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For further information, see CMDT Part 41-02: Musculoskeletal Injuries of the Shoulder

Key Features

Essentials of Diagnosis

  • Most dislocations (95%) are in the anterior direction

  • Pain and apprehension with an unstable shoulder that is abducted and externally rotated

  • Acute shoulder dislocations should be reduced as quickly as possible, using manual relocation techniques if necessary

General Considerations

  • Stabilizing the shoulder joint relies heavily on rotator cuff muscle strength and scapular control

  • Anterior dislocations/instability

    • Usually caused by a fall on an outstretched and abducted arm

    • Patients complain of pain and feeling of instability when the arm is in the abducted and externally rotated position

  • Posterior dislocations are usually caused by

    • Falls from a height

    • Epileptic seizures

    • Electric shocks

  • Traumatic shoulder dislocation can lead to instability

  • The rate of repeated dislocation is directly related to the patient's age

    • Patients aged 21 years or younger have a 70–90% risk of redislocation

    • Patients aged 40 years or older have a much lower rate (20–30%)

  • 90% of young active individuals with traumatic shoulder dislocation have labral injuries often described as Bankart lesions, which can lead to continued instability

  • Older patients (over age 55 years) are more likely to have rotator cuff tears or fractures following dislocation

  • Atraumatic shoulder dislocations

    • Usually caused by intrinsic ligament laxity or repetitive microtrauma leading to joint instability

    • Often seen in athletes involved in overhead and throwing sports (eg, swimmers, gymnasts, and pitchers)

Clinical Findings

  • For acute traumatic dislocations,

    • The humeral head is dislocated anteriorly

    • Patients hold the shoulder and arm in an externally rotated position

    • Acute pain

    • Deformity

  • Patients with recurrent dislocations can have less pain with subsequent dislocations.

  • Posterior dislocations

    • Can be easily missed because the patient usually holds the shoulder and arm in an internally rotated position, making the shoulder deformity less obvious

    • Patients complain of difficulty pushing open a door

  • Atraumatic shoulder instability

    • Usually well tolerated with activities of daily living

    • Patients usually complain of a "sliding" sensation during exercises or strenuous activities, such as throwing

    • Such dislocations may be less symptomatic and can often undergo spontaneous reduction of the shoulder with pain resolving within days after onset

Diagnosis

Clinical examination

  • The clinical examination for shoulder instability includes the

    • Apprehension test

    • Load and shift test

    • O'Brien test (Table 41–1)

  • Most patients with persistent shoulder instability have preserved range of motion

Imaging

  • Radiographs for acute dislocations should include a standard trauma series of anteroposterior (AP) and axillary lateral scapula (glenohumeral) views to determine the relationship of the humerus and the glenoid and to rule out fractures

  • Orthogonal views are used to identify a posterior shoulder dislocation, which can be missed easily with one AP view of the shoulder

  • An axillary lateral view of the ...

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