I had good results using it for a fracture. I don't have any experience using it with navicular issues, but I wouldn't hesitate to try it - it's expensive, but I think well worth it.
My daughter is using it on her mare with the start of navicular along with Osphos. She just finished the loading dose and now down to the maintenance level. She'll do xrays in the next couple months to see if theres any change.