Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
  • A61L24/00—Surgical adhesives or cements; Adhesives for colostomy devices
  • A61L24/02—Surgical adhesives or cements; Adhesives for colostomy devices containing inorganic materials
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
  • A61L2430/00—Materials or treatment for tissue regeneration
  • A61L2430/02—Materials or treatment for tissue regeneration for reconstruction of bones; weight-bearing implants

Definitions

• the present invention relates to formulations for cement preparations as bone substitutes, comprising calcium phosphate as the main component and being admixed with water or aqueous liquids to obtain pasty or paste-like masses.
• the present invention also relates to processes for the preparation of phosphate cements, particularly apatite and struvite cements, from these formulations.
• Calcium phosphate ceramics have been on the market as synthetic bone implants since the 1970's. Such ceramics, however, have fixed dimensions and have difficulty adapting bone defects which are usually irregularly shaped. A further disadvantage is that calcium phosphate ceramics are insufficiently resorbed into tissue. Such poor resorbtion results from the sintering preparation process which creates very dense structures.
• An object of the present invention is to provide a hardenable and resorbable bone or other cement preparation having improved safety and requiring less time for implanting, thus increasing the operator's freedom of choice when implanting or applying the cement preparation. It is a further object that the cement preparation have improved processing characteristics and provide increased strength of the hardened cement. It is a further object that the cement preparation have improved X-ray contrast.
• the present invention provides a cement preparation useful as a bone substitute or filler and comprising calcium phosphate as the main component.
• the calcium phosphate component will typically be a powder and will comprise other materials.
• the powder will be adapted to mix with water or an aqueous liquid to form a pasty (viscous) substance for introduction to a bone defect or other bone target location.
• An additive enhancing X-ray contrast (radiopacity) is admixed with the cement preparation, preferably the dry powder calcium phosphate component, but in some cases with aqueous compounds prior to combining the components.
• the present invention provides a process for the preparation of a cement, comprising: mixing a calcium phosphate powder, preferably an apatite material with an additive enhancing the X-ray contrast and water or an aqueous component, and allowing the mixture to harden.
• the hardening allows formation of a cement, preferably an apatite cement, as the reaction product.
• the cement preparation of the present invention comprises a mixture of salts of calcium salts, magnesium salts, and/or orthophosphates to be admixed with water and/or an aqueous liquid
• the additive for enhancing the X-ray contrast comprises at least one substance selected from the group consisting of: a barium salt; metals and inorganic and organic metal compounds, preferably metal oxides, wherein the metal is selected from the group consisting of iron, titanium, tantalum, gold, silver, rare earth elements, yttrium, ytterbium, zirconium, niobium, molybdenum, ruthenium, rhodium, palladium and tungsten; compounds of rare earth elements, preferably of gadolinium or cerium; inorganic or organic iodo compounds; and sintered hydroxyapatite and sintered tricalcium phosphate.
• the cement preparations as defined above are particularly useful as bone substitutes.
• bone substitute includes bone replacement materials, bone implants, bone fillers, bone cements, bone adhesives, and the like. Such bone substitutes are useful for the treatment of bone defects and fractures and of disease conditions of the bone system, such as osteoporosis or cancer.
• compositions and methods of the present invention solves the problem of conventional calcium phosphate containing cements which, owing to the similar chemical structure of natural bones and the applied calcium phosphate containing cements, do not provide a satisfactory X-ray contrast.
• an additive possessing the property of enhancing or intensifying, relative to the formulation or composition lacking this additive, the X-ray contrast (radiopacity) significantly improves the capability of visualizing the treated location of the bone, which are often not directly observable, and allows the operating person to evaluate the progress and/or the result of the treatment in an X-ray image.
• the availability of images having higher X-ray contrast improves the safety of treatment.
• the hardened cement of the invention also possesses good resorbtion characteristics.
• the calcium phosphate powders combined with an aqueous liquid component according to the present invention provide a material having a paste-like (pasty) consistency having good flowability characteristics. Moreover, the materials form a hardened cement with minimum or no loss of product strength.
• the calcium phosphate compositions of the present invention are preferably free of plastics materials such as poly (methyl methacrylate) (PMMA), allowing the use of a variety of X-ray contrast enhancing additives at a wide range of concentrations because calcium phosphate cements do not harden through a polymeric chain reaction.
• the radiopacity enhanced bone cement preparations of the present invention which are hardened at the target site often have improved resorbtion characteristics.
• the compositions of the present invention may be optimized depending on the desired application. Depending on the chosen type of X-ray contrast enhancer, the composition may be formulated to be highly stable with radiopacity property for long term observations. Alternatively, the radiopacity may be diminished after the operation process in order to decrease the likelihood of body irritations due to the additive. Overall, the present invention provides a good combination of processability, hardening characteristics and enhanced visualization of the operation process.
• the cement preparations of the present invention are based on a mixture of a powder component comprising mainly calcium phosphate, preferably at least about 50 percent by weight and more preferably at least about 65 percent by weight, and most preferably at least about 75 percent by weight calcium phosphate, to be mixed with an aqueous liquid component comprising water or, usually, an aqueous solution, for the hardening and the formation of a cement reaction product, typically used as a bone substitute.
• the basic powdery component preferably further comprises, in addition to calcium phosphate, orthophosphates or other salts of magnesium and optionally other metals.
• the liquid component comprises water and optionally further constituents, preferably salts and more preferably salts having a buffering effect, particularly sodium, potassium and/or ammonium salts of phosphoric acid in the primary and or secondary basic form, or the corresponding salts of carbonic acid.
• the pH of the liquid component is suitably adjusted, for example within a range of about 5 to about 12, preferably from about 7 to about 12.
• the cement preparation preferably comprises a powdery component including calcium (Ca), magnesium (Mg), and orthophosphate (P).
• a powdery component including calcium (Ca), magnesium (Mg), and orthophosphate (P).
• An additive which enhances X-ray contrast also referred to herein as a radiopacity enhancer or a radiopaque material, which will be described in more detail below, is preferably combined in the powdery component and is advantageous in that the hardening characteristics and/or the mechanical properties is /are essentially not deteriorated.
• the hardened cement has particularly good resorbtion characteristics.
• the basic cement preparation further comprises, either in the powdery component or preferably in the aqueous liquid component, an ammonium salt, in particular an ammonium phosphate salt such as (NH 4 ) 2 HPO 4 and/or (NH 4 )H 2 PO 4 .
• an ammonium salt in particular an ammonium phosphate salt such as (NH 4 ) 2 HPO 4 and/or (NH 4 )H 2 PO 4 .
• the molar ratios of Ca, Mg and P preferably lie in the range of 1.00 ⁇ Ca/P ⁇ 1.50 and 0 ⁇ Mg/P ⁇ 0.50.
• Particularly preferred formulations for cement preparations are the magnesium ammonium phosphate cement preparations disclosed in EP-A-1 296 909.
• the cement preparation provides a sufficiently enhanced radiopacity by means of selecting an appropriate type of radiopacity element or compound, and by using an appropriate amount, concentration and/or density of the radiopacity additive.
• the additive for enhancing X-ray contrast can be admixed with either the powdery component or the liquid component of the cement preparation, or both.
• the hardened reaction product obtained from the formulation or composition of the present invention may beneficially comprise crystalline compounds, particularly monocrystalline phosphate compounds, apatitic structures, hydroxyapatite structures, struvite cements, or tribarium phosphate.
• the amount of the radiopacity enhancing additive suitably constitutes a range between at least about 0.5 percent to about 25 percent by weight, preferably a range of at least about 3 percent to about 20 percent by weight, more preferably a range of at least about 5 percent to about 15 percent by weight, and most preferably at least about 10 percent by weight.
• the upper limit may be suitably selected depending on the type of the radiopacity enhancing additive and the intended application; the upper limit of the amount may, for example, be at about 50 percent by weight and more preferably at 25 percent by weight.
• the aforementioned preferred lower and upper limits of the amount of the radiopacity enhancing additive are particularly selected from the view point of a useful combination of significantly enhanced radiopacity while preserving or even improving the flowability characteristic of the cement preparations during operation when applying the cement preparation to the intended target.
• the above weight percentages are stated in relation to the weight of the powdery component.
• the aqueous liquid component is admixed with the powdery component in an amount in the range from about 0.1 to about 1.5 ml per mg powder, preferably from about 0.2 to about 0.65 ml liquid per mg powder.
• an additive is used which at the same time maintains and preferably improves the flowability of the cement preparation being admixed to the pasty mass.
• strontium salts and particularly barium salts used alone or in combination, e.g. a compound selected from the group consisting of strontium carbonate, strontium phosphate and barium sulfate.
• strontium salts and particularly barium salts used alone or in combination, e.g. a compound selected from the group consisting of strontium carbonate, strontium phosphate and barium sulfate.
• the processability of the calcium phosphate containing cement preparations is additionally improved, in particular the injectability, because the admixture of these compounds significantly improves the flowability of the cement preparation being admixed with the liquid component.
• the pressure required for injecting the cement preparation is substantially decreased thereby. The decreased injection pressure is not only more comfortable and convenient for the operating person. Rather, the so-called "filter pressing" effect is minimized thereby as well.
• strontium salt e.g. strontium carbonate or strontium phosphate
• barium salt such as barium sulfate
• barium salts By the admixture of barium salts according to the present invention, a better cohesion is achieved while ensuring at the same time appropriate hardening characteristics.
• the mechanical properties, especially the strength of the hardened cement are significantly enhanced by barium salt, when combined with calcium phosphate and preferably additionally with magnesium phosphate in the cement preparation.
• barium salts and particularly barium sulfate, tribarium phosphate, barium iodide, barium zirconate and barium wolframate a combination of significantly improved radiopacity enhancement, improved processability and especially flowing characteristics, appropriate hardening characteristics as well as mechanical product properties is achieved.
• suitable additives for enhancing radiopacity include substances selected from the group of metals, inorganic metal compounds such as metal oxides, metal nitrides, metal carbides, metal silicids, metal halides, metal phosphates, metal gluconates, metal citrates, metal fumarates and metal sulfates, and metal-organic compounds, based on iron, titan, tantalum, gold, silver, rare earth elements, yttrium, ytterbium, molybdenum, zirconium, niobium, ruthenium, rhodium, palladium and tungsten as the metallic element.
• inorganic metal compounds such as metal oxides, metal nitrides, metal carbides, metal silicids, metal halides, metal phosphates, metal gluconates, metal citrates, metal fumarates and metal sulfates, and metal-organic compounds, based on iron, titan, tantalum, gold, silver, rare earth elements, y
• Preferred metallic elements are iron and rare earth elements (lanthanides), cerium and especially gadolinium being the rare earth element of choice.
• Particularly preferred substances of this type are iron compounds, especially iron phosphate, iron oxide, iron hydroxide or iron-compound with organic acids like iron citrate, because these can be incorporated into the hardened cement product in a stable manner and are particularly effective in not deteriorating the mechanical properties of the hardened product, and also tungsten salicylate and water soluble lanthanum or rare earth compounds such as lanthanum acetate, lanthanum nitrate, lanthanum sulfate, lanthanum ammonium nitrate, cerium citrate, cerium nitrate, cerium chloride, cerium ammonium sulfate, and especially gadolinium compounds which have been found to be advantageous, e.g.
• gadolinium fluorid gadolinium chlorid
• gadolinium chelates e.g. gadolinium diethylenetriamino pentaacetate
• Gadoteridol available from Bristol-Myers Squibb.
• Suitable metals and inorganic metal compounds such as oxides, nitrides, carbides, silicides and halides may be preferably added in a fine particulate form.
• the average particle size (d 5 o) of the particulate metal or inorganic metal compound in view of processability and especially flowing characteristics suitably lies in the range of about 0.1 nm to about 10 ⁇ m.
• the lower limit of the average particle size (d 5 o) preferably is about 5 nm
• the upper limit of the average particle size (d 5 o) is preferably about 1 ⁇ m, more preferably about 500 nm and further preferably about 100 nm.
• the fine particulate substance is preferably added to the powder component of the cement composition.
• bromo compounds and particularly iodo compounds preferably organic bromo and or iodo compounds.
• water soluble compounds of ionic or non-ionic type are used according to the present invention, such as diatricoates, dioxitalamates, iopamidol, iohexol and ioxaglate or the like. Suitable examples among these iodo compounds can be found in section 35.2.2 of "Rote Liste" (Red List), ECV-Editio Cantor Verlag, Aulendorf (2003).
• sintered material may be used as the radiopacifier additive(s), preferably highly sintered materials.
• sintered hydroxyapatite and sintered tricalcium phosphate are preferred.
• the sintered material is suitably in a fine particulate form, and can be preferably added to the powder component of the cement composition, as described above in connection with the metal and inorganic metal compounds.
• the aforementioned additive(s) for enhancing radiopacity may be added to the powdery component or to the liquid component of the cement preparation. Dry or fine particulate material is preferably added to the cement powder component, and water soluble compounds are suitably added to the liquid component of the cement preparation. Mixtures of the additives can be used as well.
• the additive for enhancing radiopacity may be capable of being stably incorporated into the reaction product of the cement preparation, for example iron compounds or compounds of other radiopacity enhancing metal elements like oxides, sulfates or phosphates.
• the additive for enhancing radiopacity is capable of being loosely incorporated but eliminated from, or leaked out of the hardened cement product after being applied to the desired target, in order to improve bio-compatibility and to minimize tissue irritation at the target site; for example, a water soluble additive for enhancing radiopacity may be selected, such as a water soluble iodo compound.
• the formulations for cement preparations according to the present invention may contain other suitable additives.
• the cement preparation of the present invention is particularly suitable as a carrier material for biologically and/or pharmaceutically active agents.
• the cement preparation may comprise in addition, in the powder and/or the liquid component, a pharmaceutically and/or biologically active substance, such as an antibiotic, a cytostatic agent, an analgesic agent, a disinfectant, a preservative, a growth factor, a proliferative factor, a protein or peptide, a biopolymer or the like, or a combination of the active substances mentioned.
• Particularly preferred active agents are selected from the group consisting of gentamycine, trombamycine, clindamycine, vancomycine, ⁇ -TGF or an analogue thereof, a bone morphogenic protein (BMP) series compound or the like, or a combination thereof.
• BMP bone morphogenic protein
• Further additives include substances in the form of granular particles that are added to the powder component of the cement preparation of the present invention, wherein the granular particles of the substance possess the property of being water soluble in the liquid component of the cement preparation.
• additives include salts, carbohydrates or sugars, and polymers capable of being degraded hydrolytically.
• the main application of calcium phosphate containing cement preparations according to the present invention resides in the augmentation (filling) of bone defects.
• the filling of metaphysical depression fractures as well as vertebral bodies for stabilization in case of vertebroplasty or in case of compression fractures of osteoporotic vertebral bodies is of particular importance.
• a high risk is incurred particularly in the case of the filling of vertebral bodies by calcium phosphate containing cements, if visualization control is insufficient.
• material may extravasate from the vertebral body, e.g. may enter the spinal channel and may possibly lead to a compression of the spinal cord. The consequences thereof would be drastic for the patient, because paralysis conditions may occur.
• inventive formulations having enhanced X-ray contrast bring about a substantial improvement when implanting the calcium phosphate containing cements according to the present invention, especially in the case of operations in the region of vertebral bodies.
• the operation can be carried out much faster, and the operation risk for the patient decreases drastically.
• excellent characteristics in terms of processability and product strength are feasible.
• the advantages mentioned here likewise apply also to operations or treatments at other locations of the bones or the skeleton.
• the calcium phosphate containing cement preparations may also be used for the filling of cavities or voids created by kyphoplasty.
• Kyphoplasty is a percutaneous technique involving the use of an expandable structure, such as a balloon catheter, to correct the kyphotic deformity related to vertebral body compression fractures. The methods and instruments suitable for such treatment are more fully described in US Pat. Nos.
• Example 1 A cement powder composition with the following formulation components was provided, then thoroughly mixed with an aqueous 3.5 M (NH ) 2 HPO 4 solution (liquid component) to a pasty mass and subsequently allowed to harden:
• the obtained hardened calcium phosphate cement was evaluated for its radiopacity as visualized on an X-ray film. A well recognizable X-ray contrast was obtained.
• Example 2 Example 1 was repeated except for increasing the amount of BaSO 4 to 8g, as follows:
• Example 4 Example 3 was repeated except for replacing the radiopacity enhancer loxaglic by lobitridol, a nonionic organic iodo compound, available from Guerbet GmbH (Sulzbach-Taunus, Germany).
• Example 5 Example 4 was repeated except for increasing the amount of lobitridol to 8 g, as follows:
• the X-ray contrast is remarkably higher (darker level of the developed X-ray image) than when adding 8 g BaSO 4 .
• the strength was measured after an incubation for 2 h of the hardened cement in an aqueous solution of 0.9 percent by weight NaCI at 37°C, and a value of 17.5 Mpa was obtained.
• Examples 6 and 7 Examples 3 and 4 were repeated except for using an amount of loxaglic or lobitridol of 6g, as follows:
• Example 8 Example 1 was repeated except for replacing Ba 2 SO by another radiopacity enhancer, ammonium cer(IN)sulfat-dihydrate, as follows:
• Example 9 Further experiments have been carried out by adding various amounts of BaSO 4 or SrCO 3 to the cement powder. Best results in terms of homogeneous and more efficient admixing performance and strength of the hardened product have been achieved by adding about 10 to about 15 percent by weight BaSO 4 .
• Example 11 Example 1 was repeated except for replacing the radiopacity enhancer by gold dust, being added in the form of fine metal particles.
• Example 12 Example 1 was repeated except for replacing the radiopacity enhancer by Fe(II) or Fe(III) oxide, being added as a metal oxide, as follows:

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• 2002
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• 2003
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