Calcium phosphate/sulfate-based bone implant composition

1. A method of forming a bone graft cement wherein the cement composition comprises beta-tricalcium phosphate and calcium sulfate and slowly soluble sources of calcium ions, hydroxyl ions and an aqueous solution; containing a clinically effective quantity of a therapeutic agent; the method comprising pre-mixing the cement composition for a first period of time prior to the addition of the therapeutic agent, adding the therapeutic agent and mixing for a second period of time then allowing the mixture to hydrate and set undisturbed.

2. A method of forming a bone graft cement according to claim 1 , further comprising adding an accelerant.

3. A method of forming a bone graft cement according to claim 2 , wherein the accelerant is selected from the group consisting of potassium sulphate, sodium sulphate or sodium chloride.

4. A method of forming a bone graft cement according to claim 1 where the therapeutic agent is in a powdered or liquid form.

5. A method of forming a bone graft cement according to claim 1 where, following the second period of mixing, the mixture is pasted into a pellet mould before being allowed to hydrate and set undisturbed, to form pellets of the bone graft cement.

6. A method of forming a bone graft cement according to claim 1 where the first period of time is in the range of 15 seconds to 2 minutes.

7. A method of forming a bone graft cement according to claim 1 where the second period of time is in the range of 10 seconds to 1 minute.

8. A method of forming a bone graft cement according to claim 1 where the therapeutic agent is one that is able to retard or inhibit the setting of the bone graft cement.

9. A method of forming a bone graft cement according to claim 8 where the therapeutic agent is selected from the group consisting of an antibiotic, an antifungal agent, an antiviral, a bone morphogenetic protein or NSAID, alone or in combination.

10. A method of forming a bone graft cement according to claim 1 wherein the beta-tricalcium phosphate is in the form of granules.

11. A method of forming a bone graft cement according to claim 10 , wherein the beta-tricalcium phosphate granules have a particle size in the range of 0.4-5.0 mm.

12. A method of forming a bone graft cement according to claim 1 wherein the calcium sulphate is selected from the group consisting of dihydrate, hemi-hydrate, soluble anhydrite and insoluble anhydrite.

13. A method of forming a bone graft cement according to claim 1 wherein the source of ions are provided by compounds having a water solubility at room temperature of less than 5 grams per litre.

14. A method of forming a bone graft cement according to claim 1 wherein the source of ions are provided by compounds having a water solubility at room temperature of less than 1 gram per litre.

15. A method of forming a bone graft cement according to claim 1 , wherein the cement composition forms a bone graft cement when mixed with water or a non-acidic aqueous solution.

16. A method of forming a bone graft cement according to claim 15 wherein the aqueous solution is either water or a non-acidic aqueous solution.