Introduction Description peripheral nerve injuries encompass a range of reversible and irreversible impairments determined by injury level, axonal disruption, axon support structure damage, and time to treatment treatment can involve observation, repair, tendon transfers or nerve grafting depending on the acuity, degree of injury, and mechanism of injury. Epidemiology incidence major peripheral nerve injury sustained in 2% of patients with extremity trauma demographics males = females Pathophysiology 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 volleyball players correction of valgus in TKA leading to common 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 a 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 by phagocytes) existing Schwann cells proliferate and line endoneurial basement membrane proximal budding (occurs after 1 month) 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 neurotrophic factors (factors enhancing growth and preferential attraction to other nerves rather than other tissues) functional recovery during regeneration (in order) sympathetic activity pain temperature sensation touch proprioception motor function motor function is the first to be lost and the last to recover pathobiology Schwann cells proliferate and trophic factors are upregulated to promote regeneration pathoanatomy involvement of the axon, myelin, and supporting connective tissues influence regeneration potential myelin disruption typically occurs before axon disruption axonal disruption leads to distal degeneration, requiring regeneration or repair to regain function neuronal connective tissue structure provides a framework for regeneration endoneurium perineurium epineurium Associated conditions predictable nerve injuries arise from certain fracture patterns and clinical scenarios axillary nerve anterior shoulder dislocation radial nerve distal 1/3 humeral shaft (Holstein-Lewis) fractures prolonged compression along the humerus while intoxicated (Saturday night palsy) extension-type supracondylar humerus fracture ulnar nerve distal humerus ORIF improper positioning on OR table flexion-type supracondylar humerus fracture anterior interosseus nerve extension-type supracondylar humerus fracture sciatic nerve posterior hip dislocation common peroneal nerve correction of valgus alignment during a total knee arthroplasty superficial peroneal nerve percutaneous plating of tibial fractures (holes 11-13) Prognosis natural history of disease pain is first modality to return advancing Tinel sign is most reliable indication of recovery nerve repair or reconstruction is unpredictable after 6 months reinnervation by 18 months is the goal for muscle preservation prognostic variables age most important factor influencing success of nerve recovery (children have more favorable prognosis) level of injury second most important (the more distal the injury the better the chance of recovery) peripheral nerve injuries include those affecting the Brachial Plexus sharp transections and stretch injuries have better prognosis than crush or blast injuries repair delay worse prognosis of recovery (time limit for repair is 18 months) prognosis with treatment neurapraxia resolves with conservative measures axonotmesis and neurotmesis may improve with repair, tendon transfers, and/or nerve transfers may lead to chronic neuropathic pain Anatomy Nerve structure 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 loose fibrous tissue covering axons participates in the formation of Schwann cell tube myelin made by Schwann cells insulates axons to increase conduction velocity conduction occurs at nodes of Ranvier 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 an 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 mechanically 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 or stretch leading to reversible conduction block without Wallerian degeneration pathophysiology usually caused by local ischemia histopathology shows focal temporary demyelination of the axon (axon remains intact) endoneurium remains intact 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 incomplete nerve injury more severe than neurapraxia pathophysiology axon and myelin sheath disruption leads to focal conduction block with Wallerian degeneration endoneurium remains intact neuroma formed at proximal nerve end, glioma formed at distal nerve end electrophysiologic studies fibrillations and positive sharp waves on EMG prognosis unpredictable recovery neurotmesis encompasses Sunderland 3rd-5th degree complete nerve division with disruption of endoneurium pathophysiology all layers affecting, endoneurium disrupted focal conduction block with Wallerian degeneration electrophysiologic studies fibrillations and positive sharp waves on EMG prognosis no recovery unless surgical repair performed neuroma formation at proximal nerve end may lead to chronic pain 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-5th 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 endoneurium injured with endoneurial scarring perineurium and epineurium intact most variable degree of recovery 4th degree included within Seddon's neurotmesis perineurium injured, epineurium intact nerve in continuity but at the level of injury there is complete scarring across the nerve unsatisfactory regeneration may lead to neuroma-in-continuity 5th degree included within Seddon's neurotmesis completely severed or transected nerve involving all layers regeneration not possible without repair 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 Studies Nerve conduction studies Electromyography (EMG) Nerve conduction velocity (NCV) EMG assesses function at the neuromuscular junction often the only objective evidence of a compressive neuropathy (valuable in workers' compensation patients with secondary gain issues) characteristic findings denervation of muscle fibrillations positive sharp waves (PSW) fasciculations neurogenic lesions fasciculations myokymic potentials myopathies complex repetitive discharges myotonic discharges NCV assesses large myelinated fibers focal compression and 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 neuropraxia (1st degree) axonotmesis (2nd degree) gunshot wounds affecting brachial plexus assess extent of recovery over 3 months Operative surgical repair indications neurotmesis (3rd-5th degree) early surgical exploration: penetrating trauma, iatrogenic injury, vascular injury, progressive deficits exception: gunshot wounds affecting brachial plexus may be observed best recovery when performed within 10-14 days of injury definitive repair after 1-3 weeks in the setting of gunshot wound neurotmesis repair should be tension free in well-vascularized wound bed tensioned closures compromise perfusion; inhibit Schwann cell activation and regeneration; and cause scar formation length can be gained with nerve transposition and neurolysis nerve grafting indications large gaps unable to repair without tension autograft donors include sural, saphenous, medial/lateral antebrachial cutaneous nerves no effect on functional recovery nerve transfer indications proximal nerve injury goal to deliver new axons and stimulus before degeneration of motor endplates and irreversible muscle damage priority is to restore shoulder abduction/external rotation, elbow flexion, and finger function loss of shoulder abduction and external rotation spinal accessory nerve (CN XI) to suprascapular nerve loss of shoulder abduction and flexion Leechavengvong procedure: triceps motor branch of radial nerve to axillary nerve loss of elbow flexion Oberlin transfer: FCU motor branch to upper trunk/musculocutaneous nerve tendon transfer indications return of function through nerve regeneration is not expected Surgical Techniques Direct muscular neurotization approach insert proximal nerve stump into affected muscle belly outcomes degree of functional recovery varies decreases neuroma formation promising results with targeted muscle reinnervation (TMR) for amputees Epineurial Repair approach primary repair of the epineurium requires resection of proximal neuroma and distal glioma to healthy fascicles alignment aided by epineurial blood vessels outcomes variable and dependent on multiple factors (i.e., patient age, level of injury, type of injury, time to repair, etc.) reinnervation and sensory re-education may take several years Fascicular repair approach similar to epineural repair, but also repair the perineural sheaths (individual fascicles are approximated under a microscope) theoretically provides more accurate alignment of axons over epineurial repair fascicular matching topographical sketches can be used for visual alignment electrical stimulation proximal end: identifies sensory fascicles in awake patients distal end: identifies motor fascicles in acute injuries, before significant Wallerian degeneration staining complications potentially increased scarring and damage to blood supply outcomes similar to epineurial repair no improved results have been demonstrated compared to epineurial repair Nerve grafting approach autologous graft gold standard for segmental defects > 5cm nerve autographs harvested should result in the least morbidity possible medial and lateral antebrachial cutaneous posterior interosseus nerve terminal branches sural "cabling" used to create longer graft by connecting nerves in series acellular allograft traditionally used for gaps <5cm not as effective as autograft, but have shown promise for large defects unable to be bridged by autograft alone conduits defects up to 20 mm allow coaptation ends without tension, typically small sensory nerves synthetic polyglycolic acid, polycaprolactone, and collagen-based collagen conduits allow nutrient exchange and accessibility to neurotrophic factors to the axonal growth zone during regeneration complications donor nerve neuroma formation immune response and rejection of allograft outcomes variable and dependent on multiple factors (i.e., patient age, level of injury, type of injury, time to repair, etc.) quality of nerve recovery drops with gaps >5mm Nerve transfer approach redundant or non-essential nerve transferred to a nerve affected by a proximal injury select donor motor nerves close to target muscles coaptation techniques end-to-end end-to-side donor nerve attached to the recipient nerve through perineurial window goal to "supercharge" damaged nerve by preservation of motor endplates until new axons can regenerate from more proximal injury outcomes alternative to tendon transfer with potentially similar outcome for irreparable proximal nerve injuries Complications Neuroma formation treatment resection targeted muscle reinnervation (TMR)
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 15 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Previous Next Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK You have 100% on this question. Just skip this one for now. Take This Question Anyway (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 Type & Select Correct Answer 1 Autogenous venous nerve conduit 4% (131/3525) 2 Collegen synthetic nerve conduit 9% (332/3525) 3 Biodegradable polyglycolic acid 1% (24/3525) 4 Processed nerve allograft 2% (86/3525) 5 Nerve autograft 83% (2932/3525) L 2 Select Answer to see Preferred Response SUBMIT RESPONSE 5 You have 100% on this question. Just skip this one for now. Take This Question Anyway (OBQ13.24) Which statement most accurately describes the physiology of peripheral nerve regeneration following an axonotmesic lesion? Review Topic QID: 4659 Type & Select Correct Answer 1 The proximal nerve segment undergoes Wallerian degeneration 14% (693/4817) 2 Axon growth occurs from the distal segment to proximal segment 3% (164/4817) 3 Neurotrophic factors direct phagocytic activity 7% (315/4817) 4 Proximal axon budding allows for antegrade (or distal) axon migration 70% (3367/4817) 5 Axoplasm and myelin are degraded distally predominantly by Schwann cells for the first 12 months following injury 5% (251/4817) L 3 Select Answer to see Preferred Response SUBMIT RESPONSE 4 You have 100% on this question. Just skip this one for now. Take This Question Anyway (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 Type & Select Correct Answer 1 Axonotmesis with ischemia origin 11% (477/4268) 2 Axonotmesis with myelin disruption 18% (755/4268) 3 Neurapraxia with ischemia origin 57% (2447/4268) 4 Neurapraxia with endoneurium disruption 11% (472/4268) 5 Neurotmesis 2% (78/4268) L 4 Select Answer to see Preferred Response SUBMIT RESPONSE 3 You have 100% on this question. Just skip this one for now. Take This Question Anyway (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 Type & Select Correct Answer 1 Duration to time of repair 12% (581/5007) 2 Repair level 7% (363/5007) 3 Length of repair 9% (454/5007) 4 Postoperative physical rehabilitation 25% (1243/5007) 5 Type of autograft used 47% (2336/5007) L 4 Select Answer to see Preferred Response SUBMIT RESPONSE 5 Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK You have 100% on this question. Just skip this one for now. Take This Question Anyway (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 Type & Select Correct Answer 1 Glycolide trimethylene carbonate conduit 5% (117/2487) 2 Collagen conduit 61% (1527/2487) 3 Silicone sleeve 7% (162/2487) 4 Primary end-to-end repair 15% (379/2487) 5 Polyglycolic acid conduit 12% (294/2487) L 3 Select Answer to see Preferred Response SUBMIT RESPONSE 2 You have 100% on this question. Just skip this one for now. Take This Question Anyway (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 Type & Select Correct Answer 1 Median 23% (623/2742) 2 Ulnar 10% (269/2742) 3 Radial 60% (1639/2742) 4 Tibial 4% (97/2742) 5 Peroneal 4% (100/2742) L 3 Select Answer to see Preferred Response SUBMIT RESPONSE 3 You have 100% on this question. Just skip this one for now. Take This Question Anyway (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 Type & Select Correct Answer 1 Epineurium 23% (305/1330) 2 Endoneurium 52% (688/1330) 3 Perineurium 10% (133/1330) 4 Myelin sheath 11% (142/1330) 5 Schwann cell 3% (45/1330) L 4 Select Answer to see Preferred Response SUBMIT RESPONSE 2 You have 100% on this question. Just skip this one for now. Take This Question Anyway (OBQ05.218) Vitamin B12 deficiency is a known cause of which the following? Review Topic QID: 1104 Type & Select Correct Answer 1 Inability to whistle 0% (9/3105) 2 Peripheral sensory neuropathy 96% (2986/3105) 3 Increased deep tendon reflexes 3% (88/3105) 4 Urinary retention 0% (4/3105) 5 Hydrophobia 0% (5/3105) L 1 Select Answer to see Preferred Response SUBMIT RESPONSE 2 You have 100% on this question. Just skip this one for now. Take This Question Anyway (OBQ04.257) Which of the following peripheral nerve structures functions to cushion the nerve against external pressure? Review Topic QID: 1362 Type & Select Correct Answer 1 Endoneurium 7% (76/1136) 2 Fibronectin 2% (19/1136) 3 N-cadherin 1% (7/1136) 4 Epineurium 68% (776/1136) 5 Perineurium 23% (256/1136) L 3 Select Answer to see Preferred Response SUBMIT RESPONSE 4 You have 100% on this question. Just skip this one for now. Take This Question Anyway (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 Type & Select Correct Answer 1 Meissner's corpuscles 18% (184/1051) 2 Pacinian corpuscles 48% (502/1051) 3 Merkel's receptor 28% (292/1051) 4 Free nerve endings 2% (16/1051) 5 Ruffini corpuscles 4% (46/1051) L 5 Select Answer to see Preferred Response SUBMIT RESPONSE 3
All Videos (4) Podcasts (2) 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 613 views Upgrade to View Premium Videos Upgrade to View Premium Videos Medial Antebrachial Cutaneous Nerve Harvest - Dr. Susan E. Mackinnon Hand - Peripheral Nerve Injury & Repair 10/17/2012 348 views Upgrade to View Premium Videos Upgrade to View Premium Videos Acute Nerve Injury and Repair - Dr. Susan Mackinnon - Part 1 General - Peripheral Nerve Injury & Repair 10/7/2012 2295 views Upgrade to View Premium Videos Upgrade to View Premium Videos Double Fascicular Transfer: Median Fascicle to Biceps Branch and Ulnar Fascicle to Brachialis Branch Hand - Peripheral Nerve Injury & Repair 9/6/2012 190 views Hand ⎜Peripheral Nerve Injury & Repair Team Orthobullets (AF) Hand - Peripheral Nerve Injury & Repair Listen Now 14:37 min 10/16/2019 42 plays Question Session⎜Peripheral Nerve Injury & Repair, Ewing's Sarcoma Orthobullets Team Hand - Peripheral Nerve Injury & Repair Listen Now 19:53 min 11/11/2019 5 plays See More See Less
Frontiers in Upper Extremity Surgery Median nerve traumatic laceration in a 29M (C2707) Jason Nydick Hand - Peripheral Nerve Injury & Repair 10/17/2016 1113 7 1