DE9013067U1 - Implantable prosthesis - Google Patents

Description

THERA Patent GmbH & Cc. XG

Society for Industrial Property Rights

DEG-33 155

IMPLANTABLE PROSTHESIS

The invention relates to a cement-free implantable prosthesis according to the preamble of claim 1. Such prostheses are suitable for bone or tooth root replacement, as joint replacement or, for example, as rigid or flexible intervertebral disc implants.

With cement-free implanted prostheses, harmful side reactions of the polymerizing cement components in the organism are avoided, which can lead to tissue destruction and thus to loosening of the implant.

Known cement-free implantable prostheses are, as described for example in EP-A-O 321 389, usually provided with a coating of bioactive, partially resorbable ceramic materials based on calcium phosphates as well as polymeric plastics that are stable in the body's environment. When the ceramic part of the prosthesis anchor is resorbed, a porous plastic structure remains, into which bone tissue grows.

In addition to the porous surface coatings, which are mainly made of calcium phosphate and ceramic components, titanium plasma coatings or structures made of sintered balls of different sizes are known, which are intended to allow mechanical anchoring of the bone in the rough surface.

With the known prosthesis anchors, a considerable amount of time passes before the bone tissue has grown into the porous surface. During this time, the load-bearing capacity of the prosthesis is low and there is a risk that it will become loose again.

The invention is based on the object of creating a prosthesis of the type mentioned above, which can be easily implanted and which provides a highly resilient, permanent connection.

connection with the bone tissue is ensured.

This object is achieved by the invention characterized in claim 1. Accordingly, a large number of blind hole-like or finger-shaped depressions are arranged on the shaft surface of the prosthesis. The bone grows relatively quickly into microporosities of this shape. The fine blind holes can be made directly on the shaft surface, without the need for a coating to anchor the prosthesis. This prevents the prosthesis anchoring from coming off, as can happen with coatings.

Advantageous embodiments of the invention are specified in the subclaims.

Aligning the fine blind holes as specified in claim 5 allows targeted pressure or tensile forces to be introduced from the prosthesis surface into the bone growing into the depressions. This achieves a physiological load on the implant bed and prevents the prosthesis from becoming loose due to damage to the ingrown bone tissue.

According to Wolff's law of bone transformation, structural changes in the bone depend on the load it is subjected to. Where the bone is subjected to pressure, resorption occurs, whereas tensile loads lead to regrowth of the bone. By aligning the fine blind holes accordingly, the bone pegs growing into the depressions can be subjected to tensile loads and thus stimulated to grow. The axial direction pointing to the base of the hole then forms an acute angle with the force exerted by the prosthesis on the bone under normal load.

In certain places, the orientation of the blind holes can also be chosen so that the bone pegs are subjected to targeted pressure.

With the features specified in claims 2 to 4, a particularly strong connection with the bone is achieved soon after the prosthesis is inserted. Accordingly, approximately 20 to 100 holes per mm ² of shaft surface with a diameter of approximately 30 μm to approximately 60 μιλ and a depth of approximately 50 μm are required.

up to approx. 90 μπα. A particularly secure anchoring of the prosthesis in the bone tissue is achieved if the fine holes on the shaft surface are surrounded by bulges. This is especially true if the bulges have undercuts into which the bone tissue grows.

The design of the shaft surface as a round thread according to claim 6 enables a resilient, force- and form-fitting connection of the prosthesis anchorage to the bone soon after implantation. In addition to the mechanical effect of the screw connection, the larger surface area compared to a cylindrical shaft also contributes to this. A round thread has no sharp edges that could lead to irritation or excessive stress on the bone tissue.

Easy implantability and long-term durability of the prosthesis is achieved if, according to claim 7, the shaft tapers from the prosthesis head to the end.

A titanium alloy according to claim 8 is particularly suitable as a prosthetic material due to its stability and biocompatibility.

The holes are expediently produced according to claim 9 by means of high-energy radiation, for example by drilling with a laser beam.

Preferred embodiments of the invention are shown in the drawing.

Figure 1 a prosthesis designed as a dental implant,

Figure 2 two depressions on the shaft surface of the prosthesis in cross section, and

Figure 3 is a schematic representation of the forces acting on the prosthesis.

The prosthesis shown in Figure 1, designed as a dental implant, consists of a prosthesis head 2 and a shaft 3. The shaft 3 is partially provided with a round thread 4, which on the one hand ensures a certain stability immediately after the prosthesis is inserted and on the other hand provides an enlarged surface for contact with the bone. Depending on the area of application, it may also be more advantageous if the thread 4 extends over the entire prosthesis shaft 3. It may also be possible to dispense with a thread altogether.

To ensure that the prosthesis can be implanted into the jaw without any problems, it can be shaped so that it tapers from the prosthesis head 2 to the end.

The prosthesis head 2 shown is provided with an internal thread 22 for fastening a dental prosthesis. In addition, an anti-rotation device is provided for the screwed-on structure, which can be designed as a square or, as shown, as a hexagon 21.

To increase the surface area and to securely attach the prosthesis, the prosthesis shaft can be provided with macro pins (not shown) in its lower area instead of the thread.

The actual prosthesis anchorage consists of the finger-shaped, blind hole-like depressions 1. As shown, they can cover essentially the entire shaft surface or, depending on the desired force transmission between the prosthesis and the bone, they can only be attached at certain points.

Figure 2 shows a cross-section of the depressions 1 with a crater-shaped edge or bead 11, 12 of a laser-irradiated implant surface (ELCS, Excimer Laser Conditioned Surface). The bead 11, 12 is created by the material thrown up from the hole during the laser beam treatment. Depending on the laser parameters set (energy, beam diameter, irradiation time, etc.), a simple bead 11 or a bead 12 with undercuts can be produced. By the bone tissue growing into the depressions 1 and growing around the bead 11, 12, a double mechanical connection is achieved between the prosthesis surface and the surrounding bony implant bed. A particularly reliable transmission of both compressive and tensile forces is achieved with an undercut bead 12.

Figure 3 shows the cross-section of a prosthesis anchor. The force F with which the prosthesis is loaded and which it in turn exerts on the bone acts parallel to the surface in this example. In order to stimulate the growth of the bone tissue into the blind holes 1, these are directed in such a way that the axial direction pointing to the bottom of the hole

direction A forms an acute angle with the force F. The bone pegs growing into the depressions are therefore essentially subjected to tensile stress. According to Wolff's law of bone transformation, this stimulates their growth. The lower of the two depressions 1 in Figure 3 is attached to the surface of the thread 4 that is inclined upwards. There, by tilting the blind hole 1 more, an even more acute angle can be achieved between the axial direction A and the force F, thus increasing the force component that is effective for bone growth.

Where the bone or bone trabeculae are naturally subjected to pressure, it may also be useful to arrange the fine holes in such a way that the bone pegs growing into them can also absorb pressure.

Claims (9)

THERA Patent GmbH & Co. KG Society for industrial property rights DEG-33155 Protection claims 1. Cement-free implantable prosthesis, the shaft surface (3) of which is provided with recesses (1), characterized in that a large number of recesses are present, which are designed as fine blind holes (1). 2. Prosthesis according to claim 1, characterized in that the holes (1) have a diameter of approximately 30 µm to approximately 60 µm and a depth of approximately 50 µm to approximately 90 µm. 3. Prosthesis according to claim 1 or 2, characterized in that the holes (1) on the shaft surface (3) are surrounded by beads (11, 12). 4. Prosthesis according to one of claims 1 to 3, characterized in that approximately 20 to 100 holes (1) are provided per mm ² of shaft surface. 5. Prosthesis according to one of claims 1 to 4, characterized in that at least some of the depressions are oriented in such a way that the axial direction (A) pointing to the hole base coincides with the direction of the prosthesis under normal loading. these force exerted on the bone (F) a peak
forms an angle. 6. Prosthesis according to one of claims 1 to 5, characterized in that the shaft surface (3) is designed as a round thread (4). 7. Prosthesis according to one of claims 1 to 6, characterized in that the shaft (3) tapers from the prosthesis head (2) towards the end. 8. Prosthesis according to one of claims 1 to 7, characterized in that the shaft (3) is made of a titanium alloy
consists. 9. Prosthesis according to one of claims 1 to 8, characterized in that the holes (1) are made by laser beam drilling
are manufactured.