WO2014106636A1

WO2014106636A1 - Hip prosthesis having an optimized shaft

Info

Publication number: WO2014106636A1
Application number: PCT/EP2014/050022
Authority: WO
Inventors: Helmut D. Link
Original assignee: Waldemar Link Gmbh & Co. Kg
Priority date: 2013-01-02
Filing date: 2014-01-02
Publication date: 2014-07-10
Also published as: JP2016501651A; EP2941223A1; KR20150103189A; KR102246717B1; CN104902852A

Abstract

The invention relates to a femoral hip prosthesis, comprising a shaft (2), which is suitable for anchoring in the femur (9) and which has a medial side (M) and an opposite lateral side (L) and a distal end (22) and a proximal end (25), at which a medially facing neck piece (3) is arranged on the acetabulum by means of a bearing element (4) for pivotable support, and the shaft (2) has an S-shaped curvature between the proximal end (25) of the shaft and the distal end (22) of the shaft, wherein the shaft (2) has a round cross-section in the distal region (21) of the shaft and has a chamfer (4) at the distal end (22) of the shaft, which chamfer extends over a length corresponding to the width of the shaft in the distal region (21). The combination of the taper in the distal region with a round cross-section has an atraumatic effect and achieves good anchoring and improved insertion capability.

Description

Hip prosthesis with optimized shaft

For the treatment of pathologies in the hip joint, hip joint endoprostheses are used. They usually consist of two components, an acetabular component, which is usually designed as a bearing cup, and a femur component movably mounted therein with a bearing head. The femoral component has a shaft for anchoring in a medullary canal of the femur and a neckpiece arranged thereon, which carries the bearing head. Various types of femoral components are known for adaptation to different anatomical conditions in different people, which differ in particular with regard to the design of their shafts.

In a first known variant, the Femurkompo ^¬ component on a long shaft having a circular cross section in its lower region. Of time seen over its entire length, the shaft on an S-shaped Krüm ^¬ determination. The stem shape is thus adapted to the inner contour of the medullary canal in the femur so that when implanted shaft thanks to the S-shape, a high degree of safety against unwanted rotations of the prosthesis to the femur is achieved. In the upper part of the shaft is usually out of round, and the interior of the femur is adapted in this area formally by removing material. For the lower portion, it is only necessary to drill the femoral canal to a suitable diameter so as to accommodate the lower circular area of the stem create. As an example of a known prosthesis according to this principle, the prosthesis Link Ribbed Hip System by Waldemar Link, Hamburg, is called. The other basic concept is a form shank, which differs significantly over its entire length from a round shape, wherein it has in its lower portion substantially an oval cross-section. Due to the highly non-circular shape of the medullary cavity in the femur can not be prepared by drilling for implantation, but it is rather a complementary to the shape of the shaft forth ^{¬ working} out a specific cavity structure required. For this purpose a series of exact form rasps are provided with which the medullary canal is widened in the femur successively until finally the final kom ^{¬-complementary} to the shape of the shank design of the cavity is reached. To facilitate insertion, the ovality at the lower end of the shaft is varied so that a chamfer at the late ^¬ eral side is formed. This facilitates the insertion into the precisely shaped receiving cavity in the medullary canal, especially in its upper and middle area. The chamfer is small and extends over not more than half of the cross section at the lower end of the shaft. An ^example of a practically executed prosthesis according to this principle is model SP II from Waldemar Link, Hamburg.

Based on the last-mentioned type of prosthesis, the object of the invention is to provide a more universal prosthesis system. The solution according to the invention lies in the features of the independent claims. Advantageous further developments are subject of the dependent claims ^¬ Ge. In a femoral hip prosthesis with a suitable for anchoring in femur shaft having a medial side and an opposite lateral side and a dista ^¬ les end and opposite a proximal end, to which a medial facing neck piece with a bearing element for pivotal mounting on the acetabulum is arranged, wherein the shaft has an S-shaped curvature between the proximal and distal end is erfindungsge ^¬ provided according to that the shaft has a round cross-section in its distal region and at its distal end has a bevel which extends over one of the Wei ^¬ te of the shaft in the lower region corresponding length he stretches ^¬.

The invention is based on the idea that starting from the type of prosthesis first mentioned above with an S-shaped shape of the shaft, an improvement of the insertion of the shaft into the femur can be achieved if the shaft is round in its distal region in cross-section and there has a bevel, which is preferably large and / or extends to the distal end. By "large" is understood to mean that the Ab ^¬ bevel extends over a distance which is greater than the width of the shaft in this area. As is inserted in the implantation of the distal portion as the first in the medullary canal of the femur, this results in a verbes ^¬ serte deliverability. Surprisingly, it has been shown that nevertheless a good anchoring can be achieved with this chamfer is not only as good as which serves as a starting point prosthesis type, but also atraumatic acts. This means that with the dung OF INVENTION ^¬ designed according to the socket shape the danger of generating trauma during implantation of the stem is reduced. Overall, therefore, an improved treaty ^¬ friendliness of the shaft according to the invention to the patient. The Einsetzspektrum thereby increases.

It has also been shown that, thanks to the improved compatibility, there is a greater tolerance for deviating dimensions of the shaft. In practice, this means that a complete set of prostheses to cover the range of requirements from small and light to large and heavy patients no longer needs to cover 14 to 16 different sizes as conventionally, but rather only about half, that is only about seven different sizes are required. This means that the inventively designed stem shape has a verbes ^¬ serte adaptability to the patient's anatomy up.

While there is already so far been known to provide the distal En ^¬ de with a bevel, however, this design was restricted to a different shaft type, namely on dentures with a non-circular shaft. This requires an entirely different implantation technique, namely, with a preparation of the femur by means of a plurality of different rasps to a corresponding non-round recording on sheep ^¬ fen. This type of preparation is extremely time-consuming. It is the merit of the invention to have realized that this long-known for non-round shanks design of the distal end with a chamfer not only used in prostheses with round lower shaft but leads to significant benefits in terms of universal applicability and patient care. Conveniently, the distal end is made blunt. By "blunt" is meant here that the shank has at its distal end at least 50% of the cross-sectional area as in the area immediately before the chamfer The edge forming transition to the side surfaces of the shank may be provided with a chamfer or rounding.

Particularly useful is a round rounded design of the distal end. Thus, the distal end is at its tip free of particular sharp edges, which - unlike, for example, in a four-edged chamfering - allows a gentler implantation and thus acts particularly atraumatic ^¬ . This is especially true if the Anfa ^¬ solution does not begin immediately at the top, but at the edge of the tip a rounded area between the top and the bevel exists.

Advantageously, the bevel is arranged exclusively on the lateral side. Thus, the advantages of easier insertion according to the invention

Chamfering associated with a maintenance of the substantially round shape of the distal portion of the shaft and a blunt and in particular rounded configuration of the distal end. The beneficial atraumatic Einführei- properties of the shaft remain so fully preserved.

The bevel is expediently dimensioned such that it has a desired angle of 5 ° -15 °, preferably of 8 ° -12 °, more preferably about 10 °, with a maximum of +/- 0.5 ° deviated from the desired angle. With such a relatively flat bevel optimum Ver ^¬ bond of good insertability one hand and atraumatic as possible properties on the other hand achieved.

Conveniently, the chamfer extends over a length of 1.3 times to 1.7 times the width of the

Shaft in its lower area without consideration of the bevel. As already described above with respect to the angle of the chamfer, an optimal combination of easy insertion on the one hand and atrau ^¬ matic properties on the other hand is achieved. Conveniently, the shaft of the femoral hip prosthesis is further designed so that it is round in its central region. In this case, a region between the distal and proximal ends of the

Shaft understood that extends approximately halfway in between over about a quarter of the shaft length distally and / or reaches up to the bevel. As the shaft also has a round shape in this area, the easier implantability of the femoral hip prosthesis is increased even further. Thanks to the round design also in this middle area, the preparation of the interior of the femur for implantation for this area can also be done with a medullary drill. Not only is this considerably more labor-saving than the successive widening with rasps which is required in known, non-round shanks, it also offers advantages in terms of precision and straightness. Preferably, the neck is arranged such that its me ^¬ diale side is aligned with the medial side of the shaft in the adjacent upper area. By "alignment" is meant that the medial line from the medial side of the shaft at its upper part is continued on the medial side of the neck, with a deviation of not more than 2 mm, preferably not more than 1 mm offset. It has been shown that such were "smooth" continuation of the media- len shaft side ver ^¬ repaired the neck not only of insertion, but, surprisingly, also has advantages in terms of the range of motion of the femoral prosthesis in the implanted state. The aligned arrangement of Hal ^¬ ses remains unaffected by any internals in the transition area to the shaft, such as a neck support, as described below.

Preferably, the prosthesis in the transition region to Zvi ^¬ rule the shaft and the neck has a neck support. This neck support an improvement in the operating power supply ^¬ from the prosthesis neck with the joint piece is achieved in the Fe mur of the patient. Such neck pads are already known in principle. Conveniently, it is integrally formed with the neck. This makes implantation easier, since no separate element needs to be stored and fastened. This results in a clear association between the size of the prosthesis on the one hand and the size and location of the neck rest on the other hand. , Specifics ^¬ DERS is preferred if the neck support is designed so that the transition region between the shaft and the neck is smooth on the lateral side. That is, the neck support is not ^¬ in this area over the contour of the shaft addition. Next is expediently provided that in Transition region on the lateral side no fins or other laterally projecting projections are arranged. This further facilitates the introducibility. Preferably, along the shaft along running retaining ribs are provided, of which at least one runs as far to the distal as the chamfer. The improved hold thanks to the holding ribs combined with the better atraumatic insertability thanks to the bevel.

According to a further advantageous aspect of the invention, which may deserve independent protection, there is provided a set of femoral hip prostheses as described above, the set comprising different sizes of hip prostheses. This gives the surgeon the opportunity to provide patients of all sizes and shapes with a suitable hip prosthesis. It has been shown that thanks to the inventive design of the shaft and its good compatibility only a small number of different sizes is required, preferably a maximum of eight. This is a considerable reduced copy ^¬ tion over conventionally known from the prior art prostheses usually 14 - require 16 or even more different shaft sizes.

Advantageously, the angle of the bevel at Various ^¬ NEN sizes are identical. Surprisingly, it has been found that this manufacturing cheap design no Nachtei ^¬ le, but rather an improvement over the prior art by other prostheses with straight, non-curved stems design having, in which the slope is dependent on the size of the shaft. In particular, it has been found to be useful if the length, about which extends the chamfer, depending on the size of the Pro ^¬ thesenschaft increases. The recognition that the bevel angle always remains the same across the various sizes, but that the length of the chamfer varies with size, is unprecedented in the prior art.

The prosthesis according to the invention will be explained in more detail below with reference to the attached drawing, in which a ^{vorteilhaf ¬} tes embodiment is shown. Show it:

Fig. 1 view of the embodiment of the inventions ^{¬ to the} invention prosthesis of medial;

Fig. 2 view of the embodiment of the inventions ^{¬ to the} invention prosthesis from the front; an enlarged detail of the lower portion of the shaft with the Abschrä supply, and an example of a set of fiction, contemporary hip prosthesis with its various NEN sizes.

A femoral hip prosthesis, designated in its entirety by reference numeral 1, is shown in Figs. 1 and 2 in a medial and A-P view, respectively.

The femur bone 9, in which the femoral hip prosthesis 1 is to be implanted, is shown in dashed lines in FIGS. 1 and 2. From this is the arrangement of femoral hip prosthesis 1 in the femur bone 9 recognizable. The natural femoral neck is resected, whereby a resection surface 90 is formed in the upper medial region of the femur bone 9. In the interior of the tubular part of the femur bone 9, a medullary channel 91 can be seen, which opens at the resection surface 90. In this medullary canal 91, the femoral hip prosthesis 1 is curved with its S-shaped

Shank 2 introduced, and indeed until the neck support 5 rests on the resection surface 90. The distal part of the shaft 21 extends deep into the medullary cavity 91.

The femoral hip prosthesis 1 includes a S-shaped gekrümm ^¬ th shank 2 with a lower distal end 22 and an upper, proximal end 25 to the proximal end 25 is adjoined by a neck 3 to which is oriented medially and proximally pointing obliquely from above is. At its upper, per ^¬ ximalem end of a cone clutch 34 (not shown) for connecting with a ball head as a hinge element 4 for storage in an acetabulum arranged. The ball head is preferably made of a ceramic promotes sliding mate rial ^¬, and the femoral hip prosthesis 1, moreover preference ^¬ as titanium or a biocompatible titanium alloy.

In the transition region between the shaft 2 and the neck 3, a neck pad 5 is arranged. It projects like a collar projecting medial and frontal and posterior and thus functions as a support with which the femoral Hüftprothe ^¬ se 1 on a resection surface 90 of the femur 9 is supported ^¬. The neck support 5 is formed integrally with the neck 3. Next, the shaft 2 is free on its lateral side in the region of the transition to the neck piece 3 of projections, such as. B. ribs executed. Furthermore, it can be seen in FIG. 2 that the medial side of the neck piece 336 lies in an aligned line with a medial side 26 of the shaft 2 in the proximal region 25.

The shaft 2 comprises a lower, distal region 21 and an upper, proximal region 20. The distal region 21 terminates in the distal end 22. This has on its la ^¬ teralen side a chamfer 4, which in detail in the partial magnification view in Figure 3 is shown. Accordingly, the chamfer 4 is located on the lateral side of the shaft 2 in such a way that the chamfer ends at the distal end 22 of the shaft 2. The chamfer extends over a length B and has an angle be ^¬ attracted to a parallel to the longitudinal axis 26 of the shaft 2. In the illustrated embodiment, the angle is 10 ° and the length B 19 mm. The diameter of the

Shaft 2 in the region immediately before the beginning of the chamfer 4, ie in the area indicated by the letters CC cross-sectional lines in Figure 3, is 13 mm. The shaft 2 is made blunt at the distal end 22. Apart from the chamfer 4, it is substantially round, with the point 29 rounded all around, ie also on the lateral side (see FIG. 3). Otherwise, the shank 2 has a round cross-sectional shape in the region of the cross-sectional line CC, apart from the incorporated retaining ribs 27. Furthermore, the shank 2 has a round cross-section proximally to its central region, as it is marked by the cross-sectional line DD , Before ^¬ preferably protrudes at least one of the ribs 27 at least as far distal as the bevel. 4

A set of femoral hip prosthesis of various sizes is shown in FIG. The complete sentence um- summarizes in the illustrated embodiment seven different sizes. The different sizes cover the range of requirements to be able to supply small and light to large and heavy adult patients. The femoral hip prostheses in the different

Sizes are indicated in Figure 4 by the reference numerals 11-17. They all have the same basic shape, but they become progressively longer and larger with increasing size. A special feature is that the chamfer 4 is inclined at each of the prostheses in the different sizes 11-17 at the same angle to the longitudinal axis 26 of the shaft 2 of the respective prosthesis 11-17. However, the length of the B of the chamfer 4 is different, it increases with increasing size of the prosthesis. Preferably, the increase is such that the ratio of the length B to the diameter of the shaft in this region (preferably measured in the region of the cross section CC, see Fig. 3) remains almost constant. In the illustrated embodiment ^¬ example, the ratio is 1.52 +/- 0.1. The combination of constant helix angles and with the

The size of the prosthesis, which increases the length of the chamfer, provides a similar insertion behavior over the various sizes of prosthesis, and thus facilitates implantation for the surgeon.

The different sizes 11-17 can be modified if required according to customer requirements. Conveniently, a variation of + Δ = 5 mm to -Δ = -5 mm is provided for each size 11-17. Thus, a seamless adaptation can also be realized between the sizes.

Claims

Patent claims

Femoral hip prosthesis with a shaft (2) suitable for anchoring in the femur (9) with a medial side

(M) and an opposite lateral side (L) and a distal end (22) and a proximal end (25) to which a medially facing neck piece

(3) is arranged with a bearing element (4) for pivotable storage on the acetabulum, and the shaft

(2) has an S-shaped curvature between its proximal end (25) and its distal end (22), characterized in that the shaft (2) has a round cross section in its distal region (21) and at its distal end (22) has a bevel (4) which extends over a length corresponding to the width of the shaft in the distal region (21).

Femoral hip prosthesis according to claim 1, characterized in that the bevel (4) has a target angle of 5 - 15°, preferably 8 - 12°, more preferably about 10°, with a tolerance of max. 0.5° from the target angle.

3. Femoral hip prosthesis according to one of the preceding claims, characterized in that the bevel (4) extends over a length (B) of 1.3 to 1.7 times the width of the shaft (2) in its lower region the bevel (4) extends.

4. Femoral hip prosthesis according to one of the preceding claims, characterized in that the distal end (22) is blunt.

5. Femoral hip prosthesis according to one of the preceding claims, characterized in that the distal end (22) is rounded all around.

6. Femoral hip prosthesis according to one of the preceding claims, characterized in that the shaft (2) is round in its middle area.

Femoral hip prosthesis according to one of the preceding claims, characterized in that the bevel (4) is arranged exclusively on the lateral side (L).

Femoral hip prosthesis according to one of the preceding claims, characterized in that a neck support (5) is provided in the transition area between the shaft (2) and the neck (3), which is preferably designed in one piece with the neck (3).

Femoral hip prosthesis according to one of the preceding claims, characterized in that holding ribs (27) running along the shaft (22) are provided, at least one of which runs as far distally as the bevel (4).

Femoral hip prosthesis according to one of the preceding claims, characterized in that the shaft (2) in its upper area adjacent to the neck (3). of projections, especially on the lateral side.

Femoral hip prosthesis according to one of the preceding claims, characterized in that the neck (3) is arranged so that its medial side is aligned with the medial side of the shaft (2) in its adjacent upper region.

Set of femoral hip prostheses with a shaft (2) suitable for anchoring in the femur (9) with a medial side (M) and an opposite lateral side (L) and a distal end (22) and a proximal end (25) to which a medially facing neck piece (3) with a bearing element (4) for pivoting mounting on the acetabulum is arranged, and the shaft (2) has an S-shaped curvature between its proximal end (25) and its distal end (22), which Shaft (2) has a round cross-section in its lower region (21) and has a bevel (4) at its distal end (22) which extends over a length corresponding to the width of the shaft in the ^lower region, the femoral Hip prostheses (11-17) in different sizes are provided.

13. Set according to claim 12, characterized in that the set comprises a maximum of eight different sizes.

14. Set according to claim 12 or 13, characterized in that the angles of the bevel (4) are identical for the different sizes (11-17). Set according to one of claims 12 to 14, characterized in that the distance (B) over which the bevel (4) extends is longer for larger sizes (11-17).