DE9418963U1 - Kit for a modular hip prosthesis - Google Patents

Description

ARTOS 17 November 1994

Medical Products GmbH
12277 Berlin

AT44.G7

Kit for a modular hip joint prosthesis

Description

The invention relates to a kit for a modular hip joint prosthesis of the type specified in the preamble of claim 1.

Hip joint prostheses are manufactured in a variety of shapes and sizes as stem prostheses to

/2

· ·

AT44.G7 Sheet 2

to enable the most precise possible adaptation to the respective bone shape and also the current condition of the bone tissue, taking into account the clinical picture.

The multi-part design with a force-locking connection of the corresponding individual parts in the proximal area allows for optimal adjustment. At the same time, the joint head can be positioned independently of the shaft diameter.

From EP-Bl 0 243 298 a kit for a shaft prosthesis is known which contains a head part that can be provided with a joint ball, an end part that can be anchored in the bone and an intermediate part that can be positioned between the two.

All parts have conical holes or matching pins, which means that the prosthesis can be assembled by creating conical plug connections. The head and intermediate parts each have an axial through hole.

When the individual parts are put together, the corresponding holes are aligned axially in the direction of the shaft. The individual parts of the prosthesis are put together using a tension rod that transmits a force in the axial direction, which penetrates both the head part and subsequent shaft parts and can be screwed into the threaded hole of the end part. This pulls the head part, or the intermediate part and the end part tightly together, so that there is no risk of the individual parts of the prosthesis becoming loose due to the mechanical stress during use.

AT44.G7 Sheet 3

The solution described above has the disadvantage that with such hip joint prostheses only a prosthesis with a straight shaft can be produced. It is not possible to produce prostheses that are specially adapted to the left or right side by curvature.

Based on the deficiencies of the prior art, the invention is based on the object of creating a kit for producing a modular hip joint prosthesis of the type mentioned at the beginning, with which prostheses that can be implanted on the right or left side can be produced in a simple manner - even during the operation.

This problem is solved with the characterizing features of claim 1.

The invention includes the knowledge that, with a shaft part having a corresponding curvature, the desired prosthesis shape can be set by simply rotating the two parts relative to each other by 180°. The respective shaft shape is selected in such a way that a continuous transition is created in both configurations in the connection area, which can be achieved by a mirror-symmetrical design of the head part and the shaft part in relation to the central plane in the connection area. In this way, the number of prostheses to be kept in stock can be halved, which is associated with a significant reduction in costs. In particular, a kit-like adaptation to different size adjustments can also be carried out with half the component expenditure, so that by means of the measures according to the invention a

• · · · φ · 0 β

AT44.G7 Sheet 4

almost perfect patient-specific adaptation is possible. The connecting means - and in particular the connecting cone - are located in an area of the shaft where it has a corresponding cross-section when physiologically adapted to the cleared medullary cavity, so that no bulges or other shapes on the prosthesis are necessary which could impair its fit in the medullary cavity.

The risk of confusion between a hip joint prosthesis that can be implanted on the right side and a hip joint prosthesis that is modularly composed of a head and a shaft part when using similar head and shaft parts is reduced in an advantageous further development of the invention by providing an identification on the individual parts in such a way that a check can be carried out during assembly and adjustment. Likewise, a storage device in which the hip joint prostheses can be stored after assembly without any risk of confusion is advantageous, whereby the type of assembly or the location of the precise storage means that the application side of the prosthesis can be recognized without further thought, so that errors are inevitably excluded.

According to the preferred embodiment of the invention, the kit for modular hip joint prostheses contains head and shaft parts of essentially the same design in different sizes. The individual elements selected in each case are preferably connected to one another by plugging together their proximal or distal ends, which have corresponding conical pins or recesses.

AT44.G7 Sheet 5

which can be connected. The required stability of the plug connection is ensured by means - preferably designed as a tie rod. The respective shaft part is preferably designed as a hollow shaft, with the axially extending longitudinal bore having a thread on its proximal end section. The tie rod is guided through a cylindrical channel in the head part that lies on the same axis as the longitudinal bore in the shaft part and is screwed into the threaded shaft part.

The shaft parts are designed to adapt to the anatomical conditions of the femur in such a way that the shaft appears essentially as a straight cylinder in the dorsal/frontal view of the modular hip joint prosthesis, whereas in a medial/lateral view it has a relatively slight curvature. Due to this curvature, the distal shaft end of a prosthesis {when placed in the implantation position) points frontally.

This makes it possible, in an advantageous and simple manner, to convert a right-side implantable hip joint prosthesis into a left-side implantable prosthesis without replacing a shaft part, simply by pivoting the head part relative to the curved shaft part by an angle of approximately 180° around the longitudinal axis of the shaft cone.

According to a favorable development of the invention, the prosthetic parts of the kit for producing a hip joint prosthesis are provided with a marking in order to avoid by simple means that - due to the

/6

AT44.G7 Sheet 6

relatively slight curvature of the shaft parts - confusion can arise when applying modular hip joint prostheses. For this purpose, elements of a marking are provided on the head and shaft parts of the kit, which both ensure correct assembly and clearly indicate the position of use after the prosthesis has been assembled. The marking elements are provided dorsally and frontally on the distal end of the head part and either dorsally or frontally on the proximal end of the shaft part.

According to another development of the invention, the marking elements form a letter symbol after the modular hip joint prosthesis has been correctly assembled, for example the letters "L" or "R". The straight sections common to both letters are arranged as marking elements on the shaft part and, after the head part has been correctly rotated relative to the shaft part, are combined with the different letter parts provided at the distal end of the head part to form the complete symbol. On the other hand, it is also advantageous for easy checking of the correct assembly of the modular hip joint prosthesis to arrange the complete letter symbols at the distal end of the head parts and to provide a raised line at the proximal end of the shaft parts. When the hip joint prosthesis is correctly assembled, the straight sections present in both letter symbols are on the same axis as the line element of the shaft part.

/7

AT44.G7 Sheet 7

According to a further advantageous embodiment of the invention, at least one wall opening, for example in the form of an elongated hole, is provided at the distal end of the longitudinal bore in the shaft part of the modular hip joint prosthesis. The longitudinal bore in the shaft part simultaneously serves as a receptacle for an active ingredient dispenser, the active ingredients of which enter the medullary cavity of the bone through the wall in the opening and have a positive effect on the ingrowth of the hip joint prosthesis.

According to a favorable development of the invention, a through hole extending essentially transversely to the shaft axis is provided in the area of the distal end of the longitudinal hole and the distal end of the shaft part. This serves to engage additional anchoring means, for example a Küntscher nail, in order to fix the prosthesis shaft in the bone.

The kit for producing modular hip joint prostheses also has a device for storing the prostheses. The device, made of plastic, is designed as a flat cuboid, with two recesses on one of the broad sides, in which a hip joint prosthesis that can be implanted on the right or left side can be stored in a way that is unmistakable. The recesses are designed in such a way that the hip joint prostheses can be arranged in mirror symmetry, with the curvature of the shaft part of the prosthesis pointing downwards in relation to the storage plane. The recesses also have a

·» « i Z

AT44.G7 Sheet 8

The respective hip joint prosthesis has consistent marking.

Advantageous further developments of the invention are characterized in the subclaims or are presented in more detail below together with the description of the preferred embodiment of the invention using the figures. They show:

Figure 1 shows the preferred embodiment of the invention in a schematic partial sectional view,

Figure la is the sectional view along the line A...A according to Figure 1,

Figure 2 is a simplified representation of the preferred embodiment of the invention according to Figure 1 as a side view from the left,

Figure 3 shows a favorable further development of the invention in a schematic view from above,

Figure 4 shows a partial section along the line A...A or A ¹ ...A ¹ according to Figure 3

Figures 5a and 5b show another advantageous embodiment of the invention, each in plan view, and

Figures 6a and 6b show a favorable development of the invention shown in Figures 5a and 5b.
■

The images shown in Figures 1, la and 2 in the form of a section or a partial section and a medial/lateral side

AT44.G7 Sheet 9

The prosthesis 1 shown in the side view consists of a shaft part 2 and a head part 3 placed on the shaft part, each of which has a profile in the longitudinal direction.
5

The individual parts 2 and 3 of the prosthesis 1 shown in Figure 1, which belong to a kit for producing modular hip joint prostheses, are connected by means of a conical plug connection 10 lying on the same axis and pivoting against each other. A tie rod (not shown) is provided for "setting" the cone and for securing this plug connection against axial loosening, which is guided through the channel 5 of the head part 3, designed as a threaded hole, and screwed into the proximal area of the channel 4 provided in the subsequent shaft part 2, designed as a threaded hole β. The screwing takes place so far that the proximal end of the tie rod is supported in the recess 7 and the individual parts 2 and 3 of the modular hip prosthesis shaft 1 are moved axially against each other until the conical plug connection 10 has the desired strength.

In Figure 2, the modular hip joint prosthesis 1 shown in Figure 1, which can be implanted on the right side, is shown in a medial side view. In comparison to the partial sectional view according to Figure 1, the shaft part 2 has a uniform, relatively small curvature in relation to the longitudinal axis of the head part 3. The longitudinal bore in the shaft part 2 (compare position 4 according to Figure 1 and la) opens distally into at least one opening 9 in the shaft wall, which is designed as an elongated hole. The resulting

AT44.G7 Sheet 10

The connection of the prosthesis cavity (compare position 4 in Figure 1 and la) with the medullary cavity of the hip bone can be used to introduce active substances. Such active substances serve to improve the "ingrowth" of the prosthesis and are applied via active substance dispensers positioned inside the prosthesis.

The through hole 11 located between the wall opening 9 and the distal end of the shaft part 2 and extending transversely to the shaft axis is intended for the engagement of additional means for anchoring the prosthesis shaft 2. The dimensions of the hole 11 are selected such that so-called Küntscher nails can be used to anchor the prosthesis shaft 2.

By turning the head part 3 relative to the shaft part 2 by approximately 180°, the modular hip joint prosthesis 1 shown in Figure 2 can be easily converted into a prosthesis that can be implanted on the left side. This avoids double storage and a special right or left version can be formed at any time from a single stock. In addition, by selecting different sizes, a more precise size adjustment can be made, whereby only half of the components need to be kept in stock. The shaft shape is selected in such a way that in the transition area of the parts in every configuration there is a stepless and continuous connection that differs little or not at all from the corresponding area of a corresponding one-piece prosthesis.

•&ogr; · ·

AT44.G7 Sheet 11

Since the shaft curvature is only visible when viewed from certain directions, confusion may arise between right- and left-sided implantable prostheses.
5

The device 50 shown in schematic form in Figure 3 for storing hip joint prostheses produced with the aid of the kit therefore has two recesses 51, 52 in which a hip joint prosthesis that can be implanted on the right or left side can be stored in an unmistakable manner. The recesses 51, 52 are designed in such a way that the hip joint prostheses can be arranged in mirror symmetry, with the curved shaft part of the hip joint prosthesis pointing downwards in relation to the storage plane. This is shown in simplified form in Figure 3 as a sectional view along the line A...A or A ¹ ...A ¹ in Figure 4.

In order to prevent the risk of confusion during assembly of the hip joint prostheses by clearly identifying the intended application form as a right- or left-sided implantable prosthesis, identification elements 20.1 and 30.1 and 30.2 are also provided on the prosthesis parts 20 and 30, as shown in Figures 5a and 5b.

The marking elements 30.1, 30.2 are designed as letter symbols "R" and "L" and are located on one of the broad sides of the head part 3 at its distal end. They indicate a prosthesis that can be implanted on the right or left side, if the line marking

AT44.G7 Sheet 12

formed marking element 20.1 at the proximal end of the shaft part 2 lies on the same axis as the straight section common to both letters. The required adjustment can be easily carried out by pivoting the head part 30 around the axis of the cone at the proximal end of the shaft part 20. The recesses 51 and 52 of the device shown in Figure 3 for storing hip joint prostheses have the same letter symbols in accordance with the respective hip joint prosthesis and thus ensure clear assignment when storing the differently designed prostheses.

The embodiment of the invention shown in Figures 6a and 6b has a shaft part 21 and a head part 31 of a kit, the identification elements 21.1 and 31.1 or 31.2 of which are designed to be completed to form a letter symbol 40 or 41. The identification element 21.1 located at the proximal end of the shaft part 21 corresponds to the straight section that is common to the letters "R" and "L". At the distal end of the head part 31, the remaining sections 31.1 and 31.2 of the letter symbols "R" and "L" are provided on the broad sides. By means of a swivel movement of the head part 31 attached to the cone located at the proximal end of the shaft part 2, the identification elements 21.1 and 31.1 or 21.1 and 31.2 are completed to form a corresponding letter symbol depending on the choice of a right- or left-sided implantable hip joint prosthesis. The identification elements 21.1, 31.2 and 31.2 are advantageously in the form of knurling with straight elevations.

AT44.G7 Sheet 13

with equal spacing. This allows for precise relative positioning of the head and shaft sections during the swivel movement.

The invention is not limited in its implementation to the preferred embodiment given above. Instead, a number of variants are conceivable which make use of the solution presented even in fundamentally different embodiments.

Claims (14)

··» ft · ft · ft ft*** AT44.G7 Sheet 14 Claims 1. Kit for modular hip joint prostheses, which are composed of a head part and a shaft part, wherein the shaft part of the prosthesis can be connected to the head part by plugging it in so that it can rotate about a longitudinal axis - preferably by means of a conical connection - and means are provided for securing the plug connection, characterized, that a shaft part (2, 20, 21) is provided with such a curvature in its distal region that by rotating the head part (3, 30, 31) relative to the shaft part by an angle of substantially 180° about the longitudinal axis, a prosthesis that can be implanted either on the right or on the left side can be produced.
20 2. Modular hip joint prosthesis manufactured from a kit according to claim 1, characterized in that corresponding elements of a marking (20.1, 21.1, 30.1, 30.2, 31.1, 31.2) are provided on the head and shaft parts (2, 3, 20, 21, 30, 31), which together form either a marking that clearly defines the left or right position in both possible assembly positions, each offset by essentially 180". • . I AT44.G7 Sheet 15 3. Modular hip joint prosthesis according to claim 2, characterized in that the identification elements (30.1, 30.2, 31.1, 31.2) are provided at the distal end of the head part (30, 31) dorsally and frontally and the identification elements (20.1, 21.1) at the proximal end of the shaft part (20, 21) are provided either dorsally or frontally. 4. Modular hip joint prosthesis according to claim 3, characterized in that the identification elements (21.1 and 31.1 or 21.1 and 31.2) form a letter symbol (40, 41) after the prosthesis (1) has been assembled. 5. Modular hip joint prosthesis according to claim 4, characterized in that the marking of the correctly assembled individual parts of the hip joint prosthesis (1) corresponds to the letters "L" or "R". 6. Modular hip joint prosthesis according to claim 1, characterized in that the shaft part (2) has a longitudinal bore (4) running in the direction of the shaft axis. &Iacgr;. Modular hip joint prosthesis according to claim 6, characterized in that the longitudinal AT44.G 7 Page 16 bore (4) opens at its distal end into at least one lateral opening (9) in the shaft wall. 8. Modular hip joint prosthesis according to claim 7, characterized in that the lateral opening (9) has the shape of an elongated hole. 9. Modular hip joint prosthesis according to claim 7, characterized in that a transverse bore (11) for receiving additional fixation means is provided between the distal end of the longitudinal bore (4) and the distal shaft end. 10. Hip joint prosthesis according to claim 10, characterized in that the transverse bore (11) has dimensions for receiving a Küntscher nail. 11. Hip joint prosthesis according to one of the preceding claims, characterized by a shape design in which both in the configuration for a left-sided and in the configuration for a right-sided implantation an essentially continuous and/or no significant changes in curvature are provided in the transition area between the head and shaft parts. 12. Device for storing hip joint prostheses according to one of the preceding claims, in particular in the form AT44.G7 Sheet 17 a container for a surgical set, characterized in that the device (50) has two recesses (51, 52) in which a right-side or left-side implantable hip joint prosthesis (1) can be deposited in an unmistakable manner. 13. Device according to claim 12, characterized in that the recesses {51, 52) are designed such that the hip joint prostheses (1) can be arranged mirror-symmetrically, whereby the curvature of the shaft part (2, 20, 21) of the prosthesis is directed downwards with respect to the support plane.
15 14. Device according to claim 13, characterized in that a marking corresponding to the respective hip joint prosthesis is provided on the recesses (51, 52).