Overview Of Nerve Injury And Repair Ramy El Nakeeb, MD
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Nerve anatomy Causes of injury Diagnosis??? Indications and
contraindications of nerve repair Factors that affects results
Methods of nerve repair,, what is classical, what is new??
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From a hand surgery perspective, peripheral nerve lesions
constitute one major reason for severe and longstanding impairment
in hand function. The situation is frustrating because although a
nerve suture may be technically perfect and the rehabilitation
carried out meticulously, the outcome is unpredictable and
sometimes disappointing.
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The problem A nerve injury differs from most other types of
tissue injury in the body since not only a local repair process is
required. Transection of axons has implications for the whole
length of the neuron (i.e., all the way from the nerve cell body at
the spinal cord or dorsal root ganglion level to distal targets)
and the repair process involves outgrowth of neurites over very
long distances.
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Anatomy Of Peripheral Nerves Peripheral nerves have four basic
components: 1.Neurons 2.Schwann cells 3.Connective tissues
4.End-organs (motor end plates, sensory, and autonomic
receptors).
Classification of nerve injury Seddon proposed a classification
scheme for nerve injuries consists of neurapraxia, axonotmesis, and
neurotmesis. Sunderland expanded this classification by subdividing
axonotmesis into 3 subtypes.
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Neurapraxia Nerve not working Refers to a local conduction
block. The continuity of axons is preserved, as is the excitability
of nerve structures distal to the lesion.
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Axonotmesis Axon cutting The axon is severed, its distal
portion degenerates. Sunderland classification Type II : Axon
severed; endoneurial tube intact Type III Endoneurial tube torn
Type IV : Only epineurium intact
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Neurotemesis nerve cutting There is interruption of continuity
of all elements of a nerve. N.B: 1. Grade VI injury by Mackinnon 2.
longitudinal patterns of injury
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The Brachial Plexus Rupture: refers to a tear in one or more
nerves of the plexus, at a point away from where the nerve attaches
to the spine. Avulsion: It occurs when the nerves are torn away
from the spinal cord. Neuropraxia: The most common nerve injury.
Neuroma: refers to scar tissue that has grown around the injuried
nerves. This scar tissue may exert pressure on the injured nerve
thereby blocking signals to the muscles.
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Course of Wallerian axon degeneration. Wang J T et al. J Cell
Biol 2012;196:7-18 2012 Wang et al.
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The indications for operating on nerves after an injury include
the following:
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1. Deep paralysis after a wound over the course of a major
nerve or after an injection close to the course of that nerve
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2. Deep paralysis after closed traction injury of the brachial
plexus
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3. A nerve lesion associated with fracture or dislocation
requiring urgent open reduction and internal fixation
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4. A nerve lesion associated with an arterial injury
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5. Worsening of nerve injury while under observation ( acute
carpal tunnel) 6. Failure to progress toward recovery in the
expected time after a closed injury 7. Failure to recover from
conduction block within 6 weeks of injury 8. Treatment of painful
neuroma
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The Reasons not to proceed to repair of a transected nerve
include the following:
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1. The general condition of the patient. After having saved a
life or limb by means of successful arterial repair, the patient,
the anesthetist, and the surgeon may well have had enough.
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2. The risk of local or systemic sepsis. If local soft tissue
damage and contamination from an open fracture or high-velocity
gunshot wound is severe.
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3. Skilled surgeon not available. 4. specialized equipment 4.
specialized equipment not available.
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5. When the condition of the nerve is such that function will
more surely and more rapidly be restored by musculotendinous
transfer.
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The Dream The Truth
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Result following nerve injury and repair is dependent on
factors such as : 1.the extent of nerve cell survival after the
injury 2.the rate and quality of axonal outgrowth. 3.the
orientation and specificity in growth of regenerating axons. 4.the
survival and state of end organs, and cortical reorganizational
processes in somatosensory and motor brain cortex.
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Factors that affect Decision Making: Age Distance between
injury and end organ Gap of injury Mechanism of injury Severity of
injury Presence of pain
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Methods of nerve repair Neurolysis Direct suture Nerve graft
Neurotization
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Neurolysis Definition Internal and external neurolysis
Indications on internal neurolysis Neurolysis Vs nerve
grafting