Assessment Of Tunnel Position After ACL Reconstruction And Finite Element Analysis Of Implant Stress Based On Dual-source Computed Tomography

Experiment 1 Clinical studies of tunnel position which is on the basis of anterior cruciate ligament single-bundle reconstruction measured by dual-source CTObjective To measure and analyze the tibia and femur tunnel location after single-bundle reconstruction of anterior cruciate ligament using dual-source CT.Method DSCT scanning of the knee joint was performed in the 92 patients who underwent single-bundle ACL reconstruction from January 2013 to June 2014. These patients included 64 men and 28 women, with an average of 31.2 years. The centers of bone tunnels were marked with Adobe Photoshop CS6. The tibial tunnel center was measured with Lorenz method(relative position represented with Tx\Ty in percentage) and femoral tunnel center was measured with Bernard method(relative position represented with Fx\Fyin percentage).Results The average Tx is(54.54±3.42)%,and the average Ty is(39.58±6.72)%. The average Fx is(28.98±6.51)%, and the average Fy is(28.04±8.70)%. The difference between male and female and that between the left knee and the right knee is not statistically significant(P> 0.05).Conclusion Dual-source CT can clearly show the three-dimensional tunnel after ACL surgery. It can be used to evaluate the tunnel position and it is helpful to improve operation mode after ACL injury. In addition, it can provide help for individual anatomical reconstruction.Experiment 2 Experiment of semitendinosus tendon on stress relaxation and measurements of elastic modulusObjective Do research on viscoelastic mechanical properties of semitendinosus tendon from fresh cadaver knee and calculate the elastic modulus of single-strand semitendinosus tendon. Provide biomechanical parameters for finite element analysis.Method Remove the semetndinosus tendon from sample and trim to the same size. Use mechanics testing machine to force tensile load to tendon. Maintain the displacement when the displacement reached a predetermined route and observe the changes of force.Results Obtain the data of experiment on semitendinosus tendon stress relaxation and draw the load-displacement curve and load-time curve. Get the elastic modulus of single-stand semitendinosus tendon E=143.46±8.35 MPa by calculating.Conclusion The semitendinosus tendon possesses stress relaxation, which is one of typical biological properties of viscoelastic materials. The viscoelastic mechanical propertiesmake it could be used as ACL graft.Experiment 3 Construct finite element model on femorotibial joint following anterior cruciate ligament reconstruction and finite element analysis of graft stress based on dual-source CTObjective Construct finite element model on femorotibial joint after ACL single-bundle reconstruction, and analyze the stress intensity and distribution of graft.Method Apply dual-source CT to scan the right knee joint of one patient, who operated ACL single-bundle reconstruction and then get fault data. Import data into MIMICS and GEOMAGIC STUDIO software to build three-dimension geometric model and import this model into ANSYS software to mesh. Construct finite element model on femorotibial joint after ACL single-bundle reconstruction and simulate the same stress intensity and distribution of graft as anterior drawer test by using the model.Results 1.Successfully construct three-dimension model on femorotibial joint following ACL single-bundle reconstruction with dual-source CT fault data, MIMICS and GEOMAGIC STUDIO software. 2.Construct three-dimension finite element model on ACL single-bundle reconstruction femorotibial joint with ANSYS software. Mesh the model, constrain the boundary, and assign the materials. 3.Analyze the stress intensity and distribution of graft under the test of anterior drawer with finite element model.Conclusion 1.Accurately construct three-dimension solid model with the application of dual-source CT, MIMICS, GEOMAGIC STUDIO and other reverse engineering softwareand it could be used to observe spatial position of graft after ACL reconstruction. 2.Import three-dimension solid model into finite element analysis software—ANSYS and mesh. It can analyze the stress of graft after boundary restraint and materials assignment. 3.Stress of graft distributes bigger in the attachment of femoral tunnel. Theoretically, it is prone to fracture most.