Posterior Labral Tear

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

Shoulder loose body with posterior labral tear with posterior subluxation (C1339)