In order to approach fractures of the acetabulum safely and with maximum ease, it is necessary to understand the pathologic anatomy; otherwise, errors are inevitable. The revision of the radiological study of the innominate bone together with a comparison of sets of radiographs and operative findings and a study of anatomic specimens have lead us to propose a new classification into which all previously known forms of fracture have been placed.1–6 Discrete groups are artificial, for all the varieties of fractures and dislocations fit into a continuous spectrum; at the same time, if it is recognized that there are transitional forms between each, discrete types must be described in order to provide a classification, the basis of understanding.
The surgeon’s concept of the acetabulum must not be limited to the socket but should take into consideration the bony masses that limit and support the acetabulum. It is to these masses that the internal fixation devices must be attached to restore and maintain the shape of the socket.
It is useful to regard the acetabulum as contained within the open arms on an inverted “Y” formed by two columns of bone (Fig. 1): (1) The anterior or iliopubic column, runs obliquely downwards, in-wards and anteriorly from the anterior part of the superior iliac crest to the pubic symphysis; (2) the posterior or ilio-ischial column, voluminous and thick, descends caudad from the level of the angle of the great sciatic notch to the ischial tuberosity.
The posterior column is attached to the anterior one just above its midlevel. The summit of the angle is filled with a filet of compact bone which constitutes the roof of the acetabulum and forms the keystone of the arch.
RADIOLOGY OF THE ACETABULUM
We have come to the firm conclusion that in order to study the fractures involving the columns which enclose the acetabulum, four radiographic views suffice: A standard anteroposterior view of the whole pelvis in case there are fractures on both sides; A standard anteroposterior view centered on the affected hip (Fig. 2) and two oblique views taken accurately at 45°. The obturator oblique view (OOV) is obtained with the patient supine and rolled 45° away from the side of the injury. This view superimposes anterior and posterior iliac spines but spreads out the obturator foramen. (Fig. 3). The iliac oblique view (IOV) is taken with the patient supine but rolled 45° towards the affected side. The view spreads out the iliac wing and the obturator foramen is invisible (Fig. 4).
On each view both columns have sig-nificant landmarks which must be followed in turn, and scrutinized for possible traversing fracture lines at one or more different levels. The displacement or not of each break is appreciated.
Table 1 reports and Figure 2, 3, and 4 show the fundamental radiologic landmarks of each column on the three radiographic views.
The complete radiologic study of 647 fractures of the acetabulum, of which 582 have been operated upon, confirms the classification proposed especially in the study by Judet and Letournel,3 and only slightly improved since that date.
Acetabular fractures must be divided into two large groups: elementary and associated fractures.
Elementary fractures comprise fractures in which a part or all of one column of the acetabulum has been detached. We include with these, by virtue of its purity, the transverse fracture. There are five elementary forms: (1) fractures of the posterior wall of the acetabulum; (2) fractures of the posterior column; (3) fractures of the an-terior wall of the acetabulum; (4) fractures of the anterior column; (5) transverse fractures.
Associated fractures include at least two of the elementary forms above. There are five principal associations: (1) T-shaped fractures; (2) Fractures of the posterior column and posterior wall; (3) transverse
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