Physiochemical Mechanisms/Sacrificial Bonds 
Physiochemical mechanisms describe "how Sr (strontium) is able to affect the intrinsic tissue quality of bone by directly incorporating into bone at multiple levels, including the organic matrix and the hydrated layer surrounding hydroxyapatite (HA) crystals, forming sacrificial bonds and stabilizing hydration shells." 

Cellular Mechanisms/Ca-sensing Receptor (CaSR) 
"The cellular mechanisms are centered mainly around the Ca-sensing receptor (CaSR) and its ability to mediate bone cell function and respond to Sr, providing evidence for the dual-acting mechanism."

"Osteoclast precursors and mature osteoclasts express the CaSR on their cell membrane..."

Enhanced Bone Microarchitecture 
"Microarchitecture is an important aspect of bone strength and increased fracture risk in patients with osteoporosis is associated with trabecular thinning and increased cortical porosity."

"Clinical studies have shown SR treatment increased cortical thickness and trabecular number and decreased trabecular spacing from baseline, determined using high-resolution peripheral quantitative computed tomography (HR-pQCT)." 

https://www.sciencedirect.com/science/article/pii/S2352187220300334