MONTEGGIA FRACTURES
Pediatric Forearm | Ulnar Fracture + Radial Head Dislocation | Bado Classification | Missed Diagnosis Risk
BADO CLASSIFICATION
Critical Must-Knows
- Definition: Fracture of the ulna (proximal third usually) with dislocation of the radial head
- Missed Diagnosis: High rate of missed diagnosis (up to 50%) - always check radiocapitellar line in ALL forearm fractures
- Radiocapitellar Line: Line drawn through radial neck shaft must bisect capitellum in ALL views
- Plastic Deformation: Ulnar fracture may be subtle plastic deformation (bowing) only - requires reduction to reduce radial head
- Nerve Injury: Posterior Interosseous Nerve (PIN) most commonly injured (neurapraxia)
Examiner's Pearls
- "MUGR: Monteggia (Ulna # / Radial Head dislocation), Galeazzi (Radius # / DRUJ dislocation)
- "Radial head points to the direction of the ulnar fracture apex (and creates the Bado type)
- "If ulnar length is not restored, radial head will not reduce/stay reduced
- "In chronic missed cases, ulnar osteotomy is required to lengthen ulna and reduce head
Critical Monteggia Exam Points
The Missed Monteggia
Most common malpractice case in pediatric orthopaedics. 50% are missed on initial presentation. Any "isolated" ulnar shaft fracture MUST have the elbow (radiocapitellar line) and wrist (DRUJ) checked meticulously. Look for ulnar plastic deformation if no frank fracture.
Radiocapitellar Line
Must bisect the capitellum on ALL views. On lateral view, if the line passes anterior to capitellum = Anterior dislocation (Type I). If posterior = Posterior dislocation (Type II).
Nerve at Risk: PIN
PIN palsy (unable to extend fingers/thumb, wrist extension weak/deviates radial) is common especially in Type I and III. Usually neuropraxia and resolves spontaneously in 6-12 weeks. Don't rush to explore.
Reduction Principle
"You must reduce the ulna to reduce the radius." Anatomical reduction and length restoration of the ulna is key. The radial head reduces indirectly once the ulna is corrected. Cast in position of stability (Type I: flexion/supination).
Quick Decision Guide - Bado Classification
| Type | Deformity Direction | Frequency | Reduction Strategy |
|---|---|---|---|
| Type I | Anterior (Head & Ulna Apex) | 70% (Most common) | Traction + Flexion + Supination |
| Type II | Posterior (Head & Ulna Apex) | 6% (Rare in children) | Extension + Pronation (rarely needs ORIF) |
| Type III | Lateral (Head & Ulna Apex) | 23% (Second most common) | Valgus/Varus correction |
| Type IV | Both bones + Dislocation | 1% (Rare) | ORIF usually required for stability |
MUGRMUGR - Forearm Fracture-Dislocations
Memory Hook:MU = Monteggia Ulna (Proximal). GR = Galeazzi Radius (Distal). 'M comes before G in alphabet, proximal comes before distal'.
PINPIN - Nerve Examination
Memory Hook:PIN injury: Hand drops (wrist extension weak), fingers drop (MCP extension lost), thumb drops (IP extension lost). Sensation intact.
Overview and Epidemiology
Monteggia fracture-dislocation is a fracture of the ulnar shaft with dislocation of the radial head at the radiocapitellar joint. It is named after Giovanni Monteggia (1814).
Epidemiology:
- Peak age 4-10 years
- Rare injury (less than 2% of pediatric forearm fractures)
- Bado Type I (Anterior) is by far the most common in children
- Often associated with high-energy trauma but can occur from simple falls
Plastic Deformation Trap
The ulnar fracture is not always a clean break. In children, it often presents as plastic deformation (bowing) of the ulna. If you see a radial head dislocation but no obvious ulnar fracture lines, look for bowing! The radial head cannot dislocate without ulnar pathology or annular ligament rupture (rare in isolation).
Pathophysiology and Mechanisms
The Forearm Ring Concept
The forearm and elbow function as a ring structure containing the radius, ulna, PRUJ, and DRUJ. Disruption of one part of the ring (fracture) often leads to disruption of another (joint dislocation).
- Radius and ulna are bound by interosseous membrane
- Ulna shortening/angulation forces radius to dislocate if linked
Ligamentous Stabilizers
- Annular Ligament: The primary stabilizer of the proximal radioulnar joint (PRUJ). It encircles 4/5ths of the radial head. In Monteggia fractures, it usually ruptures or becomes interposed, blocking reduction.
- Interosseous Membrane (IOM): The central band is a stout structure that transfers load from radius to ulna and prevents excessive proximal migration of the radius.
- Quadrate Ligament: Connects the neck of the radius to the supinator crest of the ulna.
- LCL Complex: Provides varus stability to the elbow. Often injured in Type III (Varus) patterns.
Radiocapitellar Joint
- Normal alignment: Radiocapitellar line must pass through the center of the capitellum on ALL views (AP, Lateral, Oblique)
- Ossification: Radial head ossifies at 3-5 years, Capitellum at 1 year. In younger children, bisect the radial neck shaft.
Topographic Anatomy: MUGR
| Feature | Monteggia | Galeazzi |
|---|---|---|
| Bone Fractured | Ulna (Proximal) | Radius (Distal/Middle) |
| Joint Dislocated | PRUJ (Radial Head) | DRUJ (Ulnar Styloid/Head) |
| Nerve at Risk | PIN (Radial) | AIN (Median) or Ulnar |
| Mechanism | Direct blow or fall (Pronation) | Fall (Hyperextension/Pronation) |
| Treatment (Paeds) | Closed Reduction usually possible | Closed Reduction usually possible |
Radiocapitellar Joint
- Normal alignment: Radiocapitellar line must pass through the center of the capitellum on ALL views (AP, Lateral, Oblique)
- Ossification: Radial head ossifies at 3-5 years, Capitellum at 1 year. In younger children, bisect the radial neck shaft.
Check the Line!
Always draw the radiocapitellar line. On lateral view:
- Anterior to capitellum = Anterior dislocation (Type I)
- Posterior to capitellum = Posterior dislocation (Type II)
- Centered = Normal
Classification Systems
Bado Classification (1967)
Based on direction of radial head dislocation and ulnar fracture apex.
| Type | Direction | Frequency | Mechanism |
|---|---|---|---|
| I | Anterior | 70% | Forced pronation + extension |
| II | Posterior | 6% | Axial load + flexion (rare in kids) |
| III | Lateral | 23% | Varus force (adduction) |
| IV | Combined | 1% | Complex force (both bones #) |
Key Concept: The radial head points in the direction of the ulnar fracture apex.
- Type I: Ulna apex anterior → Head dislocates anterior
- Type II: Ulna apex posterior → Head dislocates posterior
- Type III: Ulna apex lateral (varus) → Head dislocates lateral
Classification dictates the reduction maneuver and the position of immobilization.
Clinical Assessment
Diagnostic Steps
- Mechanism of injury
- Pain location (elbow AND forearm)
- "Wrist" pain may be referred or Galeazzi (check both!)
- Deformity: Angulation of forearm
- Prominence: Radial head may be palpable anteriorly (Type I) or posteriorly (Type II) in antecubital fossa/posterior elbow
- Swelling: Around elbow and fracture site
- Tenderness along ulnar shaft
- Palpate radial head position relative to lateral epicondyle
- PIN Examination (Critical):
- Thumbs up (EPL)
- Hitchhiker sign
- Finger extension (MCP joints)
- Sensation is intact!
- Ulnar nerve: Less common, assess interossei
Red Flag Checklist:
- Open fracture (Gustilo I usually)
- Compartment syndrome signs (pain out of proportion)
- Skin tenting (impending open)
- Polytrauma (e.g. Monteggia + Femur fracture)
Documentation Template
Example ED Note: "6yo female, fall on outstretched hand. Isolated injury. O/E: Deformity L forearm. Closed neurovascularly intact. PIN function normal (thumbs up). X-ray: Midshaft ulna fracture with anterior radial head dislocation (Bado I). Plan: Ketamine procedural sedation for closed reduction. Discussed risks (PIN palsy, loss of reduction, cast issues) with parents. Consented."
Nerve Injury 10-20%
PIN neuropraxia is the most common complication (10-20% of cases), particularly with Type III (lateral) or Type I. It almost always resolves spontaneously. Document pre-reduction function!
Investigations
Radiographic Rules
- Include elbow and wrist: Dedicated elbow views, not just forearm views.
- True Lateral: Essential for checking radiocapitellar line.
- Ulnar Bow: Look for plastic deformation (compare to other side if unsure - normative ulna has slight posterior bow, NEVER anterior).
Radiographic Checklist
| Finding | Significance | Action |
|---|---|---|
| Radiocapitellar line deviation | Dislocated radial head | Identify Direction (I, II, III) |
| Ulnar shaft fracture | Obvious pathology | Assess angulation |
| Ulnar bowing | Plastic deformation | Requires straightening to reduce head |
| Ulnar length | Shortening | Must restore length to reduce head |
Management Algorithm
Monteggia Reduction Tips
| Phase | Tip | Reason |
|---|---|---|
| Preparation | Go to theatre | Muscle relaxation is key. ED sedation often fails due to spasm. |
| Ulnar Length | Get length first | You cannot reduce the head if the ulna is short. Pull hard! |
| Supination | Supinate fully (Type I) | Tightens membrane, relaxes biceps. Neutral is NOT enough. |
| Molding | Interosseous Mold | Squeeze radius and ulna apart to open the space. |
| Imaging | True Lateral | Don't accept obliques. The line is only valid on true lateral. |
Acute Monteggia Treatment
Goal: Anatomic reduction of the ulna (length and angulation) → Indirect reduction of radial head.
Bado I (Anterior):
- Closed Reduction: Traction + Extension (to correct length) → Flexion of elbow to 100-110° + Supination.
- Molding: Correct ulnar angulation (mold valgus/varus if needed).
- Immobilization: Long arm cast in Flexion (100-110°) and Supination.
- Why Supination? Relaxes biceps (main deforming force).
- Why Flexion? Relaxes biceps and pushes radial head back.
- Indications for Surgery (ORIF/IM Nail): Failure to maintain ulnar reduction, unstable fractures, Letts B/C types (complete/comminuted).
Bado III (Lateral):
- Closed Reduction: Traction + Extension → Valgus stress to correct ulnar varus.
- Immobilization: Long arm cast in Extension or slight flexion + Valgus mold.
- Surgery: Often need IM nail for ulna as varus is hard to hold.
Bado II (Posterior):
- Closed Reduction: Extension of elbow (reduces posterior head) + Pronation.
- Immobilization: Cast in Extension (uncommon/awkward) or surgery.
Post-Reduction Check: Ensure radiocapitellar line is restored in all views.
Surgical Technique
Flexible IM Nailing of Ulna
Indication: Unstable Type I/III fractures, failure of closed reduction.
Surgical Preparation:
- Position: Supine, arm on radiolucent hand table.
- C-Arm: Comes from head or across from surgeon (monitor at foot of bed).
- Draping: Tourniquet high on arm (sterile), drape to include shoulder to allow rotation.
- Instruments: Small frag set, flexible nails (TENs), wire driver, oscillating saw (if osteotomy needed).
- Consent Risks: Infection, nerve injury (PIN), loss of reduction, need for removal of hardware.
Tourniquet Safety
Limit tourniquet time to 90 minutes. If reduction is difficult and time is expiring, deflate for 20 minutes before re-inflating. Ensure the limb is exsanguinated but avoid excessively tight Esmarch banding over the fracture site.
Steps
- Olecranon tip (proximal to distal).
- Stab incision, awl.
- Advance appropriately sized TEN nail (2.0-3.0mm).
- Cross fracture site.
- Reduce fracture manually while advancing nail.
- Critical: Must restore LENGTH and alignment.
- Once ulna is rigidly fixed and length restored, check radial head.
- Should spontaneously reduce.
- Verify with image intensifier (rotation/flexion/extension).
Complications
Complications
| Complication | Cause | Management |
|---|---|---|
| Loss of Reduction | Casting error, untreated plastic deformation | Early recognition → Redo/ORIF |
| PIN Palsy | Nerve stretch (Type I/III) | Observation (resolves 6-12w), EMG if no recovery greater than 3mo |
| Compartment Syndrome | High energy, tight cast in hyperflexion | Fasciotomy |
| Redislocation (Late) | Failure to restore ulnar length | Ulnar osteotomy |
| Synostosis | Trauma to interosseous space | Excision if limiting rotation (late) |
Postoperative Care and Rehabilitation
Rehab Protocol
- Long arm cast (position depends on Bado type)
- Weekly X-rays for first 3 weeks (check ulnar alignment and radial head)
- Shoulder motion allowed
- Monitor for cast looseness (as swelling subsides)
- Keep Dry: Use a bag when showering. Wet cast = skin sores.
- No Poking: Do not put rulers/knitting needles down the cast.
- Wiggle Fingers: Encourage finger movement to prevent stiffness.
- Elevation: Keep hand above heart level for the first 3 days.
- Return to ED if: Pain out of proportion, fingers blue/white, cast feels too tight, or cast cracks/softens.
- Remove cast/splint
- Remove IM nail if used (typically 6-12 weeks when united)
- Begin Active ROM (Flexion/Extension, Pro/Supination)
- No passive stretching which may cause myositis
- Progressive strengthening
- Return to non-contact sports
- Monitor for heterotopic ossification (rare but possible)
- Full contact sports when radiographic union solid and full ROM
- Monitor for growth disturbance (rare)
- Assess for any residual PIN deficit
Cast Removal
Check the X-ray before removing the cast. Ensure the ulna is healing and radial head is reduced. If the ulna has angulated, the radial head may have subluxated.
Outcomes
Prognosis:
- Acute Treated: Excellent prognosis. Most children regain full ROM.
- Missed/Chronic: Guarded prognosis. Reconstruction (osteotomy) improves pain and stability but often leaves some stiffness.
- Nerve Injury: PIN neurapraxia has excellent prognosis (90%+ recover spontaneously).
- Recurrence: Rare if ulnar length maintained.
Evidence Base
Missed Monteggia Incidence
- Review of 35 missed Monteggia lesions
- 50% were missed at initial presentation
- Most common error: Failure to examine radiocapitellar line
Management of Chronic Cases
- Ulnar osteotomy with angulation/lengthening effective for chronic cases
- Annular ligament reconstruction not always necessary if bone alignment perfect
- Better outcomes if treated within 3 years of injury
PIN Palsy Recovery
- Original description of the lesion
- Noted high incidence of PIN palsy in Type III
- Spontaneous recovery is the rule
- Exploration rarely indicated unless nerve entrapped in reduction
Cast Position for Type I
- Supination relaxes the biceps
- Flexion relaxes biceps and pushes radial head posterior
- Casting in neutral led to higher redislocation rates in Type I
IM Nailing of Ulna
- Flexible IM nail provided stable fixation
- Allowed for early ROM
- Prevented redislocation better than casting in unstable patterns (Letts B/C)
Exam Viva Scenarios
Practice these scenarios to excel in your viva examination
"A 6-year-old girl falls on an outstretched hand. X-rays show a greenstick fracture of the proximal ulna. The radial head does not point to the capitellum on the lateral view."
"You see a 12-year-old boy in clinic who injured his elbow 2 months ago. He has limited flexion and a 'bump' on the front of his elbow. X-rays show a healed ulnar fracture and a dislocated radial head."
"A junior registrar calls you about a 5-year-old with a 'proximal ulnar fracture' and a 'swollen elbow'. They represent the X-rays describing a 'Greenstick proximal ulna fracture' but say the elbow looks 'a bit out'."
MCQ Practice Points
Radiocapitellar Line Question
Q: A 5-year-old presents with a forearm fracture. On the lateral view, the radiocapitellar line passes posterior to the capitellum. What is the diagnosis? A: Bado Type II (Posterior) Monteggia fracture-dislocation. (Anterior line = Type I).
Nerve Injury Question
Q: Which nerve is most commonly injured in Monteggia fractures and what is the presentation? A: Posterior Interosseous Nerve (PIN). Presents with loss of finger extension (MCP) and thumb extension. Wrist extension is preserved (radial deviation) due to ECRL innervation (proximal to PIN). Sensation is INTACT.
Mechanism of Reduction
Q: Why is supination used for Type I Monteggia reduction? A: Supination tightens the interosseous membrane (pulling bones together) and relaxes the biceps tendon (which is an anterior deforming force on the radial tuberosity and proximal radius).
CASTCAST - Immobilization Positions
Memory Hook:Know the position: I = Flex/Sup. II = Extend. III = Extend/Valgus.
Type III Associations
Q: A 7-year-old sustains a varus injury to the elbow (Bado III). What associated ligamentous injury is most likely? A: Lateral Collateral Ligament (LCL) injury or avulsion. This contributes to the instability and may require repair in chronic cases.
Radial Head Ossification
Q: At what age does the radial head ossification center appear, and why does this matter for diagnosis? A: It appears at 3-5 years. Before this, you must rely on the radial neck alignment with the capitellum. Don't mistake the unossified head for a "dislocation" if the neck points centrally, but be very suspicious of any misalignment.
Bado IV Management
Q: What characterizes a Bado IV fracture and how is it managed? A: Fracture of the proximal ulna AND radius shaft with radial head dislocation. It is highly unstable and almost always requires operative fixation of both bone fractures to maintain reduction.
Australian Context
Epidemiology:
- Common playground injury (monkey bars) in Australia.
- "Trampoline forearm" - often chaotic bouncing leads to complex falls.
Referral Pathways:
- Unreduced Monteggias or nerve injuries should be referred to pediatric orthopaedics promptly.
- Chronic missed cases are best managed in tertiary pediatric centers (RCH, SCH, QCH).
Tertiary Pediatric Handover:
- Splint: Temporary splint for comfort (does not reduce injury usually).
- Imaging: Send PACS link with hard copies.
- Neuro: Document PIN status clearly.
- Fasting: Keep fasted if transfer is immediate for potential reduction.
Centers of Excellence:
- Royal Children's Hospital (Melbourne)
- Sydney Children's Hospital / Westmead
- Queensland Children's Hospital (Brisbane)
- Perth Children's Hospital
- Women's and Children's (Adelaide)
High-Yield Exam Summary
Bado Types
- •I: Anterior (70%) - Flexion/Supination cast
- •II: Posterior (6%) - Extension cast
- •III: Lateral (23%) - Im nail / Valgus mold
- •IV: Combined (1%) - ORIF
Key Exam Steps
- •Check Radiocapitellar Line (Every view)
- •Check Ulnar Bow (Plastic deformation)
- •Check PIN (hitchhiker thumb)
- •Check Wrist (Galeazzi screen)
Reduction Mantra
- •Restore Ulnar Length
- •Correct Ulnar Angulation
- •Radial head reduces itself
- •Check radiocapitellar line on ALL views