Paediatric Monteggia Fracture Dislocation - ORIF Ulna & Radial Head Reduction

Absolute Indications

1. Acute Monteggia (Bado Type I-IV) with displaced ulnar fracture

   • Failed closed reduction of ulna and/or radial head
   • Open fractures requiring surgical debridement
   • Associated neurovascular injury requiring exploration
   • Irreducible radial head (soft tissue interposition)

2. Chronic/Missed Monteggia (>3 weeks)

   • Persistent radial head dislocation with symptomatic instability
   • Progressive cubitus valgus deformity
   • Chronic pain or mechanical symptoms
   • PIN compression from chronic dislocation

3. Complications of Initial Treatment

   • Loss of reduction after closed treatment
   • Ulnar malunion preventing radial head reduction
   • Persistent radius plastic deformation
   • Failed annular ligament healing with instability

Relative Indications

• Bado Type I in adolescent with reliable closed reduction but unstable radial head (consider CRPP ulna first)
• Minimally displaced ulnar fracture with radial head subluxation (trial closed reduction first)
• Type III lateral dislocation in young child (some treat closed if stable)

Pre-operative Planning

Imaging Assessment:

• AP and lateral forearm/elbow views
• Radiocapitellar line on ALL views (AP/lateral/oblique)
• Assess for radius plastic deformation (radial bowing on AP view)
• Contralateral comparison for subtle deformity
• CT scan if chronic case with bone block or coronoid fracture

Classification:

• Bado Type (I-IV) determines approach and prognosis
• Acute (<3 weeks) vs chronic (>3 weeks) - affects need for annular ligament reconstruction
• Associated injuries: coronoid fracture, olecranon fracture, proximal radius fracture

Surgical Planning:

• Implant selection: 2.4mm or 2.7mm plate vs intramedullary wire (based on age/fracture pattern)
• Plan for radius plastic deformation correction (osteoclasis vs formal osteotomy)
• Anticipate annular ligament reconstruction if chronic or known ligament disruption
• Consider transarticular K-wire only if reconstruction not feasible (remove 3 weeks maximum)

Special Considerations in Paediatrics:

• Minimal periosteal stripping (excellent periosteal sleeve healing)
• Avoid transphyseal screws near proximal ulna physis
• Smaller implants (2.4mm often adequate vs 2.7mm in adolescents)
• Lower threshold for intramedullary fixation in young children (less soft tissue trauma)

Surgical Anatomy

Ulnar Shaft:

• Subcutaneous along medial/posterior border (direct approach)
• Triangular cross-section: posterior subcutaneous border, anterior interosseous border, lateral border
• Ulnar nerve posterior to medial epicondyle in cubital tunnel (2-3cm medial to surgical field)
• Proximal ulna physis at coronoid/olecranon (avoid transphyseal fixation)

Radial Head and Neck:

• Articulates with capitellum (radiocapitellar joint) and radial notch of ulna (proximal radioulnar joint)
• Annular ligament wraps around radial head, attaches to anterior and posterior margins of radial notch
• Blood supply from posterolateral vessels entering radial neck (preserve soft tissue envelope)
• Radial head 15° offset from radial shaft axis (creates radiocapitellar line relationship)

Posterior Interosseous Nerve (PIN):

• Radial nerve bifurcates into PIN and superficial sensory branch at level of radiocapitellar joint
• PIN enters supinator muscle through arcade of Frohse (4-6cm distal to lateral epicondyle)
• Winds around radial neck ANTERIORLY then posteriorly within supinator
• Exits supinator 6-8cm distal to lateral epicondyle to innervate wrist/finger extensors
• At risk during radial head reduction (stretching), annular ligament reconstruction (direct injury), and radius osteoclasis (traction)

Interosseous Membrane:

• Primary stabilizer of radius-ulna relationship
• Central band is strongest component (distal to proximal oblique orientation)
• Transmits 80% of axial load from radius to ulna
• Disrupted in Monteggia injury contributing to instability

Bado Classification (Detailed)

Type I (60-70% of cases):

• ANTERIOR radial head dislocation
• Apex ANTERIOR angulation of ulnar fracture (usually proximal/middle third)
• Mechanism: fall on outstretched hand with forearm pronated, hyperextension force
• Associated injuries: coronoid fracture (rare), plastic deformation of radius (common)
• Prognosis: BEST outcomes with anatomic reduction

Type II (15% of cases):

• POSTERIOR radial head dislocation
• Apex POSTERIOR angulation of ulnar fracture
• Mechanism: direct blow to posterior forearm or axial load with elbow flexed
• Associated injuries: olecranon fracture, coronoid fracture
• Prognosis: Higher risk of stiffness, loss of flexion

Type III (20% of cases):

• LATERAL or anterolateral radial head dislocation
• Proximal ulnar METAPHYSEAL fracture (near olecranon, often greenstick)
• Mechanism: varus force to elbow with forearm supinated
• More common in younger children (2-7 years)
• Associated injuries: plastic deformation radius
• Prognosis: Good with anatomic reduction, risk of cubitus valgus if malunion

Type IV (Rare <5%):

• ANTERIOR radial head dislocation (like Type I)
• BOTH radius AND ulna shaft fractures at same level
• High energy injury mechanism
• Associated injuries: nerve injury (especially PIN), compartment syndrome
• Prognosis: More complications, longer recovery

Pathoanatomy of Injury

Acute Phase (0-3 weeks):

• Ulnar fracture with apex angulation
• Radial head dislocated in direction of ulnar apex
• Annular ligament torn or avulsed (Type I especially)
• Interosseous membrane disrupted
• Radius may have plastic deformation (no visible fracture but permanent bowing)
• PIN stretched over displaced radial head (10-20% injury rate)

Chronic Phase (>3 weeks):

• Ulnar fracture begins healing in malunited position
• Radial head remains dislocated, annular ligament contracted/healed in elongated position
• Radial head cartilage degeneration begins (6-12 weeks)
• Radiocapitellar joint incongruent, capitellum may remodel (flattening)
• Soft tissue contractures develop
• Bone block formation at radial notch (preventing reduction)

Biomechanics:

• Ulnar shortening of 2-3mm creates radial head proximal translation and anterolateral instability
• Radius plastic deformation creates bow, preventing radial head reduction even with anatomic ulna reduction
• Annular ligament provides 60-70% stability to radial head in rotation
• Loss of radiocapitellar contact increases stress on interosseous membrane by 30-40%

Step 1: Pre-operative Assessment & Classification

Pre-operative Assessment & Classification: BADO CLASSIFICATION: Type I (60-70%): anterior radial head dislocation with anterior apex ulnar fracture. Type II (15%): posterior radial head dislocation with posterior apex ulnar fracture. Type III (20%): lateral/anterolateral radial head dislocation with ulnar metaphyseal fracture. Type IV (rare <5%): anterior radial head dislocation with radius AND ulna fracture. ASSESS: (1) Radial nerve function (PIN) - thumb/finger extension, most commonly injured nerve 10-20%, usually neuropraxia. (2) Radiocapitellar relationship - should point to capitellum on ALL views. (3) Associated injuries - plastic deformation radius, coronoid fracture, olecranon fracture.

Step 2: Reduction Strategy Planning

Reduction Strategy Planning: TREATMENT ALGORITHM: (1) ACUTE (<3 weeks): ORIF ulna usually achieves radial head reduction (90% success). (2) Closed reduction ulna attempted first if suitable fracture pattern. (3) Open reduction ulna if: displaced, comminuted, failed closed reduction. (4) Plan for annular ligament reconstruction if chronic or unstable. PLASTIC DEFORMATION: if radius has plastic deformation, MUST straighten radius or radial head will not reduce - can attempt closed bending or osteoclasis.

Step 3: Positioning & Draping

Positioning & Draping: Supine, arm on radiolucent arm table. Tourniquet on upper arm (typically inflated for visualization). Shoulder abducted 70-90°, elbow flexed to relax soft tissues. Prep and drape entire arm from axilla to hand (may need forearm access). C-arm positioned for AP/lateral elbow and forearm views.

Step 4: Ulnar Approach - Subcutaneous Border

Ulnar Approach - Subcutaneous Border: Longitudinal incision centered over fracture along subcutaneous border of ulna (medial/posterior surface). Length 5-8cm depending on fracture location. Incise subcutaneous tissue directly to bone - ulna is subcutaneous. PERIOSTEAL ELEVATION: minimal stripping, preserve periosteum for healing, especially in children. Expose fracture adequately for reduction.

Step 5: Ulnar Fracture Reduction

Ulnar Fracture Reduction: REDUCTION MANEUVERS: (1) Remove interposed periosteum/muscle from fracture site. (2) Achieve ANATOMIC REDUCTION: restore ulnar LENGTH (critical for radial head reduction), correct ANGULATION, restore ROTATION (align subcutaneous border and posterior border). (3) Use reduction forceps to hold. (4) Check with C-arm - must be ANATOMIC, any shortening/angulation prevents radial head reduction.

Step 6: Ulnar Fixation - Plate Selection & Application

Ulnar Fixation - Plate Selection & Application: IMPLANT: 2.4mm or 2.7mm locking or non-locking plate (depends on bone size/age). 6-8 hole plate for adequate span. TECHNIQUE: (1) Contour plate to ulnar shape (slight bow). (2) Apply to dorsal or lateral surface of ulna. (3) Obtain 3-4 screws (6-8 cortices) on each side of fracture. (4) Lag screw through plate if oblique fracture. (5) Alternative in young children: intramedullary wire if transverse/short oblique.

Step 7: Fluoroscopic Assessment of Ulnar Reduction

Fluoroscopic Assessment of Ulnar Reduction: AP AND LATERAL views of forearm: (1) Ulnar length restored - compare to contralateral if needed. (2) No angulation any plane. (3) Hardware appropriate position. (4) Assess RADIAL BOWING - if plastic deformation present, radius will appear bowed on AP view. Must be corrected before radial head reduces.

Step 8: Radial Plastic Deformation Correction (if present)

Radial Plastic Deformation Correction (if present): If radius shows plastic deformation (bowing): CLOSED CORRECTION (osteoclasis): (1) Palpate apex of radial bow. (2) Apply three-point bending force - central pressure at apex, counter-pressure at both ends. (3) Hold pressure 2-3 minutes (creep in pediatric bone). (4) AUDIBLE/PALPABLE microfractures as deformation corrects. (5) Check C-arm - radius should be straight on AP. Alternatively: FORMAL OSTEOTOMY if deformation severe or late presentation.

Step 9: Assessment of Radial Head Reduction

Assessment of Radial Head Reduction: REDUCE RADIAL HEAD: (1) Extend elbow fully - often reduces with ulna correction alone. (2) Supinate forearm and apply direct pressure over radial head. (3) FLUOROSCOPY: radiocapitellar line must point to capitellum center on AP, LATERAL, and OBLIQUE views. (4) Palpate radial head - should be concentric with capitellum, not prominent. (5) Test stability through ROM.

Step 10: Annular Ligament Reconstruction (if needed)

Annular Ligament Reconstruction (if needed): INDICATIONS: (1) Chronic Monteggia (>3-4 weeks), (2) Unstable radial head despite anatomic ulna reduction, (3) Irreparable annular ligament tear. TECHNIQUE: (1) Lateral approach to radial head (Kocher interval: anconeus-ECU). (2) Reduce radial head (may need temporary K-wire). (3) RECONSTRUCT annular ligament: use strip of triceps fascia, lateral collateral ligament, or ECU tendon. (4) Wrap around radial neck 270-360°, secure to periosteum with sutures. (5) Check: radial head stable, rotation maintained (not too tight).

Step 11: Temporary Radial Head Stabilization (controversial)

Temporary Radial Head Stabilization (controversial): For unstable reduction, options: (1) TRANSARTICULAR K-WIRE: from capitellum through radial head, holds reduction, MUST remove at 3-4 weeks maximum (longer = severe stiffness). (2) ANNULAR LIGAMENT repair/reconstruction (preferred). (3) Intramedullary wire down radius providing indirect stability. Most surgeons avoid transarticular pin if possible due to stiffness risk.

Step 12: Final Fluoroscopic Confirmation

Final Fluoroscopic Confirmation: COMPREHENSIVE ASSESSMENT: (1) AP/LATERAL forearm: ulna anatomic reduction, plate position, no radius deformity. (2) AP/LATERAL/OBLIQUE elbow: radiocapitellar line to capitellum in ALL views, no subluxation. (3) RANGE OF MOTION under fluoro: flexion/extension, pronation/supination - radial head should remain concentrically reduced throughout. (4) Hardware position safe.

Step 13: Post-Reduction Neurovascular Examination

Post-Reduction Neurovascular Examination: ESSENTIAL: re-examine PIN function (thumb/finger extension) after radial head reduction. PIN injury can occur FROM reduction maneuvers (overstretching, traction, direct pressure). Document: (1) Radial nerve - wrist/thumb/finger extension. (2) Median nerve (especially AIN). (3) Ulnar nerve. (4) Radial pulse, perfusion. Most PIN injuries are neuropraxias that recover over 3-6 months.

Step 14: Closure & Immobilization

Closure & Immobilization: Irrigate wound. Close periosteum if possible (enhances healing). Subcutaneous layer with absorbable suture. Skin closure. IMMOBILIZATION: Long arm cast or splint at 90° flexion, forearm in SUPINATION (stabilizes radial head). If transarticular pin: splint only, remove pin at 3 weeks then cast. If stable reconstruction: cast 4-6 weeks.

Step 15: Post-operative Protocol & Follow-up

Post-operative Protocol & Follow-up: IMMOBILIZATION: 4-6 weeks long arm cast, forearm supinated. X-ray at 1 week (check maintenance reduction), 3 weeks (consider transarticular pin removal if used), 6 weeks (healing assessment). REHABILITATION: gentle active ROM after cast removal, expect full ROM by 3-6 months. LONG-TERM: follow to skeletal maturity - monitor for: (1) late radial head redislocation (rare if anatomic reduction), (2) PIN recovery (3-6 months expected), (3) cubitus valgus from ulnar overgrowth, (4) radioulnar synostosis (rare complication).

Key Complication Patterns by Bado Type

Type I (Anterior Dislocation):

• Highest PIN injury rate (15-20%)
• Best prognosis if anatomic reduction
• Annular ligament often torn (may need reconstruction)
• Lowest stiffness risk

Type II (Posterior Dislocation):

• Highest risk of elbow stiffness (30-40%)
• Loss of flexion most common
• Associated olecranon fractures common
• Lower PIN injury rate (5-10%)

Type III (Lateral Dislocation):

• Common in young children (2-7 years)
• Risk of cubitus valgus from metaphyseal malunion
• Often greenstick ulnar fracture (may displace in cast)
• Moderate PIN injury rate (10-15%)

Type IV (Both Bones):

• Highest complication rate overall
• Compartment syndrome risk (5-10%)
• Multiple nerve injuries possible
• Longer recovery, more stiffness

Outcomes by Treatment Type

Acute ORIF (<3 weeks):

• Radial head reduction rate: 90-95% if anatomic ulna reduction achieved
• PIN recovery rate: 90% by 6 months (neuropraxia)
• ROM: 85-90% patients achieve >120° flexion, >80% pronation/supination by 12 months
• Redislocation rate: 5-10% (most within first 6 weeks)
• Return to full activity: 3-6 months average

Chronic Reconstruction (>3 weeks):

• Radial head reduction rate: 70-80% (lower than acute)
• Requires annular ligament reconstruction: 80-90% of cases
• ROM: 70-80% achieve functional motion (some permanent limitation common)
• Redislocation rate: 15-25% (higher than acute)
• May need radial head excision if failed reconstruction (wait until skeletal maturity)

Plate vs Intramedullary Fixation (Pediatric):

• Plate: more stable, allows earlier mobilization, higher soft tissue trauma
• IM wire: less soft tissue dissection, lower infection risk, less stable (requires good bone quality)
• Outcomes similar in appropriate cases (transverse/short oblique fractures in younger children good for IM)
• Plate preferred for: comminuted fractures, adolescents, revision surgery

Prognostic Factors

Good Prognosis:

• Bado Type I (anterior dislocation)
• Age <10 years
• Acute presentation (<3 weeks)
• Anatomic ulna reduction achieved
• No PIN injury at presentation
• Closed injury
• Compliant with immobilization

Poor Prognosis:

• Bado Type II (posterior dislocation) - stiffness risk
• Age >12 years (approaching skeletal maturity)
• Chronic presentation (>3-6 weeks)
• Ulnar malunion or persistent shortening
• Radius plastic deformation not corrected
• High energy injury (Type IV)
• Multiple attempts at reduction (increases stiffness)

Evidence Base

Level I Evidence:

• No randomized trials comparing surgical techniques in pediatric Monteggia (rare injury, heterogeneous populations)

Level III-IV Evidence (Case Series):

• Anatomic ulna reduction achieves radial head reduction in 90% acute cases (multiple series)
• PIN injury recovers in 90% by 6 months with observation (neuropraxia)
• Chronic Monteggia (>3 weeks) requires annular ligament reconstruction in 80-90% for stability
• Transarticular K-wire left >4 weeks causes severe permanent stiffness in 60-80% (historical data)
• Plate fixation preferred over IM wire in adolescents and comminuted fractures (biomechanical studies)

Expert Consensus:

• ANATOMIC ulna reduction is essential for radial head reduction (universally accepted)
• Radius plastic deformation must be corrected (high consensus)
• Annular ligament reconstruction for chronic/unstable cases (high consensus)
• Avoid transarticular K-wire if possible, remove by 3-4 weeks maximum if used (high consensus)
• Immobilization in supination stabilizes radial head (biomechanical rationale)

Long-term Outcomes (5-10 year follow-up)

Functional Outcomes:

• 80-85% excellent/good results after acute ORIF with anatomic reduction
• 10-15% have minor limitations (slight loss of rotation, minimal pain)
• 5-10% have significant limitations (stiffness, chronic pain, recurrent instability)

Radiographic Outcomes:

• 90-95% maintain concentric radial head reduction long-term
• 5-10% develop late cubitus valgus (often asymptomatic)
• <5% develop radiocapitellar arthritis if anatomic reduction maintained
• 20-30% have radiographic changes at radial head if chronic case or redislocation occurred

Return to Activity:

• Non-contact sports: 3 months average
• Contact sports: 4-6 months with protective brace initially
• Full unrestricted activity: 6 months average (range 4-12 months)
• Recurrence of instability: rare (<2%) if anatomic reduction achieved

Quality of Life

• Minimal impact on ADLs if functional ROM achieved (>100° flexion, >70° rotation each direction)
• Cosmetic concerns from cubitus valgus deformity in 10-15%
• Parental anxiety about nerve recovery (counseling important)
• Overall satisfaction: 85-90% in acute cases, 70-75% in chronic cases