Nerve capping with a nerve conduit for the treatment of painful neuroma in the rat sciatic nerve

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.

Visualization analysis of research frontiers and trends in the treatment of sciatic nerve injury

Objective

To visualize and analyze the literature related to sciatic nerve injury treatment from January 2019 to December 2023, and summarize the current status, hotspots, and development trends of research in this field.

Methods

Using CiteSpace and VOSviewer software, we searched the Web of Science database for literature related to the treatment of sciatic nerve injury. Then we analyzed and plotted visualization maps to show the number of publications, countries, institutions, authors, keywords, references, and journals.

Results

A total of 2,653 articles were included in the English database. The annual number of publications exceeded 230, and the citation frequency increased yearly. The United States and China were identified as high-influence nations in this field. Nantong University was the leading institution in terms of close cooperation among institutions. The authors Wang Yu had the highest number of publications and were highly influential in this field. Keyword analysis and reference Burst revealed a research focus on nerve regeneration and neuropathic pain, which involve regenerative medicine and neural tissue engineering. Chronic pain resulting from sciatic nerve injury often manifests alongside anxiety, depression, cognitive-behavioral disorders, and other issues. Interventions such as stem cells, electrical stimulation, electroacupuncture, total joint replacement, pharmacological interventions, gene therapy, nerve conduits, chitosan scaffolds, and exercise promote nerve repair and alleviate pain. Schwann cells have been the focus of much attention in nerve repair and regeneration. Improving the outcome of sciatic nerve injury is a current research challenge and focus in this field. Based on keyword Burst, nerve conduits and grafts may become a potential research hotspot in the treatment of sciatic nerve injury.

Conclusion

This visual analysis summarizes research trends and developments of sciatic nerve injury treatment and predicts potential research frontiers and hot directions.

Biology and pathophysiology of symptomatic neuromas

ABSTRACT

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

Secondary Trigger Point Deactivation Surgery for Nerve Compression Headaches: A Scoping Review

Background

Primary trigger point deactivation surgery has been successful in reducing or eliminating nerve compression headaches between 79% and 90% of the time. The aim of this review article was to discuss the factors that contribute to index trigger point deactivation surgery failure, the importance of reevaluating trigger points following failure, and the options for secondary surgery.

Methods

A literature search was performed using a combination of keywords involving "chronic headache" and "nerve deactivation surgery," in databases until February 2023.

Results

Data of 1071 patients were evaluated and included (11 articles). The failure rate after index trigger point deactivation surgery occurs is approximately 12%, primarily due to incomplete primary trigger point deactivation. Secondary trigger points may not appear until the primary trigger is eliminated, which occurs in 17.8% of patients. Reevaluation of previously diagnosed trigger points as well as uncovered trigger points and additional preoperative testing is indicated to help determine candidacy for further surgical deactivation. To address scarring that could contribute to failure, corticosteroid injection, acellular dermal matrix, adipofascial fat, or expanded polytetrafluoroethylene sleeves have been described with beneficial effects. For neuroma management, regenerative peripheral nerve interface, targeted muscle reinnervation, a combination of both, relocation nerve grafting, or nerve capping have also been described. Neurectomy can be performed when patients prefer anesthesia and/or paresthesia over current pain symptoms.

Conclusion

Secondary trigger point deactivation surgery is indicated when there is suspicion of incomplete deactivation, internal scarring, neuroma, or newly-diagnosed trigger points.

Neuromas cause severe residual problems at long-term despite surgery

Pain, and disabilities after neuroma surgery, using patient reported outcome measurements (PROMs), were evaluated by QuickDASH and a specific Hand Questionnaire (HQ-8). The 69 responding individuals (response rate 61%; 59% women; 41% men; median follow up 51 months) reported high QuickDASH score, pain on load, cold sensitivity, ability to perform daily activities and sleeping difficulties. Individuals reporting impaired ability to perform daily activities and sleeping problems had higher scores for pain, stiffness, weakness, numbness/tingling, cold sensitivity and QuickDASH. Only 17% of individuals reported no limitations at all. No differences were observed between sexes. Surgical methods did not influence outcome. Symptoms and disabilities correlated moderately-strongly to each other and to ability to perform regular daily activities as well as to sleeping difficulties. Pain, cold sensitivity, sleeping difficulties and limitation to perform daily activities were associated to higher QuickDASH. A weak association was found between follow up time and QuickDASH score as well as pain on load, but not cold sensitivity. A major nerve injury was frequent among those with limitations during work/performing other regular daily activities. Despite surgical treatment, neuromas cause residual problems, which affect the capacity to perform daily activities and ability to sleep with limited improvement in long-term.

The Use of Nerve Caps after Nerve Transection in Headache Surgery: Cadaver and Case Reports

Background

Nerve transection with nerve reconstruction is part of the treatment algorithm for patients with refractory pain after greater occipital nerve (GON) and lesser occipital nerve (LON) decompression or during primary decompression when severe nerve injury or neuroma formation is present. Importantly, the residual nerve stump is often best addressed via contemporary nerve reconstruction techniques to avoid recurrent pain. As a primary aim of this study, nerve capping is explored as a potential viable alternative that can be utilized in certain headache cases to mitigate pain.

Methods

The technical feasibility of nerve capping after GON/LON transection was evaluated in cadaver dissections and intraoperatively. Patient-reported outcomes in the 3- to 4-month period were compiled from clinic visits. At 1-year follow-up, subjective outcomes and Migraine Headache Index scores were tabulated.

Results

Two patients underwent nerve capping as a treatment for headaches refractory to medical therapy and surgical decompressions with significant improvement to total resolution of pain without postoperative complications. These improvements on pain frequency, intensity, and duration remained stable at a 1-year time point (Migraine Headache Index score reductions of -180 to -205).

Conclusions

Surgeons should be equipped to address the proximal nerve stump to prevent neuroma and neuropathic pain recurrence. Next to known contemporary nerve reconstruction techniques such as targeted muscle reinnervation/regenerative peripheral nerve interface and relocation nerve grafting, nerve capping is another viable method for surgeons to address the proximal nerve stump in settings of GON and LON pain. This option exhibits short operative time, requires only limited dissection, and yields significant clinical improvement in pain symptoms.

Nerve Defect Treatment with a Capping Hydroxyethyl Cellulose/Soy Protein Isolate Sponge Conduit for Painful Neuroma Prevention

Painful neuroma, as one of the complications of nerve injury from disease or trauma, results in instinctive neuropathic pain that adversely affects a patient's quality of life. To intercept neuroma development, capping strategies have been performed as effective therapies. Nonetheless, the most appropriate biocompatible material to shield the nerves is an urgent clinical requirement. Herein, a compatible hydroxyethyl cellulose (HEC)/soy protein isolate (SPI) sponge capping conduit (HSSC) is used to prevent neuroma in vivo. Following capping on the sciatic nerve stump in vivo, the behavior of the rats and the structure of tissues are compared through histological assessment and autotomy scoring. The HSSCs gained a dismal autotomy score and enhanced the amelioration, where inflammatory invasions and overdeposition of collagen are defeated. The expression of myelin growth linked genes (Krox20, MPZ, and MAG) in the HSSC group at the eighth week was almost 2 times higher than that of the no capping group. The HSSC conduit served as a physical barrier to repress the infiltration of inflammation as well as provided an optimum microenvironment for facilitating nerve rejuvenation and intercepting neuroma development during nerve amelioration.

Sacrificial gelatin of PAM-Alginate-BC hydrogel tube with tunable diameter as nerve conduit

Peripheral nerve regeneration is still one of the biggest challenges, autologous nerve transplantation is the 'gold standard' for evaluating its alternative therapy. However, the source of autologous nerves is limited, it is imminent to synthesize a nerve-guiding catheter material with a controllable diameter of a small orifice. Sacrificial gelatin polyacrylamide-Alginate-Bacterial cellulose (PAM-Alginate-BC) hydrogel overcomes poor mechanical properties with tunable diameter. In addition, the PAM-Alginate-BC hydrogel possesses the beneficial properties required for cell scaffolding with surface adhesion ability. The PAM-Alginate-BC materials options have potential applications in peripheral nerve regeneration.

Addition of a Vascular Bundle Accelerates Bone Union in Femoral Bone Defects

BACKGROUND

 The Masquelet method has become increasingly popular for the treatment of bone defects in recent years. In this method, an induced membrane (IM) with abundant blood circulation, stem cells, and osteogenesis-promoting factors is formed by implanting bone cement during the first surgery. This IM stimulates bone formation in the bone defect after implantation of the bone graft during the second surgery. However, the Masquelet method requires two surgeries and thus a longer treatment period. In the present study, we investigated whether bone defects could be reconstructed in a single surgery by introducing a vascular bundle into the bone defect as an alternative to the IM, in addition to bone grafting.

METHODS

 Thirty-six 12-week-old female Sprague-Dawley rats were used. After creating a 5-mm long bone defect in the femur, a mixture of autologous and artificial bone was grafted into the defect, and a saphenous arteriovenous vascular bundle was introduced. The animals were divided into three groups: the control group (bone defect only), the BG group (bone grafting only), and the BG + V group (bone grafting + vascular bundle introduction). After surgery, radiological and histological evaluations were performed to assess osteogenesis and angiogenesis in bone defects.

RESULTS

 In the BG + V group, significant bone formation was observed in the bone defect on radiological and histological evaluations, and the amount of bone formation was significantly higher than that in the other two groups. Furthermore, cortical bone continuity was observed in many specimens in the BG + V group. On histological evaluation, the number of blood vessels was also significantly higher in the BG + V group than in the other two groups.

CONCLUSION

 Our results suggest that the introduction of a vascular bundle in addition to bone grafting can promote bone formation in bone defects and allow for complete bone defect reconstruction in a single surgery.

A new insight on peripheral nerve repair: the technique of internal nerve splinting

OBJECTIVE

Neuropathic pain produced by symptomatic neuromas is an important problem after peripheral nerve injury (PNI). End-to-end anastomosis of the nerve stump for PNI is well established but cannot efficiently prevent neuroma-in-continuity formation.

METHODS

Sciatic nerve injury was used in the experimental model. Seventy-two rats were randomly divided into four groups: rats with nerve anastomosis sites supported with silicone tubes represented the internal nerve splinting (INS) group (n = 18); rats with end-to-end nerve anastomosis represented control group 1 (CON1) (n = 18); rats with INS and the nerve anastomosis site represented control group 2 (CON2) (n = 18); and rats that underwent the same surgical procedures for skin and muscle operations but without sciatic nerve injury represented the normal group (n = 18).

RESULTS

Gross evaluations of the nerve anastomosis sites, gastrocnemius muscle atrophy, axonal regeneration and remyelination, neuropathic pain, and scar hyperplasia of the neuromas were performed, as well as motor function evaluations. Axonal regeneration, remyelination, and gastrocnemius muscle atrophy were similar between the INS group and CON1 (p > 0.05). However, neuropathic pain and scar hyperplasia-as evaluated according to the expression of anti-sigma-1 receptor antibody and anti-α-smooth muscle actin, respectively-and the weight ratios of the neuromas were reduced in the INS group compared with those of CON1 and CON2 (p < 0.05).

CONCLUSIONS

Application of INS in nerve repair effectively prevented traumatic neuroma-in-continuity formation and inhibited neuropathic pain without influencing nerve regeneration in rats.

Nerve-End Capping Treatment with a Polyglycolic Acid Conduit for Rat Sciatic Neuroma: A Preliminary Report

BACKGROUND

 The treatment of painful neuroma remains challenging. Recently, a nerve-end capping technique using a bioabsorbable nerve conduit was newly introduced to treat amputation neuroma. A collagen-coated polyglycolic acid (PGA) conduit has been commercially available for the reconstruction of peripheral nerve defects, yielding successful clinical outcomes. However, no experimental research has been conducted using this PGA nerve conduit as capping device for treating amputation neuroma. The purpose of this study was to investigate nerve-end capping treatment with the PGA conduit in the rat sciatic nerve amputation model, focusing on histological scar formation and neuroinflammation.

METHODS

 Forty-seven rats were divided into two groups: no capping (transected nerve stump without capping; n = 25) and capping (nerve-end capping with collagen-coated PGA nerve conduit; n = 22). Twelve weeks after sciatic neurectomy, neuropathic pain was evaluated using the autotomy score. Stump neuromas were histologically evaluated or perineural scar and neuroinflammation.

RESULTS

 While autotomy scores gradually exacerbated in both groups, they were consistently lower in the capping group at 4, 8, and 12 weeks postprocedure. Twelve weeks after surgery, the transected nerve stumps in the no-capping group had formed macroscopic bulbous neuromas strongly adhering to surrounding tissues, whereas they remained wrapped with the PGA nerve conduits loosely adhering to surrounding tissues in the capping group. Histologically, distal axonal fibers were expanded radially and formed neuromas in the no-capping group, while they were terminated within the PGA conduit in the capping group. Perineural scars and neuroinflammation were widely found surrounding the randomly sprouting nerve end in the no-capping group. In capped counterparts, scars and inflammation were limited to closely around the terminated nerve end.

CONCLUSION

 Nerve-end capping with a collagen-coated PGA conduit after rat sciatic neurectomy might prevent neuroma formation by suppressing perineural scar formation and neuroinflammation around the nerve stump, potentially relieving neuropathic pain.

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

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

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

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

A Photosealed Cap Prevents Disorganized Axonal Regeneration and Neuroma following Nerve Transection in Rats

Neuroma is a common sequela of traumatic peripheral nerve injury that can result in pain and decreased quality of life for patients. Neuromas result from axonal outgrowth in an attempt to reestablish continuity with the disrupted distal nerve end. Photosealing is a light-activated technique whereby tissues can be securely isolated in a strong and secure manner. This study investigated whether photosealing of autologous vein and crosslinked human amniotic membrane (xHAM) to cap the proximal stump of transected sciatic nerve would prevent disorganized axonal regeneration and neuroma in a rat model.

Neuroskeletal Effects of Chronic Bioelectric Nerve Stimulation in Health and Diabetes

Background/Aims

Bioelectric nerve stimulation (eStim) is an emerging clinical paradigm that can promote nerve regeneration after trauma, including within the context of diabetes. However, its ability to prevent the onset of diabetic peripheral neuropathy (DPN) has not yet been evaluated. Beyond the nerve itself, DPN has emerged as a potential contributor to sarcopenia and bone disease; thus, we hypothesized that eStim could serve as a strategy to simultaneously promote neural and musculoskeletal health in diabetes.

Methods

To address this question, an eStim paradigm pre-optimized to promote nerve regeneration was applied to the sciatic nerve, which directly innervates the tibia and lower limb, for 8 weeks in control and streptozotocin-induced type 1 diabetic (T1D) rats. Metabolic, gait, nerve and bone assessments were used to evaluate the progression of diabetes and the effect of sciatic nerve eStim on neuropathy and musculoskeletal disease, while also considering the effects of cuff placement and chronic eStim in otherwise healthy animals.

Results

Rats with T1D exhibited increased mechanical allodynia in the hindpaw, reduced muscle mass, decreased cortical and cancellous bone volume fraction (BVF), reduced cortical bone tissue mineral density (TMD), and decreased bone marrow adiposity. Type 1 diabetes also had an independent effect on gait. Placement of the cuff electrode alone resulted in altered gait patterns and unilateral reductions in tibia length, cortical BVF, and bone marrow adiposity. Alterations in gait patterns were restored by eStim and tibial lengthening was favored unilaterally; however, eStim did not prevent T1D-induced changes in muscle, bone, marrow adiposity or mechanical sensitivity. Beyond this, chronic eStim resulted in an independent, bilateral reduction in cortical TMD.

Conclusion

Overall, these results provide new insight into the pathogenesis of diabetic neuroskeletal disease and its regulation by eStim. Though eStim did not prevent neural or musculoskeletal complications in T1D, our results demonstrate that clinical applications of peripheral neuromodulation ought to consider the impact of device placement and eStim on long-term skeletal health in both healthy individuals and those with metabolic disease. This includes monitoring for compounded bone loss to prevent unintended consequences including decreased bone mineral density and increased fracture risk.

Bioabsorbable nerve conduits three-dimensionally coated with human induced pluripotent stem cell-derived neural stem/progenitor cells promote peripheral nerve regeneration in rats

Peripheral nerve regeneration using nerve conduits has been less effective than autogenous nerve grafts. To overcome this hurdle, we developed a tissue-engineered nerve conduit coated with mouse induced pluripotent stem cell (iPSC)-derived neurospheres, for the first time, which accelerated nerve regeneration in mice. We previously demonstrated the long-term efficacy and safety outcomes of this hybrid nerve conduit for mouse peripheral nerve regeneration. In this study, we investigated the therapeutic potential of nerve conduits coated with human iPSC (hiPSC)-derived neurospheres in rat sciatic nerve defects, as a translational preclinical study. The hiPSC-derived quaternary neurospheres containing neural stem/progenitor cells were three-dimensionally cultured within the nerve conduit (poly l-lactide and polycaprolactone copolymer) for 14 days. Complete 5-mm defects were created as a small size peripheral nerve defect in sciatic nerves of athymic nude rats and reconstructed with nerve conduit alone (control group), nerve conduits coated with hiPSC-derived neurospheres (iPS group), and autogenous nerve grafts (autograft group) (n = 8 per group). The survival of the iPSC-derived neurospheres was continuously tracked using in vivo imaging. At 12 weeks postoperatively, motor and sensory function and histological nerve regeneration were evaluated. Before implantation, the hiPSC-derived quaternary neurospheres that three-dimensional coated the nerve conduit were differentiated into Schwann-like cells. The transplanted hiPSC-derived neurospheres survived for at least 56 days after implantation. The iPS group showed non-significance higher sensory regeneration than the autograft group. Although there was no actual motor functional nerve regeneration in the three groups: control, iPS, and autograft groups, the motor function in the iPS group recovered significantly better than that in the control group, but it did not recover to the same level as that in the autograft group. Histologically, the iPS group demonstrated significantly higher axon numbers and areas, and lower G-ratio values than the control group, whereas the autograft group demonstrated the highest axon numbers and areas and the lowest G-ratio values. Nerve conduit three-dimensionally coated with hiPSC-derived neurospheres promoted axonal regeneration and functional recovery in repairing rat sciatic nerve small size defects. Transplantation of hiPSC-derived neurospheres with nerve conduits is a promising clinical iPSC-based cell therapy for the treatment of peripheral nerve defects.