Figure 5.15. The position of the ligaments that stabilise the pelvis.
5. TRAUMATIC UROLOGICAL EMERGENCIES 85
TABLE 5.2. The Tile classification system of pelvic ring fractures
Type A—stable A1: Fracture of pelvis not involving the
pelvic ring A2: Minimal displacement of pelvic ring with no instability
Type B—rotationally B1: Open book
(horizontally) unstable B2: Closed book; lateral compression:
ipsilateral fracture B3: Closed book; lateral compression: contralateral fracture (bucket handle fracture)
Type C—rotationally C1: Unilateral
(horizontally) and C2: Bilateral
vertically unstable C3: With acetabular fracture
Approximately 70% of unstable pelvic fractures are type B2 and B3, 10% to 20% of unstable fractures are of the open-book type (B1), and 10% to 20% are of type C. External or internal fixation is used to stabilise unstable fractures.
The open-book pelvic fracture (B1 in the Tile classification) is shown in Figure 5.16. If the symphysis pubis is disrupted (by >2.5cm) in combination with the anterior sacroiliac ligament and the sacrospinous ligament, the affected half of the pelvis is free to open outward, like a book, and this fracture is thus called the 'open-book' fracture (horizontal instability). This type of fracture is caused by an anteroposterior compression injury. In this type of fracture there is a dramatic rise in pelvic volume and this stretches vessels, nerves, and organs, such as the bladder, resulting in damage to these structures.
The closed-book pelvic fracture (B2 or B3 in the Tile classification) is shown in Figure 5.17. When a lateral compression force is applied to the pelvis, a so-called closed-book injury occurs. The pubic rami may fracture and overlap and the ilium and sacral wings may be compressed and fractured. Nerves and vessels are not stretched, but the urethra is more likely to be damaged in this type of injury than in an anteroposterior compression fracture (Zingg et al. 1990).
Thus, the type of force applied to the pelvis and the subsequent radiological appearance give some indication of the likelihood of associated bladder and urethral injuries, the open-book