Radial Head Arthroplasty

Mason Classification of Radial Head Fractures

Type I: Non-displaced

• Less than 2mm displacement
• No mechanical block
• Treatment: Conservative (sling, early ROM)
• Outcome: Excellent (90-95%)

Type II: Displaced Partial Head

• Greater than 2mm displacement
• May have mechanical block
• Treatment: ORIF if block, otherwise conservative
• Outcome: Good (80-85%)

Type III: Comminuted Entire Head

• Greater than 3 fragments
• Unreconstructable
• Treatment: Replacement or excision (if stable, low demand)
• Outcome: Variable (70-85% with replacement)

Type IV: With Elbow Dislocation

• Radial head fracture + dislocation
• Often terrible triad
• Treatment: Replacement + address instability
• Outcome: Worse (60-75% with proper management)

Mason classification guides treatment decisions and predicts outcomes.

Terrible Triad Components

Component 1: Radial Head Fracture

• Usually Mason III/IV
• Comminuted, unreconstructable
• Treatment: Replacement

Component 2: Coronoid Fracture

• Regan-Morrey classification
• Type I: Less than 50% height (may be stable)
• Type II: 50% height (may need fixation)
• Type III: Greater than 50% height (must fix)
• Treatment: Fix if greater than 50% height

Component 3: LCL/LUCL Injury

• Lateral collateral ligament disruption
• LUCL is primary restraint to PLRI
• Treatment: Repair with suture anchors

Management Principle: All three components must be addressed for stability. Failure to address any component leads to persistent instability.

Understanding terrible triad pathoanatomy is essential for proper management.

Decision Tree

Step 1: Assess Fracture Pattern

• Mason I: Conservative
• Mason II: ORIF if mechanical block, otherwise conservative
• Mason III: Replacement if greater than 3 fragments
• Mason IV: Replacement + address instability

Step 2: Assess Associated Injuries

• Terrible triad? → Address all three components
• Essex-Lopresti? → Replacement mandatory (never excise)
• Isolated fracture? → Replacement or excision (if stable, low demand)

Step 3: Assess Stability

• Stable elbow? → Replacement or excision (if low demand)
• Unstable elbow? → Replacement mandatory (never excise)

Step 4: Patient Factors

• Age, demand, compliance
• Bone quality
• Functional requirements

The goal is stable elbow with functional ROM and prevention of long-term complications.

Treatment Alternatives

ORIF:

• Indication: Reconstructable fractures (less than 3 fragments)
• Advantages: Preserves native anatomy
• Disadvantages: Higher failure rate in comminuted fractures

Excision:

• Indication: Isolated fracture in low-demand elderly with stable elbow
• Advantages: Simpler, no implant
• Disadvantages: Contraindicated in unstable elbows, Essex-Lopresti
• Modern trend: Replacement preferred over excision

Conservative:

• Indication: Mason I, stable Mason II without block
• Advantages: Non-operative
• Disadvantages: Risk of stiffness, nonunion

Understanding alternatives helps ensure replacement is truly indicated.

Pre-operative Planning Steps

1. Fracture Assessment:

• Mason classification
• Fragment number and size
• Reconstructability (less than 3 fragments = consider ORIF)

2. Associated Injuries:

• Terrible triad components (coronoid, LCL)
• Essex-Lopresti (IOM, DRUJ)
• Capitellar damage
• MCL injury

3. Templating:

• Measure radial head diameter on AP X-ray (typically 20-24mm)
• Measure height on lateral (typically 8-12mm)
• Compare with contralateral if available

4. Implant Selection:

• Modular vs monopolar
• Multiple sizes available
• Have backup sizes

5. Equipment:

• Kocher approach instruments
• Trial components
• Fluoroscopy
• Suture anchors (if ligament repair needed)

Proper planning ensures optimal sizing and addresses all injuries.

Supine Position

Setup:

• Supine with arm across chest on padded bolster
• Alternative: Lateral decubitus with arm uppermost
• Elbow flexed 90° on arm board
• Upper arm tourniquet (250mmHg)
• Fluoroscopy available

Landmarks to Mark:

• Lateral epicondyle
• Radial head (palpable)
• Kocher interval (anconeus-ECU)

Critical Points:

• Arm position allows access to lateral elbow
• Fluoroscopy positioned for AP and lateral views
• Tourniquet allows bloodless field

Proper positioning is essential for adequate exposure and fluoroscopic imaging.

Lateral Approach

Incision:

• Lateral longitudinal or slightly curved
• 6-8cm centered over lateral epicondyle
• Extends distally along posterolateral forearm
• From 3cm proximal to lateral epicondyle to 5cm distal

Superficial Dissection:

• Incise skin and subcutaneous tissue
• Identify and protect lateral antebrachial cutaneous nerve
• Develop plane to deep fascia

Interval Identification:

• Anconeus (posteriorly): Innervated by radial nerve
• ECU (anteriorly): Innervated by PIN
• Interval: Internervous plane between anconeus and ECU
• Incise fascia longitudinally in this interval

Deep Dissection:

• Split interval between anconeus and ECU
• Elevate ECU anteriorly off lateral joint capsule
• Anconeus remains posterior
• Expose LCL complex deep to interval

Danger Structures:

• PIN: 4-5cm distal to lateral epicondyle - protect with pronation
• LCL/LUCL: Preserve if intact, tag if torn for repair

Careful dissection protects PIN and preserves ligaments.

Critical Safety Measure

PIN Anatomy:

• Terminal motor branch of radial nerve
• Passes through supinator muscle
• Emerges 4-5cm distal to lateral epicondyle
• Location varies with forearm rotation

Protection Strategy:

• FULL PRONATION: Moves PIN from 1.5cm (supination) to 4cm (pronation) anterior to radial neck
• Maintain pronation throughout procedure
• Limit distal dissection to less than 4-5cm from lateral epicondyle
• Use blunt dissection around radial neck
• Avoid sharp dissection in PIN area

Consequences of Injury:

• Motor weakness: Wrist extension, finger extension, thumb extension
• Most are neuropraxias (recover 3-6 months)
• Some permanent (10-20% of injuries)

Prevention:

• Pronation is most important measure
• Identify PIN if extended exposure needed
• Careful retraction

PIN protection via pronation is the most critical safety measure.

Radial Head Fragment Management

Assessment:

• Number of fragments (greater than 3 = replacement)
• Fragment size and quality
• Articular surface damage
• Radial neck integrity

Removal Technique:

• Remove ALL radial head fragments systematically
• Use rongeur, small osteotome, curette
• SAVE LARGEST FRAGMENT for sizing reference
• Measure diameter and height

Joint Inspection:

• Remove loose fragments from joint
• Inspect anteriorly, posteriorly, and in PRUJ
• Irrigate to flush small fragments

Associated Structure Assessment:

• Capitellum: Assess cartilage quality - if severely damaged, reconsider replacement
• Coronoid: If fracture present, must be addressed
• LCL: If torn, requires repair

Preparation:

• Expose proximal radial neck and metaphysis
• Prepare for neck cut

Systematic fragment removal and joint inspection are essential.

Radial Neck Cut

Goal:

• Create flat surface perpendicular to radial shaft axis
• Minimal bone resection (2-3mm below fracture line)
• Preserve metaphyseal bone stock

Technique:

• Use oscillating saw or sagittal saw
• Cut level: 2-3mm below fracture line
• Cut perpendicular to radial shaft longitudinal axis
• Avoid excessive resection (shortening causes instability)
• Avoid inadequate resection (poor bone stock for stem)

Reaming:

• Ream medullary canal with sequential hand reamers
• Match stem diameter (typically 3-4mm)
• Depth 20-30mm adequate for standard stems
• Avoid perforation of radial cortex

Pitfalls:

• Excessive bone resection (shortens radius, disrupts DRUJ)
• Angled cut (implant malposition, instability)
• Radial shaft perforation during reaming
• Inadequate bone stock for stem fixation

Proper neck preparation ensures stable implant fixation and correct alignment.

Critical Step - Sizing

Sizing Methods:

1. Diameter:

• Measure native radial head fragment
• Use contralateral X-ray template
• Typically 20-24mm (range 18-26mm)
• Trial heads should match native diameter
• Not overhang or be too small

2. Height (MOST CRITICAL):

• Radiocapitellar line on AP fluoroscopy
• Radial head should align with lateral edge of coronoid
• Height from neck cut to top of head typically 8-12mm
• Insert trial stem and head
• Check height fluoroscopically
• Head should be flush with lateral coronoid edge
• Not proud (overlengthening) or recessed (underlengthening)

3. ROM and Stability Testing:

• Check through full ROM (0-130° flexion, pronation-supination)
• No impingement
• Smooth rotation
• Stable through stress testing

4. Fine-tuning:

• Some systems allow thin/standard/thick heads
• Standard vs long necks compensate for bone loss

Consequences of Errors:

• Overlengthening (most common, 10-20%): Capitellar erosion, pain, stiffness, early failure
• Underlengthening: Instability, valgus laxity, DRUJ instability
• Wrong diameter: Overhang (impingement) or undersizing (instability)

Meticulous sizing using radiocapitellar line prevents overlengthening.

Final Implant Placement

Press-Fit Technique (Most Common):

• Clean and dry radial canal
• Impact stem gently with mallet
• Modular systems: Insert stem first, then attach head component
• Locking taper mechanism ensures secure connection
• Ensure head fully seated and locked

Cemented Technique (Rare):

• Low-viscosity cement
• Canal pressurization
• Insert stem, hold until polymerization
• Reserved for osteoporotic bone or enlarged canal

Head Orientation:

• Some systems have elliptical or asymmetric heads
• Align anatomically
• Check with fluoroscopy

Final Checks:

• Head fully seated on taper, locked securely
• No micro-motion
• Implant perpendicular to shaft
• Fluoroscopy confirms position
• ROM smooth without impingement

Secure implant insertion ensures long-term stability and function.

LUCL Repair (If Torn)

Indication:

• LUCL torn (terrible triad or isolated injury)
• Must repair to prevent posterolateral rotatory instability

Technique:

• Prepare lateral epicondyle (remove soft tissue, expose bone)
• Place 2-3 suture anchors (2.3-2.8mm) in lateral epicondyle at LCL footprint
• Load anchors with high-strength sutures
• Pass sutures through LUCL remnant tissue
• Reduce elbow (flex 30-40°, forearm neutral, apply varus stress)
• Tie sutures securing LUCL to anatomic position
• Test stability (no PLRI, varus stable)

Augmentation:

• If LUCL tissue inadequate, consider augmentation
• Palmaris longus autograft or allograft reconstruction
• Alternative: Fix avulsed bone fragment with anchors or screws

Testing:

• Varus stress should be stable
• PLRI test should be negative
• No posterolateral subluxation

LUCL repair is essential for stability in terrible triad injuries.

Coronoid Fracture Management

Classification:

• Regan-Morrey Type I: Less than 50% height (may be stable)
• Type II: 50% height (may need fixation)
• Type III: Greater than 50% height (must fix)

Indications for Fixation:

• Type II-III coronoid fractures
• Any coronoid fracture with persistent instability after radial head replacement and LCL repair

Techniques:

• Suture lasso: For small anteromedial fragments
• Drill holes in ulna, pass sutures through fragment, tie over bone bridge
• Suture anchors: 1-2 anchors in coronoid fracture bed, secure fragment
• Screws: 2.0-2.7mm screws from posterior ulna shaft (technically demanding)

Most Common:

• Suture techniques (lasso or anchors) are technically simpler
• Screws reserved for large fragments with good bone quality

After Fixation:

• Assess stability through full ROM
• Elbow should be stable after addressing all three components

Coronoid fixation is essential for stability in terrible triad when greater than 50% height.

Final Stability Check

Comprehensive Assessment:

1. Passive ROM:

• Should achieve 0-130° flexion, 80-80° pronation-supination without force
• If limited, assess for impingement (implant overhang, oversizing, soft tissue)

2. Active ROM:

• Patient contracts muscles if awake
• Simulate with electrostimulation if needed

3. Varus/Valgus Stability:

• 0-I laxity acceptable
• II-III indicates inadequate repair

4. Posterolateral Rotatory Instability:

• Should be negative (no radial head subluxation)
• Test: Supination + valgus + axial load

5. Fluoroscopy:

• AP and lateral views confirm:
• Radial head height (radiocapitellar line)
• No subluxation
• Concentric reduction
• Coronoid position if fixed
• Appropriate joint space
• Implant alignment

If Unstable:

• Consider hinged external fixator as temporary stabilizer
• Spans elbow, allows ROM, protects repairs for 4-6 weeks

Final stability assessment ensures adequate repair and prevents complications.

Wound Closure

Irrigation:

• Copious irrigation with 2-3 liters normal saline
• Remove bone debris, blood, loose fragments

Hemostasis:

• Release tourniquet
• Achieve meticulous hemostasis with bipolar cautery

Capsule/Annular Ligament:

• Repair if sufficient tissue with 2-0 absorbable sutures
• Often destroyed in comminuted fractures
• If unrepairable, healing by secondary intention acceptable

Deep Layer:

• Repair interval between anconeus and ECU with 2-0 absorbable sutures
• Recreates lateral soft tissue envelope

Subcutaneous:

• 3-0 absorbable sutures without tension

Skin:

• 3-0 or 4-0 nylon interrupted or running
• Alternative: Subcuticular absorbable

Dressing and Splint:

• Sterile dressing
• Posterior elbow splint or hinged elbow brace at 90° flexion
• Simple RHA: Splint 5-7 days only
• Terrible triad: Splint/brace 2-4 weeks with early protected ROM

Proper closure and immobilization optimize healing and outcomes.

Isolated Radial Head Arthroplasty

Early (0-2 weeks):

• Splint 5-7 days for comfort
• Remove sutures 10-14 days
• Begin active-assisted ROM immediately after splint removal
• Full active ROM by 2-3 weeks

Intermediate (2-6 weeks):

• Progressive ROM exercises
• Begin gentle strengthening
• Return to light activities

Late (6-12 weeks):

• Full strengthening
• Return to activities 3-4 months
• Monitor for complications

Simple RHA rehabilitation is less restrictive than terrible triad.

Complex Instability Protocol

Week 0-2:

• Hinged elbow brace locked 30-100° initially
• Protects LCL repair
• Gentle active-assisted ROM within brace limits
• Hand therapist 3x daily
• Sling between exercises
• Fingers, wrist, shoulder ROM immediately

Week 2-4:

• Increase brace motion limits progressively toward full ROM (0-130°)
• Active-assisted and active ROM
• Begin forearm rotation exercises

Week 4-6:

• Remove brace if stability adequate
• Full active ROM all planes
• Begin gentle strengthening

Week 6-12:

• Progressive strengthening
• Functional activities

Month 3-6:

• Return to unrestricted activities including sports

Goal ROM:

• 30-130° flexion (100° arc functional for ADLs)
• Full pronation-supination
• Most achieve by 4-6 months with dedicated therapy

Terrible triad rehabilitation balances early ROM with repair protection.

Heterotopic Ossification Prevention

Indomethacin:

• 25mg three times daily for 6 weeks
• Reduces HO from 40-50% to 10-15%
• Use with PPI for GI protection
• Counsel on compliance despite GI side effects

Radiation:

• Single dose 7-8 Gy within 72 hours
• Very effective (less than 5% HO)
• Logistically challenging
• Reserved for very high-risk cases

Compliance:

• Critical for effectiveness
• Monitor for side effects
• Adjust if needed (PPI, dose reduction)

HO prophylaxis is standard in terrible triad cases.