Soft-Tissue Orthopedic Fixation with Shape Memory Polymers

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DESCRIPTION (provided by applicant): This exploratory research project aims to develop and validate soft tissue orthopedic fixation devices based on emerging shape memory polymers. The proposed work focuses specifically on the creation of self-deploying shape memory polymer fixation devices for Anterior Cruciate Ligament (ACL) knee reconstruction, a surgery costing the United States approximately 2 billion dollars annually. ACL reconstruction is a common and critical surgery in sports medicine, and provides an ideal testbed shape memory polymers in orthopedics. Current soft tissue fixation devices are based on inactive polymer or metal screws used to fix a tendon in a bony tunnel through forces generated during high-torque insertion or clamping. Shape memory polymers provide a potentially superior solution to minimally invasive soft tissue orthopedic fixation by providing a simpler, stronger, and more versatile method to promote fixation and uniform healing between tendon grafts and a bony tunnel. Essentially, a shape memory polymer device can be delivered into the body in a compacted state and programmed to self- deploy and impart forces once it reaches a prescribed temperature (e.g. the body temperature or a slightly elevated temperature). The research contains two specific aims: (1) evaluate the thermo-mechanical recovery properties and biocompatibility of several candidate shape memory polymer materials, and (2) evaluate the efficacy of several prototype shape memory polymer ACL anchors in an in-vitro bovine model. The present work will result in fundamental knowledge regarding the thermo-mechanical behavior and biocompatibility of candidate shape memory polymers and fundamental knowledge on the in-vitro performance of shape memory polymer orthopedic fixation devices. The results will provide proof of concept and set the stage for a larger reliability and in-vivo efficacy effort on shape memory polymer based soft-tissue orthopedic fixation devices. The work will be performed as a close collaboration between a materials scientist/mechanical engineer (Gall), a biologist (Boyan), and a sports medicine doctor (Bartz). Biomedical devices fabricated from shape memory polymers have significant potential in medical devices ranging from orthopedic fixation devices (outlined in the proposed work) to cardiovascular stents and smart sutures. The knowledge gleaned from the proposed work should have broad impact in several of these medical fields.