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Introduction
  • Definition
    • commonly referred to as a reverse Bankart lesion, or attenuation of the posterior capsulolabral complex
  • Epidemiology
    • athletes
      • weightlifters (bench press)
      • football linemen (blocking)
      • swimmers
      • gymnasts
  • Pathophysiology
    • repetitive microtrauma to the posterior capsulolabral complex
      • most common mechanism
      • posteriorly directed force with the arm in a flexed, internally rotated and adducted position
    • glenoid retroversion
      • patients with increased glenoid retroversion (~17°) were 6x more likely to experience posterior instability compared to those with less glenoid retroversion (~7°)
  • Associated injuries
    • Kim lesion
      • an incomplete and sometimes concealed avulsion of posteroinferior labrum
Anatomy
  • Posterior labrum
    • function
      • helps generate cavity-compression effect of glenohumeral joint
      • creates 50% of the glenoid socket depth
      • provides posterior stability
    • anatomy
      • composed of fibrocartilagenous tissue
      • anchors posterior inferior glenohumeral ligament (PIGHL)
  • Glenohumeral joint anatomy 
Presentation
  • Symptoms 
    • vague, nonspecific posterior shoulder pain is the most common symptoms
      • worsens with provocative activities that apply a posteriorly directed force to the shoulder
        • ex: pushing heavy doors, bench press, push-ups
    • clicking or popping in the shoulder with range of motion
    • sense of instability
      • less common
    • pain during throwing
      • late cocking phase
  • Physical exam
    • posterior joint line tenderness
    • provocative tests
      • posterior apprehension test
        • arm positioned with shoulder forward flexed 90° and adducted
        • apply anterior support to scapula
        • apply posteriorly directed force to shoulder through humerus
        • positive if patient experiences sense of instability or pain
      • posterior load and shift test
        • patient rests arm at their side
        • grasp the proximal humerus and apply a posteriorly directed force
        • assess distance of translation and patient response
          • grade 0 = no translation
          • grade 1 = to edge of glenoid
          • grade 2 = over edge of glenoid but spontaneously relocates
          • grade 3 = over edge of glenoid, does not spontaneously relocate
      • jerk test
        • arm positioned with shoulder abducted 90° and fully internally rotated
        • axially load humerus while adducting the arm across the body
        • clunk indicates subluxation of the humeral head off the posterior glenoid
          • highly sensitive and specific for a posterior labral tear
      • kim test 
        • arm positioned with shoulder abducted 90° and forward flexed 45°
        • apply posteriorly and inferiorly directed force to shoulder through humerus
        • positive if patient experiences pain
          • highly sensitive and specific for posteroinferior labral tear 
Imaging
  • Radiographs
    • recommended views
      • true AP, scapular Y and axillary views
        • axillary view required to ensure glenohumeral joint reduction
          • posterior shoulder dislocations may be missed on AP radiographs alone
    • findings
      • often normal
      • in chronic cases axillary view may show
        • glenoid retroversion or
        • posterior glenoid erosion
  • MRI 
    • indications
      • diagnostic study of choice
    • technique
      • intra-articular contrast increases sensitivity for labral pathology
Treatment
  • Nonoperative
    • activity modification, NSAIDs, PT
      • indications
        • first line of treatment
      • technique
        • rotator cuff and deltoid strengthening
        • periscapular stabilization
  • Operative
    • posterior labral repair, capsulorrhaphy 
      • indications
        • extensive nonoperative management fails
      • technique
        • arthroscopic and open techniques may be used
          • arthroscopic preferred to open given the extensive posterior surgical dissection required
            • more reliable return to play
        • suture anchor repair and capsulorrhaphy results in fewer recurrences and revisions than non-anchored repairs
        • probing of posterior labrum is required to rule out a subtle Kim lesion 
      • outcomes
        • generally good
        • return to previous level of function in overhead throwing athletes not as reproducible as other athletes
Complications
  • Axillary nerve palsy
    • posterior branch of the axillary nerve is at risk during arthroscopic stabilization 
      • travels within 1 mm of the inferior shoulder capsule and glenoid rim
        • at risk during suture passage at the posterior inferior glenoid
  • Overtightening of posterior capsule
    • can lead to anterior subluxation or coracoid impingement
 

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