**4. Computed tomography**

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 CT images.

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

CT scans can give the same information about the acetabular dome as the roof arc measurements on the antero-posterior and oblique radiographs.

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**).

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

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 a valuable addition to the imaging of acetabular fractures.

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] (**Figure 10**).

#### **Figure 9.**

*Orientation of fracture lines on two-dimensional computed tomography as they relate to fracture morphology. (A) Fracture of one or both columns. (B) Transverse fracture. (C) Anterior wall. (D) Posterior wall.*

**15**

**Figure 11.**

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

Classification of acetabular fractures is the key element in understanding the injury and is the first stage of surgical planning [17, 18]. Decisions concerning the choice of approach and the alternative fixation techniques available require full appreciation of the fracture anatomy. There are various classifications for acetabular fractures, out of them Letournel and Judet and AO/OTA classification has been

The classification of acetabular fractures that is most widely used is that of Letournel and Judet. This system divides fracture of acetabulum into five simple (elementary) and five complex (associated) patterns. The elementary fracture patterns were defined as those that separated all or parts of a single column of the acetabulum. The associated patterns are either a combination of elementary pat-

*Simple/elementary fractures: (A) posterior wall fracture, (B) posterior column fracture, (C) anterior wall* 

*fracture, (D) anterior column fracture, (E) transverse fracture.*

**5. Classification**

discussed in detail here.

• Posterior wall

• Anterior wall

• Posterior column

• Anterior column

**5.1 Letournel and Judet classification**

Elementary/simple fractures

terns with an additional fracture line (**Figures 11** and **12**).

**Figure 10.** *Three-dimensional CT reconstruction of both-column fracture.*

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