JP7765066B2 - Spinal fusion kit - Google Patents

Description

The present invention relates to a spinal fusion kit for inserting an intervertebral implant into an intervertebral disc, and an intervertebral implant suitable for use in such a spinal fusion kit.

In one spinal fusion procedure, vertebral bodies are joined together with an intervertebral implant inserted into the disc. Some intervertebral implants are inserted into the disc while being pivoted around one end that engages an insertion tool.

For example, Patent Document 1 describes an intervertebral implant 100 as shown in FIG. 9 and an insertion instrument 200 as shown in FIG. 10. The intervertebral implant 100 includes a pointed insertion end 110 and an engagement end 120 that engages with the insertion instrument 200.

The engagement end 120 has a pair of engagement walls 121, 122, between which a slot 130 is formed, into which the tip of the insertion instrument 200 is inserted. Each of the engagement walls 121, 122 has a pivot hole 123 formed therein, and multiple engagement holes 124 formed around the pivot hole 123.

On the other hand, the insertion tool 200 includes a tubular body 300 that holds the intervertebral implant 100 in a swingable manner, and a shaft 400 that is inserted into the tubular body 300 and is slidable in the axial direction of the tubular body 300. As shown in FIG. 11, the tubular body 300 includes a pair of opposing retaining walls 310, 320 that are inserted into the slot 130 of the intervertebral implant 100, and a pair of arms 330, 340 that support the retaining walls 310, 320, respectively. The arms 330, 340 face each other at a distance greater than the distance between the retaining walls 310, 320.

Each of the retaining walls 310, 320 has a boss 350 that engages with the pivot hole 123. Engagement of the pair of bosses 350 with the pair of pivot holes 123 allows the intervertebral implant 100 to swing around the pivot hole 123.

Furthermore, each of the retaining walls 310, 320 has multiple protrusions 360 around the boss 350. These protrusions 360 engage with the engagement holes 124, thereby preventing the intervertebral implant 100 from rocking.

The shaft 400 includes a plate-shaped head 410 that is interposed between the retaining walls 310, 320. The shaft 400 slides between a locked position, in which the head 410 is interposed between the retaining walls 310, 320, and a pivot position, in which the head 410 retracts between the arms 330, 340. In the pivot position, the arms 330, 340 can bend so that the retaining walls 310, 320 approach each other. Therefore, when a rotational force is applied to the intervertebral implant 100 with the shaft 400 slid into the pivot position, the arms 330, 340 bend until the protrusion 360 disengages from the engagement hole 124, causing the intervertebral implant 100 to swing about the pivot hole 123.

U.S. Pat. No. 1,047,8313

However, with the above-described intervertebral implant 100 and insertion instrument 200, when the arms 330, 340 are bent so that the projection 360 is disengaged from the engagement hole 124 at the pivot position, the engagement between the boss 350 and the pivot hole 123 becomes insufficient, which could result in the intervertebral implant 100 being released from the insertion instrument 200.

In response to this, it is possible to omit the protrusion 360 and engagement hole 124 and instead press the retaining walls 310, 320 against the engagement walls 121, 122 of the intervertebral implant 100, thereby holding the intervertebral implant 100 by friction. However, in this case, there is a risk that the intervertebral implant 100 may rock due to resistance when inserting the intervertebral implant 100 into the intervertebral disc.

The present invention aims to provide a spinal fusion kit that can switch between prohibiting and allowing the rocking of the intervertebral implant 100, and that can prevent the intervertebral implant 100 from being released from the insertion tool even when rocking of the intervertebral implant 100 is permitted, as well as an intervertebral implant suitable for use with such a spinal fusion kit.

In order to solve the above-mentioned problems, the present invention provides an intervertebral implant including an insertion end and an engagement end, wherein the engagement ends have a pair of engagement walls that face each other and form a slot therebetween, and a pair of pivot holes are provided in each of the pair of engagement walls; an insertion instrument including a rod that swingably holds the intervertebral implant, and a sleeve that is passed through the rod and is slidable in the axial direction of the rod, wherein the rod is inserted into the slot and has a pair of opposing retaining walls, a pair of bosses that are provided on each of the pair of retaining walls and engage with the pair of pivot holes, and a pair of retaining bolts that support the pair of retaining walls. A spinal fixation kit is provided, which includes a pair of arms facing each other at a distance greater than the distance between the walls, the sleeve having a tip that is inserted into the slot, and a constraint plate that is interposed between the pair of retaining walls, the sleeve sliding between a swing-prohibited position where the constraint plate is interposed between the pair of retaining walls and prohibits swing of the intervertebral implant, a swing-permitted position where the tip is pulled out a predetermined amount from the slot while the constraint plate remains interposed between the pair of retaining walls and permits swing of the intervertebral implant, and a retracted position where the constraint plate is retracted between the pair of arms.

With the above configuration, the rocking of the intervertebral implant can be inhibited or permitted simply by sliding the sleeve between the anti-rocking position and the rocking permitted position. Furthermore, in the anti-rocking position and the rocking permitted position, the restraint plate is interposed between the pair of retaining walls, maintaining engagement between the bosses on the retaining walls and the pivot holes in the intervertebral implant. This prevents the intervertebral implant from being released from the insertion instrument. Furthermore, by sliding the sleeve to the retracted position, the arms can bend so that the retaining walls approach each other, allowing the intervertebral implant to be attached to and detached from the insertion instrument.

Each of the pair of engagement walls may have an arc-shaped contour centered on the pivot hole, a plurality of recesses may be formed on the periphery of the inner surface of at least one of the pair of engagement walls, the recesses being aligned circumferentially around the pivot hole and opening radially from the pivot hole, and the tip end of the sleeve may be provided with at least one protrusion that fits into one of the plurality of recesses in the swing-preventing position and that comes out of the one recess in the swing-permitting position. With this configuration, the protrusion provided on the tip end of the sleeve fits into the recess of the intervertebral implant in the swing-preventing position, thereby firmly preventing swinging of the intervertebral implant.

For example, the multiple recesses may be formed at a pitch of 5 to 30 degrees around the pivot hole.

The present invention also provides an intervertebral implant comprising an insertion end and an engagement end, the engagement end having a pair of opposing engagement walls forming a slot therebetween, the pair of engagement walls each having a pair of pivot holes, each of the pair of engagement walls having an arc-shaped contour centered on the pivot hole, and a periphery of an inner surface of at least one of the pair of engagement walls having a plurality of recesses aligned circumferentially about the pivot hole and opening radially from the pivot hole. With this configuration, an intervertebral implant suitable for a spinal fixation kit is realized.

According to the present invention, it is possible to switch between prohibiting and allowing the rocking of the intervertebral implant 100, and even when rocking of the intervertebral implant 100 is permitted, it is possible to prevent the intervertebral implant from being released from the insertion tool.

1 is a perspective view of a spinal fusion kit according to an embodiment of the present invention, showing an intervertebral implant attached to the distal end of an insertion tool. FIG. FIG. 2 is an enlarged view of a main part of FIG. 1 . 1 is a perspective view of an intervertebral implant. FIG. 1 is a perspective view of the tip of the insertion tool. FIG. 1 is an exploded perspective view of an insertion tool. 6 is a cross-sectional view taken along line VI-VI in FIG. 2 when the sleeve is in a swing-preventing position. FIG. 10 is a cross-sectional view of the sleeve when it is in a swing-permitting position. FIG. 10 is a cross-sectional view of the sleeve in a retracted position. 1 is a perspective view of a conventional intervertebral implant. FIG. 1 is a perspective view of a conventional insertion tool. FIG. 1 is an exploded perspective view of the tip of a conventional insertion device.

Figure 1 shows a spinal fixation kit 1 according to one embodiment of the present invention. This kit 1 includes an intervertebral implant 2 to be inserted into an intervertebral disc and an insertion instrument 3 to which the intervertebral implant 2 is attached at its tip.

The intervertebral implant 2 includes a pointed insertion end 2a and an engagement end 2b that engages with the insertion instrument 3. In this embodiment, the intervertebral implant 2 has a curved shape. However, the shape of the intervertebral implant 2 is not limited to this and may be straight, similar to the conventional intervertebral implant 100 shown in Figure 9.

As shown in Figures 2 and 3, the engagement end 2b of the intervertebral implant 2 has a pair of opposing engagement walls 21, 22. A slot 23 is formed between the engagement walls 21, 22. A pair of pivot holes 24 are provided in each of the engagement walls 21, 22. Both pivot holes 24 are aligned coaxially.

In this embodiment, each of the engagement walls 21, 22 has an arc-shaped contour centered on the pivot hole 24. Furthermore, in this embodiment, a plurality of recesses 25 are formed on the periphery of the inner surface of each of the engagement walls 21, 22, and are aligned in the circumferential direction of the pivot hole 24. These recesses 25 open in the radial direction centered on the pivot hole 24. For example, the recesses 25 are formed at a pitch of 5 to 30 degrees around the pivot hole 24.

As shown in Figures 4 and 5, the insertion tool 3 includes a rod 4 that holds the intervertebral implant 2 in a swingable manner, and a sleeve 5 that is inserted through the rod 4 and can slide in the axial direction of the rod 4.

In this embodiment, as shown in FIG. 1, a grip 7 is attached to the end of the rod 4 opposite to the intervertebral implant 2, and an operating section 6 is provided in front of this grip 7.
The operating part 6 cannot move relative to the sleeve 5 in the axial direction of the sleeve 5, but can rotate relative to the sleeve 5. The operating part 6 is connected to the grip 7 by a screw structure, and by rotating the operating part 6, the operating part 6 and the sleeve 5 slide in the axial direction of the rod 4.

The configuration for sliding the sleeve 5 is not limited to this and can be modified as appropriate. For example, the operating unit 6 may be fixed to the sleeve 5, and a spring may be used to bias the operating unit 6 toward the intervertebral implant 2, and the sleeve 5 may be slid by moving the operating unit 6 toward the grip 7 against the biasing force of the spring.

Returning to Figures 4 and 5, the rod 4 includes a pair of retaining walls 41, 42 that are inserted into the slots 23 of the intervertebral implant 2, and a pair of arms 43, 44 that support these retaining walls 41, 42, respectively. The retaining walls 41, 42 face each other, and the arms 43, 44 face each other at a distance greater than the distance between the retaining walls 41, 42. The retaining walls 41, 42 are each provided with a pair of bosses 45 that engage with the pivot holes 24 of the intervertebral implant 2.

The sleeve 5 includes a cylindrical main body 51 and a distal end 52 that protrudes from the main body 51 and has a shape similar to that of a flattened main body 51. The distal end 52 is the portion that is inserted into the slot 23 of the intervertebral implant 2, similar to the retaining walls 41, 42 of the rod 4.

In this embodiment, the tip portion 52 is composed of a pair of shoulders 53 located on both sides of the retaining wall 41 and a pair of shoulders 54 located on both sides of the retaining wall 42. The tip portion 52 also has a restraining plate 55 interposed between the retaining walls 41 and 42.

The restraint plate 55 has a width greater than that of the retaining walls 41, 42, and both ends of the restraint plate 55 are sandwiched between the shoulders 53 and 54. The restraint plate 55 is fixed to the tip 52 by a pin 57 (see also Figures 7 and 8) that passes through the shoulder 53, the restraint plate 55, and the shoulder 54. For example, either the restraint plate 55 or the pin 57 is welded to the shoulders 53, 54.

The ends of the pin 57 protrude from the shoulders 53, 54 to form protrusions 56. Each protrusion 56 fits into one of the recesses 25 in the intervertebral implant 2.

The sleeve 5 slides between the non-swing position shown in Figure 6, the swing-allowed position shown in Figure 7, and the retracted position shown in Figure 8.

The anti-sway position is a position in which the restraint plate 55 is interposed between the retaining walls 41, 42. Furthermore, in the anti-sway position, each protrusion 56 engages with one of the recesses 25 of the intervertebral implant 2. This prevents the intervertebral implant 2 from swinging.

The swing-permitted position is a position in which the tip 52 is pulled out of the slot 23 by a predetermined amount while the restraint plate 55 remains interposed between the retaining walls 41, 42. In addition, in the swing-permitted position, the protrusion 56 comes out of the recess 25, thereby permitting the intervertebral implant 2 to swing.

The retracted position is a position in which the restraint plate 55 retracts between the arms 43 and 44. This allows the arms 43 and 44 to bend so that the retaining walls 41 and 42 move closer to each other.

As described above, in the kit 1 of this embodiment, the rocking of the intervertebral implant 2 can be inhibited or permitted simply by sliding the sleeve 5 between the anti-rocking position and the rocking permitted position. Moreover, in the anti-rocking position and the rocking permitted position, the restraint plate 55 is interposed between the retaining walls 41, 42, so that the bosses 45 on the retaining walls 41, 42 can be maintained engaged with the pivot holes 24 of the intervertebral implant 2. This prevents the intervertebral implant 2 from being released from the insertion instrument 3. Furthermore, by sliding the sleeve 5 to the retracted position, the arms 43, 44 can bend so that the retaining walls 41, 42 approach each other, allowing the intervertebral implant 2 to be attached to and detached from the insertion instrument 3.

In the conventional insertion instrument 200 shown in Figures 10 and 11, the arms 330, 340 bend so that the protrusion 360 disengages from the engagement hole 124 of the intervertebral implant 100, allowing the intervertebral implant 100 to swing around the pivot hole 123. However, when the intervertebral implant 100 is swung, the swing stops every time the protrusion 360 engages with the engagement hole 124. Furthermore, because the bent arms 330, 340 are pressed against the engagement walls 121, 122 of the intervertebral implant 100 while the intervertebral implant 100 is swinging, the swing of the intervertebral implant 100 is not smooth.

In contrast, in the insertion instrument 3 included in the kit 1 of this embodiment, the boss 45 is provided on the rod 4, while the protrusion 56 is provided on a sleeve 5 separate from the rod 4. This allows the intervertebral implant 2 to swing smoothly when the sleeve 5 is in the swing-permitted position.

(Modification)
The present invention is not limited to the above-described embodiment, and various modifications are possible without departing from the gist of the present invention.

For example, a recess 25 may be formed in only one of the engagement walls 21, 22 of the intervertebral implant 2, and only one protrusion 56 that fits into the recess 25 may be provided on the distal end 52 of the sleeve 5.

Alternatively, instead of the recess 25 and protrusion 56, each of the engagement walls 21, 22 of the intervertebral implant 2 may have a polygonal contour, with one side of the polygon abutting against the distal end surface of the main body 51 of the sleeve 5, thereby preventing the intervertebral implant 2 from rocking.

However, with this configuration, there is a risk that the intervertebral implant 2 may swing when a large rotational force is applied to the intervertebral implant 2 in the anti-swing position. In contrast, if the protrusion 56 on the distal end 52 of the sleeve 5 is configured to fit into the recess 25 of the intervertebral implant 2 in the anti-swing position, as in the above embodiment, the intervertebral implant 2 can be firmly prevented from swinging. An intervertebral implant 2 including such a recess 25 provides an intervertebral implant 2 suitable for use in a spinal fixation kit 17.

REFERENCE SIGNS LIST 1 Spinal fusion kit 2 Intervertebral implant 2a Insertion end 2b Engagement end 21, 22 Engagement wall 24 Pivot hole 25 Recess 3 Insertion tool 4 Rod 41, 42 Retaining wall 43, 44 Arm 45 Boss 5 Sleeve 52 Tip 55 Restraining plate 56 Protrusion

Claims (3)

an intervertebral implant including an insertion end and an engagement end, the engagement end having a pair of engagement walls facing each other to form a slot therebetween, the pair of engagement walls each having a pair of pivot holes;
an insertion instrument including a rod that swingably holds the intervertebral implant, and a sleeve that is passed through the rod and is slidable in the axial direction of the rod;
the rod includes a pair of opposing retaining walls inserted into the slot, a pair of bosses provided on each of the pair of retaining walls and engaging with the pair of pivot holes, and a pair of arms supporting each of the pair of retaining walls and opposing each other at a distance greater than a distance between the pair of retaining walls;
the sleeve has a tip end portion that is inserted into the slot, and a restraining plate that is interposed between the pair of retaining walls is provided at the tip end portion;
The sleeve slides between a swing-preventing position in which the restraining plate is interposed between the pair of retaining walls and prevents the intervertebral implant from swinging, a swing-permitting position in which the restraining plate remains interposed between the pair of retaining walls and the tip portion is pulled out of the slot by a predetermined amount and allows the intervertebral implant to swing, and a retracted position in which the restraining plate is retracted between the pair of arms. Each of the pair of engagement walls has an arcuate profile centered on the pivot hole,
a plurality of recesses, which are aligned in a circumferential direction of the pivot hole and open in a radial direction around the pivot hole, are formed on a peripheral edge of an inner surface of at least one of the pair of engagement walls;
2. The spinal fixation kit according to claim 1, wherein the tip of the sleeve has at least one protrusion that fits into one of the plurality of recesses in the non-swinging position and comes out of the one recess in the swinging-allowed position. 3. The spinal fixation kit according to claim 2, wherein the plurality of recesses are formed at intervals of 5 to 30 degrees around the pivot hole.