| Objective: Using three-dimensional finite element method comparing rotational unstable pelvic fracture(Tile B type)and vertical unstable pelvic fracture(Tile C type)of posterior ring of different internal fixation methods biomechanical stability,to provide theoretical basis for the clinical choice of internal fixation of posterior ring fracture of the pelvis.Method: Use the DICOM data obtained from CT scan at Lower lumbar and pelvic of adults,through Mimics10.1,Geomagic Studio 12,Abaqus 6.14-1 and other computer software to re-establish a normal pelvis finite element model of lower lumbar containing ligament tissue,then verify the validity.Removal of the sacroiliac joints connections and corresponding ligament organization on normal pelvic model basis to establish models of pelvic fracture rotation corresponding ligament rotation unstable type(Tile B type),verticality unstable type(Tile C type);Then remove the pubic symphysis ligament,by binding or not binding connection established the anterior ring fracture fixed and non-fixed model,divide it into four groups: group 1(Tile B type-anterior ring fixation),group 2(Tile B type-anterior ring non-fixation),group 3(Tile C type-anterior ring fixation),group 4(Tile C type-anterior ring non-fixation).Establish different posterior pelvic ring fracture internal fixation model,including typeⅠ(non-fixation-posterior ring conservative treatment),type Ⅱ(S1 iliosacral screw internal fixation),type Ⅲ(S1+S2 iliosacral screw internal nail fixation),type Ⅳ(posterior ring tension band steel plate internal fixation),type Ⅴ(modified triangular osteosynthesis internal fixation).Fixed constraint at acetabulum,apply 500 N verticalload at the upper surface of the third lumbar,select point a of the sacrum at the end of broken bone of sacroiliac joint,measure its displacement as the evaluation index,compare the biomechanical stability of each type in the group.Results: 1.During the treatment of four groups of unstable pelvic fractures,Ⅰ-Ⅴ type displacement size of posterior ring internal fixation treatment of each group is: Ⅴ type <Ⅲ type <Ⅱ type <Ⅳ type <Ⅰ type(posterior ring conservative treatment),the displacement of the end of fracture of improved triangular osteosynthesis internal fixation type is the least and,the stability is the best,close to normal pelvis,followed by S1+S2、S1 iliosacral screw internal fixation,the displacement of lacerated ends of posterior ring tension band steel plate internal fixation has significantly increased and its stability is the worst.2.The anterior ring fixation can slightly increase stability of posterior pelvic ring,Tile B type fractures can improve the stability of 1.7%-4.7%,Tile C type fractures can improve the stability of 2%-4.5%.3.The application of fixed mode in all Tile B type fracture stability is better than that of Tile C type fractures,posterior sacroiliac ligament and interosseous ligament on the stability of the posterior pelvic ring is very important.4.After the ring tension band fixation stability for Tile B type pelvic fracture and Tile C type pelvic fractures were similar to not fixed,poor of pelvic posterior ring fixation.Conclusion: Through the comparision of the biomechanical stability at different internal fixation methods of unstable pelvic fracture posterior ring by three-dimensional finite element method,it shows that improved triangular osteosynthesis type internal fixation has the best stability close to normal pelvis,followed by S1+S2 iliosacral screw internal fixation,S1 iliosacral screw internal fixation,posterior ring tension belt steel plate internal fixation has the worst stability.three-dimensional finite element method reflects the biomechanical stability of different internal fixation of unstable pelvic fracture posterior ring,providing a theoretical basis for the clinical surgical options. |
