| BACKGROUNDWith the increase of foot and ankle fractures which due to traffic injury and machine damage etc and the growing importance of the foot and ankle health recently, modern podiatry has been rapidly developed. Following treatment concept of flatfoot deformity, posterior tibial tendon insufficiency, degenerative arthritis, foot deformity, trauma and posttraumatic arthritis and other common foot disease steering from non-operation to operation, a variety of new treatment strategies and operation methods have emerged. But incorrect operation and current treatment limitations and other reasons may cause the ankle force line change, hindfoot width, arch disappeared, Varus-valgus deformity, and other deformities which led to the foot and ankle pain and walking function disorders obviously increase. These results request urgently measurements of the normal and pathology foot in vivo and knowledge of foot and ankle joints in normal and pathological conditions of the motion features, so that providing guidance for in-depth understanding of foot and ankle disease pathogenesis, formulate the correct treatment plan and accurate evaluation of operation effect. However, the current foot and ankle kinematics studies face two major problems hindered its further development. First, early studies on cadaver specimens of the foot and ankle movement provide early awareness and understanding of the ankle kinematics, but due to the loss of muscle, tendon and other soft tissue of physiologically active and important vascular perfusion, innervations, the cadaver specimens can not meet the clinical research of the foot and ankle kinematics in vivo physiological conditions. With the development of the foot and ankle kinematics research and clinical Podiatry, the foot and ankle kinematics research in vivo began to develop gradually, and various new research methods emerged, in which the sensor tracing, infrared photography capture technology and3D motion analysis system were mostly applied, but these research methods mostly is invasive, difficult to be received by subjects. Second, because of the rapid development of modern podiatry, the foot and ankle kinematics research content is no longer limited to general2D kinematics model, but turn to more fine3D motion model. However duing to the foot and ankle bones are small and irregular and the movements of foot and ankle joints are mostly fretting, composite3D motion, accurate measurements of intrinsic foot and ankle joint movement in vivo become difficulties. Following diagnostic imaging technology and computer software technology development,3D digital reconstruction technology using CT or MRI image become measurement of foot and ankle joint3D kinematics in vivo possible. An new foot and ankle in vivo three-dimensional motion measurement method with accurate, non-invasive, simple operation and clinical value to popularize, can be widely collected in the normal and pathology foot kinematic data, analyze their motion characteristics, contribute to the development of new equipment, new technology, new method. Through the contrast analysis of preoperative-intraoperative foot and ankle joint maximal exercise capacity, can evaluate operation effect, optimize the operation mode. By using MIMICS10.01software and GEOMAGIC10.0software, combined with the principle of rigid body kinematics, this study established a new digitization method for measurement the3D kinematics of foot and ankle joint in vivo. By this method the hindfoot joints3D kinematics in vivo has been measured and the effect of the medial arch of each joint3D kinematics on foot medial longitudinal arch changes has been discussed, so that providing an initial study for future in vivo digitization measurement and analysis3D kinematics of the clinical pathology foot.OBJECTIVE1. To establish a new technical method for in vivo digitization measurement3D kinematics of foot and ankle joint.2. To measure3D kinematics of the hindfoot joints in vivo by this method and acknowledge hindfoot joint motion characteristics.3. To discuss the effect of the medial arch of each joint3D kinematics on foot medial longitudinal arch changes by this method.METHODS1. Foot and ankle CT image collection in different positionFoot movement is a continuous process, and can be simplified as a motion decomposition from static initial position and the final position, the variation of the six degrees of freedom between two positions in3D space reflect changes of pre-and post-motion.During foot inversion-adduction-dorsiflexion movement, collection of computed tomography (CT) images of the foot and ankle at the initial and terminal positions, All CT scanning data was saved and exported in DICOM format.2. Reconstruction of3D digital model of foot and ankle bones and jointThe data collected above was imported into MIMICS10.0software, and the3D digital model of foot and ankle bones and joint were reconstructed. The data of reconstructed models were saved as.stl format.3. calculation3D kinematics of foot and ankle in vivoTo establish a virtual space coordinate system in GEOMAGIC10.0software, The data of3D digital reconstructed models were imported into GEOMAGIC10.0software. Based on the Principle of Rigid Body Kinematics, using two different dregistration in virtual space in GEOMAGIC10.0software, the three-dimensional space of six degrees of freedom of foot and ankle joint motion can be calculated and readed.4. statistical analysisStatistical analysis was performed using SPSS13.0. The values were expressed as the mean±standard deviation(SD). P-value<0.05was considered statistically significant.Multiple linear regression analysis was used to analyse the relationship of tibiotalar joint rotation angle (X1), subtalar joint rotation angle (X2) and ankle joint rotation angle (Y).LSD multiple comparison was used to compare hindfoot joint rotation angle around the coronary axis, around the sagittal axis, and around the vertical axis.Independent samples t test was used to compare rotation angle of tibiotalar joint and subtalar joint around the same axis, the degrees of freedom for16.Pearson correlation analysis was used to analyse the effect of the medial arch of each joint3D kinematics on foot medial longitudinal arch changes.RESULTS1. Establishment a new method for digitization measurement3D kinematics of foot and ankle joint in vivoUsing MIMICS10.01software reconstruction function and GEOMAGIC10.0 software virtual space coordinate system, based on the theory of rigid body kinematics, to establish a new method for measurement of3D ROM of foot and ankle joint in vivo.2. In vivo hindfoot3D kinematics analysis2.1In vivo hindfoot3D kinematics characteristicsDuring foot inversion-adduction-dorsiflexion, the rotation range of the tibiotalar joint is3.89±2.77°in eversion,5.29±4.47°in abduction,10.77±5.70°in dorsiflexion and the relative displacement was0.78±0.59mm towards lateral ankle,0.18±0.75mm towards the hindfoot,0.65±0.71mm towards the proximal limbs. Subtalar joint is16.46±2.94°in inversion,12.77±1.81°in adduction,6.33±4.32°in plantarflexion and5.50±1.45mm towards medial ankle,1.96±1.77mm towards the forefoot,0.43±1.18mm towards the distal limbs. Talonavicular joint is38.82±5.98°in inversion,19.71±6.33°in adduction,5.09±6.89°in plantarflexion and9.77±1.73mm towards medial ankle,3.13±1.29mm towards the hindfoot,4.64±1.42mm towards the proximal limbs.2.2In vivo hindfoot3D kinematics analysisDuring foot inversion-adduction-dorsiflexion, tibiotalaris joint was mainly ration around coronal axis and subtalar joint and talonavicular joint was mainly ration around sagittal axis, the rotation of Ankle around coronal axis is accomplished by coordination of the tibiotalar and subtalar joints, but the rotation of ankle around sagittal and perpendicular axis is mainly depend on the rotation of subtalar joint3. the effect of the medial arch of each joint3D kinematics on foot medial longitudinal arch changes3.1foot medial longitudinal arch changesDuring foot inversion-adduction-dorsiflexion, Difference of The inner arch angle of the terminal positions to the initial positions is-6.41±4.60, indicated foot arch height is increased.3.2In vivo the medial arch of each joint3D kinematics characteristicsDuring foot inversion-adduction-dorsiflexion, Subtalar joint is16.46±2.94°in inversion,12.77±1.81°in adduction,6.33±4.32°in plantarflexion and5.50±1.45mm towards medial ankle,1.96±1.77mm towards the forefoot,0.43±1.18mm towards the distal limbs. Talonavicular joint is38.82±5.98°in inversion,19.71±6.33°in adduction,5.09±6.89°in plantarflexion and9.77±1.73mm towards medial ankle,3.13±1.29mm towards the hindfoot,4.64±1.42mm towards the proximal limbs. The rotation range of the cuneonavicular joint is2.62±3.93°in eversion,1.20±3.54°in adduction,5.33±6.56°in plantarflexion and the relative displacement was0.04±1.18mm towards lateral ankle,1.65±1.59mm towards the hindfoot,1.80±1.91mm towards the proximal limbs. First tarsometatarsal joint is1.18±2.69°in inversion,0.43±2.65°in adduction,0.32±1.61°in plantarflexion and0.46±l.08mm towards medial ankle,0.48±0.34mm towards the hindfoot,0.28±l.04mm towards the proximal limbs.3.3the effect of the medial arch of each joint3D kinematics on foot medial longitudinal arch changesShift to medial ankle of talonavicular joint is Significant correlation with changes of Foot medial longitudinal arch (P<0.05); plantarflexion, adduction and shift to lateral ankle, hindfoot, proximal limbs of cuneonavicular joint is Significant correlation with changes of Foot medial longitudinal arch (P<0.05);3D ROM of Subtalar and first tarsometatarsal joint is no Significant correlation with changes of Foot medial longitudinal arch (P>0.05)CONCLUSION1. Establishment a new method for measurement3D kinematics of foot and ankle joint in vivo with accurate, non-invasive, simple operation and clinical value to popularize.2. During foot inversion-adduction-dorsiflexion, the rotation of Ankle around coronal axis is accomplished by coordination of the tibiotalar and subtalar joints, but the rotation of ankle around sagittal and perpendicular axis is mainly depend on the rotation of subtalar joint.3. During foot inversion-adduction-dorsiflexion, tibiotalaris joint was mainly ration around coronal axis and subtalar joint and talonavicular joint was mainly ration around sagittal axis.4. During foot inversion-adduction-dorsiflexion, talonavicular and cuneonavicular joint movement is major factor which causes changes of Foot medial longitudinal arch, while the effect of Subtalar and first tarsometatarsal joint on Foot medial longitudinal arch are little, indicating that the three dimensional movements of the navicular affect most significantly to the angle variation of the medial longitudinal arch among all the constituent bones of the medial longitudinal arch. |
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