A novel and easy-to-prepare strontium(II) modified calcium phosphate bone cement with enhanced mechanical properties

The aim of this study was to evaluate two different approaches to obtaining strontium-modified calcium phosphate bone cements (SrCPCs) without elaborate synthesis of Sr-containing calcium phosphate species as cement precursors that could release biologically effective doses of Sr²⁺ and thus could improve the healing of osteoporotic bone defects. Using strontium carbonate as a strontium(II) source, it was introduced into a hydroxyapatite-forming cement either by the addition of SrCO₃ to an α-tricalcium phosphate-based cement precursor mixture (A-type) or by substitution of CaCO₃ by SrCO₃ during precursor composition (S-type). The cements, obtained after setting in a water-saturated atmosphere, contained up to 2.2 at.% strontium in different distribution patterns as determined by time-of-flight secondary ion mass spectrometry and energy-dispersive X-ray spectroscopy. The setting time of CPC and A-type cements was in the range of 6.5–7.5 min and increased for substitution-type cements (12.5–13.0 min). Set cements had an open porosity between 26 and 42%. Compressive strength was found to increase from 29 MPa up to 90% in substituted S-type cements (58 MPa). SrCPC samples released between 0.45 and 1.53 mg g^?1 Sr²⁺ within 21 days and showed increased radiopacity. Based on these findings, the SrCPC developed in this study could be beneficial for the treatment of defects of systemically impaired (e.g. osteoporotic) bone.