View source for WBR0448

{{WBRQuestion
|QuestionAuthor={{Rim}} {{Alison}}
|ExamType=USMLE Step 1
|MainCategory=Anatomy
|SubCategory=Musculoskeletal/Rheumatology
|MainCategory=Anatomy
|SubCategory=Musculoskeletal/Rheumatology
|MainCategory=Anatomy
|SubCategory=Musculoskeletal/Rheumatology
|MainCategory=Anatomy
|MainCategory=Anatomy
|SubCategory=Musculoskeletal/Rheumatology
|MainCategory=Anatomy
|SubCategory=Musculoskeletal/Rheumatology
|MainCategory=Anatomy
|SubCategory=Musculoskeletal/Rheumatology
|MainCategory=Anatomy
|SubCategory=Musculoskeletal/Rheumatology
|MainCategory=Anatomy
|MainCategory=Anatomy
|SubCategory=Musculoskeletal/Rheumatology
|Prompt=A 35-year-old male, who sustained a recent trauma, presents to the physician’s office with flattening of the shoulder muscle. Upon physical examination, the patient is unable to abduct his shoulder.  Which of the following traumatic injuries is most likely responsible for the patient’s symptoms?
|Explanation=A fractured [[surgical neck of the humerus]] is most likely to injure the [[axillary nerve]] (C5-C6) that innervates the [[deltoid]] muscle.  The [[deltoid]] muscle is responsible for shoulder [[abduction]], which is injured in this patient. The [[axillary nerve]] is also called the [[circumflex nerve]], because it is grouped with the [[posterior circumflex humeral artery]] and vein, in the [[quadrangular space]] in the arm.  

|EducationalObjectives= A fractured [[surgical neck of the humerus]] is most likely to injure the [[axillary nerve]] (C5-C6) that innervates the [[deltoid]] muscle.
|References= First Aid 2014 page 411

|AnswerA=Fracture at the surgical neck of the humerus
|AnswerAExp=See explanation.
|AnswerB=Fracture at the midshaft of the humerus
|AnswerBExp=A fracture at the midshaft of the humerus most likely injures the [[radial nerve]] (C5-C8) which innervates the extensors of the hand and provides sensory innervations to the posterior arm, dorsal hand, and thumb.
|AnswerC=Compression of the axilla by crutches
|AnswerCExp=Compression of the [[axilla]] by crutches also most likely injures the radial nerve.
|AnswerD=Fracture of the supracondylar humerus
|AnswerDExp=A fracture of the [[supracondylar humerus]] most likely injures the [[median nerve]] (C5-C8 and T1).  A median nerve injury manifests with the inability to oppose the thumb, causing an “ape hand” appearance, and the loss of sensation over the dorsal and palmar aspects of the thenar eminence and the lateral 3 and ½ fingers.
|AnswerE=Fracture of medial epicondyle of the humerus
|AnswerEExp=A fracture of the [[medial epicondyle]] of the humerus most likely injures the [[ulnar nerve]] (C8 and T1).  In ulnar nerve injuries, patients frequently will be unable to flex their medial fingers and wrists and lose sensation over the hypothenar eminence and the median 1 ½ fingers.
|RightAnswer=A
|WBRKeyword=Deltoid, axillary nerve, fracture, abduct, nervous system, abduction, innervation,
|Approved=Yes
}}