Date of Award
Doctor of Philosophy (PhD)
Dr. Jeffrey N. Anker
Dr. Tzuen-Rong Jeremy Tzeng
Dr. John Desjardins
Dr. Joseph Kolis
Dr. George Chumanov
Bone fracture healing includes complex and sequence of dynamic events to restore the integrity and biomechanical properties of the bone. While most of the fractures heal without any problem, healing is sometimes compromised. Two significant fracture healing complications are orthopedic implant-associated infections and non-unions/delayed union. These can be interrelated causes as well. Implant-associated infection can cause implant loosening, and as a result, it can delay the fracture healing process. Herein, we describe two different types of sensors that can be used in monitoring biochemical and biomechanical processes of fracture healing using X-rays.
We developed a XELCI (X-ray Excited Luminescence Chemical Imaging) based biochemical sensor for monitoring implant-associated infections by decreasing pH due to acidic products of bacterial metabolism. High spatial resolution pH mapping of the intramedullary canal through bone and tissue was carried out with the XELCI imaging technique developed in our lab. Pre-pilot rabbit studies were carried out to monitor the pH variations in the intramedullary canal of the rabbit tibia by creating two infected rabbit models compared to a sterile control rabbit. We observed a pH drop in the intramedullary canal while using the pH-sensitive hydrogel-coated intramedullary rod.
Moreover, to monitor stiffness and biomechanical properties of the healing bone during fracture healing, we developed a biomechanical sensor with hydromechanical amplification read via plain radiography. The sensor was mounted on Sawbones tibia models (fractured and allograft repaired) and human cadaveric tibia and tested under cyclic loading. The sensor displayed reversible and repeatable behavior with a slope of 0.096 mm/kg and fluid level noise of 50 to 80 micrometer (equivalent to 5-10 N).
While both these sensors will address the two major issues in fracture healing providing useful insight, they can be improved with future modifications. The proposed intramedullary rod design with wells can be machined in stainless steel to be a more robust sensor. Moreover, as we carried out this study as a pre-pilot study, we can extend it into a full study also combining it with antibiotic treatment in animal models. Chromoionophore III can be investigated as a potential dye for monitoring pH as well as other analytes of interest at the fracture site.
The fluidic sensor can be improved by miniaturizing the sensor components and designing it to attach to the side of the orthopedic implant plate where there’s more room for sensor accommodation. In addition, the sensor can be applied in other types of fractures and implant plates as the senor was only studied on tibial implant plates.
Rajamanthrilage, Apeksha, "X-Ray Interrogated Implantable Chemical and Strain Sensors for Monitoring Implant Associated Infections And Fracture Healing" (2022). All Dissertations. 3242.
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