[6.1] UL 4: Dislocation

Q: What is a joint dislocation?

Total separation of the components of a joint.

Q: What are the components of the sternoclavicular joint?

Sternum + sternal/medial end of the clavicle.

Q: What is the most common type of sternoclavicular dislocation?

Anterior dislocation.

Q: Why is posterior sternoclavicular dislocation dangerous?

The clavicle moves backward and may lacerate structures behind the sternum.

Q: What are the components of the acromioclavicular joint?

Acromial end of clavicle + acromion process of scapula.

Q: What two coracoclavicular ligaments stabilize the AC joint?

Trapezoid and conoid ligaments.

Q: What happens to ACJ dislocation when the coracoclavicular ligaments are intact?

The ACJ is not severe and remains undisplaced.

Q: What happens when the coracoclavicular ligaments are torn?

The ACJ becomes displaced.

Q: What deformity is characteristic of ACJ dislocation?

Step deformity.

Q: Why does a step deformity occur in ACJ dislocation?

The acromion and scapula are pulled downward by the weight of the upper limb.

Q: What are the components of the shoulder (glenohumeral) joint?

Glenoid cavity + head of humerus.

Q: Why is shoulder dislocation very common?

Because the glenoid cavity is shallow while the humeral head is spherical.

Q: In anterior shoulder dislocation, where is the humeral head?

Anterior to the scapula, aligned with the coracoid process.

Q: In posterior shoulder dislocation, where is the humeral head?

Posterior to the scapula, aligned with the acromion.

Q: In inferior shoulder dislocation, where is the humeral head?

Inferior to the glenoid cavity, below the center of the glenoid.

Q: Where is the glenoid fossa normally located on the Y-line?

At the center of the Y-line.

Q: What is an elbow joint dislocation?

Separation/displacement of the radius and ulna from the distal humerus, often posteriorly.

Q: What is the common direction of elbow dislocation?

Posteriorly.

Q: What force can cause collateral ligament tears during elbow dislocation?

A valgus force.

Q: Which collateral ligament is especially at risk with valgus force?

The medial/ulnar collateral ligament (UCL).

Q: What is pulled elbow (nursemaid's elbow)?

Radial head subluxation.

Q: In what age group is nursemaid's elbow common?

Children <5 years old.

Q: What happens to the annular ligament in nursemaid's elbow?

The annular ligament slips over the radius bone.

Q: Why is the annular ligament susceptible in young children?

It is not fully developed.

Q: What does the annular ligament connect?

It joins the radial head to the radial notch of the ulna.

Q: What are the common symptoms of nursemaid's elbow?

Elbow pain → guarding of the elbow → reluctance to use the arm.

Q: What joint is displaced in wrist joint dislocation?

The radiocarpal joint.

Q: Which carpal bone is most commonly dislocated according to the notes?

The lunate.

Q: What bone is the lunate aligned with?

The 3rd metacarpal.

Q: What finding on Murphy's sign suggests lunate dislocation according to the notes?

If the 3rd metacarpal is aligned with the 2nd and 4th metacarpals, lunate dislocation is suspected (positive Murphy's sign).

Q: Which joints can be involved in finger dislocation?

Metacarpophalangeal (MCP) and interphalangeal (IP) joints.

Q: What clinical sign is associated with finger dislocation in these notes?

Murphy's sign.

Q: In what position should these joints be repositioned?

Extended position.

Q: Why should MCP/IP joints be repositioned in extension?

Because the collateral ligaments are loose in extension and taut/tight in flexion.