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Figure 5.16. Open-book—B1—pelvic fracture. a: Plain x-ray. The bladder neck in this case had been cut by the fractured bone. b: Ligaments disrupted in an open-book fracture.
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FIGURE 5.17. Closed-book pelvic fracture B2. a: These are the images obtained at the time of retrograde urethrography, which shows complete disruption of the posterior urethra (contrast does not progress beyond the bulbar urethra). During the process of fracturing, the overlapping bones of the fractured pubis have sheared through the urethra. b: Ligaments and bones disrupted in a closed-book fracture.
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Butterfly fracture of both superior and both inferior pubic rami
Figure 5.17. Continued
fracture being more likely to be associated with a bladder injury and the closed-book fracture with a urethral injury.
In the vertically unstable pelvic fracture (C in the Tile classification), if a sacrotuberous ligament and a posterior sacroiliac ligament are torn, the affected hemipelvis can move upward and posteriorly with respect to the sacrum (vertical instability). A fracture of the transverse process of L5 vertebra is a sign that such a fracture has occurred (i.e., it is a sign of vertical pelvic instability). Again, vessels and nerves can be damaged.
Radiologic Determination of Stability
This is based on inlet and outlet views of the pelvis, the x-ray beam being angled accordingly. These views demonstrate antero-posterior (inlet view) and vertical (outlet) displacement of the pelvic ring. CT can provide better definition of sacral, sacroiliac, and acetabular fractures and dislocations.
The degree of displacement of bone fragments, which on plain x-rays may not look too severe, usually looks much worse on CT (Fig. 5.18). Remember, the degree of bone displacement will have been more pronounced when the injury was actually taking place, and thus while the bone position you see on CT or plain x-ray represents the final position of displacement, the