Dr. Kevin Yip

Dr Kevin Yip
Orthopaedic Surgeon
MBBS(UK), FRCS(EDIN), FAM(SING), FHKCOS(ORTHO)

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Shoulder Dislocation

Basics
Description
  • The shoulder joint has the greatest ROM of all joints in the body and, thus, is at high risk for dislocations.
  • Shoulder joint stability depends on various dynamic and static anatomical restraints.
    • Dynamic restraints include:
      • Tendon of the long head of the biceps
      • Scapular stabilizers
      • Rotator cuff muscles and tendons
    • Static restraints include:
      • Osseous anatomy (the glenoid fossa and humeral head)
      • Joint capsule
      • Glenohumeral ligaments (superior, middle, and inferior)
      • Glenoid labrum
  • Shoulder dislocations are classified by:
    • Direction of dislocation (anterior, posterior, inferior, or superior)
    • Chronology (acute versus chronic)
    • Force (traumatic versus atraumatic)
    • Patient contribution (voluntary versus involuntary)
Epidemiology
  • The shoulder is the most commonly dislocated joint in the body, accounting for up to 45% of all dislocations.
  • Anterior shoulder dislocations account for ~85% of all shoulder dislocations and are 8-9 times more common than posterior dislocations.
  • Inferior and superior dislocations are rare.
Etiology
  • Trauma (direct or indirect) is the most common mechanism of injury for all shoulder dislocations, and the direction of dislocation depends on direction of force.
  • Anterior shoulder dislocation:
    • Most common mechanism is indirect trauma to the upper extremity with the shoulder in abduction, external rotation, and extension
    • An anteriorly directed force to the posterior shoulder
  • Posterior shoulder dislocation:
    • Direct trauma, which leads to a posterior shoulder dislocation when a posteriorly directed force is applied to the anterior shoulder
    • Indirect trauma:
      • Axial loading to the upper extremity with the shoulder in a position of flexion, adduction, and internal rotation
      • Common causes: Seizures and electrocution. These causes produce a violent muscular contraction during which the internal rotators overwhelm the external rotators.
  • Inferior dislocations (also known as luxatio erecta) typically result from a hyperabduction force that levers the humeral head out inferiorly as the humeral neck impinges on the acromion.
  • Superior shoulder dislocations occur as extreme anterior and superior force is applied to the adducted arm, such as during a fall from a height.
Associated Conditions
  • Anterior shoulder dislocations can be associated with:
    • Greater tuberosity humeral fractures, glenoid rim fractures, coracoid or acromion fractures, posttraumatic degenerative changes and, in patients >40 years old, rotator cuff tears
    • Nerve injuries (typically neurapraxias of the axillary or musculocutaneous nerves)
    • Rarely, vascular injuries (usually in elderly atherosclerotic patients).
  • Posterior shoulder dislocations can be associated with:
    • Lesser tuberosity fractures of the humerus, glenoid rim fractures, humeral head and shaft fractures, and recurrent instability
    • Rarely, neurovascular injury
  • Inferior shoulder dislocations can be associated with:
    • Rotator cuff tears, proximal humerus fractures, neurovascular injuries, compressive neuropathy, and thrombosis of the axillary artery
  • Superior shoulder dislocations can be associated with:
    • Fractures of the coracoid, acromion, clavicle, and humeral tuberosities
    • Injury to the AC joint
    • Biceps tendon and rotator cuff injuries
Diagnosis
Signs and Symptoms
  • Anterior dislocations, commonly associated with trauma, are difficult to overlook on patient evaluation.
  • However, posterior dislocations frequently can be missed; they often are diagnosed late.
    • Detection of posterior dislocations is facilitated by heightened clinical suspicion of the injury in high-risk individuals and by appropriate radiographic investigation.
History
  • Patients most commonly present complaining of shoulder pain and limited ROM after direct or indirect trauma to the shoulder.
  • Patients with posterior dislocations can present after a seizure or electrocution event.
Physical Exam
  • The position of the arm typically gives the examiner a clue about the direction of dislocation.
    • Anterior dislocation: Affected shoulder is held in slight abduction and external rotation.
    • Posterior dislocation: Affected shoulder is held in adduction and internal rotation.
    • Inferior dislocations: Affected shoulder is held in characteristic salute fashion, with the humerus locked in 110-160° of flexion and abduction.
    • Superior dislocation: Foreshortened upper extremity held in adduction.
  • Inspection often reveals deformity in the shoulder region that varies with the direction of dislocation.
    • Anterior dislocations:
      • Squaring of the shoulder secondary to a relative prominence of the acromion anteriorly
      • A palpable mass (the humeral head) anteriorly
      • A hollow beneath the acromion posteriorly
    • Posterior dislocation:
      • A flattening of the shoulder anteriorly
      • A palpable mass (the humeral head) posteriorly
      • A prominent coracoid anteriorly
      • Mechanical block to external rotation (often <0°)
    • Inferior dislocations:
      • Humeral head is palpable on the lateral chest wall and axilla.
      • Do not confuse this dislocation with a step-off between the distal clavicle and the acromion in a shoulder separation.
    • Superior dislocations:
      • The humeral head rides above the level of the acromion.
      • The arm is shortened compared with the contralateral side.
      • Shoulder movement is restricted.
  • Neurovascular examination:
    • Assess radial and ulnar pulses and capillary refill.
    • Focus on the integrity of the axillary nerve (which provides sensation to the lateral shoulder) is essential.
    • A sensory examination is critical because deltoid motor function often is limited secondary to pain and accompanying muscle spasm.
Tests
Imaging
  • Plain radiographs typically are the only imaging studies necessary in the diagnostic workup of acute shoulder dislocations.
    • AP view of the shoulder is diagnostic for superior and inferior dislocations.
    • The axillary view of the shoulder is definitive determination of the direction of the dislocation as anterior or posterior.
    • Radiographic findings may include:
      • A Hill-Sachs lesion of the posterior aspect of the humeral head
      • Bony Bankart lesion
      • Fracture of the anterior-inferior glenoid
  • CT scans:
    • May be useful in defining humeral head or glenoid impression fractures, loose bodies, and anterior labral bony injuries
    • Seldom are necessary for the diagnosis of acute shoulder dislocations.
Treatment
General Measures
  • Treatment consists of closed reduction of the dislocation followed by a period of immobilization.
    • Sufficient muscle relaxation for a successful outcome may require analgesia and/or sedation, or occasionally general anesthesia.
    • Anterior dislocation: Traction-countertraction, Hippocratic technique, Stimson technique, Milch technique, and scapular manipulation
    • Posterior dislocation:
      • Requires traction to the adducted arm as the humeral head is lifted into the glenoid fossa
      • Because of frequent late presentation, may become locked and difficult, if not impossible, to reduce
    • Inferior or superior dislocation: Traction countertraction maneuvers
  • Repeat neurovascular examination and radiographs (including an axillary view) should be obtained to verify the reduction.
Activity
  • The duration of immobilization after successful closed and postoperative reduction depends on patient age and dislocation direction.
    • Reduced anterior dislocation:
      • Patients <40 years old: Immobilization in neutral or external rotation for 3-4 weeks
      • Patients >40 years old: Immobilization in neutral or external rotation for ~1-2 weeks
    • Reduced posterior dislocation: Immobilization in neutral rotation for ~4 weeks
    • Reduced superior or inferior dislocation: Immobilization in neutral rotation for 3-6 weeks
  • During the immobilization period, daily elbow ROM exercises should be performed.
Special Therapy
Physical Therapy
Aggressive physical therapy should be instituted after immobilization to restore ROM not only to the affected shoulder but also to the ipsilateral hand, wrist, and elbow.
Surgery
  • The irreducible or open acute shoulder dislocation requires urgent open reduction.
  • Nonurgent surgical indications relate to associated injuries and include:
    • Tuberosity fractures displaced >5 mm
    • Lesser tuberosity fractures displaced >1 cm
    • Humeral impaction fractures involving >20% of the humeral head
    • Glenoid rim fractures >5 mm.
  • In addition, recurrent shoulder instability may be an indication for surgery (see Shoulder Instability chapter).
Follow-up
Prognosis
  • The prognosis after shoulder dislocation depends on the age of the patient and direction of dislocation.
    • Anterior dislocation:
      • The risk of recurrence is ~85% in patients who 1st dislocate at the age of <20 years and decreases to 10-15% in patients who 1st dislocate at the age of >40 years.
      • If no associated injuries or recurrent instability episodes occur, the outcome is good to excellent in most patients.
Miscellaneous
Codes
ICD9-CM
  • 831.01 Anterior dislocation of humerus
  • 831.02 Posterior dislocation of humerus
  • 831.03 Inferior dislocation of humerus
FAQ
Q: Is an axillary radiograph necessary for the evaluation of suspected shoulder dislocation?
A: Yes. The axillary view is essential to determine definitively the direction of the dislocation as anterior or posterior. It also provides an excellent view of the glenoid rim to assess for possible fractures. After a reduction maneuver, it is the best view with which to confirm appropriate reduction.
Q: What is the best method for reducing an anterior dislocation?
A: No single best method exists. Several methods (traction-countertraction, Hippocratic technique, Stimson technique, scapular manipulation, Milch technique) have proved successful. Familiarity with >1 method is useful in the event of a difficult reduction. The Kocher maneuver is not recommended because it is associated with a higher rate of fracture than other reduction methods.
Q: What is the risk of recurrent instability after a first-time dislocation?
A: The risk of recurrent instability varies with the age of the patient. The rate is ~85% in patients who 1st dislocate at the age of <20 years, and it decreases steadily to a rate of 10-15% in patients who 1st dislocate at the age of >40 years.

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