ACJ Dislocations

Modern Study Review (AI-Generated)

High-Yield Summary

Acromioclavicular joint (ACJ) dislocations are common shoulder injuries resulting from direct trauma or falls onto the shoulder. Accurate classification and treatment are essential to restore shoulder function and minimize chronic pain. Modern management balances non-operative care for low-grade injuries with surgical intervention for high-grade and unstable dislocations, guided by updated classification systems and patient-specific factors.

Key Diagnostic Findings

Anatomy

The ACJ connects the distal clavicle to the acromion of the scapula.
Stability is provided primarily by the acromioclavicular (AC) ligaments and the coracoclavicular (CC) ligaments (conoid and trapezoid).
Surrounding muscles include the deltoid and trapezius, which contribute to dynamic stability.

Clinical Presentation

Pain localized over the ACJ, swelling, and deformity (prominent distal clavicle).
Tenderness on palpation and limited shoulder range of motion, especially overhead activities.
In high-grade injuries, visible displacement or “step-off” deformity is often present.

Imaging

Standard AP and Zanca views of the shoulder are essential.
Stress views or weighted views may help assess vertical instability.
MRI or ultrasound can evaluate ligament integrity and associated soft tissue injury.
CT is rarely needed unless complex fractures or chronic instability are suspected.

Classification Systems

Classification	Description	Clinical Relevance
Tossy/Allman (Legacy)	Type I: AC ligament sprain; Type II: AC ligaments torn, CC intact; Type III: AC and CC torn	Historical; foundational but limited detail
Rockwood (Current Standard)	Types I-VI with detailed gradation of displacement and soft tissue injury: – I: Sprain – II: AC rupture, CC intact – III: AC and CC rupture, 25-100% displacement – IV: Posterior displacement into trapezius – V: Severe displacement with deltoid/trapezius detachment – VI: Inferior displacement under coracoid	Guides treatment decisions and prognosis

Current Gold Standard Treatment

Non-operative

Indicated for Rockwood Types I and II and often for Type III in low-demand patients.
Includes rest, ice, sling immobilization (1-2 weeks), followed by progressive physical therapy focusing on range of motion and strengthening.
Early mobilization is encouraged to prevent stiffness.

Operative

Indicated for Rockwood Types IV, V, and VI, and select Type III injuries in high-demand or symptomatic patients.
Surgical options include anatomic coracoclavicular ligament reconstruction, hook plate fixation, or suture-button devices.
Modern techniques favor minimally invasive arthroscopic-assisted procedures with biological augmentation to restore native biomechanics.
Timing: Early surgery (within 3 weeks) is preferred for acute injuries; chronic cases may require more complex reconstruction.

Modern Complications & Outcomes

Complications

Complication	Notes
Residual pain and instability	Common in untreated or poorly managed high-grade injuries
Hardware irritation or failure	Particularly with hook plates; may require removal
Infection	Low incidence with modern sterile techniques
Neurovascular injury	Rare but possible during surgical dissection
Post-traumatic arthritis	Can develop in chronic or malreduced cases

Outcomes

Non-operative treatment of Types I-III generally yields excellent pain relief and functional recovery.
Surgical treatment of Types IV-VI shows improved stability and return to pre-injury activity levels.
Patient-reported outcomes focus on pain reduction, restoration of shoulder strength, and return to work/sports.
Early rehabilitation and individualized treatment plans optimize long-term function.

Classic Clinical Notes

AC Dislocations

(originally Tossy and Allman-3 types)

Type I – AC ligament sprain
Type II – AC ligaments torn, C/T intact
Type III – AC, C/T all torn
Type IV – AC, C/T all torn and distal clavicle buttonholes postero-superior into trapezius – marked/fixed dislocation
Type V – IV + deltoid and trapezius tear thus very very displaced
Type VI – AC, C/T all torn and distal clavicle goes inferior and trapped under coracoid process
Type VII – Total clavicular dislocation (AC and SC dislocation)

Last Updated on January 25, 2026 by orthonet