Sacral fractures

According to AO/ASIF classi!cation system the pelvic ring fractures are graded into three types, A, B, and C, in order of increasing severity (4). Type A injuries are stable including avulsion fractures, fractures of the iliac wing and transverse fractures of the sacrum. Type B injuries are rotationally unstable but vertically and posteriorly stable. "ey may be caused by external rotatory forces (open book injuries) or internal rotatory forces (lateral compression injuries). Type C unstable injuries are complete disruptions of the posterior sacroiliac complex, involving vertical shear forces. Posterior pelvic ring injuries form the basis of the subgroups; fractures of the ilium type C1-1, sacroiliac dislocation and fracture dislocation type C1-2, and sacral fractures type C1-3. "e posterior injury may be bilateral. "e bilateral posterior lesion may be vertically stable on one side and unstable on the other (type C2), or unstable on both sides (type C3). Sacral fracture patterns are commonly categorized using the Denis classi!cation system (5). It divides sacral fractures into three zones: alar (zone 1), foraminal (zone 2) and central (zone 3). Denis, Davis and Comfort (5) found that injury to nerves occurred in 5.9% of fractures lateral to sacral foramina. In transforaminal fractures 28.4% of patients had a neurological de!cit. Central fractures had the highest prevalence (56.7%) of nerve injury. Denis’s system does not recognize the combination of the bilateral vertical and transverse fracture lines that induce spinopelvic dissociation. "is injury results in dissociation of the spine and upper central segment of the sacrum from the pelvic ring and caudal sacral segments. Roy-Camille et al. (6) described this injury but classi!ed only the transverse sacral fracture, not the bilateral vertical fracture components. RoyCamille et al. divided transverse sacral fractures into three types, and later on Strange-Vongsen and Lebech (7) added a fourth type (Figure 1). In this classi!cation, type 1 is a #exion injury without translational displacement; type 2 is a #exion injury with anterior translational displacement; type 3 is an extension injury with posterior translational displacement; and type 4 is axial loading injury with segmentally comminuted S1 body (8).