High density fibrous polymers suitable for implant

#The invention generally relates to medical devices and procedures. The invention more particularly concerns a polymeric construct having interlaced and interlocked fibers and products formed from the fibrous polymer.

#To better treat our aging population, physicians are looking for new and better products and methods to enhance the body's own mechanism to produce rapid healing of musculoskeletal injuries and degenerative diseases. Treatment of these defects has traditionally relied upon the natural ability of these types of tissue to repair themselves. In many instances the body is unable to repair such defects in a reasonable time, if at all. Advances in biomaterials has allowed for the creation of devices to facilitate wound healing in both bone and soft tissues defects and injuries. Such devices are used in tissue regeneration as tissue (e.g., bone) graft scaffolds, for use in trauma and spinal applications, and for the delivery of drugs and growth factors.

#Bone and soft tissue repair is necessary to treat a variety of medical (e.g., orthopedic) conditions. For example, when hard tissue such as bone is damaged as a result of disease or injury, it is often necessary to provide an implant or graft to augment the damaged bone during the healing process to prevent further damage and stimulate repair. Such implants may take many forms (e.g., plugs, putties, rods, dowels, wedges, screws, plates, etc.), which are placed into the tissue. Typically, such implants can be rigid, flexible, deformable, or flowable and can be prepared in a variety of shapes and sizes. For non-rigid structural repair materials (e.g., putties and pastes) to be conveniently used, they must be capable of being formed into a variety of complex shapes to fit the contours of the repair site. An accurately configured implant that substantially fills the defect site will enhance the integration of natural bone and tissue to provide better healing over time. The prior art discloses medical implants that comprise, at least partly, collagen (to be discussed later).

#FIGS. 1 A, B, and C are enlarged, representative diagrams depicting the arrangement of interlacing and interlocking fibers of the present invention, wherein a force (e.g., centrifugal) is applied in orientation represented by the arrow.

#FIG. 2 depicts a hydrated malleable mass 400 of interlaced fibers 110.

#FIG. 3 depicts a human extremity 600 that has been surgically opened to reveal bone 610. A hydrated malleable mass 500 is being inserted into an exposed osseous defect 620.

#This invention is a malleable, biodegradable, fibrous composition for application to a tissue site in order to promote new tissue growth. One aspect of this invention is a fibrous component (e.g., collagen, chitosan, alginate, hyaluronic acid, polylactic acid, poly-caprolactone, and poly-urethane, etc.) (see table 1) which provides unique mechanical and physical properties, as will be discussed.

#Fibers (e.g., collagen, chitosan, alginate, and hyaluronic acid), may be obtained, for the example of type I collagen, from bovine hide, which have been processed in a manner known by those skilled in the art. As an example, the hides are stripped from the animal carcass and the corium (i.e., the intermediate layer of an animal hide between the grain and the flesh sides) is subsequently split from the rest of the hide. The corium is limed using a calcium hydroxide solution to remove extraneous organic material. The limed corium is then neutralized using an acid solution and the excess salt produced is serially rinsed (e.g., with water). The neutralized corium is then ground using a mill type apparatus to tear apart the corium into fibers. This process maintains the native cross-links within the collagen. (During the aging process of the live animal, intermolecular and interfibrillar bonds are naturally formed between collagen fragments. These naturally occurring bonds are what distinguish the fibers of collagen as natively cross-linked fibers as opposed to reconstituted fibers of collagen). The fibers are suspended within a suspension fluid (preferably aqueous) forming a relatively homogenous slurry/dispersion. This dispersion preferably has a solid content ranging from 0.25 to 10%, but most preferably in the range of 3 to 5% by weight.

#The resultant slurry is concentrated by centrifugation; preferably, at temperatures below 60 degrees Celsius to avoid degradation of the collagen and subsequent gelatin formation. Speed and therefore force, as well as time can be varied to create the desired extent of fiber interlacing, as will be discussed later. The slurry can be spun under forces of about 500×g (times gravity) to forces as high as about 30,000×g and for times ranging from 10 seconds to 96 hours. Preferably, the suspension is spun at forces of 500×g to 10,000×g and times of 1 minute to 24 hours. Most preferably the suspension is spun at 3000×g for about 5 minutes. This creates, in a preferred embodiment, a paste or putty-like structure containing interlocked or interlaced collagen fibers, as will be discussed, that may be molded and dried by either evaporation to create a high density non-porous unit, or by lyophilization to maintain the three dimensional structure and porosity. An additional preferred embodiment comprises a material that is a flowable, yet dense, material, which may be injected or otherwise molded. This moldable embodiment may be cast into a mold, or in situ, as will be discussed.