METHODS OF DEPOSITING DISCRETE HYDROXYAPATITE REGIONS ON MEDICAL IMPLANTS

1 . A method for electrochemically depositing a discrete region of a calcium phosphate onto a medical implant comprising at least one area having an electroconductive surface, the method comprising:

a. contacting at least a portion of the electroconductive surface of the implant with an electrolyte solution comprising calcium ions and phosphate ions; and

b. applying an electrical potential between the electroconductive surface and the electrolyte solution, thereby forming a plurality of discrete regions of a calcium phosphate onto the electroconductive surface, wherein the calcium phosphate comprises a needle-shaped morphology.

2 . The method of claim 1 , wherein the applying an electrical potential comprises applying a constant current density of from about 10 to about 50 mA/cm 2 for a period of time of from about 1 to about 20 minutes, wherein the calcium phosphate phase comprises hydroxyapatite.

3 . The method of claim 2 , wherein the applying an electrical potential comprises applying a constant current density of about 40 mA/cm 2 for a period of time of from about 2 to about 5 minutes.

4 . The method of claim 1 , wherein the electrolyte solution comprises calcium chloride and ammonium dihydrogen phosphate in an amount that corresponds to a calcium:phosphate ion ratio of about 1.7:1.

5 . The method of claim 4 , wherein the concentration of calcium ions in the electrolyte solution is about 1.7 mM.

6 . The method of claim 1 , wherein the electrolyte solution is maintained at a pH of from about 3 to about 7 using hydrochloric acid or ammonium hydroxide.

7 . The method of claim 1 , wherein the contacting comprises placing the implant in a bath containing the electrolyte solution and rotating the implant during application of the electrical potential.

8 . The method of claim 1 , wherein the electrolyte solution has a pH of about 5.1, a concentration of calcium ions of about 1.7 mM, and a concentration of phosphate ions of about 1.0 mM, and wherein the applying an electrical potential comprises applying a constant current density of about 40 mA/cm 2 is provided for about 2 minutes at ambient temperature.

9 . The method of claim 1 , wherein the electrolyte solution has a pH of about 6, a concentration of calcium ions of about 0.2 mM, and a concentration of phosphate ions of about 0.1 mM, and wherein the applying an electrical potential comprises applying a constant current density of about 30 mA/cm 2 for about 10 minutes at ambient temperature.

10 . The method of claim 1 , wherein the electroconductive surface of the implant comprises a material from the group consisting of titanium, a titanium alloy, titanium nitrate, a CoCrMo alloy, stainless steel, an electroconductive polymer, and mixtures thereof.

11 . The method of claim 1 , wherein the electroconductive surface of the implant comprises nano-scale texturing.

12 . A method for electrochemically depositing a discrete region of a calcium phosphate onto a medical implant comprising at least one area having a metallic surface, the method comprising:

a. contacting at least a portion of the metallic surface of the implant with an electrolyte solution comprising calcium ions and phosphate ions; and

b. applying an electrical potential between the metallic surface as a cathode and the electrolyte solution having a constant current density of from about 10 to about 50 mA/cm 2 for a period of time of from about 1 to about 20 minutes, thereby depositing a plurality of discrete regions of needle-shaped hydroxyapatite crystals onto the metallic surface.

13 . The method of claim 12 , further comprising allowing partial dissolution of the hydroxyapatite to occur concurrent with the depositing.

14 . The method of claim 13 , wherein the electrolyte solution is maintained at a pH of from about 5 to about 7.

15 . The method of claim 12 , wherein the applying the electrical potential comprises applying the electrical potential for at least two discrete intervals of time.

16 . A process for making a plurality of medical implants having discrete regions of a calcium phosphate, comprising:

a. preparing an electrolyte solution comprising calcium ions and phosphate ions having a concentration ratio of calcium:phosphate of about 1.7:1;

b. placing a plurality of implants into the electrolyte solution, wherein each implant comprises at least one area having an electroconductive surface; and

c. applying a constant electrical potential between the electroconductive surfaces as cathodes and the electrolyte solution, wherein the electrical potential has a constant current density of from about 10 to about 50 mA/cm 2 and is applied for a period of time of from about 1 to about 20 minutes, thereby depositing a plurality of discrete regions of needle-shaped hydroxyapatite crystals onto the electroconductive surfaces.

17 . The process of claim 16 , wherein the electrolyte solution is in an inner bath container that is disposed within an outer bath container, and the outer bath container contains circulating water maintained at a temperature of about 37° C.

18 . The process of claim 16 , further comprising removing the plurality of implants from the electrolyte solution after the depositing, rinsing the implants, and anodizing the implants.

19 . The process of claim 16 , wherein the electrolyte solution comprises deionized water, calcium chloride dihydrate, and ammonium dihydrogen phosphate.

20 . The process of claim 16 , further comprising cleaning the plurality of implants using an ultrasonic wash prior to placing the plurality of implants in the electrolyte solution.