Pelvic ring fractures - Acetabulum fractures

$Acetabulum fractures$

2018-10-21 19:41:15 | 0 |

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
- 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

	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	x		• Very rare
Anterior column		x	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 • "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
  - 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
- 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 angle
    - 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
  - gull sign
    - represents impaction of superomedial roof
    - seen on obturator oblique view
    - pathognomic for posterior wall fractures
  - spur sign
    - represents most caudal part of intact ilium due to medialization of articular components
    - seen on obturator oblique view
    - pathognomic for ABC 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-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
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 > 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
  - 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 (> 2 mm)
      - 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)	• 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)	• 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)	• 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	• 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

المرفقات

1540150861 - XRAY - AP - Both Column Intro_moved.jpg 2

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الكلية - مطلوب *

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البريد الالكتروني (الجامعي)

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رقم المسلسل في قائمة الاسماء - اختياري

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Pelvic ring fractures - Acetabulum fractures

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