Nerve Capping Techniques for Neuroma Management: A Comprehensive Literature Review.

BACKGROUND/AIM OF THE STUDY: Nerve capping is a method of neuroma treatment or prevention that consists of the transplantation of a proximal nerve stump into an autograft or other material cap, after surgical removal of the neuroma or transection of the nerve. The aim was to reduce neuroma formation and symptoms by preventing neuronal adhesions and scar tissue. In this narrative literature review, we summarize the studies that have investigated the effectiveness of nerve capping for neuroma management to provide clarity and update the clinician's knowledge on the topic. METHODS: A systematic electronic search following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses criteria was performed in the PubMed database combining "neuroma," "nerve," "capping," "conduit," "treatment," "management," "wrap," "tube," and "surgery" as search terms. English-language clinical studies on humans and animals that described nerve capping as a treatment/prevention technique for neuromas were then selected based on a full-text article review. The data from the included studies were compiled based on the technique and material used for nerve capping, and technique and outcomes were reviewed. RESULTS: We found 10 applicable human studies from our literature search. Several capping materials were described: epineurium, nerve, muscle, collagen nerve conduit, Neurocap (synthetic copolymer of lactide and caprolactone, which is biocompatible and resorbable), silicone rubber, and collagen. Overall, 146 patients were treated in the clinical studies. After surgery, many patients were completely pain-free or had considerable improvement in pain scores, whereas some patients did not have improvement or were not satisfied after the procedure. Nerve capping was used in 18 preclinical animal studies, using a variety of capping materials including autologous tissues, silicone, and synthetic nanofibers. Preclinical studies demonstrated successful reduction in rates of neuroma formation. CONCLUSIONS: Nerve capping has undergone major advancements since its beginnings and is now a useful option for the treatment or prevention of neuromas. As knowledge of peripheral nerve injuries and neuroma prevention grows, the criterion standard neuroprotective material for enhancement of nerve regeneration can be identified and applied to produce reliable surgical outcomes.

Repair of Congenital Enlarged Parietal Foramina With Porous Polyethylene Implants.

Enlarged biparietal foramina is an autosomal dominant disorder that is caused by a failure of completion of ossification within the parietal bones. Enlarged parietal foramina measuring more than a few millimeters are uncommon. Even though spontaneous regression has been described, closure is rarely complete, and depending on the size of the resulting defect, an unprotected brain is a concern. There are few reports on the surgical management of persistent enlarged biparietal foramina. This is the first report describing our experience with a custom porous polyethylene implant.

The effect of thymus transplantation on donor-specific chimerism in the rat model of composite osseomusculocutaneous sternum, ribs, thymus, pectoralis muscles, and skin allotransplantation.

INTRODUCTION: Research on tolerance has proven that development of donor-specific chimerism (DSC) may accompany tolerance induction in vascularized composite allotransplantation (VCA). In this study, we aimed to determine the effect of thymus transplantation on the induction of DSC in rat VCA model of osseomusculocutaneous sternum (OMCS) and osseomusculocutaneous sternum and thymus (OMCST) allotransplantation. MATERIALS AND METHODS: A total of 20 Lewis-Brown Norway and Lewis rats, 5-6 weeks old, weighting between 120 and 150 g, were used in the study. OMCS (n = 5) and OMCST (n = 5) allografts were harvested from Lewis-Brown Norway donors (RT1l + n ) based on the common carotid artery and external jugular vein, and a heterotopic transplantation was performed to the inguinal region of the Lewis (RT1l ) recipients under cyclosporine A monotherapy (16 mg/kg) protocol tapered to 2 mg/kg and maintained for the duration of the study. The peripheral blood chimerism levels (T-cell, B-cell, and monocyte/granulocyte/dendritic cell-MGDC populations) were evaluated at days 7, 14, 35, 63, 100, and 150 posttransplant by flow cytometry. At Day 150, thymus, spleen, and liver samples were assessed by polymerase chain reaction (PCR) in the presence of DSC. RESULTS: Total chimerism level increased in both OMCST and OMCS groups at all time points. At 150 days posttransplant, chimerism in OMCST group was significantly higher (12.91 ± 0.16%) than that in OMCS group (8.89 ± 0.53%%, p < .01), and PCR confirmed the presence of donor-derived cells in the liver and spleen of all OMCST recipients and in one liver sample and two spleen samples in OMCS recipients without thymus transplant. CONCLUSIONS: This study confirmed the direct effects of thymus transplantation on the induction and maintenance of DSC in T-cell, B-cell, and MGDC populations. These results confirm correlation between thymus transplantation and DSC induction.

Application of epineural sheath conduit for restoration of 6-cm long nerve defects in a sheep median nerve model.

BACKGROUND: Due to limited number of studies, we tested feasibility of autologous epineural sheath conduit (ESC) in repair of 6-cm median nerve gaps in a sheep-the large animal model. MATERIALS AND METHODS: Eight ewes, 6-8 months old, 30-35 kg, were divided into three experimental groups: group 1-no defect repair (n = 4 nerves/group), group 2-autograft controls (n = 6 nerves/group), group 3-autologous ESC filled with saline (n = 6 nerves/group). ESC was constructed from a 6-cm long segment of sheep median nerve and tested for expression of laminin B, Glial fibrillary acidic protein (GFAP), S-100 and CD31 using immunofluorescent staining. At 6 months after nerve repair, nerve conduction velocity and somatosensory evoked potentials (SSEP) assessed neurosensory recovery, while histomorphometry tested nerve regeneration. RESULTS: Ex vivo characterization of ESC, before in vivo nerve gap repair, showed high laminin B expression, which supports axonal growth. At 6 months post-repair, structural integrity of ESC was preserved. ESC was well-vascularized and tissue adhesions were comparable to autograft controls. The maximal conduction velocities (29.80 ± 5.85 ms vs. 32.28 ± 6.75 ms; p = .44), action potential amplitudes (32.68 ± 17.44 mV vs. 44.14 ± 23.10 mV; p = .38) and SSEP amplitude values (6.18 ± 5.84 mV vs. 4.68 ± 2.53 mV; p = .28) were comparable between autograft and ESC groups. Presence of regenerating axons was confirmed in the distal segment of ESC at 6 months after repair. CONCLUSION: The feasibility of ESC in restoration of 6-cm long nerve defects in a sheep median nerve model was confirmed by nerve conduction assessments and correlated with axonal regeneration tested by histomorphometry. We confirmed ESC potential in support of regeneration of long nerve defects.

Development of Targeted Muscle Reinnervation Model in Hind Limb Amputated Rats.

BACKGROUND: Targeted muscle reinnervation (TMR) is a novel approach to postamputation neuroma pain; however, this has not been explicitly studied. The purpose of this study was to develop a TMR model in hind limb amputated rats. METHODS: Ten hind limbs from 5 Sprague Dawley cadaver rats were used. Sciatic nerve, main branches of the sciatic nerve (common peroneal, tibial, sural), motor branches from the sciatic nerve to the biceps femoris and cauda femoris, gluteal nerve and its motor branches to the semimembranosus, and biceps femoris and femoral nerve were dissected to look for consistent nerve anatomy that can be used for TMR in the rat hind limb amputation model. Transfemoral amputation was performed and two types of coaptations were made: common peroneal nerve to motor branch to biceps femoris and tibial nerve to motor branch to semimembranosus. RESULTS: The total surgical time for the dissection, amputation, and coaptation of nerves was ∼90 minutes. A total of 100 nerves were dissected in 10 rat hind limbs. Anatomical dissections were straightforward to perform. Anatomy of the dissected nerves was consistent. Hind limb amputations were performed without damaging the target muscles and nerves. Nerve lengths were sufficient for coaptation without any tension. CONCLUSIONS: To the best of our knowledge, this is the first report on TMR model in hind limb amputated rats. This model will allow for mechanical, electromyography (EMG), and histological analysis for future assessment of neuroma prevention.

A New Composite Eyeball-Periorbital Transplantation Model in Humans: An Anatomical Study in Preparation for Eyeball Transplantation.

BACKGROUND: Vascularized composite allotransplantation offers a new hope for restoration of orbital content and perhaps vision. The aim of this study was to introduce a new composite eyeball-periorbital transplantation model in fresh cadavers in preparation for composite eyeball allotransplantation in humans. METHODS: The composite eyeball-periorbital transplantation flap borders included the inferior border, outlined by the infraorbital rim; the medial border, created by the nasal dorsum; the lateral border, created by the lateral orbital rim; and the superior border, created by the superior part of the eyebrow. The pedicle of the flap included the facial artery, superficial temporal artery, and external jugular vein. The skin and subcutaneous tissues of the periorbital region were dissected and the bony tissue was reached. A coronal incision was performed and the frontal lobe of the brain was reached by means of frontal osteotomy. Ophthalmic and oculomotor nerves were also included in the flap. After a "box osteotomy" around the orbit, the dissection was completed. Methylene blue and indocyanine green injection (SPY Elite System) was performed to show the integrity of the vascular territories after facial flap harvest. RESULTS: Adequate venous return was observed within the flap after methylene blue dye injection. Laser-assisted indocyanine green angiography identified a well-defined vascular network within the entire composite eyeball-periorbital transplantation flap. CONCLUSIONS: For the first time, a novel composite eyeball-periorbital transplantation model in human cadavers was introduced. Good perfusion of the flap confirmed the feasibility of composite eyeball-periorbital transplantation in the clinical setting. Although harvesting of the flap is challenging, it introduces a new option for reconstruction of the periorbital region including the eyeball.

Comparison of Resorbable Mesh (Poly L-Lactide/Glycolic Acid) and Porous Polyethylene in Orbital Floor Fractures in an Experimental Model.

BACKGROUND: Resorbable mesh and porous polyethylene are frequently used alloplastic materials for the treatment of the orbital blowout fractures. The literature lacks reports comparing their long-term effects on experimental models. OBJECTIVE: Our aim was to radiologically and histologically evaluate the effectiveness and safety of porous polyethylene and resorbable mesh in a rabbit orbital blowout fracture model. METHODS: Twelve New Zealand white rabbits (24 orbits) were randomized to 4 groups. In group 1, only orbital floor dissection was done. In group 2, following orbital floor dissection, a 10-mm defect was created without any extra procedure. In group 3, following a 10-mm defect creation, a 12-mm-round cut porous polyethylene was placed on the defect. In group 4, following a 10-mm defect creation, a 12-mm-round cut resorbable mesh was placed on the defect. Computed tomographic analysis was performed during follow-up period. Orbital floors were evaluated histologically at month 6. RESULTS: No clinical complications were observed during follow-up period. In radiological evaluation, there was no statistically significant difference between groups regarding bone formation. In histological evaluation, the connective tissue was denser, and organized and better bone formation was observed in group 3 and 4 when compared with other groups. CONCLUSION: Although no significant radiological changes were present, porous polyethylene and resorbable mesh performed better histologically. They were effective and well tolerated for reconstruction of the isolated orbital floor defects.

HISTORIQUE: Le treillis résorbable et le polyéthylène poreux sont des matériaux alloplastiques souvent utilisés pour traiter les fractures isolées du plancher de l'orbite. Les publications ne contiennent pas de rapports sur les effets à long terme de ces matériaux dans des modèles expérimentaux. OBJECTIF: Les chercheurs visaient à évaluer l'efficacité et la sécurité du polyéthylène poreux et du treillis résorbable sur le plan radiologique et histologique dans un modèle de fracture isolée du plancher de l'orbite chez un lapin. MÉTHODOLOGIE: Douze lapins blancs néo-zélandais (24 orbites) ont été répartis au hasard en quatre groupes. Le groupe 1 a seulement subi la dissection du plancher de l'orbite. Dans le groupe 2, après cette dissection, une anomalie de 10 mm a été créée sans intervention supplémentaire. Dans le groupe 3, après la création d'une anomalie de 10 mm, une coupe ronde de polyéthylène poreux de 12 mm a été placée sur l'anomalie. Dans le groupe 4, après la création d'une anomalie de 10 mm, une coupe ronde de treillis résorbable de 12 mm a été placée sur l'anomalie. Les chercheurs ont effectué une analyse tomodensitométrique pendant la période de suivi. Au sixième mois, ils ont évalué les planchers orbitaux à l'histologie. RÉSULTATS: Les chercheurs n'ont observé aucune complication clinique pendant la période de suivi. À l'évaluation radiologique, la formation osseuse ne présentait aucune différence statistiquement significative entre les groupes. À l'évaluation histologique, les tissus conjonctifs étaient plus denses et la formation osseuse était organisée et de meilleure qualité dans les groupes 3 et 4 que dans les autres groupes. CONCLUSION: Malgré l'absence de modification significative à la radiologie, le polyéthylène poreux et le treillis résorbable donnaient de meilleurs résultats sur le plan histologique. Ces matériaux étaient efficaces et bien tolérés pour la reconstruction des anomalies isolées du plancher orbital.

Application of Epineural Sheath as a Novel Approach for Fat Volume Maintenance.

INTRODUCTION: Various methods have been suggested to improve fat graft survival and decrease graft loss. The exact mechanism of fat graft survival is still unclear, and new strategies are needed to further investigate it. MATERIALS AND METHODS: The efficacy of epineural sheath in fat volume maintenance was tested in rat model. Five experimental groups were created: group 1, fat graft without any coverage; group 2, epineural sheath tube alone; group 3, epineural sheath tube filled with fat graft; group 4, fat graft mixed with minced epineural sheath without any coverage; and group 5, fat graft covered with the epineural sheath patch. All grafts were implanted into the dorsal subcutaneous region and were followed for up to 12 weeks, when samples were harvested for hematoxylin and eosin and immunostaining for vascular endothelial growth factor expression and perilipin evaluation of fat viability. RESULTS: In groups 1 and 4, over 25% of graft loss was observed at first week, over 50% at third week, and 100% at sixth week postimplantation. The weight of fat graft within the epineural sheath tube and the weight of epineural tube (ET) alone were maintained up to 12 weeks postimplantation. The weight of fat graft within the epineural patch was maintained up to 6 weeks, but 50% of weight loss was observed between 6 and 12 weeks. Structure of the epineural sheath tubes and patches was intact, and no leakage of fat graft was observed. Based on hematoxylin and eosin staining, normal structure and integrity of the fat graft within the ET were preserved up to 12 weeks postimplantation. Characteristic adipocyte morphology was confirmed by perilipin staining, showing viable fat cells in groups 3 and 5 at 12 weeks. Increased vascular endothelial growth factor expression was observed in groups 2, 3, 4, and 5. CONCLUSIONS: Both, the ETs and epineural patches maintained 100% and 50% of fat graft weight at 12 weeks postimplantation, respectively. These results were confirmed by histology and immunostaining showing viable adipocytes within the epineural patches (6 weeks) and tubes (12 weeks). These results are encouraging and justify further evaluation of fat volume maintenance in preclinical large animal model in preparation to clinical application.

Epineural Sheath Jacket as a New Surgical Technique for Neuroma Prevention in the Rat Sciatic Nerve Model.

BACKGROUND: Terminal neuromas resulting from severe nerve injuries and traumatic or surgical limb amputations can become a source of pain, and significantly impair patients' quality of life. Recently, the number of patients with peripheral nerve injuries increased due to modern war conflicts, natural disasters, and traffic accidents. This study investigated the efficacy of the epineural sheath jacket (ESJ) as a novel technique for neuroma prevention in the rat sciatic nerve model. METHODS: A 20-mm segment of the right sciatic nerve was excised in 18 Lewis rats, and the animals were divided into 3 experimental groups (n = 6/group): group I-control, nerve stump without protection; group II-muscle burying group, nerve stump buried in the muscle; group III-ESJ group, nerve stump protected by ESJ. The ESJ was created from the excised sciatic nerve and applied as a "cap" over the proximal nerve stump. The presence of neuropathic pain was assessed weekly by pinprick test and Tinel sign, up to 24 weeks postsurgery. At 24 weeks, assessments, such as macroscopic evaluation, retrograde neuronal labeling analysis, histomorphometry, and neural/connective tissue ratio were performed. RESULTS: Epineural sheath jacket significantly reduced neuroma formation, which was associated with decreased Tinel sign (16.7%, P < 0.05) response compared with the nerve stump control. Moreover, ESJ reduced axonal sprouting, bulb-shaped nerve ending formation and perineural adhesions, as confirmed by macroscopic evaluation. Histological evaluation confirmed that nerve stumps protected with the ESJ showed less fibrosis and presented well-organized axonal structure. Neural/connective tissue ratio and retrograde neuronal labeling analysis revealed significantly improved results in the ESJ group compared to the control nerve stump group (P = 0.032 and P = 0.042, respectively). CONCLUSIONS: The protective effect of the ESJ against neuroma formation was confirmed by behavioral and histological analyses, showing outcomes comparable to the muscle burying technique-the criterion standard of neuroma management.