Optimal Design of a Biodegradable Polymeric Screw for Fractured Finger Bone

Orthopedic field is one of the most important applications of biodegradable implants. In this study, an optimized design of biodegradable orthopedic screw was introduced and evaluated. This optimization was done in such a way that could be generalized for other screws. First of all, effective parameters of the screw were identified and range of them for optimum design was investigated. Then in order to simulate the degradation process and mechanical loading reaction numerically, COMSOL was applied. Also, design of experiments (DOE) using Taguchi method was used to study the effects of parameters on changes during degradation process. Afterwards, by the analysis of signal to noise ratio, the optimum design of the screw was selected with the aim of minimize degraded molecular weight percentage and von mises stress simultaneously. The ideal orthopedic screw was designed using optimized parameters, and after 8-weeks degradation, the minimum value of the degraded molecular weight percentage and von mises stress are reported as 60.854% and 0.882e7 N/m2, respectively. At last, using a linear relation between Young's modulus changes and logarithm of molecular weight changes, the manner of Young's modulus reduction was predicted.