Knee joint implant augmentation and knee joint implant

Description

Technical field

[0001] The present disclosure relates to a knee joint implant augment for a knee joint implant and a knee joint implant.

[0002] Knee joint prostheses or implants, or knee endoprostheses, are used to replace the knee joint, which is usually damaged by knee osteoarthritis. In this procedure, the knee joint is partially or completely replaced.

[0003] Common knee implants consist of a femoral component, a tibial component, and an inlay between the femoral and tibial components. The inlay is a gliding surface over which the femoral component can slide on the tibial component. The femoral component has a stem to connect it firmly to the femur. The tibial component has a tibial stem that connects it firmly to the tibia. If a large portion of the tibia is removed, the thin tibial component alone cannot replace the lost bone. Therefore, a knee implant augment is used. The knee implant augment is essentially a (flat) plate that acts as a spacer between the removed tibia and the tibial component of the knee implant. State of the art

[0004] Such a knee joint implant augmentation is known, for example, from US 11,266,509 B2. In this case, the knee joint implant augmentation is anatomically designed to conform to the shape of the removed bone. A distal or inferior surface of the knee joint implant augmentation is essentially adapted to the cross-sectional shape of the removed tibia. The area of ​​the distal surface is smaller than the area of ​​a proximal surface of the knee joint implant augmentation. EP 1,360,950 B1, US 2020 / 281,731 A1, US 2014 / 222,155 A1, US 2014 / 277,539 A1, and US 5,458,637 A also disclose such knee joint implant augmentations. From US 2009 / 265 011 A1, a knee joint implant augment is known with a right angle between the outer surface of the knee joint implant augment and the distal and proximal surfaces of the knee joint implant augment.

[0005] With known knee joint augmentation devices, the entire tibial element must be shifted anteriorly, or forwards towards the knee, during placement to ensure proper contact of the tibial element with the knee joint augmentation on the tibia. This is because the tibia widens anteriorly in this area.

[0006] This anterior displacement, however, is disadvantageous. Firstly, it results in an undesirable overhang of the tibial element beyond the bone. Secondly, the repositioning during implant insertion disrupts the alignment with the bone's medullary canal. Revision surgeries often utilize stems that ideally should follow the medullary canal of the bone / tibia. The medullary canal thus forms a mechanical axis of the bone / tibia. Due to the anterior displacement, the tibial element, and especially its stem, is no longer aligned with the medullary canal / mechanical axis of the tibia. This repositioning error can only be corrected with adjustable stems. However, most stems are only adjustable medially-laterally and not anteriorly-posteriorly. Therefore, tibial positioning errors can occur.Therefore, known knee joint implants may be used disadvantageously.

[0007] More specifically, a conflict of objectives can arise during implant insertion. If the tibial stem is aligned with the medullary canal of the tibia, the bearing surface between the implant, and especially the knee joint implant augment, will not match the cut tibia. However, if the augment is aligned with the shape of the cut tibia, the tibial stem may deviate from the mechanical axis of the medullary canal. This conflict of objectives could be resolved by implants with adjustable stems. However, most stems are only adjustable medially and laterally. Furthermore, adjusting the stems during surgery is disadvantageous.

[0008] Brief description of the Revelation

[0009] The purpose of this disclosure is therefore to overcome or at least mitigate the disadvantages of the prior art, in particular to provide a knee joint implant augment that allows for the optimized attachment of a knee joint implant to the tibia. Specifically, a knee joint implant augment is to be provided that is adapted to the shape of the tibia. Furthermore, a knee joint implant is to be provided that can be optimally connected to the tibia.

[0010] This problem is solved by a knee joint implant augmentation according to claim 1 and a knee joint implant according to claim 7. Advantageous embodiments of the present disclosure are the subject of the attached dependent claims.

[0011] The present disclosure relates to a knee joint implant augment or a spacer for a knee joint implant, which is prepared and configured to be arranged between a knee joint implant and a tibia in an implanted state. The knee joint implant augment has a first contact surface configured to bear, at least partially, over the surface of the knee joint implant in the implanted state, a second contact surface opposite the first contact surface configured to bear, at least partially, over the surface of the tibia in the implanted state, and a circumferential surface or surface connecting an edge of the first contact surface with an edge of the second contact surface.The surface of the mantle is designed such that a section of the surface of the mantle, which is arranged patellarly in the implanted state of the knee joint implant augment, is angled from the first contact surface at an angle greater than 0° with respect to an axis in the patellar direction, with the axis being perpendicular / orthogonal to the first contact surface.

[0012] The knee implant can at least partially replace the original knee joint and can therefore be inserted or surgically implanted in a specific position within the body. The knee implant augmentation is positioned on the knee implant and is thus also positioned in a specific way relative to the knee joint and the body.

[0013] In this context, "positionally determined" means that the location and orientation of the knee joint implant augment relative to the knee joint implant is defined by suitable means on the knee joint implant augment or on the knee joint implant, or by a combination of means on both components. This specifically defines the direction in which the individual sections of the outer surface point when the entire knee joint implant is (as intended) inserted or implanted.

[0014] In this context, the patellar direction refers to the direction that points forward in humans, specifically towards the kneecap. The patellar orientation can be understood as the anterior direction of the body.

[0015] In this context, the first contact surface, or proximal surface, is the side of the knee implant that faces upwards, i.e., towards the torso or from the knee towards the thigh. The second contact surface, or caudal or distal surface, is the side of the knee implant that faces the foot or lower leg. Therefore, when the knee implant is fitted, the first contact surface rests against the implant itself, while the second contact surface is in contact with the tibia.

[0016] The tibia extends along its longitudinal axis. The medullary canal essentially follows the longitudinal axis of the tibia. The patellar surface segment is angled at a non-zero angle relative to the longitudinal axis of the tibia.

[0017] In other words, the knee joint implant augment is an augment or spacer for a knee joint implant with a preferably flat, approximately U- or horseshoe-shaped base plate. This base plate has a first (base) surface, a second (base) surface opposite the first (base) surface, and a cladding surface that connects and delimits the first and second (base) surfaces. The cladding surface has a section that, when the knee joint implant augment is in position against the knee joint implant, and more precisely against a distal surface of a tibial element of the knee joint implant, points in the patellar or anterior direction.

[0018] The knee joint implant augment therefore has a protruding nose on the patellar surface section, with the nose preferably being formed on the distal side of the surface section. Overall, the anterior section is designed and adapted such that the second contact surface of the knee joint implant augment corresponds at least partially to the shape of the (truncated) tibia.

[0019] The axis can be a normal vector to the first contact surface. Since the first and second contact surfaces are preferably parallel to each other, the axis can also be a normal vector to the first contact surface. In the implanted state of the knee joint augmentation, the axis can be aligned parallel to or corresponding to the longitudinal axis of the tibial medullary canal.

[0020] The knee implant augmentation, as described, is optimally adapted to the shape of the tibia. This ensures better adhesion of the knee implant augment to the tibia and improves the contact between the tibial element of the knee implant and the augment. In particular, the knee implant augment has a large contact area on the detached tibia. Therefore, the tibial element does not need to be shifted anteriorly / patellarly during surgery to increase the contact area between the knee implant augment and the tibia, and can thus remain in the optimal position. In the optimal position, one shaft of the tibial element is aligned with the medullary canal of the tibia. This allows for better attachment of the tibial element to the tibia and prevents tibial positioning errors. Specifically, the tibial element is aligned along the mechanical axis.aligned with the medullary canal of the tibia.

[0021] Furthermore, the production of the knee joint implant augment as described is simple and inexpensive.

[0022] The object of the present disclosure is further solved by a knee joint prosthesis / knee joint implant. The knee joint implant comprises a femoral element / implant and a tibial element / implant. The tibial element comprises a base plate, a stem extending distally from the base plate and adapted for insertion into the tibia, and preferably a (reinforcing) wing extending between the base plate and the stem. Furthermore, the knee joint implant may preferably comprise an inlay / gliding surface / insert that is positioned between the femoral element and the tibial element and allows the two elements to slide against each other.The knee joint implant further comprises a knee joint implant augment with a first contact surface, a second contact surface opposite the first contact surface, and a cladding surface that connects an edge of the first contact surface with an edge of the second contact surface. The first contact surface rests against the base plate, at least partially. The second contact surface is designed to rest against the bone, at least partially. The cladding surface is designed such that a portion of the cladding surface, which is oriented patellarly in the implanted state, is angled at a greater than 0° with respect to a longitudinal axis of the stem in the patellar direction.

[0023] In the implanted state of the knee joint implant, the stem of the tibial element extends distally from the base plate. The stem is designed to be embedded within the tibia in the implanted state. Its longitudinal axis aligns with the longitudinal axis of the tibial medullary canal.

[0024] The knee joint implant, thanks to its angled patellar surface section, can be particularly firmly bonded to the bone and is easy to insert or surgically implant because the bearing surface of the knee joint implant on the tibia is especially large. In particular, the knee joint implant, and especially the tibial lamina, does not need to be shifted forward during insertion. The knee joint implant is thus aligned with the longitudinal axis of the tibia and the longitudinal axis of the medullary canal during implantation.

[0025] The knee joint implant is preferably positioned between a distal portion of the femur and a proximal portion of the tibia. The femoral element can be connected to the femur and the tibial element to the tibia. The partial implants can be connected to the respective bones, particularly via their respective stems.

[0026] According to an optional aspect of the present disclosure, the patellar mantle section, in the implanted state of the knee joint implant augment, is angled at a greater than 0° with respect to a longitudinal axis of a tibial groove. In particular, the patellar mantle section can form a protrusion extending beyond a base area of ​​the first contact surface.

[0027] The knee joint implant augmentation can have an approximate shape of a (skew) cylinder or a truncated cone. The axis can represent a longitudinal axis of the cylinder and / or the truncated cone.

[0028] The angle between the first contact surface and the patellar mantle section can therefore be other than 90°. It is particularly desirable for the angle between the first contact surface and the patellar (angled) mantle section to be greater than 90° in the implanted state of the knee joint augmentation. This opens the angle of the patellar mantle section distally. The area of ​​the second contact surface can thus be larger than the area of ​​the first contact surface. This means that the second contact surface is at least partially adapted to a cross-section of the (removed) tibia. In other words, the patellar mantle section can form a protrusion that extends beyond the base of the first contact surface.

[0029] The angle between the second contact surface and the patellar surface section can therefore also be other than 90°. It is particularly preferred that the angle between the second contact surface and the patellar surface section be less than 90° in the implanted state of the knee joint augmentation.

[0030] Preferably, at least three sides of the lateral surface are angled relative to the first and / or second contact surface. That is, at least three sides of the lateral surface are not perpendicular to the contact surfaces, but are angled at an angle other than 90° to the contact surfaces.

[0031] According to a further optional aspect of the present disclosure, the angle of inclination between the patellar mantle surface section and the axis opens in a caudal / distal direction. This means that the area of ​​the second contact surface can be increased. This ensures that the (cut-off) tibia and the knee joint implant augment overlap over the largest possible area, thus guaranteeing a secure connection.

[0032] Preferably, the knee joint implant augmentation is approximately U- or horseshoe-shaped. The patellar surface section can be positioned in one leg of the horseshoe. The U- or horseshoe-shaped knee joint implant augmentation can have two legs extending laterally from a central section, essentially parallel to each other. The patellar surface section can be arranged on one of the two legs. The patellar surface section can be positioned such that it faces an outer side of the "horseshoe."

[0033] In the implanted state of the knee joint augmentation, the central section (of the "horseshoe") can point laterally towards the knee joint. The two arms can extend laterally from this. Thus, one arm can be positioned patellarly or anteriorly, and the other posteriorly. The patellar surface section can be specifically located on the patellar arm of the horseshoe-shaped knee joint augmentation. This allows the patellar surface section to increase the patellar bearing surface between the knee joint augmentation and the tibia, enabling the knee joint implant to be mounted aligned with the longitudinal axis of the tibia.

[0034] According to a further optional aspect of the present disclosure, an elongated recess in the (U- or horseshoe-shaped) knee joint implant augment is prepared and designed to receive a (reinforcing) wing of the knee joint implant, and the patellar mantle surface section extends substantially parallel to a longitudinal extension of the recess. The (reinforcing) wing can be inserted into the recess of the U- or horseshoe-shaped knee joint implant augment. The combination of the orientation of the (reinforcing) wing and the recess can position the knee joint implant augment on the knee joint implant in a defined manner in the implanted state. Thus, the recess can define the position and orientation of the knee joint implant augment on the knee joint implant.

[0035] Preferably, the knee joint implant augmentation has the shape of a parallelogram in a side view or in a cross-section. Both the patellar and posterior sections of the casing can be angled. In particular, the two sections can be angled parallel to each other.

[0036] It is possible that the two lateral sections are each tilted relative to the axis, but not at the same angle.

[0037] Preferably, at least part of the first base surface of the knee joint implant augment is adapted to the shape of the base plate of the tibial element. That is, the surface of the knee joint implant augment that directly abuts the base plate of the tibial element has at least a partial shape resembling the base structure. Thus, the two elements merge seamlessly.

[0038] According to a further optional aspect of the present disclosure, a portion of the second base surface of the knee joint implant augment is at least designed and adapted to correspond to an outer contour of the tibia. That is, the second base surface can essentially correspond to the shape of the tibial cross-section. Thus, the truncated tibia can transition seamlessly into the knee joint implant augment. That is, the cross-section of the truncated tibia can correspond, at least in part or section, to the second base surface.

[0039] Brief description of the characters Fig. 1 shows a state-of-the-art knee joint implant; Fig. 2 shows a perspective view of a tibial element with a state-of-the-art knee joint implant augment on a tibia; Fig. 3 shows a side view of the knee joint implant augmentation according to the state of the art; Fig. 4shows a side view of a knee joint implant augmentation according to the present disclosure; Fig. 5 shows an isometric representation of the knee joint implant augmentation according to the present disclosure; Fig. 6 shows an underside of the knee joint implant augment according to the present disclosure; and Fig. 7 shows a side view of a tibial element with the knee joint implant augment according to the present disclosure. Detailed description of the figures

[0040] The Figures 1 to 3Figure 1 shows a knee joint implant or knee prosthesis 1 according to the state of the art. The knee joint implant 1, in its implanted state, is preferably positioned between a distal portion of the femur (thigh bone) and a proximal portion of the tibia (shin bone) 2 and comprises a femoral element or implant 4, a tibial element or implant 6 with a (knee joint implant) augment 8, and an inlay / gliding layer 10. The inlay 10 is arranged between the femoral element 4 and the tibial element 6 and allows the femoral element 4 to glide relative to the tibial element 6.

[0041] The knee joint implant augment 8 is designed to be positioned between the knee joint implant 1 and the tibia 2 in the implanted state and has a proximal first contact surface 14, which is designed to bear at least partially flat against the knee joint implant 1 in the implanted state, and a distal / caudal second contact surface 16, which is designed to bear at least partially flat against the tibia 2 in the implanted state. The knee joint implant augment 8 further has a mantle surface 18 that connects an edge of the first contact surface 14 with an edge of the second contact surface 16. The mantle surface 18 has a mantle section 20 that is oriented patellarly in the implanted state of the knee joint implant augment 8.

[0042] A thin base plate 22 of the tibial element 6 rests against the first contact surface 14. The base plate 22 has a receiving structure 24 for the inlay 10 on its proximal side. A tibial shaft 26 extends distally along the caudal / distal side of the base plate 22. The tibial shaft 26 is prepared and adapted to be inserted into the tibia 2 to ensure a firm connection between the tibia 2 and the tibial element 6. In the implanted state of the knee joint implant 1, the shaft 26 corresponds to a longitudinal axis 12 of a medullary canal (not shown) of the tibia 2.

[0043] If a large portion of the tibia 2 is removed, the thin tibial element 6 cannot replace the lost bone. Therefore, the knee joint implant augment 8 is used additionally. The first contact surface 14 of the knee joint implant augment 8 is prepared and adapted to rest against a distal surface of the base plate 22.

[0044] The femoral element 4 rests against the side of the inlay 10 opposite the tibial element 6. The femoral element 4 has a connecting section 32, which connects the femoral element 4 to the femur, and a rolling section 34, which rolls on the inlay 10. The inlay 10 allows the femoral element 4 and the tibial element 6 to slide against each other and essentially acts as a bearing between the two elements 4 and 6. The connecting section 32 is essentially an elongated shaft that connects to the femur. The rolling section 34 has a convex, semicircular curve and is attached to the connecting section 32.

[0045] Fig. 4Figure 1 shows a side view of the knee joint implant augment 8 as disclosed. The knee joint implant augment 8 has the first contact surface 14, the second contact surface 16, which is opposite the first contact surface 14, and the outer surface 18, which connects the edge of the first contact surface 14 with the edge of the second contact surface 16. Furthermore, the knee joint implant augment 8 has an axis 36, which is perpendicular to the first contact surface 14 and / or the second contact surface 16. The outer surface section 20, which is oriented patellarly in the implanted state of the knee joint implant augment 8, is angled at an angle α other than 0° with respect to the longitudinal axis 12 of the medullary canal of the tibia 2.

[0046] That is, an angle α, which is spanned between the axis 36 of the knee joint implant augment 8 and the patellar surface section 20, is preferably greater than 0°. The axis 36 is a normal vector to the first contact surface 14 or the second contact surface 16. The patellar surface section 20 thus increases the bearing area between the tibia 2 and the second contact surface 16 compared to the prior art. This enables better integration of the knee joint implant augment 8 with the tibia 2. Another section of the surface 18, which is opposite the angled patellar surface section 20, is also angled. The two angled sections can have the same angle of inclination. An angle β, which is spanned between the first contact surface 14 and the patellar surface section 20, is greater than 90°.

[0047] Fig. 5Figure 1 shows an isometric view of the knee joint implant augment 8 according to the present disclosure. The knee joint implant augment 8 does not have a continuous circular or oval surface or plate, but is approximately U-shaped or horseshoe-shaped. The knee joint implant augment 8 has an elongated recess 38 which is adapted and prepared to accommodate the tibial shaft 26 and possibly the (reinforcing) wing 28 (in Fig. 7 The knee joint implant augment 8 has a central section 40 and two legs 42, which, in the implanted state, extend laterally from the central section along the recess 38. The angled patellar surface section 20 is formed on the leg 42, which is positioned patellarly in the implanted state.

[0048] The outer surface 18 is, at least in sections, not oriented perpendicular to the two contact surfaces 14 and 16. The sections of the outer surface 18, which are positioned in the central section 40 of the U-shaped knee joint implant augment 8 and on a posterior end face, are angled with respect to the longitudinal axis 36 when the knee joint implant augment 8 is implanted. The first contact surface 14 projects beyond the second contact surface 16 in sections. Thus, the shape of the knee joint implant augment 8 is essentially adapted to the shape of the tibia 2. The knee joint implant augment 8 also has two holes 44 through the base plate 12, through which the knee joint implant augment 8 is screwed to the tibial element 6.

[0049] Fig. 6Figure 1 shows the underside of the knee joint implant augment 8. The holes 44 extend through the entire thickness of the knee joint implant augment 8 and open into the second contact surface 16. The underside, or second contact surface 16, of the knee joint implant augment 8 has a number of recesses 46. The recesses 46 are adapted to allow the knee joint implant augment 8 to be fitted precisely to the tibia 2. The underside view shows that the outer surface 18 extends beyond the second contact surface 16 in a lateral and a posterior section.

[0050] Fig. 7Figure 1 shows a side view of the tibial element 6 with the knee joint implant augment 8. The first contact surface 14 of the knee joint implant augment 8 lies flat against the base plate 22 of the tibial element 6. The tibial shaft 26 protrudes from the second contact surface 16. The (reinforcing) wing 28 connects the tibial shaft 26 to the base plate 22 and is received in the recess 38 of the knee joint implant augment 8. The patellar surface section 20 is angled at a non-zero angle with respect to a longitudinal axis 48 of the tibial shaft 26. Reference symbol list

[0051] 1 Knee joint implant 2 Tibia 4 Femoral element 6 Tibial element 8 Knee joint implant augmentation 10 Inlay 12 Longitudinal axis of the medullary canal 14 First contact surface 16 Second contact surface 18 Mantle surface 20 Angled (patellar) mantle surface section 22 Base plate 24 Receiving structure 26 Tibial stem 28 (Reinforcement) wing 32 Connecting section 34 Rocker section 36 Axis of the knee joint implant augmentation 38 Recess 40 Middle section 42 Leg 44 Hole / bore 46 Recess 48 Longitudinal axis of the tibial stem αAngle of attack βAngle between the patellar lateral surface section and the first contact surface

Claims

1. A knee joint implant augmentation (8) configured to be arranged between a knee joint implant (1) and a tibia (2) in an implanted state, comprising a first contact surface (14) which, in the implanted state, is configured to rest at least partially flat on the knee joint implant (1), a second contact surface (16) lying opposite the first contact surface (14) and configured to rest at least partially flat on the tibia (2) in the implanted state, and a lateral surface (18), which connects a rim of the first contact surface (14) to a rim of the second contact surface (16), characterized in that the lateral surface (18) is configured such that a portion (20) of the lateral surface (18), which is arranged in a patellar position in the implanted state of the knee joint implant augmentation (8), is angled, starting from the first contact surface (14), at a closed angle (α) larger than 0° with respect to an axis (36) in the patellar direction, wherein the axis (36) is perpendicular to the first contact surface (14).

2. The knee joint implant augmentation (8) according to claim 1, characterized in that the first contact surface (14) points in a proximal direction in the implanted state of the knee joint implant augmentation (8).

3. The knee joint implant augmentation (8) according to claim 1, characterized in that an angle between the first contact surface (14) and the patellar lateral-surface portion (20) in the implanted state of the knee joint implant augmentation (8) is greater than 90°, wherein, in particular, a nose spanned by the patellar lateral surface portion (20) protrudes beyond a base surface of the first contact surface (14)..

4. The knee joint implant augmentation (8) according to one of claims 1 to 3, characterized in that an angle between the second contact surface (16) and the patellar lateral-surface portion (20) in the implanted state of the knee joint implant augmentation (8) is less than 90°.

5. The knee joint implant augmentation (8) according to one of claims 1 to 4, characterized in that the patellar lateral-surface portion (20) is positioned at a leg (42) of the knee joint implant augmentation (8), preferably at a leg (42) that is in a patellar position in the implanted state of the knee joint implant augmentation (8).

6. The knee joint implant augmentation (8) according to one of claims 1 to 5, characterized in that an elongated notch (38) in the knee joint implant augmentation (8) is prepared and configured to receive a reinforcing wing (28) of the knee joint implant (1), and the patellar lateral-surface portion (20) extends substantially parallel to a longitudinal extent of the notch (38).

7. A knee joint implant (1) comprising a femur element (4), a tibia element (6) comprising a base plate (22), a shaft (26) extending from the base plate (22) and preferably a reinforcing wing (28) extending between the base plate (22) and the shaft (26), and a knee joint implant augmentation (8) according to one of the preceding claims, wherein the first contact surface (14) rests at least partially flat against the base plate (22), and the portion (20) of the lateral surface (18), which, in the implanted state of the knee joint implant (1), is arranged in a patellar position, is angled in the implanted state at a closed angle larger than 0° with respect to a longitudinal axis (48) of the shaft (26).

8. The knee joint implant according to claim 7, characterized in that the first contact surface (14) at least partially corresponds to a shape of the base plate (22).