Glenohumeral instability

Shoulder instability is tendency of the glenohumeral joint to sublaxsublux or dislocate due to loss of it'sits normal functional functional or anatomical stabilizers:

• static or anatomical:
  • articular surface 
  • labrum
  • glenohumeral ligaments
  • glenohumeral joint capsule
  • coroacoacromial arch
  • negative adhesive adhesive forces 
• dynamic or functional:
  • rotator cuff
  • long head of biceps tendon

Shoulder instabilitycan further be divided into:

• anterior
  • by far the most common, accounting for up to 95% of all cases
  • also known as TUBS  TUBS (Traumatic Unilateral Unilateral dislocations with a Bankart Bankart lesion requiring Surgery Surgery)
  • most frequently due to prior prior anterior shoulder dislocation
  • usually results from anterior glenolabral injury, particularly from disruption from disruption of the anterior band of the inferior glenohumeral ligament (IGHL) e.g. Bankart lesion
• posterior
  • rare
  • also most frequently due to posterior shoulder dislocation
  • usually results from posterior glenolabral injury, particularly from disruption disruption of the posterior band of the inferior glenohumeral ligament (IGHL) e.g. reverse Bankart lesion, or disruption of the posterior labrum and/or glenoid rim e.g. Bennett lesion
• multidirectional
  • AMBRI (atraumatic, multidirectional, bilateral, rehabilitation, and occasionally requiring an inferior capsular shift)
  • usually not due to previous dislocation, but rather congenital joint capsule laxity
  • often bilateral
• superior
  • usually associated with multidirectional

As a result of this greater mobility, a number of secondaysecondary changes may become evident, including:

• subacromial spur formation
• hypertrophy of the greater tuberosity
• coracoacromial ligament hypertrophy

These changes, in turn, may lead to shoulder impingement.

Risk factors

• previous traumatic dislocation (especially anterior shoulder dislocation)
• athletes (throwing, swimming, tennis)
• congenital
  • dysplastic glenoid
  • medial anterior shoulder capsular insertion (type III)
  • absent or small glenohumeral ligaments
  • congenital laxity of capsule or ligaments

Treatment and prognosis

In general, both anterior and posterior instability requires surgical repair and strengthening of the capsule.

Multi-directional instability is usually treated conservatively with rotator cuff strengthening exercises ².