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Axillary Nerve

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Topic updated on 09/12/13 8:26am
Axillary Nerve
Innervation
  • Motor
    • deltoid
    • teres minor
  • Sensory
    • superficial lateral cutaneous nerve of arm
      • lateral shoulder sensation
Origin
  • Originates from the brachial plexus 
    • middle trunk, posterior division, posterior cord  
  • Carries fibers from C5 and C6
Course
  • Comes off posterior cord behind the axillary artery, anterior to the subscapularis muscle
  • Travels through the quadrangular space 
    • runs here with the posterior circumflex humeral artery and vein
  • Gives off an anterior, posterior, and articular terminal branch
  • Terminal branches
    • anterior branch
      • wraps around the surgical neck of the humerus on the undersurface of the deltoid
      • supplies the anterior deltoid muscle 
      • traditional "safe zone" from lateral acromion is 5 cm
        • axillary nerve has been shown to run 3-5 cm from the acromion in 20% of patients
        • damage to nerve with a muscle split here will denervate the anterior deltoid
      • terminates in small cutaneous branches for the anterior/anterolateral skin
    • posterior branch
      • supplies the teres minor   and posterior deltoid  muscles
      • pierces the deep fascia and terminates as the superior lateral cutaneous nerve of the arm
    • articular branch
      •  enters the shoulder joint inferior to the subscapularis
Injury & Clinical Conditions
  • Hornblower's test indicates teres minor pathology
    • shoulder placed in 90 degrees of abduction, 90 degrees of external rotation
    • positive if patient falls into internal rotation

 

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Qbank (1 Questions)

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(OBQ12.231) A 32-year-old female sustains a proximal humerus fracture shown in Figure A. This fracture goes on to uneventful union, but she complains of a lack of sensation over the lateral deltoid and has weakness with the Hornblower's test at final follow-up. Which of the following structures is most likely injured in this patient? Topic Review Topic
FIGURES: A          

1. Anterior branch of the axillary nerve
2. Posterior branch of the axillary nerve
3. Posterior cord of the brachial plexus
4. Suprascapular nerve
5. Musculocutaneous nerve

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