The use of conventional and invaginated autologous vein grafts for nerve repair by means of entubulation

Implantation of nerve stump inside a vein and a muscle: comparing neuroma formation in rat

Among many techniques independently reported to manage neuroma formation, manipulation of the nerve stump inside muscle and vein is the most advantageous technique. This study aimed to enrich the basic data of macroscopic appearance and histo-pathology regarding which technique generates less neuroma: nerve stump implantation inside vein or inside muscle. An experimental study with posttest-only control-group design was conducted in 24 rats that were randomly arranged into 3 groups. One centimeter of the lateral branch of the right ischiadic nerve was cut. Group A served as the control group, where the proximal nerve stumps were left as they were after the excision; whereas the stumps of groups B and C were implanted inside muscles and veins, respectively. The samples were assessed with histologic examination after 4 weeks to measure the morphometric changes in the nerve endings. The data were statistically analyzed with t test. All rats healed uneventfully. No thrombosis was found within group C, and the stumps were free of neuroma formation. The muscle group formed smaller neuroma than the control group. Statistical analysis showed significant differences between the groups (P < 0.05). The outcome of nerve stump implantation inside the lumen of a vein is superior to the implantation inside a muscle in preventing neuroma formation.

Sciatic nerve regeneration induced by transplantation of in vitro bone marrow stromal cells into an inside-out artery graft in rat

Traumatic injury to peripheral nerves results in considerable motor and sensory disability. Several research groups have tried to improve the regeneration of traumatized nerves by invention of favorable microsurgery. Effect of undifferentiated bone marrow stromal cells (BMSCs) combined with artery graft on peripheral nerve regeneration was studied using a rat sciatic nerve regeneration model. A 10-mm sciatic nerve defect was bridged using an artery graft (IOAG) filled with undifferentiated BMSCs (2 × 10(7) cells/mL). In control group, the graft was filled with phosphated buffer saline alone. The regenerated fibers were studied 4, 8 and 12 weeks after surgery. Assessment of nerve regeneration was based on behavioral, functional (Walking Track Analysis), electrophysiological, histomorphometric and immuohistochemical (Schwann cell detection by S-100 expression) criteria. The behavioral, functional and electrophysiological studies confirmed significant recovery of regenerated axons in IOAG/BMSC group (P < 0.05). Quantitative morphometric analyses of regenerated fibers showed the number and diameter of myelinated fibers in IOAG/BMSC group were significantly higher than in the control group (P < 0.05). This demonstrates the potential of using undifferentiated BMSCs combined with artery graft in peripheral nerve regeneration without limitations of donor-site morbidity associated with isolation of Schwann cells. It is also cost saving due to reduction in interval from tissue collection until cell injection, simplicity of laboratory procedures compared to differentiated BMSCs and may have clinical implications for the surgical management of patients after facial nerve transection.

Bridging peripheral nerve defects with muscle–vein combined guides

Various tubulization techniques can be used to bridge peripheral nerve lesions with substance loss. Among the different materials that have been used so far in alternative to traditional fresh nerve autografts, fresh muscle-vein combined conduits (made by a vein segment filled with fresh skeletal muscle) proved to be particularly effective. In this study, nerve repair of 10-mm long nerve defects by means of muscle-vein combined tubes was compared with repair by means of traditional nerve autografts in the rat sciatic nerve experimental model. Results did not reveal any significant difference between the two groups of regenerated nerves with respect to the total number, mean density and mean size of myelinated nerve fibers. In addition, we also report the results of an experimental study in the rabbit sciatic nerve model, which showed that fresh skeletal muscle enrichment of the vein segment made it possible to bridge 55-mm long nerve gaps. These results provide further evidence of the effectiveness of fresh muscle-vein combined grafts and support the view that this type of conduit can be used also for repairing long nerve gaps.

The use of undifferentiated bone marrow stromal cells for sciatic nerve regeneration in rats

In recent years, cell transplantation has become a focus of attention and reliable outcomes have been achieved in regeneration of the sciatic nerve. The effect of undifferentiated bone marrow stromal cells (BMSCs) on peripheral nerve regeneration was studied using a rat sciatic nerve regeneration model. A 10-mm sciatic nerve defect was bridged using an inside-out vein graft (IOVG) filled with undifferentiated BMSCs (2 × 10(7)cells/ml). In the control group, the vein was filled with phosphate buffer saline alone. The regenerated fibres were studied 4, 8 and 12 weeks after surgery. Assessment of nerve regeneration was based on functional (walking track analysis), histomorphometric and immunohistochemical (Schwann cell detection by S100 expression) criteria. The functional study confirmed significant recovery of regenerated axons in the IOVG/BMSC group (P<0.05). Quantitative morphometric analyses of regenerated fibres showed the number and diameter of myelinated fibres in the IOVG/BMSC group were significantly higher than in the control group (P<0.05). This demonstrates the potential for using undifferentiated BMSCs in peripheral nerve regeneration without the limitations of donor-site morbidity associated with isolation of Schwann cells. It also reduces costs because the interval between tissue collection and cell injection is reduced and the laboratory procedures are simpler compared to undifferentiated BMSCs.

Biomaterials for the development of peripheral nerve guidance conduits

Currently, surgical treatments for peripheral nerve injury are less than satisfactory. The gold standard of treatment for peripheral nerve gaps >5 mm is the autologous nerve graft; however, this treatment is associated with a variety of clinical complications, such as donor site morbidity, limited availability, nerve site mismatch, and the formation of neuromas. Despite many recent advances in the field, clinical studies implementing the use of artificial nerve guides have yielded results that are yet to surpass those of autografts. Thus, the development of a nerve guidance conduit, which could match the effectiveness of the autologous nerve graft, would be beneficial to the field of peripheral nerve surgery. Design strategies to improve surgical outcomes have included the development of biopolymers and synthetic polymers as primary scaffolds with tailored mechanical and physical properties, luminal "fillers" such as laminin and fibronectin as secondary internal scaffolds, surface micropatterning, stem cell inclusion, and controlled release of neurotrophic factors. The current article highlights approaches to peripheral nerve repair through a channel or conduit, implementing chemical and physical growth and guidance cues to direct that repair process.

Clinical application of inside-out vein grafts for the treatment of sensory nerve segmental defect

PURPOSE

The gold standard for the treatment of segmental nerve defect is an autogenous nerve graft. However, donor site morbidity is an inevitable complication. We substituted an autogenous nerve graft with an inside-out vein graft for the treatment of segmental sensory nerve defect and the clinical results were evaluated retrospectively.

PATIENTS AND METHODS

Eleven patients of sensory nerve defects have undertaken inside-out vein grafts for the recovery of sensation. The involved nerves were digital nerves in three cases, peroneal nerves in two cases, saphenous nerve in two cases, and superficial radial nerves in four cases. The average length of defects was 2.71 cm (1-6 cm). Donor veins were harvested 4 mm longer than nerve defects and everted to promote nerve regeneration. Patients' objective satisfactions and two-point discriminations were determined, the Semmes-Weinstein monofilament test was performed, and British Medical Council sensory functional scores were evaluated.

RESULTS

Sensory functional scores recovered to over S3 in all cases. No donor site morbidity was caused by vein harvesting, and all patients achieved satisfactory results with protective sensation at involved sites.

CONCLUSION

The inside-out vein graft offers a good surgical alternative to an autogenous nerve graft for the reconstruction of sensory nerve defects without donor site morbidity.

Isogenic venous graft supported with bone marrow stromal cells as a natural conduit for bridging a 20 mm nerve gap

In this study, we introduce a technique for bridging large neural gaps, using an isogenic vein graft supported with isogenic bone marrow stromal cells (BMSC). In three groups a nerve defect of 20 mm was bridged with a vein graft. Our first experimental group comprized an empty venous graft, in group II the venous nerve graft was filled with saline where as in group III the venous nerve graft was filled with BMSC. The animals were tested for functional recovery up to 3 months post repair. Our results show that the BMSC filled venous graft resulted in significantly better regeneration of the nerve defect compared to controls, as confirmed by the functional recovery measured by somatosensory evoked potentials, toe spread, pin prick, and gastrocnemius muscle index. Conclusively, the results confirm that the vein graft supported with BMSC is associated with better functional nerve regeneration.

Autogenous standard versus inside-out vein graft to repair facial nerve in rabbits

OBJECTIVE

To evaluate autogenous vein grafts and inside-out vein grafts as conduits for the defects repair in the rabbit facial nerves.

METHODS

The 10 mm segments of buccal division of facial nerve were transected for 48 rabbits in this study. Then the gaps were immediately repaired by autogenous vein grafts or inside-out vein grafts in different groups. All the animals underwent the whisker movement test and electrophysiologic test during the following 16 weeks at different time points postoperatively. Subsequently, the histological examination was performed to observe the facial nerve regeneration morphologically.

RESULTS

At 8 weeks after operation, the facial nerve regeneration has significant difference between the experimental group and the control group in electrophysiologic test and histological observation. However, at the end of this study, 16 weeks after operation, there was no significant difference between inside-out vein grafts and standard vein grafts in enhancing peripheral nerve regeneration.

CONCLUSION

This study suggest that both kinds of vein grafts play positive roles in facial nerve regeneration after being repaired immediately, but the autogenous inside-out vein grafts might accelerate and facilitate axonal regeneration as compared with control.

Complex injuries including flexor tendon disruption

The treatment of tendon injury in combined complex injuries to the hand is dictated by the presence of concomitant injuries. Early range of motion is desirable. To achieve this, fractures must be stabilized and the soft tissue envelope and vascular integrity maintained or reconstituted. In those instances in which these conditions cannot be met, the surgeon and patient should be prepared for secondary surgeries, including reconstruction or tenolysis. Although nerve integrity is not necessary for early functional success following tenorrhaphy, nerve injuries should be repaired or grafted primarily as the injury permits. In cases in which vascular compromise is encountered, the options of revascularization versus primary amputation should be discussed with the patient. With an understanding of the treatment principles, the complications associated with complex tendon injuries can be minimized. It is important to stress that optimal functional outcome is multifactorial and includes a physician-therapist team-oriented approach.

Beneficial effect of nerve growth factor-7S on peripheral nerve regeneration through inside-out vein grafts: An experimental study

This study investigated the effect of local administration of nerve growth factor-7S (NGF-7S) on the axonal regrowth of mixed peripheral nerves through inside-out vein grafts. Sixty male Wistar rats were randomized into two groups (n = 30). A defect 12 mm long in the right sciatic nerve was created and repaired with an inside-out vein graft from the right jugular vein. NGF-7S (group A) or phosphate-buffered saline (group B; control) was locally administered daily during the first 3 weeks. Walking-track analysis and electrophysiological and histological-morphometric studies were carried out 4, 6, 8, 10, and 12 weeks postoperatively (subgroups a, b, c, d, and e, respectively, n = 6 each). Data analysis showed that 1) the recovery of motor function, as measured by walk pattern analysis and evoked muscle action potential, and 2) the orientation, number, myelin thickness, and diameter of myelinated fibers were better in the NGF-7S than in the control group. These findings present strong evidence of the beneficial effect of NGF-7S on peripheral nerve regeneration through inside-out vein grafts.

Nerve growth factor is expressed in rat femoral vein

PURPOSE

Entubulization is a well known method of nerve repair for defects too large to be reconstructed by direct suturing without tension. Vein grafts and alloplastic tubes have been used for entubulization in peripheral and cranial nerves, but the mechanism by which they promote healing is poorly understood. The overall hypothesis of this laboratory is that nerve growth factor (NGF) plays an important role in nerve regeneration after entubulization with a vein graft. The purpose of this pilot study was to localize NGF protein expression in the rat femoral vein.

MATERIALS AND METHODS

Sciatic nerves and femoral veins were harvested from adult male Sprague-Dawley rats. Femoral arteries were also collected and used for comparison and validation of the analysis. All specimens were fixed in paraformaldehyde and embedded in paraffin. Specimens were either stained with hematoxylin and eosin or used for immunohistochemical reaction with anti-NGF antibody.

RESULTS

Sciatic nerve was used as a positive control to identify the monofascicular architecture with hematoxylin and eosin and to document the positive immunohistochemical reaction. NGF immunoreactivity was present in the tunica intima and tunica adventitia of femoral vein and artery but not in the tunica media.

CONCLUSION

The results of this pilot study indicate that NGF is detectable in both the intimal and adventitial layers of the rat femoral vein and artery but not in the smooth muscle wall. These findings suggest that vein grafts could potentially promote nerve regeneration by supplying NGF to the injured nerve.

Clinical results and thoughts on sensory nerve repair by autologous vein graft in emergency hand reconstruction

Lesions of the digital and other sensory nerves in the hand are common. Based on experimental studies on vein graft as a support for peripheral nerve regeneration, the Authors have been using a simple vein graft to bridge sensory nerve gaps when treating acute hand injuries. This is a retrospective study on the results of 22 sensory nerves repaired using vein grafts in cases in which primary suture was not feasible, in emergency hand reconstruction. Patients were informed that a secondary nerve graft could possibly be necessary in the future. Patients were reviewed by two independent observers at least one year after repair and evaluated using the Highest scale as modified by MacKinnon & Dellon. Evaluation chart included influence of repair on rehabilitation program and presence of painful neuromas and scars as well as patient satisfaction. Results were classified according to Sakellarides and 20/22 were classified as very good or good. Cases classified as poor were satisfied and no secondary nerve grafting has been carried out. Rehabilitation of the associated lesions (tendon lacerations or bone and soft tissue damage) was not influenced by the nerve repair and no painful neuroma was reported in the series. In conclusion, since the literature shows unsatisfactory results in repair of digital nerves with nerve grafts, since it's been demonstrated that an unrepaired sensory nerve leads to painful scar and painful neuroma and since we are reluctant to use nerve grafts in emergency procedures, we recommend this simple method because it is easy, low-cost and effective.