Shoulder Instability

Normal Anatomy

  • The fossa is relatively shallow and deepened by the glenoid labrum
  • The humeral head represents 2/5 of a sphere and faces superiorly, medially and posteriorly
  • The ratio of the humeral head to glenoid fossa is similar to a golf ball on a tee
  • Glenoid labrum acts to deepen the glenoid fossa to increase static stability
  • Shoulder relies on dynamic stability

Pathology

  • Excessive movement of the humerus on the glenoid which can result in dislocations or subluxation
  • Many different types of causes

Types and Mechanism of Injury

Acute Anterior Dislocation

  • Traumatic displacement of the humerus anteriorly in relation to the glenoid
  • Forceful external rotation in an abducted position
  • Direct blow to the shoulder in a posterior anterior direction
  • Falling onto an outstretched arm

Acute Posterior Dislocation

  • Rare and usually missed
  • Traumatic displacement of the humerus posteriorly in relation to the glenoid
  • Caused by fits, seizures or electrocutions
  • Falling onto an outstretched arm

Congenital Laxity

  • Connective tissue abnormality resulting in a laxity of the capsular ligaments
  • Poor motor control and use of dynamic stabilisers to provide stability
  • Laxity becomes instability as soon as it becomes pathological i.e pain, impingement, labral tear

Acquired Laxity

  • Chronic repetitive stress with overhead sports causes a weakening of the static restraints
  • The majority of the time participants in overhead sports are already lax, which is what enables them to excel at their sport
  • Positions of combined external rotation and abduction cause a particular weakening to the anterior inferior capsule

Associated Pathologies

Anterior Dislocation

Hill Sachs Lesion
  • Compression fracture behind posterolateral humeral head as its pressed posteriorly against the glenoid
Bankart Lesion
  • Tearing of inferior glenohumeral ligament complex and labrum from glenoid
  • Can also result in a fracture to the glenoid

Posterior Dislocation

Reverse Hill Sachs Lesion
  • Compression fracture behind anterior humeral head as its pressed anteriorly against the glenoid

Congenital Laxity

Chronic Dislocations
  • Repeated dislocation and subluxation, sometimes without or only relatively minor trauma

Acquired Laxity

Internal Impingement
  • See relevant hand out
SLAP Lesions
  • See relevant hand out
External Impingement
  • See relevant hand out

Examination

Anterior Dislocation

Subjective

  • Usually traumatic
  • Mechanism of injury as stated above
  • Usually attended A&E where relocation was completed and X-rays taken
  • Immobilisation by A&E

Objective

  • Step deformity if seen acutely
  • Protective posturing
  • Spasm and guarding
  • Significant pain
  • Global loss of range of movement
  • Loss of abduction and external rotation after immobilisation due to capsular scarring

Further Investigation

  • X-ray
  • MRI

Posterior Dislocation

Subjective

  • Usually traumatic
  • Mechanism of injury as stated above
  • Usually attended A&E where X-rays taken
  • Commonly missed
  • Immobilisation by A&E

Objective

  • Anterior flattening if seen acutely
  • Protective posturing
  • Spasm and guarding
  • Significant pain
  • Global loss of range of movement
  • Loss of internal rotation and horizontal adduction after immobilisation due to capsular scarring

Further Investigation

  • X-ray
  • MRI

Congenital Laxity

Subjective

  • History of recurrent dislocations
  • History of hypermobility
  • Associated connective tissue disease i.e hypermobility syndrome, Ehlers-Danlos syndrome
  • Vague aching around the shoulder

Objective

  • Excessive range of movement globally
  • Poor dynamic control
  • Beighton score 4/9 or greater

Special Tests

  • Inferior sulcus Test
  • Apprehension Sign
  • Relocation Test

Further Investigation

  • Blood Tests
  • X Ray

Acquired Laxity

Subjective

  • Overhead sports
  • Signs and symptoms consistent with associated pathology

Management

  • For detailed rehabilitation principles see (Wilk et al., 2006)

Anterior Dislocation

Conservative

  • Relocation
  • Sling for comfort
  • Immobilization to allow scaring of capsule
  • Restore Normal Mobility
  • Pain free passive mobilisations
  • Immediate Isometrics and rhythmic stabilisations
  • As pain allows
  • Closed chain exercises are usually more comfortable
  • Restore Normal Strength
  • Once ROM allows start scapular, external rotation and internal rotation strengthening

Surgery

  • Young sports people and repetitive dislocations are usually considered for surgery
  • If you’re unsure of suitability for surgery ALWAYS check with a shoulder specialist surgeon
  • Dependent on surgeon preference and associated pathologies
  • Bankhart Repair

Management

Posterior Dislocation

Conservative

  • Relocation
  • Sling for comfort
  • Immobilization to allow scaring of capsule
  • Restore Normal Mobility
  • Pain free passive mobilisations
  • Immediate Isometrics and rhythmic stabilisations
  • As pain allows
  • Closed chain exercises are usually less comfortable
  • Restore Normal Strength
  • Once ROM allows start scapular, external rotation strengthening

Surgery

  • Young sports people and repetitive dislocations are usually considered for surgery
  • If you’re unsure of suitability for surgery ALWAYS check with a shoulder specialist surgeon
  • Dependent on surgeon preference and associated pathologies

Management

Congenital Laxity

Conservative

  • Avoid aggravating activities
  • Minimal to zero stretching
  • Restore Normal Motor Control and Strength
  • Closed Chain
  • Rotator cuff, scapular stabilisers
  • Restore Proprioception
  • Return to Sport/Activity Specific Exercises

Surgery

  • Young sports people and repetitive dislocations are usually considered for surgery
  • If you’re unsure of suitability for surgery ALWAYS check with a shoulder specialist surgeon
  • Dependent on surgeon preference and associated pathologies
  • Capsular Shift

Management

Acquired Laxity

Conservative

  • Avoid aggravating activities
  • Manage associated pathology
  • Restore Normal Mobility
  • Reduced Swelling and Inflammation
  • Reduce soft tissue trauma
  • Reduce capsule restrictions if present
  • Restore Normal Motor Control and Strength
  • Closed Chain
  • Rotator cuff, scapular stabilisers
  • Restore Proprioception
  • Return to Sport/Activity Specific Exercises

Surgery

  • Dependent on surgeon preference and associated pathologies

References

(Hayes et al., 2002; Jaggi & Lambert, 2010; Reinold & Curtis, 2013; Wilk et al., 2006)

Hayes K, Callanan M, Walton J, Paxinos A, Murrell GA. Shoulder instability: management and rehabilitation. J Orthop Sports Phys Ther 2002; 32(10): 497-509.

Jaggi A, Lambert S. Rehabilitation for shoulder instability. Br J Sports Med 2010; 44(5): 333-40.

Reinold MM, Curtis AS. Microinstability of the shoulder in the overhead athlete. Int J Sports Phys Ther 2013; 8(5): 601-16.

Wilk KE, Macrina LC, Reinold MM. Non-operative rehabilitation for traumatic and atraumatic glenohumeral instability. N Am J Sports Phys Ther 2006; 1(1): 16-31.

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