Nerve injury and repair

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  • Accompanying artery and vein give off the blood supply of the nerves via vesa nervorum passing along the nerve into their epineurium which further give off smaller branches
  • Proximally : axons retract and undergo quiescence & then regenrate their multiple daughter axons that regrow towards their sensory or motor target organs…Once a functioning synapse is made,all other daughter axons degenerate.Distally: injured nerve segment undergoes degenrative changes and tissue debris are phagocytosed by macrophages..all these changes collectively make what’s known as wallerian degenration
  • Ten test for quality of sensationStatic and moving two point descrimination that measures no of fibres innervating it yet
  • Nerves have an intrinsic elastic property which makes the nerve to have horizontal or spiral bands along its length known as bands of fontana by which they can be moved to certain extent..these bands disappear when the nerve is compressed
  • In order to restore the sensory and motor modalities of a nerve..stitch the sensory & motor fascicles of proximal segment to those of distal segment if the internal topography of a nerve is clear..every nerve has a specific internal organization and u must know all of them before going into that micro repair..usually nerves r more monofascicular proximally and are polyfascicular distally and there is plexus formation in between these fascicles that diminish distally
  • Alignment is a challengeThen no of max axons…u can even reverse a long graft to have maximum axons at the distal siteExclusion of non essential nerve components..n their distal sensory ends joined to nearby sensory nerves by end to side anastomosis
  • LABN accompanying cephalic veinMABN accompanying basilic vein
  • Due to partial injury or a previous repairProper assessment of functioning fascicles by nerve stimulation testsIf neuroma is circumferential and normally functioning components are difficult to be separated then
  • Criteria for motor n sensory donor nerves
  • Limited use
  • Challenging as they can evoke immune system leading to graft rejection
  • Nerve injury and repair

    1. 1. mesoneurium perineurium Fascicles of nerve fibers epineurium endoneurium
    2. 2.           Focal contusion (gunshot wounds) Stretch/traction injury Drug injection injury Compression Crush injuries Avulsion Laceration Electrical burns Idiopathic Others(Viral infections, metabolic and neural disorders)
    3. 3.  Changes at proximal and distal site of injury
    4. 4. Seddon, Sunderland and lately by Mackinnon  6 degrees 
    5. 5.  1st degree of injury(neuraparaxia) › Segmental demylination › Axons intact › Recovery in 12 to 16 wks  2nd degree injury(axonotmesis) › Axonal injury/ distal wallerian degeneration › Regeneration at rate of 1 inch per month › Complete slow recovery
    6. 6. 3rd degree injury › Axonal injury & fibrosis of endoneurium › Incomplete recovery  4th degree injury › Axonal injury › Damage to endo and perineurium with dense scarring › Needs surgical intervention 
    7. 7.  5th degree injury(neurotmesis) › Complete nerve division  6th degree injury › Variable combination of previous five degrees of nerve injury
    8. 8. 4th degree injury 2nd degree injury 1st degree injury 6th degree injury 3rd degree injury normal
    9. 9. •History •Examination  Motor function › Movements, muscle atrophy  sensory function › Tinel sign, Ten test › Two point discrimination › Touch, vibration
    10. 10.  Tinel sign: › peripheral tingling or dysaesthesia' provoked by percussion of the nerve › Positive in axonal injuries
    11. 11.    EMG NCS Intra operative nerve action potential
    12. 12.  Microsurgical techniques › Adequate magnification › Microsurgical instruments & sutures  Different techniques: › Primary nerve repair › Nerve grafting › Nerve transfer › Nerve conduits › Nerve allografts
    13. 13.  Sharply transected nerves › Immediate repair  Crushed, avulsed, blast injuries › Nerve ends tacked together › Repair delayed for 3 weeks or until wound bed permits  Re-exploration  Neuroma excision, nerve grafts  Acute nerve grafting in the 1st sitting  Bleeding control ,trimming of fascicles ,loose epineural suturing  Closed injuries treated expectantly for 12 weeks
    14. 14.  Primary repair › Tension free repair › Mobilization of nerve ends › Discourage  Facilitation by postural position  Extreme range of joint movements
    15. 15.  Primary nerve repair › Epineural repair › Grouped fascicular repair
    16. 16. Standard repair
    17. 17.  Restore the continuity of fascicles  Internal topography  Intra-operative nerve stimulation  Neurolysis with the eyes  Priority to the motor recovery(radial and peroneal nerve)
    18. 18. Tension at site of repair  Need of postural positioning  Alignment of sensory & motor components  Maximize number of axons  Reversal of graft  Exclusion of expendable nerve 
    19. 19. Sural nerve › 30-40cm › Lateral peroneal communicating br : 10-20cm  Lateral antebrachial cutaneous nerve(LABC) › 8cm  Medial antebrachial cutaneous nerve (MABC) › Anterior & posterior division › 20 cm  Expendable nerves(peroneal and radial)  Sensory branches of ulnar and median nerves  Distal anterior interosseous nerve and so on… 
    20. 20.  Donor site scarring  Donor site sensory loss › Patient education
    21. 21. Complete : resection and repair with graft
    22. 22. Incomplete neuroma  Intra-operative nerve stimulation  Black boxing around neuroma 
    23. 23.  Indications: › Very proximal peripheral nerve injuries › Root avulsions › Excessive scarring › Level of injury unclear  Idiopathic neuritides  Radiation induced nerve injury
    24. 24.  Motor nerve transfer › Pure motor axons › Close proximity › expendable › Synergistic supply  Sensory nerve transfer › pure sensory axons › Innervates non critical area › Expendable and lying in close proximity
    25. 25. elbow flexion  Shoulder abduction  Ulnar-innervated intrinsic hand function  Forearm pronation  Radial nerve function 
    26. 26. Transfer of radial nerve to axillary nerve
    27. 27.  Veins, pseudo-sheaths, bioabsorbable tubes  short nerve gaps ≤ 3cm  Low antigenicity , biodegradability  Trials to add a nerve graft inside the conduit › neurotrophic factors
    28. 28. Extensive injuries  Limited donor material  Immunosuppressive agents  › FK506( tacrolimus ) › Prednisone , azathioprine  Processed acellular cadaveric nerve allografts › AxoGen, Inc. ,Alachua, FL.

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