Dual function prosthetic bone implant and method for preparing the same Number:7,122,140 from the United States Patent and Trademark Office (PTO) owispatent The present invention discloses a prosthetic bone implant made of a hardened calcium phosphate cement having an apatitic phase as a major phase, which includes a dense cortical portion bearing the majority of load and a porous cancellous portion allowing a rapid blood/body fluid penetration and tissue ingrowth.<H prosthetic, preparing, Dual, function, p, 7122140.html, Patent, pto, 7122140

Title: Dual function prosthetic bone implant and method for preparing the same

Abstract: The present invention discloses a prosthetic bone implant made of a hardened calcium phosphate cement having an apatitic phase as a major phase, which includes a dense cortical portion bearing the majority of load and a porous cancellous portion allowing a rapid blood/body fluid penetration and tissue ingrowth.

Patent Number: 7,122,140 Issued on 10/17/2006 to Lin, et al.

Inventors: Lin; Jiin-Huey Chern (Winnetka, IL), Ju; Chien-Ping (Carbondale, IL), Tsai; Chih-Hung (Taichung, TW)
Assignee: Calcitec, Inc. (Austin, TX)

Appl. No.: 11/060,047

Filed: February 17, 2005

Related U.S. Patent Documents


Application Number	Filing Date	Patent Number	Issue Date
10852167	May., 2004	6994726

Current U.S. Class: 264/42 ; 264/250; 264/251; 264/333; 264/49

Current International Class: A61F 2/28 (20060101); B29C 39/12 (20060101)

Field of Search: 264/42,49,333,86,87,250,251 623/16.11,17.11,23.51,23.62

References Cited [Referenced By]

U.S. Patent Documents


3679360	July 1972	Rubin et al.
4371484	February 1983	Inukai et al.
4481175	November 1984	Iino et al.
4518430	May 1985	Brown et al.
4553272	November 1985	Mears
4612053	September 1986	Brown et al.
4623553	November 1986	Ries et al.
RE33161	February 1990	Brown et al.
RE33221	May 1990	Brown et al.
4959104	September 1990	Iino et al.
5017518	May 1991	Hirayama et al.
5053212	October 1991	Constantz et al.
5092888	March 1992	Iwamoto et al.
5149368	September 1992	Liu et al.
5152791	October 1992	Hakamatsuka et al.
5164187	November 1992	Constantz et al.
5180426	January 1993	Sumita
5262166	November 1993	Liu et al.
5336264	August 1994	Constantz et al.
5338356	August 1994	Hirano et al.
5342441	August 1994	Mandai et al.
5409982	April 1995	Imura et al.
5476647	December 1995	Chow et al.
5492768	February 1996	Okimatsu et al.
5496399	March 1996	Ison et al.
5503164	April 1996	Friedman
5522893	June 1996	Chow et al.
5525148	June 1996	Chow et al.
5536575	July 1996	Imura et al.
5542973	August 1996	Chow et al.
5545254	August 1996	Chow et al.
5550172	August 1996	Regula et al.
5569490	October 1996	Imura et al.
5605713	February 1997	Boltong
5607685	March 1997	Cimbollek et al.
5652016	July 1997	Imura et al.
5683461	November 1997	Lee et al.
5683496	November 1997	Ison et al.
5695729	December 1997	Chow et al.
5697981	December 1997	Ison et al.
5702449	December 1997	McKay
5766669	June 1998	Pugh et al.
5782971	July 1998	Constantz et al.
5814681	September 1998	Hino et al.
5820632	October 1998	Constantz et al.
5846312	December 1998	Ison et al.
5891448	April 1999	Chow et al.
5899939	May 1999	Boyce et al.
5954867	September 1999	Chow et al.
5958430	September 1999	Campbell et al.
5964932	October 1999	Ison et al.
5976234	November 1999	Chow et al.
5993535	November 1999	Sawamura et al.
5997624	December 1999	Chow et al.
6005162	December 1999	Constantz
6013591	January 2000	Ying et al.
6013853	January 2000	Athanasiou et al.
6018095	January 2000	Lerch et al.
6027742	February 2000	Lee et al.
6077989	June 2000	Kandel et al.
6117456	September 2000	Lee et al.
6118043	September 2000	Nies et al.
6123731	September 2000	Boyce et al.
6132463	October 2000	Lee et al.
6149688	November 2000	Brosnahan et al.
6162258	December 2000	Scarborough et al.
6277149	August 2001	Boyle et al.
6294041	September 2001	Boyce et al.
6294187	September 2001	Boyce et al.
6323146	November 2001	Pugh et al.
6325987	December 2001	Sapieszko et al.
6325992	December 2001	Chow et al.
6332779	December 2001	Boyce et al.
6340648	January 2002	Imura et al.
6379453	April 2002	Lin et al.
6440444	August 2002	Boyce et al.
6458162	October 2002	Koblish et al.
6478825	November 2002	Winterbottom et al.
6495156	December 2002	Wenz et al.
6530955	March 2003	Boyle et al.
6547866	April 2003	Edwards et al.
6569489	May 2003	Li
6585992	July 2003	Pugh et al.
6616742	September 2003	Lin et al.
6648960	November 2003	Lin et al.
6670293	December 2003	Edwards et al.
6696073	February 2004	Boyce et al.
6719989	April 2004	Matsushima et al.
6752831	June 2004	Sybert et al.
6793725	September 2004	Chow et al.
6808561	October 2004	Genge et al.
6808585	October 2004	Boyce et al.
6840995	January 2005	Lin et al.
6929692	August 2005	Tas
6953594	October 2005	Lee et al.
6955716	October 2005	Xu et al.
6960249	November 2005	Lin et al.
2002/0019635	February 2002	Wenstrom, Jr. et al.
2002/0073894	June 2002	Genge et al.
2002/0137812	September 2002	Chow et al.
2002/0169066	November 2002	Cassidy et al.
2003/0019396	January 2003	Edwards et al.
2003/0021824	January 2003	Lacout et al.
2003/0031698	February 2003	Roeder et al.
2003/0039676	February 2003	Boyce et al.
2003/0055512	March 2003	Genin et al.
2003/0074081	April 2003	Ayers et al.
2003/0078317	April 2003	Lin et al.
2003/0120351	June 2003	Tofighi
2003/0121450	July 2003	Lin et al.
2003/0167093	September 2003	Xu et al.
2003/0216777	November 2003	Tien et al.
2004/0003757	January 2004	Chern Lin et al.
2004/0022825	February 2004	Lagow
2004/0031420	February 2004	Lin et al.
2004/0076685	April 2004	Tas
2004/0137032	July 2004	Wang
2004/0175320	September 2004	Lin et al.
2004/0180091	September 2004	Lin
2004/0185181	September 2004	Matsumoto
2004/0186481	September 2004	Chern Lin et al.
2005/0008759	January 2005	Nie et al.
2005/0076813	April 2005	Lin et al.
2005/0101964	May 2005	Lin et al.
2005/0184417	August 2005	Chern Lin et al.
2005/0186354	August 2005	Lin et al.
2005/0263919	December 2005	Lin et al.
2005/0263920	December 2005	Lin et al.
2005/0263921	December 2005	Lin et al.
2005/0263927	December 2005	Lin et al.
2005/0263928	December 2005	Lin et al.
2005/0263929	December 2005	Lin et al.
2005/0263930	December 2005	Lin et al.
2005/0263931	December 2005	Lin et al.
2005/0267587	December 2005	Lin et al.
2005/0267588	December 2005	Lin et al.
2005/0267589	December 2005	Lin et al.
2005/0267592	December 2005	Lin et al.
2005/0267593	December 2005	Lin et al.
2005/0267604	December 2005	Lin et al.

Foreign Patent Documents


0267624	May., 1988	EP
06-228011	Aug., 1994	JP
WO 03/055418	Jul., 2003	WO

Other References

PCT/US04/11637 Inetrnational Search Report/Written Opinion, Oct. 2004. cit- ed by other .
PCT/US04/11637 International Search Report/Written Opinion, mailed Mar. 11, 2005. cited by other .
Sugawara et al., "Calcium Phosphate Cement: An In Vitro Study of Dentin Hypersensitivity Using Calcium Phosphate Cement", The Journal of the Japanese Society for Dental Materials and Devices, 1989, vol. 8, pp. 282-294. cited by other .
Pickel et al., "The Effects of a Chewing Gum Containing Dicalcium Phosphate on Salivary Calcium and Phosphate", Ala. J. Med. Sci., 1965, vol. 2, pp. 286-287. cited by other .
Matsuya et al., "Effects of pH on the Reactions of Tetracalcium Phosphate and Dicalcium Phosphate", IADR Abstact, Apr. 1991. cited by other .
Sugawara et al., "Formation of Hydroxyapatite in Hydrogels from Tetracalcium Phosphate/Dicalcium Phosphate Mixtures," J. Nihon. Univ. Sch. Dent., 1989, vol. 31, pp. 372-381. cited by other .
Hong et al., "The Periapical Tissue Reactions to a Calcium Phosphate Cement in the Teeth of Monkeys," J. Biomed. Mater. Res., Apr. 1991, vol. 25(4), pp. 485-498. cited by other .
de Rijk, et al., "Clinical Evaluation of a Hydroxyapatite Precipitate for the Treatment of Dentinal Hypersensitivity," Biomedical Engineering v. Recent Developments, Proc. of 5th Southern Biomedical Engineering Conference, 1986, pp. 336-339. (Pergamon Press, New York). cited by other .
Gruninger et al., "Evaluation of the Biocompatibility of a New Calcium Phosphate Setting Cement," J. Dent. Res., 1984, 63, Abst. No. 270 (4 pages). cited by other .
Costantino et al., "Evaluation of a New Hydroxyapatite Cement: Part III: Cranioplasty in a Cat Model," The Fifth Intl. Symposium on Facial Plastic Reconstructive Surgery of the Head and Neck, Toronto, Canada, 1989. (18 pages). cited by other .
Shindo, et al., "Facial Skeletal Augmentation Using Hydroxyapatite Cement," Arch. Otolaryngol. Head Neck Surg., 1993, vol. 119, pp. 185-190. cited by other .
Briner et al., "Significance of Enamel Remineralization", J. Dent. Res., 1974, vol. 53, pp. 239-243. cited by other .
Silverstone L.M., "Remineralization Phenomena", Caries Res., 1977, vol. 11 (Supp. 1), pp. 59-84. cited by other .
Costantino et al., "Hydroxyapatite Cement: I. Basic Chemistry and Histologic Properties," Arch. Otolaryngol. Head Neck Surg., 1991, vol. 117, pp. 379-394. cited by other .
Friedman et al., "Hydroxyapatite Cement: II. Obliteration and Reconstruction of the Cat Frontal Sinus," Arch. Otolary. Head Neck Surg., 1991, vol. 117, pp. 385-389. cited by other .
Costantino et al., "Experimental Hydroxyapatite Cement Cranioplasty," Plast. Reconstr. Surg., 1992, vol. 90, No. 2, pp. 174-185. cited by other .
Miyazaki et al., "An Infrared Spectroscopic Study of Cement Formation of Polymeric Calcium Phosphate Cement," The Journal of the Japanese Society for Dental Materials and Devices, 1992, vol. 11, No. 2, pp. 278-284. cite- d by other .
Driskell et al., "Development of Ceramic and Ceramic Composite Devices for Maxillofacial Applications", J. Biomed. Mater. Res. Symposium, 1972, vol. 6, No. 2 (part 2), pp. 345-361. cited by other .
Hiatt et al., "Root Preparation I. Obturation of Dentinal Tubules in Treatment of Root Hypersensitivity", J. Periodontol., 1972, vol. 41, No. 6, pp. 373-380. cited by other .
Patel et al., "Solubility of CaHPO.sub.4 2H.sub.2O in the Quaternary System Ca(OH).sub.2-H.sub.3PO.sub.4-NaCl-H.sub.2O at 25.degree. C.," J. Res. Nat. Bur. Stand. (Physics Chem.), 1974, vol. 78A, pp. 675-681. cited by other .
Salyer et al., "Porous Hydroxyapatite as an Onlay Bone-Graft Substitute for Maxillofacial Surgery," Presented at the 54.sup.th Annual Scientific Meeting of the American Society of Plastic and Reconstructive Surgeons, Kansas City, Missouri, 1985, pp. 236-244. cited by other .
Kenney et al., "The Use of a Porous Hydroxylapatite Implant in Periodontal Defects: II. Treatment of Class II Furcation Lesions in Lower Molars," J. Periodontol, 1988, pp. 67-72. cited by other .
Zide et al., "Hydroxylapatite Cranioplasty Directly Over Dura," J. Oral Maxillofac. Surg., 1987, vol. 45, pp. 481-486. cited by other .
Waite et al., "Zygomatic Augmentation with Hydroxylapatite: A Preliminary Report," J. Oral Maxillofac. Surg., 1986, pp. 349-352. cited by other .
Verwoerd, et al. Porous Hydroxylapatite-perichondrium Graft in Cricoid Reconstruction, Acta Otolaryngol., 1987, vol. 103, pp. 496-502. cited by other .
Grote, "Tympanoplasty With Calcium Phosphate," Arch. Otolaryngol., 1984, vol. 110, pp. 197-199. cited by other .
Kent et al., "Alveolar Ridge Augmentation Using Nonresorbable Hydroxylapatite with or without Autogenous Cancellous Bone," J. Oral Maxillofac. Surg., 1983, vol. 41, pp. 629-642. cited by other .
Piecuch, J.F., "Augmentation of the Atrophic Edentulous Ridge with Porous Replamineform Hydroxyapatite (Interpore-200)", Dental Clinics of North America, 1986, vol. 30(2), pp. 291-305. cited by other .
Misch, C.E., "Maxillary Sinus Augmentation for Endosteal Implants: Organized Alternative Treatment Plans," Int. J. Oral Implant., 1987, vol. 4(2), pp. 49-58. cited by other .
Chohayeb, et al., "Evaluation of Calcium Phosphate as a Root Canal Sealer-Filler Material," J. Endod., 1987, vol. 13, pp. 384-386. cited by other .
Brown et al., "Crystallography of Tetracalcium Phosphate," J. Res. Nat. Bur. Stand. (Physics Chem.), 1965, vol. 69A, pp. 547-551. cited by other .
Sanin et al., "Particle Size Effects on pH and Strength of Calcium Phosphate Cement," IADR Abstract, Apr. 1991. cited by other .
Chow et al., "X-ray Diffraction and Electron Microscopic Characterization of Calcium Phosphate Cement Setting Reactions," IADR Abstract, 1987. cite- d by other .
Block et al. "Correction of Vertical Orbital Dystopia with a Hydroxylapatite Orbital Floor Graft," J. Oral Maxillofac. Surg., 1988, vol. 46, pp. 420-425. cited by other .
Brown, W.E., "Solubilities of Phosphates and Other Sparingly Soluble Compounds", Environmental Phosphorous Handbook, 1973, pp. 203-239. (John Wiley & Sons, New York). cited by other .
Gregory et al., "Solubility of CaHPO.sub.42H.sub.2O in the System Ca(OH).sub.2-H.sub.3PO.sub.4-H.sub.2O at 5, 15, 25, and 37.5.degree. C.," J. Res. Nat. Bur. Stand. (Physics Chem.), 1970, vol. 74A, No. 4, pp. 461-475. cited by other .
Gregory et al., "Solubility of .beta.-Ca.sub.3(PO.sub.4).sub.2 in the System Ca(OH).sub.2-H.sub.3PO.sub.4-H.sub.2O at 5, 15, 25 and 37.degree. C.," J. Res. Nat. Bur. Stand. (Physics Chem.), 1974, vol. 78A, No. 6, pp. 667-674. cited by other .
McDowell et al., "Solubility of Ca.sub.5(PO.sub.4).sub.3OH in the System Ca(OH).sub.2-H.sub.3PO.sub.4-H.sub.2O at 5, 15, 25 and 37.degree. C.,"J. Res. Nat. Bur. Stand. (Physics Chem.), 1977, vol. 91A, Nos. 2 and 3, pp. 273-281. cited by other .
McDowell et al., "Solubility Study of Calcium Hydrogen Phosphate. Ion Pair Formation," Inorg. Chem., 1971, vol. 10, pp. 1638-1643. cited by other .
Moreno et al., "Stability of Dicalcium Phosphate Dihydrate in Aqueous Solutions and Solubility of Octocalcium Phosphate," Proc. Soil Sci. Soc. Am., 1960, vol. 21, pp. 99-102. cited by other .
McDowell et al., "Solubility of Ca.sub.5(PO.sub.4).sub.3OH in the System Ca(OH).sub.2-H.sub.3PO.sub.4-H.sub.2O at 5, 15, 25 and 37.degree. C.," J. Res. Nat. Bur. Stand. (Physics. Chem.) 1977, vol. 91A, Nos. 2 and 3, pp. 273-281. cited by other .
Miyazaki et al., "Chemical Change of Hardened PCA/CPC Cements in Various Storing Solutions", The Journal of the Japanese Society for Dental Materials and Devices, 1992, vol. 11, No. 2, pp. 324-330. cited by other .
Fukase et al, "Thermal Conductivity of Calcium Phosphate Cement", IADR Abstract, Mar. 1990. cited by other .
Sugawara et al., "Biocompatibility and Osteoconductivity of Calcium Phosphate Cement", IADR Abstract, Mar. 1990. cited by other .
Miyazaki et al., "Polymeric Calcium Phosphate Cements", IADR Abstract, Mar. 1990. cited by other .
Link et al., "Composite of Calcium Phosphate Cement and Genetically Engineered Protein Bioadhesive," IADR Abstract, Mar. 1991. cited by other .
Chow, "Development of Self-Setting Calcium Phosphate Cements", Journal of The Ceramic Society of Japan, 1991, vol. 99 [10], pp. 954-964. cited by other .
Brown et al., A New Calcium Phosphate, Water Setting Cement, Cements Research Progress 1986, P.W. Brown, Ed., Westerville, Ohio: American Ceramic Society, 1988, pp. 352-379. cited by other .
Sugawara et al., "A Calcium Phosphate Root Canal Sealer-Filler" IADR Abstract, 1987. cited by other .
Sugawara et al., "In Vitro Evaluation of the Sealing Ability of a Calcium Phosphate Cement When Used as a Root Canal Sealer-Filler," J. Endodon., 1990, vol. 16, No. 4, pp. 162-165. cited by other .
Chow, L.C., "Calcium Phosphate Materials: Reactor Response," Adv. Dent. Res., 1988, vol. 2(1), pp. 181-184. cited by other .
Fukase et al., "Setting Reactions and Compressive Strengths of Calcium Phosphate Cements", J. Dent. Res., 1990, vol. 69(12), pp. 1852-1856. cite- d by other .
Miyazaki et al., "Cements," Guide to Dental Materials and Devices, 7.sup.th Edition, 1974-1975, Chapter 6. cited by other .
Sugawara et al., "Formation of Hydroxyapatite in Hydrogels from Tetracalcium Phosphate/Dicalcium Phosphate Mixtures," J. Nihon Univ. Sch. Dent., vol. 31, 372-381, 1989. cited by other .
Chow et al. "A Natural Bone Cement-A Laboratory Novelty Led to the Development of Revolutionary New Biomaterials", J. Res. Natl. Inst. Stand. Technol., 2001, vol. 106, pp. 1029-1033. cited by other .
Gburek et al., "Mechanical Activation of Tetracalcium Phsophate," J. Am. Ceramics Soc., vol. 87(2), pp. 311-313. cited by other.

Primary Examiner: Theisen; Mary Lynn
Attorney, Agent or Firm: Meyertons, Hood, Kivlin, Kowert & Goetzel, P.C. Meyertons; Eric B.

Parent Case Text

PRIORITY CLAIM

This application is a continuation of and claims priority to Non-Provisional patent application Ser. No. 10/852,167 entitled " DUAL FUNCTION PROSTHETIC BONE IMPLANT AND METHOD FOR PREPARING THE SAME" filed on May 25, 2004 now U.S. Pat. No. 6,994,726.

Claims

What is claimed is:

1. A method of making a prosthetic bone implant comprising: adding a porous component paste to one or more first molds, wherein the porous component paste comprises at least one calcium phosphate cement combined with at least one pore forming agent and at least one setting agent, wherein the setting agent comprises a liquid, and wherein the first molds are disposed in a second mold; adding a load bearing component paste to the second mold, wherein the load bearing component paste comprises at least one calcium phosphate cement combined with at least one setting agent, wherein the setting agent comprises a liquid; removing one or more of the first molds; displacing at least a portion of the liquid from the load bearing component paste and the porous component paste to form a hardened calcium phosphate article, the hardened calcium phosphate article comprising a load bearing component at least partially surrounding one or more porous components; and forming the prosthetic bone implant, wherein the prosthetic bone implant comprises the hardened calcium phosphate article.

2. The method of claim 1, further comprising immersing the hardened calcium phosphate article in one or more immersing fluids for a predetermined amount of time.

3. The method of claim 2, wherein immersion of the hardened calcium phosphate article is carried out at a temperature of from about 10.degree. C. to about 90.degree. C.

4. The method of claim 2, wherein at least one immersing liquid comprises at least one source of calcium and at least one source of phosphate.

5. The method of claim 2, wherein at least one immersing liquid comprises Hank's solution.

6. The method of claim 2, wherein at least one immersing liquid comprises substantially pure water.

7. The method of claim 2, wherein the hardened calcium phosphate article is immersed in at least one immersing liquid for a time period sufficient to remove at least a portion of the pore forming agent from the porous component.

8. The method of claim 1, wherein the pore-forming agent comprises an inorganic salt.

9. The method of claim 1, wherein the pore-forming agent comprises an organic salt.

10. The method of claim 1, wherein the porous component paste comprises at least one calcium phosphate source, and the load bearing component paste comprises at least one calcium phosphate source.

11. The method of claim 10, wherein at least one calcium phosphate source is alpha-tricalcium phosphate (.alpha.-TCP), beta-tricalcium phosphate (.beta.-TCP), tetracalcium phosphate (TTCP), monocalcium phosphate monohydrate (MCPM), monocalcium phosphate anhydrous (MCPA), dicalcium phosphate dihydrate(DCPD), dicalcium phosphate anhydrous (DCPA), octacalcium phosphate (OCP), calcium dihydrogen phosphate, calcium dihydrogen phosphate hydrate, acid calcium pyrophosphate, anhydrous calcium hydrogen phosphate, calcium hydrogen phosphate hydrate, calcium pyrophosphate, calcium triphosphate, calcium phosphate tribasic, calcium polyphosphate, calcium metaphosphate, anhydrous tricalcium phosphate, tricalcium phosphate hydrate, amorphous calcium phosphate or mixtures thereof.

12. The method of claim 10, wherein the calcium phosphate source comprises tetracalcium phosphate, wherein at least a portion of the tetracalcium phosphate particles comprise whiskers on the surface of the particles.

13. The method of claim 10, wherein at least one of the setting agents comprises substantially pure water.

14. The method of claim 1, wherein at least one of the setting agents comprises an acidic solution, and wherein the acidic solution comprises nitric acid (HNO.sub.3), hydrochloric acid (HCl), phosphoric acid (H.sub.3PO.sub.4), carbonic acid (H.sub.2CO.sub.3), sodium dihydrogen phosphate (NaH.sub.2PO.sub.4), sodium dihydrogen phosphate monohydrate (NaH.sub.2PO.sub.4H.sub.2O), sodium dihydrogen phosphate dihydrate, sodium dihydrogen phosphate dehydrate, potassium dihydrogen phosphate (KH.sub.2PO.sub.4), ammonium dihydrogen.phosphate (NH.sub.4H.sub.2PO.sub.4), malic acid, acetic acid, lactic acid, citric acid, malonic acid, succinic acid, glutaric acid, tartaric acid, oxalic acid or mixtures thereof.

15. The method of claim 1, wherein at least one of the setting agents comprises a basic solution, and wherein the basic solution comprises ammonia, ammonium hydroxide, alkali metal hydroxide, alkali earth hydroxide, disodium hydrogen phosphate (Na.sub.2HPO.sub.4), disodium hydrogen phosphate dodecahydrate, disodium hydrogen phosphate heptahydrate, sodium phosphate dodecahydrate (Na.sub.3PO.sub.412H.sub.2O), dipotassium hydrogen phosphate (K.sub.2HPO.sub.4), potassium hydrogen phosphate trihydrate (K.sub.2HPO.sub.43H.sub.2O), potassium phosphate tribasic (K.sub.3PO.sub.4), diammonium hydrogen phosphate ((NH.sub.4).sub.2HPO.sub.4), ammonium phosphate trihydrate ((NH.sub.4).sub.3PO.sub.43H.sub.2O), sodium hydrogen carbonate (NaHCO.sub.3), sodium carbonate Na.sub.2CO.sub.3, or mixtures thereof.

16. The method of claim 1, further comprising subjecting the hardened calcium phosphate article to one or more heat treatments, wherein the temperature of the heat treatments is from about 50.degree. C. to about 500.degree. C.

17. The method of claim 1, wherein displacing at least a portion of the liquid from the porous component paste and the load bearing component paste comprises reducing the liquid to powder ratio of the porous component paste and the load bearing component paste.

18. The method of claim 1, wherein displacing at least a portion of the liquid from the porous component paste and the load bearing component paste comprises applying a molding preassure to the porous component paste and the load bearing component paste.

19. The method of claim 18, wherein the molding pressure is in a range from about 1 MPa to about 500 MPa.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is related to a prosthetic bone implant made of a hardened calcium phosphate cement having an apatitic phase as a major phase, and in particular to a prosthetic bone implant comprising a dense cortical portion bearing the majority of load and a porous cancellous portion allowing a rapid blood/body fluid penetration and tissue ingrowth.

2. Description of the Related Art

It is advantageous if a prosthetic bone implant is bioresorbable and is supportive at the same time. Accordingly, an article made of calcium phosphate will be preferable than that made of a metal, if the former has strength which is comparable to a human cortical bone. One way of making such a bone implant is by sintering a calcium phosphate powder, particularly a hydroxyapatite (HA) powder, into a block material at a temperature generally greater than 1000.degree. C. Despite the fact that the high temperature-sintered HA block material has an enhanced strength, the bioresorbability of the material is largely sacrificed, if not totally destroyed, due to the elimination of the micro- and nano-sized porosity during the sintering process.

The conventional spinal fusing device is composed of a metallic cage and a bioresorbable material disposed in the metal cage, for example the one disclosed in U.S. Pat. No. 5,645,598. An inevitable disadvantage of this fusion device is the sinking of the metallic cage sitting between two vertebrae to replace or repair a defect spinal disk, because the hardness and the relatively small size of the cage wear out or break the bone tissue, and in particular the endplate of the vertebra.

SUMMARY OF THE INVENTION

A primary objective of the invention is to provide a prosthetic bone implant free of the drawbacks of the prior art.

The prosthetic bone implant constructed according to the present invention is made of a hardened calcium phosphate cement having an apatitic phase as a major phase, which comprises a dense cortical portion bearing the majority of load and a porous cancellous portion allowing a rapid blood/body fluid penetration and tissue ingrowth.

The prosthetic bone implant of the present invention is made by a novel technique, which involves i