DE8713071U1 - Endoprosthesis for replacing human joints, in particular knee endoprosthesis - Google Patents

Description

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The invention relates to an endoprosthesis for replacing A

human joints, especially knee endoprostheses, |

with at least one fixation pin which has a |

Longitudinal axis of the fixation pin coaxial or f

parallel to the free end of the pin f

has an open pin channel I

Known endoprostheses of this type are provided with at least one, usually several, fixation pins made of metal or plastic for anchoring in the bone. The surface of the fixation pins is sometimes smooth, but mostly roughened or even provided with ribs or similar profiles. This non-smooth shape is used in particular when the prosthesis is inserted without cement, so that regrowing bone can form a positive connection with the fixation pin and its hold is improved.

Since the insertion of such a prosthesis, for example |

way of a knee joint endoprosthesis, a |

operative intervention, the lead- §

A firm fit of the endoprosthesis is an enormous

interpretation. The permanent, firm anchoring of the &ngr;

Fixation pins in the bone are for long-term k

trouble-free function of the prosthesis from rash- |

of importance. The strength with which the '; known fixation pins are held in place either by cement or by regrowing cancellous bone,

However, this is limited in the case of known endoprostheses/ since the cement or the spongiosa can only lie flat against the wall of the fixation pins or grow onto it.

The object of the invention is therefore to create an endoprosthesis of the type mentioned above which allows a safer and more permanent fixation to the bone both in the case of cemented and cementless implantation.

To achieve this object, the endoprosthesis of the type mentioned at the outset has, according to the invention, the features of claim 1.

Advantageous embodiments define the subclaims.

A significant advantage of the endoprosthesis according to the invention results from the fact that bone cement (when cemented in) or regrowing bone substance (when cementless insertion) can penetrate into the interior of the fixation pin and reconnect with the external bone cement or spongiosa through the openings, so that bridges extending through the wall are created between the cement or the bone inside and outside the wall of the fixation pin. This growth around and in particular through the fixation pin by bone substance results in a maximum of stable anchoring; the same applies to insertion with bone cement.

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Furthermore, the presence of the pin channel allows the fixation pin to be filled with spongiosa on the inside when cementless is used, either by filling the pin channel with spongiosa mass before inserting the endoprosthesis or by making a ring hole with a cylinder that remains in the middle using a hollow chisel and then pushing the tube-like fixation pin over the cylinder. With a pin channel that is open at both ends, the spongiosa mass can be pressed into the pin channel from the outside even after implantation, which ensures that the pin channel is completely filled with spongiosa mass. It is obvious that in both cases, healing can be much faster and more solid.

An alternative use of the pin channel, which does not necessarily exclude ingrowth in the manner described, is when the pin channel extends coaxially or parallel to the longitudinal axis of the fixation pin and opens into an opening at both axial ends of the fixation pin. Then a screw can be screwed from the outside of the prosthesis through the pin channel into the bone underneath, which immediately creates and strengthens the connection between the prosthesis and the bone. To accommodate the screw head in a countersunk manner, the corresponding opening in the outer surface of the prosthesis is advantageously provided with a chamfer.

jjs Preferably, the openings in the wall of the fixation pin are designed as through holes? However, they can also have a different shape and be designed differently from one another.

I The wall of the fixation pin can be removed from the free

1 End in a blunt front edge or abor

I a sharp-edged, serrated or wavy

I Form front edge.

; The fixation pin is preferably

I cylindrical shape.

In the following, a preferred embodiment

&xgr; of the endoprosthesis using the example of an inventive

I knee endoprosthesis based on the attached

f Schematic drawing explains in more detail. Shown are:

Fig. 1 a knee endoprosthesis in front view with bent knee and

Fig. 2 the prosthesis according to Fig. 1 in 90°

! rotated side view with

. straight knee.

1 The endoprosthesis 10 shown in the figures comprises

1 ·&idigr;&eegr; femoral prosthesis part 16 and a tibial pro-

|. thesis part 18, which together form an artificial knee

The femoral prosthesis part 16 is attached to the thigh bone 12, the tibial prosthesis part 18 to the lower thigh bone 14 after the knee joint surfaces have been removed and the bones have been prepared accordingly.

The femoral prosthesis part 16 is made of metal. The tibial prosthesis part 18 facing the bone consists of a metal disk 19a, on which a plastic support 19b is attached, which forms the support for the tibial prosthesis part 18. Both prosthesis parts 16, 18 are provided with metal fixation pins 20, 22 and 24, 26, 28 on the bone side. These are inserted into prepared holes within the bone when the respective prosthesis part is inserted, whereby bone cement can optionally be used.

The fixation pins 20 to 28 are designed like a tube with an inner axial pin channel 30. In the embodiment, the pin channels 30 of all fixation pins 20 to 28 open at the free end of the respective fixation pin facing the bone in an opening 34, which is enclosed by a front edge of the wall of the fixation pin 20 to 28.

The pin channels 30 of the fixation pins 24, 26 of the tibial prosthetic part 18 also open into an opening 36 in the prosthetic part 18, which extends the pin channel to the outer surface of the prosthetic part 18. As shown in particular in Fig. 2, a bone screw 40 can be screwed into the lower leg bone through the opening 36 and the pin channel 30. A depression in the area of the opening 36, which is formed by a bevel 38, receives the screw head so that it does not

protrudes beyond the outer surface of the tibial prosthetic component.

In the exemplary embodiment, the walls of all fixation pins 20 to 28 are penetrated by openings, which are distributed in the form of a large number of holes over the wall surfaces of each fixation pin. These holes allow the regrowing bone substance or the bone cement to form bridges through the wall of the fixation pin 20 to 28, which fix it firmly and immovably in its position.

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Claims (5)

Dr. med. Mohammed Izadpanah, Falkenveg 54, 2945 Sande Endoprosthesis for replacing human joints, in particular knee endoprosthesis A &eegr; sayings 1* Endoprosthesis for replacing human joints, in particular knee endoprosthesis, with at least one fixation pin, which has a pin channel running coaxially or parallel to the longitudinal axis of the fixation pin (20 - 28) and open to the free end of the pin, characterized in that the wall of the fixation pin (20 - 28) is penetrated by several openings (32). 2. Endoprosthesis according to claim 1/ WWR/WM/em Martifllstrasse 24 Telefari'. *"',,'leleicjpTerer"'·; Telex Datex'P O.28ÖÖ Bremen I 0421-Ü;80;i7 · 0.42}-{32!68!34 } 244020 fepatcl 44421040311 characterized in that the openings (32) are designed as through holes. 3. Endoprosthesis according to claim 1 or 2, characterized in that the wall at the free end of the fixation pin (20 - 28) has a sharp or toothed or corrugated front edge. 4. Endoprosthesis according to one of claims 1 to 3, characterized in that the pin channel (30) has an opening (34, 36) at both axial ends. 5. Endoprosthesis according to one of claims 1 to 4, characterized in that the fixation pin (20 - 28) is cylindrical.