High Yield Overview

SUSTENTACULUM TALI FRACTURES

Medial Calcaneus | FHL at Risk | Stable Reference

RareLess than 1% of calcaneus

FHLTendon at risk

ORIFIf displaced

StableReference for reduction

FRACTURE PATTERNS

Type I

PatternNon-displaced, isolated

TreatmentConservative (cast)

Type II

PatternDisplaced, isolated

TreatmentORIF

Type III

PatternPart of calcaneal fracture

TreatmentORIF as part of calcaneal fixation

Critical Must-Knows

Sustentaculum tali = medial shelf of calcaneus, attachment site for spring ligament and deltoid ligament
FHL tendon at risk - Runs beneath sustentaculum, injury causes loss of great toe flexion
Medial plantar nerve at risk - Runs medial to sustentaculum, injury causes medial foot numbness
Stable reference for reduction - Sustentaculum usually stays attached to talus via interosseous ligament, serves as template for calcaneal fracture reduction
ORIF if displaced - Prevents subtalar arthritis and FHL dysfunction

Examiner's Pearls

"
Sustentaculum tali = medial shelf, stable reference for calcaneal fracture reduction
"
FHL tendon runs beneath sustentaculum - at risk in medial approach
"
Medial plantar nerve at risk - runs medial to sustentaculum
"
ORIF if displaced - prevents subtalar arthritis

Critical Sustentaculum Tali Fracture Exam Points

FHL at Risk

FHL (Flexor Hallucis Longus) tendon runs beneath sustentaculum tali - Injury causes loss of great toe flexion. Medial approach requires careful dissection to protect FHL. Medial plantar nerve also at risk.

Stable Reference

Sustentaculum tali is stable reference for calcaneal fracture reduction - Usually stays attached to talus via interosseous ligament. Serves as template for reducing other calcaneal fragments. Critical in calcaneal fracture ORIF.

Medial Plantar Nerve

Medial plantar nerve at risk in medial approach - Runs medial to sustentaculum, between abductor hallucis and flexor digitorum brevis. Injury causes medial foot numbness and intrinsic muscle weakness.

ORIF if Displaced

Displacement greater than 2mm requires ORIF - Prevents subtalar arthritis and FHL dysfunction. Medial approach with protection of FHL and medial plantar nerve. Screw fixation from medial to lateral.

Sustentaculum Tali Fractures - Quick Decision Guide

Pattern	Displacement	Treatment	Outcome
Type I	Non-displaced, isolated	Conservative (cast)	85-90% good results
Type II	Displaced, isolated	ORIF	80-85% good results
Type III	Part of calcaneal fracture	ORIF as part of calcaneal	75-85% good results

Mnemonic

FHLSustentaculum Tali Features

Flexor

FHL tendon beneath

Hallucis

Great toe flexor

Longus

At risk in approach

Memory Hook:FHL: Flexor Hallucis Longus - runs beneath sustentaculum, at risk in medial approach!

Mnemonic

STABLEStable Reference

Sustentaculum

Medial shelf

Talus

Attached via interosseous ligament

Anatomic

Stays in position

Bone

Stable reference

Ligament

Interosseous intact

Essential

For calcaneal reduction

Memory Hook:STABLE: Sustentaculum attached to Talus via interosseous ligament, Anatomic position, Bone reference, Ligament intact, Essential for calcaneal fracture reduction!

Mnemonic

FMPStructures at Risk

FHL

Flexor hallucis longus tendon

Medial plantar

Medial plantar nerve

Protect

Both in medial approach

Memory Hook:FMP: FHL and Medial plantar nerve - Protect both in medial approach!

Overview and Epidemiology

Sustentaculum tali fractures are rare injuries involving the medial shelf of the calcaneus, which serves as a stable reference for calcaneal fracture reduction and has important structures (FHL tendon and medial plantar nerve) at risk during surgical approach.

Definition

Sustentaculum tali fracture: Fracture of the sustentaculum tali, which:

Location: Medial shelf of calcaneus
Function: Forms part of subtalar joint (middle facet)
Attachment: Spring ligament and deltoid ligament
Stability: Usually stays attached to talus via interosseous ligament

Sustentaculum tali anatomy:

Medial shelf: Projects medially from calcaneus
Subtalar joint: Forms middle facet (articulates with talus)
FHL groove: FHL tendon runs beneath sustentaculum
Stable reference: For calcaneal fracture reduction

Epidemiology

Incidence: Less than 1% of calcaneus fractures
Age: Peak 20-40 years (trauma population)
Gender: No clear predominance
Mechanism: High-energy trauma, inversion injury, or part of calcaneal fracture
Associated injuries: Calcaneal fractures, ankle injuries

Stable Reference

Anatomy and Pathophysiology

Sustentaculum Tali Anatomy

Sustentaculum tali:

Location: Medial shelf of calcaneus
Size: 1-2cm projection medially
Function: Forms part of subtalar joint (middle facet)
Attachments: Spring ligament, deltoid ligament

Subtalar joint:

Three facets: Anterior, middle (sustentaculum), posterior
Sustentaculum: Middle facet, articulates with talus
Function: Inversion/eversion, stability

FHL (Flexor Hallucis Longus) tendon:

Course: Runs beneath sustentaculum tali
Function: Flexes great toe
Risk: At risk in medial approach

Medial plantar nerve:

Location: Medial to sustentaculum
Course: Between abductor hallucis and flexor digitorum brevis
Function: Sensory to medial foot, motor to intrinsic muscles
Risk: At risk in medial approach

Pathophysiology

Injury mechanism:

High-energy trauma: Part of calcaneal fracture
Inversion injury: Isolated sustentaculum fracture
Direct trauma: To medial heel

Why sustentaculum is stable:

Interosseous ligament: Attaches sustentaculum to talus
Strong attachment: Ligament usually intact
Template: Serves as reference for reduction

Why displacement matters:

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

Classification Systems

Pattern-Based Classification

Type I (Non-displaced, isolated):

Isolated sustentaculum fracture
Non-displaced
Treatment: Conservative (cast)
Outcome: 85-90% good results

Type II (Displaced, isolated):

Isolated sustentaculum fracture
Displaced
Treatment: ORIF
Outcome: 80-85% good results

Type III (Part of calcaneal fracture):

Sustentaculum fracture as part of calcaneal fracture
Treatment: ORIF as part of calcaneal fixation
Outcome: 75-85% good results

Pattern guides treatment approach.

Clinical Assessment

History

Symptoms:

Medial heel pain: Pain on medial side of heel
FHL dysfunction: Loss of great toe flexion (if FHL injured)
Swelling: Localised to medial heel
Difficulty weight bearing: Pain with weight bearing

Mechanism:

High-energy trauma (calcaneal fracture)
Inversion injury (isolated)
Direct trauma to medial heel

Physical Examination

Inspection:

Swelling on medial heel
Ecchymosis (may be delayed)
Deformity (rare)

Palpation:

Tenderness over sustentaculum (medial to calcaneus)
FHL dysfunction (loss of great toe flexion if injured)
Subtalar joint tenderness

Range of Motion:

Subtalar ROM limited and painful
Great toe flexion limited (if FHL injured)
Inversion/eversion painful

Special tests:

FHL function: Test active great toe flexion
Medial plantar nerve: Test sensation to medial foot
Subtalar joint stress: Pain with inversion/eversion

Clinical Examination Key Point

FHL function and medial plantar nerve sensation are key findings - FHL runs beneath sustentaculum, injury causes loss of great toe flexion. Medial plantar nerve runs medial to sustentaculum, injury causes medial foot numbness.

Investigations

Standard X-ray Protocol

Lateral view:

May show sustentaculum fracture
Less reliable than CT

Axial view (Harris view):

Shows sustentaculum from below
Better view than lateral

AP view:

May show fracture
Less reliable

Key point: CT is often needed for diagnosis and planning.

Management Algorithm

Management Pathway

Sustentaculum Tali Fracture Management

DiagnosisCT Required

CT is usually required for diagnosis - sustentaculum fractures are difficult to see on X-ray alone. Assess displacement, fragment size, and FHL relationship. Part of calcaneal fracture or isolated.

Non-displacedConservative

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

DisplacedORIF

If displaced (greater than 2mm) or part of calcaneal fracture, ORIF required. Medial approach with protection of FHL and medial plantar nerve. Screw fixation from medial to lateral. Success rate 80-85%.

Part of CalcanealCalcaneal ORIF

If part of calcaneal fracture, address sustentaculum as part of calcaneal ORIF. Sustentaculum serves as stable reference for reduction. Fix with screws from lateral plate or medial screws. Success rate 75-85%.

Surgical Technique

Medial Approach ORIF (Isolated Fractures)

Indications:

Isolated sustentaculum fracture
Displaced (greater than 2mm)

Approach:

Medial approach to calcaneus
Expose sustentaculum
Protect FHL and medial plantar nerve

Technique:

Exposure: Medial approach, identify and protect FHL tendon (runs beneath sustentaculum)
Protection: Identify and protect medial plantar nerve (runs medial to sustentaculum)
Reduction: Anatomic reduction of sustentaculum to calcaneus
Fixation: Screws (2.7-3.5mm) from medial to lateral
Verification: Confirm reduction and hardware position fluoroscopically

Advantages:

Direct access to sustentaculum
Preserves subtalar joint
Prevents arthritis

Medial approach for isolated fractures.

Complications

Complication	Incidence	Risk Factors	Prevention/Management
FHL injury	5-10%	Medial approach	Protect FHL, identify early
Medial plantar nerve injury	5-10%	Medial approach	Protect nerve, identify early
Subtalar arthritis	10-15%	Malunion, displacement	Anatomic reduction, early treatment
Nonunion	5-10%	Displacement, inadequate fixation	Rigid fixation, bone graft if needed

FHL Injury

5-10% incidence:

Cause: Medial approach, FHL runs beneath sustentaculum
Prevention: Identify and protect FHL tendon during approach
Management: Repair if injured, may need FHL transfer if severe

Medial Plantar Nerve Injury

5-10% incidence:

Cause: Medial approach, nerve runs medial to sustentaculum
Prevention: Identify and protect medial plantar nerve during approach
Management: Neuroma excision if symptomatic

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 FHL 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 (isolated):

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

ORIF (part of calcaneal):

Success rate: 75-85% (union, pain relief)
Functional outcomes: 70-75% return to pre-injury level
Subtalar arthritis: 15-20% develop arthritis

Conservative (non-displaced):

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

Long-Term Prognosis

Subtalar 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

Sustentaculum Tali Fractures

Case Series

Beavis et al • Foot Ankle Int, 2008 (2008)

Key Findings:

Usually part of calcaneal fractures
FHL and medial plantar nerve at risk
ORIF required if displaced (80-85% good results)
Prevents subtalar arthritis

Clinical Implication: Sustentaculum tali fractures are often part of larger calcaneal injuries. Displacement requires ORIF to prevent long-term subtalar arthritis and protect the FHL tendon.

Stable Reference

Case Series

Sanders • J Orthop Trauma, 1993 (1993)

Key Findings:

Stays attached to talus via interosseous ligament
Serves as stable reference for reduction
Reduce other fragments to sustentaculum
Critical in calcaneal ORIF

Clinical Implication: The sustentaculum tali acts as the 'Rosetta Stone' for calcaneal fracture reduction. Because it remains attached to the talus, it serves as the stable template to which all other fragments are reduced.

FHL at Risk

Case Series

Beavis et al • Foot Ankle Int, 2008 (2008)

Key Findings:

FHL runs beneath sustentaculum
Injury in 5-10% of medial approaches
Causes loss of great toe flexion
Protect during approach

Clinical Implication: The FHL runs directly beneath the sustentaculum and is at high risk during medial approaches. Surgeons must actively identify and protect this tendon to prevent iatrogenic injury.

Medial Plantar Nerve

Case Series

Beavis et al • Foot Ankle Int, 2008 (2008)

Key Findings:

Runs medial to sustentaculum
Injury in 5-10% of medial approaches
Causes medial foot numbness
Protect during approach

Clinical Implication: The medial plantar nerve runs medial to the sustentaculum and must be protected during the medial approach to avoid sensory deficits and intrinsic muscle weakness.

Treatment Outcomes

Case Series

Beavis et al • Foot Ankle Int, 2008 (2008)

Key Findings:

ORIF isolated: 80-85% good results
ORIF calcaneal: 75-85% good results
Conservative: 85-90% good results
Subtalar arthritis: 10-15% with treatment

Clinical Implication: Good outcomes (80-85%) can be achieved with appropriate treatment (ORIF for displaced, conservative for non-displaced), though a risk of subtalar arthritis persists.

Exam Viva Scenarios

Practice these scenarios to excel in your viva examination

VIVA SCENARIOStandard

Scenario 1: Isolated Sustentaculum Fracture

EXAMINER

"A 35-year-old patient presents with medial heel pain after inversion injury. CT shows isolated displaced sustentaculum tali fracture with 3mm displacement. Clinical examination shows loss of great toe flexion (FHL dysfunction)."

EXCEPTIONAL ANSWER

This is an isolated displaced sustentaculum tali fracture with FHL dysfunction in a 35-year-old patient. I would take a systematic approach: First, confirm the diagnosis: Isolated displaced sustentaculum tali fracture with 3mm displacement (greater than 2mm threshold), loss of great toe flexion (FHL dysfunction), and medial heel pain after inversion injury. The sustentaculum tali is the medial shelf of calcaneus, and FHL tendon runs beneath it. FHL dysfunction indicates potential FHL injury. Second, assess severity: 3mm displacement exceeds the 2mm threshold for surgical treatment. FHL dysfunction indicates functional impairment requiring ORIF. CT shows fragment size and relationship to FHL. Third, surgical management: ORIF is required for displaced fractures to restore subtalar joint congruity and prevent arthritis. Technique: Medial approach to calcaneus, identify and protect FHL tendon (runs beneath sustentaculum - critical structure), identify and protect medial plantar nerve (runs medial to sustentaculum, between abductor hallucis and flexor digitorum brevis), expose sustentaculum, reduce fragment anatomically to calcaneus, fix with screws (2.7-3.5mm) from medial to lateral, verify reduction and hardware position fluoroscopically, verify FHL function restored (test great toe flexion). 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/CT. I would counsel about good outcomes (80-85% good results with ORIF) but potential complications (FHL injury 5-10%, medial plantar nerve injury 5-10%, subtalar arthritis 10-15%). The key point is that displacement greater than 2mm with FHL dysfunction requires ORIF, and FHL and medial plantar nerve must be protected during medial approach.

KEY POINTS TO SCORE

Sustentaculum tali = medial shelf of calcaneus

FHL tendon runs beneath sustentaculum - at risk

Medial plantar nerve runs medial to sustentaculum - at risk

ORIF required if displaced (80-85% good results)

COMMON TRAPS

✗Not recognising FHL dysfunction - key finding

✗Not protecting FHL and medial plantar nerve - causes injury

✗Missing the diagnosis - CT usually required

✗Not understanding sustentaculum as stable reference

LIKELY FOLLOW-UPS

"What structures are at risk in the medial approach?"

"How does sustentaculum serve as stable reference?"

"What are the complications of untreated fractures?"

VIVA SCENARIOChallenging

Scenario 2: Sustentaculum in Calcaneal Fracture

EXAMINER

"A 30-year-old patient has a displaced calcaneal fracture (Sanders Type II). The examiner asks you to explain how you use the sustentaculum tali in the reduction."

EXCEPTIONAL ANSWER

I will explain how I use sustentaculum tali as the stable reference for calcaneal fracture reduction. Key principle: Sustentaculum tali usually stays attached to talus via interosseous ligament, so it remains in anatomic position and serves as the template for reducing all other calcaneal fragments. Technique: First, identify sustentaculum: On CT, sustentaculum is the medial shelf of calcaneus, forms middle facet of subtalar joint. It is usually intact and attached to talus. Second, use as reference: Sustentaculum serves as the Rosetta Stone of calcaneal fracture reduction - all other fragments are reduced TO the sustentaculum. The reduction sequence is: (1) Reduce lateral wall first (elevate superiorly and laterally), (2) Reduce posterior facet to sustentaculum (elevate depressed fragments, align articular surface to sustentaculum middle facet), (3) Reduce tuberosity (restore Bohler angle), (4) Correct varus. Third, verify reduction: Check posterior facet articular reduction by aligning to sustentaculum middle facet. Use Broden views on fluoroscopy (30° and 45° internal rotation) to see articular surface. Direct visualization through superior window also confirms alignment to sustentaculum. Fourth, fixation: Screws from lateral plate aim toward sustentaculum medially (capture sustentaculum fragment, provide medial support). May also place screws directly from medial if sustentaculum displaced. The key point is that sustentaculum is the only fragment that stays in anatomic position, so everything else is reduced to it. This is why it's called the stable reference.

KEY POINTS TO SCORE

Sustentaculum stays attached to talus via interosseous ligament

Serves as template for reducing other fragments

Reduce posterior facet to sustentaculum middle facet

Screws from lateral plate aim toward sustentaculum

COMMON TRAPS

✗Not identifying sustentaculum - reduction has no reference

✗Not using sustentaculum as template - leads to malreduction

✗Not verifying articular reduction to sustentaculum - causes arthritis

✗Not capturing sustentaculum with screws - loss of reduction

LIKELY FOLLOW-UPS

"Why does sustentaculum stay in anatomic position?"

"How do you verify articular reduction to sustentaculum?"

"What happens if sustentaculum is also fractured?"

MCQ Practice Points

Sustentaculum Tali

Q: What is the sustentaculum tali and why is it important in calcaneal fractures? A: Sustentaculum tali = medial shelf of calcaneus - Usually stays attached to talus via interosseous ligament, so it remains in anatomic position. Serves as stable reference for reducing other calcaneal fragments. Critical in calcaneal fracture ORIF.

FHL at Risk

Q: What structure is at risk beneath the sustentaculum tali? A: FHL (Flexor Hallucis Longus) tendon - Runs beneath sustentaculum. Injury causes loss of great toe flexion. Medial approach requires careful dissection to protect FHL. Injury occurs in 5-10% of medial approaches.

Medial Plantar Nerve

Q: What nerve is at risk medial to the sustentaculum tali? A: Medial plantar nerve - Runs medial to sustentaculum, between abductor hallucis and flexor digitorum brevis. Injury causes medial foot numbness and intrinsic muscle weakness. Protect during medial approach (5-10% injury rate).

Stable Reference

Q: How is sustentaculum tali used in calcaneal fracture reduction? A: Serves as stable reference - Usually stays attached to talus via interosseous ligament, so remains in anatomic position. All other calcaneal fragments are reduced TO the sustentaculum. Posterior facet aligned to sustentaculum middle facet.

ORIF Indications

Q: When is ORIF required for sustentaculum tali fractures? A: Displacement greater than 2mm or part of calcaneal fracture - Prevents subtalar arthritis and FHL dysfunction. Medial approach with protection of FHL and medial plantar nerve. Screw fixation from medial to lateral. Success rate 80-85%.

Australian Context

Clinical Practice

Sustentaculum fractures rare but important
Usually part of calcaneal fractures
FHL and medial plantar nerve protection critical
ORIF standard for displaced fractures

Healthcare System

Public hospitals handle most cases
Private insurance covers procedures
High-energy trauma common

Orthopaedic Exam Relevance

Sustentaculum tali fractures are a common viva topic. Know that sustentaculum = medial shelf (stable reference for calcaneal reduction), FHL tendon runs beneath (at risk in medial approach), medial plantar nerve runs medial (at risk in medial approach), ORIF required if displaced (80-85% good results), and sustentaculum serves as template for calcaneal fracture reduction. Be prepared to discuss the medial approach and structures at risk.