Introduction

The glenohumeral joint of the shoulder has minimal anatomic constraint and a high degree of mobility. It is the most commonly dislocated large joint, with injury patterns including both high- and low-energy mechanisms (▶Video 20.1).

I. Preoperative

1. 
   

   History

   
   
   
   
   1. 
      

      Either high-energy or low-energy trauma mechanisms.

      
      
   2. 
      

      Pain and inability to actively move the shoulder joint.

   
   
2. 
   

   Physical examination

   
   
   
   
   1. 
      

      Arm position:

      
      
      
      
      1. 
         

         Anterior dislocation—painful, mildly abducted, and externally rotated arm with inability to reach the hand across to the opposite shoulder.

         
         
      2. 
         

         Posterior dislocation—adducted and internally rotated arm with inability to actively externally rotate.

         
         
      3. 
         

         Inferior dislocation (Luxatio Erecta)—shoulder fixated in a flexed or abducted position following a forced traumatic hyperabduction episode.

      
      
   2. 
      

      Neurovascular examination—axillary nerve sensation on lateral aspect of the upper arm typically decreased, and there was difficulty in assessing motor function before or after reduction.

   
   
3. 
   

   Anatomy

   
   
   
   
   1. 
      

      Convex humeral head articulates with the concave glenoid fossa of the scapula–Static soft tissue constraints (see Chapter 18, Clavicle Fractures, ▶ Fig. 18.1 ).

      
      
      
      
      1. 
         

         Superior glenohumeral ligament—resists anterior translation/dislocation of the humeral head, while the shoulder is in a neutral position.

         
         
      2. 
         

         Middle glenohumeral ligament—primary restraint to anterior dislocation when the shoulder is externally rotated with abduction to approximately 45 degrees.

         
         
      3. 
         

         Anterior–inferior glenohumeral ligament—anterior restraint with shoulder abduction up to 90 degrees.

         
         
      4. 
         

         Posterior–inferior glenohumeral ligament—primary static restraint to posterior dislocation.

         
         
      5. 
         

         Fibrocartilaginous glenoid labrum—increases the contact area for the glenohumeral articular surface. Attachment surface for the capsule and glenohumeral ligaments.

         
         
      6. 
         

         Musculotendinous rotator cuff—applies stabilizing counter forces on the humerus to maintain glenohumeral alignment during active shoulder motion.

   
   
4. 
   

   Imaging

   
   
   
   
   1. 
      

      Orthogonal radiographs:

      
      
      
      
      1. 
         

         Grashey or Neer anteropoterior (AP) image (▶ Fig. 20.1a ):

         

         
         
         
         
         • 
           

           i. Taken in the coronal plane of the scapula.

           
           
         • 
           

           ii. No overlap between the reduced humeral head and the glenoid.

         
         
      2. 
         

         Scapular Y lateral image:

         
         
         
         
         • 
           

           i. Shows anterior or posterior displacement of the humeral head.

           
           
         • 
           

           ii. Can be difficult to assess due to overlapping structures.

         
         
      3. 
         

         Axillary lateral (▶ Fig. 20.1b ) or Velpeau image:

         
         
         
         
         • 
           

           i. Eliminates overlapping structures.

           
           
         • 
           

           ii. Improves lateral visualization of the glenohumeral articulation.

           
           
         • 
           

           iii. In Velpeau image, there is easier patient positioning for painful shoulder.

      
      
   2. 
      

      Advanced imaging—not routinely necessary for acute dislocation management:

      
      
      
      
      1. 
         

         Computed tomography (CT) scan—assesses bone integrity in fracture dislocations.

         
         
      2. 
         

         Magnetic resonance imaging (MRI)—evaluation of soft tissue damage for reconstruction/stabilization.

         
         
         
         
         • 
           

           i. Increasing acute utilization following traumatic dislocations due to high incidence of associated ligamentous or labral injuries.

   
   
5. 
   

   Classification

   
   
   
   
   1. 
      

      Anatomic—direction of humeral dislocation:

      
      
      
      
      1. 
         

         Anterior, posterior, and inferior.

         
         
      2. 
         

         95% of dislocations are anterior.

      
      
   2. 
      

      Descriptive classification of anterior glenohumeral dislocations:

      
      
      
      
      1. 
         

         “TUBS” injuries:

         
         
         
         
         • 
           

           i. Traumatic mechanism.

           
           
         • 
           

           ii. Unidirectional instability episodes.

           
           
         • 
           

           iii. Bankart lesion—resultant disruption of the glenoid labrum.

           
           
         • 
           

           iv. Surgical management—frequently necessary for addressing significant associated injuries with this type of dislocation.

         
         
      2. 
         

         “AMBRI” injury pattern:

         
         
         
         
         • 
           

           i. Atraumatic injury.

           
           
         • 
           

           ii. Multidirectional shoulder instability.

           
           
         • 
           

           iii. Bilateral shoulder instability issues are commonly identified.

           
           
         • 
           

           iv. Rehabilitation—expected to respond favorably to dynamic stabilization physical therapy protocols.

           
           
         • 
           

           v. Inferior capsular shift—shoulder stabilization procedure for multidirectional instability after exhausting all therapy options.

      
      
   3. 
      

      Posterior shoulder dislocations:

      
      
      
      
      1. 
         

         Occur with shoulder adducted and internally rotated—associated with seizure and electrocution. Inability to externally rotate the shoulder on physical examination.

         
         
      2. 
         

         Less than 5% of all glenohumeral dislocations.

         
         
      3. 
         

         Subtle radiographic appearance (▶ Fig. 20.2 a, b)—up to 50% are missed on initial presentation.

         

      
      
   4. 
      

      Inferior glenohumeral dislocation (Luxatio Erecta):

      
      
      
      
      1. 
         

         Shoulder fixed in significant flexion or abduction.

         
         
      2. 
         

         Highest rates of associated fractures and neurologic injuries.

   
   
6. 
   

   Coexisting Injuries—best differentiated by MRI with intra-articular contrast.

   
   
   
   
   1. 
      

      Bankart lesion:

      
      
      
      
      1. 
         

         Detachment of the anterior–inferior glenohumeral ligament and labrum.

         
         
      2. 
         

         Possible avulsion fracture of the glenoid rim.

         
         
      3. 
         

         Present in approximately 90% of traumatic anterior shoulder dislocations.

      
      
   2. 
      

      Posterior Bankart lesion:

      
      
      
      
      1. 
         

         Detachment of the posterior capsulolabral complex and the posterior band of the inferior glenohumeral ligament.

         
         
      2. 
         

         Common in posterior shoulder dislocations.

      
      
   3. 
      

      Humeral avulsion of the glenohumeral ligament (HAGL) lesion—higher rates of recurrent instability than a glenoid Bankart injury.

      
      
   4. 
      

      Anterior labral periosteal sleeve avulsion (ALPSA) injury:

      
      
      
      
      1. 
         

         Medial disruption of the static anterior stabilizing structures.

         
         
      2. 
         

         Tissues heal aberrantly along the anterior glenoid neck.

      
      
   5. 
      

      Hill-Sachs defect:

      
      
      
      
      1. 
         

         Impaction fracture of the humeral head from contact with the glenoid rim.

         
         
      2. 
         

         Posterior impaction is present in approximately 80% of anterior dislocations. Anterior humeral head defect—posterior shoulder dislocations (▶ Fig. 20.2c ).

      
      
   6. 
      

      Rotator cuff tear:

      
      
      
      
      1. 
         

         Most commonly supraspinatus tears or subscapularis avulsion injuries.

         
         
      2. 
         

         Incidence increases with patient age at the time of injury:

         
         
         
         
         • 
           

           i. First three decades of life rarely tear the rotator cuff.

           
           
         • 
           

           ii. Age > 40 years—approximately 30% will have a rotator cuff tear.

           
           
         • 
           

           iii. Age > 60 years—approximately 80% will have a rotator cuff tear.

      
      
   7. 
      

      Fractures of the proximal humerus:

      
      
      
      
      1. 
         

         Occur in up to 25% of acute shoulder dislocations.

         
         
      2. 
         

         Isolated greater tuberosity fracture (▶ Fig. 20.3 )—most common.

         

         
         
      3. 
         

         Lesser tuberosity fracture—associated with posterior dislocations.

         
         
      4. 
         

         Humeral neck fracture—typically require open surgical techniques for joint reduction.