Summary

Acromioclavicular (AC) Joint injuries are common shoulder injuries, typically occurring in young active males (rugby, cycling) from a direct blow to the adducted shoulder (point of the shoulder). The injury ranges from a simple sprain to complete dislocation with disruption of the Coracoclavicular (CC) Ligaments. The Rockwood Classification (Types I-VI) guides management. Types I and II are universally treated conservatively. Type III (complete dislocation) is controversial but increasingly treated conservatively first. Types IV, V, and VI represent significant instability and soft tissue disruption, requiring surgical reconstruction (e.g., Hook Plate, TightRope, Weaver-Dunn). [1,2]

Key Facts

• Mechanism: Direct blow to the top of the shoulder (acromion driven DOWN). The clavicle stays up.
• Anatomy:
  • AC Ligaments: Provide horizontal stability (Ant-Post).
  • CC Ligaments (Conoid & Trapezoid): Provide vertical stability (Sup-Inf).
• The "Piano Key" Sign: The distal clavicle is elevated. You can push it down (like a piano key), but it springs back up.

Clinical Pearls

"It's not the Collarbone that goes UP": The clavicle stays in its normal anatomical position (held by SCM). It is the Scapula (and Acromion) that are driven DOWN by the weight of the arm and the impact. The appearance of a "high clavicle" is an optical illusion of the shoulder drooping.

"The Zanca View": A standard AP shoulder X-ray often superimposes the spine of the scapula over the AC joint. Tilt the beam 10-15 degrees Cephalad to open up the joint and diagnose subtle fractures or osteolysis.

"Beware the Type IV": On the AP X-ray, specific displacement might be subtle. But on the Axillary View, the clavicle is punched Posteriorly into the Trapezius muscle. This is very painful and requires surgery.

                  AC JOINT INJURY
                        ↓
             ROCKWOOD CLASSIFICATION?
             ┌──────────┴───────────┐
         TYPE I/II               TYPE IV/V/VI
       (Ligaments OK)           (Severe/Post)
           ↓                          ↓
      CONSERVATIVE                 SURGERY
      (Sling 1-2w)             (Reconstruction)
           ↓
        TYPE III? (The Grey Zone)
    (Complete Dislocation <100%)
           ↓
    INITIAL CONSERVATIVE (6-12w)
           ↓
      PERSISTENT PAIN/INSTABILITY?
      ┌──────────┴───────────┐
     NO                     YES
   DISCHARGE              SURGERY
   (Accept Lump)      (Stabilisation)

1. Conservative (Type I-III)

• Indication: All Type I/II. Most Type III.
• Appliance: Broad Arm Sling.
• Protocol:
  • Week 0-2: Symptom control. Pendulums.
  • Week 2-6: Active ROM. Avoid heavy lifting.
  • Week 12: Return to contact sports.
• Outcome: Good function. Permanent lump. Some residual clicking.

2. Surgical (Type IV-VI or Chronic Painful III)

• Acute (<3 weeks):
  • Hook Plate: Rigid plate hooks under acromion. Must be removed at 3 months.
  • Suspensory Fixation (TightRope/DogBone): Button on clavicle, Button on Coracoid. Heavy suture pulls them together. No removal needed.
• Chronic (>3 weeks):
  • Weaver-Dunn Procedure:
    • Excise distal clavicle (Mumford).
    • Transfer Coracoacromial (CA) ligament to the clavicle.
    • Reinforce with suture/tendon graft.

The Type III Debate (Bannister et al.)

• Study: Conservative vs Surgical for Type III.
• Findings: Surgery gave better anatomical reduction (X-ray looked better). Conservative gave faster return to work and fewer complications.
• Function: At 1 year, NO significant difference in shoulder scores.
• Conclusion: Treat Type III conservatively first. Surgery is salvage for the 15% who remain painful.

What is a "Separated Shoulder"?

You have torn the ligaments that hold your collarbone to your shoulder blade. It's different from a "dislocated shoulder" (where the ball comes out of the socket).

Will the lump go away?

No. The lump is the end of your collarbone sticking up because the arm has dropped slightly. It will always be there. In most people, it becomes a painless bump.

Why not fix it?

We can fix it, but it involves drilling holes in your bones and using heavy cables. The ligaments often don't heal perfectly anyway, and the deformity can come back. We find that professional rugby players play with this injury without surgery. We only operate if it is still painful in 3 months.

Rehabilitation

You can start moving it as soon as the pain allows. You won't damage it further.

Q1: Defined Rockwood Type IV. A: Posterior displacement of the distal clavicle into or through the Trapezius fascia. It is often missed on AP X-ray but seen on Axillary lateral. It causes significant pain and requires reduction.

Q2: What is the Weaver-Dunn procedure? A: A salvage procedure for chronic ACJ instability. Detailed: (1) Excision of distal 1cm of clavicle. (2) Release of Coracoacromial (CA) ligament from acromion. (3) Transfer of CA ligament to the intramedullary canal of the distal clavicle. (4) Plication of trapezius fascia.

Q3: Explain the "SICK" Scapula. A: Scapular malposition, Inferior medial border prominence, Coracoid pain, and Kinesis abnormalities. It is a syndrome of muscular dyskinesis seen in chronic ACJ separations where the scapula droops and rotates.

(End of Topic)