Acromioclavicular joint instability: anatomy, biomechanics and evaluation

Area of Science:

• Orthopedics
• Sports Medicine
• Anatomy

Background:

• Acromioclavicular (AC) joint instability is a prevalent cause of shoulder pain and functional limitation.
• Injuries typically result from direct trauma to the AC joint, affecting its capsule, ligaments, and articular structures.
• Understanding the biomechanics and ligamentous support (AC and coracoclavicular ligaments) is crucial for diagnosing instability.

Purpose of the Study:

• To provide a comprehensive overview of acromioclavicular (AC) joint instability.
• To detail the anatomy and biomechanics of the AC joint and its stabilizing ligaments.
• To present the Rockwood classification system for AC joint injuries and diagnostic modalities.

Main Methods:

• Review of anatomical structures and biomechanical functions of the AC joint.
• Description of the Rockwood radiographic classification system (Types I-VI).
• Discussion of diagnostic methods, including physical examination tests (e.g., cross-body adduction stress test) and imaging techniques (e.g., Zanca view, axial view).

Main Results:

• AC joint stability relies on AC ligaments for horizontal and coracoclavicular (CC) ligaments for vertical support.
• The Rockwood classification categorizes injuries from mild sprains to severe dislocations based on ligamentous damage and clavicle displacement.
• Physical examination tests and specific radiographic views are essential for accurate diagnosis and classification of AC joint injuries.

Conclusions:

• Acromioclavicular (AC) joint instability requires a thorough diagnostic approach combining clinical assessment and specialized imaging.
• Accurate classification of AC joint injuries is vital for guiding appropriate treatment and management strategies.
• Knowledge of AC joint anatomy and biomechanics aids in understanding injury mechanisms and outcomes.