Peripheral Nerve Injuries
Chye Yew Ng MBChB(Hons) FRCS(Tr&Orth) British Diploma in Hand Surgery
European Board of Hand Surgery Diploma
Consultant Hand & Orthopaedic SurgeonFellowship Director, Upper Limb Fellowship
Wrightington Hospital
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Overview
Basic science
Classification of nerve injuries
Principles of nerve surgery
What (I think) you may be asked
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Please draw the cross section of a nerve
Axon
Fascicle
Nerve
Endoneurium
Epineurium
Perineurium
EpiPEn = Epi – Peri – Endo
A&E
Extrinsic & Intrinsic vascular supplyLongitudinal – Segmental -
Interconnected
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Degeneration & Regeneration
Lee & Wolfe. Peripheral nerve injury & repair. JAAOS 2000
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Central Neuronal Death & Neuroprotection
Neuronal death after peripheral nerve injury
Acetyl-L-carnitineArrests sensory neuronal deathSpeeds up regeneration
N-acetyl-cysteineProvides sensory and motor neuronal protection
Hart et al. Neurological Research 2008
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Nerve Injury & Recovery
Motor
Proprioception
Touch
Temperature
Pain
Sympathetic
Recovery
Inju
ry
Lee & Wolfe. Peripheral nerve injury & repair. JAAOS 2000
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Mechanoreceptors Characteristics
Meissner’s corpuscles•Rapidly adapting•Sensitive to light touch
Merkel’s discs
•Slowly adapting•Pressure, texture •Low frequency vibration•Static 2PD
Pacinian corpuscles
•Rapidly adapting•High frequency vibration•Rapid indentations of skin•Ovoid, 1mm in length
Ruffini terminals•Slowly adapting•Skin stretch
Sub
cuta
neous
Cuta
neous
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Slowly Adapting Rapidly Adapting
Low frequenc
y vibration
Merkel Meissner
High frequenc
y vibration
Ruffini Pacinian
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Mechanisms of Injuries
Crush / compression
Stretch / traction
Laceration /
transection
Metabolic disturbance
Ischaemia
Radiation
Electrical injury
Thermal injury
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Classification of Nerve Injuries
Seddon
BMJ1942
Neurapraxia(Transient Block)
Axonotmesis(Lesion in
Continuity)
Neurotmesis(Division of a
nerve)
Brain1943
• Localised degeneration of the myelin sheaths
• Complete interruption of axons
• Preservation of supporting structures (Schwann tubes, endoneurium, perineurium)
• All essential parts destroyed
• Interruption can occur without apparent loss of continuity
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Classification of Nerve Injuries
Neurapraxia Axonotmesis Neurotmesis
Motor - - -Sensory +/- - -Autonom
ic +/- - -NCS
Conduction block at the site
Distal conduction preserved
Loss of conduction both at and distal to the lesion
Loss of conduction both at and distal to the lesion
EMG No fibrillation Fibrillation ++ Fibrillation ++
Recovery
Days to weeks provided the cause is removed
Months provided the cause is removed
No recovery unless repaired
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Classification of Nerve Injuries
Sunderland
1951I II III IV V
Focalconduction
block
NO Wallerian
degeneration
AxonalDisruption
Axon+
Endoneurium
Disruption
Axon +
Endoneurium+
Perineurium
Disruption
Axon +
Endoneurium+
Perineurium+
EpineuriumDisruption
Cross-innervation
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Sunderland’s Classification
Grabb & Smith’s Plastic Surgery 6th edition. Chapter 9
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Physiological Conduction Block
Type AIntraneural circulatory arrestMetabolic block with no nerve fibre pathologyImmediately reversible
Type BIntraneural oedemaIncreased endoneurial fluid pressureReversible within days or weeks
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Classification of Nerve Injuries
Lundborg
1988
Physiological
conduction block
Myelindamage
Axonal damage
Axon +
Endodamage
Axon +
Endo +
Peridamage
Axon +
Endoneurium+
Perineurium+
Epineurium
damage
Type A
Type B
Sunder
land1951
I II III IV V
Seddon
1942
Neurapraxia(Transient Block)
Axonotmesis
(Lesion in Continuity
)
Neurotmesis(Division of a nerve)
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Classification of Nerve Injuries
Lundborg
1988
Physiological
conduction block
Myelindamage
Axonal disruptio
n
Axon +
Endo
Axon +
Endo +
Peri
Axon +
Endoneurium+
Perineurium+
Epineurium
Type A
Type B
Sunder
land1951
I II III IV V
Seddon
1942
Neurapraxia(Transient Block)
Axonotmesis
(Lesion in Continuity
)
Neurotmesis(Division of a nerve)
Non-degenerative
Degenerative
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Classification of Nerve Injuries
Lundborg
1988
Physiological
conduction block
Myelindamage
Axonal disruptio
n
Axon +
Endo
Axon +
Endo +
Peri
Axon +
Endoneurium+
Perineurium+
Epineurium
Type A
Type B
Sunder
land1951
I II III IV V
Seddon
1942
Neurapraxia(Transient Block)
Axonotmesis
(Lesion in Continuity
)
Neurotmesis(Division of a nerve)
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Sunderland ‘VI’
Grabb & Smith’s Plastic Surgery 6th edition. Chapter 9
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Nerve in Danger!
Pain, Pain, Pain• Burning• Severe
Autonomic dysfunction• Absence of sweating• Smoothness & dryness of skin
Tinel’s sign• Distal to Proximal• Regenerating touch fibres
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In clinical practice, how do you distinguish?
Axonotmesis versus Neurotmesis
Nature of injury
Serial observations
Exploration
Seddon BMJ 1942
(Imaging)
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George Bonney 1986
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Nerve Surgery
Neurolysis
Nerve repair
Nerve grafting
Nerve transfer
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Neurolysis
ExternalInternal
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Nerve repair
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Prerequisites for Nerve Repair
Skeletal stability
Healthy tissue bed
Healthy nerve ends
No undue tension
Adequate soft tissue coverage
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Epineurial versus Group Fascicular Repairs
EpineurialLess exactSimple
Group FascicularBetter alignmentMore dissection (scarring)
The functional results of group fascicular repair has not been shown to be more superior than that of epineurial repair.
Lee & Wolfe. Peripheral nerve injury & repair. JAAOS 2000
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Which of the following is false regarding fibrin glue?
a) Fibrin glue is nontoxic and does not block axon regeneration
b) It may be used in combination with suture repair
c) The outcome of fibrin glue repair is inferior to that of suture repair
d) The common components of fibrin sealants include fibrinogen, thrombin and calcium chloride e) It has low tensile strength
Tse & Ko. Nerve glue for upper extremity reconstruction. Hand Clinics 2012
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Prognostic Factors of Outcomes
•AgePatient factor
• Level of injury (distal vs proximal)
• Type of nerve (pure vs mixed functions)
• Condition of nerve ends
Injury factors
• Delay to repair• Length of gap
Surgical factors
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Nerve Grafts/Conduits
Autologous SourceNerve autograftVein (+/- muscle)
Off-the-shelfType I collagenCaprolactonePolyglycolic acid (PGA)
Processed nerve allograft
Lin et al. Nerve Allografts & Conduits in Peripheral Nerve Repair. Hand Clinics 2013Kaushik & Hammert. Options for Digital Nerve Gap. JHSAm 2015
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A 35 year-old male presented with numbness along the radial border of his right index finger 9 months after he sustained a cut in his first web. After surgical exploration and debridement, there is a 3.5cm nerve defect in the radial digital nerve.
What is the most appropriate surgical reconstructive option?
a) Flexion of digit to achieve primary repair before gradual distraction
b) Type I collagen nerve conduit
c) Autologous vein graft
d) Posterior interosseous nerve graft
e) Polyglycolic acid (PGA) conduit
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Principles of Motor Nerve Transfers
Donor nerve near target motor end platesExpendable donor nervePure motor donor nerveDonor-recipient size matchDonor function synergy with recipient functionMotor re-education improves function
Mackinnon SE, Novak CB. Hand Clin 1999