| ObjectiveTo study the clinical symptomatic cartilage defects of the knee joint in location, area, degree, then get the general rule of meniscus injury and its occurrence development with retrospective analysis method, thus providing clinical data to the diagnosis and treatment for patients with injury of knee joint cartilage; To explore the authenticity and reliability of using MRI two-dimensional image and MIMICS software to establish the adult knee joint cartilage of three-dimensional digital model; To establish normal adult knee joint cartilage model in different cartilage defect (6,8,10,12,14, 16,18 and 20 mm) with finite element simulation software for biomechanical analysis, to evaluate internal and external femoral condyle cartilage of knee joint meniscus and articular cartilage stress before and after the change tendency of the peak, to furnish biomechanical data support for patients with knee joint femoral condyle cartilage defect.Method1. To study the clinical symptomatic cartilage defects of the knee joint in location, area, degree, then get the general rule of meniscus injury and its occurrence development with retrospective analysis method.2. We selected 10 cases of double knee joint specimens from fresh corpse, then get the two-dimensional image data of knee joint cartilage with MRI scan. Import all the data to software Mimics 14.11 to reconstruct 3D image based on the finite element simulation methods, thus establish three-dimensional model of the knee joint cartilage (model group); Using measuring tool of finite element simulation software Mimics 14.11 to get internal and external condyle of femur and tibia cartilage thickness in some point. The same method of 10 cases of fresh adult corpse double knee joint specimens, measure the same area of the knee joint cartilage thickness (specimen group). The specimen group and model group were sent to T test analysis; To study the authenticity and reliability by using MRI and MIMICS software to establish the two-dimensional picture and three-dimensional digital model of normal adult knee joint cartilage.3. To establish three-dimensional finite element model from ten normal adult knees. Material mechanical properties was input to software Abaques with divided grid model, controlling boundary condition with mechanical load, then doing structural nonlinear finite element calculation. Firstly, observe the load stress distribution of knee cartilage and meniscus under the condition of normal stress, then detect meniscus cartilage stress distribution with load conditions in different defect (6,8,10, 12,14,16,18 and 20 mm) of medial and lateral femoral condyle, at last, explore the stress variation of meniscus and cartilage in knee with medial and lateral condyle defect.Result1. The most common damage were on medial femoral condyles in 246 articular cartlige injury cases, second injury were medial tibial plateau. Ⅲ, Ⅳ articular cartilage injury incidence is highest, the area is mainly distributed in 2-6 cm2; Cartilage damage area is larger as the longer of TFI.2. There are 149 cases of patients with combined meniscus injury in 246 cases of knee joint cartilage injury patients, its incidence is 60.5%, one of the most common type is medial meniscus injury; Early after injury TFI< 6 weeks, the lateral meniscus incidence is highest. With the extension of TFI, the incidence of the lateral meniscus basically stable and incidence of medial meniscus increased gradually, thus we speculated that the lateral meniscus injury may be largely due to the direct violence of the injury, while the medial meniscus with secondary injury.3. As extension of TFI,6 weeks,3 months,6 months,12 months December,2 years of five nodes classified statistics, statistical analysis results show that, the area of the cartilage defect and meniscus injury incidence were statistically difference (p< 0.05) before and after each node, in addition the longer the TFI is, the bigger area of III, IV articular cartilage injury, and thus we speculated that,in order to avoid further increase of secondary meniscus and cartilage injury area, after knee joint cartilage defects, patients may need early surgical intervention.4. There was no difference statistically (P>0.05) between specimen measurement and 3 D models measurement with the thickness of cartilage. Authenticity and reliability of three-dimensional finite element model were on the table.5. Material properties, boundary conditions and loads were defined, with the application of 3D finite element analysis software. We get the stress cloud chart and its stress data from different diameter (0 mm,6 mm,8 mm,10 mm,12 mm,14 mm, 16 mm,18 mm,20 mm) defect of cartilage and meniscus in both femoral condyle of knee joint.6.10 mm (area of 0.78 cm2) of medial femoral condyle and 12 mm (area of 1.13 cm2) of lateral femoral condyle were minimum diameters advised for operation intervention of cartilage repair.Conclution1. Medial femoral condyle cartilage defect rate was highest in patients with trauma of articular cartilage injur, by retrospectively clinical research of the knee joint cartilage injury cases.2. As TFI extend, secondary knee joint cartilage, meniscus injury and cartilage damage area could be increased because of cartilage defect. Cartilage repair surgery should be done as soon as possible.3. Taking advantage of MR images, more real three-dimensional finite element model of articular cartilage could be established rapidly and efficiently. The shape and relative position of cartilage in knee joint could be accorded with the actual condition. The model could be used for finite element analysis of various conditions and acted as primitive model in future research.4. Stress change trend of the meniscus and bilateral condyle cartilage were obtained by analysis and calculation in the knee joint, with the application of three dimensional finite element method, getting useful biomechanics information of knee joint cartilage. Results showed us that stress of cartilage and meniscus increased significantly as 10 mm (area of 0.78 cm2) in medial femoral condyle and 12 mm (area of 1.13 cm2) in lateral femoral condyle. The results conformed the clinical research conclusion provide good experimental basis for the decision of clinical surgery to repair cartilage damage. |
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