FOOSH Mechanism | Lateral X-ray Essential | Headless Screws Anterior-to-Posterior
- 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
- “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 Atlas
98% visible on lateral X-ray, often invisible on AP. Look for 'double arc' sign - two concentric arcs from capitellum and trochlear sulcus.
FOOSH with elbow extended creates coronal shear fracture. Radial head impacts capitellum, shearing it off anteriorly.
Type IV includes trochlea - involves both ulnohumeral and radiocapitellar joints. Highest stiffness rate, worst functional outcomes.
Headless screws anterior to posterior perpendicular to fracture plane. Bury heads flush or below cartilage to allow early ROM.
| 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
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
Hook:SOAP cleans the joint but watch the blood supply - fix from anterior to posterior!
LARCHSurgical Technique Steps
Hook:LARCH trees are lateral like your approach - fix it right and get moving early!
REALAssociated Injuries to Check
Hook:These injuries are REAL common with capitellum fractures - don't miss them!
Overview and Epidemiology
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.
- 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
- FOOSH with elbow extended - most common
- Radial head impacts capitellum creating coronal shear
- Direct blow to lateral elbow
- Associated with elbow dislocations in 20%
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
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).
| 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 |
- 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
- 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
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 |
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
- 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
- Look: Swelling, ecchymosis, deformity (may be subtle)
- Feel: Lateral elbow tenderness, effusion
- Move: Limited flexion/extension, painful crepitus
- Special: Assess stability after any reduction
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).
| 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 |
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.
| Diagnosis | Discriminating features | Key investigation |
|---|---|---|
| Capitellar (coronal shear) fracture | Double arc sign on lateral X-ray; AP often normal; block to flexion | Lateral radiograph then CT for planning |
| Radial head / neck fracture | Tenderness over radial head, painful supination/pronation; coexists in up to 30% | AP, lateral and radiocapitellar (Greenspan) view |
| Lateral condyle fracture (paediatric) | Child, lateral swelling, fat pad sign; involves physis and trochlear groove | Internal oblique radiograph; arthrogram/MRI if cartilaginous |
| Terrible triad / elbow fracture-dislocation | Gross instability, coronoid and radial head fractures with dislocation | Post-reduction CT for coronoid, radial head and capitellum |
| Capitellar osteochondritis dissecans (Panner equivalent) | Adolescent throwing athlete, insidious lateral pain, no acute high-energy mechanism | MRI for subchondral changes and fragment stability |
| Lateral epicondyle avulsion / soft-tissue injury | Non-articular point tenderness, no intra-articular effusion, normal joint line | Radiograph (usually normal); clinical diagnosis |
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.
| 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 |
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.
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
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 |
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.
- 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
- 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
| 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 |
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)
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.
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
| 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 |
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 (Landmark)
- ORIF of 28 capitellar and trochlear fractures (mean age 43 years, mean follow-up 56 months). The classification that bears the authors' name was derived here: types defined by capitellar/trochlear pattern and presence or absence of posterior comminution. More complex fractures (separate fragments, posterior comminution) needed more extensive surgery, had more secondary procedures and poorer outcomes; mean Mayo Elbow Performance Index 91, mean arc 19 to 138 degrees, with two comminuted nonunions converted to total elbow arthroplasty.
Apparent Capitellum Fractures Are Often More Complex (Landmark)
- Retrospective series of 21 articular distal humeral fractures fixed with implants buried beneath the articular surface. Five recurring components were identified, including the lateral trochlear ridge and posterior column - so an apparently isolated capitellar fracture is frequently a more extensive coronal articular injury. All fractures healed; mean ulnohumeral arc 96 degrees; MEPI excellent or good in 16 of 21; ten required a second operation (six for contracture release).
Headless Compression Screw Fixation via Anterolateral Approach
- Prospective series of 16 capitellar fractures fixed with headless double-threaded compression screws through an anterolateral approach. Mean time to union 3.5 months with no malunion or nonunion; mean flexion 132 degrees, mean extensor lag 10 degrees; no osteonecrosis, post-traumatic arthritis or heterotopic ossification; 10 excellent and 6 good results.
Tailoring the Surgical Approach to Fracture Pathoanatomy
- Thirty-three capitellar fractures: Bryan-Morrey I to III approached by extended lateral; Dubberley 2A/3A by anterolateral; Dubberley 2B/3B by posterior transolecranon. All united (two with AVN). Mean flexion/extension arc 133 degrees, mean MEPI 80.9; poor results occurred only in Dubberley 3B fractures.
Surgical Approach and Pooled Complications (Systematic Review)
- Systematic review and meta-analysis of 45 studies (899 patients, mean age 44.9 years). Pooled reoperation rate 13.8%; post-traumatic arthritis 21.2%; heterotopic ossification 12.0%; nerve injury 7.8%; avascular necrosis 7.4%. Complication rate in non-comparative studies was 25.8% after the extended lateral approach versus 16.7% after the anterolateral approach for Dubberley A fractures, though evidence is insufficient to mandate one approach.
Exam Viva Scenarios
Practise clinical reasoning and management decisions out loud
“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?”
“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.”
“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
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.
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.
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.
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.
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).
Guidelines, Registries & Global Practice
Capitellar (coronal shear) fractures are uncommon, so no joint registry tracks them and no single national society publishes a dedicated guideline. Practice is therefore driven by case series, by the two defining classifications (Bryan-Morrey, Dubberley) and by a systematic review of surgical approaches. Care is remarkably consistent worldwide: CT for planning, anatomic ORIF with buried headless compression screws and early motion, with fragment excision or arthroplasty reserved for unreconstructable injuries.
| Parameter | Value | Source |
|---|---|---|
| Mean patient age (pooled, 899 patients) | 44.9 years (95% CI 39.7-50.2) | Fisher 2022 systematic review (PMID 36353417) |
| Dubberley pattern distribution | Type A 38%, Type B 33% | Fisher 2022 (PMID 36353417) |
| Pooled reoperation rate | 13.8% (95% CI 9.6-19.5) | Fisher 2022 (PMID 36353417) |
| Post-traumatic arthritis | 21.2% (95% CI 18.0-24.9) | Fisher 2022 (PMID 36353417) |
| Heterotopic ossification | 12.0% (95% CI 9.2-15.6) | Fisher 2022 (PMID 36353417) |
| Nerve injury / avascular necrosis | 7.8% / 7.4% | Fisher 2022 (PMID 36353417) |
| Body / Source | Position on capitellar fractures | Evidence level |
|---|---|---|
| AO Foundation (AO/OTA 13B3) | Coronal shear = partial articular (B3); anatomic ORIF with headless compression / countersunk screws, early mobilisation | Expert consensus / Level IV-V |
| AAOS / SAE (US) | No dedicated guideline; teaching mirrors series - CT planning, ORIF for displaced fractures, headless screws, early ROM | Level IV |
| BOA / BOAST (UK) | Covered under general open-fracture and intra-articular fracture principles (timely senior review, CT, anatomic reduction); no fracture-specific BOAST | Level IV-V |
| EFORT / European series | Approach tailored to pathoanatomy - lateral for simple, anterolateral for anterior Dubberley A, transolecranon for posterior B | Level IV (Ravishankar PMID 27844160) |
| Systematic review (global) | Anterolateral approach had lower complication rate than extended lateral for Dubberley A; evidence insufficient to mandate either | Level II (Fisher PMID 36353417) |
Unlike arthroplasty topics, capitellar fractures are not captured by joint registries (NJR, AJRR, AOANJRR, SHAR). The evidence base is case series plus one systematic review, which is why the Bryan-Morrey and Dubberley classifications and the Fisher meta-analysis carry disproportionate weight in any viva.
- High-resource settings: routine CT, headless compression screws, fellowship/elbow-unit referral for Dubberley B and Type IV patterns
- Limited-resource settings: conventional AO/buried Kirschner-wire or cannulated-screw fixation where headless implants are unavailable; CT may be limited
- Approach choice (lateral vs anterolateral vs transolecranon) varies by surgeon and fracture pattern, not by country
- Diagnosis on the lateral radiograph (double arc sign); AP often normal
- Bryan-Morrey and Dubberley classifications and what each grade changes
- Anatomic ORIF with anterior-to-posterior headless screws
- Early active motion to prevent stiffness; guarded prognosis for Type IV / Dubberley B
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 / anterolateral 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
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
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)