In this segment, we focus on peripheral nerve injury and repair/reconstruction. Nerves are encased in epineurium which contains fascicles sheathed in perineurium. Fascicles contain individual nerve fibers. Nerves can be injured from stretching, compression, or laceration. Nerve regeneration is slow and is affected by patient age, level of injury, injury pattern, and timing of repair. An electromyogram is the first primary test to assess nerve function and other imaging modalities, such as MR neurography, can better characterize injury patterns. Nonoperative treatment is indicated for neuropraxia and axonotmesis while neurorrhaphy, nerve grafting, conduits, and transfers can be considered for more severe injury.
16 Peripheral Nerve Injuries and Repair and Reconstruction
Characteristic nerve course throughout upper extremity (► Fig. 16.3).
Structure (► Fig. 16.4).
Epineurium—dense external sheath of connective tissue which contains fascicles.
Fascicles are surrounded by perineurium which encompasses nerve fibers which are each individually encased in endoneurium.
II. Mechanism of Injury
Stretching by>8% can diminish a nerve’s blood supply.
Stretching by >15% can disrupt axons.
Axonal transport stops after 15 minutes of ischemia, recovers if restored within 12 to 24 hours.
Common injury patterns
“Stingers,” brachial plexus stretch with violent contralateral neck flexion.
Humeral head compression during extreme abduction.
Humeral surgical neck fracture.
Direct compression through axilla.
Compression in quadrilateral space.
Prolonged use of crutches.
Shoulder depression with contralateral neck flexion.
Prolonged compression (backpacker’s palsy).
Entrapment under transverse scapular splinoglenoid ligaments.
Trauma to scapular spine.
Trauma within pronator teres, under flexor digitorum superficialis, or to carpal tunnel.
Elbow dislocation (► Fig. 16.5).
Proximal or midshaft humerus fracture.
Proximal radius fracture.
Trauma to supinator, affecting posterior interosseous nerve (PIN).
Injury to cubital tunnel or Guyon’s canal.