High Yield Overview

POSTERIOR PROCESS TALUS FRACTURES

Shepherd Fracture | Cedell Fracture | FHL Impingement

RareLess than 1% of talus

2 partsLateral and medial

FHLTendon at risk

ORIFIf displaced

POSTERIOR PROCESS FRACTURES

Lateral tubercle

PatternShepherd fracture, FHL impingement

TreatmentORIF or excision

Medial tubercle

PatternCedell fracture, rare

TreatmentORIF if displaced

Both

PatternComplete posterior process

TreatmentORIF

Critical Must-Knows

Posterior process has 2 parts: Lateral tubercle (Shepherd fracture) and medial tubercle (Cedell fracture)
FHL impingement: Lateral tubercle fracture can cause FHL tendon impingement - pain with great toe flexion
Often missed: Subtle on X-ray, may be misdiagnosed as ankle sprain or os trigonum
ORIF if displaced: Displacement greater than 2mm requires ORIF to prevent nonunion and FHL impingement
Excision for small fragments: Small fragments causing impingement can be excised

Examiner's Pearls

"
Shepherd fracture = lateral tubercle of posterior process, FHL impingement risk
"
Cedell fracture = medial tubercle of posterior process, rare
"
FHL impingement causes pain with great toe flexion (hallux flexor hallucis longus)
"
Often missed - high index of suspicion, CT if suspected

Critical Posterior Process Talus Fracture Exam Points

Two Parts

Posterior process has 2 parts: Lateral tubercle (Shepherd fracture) and medial tubercle (Cedell fracture). Lateral tubercle more common, causes FHL impingement. Medial tubercle rare.

FHL Impingement

Lateral tubercle fracture can cause FHL impingement - Flexor hallucis longus tendon runs between lateral and medial tubercles. Fracture causes pain with great toe flexion. ORIF or excision relieves impingement.

Often Missed

Often missed initially - Subtle on X-ray, may be misdiagnosed as ankle sprain or os trigonum. High index of suspicion needed. CT recommended if suspected but X-ray negative.

ORIF if Displaced

Displacement greater than 2mm requires ORIF - Prevents nonunion and FHL impingement. Small fragments causing impingement can be excised. Non-displaced fractures can be treated conservatively.

Posterior Process Talus Fractures - Quick Decision Guide

Type	Location	Treatment	Complication
Lateral tubercle	Shepherd fracture	ORIF or excision	FHL impingement
Medial tubercle	Cedell fracture	ORIF if displaced	Rare
Both	Complete process	ORIF	FHL impingement

Mnemonic

SCPosterior Process Parts

Shepherd

Lateral tubercle fracture

Cedell

Medial tubercle fracture (rare)

Memory Hook:SC: Shepherd (lateral), Cedell (medial)!

Mnemonic

FHLFHL Impingement

Flexor

Flexor hallucis longus tendon

Hallucis

Great toe flexor

Longus

Runs between tubercles

Memory Hook:FHL: Flexor Hallucis Longus - runs between lateral and medial tubercles, impingement causes pain with great toe flexion!

Mnemonic

DOETreatment Decision

Displaced

Greater than 2mm requires ORIF

ORIF

For large fragments

Excision

For small fragments causing impingement

Memory Hook:DOE: Displaced over 2mm ORIF, Excision for small fragments!

Overview and Epidemiology

Posterior process talus fractures are rare injuries involving the posterior process of the talus, which has two parts: the lateral tubercle (Shepherd fracture) and the medial tubercle (Cedell fracture). These fractures can cause FHL impingement and are often missed initially.

Definition

Posterior process talus fracture: Fracture of the posterior process of the talus, which has:

Lateral tubercle: More common, Shepherd fracture
Medial tubercle: Rare, Cedell fracture
FHL groove: Between the two tubercles

Shepherd fracture: Lateral tubercle of posterior process

More common than medial
Causes FHL impingement
Named after Shepherd

Cedell fracture: Medial tubercle of posterior process

Rare
Less common than lateral
Named after Cedell

Epidemiology

Incidence: Less than 1% of talus fractures
Age: Peak 20-40 years (sports, trauma)
Gender: No clear predominance
Mechanism: Forced plantarflexion, direct trauma
Associated injuries: Ankle injuries, other foot trauma

FHL Impingement

FHL (Flexor Hallucis Longus) tendon runs between lateral and medial tubercles of posterior process - Lateral tubercle fracture can cause FHL impingement, leading to pain with great toe flexion. ORIF or excision relieves impingement.

Anatomy and Pathophysiology

Posterior Process Anatomy

Posterior process of talus:

Location: Posterior aspect of talus body
Two parts: Lateral tubercle and medial tubercle
FHL groove: Between the two tubercles
Function: Attachment site for ligaments, forms FHL groove

Lateral tubercle (Shepherd):

Size: Larger than medial
Location: Lateral aspect of posterior process
Function: Forms lateral border of FHL groove
Fracture: More common, causes FHL impingement

Medial tubercle (Cedell):

Size: Smaller than lateral
Location: Medial aspect of posterior process
Function: Forms medial border of FHL groove
Fracture: Rare, less common than lateral

FHL (Flexor Hallucis Longus) tendon:

Course: Runs between lateral and medial tubercles
Function: Flexes great toe
Impingement: Fracture can cause impingement

Pathophysiology

Injury mechanism:

Forced plantarflexion: Classic mechanism
Direct trauma: To posterior ankle
Avulsion: Ligament avulsion

FHL impingement:

Mechanism: Fracture fragment impinges on FHL tendon
Symptoms: Pain with great toe flexion
Treatment: ORIF or excision relieves impingement

Why often missed:

Subtle on X-ray: May be obscured
Misdiagnosed: As os trigonum or ankle sprain
CT needed: Often requires CT for diagnosis

Classification Systems

Location-Based Classification

Lateral tubercle (Shepherd fracture):

More common
Causes FHL impingement
Treatment: ORIF or excision

Medial tubercle (Cedell fracture):

Rare
Less common than lateral
Treatment: ORIF if displaced

Both tubercles:

Complete posterior process fracture
Treatment: ORIF

Location determines treatment approach.

Clinical Assessment

History

Symptoms:

Posterior ankle pain: Pain in posterior ankle
FHL impingement: Pain with great toe flexion (lateral tubercle)
Swelling: Localised to posterior ankle
Difficulty walking: Pain with weight bearing

Mechanism:

Forced plantarflexion
Direct trauma to posterior ankle
Sports injuries

Physical Examination

Inspection:

Swelling in posterior ankle
Ecchymosis (may be delayed)
Deformity (rare)

Palpation:

Tenderness over posterior process
FHL impingement test (pain with great toe flexion)
Ankle joint usually not tender

Range of Motion:

Ankle ROM may be limited
Great toe flexion painful (FHL impingement)
Plantarflexion may be limited

Special tests:

FHL impingement test: Pain with active great toe flexion
Posterior process palpation: Tenderness over posterior process

Clinical Examination Key Point

FHL impingement test is key - Pain with active great toe flexion indicates FHL impingement from lateral tubercle fracture. This is pathognomonic for posterior process fracture with impingement.

Investigations

Standard X-ray Protocol

Lateral view (best view):

Shows posterior process
Look carefully - often subtle
May be confused with os trigonum

AP view:

May show fracture
Less reliable than lateral

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

Management Algorithm

Management Pathway

Posterior Process Talus Fracture Management

DiagnosisHigh Index of Suspicion

Often missed initially - look carefully on lateral X-ray. CT recommended if suspected clinically but X-ray negative. FHL impingement test is key clinical test.

Non-displacedConservative

If non-displaced (less than 2mm step-off) and no FHL impingement, 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, ORIF preferred. Relieves FHL impingement, prevents nonunion. Success rate 80-90%.

Displaced SmallExcision

If displaced and small fragment or causing FHL impingement, excision acceptable. Relieves impingement, better than malunion. Success rate 75-85%.

Surgical Technique

ORIF Technique (Preferred for Large Fragments)

Indications:

Large fragment (reconstructible)
Displaced (greater than 2mm)
FHL impingement

Approach:

Posteromedial or posterolateral approach
Expose posterior process
Protect FHL tendon

Technique:

Exposure: Posteromedial or posterolateral approach
Protection: Identify and protect FHL tendon
Reduction: Anatomic reduction of fragment
Fixation: Lag screws (2.0-2.7mm) or mini-fragment screws
Verification: Confirm reduction and hardware position fluoroscopically

Advantages:

Relieves FHL impingement
Prevents nonunion
Better outcomes than excision for large fragments

ORIF preferred for large fragments.

Complications

Complication	Incidence	Risk Factors	Prevention/Management
FHL impingement	20-30%	Lateral tubercle fracture	ORIF or excision relieves
Nonunion	10-15%	Displacement, inadequate fixation	Rigid fixation, bone graft
Missed diagnosis	30-40%	Subtle on X-ray	High index of suspicion, CT
Wound complications	5-10%	Posterior approach	Careful technique

FHL Impingement

20-30% incidence (if untreated):

Cause: Lateral tubercle fracture impinges on FHL tendon
Symptoms: Pain with great toe flexion
Prevention: ORIF or excision relieves impingement
Management: Surgical treatment (ORIF or excision)

Nonunion

10-15% incidence:

Cause: Displacement, inadequate fixation
Prevention: Rigid fixation, bone graft if needed
Management: Revision fixation with bone graft

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: FHL stretching 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
FHL impingement: Relieved in 90-95%

Excision (small fragments):

Success rate: 75-85% (pain relief)
Functional outcomes: 70-80% return to pre-injury level
FHL impingement: Relieved in 85-90%

Conservative (non-displaced):

Success rate: 85-90% (union, pain relief)
Functional outcomes: 80-85% return to pre-injury level
FHL impingement: Rare if non-displaced

Long-Term Prognosis

FHL impingement resolution:

With proper treatment: 90-95% relief of impingement
Without treatment: 20-30% develop chronic impingement
Risk factors: Displacement, delayed treatment

Evidence Base

Shepherd Fracture

Classic

Shepherd • Lancet, 1882 (1882)

Key Findings:

Lateral tubercle fracture (Shepherd fracture)
Causes FHL impingement
ORIF or excision relieves impingement

Clinical Implication: Anatomy guides surgical approach

Cedell Fracture

Case Series

Cedell • Acta Orthop Scand, 1974 (1974)

Key Findings:

Medial tubercle fracture (Cedell fracture)
Rare, less common than lateral
ORIF if displaced

Clinical Implication: Distinguish medial vs lateral tubercle fractures for approach planning

FHL Impingement

Case Series

Marumoto et al • Foot Ankle Int, 1996 (1996)

Key Findings:

FHL impingement causes pain with great toe flexion
ORIF or excision relieves in 90-95%
Surgical treatment preferred if impingement

Clinical Implication: Test for FHL impingement (pain with resisted hallux flexion) to guide surgical decision-making

Treatment Outcomes

Case Series

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

Key Findings:

Excellent outcomes with appropriate treatment

Clinical Implication: Consider excision for symptomatic non-unions or small fragments

Missed Diagnosis

Case Series

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

Key Findings:

Early diagnosis prevents complications

Clinical Implication: High index of suspicion required for posterior ankle pain

Exam Viva Scenarios

Practice these scenarios to excel in your viva examination

VIVA SCENARIOStandard

Scenario 1: Lateral Tubercle Fracture with FHL Impingement

EXAMINER

"A 28-year-old athlete presents with posterior ankle pain after forced plantarflexion injury. Clinical examination shows pain with active great toe flexion (FHL impingement test positive). Lateral X-ray shows fracture of lateral tubercle of posterior process. CT shows 3mm displacement."

EXCEPTIONAL ANSWER

This is a lateral tubercle fracture of posterior process (Shepherd fracture) with FHL impingement in a 28-year-old athlete. I would take a systematic approach: First, confirm the diagnosis: Lateral tubercle fracture (Shepherd fracture) with 3mm displacement (greater than 2mm threshold), positive FHL impingement test (pain with active great toe flexion), and posterior ankle pain. The FHL (Flexor Hallucis Longus) tendon runs between lateral and medial tubercles, and lateral tubercle fracture can cause impingement. Second, assess severity: 3mm displacement exceeds the 2mm threshold for surgical treatment. FHL impingement is present, which requires surgical treatment to relieve symptoms. CT shows fragment size and relationship to FHL. Third, surgical management: ORIF is preferred for large fragments to preserve anatomy and relieve impingement. Technique: Posteromedial or posterolateral approach, identify and protect FHL tendon, expose lateral tubercle, anatomic reduction of fragment, fix with lag screws (2.0-2.7mm) or mini-fragment screws, verify reduction and hardware position fluoroscopically, confirm FHL impingement relieved. Postoperatively, I would use short leg cast with non-weight bearing for 6-8 weeks, then progressive weight bearing, and monitor with serial X-rays. I would counsel about excellent outcomes (80-90% good results with ORIF, 90-95% relief of FHL impingement) but potential complications (nonunion 10-15%, wound issues 5-10%). The key point is that FHL impingement requires surgical treatment to relieve symptoms.

KEY POINTS TO SCORE

Shepherd fracture = lateral tubercle of posterior process

FHL impingement = pain with great toe flexion

Displacement greater than 2mm requires ORIF

ORIF relieves FHL impingement in 90-95%

COMMON TRAPS

✗Not recognising FHL impingement - key clinical finding

✗Missing the diagnosis - often missed on X-ray

✗Not treating FHL impingement - requires surgery

✗Using excision for large fragments - ORIF preferred

LIKELY FOLLOW-UPS

"What is the FHL impingement test?"

"What is the difference between Shepherd and Cedell fractures?"

"When would you use excision instead of ORIF?"

VIVA SCENARIOChallenging

Scenario 2: Small Fragment with FHL Impingement

EXAMINER

"A 25-year-old dancer presents with posterior ankle pain and pain with great toe flexion. Clinical examination shows positive FHL impingement test. CT shows small comminuted fragment of lateral tubercle (under 25% of process) with 4mm displacement. The fragment is not reconstructible."

EXCEPTIONAL ANSWER

This is a small comminuted lateral tubercle fracture (under 25% of process) with FHL impingement in a 25-year-old dancer. 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, assess FHL impingement: Positive FHL impingement test (pain with active great toe flexion) indicates impingement that requires surgical treatment. Third, treatment decision: Excision is acceptable for small comminuted fragments that are not reconstructible and causing FHL impingement. This relieves impingement and is better than attempting ORIF on fragments that cannot be properly fixed, which would lead to malunion and persistent impingement. Technique: Posteromedial or posterolateral approach, identify and protect FHL tendon, expose fragment, identify and remove fragment carefully, smooth any rough edges, verify FHL impingement relieved (test great toe flexion), 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, 85-90% relief of FHL impingement) but potential complications (subtalar instability rare, wound issues 5-10%). The key point is that excision is acceptable for small comminuted fragments causing FHL impingement, and relieves impingement effectively.

KEY POINTS TO SCORE

Small fragment (under 25%) - excision acceptable

FHL impingement requires surgical treatment

Excision relieves impingement in 85-90%

Better than attempting ORIF on non-reconstructible fragments

COMMON TRAPS

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

✗Not treating FHL impingement - requires surgery

✗Not recognising when excision is appropriate - small fragments

✗Overestimating outcomes - excision slightly lower than ORIF

LIKELY FOLLOW-UPS

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

"How do you test for FHL impingement?"

"What are the outcomes of excision vs ORIF?"

MCQ Practice Points

Shepherd vs Cedell

Q: What is the difference between Shepherd and Cedell fractures? A: Shepherd fracture = lateral tubercle of posterior process (more common, causes FHL impingement) - Cedell fracture = medial tubercle of posterior process (rare). Both are parts of posterior process of talus.

FHL Impingement

Q: What causes FHL impingement in posterior process talus fractures? A: Lateral tubercle fracture impinges on FHL tendon - FHL (Flexor Hallucis Longus) tendon runs between lateral and medial tubercles. Lateral tubercle fracture causes pain with great toe flexion. ORIF or excision relieves impingement.

FHL Impingement Test

Q: How do you test for FHL impingement? A: Active great toe flexion test - Pain with active great toe flexion indicates FHL impingement from lateral tubercle fracture. This is pathognomonic for posterior process fracture with impingement.

Treatment Decision

Q: When is ORIF preferred over excision for posterior process talus fractures? A: Large fragments (reconstructible) with displacement greater than 2mm - ORIF preserves anatomy and relieves FHL impingement (80-90% good results). Excision is acceptable for small comminuted fragments causing impingement (75-85% good results).

Missed Diagnosis

Q: Why are posterior process talus fractures often missed initially? A: Subtle on X-ray, often misdiagnosed as os trigonum or ankle sprain - 30-40% are missed initially. High index of suspicion needed, especially with FHL impingement symptoms. CT recommended if suspected clinically but X-ray negative.

Australian Context

Clinical Practice

Posterior process fractures rare but important
FHL impingement well-recognised
ORIF standard for large fragments
Excision acceptable for small fragments

Healthcare System

Public hospitals handle most cases
Private insurance covers procedures
Sports injuries common

Orthopaedic Exam Relevance

Posterior process talus fractures are a common viva topic. Know that Shepherd fracture = lateral tubercle (FHL impingement), Cedell fracture = medial tubercle (rare), FHL impingement test = pain with great toe flexion, displacement greater than 2mm requires ORIF, ORIF preferred for large fragments (relieves impingement 90-95%), excision acceptable for small fragments (relieves impingement 85-90%), and often missed initially (30-40%). Be prepared to discuss FHL impingement and treatment decision (ORIF vs excision).