Ulna Fracture with Radial Head Dislocation
BADO CLASSIFICATION
Critical Must-Knows
- Line through radial head must bisect capitellum on ALL views
- Fix the ulna - radial head reduces spontaneously
- Adult Type II most common - posterior angulation
- Chronic - requires open reduction and annular ligament reconstruction
Clinical Pearls
- "Always get elbow X-ray with forearm fracture
- "Radiocapitellar line - most missed injury in orthopaedics
- "Type II most common in adults, Type I in children
- "Ulna length and alignment critical - use contralateral comparison
Clinical Imaging
Imaging Gallery
Critical Monteggia Exam Points
Most Common Missed Injury
Monteggia is one of the most commonly missed forearm injuries. ALWAYS check the radiocapitellar line on every forearm X-ray.
Adult vs Child
Type II (posterior) is most common in adults. Type I (anterior) is most common in children. Treatment principles differ significantly between these groups.
Key Principle
Fix the ulna anatomically - the radial head typically reduces spontaneously in acute injuries. If it doesn't reduce, suspect interposed tissue (annular ligament).
Chronic Monteggia
If more than 4 weeks: annular ligament reconstruction (Bell Tawse) is required. Results deteriorate significantly with delay—early diagnosis is critical.
Quick Decision Guide
| Bado Type | Key Feature | Radial Head Status | Treatment |
|---|---|---|---|
| Type I (Anterior) | Anterior ulna angulation | Anterior RH dislocation | Anatomic ulna ORIF - RH reduces |
| Type II (Posterior) | Posterior ulna angulation - most common adult | Posterior RH dislocation | Plate fixation ulna - check RH reduction |
| Type III (Lateral) | Ulna metaphyseal fracture | Lateral RH dislocation | Ulna fixation - may need RH ORIF |
| Type IV | Both bone fractures | Anterior RH dislocation | Fix both radius and ulna |
| Chronic (greater than 4 weeks) | Missed or delayed presentation | RH remains dislocated | Open reduction + annular ligament reconstruction |
| Paediatric | Plastic deformation possible | Check radiocapitellar line | Closed reduction if acute, open if chronic |
Mnemonics for Exam Recall
APLABADO Types by Direction
| A | Anterior Type I: Most common pediatric pattern |
| P | Posterior Type II: Most common adult pattern |
| L | Lateral Type III: Metaphyseal fracture in children |
| A | Anterior Both Type IV: Both bones fractured + RH dislocation |
| A | Anterior Type I: Most common pediatric pattern | L | Lateral Type III: Metaphyseal fracture in children |
| P | Posterior Type II: Most common adult pattern | A | Anterior Both Type IV: Both bones fractured + RH dislocation |
Hook:A Push Leads to Anterior dislocation (Type I flexion injury)
MISSMISS - Critical Checks
| M | Monteggia Check radiocapitellar line on every XR |
| I | Interposition Check if RH doesn't reduce spontaneously |
| S | Stability Assess PRUJ stability after ulna fixation |
| S | Secondary Specifically assess for PIN palsy |
| M | Monteggia Check radiocapitellar line on every XR | S | Stability Assess PRUJ stability after ulna fixation |
| I | Interposition Check if RH doesn't reduce spontaneously | S | Secondary Specifically assess for PIN palsy |
Hook:Don't MISS the Monteggia - check the line!
ULNAULNA - Fixation Goals
| U | Ulna Length Restoration of length is mandatory |
| L | Line Radiocapitellar line must bisect capitellum |
| N | No Angulation Achieve anatomic alignment to allow RH reduction |
| A | Anatomic Reduction must be absolute/perfect |
| U | Ulna Length Restoration of length is mandatory | N | No Angulation Achieve anatomic alignment to allow RH reduction |
| L | Line Radiocapitellar line must bisect capitellum | A | Anatomic Reduction must be absolute/perfect |
Hook:Fix the ULNA and the radial head follows
PINPIN - Nerve at Risk
| P | Posterior Posterior Interosseous Nerve |
| I | Interosseous Runs through the arcade of Frohse |
| N | Nerve Primary neurapraxia risk in Monteggia |
| P | Posterior Posterior Interosseous Nerve |
| I | Interosseous Runs through the arcade of Frohse |
| N | Nerve Primary neurapraxia risk in Monteggia |
Hook:PIN is at risk in Monteggia - specifically Posterior Interosseous Nerve
Overview/Epidemiology
Demographics and Distribution
Age Distribution:
- Bimodal pattern: peaks in childhood (4-10 years) and middle age (40-60 years)
- Pediatric cases: predominantly Type I (anterior)
- Adult cases: predominantly Type II (posterior)
- Elderly patients: often have more comminuted patterns
Mechanism by Age:
- Children: Falls from height, playground injuries
- Adults: High-energy trauma, sports injuries, direct blows
- Elderly: Low-energy falls with osteoporotic bone
Clinical Pearl
The bimodal age distribution reflects different mechanisms: children fall with hyperextended arm (Type I), while adults sustain direct blows or axial loading (Type II).
Anatomy/Biomechanics
Relevant Anatomy
Key Anatomical Structures:
Proximal Radioulnar Joint (PRUJ):
- Radial head articulates with radial notch of ulna
- Annular ligament encircles radial head (4/5 of circumference)
- Quadrate ligament provides secondary restraint
- Interosseous membrane connects radius and ulna throughout forearm
Annular Ligament:
- Strong fibrous band attached to anterior and posterior margins of radial notch
- Forms 4/5 of fibro-osseous ring around radial head
- Lined with cartilage on inner surface
- Prevents radial head migration during rotation
Interosseous Membrane:
- Fibers run obliquely from radius to ulna (proximal-lateral to distal-medial)
- Central band is the thickest and strongest portion
- Transmits forces from radius to ulna
- Disruption leads to proximal migration of radius
Interosseous Membrane
The interosseous membrane is often disrupted in Monteggia injuries. This affects load transfer and forearm stability. Assess for tenderness along the entire interosseous space.
Biomechanical Principles
Why Does the Radial Head Dislocate?
The ulna and radius are linked as a functional unit:
- Ulna is the fixed bone (stable at elbow via olecranon)
- Radius rotates around ulna for pronation/supination
- When ulna angulates, radial head must dislocate to accommodate
Key Concept: Radiocapitellar Line
The radiocapitellar line is a line drawn through the center of the radial shaft and head. On any view:
- This line MUST pass through the center of the capitellum
- If it doesn't, the radial head is subluxated or dislocated
- Check on AP, lateral, AND oblique views
Classification Systems
Bado Classification
Bado Classification Details
| Type | RH Dislocation | Ulna Pattern | Mechanism | Frequency Adult |
|---|---|---|---|---|
| Type I | Anterior | Anterior apex angulation | Fall on hyperextended arm | 15% |
| Type II | Posterior/Posterolateral | Posterior apex angulation | Direct blow to flexed elbow | 70% |
| Type III | Lateral | Metaphyseal fracture (valgus) | Varus force on extended arm | 10% |
| Type IV | Anterior | Both bone fractures (same level) | Hyperpronation injury | 5% |
Jupiter Type II Subclassification
Jupiter Classification (Type II)
| Subtype | Pattern | Implications |
|---|---|---|
| IIA | Ulna fracture at coronoid level | Most common subtype |
| IIB | Fracture distal to coronoid | Standard plating approach |
| IIC | Fracture at diaphysis | May need longer plate |
| IID | Fracture at ulna diaphysis + radius fracture | Both bone fixation required |
Clinical Pearl
Jupiter classification helps predict difficulty - proximal fractures near coronoid (IIA) may require different approach and have higher complication rates.
Pathomechanics
Forced hyperpronation with hyperextension
- Fall on outstretched hand
- Forearm in pronation
- Biceps pulls radial head anteriorly
- Most common in children (greenstick pattern)
Proper technique and attention to detail ensure optimal outcomes.
Clinical Assessment
Key Examination Points
Inspection
Palpation
Movement
Neurovascular
PIN Assessment
Check finger extension (EDC, EIP) specifically. PIN palsy occurs in 10-20% of Monteggia injuries. Wrist extension preserved (ECRL/ECRB) as these are innervated proximal to PIN.
Investigations
Essential Imaging
Standard Views:
- AP and lateral forearm - MUST include elbow and wrist joints
- AP and lateral elbow - confirm radial head relationship
- Contralateral comparison if ulna length questionable
Clinical Pearl
The radiocapitellar line must bisect the capitellum on EVERY view (AP, lateral, oblique). Any deviation indicates radial head subluxation/dislocation.
CT Indications:
- Coronoid fracture assessment
- Complex proximal ulna fractures
- Chronic Monteggia - assess radial head shape changes
MRI - Rarely Indicated:
- Suspected interosseous membrane disruption (Essex-Lopresti variant)
- Chronic injuries - assess cartilage integrity
- Soft tissue interposition planning
Management Algorithm
Indications:
- Anterior (Type I) or posterior (Type II) radial head dislocation
- Presentation within 4 weeks of injury
- Most common scenario in both children and adults
Treatment Approach:
- Closed reduction attempt - may provide temporary stability
- Anatomic ulna ORIF - restore length and alignment
- Intraoperative fluoroscopy - confirm radiocapitellar line
- Radial head reduces spontaneously in 95% of cases
Key Principles:
- Fix the ulna first - radial head follows
- Must restore ulna length - compare to contralateral
- 3.5mm LCP plate, 6-8 holes minimum
- If RH doesn't reduce - explore for interposed tissue
Clinical Pearl
Anatomic ulna fixation is the key - radial head reduces spontaneously in acute injuries. If it doesn't, suspect interposed tissue (annular ligament, capsule, or biceps).
Surgical Technique
Acute Management Principles
Surgical Technique
Approach: Direct posterior (Boyd approach)
Key Steps:
- Position: Supine, arm across chest or table
- Posterior incision along subcutaneous border
- Fracture reduction - restore length and alignment
- Plate fixation - 3.5mm LCP, 6-8 holes
- Check radiocapitellar relationship under fluoro
- If RH doesn't reduce - explore for interposition
Critical Points:
- Must restore ulna length - compare to contralateral
- Slight bow of ulna important for rotation
- Position plate on tension side (posterior/lateral)
Proper technique and attention to detail ensure optimal outcomes.
Pediatric Considerations
Adult vs Pediatric Monteggia
| Feature | Adult | Pediatric |
|---|---|---|
| Most common type | Type II (posterior) | Type I (anterior) |
| Ulna pattern | Complete fracture | Often greenstick/plastic |
| Treatment | Operative fixation standard | Closed reduction may succeed |
| Annular ligament | Often ruptured | Often intact |
| Chronic reconstruction | Poor outcomes | Better remodeling potential |
Clinical Pearl
Pediatric Monteggia: If ulna greenstick is corrected and radial head reduces concentrically, closed treatment with long arm cast in supination (Type I) may succeed. Follow closely for re-displacement.
Chronic Monteggia
Timing Critical
Chronic Monteggia (more than 4 weeks) has significantly worse outcomes. Early diagnosis and treatment essential. Results deteriorate rapidly with delay.
Definition: Missed injury more than 4 weeks from injury
Challenges:
- Radial head deformity and overgrowth
- Annular ligament scarring/absence
- Capitellum changes
- Limited remodeling in adults
Treatment Options:
- Ulna osteotomy - restore length and correct angular deformity
- Open reduction of radial head
- Annular ligament reconstruction (Bell Tawse technique)
- Radial head excision (adults, after skeletal maturity)
Bell Tawse Reconstruction Technique
Indications:
- Chronic Monteggia with absent/deficient annular ligament
- Most commonly used in pediatric patients
- After successful open reduction of radial head
Surgical Steps:
- Position supine, arm on table
- Posterior approach - harvest 1cm strip of triceps fascia (10-12cm long)
- Kocher approach to radial head
- Reduce radial head - excise any fibrous tissue blocking reduction
- Drill hole through proximal ulna (anterior to posterior)
- Pass triceps strip through hole
- Wrap around radial neck and suture to itself
- Temporary transarticular K-wire for 3-4 weeks
Outcomes:
- Good results in 70-80% of pediatric cases
- Results decline with increasing delay from injury
- Adult outcomes less predictable
- May require additional procedures for stiffness
Clinical Pearl
The Bell Tawse technique uses triceps fascia to create a neo-annular ligament. Originally described in 1965, it remains the gold standard for chronic pediatric Monteggia reconstruction.
Radial Head Excision
When to Consider:
- Chronic Monteggia in adults with irreducible radial head
- Significant radial head deformity
- Failed reconstruction
- Only after skeletal maturity (contraindicated in children)
Concerns:
- Loss of radiocapitellar articulation
- Potential valgus instability
- Proximal radial migration (if DRUJ unstable)
- Cubitus valgus deformity
Prerequisites:
- Intact DRUJ
- Intact MCL complex
- No associated Essex-Lopresti injury
Not in Children
Never excise the radial head in a skeletally immature patient. This leads to progressive valgus deformity and proximal migration. Always attempt reconstruction first.
Complications and Management
Common Complications
Monteggia Complications
| Complication | Incidence | Prevention/Management |
|---|---|---|
| PIN palsy | 10-20% | Usually neurapraxia - observe 3 months. Explore if no recovery. |
| Radial head redislocation | 5-10% | Anatomic ulna reduction, check intraoperative fluoro |
| Radioulnar synostosis | 2-5% | Single incision, careful soft tissue handling |
| Elbow stiffness | 10-15% | Early ROM, static progressive splinting |
| Non-union ulna | Under 5% | Compression plating, bone graft if needed |
| Heterotopic ossification | 5% | Gentle surgery, consider prophylaxis if prior HO |
Nerve Injury
PIN Palsy - Mechanism
Clinical Features
Prognosis
Exploration Indications
Associated Injuries
What is Essex-Lopresti?
- Radial head fracture + interosseous membrane disruption + DRUJ injury
- Rare but devastating combination
- Can occur with Type IV Monteggia (both bone fractures)
Recognition:
- Tenderness along entire interosseous space
- DRUJ instability on examination
- Positive ulnar variance on X-ray
Management Implications:
- Cannot excise radial head (leads to proximal migration)
- Must address DRUJ stability
- Consider radial head replacement if unfixable
Don't Miss Essex-Lopresti
If you encounter a Monteggia variant with both bone fractures (Type IV), specifically examine the DRUJ and entire interosseous membrane. Missing this leads to proximal radial migration and chronic wrist pain.
Postoperative Care and Rehabilitation
Post-operative Protocol
Key Rehabilitation Principles:
- Early motion if stable fixation achieved
- Avoid forced supination in first 4 weeks (protects annular ligament)
- Protect against varus stress if LCL repaired
- Address elbow stiffness aggressively with static progressive splinting
- Focus on forearm rotation as well as elbow flexion/extension
Return to Activities:
- Desk work: 2-4 weeks
- Manual labor: 3-6 months
- Contact sports: 6 months minimum
- Full unrestricted: When strength and ROM normalized
Managing Stiffness
Prevention
Static Progressive Splinting
Capsular Release
Heterotopic Ossification
Outcomes and Prognosis
Expected Outcomes by Type
Outcomes Summary
| Type/Scenario | Expected ROM | Union Rate | Functional Outcome |
|---|---|---|---|
| Acute Type I/II (Adult) | 80-90% of contralateral ROM | 95-98% | Good to excellent in 85-90% |
| Acute Type III/IV | 70-85% of contralateral ROM | 90-95% | Good to excellent in 70-80% |
| Chronic (More than 4 weeks, Adult) | 60-70% of contralateral ROM | N/A (osteotomy) | Fair to good in 50-60% |
| Pediatric Acute | Near-normal ROM | 98-100% | Excellent in 90-95% |
| Pediatric Chronic with reconstruction | 70-80% of contralateral ROM | N/A | Good to excellent in 70-80% |
Prognostic Factors
Favorable Factors
Unfavorable Factors
Age Considerations
Timing is Critical
Clinical Pearl
The most important prognostic factor is timing of diagnosis and treatment. Acute injuries (under 4 weeks) have excellent outcomes (85-90% good to excellent). Chronic injuries have only 50-60% good outcomes even with reconstruction.
Long-term Outcomes
Key durable endpoints (acute anatomic fixation): ulna union 95-98%, radial head stability 90-95% (re-dislocation 5-10%, higher with non-anatomic reduction), grip and forearm rotation 80-90% of the contralateral side at 1 year. Mild residual stiffness (10-15 degrees) is common but rarely functionally limiting; HO requiring excision and persistent PIN weakness each occur in under 5%.
Patient Expectations
Counsel patients that while union and stability are reliably achieved, 10-15 degrees of motion loss is common and some loss of grip strength may persist. Most return to full activities by 6 months.
Differential Diagnosis
Distinguishing Monteggia from Mimics
| Condition | Ulna | Radial Head / PRUJ | Discriminating Feature |
|---|---|---|---|
| Monteggia fracture-dislocation | Proximal/shaft fracture or plastic bowing | Dislocated (radiocapitellar line disrupted) | Ulna fracture WITH radial head dislocation - check the line on every view |
| Isolated ulna (nightstick) fracture | Mid-shaft fracture, often transverse | Located normally (line intact) | No radial head dislocation - the classic Monteggia trap if the line is not checked |
| Congenital radial head dislocation | Normal, no fracture | Chronically dislocated; convex/dome-shaped radial head, hypoplastic capitellum | Bilateral, no trauma, dysmorphic radial head - do NOT mistake for acute injury |
| Both-bone forearm fracture | Fracture | Radius fractured but radial head located | Both bones broken without PRUJ dislocation (vs Bado IV which adds RH dislocation) |
| Essex-Lopresti injury | Intact | Radial HEAD fracture + IOM + DRUJ disruption | Longitudinal forearm instability and DRUJ disruption, not proximal RU dislocation |
| Transolecranon fracture-dislocation | Olecranon fracture | PRUJ intact; ulnohumeral subluxation | Forearm translates with the proximal ulna; radiocapitellar relationship preserved |
The Number-One Pitfall
A pulled or angulated ulna shaft fracture is a Monteggia until proven otherwise. The single discriminator is the radiocapitellar line - a normal-looking "isolated ulna fracture" with a disrupted line IS a Monteggia.
Controversies & Areas of Uncertainty
Routine annular ligament reconstruction?
In chronic paediatric cases, ulna osteotomy with indirect reduction can stabilise the radial head without formal reconstruction (Song 2012). When the annular ligament is addressed, repair of the native ligament outperformed reconstruction (Zheng 2020). Many now reserve formal Bell Tawse reconstruction for cases that remain unstable intra-operatively.
Open reduction vs indirect (ulna-based) reduction in chronic cases
Whether to open the radiocapitellar joint or rely on over-correction of the ulna (angulation-translation osteotomy) remains debated; both can succeed and the choice is often driven by chronicity, radial head shape and intra-operative stability.
Temporary transarticular K-wire
Trans-capitellar/transarticular K-wires can hold a reduced radial head but carry a real risk of wire breakage and migration. Use is selective, kept short (3-4 weeks), and avoided where stable fixation alone is sufficient.
Management of the PIN palsy
Most PIN palsies are neurapraxic and recover, so early exploration is generally not indicated. The grey zone is the new, complete post-reduction palsy where nerve entrapment cannot be excluded - timing of exploration and the role of early EMG/nerve ultrasound are not standardised.
Evidence Base and Literature
Key Studies and Papers
Bado Original Classification
- Defined the Monteggia lesion and four types by direction of radial head dislocation and ulna deformity
Annular Ligament Reconstruction (Bell Tawse)
- Described use of a triceps fascia strip to create a neo-annular ligament for chronic radial head dislocation
Monteggia Fractures in Adults
- 48 adults; 38 (79%) were Bado type II; 68% of type II had an associated radial head fracture
- Excellent or good Broberg-Morrey result in 40 of 48 patients (83%) after stable anatomic plate fixation of the ulna
- 6 of 8 unsatisfactory results were type II with concomitant radial head/coronoid fractures
Monteggia Fractures in Children and Adults (Principle Review)
- Stable anatomic reduction of the ulna fracture restores anatomic reduction of the radial head
- Character of the ulna fracture (not the direction of dislocation) guides treatment
- Good non-operative results in children reflect prevalence of incomplete (stable) ulna fractures
Surgical Reconstruction of Missed Monteggia Lesions in Children
- 52 children; median time injury-to-surgery 12.9 weeks; flexion improved from 108 to 140 degrees
- Congruent radiocapitellar alignment maintained in 39 of 52 (75%); 17% redislocated, 8% resubluxated
- Repair of the native annular ligament gave more durable stability than reconstruction or no annular procedure
Indirect Reduction of the Radial Head in Chronic Paediatric Monteggia
- 10 missed paediatric Monteggia treated with angulation-translation ulna osteotomy and closed (indirect) reduction
- Radial head reduction achieved and maintained in 8 of 10 at mean 10-year follow-up
- Annular ligament reconstruction performed in only 2 cases - not required in every case
Surgical Management of Complex Adult Monteggia Fractures
- Jupiter classification subdivides Bado posterior (type II) lesions; coronoid involvement and proximal ulna comminution markedly raise complexity
- Coronoid access is difficult from a posterior approach, risking tenuous reduction and worse function
Salvage of Malaligned Posterior Monteggia Fractures
- 17 patients with malalignment after fixation of a posterior Monteggia; 15 had loose fixation
- Realignment with a dorsal contoured plate achieved union and concentric ulnohumeral reduction in all 17
- Excellent/good result in 14 of 17 at mean 59 months
Clinical Decision Scenarios
Use these scenarios to practise clinical reasoning and management decisions
Scenario 1: Acute Adult Monteggia
"A 45-year-old construction worker presents after falling from scaffolding. X-rays show proximal ulna fracture with posterior radial head dislocation."
Diagnosis and Classification:
This is a Bado Type II Monteggia fracture-dislocation. Type II is characterized by posterior or posterolateral radial head dislocation with posterior apex angulation of the ulna. This is the most common type in adults, comprising approximately 70% of cases.
Nerve at Risk and Testing:
Posterior interosseous nerve (PIN) is at risk in 10-20% of Monteggia injuries. Test by checking finger extension at MCPJs - have patient extend fingers with wrist in neutral. Also check thumb extension. Wrist extension is usually preserved as ECRL/ECRB are innervated proximal to PIN origin.
Surgical Approach and Key Principles:
Boyd posterior approach to ulna. Key principles: 1) Anatomic reduction and fixation of ulna fracture with 3.5mm LCP. 2) Restore length comparing to contralateral X-rays if needed. 3) Correct angular deformity. 4) Check radiocapitellar line fluoroscopically - if radial head is reduced, no further intervention needed. 5) If radial head doesn't reduce, explore via Kocher approach for interposed tissue.
If Radial Head Doesn't Reduce:
The radial head not reducing indicates interposed tissue - most commonly annular ligament, but can be capsule, biceps tendon, or rarely radial nerve. Approach through Kocher interval (anconeus-ECU). Identify and remove interposed tissue. Assess annular ligament - if repairable, suture. If deficient, may need reconstruction. Consider temporary transarticular K-wire for 3-4 weeks if stability questionable.
Scenario 2: Missed Pediatric Monteggia
"A 7-year-old child presents 6 weeks after a fall. Parents were told the 'wrist fracture healed well' at another hospital. You notice limited forearm rotation and prominent radial head."
Diagnosis and How It Happened:
Chronic or missed Monteggia fracture-dislocation. The radiocapitellar line was not assessed on the original forearm X-rays, and the radial head dislocation was missed. This is unfortunately common - Monteggia is one of the most missed injuries in orthopaedics. The ulna fracture would have been a greenstick pattern that was treated as an isolated injury.
Imaging Required:
Full-length AP and lateral forearm X-rays including both elbow and wrist joints. Comparison views of contralateral side for ulna length and bow. CT of elbow to assess radial head shape (may be deformed if chronically dislocated) and capitellum changes. Look for adaptive changes at the proximal radioulnar joint.
Treatment Options:
At 6 weeks, there is still reasonable chance of success with: 1) Ulna osteotomy to restore length and correct any residual angulation. 2) Open reduction of radial head via lateral approach. 3) Annular ligament reconstruction if deficient - Bell Tawse technique using triceps fascia strip. 4) K-wire fixation of radial head temporarily. Outcomes deteriorate with delay - should proceed expeditiously.
Counseling the Parents:
Counsel that delayed treatment has lower success rate than acute treatment. Goals are to restore elbow function and forearm rotation. May not achieve normal ROM. Risk of redislocation even with reconstruction. May need further surgery if reconstruction fails. Radial head excision is a salvage option but only after skeletal maturity. Encourage early rehabilitation but protect reconstruction for 6 weeks.
Scenario 3: Monteggia with PIN Palsy
"You fix an acute Type II Monteggia fracture with anatomic ulna reduction and the radial head reduces concentrically. Post-operatively, the patient cannot extend fingers at MCPJs."
Diagnosis and Mechanism:
Post-operative posterior interosseous nerve (PIN) palsy. This can occur from: 1) Pre-existing injury from the initial trauma (stretch as radial head dislocated). 2) Intraoperative traction during reduction. 3) Post-operative swelling. The most common scenario is pre-existing injury not detected pre-operatively - always document nerve function before surgery.
Was There Pre-operative PIN Palsy?
Critical to have documented pre-operative exam. If PIN palsy was present pre-operatively, this is usually a neurapraxia from the injury itself and will recover in most cases - observe. If it's new post-operatively, need to consider: Was there difficulty with reduction suggesting nerve entrapment? Is there significant swelling? Consider urgent exploration if concern for nerve entrapment in fracture site or around plate.
Management Plan if Pre-existing:
Observation is appropriate for traumatic PIN neurapraxia. Most recover spontaneously within 3-4 months. Serial clinical examinations monthly. EMG at 6 weeks to confirm neurapraxia (should show denervation but with intact motor units indicating recovery potential). Splinting for wrist/finger extension. If no recovery by 3-4 months clinically, or EMG shows complete axonotmesis, then explore PIN through Henry approach to proximal forearm.
Anatomic Relations of PIN:
PIN is the deep branch of radial nerve that branches at level of radial head. It passes through arcade of Frohse (fibrous edge of supinator). Innervates supinator, then all finger and thumb extensors (EDC, EIP, EPL, EPB, APL), ECU, and EIP. Does not supply wrist extensors (ECRL/ECRB are proximal) or sensation (sensory branch is superficial radial nerve).
MCQ Practice Points
Diagnostic Question
Q: What radiographic line must be checked on every elbow X-ray to avoid missing a Monteggia fracture?
A: The radiocapitellar line. A line drawn through the center of the radial neck must bisect the center of the capitellum on ALL views (AP, lateral, oblique). Disruption indicates radial head dislocation.
Classification Question
Q: What is the most common Bado type in adults vs children?
A: Adults: Type II (70%) - posterior radial head dislocation with posterior ulna angulation. Children: Type I - anterior radial head dislocation with anterior ulna angulation. This is commonly tested.
Treatment Question
Q: After anatomic ulna fixation, the radial head does not reduce. What is your next step?
A: The radial head should reduce spontaneously after anatomic ulna fixation. If it doesn't: 1) Confirm ulna reduction is truly anatomic (length and alignment). 2) If still subluxed, explore through Kocher approach for interposed tissue (annular ligament, capsule, or biceps).
Complication Question
Q: A patient develops finger drop after Monteggia ORIF. What is the likely diagnosis and prognosis?
A: PIN (Posterior Interosseous Nerve) palsy. Occurs in 10-20% of Monteggia injuries. Usually a neurapraxia from traction during injury (not iatrogenic). Excellent prognosis - most recover spontaneously within 3-4 months. Observe unless new post-op or concern for entrapment.
Chronic Injury Question
Q: What is the treatment for a Monteggia fracture diagnosed 6 weeks after injury?
A: Chronic Monteggia (greater than 4 weeks) has poor outcomes with simple reduction. Requires: ulna osteotomy (to restore length), open reduction of radial head, and annular ligament reconstruction (Bell Tawse technique using triceps tendon strip). Results are inferior to acute treatment.
Guidelines, Registries & Global Practice
Global Epidemiology
- Monteggia lesions are uncommon: roughly 1-2% of all forearm fractures and under 5% of paediatric elbow/forearm fractures across published series worldwide.
- Bimodal distribution: paediatric peak around 4-10 years (predominantly Bado type I) and an adult peak in middle age and the elderly (predominantly type II).
- There is no single-country pattern - the adult type II predominance and paediatric type I predominance are consistent across North American, European and Asian cohorts.
Guidelines & Society Positions (Side by Side)
How Major Bodies Frame Monteggia Management
| Body / Region | Core Position | Practical Emphasis |
|---|---|---|
| AO Foundation (global) | Anatomic reduction and stable plate fixation of the ulna; radial head reduces with correct ulna alignment | Restore ulna length, alignment and rotation; intra-op fluoroscopic check of radiocapitellar line |
| BOA / BOAST (UK, open & elbow trauma) | Treat as a fracture-dislocation - urgent assessment, documented neurovascular exam, early definitive fixation | Open injuries follow standard open-fracture pathways; senior-led decision-making |
| AAOS (US, expert/OKU consensus) | Operative fixation is standard in adults; emphasis on detecting associated radial head and coronoid injury | Address coronoid and radial head fractures at the index procedure |
| POSNA / EFORT (paediatric consensus) | Closed reduction acceptable for acute, stable (incomplete) paediatric ulna patterns; operate if unstable or chronic | Low threshold to fix unstable complete ulna fractures; never excise the radial head in a child |
Clinical Pearl
There is no dedicated randomised guideline for Monteggia fractures - guidance is consensus/expert based. The internationally shared principle across AO, BOA, AAOS and paediatric bodies is identical: fix the ulna anatomically and the radial head follows.
Registry & Resource-Setting Variation
- No national arthroplasty/implant registry tracks Monteggia outcomes specifically; evidence is from single-centre and tertiary trauma-centre series rather than registry data.
- High-resource settings: routine fluoroscopy, locking plates, on-table radial head implants, and ready paediatric subspecialty referral.
- Limited-resource settings: missed and chronic (neglected) Monteggia is proportionally far more common because the radiocapitellar line is not checked on the initial film; reconstruction (ulna osteotomy with indirect or open radial head reduction) is therefore a more frequent presentation.
Medicolegal Considerations
Monteggia fractures are among the most commonly missed injuries.
Key documentation requirements:
- Document radiocapitellar line assessment on ALL views
- Note PIN function pre- and post-operatively
- Record stability of radial head after fixation
Common litigation issues:
- Missed diagnosis (most common)
- Delayed treatment leading to chronic Monteggia
- Failure to document pre-existing PIN palsy
- Poor outcomes from chronic reconstruction
Monteggia Fractures
Clinical summary
Key Stats
- •1-2% of forearm fractures
- •Type II (posterior) = 70% in adults
- •Type I (anterior) = most common in children
- •PIN palsy 10-20%
- •Missed diagnosis rate approximately 5%
Bado Classification
- •Type I - Anterior RH dislocation, anterior ulna angulation
- •Type II - Posterior RH dislocation, posterior ulna angulation
- •Type III - Lateral RH dislocation, ulna metaphyseal fracture
- •Type IV - Anterior RH dislocation, both bone fractures
Key Principles
- •Radiocapitellar line MUST bisect capitellum on ALL views
- •Fix ulna anatomically - RH reduces spontaneously
- •If RH doesn't reduce - explore for interposed tissue
- •Chronic (more than 4 weeks) - annular ligament reconstruction needed
- •PIN palsy - usually recovers, observe 3-4 months
Surgical Steps
- •Position supine, arm on table
- •Boyd posterior approach to ulna
- •Anatomic reduction - restore length/alignment
- •3.5mm LCP plate fixation (6-8 holes)
- •Check radiocapitellar line on fluoro
- •If RH subluxed - Kocher approach to explore
Must Know for Exam
- •Most missed injury - ALWAYS check radiocapitellar line
- •Adult vs pediatric types differ (II vs I)
- •PIN palsy is neurapraxia - observe
- •Chronic has poor outcomes - emphasizes early diagnosis
- •Bell Tawse technique for annular ligament reconstruction