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)

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

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

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