Johnson wrote:Dr. Sclafani,
I read with interest the remark about stents being able to withstand flexion 40,000-50,000 times, and tried to calculate how many times one might turn ones head, cough, chew, etc., in a day. I'm sure that it would be hundreds of times a day, at least. I don't see relying on a stent for decades.
I second this question as a very important one. What happens if a stent fractures? What, if anything, can be done to save the vein? Is replacement of the stented segment impossible? 40-50 thousand neck bendings is indeed not much, Johnson, I can't find the comment you're referring to, and what stents it is based on? Perhaps Dr. Scafani has a feeling about whether steel or nitinol are more durable.
This article is relevant to the question:
It looks at the effects of torsion (bending) and axial (lengthwise) compression on various types of nitinol stents. After a few million cycles (which is a bit more comparable to the remaining lifetime of a person with MS than 50,000) many of the commonly used types had fractured. It does not discuss torsion unfortunately. Together, bending, axial compression, pinching (e.g. by neighboring muscles), and torsion should be the most important forces acting in the neck. If anybody can find material on pinching and torsion in nitinol and steel stents, that would be complementary to the above article, and very useful information for those of us planning to go to Katowice.
Also, if some of the Stanford patients could let us know what types of stents were used in them (cheerleader mentions stents specifically shaped for jugular veins), that would be helpful.