CAPITELLUM FRACTURES - CORONAL SHEAR
FOOSH Mechanism | Lateral X-ray Essential | Headless Screws Anterior-to-Posterior
BRYAN-MORREY CLASSIFICATION
Critical Must-Knows
- Coronal shear mechanism - FOOSH with elbow extended, radial head drives into capitellum
- Lateral X-ray is KEY - 'double arc' sign (capitellum + trochlear sulcus)
- Headless compression screws anterior to posterior - bury beneath cartilage
- Kocher (lateral) approach for ORIF - preserve lateral collateral ligament complex
- Type IV includes trochlea - involves ulnohumeral joint, worst prognosis
Examiner's Pearls
- "Often missed on AP view - ALWAYS check lateral radiograph
- "Associated radial head fracture in 30% - examine carefully
- "Early ROM critical to prevent stiffness - start at 48-72 hours
- "No soft tissue attachments anteriorly - AVN risk
Clinical Imaging
Imaging Gallery
Critical Capitellum Fracture Exam Points
Lateral View is Diagnostic
98% visible on lateral X-ray, often invisible on AP. Look for 'double arc' sign - two concentric arcs from capitellum and trochlear sulcus.
Coronal Shear Mechanism
FOOSH with elbow extended creates coronal shear fracture. Radial head impacts capitellum, shearing it off anteriorly.
Type IV = Worst
Type IV includes trochlea - involves both ulnohumeral and radiocapitellar joints. Highest stiffness rate, worst functional outcomes.
Screw Direction Critical
Headless screws anterior to posterior perpendicular to fracture plane. Bury heads flush or below cartilage to allow early ROM.
Quick Decision Guide
| Fracture Pattern | Fragment Quality | Key Decision | Treatment |
|---|---|---|---|
| Type I (Hahn-Steinthal) | Large fragment, good bone stock | Always fixable | ORIF headless screws - excellent prognosis |
| Type II (Kocher-Lorenz) | Thin osteochondral shell | Size dependent | ORIF if larger than 30%, excise if small |
| Type III (Comminuted) | Multiple fragments | Assess reducibility | ORIF if reconstructable, excise if severely comminuted |
| Type IV (Trochlear extension) | Capitellum + trochlea | Critical to fix | ORIF essential - involves ulnohumeral joint |
HKCTBryan-Morrey Classification
Memory Hook:H-K-C-T: Hahn is Huge (best), Trochlea is Terrible (worst). Remember the eponyms Hahn-Steinthal and Kocher-Lorenz!
SOAPCapitellum Anatomy - Why AVN Risk
Memory Hook:SOAP cleans the joint but watch the blood supply - fix from anterior to posterior!
LARCHSurgical Technique Steps
Memory Hook:LARCH trees are lateral like your approach - fix it right and get moving early!
REALAssociated Injuries to Check
Memory Hook:These injuries are REAL common with capitellum fractures - don't miss them!
Overview and Epidemiology
Clinical Significance
Capitellar fractures are rare but exam-relevant injuries. They represent only 1% of elbow fractures but are frequently tested due to their distinctive mechanism, diagnostic challenges, and specific surgical principles. The key teaching points are the lateral X-ray diagnosis and anterior-to-posterior fixation.
Demographics
- Female predominance (4:1) - osteoporotic bone
- Bimodal distribution: young males (high-energy), elderly females (low-energy)
- Mean age 45-50 years
- More common in osteoporotic bone
Mechanism
- FOOSH with elbow extended - most common
- Radial head impacts capitellum creating coronal shear
- Direct blow to lateral elbow
- Associated with elbow dislocations in 20%
Why So Rare?
The capitellum is protected by the radial head which typically fails first. Capitellar fractures occur when:
- The radial head is already fractured (30% have concurrent radial head fracture)
- The radial head is intact but the force vector creates a shear rather than axial load
- The bone quality is poor (osteoporosis)
Anatomy and Pathophysiology
Key Anatomical Principle
The capitellum has NO soft tissue attachments anteriorly. It is covered entirely by articular cartilage on its anterior surface. When fractured, the fragment receives blood supply only from its posterior bone attachment - this is why AVN is a risk and why screws are placed anterior to posterior (to avoid damaging posterior blood supply).
Key Anatomical Structures
| Structure | Location | Clinical Relevance |
|---|---|---|
| Capitellum | Lateral 1/3 of distal humeral articular surface | Articulates with radial head - forms radiocapitellar joint |
| Trochlea | Medial 2/3 of distal humeral articular surface | Type IV fractures involve trochlea - affects ulnohumeral joint |
| Lateral epicondyle | Non-articular prominence lateral to capitellum | Origin of common extensor tendons and LCL |
| LCL complex (LUCL) | Lateral ulnar collateral ligament | Must preserve during approach - posterolateral rotatory stability |
Blood Supply
- Posterior vessels only supply the capitellum
- Anterior surface is entirely articular cartilage
- Fracture fragment receives blood through posterior attachment
- AVN risk if posterior blood supply disrupted
- Fix anterior-to-posterior to preserve vessels
Biomechanics
- Capitellum transmits 60% of axial load across elbow
- Acts as secondary valgus stabilizer with radial head
- Loss of capitellum = radiocapitellar instability
- Type IV (with trochlea) = ulnohumeral instability
Exam Trap: Lateral Epicondyle vs Capitellum
Don't confuse the lateral epicondyle (non-articular, extensor origin) with the capitellum (articular surface). The capitellum is anterior and distal to the lateral epicondyle. On lateral X-ray, the capitellum creates the characteristic hemispherical shadow that, when fractured, produces the 'double arc' sign.
Classification Systems
Bryan-Morrey Classification (Most Commonly Used)
| Type | Eponym | Fragment Characteristics | Prognosis |
|---|---|---|---|
| Type I | Hahn-Steinthal | Large fragment with substantial bone stock | Best - most fixable |
| Type II | Kocher-Lorenz | Thin osteochondral shell, minimal bone | Variable - size dependent |
| Type III | - | Comminuted multiple fragments | Challenging - may need excision |
| Type IV | - | Capitellum + trochlea involved | Worst - involves both joints |
Key Point
Remember the eponyms: Type I = Hahn-Steinthal (big H for huge fragment), Type II = Kocher-Lorenz (thin K for kartilage). Type IV is the worst because the Trochlea is Terrible.
Clinical Assessment
History
- Mechanism: FOOSH with elbow extended, or direct lateral blow
- Pain pattern: Lateral elbow, worse with pronation/supination
- Swelling onset: Usually rapid due to hemarthrosis
- Loss of function: Painful and limited ROM
Examination
- Look: Swelling, ecchymosis, deformity (may be subtle)
- Feel: Lateral elbow tenderness, effusion
- Move: Limited flexion/extension, painful crepitus
- Special: Assess stability after any reduction
Don't Miss Associated Injuries!
30% have concurrent radial head fracture - always examine the radial head carefully. 20% associated with elbow dislocation - assess ligamentous stability. Look for terrible triad pattern (elbow dislocation + radial head fracture + coronoid fracture).
Physical Examination Findings
| Finding | Location | Significance |
|---|---|---|
| Lateral elbow tenderness | Over capitellum (anterolateral) | Direct sign of injury |
| Elbow effusion | Posterolateral soft spot | Hemarthrosis - suggests intra-articular fracture |
| Painful pronation/supination | Radiocapitellar joint | Fragment blocking motion or radial head injury |
| Posterolateral rotatory instability | With pivot shift test | Associated LCL injury - may need repair |
| Radial head tenderness | Proximal radius | 30% have concurrent radial head fracture |
Neurovascular Assessment
Always document radial, median, and ulnar nerve function and radial and ulnar pulses. While neurovascular injury is rare with isolated capitellar fractures, associated injuries (dislocation, radial head fracture) increase risk. Document PIN function (finger extension) as it is at risk during surgical approach.
Investigations
Imaging Protocol
Essential views: AP, lateral, and oblique. The LATERAL VIEW IS KEY - shows the 'double arc' sign. AP view may appear nearly normal.
Two concentric semicircular arcs on lateral view: (1) the displaced capitellar fragment, (2) the trochlear sulcus. 98% sensitivity on lateral view.
Gold standard for preoperative planning. Assess: fragment size, comminution, trochlear involvement (Type IV), associated injuries.
Rarely needed. Consider if occult fracture suspected with negative X-ray but high clinical suspicion, or to assess ligamentous injury.
Radiographic Findings
| View/Modality | Finding | Significance |
|---|---|---|
| Lateral X-ray | Double arc sign | DIAGNOSTIC - two concentric arcs |
| Lateral X-ray | Fat pad sign | Posterior fat pad elevation = hemarthrosis |
| AP X-ray | May appear normal | Often misses fracture - lateral is key |
| CT sagittal | Coronal shear fracture line | Best for surgical planning |
| CT 3D | Fragment size and position | Useful for complex fractures |
Why AP Misses the Fracture
The capitellar fracture line runs in the coronal plane (front to back). On AP view, you're looking along the fracture plane, so it's edge-on and nearly invisible. On lateral view, you're looking perpendicular to the fracture, making it obvious. This is why the lateral X-ray is essential.
CT Indications
Always get CT for surgical planning. Plain films cannot reliably assess:
- Fragment size (determines fixation vs excision)
- Trochlear involvement (Type IV - changes prognosis)
- Posterior column comminution (Dubberley B types)
- Associated radial head or coronoid fractures
Management Algorithm
Indications for Surgery
Most Capitellar Fractures Need Surgery
Virtually all displaced capitellar fractures require operative treatment. Non-operative treatment leads to malunion, stiffness, and arthritis. The only exceptions are truly non-displaced fractures (rare) or non-ambulatory patients.
| Indication | Rationale | Urgency |
|---|---|---|
| Displaced Type I (Hahn-Steinthal) | Excellent prognosis with ORIF | Semi-urgent |
| Displaced Type II (large fragment) | Restores articular surface | Semi-urgent |
| Type IV (trochlear involvement) | Critical to restore both joints | Semi-urgent |
| Associated elbow dislocation | Instability requires fixation | Urgent |
| Open fracture | Requires washout and fixation | Emergency |
Timing of Surgery
Semi-urgent (24-48 hours) for most isolated capitellar fractures. Urgent if associated with elbow dislocation or neurovascular compromise. Early surgery allows early mobilization which is critical for elbow outcomes.
Surgical Technique
ORIF Steps
ORIF Steps
Lateral decubitus (preferred) or supine with arm across chest. Tourniquet to upper arm. Image intensifier from opposite side.
Kocher (lateral) approach between anconeus and ECU. Develop interval, protect LCL complex. May extend proximally if needed.
Flex elbow to 90 degrees. Capsulotomy if needed for visualization. Irrigate joint and remove loose bodies/hematoma.
Anatomic reduction is critical. Use pointed reduction clamps carefully (cartilage damage). Provisional fixation with K-wires.
Headless compression screws (Herbert, Acutrak) from anterior to posterior. 2-3 screws depending on fragment size. Countersink below cartilage.
Check ROM through full arc. Check under fluoro that reduction maintained. Assess stability of radiocapitellar joint.
Screw Placement Principles
- Anterior to posterior direction - preserves posterior blood supply
- Headless compression screws - no prominent hardware
- Countersink below cartilage - allows ROM without impingement
- 2-3 screws for Type I, may need more for Type IV
Why A-to-P Direction?
- Blood supply enters from posterior humerus
- P-to-A screws would penetrate articular surface
- A-to-P placement compresses fragment to humerus
- Starting point is non-articular anterior surface
Complications
Complications and Management
| Complication | Incidence | Risk Factors | Management |
|---|---|---|---|
| Stiffness/loss of motion | 20-40% | Delayed surgery, Type IV, prolonged immobilization | Early ROM, hinged brace, may need arthrolysis |
| Post-traumatic arthritis | 15-30% | Malreduction, Type IV, comminution | Activity modification, ultimately arthroplasty |
| Avascular necrosis | 5-10% | Posterior dissection, comminution | Fix A-to-P, minimize soft tissue stripping |
| Heterotopic ossification | 5-15% | Delayed surgery, forced passive ROM, head injury | Prophylaxis: NSAIDs or radiation, excision if symptomatic |
| Malunion/nonunion | Under 5% | Technical error, AVN | Revision surgery if symptomatic |
| Hardware prominence | 5-10% | Screws not countersunk | Use headless screws, countersink properly |
Stiffness is the Most Common Problem
Loss of motion occurs in 20-40% of patients. The elbow is highly prone to stiffness after trauma. Prevention:
- Anatomic reduction to allow early motion
- Start ROM at 48-72 hours
- Use headless screws to avoid impingement
- Avoid forced passive motion (increases HO)
HO Prophylaxis
Consider HO prophylaxis in high-risk patients:
- Indomethacin 75mg daily for 6 weeks, OR
- Single dose radiation 7Gy within 72 hours
High-risk factors: head injury, burns, prolonged intubation, prior HO, delayed surgery.
Postoperative Care
Postoperative Protocol
Rehabilitation Timeline
Backslab in 90 degrees flexion. Elevation, ice. Plan early ROM - timing is critical.
Remove backslab, start active ROM. Gravity-assisted flexion/extension. No passive motion (HO risk).
Full active ROM encouraged. Hinged brace if unstable. No resistance exercises. Serial X-rays at 2, 6 weeks.
Progressive strengthening. Light resistance. Return to activities as tolerated.
Return to full activities. May take 6-12 months for maximum recovery.
Early ROM is Essential
Start active ROM at 48-72 hours. The elbow stiffens rapidly after injury. Delayed mobilization leads to:
- Flexion contracture
- Heterotopic ossification
- Poor functional outcomes
Avoid passive forced motion which increases HO risk.
Outcomes and Prognosis
Prognostic Factors
| Factor | Impact on Outcome | Notes |
|---|---|---|
| Fracture type | Most important | Type I best, Type IV worst |
| Quality of reduction | Critical | Anatomic reduction = better outcomes |
| Time to surgery | Significant | Early surgery (under 2 weeks) preferred |
| Associated injuries | Negative | Radial head, dislocation worsen prognosis |
| Patient age | Moderate | Younger patients have better outcomes |
| Rehabilitation compliance | Important | Early ROM essential for good outcome |
Functional Outcomes
Expected ROM after Type I ORIF: Flexion-extension arc 100-130 degrees (10-20 degree loss of terminal extension is common and well-tolerated). Pronation-supination usually full. Mayo Elbow Performance Score: 85-90 (good/excellent) in majority.
Evidence Base
Dubberley Classification and Outcomes
- Analysis of 47 capitellar fractures: Type 2B and 3B (with posterior comminution) had significantly worse outcomes. Overall complication rate 54%, stiffness in 46%.
Headless Compression Screw Fixation
- Review of 16 capitellar fractures fixed with headless compression screws showed 95% good/excellent results, mean flexion arc 136 degrees.
Anterior-to-Posterior Screw Placement
- Biomechanical and clinical study showing A-to-P screws preserve posterior blood supply while achieving compression. P-to-A risks articular penetration.
CT for Surgical Planning
- CT changed surgical plan in 28% of capitellar fractures compared to plain radiographs alone. Better characterized trochlear involvement and comminution.
Early ROM and Outcomes
- Review of distal humerus fractures (including capitellar) showed early ROM (under 2 weeks) resulted in significantly better final ROM compared to delayed mobilization.
Exam Viva Scenarios
Practice these scenarios to excel in your viva examination
Scenario 1: Type I Capitellum Fracture (~2-3 min)
"A 48-year-old woman presents after falling onto her outstretched hand with her elbow extended. She has lateral elbow pain and limited motion. AP X-ray shows only soft tissue swelling. How would you proceed?"
Scenario 2: Type IV Fracture with Trochlear Extension (~3-4 min)
"A 35-year-old man involved in a motorcycle accident has a complex elbow injury. CT shows a capitellar fracture extending to involve the trochlea with moderate comminution. The radial head appears intact. Describe your classification and management."
Scenario 3: Post-operative Stiffness (~2-3 min)
"You review a 45-year-old woman 3 months after ORIF of a Type I capitellar fracture. She has an arc of motion of only 45-100 degrees (55 degrees total) and is very frustrated. X-rays show united fracture with good reduction. How do you manage this?"
MCQ Practice Points
Imaging Question
Q: What radiographic sign is pathognomonic for capitellar fractures? A: The 'double arc' sign on lateral X-ray - two concentric semicircular arcs representing the displaced capitellar fragment and the underlying trochlear sulcus. This sign has 98% sensitivity on the lateral view.
Classification Question
Q: In the Bryan-Morrey classification, which type has the worst prognosis and why? A: Type IV has the worst prognosis because it involves both the capitellum and trochlea, affecting both the radiocapitellar and ulnohumeral joints. This leads to higher rates of stiffness, arthritis, and poor functional outcomes.
Anatomy Question
Q: Why are headless screws placed from anterior to posterior in capitellar fixation? A: To preserve the blood supply. The capitellum has no soft tissue attachments anteriorly and receives blood supply only from posterior vessels. A-to-P screw placement avoids penetrating the articular surface posteriorly and preserves the posterior blood supply, reducing AVN risk.
Treatment Question
Q: What is the most common complication after capitellar fracture fixation? A: Stiffness/loss of motion occurs in 20-40% of cases. The elbow is highly prone to contracture after trauma. Prevention requires anatomic reduction allowing early active ROM (start 48-72 hours), use of headless screws, and avoiding forced passive motion.
Eponym Question
Q: What eponyms are associated with Bryan-Morrey Type I and Type II fractures? A: Type I = Hahn-Steinthal (large fragment with significant bone), Type II = Kocher-Lorenz (thin osteochondral shell with minimal bone). Memory aid: "H" for Huge fragment (Hahn-Steinthal), "K" for thin Kartilage (Kocher-Lorenz).
Australian Context and Medicolegal Considerations
Australian Practice
- Rare fracture - most surgeons see only a few per year
- Typically managed at tertiary referral centres
- Typically managed via ORIF procedures
- Headless compression screws available in most centres
RACS/AOA Competencies
- Core knowledge topic for orthopaedic exam
- Emphasis on lateral X-ray diagnosis
- Surgical technique principles commonly tested
- Classification and prognosis important
Medicolegal Considerations
Documentation requirements:
- Document that lateral X-ray was reviewed (not just AP)
- Document neurovascular status pre- and post-operatively
- Document PIN function (at risk during lateral approach)
- Consent must include: stiffness (most common), AVN, post-traumatic arthritis, need for further surgery, guarded prognosis for Type IV
Pitfalls to avoid:
- Missing fracture on AP view alone
- Delayed diagnosis leading to worse outcomes
- Inadequate rehabilitation instructions
Informed Consent
Specific risks to discuss for capitellar ORIF:
- Stiffness (20-40%) - most common complication
- Post-traumatic arthritis (15-30%)
- AVN (5-10%)
- Heterotopic ossification (5-15%)
- PIN palsy - transient, usually recovers
- Need for further surgery - arthrolysis, hardware removal
- Guarded prognosis if Type IV - counsel specifically
CAPITELLUM FRACTURES
High-Yield Exam Summary
Key Facts
- •1% of elbow fractures, 6% of distal humerus fractures
- •4:1 female predominance, mean age 45 years
- •FOOSH with extended elbow = coronal shear mechanism
- •30% have concurrent radial head fracture
Imaging
- •LATERAL X-RAY IS KEY - 98% sensitivity
- •Double arc sign = displaced capitellum + trochlear sulcus
- •AP view often NORMAL - don't be fooled
- •CT for surgical planning - assess trochlea, comminution
Bryan-Morrey Classification
- •Type I (Hahn-Steinthal): Large bony fragment - BEST prognosis
- •Type II (Kocher-Lorenz): Thin osteochondral shell
- •Type III: Comminuted - may need excision
- •Type IV: Includes trochlea - WORST prognosis
Surgical Technique
- •Kocher approach (lateral): between anconeus and ECU
- •Headless compression screws (Herbert, Acutrak)
- •ANTERIOR to POSTERIOR direction - preserves blood supply
- •Countersink below cartilage for early ROM
Postoperative
- •Early ROM is CRITICAL - start 48-72 hours
- •Active motion only - avoid forced passive (HO risk)
- •Hinged brace if stability concern
- •Expect 10-20 degree loss of terminal extension
Complications
- •Stiffness: 20-40% (MOST COMMON)
- •Post-traumatic arthritis: 15-30%
- •AVN: 5-10% (fix A-to-P to prevent)
- •HO: 5-15% (prophylax high-risk patients)