Background
Anterior posterior compression(APC)type II pelvis fracture is considered to be a typical one caused by the destruction of pelvic ligaments, while the mechanism of ligaments injury is still controversial. This study aims to explore ligaments injury in APC type II pelvic injury.
Method:
Fourteen human cadaveric pelvis samples with sacrospinous ligament (SPL), sacrotuberous ligament (SBL), anterior sacroiliac ligament (ASL) and partial bone retaining unilaterally were made for this study. They were divided into hemipelvis restricted group and unrestricted group randomly. Record the separation distance of pubic symphysis and anterior sacroiliac joint, external rotation angle and force when the ASL ruptured. Continuing external rotation violence, observing bone and pelvic ligaments change.
Result
When ASL failed, there were no significant differences in mean separation distance of pubic symphysis (28.6 ± 8.4 mm to 23.6 ± 8.2 mm,P = 0.11) and anterior sacroiliac joint (11.4 ± 3.8 mm to 9.7 ± 3.9 mm ,P = 0.30) between restricted group and unrestricted group, but external rotation angle(33.9 ± 5.5° to 48.9 ± 5.2°,P < 0.01) and force(553.9 ± 82.6 N to 756.6 ± 41.4 N,P < 0.01) were not. In restricted group, both of SAL and SPL injury occurred, which was different in unrestricted group. Besides, separation distance of pubic symphysis between two groups ranged from 14 mm to 40 mm. With external rotation violence continuing, SPL ruptured firstly, then SBL ruptured and the interosseous sacroiliac ligament was damaged while posterior ligament was not; in another group, interosseous sacroiliac ligament, posterior sacroiliac ligaments were damaged while SAC and SPL were not. When all of ASL, SBL, SPL failed, mean separation distance of pubic symphysis and anterior sacroiliac joint between two groups increased significantly (from 28.6 ± 8.4 to 42.0 ± 7.6 mm, 11.4 ± 3.8 to 16.7 ± 4.2 mm respectively, all P < 0.05).
Conclusion
First, pelvic external rotation injury can divide into hemipelvis is restricted and unrestricted, which result into different outcomes; When ASL ruptures, the unrestricted group needs more external rotation angle and force, without SBL or SPL injury. But in restricted group, both of two ligaments are injured. Second, when ASL fails, pubic symphysis displacement has a high fluctuation. Third, ASL rupture does not mean SBL and SPL are injured inevitably.