Anterior Shoulder Instability

February 18, 2021 | By : OrthoFixar | Sports Medicine
| Last updated on April 28, 2021


  • Shoulder instability Can be divided as unidirectional and multidirectional with an acronyms TUBS and AMBRI as mnemonics.
    1. TUBS: Traumatic unilateral dislocations with a Bankart lesion often necessitate surgery (Anterior Shoulder Instability).
    2. AMBRI: Atraumatic multidirectional bilateral shoulder dislocation/subluxation often responds to rehabilitation, and sometimes an inferior capsular shift or plication is required.

Anterior Shoulder Instability

  • Anterior Shoulder Instability is a pathologic state characterized by abnormal translation of the humeral head on or over the glenoid, leading to frank anterior dislocation, functional impairments, or pain.
  • Anterior Shoulder Instability is the Most common type of shoulder instability.

Anatomy

  • Glenohumeral joint has a dynamic and a static constraints.
  • Dynamic constraints include:
    1. Rotator cuff muscles.
    2. Long head of biceps tendon.
  • Static Constraints include:
    1. Bony anatomy.
    2. Joint capsule.
    3. Joint labrum.
    4. Negative intraarticular pressure
    5. Glenohumeral ligaments:
      • Superior glenohumeral ligament (SGHL).
      • Middle glenohumeral ligament (MGHL).
      • Inferior glenohumeral ligament (IGHL).
      • Coracohumeral ligament (CHL).

See Also: Rotator Cuff of the Shoulder

Pathoanatomy

  • The pathoanatomy of the anterior shoulder instability can be capsulo-labral, osseous, or both.

Capsulo-labral pathoanatomy

  1. Bankart lesion:
    • Bankart lesion is an avulsion of the anterior-inferior capsulo-labral complex with extension into the scapular periosteum and rupture of the periosteal tissue.
      • The weakest region of the capsule is generally anteriorly and inferiorly in the interval between the lower border of the subscapularis and the long head of the triceps muscle.
    • Found to occur in 90% of patients with recurrent anterior shoulder instability.
  2. Humeral avulsion of the glenohumeral ligaments (HAGL) lesion:
    • HAGL lesion is an avulsion of glenohumeral ligaments from their humeral-sided attachment.
  3. Anterior labro-ligamentous periosteal sleeve avulsion (ALPSA) lesion:
    • ALPSA is an avulsion of anterior-inferior glenolabral complex with stripping of medial scapular neck periosteum but preservation of a medial hinge, loose fragment subsequently scars medially down scapular neck.
  4. Perthes lesion:
    • It’s an avulsion of anterior-inferior glenolabral complex with preservation of medial scapular neck periosteum.
See Also: What is SLAP Lesion?

Osseous pathoanatomy

  1. Bony Bankart lesion:
    • Osseous avulsion fracture of anterior-inferior glenolabral complex.
    • It is usually present in 40% in the first-time dislocations, and in 85% in the recurrent dislocations.
    • The bone fragment in a bony Bankart lesion undergoes rapid absorption within 1 year of the primary injury.
  2. Hill-Sachs lesion:
    • It’s a bone injury typically occurs to the posterior superior humeral head with Anterior Shoulder Instability.
    • A Hill-Sachs lesion can be found in:
      • 40% of patients with recurrent subluxations,
      • 90% of first-time dislocations,
      • Almost 100% of recurrent anterior shoulder instability.

The most important factor in predicting anterior shoulder instability recurrence is the age at first dislocation:
1. Almost 100% in persons with open growth plates.
2. 70% to 95% of persons younger than 20 years.
3. 60% to 80% in persons aged 20 to 30 years.
4. 15% to 20% in persons older than 40 years.

Associated injuries in anterior shoulder instability

  • Up to 40% of patients with anterior shoulder instability have an associated injury.
    1. Greater tuberosity fracture: it is associated with anterior dislocation in patients > 50 years of age.
    2. Lesser tuberosity fracture: it is associated with posterior dislocations.
    3. Axillary nerve injury: occurs in 5% of patients, it’s most often a transient neurapraxia.
    4. Rotator cuff tears:
      • Occurs in 30% of patients > 40 years of age.
      • Occurs in 80% of patients > 60 years of age.

Clinical Evaluation

  • There is a history of trauma prior to anterior shoulder instability.
  • The patient feels the instability.
  • Shoulder pain.
  • Physical examination to evaluate anterior shoulder instability includes:
    1. The apprehension and relocation test.
    2. Sulcus sign.
    3. The anterior load-and-shift test can be used to classify degrees of anterior shoulder instability based on distance of humeral head translation:
      • 1+: 0 to 1 cm of translation to before glenoid rim.
      • 2+: 1 to 2 cm of translation to glenoid rim.
      • 3+: more than 2 cm translation or over glenoid rim.

Imaging Evaluation

Radiographic imaging:

ViewsConditions
True Anterior-posterior viewShoulder dislocation
Axillary viewShoulder dislocation direction.
West Point viewBony Bankart lesion seen with instability
Apical oblique (Garth) viewBony Bankart lesion – Hill-Sachs defect
Stryker notchHill-Sachs impression fracture
Anteroposterior internal rotationHill-Sachs defect
Shoulder imaging views to evaluate Anterior Shoulder Instability

CT scan:

  • Accurately identify of glenoid bone loss.
    • Three-dimensional reconstructions are more reliable for measurement purposes.

MRI:

  • It is helpful in detecting capsular or labral damage and detecting humeral avulsion of the inferior glenohumeral ligament (HAGL) lesions, which require repair.
  • An ABduction-External Rotation (ABER) view further increases sensitivity.

Treatment of Anterior Shoulder Instability

Non-operative treatment:

  • Reduction, sling immobilization and follow up physical therapy:
    • In acute dislocations.
    • Reduction techniques:
      • Traction-countertraction is most commonly employed.
      • The Milch maneuver (slow abduction and external rotation) has some evidence suggesting increased success rates.
    • Immobilization:
      • A meta-analyses suggest no difference between immobilization in internal or external immobilization. 1
      • Immobilization period for more than 1 week did not improve recurrence rates. 2
    • Physical therapy:
      • Should begin after the immobilization period.
      • It’s aimed to strengthen the dynamic stabilizers of the shoulder (rotator cuff and periscapular musculature).

Operative treatment:

Open surgey:
  1. Bankart repair:
    • Reattach labrum and IGHL to anterior glenoid, often combined with capsular shift.
    • Gold standard when glenoid bone loss < 20 %.
    • Ocasionally preferred in contact athletes.
  2. Latarjet coracoid transfer (Bristow Procedures):
    • The distal 2 cm of coracoid is transferred to anterior glenoid neck with two-screw fixation and reattachment of Coracoacromial (AC) ligament to anterior glenohumeral capsule.
    • Primary procedure in patients with > 25% glenoid bone loss.
  3. Anterior capsulo-labral reconstruction:
    1. Glenoid-based capsular shift.
    2. Designed for overhead athletes; may be performed as adjunct to Bankart.
Arthroscopic:
  1. Bankart repair:
    • Reattach labrum and IGHL to anterior glenoid with use of suture anchors.
    • It’s the most common operation for anterior instability.
  2. Coracoid transfer (hybrid Bristow-Latarjet):
    • Distal 2 cm of coracoid transferred to anterior glenoid neck.
    • The coracoacromial (CA) ligament is preserved.
Supplementary Procedures:
  1. Remplissage:
    • Arthroscopic infraspinatus and posterior capsule fixation into Hill-Sachs lesion using suture anchors.
    • Performed in moderate to large Hill-Sachs lesions; .
    • Medialized sutures limit external rotation
  2. Humeral head allograft:
    • Osteoarticular allograft inserted into HillSachs lesion.
    • Performed in large Hill-Sachs lesions
  3. Partial humeral head resurfacing:
    • Cobalt-chrome component inserted into Hill-Sachs lesions.
    • Typically performed with Latarjet procedure.
    • Alternative to humeral head allograft
  4. Rotator interval closure:
    1. Open or arthroscopic superior capsular shift of middle glenohumeral ligament (MGHL) to superior glenohumeral ligament (SGHL) .
    2. Limits external rotation.

Revision Procedures:
  1. Allograft bone grafting of glenoid:
    • Iliac crest or distal tibia secured to anterior glenoid neck with screws.
    • Performed in severe glenoid bone loss.
  2. Humeral hemiarthroplasty:
    • Humeral component retroverted 50 degrees to achieve stability.
    • Indicated in older patients with > 45% of humeral head bone loss and glenohumeral arthritis.
  3. Rotational humeral osteotomy:
    • Subcapital external rotational osteotomy to rotate Hill-Sachs lesion outside glenoid track.
    • Performed in severe Hill-Sachs lesions.
  4. Allograft anterior capsulolabral reconstruction:
    • Allograft tendon used to reconstruct anterior band of inferior glenohumeral ligament (IGHL) and middle glenohumeral ligament (MGHL).
    • Performed in severe capsular deficiency due to systemic soft tissue disorders, electrothermal capsular necrosis, or repeated surgical procedures without bone loss.
Historical Procedures:
  1. Bristow coracoid transfer:
    • Distal 1 cm of coracoid transferred and secured with 1 screw.
    • Coracoacromial CA ligament is preserved
    • Higher rate of recurrence
  2. Caspari technique:
    • Arthroscopic transglenoid suture repair of glenoid labrum.
    • Higher rate of recurrence.
    • Injury to suprascapular nerve.
  3. Staple capsulorrhaphy:
    • Reattachment of capsule to glenoid neck with a staple.
    • High rate of pain, recurrence, reduced internal and external rotation and staple migration.
  4. Putti-Platt:
    • Subscapularis advancement and shortening
    • Reduced external rotation.
    • posterior glenoid arthritis
  5. Magnusson-Stack:
    • Subscapularis transfer to greater tuberosity.
    • Reduced external rotation
  6. Thermal capsular shrinkage:
    • Use of thermal energy to reduce capsular volume.
    • Higher rate of recurrence.
    • Can result in capsular deficiency and chondral damage.
Instability Severity Index Score
  • Instability Severity Index Score is a simple preoperative score to select patients for arthroscopic or open shoulder stabilization.
  • It’s Based on a Preoperative Questionnaire, Clinical Examination, and Radiographs.
  • If score < 6 points:
    • An acceptable recurrence risk of 10% with arthroscopic stabilization.
  • If score > 6 points:
    • A score of > 6 points has an unacceptable recurrence risk of 70% and should be advised to undergo open surgery (i.e. Laterjet procedure).
Prognostic FactorsDescriptionPoints
Age– < 20 years
– > 20 years
2
0
Degree of sport participation– Competitive
– Recreational or none
2
0
Type of sport– Contact or forced overhead.
– Other
1
0
Shoulder hyperlaxity– Shoulder hyperlaxity (anterior or inferior).
– Normal laxity
1
0
Hill-Sachs lesion on AP radiograph
– Visible in external rotation
– Not visible in external rotation
2
0
Glenoid loss of contour on AP radiographs– Loss of contour
– No lesion
2
0
Total Points10
From Balg F, Boileau P (From Campbel’s Operative Orthopaedics 12th book)

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