Percentage of nerve injuries in which primary repair can be achieved by end-to-end approximation: review of 2,181 nerve lesions

Assessment, management, and rehabilitation of traumatic peripheral nerve injuries for non-surgeons

Electrodiagnostic evaluation is often requested for persons with peripheral nerve injuries and plays an important role in their diagnosis, prognosis, and management. Peripheral nerve injuries are common and can have devastating effects on patients' physical, psychological, and socioeconomic well-being; alongside surgeons, electrodiagnostic medicine specialists serve a central function in ensuring patients receive optimal treatment for these injuries. Surgical intervention-nerve grafting, nerve transfers, and tendon transfers-often plays a critical role in the management of these injuries and the restoration of patients' function. Increasingly, nerve transfers are becoming the standard of care for some types of peripheral nerve injury due to two significant advantages: first, they shorten the time to reinnervation of denervated muscles; and second, they confer greater specificity in directing motor and sensory axons toward their respective targets. As the indications for, and use of, nerve transfers expand, so too does the role of the electrodiagnostic medicine specialist in establishing or confirming the diagnosis, determining the injury's prognosis, recommending treatment, aiding in surgical planning, and supporting rehabilitation. Having a working knowledge of nerve and/or tendon transfer options allows the electrodiagnostic medicine specialist to not only arrive at the diagnosis and prognosticate, but also to clarify which nerves and/or muscles might be suitable donors, such as confirming whether the branch to supinator could be a nerve transfer donor to restore distal posterior interosseous nerve function. Moreover, post-operative testing can determine if nerve transfer reinnervation is occurring and progress patients' rehabilitation and/or direct surgeons to consider tendon transfers.

Dynamic three-dimensional coculture model: The future of tissue engineering applied to the peripheral nervous system

Traumatic injuries to the peripheral nervous system (PNI) can lead to severe consequences such as paralysis. Unfortunately, current treatments rarely allow for satisfactory functional recovery. The high healthcare costs associated with PNS injuries, worker disability, and low patient satisfaction press for alternative solutions that surpass current standards. For the treatment of injuries with a deficit of less than 30 mm to bridge, the use of synthetic nerve conduits (NGC) is favored. However, to develop such promising therapeutic strategies, in vitro models that more faithfully mimic nerve physiology are needed. The absence of a clinically scaled model with essential elements such as a three-dimension environment and dynamic coculture has hindered progress in this field. The presented research focuses on the development of an in vitro coculture model of the peripheral nervous system (PNS) involving the use of functional biomaterial which microstructure replicates nerve topography. Initially, the behavior of neuron-derived cell lines (N) and Schwann cells (SC) in contact with a short section of biomaterial (5 mm) was studied. Subsequent investigations, using fluorescent markers and survival assays, demonstrated the synergistic effects of coculture. These optimized parameters were then applied to longer biomaterials (30 mm), equivalent to clinically used NGC. The results obtained demonstrated the possibility of maintaining an extended coculture of SC and N over a 7-day period on a clinically scaled biomaterial, observing some functionality. In the long term, the knowledge gained from this work will contribute to a better understanding of the PNS regeneration process and promote the development of future therapeutic approaches while reducing reliance on animal experimentation. This model can be used for drug screening and adapted for personalized medicine trials. Ultimately, this work fills a critical gap in current research, providing a transformative approach to study and advance treatments for PNS injuries.

Thermoelectric Freeze-Casting of Biopolymer Blends: Fabrication and Characterization of Large-Size Scaffolds for Nerve Tissue Engineering Applications

Peripheral nerve injuries (PNIs) are detrimental to the quality of life of affected individuals. Patients are often left with life-long ailments that affect them physically and psychologically. Autologous nerve transplant is still the gold standard treatment for PNIs despite limited donor site and partial recovery of nerve functions. Nerve guidance conduits are used as a nerve graft substitute and are efficient for the repair of small nerve gaps but require further improvement for repairs exceeding 30 mm. Freeze-casting is an interesting fabrication method for the conception of scaffolds meant for nerve tissue engineering since the microstructure obtained comprises highly aligned micro-channels. The present work focuses on the fabrication and characterization of large scaffolds (35 mm length, 5 mm diameter) made of collagen/chitosan blends by freeze-casting via thermoelectric effect instead of traditional freezing solvents. As a freeze-casting microstructure reference, scaffolds made from pure collagen were used for comparison. Scaffolds were covalently crosslinked for better performance under load and laminins were further added to enhance cell interactions. Microstructural features of lamellar pores display an average aspect ratio of 0.67 ± 0.2 for all compositions. Longitudinally aligned micro-channels are reported as well as enhanced mechanical properties in traction under physiological-like conditions (37 °C, pH = 7.4) resulting from crosslinking treatment. Cell viability assays using a rat Schwann cell line derived from sciatic nerve (S16) indicate that scaffold cytocompatibility is similar between scaffolds made from collagen only and scaffolds made from collagen/chitosan blend with high collagen content. These results confirm that freeze-casting via thermoelectric effect is a reliable manufacturing strategy for the fabrication of biopolymer scaffolds for future peripheral nerve repair applications.

Autologous Fibrin Glue Versus Microsuture in the Surgical Reconstruction of Peripheral Nerves: A Randomized Clinical Trial

PURPOSE

This study compared the motor and sensory recovery and the operative time of autologous fibrin glue application with conventional microsuturing technique in repairing peripheral nerves at the forearm and wrist levels METHODS: Eighty-five patients with injuries of the median, ulnar, or both nerves at the wrist and forearm levels underwent nerve repair between September 2014 and June 2018. Patients were randomly assigned at the time of diagnosis to a microsuture group (42 patients), in which standard epineurial microsurgical suturing was performed, or a fibrin glue group (43 patients), in which nerve repair was performed using autologous fibrin glue. The primary outcome measure was motor and sensory recovery. Operative time was the secondary outcome measure. Other outcome measures that were added post hoc, after trial initiation, included time to motor and sensory recovery; grip strength; pinch strength; Michigan hand outcome score; amplitude, latency, and duration of the compound motor unit action potential; and complications. All patients were followed up a minimum of 1 year.

RESULTS

At the final follow-up, both groups had regained similar motor and sensory function. The mean operative time was shorter in the fibrin glue group. Both groups had similar amplitude, latency, and duration of the compound motor unit action potential. Michigan Hand Outcome scores and mean percent recovery of grip strength and pinch strength were also similar. Six of 43 patients in the fibrin glue group compared with 8 of 42 patients in the microsuture group developed postoperative complications.

CONCLUSIONS

The use of fibrin glue to repair peripheral nerves is as effective as microsuturing in regaining motor and sensory functions and is associated with shorter operative time.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic II.

Muscle in vein conduits: our experience

Muscle in vein (MIV ) conduits have gradually been employed in the last 20 years as a valuable technique in bridging peripheral nerve gaps after nerve lesions who cannot undergo a direct tension-free coaptation. The advantages of this procedure comparing to the actual benchmark (autograft) is the sparing of the donor site, and the huge availability of both components (i.e. muscle and veins). Here we present a case serie of four MIV performed at our hospital from 2018 to 2019. The results we obtained in our experi-ence confirmed its effectiveness both in nerve regeneration (as sensibility recovery) and in neuropathic pain eradication. Our positive outcomes encourage its use in selected cases of residual nerve gaps up to 30 mm.

Sensory Restoration of the Facial Region

Normal sensitivity of the face is very important for preserving its integrity and function as an efferent source of information for the brain. The trigeminal nerve, which is the largest cranial nerve, conducts most of facial sensory function through its 3 branches: the ophthalmic nerve (V1), the maxillary nerve (V2), and the mandibular nerve (V3). The trigeminal nerve may be damaged by a variety of etiologies including inflammatory disorders, brain tumor resection, trauma, iatrogenic injury, or congenital anomalies. Temporary or permanent damage can lead to numbness, lip-biting injury, corneal anesthesia, and, in the worst scenario, even blindness. Different age groups, mechanisms of the injury, and the time between injury and repair can affect the final result of the nerve repair. Unlike the well-understood facial nerve palsy, so far there is no universal approach to restore the facial sensory function. This article serves to thoroughly review the basic anatomy of trigeminal nerve, diagnosis of sensory nerve dysfunction, and attempts to establish a protocol for treatment and rehabilitation of affected patients.

Skeletal muscle-derived cells repair peripheral nerve defects in mice

Skeletal muscle-derived cells have strong secretory function, while skeletal muscle-derived stem cells, which are included in muscle-derived cells, can differentiate into Schwann cell-like cells and other cell types. However, the effect of muscle-derived cells on peripheral nerve defects has not been reported. In this study, 5-mm-long nerve defects were created in the right sciatic nerves of mice to construct a peripheral nerve defect model. Adult female C57BL/6 mice were randomly divided into four groups. For the muscle-derived cell group, muscle-derived cells were injected into the catheter after the cut nerve ends were bridged with a polyurethane catheter. For external oblique muscle-fabricated nerve conduit and polyurethane groups, an external oblique muscle-fabricated nerve conduit or polyurethane catheter was used to bridge the cut nerve ends, respectively. For the sham group, the sciatic nerves on the right side were separated but not excised. At 8 and 12 weeks post-surgery, distributions of axons and myelin sheaths were observed, and the nerve diameter was calculated using immunofluorescence staining. The number, diameter, and thickness of myelinated nerve fibers were detected by toluidine blue staining and transmission electron microscopy. Muscle fiber area ratios were calculated by Masson’s trichrome staining of gastrocnemius muscle sections. Sciatic functional index was recorded using walking footprint analysis at 4, 8, and 12 weeks after operation. The results showed that, at 8 and 12 weeks after surgery, myelin sheaths and axons of regenerating nerves were evenly distributed in the muscle-derived cell group. The number, diameter, and myelin sheath thickness of myelinated nerve fibers, as well as gastrocnemius muscle wet weight and muscle area ratio, were significantly higher in the muscle-derived cell group compared with the polyurethane group. At 4, 8, and 12 weeks post-surgery, sciatic functional index was notably increased in the muscle-derived cell group compared with the polyurethane group. These criteria of the muscle-derived cell group were not significantly different from the external oblique muscle-fabricated nerve conduit group. Collectively, these data suggest that muscle-derived cells effectively accelerated peripheral nerve regeneration. This study was approved by the Animal Ethics Committee of Plastic Surgery Hospital, Chinese Academy of Medical Sciences (approval No. 040) on September 28, 2016.

Collagen Nerve Conduits and Processed Nerve Allografts for the Reconstruction of Digital Nerve Gaps: A Single-Institution Case Series and Review of the Literature

OBJECTIVE

A single-institution case series is reported and a review of the literature on the outcomes of digital nerve gap reconstruction with the NeuraGen type 1 collagen nerve conduit (Integra Life Sciences, Plainsboro New Jersey, USA) and the Avance Nerve Graft (Axogen Inc., Alachua, Florida, USA) is presented.

METHODS

Thirty-seven patients were included with a minimal follow-up of 12 months. Primary outcome was postoperative sensory recovery measured by static 2-point discrimination test or the Semmes-Weinstein monofilament test. Secondary outcome measurements were perioperative or postoperative complications. Final outcome data were stratified to grade results as excellent, good, or poor.

RESULTS

The mean nerve gap length was 14 ± 4.9 mm for the collagen conduits versus 18.4 ± 9.3 for nerve allografts. After 12 months, outcomes were graded as excellent sensory recovery in 48% of the collagen conduit repairs and 39% of the nerve allografts (P = 0.608), good in 26% of the conduits and 55% of the allografts (P = 0.074), and poor in 26% of the conduits versus 6% of the allografts (P = 0.091). One neuroma and 1 infection were reported. Graft rejection or extrusion was not observed.

CONCLUSIONS

Nerve conduits and processed nerve allografts offer convenient off-the-shelf options for digital nerve gap repair. Both techniques offer effective means of reconstructing a digital nerve gap <2.5 cm at a minimum of 12 months of follow-up. Future prospective randomized large sample size studies comparing nerve conduits with allografts are needed to perform subgroup analyses and to define their exact role in digital nerve injuries.

Use of Processed Nerve Allografts to Repair Nerve Injuries Greater Than 25 mm in the Hand

Processed nerve allografts (PNAs) have been demonstrated to have improved clinical results compared with hollow conduits for reconstruction of digital nerve gaps less than 25 mm; however, the use of PNAs for longer gaps warrants further clinical investigation. Long nerve gaps have been traditionally hard to study because of low incidence. The advent of the RANGER registry, a large, institutional review board-approved, active database for PNA (Avance Nerve Graft; AxoGen, Inc, Alachua, FL) has allowed evaluation of lower incidence subsets. The RANGER database was queried for digital nerve repairs of 25 mm or greater. Demographics, injury, treatment, and functional outcomes were recorded on standardized forms. Patients younger than 18 and those lacking quantitative follow-up data were excluded. Recovery was graded according to the Medical Research Council Classification for sensory function, with meaningful recovery defined as S3 or greater level. Fifty digital nerve injuries in 28 subjects were included. There were 22 male and 6 female subjects, and the mean age was 45. Three patients gave a previous history of diabetes, and there were 6 active smokers. The most commonly reported mechanisms of injury were saw injuries (n = 13), crushing injuries (n = 9), resection of neuroma (n = 9), amputation/avulsions (n = 8), sharp lacerations (n = 7), and blast/gunshots (n = 4). The average gap length was 35 ± 8 mm (range, 25-50 mm). Recovery to the S3 or greater level was reported in 86% of repairs. Static 2-point discrimination (s2PD) and Semmes-Weinstein monofilament (SWF) were the most common completed assessments. Mean s2PD in 24 repairs reporting 2PD data was 9 ± 4 mm. For the 38 repairs with SWF data, protective sensation was reported in 33 repairs, deep pressure in 2, and no recovery in 3. These data compared favorably with historical data for nerve autograft repairs, with reported levels of meaningful recovery of 60% to 88%. There were no reported adverse effects. Processed nerve allograft can be used to reconstruct long gap nerve defects in the hand with consistently high rates of meaningful recovery. Results for PNA repairs of digital nerve injuries with gaps longer than 25 mm compare favorably with historical reports for nerve autograft repair but without donor site morbidity.

Lateral Antebrachial Cutaneous Nerve as a Donor Source for Digital Nerve Grafting: A Concept Revisited

Objective:

The main objective of this study is to evaluate the availability of lateral antebrachial cutaneous nerve (LACN) autograft for acute or delayed repair of segmented digital nerve injuries.

Patients and Methods:

13 digital nerve defects of 11 patients; treated with interposition of LACN graft that harvested from ipsilateral extremity were included in the study. Mean follow up period was 35, 7 months. The mean time from injury to grafting is 53, 3 days. The results of the mean 2PDT and SWMT values of injured /uninjured finger at the end of follow up period were evaluated with Paired T test. The correlation between the defect length and the difference of 2PDT, SWMT values between the uninjured and injured finger at the end of follow up period; were evaluated with Pearson - correlation analysis.

Results:

The mean value of our 2PDT and SWMT results are ~5,923, ~3, 52, respectively in which can be interpreted between the normal and diminished light touch. The defect length and difference percentage of SWMT values is positively and significantly correlated statistically. Mean length of interposed nerve grafts was 18.5 mm. The age of the patient and the mean values of 2PDT and SWMT with the difference % of 2PDT and % of SWMT are not statistically correlated.

Conclusion:

Based on results regarding sensory regaining at recipient side and negligible sensory deficit at harvesting side, we suggest that lateral antebrachial cutaneous nerve might be a valuable graft option for digital nerve defects.

Reinnervation of denervated muscle by implantation of nerve-muscle-endplate band graft to the native motor zone of the target muscle

INTRODUCTION

Motor endplate reinnervation is critical for restoring motor function of the denervated muscle. We developed a novel surgical technique called nerve-muscle-endplate band grafting (NMEG) for muscle reinnervation.

METHODS

Experimentally denervated sternomastoid muscle in the rat was reinnervated by transferring a NMEG from the ipsilateral sternohyoid muscle to the native motor zone (NMZ) of the target muscle. A NMEG pedicle contained a block of muscle (~ 6 × 6 × 3 mm), a nerve branch with axon terminals, and a motor endplate band with numerous neuromuscular junctions. At 3 months after surgery, maximal tetanic muscle force measurement, muscle mass and myofiber morphology, motoneurons, regenerated axons, and axon-endplate connections of the muscles were analyzed.

RESULTS

The mean force of the reinnervated muscles was 82% of the contralateral controls. The average weight of the treated muscles was 89% of the controls. The reinnervated muscles exhibited extensive axonal regeneration. Specifically, the mean count of the regenerated axons in the reinnervated muscles reached up to 76.8% of the controls. The majority (80%) of the denervated endplates in the target muscle regained motor innervation.

CONCLUSIONS

The NMZ of the denervated muscle is an ideal site for NMEG implantation and for the development of new microsurgical and therapeutic strategies to achieve sufficient axonal regeneration, rapid endplate reinnervation, and optimal functional recovery. NMEG-NMZ technique may become a useful tool in the treatment of muscle paralysis caused by peripheral nerve injuries in certain clinical situations.

Nerve Repair and Nerve Grafting

Direct repair and nerve autografting are primary options in the treatment of upper extremity peripheral nerve injuries. Deciding between these surgical options depends on the mechanism of injury, time since injury, and length of repair defect. Principles of direct repair and nerve autografting are reviewed. Finally, a literature-based review of the outcomes of upper extremity peripheral nerve repair and autografting is provided. Taken together, this article provides relevant and recent data for surgeons regarding patient selection, technique selection, surgical technique, surgical outcomes, and prognostic factors that will aid surgeons treating patients with upper extremity peripheral nerve injuries.

The normal sensibility of the hand declines with age--a proclamation for the use of delta two-point discrimination values for sensibility assessment after nerve reconstruction

The scores used to evaluate sensibility after digital nerve reconstruction do not take the patient's age into consideration, although there is evidence that the outcome after digital nerve reconstruction is age-dependent. However, it is not clear if the normal sensibility of the hand is also age-dependent, as the existing studies have major limitations. We evaluated the normal sensibility of the hand in 232 patients using static and moving two-point discrimination (2PD) tests and the Semmes-Weinstein-monofilament test. We found the climax of sensibility in the third decade with age-dependent deterioration afterwards in all three tests. Mean 2PD values of the radial digital nerve of the index finger (N3) showed to be significantly lower than values of the ulnar digital nerve of the small finger (N10). To overcome shortcomings of classification systems that do not consider the patient's age and inter-individual differences, we suggest using the difference of the static 2PD values of the injured to the uninjured contralateral nerve (delta 2PD) for assessment of sensibility after digital nerve reconstruction.

Radial nerve lacerations--the outcome of end-to-end repairs in penetrating trauma

Due to its mostly motor content, repair of the radial nerve is considered to yield favourable results. This is despite the fact that there are limited studies looking at the outcomes of end-to-end repair secondary to sharp penetrating trauma. We retrospectively reviewed the outcome of a series of repaired level 2 and level 3 radial nerves following penetrating stab injuries. Twenty-seven cases with adequate follow-up were included. All the patients underwent direct end-to-end repair. We evaluated the motor recovery of the target muscles using the British Medical Research Council (MRC) grading system. Wrist extension recovered in 93% of cases at a mean of six months. Finger extension recovered in 74% and thumb extension in 52% of cases within the follow-up period. We conclude that end-to-end repair is possible in the majority of level 2 and level 3 radial nerve lacerations secondary to penetrating stab injuries. Acceptable results can be expected.

Progress of electrospun fibers as nerve conduits for neural tissue repair

Nerve tissue regeneration approaches have gained much attention in recent years, and nerve conduits (NCs), which facilitate nerve tissue regeneration, have become an attractive alternative to nerve autologous graft. Several methods are proposed to fabricate NCs, including electrospinning, which is a widely used approach for NCs and other tissue scaffolds, and has advantages such as the ability to control the thickness, diameter and porosity of fibers, as well as its simple experimental set up. This article gives an overview of electrospun fibers for nerve conduits utilized in peripheral and central nerve regeneration. Natural and synthetic materials with different mechanical strength, degradation rates and biocompatibility are proposed. Several bioactive proteins that can help the process of nerve regeneration are introduced. Finally, some approaches to control the morphology of electrospun fibers and to deliver bioactive proteins are discussed in detail.

Muscle reinnervation with nerve-muscle-endplate band grafting technique: correlation between force recovery and axonal regeneration

BACKGROUND

This study was designed to determine the correlation between functional recovery and the extent of axonal regeneration after muscle reinnervation with our recently developed nerve-muscle-endplate band grafting (NMEG) technique in a rat model.

MATERIALS AND METHODS

The right experimentally paralyzed sternomastoid (SM) muscle by nerve transection was immediately reinnervated with an NMEG pedicle harvested from a neighboring sternohyoid muscle. The NMEG pedicle contained a muscle block (6 × 6 × 3 mm), a donor nerve branch with nerve terminals, and a motor endplate band. Three months after surgery, the tetanic force of the SM muscle was measured and the regenerated axons in the muscle were detected using neurofilament immunohistochemistry.

RESULTS

The results showed that the maximal tetanic force (a measure of muscle functional recovery) of the NMEG-reinnervated SM muscle reached up to 66.0% of the normal control. The wet weight of the reinnervated SM muscle (a measure of muscle mass recovery) was 87.2% of the control. The area fraction of the regenerating axons visualized with neurofilament staining within the NMEG-reinnervated SM muscle (a measure of muscle reinnervation) was 42.3%. A positive correlation was revealed between the extent of muscle reinnervation and maximal muscle force.

CONCLUSIONS

Our newly developed NMEG technique results in satisfactory functional outcomes and nerve regeneration. Further improvement in the functional recovery after NMEG reinnervation could be achieved by refining the surgical procedure and creating an ideal environment that favors axon-endplate connections and accelerates axonal growth and sprouting.

Sensory recovery following decellularized nerve allograft transplantation for digital nerve repair

This study reported preliminary clinical experience of using decelluarised nerve allograft material for repair of digital nerve defect in five hand injury patients. From October 2009 to July 2010, five patients with traumatic nerve defect were treated with nerve repair using AxoGen® nerve allograft (AxoGen Inc, Alachua, FL) in California Hospital Medical Center. All patients were followed at least for 12 months, and sensory recovery and signs of infection or rejection were documented by a hand therapist. Average two-point discrimination was 6 mm, and average Semmes-Weinstein Monofilaments test was 4.31. No wound infections or signs of rejections were observed at wound site. All patients reported sensory improvement during the follow-up period after operation. It is believed that decellularised nerve allografts may provide a readily available option for repair of segmental nerve defect.

The effects of adjuvant fibrin sealant on the surgical repair of segmental nerve defects in an animal model

PURPOSE

Nerve repair after a segmental defect injury remains a challenge for surgeons. Fibrin glue can be used to expedite surgical procedures and maintain proper nerve spatial orientation to potentially optimize recovery, yet surgeons hesitate to use it owing to concerns about fibrin's inhibiting regeneration and increasing scar formation. The purpose of these experiments was to evaluate whether fibrin glue impedes nerve regeneration.

METHODS

A critical-size defect of 10 mm was created in 32 Sprague-Dawley rats with 4 different forms of repair: a collagen type-I conduit (n = 8), a collagen type-I conduit filled with fibrin glue (n = 8), an autologous nerve graft (n=8), and an autologous nerve graft with fibrin glue (n = 8). Behavioral tests, including sciatic functional indices, were used to evaluate functional recovery. Neurophysiology, immunohistochemistry, and nerve morphometry were used to critically analyze nerve regeneration.

RESULTS

Multiple outcome parameters for nerve regeneration, remyelination, behavior, and electrophysiology were used to determine that the addition of fibrin did not influence recovery for the autograft groups. Similarly, within the conduit group, behavioral tests showed comparable functional recovery and indistinguishable results in compound motor action potential and nerve morphometry. Immunohistochemistry revealed identical degrees of Wallerian degeneration and scarring between conduit groups.

CONCLUSIONS

The addition of fibrin to either the conduit or the autograft group did not result in any meaningful differences in recovery. Our data demonstrate that fibrin glue does not impede nerve regeneration or functional recovery after surgical repair of a segmental nerve defect in a rat model.

CLINICAL RELEVANCE

The clinical use of fibrin glue as an adjunct with peripheral nerve repair may be considered safe because it does not impair nerve regeneration with critical size defects in an animal model.

Comparison of muscle force after immediate and delayed reinnervation using nerve-muscle-endplate band grafting

BACKGROUND

Because of poor functional outcomes of currently used reinnervation methods, we developed novel treatment strategy for the restoration of paralyzed muscles-the nerve-muscle-endplate band grafting (NMEG) technique. The graft was obtained from the sternohyoid muscle (donor) and implanted into the ipsilateral paralyzed sternomastoid (SM) muscle (recipient).

METHODS

Rats were subjected to immediate or delayed (1 or 3 mo) reinnervation of the experimentally paralyzed SM muscles using the NMEG technique or the conventionally used nerve end-to-end anastomosis. The SM muscle at the opposite side served as a normal control.

RESULTS

NMEG produced better recovery of muscle force as compared with end-to-end anastomosis. A larger force produced by NMEG was most evident for small stimulation currents.

CONCLUSIONS

The NMEG technique holds great potential for successful muscle reinnervation. We hypothesize that even better muscle reinnervation and functional recovery could be achieved with further improvement of the environment that favors axon-end plate connections and accelerates axonal growth and sprouting.

Nerve regeneration with aid of nanotechnology and cellular engineering

Repairing nerve defects with large gaps remains one of the most operative challenges for surgeons. Incomplete recovery from peripheral nerve injuries can produce a diversity of negative outcomes, including numbness, impairment of sensory or motor function, possibility of developing chronic pain, and devastating permanent disability. In the last few years, numerous microsurgical techniques, such as coaptation, nerve autograft, and different biological or polymeric nerve conduits, have been developed to reconstruct a long segment of damaged peripheral nerve. A few of these techniques are promising and have become popular among surgeons. Advancements in the field of tissue engineering have led to development of synthetic nerve conduits as an alternative for the nerve autograft technique, which is the current practice to bridge nerve defects with gaps larger than 30 mm. However, to date, despite significant progress in this field, no material has been found to be an ideal alternative to the nerve autograft. This article briefly reviews major up-to-date published studies using different materials as an alternative to the nerve autograft to bridge peripheral nerve gaps in an attempt to assess their ability to support and enhance nerve regeneration and their prospective drawbacks, and also highlights the promising hope for nerve regeneration with the next generation of nerve conduits, which has been significantly enhanced with the tissue engineering approach, especially with the aid of nanotechnology in development of the three-dimensional scaffold. The goal is to determine potential alternatives for nerve regeneration and repair that are simply and directly applicable in clinical conditions.

Force characteristics of the rat sternomastoid muscle reinnervated with end-to-end nerve repair

The goal of this study was to establish force data for the rat sternomastoid (SM) muscle after reinnervation with nerve end-to-end anastomosis (EEA), which could be used as a baseline for evaluating the efficacy of new reinnervation techniques. The SM muscle on one side was paralyzed by transecting its nerve and then EEA was performed at different time points: immediate EEA, 1-month and 3-month delay EEA. At the end of 3-month recovery period, the magnitude of functional recovery of the reinnervated SM muscle was evaluated by measuring muscle force and comparing with the force of the contralateral control muscle. Our results demonstrated that the immediately reinnervated SM produced approximately 60% of the maximal tetanic force of the control. The SM with delayed nerve repair yielded approximately 40% of the maximal force. Suboptimal recovery of muscle force after EEA demonstrates the importance of developing alternative surgical techniques to treat muscle paralysis.

Nerve-muscle-endplate band grafting: a new technique for muscle reinnervation

BACKGROUND

Because currently existing reinnervation methods result in poor functional recovery, there is a great need to develop new treatment strategies.

OBJECTIVE

To investigate the efficacy of our recently developed nerve-muscle-endplate band grafting (NMEG) technique for muscle reinnervation.

METHODS

Twenty-five adult rats were used. Sternohyoid (SH) and sternomastoid (SM) muscles served as donor and recipient muscle, respectively. Neural organization of the SH and SM muscles and surgical feasibility of the NMEG technique were determined. An NMEG contained a muscle block, a nerve branch with nerve terminals, and a motor endplate band with numerous neuromuscular junctions. After a 3-month recovery period, the degree of functional recovery was evaluated with a maximal tetanic force measurement. Retrograde horseradish peroxidase tracing was used to track the origin of the motor innervation of the reinnervated muscles. The reinnervated muscles were examined morphohistologically and immunohistochemically to assess the extent of axonal regeneration.

RESULTS

Nerve supply patterns and locations of the motor endplate bands in the SH and SM muscles were documented. The results demonstrated that the reinnervated SM muscles gained motor control from the SH motoneurons. The NMEG technique yielded extensive axonal regeneration and significant recovery of SM muscle force-generating capacity (67% of control). The mean wet weight of the NMEG-reinnervated muscles (87% of control) was greater than that of the denervated SM muscles (36% of control).

CONCLUSION

The NMEG technique resulted in successful muscle reinnervation and functional recovery. This technique holds promise in the treatment of muscle paralysis.

Inducible nerve growth factor delivery for peripheral nerve regeneration in vivo

BACKGROUND

HEK-293 cells can be genetically modified to release and regulate nerve growth factor (NGF) in vitro. The aim of this study was to evaluate the impact of this NGF delivery system on peripheral nerve regeneration in vivo.

METHODS

HEK-293 cells were transfected with an ecdysone receptor, NGF cDNA, and herpes simplex virus-thymidine kinase suicide vector. NGF production is induced by ponasterone A and stopped by ganciclovir. A 13-mm sciatic nerve gap was bridged with Silastic conduits in 120 nude rats, and transfected HEK-293 cells were added, induced, and boostered to secrete bioactive NGF.

RESULTS

The induction of the cell line and additional booster with ponasterone A demonstrated significantly higher levels of bioactive NGF, enhanced macroscopic nerve growth, improved functional recovery, and histologic regeneration when compared with control groups after 7, 14, and 21 days, and 2 and 4 months. The treatment with ganciclovir resulted in suppression of the NGF production and decreased functional and histologic outcomes.

CONCLUSIONS

Transfected HEK-293 cells can be regulated to inducibly produce bioactive NGF in vivo over prolonged periods. This tissue-engineered nerve construct including the NGF delivery system is able to improve peripheral nerve regeneration and functional recovery and appears to be superior to nerve isografts.

Locations of the motor endplate band and motoneurons innervating the sternomastoid muscle in the rat

Sternocleidomastoid (SCM) is a long muscle with two bellies, sternomastoid (SM) and cleidomastoid (CM) in the lateral side of the neck. It has been widely used as muscle and myocutaneous flap for reconstruction of oral cavity and facial defects and as a candidate for reinnervation studies. Therefore, exact neuroanatomy of the SCM is critical for guiding reinnervation procedures. In this study, SM in rats were investigated to document banding pattern of motor endplates (MEPs) using whole-mount acetylcholinesterase (AChE) staining and to determine locations of the motoneurons innervating the muscle using retrograde horseradish peroxidase (HRP) tracing technique. The results showed that the MEPs in the SM and CM were organized into a single band which was located in the middle portion of the muscle. After HRP injections into the MEP band of the SM, ipsilaterally labeled motoneurons were identified in the caudal medulla oblongata (MO), C1, and C2. The SM motoneurons were found to form a single column in lower MO and dorsomedial (DM) nucleus in C1. In contrast, the labeled SM motoneurons in C2 formed either one (DM nucleus), two [DM and ventrolateral (VL) nuclei], or three [DM, VL, and ventromedial (VM)] columns. These findings are important not only for understanding the neural control of the muscle but also for evaluating the success rate of a given reinnervation procedure when the SM is chosen as a target muscle.

Nerve injuries of the upper extremity-expected outcome and clinical examination

Nerve injuries are common in trauma surgery and appear more frequently if the upper extremity is affected. The aim of this study is to estimate possible predictors of the outcome after nerve injury of the upper extremity and to demonstrate feasible tools to follow up postoperative nerve regeneration for the daily clinical practice. During January 2000 until December 2004, a total of 372 nerve lesions of the upper extremity have been treated in our clinic. Patient's age, site of nerve lesion, concomitant injuries, and the timing of surgical repair could be outlined to be significant predictors for clinical outcome. Digital nerve lesions showed the best regenerative capacity. Most predictors of clinical outcome such as patient's age, concomitant injuries, and site of lesion cannot be influenced. But knowing the predictors helps specify the prognosis of nerve regeneration. For the daily clinical practice, static two-point discrimination, location of Tinel's sign, and grip strength measurement seem to be fast and reproducible tools to follow up nerve regeneration at the upper extremity.

Nerve conduits and growth factor delivery in peripheral nerve repair

Peripheral nerves possess the capacity of self-regeneration after traumatic injury. Transected peripheral nerves can be bridged by direct surgical coaptation of the two nerve stumps or by interposing autografts or biological (veins) or synthetic nerve conduits (NC). NC are tubular structures that guide the regenerating axons to the distal nerve stump. Early synthetic NC have primarily been made of silicone because of the relative flexibility and biocompatibility of this material and because medical-grade silicone tubes were readily available in various dimensions. Nowadays, NC are preferably made of biodegradable materials such as collagen, aliphatic polyesters, or polyurethanes. Although NC assist in guiding regenerating nerves, satisfactory functional restoration of severed nerves may further require exogenous growth factors. Therefore, authors have proposed NC with integrated delivery systems for growth factors or growth factor-producing cells. This article reviews the most important designs of NC with integrated delivery systems for localized release of growth factors. The various systems discussed comprise NC with growth factors being released from various types of matrices, from transplanted cells (Schwann cells or mesenchymal stem cells), or through genetic modification of cells naturally present at the site of injured tissue. Acellular delivery systems for growth factors include the NC wall itself, biodegradable microspheres seeded onto the internal surface of the NC wall, or matrices that are filled into the lumen of the NC and immobilize the growth factors through physical-chemical interactions or specific ligand-receptor interactions. A very promising and elegant system appears to be longitudinally aligned fibers inserted in the lumen of a NC that deliver the growth factors and provide additional guidance for Schwann cells and axons. This review also attempts to appreciate the most promising approaches and emphasize the importance of growth factor delivery kinetics.

Long-term results after primary microsurgical repair of ulnar and median nerve injuries

OBJECTIVE

The aim of this retrospective study was to analyze the long-term results of primary repair of median and ulnar nerve lesions. Clinical influence factors for nerve reconstruction were investigated. Furthermore, current score systems were inquired and evaluated on their effectiveness to illustrate the success of repair.

PATIENTS AND METHOD

Sixty-five patients with 71 lesions of the median and ulnar nerve were assessed on average 8.2 years after reconstruction. The results were classified according to the DASH (disability of arm, shoulder, and hand) Score, the Rosen's hand protocol and the Highet Scale.

RESULTS

On average the patients regained 70% of their original hand function (evaluated by Rosen Score: median nerve 2.2/for ulnar nerve 1.92 out of 3.0). Although we noticed inferior motor recovery in ulnar nerve lesions, no significant differences between the overall results of both nerves were observed. Neither accompanying artery and flexor tendon injuries nor the suture technique influenced the recovery. The age of the patient was confirmed as an important influence factor. The results of the DASH Score, Rosen Score and Highet Score correlated significantly.

CONCLUSION

For a sufficient outcome measurement we underline the importance of evaluation of patient's estimation of their impact on their activities of daily living. For this a combination of the functional Rosen Score and the DASH Score is suggested.

Long-term functional results of primary reconstruction of severe forearm injuries

Severe forearm injuries caused by machinery such as a power saw represented about 0.2% of all upper limb injuries operated on in the plastic surgery section of our institute between 1993 and 1997. These are complex and contaminated injuries with severe damage to skin, muscles, tendons, nerves, vessels and bones. Primary repair or reconstruction of all the divided vital structures was carried out in our series of four patients, including one 4-cm cable nerve graft for a median nerve defect. After an average 22-month follow up, the functional results showed grade M4 motor recovery and better than grade S3+ sensory recovery of the hand in all four patients. We suggest that a definitive primary procedure is best when possible. This will achieve a better functional outcome from early neural regeneration, and will reduce the frequency of secondary procedures, cause less scarring, and shorten the duration of hospital stays and rehabilitation periods.

Functional reinnervation of the canine bladder after spinal root transection and immediate end-on-end repair

The goal of this study was to transect and immediately repair ventral roots, selected by their ability to stimulate bladder contraction, to assess the feasibility of bladder reinnervation in a canine model. Brain-derived neurotrophic factor (BDNF) was delivered via an osmotic pump (0.5 or 5 mg/mL) to a cuff surrounding the reanastomosis site to the two root bundles on one side. Electrodes were implanted bilaterally immediately proximal to the site of surgical reanastomosis. Results were compared to four root-intact, control animals that also received bilateral electrode implantation. At 6-12 months post-surgery, five of eight nerve transected and repaired animals showed increased pressure and bladder emptying during electrical stimulation of the repaired ventral roots contralateral to the BDNF delivery side. Nerve tracing studies one year postoperatively determined the repaired roots to be S1 and S2 and showed regrowth of axons from the spinal cord to nerve sites proximal to the repair site and to the bladder, and the presence of neurofilament-labeled axons growing across the ventral root repair site. In conclusion, transected ventral and dorsal roots in the sacral spine can be repaired and are capable of functionally reinnervating the urinary bladder. This feasibility study paves the way for future studies utilizing other more proximal motor nerves to bypass the transection site for bladder reinnervation.

Effect of tension on nerve regeneration in rat sciatic nerve transection model

Excessive tension across a nerve repair is known to impair nerve regeneration. However, it is uncertain whether nerve grafting is necessary when end-to-end repair would result in only mild to moderate tension. This study investigated the effect of tension on nerve regeneration. Sciatic nerves of 48 Lewis rats were transected and then repaired primarily after resection of 0-, 3-, 6-, or 9-mm lengths of nerve. Postoperative tension levels were quantified using a tensometer. Robust nerve regeneration was observed at 4 weeks in all except the 9-mm repair group, which showed lower nerve fiber counts, percent neural tissue, and nerve density (P < 0.05) and decreased functional recovery. These data indicate that modest levels of tension are well tolerated, but nerve regeneration drops precipitously once a critical tension threshold is exceeded. This threshold was between 0.39 and 0.56 N in the model studied, corresponding to a nerve defect between 6 mm and 9 mm.

Exogenous leukaemia inhibitory factor enhances nerve regeneration after late secondary repair using a bioartificial nerve conduit

The clinical outcome of peripheral nerve injuries remains disappointing, even in the ideal situation of a primary repair performed with optimal microsurgical techniques. Primary repair is appropriate for only about 85% of injuries, and outcome is worse following secondary nerve repair, partly owing to the reduced regenerative potential of chronically axotomised neurons. Leukaemia inhibitory factor (LIF) is a gp-130 neurocytokine that is thought to act as an 'injury factor', triggering the early-injury phenotype within neurons and potentially boosting their regenerative potential after secondary nerve repair. At 2-4 months after sciatic nerve axotomy in the rat, 1 cm gaps were repaired using either nerve isografts or poly-3-hydroxybutyrate conduits containing a calcium alginate and fibronectin hydrogel. Regeneration was determined by quantitative immunohistochemistry 6 weeks after repair, and the effect of incorporating recombinant LIF (100 ng/ml) into the conduits was assessed. LIF increased the regeneration distance in repairs performed after both 2 months (69%, P=0.019) and 4 months (123%, P=0.021), and was statistically comparable to nerve graft. The total area of axonal immunostaining increased by 21% (P>0.05) and 63% (P>0.05), respectively. Percentage immunostaining area was not increased in the 2 months group, but increased by 93% in the repairs performed 4 months after axotomy. Exogenous LIF, therefore, has a potential role in promoting peripheral nerve regeneration after secondary repair, and can be effectively delivered within poly-3-hydroxybutyrate bioartificial conduits used for nerve repair.

Primary sciatic nerve repair using titanium staples

The primary epineural repair of human peripheral nerves is most often achieved using non-absorbable microsutures, which can elicit a foreign-body reaction. We describe a new system for neural-tissue approximation, consisting of non-penetrating vascular closure staples (VCS) applied to the epineurium. These clips were initially developed for use in microvascular anastomosis, with no knowledge of their effectiveness in neural-tissue approximation. We compare the efficacies of VCS clips and monofilament nylon microsutures in the repair of transected sciatic nerves in 36 adult Sprague Dawley rats (18 treated with 9/0 sutures and 18 treated with VCS clips). In the rat, regeneration starts by day 5, and is well advanced by 4 weeks. To assess the overall repair success, the site of injury, after perfusion fixation, was harvested at 5, 7 and 30 days. The two methods were compared in terms of operative time, the degree of self-mutilation (autotomy), the macroscopic specimens in vivo and the microanatomical continuity through the repair site. Continuity was studied by using PGP-9.5-labelled cryosections and fluorescent secondary antibodies to visualise axonal regeneration. Clip repair was significantly faster in the VCS group (mean +/- s.e.m. = 7.09 +/- 0.36 min versus mean +/- s.e.m. 11.56 +/- 0.51 min in the sutured group) and an equal and minimal degree of autotomy was observed. Macroscopically, all 36 nerves were in continuity and free from neuroma. The use of VCS clips resulted in equivalent visualised regeneration across the repair site at each time point. We believe the use of VCS clips to be a faster and comparable alternative to non-absorbable sutures in primary nerve repair in this experimental model.

Regeneration of sudomotor and sensory nerve fibres after digital replantation and microneurovascular toe-to-hand transfer

The end-stage sudomotor and sensory recovery in patients with replanted fingers and patients after microneurovascular toe-to-hand transfer was studied using quantitative electrophysiological investigations (recovery of sensory nerve action potentials and the sympathetic skin response), the ninhydrin test and clinical testing of sensory regeneration (light touch, pain, static and dynamic two-point discrimination). 13 adult patients with 22 replanted digits (11 males, 2 females) aged 21-58 years (mean 42.2 years) and 12 adults and adolescents (8 males, 4 females) aged 13-45 years, (mean 26.8 years) following 14 microneurovascular great and/or second toe-to-hand transfers were studied. The replanted fingers were examined 2-7 years after injury and replantation. The toe-to-hand transfers were examined 2-12 years after injury and transfer. The results show better end-stage recovery of sudomotor and sensory function following finger replantation when compared to microneurovascular toe-to-hand transfer.

The epidemiology and management of upper limb peripheral nerve injuries in modern practice

This paper reports an epidemiological and clinical study of 813 patients with 1,111 peripheral nerve injuries who were treated for upper limb trauma, which included nerve injury, at two plastic surgery units in south-east England, predominantly between the years 1982 and 1991. The frequency distributions of the levels of nerve injury, and the causes of nerve injury in the sample, are presented, together with the surgical management and timing of nerve repair in these patients. 1,018 clinically suspected nerve injuries in 730 patients (91.6% of nerves, 89.8% of patients) were treated by primary nerve repair, elective delayed nerve repair or primary surgical exploration alone. Divisions of 93 nerves in 83 patients (8.3% of nerves, 10.2% of patients) were treated other than by primary repair or elective delayed repair, due to delayed referral from accident and emergency departments, resulting from missed or uncertain diagnosis at presentation or otherwise unaccounted delay in the initial referral.