Design of a calcium phosphate bone cement suitable for the fixation of metal endoprostheses

In order to be suitable for the fixation of metal endoprostheses a calcium phosphate bone cement CPBC must be injectable, whereas strict conditions must be fulfilled for the mixing time MT, the dough time DT, the cohesion time CT, the initial and the final setting time IST and FST as well as the compressive strength CS. Due to the fact that CPBC's build up their strength in not less than 12 hours, the initial fixation of the prostheses must be done by press-fit. However, osteointegration is a matter of days so that from then on the structure is load-bearing all around. Starting with the Biocement H, a CPBC developed earlier, we now succeded in making a formulation called Biocement D which fulfills all requirements: MT < 1 min, DT approximate to CT = 3.5 min, IST = 4.5 min, FST = 13 min and CS = 33 MPa. CS is thought to be sufficient for load-bearing applications because it is higher than the maximum compressive strength of human trabecular bone (30 MPa). This CPBC is osteotransductive, i.e. it is transformed into new bone after implantation in contact with living bone so that the final situation is that of the metal endoprosthesis surrounded by and incorporated in the bone structure.