12/16/2025
๐ ๐๐ฐ๐ฟ๐ผ๐บ๐ถ๐ผ๐ฐ๐น๐ฎ๐๐ถ๐ฐ๐๐น๐ฎ๐ฟ (๐๐) ๐๐ผ๐ถ๐ป๐ ๐๐ป๐ท๐๐ฟ๐ถ๐ฒ๐: ๐ ๐๐ผ๐บ๐ฝ๐ฟ๐ฒ๐ต๐ฒ๐ป๐๐ถ๐๐ฒ ๐ข๐๐ฒ๐ฟ๐๐ถ๐ฒ๐
โ Acromioclavicular (AC) joint injuries, often referred to as "shoulder separations," range from mild ligament sprains to severe dislocations requiring surgical reconstruction.
โ These injuries are prevalent, accounting for approximately 9% of all shoulder injuries in the general population and up to 40% in elite athletes involved in contact sports.
๐ฆด ๐๐ป๐ฎ๐๐ผ๐บ๐ ๐ฎ๐ป๐ฑ ๐๐๐ป๐ฐ๐๐ถ๐ผ๐ป
โ The AC joint connects the clavicle (collarbone) to the acromion of the scapula (shoulder blade), linking the upper extremity to the axial skeleton.
โ Stability is provided by two primary ligament groups:
โก AC Ligaments: These control horizontal stability. The superior AC ligament is the largest and most critical for preventing posterior clavicle translation.
โก Coracoclavicular (CC) Ligaments: Comprising the conoid and trapezoid ligaments, these are the primary vertical stabilizers.
โ The clavicle acts as a strut, and the AC joint allows the scapula to move and adjust to the shape of the thorax during arm movement.
๐ฅ ๐ ๐ฒ๐ฐ๐ต๐ฎ๐ป๐ถ๐๐บ ๐ผ๐ณ ๐๐ป๐ท๐๐ฟ๐
โ AC joint injuries are most commonly caused by direct trauma, such as a blow to the lateral aspect of the shoulder with the arm adducted (e.g., a fall). This force drives the acromion inferiorly relative to the clavicle.
โ Less frequently, indirect trauma from a fall on an outstretched hand can drive the humeral head up into the acromion.
๐งญ ๐๐น๐ฎ๐๐๐ถ๐ณ๐ถ๐ฐ๐ฎ๐๐ถ๐ผ๐ป (๐ฅ๐ผ๐ฐ๐ธ๐๐ผ๐ผ๐ฑ ๐ฆ๐๐๐๐ฒ๐บ)
โ Type I: Sprain of the AC ligaments; CC ligaments are intact. No X-ray displacement.
โ Type II: Partial tear of AC ligaments; CC ligaments intact. Minimal displacement.
โ Type III: Complete disruption of both AC and CC ligaments. The clavicle is elevated (25โ100% increase in CC distance).
โก Type IIIA: Stable without scapular dysfunction.
โก Type IIIB: Presents with persistent pain and scapular dyskinesis.
โ Type IV: Posterior displacement of the distal clavicle through the trapezius muscle.
โ Type V: Severe superior displacement (>100% increase in CC distance) with significant skin tenting.
โ Type VI: Rare inferior displacement of the clavicle into a subacromial or subcoracoid position.
๐ฉบ ๐๐น๐ถ๐ป๐ถ๐ฐ๐ฎ๐น ๐ฃ๐ฟ๐ฒ๐๐ฒ๐ป๐๐ฎ๐๐ถ๐ผ๐ป ๐ฎ๐ป๐ฑ ๐๐ถ๐ฎ๐ด๐ป๐ผ๐๐ถ๐
โ Patients typically present with pain, swelling, and a deformity (step-off) over the AC joint.
โ Physical examination may reveal a "piano key sign," where the elevated clavicle can be pushed down and rebounds upon release.
๐ Provocative Testing
โ Cross-body adduction test: Adducting the arm across the chest elicits pain.
โ Paxinos sign: Squeezing the acromion and clavicle together provokes symptoms.
โ O'Brien active compression test: Can distinguish AC pathology from labral tears.
๐ผ๏ธ Imaging
โ X-ray is the primary diagnostic tool.
โ A Zanca view is specifically recommended because it allows for accurate measurement of the AC and CC distances and comparison with the uninjured side.
โ An axillary view is critical to rule out posterior displacement (Type IV).
โ MRI is reserved for unclear cases or to identify concomitant injuries like labral tears, which occur in nearly 20% of acute high-grade dislocations.
๐ ๏ธ ๐ ๐ฎ๐ป๐ฎ๐ด๐ฒ๐บ๐ฒ๐ป๐ ๐ฆ๐๐ฟ๐ฎ๐๐ฒ๐ด๐ถ๐ฒ๐
๐ฆ Nonoperative Management
โ Standard for Type I and Type II injuries and the majority of Type III injuries.
โ Protocol: Immobilization in a sling (days to weeks), pain management, and physical therapy focused on scapular control and restoring motion.
โ Outcomes: Most patients recover fully within 6โ12 weeks.
โ Type III Consensus: These are generally treated nonoperatively first. If the patient has persistent pain or scapular dyskinesis (Type IIIB) after 3โ6 weeks of rehab, surgery may be considered.
๐ฅ Operative Management
โ Surgery is typically indicated for Types IV, V, and VI, and for Type III injuries that fail conservative care.
๐ Timing
โ Acute (3 weeks): Ligament healing potential is low. Reconstruction usually requires a biological graft (allograft or autograft) to augment stability.
๐ง Surgical Techniques
โ Anatomic CC Reconstruction: Recreates the conoid and trapezoid ligaments. This restores both vertical and horizontal stability better than older methods.
โ Hook Plate Fixation: Uses a metal plate to lever under the acromion; often requires later removal and has high rates of subacromial impingement or osteolysis.
โ Weaver-Dunn (Nonanatomic): Transfers the coracoacromial ligament to the clavicle; biomechanically weaker, may lead to residual instability.
โ Arthroscopic vs. Open: Arthroscopic techniques may result in less early postoperative pain; long-term outcomes often similar.
๐
๐ฃ๐ฟ๐ผ๐ด๐ป๐ผ๐๐ถ๐ ๐ฎ๐ป๐ฑ ๐ฅ๐ฒ๐๐๐ฟ๐ป ๐๐ผ ๐ฆ๐ฝ๐ผ๐ฟ๐
โ Return to Play: Rates 76% to 100%.
โ Timeline: Around 4 months for surgical patients; varies by sport and position.
โ Complications:
โก Operativeโhigher rates: infection, hardware failure, loss of reduction.
โก Nonoperativeโcosmetic deformity, possible persistent instability or pain.