| Objective:To establish a three-dimensional finite element model of the knee joint, and to analyze the biomechanics of MCL inclding SMCL and DMCL with the model.Methods:MCL was dissected on 10 frozen fresh knees of cadaversand the thickness of superficial medial collateral ligment and deep med-ial collateral ligment were measured and recorded.A healthy person was selected as a volunteer, who is a male and 27 years old. The X-ray sh-owed his right knee had no lesions.Then the volunteer’s right knee was scanned by 64-slice spiral CT and 3.0T MRI machine with the knee in a full extension position.All data that we got were imported to the interactive medical imaging control system MIMICS14.0 software in DI-COM format, and then preprocessed to reconstruct 3D models of the a-nterior crueiate ligament,posterior crueiate ligameflt,medial collateral lig-ment, lateral collateral ligament, patellar ligament, meniscus, distal femur, proximal tibia, proximal fibula and patella.Then these models were im-ported to the automate reverse engineering software Geomagic Studio12.0 in STL format respectively.More precise modles were produced by thefunction of cut, close, expand, and shift. And in this software SMCL a-nd DMCL were separated by the function of cut, stretch, and Boolean calculation according to their proportion of anatomical structure in len-gth,width and thickness.Then all these models were preliminarily mesh-ed in 3-matic module of MIMICS14.0 software. After successfully reco-nstructed, these models were imported to the finite element analysis sof-tware ANSYS Workbench in cdb format.In this software they were putt-ogether and then given the material properties.Set the contact mode bet-ween the insection of lingments and the bone as bonded, as so as SMCL and meniscus, DMCL and meniscus.The contact mode of all theother part were defined as no separation.Then these models were mes-hed in ANASYS Workbench again by the pentahedron combined with the he-xahedral,with a total of 877070 nodes and 354003 units obtaine-d. Fix all the direction of the top of the femur. Apply a force of 134 Nto the model in anterior and posterior translation, and apply a moment of 10N·m to the model in valgus, internal and external rotation respec-tively.Then observe the displacement or the valgus or rotation angle ofthe ti-bia and the stress size and distribution of SMCL and DMCL in cases of intact MCL, SMCL rupture, DMCL rupture and MCL rupture.Results:1 Afer the model applied a force of 134 N in anterior translation,the displacement of the tibia changed from 4.89 mm in case of intact MCL to 5.17 mm in case of SMCL rupture, 5.04 mm in case of DMCL rupture and 5.17 mm in case of MCL rupture. The peak stress of ACL was maximum, SMCL’s was smaller, and DMCL’s was minimum. The peak stress of ACL and SMCL were mainly distributed in the insertion areas of the femur, and DMCL’s was mainly distributed in the insertion areas of the femur and tibia.2 Afer the model applied a force of 134 N in posterior translation, the displacement of the tibia changed from 4.98 mm in case of intact MCL to 4.99 mm in case of SMCL rupture, 4.92 mm in case of DMCL rupture and 5.02 mm in case of MCL rupture. The peak stress of PCL was maximum, SMCL’s was smaller, and DMCL’s was minimum. The peak stress of PCL was mainly distributed in the insertion areas of the femur and tibia, SMCL’s was mainly distributed in the insertion areas of the femur, and DMCL’s was mainly distributed in the insertion areas of the femur and tibia.3 Afer the model applied a moment of 10N·m in valgus,the valgus angle of the tibia changed from 4.06° in case of intact MCL to 6.08° in case of SMCL rupture, 4.86° in case of DMCL rupture and 6.22° in case of MCL rupture. The peak stress of SMCL was maximum, DMCL’s was smaller, and ACL and PCL’s was minimum. The peak stress of SMCL was mainly distributed in the insertion areas of the femur and anterior portion, and DMCL’s was mainly distributed in the insertion areas of the femur and tibia.4 Afer the model applied a moment of 10N·m in external rotation,the rotation angle of the tibia changed from 5.92° in case of intact MCL to 5.95° in case of SMCL rupture, 5.94° in case of DMCL rupture and 6.10° in case of MCL rupture. The peak stress of SMCL was maximum, ACL and PCL’s was smaller, and DMCL’s was minimum. The peak stress of SMCL was mainly distributed in the insertion areas of the femur and posterior portion, and DMCL’s was mainly distributed in the insertion areas of the femur and tibia.5 Afer the model applied a moment of 10N·m in internal rotation,the rotation angle of the tibia changed from 6.64° in case of intact MCL to 7.48° in case of SMCL rupture, 6.72° in case of DMCL rupture and 7.57° in case of MCL rupture. The peak stress of SMCL was maximum, ACL and PCL’s was smaller, and DMCL’s was minimum. The peak stress of SMCL was mainly distributed in the insertion areas of the femur, and DMCL’s was mainly distributed in the insertion areas of the femur and tibia.Conclusions:1 The method of CT and MRI image data combined with three re-construction software, MIMICS, Geomagic and ANSYS, is applicable toreconstruct the 3D finite element model of the living subject knee joi-nt,which retains the anatomical features of knee-related anatomical stru-ctures.2 The biomechanical function of MCL can be effectively analyzed by establishing the 3D finite element model of the knee joint to simulate the anterior-posterior translation,valgus and internal-external rotation of the knee joint.The results show that MCL mainly resists valgus stress and it also can limit anterior translation and internal-external rotation of the knee joint, in which SMCL plays an more important role than DMCL with the knee in the full extension position.The femoral insertion of SMCL is the easiest to be damaged in all movement of the knee joint,while the anterior portion of SMCL is easy to be damaged in valgus rotation and the posterior portion of SMCL is easy to be damaged in external rotation. But the risk of the injury of DMCL is low,and if happened, the insertion areas of the femur and tibia of DMCL is easy to be damaged. |
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