WO2020161944A1 - Screw for vertebral arch and vertebral arch spacer kit - Google Patents

Abstract

An objective of the present invention is to provide a screw for a vertebral arch with which insertability and straightness into a lower hole of a vertebral arch during laminoplasty can be improved, and a vertebral arch spacer kit comprising said screw for a vertebral arch. Provided is a screw for a vertebral arch, comprising: a tapering screw part (2) having a screw thread (2a), said tapering screw part (2) extending along a longitudinal axis (A) and tapering from a base end side toward a leading end side; a head part (3) which is positioned at the base end side of the screw part (2); and a shaft part (4) which is positioned at the leading end side of the screw part (2), extends along the longitudinal axis (A), and has a substantially cylindrical outer circumference surface (4a) at the outermost side in the radial direction which is perpendicular to the longitudinal axis (A).

Description

Vertebral screw and vertebra spacer kit

The present invention relates to a pedicle screw and a laminar spacer kit.

Conventionally, screws for orthopedic surgery have been known (for example, see Patent Documents 1 and 2).

Japanese Patent Publication No. 2016-512093 Japanese Patent No. 4358726

Laminoplasty is known as a treatment method for cervical spondylotic myelopathy, posterior longitudinal ligament ossification, yellow ligament ossification, disc herniation, etc. Laminoplasty is a method in which the spinous process is excised, the lamina is cut, and a spacer is inserted between the cut surfaces of the lamina. Spacers placed between the cut planes of the lamina allow the diameter of the spinal canal to be increased.

Prior to inserting the spacer between the cut surfaces, a screw for attaching the spacer to the lamina is screwed into the lamina. That is, the cut planes of the lamina are enlarged, a prepared hole is formed in the lamina, and the screw is screwed into the prepared hole from the cut plane side. At this time, the operator views the cut surface of the lamina in the body from the back of the patient, that is, from a direction substantially parallel to the cut surface or an oblique direction. In addition, blood or the like may adhere to the cut surface of the lamina. Further, the cut end portion of the cut lamina is wobbled because it is supported only by the pedicle. In this way, the visibility of the prepared hole of the cutting surface is poor for the operator, and the position of the cutting end is not stable, so the screw position and angle are accurately aligned with the prepared hole of the cutting surface and straight into the prepared hole. It is difficult to insert the screw into the

The present invention has been made in view of the above-described circumstances, and in a laminoplasty, a vertebral arch screw that can improve the insertability and straightness of insertion into the pilot hole of the vertebral arch and a vertebral arch including the same. It is intended to provide a spacer kit.

One aspect of the present invention has a tapered threaded portion having a thread, extending along a longitudinal axis, and tapering from a proximal end side toward a distal end side, and the threaded portion is located on the proximal end side. A head portion; and a shaft portion that is located on the distal end side of the screw portion, extends along the longitudinal axis, and has a substantially cylindrical outer peripheral surface at the outermost radial direction orthogonal to the longitudinal axis. It is a screw for a laminar arch.

Another aspect of the present invention comprises a laminar spacer disposed between the cut ends of a cut laminae, and the pedicle screw screwed into the cut ends, the laminar screw of A laminar spacer kit wherein the head portion is substantially spherical and the vertebral arch spacer is engageable with the head portion.

According to the present invention, it is possible to improve the insertability and straightness of the screw into the prepared hole of the pedicle in the laminoplasty.

It is a figure explaining the usage method of the laminar spacer kit which concerns on one Embodiment of this invention, and is a figure which shows the state which inserted the screw for vertebral arches into the cutting end part of the lamina. It is a figure explaining the usage method of the vertebral arch spacer kit which concerns on one Embodiment of this invention, and is a figure which shows the state which attached the vertebral arch spacer to the screw for vertebral arches of FIG. It is a side view of the screw for vertebral arches concerning one embodiment of the present invention. It is a figure explaining the usage method of the screw for vertebral arches of FIG. 3, and is a figure which shows the state which inserted the shaft part in the prepared hole of the lamina. It is a figure explaining the usage method of the screw for pedicles of FIG. 3, and is a figure which shows the state which screwed the screw part in the prepared hole of a lamina until the flange part hits a cutting surface. It is a partial longitudinal cross-sectional view of the screw of FIG. FIG. 3 is a perspective view of a laminar spacer according to an embodiment of the present invention. FIG. 8 is a side view of the laminar spacer of FIG. 7. It is a side view of the modification of the screw for pedicles of FIG.

Hereinafter, a vertebral arch screw 1 according to an embodiment of the present invention and a vertebral arch spacer kit including the same will be described with reference to the drawings.
The laminar spacer kit according to the present embodiment is used for laminoplasty, as shown in FIGS. 1 and 2. The pedicle spacer kit includes two pedicle screws 1 (see FIG. 3) and a pedicle spacer 10 (see FIGS. 7 and 8).

In a laminoplasty procedure, as shown in FIG. 1, the spinous process of the pedicle is excised, the lamina B is cut into two cutting ends C1 and C2, and the vertebrae are cut into each of the cutting ends C1 and C2. The bow screw 1 is screwed in. As shown in FIG. 2, the laminar spacer 10 is inserted between the cutting ends C1 and C2 and attached to the cutting ends C1 and C2 by engaging with the head portion 3 of the pedicle screw 1. The pedicle screw 1 and the pedicle spacer 10 are placed on the patient's lamina B and fixed to the lamina B by bone fusion with the lamina B.

The pedicle screw 1 (hereinafter simply referred to as “screw 1”) has a longitudinal axis A connecting the proximal end and the distal end, as shown in FIG. Further, the screw 1 includes a screw portion 2 extending along the longitudinal axis A, a head portion 3 located on the proximal end side of the screw portion 2, a shaft located on the tip end side of the screw portion 2 and extending along the longitudinal axis A. And a section 4. As shown in FIGS. 4 and 5, the screw 1 is screwed into the prepared hole D penetrating the cut ends C1 and C2 while being screwed by itself. In FIGS. 4 and 5, the suffix E indicates cancellous bone and the reference F indicates cortical bone.

The screw 1 is made of a titanium alloy (for example, 64 titanium (Ti-6AL-4V)). The material of the screw 1 may be another material having high strength and biocompatibility. For example, the main material of the screw 1 may be a metal material such as stainless steel or pure titanium such as SUS316L (JIS standard symbol), or a polymer material such as PEEK (polyether ether ketone). Good.

The screw portion 2 is a male screw having a thread 2a, and has a taper shape that tapers from the base end side toward the tip end side. Specifically, the outer diameter of the threaded portion 2 and the diameter of the valley 2b are gradually reduced from the base end side to the tip end side. The outer diameter of the threaded portion 2 is the diameter of a virtual cone that contacts the top of the thread 2a. The diameter of the valley 2b of the threaded portion 2 is the diameter of an imaginary cone that contacts the root of the threaded portion 2.

The head portion 3 is fixed to the base end of the screw portion 2 with a cylindrical neck portion 5 and a disc-shaped flange portion 6 separated. The head portion 3 is substantially spherical and has a diameter larger than the diameter of the neck portion 5. The flange portion 6 is arranged between the neck portion 5 and the screw portion 2 and has a diameter larger than the maximum outer diameter of the screw portion 2. As shown in FIG. 5, the threaded portion 2 is screwed into the cut end portions C1 and C2 until the end surface of the flange portion 6 abuts the cut surface G of the cut end portions C1 and C2.

The threaded portion 2 has a length Lt that reaches the cortical bone F with the threaded portion 2 inserted in the prepared hole D until the flange portion 6 hits the cut surface G of the cut end portions C1 and C2. The maximum thickness of the cortical bone F is about 3 mm, and the thickness of the cancellous bone E at the cut ends C1 and C2 is about the same as that of the cortical bone F. Further, the screw portion 2 may be inserted into the prepared hole D formed obliquely with respect to the stacking direction of the bones E and F. In consideration of such circumstances, the length Lt of the screw portion 2 is preferably 3 mm or more.

The shaft part 4 is fixed to the tip of the screw part 2. The shaft portion 4 has a cylindrical shape and has a cylindrical outer peripheral surface 4 a coaxial with the longitudinal axis A at the outermost side in the radial direction orthogonal to the longitudinal axis A. That is, the shaft portion 4 does not have a convex portion that projects outward in the radial direction such as a screw thread, and has a smooth outer shape along the cylindrical surface. The outer peripheral surface 4a has a constant diameter φs. The diameter φs is, for example, 1.2 mm or more and 3.5 mm or less. The diameter φs is larger than the diameter of the valley 2b on the most distal end side of the screw portion 2 and smaller than the outer diameter of the thread crest 2a on the most distal end side of the screw portion 2. The diameter of the prepared hole D is substantially equal to the diameter φs of the outer peripheral surface 4a. Therefore, the shaft portion 4 passes through the inside of the prepared hole D without deforming the prepared hole D, and the threaded portion 2 is screwed into the prepared hole D following the shaft portion 4 while being threaded by the threads 2a.

The shaft portion 4 functions as a guide for guiding the screw 1 in the prepared hole D along the longitudinal direction of the prepared hole D. In order to enhance the function as a guide, the length Ls of the shaft portion 4 in the direction along the longitudinal axis A is preferably 1 times or more the diameter φs, and more preferably 1.5 times or more the diameter φs. preferable. The excessive length of the shaft portion 4 does not contribute to improvement of insertability and straightness. Therefore, the length Ls is preferably 10 times or less the diameter φs.

In order to improve the insertability of the shaft portion 4 into the prepared hole D, the distal end portion 4b of the shaft portion 4 is tapered from the proximal end side toward the distal end side as shown in FIG. It is preferable that the front end surface of No. 4 is formed into a convex curved surface by R chamfering. Since the tip portion 4b has such a shape, the deformation of the prepared hole D by the shaft portion 4 can be prevented more reliably.

The screw portion 2 has an outer peripheral surface 2c offset between the most distal thread 2a and the base end of the shaft portion 4 on the longitudinal axis A side with respect to the outer peripheral surface 4a of the base end of the shaft portion 4. Since such an outer peripheral surface 2c exists on the tip side of the most advanced screw thread 2a, the torque required at the start and initial stage of tapping of the screw portion 2 to each position on the inner surface of the prepared hole D is small. Complete. As a result, the load applied to the cut ends C1 and C2, particularly the hard cortical bone F, can be reduced and the cortical bone F can be protected. Further, by forming new bone in the space between the outer peripheral surface 2c that is recessed from the outer peripheral surface 4a of the shaft portion 4 and the inner surface of the prepared hole D, the direction along the longitudinal axis A of the screw 1 with respect to the lamina B is determined. The fixing force of can be increased.

The length Ls of the shaft portion 4 is shorter than the length Lt of the screw portion 2. The ratio (Ls:Lt) between the length Ls of the shaft portion 4 and the length Lt of the screw portion 2 is preferably 1:1.4 to 1:2.5. When the ratio of the length Ls to the length Lt is within the above range, the function of the shaft portion 4 as a guide can be ensured while preventing the shaft portion 4 from excessively protruding from the prepared hole D. it can.
In FIG. 5, a part of the shaft portion 4 projects from the pilot hole D, but the entire shaft portion 4 projects from the pilot hole D, or the entire shaft portion 4 is arranged in the pilot hole D. As described above, the length of each of the screw portion 2 and the shaft portion 4 may be designed.

As shown in FIG. 6, it is preferable that the screw 1 is provided with a coating film 7 of a biocompatible substance that covers at least the surface of the tip portion of the screw portion 2 (the portion within the rectangle of the broken line in FIG. 3). The biocompatible substance is a substance having osteoconductivity, such as titanium oxide. The coating 7 covering the surface of the tip portion of the screw portion 2 can promote bone union with the cortical bone F at the tip portion of the screw portion 2. In order to further promote the bone union of the screw 1, the coating 7 may be provided on the surface of a portion other than the tip portion of the screw portion 2. For example, the coating 7 may cover the entire surface of the screw portion 2 or the entire surface of the screw 1.

The laminar spacer 10 includes a columnar main body 11 as shown in FIG. 7. The body portion 11 shown in FIG. 7 is a quadrangular prism having trapezoidal side surfaces in which end faces on both sides in the longitudinal direction are inclined in directions opposite to each other with respect to the longitudinal direction. The shape of the main body 11 is not limited to this, and may be another shape. For example, the main body 11 may have a rectangular parallelepiped shape having end faces parallel to each other, or may have a cylindrical shape.

Like the material of the screw 1, the material of the main body 11 can be arbitrarily selected as long as it has high strength and biocompatibility. For example, the main material of the main body 11 may be a metal material such as stainless steel such as SUS316L (JIS standard symbol), pure titanium or a titanium alloy, or a polymer material such as PEEK.

As shown in FIG. 8, inside the main body portion 11, there are two substantially spherical accommodation holes 12 each having a diameter slightly larger than the diameter of the head portion 3 and capable of accommodating the head portion 3, and each accommodation hole. An introduction hole 13 is formed in the accommodation hole 12 provided for the head 12 through which the neck portion 5 of the screw 1 in which the head portion 3 is accommodated passes. The two accommodation holes 12 are provided at intervals in the longitudinal direction of the main body 11.

The introduction hole 13 is a substantially cylindrical hole that connects the inside of the accommodation hole 12 and the outside of the main body 11 to each other. One end of the introduction hole 13 is opened to the accommodation hole 12, and the other end of the introduction hole 13 is opened to the end surface and the side surface 11 a of the main body 11. The side surface 11a is a ventral side surface that is arranged on the spinal canal side (ventral side) in the laminoplasty. The opening 13 a at one end of the introduction hole 13 connected to the accommodation hole 12 has a diameter larger than the diameter of the neck 5 and smaller than the diameter of the head 3.

A groove 14 is formed in the body 11 to divide the body 11 into two gripping pieces 11A and 11B in a direction that passes through the two accommodation holes 12 and the two introduction holes 13 and intersects the lengthwise direction. Each accommodation hole 12 and each introduction hole 13 is divided into two substantially equal parts by a groove 14. The two gripping pieces 11A and 11B are connected to each other by a spring portion 15 on a back side surface (a side surface facing the ventral side surface 11a) 11b of the main body 11. The gripping pieces 11A and 11B swing relative to each other around the spring portion 15, whereby the ventral side surface 11a side of the gripping pieces 11A and 11B opens and closes. The spring portion 15 is made of an elastic material and urges the pair of gripping pieces 11A and 11B in a closing direction. As a result, the pair of gripping pieces 11A and 11B open and close in a clip manner.

When the pair of gripping pieces 11A and 11B are open, the diameter of the opening 13a is enlarged to a size larger than the diameter of the head 3.
On the other hand, in the state where the pair of gripping pieces 11A and 11B are closed, the diameter of the opening 13a is smaller than the diameter of the head portion 3. Therefore, the head part 3 in the accommodation hole 12 engages with the main body part 11 in the direction along the longitudinal axis A and in the direction intersecting the longitudinal axis A, and the head part 3 in the accommodation hole 12 comes off from the pedicle spacer 10. There is no such thing.

Next, the operation of the vertebral arch spacer kit according to the present embodiment will be described by taking as an example a laminoplasty using a spinous process longitudinal splitting method for vertically splitting a spinous process. The vertebral arch spacer kit may be used for a unilateral laminoplasty for cutting one of the left and right lamina B, instead of the spinous process longitudinal division method.
In laminoplasty, the spinous process and lamina B are longitudinally split as shown in FIG. 1 after excision of the end of the spinous process.

Next, the screw 1 is inserted into the cut ends C1 and C2 of the lamina B from the cut surface G side, respectively. Specifically, a prepared hole D opening to the cut surface G is formed in each of the cut ends C1 and C2 by using an instrument such as a drill. Next, as shown in FIG. 4, the shaft portion 4 is inserted into the prepared hole D from the cut surface G side. Next, as shown in FIG. 5, the screw portion 2 is screwed into the prepared hole D until the flange portion 6 abuts the cut surface G. Since the cancellous bone E is exposed on the cut surface G, the screw portion 2 is screwed into the cortical bone F from the cancellous bone E.

Next, the pair of gripping pieces 11A and 11B are opened, and the pair of gripping pieces 11A and 11B are put on the two screws 1 from the head part 3 side so that the head part 3 is inserted into the accommodation hole 12. Next, the grip pieces 11A and 11B are closed, and the head portion 3 is gripped between the grip pieces 11A and 11B. As a result, as shown in FIG. 2, the laminar spacer 10 is attached between the cut ends C1 and C2 of the lamina B via the two screws 1, and the laminar spacer 10 changes the diameter of the spinal canal. It can be maintained in its expanded state.
The screw 1 and the pedicle spacer 10 are placed on the lamina B. In the prepared hole D, new bone is formed around the screw 1, the screw 1 fuses with the surrounding cancellous bone E and cortical bone F, and the screw 1 is fixed to the bones E and F.

As described above, according to the present embodiment, the shaft portion 4 at the tip of the screw 1 is inserted into the prepared hole D before the screw portion 2 is screwed into the prepared hole D. Unlike the threaded portion 2 that is inserted into the prepared hole D while tapping, insert a cylindrical shaft portion 4 having a smooth outer peripheral surface 4a into the prepared hole D along the longitudinal direction of the prepared hole D. Is easy. Therefore, even when it is difficult to visually recognize the prepared hole D of the cut surface G or the positions of the cut ends C1 and C2 are not stable, the operator inserts the shaft portion 4 that is the tip end of the screw 1 into the prepared hole D. It can be easily inserted inside. That is, the insertability of the screw 1 into the prepared hole D can be improved. Further, since the tip portion 4b of the shaft portion 4 is tapered, the insertability of the screw 1 can be further improved.

Further, the screw portion 2 is screwed into the prepared hole D after the shaft portion 4 is inserted into the prepared hole D. That is, at the time of starting the screwing of the screw portion 2 into the cancellous bone E, the shaft portion 4 has already been arranged along the inside of the prepared hole D. Then, the threaded portion 2 is guided straight in the prepared hole D by the shaft portion 4 that advances straightly in the prepared hole D. Thereby, the straightness of the screw 1 in the prepared hole D can be improved.
Further, since the shaft portion 4 has the smooth outer peripheral surface 4a on the outermost side in the radial direction, the shaft portion 4 does not need to widen the prepared hole D or form a groove on the inner surface of the prepared hole D. Go inside D. That is, the shaft portion 4 does not affect the fastening force of the screw portion 2 with the bones E and F.

Also, cortical bone F is hard, whereas spongy cancellous bone E is soft. Therefore, in the case of a screw part having a constant outer diameter, a high fixing force can be obtained for the cortical bone F, but it is difficult to obtain a high fixing force for the cancellous bone E. According to the present embodiment, the threaded portion 2 is a taper screw that tapers from the base end side toward the tip end side, so that the threaded portion 2 is screwed into the cancellous bone E more tightly as it advances in the prepared hole D. Be done. Therefore, the fixing force of the screw part 2 with respect to the cancellous bone E is improved, and even immediately after the screw part 2 is screwed into the prepared hole D, the high fixing force of the screw part 2 with respect to both the cancellous bone E and the cortical bone F. Can be obtained.

In the above embodiment, the shaft portion 4 may have a recess 4c that opens to the outer peripheral surface 4a, as shown in FIG. By forming new bone in the recess 4c in the prepared hole D, the fixing force after bone fusion in the direction along the longitudinal axis A of the screw 1 with respect to the lamina B can be further increased.
The recess 4c may extend in the circumferential direction around the longitudinal axis A, or may have a spiral shape. When the recess 4c has a spiral shape, the fixing force in the direction along the longitudinal axis A can be more effectively increased.

In the above embodiment, the diameter φs of the shaft portion 4 is constant, but the shaft portion 4 may be tapered toward the tip as long as the function as a guide is not impaired.
Further, the shape of the tip end surface of the shaft portion 4 may be a shape other than the convex curved surface. For example, the tip end surface of the shaft portion 4 may be a flat surface that intersects the longitudinal axis A as shown in FIG.

In the above-described embodiment, the head portion 3 has a substantially spherical shape, but it may have another shape instead. For example, the head unit 3 may have a polyhedral shape or a truncated cone shape.
The shape of the accommodation hole 12 may be changed according to the shape of the head portion 3. For example, the inner surface shape of the accommodation hole 12 may be a polyhedron shape, or may be a shape complementary to the shape of the head unit 3.

DESCRIPTION OF SYMBOLS 1 Screw for pedicle 2 Screw part 2a Thread ridge 2b Valley 2c Outer peripheral surface 3 Head part 4 Shaft part 4a Outer peripheral surface 4b Tip part 4c Recess 5 Neck part 6 Flange part 7 Coat 10 Vertebral spacer A Longitudinal axis B Lamina C1 C2 Cut end E Cancellous bone F Cortical bone H Prepared hole

Claims (7)

A tapered threaded portion having a thread, extending along the longitudinal axis and tapering from the proximal end side toward the distal end side;
A head portion located on the base end side of the screw portion,
A shaft portion located on the tip side of the threaded portion, extending along the longitudinal axis, and having a substantially cylindrical outer peripheral surface on the outermost side in the radial direction orthogonal to the longitudinal axis.
A screw for a pedicle. The pedicle screw according to claim 1, wherein a diameter of the outer peripheral surface of the shaft portion is larger than a diameter of a valley on the most distal end side of the screw portion. The ratio between the length of the shaft portion in the direction along the longitudinal axis and the length of the screw portion in the direction along the longitudinal axis is 1:1.4 to 1:2.5. Item 2. The laminar screw according to Item 2. The outer peripheral surface of the threaded portion between the most distal end side thread and the base end of the shaft portion is offset to the longitudinal axis side from the outer peripheral surface of the shaft portion. The screw for vertebral arch according to any one of 3 above. The pedicle screw according to any one of claims 1 to 4, comprising a coating of a biocompatible substance that covers at least a surface of a tip portion of the screw portion. The pedicle screw according to any one of claims 1 to 5, wherein a distal end portion of the shaft portion is tapered from a proximal end side toward a distal end side, and a distal end surface of the shaft portion is a convex curved surface. .. A laminar spacer disposed between the cutting ends of the severed laminae,
The vertebral arch screw according to any one of claims 1 to 6, which is screwed into the cut end portion,
The head portion of the pedicle screw is substantially spherical,
A laminar spacer kit, wherein the laminar spacer is engageable with the head portion.

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