Design And Application Research Of 3D Printed Ankle Foot Orthosis

Varus foot is a common clinical disorder in stroke patients,which affects the functions of the lower limbs,knees,hips,and other joints,causing patients to be unable to work normally or even conduct daily life.Three-point mechanics is an effective method for correcting varus foot with ankle foot orthoses.In recent years,the focus of correcting varus foot is mostly on the innovative design of the orthosis structure,The position and magnitude of the corrective force are still unclear,the corrective effect and principle are still indistinct,lacking relevant biomechanical empirical verification.In response to the above problems,a personalized and lightweight design method for a new type of 3D printing orthosis was proposed in this paper,and it is based on the three-point force correction principle to further improve the orthopedic mechanism and verify the corrective effect of the orthosis,which provides important biomechanical support and reference for orthopedic doctors and orthotists in the future when correcting varus foot.The main research contents and conclusions of this article are as follows:(1)Three-dimensional reconstruction of bone and soft tissue models was completed with CT imaging technology,and the reconstruction of NURBS surface and data optimization of three-dimensional models such as foot bones and soft tissue were finished based on reverse engineering technology,an orthopedic model that conforms to the curvature of the body was designed combining with three-point force and according to patient’s contour,besides,the major regions were modified.Finally,the deviation analysis of the above models was completed to obtain a high accuracy geometric model that conforms to human physiological and anatomical characteristics.(2)The effectiveness of the above model was verified using workbench module in ANSYS,static and dynamic landing finite element simulation of normal people and varus foot was carried out to analyze the discrepant positions of varus metatarsal bone and healthy people under different varus angles and pressure loads,the data indicates that the difference is in the fourth and third metatarsals,the stress changes of the metatarsal bone at different times of landing in the varus foot were obtained through the dynamic module,which determined the force application point that should be corrected after wearing the orthosis for subsequent content.(3)The corrective effect of the varus foot orthosis was analyzed based on the principle of three-point force,it is concluded that when meeting the pain threshold of the human lower limb,it was found that the corrective force system under the combined action of two planes had the best effect by comparing with the effects of three point force on the coronal plane and the horizontal plane,the data showed that the optimal force application position of the orthosis was the first metatarsal bone and the medial side of the calcaneus,the varus angle of the rear foot was corrected from 10.21 ° to 7.25 °,and the varus angle between the front foot and the ground was also significantly reduced under the action of10 N,20N,25 N,and 10 N on the outer ankle,above the inner ankle,inside the heel,and first metatarsal shaft,the varus deformation of the foot was reduced from 1.81 mm to 0.44 mm,and the deformation rate was reduced by 75.7% under a 1 N · m varus load with the stable support of the orthosis,which verified the effectiveness of the orthosis.(4)The optimal printing material and thickness for wearing orthoses were selected as PLA and 2mm with finite element method and mechanical properties as indicators.And the optimal solution was determined to be the Tyson polygon texture when using grasshopper parametric software to hollow out design.FDM technology was used to print physical products and install accessories after topology optimization,what’s more,the comfort and satisfaction were evaluated for volunteers,the plantar pressure test data showed that the distribution of plantar pressure load on the affected side was improved when patients wearing orthosis,increasing walking speed,which furtherly verified the effectiveness of orthosis.In summary,a personalized 3D printing ankle foot orthosis design process was proposed,and the orthopedic mechanism of the three point mechanics of the orthosis for patients with varus foot was thoroughly studied,verifying the reliability of the ankle orthosis,which provides important mechanical theoretical support and reference for clinical correction of varus foot.