EP0683652A1

EP0683652A1 - Prosthesis shaft set

Info

Publication number: EP0683652A1
Application number: EP94915095A
Authority: EP
Inventors: R. Peter Huhle
Original assignee: DePuy Orthopaedie GmbH; MedTechControl GmbH
Current assignee: DePuy Orthopaedie GmbH; MedTechControl GmbH
Priority date: 1993-04-22
Filing date: 1994-04-22
Publication date: 1995-11-29
Also published as: DE4313201C2; WO1994024963A1; AU6647294A; DE4313201A1

Abstract

A prosthesis shaft set for cementing a prosthesis shaft (3) into bones, in particular in the case of hip endoprostheses, has a throughbore (13) which extends along the shaft (3) through which a removable guiding spike (5) is inserted. In order to position the prosthesis shaft (3), the guiding spike (5) can be detachably secured to a marrow cavity stopper (7) to be anchored in the bone. The throughbore (13) for the centering spike (5) is designed at the same time as a viscous bone cement supply channel (13) known per se. The cement outlet is arranged in a manner also known per se at the lower end of the cement supply channel (13). The distal end of the prosthesis shaft (3) with the cement outlet and the opposite proximal end of the marrow cavity stopper (7) are designed to ensure a uniform, all-round distribution of the cement and its uniform rise from the distal to the proximal end. In particular, the distal end of the prosthesis shaft (3) and the proximal end of the marrow cavity stopper (7) are designed to impart a twisting motion to the rising bone cement. For that purpose, the marrow cavity stopper (7) is provided at its proximal end with spiral guides (15) for the bone cement which leaves the distal end of the prosthesis shaft (3).

Description

DESCRIPTION

PROTHE S ENSCHAFT- ET

According to the preamble of claim 1, the invention relates to a

Prosthetic stem set for cementing the prosthetic stem in bones, especially for hip endoprostheses.

An example of such a prosthesis socket set has become known from EP-B 1 0331 623. In order to simplify the work for the operator when inserting and cementing the shaft in a central position, it is provided that the length of the cementing rod is at least twice the length of the shaft measured in the longitudinal axis and that the centering rod is detachably attached at one end to a rake lock is attachable. Regardless of whether the shaft is inserted into the bone before or after the bone cement, the surgeon should be able to keep the shaft centered at the distal end centered over its entire length or press it into the bone cement.

DE 3304476 A 1 also shows a hip joint prosthesis. This is provided for connection to a hollow bone nail and has a longitudinal recess in the longitudinal direction for the passage of a guide mandrel. When installed, this prosthesis is surrounded at its distal end by the bone nail, while its proximal end extends through the medullary canal. EP 434 604 A1 has already disclosed an anchoring shaft for a femoral head prosthesis (thigh prosthesis) which has a central feed channel for viscous bone cement. The shaft has lateral outlet openings for the bone cement in its distal end region, while the distal end of the bone cell supply channel is closed by a medullary plug provided with elastic centering flaps.

EP A 2 0129531 also shows a prosthesis socket provided with a centering plug at the lower end. This prosthetic socket should be made using the impression technique and thus be fitted into the bone.

A further example of a prosthesis to be cemented in a proximal bone cavity is shown in US Pat. No. 4,274,163. In this case, the prosthesis body is provided on the side with a detachably screwed-on connection coupling for a supply tube for bone cement and has a system of distribution channels for the bone cement in its interior, the some have lateral outlet openings and also a distal outlet opening above a medullary barrier.

According to this prior art, a screw clamp to be attached to the bone with a centering device for the prosthesis is used to hold the prosthesis body during the anchoring process.

Despite intensive work in the field of insert prostheses for bones, there is still room for improvement in terms of ease of handling during the operation and safety and durability of the anchoring of the prosthesis socket using the bone cement. The present invention has for its object to enable a cheap cementing of the prosthesis socket with uniform distribution of the bone cement during the insertion process.

Starting from a prosthesis socket set of the type initially assumed to be known, the solution to this problem is characterized in claim 1.

Such a design enables a particularly uniform cement distribution in a simple manner without requiring special attention from the surgeon for the cement distribution, and the prosthesis socket is reliably and permanently seated.

Claim 2 characterizes a particularly advantageous further development in that the distal end of the prosthesis socket and the proximal end of the medullary plug are designed to impart a swirl movement for the ascending bone cement.

Preferably, according to claim 3 (according to FIG. 2), the medullary plug is designed proximally with spiral guides for the bone cement emerging distally from the prosthesis socket.

The subclaims characterize advantageous refinements and developments of the invention.

ERSÄΓZBLAΓT (RULE 26) There follows an exemplary description of the invention with reference to drawings.

FIG. 1 a shows schematically a femur freed from the marrow (thigh bone) with a prosthesis shaft pre-positioned by means of a guide rod (without joint ball)

Figure lb shows the arrangement of Figure 1 after removal of the guide mandrel when pouring cement, which rises evenly from distal to proximal;

Figure lc shows the cemented prosthesis socket;

FIG. 2 shows the outer side view of a medullary plug which can be used in the arrangement according to FIGS. 1a-1c and which can be anchored in the bone with an expansion effect;

Figure 3 shows the inside view of the

Medullary plug with central threaded hole for the centering mandrel and spiral guides to communicate a swirl to the filled cement;

Figure 4 shows schematically the guide mandrel with screwed medullary plug and screwed handle (outside the bone);

FIG. 5 illustrates the anatomical shape of the prosthesis socket with an attached adapter for cement filling and a conical attachment for attaching a joint ball and a positioning claw to be driven into the bone at the top;

Figure 6 shows the positioning claw with

Through holes for the conical attachment and the cement adapter in top view; FIG. 7 shows the adapter for filling the cement in detail;

FIG. 8a schematically shows, in the ventral-dorsal viewing direction, the prosthesis socket anatomically adapted to the femoral cavity with the cement filling indicated centrally to the medullary plug;

FIG. 8b shows the arrangement according to FIG. 8a with a lateral viewing direction.

In the following description, the prosthesis socket set according to the present invention is described with regard to the attachment of an artificial hip joint ball, for the anchoring of which the prosthesis socket shown is used. The hip joint ball itself can be placed separately on a conical shoulder 1 (FIG. 5) of the prosthesis socket 3.

Figures la - lc illustrate schematically and also without depicting a hip joint ball (and also not the cone attachment) the pre-positioning of the prosthesis stem by means of a centering and guide mandrel 5 (screwed into a medullary plug 7), and the filling of Cement and its steady ascent from distal (away from the patient's body) to proximal (towards the patient's body).

The main problem areas in cement processing for attaching hip prosthesis stems and cementing them in are laminations, folds, blood-cement mixtures (PMMA bone cement) and air pockets. As a result of defective cementing technology, the mechanical strength of the bone-cement-prosthesis stem of the endoprosthesis can be drastically reduced. The normally processed PMMA bone cement is of relatively high viscosity so that the prosthesis socket pressed into the femur (thigh bone) does not change its position as far as possible, and at the same time the transfer of polymers into the bloodstream is reduced.

To achieve the desired steady ascent of the bone cement (Fig. Lb - lc) porthesis shaft 3, guide pin 5 and medullary plug 7 are coordinated as a prosthesis shaft set, this also a positioning claw 9 (Fig. 5) and expediently a cement filler adapter 11 has. The elements of the prosthesis socket set have the following design:

5 is adapted to the anatomical shape of the proximal femoral medullary canal in the manner illustrated in FIGS. 8a and 8b. On the basis of a larger number of measured femoral marrow spaces, an optimized shaft design was designed for different sizes, which is used for the purposes of the present invention. Such profile prosthesis stems are available from DePuy in 5 different sizes, each for right use and left use. They are designed for a gap of about 2 mm between the prosthesis socket and the rasped bone wall, which is then filled by the cement.

In the exemplary embodiment shown, the profile prosthesis socket is now provided with a through-bore 13 of 4 mm diameter, which on the one hand can accommodate the guide and centering mandrel 5, but also serves as a cement supply channel.

The through hole 13 of 4 mm inner diameter is provided at the end with a threaded hole for a 6 mm thread (M6), and has a length of about 6 mm. The threaded hole serves to screw in the corresponding M6 thread of the cement filling adapter shown in FIG. 7. Like the prosthesis shaft, the adapter has a 4 mm through hole for centering the guide mandrel 5. The positioning claw 11, which has a centering hole 21, ensures the position of the bone in a manner to be described in more detail below.

Instead of the cement filling adapter 11, an instrument for pulling out the prosthetic socket can also be screwed into the M6 thread. Da.- ^* , distal end 15 of the prosthesis socket has a rounded design that fits at a distance into the cavity of the medullary plug and acts aerodynamically with the design of the medullary plug 7 to be explained in more detail in the sense of the one illustrated in FIG. 1b uniform ascent of the cement from distal to proximal together.

The through hole 5 can also serve to pass a blood suction tube, not shown in detail. The graphic representation would correspond schematically to that of the centering and guide mandrel 5.

The medullary plug 7 has claw-like engagement grooves on the outside, which secure it with a wedge effect in the bone.

The distal end of the prosthesis shaft and the medullary plug 7 are matched to one another in the sense of a swirl design in order to give the cement emerging from the distal end of the prosthesis shaft a swirl which allows it to rise as evenly as possible around the prosthesis shaft, as in FIGS. lc illustrates.

Figure 3 illustrates the interior design of the medullary plug 7 with turbine blade-like spiral grooves or guides 15. In Fig. 4 you can see the pot-like design of the medullary plug 7. The arrangement advantageously comprises 6 or 9 spiral grooves. The number, depth and slope of the spiral grooves can be matched to the viscosity of the cement used, which is chosen to be low-viscosity. For an inexpensive cement injection process, the entry plane of the medullary plug and the distal end of the prosthesis shaft are approximately 5 mm apart

SPARE BLADES (RULE 26) positioned. A raised base 17 is provided in the central area of the medullary plug, which has a central M3 threaded hole for screwing in a threaded end of the centering and guide mandrel 5.

At the opposite end of the centering and guide mandrel 5, an opposing M4 thread is provided, onto which a handle 19 can be screwed, which allows the dome 5 to be unscrewed after the medullary plug 7 has been inserted into the bone.

The distal section of the prosthesis shaft, which forms the outlet end of the bone cement towards the medullary plug 7, can also be expanded and equipped with spiral-shaped spiral guides, for example 9 mm high, to communicate a swirl to the outflowing bone cement.

However, a smooth design of the outflow end of the prosthesis socket has also proven its worth, and such a smooth design is also advantageous in terms of cost, since the prosthesis socket generally has to be made from metallic alloy material.

The medullary plug, however, can be produced as a simple plastic pressed part, and therefore the spiral guides 15 are preferably provided in the medullary plug 7 in the manner illustrated in FIG. 3. Depending on the application, the pot part of the medullary plug can have a diameter of about 12 - 22 mm and, for example, without the thread, can be 12 mm deep.

In conjunction with a low-viscosity bone cement, the described design of the prosthesis socket and medullary plug allows the cement to rise uniformly, so that the previously problematic laminations, folds, blood-cement mixtures and Air pockets can be avoided. Cement injection can be accomplished in less than 60 seconds.

For the positioning process, the prosthesis shaft 3 is to be secured in its position on the femur by means of the positioning claw 9 shown in FIGS. 5 and 6. Such positioning claws 9 are expediently manufactured in dimensions corresponding to three different shaft sizes. At 19 the claw tips intended to be driven into the femur can be seen.

The positioning claw 9 has a bore 21 which is used for centering the cement filling adapter 11 and thus also centers the guide mandrel 5.

A plastic tube can also be inserted through the through hole of the cement filling adapter, through which the necessary flushing can be carried out.

The centering and guide mandrel is provided with a length marking (not shown in more detail) in order to be able to exactly determine the position of the medullary plug in the femoral canal. The positioning claw 9, together with the cement filling adapter temporarily screwed to it, ensures that the prosthesis shaft maintains its centered position in the femur, as it results after threading the prosthesis shaft on the mandrel 5 screwed to the medullary plug 7. After setting the optimal position of the prosthesis socket, the adapter 11 and the claw 9 at the proximal end of the prosthesis socket provide the necessary fixation.

The positioning claw 9 also seals against the leakage of bone cement and ensures compression of the cement, which is introduced, for example, at 8 bar. When the cement has hardened, the positioning claw is also removed. The cement guide adapter can be produced as a sterile single-use product made of polyurethane and can be added to the prosthesis socket set together with the medullary plug 7 and a positioning claw 9. The centering and guide mandrel can also be included in a uniform set or used several times.

Depending on requirements, the components explained in detail above can be supplied individually or in groups of several or all together as a set. What is essential is the coordination that takes place for cheap handling and a good cement flow. The described swirl design in the area of the medullary plug 7 and possibly the distal end of the shaft prosthesis is designed in accordance with the flow behavior of the bone cement selected in each case. Depending on the flow behavior of the selected bone cement, the desired uniform circumferential distribution of the bone cement emerging distally from the prosthesis socket can also be achieved without spiral guides, if such spiral guides, as shown in FIG. 3 at 15, have also proven to be particularly effective.

Claims

PATENT CLAIMS

1. prosthesis socket set for cementing the prosthesis socket into bone, in particular for hip endoprostheses, with a through hole running lengthwise in the shaft for inserting a removable guide mandrel, which can be detachably fastened in a medullary plug to be anchored in the bone for positioning the prosthesis socket, so that it is

that the through hole (13) for the centering mandrel (R) is at the same time designed as a feed channel for viscous bone cement which is known per se,

that the cement outlet opening, as is also known per se, is arranged at the lower end of the cement supply channel, and

that the distal end of the prosthesis shaft (3) with the cement outlet opening and the opposite proximal end of the medullary plug (7) for a swirl mediation for a uniform all-round distribution of the emerging cement and its uniform rise from distal to proximal are coordinated.

2. prosthesis socket set according to claim 1, characterized in that the distal end of the prosthesis socket and the proximal end of the medullary plug (7) are designed to impart a swirl movement for the ascending bone cement.

3. prosthesis socket set according to claim 2, d a d u r c h g e k e n n z e i c h n e t that the medullary plug proximally designed with spiral guides (15) for the bone cement emerging distally from the prosthesis socket.

4. prosthesis socket set according to claim 3, so that the area surrounding the cement outlet opening of the prosthesis socket has a design coordinated with the spiral guides (15) of the medullary plug for promoting the swirl movement of the bone cement.

5. prosthesis socket set according to claim 4, d a d u r c h g e k e n n e e c h n e t that the medullary plug is preferably designed as a proximally enlarged hollow cup with internal spiral guides (15).

6. prosthesis socket set according to claim 5, that the distal end of the prosthesis socket is rounded all around and fits with the surrounding distance into the hollow bowl of the medullary plug (7).

7. prosthesis stem set according to claim 5 or 6, g e k e n n z e i c h n e t d u r c h a raised in the central region floor (17) of the hollow cup of the medullary canal plug and a central screw thread hole (M3) for screwing in the distal end of the guide mandrel.

8. prosthesis socket set according to claim 7, that the proximal end of the guide mandrel (5) has an opposing thread (M4) for a handle (19)

HSH BUIT LEVEL "» for the screwing and unscrewing movement of the guide mandrel.

9. prosthesis socket set according to one or more of the preceding claims, characterized in that the proximal end of the through-hole (13) serving as a cement feed channel has a screw thread (M6) for temporarily connecting an adapter (11) for a cement gun or the like. having.

10. prosthesis socket set according to one or more of the preceding claims, characterized by a positioning claw (9) which can be removed in a manner known per se for driving in at the proximal end of the bone, and is provided with a centering through-opening (21) for the adapter (11) for the Cement supply, as well as a centering lateral passage opening for a proximal prosthesis socket attachment (1), which is used for attaching a joint ball or the like.

11. prosthetic stem set according to one or more of the preceding claims, g e k e n n z e i c h n e t d u r c h an anatomical shaft shaping according to an average femur for different femur size ranges.

12. prosthesis stem set according to claim 9 and 10, so that the bore of the cement supply adapter is also designed as a guide for the guide mandrel.

HEAT SHEET HEGEL 26)

13. prosthesis socket for a prosthesis socket set according to the characteristics of the prosthesis socket (3) according to one or more of the preceding claims.

14. medullary plug for a prosthesis socket set according to the characteristics of the medullary plug (7) according to one or more of the preceding claims.

15. Positioning claw for a prosthetic socket set according to the labeling features of

Positioning claw (9) according to patent claims 10 and 12.

16. Centering and guiding mandrel for a prosthesis socket set according to the characteristics of the centering and guiding mandrel (5) according to one or more of the preceding claims.