By: Josh Erndt-Marino, Sal Ghodbane , Chris Pachomski & Drew White
Adviser: Dr. M. Paliwal(MEC)
There are about 14.5 occurrences of fracture fixation per every 100,000 in the population every year. As a result, approximately 370,000 hospitals visits occur every year. Presently, there are two exclusive schools of thought for internal fracture fixation: rigid and biological fixation. Rigid fixation utilizes stiffer implants for precise fragment positioning. However, significant stress shielding occurs as a result of the fixation. Biological fixation utilizes more flexible implants to reduce surgical trauma and allow for more functional healing but the possibility of non-union and delayed healing increases as well. We aimed to combine these previously exclusive schools of thought by developing a proof-of-concept biphasic internal fixator which varies its stiffness between the typical stiffness of the two schools. The design will implement a shape memory polymer (SMP) to allow for biphasic actuation of the device. We will inductively heat the polymer above its glass transition temperature (Tg) changing the SMP layer from a thicker initial shape to a preprogrammed “memorized” thinner shape. This will cause a change of cross-sectional area and moment of inertia of the overall device resulting in a decrease of its spring stiffness for axial, torsional, and bending loadings; thus, reducing the effects of stress shielding while ensuring precise fragment union.