2.4 Defining the injury: assessment and principles of management of acetabular fractures

10.1055/b-0035-121649

2.4 Defining the injury: assessment and principles of management of acetabular fractures

Markku T Nousiainen, Philip A Brady, Marvin Tile

1 Introduction

A precise understanding of both the injured patient and the acetabular fracture pattern sustained is crucial because the anatomical relationships of the acetabulum are complex and the correct choice of surgical approach to manage the fracture imperative. Although a careful clinical assessment can outline the patient’s general status and the forces that produced the injury, only a complete radiographic examination can reveal the exact nature of the fracture. Together, the patient and fracture factors define the injury personality and lead to logical decision making in treatment.

2 Clinical assessment

2.1 History

As always, the treatment decision process starts from a thorough understanding of the patient’s general medical profile and posttrauma status. The age and the premorbid functional status of the patient, as well as the condition of the bone (whether osteopenic or not), figure prominently in decision making. The patient may be able to describe the mechanism of injury, which should give the surgeon some insight into the fracture. Different fracture patterns are produced when force is directed at the greater trochanter compared to when force is directed through the knee joint (the so-called dashboard injury). With the dashboard injury, associated lesions in the knee are common and must not be missed.

**Fig 2.4-1** Large Morel-Lavallée lesion in a patient who sustained multiple traumas.

2.2 Physical examination

Careful overall assessment is mandatory. As with pelvic ring disruptions, hemorrhage may be significant and significant associated injuries are common. Examination of the affected limb is helpful in determining the mechanism of injury. The position of the limb may suggest a dislocation: internal rotation, a posterior dislocation; external rotation, or an anterior dislocation. Inspection may reveal bruising at the greater trochanter or knee. Posterior subluxation of the knee, a fractured patella, an open wound or a Morel-Lavallée lesion ( Fig 2.4-1 ), and/or a sciatic or peroneal nerve lesion must be ruled out. Because nerve injury is relatively common, careful neurological assessment is necessary and must be documented before any treatment is undertaken.

3 Radiographic assessment

An accurate anatomical diagnosis, essential for decision making and especially for surgical planning, can be reached by conducting a thorough radiographic assessment. High-quality plain x-rays, including AP pelvis and Judet views (iliac and obturator oblique), when combined with cross-sectional computed tomography (CT) (and, in rare instances, with magnetic resonance imaging [MRI]) provide detailed information on the fracture pattern and surrounding soft-tissue injuries.

3.1 Pelvic views

Because many acetabular fractures are associated with pelvic ring disruption or an ipsilateral sacroiliac injury, the three standard radiographic views of the pelvis—AP, inlet, and outlet—may be indicated.

3.2 Acetabular views

In addition to the standard AP x-ray of the pelvis, Judet et al [1] recommend two oblique views (iliac and obturator views). In most cases, careful study of the three views, AP, iliac oblique, and obturator oblique, facilitates an accurate anatomical diagnosis. When studying these views, the surgeon should have a dried pelvis at hand; otherwise, the various lines and columns may be confusing. The introduction of 3-D CT has not diminished the need to obtain these three radiographic views; but it has made it more important because a study of the same three views seen in a 3-D format enhances understanding of the fracture pattern.

3.3 AP view

All six major landmarks may be seen on AP view ( Fig 2.4-2 ): the iliopectineal line (the pelvic brim, or border of the anterior column); the ilioischial line (the border of the posterior column); the roof; the teardrop (or medial wall of the acetabulum); the anterior border of the acetabular wall; and the posterior border of the acetabular wall. The teardrop is a complicated anatomical structure, representing a confluence of lines that are projected from different coronal planes. The base of the teardrop is the upper border of the obturator fossa, the lateral border is the midportion of the acetabular (cotyloid) fossa, and the medial border is formed by the outer wall of the obturator canal merging posteriorly with the outline of the quadrilateral surface of the ilium.

**Fig 2.4-2a–b** AP view of the hip. The six fundamental radiographic landmarks of Letournel: posterior wall of acetabulum (1); anterior wall of acetabulum (2); roof (dome or tectum) (3); teardrop (4); ilioischial line (posterior column) (5); and iliopectineal line (anterior column) (6).

3.4 Obturator oblique view

The obturator oblique view ( Fig 2.4-3 ) is obtained by elevating the affected hip 45° from horizontal by means of a wedge and directing the x-ray beam through the hip joint. Raising the injured hip places the hemipelvis in internal rotation, enabling visualization of the entire obturator foramen. In addition to the obturator foramen, this view outlines the anterior column and the posterior lip or wall of the acetabulum. The iliac wing is seen perpendicular to its broad surface, revealing the so-called spur sign, which indicates a both-column fracture above the true acetabulum.

3.5 Iliac oblique view

For the iliac oblique view ( Fig 2.4-4 ), the patient is rolled to 45° of external rotation by elevating the uninjured side. The x-ray beam is centered on the hip joint, just below the anterior superior iliac spine and midway between the spine and the midline. On this view, the entire iliac wing is seen but the obturator foramen disappears. This view clearly outlines the posterior column, including the ischial spine, the anterior border of the acetabulum, and the full expanse of the iliac wing.

Acutely injured patients occasionally report severe pain with attempts to rotate the pelvis. In such a case, it may be easier to tilt the x-ray tube (rather than the patient) 45° in both directions. The view obtained shows an exaggerated but accurate picture of the acetabulum. Although a precise diagnosis can be made with the views already described, more sophisticated cross-sectional imaging techniques are helpful in completely understanding the fracture pattern sustained.

**Fig 2.4-3a–b** Obturator oblique view (Judet): it is useful to assess the obturator ring, posterior wall (1) and anterior column (6). The pelvis is rotated 45° toward the uninjured side to provide a complete view of the obturator ring and a profile of the iliac wing.

**Fig 2.4-4a–b** Iliac oblique view (Judet): it is useful to assess the anterior wall (2) and posterior column (5). The pelvis is rotated 45° toward the injured side to provide a complete view of the iliac wing and a profile of the obturator ring.

3.6 Computed tomography

3.6.1 Plain CT

Computed tomography has revolutionized diagnostic imaging of musculoskeletal diseases, especially acetabular trauma because a 3-D understanding of acetabular fractures is vital for diagnosis and treatment. Conventional axial CT consists of contiguous or overlapping thin sections through the area of injury to provide optimal image quality in the shortest time. Contiguous sections of 2.5 mm are obtained through the pelvis for edge definition. Advances in multidetector CT technology and high-speed computing have also made it possible to review multiplanar reformatted images in any arbitrary plane and obtain high-quality 3-D images for viewing in any direction.

One main advantage of CT is that the examination can be completed without moving or turning the patient, which is not possible with the conventional radiographic views [2]. Crucial to interpretation of the axial CT images is an understanding of the normal cross-sectional anatomy of the acetabulum, as described in several reports [3−5]. Excellent anatomical correlation has been obtained by sectioning a cadaver pelvis into axial slices that correspond to the CT sections.

Routine axial images have proved to be more sensitive than plain x-rays for determining the type of acetabular fracture, the location and extent of acetabular wall fractures ( Fig 2.4-5 ), the degree of comminution and impaction of the weight-bearing acetabular dome ( Fig 2.4-6 ), intraarticular fragments ( Fig 2.4-7 ), injury to the femoral head ( Fig 2.4-8 ), pelvic hematoma ( Fig 2.4-9 ), and sacroiliac joint integrity [6−10]. Although subluxations or dislocations of the hip are usually apparent on plain x-rays, CT may occasionally demonstrate a subluxation or dislocation that is not apparent on routine x-rays ( Fig 2.4-10 ).