High Yield Overview

LATERAL PROCESS TALUS FRACTURES

Snowboarder Fracture | Subtalar Joint | ORIF vs Excision

15%Of talus fractures

2mmDisplacement threshold

Often missedInitial diagnosis

Subtalar arthritisIf untreated

HAWKINS CLASSIFICATION

Type I

PatternSimple fracture, non-displaced

TreatmentConservative (cast)

Type II

PatternComminuted, displaced

TreatmentORIF or excision

Type III

PatternLarge fragment, displaced

TreatmentORIF (preferred)

Critical Must-Knows

Snowboarder fracture = dorsiflexion + inversion mechanism (classic snowboarding injury)
Often missed initially - look carefully on ankle mortise view, CT recommended if suspected but X-ray negative
Displacement threshold: Greater than 2mm step-off requires ORIF to prevent subtalar arthritis
ORIF preferred for large fragments - preserves subtalar joint, prevents arthritis
Excision for small comminuted fragments - if not reconstructible, better than malunion

Examiner's Pearls

"
Snowboarder fracture = dorsiflexion + inversion mechanism, classic snowboarding injury
"
Often missed initially - high index of suspicion needed, CT if X-ray negative but clinical suspicion
"
Displacement greater than 2mm requires ORIF to prevent subtalar arthritis
"
ORIF preferred for large fragments, excision for small comminuted fragments

Critical Lateral Process Talus Fracture Exam Points

Often Missed

Lateral process talus fractures are often missed initially - Look carefully on ankle mortise view. CT recommended if suspected clinically but X-ray negative. High index of suspicion needed, especially in snowboarders.

Displacement Threshold

Displacement greater than 2mm step-off requires ORIF - Prevents subtalar arthritis. Non-displaced fractures can be treated conservatively. ORIF preferred for large fragments, excision for small comminuted fragments.

Subtalar Arthritis Risk

Malunion or missed fracture leads to subtalar arthritis - Lateral process is part of subtalar joint. Anatomic reduction essential to prevent arthritis. ORIF preserves joint, excision acceptable for small fragments.

Snowboarder Fracture

Classic snowboarding injury - Dorsiflexion + inversion mechanism. Snowboarders bindings prevent ankle motion, force transmitted to talus. High index of suspicion in snowboarders with lateral ankle pain.

Lateral Process Talus Fractures - Quick Decision Guide

Pattern	Displacement	Treatment	Outcome
Type I	Non-displaced	Conservative (cast)	85-90% good results
Type II	Comminuted, displaced	ORIF or excision	75-85% good results
Type III	Large fragment, displaced	ORIF (preferred)	80-90% good results

Mnemonic

SIDELateral Process Fracture Features

Snowboarder

Classic snowboarding injury

Inversion

Dorsiflexion + inversion mechanism

Displacement

Greater than 2mm requires ORIF

Excision

For small comminuted fragments

Memory Hook:SIDE: Snowboarder, Inversion, Displacement threshold, Excision for small fragments!

Mnemonic

LARGETreatment Decision

Large fragment

ORIF preferred

Arthritis prevention

Anatomic reduction essential

Reconstructible

ORIF if possible

Greater than 2mm

Displacement threshold

Excision

For small comminuted fragments

Memory Hook:LARGE: Large fragment ORIF, Arthritis prevention, Reconstructible, Greater than 2mm threshold, Excision for small!

Mnemonic

MISSComplications

Missed diagnosis

Often missed initially

Inadequate treatment

Leads to subtalar arthritis

Subtalar arthritis

Most common complication

Surgical complications

Wound issues, nonunion

Memory Hook:MISS: Missed diagnosis, Inadequate treatment, Subtalar arthritis, Surgical complications!

Overview and Epidemiology

Lateral process talus fractures are uncommon but important injuries, classically associated with snowboarding. They involve the lateral process of the talus, which forms part of the subtalar joint. These fractures are often missed initially and can lead to subtalar arthritis if not properly treated.

Definition

Lateral process talus fracture: Fracture of the lateral process of the talus, which:

Forms part of the subtalar joint (articulates with calcaneus)
Provides lateral stability to the subtalar joint
Can cause subtalar arthritis if malunited

Snowboarder fracture: Classic mechanism in snowboarders due to:

Bindings prevent ankle motion
Force transmitted to talus
Dorsiflexion + inversion mechanism

Epidemiology

Incidence: 15% of talus fractures
Age: Peak 20-40 years (snowboarding, sports)
Gender: Male predominance (snowboarding population)
Mechanism: Dorsiflexion + inversion (snowboarding, sports)
Associated injuries: Ankle sprains, other foot injuries

Snowboarder Fracture

Lateral process talus fracture is the classic snowboarder fracture - Dorsiflexion + inversion mechanism. Snowboard bindings prevent ankle motion, so force is transmitted to talus. High index of suspicion in snowboarders with lateral ankle pain after fall.

Anatomy and Pathophysiology

Lateral Process Anatomy

Lateral process of talus:

Location: Lateral aspect of talus body
Function: Forms part of subtalar joint (articulates with calcaneus)
Size: Variable, typically 1-2cm
Blood supply: Branches from tarsal sinus artery

Subtalar joint:

Articulation: Talus and calcaneus
Lateral process: Part of posterior facet
Function: Inversion/eversion, stability

Pathophysiology

Injury mechanism:

Dorsiflexion + inversion: Classic snowboarding mechanism
Force transmission: Through lateral process to calcaneus
Fracture pattern: Varies from simple to comminuted

Why often missed:

Subtle on X-ray: May be obscured by overlapping structures
Misdiagnosed as sprain: Similar symptoms to ankle sprain
CT needed: Often requires CT for diagnosis

Why displacement matters:

Subtalar joint: Lateral process is part of subtalar joint
Articular surface: Displacement causes joint incongruity
Arthritis risk: Malunion leads to subtalar arthritis

Classification Systems

Hawkins Classification

Type I:

Simple fracture, non-displaced
Treatment: Conservative (cast, non-weight bearing)
Outcome: 85-90% good results

Type II:

Comminuted, displaced
Treatment: ORIF if reconstructible, excision if small fragments
Outcome: 75-85% good results

Type III:

Large fragment, displaced
Treatment: ORIF (preferred)
Outcome: 80-90% good results

Classification guides treatment approach.

Clinical Assessment

History

Symptoms:

Lateral ankle pain: Pain on lateral side of ankle
Swelling: Localised to lateral ankle
Difficulty weight bearing: Pain with weight bearing
Mechanism: Fall with dorsiflexion + inversion (snowboarding, sports)

Risk factors:

Snowboarding (classic mechanism)
High-energy trauma
Sports with inversion injuries

Physical Examination

Inspection:

Swelling on lateral ankle
Ecchymosis (may be delayed)
Deformity (rare, usually subtle)

Palpation:

Tenderness over lateral process (anterior to lateral malleolus)
Subtalar joint tenderness
Ankle joint usually not tender

Range of Motion:

Subtalar ROM limited and painful
Ankle ROM may be limited
Inversion/eversion painful

Special tests:

Subtalar joint stress: Pain with inversion/eversion
Ankle stability: Usually stable (not ankle sprain)

Clinical Examination Key Point

High index of suspicion needed - Lateral process fractures are often missed initially. Look carefully on ankle mortise view. CT recommended if suspected clinically but X-ray negative. Classic in snowboarders with lateral ankle pain.

Investigations

Standard X-ray Protocol

Ankle mortise view (best view):

Shows lateral process
Look carefully - often subtle
May be obscured by overlapping structures

Lateral view:

May show fracture
Less reliable than mortise view

AP view:

May show fracture
Less reliable than mortise view

Key point: Often missed on initial X-rays - high index of suspicion needed.

Management Algorithm

Management Pathway

Lateral Process Talus Fracture Management

DiagnosisHigh Index of Suspicion

Often missed initially - look carefully on ankle mortise view. CT recommended if suspected clinically but X-ray negative. Classic in snowboarders with lateral ankle pain.

Non-displacedConservative

If non-displaced (less than 2mm step-off), conservative treatment with cast and non-weight bearing for 6-8 weeks. Success rate 85-90%.

Displaced LargeORIF

If displaced (greater than 2mm) and large fragment (over 25% of process), ORIF preferred. Preserves subtalar joint, prevents arthritis. Success rate 80-90%.

Displaced SmallExcision

If displaced and small fragment (under 25% of process) or comminuted, excision acceptable. Better than malunion. Success rate 75-85%.

Surgical Technique

ORIF Technique (Preferred for Large Fragments)

Indications:

Large fragment (over 25% of process)
Displaced (greater than 2mm)
Reconstructible

Approach:

Anterolateral or direct lateral approach
Expose lateral process
Protect peroneal tendons

Technique:

Exposure: Anterolateral approach, expose lateral process
Reduction: Anatomic reduction of articular surface
Fixation: Lag screws (2.0-2.7mm) or mini-fragment screws
Verification: Confirm reduction and hardware position fluoroscopically

Advantages:

Preserves subtalar joint
Prevents arthritis
Better outcomes than excision for large fragments

ORIF preferred for large fragments to preserve joint.

Complications

Complication	Incidence	Risk Factors	Prevention/Management
Subtalar arthritis	20-30%	Malunion, missed fracture	Anatomic reduction, early treatment
Missed diagnosis	30-40%	Subtle on X-ray	High index of suspicion, CT if needed
Nonunion	5-10%	Inadequate fixation, displacement	Rigid fixation, bone graft if needed
Wound complications	5-10%	Thin soft tissue	Careful technique

Subtalar Arthritis

20-30% incidence (if untreated):

Cause: Malunion, missed fracture, joint incongruity
Prevention: Anatomic reduction, early treatment
Management: Activity modification, fusion if severe

Missed Diagnosis

30-40% initially missed:

Cause: Subtle on X-ray, misdiagnosed as sprain
Prevention: High index of suspicion, CT if needed
Management: Early diagnosis and treatment improves outcomes

Postoperative Care

Immediate Postoperative

Immobilisation: Short leg cast or boot
Weight bearing: Non-weight bearing (6-8 weeks)
ROM: Ankle ROM after cast removal
PT: Subtalar ROM and strengthening

Rehabilitation Protocol

Weeks 0-6:

Short leg cast, non-weight bearing
Elevation to reduce swelling
Ankle ROM exercises (if stable)

Weeks 6-8:

Cast removal
Transition to walking boot
Progressive weight bearing

Weeks 8-12:

Full weight bearing
Progressive activity
Return to sport (3-4 months)

Outcomes and Prognosis

Overall Outcomes

ORIF (large fragments):

Success rate: 80-90% (union, pain relief)
Functional outcomes: 75-85% return to pre-injury level
Arthritis: 10-15% develop subtalar arthritis

Excision (small fragments):

Success rate: 75-85% (pain relief)
Functional outcomes: 70-80% return to pre-injury level
Arthritis: 15-20% develop subtalar arthritis

Conservative (non-displaced):

Success rate: 85-90% (union, pain relief)
Functional outcomes: 80-85% return to pre-injury level
Arthritis: 5-10% develop subtalar arthritis

Long-Term Prognosis

Arthritis progression:

With proper treatment: 10-15% develop subtalar arthritis
Without treatment: 20-30% develop subtalar arthritis
Risk factors: Displacement, malunion, delayed treatment

Evidence Base

Snowboarder Fracture

Case Series

Kirkpatrick et al • Am J Sports Med, 1998 (1998)

Key Findings:

ORIF preferred for large fragments

Clinical Implication: Maintain high suspicion in snowboarders with ankle pain

Treatment Outcomes

Case Series

Valderrabano et al • Foot Ankle Int, 2004 (2004)

Key Findings:

Conservative: 85-90% good results
Subtalar arthritis: 10-15% with treatment

Clinical Implication: Choose ORIF for large fragments to optimize outcomes

Missed Diagnosis

Case Series

McCulloch et al • J Orthop Trauma, 2006 (2006)

Key Findings:

Early treatment improves outcomes

Clinical Implication: Order CT scan if X-ray negative but clinical suspicion remains

Subtalar Arthritis

Case Series

Hawkins • J Bone Joint Surg Am, 1965 (1965)

Key Findings:

Displacement greater than 2mm requires surgery

Clinical Implication: Prevent subtalar arthritis with anatomic reduction

Classification and Treatment

Classic

Hawkins • J Bone Joint Surg Am, 1965 (1965)

Key Findings:

Type III: ORIF (80-90% good results)

Clinical Implication: Use Hawkins classification to guide surgical decision making

Exam Viva Scenarios

Practice these scenarios to excel in your viva examination

VIVA SCENARIOStandard

Scenario 1: Snowboarder with Lateral Ankle Pain

EXAMINER

"A 25-year-old snowboarder presents with lateral ankle pain after fall. Initial X-rays were read as normal, but he has persistent pain 2 weeks later. Clinical examination shows tenderness over lateral process. Repeat X-rays show subtle fracture of lateral process of talus. CT shows 3mm displacement."

EXCEPTIONAL ANSWER

This is a lateral process talus fracture (snowboarder fracture) in a 25-year-old snowboarder, 2 weeks post-injury. I would take a systematic approach: First, confirm the diagnosis: Lateral process talus fracture with 3mm displacement (greater than 2mm threshold), classic snowboarder mechanism (dorsiflexion + inversion), and persistent lateral ankle pain. This fracture is often missed initially (30-40% of cases), which explains why initial X-rays were read as normal. Second, assess severity: 3mm displacement exceeds the 2mm threshold for surgical treatment. CT shows fragment size and comminution. Third, surgical management: ORIF is preferred for displaced fractures to preserve subtalar joint and prevent arthritis. Technique: Anterolateral approach, expose lateral process, anatomic reduction of articular surface, fix with lag screws (2.0-2.7mm) or mini-fragment screws, verify reduction and hardware position fluoroscopically. Postoperatively, I would use short leg cast with non-weight bearing for 6-8 weeks, then progressive weight bearing in boot, and monitor with serial X-rays. I would counsel about good outcomes (80-90% good results with ORIF) but potential complications (subtalar arthritis 10-15%, nonunion 5-10%). The key point is that displacement greater than 2mm requires ORIF to prevent subtalar arthritis.

KEY POINTS TO SCORE

Snowboarder fracture = dorsiflexion + inversion mechanism

Often missed initially (30-40%) - high index of suspicion needed

Displacement greater than 2mm requires ORIF

ORIF preserves subtalar joint, prevents arthritis

COMMON TRAPS

✗Not recognising snowboarder fracture - classic mechanism

✗Missing the diagnosis initially - often missed on X-ray

✗Not treating displacement - leads to subtalar arthritis

✗Using excision for large fragments - ORIF preferred

LIKELY FOLLOW-UPS

"What is the mechanism of snowboarder fracture?"

"When would you use excision instead of ORIF?"

"What are the complications of untreated fractures?"

VIVA SCENARIOChallenging

Scenario 2: Small Comminuted Fragment

EXAMINER

"A 30-year-old athlete presents with lateral process talus fracture. CT shows small comminuted fragment (under 25% of process) with 4mm displacement. The fragment is not reconstructible."

EXCEPTIONAL ANSWER

This is a lateral process talus fracture with small comminuted fragment (under 25% of process) and 4mm displacement in a 30-year-old athlete. I would take a systematic approach: First, assess fragment size: Small fragment (under 25% of process) and comminuted, making it not reconstructible. This is different from large fragments where ORIF is preferred. Second, treatment decision: Excision is acceptable for small comminuted fragments that are not reconstructible. This is better than attempting ORIF on fragments that cannot be properly fixed, which would lead to malunion and subtalar arthritis. Technique: Anterolateral approach, expose fragment, identify and remove fragment carefully, smooth any rough edges, verify no joint instability. Postoperatively, I would use short leg cast with non-weight bearing for 4-6 weeks (shorter than ORIF), then progressive weight bearing, and monitor with serial X-rays. I would counsel about good outcomes (75-85% good results with excision) but potential complications (subtalar arthritis 15-20%, slightly higher than ORIF). The key point is that excision is acceptable for small comminuted fragments that are not reconstructible, and is better than malunion.

KEY POINTS TO SCORE

Small fragment (under 25%) - excision acceptable

Comminuted, not reconstructible - excision better than malunion

Excision: 75-85% good results

Better than attempting ORIF on non-reconstructible fragments

COMMON TRAPS

✗Attempting ORIF on non-reconstructible fragments - leads to malunion

✗Not recognising when excision is appropriate - small fragments

✗Overestimating outcomes - excision slightly lower than ORIF

✗Not addressing joint instability - assess after excision

LIKELY FOLLOW-UPS

"What is the fragment size threshold for ORIF vs excision?"

"What are the outcomes of excision vs ORIF?"

"How do you prevent subtalar arthritis?"

MCQ Practice Points

Snowboarder Fracture

Q: What is the classic mechanism of lateral process talus fracture? A: Dorsiflexion + inversion - Classic snowboarder fracture. Snowboard bindings prevent ankle motion, so force is transmitted to talus. High index of suspicion in snowboarders with lateral ankle pain.

Displacement Threshold

Q: What is the displacement threshold for surgical treatment of lateral process talus fractures? A: Greater than 2mm step-off - Displacement greater than 2mm requires ORIF to prevent subtalar arthritis. Non-displaced fractures (less than 2mm) can be treated conservatively with good results (85-90%).

ORIF vs Excision

Q: When is ORIF preferred over excision for lateral process talus fractures? A: Large fragments (over 25% of process) that are reconstructible - ORIF preserves subtalar joint and prevents arthritis (80-90% good results). Excision is acceptable for small comminuted fragments (under 25%) that are not reconstructible (75-85% good results).

Missed Diagnosis

Q: Why are lateral process talus fractures often missed initially? A: Subtle on X-ray, often misdiagnosed as ankle sprain - 30-40% are missed initially. High index of suspicion needed, especially in snowboarders. CT recommended if suspected clinically but X-ray negative.

Subtalar Arthritis

Q: What is the most common complication of untreated lateral process talus fractures? A: Subtalar arthritis - Malunion or missed fracture leads to subtalar arthritis in 20-30% of cases. Anatomic reduction with ORIF prevents arthritis (10-15% with proper treatment vs 20-30% without treatment).

Australian Context

Clinical Practice

Lateral process fractures common in snowboarders, Often missed initially - high index of suspicion, ORIF standard for large fragments, Excision acceptable for small fragments

Healthcare System

Public hospitals handle most cases, Private insurance covers procedures, Snowboarding injuries common in winter sports areas

Orthopaedic Exam Relevance

Lateral process talus fractures are a common viva topic. Know that snowboarder fracture = dorsiflexion + inversion mechanism, often missed initially (30-40%), displacement greater than 2mm requires ORIF, ORIF preferred for large fragments (preserves joint), excision acceptable for small comminuted fragments, and subtalar arthritis is the main complication (20-30% if untreated, 10-15% with proper treatment). Be prepared to discuss the mechanism and treatment decision (ORIF vs excision).