Joint socket for a prosthetic joint
Patent Information
- Application Number
- EP2023817069
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2022-12-06
- Filing Date
- 2023-11-29
- Publication Date
- 2025-10-15
AI Technical Summary
Existing joint prostheses weaken the bone structure due to required depressions, leading to increased risk of fractures and reduced holding forces, especially during revision operations, and radial spreading forces can cause detachment of the implant from the bone tissue.
A joint socket design featuring projections that engage in a groove-shaped recess in the bone structure, providing a clamping effect to absorb forces transverse to the axis and prevent radial spreading forces, with a ring-shaped projection enclosing the socket insert and adjustable geometry for optimal positioning and fixation.
The design significantly increases holding forces, preventing detachment and fracture progression, while minimizing bone removal and allowing for secure fixation under heavy loads, with improved bone resilience and reduced risk of bone structure weakening.
Smart Images
Figure 1.1
Abstract
Description
[0001] Joint socket for a joint prosthesis
[0002] The invention relates to a joint socket for a joint prosthesis which can be fixed in a bone structure and has a socket insert for receiving an at least partially spherical joint body.
[0003] Joint prostheses with anchoring components that can be screwed into the bone are already known in various designs and applications, particularly in hip joint prostheses. In this case, the socket is inserted, tapered side first, into a surgically prepared recess in the bone.
[0004] In practice, conical or spherical acetabular cups are commonly used, each comprising a metallic outer shell and an insert or inlay arranged within the shell, usually made of ceramic, plastic or metal.
[0005] One advantage of using spherical cups is that less bone substance from the pelvic bone needs to be removed when pre-milling the spherical cavity than with a conical-shaped cup. The milling itself is also easier with spherical cups, as orientation has little influence.
[0006] In addition to the standard spherical cup design, which corresponds to a hemisphere, press-fit versions are also used. The press-fit cups are slightly flattened at the pole and slightly larger in diameter than the pre-milled hemispherical bed in the bone. This ensures a press fit of the cup in the pre-milled bone. A rough surface coating on the commonly used shells made of metals such as pure titanium facilitates the grafting of bone cells to the implant. This is intended to ensure optimal stabilization. In contrast to screw-in cups, the spherical cups without threads, and especially the press-fit cups, are impacted or pressed into the pre-milled bed in a linear motion.
[0007] EP 0 169 978 B1 discloses an endoprosthesis for an acetabular cup, consisting of an inner cup body and an outer shell, suitable for cementless anchoring. The cup body is provided with a conical shell and the outer shell with a cavity adapted to the shell. The outer shell and the cup body are held together by a locking structure. Several slots are evenly distributed around the circumference of the outer shell, and the surface of the outer shell is provided with a structure consisting of projections. The projections are pin-shaped and are placed on the surface of the expansion cup.
[0008] EP 0 242 633 B1 discloses an endoprosthesis for an acetabular cup, consisting of an inner cup body and an outer shell, suitable for cementless anchoring. The endoprosthesis has a structure consisting of several peripheral rows of projections in the equator-facing region of the outer shell surface. The projections are thorn-shaped and arranged on concentric circles on the surface of the expansion cup.
[0009] DE 35 18246 A1 relates to an acetabular cup prosthesis with a conical outer shape for insertion into a correspondingly shaped hole in a bone, wherein the conicity of the conical shape is designed for permanent engagement with the surrounding bone.
[0010] In the joint prosthesis known from DE 2925 089 A1, an inner cup and an outer ring are provided, wherein the cup is subjected to an annular bandaging load which is exerted on the cup by the outer ring either directly or by means of a possibly interposed intermediate ring piece which is arranged between the cup and the ring.
[0011] DE 3347 983 C2 relates to a joint socket prosthesis with a shell that can be fixed to a bone and with an insert that can be inserted into the shell and consists of two bearing segments that enclose the joint ball without any division. A slotted ring can be elastically expanded so that it can be pushed over the joint ball. DE 102006 019620 B4 relates to an artificial joint socket with a number of radial through holes for the passage of a bone screw for anchoring the socket in the adjacent bone area.
[0012] From WO 1985 / 02 535 A1, an artificial acetabulum for a hip joint is already known, comprising a shell having a spherical cap-shaped inner surface and a hollow cylindrical anchoring part which, on the one hand, rests against the shell and, on the other hand, is open at its free end facing away from the shell.
[0013] US 11 478 358 B2 describes an implant comprising a shell with a body defining a bone-facing recess, wherein the bone-facing recess comprises an annular surface and a convex surface. The annular surface has a profile corresponding to the outer bone ring and may include retaining elements, such as projections or recesses, that engage the bone.
[0014] A disadvantage of the current state of the art is that bone implants weaken the bone substance due to the necessary indentations, resulting in an increased risk of possible fractures. This is especially true for revision surgeries, which are usually associated with further bone loss.
[0015] A particular disadvantage of expansion cups for hip joint prostheses is that the projections on the expansion cup are arranged in such a way that forces acting in the bone tissue opposite to the implantation direction of the expansion cup can cause the expansion cup to detach from the bone tissue.
[0016] A particularly disadvantageous factor is the direction of the fixation forces, which in most fixation options used in practice are essentially directed radially outward, creating spreading forces. These spreading forces can be a cause of a not uncommon reduction in the holding force of the acetabulum in the bone structure.
[0017] The invention is based on the object of creating a way to largely compensate for the unavoidable weakening of the bone substance through the design of the acetabulum, so that the load-bearing capacity of the bone structure is not reduced but improved. In particular, the introduction of radial spreading forces into the bone structure surrounding the acetabulum is to be avoided. This object is achieved according to the invention with an acetabulum according to the features of claim 1. The further embodiment of the invention can be found in the subclaims.
[0018] According to the invention, a joint socket is therefore provided in which the joint socket has at least one projection facing the bone structure and intended to engage in a groove-shaped recess in the bone structure which is radially spaced from the depression for the socket insert in the bone structure, which projection encloses the socket insert circumferentially, in particular concentrically, at a small distance, wherein the projection has, at least in sections, a convex outer surface delimited by an outer, annularly closed contour, and a concave inner surface delimited by an inner, annularly closed contour, so that the projection can be inserted into the groove-shaped recess in a form-fitting manner with the outer surface and the inner surface, and the outer surface and the inner surface each bear against a wall surface delimiting the groove-shaped recess.
[0019] The invention is based on the finding that the load-bearing capacity of the bone structure weakened due to the loss of substance required to accommodate the acetabulum can be restored by enclosing the acetabulum insert with one or more projections of the acetabulum, similar to a ring clamp or a cuff. In particular, the introduction of radial spreading forces into the bone structure surrounding the acetabulum is to be avoided.
[0020] The effect according to the invention is based on the fact that the load-bearing capacity of the bone receiving the acetabulum, for example the pelvic bone, is improved in that the forces acting transversely to the axis, namely on the one hand the spreading forces due to the inserted acetabulum and on the other hand due to external forces, in particular as a result of joint loading, can be reliably absorbed by the projection, thus avoiding additional forces acting on the bone structure. For example, bending forces of the bone are also absorbed in that strains in the plane of the bone surface are absorbed by the at least one projection. For the first time, the prosthesis can therefore also absorb tensile forces transversely to the axis of symmetry of the acetabulum. This creates a clamping in the surface and the enclosed area supporting the shell insert remains free from unwanted forces.At the same time, the achievable fixation forces of the acetabulum are also increased, ensuring that it remains reliably fixed even under heavy loads and does not detach from the bone structure because the holding forces within the bone are significantly increased. It has been shown that the fixation can even prevent the progression of a fracture in the bone structure, and that the acetabulum remains securely fixed even if such a fracture occurs. Due to the significantly increased holding forces compared to the state of the art, the amount of bone structure that needs to be removed can be kept to a minimum.
[0021] It has already proven particularly advantageous if the projection is closed in a ring shape and encloses the cup insert on the periphery. This makes the effect of the circumferential clamping independent of direction, which also simplifies the fixation of the projection in the groove-shaped recess. In practice, the resulting clamping forces alone lead to sufficient fixation.
[0022] Furthermore, it is particularly promising if the projection has a circular cross-section with a constant wall thickness and concentrically encloses the acetabulum. Due to the rotationally symmetrical design of the circular or conical projection, the achievable holding forces are independent of the angular position, allowing the acetabulum to be inserted in any angular position, thus facilitating the operation. A core drill, preferably in conjunction with a depth stop, can be used particularly easily to create the groove-shaped recess, thus eliminating the effort associated with using milling tools.
[0023] In another, equally particularly useful modification of the invention, several projections are arranged within an annular region delimited by the outer contour and by the inner contour, spaced apart from one another in the circumferential direction. This allows several, preferably geometrically matching, projections to be used for fixation, thus further increasing the fixation forces. For this purpose, the projections can have angled or bent portions on the front side that penetrate the bone structure upon rotation of the joint socket. Furthermore, the projections can transmit increased clamping forces if at least some of the projections are adjustable, for example, in order to brace them within the recess against the delimiting wall surfaces.
[0024] Particularly preferably, several spaced-apart projections are arranged evenly distributed around the circumference, so that the holding forces are introduced into the bone structure evenly over the entire circumference. The adjacent projections can have a different geometry and also a different length. However, it is particularly advantageous if the axial extension of the projection in the circumferential direction is constant and / or the axial extension of adjacent, in particular all, projections is identical, so that the joint socket reliably reaches a depth position within the bone structure predetermined by the groove-shaped recess and this position is permanently maintained.
[0025] Furthermore, according to a further useful modification of the invention, the at least one projection can be fixed in different positions, particularly continuously, in the axial direction parallel to the axis of symmetry of the joint socket. This allows the depth position of the joint socket to be adjusted using the projection, thus achieving optimal positioning. By adjusting the axial depth position differently for several projections distributed around the circumference, a desired angle of inclination of the joint socket can also be set as needed.
[0026] In practical testing, it has already proven to be useful if the radial distance of the projection relative to the cup insert is between 0.5 mm and 10 mm, the depth of the groove-shaped recess is between 5 mm and 35 mm and the distance between the convex outer surface and the concave inner surface is between 1 mm and 5 mm.
[0027] A further, particularly advantageous embodiment of the invention is achieved when the at least one projection has ingrowth openings on its outer surface and / or inner surface. These ingrowth openings, also referred to as ingrowth indentations, promote the ingrowth of the surrounding bone substance and, after a short time, form undercuts with the acetabulum, which is thereby reliably fixed.
[0028] A variant of the invention has already proven particularly promising, in which the acetabulum has a retaining frame with a passage width smaller than the great circle diameter of the acetabulum insert. This secures a spherical joint body inserted into the acetabulum insert by the retaining frame, preventing dislocation of the joint.
[0029] Preferably, the opening width can be expanded to the great circle diameter, counter to an elastic restoring force of the holding frame, so that the joint body is secured in the socket insert according to the principle of a snap lock. By having a bottom side of the socket facing the bone structure within the recess, which, in the implanted position, is inserted into the recess at a distance from the bone structure, a gap is created so that the fixation forces are introduced into the recess of the bone structure exclusively or at least largely by means of the projection.
[0030] The invention allows for various embodiments. To further clarify its basic principle, one of them is shown in the drawing and is described below. This shows in
[0031] Fig. 1 is a front perspective view of an acetabular cup according to the invention;
[0032] Fig. 2 is a rear perspective view of an acetabular cup according to the invention;
[0033] Fig. 3 is a front perspective view of a bone structure with a recess for a socket insert of the acetabulum and with a concentric groove-shaped recess;
[0034] Fig. 4 is a sectional view of the bone structure shown in Figure 3 with the recess for the socket insert of the lateral groove-shaped recess;
[0035] Fig. 5 is a front perspective view of the bone structure shown in Figure 3 with the acetabulum fixed therein;
[0036] Fig. 6 a sectional view of the bone structure shown in Figure 5 with the acetabulum fixed therein:
[0037] Fig. 7 is a front perspective view of another joint socket according to the invention;
[0038] Fig. 8 is a rear perspective view of the acetabulum shown in Figure 7;
[0039] Fig. 9 is a front perspective view of another joint socket according to the invention; Fig. 10 is a rear perspective view of the joint socket shown in Fig. 9;
[0040] Fig. 11 is a perspective view of a holding frame;
[0041] Fig. 12 the acetabulum shown in Figure 9, which is anchored in a bone structure;
[0042] Fig. 13 a sectional view of the bone structure shown in Figure 12 with the acetabulum fixed therein;
[0043] Fig. 14 is a perspective view of another joint socket according to the invention with an eccentrically designed socket insert;
[0044] Fig. 15 a sectional view of the bone structure shown in Figure 14 with the acetabulum fixed therein.
[0045] A joint prosthesis 1 with an inventive joint socket 2, which includes a socket insert 3 for receiving a joint body (not shown), is explained in more detail below with reference to Figures 1 to 13. The joint socket 2 has a cylindrical outer contour 4 in its basic shape. At a section facing away from an opening 5 of the joint socket 2, the outer contour 4 is designed in the shape of a circular tube as a circumferential edge and thereby forms a projection 7 facing a bone structure 6 shown merely as an example. The projection 7 is concentric to the socket insert 3, as can be seen particularly in Figures 4 and 5.The projection 7 serves to fix the joint socket 2 in a recess 8 intended for the socket insert 3 and is for this purpose inserted into a groove-shaped recess 9 in the bone structure 6 which radially encloses the recess 8, whereby the projection 7 concentrically encloses the socket insert 3 with a small radial distance. For this purpose, the projection 7 can be applied with its convex outer surface 10 and its concave inner surface 11 against a respective wall surface of the groove-shaped recess 9 in a force-fitting manner. The projection 7 thereby forms a clamping sleeve around the socket insert 3, whereby the load-bearing capacity of the bone structure 6, which has been weakened for the joint socket 2 due to the loss of substance caused by the recess 8 in the bone structure 6, is restored by absorbing both radial spreading forces due to the fixation of the joint socket 2 and external forces, and the bone structure 6 is not subjected to any further stress.As can be seen in particular in Figures 1, 2 and 5, the projection 7 has on its outer contour 4 a plurality of ingrowth openings 12 into which the surrounding bone substance 6 grows and thereby forms an undercut that fixes the joint socket 2.
[0046] As can be seen in particular in Figures 6 and 13, a bottom side 13 of the joint socket 2 is fixed in the bone structure 6 within the recess 8 in the implanted position at a distance A from the bone structure 6 in order to concentrate the force introduction on the projection 7.
[0047] Figure 11 shows a holding frame 14, which can be seen in an assembled position in Figures 9, 10, 12, and 13. The holding frame 14 has a smaller opening width D than the great circle diameter of the socket insert. As a result, a spherical joint body inserted into the socket insert is secured by the holding frame, preventing dislocation of the joint. The holding frame 14, in turn, has two projections 7', which are connected flush with the projections 7 of the socket 2, as can be seen in Figures 9 and 10.
[0048] Figures 14 and 15 show yet another variant of a further joint socket 2 according to the invention with an eccentrically designed socket insert 3 in a perspective view and a sectional side view. The joint socket 2 has a cylindrical outer contour 4 in its basic form with a circular ring-shaped edge as a projection 7, which is arranged concentrically to the outer contour 4 of the socket insert 3. A receptacle 16 for a joint ball (not shown) is not coaxial, but is arranged eccentrically with respect to the outer contour 4 with an offset V of a central axis 17 of the receptacle 16 relative to a central axis 15 of the joint socket 2, so that different edge distances R, r result in different circumferential sections.By changing the angular position of the projection 7 within the groove-shaped recess 9, shown, for example, in Figure 13, the central axis 17 of the receptacle 16 can be easily aligned and positioned optimally relative to the bone structure 6. The recesses designed as ingrowth openings simultaneously serve as tool receptacles 18 for manually transmitting the rotational movement of the acetabulum 2. REFERENCE SYMBOL LIST.
[0049] 1 joint prosthesis
[0050] 2 acetabulum
[0051] 3 pan inserts
[0052] 4 Outer contour
[0053] 5 Opening
[0054] 6 Bone structure
[0055] 7 lead
[0056] 8 Deepening
[0057] 9 Recess
[0058] 10 Exterior area
[0059] 11 Inner surface
[0060] 12 Ingrowing opening
[0061] 13 Subpage
[0062] 14 holding frames
[0063] 15 Central axis
[0064] 16 recording
[0065] 17 Central axis
[0066] 18 Tool holder
[0067] A distance
[0068] D Passage width
[0069] V offset r, R edge distance
Claims
PATENT CLAIMS E 1. A joint socket (2) for a joint prosthesis (1) which can be fixed in a bone structure (6) and has a socket insert (3) for receiving a joint body which is at least partially spherical, wherein the joint socket (2) has at least one projection (7) facing the bone structure (6) and intended to engage in a groove-shaped recess (9) in the bone structure (6) which is radially spaced from the depression (8) for the socket insert (3) in the bone structure (6), which projection encloses the socket insert (3) on the circumferential side, in particular concentrically, and wherein the projection (7) has at least partially a convex outer surface (10) and a concave inner surface (11), such that the projection (7) can be inserted into the groove-shaped recess (9) with the outer surface (10) and the inner surface (11) in a form-fitting manner.
2. Joint socket (2) according to claim 1, characterized in that the projection (7) is annularly closed and encloses the socket insert (3) on the circumference.
3. Joint socket (2) according to claim 1 or 2, characterized in that the projection (7) is tubular, in particular circular tubular, and concentrically encloses the socket insert (3).
4. Joint socket (2) according to at least one of the preceding claims, characterized in that a plurality of projections (7) are arranged spaced apart from one another in the circumferential direction within an annular region delimited by the outer contour and by the inner contour.
5. Joint socket (2) according to claim 3, characterized in that several projections (7) spaced apart from one another are arranged evenly distributed around the circumference.
6. Joint socket (2) according to at least one of the preceding claims, characterized in that the axial extent of the projection (7) is constant in the circumferential direction and / or the axial extent of adjacent, in particular all, projections is the same.
7. Joint socket (2) according to at least one of the preceding claims, characterized in that the at least one projection (7) can be fixed in different positions, in particular continuously, in the axial direction parallel to the axis of symmetry of the joint socket (2).
8. Joint socket (2) according to at least one of the preceding claims, characterized in that the radial distance of the projection (7) relative to the socket insert (3) is between 0.5 mm and 10 mm and / or the distance between the convex outer surface (10) and the concave inner surface (11) is between 1 mm and 5 mm.
9. Joint socket (2) according to at least one of the preceding claims, characterized in that the joint socket (2) and / or the at least one projection (7) has ingrowth openings (12) on its outer surface (10) and / or its inner surface (11).
10. Joint socket (2) according to at least one of the preceding claims, characterized in that the joint socket (2) has a holding frame (14) with a passage width (D) which can be changed, in particular against an elastic restoring force, and which is smaller than the great circle diameter of the socket insert (3).
11. Joint socket (2) according to at least one of the preceding claims, characterized in that the joint socket (2) has a bottom side (13) facing the bone structure (6) within the recess (8), which bottom side can be inserted at a distance from the bone structure (6) in the implanted position.
12. Joint socket (2) according to at least one of the preceding claims, characterized in that a receptacle (16) for a joint ball is arranged eccentrically with respect to the outer contour (4) with an offset (V) of a central axis (17) of the receptacle (16) with respect to a central axis (15) of the joint socket (2).
13. Joint socket (2) according to at least one of the preceding claims, characterized in that the socket insert (3) and the projection (7) are made in one piece and / or in one piece, in particular from a plastic.