DE4204979A1 - Hip joint prosthesis with damping device - is formed with stack of disc springs inserted in hole in ball for neck prosthesis. - Google Patents

Abstract

The prosthesis is fitted with a damping device which consists of a stack of disc springs (8). These are fitted in the chamber (5) formed between the end face of the neck (2) and the floor (6) of the blind hole and damp out any shock loads in the axial direction. The dia. of each disc spring is such that when compressed flat the OD is smaller than the dia. of the hole (4) in the ball (1). The neck has a self lubricating cover (10) along its length. USE/ADVANTAGE - The disc springs in the hip joint prosthesis are less susceptible to fatigue failure than the helical coil springs which are usually fitted.

Description

The invention relates to a joint prosthesis, in particular Hip prosthesis, with one implan in a bone animal prosthesis socket, which at its free end wears a prosthetic neck on which one with the Pro assigned to the thesis neck, preferably as a blind bore trained bore provided, preferably as a Ge Steering ball-shaped joint part under the intermediate scarf device of a damping device in the axial direction is slidably receivable.  

A joint prosthesis of this type is, for example, from the DE 38 02 213 A1 known. In this known arrangement is the damping device as the prosthesis neck over gripping, elastic cap formed from elasti chemical material or by a liquid containing gas mixture in several chambers shared container can be formed. Arrangements of this Kind, however, are not variable enough as to their adaptations ability to cope with different applications, esp in particular to different body weights of the prostheses sluggish, concerned. It also requires the well-known arrangement a comparatively large bore diameter as well as a complicated bore geometry with rear cuts, which adversely affects the achievable Strength and durability can impact. Except it is to be feared that with orders lying type also in the area of the damping device not the desired robustness and long-term security can be achieved. In this context it is namely assume that the known damping device at Wear or is completely unusable in the event of a leak and needs to be replaced. The service life of an implan However, the joint prosthesis is intended to be damped direction not limited, but rather increased the. It is therefore important that the damping direction works over a long service life remains.

There are also arrangements of the type mentioned at the beginning have been proposed in which the damping device is designed as a gas spring. These are in the sack hole  two chambers connected by valves, one of which is formed by a piston like a piston the prosthesis neck is limited. The realization however, this proposal would be too comparative lead complicated and elaborate constructions. In addition, this would also result in a high space and Parts requirements, since not only a comparatively large one Volume of gas would be required, but also one Biasing of the gas should be present. Besides, is to fear that certain leaks will not persist avoided. The consequences of this would already be with Partial leakage distance changes and a negative impact effect.

Another proposal aims to be the damping direction as screw pressure encompassing the prosthesis neck train spring. Orders of this kind also prove however, prove to be not variable and safe enough. In this connection it can be assumed that at given spring length only with the help of different Different spring forces would be reachable the. There would have to be a large number of different ones Feathers are ready. It also requires one Helical compression spring a certain minimum spring length what has an adverse effect on the space requirement. Furthermore would also result from the fact that it includes the prosthesis neck send arrangement of the helical compression spring a ver equally large bore diameter. Another The disadvantage is that helical compression springs after a certain number of load changes  are at risk and in the event of a spring break their parts could lead to complications.

Based on this, it is therefore the task of the present the invention, a joint prosthesis of the generic type while avoiding the disadvantages of the known arrangements to improve so that despite simple, inexpensive and compact design, high variability and safety are guaranteed.

This task is there in a surprisingly simple way solved by that the damping device as between Support surfaces inlaid on the shaft and joint part Disc spring arrangement is formed.

Disc springs are advantageously available as standard Liche articles available, which means low production costs guaranteed. Also based on past experience assume that disc springs even with robust loading load ratios a practically unlimited life have duration. Apart from that, it would also remain untrue in the event of a break, some kung available. Another advantage of the invention Measures can be seen in the fact that a Tellerfe accommodate the package in a comparatively small space lets and that with the help of a comparatively compact Disc spring pack comparatively high spring forces are producible or recordable, which is generally favorable affects the space requirement. Another very special one rer advantage of the measures according to the invention is to see that with one and the same Belleville spring  disc spring packages with different spring characteristics teristik can be put together. It is therefore with simple means possible, the spring characteristic to the Ratios of the individual case, for example to the body per weight of the prosthesis wearer to adjust without different spring elements would be needed. Rather leaves this is done simply by different layering and reach the same spring element. It therefore follows also a very simple and inexpensive stock tung. Another advantage is that Tel ler spring elements, if necessary, in a simple manner with a protective coating, for example for prevention a rejection reaction can be provided and the This protective coating does not affect the suspension properties flows and is not influenced by this itself.

Advantageous configurations and practical training General measures are in the subclaims Chen specified. So the plate spring arrangement according to a particularly preferable advanced training of the ordered measures appropriately between the front of the Prosthesis neck and the reason opposite this the blind hole must be inserted. An arrangement of this kind is not only suitable for Initial applications, but also for simple retrofitting of all existing joint prostheses where one Joint part is attached to a prosthesis neck. In addition there is practically one in the aforementioned training closed chamber for receiving the Disc spring arrangement so that it is practical with tissue does not come into contact with any of them  Can lead to rejection. It also does this ensured that even in the most unlikely In the event of a spring break, no spring parts can escape nen. Another advantage is that the Prosthetic neck and the blind bore cylindrical Shell surfaces can have what the manufacture facilitated.

Another advantageous measure can consist in that the diameter of the elements of the plate spring assembly at least by its radial extent smaller than that Diameter of the blind hole in the disc spring arrangement assigned section. This will secure provides that constraining forces are reliably avoided.

In further training the higher-level measures can the prosthesis neck on the circumference with an elastic Be surrounded by the coat. This allows a certain Carry out damping in the radial direction. It can also in this context a material with self-smear what properties are used if advantageous, to achieve a long service life can impact.

Further advantageous configurations and expedient There are further training courses for the higher-level measures from the remaining subclaims in connection with the following example description.

The following is a particularly preferred embodiment example of the invention with reference to the drawing tert.

The drawing shows:

Fig. 1 joint prosthesis a joint head of a hip according to the invention, partly in section,

Fig. 2, the spring characteristic of disc spring packet with the same direction stratification,

Fig. 3, Fig. 2 underlying plate spring packet,

Fig. 4 shows the spring characteristic of a plate spring assembly with opposite stratification and

Fig. 5, Fig. 4 packet underlying plate spring.

The articulated head of FIG. 1 of a Hivelge prosthesis consists of a joint part, here in the form of an acetabular cup engaging in the implanted state in a hip socket (not shown in more detail ) , which is on a coaxial to the hip or slightly inclined here towards a prosthetic neck 2 in the thigh bone a prosthesis wearer implantable shaft 3 is added. The prosthesis neck 2 can be molded onto the shaft 3 or fastened thereon. The joint ball 1 is slidably received in the direction of the axis of the prosthesis neck 2 on this. The joint ball 1 is accordingly provided with a blind hole 4 assigned to the prosthesis neck 2 , into which the prosthesis neck 2 engages with a sliding fit. The body's own liquid automatically lubricates the seats.

The depth of the blind hole 4 is greater than the engagement length of the prosthesis neck 2, so that a closed from the prosthesis neck 2 chamber 5 results in, on the one hand by the bottom 6 of the blind hole 4, and the other is hand, limited by the end 7 of the prosthesis neck. 2 In the chamber 5 , a plate spring assembly 8 is inserted, which rests on the one hand on the bottom 6 of the blind bore 4 and on the other hand on the end face 7 of the prosthesis neck 2 and accordingly has a support on the joint ball side and on the shaft side. The plate spring assembly 8 functions as a damping device for damping the shocks occurring during the physiological movement sequence.

The diameter of the blind bore has in the area of the plate spring assembly 8 receiving chamber 5 compared to the diameter of the plate spring assembly 8 Tel lerfederelemente 9 slight oversize. This is in the range of loading the disc spring assembly 8, resulting radial diameter enlargement of the Tellerfe derelemente 9th Therefore, even in the event of a load, these do not run against the wall of the blind bore on the circumference, so that there are no constraining forces. Since the plate spring assembly 8 rests on the end face 7 of the prosthesis neck 2 , this does not require a support collar. The same applies to the support of the plate spring assembly 6 by the bottom 7 of the blind hole 4 , which thus also does not require a support collar. The prosthesis neck 2 can accordingly be formed on its entire, at the rounded, shaft-side connection area to the subsequent length as a cylinder pin with the same length over the entire length. Likewise, the blind bore 4 can be designed as a cylinder bore having the same diameter over its entire depth, so that overall a very simple manufacture results and at the same time the generation of notch stresses is prevented.

The chamber 5 receiving the plate spring assembly 8 is hermetically sealed by the prosthesis neck 2 . The plate spring elements 9 therefore do not come into contact with the tissue surrounding the prosthesis, so that even when using inexpensive steel material to form the plate spring elements 8, no repulsion reaction is to be feared. But it would also be easily conceivable to coat the plate spring elements 9 with human-compatible material or to produce steel from repellent-proof stainless steel. As a result of the reliable closure of the chamber 5, it is also ensured that no fragments can escape from the chamber 5 even in the event of a highly unlikely spring break.

The liquid that is automatically present in the body is sufficient to lubricate the seating surfaces between the prosthesis neck 2 and the blind bore 4 . To improve the sliding properties, the prosthesis neck 2 and / or the blind bore 4 can be provided with a sliding coating. In the example shown, the prosthesis neck 2 is provided with a jacket-like cover 10 for this purpose. This can consist of a self-lubricating, human-compatible material, for example a suitable plastic material. Accordingly, the cover 10 simultaneously forms an elastic jacket, which allows a certain amount of suspension in the radial direction.

The inserted in the chamber 5 plate spring assembly 8 can be composed of several identical plate spring elements 9 . To achieve different Federcharak teristiken and thus to adjust the spring properties, for example to the body weight of the prosthesis wearer, different layers of the Tel lerfederelemente 9 are easy to use.

In the case of a stratification of the plate spring elements 9 in the same direction, the spring force is proportional to the number of plate spring elements 9 for a given spring travel, as can be seen from FIG. 2. The curve 11 denotes the spring characteristic of a single Tellerfe derelements 9th Curve 12 denotes the spring characteristic of a plate spring assembly 12 a indicated in FIG. 3 with two liner spring elements stacked in the same direction Tel. With the same travel s there is twice the spring force F.

With alternating stringing of the plate spring elements 9 , as is shown in FIG. 1, the spring travel is proportional to the number of plate spring elements present, as shown in FIG . Curve 11 corresponds here again to the spring characteristic of a single plate spring element 9 . The curve 13 corresponds to the spring characteristic of a plate spring assembly 13 a indicated in FIG. 5 with four plate spring elements arranged in alternating rows. For a given spring force F, the achievable spring travel s in the case of curve 13 is four times as large as in the case of curve 11 .

The types of stratification described above can also be combined with one another. Spring packs can be strung together with increasing or decreasing number of individual spring elements. As a result, practically any desired shape of a total spring characteristic, for example progressive or degressive, rose. Nevertheless, the individual Tellerfe derelemente 9 can be the same with each other, so that you can get by practically with a kind of plate spring element. Of course, it would also be conceivable to combine disc spring elements of different thicknesses in order to obtain the desired spring characteristic.

Above is a preferred embodiment the invention explained in more detail, but without hereby a restriction is said to be associated. So it would be with for example also possible without further ado measures as part of a knee prosthesis put.

Claims (10)

1. joint prosthesis, in particular hip joint prosthesis, with a prosthesis shaft ( 3 ) which can be implanted in a bone and which carries at its free end a prosthesis neck ( 2 ) on which a prosthesis neck ( 2 ) is assigned, preferably a blind bore ( 4 ) Bore provided, preferably designed as a joint ball ( 1 ) Ge steering part with the interposition of a damping device is displaceable in the axial direction on, characterized in that the damping device is designed as a disc spring arrangement inserted between the shaft-side and the steering-part-side support surfaces ( 8 ). 2. Joint prosthesis according to claim 1, characterized in that the plate spring arrangement ( 8 ) between the end face ( 7 ) of the prosthesis neck ( 2 ) and the opposite base ( 6 ) of the blind bore ( 4 ) is inserted. 3. Articular prosthesis according to one of the preceding claims, characterized in that the diameter of the plate spring arrangement ( 8 ) forming plate spring elements ( 9 ) is at least smaller by its radial diameter than the diameter of the blind bore ( 4 ) in the plate spring arrangement ( 8 ) assigned section. 4. Articular prosthesis according to one of the preceding claims, characterized in that the diameter of the blind bore ( 4 ) is the same over its entire length. 5. Joint prosthesis according to one of the preceding Ansprü surface, characterized in that the diameter of the prosthesis neck (2), which engages with a sliding fit in the blind bore (4), over its entire length is the same. 6. Articular prosthesis according to one of the preceding claims, characterized in that the neck of the prosthesis ( 2 ) is provided on the circumferential side with a cover ( 10 ). 7. Joint prosthesis according to claim 6, characterized in that the cover ( 10 ) consists of an elastic, preferably before self-lubricating material. 8. Joint prosthesis according to claim 7, characterized in that the cover ( 10 ) is formed out as a plastic jacket. 9. Articular prosthesis according to one of the preceding Ansprü surface, characterized in that the Tellerfederan arrangement of mutually identical Tellerfederele elements ( 9 ) existing disc spring assembly ( 8 ) is out. 10. Joint prosthesis according to claim 9, characterized in that the layering of the plate spring arrangement ( 8 ) forming plate spring elements ( 9 ) is adapted to the body weight of the prosthesis wearer.