Anything applied externally to an extremity, including fingers or toes, that would act or function like a tourniquet would constitute an External Constriction. This could be a thread, string, rubber band, etc. that would constrict/restrict circulation to and from the extremity/digit distally. If left in place too long it can do severe/significant and permanent damage. That is why in surgery, the tourniquet time and pressure is monitored so closely. Finger and toe rings can do this in extremity trauma situations when there is rapid and significant swelling, and the ring gets too tight. Rings often have to be cut off in the ER when extremity trauma occurs and the swelling is too great to remove it easily and manually.
This is not the same as Congenital Constriction Bands which can occur at the wrist and fingers, or the ankle and toes. If severe enough, they can have the same/similar effects, and usually require Plastic Surgery correction, though rarely as an emergency.
I hope this helps.
Respectfully submitted, Alan Pechacek, M.D.
icd10orthocoder.com