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Glenoid Bone Deficiency in Recurrent Anterior Shoulder Instability

Reviewed by

Dr David Shepherd
MBBS | Accredited Orthopaedic Registrar

Glenohumeral anatomy

  • Stability conferred by
    • Joint congruity/ anatomy
    • Passive stabilisers
    • Muscle force and coordination
  • Glenoid
    • 5 cm2
    • 5-15 degrees retroverted to scapula
  • Humeral head
    • 30-50 degrees retroverted
    • 15 cm2

Bone lesions

  • Hill-Sachs
    • Posterolateral in anterior dislocation
    • Anteromedial in posterior dislocation
  • Bankart
    • Bony / soft tissue

Anatomy

  • SGHL
    • Protects anterior instability in outstretched arm
    • Prevents inferior translation in adduction
  • IGHL
    • Tight in abduction, ER
    • Labral lesion without IGHL injury
      • Not unstable anteriorly
    • IGHL injury without Labral injury
      • Anterior instability
    • Posterior band
      • Prevents inferior translation in IR
    • Multidirectional instability
      • Entire IGHL complex and capsule laxity

Instability

  • Direction
    • Anterior dislocation
      • 96-98%
      • Indirect trauma to Abducted, extended, ER arm
    • Posterior dislocation
      • Axial, posterior force on an IR adducted arm
    • Inferior (luxatio erecta)
  • Mechanism of Injury
    • 96% traumatic
  • Associated Nerve lesions
    • Axillary 42%
    • Suprascapular 14%
    • Musculocutaneous 12%

Management

  • Immobilise 3 weeks
    • Early use
  • Goals
    • Strengthen dynamic stabilisers
    • Regain ROM
    • Avoid provocative positions
    • Muscles
      • RC, Deltoid, Pec major, Latissimus
        • Resistive exercises, isometric progressing to isokinetic
    • Proprioception

Recurrence

  • Age
    • <20
      • 95%
    • 20-40
      • 40-75%
    • >40
      • 0-20%

Management Recurrent Instability

  • Anterior instabilty
    • Open
      • Bone anchor/trans-osseos sutures of Bankart
        • 2-8% recurrence rate
      • Putti-Platt, Capsular shift alone
        • poor results
    • Arthoscopic
      • 4-49% recurrence
      • Range of techniques – sutures, bony anchors, bioabsorable tacks
  • Posterior instability
    • No consensus, poorer outcomes up to 80% unsatisfactory
    • Open with bony augmentation + capsular shift
    • Arthroscopic
      • aim for capsular shift + labral repair
  • Multidirectional
    • Open Inferior Shift ( Neer) – 97% satsifactory

Epidemiology of Bone loss.

  • Lack of uniform measure for bone loss accounts for lack of consistency in literature
  • Bone deficiency
    • 22% initial dislocations
    • Up to 90% recurrent instability
    • Up to 89% failed stabilisation procedures
  • Nature of defect (recurrent anterior instability)
    • Fracture fragments
    • Attritional bone loss
    • Combination
  • Most common location
    • Anterior to glenoid face
    • Majority between 2:30 – 4:20
  • Mechanism
    • Dislocation with greater axial load (rugby) vs rotational ( avulsion by inferior GH ligament)
  • Defects may
    • Occur at injury
    • Develop with recurrent instability
  • Natural History
    • Acute recurrence
      • Fracture fragments often present
    • Delayed recurrence (15/12)
      • Attritional pattern – no identifiable fragment
      • Fragments have partially resorbed
  • Biomechanics
    • Gleno-humeral mismatch
      • Decreased concavity to prevent dislocation
      • Smaller area to resist axial force, increasing the shear forces to a repaired capsulo-labral interface
  • Pertinent History
    • Preinjury activity level
    • Details of dislocation
      • High energy, axial load
    • Recurrent instability
      • in mid-range 20 – 60 deg
      • Low energy events
    • Previous surgery

Examination findings

  • Routine examination
    • Deformity, scars, RC atrophy
    • ROM (active, passive), Cuff strength
    • Provocative labral signs
    • Stability
      • Direction, magnitude of laxity
    • Early and midrange apprehension, unidirectional suggestive of bony deficiency.

Imaging

Xray

  • AP
  • axillary views
  • Apical oblique
  • Didiee
  • West Point
  • Angles relative to glenoid face – higher yield

CT

  • Estimate bone loss
  • detect rim fracture fragments
  • Quantified as percentage of normal inferior glenoid surface area
    • Best fit circle on inferior 2/3 of glenoid
    • Degree of bone loss as a percentage of area of circle

Arthroscopic Quantification of Bone Loss

    • Normal Glenoid average diameter 24mm
    • Bare area = centre of glenoid
    • % bone loss = Distance to Post rim – Distance to Anterior rim

            • 2 X distance to Posterior Rim

  • Defect often has a posterior slope, creating a narrower inferior glenoid

Critical Limit of Bone loss

  • Several studies
    • Sequential removal of 9%, 21%, 34%, 46%
    • Osteotomy at 45 degrees to long axis
    • Significant instability at defects> 21%
    • Bone loss of 6 -7mm of the inferior glenoid circle are significant
  • Inverted Pear appearance
    • Range from 7.5mm (28%) – 8.6 mm (36%) of bone
    • high rate of failure of labral repairs in inverted pear appearance

Management

Non-Operative

  • Goal
    • maintenance of shoulder stability during functional activity
  • Methods
    • Strengthening of Dynamic stabilisers - periscapular muscles and RC.
    • No role for external rotation bracing in presence of bone loss
  • Indications
    • Low demand patient
    • Small defect < 20%

Operative managment

  • Considerations
    • patient activity level
    • degree of bone loss
  • Bone Loss < 15%
    • Majority of patients with recurrent anterior instability
    • Results
      • Bigliani –Open repair case series - 10-15%
        • 94% of fractures remained stable
        • 72% normal post-op stability
        • If bone fragment ignored – 40% recurrence
  • Bone Loss 15 -25%
    • Increased failure of soft tissue only repair
    • Consider open glenoid augmentation
    • Results
      • Sugaya –case series 42 shoulders. 6/12 of instability
        • Arthroscopic reduction and suture anchor fixation
        • 34 month follow up. 93% good/excellent, 95% return to sport
        • Post operative CT scans in 12 patients – union of fragment
      • Mologne
        • 14.2 % failure rate of arthroscopic repair if attritional bone loss and no fragment to repair
      • Burkhart & DeBeer – 89% failure rate in overhead athletes in soft tissue only repair
  • Bone Loss >25%
    • Acute
      • open fracture repair
    • Chronic
      • More commonly – arthroscopically deficient glenoid – inverted pear
        • Bone fragment is absent (attritional loss) or resorbed
    • Glenoid augmentation required
      • Options
        • Corocoid to transfer to anterinferior glenoid
          • Bristow
            • Corocoid osteotomised transversely and fixed perpendicular to glenoid at base
          • Laterjet
            • Long axis parallel to anterior glenoid rim
            • Cuff of coracoacromial ligament for capsulolabral attachment
            • More anatomic restoration of arc
          • Results
            • Hovelius
              • 118 patients with recurrent instability, 15 year follow up
              • 3.4% redislocation, 10% subluxation
              • Good/Excellent in 86%
              • Arthropathy
                • 14 % moderate to severe,
                • 35% mild
        • Iliac Crest autograft
          • High rates of arthrosis and 18% recurrent instability

Take home message

  • High frequency of traumatic recurrent anterior instability cases involve glenoid bone loss
  • Xray, CT scan and Arthroscopy to assess extent of bone loss
  • Bone Loss
    • <15%
      • Soft tissue bankart repair
    • 15-30%
      • patient activity denotes bony procedure
      • Repair of fragment or augmentation
    • >30%
      • Anatomical fiaxtion or augmentation.

References

  • Glenoid bone deficiency in recurrent anterior shoulder instability: diagnosis and management.
    • Piasecki DP, Verma NN, Romeo AA, Levine WN, Bach BR Jr, Provencher MT.
    • J Am Acad Orthop Surg. 2009 Aug;17(8):482-93. Review