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Introduction
  • Acetabulum fractures can involve one or more of the two columns, two walls or roof within the pelvis
  • Epidemiology
    • demographics
      • 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)
  • Pathoanatomy  
    • fracture pattern predominately determined by
      • force vector
      • position of femoral head at time of injury
      • bone quality (e.g., age)
  • Associated conditions
    • orthopaedic manifestations
      • lower extremity injury (36%)
      • nerve palsy (13%)
      • spine injury (4%)
    • systemic injuries
      • head injury (19%)
      • chest injury (18%)
      • abdominal injury (8%)
      • genitourinary injury  (6%)
  • Prognosis
    • poor outcomes are associated with:
      • multi-system trauma
      • increasing age
      • poor articular congruency
      • associated femoral head articular injury
      • post-traumatic arthritis
Anatomy
  • Osteology
    • 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
  • Vascular
    • corona mortis 
      • anastomosis of external iliac (epigastric) and internal iliac (obturator) vessels
      • at risk with lateral dissection over superior pubic ramus
Letournel Classification
  • Judet and Letournel
    • most common referenced classification system
      • classifed as 5 elementary and 5 associated fracture patterns

 
Illus.
AP
Obt.Obl.
Iliac.Obl.
CT
Comments
Elementary 
Posterior wall 
 x
• Most common
"gull sign" on obturator oblique view
Posterior column 
• check for injury to superior gluteal NV bundle
Anterior wall
 
 x
• Very rare
Anterior column 
 x
 x 
  
• More common in elderly patients with fall from standing (most common in elderly is "anterior column + medial wall")
Transverse    
 x 
 x 
 x 
 x  

• Axial CT shows anterior to posterior fx line 
• Only elementary fx to involve both columns

Associated 
Associated Both Column 

 

Characterized by dissociation of the articular surface from the inonimate bone  ; will see "spur sign" on obturator oblique  

Transverse + Post. Wall

 
 x

• Most common associated fx
T Shaped

 x
x

• May need combined approach
Anterior column or wall + Post. hemitransverse
x
x

• Common in elderly patients

Post. column + Post. wall
x
x
x
x
• Only associated fracture that does not involve both columns
 
Imaging
  • Radiographs
    • recommended views
      • AP pelvis
      • Judet views (45 degree oblique views)
        • 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 
    • additional views
      • inlet and outlet if concerned for pelvic ring involvement
      • examination under anesthesia (EUA)
        • assess posterior wall stability
          • obturator oblique view 
        • hip postition in flexion, adduction and axial load
          • opening of the medial clear space suggests instability of the posterior wall fracture  
    • findings
      • radiographic landmarks of the acetabulum 
        • 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
      • roof arc measurements 
        • help to define fracture pattern stability
          • considered stable if the fracture line exits outside the weight bearing dome of the acetabulum 
          • defined as > 45 degrees 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
      • 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
  • CT scan 
    • 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 arm measurements
      • view
        • 2mm 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
        • >2mm incongruity in the articular segment is considered unstable
  • Duplex doppler ultrasound
    • indications
      • delayed presentation to treating hospital
      • rule out DVT
Treatment
  • Nonoperative
    • 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 > 3weeks
        • fracture characteristics
          • minimally displaced fracture (< 2mm)
          • < 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 degrees in AP and Judet views or >10 mm on axial CT cuts
      • technique
        • 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
  • Operative treatment
    • open reduction and internal fixation 
      • 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 (>2mm)
          • unstable fracture pattern (e.g. posterior wall fracture involving > 40-50%)
          • marginal impaction
          • intra-articular loose bodies
          • irreducible fracture-dislocation
      • approaches
        • anterior 
          • ilioinguinal 
          • iliofemoral 
          • modified stoppa
        • posterior
          • Kocher-Langenbach
        • combined
          • extended ilifemoral
      • 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
      • 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
    • total hip arthroplasty  
      • indications
        • usually elderly patients with 
          • significant osteopenia and/or significant comminution
          • pre-existing arthritis
        • post-traumatic arthritis in all ages
      • 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 
      • 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%
Techniques
  • Percutaneous fixation with column screws
    • approach
      • anterograde (from iliac wing to ramus)
      • retrograde (from ramus to iliac wing)
      • posterior column screws
    • imaging  
      • obturator oblique best view to rule out joint penetration  
      • inlet iliac oblique view best to determine anteroposterior position of screw within the pubic ramus 
      • obturator oblique inlet view best to determine position of a supraacetabular screw within tables of the ilium 
  • ORIF
    • approaches
      • approach depends on fracture pattern
      • two approaches can be combined
Approaches
Indications
Risks
Anterior Approach (Ilioinguinal) topic

• anterior wall and anterior column 
• both column fracture
• posterior hemitransverse

• femoral nerve injury
• LFCN injury
• thrombosis of femoral vessels
• laceration of corona mortis in 10-15%.   

Posterior Approach (Kocher-Langenbach) topic

• posterior wall and posterior column fx  
• most transverse and T-shaped
• combination of above 

• increased HO risk compared with anterior approach 

• sciatic nerve injury (2-10%)   
• damage to blood supply of femoral head (medial femoral circumflex)

Extensile Approach (extended iliofemoral) topic

• only single approach that allows direct visualization of both columns
• associated fracture pattern 21 days after injury
• some transverse fxs and T types 
• some both column fxs (if posterior comminution is present)

• massive heterotopic ossification
• posterior gluteal muscle necrosis

Modified Stoppa Approach topic • access to quadrilateral plate to buttress comminuted medial wall fractures • Corona mortis must be exposed and ligated in this approach
 
Complications
  • 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
 

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