Long-term results of peripheral nerve repair: A comparison of nerve anastomosis with ethyl-cyanoacrylate and epineural sutures

Tensile strength of adhesives in peripheral nerve anastomoses: an in vitro biomechanical evaluation of four different neurorrhaphies

BACKGROUND

The fundamental prerequisite for prognostically favorable postoperative results of peripheral nerve repair is stable neurorrhaphy without interruption and gap formation.

METHODS

This study evaluates 60 neurorrhaphies on femoral chicken nerves in terms of the procedure and the biomechanical properties. Sutured neurorrhaphies (n = 15) served as control and three sutureless adhesive-based nerve repair techniques: Fibrin glue (n = 15), Histoacryl glue (n = 15), and the novel polyurethane adhesive VIVO (n = 15). Tensile and elongation tests of neurorrhaphies were performed on a tensile testing machine at a displacement rate of 20 mm/min until failure. The maximum tensile force and elongation were recorded.

RESULTS

All adhesive-based neurorrhaphies were significant faster in preparation compared to sutured anastomoses (p < 0.001). Neurorrhaphies by sutured (102.8 [cN]; p < 0.001), Histoacryl (91.5 [cN]; p < 0.001) and VIVO (45.47 [cN]; p < 0.05) withstood significant higher longitudinal tensile forces compared to fibrin glue (10.55 [cN]). VIVO, with △L/L0 of 6.96 [%], showed significantly higher elongation (p < 0.001) compared to neurorrhaphy using fibrin glue.

CONCLUSION

Within the limitations of an in vitro study the adhesive-based neurorrhaphy technique with VIVO and Histoacryl have the biomechanical potential to offer alternatives to sutured neuroanastomosis because of their stability, and faster handling. Further in vivo studies are required to evaluate functional outcomes and confirm safety.

Efficacy of platelet-rich fibrin and tacrolimus on facial nerve regeneration: an animal study

This study was performed to investigate the effect of platelet-rich fibrin membrane (PRFM), alone and with topical tacrolimus application, on regeneration of the crushed facial nerve (FN). Thirty healthy 7-week-old albino rats were used. The left FN was damaged by crushing in all rats. Three random groups of rats were formed: group 1, untreated; group 2, treated with PRFM; group 3, treated with PRFM plus topical tacrolimus. Functional recovery and histological and immunohistochemical evaluations were performed 4 and 8 weeks later. Anti-S100 was used to detect myelin sheath. At 4 weeks, blinking reflex recovery was more rapid in group 3 than in groups 2 and 1 (4.30 ± 0.48, 3.40 ± 0.52, and 2.20 ± 0.42, respectively); the difference was statistically significant (P = 0.001). Histologically, group 3 showed more apparent normal FN structures than the other groups. Immunohistochemical caspase-3 evaluation of the axon area revealed a significant difference between group 2 (PRFM alone; 8.67 ± 0.029) and group 3 (PRFM plus topical tacrolimus; 4.42 ± 0.028) (P = 0.001). Group 3 showed the greatest positive staining in the myelin sheath. Based on the results of this animal study, clinical studies should be performed to determine whether the combination of PRF and tacrolimus also improves the outcome of nerve regeneration in humans.

Short-chain cyanoacrylates and long-chain cyanoacrylates (Dermabond) have different antimicrobial effects

Objective

To compare the antimicrobial effect in vitro of a short-chain cyanoacrylate with a long-chain cyanoacrylate (Dermabond, Ethicon, Johnson and Johnson, USA) against bacterial strains.

Methods and analysis

The following bacterial strains were analysed: Staphylococcus aureus, Escherichia coli, Klebsiella pneumonia and Pseudomonas aeruginosa. For each microorganism, standardised sterile discs (6 mm) containing 10 µL of ethyl-cyanoacrylate and 2-octyl cyanoacrylate were applied to the plate. All plates received a blank filter-paper disc with no adhesive (control). All plates were incubated for 24 hours, after which the bacterial inhibitory halos, if present, were measured in millimetres in its greater length.

Results

Inhibitory halos were observed for both adhesives for S. aureus. Inhibition halos were observed only for ethyl-cyanoacrylate for K. pneumoniae and E. coli. No inhibition halo was observed for P. aeruginosa in any sample. The relationship between the total size of the inhibition halos and the diameter of the paper filter for S. aureus was statistically significant compared with 2-octyl cyanoacrylate.

Conclusion

Data shown conclude that ethyl-cyanoacrylate showed in vitro bacteriostatic activity for S. aureus, E. coli and K. pneumoniae. 2-Octyl cyanoacrylate showed in vitro lower bacteriostatic activity only against S. aureus when compared with ethyl-cyanoacrylate. No in vitro bactericidal activity of ethyl-cyanoacrylate or 2-octyl cyanoacrylate was observed.

Fibrin Glue and Its Alternatives in Peripheral Nerve Repair

Over the past century, many advancements have been made in peripheral nerve repair, yet these reconstructions still remain a challenge. Although sutures have historically been used for neurorrhaphy, they sometimes fail to provide optimal outcomes. As a result, multiple adhesive compounds are currently being investigated for their efficacy in nerve repair. Recently, fibrin glue has shown utility in peripheral nerve repair, and the body of evidence supporting its use continues to grow. Fibrin glue has been shown to reduce inflammation, improve axonal regeneration, and provide excellent functional results. This alternative to traditional suture neurorrhaphy could potentially improve outcomes of peripheral nerve reconstruction.

Comparison of peripheral nerve repair using ethyl-cyanoacrylate and conventional suture technique in a rat sciatic nerve injury model

OBJECTIVE

The aim of this study was to compare the outcomes of primary nerve repair using either ethyl-cyanoacrylate or conventional microsuture technique in a rat peripheral nerve injury model.

METHODS

In this study, a total of 30 Wistar Albino rats weighing between 220 and 275 g were used. The rats were randomly divided into three groups (10 in each), including one control (group 1) and two experimental groups (group 2, conventional microsuture repair; group 3, cyanoacrylate repair). In each group, the sciatic nerve was identified and transected. No further intervention was performed in group 1. The nerve was repaired using the epineural technique with a 10/0 atraumatic nylon in group 2 and synthetic cyanoacrylate adhesive in group 3. At the fifth postoperative week, needle electromyography (EMG) was performed to measure distal latency, combined muscle action potential (CMAP), and motor nerve conduction velocity (MNCV). Following the EMG recordings, animals were euthanized. Nerve samples were collected to evaluate vacuolar degeneration, fibrosis, and foreign body reaction histopathologically.

RESULTS

In the EMG analysis, mean distal latency was significantly shorter in group 1 (0.85±0.09 ms) than in groups 2 (1.17±0.25 ms) (p=0.0052) and 3 (1.14±0.14 ms) (p=0.0026) while no significant differences existed between groups 2 and 3 (p>0.9999). The mean CMAP was greater in group 1 (10.5±0.35 mV) than in groups 2 (2.86±1.28 mV) (p=0.011) and 3 (2.16±1.34 mV) (p=0.0002), but there was no significant difference between groups 2 and 3 (p>0.9999). The mean MNCV was 53.5±5.95, 39.62±7.31, and 39.84±4.73 mm/sec in groups 1, 2, and 3, respectively. There was a significant difference between groups 1 and 2 (p=0.0052) and between 1 and 3 (p=0.0026), but not between 2 and 3 (p>0.9999). In the histopathological evaluation, the mean vacuolar degeneration score was 0, 2.12, and 1.88 in groups 1, 2, and 3, respectively. No obvious difference was observed between groups 2 and 3 (p=0.743). The mean fibrosis score was 0, 1.62, and 1.77 in groups 1, 2, and 3, respectively. There was no significant difference between groups 2 and 3 (p=0.888). The mean foreign body reaction score was 0, 2.5, and 2.44 in groups 1, 2, and 3, respectively. No difference was present between groups 2 and 3 (p=0.743).

CONCLUSION

Primary nerve repair using the cyanoacrylate adhesive may provide similar electrophysiological and histopathological results as compared to the conventional microsuture repair.

Animal models used to study direct peripheral nerve repair: a systematic review

Objective:

Peripheral nerve repair is required after traumatic injury. This common condition represents a major public health problem worldwide. Recovery after nerve repair depends on several factors, including the severity of the injury, the nerve involved, and the surgeon’s technical skills. Despite the precise microsurgical repair of nerve lesions, adequate functional recovery is not always achieved and, therefore, the regeneration process and surgical techniques are still being studied. Pre-clinical animal models are essential for this research and, for this reason, the focus of the present systematic review (according to the PRISMA statement) was to analyze the different animal models used in pre-clinical peripheral nerve repair studies.

Data sources:

Original articles, published in English from 2000 to 2018, were collected using the Web of Science, Scopus, and PubMed databases.

Data selection:

Only preclinical trials on direct nerve repair were included in this review. The articles were evaluated by the first two authors, in accordance with predefined data fields.

Outcome measures:

The primary outcomes included functional motor abilities, daily activity and regeneration rate. Secondary outcomes included coaptation technique and animal model.

Results:

This review yielded 267 articles, of which, after completion of the screening, 49 studies were analyzed. There were 1425 animals in those 49 studies, being rats, mice, guinea pigs, rabbits, cats and dogs the different pre-clinical models. The nerves used were classified into three groups: head and neck (11), forelimb (8) and hindlimb (30). The techniques used to perform the coaptation were: microsuture (46), glue (12), laser (8) and mechanical (2). The follow-up examinations were histology (43), electrophysiological analysis (24) and behavioral observation (22).

Conclusion:

The most widely used animal model in the study of peripheral nerve repair is the rat. Other animal models are also used but the cost-benefit of the rat model provides several strengths over the others. Suture techniques are currently the first option for nerve repair, but the use of glues, lasers and bioengineering materials is increasing. Hence, further research in this field is required to improve clinical practice.

Photocrosslinkable Gelatin/Tropoelastin Hydrogel Adhesives for Peripheral Nerve Repair

Suturing peripheral nerve transections is the predominant therapeutic strategy for nerve repair. However, the use of sutures leads to scar tissue formation, hinders nerve regeneration, and prevents functional recovery. Fibrin-based adhesives have been widely used for nerve reconstruction, but their limited adhesive and mechanical strength and inability to promote nerve regeneration hamper their utility as a stand-alone intervention. To overcome these challenges, we engineered composite hydrogels that are neurosupportive and possess strong tissue adhesion. These composites were synthesized by photocrosslinking two naturally derived polymers, gelatin-methacryloyl (GelMA) and methacryloyl-substituted tropoelastin (MeTro). The engineered materials exhibited tunable mechanical properties by varying the GelMA/MeTro ratio. In addition, GelMA/MeTro hydrogels exhibited 15-fold higher adhesive strength to nerve tissue ex vivo compared to fibrin control. Furthermore, the composites were shown to support Schwann cell (SC) viability and proliferation, as well as neurite extension and glial cell participation in vitro, which are essential cellular components for nerve regeneration. Finally, subcutaneously implanted GelMA/MeTro hydrogels exhibited slower degradation in vivo compared with pure GelMA, indicating its potential to support the growth of slowly regenerating nerves. Thus, GelMA/MeTro composites may be used as clinically relevant biomaterials to regenerate nerves and reduce the need for microsurgical suturing during nerve reconstruction.

A novel chronic nerve compression model in the rat

Current animal models of chronic peripheral nerve compression are mainly silicone tube models. However, the cross section of the rat sciatic nerve is not a perfect circle, and there are differences in the diameter of the sciatic nerve due to individual differences. The use of a silicone tube with a uniform internal diameter may not provide a reliable and consistent model. We have established a chronic sciatic nerve compression model that can induce demyelination of the sciatic nerve and lead to atrophy of skeletal muscle. In 3-week-old pups and adult rats, the sciatic nerve of the right hind limb was exposed, and a piece of surgical latex glove was gently placed under the nerve. N-butyl-cyanoacrylate was then placed over the nerve, and after it had set, another piece of glove latex was placed on top of the target area and allowed to adhere to the first piece to form a sandwich-like complex. Thus, a chronic sciatic nerve compression model was produced. Control pups with latex or N-butyl-cyanoacrylate were also prepared. Functional changes to nerves were assessed using the hot plate test and electromyography. Immunofluorescence and electron microscopy analyses of the nerves were performed to quantify the degree of neuropathological change. Masson staining was conducted to assess the degree of fibrosis in the gastrocnemius and intrinsic paw muscles. The pup group rats subjected to nerve compression displayed thermal hypoesthesia and a gradual decrease in nerve conduction velocity at 2 weeks after surgery. Neuropathological studies demonstrated that the model caused nerve demyelination and axonal irregularities and triggered collagen deposition in the epineurium and perineurium of the affected nerve at 8 weeks after surgery. The degree of fibrosis in the gastrocnemius and intrinsic paw muscles was significantly increased at 20 weeks after surgery. In conclusion, our novel model can reproduce the functional and histological changes of chronic nerve compression injury that occurs in humans and it will be a useful new tool for investigating the mechanisms underlying chronic nerve compression.

Epineurial Window Is More Efficient in Attracting Axons than Simple Coaptation in a Sutureless (Cyanoacrylate-Bound) Model of End-to-Side Nerve Repair in the Rat Upper Limb: Functional and Morphometric Evidences and Review of the Literature

End-to-side nerve coaptation brings regenerating axons from the donor to the recipient nerve. Several techniques have been used to perform coaptation: microsurgical sutures with and without opening a window into the epi(peri)neurial connective tissue; among these, window techniques have been proven more effective in inducing axonal regeneration. The authors developed a sutureless model of end-to-side coaptation in the rat upper limb. In 19 adult Wistar rats, the median and the ulnar nerves of the left arm were approached from the axillary region, the median nerve transected and the proximal stump sutured to the pectoral muscle to prevent regeneration. Animals were then randomly divided in two experimental groups (7 animals each, 5 animals acting as control): Group 1: the distal stump of the transected median nerve was fixed to the ulnar nerve by applying cyanoacrylate solution; Group 2: a small epineurial window was opened into the epineurium of the ulnar nerve, caring to avoid damage to the nerve fibres; the distal stump of the transected median nerve was then fixed to the ulnar nerve by applying cyanoacrylate solution. The grasping test for functional evaluation was repeated every 10-11 weeks starting from week-15, up to the sacrifice (week 36). At week 36, the animals were sacrificed and the regenerated nerves harvested and processed for morphological investigations (high-resolution light microscopy as well as stereological and morphometrical analysis). This study shows that a) cyanoacrylate in end-to-side coaptation produces scarless axon regeneration without toxic effects; b) axonal regeneration and myelination occur even without opening an epineurial window, but c) the window is related to a larger number of regenerating fibres, especially myelinated and mature, and better functional outcomes.

Nerve repair: toward a sutureless approach

Peripheral nerve repair for complete section injuries employ reconstructive techniques that invariably require sutures in their application. Sutures are unable to seal the nerve, thus incapable of preventing leakage of important intraneural fluids from the regenerating nerve. Furthermore, sutures are technically demanding to apply for direct repairs and often induce detrimental scarring that impedes healing and functional recovery. To overcome these limitations, biocompatible and biodegradable glues have been used to seal and repair peripheral nerves. Although creating a sufficient seal, they can lack flexibility and present infection risks or cytotoxicity. Other adhesive biomaterials have recently emerged into practice that are usually based on proteins such as albumin and collagen or polysaccharides like chitosan. These adhesives form their union to nerve tissue by either photothermal (tissue welding) or photochemical (tissue bonding) activation with laser light. These biomaterial adhesives offer significant advantages over sutures, such as their capacity to unite and seal the epineurium, ease of application, reduced invasiveness and add the potential for drug delivery in situ to facilitate regeneration. This paper reviews a number of different peripheral nerve repair (or reconstructive) techniques currently used clinically and in experimental procedures for nerve injuries with or without tissue deficit.

Nerve glue for upper extremity reconstruction

Nerve glue is an attractive alternative to sutures to improve the results of nerve repair. Improved axon alignment, reduced scar and inflammation, greater and faster reinnervation, and better functional results have been reported with the use of nerve glue. The different types of nerve glue and the evidence to support or oppose their use are reviewed. Although the ideal nerve glue has yet to be developed, fibrin sealants can be used as nerve glue in select clinical situations. Technology to allow suture-free nerve repair is one development that can potentially improve functional nerve recovery and the outcomes of upper extremity reconstruction.

Effectiveness of fibrin adhesive in facial nerve anastomosis in dogs compared with standard microsuturing technique

PURPOSE

Epineural suturing is the most common technique used for peripheral nerve anastomosis. In addition to the foreign body reaction to the suture material, the surgical duration and difficulty of suturing in confined anatomic locations are major problems. We evaluated the effectiveness of fibrin glue as an acceptable alternative for nerve anastomosis in dogs.

METHODS

Eight adult female dogs weighing 18 to 24 kg were used in the present study. The facial nerve was transected bilaterally. On the right side, the facial nerve was subjected to epineural suturing; and on the left side, the nerve was anastomosed using fibrin adhesive. After 16 weeks, the nerve conduction velocity and proportion of the nerve fibers that crossed the anastomosis site were evaluated and compared for the epineural suture (right side) and fibrin glue (left side). The data were analyzed using the paired t test and univariate analysis of variance.

RESULTS

The mean postoperative nerve conduction velocity was 29.87 ± 7.65 m/s and 26.75 ± 3.97 m/s on the right and left side, respectively. No statistically significant difference was found in the postoperative nerve conduction velocity between the 2 techniques (P = .444). The proportion of nerve fibers that crossed the anastomotic site was 71.25% ± 7.59% and 72.25% ± 8.31% on the right and left side, respectively. The histologic evaluation showed no statistically significant difference in the proportion of the nerve fibers that crossed the anastomotic site between the 2 techniques (P = .598).

CONCLUSIONS

The results suggest that the efficacies of epineural suturing and fibrin gluing in peripheral nerve anastomosis are similar.

Histomorphometric changes in repaired mouse sciatic nerves are unaffected by the application of a scar-reducing agent

Microsurgical repair of transected peripheral nerves is compromised by the formation of scar tissue and the development of a neuroma, thereby limiting the success of regeneration. The aim of this study was to quantify histomorphometrically the structural changes in neural tissue that result from repair, and determine the effect of mannose-6-phosphate (M6P), a scar-reducing agent previously shown to enhance regeneration. In anaesthetised C57-black-6 mice, the left sciatic nerve was sectioned and repaired using four epineurial sutures. Either 100 μL of 600 mm M6P (five animals) or 100 μL of phosphate-buffered saline (placebo controls, five animals) was injected into and around the nerve repair site. A further group acted as sham-operated controls. After recovery for 6 weeks, the nerve was harvested for analysis using light and electron microscopy. Analysis revealed that when compared with sham controls, myelinated axons had smaller diameters both proximal and distal to the repair. Myelinated axon counts, axonal density and size all decreased across the repair site. There were normal numbers and densities of non-myelinated axons both proximal and distal to the repair. However, there were more Remak bundles distal to the repair site, and fewer non-myelinated axons per Remak bundle. Application of M6P did not affect any of these parameters.

Selectivity in the reinnervation of the lateral gastrocnemius muscle after nerve repair with ethyl cyanoacrylate in the rat

There is a need for complementary surgical techniques that enable rapid and reliable primary repair of transected nerves. Previous studies after peripheral nerve transection and repair with synthetic adhesives have demonstrated regeneration to an extent comparable to that of conventional techniques. The aim of this study was to compare two different repair techniques on the selectivity of muscle reinnervation after repair and completed regeneration. We used the cholera toxin B technique of retrograde axonal tracing to evaluate the morphology, the number, and the three-dimensional location of α-motoneurons innervating the lateral gastrocnemius muscle and compared the results after repair with either ethyl cyanoacrylate (ECA) or epineural sutures of the transected parent sciatic nerve. In addition, we recorded the wet weight of the muscle. Six months after transection and repair of the sciatic nerve, the redistribution of the motoneuron pool was markedly disorganized, the motoneurons had apparently increased in number, and they were scattered throughout a larger volume of the spinal cord gray matter with a decrease in the synaptic coverage compared to controls. A reduction in muscle weight was observed as well. No difference in morphometric variables or muscle weight between the two repair methods could be detected. We conclude that the selectivity of motor reinnervation following sciatic nerve transection and subsequent repair with ECA is comparable to that following conventional micro suturing.

Treatment of transected peripheral nerves with artemin improved motor neuron regeneration, but did not reduce nerve injury-induced pain behaviour

Incomplete recovery of function and neuropathic pain are common problems after peripheral nerve injury. To develop new treatment strategies for peripheral nerve injuries we investigated whether the neurotrophic factor artemin could improve outcome after sciatic nerve injuries in rats. Artemin is a member of the glial cell line-derived neurotrophic factor (GDNF) family and exerts neuroprotective effects on sensory neurons as well as influencing behavioural thermal sensitivity. We additionally evaluated if fibrin sealant, which is sometimes used as a nerve glue, had any effects on neuropathic pain-related behaviour. After the sciatic nerve had been transected, 30 animals were randomised to one of three groups: treatment with a fibrin sealant that contained artemin in conjunction with sutures; fibrin sealant with no artemin (sham) in conjunction with sutures; or sutures alone (n=10 in each group). Motor function, sensory function, and autotomy were evaluated from 1 to 12 weeks after injury. Retrograde flourogold tracing 12 weeks after injury showed that the addition of artemin increased the number of regenerating motor neurons. However, it did not improve their performance, as measured by the Sciatic Function Index, compared with sham or suture alone. Animals treated with artemin had a non-significant increase in motor nerve conduction velocity compared with sham. However, artemin did not reverse nerve injury-induced pain behaviour such as cold or heat hypersensitivity. Fibrin sealant in itself did not ameliorate motor performance, or regeneration of motor neurons, or give rise to nerve injury-induced pain behaviour. The results indicate that artemin is of value as a treatment for peripheral nerve injuries, although the effects were limited. As the artemin high-affinity receptor GFRalpha-3 is present in Schwann cells and not in motor neurons, the effect on motor neuron axon regeneration may result from an indirect effect through Schwann cells in the injured nerve.

Effectiveness and safety of CEUS-guided haemostatic injection for blunt splenic trauma: an animal experiment

The aim of this study was to investigate whether complications occur after haemostatic agents are injected into blunt splenic injuries. After undergoing ultrasound (US), contrast-enhanced US (CEUS) and contrast-enhanced computed tomography (CECT) examinations, dogs with grade III-IV injury received the minimally invasive therapy. After treatment, CEUS was performed to observe changes in the regions treated. In the immediate group, dogs underwent laparotomy 30 min after treatment to observe the haemostatic effect. In the survival group, animals underwent CEUS and CECT examinations to observe the short-term healing outcome and complications at 3, 7, 14, and 21 days after the injection. After undergoing CEUS and CECT examinations, 12 dogs with grade III-IV injury received the minimally invasive therapy. Before injection, CEUS examinations showed anechoic and/or hypoechoic perfusion defects and active bleeding at the injury sites, and CECT showed traumatic lesions as low-density regions without enhancement. After treatment, CEUS demonstrated the disappearance of active bleeding, and hyperechoic spots emerged at the injury sites. Uneven density regions were displayed on CECT. Treated areas were covered by blood clots and glue membrane in the immediate-group animals. Three weeks later, CEUS showed a decrease of hyperechoic spots in the survival group, and the splenic parenchyma enhanced uniformly on CECT. Laparotomy showed that the greater omentum had moved upwards and partly covered the wound in four animals, and the injury sites had completely healed. Histopathological examination showed that fibrous connective tissue covered the splenic capsule and that the haemostatic glue had degraded. No complication occurred, such as delayed splenic haemorrhage, splenic abscesses, splenic pseudoaneurysms, intestinal obstruction or intestinal adhesions. CEUS-guided haemostatic injection is not only effective in stopping active bleeding immediately, but it is also safe in that no complications occurred during the 3 weeks of follow-up. This study indicates that CEUS-guided percutaneous injection may provide a safe, feasible and effective therapy for blunt splenic trauma.

The role of immediate recurrent laryngeal nerve reconstruction for thyroid cancer surgery

Unilateral vocal fold paralysis (UVFP) is one of the most serious problems in conducting surgery for thyroid cancer. Different treatments are available for the management of UVFP including intracordal injection, type I thyroplasty, arytenoid adduction, and laryngeal reinnervations. The effects of immediate recurrent laryngeal nerve (RLN) reconstruction during thyroid cancer surgery with or without UVFP before the surgery were evaluated with videostroboscopic, aerodynamic, and perceptual analyses. All subjects experienced postoperative improvements in voice quality. Particularly, aerodynamic analysis showed that the values for all patients entered normal ranges in both patients with and without UVFP before surgery. Immediate RLN reconstruction has the potential to restore a normal or near-normal voice by returning thyroarytenoid muscle tone and bulk seen with vocal fold denervation. Immediate RLN reconstruction is an efficient and effective approach to the management of RLN resection during surgery for thyroid cancer.

In vivo study of ethyl-2-cyanoacrylate applied in direct contact with nerves regenerating in a novel nerve-guide

Stitch suture is still the most recommended method to hold a nerve-guide in place but stitch suture is a well known cause of local inflammatory response. Glues of several kinds have been proposed as an alternative but they are not easy to apply in a real surgical setting. In 2006 authors developed a new concept of nerve-guide termed "NeuroBox" which is double-halved, not-degradable and rigid, and allows the use of cyanoacrylic glues. In this study, Authors analyzed histologically the nerve-glue interface. Wistar rats were used as animal model. In group 1, animals were implanted a NeuroBox to promote the regeneration of an experimentally produced 4 mm gap in the sciatic nerve. In group 2, the gap was left without repair ("sham-operated" group). Group 3 was assembled by harvesting 10 contralateral intact nerves to document the normal anatomy. Semi-thin sections for visible light microscopy and ultra-thin sections for Transmission Electron Microscopy were analyzed. Results showed that application of ethyl-2-cyanoacrylate directly to the epineurium produced no significative insult to the underlining nerve fibers nor impaired nerve regeneration. No regeneration occurred in the "sham-operated" group.

Ethyl-cyanoacrylate is acutely nontoxic and provides sufficient bond strength for anastomosis of peripheral nerves

Anastomosis is a common technique for the union of severed nerve trunks. This is commonly performed with sutures, a process that can be both time consuming and injurious to tissue. One promising alternative to suturing is the use of adhesives to join the severed segments. Cyanoacrylate-based glues have been used clinically as a surgical adhesive for soft tissues. However, the acute effects of these glues on nerve electrophysiology and the tensile strength of the rejoined tissues have not been evaluated. Using a guinea pig model, we analyzed the mechanical properties of transected sciatic nerves repaired with epineural application of ethyl-cyanoacrylate and the short term consequences of cyanoacrylate application on impulse conduction. Results showed that nerves coapted with ethyl-cyanoacrylate were capable of bearing in vivo forces. Additionally, no acute effects on conduction were observed in uninjured sciatic nerves exposed to ethyl-cyanoacrylate. In conjunction with long term in vivo reports from literature, the current results support the use of cyanoacrylates in nerve repair.

Platelet rich plasma may enhance peripheral nerve regeneration after cyanoacrylate reanastomosis: a controlled blind study on rats

The aim of this study was to explore the ability of platelet rich plasma (PRP) to promote peripheral nerve regeneration after cyanoacrylate reanastomosis in rats. A total of 18 rats were used in this study. Bilateral sciatic neurotomies were performed in 15 rats, and then immediately reanastomosed with cyanoacrylate glue. On one side (G1), the anastomosed nerves were treated with prepared autologous PRP gel; on the contralateral side (G2) the nerves received no additional treatment. Sham surgery was undertaken on the remaining 3 rats (6 cases) where bilateral sciatic nerves were surgically approached but not cut (passive control group, (G3). Biopsies were harvested 12 weeks postoperatively and examined under the light microscope using osmic acid stain. The number of nerve fibers in the distal and proximal nerve segments of G1 and G2 as well as in G3 were counted and the results analyzed and compared. Animals in G1 and G2 showed some weakness and ulceration in their right and left feet for a few weeks postoperatively, which gradually improved during the follow-up period. The histomorphometric assessment showed a higher axon count in the distal segment of G1 (291.7 axons) compared with that of G2 (280.5 axons) (P=0.001). Similar results were noticed when the proximal segments of both groups were compared (P=0.040). These results were reflected in the values of the neurotization indices of G1 (91.9%) and G2 (89.5%) (P=0.008). The number of nerve fibers in G1 and G2 remained lower than in G3 (P=0.0001). The authors conclude that PRP may enhance the number of regenerating nerve fibers after cyanoacrylate neruoanastomosis.

Local tissue reactions after nerve repair with ethyl-cyanoacrylate compared with epineural sutures

Anastomosis of a nerve with cyanoacrylate following a lesion has previously been shown to indicate morphological and functional recovery to an extent comparable to that of conventional epineural sutures. In this study we examined the local tissue reactions after transection and repair of rat sciatic nerve, and compared sutures with a synthetic ethyl-cyanoacrylate adhesive. Many ED-1-immunoreactive macrophages were found accumulating on either side of the repair site whereas neurofilament labelling was less pronounced distal to the repair site seven days after reparation with cyanoacrylate compared with sutures. After six months, when reinnervation was completed, the difference in ED-1-immunoreactivity was still present but to a less extent. These results indicate that ethyl-cyanoacrylate seems to induce an increased inflammatory reaction, which may lead to accelerated Wallerian degeneration, and could therefore have benefits over conventional sutures for reconstruction of peripheral nerves.

Cyanoacrylate glue versus suture in peripheral nerve reanastomosis

OBJECTIVE

To assess the effectiveness of n-butyl-2-cyanoacrylate glue compared with microsuturing technique in peripheral nerve reanastomosis in rats.

STUDY DESIGN

Fourteen young adult white rats were used. Bilateral sciatic neurotomies were performed in 12 of them and then reanastomosed with 3 epineural microsutures in the right side (study group G1) and with n-butyl-2-cyanoacrylate glue in the left side (study group G2). On the remaining 2 rats (control group G3), sham surgery was done on both sides. Biopsies were harvested 12 weeks after surgery and examined under light microscope using Osmic acid stains. The number of nerve fibers was counted in the distal and proximal nerve segments, and the results were analyzed and compared in all groups.

RESULTS

Adequate regeneration with no anastomotic ruptures was seen 12 weeks after surgery in G1 and G2. The histomorphometric assessment showed no statistically significant difference (P = .960) in the neurotization index of G1 (89.01%) compared with G2 (88.97%). There was a significant (P = .001) reduction in the mean number of axon counts distal to the repair in G1 (271.3) and G2 (272.8) compared with that of the proximal segments of each study group (304.6 and 303, respectively, as well as to that of G3 (348.5).

CONCLUSION

Both n-butyl-2-cyanoacrylate adhesive and 3-microsuture techniques showed comparable neurotization indices and were equally adequate to stabilize the nerve during regeneration period.