High Yield Overview

CORONOID FRACTURES - ANTERIOR BUTTRESS OF ELBOW

O'Driscoll Classification | Elbow Stability Keystone | Terrible Triad Component

2-15%Of elbow fractures

75%+With elbow dislocation

50%Threshold for instability

AnteriorButtress function

O'DRISCOLL CLASSIFICATION

Type I (Tip)

PatternTip fracture (less than 2mm)

TreatmentUsually stable, treat associated injuries

Type II (Anteromedial)

PatternAnteromedial facet (Subtype 1-3)

TreatmentFix if unstable - buttress plate/screws

Type III (Basal)

PatternBasal (over 50% height)

TreatmentAlways unstable - fix with plate

Critical Must-Knows

Coronoid is the anterior buttress - prevents posterior subluxation
Over 50% height = unstable - requires operative fixation
Terrible triad component - dislocation + radial head + coronoid
Anteromedial facet fractures are often varus-posteromedial pattern
Never ignore - instability leads to poor outcomes

Examiner's Pearls

"
Anteromedial facet fractures have different mechanism - varus stress, not dislocation
"
Coronoid tip fractures in terrible triad may need fixation despite small size
"
Basal fractures always unstable - include brachialis insertion
"
Sublime tubercle involvement means MCL attachment disrupted

AP and lateral radiographs showing terrible triad of the elbow — Terrible triad of the elbow. (a) AP radiograph with arrows indicating the coronoid fracture fragment (white arrow) and comminuted radial head fracture (black arrows). (b) Lateral radiograph demonstrating posterior dislocation with the coronoid fragment (white arrow) and radial head fragments (black arrow) visible posteriorly. This injury pattern requires systematic surgical addressing of all three components.Credit: Mathew PK et al., J Am Acad Orthop Surg 2009 (PMC4511680) - CC-BY 4.0

Clinical Imaging

Imaging Gallery

Comparison of X-ray and CT for coronoid fracture assessment — Comparison of plain radiograph and CT for coronoid fracture assessment. (a) Lateral X-ray with arrow indicating the coronoid fracture - note how subtle the finding can be on plain films. (b) Sagittal CT reconstruction clearly delineates the coronoid fracture fragment (arrow). CT is essential for accurate classification and surgical planning of coronoid fractures, as it reveals fracture morphology, fragment size, and involvement of the anteromedial facet that may not be apparent on radiographs.Credit: Open Access - CC BY 4.0

Coronoid fracture surgical treatment sequence — Surgical management of coronoid fracture with buttress plate fixation. (A-B) Preoperative AP and lateral radiographs showing the injury. (C) 3D CT reconstruction delineating the fracture pattern for surgical planning. (D) Intraoperative lateral fluoroscopy. (E-F) Postoperative AP and lateral radiographs demonstrating anatomic reduction with buttress plate fixation of the coronoid. Plate fixation provides stable buttress support for anteromedial facet and larger coronoid fractures.Credit: Open Access - CC BY 4.0

Critical Coronoid Fracture Exam Points

Anterior Buttress

Coronoid is the anterior buttress of the elbow. It resists posterior displacement of the ulna. Loss of over 50% height = elbow instability. Must reconstruct for stability.

Pattern Recognition

Tip fractures (Type I) often with posterolateral dislocation. Anteromedial facet (Type II) with varus-posteromedial instability. Basal (Type III) always unstable.

Associated Injuries

75%+ occur with elbow dislocation. Part of terrible triad (with radial head fracture, LCL). May have isolated anteromedial pattern with MCL injury.

Fixation Priority

Fix coronoid to restore stability. Options include suture lasso, screw fixation, or plate buttress. Approach depends on pattern - lateral vs medial.

Quick Decision Guide

O'Driscoll Type	Key Finding	Treatment
Type I (Tip) - Stable	Elbow stable after reduction	Treat associated injuries, no coronoid fixation
Type I (Tip) - Unstable	Part of terrible triad, persistent instability	Consider suture lasso fixation
Type II (Anteromedial) - Small	Subtype 1, less than 50% of facet	May be stable - assess carefully
Type II (Anteromedial) - Large	Subtype 2-3, medial instability	Buttress plate via medial approach
Type III (Basal) - Any	Always unstable, over 50% height	Plate fixation mandatory
Sublime Tubercle	MCL attachment involved	Fix fragment = fixes MCL insertion

Key Mnemonics for Exam Recall

Mnemonic

O'DRISCOLL - Classification Framework

One (Type I)

Tip fractures - small, anterior capsule attachment

Duo (Type II)

Anteromedial facet - varus-posteromedial pattern

Radial head often associated

Type I often with terrible triad

Instability if over 50%

Basal fractures always unstable

Sublime tubercle (Type II)

Subtype 1 - MCL attachment involved

Complete basal (Type III)

More than 50% height, brachialis attached

Operative for instability

Fix if unstable pattern present

Lateral or medial approach

Depends on fracture pattern

LCL always ruptured if dislocated

Address in terrible triad

Memory Hook:O'Driscoll described it - Types go from tip to base with increasing instability

Mnemonic

BUTTRESS - Coronoid Function

Blocks posterior translation

Primary anterior buttress

Ulnohumeral stability

Critical for elbow congruency

Terrible triad component

Part of the instability pattern

Tip vs anteromedial vs basal

Pattern determines treatment

Reconstruction essential

For over 50% involvement

Evaluate MCL

Sublime tubercle = MCL insertion

Stability assessment critical

Intraoperative testing essential

Surgical approach varies

Lateral or medial depending on pattern

Memory Hook:The coronoid BUTTRESS prevents posterior subluxation

Mnemonic

SUBLIME - Tubercle Anatomy

Stabilizer

MCL attachment site

Ulnar side of coronoid

Medial/anteromedial location

Bundle (anterior) of MCL

Most important MCL component

Ligament anchor point

Critical for valgus stability

If fractured = MCL disrupted

Bony avulsion of MCL

Medial approach for fixation

FCU splitting or over-the-top

Essential to fix

Restores MCL function

Memory Hook:SUBLIME tubercle = MCL insertion - fixing it = fixing the MCL

Mnemonic

TRIAD - Terrible Triad Management

Three components

Dislocation, radial head, coronoid

Radial head - fix or replace

Over 4 fragments = replace

Instability must be addressed

Test under fluoroscopy

Approach - lateral (Kocher)

Access to all three components

Don't forget coronoid

Even small tips may need fixation

Memory Hook:The TERRIBLE TRIAD requires addressing all three components systematically

Overview and Epidemiology

Coronoid fractures are typically associated with elbow instability. Isolated coronoid fractures are rare; most occur with elbow dislocation or other fracture patterns. The coronoid is a critical structure for elbow stability.

Mechanism of injury:

Posterolateral dislocation - most common (Type I tip fractures)
- Elbow dislocates, shearing off the coronoid tip
- Part of terrible triad pattern
Varus-posteromedial rotational instability (Type II anteromedial)
- Axial load with varus stress
- Different mechanism from posterolateral dislocation
High-energy direct trauma (Type III basal)
- Significant force through ulnohumeral joint

Two Different Mechanisms

Tip fractures occur with posterolateral dislocation - the coronoid is sheared off as the elbow dislocates. Anteromedial facet fractures occur with varus stress without dislocation - a distinct mechanism and injury pattern requiring different treatment approach.

Associated injuries:

Elbow dislocation (75%+)
Radial head fracture (terrible triad)
LCL complex rupture (always with dislocation)
MCL rupture (with anteromedial facet fractures)
Olecranon fracture (transolecranon pattern)

Mechanism diagram showing coronoid fracture pathophysiology — Coronoid fracture mechanism. Top: Stable elbow. The same varus + external rotation force can result in either simple dislocation (left pathway - pure ligamentous injury) or coronoid fracture (right pathway - bony failure at the anteromedial facet). Understanding this mechanism explains why anteromedial facet fractures occur without frank dislocation and require a different treatment approach than tip fractures from posterolateral dislocation.Credit: O'Driscoll SW et al., J Shoulder Elbow Surg (PMC7455792) - CC-BY 4.0

Anatomy and Biomechanics

Coronoid anatomy:

Anterior projection of the proximal ulna
Forms anterior buttress of the greater sigmoid notch
Tip is attachment of anterior capsule
Sublime tubercle - medial aspect, MCL (anterior bundle) attachment
Brachialis insertion - on anterior surface of coronoid base

Key anatomical relationships:

Anterior capsule attaches to tip
MCL anterior bundle attaches to sublime tubercle
Brachialis attaches across base
Lateral facet articulates with radial head via radioulnar joint

Biomechanical function:

Anterior Buttress Function

The coronoid provides the primary anterior buttress against posterior subluxation. Loss of more than 50% of coronoid height results in significant elbow instability. Even smaller fractures can contribute to instability in the presence of ligamentous injury.

Stability contribution:

Primary constraint to posterior translation (with olecranon)
Secondary valgus stabilizer (with MCL and radial head)
Works with radial head to resist axial loading

50% Rule:

Loss of over 50% of coronoid height = unstable elbow
Applies to sagittal plane (anterior-posterior height)
Even smaller fractures may be unstable with ligament injuries

Classification Systems

O'Driscoll Classification (most commonly used)

Type	Subtype	Description	Mechanism
I	Tip	Tip fracture (less than 2mm)	Posterolateral dislocation
II	1	Sublime tubercle (medial)	Varus-posteromedial
II	2	Anteromedial rim	Varus-posteromedial
II	3	Anteromedial rim + tip	Varus-posteromedial
III	1	Basal - less than 50%	High energy
III	2	Basal - more than 50%	High energy

Key O'Driscoll Concept

Type II anteromedial facet fractures have a different mechanism than Type I tip fractures. They result from varus-posteromedial rotational instability, not posterolateral dislocation. This affects both approach and treatment strategy.

Clinical Assessment

History:

Mechanism (fall, direction of force)
Any sense of instability or dislocation
Whether elbow was relocated (self-reduced or reduced)
Previous elbow problems
Hand dominance, occupation

Physical examination:

Physical Examination Findings

Finding	Significance	Action
Elbow effusion	Intra-articular injury	X-ray, CT if fracture suspected
Anteromedial tenderness	Coronoid/anteromedial facet	CT for classification
Valgus instability	MCL injury	Consider sublime tubercle involvement
Varus instability	LCL injury	May have anteromedial facet pattern
Posterolateral apprehension	PLRI pattern	Likely had posterolateral dislocation
Gross instability	Multiple structure involvement	Urgent surgical planning

Stability testing:

Instability Patterns

Posterolateral rotational instability (PLRI): Elbow subluxes posterolaterally - associated with tip fractures. Varus-posteromedial instability: Ulna rotates posteromedially - associated with anteromedial facet fractures. Different patterns require different approaches.

Key examination points:

Range of motion - assess for mechanical block
Valgus stress test - MCL integrity
Varus stress test - LCL integrity
Posterolateral rotatory instability test - pivot shift
Neurovascular status - especially ulnar nerve

Investigations

Radiographic assessment:

Lateral X-ray and sagittal CT comparison of coronoid fracture — Imaging comparison for coronoid fracture assessment. (a) Lateral elbow radiograph with arrow indicating coronoid fracture fragment - may be subtle on plain films. (b) Sagittal CT reconstruction clearly demonstrating the coronoid fracture fragment and its relationship to the joint. CT is essential for accurate classification (O'Driscoll typing) and surgical planning as it reveals fragment size, displacement, and associated injuries not visible on plain radiographs.Credit: Regan W et al., Clin Sports Med (PMC7455792) - CC-BY 4.0

Standard views:

AP elbow - may see coronoid fracture
Lateral elbow - best view for coronoid height
Oblique views - anteromedial facet visualization

Lateral X-ray Assessment

On the lateral X-ray, assess coronoid height - the anterior projection of the ulna. Compare to the opposite side if needed. Loss of the normal triangular projection suggests coronoid fracture.

CT imaging:

Indications (essential for coronoid fractures):

All suspected coronoid fractures
Classification (O'Driscoll typing)
Fragment size and displacement assessment
Surgical planning
Associated injuries (radial head, olecranon)

CT assessment checklist:

Fragment size (% of coronoid height)
Fragment location (tip vs anteromedial vs basal)
Sublime tubercle involvement
Associated radial head fracture
Articular step-off

3D CT reconstruction:

Helpful for complex patterns
Surgical planning
Understanding fragment geometry

MRI:

Rarely indicated acutely
May assess ligamentous structures
Consider for chronic instability evaluation

Management Algorithm

Conservative management:

Indications

Type I tip fracture with stable elbow
Concentric reduction maintained
No mechanical block
No associated operative injuries

Protocol

Posterior splint at 90 degrees initially
Begin motion at 1-2 weeks if stable
Active ROM in flexion-extension arc
Avoid terminal extension initially
Progressive motion over 6 weeks

Follow-up

Weekly X-rays initially
Assess for subluxation
Progress motion if maintaining reduction

Conservative Criteria

Conservative management only appropriate for Type I tip fractures with a stable, concentrically reduced elbow. Any instability, incongruency, or associated injuries requiring surgery = fix the coronoid.

Surgical Technique

Lateral Approach (for terrible triad):

Kocher or lateral column approach
Addresses radial head and LCL
Can reach coronoid from lateral (over-the-top)
Suture lasso technique for tip fractures

Medial Approach (for anteromedial facet):

FCU splitting or over-the-top of flexor mass
Identify and protect ulnar nerve
Direct access to anteromedial facet
Can also assess/repair MCL

Posterior Approach:

For transolecranon fracture-dislocations
Direct visualization through olecranon fracture
Fix coronoid from posterior

Approach selection depends on fracture pattern and associated injuries.

Complications

Complications of Coronoid Fracture Treatment

Complication	Incidence	Management
Recurrent instability	5-15%	Revision fixation, ligament repair, hinged fixator
Stiffness	20-30%	Early motion, physio, capsular release if severe
Post-traumatic arthritis	15-25%	Activity modification, eventual arthroplasty
Heterotopic ossification	5-15%	Prophylaxis, excision if limiting
Ulnar neuropathy	5-10%	Often transient, protect during medial approach
Hardware prominence	Variable	Hardware removal if symptomatic
Nonunion	Rare	Revision fixation, bone graft

Recurrent instability:

Most significant complication
Usually due to inadequate coronoid reconstruction
Or missed associated injuries
May require revision surgery, hinged external fixator

Stiffness:

Common with complex elbow trauma
Prevention: stable fixation, early motion
Treatment: physiotherapy, dynamic splinting, capsular release

AP elbow radiograph showing heterotopic ossification at 7 months post-operative — Heterotopic ossification (HO) complication. AP elbow radiograph at 7 months post-operative showing mature heterotopic bone formation both medially and laterally (white arrows). HO occurs in 5-15% of complex elbow trauma and can significantly limit motion. Prevention strategies include indomethacin prophylaxis or single-dose radiation. Established HO may require surgical excision once mature (12+ months) if functionally limiting.Credit: Mathew PK et al., J Am Acad Orthop Surg 2009 (PMC4511680) - CC-BY 4.0

Ulnar Nerve Protection

The ulnar nerve is at risk during the medial approach. Options include in-situ protection (preferred for brief procedures) or anterior transposition (for prolonged retraction or if nerve subluxing). Always identify and protect before deep dissection.

Postoperative Care and Rehabilitation

Postoperative protocol:

Day 0-7

Posterior splint at 90 degrees
Elevation, ice
Finger motion
Wound check at 5-7 days

Week 1-2

Begin active ROM if stable fixation
May use hinged brace if borderline stable
Focus on flexion-extension
Avoid varus/valgus stress

Week 2-6

Progressive active ROM
Target functional ROM by 6 weeks
No resistance until 6 weeks
Dynamic splinting if stiff

Week 6-12

Begin gentle strengthening
Progressive loading
Return to light activities

3-6 months

Full strengthening
Return to sport/work
Final outcome assessment

Key rehabilitation principles:

Early motion critical to prevent stiffness
Stable fixation allows early motion
If stability borderline - hinged external fixator
Avoid varus/valgus stress early
May need extension block initially

Hinged External Fixator

If the elbow remains borderline unstable after addressing all injured structures, a hinged external fixator allows early motion while protecting the repair. It centers rotation at the elbow axis and prevents subluxation during rehabilitation.

Outcomes and Prognosis

Outcomes by pattern:

Pattern	Good/Excellent	Key Factors
Type I tip (isolated)	80-90%	Stable reduction critical
Type I in terrible triad	70-80%	Address all components
Type II anteromedial	70-80%	Adequate buttress fixation
Type III basal	60-75%	High energy, complex

Prognostic factors:

Associated injuries (worse with complex patterns)
Quality of reconstruction
Time to surgery
Patient compliance
Pre-existing elbow conditions

Terrible Triad Outcomes

Terrible triad injuries have worse outcomes than isolated coronoid fractures. Despite addressing all three components (radial head, coronoid, LCL), expect higher rates of stiffness and residual instability. Counsel patients about guarded prognosis.

Evidence Base

Level IV

📚 O'Driscoll et al. Classification

Key Findings:

Proposed classification based on location and mechanism. Identified anteromedial facet fractures as distinct pattern with varus-posteromedial instability mechanism.

Clinical Implication: Treatment approach depends on fracture pattern - tip fractures (posterolateral mechanism) vs anteromedial facet (varus mechanism) require different approaches.

Source: J Bone Joint Surg Am 2003

Level IV

📚 Ring et al. Coronoid Fractures

Key Findings:

In terrible triad, even small coronoid fractures may contribute to instability. Addressing coronoid improves stability after radial head and LCL treatment.

Clinical Implication: Don't ignore small coronoid fractures in unstable patterns. Fix if elbow remains unstable after other structures addressed.

Source: J Bone Joint Surg Am 2006

Level IV

📚 Doornberg et al. Anteromedial Facet

Key Findings:

Anteromedial facet fractures create varus-posteromedial instability. Often associated with LCL injury despite being a 'medial' fracture. Buttress plating via medial approach effective.

Clinical Implication: Anteromedial facet fractures require medial approach for fixation. Check LCL even though fracture is medial.

Source: J Bone Joint Surg Am 2006

Level IV

📚 Pugh et al. Terrible Triad

Key Findings:

Standard approach to terrible triad: fix/replace radial head, repair LCL, fix coronoid if large or unstable. Protocol resulted in 72% good/excellent results.

Clinical Implication: Systematic approach to all three components of terrible triad improves outcomes. Coronoid fixation is part of the protocol.

Source: J Bone Joint Surg Am 2004

Level IV

📚 Sanchez-Sotelo et al. Elbow Instability

Key Findings:

Complex elbow instability outcomes are worse than simple dislocations. Stiffness is common. Early stable fixation allowing motion is critical.

Clinical Implication: Set appropriate patient expectations. Prioritize stable fixation to allow early motion and prevent stiffness.

Source: Clin Orthop 2014

Viva Scenarios

Practice these scenarios to excel in your viva examination

VIVA SCENARIOStandard

Scenario 1: Terrible Triad with Coronoid Fracture

EXAMINER

"A 45-year-old woman falls from a ladder. Her elbow was dislocated and has been reduced. CT shows a comminuted radial head fracture with more than 4 fragments and a small coronoid tip fracture. How do you approach this injury?"

EXCEPTIONAL ANSWER

Thank you. This patient has the **terrible triad of the elbow** - posterior elbow dislocation with radial head fracture and coronoid fracture. This is a significant injury pattern requiring a systematic approach. **Initial Assessment:** - Confirm neurovascular status post-reduction - Assess reduction quality on fluoroscopy - Splint in 90 degrees of flexion for stability **CT Assessment:** The CT shows: - Comminuted radial head (greater than 4 fragments) - unreconstructable - Small coronoid tip fracture (O'Driscoll Type I) - I would also assess for any other injuries **Surgical Plan - Address All Three Components:** **1. Radial Head:** With more than 4 fragments, this is unreconstructable. I would perform **radial head arthroplasty** using a metallic modular prosthesis. **2. LCL Complex:** By definition, the LCL is ruptured as the elbow dislocated posterolaterally. I would **repair the LCL** using suture anchors to the lateral epicondyle. **3. Coronoid:** After radial head replacement and LCL repair, I would **assess stability under fluoroscopy**. If the elbow remains unstable, I would address the coronoid with a **suture lasso technique** - capturing the tip fragment and anterior capsule. **Approach:** Single **lateral approach** (Kocher) provides access to: - Radial head for replacement - LCL for repair - Coronoid (over-the-top approach for suture lasso) **Intraoperative Stability Assessment:** After addressing all structures, test stability through full ROM under fluoroscopy. If still unstable, consider hinged external fixator. **Rehabilitation:** Early motion is critical - begin active ROM within 1-2 weeks. The goal is stable fixation allowing early motion to prevent stiffness.

KEY POINTS TO SCORE

This is the terrible triad - dislocation, radial head, coronoid

LCL is ruptured by definition with posterolateral dislocation

Address all three components systematically

Radial head with more than 4 fragments = arthroplasty not ORIF

Lateral approach provides access to all structures

Coronoid tip - may need fixation if unstable after other structures addressed

Suture lasso technique for tip fractures

Assess stability under fluoroscopy after each step

May need hinged external fixator if borderline stable

Early motion critical to prevent stiffness

COMMON TRAPS

✗Treating as simple radial head fracture

✗Not addressing the LCL

✗Ignoring the coronoid tip fracture

✗Attempting ORIF of unreconstructable radial head

✗Not assessing stability after fixation

LIKELY FOLLOW-UPS

"What if the elbow remained unstable after all three components addressed?"

"Would you manage differently if the coronoid was basal rather than tip?"

VIVA SCENARIOChallenging

Scenario 2: Anteromedial Facet Fracture

EXAMINER

"A 38-year-old man presents after a fall onto his arm. He has no history of dislocation. CT shows an anteromedial facet fracture involving approximately 40% of the coronoid with the sublime tubercle involved. What is your diagnosis and management approach?"

EXCEPTIONAL ANSWER

Thank you. This is an **O'Driscoll Type II anteromedial facet fracture** with sublime tubercle involvement - specifically a **Type II Subtype 1**. This is an important pattern to recognize as it has a different mechanism from the typical terrible triad coronoid fracture. **Understanding the Injury:** This pattern results from **varus-posteromedial rotational instability** rather than posterolateral dislocation. The mechanism is: - Axial load with varus stress - The anteromedial facet fails as a buttress - Creates posteromedial rotational instability **Sublime Tubercle Significance:** The sublime tubercle is the **insertion of the MCL (anterior bundle)**. When fractured, the MCL is effectively avulsed from its ulnar insertion. Fixing this fragment restores MCL function. **Associated Injuries:** Paradoxically, anteromedial facet fractures are often associated with **LCL injury** despite being a "medial" fracture. I would assess: - LCL integrity (may be disrupted) - Radial head (may have associated fracture) **Surgical Management:** **Approach:** **Medial approach** - either FCU splitting or over-the-top of flexor mass: - Identify and protect the ulnar nerve - Expose the anteromedial coronoid - Visualize the fragment and sublime tubercle **Fixation:** - **Buttress plate** on the anteromedial facet using a small locking plate - This captures the fragment and sublime tubercle - Restores the anterior buttress and MCL insertion **LCL Assessment:** After medial fixation, assess LCL through a lateral incision. If disrupted (common), repair with suture anchors. **Key Technical Points:** - Protect ulnar nerve throughout - Ensure adequate buttress of anteromedial facet - Plate must capture sublime tubercle to restore MCL - Check lateral side for LCL injury **Rehabilitation:** - Early ROM in hinged brace if stable - Avoid varus stress - Progress motion over 6 weeks

KEY POINTS TO SCORE

This is O'Driscoll Type II (anteromedial facet) with sublime tubercle involvement

Different mechanism from terrible triad - varus-posteromedial rotational instability

Sublime tubercle = MCL (anterior bundle) insertion

Fixing the fragment restores MCL function

Requires medial approach - cannot fix adequately from lateral

FCU splitting or over-the-top of flexor mass approach

Protect ulnar nerve throughout

Buttress plate fixation on anteromedial facet

Paradoxically often associated with LCL injury

Check and repair LCL through separate lateral incision

COMMON TRAPS

✗Treating as simple coronoid fracture via lateral approach

✗Not recognizing sublime tubercle involvement as MCL injury

✗Missing associated LCL injury

✗Inadequate fixation that doesn't buttress the facet

✗Not protecting the ulnar nerve

LIKELY FOLLOW-UPS

"How would you manage the ulnar nerve?"

"What if there was no LCL injury?"

VIVA SCENARIOCritical

Scenario 3: Basal Coronoid Fracture

EXAMINER

"A 52-year-old man involved in a motorcycle accident has a complex elbow injury. CT shows a basal coronoid fracture involving approximately 60% of the coronoid height. The elbow is grossly unstable. What are your key considerations?"

EXCEPTIONAL ANSWER

Thank you. This is an **O'Driscoll Type III basal coronoid fracture** - involving more than 50% of the coronoid height. By definition, this is an **unstable injury** requiring operative fixation. The high-energy mechanism in a motorcycle accident is consistent with this pattern. **Why Basal Fractures Are Always Unstable:** - Involve more than 50% of coronoid height - Loss of the primary anterior buttress function - Often include the **brachialis insertion** on the fragment - Inability to maintain concentric reduction **Associated Injuries - High Energy Pattern:** With this mechanism, I would carefully assess for: - Radial head fracture - Olecranon fracture (transolecranon pattern) - LCL and MCL injuries - Neurovascular injuries (high energy) - Other extremity injuries **Surgical Planning:** **Approach Options:** - **Medial approach** - best direct visualization of coronoid base - **Posterior approach** - if transolecranon component present - May need combined approaches for complex patterns **Fixation:** - **Plate fixation is mandatory** for basal fractures - Buttress plate on the anteromedial surface - Must capture the fragment adequately - May need multiple plates for comminuted patterns **Technical Considerations:** - Protect ulnar nerve (may need transposition) - Reduce and provisionally fix coronoid first - Then address other injuries - May need to reconstruct brachialis attachment **Stability Assessment:** Even after coronoid fixation, assess: - Elbow stability through ROM - Ligamentous stability (varus/valgus) - May need ligament repair in addition **Hinged External Fixator:** With a grossly unstable elbow and high-energy basal fracture, I would have a **low threshold for hinged external fixator** even after adequate fixation. This protects the repair while allowing early motion. **Rehabilitation:** - Early motion essential to prevent stiffness - Hinged fixator if stability borderline - Long rehabilitation expected - Counsel about guarded prognosis with high-energy injuries

KEY POINTS TO SCORE

Type III basal fracture - always unstable by definition

Involves over 50% of coronoid height

May include brachialis insertion on fragment

High-energy mechanism - assess for associated injuries

Plate fixation is mandatory - not screws alone

Medial approach for direct visualization

May need combined approaches

Protect ulnar nerve - may need transposition

Low threshold for hinged external fixator

Guarded prognosis with high-energy injuries

COMMON TRAPS

✗Underestimating the instability

✗Attempting conservative management

✗Using only screw fixation (inadequate for basal fractures)

✗Not having external fixator available

✗Missing associated injuries in high-energy trauma

LIKELY FOLLOW-UPS

"What would you do if you couldn't achieve stable fixation?"

"How would you counsel this patient about expected outcomes?"

MCQ Practice Points

Classification Question

Q: What defines an O'Driscoll Type II coronoid fracture? A: Anteromedial facet fracture - includes subtypes involving the sublime tubercle (MCL insertion), anteromedial rim, or combination. This pattern results from varus-posteromedial rotational instability, not posterolateral dislocation.

Stability Question

Q: What percentage of coronoid height loss results in elbow instability? A: Greater than 50%. Basal fractures (O'Driscoll Type III) involving more than 50% of coronoid height are always unstable and require operative fixation.

Anatomy Question

Q: What structure attaches to the sublime tubercle? A: The MCL (specifically the anterior bundle). The sublime tubercle is the ulnar insertion of the most important stabilizing bundle of the MCL. Fractures involving this area are essentially bony MCL avulsions.

Mechanism Question

Q: What is the mechanism of anteromedial facet fractures? A: Varus-posteromedial rotational instability - an axial load with varus stress, NOT posterolateral dislocation. This is distinct from tip fractures which occur with posterolateral dislocation.

Treatment Question

Q: What approach is required for anteromedial facet fracture fixation? A: Medial approach (FCU splitting or over-the-top). These fractures cannot be adequately visualized or fixed from a lateral approach. Must protect the ulnar nerve.

Australian Context

Epidemiology:

Common in sports injuries and falls
Motorcycle accidents significant contributor
Occupational falls (construction, agriculture)

Management considerations:

Subspecialty referral for complex patterns
Access to hinged external fixators varies by centre

Transfer considerations:

Complex patterns should be managed at trauma centres
Hinged external fixator capability required
Elbow subspecialty expertise beneficial

Exam Context

Be prepared to discuss coronoid classification, recognize the difference between tip and anteromedial facet patterns, understand the sublime tubercle anatomy, and know when plate fixation vs suture lasso is appropriate. These are common viva topics.

CORONOID FRACTURES

High-Yield Exam Summary

O'DRISCOLL CLASSIFICATION

•Type I: Tip fracture - posterolateral dislocation mechanism
•Type II: Anteromedial facet - varus-posteromedial mechanism
•Type III: Basal - over 50% height, always unstable
•Subtypes: I.1/I.2, II.1/II.2/II.3, III.1/III.2 by fragment size

KEY ANATOMY

•Coronoid = anterior buttress of elbow
•Sublime tubercle = MCL (anterior bundle) insertion
•Brachialis inserts on coronoid base
•Over 50% height loss = unstable

PATTERN RECOGNITION

•Type I tip - part of terrible triad (posterolateral dislocation)
•Type II anteromedial - varus stress mechanism, different approach needed
•Type III basal - always operative, plate fixation
•Isolated Type I can be treated conservatively if elbow stable

SURGICAL APPROACHES

•Tip fractures - lateral approach, suture lasso
•Anteromedial facet - MEDIAL approach, buttress plate
•Basal - medial or posterior, plate fixation
•Protect ulnar nerve on medial approach

FIXATION TECHNIQUES

•Suture lasso - for tip fractures (Type I)
•Screws - for larger single fragments
•Buttress plate - for anteromedial facet (Type II)
•Plate - mandatory for basal (Type III)

TERRIBLE TRIAD PROTOCOL

•1. Fix/replace radial head
•2. Repair LCL
•3. Assess stability - fix coronoid if unstable
•4. Consider hinged fixator if still borderline

O'Driscoll Type

Key Finding

Treatment

Type I (Tip) - Stable

Elbow stable after reduction

Treat associated injuries, no coronoid fixation

Type I (Tip) - Unstable

Part of terrible triad, persistent instability

Consider suture lasso fixation

Type II (Anteromedial) - Small

Subtype 1, less than 50% of facet

May be stable - assess carefully

Type II (Anteromedial) - Large

Subtype 2-3, medial instability

Buttress plate via medial approach

Type III (Basal) - Any

Always unstable, over 50% height

Plate fixation mandatory

Sublime Tubercle

MCL attachment involved

Fix fragment = fixes MCL insertion

Type

Subtype

Description

Mechanism

Tip

Tip fracture (less than 2mm)

Posterolateral dislocation

Sublime tubercle (medial)

Varus-posteromedial

Anteromedial rim

Varus-posteromedial

Anteromedial rim + tip

Varus-posteromedial

III

Basal - less than 50%

High energy

III

Basal - more than 50%

High energy

Finding

Significance

Action

Elbow effusion

Intra-articular injury

X-ray, CT if fracture suspected

Anteromedial tenderness

Coronoid/anteromedial facet

CT for classification

Valgus instability

MCL injury

Consider sublime tubercle involvement

Varus instability

LCL injury

May have anteromedial facet pattern

Posterolateral apprehension

PLRI pattern

Likely had posterolateral dislocation

Gross instability

Multiple structure involvement

Urgent surgical planning

Lateral Approach (for terrible triad):

Kocher or lateral column approach
Addresses radial head and LCL
Can reach coronoid from lateral (over-the-top)
Suture lasso technique for tip fractures

Medial Approach (for anteromedial facet):

FCU splitting or over-the-top of flexor mass
Identify and protect ulnar nerve
Direct access to anteromedial facet
Can also assess/repair MCL

Posterior Approach:

For transolecranon fracture-dislocations
Direct visualization through olecranon fracture
Fix coronoid from posterior

Approach selection depends on fracture pattern and associated injuries.

Complication

Incidence

Management

Recurrent instability

5-15%

Revision fixation, ligament repair, hinged fixator

Stiffness

20-30%

Early motion, physio, capsular release if severe

Post-traumatic arthritis

15-25%

Activity modification, eventual arthroplasty

Heterotopic ossification

5-15%

Prophylaxis, excision if limiting

Ulnar neuropathy

5-10%

Often transient, protect during medial approach

Hardware prominence

Variable

Hardware removal if symptomatic

Nonunion

Rare

Revision fixation, bone graft

Pattern

Good/Excellent

Key Factors

Type I tip (isolated)

80-90%

Stable reduction critical

Type I in terrible triad

70-80%

Address all components

Type II anteromedial

70-80%

Adequate buttress fixation

Type III basal

60-75%

High energy, complex

Type	Description	Treatment
I	Tip avulsion (less than 10% height)	Usually conservative
II	Less than 50% coronoid height	Fix if unstable
III	Over 50% coronoid height	Always operative