Shoulder conditions Flashcards
When do fractures of the scapula occur and how common is it?
Is fixation required?
Relatively uncommon (leads to chest trauma)
Cases: high speed road collisions, crushing injuries, high-impact sports
Fixation: not required because the tone of the surrounding muscles holds the fragments in place while healing occurs
What are the key neurovascular structures at risk when fracture of the surgical neck of the humerus occurs
Axillary nerve (paralysis of deltoid & teres major
Posterior circumflex artery
Why is anterior shoulder dislocation more common than posterior dislocation
-The glenoid fossa is shallow
-The joint is weak at its inferior aspect so the head of the humerus dislocates anteroinferiorly but displaced in anterior due to the pull of the muscles and disruption of the anterior capsule & ligaments
What are the types/causes of anterior shoulder dislocation
-Disruption of the anterior capsule and ligaments
-The head of the humerus may come to lie antero-inferior to the glenoid
What are the mechanisms for anterior shoulder dislocation
-Arm positioned in ABduction & external rotation and pushing it posteriorly (humeral head dislocated antero-inferiorly from the glenoid)
-Direct blow to the posterior shoulder
What causes a Hill-Sachs lesion and what risk does it increase
When humeral head is dislocated anteriorly, (the tone of the infraspinatus & teres minor muscles means) the posterior aspect of the humeral head becomes jammed against the anterior lip of the glenoid fossa
Risk: secondary osteoarthritis
What causes Bankart lesion/labral tear
The force of the humeral head popping out of the socket
What is Bankart lesion
Part of the glenoid labrum being torn off
(sometimes small pieces of bone)
What groups of people are likely to develop Hill-Sachs lesion
<40 yrs with anterior shoulder dislocation
Ppp. with recurrent dislocation
What is Hill-Sachs lesion
Dent (indentation fracture) in the posterolateral humeral head in anterior shoulder dislcation
Causes of posterior dislocation
Violent muscle contraction due to…
-epileptic seizure
-electrocution of lightning strike
Mechanisms of posterior shoulder dislocation
-Blow to the anterior shoulder
-Arm is flexed across the body and pushed posteriorly
What is the presentation of posterior shoulder dislocation
-Arm internally rotated & ADducted
-Flattening/squaring of the shoulder with a prominent coracoid process
-Can’t be externally rotated
How is posterior shoulder dislocation displayed in X-rays
‘Light bulb’ sign- humeral head is more rounded
Glenohumeral distance is increased
(Both anterior&posterior) Scapular/ Y view: head of the humerus should be directly in line with the glenoid fossa (e.g. bifurcation of the Y)
Injuries associated with posterior dislocation
Fractures
Rotator cuff tears
Hill-Sach lesions
Causes of inferior dislocatiton
Hyperabducting the arm: causes humeral head to displace from the inferior aspect of glenoid
Injuries associated with inferior dislocation
Damage to nerves
Rotator cuff tears
Injury to BV
Most common complication of shoulder dislocation and its cause
Recurrent dislocation: damage to the stabilising tissues surrounding the shoulder