CROSS REFERENCE TO RELATED APPLICATION
This application is a continuation of U.S. application Ser. No. 12/260,898, filed Oct. 29, 2008, which is a continuation of U.S. application Ser. No. 11/007,679, filed Dec. 8, 2004, which is a division of U.S. application Ser. No. 09/942,537, filed Aug. 29, 2001, now U.S. Pat. No. 6,893,462, which is a continuation-in-part of copending U.S. application Ser. No. 09/782,594, filed Feb. 12, 2001, and a continuation-in-part of U.S. application Ser. No. 09/750,192, filed Dec. 28, 2000, now abandoned, and a continuation of U.S. application Ser. No. 09/481,319, filed on Jan. 11, 2000, now U.S. Pat. No. 6,497,726. This application also claims priority from U.S. Provisional Application No. 60/181,622, filed Feb. 10, 2000, and U.S. Provisional Application No. 60/296,530, filed Jun. 6, 2001. The foregoing provisional and nonprovisional applications are incorporated by reference herein.
- Top of Page
OF THE INVENTION
Orthopedic medicine is increasingly becoming aware of the vast potential and advantages of using grafts made from allograft bone to treat and repair spinal and common joint injuries, such as Anterior Cruciate Ligament (ACL) or Posterior Cruciate Ligament (PCL) tears. In the case of injuries involves surgically reconnecting the torn portions of a damaged ligament. However, this technique is often not possible, especially when the damage to the ligament is extensive. The recent utilization of bone/tendon grafts has dramatically improved the results of joint repair in cases of severe trauma. Even in cases of extensive damage to the joint ligaments, orthopedic surgeons have been able to achieve 100 percent range of motion and stability using donor bone/tendon grafts.
Despite these realized advantages, there have been some difficulties encountered with utilizing bone/tendon grafts. For example, surgical procedures involving transplantation and fixation of these grafts can be tedious and lengthy. Currently, bone/tendon/bone grafts must be specifically shaped for the recipient during surgery, which can require thirty minutes to over an hour of time. Further, surgeons must establish a means of attaching the graft, which also takes up valuable surgery time.
Another difficulty associated with using allograft implants, such as bone/tendon grafts, is that there is only a limited supply of source tissue. As a result, patients often have to settle for inferior surgical procedures simply based on the lack of availability of tissue. Accordingly, there is a need in the art for the development of implants that implement unrealized sources of tissue.
- Top of Page
OF THE INVENTION
One aspect of the subject invention concerns methods of production and compositions for a novel dermis-derived graft (DDG) that facilitates an easier and more efficient surgery for reconstructing ligaments in a joint. While the embodiments herein exemplify the use of dermis tissue, it is understood that other tissue types can be adapted for use in accord with the teachings herein. Specifically, other soft tissues can be used such as ligament, tendon, muscle, dura, pericardium, fascia, and peritoneum, as well as demineralized bone. Tissues can be derived from allogenic, autogenic, or xenogenic sources. Alternatively synthetic materials may be used alone or in combination with natural materials. In one embodiment, the subject invention pertains to a DDG that comprises a section of processed dermis that is rolled to a cylindrical shape, and two bone blocks positioned at opposite ends of the rolled dermis, wherein the bone blocks are preshaped for uniform and consistent alignment into a recipient bone.
In a specific aspect, the subject invention pertains to a dermis derived bone-ended graft useful in orthopedic surgery comprising one or more bone blocks, and processed dermis attached to said one or more bone blocks; wherein said one or more bone blocks is cut to provide a groove sufficient to accommodate a fixation screw. Alternatively, the subject invention pertains to a dermis derived bone-ended graft useful in orthopedic surgery comprising one or more bone blocks and processed dermis attached to said one or more bone blocks, wherein said one or more bone blocks is pre-shaped into a dowel.
Another aspect of the invention regards a process for calcification of all or part of a dermis implant. Comparative data are provided that show the relative performance of processed dermis implants in laboratory rats, in which dermis implants had been calcified prior to implantation.
Another aspect of the invention regards the calcification of all or part of a tissue selected from: soft tissue; pericardium; fascia; woven soft tissue (as from skeletal muscle); urinary bladder membrane (UBM); and SIS.
Another aspect of the invention is the use of processed dermis as a replacement or as auxiliary support for the Anterior Longitudinal Ligament (ALL), and for use as a Spinal Tension Band (STB) or other type of tension band. For the ALL and STB, the dermis is formed into a shape that spans the anterior of at least two vertebrae (for an ALL support structure) or at least four vertebrae (for an STB), and the ends are affixed to a part of the vertebrae. The preferred attachment points for an STB are at the spinous processes of the adjacent vertebrae. This minimizes movement of (and thereby reduces degradation of) of the vertebrae adjacent to the vertebrae that are being fused. Such adjacent vertebrae are known to undergo excessive wear due to the lack of motion of the adjacent fused vertebrae. The ALL- and STB-type DDGs provide tensioning to help prevent excessive back bending due to the partial or total functional loss of the ALL owing to surgery or traumatic injury. As disclosed herein, the ends of dermis for such use preferably are calcified, and starting materials other than dermis may be used for such applications.
Preferably, the dermis is processed according to a method that preserves the dermis basement membrane. A process known to accomplish this is the subject of U.S. Patent Application Ser. No. 60/296,530, which is incorporated by reference. In yet another aspect, the subject invention pertains to a method of conducting orthopedic surgery on an animal comprising obtaining a dermis derived bone-ended graft, said graft comprising processed dermis having two ends, and one or more bone blocks attached to said processed dermis, wherein at least one of said one or more bone blocks has a groove suitable for accommodating a fixation screw.
An alternative aspect of the invention pertains to an implant comprising a bone block and processed dermis, wherein the bone block comprises a groove for accommodating a fixation screw.
These and other advantageous aspects of the subject invention are described in further detail below.
- Top of Page
OF THE DRAWINGS
FIG. 1 shows diagrams depicting different shapes and constructions of an implant in accordance with the subject invention. FIG. 1A shows a bone-tendon-bone type implant. FIGS. 1B-E represent an implant comprising a specific assembled bone block.
FIG. 2 is a diagram depicting implant embodiments in accord with the teachings herein.
FIG. 3 depicts a first embodiment FIG. 3A and depicts a second embodiment FIG. 3B of an anterior longitudinal replacement for limiting motion between adjacent vertebrae to be fused.
FIG. 4 depicts a band for limiting the motion and reducing the degradation of vertebrae juxtaposed to vertebrae undergoing spinal fusion (i.e., as a spinal tension band) or for being affixed to any other anatomical structures to minimize motion of such structures in relation to each other.
FIG. 5 shows plan and perspective views of a bone fixation plug that compresses the soft tissue graft component of the implant as the plug is being tightened into a hole.
DISCLOSURE OF THE INVENTION
- Top of Page
The present invention uses processed dermis as a material for implants which can be used as replacement or reinforcing tendons, ligaments, and the like. Particular features of the methods and the products of the present invention provide for a dermis-based implant that remodels into a ‘new’ replacement tendon or ligament. The present invention also discloses a process for the calcification of dermis and other tissues, including soft tissue, pericardium, fascia, woven soft tissue (as from skeletal muscle), urinary bladder membrane (UBM), and small intestine submucosa (SIS). These collectively are referred to as “implant material,” and when processed, as “processed implant material.” The bone that is used in this application, for instance to comprise bone blocks, may be selected from cortical, cancellous, cortico-cancellous, or demineralized bone, obtained from human or xenograft sources. Optionally, synthetic material may be incorporated in combination with such bone. Also, bone blocks may be comprised of two or more segments assembled together in a assembled allograft implant. The construction and use of assembled allograft implants is disclosed more fully in U.S. patent application Ser. No. 09/782,594, which is incorporated by reference.
Other features provide for implants fabricated for specific applications, such as to supplement or replace the anterior longitudinal ligament of the spine. Methods of initial preparation and production of dermis implants, and of specific production for use as ALL- and STB-type implants are also disclosed.
I. Preparation of Dermis Derived Graft Material
For the purposes of this disclosure, the term “tendon”, unless otherwise indicated, is taken to mean flexible fibrous connective tissue that attaches muscle to bone. In the context of bone/tendon/bone grafts, tendon can refer to the fibrous connective tissue that connects the patella to the femur and tibia. The term “ligament” is taken to mean the more general term of any fibrous structure connecting one body part to another, and more particularly to flexible, fibrous connective tissue that connects bone to bone or holds organs in place. Also, the term “processed dermis” is taken to mean dermis that has been processed by the initial processing described herein, or another method of decellularizing dermis, and by the secondary process described herein, in which the initially processed dermis is formed into an implant. A dermis derived graft (DDG) is synonymous with a dermis derived implant, and these terms are defined to indicate a graft or implant substantially comprised of processed dermis.
The term “processed dermis” as used herein is intended in a broad sense and refers to fibrous connective tissue for use in grafts derived from dermis of a donor, or from dermis cultured in vitro. The preferred initial processing is that described in U.S. Patent Application Ser. No. 60/296,530, which is incorporated by reference. The initial processing provides a decellularized dermis sample that retains the structural functionality of the basement membrane. This results in superior structural and functional properties of the final dermis derived implant.
Basic steps of a preferred initial processing method are summarized as follows:
1. Contacting the donor dermis with a viral inactivating agent that includes benzalkonium chloride; and
2. Contacting the dermis with one or more decellularizing agents, for instance about 0.5 percent TWEEN 20 and about 0.5 percent hydrogen peroxide. Additional possible steps include contacting the dermis with calcium hydroxide (to aid in virus inactivation), with a chelating agent, for instance EDTA, sonicating the dermis during such treatments, and drying the dermis, such as by freeze-drying.