So 81% were post-menopausal and the strontium citrate dose was 680mg, considered therapeutic in the integrative medicine world.

There is a discussion of how strontium replaces calcium, but no reference to how this affects the DEXA (since strontium is denser than calcium).

Here is the discussion:

Since strontium is a metal in the same group of periodic elements as calcium, it has been recognized that strontium in high concentrations may displace and replace calcium in bone by heteroionic exchange [54], a phenomenon which has elicited disparaging regard for strontium therapy among some bone specialists. Rather than an increased BMD, however, this physiochemical process in the presence of excessive strontium ultimately results in decreased bone calcium content [55], dissolution of mineralized bone [56], disruption of bone architecture [57], and lower BMD [58]. This phenomenon only appears to be the consequence of disproportionately high doses of strontium intake, not regular supplemental levels at low dose.

At low supplemental doses of strontium, in fact, there is evidence of an increase in both the bone formation rate and the trabecular bone density related to a strontium-induced stimulation of osteoblastic activity [58]. Furthermore, at low doses, strontium is not associated with any mineralization defect or any increase in the number of active bone-resorbing cells [59, 60]. In addition, it has recently been found that the mechanism of strontium benefit may also involve a calcium preservation effect as the rate of calcium release was almost halved after strontium treatment was assessed in recent research on teeth [61]. Finally, strontium supplementation, unlike use of calcium supplementation, shows ability to recalcify osteopenic areas in pathological bone conditions characterized by accelerated bone loss and extensive demineralization [58, 62].