OLECRANON FRACTURES - TRICEPS AVULSION INJURY
Extensor Mechanism Disruption | Tension Band Principle | Articular Involvement
MAYO CLASSIFICATION
Critical Must-Knows
- Triceps insertion - olecranon fractures disrupt the extensor mechanism
- Articular fracture - olecranon forms proximal ulnohumeral articulation
- Tension band principle - converts tensile forces to compressive forces at articular surface
- Plate fixation preferred for comminuted and unstable patterns
- Symptomatic hardware is common - discuss removal with patients
Examiner's Pearls
- "Tension band only works for simple transverse or oblique fractures
- "Comminution or oblique patterns require plate fixation
- "Mayo Type III indicates elbow instability - more complex treatment
- "Check for associated coronoid and radial head fractures (terrible triad)
Clinical Imaging
Imaging Gallery
Critical Olecranon Fracture Exam Points
Extensor Mechanism
The olecranon is the triceps insertion. Fractures disrupt active elbow extension. Patient cannot extend against gravity = functional test for complete disruption.
Tension Band Principle
Figure-of-8 wire converts tensile forces to compression at the articular surface. Only works for simple transverse/short oblique fractures. Comminution requires plate.
Plate Indications
Plate fixation preferred for: oblique fracture (greater than 30 degrees), comminuted, Monteggia variant, Mayo Type III, osteoporotic bone, trans-olecranon fracture-dislocations.
Hardware Issues
80% hardware removal with tension band wiring due to prominence. Pre-operative counseling essential. Plate fixation has lower but still significant removal rates (20-30%).
Quick Decision Guide
| Fracture Pattern | Mayo Type | Treatment |
|---|---|---|
| Undisplaced (less than 2mm) | Type I | Conservative - cast/splint, early motion |
| Simple transverse, stable elbow | Type IIA | Tension band wiring (TBW) |
| Comminuted, stable elbow | Type IIB | Plate fixation |
| Displaced with elbow instability | Type III | Plate fixation + address instability |
| Trans-olecranon fracture-dislocation | Complex | Plate fixation + restore ulnohumeral joint |
| Osteoporotic/elderly with comminution | Variable | Consider plate or fragment excision + triceps repair |
MAYO - Classification Framework
Memory Hook:MAYO classification: displacement + stability + comminution guide treatment
TBW - Tension Band Wiring Technique
Memory Hook:TBW: Two wires Behind the cortex, Wire in figure-8
PLATE - When to Use Plate Fixation
Memory Hook:PLATE fixation for these specific indications
2-30-80 Rule
Memory Hook:2mm triggers surgery, 30 degrees triggers plate, 80% need hardware out
Overview and Epidemiology
Olecranon fractures are common elbow injuries that disrupt the extensor mechanism and the ulnohumeral articulation. Understanding the biomechanics is essential for appropriate management.
Bimodal distribution:
- Young adults (20-40): High-energy trauma (MVA, sports, falls from height)
- Elderly (60+): Low-energy falls, osteoporotic bone
Mechanism of injury:
- Direct blow - fall onto point of elbow (most common)
- Indirect - fall on outstretched hand with triceps contraction (avulsion)
- Combined - direct blow + muscle contraction
Functional Significance
The olecranon is the insertion of the triceps and forms the proximal ulnohumeral articulation. Fractures cause loss of active extension (extensor mechanism disruption) and articular incongruity (affecting elbow function).
Anatomy and Biomechanics
Bony anatomy:
- Olecranon process - proximal ulna, forms posterior elbow prominence
- Greater sigmoid notch (trochlear notch) - articular surface for trochlea
- Coronoid process - anterior buttress, critical for stability
- Subcutaneous position - minimal soft tissue coverage
Muscular attachments:
- Triceps brachii - inserts on posterior olecranon tip
- Anconeus - lateral to olecranon, dynamic stabilizer
Biomechanics:
Tension Band Principle
The triceps generates tensile forces on the posterior olecranon. The tension band (figure-of-8 wire) converts these to compressive forces at the articular surface. This requires intact anterior cortex to work as a compression hinge.
Key biomechanical concepts:
- Triceps force: up to 3x body weight
- Posterior tension, anterior compression during flexion
- Tension band only works with intact anterior cortex
- Comminution disrupts the hinge - plate fixation required
Neurovascular considerations:
- Ulnar nerve - posterior to medial epicondyle, at risk with medial dissection
- Subcutaneous position - easy access but high hardware prominence
Classification Systems
Mayo Classification (most widely used)
| Type | Displacement | Stability | Subtype |
|---|---|---|---|
| I | Undisplaced (less than 2mm) | Stable | - |
| II | Displaced | Stable | A = non-comminuted, B = comminuted |
| III | Displaced | Unstable | A = non-comminuted, B = comminuted |
Stability Definition
Stable = intact ulnohumeral joint with no subluxation. Unstable = associated elbow instability, subluxation, or fracture-dislocation pattern. Type III requires addressing both fracture and instability.
Clinical Presentation and Assessment
History:
- Mechanism (direct blow, fall, sports)
- Ability to extend elbow post-injury
- Previous elbow problems
- Hand dominance
- Occupation and activity level
Physical examination:
Physical Examination Findings
| Finding | Significance | Action |
|---|---|---|
| Palpable gap posteriorly | Displaced fracture | Confirms diagnosis |
| Cannot extend against gravity | Extensor mechanism disruption | Surgical indication |
| Skin abrasion/laceration | Open fracture or at risk | Antibiotics if open, protect skin |
| Elbow instability on stress | Mayo Type III pattern | Plan for additional stabilization |
| Crepitus on flexion | Articular involvement | CT for surgical planning |
Functional testing:
- Active extension test: Patient attempts to extend elbow against gravity
- Inability to extend = complete extensor mechanism disruption = surgical indication
- Intact extension with minimal displacement may be treated conservatively
Neurovascular examination:
- Ulnar nerve function (little finger sensation, FDI strength)
- Median and radial nerve function
- Vascular status
Skin Assessment
The olecranon is subcutaneous. Direct trauma often causes skin abrasion or laceration. Assess carefully for open injury. Even closed fractures may have compromised skin that affects surgical timing and approach.
Investigations
Radiographic assessment:
Standard views:
- True lateral elbow - most important view
- Shows fracture pattern, displacement, articular involvement
- Assess ulnohumeral alignment
- AP elbow - confirms fracture, shows medial/lateral extent
- Oblique views - may help characterize pattern
Lateral View Key
The true lateral X-ray is essential. It shows fracture displacement, angulation, comminution, and most importantly ulnohumeral joint alignment. Anterior subluxation suggests Type III or trans-olecranon fracture-dislocation.
CT imaging:
Indications:
- Complex/comminuted fractures
- Trans-olecranon fracture-dislocations
- Associated coronoid or radial head fractures
- Surgical planning for plate placement
What to assess:
- Fracture pattern and comminution
- Articular surface involvement
- Coronoid integrity
- Associated injuries
Management
Conservative management criteria:
Conservative Treatment Criteria
| Criterion | Requirement |
|---|---|
| Displacement | Less than 2mm step-off |
| Extensor mechanism | Intact (can extend against gravity) |
| Stability | No elbow instability |
| Patient factors | Low-demand, compliant with restrictions |
Protocol:
- Posterior splint at 45-90 degrees flexion
- Begin ROM exercises at 1-2 weeks
- Avoid resisted extension for 6 weeks
- Serial X-rays to monitor displacement
Watch for Displacement
Fractures treated conservatively must be monitored closely. Displacement can occur in first 2 weeks. Weekly X-rays initially, convert to surgery if displacement exceeds 2mm.
Surgical Technique
Tension Band Wiring (TBW) - classic technique
Indications:
- Simple transverse or short oblique fractures
- Non-comminuted (Mayo IIA)
- Intact anterior cortex
Technique:
- Posterior longitudinal incision
- Reduce fracture anatomically
- Two parallel 1.6-2.0mm K-wires, intramedullary or bicortical
- Figure-of-8 wire (1.0-1.2mm) deep to triceps, superficial to K-wires
- Tighten wire to achieve compression
- Bend and bury K-wire ends
Key points:
- K-wires should engage anterior cortex distally
- Wire must be posterior to K-wires (on tension side)
- Check reduction with flexion-extension before final tightening
TBW Biomechanics
Tension band only works when the anterior cortex is intact to act as a compression hinge. With elbow flexion, tensile forces on posterior wire are converted to compression at the articular surface.
Complications
Complications of Olecranon Fracture Treatment
| Complication | Incidence | Management |
|---|---|---|
| Symptomatic hardware | 80% TBW, 20-30% plate | Hardware removal after union |
| Elbow stiffness | 10-20% | Physiotherapy, dynamic splinting, release if severe |
| Nonunion | 5-10% | Revision fixation with bone graft |
| Infection | 2-5% | Antibiotics, debridement, may need hardware removal |
| Post-traumatic arthritis | 5-15% | Arthroplasty if severe and symptomatic |
| Ulnar neuropathy | 2-5% | Usually neurapraxia, protect nerve intraoperatively |
| K-wire migration | 5-10% TBW | Bend ends, early removal if backing out |
Hardware-related issues:
Hardware Counseling
Pre-operative counseling about hardware prominence is essential. The olecranon is subcutaneous with minimal soft tissue coverage. Most TBW patients require hardware removal. Plate fixation has lower but still significant removal rates.
Stiffness:
- Common after elbow trauma
- Goal: functional arc 30-130 degrees
- Prevention: stable fixation, early motion
- Treatment: physiotherapy, splinting, surgical release
Nonunion:
- More common with inadequate fixation or infection
- Treatment: revision with plate fixation and bone graft
- May need triceps advancement if fragment excision required
Postoperative Care and Rehabilitation
Post-fixation protocol:
- Posterior splint at 90 degrees
- Elevation, ice
- Finger motion encouraged
- Wound check
- Begin active ROM
- Splint between exercises if needed
- No resisted extension
- Gravity-assisted extension
- Progressive active ROM
- Goal: full extension by 6 weeks
- Continue avoiding resisted extension
- May use dynamic splinting if stiff
- Begin gentle strengthening
- Progressive loading
- Functional activities
- Full strengthening
- Return to sport/work
- Hardware removal if symptomatic (after union confirmed)
Key rehabilitation principles:
- Early motion is essential
- Avoid resisted extension until 6 weeks
- Stable fixation permits aggressive ROM
- Hardware prominence may limit motion (remove if symptomatic)
Outcomes and Prognosis
Outcomes by treatment:
| Treatment | Good/Excellent | Key Points |
|---|---|---|
| TBW | 85-95% | High hardware removal rate |
| Plate | 85-95% | Lower hardware issues |
| Excision | 70-85% | Reserved for elderly, selected cases |
| Conservative | 80-90% | Only for truly undisplaced |
Prognostic factors:
- Fracture complexity (comminution worse)
- Associated injuries (coronoid, radial head)
- Quality of reduction
- Patient compliance with rehabilitation
- Bone quality
TBW vs Plate Outcomes
Functional outcomes are similar between TBW and plate fixation. The main difference is hardware-related complications - higher with TBW. Plate fixation is increasingly preferred, especially for comminuted patterns.
Evidence Base
- No significant difference in functional outcomes between TBW and plate fixation. Plate fixation had lower re-operation rate (2% vs 22%) primarily due to less hardware removal.
- Classic tension band wiring study. 96% good/excellent results at 2 years. 85% required hardware removal for prominence.
- Plate fixation for olecranon fractures produced 92% good/excellent results. Particularly useful for comminuted and oblique patterns where TBW is biomechanically inferior.
- Excision of up to 50% of olecranon with triceps advancement produces acceptable results in elderly, low-demand patients. Beyond 50% risks instability.
- Trans-olecranon fracture-dislocations are distinct from Monteggia injuries. Plate fixation restoring ulnohumeral joint produces good outcomes.
Exam Viva Scenarios
Practice these scenarios to excel in your viva examination
Scenario 1: Simple Displaced Fracture
"A 35-year-old man falls directly onto his left elbow. X-rays show a displaced transverse olecranon fracture with 5mm of articular step-off. The elbow is stable on examination. Describe your management."
Scenario 2: Trans-Olecranon Fracture-Dislocation
"A 72-year-old woman with osteoporosis falls and sustains a comminuted olecranon fracture. The lateral X-ray shows the ulna is anteriorly subluxated relative to the trochlea. How do you manage this?"
Scenario 3: Hardware Complication
"A patient returns 3 months after TBW for an olecranon fracture. They have united but have prominent hardware causing pain and skin irritation. The K-wire is backing out. What is your management?"
MCQ Practice Points
Classification Question
Q: According to the Mayo classification, what defines a Type III olecranon fracture? A: Displaced fracture with elbow instability. Type I = undisplaced, Type II = displaced but stable, Type III = displaced and unstable. Subtype A = non-comminuted, B = comminuted.
Biomechanics Question
Q: How does tension band wiring work? A: The figure-of-8 wire converts tensile forces (from triceps pull) to compressive forces at the articular surface. This requires an intact anterior cortex to act as a fulcrum/hinge. With elbow flexion, compression increases at the fracture site.
Technique Question
Q: Where should the K-wires engage in tension band wiring? A: The K-wires should engage the anterior cortex of the ulna distally. This creates a more stable construct. Intramedullary placement with engagement of anterior cortex is preferred.
Indication Question
Q: When is plate fixation preferred over tension band wiring for olecranon fractures? A: Oblique fractures (greater than 30 degrees), comminuted fractures, osteoporotic bone, Monteggia variants, trans-olecranon fracture-dislocations, and Mayo Type III (unstable).
Complication Question
Q: What is the approximate rate of hardware removal after tension band wiring for olecranon fractures? A: 80%. Hardware prominence is very common due to the subcutaneous position of the olecranon. Plate fixation has lower removal rates (20-30%).
Australian Context
Epidemiology:
- Common injury in falls, cycling, and contact sports
- Bimodal distribution similar to international data
- Increasing elderly population with osteoporotic fractures
Management considerations:
- Day surgery often possible for straightforward fixation
- Consideration of plate vs TBW may depend on resources
- Hardware removal is a separate procedure
Rehabilitation:
- Hand therapy referral standard practice
- Occupational therapy for return to work/ADLs
- WorkCover considerations for occupational injuries
Exam Context
Be prepared to discuss TBW versus plate fixation with indications for each. Understand that plate fixation is increasingly favored due to lower re-operation rates. Know the biomechanics of tension band principle.
OLECRANON FRACTURES
High-Yield Exam Summary
KEY CONCEPTS
- •Triceps insertion - extensor mechanism disruption
- •Articular fracture - affects ulnohumeral joint
- •Subcutaneous - high hardware prominence
- •2mm step-off threshold for surgery
MAYO CLASSIFICATION
- •Type I: Undisplaced (less than 2mm)
- •Type II: Displaced, stable (A = simple, B = comminuted)
- •Type III: Displaced, unstable (A = simple, B = comminuted)
- •Stability = ulnohumeral joint status
TBW INDICATIONS
- •Simple transverse or short oblique fracture
- •Non-comminuted (Mayo IIA)
- •Intact anterior cortex (for tension band to work)
- •Accept 80% hardware removal rate
PLATE INDICATIONS
- •Oblique fracture (greater than 30 degrees)
- •Comminuted (Mayo IIB, IIIB)
- •Osteoporotic bone
- •Trans-olecranon fracture-dislocation
- •Mayo Type III (unstable)
TBW TECHNIQUE
- •Two parallel K-wires (1.6-2.0mm)
- •Intramedullary or bicortical - engage anterior cortex
- •Figure-of-8 wire (1.0-1.2mm)
- •Wire deep to triceps, superficial to K-wires
- •Tension wire on posterior (tension) side
TRAPS AND PEARLS
- •TBW only for simple patterns - plate for comminution
- •Check for trans-olecranon subluxation on lateral
- •80% TBW hardware removal - counsel pre-op
- •Anterior cortex must be intact for TBW to work
- •Early motion essential to prevent stiffness