Radial Nerve Injuries



Radial Nerve Injuries


Lisa M. Kruse

Bryan Loeffler



INTRODUCTION



  • Anatomy1



    • Arises from the posterior cord of the brachial plexus (C5-C8 and/or T1)


    • Traverses the triangular interval (teres major, long head of triceps, humerus) to enter the posterior compartment of the arm



      • Innervates long head of triceps (7 cm from acromion), medial head of triceps (9 cm from acromion)


    • Runs along posterior humerus medial to lateral between medial and lateral heads of triceps


    • Travels adjacent to spiral groove



      • Innervates medial and lateral heads of triceps and anconeus


    • Pierces lateral intermuscular septum



      • Gerwin et al2: 20.7 cm proximal to medial epicondyle and 14.2 cm proximal to lateral epicondyle


      • Guse and Ostrum3: laterally nerve located on average 12.6 cm proximal to lateral epicondyle and never closer than 10 cm


      • Bono4: pierces lateral intermuscular septum 16.0 cm from distal humerus


    • Innervates lateral brachialis muscle


    • Between brachialis and brachioradialis (BR) and then between brachialis and extensor carpi radialis longus (ECRL)



      • Innervates BR and ECRL


    • Divides into superficial branch of the radial nerve (SBRN) and posterior interosseous nerve (PIN) (approximately 3.6 cm proximal to leading edge of supinator) (Figure 40.1)




      • Extensor carpi radialis brevis (ECRB) innervated by radial nerve, SBRN, or PIN


      • Supinator innervated by radial nerve or PIN


    • SBRN descends deep to BR



      • 9 cm proximal to radial styloid emerges superficial to abductor pollicis longus (APL) and extensor pollicis brevis (EPB)


      • Branches to provide sensation to dorsum of hand



    • PIN passes beneath the arcade of Frohse and then between deep and superficial heads of supinator



      • Runs between APL/extensor carpi ulnaris (ECU) and extensor digiti minimi (EDM)/extensor digitorum communis (EDC)


      • Innervates in order: ECU, EDC, EDM, APL, extensor pollicis longus (EPL), EPB, extensor indicis proprius (EIP)


      • Terminates in the floor of the fourth dorsal compartment, giving sensation and proprioception to the wrist joint


  • Mechanisms of injury



    • Compression neuropathies



      • Compression from C-spine



        • Diagnosis and physical examination findings



          • ▲ C6: weakness of wrist extensors, decreased sensation thumb, BR reflex


          • ▲ C7: weakness of triceps, decreased sensation in dorsal hand, triceps weakness


        • Imaging



          • ▲ C-spine radiographs


          • ▲ C-spine MRI


    • Proximal compression sites



      • Compression in axilla by anomalous muscle: accessory subscapularis-teres-latissimus5


      • Penetration of nerve by subscapular artery forming a neural loop6


      • Lateral head of triceps7


    • Radial tunnel syndrome



      • Diagnosis: aching pain in forearm



        • Pain with palpation over radial tunnel (dorsal and volar) 6 cm distal to lateral epicondyle


        • Most prominent with elbow extended, forearm pronated, and wrist flexed8


        • Pain with long finger extension


        • Pain with resisted supination


        • Electrodiagnostic evaluation usually negative


        • May occur along with lateral epicondylitis


      • Sites of compression (FREAS)8



        • Fascia adjacent to radiocapitellar joint


        • Radial recurrent artery and veins (leash of Henry)


        • ECRB tendinous margin


        • Arcade of Frohse


        • Supinator (including distal edge)



      • Treatment



        • Immobilization


        • Anti-inflammatory medications


        • Wrist cock-up splint


        • Corticosteroid injections


        • Radial tunnel decompression



          • ▲ No long-term studies comparing operative and nonoperative treatments9


          • ▲ Lister et al improvement in 19 of 20 patients: outcome dependent on correct diagnosis8 and 51% success rate for surgery10


    • PIN syndrome



      • Pressure on the nerve with loss of motor function



        • May result from elbow synovitis in rheumatoid arthritis, ganglion cysts, or lipomas9


      • Diagnosis: weakness or paralysis of wrist and digital extensors


      • Physical examination findings



        • Weakness of finger extension (EDC/EIP), weakness of thumb extension (EPL/EPB) and abduction (APL)


        • Electrodiagnostic studies demonstrate compression.


        • Advanced imaging to evaluate mass effect


        • May occur along with lateral epicondylitis


      • Treatment



        • Initial nonoperative treatment similar to radial tunnel syndrome


        • No improvement in 90 days surgical decompression


      • Outcome



        • After 18 months muscle fibrosis occurs with irreversible changes.11


        • If no return of function after 18 months, consider tendon transfers9


    • Wartenberg syndrome (cheiralgia paresthetica)

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May 7, 2019 | Posted by in ORTHOPEDIC | Comments Off on Radial Nerve Injuries

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