Acromioclavicular joint injury

Background

Right shoulder anatomy with AC Ligaments.

• Occurs via direct trauma to the adducted shoulder
• Accounts for 40% of all shoulder injuries and 10% of all injuries in collision sports (football, hockey, etc.)
• Acromioclavicular (AC) and coracoclavicular (CC) ligaments may be affected
• Routine use of stress radiographs is controversial (low yield)

Clinical Features

Acromion-clavicle injury. Note that the left shoulder is lower and the "piano key"; Screws on the radiography are a former trauma repair and unrelated to present trauma.

• 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
• Ability to touch contralateral shoulder with injured arm suggests lack of shoulder dislocation

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

Workup

• 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

Diagnosis

AC joint separation

Classification	Anatomic Injury	Exam	X-ray	Image
Type I	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 II	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 III	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 IV	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 V	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 VI	Complete dislocation with clavicle displaced inferiorly		Complete disruption of the AC and CC ligaments

Management

Type I

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

Type II

• 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 III

• 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 IV-VI

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

Disposition

• Admission Criteria
  • Neurovascular compromise
  • Open or unstable fractures
  • Admission for operative repair may be needed for Types IV, V, and VI
• Discharge Criteria
  • Type I/Type II may be discharged with orthopedic follow-up
  • Type III may be discharged with urgent orthopedic follow-up

See Also

• Shoulder diagnoses