METHOD OF COATING MEDICAL IMPLANTS WITH HYDROXYAPATITE AND DEVICE FOR IMPLEMENTING THE SAME

Abstract

A method of coating a medical implant with hydroxyapatite comprises steps of: (a) plasma treating said medical implant by a plasma electrolytic oxidation bath within an electrolyte; (b) hydroxyapatite coating a plasma treated medical implant in a hydrothermal pressurized reactor; (c) washing a hydroxyapatite coated medical implant; and (d) drying a washed medical implant. At least one of steps a and b further comprises a sub-step of forming crystallization seeds on a surface of said medical implant.

Claims

1-20 (canceled)

21. A method of coating a medical implant with hydroxyapatite; said method comprising steps of: a. plasma treating said medical implant by a plasma electrolytic oxidation bath within an electrolyte; b. hydroxyapatite coating a plasma treated medical implant in ahydrothermal pressurized reactor; c. washing a hydroxyapatite coated medical implant; and d. drying a washed medical implant; wherein said electrolyte comprises a molten salt doped with precursors of Calcium and Phosphorus such that crystallization seeds on a surface of said medical implant are formed.

22. The method according to claim 21, wherein said molten salt said comprises a salt selected from the group consisting of nitrate, carbonate, sulfate, silicate, chloride and any combination thereof.

23. The method according to claim 21, wherein said molten salt is doped with calcium.

24. The method according to claim 23, wherein said molten salt comprises calcium dichloride.

25. The method according to claim 21, wherein said molten salt is doped with phosphorus.

26. The method according to claim 25, wherein said molten salt comprises trisodium phosphate.

27. The method according to claim 21, wherein said step of hydroxyapatite coating comprises treating said medical implant in aqueous solution of potassium hydroxide.

28. The method according to claim 21, wherein said step of hydroxyapatite coating comprises treating said medical implant in aqueous solution of ammonium phosphate.

29. The method according to claim 21, wherein said medical implant is made of an alloy comprising metals selected from the group consisting of Aluminum, Tantalum, Niobium, Zirconium, Titanium, Bismuth, Stibium, Magnesium, Zink, Cadmium, Tungsten, Stannum, Iron, Silver, Hafnium, Beryllium, Germanium, Silicon, Uranium and any combination thereof.

30. A device for coating a medical implant with hydroxyapatite; said device comprising: a. a plasma electrolytic oxidation bath accommodating an electrolyte; and b. a hydrothermal pressurized reactor accommodating an alkaline solution; wherein at least one of plasma electrolytic oxidation bath comprising comprises a molten salt doped with precursors of Calcium and Phosphorus such that crystallization seeds on a surface of said medical implant are formed.

31. The device according to claim 30, wherein said molten salt said comprises a salt selected from the group consisting of nitrate, carbonate, sulfate, silicate, chloride and any combination thereof.

32. The device according to claim 30, wherein said molten salt is doped with calcium.

33. The device according to claim 32, wherein said molten salt comprises calcium dichloride.

34. The device according to claim 30, wherein said molten salt is doped with phosphorus.

35. The device according to claim 34, wherein said molten salt comprises trisodium phosphate.

36. The device according to claim 30, wherein said alkaline solution is an aqueous solution of potassium hydroxide.

37. The device according to claim 30, wherein said alkaline solution is an aqueous solution of ammonium phosphate.

38. The device according to claim 30, wherein said medical implant is made of an alloy comprising metals selected from the group consisting of Aluminum, Tantalum, Niobium, Zirconium, Titanium, Bismuth, Stibium, Magnesium, Zink, Cadmium, Tungsten, Stannum, Iron, Silver, Hafnium, Beryllium, Germanium, Silicon, Uranium and any combination thereof.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to understand the invention and to see how it may be implemented in practice, a plurality of embodiments is adapted to now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which

[0024] FIG. 1 is a schematic view of a device for coating a medical implant made of an alloy containing a valve metal with hydroxyapatite; and

[0025] FIG. 2 is a flowchart of a method of coating a medical implant made of an alloy containing a valve metal with hydroxyapatite.

DETAILED DESCRIPTION OF THE INVENTION

[0026] The following description is provided, so as to enable any person skilled in the art to make use of said invention and sets forth the best modes contemplated by the inventor of carrying out this invention. Various modifications, however, are adapted to remain apparent to those skilled in the art, since the generic principles of the present invention have been defined specifically to provide a method of coating a medical implant made of an alloy containing a valve metal with hydroxyapatite and a device for implementing the same.

[0027] Reference is now made to FIG. 1 presenting a schematic view of a device for coating a medical implant made of an alloy containing a valve metal with hydroxyapatite. The device comprises plasma electrolytic oxidation (PEO) bath 10 and hydrothermal treatment reactor 20. In PEO bath 10, numeral 40 refers to a furnace with automatic temperature control. The furnace includes heating element 45 energized by power supply 100 which is configured for heating metallic crucible 30 made of a nickel alloy. Crucible 30 accommodates electrolyte 35 comprising molten salts. Crucible 30 is supported by ceramic stand 70. Article 50 made of an alloy containing a valve metal is oxidized within molten salts such that PEO treatment is performed. Numerals 80 and 90 refer to a data logger and a pulse generator, respectively.

[0028] According to an exemplary embodiment of the present invention, article 50 made of a titanium alloy is treated in PEO bath accommodating molten KNO.sub.3 and NaNO.sub.3. Other salts selected from the group consisting of nitrate, carbonate, sulfate, silicate, chloride are also in the scope of the present invention. The following parameters of the PEO treatment are feasible: [0029] Temperature in PEO bath: ±300° C. form the melting point of the electrolyte; [0030] Current density: 0.05-100 A/dm.sup.2; [0031] Voltage: 10-500V; [0032] Mode: potentiostatic or potentiodynamic; [0033] Polarity: DC (unipolar or bipolar); AC (symmetric or asymmetric); impulse (unipolar or bipolar); [0034] Impulse sweep: square-wave, trapezoid, sinusoidal, etc.; [0035] Frequency: 0-5000 Hz; [0036] Duty cycle: 1-100%.

[0037] The purpose of the present invention is to form crystallization seeds on a surface of treated article 50. According to one embodiment of the present invention, Ca and P precursors can introduced into electrolyte 35 (for example, calcium dichloride and trisodium phosphate). Then, article 50 is transferred into hydrothermal treatment reactor 20 filled with alkaline solution (for example, potassium hydroxide).

[0038] Hydrothermal treatment reactor 20 comprises stirring-heating plate 210 including control units 180, 190 and 200 configured for controlling stirring speed, temperature and pressure and, respectively. Unit 200 is configured for receiving data from pressure gauge 110, unit 190 from thermocouple 130. Stainless steel crucible 160 is placed into isolating chamber 140. Crucible 160 is filled with alkaline solution 150.

[0039] According to one embodiment of the present invention, calcium and phosphorus precursors are formed into electrolyte 35.

[0040] The hydrothermal treatment is carried out in pressurized reactor 20 in aqueous solution of KOH for 2 h at 200° C., 16atm and pH=11. Finally, Ti based alloy with hydroxyapatite-based coating with the high surface area is formed.

[0041] According to an alternative embodiment of the present invention, calcium precursors are formed in PEO electrolyte 35 by introducing calcium dichloride, while potassium hydroxide solution is replaced with an aqueous solution of ammonium phosphate in order to form phosphorous precursors.

[0042] Reference is now made to FIG. 2 presenting a flowchart of method 300 of for coating a medical implant made of an alloy containing a valve metal with hydroxyapatite. An article made of an alloy containing a valve metal is treated in electrolyte of plasma electrolytic oxidation bath at step 310. Then, the article is coated with hydroxyapatite in a hydrothermal treatment reactor at step 320. The treated article is washed and dried at steps 330 and 340, respectively.

[0043] It should be emphasized that method 300 is specifically directed to producing coatings on valve metal alloys adapted for osseointegration of medical implants when installed.

[0044] Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventor expects skilled artisans to employ such variations as appropriate, and the inventor intends for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.