DE2805305A1 - ARTIFICIAL HIP JOINT - Google Patents

Description

Artificial hip joint

The invention relates to an artificial hip joint according to the preamble of claim 1 as a replacement for a defective hip joint and hip and thigh sections suitable for the artificial hip joint.

When using prostheses to replace damaged hip joints there is a risk of failure of the entire hip system. When the patient moves, considerable forces are exerted on the prosthesis and the affected bone structure. With a jump For example, from a height of 60 to 90 cm, forces are applied to the hip joint Exercised by a multiple of the body weight and when jumping from even greater heights, these stress factors multiply still considerable. The failure of the entire hip system can result in a breakdown of the bone structure, a breakdown of the cement. and a fracture of the thigh portion of the hip joint.

Before the use of cement in the hip system was introduced, many different shapes were used for the femoral sections. Since cement has been used in such systems, the thigh sections with their sharp edges have caused cuts in the cement, fractures and other disadvantages. In addition, recesses or undercut portions are provided in the known sections which lock the thigh portion after hardening in its' * ■ seat against removal, so that it is schv / ierig, the prosthesis to be removed, if for some reason a further O;> ration to remove and replace an inserted prosthesis should be necessary.

Hip joints of the type mentioned are for example in the US patents 3,918 102, 3 965 490, 3 922 726, 3 863 273 and D-235 485. Another joint is known as the "Charnley Total Hip" and has a shaft whose posterior. and anterior Surfaces are flat, which has a substantially uniform thickness in its anterior / posterior direction and a Has a neck with a circular cross-section. Finally, a total hip system with the trademark "Protasul" is also known.

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ORIGINAL INSPECTED

The invention is based on the described disadvantages to be eliminated by an improved artificial hip joint of the type mentioned at the beginning.

To solve this problem, the characterizing features of claim 1 are provided.

A particularly preferred embodiment of the invention is characterized by the features of claim 2.

Due to the design of the shaft according to the invention, the loads exerted on it are distributed over its entire length. In addition, the inventive design of the shaft has the consequence, that, on the one hand, when the prosthesis is inserted, the cement is pressed into the cavities and crevices of the bone in the manner of a wedge effect, while on the other hand, easy removal of the stem is possible if correction needs to be made. So on the one hand is one firm support created for the shaft so that it is firmly locked against undesired movements during use, while the stem, on the other hand, is not so locked in the cement that it will not re-establish in the event of a required correction can be pulled out. In addition, there is the advantage that in the medial / lateral plane, where the load is in the case of weight-bearing Movement of the leg is greatest, a larger amount of material is available.

The outer surface of the shaft is preferably smooth and rounded Provide edges so that no breaks or cuts in the cement are possible.

The cross section of the neck in the anterior / Posterior dimension narrower than in the lateral / medial dimension, thus in the lateral / medial direction, which absorbs the greatest load, an enlarged one, in contrast in the anterior / posterior dimension a smaller amount of material is provided, resulting in greater back and forth movement of the neck and therefore the leg of the Patient enables.

The hip section of the hip joint according to the invention preferably has a substantially hemispherical body, the

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Inner surface forms the pan and its outer surface in such a way from the Inner surface is spaced so that the body has a constant thickness. This results in less wear and tear on the hip section Compared to known hip sections given in their body Grooves are cut. It is also provided that the hip section does not overhang the head, but is essentially flush with it this is, as a result of which there is greater freedom of movement for the thigh section relative to the hip section.

For different sizes of the thigh section, according to the invention, there is a relationship between the elongated neck and the angle of the Neck so provided that the leg or thigh for the purpose better weight bearing in a straight position below the Hip is held.

Further advantageous features of the invention emerge from the subclaims.

The invention is described below in connection with the accompanying Drawing explained in more detail using an exemplary embodiment. Show it:

1 shows the front view of the thigh section of a hip joint according to the invention;

FIG. 2 shows a plan view of the thigh section according to FIG. 1;

3 to 7 sections along the lines TII-III to VII-VII of FIG Fig. 1;

8 shows a partial section through the hip according to the invention hip joint implanted in the thigh;

9 shows the side view of the hip section according to the invention; Fig. 10 is a plan view of the waist section of Fig. 9; 11 shows a section along the line XI-XI in FIG. 10; and

Figures 12-14 are front views of three different sizes according to the invention Thigh sectiona * where the relationship

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can be seen between different lengths, distances and angles.

8 includes a prosthetic hip joint according to the invention a thigh section 13, which by means of cement C in the medullary canal M of the thigh F is inserted, and a hip section 15 for implantation in the acetabulum A using Cement C.

The thigh section 13 includes a head 17, a neck 19, a shaft 21 and a shoulder 23 adjoining the junction between the neck 19 and the shaft 21. The thigh section 13 is preferably made in one piece and consists of one

v / ie suitable rigid, biocompatible material / chromium cobalt or stainless steel, the head 17 being rigidly connected to one end of the neck 19, the other end being rigidly connected to the proximal end End 25 of the shaft 21 is connected. The shoulder 23 is provided at that end of the neck 19 which is at its point of contact adjoins the shaft 21.

The head 17 has an outer surface, the larger part 29 of which is spherical is designed so that the head into the socket 31 of the waist section 15 matches (Fig. 8). The head 17 is preferably flat along a base 33, the base 33 being the connection point of the Surrounds the head 17 with the neck 19, and where at the junction? a radius 33 'is provided.

The cross-section of the neck 19 is elliptical, the narrower being Part or the shorter diameter of the ellipse in the one through the line A-P extends in the anterior / posterior direction, during the wider part or the longer diameter of the ellipse in the through the line L-M is indicated in the lateral / medial direction. Included Note that the terms "Anterior / Posterior" and "Lateral / Medial" - directions by the orientation of the implanted Thigh section 13 relative to the body of the patient festcelee '. i.e. the anterior / posterior direction runs relative to the body from front to back and the lateral / medial direction sideways. It follows that the shaft 21 in the lateral / medial direction or -The level where the loads are greatest has more metal,

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ORIGINAL INSPECTED

while at the same time the neck in the anterior / posterior direction or -Plane is thinner, so less interference with the hip section 15 occur, which gives more leeway for the forward and backward movement of the thigh portion 13 and the thigh F results. Also note that the neck is 19 in the area 37 located just below its point of contact with the head 17 is narrower and extends outward from there to his Extended end where the shoulder 23 is provided at the junction with the shaft 21. The shoulder 23 overhangs the proximal one End 25 of shaft 21 at the anterior, posterior and medial Side, while the lateral edge of the neck 19 is essentially flush flush with the lateral side of the proximal end 25 of the shaft 21.

The stem 21 is curved in the manner shown in FIG. 1, front view, and in its proximal section 41 is thicker than in the straight i distal portion 43. In the plan view of FIG. 2, the shaft 21 is substantially straight.

One of the essential features of the invention is configuration of the shaft 21. The shaft has a smooth, uninterrupted outer surface 45 without indentations and is in. from the proximal end 25 Direction of the distal end 47 in both the anterior / posterior as also in the lateral / medial dimensions or levels continuously beveled. Thus, the cross section of the shaft 21 is oval, where dna Increasing oval from the proximal end 25 in the direction of the distal end 47 becomes smaller, as can be seen from the sections of the shaft 21 shown in FIGS. The larger diameter of the Ovals are arranged in the lateral / medial direction (L-M), while the shorter diameters of the ovals are arranged along the anterior / posterior direction. Furthermore, the corners are rounded and no sharp edges that could cut into the cement and cause breaks or cuts in the cement. With the special described Configuration of the shaft 21, synergistic results are obtained from the following description of the application the hip joint prosthesis 11 can be understood.

There are preferably at least three sizes of the thigh section 13 are provided, which are designed so that they on the one hand

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are anatomically compatible, but on the other hand there is a minimal concentration of tension in the thigh sections, combined with an improved distribution of the weight load and an increased range of motion. FIGS. 12-14 show how the different sizes are preferably related to one another. FIG. 12 shows a thigh section with a small neck, FIG. 13 shows a thigh section with a medium-sized neck, and FIG. 14 shows a thigh section with a longer neck. For the sake of clarity, the reference numerals of the different parts of the thigh section with the short neck are provided with a prime (e.g. 13 '), while the reference numerals of the thigh sections having the medium-sized neck or the long neck are provided with a double prime (e.g. 13'') ) or with a three-mark (e.g. 13 ^MI ). From Fig. 12 to 14 it follows that the distances D ¹ , D "and D *" between the lines L ', L "and L" ¹ through the centers of the heads 17', 17 "and 17"'and parallel to the lateral edges 44 ', 44 ^1? and 44 '"of the straight sections 43', 43" and 43 '"are the same size for all three sizes, and that the angles S', S" and S '"' between the neck axes N ', N' to create different neck sizes 'and N ¹¹¹ and the lateral edges Vi ¹ , 44' · and 44 '·' of the straight sections 43 ', 43 "and 43"' are of different sizes. The specific dimensions of the three sizes are when using a 25mm head such as follows:

Neck length * "

Thigh Section 13 '44.5 mm (1.75 ") Thigh Section 13" 50.8 mm (2.00 ") Thigh Section 13 "'57.15mm (2.25")

^ measured from the top of the head to the bottom of the neck.

Other head sizes can also preferably be provided, for example a head size of 32 mm, which would include different neck lengths.

The waist portion 15 is preferably made of plastic, for example polyethylene with ultra high molecular weight in one piece. Of the

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Neck angle 0 135 0 144 / 7 ° 149

Waist section 15 includes a substantially hemispherical Body 55, the inner surface of which is defined by the pan 31 and the outer surface 57 thereof protrudes outwardly from the pan 31 ■ is ". -. An important feature of the hip section 15 is that the body 55 from the pan 31 to the outer surface 57 a has constant thickness, so that a uniform wear thickness or a section is provided that has no thin areas, as is the case with some known hip sections, in the outer surfaces of which grooves for receiving the cement are formed that extend towards the pan and in these areas Reduce the thickness of the body, adding rings between these grooves. In contrast, the hip section has 15 does not have any grooves in the form of indentations machined into the body 55. Instead, a number of rings are 59 provided, which are made in one piece with the body 55, of which Outer surface 57 of the body '55 protrude outward and for the purpose of formation are spaced from receiving grooves 61 for the cement.

The waist portion 15 also has an entrance opening 63, the leads to the pan 31 and from an annular section 65 to ^ ebon which is made in one piece with the body 55 and ends in an annular surface 67. In rings 59 and in section 65 notches 69 are provided which are spaced around the rings 69 and the section 65 are arranged.

When implanting the artificial hip joint 11, the usual surgical methods for implanting the hip section a 15 in the acetabulum A and the thigh section 13 in the thigh F by means of cement C are used. Using the invention, various synergistic results are obtained, particularly in connection with the structure and configuration of the two sections. This includes, inter alia, the wedge effect or the outward driving of the cement into the cavities of the bone when the shaft 21 is inserted into the medullary canal M of the thigh F due to the continuous beveling of the shaft 21 from the proximal end to the distal end. Due to this wedge effect, the shaft is also firmly secured against wobbling after the cement has hardened. In addition, a uniform distribution of the load along the entire length of the shaft is ensured, while in known

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A concentration of stresses in a particular sections Area takes place so that the stress in this area is so great is that the shaft can even break. Still allows continuous Bevel a slight removal of the shaft 21 at a later point in time, if this is for example on the occasion of a Correction should be needed. From the above-mentioned angular relationship between the thigh sections with increasingly long ones Necks ultimately result in anatomical compatibility with improved thigh support. Other advantages result from the description above. '

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Claims (10)

2605305 Patent attorney, physicist Reinfräed FrEiir. v. D-35OO Kassel Brüder-Grimm-Platz 4 Telephone (0561) 1 5335 D 4805 RICHARDS MANUFACTURING COMPANY, INC, Memphis, Tennessee, USA Claims (ii Artificial hip joint, consisting of a hip section with a Pan and a thigh section with a movably mounted head in the pan and a head to be implanted in the thigh , a shaft having a proximal and a distal end, characterized in that the shaft (21) has an uninterrupted! Has outer surface, is continuously beveled from the proximal to the distal end and between the head (17) and its proximal end The end (25) has a neck (19) rigidly attached to these two, "" ■ - "■ '■■ .. 2. Artificial hip joint according to claim 1, characterized in that that the shaft (21) has an oval cross-section, in the egg: planted Condition of the shaft (21) the larger diameter in a medial / laterally plane and the smaller diameter in an anterior / Posterior plane is arranged, and that the shaft (21) both in the Medial / lateral direction as well as in the anterior / posterior direction is beveled. 3. Artificial hip joint according to claim 1 or 2, characterized in that that the cross-section of the neck (19) in the anterior / posterior dimension is narrower than in the medial / lateral dimension. ORIGINAL INSPECTED 809833/0893 4. Artificial hip joint according to one of claims 1 to 3, characterized characterized in that the outer surface of the shaft (21) is smooth and rounded. 5. Artificial hip joint according to one of claims 1 to 4, characterized characterized in that the waist portion (15) has a substantially hemispherical body (55), the inner surface of which forms the pan (31) and the outer surface (57) of which from the inner surface is spaced that the body (55) has a constant thickness, and that on the outer surface (57) at a distance several outwardly projecting Rings (59) are provided for the formation of receiving grooves (61) for cement (C). 6. Artificial hip joint according to claim 5, characterized in that the head (17) is substantially flat at its end connected to the neck (19), that an inlet opening (63) leading to the socket (31) is provided in the hip section (15) is that of an annular, with the body (55) in one piece and ending in an annular surface (67) up / jcben portion (65), and that the flat end (33) of the head (17) in a Position is movable in which it is arranged substantially flush with the annular surface (67). 7. Artificial hip joint according to one of claims 1 to 6, characterized characterized in that the neck (19) on the connecting parts with the proximal end (25) of the shaft (21) forms a shoulder (23). 8. Artificial hip joint according to one of claims 1 to 7, characterized it is indicated that the hip section (15) is made of plastic. 9. Hip section for an artificial hip joint, characterized by at least one of the features of claims 5 and 7. 10. thigh section for an artificial hip joint, characterized by at least one of the features of claims 1 to 4 and 6. EAD QRiQiNAL 809833/0 893