Blood filters ar not commonly placed in the inner thigh. While it may be possible that this is required for a specific situation, it may be that you misunderstood your doctor
. I would strongly recommend that you talk to your doctor regarding this.
That being said, there are blood filters. These are placed in the inferior vena cava (IVC) which is the blood vessel that drains blood from both legs and then returns it to the heart. The way the filters are placed are by entering a smaller vessel in the inner thigh named the femoral vein. The operator will then thread the filter up into the inferior vena cava. This may be where the confusion is coming from.
Indications for blood filters are mostly for people who develop blood clots in their legs. Blood clots can be caused because of injury
to the vessels, or if someone has "thicker" blood for some reason. Blood clots in the legs have a potential to break off and go to the heart and lungs. This can be fatal. Therefore, in rare cases doctors
place a filter to catch the clots before it gets to the heart and lungs.
Talk to your doctor if the "IVC filter" is required for your case.