JP2016501651A - Hip prosthesis with optimized shaft - Google Patents

Abstract

The present invention relates to a femoral hip prosthesis with a shaft (2), which is suitable for anchoring to the femur and has a medial side (M), an opposed lateral side (L), a distal end ( 22) and a proximal end (25), at which the inwardly facing neck (3) is placed on the acetabulum by a pivotable support element (4). The shaft (2) has an S-shaped curve between the proximal end (25) and the distal end (22) of the shaft. The shaft (2) has a round cross section at the distal region (21) of the shaft and has a chamfer (4) at the distal end (22) of the shaft, the chamfer being a shaft at the distal region (21). Extends over a length corresponding to the width of the. The combination of tapers in the distal region (21) having a round cross-section has a non-invasive effect and achieves good fixation and improved insertion characteristics. (Figure 2)

Description

  Hip endoprostheses are used to treat hip pathology. They are usually made of two parts. That is, an acetabular part, which is primarily designed as a bearing socket, and a femoral part, which is movably attached to the acetabular part and has a bearing head. The femoral component has a shaft for anchoring to the medullary canal of the femur and a neck portion disposed on the shaft and supporting the bearing head. Various types of femoral components are known to accommodate different anatomical conditions that exist for different people, and these differ especially with respect to their shaft design.

  In a first known variant, the femoral component has an elongate shaft and has a circular cross section in its lower region. When viewed along its entire length, the shaft has an S-shaped curve. Thus, the shape of the shaft is suitable for the internal contour of the medullary canal in the femur so that the S-shape ensures a high degree of safety against undesired twisting of the prosthesis with respect to the femur with the shaft inserted Yes. The shaft is generally not circular in the upper region, and because of the shape in this region, the interior of the femur is suitable for tool removal. With respect to the lower region, it is only necessary to puncture the femoral canal to the appropriate diameter in order to create a seat that accepts the circular region below the shaft. An example of a known prosthesis according to this principle is the Link Ribbed Hip System from Waldemar Link, Hamburg, Germany.

  Another basic idea involves a shaft that is distinctly circular and has a substantially elliptical cross section in its lower region along its entire length. Obviously the non-circular shape means that the space for implantation in the bone marrow of the femur cannot be prepared by drilling, and instead a cavity structure defined to match the shape of the shaft must be dug out. For this purpose, a series of accurate and appropriate filings are performed in which the bone marrow space in the femur is continuously expanded until the final structure of the cavity matching the shape of the shaft is finally obtained. To make insertion easier, the oval shape at the lower end of the shaft is changed so that the chamfered portion is on the outer side. In this way, insertion into a precision machined receiving cavity in the medullary canal is facilitated, especially in the upper and middle areas. The chamfer is small and extends over half of the cross section at the lower end of the shaft. An example of a prosthesis actually designed according to this principle is the model SP II from Waldemar Link, Hamburg, Germany.

  Developing from the last-mentioned prosthesis type, the object of the present invention is to make a more general prosthesis system available.

  The solution according to the invention lies in the features of the independent claims. Useful development is the subject matter of the dependent claims.

  In a femoral hip prosthesis having a shaft, it is suitable for anchoring to the femur and has a medial side, an opposed lateral side, a distal end, and an opposed proximal end. At the distal end, the inwardly facing neck is placed on the acetabulum by a pivoting element for pivotal support, where the shaft has an S-shaped curve between the proximal and distal ends. The shaft has a circular cross section in its distal region and has a chamfer at its distal end, the chamfer extending over a length corresponding to the width of the shaft in the lower region. Offer to be extended.

  The present invention has advanced from the first mentioned prosthetic type in which the shaft has an S-curved configuration, where the shaft is circular in cross section at its distal region, preferably large there, and / or Alternatively, it is based on the concept that an improved insertion of the shaft into the femur can be achieved if it has a chamfer extending to the distal end. “Large” here is understood to mean that the chamfer extends by a distance greater than the width of the shaft in this region. Because this distal region is initially inserted into the medullary canal of the femur during implantation, improved insertability is achieved. Surprisingly, it has been found that a good anchoring can be achieved further with this chamfer, which is not only good but also non-invasive in the prosthetic type serving as a starting point. . This means that the shaft formed according to the invention reduces the risk of creating trauma during shaft implantation. Overall, the shaft according to the invention is therefore more compatible with the patient. Therefore, the range of applications is expanded.

  Thanks to the improved suitability, it further shows that there is a greater tolerance for shaft dimensional deviations. This means that, in fact, the complete prosthesis prepared to cover the required range from short and light patients to heavy and heavy patients is 14 to 16 different sizes as before. Has the effect that instead only about half, ie only about seven different sizes, are required. This means that the shaft shaped according to the present invention has improved patient adaptability to the human body.

  Although it is already known to provide a distal end with a chamfer, this design was for a prosthesis with only another type of shaft, i.e. a non-circular shaft. This latter requires a completely different implantation technique, i.e. a technique with a femur prepared by a number of different files to create a corresponding non-circular seat. This kind of preparation is very complicated. The contribution of the present invention is that this configuration of chamfered distal end, which has been known for many years with non-circular shafts, can also be used in prostheses with circular lower shafts, and more It has been recognized that it leads to significant advantages with regard to many common applications and patient protection.

  It is advantageous that the distal end is blunt. “Dull” here is understood to mean that the shaft has at least 50% of its cross-sectional surface area at its distal end as in the area immediately before the chamfer. The edge forming transition to the outer surface of the shaft can be inclined or rounded.

  A particularly advantageous design is one in which the distal end is completely rounded. Thus, at its tip, the distal end has no sharp edges, and in particular, for example, as opposed to a square slope, allows for gentle implantation and is therefore particularly non-invasive. This is especially true when the slope does not start immediately at the tip, and instead there is a rounded area at the tip edge between the tip and the chamfer.

  Advantageously, the chamfer is arranged exclusively on the outer side. Thus, the advantage of easy insertability due to the chamfer according to the invention leads to a substantially circular protection of the distal region of the shaft and a dull, particularly rounded configuration protection of the distal end. Thus, the beneficial non-invasive insertion characteristics of the shaft are well maintained.

  The chamfer is dimensioned in a preferred manner so that it has a maximum tolerance of +/− 0.5 ° from the nominal angle at a nominal angle of 5-15 °, preferably 8-12 °, more preferably about 10 °. Is done. With this kind of relatively flat chamfer, an optimal combination of good insertability on the one hand and non-invasive characteristics on the other hand can be achieved.

  The chamfer preferably extends in the lower region over the length of 1.3 to 1.7 times the width of the shaft without taking into account the chamfer. As already mentioned above with respect to the angle of the chamfer, an optimal combination of easy insertion on the one hand and non-invasive characteristics on the other hand is achieved.

  Furthermore, the shaft of the femoral hip prosthesis is preferably designed to be circular in its intermediate region. The intermediate region is here the region located between the distal and proximal ends of the shaft, starting approximately in the middle between them and about a quarter of the length of the shaft in the distal direction. It is understood as a region that extends over and / or reaches the chamfer. Also, the ease of implantation of the femoral hip prosthesis is further increased because the shaft has a circular shape in this region. Also, thanks to the circular configuration in this intermediate region, preparation within the femur for implantation can be done in this region as well using a medullary drill. This not only includes substantially less work than the continuous widening operation with a forming file, which is required in known non-circular shafts, but also provides advantages in terms of accuracy and straightness.

  The neck is preferably arranged such that its inner side is flush with the inner side of the shaft in the adjacent shaft upper region. Here, the “same surface” means that the medial line defined by the inner side surface of the shaft in the upper region of the shaft continues to the inner side surface of the neck, specifically 2 mm or less, preferably 1 mm. It is understood to mean that it continues with the following displacement. The so-called “smooth” continuation of the inner side of the shaft at the neck not only improves insertability, but also surprisingly provides an advantage regarding the range of travel of the femoral prosthesis in the implanted state. all right. The coplanar arrangement of the neck remains unaffected by the parts that may be incorporated in the transition region to the shaft, for example the neck support of the type described below.

  The prosthesis preferably has a neck support in the transition region between the shaft and the neck. With this neck support, an improvement is achieved in the transmission of force from the prosthetic neck with joints to the patient's femur. This type of neck support is already known in principle. This is preferably designed in one piece with a neck. Thus, implantation is easier because it is not necessary to house and fix separate elements. Thus, there is a clear relationship between the size of the prosthesis on the one hand and the size and position of the neck support on the other hand. It is particularly preferred if the neck support is configured so that the transition area between the shaft and the neck is smooth on the outer side. That is, the neck support does not protrude beyond the contour of the shaft in this region. Furthermore, it is preferably provided that fins or other outwardly projecting protrusions are not arranged on the outer side surface in the transition region. This further facilitates insertability.

  The retaining rib is preferably provided extending along the shaft, at least one rib of which extends to the distal region of the chamfer. Thus, improved retention by the retaining ribs is combined with better non-invasive insertability by the chamfer.

  According to another beneficial aspect of the present invention, perhaps worthy of independent protection, a plurality of sets of femoral hip prostheses as described above are provided, wherein the set comprises a plurality of Provide hip prostheses of different sizes. Thus, the surgeon can provide the patient with a suitable hip prosthesis of different heights and incorporate a suitable hip prosthesis. Due to the creative design of the shaft and its good fit, it has been found that only a few different sizes are required, preferably a maximum of eight. This is a considerable reduction compared to conventional prostheses known from the prior art, which generally require 14 to 16 or more different shaft sizes.

  The angle of the chamfer is advantageously the same for different sizes. Surprisingly, this design is advantageous from a manufacturing point of view and has no disadvantages, but instead has a chamfered portion with a straight, uncurved shaft that depends on the size of the shaft. It has been found to allow improvements over the known design from the prosthesis. In particular, it has proved advantageous if the length over which the chamfer extends increases with the size of the shaft of the prosthesis. Although the angle of the chamfered portion always remains constant over different sizes, the recognition that the length of the chamfered portion varies with size is unprecedented in the prior art.

Fig. 3 shows a view from the inside of an exemplary embodiment of a prosthesis according to the invention. 1 shows a front view of an illustrative embodiment of a prosthesis according to the present invention. FIG. Figure 3 shows an enlarged detail of the lower region of the shaft with chamfers. 1 shows an example of a set of hip prostheses in different sizes according to the present invention.

  The prosthesis according to the present invention will be described in more detail below with reference to the accompanying drawings, in which preferred and illustrative embodiments are shown.

  The femoral hip prosthesis, indicated as a whole by the reference 1, is shown in FIG. 1 in a view from the inside and in FIG. 2 in a anteroposterior view.

  The femur 9 in which the femoral hip prosthesis 1 is to be implanted is shown in broken lines in FIGS. These reveal the placement of the femoral hip prosthesis 1 in the femur 9. The natural neck of the femur is resected, so that a resected surface 90 is formed in the upper medial region of the femur 9. The medullary canal 91 is open outward at the ablation surface 90, which can be seen in the inner tubular portion of the femur 9. The femoral hip prosthesis 1 is inserted into the bone marrow canal 91 by its curved S-shaped shaft 2, and in particular, until the neck support 5 is leaning against the resection surface 90. The distal portion of the shaft 21 extends deeply into the medullary cavity 91.

  The femoral hip prosthesis 1 comprises an S-shaped curved shaft 2 having a lower distal end 22 and an upper proximal end 25. The neck 3 is adjacent to the proximal end 25 and is inclined and oriented pointing upwards inwardly and proximally. At its upper proximal end, the conical joint 34 is arranged to connect to a ball head that functions as a bearing element 4 for bearing in an acetabulum (not shown). The ball head is preferably made of a ceramic material that promotes sliding, and the remaining portion of the femoral hip prosthesis 1 is preferably made of titanium or a biocompatible titanium alloy.

  The neck support 5 is arranged in the transition area between the shaft 2 and the neck 3. This protrudes inwardly like a collar in the anterior-posterior direction, thus functioning as a support on which the femoral hip prosthesis 1 weights the resection surface 90 of the femur 9. The neck support part 5 is formed in one piece together with the neck part 3. Furthermore, the shaft 2 is designed on the outer side surface thereof without, for example, a rib projection in the transition region to the neck portion 3. It can also be seen from FIG. 2 that the inner side surface of the neck 336 is aligned with the inner side surface 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 ends at the distal end 22. The latter, on its outer side, has a chamfer 4 which is shown partially enlarged in FIG. Accordingly, the chamfered portion 4 is provided on the outer side surface of the shaft 2, and in particular, the chamfered portion is provided so as to end at the distal end 22 of the shaft 2. The chamfer extends over the length B and has an angle α with respect to a line parallel to the longitudinal axis 26 of the shaft 2. In the illustrative embodiment shown, the angle α is 10 ° and the length B is 19 mm. In the region immediately before the start of the chamfered portion 4, that is, in the region of the line of the cross section indicated by the letters CC in FIG. 3, the diameter of the shaft 2 is 13 mm.

  The shaft 2 is blunt at the distal end 22. It is basically circular apart from the chamfer 4 and the tip 29 is completely round, i.e. also rounded on the outer side (see FIG. 3). The remaining part of the shaft 2 has a circular cross-sectional shape in the region of the cross-section line CC, apart from the incorporated retaining ribs 27. Furthermore, the shaft 2 has a circular cross section to the extent proximal to its middle region, as indicated by the cross-sectional line DD. Preferably, at least one of the ribs 27 protrudes to the distal region of the chamfer 4.

  One set of femoral hip prostheses in different sizes is shown in FIG. In the illustrative embodiment shown, the complete set comprises seven different sizes. The different sizes cover the range required to be able to treat from tall and light adult patients to tall and heavy adult patients. Femoral hip prostheses in different sizes are indicated by reference numerals 11-17 in FIG. They all have the same basic shape, but as size increases they become increasingly longer and more dimensioned. A special feature is that the chamfer 4 in each of the prostheses in different sizes is inclined at the same angle α with respect to the longitudinal axis 26 of the shaft 2 of the respective prosthesis 11-17. However, the length of B of the chamfered portion 4 is different. That is, it increases as the size of the prosthesis increases. This increase is preferably adjusted so that the ratio of shaft diameter to length B in this region (preferably measured in the region of section C-C; see FIG. 3) remains almost constant. . In the illustrated exemplary embodiment, the ratio is 1.52 +/− 0.1. The combination of the constant tilt angle and the chamfer length with increasing prosthesis size ensures uniform insertion behavior across different prosthesis sizes, thus making it easier for the surgeon to implant.

  When requested, the different sizes 11 to 17 can be changed according to the user's request. Variations from + Δ = 5 mm to -Δ = -5 mm are preferably provided for each size 11-17. Thus, it is also possible to achieve a seamless modification between sizes.

Claims (15)

A femoral hip prosthesis having a shaft (2), suitable for anchoring to the femur (9) and having an inner lateral surface (M), an opposing lateral lateral surface (L), a distal end ( 22) and a proximal end (25), at the proximal end having an inwardly facing neck (3) with a bearing element (4) for pivotally supporting in the acetabulum, and The shaft (2) has an S-shaped curve between its proximal end (25) and its distal end (22);
The shaft (2) has a circular cross section at its distal region (21) and has a chamfered portion (4) at its distal end (22), the chamfered portion (4) being a distal region (21). Extending over a length corresponding to the width of the shaft,
A femoral hip prosthesis characterized by the above.   The chamfer (4) has a nominal angle of 5-15 °, preferably 8-12 °, more preferably about 10 °, and has a maximum tolerance of 0.5 ° from the nominal angle. The femoral hip prosthesis as described.   The chamfer (4) extends over a length (B) 1.3 to 1.7 times the width of the shaft (2) in the lower region in front of the chamfer (4). The femoral hip prosthesis as described.   The femoral hip prosthesis according to any of claims 1 to 3, wherein the distal end (22) is blunt.   The femoral hip prosthesis according to any of the preceding claims, wherein the distal end (22) is completely rounded.   The femoral hip prosthesis according to any of claims 1 to 5, wherein the shaft (2) is circular in its intermediate region.   The femoral hip prosthesis according to any one of claims 1 to 6, wherein the chamfered portion (4) is arranged exclusively on the outer side surface (L).   Neck support (5) is present in the transition region between the shaft (2) and the neck (3) and is preferably designed in one piece with the neck (3). The femoral hip prosthesis described in the above.   The retaining rib (27) is present extending along the shaft (22), at least one rib extending to a distal extent of the chamfer (4). The femoral hip prosthesis described in the above.   The femoral hip prosthesis according to any of the preceding claims, wherein the shaft (2) has no protrusions in the upper region adjacent to the neck (3), in particular on the outer side surface (L).   11. The femoral hip prosthesis according to claim 1, wherein the neck (3) is arranged such that its inner side is flush with the inner side in the upper region of the adjacent shaft (2). . A set of femoral hip prosthesis having a shaft (2), suitable for anchoring to the femur (9), and having an inner lateral surface (M), an opposing lateral lateral surface (L), a distal A proximal end (22) and a proximal end (25), which has an inwardly facing neck (3) with a bearing element (4) for pivotally supporting in the acetabulum. And the shaft (2) has an S-shaped curve between its proximal end (25) and its distal end (22), and the shaft (2) has its lower region (21) At its distal end (22) with a chamfer (4), the chamfer (4) extending over a length corresponding to the width of the shaft in the lower region,
The femoral hip prosthesis (11-17) has different sizes,
A set of femoral hip prosthesis, characterized in that.   The set of femoral hip prostheses according to claim 12, wherein the set of femoral hip prostheses comprises up to eight different sizes.   14. A set of femoral hip prostheses according to claim 12 or 13, wherein the angle of the chamfer (4) is the same in different sizes (11-17).   15. A set of femoral hip prostheses according to any one of claims 12 to 14, wherein the distance (B) over which the chamfer (4) extends increases as the size of the femoral hip prosthesis increases.

Images