Complete acetabular dissociation from axial skeleton - the 'floating acetabulum'
Letournel Classification - Associated Pattern
Critical Must-Knows
- SPUR SIGN is PATHOGNOMONIC - intact ilium above detached columns
- Entire articular surface is FLOATING (not attached to spine)
- Most common associated pattern in Letournel classification
- Secondary congruence may allow conservative treatment in elderly
- Young patients with displaced fractures need ORIF
Clinical Pearls
- "Spur sign = both column (on obturator oblique view)
- "Distinguishing from transverse: transverse maintains some dome attachment
- "Iliopectineal AND ilioischial lines both disrupted
- "Secondary congruence: femoral head pushes fragments into alignment
- "Combined approaches often needed (ilioinguinal + Kocher-Langenbeck)
Exam Warning
The Pathognomonic Sign
Spur Sign (Obturator Oblique): Represents intact superior ilium above the floating acetabulum. The key diagnostic feature.
The 'Floating' Concept
Total Dissociation: NO part of the articular surface remains attached to the axial skeleton.
Distinction from Transverse
Transverse: Roof remains attached to ilium. Both Column: Roof is detached (floating).
Radiographic Lines
Double Trouble: Both iliopectineal (anterior) AND ilioischial (posterior) lines are disrupted.
Both Column Acetabular Fractures: Quick Decision Guide
| Assessment | Finding | Action |
|---|---|---|
| Spur sign present | Pathognomonic for both column | CT scan for surgical planning |
| Secondary congruence | Femoral head reduces fragments | Consider non-operative in elderly |
| No secondary congruence | Displaced fragments, incongruent | ORIF indicated |
| Young active patient | Any displacement beyond 2mm | Surgical fixation required |
| Hip joint stability | Femoral head centered under roof | May tolerate some displacement |
BOTHBOTH - Both Column Key Features
| B | Both columns completely fractured |
| O | Obturator oblique shows the SPUR SIGN |
| T | Total dissociation from axial skeleton |
| H | Hip articulates with floating segment |
| B | Both columns completely fractured | T | Total dissociation from axial skeleton |
| O | Obturator oblique shows the SPUR SIGN | H | Hip articulates with floating segment |
Hook:BOTH columns fractured with NO attachment to spine - look for the SPUR sign
SPURSPUR - The Pathognomonic Sign
| S | Superior ilium remains intact |
| P | Projection seen on obturator oblique |
| U | Unattached acetabulum below the spur |
| R | Reliably indicates both column pattern |
| S | Superior ilium remains intact | U | Unattached acetabulum below the spur |
| P | Projection seen on obturator oblique | R | Reliably indicates both column pattern |
Hook:The SPUR sign on obturator oblique confirms both column - intact ilium above floating acetabulum
FLOATFLOAT - Floating Acetabulum Concept
| F | Free from axial skeleton |
| L | Lines disrupted iliopectineal AND ilioischial |
| O | Obturator view shows spur sign |
| A | Articular surface completely detached |
| T | Total column involvement required |
| F | Free from axial skeleton | A | Articular surface completely detached |
| L | Lines disrupted iliopectineal AND ilioischial | T | Total column involvement required |
| O | Obturator view shows spur sign |
Hook:The entire acetabulum FLOATs free - no attachment to spine in both column fractures
Overview and Epidemiology
Introduction
Both column acetabular fractures are the most common associated pattern in the Letournel classification, representing 20-25% of all acetabular fractures. The defining characteristic is that both the anterior and posterior columns are completely fractured, with no portion of the articular surface remaining attached to the intact ilium above.
This creates a "floating acetabulum" where the entire articular segment is dissociated from the axial skeleton. The intact superior ilium remains attached to the sacrum, but the entire acetabulum floats free below.

Key Concept: The Floating Acetabulum
What Makes Both Column Unique:
- Both anterior AND posterior columns fractured
- Fracture lines extend ABOVE the dome (roof)
- No articular fragment attached to axial skeleton
- Entire weight-bearing surface is "floating"
- Intact ilium forms the "spur" sign
Contrast with Transverse:
- Transverse: Some dome remains attached to ilium above
- Both column: NO dome attachment to axial skeleton
Epidemiology
Incidence:
- 20-25% of all acetabular fractures
- Most common associated pattern
- Complex injury requiring expert management
Mechanism:
- High-energy trauma (MVA, falls)
- Axial load through femoral head
- Force transmitted to both columns
- Often associated with dashboard injuries
Demographics:
- Young patients: High-energy trauma
- Elderly: Lower energy (osteoporotic bone)
- Male predominance in young
- Bimodal age distribution
Anatomy and Biomechanics
Acetabular Anatomy
Understanding the column concept is essential for classifying acetabular fractures.
The Two-Column Model
Anterior Column (Iliopubic):
- Extends from iliac crest to symphysis
- Includes: Iliac wing anterior portion, anterior wall, pubic ramus
- Forms anterior half of acetabular dome
- Represented by iliopectineal line on X-ray
Posterior Column (Ilioischial):
- Extends from greater sciatic notch to ischial tuberosity
- Includes: Greater sciatic notch, posterior wall, ischial tuberosity
- Forms posterior half of acetabular dome
- Represented by ilioischial line on X-ray
Radiographic Lines
Iliopectineal Line:
- Runs from iliac crest to pubis
- Represents anterior column
- Disrupted in anterior column fractures
Ilioischial Line:
- Runs from greater sciatic notch to ischium
- Represents posterior column
- Disrupted in posterior column fractures
Both Column Fracture:
- BOTH iliopectineal AND ilioischial lines disrupted
- Plus SPUR SIGN

Classification Systems
Elementary Patterns (5):
Anterior wall involves isolated anterior wall fracture. Anterior column extends from iliac crest to pubis. Posterior wall is the most common elementary pattern. Posterior column involves the ilioischial line. Transverse fracture divides acetabulum into superior and inferior halves.
Associated Patterns (5):
T-shaped combines transverse with vertical component. Posterior column plus posterior wall is a common combination. Transverse plus posterior wall involves additional instability. Anterior column/wall plus posterior hemitransverse is complex associated pattern. Both column (this topic) is the most common associated pattern at 20-25%.
Classification Pearl
Both column fracture is distinguished from transverse by the spur sign and complete dissociation. In transverse fractures, some dome remains attached to axial skeleton above the fracture. In both column, NO articular surface has any attachment to the spine - the entire acetabulum floats.
Differential Diagnosis (Distinguishing Patterns)
Both Column vs Its Look-Alikes
| Pattern | Discriminating feature | Lines / sign | Why it matters |
|---|---|---|---|
| Both column | NO articular fragment attached to axial skeleton (floating acetabulum) | Spur sign on obturator oblique; both lines disrupted | Only pattern with secondary congruence; anterior/combined access |
| Transverse | Roof segment remains attached to intact ilium | No spur sign; both lines broken at one level | No secondary congruence; level dictates approach |
| Anterior column + posterior hemitransverse | Posterior column broken only below (hemitransverse); part of roof stays attached | Iliopectineal line broken; partial ilioischial break | Mimics both column but NOT floating - no true spur |
| T-shaped | Transverse plus vertical (stem) split of the inferior fragment | Both lines plus obturator ring disruption | Quadrilateral plate displacement; harder reduction |
| Associated posterior wall | Marginal impaction / posterior instability dominates | Posterior wall fragment on obturator oblique | Hip instability and AVN risk dominate |
Clinical Assessment
History and Mechanism
High-Energy Mechanisms:
- Motor vehicle accident (dashboard injury)
- Motorcycle accident
- Fall from height
- Pedestrian struck
- Sports (skiing, equestrian)
Force Transmission:
- Axial load through femoral head
- Position of hip determines fracture pattern
- Both columns receive force
Physical Examination
General Assessment:
- Polytrauma common - ATLS approach
- Associated pelvic ring injury possible
- Ipsilateral lower extremity injuries
Hip-Specific:
- Shortened, externally rotated limb (if dislocated)
- Pain with hip motion
- Unable to bear weight
- Tenderness over hip/pelvis
Neurovascular Assessment:
Sciatic nerve injury occurs in 10-15% of acetabular fractures, especially posterior patterns. Document detailed L5 (great toe extension) and S1 (ankle plantarflexion) function BEFORE any intervention. Peroneal division is more vulnerable - foot drop is the classic presentation.
Motor:
- Hip flexion (L1-2)
- Knee extension (L3-4)
- Ankle dorsiflexion (L4-5)
- Great toe extension (L5) - most vulnerable
- Ankle plantarflexion (S1)
Sensory:
- Lateral thigh (L2)
- Medial leg (L4)
- Dorsum foot (L5)
- Lateral foot (S1)
Associated Injuries
Common Associations:
- Femoral head fractures (Pipkin)
- Femoral neck fractures
- Hip dislocation
- Ipsilateral knee injuries (dashboard)
- Contralateral injuries
Investigations
Imaging Protocol
Plain Radiography (Judet Views)
Standard Series:
- AP pelvis
- Obturator oblique (45 degrees)
- Iliac oblique (45 degrees)
AP Pelvis:
- Both iliopectineal AND ilioischial lines disrupted
- Roof involvement
- Femoral head position
Obturator Oblique (KEY VIEW):
- SPUR SIGN visible - pathognomonic
- Anterior column profile
- Posterior wall en face
Iliac Oblique:
- Posterior column profile
- Anterior wall en face
- Greater sciatic notch
CT Imaging
Essential for Surgical Planning:
- 2mm axial cuts through acetabulum
- 3D reconstructions extremely helpful
- Coronal and sagittal reformats

Key Findings on CT:
- Fracture extent in both columns
- Articular surface congruence
- Femoral head integrity
- Intra-articular fragments
- Marginal impaction
CT with 3D Reconstruction:
- Demonstrates both column disruption
- Shows floating acetabulum concept
- Excellent for surgical planning
- Communication with patient/team
Secondary Congruence Assessment
Definition:
- Femoral head pushes fractured acetabular fragments into alignment
- Creates acceptable articular surface despite fracture
- May allow conservative treatment in select cases
CT Criteria:
- Roof arc measurements
- Articular step-off
- Gap assessment
- Overall congruence

Management
Indications:
Secondary congruence present with femoral head molding fragments into alignment. Elderly low-demand patients with acceptable articular surface. Medical comorbidities precluding major surgery. Roof arc measurements greater than 45 degrees in all planes. Minimal displacement with acceptable articular congruence.
Secondary Congruence Concept:
Femoral head acts as mold and pushes fragments into alignment. Creates functional weight-bearing surface despite fracture. More common in elderly patients with comminuted fractures. Unique to both column fractures where entire acetabulum floats.
Protocol:
Skeletal traction initially for 2-4 weeks followed by progressive mobilization. Weight-bearing restrictions maintained for 6-12 weeks. Serial radiographs to monitor alignment. Conversion to surgery if alignment lost.
Management Decision
The key to both column management is secondary congruence assessment. If the femoral head has molded the floating acetabulum into acceptable alignment, conservative treatment may succeed in elderly patients. Young patients with displacement need ORIF regardless of secondary congruence.
Surgical Technique
Access Provided:
Anterior column from iliac crest to pubic symphysis. Quadrilateral surface and inner table of ilium. Superior pubic ramus and pelvic brim.
Indications:
Anterior column-predominant both column fractures. High both column variants exiting through iliac crest.
Key Structures at Risk:
External iliac vessels in middle window. Femoral nerve lateral to vessels. Lateral femoral cutaneous nerve over ASIS. Corona mortis (aberrant obturator artery) in 15-30% of cases.
Technique Highlights:
Three windows created (lateral, middle, medial). Lateral femoral cutaneous nerve identified and protected. Iliac vessels and femoral nerve protected in middle window.

Neurovascular Structures
Anterior approach: Corona mortis crosses surgical field in 15-30% - ligate before division. External iliac vessels protected in middle window. Posterior approach: Sciatic nerve must be identified and protected throughout. Avoid excessive retraction which damages medial femoral circumflex artery.
Complications
Early Complications
Nerve Injury:
- Sciatic nerve (10-15%)
- Peroneal division most vulnerable
- Document preoperatively
Vascular Injury:
- Corona mortis (ilioinguinal approach)
- Superior gluteal artery (posterior approach)
- External iliac vessels
Thromboembolic:
- Very high DVT risk
- PE significant concern
- Prophylaxis essential
Infection:
- Surgical site infection
- Higher with extensive approaches
- Proper skin handling important
Late Complications
Post-traumatic Arthritis:
- Most common long-term complication
- Related to reduction quality
- Greater than 3mm step-off strongly predictive
- May need THR
Heterotopic Ossification:
- Common after extensive approaches
- Prophylaxis: Indomethacin or radiation
- May limit ROM
AVN of Femoral Head:
- Associated posterior dislocation
- Delay in reduction
- Poor prognosis
Postoperative Care
First 48-72 Hours:
Monitor for compartment syndrome and neurovascular status. DVT prophylaxis is mandatory given high risk. Wound care with drain removal at 24-48 hours. Pain management and early mobilization as tolerated.
Weight-Bearing:
Touch weight-bearing initially with crutches or frame. Progression based on fracture pattern and fixation stability. Protected weight-bearing for 8-12 weeks typically.
Outcomes/Prognosis
Surgical Outcomes
Anatomic reduction (less than 1mm) achieves 80% good to excellent results. Reduction quality is the strongest predictor of outcome. Combined approaches allow adequate access for most patterns.
Risk Factors for Arthritis
Articular step-off greater than 3mm strongly predicts arthritis. Associated femoral head injury worsens prognosis. Delay in surgery beyond 3 weeks compromises reduction.
Outcome by Reduction Quality
| Reduction | Step-off | Good/Excellent Outcome |
|---|---|---|
| Anatomic | Less than 1mm | 80-90% |
| Satisfactory | 1-3mm | 60-70% |
| Poor | Greater than 3mm | Less than 30% |
Evidence Base
Letournel Classification & Congruence (Founding Paper)
- Letournel's founding paper codified the ten-pattern column classification and the principle that outcome is governed by congruence between the femoral head and acetabular roof.
- Defined total, partial and apparent (secondary) incongruence; in nine fractures, displaced fragments regrouped around the femoral head to give apparent congruence, with seven achieving very good clinical results despite overall displacement.
Both-Column Outcomes & Secondary Congruence Biomechanics
- In a cohort of both-column fractures treated with anterior and posterior (bicolumnar) plating, 80% achieved excellent-to-good results with a mean modified Harris Hip Score of 85.7.
- Highlights that biomechanical data show non-operative reliance on secondary congruence raises peak supra-acetabular contact pressures, with a risk of post-traumatic osteoarthritis, supporting operative reconstruction in fit patients.
Operative Series: Both-Column Most Common Associated Pattern
- In 262 displaced acetabular fractures operated within 21 days, associated patterns accounted for 79%, with both-column the single most common type (92 hips, 35%).
- The vast majority were managed through a single approach (Kocher-Langenbeck, ilioinguinal or extended iliofemoral); only 4 hips required a combined ilioinguinal plus Kocher-Langenbeck exposure.
Acute Total Hip Arthroplasty for Selected Fractures
- In 57 patients (mean age 69) with displaced acetabular fractures and features predicting poor ORIF outcome (articular comminution, full-thickness cartilage loss, femoral head impaction, acetabular impaction of more than 40% of the joint surface), acute THA gave 79% excellent or good results at a mean of 8.1 years.
- No cup or stem developed late loosening, establishing acute arthroplasty as a viable primary option in the elderly with non-reconstructable joint surfaces.
Corona Mortis Anatomy: Surgical Hazard
- In 62 hemipelvises dissected via the anterior intrapelvic approach, a corona mortis anastomosis between the obturator and external iliac systems was present in 50 (80.6%).
- The venous variant (40.3%) was more frequent than the arterial variant (16.1%); venous bleeding behind the superior pubic ramus is harder to control.
Reduction Quality Predicts Outcome (Matta Series)
- Across 262 displaced acetabular fractures, anatomical reduction was achieved in 71% and correlated closely with the clinical result; the overall outcome was excellent or good in 76% of hips.
- The rate of anatomical reduction fell with increasing fracture complexity, older age and longer injury-to-surgery interval; outcome was worsened by femoral head injury and operative complications.
Viva Scenarios
Clinical Decision Scenarios
Use these scenarios to practise clinical reasoning and management decisions
Both Column Fracture Management
"A 35-year-old woman is in a high-speed MVA. X-rays show disruption of both iliopectineal and ilioischial lines, with a spur sign on obturator oblique. CT confirms both column acetabular fracture with 5mm articular step-off. Describe your management approach."
Recognition: Both column acetabular fracture confirmed by spur sign and disruption of both radiographic lines. Significant displacement (5mm step-off).
Initial Management:
- ATLS approach - exclude polytrauma
- Document sciatic nerve function (L5, S1)
- Skeletal traction (distal femur or proximal tibia)
- Adequate analgesia
- DVT prophylaxis
Imaging Assessment:
- Judet views confirm both column pattern
- Spur sign pathognomonic
- CT with 3D reconstruction for surgical planning
- Greater than 5mm step-off exceeds acceptable threshold
- No secondary congruence present
Surgical Indication:
- Young patient (35 years) with high demands
- Displaced fracture (greater than 2mm step-off)
- No secondary congruence
- Clear indication for ORIF
Surgical Planning:
- Timing: Within 2 weeks ideally
- Approach: Likely combined (ilioinguinal + Kocher-Langenbeck)
- Evaluate which column more displaced to determine primary approach
- May stage if medically needed
Goals:
- Anatomic reduction (less than 2mm, ideally less than 1mm)
- Stable fixation
- Restore articular congruence
- Early mobilization
The Spur Sign
"Explain the spur sign and how it distinguishes both column fractures from transverse fractures."
The Spur Sign:
- Seen on OBTURATOR OBLIQUE radiograph
- Represents intact superior ilium
- Located above the completely detached columns
- Pathognomonic for both column fractures
Why It Occurs:
- In both column fractures, both anterior AND posterior columns separate from axial skeleton
- The intact ilium above remains attached to sacrum
- This creates a "spur" of bone projecting into the defect
- Best seen on obturator oblique (45-degree rotation)
Distinction from Transverse:
Transverse Fracture:
- Single fracture line across acetabulum
- Divides acetabulum into superior and inferior portions
- SUPERIOR (roof) portion remains attached to ilium
- No spur sign - roof attached above fracture
Both Column Fracture:
- Both columns completely fractured
- Fracture lines extend ABOVE the dome
- NO articular segment attached to ilium
- Spur sign PRESENT - ilium above floating columns
Clinical Importance:
- Both column may develop secondary congruence (conservative option)
- Transverse usually requires surgery to restore roof congruence
- Surgical approach differs based on pattern
Secondary Congruence Management
"An 80-year-old woman with multiple comorbidities has a both column acetabular fracture from a low-energy fall. CT shows secondary congruence with acceptable articular alignment. How would you manage this patient?"
Assessment:
- Both column fracture confirmed
- Secondary congruence PRESENT - key finding
- Low-energy mechanism in elderly
- Multiple medical comorbidities
Secondary Congruence Concept:
- Femoral head acts as template
- Pushes fractured acetabular segments into acceptable position
- Creates congruent weight-bearing surface
- Despite lack of fixation, acceptable function possible
Conservative Management Indicated:
- Elderly patient with limited demands
- Multiple comorbidities increase surgical risk
- Secondary congruence provides acceptable alignment
- Low-energy suggests osteoporotic bone (poor fixation)
Protocol:
- Initial skeletal traction (2-3 weeks)
- Monitor for maintaining congruence
- Progress to chair sitting
- Non-weight bearing with walker (6-8 weeks)
- Progressive weight bearing by 10-12 weeks
- Serial radiographs to monitor alignment
Monitoring:
- Weekly radiographs initially
- Watch for loss of congruence (would indicate surgery)
- DVT prophylaxis throughout
- Pressure area care
- Accept some late arthritis (may need THR in future)
Expected Outcome:
- Reasonable function for low-demand patient
- May develop post-traumatic arthritis over years
- THR remains future option if needed
MCQ Practice Points
Pathognomonic Sign Question
Q: Which radiographic sign is pathognomonic for both column acetabular fractures?
A: SPUR sign on obturator oblique view. The spur represents intact superior ilium above the completely detached anterior and posterior columns. This sign confirms that NO articular surface remains attached to the axial skeleton.
Differentiation Question
Q: How do you differentiate both column fracture from transverse fracture?
A: Spur sign is present only in both column fractures. In transverse fractures, some dome remains attached to the axial skeleton above the fracture line. In both column, NO articular surface has any attachment to the spine - the entire acetabulum floats.
Radiographic Lines Question
Q: Which radiographic lines are disrupted in both column acetabular fractures?
A: BOTH iliopectineal AND ilioischial lines are disrupted. Iliopectineal represents anterior column, ilioischial represents posterior column. Disruption of both confirms involvement of both columns.
Secondary Congruence Question
Q: What is secondary congruence and when does it allow conservative treatment?
A: Secondary congruence occurs when the femoral head molds the floating acetabular fragments into acceptable alignment. It is unique to both column fractures and may allow conservative treatment in elderly, low-demand patients with acceptable roof arc measurements.
Outcome Predictor Question
Q: What is the most important prognostic factor after acetabular fracture surgery?
A: Reduction quality. Anatomic reduction (less than 1mm step-off) achieves 80-90% good outcomes. Greater than 3mm step-off is strongly predictive of post-traumatic arthritis.
Guidelines, Registries & Global Practice
Global Epidemiology
According to large registry data, the epidemiology of acetabular fractures is shifting worldwide from high-energy injuries in young men towards low-energy falls in older adults. In the German Pelvic Multicentre registry of 2,853 unilateral acetabular fractures, the mean age was 61.5 years and rising, with a parallel shift from simple patterns to complex fractures involving the anterior column. Both-column fractures are the single most common associated pattern, accounting for roughly a third of operatively treated acetabular fractures in the Matta series.
National Registry: Epidemiologic & Treatment Trends
- German Pelvic Multicentre registry: 2,853 acetabular fractures over 10 years; mean age 61.5 years and rising, with a shift from simple patterns towards complex anterior-column-involving fractures.
- Operative treatment in 62.5%; anterior intrapelvic approaches progressively replaced the extrapelvic ilioinguinal approach. Anatomical reduction in only 47.4% (31.7% imperfect, 20.9% poor); high-volume centres achieved significantly better reductions. In-hospital mortality stable at 3.3%.
Guideline & Society Positions (Side by Side)
How Major Bodies Frame Acetabular Fracture Care
| Body / Region | Position | Evidence basis |
|---|---|---|
| AO Foundation (global) | Restore congruent, stable joint; anatomical reduction of articular surface; anterior intrapelvic / ilioinguinal for anterior-dominant both-column | Expert consensus + observational series |
| BOA / BOAST (UK) | Suspected acetabular fractures referred early to a specialist pelvic & acetabular unit; CT for all; definitive surgery by a specialist team | Standard of care / consensus |
| EFORT / European | Centralisation to high-volume centres improves reduction quality and outcome | Registry & observational |
| Elderly / fragility | Consider fix-and-replace or acute total hip arthroplasty when articular surface is non-reconstructable | Level IV (Mears) |
Registry Evidence
Joint and trauma registries (the German Pelvic Registry, and for the arthroplasty endpoint the NJR of England and Wales, AOANJRR in Australia, AJRR in the USA and the Swedish/Nordic registries) consistently show two themes: reduction quality and outcome improve with surgeon and centre volume, and a growing proportion of older patients are managed with primary or salvage total hip arthroplasty rather than ORIF.
Global Practice Variation
- High-resource settings: routine CT with 3D reconstruction, anterior intrapelvic (Stoppa-type) approaches, and increasing fix-and-replace/acute THA in the elderly.
- Limited-resource settings: greater reliance on traction and non-operative management exploiting secondary congruence, and on single-approach plating where combined exposures or arthroplasty are not feasible.
- Universal principles: early specialist referral, meticulous documentation of sciatic nerve function, thromboprophylaxis, and heterotopic ossification prophylaxis (indometacin or single-dose radiotherapy) after extensile posterior exposures.
Both Column Acetabular Fractures
Clinical summary
Key Features
- •20-25% of acetabular fractures (most common associated)
- •NO articular segment attached to axial skeleton
- •BOTH iliopectineal AND ilioischial lines disrupted
- •SPUR sign on obturator oblique is pathognomonic
Radiographic Findings
- •Obturator oblique shows SPUR sign
- •Both column lines disrupted
- •CT with 3D for surgical planning
- •Assess for secondary congruence
Management
- •Young patient displaced: ORIF (combined approaches)
- •Elderly with secondary congruence: conservative
- •Timing: within 2 weeks for best outcomes
- •Reduction goal: less than 2mm step-off
Surgical Approaches
- •Ilioinguinal for anterior column
- •Kocher-Langenbeck for posterior column
- •Combined approaches often needed
- •Sciatic nerve injury risk 10-15%
Key Pitfalls
- •Missing spur sign (only on obturator oblique)
- •Confusing with transverse (transverse has dome attached)
- •Not documenting sciatic nerve preoperatively
- •Delaying surgery beyond 2 weeks
