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

Acetabular FracturesAcetabular Fractures

Evaluation, Anatomy and Evaluation, Anatomy and ClassificationClassification

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.

Anatomic landmarks in AP view

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

Iliac oblique radiograph

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 wall3. Anterior half of

the joint4. The iliac wing

profile (the spur sign site)

Obturator oblique radiograph

AP pelvis Iliac oblique Obturator oblique

AW—anterior wall;AC—anterior column; PC—posterior column; PW—posterior wall; OR—obturator ring.

Inlet Pelvis X-ray

Skeletal anatomy represented on inlet

view

Outlet Pelvis XR

Skeletal anatomy represented on outlet view

Radiological Study

Radiographic evaluation

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.

Radiographic evaluation

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

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Post. wall

Post. column

Ant. wall

Ant. column

Transverse

Classifications

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

Posterior Column Fracture

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

Anterior Wall Fracture

Anterior Column Fracture

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

AP pelvic radiograph

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

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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

2-D CT cut of T-type fracture

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

disassociated

40-year-old man with T-shaped acetabular fracture

AP pelvic radiograph

Bilateral oblique pelvic 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 posterior wall element.

Transverse and posterior wall fracture

Transverse and posterior wall fracture

20-year-old man showing transverse with posterior wall acetabular fracture

AP pelvic radiograph

Bilateral oblique pelvic 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.

Both-column fracture(formerly called ‘central acetabular

fracture’)

"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.

Both-column fracture(formerly called ‘central acetabular

fracture’)

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

AP pelvic radiograph

Bilateral oblique pelvic radiographs

Axial CT scan sagittal reconstruction CT scan

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

Cases

Case 1

Disrupción del anillo obturador + extensión a

pala iliaca FRACTURA

BICOLUMNARIA

Case 2

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