clinical translation.

Physical exercise to promote regeneration after peripheral nerve injury in animal models: A systematic review

Peripheral nerve injuries are common injuries that often have a drastic effect on patient's activities of daily living and physical function. While techniques for the surgical repair of these injuries have improved over time, rehabilitation methods following these repairs have been non-standardized and under researched. Electronic searches were conducted in Ovid/Medline and SCOPUS to identify articles that discuss rehabilitation and exercise following peripheral nerve injury in animal models and its effects on peripheral nerve regeneration and recovery of function. Thirty-eight articles met inclusion criteria; all were prospective studies in animal models. This systematic review suggests that exercise is a useful tool in returning autonomy to the individual and has beneficial effects in the recovery from peripheral nerve injury. It is beneficial to use rehabilitation exercises following the repair of peripheral nerve injuries to promote regeneration, and timing of that exercise may be just as important as the exercise prescribed. However, further studies with standardized models and outcome measures need to be conducted before translation to clinical trials.

Limited Nerve Regeneration across Acellular Nerve Allografts (ANAs) Coincides with Changes in Blood Vessel Morphology and the Development of a Pro-Inflammatory Microenvironment

The use of acellular nerve allografts (ANAs) to reconstruct long nerve gaps (>3 cm) is associated with limited axon regeneration. To understand why ANA length might limit regeneration, we focused on identifying differences in the regenerative and vascular microenvironment that develop within ANAs based on their length. A rat sciatic nerve gap model was repaired with either short (2 cm) or long (4 cm) ANAs, and histomorphometry was used to measure myelinated axon regeneration and blood vessel morphology at various timepoints (2-, 4- and 8-weeks). Both groups demonstrated robust axonal regeneration within the proximal graft region, which continued across the mid-distal graft of short ANAs as time progressed. By 8 weeks, long ANAs had limited regeneration across the ANA and into the distal nerve (98 vs. 7583 axons in short ANAs). Interestingly, blood vessels within the mid-distal graft of long ANAs underwent morphological changes characteristic of an inflammatory pathology by 8 weeks post surgery. Gene expression analysis revealed an increased expression of pro-inflammatory cytokines within the mid-distal graft region of long vs. short ANAs, which coincided with pathological changes in blood vessels. Our data show evidence of limited axonal regeneration and the development of a pro-inflammatory environment within long ANAs.

Long-term outcomes of autologous vein bypass for repair of upper and lower extremity major arterial trauma

OBJECTIVE

Autologous vein is the preferred bypass conduit for extremity arterial injuries owing to superior patency and low infection risk; however, long-term data on outcomes in civilians are limited. Our goal was to assess short- and long-term outcomes of autologous vein bypass for upper and lower extremity arterial trauma.

METHODS

A retrospective review was performed of patients with major extremity arterial injuries (2001-2019) at a level I trauma center. Demographics, injury and intervention details, and outcomes were recorded. Primary outcomes were primary patency at 1 year and 3 years. Secondary outcomes were limb function at 6 months, major amputation, and mortality. Multivariable analysis determined risk factors for functional impairment.

RESULTS

There were 107 extremity arterial injuries (31.8% upper and 68.2% lower) treated with autologous vein bypass. Mechanism was penetrating in 77% of cases, of which 79.3% were due to firearms. The most frequently injured vessels were the common and superficial femoral (38%), popliteal (30%), and brachial arteries (29%). For upper extremity trauma, concomitant nerve and orthopedic injuries were found in 15 (44.1%) and 11 (32.4%) cases, respectively. For lower extremities, concomitant nerve injuries were found in 10 (13.7%) cases, and orthopedic injuries in 31 (42.5%). Great saphenous vein was the conduit in 96% of cases. Immediate intraoperative bypass revision occurred in 9.3% of patients, most commonly for graft thrombosis. The in-hospital return to operating room rate was 15.9%, with graft thrombosis (47.1%) and wound infections (23.5%) being the most common reasons. The median follow-up was 3.6 years. Kaplan-Meier analysis showed 92% primary patency at 1 year and 90% at 3 years. At 6 months, 36.1% of patients had functional impairment. Of patients with functional impairment at 6 months, 62.9% had concomitant nerve and 60% concomitant orthopedic injuries. Of those with nerve injury, 91.7% had functional impairment, compared with 17.8% without nerve injury (P < .001). Of patients with orthopedic injuries, 51.2% had functional impairment, vs 25% of those without orthopedic injuries (P = .01). On multivariable analysis, concomitant nerve injury (odds ratio, 127.4; 95% confidence interval, 17-957; P <. 001) and immediate intraoperative revision (odds ratio, 11.03; 95% confidence interval, 1.27-95.55; P = .029) were associated with functional impairment.

CONCLUSIONS

Autologous vein bypass for major extremity arterial trauma is durable; however, many patients have long-term limb dysfunction associated with concomitant nerve injury and immediate intraoperative bypass revision. These factors may allow clinicians to identify patients at higher risk for functional impairment, to outline patient expectations and direct rehabilitation efforts toward improving functional outcomes.

Enhancing sciatic nerve regeneration with osteopontin-loaded acellular nerve allografts in rats: Effects on macrophage polarization

Osteopontin (OPN) is a multifunctional matrix glycoprotein with neuroprotective and immunomodulatory properties. This study explored the potential of OPN-loaded acellular nerve allografts (ANAs) to repair sciatic nerves in male Wistar rats. The research also delved into the impact of OPN on macrophage phenotypes. We reconstructed a 10 mm nerve gap with ANAs containing OPN at 2 nM and 4 nM. The sciatic functional index (SFI) and paw withdrawal reflex latency (WRL) showed the significant efficacy of ANA/OPN (2 nM) in enhancement of target organ reinnervation and subsequent sensorimotor recovery compared to other groups. Electrophysiological and histomorphometric analyses further supported the regenerative properties of ANA/OPN (2 nM). Additionally, ANA/OPN (2 nM) promoted macrophage polarization towards an M2 phenotype and reduced proinflammatory cytokines at the injury site. In conclusion, the study suggested that ANA loaded with 2 nM OPN effectively repaired transected sciatic nerves in rats, potentially through enhancing axonal sprouting and exerting anti-inflammatory effects.

A Systematic Review of Registered Clinical Trials for Peripheral Nerve Injuries

ABSTRACT

Upper extremity peripheral nerve injuries (PNIs) significantly impact daily functionality and necessitate effective treatment strategies. Clinical trials play a crucial role in developing these strategies. However, challenges like retrospective data collection, reporting biases, inconsistent outcome measures, and inadequate data sharing practices hinder effective research and treatment advancements. This review aims to analyze the landscape of reporting, methodological design, outcome measures, and data sharing practices in registered clinical trials concerning upper extremity PNIs. It seeks to guide future research in this vital area by identifying current trends and gaps.A systematic search was conducted on ClinicalTrials.gov and WHO International Clinical Trials Registry Platform up to November 10, 2023, using a combination of MeSH terms and keywords related to upper extremity nerve injury. The PRISMA 2020 guidelines were followed, and the studies were selected based on predefined inclusion and exclusion criteria. A narrative synthesis of findings was performed, with statistical analysis for associations and completion rates.Of 3051 identified studies, 96 met the inclusion criteria. These included 47 randomized controlled trials, 27 nonrandomized trials, and others. Sensory objective measures were the most common primary outcomes. Only 13 studies had a data sharing plan. The analysis revealed varied intervention methods and inconsistencies in outcome measures. There was a significant association between study funding, design, and completion status, but no association between enrollment numbers and completion.This review highlights the need for standardized outcome measures, patient-centered assessments, and improved data sharing in upper extremity PNI trials. The varied nature of interventions and inconsistency in outcome measures indicate the necessity for more rigorous and transparent research practices to strengthen the evidence base for managing these injuries.

Advancements in autologous peripheral nerve transplantation care: a review of strategies and practices to facilitate recovery

Autologous peripheral nerve transplantation, a pioneering technique in nerve injury treatment, has demonstrated remarkable progress. We examine recent nursing strategies and methodologies tailored to various anatomical sites, highlighting their role in postoperative recovery enhancement. Encompassing brachial plexus, upper limb, and lower limb nerve transplantation care, this discussion underscores the importance of personalized rehabilitation plans, interdisciplinary collaboration, and innovative approaches like nerve electrical stimulation and nerve growth factor therapy. Moreover, the exploration extends to effective complication management and prevention strategies, encompassing infection control and pain management. Ultimately, the review concludes by emphasizing the advances achieved in autologous peripheral nerve transplantation care, showcasing the potential to optimize postoperative recovery through tailored and advanced practices.

Depression, anxiety, and post-traumatic stress disorder following upper versus lower extremity fractures

INTRODUCTION

Orthopaedic trauma has been linked to major depressive disorder (MDD), generalized anxiety disorder (GAD), and post-traumatic stress disorder (PTSD). Post-injury rates of psychiatric diagnoses and their relationship to various injury characteristics are not well characterized. We aimed to determine the association between orthopaedic trauma and MDD, GAD, and PTSD diagnoses at 5-year follow-up.

METHODS

A national insurance claims database was used to create upper extremity fracture (UEF) and lower extremity fracture (LEF) cohorts, with further stratification by isolated versus multiple fractures. Patient undergoing elective upper or lower extremity orthopaedic procedures served as controls. Rates of post-injury psychiatric diagnoses were calculated. Univariate logistic regression was conducted after matching in a 1:1 ratio based on relevant comorbidities such as psychiatric history. All significant variables were included in multivariate analysis.

RESULTS

A total of 308,578 UEF patients and 360,510 LEF patients were identified. Within the UEF cohort, the diagnosis rates following either isolated or multiple fractures were identified: MDD (25% to 30%), GAD (10% to 11%), and PTSD (4%). LEF cohort rates were as follows: MDD (30% to 38%), GAD (11% to 14%), and PTSD (4% to 7%). Compared to non-injured controls, both the UEF and LEF cohorts were associated with higher rates of all psychiatric diagnoses. In comparing UEF and LEF cohorts, isolated UEF was associated with MDD, GAD, and PTSD; however, multiple UEF was associated with MDD and GAD, whereas multiple LEF was associated with PTSD.

CONCLUSION

Psychiatric pathology is prevalent following orthopaedic trauma. Even after controlling for psychiatric history, orthopaedic trauma is independently associated with post-injury psychiatric diagnoses and may be more predictive of PTSD and GAD than of MDD. Upper extremity fractures may portend higher psychiatric risk. With negative stigma surrounding mental health and the early role of orthopaedic surgeons in providing care, it is imperative to normalize psychiatric care with patients and discuss warning symptoms that may indicate the onset of psychiatric disorders.

LEVEL OF EVIDENCE

Prognostic, Level III.

Rab32 facilitates Schwann cell pyroptosis in rats following peripheral nerve injury by elevating ROS levels

BACKGROUND

Peripheral nerve injury (PNI) is commonly observed in clinical practice, yet the underlying mechanisms remain unclear. This study investigated the correlation between the expression of a Ras-related protein Rab32 and pyroptosis in rats following PNI, and potential mechanisms have been explored by which Rab32 may influence Schwann cells pyroptosis and ultimately peripheral nerve regeneration (PNR) through the regulation of Reactive oxygen species (ROS) levels.

METHODS

The authors investigated the induction of Schwann cell pyroptosis and the elevated expression of Rab32 in a rat model of PNI. In vitro experiments revealed an upregulation of Rab32 during Schwann cell pyroptosis. Furthermore, the effect of Rab32 on the level of ROS in mitochondria in pyroptosis model has also been studied. Finally, the effects of knocking down the Rab32 gene on PNR were assessed, morphology, sensory and motor functions of sciatic nerves, electrophysiology and immunohistochemical analysis were conducted to assess the therapeutic efficacy.

RESULTS

Silencing Rab32 attenuated PNI-induced Schwann cell pyroptosis and promoted peripheral nerve regeneration. Furthermore, our findings demonstrated that Rab32 induces significant oxidative stress by damaging the mitochondria of Schwann cells in the pyroptosis model in vitro.

CONCLUSION

Rab32 exacerbated Schwann cell pyroptosis in PNI model, leading to delayed peripheral nerve regeneration. Rab32 can be a potential target for future therapeutic strategy in the treatment of peripheral nerve injuries.

Skeletal muscle reprogramming enhances reinnervation after peripheral nerve injury

Peripheral Nerve Injuries (PNI) affect more than 20 million Americans and severely impact quality of life by causing long-term disability. The onset of PNI is characterized by nerve degeneration distal to the nerve injury resulting in long periods of skeletal muscle denervation. During this period, muscle fibers atrophy and frequently become incapable of "accepting" innervation because of the slow speed of axon regeneration post injury. We hypothesize that reprogramming the skeletal muscle to an embryonic-like state may preserve its reinnervation capability following PNI. To this end, we generated a mouse model in which NANOG, a pluripotency-associated transcription factor can be expressed locally upon delivery of doxycycline (Dox) in a polymeric vehicle. NANOG expression in the muscle upregulated the percentage of Pax7+ nuclei and expression of eMYHC along with other genes that are involved in muscle development. In a sciatic nerve transection model, NANOG expression led to upregulation of key genes associated with myogenesis, neurogenesis and neuromuscular junction (NMJ) formation, and downregulation of key muscle atrophy genes. Further, NANOG mice demonstrated extensive overlap between synaptic vesicles and NMJ acetylcholine receptors (AChRs) indicating restored innervation. Indeed, NANOG mice showed greater improvement in motor function as compared to wild-type (WT) animals, as evidenced by improved toe-spread reflex, EMG responses and isometric force production. In conclusion, we demonstrate that reprogramming the muscle can be an effective strategy to improve reinnervation and functional outcomes after PNI.

Progress in methods for evaluating Schwann cell myelination and axonal growth in peripheral nerve regeneration via scaffolds

Peripheral nerve injury (PNI) is a neurological disorder caused by trauma that is frequently induced by accidents, war, and surgical complications, which is of global significance. The severity of the injury determines the potential for lifelong disability in patients. Artificial nerve scaffolds have been investigated as a powerful tool for promoting optimal regeneration of nerve defects. Over the past few decades, bionic scaffolds have been successfully developed to provide guidance and biological cues to facilitate Schwann cell myelination and orientated axonal growth. Numerous assessment techniques have been employed to investigate the therapeutic efficacy of nerve scaffolds in promoting the growth of Schwann cells and axons upon the bioactivities of distinct scaffolds, which have encouraged a greater understanding of the biological mechanisms involved in peripheral nerve development and regeneration. However, it is still difficult to compare the results from different labs due to the diversity of protocols and the availability of innovative technologies when evaluating the effectiveness of novel artificial scaffolds. Meanwhile, due to the complicated process of peripheral nerve regeneration, several evaluation methods are usually combined in studies on peripheral nerve repair. Herein, we have provided an overview of the evaluation methods used to study the outcomes of scaffold-based therapies for PNI in experimental animal models and especially focus on Schwann cell functions and axonal growth within the regenerated nerve.

Review of Piezoelectrical Materials Potentially Useful for Peripheral Nerve Repair

It has increasingly been recognized that electrical currents play a pivotal role in cell migration and tissue repair, in a process named "galvanotaxis". In this review, we summarize the current evidence supporting the potential benefits of electric stimulation (ES) in the physiology of peripheral nerve repair (PNR). Moreover, we discuss the potential of piezoelectric materials in this context. The use of these materials has deserved great attention, as the movement of the body or of the external environment can be used to power internally the electrical properties of devices used for providing ES or acting as sensory receptors in artificial skin (e-skin). The fact that organic materials sustain spontaneous degradation inside the body means their piezoelectric effect is limited in duration. In the case of PNR, this is not necessarily problematic, as ES is only required during the regeneration period. Arguably, piezoelectric materials have the potential to revolutionize PNR with new biomedical devices that range from scaffolds and nerve-guiding conduits to sensory or efferent components of e-skin. However, much remains to be learned regarding piezoelectric materials, their use in manufacturing of biomedical devices, and their sterilization process, to fine-tune their safe, effective, and predictable in vivo application.

Assessment, patient selection, and rehabilitation of nerve transfers

Peripheral nerve injuries are common and can have a devastating effect on physical, psychological, and socioeconomic wellbeing. Peripheral nerve transfers have become the standard of care for many types of peripheral nerve injury due to their superior outcomes relative to conventional techniques. As the indications for, and use of, nerve transfers expand, the importance of pre-operative assessment and post-operative optimization increases. There are two principal advantages of nerve transfers: (1) their ability to shorten the time to reinnervation of muscles undergoing denervation because of peripheral nerve injury; and (2) their specificity in ensuring proximal motor and sensory axons are directed towards appropriate motor and sensory targets. Compared to conventional nerve grafting, nerve transfers offer opportunities to reinnervate muscles affected by cervical spinal cord injury and to augment natural reinnervation potential for very proximal injuries. This article provides a narrative review of the current scientific knowledge and clinical understanding of nerve transfers including peripheral nerve injury assessment and pre- and post-operative electrodiagnostic testing, adjuvant therapies, and post-operative rehabilitation for optimizing nerve transfer outcomes.

Long-term tactile hypersensitivity after nerve crush injury in mice is characterized by the persistence of intact sensory axons

ABSTRACT

Traumatic peripheral nerve injuries are at high risk of neuropathic pain for which novel effective therapies are urgently needed. Preclinical models of neuropathic pain typically involve irreversible ligation and/or nerve transection (neurotmesis). However, translation of findings to the clinic has so far been unsuccessful, raising questions on injury model validity and clinically relevance. Traumatic nerve injuries seen in the clinic commonly result in axonotmesis (ie, crush), yet the neuropathic phenotype of "painful" nerve crush injuries remains poorly understood. We report the neuropathology and sensory symptoms of a focal nerve crush injury using custom-modified hemostats resulting in either complete ("full") or incomplete ("partial") axonotmesis in adult mice. Assays of thermal and mechanically evoked pain-like behavior were paralleled by transmission electron microscopy, immunohistochemistry, and anatomical tracing of the peripheral nerve. In both crush models, motor function was equally affected early after injury; by contrast, partial crush of the nerve resulted in the early return of pinprick sensitivity, followed by a transient thermal and chronic tactile hypersensitivity of the affected hind paw, which was not observed after a full crush injury. The partially crushed nerve was characterized by the sparing of small-diameter myelinated axons and intraepidermal nerve fibers, fewer dorsal root ganglia expressing the injury marker activating transcription factor 3, and lower serum levels of neurofilament light chain. By day 30, axons showed signs of reduced myelin thickness. In summary, the escape of small-diameter axons from Wallerian degeneration is likely a determinant of chronic pain pathophysiology distinct from the general response to complete nerve injury.

Imaging diagnosis in peripheral nerve injury

Peripheral nerve injuries (PNIs) can be caused by various factors, ranging from penetrating injury to compression, stretch and ischemia, and can result in a range of clinical manifestations. Therapeutic interventions can vary depending on the severity, site, and cause of the injury. Imaging plays a crucial role in the precise orientation and planning of surgical interventions, as well as in monitoring the progression of the injury and evaluating treatment outcomes. PNIs can be categorized based on severity into neurapraxia, axonotmesis, and neurotmesis. While PNIs are more common in upper limbs, the localization of the injured site can be challenging. Currently, a variety of imaging modalities including ultrasound (US), computed tomography (CT) and magnetic resonance imaging (MRI) and positron emission tomography (PET) have been applied in detection and diagnosis of PNIs, and the imaging efficiency and accuracy many vary based on the nature of injuries and severity. This article provides an overview of the causes, severity, and clinical manifestations of PNIs and highlights the role of imaging in their management.

Advancing Nerve Regeneration: Translational Perspectives of Tacrolimus (FK506)

Peripheral nerve injuries have far-reaching implications for individuals and society, leading to functional impairments, prolonged rehabilitation, and substantial socioeconomic burdens. Tacrolimus, a potent immunosuppressive drug known for its neuroregenerative properties, has emerged in experimental studies as a promising candidate to accelerate nerve fiber regeneration. This review investigates the therapeutic potential of tacrolimus by exploring the postulated mechanisms of action in relation to biological barriers to nerve injury recovery. By mapping both the preclinical and clinical evidence, the benefits and drawbacks of systemic tacrolimus administration and novel delivery systems for localized tacrolimus delivery after nerve injury are elucidated. Through synthesizing the current evidence, identifying practical barriers for clinical translation, and discussing potential strategies to overcome the translational gap, this review provides insights into the translational perspectives of tacrolimus as an adjunct therapy for nerve regeneration.

Quantifying Hand Strength and Isometric Pinch Individuation Using a Flexible Pressure Sensor Grid

Modulating force between the thumb and another digit, or isometric pinch individuation, is critical for daily tasks and can be impaired due to central or peripheral nervous system injury. Because surgical and rehabilitative efforts often focus on regaining this dexterous ability, we need to be able to consistently quantify pinch individuation across time and facilities. Currently, a standardized metric for such an assessment does not exist. Therefore, we tested whether we could use a commercially available flexible pressure sensor grid (Tekscan F-Socket [Tekscan Inc., Norwood, MA, USA]) to repeatedly measure isometric pinch individuation and maximum voluntary contraction (MVC) in twenty right-handed healthy volunteers at two visits. We developed a novel equation informed by the prior literature to calculate isometric individuation scores that quantified percentage of force on the grid generated by the indicated digit. MVC intra-class correlation coefficients (ICCs) for the left and right hands were 0.86 (p < 0.0001) and 0.88 (p < 0.0001), respectively, suggesting MVC measurements were consistent over time. However, individuation score ICCs, were poorer (left index ICC 0.41, p = 0.28; right index ICC -0.02, p = 0.51), indicating that this protocol did not provide a sufficiently repeatable individuation assessment. These data support the need to develop novel platforms specifically for repeatable and objective isometric hand dexterity assessments.