Clinical And Biomechanical Three-Dimensional Finite Element Research Of Knee Meniscus Using MRI

Part I MRI quantitative measurements on normal meniscus of the knee and evaluation of meniscal movementI . MRI quantitative measurements on normal meniscus of the knee and its clinical significanceObjective: The aim of this study was to investigate the dimensions of normal meniscus with MRI, which can supply objective data for diagnosis of various meniscal diseases and meniscal replacement.Materials and Methods: Fifty seven normal knee joints were investigated. The height and width of the anterior, mid-body and posterior horn of medial and lateral menisci were measured on a dedicated MRI for limbs. The width of tibial plateau was also measured.Results: For the medial meniscus, the height and width of the anterior horn were 7.74mm±1.41mm and 4.48mm±0.77mm, the height and width of the mid-body were 8.43mm ± 1.91mm and 4.49mm ± 0.72mm, and the height and width of posterior were 10.89mm±2.22mm and 5.50mm±1.01mm,respectively. For the lateral meniscus, the height and width of the anterior horn were 8.96mm+2.06mm and 4.28mm ± 0.70mm, the height and width of the mid-body were 9.18mm ±2.12mm and 4.74mm±0.90mm, the height and width of posterior were 9.64mm±2.26mm and 5.56mm±0.86mm,respectively. The ratio of normal lateral meniscus to the tibia plateau was 13.97%.Conclusions. The measurement data of Chinese normal knee joint obtained in this study are of important reference value in the diagnosis of meniscus of the knee joint and meniscal replacement. II. Kinematics MRI evaluation of meniscal movement in vivo under loading bearing condition and flexionObjective: The aim of this study was a quantitative evaluation of meniscal movement in vivo under load bearing conditions and knee flexion, and discusses its forming mechanism and clinical significance.Methods: The subjects were placed in an open kinematics MRI that enabled measurements under load bearing and in different flexion grades. Sagittal and coronal Tl-weighted MRI images of 20 knees were evaluated. Series of images of the medial and lateral meniscus without load, with 1/4 and half body weight load and in full extension and 30° flexion were taken. The amount of the medial and lateral meniscal body protrusion which was defined distance from the most peripheral border of meniscal body to edge of the tibial plateau articular surface was measured on midcoronal MR images through middle meniscal body and the inner distance between the anterior and posterior horns of the menisci was measured in midsagittal MR images.Results: The inner and outer distance between the anterior and posterior horns increased with load and decreased with increase of flexion from 0° to 30° . The meniscal body protrusion was not influenced by the load bearing, but increased with knee flexion from 0° to 30° and averaged less than 3mm in normal knee in coronal MR imaging plane.Conclusions. Knee loading leads to increasing the anterior and posterior horns distance which may be related deformation of meniscus. Knee loading bear compressed meniscal periphery from the inside to outside. It allows early postoperative mobilization. Knee flexion normally leads to increasing meiniscal protrusion shortening of the inner distance which may be related to the positioning and curvature of femoral condoyle. Part II The study of meniscal protrusion of the knee with clinicalMRIIII. Preliminary study on the effects of meniscal protrusion of the knee with symptomatic knee OAObjective: To evaluate the meniscal position on MRI of the knee with andwithout symptom, and to explore the meniscal protrusion of knee with symptomatic knee OA and else symptomatic knee.Methods: MRI images of 120 cases with symptomatic knee and 20 cases asymptomatic controls were retrospectively reviewed. According to ACR criteria for knee OA and MRI, the knees were classified as symptomatic knee OA, else symptomatic knee and normal controls. The amount of the medial and lateral meniscal body protrusion which was defined distance from the most peripheral border of meniscal body to edge of the tibial plateau articular surface was measured on midcoronal MR images through middle meniscal body. Meniscal subluxation was defined the distance>3mm. The degrees of meniscal protrusion and the prevalence subluxation were compared in cases with symptomatic knee OA, else symptomatic knee and controls.Results: Medial meniscal protrusion was (3.68 + 1.25)mm in symptomatic knee OA, (2.82+1.50)mm in else symptomatic knee, and (2.17 + 0.85)mm in controls. Lateral meniscal protrusion was (1.55 +1.15)mm in symptomatic knee OA, (0.77 + 0.94)mm in else symptomatic knee and (0.85 + 0.69)mm in controls. The prevalence of medial meniscal subluxation in symptomatic knees OA, else symptomatic knees and controls was 69%(43/62),49%(19/39)andl4%(5/36). With aged adjusted, symptomatic knees OA and else symptomatic knees had more medial protrusion than controls(p<0.05), symptomatic knees OA had more lateral protrusion than else symptomatic knees and controls, symptomatic knees OA had higher prevalence of medial meniscal subluxation than else symptomatic knees and controls.Conclusions: Medial meniscal protrusion is more degree in symptomatic knee; medial and lateral meniscal protrusion is more degree in symptomatic knee OA. Medial meniscal subluxation is associated with symptomatic knee OA. IV. Effect of medial meniscal protrusion of the knee joint space narrowing with knee OAObjective: To evaluate the effect of meniscal protrusion to knee joint space narrowing with knee osteoarthritis.Methods: 65 patients with osteoarthritis and 36 with normal knee were investigated by conventional radiographs and magnetic resonance imaging (MRI). Medial joint space narrowing on conventional AP radiographs was assessed accordingto Kellgren-Lawrence (K-L) scoring system. The degree of meniscal protrusion was evaluated from MRI. The degrees of medial meniscal protrusion were compared with knee O A and controls. The correlation of degree of medial meniscal with joint space narrowing (K-L Grade) was analyzed.Results: There were 13 knees with K-L I narrowing, 19 knees with K-L II narrowing, 22 knees with K-LIII narrowing ,8 knees with K-L IV narrowing in knee OA. All normal knees had normal joint space (K-L Grade 0).There were 3 knees with normal meniscal protrusion, 16 knees with mild meniscal protrusion, 20 knees with moderate meniscal protrusion, and 23 knees with severe meniscal protrusion in knee OA. Normal knees had 11 knees with normal meniscal protrusion, 20 knees mild meniscal protrusion, 5 knees with moderate meinscal protrusion. The medial meniscal protrusion degrees were significant difference between two groups. There was moderate relationship between K-L grade and degree of meniscal protrusion.Conclusions: Medial meniscal protrusion is associated with knee OA. Increasing medial meniscal protrusion correlates with severity of joint space narrowing. Part UT Three Dimension Finite Element Model of Knee Joint Reconstructed using MRI Images and for Meniscal BiomechanicsV. Three Dimension Finite Element Model of Knee Joint Reconstructed from MRI Images.Objective: To development a three dimension finite element model of the human knee and to provide a method and platform for analysis of injury mechanism and therapeutic measure of knee joint.Methods: According to the model building principle from point to line to area to volume of ANSYS software, a three dimension finite element model of the knee joint was reconstructed on the basis of the images of MRI and was meshed with tetrahedron 4 nodes.Results: A three dimension finite element model of the knee joint, which including meniscus and articular cartilage and bone was reconstructed and was divided into nodes and units.Conclusions: A three dimension finite element model of the knee joint, whichcan reflect the real geometry structures of knee joint and can used as a basement forsubject-specific finite element simulation is reconstructed.VI. Three dimension finite element analysis on meniscal biomechanics ofkneeObjective: The objectives of study evaluate stress distribution of intact menisci, total menisectomy, partial menisectomy in knee joint by three dimension finite model reconstructed from magnetic resonance images, and to better understood the biomechanical behavior of the meniscus in knee joint.Methods: The three -dimensional finite element model of the normal knee joint was meshed using element in ANSYS. On the basis of the normal model, 4 three-dimensional finite element models of different types of mensici were sequentially formed by deleting or shifting corresponding unit of the meniscus model according to study cases, a low, non-physiologic compressive load of 400N and a higher, more physiologic compressive load of 1200 N simulating the virtual magnitude and orientation of load on articular surfaces weight-borne knees was applied to 4 models respectively, to calculate out the stress distribution of each model. 4 different cases were analyzed and compared.Results: The VMS stress on the normal knee was even-distributed .and middle parts of articula surfaces were found to bear the most stress. After total or partial meniscectomy , raises VMS stress on corresponding to side of articular surface was observed, A trend indicating VMS stress centralization towards the intermediate part of articular surface(close to intercondylar eminence of tibia) was observed on the meniscectomy side. After meniscectomy, there is difference of stress for loads. The change of stress is more obviously when a higher load is used.Conclusions: 1. The three-dimensional model from MRI can be reliably used to analyze biomechanical behavior of human knee joints. 2. Menisci functionally conduct stress load, lessen the stress per unit area and distribute stress evenly to the articular surface. 3. Total or partial meniscectomy and meniscal radial displacement affects the stress distribution in knee joints, leading articular cartilage not suiting to biomechanical situation in knee joint, which is a reason for joint retrogression. 4. a higher, more physiologic compressive load is recommended in experimental biomechanical study of knee.