DE19508647A1 - Implant for marrow cavity of hollow bone - Google Patents

Abstract

Marrow cavity of a hollow bone is closed off by an implant formed by a circular slotted disc (1), mfd. from an elastic and permanently deformable, bioresorbable, biocompatible material, pref. a copolymer of types poly(L-lactide-CO-D,L-lactide) 70:30 or poly(L-lactide-CO-E-caprolactone) 95:5. The material may also include up to 35 vol.% inorganic material, pref. selected from the gp. of tri-Ca phosphate, Ca diphosphate, rapidly resorbable glass ceramics or mixtures of these. Slots are pref. formed as three equal circular segments with an angle of 120 deg.

Description

The invention relates to an implant, in particular one in the medullary cavity of a tubular bone insertable medullary barrier. It serves the purpose change in the penetration of bone cement into unwanted areas of the Marrow cavity when using a cementable endoprosthesis.

For the artificial joint replacement, it is necessary to insert the sliding partner in the to anchor bony bearings. In the majority of cases, e.g. B. at Hip Ge steering implants in the Federal Republic of Germany with a share of approx. 70%, this anchoring takes place cohesively by inserting kno cements. In addition to the void-free distribution of the kno chenzementes between prosthesis and bone in a layer thickness between 3 and 5 mm must continue the bone cement in the Medullary cavity can be prevented. This is done through so-called marks Raumstopper or marrow block, which is firmly connected to the prosthesis can be or used individually, as plug-like parts.

In DE-OS 42 22 763 a medullary tract is described which consists of consists of a hollow body, the wall of which is at least partially porous and is elastic, viscoelastic or plastically deformable. Preferably points the hollow body has the shape of a hemisphere, but it can also have the shape a hollow sphere or an ellipsoid of revolution. The hollow body is pressed from resorbable thread material in the form of a felt. Around to cover the diameter range in question for medullary cavities, the hollow body has different external dimensions, preferably between 12 and 16 mm. In addition, the hollow body is deformable in hot water and can be better adapted to the medullary canal.

A technical solution in which the medullary barrier is firmly attached to the Prothe is connected in DE-OS 40 11 887 and DE-OS  39 37 786 indicated. The medullary block has various forms, e.g. B. that of a plug, a balloon shape or the shape of an umbrella mes. It is made from resorbable or non-resorbable ceramic Materials, metal, elastic plastic or porous material poses. It is at least during the cementing process with the Pro connected thesis end. In these cases, the medullary block is in its Applicability tailored to a specific cementable prosthesis.

A cylindrical medullary barrier, for integration into a drainage and Ventilation system is provided in the German utility model G 93 19 132.4. The medullary block has a system for this Slots and holes. At the same time, the medullary canal centers that End of the prosthesis shaft remote from the joint by means of a centering opening.

In EP 338 981 a plug-shaped medullary block is made of random packed, coil spring crimped thread pieces from a resor described polymeric material. The medullary barrier fits due to its elasticity, it adheres well to the contours of the medullary cavity permeable to air and thin liquids, but is impermeable to pasty bone cement. For this reason, the medullary block increases the quality of the hardened bone cement. The medullary block is frustoconically pressed and fixed in shape so that they are porous and ela remains structurally deformable.

As a medullary barrier, especially for tubes that expand inwards bone, serves a permanently deformed and elastically deformable rosette made of metal, as described in EP 220 427. The medullary barrier is so porous that it remains permeable to blood, fat and gases pasty bone cement, however, holds back. It stands out simple manufacture and is easy to position. Preferably the medullary block consists of a punched out of a wire mesh  Rosette of eight leaves that are continuous in width from the core increase. The rosette is permanently shaped like a goblet. The wire mesh consists of several layers for strength reasons. As Metals use titanium or titanium alloys.

There is also a mark for inward-expanding tubular bones Room lock, which is claimed for protection in EP 58 744. she consists from a deformable and expandable outer body, the jacket consists of a number of individual segments and a conical one Spreading body that is drawn into the outer body and thus its Spreading causes. Outer and expanding body are by in each other interlocking gears firmly connected. As a favorite Material for the two individual bodies are usually used in the Implant technology used body-friendly and body-stable Plastics, especially polyethylene of the specifications HDPE and UHMWPE. It is also envisaged that the individual body from one of the for To manufacture endoprostheses usual metals or metal alloys. With three Different sizes of medullary canal diameters between 10 shut off up to 35 mm.

Disadvantages of the prior art arise in the known technical solutions especially the complicated constructive design of the Medullary blockage and / or the use of non-absorbable, as a foreign body materials remaining in the organism and / or the requirement of several Devices graded in diameter for the practically occurring To have to use medullary cavity diameter. An elaborate con structural design goes hand in hand with a cost disadvantage, while the Use of non-absorbable materials especially for short-term Function of the medullary lock in the minute range appears unacceptable. A restriction of the use of the medullary barrier to certain Diameter ranges or medullary cavity shapes make handling difficult  through additional required fittings and decisions during the Surgery.

The object of the invention is to overcome the disadvantages of the prior art a simple and inexpensive constructive design of a medullary canal to avoid lock. By using only absorbable Biomaterials for the medullary canal should prevent the unwanted remaining Foreign bodies in the organism can be excluded. Due to the specifi The constructive design of the medullary barrier should be of one size practical requirements regarding the shape and size of marrow len are taken into account.

According to the invention, the task is accomplished by creating a bioresorbier solvable and elastic and permanently deformable implant solved, the ins is particularly suitable as a medullary barrier.

The implant according to the invention is a medullary block in the medullary cavity a tubular bone in connection with a cementable endoprosthesis can be used and prevents the ingress of bone cement unwanted areas of the marrow cavity. At the same time, it remains permeable to Air, blood and / or irrigation fluid.

To achieve this effect, the implant has the basic shape of a circular, slotted disc and consists of an elastic and permanently deformable, bioresorbable and biocompatible material.

The dimensions and internal geometry of the marrow cavity of long bones covers a relatively wide range of diameters. In addition, it has to make sure that the medullary cross-section has asymmetries that a require high flexibility of the medullary barrier.  

The medullary block according to the invention has the basic shape of a circular moderate, slotted disc caused by the overlap of each circle segments and the elastic properties of the material used a good adaptation to different market cavity diameters and Medullary cavity geometries allowed.

The use of a medullary block is limited to the time of the application of the bone cement until it hardens and lies in the Minute range. For this reason, the Im according to the invention implant made from a bioabsorbable, biocompatible material, preferred example from a copolymer of the types poly (L-lactide-co-D, L-lactide) 70:30 or poly (L-lactide-co-ε-caprolactone) 95: 5. This avoids that the Medullary block after fulfilling its function as a foreign body in the organ mus remains.

To modify the mechanical properties of the bioabsorbable biocompatible material advantageously also contains this bioabsorbable, inorganic materials up to a content of 35 Vol%. These bioabsorbable, inorganic materials come from preferably from the group of calcium phosphates and relate in particular re tricalcium phosphate, calcium diphosphate or rapidly absorbable glass ceramics according to PCT WO 91107357 or mixtures thereof.

A preferred embodiment of the circular, slotted disc consists of three equal circle segments with an angle of 120 °. It goes without saying that any other division of the disk is also possible possible. To cover the entire, practically relevant diameter range for The circular, slotted disc has painting over medullary caves a diameter d in the range of preferably 40 <d <70 mm. To one secure sealing and good elastic properties as well as sufficient To ensure adequate deformation stability, has the Invention  implant a thickness s of preferably 0.2 <s <0.6 mm. The Schlit ze in the circular, slotted disc have one disc diameter d of 70 mm a length l of 30 mm, but it can other dimensions may also be appropriate.

A preferred embodiment of the implant has circular segments, whose corners lying on the circumference of the pane are rounded. Your radius r is preferably in a range of 3 <r <6 mm. For better handling The implant is permanently deformed like a hollow cone and has one side a central receptacle for fixing a slide-in instrument set. The the center mount for fixing the slide-in instruments is before pulls formed by a raised ring, the outer diameter of which is the same or smaller than the diameter of an imaginary connecting circle of the end of the slots in the circular, slotted disc is. With hollow cone-like preforming of the implant is this receptacle for fixing the insertion instruments in the inner center of the hollow cone. The raised ring has a height h of preferably 0.5 <h <3 mm, which is generally sufficient stable fixation guaranteed.

Compared to the prior art, the invention is characterized by a simple constructive design and handling and thus allows a particularly inexpensive seal against intrusion the bone cement.

By using an elastic and permanently deformable bioresorbier good, biocompatible material arbitrary medullary cavity geometries reached, on the other hand remain Absorption of the medullary canal no foreign bodies in the organism. Prak All relevant requirements for a medullary canal can be met with the Embodiment according to the invention can be realized in one size.

In the following, the invention will be explained using several exemplary embodiments. of the drawings.

Fig. 1 shows schematically the medullary canal lock 1 according to the invention with slots 2 during the positioning in the medullary cavity 3 of a long bone. 4 It can be seen that the circular segments 5 overlap each other when inserted into the medullary cavity 3 .

In Fig. 2, a special embodiment of the Mar kraumsperre 1 according to the invention with slots 2 and receptacle 6 for fixing a plug-in instrument set is given.

Fig. 3 shows the medullary canal lock 1 according to the invention in a preferred embodiment with rounded corners 7 of the circle segments 5 as well as V-shaped slots 2 with rounded slot base.

Reference list

1 medullary block = circular, slotted disc
2 slots
3 marrow cave
4 long bones
5 circle segment
6 recording
7 Rounded corner of a segment of a circle

Claims (13)

1. Implant, in particular an intramedullary space barrier implantable in the medullary cavity of a long bone in connection with the use of a cementable endoprosthesis, characterized in that the implant has the basic shape of a circular, slotted disc ( 1 ) and consists of an elastically and permanently deformable, biore sorbable, biocompatible material. 2. Implant according to claim 1, characterized in that the elastic and permanently deformable, bioresorbable, biocompatible Material preferably uses a copolymer of the types Poly (L-lactide-co-D, L- lactide) 70:30 or poly (L-lactide-co-e-caprolactone) 95: 5. 3. Implant according to claim 1 and 2, characterized in that the elastic and permanently deformable, bioabsorbable, biokom compatible material additionally bioabsorbable inorganic, biocom contains compatible materials up to a content of 35 vol .-%. 4. Implant according to claim 3, characterized in that the bioabsorbable inorganic, biocompatible materials moves quickly from the group of tricalcium phosphate, calcium diphosphate resorbable glass ceramics according to PCT WO 91107357 or their Mixtures exist. 5. Implant according to claim 1 to 4, characterized in that the circular, slotted disc ( 1 ) preferably consists of three circle segments ( 5 ) of the same size with an angle α of 120 ° and the diameter d in the range of 40 <d <70 mm and has a thickness s in the range of 0.2 <s <0.6 mm. 6. Implant according to claim 1 to 5, characterized in that the slots ( 2 ) in the circular, slotted disc ( 1 ) have a length l in the range of 15 <l <30 mm. 7. Implant according to claim 1 to 6, characterized in that the slots ( 2 ) in the circular, slotted disc ( 1 ) in the Rich direction of the disc edge expanded V-shaped and rounded in the slot base. 8. Implant according to claim 1 to 7, characterized in that the on the circumference of the circular, slotted disc ( 1 ) lying corners ( 7 ) of the circular segments ( 5 ) are preferably rounded. 9. Implant according to claim 8, characterized in that the radius r of the on the circumference of the circular, slotted disc ( 1 ) lying, rounded corners ( 7 ) of the circular segments ( 5 ) is in the range of 3 <r <6 mm. 10. Implant according to claim 1 to 9, characterized in that the circular, slotted disc ( 1 ) is permanently shaped like a hollow cone and the cone shell includes an angle in the range of preferably 90 <α <180 °. 11. Implant according to claim 1 to 10, characterized in that the circular, slotted disc ( 1 ) has a receptacle ( 6 ) in the center for fixing an insertion instrument. 12. Implant according to claim 11, characterized in that the receptacle ( 6 ) for fixing the insertion instruments is designed as a raised ring on one side with an outer diameter equal to or smaller than the diameter of the connecting circle of the ends of the slots ( 2 ) directed towards the center of the disc. 13. Implant according to claim 10, 11 and 12, characterized in that the receptacle ( 6 ) for fixing the insertion instruments lies in the inner center of the hollow cone.