Excerpts from the book "How Design Changed America" by Henry Keck
We are all familiar with the inspiring advances in medicine made during our lifetime. Included in the great litany of advances are many devices implanted in the human body with life saving attributes. Pacemakers, stents, orthopedic plates, knee replacements are a few of these implants. Among these products is the mechanical heart valve. Among the most important and widely used by doctors around the world is the Bjork-Shiley Convexo-Concave valve.
Our first task was to review the production techniques used by the company. We found that despite the excellent design of the valve the assembly techniques were primitive. Assemblers armed with fine pliers inserted the carbon disc into the metal ring enclosure. They then bent the strut holding the disc in place back and forth until it was properly adjusted.
To remedy the situation Keck-Craig developed a small fixture which permitted assembly of the valve to close tolerances with only one closure movement so that work hardening of the metal was minimized. Although this was a major and useful fix to the assembly procedure there were already so many valves implanted worldwide that thousands of heart patients were in jeopardy.