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)

Diagnosis

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

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 w/ 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 fx
    • Helps to confirm ant-post position of clavicle in injury types III-IV

Classification

• Type 1
  • AC ligament sprain; AC joint intact
  • Exam
    • 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
  • X-ray
    • 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
  • Exam
    • Prominent and tender AC joint w/ significant swelling
    • Minimal tenderness of CC ligaments reflecting lack of significant injury
    • May be instability of the distal clavicle in the horizontal plane
  • X-ray
    • Partial elevation of the distal clavicle w/ no or minimal widening of CC distance
• Type 3
  • AC and CC ligaments torn; complete dislocation of the joint
  • Exam
    • Deformity of the AC joint is clearly visible
    • Marked tenderness of CC ligaments (helps distinguish Type 3 from type 2)
  • X-ray
    • Elevated distal clavicle and increased CC distance
    • Distal clavicle is positioned above the plane of the top of the acromion
• Type 4
  • Complete dislocation w/ posterior displacement of distal clavicle in/through trapezius
  • Exam
    • Palpable posterior fullness or deformity despite significant swelling
    • SC dislocation may be appreciated
  • X-ray
    • 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
  • Exam
    • 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 pt shrugs shoulder
  • X-ray
    • Clavicle is elevated above acromion approximately 1-3x width of the clavicle
    • CC distance is increased 2-3x normal range
• Type 6
  • Complete dislocation w/ clavicle displaced inferiorly
  • X-ray
    • Complete disruption of the AC and CC ligaments

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

Treatment

• 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 x3-7 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

See Also

Shoulder diagnoses