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A shoulder forced back while blocking
A 20-year-old volleyball player blocks a hard spike overhead, and his arm is forced into abduction and external rotation. He holds the arm slightly abducted and externally rotated, and the shoulder looks squared off.
Step 1 of 4
Which way has the shoulder dislocated?
Correct answer: A
Abduction + external rotation drives the humeral head anteroinferiorly. Anterior dislocation is by far the most common; posterior dislocation classically follows seizures or electric shock (see glenohumeral joint).
Show answer
A
Abduction + external rotation drives the humeral head anteroinferiorly. Anterior dislocation is by far the most common; posterior dislocation classically follows seizures or electric shock (see glenohumeral joint).
Step 2 of 4
Which nerve must be checked and documented before and after reduction?
Correct answer: A
The displaced head stretches the axillary nerve, which winds around the surgical neck. Test regimental badge sensation and deltoid function before and after reduction.
Show answer
A
The displaced head stretches the axillary nerve, which winds around the surgical neck. Test regimental badge sensation and deltoid function before and after reduction.
Step 3 of 4
Which radiographs make up the shoulder trauma series?
Correct answer: A
The trauma series is an AP (or Grashey), a scapular Y and an axillary view. A single AP view can miss a posterior dislocation.
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A
The trauma series is an AP (or Grashey), a scapular Y and an axillary view. A single AP view can miss a posterior dislocation.
Step 4 of 4
Which associated lesion is an impaction fracture of the posterolateral humeral head?
Correct answer: A
The Hill–Sachs lesion is an impaction of the posterolateral head against the glenoid rim. The Bankart lesion is an anteroinferior labral tear (± glenoid rim fracture). Reverse Hill–Sachs and the lightbulb sign go with posterior dislocation.
Show answer
A
The Hill–Sachs lesion is an impaction of the posterolateral head against the glenoid rim. The Bankart lesion is an anteroinferior labral tear (± glenoid rim fracture). Reverse Hill–Sachs and the lightbulb sign go with posterior dislocation.
Key points
- Abduction + external rotation → anterior dislocation; seizure or electrocution → posterior.
- Check the axillary nerve (regimental badge) before and after reduction.
Study: Glenohumeral joint, Axillary nerve, Humerus, Deltoid