A spacer for insertion between two vertebrae

ES 2 390 567 T3

DESCRIPTION

Separator for insertion between two vertebrae

The invention relates to a spacer for insertion between two vertebrae. In particular, the invention relates to a spacer with adjustable axial length that can be filled with bone graft after inserting it between the vertebrae.

US 6,200,348 discloses a spacer with adjustable axial length. The spacer comprises a first sleeve-shaped member and a second member that is slidably guided within the first member to adjust the overall length of the spacer. The adjustment of the axial length is carried out by means of ratchet notches provided on the outer wall of the second element and a coupling element provided on the first element. The wall of the retractor has multiple openings that allow the insertion of bone cement and the growth of blood vessels.

Typically, the retractor is filled with bone cement by infusion after insertion between the vertebrae, or filled with bone material, particularly bone graft, through the open ends of the tubular retractor prior to implanting the latter into the body of the a patient. The length of the known spacer can be adjusted once the spacer is inserted between two vertebrae. In certain situations, it is desirable to add bone material to the interior of the retractor, or remove bone material therefrom, after adjusting the axial length of the retractor.

Document US 6,616,695 B1 describes a spacer for insertion between two vertebrae, the axial length of which can be adjusted. The spacer comprises a first tubular part having a threaded inner surface and a second tubular part having a threaded outer surface, said parts forming a screw-nut connection that allows the axial length of the spacer to be adjusted. The first tubular part has multiple circular openings in the wall. The second tubular part has multiple elongated openings in the wall. The length of the spacer can be adjusted by rotating the parts relative to each other. This requires more space than a sliding motion to adjust the length. In addition, the serrated end plate of the spacer can damage the body of the vertebra during the twisting motion. The elongated openings serve to insert a set screw. The openings in the wall are too small to insert bone graft.

US 5,290,312 describes a prosthetic vertebra with adjustable axial length, comprising a first parallelepiped-shaped hollow component and a second parallelepiped-shaped hollow component that can be slidable within the first component. Each component has an end contact surface for support of a vertebra and an anchoring window formed in the contact surface. In addition, each component has a first open side that constitutes an access window and an open end formed in front of the contact end. The spacer comprises means to prevent sliding movement between the components in order to establish a desired length. To connect the retractor to the vertebrae, flexible bone cement is infused into the components through the access window, exiting through the anchoring windows and hardening. Since each component has an open side, a bone graft inserted through that side could easily come out. Also, the open side reduces stability.

US 6,524,341 B2 also discloses an adjustable length spacer. For the extension and retraction of the separator parts from each other, a turning movement is necessary.

US 6,176,881 B1 discloses an adjustable length spacer. The spacer includes an inner hollow body and an outer hollow body. The inner body has a retention mechanism on its outer surface and the outer body includes an elastic element that hooks onto the retention mechanism, thus fixing the length of the spacer so that it is resistant to compression. If a blocking of the hollow bodies against expansion is also desired, a fixing screw arranged on one side of the spacer is used. If it is necessary to reduce the length of the spacer again, the elastic element is actuated with a tool acting on the opposite side of the spacer. A separator with the trade mark Synex is already known, which is similar to that described in US 6,176,881 B1. This spacer additionally has an access opening for the introduction of bone graft.

EP 1 080 703 A2 discloses a corpectomy device having an inner member telescopically arranged within an outer member, so that the inner member can be moved in an axial direction. The inner and outer elements are hollow, so that they define a chamber, and include openings in communication with the chamber. A locking clip acts on the inner and outer elements to fix the position of the inner element relative to the outer element. The longitudinal dimension of the device can be adjusted by biasing the inner member so that it extends from the outer member and moving the locking clip from an unlocked position to a locked position.

An object of the invention is to provide a spacer for insertion between two vertebrae, which has adjustable length and which can be filled in situ not only with bone cement, but also with bone graft, and which has better manipulability.

This object is achieved by a spacer according to claim 1. Further developments are indicated in the dependent claims.

ES 2 390 567 T3

The separator can be filled with bone graft before its insertion between two vertebrae in the usual way. After inserting the retractor between the vertebrae and adjusting the axial length, additional bone graft can be inserted through the access opening. Alternatively, the entire bone graft can be inserted after inserting the retractor between the vertebrae and adjusting its length.

The separator can be extended by a sliding movement, which requires less space and time for operation than an extension by means of a twisting movement.

The access opening has a closed edge that gives the separator greater mechanical stability compared to an access window on an open side.

The length adjusting elements and the length fastening elements are accessible from the same side of the spacer. This improves handling. In addition, the length adjusting and length fixing elements are accessible from one side allowing MIS or MOS approaches.

The end section can be formed as a multiple cage structure. This improves fixation on the vertebra due to the larger contact area and decreases the depth of penetration into the bone at the contact area, thus reducing damage to the adjacent vertebrae. The contour of the outer cage of the multi-cage structure can be adapted to the contour of the surface of the vertebral body.

The separator can be produced from tubes, which are easier to manufacture than parts of other shapes.

Other advantages of the invention emerge from the description of the embodiment together with the accompanying drawings.

In the figures:

Figure 1 shows an exploded perspective view of one embodiment of the separator.

Figure 2 shows a side perspective view of the assembled spacer with an axial length close to the minimum possible length.

Figure 3 shows a perspective view of the assembled spacer, extended for a length greater than that shown in Figure 2.

Figure 4 shows a side view of the separator of Figure 2.

Figure 5 shows a top view of the separator of Figure 2.

Figure 6 shows a bottom view of the separator of Figure 2.

Figure 7 shows a schematic exploded representation of the final section of the separator, according to a first example seen from above.

Figure 8 shows a schematic exploded representation of the final section of the separator, according to a second example seen from above.

Figure 9 shows a perspective view of a locking element.

Figure 10 shows a side view of the locking element of Figure 9.

Figure 11 shows a sectional view of the locking structure for fixing the axial length of the spacer.

Figure 12 shows a side perspective view of the spacer engaged with a length adjustment tool.

Figure 13 shows a perspective view of the length adjustment tool.

As can be seen in Figures 1 to 6, the separator 1, according to one embodiment of the invention comprises a first cylindrical tubular element 2 and a second cylindrical tubular element 3. The outer diameter of the second tubular element 3 is chosen so allowing a sliding guide of the second tubular element 3 within the first tubular element 2.

The first tubular element 2 has a first end 4, a second opposite end 5 and a hollow interior surrounded by the wall of the tube. In the wall, at a predetermined distance from the first end 4, an access opening 6 is provided which extends approximately half the length of the first tubular element 2. In the embodiment shown, the access opening is a rectangular opening. The length of the long side of the rectangle corresponds approximately to half the length of the first tubular element 2 and the length of the short side corresponds approximately to a quarter of the length of the first tubular element 2. The dimensions of the access opening 6 allow insert or remove natural bone graft through the opening during or after surgery.

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Similarly, the second tubular element has a first end 7 and an opposite second end 8, a hollow interior, and a wall defined by the tube. In the wall of the second tubular element an access opening 9 is provided at a certain distance from the second end. The access opening 9 extends along approximately half the length of the second tubular element 3. In the embodiment shown, the access opening 9 has a rectangular shape with the same dimensions as the access opening 6 of the first tubular element. In the mounting situation shown in Figure 2, the second tubular element 3 is inserted into the first tubular element 2 in such a way that the access opening 6 of the first tubular element and the access opening 9 of the second tubular element are aligned in radial direction.

Since the access opening of each of the tubular elements is arranged at a distance from the first and second ends, respectively, the access openings are separated from said first and second ends, respectively, by a part of the wall, therefore that have a closed edge.

The position of the second tubular member 3 relative to the first tubular member 2 in the direction of the longitudinal axis L of the spacer can be fixed by a locking structure. The locking structure is formed by multiple threaded openings 10 aligned in axial direction in the wall of the first tubular element 2. Threaded openings 10 are arranged on one side of access opening 6 and close to it, such that the surgeon can access the threaded openings during surgery from the same side as the access opening. Furthermore, the locking structure comprises multiple hemispherical recesses 11 arranged in line in the direction of the longitudinal axis L of the spacer, on the outer surface of the wall of the second tubular element 3. The recesses 11 are formed next to each other and have a depth less than their radius. The line of recesses 11 is arranged on one side of the access opening 9 of the second tubular element 3 and close to it, such that, in the mounting situation shown in Figures 2 and 3, the line of threaded openings 10 coincides with the line of recesses 11. The locking structure also comprises locking screws 12 that can be screwed into the threaded openings 10. The locking screw 12 has on one side a spherical segment-shaped projection 13 (FIG. 10) that fits into the spherical segment-shaped recesses 11. On the opposite side, the locking screw 12 has a recess for engaging a screwdriver. The line of recesses 11 extends at least along a length equal to that of the line of threaded openings 10. An unthreaded opening 10b may also be provided in the line of threaded openings for engaging a clamping tool (not shown).

As can be seen in Figures 2, 3 and 12, the first tubular element 2 comprises an elongated opening 15 that extends from a point located at a certain distance from the first end 4 to another point located at a certain distance from the second end 5. The elongated opening 15 has a length that is approximately equal to the length of the access opening 6 and a width that is considerably smaller than the width of the access opening

6, so that a bone graft cannot pass through the elongated opening 15. Furthermore, the first tubular element 2 comprises multiple rhomboidal openings 16 arranged in an area adjacent to the second end 5. The rhomboidal openings 16 are smaller than the access opening 9, such that a bone graft cannot pass through them. The rhomboid openings 16 are arranged in circumferential rows, one row being offset from the adjacent row by a distance corresponding to half the height of the rhomboid in the axial direction. The row of rhomboidal openings 16 closest to the second end 5 is cut so that the openings are open to the second end 5 forming teeth 17 for engagement with the adjacent vertebra.

As can be seen in particular in Figures 1 and 4, the first tubular element 2 additionally comprises multiple circular openings 18 in a zone beginning at the first end 4. The circular openings 18 are of a size that does not allow introduction or removal. bone graft removal. The rhomboidal openings 16 and the circular openings 17 serve to allow the growth of blood vessels and tissue.

Similarly, the second tubular element 3 comprises multiple circular openings 19 next to its second end 8 and multiple diamond openings next to the first end 7. The circular openings 19 and the diamond openings 20 are dimensioned such that no graft can be inserted or removed. bone through them. Similar to the first tubular member 2, the row of rhomboidal openings 20 closest to the first end 7 of the second tubular member is cut so as to form teeth 21 for engagement with the vertebral body.

As can be seen in Figures 1 and 4, a pin 25 is provided which can be fixed for example to the first tubular element 2 and guided in an elongated slot 28 (Figure 4) provided in the second tubular element 3 to prevent rotation and forming a stop in order to prevent separation of the first and second tubular elements.

The spacer also comprises a third tubular element 22 whose axial length corresponds approximately to the axial length of the area of ​​the second tubular element in which the rhomboidal openings 20 are located. The third tubular element 22 also comprises rhomboidal openings 23 in its wall and teeth. 24 at both ends free. The third tubular member 22 is fixedly connected to the second tubular member by means of pins 26, as shown in the exploded schematic representation of Figures 7 and 8, or with screws, rivets or the like. The third tubular member 22 may have an oval cross section, as shown in Figure

7, or a circular cross section, as shown in Figure 8. The third tubular member and the end section of the second tubular member form a double cage structure that increases the area of ​​contact with the vertebra compared to the area of contact of the second tubular element alone. Since the outer diameter of the second tubular member is smaller than that of the first tubular member, the third tubular member can be used to

ES 2 390 567 T3 increase the contact area and adapt the shape of the tooth ring to the contour of the final surface of the vertebral body with which it is to be coupled.

As can be seen in Figures 1 to 6, within the second end 5 of the first tubular element 2 a fourth tubular element 27 is provided, which is similar to the third tubular element 22 and which is connected with the first tubular element 2 to form a double cage structure. The fourth tubular member 27 also comprises rhomboidal openings and teeth for engagement with bone.

When the spacer is assembled, the elongated opening 15 covers at least one of the circular openings 19 or the rhomboidal openings 20 of the second tubular element 3. The elongated opening of the first tubular element and one of the circular or rhomboidal openings of the second tubular element form an example of a length adjustment structure that allows the expansion and compression of the two tubular elements with respect to each other through the application of a tool.

In the embodiment shown, the access opening, locking structure, and length adjusting structure in the assembled situation are disposed within about half or less of the circumference of the spacer.

In Figures 12 and 13 a length adjustment tool is shown for telescopically displacing the second tubular member 3 with respect to the first tubular member 2. The tool 30 comprises a tube 31 with a cuff 32 at one end and a section in the shape of a fork 33 at the other end. An axis of rotation 34 joins the two arms of the forked section 33 at the free end. A scissor-like structure 35 is pivotally connected to the hairpin-shaped section 33. The scissor-like structure 35 can pivot around the axis 34. It comprises arms 35a and 35b, which can be moved between a folded position. and a deployed position. One of the arms is structured to engage with the elongated opening 15 of the first tubular element 2 and the other arm is structured to engage one of the circular or rhomboidal openings of the second tubular element 3.

The tool also comprises a bar with a grip 37 at its free end. The bar is housed in the tube 31 and extends into the forked section 33. By rotating the bar with the handle 37, the scissor-like structure 35 is moved such that the arms 35a or 35b are open or close, respectively.

In practice, the spacer is first filled with bone graft before inserting it between the vertebrae. The spacer then has its minimum length. The retractor is then inserted between two adjacent vertebrae, for example to occupy the space after removing a vertebra. The length of the spacer is then adjusted by telescoping the second tubular member away from the first tubular member. This movement is a sliding movement without rotation. The tool shown in Figures 12 and 13 is used such that the scissor-like structure is inserted into the elongated hole 15 of the first tubular element with an arm 35a and engages one of the holes 19 or 20 of the second element. tubular with the other arm 35b. By rotating the bar, the scissor-like structure pivots and the second tubular member is telescopically displaced out of the first tubular member. Once the desired length is reached, the locking screws 12 are inserted into the threaded openings 10 until the spherical segment-shaped protrusion engages one of the hemispherical recesses 18. Given that the access openings of the first tubular element and the second tubular element, respectively, are aligned, the spacer still has openings large enough to insert the bone graft. Additional bone graft is then inserted to completely fill the interior of the retractor.

Since the locking structure and the elongated opening 15 serving for expansion or compression are located on the same side, the spacer can be quickly adjusted to its desired axial length and fixed in this position. Since the access openings of the first and second tubular members are on the same side near the locking structure, bone graft can be rapidly inserted during surgery.

The spacer may be coated to enhance tissue or blood vessel growth. The spacer can be coated with different materials on the outer surface and the inner surface of the tubular elements, respectively. The first and second tubular elements can be lined with different materials.

Modifications can also be made to the embodiment shown. The access opening need not be rectangular in shape. It can be of any shape as long as it is large enough to allow for bone graft insertion. It is possible to provide more than one elongated opening 15.

The circular openings and the rhomboidal openings can be omitted or can have any other shape as long as they are small enough not to allow removal or insertion of bone graft. In this case, instead of an opening in the second tubular element for coupling with the tool, another surface structure can be provided on the second tubular element.

The locking structure can also be modified. The spherical recesses 11 can be arranged in the inner wall of the first tubular element and the threaded openings can be arranged in the wall of the second tubular element. The locking screw is then screwed into the threaded openings from the hollow interior.

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The tubular elements shown are circular in shape. However, any other cross-sectional shape is also possible. For example, the cross-sectional shape of the tubular elements can be adapted to the contour of the end surface of a vertebral body.

The third tubular member and the fourth tubular member may also have a cross section other than a circular cross section or an oval cross section.

More tubular elements can also be added to the end section of the first and / or second tubular element, to form a multiple cage structure. Alternatively, the third and fourth tubular members can be omitted.