Calcium phosphate cements as long-term stable pastes with adjustable porosity: Fid-Bau Portal

Calcium phosphate cements as long-term stable pastes with adjustable porosity

Nies, B. / Reinstorf, A. / Porstendörfer, U. / Vater, C. / Müller, J.

Calcium phosphate bone cement (CPC) manufactures try to overcome the challenge of powder/liquid mixing by the operation room team by offering sophisticated mixing systems. A considerable advantage for the medical use of CPC could be gained by developing a stable and ready-to-use paste that eliminates powder/liquid mixing or even needs no mixing at all, while the cement sets upon contact with a fluid. In the present feasibility study is reported on the development of a new concept for ready-to-use organo-mineral reactive systems that combine sufficient mechanical properties, good biocompatibility, and extended storage stability with excellent handling and application properties.Two different paste systems for CPCs were evaluated, a one-paste CPC (1PCPC) and a two-paste-CPC (2PCPC). In both cases, the pastes contained 80% CPC powder of the composition Biocement D. For a 1PCPC, the cement powder was thoroughly kneaded with 15% Miglyol 812, 3% Tween 80, 1% emulsifier and 1% finely ground Na2HPO4 to obtain a paste that could be extruded from a conventional syringe. For the 2PCPC, one water-free paste was prepared by mixing CPC powder with 17% Miglyol 812, 2% Tween 80 and 1% emulsifier. A second, aqueous paste was prepared with 95% water, 4% Na2HPO4 and 1% carboxy methyl starch. Both 2PCPC-pastes were then mixed either manually or with a double cartridge system. For 1PCPC setting started by injecting the paste into simulated body fluid; 2PCPC setting started when the first and the second paste were mixed with one another. Addition of 25% of different particle sizes of sucrose was used in some experiments to create additional macro-porosity. Both PCPCs show very good cohesion after injection from a syringe into water. Consistency and cohesion of the pastes was unchanged after storage in syringes for 6 months. Setting times were determined at 3 - 4 min for the initial and 15 min for the final setting time with the Gillmore needle. Compressive strength (n =8) was 10 - 16 MPa for the 1PCPC and 12 - 19 MPa for the 2PCPC. Conversion of the cement components to Hap was not yet completed after 100 h (XRD). Porosity of the plain cements was determined at 23 %. The addition of sucrose increased porosity by 30%. The compressive strength of the porous PCPC was 60% that of the plain material.