Multidirectional shoulder instability

Last revised by Henry Knipe on 30 Nov 2021

Multidirectional shoulder instability is characterized by recurrent atraumatic instability of the glenohumeral joint due to a lax joint capsule.

Also known as AMBRII - atraumatic, multidirectional, bilateral, responds to rehabilitation, inferior capsular shift, and interval closure 4.

It is more common in young female patients less than 30 years of age.

Multidirectional instability is due to congenital laxity of the joint capsule. It is atraumatic and commonly bilateral. Poor coordination of the rotator cuff muscles contributes to the worsening of laxity. In some cases, it may have ​psychiatric cause with subjective symptoms that are not relieved by surgery. There is a positive family history in a minority of cases with genetic abnormal collagen production or cross-linking; e.g. Marfan or Ehlers-Danlos syndrome

Usually, there is no abnormality of the labrum, ligaments or tendons nor evidence of previous shoulder dislocation. However, gradually the longterm subluxation results in labral injury and rotator cuff impingement.

Some of the possible radiologic findings are:

Treatment is mainly rehabilitation; if surgery required then tightening of the inferior capsule and rotator interval may prove helpful. 

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