High Yield Overview
RADIAL HEAD FRACTURES
Secondary Valgus Stabilizer | Mason Classification | Rule of 3
33%Of elbow fractures
3:1Female to Male
30%Associated injuries
110°Safe Zone arc
MASON CLASSIFICATION
Type I
PatternNon-displaced (less than 2mm)
TreatmentSling, Early ROM (Best prognosis)
Type II
PatternDisplaced (greater than 2mm) partial head
TreatmentORIF if mechanical block
Type III
PatternComminuted entire head
TreatmentReplacement vs ORIF
Type IV
PatternWith elbow dislocation
TreatmentAddress instability (Terrible Triad)
Critical Must-Knows
- Secondary valgus stabilizer - critical if MCL is torn
- Mechanical block needs aspiration to confirm (remove pain)
- Safe Zone (90-110 degrees) for hardware placement to avoid impingement
- Essex-Lopresti - always check DRUJ/wrist for tenderness
- Terrible Triad = Radial Head + Coronoid + Dislocation
Examiner's Pearls
- "Aspirate hemarthrosis + inject L.A. to assess true ROM
- "Fat pad sign may be the only radiological sign
- "Excision contraindicated if forearm instability (check wrist!)
- "Use bare metal stems for replacement (cemented or press-fit)
Clinical Imaging
Imaging Gallery
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Exam Essentials
Rule of Threes
Fractures often come in threes (Terrible Triad):
- Radial Head Fracture
- Coronoid Fracture
- Elbow Dislocation (LCL injury) Always look for the other two!
The 'Safe Zone'
90-110 degree arc of the radial head that does not articulate with the proximal radioulnar joint.
- Safe for plate/screw prominent heads
- Determine intra-operatively using reference marks
Don't Miss Essex-Lopresti
Longitudinal Radioulnar Dissociation.
- Radial Head Fracture
- Interosseous Membrane (IOM) tear
- DRUJ Dislocation Exam Trap: Always document "Non-tender DRUJ" or get wrist X-rays.
Surgical Threshold
Mechanical Block is the primary indication for Type II.
- Must aspirate hematoma and inject local anaesthetic first
- If block resolves then Non-operative
- If block persists then Surgery
Quick Decision Guide
| Mason Type | Key Feature | Stability | Treatment |
|---|---|---|---|
| Type I | Non-displaced (less than 2mm) | Stable | Sling for comfort, Early ROM (start within 1 week) |
| Type II | Displaced greater than 2mm | Usually Stable | ORIF if mechanical block, otherwise conservative |
| Type III | Comminuted | Variable | ORIF (if less than 3 fragments) OR Replacement (if more than 3 fragments) |
| Type IV | + Dislocation | Unstable | Reduce, Fix/Replace Head, Repair LCL, Fix Coronoid |
Mnemonic
BLOCKIndications for Surgery
B
Block to motion
Mechanical block after LA injection
L
Loose bodies
Intra-articular fragments
O
Open fracture
Requires washout/fixation
C
Complex instability
Type IV (Terrible Triad) or Essex-Lopresti
K
Kill greater than 2mm displacement?
Controversial - displacement alone not absolute indication
Memory Hook:If there's a BLOCK, you need to unlocking it (Surgery).
Mnemonic
RCDTerrible Triad Components
R
Radial Head Fracture
Usually Type III/IV
C
Coronoid Fracture
Usually Type I/II (Regan-Morrey)
D
Dislocation (LCL)
Posterolateral dislocation
Memory Hook:RCD - Reality Check Required (It's worse than it looks)
Mnemonic
MCEAssociated Injuries
M
MCL Injury
Assess valgus stability
C
Coronoid/Capitellum
Associated fractures
E
Essex-Lopresti
DRUJ injury + IOM tear
Memory Hook:MCE - Must Check Everything (Wrist, Medial side, CT)
Overview and Epidemiology
Mechanism of Injury
FOOSH (Fall on Outstretched Hand):
- Axial load + Valgus force leads to Radial Head impacting Capitellum.
- Pronation: Anterolateral fragment (most common).
- Extension: Posterior dislocation.
Demographics
- Most common adult elbow fracture (33% of elbow, 4% of all fractures)
- Peak age 30-40 years
- Females greater than Males (3:1)
Biomechanics
- Primary stabilizer: Radiocapitellar contact (60% load transfer)
- Secondary valgus stabilizer: Resists valgus if MCL is incompetent. Contributes 30% to valgus stability.
- Longitudinal stability: Prevents proximal migration of radius
The Secondary Stabilizer Concept
The radial head is a secondary stabilizer to valgus stress. If the MCL (primary stabilizer) is intact, the radial head is less critical for stability. If the MCL is torn (e.g., Mason IV), the radial head becomes critical to prevent valgus instability. Thus, excision is contraindicated in Mason IV or Essex-Lopresti.
Anatomy and Pathophysiology
Anatomical Structures
| Structure | Significance | Surgical Relevance |
|---|---|---|
| Safe Zone | 90-110° non-articulating arc | Place plates/screws here to avoid PRUJ impingement |
| LCL Complex | Lateral stabilizers | Often torn in Type IV - repair after head fixation |
| Posterior Interosseous Nerve (PIN) | Motor nerve to extensors | At risk during Kocher approach (pronate to protect) |
| Blood Supply | Radial recurrent artery | Retrograde flow - risk of AVN/Non-union in neck fractures |
Finding the Safe Zone
Intra-operatively, the Safe Zone can be identified by using reference marks:
- Radial Styloid (Lateral) corresponds to midpoint of safe zone in some citations, but unreliable.
- Lister's Tubercle alignment? Best Method: Mark the radial head in full pronation and supination relative to the sigmoid notch. The area that does not articulate with the lesser sigmoid notch of the ulna is the safe zone. Roughly corresponds to the lateral aspect of the head when forearm is in neutral.
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The Kocher Interval
- The interval is between Anconeus (Radial N) and ECU (PIN).
- It is safe distally but the PIN crosses the radial neck proximally within the supinator.
- Pronation moves the PIN anteriorly, away from the surgical field, making the dissection safer.
Kaplan Interval
- Between ECU and EDC.
- Better access to anterolateral coronoid and anterior capsule.
- Higher risk to PIN and LCL if extended proximally.
- Often preferred for Terrible Triad injuries to access coronoid.
Classification Systems
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Mason Classification (Modified by Broberg & Morrey)
| Type | Description | Stability | Treatment |
|---|---|---|---|
| Type I | Non-displaced (less than 2mm), no block | Stable | Conservative |
| Type II | Displaced greater than 2mm, partial head | Usually Stable | ORIF if block/large fragment |
| Type III | Comminuted entire head | Variable | Replacement (or ORIF if simple) |
| Type IV | Fracture + Ulnohumeral Dislocation (Terrible Triad likely) | Unstable | Surgery (usually Replacement + LCL repair) |
This classification is simple but guides surgical decision making effectively.
Clinical Assessment
History
- Mechanism: Fall on outstretched hand.
- Pain: Lateral elbow pain, worse with pronation/supination.
- Mechanical Sx: Locking or clicking (loose bodies).
- Wrist pain: Ask specifically! (Essex-Lopresti).
Examination
- Tenderness: Radial head, LCL origin, DRUJ (wrist).
- ROM: Assess flexion/extension and pro/supination.
- Mechanical Block: Hard stop vs pain inhibition.
- Stability: Valgus stress (MCL), Pivot shift (LCL).
The Aspiration Test
Pain inhibition can mimic a mechanical block.
- Aseptically aspirate hematoma from the 'soft spot'.
- Inject 5-10ml of Local Anaesthetic (Lignocaine/Marcaine).
- Re-examine ROM. Result: If full ROM returns = Type I (No block). If block persists = Type II (Mechanical Block) leads to Surgery.
Investigations
Imaging Protocol
X-RayStandard Views
AP, Lateral, Radiocapitellar (Greenspan) views.
- Look for: Cortical disruption, step-off, fat pad sign (sail sign).
- Check DRUJ context.
CT ScanComplexity Assessment
Indicated for:
- Comminuted fractures (Type III)
- Associated coronoid fractures
- Dislocation/Subluxation
- Surgical planning (ORIF vs Replacement)
MRIRarely Needed
Only for subtle ligamentous injury or occult fractures if CT equivocal. Mostly clinical diagnosis for ligaments.
Radiocapitellar View
The Radiocapitellar (Greenspan) View is taken with the beam angled 45 degrees to the shoulder. It profiles the radial head without overlap from the coronoid/ulna, making it excellent for detecting subtle fractures.
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Management Algorithm
📊 Management Algorithm
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Indication: Type I, Type II without block
Protocol:
- Sling for comfort (max 3-5 days).
- Early Active ROM immediately as pain allows.
- Resolution of hematoma allows movement.
- X-ray at 1 week to check displacement.
Outcomes: Excellent (90-95%). Stiffness is main risk if immobilized too long.
Surgical Technique
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ORIF Principles
- Approach: Kocher (between Anconeus and ECU) or Kaplan (between ECU and EDC).
- Protection: Pronate forearm to protect PIN (moves it medially away from field).
- Reduction: K-wires for temporary hold.
- Fixation: Mini-fragment screws (2.0/2.4mm) or Headless Compression Screws.
- Plate Position: Must be in Safe Zone (lateral aspect in neutral rotation).
- Check: Range of motion intra-op. Impingement?
Ensure anatomic reduction to prevent arthritis.
Kocher Interval
The Kocher Interval is between the Anconeus (Radial n.) and ECU (PIN). It is the true internervous plane? Actually, both are supplied by Radial nerve branches, but the plane is safe distally. Pronation moves the PIN anteriorly and away from the radial neck, increasing the safe zone for dissection.
Complications
Complications Management
| Complication | Incidence | Prevention/Management |
|---|---|---|
| Stiffness | 15-20% | Early ROM! Avoid prolonged immobilization (greater than 1 week). |
| Heterotopic Ossification | 5-10% | Gentle tissue handling. Indomethacin/Radiation if high risk. |
| PIN Palsy | 1-3% | Pronate during exposure. Retract gently anteriorly. |
| Implant Failure/Loosening | 5% | Safe zone placement. Avoid overstuffing replacement. |
| Proximal Radial Migration | Variable | Occurs after Excision if IOM incompetent (Essex-Lopresti). |
Postoperative Care
Rehab Protocol
0-1 WeekImmobilization
Splint/Sling for comfort. Elevate. Start active ROM as soon as block/pain allows (usually Day 3-5). If LCL repaired: Elbow hinge brace needed.
2-6 WeeksMotion Phase
Active Flexion/Extension, Pro/Supination. Avoid passive stretching (HO risk). Wean sling.
6-12 WeeksStrengthening
Start strengthening once union evident (ORIF) or soft tissue healed (Arthroplasty).
3-6 MonthsReturn to Sport
Full activity. Contact sports depend on fracture healing.
Outcomes
Prognostic Factors
| Factor | Impact | Explanation |
|---|---|---|
| Mason Type | High | Type I/II do better than Type III/IV |
| Associated Injuries | Critical | Dislocation or Coronoid fracture worsens prognosis significantly |
| Time to ROM | High | Early mobilization is key to preventing stiffness |
| Workers Comp | Moderate | Poorer subjective outcomes reported |
Replacement vs Excision
Long-term studies show that Radial Head Replacement generally provides better functional scores and prevention of valgus drift compared to Excision, especially in high-demand patients. Excision is reserved for low-demand, stable elbows.
Evidence Base
ORIF vs Replacement for Mason III
📚 Chen et al.
Key Findings:
- RCT comparing ORIF vs Replacement for Mason III fractures.
- Replacement group had significantly better DASH scores and ROM.
- Higher complication rate (non-union, failure) in ORIF group for comminuted fractures.
Clinical Implication: For comminuted Mason III fractures, Replacement is often superior to ORIF.
Source: J Bone Joint Surg Am. 2011
Early Mobilization
📚 Li et al.
Key Findings:
- Early mobilization (within 1 week) resulted in better ROM and less pain compared to immobilization for more than 3 weeks.
- No increase in displacement or non-union.
Clinical Implication: Start moving Mason I/II fractures immediately. Stiffness is the enemy.
Source: Journal of Orthopaedic Trauma. 2014
Safe Zone Anatomy
📚 Smith and Hotchkiss
Key Findings:
- Defined the 110-degree non-articulating arc.
- Demonstrated that placing hardware outside this zone impinges on the lesser sigmoid notch, causing loss of rotation.
Clinical Implication: Adhere strictly to the Safe Zone for all hardware.
Source: J Hand Surg Am. 1996
Metal vs Silicone Heads
📚 van Riet et al.
Key Findings:
- Silicone heads had high failure rate (fracture, synovitis).
- Metal heads restored stability better.
- Recommendation to abandon silicone implants.
Clinical Implication: Use metallic modular heads. Avoid silicone.
Source: J Bone Joint Surg. 2003
Terrible Triad Outcomes
📚 Pugh and McKee
Key Findings:
- Standardized protocol (Coronoid fixation + Radial Head Repair/Replace + LCL Repair) yielded predictable stability and functional ROM.
- Mean arc obtained was 100 degrees.
Clinical Implication: Systematic 'inside-out' approach is gold standard for Terrible Triad.
Source: J Bone Joint Surg Am. 2002
Exam Viva Scenarios
Practice these scenarios to excel in your viva examination
VIVA SCENARIOStandard
Scenario 1: Mason II Management
EXAMINER
"A 35-year-old carpenter presents with a radial head fracture after a fall. X-ray shows a Type II fracture with 3mm displacement. He has limited pronation. Talk me through your management."
EXCEPTIONAL ANSWER
**Assessment:** My primary goal is to determine if this is a surgical candidate. The X-ray shows displacement greater than 2mm, but the critical factor is **functional block**. 1. **Aspiration Test:** I would aspirate the hematoma and inject local anaesthetic. 2. **Re-examine:** If the mechanical block to pronation resolves then **Conservative Management** (Sling 3 days, Early ROM). 3. **Persisting Block:** If the block remains, it implies the fragment is physically obstructing the joint leads to **Surgery (ORIF)**. **Surgical Plan:** - Kocher Approach. - Open Reduction Internal Fixation with headless compression screws or low-profile plate. - **Safe Zone** placement to avoid impingement. - Early ROM post-op. **Rationale:** In a young manual worker, preserving anatomy is preferred over excision or replacement if reconstructable.
KEY POINTS TO SCORE
Aspiration test is the decision maker
Displacement alone isn't absolute indication
Block to motion = Surgery
Safe zone placement
COMMON TRAPS
✗Sending for surgery based solely on X-ray displacement
✗Failing to check the wrist (Essex-Lopresti)
✗Prolonged immobilization leading to stiffness
LIKELY FOLLOW-UPS
"What is the Safe Zone?"
"What nerves are at risk in the approach?"
VIVA SCENARIOChallenging
Scenario 2: Terrible Triad
EXAMINER
"You are called to ED for a 40-year-old female with an unstable elbow after reduction of a dislocation. X-ray shows a comminuted radial head fracture and a coronoid tip fracture. How do you manage this?"
EXCEPTIONAL ANSWER
**Diagnosis:** This is a **Terrible Triad Injury** (Dislocation + Radial Head + Coronoid). The elbow is unstable because of loss of: 1. Anterior constraint (Coronoid). 2. Valgus/Posterolateral constraint (Radial Head). 3. LCL complex (torn in dislocation). **Management:** This requires **Urgent Surgical Fixation**. **Sequence (Standard Protocol):** 1. **Coronoid:** Fix or suture lasso the coronoid/capsule (Approach: Medial or Lateral depending on size). Often done first or after radial head. 2. **Radial Head:** Since it's comminuted (Type III) and we NEED stability then **Radial Head Replacement** (Arthroplasty). Excision is contraindicated. 3. **LCL Repair:** Reattach LCL to the lateral epicondyle (usually with anchors) to restore varus stability. **Post-op:** Hinge brace, early active motion within stable arc (usually pronation helps stability).
KEY POINTS TO SCORE
Terrible Triad = Unstable
Restore bony constraints first, then ligaments
Replacement preferred over fixation for comminution to ensure stability
LCL repair is the final step
COMMON TRAPS
✗Excising radial head (causes gross instability)
✗Ignoring the coronoid fragment
✗Immobilizing in full extension
LIKELY FOLLOW-UPS
"Why not excise the radial head?"
"What is the Regan-Morrey classification for coronoid?"
VIVA SCENARIOChallenging
Scenario 3: Essex-Lopresti
EXAMINER
"A patient with a comminuted radial head fracture also complains of severe wrist pain. X-rays of the wrist show ulnar positive variance. What is the diagnosis and management implication?"
EXCEPTIONAL ANSWER
**Diagnosis:** **Essex-Lopresti Lesion** (Longitudinal radioulnar dissociation). - Components: Radial Head Fracture + IOM tear + DRUJ disruption. - The radius has migrated proximally due to loss of head support and IOM. **Management Implication:** - **Contraindication to Excision:** You CANNOT excise the radial head, or the radius will migrate further, worsening wrist pain/impaction. - **Treatment:** You must **restore radial length**. - If repairable: ORIF. - If comminuted: **Radial Head Replacement**. - **DRUJ:** Examine stability after fixing head. If unstable, pin DRUJ in supination for 4-6 weeks. **Prognosis:** Often poor despite treatment (stiffness, chronic wrist pain).
KEY POINTS TO SCORE
Wrist pain = Essex-Lopresti until proven otherwise
Excision is absolutely contraindicated
Must restore length with Replacement/ORIF
Address DRUJ instability
COMMON TRAPS
✗Excising the head
✗Missing the wrist diagnosis
✗Failure to pin unstable DRUJ
LIKELY FOLLOW-UPS
"How do you assess DRUJ stability?"
"What is the IOM's function?"
MCQ Practice Points
Safe Zone
Q: What describes the 'Safe Zone' for radial head fixation? A: A 90-110 degree arc on the lateral aspect (in neutral) that does not articulate with the ulna. Hardware here avoids impingement.
Kocher Approach Nerve Risk
Q: Which nerve is most at risk during the Kocher approach to the radial head? A: Posterior Interosseous Nerve (PIN). It winds around the radial neck within the supinator. Pronation moves it anteriorly and safely away.
Valgus Stability
Q: The radial head is the secondary stabilizer against which force? A: Valgus force. The MCL is primary. Radial head is critical only if MCL is deficient.
Mason IV Treatment
Q: What is the treatment for a Mason IV fracture (Dislocation + Fracture)? A: Surgery. Requires reduction, stabilization of the head (Fix or Replace), and usually LCL repair. Excision is contraindicated due to instability.
Aspiration Test
Q: What is the purpose of aspirating a radial head fracture hematoma? A: To relieve pain and mechanical block caused by fluid pressure, allowing assessment of true mechanical block vs pain inhibition. Distinguishes surgical vs non-surgical Type II.
Australian Context and Medicolegal
Practice Points
- WorkCover: Common injury in manual labourers. Documentation of ROM is critical for impairment rating.
- Referral: Complex patterns (Terrible Triad) often referred to upper limb specialists.
- Implants: Specific prostheses availability (e.g., Acumed, Wright) varies by hospital.
Medicolegal
- Missed Essex-Lopresti: Major source of litigation if radial head excised.
- Stiffness: Failure to counsel about loss of extension (common outcome).
- PIN Injury: Iatrogenic nerve injury during approach.
RADIAL HEAD FRACTURES
High-Yield Exam Summary
Classification (Mason)
- •Type I: Non-displaced (less than 2mm)
- •Type II: Displaced partial head
- •Type III: Comminuted
- •Type IV: Associated Dislocation
Key Concepts
- •Secondary Valgus Stabilizer
- •Safe Zone (110° arc)
- •Aspiration Test for Block
- •Terrible Triad (Head + Coronoid + D/L)
Surgery Indications
- •Mechanical Block (Type II)
- •Open Fracture
- •Type III/IV (Instability)
- •Essex-Lopresti Association
Treatment Options
- •Type I: Early ROM (less than 1 wk)
- •Type II: ORIF (Headless screws)
- •Type III: Replacement (Metal)
- •Excison: ONLY if stable (Rare)
Complications
- •Stiffness (Most common)
- •PIN Nerve Palsy
- •HO (Heterotopic Ossification)
- •Implant Loosening