ABSTRACT
An Ankle-foot orthosis (AFO) is a structure that spans from the lower leg to the foot and controls ankle joint movement. It prevents or assists the human body's lower leg and foot in replicating a normal human gait. The purpose of AFO is to achieve a stable gait by controlling the musculoskeletal system adequately. The mechanical features of AFO stiffness will play an essential role in helping gait, if this stiffness is not matching to the patient's conditions, gait will decrease and knee joint motion will be compromised. In general, trimline cut were introduced in the AFO medial and lateral side to control the stiffness of orthosis. However, this will result in stress concentration in the ankle region and lead to failure of AFO. In this study first evaluate the effects of trimline cut in AFOs using finite element analysis with three geometrical shapes like circle, elliptical and slot were introduced on the dorsal side. The stress concentration and stiffness of AFOs in the ankle region were computed. The stiffness of the basic model and trimline cut AFO model were compared and found elliptical trimline cut model is optimum one. The experimental analysis was performed using 3D Printed AFOs and calculated stiffness. It was observed that finite element analysis results, stress concentration of trimline cut models were reduced maximum of 2 % with basic model (without trimline cut)., whereas, in the experimental study of 3D-Printed AFO of trimline cut model, stiffness were reduced around 16 % compared with basic models. This study clearly indicates that, geometrical shapes trimline cut influencing on stiffness of AFOs. It will give the insight's for orthosis designers to make custom design of AFOs in particularly foot drop conditions to optimized the stiffness of orthosis.
ABSTRACT
Significant advances in 3D printing technology have paved the way for improvements in the integrity and biological characteristics of polymer implants. The principal objective of this research is the construction of a heterogeneous implant structure using a multi-material approach and 3D printing. Due to their advantageous strength-to-weight ratio, biocompatible polymers have an increasing application in the field of medicine. The osteo-integration process, in which implants bind to the bone over time, can be made more effective by incorporating these materials into implants. In this work, we focused especially on analyzing the strength and integrity of polymer material implants that were created using a combination of different materials, and their stress distribution, and the deformation of these multi-material structures when they were subjected to physiological loading through finite element analysis. The evidence from the frontal bite condition has led to some fascinating conclusions. The variations in stress were observed in homogenous structures, with values ranging from 37.42 MPa for the TPU to 41.07 MPa for the PETG. In contrast, stress distributions in multi-material constructions ranged from 52.31 MPa (in the case of TPU +TPU) to 73.55 MPa (in the case of PLA+ PCL). Similarly, the maximum deformation in homogeneous constructions ranged from 0.81mm (PLA) to 6.85mm (PCL). The deformation of multi-material structures composed of several different materials ranged from 0.68mm (PLA+ PLA) to 5.74 mm (PCL+PCL).These findings provide conclusive evidence that multi-material architectures have a considerable impact on known stress and strain levels. Particularly noteworthy is the fact that the combination of PLA+PLA and PLA+PETG displayed deformation that was equivalent to that of the intact bone model while having lower stress levels. The results of this study provide useful information that can be used to select optimal multi-material combinations that can be 3D printed for implants.
