Establishment of a three-dimensional finite element model of pelvic anteroposterior compression for analysis of related ligamentous damages / 中华创伤骨科杂志

ABSTRACT

Objective To establish a three-dimensional finite element model of pelvic anteroposterior compression (APC) for analysis of mechanisms for related liganentous damages.Methods A finite element model and a laboratory mechanical model of APC were established using the same pelvic specimens.In a finite element model of normal pelvic bones and ligaments,after the right pelvis was fixated the pubic symphysis (PS) was sectioned.Next,a manual external mobile force was gradually applied to the left hemipelvis to make the PS diastasis 10,20,30,40,60,80 and 100 mm apart.The mechanical experiment revealed the anterior sacroiliac ligament (ASIL) was ruptured when the PS diastasis reached 28 mm.After the strain value of ASIL was calculated through the finite element model,it was applied to the other pelvic ligaments.The displacement in front of the sacroiliac joint (SIJ),stress,strain and extent of injury and disruption of sacrotuberous/sacrospinous ligaments (STL/SSL) with a corresponding PS diastasis were observed and recorded.Results ASIL failed at the point when the PS diastasis was 28 mm and the displacement in front of SIJ was 7.41 ± 1.14 mm.The strain and maximum principal stress of ASIL calculated in the finite element model were 259.5％ and 543.24 MPa respectively.The maximum principal stress value of SSL was 35.00 MPa at the point of failure when the PS diastasis and the displacement in front of SIJ were 51 mm and 15.23 ±2.88 mm,respectively.When the PS diastasis and the displacement in front of SIJ were 100 mm and 7.5 mm respectively,the maximum principal stress value of STL was 16.17 MPa but the strained ligament was not ruptured.When the pelvis was rotated externally step by step,the ASIL failure was followed by the rupture of SSL but not necessarily by the STL failure.Conclusion As the finite element pelvic bone-ligament model established in this study can effectively simulate the mechanisms for APC injury,it can be used to evaluate different extents of pelvic ligamentous injury,providing a basis for the biomechanical study of pelvic bones and ligaments.