Shoulder Arthroplasty

Indications & Contraindications - Who Needs New Shoulder?

• Indications (PASTA-O):
  • Pain: Severe, unresponsive to conservative Rx
  • Arthritis: Osteoarthritis (OA), Rheumatoid Arthritis (RA), Post-traumatic
  • Stiffness: Significant functional limitation
  • Trauma: Complex fractures (e.g., 4-part proximal humerus #), fracture-dislocations
  • Avascular Necrosis (AVN) of humeral head
  • Osteonecrosis
  • Rotator cuff tear arthropathy (Reverse TSA)
• Contraindications:
  • Active infection
  • Neuropathic joint (Charcot)
  • Paralysis with inability to stabilize prosthesis
  • Inadequate bone stock
  • Non-compliance

⭐ Glenohumeral OA is the most common indication for anatomic total shoulder arthroplasty (TSA).

Types of Arthroplasty - Hemi, Total, or Reverse?

• Hemiarthroplasty (HA): Replaces humeral head only; glenoid cartilage must be intact.
  • Indications: Humeral head AVN (cuff intact), complex proximal humerus fractures (elderly), select cuff tear arthropathy (CTA) in low-demand elderly.
• Total Shoulder Arthroplasty (TSA): Replaces both humeral head & glenoid; requires functional rotator cuff (esp. subscapularis).
  • Indications: Osteoarthritis (OA), Rheumatoid Arthritis (RA) with intact cuff.
• Reverse Total Shoulder Arthroplasty (rTSA): Glenoid component is convex (glenosphere), humeral component is concave; deltoid function becomes primary elevator.
  • Indications: CTA, massive irreparable cuff tears with pseudoparalysis, complex fractures (elderly), revision of failed TSA/HA.

⭐ In rTSA, the centre of rotation is medialized & inferiorized, improving deltoid lever arm & function.

Surgical Pearls & Anatomy - Navigating the Joint

• Key Anatomy:
  • Glenoid: Pear-shaped; version (retroversion <10-15°).
  • Humeral Head: Retroversion 20-30°; inclination 130-140°.
  • Rotator Cuff: Subscapularis (repair crucial).
  • Axillary Nerve: ~5-7 cm distal to acromion. 📌 "Danger zone".
• Approaches:
  • Deltopectoral: Workhorse; spares deltoid.
  • Anterosuperior.
  • Superior (deltoid-splitting).
• Pearls:
  • Glenoid exposure: Crucial for placement.
  • Humeral sizing/version: For kinematics.
  • Soft tissue balance: For stability/ROM.
  • Subscapularis repair: Vital.

  ⭐ Axillary nerve is most at risk during deltoid-splitting approaches and inferior capsulectomy.

Implants & Biomechanics - Making It Work

• Materials: Co-Cr/Titanium alloys; Ultra-High Molecular Weight Polyethylene (UHMWPE) bearings.
• Anatomic TSA (aTSA):
  • Replicates native anatomy: metal humeral head, polyethylene glenoid.
  • Requires functional rotator cuff for stability and movement.
  • Maintains anatomic Center of Rotation (COR).
• Reverse TSA (rTSA):
  • Indicated for rotator cuff arthropathy.
  • Design: metal glenosphere (glenoid side), polyethylene cup (humeral side).
  • Biomechanics: Medializes & inferiorizes COR.
  • Enhances deltoid function: ↑ lever arm, ↑ tension. Deltoid becomes primary elevator.

  ⭐ rTSA converts glenohumeral shear forces to compressive forces, improving stability in cuff-deficient shoulders.

Complications & Management - Uh Oh, Fix It!

• Infection:
  • Early (<6 wks): DAIR (Debridement, Antibiotics, Implant Retention).
  • Late (>6 wks): Two-stage revision arthroplasty.
• Instability/Dislocation:
  • Anterior most common.
  • Tx: Closed reduction, sling, physiotherapy. Revision for recurrent instability.
• Periprosthetic Fracture:
  • Intra-op or post-op.
  • Tx: ORIF; component revision if implant is loose.
• Glenoid Loosening (Anatomic TSA):
  • Most common long-term issue.
  • Tx: Revision to new glenoid or Reverse Shoulder Arthroplasty (RSA).

  ⭐ Aseptic glenoid loosening is the leading indication for revision surgery in anatomic Total Shoulder Arthroplasty.

• Rotator Cuff Failure (Post-TSA):
  • Leads to pain, ↓ function.
  • Tx: Physiotherapy; consider revision to RSA.
• Nerve Injury:
  • Axillary nerve (deltoid weakness) most vulnerable.
  • Tx: Observation, EMG; surgical exploration rare.
• Stiffness (Arthrofibrosis):
  • Painful restricted motion.
  • Tx: Aggressive physiotherapy, Manipulation Under Anesthesia (MUA).

High‑Yield Points - ⚡ Biggest Takeaways

• Reverse Shoulder Arthroplasty (RSA) is the choice for cuff tear arthropathy, massive irreparable cuff tears, and complex proximal humerus fractures in the elderly.
• Total Shoulder Arthroplasty (TSA) is preferred for osteoarthritis with an intact rotator cuff and adequate glenoid bone stock.
• Hemiarthroplasty is considered for acute proximal humerus fractures in younger patients or when glenoid cartilage is preserved.
• Key complications include infection, instability, glenoid loosening (especially in TSA), and periprosthetic fracture.
• Scapular notching is a well-recognized radiographic finding and potential complication specific to RSA.
• Deltoid dysfunction is a major contraindication for RSA as it relies on a functional deltoid.
• Glenoid version and bone loss are critical pre-operative considerations influencing implant choice and surgical technique.