DE20303642U1 - Implant for reconstruction of human vertebra which has lost some of its load-carrying capacity or is broken consists of edgeless implant elements introduced singly - Google Patents

Abstract

The implant (30) for reconstruction of a human vertebra (16) which has lost some of its load-carrying capacity or is broken consists of edgeless implant elements (28) introduced singly into an internal space (17) of the vertebra. An independent claim is also included for an implantation system with a sleeve (24) for introduction of the implant elements.

Description

A 57 182 u Applicant: Aesculap AG & Co. KG

February 28, 2003 At Aesculap Square

z-286 78532 Tuttlingen

Implant and implant system for reconstruction of a vertebral body

The invention relates to an implant for reconstructing a vertebral body of a human spine that is restricted in its function or broken, as well as to an implant system comprising an implant and an insertion device for introducing the implant into an interior of the vertebral body.

A vertebral body in the human spine can be limited in its load-bearing capacity due to illness or can be broken due to an accident or illness. Damage to the vertebral body due to illness can be caused by osteoporosis, for example.

Osteoporosis is a disease of the entire skeleton, which is characterized by low bone mass and an impairment of the microarchitecture of the bone tissue, leading to increased bone fragility. The treatment of osteoporotic vertebral fractures is extremely difficult. One known treatment option is percutaneous vertebroplasty. In this procedure, the fractured vertebral body is filled with liquid bone cement, thus increasing its stability. The operation is carried out using a percutaneously inserted hollow cannula, which is placed transpedicularly in the vertebral body. Either a sterile bone cement is used, which remains thin for a relatively long time, or injectable biodegradable calcium phosphate. The prerequisite for such an operation is that the rear edge of the vertebral body to be treated is intact, in order to

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To prevent bone cement from entering the spinal canal of the spine.

The problem with percutaneous vertebroplasty is that the bone cement has to be injected in liquid form under pressure. This carries the risk of embolisms. To avoid this, the bone cement can also be injected into a sheath that is placed in the vertebral body before injection, from which it cannot escape.

Another method is described in WO 02/47563 A1, in which a filling material is filled into an expandable pocket introduced into the vertebral body.

It is therefore an object of the present invention to improve an implant, an implant system and a method of the type described above so that the surgical procedure for inserting the implant can be carried out easily and safely.

This object is achieved according to the invention in an implant of the type described above in that the implant consists of a plurality of body-compatible, edge-free implant elements which can be individually inserted into an interior of the vertebral body.

The implant according to the invention has the advantage over the injection of liquid bone cement into the vertebral body that no embolisms can occur. In addition, the procedure is simplified because the implantation time is not limited by the hardening time of the bone cement,

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This is because the implant elements of the present implant are already inserted into the vertebral body in their final form. Furthermore, an additional sleeve for holding the implant elements in the vertebral body is not required. This shortens the operation time on the one hand and enables the use of a particularly simple insertion instrument on the other.

Preferably, the implant elements are essentially inelastic. After the implant elements have been introduced into the vertebral body, they support each other and thus keep the re-erected vertebral body in a desired shape that essentially corresponds to its original natural shape.

The implant elements are particularly easy to insert if they are essentially in the shape of a ball, as this shape means they are practically impossible to jam. In addition, the natural bone substance can grow through the inserted implant in an optimized way, as even with the balls packed very tightly there are still gaps between them.

A particularly high level of stability is achieved when the implant elements have a diameter in the range of 3 to 8 mm. This also prevents implant elements from escaping from the vertebral body that is no longer completely closed due to a fracture.

It is advantageous if the implant elements are made of hardened bone cement. When using hardened bone cement,

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ment, there can usually be no rejection reactions of the body.

According to a preferred embodiment of the invention, the bone cement can contain calcium phosphate (CaP). This enables the use of bone cements that are already known and have proven themselves in practice.

The object set out at the outset is further achieved according to the invention in an implant system of the type described at the outset in that the implant is one of the implants described above, that the insertion device comprises an insertion sleeve which can be inserted into the vertebral body and that the insertion sleeve has an inner cross-section which essentially corresponds to the outer dimensions of an implant element.

With such an implant system, implant elements can be easily inserted into the vertebral body individually, i.e. one after the other. This allows the vertebral body to be filled with the implant in a controlled manner.

The implant elements can be injected into the vertebral body particularly safely if the insertion sleeve has a circular inner cross-section and if the inner cross-section is a maximum of 10% larger than the outer diameter of an individual implant element. An insertion sleeve with such an inner cross-section makes it possible to insert the implant elements individually and one after the other into the vertebral body without blocking them in the insertion sleeve.

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In principle, it would be conceivable to lead the implant out of the insertion sleeve in the longitudinal direction of the sleeve. However, it is advantageous if the insertion sleeve has at least one exit opening pointing in a radial direction at a distal end. The advantage of the implant emerging from the insertion sleeve at the side is that the implant is optimally distributed in the interior of the vertebral body. It can also prevent the implant from being pushed out of the vertebral body. It would also be conceivable, for example, to provide two radially outward-pointing, diametrically opposed slots on the insertion sleeve.

A vertebral body that is limited in its load-bearing capacity or fractured can be reconstructed by inserting an insertion instrument in the form of an insertion sleeve into an interior of the vertebral body and by injecting an implant of the type described above into the unprepared vertebral body by inserting implant elements into the vertebral body one after the other.

This makes it possible to reconstruct a damaged vertebral body, for example one with osteoporosis, in the simplest way. The vertebral body does not have to be prepared before the implant is inserted, i.e. the implant elements are inserted directly into the vertebral body. This also means that no additional container has to be inserted into the vertebral body into which the implant is inserted in known procedures. In this way, operation times can be shortened. Furthermore, the implant adapts optimally to the vertebral body to be reconstructed using the method according to the invention.

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To simplify the insertion of the implant, it can be advantageous if the spine is stretched before and during the insertion of the implant. In this way, only relatively low thrust forces are required to insert the implant elements into the vertebral body.

It can be advantageous if the implant is inserted through a pedicle canal. A pedicle provides easy access to the interior of the vertebral body.

It is beneficial if access to the interior of the vertebral body is closed after the implant has been inserted. This prevents the implant from coming out again through the access if, for example, forces are exerted on the vertebral body and thus on the implanted implant.

A particularly simple way to prevent the implant from coming out of the vertebral body is to close the access with a plug or bone cement.

It is advantageous if the implant is pushed radially out of the insertion sleeve. In this way, it can be distributed particularly well and evenly in the interior of the vertebral body. Furthermore, the risk of the implant being pushed out of the vertebral body again immediately after insertion is minimized, for example through an open area due to a fracture or through a weakened wall of the vertebral body.

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The following description of a preferred embodiment of the implant, the implant system and a method for reconstructing an osteoporotic vertebral body serves to provide further explanation in conjunction with the drawing. They show:

Figure 1: a schematic representation of the insertion of an implant according to the invention with an insertion instrument into a fractured vertebral body of a spine;
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Figure 2: a schematic representation of a fractured vertebral body reconstructed with an implant according to the invention.

Figure 1 shows a section of a spinal column 10 of a human body. Between two intervertebral discs 12 and 14, a vertebral body 16 of a vertebra 18 has collapsed and partially broken on a ventral side 20 due to an osteoporotic change.

To rebuild the vertebral body 16, a cannula 24 is inserted transpedicularly, i.e. through an access opened in the pedicle 22, through a pedicle 22 of the vertebra 18, until a front end 26 of the cannula 24 has penetrated into an interior 17 in the vertebral body 16. The spine 10 can, but does not have to, be stretched through the cannula 24 during the insertion of an implant 30 consisting of a plurality of calcium phosphate beads 28, so that the intervertebral discs 12 and 14 adjacent to the vertebral body 16 to be treated are already stretched during the injection

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of the implant 30 assume their original position, essentially parallel to each other.

The injection or introduction of the implant consists in pushing the beads 28 through the cannula 24 in the direction of arrow A until they emerge from a lateral opening 34 in the area of the front end 26 of the cannula 24. The emergence is facilitated by a deflection surface 36 that is inclined or curved towards the opening 34. The beads 28 then fill cavities in the vertebral body 16. In particular, brittle bone tissue is displaced and compacted by the beads 28. By rotating the cannula 24, the beads 28 can be introduced into the interior 17 in different directions. Optimized filling of the interior 17 of the vertebral body 16 is achieved if the cannula 24 is rotated and slowly withdrawn while the beads 28 are being injected. In this way, the beads 28 can compactly fill the interior space 17 of the vertebral body 16, as shown in Figure 2.

After completion of the implantation, the implant 30 fills a portion of the vertebral body 16 and maintains it essentially in its original shape.

After successful implantation, the cannula 24 is removed from the vertebra 18 and the vertebral body 16 is closed by means of a suture or other means if necessary. It is also conceivable to close the access opened in the pedicle 22 with a plug made of a biocompatible material or with bone cement.

Claims (9)

1. Implant ( 30 ) for reconstructing a vertebral body ( 16 ) of a human spine ( 10 ) which is limited in its load-bearing capacity or has been broken, characterized in that the implant ( 30 ) consists of a plurality of body-compatible, edge-free implant elements ( 28 ) which can be individually introduced into an interior space ( 17 ) of the vertebral body ( 16 ). 2. Implant according to claim 1, characterized in that the implant elements ( 28 ) are substantially inelastic. 3. Implant according to one of the preceding claims, characterized in that the implant elements ( 28 ) have substantially the shape of a sphere. 4. Implant according to one of the preceding claims, characterized in that the implant elements ( 28 ) have a diameter in the range of 3 to 8 mm. 5. Implant according to one of the preceding claims, characterized in that the implant elements ( 28 ) are made of a hardened bone cement. 6. Implant according to claim 5, characterized in that the bone cement contains calcium phosphate (CaP). 7. Implant system comprising an implant ( 30 ) and an insertion device for inserting the implant ( 30 ) into an interior space ( 17 ) of a vertebral body ( 16 ), characterized in that the implant ( 30 ) is an implant ( 30 ) according to one of the preceding claims, that the insertion device comprises an insertion sleeve ( 24 ) insertable into the vertebral body ( 16 ) and that the insertion sleeve ( 24 ) has an inner cross section ( 32 ) which essentially corresponds to the outer dimensions of an implant element ( 28 ). 8. Implant system according to claim 7, characterized in that the introduction sleeve ( 24 ) has a circular inner cross-section ( 32 ) and that the inner cross-section ( 32 ) is a maximum of 10% larger than an outer diameter of an individual implant element ( 28 ). 9. Implant system according to one of claims 7 or 8, characterized in that the insertion sleeve ( 24 ) has at least one outlet opening ( 34 ) pointing in the radial direction at a distal end ( 26 ).