Reverse Shoulder Arthroplasty

Introduction & Early Designs

• 1974: Concept introduced by Charles Neer

  • Intended to treat:

    • Glenohumeral arthrosis

    • Rotator cuff deficiency

• Early implant designs faced major limitations:

  • Glenoid component loosening

  • Implant breakage due to constrained designs

  • Lateralized center of rotation leading to high mechanical stress

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Grammont’s Contribution (1985)

Introduced a reverse ball-and-socket design based on four key principles:

• Medialization of center of rotation

  • Reduces mechanical torque at the glenoid–implant interface

• Inferior positioning of humerus

  • Increases deltoid tension

  • Improves deltoid recruitment

• Fixed center of rotation

  • Enhances implant stability

• Large glenosphere

  • Increases range of motion

  • Allows a semi-constrained articulation

These principles form the foundation of modern RTSA.

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What is Reverse Shoulder Arthroplasty?

• A form of shoulder arthroplasty where:

  • Convex glenosphere is placed on the glenoid

  • Concave cup is placed on the humeral side

• Reverses normal shoulder anatomy:

  • Glenoid fossa ? baseplate + glenosphere

  • Humeral head ? stem + concave polyethylene cup

• Alters shoulder biomechanics by:

  • Medializing and inferiorly shifting the center of rotation

  • Increasing deltoid tension and moment arm

• Result:

  • Improved shoulder elevation despite rotator cuff deficiency

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Indications for Reverse Shoulder Arthroplasty

• Cuff tear arthropathy

• Pseudoparalysis due to massive rotator cuff tear (without arthritis)

• Multiple failed rotator cuff repairs with:

  • Poor function

  • Anterosuperior instability

• Three- and four-part proximal humerus fractures in elderly patients

• Proximal humeral nonunions

• Greater tuberosity malunions

• Failed hemiarthroplasty with anterosuperior escape

• Tumour-related shoulder pathology

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Patient Selection Criteria

• Essential requirements:

  • Intact and functioning deltoid muscle

  • Adequate glenoid bone stock

  • No active infection or sepsis

• Avoid in patients with:

  • Severe neurological disorders (Parkinson’s disease, Charcot joint, syringomyelia)

  • Very high functional demands unsuitable for RTSA

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Biomechanics of RTSA

• Medialized and inferior center of rotation:

  • Allows deltoid to act on a longer lever arm

  • Compensates for deficient rotator cuff

• Benefits:

  • Improved shoulder abduction and elevation

• Limitations:

  • Limited improvement in internal and external rotation

• External rotation may be improved with:

  • Latissimus dorsi transfer in selected cases

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Preoperative Planning

Radiographs

Recommended views:

• True AP (Grashey view)

  • Assess arthritis

  • Identify superior humeral migration

• Axillary lateral view

  • Detect posterior glenoid wear

• Scapular Y view

  • Evaluate scapular alignment

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CT Scan

Indicated when axillary view is inadequate or deformity is suspected:

• Evaluates:

  • Glenoid version

  • Glenoid bone stock

  • Bone quality and osteopenia

• Helps plan:

  • Glenoid correction

  • Implant positioning

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MRI

Used selectively to:

• Assess rotator cuff integrity

• Evaluate fatty infiltration

• Plan soft-tissue management in complex cases

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Contraindications to RTSA

Absolute

• Global deltoid deficiency

• Active infection

• Severe glenoid bone loss preventing fixation

Relative

• Partial deltoid deficiency

• Axillary nerve dysfunction

• Severe glenoid osteoporosis

• Surgeon inexperience

• Younger age (<70 years) – now acceptable in select cases

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Surgical Approaches for RTSA

Deltopectoral Approach (Preferred)

Advantages:

• Preserves deltoid muscle

• Lower risk of axillary nerve injury

• Better exposure of inferior glenoid

• Allows extension inferiorly if required

• Enables simultaneous latissimus dorsi transfer

Disadvantages:

• Requires subscapularis takedown

• Extensive capsular release needed

• Limited posterior glenoid exposure

• Risk of postoperative stiffness

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Other Approaches (Not Recommended Routinely)

• Anterolateral / transdeltoid lateral approaches

• Higher risk of:

  • Axillary nerve injury

  • Deltoid damage

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Structures to Be Protected

• Cephalic vein

• Anterior circumflex humeral artery

• Ascending arcuate branch

• Posterior circumflex humeral artery

• Musculocutaneous nerve

• Axillary nerve

• Suprascapular nerve and artery

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Patient Positioning

• Beach-chair position

  • Trunk elevated 30–70°

  • Allows excellent visualization and access

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Surgical Landmarks

• Coracoid process

• Acromion

• Proximal humeral shaft

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Incision & Exposure (Deltopectoral)

• 12–14 cm incision between:

  • Coracoid

  • Proximal humeral shaft

• Develop deltopectoral interval

• Incise clavipectoral fascia

• Identify:

  • Conjoint tendon

  • Subscapularis tendon (divided vertically)

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Glenoid Preparation

• Complete soft-tissue and labral release

• Remove biceps remnants

• Place guide plate aligned with inferior glenoid circle

• Central K-wire placement confirmed with pre-op planning

• Ream glenoid surface

• Drill central peg

• Fix baseplate with screws

• Implant glenosphere:

  • Larger than AP glenoid diameter

  • Slight inferior overhang to reduce scapular notching

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Humeral Preparation

• Humeral head osteotomy:

  • 0–30° retroversion (commonly 20°)

  • Increased retroversion may improve external rotation

• Canal preparation with sequential reaming

• Trial stem insertion:

  • Recommended retroversion: ~10°

• Reduce trial prosthesis and assess:

  • Stability

  • Deltoid tension

  • Impingement

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Final Implantation

• Cemented humeral stem fixation

• Insert definitive polyethylene inlay

• Reduce prosthesis

• Tuberosity fixation:

  • Secure subscapularis and infraspinatus

  • Tie sutures to prevent superior migration

• Confirm implant position with fluoroscopy

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Rehabilitation Protocol

Weeks 0–2

• Sling for comfort

• Pendulum exercises

• Hand, wrist, elbow motion

• Active-assisted elevation to 90°

• External rotation limited to ~10°

Weeks 2–6

• Discontinue sling

• Active-assisted ? active ROM

• Scapular stabilization exercises

Weeks 6–12

• Begin deltoid strengthening

• Continue ROM

• Avoid free weights

After 12 Weeks

• Gradual lifting and functional use as tolerated

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Outcomes

• Better outcomes in:

  • Primary RTSA

• Inferior outcomes in:

  • Post-traumatic cases

  • Revision surgery

• Typical protocol:

  • Immobilization: 6 weeks

  • Active ROM: 6 weeks

  • Deltoid strengthening: 12 weeks

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Complications of RTSA

• Scapular notching

• Dislocation

• Glenoid loosening

• Deep infection

• Acromial or scapular spine fractures

• Axillary nerve neurapraxia

• Aseptic loosening of glenoid screws

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Key Take-Home Messages

• RTSA is a biomechanically driven solution for cuff-deficient shoulders

• Proper patient selection and planning are critical

• Deltoid integrity is essential

• Glenoid positioning determines long-term success

• Rehabilitation is as important as surgery