DE102004022505A1 - Industrially-produced (especially cage) implant is predominantly made from a bone substitute material, especially PMMA, and can be patient-specific - Google Patents

Abstract

An industrially-produced (especially cage) implant is predominantly made from a bone substitute material. An independent claim is also included for production of the implant using a mold.

Description

The Invention relates first an industrially manufactured implant and a manufacturing process therefor. The industrially manufactured implant can be, for example, a cage implant be.

Further the invention relates to a substance, namely bone substitute material, especially bone cement, especially PMMA, for use with such Implant or as a material for its production.

Cage implants are also called cages or spacers. Cage implants have been around for some time Years, especially in spinal surgery known. she are used as stabilizing placeholders. The main application Cage implants are in the field of degenerative treatment Diseases of the cervical spine and lumbar spine. at A surgical procedure is often an intervertebral disc between two vertebral bodies the cervical spine or the lumbar spine removed and thus the resulting space through a cage implant refilled. The cage implant is common a substantially rectangular or trapezoidal ring body with a passage in its center, with the cage implant as a whole rather disk-shaped is. The disk-shaped Implant will be during the Engaged between the two adjacent vertebrae pushed and there under other by the natural Clamping between the vertebral bodies fixed. In the following Healing process fused the two adjacent vertebral bodies. The Cage implant fixes them in terms of their distance and their exact position to each other.

Cage implants are among others by the company Stryker Spine ("Solis cage"), Acromed / Johnson & Johnson ("Cervical IF Cage), Aesculap ("CESPACE"), Weber ("Weber Spacer"), Medinorm ("Wing Cage") and Intromed ("Intromed Spacer"). she Made of plastic, especially carbon reinforced plastic polymers or titanium with a pure titanium coating.

The Shaping of the cage implants takes place for artificial and metallic materials Materials equal: in both cases the cage implant is worked from the full. The cage implants are in different sizes available. In any case, however, are complex molds and machine tools, in addition, a series production of cage implants only without variations economically allow.

Of the Invention is the object of an implant available put, which on cost-effective Made and individual requirements of individual Patients can be adjusted, taking a tolerability of the implant no less guaranteed should be.

The Task is solved by an industrially manufactured implant, which at least predominantly made of a bone substitute material. Bone replacement materials offer the advantage that they are even without expensive tooling machinery can be brought into a required shape. In addition, bone substitute material hardens at least on the for a common one Implant required compressive and tensile strength. The strength is for many implants are a particularly important factor. exemplary For example, the industrially manufactured implant may be an industrially manufactured one Cage implant. Bone replacement material hardens Furthermore depending on the mixture relatively fast and reached so after a short time Time a strength sufficient to the industrially produced Implant transportable pack and this example, to be able to stack.

Preferably may be for producing an industrially manufactured implant bone cement be used as a bone substitute material. Bone cements are commercially available as two component materials. They consist of a powdery Base material and a liquid Binder or activator. After mixing the two components cure the Cement materials in the powdery phase to form a solid matrix. Exact characteristics of the implant in terms of its mechanical Behavior can by the mixture of the bone cement, in particular by a proportionate shift between powdery and liquid phase or by adding substances to reliable Be controlled manner.

In a preferred embodiment of the industrially manufactured implant, this is made of PMMA (polymethyl methacrylate) produced. This bone cement has been in use for about 30 years Used surgery and has proven excellent. The powdery component consists essentially of polymer, namely polymethylmethacrylate, and its copolymers; In contrast, indicates the liquid Component with methyl methacrylate to an associated monomer. As X-ray contrast agent can the powder component, for example, zirconium dioxide and / or barium sulfate be mixed. In the liquid Component are often hydroquinone and / or ascorbic acid as radical scavengers used. For dyeing of the material chlorophyll can be used. In addition, the Powder component slightly with antibiotic, for example with gentamicin, be loaded.

It should be noted that an industrially manufactured implant, in particular a Ca ge implant, even if it is loaded with an antibiotic, is advantageous and inventive regardless of its base material. Especially for cage implants loading with antibiotics can lead to excellent tolerability in the patient.

Next the fact that thus simplifies the manufacture of the cage implant is, it represents a further advantage that now a well-known and proven material used to make a cage implant becomes. That this material is for this medical indication is completely surprising and neither therapeutically nor economically been considered. In this context, it should also be noted that a new material must overcome significant obstacles to surgical intervention Application to be allowed to. Among other things certain requirements with regard to durability, modulus of elasticity, the compression modulus, tensile modulus, fatigue strength, fracture ability, the fatigue crack growth, the static strength, the flexural strength, the compressive strength, the tensile strength, the shear strength, the viscoelasticity, the durability and the processing properties.

Independent of These advantages are the industry with the use of bone substitute material for a industrially manufactured implant or as a material for its Manufacturing able to mass-produce in a cost effective manner to provide the implants. Bone replacement material has been so far exclusively used in the operating room and stirred there and for the production of dowel-like Components applied. In contrast, implants according to the invention decentralized, ie industrial, are produced and also cure there, so they are commercially available in their finished form intended for use arrive and can be transported.

So far there are outside from operating theaters no implants made of bone substitute material. This is surprising even more so than that the invention with surprising simplicity extraordinary economical Benefits opens up.

Also Medical technology is a great step forward by the invention reached. For certain indications, for example inflammation in the intervertebral disc space, hitherto known implants can not be used. This possibility is first developed by the present invention.

Furthermore If an implant made of bone substitute material can still be changed secondarily, for example by milling or other machining methods. This is especially true at a possibly necessary revision operation of inestimable Value. In contrast, A titanium implant is so tight that it can get through in the operating room used tools can not be changed.

When Drug is an outside a piece of bone cement made under an operating room the registered trademark Palacos known. These are so-called septopal chains, ie a pure antibiotic carrier made of PMMA, for infection treatment. This drug is not an implant.

It has already been explained that a cage implant is a substantially rectangular or trapezoidal ring body with a passage, wherein the cage implant is a disc-shaped whole has an upper and a lower bearing side. To the mutual Mechanical stress on the vertebral body and cage implant as low as possible It is suggested that a bearing surface for a vertebral body at least about half, preferably more than two-thirds, makes up a bearing side. The means that of the available standing entirety of the upper or lower side of the disc of the predominant Part as storage area is formed while only a minor part for a passage is omitted. Such a shaping causes an enlargement of the bearing surface in relation to the cages known in the art one and a half times to two times. It should be noted that Bearing sides can not only be found on cage implants; much more Many types of implants have one for holding a particular one Force mainly intended area. This is for these implant types the bearing surface. Analogous to the proposal for The cage implant will also be used for These types of implants suggested that a bearing surface on the Bearing side at least about half, preferably more than two-thirds, makes up the bearing side.

Around The surrounding tissue and the surrounding muscles will not disturb suggested that the industrially manufactured implant a parabolically has rounded edge contour. In addition, such a diminishes Edge contour the risk of breaking into a vertebral body or another body, which exerts forces on the implant when the implant is inserted.

A rib structure on a bearing surface, in the case of a cage implant, in particular for a vertebral body, makes it possible to primarily fix the industrially produced implant during implantation. The ribs of at least one bearing surface can advantageously be aligned parallel to one another, since in this way twisting of the industrially manufactured implant during insertion between the adjacent vertebral body is prevented.

It is independent This is advantageous if a surface, in particular a bearing surface, of the industrial structured implant to increase its surface area is. According to investigations by the inventors, roughness values in particular would be favorable the surface between Ra = 12.5 to 18 and Rz = 54.5 to 75.1 (rating after VDI 3400 Rgf. Class 42 to 45).

alternative and solves cumulatively to the aforementioned the object of a method for producing an industrially manufactured Implant in which a bone substitute material for shaping the Implant is used.

For a serial production with nevertheless given variability It is proposed to use a multi-part tool for shaping the industrially manufactured implant to use. The multipart tool In particular, it can be of modular design and exchangeable modules for the Have shape. The implant can do so in particular geometrically similar adapted to every individual patient situation.

interchangeable Modules on the tool can In particular, allow it for different widths of the implant to set different heights. Therefore, it is proposed, first make a measurement on the patient and the acquired from it Measurement data for individualizing the shape of the implant to use.

It be explicit noted that the use of bone substitute material, in particular Bone cement, especially PMMA, as a material for producing a already implanted by itself innovative and innovative is. The material is according to the prior art in the spinal area used only in the form of hand-formed masses. These will in the operating room and directly installed.

The Pieces made in the operating room have no defined Shape, but each will be different according to individual patient needs produced. The exact form is essentially random because from the doctor performing the operation a hand molding is done on the bone cement. Often become dowel-like Components manufactured. The dowels For example, have a frusto-conical shape with a largest diameter of about 6 mm, a smaller diameter of at least 2 mm and a longitudinal extension from about three times to five times their thickness. The dowels However, they are geometrically indefinite and of the respective situation only roughly adjusted. You can relatively easy to slip. Use as an industrially manufactured implant and / or as cage implant is not yet known.

insofar already lies in the use of bone replacement material, in particular Bone cement, especially PMMA, for the industrial prefabrication of geometrically determined implants in larger quantities an invention.

The Production of the industrially manufactured bone cement implant can be based for example in connection with the plastic injection molding, wherein a to be spilled Polymer within a preferably multi-part tool with pressure is formed under the action of vacuum to the desired geometry.

The Invention will now be described with reference to an embodiment with reference closer to the drawing explains wherein like components in different figures have the same reference numerals wear. As an exemplary embodiment a cage implant was chosen. The mentioned Features and advantages equally extend to numerous other implant types of the invention. In the drawing show

1 a perspective view of a cage implant according to the invention,

2 a plan view of the cage implant 1 and

3 a view of the cage implant from the 1 and 2 according to marking III-III in 2 and

4 a section of the cage implant from the 1 . 2 and 3 according to marking IV-IV in 2 ,

The cage implant 1 in the 1 to 4 consists essentially of an annular disk body 2 with a trapezoidal floor plan. Within a circumferential ring 3 of the cage implant 1 is a passage 4 intended.

The ring body 3 is made of PMMA in large-scale industrial series and has already been pre-cured for durability in the factory.

At an upper bearing side 5 and on a lower bearing side 6 has the cage implant 1 each a substantially trapezoidal edge bearing surface (exemplified with 7 characterized) for supporting a vertebral body. The area of the passage 4 on the total area of the bearing side 5 respectively. 6 of the cage implant 1 is about a quarter to a fifth. Penetration into a vertebral body is thus avoided particularly reliably.

Every storage area 7 carries parallel, mutually approximately equally spaced grooves (exemplified figured with 8th ). Between the ribs 8th the roughness is about Ra = 15 and Rz = 60.

The annular disk body 2 of the cage implant 1 has one from a first page 9 to a second page 10 linearly increasing thickness. Ribs 8th are the same size over the entire area of the bearing surfaces and provided with an approximately triangular cross-section. This results along bearing edges 11 (numbered as an example) a planar interface of the cage implant 1 at the upper bearing side 5 and on the lower bearing side 6 ,

Claims (15)

Industrially produced implant, in particular Cage implant, characterized in that the implant is at least predominantly made of a bone replacement material. Implant according to claim 1, characterized in that that a bone substitute material bone cement, in particular PMMA, is. Implant according to claim 1 or 2, characterized that a storage area for one vertebra at least about half, preferably more than two-thirds, makes up a bearing side. Implant according to one of the preceding claims, characterized characterized in that an edge contour is rounded parabolic. Implant according to one of the preceding claims through ribs on a storage area. Implant according to one of the preceding claims, characterized characterized in that ribs are aligned parallel to each other. Implant according to one of the preceding claims by a surface roughness a storage area from Ra = 12.5 to 18 and Rz = 54.5 to 75.1. Implant according to one of the preceding claims by loading with an antibiotic, especially gentamicin. Method for producing an industrially produced Implant, in particular a cage implant, according to one of the preceding Claims. Method according to claim 9, characterized in that that a solid shape for producing a geometrically determined Implant is used on a tool. Method according to claim 9 or 10, characterized that a form to the individual shape needs of a patient, in particular a different width, is set. Method according to one of claims 9 to 11, characterized that a multipart tool, in particular a modular tool, used to manufacture the implant. Bone replacement material, in particular bone cement, especially PMMA, for use as a material for producing a industrially produced implant, in particular a cage implant preferred according to one of the claims 1 to 8. Use of bone substitute material, especially Bone cement, especially PMMA, for an industrially manufactured implant, in particular for a cage implant. Use according to claim 14 for an implant after a the claims 1 to 8.