Three-dimensional Reconstruction Of Subject-specific Dynamic Patellofemoral Joint With Static Magnetic Resonance Imaging Based Methodology And Its Preliminary Application

Objective The used reconstruction of 3-dimensional motion model of patellofemoral was time-consuming, complicated process of operation, and mostly of the models were static. Rapidly and accuracy reconstruction of the quasi dynamic 3-dimensional motion model of patellofemoral joint is urgent in the research of biomechanics and clinic development. This experiment aim to reconstruct the 3-dimensional dynamic patellofemoral model based on multi-angle static magnetic resonance scanning, then calculate the patellar tracking and finite so as to provide the theoretical basis for the reconstruction and movement regulation research of the patellofemoral joint.Methods A healthy adult male, 30 years old, weight 65 kg, 172 cm tall, body mass index of 21.97kg/m2 was assembled, who has no history of knee joint disease through imaging and physical examination. The right knee was scanned with the magnetic resonance machine(Siemens 3.0T, Germany) at 0?, 30?, 60?,90?, and 120? of knee flexion using T1 se sag scan sequences and flexible coil, the scan slices were range from 90-110 layers, then import the magnetic resonance imges into the Mimics in Dicom format, extraction the shape of patella, patellar cartilage, distal femur and femoral cartilage manually to calculate the static 3-dimensional model of patellofemoral joint at the five flexion angles. Then import the five static models into Rapid Form at the same coordinate system to matching the dynamic model using spline interpolation algorithm, calculate the patella tracking and finite helical axis of patellofemoral then compare with the experiments in literatures.Results The dynamic 3-dimensional model of patellofemoral joint was successfully reconstructed which included patella, patellar cartilage, distal femur and femoral cartilage and cover the process from fully extension to the maximum flextion, during the flexion of knee, the patellar keeping rotation and mild flex and tilt at the same time,the finite helical axis float near the femoral epicondyle axis. The patella tracking and finite helical axis was within the range of in vivo experimental measurements in literatures.Conclusion Using static magnetic resonance scanning technology could reconstruct the quasi dynamic 3-dimensional motion model of patellofemoral joint accurately and without radiation. The dynamic model could be used to calculate the patellar tracking and finite helical axis which provide reference for the research of the movement regular and clinical application.