Posterior Shoulder Instability

Abstract

Posterior shoulder instability describes a variety of conditions ranging from acute traumatic dislocation to chronic subluxation. It accounts for up to 5% of all dislocations. Potential causes include repetitive posterior loading, high-energy trauma, electrocution, and seizures. Undiagnosed posterior shoulder instability can lead to chronic pain and reduced range of motion. Recognition of injury, acute reduction of any dislocation, and early rehabilitation are critical to maximizing the return of function and potential clearance for sport.

Keywords

posterior, shoulder, instability, dislocation, subluxation, electrocution, seizure

ICD-10-CM Codes

M25.311	Posterior shoulder instability, right shoulder
M25.312	Posterior shoulder instability, left shoulder
S43.024A	Posterior dislocation humeral head, initial encounter, right shoulder
S43.025A	Posterior dislocation humeral head, initial encounter, left shoulder
S43.025D	Posterior dislocation humeral head, subsequent encounter (right and left shoulders)
S43.025S	Posterior dislocation humeral head, sequela (right and left shoulders)
S43.021A	Posterior subluxation humeral head, initial encounter, right shoulder
S43.022A	Posterior subluxation humeral head, initial encounter, left shoulder
S43.021D	Posterior subluxation humeral head, subsequent encounter, right shoulder
S43.022D	Posterior subluxation humeral head, subsequent encounter, left shoulder
S43.021S	Posterior subluxation humeral head, sequela, right shoulder
S43.022S	Posterior subluxation humeral head, sequela, left shoulder

Key Concepts

•

Posterior shoulder instability describes a variety of conditions ranging from acute traumatic dislocation to chronic subluxation ( Fig. 27.1 ).
- •
  
  Dislocation: humeral head is forced out of glenoid cavity.
- •
  
  Subluxation: posterior movement of humeral head without complete escape from the glenoid rim; usually reduces spontaneously
Fig 27.1

Posterior instability.
•

Nonacute posterior instability is divided into three groups:
- •
  
  Recurrent dislocation
- •
  
  Recurrent subluxation
- •
  
  Pain with forward flexion, adduction, internal rotation, which is a position of instability
•

Approximately 50% of recurrent posterior instability has had an inciting injury, and up to 5% of patients with shoulder instability include a posterior element.
•

Posterior instability is often a result of subluxation more than dislocation.
•

Acute traumatic posterior instability usually occurs with a posterior force while the arm is in a position of instability.
- •
  
  Can be seen with electrocution, high-energy trauma, and seizure activity
•

Less than 5% of shoulder dislocations are posterior.
•

Chronic dislocations are those diagnosed more than 6 weeks from initial trauma.
•

Undiagnosed posterior dislocation can lead to chronic loss of range of motion.
•

Associated humeral head fractures may prevent self-reduction of acute posterior dislocations.
•

Posterior instability can be associated with posterior labral injury, posteroinferior capsular ligament damage, and/or poor rotator cuff function.
•

Glenoid hypoplasia or lack of normal concavity may increase the risk of multiple types of shoulder instability.

History

•

Obtain mechanism of injury (traumatic versus atraumatic), focus on arm position or activities that reproduce symptoms, and delineate between voluntary and involuntary instability.
•

Symptoms can range from mild discomfort with sport-specific activity to severe diffuse pain with limited range of motion and inability to perform activities of daily living.

Only gold members can continue reading. Log In or Register to continue