Reverse Total Shoulder Arthroplasty

Reverse total shoulder arthroplasty (RTSA) has revolutionized the management of complex shoulder conditions, particularly rotator cuff arthropathy. By reversing the ball-and-socket anatomy, placing a convex glenosphere on the glenoid and a concave socket on the humerus, RTSA converts the deltoid muscle into the primary arm elevator.

Epidemiology:

• Exponential growth in utilization over the past decade (over 300 percent increase)
• Now represents over 60 percent of all shoulder arthroplasties in some series
• Mean patient age 65-75 years, though indications expanding to younger patients
• Female predominance (60-65 percent) reflecting rotator cuff arthropathy demographics

Historical Development:

• Professor Paul Grammont (Lyon, France) developed the modern design in 1985
• Key innovation was the Grammont principle: medialization of center of rotation
• Earlier designs (Neer Mark I, II) failed due to glenoid loosening from eccentric loading
• Modern semi-constrained designs achieve over 90 percent 10-year survivorship

Rotator Cuff Tear Arthropathy (CTA):

Cuff tear arthropathy represents the end-stage of massive rotator cuff tear with secondary degenerative changes. It is the most common indication for RTSA.

Pathophysiological Cascade:

1. Massive rotator cuff tear: Usually supraspinatus and infraspinatus
2. Loss of force couple: Deltoid pulls humeral head superiorly unopposed
3. Superior migration: Humeral head articulates with undersurface of acromion
4. Mechanical changes: Increased joint reaction forces, synovial fluid changes
5. Cartilage destruction: Both glenoid and humeral head articular surfaces
6. Bony remodeling: Femoralization of humeral head, acetabularization of glenoid

Grammont Biomechanical Principles:

The Grammont design addressed the failures of earlier reverse designs through key biomechanical innovations:

Functional Outcomes Explained by Biomechanics:

• Forward elevation: Typically restored to 120-140 degrees (deltoid-powered)
• External rotation: Often limited (0-30 degrees) due to posterior cuff deficiency
• Internal rotation: Variable, often limited to buttock level
• Strength: Improved compared to preoperative pseudoparalysis

History:

Physical Examination:

Key findings in cuff tear arthropathy:

• Inspection: Deltoid atrophy rare (if present, reconsider RTSA), anterior prominence (superior humeral migration)
• Palpation: Tenderness anterior shoulder, AC joint often arthritic
• Active range of motion: Severely limited elevation (pseudoparalysis less than 90 degrees)
• Passive range of motion: Preserved (distinguishes from frozen shoulder)
• Strength testing: Positive Hornblower's sign, positive external rotation lag

Differential Diagnosis of the Painful, Weak, Elevation-Limited Shoulder:

Specific Preoperative Assessment for RTSA:

Instability Patterns:

• Anterior: Most common, excessive retroversion, subscapularis failure
• Posterior: Rare, excessive anteversion
• Superior: Very rare, deltoid dysfunction

Activity Restrictions (Long-term):

• Avoid lifting greater than 10-15kg (risk of acromial stress fracture, instability)
• No contact sports or high-impact activities
• Swimming, golf, and tennis often possible with low demand

Functional Outcomes:

• Forward elevation: Improves from mean 50 degrees to 120-140 degrees
• External rotation: Often limited postoperatively (0-30 degrees average)
• Internal rotation: Variable, often to sacrum/buttock level
• Pain relief: Excellent in over 90 percent of patients

Survivorship:

• 92-95 percent 10-year implant survivorship in modern series
• Revision rates higher in younger patients (under 60)
• Glenoid loosening is long-term concern with medialized designs
• Lateralized designs may have improved long-term outcomes (under investigation)

Predictors of Good Outcome:

• Intact teres minor (better external rotation)
• Adequate deltoid function preoperatively
• Patient understanding of activity restrictions
• Primary indication (CTA) vs complex revision
• Surgeon experience with RTSA technique

RTSA is a young procedure with rapidly evolving design philosophy. Examiners reward candidates who can discuss genuine controversy rather than recite dogma.

Global Epidemiology and Utilization:

• RTSA utilization has grown several-fold over the past two decades and is now the most common shoulder arthroplasty in many high-income health systems
• It overtook anatomic TSA in the US around the late 2010s and continues to expand into fracture and revision indications
• Mean age at surgery is typically 70-75 years with a female predominance (around 60-65 percent), mirroring cuff tear arthropathy demographics

Registry Evidence:

• National registries (AOANJRR in Australia, NJR in the UK, the Nordic registries and emerging US data via AJRR) consistently confirm rising RTSA volumes and document higher revision rates in younger patients
• Registries show that fracture and revision indications carry higher early revision than primary cuff tear arthropathy
• Implant survival around 90 percent at 10 years is reproduced across registry and cohort data, broadly matching the Guery/Favard survivorship findings

High- vs Limited-Resource Practice Variation:

• In well-resourced systems, preoperative CT (often with 3D planning or patient-specific guides) and a wide range of lateralized implants are standard
• In limited-resource settings, plain radiographs may guide planning, implant choice is narrower, and hemiarthroplasty or non-operative management remains more common for fractures and cuff arthropathy
• Access, surgeon volume and implant availability - not biology - drive much of the global variation in who receives an RTSA