Shoulder Dislocation & Instability

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