An acromioclavicular joint separation, or AC joint separation or shoulder separation, occurs when the clavicle separates from the scapula. It is commonly caused by a fall directly on the ‘point’ of the shoulder or by a direct blow received in a contact sport. Grade I and II separations very rarely require surgery. Even Grade III injuries usually allow a return to full activity with few restrictions. In some cases a painful lump may persist, necessitating partial clavicle excision in selected individuals such as high caliber throwing athletes. Leaving your AC joint injury untreated means your condition can worsen, which can have serious consequences, such as Severe shoulder separation. Serious displacement or collarbone fracture. Arthritis in your shoulder.
Other Names
- Shoulder Separation
- Shoulder Sprain
- AC Sprain
- AC Dislocation
- Acromioclavicular Joint Dislocation
Background
- This page refers to all traumatic injuries to the Acromioclavicular Joint including
- Sprains
- Dislocations
- Separations
- Thought to be under-estimated due to many mild injuries not seeking medical attention
- Represents 9% of all shoulder injuries (need citation)
- 50% of all AC dislocations occur to individuals in their 20s (need citation)
- Types 1 and 2 injuries account for most AC separations
- Mechanism of injury is primarily by direct impact over the AC joint
- From fall or contact sport
- Arm is adducted
Causes
- Many causes
- Simple falls
- High energy trauma
- Sports
Pathoanatomy
- AC Joint
- Diarthrodial joint
- Motion: primarily gliding, only 8° rotation through AC joint
- fibrocartilaginous intraarticular disc (similar to meniscus of knee)
- Stabilizers
- Joint Capsule
- Acromioclavicular Ligament (anterior-posterior stability)
- Coracoclavicular Ligaments (superior-inferior stability)
- Muscles: Deltoid, Trapezius
Associated Injuries
- Intra-articular shoulder injury (18.2%)[1]
- SLAP Lesion
- Rotator Cuff Injury
- Male > Female
- Sports
- Contact and collision sports
- Skiing
- Cycling
Differential Diagnosis
- Fractures
- Proximal Humerus Fracture
- Humeral Shaft Fracture
- Clavicle Fracture
- Scapula Fracture
- First Rib Fracture (traumatic or atraumatic)
- Dislocations & Seperations
- Acromioclavicular Joint Separation
- Glenohumeral Dislocation (Acute)
- Sternoclavicular Joint Dislocation
- Glenohumeral Instability (Chronic)
- Arthropathies
- Glenohumeral Arthritis
- Acromioclavicular Joint Arthritis
- Muscle & Tendon Injuries
- Pectoralis Major Injuries
- Pectoralis Minor Injuries
- Proximal Biceps Tendon Injuries
- Scapular Dyskinesis
- Rotator Cuff
- Rotator Cuff Tear
- Rotator Cuff Tendonitis
- Calcific Tendinitis of the Rotator Cuff
- Subcoracoid Impingement Syndrome
- Bursopathies
- Subacromial Bursitis
- Scapulothoracic Bursitis
- Ligament Injuries
- Glenoid Labral Tears
- Neuropathies
- Suprascapular Nerve Injury
- Parsonage-Turner Syndrome
- Quadrilateral Space Syndrome
- Winged Scapula
- Other
- Adhesive Capsulitis
- Paget-Schroetter Syndrome
- Pediatrics
- Coracoid Avulsion Fracture
- Humeral Head Epiphysiolysis (Little League Shoulder)
Symptoms
- General: Physical Exam Shoulder
- History
- Patient should describe some trauma
- Shoulder pain at or close to AC joint
- Physical
- Most commonly, tenderness over AC joint
- Inspection may show asymmetry of shoulders or swell at the AC joint
- Range of Motion is usually reduced due to pain acutely
- Pain with adduction of the shoulder and possibly with shoulder abduction and flexion
- Deformity (step-off) of AC joint with type III injuries and higher
- Type III and V may show instability of the lateral clavicle when depressed manually (“piano key” phenomenon)
- Special Tests
- Crossover Test: shoulder flexed to 90°, passively adducted across chest, reproduces pain over the AC joint
- Resisted AC Joint Extension Test: abduction against resistance with shoulder flexed to 90°
- OBriens Test: Arm flexed to 90° and then supinated and pronated against resistance
Diagnosis
Radiographs
- Standard Radiographs Shoulder
- Zanca view (sometimes referred to as the AC joint view)[2]
- Beam is tilted cephalic 10 – 15°
- Provides superior AC joint evaluation
- Recommend bilateral evaluation for comparison
- The average distance between the inferior aspect of the clavicle and the coracoid is 1.1 to 1.3 cm
- Basmania view: scapular Y performed with cross-body adduction stress
- Stryker notch views can assess for coracoid fracture
- Note: Weighted stress views are no longer used
CT
- CT has not been shown to improve diagnostic yield
MRI
- Can directly assess AC and CC ligaments
- Useful if surgical intervention is being considered
Ultrasound
- Can be used to evaluate the AC joint
Classification
Rockwood Classification of Acromioclavicular Injuries
| Type | AC Ligaments | CC Ligaments | Deltopectoral Fascia | CC Distance | AC Joint (Xray) |
| I | Sprained | Intact | Intact | Normal | Normal |
| II | Disrupted | Sprained | Intact | <25% | Widened |
| III | Disrupted | Disrupted | Disrupted | 25%-100% | Widened |
| IV | Disrupted | Disrupted | Disrupted | Increased | Posterior displaced clavicle |
| V | Disrupted | Disrupted | Disrupted | 100-300% | N/A |
| VI | Disrupted | Disrupted | Disrupted | Decreased | Inferior displaced clavicle |
Treatment
Types I and II
- Universally nonoperative
- Analgesia with ice, NSAIDS, Acetaminophen, et
- Immobilization: Shoulder Sling
- Discontinue once asymptomatic
- Type I: Typically 1-3 weeks
- Type II: Longer, up to 4 weeks[3]
- Activity modification
- Type II injuries may require early rehabilitation program with passive and active shoulder ROM exercises
- Rotator cuff, scapular stabilization, and trunk strengthening exercises as pain resolves
- Heavy lifting and contact activities only once extremity is pain free and symmetric ROM is acheived
- Consider Corticosteroid Injection in refractory cases
Type III
- Management is controversial
- Not a lot of high level evidence to guide decision making
- General consensus is to advocate for initial nonoperative management.
- Individualized treatment based on patient activity level, impairment, and occupation
- Consider surgical repair in acute, young patients
- Comparably high satisfaction with operative and nonoperative treatment though higher complication rates in those treated surgically[4]
- Nonoperative treatment
- Similar to Type I, II
Type IV – VI
- Generally considered surgical
- Technique
- Many described in the literature
- ORIF most common
Rehab and Return to Play
Rehabilitation
- Needs to be updated
Return to Play
- Return to play once pain completely resolved and equal active ROM in bilateral shoulders. Followed by adequate strength training.
- Recovery generally takes 6 weeks for Type II injuries and 12 weeks for Type III injuries
Complications
- Acromioclavicular Joint Pain
- Experienced by 1/3 of patients at 6 months after injury and up to 6 years of follow up[5]
- Decrease in bench press strength (need citation)
- Cosmetic deformity is very common
- Crepitus, clicking
- AC Joint Arthritis
- Distal Clavicle Osteolysis
