Bone putty and method

Details Bone putty and method Bone putty and method

2000-11-13

2003-06-10

Low, Christopher S. F. (Department: 1653)

Drug, bio-affecting and body treating compositions

Preparations characterized by special physical form

Implant or insert

C424S422000, C424S426000, C424S549000, C514S801000, C514S802000, C623S016110, C623S013190

Reexamination Certificate

active

06576249

ABSTRACT:

FIELD OF THE INVENTION
This invention pertains to a bone matrix suspension in forms suitable for surgical grafting or other medical uses and a method for making same.
BACKGROUND OF THE INVENTION
Malleable bone putty or bone gel is used to correct surgical defects that may be caused by trauma, pathological disease, surgical intervention or other situations where defects need to be managed in osseous surgery. It is important to have the defect filler in the form of a stable, viscous gel or putty to facilitate the placement of the bone growth medium into the surgical site which is usually uneven in shape and depth. The surgeon will take the gel or putty on a spatula or other instrument and trowel it into the site or take it in his/her fingers to shape the bone inducing material into the proper configuration to fit the site being corrected.
It is well known in the art that for several decades surgeons have used a patient's own blood as a vehicle in which to mix the patient's bone chips or bone powder, or demineralized bone powder so as to form a defect filling paste. Blood is a useful carrier because it is available from the bleeding operative site, is non-immunogenic to the patient and contains bone morphogenic proteins which facilitate wound healing through new bone growth. However, stored blood from other patients has the deficiencies that any blood transfusion would have such as blood type compatibility, possibility of transmission of disease and unknown concentration of bone morphogenic proteins (BMP) which are to a great extent dependent upon the age of the donor.
While blood contains from forty percent (40%) to fifty percent (50%) cell mass, it is a satisfactory carrier for demineralized bone powder because it contains both mono- and polysaccharides which contribute to the blood viscosity and provide the bulk viscosity to the paste created by mixing the bone powder and blood. Specific monosaccharides in blood are glucose at a concentration of 60-100 mg/100 ml (0.1%) and polysaccharides such as hexose and glucosamine at approximately 0.1%. Glucuronic acid is also present at approximately 0.4-1.4 mg/100 ml (average 0.01%).
The problems inherent with using the patient's blood as a carrier for demineralized bone powder are the difficulties of mixing the same at the operating site, the difficulty in obtaining a bone paste consistency which can be easily applied to the surgical area, the guesswork in mixing a usable composition at the site and the problem of having a bone paste or gel which will promote optimum bone replacement growth and not be carried away by the body fluids at the operation site or simply fall out of the bone defect site. In an attempt to solve these and other problems, there have been a number of other attempts using other alternative mixtures and compositions.
Demineralized allograft bone matrix (DBM) is produced from banked human bone taken from cadavers. Demineralized allograft bone is usually available in a lyophilized or freeze dried and sterile form—such as cubes, shavings, or powder—to provide for extended shelf life. The bone in this form is usually very coarse and dry and is difficult to manipulate by the surgeon. One solution to use such freeze dried bone has been provided in the form of a gel, GRAFTON®, a registered trademark of Osteotech Inc., which is a simple mixture of glycerol and lyophilized, demineralized bone powder of a particle size in the range of 0.1 cm to 1.2 cm (1000 microns to 12,000 microns) as is disclosed in U.S. Pat. No. 5,073,373.
GRAFTON® works well to allow the surgeon to place the allograft bone material at the site. However, the carrier, glycerol, has a very low molecular weight (92 Daltons) and is very soluble in water—the primary component of the blood which flows at the surgical site. Glycerol also experiences a marked reduction in viscosity when its temperature rises from room temperature (typically 22° C. in an operating room) to the temperature of the patient's tissue, typically 37° C. This combination of high water solubility and reduced viscosity causes the allograft bone material to be “runny” and to flow away from the site almost immediately after placement; this prevents the proper retention of the bone within the site as carefully placed by the surgeon.
These problems with GRAFTON® gel have been attempted to be resolved by using a much larger particle size of allograft bone, specifically lamellae or slivers of bone created by milling or slicing the bone before mixing it with the glycerol carrier. This improves both the bulk viscosity and the handling characteristics of the mixture but still leaves the problem of the fast rate of dissipation of the carrier and some bone due to the solubility of the glycerol carrier. The larger particles of demineralized bone may also retard the development of new bone by the patient because the large bony lamellae do not pack as well as the smaller grainy particles of bone. This will leave more open space and could lengthen the tine required to grow new bone and properly fill the defect. Another deficiency of using the bony lamellae is that the ends of the bony fragments are uneven and when packed into the surgical defect, leave uneven filaments of bone protruding out from the defect which can compromise the healing rate.
U.S. Pat. No. 5,290,558 discloses a flowable demineralized bone powder composition using a osteogenic bone powder with a large particle size ranging from about 0.1 to about 1.2 cm, mixed with a low molecular weight polyhydroxy compound possessing from 2 to about 18 carbons including a number of classes of different compounds such as monosaccharides, disaccharides, water dispersible oligosaccharides and polysaccharides.
Hence, the advantages of using the smaller bone particle sizes as disclosed in the U.S. Pat. No. 5,073,373 gel patent were compromised by using bone lamellae in the shape of threads or filaments and retaining the low molecular weight glycerol carrier. This later prior art is disclosed in U.S. Pat. Nos. 5,314,476 and 5,507,813, and the tissue forms described in these patents are known commercially as the GRAFTON® Putty and Flex, respectively.
The use of the very low molecular weight glycerol carrier also requires a very high concentration of glycerol to be used to achieve the bulk viscosity. Glycerol and other similar low molecular weight organic solvents are toxic and irritating to the surrounding tissues. Furthermore glycerol has been reported to be specifically neurotoxic and this problem is compounded when the concentration of glycerol is at the 20-95% level, as disclosed in U.S. Pat. No. 5,073,373.
Another attempt to solve the bone composition problem is shown in U.S. Pat. No. 4,172,128, which discloses demineralized bone material mixed with a carrier used to reconstruct tooth or bone material, and made by adding a mucopolysaccharide to a mineralized bone colloidal material. The composition is formed from a demineralized coarsely ground bone material, which may be derived from human bones and teeth, dissolved in a solvent forming a colloidal solution to which is added a physiologically inert polyhydroxy compound such as mucopolysaccharide or polyuronic acid in an amount which causes orientation when hydrogen ions or polyvalent metal ions are added to form a gel. The gel will be flowable at elevated temperatures above 35° C. and will solidify when brought down to body temperature. Example 25 of the patent notes that mucopolysaccharides produce pronounced ionotropic effects and that hyaluronic acid is particularly responsible for spatial cross-linking. Unfortunately this bone gel is difficult to manufacture and requires a pre-molded gel form.
U.S. Pat. No. 4,191,747 teaches a bone defect treatment with coarsely ground, denatured bone meal freed from fat and ground into powder. The bone meal is mixed with a polysaccharide in a solution of saline and applied to the bone defect site.
Another prior art product is the formulation of demineralized allograft bone particles in collagen. Both bovine and human collagen have been used f

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