Acromioclavicular joint osteoarthritis is a type of shoulder arthritis that involves degenerative changes to the cartilage and other structures in the acromioclavicular joint. AC joint arthrosis or osteoarthritis of the acromioclavicular joint is most common in people who are middle-aged. It develops when the cartilage in the AC joint begins to wear out. With this condition, there is usually pain that limits the motion of the arm. Initial treatment of AC joint arthritis is non-operative and includes activity modification, physical therapy, non-steroidal anti-inflammatory medications (NSAIDs), and local AC joint injection of anesthetics or corticosteroids
Other Names
- AC Joint OA
- Acromioclavicular Joint Osteoarthritis
- Degenerative Joint Disease of the Acromioclavicular Joint
Pathophysiology
Primary Osteoarthritis
- Refers to age-related degeneration
- Intra-articular disc
- Functions like the meniscus of the knee
- Prone to fraying, tearing, and forming holes, macerated by defects in the chondral surface
Secondary Osteoarthritis
- Post-traumatic
- Most commonly occurring with an axial load on an abducted arm
- Distal clavicle osteolysis
- Related to repetitive microtrauma
- Most commonly in weight lifters, less commonly basketball, swimming
- Inflammatory arthropathies including Rheumatoid Arthritis, Gout, and Pseudogout
- Septic arthritis
- Uncommon in AC joint but risk factors include trauma, recent surgery, IV drug abuse, immune-compromised, and hematogenous seeding among many others
- Joint instability
- Due to local elevation of contact stresses, dynamic loss of joint congruity, and alterations in range of motion
- Static Stabilizers
- Acromioclavicular Ligament
- Coracoclavicular Ligaments
- Dynamic Stabilizers
- Deltoid
- Trapezius
- Serratus Anterior
Associated Injuries
- Includes, but not limited to[5]
- Rotator Cuff Tear
- Rotator Cuff Tendonitis
- Glenoid Labral Tears
- Proximal Biceps Tendon Injuries
- Sports
- Weightlifting
- Basketball
- Swimming
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)
Diagnosis
- History
- Can be difficult to distinguish from other causes of shoulder pain
- Often another pathology co-occurs including rotator cuff tears, labral injuries, and biceps tendonitis
- The patient may report pain with passive and active range of motion
- Pain typically anterior shoulder but can be referred to as anterolateral neck, anterolateral deltoid, and trapezius[6]
- Physical: Physical Exam Shoulder
- Inspection: AC Joint may demonstrate swelling, deformity, or prominence[7]
- Tenderness to AC joint is sensitive, not specific[8]
- Special Tests
- Crossover Test: Examiner passively flexes, adducts arm across body
- Resisted AC Joint Extension Test: Flex, internally rotate the shoulder and abduct against resistance
- OBriens Test: Shoulder flexed to 90, flexes further against resistance
- The crossover test most sensitive (77%), O’Briens Test is the most specific (95%)[9]
- One Finger Test: Have the patient point to the most painful spot with 1 finger (AC joint = positive)
Ultrasound demonstrating AC joint OA
- Radiographs
- Typically begin with Standard Radiographs Shoulder
- Zanca View: 10-15° cephalad tilt best visualizes joint
- OA Findings: joint space narrowing, subchondral cysts, osteophytes, and subchondral sclerosis
- May see distal clavicle osteolysis
- Asymptomatic AC joint OA findings are common (need citation)
- CT
- Allows superior osseous visualization[10]
- MRI
- Superior visualization of soft tissue lesions
- Ultrasound
- Ultrasound can detect AC joint changes reliably[11]
- Sensitivity and specificity for arthritis are unknown
- Diagnostic Injection
- See: Acromioclavicular Joint Injection
- The diagnostic injection can help clarify the etiology of shoulder pain
- Ultrasound improves injection accuracy from 70%-75% to 90%-98%[12][13]
Treatment
Nonoperative
- First-line therapy in most patients
- Activity Modification
- Avoid: aggravating activities such as cross-body, pushing, weight lifting, throwing, overhead work
- Physical Therapy
- Can help with range of motion, flexibility, and strength[14]
- Temporary immobilization with Shoulder Sling in the setting of acute exacerbation
- Medications including NSAIDs, Acetaminophen
- Corticosteroid Injection
- See: Acromioclavicular Joint Injection
Operative
- Indications
- Failure of non-operative therapy
- Technique
- Arthroscopic clavicle resection
- Open clavicle resection (Mumford procedure)
