Posterior Labral Tear - Shoulder & Elbow

summary
- A posterior labral tear is referred to as a reverse Bankart lesion, or attenuation of the posterior capsulolabral complex, and commonly occurs due to repetitive microtrauma in athletes.
- Diagnosis can be made clinically with positive posterior labral provocative tests and confirmed with MRI studies of the shoulder.
- Treatment may be nonoperative or operative depending on chronicity of symptoms, degree of instability, and patient activity demands.

Epidemiology
- Demographics
  - athletes
    
    weightlifters (bench press)
    
    football linemen (blocking)
    
    swimmers
    
    gymnasts
    
    wrestlers

Etiology
- 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
    
    failure risk increases if adduction and internal rotation are not avoided in the acute postoperative period

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