High Yield Overview

SACRAL FRACTURES

High-Energy Posterior Pelvic Injuries | Denis Zones | Neurological Risk

45%Of pelvic fractures

30-50%Missed on plain X-ray

5-60%Neurological injury (zone-dependent)

Denis I/II/IIIKey classification zones

DENIS CLASSIFICATION (ZONES)

Zone I (Lateral)

PatternLateral to foramina - L5 nerve at risk

Treatment5-10% neuro injury rate

Zone II (Transforaminal)

PatternThrough foramina - S1-S2 roots at risk

Treatment25-30% neuro injury rate

Zone III (Central)

PatternMedial to foramina - cauda equina at risk

TreatmentUp to 60% neuro injury rate

Critical Must-Knows

Denis zones predict NEUROLOGICAL injury risk (lateral to central progression)
CT is ESSENTIAL - 30-50% missed on plain radiographs
Zone III involves sacral canal = cauda equina symptoms (bowel/bladder/sexual)
Spinopelvic dissociation = complete disconnection of spine from pelvis
Document bowel, bladder, sexual function (sacral roots S2-S4)

Examiner's Pearls

"
Zone I: 5-10% neuro injury (L5 nerve - foot drop risk)
"
Zone II: 25-30% neuro injury (S1-S2 roots - plantarflexion/sensation)
"
Zone III: Up to 60% neuro injury (cauda equina - emergency!)
"
U-shaped (Roy-Camille) fractures = spinopelvic dissociation = highest neuro rate
"
SI screws must avoid foramina and target S1 body (safe corridor)

Clinical Imaging

Imaging Gallery

Sacral fracture typing by Denis. (a) Denis I, II and III zones of the sacrum (a1 anterior view, a2 posterior view); (b) a case (male, age 38) of a Denis II type left sacral fracture treated with percu — Sacral fracture typing by Denis. (a) Denis I, II and III zones of the sacrum (a1 anterior view, a2 posterior view); (b) a case (male, age 38) of a DenCredit: Chen H et al. via BMC Musculoskelet Disord via Open-i (NIH) (Open Access (CC BY))

Exam Warning

Sacral fractures are frequently MISSED on plain radiographs (30-50%). CT is ESSENTIAL for diagnosis and surgical planning. The Denis classification predicts neurological injury based on fracture location: Zone I (5-10%), Zone II (25-30%), Zone III (up to 60%). Zone III fractures involve the sacral canal and can cause cauda equina syndrome with bowel, bladder, and sexual dysfunction.

At a Glance Table

Sacral Fractures - Quick Reference

Feature	Zone I	Zone II	Zone III
Location	Lateral to foramina	Through foramina	Medial to foramina
Structure	Alar region	Transforaminal	Sacral canal
Nerve at risk	L5	S1-S4 roots	Cauda equina
Neuro injury rate	5-10%	25-30%	Up to 60%
Key deficit	Foot drop	Weak plantarflexion	Bowel/bladder/sexual
Stability	Usually stable	Variable	Usually unstable

Mnemonic

SACRUMSACRUM - Key Sacral Fracture Concepts

Scan with CT

plain films miss 30-50%

Alar fractures

Zone I) have lowest neuro risk

Central fractures

Zone III) have highest neuro risk

Roots at risk: L5

I), S1-2 (II), cauda (III

U-shaped fractures =

spinopelvic dissociation

Mandatory neuro exam

bowel, bladder, sexual function

Memory Hook:Remember SACRUM for sacral fractures - CT is essential, zones predict neuro injury

Overview

Introduction

Sacral fractures occur in approximately 45% of pelvic ring injuries and are among the most commonly missed fractures in trauma. The dense bony overlap on plain radiographs makes visualization difficult, and CT imaging is essential for diagnosis.

The sacrum plays a critical role as the posterior keystone of the pelvic ring, transferring weight from the spine to the lower extremities. Sacral fractures can occur in isolation (stress fractures, falls) or as part of complex pelvic ring injuries (vertical shear, LC, APC patterns).

Clinical Significance

Why Sacral Fractures Matter:

Frequently missed: Up to 50% missed on plain X-ray
Neurological injury: 5-60% depending on zone
Pelvic stability: Posterior structures provide 60% of ring stability
Chronic pain: Sacroiliac dysfunction common
Associated injuries: Often part of complex polytrauma

Epidemiology

Incidence:

Present in 45% of pelvic ring injuries
Often underdiagnosed (30-50% missed initially)
Insufficiency fractures in elderly common

Mechanism:

High-energy trauma (MVA, falls)
Vertical shear injuries
Lateral compression injuries
Insufficiency fractures (osteoporosis)

Demographics:

Bimodal distribution
Young: High-energy trauma
Elderly: Insufficiency fractures

Anatomy and Biomechanics

Sacral Anatomy

Bony Anatomy

Sacrum Structure:

Triangular bone of 5 fused vertebrae (S1-S5)
Forms posterior wall of pelvis
Articulates with L5 above, coccyx below
SI joints bilaterally

Sacral Ala:

Lateral wing-like extensions
L5 nerve root runs on anterior surface
Zone I fractures occur here

Sacral Foramina:

Anterior and posterior openings
Transmit sacral nerve roots
Zone II fractures through these

Sacral Canal:

Central canal housing cauda equina
Zone III fractures involve this
Highest neurological risk

Neural Anatomy

Lumbosacral Plexus:

L5 root: Exits under sacral ala, anterior surface
S1-S4 roots: Exit through sacral foramina
Cauda equina: Within sacral canal

Function by Level:

L5: Great toe extension, dorsiflexion
S1: Ankle plantarflexion, ankle jerk
S2-S4: Bowel, bladder, sexual function

Classification Systems

Denis Classification (Most Important)

The Denis classification divides the sacrum into three longitudinal zones based on location relative to the sacral foramina. This classification predicts neurological injury risk.

Location:

Lateral to sacral foramina
Sacral ala region (wing)

Neural Structures at Risk:

L5 nerve root (runs on anterior ala surface)

Neurological Injury Rate:

5-10%

Clinical Presentation:

Foot drop (L5 weakness)
Weak great toe extension
Sensory loss dorsum of foot
Usually stable fracture

Management:

Often conservative if minimally displaced
SI screws if unstable or displaced

Roy-Camille Classification (Transverse Fractures)

For transverse sacral fractures specifically:

Type I: Flexion injury, no kyphosis Type II: Flexion with posterior displacement and angulation Type III: Extension injury with anterior displacement Type IV: Comminuted fracture pattern

Spinopelvic Dissociation

Definition:

Complete disconnection of spine from pelvis
Usually bilateral transverse sacral fractures
U-shaped or H-shaped patterns

Key Features:

Upper sacrum moves with spine
Lower sacrum/pelvis moves independently
Highest neurological injury rates (often greater than 60%)
Requires lumbopelvic fixation

Recognition:

Bilateral vertical fractures through sacrum
Connecting transverse fracture component
On imaging: spine-pelvis discontinuity

Mnemonic

ZONESZONES - Neuro Injury Rates

Zone I = 5-10%

five percent for Zone one

Oh! Zone II = 25-30%

twenty-five to thirty

Now Zone III = Up to 60%

highest

Each zone moves

medial = increasing risk

Sacral canal involvement

= cauda equina

Memory Hook:ZONES increase in neuro risk as you move medially toward the canal

Clinical Assessment

Primary Survey

Sacral fractures occur in major trauma context. Assessment follows ATLS principles.

Mechanism History

High-Energy:

Motor vehicle accident
Fall from height
Pedestrian struck
Motorcycle accident

Low-Energy:

Insufficiency fractures
Falls in elderly
Osteoporosis-related

Physical Examination

Inspection:

Ecchymosis over sacrum (Morel-Lavallee lesion possible)
Lower extremity posture
Gluteal swelling

Palpation:

Sacral tenderness
Step-off or crepitus
SI joint tenderness

Rectal Examination:

Assess rectal tone (S2-S4)
Rule out open fracture
Palpate for bony fragments

Neurological Examination (CRITICAL)

Document DETAILED neurological examination in ALL sacral fractures. Include motor function (L5-S1), sensory examination, rectal tone, bulbocavernosus reflex, and specifically ask about bowel, bladder, and sexual function. Zone III fractures can cause permanent cauda equina syndrome.

Motor Assessment:

Hip extension (L5-S1)
Knee flexion (S1-2)
Great toe extension (L5) - KEY
Ankle plantarflexion (S1-2)
Ankle dorsiflexion (L4-5)

Sensory Assessment:

Dorsum of foot (L5)
Lateral foot (S1)
Posterior thigh (S2)
Perianal sensation (S2-S4) - saddle area

Reflex Testing:

Ankle jerk (S1-2)
Bulbocavernosus reflex (S2-S4)
Anal wink (S2-S4)

Specific Questions:

Urinary retention or incontinence
Fecal incontinence
Erectile dysfunction (males)
Vaginal sensation (females)

Investigations

Imaging Protocol

Plain Radiography

AP Pelvis:

Often inadequate for sacral fractures
Look for: Asymmetry, cortical disruption
Foraminal lines may be disrupted
Miss rate: 30-50%

Lateral Sacrum:

Better visualization
Assess for kyphosis
Still often inadequate

Ferguson View (AP Sacrum):

30-degree cephalad tilt
Better visualization of foramina
Rarely used in acute trauma

CT Imaging (ESSENTIAL)

Why CT is Mandatory:

Plain films miss 30-50%
Defines fracture pattern precisely
Denis zone classification
Foraminal involvement
Associated pelvic injuries

Key Findings:

Fracture location (Denis zone)
Transverse vs longitudinal
Displacement and comminution
Foraminal compromise
Sacral canal involvement

3D Reconstruction:

Excellent for surgical planning
Demonstrates complex patterns
Communication tool

MRI

Indications:

Neurological deficit
Suspected cauda equina compression
Insufficiency fractures (edema pattern)
Soft tissue assessment

Findings:

Nerve root compression
Canal stenosis
Bone marrow edema
Soft tissue injury

Management Algorithm

Decision-Making Framework

Indications:

Zone I with minimal displacement (less than 5mm)
Stable pelvic ring
No neurological deficit
Insufficiency fractures (first line)

Protocol:

Initial bed rest (2-4 weeks)
Progressive mobilization
Weight-bearing as tolerated
Analgesia (paracetamol, NSAIDs, opioids)
DVT prophylaxis (LMWH)
Serial radiographs (1, 2, 6 weeks)
Physiotherapy for mobilization

Expected Outcomes:

Most heal at 6-12 weeks
Return to function gradual
Monitor for late complications

Surgical Technique

Percutaneous Sacroiliac Screws

Indications:

Zone I and II fractures
Longitudinal sacral fractures
SI joint instability
Stable to moderately unstable patterns

Patient Positioning:

Supine on radiolucent table
Lateral decubitus alternative

Equipment:

7.3mm or 7.0mm cannulated screws
Fluoroscopy (inlet, outlet, lateral views)
Guidewires, cannulated instruments

Technique Steps:

Imaging Setup:
- Obtain true AP pelvis (inlet view)
- Obtain outlet view (40 degrees caudal)
- Obtain lateral sacrum view
- Mark S1 body corridor
Entry Point:
- Posterior ilium lateral to SI joint
- Approximately 1cm superior to greater sciatic notch
- Avoid L5 nerve anteriorly
Guidewire Insertion:
- Advance under fluoroscopic guidance
- Check all three views continuously
- Target S1 body (safe zone)
- Avoid sacral canal medially
- Avoid anterior cortex breach
Screw Placement:
- Measure guidewire depth
- Insert cannulated screw over wire
- Ensure bicortical purchase
- Final confirmation all views
S2 Screw (Optional):
- For greater stability
- Enter more cephalad
- Similar technique

Dangers:

L5 nerve anterior to ala
Sacral canal medially
Anterior vascular structures
Dysmorphic sacrum variants

Mnemonic

SCREWSCREW - SI Screw Safe Placement

S1 body is the safe zone

not ala

Check inlet, outlet,

and lateral views

Recognize L5 nerve

anterior to ala

Enter posterior ilium

lateral to SI joint

Watch for dysmorphic

sacrum variants

Memory Hook:Use SCREW safely - target S1 body with three fluoroscopic views

Complications

Early Complications

Neurological Injury:

Most significant complication
Zone-dependent rates (I: 5-10%, II: 25-30%, III: up to 60%)
May be permanent especially Zone III
Document baseline and monitor closely

Hemorrhage:

Presacral venous plexus injury
Part of pelvic hemorrhage with ring injuries
Usually managed with pelvic trauma protocol
Angioembolization if ongoing bleeding
Rarely requires surgical exploration

Thromboembolic Events:

High DVT risk (pelvic trauma)
Prolonged immobility increases risk
Chemical prophylaxis essential (LMWH)
Mechanical prophylaxis (compression devices)
Early mobilization when possible

Infection:

Wound infection (surgical cases)
Deep infection rare
Higher risk with open fractures
Prophylactic antibiotics per protocol

Late Complications

Chronic Pain:

Sacroiliac dysfunction common (30-40%)
Neuropathic pain
Mechanical pain
May require multimodal management
SI joint injections
Pain clinic referral

Malunion:

Kyphotic deformity (transverse fractures)
Leg length discrepancy possible
Gait abnormality
SI joint dysfunction
May need corrective surgery

Nonunion:

Rare with adequate fixation (less than 5%)
More common with conservative treatment
May need revision surgery
Bone grafting and rigid fixation

Sexual Dysfunction:

S2-S4 root involvement
Erectile dysfunction in males
Vaginal sensation loss in females
Counseling important
May be permanent
Impacts quality of life significantly

Bowel/Bladder Dysfunction:

S2-S4 root injury
May require long-term management
Intermittent catheterization
Bowel regimen
Multidisciplinary approach
Urology/colorectal consultation

Implant-Related Complications:

Screw malposition
Nerve injury from screw
Implant prominence (lumbopelvic fixation)
Implant failure (rare with modern techniques)
May require removal after union

Postoperative Care

Immediate Postoperative Period

Monitoring:

Neurological observations (especially if decompression performed)
Motor and sensory function q4h initially
Bowel and bladder function
Wound checks
DVT prophylaxis

Pain Management:

Multimodal analgesia
IV opioids initially
Transition to oral medications
Neuropathic pain agents if needed (gabapentin, pregabalin)

Early pain control is essential for neurological recovery and patient comfort.

Outcomes and Prognosis

Union Rates

Operative Management:

SI screw fixation: Greater than 90% union rate
Lumbopelvic fixation: Greater than 85% union rate
Higher union rates with stable fixation
Nonunion rare with adequate fixation

Conservative Management:

Most heal with conservative treatment
Takes longer (12-16 weeks)
Insufficiency fractures: Good healing rates
May have residual pain even with union

Union typically occurs within 12-16 weeks with appropriate management.

Special Patterns

Insufficiency Fractures

Definition:

Fracture through weakened bone under normal physiological load
Osteoporosis most common cause

Presentation:

Elderly patient
Low back/buttock pain
Gradual onset
No significant trauma

Imaging:

X-ray often negative initially
MRI: Bone marrow edema pattern
CT: Subtle fracture lines

Management:

Usually conservative
Analgesia
Osteoporosis treatment
Sacroplasty if refractory

Stress Fractures

Population:

Athletes, military recruits
Long-distance runners

Presentation:

Activity-related pain
Gradual onset
Improves with rest

Management:

Activity modification
Typically heals with rest
Bone health assessment

H-Type and U-Type Sacral Fractures

H-Type:

Bilateral vertical fractures
Connected by transverse fracture
H-shaped pattern

U-Type:

Bilateral vertical fractures through ala
Connected by transverse fracture through body
Complete spinopelvic dissociation

Significance:

Highest neurological injury rates
Complete spine-pelvis disconnection
Requires lumbopelvic fixation

Evidence and Guidelines

Denis Classification Neurological Outcomes

Level III

Denis F et al. • Clinical Orthopaedics (1988)

Key Findings:

Neurological injury rates increase with zone: Zone I (5-10%), Zone II (25-30%), Zone III (up to 60%). Central fractures involving the sacral canal have highest risk of permanent deficit.

Clinical Implication: Use Denis zones to counsel patients about neurological prognosis. Zone III requires urgent evaluation for canal decompression.

CT Detection of Sacral Fractures

Level III

Frymoyer JW et al. • Spine (1990)

Key Findings:

Plain radiographs miss 30-50% of sacral fractures due to overlying bowel gas and bony complexity. CT imaging is the gold standard for detection and classification.

Clinical Implication: CT is mandatory for suspected sacral fractures. Never rely on negative plain radiographs to exclude sacral injury.

Lumbopelvic Fixation for Spinopelvic Dissociation

Level IV

Schildhauer et al. • Journal of Orthopaedic Trauma (2006)

Key Findings:

Lumbopelvic fixation (triangular osteosynthesis) provides stable fixation for spinopelvic dissociation. Allows early mobilization and has acceptable union rates.

Clinical Implication: Lumbopelvic fixation is the treatment of choice for U-type fractures and spinopelvic dissociation.

Timing of Sacral Decompression

Level IV

Lindahl et al. • Journal of Bone and Joint Surgery (1999)

Key Findings:

Early decompression (less than 72 hours) in Zone III fractures with neurological deficit associated with better neurological recovery compared to delayed decompression.

Clinical Implication: Zone III fractures with neurological deficit are surgical emergencies. Plan for early decompression when cauda equina is compromised.

Sacroplasty for Insufficiency Fractures

Level IV

Frey ME et al. • American Journal of Neuroradiology (2007)

Key Findings:

Sacroplasty provides significant pain relief for sacral insufficiency fractures refractory to conservative treatment. Complication rates are low in experienced hands.

Clinical Implication: Consider sacroplasty for persistent pain from insufficiency fractures after failed conservative management.

Viva Scenarios

Exam Viva Scenarios

Practice these scenarios to excel in your viva examination

VIVA SCENARIOStandard

Zone II Sacral Fracture with Neuro Deficit

EXAMINER

"A 28-year-old motorcyclist is brought in after a high-speed collision. CT shows a Zone II sacral fracture with displacement through the left S1 and S2 foramina. He has 4/5 left ankle plantarflexion and absent left ankle jerk. Describe your assessment and management."

EXCEPTIONAL ANSWER

Recognition: Zone II (transforaminal) sacral fracture with neurological deficit (S1 dysfunction).

Immediate Assessment:

ATLS approach - evaluate polytrauma
Complete neurological examination including bowel/bladder
Assess for associated pelvic ring injury
Evaluate for other injuries (head, chest, abdomen)

Neurological Documentation:

Motor: L5 (great toe extension), S1 (plantarflexion - 4/5)
Sensory: L5, S1, S2-S4 dermatomal testing
Reflexes: Ankle jerk absent left
Bulbocavernosus reflex, rectal tone
Ask about urinary retention, bowel function

Management:

Neurological deficit with foraminal compromise requires surgery
Options: Percutaneous SI screws with/without decompression
May need posterior approach if decompression required
Address pelvic ring if unstable

KEY POINTS TO SCORE

Zone II = transforaminal = 25-30% neuro injury rate

Document detailed S1 motor (plantarflexion) and sensory

Check bowel/bladder/sexual function (S2-S4)

Incomplete injury has better prognosis than complete

COMMON TRAPS

✗Missing associated pelvic ring injury

✗Not documenting bowel/bladder function

✗Relying on plain X-ray (misses 30-50%)

LIKELY FOLLOW-UPS

"What imaging is essential for sacral fractures?"

"What is the prognosis for Zone II neurological injury?"

"When would you decompress vs stabilize only?"

VIVA SCENARIOStandard

Denis Classification

EXAMINER

"Explain the Denis classification for sacral fractures. Why is this classification clinically important?"

EXCEPTIONAL ANSWER

Denis Classification Overview:

Divides sacrum into three longitudinal zones based on relationship to sacral foramina.

Zone I (Alar/Lateral):

Location: Lateral to all sacral foramina
Involves the sacral ala (wing)
Nerve at risk: L5 (runs on anterior ala surface)
Neurological injury rate: 5-10%
Clinical deficit: Foot drop, dorsum foot numbness

Zone II (Transforaminal):

Location: Through one or more sacral foramina
Most common location for traumatic fractures
Nerves at risk: S1-S4 roots
Neurological injury rate: 25-30%
Clinical deficit: Weak plantarflexion, sensory loss, possible bladder

Zone III (Central):

Location: Medial to foramina, involving sacral canal
Nerves at risk: Cauda equina, all sacral roots
Neurological injury rate: Up to 60%
Clinical deficit: Cauda equina syndrome - bowel, bladder, sexual dysfunction, saddle anesthesia

Clinical Importance:

Predicts neurological injury risk accurately
Guides urgency of intervention
Zone III may require urgent decompression
Helps counsel patients on prognosis
Determines need for detailed bowel/bladder assessment

KEY POINTS TO SCORE

Zone I = lateral to foramina = L5 at risk = 5-10%

Zone II = transforaminal = S1-S4 roots = 25-30%

Zone III = central/canal = cauda equina = up to 60%

Classification predicts neurological risk and guides urgency

COMMON TRAPS

✗Confusing zone locations (I is lateral, III is medial)

✗Underestimating Zone III risk

✗Not explaining clinical relevance of each zone

LIKELY FOLLOW-UPS

"What structure runs on the anterior alar surface?"

"Why is Zone III a surgical emergency?"

"What is spinopelvic dissociation?"

VIVA SCENARIOStandard

Sacral Insufficiency Fracture

EXAMINER

"A 75-year-old woman with osteoporosis presents with 6 weeks of low back and buttock pain. X-rays are unremarkable. MRI shows bone marrow edema in the sacrum bilaterally. What is the diagnosis and management?"

EXCEPTIONAL ANSWER

Diagnosis: Sacral insufficiency fracture

Definition:

Fracture through pathologically weakened bone
Normal physiological load causes fracture
Osteoporosis is primary cause

Clinical Features:

Elderly patient with osteoporosis
Low back/buttock pain
Gradual onset without significant trauma
Often bilateral (H-pattern on MRI)
Weight-bearing worsens pain

Imaging:

X-ray: Often negative initially (this case)
MRI: Bone marrow edema - diagnostic
CT: May show subtle fracture lines
Bone scan: Sensitive but less specific

Conservative Management (First Line):

Analgesia (paracetamol, opioids if needed)
Activity modification
Walking aids
Gradual mobilization as tolerated
DVT prophylaxis if immobile

Osteoporosis Treatment:

DEXA scan to confirm osteoporosis
Calcium and vitamin D supplementation
Bisphosphonates or other anti-resorptive therapy
Falls prevention assessment

Sacroplasty (if Conservative Fails):

CT-guided PMMA injection
Indicated for persistent severe pain
Good pain relief in appropriately selected patients

Prognosis:

Most heal with conservative treatment (6-12 weeks)
Risk of contralateral fracture
Address underlying osteoporosis to prevent recurrence

KEY POINTS TO SCORE

Insufficiency fracture = fragility fracture in weakened bone

X-rays often negative - MRI is diagnostic

Conservative first: analgesia, activity modification, osteoporosis treatment

Sacroplasty for refractory cases

COMMON TRAPS

✗Missing diagnosis because X-rays are normal

✗Not treating underlying osteoporosis

✗Rushing to surgery when conservative effective

LIKELY FOLLOW-UPS

"What pattern does MRI show in insufficiency fractures?"

"When is sacroplasty indicated?"

"How do you prevent recurrence?"

MCQ Practice Points

Denis Classification

Q: What are the neurological injury rates for each Denis zone? A: Zone I (alar) = 5-10% (L5 nerve), Zone II (transforaminal) = 25-30% (S1-S2 roots), Zone III (central) = up to 60% (cauda equina). Zones move lateral to medial with increasing neurological risk.

Imaging Requirements

Q: What is the miss rate for sacral fractures on plain X-ray? A: 30-50% of sacral fractures are missed on plain radiographs. CT is mandatory for diagnosis and classification. MRI is best for neurological assessment.

SI Screw Technique

Q: What is the safe zone for SI screw placement? A: The S1 body is the target. Use three fluoroscopic views (inlet, outlet, lateral). L5 nerve is at risk anteriorly, sacral canal at risk medially. Watch for dysmorphic sacrum.

Spinopelvic Dissociation

Q: What is spinopelvic dissociation and how is it treated? A: Complete disconnection of spine from pelvis seen in U-shaped or H-shaped sacral fractures. Requires lumbopelvic fixation (triangular osteosynthesis) with L4/L5 pedicle screws to bilateral iliac screws.

Zone III Emergency

Q: Why is Zone III a surgical emergency? A: Zone III involves the sacral canal causing cauda equina syndrome with bowel, bladder, and sexual dysfunction (S2-S4). Early decompression (less than 72 hours) improves neurological outcomes.

Australian Context

Epidemiology in Australia

Sacral fractures in Australia follow similar patterns to international data, occurring in approximately 45% of major pelvic trauma cases. High-energy motor vehicle accidents remain the most common mechanism in younger patients, while insufficiency fractures are increasingly recognized in the aging Australian population with osteoporosis.

Trauma System Considerations

Major trauma patients with suspected pelvic and sacral fractures are managed through state trauma systems with direct transfer to major trauma centers. Early CT imaging is routine in Australian trauma protocols, improving sacral fracture detection rates compared to historical plain radiography-only approaches.

Surgical Access and Expertise

Percutaneous SI screw fixation and lumbopelvic fixation for sacral fractures are performed at major trauma centers across Australia. Specialized pelvic trauma surgeons are available in metropolitan centers. Regional patients with complex sacral fractures may require retrieval to tertiary centers for definitive management.

Rehabilitation Services

Comprehensive spinal and pelvic rehabilitation programs are available through public and private systems. Patients with significant neurological deficits, particularly bowel and bladder dysfunction, have access to specialized spinal injury rehabilitation units in major cities.

Osteoporosis Management

Following insufficiency fractures, patients are referred for bone health assessment and osteoporosis treatment. DEXA scanning is widely available, and bisphosphonates are commonly prescribed. Multidisciplinary falls prevention programs help reduce recurrent fracture risk in elderly patients.

Exam Focus Points

High-Yield Concepts

Exam Pearl

DENIS ZONES = NEUROLOGICAL RISK: Zone I = 5-10% (L5), Zone II = 25-30% (S1-S2), Zone III = Up to 60% (cauda equina). The zones move lateral to medial, with risk increasing toward the canal. Zone III involves the sacral canal and can cause bowel/bladder/sexual dysfunction.

Key Numbers

30-50%: Miss rate on plain X-ray
Zone I: 5-10% neuro injury
Zone II: 25-30% neuro injury
Zone III: Up to 60% neuro injury

Surgical Decision-Making

Conservative:

Stable, minimally displaced Zone I
No neurological deficit
Insufficiency fractures

Operative:

Neurological deficit with canal compromise
Unstable pelvic ring
Spinopelvic dissociation
Zone III with cauda equina

Special Patterns

U-shaped/H-shaped: Spinopelvic dissociation, lumbopelvic fixation required
Insufficiency fractures: Conservative first, sacroplasty if refractory