Shoulder

Shoulder Dislocation

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Shoulder Dislocation, Glenohumeral Dislocation, Anterior Shoulder Dislocation, Posterior Shoulder Dislocation, Inferior Shoulder Dislocation, Luxatio Erecta

  • Epidemiology
  1. Incidence: 24 per 100,000 persons per year
    1. Most commonly dislocated joint (50% of all major joint dislocations)
  • Types
  • Dislocation
  1. Anterior dislocation (most common, 90% of dislocations)
    1. Humerus is displaced anteriorly relative to the glenoid cavity
    2. Results from fall on externally rotated, abducted and extended arm (throwing position)
    3. Humeral head lie may be subcoracoid (most common), subglenoid, subclavicular or intrathoracic
  2. Posterior dislocation (<4% of all Shoulder Dislocations)
    1. Large force at anterior Shoulder directed posteriorly against internally rotated arm, flexed Shoulder
    2. Often occurs secondary to Generalized Seizure (via forced internal rotation and adduction)
    3. Some patients can posteriorly dislocate voluntarily
    4. Often missed on provider evaluation
  3. Multidirectional instability
    1. Lax joint capsule allows multidirectional dislocation
  4. Inferior dislocation (Luxatio Erecta): Rare (<0.5% of all Shoulder Dislocations)
    1. Variant of anterior dislocation
    2. Result of high energy mechanism with exaggerated abduction, tearing the inferior capsule and labrum
    3. Associated with Fracture, Rotator Cuff Injury and neurovascular injury
    4. Patient presents locked with Forearm to forehead position, unable to move the arm out of this position
  • Pathophysiology
  • Mechanism
  1. General
    1. The Shoulder joint is unstable by nature
    2. The shallow glenoid fossa articulates only 20-30% of the humeral head
    3. Requires ligamentous (e.g. labrum) and tendons (rotator cuff) for stability
  2. Young patient
    1. Direct Trauma or sports injury (Contact Sports, Bicycle accident)
  3. Older patient
    1. Results from fall (often with Fracture)
  • Pathophysiology
  • Mnemonic TUBS-AMBRI
  1. First Type of Shoulder Dislocation (TUBS)
    1. Traumatic mechanism of injury
    2. Unilateral Shoulder involvement
    3. Bankart and Hill-Sachs glenohumeral Fractures
      1. Bankart lesion (Glenoid fossa avulsion)
      2. Hill-Sachs lesion (Humeral head avulsion)
    4. Surgery often required for management
  2. Second Type of Shoulder Dislocation (AMBRI)
    1. Atraumatic mechanism
    2. Multidirectional instability
    3. Bilateral Shoulder involvement
    4. Rehabilitation as primary management
    5. Inferior Capsular shift surgery
      1. Indicated for failed conservative therapy
  • Signs
  1. Acromion much more prominent
  2. Humeral head fullness absent under deltoid
    1. Leaves prominent cavity
    2. Dimpling at lateral Shoulder (inferior to acromion)
  3. Severe pain with any range of motion
    1. Arm "locked" in place (may be cradled by other hand)
    2. Patient refuses to move arm
  4. Anterior dislocation
    1. Affected Shoulder has squared off appearance
    2. Arm held externally rotated, and slightly abducted
    3. Anterior Shoulder appears full with anterior bulge
    4. Space below acromion appears empty
    5. Internal rotation painful
  5. Posterior dislocation
    1. Arm held in internal rotation and adduction
    2. Forearm rests on Abdomen
    3. Anterior Shoulder flat
    4. Prominent coracoid process
    5. External rotation painful and limited
    6. Assess neurovascular structures
      1. Check axillary nerve with deltoid sensation (lateral Shoulder sensation)
  6. Inferior dislocation
    1. Arm held abducted overhead with Forearm pronation (Luxatio Erecta)
    2. Evaluate carefully for associated neurovascular injury, Fracture or tendon/ligament injury
      1. Axillary artery injury (39% of cases)
      2. Brachial Plexus Injury (60% of cases)
      3. Labral and joint capsule injury
      4. Humerus Fracture
      5. Rotator Cuff Tear
  7. Other evaluation
    1. Evaluate for neurovascular injury with distal pulses, motor and sensation (esp. posterior dislocation)
    2. Evaluate for Axillary Nerve Injury (shrugging Shoulder)
  • Differential Diagnosis
  1. Acromioclavicular Separation (or AC Sprain)
  2. Distal Clavicle Fracture
  3. Humeral Neck Fracture
  1. Precautions: Posterior Shoulder Dislocation
    1. Easily missed on XRay since the humeral head will be roughly in proximity to glenoid (on AP film)
      1. However, Scapular Y View XRay should identify the Fracture (esp. with comparison views)
    2. Humeral head will have rounded appearance (lightbulb sign, gun barrel sign, drumstick sign)
      1. Results from internal rotation of the arm
      2. Loss of visibility of the greater tuberosity and lesser tuberosity contours
  2. Pre-reduction Shoulder XRay
    1. Not needed if low force mechanism with findings consistent with uncomplicated Anterior Shoulder Dislocation
      1. Especially on sideline (if no obvious signs of Fracture) or recurrent dislocator with atraumatic mechanism
      2. Early relocation without delay allows for an easier relocation prior to development of spasm
    2. Imaging Indications
      1. Age over 40 years or other risks for pathologic Fracture
      2. First-time Shoulder Dislocation
      3. Traumatic mechanism suggests risk for more significant injury (suspected Fracture)
      4. Unclear diagnosis
      5. Emond (2004) Acad Emerg Med 11(8): 853-8 [PubMed]
  3. Post-reduction Shoulder XRay
    1. Obtain in all cases
  4. Standard Views
    1. Anteroposterior (AP)
    2. Lateral Shoulder XRay (Transaxillary lateral often easiest)
    3. Scapular Y Xray
  5. Other XRay Views
    1. West Point View (glenoid cavity)
    2. Stryker View (Hill-Sachs Fracture)
  6. References
    1. Mallon (2013) Shoulder disorders, EM Bootcamp, Las Vegas
  • Management
  1. Acute Management
    1. See Shoulder Dislocation Management
    2. Do not attempt to reduce a chronic Shoulder Dislocation present for >3-4 weeks (>1 week in elderly)
      1. Prolonged dislocations form adhesions between Humerus and axillary artery
      2. Risk of axillary artery rupture on relocation maneuvers
      3. Relocation should be by orthopedic surgery typically in the operating room
      4. Herbert and Webley in Herbert (2015) EM:RAP 15(3): 1
      5. Verhaegen (2012) Acta Orthop Belg 78(3): 291-5 [PubMed]
      6. Sahajpal (2008) J Am Acad Orthop Surg 16(7): 385-98 [PubMed]
    3. Emergent orthopedic Consultation
      1. Neurovascular Injury
      2. Inferior Shoulder Dislocation
      3. Concurrent Proximal Humerus Fracture (e.g. surgical neck Fractures)
      4. Bankart fracturs >20% of inferior glenoid
      5. Failed emergency department reduction
        1. Soft tissue (long head biceps, subscapularis tendon) may block Shoulder relocation
  2. Chronic Management and prevention of recurrence
    1. See Shoulder Instability
  • Course
  • Primary Dislocation
  1. Anterior Shoulder Dislocation in under 25 years (even first episode)
    1. Surgical management results in fewer future dislocations
    2. Surgery also offers less risk of longterm instability and Traumatic Arthritis
  2. Age under 30 years
    1. Recurrence rate: 50%
    2. Surgery indicated for recurrent dislocation or Hill-Sachs lesion
      1. Restrict rotation
      2. Reinforce joint capsule
  3. Age over 40 years
    1. Shoulder stiffness common
    2. Dislocation recurs less frequently
  4. Age over 50 years
    1. Risk of concurrent Rotator Cuff Rupture: 50%
  • Complications
  1. Hill-Sachs Deformity (35-40% of cases)
    1. Cortical depression of humeral head (where it contacted the glenoid rim)
  2. Rotator Cuff Injury
    1. Age over 40 years old predicts Rotator Cuff Tear in 35% of dislocation cases
    2. Greater tuberosity Fracture predicts Rotator Cuff Tear in 40% of dislocation cases
    3. Axillary Nerve Injury predicts Rotator Cuff Tear in 100% of dislocation cases
  3. Neurovascular injury (esp.in elderly, inferior dislocation)
    1. Axillary Nerve Injury
    2. Brachial Plexus Injury
  4. Shoulder Labral Tear
    1. Anterior glenoid Labral Tear is most common
  5. Shoulder Instability
    1. Recurrent Shoulder Dislocation or Shoulder Subluxation
  6. Missed Posterior Shoulder Dislocation
    1. Humeral Head Avascular Necrosis
    2. Glenohumeral joint degeneration
    3. Chronic Shoulder Pain
  7. Adhesive Capsulitis
    1. Highest risk in Diabetes Mellitus and older patients
    2. Early Shoulder mobilization is preventive
  • References
  1. Dolbec (2019) Crit Dec Emerg Med 33(1): 17-25
  2. Kiel and Koneru (2019) Crit Dec Emerg Med 33(9): 17-27
  3. Hendey (2000) Ann Emerg Med 36:108-13 [PubMed]
  4. Hovelius (1996) J Bone Joint Surg 78-A: 1677-84 [PubMed]
  5. Monica (2016) Am Fam Physician 94(2): 119-27 [PubMed]