Expandable Shape-Memory Polymers for Suture Anchors

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DESCRIPTION (provided by applicant): This project will develop a shape-memory polymer suture anchor capable of dynamic expansion that will be specifically designed for patients with poor bone mass density. Suture anchors are screw or wedge-like devices that fasten into the bone and are used to secure a detached tendon back onto the bone. Rotator cuff repairs are common surgical procedures involving suture anchors to reduce pain and restore use to an injured shoulder. In 2007, over 460,000 rotator cuff repairs were performed in the US using 1,030,000 suture anchors. Approximately 25 to 35% of rotator cuff repairs are considered unsuccessfully. A general challenge and constraint in rotator cuff repair is the large amount of soft cancellous bone where the anchors must be placed, which makes the anchors more susceptible to migration, loosening/tunnel widening, and pullout. Furthermore, a growing number of patients over 60 years of age are receiving rotator cuff repairs and suffer from osteoporosis. In recent studies, over 54% of patients over the age of 60 with shoulder pain had evidence of rotator cuff tears. Patients with poor bone mass densities are highly at risk of device failure as bone density have been correlated to the fixation strength of the suture anchors. The proposed shape-memory suture anchor will be developed as a tap-in style device, in which the shape- memory effect will be mechanically activated to expand into a wing-shaped device and offer instant fixation. The main advantages of this device are its superior fixation strength in soft bone and increased cyclic performance due to the design's use of shape-memory polymers. The shape-memory suture anchor will also offer reduced complexity and time during installation as a tap-in device, which can utilize a knotless suture approach. Knotless suture anchors instantly secure tendon fixation upon anchor insertion and do not require the surgeon to tie and pass knots of suture from the anchor to the tendon as in traditional anchors. The broad impact of this work will challenge the paradigm of how suture anchors are designed to work in soft bone by utilizing shape-memory materials and a model to predict pullout strength, which was developed in Phase I. This Phase II looks to continue and expand upon the feasibility demonstrated and fundamental information obtained in the successful Phase I efforts of this project. The aims of the Phase II have specifically been designed to fundamentally investigate the design and performance of suture anchors while following an aggressive path towards regulatory approval. The aims involve (1) finalizing the design, (2) developing instrumentation, (3) assessing biocompatibility, (4) validating sterilization, (5) validating performance, and (6) performing a pilot animal study to prove the use of shape-memory suture anchors in-vivo. The primary research team will consist of Chris Yakacki PhD (PI), who is an expert in shape-memory polymers and device testing; Ken Gall PhD, a full professor from Georgia Tech who specializes in shape-memory materials and medical device testing; and Reed Bartz MD, an orthopedic surgeon and expert in arthroscopic shoulder repair. PUBLIC HEALTH RELEVANCE: A growing percentage of the population is remaining physically active as they age. This project is relevant to this percentage of people that experience a debilitating injury such as a rotator cuff tear and suffer from poor bone quality. This project will provide a means to restore function to repaired injury sites with less occurrence of surgical failure and increase patient quality of life.