FI70129B - LAORBENSDEL FOER HOEFTLEDSENDOPROTES I ETT STYCKE - Google Patents

Abstract

1. A one-piece femoral portion of a hip joint endoprosthesis comprising a head (11), a shank (10) having in the frontal plane respectively concavely or convexly curved sides, said shank constantly tapering downwardly in the frontal plane and adapted to be anchored in the femur with bone cement, and a neck portion (12) arranged between the shank (10) and the head (11), characterized in that the medial side (14) of the shank (10) extending longitudinally of the shank is convexly curved and the lateral side (13) extending longitudinally of the shank is concavely curved, with the curvature being selected such that the medium region of the shank (10) in the implanted condition rests against the medial corticalis of the femur with the lower end region (25) of the shank (10) being formed in such a manner that it is supported at the lateral corticalis in the implanted condition.

Description

NOTICE 7 f) d O Q

«TSPl? ™ 11 UTLÄGGNINGSSKRIFT / UlZy c (45) Pr te .Iti ... yϋtty (51) Kv.lk. * / Lnt.CI. «A 61 F 2/32 (21) Patent application - Patentansöknlng 800731 (22) Application date - Ansökningsdag 1 0.03.8 0 (Fl) * * (23) Start date - Giltighetsdag 10.03.80 (41) Has become public - Blivit offentlig 05.02.81

National Board of Patents and Registration of Finland Date of display and moonshine. - 28.02 86

Patent and registration authorities Ansökan utlagd och utl.skriften publicerad (32) (33) (31) Pyydetty etuoikeus - Begärd priority 04.08 .79

Republic of Germany-Förbundsrepubliken Tyskland (DE) P 2931750.8 Proven-Styrkt (71) Howmedica International, Inc., Zweigniederlassung Kiel,

Professor-Κϋηtscher-St rasse 1-5, 2301 Schönkirchen il. Kiel,

Federal Republic of Germany-Förbundsrepubliken Tyskland (DE) (72) Hartmut Seidel, Hamburg, Karl M. Richter, Wendtorf,

Hans Erich Harder, Probsteierhagen, Klaus Behrens, Rickling,

(1) an anchored arm having concavely and convexly curved sides in the front plane and which in the front plane is continuously tapered downwards and a neck portion arranged between the arm and the head.

One such hip prosthesis has already become known (German Offenlegungsschrift Publication No. 27 47 867). The stem is attached with bone cement to the femoral core cavity, and the articular head interacts with the hip vase in the pelvic bone or the hip vase in metal or plastic, which replaces the cartilage layer of the hip vase. The downwardly tapering prosthesis arm is curved into a banana shape, with the convexity of the curvature directed laterally.

Alloplastic hip replacements are subject to considerable static and dynamic loads, so that despite considerable progress in the design of internal prostheses as well as medical care, the risk of loosening over time has been eliminated. disappears.

It is therefore an object of the present invention to provide a one-piece hip prosthesis which can be attached with maximum certainty to the femoral core cavity with the best possible transmission of dynamic and static forces and strength of the joint.

This problem is solved in that the longitudinally extending inner side of the stem has a convex curvature and the longitudinally extending outer side has a concave curvature, the curvature being selected so that the center of the stem in the attached state contacts the central femur and the lower end region is rests against the lateral cortex of the femur.

In contrast to the known hip prostheses, according to the present invention, the curvature or curvature of the prosthesis arm is opposite, namely directed inwards. This curvature of the stem allows for a wide cement filling at Trochanter minor and the best possible utilization of Trochanter Major.

In the known prosthesis, when the arm is curved in the bending direction, the curvature of the prosthesis according to the present invention is opposite and acts like a drawbar, and shows its effect with excellent advantage over the tensile and bending stress. This fact is of more considerable significance than the occasional deflections of the prosthesis arm due to load pulses which result in loosening of the joint with the bone cement.

The hip prosthesis according to the invention provides a secure and durable attachment in the femoral core cavity. In this connection, an embodiment of the invention is designed in such a way that the curvature is chosen so that the central region of the arm rests against the central shell of the femur.

3,70129

A double support is obtained when, according to an embodiment of the invention, the lower end region of the arm is shaped so as to rest against the lateral shell of the bone. Double surface contact with opposite sides of the shaft results in excellent security in the core cavity and resists deformation of the shaft so that the risk of loosening is greatly avoided.

An embodiment of the invention is characterized in that the width of the arm in the front plane is greater in the upper region and in the central region than perpendicular to it, preferably approximately 1 1/2 to 2 times greater. This achieves a wide surface support of the prosthesis to the bone cement and prevents fragmentation of the cement.

An embodiment of the invention is characterized in that the front and / or back part of the arm in the front plane is provided with a plurality of notches, which are preferably formed in a honeycomb manner. The honeycomb shape allows for even wider support of the prosthesis in the cement and improves the dissipation of polymerization heat as the bone cement hardens.

An embodiment of the invention is characterized in that the neck part gradually becomes a wider collar, the underside of which forms a shoulder surface for resting on the proximal end of the femur to be treated. In this way, the support of the prosthesis is provided, which, under load, acts against the bone-breaking wedge effect of the prosthesis. Otherwise, the tensile and bending stress of the arm is reduced by the effect of the support on the bone. The structure of such a collar is known per se (German Offenlegungsschrift No. 27 47 867). However, it is very advantageous in connection with the prosthesis according to the present invention.

There is a risk of joint damage when inserting tentative hip prostheses. Therefore, according to an embodiment of the invention, a connecting shoulder is formed on the outer side of the neck area. With the help of a suitable device, the prosthesis can be placed 4 70129 firmly in place without damaging the head. In addition, the connecting shoulder can be used for removal purposes when, according to yet another embodiment of the invention, it is made to have a hole, a back section or the like, for the purpose of cooperating with the removal tool.

An embodiment of the invention will be explained in more detail below with reference to the accompanying drawing, in which:

Figure 1 shows a side view of a right hip joint prosthesis according to the invention.

Figure 2 shows a partial section of the prosthesis of Figure 1.

Figure 3 shows a section taken along line 3-3 of the prosthesis of Figure 1.

Before going into the details of the application example, it should be emphasized that all the details shown and explained in the drawing alone and in connection with the features of the claims are essential to the invention.

The hip prosthesis shown in Figures 1-3 for the right hip joint has an arm 10, a spherical head 11 and a neck 12. The one-piece prosthesis is made of Co Cr Mo material. The end 11 has a brilliant-polished surface, while the rest of the prosthesis is opaque. The diameter of the head is preferably 32 mm.

The longitudinal side 13 of the prosthesis arm 10 is bent concavely curved and the inner side 14 convexly curved. The curvature preferably takes place with the same radius, most preferably with a radius of 600 mm. The concave curvature of the side 13 ends at 15 at the bottom and the convex curvature at 16. At 15 and 16, the latter being slightly higher, the arm 10 tapers downwards to the triangularly rounded tip 17 according to Figure 1. According to Figure 1, the left side of the lower end region is indicated by reference numeral. 13, forms a contact surface 5 70129 against the side shell of the femoral cavity, not shown, for placement. As can be seen from Figures 1 and 2, the lower end region approximately forms a truncated cone.

It can be seen from Figure 1 that the front and rear sides of the arm 10 decrease slightly in width down to points 15 and 16. The smallest taper also occurs in a plane perpendicular to the width, as can be seen in Figure 2. However, the taper angle in the vertical direction is only 1 °.

Furthermore, it can be seen from Figures 1-3 that the diameter of the arm 10 in the front plane is considerably larger than in the plane perpendicular thereto. Preferably, the larger diameter is one and a half - twice the smaller diameter. It can be seen from Figure 3 that the front and rear sides of the arm 10 run parallel to each other and the side 13 and the inner side 14 are preferably curved with the same radius.

The front and rear sides of the arm 10 have a row of notches 18 with a rectangular contour and a flat bottom surface, whereby the size of the notches 18 decreases from top to bottom. The notches 18 give the shaft a honeycomb structure. The individual cavities are separated from each other by partitions 19, the upper edges of which extend to the outer and inner sides 13 of the arm, respectively. 14, as shown in Figure 2.

The neck portion 12 expands approximately conically in the direction of the arm 10 and thus forms a collar 20 which on its lower surface forms a planar shoulder surface 21 at an angle 113 113 ° to the axis of the neck 12 and the head. This angle corresponds approximately to the angle of the femoral neck with respect to the femoral axis in older people.

The arm 10 becomes a collar 20 through a concave portion 22.

A connecting shoulder 23 with an opening 24 is arranged on the longitudinal side of the neck part 12. On the left side in Fig. 1, the connecting shoulder 23 evenly joins the side of the arm 10. The upper side of the connecting shoulder 23 serves to position the prosthesis shown 6 701 29, while the opening 24 can be used for removal.

The prosthesis shown allows double support in the core space and specifically from the inside against the shell in the central region of the arm 10 and laterally against the shell at the tip of the prosthesis arm, namely with the surface 18. The curvature of the shaft 10 as shown in Figure 1 allows for a wide cement filling at the Trochanter minor and the best possible utilization of the Trochanter Major for fixing. The honeycomb shape improves the support of the prosthesis in the cement and the dissipation of the polymerization heat. The relatively wide front and back surfaces of the shaft 10 prevent the cement from fragmenting.

The wide support of the prosthesis when loaded by the shoulder surface 21 counteracts the bone-breaking wedge effect of the prosthesis and reduces the tensile and bending stress of the arm.

Claims (11)

1. A piece of hip joint for a hip joint endoprosthesis, with a head (11), a bone cement in a femur anchoring shaft (10) having concave and convex curved sides, respectively, which in the frontal plane continuously tapering downwards, and one between the shaft (10) and the head (11) arranged neck portion (.12), characterized in that the medial side (14) of the shaft (10) extending in the shaft lengthwise direction has convex curvature and the lateral side extending in the shaft length direction (10). 13) has concave curvature, with the curvature being so selected that the middle region of the shaft (10) in the implanted state abuts against the medial Corticalis of the femur and the lower end region (25) of the shaft (10) is so shaped that it in the implanted state supports lateral corticalis. 2. The leg portion according to claim 1, characterized in that the lower end region has an approximation parallel to the wall of the nerve tube in the lateral cortical region (25) extending laterally. The leg portion according to claim 1 or 2, characterized in that the shaft width (10) in the frontal plane is larger in the upper region and the middle region than perpendicular thereto, preferably approximately 1 1/2 to 2 times larger. in 4. Leg portion according to any one of claims 1-3, characterized in that the front and / or back side of the shaft (10) lying in the frontal plane has several recesses (18). 5. Leg portion according to claim 4, characterized in that the front and / or back side of the shaft (10) has a honeycomb structure. 6. Leg portion according to any one of claims 1-5, characterized in that the neck section (12) in the direction of the shaft transmits in a progressively wider collar (20) forming on the underside a shoulder surface (21) for abutment towards the proximal end. of femur processed.