Posterior Shoulder Instability and Posterior Dislocation

Question 1

What percent of of traumatic posterior dislocations seen in the emergency department are undiagnosed?

Answer 1

50%

Question 2

Which patient scenarios do posterior dislocations occur?

Answer 2

1) Seizure or shock

2) weight-lifters, linemen and overhead athletes (repetitive microtrauma stretches posterior capsule)

Question 3

What lesions are a/w posterior shoulder dislocation?

Answer 3

1) Isolated lesser tuberosity fracture
2) Posterior glenoid rim fx
3) avulsion of posterior IGHL
4) Posterior Bankhart or Hill-Sachs
5) Posterior labral cyst

Question 4

Which test’s are positive for posterior labral tear?

Answer 4

1) Jerk test- shoulder abducted to 90° and IR, axial force applied (positive if clunk; posterior subluxation)
2) Kim test- arm at 90° abduction, followed by flexing the shoulder to 45 forward flexion shoulder has posteriorly directed axial force (pain is positive)

Question 5

What is a McLaughlin procedure in the shoulder and what are its indications?

Answer 5

Transfer of the lesser tuberosity and subscapularis tendon into a reverse Hill Sachs defect in the humerus after a posterior dislocation.
Chronic dislocations 50% then hemiarthroplasty

Question 6

What are the indications for hemiarthroplasty in a chronic posterior shoulder dislocation?

Answer 6

1) chronic dislocation > 6 months old
2) severe humeral head arthritis
3) collapse of humeral head during reduction
4) reverse Hill-Sachs defect > 50% of articular surface

Question 7

An acute posterior shoulder dislocation should be suspected in a patient with pain and the shoulder locked in what position?

Answer 7

Internal rotation