Cartilage Surface Fixing Device Design Based On Three-dimensional Morphometry Of The Femoral Condyle And Experimental Study

Objective According to three-dimensional geometry morphometry of the femoral condyle articular surface, we design the fixing device that attached to cartilage surface of the femoral condyle. It is used fixation of graft at the autologous chondrocyte implantation. The present study compared five different scaffold fixation techniques, explore advantages to use the new cartilage surface fixing device, it provide theoretical basis for the choice of a fixed method for clinical autologous chondrocyte implantation.Methods 1、we select 100 normal knee MRI images,64 males and 36 females, aged 20 to 40 years of age, with an average age of 28.5. we will get the "DICOM" format MRI tomography data to import Mimics15.0 software, to processe grayscale of the image, to determine the contour of the articular cartilage surface. We import data to use the SKETCH TRACER module of CATIA software, to fit best curve to select point. We measure the arc radius of the femoral condylar articular surface, the sagittal profiles were reconstructed by means of two circular arcs and the radial profiles by means of one circular arc. We analyze the measured parameters to use statistical methods.100 normal knee MRI images were selected, half males and half females, aged 24 to 32 years of age, with an average age of 27.8. the data was imported into 3D reconstruction software Simpleware6.0 to complete the 3D reconstruction of femoral condylar bone structure and cartilage, and the data was saved with "STL" format. The "STL" format data was imported into Geomagicll.0 software, Create 3-D feature. We select joint articular surface of the medial and lateral femoral trochleas. A close-fit sphere was generated on the surface of the medial and lateral trochlear articular surface, respectively. The radii of the spheres was measured. We analyze the measured parameters to use statistical methods.2、According to three-dimensional geometry morphometry of the femoral condyle articular surface, we design the fixing device that attached to cartilage surface of the femoral condyle.3、 Experimenter obtained 30 integrity pig legs from the local abattoir, all limbs were no trauma and deformity. We mark circle area about 2.5cm2 at the femoral medial condyle, create a full-thickness cartilage defect in animal models. The present study compared five different scaffold fixation techniques: Cartilage surface fixing device, fibrin glue (FG), transosseous (TS) fixation, biodegradable pin (BP) fixation and continuous cartilage sutures (CS). After 60 and 210 continuous cycles, the knees were reopened and the implantation sites photographed for later macroscopic analysis. After the total of 210 cycles, an additional endpoint fixation test was performed. For each fixation technique, the average scores and standard deviations per scoring item were calculated after both 60 and 150 motion cycles, per scoring item were analyzed to use statistical methods.Results 1、Three-dimensional geometry measurement of the femoral condyles. Sagittal profiles: the average radii of the distal part and posterior part were computed to be 34.27mm ± 4.54mm and 18.97mm ± 3.05mm respectively for the medial condyle, and 37.63mm±4.41mm and 19.75mm±2.45mm respectively for the lateral condyle. Coronal plane: the average radii were computed to be 21.34mm±2.10mm for the medial condyle, the average radii of the distal part and posterior part were computed to be 23.75mm±2.35mm and 18.78mm±2.47mm respectively for the lateral condyle. The average radii of the femoral trochlea were 23.7mm± 3.9mm and 28.4mm ± 4.5mm for the medial and lateral femoral trochleas, respectively.2、The present study compared five different scaffold fixation techniques. Area coverage: There was no statistically significant difference between CS and fixing device. There was no statistically significant difference between FG、BP and TS. CS and fixing device scored higher than other fixation techniques score of area coverage (P≤ 0.05); Outline attachment:There was no statistically significant difference between CS and fixing device. There was no statistically significant difference between FG、 BP and TS. CS and fixing device scored higher than other fixation techniques score of outline attachment (P≤0.05); Scaffold integrity: There was no statistically significant difference between CS、BP and TS. Fixing device scored higher than FG of scaffold integrity (P≤0.05), FG scored higher than other fixation techniques score of scaffold integrity (P≤0.05); Endpoint fixation:There was no statistically significant difference between BP and FG. Fixing device scored higher than CS of endpoint fixation, CS scored higher than TS of endpoint fixation, TS scored higher than BP and FG of endpoint fixation (P≤0.05)Conclusion 1、Fixing device can not only good maintain implant area coverage、 outline attachment and scaffold integrity, also can provide a more solid fixation at the autologous chondrocyte implantation. Fixing device is more superior fixed technology compared with the traditional fixed technology.2、Clinical commonly used four fixed technology at present, CS is a safe and effective way of fixation.