Is tendon surgery for footdrop possible after several years (cause hip revision) ?

Yes: But with all you have listed as your conditions, i wouldn't advise it. I would recommend pt and for you to constantly try to strengthen your legs. Possibly try an AFO brace.

Foot drop: Is a problem with the nerve that innervate a the foot. Treatment is usually a ankle foot brace known as an afo.

Drop foot: Yes. Surgery can be performed to correct the drop foot usually an ankle fusion vs tendon transfers would be indicated.

Yes: Yes, it's possible to treat surgically after exhaustion of nonsurgical care (bracing, therapies, etc). However, sometimes the surgery may entail more than just tendon work as you may have to have bone surgery to correct deformity, add stability, and have a walkable foot. Hope this helped.

Foot Drop Tendon: This depends on the tendon and muscles. First, an exam would have to be done to see how well each tendon/muscle component is working and then a determination can be made as to if a surgery (either lengthening of tendon or tendon transfer) can be performed. A tendon transfer is used to take a tendon from one part of the foot and use it to hold the foot up and prevent foot drop.