What is the step by step procedure for treating Acromioclavicular (AC) joint dislocation using Endobutton fixation?

Endobutton Fixation Procedure for AC Joint Dislocation

The surgical treatment of acromioclavicular (AC) joint dislocation using endobutton fixation is a minimally invasive technique that provides excellent joint reduction and stability with fewer complications compared to other fixation methods.

Preoperative Assessment

• Obtain standard radiographs including anteroposterior (AP) views in internal and external rotation and an axillary or scapula-Y view to confirm AC joint dislocation 1
• CT scan may be necessary for better characterization of complex fracture patterns if radiographs are equivocal 1
• MRI may be considered to evaluate associated soft tissue injuries including labral tears 1
• Classify the AC joint dislocation according to the Rockwood classification (types III-V typically require surgical intervention)

Surgical Procedure: Step-by-Step

Patient Positioning and Preparation

1. Position the patient in a beach chair position with the affected shoulder exposed
2. Prepare and drape the shoulder in a sterile fashion
3. Mark anatomical landmarks including the clavicle, acromion, and coracoid process

Surgical Approach

1. Make a small 2-3 cm incision over the distal clavicle, centered approximately 2-3 cm medial to the AC joint
2. Expose the superior surface of the distal clavicle
3. Make a second small incision (1-2 cm) at the level of the coracoid process

Tunnel Creation

1. Identify the center of the clavicle approximately 2-3 cm medial to the AC joint
2. Use a drill guide positioned on the superior surface of the clavicle and directed toward the base of the coracoid process
3. Drill a 4.0 mm guide pin from the clavicle to the coracoid process
4. Overdrill the guide pin with a 4.5-6.0 mm cannulated drill to create the tunnel

Endobutton Placement

1. Prepare the endobutton construct with four strands of high-strength suture
2. Pass the endobutton device through the drill tunnel from the clavicle to the coracoid
3. Deploy the first endobutton under the coracoid process
4. Reduce the AC joint by applying downward pressure on the clavicle while pulling the sutures upward
5. Secure the second endobutton on top of the clavicle while maintaining reduction
6. Tie the sutures over the superior endobutton with appropriate tension

For Double Endobutton Technique (Preferred)

1. Create a second tunnel approximately 1 cm lateral to the first tunnel
2. Repeat the endobutton placement process through the second tunnel
3. The double endobutton technique provides better outcomes with fewer complications compared to single endobutton fixation 2

Wound Closure

1. Irrigate the wounds thoroughly
2. Close the deep fascia with absorbable sutures
3. Close the skin with subcuticular sutures or skin staples
4. Apply sterile dressings

Postoperative Management

Immediate Postoperative Care

1. Immobilize the shoulder in a sling for 4-6 weeks
2. Prescribe appropriate pain management including NSAIDs as first-line treatment 3
3. Obtain postoperative radiographs to confirm adequate reduction

Rehabilitation Protocol

• Phase 1 (0-4 weeks): Pain control and protected range of motion

  • Maintain sling immobilization
  • Begin gentle passive range of motion exercises

• Phase 2 (4-8 weeks): Progressive strengthening exercises

  • Discontinue sling
  • Begin active-assisted range of motion exercises
  • Initiate light strengthening exercises

• Phase 3 (8-12 weeks): Sport-specific or occupation-specific training

  • Progress to full active range of motion
  • Advance strengthening program
  • Begin sport-specific or occupation-specific activities 3

Follow-up Schedule

1. First follow-up at 2 weeks for wound check
2. Subsequent follow-ups at 6 and 12 weeks to assess healing and function
3. Final follow-up at 6 months to evaluate long-term outcomes 3

Outcomes and Complications

Expected Outcomes

• Mean correction of coracoclavicular distance: approximately 12.6 mm 4
• Average QuickDASH scores: 4.2 (range 0-6.8) 4
• Return to full activities: typically 3-6 months postoperatively

Potential Complications

• Redislocation
• Button slippage
• Erosion
• AC joint instability
• Hardware pain

Clinical Pearls

• Double endobutton technique achieves better outcomes with fewer complications compared to single endobutton technique 2
• Avoid overreduction of the clavicle; compare to the contralateral side
• Ensure proper tunnel positioning to prevent button cutout through the clavicle or coracoid
• The arthroscopy-assisted modified triple endobutton plate fixation can further reduce operative time and complications 5
• Return to full activity should be permitted only when the patient demonstrates complete resolution of pain, full range of motion, and strength symmetry >90% compared to the uninjured side 3

This procedure provides excellent reduction of the AC joint with minimal invasiveness and good functional outcomes when performed correctly.