Acromioclavicular Dislocation: Evaluation and Treatment
For AC joint dislocations, obtain standard shoulder radiographs first, classify the injury by Rockwood type, then treat types I-II and most type III injuries nonoperatively with sling immobilization and early rehabilitation, reserving surgery for types IV-VI and the rare symptomatic type III that fails conservative management after 3 months.
Initial Evaluation
Start with anteroposterior shoulder radiographs including a Zanca view (10-15 degree cephalic tilt) to assess the AC joint 1. Measure the coracoclavicular distance and compare to the uninjured side—an increase >25% indicates significant ligamentous disruption 2. The mechanism is typically a direct blow to the acromion with the arm adducted 3, 4.
Key Physical Examination Findings
- Point tenderness directly over the AC joint
- Visible/palpable step-off deformity (higher grade injuries)
- Pain with cross-body adduction
- Assess for horizontal instability with anterior-posterior stress
Rockwood Classification (Critical for Treatment Decisions)
- Type I: AC ligament sprain, intact coracoclavicular (CC) ligaments
- Type II: AC ligament torn, CC ligaments sprained, <25% increase in CC distance
- Type III: Both AC and CC ligaments torn, 25-100% increase in CC distance
- Type IV: Posterior clavicle displacement into trapezius
- Type V: Severe superior displacement, >100% increase in CC distance
- Type VI: Inferior clavicle displacement (rare)
Treatment Algorithm
Types I and II: Nonoperative Management
Treat with sling immobilization for comfort (typically 1-2 weeks), ice, NSAIDs, and early range-of-motion exercises as pain allows 3, 4, 5. Begin strengthening at 2-3 weeks. Return to activity when normal motion and strength are restored compared to the contralateral shoulder 4.
Type III: Predominantly Nonoperative
This is the most controversial category, but recent high-quality evidence strongly favors nonoperative treatment 2. A 2024 prospective study showed 91% of type III injuries recovered well without surgery, with no functional difference compared to type V injuries treated conservatively 2.
Implement a structured 3-month home-based rehabilitation program 2. Reserve delayed surgical reconstruction only for:
- Persistent symptomatic instability after 3 months of rehabilitation
- High-demand overhead athletes who fail conservative treatment
- Manual laborers with persistent pain and weakness 4, 5
Important caveat: Only 9.5% of patients required delayed surgery in the most recent prospective cohort 2, suggesting the traditional bias toward early surgery for type III injuries is outdated.
Types IV, V, and VI: Surgical Management
Operate within 2-3 weeks of acute injury 5. These high-grade injuries require anatomic reduction and ligament reconstruction 3, 4.
Surgical Technique Considerations
When surgery is indicated, prioritize anatomic coracoclavicular ligament reconstruction over rigid fixation methods 6, 7. Modern techniques focus on:
- Cortical button systems with synthetic or biologic grafts for CC ligament reconstruction 6, 7
- Combined AC and CC stabilization to address both vertical and horizontal instability 5, 6
- Repair of the posterosuperior AC capsuloligamentous complex for horizontal stability 6
Avoid hook plates when possible—they are associated with subacromial osteolysis, acromial erosion, and require a second surgery for removal 7. While they provide rigid stability, outcomes are inferior to anatomic CC reconstruction 7.
No clear superiority exists between:
Return to Activity
After nonoperative treatment, return when the shoulder is asymptomatic with normal motion and strength compared to the uninjured side 4. This typically occurs at 6-12 weeks for types I-II.
After surgical reconstruction, the overall return-to-play rate is 91.5%, with 85.6% returning to the same level 8. Mean time to return is 5.7 months 8. Type III injuries return earliest at 4.9 months 8.
Common Pitfalls
- Underdiagnosing horizontal instability: Use axillary or Alexander views to detect dynamic horizontal displacement 5
- Operating too early on type III injuries: The 2024 evidence shows excellent nonoperative outcomes 2
- Using MRI as first-line imaging: Standard radiographs are sufficient for classification 1, 5
- Choosing hook plates for convenience: Higher complication rates make them a poor choice despite ease of insertion 7