REVERSE TOTAL SHOULDER ARTHROPLASTY
Rotator Cuff Arthropathy | Grammont Principles | Deltoid-Powered | 10 Year Survivorship over 90 percent
PRIMARY INDICATIONS FOR RTSA
Critical Must-Knows
- Grammont Principle: Medialize center of rotation to glenoid surface. Distalize humerus to tension deltoid.
- Cuff Tear Arthropathy: Superior migration of humeral head. Femoralization. Acetabularization.
- Deltoid Function: RTSA converts deltoid from a short muscle with poor mechanical advantage to efficient arm elevator.
- Scapular Notching: Most common complication (up to 96 percent in early series). Inferior baseplate tilt helps prevent.
- Acromial Fractures: Risk 2-7 percent. Increased deltoid tension. May be stress or traumatic.
Examiner's Pearls
- "RTSA increases deltoid moment arm by 30-40 percent through medialization of center of rotation
- "Scapular notching reduced by inferior tilt of baseplate and larger glenosphere
- "Intact deltoid is ABSOLUTE requirement - check axillary nerve function preoperatively
- "Active external rotation preserved if teres minor intact (often limited postoperatively)
Critical RTSA Exam Points
Grammont Principles
Medialization and distalization are fundamental. Center of rotation moved to glenoid surface eliminates eccentric loading and maximizes deltoid efficiency. Lengthening the arm tensions deltoid for improved elevation. Vivas will ask you to explain these biomechanical principles.
Scapular Notching
Most common complication. Caused by mechanical impingement of humeral component on inferior glenoid rim. Prevented by: inferior baseplate tilt (10-15 degrees), larger glenosphere (38-42mm), inferior glenosphere overhang, lateralized designs.
Deltoid Dependency
RTSA is deltoid-powered. Intact deltoid and axillary nerve are ABSOLUTE requirements. Preoperatively assess: deltoid bulk, axillary nerve function, prior surgical approaches (deltopectoral vs lateral). Previous deltoid detachment is relative contraindication.
External Rotation Deficit
Most patients have limited active external rotation postoperatively because posterior cuff (infraspinatus, teres minor) is deficient. If teres minor intact, ER preserved. Latissimus dorsi transfer can improve ER in select cases.
Quick Decision Guide - RTSA vs Anatomic TSA
| Feature | Anatomic TSA | Reverse TSA | Key Pearl |
|---|---|---|---|
| Rotator cuff | Intact or repairable | Deficient or irreparable | RTSA does not require rotator cuff |
| Primary motor | Rotator cuff | Deltoid | Deltoid MUST be intact for RTSA |
| Center of rotation | Native (lateral to glenoid) | Medialized to glenoid surface | Grammont principle |
| CTA indication | Contraindicated | Primary indication | Superior migration means cuff deficient |
| External rotation | Preserved | Often limited | Posterior cuff deficiency limits ER |
| Glenoid loosening | Major concern (rocking horse) | Less eccentric loading | Medialization reduces glenoid torque |
GRAMMONTGRAMMONT - Reverse Shoulder Principles
Memory Hook:Professor Paul GRAMMONT designed the modern reverse shoulder - each letter of his name teaches a principle!
NOTCHNOTCH - Scapular Notching Prevention
Memory Hook:To prevent scapular NOTCH, remember all five prevention strategies!
DELTOIDDELTOID - Essential Preoperative Checks
Memory Hook:Before RTSA, check the DELTOID - the entire procedure depends on it!
Overview and Epidemiology
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
Expanding Indications
RTSA indications have expanded beyond rotator cuff arthropathy to include: acute proximal humerus fractures in the elderly, failed hemiarthroplasty, revision of failed anatomic TSA, tumor reconstruction, and inflammatory arthritis with cuff deficiency. However, the core indication remains cuff tear arthropathy with pseudoparalysis.
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
Anatomy and Pathophysiology
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:
- Massive rotator cuff tear: Usually supraspinatus and infraspinatus
- Loss of force couple: Deltoid pulls humeral head superiorly unopposed
- Superior migration: Humeral head articulates with undersurface of acromion
- Mechanical changes: Increased joint reaction forces, synovial fluid changes
- Cartilage destruction: Both glenoid and humeral head articular surfaces
- Bony remodeling: Femoralization of humeral head, acetabularization of glenoid
Hamada Classification of Cuff Tear Arthropathy
| Grade | Description | Acromiohumeral Distance | Treatment |
|---|---|---|---|
| 1 | Acromiohumeral distance over 6mm | Greater than 6mm | Conservative or cuff repair |
| 2 | Acromiohumeral distance 5-6mm | 5-6mm | Maximum conservative, consider repair |
| 3 | Acromiohumeral less than 5mm with acetabularization | Under 5mm | RTSA candidate if symptomatic |
| 4a | Narrowing without acetabularization | Under 5mm | RTSA (primary indication) |
| 4b | Narrowing with acetabularization of acromion | Under 5mm | RTSA (primary indication) |
| 5 | Humeral head collapse | N/A | RTSA (salvage) |
Grammont Biomechanical Principles:
The Grammont design addressed the failures of earlier reverse designs through key biomechanical innovations:
Medialization of Center of Rotation
Moving the center of rotation from the lateral humeral head to the glenoid surface eliminates the moment arm that caused glenoid loosening in earlier designs. This reduces eccentric loading on the glenoid fixation by over 90 percent.
Distalization of Humerus
The arm is effectively lengthened by 1-3cm, tensioning the deltoid muscle. This increases the deltoid moment arm by 30-40 percent and converts it from a short, relatively weak elevator to an efficient arm elevator.
Deltoid Absolute Requirement
Intact deltoid and axillary nerve function are ABSOLUTE requirements for RTSA. The entire design depends on deltoid function for arm elevation. Preoperative assessment must include: deltoid bulk inspection, axillary nerve sensation, deltoid strength testing, and review of prior incisions for deltoid detachment.
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
Classification Systems
Hamada Classification of Rotator Cuff Tear Arthropathy
The Hamada classification grades the severity of cuff tear arthropathy based on radiographic findings.
| Grade | Acromiohumeral Interval | Findings | Significance |
|---|---|---|---|
| 1 | Greater than 6mm | Minimal changes | Conservative management |
| 2 | 5-6mm | Early narrowing | Monitor progression |
| 3 | Under 5mm + acetabularization | Acromion remodeling | Consider RTSA |
| 4a | Under 5mm | GH joint narrowing | RTSA indication |
| 4b | Under 5mm + acetabularization | Advanced changes | RTSA indication |
| 5 | Collapse | Humeral head collapse | Salvage RTSA |
Normal acromiohumeral interval is 7-14mm. Less than 7mm indicates massive cuff tear.
Clinical Assessment
History:
Pain Characteristics
- Location: Anterolateral shoulder, may radiate to deltoid
- Timing: Night pain common, difficulty sleeping on affected side
- Activity: Pain with overhead activities, reaching
- Duration: Often chronic and progressive over years
Functional Status
- Active elevation: Severely limited (pseudoparalysis)
- Passive motion: Preserved (excludes frozen shoulder)
- Daily activities: Unable to comb hair, reach overhead
- Previous treatment: Failed injections, physiotherapy, cuff repair
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
Pseudoparalysis Definition
Pseudoparalysis: Inability to actively elevate the arm above 90 degrees with preserved passive motion. This indicates a massive, irreparable rotator cuff tear with loss of the force couple. Pseudoparalysis is a key indication for RTSA over anatomic TSA.
Specific Preoperative Assessment for RTSA:
Preoperative Checklist for RTSA
| Assessment | What to Check | Significance |
|---|---|---|
| Deltoid function | Bulk, strength, axillary nerve (regimental badge area) | ABSOLUTE requirement for RTSA |
| Prior surgery | Deltopectoral vs lateral approach, cuff repairs | Deltoid detachment is relative contraindication |
| Teres minor integrity | Horn blower sign negative indicates intact | Predicts postoperative ER |
| Glenoid bone stock | CT scan for morphology and version | May need bone graft if eroded |
| AC joint arthritis | Tenderness, cross-body adduction pain | Consider distal clavicle excision |
Investigations
Imaging Protocol for RTSA Planning
Standard shoulder series: AP (neutral, IR, ER), scapular Y, axillary lateral
Key findings to assess:
- Acromiohumeral interval (less than 7mm indicates massive tear)
- Superior migration of humeral head
- Femoralization of humeral head (rounding)
- Acetabularization of acromion and glenoid
- Glenohumeral arthritis severity
- Acromioclavicular joint arthritis
Critical for surgical planning
Glenoid assessment:
- Bone stock: anterior, posterior, inferior
- Version: excessive retroversion (over 15 degrees) may need augmentation
- Erosion pattern: centered vs decentered (Seebauer)
- Vault depth and screw trajectory planning
- Prior hardware if revision
Not essential if diagnosis clear, but useful for:
- Teres minor integrity (predicts postoperative ER)
- Fatty infiltration grading (Goutallier)
- Subscapularis status (repair vs leave)
- Biceps pathology
- Exclude infection if revision
CT Planning Importance
CT scan with 3D reconstruction is essential for RTSA planning. It allows assessment of glenoid version, bone stock, and optimal baseplate trajectory. Excessive retroversion (over 15 degrees) may require bony increased offset (BIO) augmentation or posterior augmented baseplate. The inferior screw trajectory must be planned to avoid scapular spine.
Management Algorithm
RTSA Indications
Primary Indications:
- Rotator cuff tear arthropathy (CTA): Hamada Grade 3-5 with pseudoparalysis
- Massive irreparable rotator cuff tear: With pseudoparalysis, without arthritis
- Proximal humerus fracture: Elderly (over 70), comminuted, poor bone quality
- Failed hemiarthroplasty: With cuff deficiency or tuberosity non-union
Expanding Indications:
- Revision of failed anatomic TSA with cuff deficiency
- Primary rheumatoid arthritis with massive cuff tear
- Tumor reconstruction (proximal humerus)
- Fracture sequelae (malunion, nonunion)
All indications require intact deltoid function - this is non-negotiable.
Surgical Technique
Patient Positioning
Beach chair position:
- Upright 60-70 degrees, head secured
- Arm free-draped for full access
- Ensure ability to maximally extend arm for humeral preparation
- Radiolucent table for intraoperative imaging
Surgical Approach
Deltopectoral approach (most common):
Deltopectoral Approach Steps
Start from coracoid, extend distally over deltopectoral groove (approximately 15cm). Identify cephalic vein and retract laterally (protects deltoid blood supply).
Develop deltopectoral interval. Identify conjoint tendon (medial), coracoid. Release clavipectoral fascia lateral to conjoint. Identify subscapularis and biceps.
Options: tenotomy, lesser tuberosity osteotomy, or peel. Lesser tuberosity osteotomy provides best healing in RTSA. Tenotomy also acceptable given cuff already deficient.
Dislocate shoulder anteriorly. Use cutting guide or freehand. Resection level and version critical. Many systems use 20-30 degrees retroversion. Preserve deltoid attachment.
Deltopectoral approach preserves deltoid origin and is preferred for RTSA.
Complications
RTSA Complications Overview
| Complication | Incidence | Prevention | Management |
|---|---|---|---|
| Scapular Notching | 20-50 percent | Inferior tilt, large glenosphere, lateralized design | Observation unless symptomatic/progressive |
| Instability | 2-10 percent | Appropriate tensioning, avoid excessive retroversion | Revision with larger glenosphere, humeral insert |
| Acromial Fractures | 2-7 percent | Avoid excessive arm lengthening | Brace, limited abduction, rarely ORIF |
| Infection | 1-4 percent | Antibiotics, sterile technique | Debridement or staged revision |
| Nerve Injury | 1-2 percent (usually neurapraxia) | Careful retraction, avoid overtensioning | Observation, usually recovers |
| Periprosthetic Fracture | 1-3 percent | Careful technique, assess bone quality | ORIF or revision |
Acromial Fractures
Acromial fractures are unique to RTSA due to increased deltoid tension. Risk factors include: excessive arm lengthening, osteoporotic bone, female sex, and rheumatoid arthritis. Present with sudden pain and weakness. Management is often conservative with limited abduction and sling immobilization. May catastrophically affect outcome if displaced.
Instability Patterns:
- Anterior: Most common, excessive retroversion, subscapularis failure
- Posterior: Rare, excessive anteversion
- Superior: Very rare, deltoid dysfunction
Postoperative Care
RTSA Rehabilitation Protocol
- Sling immobilization for 4-6 weeks
- No active shoulder motion
- Elbow, wrist, hand exercises permitted
- Pendulum exercises (gravity-assisted) from week 2
- Avoid combined abduction and external rotation (instability position)
- Begin active-assisted ROM exercises
- Progress to active ROM as tolerated
- Forward flexion and abduction focus
- Gentle external rotation (often limited, do not force)
- Periscapular strengthening
- Progressive deltoid strengthening
- Isometric to isotonic exercises
- Functional activities as tolerated
- Avoid heavy lifting (greater than 10kg) long-term
- Full activities of daily living expected
- Ongoing home exercise program
- Lifelong activity modifications (no contact sports, heavy lifting)
- Annual follow-up with radiographs
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
Outcomes and Prognosis
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
Evidence Base
Grammont Design Outcomes
- Early series of 60 RTSAs with mean 33 month follow-up
- ASES score improved from 34 to 68
- Forward elevation improved from 55 to 105 degrees
- Scapular notching in 96 percent of patients
Long-term Survivorship of RTSA
- Series of 527 Grammont-design RTSAs
- 89 percent survival at 10 years
- Glenoid loosening most common failure mode
- Younger patients had higher revision rates
BIO-RSA Lateralization Study
- Compared standard Grammont to BIO-RSA with lateral bone graft
- BIO-RSA showed reduced scapular notching (19 vs 62 percent)
- No difference in instability or ROM at 2 years
- Lateralization may improve impingement-free ROM
RTSA for Proximal Humerus Fractures
- Randomized trial comparing RTSA to hemiarthroplasty for complex PHF in elderly
- RTSA superior at 2 years: Constant score 56 vs 40
- Greater tuberosity healing not required for RTSA function
- Higher complication rate with hemiarthroplasty (tuberosity failure)
Teres Minor Integrity and External Rotation
- Intact teres minor predicted better external rotation postoperatively
- Hornblower positive patients had limited ER (mean 10 degrees)
- Hornblower negative patients had better ER (mean 30 degrees)
- MRI assessment of teres minor helpful preoperatively
Exam Viva Scenarios
Practice these scenarios to excel in your viva examination
"A 72-year-old female presents with a 2-year history of right shoulder pain and progressive weakness. She cannot lift her arm above 90 degrees. X-ray shows superior migration of the humeral head with acromiohumeral distance of 4mm."
This patient likely has rotator cuff tear arthropathy (CTA). My approach:
History
- Duration and progression of symptoms
- Night pain, functional limitations
- Previous treatments (injections, physiotherapy, prior surgery)
- Hand dominance and activity demands
Examination
- Deltoid function: Bulk, strength, axillary nerve sensation - CRITICAL
- Active vs passive ROM (pseudoparalysis if active less than 90, passive full)
- External rotation lag sign, Hornblower's test (teres minor)
- Prior surgical scars
Investigations
- Full X-ray series confirms CTA (Hamada Grade 4)
- CT with 3D reconstruction for glenoid morphology and planning
- MRI to assess teres minor integrity (optional)
Management
With Hamada Grade 4 CTA, pseudoparalysis, and intact deltoid, I would recommend Reverse Total Shoulder Arthroplasty.
I would counsel her on expected outcomes: good pain relief, forward elevation to 120-140 degrees, but limited external rotation. Activity restrictions include avoiding lifting over 10kg.
"You are discussing consent for RTSA. The patient asks about the main complications."
I would discuss the following complications:
Common Complications
- Scapular notching (20-50 percent): Wear from humeral component impinging on inferior glenoid. Usually asymptomatic, modern techniques have reduced incidence.
- Limited external rotation: Expected due to posterior cuff deficiency, not a complication per se.
Less Common but Important
- Infection (1-4 percent): May require washout or staged revision.
- Instability (2-10 percent): May require revision surgery.
- Acromial fractures (2-7 percent): Due to increased deltoid tension. Managed conservatively unless displaced.
- Nerve injury (1-2 percent): Usually temporary (neurapraxia).
Long-term Issues
- Component loosening: May occur over 10-15 years, revision may be required.
- Activity restrictions: Lifelong avoidance of heavy lifting and contact sports.
Overall, 10-year survivorship is over 90 percent and patient satisfaction is high in appropriately selected patients.
"A 68-year-old male is 6 weeks post-RTSA and presents with sudden pain and inability to lift his arm. He denies trauma. X-ray shows an acromial fracture."
Acromial fracture is a recognized complication of RTSA. My approach:
Assessment
- History: Sudden onset pain, any precipitating event, mechanism
- Examination: Tenderness over acromion, assess for displacement, deltoid function
- Imaging: AP and scapular Y views, CT if needed for fracture characterization
Classification (Levy and Badman)
- Type I: Acromial spine
- Type II: Posterior acromion
- Type III: Anterior acromion (worst prognosis, deltoid origin affected)
Management
- Non-displaced fractures: Conservative management with sling, limited abduction for 6-12 weeks. Most heal with fibrous union.
- Displaced fractures: May require ORIF with plate fixation, though surgical outcomes are unpredictable.
- Type III with deltoid disruption: Very poor prognosis, may be unsalvageable.
Prevention is key: avoid excessive arm lengthening, recognize osteoporotic patients at higher risk.
MCQ Practice Points
Grammont Principle
Q: What is the key biomechanical principle of the Grammont design? A: Medialization of the center of rotation to the glenoid surface, which eliminates eccentric loading on the glenoid component and increases the deltoid moment arm by 30-40 percent.
Scapular Notching Prevention
Q: How do you prevent scapular notching in RTSA? A: Inferior tilt of baseplate (10-15 degrees), larger glenosphere diameter (38-42mm), inferior glenosphere overhang, and consider lateralized (BIO-RSA) designs.
Deltoid Requirement
Q: What is the absolute requirement for RTSA? A: Intact deltoid function and axillary nerve. RTSA is deltoid-powered and cannot function without it.
Hamada Classification
Q: What Hamada grade indicates RTSA is the appropriate treatment? A: Hamada Grade 4 or 5 with pseudoparalysis. Grade 4a/4b show acromiohumeral interval under 5mm with glenohumeral arthritis. Grade 5 shows humeral head collapse.
External Rotation Prediction
Q: What predicts external rotation after RTSA? A: Teres minor integrity. If Hornblower's sign is negative (teres minor intact), expect better postoperative external rotation (mean 30 degrees). If positive, expect limited ER (mean 10 degrees).
Acromial Fractures
Q: What complication is unique to RTSA compared to anatomic TSA? A: Acromial stress fractures (2-7 percent) due to increased deltoid tension from arm lengthening. Usually managed conservatively unless displaced.
Australian Context
Prevalence and Practice:
- RTSA utilization has increased dramatically in Australia over the past decade
- Now represents the majority of shoulder arthroplasties for rotator cuff arthropathy
- Australian Joint Replacement Registry (AOANJRR) tracks outcomes nationally
Access to Care:
- Available in major metropolitan centers and larger regional hospitals
- Public hospital wait times may be 6-12 months
- Private sector typically offers shorter wait times
- Specialist shoulder surgeons perform majority of RTSAs
Medicare Considerations:
- Medicare benefits available for RTSA procedure
- Prosthesis benefits list covers implants
- Gap payments may apply depending on surgeon and private health insurance
Training:
- RTSA technique included in AOA orthopaedic training curriculum
- Subspecialty shoulder fellowship recommended for complex cases
- Regular cadaveric and simulation training courses available
RTSA Exam Essentials
High-Yield Exam Summary
Grammont Principles
- •Medialize center of rotation to glenoid surface
- •Distalize humerus to tension deltoid (increase moment arm 30-40 percent)
- •Eliminates eccentric glenoid loading
- •Deltoid becomes primary arm elevator
Indications
- •Rotator cuff tear arthropathy (Hamada 4-5) is primary indication
- •Massive irreparable RC tear with pseudoparalysis
- •Complex proximal humerus fracture in elderly (over 70)
- •Failed anatomic TSA or hemiarthroplasty with cuff deficiency
Complications
- •Scapular notching (20-50 percent) - prevent with inferior tilt and larger glenosphere
- •Acromial fractures (2-7 percent) - unique to RTSA
- •Instability (2-10 percent) - anterior most common
- •Limited external rotation - expected with posterior cuff deficiency
Exam Traps
- •Deltoid MUST be intact - absolute requirement for RTSA
- •Anatomic TSA contraindicated in CTA (cuff deficient)
- •Teres minor integrity predicts postoperative ER
- •Counsel on lifelong activity restrictions