A fracture could occur more easily than you might imagine. Pay attention to changes in spasticity or occurrences of autonomic dysreflexia. These could indicate a fracture that might not otherwise be apparent. If you hear a snap or other unusual sound, don't ignore it. A bruise from internal bleeding is another potential sign, which you could mistakenly assume is from an impact you didn't feel during the day.
Spasticity has a mixed impact on osteoporosis.
When muscles spasm, they place a load on bones that help maintain their density. But severe spasms can break osteoporitic bones. For people who never stand, managing extreme spasticity is all the more important. Standing frames are promoted as a means of preventing osteoporosis, but physicians are not in agreement that spending a little time each day in a standing frame is sufficient to duplicate the loads your bones would experience in walking. Standing frames clearly benefit circulation and range of motion, but it is less clear that they are a solution for avoiding brittle bones.