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 myeliuation. 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.

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.

Role of stem cells-based in facial nerve reanimation:A meta-analysis of histological and neurophysiological outcomes

BACKGROUND Treatments involving stem cell(SC)usage represent novel and potentially interesting alternatives in facial nerve reanimation.Current literature includes the use of SC in animal model studies to promote graft survival by enhancing nerve fiber growth,spreading,myelinization,in addition to limiting fibrotic degeneration after surgery.However,the effectiveness of the clinical use of SC in facial nerve reanimation has not been clarified yet.AIM To investigate the histological,neurophysiological,and functional outcomes in facial reanimation using SC,compared to autograft.METHODS Our study is a systematic review of the literature,consistently conducted according to the preferred reporting items for systematic reviews and meta-analyses statement guidelines.The review question was:In facial nerve reanimation on rats,has the use of stem cells revealed as effective when compared to autograft,in terms of histological,neurophysiological,and functional outcomes?Random-effect meta-analysis was conducted on histological and neurophysiological data from the included comparative studies.RESULTS After screening 148 manuscript,five papers were included in our study.43 subjects were included in the SC group,while 40 in the autograft group.The meta-analysis showed no significative differences between the two groups in terms of myelin thickness[CI:-0.10(-0.20,0.00);I^(2)=29%;P=0.06],nerve fibers diameter[CI:0.72(-0.93,3.36);I^(2)=72%;P=0.6],compound muscle action potential amplitude[CI:1.59(0.59,3.77);I^(2)=89%;P=0.15]and latency[CI:0.66(-1.01,2.32);I^(2)=67%;P=0.44].The mean axonal diameter was higher in the autograft group[CI:0.94(0.60,1.27);I^(2)=0%;P≤0.001].CONCLUSION The role of stem cells in facial reanimation is still relatively poorly studied,in animal models,and available results should not discourage their use in future studies on human subjects.

Mitral valve cleft gapping mechanism in functional mitral regurgitation:An in-vitro study

Background and aim:Gapping formation of the mitral valve cleft is unknown.The objective of this study was to quantify the geometry of mitral valve cleft coaptation in the asymmetric and symmetric papillary muscles(PMs)positions in a dilated annulus in order to reveal mitral valve gapping mechanism.Methods:Nine fresh porcine mitral valves with the posterior leaflet clefts were sutured onto a saddle-shaped dilated annulus in an in-vitro experiment to simulate mitral valve closure at hydrostatic pressure.PMs were adjusted to the normal position,and subsequently to positions of asymmetric and symmetric PM displacement.Sonomicrometry was used to measure positions of the lateral and medial clefts.Results:PM displacement tethered the leaflets.Both the opening angle and contact angle of the lateral cleft,but not of the medial cleft,increased in the asymmetric PM displacement.Neither the opening angle nor contact angle of both clefts increased in the symmetric PM displacement.Conclusions:Displacement of the postero-medial PM moves the posterior leaflet medially and impairs coaptation of the lateral cleft,but not medial cleft,which suggest that the medial cleft displacement in the asymmetric PM position is another mechanism of gap formation in addition to leaflet tenting due to apical leaflet displacement.Symmetric PM displacement cause leaflet tenting,but doesn’t impair the leaflet cleft coaptation,which suggest that the asymmetric PM position is even worse than the symmetric PM position.

Nerve transfers in distal forearm and in the hand

Nerve transfers were used,originally,to restore shoulder and elbow function in brachial plexus lesions.This concept has been developed over the years and applied to distal nerve injuries in which lower functionality was expected because of the gap between the injury site and the target muscle.The aim of this review is to describe nerve transfers in the distal forearm and hand for isolated lesions of the median,ulnar and radial nerves.The different advantages achieved by transposition of a functional nerve stump near the effector muscle have opened up new options for the management of nerve lesions.Some of these alternatives have only been recently reported and a few are exclusively case reports.