| Part 1 Establishment of a three-dimensional finite element model for osteoarthritis of the right knee jointObjective:To establish a personalized three-dimensional finite element model of a complete knee osteoarthritis based on continuous CT tomographic images and MRI image data of a female osteoarthritis patient,and to verify the validity of the model.For the further study of discussing and observing the biomechanical change in the knee joint of the different-locations fibula osteotomy for the treatment of knee osteoarthritis.Methods:A 56-year-old female patient with a height of 162 cm and a weight of 59 kg of knee osteoarthritis was included.Before the CT and MRI data of the two knees were collected,the bilateral positions of the knees showed that both knees were medial compartment knee osteoarthritis with varus deformity of both knees.Kellgren-Lawrence grade III in the left knee;Kellgren-Lawrence grade II in the right knee.Take the patient’s right knee joint fully extended,collected the patient’s knee CT and MRI thin layer data set,import the patient’s right knee CT and MRI thin layer image data set into Mimics 20.0 software to establish the digital models of femur,tibia,fibula,the distal femoral and proximal tibial articular cartilage,medial and lateral meniscus,anterior and posterior cruciate ligaments,and medial and lateral collateral ligaments.We imported these digital models into 3-matic 12.0 to complete the model matching.After the physical transformation of the above digital model structures in Geomagic Studio 2012 software,the models were meshed in Hypermesh 14.0 software.Finally,in the Abaqus/Standard 6.14 software,the boundary conditions were set,the model material properties were assigned,and a vertical 600N load was applied(simulating the weight-bearing condition of the right knee when the patient is standing on one foot).The load distribution,contact area and contact stress of the medial and lateral compartment of the knee joint were compared with previous studies to verify the validity of intact knee model.Results:A detailed individualized finite element model of right knee osteoarthritis was established,with a total of 296,264 elements and 126,456 nodes.The anatomical shape of the model is similar to the real knee model.Under a vertical load of 600N,the contact pressure of the medial and lateral compartments of the knee joints was 3.78MPa and 2.90MPa,and the contact area was 301mm2 and 245mm2,respectively,which was close to the previous studies.Conclusion:The structure of the individualized fine knee osteoarthritis finite element model established in this research is relatively complete,the model built is realistic,and the geometric similarity is good.The model has been verified by anatomical morphology and biomechanics,and can be used in the next finite element analysis of fibular osteotomy.Part 2 A finite element analysis of fibular osteotomy on biomechanical changes in knee jointObjective:The reduction of stress in the medial compartment of the knee joint after proximal fibular osteotomy may be the main reason for the post-operative knee joint pain relief in patients with osteoarthritis,but the exact mechanical mechanism of this procedure for the treatment of osteoarthritis is still unknown.In addition,the operation method maybe has poor postoperative effects and complications of common peroneal nerve or superficial peroneal nerve injury.Based on the finite element model of knee osteoarthritis established in the first part,we designed 6 different heights of fibula osteotomy operation at the upper,middle and lower segments of the fibula.The variable elastic modulus method was used to simulate the fibular osteotomy,explore the biomechanical changes of the knee joint after the proximal fibular osteotomy,and explore the changes of the contact pressure in the knee joint after fibular osteotomy at different positions of the upper,middle and lower parts of the fibula.Looking for a safer osteotomy method to provide biomechanical theory of fibular osteotomy for the treatment of knee osteoarthritis.Method:Based on the finite element model of knee osteoarthritis established in the first part,a total of 7 working conditions(6 different heights of the fibula osteotomy)were designed,including F0(intact fibula without osteotomy),F1(proximal fibular osteotomy at 8 cm below the fibular head),F2(upper fibula osteotomy at 10 cm below the fi bular head),F3(middle fibular osteotomy at 12 cm below the fibular head),F4(middle fibular osteotomy at 14 cm below the fibular head)),F5(inferior fibula osteotomy at 16 cm below the fibular head)and F6(inferior fibular osteotomy at 18 cm below the fibular head).The variable elastic modulus method was used to simulate the fibula osteotomy by changing the bone material of the fibula osteotomy into fibrous tissue material.Under the same constraint conditions of the model,a vertical downward load of 600N was applied to the model(simulating the weight-bearing condition of the right knee when the patient is standing on one foot).The biomechanical changes of the knee joints of intact fibula,upper fibular osteotomy,middle fibular osteotomy and inferior fibular osteotomy were compared.Results:Under the same constraints and loads,the calculation and prediction results of the right knee osteoarthritis finite element model found that the contact stress of the medial compartment of the knee joint was 3.779MPa and the contact area was 301.124mm2,and the stress of the lateral compartment of the knee joint was 2.897MPa and the contact area was 245.315mm2 when the fibula is intact(F0).After the operation of upper fibula osteotomy(F1 and F2),the contact stress of the medial compartment was 3.882MPa(3%higher than that before surgery)and 3.882MPa(about 3%higher than that before surgery),the contact area of the medial compartment was 296.914mm2(1.3%lower than that before surgery)and 296.912mm2(1.3%lower than that before surgery),the contact stress of the lateral compartment was 2.442MPa(16%lower than that before surgery)and 2.441 MPa(16%lower than that before surgery)and the contact area of the lateral compartment was 239.598mm2(2.3%lower than that before surgery)and 239.604mm2(2.3%lower than that before surgery).After middle fibular osteotomy(F3 and F4),the contact stress of the medial compartment was 3.883MPa(3%higher than that before surgery)and 3.883MPa(about 3%higher than that before surgery),the contact area of the medial compartment was 297.216mm2(1.3%lower than that before surgery)and 296.828mm2(1.3%lower than that before surgery),the contact stress of the lateral compartment was 2.445MPa(16%lower than that before surgery)and 2.442MPa(16%lower than that before surgery)and the contact area of the lateral compartment was 239.612mm2(2.3%lower than that before surgery)and 239.618mm2(2.3%lower than that before surgery).After inferior fibular osteotomy(F5 and F6),the contact stress of the medial compartment was 3.884MPa(3%higher than that before surgery)and 3.884MPa(about 3%higher than that before surgery),the contact area of the medial compartment was 296.831mm2(1.3%lower than that before surgery)and 296.580mm2(1.3%lower than that before surgery),the contact stress of the of the lateral compartment was 2.43 8MPa(16%lower than that before surgery)and 2.437MPa(16%lower than that before surgery),and the contact area the of the lateral compartment was 239.624mm2(2.3%lower than that before surgery)and 239.627mm2(2.3%lower than that before surgery).According to the prediction results calculated by the model,it is found that:1.after osteotomy at different heights of the fibula,the stress in the medial compartment of the knee joint did not decrease,but increased;the stress in the lateral compartment of the knee joint did not increase,but decreased;the contact area between the tibia cartilage and the medial or lateral meniscus were decreased after fibular osteotomy;2.after the fibular osteotomy at different heights,the stress in the medial,lateral,and lateral compartments of the knee joints does not change much.Conclusion:The prediction of the results of this part of the finite element model shows that after fibula osteotomy,there is no stress transfer from the medial compartment to the lateral compartment of the knee joint,the stress in the medial compartment of the knee does not decreased but increased,and the stress in the lateral compartment does not increased but decreased.The contact area between the tibia cartilage and the medial and lateral meniscus were decreased after fibular osteotomy.Proximal fibular osteotomy is easy to injure the common peroneal or superficial fibular nerve,while inferior fibular osteotomy is easy to cause instability of the ankle joint.In this study,we found that the changes of the contact pressure in the knee joint after the fibular osteotomy at different locations were similar,which suggesting that with similar efficacy for the treatment of knee osteoarthritis,the middle fibular osteotomy may be a safer location to reduce the surgical complication. |
PDF Full Text Request