Acromioclavicular joint injury

Background

• Occurs via direct trauma to the adducted shoulder
• Acromioclavicular and coracoclavicular ligaments may be affected
• Routine use of stress radiographs is controversial (low yield)

Clinical Features

• Tenderness directly over AC joint (with possible deformity)
• AC compression test
  • Passively flex arm so It is parallel with ground; then passively adduct across body
    • Pain suggests AC joint injury

Differential Diagnosis

Shoulder and Upper Arm Diagnoses

Traumatic/Acute:

• Shoulder Dislocation
  • Anterior shoulder dislocation
  • Posterior shoulder dislocation
  • Inferior shoulder dislocation
• Clavicle fracture
• Humerus fracture
• Scapula fracture
• Acromioclavicular joint injury
• Glenohumeral instability
• Rotator cuff tear
• Biceps tendon rupture
• Triceps tendon rupture
• Septic joint

Nontraumatic/Chronic:

• Rotator cuff tear
• Impingement syndrome
• Calcific tendinitis
• Adhesive capsulitis
• Biceps tendinitis
• Subacromial bursitis
• Cervical radiculopathy

Refered pain & non-orthopedic causes:

• Referred pain from
  • Neck
  • Diaphragm (e.g. gallbladder disease)
• Brachial plexus injury
  • Rucksack paralysis
• Axillary artery thrombosis
• Thoracic outlet syndrome
• Subclavian steal syndrome
• Pancoast tumor
• Myocardial infarction
• Pneumonia
• Pulmonary embolism

Evaluation

Imaging

AC joint separation

• AP shoulder (highly consider comparison view)
  • AC joint
    • Normal width of AC joint in adults is 1-3mm
    • By age 60 width is often less than 1mm
    • Children and adolescents have a slightly wider joint space
  • CC joint
    • Normal distance is 11-13mm
    • Comparison to opposite CC joint space is more important
      • Increase in CC distance of 25-50% indicates complete CC ligament disruption
  • Zanca view (AP with 10-15 degree cephalic tilt)
    • Consider if AP view is ambiguous, concern for type II injury or distal clavicle injury
  • Axillary view
    • Obtain if coracoid tenderness is present to rule-out associated coracoid fracture
    • Helps to confirm ant-post position of clavicle in injury types III-IV

Classification

Classification	Anatomic Injury	Exam	X-ray
Type 1	AC ligament sprain AC joint intact	Mild swelling, no deformity CC ligaments are nontender Only distal-most 1-2cm of clavicle is tender Active overhead and cross-body ROM are limited by pain	Often no abnormality is seen on xray Slight widening of the AC joint may occur
Type 2	AC ligament torn Coracoclavicular (CC) ligament may be partially torn but is intact	Prominent and tender AC joint with significant swelling Minimal tenderness of CC ligaments reflecting lack of significant injury May be instability of the distal clavicle in the horizontal plane	Partial elevation of the distal clavicle with no or minimal widening of CC distance
Type 3	AC and CC ligaments torn Complete dislocation of the joint	Deformity of the AC joint is clearly visible Marked tenderness of CC ligaments (helps distinguish Type 3 from type 2) Palpable posterior fullness or deformity despite significant swelling	Elevated distal clavicle and increased CC distance Distal clavicle is positioned above the plane of the top of the acromion
Type 4	Complete dislocation with posterior displacement of distal clavicle in/through trapezius	SC dislocation may be appreciated	Axillary view required to visualize the posterior dislocation
Type 5	More severe form of type III injury Superior dislocation of the joint of 1-3x the normal spacing CC ligament distance is increased 2-3x normal *Disruption of the deltotrapezial fascia	Shoulder appears to droop Severe superior displacement of clavicle (may cause tenting, ischemia of skin) Clavicle is perhced above the muscle and does not reduce when patient shrugs shoulder	Clavicle is elevated above acromion approximately 1-3x width of the clavicle CC distance is increased 2-3x normal range
Type 6	Complete dislocation with clavicle displaced inferiorly		Complete disruption of the AC and CC ligaments

Management

Type 1

• Rest, ice, sling
• ROM and strengthening exercises as soon as tolerated
• Return to sport or work is limited only by pain

Type 2

• Rest, ice, sling x 3-7 days
• ROM and strenghtnening exercises as soon as tolerated
• Return to sport or work once full ROM and strength are regained

Type 3

• Rest, ice, sling x2-3 weeks
• ROM and strengthening exercises as soon as tolerated
• Return to sport or work 6-12 weeks following injury
• Ortho consultation within 1 week

Types 4-6

• Require orthopedic evaluation; emergent if neurovascular compromise exists
• Generally operative

Disposition

• Generally outpatient, unless neurovascular compromise

See Also

• Shoulder diagnoses