A biomechanical study of ligament injury associated with anteroposterior compression of Young-Burgess type II

Objective To investigate the injury and disruption of anterior sacroiliac ligament (ASIL) and sacrotuberous/sacrospinous ligament complex(STL/SSL), as well as the displacement of pubic symphysis (PS) and sacroiliac joint (SIJ), associated with anterior-posterior compression (APC) of Young-Burgess type Ⅱ. Methods Test models of APC of Young-Burgess type Ⅱ were created in 10 fresh human pelvic cadaveric specimens which were randomized into 2 equal groups (n=5). The right hemipelvis in one group was fixed to a table (the limited group) while that in the other was not (the unlimited group). At the disruption point of ASIL during external rotation of the hemipelvis, displacement of PS, separation distance between the anterior parts of the sacroiliac joint, and injury and disruption of STL/SSL were recorded. When STL/SSL was gradually made to breakdown and fracture with continuous external rotation of the hemipelvis, bony changes and injuries to the posterior pelvic ligaments were observed and recorded. Results At the failure point of ASIL, the mean displacement of PS was 23.8±2.8 mm and that of SIJ was 10.9±4.4 mm, showing no significant difference between the limited and unlimited groups (P >0.05); the mean external rotation angle was 40.1°±9.8° and the mean torsion was 646.7±131.5 N, showing significant differences between the limited and unlimited groups (P< 0.05). At the disruption point of ASIL, obvious injuries or disruption of STL/SSL were not observed in the unlimited group but observed in the limited group. With extreme external rotation, obvious disruption of STL/SSL was not found in the unlimited group but observed in the limited group. When ASIL and STL/SSL were all fractured, the mean displacement of PS was 41.8 mm and that of SIJ was 16.8 mm in the limited group. Conclusions Since APC injury can lead to 2 situations, limited or unlimited hemipelvis, external rotation injuries to the ligaments differ in the 2 different situations. When ASIL fails, the displacement of PS will fluctuate greatly. Key words: Pelvis; Ligaments; Wounds and injuries; Biomechanics