RESUMO
BACKGROUND:The medial patellofemoral ligament reconstruction is the most commonly used method for the treatment of lateral dislocation of patella at present.The ultimate goal is to adjust the patella to the normal anatomical position and restore the patella track.Currently,the main core problem of medial patellofemoral ligament reconstruction is the selection of its femoral end fixation point. OBJECTIVE:Finite element method was used to analyze the limiting effect of the reconstructed medial patellofemoral ligament on the patella at different flexion angles of the knee joint,and to simulate the limiting effect of medial patellofemoral ligament reconstruction at different fixation points of the femoral end on the patellofemoral end,so as to provide help for the selection of fixation points of the femoral end during the reconstruction of the medial patellofemoral ligament. METHODS:A finite element model of knee including bone and soft tissue was established according to the extracted CT and MRI data of knee joint.When the knee flexion angle of 30° and 60° was simulated,the medial patellofemoral ligament was constructed by selecting different fixation points of femur end.The contact stress and contact area between patellofemoral joints at different points were compared,as well as the transverse binding force on patella.The equilength of the medial patellofemoral ligament constructed from the same fixation point of the femoral end at different flexion angles was verified to study the effect of various reconstruction positions of the medial patellofemoral ligament. RESULTS AND CONCLUSION:(1)A three-dimensional finite element model of the knee joint at 30° and 60° flexion angles was established to construct the medial patellofemoral ligament at different fixation points of the femur end.The medial patellofemoral ligament constructed at the same position of the femur end had usable isometric length at different flexion angles.(2)After the lateral displacement of the patella,in the transverse direction,the medial patellofemoral ligament constructed at different fixed points of the femur end produced different transverse binding force on the patella,and the transverse binding force was maximum at the anterior 10 mm and minimum at the proximal 5 mm.In the longitudinal direction,the location and size of stress concentration points on the patella cartilage were roughly the same,and the contact pressure did not change much.However,the contact area between the patella cartilage and the femoral cartilage was significantly different,with the maximum contact area at 10 mm at the front end and the minimum contact area at 5 mm at the proximal end.(3)The medial patellofemoral ligament constructed at the center of the saddle region has a good lateral restriction on the patella,but does not cause excessive restriction on the patella in the longitudinal restriction,and can achieve a good restriction on the patella.
RESUMO
Objective To investigate the application value of eye tracking in lie detection. Methods The 40 subjects were randomly divided into two groups. The pupil diameter, fixation duration, points of fixation and blink frequency of the subjects in the experimental group in observing target stimulation and non-target stimulation were recorded with eye tracker after they accomplished the mock crime. The eye movement parameters of subjects in the control group were directly collected. The differences in eye movement parameters of the experimental group and the control group in observing target stimulation and non-target stimulation were analyzed by t-test. Pearson coefficient analysis of correlation between eye movement parameters that had differences was conducted. The effectiveness of eye movement parameters to distinguish between the experimental group and the control group was calculated by the receiver operator characteristic （ROC） curve. Results Participants from the experimental group had shorter average pupil diameter, longer average fixation duration and fewer fixation points （P<0.05）, but the differences in blink frequency had no statistical significance. The differences in the above indicators of the control group in observing target stimulation and non-target stimulation had no statistical significance. The average fixation duration showed a negative correlation with fixation points （r=-0.255, P<0.05）; the average fixation duration showed a negative correlation with average pupil diameter （r=-0.218, P<0.05）; the fixation points showed a positive correlation with average pupil diameter （r=0.09, P<0.05）. The area under the curve of average pupil diameter, average fixation duration and fixation points was 0.603, 0.621 and 0.580, respectively. Conclusion The average pupil diameter, average fixation duration and fixation points obtained by the eye tracker under laboratory conditions can be used to detect lies.