SC Joint Dislocation: Anterior vs Posterior, Danger Signs & Practice MCQs

Sternoclavicular (SC) Joint Dislocation

SC Joint Dislocation connects the upper limb to the axial skeleton. While uncommon, identifying the direction of dislocation is a critical skill, as one type is a cosmetic nuisance while the other is a life-threatening emergency.

1. Classification (Direction)

• Anterior Dislocation (Most Common): The medial clavicle pops outward. Usually caused by a blow to the anterior shoulder. It is cosmetically prominent but rarely dangerous.
• Posterior Dislocation (Rare but Dangerous): The clavicle is pushed inward behind the sternum (mediastinum). This is an emergency.

2. Clinical Features

⚠ DANGER SIGNS (Posterior Dislocation):
If the clavicle presses on mediastinal structures, look for:
- Dyspnea: Trachea compression.
- Dysphagia: Esophagus compression.
- Venous Congestion: Superior Vena Cava/Subclavian vein compression.
- Hoarseness: Laryngeal nerve irritation.

3. Diagnosis

• X-Ray: "Serendipity View" (40-degree cephalic tilt) is required. Standard AP views often miss it.
• CT Scan: The Gold Standard. Essential to see the relationship with blood vessels.

4. Treatment & PT

• Anterior: Usually conservative. Sling for comfort. Closed reduction often pops back out (unstable) but function remains good.
• Posterior: Requires Closed Reduction (Abduction + Traction) often under GA with a Thoracic Surgeon on standby. If failed, Open Reduction is needed.

25 Practice MCQs

Q1. Which SC joint dislocation is a medical emergency?

Answer: B). Because it compresses vital mediastinal structures.

Q2. The "Serendipity View" requires the X-ray beam to be tilted:

Answer: A). This projects the clavicles away from other structures for comparison.

Q3. In patients under 25, an apparent SC dislocation is often actually:

Answer: A). The medial clavicle epiphysis is the last to fuse (age 23-25).

Q4. Dysphagia in a posterior dislocation indicates compression of:

Answer: B). Dysphagia = Difficulty swallowing = Esophagus.

Q5. The primary stabilizer of the SC joint is:

Answer: B). The posterior capsule and Costoclavicular ligament are strongest.

Q6. Anterior dislocations are usually caused by:

Answer: A). Levering the clavicle anteriorly.

Q7. Is closed reduction recommended for chronic anterior dislocation?

Answer: B). It is usually asymptomatic and stable; reduction attempts often fail or cause instability.

Q8. Hoarseness of voice implies injury to:

Answer: A). Compression of this nerve causes voice changes.

Q9. The shape of the SC joint is:

Answer: B). It allows movement in multiple planes.

Q10. Reduction of Posterior Dislocation often involves:

Answer: B). Extension and traction help pull the clavicle out from the mediastinum.

Q11. Which imaging is Gold Standard for Posterior Dislocation?

Answer: B). Essential to rule out vascular injury.

Q12. Spontaneous atraumatic subluxation of the SC joint is seen in:

Answer: A). Often bilateral and multidirectional. Treatment is reassurance, not surgery.

Q13. The intra-articular disc of the SC joint:

Answer: A). It acts as a shock absorber and prevents medial displacement.

Q14. How much clavicular rotation occurs at the SC joint during full shoulder elevation?

Answer: C). Essential for full overhead abduction.

Q15. Septic arthritis of the SC joint is often seen in:

Answer: A). A red flag for SC joint pain without trauma.

Q16. Anterior dislocation is usually managed with a sling for:

Answer: B). To allow soft tissue healing.

Q17. Which surgeon should be available during reduction of posterior dislocation?

Answer: B). In case of rupture of the great vessels.

Q18. SC joint osteoarthritis typically affects:

Answer: A). Common in older females.

Q19. The "Hobbs View" is another name for:

Answer: B). High angle views help visualize the joint.

Q20. Recurrent anterior instability is treated with:

Answer: A). Surgery leaves ugly scars and has risks; functional stability is usually good.

Q21. Friedrich’s disease is:

Answer: A). A rare condition causing pain and swelling.

Q22. The medial clavicle articulates with the Sternum and:

Answer: B). The 1st rib cartilage is part of the joint complex.

Q23. Direct force to the anterolateral shoulder usually causes:

Answer: B). Force pushes the shoulder back, leveraging the medial clavicle backwards (Posterior).

Q24. For anterior dislocation, elevation of the arm is limited for:

Answer: C). To prevent redislocation during healing.

Q25. Is the SC joint a synovial joint?

Answer: A). It is a synovial, saddle-type joint.