**3.1 Antero-posterior radiograph**

There are six basic landmarks (**Figure 7**)


*The Iliopectineal Line* is the major landmark of the anterior column. The pelvic brim is represented by anterior three-quarters of the iliopectineal line. The posterior quarter of this line is formed by the tangency of the x-ray beam to the internal cortical surface of the sciatic buttress and the internal part of the roof of the greater sciatic notch.

*The Ilioischial Line* is considered a radiographic landmark of the posterior column. It is formed by the tangency of the x-ray beam to the posterior portion of the quadrilateral surface.

*The Radiographic Tear drop* is not a true anatomic structure. It represents a radiographic finding and consists of a medial and lateral limb. The lateral limb represents the inferior aspect of the anterior wall in the acetabulum whereas the medial limb is formed by the obturator canal and the antero inferior portion of the quadrilateral surface. Dissociation of the teardrop and the ilioischial line indicates a fracture of the quadrilateral surface.

*The Roof of the Acetabulum* is a radiographic landmark that results from the tangency of the x-ray beam to a narrow portion of the subchondral bone of the superior acetabulum. Dissociation of the radiographic line of the roof indicates a fracture involving the superior acetabulum.

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be detected.

**Figure 7.**

*Surgical Anatomy of Acetabulum and Biomechanics DOI: http://dx.doi.org/10.5772/intechopen.92330*

*The Anterior Rim of the Acetabulum* represents the lateral margin in the anterior wall of the acetabulum and is contiguous with the inferior margin of the superior pubic ramus. The anterior rim is typically medial to the posterior rim and has a

*The Posterior Rim of the Acetabulum* represents a lateral margin in the posterior wall of the acetabulum. Inferiorly, the posterior rim is contiguous with the thickened condensation of the posterior horn of the acetabulum and approximates a

This view is obtained by rotating the patient so that the injured hemipelvis is tilted 45 degrees away from the x-ray beam. Structures visible on this view are greater and lesser sciatic notches, anterior rim of acetabulum and iliac wing in its largest dimension. This is the best view to see the fractures involving posterior column. Fractures of the anterior column traversing the iliac wing can also

characteristic undulation in its midcontour in the AP pelvis view.

**3.2 The iliac oblique view (also known as external oblique view)**

**3.3 The obturator oblique view (also known as internal oblique view)**

acetabulum is best visualized in the obturator oblique view.

delay the reduction of a known dislocated hip (**Figure 8**).

This view is obtained by rotating the patient so that the injured hemipelvis is rotated 45 degrees toward the x-ray beam. This view shows the obturator foramen in its largest dimension and profiles the anterior column. The posterior rim of the

Posterior subluxation of femoral head can be detected by comparing the relationship of the femoral head with the posterior wall on the normal hip and the injured hip on the obturator oblique view. A dislocated hip will become more obvious in the obturator oblique view, and this view has been advocated for routine evaluation of all posterior fracture dislocations of the hip joint. It is prudent not to

Dynamic stress views under general anesthesia have also been used in acetabular fractures. They serve as a clinical measure of dynamic stability and congruence of

straight line, being more vertical than the anterior wall.

*Radiographic landmarks on AP radiograph of hip.*

*Surgical Anatomy of Acetabulum and Biomechanics DOI: http://dx.doi.org/10.5772/intechopen.92330*

*Essentials in Hip and Ankle*

known as the sciatic buttress.

cortical bone.

fractures of acetabulum are as follows:

**3.1 Antero-posterior radiograph**

• The radiographic teardrop

• The roof of the acetabulum

• The anterior rim of the acetabulum

• The posterior rim of the acetabulum

fracture involving the superior acetabulum.

• Iliopectineal line

• The ilioischial line

the quadrilateral surface.

the quadrilateral surface.

There are six basic landmarks (**Figure 7**)

• The antero-posterior view of the pelvis

• The obturator (or 45-degree internal, Judet) oblique view

• The iliac (or 45-degree external, Judet) oblique view

anatomy of the innominate bone [17–19]. Two limbs of an inverted *"Y"* of bone support the articular surface of acetabulum. These columns are connected to the sacroiliac articulation by a thick strut of bone lying above the greater sciatic notch

The radiographic anatomy of the acetabulum can be determined using AP pelvis and two 45-degree oblique radiographs as proposed by Judet and Letournel. Therefore, three radiographic projections of the pelvis that are used to evaluate the

These plain films are interpreted based on the understanding of normal radiographic landmarks of the acetabulum, and disruption of these landmarks represents a fracture involving that portion of the bone. These landmarks are referred to as "lines". They are generated by the tangency of the applied x-ray beam to a region of

*The Iliopectineal Line* is the major landmark of the anterior column. The pelvic brim is represented by anterior three-quarters of the iliopectineal line. The posterior quarter of this line is formed by the tangency of the x-ray beam to the internal cortical surface of the sciatic buttress and the internal part of the roof of the greater sciatic notch. *The Ilioischial Line* is considered a radiographic landmark of the posterior column. It is formed by the tangency of the x-ray beam to the posterior portion of

*The Radiographic Tear drop* is not a true anatomic structure. It represents a radiographic finding and consists of a medial and lateral limb. The lateral limb represents the inferior aspect of the anterior wall in the acetabulum whereas the medial limb is formed by the obturator canal and the antero inferior portion of the quadrilateral surface. Dissociation of the teardrop and the ilioischial line indicates a fracture of

*The Roof of the Acetabulum* is a radiographic landmark that results from the tangency of the x-ray beam to a narrow portion of the subchondral bone of the superior acetabulum. Dissociation of the radiographic line of the roof indicates a

**10**

**Figure 7.** *Radiographic landmarks on AP radiograph of hip.*

*The Anterior Rim of the Acetabulum* represents the lateral margin in the anterior wall of the acetabulum and is contiguous with the inferior margin of the superior pubic ramus. The anterior rim is typically medial to the posterior rim and has a characteristic undulation in its midcontour in the AP pelvis view.

*The Posterior Rim of the Acetabulum* represents a lateral margin in the posterior wall of the acetabulum. Inferiorly, the posterior rim is contiguous with the thickened condensation of the posterior horn of the acetabulum and approximates a straight line, being more vertical than the anterior wall.

## **3.2 The iliac oblique view (also known as external oblique view)**

This view is obtained by rotating the patient so that the injured hemipelvis is tilted 45 degrees away from the x-ray beam. Structures visible on this view are greater and lesser sciatic notches, anterior rim of acetabulum and iliac wing in its largest dimension. This is the best view to see the fractures involving posterior column. Fractures of the anterior column traversing the iliac wing can also be detected.

## **3.3 The obturator oblique view (also known as internal oblique view)**

This view is obtained by rotating the patient so that the injured hemipelvis is rotated 45 degrees toward the x-ray beam. This view shows the obturator foramen in its largest dimension and profiles the anterior column. The posterior rim of the acetabulum is best visualized in the obturator oblique view.

Posterior subluxation of femoral head can be detected by comparing the relationship of the femoral head with the posterior wall on the normal hip and the injured hip on the obturator oblique view. A dislocated hip will become more obvious in the obturator oblique view, and this view has been advocated for routine evaluation of all posterior fracture dislocations of the hip joint. It is prudent not to delay the reduction of a known dislocated hip (**Figure 8**).

Dynamic stress views under general anesthesia have also been used in acetabular fractures. They serve as a clinical measure of dynamic stability and congruence of

#### **Figure 8.**

*(A) obturator oblique view and (B) iliac oblique view.*


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(**Figure 10**).

*Surgical Anatomy of Acetabulum and Biomechanics DOI: http://dx.doi.org/10.5772/intechopen.92330*

applicable to the fractures of posterior wall.

reduction (**Table 1**).

CT images.

**4. Computed tomography**

the disruption or intactness of the radiographic landmarks.

the hip thus helps in assessing the need for operative treatment in small and intermediate fractures of the posterior acetabular wall. This stress examination is most

Each fracture pattern in the classification of Letournel and Judet has typical radiographic characteristics. These fracture patterns are described with respect to

In the operating room, the three standard views can be obtained with fluoroscopy. The restoration of the radiographic landmarks marks the adequacy of fracture

CT plays a pivotal role in the treatment of acetabular fractures [18, 19]. Axial cuts should be taken with thin (3-mm) intervals and corresponding slice thicknesses. To avoid missing a portion of the fracture the entire pelvis is generally included and comparison to the opposite hip is performed routinely. In general, the transverse fracture lines and fractures of the anterior and posterior walls are in the sagittal plane, paralleling the quadrilateral surface when they are viewed on axial

Some authors have suggested that axial CT images overestimate the extent of comminution of acetabular fractures. An oblique fracture line divides the acetabulum, so the more inferior CT cuts appear to have three fragments when in reality there are only two. By studying the individual fragments on multiple successive cuts, the entire fracture can be appreciated, giving a true mental three-dimensional picture. High-resolution coronal and sagittal reconstructions of the fracture are helpful in the preoperative evaluation of complex fractures by delineating the

CT scans can give the same information about the acetabular dome as the roof

Three-dimensional CT reconstructions of a fracture have become sophisticated and can be projected in many different views with the subtraction of the femoral head that show unique features of the various fracture patterns [16] (**Figure 9**).

The late 1970s and early 1980s saw the development of software and hardware that made it possible to produce 3D reformats of complex anatomical structures from sets of transaxial CT images [19]. However, the acceptance of 3D was limited because of poor image quality, lack of user-friendly systems, and limited display flexibility. In past few years, several manufacturers have introduced software that is easier to use and that produces 3D views much faster than the earlier systems. Several investigators now believe that the spatial analysis of a complex acetabular fracture is best made with 3D imaging. Some investigators have stated that 3D CT is

The original transaxial slices show the diagnostic details, but 3D imaging integrates the finding into a whole that is more easily assimilated than the sum of its parts. By having an access to a 3D image, the surgeon can decide whether or not to operate and which approach to use. Although 3D images may present less detail to the radiologist than the 2D series, but for an operating surgeon 3D images are very helpful for re orientation during surgical repair. Minor nondisplaced fractures are unlikely to require or benefit from 3D reformats [23–26]

fracture lines that lie directly in the plane of a given axial CT image.

arc measurements on the antero-posterior and oblique radiographs.

**4.1 Role of 3D CT in acetabular fractures**

a valuable addition to the imaging of acetabular fractures.

#### **Table 1.**

*Information obtained from X-ray landmarks on each standard view [17–19].*

*Essentials in Hip and Ankle*

**X-ray view Information regarding**

Iliopectineal line Anterior column Ilioischial line Posterior column Posterior lip Posterior column or wall Anterior lip Anterior column or wall Roof Superior articular surface Teardrop Relationship of columns

*(A) obturator oblique view and (B) iliac oblique view.*

Pelvic brim Anterior column Posterior rim Posterior column or wall Obturator ring Column involvement Roof Superior articular surface

Anterior lip Anterior column or wall Iliac wing Anterior column

Roof Superior articular surface

*Information obtained from X-ray landmarks on each standard view [17–19].*

Greater and lesser sciatic notch Posterior column (posterior border of innominate bone) Quadrilateral surface of ischium Posterior column (posterior border of innominate bone)

**Antero-posterior pelvis**

**Figure 8.**

**Obturator oblique**

**Iliac oblique**

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**Table 1.**

the hip thus helps in assessing the need for operative treatment in small and intermediate fractures of the posterior acetabular wall. This stress examination is most applicable to the fractures of posterior wall.

Each fracture pattern in the classification of Letournel and Judet has typical radiographic characteristics. These fracture patterns are described with respect to the disruption or intactness of the radiographic landmarks.

In the operating room, the three standard views can be obtained with fluoroscopy. The restoration of the radiographic landmarks marks the adequacy of fracture reduction (**Table 1**).
