Management of nerve gaps: autografts, allografts, nerve transfers, and end-to-side neurorrhaphy

Managing surface energy dynamics for enhanced axonal growth: An overview of present and future challenges

To create functional neuronal circuit units during nervous system development and/or regeneration, axons are subjected to guidance signals. Expression of these signals occurs in spatiotemporal variations and is translated by the growth cone into a pathway to reach the connecting target which can be a neuron or a non-neuronal cell such as a muscle cell. This path is generated by interactions with the surrounding environment such as cells or the extracellular matrix, a complex molecular substrate. Understanding the interactions with this last component is essential to stimulate nerve regeneration in the context of motor peripheral nerve trauma, the most common source of disabilities, increasing with aging. The goal is to mimic its composition and specific characteristics using innovative biomaterials and/or implants. This review highlights some aspects of the recent findings in nerve repair. After an introduction to the peripheral nervous system, we present an overview of nerve degeneration and regeneration mechanisms before detailing the strategies used nowadays to optimize nerve (re)growth with a specific focus on the use of electric field. We discuss the advantages and limits of each option in terms of therapeutic applications.

The Medial Antebrachial Cutaneous Nerve Is a Low-Morbidity Alternative to the Standard Sural Nerve Autograft

BACKGROUND

Nerve interposition grafting is an important technique in nerve reconstructive surgery that is used when a primary repair is not feasible without significant tension. This study sought to evaluate the long-term morbidity of the medial antebrachial cutaneous (MABC) nerve as an alternative donor nerve in comparison with sural nerve harvest.

METHODS

A single surgeon and institution retrospective chart review was performed to identify all patients who underwent nerve autografting using the sural and MABC as donor nerves between January 1, 2000 and December 31, 2019. Surveys assessed overall patient satisfaction with surgery, as well as donor and recipient site morbidity, satisfaction, pain, numbness, and cold sensitivity.

RESULTS

Of the 73 patients contacted, 54 agreed to participate, and 43 of 73 (58.9%) ultimately completed the survey: 28 MABC (65.1%) and 15 sural (34.9%). There were no significant differences between the sural and MABC groups in overall satisfaction with surgery, donor and recipient site satisfaction, pain, cold sensitivity, and effect on quality of life. Even though 66.7% of sural donor sites and 75% of MABC donor sites had residual numbness, the effect this had on quality of life was very low (2 and 3, respectively).

CONCLUSION

The MABC is a safe alternative to the traditional sural nerve autograft. A small subset of patients undergoing nerve autograft harvest will experience long-term morbidity in the form of pain. Conversely, the more common presence of numbness is not reported as bothersome.

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.

Electrically conductive and photocurable MXene-modulated hydrogel conduits for peripheral nerve regeneration: In vitro and in vivo studies

Electroconductive biomaterials, as advanced nerve guidance conduits (NGCs), have shown great promise to accelerate the rate of peripheral nerve repair and regeneration (PNR) but remain among the greatest challenges in regenerative medicine because of frail recovery. Herein, we introduce injectable nanocomposite nerve conduits based on gelatin methacrylate (GelMa) and MXene nanosheets (MX) for PNR. Microstructural studies determine that the addition of MX increases the mean pore size of GelMa NH from 5.8 ± 1.2 μm to 8.4 ± 1.6 μm for the hydrogel containing 0.25 mg/mL MX, for example, leading to higher swelling and degradation rates. The highest electrical conductivity (∼910 μS/cm) is attained for the GelMa-based nanocomposite composed MX with the concentration of 0.125 mg/mL, for the reason that at higher concentrations, agglomeration of the MXs happens. In vitro investigations, including metabolic activity and live-dead assessments by PC12 cells, reveal the biocompatibility of developed nanocomposite hydrogels (NHs) containing different concentrations of MX nanosheets in the range of 0.025-0.25 mg/mL. Implantation of GelMa-MX conduits in a rat model of peripheral nerve injury (PNI) leads to the impressive recovery of the injured sciatic nerve's sensory, motor, and sensory-motor function. Electrophysiological analysis also indicates a significant increase in compound muscle action potential and nerve conduction velocity with a decrease in terminal latency in animals implanted with GelMa-MX conduits compared to control groups (animals implanted with GelMa and animals without implantation). Moreover, histological analysis exhibits a notable absence of fibrous connective tissue in the regenerated nerve fibers with a substantial increase in more organized myelinated axons. Our results demonstrate that GelMa-MX conduits promote regeneration of the injured sciatic nerve and could be promising for peripheral nerve tissue engineering.

Corneal Neurotization: Paving the Path to Reinnervation

Neurotrophic keratopathy (NK), a degenerative corneal disease characterized by the loss of innervation to the cornea, has historically required long-term supportive treatment with a poor prognosis for rehabilitation. Corneal neurotization restores corneal sensation, permanently addressing the underlying pathophysiology of NK. Surgical approaches to corneal neurotization are expanding and undergoing refinement as more centers perform this intervention. This article describes the indications, surgical approaches, outcomes, and future directions of corneal neurotization.

Advanced techniques and innovations in peripheral nerve repair: a comprehensive review for clinical and experimental reference

Peripheral nerve injury, resulting from various physical and chemical causes, has a high incidence and significant functional impact. This injury, affecting both sensory and motor functions, can severely diminish quality of life and cause mental health issues. Consequently, it is a major focus of current research. Recent advancements in peripheral nerve repair technology, including the application of new techniques and materials, have expanded the options for nerve repair methods. A comprehensive article that combines the pathological process of peripheral nerve repair with these methods is needed to advance research in this field. This review aims to provide a comprehensive overview of various techniques for repairing peripheral nerve injuries. Beginning with the histopathology of nerve injury, it evaluates these techniques in detail to offer clinical guidance. This review summarizes the advantages and disadvantages of various peripheral nerve repair methods, including photobiological modulation therapy, suture repair, nerve graft repair, vein graft catheter repair, muscle graft repair, laser welding repair, nerve catheter repair, nerve sliding repair technology, growth factor-assisted repair, stem cell therapy, and exosome therapy. Additionally, it explores future directions in the treatment of peripheral nerve injuries, providing valuable references for experimental research and clinical treatment.

Optimizing Peripheral Nerve Regeneration: Surgical Techniques, Biomolecular and Regenerative Strategies-A Narrative Review

Peripheral nerve injury disrupts the function of the peripheral nervous system, leading to sensory, motor, and autonomic deficits. While peripheral nerves possess an intrinsic regenerative capacity, complete sensory and motor recovery remains challenging due to the unpredictable nature of the healing process, which is influenced by the extent of the injury, age, and timely intervention. Recent advances in microsurgical techniques, imaging technologies, and a deeper understanding of nerve microanatomy have enhanced functional outcomes in nerve repair. Nerve injury initiates complex pathophysiological responses, including Wallerian degeneration, macrophage activation, Schwann cell dedifferentiation, and axonal sprouting. Complete nerve disruptions require surgical intervention to restore nerve continuity and function. Direct nerve repair is the gold standard for clean transections with minimal nerve gaps. However, in cases with larger nerve gaps or when direct repair is not feasible, alternatives such as autologous nerve grafting, vascularized nerve grafts, nerve conduits, allografts, and nerve transfers may be employed. Autologous nerve grafts provide excellent biocompatibility but are limited by donor site morbidity and availability. Vascularized grafts are used for large nerve gaps and poorly vascularized recipient beds, while nerve conduits serve as a promising solution for smaller gaps. Nerve transfers are utilized when neither direct repair nor grafting is possible, often involving re-routing intact regional nerves to restore function. Nerve conduits play a pivotal role in nerve regeneration by bridging nerve gaps, with significant advancements made in material composition and design. Emerging trends in nerve regeneration include the use of 3D bioprinting for personalized conduits, gene therapy for targeted growth factor delivery, and nanotechnology for nanofiber-based conduits and stem cell therapy. Advancements in molecular sciences have provided critical insights into the cellular and biochemical mechanisms underlying nerve repair, leading to targeted therapies that enhance axonal regeneration, remyelination, and functional recovery in peripheral nerve injuries. This review explores the current strategies for the therapeutic management of peripheral nerve injuries, highlighting their indications, benefits, and limitations, while emphasizing the need for tailored approaches based on injury severity and patient factors.

Comparing Primary Coaptation and Allograft in Deep Inferior Epigastric Perforator Flap Breast Reconstruction: Long-Term Sensory and BREAST-Q Outcomes

BACKGROUND

Loss of breast sensation after mastectomy and breast reconstruction is associated with decreased psychosocial outcomes and quality-of-life, spurring applications of peripheral nerve repair to autologous breast reconstruction. While direct nerve coaptation is the gold standard for neurotization, the development of nerve allografts has increased candidacy for neurotization. Herein, we investigate long-term sensory and BREAST-Q outcomes in patients receiving deep inferior epigastric perforator (DIEP) flap reconstruction neurotized by direct coaptation and nerve allograft.

METHODS

Patients with neurotized DIEP reconstruction with direct coaptation or nerve allograft were retrospectively identified and invited to undergo breast sensation testing with a pressure-specified sensory device. Patients also completed the Reconstruction and Breast Sensation modules of the BREAST-Q questionnaire.

RESULTS

30 patients (53 flaps) were included in this study, with 18 flaps reconstructed with direct nerve coaptation and 35 flaps reconstructed with an allograft. The overall breast cutaneous sensitivity measurement was 64.58 g/mm2 [40.06, 78.99] in the direct coaptation group and 78.28 g/mm2 [40.60, 82.06] in the nerve allograft group, with no significant differences overall (P = 0.680) or at any specific breast area. BREAST-Q surveys were completed at an average follow-up time of 94.42 months in the direct coaptation group and 61.56 months in the allograft group. The two groups had comparable scores for all survey scales (P > 0.05).

CONCLUSION

DIEP flaps neurotized by direct coaptation and nerve allograft have comparable long-term objective and patient-reported breast sensation. Nerve grafting is a viable alternative for patients who are not candidates for direct end-to-end nerve coaptation.

The Use of Grayscale Muscle Ultrasound to Indicate Muscle Recovery after Peripheral Nerve Reconstruction

BACKGROUND

This study aimed to validate the use of grayscale muscle ultrasound by measuring echo intensity to longitudinally evaluate functional muscle reinnervation in a rabbit peroneal nerve defect model.

METHODS

Eighteen New Zealand white rabbits underwent a 30-mm peroneal nerve reconstruction with autografts or decellularized allografts. Ultrasound measurements of tibialis anterior muscles were performed before surgery and at 4, 8, 12, 16, 20, and 24 weeks postoperatively and included cross-sectional muscle area, mean gray value (MGV), and mean gray value normalized for area (MGVA). At 24 weeks, functional motor recovery was evaluated with isometric tetanic force (ITF) and compound muscle action potential (CMAP). MGVA data were compared with ITF and CMAP measurements by calculating the Spearman correlation coefficient.

RESULTS

Muscle area (left/right [L/R] ratio) of autografts was superior to allografts at 4, 12, 16, 20, and 24 weeks ( P < 0.03 for all comparisons). MGVs of the operated side were significantly higher for autografts at 4, 8, and 12 weeks and at 12, 16, 20, and 24 weeks for allografts ( P < 0.01 for all comparisons), compared with their unoperated sides. Similar patterns were seen in both groups for MGVA (operated versus control side). MGVA (L/R) demonstrated a strong correlation with ITF (L/R) for autografts (ρ = -0.7) and allografts (ρ = -0.87), but inconsistent with CMAPs (L/R).

CONCLUSIONS

Quantitative muscle ultrasound demonstrated a reliable, noninvasive tool for evaluating motor recovery in a rabbit peroneal nerve reconstruction model. Clinical translation could provide valuable insights into muscle health and structural changes following nerve reconstruction.

Engineering the Future of Restorative Clinical Peripheral Nerve Surgery

Peripheral nerve injury is a significant clinical challenge, often leading to permanent functional deficits. Standard interventions, such as autologous nerve grafts or distal nerve transfers, require sacrificing healthy nerve tissue and typically result in limited motor or sensory recovery. Nerve regeneration is complex and influenced by several factors: 1) the regenerative capacity of proximal neurons, 2) the ability of axons and support cells to bridge the injury, 3) the capacity of Schwann cells to maintain a supportive environment, and 4) the readiness of target muscles or sensory organs for reinnervation. Emerging bioengineering solutions, including biomaterials, drug delivery systems, fusogens, electrical stimulation devices, and tissue-engineered products, aim to address these challenges. Effective translation of these therapies requires a deep understanding of the physiology and pathology of nerve injury. This article proposes a comprehensive framework for developing restorative strategies that address all four major physiological responses in nerve repair. By implementing this framework, we envision a paradigm shift that could potentially enable full functional recovery for patients, where current approaches offer minimal hope.

Intra-septal sensory branch as an alternative to the sural nerve grafting in radial nerve reconstruction: Anatomical and histomorphological study

INTRODUCTION

Nerve grafting with the sural nerve is a standard treatment method for radial nerve injury that requires another incision at the lateral ankle distal from the injured upper limb. The aim of this study was to investigate the common trunk (CTCB) of the inferior lateral brachial cutaneous nerve (ILBCN) and posterior antebrachial cutaneous nerve (PACN) as a possible donor inside the lateral intermuscular septum.

MATERIALS AND METHODS

The arms and legs of 8 formalin-embalmed cadaver specimens were studied. The radial nerve, common trunk of the ILBCN and PACN, and the sural nerve were identified and measured in length and diameter. For histological examination, nerve samples from 6 fresh cadavers were harvested and processed for further axonal counting.

RESULTS

The average length of the CTCB was 114.92 ± 18.9 mm. To match the diameter of the radial nerve at its proximal third, 3 cables of CTCB graft were necessary, which corresponds to a defect length of 3.8 cm. At the level of the distal third, the number of grafts was reduced to 2 with a corresponding defect length of 5.7 cm. The radial nerve contained 15162 ± 318 axons, and the CTCB comprised 3959 ± 176 axons. To match the axon count of the recipient nerve, 4 grafts of CTCB were necessary, which corresponded to a defect length of 2.8 cm.

CONCLUSION

CTCB is a consistent and easily dissected cutaneous nerve branch of the radial nerve that can be used for bridging small gaps after neuroma-in-continuity in radial nerve palsy.

Adhesive and Conductive Fibrous Hydrogel Bandages for Effective Peripheral Nerve Regeneration

Peripheral nerve injury is a common disease resulting in reversible and irreversible impairments of motor and sensory functions. In addition to conventional surgical interventions such as nerve grafting and neurorrhaphy, nerve guidance conduits are used to effectively support axonal growth without unexpected neuroma formation. However, there are still challenges to secure tissue-mimetic mechanical and electrophysiological properties of the conduit materials. Herein, the phenylborate-tethered hydrogel-assisted doping effect is elucidated on conductive polymers, enhancing peripheral nerve regeneration when used as a sutureless bandage on the injured nerve. The adhesive and conductive nerve bandage consists of biocompatible hyaluronic acid hydrogel microfibers produced by electrospinning, followed by in situ conductive polypyrrole polymerization on the fibrous mat. Particularly, phenylborate groups enable high adsorption of pyrrole without mechanical crack on the hydrogel network and allow tissue-like stretchability and on-nerve adhesiveness. In a rat crushed nerve injury model, the nerve bandage can effectively promote nerve regeneration through stable sutureless wrapping followed by great electrical transmission on the defect region, showing anatomical and functional recovery of the nerve tissues and preventing muscular atrophy. Such hydrogel fibrous bandages will be a promising surgical dressing to be combined with versatile biomedical devices/materials for peripheral nerve repair.

An Updated Evaluation of the Management of Nerve Gaps: Autografts, Allografts, and Nerve Transfers

Within the past decade, there have been multiple innovations in the field of nerve surgery. In this review, we highlight critical changes and innovations that have helped advance the field and present opportunities for further study. This includes the modification and clarification of the classification schema for nerve injuries which informs prognosis and treatment, and a refined understanding and application of electrodiagnostic studies to guide patient selection. We provide indications for operative intervention based on this nerve injury classification and propose strategies best contoured for varying injury presentations at differing time points. Lastly, we discuss new developments in surgical techniques and approaches based on these advancements.

Innovative spiral nerve conduits: Addressing nutrient transport and cellular activity for critical-sized nerve defects

Large-gap nerve defects require nerve guide conduits (NGCs) for complete regeneration and muscle innervation. Many NGCs have been developed using various scaffold designs and tissue engineering strategies to promote axon regeneration. Still, most are tubular with inadequate pore sizes and lack surface cues for nutrient transport, cell attachment, and tissue infiltration. This study developed a porous spiral NGC to address these issues using a 3D-printed thermoplastic polyurethane (TPU) fiber lattice. The lattice was functionalized with poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) electrospun aligned (aPHBV) and randomly (rPHBV) oriented nanofibers to enhance cellular activity. TPU lattices were made with 25 %, 35 %, and 50 % infill densities to create scaffolds with varied mechanical compliance. The fabricated TPU/PHBV spiral conduits had significantly higher surface areas (25 % TPU/PHBV: 698.97 mm2, 35 % TPU/PHBV: 500.06 mm2, 50 % TPU/PHBV: 327.61 mm2) compared to commercially available nerve conduits like Neurolac™ (205.26 mm2). Aligned PHBV nanofibers showed excellent Schwann cell (RSC96) adhesion, proliferation, and neurogenic gene expression for all infill densities. Spiral TPU/PHBV conduits with 25 % and 35 % infill densities exhibited Young's modulus values comparable to Neurotube® and ultimate tensile strength like acellular cadaveric human nerves. A 10 mm sciatic nerve defect in Wistar rats treated with TPU/aPHBV NGCs demonstrated muscle innervation and axon healing comparable to autografts over 4 months, as evaluated by gait analysis, functional recovery, and histology. The TPU/PHBV NGC developed in this study shows promise as a treatment for large-gap nerve defects.

Scoping Review of the Published Guidelines for the Management of Traumatic Brachial Plexus Injuries

A traumatic brachial plexus injury (TBPI) is a rare yet debilitating condition with a typical incidence of 0.6-3.9 per 100000 annually, predominantly affecting young, economically active males following motorcycle accidents. Delayed diagnosis and treatment are associated with poorer functional outcomes, significant individual disability, and societal burdens, including loss of vocational potential and increased care costs. Individuals in resource-limited settings are particularly vulnerable to receiving suboptimal care. This study aimed to identify and evaluate existing published guidelines for the management of TBPI. A systematic review of literature from nine medical databases, using standardized search methods with results screened for relevance and analyzed using modified Appraisal of Guidelines for Research and Evaluation II-global rating scale (AGREE II-GRS) guidelines to determine quality. The search identified 1163 papers, of which eight met the inclusion criteria: six original research articles, one national guideline, and one departmental guideline. Six studies included treatment algorithms; however, only two categorized nerve transfers by pathology (upper (C5-6 ± C7), lower (C8-T1), or pan-plexus). None provided a sequenced or ordered approach to surgical management. Outcome reporting was inconsistent across studies. A modified AGREE II-GRS analysis indicated that the guidelines were appropriately targeted to relevant professional and patient groups. At present, there are no TBPI guidelines with structured, consensus-based recommendations for managing this condition within acute or secondary care settings in low- and middle-income countries (LMICs). Our study identified eight published and accessible guidelines with treatment algorithms, but none provided a comprehensive management regimen covering all aspects of TBPI care. Developing such a guideline for LMICs is challenging due to the rarity, variability, and complexity of this pathology. Any guideline designed for this context must account for the health economics, resource availability, logistical barriers, and personnel constraints required to ensure a fit-for-purpose management plan for a TBPI service.

GalT Knockout Porcine Nerve Xenografts Support Axonal Regeneration in a Rodent Sciatic Nerve Model

BACKGROUND

Nerve xenografts harvested from transgenic α1,3-galactosyltransferase knockout pigs lack the epitope responsible for hyperacute rejection in pig-to-primate transplants. It is unknown whether these cold-preserved nerve grafts support axonal regeneration in another species during and after immunosuppression. The authors compared outcomes between autografts and cold-preserved xenografts in a rat sciatic model of nerve gap repair.

METHODS

Fifty male Lewis rats had a 1-cm sciatic nerve defect repaired using autograft and suture ( n = 10); 1-week or 4-week cold-preserved xenograft and suture ( n = 10 per group); or 1-week or 4-week cold-preserved xenograft and photochemical tissue bonding using a human amnion wrap ( n = 10 per group). Rats with xenografts were given tacrolimus until 4 months postoperatively. At 4 and 7 months, rats were killed and nerve sections were harvested. Monthly sciatic functional index (SFI) scores were calculated.

RESULTS

All groups showed increases in SFI scores by 4 and 7 months. The autograft suture group had the highest axon density at 4 and 7 months. The largest decrease in axon density from 4 to 7 months was in the group with 1-week cold-preserved photochemical tissue bonding using a human amnion wrap. The only significant difference between group SFI scores occurred at 5 months, when both 1-week cold-preserved groups had significantly lower scores than the 4-week cold-preserved suture group.

CONCLUSIONS

The results suggest that α1,3-galactosyltransferase knockout nerve xenografts may be viable alternatives to autografts. Further studies of long-gap repair and comparison with acellular nerve allografts are needed.

CLINICAL RELEVANCE STATEMENT

This proof-of-concept study in the rat sciatic model demonstrates that cold-preserved α1,3-galactosyltransferase knockout porcine xenografts support axonal regeneration and viability following immunosuppression withdrawal. These results further suggest a role for both cold preservation and photochemical tissue bonding in modulating the immunological response at the nerve repair site.

Schwann cell autotransplantation for the treatment of peripheral nerve injury

Peripheral nerve injury occurs in a relatively large proportion of trauma patients, in whom it generally results in severe functional impairment and permanent disability. At present, however, there are no effective treatments available. Studies have shown that Schwann cells play an indispensable role in removing myelin debris and guiding axonal regeneration, and transplantation using autologous Schwann cells has shown good efficacy for patients with peripheral nerve injury. In recent years, Schwann cell autologous transplantation therapy has become an area of intensive research and is anticipated to provide a new strategy for the clinical treatment of peripheral nerve injury. In this article, we review the rationale for selecting Schwann cell autotransplantation therapy and the latest progress in key aspects of cell transplantation and clinical efficacy, and also summarize the future directions of research on this therapy. All of the above provide a strong basis for the further improvement and clinical promotion of this therapy.

Rapid Forming, Robust Adhesive Fungal-Sourced Chitosan Hydrogels Loaded with Deferoxamine for Sutureless Short-Gap Peripheral Nerve Repair

Clinically, conventional sutures for repair of short-distance nerve injuries (< 5 mm) may contribute to uncontrolled inflammation and scar formation, thus negatively impacting nerve regeneration. To repair transected peripheral nerves with short distances, a rapid-forming, robust adhesive chitosan hydrogel is prepared by synthesizing maleic and dopamine bi-functionalized fungal-sourced chitosan (DM) and subsequently photopolymerizing DM precursor solution. The hydrogel rapidly polymerized under UV light irradiation (≈2 s) and possessed a strong adhesive strength (273.33 ± 55.07 kPa), facilitating a fast bonding of nerve stump. Especially, its tailored degradation profile over 28 days supported both early gap bridging and subsequent nerve regeneration. Furthermore, deferoxamine (DFO), a pro-angiogenic drug, is loaded into the hydrogel to reach sustainable release, accelerating axonal growth synergistically. A 3 mm long sciatic nerve defects model in rats is used to investigate the efficacy of DM@DFO hydrogel for repairing peripheral nerve defects. After 60 days, the DM@DFO hydrogel significantly outperformed conventional sutures and fibrin glue, improving motor and sensory recovery by reducing inflammation, inhibiting scar formation, and accelerating vascular regeneration within 14 days post-repair. This work highlights the DM@DFO hydrogel as a promising tissue adhesive for effective short-distance peripheral nerve repair.

Implantable Self-Powered Systems for Electrical Stimulation Medical Devices

With the integration of bioelectronics and materials science, implantable self-powered systems for electrical stimulation medical devices have emerged as an innovative therapeutic approach, garnering significant attention in medical research. These devices achieve self-powering through integrated energy conversion modules, such as triboelectric nanogenerators (TENGs) and piezoelectric nanogenerators (PENGs), significantly enhancing the portability and long-term efficacy of therapeutic equipment. This review delves into the design strategies and clinical applications of implantable self-powered systems, encompassing the design and optimization of energy harvesting modules, the selection and fabrication of adaptable electrode materials, innovations in systematic design strategies, and the extensive utilization of implantable self-powered systems in biological therapies, including the treatment of neurological disorders, tissue regeneration engineering, drug delivery, and tumor therapy. Through a comprehensive analysis of the latest research progress, technical challenges, and future directions in these areas, this paper aims to provide valuable insights and inspiration for further research and clinical applications of implantable self-powered systems.

Combining external physical stimuli and nanostructured materials for upregulating pro-regenerative cellular pathways in peripheral nerve repair

Peripheral nerve repair remains a major clinical challenge, particularly in the pursuit of therapeutic approaches that ensure adequate recovery of patient's activity of daily living. Autografts are the gold standard in clinical practice for restoring lost sensorimotor functions nowadays. However, autografts have notable drawbacks, including dimensional mismatches and the need to sacrifice one function to restore another. Engineered nerve guidance conduits have therefore emerged as promising alternatives. While these conduits show surgical potential, their clinical use is currently limited to the repair of minor injuries, as their ability to reinnervate limiting gap lesions is still unsatisfactory. Therefore, improving patient functional recovery requires a deeper understanding of the cellular mechanisms involved in peripheral nerve regeneration and the development of therapeutic strategies that can precisely modulate these processes. Interest has grown in the use of external energy sources, such as light, ultrasound, electrical, and magnetic fields, to activate cellular pathways related to proliferation, differentiation, and migration. Recent research has explored combining these energy sources with tailored nanostructured materials as nanotransducers to enhance selectivity towards the target cells. This review aims to present the recent findings on this innovative strategy, discussing its potential to support nerve regeneration and its viability as an alternative to autologous transplantation.

Fabrication of Anatomically Equivalent Pectin-Based Multifilament Nerve Conduits

Reuniting denuded nerve ends after a long segmental peripheral nerve defect is challenging due to delayed axonal regeneration and incomplete, nonspecific reinnervation, as conventional hollow nerve guides fail to ensure proper fascicular complementation and obstruct axonal guidance across the defects. This study focuses on fabricating multifilament conduits using a plant-derived anionic polysaccharide, pectin, where the abundant availability of carboxylate (COO-) functional groups in pectin facilitates instantaneous sol-gel transition upon interaction with divalent cations. Despite their advantages, pectin hydrogels encounter structural instability under physiological conditions. Hence, pectin is conjugated with light-sensitive methacrylate residues (49.8% methacrylation) to overcome these issues, enabling the fabrication of dual cross-linked multifilament nerve conduits through an ionic interaction-driven, template-free 3D wet writing process, followed by photo-cross-linking at 525 nm. The anatomical equivalence including peri-, epi-, and endoneurium structures of the customized multifilament conduits was confirmed through scanning electron micrographs and micro-CT analysis of rat and goat sciatic nerve tissues. Furthermore, the fabricated multifilament nerve conduits demonstrated cytocompatibility and promoted the expression of neuron-specific intermediate filament protein (NF-200) in PC12 cells and neurite outgrowth of 16.90 ± 1.82 μm on day 14. Micro-CT imaging of an anastomosed native goat sciatic nerve with an 8-filament conduit demonstrated precise fascicular complementation in an ex vivo interpositional goat model. This approach not only eliminates the need for a suture-intensive ligation process but also highlights the customizability of multifilament conduits to meet patient- and injury-specific needs.

Nerve Versus Tendon Transfers in the Management of Isolated Upper Extremity Peripheral Nerve Injuries

Upper extremity peripheral nerve injuries present functional deficits that are amenable to management by tendon or nerve transfers. The principles of tendon and nerve transfers are discussed, with technical descriptions of preferred tendon and nerve transfers for radial, median, and ulnar nerve 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.

Anterior Interosseus to Ulnar Motor Nerve Transfers: A Canadian Perspective

BACKGROUND

The anterior interosseus nerve (AIN) to ulnar motor nerve transfer has been popularized as an adjunct to surgical decompression in patients with severe cubital tunnel syndrome (CuTS) and high ulnar nerve injuries. The factors influencing its implementation in Canada have yet to be described.

METHODS

An electronic survey was distributed to all members of the Canadian Society of Plastic Surgery (CSPS) using REDCap software. The survey examined 4 themes: previous training/experience, practice volume of nerve pathologies, experience with nerve transfers, and approach to the treatment of CuTS and high ulnar nerve injuries.

RESULTS

A total of 49 responses were collected (12% response rate). Of all, 62% of surgeons would use an AIN to ulnar motor supercharge end-to-side (SETS) transfer for a high ulnar nerve injury. For patients with CuTS and signs of intrinsic atrophy, 75% of surgeons would add an AIN-SETS transfer to a cubital tunnel decompression. Sixty-five percent would also release Guyon's canal, and the majority (56%) use a perineurial window for their end-to-side repair. Eighteen percent of surgeons did not believe the transfer would improve outcomes, 3% cited lack of training, and 3% would preferentially use tendon transfers. Surgeons with hand fellowship training and those less than 30 years in practice were more likely to use nerve transfers in the treatment of CuTS (P < .05).

CONCLUSIONS

Most CSPS members would use an AIN-SETS transfer in the treatment of both a high ulnar nerve injury and severe CuTS with intrinsic atrophy.

[Research progress of silk-based biomaterials for peripheral nerve regeneration]

Objective

To describe the research progress of silk-based biomaterials in peripheral nerve repair and provide useful ideals to accelerate the regeneration of large-size peripheral nerve injury.

Methods

The relative documents about silk-based biomaterials used in peripheral nerve regeneration were reviewed and the different strategies that could accelerate peripheral nerve regeneration through building bioactive microenvironment with silk fibroin were discussed.

Results

Many silk fibroin tissue engineered nerve conduits have been developed to provide multiple biomimetic microstructures, and different microstructures have different mechanisms of promoting nerve repair. Biomimetic porous structures favor the nutrient exchange at wound sites and inhibit the invasion of scar tissue. The aligned structures can induce the directional growth of nerve tissue, while the multiple channels promote the axon elongation. When the fillers are introduced to the conduits, better growth, migration, and differentiation of nerve cells can be achieved. Besides biomimetic structures, different nerve growth factors and bioactive drugs can be loaded on silk carriers and released slowly at nerve wounds, providing suitable biochemical cues. Both the biomimetic structures and the loaded bioactive ingredients optimize the niches of peripheral nerves, resulting in quicker and better nerve repair. With silk biomaterials as a platform, fusing multiple ways to achieve the multidimensional regulation of nerve microenvironments is becoming a critical strategy in repairing large-size peripheral nerve injury.

Conclusion

Silk-based biomaterials are useful platforms to achieve the design of biomimetic hierarchical microstructures and the co-loading of various bioactive ingredients. Silk fibroin nerve conduits provide suitable microenvironment to accelerate functional recovery of peripheral nerves. Different optimizing strategies are available for silk fibroin biomaterials to favor the nerve regeneration, which would satisfy the needs of various nerve tissue repair. Bioactive silk conduits have promising future in large-size peripheral nerve regeneration.

Psychological Aspects of Nerve Gap Reconstruction: Addressing Patient Perspectives and Expectations

Purpose

Preoperative expectations play a major role in determining patient satisfaction after surgery. The aim of this study was to characterize patient's preoperative expectations and postoperative perceptions of nerve gap repair surgery.

Methods

We conducted a search of Embase, Scopus, and Web of Science databases for peer-reviewed articles that studied patient expectations, perceptions, and impressions of nerve gap repair in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Studies related to lumbar plexus radiculopathy, reimplantation, or patient satisfaction scores without patient testimony were excluded. Primary and secondary outcomes were patient's preoperative expectations and postoperative perceptions of nerve gap repair surgery, respectively.

Results

We included 11 studies evaluating a total of 462 patients. One study evaluated only patient expectations, six studies evaluated only patient perspectives, and four studies evaluated both. Patients were generally overly optimistic in their expectations of surgery. Postoperative satisfaction ranged from 82% to 86%, and 81% to 87% of patients would choose to undergo their surgery again knowing what they know now.

Conclusions

Patient expectations in nerve gap repair are optimistic, and at times unrealistic. Patient satisfaction with nerve gap repair is high and subject to influence from preoperative education and postoperative outcomes of functional and sensory recovery.

Clinical relevance

Surgeons should be aware that patient expectations of their postoperative outcomes can have substantial impacts on their perceived management and overall satisfaction. More emphasis should be placed on preoperative education and expectation management to optimize patient satisfaction.

3D fascicular reconstruction of median and ulnar nerve: initial experience and comparison between high-resolution ultrasound and MR microscopy

BACKGROUND

The complex anatomy of peripheral nerves has been traditionally investigated through histological microsections, with inherent limitations. We aimed to compare three-dimensional (3D) reconstructions of median and ulnar nerves acquired with tomographic high-resolution ultrasound (HRUS) and magnetic resonance microscopy (MRM) and assess their capacity to depict intraneural anatomy.

METHODS

Three fresh-frozen human upper extremity specimens were prepared for HRUS imaging by submersion in a water medium. The median and ulnar nerves were pierced with sutures to improve orientation during imaging. Peripheral nerve 3D HRUS scanning was performed on the mid-upper arm using a broadband linear probe (10-22 MHz) equipped with a tomographic 3D HRUS system. Following excision, nerves were cut into 16-mm segments and loaded into the MRM probe of a 9.4-T system (scanning time 27 h). Fascicle and nerve counting was performed to estimate the nerve volume, fascicle volume, fascicle count, and number of interfascicular connections. HRUS reconstructions employed artificial intelligence-based algorithms, while MRM reconstructions were generated using an open-source imaging software 3D slicer.

RESULTS

Compared to MRM, 3D HRUS underestimated nerve volume by up to 22% and volume of all fascicles by up to 11%. Additionally, 3D HRUS depicted 6-60% fewer fascicles compared to MRM and visualized approximately half as many interfascicular connections.

CONCLUSION

MRM demonstrated a more detailed fascicular depiction compared to 3D HRUS, with a greater capacity for visualizing smaller fascicles. While 3D HRUS reconstructions can offer supplementary data in peripheral nerve assessment, their limitations in depicting interfascicular connections and small fascicles within clusters necessitate cautious interpretation.

CLINICAL RELEVANCE STATEMENT

Although 3D HRUS reconstructions can offer supplementary data in peripheral nerve assessment, even in intraoperative settings, their limitations in depicting interfascicular branches and small fascicles within clusters require cautious interpretation.

KEY POINTS

3D HRUS was limited in visualizing nerve interfascicular connections. MRM demonstrated better nerve fascicle depiction than 3D HRUS. MRM depicted more nerve interfascicular connections than 3D HRUS.

Research advancements on nerve guide conduits for nerve injury repair

Peripheral nerve injury (PNI) is one of the most serious causes of disability and loss of work capacity of younger individuals. Although PNS has a certain degree of regeneration, there are still challenges like disordered growth, neuroma formation, and incomplete regeneration. Regarding the management of PNI, conventional methods such as surgery, pharmacotherapy, and rehabilitative therapy. Treatment strategies vary depending on the severity of the injury. While for the long nerve defect, autologous nerve grafting is commonly recognized as the preferred surgical approach. Nevertheless, due to lack of donor sources, neurological deficits and the low regeneration efficiency of grafted nerves, nerve guide conduits (NGCs) are recognized as a future promising technology in recent years. This review provides a comprehensive overview of current treatments for PNI, and discusses NGCs from different perspectives, such as material, design, fabrication process, and composite function.

Nanomedicine in Neuroprotection, Neuroregeneration, and Blood-Brain Barrier Modulation: A Narrative Review

Nanomedicine is a newer, promising approach to promote neuroprotection, neuroregeneration, and modulation of the blood-brain barrier. This review includes the integration of various nanomaterials in neurological disorders. In addition, gelatin-based hydrogels, which have huge potential due to biocompatibility, maintenance of porosity, and enhanced neural process outgrowth, are reviewed. Chemical modification of these hydrogels, especially with guanidine moieties, has shown improved neuron viability and underscores tailored biomaterial design in neural applications. This review further discusses strategies to modulate the blood-brain barrier-a factor critically associated with the effective delivery of drugs to the central nervous system. These advances bring supportive solutions to the solving of neurological conditions and innovative therapies for their treatment. Nanomedicine, as applied to neuroscience, presents a significant leap forward in new therapeutic strategies that might help raise the treatment and management of neurological disorders to much better levels. Our aim was to summarize the current state-of-knowledge in this field.

The Application of Regenerated Silk Fibroin in Tissue Repair

Silk fibroin (SF) extracted from silk is non-toxic and has excellent biocompatibility and biodegradability, making it an excellent biomedical material. SF-based soft materials, including porous scaffolds and hydrogels, play an important role in accurately delivering drugs to wounds, creating microenvironments for the adhesion and proliferation of support cells, and in tissue remodeling, repair, and wound healing. This article focuses on the study of SF protein-based soft materials, summarizing their preparation methods and basic applications, as well as their regenerative effects, such as drug delivery carriers in various aspects of tissue engineering such as bone, blood vessels, nerves, and skin in recent years, as well as their promoting effects on wound healing and repair processes. The authors expect SF soft materials to play an important role in the field of tissue repair.

Silicon-induced biofilm improves peripheral nerve defect in rats mediated by VEGF/VEGFR2/ERK

Background: Injury of peripheral nerve capable of regeneration with much poorer prognosis affects people's life quality. The recovery of nerve function after transplantation for peripheral nerve injury remain a worldwide problem. Silicon-induced biofilms as vascularized biological conduits can promote nerve regeneration by encapsulating autologous or allogeneic nerve graft.Objective: We proposed to explore the effect of silicon-induced biofilms on nerves regeneration and whether the VEGF/VEGFR2/ERK pathway was involved in the present study.Methods: Biofilms around the transplanted nerves in peripheral nerve injury rats were induced by silicon. Vascularization and proteins related to VEGF/VEGFR2/ERK were measured. Pathology and morphology of nerves were investigated after encapsulating the transplanted nerves by silicon-induced biofilms.Results: Our results indicated that the biofilms induced by silicon for 6 weeks showed the most intensive vascularization and the optimal effect on nerve regeneration. Moreover, silicon-induced biofilms for 4, 6 and 8 weeks could significantly secrete VEGF with the highest content at week 6 after induction. VEGFR2, VEGF, p-VEGFR2, ERK1, ERK2, p-ERK1 and p-ERK2 were expressed in the biofilms. p-VEGFR2, p-ERK1 and p-ERK2 expression were different at each time point and significantly increased at week 6 compared with that at week 4 or week 8 which was consistent with that 6 week of was the optimum time for biofilms induction to improve the nerve repair after peripheral nerve injury.Conclusion: Our results suggested that combination of silicon-induced autologous vascularized biofilm and autologous transplantation may promote the repair of rat sciatic nerve defect quickly through VEGF/VEGFR2/ERK pathway.

SCOPING: A Pilot Study Exploring the Role of A Series of Clinical Observational Parameters as Indicators of Nerve Regeneration

Background

Following the repair of a mixed peripheral nerve, functional recovery requires successful nerve regeneration across the repair site and, eventually, reinnervation of distal targets. Reliably determining a failing nerve repair so that revision may be performed before irreversible muscle atrophy remains a challenge in peripheral nerve surgery. This study aimed to ascertain whether any commonly used clinical examination tests during surveillance after nerve repair can detect a failing repair and prompt earlier salvage intervention.

Methods

A prospective observational cohort study was performed to evaluate commonly used clinical determinants of neuron regeneration that may provide early surrogate recovery measures. Sequential cutaneous thermography was used to identify temperature differences between denervated and normal skin in the hand operated on, with the contralateral hand as a control.

Results

Six out of nine patients completed between 6 and 18 months of follow-up. Tinel sign progression was observed in all subjects. Tinel progression rate was associated with motor and sensory Medical Research Council grade. The delta temperature was calculated to document the size and direction of any temperature differentials in the hand detected by thermography, but we did not have sufficient data to calculate any correlations with motor and sensory Medical Research Council grade.

Conclusions

Specifically, the progression of Tinel sign is associated with recovery measured by progression of the British Medical Research Council motor and sensory grades. The use of thermographic imaging demonstrates that there is a difference in temperature between an injured and noninjured nerve. Future studies could investigate to what extent thermographic imaging predicts final nerve repair outcomes.

Transplantation of Neural Progenitor Cells Derived from Stem Cells from Apical Papilla Through Small-Molecule Induction in a Rat Model of Sciatic Nerve Injury

BACKGROUND

Stem cell-based transplantation therapy holds promise for peripheral nerve injury treatment, but adult availability is limited. A cell culture protocol utilizing a small-molecule cocktail effectively reprogrammed stem cells from apical papilla (SCAPs) into neural progenitor cells, subsequently differentiating into neuron-like cells. This study aims to evaluate neural-induced SCAPs, with and without small-molecule cocktail, for sciatic nerve repair potential.

METHODS

A scaffold-free cell sheet technique was used to construct a three-dimensional cell sheet. Subsequently, this cell sheet was carefully rolled into a tube and seamlessly inserted into a collagen conduit, which was then transplanted into a 5 mm sciatic nerve injury rat model. Functional sciatic nerve regeneration was evaluated via toe spread test, walking track analysis and gastrocnemius muscle weight. Additionally, degree of sciatic nerve regeneration was determined based on total amount of myelinated fibers.

RESULTS

Small-molecule cocktail induced SCAPs enhanced motor function recovery, evident in improved sciatic function index and gastrocnemius muscle retention. We also observed better host myelinated fiber retention than undifferentiated SCAPs or neural-induced SCAPs without small-molecule cocktail. However, clusters of neuron-like cell bodies (surrounded by sparse myelinated fibers) were found in all cell sheet-implanted groups in the implantation region. This suggests that while the implanted cells likely survived transplantation, integration was poor and would likely hinder long-term recovery by occupying the space needed for host nerve fibers to project through.

CONCLUSION

Neural-induced SCAPs with small-molecule cocktail demonstrated promising benefits for nerve repair; further research is needed to improve its integration and optimize its potential for long-term recovery.

Roles of SMAD and SMAD-Associated Signaling Pathways in Nerve Regeneration Following Peripheral Nerve Injury: A Narrative Literature Review

Although several methods are being applied to treat peripheral nerve injury, a perfect treatment that leads to full functional recovery has not yet been developed. SMAD (Suppressor of Mothers Against Decapentaplegic Homolog) plays a crucial role in nerve regeneration by facilitating the survival and growth of nerve cells following peripheral nerve injury. We conducted a systematic literature review on the role of SMAD in this context. Following peripheral nerve injury, there was an increase in the expression of SMAD1, -2, -4, -5, and -8, while SMAD5, -6, and -7 showed no significant changes; SMAD8 expression was decreased. Specifically, SMAD1 and SMAD4 were found to promote nerve regeneration, whereas SMAD2 and SMAD6 inhibited it. SMAD exerts its effects by promoting neuronal survival and growth through BMP/SMAD1, BMP/SMAD4, and BMP/SMAD7 signaling pathways. Furthermore, it activates nerve regeneration programs via the PI3K/GSK3/SMAD1 pathway, facilitating active regeneration of nerve cells and subsequent functional recovery after peripheral nerve damage. By leveraging these mechanisms of SMAD, novel strategies for treating peripheral nerve damage could potentially be developed. We aim to further elucidate the precise mechanisms of nerve regeneration mediated by SMAD and explore the potential for developing targeted nerve treatments based on these findings.

Exosomes repairment for sciatic nerve injury: a cell-free therapy

Sciatic nerve injury (SNI) is a common type of peripheral nerve injury typically resulting from trauma, such as contusion, sharp force injuries, drug injections, pelvic fractures, or hip dislocations. It leads to both sensory and motor dysfunctions, characterized by pain, numbness, loss of sensation, muscle atrophy, reduced muscle tone, and limb paralysis. These symptoms can significantly diminish a patient's quality of life. Following SNI, Wallerian degeneration occurs, which activates various signaling pathways, inflammatory factors, and epigenetic regulators. Despite the availability of several surgical and nonsurgical treatments, their effectiveness remains suboptimal. Exosomes are extracellular vesicles with diameters ranging from 30 to 150 nm, originating from the endoplasmic reticulum. They play a crucial role in facilitating intercellular communication and have emerged as highly promising vehicles for drug delivery. Increasing evidence supports the significant potential of exosomes in repairing SNI. This review delves into the pathological progression of SNI, techniques for generating exosomes, the molecular mechanisms behind SNI recovery with exosomes, the effectiveness of combining exosomes with other approaches for SNI repair, and the changes and future outlook for utilizing exosomes in SNI recovery.

Electrical stimulation enhances sciatic nerve regeneration using a silk-based conductive scaffold beyond traditional nerve guide conduits

Despite recent advancements in peripheral nerve regeneration, the creation of nerve conduits with chemical and physical cues to enhance glial cell function and support axonal growth remains challenging. This study aimed to assess the impact of electrical stimulation (ES) using a conductive nerve conduit on sciatic nerve regeneration in a rat model with transection injury. The study involved the fabrication of conductive nerve conduits using silk fibroin and Au nanoparticles (AuNPs). Collagen hydrogel loaded with green fluorescent protein (GFP)-positive adipose-derived mesenchymal stem cells (ADSCs) served as the filling for the conduit. Both conductive and non-conductive conduits were applied with and without ES in rat models. Locomotor recovery was assessed using walking track analysis. Histological evaluations were performed using H&E, luxol fast blue staining and immunohistochemistry. Moreover, TEM analysis was conducted to distinguish various ultrastructural aspects of sciatic tissue. In the ES + conductive conduit group, higher S100 (p < 0.0001) and neurofilament (p < 0.001) expression was seen after 6 weeks. Ultrastructural evaluations showed that conductive scaffolds with ES minimized Wallerian degeneration. Furthermore, the conductive conduit with ES group demonstrated significantly increased myelin sheet thickness and decreased G. ratio compared to the autograft. Immunofluorescent images confirmed the presence of GFP-positive ADSCs by the 6th week. Locomotor recovery assessments revealed improved function in the conductive conduit with ES group compared to the control group and groups without ES. These results show that a Silk/AuNPs conduit filled with ADSC-seeded collagen hydrogel can function as a nerve conduit, aiding in the restoration of substantial gaps in the sciatic nerve with ES. Histological and locomotor evaluations indicated that ES had a greater impact on functional recovery compared to using a conductive conduit alone, although the use of conductive conduits did enhance the effects of ES.

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.

Ulnar Neuropathy after Distal Radius Fractures - A Case Series and Review of Literature

Background: Ulnar neuropathy after a distal radius fracture is rare and has limited reports in literature. As such, there is no consensus regarding the optimal treatment and management of such injuries. We report our experience with managing these uncommon injuries. Methods: A retrospective review was conducted where patients presenting with ulnar neuropathy after sustaining a distal radius fracture were identified from January 2021 to December 2023 from our hospital database. Results: A total of four patients were identified. All of them underwent surgical fixation for their respective fractures. None of them underwent immediate or delayed exploration and decompression of the ulnar nerve. All patients had clinical improvement at 3 months after their initial injuries. Three patients eventually had resolution of the neuropathy between 5 and 9 months post injury, while one had partial recovery and developed a neuroma but declined surgery due to symptoms minimally affecting work and daily activities. Conclusions: Ulnar neuropathy after distal radius fractures may not be as rare as previously thought. Expectant management of the neuropathy would be a reasonable treatment as long as there is no evidence of nerve discontinuity or translocation and that there is clinical and/or electrodiagnostic improvement at 3-4 months after the initial injury. Level of Evidence: Level IV (Therapeutic).

Development and Application of an Advanced Biomedical Material-Silk Sericin

Sericin, a protein derived from silkworm cocoons, is considered a waste product derived from the silk industry for thousands of years due to a lack of understanding of its properties. However, in recent decades, a range of exciting properties of sericin are studied and uncovered, including cytocompatibility, low-immunogenicity, photo-luminescence, antioxidant properties, as well as cell-function regulating activities. These properties make sericin-based biomaterials promising candidates for biomedical applications. This review summarizes the properties and bioactivities of silk sericin and highlights the latest developments in sericin in tissue engineering and regenerative medicine. Furthermore, the extended application of sericin in developing flexible electronic devices and 3D bioprinting is also discussed. It is believed that sericin-based biomaterials have great potential of being developed into novel tissue engineering products and smart implantable devices for various medical applications toward improving clinical 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.

Effect of vascularized jejunal conduit flap on peripheral nerve regeneration in rats

Background/aim

In the literature, almost all of the nerve conduits proposed for obtaining better nerve recovery were applied as graft materials. In this study, we aimed to propose a new nerve conduit model with a flap pattern and evaluate the effect of a pedicled vascularized jejunal flap on nerve regeneration after wrapping it around a sciatic nerve.

Materials and methods

A total of 90 Wistar albino rats were randomly divided into nine groups with 10 rats in each. The first three groups constituted the control groups, whereas Groups 4-6 were the jejunum conduit (JC)-applied groups. A mucosa-resected JC (MRJC) was applied in Groups 7 and 8. Epineurial neurorrhaphy was performed in Groups 1, 4, and 7; repair with a nerve graft was applied in Groups 2, 5, and 8; and a 1-cm-long nerve defect was created in Groups 3, 6, and 9. After 2 months of follow-up, nerve regeneration was assessed by statistical analyses of the Sciatic Functional Index (SFI) and histopathological evaluation.

Results

The MRJC groups had significantly better results in terms of SFI (p = 0.005). Statistical differences in axonal degeneration, axonal density, myelination, and disorganization were found between all control groups and MRJC groups (p = 0.022, p = 0.001, p = 0.001, and p = 0.039, respectively).

Conclusion

In this study, the feasibility of wrapping around the nerve repair zones of pedicled autologous flaps designed in a tubular fashion was observed in a small rat model. The findings must be further validated with larger animals before clinical testing.

Electrical aligned polyurethane nerve guidance conduit modulates macrophage polarization and facilitates immunoregulatory peripheral nerve regeneration

Biomaterials can modulate the local immune microenvironments to promote peripheral nerve regeneration. Inspired by the spatial orderly distribution and endogenous electric field of nerve fibers, we aimed to investigate the synergistic effects of electrical and topological cues on immune microenvironments of peripheral nerve regeneration. Nerve guidance conduits (NGCs) with aligned electrospun nanofibers were fabricated using a polyurethane copolymer containing a conductive aniline trimer and degradable L-lysine (PUAT). In vitro experiments showed that the aligned PUAT (A-PUAT) membranes promoted the recruitment of macrophages and induced their polarization towards the pro-healing M2 phenotype, which subsequently facilitated the migration and myelination of Schwann cells. Furthermore, NGCs fabricated from A-PUAT increased the proportion of pro-healing macrophages and improved peripheral nerve regeneration in a rat model of sciatic nerve injury. In conclusion, this study demonstrated the potential application of NGCs in peripheral nerve regeneration from an immunomodulatory perspective and revealed A-PUAT as a clinically-actionable strategy for peripheral nerve injury.

Electrospun drug-loaded scaffolds for nervous system repair

Nervous system injuries, encompassing peripheral nerve injury (PNI), spinal cord injury (SCI), and traumatic brain injury (TBI), present significant challenges to patients' wellbeing. Traditional treatment approaches have limitations in addressing the complexity of neural tissue regeneration and require innovative solutions. Among emerging strategies, implantable materials, particularly electrospun drug-loaded scaffolds, have gained attention for their potential to simultaneously provide structural support and controlled release of therapeutic agents. This review provides a thorough exploration of recent developments in the design and application of electrospun drug-loaded scaffolds for nervous system repair. The electrospinning process offers precise control over scaffold characteristics, including mechanical properties, biocompatibility, and topography, crucial for creating a conducive environment for neural tissue regeneration. The large surface area of the resulting fibrous networks enhances biomolecule attachment, influencing cellular behaviors such as adhesion, proliferation, and migration. Polymeric electrospun materials demonstrate versatility in accommodating a spectrum of therapeutics, from small molecules to proteins. This enables tailored interventions to accelerate neuroregeneration and mitigate inflammation at the injury site. A critical aspect of this review is the examination of the interplay between structural properties and pharmacological effects, emphasizing the importance of optimizing both aspects for enhanced therapeutic outcomes. Drawing upon the latest advancements in the field, we discuss the promising outcomes of preclinical studies using electrospun drug-loaded scaffolds for nervous system repair, as well as future perspectives and considerations for their design and implementation. This article is categorized under: Implantable Materials and Surgical Technologies > Nanomaterials and Implants Implantable Materials and Surgical Technologies > Nanotechnology in Tissue Repair and Replacement Therapeutic Approaches and Drug Discovery > Emerging Technologies.

Epidemiology of peripheral nerve and brachial plexus injuries in a trauma population

BACKGROUND

Understanding patterns of peripheral nerve injuries (PNIs) and brachial plexus injuries (BPIs) is essential to preventing and appropriately managing nerve injuries. We sought to assess the incidence, cause, and severity of PNIs and BPIs sustained by patients with trauma.

METHODS

We conducted a retrospective review of the Trauma Registry Database (January 2002 to December 2020) to identify patients with PNIs or BPIs.

RESULTS

We evaluated data from 24 905 patients with trauma; 335 (1.3%) sustained PNIs (81% male; mean age 36 yr, standard deviation [SD] 16 yr) and 64 (0.3%) sustained BPIs (84% male; mean age 35, SD 15 yr). Nerves in the upper extremities were more commonly affected than those in the lower extremities. Sharp injuries (39.4%) and motorcycle accidents (32.8%) were the most frequent causes of PNIs and BPIs, respectively. Other common causes of PNI were motor vehicle collisions (16.7%) and gunshot wounds (12.8%). Many patients with PNIs (69.0%) and BPIs (53%) underwent operative management. The most frequent reconstruction for PNI was primary nerve repair (66%), while nerve transfers (48%) were more frequently used for BPI.

CONCLUSION

Nerve injuries in the trauma population have decreased over the last 3 decades with shifts in mechanisms of injury and use of imaging, electrodiagnostic tests, and surgery. Nerve injuries are often complex and time-sensitive to treat; understanding changes in trends is important to ensure optimal patient management.

Silk fibroin-based scaffolds for tissue engineering

Silk fibroin is an important natural fibrous protein with excellent prospects for tissue engineering applications. With profound studies in recent years, its potential in tissue repair has been developed. A growing body of literature has investigated various fabricating methods of silk fibroin and their application in tissue repair. The purpose of this paper is to trace the latest developments of SF-based scaffolds for tissue engineering. In this review, we first presented the primary and secondary structures of silk fibroin. The processing methods of SF scaffolds were then summarized. Lastly, we examined the contribution of new studies applying SF as scaffolds in tissue regeneration applications. Overall, this review showed the latest progress in the fabrication and utilization of silk fibroin-based scaffolds.

Heterologous fibrin biopolymer as an emerging approach to peripheral nerve repair: a scoping review

Nerve injuries present a substantial challenge within the medical domain due to their prevalent occurrence and significant impact. In nerve injuries, a range of physiopathological and metabolic responses come into play to stabilize and repair the resulting damage. A critical concern arises from the disruption of connections at neuromuscular junctions, leading to profound degeneration and substantial loss of muscle function, thereby hampering motor tasks. While end-to-end neurorrhaphy serves as the established technique for treating peripheral nerve injuries, achieving comprehensive morphofunctional recovery remains a formidable challenge. In pursuit of enhancing the repair process, alternative and supportive methods are being explored. A promising candidate is the utilization of heterologous fibrin biopolymer, a sealant devoid of human blood components. Notably, this biopolymer has showcased its prowess in establishing a stable and protective microenvironment at the site of use in multiple scenarios of regenerative medicine. Hence, this scoping review is directed towards assessing the effects of associating heterologous fibrin biopolymer with neurorrhaphy to treat nerve injuries, drawing upon findings from prior studies disseminated through PubMed/MEDLINE, Scopus, and Web of Science databases. Further discourse delves into the intricacies of the biology of neuromuscular junctions, nerve injury pathophysiology, and the broader utilization of fibrin sealants in conjunction with sutures for nerve reconstruction procedures. The association of the heterologous fibrin biopolymer with neurorrhaphy emerges as a potential avenue for surmounting the limitations associated with traditional sealants while also mitigating degeneration in nerves, muscles, and NMJs post-injury, thereby fostering a more conducive environment for subsequent regeneration. Indeed, queries arise regarding the long-term regenerative potential of this approach and its applicability in reconstructive surgeries for human nerve injuries.

Multichannel Conduits with Fascicular Complementation: Significance in Long Segmental Peripheral Nerve Injury

Despite the advances in tissue engineering approaches, reconstruction of long segmental peripheral nerve defects remains unsatisfactory. Although autologous grafts with proper fascicular complementation have shown meaningful functional recovery according to the Medical Research Council Classification (MRCC), the lack of donor nerve for such larger defect sizes (>30 mm) has been a serious clinical issue. Further clinical use of hollow nerve conduits is limited to bridging smaller segmental defects of denuded nerve ends (<30 mm). Recently, bioinspired multichannel nerve guidance conduits (NGCs) gained attention as autograft substitutes as they mimic the fascicular connective tissue microarchitecture in promoting aligned axonal outgrowth with desirable innervation for complete sensory and motor function restoration. This review outlines the hierarchical organization of nerve bundles and their significance in the sensory and motor functions of peripheral nerves. This review also emphasizes the major challenges in addressing the longer nerve defects with the role of fascicular arrangement in the multichannel nerve guidance conduits and the need for fascicular matching to accomplish complete functional restoration, especially in treating long segmental nerve defects. Further, currently available fabrication strategies in developing multichannel nerve conduits and their inconsistency in existing preclinical outcomes captured in this review would seed a new process in designing an ideal larger nerve conduit for peripheral nerve repair.

Preparation of PLCL/ECM nerve conduits by electrostatic spinning technique and evaluationin vitroandin vivo

Objective. Artificial nerve scaffolds composed of polymers have attracted great attention as an alternative for autologous nerve grafts recently. Due to their poor bioactivity, satisfactory nerve repair could not be achieved. To solve this problem, we introduced extracellular matrix (ECM) to optimize the materials.Approach.In this study, the ECM extracted from porcine nerves was mixed with Poly(L-Lactide-co-ϵ-caprolactone) (PLCL), and the innovative PLCL/ECM nerve repair conduits were prepared by electrostatic spinning technology. The novel conduits were characterized by scanning electron microscopy (SEM), tensile properties, and suture retention strength test for micromorphology and mechanical strength. The biosafety and biocompatibility of PLCL/ECM nerve conduits were evaluated by cytotoxicity assay with Mouse fibroblast cells and cell adhesion assay with RSC 96 cells, and the effects of PLCL/ECM nerve conduits on the gene expression in Schwann cells was analyzed by real-time polymerase chain reaction (RT-PCR). Moreover, a 10 mm rat (Male Wistar rat) sciatic defect was bridged with a PLCL/ECM nerve conduit, and nerve regeneration was evaluated by walking track, mid-shank circumference, electrophysiology, and histomorphology analyses.Main results.The results showed that PLCL/ECM conduits have similar microstructure and mechanical strength compared with PLCL conduits. The cytotoxicity assay demonstrates better biosafety and biocompatibility of PLCL/ECM nerve conduits. And the cell adhesion assay further verifies that the addition of ECM is more beneficial to cell adhesion and proliferation. RT-PCR showed that the PLCL/ECM nerve conduit was more favorable to the gene expression of functional proteins of Schwann cells. Thein vivoresults indicated that PLCL/ECM nerve conduits possess excellent biocompatibility and exhibit a superior capacity to promote peripheral nerve repair.Significance.The addition of ECM significantly improved the biocompatibility and bioactivity of PLCL, while the PLCL/ECM nerve conduit gained the appropriate mechanical strength from PLCL, which has great potential for clinical repair of peripheral nerve injuries.

Perspectives on the Novel Multifunctional Nerve Guidance Conduits: From Specific Regenerative Procedures to Motor Function Rebuilding

Peripheral nerve injury potentially destroys the quality of life by inducing functional movement disorders and sensory capacity loss, which results in severe disability and substantial psychological, social, and financial burdens. Autologous nerve grafting has been commonly used as treatment in the clinic; however, its rare donor availability limits its application. A series of artificial nerve guidance conduits (NGCs) with advanced architectures are also proposed to promote injured peripheral nerve regeneration, which is a complicated process from axon sprouting to targeted muscle reinnervation. Therefore, exploring the interactions between sophisticated NGC complexes and versatile cells during each process including axon sprouting, Schwann cell dedifferentiation, nerve myelination, and muscle reinnervation is necessary. This review highlights the contribution of functional NGCs and the influence of microscale biomaterial architecture on biological processes of nerve repair. Progressive NGCs with chemical molecule induction, heterogenous topographical morphology, electroactive, anisotropic assembly microstructure, and self-powered electroactive and magnetic-sensitive NGCs are also collected, and they are expected to be pioneering features in future multifunctional and effective NGCs.