Summary Peripheral nerve injuries encompass a range of reversible and irreversible impairments determined by injury level, axonal disruption, and time to treatment. Diagnosis can be made based on clinical examination and confirmed with EMG/NCS. 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 nerve injuries account for approximately 3% of injuries affecting the upper extremity and hand Demographics males = females Risk factors penetrating injuries displaced fractures Etiology Pathophysiology mechanism of injury 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 chronic compression leads to Schwann cell proliferation and apoptosis 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 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 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) Anatomy Blood supply extrinsic vessels run in loose connective tissue surrounding nerve trunk intrinsic vessels plexus lies in epineurium, perineurium, and endoneurium 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 Nerve fiber types Fiber Type Diameter (uM) Myelination Speed Example A 10-20 heavy fast touch B < 3 moderate medium autonomic nervous system (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-4th degree incomplete nerve injury more severe than neurapraxia pathophysiology axon and myelin sheath disruption leads to focal conduction block with Wallerian degeneration variable degree of connective tissue disruption electrophysiologic studies fibrillations and positive sharp waves on EMG prognosis unpredictable recovery neurotmesis encompasses Sunderland 5th degree complete nerve division with disruption of endoneurium pathophysiology all connective tissues 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 Classification Seddon Type Myelin intact Endoneurium intact Wallerian Degeneration Reversible Neuropraxia No Yes No Reversible Axonotmesis No Variable Yes Variable Neurotmesis No No Yes Irreversible Sunderland Classification 1st degree same as Seddon's neurapraxia (loss of myelin sheath) 2nd degree included within Seddon's axonotmesis intact endoneurium, perineurium and epineurium 3rd degree included within Seddon's axonotmesis endoneurium injured with endoneurial scarring intact perineurium and epineurium most variable degree of recovery 4th degree included within Seddon's axonotmesis endoneurium and perineurium injured intact epineurium 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 same as Seddon's neurotmesis completely severed or transected nerve involving all layers regeneration not possible without repair Sutherland Classification Grade Axon Endoneurium Perineurium Epineurium I Intact Intact Intact Intact II Disrupted Intact Intact Intact III Disrupted Disrupted Intact Intact IV Disrupted Disrupted Disrupted Intact V 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 indications neuropraxia (1st degree) axonotmesis (2nd degree) gunshot wounds affecting brachial plexus assess extent of recovery over 3 months outcomes variable recovery depending on degree of injury most nerve deficits that present after a closed fracture or dislocation will resolve with observation alone Operative direct muscular neurotization indications transected unrepairable nerve ending at risk of forming neuroma plan for integrated prosthesis outcomes degree of functional recovery varies decreases neuroma formation promising results with targeted muscle reinnervation (TMR) for amputees 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 1-3 weeks after gunshot injury with confirmed neurotmesis allows time for zone of injury to be declared outcomes variable and dependent on multiple factors (i.e., patient age, level of injury, type of injury, time to repair, etc.) fascicular repair outcomes are similar to epineurial repair best recovery when performed within 7-14 days of injury reinnervation and sensory re-education may take several years nerve grafting indications gaps that prevent tension-free direct repair 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 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 outcomes potentially similar outcomes as tendon transfer for irreparable proximal nerve injuries tendon transfer indications return of function through nerve regeneration is not expected outcomes better with age <30 and more distal locations due improved in children due to neuroplasticity one grade of motor strength loss is expected following transfer Techniques Observation with sequential EMG technique 'active surveillance' daily or weekly by the same surgeon exploration indicated if no functional recover after 3 months functional splinting rehabilitation focusing on sensory reeducation and prevention of joint contracture Direct muscular neurotization technique insert proximal nerve stump into nearby muscle belly Surgical repair 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 technique resect zone of injury until "mushrooming" of the fascicles is observed 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 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 technique 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 histologic staining complications potentially increased scarring and damage to blood supply Nerve grafting approach create tension-free repair by using a graft that is at least 10% longer than gap ensure scar from nerve ends is completely resected technique autologous graft gold standard for segmental defects > 5cm nerve autografts harvested should result in the least morbidity possible medial and lateral antebrachial cutaneous posterior interosseus nerve terminal branches sural cabling can be used for donor-recipient size mismatch acellular allograft shown to be effective for gaps < 5cm not as effective as autograft, but have shown promise for large defects unable to be bridged by autograft alone conduits made up of type 1 collagen indications 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 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 technique 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 Tendon transfer approach maintain or restore passive joint mobility before tendon transfer redundant or non-essential muscle-tendon unit transferred to restore a lost function optimal to have one straight line of pull and transfer of muscle synergistic to lost function one tendon transfer should perform one function technique select donor and recipient with similar power power determined by cross-sectional area select synergistic donor and recipient i.e. wrist extensors and finger flexors set appropriate excursion can be adjusted with pulley or tenodesis effect Smith 3-5-7 rule 3 cm excursion - wrist flexors, wrist extensors 5 cm excursion - EDC, FPL, EPL 7 cm excursion - FDS, FDP complications adhesions, poor tendon gliding Complications Neuroma formation incidence true incidence unknown due to most being asymptomatic up to 30% in amputees has been reported treatment non-operative pharmacolgical (i.e., gabapentin, anticonvulsants, antidepressants, etc.) local nerve distruction (i.e., injection of phenol or botulinum toxin, cautery, etc.) rehabilitation work modification operative resection targeted muscle reinnervation (TMR) 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 favorable younger age most important factor influencing success of nerve recovery (children have more favorable prognosis) distal 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 negative older age proximal level of injury crush injuries repair delay worse prognosis of recovery (time limit for repair is 18 months) Prognosis with treatment variable on several factors including injury location, age of patient, and type of injury neurapraxia resolves with conservative measures axonotmesis and neurotmesis may improve with repair, tendon transfers, and/or nerve transfers the endoneurium must be intact for full recovery of an injured peripheral nerve may lead to chronic neuropathic pain
Technique Guide Technique guides are not considered high yield topics for orthopaedic standardized exams including ABOS, EBOT and RC. Epineural Nerve Repair Orthobullets Team Hand - Peripheral Nerve Injury & Repair Technique Guide Technique guides are not considered high yield topics for orthopaedic standardized exams including ABOS, EBOT and RC. Conduit Repair Orthobullets Team Hand - Peripheral Nerve Injury & Repair
QUESTIONS 1 of 19 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 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 (OBQ18.155) A 36-year-old male injured his right arm after a fall. His injury radiograph is shown in Figure A. On physical examination, he was found to have a nerve injury. Which function is the last to return? QID: 213051 FIGURES: A Type & Select Correct Answer 1 Pain sensation to the radial portion of the dorsum of the hand 3% (67/2116) 2 Temperature sensation to the radial portion of the dorsum of the hand 7% (146/2116) 3 Sensation of light touch to the radial portion of the dorsum of the hand 24% (501/2116) 4 Wrist extension 63% (1340/2116) 5 Elbow extension 1% (28/2116) L 3 Question Complexity A Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 4 Review Tested Concept Review Full Topic (OBQ18.16) A 16-year-old male presents with a gunshot wound to his right upper arm. On examination, he has a wrist drop and reports loss of sensation in his radial nerve distribution. There is a 1.5cm entrance wound on the lateral aspect of the arm with a 6.8 cm stellate exit wound anteromedially. Figures A and B are the radiographs of the injury. The patient is taken to the operating room for fixation, and the radial nerve is found to be completely transected. When is the optimal timing for definitive nerve repair? QID: 212912 FIGURES: A B Type & Select Correct Answer 1 At the time of initial debridement 14% (345/2383) 2 At the time of definitive fracture fixation 39% (923/2383) 3 After 3 months from the injury 10% (242/2383) 4 After 1-3 weeks from the injury 36% (856/2383) 5 Once a neuroma has formed on MRI 0% (5/2383) L 5 Question Complexity A Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 4 Review Tested Concept Review Full Topic (OBQ18.3) A 42-year-old male laborer sustains the injury shown in Figure A. He is taken to the operating room and found to have a partial laceration of the median nerve. Figure B shows a cross-sectional image of a nerve. Which of the following represents item D? QID: 212899 FIGURES: A B Type & Select Correct Answer 1 Epineurium 7% (151/2312) 2 Perineurium 47% (1093/2312) 3 Nerve fiber 18% (420/2312) 4 Myelin 1% (27/2312) 5 Endoneurium 26% (610/2312) L 1 Question Complexity A Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 2 Review Tested Concept Review Full Topic 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 (OBQ13.24) Which statement most accurately describes the physiology of peripheral nerve regeneration following an axonotmesic lesion? QID: 4659 Type & Select Correct Answer 1 The proximal nerve segment undergoes Wallerian degeneration 15% (873/5887) 2 Axon growth occurs from the distal segment to proximal segment 3% (191/5887) 3 Neurotrophic factors direct phagocytic activity 6% (379/5887) 4 Proximal axon budding allows for antegrade (or distal) axon migration 70% (4107/5887) 5 Axoplasm and myelin are degraded distally predominantly by Schwann cells for the first 12 months following injury 5% (302/5887) L 3 Question Complexity B Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 4 Review Tested Concept Review Full Topic (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? QID: 4644 FIGURES: A Type & Select Correct Answer 1 Autogenous venous nerve conduit 3% (160/4712) 2 Collegen synthetic nerve conduit 9% (407/4712) 3 Biodegradable polyglycolic acid 1% (35/4712) 4 Processed nerve allograft 3% (142/4712) 5 Nerve autograft 84% (3942/4712) L 2 Question Complexity B Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 5 Review Tested Concept Review Full Topic (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: QID: 4570 Type & Select Correct Answer 1 Axonotmesis with ischemia origin 11% (587/5366) 2 Axonotmesis with myelin disruption 18% (992/5366) 3 Neurapraxia with ischemia origin 57% (3037/5366) 4 Neurapraxia with endoneurium disruption 11% (612/5366) 5 Neurotmesis 2% (92/5366) L 1 Question Complexity C Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 3 Review Tested Concept Review Full Topic (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? QID: 4406 FIGURES: A Type & Select Correct Answer 1 Duration to time of repair 11% (676/6060) 2 Repair level 7% (444/6060) 3 Length of repair 9% (562/6060) 4 Postoperative physical rehabilitation 25% (1485/6060) 5 Type of autograft used 47% (2860/6060) L 4 Question Complexity C Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 5 Review Tested Concept Review Full Topic Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK (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? QID: 3081 Type & Select Correct Answer 1 Glycolide trimethylene carbonate conduit 5% (180/3392) 2 Collagen conduit 59% (2002/3392) 3 Silicone sleeve 7% (233/3392) 4 Primary end-to-end repair 18% (595/3392) 5 Polyglycolic acid conduit 11% (370/3392) L 3 Question Complexity C Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 2 Review Tested Concept Review Full Topic (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? QID: 416 Type & Select Correct Answer 1 Median 24% (855/3588) 2 Ulnar 10% (350/3588) 3 Radial 58% (2091/3588) 4 Tibial 4% (130/3588) 5 Peroneal 4% (145/3588) L 3 Question Complexity C Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 3 Review Tested Concept Review Full Topic (OBQ05.66) Axon regeneration almost always occurs following a Sunderland second-degree nerve injury because which anatomic structure is not injured? QID: 952 Type & Select Correct Answer 1 Epineurium 23% (474/2065) 2 Endoneurium 53% (1094/2065) 3 Perineurium 10% (205/2065) 4 Myelin sheath 10% (198/2065) 5 Schwann cell 4% (73/2065) L 4 Question Complexity D Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 2 Review Tested Concept Review Full Topic (OBQ05.218) Vitamin B12 deficiency is a known cause of which the following? QID: 1104 Type & Select Correct Answer 1 Inability to whistle 0% (11/3779) 2 Peripheral sensory neuropathy 96% (3634/3779) 3 Increased deep tendon reflexes 3% (107/3779) 4 Urinary retention 0% (7/3779) 5 Hydrophobia 0% (5/3779) L 1 Question Complexity D Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 2 Review Tested Concept Review Full Topic (OBQ04.257) Which of the following peripheral nerve structures functions to cushion the nerve against external pressure? QID: 1362 Type & Select Correct Answer 1 Endoneurium 7% (128/1810) 2 Fibronectin 2% (30/1810) 3 N-cadherin 0% (9/1810) 4 Epineurium 69% (1248/1810) 5 Perineurium 21% (389/1810) L 3 Question Complexity D Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 4 Review Tested Concept Review Full Topic (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? QID: 1353 Type & Select Correct Answer 1 Meissner's corpuscles 17% (287/1646) 2 Pacinian corpuscles 46% (763/1646) 3 Merkel's receptor 28% (462/1646) 4 Free nerve endings 2% (31/1646) 5 Ruffini corpuscles 5% (87/1646) L 1 Question Complexity C Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 3 Review Tested Concept Review Full Topic
All Videos (7) Podcasts (1) Login to View Community Videos Login to View Community Videos 7th Annual Frontiers in Upper Extremity Surgery Technical Tips Nerve Repair/Reconstruction - Brandon S. Smetana, MD Brandon Smetana Hand - Peripheral Nerve Injury & Repair 11/7/2022 36 views 0.0 (0) Login to View Community Videos Login to View Community Videos Cleveland Combined Hand Fellowship Lecture Series 2020-2021 Peripheral Nerve Injury - Matthew Hadad, MD Matthew Hadad Hand - Peripheral Nerve Injury & Repair B 3/15/2021 112 views 5.0 (1) Login to View Community Videos Login to View Community Videos Cleveland Combined Hand Fellowship Lecture Series 2018-2019 Managing the Transected Nerve: Evolution of Repair - Peter J. Evans, MD, PhD, FRCSC Peter J. Evans Hand - Peripheral Nerve Injury & Repair D 10/1/2020 89 views 0.0 (0) HandâPeripheral Nerve Injury & Repair Hand - Peripheral Nerve Injury & Repair Listen Now 31:41 min 10/16/2019 984 plays 4.5 (2) See More See Less
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