Acetabular Fractures

Question 1

demographics

Answer 1

fractures occur in a bimodal distribution

• high energy trauma in younger patients (e.g., motor vehicle accidents)
• low energy trauma in elderly patients (e.g., fall from standing height)

Question 2

Prognosis

Answer 2

poor outcomes are associated with:

• multi-system trauma
• increasing age
• poor articular congruency
• associated femoral head articular injury
• post-traumatic arthritis

Question 3

Osteology

Answer 3

• acetabular inclination & anteversion
  
  • mean lateral inclination of 40 to 48 degrees
  • anteversion of 18 to 21 degrees
• column theory
  
  • acetabulum is supported by two columns of bone
  • form an “inverted Y”
  • connected to sacrum through sciatic buttress
    
    • posterior column
      
      • comprised of
        
        • quadrilateral surface
        • posterior wall and dome
        • ischial tuberosity
        • greater/lesser sciatic notches
    • anterior column
      
      • comprised of
        
        • anterior ilium (gluteus medius tubercle)
        • anterior wall and dome
        • iliopectineal eminence
        • lateral superior pubic ramus

Question 4

Letournel Classification

Answer 4

Judet and Letournel

• most common referenced classification system
  
  • classifed as 5 elementary and 5 associated fracture patterns
• most common fracture patterns
  
  • younger
    
    • posterior wall
    • transverse fracture “family”
      
      • transverse
      • T-type
      • transverse + posterior wall
  • elderly
    
    • anterior column (e.g., quadrilateral plate fractures)
    • anterior column, posterior hemitransverse
    • assoicated both column fractures

Question 5

Radiographs

Answer 5

• Recommended views
  
  • AP
  • judet
    
    • obturator oblique
      
      • shows profile of obturator foramen
      • shows anterior column and posterior wall
    • iliac oblique
      
      • shows profile of involved iliac wing
      • shows posterior column and anterior wall
• Optional views
  
  • inlet/outlet if concerned for pelvic ring involvement
  • examination under anesthesia (EUA)
    
    • used to assess posterior wall stability
    • hip positioned in flexion, adduction and axial load
    • obtain obturator oblique view
    • opening of the medial clear space suggests instability of the posterior wall fracture

Question 6

Radiographs Findings

Answer 6

1. radiographic landmarks of the acetabulum
2. roof arc angle
3. gull sign
4. spur sign

Question 7

radiographic landmarks of the acetabulum

Answer 7

• iliopectineal line (anterior column)
• ilioischial line (posterior column)
• anterior wall
• posterior wall
• teardrop
• weight bearing roof
  
  • superior acetabular rim may show os acetabuli marginalis superior which can be confused for fracture in adolescents
• Shenton’s line

Question 8

roof arc angle

Answer 8

• angle between vertical line through femoral head and line through fracture
• helps to define fracture pattern stability
• considered stable if the fracture line exits outside the weight bearing dome of the acetabulum
• defined as > 45° on AP, obturator and iliac oblique views
• not applicable for associated both column or posterior wall pattern because no intact portion of the acetabulum to measure

Question 9

gull sign

Answer 9

• represents impaction of superomedial roof
• seen on obturator oblique view
• pathognomic for posterior wall fractures

Question 10

spur sign

Answer 10

• represents most caudal part of intact ilium due to medialization of articular components
• seen on obturator oblique view
• pathognomic for ABC fractures

Question 11

CT scan

Answer 11

• indications
  
  • now considered a gold standard in management
• findings
  
  • fracture pattern orientation
  • define fragment size and orientation
  • identify marginal impaction
  • identify loose bodies (e.g., post-reduction)
  • look for articular gap or step-off
• roof-arc measurements
  
  • view
    
    • 2 mm fine cuts on axial view
  • findings
    
    • assess stability of the weight bearing dome based on the exiting fracture line
    • defined as an intact subchonral ring in the superior 10 mm of the acetabulum
    • > 2 mm incongruity in the articular segment is considered unstable

Question 12

Duplex doppler ultrasound

Answer 12

indications

• delayed presentation to treating hospital
• rule out DVT

Question 13

Nonoperative indications

Answer 13

protected weight bearing for 6-8 weeks

indications

• patient factors
  
  • high operative risk (e.g., elderly patients, presence of DVT)
  • morbid obesity
  • open contaminated wound
  • late presenting > 3 weeks
• fracture characteristics
  
  • minimally displaced fracture (< 2 mm)
  • < 20% posterior wall fractures
    
    • treatment based on size of posterior wall is controversial
    • recommend an exam under anesthesia (EUA) using fluoroscopy best method to test stability
  • femoral head congruency with weight bearing roof (out of traction)
    
    • both column fracture pattern with secondary congruence (out of traction)
  • displaced fracture with roof arcs > 45° in AP and Judet views or >10 mm on axial CT cuts

Question 14

Nonoperative technique

Answer 14

• skeletal traction NOT required if stable fracture pattern, outside the weight-bearing dome
• activity as tolerated with crutches/walker
• weight-bearing
  
  • lowest joint reactive forces seen with toe-touch weight bearing and passive hip abduction
    
    • greatest joint contact force seen when rising from a chair on the affected extremity
• DVT prophylaxis if slow to mobilize
• close radiographic follow-up

Question 15

Operative treatment

Answer 15

1. open reduction and internal fixation
2. total hip arthroplasty

Question 16

open reduction and internal fixation indications

Answer 16

indications

• patient factors
  
  • < 3 weeks from date of injury
  • physiologically stable
  • adequate soft-tissue envelope
  • no local infection
    
    • pregnancy is not contraindication to surgical fixation
• fracture factors
  
  • displacement of roof (> 2 mm)
  • unstable fracture pattern (e.g. posterior wall fracture involving > 40-50%)
  • marginal impaction
  • intra-articular loose bodies
  • irreducible fracture-dislocation

Question 17

open reduction and internal fixation approaches

Answer 17

approaches

• anterior
  
  • ilioinguinal
  • iliofemoral
  • modified stoppa
• posterior
  
  • Kocher-Langenbach
• combined
  
  • extended ilifemoral

Question 18

open reduction and internal fixation techniques

Answer 18

techniques

• factors considered for fiaxtion methodology
  
  • location (column and/or wall) and level (high or low) of the fracture pattern
  • amount of displacement
  • marginal impaction
  • assoicated injury
• fixation modalities
  
  • column fixation strategies
    
    • reconstruction bridging plate and screws
    • percutaneous column screws
    • cable fixation
  • wall fixation strategies
    
    • bridge plate and screws
    • lag screw and neutralization plate
    • spring (butress) plate

Question 19

open reduction and internal fixation outcomes

Answer 19

outcomes

• timing
  
  • associated hip dislocations should be reduced within 12 hours for improved outcomes
  • worse outcomes with fixation of fracture > 3 weeks from time of injury
    
    • earlier operative treatment associated with increased chance of anatomic reduction
• peri-operative
  
  • clinical outcome correlates with quality of articular reduction
    
    • postoperative CT scan is most accurate way to determine posterior wall accuracy of reduction which has greatest correlation with clinical outcome
    • ideally articular reduction <2mm
• post-operative
  
  • greatest stress on acetabular repair occurs when rising from a seated position using the affected leg, and occurs in the posterior superior portion of the acetabulum
  • functional outcomes most strongly correlate with hip muscle strength and restoration of gait postoperatively

Question 20

total hip arthroplasty indications

Answer 20

indications

• usually elderly patients with
  
  • significant osteopenia and/or significant comminution
  • pre-existing arthritis
• post-traumatic arthritis in all ages

Question 21

total hip arthroplasty indications

Answer 21

techniques

• timing
  
  • immediate vs. delayed THA
    
    • immediate THA (with, or without, fracture fixation)
      
      • wall fractures
        
        • butress plate with multi-hole cup
      • column fracture
        
        • cage and cup constructs
    • delayed THA

Question 22

total hip arthroplasty indications

Answer 22

outcomes

• patients older than 60 years have approx. a 30% late conversion rate to THA after acetabular fractures
• 10-year implant survival noted to be around 75-80%

Question 23

Complications

Answer 23

• Post-traumatic DJD
  
  • most common complication
  • 80% survival noted at 20 years for patients s/p ORIF
  • risk factors for DJD include
    
    • age >40
    • associated fracture patterns
    • concomitant femoral head injury
  • treat with hip fusion or THA
• Heterotopic Ossification
  
  • highest incidence with extensile approach
    
    • treat with
      
      • indomethacin x 5 weeks post-op
      • low dose external radiation (no difference shown in direct comparison)
  • lowest incidence with anterior ilioinguinal approach
• Osteonecrosis
  
  • 6-7% of all acetabular fractures
  • 18% of posterior fracture patterns
• DVT and PE
• Infection
• Bleeding
• Neurovascular injury
• Intraarticular hardware placement
• Abductor muscle weakness