Associated Fractures

In associated posterior column with posterior wall fractures, the anatomy of the wall fracture and of the posterior column injury must each be considered. Similar to isolated posterior wall fractures, the size, number of fragments, degree of marginal impaction, and site of the wall fragment determine the instability of the hip and potential for post-traumatic arthritis. The column fracture may often be minimally displaced and incomplete. In some, however, there can be significant comminution and displacement. Therefore, careful analysis of both the wall and column fractures is required prior to decision-making regarding the techniques of fracture reduction and the method of fixation.

Transverse with posterior wall fractures is a frequent combination (Fig. 5). In these injuries there is segmental disruption of the posterior rim of the acetabulum, with involvement of the iliopectineal and ilioischial lines, and usually an intact obturator foramen. These injuries are caused by high-energy mechanisms, and a high rate of complications is common. Sciatic nerve injury and avascular necrosis of the femoral head can be devastating and can cause irreversible secondary injuries. The transverse fracture component may appear undisplaced on initial radiographs. There is a significant risk of secondary displacement if this fracture is not fixed concomitant with the posterior wall fixation.

The T-shaped fracture (Fig. 6) is a transverse fracture associated with a vertical split that enters the obturator foramina. The transverse fracture component can divide the acetabulum at any level and in the variety of orientations possible with the isolated pattern. The vertical fracture divides the anterior and posterior columns and enters the inferior pubic ramus. The split usually runs through the central portion of the acetabu-lum but can exit more obliquely either anteriorly or posteriorly. Letournel includes associated posterior column and anterior hemitransverse fractures within this group, as radiographically and surgically they require a similar approach. These fracture combinations may be associated with a central dislocation of the femoral head, particularly with high-energy mechanisms or osteoporotic bone.

The anterior column or wall with posterior hemitransverse fracture (Fig. 7) is described as a variant of the T-shaped pattern by Tile. Letournel states that the differences are subtle and often require CT scanning to determine the classification. In the T-shaped fracture, the anterior fracture runs vertically on the CT scan, disrupting the anterior rim. While in the associated anterior column or wall with posterior hemitrans-verse fracture the anterior breach exits higher with either a horizontal (column fracture) or a 45° oblique fracture plane (wall fracture). The posterior column fracture behaves similarly to the transverse pattern and can exit at the same levels as described above.

Both-column fractures (Fig. 8) are unique among the other associated patterns that involve the anterior and posterior columns. In both-column fractures, the articular surface is completely separated from the posterior ilium, which remains attached to the axial skeleton. It is this intact posterior segment of the innominate bone that produces the spur sign on the obturator oblique view as the articular elements are displaced medially. The both-column fracture can be regarded as a floating acetabulum or complete

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Figure 5 (A) Obturator oblique view radiograph of a transverse with posterior wall fracture, (B) iliac oblique view radiograph of a transverse with posterior wall fracture, (C) computed tomography of a transverse with posterior wall fracture, (arrow) shows transverse element.
Legg Calv Perthes
Figure 6 (A) Anteroposterior radiograph of a T-shaped fracture, (B) obturator oblique view radiograph of a T-shaped fracture, (C) iliac oblique view radiograph of a T-shaped fracture, (D) computed tomography of a T-shaped fracture, (arrow) shows vertical split.

Figure 7 (A) Anteroposterior radiograph of an anterior column with posterior hemitrans-verse fracture, (B) obturator oblique view radiograph of an anterior column with posterior hemi-transverse fracture, (C) iliac oblique view radiograph of an anterior column with posterior hemitransverse fracture. (Continued)

Figure 7 (A) Anteroposterior radiograph of an anterior column with posterior hemitrans-verse fracture, (B) obturator oblique view radiograph of an anterior column with posterior hemi-transverse fracture, (C) iliac oblique view radiograph of an anterior column with posterior hemitransverse fracture. (Continued)

Figure 7 (Continued) (D) Computed tomography of an anterior column with posterior hemi-transverse fracture, showing anterior column fracture line, (E) CT of an anterior column with posterior hemitransverse fracture, (F) CT of an anterior column with posterior hemitransverse fracture, (arrow) shows posterior split.

Figure 8 (A) Anteroposterior radiograph of a both-column fracture, (B) obturator oblique view radiograph of a both-column fracture, showing spur sign (arrow), (C) iliac oblique view radiograph of a both-column fracture.

articular dissociation. In some cases, the anterior and posterior columns reduce to the femoral head, producing secondary congruence. There are several varieties of the both-column pattern characterized by the exit level of the ilial fracture; low, high, or involving the sacro-iliac joint.

Tile's AO modification of Letournel's classification attempts to fit the various fracture patterns into the nomenclature of a comprehensive classification. The three types, Type A, fractures of one column or wall, Type B, fractures involving both columns but leaving part of the articular surface attached to the axial skeleton, and Type C, fractures involving both columns with complete articular separation, can each be subdivided into groups 1, 2, and 3 (Table 1) and further into subgroups and qualifiers (3). In the AO comprehensive classification system, fractures are assigned an alpha numerical code depending on the anatomical position of the fracture and its morphology. The numerical code of an acetabulum fracture is 62. Each fracture can therefore be assigned a unique identifier, which allows for easy data entry and classification recollection. For example, a posterior column fracture through the obturator ring involving the tear drop is a 62-A2.22.

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