Neurorrhaphy after loss of a nerve segment: comparison of epineurial suture under tension versus multiple nerve grafts

Repair of peripheral nerve defects by nerve transposition using small gap bio-sleeve suture with different inner diameters at both ends

During peripheral nerve transposition repair, if the diameter difference between transposed nerves is large or multiple distal nerves must be repaired at the same time, traditional epineurial neurorrhaphy has the problem of high tension at the suture site, which may even lead to the failure of nerve suture. We investigated whether a small gap bio-sleeve suture with different inner diameters at both ends can be used to repair a 2-mm tibial nerve defect by proximal transposition of the common peroneal nerve in rats and compared the results with the repair seen after epineurial neurorrhaphy. Three months after surgery, neurological function, nerve regeneration, and recovery of nerve innervation muscle were assessed using the tibial nerve function index, neuroelectrophysiological testing, muscle biomechanics and wet weight measurement, osmic acid staining, and hematoxylin-eosin staining. There was no obvious inflammatory reaction and neuroma formation in the tibial nerve after repair by the small gap bio-sleeve suture with different inner diameters at both ends. The conduction velocity, muscle strength, wet muscle weight, cross-sectional area of muscle fibers, and the number of new myelinated nerve fibers in the bio-sleeve suture group were similar to those in the epineurial neurorrhaphy group. Our findings indicate that small gap bio-sleeve suture with different inner diameters at both ends can achieve surgical suture between nerves of different diameters and promote regeneration and functional recovery of injured peripheral nerves.

Direct Nerve Sutures in (Extended) Upper Obstetric Brachial Plexus Repair

Background  In rare, selected cases of severe (extended) upper obstetric brachial plexus palsy (OBPP), after supraclavicular exposure and distal mobilization of the traumatized trunks and careful neuroma excision, we decided to perform direct nerve coaptation with tolerable tension and immobilized the affected arm positioned in adduction and 90-degree elbow flexion for three weeks.

Objectives  We present our surgical technique and preliminary results in a prospective open patient series, including 22 patients (14 right and 8 left side affected) between 2009 and 2016, operated at a mean age of 8.4 months.

Methods  Analysis of functional results after a minimum of 18 months was conducted using the British Medical Research Council (BMRC) scale.

Results  All children reached 60–90° of elbow flexion and 75° of shoulder abduction at already six months after surgery. For those patients having already passed one year post surgery, the mean active shoulder abduction reached 92°, and for those who past the 18 months 124°. We discuss the actual knowledge about nerve coaptation under “reasonable” tension including its advantages and drawbacks.

Conclusion  This technique may be indicated in preoperatively selected cases of (extended) upper OBPP and may give good functional results.

Acute Limb Shortening for Major Near and Complete Upper Extremity Amputations with Associated Neurovascular Injury: A Review of the Literature

In the setting a near or complete upper extremity amputations with significant soft tissue loss and neurovascular compromise, upper extremity surgeons are faced with the challenge of limb salvage. There are a multitude of treatment options for managing skeletal and soft tissue injuries including provisional fixation, staged reconstruction, and an acute shortening osteotomy with primary rigid internal fixation. However, many complications are associated with these techniques. Complications of provisional fixation include pin tract infection and loosening, tethering of musculotendinous units, nonunion, and additional surgeries. Staged reconstruction includes a variety of techniques: distraction osteogenesis, bone transport, or vascularized and non-vascularized structural autograft or allograft, but the risks often outweigh the benefits. Risks include nonunion, postoperative vascular complications necessitating reoperation, and the inability to return to the previous level of function at an average of 24 months. Acute shortening osteotomy with internal fixation offers the advantage of a single-stage procedure that provides for decreasing the soft tissue loss, provides a rigid platform to protect the delicate neurovascular repair, and alleviates unwanted tension at the repair sites. This review discusses the literature on the surgical treatment of severe upper extremity trauma with associated neurovascular injury over the past 75 years, and aims to evaluate the indications, surgical techniques, clinical and functional outcomes, and complications associated with acute shortening osteotomy with rigid internal fixation. Although this technique is not without risks, it is well-tolerated in the acute setting with a complication profile comparable to other techniques of fixation while remaining a single procedure.

Effect of new neuronal growth factor on healing of sciatic nerve in rats

OBJECTIVE

The study aimed to investigate the effect of a new peptide new nerve growth factor (NNGF) on the healing of divided sciatic nerves in rats.

MATERIAL AND METHODS

Twenty Sprague-Dawley rats of 250-300g were divided into two groups (group 1 - study group and group 2 - control group). Under ketamine intramuscular anesthesia sciatic nerves were exposed, divided and repaired using 10/0 dexon. Study animals had 10mg/kg body weight of NNGF added to the repair. Electromyographic studies of the hind libs were carried out after 8weeks. The average stimulation was 50mA for 200μS and four twitches (T) were recorded. The animals were euthanized and the sciatic nerves were removed for histological analysis.

RESULTS

There were no deaths in either of the groups. Electromyographic study showed that in the control group the average T1-T4 was 0.587±0.17% and in the study group the average was 87.89±5.02% (p value of 0.001). Histologically the control group showed regenerated axons sprouting from the proximal segment of cut nerve with empty endoneurial channels, while in the study group whole nerve trunks were seen within endoneurial channels.

CONCLUSION

This study shows that the NNGF has a positive influence on the experimental healing of sciatic nerves in animals.

Mannose-6-phosphate facilitates early peripheral nerve regeneration in thy-1-YFP-H mice

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We have visualized and quantified nerve regeneration at an axonal level.

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Axons cross the repair site more directly following mannose-6-phosphate treatment.

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Mannose-6-phosphate alters axon sprouting just distal to axon entry into the graft.

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Mannose-6-phosphate may enable more favorable collagen fibril alignment.

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Our data add further evidence that mannose-6-phosphate improves nerve regeneration.

The formation of scar tissue following nerve injury has been shown to adversely affect nerve regeneration and evidence suggests that mannose-6-phosphate (M6P), a potential scar reducing agent that affects transforming growth factor (TGF)-β activation, may enhance nerve regeneration. In this study we utilized thy-1-YFP-H mice – a transgenic strain expressing yellow fluorescent protein (YFP) within a subset of axons – to enable visual analysis of axons regenerating through a nerve graft. Using this strain of mouse we have developed analysis techniques to visualize and quantify regeneration of individual axons across the injury site following the application of either M6P or vehicle to the site of nerve injury.

No significant differences were found in the proportion of axons regenerating through the graft between M6P- and vehicle-treated grafts at any point along the graft length. Maximal sprouting occurred at 1.0 mm from the proximal graft ending in both groups. The maximum change in sprouting levels for both treatment groups occurred between the graft start and 0.5-mm interval for both treatment groups. The difference between repair groups was significant at this point with a greater increase seen in the vehicle group than the M6P group. The average length of axons regenerating across the initial graft entry was significantly shorter in M6P- than in vehicle-treated grafts, indicating that they encountered less impedance.

Application of M6P appears to reduce the disruption of regenerating axons and may therefore facilitate quicker recovery; this is likely to result from altered scar tissue formation in M6P grafts in the early stages of recovery. This study also establishes the usefulness of our methods of analysis using the thy-1-YFP-H mouse strain to visualize and quantify regeneration at the level of the individual axon.

Effects of eliminating tension by means of epineural stitches: a comparative electrophysiological and histomorphometrical study using different suture techniques in an animal model

Epineural stitches are a means to avoid tension in a nerve suture. We evaluate this technique, relative to interposed grafts and simple neurorraphy, in a rat model. METHOD: Twenty rats were allocated to four groups. For Group 1, sectioning of the sciatic nerve was performed, a segment 4 mm long discarded, and epineural suture with distal anchoring stitches were placed resulting in slight tension neurorraphy. For Group 2, a simple neurorraphy was performed. For Group 3, a 4 mm long graft was employed and Group 4 served as control. Ninety days after, reoperation, latency of motor action potentials recording and axonal counts were performed. Inter-group comparison was done by means of ANOVA and the non-parametric Kruskal-Wallis test. RESULTS: The mean motor latency for the simple suture (2.27±0.77 ms) was lower than for the other two surgical groups, but lower than among controls (1.69±0.56 ms). Similar values were founding in both group 1 (2.66±0.71 ms) and group 3 (2.64±0.6 ms). When fibers diameters were compared a significant difference was identified between groups 2 and 3 (p=0.048). CONCLUSION: Good results can be obtained when suturing a nerve employ with epineural anchoring stitches. However, more studies are needed before extrapolating results to human nerve sutures.

Comparison of the performance of chronically versus freshly denervated autograft in nerve repair

PURPOSE

Graft choice is one of the few variables over which the surgeon has control when reconstructing nerve gaps. Because repair of chronically denervated nerves generally yields inferior recovery, we hypothesized that the use of chronically denervated nerve tissue as a graft source may compromise axonal regeneration and clinical results.

METHODS

A total of 45 immature female Sprague-Dawley rats underwent transection of one peroneal nerve before being divided into 3 experimental groups: group A (n = 15) had acutely denervated nerve graft, group B (n = 15) had 2-month denervated nerve graft, and group C (n = 15) had 4-month denervated nerve graft. We included 10 additional rats as a sham group. After 2 months, groups A and B underwent removal of 1 cm of the contralateral peroneal nerve. For group A, this section of nerve was immediately sutured back in place to serve as a model for acute denervation. For group B, the defect was repaired with a 1-cm graft from the distal stump of the previously transected (denervated) peroneal nerve. Group C underwent the same procedure as group B, but after an additional 2 months. After 8 weeks of regeneration time, the 3 experimental groups and the sham group underwent testing. We assessed twitch contraction forces of the reinnervated extensor digitorum longus before we harvested the muscle belly for morphologic measurements. Histological nerve tissue evaluation assessed axonal regeneration.

RESULTS

We detected no statistical differences for mean muscle contraction strengths between the experimental groups; nevertheless, the reinnervated extensor digitorum longus muscle bellies from the 4-month denervated nerve graft group were statistically smaller than muscles from the other 2 experimental groups (p < .05). Axon counts decreased, whereas axon diameters increased in direct correlation with the length of time of graft denervation (p < .05). No difference in axon myelination was found between experimental groups.

CONCLUSIONS

Prolonged denervation of nerve graft material compromised both axon and reinnervated muscle recovery in this rodent model.

The role of nerve allografts and conduits for nerve injuries

Nerve repair after transection has variable and unpredictable outcomes. In addition to advancements in microvascular surgical techniques, nerve allografts and conduits are available options in peripheral nerve reconstruction. When tensionless nerve repair is not feasible, or in chronic injuries, autografts have been traditionally used. As substitute to autografts, decellularized allografts and conduits have become available. These conduits can reduce donor site morbidity, functional loss at the donor area in cases where autografts are used, and immune reaction from transplants or unprocessed allografts. The development of new biomaterials for use in conduits, as well as use of cytokines, growth factors, and other luminal fillers, may help in the treatment of acute and chronic nerve injuries. The indications and properties of nerve conduits and allografts are detailed in this article.

Chapter 8: Current techniques and concepts in peripheral nerve repair

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

Cutaneous saphenous nerve graft for the treatment of sciatic neurotmesis in a dog

CASE DESCRIPTION

A 2-year-old Griffon Vendéen was examined because of a 1-month history of right hind limb lameness after a traumatic injury.

CLINICAL FINDINGS

Neurologic examination revealed monoplegia and anesthesia of the right hind limb distal to the stifle (femorotibial) joint except for the area supplied by the cutaneous saphenous nerve. Results of electromyographic testing were consistent with a severe lesion of the tibial and peroneal nerves at the level of the stifle joint.

TREATMENT AND OUTCOME

Exploratory surgery revealed an 80-mm-long gap in both the peroneal and tibial branches of the right sciatic nerve. A section of the left cutaneous saphenous nerve was interposed to graft the nerve defects. The dog received joint mechanotherapy and electrophysiologic therapy during the reinnervation process. Ten months after surgery, the dog had recovered almost completely. Neurologic examination revealed diminished flexion of the tarsal and digital joints. Repeat electromyographic testing revealed no abnormal spontaneous electrical activity in the right hind limb musculature, and small compound muscle action potentials were recorded in the right interosseous and cranial tibial muscles.

CLINICAL RELEVANCE

Without surgical treatment, neurotmesis injury results in poor recovery of motor and sensory functions and may result in amputation. If a nerve defect exists, nerve grafting should be considered, even if the procedure is delayed until well after the injury. The sensory portion of the cutaneous saphenous nerve is a potential source of peripheral nerve for grafting in dogs. Reinnervation is a long-term process and physiologic support and owner involvement are necessary, but nearly complete functional recovery is possible.

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.

Articulating external fixation to overcome nerve gaps in lower extremity trauma

This report describes the use of articulating external fixation in patients with lower extremity trauma with segmental nerve defects. Four patients who would otherwise require nerve grafting underwent application of an articulated external fixator, allowing optimal positioning for end-to-end, tension-free nerve repair followed by gradual lengthening. After three weeks of immobilization, the fixator was gradually advanced through the arc of the hinge. At an average follow-up of 44 months, motor function testing revealed gastroc-soleus function in all cases with a median motor grade of M4. Sensory function testing with Semmes-Weinstein monofilaments demonstrated protective plantar sensation in all cases with a median monofilament size of 3.84 on the injured limb compared with 3.22 on the contralateral side. This series of patients demonstrates that joint positioning through external fixation may be used safely and effectively to facilitate primary neurorrhaphy and subsequent limb salvage.

Effects of tension at the site of coaptation on recovery of sciatic nerve function after neurorrhaphy: evaluation by walking-track measurement, electrophysiology, histomorphometry, and electron probe X-ray microanalysis

The effects of tension at the site of coaptation on recovery of sciatic nerve function after neurorrhaphy were studied by evaluating walking-track measurements, nerve conduction velocity measurements, histomorphometry, and electron probe X-ray microanalysis. Forty adult male Lewis rats underwent right sciatic nerve (SN) transection followed by one of four different nerve repair procedures (N = 10 rats per group). In Group 1, the gap was repaired by end-to-end epineural coaptation. In Group 2, a 5-mm segment of SN was resected, and the defect was repaired under high tension by epineural neurorrhaphy. In Group 3, a 5-mm segment of SN was resected, and the defect was repaired with a 5-mm interposition nerve graft. In Group 4, a 5-mm segment of SN was resected. Then, to lessen the tension that follows neurorrhaphy, an anchoring suture was added. Finally, end-to-end coaptation was performed. Walking-track analysis showed better functional recovery in Group 1 than in Group 2, and better recovery in Group 3 than in Group 2. Group 4 showed a tendency toward better recovery comparing with Group 2. Electron probe X-ray microanalysis revealed higher Na, Cl, and K peaks in axoplasm accompanied by increase in the endoneural fluid pressure (EFP) in Group 2 than those of Group 1. This higher level of Na, Cl and K may be due to impairment of axonal sodium and potassium transport mechanism in Group 2. Increase in EFP may affect nerve regeneration.

Peripheral nerve repair and grafting techniques: a review

In this review, various conventional nerve repair techniques including direct epineurial repair, grouped fascicular repair, fascicular repair, and nerve grafting are described. The indications for use, as well as the relative advantage and disadvantage, of each technique are discussed. The experimental and clinical evidence from a review of the pertinent literature does not demonstrate a significant difference in outcome of one method over the others. Surgical decisions should be made by a thorough evaluation of all aspects of the nerve injury and surgical methods. All nerve injuries cannot be repaired using only one type of nerve repair method. The surgeon should be familiar with all the techniques described and be prepared to use them under appropriate circumstances.

An experimental study of three methods of lingual nerve defect repair

PURPOSE

This study compares three methods of lingual nerve defect repair.

MATERIALS AND METHODS

The recovery of the mechanosensitive and thermosensitive afferent fibers in the lingual branch of the trigeminal nerve in cats was studied using electrophysiological techniques 24 weeks after the removal of a segment of lingual nerve and repair of the defect by one of three methods. The nerve gap was closed by either stretching the nerve ends together and repairing under tension, insertion of a sural nerve graft, or use of a freeze-thawed muscle graft. The characteristics of the regenerated fibers were investigated and the data were compared with that from normal control animals.

RESULTS

After nerve repair, integrated whole-nerve activity evoked by thermal (cold) stimulation of the tongue was smaller than in the controls, but there were no differences between the repaired groups. However, recordings made from single axons in filaments dissected from the nerve revealed differences between the groups; the units were less sensitive after either method of grafting than after stretch repair.

CONCLUSIONS

It is concluded that repair of a short gap in the lingual nerve by stretch repair with an end-to-end anastomosis, even with some degree of tension, is followed by better recovery than by grafting. However, where a graft is necessary, a similar level of recovery will result from use of a frozen muscle graft or a sural nerve graft.

The nerve gap dilemma: a comparison of nerves repaired end to end under tension with nerve grafts in a primate model

The objective of this study was to compare, in a clinically relevant primate model, axon regeneration after epineurial repair under tension (15 mm gap) with interfascicular nerve grafts with the use of either standard microsuture techniques or a new interfascicular nerve graft technique termed fascicular tubulization that uses a hypoantigenic collagen membrane formed into a tube to approximate nerve ends. Electrophysiologic analysis demonstrated that the percentage of proximal axons that conducted across the repair site was greater in those nerves repaired under tension with epineurially placed sutures than in either of the tensionless repairs involving interfascicular graft techniques. The mean diameters of the regenerated axons repaired under tension with epineurial sutures were greater than those of the nerves repaired with interfascicular grafts, although the difference was not statistically significant. Interfascicular nerve grafting with tubulization using the current collagen tube resulted in regeneration equal to the sutured interfascicular nerve grafts. For modest defects (perhaps up to 3 to 4 cm in the adult), it seems advantageous to accept the modest tension associated with an epineurial repair rather than to use an autograft (or artificial graft) to achieve a tension-free repair.

Surgical repair of peripheral nerve injury

Magnification, use of fine interfascicular grafts for repair, and development of intraoperative electrophysiologic measurements of function have had a substantial impact on this field in the last 10 to 20 years. Basic surgical principles established during and since World War II remain the foundation for surgical repair of peripheral nerve injury but have been complemented nicely by these more recent advances. Selection of patients for surgery, as well as the timing of such, has been reviewed with emphasis on the differences between suspected transections and lesions in continuity, as well as comments on serious peripheral entrapments and tumors affecting nerve. The importance of not only preoperative electromyographic studies but also the intraoperative use of stimulation and stimulation and recording of nerve action potentials (NAPs) for lesions in continuity has been stressed. Operative techniques such as neurolysis, NAP recordings, suture, split repair, and interfascicular graft repair have been reviewed and some commentary on results provided. There has been a gradual evolution of centers in this country and abroad for care of the more serious surgical nerve problems. It is anticipated that in the future, such centers will be able to provide improved data concerning results with civilian nerve injuries.

An electrophysiological and histological study of myelinated axon regeneration after peripheral nerve injury and repair in the cat

Electrophysiological and histological methods have been combined to obtain quantitative measures of the success of regeneration of myelinated axons in a cutaneous nerve after injury and repair by a variety of procedures. Following a simple transection injury more axons regenerated successfully when the nerve was repaired by epineurial suturing or stump suturing than when it was left unrepaired; both types of repair gave similar results. After loss of a 10-mm piece of the nerve trunk, repair with an autograft produced more regeneration than when the nerve was left untouched, but repair by stump mobilization with epineurial suturing made matters worse. On the whole, the regenerated afferents had receptive field properties similar to those found in control animals but there was a higher incidence of units that could not be typed using conventional criteria. A small proportion of them had split receptive fields. Fibre diameters and conduction velocities were reduced compared with controls; this was particularly so through the neuroma and in the distal stump. There was also evidence of abnormal interactions, possibly ephaptic, between some regenerated axons.

Sciatic nerve regeneration after autologous sural nerve transplantation in the rat

The present study is concerned with the question as to whether the size of a nerve used as a transplant to bridge a gap between the stumps of transected nerves has a bearing on the number of axons and the cytological structure of the regenerate. The paradigm is rat sciatic nerve transection with 8 mm of nerve removed with the stumps placed in a silicone tube and two strands of the smaller sural nerve used as bridging transplants. The comparisons are with previously published results where the transplant, which is the removed piece of sciatic nerve, is exactly matched in size and with no transplant in the same regeneration paradigm. One surprising finding is that the size of the transplant does not seem to determine the size of the regenerated nerve. The cytological structure of the regenerated nerve is related to the size of the transplant, however, in that the proportion of axons that regenerate inside and outside the transplanted perineurial tubes differs in relation to the size of the transplant. In addition, although there is an increase in the number of blood vessels in all of these paradigms, the greatest increase is with the sural nerve transplants. The key finding in the study, however, is the similarity in numbers of regenerated axons in the gap, distal stump and tributary nerves when regeneration after sciatic nerve transplantation is compared with regeneration after sural nerve transplantation. Thus, notwithstanding the cytologic differences of the two types of regenerate, regenerated axon numbers are approximately the same. The conclusion is that the size of the transplant determines neither the size of the regenerate nor the numbers of regenerated axons in this paradigm. On the assumption that regeneration is better when axonal numbers are closer to normal, the non-matched sural nerve transplant is approximately equal to the matched sciatic nerve transplant and both are superior to the regeneration that takes place in the absence of a transplant in this paradigm.