Drug – bio-affecting and body treating compositions – Preparations characterized by special physical form – Implant or insert
Reexamination Certificate
2001-02-23
2003-10-07
Page, Thurman K. (Department: 1615)
Drug, bio-affecting and body treating compositions
Preparations characterized by special physical form
Implant or insert
C424S423000, C424S426000, C424S484000, C424S501000
Reexamination Certificate
active
06630153
ABSTRACT:
FIELD OF THE INVENTION
The present invention is directed to compositions and methods for making bone graft substitutes. More specifically, the present invention is directed to manufacturing a bone graft substitute (BGS) by powder compaction.
BACKGROUND OF THE INVENTION
Bone graft is used to fill spaces in bone tissue that are the result of trauma, disease degeneration or other loss of tissue. Clinicians perform bone graft procedures for a variety of reasons, often to fill a bone void created by a loss of bone or compaction of cancellous bone. In many instances, the clinician also must rely on the bone graft material to provide some mechanical support, as in the case of subchondral bone replacement or compaction grafting around total joint replacement devices. In these instances, clinicians pack the material into the defect to create a stable platform to support the surrounding tissue and hardware.
There are several options available to the orthopaedic clinician for bone graft material. Most commonly, the source of the graft material is either the patient (autograft), which is clinically preferable, or a donor (allograft). However, autograft has the potential drawback of increased pain and morbidity associated with a second surgical procedure, in addition to having a limited supply of the bone. In autograft and, to a lesser extent, in allograft there are biological factors such as proteins or cells that are present that can assist in the fracture healing process. Xenografts and bone graft substitutes are other options.
Moreover, synthetically derived substitute material has advantages over human derived bone graft and naturally derived substitutes, including: 1) more control over product consistency; 2) less risk for infection and disease; 3) no morbidity or pain caused by harvesting of the patient's own bone for graft; and 4) availability of the substitute in many different volumes (that is, it is not limited by harvest site of the patient).
The BGS materials that have been used commercially exhibit various levels of bioactivity and various rates of dissolution. BGS products are currently available in several forms: powder, gel, slurry/putty, tablet, chips, morsels, and pellet, in addition to shaped products (sticks, sheets, and blocks). In many instances, the form of BGS products is dictated by the material from which they are made. Synthetic materials (such as calcium sulfates or calcium phosphates) have been processed into several shapes (tablets, beads, pellets, sticks, sheets, and blocks) and may contain additives such as antibiotics (e.g., Osteoset®-T (Wright Medical Technology; Arlington, Tenn.)) or bioactive agents (e.g., Rhakoss® (Orthovita®; Malvern, Pa.)). Allograft products, in which the source of the bone graft material is a donor, are typically available as chips and can be mixed with a gel to form a composite gel or putty. None of the current products and technologies offered for BGS is capable of offering an allograft granule or shape for easy delivery and scaffold structure, in addition to being conformable to the surgical site. Furthermore, none but one (Osteoset®-T) of the current products and technologies offered for BGS is capable of offering an allograft or synthetic granule or shape containing a bioactive agent or agents, such as an antibiotic or bone morphogenetic proteins.
Past solutions to produce BGS products have included gel, putty, paste, formable strips, blocks, granules, chips, pellets, tablets, and powder. A skilled artisan recognizes there are multiple references directed to bone graft substitutes, including
Medica Data International, Inc.,
Report #RP-591149, Chapter 3: Applications for Bone Replacement Biomaterials and Biological Bone Growth Factors (2000) and
Orthopaedic Network News,
Vol. 11, No 4, October 2000, pp. 8-10.
To date, DBM products have been produced in chips, granules, gel, or putty forms only. No solid DBM product (as opposed to a putty) which has undergone a shaping process is currently available to the health care provider. It is a disadvantage of the presently available products to have no shape which is interlocking, and the irregularly-shaped chips of presently available products do not compact sufficiently and also fail to generate reproducible results. Other calcium sulfate-based products have been made using a casting or molding process, as opposed to a dry powder compaction process of the present invention. Osteoset®-T pellets are likely to have been tableted because of their simple shape. A more complicated shape that could provide improved interlocking between the granules over the tableting process used in the art requires the use of a more advanced manufacturing process. The manufacturing of JAX™ (Smith+Nephew, Inc.; Memphis, Tenn.) bone void filler requires the use of a powder compaction process to be able to produce the advanced interlocking granule shape.
U.S. Pat. Nos. 6,030,636; 5,807,567; and 5,614,206 are directed to calcium sulfate controlled release matrix. They provide forming a pellet prepared by the process comprising mixing powder consisting essentially of alpha-calcium sulfate hemihydrate, a solution comprising water, and, optionally, an additive and a powder consisting essentially of beta-calcium sulfate hemihydrate to form a mixture, and forming the mixture into the pellet. The pellets were formed by pouring a slurry mixture of the desired components into cylindrical molds.
U.S. Pat. Nos. 5,569,308 and 5,366,507 regard methods for use in bone tissue regeneration utilizing a conventional graft material/barrier material layered scheme. The barrier material is a paste formed immediately prior to its use by mixing calcium sulfate powder with any biocompatible, sterile liquid, whereas the graft material is also a paste form comprised of a mixture of water and at least autogenous cancellous bone, DFDBA, autogenous cortical bone chips, or hydroxylapatite.
U.S. Pat. No. 4,619,655 is directed to Plaster of Paris as a bioresorbable scaffold in implants for bone repair. The inventors provide an animal implant composed of a binder lattice or scaffold of Plaster of Paris and a non-bioresorbable calcium material such as calcium phosphate ceramic particles and, in a specific embodiment, the implant may contain an active medicament bound within the plaster. The implant composition of the invention may be preformed into the desired shape or shapes or it may be made up as a dry mix which can be moistened with water just prior to use to provide a fluid or semisolid, injectable formulation which can be injected into the appropriate body space as required for bone reconstruction.
U.S. Pat. No. 4,384,834 is directed to devices for compacting powder into a solid body, comprising a compaction chamber, a moveable support for the powder which extends into the compaction chamber, and means for launching a punch against the powder to form the solid body. The compaction chamber is formed by a block having a conical bore and a conical sleeve having a continuous uncut sidewall moveable within the conical bore to be radially compressed thereby.
U.S. Pat. No. 5,449,481 concerns apparatus and methods for producing a powder compact comprising loading a rubber mold having a cavity shaped according to a desired configuration of the powder compact into a recess formed by a die, in addition to a lower punch inserted into the die. The method steps include filling a cavity of the rubber mold with powder, placing an upper punch in contact with an opposing surface of the die, and pressing the rubber mold filled with powder in a space formed by the die, the lower punch and the upper punch. In specific embodiments, the upper or lower punches are secured.
U.S. Pat. No. 5,762,978 is directed to a batching device having a series of die holes which are fed powder or granular material, upper and lower punches for each die hole, wherein the punches have counterfacing respective working heads, in addition to a rotary turret comprising the die holes, and driving means for adjusting distances between the working heads of the punches
Allen Trevor
Cooper Michael B.
Kinnane Keith M.
Long Marc
Schryver Jeff
Fubara Blessing
Fulbright & Jaworski LLP
Smith & Nephew Inc.
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