Background

Anatomy

 

Unusual anatomic convergence of ilium, pubis and ischium

- covered entirely by hyaline cartilage

- except at acetabular fossa, which is the site of attachment of the ligamentum teres

- deepened by peripheral fibrocartilage labrum

 

2 column theory (Letournel and Judet)

 

Anterior Column 

- superior pubic ramus

- anterior acetabular wall, anterior dome

- anterior iliac spines and anterior ilium

 

 

Posterior Column 

- ischium

- posterior acetabular wall, posterior dome

- posterior ilium

 

 

Quadrangular Plate

 

 

Mechanism

 

Axial load applied through femur

- type of fracture depends on position of femur at time of injury

- IR - posterior column

- ER - anterior column

 

Examination

 

Resuscitation EMST

 

Detailed neurological exam

- sciatic nerve damaged in 20% cases with posterior wall or column injury 

- usually peroneal division

 

Careful soft tissue evaluation

- closed degloving injury

- 'Morel-Lavallee' lesion

- the serosanginous fluid collection can be culture positive in up to 30%

 

X-ray / 5 standard views

 

AP / Six X-ray Landmarks

 

 

1.  Iliopectineal line 

- along pelvic brim to pubic symphysis

- anterior column

 

2.  Ilioischial Line 

- pelvic brim to ischial tuberosity

- posterior column

- formed by posterior 4/5 of quadrilateral surface ilium

 

3.  The Teardrop 

- lateral: subchondral bone condensation at anterior margin of cotyloid fossa 

- medial:  anterior flat part of quadrilateral surface of iliac bone

 

4.  Roof of acetabulum

 

5.  Anterior rim of acetabulum

- semilunar

 

6.  Post rim of acetabulum

 

Judet views  / 45^o obliques

 

Internal Oblique / Obturator Oblique

- affected side rotated forward

- anterior column + posterior wall

 

 

External Oblique / Iliac Oblique

- unaffected side rotated forward

- posterior column + anterior wall

 

Inlet view / Outlet view

 

Indicated for pelvic fractures usually

 

 

CT

 

Configuration

 

1-2 mm sections

 

CT reconstruction

- remove head to view acetabulum

- beware volume averaging

- used to guide surgery

 

 

Diagnose

 

Loose bodies

Femoral head fractures

Subtle subluxation

Articular steps

Roof arc measurement

 

Letournel Classification

 

5 Elementary

5 Complex

 

Elementary / One primary fracture line

 

1.  Posterior Wall

- often associated with posterior dislocation

- may be in one or many pieces

- may have marginal impaction fracture

 

 

2.  Posterior Column

- whole posterior column separated in one piece

- fracture greater sciatic notch

- through inferior acetabulum

- into obturator foramen

- through inferior pubic rami

 

 

 

3.  Anterior Wall

 

 

4.  Anterior Column

- from ilium above ASIS

- through inferior acetabulum  

- across obturator foramen

- out through inferior rami

 

 

5.  Transverse

- from greater sciatic notch to AIIS

- obturator foramen not fractured

 

 

High - above acetabulum 

Low - through acetabulum

 

Complex / More than one primary fracture line

 

1.  Posterior column & posterior wall

 

2.  Transverse & posterior wall

 

3.  T-shaped

- transverse through acetabulum

- inferior fracture line to obturator foramen

 

4.  Anterior & posterior hemi-transverse

 

5.  Both column

- Y Shaped transverse above acetabulum

 

 

 

Determinants of outcome

 

1.  Fracture displacement

- < 2mm articular step

 

 

2.  Fracture location

 

Early onset of arthritis and poor clinical results correlate with 

- displacement present at the time of union within the weight bearing dome

- any roof arc measurement less than 45°

- a broken CT subchondral ring

 

A.  Matta roof arc measurements

 

Describe location of fracture lines in relation to roof of acetabulum

- integrity of acetabular roof

- must be no hip subluxation

 

3 roof arc measurements

- AP, 2 Judet's views

- vertical line to centre of head

- line to where fracture enters joint

- the larger the arc, the further the fracture from the roof

- 10^o - fracture in roof

- 90⁰ - low fracture

 

Weight bearing dome is intact if angle > 45^o on all 3 views

 

B.  CT subchondral arc

- 10 mm below subchondral bone of roof

- similar to xray roof arc measurements

 

 

3.  Stability / Concentric reduction

 

Subluxation

- incongruency between the head and the roof

- poor clinical results are obtained in more than 50% of fractures in which the head is subluxed  

- may also have an element of dynamic instability, with certain posterior wall fractures

 

 

Any subluxation on CT demonstrates clinical instability

- fractures affecting 40% or more of the posterior wall are usually associated with instability

- fractures less than 40% should be screened for stability under II

 

4.  Other factors

 

Direct cartilage injury at time of impact

Neurological injury

AVN of head