High Yield Overview

REVERSE SHOULDER ARTHROPLASTY (RSA)

Deltopectoral Approach | Grammont Design Principles

Clinical Assessment

Mnemonic

R-E-V-E-R-S-EREVERSE - Indications for RSA

Mnemonic

G-R-A-M-M-O-N-TGRAMMONT - Design Principles

Primary Indications:

Cuff tear arthropathy (Hamada grade 4-5) - most common indication
Massive irreparable rotator cuff tear with pseudoparalysis (elevation less than 90°)
Complex proximal humerus fractures in elderly (>70 years, 3-4 part, head-split, fracture-dislocation)
Failed rotator cuff repair with stiffness and pain
Revision TSA with rotator cuff deficiency
Rheumatoid arthritis with cuff destruction

Expanding Indications:

Tumour reconstruction of proximal humerus
Severe bone loss in revision setting
Complex instability in elderly with cuff deficiency
Selected cases of acute fractures (controversial in younger patients)

ABSOLUTE Requirement:

Functioning deltoid muscle with intact axillary nerve
Without deltoid, RSA WILL NOT WORK

Exam Pearl

Examiner Question: "A 65-year-old active man has cuff tear arthropathy. Is RSA appropriate at his age?"

Model Answer: "Age 65 is at the younger end for RSA. Traditional threshold was 70+ years due to concerns about glenoid baseplate loosening (5-10% at 10 years) and limited revision options. However, expanding indications now include age 60-70 if: (1) True pseudoparalysis (elevation <90°); (2) Failed alternative treatments; (3) Realistic expectations about longevity and activity. I would counsel him about 10-15 year implant survival, limited external rotation, and that revision is more complex than primary. Australian AOANJRR data supports RSA in carefully selected patients >60."

Indication Red Flags

RSA for primary OA with intact cuff - TSA is indicated, not RSA (higher complication rate)
Missing axillary nerve palsy - RSA will FAIL without functioning deltoid
Young high-demand patient - RSA is NOT for return to heavy sport/labor
Not recognizing pseudoparalysis - <90° active elevation indicates cuff deficiency regardless of X-ray

Critical Danger Structures

Axillary Nerve

Location: Exits quadrangular space, runs on ANTERIOR-INFERIOR capsule 5-7cm below acromion

Course: Wraps around surgical neck of humerus posteriorly

CRITICAL: Injury = complete RSA failure. Deltoid paralysis = no elevation

Protection: Careful inferior capsular release UNDER DIRECT VISION. Do not blindly release inferiorly. Place inferior retractor carefully.

EXAM KEY: RSA depends ENTIRELY on deltoid. Axillary nerve injury is CATASTROPHIC.

Musculocutaneous Nerve

Location: Enters conjoint tendon 5-8cm distal to coracoid (mean 5.5cm)

Course: Pierces coracobrachialis, lies between biceps and brachialis

Risk: Medial retractor placement too distal

Protection: Place medial retractor SUPERIOR, within 5cm of coracoid

Injury Result: Biceps weakness, lateral forearm numbness

Suprascapular Nerve

Location: Posterior to glenoid in suprascapular notch

Risk: Posterior glenoid screw placement

Protection: Direct posterior screw at scapular body, ANTERIOR to suprascapular notch

Injury Result: Infraspinatus paralysis (already non-functional in RSA indication, but denervation pain possible)

Brachial Plexus

Location: Deep to conjoint tendon, medial

Risk: Overzealous medial dissection, deep retractor placement

Protection: Stay lateral to conjoint, avoid deep medial dissection

Injury: Variable upper limb weakness and numbness

Equipment

Implants and Instruments

Glenoid Components:

Baseplate (central fixation + peripheral locking screws)
Glenosphere: typically 36mm or 38mm diameter (larger = more stability, less notching)
Standard vs eccentric/lateralized designs (affect notching and ROM)

Humeral Components:

Metaphyseal-engaging uncemented stem (most common)
Long cemented stem (for revision, poor bone quality)
Polyethylene liner (various thicknesses: 6mm, 9mm, 12mm, 15mm)
+/- humeral tray options

Instruments:

Deltopectoral retractor set (Kolbel, Bankart)
Humeral resection guide
Sequential humeral broaches
Glenoid exposure retractors
Baseplate guide with central pin
Glenoid reamers (powered)
Impactors for baseplate and glenosphere
Fluoroscopy for baseplate positioning confirmation

Additional:

Beach chair positioner with arm holder
Bump/bolster for medial scapular border
Bipolar cautery
Deep drain

Modern Design Variations:

Standard Grammont (medialized, no lateral offset)
Lateralized glenoid (bony increase offset - BIO RSA)
Lateralized humeral (135° neck shaft angle with offset)
Combined lateralization designs (for better ROM, less notching)

Positioning and Preparation

Patient Position: Beach chair at 70-80° (more upright than TSA - glenoid access critical)

Head secured in horseshoe headrest
Large bump under medial scapular border (brings glenoid anteriorly)
Table break at shoulder level
Arm draped free to fingertips

Landmarks:

Coracoid process (KEY landmark - palpate for every step)
Clavicle
Acromion
AC joint
Spine of scapula (mark before draping)

Surgical Approach: Deltopectoral - TRUE internervous plane

Incision: 15-18cm curvilinear from coracoid distally toward deltoid insertion

Longer than TSA (glenoid access more demanding)
Can extend proximally along clavicle if needed

Key Setup Points:

Fluoroscopy available for baseplate positioning confirmation
Patient cannot slide - secure torso
Arm must be freely mobile for manipulation

Operative Technique

Step 1: Positioning and Setup

Beach chair position at 70-80° (more upright than TSA). Head secured. Large bump under medial scapular border - this is CRITICAL in RSA to bring the glenoid face anteriorly. Table break at shoulder. Arm draped completely free. Mark coracoid, clavicle, acromion, AC joint, spine of scapula.

Exam Pearl

Technical Tip: Positioning in RSA is more upright than TSA because glenoid exposure, particularly the INFERIOR glenoid, is critical. The bump under the medial scapular border rotates the scapula and brings the glenoid face anteriorly. This makes the inferior glenoid accessible for correct baseplate positioning.

Positioning Dangers

Patient slipping - secure torso well, steep beach chair position increases slide risk
Inadequate scapular bump - if glenoid not brought forward, inferior exposure impossible
Brachial plexus stretch - avoid excessive head tilt away from operative side
Venous air embolism - rare but reported in beach chair, keep BP adequate

Step 2: Incision and Deltopectoral Interval

15-18cm incision from coracoid distally. Identify deltopectoral groove and cephalic vein. Retract vein LATERALLY with deltoid (90% of surgeons). Develop interval proximally to clavicle, distally 8-10cm.

TRUE INTERNERVOUS PLANE:

Deltoid (axillary nerve) laterally
Pectoralis major (medial/lateral pectoral nerves) medially

Protect the Deltoid

The deltoid is the MOTOR for RSA. Protect it absolutely. Use self-retaining retractors carefully. Avoid excessive lateral retraction. Any deltoid injury compromises RSA function significantly.

Exam Pearl

Examiner Question: "Which way do you retract the cephalic vein in the deltopectoral approach?"

Model Answer: "90% of surgeons retract laterally with deltoid. Rationale: the vein has more tributaries from the deltoid side, so lateral retraction keeps these tethered branches under direct vision. However, some retract medially claiming the pectoralis side is safer. The key is consistency - always retract the same way so you know where the vein is. If torn, ligate both ends and continue. The vein is not expendable but its injury is manageable."

Step 3: Deep Exposure

Identify conjoint tendon medially. Note that musculocutaneous nerve enters 5-8cm distal to coracoid - place medial retractor SUPERIOR to this. Release upper pectoralis major insertion if needed. Identify subscapularis - often ABSENT or severely atrophic in cuff tear arthropathy. If present, can release without repair (RSA does not depend on subscapularis).

Exam Pearl

Examiner Question: "How do you protect the musculocutaneous nerve during RSA?"

Model Answer: "The musculocutaneous nerve enters the coracobrachialis (conjoint tendon) 5-8cm distal to the coracoid (mean 5.5cm). I protect it by: (1) Palpating the coracoid as my reference; (2) Placing the medial retractor within 5cm of the coracoid; (3) Avoiding excessive medial dissection distal to this safe zone; (4) Never blindly retracting the conjoint. If injured, it causes biceps weakness and lateral forearm numbness."

Deep Exposure Hazards

Musculocutaneous nerve - enters conjoint 5-8cm from coracoid, keep medial retractor proximal
Subscapularis in RSA - often atrophied or absent, don't waste time searching
Conjoint tendon traction - gentle retraction only, excessive force risks brachial plexus
Upper pec release - if needed, stay on bone to protect anterior circumflex vessels

Step 4: Capsulectomy and Joint Entry

Perform AGGRESSIVE 360° capsular release - more extensive than TSA:

Superior release (remove remnant cuff)
Anterior release with subscapularis
INFERIOR release - CRITICAL but PROTECT axillary nerve (5-7cm below acromion on anterior-inferior capsule)
Posterior release

Exam Pearl

EXAM KEY: The inferior capsular release in RSA is essential for glenoid exposure but is the most dangerous part of the operation. The axillary nerve runs on the anterior-inferior capsule 5-7cm below the acromion with the posterior circumflex humeral artery. Perform this release under DIRECT VISION, not blindly.

Capsulectomy Dangers - CRITICAL STEP

Axillary nerve - 5-7cm below acromion on anterior-inferior capsule, release UNDER DIRECT VISION
Posterior circumflex humeral artery - travels with axillary nerve, cauterise before transecting
Blind inferior release - NEVER acceptable, must visualise what you are cutting
Incomplete release - if cannot expose inferior glenoid, baseplate will be too superior

Step 5: Humeral Head Removal

Externally rotate, extend, and adduct to deliver humeral head. Make humeral neck cut at ANATOMIC NECK (more proximal than TSA). Cut angle 135-145° (more valgus than TSA). This preserves metaphyseal bone for stem fixation and accommodates the medialized center of rotation.

Exam Pearl

Examiner Question: "How does the humeral cut in RSA differ from TSA?"

Model Answer: "In RSA, the cut is more proximal (anatomic neck) and more valgus (135-145°) compared to TSA. Reasons: (1) The medialized center of rotation requires less lateral offset; (2) Preserving metaphyseal bone provides better stem fixation; (3) The higher cut accommodates the reversed biomechanics. In TSA, the cut is at the surgical neck with 20-30° retroversion to match native anatomy. RSA uses 0-20° retroversion to optimize external rotation."

Humeral Head Removal Hazards

Fracture during delivery - osteoporotic bone common in RSA indications, gentle manipulation
Excessive bone removal - cut too distal compromises metaphyseal fixation
Varus cut - leads to varus stem alignment and instability
Soft tissue stripping - preserve deltoid insertion, avoid excessive periosteal stripping

Step 6: Glenoid Exposure (CRITICAL)

Place three retractors:

Anterior retractor over anterior rim
Posterior retractor into capsule
INFERIOR retractor into axillary recess (protect axillary nerve!)

Must expose ENTIRE glenoid face including INFERIOR border. Remove all labrum, capsule, osteophytes. If cannot see inferior glenoid, cannot position baseplate correctly.

Inferior Glenoid Exposure

If you cannot see the inferior glenoid rim clearly, you will position the baseplate too superiorly, causing scapular notching. Take time for meticulous inferior exposure. This is the most technically demanding step.

Exam Pearl

Examiner Question: "What is the most technically demanding step in RSA and why?"

Model Answer: "Glenoid exposure, particularly the inferior glenoid. In RSA, the baseplate MUST sit flush with the inferior glenoid rim with 5-10° inferior tilt. If the inferior glenoid is not visible, the baseplate ends up too superior, causing scapular notching in 50-80% of cases. This exposure requires: (1) Complete capsulectomy; (2) Three retractors (anterior, posterior, inferior); (3) Adequate scapular bump positioning; (4) Patience. The inferior retractor placement must protect the axillary nerve."

Step 7: Baseplate Positioning (CRITICAL DECISION)

Baseplate position determines RSA success. Goals:

INFERIOR TILT: 5-10° inferior tilt, baseplate FLUSH with inferior glenoid rim
NEUTRAL VERSION: 0-5° anteversion or retroversion
CENTRAL POSITION: not superior

Place central guide pin aiming toward coracoid base. Confirm position with fluoroscopy. Ream glenoid face flat to bleeding bone.

Exam Pearl

EXAM KEY: Baseplate positioning is THE critical step in RSA. The baseplate must sit flush with the inferior glenoid with 5-10° of inferior tilt. If it sits too superiorly, scapular notching occurs in 50-80% of cases, leading to polyethylene wear and potential loosening. The central pin should aim toward the coracoid base.

Baseplate Positioning Errors

Superior placement - most common error, causes scapular notching in 50-80%
Excessive retroversion - aim for neutral, >10° retroversion causes posterior instability
Excessive anteversion - causes anterior impingement and instability
Not confirming with fluoroscopy - use image guidance to verify inferior position

Step 8: Baseplate Fixation

Insert baseplate with central fixation (press-fit or screw). Place 2-4 peripheral locking screws:

Superior screw: aims toward coracoid base (strong bone)
Inferior screw: parallel to glenoid face or slight inferior
Posterior screw: aim at scapular body, ANTERIOR to suprascapular notch (nerve)
Anterior screw: safe direction

All screws bicortical (28-40mm depending on bone stock). Insert glenosphere (typically 36mm or 38mm).

Exam Pearl

Examiner Question: "Where do you aim the posterior screw in RSA baseplate fixation?"

Model Answer: "The posterior screw must aim at the scapular body ANTERIOR to the suprascapular notch. The suprascapular nerve runs in the notch and can be injured by a posteriorly-directed screw. Safe technique: angle the screw 10-15° anterior to the glenoid plane, aiming toward the scapular spine base. I use bicortical fixation (28-40mm screws) for maximum purchase. The superior screw aims toward the coracoid base which has the strongest bone."

Baseplate Fixation Dangers

Posterior screw - avoid suprascapular notch, aim screw anterior to prevent nerve injury
Unicortical screws - always aim for bicortical purchase (28-40mm)
Inadequate screw length - poor fixation leads to baseplate loosening (5-10% at 10 years)
Glenosphere size - too small increases notching risk, 36-38mm preferred

Step 9: Humeral Preparation

Open humeral canal with box chisel in CENTER of metaphysis. Sequential broaching to metaphyseal contact.

Key RSA Difference: Humeral retroversion is 0-20° (LESS than TSA's 20-30°). Decreased retroversion in RSA helps improve external rotation which is often limited in these patients.

Exam Pearl

Examiner Question: "What humeral version do you use in RSA and why is it different from TSA?"

Model Answer: "RSA uses 0-20° retroversion compared to TSA's 20-30°. The reason is external rotation optimization. RSA patients have deficient external rotators (teres minor, infraspinatus) and the medialized center of rotation further limits ER. By reducing humeral retroversion, we position the arm in relatively more external rotation at rest, improving functional ER. Some modern stems allow intraoperative version adjustment to fine-tune ROM."

Humeral Preparation Hazards

Varus entry point - causes stem malalignment and instability, enter CENTER of metaphysis
Eccentric broaching - risks perforation, follow anatomic axis
Excessive retroversion - worsens already limited external rotation
Fracture during broaching - osteoporotic bone common, gentle sequential broaching

Step 10: Humeral Trial and Assessment

Insert trial stem and polyethylene liner (typically 6mm, 9mm, or 12mm). Reduce shoulder. Assess:

STABILITY: Test in adduction (inferior instability most common in RSA)
ROM: Forward elevation should easily exceed 90°, aim for 120-140°
External rotation: Often limited (0-20°) due to loss of external rotators
Scapular notching: Feel for impingement between polyethylene and lateral scapula

Exam Pearl

Stability Testing: In RSA, the most common direction of instability is INFERIOR (opposite to TSA where it's posterior). Test stability with the arm adducted and apply distraction. If unstable inferiorly, use a thicker polyethylene liner.

Trial Assessment Pitfalls

Only testing forward elevation - must test INFERIOR stability (arm adducted, distract)
Accepting minimal instability - leads to postoperative dislocation (2-5%)
Not documenting ROM - record intraoperative elevation and ER for medicolegal purposes
Impingement with adduction - indicates potential notching, may need larger glenosphere

Step 11: Final Component Implantation

Insert final humeral stem (cemented or uncemented based on bone quality). Assemble polyethylene liner. Reduce shoulder - may feel clunk as concave poly engages convex glenosphere.

Exam Pearl

Examiner Question: "When do you cement the humeral stem in RSA?"

Model Answer: "I consider cementing for: (1) Poor bone quality - severe osteoporosis with wide medullary canal; (2) Metaphyseal defects - from fractures or revisions; (3) Channal/stem mismatch - if broach doesn't achieve adequate metaphyseal fit; (4) Periprosthetic fracture during surgery. Most primary RSA uses uncemented metaphyseal-engaging stems in good bone. If cementing, I use third-generation technique with canal preparation, restrictor, pressurization, and stem centralizer."

Final Implantation Hazards

Periprosthetic fracture - watch for proximal humerus fracture during impaction
Component disengagement - ensure polyethylene fully seated before reduction
Cement extravasation - if cementing, avoid posterior extrusion near nerves
Wrong polyethylene size - double-check liner matches trial that was stable

Step 12: Subscapularis Management (Controversial)

If subscapularis was present and released, repair is OPTIONAL in RSA (unlike TSA where it's critical). Many surgeons do NOT repair in RSA as function does not depend on it. If repairing: use heavy sutures to lesser tuberosity if good tissue quality.

Exam Pearl

Examiner Question: "Do you repair the subscapularis in RSA? Why is this different from TSA?"

Model Answer: "In RSA, subscapularis repair is OPTIONAL - many surgeons do not repair. Key differences: (1) RSA does not depend on cuff - deltoid is the sole motor via Grammont mechanism; (2) Subscapularis is often atrophied/absent in cuff tear arthropathy; (3) Internal rotation is preserved by pectoralis major, latissimus dorsi; (4) Anterior stability is inherent to conforming articulation. In TSA, subscapularis repair is CRITICAL because cuff function is required and anterior instability is the main concern. If I repair in RSA, it's for potential anterior stability benefit in borderline cases."

Subscapularis Decisions

Don't waste time searching - in CTA, subscapularis is often absent or non-functional
TSA thinking - don't apply TSA principles to RSA, cuff repair is not essential
Repair quality - if you repair, ensure tissue is adequate, don't repair rubbish tissue
Repair for stability only - consider if borderline anterior stability on trials

Step 13: Final Stability and ROM Check

Systematic testing:

Inferior stability (arm adducted, distract)
Anterior stability (extension, external rotation)
Posterior stability (forward flexion, internal rotation)
ROM: Forward elevation >90° easily, external rotation to neutral

Document intraoperative ROM.

Exam Pearl

Examiner Question: "What is the most common direction of instability in RSA and how do you test for it?"

Model Answer: "INFERIOR instability is most common in RSA - opposite to TSA where posterior instability predominates. Testing: (1) Hold arm adducted at side; (2) Apply inferior distraction force; (3) Assess for subluxation or dislocation inferiorly. If unstable: use thicker polyethylene liner (go from 6mm to 9mm or 12mm). Inferior instability occurs because the concave polyethylene sits on the convex glenosphere, and with arm adducted, the polyethylene can ride off inferiorly. The abduction pillow postoperatively helps prevent this."

Final Check Requirements

Test ALL directions - inferior (most common), anterior, and posterior stability
Accept nothing less than stable - instability = dislocation postoperatively
Document ROM - record forward elevation and external rotation achieved
Compare to trials - if final stability differs from trial, reassess components

Step 14: Closure and Immobilization

Copious irrigation (9-12L). Meticulous hemostasis. Place deep drain. Close deltopectoral interval loosely (overtightening restricts deltoid). Layered closure. Apply sling with ABDUCTION PILLOW (30° abduction) - prevents inferior instability.

Exam Pearl

Examiner Question: "Why do you use an abduction pillow after RSA and not a simple sling?"

Model Answer: "The abduction pillow maintains the shoulder at 30° abduction for two reasons: (1) Prevents inferior instability - the most common direction of dislocation in RSA. With arm adducted, the concave polyethylene can sublux off the glenosphere inferiorly; (2) Reduces tension on deltopectoral repair - the deltoid is the motor for RSA, so we must protect the soft tissue interval. This differs from TSA where posterior instability is the concern and a simple sling suffices. Duration is typically 6 weeks."

Closure and Immobilization Errors

Overtightening deltopectoral interval - restricts deltoid function, the motor for RSA
No drain - hematoma common, increases infection risk
Simple sling - must use ABDUCTION pillow (30°) to prevent inferior instability
Inadequate irrigation - RSA has higher infection rate than TSA (2-4%), irrigate thoroughly

Post-operative Protocol

Immobilization:

Sling with abduction pillow (30°) for 6 weeks
Different from TSA - can start passive forward elevation immediately (no subscapularis to protect)

Weeks 0-6:

Passive ROM: forward elevation to 120°, external rotation to 20°
Pendulum exercises
NO active elevation (protect deltoid healing and soft tissue)

Weeks 6-12:

Active-assisted then active ROM
Begin deltoid strengthening
Progressive ROM

Weeks 12+:

Unrestricted activities
Advanced strengthening

Follow-up Imaging:

X-rays at 6 weeks, 3 months, 1 year, then annually
Monitor for scapular notching and baseplate fixation

Expected Outcomes:

Pain relief: excellent (90%+)
Forward elevation: 120-140° typically
External rotation: often limited (neutral to 20°)
Patient satisfaction: 90%+

Complications

Complication Management

Exam Viva Scenarios

Practice these scenarios to excel in your viva examination

VIVA SCENARIOStandard

EXAMINER

"A 75-year-old woman presents with severe shoulder pain and inability to lift her arm above horizontal for the past 2 years. X-ray shows superior migration of the humeral head with acetabularization of the acromion. What is your diagnosis and management?"

EXCEPTIONAL ANSWER

This clinical and radiological picture is classic for **cuff tear arthropathy** (CTA) - the most common indication for RSA. **Diagnosis:** The combination of: 1. Pseudoparalysis (cannot actively elevate above horizontal) 2. Superior humeral head migration 3. Acetabularization of acromion (concave undersurface from chronic articulation) This represents Hamada Grade 4-5 cuff tear arthropathy. The rotator cuff is completely deficient with secondary arthritic changes. **Pre-operative Assessment:** 1. Confirm pseudoparalysis: active elevation less than 90° 2. Assess deltoid function - CRITICAL for RSA (examine bulk, strength, axillary nerve sensation) 3. CT scan: glenoid bone stock, version, morphology 4. MRI: confirm cuff status, fatty infiltration (Goutallier), deltoid quality 5. Medical optimization (age 75 - cardiac, respiratory fitness) **Why NOT TSA?** TSA requires intact rotator cuff. In CTA, the cuff is completely deficient, so TSA would result in: - Superior escape of humeral head - Edge loading of glenoid component - Rapid glenoid loosening (rocking-horse phenomenon) **Treatment - RSA:** Reverse shoulder arthroplasty is indicated because: 1. It provides a fixed fulcrum at the glenoid (glenosphere) 2. Medializes center of rotation - increases deltoid moment arm 3. Distalizes humerus - tensions deltoid 4. Allows deltoid ALONE to elevate the arm without cuff **Key Surgical Points:** - Deltopectoral approach - Baseplate flush with inferior glenoid (prevent notching) - Glenosphere typically 36-38mm - Humeral version 0-20° (less than TSA) - No subscapularis repair required **Expected Outcomes:** - Pain relief: 90%+ excellent - Forward elevation: 120-140° typical - External rotation: often limited (neutral) - counsel patient - 10-year survival: 90-95%

VIVA SCENARIOStandard

EXAMINER

"What is scapular notching, why does it occur, and how do you prevent it?"

EXCEPTIONAL ANSWER

**What is Scapular Notching?** Scapular notching is mechanical impingement and erosion of the lateral scapular border (scapular pillar) by the polyethylene humeral component during adduction. It is visible on AP X-rays as bone erosion below the glenosphere. **Sirveaux Classification:** - Grade 1: Small defect confined to scapular pillar - Grade 2: Defect extending to inferior screw - Grade 3: Defect extending over inferior screw - Grade 4: Defect extending under baseplate (loosening risk) **Incidence:** 50-80% of RSA cases show some degree of notching on radiographs, though many are asymptomatic Grade 1-2. **Why Does It Occur?** The medialized center of rotation in RSA (Grammont design) means the polyethylene moves in close proximity to the scapular pillar during adduction. Contributing factors: 1. **Superior baseplate position** - most important preventable factor 2. Small glenosphere diameter 3. Standard (non-lateralized) designs 4. Excessive humeral neck cut 5. Extended arm use (repeated adduction cycles) **How to Prevent It:** **Surgical Technique (Most Important):** 1. Position baseplate FLUSH with INFERIOR glenoid rim 2. Use 5-10° inferior tilt on baseplate 3. Aim central guide pin toward coracoid base 4. Expose inferior glenoid completely before inserting baseplate **Implant Selection:** 1. Larger glenosphere (38mm vs 36mm) - moves impingement point inferiorly 2. Lateralized glenoid designs (BIO RSA with bone graft, lateralized baseplates) 3. Inferior-eccentric glenospheres 4. Avoid excessive glenoid reaming (preserves inferior bone) **Clinical Significance:** - Grade 1-2: Usually asymptomatic, may not progress - Grade 3-4: Risk of progressive loosening, polyethylene wear - Advanced notching with loosening requires complex revision **Key Point:** Most notching is caused by surgical technique (baseplate too superior). The surgeon can prevent this by meticulous inferior glenoid exposure and correct baseplate positioning.

VIVA SCENARIOStandard

EXAMINER

"Explain the Grammont design principles and how RSA biomechanics differ from the native shoulder and TSA."

EXCEPTIONAL ANSWER

**The Grammont Design Principles:** Paul Grammont developed RSA in the 1980s based on key biomechanical concepts to allow shoulder function WITHOUT a functioning rotator cuff. **Key Design Changes:** **1. Medialized Center of Rotation:** - Native shoulder: center of rotation is at humeral head (lateral) - RSA: center of rotation moves to the glenoid face (medial) - Effect: Increases deltoid moment arm by 30-40% - The deltoid becomes a more efficient elevator **2. Distalized Humerus:** - The convex-on-concave articulation (ball on socket side) moves humerus distally - Effect: Tensions the deltoid by 2-3cm - Pretensioned deltoid generates more force **3. Fixed Fulcrum:** - Glenosphere provides a fixed fulcrum on the glenoid - Effect: Deltoid can act as a more efficient lever - No superior escape (unlike failed TSA) **4. Inversion of Articular Surfaces:** - Native/TSA: Convex humeral head in concave glenoid - RSA: Concave polyethylene on convex glenosphere - Effect: Inherent stability from conforming articulation **Biomechanical Comparison:** | Feature | Native Shoulder | TSA | RSA | |---------|----------------|-----|-----| | Center of rotation | Humeral head | Humeral head | Glenoid face | | Cuff requirement | Essential | Essential | Not required | | Motor for elevation | Supraspinatus + deltoid | Supraspinatus + deltoid | Deltoid alone | | Stability | Dynamic (cuff) | Dynamic (cuff) | Static (conforming) | | Deltoid moment arm | Standard | Standard | Increased 30-40% | **Functional Consequences:** **Advantages of RSA:** - Allows elevation without cuff (90%+ achieve >90° elevation) - Stable articulation - Reliable pain relief **Trade-offs of RSA:** - Limited external rotation (loss of external rotators + medialized fulcrum) - Scapular notching risk (medial center of rotation) - Not for young patients (higher revision burden) - Altered deltoid recruitment patterns **Modern Modifications:** - Lateralized designs (BIO RSA, 135° stems) aim to restore some lateral offset - Reduce notching, improve ER - Balance between stability and motion

Reverse Shoulder Arthroplasty - Exam Summary

High-Yield Exam Summary

References

Grammont PM, Baulot E. Delta shoulder prosthesis for rotator cuff rupture. Orthopedics. 1993;16(1):65-68.
Boileau P, Watkinson DJ, Hatzidakis AM, Balg F. Grammont reverse prosthesis: design, rationale, and biomechanics. J Shoulder Elbow Surg. 2005;14(1 Suppl S):147S-161S.
Sirveaux F, Favard L, Oudet D, et al. Grammont inverted total shoulder arthroplasty in the treatment of glenohumeral osteoarthritis with massive rupture of the cuff. J Bone Joint Surg Br. 2004;86(3):388-395.
Guery J, Favard L, Sirveaux F, et al. Reverse total shoulder arthroplasty: survivorship analysis of eighty replacements followed for five to ten years. J Bone Joint Surg Am. 2006;88(8):1742-1747.
Wall B, Nove-Josserand L, O'Connor DP, et al. Reverse total shoulder arthroplasty: a review of results according to etiology. J Bone Joint Surg Am. 2007;89(7):1476-1485.
Frankle M, Siegal S, Pupello D, et al. The Reverse Shoulder Prosthesis for glenohumeral arthritis associated with severe rotator cuff deficiency. J Bone Joint Surg Am. 2005;87(8):1697-1705.
Zumstein MA, Pinedo M, Old J, Boileau P. Problems, complications, reoperations, and revisions in reverse total shoulder arthroplasty: a systematic review. J Shoulder Elbow Surg. 2011;20(5):827-836.
Lädermann A, Denard PJ, Boileau P, et al. Effect of humeral stem design on humeral position and range of motion in reverse shoulder arthroplasty. Int Orthop. 2015;39(11):2205-2213.
Australian Orthopaedic Association National Joint Replacement Registry. Annual Report 2023. Adelaide: AOA.
Flatow EL, Harrison AK. A history of reverse total shoulder arthroplasty. Clin Orthop Relat Res. 2011;469(9):2432-2439.

Reverse Shoulder Arthroplasty (RSA)