Views from Industries

Sunday, January 15, 2006

Mechanics in Medical Implant Industry

The major challenge in medical implant industry is the knowledge about human body. Had we know the human body and its functions better, we can make better and reliable implants. Below are two examples that I have learned.

Let's start from stent, a small, lattice-shaped, metal tube that is inserted permanently into an artery. The stent opens the narrowed artery so that an adequate supply of blood can be restored. See this FDA site for further detail.

Stent has revolutionized the treatments for cardiovascular disease and the interventional system. However, stent fractures are commonly observed in-vivo in the past years and has become a concern for patient wellness and therefore a challenge/opportunity for mechanical engineering. Both the engineering and the medical care societies have to work together to solve this issue. It is very surprising that little publications are available to study the key issues such as artery deformation, motion, its mechanical properties and its variations among patient age, race, and other factors. As a result, current stents, even they have been proven to be lifesavers for many patients, they are not necessarily a satisfactory product for a mechanical engineer. We can not wait for the medical care society to give us the information because they often concern and focus on different issues than us. In addition, they can not work alone to come up with the necessary equipments. Therefore, we need proactive to interact and help each other to get what we want. The day we know our interventional system better is the day that we can make better stents because stents can only be as good as our knowledge to the interventional system.

My next example is replacement heart valve. Mechanical heart valve is a very successful medical implant and is very well engineered from design, processing all the way to quality control. It is amazing how a ceramic material, i.e., pyrolitic carbon could be engineered to make a long lasting, great functional mechanical heart valve. However, there are also issues such as leaflet fluttering, backflow and hinge thrombosis that can eventually lead malfunction of the valve leaflets. The sound when leaflet closes also bothers some patients. The medication for thinner the blood is also made the patient life inconvenience and subjected to other threatens such as internal or external bleeding. Therefore as alternatives, flexible heart valves are developed, yet the durability is an issue there.

I hope these two issues convince you that the roles of mechanical engineering are different in medical implants from traditional industry. In latter case, often a design space is known or anticipated. In medical implant industry, to date, it is unfortunate that many key issues are answered only during clinical studies at the potential cost of the patient lives. We have to develop and constantly improve the design space for medical implants and develop the associated in-vitro tests in the lab. Our ultimate goal is to break the parts in the lab to prevent them from fractures inside human body.

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