Calcium Phosphate Bone Cements Explained
Educational overview - not medical advice.
When bone is lost to trauma, disease or surgical removal, the resulting void needs to be filled to restore structural support and give the body a scaffold on which to rebuild natural bone. Historically, this has been done with bone grafts (the patient's own bone, donor bone, or synthetic substitutes) or with acrylic bone cements such as PMMA. Calcium phosphate cements (CPCs) are a newer category designed to more closely mimic the mineral composition of natural bone.
Why calcium phosphate?
Natural bone is largely composed of a calcium phosphate mineral called hydroxyapatite. Synthetic calcium phosphate cements - typically blends of compounds such as α-tricalcium phosphate, calcium carbonate and precipitated hydroxyapatite - are formulated to set, in the presence of moisture, into a similar calcium-deficient hydroxyapatite structure. Because the resulting material is chemically similar to bone mineral, it is considered osteoconductive: it can act as a scaffold that the body's own bone-forming cells gradually remodel into living bone.
Ready-to-use formulations
Older bone cements often required intraoperative mixing under time pressure, since the material would begin to set as soon as its components were combined. Newer ready-to-use pastes are supplied pre-mixed in a syringe and are formulated to remain workable until they contact an aqueous (moist) environment, such as bone tissue - meaning the surgeon controls when setting begins, not the clock. This can simplify handling during procedures such as trauma fixation, revision surgery, tumor-related reconstruction, or correction of congenital bone defects, including via arthroscopic techniques.
What the evidence shows
Published data on ready-to-use calcium phosphate cements shows a progressive setting and remodeling process: dimensional stability within minutes of application, mechanical strength comparable to cancellous (spongy) bone within 24 hours, and a structure resembling natural bone within about a week. Compressive strength continues to rise over the following days as the material fully sets. In a sheep implantation study evaluating a ready-to-use calcium phosphate cement in drill-hole bone defects, histological examination showed an initial remodeling reaction at 4 weeks, substantial osseointegration by 3 months, and complete integration into lamellar bone by 6 to 18 months, with no decline in osseointegration observed over that period.
Where it fits in orthopedic care
Calcium phosphate bone cements are generally indicated for filling or reconstructing non-load-bearing bone defects, or defects that are otherwise mechanically stabilized (for example, by plates, screws or other fixation hardware) - not as a substitute for structural fixation itself. As with any bone graft substitute, appropriate patient selection and surgical technique remain central to a good outcome.
Source: Nies, B. A histological evaluation of a novel ready-to-use, self setting Calcium phosphate bone substitute cement in a sheep implantation model, in collaboration with the Laboratory for Experimental Traumasurgery of the University Hospital of Giessen and Marburg. INNOTERE GmbH, 2013.