Anterior pelvic ring external fixators of two new configurations in the treatment of Tile type C1 pelvic fracture: a biomechanical study / 中华创伤杂志

ABSTRACT

Objective:To investigate the biomechanical properties of anterior pelvic ring external fixators of two new configurations [iliac crest (IC)+anterior inferior iliac spine (AIIS), anterior superior iliac spine(ASIS)+AIIS] in the treatment of Tile type C1 pelvic fracture.Methods:A 3-dimensional finite element model of Tile type C1 pelvic ring injury (unilateral longitudinal sacral fracture and ipsilateral pubic fracture) was produced. The pelvis was fixed with external fixators of IC, AIIS, combination of IC and AIIS, combination of ASIS and AIIS, and S 1 sacroiliac screw in 5 types of models. In the simulated bipedal standing position and semi-recumbent position, the longitudinal displacement and back rotation angle displacement of the midpoint on the upper surface of S 1 were quantified and compared. Under the simulated left-right compression load state, the lateral displacements of the highest point of the lateral sacral fracture and the highest point of the lateral pubic fracture end were quantified and compared. Under the simulated anterior-posterior shear load state, the backward displacements of the highest point of the lateral sacral fracture end and the highest point of the lateral pubic fracture end were quantified and compared. Results:(1) In the simulated bipedal standing position under the vertical and longitudinal load state, the results of the longitudinal downward displacement of the midpoint on the upper surface of S 1 were consistent with the backward rotation angle displacement, and the order from largest to smallest was IC, AIIS, ASIS+AIIS, IC+AIIS and S 1 sacroiliac screw. The longitudinal downward displacement of IC was significantly larger than that of other models. The longitudinal downward displacement and backward rotation angle displacement of ASIS+AIIS and IC+AIIS were similar, and the latter was smaller. (2) In the simulated semi-recumbent position under the vertical and longitudinal load state, the results of the longitudinal downward displacement and backward rotation angle displacement of the midpoint on the upper surface of S 1 were also consistent, and the order from largest to smallest was IC, AIIS, ASIS+AIIS, IC+AIIS and S 1 sacroiliac screw. (3) Under the simulated left-right compression load state, the results of the lateral displacement of the highest point of the lateral sacral fracture end were consistent with that of the highest point of the lateral pubic fracture end, and the order from largest to smallest was S 1 sacroiliac screw, IC, AIIS, ASIS+AIIS and IC+AIIS. Among them, Among them, The lateral displacement of S 1 sacroiliac screw and IC was larger. The lateral displacement of ASIS+AIIS and IC+AIIS was similar, and the latter was smaller, significantly smaller than that of other models. (4) Under the simulated anterior-posterior shear load state, the results of the backward displacement of the highest point of the lateral sacral fracture end and the highest point of the lateral pubic fracture end were also consistent, and the order from largest to smallest was IC, AIIS, ASIS+AIIS, IC+AIIS and S 1 sacroiliac screw. Among them, the backward displacement of IC and AIIS was larger. The backward displacement of ASIS+AIIS and IC+AIIS was similar, and the latter was smaller. Conclusions:For type C1 pelvic fracture, the biomechanical stabilities of IC+AIIS and ASIS+AIIS are superior to those of IC or AIIS, with ASIS+AIIS being slightly inferior to IC+AIIS. Compared with S 1 sacroiliac screw, IC or AIIS, the lateral stabilities of IC+AIIS and ASIS+AIIS are particularly prominent. The two new external fixator configurations in this study are worthy of clinical application.