Radial Head Arthroplasty (RHA)

Elbow Stabilizers Anatomy

The elbow is one of the most congruent and stable joints, with stability provided by:

Osseous Constraints (50% stability):

• Ulnohumeral articulation: Trochlea-olecranon-coronoid forms primary constraint
• Radiocapitellar joint: Secondary buttress, especially important in valgus loading
• Coronoid process: Anterior buttress preventing posterior subluxation - height critical

Ligamentous Constraints (50% stability):

• Medial Collateral Ligament (MCL): Primary valgus restraint, anterior bundle most important
• Lateral Collateral Ligament Complex (LCLC): Four components
  • LUCL (Lateral Ulnar Collateral Ligament): Primary restraint to PLRI, runs from lateral epicondyle to crista supinatoris
  • RCL (Radial Collateral Ligament): Blends with annular ligament
  • Annular Ligament: Encircles radial head, attaches to anterior/posterior margins of radial notch of ulna
  • Accessory LCL: Variable, reinforces lateral complex

Radial Head Biomechanics:

• Valgus stability: Secondary restraint - becomes primary if MCL deficient (Essex-Lopresti)
• Axial load transmission: 60% of axial load transmitted through radiocapitellar joint (40% through ulnohumeral)
• Longitudinal forearm stability: Critical link in interosseous membrane - radius-IOM-ulna unit
• Rotation: Smooth articulation with capitellum and PRUJ required for pronation-supination

Terrible Triad Pathomechanics

Mechanism: Fall on outstretched hand with elbow flexed, forearm supinated, valgus and axial load. Results in:

1. Elbow dislocation (posterolateral)
2. Radial head fracture (impact on capitellum)
3. Coronoid fracture (shear as ulna translates posteriorly)
4. LUCL disruption (tension failure)

Why "Terrible": All primary stabilizers injured simultaneously - osseous (radial head + coronoid) and ligamentous (LUCL ± MCL). Results in severe instability, high complication rates (stiffness, recurrent instability, HO), technically demanding treatment.

Kocher Approach Anatomy

Internervous Interval:

• Anconeus (posteriorly): Innervated by radial nerve main trunk (branch off before spiral groove)
• Extensor Carpi Ulnaris (anteriorly): Innervated by posterior interosseous nerve (terminal branch of radial nerve)

Approach Layers:

1. Skin and subcutaneous tissue
2. Deep fascia (incise longitudinally in Kocher interval)
3. Muscle interval (anconeus-ECU split)
4. Lateral capsule and annular ligament (incise to expose joint)
5. Radial head and radiocapitellar joint

Advantages:

• True internervous plane
• Excellent radial head exposure
• Extensile (can extend proximally for lateral epicondyle, distally for proximal radius)
• Preserves lateral collateral ligament if intact (or allows repair if torn)

Limitations:

• Limited medial access (if MCL repair needed, requires separate incision)
• PIN at risk if dissection extends >4-5cm distal or if forearm supinated
• LUCL vulnerable if not carefully identified and protected

Indications for Radial Head Arthroplasty

Primary Indications:

1. Mason III fracture: Comminuted with >3 fragments, not amenable to stable ORIF
2. Mason IV fracture: Radial head fracture with elbow dislocation (terrible triad)
3. Essex-Lopresti injury: Radial head fracture + DRUJ disruption - radial head replacement MANDATORY to restore longitudinal forearm stability
4. Irreparable radial head fracture with need for stability: Young active patient, MCL-deficient elbow, or valgus-loading occupation/sport

Secondary Indications:

• Failed ORIF with painful malunion limiting rotation
• Post-traumatic radiocapitellar arthritis (young patient, alternative to excision)
• Chronic radial head nonunion with instability
• Radial head excision with subsequent instability or DRUJ problems

Relative Contraindications:

• Severe capitellar cartilage damage (consider interposition arthroplasty or TEA in older patient)
• Active infection
• Poor bone quality precluding stem fixation
• Severe comminution extending into radial neck/shaft (may need longer stem or alternative fixation)
• Patient unable to comply with rehabilitation

Radial Head Excision vs Replacement Decision:

Excision appropriate when:

• Isolated radial head fracture, no associated injuries
• Low-demand patient
• Elbow stable through ROM after excision
• MCL and LCL intact
• No DRUJ instability

Replacement required when:

• Terrible triad (instability without radial head support)
• Essex-Lopresti (DRUJ instability)
• MCL deficiency (radial head is secondary valgus restraint)
• High-demand patient with valgus loading activities

Preoperative Planning

Imaging:

• AP and lateral elbow X-rays: Mason classification, associated fractures
• Radiocapitellar oblique view: Better radial head visualization
• CT scan: For complex fractures - assess comminution, coronoid involvement, capitellar injury
• Contralateral elbow X-rays: Template radial head diameter and height
• Forearm and wrist X-rays: Rule out Essex-Lopresti (DRUJ widening, ulnar variance)
• MRI: If concerned about MCL/LCL injury, capitellar osteochondral injury

Templating:

• Radial head diameter: Measure on AP X-ray or contralateral elbow - typically 20-24mm (range 18-26mm)
• Radial head height: Measure on lateral X-ray - typically 8-12mm from radial neck to articular surface
• Neck-shaft angle: 15° valgus - important for implant alignment

Implant Selection:

Modular Systems (preferred):

• Separate stem and head components
• Intraoperative flexibility
• Multiple head diameters (18-26mm in 2mm increments)
• Multiple head shapes (smooth, anatomic contoured)
• Multiple neck lengths (standard, +2mm, +4mm long for bone loss)
• Multiple stem diameters and lengths
• Examples: Evolve (Wright), rHead (SBi), Acumed RHS

Monopolar Systems (older):

• One-piece design
• Limited size options
• Less versatile
• Rarely used currently

Have available: Multiple head sizes and neck lengths for intraoperative customization

Associated Injuries Assessment

Terrible Triad Components:

1. Radial head fracture: Replacing
2. Coronoid fracture: Regan-Morrey Type I (<50% - observe), II (50% - may fix), III (>50% - MUST fix). O'Driscoll classification: tip, anteromedial, basal
3. LUCL injury: By definition torn in terrible triad - MUST repair

Essex-Lopresti Components:

1. Radial head fracture: Replacing
2. Interosseous membrane disruption: Clinical (forearm pain, DRUJ instability)
3. DRUJ injury: Assess stability, may need reconstruction

Additional Injuries to Assess:

• MCL injury: Valgus instability (5-10% of terrible triads)
• Capitellar osteochondral injury: May contraindicate replacement
• Medial epicondyle avulsion: May require fixation
• Ulnar nerve injury: Pre-existing or iatrogenic risk if medial approach needed

Positioning and Setup

Patient Position:

• Supine: Arm across chest on padded bolster OR arm on radiolucent arm board
• Lateral decubitus: Affected arm uppermost on arm board (alternative)
• Elbow flexed 90° for approach
• Upper arm tourniquet: 250mmHg (release before closure for hemostasis)

Equipment:

• C-arm fluoroscopy positioned for AP and lateral elbow views
• Radial head implant sets (multiple sizes available)
• Small fragment instrument set
• Suture anchors (2.3-2.8mm) for LUCL/MCL repair
• Hohmann retractors (various sizes)
• High-speed burr (optional for neck preparation)
• Intraoperative sizing guides and trial components

Critical Operative Steps

Step 1: Kocher Approach and Superficial Dissection

Incision: Lateral longitudinal 6-8cm, centered over lateral epicondyle, extending from 3cm proximal to epicondyle to 5cm distal along supinator ridge. Can curve slightly posteriorly for cosmesis.

Superficial dissection:

• Incise skin and subcutaneous tissue
• Identify and protect lateral antebrachial cutaneous nerve branches (retract gently if encountered)
• Expose deep fascia overlying anconeus and ECU

Interval identification:

• Anconeus (posterior): Fibers run obliquely from lateral epicondyle to lateral olecranon
• ECU (anterior): Fibers run longitudinally along forearm
• Interval usually obvious - anconeus more posterior, ECU more anterior
• Incise fascia longitudinally between muscles

Step 2: Deep Dissection and PIN Protection

CRITICAL STEP - Forearm Position:

• FULLY PRONATE FOREARM and maintain pronation throughout
• Pronation moves PIN anteriorly around radial neck: 4cm anterior in pronation vs only 1.5cm in supination
• This is single most important step for PIN safety

Deep dissection:

• Bluntly split anconeus-ECU interval with finger or instrument
• Elevate ECU anteriorly off lateral capsule
• Anconeus remains posterior
• Expose lateral collateral ligament complex deep to interval

LUCL management:

• Identify LUCL origin on lateral epicondyle and insertion on crista supinatoris
• If intact: carefully preserve - retract anteriorly to expose capsule
• If torn (terrible triad): tag with heavy suture for later repair - do NOT let retract

Capsular exposure:

• Incise lateral capsule and annular ligament longitudinally anterior to LUCL (or where LUCL was)
• Opens radiocapitellar joint
• Insert Hohmann retractors BLUNTLY around radial neck (never sharp dissection)
• Limit distal dissection to 4-5cm from lateral epicondyle (PIN safety)

Step 3: Radial Head Fragment Assessment and Removal

Assessment:

• Fully expose fracture
• Assess number of fragments: ≤2-3 large fragments with good bone = consider ORIF instead
• Assess comminution: >3 small fragments = proceed with replacement
• Assess articular surface damage
• Assess radial neck integrity

Fragment removal:

• Remove ALL radial head fragments systematically with rongeur, small osteotome, curette
• SAVE LARGEST FRAGMENT for sizing reference (measure diameter and height with calipers)
• Remove loose fragments from joint - inspect anteriorly, posteriorly, PRUJ
• Copious irrigation to flush small fragments

Associated injury assessment:

• Capitellum: Inspect cartilage quality - if severely damaged, reconsider replacement (may need excision or TEA)
• Coronoid: Assess for fracture - measure height, classify (Type I-III)
• LUCL: Confirm intact vs torn
• MCL: Palpate medially for tenderness suggesting injury

Step 4: Radial Neck Preparation

Neck cut:

• Goal: Flat surface perpendicular to radial shaft axis, minimal bone resection
• Use oscillating saw or sagittal saw
• Cut level: 2-3mm below fracture line (preserves bone stock)
• Check with trial to ensure adequate seating surface
• Verify cut perpendicular to shaft (not angled anteriorly/posteriorly)

Canal preparation:

• Ream medullary canal with sequential hand reamers
• Start small (2.5-3mm), increase to final stem size (typically 3-4mm)
• Depth 20-30mm adequate for standard stems
• Feel for cortical engagement, avoid perforation
• If canal widened by fracture, may need larger diameter stem or cement

Step 5: Implant Sizing - CRITICAL STEP

DIAMETER Sizing:

• Measure saved radial head fragment with calipers OR use contralateral X-ray template
• Typical diameter: 20-24mm (range 18-26mm)
• Trial heads: Should match native diameter
• No overhang (causes PRUJ impingement)
• Not undersized (instability, edge loading)

HEIGHT Sizing - Radiocapitellar Line Method:

• Insert trial stem and head component
• Obtain AP fluoroscopy view of elbow
• RADIOCAPITELLAR LINE: Top of radial head should align with LATERAL EDGE OF CORONOID PROCESS
• If proud (overlengthened): Decrease head thickness or use shorter neck
• If recessed (underlengthened): Increase head thickness or use longer neck
• Typical height from neck cut to articular surface: 8-12mm

Functional Sizing:

• Check ROM with trials: 0-130° flexion, 80-80° pronation-supination
• No impingement or catching
• Smooth rotation
• Slight distraction acceptable, no subluxation

Fine-tuning:

• Some systems offer thin/standard/thick heads (1-2mm increments)
• Neck length options: standard, +2mm, +4mm (for bone loss)
• Goal: Restore native anatomy as closely as possible

Step 6: Trial Reduction and Stability Testing

Stability Assessment with Trials:

1. ROM Testing: Passive flexion-extension 0-130°, pronation-supination 80-80° - should be smooth, no subluxation

2. Valgus Stress: Elbow 30° flexion, forearm neutral, apply valgus stress

   • Grade 0: No opening
   • Grade I: 5mm opening
   • Grade II: 10mm opening
   • Grade III: >10mm opening, no endpoint
   • Grade II-III indicates MCL injury

3. Varus Stress: Same position, varus stress - tests LCL integrity

4. PLRI Test: Supination + valgus + axial compression with elbow flexion

   • Positive: Radial head subluxes posteriorly (LUCL incompetent)
   • If positive: LUCL MUST be repaired
   • After LUCL repair, retest - should be negative

5. Fluoroscopy: AP and lateral views

   • Confirm radiocapitellar line alignment
   • No subluxation
   • Concentric radiocapitellar joint
   • If terrible triad, assess coronoid position

Decision Points:

• If unstable despite appropriate radial head sizing: Address associated injuries (coronoid, LUCL, MCL)
• If terrible triad: Must address all three components for stability

LUCL Repair Technique

Indications: LUCL torn (terrible triad) or positive PLRI test

Technique:

1. Prepare lateral epicondyle - remove soft tissue, expose bone at LCL footprint (slightly anterior and distal to isometric point)
2. Place 2-3 suture anchors (2.3-2.8mm) loaded with high-strength braided sutures
3. Pass sutures through LUCL remnant tissue using horizontal mattress or modified Krakow technique
4. Reduce elbow: 30-40° flexion, forearm neutral, apply slight varus stress
5. Tie sutures securing LUCL anatomically
6. Test stability: PLRI test should be negative, varus stress stable

Augmentation: If LUCL tissue inadequate (chronic injury, poor quality), consider:

• Palmaris longus autograft reconstruction
• Gracilis autograft
• Allograft (semitendinosus, plantaris)
• Drill tunnels in lateral epicondyle and crista supinatoris, weave graft in figure-8 or docking technique

Outcomes: Proper LUCL repair critical for terrible triad stability - failure leads to recurrent PLRI and dislocation

Coronoid Fixation Technique

Indications:

• Regan-Morrey Type II (50% height) if persistent instability
• Type III (>50% height) - MANDATORY fixation
• O'Driscoll Type II-III (anteromedial facet, basal)

Suture Lasso Technique (most common for small fragments):

1. Reduce coronoid fragment anatomically
2. Drill 2-3 holes in ulna metaphysis distal to fracture, exiting anteriorly
3. Pass sutures (2-0 FiberWire or Ethibond) through holes
4. Loop sutures around/through coronoid fragment
5. Tie sutures over posterior ulna bridge, securing fragment
6. Check reduction with fluoroscopy

Suture Anchor Technique:

1. Prepare coronoid fracture bed (minimal debridement)
2. Place 1-2 small suture anchors (2.0-2.3mm) in fracture bed
3. Pass sutures through coronoid fragment
4. Reduce and tie, securing fragment anatomically

Screw Fixation (for large fragments with good bone):

1. Approach: Can use antegrade (from posterior ulna shaft) or posteromedial approach
2. Reduce fragment anatomically, hold with K-wires
3. Insert 2.0-2.7mm screws from posterior ulna into fragment
4. Countersink heads below cortex
5. Danger: Ulnar nerve anteriorly - must protect if posteromedial approach used
6. Technically demanding, suture techniques often preferred

Check: Fluoroscopy confirms anatomic reduction, stable fixation

MCL Assessment and Repair

When to Assess: After radial head replacement, LUCL repair, coronoid fixation complete

Testing: Valgus stress with elbow 30° flexion, forearm neutral

• Grade 0-I: MCL intact or minor sprain - heals nonoperatively
• Grade II: Moderate opening but endpoint - may heal with protection
• Grade III: Severe opening, no endpoint - consider repair

MCL Repair Indications:

• Grade III valgus instability despite all other repairs
• Open MCL disruption noted intraoperatively
• High-demand overhead athlete

Technique (requires separate medial incision):

1. Medial utility incision along medial epicondyle
2. Identify and protect ulnar nerve (decompress and transpose if needed)
3. Expose MCL anterior bundle origin (medial epicondyle) and insertion (sublime tubercle)
4. Repair with suture anchors similar to LCL technique
5. Test valgus stability

Note: MCL repair less common in terrible triad than LUCL repair - most terrible triads have posterolateral instability pattern, not medial

Hinged External Fixator

Indications:

• Persistent instability despite addressing radial head, coronoid, LCL, MCL
• Complex terrible triad variants
• Poor tissue quality precluding secure ligament repair
• Concern for re-dislocation during healing

Application:

• Spanning elbow joint with axis aligned to elbow axis of rotation
• Allows flexion-extension motion (protects against stiffness)
• Blocks varus-valgus and rotational instability
• Typically 4-6 weeks, then remove and continue protected ROM

Outcomes: Allows early ROM while protecting repairs - balances stiffness prevention with stability

Immobilization Protocol

Simple RHA (isolated radial head):

• Posterior elbow splint at 90° flexion for 5-7 days
• Remove splint, begin active-assisted ROM immediately
• No specific precautions after splint removal
• Sling for comfort 1-2 weeks

Terrible Triad:

• Hinged elbow brace initially locked 30-100° flexion for 2 weeks (protects LCL repair)
• ROM allowed within brace limits with hand therapist supervision
• Sling between exercises
• Week 2-4: Progressive brace arc extension to 0-130° based on stability
• Week 4-6: Remove brace if stable, transition to unrestricted active ROM
• Strengthening begins week 6-8

Rehabilitation Protocol

Phase 1 (Weeks 0-2) - Protection:

• Gentle active-assisted ROM within brace limits (30-100°)
• Hand therapist supervised sessions 3x daily: flexion-extension, forearm rotation
• Edema control: Ice, elevation, compression
• Finger, wrist, shoulder ROM immediately (prevent stiffness)
• Sling between exercises

Phase 2 (Weeks 2-4) - Progressive Motion:

• Increase brace motion arc progressively: 20-110°, 10-120°, 0-130°
• Active-assisted and active ROM all planes
• Forearm rotation exercises (pronation-supination critical)
• Gentle stretching if stiffness developing
• Continue edema control

Phase 3 (Weeks 4-6) - Active Motion:

• Remove brace if stability adequate (check with surgeon)
• Full active ROM exercises - goal 0-130° flexion, 80-80° rotation
• Begin gentle strengthening: isometrics, light resistance
• Functional activities simulation
• Address any motion deficits with aggressive therapy

Phase 4 (Weeks 6-12) - Strengthening:

• Progressive resistance training: biceps, triceps, forearm, wrist
• Eccentric exercises
• Proprioceptive training
• Sport/work-specific exercises
• Advance resistance as tolerated

Phase 5 (Months 3-6) - Return to Activity:

• Unrestricted strengthening
• Return to full activities including sports
• Continued stretching to maintain ROM
• Most patients achieve maximum improvement by 6 months

ROM Goals:

• Flexion-extension: 30-130° (100° arc functional for ADLs)
• Pronation-supination: 80-80° (full rotation critical for function)
• 80-85% patients achieve functional ROM after simple RHA
• 70-75% after terrible triad (stiffness main issue)

Heterotopic Ossification Prophylaxis

Incidence: 20-50% after terrible triad without prophylaxis

Indomethacin Protocol (standard in Australia):

• Dose: 25mg TDS (three times daily) x 6 weeks starting postop day 1
• Mechanism: COX inhibitor reduces prostaglandin-mediated osteoprogenitor differentiation
• Efficacy: Reduces HO to 10-15%
• Side effects: GI upset (dyspepsia, nausea - use with PPI if needed), renal dysfunction (monitor creatinine), bleeding (avoid in high-risk)
• Contraindications: Active PUD, severe renal disease, allergy to NSAIDs
• PBS listing: Yes, cost-effective
• Counsel patient: GI side effects common but compliance critical - don't stop without discussing with surgeon

Radiation Therapy (alternative):

• Single dose 7-8 Gy to elbow within 72 hours postoperatively
• Mechanism: Inhibits osteoprogenitor cell proliferation
• Efficacy: Very effective (HO rate <5%)
• Indications: Indomethacin contraindicated, very high-risk cases (prior HO, severe trauma), HO recurrence after excision
• Limitations: Radiation exposure, availability, logistics, requires radiation oncology coordination
• Use: Selective at specialized centers in Australia

High-Risk Factors for HO:

• Severe trauma (terrible triad, multiply injured patient)
• Delay to surgery (>1 week)
• Head injury (CNS injury increases HO dramatically)
• Heterotopic ossification in other joints
• Severe soft tissue injury

Follow-Up Schedule

2 Weeks:

• Wound check, remove sutures
• Assess early ROM progress
• Adjust brace settings if terrible triad
• Confirm hand therapy compliance

6 Weeks:

• X-rays: AP, lateral elbow
• Assess implant position (alignment, height)
• Look for radiolucent lines (early loosening)
• Assess early HO formation
• ROM measurement
• Remove brace if stable
• Advance strengthening

3 Months:

• Clinical exam: ROM, strength, stability
• X-rays: Assess consolidation, HO maturation, implant fixation
• Address any complications (stiffness, pain, instability)

6 Months:

• Functional assessment
• X-rays: Implant fixation, capitellar cartilage, HO
• Most patients plateau by this point

1 Year:

• Final outcome assessment
• Long-term X-ray surveillance protocol (yearly initially, then every 2-3 years)
• Monitor for late complications (loosening, erosion, HO, instability)

Long-term Surveillance:

• Yearly X-rays first 3 years
• Then every 2-3 years lifelong
• Watch for progressive radiolucencies, capitellar erosion, subsidence, HO progression