Strontium affects the way the DEXA sees bone density. There seems to be some disagreement on its effect on bone quality. I wish there was more consistent info!

First, on the ranelate form, which says it builds bone as well as inhibiting resorption, so bone quality would be better than with Fosamax presumably : "Strontium ranelate acts through dual mechanisms of inhibiting resorption by osteoclasts and maintaining or stimulating bone formation by osteoblasts. It has shown only a modest effect in preventing recurrent vertebral fractures. " https://americanbonehealth.org/medications-bone-health/why-strontium-is-not-advised-for-bone-health/

Then there is this:

But doesn’t supplemental strontium strengthen weak bone? The jury is in: and the answer is, it does not!. In a 2016 clinical trial in Osteoporosis International of elderly patients with wrist fractures, supplemental strontium (alongside calcium and vitamin D) did not significantly improve healing within a few months of injury. However, most research indicating that strontium strengthens bones has referenced its positive effect on bone mineral density in patients with osteoporosis, not a single fracture.

Consider that quantity does not guarantee quality. Bone naturally contains minerals such as calcium, magnesium, and phosphorus. The mineral strontium has a similar electric charge to calcium and can take its place in bone. The more mineral in bone matrix, the more dense the bone. Strontium increases bone density, especially the thickness of the outer, or cortical, layer of bone. While this increases bone’s compressive strength, it does not improve and can actually lower bone’s tensile strength- the ability to elongate and flex under pressure. Lacking elasticity, bone becomes brittle like a dried up tree branch. Your fracture risk is higher with more brittle bone. Moreover, strontium is heavier than calcium, so lots of strontium in bone artificially increases your score on a bone mineral density test without improving tensile strength. https://caltonnutrition.com/strontium-does-not-strengthen-your-bones/#:~:text=Strontium%20increases%20bone%20density%2C%20especially%20the%20thickness%20of,becomes%20brittle%20like%20a%20dried%20up%20tree%20branch.

Aside from this issue, it was determined to increase cardiovascular risks and clots.