26. acetabular fractures anatomy, evaluation and classification - muhammad abdelghani

Acetabular FracturesAcetabular Fractures
Evaluation, Anatomy and ClassificationEvaluation, Anatomy and Classification
Muhammad Abdelghani

Normal Anatomy: Columns and
Walls

 From the lateral aspect of the
pelvis, the innominate osseous
structural support of the
acetabulum may be
conceptualized as a two-
columned construct forming an
inverted Y:
1. Anterior column (iliopubic
component): extends from iliac
crest to symphysis pubis and
includes the anterior wall of the
acetabulum.
2. Posterior column (ilioischial
component): extends from
superior gluteal notch to ischial
tuberosity and includes the
posterior wall of the
acetabulum.

 The anterior and posterior walls
extend from each respective
column and form the cup of the
acetabulum.
 The anterior and posterior
columns connect to the axial
skeleton through a strut of bone
called the sciatic buttress.

 When looking at the acetabulum en face, the
anterior and posterior columns have the
appearance of the Greek letter lambda (λ).
 The anterior column represents the longer,
larger portion, which extends superiorly from
the superior pubic ramus into the iliac wing.
The posterior column extends superiorly from
the ischiopubic ramus as the ischium toward
the ilium.
 The anterior and posterior columns of bone
unite to support the acetabulum.
 In turn, the sciatic buttress extends posteriorly
from the anterior and posterior columns to
become the articular surface of the sacroiliac
joint, which attaches the columns to the axial
skeleton.
 The anterior and posterior walls, which extend
from the columns and support the hip joint, are
well seen on an axial CT.

 The anterior and posterior walls, which extend
from the columns and support the hip joint, are
well seen on an axial CT.
Axial section
through
acetabulum
shows anterior
(arrowhead)
and posterior
(arrow) walls.

Acetabular dome: The superior weight-bearing
portion of the acetabulum at the junction of
the anterior and posterior columns, including
contributions from each.

Anterior
coulmn
Posterior
column
Sciatic
buttress

Anterior column in white, posterior column
in red

Mechanism of injury
Like pelvis fractures, these injuries are
mainly caused by high-energy trauma
secondary to a motor vehicle, motorcycle
accident, or fall from a height.

Mechanism of injury
The fracture pattern depends on
 Position of femoral head at the time of injury,
 Magnitude of force, &
 Age of patient.

Mechanism of injury
Direct impact to greater trochanter with:
 Hip in neutral: transverse acetabular fracture
 An abducted hip: low transverse fracture,
 An adducted hip: high transverse fracture.
 Hip externally rotated and abducted:
anterior column injury.
 Hip internally rotated: posterior column
injury.

Mechanism of injury
With indirect trauma, (e.g., a ‘dashboard’
injury to the flexed knee):
 As the degree of hip flexion increases, the posterior
wall is fractured in an increasingly inferior position.
 Similarly, as the degree of hip flexion decreases,
the superior portion of posterior wall is more likely
to be involved.

Clinical evaluation
 Trauma evaluation: with attention to ABCD, depending on the
mechanism of injury.
 Patient factors (age, degree of trauma, presence of associated
injuries, & general medical condition) affect treatment
decisions as well as prognosis.
 Neurovascular assessment:
 Sciatic nerve injury may be present in up to 40% of posterior column
disruptions.
 Femoral nerve involvement with anterior column injury is rare,
although compromise of the femoral artery by a fractured anterior
column has been described.
 Presence of associated ipsilateral injuries must be ruled out,
with particular attention to the ipsilateral knee in which
posterior instability and patellar fractures are common.
 Soft tissue injuries (e.g., abrasions, contusions, subcutaneous
hemorrhage) may provide insight into the mechanism of injury.

Radiographic evaluation
 5 Pelvic X-rays:
 AP view
 2 Judet views (iliac &
obturator oblique views)
 Inlet and Outlet Pelvis X-rays
 CT scan

Anatomic landmarks in AP
view
 Iliopectineal line (limit of anterior
column),
 Ilioischial line (limit of posterior
column),
 Anterior lip,
 Posterior lip,
 Line depicting the superior
weight-bearing surface,
terminating as the medial
teardrop.

Teardrop
 Internal limb = outer
wall of obturator canal
 External limb = middle
1/3 of cotyloid fossa
 Inferior border =
ischiopubic notch

Iliac oblique radiograph
(45-degree external rotation view)
 Taken by rotating the
patient into 45° of external
rotation by elevating the
uninjured side on a wedge.
 This best demonstrates:
 Posterior column (ilioischial
line),
 Iliac wing,
 Anterior wall of acetabulum.

Iliac-oblique view
1. Border of sciatic
notch
2. Anterior wall
3. Posterior column
4. Iliac wing
5. Posterior wall

Obturator oblique radiograph
(45-degree internal rotation view)
 This is best for evaluating
the anterior column and
posterior wall of the
acetabulum.
 Taken by elevating the
affected hip 45° to the
horizontal by means of a
wedge and directing the
beam through the hip joint
with a 15° upward tilt.

Obturator-oblique view
1. Ilio-pectineal line.
2. Posterior wall
3. Anterior half of the
joint
4. The iliac wing
profile (the spur
sign site)

AP pelvis Iliac oblique Obturator oblique
AW—anterior wall;
AC—anterior column;
PC—posterior column;
PW—posterior wall;
OR—obturator ring.

Skeletal anatomy
represented on inlet
view

Skeletal anatomy represented on outlet view

 CT scan
Provides additional information regarding size
& position of column fractures, impacted
fractures of acetabular wall, retained bone
fragments in the joint, degree of comminution,
and sacroiliac joint disruption.
 Two- and three-dimensional CT scans are
useful in evaluating intra-articular fragments as
well as specific morphologic characteristics of
any given fracture pattern.

 CT scan
 Before a 3-dimensional CT
scan is ordered, the fracture
patterns should be drawn on a
3-dimensional model of the
pelvis to compare the 3-
dimensional reconstructions.
 Three-dimensional
reconstruction allows for
digital subtraction of femoral
head, with full delineation of
the acetabular surface.

CT scan transverse cuts through the acetabulum.

3-D CT scan of a both-
column acetabular
fracture; obturator
oblique view
3-D CT scan of a both-
column acetabular fracture;
iliac oblique view

Line drawing of fracture on a pelvic
model

 Accurate classification of acetabular fractures is
important for determining the proper surgical
treatment.
 Although radiographic examination provides
essential information for acetabular classification,
CT, including multiplanar reconstruction, is
helpful in the visualization of complex fractures.
Classification

 Because of the complex acetabular anatomy, various
classification schemes have been suggested, but the
Judet-Letournel classification system remains the
most widely accepted.
 This classification system subdivides acetabular
fractures into
 Elementary Fracture Types (posterior wall, posterior
column, anterior wall, anterior column and transverse)
 Associated Fracture Types (T-shaped, posterior column and
wall, anterior wall or column with posterior hemitransverse,
and both column).
Classification
(Judet-Letournel)

Elementary fractures
 Poserior wall
 Posterior column
 Anterior wall
 Anterior column
 Transverse
Classification
(Judet-Letournel)

Classification
(Judet-Letournel)
Associated fractures
 T-shaped
 Posterior column + posterior wall
 Transverse + posterior wall
 Anterior column + posterior
hemitransverse
 Both-column

Elementary types
Post wall Post column Ant wall Ant column Transverse

www.pelvisandhip.comwww.pelvisandhip.com
Othopaedic Review CourseOthopaedic Review Course
January 2010January 2010
Post. wall
Post. column
Ant. wall
Ant. column
Transverse

Classification algorithm for 5
common acetabular fractures

 The isolated posterior wall
fracture is one of the most
common types of acetabular
fracture, with a prevalence of
27%.
 The ischium is disrupted.
 The fracture line originates
at the greater sciatic notch,
travels across the
retroacetabular surface, exits
at the obturator foramen.
 The ischiopubic ramus is
fractured.
Posterior wall fractures

 An isolated posterior wall fracture does not
have a complete transverse acetabular
component.
Therefore, the iliopectineal line is not disrupted,
which excludes classification of the transverse
with posterior wall fracture.
 However, disruption of the ilioischial line may or
may not be present as an extension of the
comminuted posterior wall component.
 Oblique (Judet) radiographs and CT are helpful
in showing the isolated posterior wall fracture.
Posterior column fractures

18-year-old man with isolated posterior wall acetabular fracture
AP pelvic radiograph
Bilateral oblique
pelvic radiographs
Axial CT
images

18-year-old man with isolated posterior wall acetabular fracture
Parasagittal
reconstruction CT
image

 Posterior wall and posterior
column fractures can be
distinguished easily.
 In a posterior column fracture, the
ilioischial line is interrupted.
 In a posterior wall fracture, only
the retroacetabular surface is
disrupted.
Posterior column fractures

 Anterior wall and anterior column
fractures can be distinguished by
the additional break in the
ischiopubic segment of the pelvis
present in the anterior column
fracture.
Anterior wall and anterior
column fractures

A transverse acetabular fracture
involves a fracture line that goes
through both columns of the
acetabulum, but a portion of the
dome of the acetabulum remains
attached to the constant
fragment of the iliac wing.
Transverse Fracture

Obturator oblique
view of transverse
fracture
Iliac oblique view
of transverse
fracture

Types (depending on the orientation of the fracture line relative to the
dome or tectum of the acetabulum):
1. Transtectal: through the acetabular dome.
2. Juxtatectal: through the junction of acetabular dome &
fossa acetabuli.
3. Infratectal: through the fossa acetabuli.
Transtectal fractures are less forgiving and must be
reduced anatomically, whereas infratectal fractures, if
low enough, can be treated without surgery,
depending on the pattern.
The femoral head follows the inferior ischiopubic
fragment and may dislocate centrally.
Transverse Fracture

Infratectal Juxtatectal Transtectal

23-year-old woman with transverse acetabular fracture
Bilateral oblique pelvic
radiographs
Axial CT scan
surface-
rendering
3D CT
viewed
laterally,
with right
hemipelvis
and femur
removed

Transverse fractures are sagittal plane
fractures whereas both column
fracturesare coronal plane fractures.
Transverse Fracture

A.Coronal plane fracture
B.Sagittal plane fracture

CT cut of transverse fracture
in the sagittal plane

Associated types
Post. Wall
& post.
column
Transverse &
post. Wall or
column
T-shaped
Ant column or
wall & post
hemitransverse
Both
columns

Othopaedic Review CourseOthopaedic Review Course
January 2010January 2010
T-fracture Transverse/post.wall
Post.wall/post.column Ant.post.hemitrans.
Ass.both.column

Posterior Column-Posterior Wall

Transverse fracture of any type
+
Vertical fr through the isciopubic fragment
The vertical component is best
seen on the obturator oblique
view.
T-shaped fracture

The T-shaped fracture is
similar to a both-column fracture
in that it disrupts the obturator
ring.
Another similarity is disruption of
both the iliopectineal and
ilioischial lines.
However, the superior extension
of the fracture does not involve
the iliac wing, which allows
differentiation from the both-
column fracture.
T-shaped fracture

One area of potential confusion with the Tshaped
fracture is in regard to the transverse component.
The transverse fracture line is not actually in the
anatomic transverse plane, but rather it is
transverse relative to the acetabulum.
Because the cup shape of the acetabulum is
normally tilted inferiorly and anteriorly, the
transverse fracture plane assumes a similar
orientation.
Therefore, on radiographs, the fracture lines that
disrupt the iliopectineal and ilioischial lines course
superiorly and medially in an oblique plane from
the acetabulum.
This is best appreciated by looking at the
acetabulum en face.
On CT, this transverse fracture component is
seen as a sagittally oriented fracture coursing
medially and superiorly from the acetabulum.
T-shaped fracture

T-type fractures differ from transverse fractures by the additional
fracture line that runs through the quadrilateral surface.
As a result, the anterior column and posterior column are
separated by fracture lines.
This becomes important when choosing a surgical approach to
the acetabulum.
In a pure transverse fracture, the anterior and posterior columns
may be reduced through a single approach.
Once the anterior column has been reduced, the posterior
column will follow the reduction and can be palpated indirectly.
T-shaped fracture

 Radiograph of
a T-type
fracture.
 Note the
undisplaced
fracture in the
ischiopubic
ramus.
 This break in the
obturator ring
correlates with
an additional
fracture line in
the
quadrilateral
plate.

In a T-type fracture, the 2 columns must
be reduced independently.
This becomes extremely important when
choosing a surgical approach; therefore,
it is important to recognize the subtle
difference between transverse and T-type
fractures when they are not significantly
displaced.
T-shaped fracture

Note in the T-type fracture the anterior
and posterior columns are disassociated

40-year-old man with T-shaped acetabular fracture
radiographs
Axial CT scan
Surface-rendering 3D CT viewed laterally, with right
hemipelvis and femur removed

Transverse fracture
+
Comminuted posterior wall
fracture (usually displaced)
The iliopectineal and
ilioischial lines are
disrupted.
The obturator oblique view
best demonstrates the
position of the transverse
component as well as the
Transverse and
posterior wall fracture

Transverse and posterior wall
fracture

20-year-old man showing transverse with posterior wall acetabular
fracture
radiographs
axial
CT
scan
surface-
rendering
3D CT
viewed
laterally,
with right
hemipelvis
and femur
removed

Anterior Column-Posterior
Hemitransverse

Both columns are separated from
each other and from the axial
skeleton, resulting in a ‘floating’
acetabulum
This is the most complex type of
acetabular fracture.
A both columns fracture can be
considered a ‘high’ T-shaped
fracture where both columns have
been separated from the sciatic
buttress.
Both-column fracture
(formerly called ‘central acetabular fracture’)

The "spur-sign," best seen on the
obturator oblique view, is
pathognomonic for the both-column
fracture.
This sign represents posterior
displacement of the sciatic buttress
of the iliac wing fracture, which
essentially disconnects the roof of
the acetabulum from the axial
skeleton.
When this occurs, weight from the
torso and upper body can no
longer be supported by the
acetabulum.
"Spur-sign" seen on the
obturator oblique view

On radiographs and CT, the
spur sign appears as a shard
of bone extending posteriorly
at the level of the superior
acetabulum.
Evaluation of sequential CT
images shows the fracture,
which separates the sciatic
buttress from the acetabular
roof.

35-year-old man with a both-column fracture
Oblique pelvic radiograph (A) and axial CT image (B) show
spur sign (arrow), which represents displacement of fracture
involving sciatic buttress (arrowheads).
Note that sciatic buttress (arrowheads, B) no longer connects
to weight-bearing portion of acetabulum.
A B

45-year-old man with both-column acetabular fracture
Bilateral oblique pelvic radiographs
Axial CT scan
sagittal
reconstruction
CT scan

3-D CT scan of a both-column acetabular fracture; obturator3-D CT scan of a both-column acetabular fracture; obturator
oblique viewoblique view

3-D CT scan of a both-column acetabular fracture; iliac oblique view3-D CT scan of a both-column acetabular fracture; iliac oblique view

Line drawing
of fracture on
a pelvic
model

Disrupción del anillo
obturador + extensión a
pala iliaca  FRACTURA
BICOLUMNARIA

Disrupción del anillo
obturador + SIN extensión
a pala iliaca  FRACTURA
en “T”

 Subsequent to the pioneering work of Judet and Letournel,
their classification was then used as the basis for formulating
an alphanumeric computerized format and the Comprehensive
Classification of Fractures of the Acetabulum was developed.
 This effort was spearheaded by SICOT International
Documentation and Evaluation Committee and the AO/ASIF
Foundation under the leadership of Maurice E. Muller.
 Each fracture is classified according to morphological
characteristics, and subdivided into types, groups, and
subgroups.
 The system is especially beneficial for research database
applications.
Classification
(The Comprehensive Classification of Fractures of the
Acetabulum)

The Comprehensive Classification of Fractures of the Acetabulum

References
 Durkee NJ, Jacobson J, Jamadar D, Karunakar MA,
Morag Y, Hayes C: Classification of Common
Acetabular Fractures: Radiographic and CT
Appearances. AJR 2006; 187: 915-925
 Gänsslen A, Oestern HJ: Azetabulumfrakturen. Chirurg
2011; 82:1133–1150
 Jimenez ML: Classification of Acetabular Fractures.
Medscape.com
 Pagenkopf E, Grose A, Partal G, Helfet DL: Acetabular
Fractures in the Elderly: Treatment Recommendations.
HSSJ (2006) 2: 161–171

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