JP2992878B2 - Artificial facet joint - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION Surgery is used to remove diseased parts due to diseases such as herniated discs, age-related changes, deformation of the spine caused by long-standing habits, and disorders in the discs and facet joints. It relates to a facet prosthesis which is attached between the vertebrae after the procedure.

[0002]

2. Description of the Related Art Conventionally, when disorders of the intervertebral discs and facet joints have become advanced due to illness, age-related changes, and long-standing habits, the affected intervertebral discs are removed by surgery, Remove joints and parts of the deformed spine, and if there is compression of nerves such as the spinal cord or nerve roots by ligaments or bones, completely remove these compressions and then remove the iliac or artificial bone (Inorganic material such as apatite), as shown in FIG. 6, and as shown in FIG. A metal screw F is screwed into the body K from the ridge J, and one metal plate G is attached to the tips of the two screws F, F corresponding to the upper and lower sides, and the upper and lower adjacent vertebrae A and B are completely connected. To address pain and spinal instability .

[0003] However, even though such vertebrae A and B are originally movable, they are completely fixed by a metal plate so as not to move, so that a large stress is applied to the fixed vertebrae. Furthermore, forcibly bending, bending, or twisting the body will also apply excessive load to the adjacent vertebrae above and below the fixed spine, damaging the disc just above and below the fixed spine. It often caused new obstacles.

[0004]

DISCLOSURE OF THE INVENTION The present invention relates to a facet joint that moves without exerting excessive stress on the spine and brakes the movement when the body is forcibly bent, bent or twisted. The purpose of the present invention is to provide an artificial facet joint that reconstructs the function of the spine without damaging the disc or the intervertebral disc.

[0005]

Means for Solving the Problems The present invention has been made to solve the above-mentioned problems, and the means comprises, as described in claim 1, a cylindrical member and a piston member movably fitted thereto. The piston-like portion is fitted in a direction perpendicular to the direction of movement in the cylinder-like portion so that it can rotate at an angle equal to or less than the angle of rotation of the spine of a healthy person, and has a cylindrical shape. An artificial facet joint characterized in that an attachment portion is provided at each end of the portion and the piston-like portion for attachment between adjacent vertebrae with a damaged intervertebral disc interposed therebetween.

[0006] A mounting portion at the end of the cylindrical portion and a mounting portion at the end of the piston-like portion are respectively attached to two vertically adjacent vertebrae of the damaged intervertebral disc. Attach an artificial facet joint to the head.

[0007] The piston-like portion is movably fitted in the cylinder-like portion, and the piston-like portion is also equal to or equal to the rotation angle of the spine of a healthy person in a direction perpendicular to the direction of movement in the cylinder-like portion. Because it can rotate to an angle less than that, even when bending or stretching the body back and forth, bending left and right, twisting, the piston-like part moves within the cylindrical part, the two vertically adjacent vertebrae are not fixed. Can move. As a result, the spine is not overstressed.

[0008] According to another aspect of the present invention, in the artificial facet joint according to the first aspect, the inner surface of the cylindrical portion is elasticized to allow the piston to rotate inside the cylindrical portion. An artificial facet joint, characterized in that it is lined with a substance and further provided with a spring between the bottom of the piston-like portion and the lid.

[0009] The rotation of the piston in the cylindrical portion is allowed within a range in which the elastic material lining the inner surface of the cylindrical portion bends when the piston is rotated. As the piston moves, a spring provided between the bottom of the piston and the lid is compressed to allow movement of the piston within the cylinder.

According to another aspect of the artificial facet joint according to the first or second aspect, the cross section of both the cylindrical portion and the piston-like portion is an ellipse or an ellipse. An artificial facet joint characterized in that the piston-shaped part is rotated at an angle equal to or less than the rotation angle of the spine of a healthy person with respect to the cylinder-shaped part.

When trying to twist the body, the cross-section of each of the cylindrical portion and the piston-shaped portion is an ellipse, so that the angle of the piston-shaped portion with respect to the cylindrical portion is equal to or smaller than the rotation angle of the spine of a healthy person. It only rotates to the following angles,
It doesn't move anymore.

According to another aspect of the present invention, there is provided an artificial facet joint according to claim 2, 3 or 4, wherein the elastic substance is polyurethane.

Since polyurethane has great elasticity,
The rotation of the piston within the cylinder is largely tolerated.

According to a sixth aspect, in the artificial facet joint according to the first, second, third, fourth or fifth aspect,
An artificial facet joint, wherein the piston-like portion is made of polyolefin.

Since polyolefin has self-lubricating properties and abrasion resistance, it ensures lubricating movement of the piston-like portion in the cylinder-like portion, and causes less wear even after long-term use.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, reference numeral 1 denotes an artificial facet joint of the present invention. The artificial facet joint 1 comprises a cylindrical part 2 and a piston-like part 3 movably fitted thereto. Consists of

The cylindrical portion 2 has an attachment portion 2c fixed to the closed end 2b for attaching to the spine A adjacent to the injured disc C.

As shown in FIGS. 1 and 4, the piston 3 comprises a piston 3a and a rod 3c attached to its bottom 3b. The piston-shaped part 3 is also equal to or less than the angle of rotation of the spine of a healthy person (up to about 15 degrees left and right) in a direction perpendicular to the direction of movement in the cylinder-shaped part 2, for example, It is fitted into the cylindrical part 2 so that it can rotate about 10 degrees.

As shown in FIG. 4, the upper half of the piston 3a has a substantially circular shape so that the piston 3 can tilt in the cylinder 2.

The tip 3c-1 of the rod 3c is shown in FIG.
As shown in FIG. 6, the screw 9 is screwed to the attachment portion 9, and the attachment portion 9 is attached to another vertebra B adjacent to the injured disc C.

The inner surface of the cylindrical portion 2 is lined with an elastic material 2A, for example, polyurethane. When the piston 3 is turned in the cylindrical portion 2, the elastic material 2A bends. , To allow the rotation to a certain extent. In addition, as shown in FIG. 4, a tapered surface 2B is formed in the lower half of the elastic material 2A so that the piston 3 can be smoothly tilted in the cylindrical portion 2.

As shown in FIG. 4, a lid 5 having a hole 5a through which the rod 3c is inserted at the center is attached to the open end 2a of the cylinder 2 and the piston 3a.
A spring 6, which is, for example, a coil spring, is provided between the bottom 3b and the lid 5 so that the piston 3 can move within the cylinder 2 against the spring 6.

Since the rod 3c is passed through the hole 5a, the diameter of the hole 5a is larger than the diameter of the rod 3c. However, since the lid 5 supports the spring 6, the diameter of the hole 5 a is smaller than the diameter of the spring 6.

Although the cylindrical portion 2 is made of titanium,
It may be made of stainless steel or a cobalt-chromium alloy.

The cylindrical section 2 has an oval cross section or an elliptical cross section as shown in FIG.

As shown in FIG. 1, the mounting portion 2c of the cylindrical portion 2 has a long groove 8 into which the tip Fa of the screw F is inserted, as shown in FIG.

As described above, polyurethane is used as the elastic material 2A lined on the inner surface of the cylindrical portion 2, but polyacetal such as Delrin (registered trademark) or polymethyl methacrylate (PMMA) is also used.

The piston 3 has an oval cross section or an elliptical cross section as shown in FIG. 3. The piston 3 is made of a polyolefin such as high-density polyethylene (HDP) or polypropylene (PP). However, they may be made of ceramics, titanium, stainless steel, or a cobalt-chromium alloy.

The rod 3c is made of a metal such as titanium or stainless steel.

The mounting portion 9 is a narrow rectangular parallelepiped, and has a width slightly larger than the diameter of the tip F'a of the screw F 'in the longitudinal direction of the center as shown in FIG. It has a long groove 10.

As shown in FIG. 4, a piston 6 is inserted into a cylindrical portion 2 having an elastic material 2A lined on an inner surface thereof, and a spring 6 such as a coil spring is surrounded by a rod 6 so as to surround a rod 3c. After passing through the mounting portion 9, it is inserted into the cylindrical portion 2. Further, the lid 5 is attached to the open end 2a of the cylindrical portion 2, the rod 3c is extended out of a hole 5a provided at the center thereof, and the lid 5 is attached to the cylindrical portion 2 with a screw 5b. Tie up. Then, as described above, the mounting portion 9 is attached to the tip 3c-1 of the rod 3c.
Screw.

As shown in FIGS. 1 and 2 (A) and 2 (B), screws are inserted from the pedicles J, J of the vertebrae A, B vertically adjacent to each other across the injured disc C to the vertebral bodies K, K. Drill holes and screw F, F ', F-1, F-1' into each hole. Of these screws, two artificial facet joints 1A and 1B are attached to the tips of two upper and lower screws F and F 'and F-1 and F-1', respectively.

Screws F, F ', F-1, F-1'
Is made of titanium, but may be made of stainless steel. Also, to improve the adhesion to bone, screw F,
F ', F-1, and F-1' may be coated with hydroxyapatite.

The screws F and F 'of the artificial facet joint 1
The attachment to the screws F-1 and F-1 'will be described in detail below.

The mounting portion 2c of the cylindrical portion 2 is attached to the screw F screwed into the spine A located on the obstacle disc C.
And the mounting portion 2c is attached to the seating portion Fb of the screw F.
At this time, the tip Fa of the screw F passes through the long groove 8. In this state, the mounting portion 2c is moved to adjust the mounting position of the cylindrical portion 2 with respect to the screw F, and then the mounting portion 2c is fastened with the nut 7.

Further, the spine B located below the injured disc C
Attach the mounting part 9 to the screw F 'screwed into
The mounting portion 9 is placed on the seating portion F'b of the screw F '. At this time, the tip F'a of the screw F' passes through the long groove 10. In this state, the mounting portion 9 is moved,
After adjusting the mounting position of the piston-like portion 3 with respect to the screw F ′, the mounting portion 9 is fastened with the nut 7.

As shown in FIG. 2A, the vertebrae A and B
When two artificial facet joints 1A, 1B of the present invention are attached to the left and right sides of the spinous processes D, D, the vertebrae A, B are bent as shown by the arrow α in FIG. At this time, the elastic material 2A in which the head 3d of the piston 3 is lined with the top 2d of the inner surface of the cylinder 2
, The piston 3 moves toward the top 2d of the cylinder 2 so that the vertebrae A and B can move without being fixed, and the body can be turned back.

In addition, if the body is forced to bend over a certain range, the piston-like portion 3 hits the elastic material 2A lined at the top 2d of the cylinder-like portion 2, and the piston-like portion 3 becomes cylindrical. The movement is restricted in the section 2 and the body is warped any more.

When the body is bent, the vertebra A and the vertebra B adjacent to each other above and below move as indicated by the arrow β in FIG.
At this time, the piston 3 moves in the axial direction against the spring 6, so that the vertebrae A and B move without being fixed, and the body can bend.

However, if the user tries to forcibly bend the body forward, the movement of the piston-shaped portion 3 is regulated, so that any further bending of the body forward is braked.

Further, when the body is bent left and right, the vertically adjacent vertebra A and spine B move as indicated by the arrow γ in FIG. 2 (B). In, since the head 3d of the piston-like portion 3 moves toward the top 2d of the cylindrical portion 2 until the head 3d of the piston-like portion 3 hits the elastic substance 2A, the artificial facet joint 1B contracts, while the space between the vertebrae expands. On the side, the artificial facet joint 1A extends as the piston 3 moves within the cylinder 2 to compress the spring 6. Therefore, the vertebrae A and B move without being fixed, and the body bends right and left.

However, when the body is forcibly bent right and left, in the artificial facet joint 1B on the contracted side,
The piston-like portion 3 hits the elastic substance 2A lined on the top 2d of the cylindrical portion 2, and the movement of the piston-like portion 3 is restricted in the cylindrical portion 2. In the prosthetic facet joint 1A on the expanded side, the spring 6 no longer compresses, and the cylindrical portion 2
Movement within is regulated. To that end, further bending of the body is braked.

Next, when twisting the body, the artificial facet joint 1
In A and 1B, an oval or a piston-like portion 3 having an elliptical cross section as shown in FIG. 3 deflects the elastic material 2A lined on the inner surface of the cylindrical portion 2 to form an oval. Or the angle of rotation of the spine of a healthy person with respect to the cylindrical portion 2 having an elliptical cross section is equal to or less than the angle of rotation, and the piston-shaped portion 3 is rotated.
Also compresses the spring 6, so the artificial facet joints 1A and 1B
Stretch together. Thereby, the vertebrae A and B move without being fixed, and the body can be twisted.

There is an embodiment shown in FIG. 5 which is different from the above-described embodiment of the present invention. In this embodiment, two artificial facet joints 1C and 1C are sandwiched between spinous processes D and D. It is attached to both sides.

The artificial facet joints 1C, 1C are replaced with mounting members 11A, 11B,
It is attached between the spinous processes D of the spine A and the spinous processes D of the spine B using 11'A, 11'B, bolts 13 and nuts 14. In addition, this artificial facet joint 1C
The mounting portion 2c of the cylindrical portion 2 is provided with a mounting hole 8 'instead of the long groove 8, and the mounting portion 9 of the rod 3c is provided.
The artificial facet joints 1A, 1B according to the above embodiment, except that an attachment hole 10 'is provided instead of the long groove 10.
Not different.

The mounting members 11A, 11'A, 11B,
As shown in FIG. 5 (B), 11′B has a long groove 11a in the central longitudinal direction, and has a screw portion 12 on one surface,
As shown in FIG. 5 (C), the clamping surface 11b is formed in a rack shape in order to ensure the fixation when it is attached to the spinous process D.

As shown in FIG. 5 (A), the mounting portion 2c of the cylindrical portion 2 is mounted on the screw portion 12, and the tip of the screw portion 12 is inserted through the mounting hole 8 '. 2
c is fastened with a nut 7, and the mounting portion 2c is mounted on the mounting member 1.
It is attached to 1A in advance.

Also, the mounting portion 9 of the piston-like portion 3 is mounted on the screw portion 12 of another mounting member 11'A,
2 is inserted into the mounting hole 10 ', the mounting portion 9 is fastened with a nut 7, and the mounting portion 9 is attached to the mounting member 1.
1'A is attached in advance.

Similarly, for the mounting member 11B, the mounting portion 2c of the cylindrical portion 2 is mounted on the screw portion 12, the tip of the screw portion 12 is inserted into the mounting hole 8 ', and the mounting portion 2c is And the mounting portion 2c is previously mounted on the mounting member 11B.

Further, the mounting portion 9 of the piston-like portion 3 is mounted on the screw portion 12 of the other mounting member 11'B,
2 is inserted into the mounting hole 10 ', the mounting portion 9 is fastened with a nut 7, and the mounting portion 9 is attached to the mounting member 1.
It is attached to 1'B in advance.

A hole is made in the spinous process D of the spine A located above the injured intervertebral disc C, and the mounting portions 11A and 11B are mounted on both sides of the spinous process D as shown in FIG. , The hole of the spinous process D and the mounting member 11A, 1
The bolts 13 are inserted into the long grooves 11a, 11a of FIG.
Is moved to adjust the mounting positions of the mounting members 11A and 11B and the cylindrical portions 2 and 2, and then the main fastening is performed.

Similarly, a hole is made in the spinous process D of the spine B located below the injured disc C, as shown in FIG.
The attachment members 11'A and 11'B are attached with the spinous process D interposed therebetween.
A bolt 13 is inserted through the long grooves 11a, 11a of 1'A, 11'B and temporarily tightened with a nut 14, so that the mounting member 1
1'A, 11'B to move the mounting member 11 '.
A, 11'B and the mounting position of the piston-like portion 3 are adjusted, and then the main tightening is performed.

The artificial facet joints 1C, 1C of this embodiment
When the body is turned back, the head 3d of the piston 3 moves until it hits the elastic material 2A lined on the top of the inner surface of the cylinder 2, so that the vertebrae A and B are not restrained. Can move and deflect the body.

However, when the body is forcibly turned backward, the elastic material 2A lined on the top of the cylindrical portion 2
, And the movement of the piston-shaped portion 3 in the cylinder-shaped portion 2 is restricted, so that the further bending of the body is braked.

When the body leans forward, the piston 3 moves in the axial direction against the spring 6, so that the vertebrae A and B move without being fixed, and the body moves forward. Can bow down.

However, when the body is forcibly bent forward, the spring 6 does not compress any more, the movement of the piston 3 in the cylinder 2 is regulated, and the body is further moved forward. I will not bend.

Further, when the body is bent left and right, the piston-like portion 3
As the head 3d moves toward the top of the cylindrical portion 2 until it hits the elastic substance 2A, the artificial facet joint 1C shrinks, while the piston between the vertebrae A and the spine B expands. As the prosthesis 3 moves within the cylinder 2 to compress the spring 6, the prosthetic facet joint 1C extends. Therefore, the vertebrae A and B move without being fixed, and the body bends right and left.

However, trying to forcibly bend the body left and right,
In the artificial facet joint 1C on the contracted side, the piston-like portion 3 hits the elastic material 2A lined on the top of the cylindrical portion 2, and the movement of the piston-like portion 3 is restricted in the cylindrical portion 2, and the piston-like portion 3 spreads. In the artificial facet joint 1C on the other side, the spring 6 does not compress any more, and the movement of the piston 3 in the cylinder 2 is restricted. To that end, further bending of the body is braked.

Next, when twisting the body, in the artificial facet joints 1C, 1C, a piston-like portion 3 having an oval or elliptical cross section is fitted with an elastic material lined on the inner surface of the cylindrical portion 2. 2A is deflected to rotate the cylinder 2 having an oval or elliptical cross section at an angle equal to or less than the angle of rotation of the spine of a healthy person, and the piston 3 is provided with a spring. By compressing 6, the vertebrae A and B can move without being fixed and twist the body.

However, if the user tries to twist the body beyond the amount of bending of the elastic substance 2A, the rotation of the piston-like portion 3 in the cylindrical portion 2 is restricted, so that the body is no longer twisted.

[0061]

In the artificial facet joint according to the first aspect of the present invention, the piston-like portion is movably fitted into the cylinder-like portion, and the piston-like portion moves in the direction of movement in the cylinder-like portion. In the direction perpendicular to the direction of rotation, the spine of the healthy person can be rotated by an angle equal to or less than the angle of rotation, so when bending and stretching the body, bending left and right, twisting, etc. The upper and lower adjacent vertebrae can be moved within a range regulated by the intervertebral joint, so that the vertebrae above and below the failed intervertebral disc are not overly stressed.

In the artificial facet joint according to the second aspect of the present invention, when the body is twisted right and left, the elastic material lined on the inner surface of the cylindrical portion bends to rotate the piston-like portion in the cylindrical portion. In addition, the spring provided between the bottom of the piston and the lid also compresses, allowing the movement of the piston within the cylinder, so that the attached spine is restricted by the artificial facet joint. It can be moved within a certain range, and has the effect of not applying excessive stress to the spine.

In the artificial facet joint according to the third or fourth aspect of the present invention, the cross section of each of the cylindrical portion and the piston-like portion is an ellipse or an ellipse. Because the part rotates only a small angle with respect to the cylindrical part, even if you try to forcibly twist the body, the movement of the piston part within the cylindrical part is immediately restricted, and the vertebra is not overloaded. In addition, the function of the spine joint can be reconstructed without damaging the disc.

In the artificial facet joint according to the fifth aspect of the present invention, since the elastic material is made of polyurethane, the elastic material bends due to its large elasticity to allow rotation of the piston-like portion in the cylindrical portion. It has the effect of not applying excessive stress.

In the artificial facet joint according to the sixth aspect of the present invention, since the piston-like portion is made of polyolefin, the lubrication of the piston-like portion in the cylinder-like portion is caused by the self-lubricating property and wear resistance of the polyolefin. Movement can be ensured, and there is an effect that wear is small even after long-term use.

[Brief description of the drawings]

FIG. 1 is a schematic view showing the artificial facet joint of the present invention attached to a spine.

FIG. 2A is a schematic view showing a state where two artificial facet joints of the present invention are attached to a spine. (B) is a schematic view showing a state of an artificial facet joint when two artificial facet joints of the present invention are attached to a spine and the body is twisted right and left.

FIG. 3 is a cross-sectional view of the artificial facet joint of the present invention.

FIG. 4 is a longitudinal sectional view of the artificial facet joint of the present invention.

FIG. 5 (A) is a schematic view showing a state where the artificial facet joint according to another embodiment of the present invention is attached to both sides of the spinous process of the spine. (B) is a top view of a mounting member.
(C) is a bottom view of the mounting member.

FIG. 6 is a schematic view showing a conventional intravertebral fixation device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Artificial facet joint 2 Cylindrical part 2A Elastic substance 2a Open end 2b Closed end 2c Attachment part 3 Piston-like part 6 Spring 9 Another attachment part

Claims (6)

(57) [Claims] 1. A cylinder-like portion and a piston-like portion movably fitted to the cylinder-like portion, the piston-like portion also being able to rotate the spine of a healthy person in a direction perpendicular to the direction of movement in the cylinder-like portion. Attached so as to be able to rotate to an angle equal to or less than that, and provided at each end of the cylindrical portion and the piston-shaped portion with an attaching portion for attaching between the adjacent vertebrae with the damaged disc interposed therebetween. An artificial facet joint, characterized in that: 2. The artificial facet joint according to claim 1, wherein an inner surface of the cylindrical portion is lined with an elastic material to allow rotation of the piston portion within the cylindrical portion, and further, a bottom portion of the piston portion. An artificial facet joint comprising a spring provided between the head and the lid. 3. The artificial facet joint according to claim 1, wherein the cross section of each of the cylindrical portion and the piston-shaped portion is an ellipse, and the piston-shaped portion of the spine of a healthy person is formed with respect to the cylindrical portion. An artificial facet joint, which is rotated at an angle equal to or less than the angle of rotation. 4. The artificial facet joint according to claim 1, wherein both the cylindrical portion and the piston-like portion have an elliptical cross section. 5. The artificial facet joint according to claim 2, wherein the elastic substance is polyurethane. 6. The artificial facet joint according to claim 1, wherein the piston-like part is made of polyolefin.