Vertical Shear (VS) Pelvic Injuries
Complete pelvic ring disruption with vertical/cephalad hemipelvic displacement
Young-Burgess VS Classification
Critical Must-Knows
- VERTICAL displacement distinguishes VS from LC/APC patterns
- Always Tile C - completely unstable rotationally AND vertically
- Highest energy mechanism - fall from height or MVA with axial load
- ALL ligaments disrupted - no inherent stability remains
- Both anterior AND posterior fixation MANDATORY
Examiner's Pearls
- "Limb length discrepancy is pathognomonic (hemipelvis migrates cephalad)
- "Look for 'Destot sign' - perineal/scrotal hematoma from hemorrhage
- "Neurological injury common - L5, lumbosacral plexus
- "Combined patterns exist (VS + LC, VS + APC) - look for rotation too
- "Often associated with acetabular fractures
Exam Warning
Vertical shear injuries are the HIGHEST ENERGY pelvic injuries with COMPLETE instability. The hemipelvis displaces VERTICALLY (cephalad), not just rotationally. This distinguishes VS from LC-III and APC-III, which have rotational instability but limited vertical displacement. VS injuries ALWAYS require both anterior AND posterior fixation - there is no conservative option for true VS patterns.
At a Glance: VS vs Other Unstable Patterns
| Feature | LC-III | APC-III | VS |
|---|---|---|---|
| Primary displacement | Rotational | Rotational | Vertical (cephalad) |
| Mechanism | Internal rotation | External rotation | Axial load |
| Vertical instability | Variable | Variable | Always present |
| Rotational instability | Yes | Yes | May be minimal |
| Limb shortening | Minimal | Minimal | Significant |
| Tile equivalent | C1 | C1 | C1-C3 |
| Hemorrhage risk | Moderate | Highest | High |
| Neurological injury | Lower | Moderate | Highest (30-50%) |
VERTICALVERTICAL - VS Injury Features
Memory Hook:VS injuries cause VERTICAL displacement - remember the complete instability and mandatory surgical fixation
Overview
Introduction
Vertical shear (VS) pelvic injuries represent the most severe form of pelvic ring disruption. Unlike lateral compression (LC) and anteroposterior compression (APC) injuries, which have components of rotational instability, VS injuries have complete disruption of all stabilizing structures allowing the hemipelvis to migrate vertically (cephalad) relative to the sacrum.
These injuries result from high-energy axial loading mechanisms and are characterized by the complete loss of the weight-bearing function of the pelvic ring. The term "vertical shear" refers to the direction of the displacing force and resultant displacement pattern.
Epidemiology
Incidence:
- 5-10% of all pelvic ring injuries
- Least common of the major injury patterns
- Most severe subtype
Mechanism:
- Fall from height landing on extended leg (most common)
- Motor vehicle collision with axial load
- Motorcycle ejection
- Pedestrian struck
Demographics:
- Young adults predominate
- Often high ISS scores
- Polytrauma almost universal
- Occupational (falls from scaffolding, construction)
Clinical Significance
Why VS Injuries Are Most Severe:
- Complete instability: No residual ligamentous support
- High energy: Greater associated injuries
- Weight-bearing lost: Cannot transmit load
- Neurological injury: Traction on lumbosacral plexus
- Hemorrhage: Significant (though less than APC typically)
Anatomy and Pathophysiology
Pelvic Ring Stability
The pelvis functions as a ring structure. When disrupted, the injury cannot occur at a single location - there must be a second break in the ring (or a combination of bone and ligament injuries).
Stabilizing Structures
Posterior Tension Band (Primary Stability):
- Posterior SI ligaments (strongest)
- Interosseous SI ligaments
- Sacrotuberous ligament
- Sacrospinous ligament
- Iliolumbar ligaments
Anterior Structures:
- Pubic symphysis
- Pubic rami
- Anterior SI ligaments
VS Injury Pathoanatomy
In vertical shear injuries, BOTH anterior and posterior structures fail completely:
Anterior Disruption:
- Symphysis diastasis, OR
- Pubic rami fractures (ipsilateral), OR
- Combined symphysis and rami injury
Posterior Disruption:
- Sacral fracture (Denis zone I-III), OR
- SI joint diastasis (complete), OR
- Iliac wing fracture (crescent pattern)
Force Vectors
Classic Mechanism:
- Axial load through extended lower extremity
- Force transmitted through femur to acetabulum
- Hemipelvis driven cephalad
- Sequential failure: anterior then posterior, or vice versa
Resultant Displacement:
- Vertical (cephalad) translation
- May have rotational component (combined injury)
- Shortening of affected lower limb
Associated Soft Tissue Injuries
Vascular:
- Superior gluteal artery
- Internal iliac branches
- Presacral venous plexus
- Less severe bleeding than APC (closed ring effect)
Neurological:
- L5 nerve root (exits under ala)
- Lumbosacral trunk
- S1-S4 roots (sacral fractures)
- Overall neurological injury rate: 30-50%
SHEARSHEAR - Posterior Injury Patterns
Memory Hook:VS injuries SHEAR the posterior structures - sacral fractures are most common
Classification
Classification
Vertical Shear (VS)
Definition:
- Complete anterior AND posterior pelvic ring disruption
- Vertical (cephalad) displacement of hemipelvis
- No rotational component (distinguishes from LC-III, APC-III)
Key Features:
- Axial load mechanism
- Complete ligamentous disruption posteriorly
- Tile C equivalent
- Always surgically treated
Combined Mechanical Injury (CMI)
Definition:
- VS pattern combined with LC or APC component
- Also known as "complex" pelvic injuries
Examples:
- VS + LC: Vertical displacement with internal rotation
- VS + APC: Vertical displacement with external rotation (windswept)
Clinical Relevance:
- More complex surgical planning
- May need combined approaches
- Higher complication rates
These combined patterns require careful preoperative planning and may necessitate multiple surgical approaches.
DENISDENIS - Sacral Fracture Zones
Memory Hook:DENIS classification for sacral fractures - zones go lateral to medial with increasing neuro risk
Clinical Assessment
Primary Survey
VS injuries occur in major trauma context. Assessment follows ATLS principles.
Mechanism History
High-Risk Mechanisms:
- Fall from height greater than 3 meters
- Motorcycle ejection
- Pedestrian vs vehicle
- Industrial crush injury
- Landing on extended leg
Physical Examination
Inspection:
- Limb length discrepancy (SHORT LEG on affected side)
- Asymmetric iliac crest heights
- Destot sign: Scrotal/labial hematoma
- Perineal ecchymosis
- External rotation or internal rotation component
TRUE LIMB LENGTH DISCREPANCY with a pelvic fracture indicates VERTICAL SHEAR until proven otherwise. The affected limb appears shortened because the hemipelvis has migrated cephalad. This is NOT the same as apparent shortening from hip pathology.
Palpation:
- Iliac crest height asymmetry
- SI joint tenderness
- Symphysis gap or step-off
- Single pelvic spring test (ONCE only)
Measurement:
- Measure ASIS to medial malleolus bilaterally
- True shortening indicates vertical displacement
- Document amount of leg length discrepancy
Neurological Examination (CRITICAL)
Motor Assessment:
- Hip flexion (L1-2)
- Knee extension (L3-4)
- Ankle dorsiflexion (L4-5) - L5 most vulnerable
- Great toe extension (L5)
- Ankle plantarflexion (S1-2)
Sensory Assessment:
- L5 dermatome: Dorsum of foot
- S1 dermatome: Lateral foot
- Perineal sensation: S2-S4
Reflexes and Special Tests:
- Ankle jerk (S1)
- Bulbocavernosus reflex (sacral roots)
- Rectal tone
Documentation:
- ASIA score if complete injury
- Detailed motor/sensory documentation
- Serial examinations (may evolve)
Associated Injuries
Common Associations:
- Acetabular fractures
- Proximal femur fractures
- Lumbar spine fractures
- Intra-abdominal injuries
- Head injuries
Investigations
Imaging Approach
Plain Radiography
AP Pelvis:
- First-line in trauma bay
- Assess for vertical displacement
- Compare iliac crest heights
- Compare obturator foramen size (smaller on elevated side)
Radiographic Signs of Vertical Displacement:
- Cephalad migration of hemipelvis
- Asymmetric iliac crest heights
- Different sized obturator foramina
- Superior displacement of ischial tuberosity
Inlet View:
- Posterior displacement
- SI joint widening
- Rotational component
Outlet View:
- Vertical displacement best seen
- Sacral fracture visualization
- Foraminal involvement
CT Imaging
Essential for All VS Injuries:
- Defines posterior injury precisely
- Sacral fracture pattern (Denis zone)
- SI joint injury morphology
- Associated acetabular injury
- Soft tissue hematoma
Key Findings:
- Sacral fracture location and comminution
- SI joint widening and displacement
- Anterior injury pattern
- Vertical displacement measurement
3D Reconstruction:
- Surgical planning
- Demonstrates displacement clearly
- Communication with patient/team
MRI (Selective Use)
Indications:
- Neurological deficit
- Suspected cauda equina injury
- Soft tissue planning for complex reconstruction
Findings:
- Nerve root compression
- Disc herniation (traumatic)
- Ligament integrity
Management Algorithm
Treatment Decision-Making
Hemorrhage Control
Pelvic Binder:
- Apply as per protocol
- Less effective for VS than APC (vertical, not rotational displacement)
- Still provides some stabilization
- Does NOT reduce vertical displacement
Skeletal Traction:
- May help with vertical reduction
- Distal femoral pin preferred
- 10-15kg initial weight
- Temporizing measure
Damage Control
Principles:
- External fixation if hemodynamically unstable
- Does NOT address vertical displacement
- Bridge to definitive fixation
- May need skeletal traction additionally
Damage control is a temporizing measure only - definitive fixation required once stable.
FIXFIX - VS Surgical Principles
Memory Hook:VS injuries need complete FIX - anterior AND posterior fixation is mandatory
Surgical Technique
Percutaneous Iliosacral Screw Fixation
Indications
- SI joint dislocation
- Sacral ala fractures (Denis Zone I-II)
- Most common posterior fixation method
Positioning
- Supine on radiolucent table (allows anterior access if needed)
- Alternative: Prone or lateral decubitus
- C-arm positioned for inlet, outlet, and lateral sacral views
Anatomical Safe Zones
S1 Body:
- Primary target zone
- Widest safe corridor
- Parallel to S1 superior endplate
Dangers:
- Anterior: Iliac vessels, L5 nerve root
- Lateral: L5 nerve in ala
- Superior: L5-S1 disc
- Inferior: S1 foramen
Understanding the safe corridor within the S1 body is essential for safe SI screw placement.
Complications
Early Complications
Hemorrhage:
- Significant but typically less than APC
- Retroperitoneal hemorrhage
- Presacral venous plexus
Neurological Injury:
- Most common complication (30-50%)
- L5 root most vulnerable
- Sacral root injuries with sacral fractures
- Cauda equina syndrome with Zone III
Thromboembolic:
- Very high DVT risk
- Early prophylaxis essential
- May need IVC filter if anticoagulation contraindicated
Infection:
- Open fractures: High risk
- Surgical site infection
- Higher with extensive approaches
Late Complications
Malunion:
- Residual vertical displacement
- Limb length discrepancy
- Gait abnormality
- Painful weight bearing
Nonunion:
- Sacral nonunion (more common with vertical pattern)
- SI joint nonunion
- May need revision fixation or fusion
Neurological Deficit (Permanent):
- Footdrop (L5)
- Bladder/bowel dysfunction (sacral roots)
- Sexual dysfunction
- May require long-term management
Hardware Complications:
- SI screw loosening
- Screw migration
- Symptomatic hardware
Chronic Pain:
- SI joint arthritis
- Sacral pain
- Low back pain
Postoperative Care
Immediate Postoperative Management
Weight Bearing:
- Non-weight bearing for 8-12 weeks minimum
- Bilateral VS injuries: May need 12-16 weeks
- Gradual progression based on healing
Mobilization:
- Bed to chair with walker assistance
- Upper extremity strengthening
- Core stability exercises (non-weight bearing)
DVT Prophylaxis:
- Essential given immobility
- LMWH or direct oral anticoagulants
- Sequential compression devices
- Continue until mobile
Pain Management:
- Multimodal analgesia
- Regional techniques if available
- Minimize opioids when possible
Monitoring
Serial Neurological Exams:
- Daily for first week
- Document any changes
- May see delayed deficits
Radiographic Follow-up:
- AP pelvis at 2, 6, 12 weeks
- Inlet/outlet views as needed
- CT if concern for loss of reduction
Wound Care:
- Monitor for infection
- Percutaneous wounds typically heal quickly
- Open approaches need standard care
Rehabilitation Protocol
Phase 1 (0-6 weeks):
- Non-weight bearing
- Upper body conditioning
- Hip isometrics
- Core strengthening
Phase 2 (6-12 weeks):
- Progressive weight bearing if healing confirmed
- Gait training with assistive devices
- Hip strengthening
- Balance exercises
Phase 3 (12+ weeks):
- Full weight bearing
- Advanced strengthening
- Proprioceptive training
- Return to activities
Long-term Follow-up
Clinical Assessment:
- Gait pattern
- Leg length discrepancy (persistent)
- Neurological status
- Pain levels
Functional Goals:
- Independent ambulation
- Return to work (variable timeline)
- Activities of daily living
Complications Monitoring:
- SI joint arthritis symptoms
- Hardware symptoms
- Chronic pain
Outcomes/Prognosis
Functional Outcomes
Overall Results
Good to Excellent Outcomes:
- 60-70% with appropriate treatment
- Depends heavily on:
- Neurological injury
- Associated injuries
- Quality of reduction
- Fixation stability
Poor Prognostic Factors:
- Neurological injury (30-50% incidence)
- Bilateral injuries
- Zone III sacral fractures
- Delayed fixation
- Malunion/nonunion
Neurological Recovery
Complete Recovery:
- L5 nerve: 50-60% recovery rate
- S1 nerve: 60-70% recovery rate
- Sacral roots: Variable, often partial
Permanent Deficits:
- Footdrop requiring AFO: 15-20%
- Bladder dysfunction: 5-10% (Zone III injuries)
- Sexual dysfunction: Variable
Recovery Timeline:
- Improvement may continue 12-24 months
- Peak recovery typically 6-12 months
Return to Activities
Ambulation:
- Independent walking: 3-6 months
- Normal gait pattern: 6-12 months
- May have permanent limp
Work:
- Sedentary: 3-6 months
- Physical labor: 6-12 months
- May need modifications
Sports:
- Low-impact: 6-9 months
- High-impact: 9-12+ months
- Some activities may be permanently limited
Mortality
Acute Mortality:
- 10-15% in polytrauma setting
- Related to associated injuries
- Higher with bilateral patterns
Long-term Outcomes:
- Most survivors achieve independent function
- Quality of life depends on neurological recovery
- Chronic pain common (30-40%)
Radiographic Outcomes
Union Rates:
- SI joint: 85-90%
- Sacral fractures: 80-85%
- Symphysis: Greater than 95%
Malunion:
- Residual displacement common
- Affects long-term outcomes
- May need corrective surgery
Hardware:
- Removal rarely needed (10-15%)
- SI screws typically well-tolerated
Evidence and Guidelines
Neurological Injury in Vertical Shear
- Neurological injury occurs in 30-50% of vertical shear pelvic injuries, significantly higher than LC (5%) or APC (15%) patterns. L5 and lumbosacral plexus most commonly affected.
Posterior Fixation is Mandatory
- Anterior fixation alone is insufficient for vertically unstable pelvic injuries. Posterior fixation is essential for restoring pelvic stability and allowing weight bearing.
Percutaneous SI Screw Fixation
- Percutaneous iliosacral screw fixation is effective for posterior pelvic ring injuries. Proper technique with fluoroscopic guidance in three planes minimizes nerve injury risk.
Denis Sacral Fracture Classification
- Sacral fractures classified by zone have predictable neurological injury rates: Zone I (5-10%), Zone II (25-30%), Zone III (up to 60%). Zone III injuries often have bowel/bladder dysfunction.
Lumbopelvic Fixation for Spinopelvic Dissociation
- Triangular osteosynthesis (lumbopelvic fixation) provides superior stability for bilateral sacral fractures and spinopelvic dissociation compared to SI screws alone.
Viva Scenarios
Exam Viva Scenarios
Practice these scenarios to excel in your viva examination
"A 32-year-old construction worker fell 8 meters from scaffolding, landing on his feet. He has a shortened right leg and cannot bear weight. AP pelvis shows right hemipelvic cephalad displacement with symphysis diastasis and right sacral fracture. Describe your assessment and management."
Recognition: This is a VERTICAL SHEAR injury - high-energy axial load with vertical hemipelvic displacement.
Initial Assessment:
- ATLS primary survey - high-energy mechanism
- Pelvic binder application (helps, but less effective for VS)
- Document leg length discrepancy (true shortening)
- DETAILED neurological examination - L5, S1, sacral roots
- Perineal sensation, rectal tone (Zone III implications)
- Associated injuries - lumbar spine, calcaneus, acetabulum
Imaging:
- CT pelvis with 3D reconstruction - ESSENTIAL
- Define sacral fracture zone (Denis classification)
- Assess SI joint integrity
- CT spine if clinical concern
Classification:
- Young-Burgess: Vertical Shear (VS)
- Tile: C1.3 (unilateral, sacral fracture)
- Denis: Determine zone from CT
Surgical Management:
- BOTH anterior AND posterior fixation required
- Skeletal traction preoperatively
- Posterior first: SI screws or open reduction depending on pattern
- Anterior: Symphysis plating
- If Zone III sacral fracture - may need lumbopelvic fixation
Postoperative:
- Serial neurological examinations
- Non-weight bearing 8-12 weeks minimum
- DVT prophylaxis
- Physiotherapy when stable
"Explain the difference between vertical shear injuries and APC-III injuries. Why is this distinction important for management?"
Key Distinctions:
Mechanism:
- VS: Axial load (fall on extended leg, vertical vector)
- APC-III: External rotation force (AP compression, horizontal vector)
Displacement Pattern:
- VS: VERTICAL (cephalad) displacement of hemipelvis
- APC-III: ROTATIONAL (external rotation) displacement
- VS shows limb shortening; APC shows widening without shortening
Radiographic Differences:
- VS: Asymmetric iliac crest heights, smaller obturator foramen on elevated side
- APC-III: Symphysis widening, SI widening, but SYMMETRIC iliac crest heights
Clinical Examination:
- VS: True leg length discrepancy (shortened)
- APC-III: May have apparent shortening but not true shortening
Why It Matters:
- Pelvic binder: Very effective for APC (closes book), less effective for VS (doesn't address vertical displacement)
- Skeletal traction: Essential for VS (reduces vertical displacement), not needed for APC
- Reduction: VS needs longitudinal traction; APC needs internal rotation
- Neurological risk: Higher in VS (30-50%) than APC (15%)
Both Require:
- Anterior AND posterior fixation
- But reduction techniques differ significantly
"Describe your technique for percutaneous iliosacral screw fixation. What are the key anatomical considerations and how do you avoid complications?"
Indications:
- SI joint dislocation/subluxation
- Sacral ala fractures (Denis Zone I-II)
- Posterior component of VS injury
Positioning:
- Supine on radiolucent table (preferred for VS - allows anterior access)
- Alternative: Prone or lateral
- Fluoroscopy positioned for inlet, outlet, lateral sacral views
Anatomical Safe Zone:
- Target: S1 BODY (not ala)
- Ala is danger zone - L5 nerve root runs anteriorly
- Safe corridor is within S1 body, parallel to superior endplate
Fluoroscopic Views:
- Inlet: Shows AP position, avoid anterior sacrum
- Outlet: Shows vertical position, avoid foramina
- Lateral sacral: Shows trajectory into S1 body
Technique:
- Entry point: Posterior iliac cortex, lateral to SI joint
- Guide wire advanced under fluoroscopy
- Confirm position in all three views
- Drill and measure
- 7.3mm cannulated partially threaded screw (washer optional)
- May need 2 screws for VS (superior stability)
Avoiding Complications:
- L5 nerve injury: Stay in S1 body, avoid ala, use all three views
- Iliac vessel injury: Confirm position on inlet (not too anterior)
- Malreduction: Reduce BEFORE fixation, not with screw
- Loss of fixation: Adequate screw length, two screws if unstable
MCQ Practice Points
High Yield
Q: What is the KEY distinguishing feature of vertical shear pelvic injuries compared to LC-III and APC-III injuries?
A: VERTICAL (cephalad) displacement of the hemipelvis causing TRUE limb length discrepancy (shortened limb on affected side). Compare iliac crest heights which are asymmetric in VS. LC-III and APC-III have rotational instability but minimal vertical displacement.
High Yield
Q: What is the neurological injury rate in vertical shear injuries and which nerve root is most vulnerable?
A: 30-50% neurological injury rate (highest of all pelvic patterns). L5 nerve root is MOST vulnerable, running anteriorly through the sacral ala. Denis Zone III (central) has highest risk at 60%, Zone II (transforaminal) has 25-30%, and Zone I (alar) has 5-10% risk.
High Yield
Q: A patient with a vertical shear pelvic injury has good reduction achieved with external fixation anteriorly. Can you leave the posterior pelvis untreated if the reduction is maintained?
A: NO - this is a critical exam trap. VS injuries ALWAYS require BOTH anterior AND posterior fixation. Anterior fixation alone is inadequate. The posterior injury is the PRIMARY stability problem. Never leave a VS injury with only anterior stabilization - no exceptions.
High Yield
Q: Where should the iliosacral screw be placed in VS injuries and what is the most serious complication of improper placement?
A: Target the S1 BODY (not the ala), placing the screw parallel to the S1 superior endplate. Three fluoroscopic views required: inlet, outlet, and lateral. L5 nerve injury is the most serious complication from screw placement through the sacral ala. Stay within S1 body to avoid the L5 nerve.
High Yield
Q: A patient fell 10 meters and presents with a shortened right leg and pelvic fracture. What classification is this and what treatment is required?
A: This is a vertical shear injury (Young-Burgess VS, Tile C). Treatment requires BOTH anterior AND posterior fixation. Next steps: detailed neurological exam (especially L5 and sacral roots), CT pelvis with 3D reconstruction to define fracture pattern, and surgical planning for combined fixation.
High Yield
Q: What is the role of pelvic binders in vertical shear injuries compared to APC injuries?
A: Pelvic binders are LESS effective for VS than APC injuries. While binders help with hemorrhage control, they do NOT reduce vertical displacement effectively. VS injuries primarily displace vertically (cephalad), whereas binders work by closing the pelvic ring rotationally. Skeletal traction is more useful for vertical reduction in VS.
Australian Context
Epidemiology
Vertical shear injuries in Australia commonly result from falls in construction and mining industries, particularly in rural and regional areas. Occupational health and safety regulations mandate fall protection, but high-energy falls remain a significant mechanism. Motor vehicle crashes and motorcycle accidents on rural highways also contribute to the VS injury burden.
Trauma Systems
Major Trauma Centers:
- VS injuries require Level 1 trauma center management
- Early transfer essential for definitive fixation
- Retrieval services play critical role in rural areas
Timing:
- Aim for definitive fixation within 24-48 hours once resuscitated
- May need damage control external fixation initially
- Transfer to specialized pelvic trauma unit when appropriate
DVT Prophylaxis
Australian guidelines emphasize extended VTE prophylaxis given prolonged immobility:
- LMWH (enoxaparin 40mg daily) or apixaban 2.5mg BD
- Continue until mobile and weight bearing
- High-risk patients may need 4-6 weeks prophylaxis
- Sequential compression devices in hospital
Rehabilitation
Mobility:
- Early engagement with physiotherapy
- Non-weight bearing walker training
- Upper limb strengthening
- Graduated return to weight bearing under supervision
Return to Work:
- Occupational therapy assessment
- WorkCover claims common given mechanism
- May need workplace modifications
- Physical labor roles often require extended time off (6-12 months)
Neurological Outcomes
Permanent neurological deficits may qualify for disability support. L5 footdrop requiring ankle-foot orthosis is a recognized disability. NDIS support may be available for patients with significant functional limitations from neurological injury.
Exam Focus Points
High-Yield Concepts
Exam Pearl
The KEY distinguishing feature of VS injuries is VERTICAL (cephalad) displacement of the hemipelvis. This causes TRUE leg length discrepancy - measure ASIS to medial malleolus bilaterally. LC-III and APC-III have rotational instability but minimal vertical displacement.
Quick Differentiation
VS vs LC-III:
- VS: Vertical displacement, axial mechanism, high neuro risk
- LC-III: Internal rotation, lateral mechanism, windswept pelvis
VS vs APC-III:
- VS: Vertical displacement, limb shortened
- APC-III: External rotation, open book, highest hemorrhage
Surgical Principles
Non-Negotiables:
- BOTH anterior AND posterior fixation
- Reduce vertical displacement first (traction)
- Posterior fixation is primary stabilization
- SI screws into S1 BODY (not ala)
- Document neurology before and after surgery
Denis Zone Significance
- Zone I: L5 at risk, 5-10% neuro injury
- Zone II: S1 at risk, 25-30% neuro injury
- Zone III: Cauda equina, up to 60%, often permanent
Vertical Shear Injuries - Exam Day Cheat Sheet
High-Yield Exam Summary
Quick Facts
- •Mechanism: Axial load on extended leg (fall from height)
- •Key finding: VERTICAL hemipelvic displacement
- •Clinical sign: True limb length discrepancy (shortening)
- •Destot sign: Scrotal/labial hematoma
- •Neuro risk: 30-50% (highest of all patterns)
- •Tile equivalent: Always Tile C (complete instability)
- •Treatment: BOTH anterior AND posterior fixation
- •SI screw target: S1 BODY (not ala - L5 nerve risk)
Critical Actions
- •VS injury identified → Detailed neuro exam, skeletal traction, plan both anterior and posterior fixation
- •Denis Zone III sacral fracture → High neurological risk, may need lumbopelvic fixation
- •Bilateral VS injury → Consider lumbopelvic fixation (triangular osteosynthesis)
- •SI screw placement → Target S1 body, confirm on inlet/outlet/lateral views, avoid ala
Exam Day Tips
- •VS = VERTICAL displacement = TRUE limb shortening = Tile C
- •30-50% neurological injury rate - document before surgery
- •BOTH anterior AND posterior fixation is mandatory
- •SI screw goes in S1 BODY - ala is danger zone (L5)
- •Denis Zone III = cauda equina risk = may need lumbopelvic fixation
Common Pitfalls
- •Treating with anterior fixation alone (must fix posterior)
- •Missing vertical displacement (compare iliac crest heights)
- •SI screw in ala instead of S1 body (L5 nerve injury)
- •Not documenting neurology preoperatively
- •Relying on binder alone (doesn't address vertical displacement)