DE19508647C2 - Medullary block - Google Patents

Description

The invention relates to a medullary barrier, in particular one in the Intramedullary cavity of a tubular bone. she serves preventing bone cement from entering undesirable Areas of the marrow cavity when using a cementable endoprosthesis se.

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 introducing Bone cements. In addition to a void-free distribution of the Bone cement between the prosthesis and bone in a layer thickness between 3 and 5 mm the bone cement must continue to run into the Medullary cavity can be prevented. This is done by so-called Medullary space stop or medullary block, which is firmly connected to the prosthesis can be used individually or as plug-like parts.

DE 42 22 763 A1 describes a medullary block that consists of consists of a hollow body, the wall of which is at least partially porous and is elastic, viscoelastic or plastically deformable. Preferably, the Hollow body in the shape of a hemisphere, but it can also have the shape of a Have hollow sphere or an ellipsoid of revolution. The hollow body will made of resorbable thread material in the form of a felt. To the in Covering the coming diameter range for marrow cavities  the hollow body has different external dimensions, preferably between 12 and l6 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 block is firmly attached to the prosthesis shaft is connected, is in DE 40 11 887 A1 and DE 39 37 786 A1 specified. The medullary barrier has various forms, e.g. B. the of a plug, a balloon shape or the shape of an umbrella. she is made of resorbable or non-resorbable ceramic materials, Made of metal, elastic plastic or porous material. she is at least during the cementing process with the end of the prosthesis connected. In these cases, the medullary block is applicable 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 DE 93 19 132 U1 described. 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 A1 a plug-shaped medullary block made of irregular packed, coil spring-like crimped thread pieces from a resorbier baren, polymeric material described. 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 it is porous and elastic remains 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 A1. 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. Preferred meadow 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 may consist of several layers for manufacturing reasons. As Metals use titanium or titanium alloys.

There is also one for inward expanding bones Medullary block, for which protection is claimed in EP 58 744 A1. she consists of a deformable and expandable outer body, the Jacket consists of a number of individual segments and one conical expansion body that is drawn into the outer body and so its spreading causes. The outer and expansion bodies are joined together other gear teeth 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 can be found between 10 to Shut off 35 mm.

According to the patent specification EP 0 487 433 B1 is a partially cemented Femurpro these are known which have an asymmetrical sealing or  Collection device for bone cement made of elastic, bioabsorbable Has material.

Disadvantages of the prior art arise in the known techni solutions above all 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 construct tive design goes hand in hand with a cost disadvantage during use of non-absorbable materials especially for short-term function the medullary lock in the minute range appears unacceptable. A Restriction of the use of the medullary canal to certain diameters Areas or marrow cavity shapes make handling difficult additional necessary fittings and decisions during the opera tion.

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 resorbable biomas materials for the medullary block should prevent the undesired remaining of Foreign bodies in the organism can be excluded. By the specific constructive design of the medullary barrier should be of one size all practical requirements regarding the shape and size of marrow len are taken into account.

According to the invention the object is achieved by creating a bioresorbier removable, elastic and permanently deformable medullary space barrier. The medullary block according to the invention is in the medullary cavity of a tube can be used in conjunction with a cementable endoprosthesis  and prevents bone cement from entering unwanted areas surface of the medullary cavity. At the same time, it remains permeable to air, blood and / or Rinsing liquid.

The medullary block has the basic form to achieve this effect 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 should be noted 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 Circular segments and the elastic properties of the material used fes 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 implant according to the invention exists made from a bioabsorbable, biocompatible material, preferably 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 The biocompatible material advantageously also contains biore sorbable, inorganic materials up to a content of 35% by volume.  

These bioresorbable, inorganic materials preferably originate from the group of calcium phosphates and particularly concern Tricalci umphosphate, calcium diphosphate or rapidly absorbable glass ceramics according to PCT WO 91/07357 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 correct deformation stability, has the invention The medullary space barrier has a thickness s of preferably 0.2 <s <0.6 mm. The slit in the circular, slotted disc showed one disc through knife d of 70 mm a length l of 30 mm, but it can also other dimensions may be appropriate.

A preferred embodiment of the medullary block has circular segments te, the corners of which are rounded on the circumference of the pane. you Radius r is preferably in a range of 3 <r <6 mm. For better The medullary canal is permanently deformed and shaped like a hollow cone has a central receptacle on one side for fixing an insert mentariums. The central receptacle for fixing the insertion instruments um is preferably formed by a raised ring, the Outside diameter is equal to or smaller than the diameter of a roof th connecting circle of the end directed towards the center of the pane Slots in the circular, slotted disc. With hollow cone-like Preforming the medullary canal is this fixation fixation of 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 in generally ensures a sufficiently stable fixation.

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. Practically all relevant requirements for a medullary canal can be met with the embodiment of the invention can be realized in one size.

In the following, the invention is illustrated using several exemplary embodiments. of the drawings.

Fig. 1 shows schematically the medullary block 1 according to the invention with Schlit zen 2 during the positioning process in the medullary cavity 3 of a tube 4. It can be seen that the circular segments 5 overlap each other when inserted into the medullary cavity 3 .

FIG. 2 shows a special embodiment of the medullary space barrier 1 according to the invention with slots 2 and receptacle 6 for fixing an insertion instrument set.

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 blockage = circular, slotted disc

2nd

Slits

3rd

Marrow cave

4th

Long bones

5

Circle segment

6

admission

7

Rounded corner of a segment of a circle

Claims (13)

1. marrow block, in particular in the marrow cavity of an implantable marrow block, consisting of a permeable elastic rule's body as a metal rosette, characterized in that it has the basic shape of a circular, slotted disc ( 1 ) and from an elastically and permanently deformable, bioresorbable , biocompatible material. 2. marrow block according to claim 1, characterized in that the elastic and permanently deformable, bioresorbable, biocompatible Material preferably a copolymer of the types poly (L-lactide-co-D, L-lactide) 70:30 or poly (L-lactide-co-e-ca-prolactone) 95: 5. 3. marrow block according to claim 1 or 2, characterized in that the elastic and permanently deformable, bioresorbable, biocompatible Material additionally bioabsorbable inorganic, biocompatible materia contains up to a content of 35% by volume. 4. marrow block according to claim 3, characterized in that the bioresorbable inorganic, biocompatible materials preferably from the group tricalcium phosphate, calcium diphosphate,  rapidly resorbable glass ceramics according to PCT WO 91/07357 or their Mixtures exist. 5. medullary block according to one of claims 1 to 4, characterized in that the circular, slotted disc ( 1 ) preferably consists of three circle segments of the same size ( 5 ) with an angle α of 120 ° and a diameter d in the range of 40 < d <70 mm and a thickness s in the range of 0.2 <s <0.6 mm. 6. marrow block according to one of claims 1 to 5, characterized in that the slots ( 2 ) in the circular, slotted disc ( 1 ) have a length l in the range of 15 <1 <30 mm. 7. medullary space barrier according to one of claims 1 to 6, characterized in that the slots ( 2 ) in the circular, slotted disc ( 1 ) in the direction of the disc edge V-shaped and rounded in the slot base. 8. medullary space barrier according to one of claims 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. marrow block according to claim 8, characterized in that the radius r of the circumferential 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. medullary barrier according to one of claims 1 to 8, characterized in that the circular, slotted disc ( 1 ) is permanently deformed and the cone shell encloses an angle in the range of preferably 90 <a <180 °. 11. medullary block according to one of claims 1 to 10, characterized in that the circular, slotted disc ( 1 ) has a receptacle ( 6 ) in the center for fixing an insertion instrument. 12. marrow block 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. marrow block according to claim 11 or 12, characterized in that the receptacle ( 6 ) for fixing the insertion instruments is in the inner center of the hollow cone.