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Introduction ⬇

Incidence

Anterior dislocations represent 96% of shoulder dislocations.

Mechanism of Injury ⬆ ⬇

Anterior glenohumeral dislocation may occur as a result of trauma, secondary to either direct or indirect forces.

  • Indirect trauma to the upper extremity with the shoulder in abduction, extension, and external rotation is the most common mechanism.
  • Direct, anteriorly directed impact to the posterior shoulder may produce an anterior dislocation.
  • Convulsive mechanisms and electrical shock typically produce posterior shoulder dislocations, but they may also result in an anterior dislocation.
  • Recurrent instability related to congenital or acquired laxity or volitional mechanisms may result in anterior dislocation with minimal trauma.

Evaluation ⬆ ⬇

Clinical Evaluation

  • It is helpful to determine the nature of the trauma, the chronicity of the dislocation, pattern of recurrence with inciting events, and the presence of laxity or a history of instability in the contralateral shoulder.
  • The patient typically presents with the injured shoulder held in slight abduction and external rotation. The acutely dislocated shoulder is painful with muscular spasm.
  • Examination typically reveals squaring of the shoulder owing to a relative prominence of the acromion, a relative hollow beneath the acromion posteriorly, and a palpable mass anteriorly.
  • A careful neurovascular examination is important with attention to axillary nerve integrity. Deltoid muscle testing is usually not possible, but sensation over the deltoid may be assessed. Deltoid atony may be present and should not be confused with axillary nerve injury. Musculocutaneous nerve integrity can be assessed by the presence of sensation on the anterolateral forearm (Fig. 14.4).
  • Patients may present after spontaneous reduction or reduction in the field. If the patient is not in acute pain, examination may reveal a positive apprehension test, in which passive placement of the shoulder in the provocative position (abduction, extension, and external rotation) reproduces the patient’s sense of instability and pain (Fig. 14.5).

Radiographic Evaluation

  • Trauma series of the affected shoulder: Anteroposterior (AP), scapular-Y, and axillary views taken in the plane of the scapula (Figs. 14.6 and 14.7)
    • Prereduction radiographs should be considered in all first-time dislocations, patients over age 40 years, and following high-energy trauma because these patients have a higher risk of associated fracture.
  • Velpeau axillary: If a standard axillary cannot be obtained because of pain, the patient may be left in a sling and leaned obliquely backward 45 degrees over the cassette. The beam is directed caudally, orthogonal to the cassette, resulting in an axillary view with magnification (Fig. 14.8).
  • Special views:
    • West Point axillary: This is taken with patient prone with the beam directed cephalad to the axilla 25 degrees from the horizontal and 25 degrees medial. It provides a tangential view of the anteroinferior glenoid rim (Fig. 14.9).
    • Hill-Sachs view: This AP radiograph is taken with the shoulder in maximal internal rotation to visualize a posterolateral defect.
    • Stryker notch view: The patient is supine with the ipsilateral palm on the crown of the head and the elbow pointing straight upward. The x-ray beam is directed 10 degrees cephalad, aimed at the coracoid. This view can visualize 90% of posterolateral humeral head defects (Fig. 14.10).
  • Computed tomography may be useful in defining humeral head or glenoid impression fractures, loose bodies, and anterior labral bony injuries (bony Bankart lesion).
  • Single- or double-contrast arthrography may be utilized to evaluate rotator cuff pathologic processes.
  • Magnetic resonance imaging may be used to identify rotator cuff, capsular, and glenoid labral (Bankart lesion) pathologic processes.

Classification ⬆ ⬇

Degree of stability:Dislocation versus subluxation
Chronology:
  • Congenital
  • Acute versus chronic
  • Locked (fixed)
  • Recurrent
  • Acquired: generally, from repeated minor injuries (swimming, gymnastics, weights); labrum often intact but with capsular laxity; increased glenohumeral joint volume; subluxation common
Force:
  • Atraumatic: usually owing to congenital laxity; no injury; often asymptomatic; self-reducing
  • Traumatic: usually caused by one major injury; anterior or inferior labrum may be detached (Bankart lesion); unidirectional; generally requires assistance for reduction
Patient contribution:Voluntary versus involuntary
Direction:
  • Subcoracoid
  • Subglenoid
  • Intrathoracic

Treatment ⬆ ⬇

Nonoperative

  • Closed reduction should be performed after adequate clinical evaluation and administration of analgesics, intra-articular block, and/or sedation.
    • Traction–countertraction (Fig. 14.11)
    • Hippocratic technique: This is effective with only one person performing reduction, with one foot placed across the axillary folds and onto the chest wall, with gentle internal and external rotation with axial traction on the affected upper extremity.
    • Stimson technique: After administration of analgesics and/or sedatives, the patient is placed prone on the stretcher with the affected upper extremity hanging free. Gentle, manual traction or 5 lb of weight is applied to the wrist, with reduction effected over 15 to 20 minutes (Fig. 14.12).
    • Scapular manipulation technique: The patient is placed prone similar to the Stimson technique. Once the patent is relaxed, the inferior tip of the scapula is pushed medial and inferior while the superomedial scapula is held stationary.
    • Milch technique: With the patient supine and the upper extremity abducted and externally rotated, thumb pressure is applied by the physician to push the humeral head into place.
    • Kocher maneuver: The humeral head levered on the anterior glenoid to effect reduction; this is not recommended because of increased risk of fracture.
  • Postreduction care includes immobilization for 2 to 5 weeks. A shorter period of immobilization may be used for patients older than 40 years of age because stiffness of the ipsilateral hand, wrist, elbow, and shoulder tends to complicate treatment. Younger patients with a history of recurrent dislocation may require longer periods of immobilization.
  • In comparison to a simple sling, immobilization in a Velpeau dressing does not appear to alter the subsequent development of recurrent instability.
  • Controversy exists whether immobilization in internal or external rotation can better prevent recurrence of dislocation.
  • Therapy should be instituted following immobilization, including increasing degrees of shoulder external rotation, flexion, and abduction as time progresses, accompanied by full, active range of motion to the hand, wrist, and elbow.
  • Irreducible acute anterior dislocation (rare) is usually the result of interposed soft tissue and requires open reduction.

Operative

  • Indications for surgery include:
    • First-time dislocation in young active men
    • Soft tissue interposition
    • Displaced greater tuberosity fracture that remains >5 mm superiorly displaced following joint reduction
    • Glenoid rim fracture >5 mm in size
  • Surgery for stabilization typically involves arthroscopic ligamentous repair of the anterior/inferior labrum (Bankart lesion). Procedures such as capsular shift, capsulorrhaphy, muscle or tendon transfers, and bony transfers are reserved for refractory cases.
  • Postoperative management typically includes the use of a shoulder sling or immobilizer for up to 3 weeks in patients <30 years, 2 weeks for patients 30 to 40 years, and 1 to 2 weeks for patients >50 years of age, depending on the type of surgical stabilization. Patients are allowed to remove the immobilizer two to four times per day for shoulder, wrist, and hand range-of-motion exercises. Therapy is aimed at active and passive range of motion and regaining upper extremity strength.

Complications ⬆

  • Recurrent anterior dislocation: related to ligament and capsular changes
    • The most common complication after dislocation is recurrent dislocation.
    • Incidence:
      • Age 20 years: 80% to 92% (lower in nonathletes)
      • Age 30 years: 60%
      • Age 40 years: 10% to 15%
    • Most recurrences occur within the first 2 years and tend to occur in men.
    • Prognosis is most affected by age at the time of initial dislocation.
    • Incidence is unrelated to the type or length of immobilization.
    • Patient activity has been identified as an independent factor for developing recurrent instability.
  • Osseous lesions:
    • Hill-Sachs lesion
    • Glenoid lip fracture (“bony Bankart lesion”)
    • Greater tuberosity fracture
    • Fracture of acromion or coracoid
    • Posttraumatic degenerative changes
  • Soft tissue injuries:
    • Rotator cuff tear (older patients)
    • Capsular or subscapularis tendon tears
  • Vascular injuries: These typically occur in elderly patients with atherosclerosis and usually involve the axillary artery. They may occur at the time of open or closed reduction.
  • Nerve injuries: These involve most commonly the musculocutaneous and axillary nerves, usually in elderly individuals; neurapraxia almost always recovers, but if it persists beyond 3 months, it requires further evaluation with possible exploration.