WO2018181895A1

WO2018181895A1 - Interspinous process implant

Info

Publication number: WO2018181895A1
Application number: PCT/JP2018/013602
Authority: WO
Inventors: 康太郎西田; 努向野
Original assignee: 国立大学法人神戸大学
Priority date: 2017-03-30
Filing date: 2018-03-30
Publication date: 2018-10-04
Also published as: JP6963775B2; JPWO2018181895A1

Abstract

The purpose of the present invention is to provide an interspinous process implant capable of being inserted by screwing more easily than in the past when percutaneously inserting the implant by screwing the implant into the body. A screw part 1 of an interspinous process implant 100 has a first screw part 4 and a second screw part 5, in order from the distal end side. In the first screw part 4, a virtual plane S1 connecting the apices of the screw threads has a tapered conical shape recessed on the outside. In the second screw part 5, a virtual plane S2 connecting the apices of the screw threads has a truncated cone shape that bulges outward.

Description

Interspinous process implant

The present invention relates to an implant fitted between spinous processes.

As this type of technology, for example, there are those described in

Patent Documents

1 and 2. The interspinous process spacer described in Patent Document 1 includes a substantially conical screw part screwed between the spinous processes, a spacer part formed in the longitudinal direction of the screw part, and an appropriate tool that can be freely engaged or connected. The implant includes a member and an attachable head, and has a screw part, a spacer part, and a through-hole in the axial center of the head.

According to the above interspinous process spacer, using the opening force generated when the screw part is screwed between the spinous processes, the interspinous process is easily expanded, and the spacer part is fitted between the spinous processes. Can do. Thereby, even under local anesthesia, the interspinous process spacer can be percutaneously screwed into the body and inserted, and placed between the spinous processes.

The interspinous process implant described in Patent Document 2 is an improvement of the interspinous process spacer described in Patent Document 1, and has the following configuration as a new configuration. A plurality of slits or grooves having a length of 1/3 or more of the entire length of the interspinous process implant are formed in the axial direction of the interspinous process implant. These slits or grooves are slits or grooves having a depth that reaches a through hole penetrating the shaft center. Further, these slits or grooves are provided at substantially equal intervals of less than 180 ° around the axis.

According to the interspinous process implant described in Patent Document 2, the entire interspinous process implant can be made elastic and flexible, and insertion and installation of the interspinous process implant can be simplified. Further, excessive stress is prevented from being applied to the spinous processes that come into contact with the interspinous process implant. Thereby, the effect of the enlargement between the spinous processes can be maintained for a long time. In other words, bone destruction of the spinous process can be prevented.

Japanese Patent No. 4797174 Japanese Patent No. 5272279

However, the interspinous process spacer described in Patent Document 1 and the interspinous process implant described in Patent Document 2 in which this is improved still have problems to be improved.

The screw part of the conventional implants (interspinous process spacer, interspinous process implant) described in

Patent Documents

1 and 2 has a substantially conical shape in which the middle part is swollen. In this configuration, the diameter of the screw suddenly increases at the initial stage when the implant is percutaneously screwed into the body and inserted, so that the implant receives a large resistance when the screw does not penetrate into the body tissue. End up.

Immediately below the skin is a tough fascia made of collagen fibers. This fascia is a major cause of the resistance described above. In the procedure using the conventional implants described in

Patent Documents

1 and 2, it is necessary to perform fasciotomy in addition to skin incision in order to smoothly insert the implant into the body at the initial stage.

Also, between the spinous processes, there is a thick interspinous ligament mainly composed of collagen fibers that connects adjacent upper and lower spinous processes. In the procedure using the conventional implants described in

Patent Documents

1 and 2, in order to smoothly insert the screw portion between the spinous processes, it was necessary to make a hole as the passage in the interspinous ligament in advance. .

The present invention has been made in view of the above circumstances, and an object of the present invention is to be able to screw and insert an implant percutaneously into a body more easily than before. It is to provide an interprocess implant.

The present invention provides a spine comprising: a substantially conical screw portion having a screw-shaped outer peripheral surface; a head portion coaxial with the screw portion; and a spacer portion formed between the screw portion and the head portion. An interspinous process implant that fits between the processes. The screw part has a first screw part and a second screw part in order from the tip side. The first screw part has a tapered conical shape in which a virtual surface connecting the tops of the threads is recessed outward, and the second screw part has a virtual surface connecting the tops of the threads. It has a truncated cone shape that bulges outward.

According to the present invention, the imaginary surface that connects the vertices of the thread of the first screw portion on the tip side of the screw portion, in particular, the configuration requirement of the present invention is a tapered conical shape recessed outward. As a result, the diameter of the screw of the first screw portion gradually increases in the direction from the tip of the screw portion to the spacer portion. Thereby, the screw portion is easily sharply cut into the tissue in the body along the screw thread without receiving a large resistance.

That is, according to the interspinous process implant of the present invention, when inserting the implant percutaneously into the body, it can be screwed and inserted more easily than before.

1 is a perspective view of an interspinous process implant according to an embodiment of the present invention. It is a side view of the implant between spinous processes shown in FIG. FIG. 3 is a cross-sectional view taken along line AA in FIG. 2. It is a figure for demonstrating the structure of the screw of a screw part. It is the photograph under the X-ray fluoroscopy of the state in which the guide pin is being inserted between the spinous processes of the pig (taken from the side of the pig's back). It is a photograph under the X-ray fluoroscopy of the state in the middle of inserting the interspinous process implant between the spinous processes of the pig (the pig's back is taken from the front). It is a photograph under the X-ray fluoroscopy in the state where the insertion of the interspinous process implant between the spinous processes of the pig was completed (the back of the pig was taken from the front). It is a photograph under X-ray fluoroscopy in a state where the insertion of the interspinous process implant between the spinous processes of the pig has been completed (taken from the side of the pig's back). It is a CT image of a pig after 3 months have passed since the interspinous process implant was fitted between the spinous processes. It is a side view of the implant between spinous processes which concerns on other embodiment of this invention. FIG. 11 is a sectional view taken along line BB in FIG. 10. FIG. 12 is a photograph showing a state in which an implant, which is an example of the interspinous process implant shown in FIGS. 10 and 11, is filled with crushed bone (artificial bone) containing water. FIG.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

(Structure of interspinous implant)
The configuration of the interspinous process implant 100 according to an embodiment of the present invention will be described with reference to FIGS. The interspinous process implant 100 is an implant that is fitted between the spinous processes, and has a spindle shape as a whole. The interspinous process implant 100 includes an implant body 6, a front insert 7 (metal member) attached to the distal end portion of the implant body 6, and a rear insert 8 (metal member) attached to the rear end portion of the implant body 6. Are the main components. The implant body 6 of the present embodiment is formed of PEEK resin (polyether ether ketone resin). Examples of the material of the implant body 6 other than the PEEK resin include metal materials such as titanium, titanium alloy, and stainless steel, and ceramics. Further, a resin (medical plastic) other than the PEEK resin may be used as the material of the implant body 6. Examples of applicable resins other than PEEK resin include polyvinyl chloride (PVC) resin, polypropylene (PP) resin, polyethylene (PE) resin, and polycarbonate (PC) resin. Moreover, the front insert 7 and the rear insert 8 of this embodiment are formed of a titanium alloy. Examples of the material of the front insert 7 and the rear insert 8 other than the titanium alloy include metal materials such as tantalum and stainless steel, and ceramics.

The overall length of the interspinous implant 100 is not limited to this, but is, for example, 30 mm to 40 mm.

Here, each part of the interspinous process implant 100 in which the front insert 7 and the rear insert 8 are attached to the implant body 6 includes a substantially conical (conical) screw part 1 having a screw-shaped outer peripheral surface, and a screw part. 1 is roughly divided into a head 2 coaxial with 1 and a spacer 3 formed between the screw 1 and the head 2.

<Screw part>
As shown in FIG. 2 etc., the screw part 1 is a taper-shaped screw as a whole, and has the 1st screw part 4 and the 2nd screw part 5 in an order from the front end side. Here, the 1st screw part 4 is made into the tapered cone shape which the virtual surface S1 which connects the vertex of a screw thread was dented outside. On the other hand, the second screw part 5 has a frustum shape in which a virtual surface S2 connecting the vertices of the threads swells outward. In FIG. 2, the curves indicating the virtual surfaces S <b> 1 and S <b> 2 are shown slightly apart from the screw part 1 in consideration of the visibility of the drawing. A symbol P indicates an inflection point. When the axial length of the screw part 1 is L, the inflection point P is at a position of about 0.3 L from the tip of the screw part 1, but the position of the inflection point P is not limited to this.

The detailed structure of the screw of the screw part 1 will be described with reference to FIGS. In FIG. 4, what is indicated by reference numeral 30 is the material of the implant body 6 before the thread groove 13 (see FIG. 2) is formed. The thread groove 13 of the screw part 1 of the present embodiment is formed by using two types of ball end mills having different sizes. One is a ball end mill in which the diameter of the ball part 31 at the tip is φ6, and the other is a ball end mill in which the diameter of the ball part 32 at the tip is φ2. A cutting locus 33 of the ball portion 31 of the φ6 ball end mill and a cutting locus 34 of the ball portion 32 of the φ2 ball end mill are shown in FIG. The thread groove processing by the φ6 ball end mill is performed in a spiral shape from a fitting recess 14 (described later) provided in the spacer portion 3 toward the front end side of the material 30. The thread groove machining by the φ2 ball end mill is spirally formed from the midway between the fitting recess 14 and the tip of the material 30 toward the tip of the material 30. Prior to the thread groove machining by the φ2 ball end mill, the thread groove machining by the φ6 ball end mill is performed. That is, the thread groove machining by the φ2 ball end mill is performed after the thread groove machining by the φ6 ball end mill.

Here, the above-described thread groove machining by the φ6 ball end mill and the φ2 ball end mill is performed from two points that are 180 degrees out of phase in the circumferential direction of the material 30. That is, the screw part 1 (the first screw part 4 and the second screw part 5) is a double thread.

Due to the thread groove machining by the φ6 ball end mill, the bottom surface of the thread groove 13 adjacent to the spacer portion 3 of the second screw portion 5 becomes a curved surface of R3 (radius 3 mm, the same shall apply hereinafter). The outer edge of the spinous process (a part of the spinous process) can pass through. Moreover, the top part of the thread on the spacer part 3 side of the second screw part 5 is a curved surface that is not sharpened in the implant axial direction. The radius of the bottom surface of the screw groove 13 adjacent to the spacer portion 3 of the second screw portion 5 is, for example, not less than 2 times and not more than 4 times the radius of the bottom surface of the screw groove 13 of the first screw portion 4. . The radius of the bottom surface of the screw groove 13 adjacent to the spacer part 3 of the second screw part 5 is preferably R3 or more so that the outer edge part of the spinous process (a part of the spinous process) enters the groove. .

By the thread groove machining by the φ2 ball end mill, the bottom surface of the thread groove 13 becomes a curved surface of R1 (radius 1 mm, the same applies hereinafter) from the middle part of the second screw part 5, and the width of the thread groove 13 is narrowed. Moreover, as shown in FIG. 3, the vertex of the thread of the 1st screw part 4 is made sharp. In addition, the radius of the bottom face of the thread groove 13 of the first screw part 4 (including the thread groove R1 of the second screw part 5) is not limited to R1.

Here, the screw pitch of the screw part 1 is set to 1.8 mm, 1.4 mm, 2.1 mm, and 2.3 mm every half rotation from the tip side toward the fitting recess 14 (spacer part 3). Thus, the screw pitch of the screw portion 1 is a variable pitch in which the pitch decreases from the front end side toward the spacer portion 3 in the first screw portion 4 and increases in the subsequent second screw portion 5. It is said that.

First, by setting the screw pitch of the second screw part 5 to a variable pitch that increases from the tip side toward the spacer part 3, an imaginary surface that connects the vertices of the screw thread on the tip side of the screw part 1. In the case where S1 is a tapered conical shape recessed outward and the imaginary surface S2 connecting the apexes of the threads on the spacer portion 3 side of the screw portion 1 is a conical shape bulging outward, The screw groove 13 of the 2 screw part 5 and the fitting recessed part 14 provided in the spacer part 3 to be described later can be connected without a large step (smoothly). As a result, the fitting recess 14 of the spacer portion 3 can be easily guided to the outer edge portion of the spinous process.

Further, in addition to increasing the screw pitch of the second screw part 5 from the tip side toward the spacer part 3, the first screw part 4 reverses the screw pitch from the tip side toward the spacer part 3. When the virtual surface S1 has a tapered conical shape that is recessed outward and the virtual surface S2 has a truncated cone shape that bulges outward, the thread groove of the first screw part 4 13 and the screw groove 13 of the second screw part 5 can be easily connected without a large step (smoothly). When the screw grooves 13 of the first and second screw parts are connected to each other without a large step (smoothly), the screw groove 13 of the second screw part 5 is easily guided to the outer edge of the spinous process.

Note that the numerical value of the screw pitch is not limited to the above. Regarding the variable pitch, for example, the screw pitch is constant in the first screw portion 4, and the screw pitch in the second screw portion 5 is a variable pitch that increases from the tip side toward the spacer portion 3. It may be. Even with such a variable pitch, the imaginary surface S1 connecting the apexes of the threads on the tip side of the screw part 1 has a tapered conical shape recessed outward, and the thread on the spacer part 3 side of the screw part 1 When the imaginary surface S2 connecting the vertices is formed into a truncated conical shape that bulges outward, the screw groove 13 of the first screw part 4 and the screw groove 13 of the second screw part 5 are not greatly stepped (smoothly ) Can be connected.

Here, in this embodiment, the thread groove 13 of the first screw part 4 and the thread groove 13 of the second screw part 5 are smoothly connected. Further, the thread groove 13 of the second screw part 5 and the fitting recess 14 described later provided in the spacer part 3 are also smoothly connected. Since the screw groove 13 of the first screw part 4 and the screw groove 13 of the second screw part 5 are smoothly connected, the screw groove 13 of the second screw part 5 can be easily guided to the outer edge part of the spinous process. Become. In addition, since the thread groove 13 of the second screw portion 5 and a fitting recess 14 described later provided in the spacer portion 3 are smoothly connected, the spacer portion 3 is fitted to the outer edge portion of the spinous process. It becomes easy to guide the recess 14. Note that “smooth connection” mathematically refers to a surface in which the tangent plane of a point (X0, Y0, Z0) on a curved surface is uniquely determined regardless of the direction. “The tangent plane is uniquely determined regardless of the direction” means that the point on the curved surface is (X0, Y0, Z), and the tangent plane obtained from the Z coordinate as Z → Z0 is (X0 , Y, Z0), the tangent plane obtained from the Y coordinate as Y → Y0, and the tangent plane obtained from the point on the curved surface as (X, Y0, Z0) and the X coordinate as X → X0 are uniquely determined. That means. The “smooth connection” in the present invention is not limited to the strict meaning described above. The tangent plane need not be completely unique, and the coefficient of the tangent plane equation may have an error of about 6% (preferably an error of about 3%).

Further, as shown in FIG. 3, the virtual plane T connecting the bottoms of the thread grooves of the second screw part 5 has a substantially frustoconical shape (conical frustum shape bulging outward). Thereby, the implant can be screwed and inserted between the spinous processes while the space between the spinous processes is gradually widened on the bottom surface of the thread of the second screw portion 5 or the like.

On the other hand, the axial center of the implant body 6 is provided with a hole 6a in which the front insert 7 is embedded, and a hole 6b having a diameter larger than that of the hole 6a. The front insert 7 is a metal member attached to the tip of the first screw portion 4 and has a cylindrical shape. The outer diameter of the front insert 7 is about 2.5 mm, for example. The front end 7a of the front insert 7 is sharpened by various processes.

<Spacer part>
The spacer portion 3 is a portion that fits between the spinous processes. As shown in FIG. 2, the spacer portion 3 has two fitting concave portions 14 (two fitting concave portions 14 having a phase difference of 180 degrees around the axial direction) facing each other in a U shape in a side view. . A spinous process fits into the fitting recess 14. The fitting recess 14 is an R6 curved surface as viewed from the side. Further, in FIG. 2, as indicated by a curved arrow on the surface portion of the fitting recess 14, the fitting recess 14 has both sides more than the center portion in a cross-sectional view orthogonal to the axial direction of the implant. The curved surface has a low shape (a shape similar to a saddle of a so-called harness). In this way, the U-shaped fitting recess 14 in a side view is a curved surface (a shape similar to the above-described wrinkles) whose both sides are lower than the central portion in a cross-sectional view orthogonal to the axial direction of the implant. Thus, the screw groove 13 adjacent to the spacer portion 3 of the second screw portion 5 and the fitting recess 14 of the spacer portion 3 can be easily connected without a large step (smoothly). Note that the radius of the bottom surface of the fitting recess 14 in a side view is not limited to R6.

If the two fitting recesses 14 are provided to face each other, the spinous process is easily fitted into the spacer portion 3. In addition, since the fitting recess 14 is U-shaped in a side view, it is possible to prevent stress from being excessively applied to the spinous process contacting the interspinous implant 100.

Here, as for the thread groove 13 of the 2nd screw part 5, the depth of the groove | channel of the part 13a (refer FIG. 2) connected to the fitting recessed part 14 is shallower than the depth of the groove | channel of the near side (front side of a screw front end side). It is preferable that In this way, although the load at the time of passing the spinous process is slightly increased, it feels like the spinous process gets over the portion 13a, and when the spinous process is fitted into the fitting recess 14, the reverse rotation of the implant is prevented. be able to.

Also, X-ray marker pins 9 are embedded as identification members that can be identified by X-ray fluoroscopy on both sides of the fitting recess 14 in the axial direction of the implant. The X-ray marker pin 9 of this embodiment is made of titanium. Examples of the material of the X-ray marker pin 9 other than titanium include platinum, gold, cobalt, nickel, chromium, tantalum, stainless steel, and alloys thereof. Since these metals including titanium are metals that attenuate X-rays, the X-ray marker pins 9 can be identified by X-ray fluoroscopy.

The X-ray marker pin 9 is embedded in the side part of the implant body 6 so that the longitudinal direction thereof is directed to the axial center of the implant. A total of four X-ray marker pins 9 are embedded in the implant body 6, one on each side of the two opposing fitting recesses 14.

<Head>
The head 2 is a portion to which a screwing torque is applied when the interspinous process implant 100 is screwed into the body. A rear insert 8 is embedded in the head 2. The rear insert 8 and the implant body 6 are fixed by pins 11. As shown in FIG. 3, the axial center of the rear insert 8 is provided with a circular hole 8a in which a female screw is formed and a hexagonal hole 8b in this order from the front end side. The hexagonal hole 8b is a hole into which a tool such as a screwdriver is inserted, and the rear insert 8 is made of metal, so that the screwing torque can be reliably transmitted to the implant using a tool such as a screwdriver. Can do. Here, when the screw part 1 is a right-hand thread, the female screw formed in the hole 8a is a left-hand thread, and when the screw part 1 is a left-hand thread, the female screw formed in the hole 8a is a right-hand thread. In this embodiment, since the screw part 1 is a right-hand thread, the female thread formed in the hole 8a is a left-hand thread. The screw in the screw part 1 and the female screw formed in the hole 8a is a screw that is twisted in the opposite direction. This is the direction in which the interspinous process implant 100 is inserted into the body when it is removed from the body. This is because the screw can be easily removed by rotating the screw in the opposite direction.

In addition, the interspinous process implant 100 is provided with a through hole 10 penetrating its axis. The through hole 10 includes a hole 7 b of the front insert 7, a hole 6 b of the implant body 6, and holes 8 a and 8 b of the rear insert 8. The through hole 10 is a hole that is passed through the guide wire. By providing the through-hole 10 penetrating the axial center, the interspinous process implant 100 can be inserted using a guide wire toward the spinous processes.

Here, a guide wire is also used when removing the implant. The tip of the hole 6b of the implant body 6 is a conical inclined surface 6bf so that the hole 6b is tapered. In addition, it is preferable that the inclination | tilt angle (alpha) with respect to the axial direction of the inclined surface 6bf is 45 degrees or less. By setting the inclination angle α to 45 degrees or less, the guide wire can be easily inserted into the through-hole 10 of the implant when the implant placed between the spinous processes is removed. The lower limit angle of the inclination angle α is, for example, 10 degrees.

Also, scar tissue may intervene in a cavity such as the hole 8a of the interspinous process implant 100 placed between the spinous processes. Here, the rear end portion of the hole 8a of the present embodiment is a tapered conical inclined surface 8ar. By doing so, it becomes easy to screw the tip of the driver into the hole 8a and to easily insert the guide wire into the implant when the implant is removed.

Further, as shown in FIGS. 1 to 3, the side surface of the implant body 6 is provided with slits 12 extending in the axial direction at two locations. Two slits 12 are provided with a phase difference of 180 degrees around the axial direction. More specifically, two are provided with a phase difference of 90 degrees around the axial direction with respect to the fitting recess 14 while avoiding the fitting recess 14 of the spacer portion 3.

As shown in FIGS. 1 and 2, the slit 12 extends from the middle part of the second screw part 5 to the middle part of the head part 2, and both ends thereof are rounded to avoid stress concentration. As can be seen from FIG. 3, the slit 12 communicates with the hole 6 b of the implant body 6 that constitutes the through hole 10 that penetrates the axial center.

Since the slit 12 imparts elasticity to the interspinous process implant 100, it is possible to prevent excessive stress from being applied to the spinous process that contacts the interspinous process implant 100.

(How to use an interspinous process implant)
A method of using the interspinous implant 100 will be described. The interspinous process implant 100 was developed mainly for the purpose of performing minimally invasive treatment for lumbar spinal canal stenosis. By inserting the interspinous process implant 100 between the spinous processes through a small skin incision under local anesthesia, the stenosis of the spinal canal is expanded and improvement of symptoms is expected.

Here, the photographs shown in FIGS. 5 to 8 are excerpts taken from X-ray fluoroscopic video images of the state of the test conducted on pigs. In the following description, a method for inserting (inserting) the interspinous process implant 100 between the spinous processes of the human body will be described with reference to FIGS. 5 to 8 as appropriate.

First, the surgeon incises the skin on the back of the human body, for example, 20 to 25 mm, and inserts the guide wire 50 from the incised site toward the space between the spinous processes 60 under fluoroscopic observation (see FIG. 5). . Here, the guide wire 50 is inserted until its tip exceeds the facet joint.

Next, using the through-hole 10 of the interspinous process implant 100, the interspinous process implant 100 is passed through the guide wire 50, and the interspinous process implant 100 is inserted into the body from the screw part 1 side.

As described above, there is a fascia made of tough collagen fibers directly under the skin. The surgeon inserts the driver 51 into the hexagonal hole 8b of the rear insert 8 at the rear end portion of the implant, and twists the tip of the first screw portion 4 into the body while applying a turning force to the driver 51. . Here, since the virtual surface S1 connecting the tops of the threads of the first screw part 4 has a tapered conical shape recessed outward, the first screw part is directed from the tip toward the front (rear). The diameter of the screw 4 gradually increases. Therefore, the distal end portion of the screw portion 1 does not receive a great resistance, and tends to sharply bite into the body tissue along the screw thread. In fact, in the swine test, there was no problem even if the fascia was not incised.

In addition, since the 1st screw part 4 is made into 2 threads instead of 1 thread, the trigger of the bite to the tissue in a body is doubled rather than the case of 1 thread. As a result, the interspinous implant 100 is further improved in biting into tissue in the body. Further, the front insert 7 having a sharp tip is embedded in the tip portion of the first screw portion 4, and the top of the thread of the first screw portion 4 is sharp as shown in FIG. Even in this case, the interspinous process implant 100 is further improved in biting into tissue in the body.

When the interspinous process implant 100 is screwed into the body along the guide wire 50 while applying a rotational force to the driver 51, the X-ray marker pins 9 embedded on both sides of the two fitting recesses 14 of the spacer portion 3. Is observed on an X-ray monitor (see FIG. 6). Therefore, the operator can clearly grasp the position and posture of the interspinous process implant 100. Since the X-ray marker pin 9 is embedded in the side part of the implant body 6 so that the longitudinal direction thereof is directed to the center of the rotation axis of the implant, it can be seen that it rotates.

As the interspinous process implant 100 is advanced, the tip of the implant reaches the interspinous ligament. In a conventional procedure using an implant, a hole as a passage for the implant was previously drilled in an interspinous ligament using a tool. On the other hand, according to the interspinous process implant 100 of the present embodiment, since the bite property of the tip portion of the screw part 1 is greatly improved, a hole as a passage for the implant is formed in the interspinous ligament using a tool. The implant can be screwed between the spinous processes without being opened beforehand.

When the implant is screwed between the spinous processes, the thread groove 13 of the first screw part 4 and the thread groove 13 of the second screw part 5 are smoothly connected, so that the first screw part 4 The outer edge part (part) of the spinous process 60 can be smoothly transferred to the thread groove 13 of the second screw part 5.

When the latter half of the screw part 1 reaches the vicinity of the space between the spinous processes 60, the screw groove 13 adjacent to the spacer part 3 of the second screw part 5 is connected to the outer edge (part) of the spinous process 60 in the screw groove 13. Since the outer diameter of the spinous process 60 is fitted in the screw groove 13, the implant is screwed between the spinous processes 60. Thereby, it is prevented that the space between the spinous processes 60 is excessively spread. Further, since the screw groove 13 is screwed in such a manner as to sandwich the spinous process 60, the spinous process 60 is supported by the inner wall surface of the screw groove 13. These prevent the spinous process 60 from being damaged. In the second screw part 5, since the diameter of the screw thread increases gently toward the spacer part 3, even if the spinous process 60 is removed from the screw groove 13, damage to the spinous process 60 is suppressed. The

Also, since the second screw part 5 is a double thread, there are screw grooves 13 corresponding to the position of the phase difference of 180 degrees around the axial direction. Therefore, when the screw is inserted between the spinous processes 60, the two thread grooves of the implant serve as a guide with respect to the spinous processes 60, so that the spinous processes 60 are not inclined greatly from the insertion axis direction (with respect to the spinous processes 60). The implant can be screwed at an angle close to vertical).

When the second screw portion 5 of the screw portion 1 exceeds the space between the spinous processes 60, the spinous processes 60 are fitted into the fitting concave portions 14 of the spacer section 3. If the implant is further pushed in, the spinous process 60 hits the implant head 2 without the screw groove 13 and the resistance felt by the operator's finger increases. The surgeon can confirm that the spinous process 60 has been fitted into the fitting concave portion 14 of the spacer portion 3 by visually recognizing the felt resistance and the X-ray marker pin 9. Thereafter, the surgeon operates the driver 51 so that the direction in which the adjacent spinous processes 60 are connected to each other and the direction in which the mating concave portions 14 of the spacer portion 3 are connected to each other coincide with each other. On the other hand, the posture of the interspinous process implant 100 is finely adjusted with the X-ray marker pin 9 so that the implant is substantially vertical. By completing the fine adjustment, the insertion of the interspinous implant 100 is completed (see FIGS. 7 and 8). The guide wire 50 is extracted from the body when the implant is inserted between the spinous processes 60 to some extent.

Here, Table 1 shows a plurality of examples of the time required for the operation of fitting one interspinous process implant 100 of this embodiment between the spinous processes 60 of the pig. As can be seen from Table 1, the time required for the treatment was 16 minutes at the longest, 6 minutes at the shortest, and about 10 minutes on the average. Thus, the surgeon was able to insert the implant between the spinous processes 60 of the pig in a very short time. That is, according to the interspinous process implant 100 of this embodiment, when the implant is percutaneously screwed into the body and inserted, the implant can be screwed and inserted into the body more easily than before.

FIG. 9 is a CT image of a pig after three months have passed since the interspinous process implant 100 was fitted between the spinous processes 60. FIG. 9A is a CT scan image when the back of the pig is viewed from the front, and FIG. 9B is a CT scan image when the back of the pig is viewed from the side. In the test using pigs, two interspinous process implants 100 were fitted between different spinous processes 60, respectively.

As can be seen from FIG. 9, the interspinous process implant 100 is firmly fitted between the spinous processes 60 at the same position and posture as immediately after the operation without falling out from between the spinous processes 60 at the stage when three months have passed after the fitting. It was maintaining the state.

<Removal of interspinous implant>
The interspinous implant 100 is also devised so that it can be easily removed from the body. When the interspinous process implant 100 is removed, a rod-shaped member in which a male screw (left screw) is formed only at the tip portion in the hole 8a in which the female screw (left screw) of the rear insert 8 at the rear end portion of the implant is formed. Screw (not shown, screwdriver). In this state, the interspinous process implant 100 is pulled out from the body while rotating the rod-like member counterclockwise. The interspinous process implant 100 is pulled out from the body while rotating in the direction opposite to that during insertion into the body. Since the screw portion 1 is a right-hand thread, the interspinous implant 100 is smoothly pulled out from the body. In addition, since the outer edge part of the spinous process 60 passes through the screw groove 13 adjacent to the spacer part 3, it is prevented that the space between the spinous processes is excessively widened at the top of the screw thread of the screw part 1. That is, even when the implant is removed, the spinous process 60 is prevented from being damaged.

(When using an interspinous implant for intervertebral fixation)
An embodiment in which an interspinous process implant is used for intervertebral fixation will be described with reference to FIGS.

The interspinous implant 100 was developed mainly for the purpose of minimally invasive treatment for lumbar spinal canal stenosis. By inserting the interspinous process implant 100 between the spinous processes through a small skin incision under local anesthesia, the stenosis of the spinal canal is expanded and improvement of symptoms is expected. On the other hand, the interspinous process implant 101 shown in FIGS. 10 and 11 is developed mainly for the purpose of minimally invasive intervertebral fixation by inducing bone fusion from the adjacent spinous process to the pedicle. It has been done.

In addition, in FIG. 10, 11, illustration of the screw shape (a thread, a thread groove) of the screw part 1 (1st screw part 4 and 2nd screw part 5) of an implant is abbreviate | omitted. 10 and 11, the same reference numerals are given to the same components as those of the interspinous process implant 100 shown in FIGS.

Further, it is naturally possible to apply the configuration and material of each part of the above-described interspinous implant 100 and various modifications of the above-described parts to the interspinous implant 101 described below.

Hereinafter, the difference between the interspinous process implant 101 and the interspinous process implant 100 will be mainly described.

(Structure of interspinous implant)
Similarly to the interspinous process implant 100, also in the interspinous process implant 101, a slit 15 extending in the axial direction and communicating with the through hole 10 (6 b) extends from the head 2 through the spacer part 3 to the screw part 1. It is provided on the side.

The slit 15 is a slit for accommodating crushed bone, and is wider than the slit 12 provided on the side surface of the interspinous process implant 100. Note that “crushed bone” refers to transplanted bone (patient bone), artificial bone, and the like.

Further, as shown in FIG. 11, in the present embodiment, the outer shape of the cross section of the spacer portion 3 perpendicular to the axial direction is substantially triangular. In addition, not only a substantially triangular shape but also a substantially polygonal shape such as a substantially rectangular shape or a substantially pentagonal shape may be used. A substantially polygon is not a polygon with sharp corners, but a polygon with rounded corners (R-processed), and each side is a straight line or a curved line. . In addition, when each side is made into a curve, it is preferable to be a curve that bulges outward rather than a curve that is recessed outward.

The slits 15 are provided on each side of the substantially triangular spacer portion 3, that is, a plurality of slits 15 are provided around the axial direction, and the widths W are the same in this embodiment. Note that the widths W are not necessarily the same. In the present embodiment, three slits 15 are provided at equal intervals around the axial direction. In the case of the substantially triangular spacer portion 3, two or three slits 15 are preferably provided at equal intervals around the axial direction.

Here, in order to accommodate a sufficient amount of crushed bone in the slit 15 and the through hole 10 (6b), the width W of the slit 15 is preferably 2 mm or more, or 4 mm or more. . In order to ensure a certain level of strength of the spacer portion 3, the width W is preferably 10 mm or less, or 8 mm or less.

In addition, the length of the slit 15 is preferably set to a length of 1/3 or more of the entire length of the interspinous process implant 101. According to this, with respect to the mother bed for bone fusion, which will be described later, it is possible to arrange the crushed bone in the width direction of the spinous process without any shortage.

In addition, the crushed bone may be accommodated as it is in the slit 15 and the through hole 10 (6b), but in order to prevent the crushed bone from falling from the slit 15 and the like, moisture is contained. It is preferable to store the crushed bone in the slit 15 and the through hole 10 (6b).

Here, FIG. 12 is a photograph of a state in which the interospinous process implant 102, which is an example of the interspinous process implant 101 shown in FIGS. When moisture is imparted to the crushed bone, the crushed bone becomes a so-called sand bar shape. Therefore, as shown in FIG. 12, the artificial bone 70 (crushed bone) can be accommodated in the slit 15 in such a manner that a part overflows outward from the slit 15. If the artificial bone 70 (crushed bone) is accommodated in the slit 15 in such a manner that a part overflows outward from the slit 15, the mother bed described later when the interspinous process implant 102 is placed between the spinous processes. The artificial bone 70 (crushed bone) can be more reliably brought into contact with the (cancellous bone portion from which the cortical bone has been cut off), and as a result, bone fusion can be further promoted.

(How to use an interspinous process implant)
A method of using the interspinous implant 101 will be described. Since the method of using the interspinous process implant 101 of the present embodiment is similar to the method of using the interspinous process implant 100, a specific method of using the interspinous implant 101 of the present embodiment will be mainly described. I will do it.

The interspinous process implant 101 is an interspinous process implant suitable for performing intervertebral fixation in a minimally invasive manner by inducing bone fusion from the adjacent spinous process to the pedicle.

First, the operator prepares the interspinous process implant 101 filled with crushed bone in the following manner to place it between the spinous processes. The surgeon makes an incision or the like on the skin on the back of the human body, for example, by 20 to 25 mm, and then creates a pilot hole between the spinous processes using a tool. Next, in the pilot hole portion, the spinous process and the cortical bone of the vertebra are cut off from the spinous process to the pedicle, and the cancellous bone is taken out to create a mother bed.

Thereafter, the surgeon inserts the interspinous process implant 101 filled with the crushed bone into the mother bed part between the spinous processes in the same manner as in the method of using the interspinous process implant 100 and places the implant. . The crushed bone is filled in advance into the slit 15 and the through-hole 10 (6b) of the interspinous process implant 101 as it is or in a state containing moisture. In the case of using crushed bone containing water, the patient's blood, physiological saline, or the like is used to apply moisture to the crushed bone.

When the interspinous process implant 101 is placed between the spinous processes, the bones that have been filled in the slits 15 of the interspinous process implant 101 are eventually healed from the adjacent spinous process to the pedicle. In addition, since any one of the sides of the substantially triangular spacer portion 3 faces the mother floor, a slit 15 is provided on each side of the spacer portion 3. Is filled, the contact between the crushed bone and the mother bed becomes more reliable, and the progress of bone fusion is further promoted.

According to the interspinous process implant 101 of this embodiment, bone fusion can be induced from the adjacent spinous process to the pedicle, and intervertebral fixation can be performed in a minimally invasive manner. Compared to the conventional intervertebral fixation that hits and connects the vertebrae, long-term stabilization of the intervertebral fixation can be obtained.

Table 2 shows a plurality of examples of the time required for the operation of inserting one interspinous process implant 102 shown in FIG. 12 in which the artificial bone 70 is filled with moisture into the spinous process of the pig. As can be seen from Table 2, the time required for the treatment was 12 minutes at the longest, 4 minutes at the shortest, and 7 minutes on the average. Thus, the surgeon was able to insert the implant between the spinous processes of the pig in a very short time. That is, according to the interspinous process implant 101 of the present embodiment, when the implant is percutaneously screwed into the body and inserted, the implant is inserted even if the fractured bone is filled in the implant. It can be easily screwed into the body.

(Modification)
When the implant body 6 is formed of a metal material such as titanium alloy or ceramic, the front insert 7 and the rear insert 8 are not separated from the implant body 6, and the implant body 6, the front insert 7, and the rear insert 8 are You may integrally form with metal materials, such as a titanium alloy.

Further, when the implant body 6 is formed of PEEK resin as in the above-described embodiment, at least one of the front insert 7 and the rear insert 8 is formed integrally with the implant body 6 from PEEK resin. May be.

The outer shape of the cross section perpendicular to the implant axial direction of the spacer portion 3 which is a portion fitted between the spinous processes is similar to the spacer portion of the interspinous process implant described in Patent Document 2 (Japanese Patent No. 5272279). It may be circular, elliptical or the like.

The embodiment of the present invention and its modifications have been described above. In addition, it is possible to make various changes within a range that can be assumed by those skilled in the art.

1: Screw part 2: Head part 3: Spacer part 4: First screw part 5: Second screw part 7: Front insert (metal member)
8a: Hole (through hole provided in the axial center of the head)
9: X-ray marker pin (identification member)
10: Through-hole 12, 15: Slit 13: Screw groove 14: Fitting recess S1, S2: Virtual surface T: Virtual surface 100, 101: Interspinous process implant

Claims

A substantially conical screw portion having a screw-shaped outer peripheral surface;
A head coaxial with the screw part;
A spacer portion formed between the screw portion and the head portion;
An interspinous process implant fitted between the spinous processes,
The screw part is
In order from the front end side, it has a first screw part and a second screw part,
The first screw part has a tapered conical shape in which a virtual surface connecting the tops of the threads is recessed outwardly,
The second screw part is an interspinous process implant in which a virtual surface connecting the tops of the threads is formed in a truncated cone shape that swells outward.
The interspinous process implant of claim 1,
The interspinous process implant, wherein a thread groove adjacent to the spacer part of the second screw part is formed with a dimension that allows an outer edge part of the spinous process to pass through the thread groove.
The interspinous process implant according to claim 1 or 2,
An interspinous process implant in which the first screw portion and the second screw portion are double-threaded screws.
The interspinous process implant according to any one of claims 1 to 3,
The interspinous process implant in which the screw pitch of the second screw part is a variable pitch that increases from the distal end side toward the spacer part.
The interspinous process implant according to claim 4,
The interspinous process implant, wherein the screw pitch of the screw portion is a variable pitch that decreases from the distal end side toward the spacer portion in the first screw portion.
The interspinous process implant according to any one of claims 1 to 5,
The interspinous process implant, wherein a virtual plane connecting the bottoms of the thread grooves of the second screw part is substantially frustoconical.
The interspinous process implant according to any one of claims 1 to 6,
The spacer portion has an interspinous process implant having two fitting concave portions facing each other in a U shape in a side view.
The interspinous process implant of claim 7,
The spinous process in which the thread groove of the first screw part and the thread groove of the second screw part are smoothly connected, and the thread groove of the second screw part and the fitting recess are smoothly connected Interim implant.
The interspinous process implant according to claim 7 or 8,
An interspinous process implant provided with identification members that can be identified by fluoroscopy on both sides of the fitting recess in the axial direction.
The interspinous process implant according to any one of claims 1 to 9,
An interspinous process implant, wherein a through-hole penetrating the axis is provided in the interspinous process implant.
The interspinous process implant according to any one of claims 1 to 10,
An interspinous process implant provided with axially extending slits on the sides.
The interspinous process implant according to any one of claims 1 to 11,
A female screw is formed in a through hole provided in the axial center of the head,
The interspinous process implant, wherein when the screw part is a right-hand thread, the female thread is a left-hand thread, and when the screw part is a left-hand thread, the female thread is a right-hand thread.
The interspinous process implant according to any one of claims 1 to 12,
An interspinous process implant in which the apex of the thread of the first screw part is sharp.
The interspinous process implant according to any one of claims 1 to 13,
An interspinous process implant, wherein a metal member with a sharp tip is attached to the tip of the first screw portion.
The interspinous process implant according to any one of claims 1 to 6,
A through-hole penetrating the axis is provided in the interspinous implant,
An interspinous process implant, wherein a slit extending in the axial direction and accommodating the fractured bone is provided on a side surface from the head to the screw part through the spacer part.
The interspinous process implant of claim 15,
An interspinous process implant in which the width of the slit is 2 mm or more and 10 mm or less.
The interspinous process implant according to claim 15 or 16,
The interspinous process implant, wherein the slit has a length of 1/3 or more of the total length of the interspinous process implant.
The interspinous process implant according to any of claims 15 to 17,
The outer shape of the cross section perpendicular to the axial direction of the spacer portion is substantially polygonal,
An interspinous process implant, wherein the slit is provided on each side of the substantially polygonal spacer portion.