The Research Of Biomechanics On The Therapy Of Acetabular Hypoplasia With Acetabulum Covers

Objective: To explore the effect of Biomechanics on the therapy of acetabular hypoplasia with acetabulum covers.Methods:(1) Grouping and Modeling: Select 15 fresh able-bodied pelvic specimens, choose one side of the acetabulum as normal control(group N);The other side were randomly divided into three groups with the model of acetabulum hypoplasia(group A)、Acetabulum combined with bone grafting model(group B) and Bone graft model fixed by Kirschner wire. For the model of acetabulum hypoplasia(group A): Take X-ray photos of the experimental specimens; design and cut the edge of the acetabulum to make the angle bigger than 30 °;make it into aacetabulum hypoplasia model; For acetabulum combined with bone grafting model(group B) : use the same way to produce acetabulum hypoplasia model, after that take a iliac bone in the proper size to do the bone grafting to the damage part of the acetabulum, and take a Acetabulum cover to fasten the hip bone and bone graft in three-dimensional fixation; And the bone graft model fixed by Kirschnerwire: use the same method to make acetabulum hypoplasia model and take a iliac bone in the proper size to do the bone grafting to the damage part of the acetabulum, then use the Kirschner wire to fix iliac bone in defect of the hip(2). Biomechanical test: Adopt the 858 mini Bionix II testing machines to simulate whirlbone axial loading till the hip damaged or dislocated, record and compare the resilience of the outer margin of the acetabular bone at load of 300 n and the maximum loads while the hip was damaged or dislocated separately. Using SPSS18.0 statistical software package for data analysis, take two two comparison within the group by T test, the test level for alpha = 0.05.Results:(1) At 300 N load, the strain values of acetabulum on the outer margin are: 1177.69±374.74(Group N); 149.30±144.13(Group A); 740.50±248.61(Group B); 253.49 + /- 97.53(Group C); the comparative differences between these groups was very obvious(P < 0.001).(2) The maximum load when the hip was damaged or dislocated is group N: 1312 + 315, group A: 392 + 117, group B: 947 + 184 and group C: 564.21±167.73. the comparative differences between these groups was very obvious(P < 0.001). Above all, when the hip of the model of acetabulum hypoplasia axial loading to 300 N, the differences between the maximum load when the outer margin of acetabulum has changed or the hip was damaged or dislocated and the normal acetabulum model are significant. To be compared, acetabulum combined with bone grafting model is much closer to the normal acetabulum model, although acetabulum combined with bone grafting and bone graft fixed by Kirschner wire all can not renew the biomechanical ability of the hip significantly. Conclusion:(1)The maximum loads of Four groups of experimental models when the hip axial loading caused the acetabulum’s resilience of the outer margin or the damage or dislocation of acetabulum are different.(2) Acetabulum combined with bone grafting and bone graft fixed by Kirschner wire all can renew the biomechanical ability of the acetabulum hypoplasia significantly but the acetabulum combined with bone grafting is much closer to a normal one.