Biphasic implant device transmitting mechanical stimulus

Abstract

Tissue implants prepared for the repair of tissues, especially avascular tissues such as cartilage. One embodiment presents an electric potential capable of receiving and accumulating desirable factors or molecules from surrounding fluid when exposed to dynamic loading. In another embodiment the implant promotes tissue conduction by retarding, restricting and controlling cellular invasion through use of gradients until competent tissue forms. Further embodiments of the tissue implants may be formed into a multi-phasic device that provides deep tissue mechanical stimulus by conduction of mechanical and fluid forces experienced at the surface of the implant.

Description

BACKGROUND OF THE INVENTION[0001]What is disclosed is a device for repairing and replacing lost or damaged tissue. Particularly, one embodiment is directed to a multi-phasic prosthetic device for repairing or replacing cartilage or cartilage-like tissues. Said prosthetic devices are useful as articular cartilage substitution material and as a scaffold for regeneration of articular cartilaginous tissues.[0002]Cartilage is found throughout the body, such as in the supporting structure of the nose, ears, ribs (elastic cartilage), within the meniscus (fibrous cartilage), and on the surfaces of joints (hyaline cartilage or articular cartilage). A joint is a bending point where two bones meet. The knee, hip, and shoulder are the three largest joints.[0003]The specialized covering on the ends of bones that meet to form an articulating joint is called hyaline or articular cartilage. It is the cartilage that is damaged and wears as one ages, or sustains an injury. Articular cartilage is uniq...

AI Technical Summary

Benefits of technology

[0034]In another aspect of the invention, the implant provides for the systematic tissue conduction and growth from the surrounding cartilage tissue, and retards the formation of tissue in the interior of the implant. In this manner, it is believed that the growth of the incorrect type of tissue can be avoided, and better ensure that only the desirable hyaline cartilage is formed. In an embodiment, the device may comprise a gradient, where the gradient is arranged to retard the tissue formation most at or near the center of the implant (when viewed top down), and transitions to little or no retardation of tissue formation towards the perimeter of the implant, adjacent to normal cartilage tissue. The gradient may be in the form of a circular gradient, and may be uniform throughout the device from upper surface to lower surface, or alternatively may vary from top to bottom. The gradient may be a smooth transition or gradual gradient, or alternatively a stepwise gradient having well defined regions within the gradient. The gradient may be a concentration gradient, such as biologically active agents, additives, or combinations thereof. The gradient may be a physical gradient, such as porosity, density, expansion, swelling, elasticity, hardness, compressibility, and combinations thereof. The gradient may be a material gradient, or chemical gradient, such as molecular weight, cross-linking, hydrophobicity, polarity, crystallinity, and combinations thereof. The gradient may be part of the first phase of a multiphasic device, and corresponds to the cartilage region, and may be attached to a rigid base corresponding to the bone region.

[0035]In another aspect of the invention, the multiphasic implant provides for the transmission or conduction of pressure forces through the device, down to...

Problems solved by technology

Bone is very sensitive and the sharp pain of arthritis often comes from irritation of bone nerve endings and since human tissue has a very limited capacity to heal without a blood supply, articular cartilage cannot repair itself effectively.

Without articular cartilage, stress and friction would occur to the extent that the joint would not permit motion.

As stated above, articular cartilage has only a very limited capacity to regenerate.

If this tissue is damaged or lost by traumatic events, or by chronic and progressive degeneration, it usually leads to painful arthrosis and decreased range of joint motion.

Articular cartilage repair following injury or degeneration represents a major clinical problem, with treatment modalities being limited and joint replacement being regarded as appropriate only for the older patient.

(Extensive use of cortisone not only has a wide variety of harmful effects, but is also believed to harm cartilage.)

These were safer than Aspirin and cortisone but had potent side effects, especially causing bleeding within the stomach and intestinal ulcers.

While much safer and seemingly more effective, Vioxx was found to have significant cardiac side effects and is no longer available.

However, these anti-inflammatory medications only treat the symptoms of cartilage damage and arthritis and do not promote repair.

Currently, hyaluronate injections are approved for the treatments of osteoarthritis of the knee in those who have failed to respond to more conservative therapy, Once again, this procedure only treats the symptoms of cartilage damage and arthritis and does not promote repair.

But this is not a final solution as the degenerative process continues to wear away at the articular cartilage.

Although successful, the window of opportunity for this procedure is often missed, as the few clinical symptoms showing the need for this treatment are not evident until the defect deepens to involve the underlying bone, thus the damage encountered upon detection is frequently too extensive for repair through ACI.

Studies have shown that microfracture techniques do not fill in the chondral defect fully and the repair material formed is fibrocartilage.

The fibrocartilage tissue can temporarily return function for activities such as running and a sport play, but ultimately fails, as fibrocartilage is unable to mechanically share and disipate loading forces as effectively as the original hyaline cartilage.

Fibrocartilage is much denser and isn't able to withstand the demands of everyday activities as well as hyaline cartilage and is therefore at higher risk of breaking down.

Several plugs can fill up rather larger defects and will grow to re-supply a new joint surface.

Unfortunately, this procedure leaves defects of equal or worse proportions elsewhere and often the harvested tissue is not viable due to the traumatic harvesting procedure.

Due to the problems associated with current state of the art treatments, much work has been done to produce a synthetic off-the-shelf scaffold to be used in place of the harvested osteochondral plug.

However, these single-phase scaffold implants proved unsuccessful in healing of the complex multiphasic articular cartilage along with the underlying bone.

While these showed an improvement over single phase devices, it is evident that th...

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