@marialyce
build as a verb can have the meaning of collect or increase. Foxamax causes bone to collect that would otherwise be lost. The bone it collects is older usually fissured and more brittle less vascular with fewer nerves and is bone that osteoclasts think needs to be replaced.
Except that osteoclasts don't think.
I do like your point. And I like knowing the mechanisms of action of each medication.
Joshedward's friend's surgeon can know if the friends bones were weak and brittle, but can't know if Fosamax had helped the friend prevented other fractures or/and delayed the fracture under consideration. Both of which are likely.