hi, rashida.
thanks for the question. You'll see I had some fun with it.
The direct answer to the question is that Tymlos doesn't get rid of the old bone. Your blood takes it away. Fragments of that bone are measured in the serum bone marker CTX.
Tymlos does provide the environment that encourages the natural process of renewal in stimulating the development of more active, importantly here, more vascular bone. Because of this vascularity, neither Tymlos or Forteo have warnings of osteonecrosis.

Tymlos increases the calcium levels in our blood, but just for about 4 hours. It pulls calcium from the digestive track, back from the kidneys and even from the bone. That calcium signals that your body is losing bone. While this signals the need for osteoblasts--the cells that build bone. It is the osteoblasts themselves that signal for the cells that dissolve damaged bone.
Extending the question leads to answers about how Tymlos or Forteo increase the cells that dissolve fissured bone.
https://www.google.com/search
RANKL Receptor activator of NF-κB (nuclear factor-kappa B) ligand
OPG Osteoprotegerin