11.4 Dislocation

Question 1

A patient comes in with contusion to the shoulder. What structures within the shoulder might be damaged to cause this?

Answer 1

• Bursa
• Blood vessels
• Tendons
• Muscles

Question 2

Describe the principles of load and deformation that underlie fracture, dislocation and tendon injury

Answer 2

• All soft tissue can be stretched within a certain range (i.e., lifting your arm deforms muscles etc.)
• outside this range, the tissue can be damaged. Depending on the degree of force, the exact nature of the damage can vary

Question 3

Along what axis does the sternoclavicular joint most commonly dislocate? Considering surrounding neurovascular structures, what is one life-threatening complication of this?

Answer 3

• Most commonly dislocates anteriorly or posteriorly
• In the setting of posterior fractures, can compress the aorta or the vessels of the aortic arch

Question 4

Which ligaments most commonly rupture in the setting of AC joint dislocation?

Answer 4

Coracoclavicular

Question 5

A patient presents complaining that their shoulder feels like it pops out of place during certain activities. No history of recurrent dislocations. Which structure of the shoulder joint is most likely affected?

Answer 5

The glenoid labrum

Question 6

Which nerve is most commonly affected in traction injuries of the shoulder? Based on its function, which muscle can we use to test its function? Describe the relevant anatomical feature of the nerve that makes this possible.

Answer 6

• Axillary nerve is most commonly affected
• Can be tested by testing the deltoid muscle, which is innervated by the axillary nerve
• Wraps around head of humerus, making it especially vulnerable

Question 7

At what three joints can elbow dislocations occur? What are the three types of joints? How does this relate to nomenclature?

Answer 7

Joints: Radiocapitellar, proximal radioulnar, ulnohumeral

Classes: simple, complex (w/ fracture), and complicated (w/ neurovascular complications)

Question 8

Olecranon vs proximal ulna fracture

Answer 8

Olecranon: involves/affects articular surface

Proximal ulna: close to olecranon, but articular surface remains intact

Question 9

Why are radial head and capitellar fractures particularly important to reduce quickly?

Answer 9

Because, in their displaced form, they can become avascular. If left long enough, the structures will no longer have a chance to heal.

Question 10

What are the three signs of a Monteggia injury? Provide a mech to help make this easier to remember

Answer 10

1. Ulnar shaft fracture

Which makes it easier for the radius to:

2. Dislocate from the proximal radioulnar joint

And therefore:

3. Dislocate from the capitellum

Question 11

Describe simple reduction of an elbow dislocation

Answer 11

1. Traction the elbow
2. Full supination of forearm
3. Full elbow flexion

Question 12

What are the normal max distances of the acromioclavicular and coracoclavicular joints?

Answer 12

AC: 8mm (eight-C)
CC: 13mm

Question 13

What is an impaction fracture?

Answer 13

A fracture that occurs when bone is crushed following displacement, such as caused by trauma.

Question 14

A patient presents with abnormal posturing. Frontal chest x ray shows lightbulb sign at glenohumeral joint. Diagnosis?

Answer 14

Posterior glenohumeral dislocation

Question 15

Recall the CRITOE 1,3,5,7,9,11 acronym. What does it stand for?

Answer 15

Areas of ossification in the elbow occurring at different ages.

C: Capitellum (1)
R: Radial Head (3)
I: Internal epicondyle (5)
T: Trochela (7)
O: Olecranon (9)
E: External epicondyle (11)

Question 16

What is involved in a Galleazi fracture?

Answer 16

• Radial shaft fracture
• Distal RU joint dislocation