Shoulder instability

Shoulder instability can be functional or anatomical and can further be divided into:

• anterior
  • by far the most common, accounting for up to 95% of all cases
  • most frequently due to prior anterior shoulder dislocation
  • usually results from disruption of the anterior band of the inferior glenohumeral ligament (IGHL) e.g. Bankart lesion
• posterior
  • rare
  • also most frequently due to dislocation (posterior of course)
  • usually results from 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
  • 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 seconday 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.

Predisposing 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

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

See also

• shoulder dislocation