Case 1
Anterior Dislocation
Clinical:
History – This patient collided with another player on the soccer field. He immediately experienced moderate right shoulder pain. He has never had shoulder problems before.
Symptoms – He reports having a painful right shoulder with limited range of motion.
Physical – The shoulder was deformed and there is a vacant space where the humeral head should be. There was very limited, painful, range of motion.
DDx:
Humeral Dislocation
Humeral Fracture
Imaging Recommendation
ACR – MSK – Acute Shoulder Pain, Variant 1
X-rays
Imaging Assessment
Findings:
The humerus was dislocated anteriorly and resides in a subcoracoid location. No fractures identified.
Interpretation:
Anterior humeral dislocation
Diagnosis:
Anterior Dislocation of the Humerus
Discussion:
Glenohumeral joint dislocation accounts for >50% of all dislocations in the body. Anterior/subcoracoid shoulder dislocation is most common form of shoulder dislocation (96%).
Mechanism: Direct blow to a externally rotated, abducted, and extended arm.
Age – Younger individuals
Anterior humeral dislocation may be associated with:
- Hill-Sachs defect (50%), is a depression fracture of the posterolateral surface of the humeral head from impaction of the head against the glenoid rim. Best demonstrated on the anteroposterior projection with the arm internally rotated.
- Bankart lesion is a fracture of anterior aspect of inferior glenoid rim. Only the cartilaginous portion of the glenoid labrum may be injured, which may only be visible on MRI.
- Fracture of greater tuberosity (15%).
Case 2
Posterior Dislocation
Clinical:
History – This patient was accidentally electrocuted while installing an oven. He has had recurrent shoulder dislocations secondary to a seizure disorder.
Symptoms – Burns on his hands from the cross-current. Confusion. Painful, immobile right shoulder.
Physical – The shoulder was deformed and almost immobile. Mobility attempts cause severe pain.
Laboratory – None.
DDx:
Posterior humeral dislocation
Humeral fracture
Imaging Recommendation
ACR – MSK – Acute Shoulder Pain, Variant 1
X-rays
ODIN Link for Posterior Humeral Dislocation images, Figure 14.6A and B: https://mistr.usask.ca/odin/?caseID=20150209145146474
Imaging Assessment
Findings:
The humerus was vertically oriented and had the appearance of a light bulb on the AP view. There was a posterior dislocation of the humerus. The head/neck junction was sclerotic and had a deep groove where it had chronically impacted the glenoid rim at the time of previous dislocations. The acromioclavicular joint was fused due to arthritic change.
Interpretation:
Posterior Dislocation of the Humerus
Diagnosis:
Posterior Dislocation with Reverse Hills-Sachs Deformity
Discussion:
Posterior humeral dislocations account for 14% of all glenohumeral dislocations. The patient most often has a seizure disorder.
The humeral head is fixed in internal rotation and looks like a light bulb on all views of the shoulder. Look at the axillary or Y-view to see if the head still lies within the glenoid fossa. On the Y-view (an oblique view of the shoulder), the head will lie lateral to the glenoid in a posterior dislocation.
May be associated with:
A Reverse Hills-Sachs deformity where an anterior-medial humeral head depression is formed from chronic impaction of the humeral head upon the glenoid.