1 2016200441 17 Μ 2017
REVISION CUP ARRANGEMENT FOR HIP PROSTHESIS
[0001] The present invention relates to a revision cup arrangement for hip prosthesis. Such an acetabular revision system for hip prosthesis is known, for example, from DE 10 2006 002 210, DE 197 01 778 and DE 201 05 862, respectively. Revision cup arrangements for hip prosthesis are characterized in that the cup, i.e. that body of the cup arrangement for hip prosthesis which is attached to the hip side i.e. to the acetabular side to the bone, has a non-rotationally symmetrical, i.e. oval base surface. This reflects the fact that when employing the revision cup, which is implanted as a replacement for a previously implanted cup during first-time hip prosthetics of the respectively damaged hip joint, the bone material usually destroyed when the first original cup failed must be replaced since it is now no longer available for supporting the cup in the hip. An area must by covered by the cup which is larger than with the cup for the initial treatment, the outer circumferential surface of which essentially corresponds to that of a spherical zone, so that the spherical outer surface being provided between the upper flat terminations of the spherical zone side is designed in a strictly rotationally symmetrical manner.
[0002] Though the spherical outer surface of a cup of a revision prosthesis is substantially also located between two flattened face side surface that are provided at least predominantly parallel to each other, of which the lower face side surface leaves an opening to the inner seat exposed, the convex outer surface, however, is not rotationally symmetrical.
[0003] A longitudinal axis can for arthroplasty with conventional cups be laid through a bore which serves as a mounting aid for installing the cup and can be penetrated by a mounting rod to mount the cup in the hip bone. The face side surfaces commonly extend at a right angle to this central longitudinal axis.
[0004] The present invention seeks to provide a revision cup arrangement for hip prosthesis that reduces the risk of luxation of the hip bone.
[0005] The present invention accordingly relates to a revision cup arrangement for hip prosthesis with (13353242_1 ):KEH 1a 2016200441 17 Jul 2017 an oval cup forming an inner seat for pivotally seating the femur and having a convex outer surface which is not rotationally symmetrical, at least in one plane, an insert having a spherical outer surface for spherical seating within said inner seat and a spherical inner surface for spherical seating of a spherical head which is connected to the femur for forming a ball joint between the insert and the spherical head attached to the femur, an inlay which is connected to said cup and forms a spherical mating surface for said spherical outer surface of said insert for forming a ball joint between the inlay and the insert, and at least one attachment flange protruding from said cup formed with said cup as an integral component, wherein the outer circumferential surface of the cup is provided with a surface configuration in form of an open mesh promoting bone growth, wherein the inlay is made of metal and is provided with a tapering section and that the cup defines a seat for the inlay with a tapering mating surface for the tapering section and that the inlay is frictionally held in the cup by cooperation between the tapering section and the tapering mating surface, wherein the insert is made of PE, wherein the oval cup has a center bore defining a longitudinal axis and bores each provided with an internal thread and arranged around said longitudinal axis for the provision of an attachment stud projection over the dome.
(13353242_1): KEH 2 2016200441 27 Jan 2016 [0006] To solve this problem, the present invention proposes a revision cup arrangement for hip prosthesis having the features of claim 1. The revision cup arrangement for hip prosthesis comprises a commonly known oval cup forming an inner seat for pivotally seating the femur. However, pivotally seating the spherical head being attached to the femur does not occur immediately within this seat, but with the interposition of an insert having a spherical outer surface for spherical seating within the seat and a spherical inner surface for spherical seating of the spherical head. Thus the insert forms part of a ball joint for the spherical head and also forms part of a ball joint relative to the cup.
[0007] Distribution of the scope of motion onto two articulation surfaces is achieved with this embodiment. Articulation in the revision prosthesis according to the invention occurs, firstly, between the cup firmly fixed on the side of the acetabulum and the insert as well as, secondly, between the insert and the spherical head. This separation of the relative motions arising between the hip and the femur corresponds in a particular manner to the needs of patients whose cup arrangement for hip prosthesis has been replaced once or even several times and accordingly have extensive bone defects, in particular acetabular bone defects and ligament instabilities. The concept of dual mobility in combination with an oval cup is particularly suitable for this patient clientele.
[0008] The cup can there per se be configured as an integrally formed element, for example, by way of casting, EBM and SLM and form a spherical inner surface for spherically seating the insert. Commonly and according to a preferred embodiment of the present invention, however, an inlay, preferable made of metal, more specifically of a Co alloy is provided that is connected to the cup and forms a spherical mating surface for the spherical outer surface of the insert. The insert is accordingly via the inlay seated spherically in the cup. The inlay can be connected to the cup by means of a force closure, a positive fit and/or by frictional engagement. The inlay can be connected to the cup in various ways, for example, be glued, or by way of a screw and/or locking connection or by clamping i.e. by way of a tapered connection. The cup of the invention defines a seat adopted to receive the inlay, which seat is closed on the outer circumference in the mounted state in order to prevent ingrowth of cells into the seat. Thus, the inlay may be replaced easily without affecting the fixing of the cup to the human body by cells grown onto the outer surface of the cup. AH25(10934513_1) 3 2016200441 28 Mar 2017 [0009] According to a preferred embodiment of the present invention, at least one attachment flange protruding from the cup is provided on the cup. This attachment flange typically comprises one or more bores which can be penetrated by screws that are screwed to the acetabulum to enable reliable fixation of the cup.
[0010] The flange can there be formed together with the cup as an integrally formed component. Alternatively, the flange can be provided on a shaped sheet-metal element which comprises a dome covering the seat and is on an outer circumferential surface provided with a surface configuration promoting bone growth. Such a surface configuration can be connected by way of welding to the outer surface of the sheet-metal element and be formed, for example, by a wire mesh. The surface configuration can also be applied in a known manner by plasma spraying or be provided by EBM or SLM, respectively.
[0011] A surface configuration promoting bone growth of the aforementioned kind can be provided in the manner described above also on the integrally formed component shaping the flange and the cup.
[0012] Preferred embodiments of the present invention will now be described, by way of examples only, with reference to the accompanying drawings: [0013] Fig. 1 [0014] Fig. 2 [0015] Fig. 3 [0016] Fig. 4 shows a sectional view of an embodiment in an exploded illustration; shows the cup of the embodiment shown in Figure 1 in a different sectional view; shows a side view; and shows a plan view of an oval cup of another embodiment.
[0017] In the longitudinal sectional view of Figure 1, reference numeral 10 denotes a cup, reference numeral 20 a metal inlay and reference numeral 30 an insert. These elements constitute the elements of the revision cup arrangement for hip prosthesis. Reference numeral 40 graphically adds a spherical head which is after the arthroplasty treatment of the patient connected via a shaft to the femur of the patient and can be seated spherically in an inner circumferential surface 31 of the insert. The insert 30 is made of PE, in particular high density PE (HDPE). Insert 30 has a spherical outer circumferential surface 32 that is spherically in 12852269_1 :hxa 4 2016200441 27 Jan 2016 abutment with a spherical mating surface 21 formed by inlay 20 and spherically seated there. Inlay 20 is formed from metal, for example steel, and in the region of the opening to the mating surface 21 on the outside comprises a tapering section 22 that can interact with a tapering mating surface 11 in part defining a seat 12 of cup 10 in order to connect inlay 20 to cup 10 and secure it thereon in a rotationally-fixed manner. Corresponding mounting of inlay 20 and cup 10 is shown in Figure 2. As is further illustrated by Figures 1 and 2, cup 10 comprises a flange 10a protruding from its spherical base body and being provided with several bores. The base body of cup 10 is penetrated by a center bore 13 with an internal thread defining a longitudinal axis L. In the region of the dome and the base body of cup 10, additional bores 14 are provided which are each provided with an internal thread to mount either a cover cap connection to the dome side or an attachment stud projection over the dome. As further illustrated by the hatching on the convex outer surface of cup 10, the latter is provided with a surface configuration 15 promoting bone growth. This is presently an open mesh that is welded on and provides a plurality of cavities for the bone cells to grow into. This surface configuration 15 is about the longitudinal axis L defined by material of the base body of cup 10 which forms a first small face side surface 16 extending at a right angle to the central longitudinal axis L. A second face side surface 17 on the oppositely disposed side defines seat 12.
[0018] Figures 3 and 4 demonstrate the oval shape of the cup base body, i.e. of the cup without flange 12. Figure 3 there shows a side view in a plane perpendicular to the plane of face side surfaces 16 and 17, respectively, and parallel to longitudinal axis L. Longitudinal axis L crosses a first transverse axis Q1. The point of intersection of the two lines L, Q1 is the center of a first sphere K1 with a diameter of 56 mm. Drawn in parallel to line Q1 is a second line Q2 which is in the direction toward larger face side surface 17 provided slightly offset relative to line Ql. Drawn in with an offset VI of presently 8 mm, but parallel to longitudinal axis L, is a second longitudinal axis L2. Point of intersection L2, Q2 forms the center of a second sphere K2 with a diameter of 52 mm. Parts of the two sphere surfaces form the outer surface of cup 10, which is therefore not formed as being rotationally symmetrical, as evidenced by contours ΚΙ, K2 in Fig. 3 and Fig. 4. Fig. 4 there illustrates a top view in a plane perpendicular to longitudinal axis L and onto smaller face side surface 16 of sphere 10. This configuration gives rise to an oval design with a cranial structure A having an offset V2 of 6 mm relative to the sphere surface of sphere K1. In the embodiment shown in Figures 3 and 4, the base body of the cup is made of cobalt-chromium-molybdenum cast material onto which surface configuration 15 is applied as a AH25( 10934513 1) 5 2016200441 27 Jan 2016
TiNb coating. As is evident, axes Ql, Q2 are in this plan view congruent, so that cranial structure A is mirror-symmetrical to transverse axes Ql and Q2.
List of reference numerals 10 cup 11 tapering surface 12 seat 10a flange 13 center bore 14 lateral bores 15 surface configuration promoting bone growth 16 smaller face end surface 17 larger face end surface 20 inlay 21 mating surface 22 tapering surface 30 insert 31 inner circumferential surface 32 outer circumferential surface 40 sphere head A cranial structure L longitudinal axis L2 second longitudinal axis K1 first sphere K2 second sphere
Ql first transverse axis Q2 second transverse axis AH25(10934513_1)