DE4012622C1 - Two-part metal vertebra implant - has parts locked by two toothed racks, pre-stressed by elastic cushion between both implant parts - Google Patents

Abstract

Metal vertebra implant comprises two mutually adjustable and lockable parts. They are held permanently in the required position by an arrester. The parts are locked by two toothed racks, which are prestressed using a flexible pad between the two omplant parts so that the racks can only move in one direction towards one another. Pref. the permanent arrester consists of an elongated hole in the leg of the first part to take a screw engaging a hole in the web of the second part. The flexible pads are sterilisable silicone components which are fixed to and reach into a recess on the first part. ADVANTAGE - Implant adjusts in situ to suit situation using latching racks to take load when engaged. (Previously notified in Week 9129)

Description

The invention relates to a Vertebral implant made of metal for implantation in the human spine. Here it serves depending on Indication and the corresponding embodiment for Replacement of one vertebral body or for the fusion of two Vertebral body.

It is a vertebral implant in the form of a known as a Keystone implant. This one-piece metal block is used for ventral fusion two vertebrae (DE 36 20 549 A1).

According to the individual patient There is a need for a variety such implants of different sizes manufacture and for example in the clinic Keep stock. This increases the cost of production and Considerable use of the known implant.

Implants are adjustable in length from DE 37 29 600 C2 and DE 30 23 942 C3 known. The first mentioned publication shows an implant that consists of two parts, a caudal and a cranial part. Part of it is one towards the other part extending guide sleeve with an external thread intended. The other part has one in the Guide sleeve with movable guide rod also on an external thread. The connection between both parts is made by a mother made a threaded hole on one side  according to the external thread on the guide rod and a threaded hole on the other side corresponding to the external thread of the guide sleeve having. The length setting of the implant is done by moving the management staff in the Guide sleeve. It becomes by tightening the mother fixed.

This implant can only be very imprecise to adjust. In particular, it is practically impossible the length setting directly at the implantation site to make, because only in a cumbersome way once set length by tightening the nut should be fixed.

From DE 30 23 942 C2 is a known two-piece implant, which like that A sleeve and a part of the above other part has a guide rod which in the sleeve is mounted so that it can move longitudinally To be able to adjust the length of the implant. The Rod and the sleeve have locking devices, for example only on parts of its periphery co-operating threads, with which after Setting the desired length of the implant the two parts are engaged can by twisting the parts against each other. The implant should be in collapsed state to the place of Can be brought where it is on the implantation desired length should be distracted. To the two parts must be in the position are located in the longitudinal direction against each other are movable. So you don't take hers Lock setting on. But now rule in Spine considerable forces on insertion of an implant can be overcome first  have to. So that the implant mentioned in his longitudinally displaceable condition not due to the forces just mentioned in its lowest position Extent is pushed back in the said Document mentioned a special pliers with which the Implant can be spread apart and finally one part against the other into the Locking position can be rotated.

That being said, all of this handling Implant is very cumbersome, must be in situ Part twisted against the other, causing the exact position of the implant in the spine cannot be predetermined. Keep that in mind the compression forces in the spine, can not be excluded that the whole Implant during the rotation of one Partly from its location in the spine is turned out by means of a compensatory movement. From today's perspective, these disadvantages are no longer portable.

Incidentally, in the area of body implants Use of toothed racks as locking devices for a length adjustment of one of several parts existing implant known. So the DE shows 29 51 251 C2 an articular ligament endoprosthesis, the one on Bone attachable plate and as a counterpart  has a plate-shaped connecting device. Both parts are facing each other Provide toothed racks, with the help of which the parts Setting of the desired position can be locked are. The permanent locking takes place by means of a Parts penetrating bone screw.

The object of the present invention is before this Background, a vertebral implant the aforementioned kind so that it is easy and is safe to use.

This task is solved by a Vertebral implant with the characteristics of the characterizing part of claim 1.

A distinction is made between implants for Replacement of a vertebral body on the one hand and Implants for the fusion of two vertebral bodies on the other hand. Both types of implants are the solution the specified task in common that the Latching between the first part and the  second part by two toothed strips, which by at least one between the first and the second part arranged elastic pad are biased and only in are movable in one direction, works.

By shifting the first part over the the second part can be the size or length of the Implant can be adjusted individually in situ. So that both parts in the expanded state of the Implant not readily due to the in the Spine powers during the Implantation again in the opposite direction can slide, i.e. in the contracted state arrive, it is provided as a precautionary measure that directly or indirectly between the two parts a latching between the toothed strips acts, so that the movement of the first part against the second part blocked in the direction mentioned is. There is at least one between the parts elastic pad provided that already in unimplanted state of the implant for one resilient engagement of the toothed strips ensures. These Measure ensures that the parts before and controlled with each other during implantation can be positioned, the mentioned Latch already in this state to bear is coming. This will expand the implant first part against the second part below temporary suspension of the aforementioned resilient Locking against the resilient effect of the elastic padding around one or more tooth elements the toothed racks moved, whereupon due to the  the bias generated by the cushion element Latching is restored immediately, so that a movement of the parts towards each other in the Opposite direction is prevented.

In the formation of the invention Vertebral implant as a vertebral body replacement the first part one in essential T-shaped cross section and the second Part one essentially U-shaped cross-section, in the recess of which Bridge of the first  Partly can be introduced, one of which is for the Locking necessary rack on the outside on one side on the web of the first part and the other of the toothed strips on the Inside of one leg of the second part is provided, the elastic pad between the other side of the web and the inside of the other leg is arranged.

Preferably, the is substantially U-shaped Cross section of the second part in the area of the base the "U" expanded so that the recess as Represents trapezoid. This measure allows during the implantation a release of the locking both parts in the event that the implant is too wide has been expanded. This is the first part slightly tilted in the recess of the second part, so that the toothed strips come out of engagement and that first part towards the base of the recess of the second part, whereupon the elastic pad mentioned ensures that the The toothed racks come back under resilient engagement.

The permanent locking means mentioned can be formed be one in one leg of the second part provided longitudinal bore through which a Screw into a hole in the web of the first Partly takes hold. The screw is used for locking tightened.

As a permanent locking device is also one in one Leg provided groove possible in the one flattened round pin can be placed. If the through Rotation of the pin protruding into the recess Rounding in line with the bridge of the first part comes, this is permanently in the recess of the second part tense.  

That or the elastic cushions can with the described embodiment as in the Recess of the second part protruding and on this attached sterilizable silicone body. Usage would also be conceivable, for example a leaf spring to achieve the desired effect achieve.

The rack on the inside of the recess one leg of the second part and on the Point outside of the web of the first part advantageous teeth on whose tooth flanks face in the direction the allowable movement, d. H. in the direction of expansion of the implant an angle of rise to this Have direction of about 30 ° and their falling tooth flanks approximately vertically stand in the direction mentioned. The angle of rise allows the parts to be moved relatively easily to each other, while the angle of fall of about 90 ° with great certainty for blocking one Movement in the opposite direction ensures.

In one embodiment of the implant according to the invention as an implant for ventral fusion of two vertebrae shows that first part on the inside a wedge-shaped recess in which a wedge-shaped sliding block into a Is slidably mounted in the direction essentially perpendicular to the direction of expansion of the implant. The sliding block is on top of that the second part facing side with a rack, the other Tooth ledge on the inside of the second Can be partially locked, the elastic pad between the wall of the wedge-shaped Recess and the side of the slide block is arranged, which is directed to the first part. In this embodiment acts the latching between the first part and the second part indirectly over the mentioned Sliding block.  

For example, during implantation a gear mechanism, for example via a Worm gear, the sliding block in the intended Direction. In turn, the elastic padding for resilient engagement Toothed strips already in the non-implanted state of the implant.

This embodiment is advantageous trained that the first part with two attached to it, in the horizontal direction pointing guide pins is provided, which in two corresponding guide channels in the second part are guided, the guide pins together with the Guide channels the maximum distance the allowable movement in limit horizontal direction.

The guide channels can be in a special simple execution be stepped bores. In this The guide pins can fall into this hole settable cylinder head screws with one each threadless shaft in the head area (Thin shank screws) and a thread that in corresponding threaded holes in the first part is screwable. The screws mentioned form at the same time the permanent locking means of Implant.

In the aforementioned embodiment, the Tooth flanks of the toothed strips in the sliding direction of the Sliding blocks to this an angle of rise in Range from 30 °. The falling tooth flanks are, however, essentially perpendicular to the direction mentioned. Here the Angle of rise again a relatively easy one Moving the sliding block in its  Sliding direction, whereas the mentioned angle of descent of about 90 ° a great security against one Sliding back the sliding block between the caudal and the cranial part.

The invention is based on two Exemplary embodiments with reference to the drawing explained.

Here shows

Fig. 1 is a perspective view of the parts of a vertebral body implant and vertebral body replacement,

Fig. 2 is a sectional view of the implant of FIG. 1,

Fig. 3 is a perspective view of the parts of a vertebral implant for fusion of two anterior vertebral body according to one embodiment,

Fig. 4 is a sectional view of the implant according to Fig. 3, and

Fig. 5 is a schematic view of two toothed strips used.

Below are the same parts with the same Provide reference numerals.

In Figs. 1 and 2, a first embodiment is shown of a vertebral body implant according to the invention, which is designed as a vertebral body replacement.

The first part 1 has a substantially T-shaped cross section.

A rack 3 with teeth 5 is provided on the outside of the web 11 . On its upper side, part 1 is provided with a metallic open-cell covering 8 .

Seen ventrally, the second part 2 has an essentially U-shaped cross section, into whose slightly trapezoidal recess 10 the web 11 of the first part 1 can be inserted. On the inside of one leg 13 of part 2 , a toothed strip 4 is provided, which can be locked with the toothed strip 3 of part 1 . On the opposite leg 12 , two elastic pads 30 , for example made of silicone, protrude into the recess 10 .

A longitudinal groove 32 in the leg 12 of the second part 2 , together with a flattened round pin 31 which can be inserted therein, forms the permanent locking means in the exemplary embodiment shown.

On the lower side, the second part 2 is provided with an open-cell metallic coating 8 .

A recess 35 in the base of the second part 2 offers a possibility of engagement for a tool (not shown) in order to release the locking of the toothed strips 3, 4 if necessary, for example if the first part 1 has been moved too far out of the second part.

When inserting the web 11 into the recess 10 , the cushions 30 are compressed and accordingly placed under prestress, so that the toothed strips 3, 4 come into resilient engagement. During the implantation, the pin 31 is rotated in the groove 32 so that its flattened segment faces the recess 10 . The surgeon will move the first part 1 in situ with a tool (not shown) relative to the second part in the expansion direction X until the implant has reached the required length. The movement is made possible by the fact that the toothed strips 3 and 4 , as shown in FIG. 5, have teeth 5 , the tooth flanks 6 of which have an angle of increase in the direction X of the movement of approximately 30 ° to the latter, and the tooth flanks 7 of which decrease a angle of decline of approximately 90 ° to the X direction. The rise angle of approximately 30 ° enables the first part 1 to move relatively easily with respect to the second part 2 while briefly canceling the resilient engagement of the toothed strips 3, 4 . After reaching the next row of teeth, the toothed strips 3, 4 come back into resilient engagement.

In the opposite direction, the first part 1 is not readily possible due to the formation of the teeth 5 in the sense described. Only by placing a tool in the recess 35 can the first part 1 be pivoted in the trapezoidal recess 10 of the part 2 with the effect that the toothed strips 3, 4 come out of engagement and the first part 1 can be displaced in the direction . As already mentioned, the latter will only be necessary if part 1 has been pulled too far out of recess 10 .

After setting the desired size or length of the implant, the pin 32 is rotated so that its round portion protrudes into the recess 10 and comes into contact with the leg 11 of the first part 1 , as shown in Fig. 2. In this way, both parts 1, 2 can be permanently locked.

In FIGS. 3 and 4 is shown as a further embodiment of the intervertebral implant according to the invention, a first embodiment of the implant for the anterior fusion of two vertebral bodies.

The first part 1 has a wedge-shaped recess 17 . In this, a wedge-shaped sliding block 18 is mounted displaceably in the Y direction. On its base, the sliding block 18 is provided with a toothed bar 3 , which corresponds to a toothed bar 4 on the inside of the second part 2 and can be locked with the latter.

After the parts 1, 2 and 18 have been assembled, an elastic cushion 30 in the wedge-shaped recess 17 of the first part 1 ensures a resilient engagement of the toothed strips 3, 4 .

Two thin screws 20, 21 are provided as permanent locking means, which can be screwed through a stepped bore 22, 23 in the second part 2 into two correspondingly arranged threaded bores 33, 34 in the first part.

The screws 20, 21 form guide pins pointing in the direction X of the permissible movement, that is to say in the direction of expansion of the implant. The stepped bores 22, 23 form guide channels. The depth of the stepped bores 22, 23 can therefore limit the maximum expansion movement of the first part 1 with respect to the second part 2 .

The toothed strips 3, 4 are designed so that the tooth flanks their teeth in the direction Y, that is, in the direction of the permissible movement of the sliding block 18 , have an angle of inclination to this direction Y in the range of 30 °, while the falling tooth flanks are essentially perpendicular in the Y direction. This enables the movement of the sliding block 18 in the Y direction, but reliably blocks it in the opposite direction.

The latching between the first part 1 and the second part 2 in the present case acts indirectly through the sliding block 18 . It is understandable that with increasing movement distance of the sliding block 18 in the Y direction, the first part 1 moves in the X direction. This can be made possible, for example, by a worm gear (not shown) that engages the sliding block 18 .

All claimed within the scope of the invention Vertebral implant is common to that with a between the first and the second part of the Implant acting latch for a large Security against slipping against one another the other part is taken care of, an individual Attitude to patient needs due to the formation of the tooth racks, however is possible.

Claims (8)

1. vertebral body implant made of metal, which consists of at least a first part and a second part, which are displaceable relative to one another and can be fixed in their desired end position with each other by means of a latch, and which has a permanent locking means which permanently clamps both parts together in the implanted state, characterized in that the latching between the first part ( 1 ) and the second part ( 2 ) by two toothed strips ( 3, 4 ) which are arranged by at least one elastic cushion ( 30. ) arranged between the first and the second part ( 1, 2 ) ) are biased and can only be moved in one direction (x) against each other. 2. vertebral body implant as a vertebral body replacement according to claim 1, characterized in that the first part ( 1 ) has a T-shaped cross section and the second part ( 2 ) has a U-shaped cross section, in the recess ( 10 ) of the web ( 11 ) of the First part ( 1 ) can be inserted that one of the toothed strips ( 3 ) on the outside on one side on the web ( 11 ) of the first part ( 1 ) and the other of the toothed strips ( 4 ) on the inside of a leg ( 13 ) of the second part ( 2 ) is provided and that the elastic pad ( 30 ) between the other side of the web ( 11 ) and the inside of the other leg ( 12 ) is arranged. 3. vertebral body implant according to claim 2, characterized in that the permanent locking means is formed from a in the leg ( 12 ) of the first part ( 1 ) provided longitudinal bore through which a screw into a bore in the web ( 11 ) of the second part ( 2 ) takes hold. 4. vertebral body implant according to claim 2 or 3, characterized in that the elastic pads ( 30 ) in the recess ( 10 ) of the first part ( 1 ) projecting and attached to this, sterilizable silicone body. 5. vertebral body implant according to one of claims 1 to 4, characterized in that the toothed strips ( 3, 4 ) have teeth ( 5 ) whose tooth flanks ( 6 ) in the direction (x) of the permissible movement an angle of increase to the direction (x) of about Have 30 ° and the falling tooth flanks ( 7 ) are approximately perpendicular to the direction (x) of the permissible movement. 6. vertebral body implant for ventral fusion of two vertebral bodies according to claim 1, characterized in that the first part ( 1 ) has on the inside a wedge-shaped recess ( 17 ) in which a wedge-shaped sliding block ( 18 ) is displaceably mounted in the direction (y), which on the side facing the second part ( 2 ) is provided with a toothed strip ( 3 ) which can be locked with the other toothed strip ( 4 ) on the inside of the second part ( 2 ) and that the elastic cushion ( 30 ) between the Wall of the wedge-shaped recess ( 17 ) and the side of the sliding block ( 18 ) is arranged, which is directed in part ( 1 ). 7. vertebral body implant according to claim 6, characterized in that in the horizontal direction (x) facing guide pins ( 20, 21 ) are provided, which are guided in two corresponding guide channels ( 22, 23 ) in the second part ( 2 ), and that the guide pins ( 20 , 21 ) together with the guide channels ( 22, 23 ) limit the maximum distance of the permitted movement in the horizontal direction. 8. vertebral body implant according to claim 6 or 7, characterized in that the tooth flanks ( 6 ) of the toothed strips ( 3, 4 ) in the vertical direction (y) have an angle of rise in the vertical direction (y) of about 30 ° and the tooth flanks ( 7 ) run approximately horizontally.