Orthopedic injuries are a common cause of disabilities for soldiers, veterans, and civilians; and such injuries are extremely difficult and costly to treat. Regardless of the cause -- whether by trauma or congenital deformity from birth -- orthopedic disabilities induce substantial discomfort and loss of functionality, and advanced treatments are critical for improving patients’ quality of life. Dr. James Henderson, Associate Professor of Biomedical and Chemical Engineering at Syracuse University, brings shape-memory polymers in vitro and in vivo to study mechanobiology and to develop new strategies for tissue engineering and regenerative medicine, with the goal of increasing the speed with which these injuries can be treated. Through novel methods of grafting and stabilizing complex fractures with these unique biomaterials, Dr. Henderson hopes to help people achieve a higher level of function more rapidly as they return to normal activity and to reduce pain, inconvenience, and cost.

Shape-memory polymers (SMP) have the ability to ‘‘memorize’’ a permanent shape, which can then be heated, elastically deformed, cooled and “fixed” into a temporary shape though an immobilizing transition and then later recover to the permanent shape through a triggering event, like heating or hydration. Dr. Henderson’s interdisciplinary team and collaborators focus on understanding the mechanobiology of tissue development, maintenance, and disease progression, and exploiting the SMP technology to incorporate this understanding in tissue-engineering and regenerative medicine approaches. His work, therefore, has the potential to lead to improvements in clinical practice that may achieve faster outcomes with fewer surgeries, less pain and risk to the patient, more rapid resumption of activity, and improved quality of life, thereby positively impacting a significant proportion of civilians, military service members, and veterans.

Current research includes:

• Stabilizing Biodegradable Self-Tightening Internal Casts: Support, or stabilization, is required for a complex fracture to heal, and currently the most common methods of support are metal plates, rods, and screws that are implanted internally to hold the bones in place or external pins penetrating the skin to connect to and stabilize the underlying bone fragments. Complications of these methods can include: additional loss of bone as the metal hardware bears too much of the load; multiple surgeries to remove or replace the metal hardware; and difficult-to-cure infections on or around the impact materials. To this end, Dr. Henderson leverages the programmable capabilities of SMPs to conform to the fracture for more effective stabilization, creating  “smart sleeves” that can serve as an alternative option for surgeons. These experiments were performed in mice, and Dr. Henderson hopes to now test them in more clinically relevant model of complex fractures for clinical use.
• Medically Motivated Synthetic Grafts: In segmental defects, a graft must be used to fill the bone gap in addition to stabilizing the fracture. A piece of bone from the same patient is the best graft option currently available, but there is seldom enough “extra” bone elsewhere in the body. As a result, doctors must frequently resort to grafts from cadavers, which often fracture after use, carry risk of infection and disease transmission, and are expensive. Dr. Henderson is thus developing the “smart graft” made from shape-memory polymers, designed to expand and anchor itself against the remaining intact bone at the edges of a segmental defect.
• Mechanobiology Platform Development: Mechanobiology is the study of how biomechanical stimuli—such as extracellular stresses, strains, matrix architecture, or stiffness—contribute to development, disease, and healing. In order to understand mechanobiology, it is critical to study how cells respond when their biomechanical environment changes over time. To answer fundamental questions about mechanobiological events during development, disease, and healing, Dr. Henderson has begun to create two-dimensional and three-dimensional biomaterial platforms to probe the process, and is developing analytical tools that will be necessary to fully employ these new biomaterial platforms.
   
• Other Applications Outside Fracture: During mechanobiological events, cells experience a change in the architecture and the shape of their environment that affects their behavior. Some of the 3D SMP platforms are used for in vitro models of tissue development in diseases such as cancer, which can particularly be used to study how breast cancer cells associated with pregnancy respond to changes in their local architecture as the fiber stretcher in the breast changes over time. Other applications include collagen fiber orientation during wound healing in skin.