Shoulder Instability

Anterior Instability
Anterior instability can be defined subluxation or full dislocation of the humeral head in the glenoid fossa.  Anterior dislocation account for 95% of all dislocations.   Dislocations can occur secondary to blunt trauma, or non-competent soft tissue secondary to weakness, laxity or repetitive stress and micro trauma. 
The humeral head may also sublux, where the humeral head shifts anteriorly but reduces back to the join spontaneously.  Recurrent subluxation will increase joint laxity and can lead to further tissue damage and eventual dislocation.  Once a full dislocation is performed the recurrent rate for subsequent dislocations is approximately 70%. 
Dislocations will typically occur when the arm is abducted and externally rotated.  This may occur with blunt trauma, overhead activity during athletic events such volleyball or tennis, and or working overhead i.e. hammering above one’s head. 
The glenoid fossa is extremely shallow, allowing for large degrees of movement.  With little articulating surface available, boney congruency provides little stability.  The primary stabilizers of the Shoulder is provided by the capsular ligaments specifically, the superior, middle and inferior glenohumeral ligaments.  Based upon there anatomic locations the infraspinatus and teres minor both provide the most structural support and resistance to anterior translation of the humeral head during dynamic movement. 
It is important to note that an anterior dislocation can cause several lesions.
Bankart lesion: Detachment of the joint capsule from the fibro cartilaginous fossa/ligament
Hill-sachs lesion: A cortical depression of the humeral head resulting from a forceful anterior dislocation
Other damage: Glenoid Rim damage, Deficiencies in subscapularis, SLAP Lesion
Baker categorized Bankhart lesions as the following:
Type I – Pure capsular lesion
Type II – Partial labral detachment
Type III – Complete detachment of the inferior-labral complex
Clinical presentation:
Anterior Dislocation:
-Slight abduction
-ER
-Humeral head palpable
-Limited IR and adduction
-High pain
Posterior Dislocation:
-Adducted
-IR
-ER limited
-Posterior prominence noted
-Coracoid process is more prominent
Inferior dislocation:
-+ sulcus sign

Complications:
Axillary nerve injury: See axillary nerve injury page
Surgical interventions:
Bankhart- Reattachment of the labrum and anterior capsule to the glenoid lip without capsular tightening and subscap shortening
Putti-Platt-Subscapularis divided and shortened
Manson-Stack- Subscap insertion transferred to greater tuberosity
Bistrow- Transferring the tip of the coracoid process and its musculature attachments to the anterior glenoid provided a boney “block”.

General information Post op:
-Sling and immobilizer for 3-4 weeks, even during sleep
-Avoid any abduction an ER until protocol warrants
-Subscapularis is usually involved to early avoidance of Active or resistive IR
-Focus on ER mobilization at appropriate healing time