Journal of Peripheral Nerve SurgerySurgery (Volume 2, No. 1, July 2018) 41-48 41 REVIEW ARTICLE Basic Techniques of Peripheral Nerve Repair Nikhil Panse1, Ameya Bindu2 Abstract Classification Systems and Pathophysiology of Peripheral nerve injuries are commonly encountered Nerve Repair in clinical practice. Early diagnosis of nerve injuries Peripheral nerve injuries can be a part of medium to and application of basic concepts in their repair and high energy trauma or present as a result of a low management gives positive outcomes. energy compressive forces or an ischemic lesion. The This article is a brief guide on the basic techniques management options and prognosis of a nerve injury of peripheral nerve repair. are dependent on the level and degree of the injury. The pre-op assessment, indications and timing of Seddon, Sunderland and MacKinnon have proposed nerve surgery and techniques of nerve repair are classifications of nerve injuries which serve as a guide for management and prognostication of these discussed. In addition the approach to the management 3,4,5 of nerve gaps is also discussed with due consideration injuries . to the various options available for management of Basic understanding of the pathophysiology of nerve gaps. nerve degeneration and regeneration are essential for a reconstructive surgeon managing a nerve injury, so Introduction that the physiological process of regeneration can be Peripheral nerve injuries are commonly seen, affecting supplemented and optimised by means of the surgical about 2.8% patients presenting with trauma. These procedure performed. The process of reinnervation injuries are associated with considerable disability and and functional recovery takes many months as the loss of productivity, especially when associated with axonal regeneration needs to reach the distal end hand injuries1,2. A thorough knowledge and organs, which is occurring at the rate of around 1mm understanding of the anatomy and the pathophysiology per day.6 The misdirection and uncontrolled branching of the nerve injury coupled with a high index of of the growing axons at the site of injury are some of suspicion is essential for an early and correct diagnosis the commonly seen errors in nerve regeneration 7 of any nerve injury. Management of peripheral nerve which can be avoided by practice of precise surgical injuries still remains an enigma for the reconstructive technique. surgeons despite the progress and ongoing research in molecular neurobiology of regeneration and Management of nerve Injury microsurgical techniques. To achieve consistent and Preoperative assessment improving outcomes, the basic concept and principles of nerve repair should be complemented with the A thorough clinical examination is paramount to application of advances in microsurgical and molecular diagnose the degree and level of injury and to formulate biological tools into clinical practice. The present article the treatment plan. The surgeon should adopt a focuses on the basic techniques of peripheral nerve standardised stepwise approach for uniform evaluation repairs. of the central and the peripheral nervous system so that the subtle aberrations can be picked up and noted. It involves assessment of sensory deficit, motor losses, Nikhil Panse vasomotor changes and joint examination. Vimal Niwas, Sudarshan Society, Model Colony, Shivajinagar, Pune 411016 Electrophysiological studies like Electromyography +91 9422314809 (EMG) and Nerve conduction velocity (NCV) allows [email protected] to assess the pattern and the prognosis of functional 1,2 Department of Plastic Surgery, B.J.Govt. Medical College & recovery as well as guide for a surgical intervention8. Sassoon Hospital, Pune 42 Journal of Peripheral Nerve Surgery Indications of surgery 2. Appropriate microsurgical instrumentation with suture materials and/or tissue glue Surgery can be guided by the classification of injury and the clinical judgement of the surgeon. Some of 3. Use a tourniquet wherever possible the scenarios which indicate an operative intervention 4. Use of short acting paralysing agent if for nerve injuries can be enlisted as: intraoperative nerve stimulation is contemplated 1. Definitive nerve injuries or trauma along a major 5. Position of the patient and the operative field as nerve trunk with neurological deficit, like open per surgeon’s comfort fractures, crush injuries, iatrogenic nerve injuries, 6. Liberal and wide surgical exposures with sharp cut wounds, post reduction injuries, etc. dissection preferred from virgin tissue to scarred 2. Probable neuropraxia with failure to recover after or injured tissue and minimal disruption of local 3 months of conservative management. blood supply. 3. Associated vascular or orthopaedic injuries 7. Blood free field with adequate hemostasis requiring intervention. 8. Attempt to preserve the mesoneurium and the 4. Persistent pain or chronic painful neuromas. gliding planes of the nerve13 with keeping the 5. Arrest of improvement or worsening clinically and dissection and skeletonisation of the nerve ends to on electrodiagnostic studies. minimum 9. Careful handling of the nerve tissues and fascicles Timing of surgery with either atraumatic microinstruments, using Early nerve repair, whenever feasible, is advocated mesoneurium, or passing epineurial stay suture to as delay in intervention leads to irreversible facilitate manipulation as well as serve as a guide degenerative changes in the distal nerve end as well for gross fascicular matching as the motor end plate, along with atrophy and the 10. During nerve suturing, the fascicular pattern of the fibrosis in the innervated muscle which diminishes any nerve must be taken into consideration chances of functional recovery9,10,11. Experimental animal model studies have proved the neuronal Primary neurorrhaphy preservation and improved clinical outcome after early Direct nerve repair (primary neurorrhaphy) with nerve repair12. Thus, whenever clinical evidence epineurial microsutures is our preferred technique and mandates a surgical nerve repair, like sharp nerve considered as gold standard for the surgical repair of transections, the procedure is undertaken without any peripheral nerves.The procedure of primary delay, and is labelled as ‘Primary Nerve Repair’. This neurorrhaphy can be divided into 4 major surgical has the advantage of minimal intraneural and peineural steps: scarring. 1. Preparation Principles of nerve repair Before repair, the traumatised nerve ends need to be The surgeon should follow certain basic principles of prepared and the necrotic and scarred tissue debrided peripheral nerve repair to achieve the best possible with sharp microscissors or using a fine surgical blade. and consistent results. Careful attention to each surgical Healthy fascicles tend to pout out or herniate owing to step, perseverance, practice and spending that extra the high endoneurial fluid pressure and tissue viability time to achieve perfection is often rewarded with can also be judged from the pin point bleeding at the success and reduces the reexploratory procedures. nerve ends. Also, the pouting out fascicles need to be The goal of any nerve repair surgery should be to trimmed appropriately a second time in relation to the provide for and facilitate the growth of the regenerating epineurium to prevent bending or bunching up of the axons into the endoneurial tubes of the distal nerve fascicles leading to misdirection of the regenerating stump with minimal loss of fascicles. axons after the repair. Salient operative principles that are common to all Some important points to be considered are- the nerve surgeries can be enlisted as: a. When handling a nerve, only the epineurium should 1. Adequate illumination with magnification in the be caught with forceps, and damage to follicles form of loupes or a microscope must be avoided. Journal of Peripheral Nerve Surgery 43 b. While trimming the nerve to the non injured tissue, choice as it leads to minimal foreign body reaction and excess pull on the epineurium must be avoided to scarring18. Two lateral sutures at 180 degrees apart prevent proximal retraction of the epineurium after followed by 2 to 4 epineural sutures, depending on the cutting the ends. This causes exposure of the diameter of the nerve to be repaired, are usually fascicles, and makes suturing difficult afterwards. adequate. We must resist the temptation of overzealous 2. Approximation or tight suturing, keeping in mind that every suture leads to fibrosis. Fibrin glue can be used to supplement and After adequate preparation, the nerve ends are seal the repair in addition to sutures (Fig 3), but when approximated so as to judge the tension at the repair used alone, it lacks the necessary tensile strength19. site by keeping the related joints in neutral or extended position. Length of the gap is assessed. Slight It is also very import to coapt the nerves with the mobilisation of the nerve ends is almost always proper alignment of sensory and motor fascicles, necessary so as to reduce the tension at the repair especially in cases of ulnar nerve at the wrist level site. Due care is taken to prevent damage to the which consists of 40% motor and 60% sensory mesoneurium during mobilisation of the nerve14. Care fascicles.Improper realignment can result in excellent regeneration, put poor functional outcomes if sensory is taken to avoid excessive intrafascicular dissection. 20 Extensive dissection and mobilisation of the nerve and motor fascicles are not properly