| Objective: To construct a three-dimensional digital model of ankle joint under non-weight-bearing condition by using three-dimensional image reconstruction technique and MR scanning images.By measuring the length,width,thickness and volume of ATFL and the distance from the starting point of fibula and talus to each anatomical mark,to provide in vivo anatomical data for the diagnosis and surgical reconstruction of ATFL injury,and to explore the influence of the position of talus tunnel on the isometric of graft during ATFL reconstruction.Methods:(1)To construct a three-dimensional digital model of the ankle joint without weight-bearing: 1)Using Siemens 1.5T multi-source emission 8cm,32 healthy volunteers were scanned with the ankle space as the center line and the upper and lower MRI as the scanning range.The bilateral ankle joints were scanned in 15°dorsal extension position,0°neutral position,15°metatarsal flexion position and 30°metatarsal flexion position respectively.The scanning sequence was 3D-SPACE sequence.The parameters are as follows:the field strength is 1.5T,the thickness of the layer is 0.8mm,and the resolution of the main scan surface is 256 × 256,the field strength is 1.5T,the thickness of the layer is 0.8mm,and the resolution of the main scan surface is 256 × 256.MRI tomographic data of ankle joint were stored according to DICOM standard.2)3D reconstruction of MRI sectional image,using Mimics19.03D reconstruction software,according to the gray level of bones and ligaments in the image,carry out threshold segmentation,manual repair,generate "3D Object" file and other steps.The ankle joint tibia,fibula,talus,calcaneus and ATFL,were modeled respectively,and finally combined into a whole,exported and saved in STL format.(2)Morphological measurement of ATFL of ankle joint: the length,width and thickness of ATFL were measured when the ankle was in dorsal extension position 15°,neutral position 0°,metatarsal flexion position 15°and metatarsal flexion position 30°.When the ankle joint was in neutral position,the volume and the distance from the starting point of ATFL fibula and talus to each anatomical landmark were measured quantitatively.(3)When the ankle joint is in the neutral position,quantitatively measure the volume and the distance from the ATFL fibula start point and the talar end point to each anatomical landmark.(4)In the neutral position of the ankle joint,foot length is related to ATFL length,width,and thickness;height is related to ATFL length,width,and thickness;weight is related to ATFL length,width,and thickness;and body mass index is related to ATFL length,width,and thickness.,Correlation analysis between age and ATFL length,width,and thickness.(5)Using fibula as the starting body,the fibula was registered in 15°dorsal extension position,0°neutral position,15°metatarsal flexion position and 30°metatarsal flexion position by Geomagic studio14.0software,and the models of different movement angles were obtained.The ankle model talus tunnel positioning points A,B,C and D were fitted as control points,and the changes of the spatial distance between ATFL talus attachment center and fibula attachment center were calculated and analyzed.Results:(1)When the ankle dorsal extension is 15°,ATFL length: upper boundary 17.49±2.17 mm,middle 17.03±2.41 mm,lower boundary 15.36±2.64 mm,ATFL width: fibula starting point 6.95±1.89 mm,middle 7.07±1.88 mm,Talar anchor point is 6.35±1.93 mm,and the thickness of ATFL is 1.70±0.50 mm.(2)There was no statistically significant difference in ATFL length between different sexes(P>0.05),no significant difference in width(P>0.05),and no significant difference in thickness(P>0.05);ATFL length between the same sex The difference between the left and right sides was not statistically significant(P>0.05).(3)There was no statistically significant difference in ATFL volume in different genders(P>0.05);there was no statistically significant difference in ATFL volume between the left and right sides of the same gender(P>0.05).(4)The vertical distance between ATFL’s talar end point and the cartilaginous surface of the upper edge of the talar neck is 12.68±2.12 mm;the distance between ATFL’s talar end point and the subtalar joint is 14.32±2.65 mm.The distance between the origin of ATFL at the fibula side and the hidden tubercle of the fibula is7.32±1.80 mm;the distance between the origin of ATFL at the fibula side and the tip of the fibula is 8.16±1.66 mm,and the distance between the origin of ATFL at the fibula side and the anterior tuberosity of the fibula is 19.59±2.05 mm.The relative stability of each anatomical landmark was measured by the degree of variability as follows: ATFL talar anchor point to anterolateral cartilaginous surface AC(16.72%)<AS(18.51%);ATFL fibula starting point to fibula anterior tubercle AA(10.46%)< AT(20.34%)<AO(24.59%).(5)Foot length and ATFL length(r=0.353,P=0.0001),height and ATFL length(r=0.356,P=0.046)are positively correlated,respectively,with a moderate degree of correlation.Among them,male foot length and ATFL length(r=0.306,P=0.018),female foot length and ATFL length(r=0.376,P=0.0058),male height and ATFL length(r=0.47,P=0.004),female height and ATFL length(r=0.342,P=0.012)are all showed a positive correlation.(6)This study found that different talar tunnel positioning points have an impact on the length of the graft.Among them,the central point T of the talar attachment area and the fixed point C have good isometric characteristics,and with the change of the ankle joint flexion and extension angle,ATFL The distance between the attachment center of the talus and each control point to the center of the fibula attachment area changed to varying degrees.Conclusion:(1)Based on the static MRI two-dimensional image data of four different motion terminals,the three-dimensional geometric solid model of ankle joint is successfully constructed by using Mimics software.this modeling method is feasible,realistic and non-radiation,and the model is highly similar to the geometric solid model,which provides a digital platform for the follow-up research of ankle joint.(2)The length of ATFL varies in different positions of the ankle joint.Compared with the neutral position,the length of the foot is shortened in the extended position,and the length is extended in the plantar flexion position;the length of the foot is positively correlated with the length of the ATFL,and the height of the ATFL is positively correlated with the length of the ATFL.There are varying degrees of variation in the distance from the center of the ATFL starting and ending point to each anatomical landmark.The repair or reconstruction of ATFL should be individualized treatment based on the characteristics of its length and location.(3)In the ATFL reconstruction process,when the fibula canal is accurately established,the change of the location of the talar tunnel has an impact on the length of the graft.The area between the attachment point T and fixation point C of ATFL talus on the lateral side of talus is the most ideal area for surgical isometric reconstruction. |
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