WO2001066045A1

WO2001066045A1 - Device for closing the medullary space of the femur used for endoprosthetic implants

Info

Publication number: WO2001066045A1
Application number: PCT/EP2000/002035
Authority: WO
Inventors: Klaus Wilhelm Alfred Otten
Original assignee: Coripharm Medizinprodukte Gmbh & Co. Kg
Priority date: 1998-12-18
Filing date: 2000-03-09
Publication date: 2001-09-13
Also published as: DE29822534U1

Abstract

The invention relates to a device (10) for closing the medullary space of the femur or of other tubular bones used in endoprosthetic implants. The inventive device is configured as an undersized plug element (12) that is introduced into the medullary space and that has a plug body (16). A plurality of lamellae (18) are joined to said plug body and are off-set from one another at an angle in the circumferential direction. The lamellae, which are retracted in the position of introduction, are associated with an expansion element (24) that has a shank (22) that can be axially retracted in a through bore (14) of the plug body (16) and with an expansion body (26) that is joined at the distal end of the plug body. In the initial position, said expansion body (26) is disposed in the area of the free ends of the lamellae. When the shank (22) is retracted into the through bore (14) of the plug body (24), the expansion body is drawn between the lamellae and radially expands them. A number of thin cover wings (36) are disposed on the plug body (16) radially off-set from one another in the circumferential direction between the expansible lamellae (18) of the expansion element (12). These cover wings widen outwardly in the shape of sectors and are swivelably disposed on the plug body (16) in a position in which the cover wings (36) are disposed above an associated space (30) between adjoining lamellae (18) of the plug element (12).

Description

Device for closing the medullary cavity of the _-emur during the implantation of endoprostheses

The invention relates to a device for closing the medullary canal of the femur - or other tubular bones - during the implantation of endoprostheses in the form of a plug element which can be inserted into the medullary canal and is undersized in relation to the medullary canal, consisting of a plug body on which a number of angularly offset in the circumferential direction In the insertion position, slats pointing essentially in the direction of the medullary canal are attached, to which an expansion element with a shaft axially retractable into a through hole in the stopper body and an expansion body attached to its end facing away from the stopper body and in the initial state lying in the region of the free ends of the slats is assigned , which at the puller. of the shaft is pulled into the through hole of the plug body between the lamellae and spreads them radially.

When implanting endoprostheses in the hip joint area of the femur of patients, a method has been used for years in which the anchoring part of the prosthesis is introduced into the medullary canal and fixed by first processing the medullary canal so that it is slightly larger than that in it part of the prosthesis to be recorded is worked out, whereupon bone cement is introduced and the prosthesis is inserted into the still plastic bone cement. After the bone cement has hardened, the endoprosthesis is firmly attached to the bone. by virtue of refined surgical techniques and improved mixing techniques for bone cement, this method has prevailed over the previously used cementless method. An improvement of this method was the introduction of the medullary occlusion when cementing the prosthesis. A stopper was initially placed in the medullary canal for a short time - usually about 2 cm - below the expected prosthesis tip. The purpose of this stopper is to stop the flow of the bone cement so that it cannot enter the medullary canal beyond the stopper. When using vacuum when applying bone cement, the stopper also acts as a filter, which prevents blood or marrow from penetrating into the upper part of the medullary canal. These stoppers were made from cancellous bone, collagen or plastics such as polymethyl methacrylate (PMMA) or polyethylene (PE). The disadvantage of this technique is that the plugs had a solid geometric shape, so that a large number of plugs of different sizes were required. In addition, the plugs could only be used to a limited extent if the placement site was below the narrowing of the medullary cavity. For this reason, devices of the type mentioned at the outset have been developed - in the parlance of orthopedic surgeons also referred to as medullary blockers (DE 44 39 049 C2) - which immediately attracted a great deal of interest, since they enable a considerable increase in diameter when placing in the medullary canal is, so that they can be used universally regardless of the individual dimensions of a certain medullary canal. It has been shown that, in particular when these expandable medullary space blockers are placed in medullary canals of relatively large diameter, in which a considerable increase in diameter is required for setting, the gaps between the lamellae which are radially swung open during spreading can reach such a size that a passage can occur from freshly prepared and still plastic bone cement is not completely excluded by this column. Next An increased consumption of bone cement can also mean that the full filling of the part of the medullary canal located in front of the medullary canal is not guaranteed in every case after the anchoring part of the prosthesis has been inserted, because when the prosthesis is inserted, bone cement is placed in the rear of the medullary canal - Blocker lying part of the medullary canal can be displaced. After the bone cement has hardened, the desired load-bearing capacity of the connection between the prosthesis and the bone is not achieved.

The invention has for its object to develop the known device so that even if, as a result of a relatively large diameter of the medullary canal, the lamellae must be pivoted to a considerable extent during the spreading process, no gaps allowing the passage of bone cement occur between the individual lamellae ,

Starting from a device of the type mentioned at the outset, this object is achieved according to the invention in that on the plug body of the plug element radially offset from one another in the circumferential direction, in one position, the number of interspaces between the expandable lamellae of the expansion element corresponds to the number of thin cover wings that widen outwards in the form of a sector are pivotally attached to the stopper body, in which the cover wings are each above an assigned space between the adjacent lamellae of the stopper element. The gaps created when the device according to the invention is spread out by spreading the lamellae are thus closed by the sector-shaped cover wings. The bone cement introduced into the medullary canal after placement of the device then presses the thin cover wings into abutment with the adjacent lamellae, so that an absolutely tight seal of the medullary canal is obtained. In a preferred development of the invention, the cover wings are arranged on a retaining ring which is arranged on the stopper body. The retaining ring and cover wing then form a separately produced sealing element that can be mounted on the plug body,

In order to ensure that the cover wings are still aligned in the intended sealing position relative to the lamellae after the device has been set, even in the case of complex manipulations during the setting process, it is advisable to arrange the retaining ring on the plug body so that it cannot twist.

Basically, it is conceivable to glue the mounting ring to the plug body. However, the dimensioning of the inside diameter of the mounting ring is preferably chosen essentially in accordance with the outside diameter of the cylindrical plug body, the anti-rotation securing of at least one groove in the mounting ring or the plug body running parallel to the longitudinal central axis of the through-bore in the cylindrical plug body and at least one assigned one from the outside cylindrical circumferential surface of the plug body or the inner cylindrical circumferential surface of the retaining ring, which protrudes and engages in the groove, can be formed. Alternatives to this anti-rotation device are, for example, configurations in which the stopper body has a polygonal cross section in the receiving area of the mounting ring and the mounting ring in turn has a complementary polygonal through opening.

In order to prevent the holder ring from being accidentally pushed off the plug body, it is advisable to arrange the holder ring with an at least slight press fit on the plug body. The retaining ring and the cover wings of the sealing element are preferably designed as an integral plastic injection-molded part, the same plastic being expediently used as is also used for the stopper body and the fins attached to it and the expansion body.

The invention is explained in more detail in the following description of an exemplary embodiment in conjunction with the drawing, which shows:

1 shows a device designed in the manner according to the invention for closing the medullary canal in the state of smallest diameter assumed in a medullary canal before insertion, the side view of the sealing element in the unassembled state at a distance above the plug body shown in the longitudinal central section is shown;

FIG. 2 shows a representation of the device according to the invention corresponding to the representation of FIG. 1 in the expanded state, the same also with

Distance above the plug body shown sealing element is also shown in the longitudinal center section;

Fig. 3 is a plan view of the device seen in the direction of arrow 3 in

Fig. 2; and

4 is a top view of the sealing element seen in the direction of arrow 4 in FIG. 2. The exemplary embodiment of a device according to the invention for closing the medullary cavity of the femur or another tubular bone shown in the drawing, designated in its entirety by 10, has a total of three parts.

The first or main part is a stopper element 12, which is formed by an essentially cylindrical stopper body 16 provided with a through hole 14, on the lower edge of which a number of staggered circumferentially offset one another, in the - in FIG Slats 18 essentially pointing into the interior of the medullary canal of the bone are integrally attached via in each case a thinner web 20 forming a film hinge. The front end of the shaft 22 of an expansion element 24 engages longitudinally displaceably in the through bore 14, and an enlarged diameter expansion body 26 is integrally attached to the lower end thereof facing away from the plug body, which in the insertion position (FIG. 1) is directly in front of the free ends of the lamellae 18 , If the shaft 22 is drawn into the through hole 14 by means of a suitable setting tool, the expansion body 26 penetrating into the space between the lamellae 18 forces the lamellae apart so that they are pivoted radially outwards until their free ends - e.g. from the wall of a medullary canal - be prevented from further pivoting.

In Fig. 2 the maximum possible pivoted position of the slats 18 is shown in the illustrated embodiment. It can be seen that the outer diameter of the expansion element 12 measured over the free ends of the lamellae 18 increases from dimension a in the insertion position (FIG. 1) to more than twice the dimension A (FIG. 2). The joints around which the slats 18 are pivoted radially upward during the expansion process are each formed by the thin webs 20 acting as film hinges, by means of which the slats 18 are integrally connected to the plug body 16.

The slats 18 themselves are made stiffer than the webs 20 due to a correspondingly increased wall thickness, but can still bend elastically. On the longitudinal edges of three of the six slats 18 in the exemplary embodiment shown, flaps 28 are still integrally attached on both sides, which during the initial expansion process of the slats cover the spaces between adjacent flapless slats. However, with increasing spreading, as can be seen in particular in FIG. 3, gaps 30 between the lamellae 18 that enlarge radially outward arise.

This column 30 is sealed by the third component of the device 10, namely the sealing element 32 shown separately in FIGS. 1 and 2 above the stopper element 12 and in FIG. 4 against the passage of still flowable bone cement. For this purpose, a small mounting ring 34 with a relatively small thickness, which radially outwardly extends from the ring in a sector-shaped manner, is provided on a low mounting ring 34, which corresponds essentially to the outside diameter of the plug body 16, and which, after the mounting of the Retaining ring 34 on the stopper body 16 in the position indicated by dash-dotted lines in FIGS. 1 and 2 covers the gaps 30 which arise between the lamellae 18 during the expansion. In order to ensure that the sealing element 32 is mounted in the correct covering position of the cover flaps 36 to the gaps 30 and that this alignment is not changed on the plug body 22 by subsequent manipulation - for example by turning the mounting ring 34. can change, on the outer cylindrical circumferential surface of the plug body 22 diametrically opposite two ribs running parallel to the longitudinal center axis of the through hole 14 are integrally attached, to which complementary corresponding longitudinal grooves 40 are assigned in the assigned inner circumferential surface of the mounting ring 34. The cooperating ribs 38 and longitudinal grooves 40 thus prevent rotation of the mounting ring 34 on the plug body 22 in such a way that the cover wings 36 are displaced from their intended cover position.

By means of a corresponding fit of the inside diameter of the mounting ring with a small undersize relative to the outside diameter of the plug body 22, the sealing element 32 is held after it is mounted on the plug body 16 with a press fit against being pushed off the plug body. The sealing element 32 is - like the plug element 12 and the expansion element 24 by injection molding - made of a suitable thermoplastic, e.g. Polyethylene.

Claims

Patent claims

1. Device (10) for closing the medullary cavity of the femur or other tubular bones when implanting

Endoprostheses in the form of a stopper element (12) which can be inserted into the medullary canal and is undersized compared to the medullary canal, consisting of a stopper body (16), on which a number of angularly offset in the insertion position essentially in

Slats (18) pointing in the direction of the medullary canal are attached, to which a spreading element (24) with a shaft (22) axially retractable into a through hole (14) in the plug body (16) and with an end attached to its end facing away from the plug body in the initial state in the area the free ends of the lamellae lying expansion body (26) is assigned, which is drawn when the shaft (22) is pulled into the through hole (14) of the plug body (16) between the lamellae (18) and spreads them radially, characterized in that on the plug body (16) radially offset from one another in the circumferential direction, a number of thin cover wings (36) corresponding to the number of spaces (30) between the expandable lamellae (18) of the expansion element (12) in a position on the plug body ( 16) are pivotally attached, in which the cover wings (36; each over an assigned space (30) stand between adjacent lamellae (18) of the plug element (12).

2. Device according to claim 1, characterized in that the cover wings (36) on a mounting ring (34) are arranged, which is arranged on the plug body (16).

3. Apparatus according to claim 2, characterized in that the retaining ring (34) on the plug body (16) is arranged secured against rotation.

4. The device according to claim 3, characterized in that the inner diameter of the retaining ring (34) substantially corresponds to the outer diameter of the cylindrical plug body (16), and that the rotation of at least one parallel to the longitudinal central axis of the through hole (14) in the plug body (16) extending groove (40) in the retaining ring (34) or the plug body (16) and at least one associated, emerging from the outer cylindrical peripheral surface of the plug body (16) or the inner cylindrical peripheral surface of the retaining ring (34) into the groove (40 ) engaging rib-like projection (38) is formed.

5. Device according to one of claims 2 to 4, characterized in that the mounting ring (34) is arranged with an at least slight press fit on the plug body (16).

6. Device according to one of claims 2 to 5, characterized in that the retaining ring (34) and the cover wings (36) of the sealing element (32) are designed as an integral plastic injection molded part.