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WEEK 24:
Surgery on broken bones and nerve injuries:
| Question | Answer |
|---|---|
| nerve structure consists of (4) | endoneurium, perineurium, epineurium, and blood supply |
| endoneurium | around nerve fibre |
| perineurium | around nerve bundles |
| epineurium | around nerve trunk |
| types of blood supply in nerve structure (2) | extrinsic and intrinsic |
| mallest to largest layers in nerves | endoneurium -> perineurium -> epineurium |
| schwann cells | surround multiple fibrils and produce part of myelin sheath which contributes to regeneration of PNS axons |
| acute mechanism of injury | how peripheral nerves get injured in trauma |
| about 2% of patients with limb trauma have | major peripheral nerve injury |
| types of stretch injuries in acute limb trauma leading to nerve injury | vascular changes (8%) and axon damage (15%) |
| explain how a laceration occurs from acute injury (2) | at fracture ends and penetrating trauma |
| causes of acute injury (3) | stretch (vascular changes and axon damage), compression/crush, and laceration |
| acute: anterior shoulder dislocation leads to | injure axillary nerve |
| acute: distal 1/3 humerus fracture lead to | injure radial nerve |
| acute: distal humerus fractures lead to | injure median nerve |
| acute: hip dislocation leads to | injure sciatic nerve |
| acute: proximal fibular fracture leads to | common peroneal nerve |
| causes of chronic injury | compression/crush |
| paraesthesia (tingling) due to chronic injury occurs at | 30mmHg crush/compression |
| conduction block due to chronic injury occurs at | 60mmHg crush/compression |
| BP cuff results from chronic injury | 150-200mmHg |
| torniquet results from chronic injury | <300mmHg |
| chronic: CTS (carpel tunnel syndrome) affects | median nerve |
| chronic: funny bone injury affects | ulnar nerve |
| chronic: saturday night palsy affects | radial nerve |
| chronic: disc prolapse affects | sciatic nerve |
| chronic: vicious cycle/ Alcock's canal affects | pudenal nerve |
| order of recovery (6) | sympathetic, pain, temperature, touch, propioception (aware of what position in), and motor function (1st to go is last to return) |
| investigations used to assess injury | neurological examination - nerve conduction studies (EMG and NCV) |
| electro-myography (EMG) investigates what | assesses NMJ and can show denervation of muscle |
| nerve conduction velocity (NCV) investigates what | large myelinated fibres, focal compression, and demyelination |
| consequences of nerve injury | neuroma formation (thickening), chronic pain, muscle wasting, paralysis, contractures (shortening and hardening of muscle), loss of protective sensation, charcot joint (degenerative joint), amputation, and phantom limb pain |
| treatment of nerve injury (2) | observation of operative |
| operative options for nerve injury treatment (5) | direct muscular neurotisation, nerve repair, nerve graft, nerve transfer, and tendon transfer |
| observation as treatment for nerve injury includes | NCS (conduction studies) for 6/52 (6 weeks) |
| what happens if in observation (NCS 6/52) no improvement is seen | may need splint to prevent contracture (eg wrist drop in radial nerve palsy) or physiotherapy to maintain passive ROM (range of motion) |
| indications for direct muscular neurotisation | transected nerve ends at risk of developing painful neuroma, particularly if planning use of prosthesis after amputation. Transected nerve attached into muscle belly and degree of muscle recovery is variable |
| indications for surgical repair | neurotmesis, penetrating/ iatrogenic injury, tension free repair possible |
| outcomes of surgical repair | variable, best if performed within 7-14 days and reinnervation and sensory retraining may take several years |
| indications for nerve grafting | tension free repair not possible |
| technique used for nerve grafting | Autograft – gold standard, Allograft - <5cm, Conduit - <20cm |
| outcomes of nerve grafting | variable, success drops with gaps >5mm |
| nerve transfer indications | proximal nerve injury eg brachial plexus, restore axons before degeneration of motor end plate, restore shoulder abdn, ER, elbow flex, finger fxn eg spinal accessory nerve (CNXI) to suprascapular nerve |
| outcomes of nerve transfer | similar to tendon transfers |
| indications for tendon transfer | function through nerve regeneration unlikely |
| technique for tendon transfer | similar power/ excursion and synergist |
| outcomes for tendon transfer | loss of at least one motor grade and is better in children due to neuroplasticity |
| impairment of peripheral nerve injuries are determined by | injury level, axonal disruption and time to treatment |
Created by:
kablooey
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