Introduction Mechanism stretching injury 8% elongation will diminish nerve's microcirculation 15% elongation will disrupt axons examples "stingers" refer to neurapraxia from brachial plexus stretch injury suprascapular nerve stretching injuries in volley ball players correction of valgus in TKA leading to peroneal nerve palsy compression/crush fibers are deformed local ischemia increased vascular permeability endoneurial edema leads to poor axonal transport and nerve dysfunction fibroblasts invade if compression persists scar impairs fascicular gliding 30mm Hg can cause paresthesias increased latencies 60 mm Hg can cause complete block of conduction laceration sharp transections have better prognosis than crush injuries continuity of nerve disrupted ends retract nerve stops producing neurotransmitters nerve starts producing proteins for axonal regeneration Pathophysiology regeneration process after transection distal segment undergoes Wallerian degeneration (axoplasm and myelin are degraded distally by phagocytes) existing Schwann cells proliferate and line up on basement membrane proximal budding (occurs after 1 month delay) leads to sprouting axons that migrate at 1mm/day to connect to the distal tube variables affecting regeneration contact guidance with attraction to the basal lamina of the Schwann cell neurotropism neurotrophism neurotrophic factors (factors enhancing growth and preferential attraction to other nerves rather than other tissues) Prognosis factors affecting success of recovery following repair age is single most important factor influencing success of nerve recovery level of injury is second most important (the more distal the injury the better the chance of recovery) sharp transections have better prognosis than crush injuries repair delay worsen prognosis of recovery (time limit for repair is 18 months) return of function pain is first modality to return Anatomy Highly organized structure consisting of nerve fibers, blood vessels, and connective tissue Functional structures epineural sheath surrounds peripheral nerve epineurium surrounds a group of fascicles to form peripheral nerve functions to cushion fascicles against external pressure perineurium connective tissue covering individual fascicles primary source of tensile strength and elasticity of a peripheral nerve provides extension of the blood-brain barrier provides a connective tissue sheath around each nerve fascicle fascicles a group of axons and surrounding endoneurium endoneurium fibrous tissue covering axons participates in the formation of Schwann cell tube myelin made by Schwann cells functions to increase conduction velocity neuron cell cell body - the metabolic center that makes up < 10% of cell mass axon - primary conducting vehicle dendrites - thin branching processes that receive input from surrounding nerve cells Blood supply extrinsic vessels run in loose connective tissue surrounding nerve trunk intrinsic vessels plexus lies in epineurium, perineurium, and endoneurium Physiology presynaptic terminal & depolarization electrical impulse transmitted to other neurons or effector organs at presynaptic terminal resting potential established from unequal distribution of ions on either side of the neuron membrane (lipid bilayer) action potential transmitted by depolarization of resting potential caused by influx of Na across membrane through three types of Na channels voltage gate channels mechanical gated channels chemical-transmitter gated channels nerve fiber types Fiber Type Diameter (uM) Myelination Speed Example A 10-20 heavy fast touch B < 3 moderate medium ANS C < 1.3 none slow pain Classification Seddon Classification neurapraxia same as Sunderland 1st degree, "focal nerve compression" nerve contusion leading to reversible conduction block without Wallerian degeneration histology histopathology shows focal demyelination of the axon sheath (all structures remain intact) usually caused by local ischemia electrophysiologic studies nerve conduction velocity slowing or a complete conduction block no fibrillation potentials prognosis recovery prognosis is excellent axonotmesis same as Sunderland 2nd degree axon and myelin sheath disruption leads to conduction block with Wallerian degeneration endoneurium remains intact fibrillations and positive sharp waves on EMG neurotmesis complete nerve division with disruption of endoneurium no recovery unless surgical repair performed fibrillations and positive sharp waves on EMG Seddon Type Degree Myelin Intact Axon Intact Endoneurim Intact Wallerian Degen. Reversible Neurapraxia 1st No Yes Yes No reversible Axonotmesis 2nd No No Yes Yes reversible Neurotmesis 3rd No No No Yes irreversible Sunderland Classification 1st degree same as Seddon's neurapraxia 2nd degree same as Seddon's axonotmesis 3rd degree included within Seddon's neurotmesis injury with endoneurial scarring most variable degree of ultimate recovery 4th degree included within Seddon's neurotmesis nerve in continuity but at the level of injury there is complete scarring across the nerve) 5th degree included within Seddon's neurotmesis Sunderland Grade Myelin Sheath Axon Endoneurim Perineurium Epineurium I Disrupted Intact Intact Intact Intact II Disrupted Disrupted Intact Intact Intact III Disrupted Disrupted Disrupted Intact Intact IV Disrupted Disrupted Disrupted Disrupted Intact V Disrupted Disrupted Disrupted Disrupted Disrupted Evaluation EMG often the only objective evidence of a compressive neuropathy (valuable in workcomp patients with secondary gain issues) characteristic findings denervation of muscle fibrillations positive sharp waves (PSW) fasiculations neurogenic lesions fasiculations myokymic potentials myopathies complex repetitive discharges myotonic discharges NCV focal compression / demyelination leads to increase latencies (slowing) of NCV distal sensory latency of > 3.2 ms are abnormal for CTS motor latencies > 4.3 ms are abnormal for CTS decreased conduction velocities less specific that latencies velocity of < 52 m/sec is abnormal motor action potential (MAP) decreases in amplitude sensory nerve action potential (SNAP) decreases in amplitude Treatment Nonoperative observation with sequential EMG indications neuropraxia (1st degree) axonotmesis (2nd degree) Operative surgical repair indications neurotomesis (3rd degree) Definitive repair after 1-3 weeks in the setting of gunshot wound neurotmesis nerve grafting indications defects > 2.5 cm type of autograft (sural, saphenous, lateral antebrachial, etc) no effect on functional recovery Surgical Techniques Direct muscular neurotization insert proximal nerve stump into affected muscle belly results in less than normal function but is indicated in certain cases Epineural Repair primary repair of the epineurium in a tension free fashion first resect proximal neuroma and distal glioma it is critical to properly align nerve ends during repair to maximize potential of recovery Fasicular repair indications three indications exist for grouped fascicular repair median nerve in distal third of forearm ulnar nerve in distal third of forearm sciatic nerve in thigh technique similar to epineural repair, but in addition repair the perineural sheaths (individual fascicles are approximated under a microscope) outcomes no improved results have been demonstrated over epineural repair Nerve grafting autologous graft indications ≥ 3cm gap digital nerve defects at wrist to common digital nerve bifurcation - use sural nerve at MCP to DIP level - use lateral antebrachial cutaneous nerve at DIP level - use AIN, PIN or medial antebrachial cutaneous nerve outcomes gold standard for segmental defects > 5cm collagen conduit tensioned closures inhibit Schwann cell activation and axon regeneration, compromise perfusion and lead to scarring collagen conduits allow nutrient exchange and accessibility to neurotrophic factors to the axonal growth zone during regeneration indications defects ≤ 2cm outcomes equal results to autologous grafting when gap ≤5mm quality of nerve recovery drops with gaps >5mm allograft off-the-shelf option for defects up to 5cm
Technique Guide Technique guide are not considered high yield topics for orthopaedic standardized exams including the ABOS, EBOT and RC. Epineural Nerve Repair Orthobullets Team Hand - Peripheral Nerve Injury & Repair Technique Guide Technique guide are not considered high yield topics for orthopaedic standardized exams including the ABOS, EBOT and RC. Conduit Repair Orthobullets Team Hand - Peripheral Nerve Injury & Repair
QUESTIONS 1 of 12 1 2 3 4 5 6 7 8 9 10 11 12 Previous Next (OBQ13.9) Figure A shows a traumatic laceration of the distal forearm with a 5cm segmental median nerve defect. Which of the following repair or reconstruction techniques would allow for the best recovery of motor function? Review Topic QID: 4644 FIGURES: A 1 Autogenous venous nerve conduit 4% (115/3070) 2 Collegen synthetic nerve conduit 9% (284/3070) 3 Biodegradable polyglycolic acid 1% (19/3070) 4 Processed nerve allograft 2% (67/3070) 5 Nerve autograft 84% (2566/3070) ML 2 Select Answer to see Preferred Response PREFERRED RESPONSE 5 Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK (OBQ13.24) Which statement most accurately describes the physiology of peripheral nerve regeneration following an axonotmesic lesion? Review Topic QID: 4659 1 The proximal nerve segment undergoes Wallerian degeneration 14% (637/4512) 2 Axon growth occurs from the distal segment to proximal segment 3% (146/4512) 3 Neurotrophic factors direct phagocytic activity 6% (293/4512) 4 Proximal axon budding allows for antegrade (or distal) axon migration 70% (3176/4512) 5 Axoplasm and myelin are degraded distally predominantly by Schwann cells for the first 12 months following injury 5% (235/4512) ML 3 Select Answer to see Preferred Response PREFERRED RESPONSE 4 (OBQ05.66) Axon regeneration almost always occurs following a Sunderland second-degree nerve injury because which anatomic structure is not injured? Review Topic QID: 952 1 Epineurium 23% (282/1219) 2 Endoneurium 51% (626/1219) 3 Perineurium 10% (122/1219) 4 Myelin sheath 11% (132/1219) 5 Schwann cell 4% (44/1219) ML 4 Select Answer to see Preferred Response PREFERRED RESPONSE 2 (OBQ09.268) You are seeing a 24-year-old male in the emergency room after he was involved in a knife fight. He has severed the common digital nerve to the index finger on his dominant hand, with an 8mm gap between nerve ends. In counseling him about repair, which of the following options is as good as autologous nerve grafting? Review Topic QID: 3081 1 Glycolide trimethylene carbonate conduit 4% (103/2300) 2 Collagen conduit 62% (1424/2300) 3 Silicone sleeve 7% (153/2300) 4 Primary end-to-end repair 15% (336/2300) 5 Polyglycolic acid conduit 12% (276/2300) ML 3 Select Answer to see Preferred Response PREFERRED RESPONSE 2 (OBQ12.210) A 55-year-old male laborer comes in with a chief complaint of clumsiness with his right hand for the past 3 months including difficulty using a hammer while at work. He has had no injury to the right upper extremity. On physical examination, he has persistent small finger abduction/extension with finger extension and active adduction. An EMG is performed and demonstrates ulnar nerve conduction velocities of 31 m/sec (normal >52m/sec). The patient symptoms are most accurately described as Review Topic QID: 4570 1 Axonotmesis with ischemia origin 11% (455/4034) 2 Axonotmesis with myelin disruption 17% (702/4034) 3 Neurapraxia with ischemia origin 57% (2318/4034) 4 Neurapraxia with endoneurium disruption 11% (447/4034) 5 Neurotmesis 2% (74/4034) ML 4 Select Answer to see Preferred Response PREFERRED RESPONSE 3 (OBQ12.46) The patient sustains the injury seen in Figure A from a gunshot injury. The physical exam is notable for lack of sensation in his fourth and fifth digits as well as a positive Froment's sign. Which of the following factors has not been shown to be a significant prognostic indicator of functional recovery following nerve repair? Review Topic QID: 4406 FIGURES: A 1 Duration to time of repair 11% (547/4778) 2 Repair level 7% (338/4778) 3 Length of repair 9% (421/4778) 4 Postoperative physical rehabilitation 25% (1207/4778) 5 Type of autograft used 47% (2243/4778) ML 4 Select Answer to see Preferred Response PREFERRED RESPONSE 5 (OBQ08.30) Which of the following nerves has the most favorable regenerative potential in restoring motor function after a graft repair within half a year after being injured? Review Topic QID: 416 1 Median 22% (562/2559) 2 Ulnar 10% (250/2559) 3 Radial 61% (1551/2559) 4 Tibial 4% (92/2559) 5 Peroneal 4% (90/2559) ML 3 Select Answer to see Preferred Response PREFERRED RESPONSE 3 (OBQ05.218) Vitamin B12 deficiency is a known cause of which the following? Review Topic QID: 1104 1 Inability to whistle 0% (9/2997) 2 Peripheral sensory neuropathy 96% (2881/2997) 3 Increased deep tendon reflexes 3% (85/2997) 4 Urinary retention 0% (4/2997) 5 Hydrophobia 0% (5/2997) ML 1 Select Answer to see Preferred Response PREFERRED RESPONSE 2 (OBQ04.257) Which of the following peripheral nerve structures functions to cushion the nerve against external pressure? Review Topic QID: 1362 1 Endoneurium 6% (57/912) 2 Fibronectin 2% (16/912) 3 N-cadherin 1% (7/912) 4 Epineurium 70% (634/912) 5 Perineurium 21% (196/912) ML 3 Select Answer to see Preferred Response PREFERRED RESPONSE 4 (OBQ04.248) Which of the following structures are slowly adapting skin receptors that detect pressure, texture, and low frequency vibration and are best evaluated by static two-point discrimination? Review Topic QID: 1353 1 Meissner's corpuscles 18% (168/943) 2 Pacinian corpuscles 47% (440/943) 3 Merkel's receptor 29% (274/943) 4 Free nerve endings 1% (14/943) 5 Ruffini corpuscles 4% (36/943) ML 5 Select Answer to see Preferred Response PREFERRED RESPONSE 3
Login to View Community Videos Login to View Community Videos California Orthopaedic Association Annual Meeting - 2017 Peripheral Nerve Injury and Repair Options– Eric Hentzen, M.D.(COA 2017, 5.1) Eric Hentzen Hand - Peripheral Nerve Injury & Repair 4/12/2018 505 views Upgrade to View Premium Videos Upgrade to View Premium Videos Medial Antebrachial Cutaneous Nerve Harvest - Dr. Susan E. Mackinnon Derek Moore Hand - Peripheral Nerve Injury & Repair 10/17/2012 328 views Upgrade to View Premium Videos Upgrade to View Premium Videos Acute Nerve Injury and Repair - Dr. Susan Mackinnon - Part 1 Derek Moore General - Peripheral Nerve Injury & Repair 10/7/2012 2135 views See More See Less
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