| Aimed to the actual needs of passive rehabilitation for ankle fracture patients,this thesis takes parallel external fixator as the platform of passive rehabilitation,and studies the overall design of passive rehabilitation program,the establishment of ankle joint’s motion model,the inverse kinematics of parallel external fixator and the finite element analysis of rehabilitation program.The main research achievements are as follows:1.The overall design of passive rehabilitation program for ankle joint based on parallel external fixator.Taking the ankle fracture with parallel external fixator as the research scenes,combined with the clinical continuous passive motion(CPM)rehabilitation concept,the overall program of passive rehabilitation for ankle fracture is proposed.In this program,6-UPS parallel external fixator is used as the platform of rehabilitation.NDI Optotrak Certus 3D dynamic measurement system is used as the motion capture device for normal ankle.The motion of moving platform of external fixator is related with the rehabilitation trajectory,and the length of branch chain is calculated based on the inverse kinematics of parallel mechanism.The passive rehabilitation process is simulated by finite element software and the rehabilitation trajectory is optimized.2.The establishment of normal ankle’s motion model and its general description.Through the difference analysis of the ankle motion measurement,it is proved that there is a universal law of ankle joint movement.Based on the markers’ coordinates of the internal and external ankle tip,the equivalent motion axis of the ankle joint is obtained.When ankle is doing plantar flexion and dorsiflexion movement,the axis is fixed.When the ankle is doing free movement or other forms of motion,the axis are distributed in the shape of "opposite top cone".Taking the center of the ankle motion as a reference,the range of ankle motion angles is obtained.The angle range of plantar flexion and dorsiflexion motion is-31.4°～33.8°,the angle range of varus and eversion motion is-45.0°～30.6°,and the angle range of adduction and abduction motion is-25.0°～21.7°.Based on the coordinate of ankle centroid,the boundary of ankle joint trajectory is obtained,that is,the trajectory of normal ankle joint centroid is included in the semi ellipsoid surface formed by the boundary.3.The biomechanical analysis of passive rehabilitation for ankle fracture.Based on the motion law of ankle joint,the curves of plantar flexion and dorsiflexion and varus and eversion are selected as passive rehabilitation trajectories,and the curves are fitted and discretized.Using the closed-loop vector method,inverse kinematics of the parallel external fixator is obtained,and the length of six branches of the external fixator is calculated under different positions and postures of the moving platform.Using Mimics software,the finite element model of medial malleolus fracture in ANSYS is obtained by 3D reconstruction of CT plain film.The ankle joint finite element model is made to move according to the rehabilitation trajectories to simulate the passive rehabilitation process,and the effectiveness of the rehabilitation trajectories is judged by the stress of the fracture end.Based on the results of finite element simulation,the invalid part of rehabilitation trajectories is screened out and the optimized branch chain adjustment are generated.In this thesis,starting from the measurement of ankle joint motion,the general description of normal ankle joint movement is proposed,and the passive rehabilitation trajectories is screened out from it.Then,the positions and postures of external fixator’s moving platform is obtained and the finite element simulation of rehabilitation process is realized.The research of this thesis can promote the functional rehabilitation of ankle fracture patients as soon as possible,and provide research ideas and theoretical support for the integration of fracture reduction and rehabilitation with parallel external fixator. |
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