Progress in peripheral nerve reconstruction

Functional Outcomes of Nerve Allografts Seeded with Undifferentiated and Differentiated Mesenchymal Stem Cells in a Rat Sciatic Nerve Defect Model

BACKGROUND

Mesenchymal stem cells have the potential to produce neurotrophic growth factors and establish a supportive microenvironment for neural regeneration. The purpose of this study was to determine the effect of undifferentiated and differentiated mesenchymal stem cells dynamically seeded onto decellularized nerve allografts on functional outcomes when used in peripheral nerve repair.

METHODS

In 80 Lewis rats, a 10-mm sciatic nerve defect was reconstructed with (1) autograft, (2) decellularized allograft, (3) decellularized allograft seeded with undifferentiated mesenchymal stem cells, or (4) decellularized allograft seeded with mesenchymal stem cells differentiated into Schwann cell-like cells. Nerve regeneration was evaluated over time by cross-sectional tibial muscle ultrasound measurements, and at 12 and 16 weeks by isometric tetanic force measurements, compound muscle action potentials, muscle mass, histology, and immunofluorescence analyses.

RESULTS

At 12 weeks, undifferentiated mesenchymal stem cells significantly improved isometric tetanic force measurement and compound muscle action potential outcomes compared to decellularized allograft alone, whereas differentiated mesenchymal stem cells significantly improved compound muscle action potential outcomes. The autografts outperformed both stem cell groups histologically at 12 weeks. At 16 weeks, functional outcomes normalized between groups. At both time points, the effect of undifferentiated versus differentiated mesenchymal stem cells was not significantly different.

CONCLUSIONS

Undifferentiated and differentiated mesenchymal stem cells significantly improved functional outcomes of decellularized allografts at 12 weeks and were similar to autograft results in the majority of measurements. At 16 weeks, outcomes normalized as expected. Although differences between both cell types were not statistically significant, undifferentiated mesenchymal stem cells improved functional outcomes of decellularized nerve allografts to a greater extent and had practical benefits for clinical translation by limiting preparation time and costs.

Surgical Angiogenesis of Decellularized Nerve Allografts Improves Early Functional Recovery in a Rat Sciatic Nerve Defect Model

BACKGROUND

Surgical angiogenesis applied to nerve grafts has been suggested to enhance nerve regeneration after nerve injury. The authors hypothesized that surgical angiogenesis to decellularized nerve allografts would improve functional recovery in a rat sciatic nerve defect model.

METHODS

Sixty Lewis rats were divided in three groups of 20 animals each. Unilateral sciatic nerve defects were repaired with (1) autografts, (2) decellularized allografts, and (3) decellularized allografts wrapped with a superficial inferior epigastric artery fascial flap to add surgical angiogenesis. Twelve and 16 weeks after surgery, nerve regeneration was assessed using functional, electrophysiologic, histologic, and immunofluorescence analyses. Ultrasonography was used during the survival period to noninvasively evaluate muscle atrophy and reinnervation by measuring cross-sectional muscle area.

RESULTS

Surgical angiogenesis of allografts demonstrated significantly improved isometric tetanic force recovery at 12 weeks, compared to allograft alone, which normalized between groups at 16 weeks. Cross-sectional muscle areas showed no differences between groups. Electrophysiology showed superiority of autografts at both time points. No differences were found in histologic analysis, besides a significantly inferior N ratio in allografts at 12 weeks. Immunofluorescent expression of CD34, indicating vascularity, was significantly enhanced in the superficial inferior epigastric artery fascial group compared to allografts at 12 weeks, with highest expression at 16 weeks compared to all groups.

CONCLUSION

Surgical angiogenesis with an adipofascial flap to the nerve allograft increases vascularity in the nerve graft, with subsequent improvement of early muscle force recovery, comparable to autografts.

Stem-cell-based therapies to enhance peripheral nerve regeneration

Peripheral nerve injury remains a major cause of morbidity in trauma patients. Despite advances in microsurgical techniques and improved understanding of nerve regeneration, obtaining satisfactory outcomes after peripheral nerve injury remains a difficult clinical problem. There is a growing body of evidence in preclinical animal studies demonstrating the supportive role of stem cells in peripheral nerve regeneration after injury. The characteristics of both mesoderm-derived and ectoderm-derived stem cell types and their role in peripheral nerve regeneration are discussed, specifically focusing on the presentation of both foundational laboratory studies and translational applications. The current state of clinical translation is presented, with an emphasis on both ethical considerations of using stems cells in humans and current governmental regulatory policies. Current advancements in cell-based therapies represent a promising future with regard to supporting nerve regeneration and achieving significant functional recovery after debilitating nerve injuries.

Transected sciatic nerve repair by diode laser protein soldering

BACKGROUND AND OBJECTIVE

Despite advances in microsurgical techniques, repair of peripheral nerve injuries (PNI) is still a major challenge in regenerative medicine. The standard treatment for PNI includes suturing and anasthomosis of the transected nerve. The objective of this study was to compare neurorraphy (nerve repair) using standard suturingto diode laser protein soldering on the functional recovery of transected sciatic nerves.

STUDY DESIGN/MATERIALS AND METHODS

Thirty adult male Fischer-344 Wistar rats were randomly assigned to 3 groups: 1. The control group, no repair, 2. the standard of care suture group, and 3. The laser/protein solder group. For all three groups, the sciatic nerve was transected and the repair was done immediately. For the suture repair group, 10.0 prolene suture was used and for the laser/protein solder group a diode laser (500mW output power) in combination with bovine serum albumen and indocyanine green dye was used. Behavioral assessment by sciatic functional index was done on all rats biweekly. At 12weeks post-surgery, EMG recordings were done on all the rats and the rats were euthanized for histological evaluation of the sciatic nerves. The one-way ANOVA test was used for statistical analysis.

RESULTS

The average time required to perform the surgery was significantly shorter for the laser-assisted nerve repair group compared to the suture group. The EMG evaluation revealed no difference between the two groups. Based on the sciatic function index the laser group was significantly better than the suture group after 12weeks (p<0.05). Histopathologic evaluation indicated that the epineurium recovery was better in the laser group (p<0.05). There was no difference in the inflammation between the suture and laser groups.

CONCLUSION

Based on this evidence, laser/protein nerve soldering is a more efficient and efficacious method for repair of nerve injury compared to neurorraphy using standard suturing methods.

Scaffoldless tissue-engineered nerve conduit promotes peripheral nerve regeneration and functional recovery after tibial nerve injury in rats

Damage to peripheral nerve tissue may cause loss of function in both the nerve and the targeted muscles it innervates. This study compared the repair capability of engineered nerve conduit (ENC), engineered fibroblast conduit (EFC), and autograft in a 10-mm tibial nerve gap. ENCs were fabricated utilizing primary fibroblasts and the nerve cells of rats on embryonic day 15 (E15). EFCs were fabricated utilizing primary fibroblasts only. Following a 12-week recovery, nerve repair was assessed by measuring contractile properties in the medial gastrocnemius muscle, distal motor nerve conduction velocity in the lateral gastrocnemius, and histology of muscle and nerve. The autografts, ENCs and EFCs reestablished 96%, 87% and 84% of native distal motor nerve conduction velocity in the lateral gastrocnemius, 100%, 44% and 44% of native specific force of medical gastrocnemius, and 63%, 61% and 67% of native medial gastrocnemius mass, respectively. Histology of the repaired nerve revealed large axons in the autograft, larger but fewer axons in the ENC repair, and many smaller axons in the EFC repair. Muscle histology revealed similar muscle fiber cross-sectional areas among autograft, ENC and EFC repairs. In conclusion, both ENCs and EFCs promoted nerve regeneration in a 10-mm tibial nerve gap repair, suggesting that the E15 rat nerve cells may not be necessary for nerve regeneration, and EFC alone can suffice for peripheral nerve injury repair.

In Vitro and In Vivo Effects of Ginkgo biloba Extract EGb 761 on Seeded Schwann Cells within Poly(DL-lactic acid-co-glycolic acid) Conduits for Peripheral Nerve Regeneration

This study investigated the effects of Ginkgo biloba (EGb 761) extract on seeded Schwann cells within poly(DL-lactic acid-co-glycolic acid) (PLGA) conduits by in vitro and in vivo trials for peripheral nerve regeneration. The seeding efficiency of Schwann cells in serum-deprived culture medium, which simulated the environment of mechanical trauma on an injured nerve site, was improved by adding different dosages of EGb 761 (0, 1, 10, 20, 50, 100, 200 mg/mL). The analytical results showed enhanced cell attachment and survival, reduced LDH release and increased MTT values, particularly in the range 10-100 mg/mL. The PLGA nerve conduits seeded with Schwann cells (6 103 cells) and filled with gelatin containing EGb 761 (0, 10, 50, 100 mg/mL) were implanted to 10-mm right sciatic nerve defects in rats. Autograft was performed as another control. Electromyography was assessed based on the motor unit action potential (MUAP) and fibrillation potential (Fib) at 2, 4, and 6 weeks during all periods. The specimens of the experimental and control groups were harvested for histological analysis at 6 weeks after surgery. The Fib was found to gradually decay, and the MUAP was found not to be present until 4 weeks after surgery. Meanwhile, the experimental groups were all statically better than the control group (without EGb 761) and autografts were observed at 6 weeks, especially at the concentration of 10 mg/mL, where there was higher amplitude of MUAP and a significantly larger number of myelinated axons. This study concluded that a proper concentration of EGb 761 (10-50 mg/mL) promoted seeding efficiency of Schwann cells in a tissue-engineered PLGA conduit. Addition of EGb 761 in Schwann cells-seeded conduit could increase the total number of myelinated axons in nerve regeneration and improve peripheral nerve functional recovery.

The influence of vascularization of transplanted processed allograft nerve on return of motor function in rats

Processed nerve allografts have become an alternative to repair segmental nerve defects, with results comparable with autografts regarding sensory recovery; however, they have failed to reproduce comparable motor recovery. The purpose of this study was to determine how revascularizaton of processed nerve allograft would affect motor recovery. Eighty-eight rats were divided in four groups of 22 animals each. A unilateral 10-mm sciatic nerve defect was repaired with allograft (group I), allograft wrapped with silicone conduit (group II), allograft augmented with vascular endothelial growth factor (group III), or autograft (group IV). Eight animals from each group were sacrificed at 3 days, and the remaining animals at 16 weeks. Revascularization was evaluated by measuring the graft capillary density at 3 days and 16 weeks. Measurements of ankle contracture, compound muscle action potential, tibialis anterior muscle weight and force, and nerve histomorphometry were performed at 16 weeks. All results were normalized to the contralateral side. The results of capillary density at 3 days were 0.99% ± 1.3% for group I, 0.33% ± 0.6% for group II, 0.05% ± 0.1% for group III, and 75.6% ± 45.7% for group IV. At 16 weeks, the results were 69.9% ± 22.4% for group I, 37.0% ± 16.6% for group II, 84.6% ± 46.6% for group III, and 108.3% ± 46.8% for group IV. The results of muscle force were 47.5% ± 14.4% for group I, 21.7% ± 13.5% for group II, 47.1% ± 7.9% for group III, and 54.4% ± 10.6% for group IV. The use of vascular endothelial growth factor in the fashion used in this study improved neither the nerve allograft short-term revascularization nor the functional motor recovery after 16 weeks. Blocking allograft vascularization from surrounding tissues was detrimental for motor recovery. The processed nerve allografts used in this study showed similar functional motor recovery compared with that of the autograft.

Peripheral nerve reconstruction after injury: a review of clinical and experimental therapies

Unlike other tissues in the body, peripheral nerve regeneration is slow and usually incomplete. Less than half of patients who undergo nerve repair after injury regain good to excellent motor or sensory function and current surgical techniques are similar to those described by Sunderland more than 60 years ago. Our increasing knowledge about nerve physiology and regeneration far outweighs our surgical abilities to reconstruct damaged nerves and successfully regenerate motor and sensory function. It is technically possible to reconstruct nerves at the fascicular level but not at the level of individual axons. Recent surgical options including nerve transfers demonstrate promise in improving outcomes for proximal nerve injuries and experimental molecular and bioengineering strategies are being developed to overcome biological roadblocks limiting patient recovery.

Peripheral nerve reconstruction after injury: a review of clinical and experimental therapies

Unlike other tissues in the body, peripheral nerve regeneration is slow and usually incomplete. Less than half of patients who undergo nerve repair after injury regain good to excellent motor or sensory function and current surgical techniques are similar to those described by Sunderland more than 60 years ago. Our increasing knowledge about nerve physiology and regeneration far outweighs our surgical abilities to reconstruct damaged nerves and successfully regenerate motor and sensory function. It is technically possible to reconstruct nerves at the fascicular level but not at the level of individual axons. Recent surgical options including nerve transfers demonstrate promise in improving outcomes for proximal nerve injuries and experimental molecular and bioengineering strategies are being developed to overcome biological roadblocks limiting patient recovery.

Epineurial repair of an iatrogenic facial nerve neurotmesis after total ear canal ablation and lateral bulla osteotomy in a dog with concurrent cranio-mandibular osteopathy

A 7-year-old male entire West Highland white terrier was referred to the Small Animal Hospital at the University of Glasgow for bilateral, chronic, medically unresponsive otitis media and externa. A history of cranio-mandibular osteopathy was also reported. Bilateral total ear canal ablation and lateral bulla osteotomy was performed with the aid of a pneumatic burr. Extensive bone proliferation was present bilaterally originating from the caudal mandibular ramus and tympanic bulla which incorporated the horizontal canal on each side. The right facial nerve was identified leaving the stylomastoid foramen and running in a cranial direction through a 1.5 cm diameter cuff of bone surrounding the horizontal canal and external acoustic meatus. Despite careful dissection, a facial nerve neurotmesis ensued which required microsurgical epineurial repair. Neurologic examination performed 12 h post-operatively revealed abnormalities consistent with right facial nerve paralysis. At 3 months, the facial nerve function was found to have improved significantly and was assessed to be normal four months after surgery. To the authors' knowledge, this clinical communication described the first reported clinical case where unilateral facial nerve paralysis resulting from iatrogenic facial nerve neurotmesis was successfully treated by microsurgical epineurial repair.

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.

Promoting nerve regeneration in a neurotmesis rat model using poly(DL-lactide-ε-caprolactone) membranes and mesenchymal stem cells from the Wharton's jelly: in vitro and in vivo analysis

In peripheral nerves MSCs can modulate Wallerian degeneration and the overall regenerative response by acting through paracrine mechanisms directly on regenerating axons or upon the nerve-supporting Schwann cells. In the present study, the effect of human MSCs from Wharton's jelly (HMSCs), differentiated into neuroglial-like cells associated to poly (DL-lactide-ε-caprolactone) membrane, on nerve regeneration, was evaluated in the neurotmesis injury rat sciatic nerve model. Results in vitro showed successful differentiation of HMSCs into neuroglial-like cells, characterized by expression of specific neuroglial markers confirmed by immunocytochemistry and by RT-PCR and qPCR targeting specific genes expressed. In vivo testing evaluated during the healing period of 20 weeks, showed no evident positive effect of HMSCs or neuroglial-like cell enrichment at the sciatic nerve repair site on most of the functional and nerve morphometric predictors of nerve regeneration although the nociception function was almost normal. EPT on the other hand, recovered significantly better after HMSCs enriched membrane employment, to values of residual functional impairment compared to other treated groups. When the neurotmesis injury can be surgically reconstructed with an end-to-end suture or by grafting, the addition of a PLC membrane associated with HMSCs seems to bring significant advantage, especially concerning the motor function recovery.

Challenges for nerve repair using chitosan-siloxane hybrid porous scaffolds

The treatment of peripheral nerve injuries remains one of the greatest challenges of neurosurgery, as functional recover is rarely satisfactory in these patients. Recently, biodegradable nerve guides have shown great potential for enhancing nerve regeneration. A major advantage of these nerve guides is that no foreign material remains after the device has fulfilled its task, which spares a second surgical intervention. Recently, we studied peripheral nerve regeneration using chitosan-γ-glycidoxypropyltrimethoxysilane (chitosan-GPTMS) porous hybrid membranes. In our studies, these porous membranes significantly improved nerve fiber regeneration and functional recovery in rat models of axonotmetic and neurotmetic sciatic nerve injuries. In particular, the number of regenerated myelinated nerve fibers and myelin thickness were significantly higher in rat treated with chitosan porous hybrid membranes, whether or not they were used in combination with mesenchymal stem cells isolated from the Wharton's jelly of the umbilical cord. In this review, we describe our findings on the use of chitosan-GPTMS hybrids for nerve regeneration.

Human muscle-derived stem/progenitor cells promote functional murine peripheral nerve regeneration

Peripheral nerve injuries and neuropathies lead to profound functional deficits. Here, we have demonstrated that muscle-derived stem/progenitor cells (MDSPCs) isolated from adult human skeletal muscle (hMDSPCs) can adopt neuronal and glial phenotypes in vitro and ameliorate a critical-sized sciatic nerve injury and its associated defects in a murine model. Transplanted hMDSPCs surrounded the axonal growth cone, while hMDSPCs infiltrating the regenerating nerve differentiated into myelinating Schwann cells. Engraftment of hMDSPCs into the area of the damaged nerve promoted axonal regeneration, which led to functional recovery as measured by sustained gait improvement. Furthermore, no adverse effects were observed in these animals up to 18 months after transplantation. Following hMDSPC therapy, gastrocnemius muscles from mice exhibited substantially less muscle atrophy, an increase in muscle mass after denervation, and reorganization of motor endplates at the postsynaptic sites compared with those from PBS-treated mice. Evaluation of nerve defects in animals transplanted with vehicle-only or myoblast-like cells did not reveal histological or functional recovery. These data demonstrate the efficacy of hMDSPC-based therapy for peripheral nerve injury and suggest that hMDSPC transplantation has potential to be translated for use in human neuropathies.

Long-Term Regeneration and Functional Recovery of a 15 mm Critical Nerve Gap Bridged by Tremella fuciformis Polysaccharide-Immobilized Polylactide Conduits

Novel peripheral nerve conduits containing the negatively charged Tremella fuciformis polysaccharide (TF) were prepared, and their efficacy in bridging a critical nerve gap was evaluated. The conduits were made of poly(D,L-lactide) (PLA) with asymmetric microporous structure. TF was immobilized on the lumen surface of the nerve conduits after open air plasma activation. The TF-modified surface was characterized by the attenuated total reflection Fourier-transformed infrared spectroscopy and the scanning electron microscopy. TF modification was found to enhance the neurotrophic gene expression of C6 glioma cells in vitro. TF-modified PLA nerve conduits were tested for their ability to bridge a 15 mm gap of rat sciatic nerve. Nerve regeneration was monitored by the magnetic resonance imaging. Results showed that TF immobilization promoted the nerve connection in 6 weeks. The functional recovery in animals receiving TF-immobilized conduits was greater than in those receiving the bare conduits during an 8-month period. The degree of functional recovery reached ~90% after 8 months in the group of TF-immobilized conduits.

Return of motor function after segmental nerve loss in a rat model: comparison of autogenous nerve graft, collagen conduit, and processed allograft (AxoGen)

BACKGROUND

An effective alternative to nerve autograft is needed to minimize morbidity and solve limited-availability issues. We hypothesized that the use of processed allografts and collagen conduits would allow recovery of motor function that is equivalent to that seen after the use of autografts.

METHODS

Sixty-five Lewis rats were divided into three experimental groups. In each group, a unilateral 10-mm sciatic nerve defect was repaired with nerve autograft, allograft treated by AxoGen Laboratories, or a 2.0-mm-inner-diameter collagen conduit. The animals were studied at twelve and sixteen weeks postoperatively. Evaluation included bilateral measurement of the tibialis anterior muscle force and muscle weight, electrophysiology, assessment of ankle contracture, and peroneal nerve histomorphometry. Muscle force was measured with use of our previously described and validated method. Results were expressed as a percentage of the values on the contralateral side. Two-way analysis of variance (ANOVA) corrected by the Ryan-Einot-Gabriel-Welsch multiple range test was used for statistical investigation (α = 0.05).

RESULTS

At twelve weeks, the mean muscle force (and standard deviation), as compared with that on the contralateral (control) side, was 45.2% ± 15.0% in the autograft group, 43.4% ± 18.0% in the allograft group, and 7.0% ± 9.2% in the collagen group. After sixteen weeks, the recovered muscle force was 65.5% ± 14.1% in the autograft group, 36.3% ± 15.7% in the allograft group, and 12.1% ± 16.0% in the collagen group. Autograft was statistically superior to allograft and the collagen conduit at sixteen weeks with regard to all parameters except histomorphometric characteristics (p < 0.05). The collagen-group results were inferior. All autograft-group outcomes improved from twelve to sixteen weeks, with the increase in muscle force being significant.

CONCLUSIONS

The use of autograft resulted in better motor recovery than did the use of allograft or a collagen conduit for a short nerve gap in rats. A longer evaluation time of sixteen weeks after segmental nerve injuries in rats would be beneficial as more substantial muscle recovery was seen at that time.

Comparison between two different methods of immobilizing NGF in poly(DL-lactic acid-co-glycolic acid) conduit for peripheral nerve regeneration by EDC/NHS/MES and genipin

For surface modification and nerve regeneration, chitosan, followed by nerve growth factor (NGF), was immobilized onto the interior surface of poly (lactic acit-co-glycolic) conduits, using EDC/NHS/MES system (EDCs) and genipin (GP). Four new conduits were, therefore, obtained and named by immobilizing order-EDCs/EDCs, GP/EDCs, EDCs/GP, and GP/GP groups. The immobilized methods used were evaluated and compared, respectively. The researchers found that the EDCs- and GP-cross-linked chitosan displayed higher hydrophilic than pure poly (DL-lactic acid-co-glycolic acid) (PLGA) in water contact angle experiment, which meant the cell compatibility was improved by the modification. Scanning electron microscopic observations revealed that the GP-cross-linking of chitosan greatly improved cell compatibility while cultured rat PC12 cells were flatter and more spindle-shaped than EDCs-cross-linked chitosan. The results concerning the GP-cross-linked chitosan revealed significant proliferation of the seeded cells relative to pure PLGA films, as determined by counting cells and MTT assay. The NGF was released from the modified conduits in two separate periods--an initial burst in 5 days and then slow release from day 10 to day 40. The GP/EDCs group had the highest NGF value among all groups after the 5th day. Finally, the controlled-release conduits were used to bridge a 10 mm rat sciatic nerve defect. Six weeks following implantation, morphological analysis revealed the highest numbers of myelinated axons in the midconduit and distal regenerated nerve in GP/EDCs group. Therefore, the results confirm that GP/EDCs groups with good cell compatibility and effective release of NGF can considerably improve peripheral nerve regeneration.

Microscopic evidences that bone marrow mononuclear cell treatment improves sciatic nerve regeneration after neurorrhaphy

Cell therapy constitutes a possibility for improving nerve regeneration, increasing the success of nerve repair. We evaluate the use of mononuclear cells in the regeneration of the sciatic nerve after axotomy followed by end-to-end neurorrhaphy. Forty adult male Wistar rats (250-300 g) were divided into four groups: (1) sham, (2) neurorrhaphy: the sciatic nerve was sectioned and repaired using epineural sutures, (3) culture medium: after the suture, received an injection of 10 μL of culture medium into the nerve, and (4) mononuclear cell: after the suture, a concentration of 3 × 10(6) of mononuclear cell was injected in epineurium region. Mononuclear cells were obtained from the bone marrow aspirates and separated by Ficoll-Hypaque method. The histological analyses were performed at the 4th postoperative day. The sciatic functional index, histological, and morphometric analyzes were used to evaluate nerve regeneration at the 6th postoperative week. Six rats were used for immunohistochemical analysis on the 4th postoperative day. In the group 4, on the fourth day, the histological analysis demonstrated a more accelerated degenerative process and an increase of the neurotrophic factors was observed. In the 6th week, all the morphometric results of the group 4 were statistically better compared with groups 2 and 3. There was a statistically significant improvement in the sciatic functional index for group 4 compared with groups 2 and 3. Mononuclear cells stimulated nerve regeneration, most probably by speeding up the Wallerian degeneration process as well as stimulating the synthesis of neurotrophic factors.

NERVE TRANSFER SURGERY FOR ADULT BRACHIAL PLEXUS INJURY

OBJECTIVE

To review the clinical outcomes in our patients who have undergone nerve transfer operations for brachial plexus reconstruction at the Louisiana State University (LSU) over a 10-year period. A secondary objective is to compare clinical outcomes in patients who had only nerve transfer operations as compared with patients whose nerve transfers were supplemented with direct repair of brachial plexus elements.

METHODS

Retrospective review of the medical records, imaging, and electrodiagnostic studies (electromyographic and nerve conduction studies) of patients with brachial plexus injuries who underwent nerve transfer operations at LSU over a period of 10 years.

RESULTS

A total of 81 patients were treated between 1995 to 2005 at the LSU Health Sciences Center; 7 of these patients were lost to follow-up, leaving 74 patients, with an average follow-up of 3.5 years, for review. We evaluated recovery of elbow flexion and shoulder abduction. Ninety percent of patients with medial pectoral to musculocutaneous nerve transfers recovered to LSU grade 2 (Medical Research Council grade 3), and 60% of those patients with intercostal to musculocutaneous nerve transfer regained similar strength in elbow flexion. Shoulder abduction recovery to LSU grade 2 (Medical Research Council grade 3) after spinal accessory to suprascapular and/or thoracodorsal to axillary nerve transfer, was 95% and 36%, respectively. There was a tendency for better motor recovery when nerve transfer operations were combined with direct repair of plexus elements.

CONCLUSION

Nerve transfers for repair of brachial plexus injuries result in excellent recovery of elbow and shoulder functions. Patients who had direct repair of brachial plexus elements in addition to nerve transfers tended to do better than those who had only nerve transfer operations.

[Combined flexor tendon and nerve injury of the hand]

Any restoration of hand function following tendon and nerve injury has to include the repair or replacement of the hand's ability to perform a great many tasks. It is hard at first to appreciate fully the loss that occurs with flexor tendon injury. Also sensibility can be compromised from tendon injury without direct injury to the nerve, as object recognition in the absence of vision requires finger movement. When peripheral nerve injury is combined with flexor tendon injury, sensibility is directly impaired. There is a loss in the sense of finger or thumb position, pain temperature and touch or pressure recognition, in addition to the tendon injury. However, the outcome after operative treatment of these"minor" injuries of the hand is horrible. Therefore, we try to summarize practical consequences for the repair of combined flexor tendon and nerve injuries which will improve operative outcome. These guidelines are based on current scientific knowledge and our own experience.

Use of PLGA 90:10 scaffolds enriched with in vitro-differentiated neural cells for repairing rat sciatic nerve defects

Poly(lactic-co-glycolic acid) (PLGA) nerve tube guides, made of a novel proportion (90:10) of the two polymers, poly(L-lactide): poly(glycolide) and covered with a neural cell line differentiated in vitro, were tested in vivo for promoting nerve regeneration across a 10-mm gap of the rat sciatic nerve. Before in vivo testing, the PLGA 90:10 tubes were tested in vitro for water uptake and mass loss and compared with collagen sheets. The water uptake of the PLGA tubes was lower, and the mass loss was more rapid and higher than those of the collagen sheets when immersed in phosphate-buffered saline (PBS) solution. The pH values of immersing PBS did not change after soaking the collagen sheets and showed to be around 7.4. On the other hand, the pH values of PBS after soaking PLGA tubes decreased gradually during 10 days reaching values around 3.5. For the in vivo testing, 22 Sasco Sprague adult rats were divided into four groups--group 1: gap not reconstructed; group 2: gap reconstructed using an autologous nerve graft; group 3: gap reconstructed with PLGA 90:10 tube guides; group 4: gap reconstructed with PLGA 90:10 tube guides covered with neural cells differentiated in vitro. Motor and sensory functional recovery was evaluated throughout a healing period of 20 weeks using sciatic functional index, static sciatic index, extensor postural thrust, withdrawal reflex latency, and ankle kinematics. Stereological analysis was carried out on regenerated nerve fibers. Both motor and sensory functions improved significantly in the three experimental nerve repair groups, although the rate and extent of recovery was significantly higher in the group where the gap was reconstructed using the autologous graft. The presence of neural cells covering the inside of the PLGA tube guides did not make any difference in the functional recovery. By contrast, morphometric analysis showed that the introduction of N1E-115 cells inside PLGA 90:10 tube guides led to a significant lower number and size of regenerated nerve fibers, suggesting thus that this approach is not adequate for promoting peripheral nerve repair. Further studies are warranted to assess the role of other cellular systems as a foreseeable therapeutic strategy in peripheral nerve regeneration.

Chapter 8: Current techniques and concepts in peripheral nerve repair

Despite the progress in understanding the pathophysiology of peripheral nervous system injury and regeneration, as well as advancements in microsurgical techniques, peripheral nerve injuries are still a major challenge for reconstructive surgeons. Thorough knowledge of anatomy, pathophysiology, and surgical reconstruction is a prerequisite of proper peripheral nerve injury management. This chapter reviews the currently available surgical treatment options for different types of nerve injuries in clinical conditions. In overview of direct nerve repair, various end-to-end coaptation techniques and the role of end-to-side repair for proximal nerve injuries is described. When primary repair cannot be performed without undue tension, nerve grafting or tubulization techniques are required. Current gold standard for bridging nerve gaps is nerve autografting. However, disadvantages of this approach, such as donor site morbidity and limited length of available graft material encouraged the search for alternative means of nerve gap reconstruction. Nerve allografting was introduced for repair of extensive nerve injuries. Tubulization techniques with natural or artificial conduits are applicable as an alternative for bridging short nerve defects without the morbidities associated with harvesting of autologous nerve grafts. Achieving better outcomes depends both on the advancements in microsurgical techniques and introduction of molecular biology discoveries into clinical practice. The field of peripheral nerve research is dynamically developing and concentrates on more sophisticated approaches tested at the basic science level. Future directions in peripheral nerve reconstruction including, tolerance induction and minimal immunosuppression for nerve allografting, cell based supportive therapies and bioengineering of nerve conduits are also reviewed in this chapter.

Sural nerve autografts for high radial nerve injury with nine centimeter or greater defects

PURPOSE

The purpose of this study is to present the outcome of sural nerve grafting that focuses on motor fascicles in 6 patients with high radial nerve injuries with defects of more than 9 cm.

METHODS

Six patients with a high radial nerve complete injury were treated with a sural nerve autograft during a 6-year interval from June 1994 to June 2000. The gap of the radial nerve, which was measured in the surgical field, was 9 cm in 1 patient, 10 cm in 4 patients, and 11 cm in 1 patient. There were 4 men and 2 women with an average age of 32 years (range, 14-49 years). The causes of the injuries were a fracture of the humerus in 4 patients and surgery-related complications in 2 patients. Two or 3 multiple interfascicular nerve autografts of the sural nerve were sutured to the areas that have motor fascicles dominantly. The average delay from the injury to surgery was 6 months (range, 0.5-12 months), and the average duration of the follow-up after surgery was 48 months.

RESULTS

The overall motor recovery was M5 in 2 patients, M4 in 3 patients, and M2 in 1 patient. The overall sensory recovery was S3+ in 2 patients, S3 in 3 patients, and S1 in 1 patient.

CONCLUSIONS

In summary, good to excellent motor recovery can be expected in 83% of patients who have a large gap of the radial nerve when sural nerve autografts are sutured to the areas that have motor fascicles dominantly. Even for large gaps, within 8 months, an attempt at nerve reconstruction before proceeding to tendon transfers appears to be indicated.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.

Nervo alógeno conservado em glicerol: estudo experimental em ratos

A utilização de aloenxerto de nervo conservado em glicerol é uma alternativa a auto-enxertia em casos de lesões de nervos periféricos com perda de substância que diminui a morbidade cirúrgica e provem material suficiente para a reparação neural. O objetivo deste trabalho foi comparar o grau de reparação nervosa, utilizando análises histológica e funcional, através da interposição de enxerto autógeno (grupo A), de tubo de veia conservada em glicerol (grupo B) e de interposição de nervo alógeno conservado em glicerol (grupo C) em defeitos de 5 mm no nervo fibular de ratos Wistar. A análise histológica foi feita após o sacrifício dos animais( 6 semanas) , usando o corante azul de toluidina a 1%. No grupo A (auto-enxerto) verificou-se reação tecidual perineural e escape de fibras axonais mielinizadas para fora dos limites do epineuro que foi maior se comparada ao verificado no Grupo B (Veia autógena + glicerol) e Grupo C (aloenxerto de nervo).A avaliação funcional foi feita através da análise dos padrões das pegadas das patas posteriores dos ratos ("Walking Track Analysis"), nos períodos: pré-operatório, pós-operatório imediato, na terceira e sexta semanas. Na recuperação funcional, não houve diferença estatisticamente significativa entre os três grupos em nenhum dos períodos avaliados.

Median to radial nerve transfer for treatment of radial nerve palsy. Case report

The purpose of this study is to report a surgical technique of nerve transfer to restore radial nerve function after a complete palsy due to a proximal injury to the radial nerve. The authors report the case of a patient who underwent direct nerve transfer of redundant or expendable motor branches of the median nerve in the proximal forearm to the extensor carpi radialis brevis and the posterior interosseous branches of the radial nerve. Assessment included degree of recovery of wrist and finger extension, and median nerve function including pinch and grip strength. Clinical evidence of reinnervation was noted at 6 months postoperatively. The follow-up period was 18 months. Recovery of finger and wrist extension was almost complete with Grade 4/5 strength. Pinch and grip strength were improved postoperatively. No motor or sensory deficits related to the median nerve were noted, and the patient is very satisfied with her degree of functional restoration. Transfer of redundant synergistic motor branches of the median nerve can successfully reinnervate the finger and wrist extensor muscles to restore radial nerve function. This median to radial nerve transfer offers an alternative to nerve repair, graft, or tendon transfer for the treatment of radial nerve palsy.

PLGA 90/10 and caprolactone biodegradable nerve guides for the reconstruction of the rat sciatic nerve

The purpose of this study was to test in vivo two different nerve guides for promoting nerve regeneration across a 10-mm gap of the rat sciatic nerve: 1) one made of PLGA in a novel proportion (90:10) of the two polymers poly(L-lactide):poly(glycolide); 2) another made of (DL-lactide-epsilon-caprolactone) copolyester (Neurolac) tube, by comparing its healing efficacy with that of the more traditional methods of end-to-end nerve suture and autologous graft. Motor and sensory functional recovery were assessed throughout the healing period of 20 weeks, and the repaired nerves were processed for morphological and histomorphometrical analysis. Both motor and sensory functions improved significantly in all experimental nerve repaired groups. At the end of the 20-week follow-up, the end-to-end group showed better recovery of motor function when compared with the groups treated with guiding tubes. However, at this time point, the level of motor function in the Neurolac(R) and PLGA groups was similar to the one of the graft group. Nociception function also recovered faster in the end-to-end group compared with the Neurolac(R) and PLGA groups, and in this case, recovery was also delayed in the graft group. At the end of follow-up, nociception was similar in all experimental groups. Morphological and histomorphometrical analysis showed that axon regeneration occurred in both PLGA and Neurolac(R) experimental groups, with no significant differences in the total number of regenerated fibers, but disclosed a different pattern of degradation of the two types of tubes with larger biodegradation of PLGA material by the end of 20 weeks. These results suggest that both types of biomaterials are a good substrate for preparing tubular nerve guides, and their different pattern of degradation does not seem to influence the degree of nerve regeneration.

Utilização da veia glicerolada na regeneração neural: Estudo experimental em ratos

A auto-enxertia de nervo é o tratamento de escolha para grandes perdas de tecido neural que não podem ser reparadas por meio de rafia primária. A utilização do enxerto venoso previamente conservado em glicerol seria uma alternativa para diminuir o tempo operatório e a morbidade cirúrgica nesses casos. Os vasos preservados em glicerol não apresentam destruição de sua estrutura, o que permite seu uso na microcirurgia vascular, tendo a vantagem de diminuir a imunogenicidade do enxerto. O objetivo deste trabalho experimental foi comparar o grau de reparação nervosa, utilizando análise histológica, contagem do número de axônios mielinizados regenerados e análise funcional, obtida com a interposição de enxerto autógeno (grupo A) e de tubo de veia glicerolada (grupo B) em defeitos de 5 mm no nervo fibular de ratos Wistar. Somente no grupo A foi observado a formação de neuroma. O grupo B apresentou padrões histológicos compatíveis com diminuição quantitativa do número de axônios mielinizados regenerados em menor número em relação ao grupo A (controle). Na recuperação funcional, não houve diferença estatisticamente significativa entre os dois grupos.

Tissue engineered nerve constructs: where do we stand?

Driven by enormous clinical need, interest in peripheral nerve regeneration has become a prime focus of research and area of growth within the field of tissue engineering. While using autologous donor nerves for bridging peripheral defects remains today's gold standard, it remains associated with high donor site morbidity and lack of full recovery. This dictates research towards the development of biomimetic constructs as alternatives. Based on current concepts, this review summarizes various approaches including different extracellular matrices, scaffolds, and growth factors that have been shown to promote migration and proliferation of Schwann cells. Since neither of these concepts in isolation is enough, although each is gaining increased interest to promote nerve regeneration, various combinations will need to be identified to strike a harmonious balance. Additional factors that must be incorporated into tissue engineered nerve constructs are also unknown and warrant further research efforts. It seems that future directions may allow us to determine the "missing link".

The effect of high outflow permeability in asymmetric poly(dl-lactic acid-co-glycolic acid) conduits for peripheral nerve regeneration

This study attempted to accelerate the peripheral nerve regeneration, using the high outflow rate of asymmetric poly(dl-lactic acid-co-glycolic acid) (PLGA) nerve conduits. Asymmetric PLGA nerve conduits of monomer ratio 85/15 were prepared by immersion-precipitation method to serve as possible materials. In this study, mandrels were immersed into a 20% (wt/wt) of PLGA/1,4-dioxane solution and precipitated in a non-solvent bath followed by freeze-drying. Different concentrations of isopropyl alcohol (95%, 40% and 20%) were used as precipitation baths where non-asymmetric (95%) and asymmetric (40% and 20%) conduits could easily form. The asymmetric nerve conduits that consisted of macrovoids on the outer layer, and interconnected micropores in the inner sublayer, possessed characters of larger outflow rate than inflow rate. The asymmetric conduits were implanted to 10mm right sciatic nerve defects in rats. Autografts, silicone and non-asymmetric PLGA conduits were performed as the control and the contrast groups. Implanted graft specimens of all groups were harvested for histological analysis at 4 and 6 weeks following surgery. The asymmetric PLGA conduits maintained a stable supporting structure and inhibited exogenous cells invasion during entire regeneration process. Asymmetric PLGA conduits were found to have statistically greater number of regenerated axons at the midconduit and distal nerve site of implanted grafts, as compared to the silicone and non-asymmetric groups at 4 and 6 weeks. Of interest was that the results of 4 weeks in asymmetric groups were better than the non-asymmetric groups at 6 weeks in number of axons. According to the results of permeability, the asymmetric structure in the conduit wall seemed to enhance the removal of the blockage of the waste drain from the inner inflamed wound in the early stage, which may have improved the efficacy of the peripheral nerve regeneration. The asymmetric structure could be adequately employed in the future as optimal nerve conduits in peripheral nerve regeneration.

Low-intensity-ultrasound-accelerated nerve regeneration using cell-seeded poly(D,L-lactic acid-co-glycolic acid) conduits: an in vivo and in vitro study

This study investigated the effects of low intensity ultrasound on seeded Schwann cells within poly(DL-lactic acid-co-glycolic acid) (PLGA) conduits by in vitro and in vivo trials for peripheral nerve regeneration. The possible differences in the ultrasonic effects when using biodegradable and non-biodegradable materials as the conduits were also studied, using silicone rubber tubes as comparisons. In the in vitro study, seeded Schwann cells were cultured in serum deprivation culture medium that simulated the environment of mechanical trauma on injury nerve site. After 12, 24, and 48 h, only the PLGA conduit groups exposed to 0.05 W/cm(2), 3 min/treatment of ultrasound exhibited decreased LDH release and increased MTT values compared to the sham groups. Based on the results of the in vitro experiment in LDH and MTT testing, the silicone conduits with seeded Schwann cells group was ignored in the in vivo study. The PLGA nerve conduits seeded with Schwann cells (9 x 10(3) cells) were implanted to 15-mm right sciatic nerve defects in rats. Each conduit received 12 ultrasonic treatment sessions over 2 weeks after 1 day of rest. Ultrasound was applied as follows: frequency, 1MHz; intensity, 0.3 W/cm(2) (SATP); treatment, 5 min/day. Implanted graft specimens were harvested for histological analysis at 8 weeks following surgery. PLGA groups (with and without Schwann cells) treated with pulsed ultrasonic stimulation were found to have significantly greater number and area of regenerated axons at the mid-conduit of implanted grafts, as compared to the sham groups. Ultrasonic stimulation on silicone groups was found to induce a mass of fibrous tissues that covered the nerve conduits and retarded axon regeneration.

Alpha-conotoxin Vc1.1 alleviates neuropathic pain and accelerates functional recovery of injured neurones

This paper demonstrates the capacity of the neuronal nicotinic acetylcholine receptor (nAChR) antagonist alpha-conotoxin Vc1.1 to inhibit pain responses in vivo. Vc1.1 suppressed pain behaviors when tested in two models of peripheral neuropathy of the rat sciatic nerve, the chronic constriction injury (CCI) and partial nerve ligation (PNL) models. Mechanical hyperalgesia was assessed using an Ugo Basile Analgesymeter. Vc1.1 was administered by intramuscular bolus injection near the site of injury at doses of 0.036 microg, 0.36 microg and 3.6 microg in CCI rats and at a dose of 0.36 microg in PNL rats. Vc1.1 was also administered contralaterally in CCI rats at doses of 0.36 microg and 3.6 microg. Treatment started after the development of hyperalgesia and continued for 7 days. Vc1.1 significantly attenuated mechanical hyperalgesia in both CCI and PNL rats for up to a week following cessation of treatment. Vc1.1 also accelerated functional recovery of injured neurones. A blister was raised over the footpad innervated by the peripheral terminals of the injured nerve. The ability of these terminals to mount an inflammatory vascular response upon perfusion of the blister base with substance P provided a measure of functional recovery. This study shows that alpha-conotoxin Vc1.1, a neuronal nAChR antagonist, suppressed mechanical pain responses associated with peripheral neuropathy in rats in vivo and accelerated functional recovery of the injured neurones. A role for neuronal nAChRs in the analgesic activity of Vc1.1 is proposed.

Use of Skeletal Muscle Tissue in Peripheral Nerve Repair: Review of the Literature

The management of peripheral nerve injury continues to be a major clinical challenge. The most widely used technique for bridging defects in peripheral nerves is the use of autologous nerve grafts. This technique, however, necessitates a donor nerve and corresponding deficit. Many alternative techniques have thus been developed. The use of skeletal muscle tissue as graft material for nerve repair is one example. The rationale regarding the use of the skeletal muscle tissue technique is the availability of a longitudinally oriented basal lamina and extracellular matrix components that direct and enhance regenerating nerve fibers. These factors provide superiority over other bridging methods as vein grafts or (non)degradable nerve conduits. The main disadvantages of this technique are the risk that nerve fibers can grow out of the muscle tissue during nerve regeneration, and that a donor site is necessary to harvest the muscle tissue. Despite publications on nerve conduits as an alternative for peripheral nerve repair, autologous nerve grafting is still the standard care for treatment of a nerve gap in the clinical situation; however, the use of the skeletal muscle tissue technique can be added to the surgeon's arsenal of peripheral nerve repair tools, especially for bridging short nerve defects or when traditional nerve autografts cannot be employed. This technique has been investigated both experimentally and clinically and, in this article, an overview of the literature on skeletal muscle grafts for bridging peripheral nerve defects is presented.

Correlative high-resolution MR-anatomic study of sciatic, ulnar, and proper palmar digital nerve

Aim of this study was o evaluate the effectiveness of high-resolution MR imaging in demonstrating the anatomic structure of peripheral nerves of different diameter and composition. The dissected sciatic, ulnar, and proper palmar digital nerve of fresh cadavers were imaged at pre-selected landmarks on a 3T MR scanner. The nerves were then embedded in formalin, sliced, stained, and microscopically analyzed. The size, shape, and signal intensity of the sheath and axonal structures in the nerves at the landmarks were identified in MR images by comparison with histologic sections. The fascicles were clearly distinguished and counted in all specimens with MR imaging and showed only small differences from the histologic evaluation. High resolution MR imaging has the potential to visualize the fascicular structure in nerves of all sizes, which may be helpful in the preoperative assessment.

A review of neurophysiological testing

The rapid advances in the technology of, and accumulation of pertinent data in, electrophysiological testing has increased exponentially in the past decade. This is attributable to continued advances in computer technology, biomedical engineering, and now the coregistration of the electrophysiological data with neuroimaging results. Knowledge of normal function and electrophysiological response at rest or on stimulation of the central and peripheral nervous systems is important to the neurosurgeon. Only by a basic understanding of normal and abnormal recordings may diagnoses and localizations be achieved. Intraspinal and intracranial surgical procedures are predicated on nontrauma to the neuraxis. This can be accomplished by performing electrophysiological testing to monitor the function of the spinal and cranial nerves, spinal cord, brainstem, basal ganglia, and cerebrum. If the surgeon cannot delineate critical cortex or pathways, he or she will be unable to avoid these areas in the patient.

Functional assessment of sciatic nerve recovery: biodegradable poly (DLLA-epsilon-CL) nerve guide filled with fresh skeletal muscle

The aim of this study was to compare functional peripheral nerve recovery in the rat sciatic nerve model after reconstruction of a 10-mm gap with a biodegradable poly (DLLA-epsilon-CL) nerve guide, as filled with either fresh skeletal muscle or phosphate-buffered saline (PBS). During 24 weeks of recovery, motor and sensory functional evaluation was tested by extensor postural thrust (EPT) and withdrawal reflex latency (WRL), respectively. At the end of the experiment, anesthetized animals were prepared for motor nerve conduction velocity (MNCV) studies, followed by gastrocnemius and soleus muscle weight measurement. Motor functional recovery was greater in the muscle-grafted group, and reached a significant difference from weeks 8-12 (P < 0.05). The results of this investigation suggest that filling a nerve guide with fresh skeletal muscle induces faster maturation of regenerated nerve fibers in comparison with traditional tubular repair.

The Single-Fascicle Method of Nerve Grafting

In this study a single-fascicle technique for neural deficits repair was evaluated using a rat sciatic nerve model. Twenty-four Lewis rats were divided into 4 groups: group 1, 1.5-cm deficit without repair; group 2, conventional autograft; group 3, large-fascicle autograft; and group 4, small-fascicle autograft. Nerve regeneration was evaluated by pin-prick and toe-spread tests. Nerve samples were estimated by histomorphometry. Group 1 presented no recovery. Groups 3 and 4 demonstrated significantly better pin-prick results compared with those from conventional repair. Histology revealed a significantly higher number of axons and myelin thickness in the small-fascicle (2.8 +/- 0.4 x 10(3) axons, 4.22 +/- 0.41 microm) and large-fascicle (5.1 +/- 1.7 x 10(3) axons, 4.62 +/- 0.28 microm) groups compared with the conventional autograft group (2.1 +/- 0.3 x 10(3) axons, 2.93 +/- 0.20 microm). The small-fascicle group had a significantly greater mean axon area (58.59 +/- 15.81 microm2) than the large-fascicle group (29.66 +/- 12.67 microm2) and the conventional group (25.35 +/- 7.52 microm2). In this study, peripheral nerve repair using a single-fascicle graft resulted in faster functional recovery and better morphometric outcome compared with conventional nerve repair.

Toe out angle: a functional index for the evaluation of sciatic nerve recovery in the rat model

In experimental peripheral nerve studies, the rat sciatic nerve model is widely used to examine functional outcome following nerve injury and repair. A variety of evaluation methods exist in the literature, but an adequate selection continues to be a critical point for the researcher. Rats with sciatic nerve injury typically ambulate with an external rotation of the foot. A new functional assessment instrument, the toe out angle (TOA) is quantified using computerized gait analysis. We compared Sciatic Functional Index (SFI) with TOA parameter after peripheral nerve transection and entubulation repair. We found a good correlation between SFI and TOA measurements in terms of predicting functional recovery. Moreover, the TOA provides information on the biomechanical consequences of the external rotation of the foot in the stance phase of walking.

Approaches to tissue engineered peripheral nerve

The late 1980s and early 1990s brought excitement to the idea that we would be able to replace body tissues and organs through the field of tissue engineering. This enthusiasm was soon replaced by the realization of the limitations in our knowledge for specific tissue types and replication efforts. Such is the case with nerve tissue. We have progressed in this field of knowledge; however, full elucidation to the complex interactions of nerve repair falls short.

Evaluation of morphological and functional regeneration of rat nerve-muscle units after temporary and permanent tubulization

We compared the ability of temporary and permanent tubing to achieve morphological and functional recovery of nerve-muscle units, following experimental nerve transection (8-mm gap) in rat tibial nerve. Electrical stimulation of the sciatic nerve was used to analyze tension output, evoked electromyogram and conduction-transmission time (CTT) of denervated nerve-muscle units. Morphological analysis of the nerve and muscle was also performed. Within 6 weeks, the nerve gap had been bridged by a thin nerve trunk, and a few myelinated fibers were observed, although there was still no functional recovery. The rats were divided into two groups: permanent tubing (PT) and temporary tubing (TT; tubing subsequently removed). At 10 weeks after the operation, the TT group showed apparently greater thickness of regenerated nerve trunks, significantly higher tension output of plantar flexors, shorter CTT, and heavier muscle mass. These results were consistent with the presence of myelinated fibers in the regenerated nerve trunks, as shown histologically. Thus, removal of the silicone chamber results in faster and better recovery than tubing left permanently in place.

A novel technique for peripheral nerve repair

OBJECTIVE

To evaluate a novel technique for the repair of neural deficits using a single fascicle to bridge an injury in the rat sciatic nerve.

STUDY DESIGN

Twenty-four male Lewis rats were divided into four groups as follows: group 1 (control group), 1.5-cm deficit without repair; group 2, conventional epineural repair with autografts (100% diameter); group 3, nerve repair with large single autograft fascicle (50% diameter); and group 4, nerve repair with small single autograft fascicle (25% diameter).

METHODS

Nerve regeneration was evaluated at 3, 6, and 12 weeks by somatosensory evoked potential (SSEP) evaluation and standardized pin-prick and toe-spread tests. Nerve samples were harvested at 12 weeks and stained with toluidine blue to assess the total number of myelinated axons, axon area, and myelin sheath thickness.

RESULTS

In group I, the pin-prick and toe-spread tests showed no response at 3, 6, and 12 weeks. Rats in groups 3 and 4 demonstrated significantly better pin-prick test results and a trend toward better toe-spread test responses compared with conventional-repair animals. The SSEP evaluations displayed nondiagnostic waves in rats in group 1 rats. There was no evidence that the other surgery groups differed significantly in median SSEP latencies. Histological evaluation revealed fibrosis in rats in group 1 rats and a significantly higher median number of axons and myelin thickness in the small single fascicle (1296 axons and 4.22 microm, respectively) and large fascicle (2682 axons and 4.62 microm, respectively) groups compared with the conventional autograft group (630 axons and 2.93 microm, respectively). The small fascicle group had a significantly greater mean axon area (58.59 micro m2) than the large fascicle (29.66 micro m2) and conventional autograft (25.35 micro m2) groups.

CONCLUSIONS

Peripheral nerve repair using a single fascicle graft resulted in better functional recovery and morphometric outcome without a significant difference in electrophysiological status compared with conventional nerve repair. This technique may provide expanded sources of nerve autografts and alleviate the morbidity of harvesting peripheral nerves from multiple sites for individuals with extensive peripheral nerve injuries.

Microsurgery of peripheral nerve injuries: Analysis of twenty-five year experiences

Microsurgical procedures on injured peripheral nerves have been performed in Institute of neurosurgery in Belgrade for twenty-five years. During this period 1284 procedures, including 1029 on peripheral nerves, and 255 on brachial plexus were done. In this paper we analyze surgical results of individual procedures and the other factors influencing the outcome. Despite advances caused by introduction of the operating microscope, there are numerous controversies mainly in microsurgical technique that are discussed.

Nerve transfer in brachial plexus injuries: Comparative analysis of surgical procedures

Nerve transfer is the only possibility for nerve repair in cases of the brachial plexus traction injuries with spinal roots avulsion. From 1980. until 2000. in Institute of Neurosurgery, Clinical Center of Serbia, nerve transfer has been performed in 127(79%) of 159 patients with traction injuries of brachial plexus, i.e., 204 reinnervation procedures has been performed using different donor nerves. We achieved good or satisfactory arm abduction and full range or satisfactory elbow flexion through reinnervation of the axillary and musculocutaneous nerve using different donor nerves in 143 of 204 reinnervations, which presents general rate of useful functional recovery in 70,1% of cases. Mean values of the rate of useful functional recovery in individual modalities of nerve transfer in our series are 50,1% for intercostal and/or spinal accessory nerve transfer, 64,5% for plexo-plexal nerve transfer, 81,7% for regional nerve transfer, and 87,1% for combine nerve transfer.

Peripheral nerve regeneration by bone marrow stromal cells

Adult bone marrow contains stem cells that have attracted interest through their possible use for cell therapy in neurological diseases. Bone marrow stromal cells (MSCs) were harvested from donor adult rats, cultured and pre-labeled with bromodeoxyuridine (BrdU) previously to be injected in the distal stump of transected sciatic nerve of the rats. Distal nerve stump of control rats received culture medium solution. MSCs-treated rats exhibit significant improvement on walking track test at days 18 and 33 compared to controls. Dual immunofluorescence labeling shows that BrdU reactive cells survive in the injected area of transected sciatic nerve at least 33 days after implantation, and almost 5% of BrdU cells express Schwann cell-like phenotype (S100 immunoreactivity). Because MSCs injected in a lesioned peripheral nerve can survive, migrate, differentiate in Schwann cells, and promote functional recovery, they may be an important source for cellular therapy in several neurological diseases.

Omental graft improves functional recovery of transected peripheral nerve

The omentum has several properties that are advantageous for neuronal sprouting and direction. We have therefore analyzed functional recovery following transection of rat sciatic nerve using omental graft to bridge the nerve defect. In group 1, a 25-30-mm nerve defect was produced and bridged with omental graft, whereas in group 2, an end-to-end repair was performed. The sciatic function index (SFI) was assessed at 2-week intervals until 8 weeks after surgery. Functional recovery was faster in group 1 than in group 2. After 8 weeks, SFI was improved significantly from -100% to -45% (+/- -4%) in group 1 (P < 0.001) compared to -72% +/- -2% in group 2 (n = 10). Histologically, the omental graft contained more newly developed nerve fibers and less scar tissue than the end-to-end repair. Thus, omental graft appears to improve directional growth of regenerating axon sprouts and may be a means of treating peripheral nerve injury.