Anteroposterior Compression (APC) Pelvic Injuries
External rotation/open book injuries - high hemorrhage risk
Young-Burgess APC Classification
Critical Must-Knows
- HEMORRHAGE is the primary killer - massive pelvic volume expansion
- External rotation opens pelvic ring increasing pelvic volume
- Binder/sheet CLOSES the book - early hemorrhage control
- APC-II = 'open book' with intact posterior SI ligaments
- APC-III = complete SI disruption = highest mortality
Examiner's Pearls
- "Symphysis widening 2.5cm is key threshold (APC-I vs II)
- "Posterior injury determines stability - not anterior widening
- "Urgent pelvic binder before imaging in unstable patients
- "External fixator for anterior stabilization, NOT definitive for posterior
- "Assess for urological injury - bladder and urethra at high risk
Exam Warning
Hemorrhage Mechanism
Volume Expansion: External rotation 'opens the book', creating a massive potential space for venous bleeding.
Life-Saving Maneuver
CLOSE THE BOOK: Pelvic binder/sheet at GT level restores tamponade. Do this before CT if unstable.
The 2.5cm Rule
<2.5cm: APC-I (Posterior ligaments intact, stable). >2.5cm: APC-II (Anterior SI torn, rotationally unstable).
Stability Check
Do NOT 'spring' the pelvis repeatedly. One gentle check only. Clots can dislodge.
At a Glance
| Feature | APC-I | APC-II | APC-III |
|---|---|---|---|
| Symphysis widening | Less than 2.5cm | Greater than 2.5cm | Greater than 2.5cm + vertical |
| Posterior SI ligaments | Intact | Intact | Disrupted |
| Sacrospinous ligament | Intact | Torn | Torn |
| Rotational stability | Stable | Unstable | Unstable |
| Vertical stability | Stable | Stable | Unstable |
| Hemorrhage risk | Moderate | High | Very high |
| Typical management | Conservative | Surgical fixation | Urgent surgical fixation |
OPENAPC - Key Features
Memory Hook:APC injuries OPEN the pelvis - remember to CLOSE it with a binder
BLEEDBLEED - Why APC Hemorrhages
Memory Hook:APC injuries BLEED - the open book loses tamponade
2.5TWO-FIVE - APC-I vs APC-II Threshold
Memory Hook:2.5cm symphysis widening separates APC-I (conservative) from APC-II (surgical)
BINDBIND - Pelvic Binder Protocol
Memory Hook:BIND the pelvis to close the open book - applied at trochanter level
Overview
Introduction
Anteroposterior compression (APC) injuries result from external rotation forces applied to the pelvis, classically from direct anterior impact or forced external rotation of the lower extremities. These injuries "open" the pelvic ring like a book, disrupting anterior structures first and progressing posteriorly with increasing force.
APC injuries are critical to understand because they have the highest hemorrhage risk of all pelvic injury patterns. The external rotation mechanism opens the pelvic ring, dramatically increasing pelvic volume and allowing massive retroperitoneal hemorrhage from venous plexus disruption and arterial bleeding.
Epidemiology
Incidence:
- 15-20% of all pelvic ring injuries
- Second most common pattern after LC injuries
- Most common cause of massive pelvic hemorrhage
Mechanism:
- Motorcycle accidents (handlebar impact)
- Pedestrian vs vehicle (direct anterior blow)
- Falls with legs forced into external rotation
- Crush injuries with AP vector
Demographics:
- Young males predominate (high-energy trauma)
- Associated polytrauma in majority
- Higher ISS scores than LC injuries typically
Clinical Significance
Why APC Injuries Are High-Stakes:
- Hemorrhage risk: Highest of all patterns
- Volume expansion: Pelvis can accommodate several liters of blood
- Venous plexus: Presacral venous plexus disruption
- Arterial injury: Superior gluteal artery vulnerable
- Urological injury: Bladder and urethra directly affected by symphysis disruption
Anatomy and Pathophysiology
Pelvic Ring Biomechanics
The pelvis functions as a ring structure with anterior and posterior components. Stability primarily depends on the posterior structures.
Anterior Structures
Pubic Symphysis:
- Fibrocartilaginous joint
- Minimal inherent stability
- Disruption alone does not cause instability
- Normal width approximately 5mm
Pubic Rami:
- Connect symphysis to acetabulum
- Fractures common with symphysis disruption
- Bilateral rami fractures may occur
Posterior Structures (Critical for Stability)
Sacroiliac Joint:
- Anterior SI ligaments: First to fail in APC
- Interosseous SI ligaments: Main restraint to external rotation
- Posterior SI ligaments: Ultimate stability (strongest)
- Sacrospinous ligament: Resists external rotation
- Sacrotuberous ligament: Resists vertical displacement
APC Injury Progression
Force applied anteriorly causes sequential failure:
- Stage 1 (APC-I): Symphysis diastasis, anterior SI strain, posterior intact
- Stage 2 (APC-II): Complete anterior SI tear, sacrospinous ligament tear, posterior SI intact
- Stage 3 (APC-III): Complete SI disruption including posterior ligaments
Hemorrhage Mechanism
Why APC Bleeds Most:
Volume Expansion:
- Normal pelvic volume approximately 1.5L
- APC-III can increase to greater than 4L
- Tamponade effect lost when ring opens
Vascular Anatomy:
- Presacral venous plexus: Low pressure, high volume
- Internal iliac branches: Superior gluteal artery most common
- Corona mortis: Aberrant obturator vessels (present in 30%)
Bleeding Sources:
- 80-90% venous (plexus disruption)
- 10-20% arterial (often superior gluteal)
- Cancellous bone surfaces contribute
Classification
Young-Burgess APC Classification
The Young-Burgess classification stratifies APC injuries by severity and stability based on progressive ligamentous disruption.
APC-I (Stable)
Definition: Symphysis widening less than 2.5cm
Structures Disrupted:
- Symphysis pubis (partial)
- Anterior SI ligaments (sprained, not torn)
Structures Intact:
- Sacrospinous ligament
- Sacrotuberous ligament
- Posterior SI ligament complex
- Interosseous SI ligaments
Clinical Features:
- Mechanically stable
- Moderate hemorrhage risk
- Usually ambulatory with weight-bearing restrictions
- Conservative management often appropriate
The 2.5cm threshold is the key differentiator for APC-I injuries.
Clinical Assessment
Primary Survey
APC injuries are diagnosed in the context of major trauma. Pelvic assessment follows ATLS principles.
Mechanism History
High-Risk Mechanisms:
- Motorcycle collision (handlebars)
- Pedestrian struck anteriorly
- Frontal vehicle collision with AP force vector
- Crush injury with anterior compression
- Fall from height with legs apart
Physical Examination
Inspection:
- Limb length discrepancy (APC-III)
- External rotation deformity of lower limbs
- Perineal swelling/ecchymosis
- Scrotal or labial hematoma
- Visible symphysis widening (severe cases)
- Blood at urethral meatus
Do NOT repeatedly "spring" or compress the pelvis. A single gentle assessment is acceptable - repeated manipulation can dislodge clot and restart hemorrhage. If instability is suspected, apply a binder and obtain imaging.
Palpation (gentle, once only):
- Symphysis gap palpable
- Tenderness over SI joints posteriorly
- Iliac crest tenderness
Associated Injuries (Always Assess):
Urological:
- Blood at meatus: High-riding prostate, urethral injury
- Hematuria: Bladder injury
- Do NOT catheterize if urethral injury suspected
Vascular:
- Peripheral pulses
- Signs of hypovolemic shock
- Expanding hematoma
Neurological:
- L5/S1 nerve root function
- Perineal sensation (S2-4)
- Rectal tone
Hemodynamic Assessment
Unstable Patient:
- Tachycardia greater than 100 bpm
- Hypotension (SBP less than 90mmHg)
- Reduced GCS (hypoperfusion)
- Poor peripheral perfusion
- Need for ongoing resuscitation
Presumed Pelvic Source If:
- Pelvic instability on examination
- No other obvious hemorrhage source
- High-risk mechanism
- APC pattern on imaging
Investigations
Imaging Approach
Plain Radiography
AP Pelvis:
- First-line imaging in trauma
- Can be done in resuscitation bay
- Assess symphysis width (normal approximately 5mm)
- Greater than 25mm suggests APC-II or higher
- Look for associated pubic rami fractures
- Evaluate SI joint symmetry
Inlet View:
- Demonstrates AP displacement
- Shows symphysis diastasis clearly
- Evaluates SI joint anteriorly
Outlet View:
- Demonstrates vertical displacement
- Better view of sacrum
- Helps differentiate APC-III from APC-II
CT Imaging
Indications:
- All stable patients with suspected pelvic injury
- Hemodynamically stable patients for surgical planning
- Define posterior injury pattern precisely
Findings:
- Symphysis diastasis measurement
- Anterior SI joint widening
- Posterior SI ligament integrity
- Associated fractures (sacrum, rami)
- Contrast extravasation (CT angiography)
CT Angiography:
- Active arterial extravasation
- Guides angioembolization
- Superior gluteal artery most common source
Retrograde Urethrogram
Indications:
- Blood at urethral meatus
- High-riding prostate on DRE
- Perineal hematoma
- Before catheterization if urethral injury suspected
Technique:
- 20-30mL water-soluble contrast
- Inject gently via meatus
- Fluoroscopic or plain film guidance
Cystogram
Indications:
- Hematuria with pelvic fracture
- After urethral integrity confirmed
- Evaluate for bladder rupture
Findings:
- Intraperitoneal rupture: Contrast around bowel
- Extraperitoneal rupture: Flame-shaped extravasation (more common with APC)
Management
Acute Hemorrhage Control
The pelvic binder is FIRST-LINE treatment for suspected APC injury with hemodynamic instability. Apply BEFORE imaging. The binder CLOSES the open book, reducing pelvic volume and restoring tamponade. Do not wait for X-ray confirmation.
Pelvic Binder Application
Principles:
- Applies internal rotation force
- Closes the "open book"
- Reduces pelvic volume
- Restores tamponade effect
- Temporary measure (not definitive)
Technique:
- Position at level of greater trochanters (NOT iliac crests)
- Apply circumferential compression
- Commercial binder or sheet wrap acceptable
- Do not over-tighten (skin necrosis risk)
- Re-evaluate after 24-48 hours maximum
Contraindications:
- LC injuries (already internally rotated - binder makes worse)
- Acetabular fractures (may displace)
Damage Control Resuscitation
Principles:
- Permissive hypotension (SBP 80-90mmHg)
- Balanced transfusion (1:1:1 ratio)
- Avoid crystalloid overload
- Early TXA administration
- Correct coagulopathy aggressively
Early mechanical stabilization combined with damage control resuscitation saves lives.
Surgical Technique
Anterior Symphysis Fixation
Indications:
- APC-II injuries (symphysis widening over 2.5cm)
- APC-III injuries (combined with posterior fixation)
- Symphysis diastasis over 2.5cm with rotational instability
Pfannenstiel Approach:
- Transverse skin incision 2cm above symphysis
- Incise linea alba vertically
- Protect bladder (retract inferiorly)
- Expose symphysis and superior pubic rami
- Reduce symphysis with clamp
- Apply superior pubic plate (3.5mm reconstruction plate)
- 4-6 hole plate preferred for stability
Technical Pearls:
- Reduce symphysis before plating
- Superior plate position (strongest)
- Protect bladder throughout
- Consider second inferior plate for APC-III
The Pfannenstiel approach provides excellent access with minimal soft tissue damage.
Complications
Associated Injuries
Urological Injuries
Bladder Injury:
- 15-25% of APC injuries
- Extraperitoneal more common (symphysis disruption)
- Intraperitoneal with full bladder at impact
- Hematuria is key finding
Management:
- Extraperitoneal: Catheter drainage 10-14 days
- Intraperitoneal: Surgical repair required
Urethral Injury:
- More common in males (long membranous urethra)
- Blood at meatus, high-riding prostate
- Do NOT blind catheterize
- Retrograde urethrogram first
- Suprapubic catheter if complete disruption
Vascular Injuries
Arterial:
- Superior gluteal artery most common
- Internal iliac branches
- Corona mortis (variant obturator vessels)
Venous:
- Presacral venous plexus (major source)
- Internal iliac veins
- Low pressure but high volume bleeding
Neurological Injuries
Lumbosacral Plexus:
- L5 nerve root most vulnerable
- Foot drop, sensory loss
- S2-4 sacral roots: Bladder, bowel, sexual function
Documentation Essential:
- Motor function L2-S1
- Sensory examination
- Perineal sensation
- Rectal tone
Open Pelvic Fractures
Faringer Classification:
- Type I: Iliac wing (low risk)
- Type II: Perineum/buttock (moderate)
- Type III: Rectum/vagina (high mortality)
Management:
- Fecal diversion for rectal involvement
- Wound debridement
- Broad spectrum antibiotics
- High mortality (up to 50%)
Early Complications
Hemorrhagic Shock:
- Most common cause of early death
- Massive transfusion requirements
- Coagulopathy compounds bleeding
Thromboembolic Events:
- High DVT risk (venous stasis, injury)
- PE can be fatal
- Early prophylaxis when safe
Infection:
- Open fractures: High mortality
- Surgical site infections
- Osteomyelitis rare with closed injuries
Late Complications
Malunion:
- Residual diastasis
- SI joint malreduction
- Affects gait and pain
Nonunion:
- Rare with adequate fixation
- Symphysis nonunion: Painful instability
- SI nonunion: May need fusion
Hardware Issues:
- Symphysis plate loosening (activity related)
- Screw pullout
- May need removal if symptomatic
Chronic Pain:
- SI joint arthritis
- Symphysis pain
- May benefit from SI fusion
Sexual and Urological:
- Dyspareunia
- Erectile dysfunction
- Chronic urethral stricture
Postoperative Care
Immediate Postoperative (Days 0-14)
ICU Management:
- Continued hemodynamic monitoring
- Serial hemoglobin checks
- DVT prophylaxis (LMWH when hemostasis achieved)
- Early removal of pelvic binder (once fixation stable)
Mobility:
- Bed rest initially for severe injuries
- Toe-touch weight-bearing when hemodynamically stable
- Log-roll precautions for posterior fixation
Wound Care:
- Monitor surgical incisions
- Pin site care for external fixation
- Watch for infection signs
Early mobilization improves outcomes but must be balanced against injury stability.
Outcomes and Prognosis
Overall Outcomes
Mortality:
- APC-I: Under 5%
- APC-II: 5-15%
- APC-III: Up to 25%
- Mortality correlates with associated injuries and hemorrhage
Functional Outcomes:
Outcomes by APC Grade
| APC Grade | Union Rate | Return to Work | Chronic Pain |
|---|---|---|---|
| APC-I | Over 95% | 3-4 months | 10-15% |
| APC-II | 90-95% | 4-6 months | 20-30% |
| APC-III | 85-90% | 6-12 months | 40-50% |
Long-term Complications
Chronic Pain:
- SI joint pain: 20-40% of APC-II/III
- Symphysis pain: 15-25%
- Sacral fracture malunion: contributor to pain
Sexual Dysfunction:
- More common with urethral injury
- Erectile dysfunction: 15-30% in males
- Dyspareunia: 20-40% in females
Leg Length Discrepancy:
- Rare with accurate reduction
- May result from malreduction of vertical component
Prognosis depends heavily on initial injury severity and associated injuries.
Evidence Base
Pelvic Binder Timing
- Early pelvic binder application (less than 30 minutes from injury) associated with reduced transfusion requirements and improved survival in hemodynamically unstable pelvic fractures.
Symphysis Fixation Threshold
- Symphysis widening greater than 2.5cm associated with anterior SI ligament disruption and rotational instability. Threshold for surgical intervention.
Damage Control Orthopedics
- Damage control approach with external fixation followed by delayed definitive fixation reduces complications in polytrauma patients compared to early definitive surgery.
Angioembolization for Pelvic Hemorrhage
- Angioembolization effective for arterial hemorrhage in pelvic fractures. Success rate greater than 85% for arterial bleeding control. Does not address venous bleeding (majority of hemorrhage).
REBOA in Pelvic Trauma
- Zone III REBOA can temporize exsanguinating pelvic hemorrhage as bridge to definitive intervention. Requires trained personnel and should not delay definitive care.
Viva Scenarios
Exam Viva Scenarios
Practice these scenarios to excel in your viva examination
Unstable APC Injury Management
"A 35-year-old motorcyclist presents after a head-on collision. He is tachycardic (HR 125), hypotensive (BP 85/50), and has gross external rotation of both lower limbs. AP pelvis shows symphysis diastasis of 4cm. Describe your immediate management."
Immediate Recognition: This is an APC-II or APC-III injury with hemodynamic instability - life-threatening hemorrhage.
Immediate Actions (Simultaneous):
- Pelvic binder at greater trochanter level - CLOSE THE BOOK
- Massive transfusion protocol activation (1:1:1)
- TXA administration (1g IV)
- Permissive hypotension (target SBP 80-90)
- Avoid crystalloid overload
Secondary Assessment:
- Complete ATLS primary and secondary survey
- Identify other hemorrhage sources
- Check for blood at urethral meatus - do NOT blind catheterize
- Perineal/rectal examination for open fracture
If Responding to Resuscitation:
- CT with angiography
- Define posterior injury (APC-II vs III)
- Angioembolization if arterial blush
- Definitive fixation when stable
If NOT Responding:
- Consider external fixator in ED
- Preperitoneal packing
- Angioembolization if available
- REBOA as bridge if trained personnel
Young-Burgess APC Classification
"Describe the Young-Burgess APC classification and explain why understanding this system is important for management decisions."
Young-Burgess APC Classification:
APC-I:
- Symphysis widening less than 2.5cm
- Anterior SI ligaments sprained but intact
- Posterior ligaments completely intact
- Mechanically STABLE
- Usually conservative management
APC-II (Open Book):
- Symphysis widening greater than 2.5cm
- Anterior SI ligaments disrupted
- Sacrospinous ligament torn
- Posterior SI ligaments INTACT (key distinction)
- Rotationally unstable, vertically stable
- Surgical fixation of symphysis usually required
APC-III:
- Complete SI disruption (anterior AND posterior)
- Hemipelvic external rotation
- Rotationally AND vertically unstable
- Highest hemorrhage and mortality risk
- Requires anterior AND posterior fixation
Clinical Importance:
- Hemorrhage risk increases with grade
- APC-I may be managed conservatively
- APC-II needs anterior fixation only
- APC-III needs BOTH anterior and posterior fixation
- Posterior injury determines stability - not anterior widening
Symphysis Fixation Technique
"A patient with an APC-II pelvic injury is scheduled for symphysis fixation. Describe your surgical approach and technique."
Preoperative Planning:
- Confirm APC-II (CT showing intact posterior SI ligaments)
- Review for associated injuries (bladder, urethra)
- Ensure hemodynamic stability
- Discuss with urology if catheter issues
Positioning:
- Supine on radiolucent table
- Ensure fluoroscopy access (inlet, outlet, AP views)
- Prep widely including both iliac crests
Approach:
- Pfannenstiel incision (transverse, 2cm above symphysis)
- Incise rectus sheath transversely
- Separate rectus muscles in midline (do NOT detach)
- Identify and protect bladder (often contused)
- Expose superior pubic ramus bilaterally
Reduction:
- Large pointed reduction forceps across symphysis
- Reduce internal rotation to close the book
- Confirm reduction on inlet view (symmetric ring)
- Accept less than 1cm residual diastasis
Fixation:
- 3.5mm reconstruction plate or specific symphysis plate
- Position on superior aspect of pubis
- 2-hole plate for simple diastasis
- 4-hole plate if rotational control needed
- Consider second plate superiorly if highly unstable
Closure:
- Close rectus sheath securely
- Subcutaneous and skin closure
- Catheter remains for bladder monitoring
MCQ Practice Points
Classification Question
Q: What symphysis widening threshold distinguishes APC-I from APC-II? A: 2.5cm. Less than 2.5cm = APC-I (stable, usually conservative). Greater than 2.5cm = APC-II or III (unstable, usually surgical).
Stability Question
Q: What determines stability in APC injuries - anterior or posterior structures? A: Posterior ligaments. The posterior SI ligament complex determines stability. APC-II has intact posterior ligaments (rotationally unstable). APC-III has complete disruption (globally unstable).
Pelvic Binder Question
Q: Where should the pelvic binder be positioned? A: At the level of the greater trochanters (NOT the iliac crests). This applies internal rotation force to close the "open book."
Contraindication Question
Q: What pelvic injury pattern is a CONTRAINDICATION to pelvic binder? A: Lateral compression (LC) injuries. The pelvis is already internally rotated - a binder would worsen the deformity.
Hemorrhage Question
Q: What percentage of pelvic hemorrhage is venous vs arterial? A: 80% venous, 20% arterial. The pelvic binder addresses venous bleeding by restoring tamponade. Angioembolization targets arterial bleeding.
Australian Context
APC pelvic injuries represent a significant trauma burden in Australia, particularly in rural and remote areas where high-speed motor vehicle accidents are common. Australian trauma systems have developed robust protocols for pelvic injury management, with major trauma centers following standardized approaches to hemorrhage control and surgical stabilization.
The Australian Trauma Registry captures outcomes data that informs best practice, showing that early pelvic binder application and adherence to massive transfusion protocols significantly improve survival in unstable pelvic injuries. Australian guidelines align with international consensus on the 2.5cm symphysis widening threshold and the importance of posterior ligament assessment for determining stability.
DVT prophylaxis follows Australian guidelines with LMWH (enoxaparin) as the standard agent, typically commenced once hemostasis is achieved and continued for 4-6 weeks. Extended prophylaxis is recommended for high-risk patients with prolonged immobility. The PBS listing for enoxaparin supports cost-effective prevention of thromboembolic complications.
Rehabilitation services through state-funded trauma networks support functional recovery, with most major centers offering dedicated pelvic trauma physiotherapy programs. Long-term outcomes data from Australian registries demonstrates good functional recovery in appropriately treated patients, though chronic pain remains a significant issue in severe injuries.
Exam Focus Points
High-Yield Concepts
Exam Pearl
The 2.5cm symphysis widening threshold is CRITICAL for exam purposes. Less than 2.5cm = APC-I (stable, usually conservative). Greater than 2.5cm = APC-II or III (unstable, usually surgical). This simple number drives management decisions.
Key Differentiators
APC vs LC Injuries:
- APC: External rotation, pelvis OPENS
- LC: Internal rotation, pelvis CLOSES
- APC: Higher hemorrhage (volume expands)
- LC: Associated head injury (same vector)
APC-II vs APC-III:
- Both have symphysis widening greater than 2.5cm
- APC-II: Posterior SI ligaments INTACT (key)
- APC-III: Complete SI disruption
- APC-II: Anterior fixation only
- APC-III: Anterior AND posterior fixation
Hemorrhage Management Sequence
- Recognize APC pattern and instability
- BIND - Pelvic binder at trochanters
- Resuscitate - MTP, TXA, permissive hypotension
- Image - When stable enough for CT
- Intervene - Angioembolization if arterial source
- Fix - Definitive surgical stabilization
Surgical Fixation Principles
Anterior (Symphysis):
- Pfannenstiel approach
- Superior plate position
- Protect bladder
- 2-4 hole plate
Posterior (SI Joint):
- Percutaneous SI screws (most common)
- S1 body target (avoid ala)
- Protect L5 nerve root
- May need multiple screws
APC Pelvic Injuries
High-Yield Exam Summary
Classification
- •APC-I: Symphysis less than 2.5cm, stable
- •APC-II: Symphysis greater than 2.5cm, posterior SI intact
- •APC-III: Complete SI disruption, unstable
- •Posterior ligaments determine stability
Hemorrhage
- •HIGHEST hemorrhage risk of all patterns
- •80% venous, 20% arterial bleeding
- •Pelvic binder addresses venous component
- •Angioembolization for arterial bleeding
Immediate Management
- •Pelvic binder at TROCHANTERS (not iliac crests)
- •MTP activation (1:1:1 ratio)
- •TXA 1g IV
- •Permissive hypotension (SBP 80-90)
Surgical Fixation
- •APC-II: Symphysis plating only
- •APC-III: BOTH anterior AND posterior fixation
- •Pfannenstiel approach for symphysis
- •SI screws target S1 body (avoid ala)
Key Pitfalls
- •Delaying binder for imaging
- •Binder at iliac crests (too high)
- •Blind catheterization with blood at meatus
- •LC injuries contraindicate binder