student bergen technical highschool teterboro Saddle River, New Jersey, United States
Introduction: Approximately 2 million Americans each year are diagnosed with deep vein thrombosis, a debilitating condition which has large blood clots that slow down the blood's circulation [3]. When blood clotting is excessive in the body it can severely damage tissues in the body and lead to serious conditions such as stroke, heart attack, kidney failure, deep vein thrombosis or pulmonary embolism [5, 6]. Excessive blood clotting commonly occurs in patients that are inactive or are over the age of 60.
Healthcare professionals currently treat blood clots using anticoagulants or blood thinners and Inferior Vena Cava (IVC) filters. Blood thinners have been shown to have side effects such as excessive bleeding, back pain, and trouble breathing. As a result, IVC filters, which are small, wiry devices used to prevent blood clots from entering the lungs are commonly [1]. These filters are placed through a small incision of the groin or neck and retrieved once the treatment has been concluded. The retrieval of these IVC filters is problematic once they are placed in the body. Annually, approximately 65,000 IVC filters are placed in the United States with only 35% of filters that can be retrieved [2]. During removal, the failure of the small hooks detaching cause penetration of the veins walls which could eventually lead to excess bleeding, blockage of blood flow through the vena cava, and even damage to surrounding organs. To mitigate the issue of IVC filters breaking during the removal process, a more flexible and degradable material is introduced.
Materials and
Methods: In this study, the current material properties of titanium were investigated. Using Solidworks 2023, an IVC filter was designed as shown in Figure 1. A Finite Element Analysis (FEA) was conducted to assess the strength of the hook when placed inside the vena cava. To simulate the flow of blood , various ranges of blood pressures were applied. First, 2.7 psi was applied to the filter to simulate the average blood pressure. Next, the pressure 5.4 psi (150 mmHg) was applied to the filter to simulate hypertension. A factor of safety of 2 was used. Next, the properties of a polyurethane material was researched as an alternative solution and compared to Titanium medical grade, Ti-6Al-4V.
Results, Conclusions, and Discussions: To test the IVC filter, a Finite Element Analysis was conducted in SolidWorks 2023 on an IVC filter design. Testing was performed through varying blood pressures ranging from the average blood pressure (2.7psi) to high blood pressure(hypertension) at 5.4psi. The FEA showed that a considerable amount of stress and displacement was present in the base of the hooks. These weaknesses were found in both ranges of blood pressure, meaning that even a person with perfectly normal blood pressure will have a chance of their IVC filter fracturing.
As illustrated in Figure 2, there are stresses present on the design especially at the base. This can be improved by redesigning the filter. Another way to improve this design is by reducing the stresses with an alternative material. Polyurethane is a smart polymer that is currently used in orthopedic implants and bone tissue engineering (7). By using its strength and biodegradable properties, it can be used instead of Titanium. Table 1 shows the properties of a polyurethane-based shape memory polymer which is found to be stronger than titanium in tensile strength and yield strength. However, titanium has a significantly larger elastic modulus which can be increased by adding another material to increase its stiffness. While polyurethane alone is less stiff, it makes up for this deficiency with its biodegradable feature.
In this study, the mechanical properties of IVC filters were investigated to determine why they fail during removal. A Finite Element Analysis was conducted in Solidworks to determine where and why they fail. The analysis has shown high levels of stress within the base of the hook, which would explain the staggering amounts of hooks broken off during removal surgery. With polyurethane-based shape memory polymers, the issues of detaching hooks and removal surgery will be eliminated. This study has shown with either a design change to reduce the stresses at the base of the hook or introducing a new material, less injury will occur in patients.
Acknowledgements (Optional): I would like to thank my teachers at Bergen Technical High School and the Aerospace Engineering Program.
