JP3792958B2 - Tibial tray - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a tibial tray in an artificial knee component.
[0002]
[Prior art]
The movement of the knee joint involves complicated movement, and forces such as rotational force, axial force and shearing force are applied to the joint surfaces of the femur and tibia in a complicated manner. Therefore, a similar force is applied to the artificial knee joint used to replace those joint surfaces. If the artificial knee joint design is not adequately resistant to these forces, the interface between the bone and the artificial knee joint will become unstable, causing the knee prosthesis to loosen, sink, etc., impairing knee movement In some cases, the artificial knee must be replaced again.
[0003]
In the existing tibial tray, the separation type tibial tray that can separate the upper tray part and the lower stem part is weak against the rotational force, and sometimes the stem part may rotate and come off. is there. In addition, as a measure to prevent rotation between the stem and the tray, there is one provided with a projection and a notch corresponding to this, but when the stem rotates, this projection and the notch collide and sink. Moreover, there is a risk that metal powder or the like that causes loosening may be discharged.
[0004]
As a method of ensuring the stability of the artificial knee joint by appropriately resisting each force described above, in order to resist the rotational force in particular, the conventional tibial tray is integrated with the tray portion and the stem portion, A plurality of round protrusions are provided below the tray portion, and plate-like fins are attached in the outer diameter direction (Japanese Patent Laid-Open Nos. 62-139649, 3-267055, and 5- 269161, 9-511675, etc.), through holes for bone penetration on top of fins (see Japanese Patent Laid-Open No. Sho 64-68256), or part of the back of the tray There is also an artificial prosthesis (see Japanese Patent Application Laid-Open No. 8-243117) in which bone or cement penetrates into the cut-out portion and becomes resistance to rotation.
[0005]
[Problems to be solved by the invention]
In general, bone is composed of hard cortical bone on the outer periphery and relatively soft cancellous bone in the center, so it is known that the fin system increases resistance to rotation and improves stability. ing. FIG. 4 shows the tibial component of the first conventional example. In the tibial tray 11, the fins 15 are integrated with the tray portion 13 and the stem portion 14, and are suspended from the lower surface of the tray portion 13 without a gap. However, it extends in the outer diameter direction. Such a tibial tray 11 is known to have a strong resistance to rotation. However, when X-rays are taken, it is difficult to determine the fixation state of the bone or cement and the tibial tray at the central portion of the stem portion 14 of the tibial tray 11. was there.
[0006]
On the other hand, FIG. 5 shows the tibial component of Conventional Example 2. The illustrated tibial tray 11 is a stem separation type tibial tray in which a tray portion 13 and a stem portion 14 are connected by a stem shaft 16; The stem portion 14 and the fin 15 are integrated, and a protrusion 18 is provided below the tray portion 13, while an engagement notch 19 is provided in a recessed portion at a position corresponding to the protrusion 18 of the stem portion 14. It is a structured. In such a tibial tray 11, a slit 17 is formed between the tray portion 13 and the stem portion 14, so that the bone or cement near the center of the stem portion 14 of the tibial tray 11 and the tibial tray are fixed by X-ray imaging. However, in the engagement between the protrusion 18 and the notch 19, there is a problem in that there is a limit to the rotational resistance and the stability of the implant itself.
[0007]
In view of the problems of the conventional examples, the present inventors have made various studies on the optimal tibial tray shape by the fin method. As a result, it was found that when the fins of the tibial tray were extended to the vicinity of the hard cortical bone of the tibia, the resistance to rotation increased, and the stability could be further improved. On the other hand, the ability to easily determine the fixation state of the tibial tray and bone or bone cement with an X-ray imaging device after surgery enables quick knowledge of tibial tray looseness, subsidence, etc., and allows clinically appropriate measures to be taken Therefore, it came to recognize again that it is an important point.
[0008]
However, the fins of the tibial tray generally have an outer diameter extending from near the central axis of the tibial component, so the fixation state at the interface between the bone and the prosthesis is confirmed by X-rays. In this case, the tibial tray is made of a metal such as Ti alloy, Co-Cr-Mo alloy or ceramics such as alumina, and is difficult to transmit X-rays. The fixation of the tibial tray and bone or cement could not be easily confirmed.
[0009]
The present invention has been made to solve such problems of the conventional tibial tray. Accordingly, the object of the present invention is to ensure rotational stability in the tibial tray in artificial knee replacement surgery. Another object of the present invention is to provide an improved tibial tray that can easily confirm the fixed state between the postoperative bone and the tibial tray, which has been difficult in the past.
[0010]
[Means for Solving the Problems]
The present invention has the following configuration in order to achieve the above object. That is, the invention of claim 1 according to the present invention is a part of a knee joint prosthesis, and includes a tray portion 3, a stem portion 4 that integrally extends downward from the lower surface of the tray portion 3, and a lower portion of the tray portion 3. In the tibial tray 1 having at least one plate-like fin 5 integrally extending from the side surface of the stem portion 4 in the outer diameter direction and mounted on the bone marrow cavity of the resected proximal tibia excellent in turning resistance, the fin 5 Further, the tibial tray is characterized in that a through hole 6 or a slit 7 is provided in contact with the lower surface of the tray portion 3.
[0011]
According to a second aspect of the present invention, in the tibial tray according to the first aspect, a length Wmm from the center to the end of the stem portion 4 of the projected image of the fin 5 is the stem portion in the projected image direction. The length Lmm from the center of 4 to the outer peripheral edge 8 of the tray is L / 2 ≦ W ≦ (L−2).
[0012]
According to a third aspect of the present invention, in the tibial tray according to the first or second aspect, the length along the bottom surface of the tray portion 3 of the through hole 6 or the slit 7 provided in the fin 5 is 5 mm or more. It is set as the structure which is.
[0013]
According to the present invention, the fin 5 has a long length and excellent rotational resistance, so that the tibial tray 1 can be fixed to the bone and the through hole 6 or the slit 7 is provided in the fin 5. Therefore, it is possible to easily observe the space between the interface between the tibial tray 1 and the bone, which has been difficult to confirm with X-rays. Therefore, it is possible to know the bone growth, the cemented bone joint condition, and the like, and to clinically confirm the loosening and sinking of the artificial knee, so that appropriate clinical treatment can be performed.
[0014]
Here, if the length of the fin is too long, the cortical bone may be broken, which may cause a problem such as a starting point of a fracture. Therefore, a fin that does not affect the cortical bone is desirable. The present invention is also effective for a tibial tray made of ceramics and the like that is difficult to transmit X-rays because it can be easily confirmed by X-rays. Moreover, since the fin 5 is united with the tray part 3 and the stem part 4, the implant excellent in strength stability can be provided. Furthermore, in order to improve the stability between the tibial tray 1 and the bone, it is desirable that the angle θ of the fin 5 is 70 ° to 180 °.
[0015]
Further, according to the present invention, it is preferable that the length of the through hole 6 provided in the fin 5 or the slit 7 along the lower surface of the tray 3 is 5 mm or more, whereby the cement and bone can be joined well. I can observe. In the case of the slit, more preferably, the slit is formed in a portion excluding the stem portion 4, and in the case of the through hole, the slit is formed in a range excluding 2 mm from the tips of the stem portion 4 and the fin 5. It is a form. A form in which a plurality of through holes 6 are provided in a direction along the lower surface of the tray portion 3 is also preferable because the turning resistance can be secured.
[0016]
Here, the vertical width of the through hole 6 or the slit 7 is not particularly limited, but if it is 1 mm or more, the bonding condition can be sufficiently observed, and the object of the present invention can be achieved. In the case of a surgical technique using cement, it is preferably set to 5 mm or more in order to confirm the joint state of the implant, cement and bone and the growth of bone.
[0017]
In the present invention, the size of the through hole 6 is preferably as large as possible so that the bonding state of the bone or cement and the tibial tray can be observed, but the fin 5 except the portion where the fin 5 is in contact with the lower surface of the tray portion 3. By making the width of 2 mm or more, it is possible to satisfactorily ensure the rotation stability that is the subject, and to achieve the object suitably. Further, the vertical width of the slit 7 is preferably as large as possible so that the joining state can be observed. However, if the vertical width of the slit 7 is large, the swirling resistance of the fin 5 is reduced, so that the balance between the two is set. There is a need. The preferred range differs depending on the size and shape of the fin, but if it is set between 1 and 10 mm, both the ease of observation and the turning resistance can be achieved, and good results are obtained.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 shows an outline of the structure of the tibial component according to the first embodiment of the present invention. (A) is a front view showing a cross section, and (B) is also a right side view. .
[0019]
The illustrated tibial component is mainly constituted by two members, a tibial tray 1 and a tibial insert 2 incorporated in the tibial tray 1. The tibial tray 1 is made of stainless steel, titanium alloy, Co—Cr alloy or the like that has rust resistance and is gentle to living bodies. In addition to these metals, it may be made of ceramics. On the other hand, the tibial insert 2 is made of a polyethylene material having high wear resistance, such as a UHMWPE material. In some tibial components, the entire component is integrally formed of a polyethylene material without using a metal tibial tray.
[0020]
The tibial tray 1 includes a tray portion 3, a stem portion 4 extending downward from the lower surface of the tray portion 3, a side surface of the stem 4 portion, and a substantially central portion of the lower surface of the tray portion 3. The fin 5 is integrally provided with a plate-like fin 5 extending in the outer diameter direction toward the peripheral edge, and the fin 5 is provided with a through hole 6 in contact with the lower surface of the tray portion 3. Since the X-ray easily passes through the through hole 6, when the tibial tray 1 is mounted on the proximal bone marrow cavity of the resected tibia, the fixation state of the bone or cement and the tibial tray 1 is easy through the through hole 6. Can be confirmed.
[0021]
In addition, as a form of the through-hole 6, it is preferable that the length along the lower surface of the tray portion 3 is 5 mm or more in that the bonding condition can be observed well, and this is as described above.
[0022]
FIG. 2 shows an outline of the structure of the tibial component according to the second embodiment of the present invention, in which (A) is a front view showing a section, and (B) is a right side view. The embodiment shown in FIG. 2 is similar to the first embodiment, and corresponding members are denoted by the same reference numerals and description thereof is omitted. In the second embodiment, the structure in which a slit 7 is opened instead of the through hole 6 is different from the first embodiment, and the action of the slit 7 is the same as that of the through hole 6. Thus, the fixation state of the bone or cement and the tibial tray 1 can be easily confirmed. Note that the size of the slit 7 is the same as that of the through hole 6.
[0023]
FIG. 3 shows a bottom view of a tibial component according to an embodiment of the present invention. FIG. 3 shows a state in which the tibial tray 1 is mounted on the tibial osteotomy surface. In this state, the longer the fin 5 is, the greater the rotational resistance force to the tibia is, but it is too long. The cortical bone 9 must be notched, which is not preferable because it may be a starting point for fractures. Therefore, the tips of the fins 5 need to be inside at least 2 mm away from the tray outer peripheral edge 8. Moreover, since the rotational resistance force is small when the length of the fin 5 is short, the length Wmm from the center of the stem 4 to the end of the projected image of the fin 5 on the lower surface of the tray 3 is the stem in the projected image direction. It is desirable that at least L / 2 or more with respect to the length Lmm from the center of the tray 4 to the outer peripheral edge 8 of the tray. From the above, the relational expression of L / 2 ≦ W ≦ (L−2) is established.
[0024]
Furthermore, from the viewpoint of improving the stability between the tibial tray and the bone, when a plurality of fins 5 are provided, the intersection angle between the fins with respect to the center of the stem portion 4 is within a range of 70 ° to 180 °. Is desirable. In other words, if the crossing angle is less than 70 °, the rotational resistance is reduced, which is none other than.
[0025]
As described above, in both of the embodiments described above, the stem portion 4 has a round cross-sectional shape perpendicular to the axis. However, the stem portion 4 may be formed by attaching fins to a non-circular stem portion such as a quadrangle or a polygon. It goes without saying that the same effect can be obtained by this, and accordingly, such modifications are also included in the scope of the present invention.
[0026]
Further, in the present invention, it is important that the slit 7 is in contact with the lower surface of the tray part 3, but as shown in FIGS. It is preferable to provide the preliminary fin 10 so that the turning resistance is increased. In this case, if the height is 0.5 mm or less, the object of the present invention can be achieved without substantial trouble in X-ray observation. More preferably, the spare fins 10 having a size of 0.1 mm to 0.3 mm are provided. Similarly, in the case of the through hole 6, it is preferable that a fin of 0.5 mm or less is left between the hole and the lower surface of the tray portion to increase the turning resistance. More preferably, it is a structure that leaves 0.1 mm to 0.3 mm fins.
[0027]
In the present invention, the stem portion 4 and the fin 5 extending below the tray portion 3 may be provided in a shape that is apparently indistinguishable. In this case, the through-hole 6 or the slit 7 is provided in a portion that imparts turning resistance to the tibial tray, that is, a portion that extends in the outer diameter direction.
[0028]
【The invention's effect】
The present invention is implemented in the form as described above, and has the following effects. That is, according to the present invention, the fins are integrally provided on the stem portion integrated with the tray portion, and the fins are formed in an appropriate and sufficient length, so that the rotational resistance is large. Therefore, an implant having excellent strength stability can be provided.
[0029]
Furthermore, in the present invention, since a through hole or a slit is provided at a position in contact with the lower surface of the tray portion of the fin, it is possible to easily observe between the tibial tray and the bone interface, which has been difficult to confirm by X-rays. As a result, bone growth, cement-bone joint status, etc. can be easily understood, and the knees can be clinically checked for loosening and sinking, providing an excellent medical effect for appropriate clinical treatment. .
[Brief description of the drawings]
FIG. 1A is a front view showing a cross section of a tibial component according to a first embodiment of the present invention, and FIG. 1B is a right side view of the same.
2A is a front view showing a cross section of a tibial component according to a second embodiment of the present invention, and FIG. 2B is a right side view of the same.
FIG. 3 is a bottom view of a tibial component according to an embodiment of the present invention.
4A is a front view showing a cross section of a tibial component of Conventional Example 1, and FIG. 4B is a right side view of the same.
5A is a front view showing a cross section of a tibial component of Conventional Example 2, and FIG. 5B is a right side view of the same.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Tibial tray 2 ... Tibial insert 3 ... Tray part 4 ... Stem part 5 ... Fin 6 ... Through-hole 7 ... Slit 8 ... Outer peripheral edge of tray part 9 ... Cortical bone

Claims (3)

It is a component of a knee joint prosthesis, and includes at least a tray portion, a stem portion integrally extending downward from the lower surface of the tray portion, and an outer diameter direction integrally extending from a side surface of the stem portion below the tray portion. In a tibial tray equipped with one plate-like fin and attached to the bone marrow cavity of the resected proximal tibia having excellent turning resistance, the fin is provided with a through-hole or a slit in contact with the lower surface of the tray portion. Features a tibial tray. The length Wmm from the stem portion center to the end portion of the projected image of the fin is L / 2 ≦ W ≦ () with respect to the length Lmm from the stem portion center to the outer periphery of the tray portion in the projected image direction. The tibial tray according to claim 1, which is L-2). The tibial tray according to claim 1 or 2, wherein a length following a lower surface of the tray portion of the through hole or slit provided in the fin is 5 mm or more.

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