Quantitative Assessment Of Dynamic MRI In The Patellofemoral Alignment

ObjectiveTo develope the method and the values of the dynamic MRI in the quantitative assessment of the patellofemoral alignment;Using dynamic MRI in order to determine the characteristics of the patellofemoral relationships and the patellar tracking patterns from the knee extension to flexion in healthy volunteers and to describe the characteristics of the patellofemoral malalignment for the diagnosis of the patellofemoral disorder and the reliable information provided for the clinicians. Materials and MethodsOf 30 healthy volunteer (total 60 knees), respectively) 15 male (30 knees) as healthy male control group, and 15 female as healthy female control group(30 knees), and 14 patients (total 28 knees, 6 males and 8 females) with the affected sides of knees as the disorder group(14 knees) while the opposite side of knees as asymptomatic group(14 knees). Imaging was performed with open MR system using FE3D sequence, the special positioning device permitted passive action from knee extension0 degree to 90 degrees flexion (with a interval of 5 degrees) . The patellofemoral alignment was evaluated by measuring the followings : sulcus angle(SA), patellar tilt angle(PTA), bisect offset(BSO) on axial image during knee flexion from 0 degree to 45 degrees, and Insall-Salvati index(ISI) on sagittal image during knee flexion from 0 degree to 90 degrees (interval 10 degrees). The measurements of SA, PTA, BSO and ISI are going to describe patellar motion tracking and characteristics of patellofemoral relationships during knee flexion. The measurements in bilateral and gender differences were statistical analyzed and compared with the knee in different angle of passive action among the three groups.ResultsThe SA, PTA, BSO and ISI were not significantly different between the two sides in the healthy female group and the healthy male group respectively. Then the mean values were acquired in SA, PTA, BSO and ISI of the right knee and the left knee. The results of statistical analysis demonstrated the statistical differences in BSO and ISI in all the angles of the knee flexion;There were statistically significant differences of SA at 5 degrees, 20 degrees, 30 degrees of flexion and of PTA at 45 degrees of flexion. The tendency analysis revealed statistically significantdifferences in SA, PTA, BSO and ISI of the intra-group in the healthy female control group and the healthy male control group, but there were not significant differences in SA, PTA and ISI of the inter-group between the genders.There were significant differences in SA and PTA between the male disorder group and the male control group at all angles of knee flexion and in BSO at 30 degrees. There was not significant difference in ISI at 0 degree, 10 degrees and 20 degrees of the knee flesion.There were significant differences in PTA, BSO and ISI between the female disorder group and the female control group with all angles of flexion and in SA at 0 degree, 5 degrees and 10 degrees of the knee flexion.There were not significant differences in PTA, BSO and ISI between the disorder group and the asymptomatic group in male and female respectively. The tendency analysis revealed that there was no statistically significant difference in SA, PTA, BSO and ISI of the inter-group between the disorder group and the asymptomatic in male and female respectively.Conclusion1. The similar motion regularity of the human bilateral knee joint isdemonstrated. In our study, normal patellar motion is characterized by subtle medial tilt from 5 degrees to 15 degrees, which revealed a tendency toward mild increasing patellar lateral tilt and displacement during the knee flexion. The similar abnormal motion regularity of the disorder knee joint with opposite joint is also revealed. These findings indicated that the evaluation of the disorder knee joint with the opposite joint as control group are not appropriated.2. The measurements of SA, PTA, BSO and ISI of the knee joint reveal the variability. From 0 degree to 45 degrees of the knee joint, the reference value of SA are 148.7°—118.2° in male and 149.9°— 119.4° in female;the reference value of PTA is 18.0°—11.6° in male and 19.7°-16.3° in female;the reference value of BSO is 0.51—0.58 in male and 0.46—0.51 in female, while from 0 degree to 90 degrees of the knee joint, the reference value of ISI is 0.87—0.64 in male and 0.99—0.75 in female o3. This study indicates that the bony structure is an important determinant of patellar kinematics at the end-range knee extention and the shallow of the intercondyler groove from 10 degrees to 20 degrees of the knee flexion is potential indicative of instability of the patellar. There is limitation thatthe conclusion of the no significant difference that the intercondyler groove morphosis between disorder group and healthy control group at the 30 degrees of the CT scanning.4. This study verified that the sagittal position of the patellar is the significance in diagnosed of the patellofemoral disorder. The patellar position can provide the dignosis information for the clinicians.5. This study indicates that there is limitation in the evaluation of the patellofemoral malalignment by only single degree of the knee flexion (commonly in 30 degrees of flexion). Dynamic MRI could not only provide the extent of the patellofemoral malalignment, but could also demonstrate the degree of flexion where patellar malalignment is maximal and assess whether or not it reduces. Dynamic MRI studies present us a new perspective for dignose of the patellofemoral joint.