Lateral Compression Pelvic Injuries

Lateral compression (LC) injuries are the most common pelvic ring injury pattern, accounting for 50-60% of all pelvic fractures. They result from a laterally directed force causing internal rotation of the hemipelvis, with the injury severity ranging from stable rami fractures (LC-I) to rotationally and vertically unstable patterns (LC-III).

Epidemiology

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Incidence:

• Most common pelvic ring injury pattern (50-60% of all pelvic fractures)
• LC-I accounts for 70% of lateral compression injuries
• More common in motor vehicle accidents (T-bone collisions)
• Also common in pedestrian strikes

Demographics:

• All age groups affected
• Bimodal distribution: Young (high-energy MVA) and elderly (low-energy falls)
• No significant gender predilection
• Higher incidence in areas with higher traffic volume

Mechanism Distribution:

• Motor vehicle accidents: 60-70%
• Pedestrian vs vehicle: 15-20%
• Falls from height: 10-15%
• Other mechanisms: 5%

Associated Injuries:

• Head injuries: 40-50% (same lateral impact)
• Acetabular fractures: 20-30%
• Long bone fractures: 30-40%
• Thoracic injuries: 20-30%
• Neurological injuries: 10-20% (sacral fractures)

Pelvic Ring Anatomy

Pelvic Ring Concept

Osseous Ring Components:

• Anterior ring: Pubic symphysis + superior/inferior pubic rami
• Posterior ring: Sacrum + sacroiliac joints + posterior ilium

Key Principle: The pelvic ring cannot break in one place - if there's an anterior injury, there MUST be a posterior injury (and vice versa). Always search for the second break.

Mechanism of Injury

Lateral Compression Force:

• Force directed laterally (side impact)
• Common scenarios: MVA (T-bone), pedestrian struck, fall from height landing on side
• Force causes internal rotation of the hemipelvis

Resultant Deformity:

• Hemipelvis rotates INTERNALLY
• Pelvis narrows (in contrast to APC which widens)
• Creates compression anteriorly and posteriorly

Associated Injuries - Important for LC

Head Injuries:

• Very common with LC mechanism
• Same lateral force that hits pelvis also hits head
• Always assess neurological status

Morel-Lavallee Lesion:

• Closed internal degloving injury
• Shear between skin/fat and underlying fascia
• Typically over greater trochanter
• Can occur without external wound
• Delayed presentation possible
• MRI for diagnosis if suspected

Pelvic Stability Determinants

Posterior Ring is Key:

• 60% of pelvic stability from posterior structures
• SI ligament complex (anterior, posterior, interosseous)
• Posterior tension band (iliolumbar, lumbosacral, sacrospinous, sacrotuberous ligaments)

In LC Injuries:

• LC-I: Posterior ligaments intact, sacral impaction only = STABLE
• LC-II: Partial posterior disruption (crescent fracture) = VARIABLE stability
• LC-III: Both SI joint disruptions (ipsi LC + contra APC) = UNSTABLE

Young-Burgess Classification

Tile Classification Correlation

Initial Assessment

Presentation

History:

• Mechanism of injury (lateral impact)
• Level of consciousness (associated head injury common)
• Ability to ambulate
• Pain location

Primary Survey:

• ABC assessment
• Hemodynamic status
• Pelvic stability testing (ONCE only, gently)
• Associated injuries

Examination

Inspection:

• Leg length discrepancy
• Rotational deformity
• Ecchymosis over pelvis/perineum
• Open wounds (including perineum, vagina, rectum)
• Morel-Lavallee lesion (bruising/fluctuance over trochanter)

Palpation:

• Tenderness over symphysis
• Tenderness over SI joints
• Tenderness over iliac crests
• Crepitus (may indicate unstable fragments)

Associated Injuries to Assess

Urogenital:

• Blood at urethral meatus = urethral injury (do NOT catheterize)
• Hematuria
• High-riding prostate on DRE
• Vaginal/scrotal hematoma

Neurological:

• Lumbosacral plexus injury
• L4-S1 nerve roots (sacral fractures)
• Assess motor and sensory function

Other:

• Head injury (very common with LC)
• Abdominal injuries
• Long bone fractures
• Acetabular fractures (same mechanism)

Hemodynamic Considerations

LC Injuries Generally Bleed Less Than APC:

• Internal rotation closes pelvis
• Tamponades bleeding to some extent
• But can still have significant hemorrhage

Don't Be Complacent:

• LC-III can have substantial bleeding
• Associated injuries may contribute
• Assess and reassess hemodynamic status

Differential Diagnosis

When an AP pelvis shows rami fractures or pelvic pain after a fall or collision, distinguish lateral compression from its main mimics. The discriminating features are the direction of the deforming force, the posterior ring lesion on CT, and the patient's bone quality.

Imaging Protocol

Plain Radiographs

AP Pelvis (First-Line):

• Standard in all trauma patients
• Assess pelvic ring continuity
• Look for rami fractures
• Assess symphysis width
• Assess SI joint symmetry

Inlet View:

• AP/internal rotation assessment
• Assess posterior displacement
• Shows sacral impaction

Outlet View:

• Superior/inferior displacement
• Assess sacral fractures
• Neural foramina assessment

CT Scan (Essential)

CT Assessment:

• Sacral fracture pattern (Zone 1, 2, 3)
• SI joint integrity
• Crescent fracture identification
• Posterior ligamentous structures
• Neural canal involvement
• Associated acetabular fractures

MRI (Selected Cases)

Indications:

• Suspected ligamentous injury without fracture
• Neurological deficit evaluation
• SI joint instability assessment
• Morel-Lavallee lesion evaluation

Sacral Fracture Zones (Denis)

Algorithm

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Initial Stabilization

Pelvic Binder:

• Apply in ED if instability suspected
• Centered at level of greater trochanters (NOT iliac crests)
• Can be improvised with sheet if commercial binder unavailable
• Monitor skin under binder

For LC Injuries:

• Binder less effective than APC (pelvis already closed)
• Still apply if unstable
• May actually worsen internal rotation - monitor carefully

Conservative Management (LC-I)

Indications:

• Stable LC-I injuries
• Minimal displacement
• Patient can tolerate limited mobilization

Protocol:

• Analgesia (multimodal)
• DVT prophylaxis (critical)
• Early mobilization as tolerated
• Weight-bearing as tolerated (depends on symptoms)
• PT assessment
• Follow-up imaging at 6 weeks

Surgical Management

Indications for Surgery:

• LC-II with instability
• All LC-III injuries
• Significant displacement
• Associated acetabular fracture requiring fixation
• Polytrauma requiring mobilization

Surgical Options

Anterior Fixation:

• Symphyseal plating (if symphysis disrupted in LC-III)
• Rami plating (rarely needed for LC)
• External fixation (damage control)

Posterior Fixation:

• Percutaneous SI screws (most common)
• Posterior plating
• Spinopelvic fixation (severe instability)

Timing:

• Damage control: External fixation acutely
• Definitive fixation: When patient optimized (24-72h typically)
• LC-I may never need surgery

Fixation Techniques for LC Injuries

Early and Late Complications

Early Complications

Hemorrhage:

• Less than APC but still significant
• Arterial (superior gluteal, pudendal) or venous
• May need angioembolization or packing

Associated Injuries:

• Urethral injury (less common in LC than APC)
• Bladder injury
• Neurological injury (sacral fractures)

Morel-Lavallee Lesion:

• May need drainage or debridement
• Can delay wound healing
• Infection risk if not addressed

Late Complications

Malunion:

• Leg length discrepancy
• Pelvic obliquity
• Gait abnormality
• Sitting difficulty

Post-Traumatic Arthritis:

• SI joint arthritis
• May develop despite good reduction

Chronic Pain:

• SI joint pain common
• May need delayed fusion

Neurological:

• Persistent nerve injury (L5, S1-S4)
• More common with sacral fractures through foramina

Immediate Postoperative Management

First 24-48 Hours:

• Monitor neurovascular status
• Pain control (multimodal analgesia)
• DVT prophylaxis (critical - high risk)
• Incentive spirometry
• Early mobilization to chair

Weight-Bearing Status

LC-I (Conservative Treatment):

• Weight-bearing as tolerated
• May use walking aids initially
• Progress based on pain

LC-II/III (Surgical Fixation):

• First 6 weeks: Touch weight-bearing (10-15kg) with crutches or frame
• 6-12 weeks: Progressive weight-bearing if radiographic healing
• 12+ weeks: Full weight-bearing once healed

Special Considerations:

• Bilateral injuries may need wheelchair initially
• Posterior ring instability delays full weight-bearing
• Follow serial X-rays to assess healing

DVT Prophylaxis

Critical Importance:

• Pelvic fractures = high VTE risk
• Combined mechanical and pharmacological prophylaxis

Protocol:

• LMWH or fondaparinux (start when safe)
• Compression stockings/intermittent pneumatic compression
• Early mobilization
• Continue for 6 weeks minimum
• Consider 3 months for high-risk patients

Rehabilitation Protocol

Phase 1 (0-6 weeks):

• Protected weight-bearing
• Gentle ROM exercises (hip, knee)
• Core strengthening (isometric)
• Gait training with aids

Phase 2 (6-12 weeks):

• Progressive weight-bearing
• Strengthening exercises
• Balance and proprioception training
• Pool therapy if available

Phase 3 (12+ weeks):

• Full weight-bearing
• Sport-specific rehabilitation
• Return to work planning
• Address any residual deficits

Follow-Up Schedule

Timing:

• 2 weeks: Wound check, neurovascular assessment
• 6 weeks: X-rays, assess healing, advance weight-bearing
• 12 weeks: X-rays, consider full weight-bearing
• 6 months: Final X-rays, functional assessment
• 12 months: Long-term outcome evaluation

Red Flags to Monitor:

• Increasing pain (hardware failure, non-union)
• Loss of reduction
• Neurological changes
• Wound complications
• Signs of DVT/PE

OrthoVellum is a worldwide resource: this section gives the global standard of care for lateral compression injuries plus the regional differences a candidate may be examined on. Lateral compression is the most common pelvic ring pattern internationally, and the principles below apply across all major trauma systems.

Global Epidemiology

A second, growing population is the elderly low-energy fragility fracture of the pelvis, which is rising with ageing populations worldwide and behaves differently from the high-energy LC injury above.

Major Guidelines Side by Side

Key area of genuine convergence: stable LC-I is treated nonoperatively with early weight-bearing; key area of evolving practice: how aggressively to detect occult instability in LC-1 with a complete sacral fracture (stress examination vs early fixation).

Registry and Trauma-System Evidence

• Trauma registries (e.g. the UK TARN and the Victorian State Trauma Registry) define the small, resource-intensive subgroup of haemodynamically unstable pelvic ring injuries and have shown that survival is driven by haemodynamic control rather than which centre delivers definitive care (Gabbe 2011, PMID 21733513).
• Joint-replacement registries (NJR, AJRR, AOANJRR) are not applicable to acute LC fixation; registry evidence here comes from trauma rather than arthroplasty registries.

Global Practice Variation

Thromboprophylaxis (Global Principle)

Pelvic fractures carry a high venous thromboembolism risk, so combined mechanical and pharmacological prophylaxis is standard worldwide. Low-molecular-weight heparin is the usual agent, started once haemorrhage is controlled, with renal dose adjustment, plus intermittent pneumatic compression and early mobilisation. Extended prophylaxis (commonly up to 6 weeks, longer in high-risk patients) is recommended for major pelvic injury, in line with international guidance.