Functional and morphometric evaluation of end-to-side neurorrhaphy for muscle reinnervation

Modified Urethral Graciloplasty Cross-Innervated by the Pudendal Nerve for Postprostatectomy Urinary Incontinence: Cadaveric Simulation Surgery and a Clinical Case Report

An artificial sphincter implanted in the bulbous urethra to treat severe postprostatectomy urinary incontinence is effective, but embedding-associated complications can occur. We assessed the feasibility, efficacy, and safety of urethral graciloplasty cross-innervated by the pudendal nerve. A simulation surgery on three male fresh cadavers was performed. Both ends of the gracilis muscle were isolated only on its vascular pedicle with proximal end of the obturator nerve severed and transferred to the perineum. We examined whether the gracilis muscle could be wrapped around the bulbous urethra and whether the obturator nerve was long enough to suture with the pudendal nerve. In addition, surgery was performed on a 71-year-old male patient with severe urinary incontinence. The postoperative 12-month outcomes were assessed using a 24-hour pad test and urodynamic study. In all cadaveric simulations, the gracilis muscles could be wrapped around the bulbous urethra in a γ-loop configuration. The length of the obturator nerve was sufficient for neurorrhaphy with the pudendal nerve. In the clinical case, the postoperative course was uneventful. The mean maximum urethral closure pressure and functional profile length increased from 40.7 to 70 cm H 2 O and from 40.1 to 45.3 mm, respectively. Although urinary incontinence was not completely cured, the patient was able to maintain urinary continence at night. Urethral graciloplasty cross-innervated by the pudendal nerve is effective in raising the urethral pressure and reducing urinary incontinence.

A Rabbit Model for Peripheral Nerve Reconstruction Studies Avoiding Automutilation Behavior

Background  The rabbit sciatic nerve injury model may represent a valuable alternative for critical gap distance seen in humans but often leads to automutilation. In this study, we modified the complete sciatic nerve injury model for avoiding autophagy.

Materials and Methods  In 20 adult female New Zealand White rabbits, instead of transecting the complete sciatic nerve, we unilaterally transected the tibial portion and preserved the peroneal portion. Thereby loss of sensation in the dorsal aspect of the paw was avoided. The tibial portion was repaired in a reversed autograft approach in a length of 2.6 cm. In an alternative repair approach, a gap of 2.6 cm in length was repaired with a chitosan-based nerve guide.

Results  During the 6-month follow-up period, there were no incidents of autotomy. Nerve regeneration of the tibial portion of the sciatic nerve was evaluated histologically and morphometrically. A clear difference between the distal segments of the healthy contralateral and the repaired tibial portion of the sciatic nerve was detectable, validating the model.

Conclusion  By transecting the isolated tibial portion of the rabbit sciatic nerve and leaving the peroneal portion intact, it was possible to eliminate automutilation behavior.

Myelination, axonal loss and Schwann cell characteristics in axonal polyneuropathy compared to controls

Introduction

Polyneuropathy is a debilitating condition characterized by distal sensory and motor deficits. Schwann cell dysfunction and axonal loss are integral factors in pathophysiology and disease progression of polyneuropathy.

Aims

The aim of this study was the assessment of Schwann cell characteristics, nerve fibers and myelination parameters in polyneuropathy patients compared to controls.

Methods

Nerve tissue was obtained from polyneuropathy patients (n = 10) undergoing diagnostic sural nerve biopsies. Biopsies of healthy peripheral nerves (n = 5) were harvested during elective sural nerve grafting for chronic peripheral nerve lesions. Exclusion criteria for the healthy control group were recent neurological trauma, diabetes, neurological and cardiovascular disease, as well as active malignancies and cytotoxic medication within the last 12 months. The over-all architecture of nerve sections and myelination parameters were histomorphometrically analyzed. Immunofluorescent imaging was used to evaluate Schwann cell phenotypes, senescence markers and myelination parameters.

Results

Histomorphometric analysis of nerve biopsies showed significant axonal loss in polyneuropathy patients compared to controls, which was in accordance with the neuropathological findings. Immunofluorescent staining of Schwann cells and myelin basic protein indicated a significant impairment of myelination and lower Schwann cell counts compared to controls. Phenotypic alterations and increased numbers of non-myelinating p75-positive Schwann cells were found in polyneuropathy patients.

Discussion

This study provided quantitative data of axonal loss, reduced myelination and Schwann cell dysfunction of polyneuropathy patients compared to neurologically healthy controls. Phenotypic alterations of Schwann cells were similar to those seen after peripheral nerve injury, highlighting the clinical relevance of Schwann cell dysfunction.

Assessment of axonal sprouting and motor performance after hypoglossal-facial end-to-side nerve repair: experimental study in rats

Hypoglossal-facial nerve anastomosis (HFA) aims to reanimate denervated mimic muscles with hypoglossal axons when the transected facial nerve is not accessible. The aim of this study was to evaluate the recovery of HFA using a "Y" tube in two variants: (1) the proximal stump of the hypoglossal nerve was entubulated to the "Y" tube (classic "Y" tube HFA) and (2) the "Y" tube was sutured to an epineurial window of a slightly damaged hypoglossal nerve (end-to-side "Y" tube HFA). A total of 48 adult female rats were divided into four groups: intact controls (group 1), sham operated (group 2), classic "Y" tube HFA (group 3) and end-to-side "Y" tube HFA (group 4). The abdominal aorta with both common iliac arteries of isogeneic male rats served as the Y-tube conduit. Animals from group 4 recovered better than those from group 3: the degree of collateral axonal branching (3 ± 1%) was significantly lower than that determined in group 3 (13 ± 1%). The mean deviation of the tongue from the midline was significantly smaller in group 4 (6 ± 4°) than that measured in animals from group 3 (41 ± 6°). In the determination of vibrissal motor function in group 3 and group 4, a decrease in amplitude was found to be - 66% and - 92%, respectively. No differences in the reinnervation pattern of the target muscles were detected. As a result, these surgical models were not determined to be able to improve vibrissal movements. It was concluded that performance of end-to-side "Y" tube HFA diminishes collateral axonal branching at the lesion site, which in turn, promotes better recovery of tongue- and vibrissal-motor performance.

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

Objective:

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

Data sources:

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

Data selection:

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

Outcome measures:

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

Results:

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

Conclusion:

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

Axon numbers and landmarks of trigeminal donor nerves for corneal neurotization

Purpose

Corneal anesthesia leads to chronic corneal injury. This anatomical study characterizes the donor nerve branches of the supratrochlear and supraorbital nerves used for corneal neurotization.

Methods

In 13 non-embalmed cadavers, the supratrochlear and supraorbital nerves were dissected and distances to anatomical landmarks measured. Cross-sections of supratrochlear and supraorbital donor nerves were harvested and histomorphometrically analyzed to assess the number of myelinated axons.

Results

The donor axon counts were 3146 ± 1069.9 for the supratrochlear and 1882 ± 903 for the supraorbital nerve distal to the supraorbital notch. The supratrochlear nerve was dissected on the medial upper eyelid 2 cm lateral to the facial midline and the branch of the supraorbital nerve 1 cm medial to the mid-pupillary line.

Conclusion

The supraorbital and supratrochlear branches of the trigeminal nerve are potent donor nerves for corneal neurotization in the treatment of neuropathic keratopathy and can be reliably dissected using anatomical landmarks.

Comparison of conduit and autograft efficiency in repairing femoral nerve injury in New Zealand rabbits

Background: Peripheral nerve injuries may affect all age groups and exert devastating impacts on the professional and personal life of the patients. The investigation of nerve regeneration and use of biomaterials and synthetic materials have resulted in advancements in the treatment of peripheral nerve injuries and lesions. Nerve conduits can be used to adjoin the digital sensory nerve spaces of less than 3 cm, especially when the direct tension-free repair of peripheral nerve lesions is not possible. The present study was conducted to evaluate the use of nerve conduits by functional and nonfunctional parameters (i.e. histological study). Methods: This experimental study was conducted on 30 male rabbits. After cutting or crushing the right femoral nerve of the rabbits, they were divided into 3 groups: group 1, with right femoral nerve cut; group 2, with right femoral nerve crushed; and group 3, with right femoral nerve cut using a conduit. The 3 groups were evaluated after 1, 8, and 16 weeks for functional parameters (i.e. walking track analysis). In addition, they were subjected to nonfunctional examination (i.e. histological study) after 16 weeks, then, the results were compared. Results: The 3 groups showed no statistically significant differences in motor recovery in the eighth and 16th weeks (p>0.05). Based on the histological study, group 3 with an end-to-end nerve cutting using a conduit, showed a significantly higher axon count compared to groups 2 and 3 (p<0.05). Conclusion: End-to-end anastomosis using conduit led to axon growth; moreover, comparable functional recovery was observed with end-to-end neurorrhaphy in a rabbit model. Given that the diameter of the nerves and muscles, which might be neurotized in humans, and is much bigger and not comparable to that of the rabbits, it is highly recommended to conduct studies on animals with the larger size, such as primates, to facilitate the generalization of the results to humans.

The reasons for end-to-side coaptation: how does lateral axon sprouting work?

Nerve fibers are attracted by sutureless end-to-side nerve coaptation into the recipient nerve. Opening a window in the epineurium enhances axon attraction and myelination. The authors analyze the features of nerve repair by end-to-side coaptation. They highlight the known mechanisms of axon sprouting and different hypotheses of start up signals (presence or absence of an epineurial window, role of Schwann cells, signaling from the distal trunk). The clinical literature is also presented and differences between experimental and clinical applications are pointed out. The authors propose their point of view and perspectives deriving from recent experimental and clinical experiences.

Comparison of Peripheral Nerve Regeneration with Side-to-side, End-to-side, and End-to-end Repairs: An Experimental Study

Background:

The present study was conducted to find out a tool to enable improved functional recovery with proximal nerve injury. In this experimental study, nerve regeneration was compared between side-to-side (STS), end-to-side (ETS), and end-to-end repairs.

Methods:

The walk track analysis was used as an outcome of functional recovery. Nerve regeneration was studied with morphometry and histology 6 or 26 weeks postoperatively.

Results:

All 3 repair techniques showed regeneration of the nerve. From 12 weeks onward, the functional results of the 3 intervention groups were significantly better compared with the unrepaired control group. End-to-end repair was significantly better when compared with the STS and ETS groups. At 26 weeks, the functional and morphometric results and histologic findings did not differ between the STS and ETS groups. The functional results correlated with the morphometric findings in all groups.

Conclusions:

STS neurorrhaphy showed nerve regeneration, and the end results did not differ from clinically widely used ETS repair. Further studies are warranted to optimize the neurorrhaphy technique and examine possible applications of STS repair in peripheral nerve surgery.

The Spinal Accessory Nerve for Functional Muscle Innervation in Facial Reanimation Surgery: An Anatomical and Histomorphometric Study

INTRODUCTION

Facial reanimation surgery is performed in severe cases of facial palsy to restore facial function. In a 1-stage procedure, the spinal accessory nerve can be used as a donor nerve to power a free gracilis muscle transplant for the reanimation of the mouth. The aim of this study was to describe the surgical anatomy of the spinal accessory nerve, provide a guide for reliable donor nerve dissection, and analyze the available donor axon counts.

METHODS

Dissections were performed on 10 nonembalmed cadavers (measurements of 20 nerves). Surgical anatomy of the spinal accessory nerve was described and distances to important landmarks were measured. Nerve biopsies were obtained of the main nerve trunk distal to the skull base, caudoposterior to the sternocleidomastoid muscle, proximal to the trapezius muscle and at the level of donor nerve harvest to analyze the myelinated axon count throughout the course of the spinal accessory nerve. The donor nerve length and available donor nerve axon count were the primary outcome parameters in this study.

RESULTS

The mean donor nerve length was 11.6 cm. The spinal accessory nerve was transferred to the mandibular angle without tension for ideal coaptation to the free muscle transplant. After retraction of the trapezius muscle, a small distal nerve branch that leaves the main nerve trunk at a 90-degree angle medially was used as a landmark to indicate the level of donor nerve transection. On average, 1400 myelinated donor axons were available for innervation of the gracilis muscle transplant.

CONCLUSIONS

This study gives a practical guide for spinal accessory nerve dissection for its application in facial reanimation as a motor source for the innervation of a free muscle transplant.

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

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

Macroscopic in vivo imaging of facial nerve regeneration in Thy1-GFP rats

IMPORTANCE

Facial nerve injury leads to severe functional and aesthetic deficits. The transgenic Thy1-GFP rat is a new model for facial nerve injury and reconstruction research that will help improve clinical outcomes through translational facial nerve injury research.

OBJECTIVE

To determine whether serial in vivo imaging of nerve regeneration in the transgenic rat model is possible, facial nerve regeneration was imaged under the main paradigms of facial nerve injury and reconstruction.

DESIGN, SETTING, AND PARTICIPANTS

Fifteen male Thy1-GFP rats, which express green fluorescent protein (GFP) in their neural structures, were divided into 3 groups in the laboratory: crush-injury, direct repair, and cross-face nerve grafting (30-mm graft length). The distal nerve stump or nerve graft was predegenerated for 2 weeks. The facial nerve of the transgenic rats was serially imaged at the time of operation and after 2, 4, and 8 weeks of regeneration. The imaging was performed under a GFP-MDS-96/BN excitation stand (BLS Ltd).

INTERVENTION OR EXPOSURE

Facial nerve injury.

MAIN OUTCOME AND MEASURE

Optical fluorescence of regenerating facial nerve axons.

RESULTS

Serial in vivo imaging of the regeneration of GFP-positive axons in the Thy1-GFP rat model is possible. All animals survived the short imaging procedures well, and nerve regeneration was followed over clinically relevant distances. The predegeneration of the distal nerve stump or the cross-face nerve graft was, however, necessary to image the regeneration front at early time points. Crush injury was not suitable to sufficiently predegenerate the nerve (and to allow for degradation of the GFP through Wallerian degeneration). After direct repair, axons regenerated over the coaptation site in between 2 and 4 weeks. The GFP-positive nerve fibers reached the distal end of the 30-mm-long cross-face nervegrafts after 4 to 8 weeks of regeneration.

CONCLUSIONS AND RELEVANCE

The time course of facial nerve regeneration was studied by serial in vivo imaging in the transgenic rat model. Nerve regeneration was followed over clinically relevant distances in a small number of experimental animals, as they were subsequently imaged at multiple time points. The Thy1-GFP rat model will help improve clinical outcomes of facial reanimation surgery through improving the knowledge of facial nerve regeneration after surgical procedures.

LEVEL OF EVIDENCE

NA.

Non-invasive isometric force measurement of plantar flexors in rats

INTRODUCTION

Isometric muscle force measurement is a sensitive marker for motor function recovery in rat nerve repair models. Current methods of eliciting maximal isometric force with nerve stimulation cannot provide longitudinal data.

METHODS

We developed a novel method for measuring isometric muscle force with a device designed to allow minimally invasive nerve stimulation and measurement of plantar flexion force. This indirectly elicited muscle force was compared with muscle force elicited by direct muscle stimulation in 3 surgical models.

RESULTS

The force measured after sciatic nerve transection and repair followed a parabolic trend. There was a postinjury decrease in force that continued until postoperative day 42, after which the force increased with time, indicating muscle reinnervation.

CONCLUSIONS

This approach can track longitudinal changes in force in the most common animal model for studies of clinically relevant problems in the peripheral nerve field.

Effect of electrical stimulation of the cranial tibial muscle after end-to-side neurorrhaphy of the peroneal nerve in rats

PURPOSE

To investigate the efficiency of electrical stimulation in the muscle maintenance and nerve regeneration after end-to-side neurorrhaphy (ESN).

METHODS

Sixty male Wistar rats (Rattus norvegicus) were divided into four experimental groups. Control group (Control), Denervated Group (Denervated); Group with End-to-side neurorrhaphy (ESN); Group with End-to-side neurorrhaphy and electrical stimulation (ESN + ES). We perform electrical stimulation in rats after they had undergone muscle reinnervation by ESN. We collected morphometric and functional data.

RESULTS

When comparing the mass of the treated side of cranial tibial muscle (CTM) and that of normal side of CTM, the group ESN + ES (26.12%) exhibited lower mass loss than that of group ESN (37.23%). The peroneal functional index showed that group ESN + ES equaled that of the Control group and showed an evolution of 60.5% while group ESN showed an evolution of 9.5%. In measuring maximum strength of CTM, the group ES + ESN outperformed group ESN. The muscle and nerve morphometry showed superiority of group ES+ESN over ESN group in all parameters.

CONCLUSION

Electrical stimulation is an effective means of maintaining functional muscle and nerve regeneration after end-to-side neurorrhaphy.

The Reliability of a Three-Dimensional Photo System- (3dMDface-) Based Evaluation of the Face in Cleft Lip Infants

Ample data exists about the high precision of three-dimensional (3D) scanning devices and their data acquisition of the facial surface. However, a question remains regarding which facial landmarks are reliable if identified in 3D images taken under clinical circumstances. Sources of error to be addressed could be technical, user dependent, or patient respectively anatomy related. Based on clinical 3D photos taken with the 3dMDface system, the intra observer repeatability of 27 facial landmarks in six cleft lip (CL) infants and one non-CL infant was evaluated based on a total of over 1,100 measurements. Data acquisition was sometimes challenging but successful in all patients. The mean error was 0.86 mm, with a range of 0.39 mm (Exocanthion) to 2.21 mm (soft gonion). Typically, landmarks provided a small mean error but still showed quite a high variance in measurements, for example, exocanthion from 0.04 mm to 0.93 mm. Vice versa, relatively imprecise landmarks still provide accurate data regarding specific spatial planes. One must be aware of the fact that the degree of precision is dependent on landmarks and spatial planes in question. In clinical investigations, the degree of reliability for landmarks evaluated should be taken into account. Additional reliability can be achieved via multiple measuring.

Double muscle innervation using end-to-side neurorrhaphy in rats

CONTEXT AND OBJECTIVE

One of the techniques used for treating facial paralysis is double muscle innervation using end-to-end neurorrhaphy with sectioning of healthy nerves. The aim of this study was to evaluate whether double muscle innervation by means of end-to-side neurorrhaphy could occur, with maintenance of muscle innervation.

DESIGN AND SETTING

Experimental study developed at the Experimental Research Center, Faculdade de Medicina de Botucatu, Unesp.

METHODS

One hundred rats were allocated to five groups as follows: G1, control group; G2, the peroneal nerve was sectioned; G3, the tibial nerve was transected and the proximal stump was end-to-side sutured to the intact peroneal nerve; G4, 120 days after the G3 surgery, the peroneal nerve was sectioned proximally to the neurorrhaphy; G5, 120 days after the G3 surgery, the peroneal and tibial nerves were sectioned proximally to the neurorrhaphy.

RESULTS

One hundred and fifty days after the surgery, G3 did not show any change in tibial muscle weight or muscle fiber diameter, but the axonal fiber diameter in the peroneal nerve distal to the neurorrhaphy had decreased. Although G4 showed atrophy of the cranial tibial muscle 30 days after sectioning the peroneal nerve, the electrophysiological test results and axonal diameter measurement confirmed that muscle reinnervation had occurred.

CONCLUSION

These findings suggest that double muscle innervation did not occur through end-to-side neurorrhaphy; the tibial nerve was not able to maintain muscle innervation after the peroneal nerve had been sectioned, although muscle reinnervation was found to have occurred, 30 days after the peroneal nerve had been sectioned.

RETROGRADE TRACING AND ELECTROPHYSIOLOGICAL FINDINGS OF COLLATERAL SPROUTING AFTER END-TO-SIDE NEURORRHAPHY

The aim of this study was to seek more potent evidences of collateral sprouting for both motor and sensory nerve fibres after end-to-side neurorrhaphy using a modified double-labelling retrograde tracing method and to investigate the function of regenerated motor axons with electrophysiological evaluation. Four groups (n=4 for each group) were used: end-to-end coaptation (six months postoperatively), end-to-side coaptation (four months and six months postoperatively) and normal control. Two fluorescent tracers (true blue and diamidino yellow) were applied to the proximal ends of tibial and common peroneal nerves, respectively after four or six months of nerve coaptation. Five days later, we only found single-labelled motor and sensory neurons in the normal and end-to-end coaptation groups, while some dual-labelled neurons can be identified in end-to-side coaptation groups. Four months after surgery, the motor nerve conduction velocity in end-to-side coaptation was significantly slower than in the normal control. But no difference was found in the sixth month. These results suggest that end-to-side neurorrhaphy can induce the functional collateral sprouting of both motor and sensory axons in the peripheral nerve.

Experimental and clinical employment of end-to-side coaptation: our experience

The last 15 years have seen a growing interest regarding a technique for nerve repair named end-to-side coaptation. Since 2000, we have carried out experimental studies on end-to-side nerve repair as well as employed this technique to a series of selected clinical cases. Here we report on the results of this experience.For experimental studies, we have used the model represented by median nerve repair by end-to-side coaptation either on the ulnar (agonistic) or the radial (antagonistic) nerve. For time course assessment of median nerve functional recovery we used the grasping test, a test which permits to assess voluntary control of muscle function. Repaired nerves were processed for resin embedding to allow nerve fibre stereology and electron microscopy. Results showed that, in either experimental group, end-to-side-repaired median nerves were repopulated by axons regenerating from ulnar and radial donor nerves, respectively. Moreover, contrary to previously published data, our results showed that voluntary motor control of the muscles innervated by the median nerve was progressively recovered also when the antagonistic radial nerve was the donor nerve.As regards our clinical experience, results were not so positive. We have treated by end-to-side coaptation patients with both sensory (n = 7, collateral digital nerves) and mixed (n = 8, plexus level) nerve lesions. Results were good, as in other series, in sensory nerves whilst they were very difficult to investigate in mixed nerves at the plexus level.Take together, these results suggest that clinical employment of end-to-side coaptation should still be considered at the moment as the ultima ratio in cases in which no other repair technique can be attempted. Yet, it is clear that more basic research is needed to explain the reasons for the different results between laboratory animal and humans and, especially, to find out how to ameliorate the outcome of end-to-side nerve repair by adequate treatment and rehabilitation.

Intrinsic hand muscle reinnervation by median-ulnar end-to-side bridge nerve graft: case report

Recovery of either the motor or sensory functions has not been consistently achieved in upper extremity end-to-side neurorrhaphy; this technique was only indicated when more conventional nerve repair was not possible. In most studies, the whole median or ulnar nerve was used for end-to-side neurotization. In this report, we present 4 cases of high-median or ulnar nerve laceration in which a nerve graft was placed end-to-side between the median and ulnar motor fascicles close to the wrist. At 4 months after surgery, 3 of 4 patients began to recover active movement of the affected small muscles of the hand. EMG and nerve conduction studies confirmed that nerve conduction was through the nerve grafts.

End-to-side nerve repair: Attachment of a distal, compared with a proximal and distal, nerve segment

Regeneration occurs if a distal nerve segment is attached end-to-side to an intact donor nerve after the nerve has been injured. We investigated if attachment of a proximal nerve segment as well, as an extra source of axons, had any advantage over the single attachment of a distal nerve segment to the same donor nerve. In rats, a single distal radial nerve, or both the proximal and distal radial nerve segments, were attached end-to-side to the musculocutaneous nerve, and effects were examined up to eight months after the repair. Cell profiles were double-labelled, indicating recruitment of axons by collateral sprouting, but there were few such cells. There was a shift in the distribution of retrograde labelled neuronal cell profiles in spinal cord and in DRGs between the two types of repair. Both procedures resulted in axonal outgrowth and some functional recovery, but there was no improvement if a proximal nerve segment was also used as a source for axons.

Contribution of the proximal nerve stump in end-to-side nerve repair: in a rat model

Background

The aim of this study was to evaluate the contribution of the proximal nerve stump, in end-to-side nerve repair, to functional recovery, by modifying the classic end-to-side neurorrhaphy and suturing the proximal nerve stump to a donor nerve in a rat model of a severed median nerve.

Methods

Three experimental groups were studied: a modified end-to-side neurorrhaphy with suturing of the proximal nerve stump (double end-to-side neurorrhaphy, Group I), a classic end-to-side neurorrhaphy (Group II) and a control group without neurorrhaphy (Group III). Twenty weeks after surgery, grasping testing, muscle contractility testing, and histological studies were performed.

Results

The grasping strength, muscle contraction force and nerve fiber count were significantly higher in group I than in group II, and there was no evidence of nerve recovery in group III.

Conclusions

The contribution from the proximal nerve stump in double end-to-side nerve repair might improve axonal sprouting from the donor nerve and help achieve a better functional recovery in an end-to-side coaptation model.

Location of collateral sprouting of donor nerve following end-to-side neurorrhaphy

Various studies have demonstrated collateral regeneration of the donor nerve following end-to-side neurorrhaphy, but the location of collateral sprouting remains controversial. In a rat end-to-side neurorrhaphy model we isolated nerve fibers from the donor nerve at the neurorrhaphy site utilizing a micro-tease technique. We found that axons sprouted collaterally from a myelinated nerve fiber at the node of Ranvier. Based on this preliminary result we conclude that myelinated nerve fibers could sprout collateral branches at the node of Ranvier at an end-to-side neurorrhaphy site. These findings show that end-to-side neurorrhaphy may be an alternative for peripheral nerve repair.

RESULTS OF END-TO-SIDE NERVE COAPTATION IN SEVERE OBSTETRIC BRACHIAL PLEXUS LESIONS

OBJECTIVE

Options for nerve repair are limited in brachial plexus lesions with multiple root avulsions because an insufficient number of proximal nerve stumps are available to serve as lead-out for nerve grafts. End-to-side nerve repair might be an alternative surgical technique for repair of such severe lesions. In this technique, an epineurial window is created in a healthy nerve, and the distal stump of the injured nerve is coapted to this site. Inconsistent results of end-to-side nerve repairs in traumatic nerve lesions in adults have been reported in small series. This article evaluates the results of end-to-side nerve repair in obstetric brachial plexus lesions and reviews the literature.

METHODS

A retrospective analysis was performed of 20 end-to-side repairs in 12 infants. Evaluation of functional recovery of the target muscle was performed after at least 2 years of follow up (mean, 33 mo).

RESULTS

Five repairs failed (25%). Seven times (35%) good function (Medical Research Council at least 3) of the target muscle occurred in addition to eight partial recoveries (40%). In the majority of patients, however, the observed recovery cannot be exclusively attributed to the end-to-side repair. The reinnervation may be based on axonal outgrowth through grafted or neurolyzed adjacent nerves. It seems likely that recovery was solely based on the end-to-side repair in only two patients. No deficits occurred in donor nerve function.

CONCLUSION

This study does not convincingly show that the end-to-side nerve repair in infants with an obstetric brachial plexus lesion is effective. Its use cannot be recommended as standard therapy.

Motor reinnervation of a denervated muscle by using a sensory nerve: an experimental study on gluteus maximus muscle of the rat

PURPOSE

This study aimed at developing a new muscle reinnervation technique using a sensory nerve.

METHODS

We attempted innervation of the rat gluteus maximus muscle using the lateral femoral cutaneous nerve (LFCN). We placed the gluteus maximus muscle into the fibroadipose tissue in the distribution of the LFCN in 24 rats. In one group, the original innervation remained intact. In the second and third groups, the muscles were denervated, and in the third group, the proximal end of the nerve to the gluteus maximus was sutured to the distal end of the divided LFCN. We compared muscle reinnervations of the groups by using electrophysiologic evaluation of the muscle contractions, light microscope evaluation of the axonal regenerations, and scanning electron microscope evaluation of the actin-myosin structures of the muscles at the end of an elapsed waiting period.

RESULTS

At the end of electrophysiologic evaluation, the mean area of compound muscle action potentials measured in group 1 was 3.8 ms/mV; in group 2, 0.0; and in group 3 (experimental group), 0.5. Axonal regeneration was observed distal to the coaptation, and actin-myosin structures were mostly spared in group 3.

CONCLUSIONS

This study explored the feasibility of a new flap prefabrication method that aims at developing reinnervation of a denervated muscle by means of a sensory nerve. In light of histologic and electrophysiologic findings, this type of reinnervation is possible.

Motor neuron regeneration through end-to-side repairs is a function of donor nerve axotomy

BACKGROUND

Over the past decade, a growing body of literature has emerged supporting the use of end-to-side (terminolateral) neurorrhaphy for the treatment of selected peripheral nerve injuries. It remains unclear, however, whether injury to the donor nerve is necessary to achieve significant regeneration through such repairs.

METHODS

End-to-side repair was studied in a rodent model in which the terminal limb of a transected peroneal nerve was sutured to the lateral aspect of the tibial nerve. Twenty-eight Lewis rats were randomized to four groups of seven animals each corresponding to incrementally greater donor nerve injuries as follows: group 1, conventional end-to-side neurorrhaphy; group 2, end-to-side neurorrhaphy with proximal crush injury; group 3, end-to-side neurorrhaphy with neurotomy; and group 4, end-to-end repair of transected peroneal nerve (positive control).

RESULTS

At 12 weeks, retrograde labeling of cell bodies of the ventral horn demonstrated significant differences between experimental groups, with mean counts in group 4 (1237 +/- 171) > group 3 (522 +/- 204) > group 2 (210 +/- 132) > or = group 1 (126 +/- 146). This association between nerve injury and motor neuron counts was closely mirrored in quantitative assessments of peripheral nerve regeneration and normalized wet muscle masses.

CONCLUSIONS

These data support the hypothesis that donor nerve injury is a prerequisite for significant motor neuronal regeneration across end-to-side repairs. Motor neuron regeneration through end-to-side repairs is optimized by deliberate transection of donor nerve axons.

End-to-side (terminolateral) nerve regeneration: a challenge for neuroscientists coming from an intriguing nerve repair concept

The last 15 years have seen a growing interest regarding a technique for nerve repair named end-to-side (terminolateral) neurorrhaphy. This technique is based on the concept that nerve fiber regeneration along the distal stump of a transected nerve, the proximal stump of which was lost, can be obtained by just suturing the proximal end of its distal stump to the epinerium of a neighbor healthy and undamaged donor nerve. A large body of experimental studies have shown that end-to-side neurorrhaphy, in fact, is able to induce collateral sprouting from donor nerve's axons which is at the basis of the massive repopulation of the distal nerve stump. The regenerating nerve fibers eventually reinnervate the periphery of the severed nerve leading to a recovery of the lost function the degree of which varies depending on factors that still have to be elucidated. Surprisingly, this puzzling concept of nerve regeneration has attracted very little attention from basic neuroscientists so far and, thus, the present paper is intended to call for more biological research on it by overviewing the relevant literature and indicating the several unanswered questions that this concept asks to the neuroscience community.

Microneurovascular anatomy of the peroneus brevis muscle in the NZW-rabbit: a new model for free functional muscle transplantation

This study introduces the peroneus brevis muscle of the NZW-rabbit as a new model for free functional muscle transplantation. The muscle originates from the lateral aspect of the knee joint and inserts on the 5th metatarsal with a circumscript tendon. It can be harvested with a 7 cm long motor nerve branch. In a series of 22 animals divided in two groups with a body weight of 3.19 +/- 0.30 kg and 4.81 +/- 0.38 kg respectively, vessel diameter of the supplying artery was found to be 0.3-0.35 mm in group one and 0.40-0.45 mm in group two, the two concomitant veins were 1.1-1.4 mm in diameter in the first group and 1.2-1.6 mm in the second group. Histomorphometric analysis stained with NADH showed 3.67 +/- 3.21% type I fibers, 25.41 +/- 7.87% type IIa fibers, and 70.93 +/- 9.12% type IIb/d fibers.

Influence of Aging on Regeneration in End-to-Side Neurorrhaphy

Aging profoundly affects the structural and functional characteristics of the peripheral nervous system. Although several experiments have investigated the effect of aging on nerve regeneration after crush and transection nerve injuries, little is known about the influence of age on end-to-side nerve repairs. It was hypothesized that decreased terminal and collateral sprouting in older animals would be associated with less robust regeneration through end-to-side nerve repairs. In this study, 27 Lewis rats underwent end-to-side repair at ages 2 weeks, 3 months, or 1 year. Histomorphometric assessments at 12 weeks demonstrated increased fiber width, percent neural tissue, and neural density in animals undergoing nerve reconstruction at the age of 2 weeks (P < 0.05). A trend toward further decline in regeneration was noted at ages 1 year versus 3 months. After end-to-side nerve repair, younger animals exhibit a more robust regenerative response, consistent with prior experience in other nerve injury models.

End-to-side nerve coaptation: a qualitative and quantitative assessment in the primate

There are several reasons why end-to-side nerve coaptation has not been widely adopted clinically. Among these are the putative damage inflicted on the donor nerve and the variable quality of the regeneration in the recipient nerve. So far experiments on end-to-side nerve repair have been short term and mostly carried out on rats. This long-term study of end-to-side nerve repair of ulnar to median and median to ulnar nerve was performed using adult nonhuman primates. Eleven nerve repairs were studied at different time points. Eighteen, 22, 33 and 57 months after surgery a qualitative and quantitative analysis of the donor nerve and regenerating nerve revealed variable levels of percentage axonal regeneration compared with matched controls (1.4%-136%). Morphological evidence of donor nerve damage was identified distal to the coaptation site in four of the 11 cases, and in these cases the best axonal regeneration in the corresponding recipient nerves was observed. This donor nerve damage could neither be demonstrated in terms of a decrease in axon counts distal to the coaptation nor as donor target organ denervation. Recipient target organ regeneration like the axonal regeneration varied, with evidence of motor regeneration in eight out of 11 cases and sensory regeneration, as measured by percentage innervation density compared with matched controls, varied from 12.5% to 49%. Results from the present study demonstrate that the end-to-side coaptation technique in the nonhuman primate does not give predictable results. In general the motor recovery appeared better than the sensory and in those cases where donor nerve damage was observed there was better motor and sensory regeneration overall than in the remaining cases.

Use of an intact sensory nerve to bridge a motor nerve defect: an experimental study

Object

End-to-side neurorrhaphy has recently became popular for peripheral nerve repair. Although this method is mainly indicated in nerve defects in which there is an absent proximal nerve stump, bridging a motor nerve defect by coapting the proximal and distal ends of the defect to a neighboring mixed nerve in an end-to-side fashion has been another experimental use of this method. In this situation, however, the source of the regenerating axons is unclear because the axons in both the proximal end of the defect and the bridging intact nerve have the capacity for regeneration. The goal of this study was to identify the source of the regenerating axons.

Methods

In this experimental study, the authors used a sensory nerve to bridge a motor nerve defect so that they could elucidate the source of the regenerating motor axons in the distal part of the motor nerve. One advantage of using a sensory nerve was that it eradicated the risk of damaging another motor nerve. Tests used in the analysis included gait evaluation, electrophysiological tests, and histological assessment.

Conclusions

Results of this study showed that, in the rat model, a sensory nerve can be used to bridge a motor nerve defect, thereby eliminating the need for nerve grafting.

Functional upgrading of partially recovered facial palsy by cross-face nerve grafting with distal end-to-side neurorrhaphy

BACKGROUND

Cross-face nerve grafting combined with functional muscle transplantation has become the standard in reconstructing an emotionally controlled smile in complete irreversible facial palsy. A special problem exists in incomplete or partially recovered facial palsies, when the little existing function should be preserved but the existing function alone is clinically insufficient.

METHODS

In this situation, cross-face nerve grafting performed by means of end-to-end coaptation to a zygomatic branch of the healthy side and by end-to-side neurorrhaphy to a corresponding branch of the incompletely paralyzed side is proposed to upgrade smile function on the latter side and contribute to more static and dynamic overall symmetry. The interposition nerve graft is set in overlength to preserve the possibility of a later muscle transplantation in case of unsatisfying functional result through the additional neuronal input. The authors have used this concept in seven patients with irreversible partial facial palsy. Three cases have a sufficiently long follow-up to be presented here. Outcome was objectively quantified with three-dimensional video analysis of facial movements.

RESULTS

In all three cases, functional improvement and a positive effect on the static and dynamic symmetry of the face could be measured. None of the patients was disappointed by the smile function achieved or wanted to undergo additional muscle transplantation.

CONCLUSION

On the basis of these first clinical experiences, the authors recommend cross-face nerve grafting with overlength and a distal end-to-side neurorrhaphy in patients with irreversible incomplete facial palsy affecting the smile.

Simultaneous end-to-side coaptations of two severed nerves to a single healthy nerve in rats

Object

This experimental study was designed to evaluate functional and sensory outcomes and morphological features observed after simultaneous end-to-side coaptations of distal stumps of two nerves to a single neighboring nerve. Studies were performed using both parallel and end-to-side coaptation (PEC) and serial end-to-side coaptation (SEC) methods in a rat model.

Methods

In the PEC group, distal stumps of the sural and common fibular nerves were coapted to the intact tibial nerve 1 cm apart from each other in an end-to-side fashion. In the SEC group, identical surgical procedures apart from the coaptation method were conducted. For the coaptation method in this group, the distal stump of the common fibular nerve was first coapted to the side of the intact tibial nerve, and then the distal stump of the sural nerve was coapted to the side of the common fibular nerve 1 cm apart from the first coaptation site.

Nonoperated contralateral sides were used as controls. Nerve regeneration in both groups was evaluated functionally, electrophysiologically, and histomorphometrically.

Conclusions

When there is a need for two end-to-side coaptations of two severed nerves, PEC is the recommended method of choice to obtain better axonal regeneration into both nerves.

End-to-Side Nerve Coaptation

The aim of this experimental study was to evaluate the effects of end-to-side coaptation of the proximal end of a severed nerve to the same intact nerve, in addition to traditional end-to-side coaptation of the distal end, with an aim to use the intact nerve as a nerve conduit in a rat model and to compare the functional and histologic results of this modality to those obtained after nerve grafting and traditional end-to-side nerve coaptation. In group A, a peroneal nerve defect measuring 1 cm was created in the left hind limb, and a nerve graft 1 cm long was used to bridge the defect. In group B, only the distal stump of the peroneal nerve was coapted to the intact tibial nerve. In group C, both ends of the peroneal nerve defect were coapted to the intact tibial nerve in an end-to-side fashion 1.5 cm apart from each other, and in group D, the peroneal nerve defect was left unrepaired. Group E was consisted of nonoperated peroneal nerves that were used to obtain normative data. Although significantly higher myelinated axon densities were observed in groups B and C compared with group A and group E, total number of the myelinated axons was significantly higher only in group C. Peroneal functional index assessments demonstrated that nerve recovery in the peroneal nerve was similar in groups A and C, and both were better than those observed in groups B and D. Collectively, these results suggest that end-to-side coaptation of both ends of a severed nerve to an intact nerve, in case of a nerve defect in this length, may serve as an alternative for nerve grafting.

Anatomic bases of graciloplasty using end-to-side nerve pudendal anastomosis

The objective of this study was to evaluate the possibilities of reinnervation of the gracilis muscle, transposed around the anus, by the pudendal nerve using an end-to-side nerve anastomosis. This study was carried out in 14 cases (7 adult human cadavers bilaterally). The gracilis muscle and its vascular-nervous bundle have been dissected and the nerve innervating the gracilis muscle has been cut at its origin. The gracilis muscle, accompanied by its nerve, has then been transposed around the anus. The pudendal nerve has been dissected from its extrapelvic part. The reinnervation using an end-to-side nerve anastomosis has been considered as feasible when the proximal ending of the nerve of the gracilis was put into a tension-free contact with the extrapelvic part of the pudendal nerve. The extrapelvic part of the pudendal nerve has a common trunk in 12 cases. The width of the extrapelvic part of the pudendal nerve was 2.6+/-0.7 mm, range 1-3.5. The width of the proximal endings of the nerve innervating the gracilis muscle was 2.3+/-0.5 mm, range 2-3. The reinnervation of the gracilis muscle by the pudendal nerve has been possible in 14 cases. An average supplementary length of 17.4+/-15.4 mm was available (range 5-52). These results suggest an eventual practical aspect of this technique for the reconstruction of a functional sphincter using the gracilis muscle transposed around the anus.

Repair of brachial plexus lesions by end-to-side side-to-side grafting neurorrhaphy: experience based on 11 cases

Eleven brachial plexus lesions were repaired using end-to-side side-to-side grafting neurorrhaphy in root ruptures, in phrenic and spinal accessory nerve neurotizations, in contralateral C7 neurotization, and in neurotization using intact interplexus roots or cords. The main aim was to approximate donor and recipient nerves and promote regeneration through them. Another indication was to augment the recipient nerve, when it had been neurotized or grafted to donors of dubious integrity, when it was not completely denervated, when it had been neurotized to a nerve with a suboptimal number of fibers, when it had been neurotized to distant donors delaying its regeneration, and when it had been neurotized to a donor supplying many recipients. In interplexus neurotization, the main indication was to preserve the integrity of the interplexus donors, as they were not sacrificeable. The principles of end-to-side neurorrhaphy were followed. The epineurium was removed. Axonal sprouting was induced by longitudinally slitting and partially transecting the donor and recipient nerves, by increasing the contact area between both of them and the nerve grafts, and by embedding the grafts into the split predegenerated injured nerve segments. Agonistic donors were used for root ruptures and for phrenic and spinal accessory neurotization, but not for contralateral C7 or interplexus neurotization. Single-donor single-recipient neurotization was successfully followed in phrenic neurotization of the suprascapular (3 cases) and axillary (1 case) nerves, spinal accessory neurotization of the suprascapular nerve (1 case), and dorsal part of contralateral C7 neurotization of the axillary nerve (2 cases). Apart from this, recipient augmentation necessitated many donor to single-recipient neurotizations. This was successfully performed using phrenic-interplexus root to suprascapular transfers (2 cases), phrenic-contralateral C7 to suprascapular transfer (1 case), and spinal accessory-interplexus root to musculocutaneous transfer (1 case). Both recipient augmentation and increasing the contact area between grafts and recipients necessitated single or multiple donor to many recipient neurotizations. This was applied in root ruptures (3 cases), with results comparable to those obtained in classical nerve-grafting techniques. It was also applied in ventral C7 transfer to the lateral or medial cords (3 cases) with functional recovery occurring in the biceps and pronator teres muscles, but not in dorsal C7 transfer to the axillary and radial nerves (3 cases) with functional recovery occurring in the deltoid and triceps muscles, and in whole C7 transfer to C5, 6, 7, 8T1 roots with functional recovery occurring in the deltoid (M4), biceps (M4), pronator teres (M4), and triceps (M3) (3 cases), and less so in the flexor carpi ulnaris and FDP (M3) (1 case) and the extensor digitorum longus (M3) (1 case). Contralateral C7 transfer to the lateral and posterior cords (4 cases) was followed by cocontractions that took 1 year to improve and that involved the rotator cuff, deltoid, biceps, and pronator teres (all agonists). Functional recovery in the triceps muscle was less than in the above muscles. Contralateral C7 transfer to C5-7 (1 case) was followed by cocontractions that took 1 year to resolve and that occurred between the deltoid, biceps, and flexor digitorum profundus. Interplexus root neurotization was done only in conjunction with other neurotization techniques, and so its role is difficult to judge. Though the same applies to regenerated lateral cord transfer to the posterior cord (2 cases), the successful results obtained from medial cord neurotization to the axillary, musculocutaneous, and radial nerves (1 case), and from ulnar and median nerve neurotization to the radial nerve (1 case), show that neurotization at the interplexus cord level may play a role in brachial plexus regeneration and may even be used to neurotize nerves and muscles distal to the elbow. The timing of repair was within 6 months after injury, except for 2 cases. In the first case, contralateral C7 transfer was successfully performed more than 1 year after injury. The second case was an obstetric palsy operated upon at age 8. Deterioration in motor power of the donor muscles that improved in 6 months was observed in 2 cases of interplexus neurotization at the cord level, because of looping the sural nerve grafts tightly around the donor nerves. Deterioration in donor-muscle motor power as a consequence of end-to-side neurorrhaphy was noted in the obstetric palsy case, when the flexor carpi radialis (donor) became grade 3 instead of grade 4. This was associated with cocontractions between it and the extensors. It took nearly 1 year to improve.

End-to-side nerve grafting of the tibial nerve to bridge a neuroma-in-continuity

Standard treatment for a neuroma-in-continuity with partial retained function is neurolysis with or without grafting. The present study tests the outcome of a novel partial nerve lesion bypassed with an end-to-side bridge graft, intended to increase the number of axons crossing the defect while not disturbing intact axons. An 8-mm portion of tibial nerve was resected in 20 rats. Three weeks later, half had the defect repaired with an end-to-side bridge allograft and perineurial windows; controls had only neurolysis. Recovery was evaluated using walking-track analysis, allodynia testing, muscle weight ratios, and histology at 8 weeks. No significant differences in motor or sensory functional recovery were noted between the two groups. Histology showed good axonal regeneration through the defect in all specimens. The experimental group also had regenerated axons in the bridge graft, but their maturity was less advanced, presumably due to delays in regeneration.

Low-power laser biostimulation enhances nerve repair after end-to-side neurorrhaphy: a double-blind randomized study in the rat median nerve model

Previous studies have shown that low-power laser biostimulation (lasertherapy) promotes posttraumatic nerve regeneration. The objective of the present study was to investigate the effects of postoperative lasertherapy on nerve regeneration after end-to-side neurorrhaphy, an innovative technique for peripheral nerve repair. After complete transection, the left median nerve was repaired by end-to-side neurorrhaphy on the ulnar "donor" nerve. The animals were then divided into four groups: one placebo group, and three laser-treated groups that received lasertherapy three times a week for 3 weeks starting from postoperative day 1. Three different types of laser emission were used: continuous (808 nm), pulsed (905 nm), and a combination of the two. Functional testing was carried out every 2 weeks after surgery by means of the grasping test. At the time of withdrawal 16 weeks postoperatively, muscle mass recovery was assessed by weighing the muscles innervated by the median nerve. Finally, the repaired nerves were withdrawn, embedded in resin and analyzed by light and electron microscopy. Results showed that laser biostimulation induces: (1) a statistically significant faster recovery of the lesioned function; (2) a statistically significant faster recovery of muscle mass; (3) a statistically significant faster myelination of the regenerated nerve fibers. From comparison of the three different types of laser emissions, it turned out that the best functional outcome was obtained by means of pulsed-continuous-combined laser biostimulation. Taken together, the results of the present study confirm previous experimental data on the effectiveness of lasertherapy for the promotion of peripheral nerve regeneration and suggest that early postoperative lasertherapy should be considered as a very promising physiotherapeutic tool for rehabilitation after end-to-side neurorrhaphy.

Effect of Perineurial Window Size on Nerve Regeneration, Blood–Nerve Barrier Integrity, and Functional Recovery

End-to-side neurorrhaphy is used clinically to reconstruct nerve injuries when the lack of a suitable proximal nerve stump precludes conventional approaches to microsurgical repair. In end-to-side neurorrhaphy, the distal stump of a transected nerve is sutured to the side of an intact nerve that serves as an axon donor. Prior studies suggest that this perineurial window is a prerequisite for effective nerve regeneration into the recipient nerve. However, the optimal size for this perineurial window remains uncertain. This study evaluated the effect of perineurial window size on collateral axonal sprouting, blood-nerve barrier architecture, and functional impairment of the donor nerve. One hundred twenty Lewis rats were randomized to 1 and 5 mm perineurial window groups and examined at serial time points. The 5 mm perineurial window group exhibited significantly greater fiber counts at the repair zone than the 1mm group within 4 weeks (p < 0.005). Marked breakdown of the blood-nerve barrier was present 2 week postoperatively and resolved by 4 weeks regardless of 1 versus 5 mm perineurial window size. Tibial function indices in both groups normalized between 4 and 6 weeks postoperatively. A large (5 mm) perineurial window induced greater collateral sprouting or regenerative response than a small (1 mm) perineurial window without increasing cross sectional nerve injury or delaying functional recovery.

Reinnervation of denervated muscle in a split-nerve transfer model

This study was performed to quantify the reinnervation of denervated muscle in a split-nerve transfer model and to determine any possible downgrading effects on the donor nerve and its end organ. Fifty-four adult Wistar rats weighing 200 to 250 g were used. The experimental design consisted of two groups. The motor nerve branch to the anterior tibial muscle and gastrocnemius muscle of the right hind limb were dissected in all rats. In the experimental group (N = 36), the motor nerve branch of the tibial nerve to the gastrocnemius muscle was exposed, cut, and ligated. The motor nerve branch to the anterior tibial muscle was split and transected longitudinally, and the medial half was routed posteriorly. End-to-end neural anastomosis was performed between this medial half of the split nerve and the distal stump of the gastrocnemius nerve. In the control group (N = 18), while the same surgical preparation was performed, the motor nerve branch to the anterior tibial muscle and gastrocnemius nerve were exposed and transected, and the nerve endings were ligated, but neural anastomosis was not performed between these nerves. The left hind limb of all rats served as a normal comparison side without any surgical intervention. Both of the groups were divided into three subgroups (12 rats each for the experimental groups and 6 rats each for the control group) to evaluate the results after periods of 1, 3, and 6 months. Electromyography, light microscopic and morphometric examination, and muscle weight measurements were used to document the results. Although stimulation of the peroneal and tibial nerves did not produce any compound muscle action potential (CMAP) recordings from either the anterior tibial or the gastrocnemius muscle in the control group, the normalized CMAP areas of the tibial nerve were (mean +/- standard deviation) 16.2 +/- 30.8% in the 1-month group, 63.4 +/- 34.7% in the 3-month group, and 72.4 +/- 16.3% in the 6-month group. For the peroneal nerve, the normalized CMAP areas were 17.0 +/- 32.2%, 53.4 +/- 29.4%, and 54.4 +/- 14.5% for the 1-, 3-, and 6-month groups in the experimental groups respectively. A high number of regenerating myelinated nerve fibers was identified in the distal part of the coapted motor nerve branch to the gastrocnemius muscle. The average number of myelinated fibers in the lateral half of the split nerve in the experimental group was 15,108 fibers per square millimeter, 14,167 fibers per square millimeter, and 19,830 fibers per square millimeter at months 1, 3, and 6 respectively. The average number of fibers proximal to the nerve anastomotic site was 15,423 fibers per square millimeter, 19,200 fibers per square millimeter, and 20,774 fibers per square millimeter. Distal to the nerve anastomotic site, the number of myelinated fibers was 17,941 fibers per square millimeter, 18,885 fibers per square millimeter, and 18,895 fibers per square millimeter at 1, 3, and 6 months respectively. There were no myelinated fibers in the control group sections. There were significant differences in muscle weight between the experimental and control groups at the end of month 6. The difference between the experimental side and the untouched normal healthy side was not significant in the weight measurements of both muscles. The results show acceptable reinnervation by split-nerve transfer with minimal functional impairment of the donor muscle. This study confirms that split-nerve transfer is a reliable method of reconstruction for paralyzed muscle with minimal donor area morbidity.

End-to-side neurorrhaphy and lateral axonal sprouting in a long graft rat model

OBJECTIVE/HYPOTHESIS

Controversy exists regarding collateral axonal sprouting across an end-to-side neurorrhaphy to provide functional motor reinnervation of a target organ without compromise of the donor nerve. Rat models may be limited in the study of end-to-side repair given potential contamination from the proximal nerve stump of the recipient distal nerve and the use of antagonistic muscle groups for donor and recipient. The current study attempts to address these issues by using a rat model in which an end-to-side coaptation is performed with a long graft interposed between the intact donor tibial nerve and the divided, distal contralateral tibial nerve.

MATERIALS AND METHODS

The graft used in proximal end-to-side coaptation consisted of both sciatic nerves in a donor syngeneic animal. The distal repair to the contralateral tibial nerve was done immediately or in a delayed fashion to allow potential motor axons to transverse the graft before division of the recipient tibial nerve.

RESULTS

After 24 weeks, axons were noted to transverse the entire distance of the graft and into the contralateral distal posterior tibial nerve. A significant increase in axonal numbers was observed in the immediate repairs compared with the delayed. No animal recovered functional motor ability on the contralateral side as assessed by walking tracks.

CONCLUSIONS

These findings suggest the importance of immediate distal neurotrophic factors in encouraging nerve regeneration even in a long graft end-to-side repair. Our model is successful in demonstrating innervation through an end-to-side coaptation but questions its use given the lack of motor recovery.