ZA200202587B

ZA200202587B - Apparatus for distracting or compressing bones or bone parts.

Info

Publication number: ZA200202587B
Application number: ZA200202587A
Authority: ZA
Inventors: Fridolin Schlapfer; Martin Hess
Original assignee: Synthes Ag
Priority date: 2002-04-03
Filing date: 2002-04-03
Publication date: 2003-03-26

Description

1755/PCT" oO

English Translation of the International Patent Application

No. PCT/CH99/00598 «Apparatus for distracting or compressing bones or bone parts“ in the name of Synthes AG

Chur

Apparatus for distracting or compressing bones or bone parts

The invention relates to an apparatus for applying axial forces upon at least two bone fragments or vertebral bodies connectable with the apparatus as claimed in the precharacterising part of claim 1.

If for example a vertebral body develops a disease or suffers damage, it may become necessary to remove this vertebral body from the spinal column. In replacement of this vertebral body, spacer implants are subsequently inserted. These implants usually comprise parts displaceable towards and away from each other as well as ‘ two specific end plates adapted to fixate the implant on the adjacent, intact vertebral bodies. On he other hand, an internal fixating system is often applied in such a way that two vertebral bodies are connected to each other by means of the fixating system while with the aid of said fixating system one or even several damaged vertebral bodies are bridged. In the case of these essentially plate- shaped implants, the plate-like end portions are fixed to the vertebral bodies by means of bone screws. The connecting members situated between said plate-like end portions are telescopic so that the vertebral bodies adjoining the damaged vertebral bodies can be moved in a distracting or a compressing manner parallel to the axis of the spinal column. Other spinal column fixation systems consist of rod-like, longitudinal carriers which can be fixed to pedicle screws by means of connecting devices.

These connecting devices are designed in such a way as to be axially displaceable on the longitudinal carriers, thus permitting a distraction and/or a compression of the vertebral bodies. In fact, such applications often require a spreading apart or a compression of vertebral bodies or implant parts by means of appropriate instruments.

An apparatus for the spreading apart of vertebral bodies is known from US 4,898,161 GRUNDEI. This known spreading apparatus is shaped in the form of a forceps and includes two levers as well as two jaws which are arranged in their axial prolongations and may be equipped with pins. The jaws comprise special guides and are displaced parallel to each other as the forceps is opened or closed. By means of a pivotable screw/nut connection existing between the two levers, the forceps-like spreading apparatus may be locked in the desired position. A disadvantage of this known type of spreading apparatus is that it does not allow to carry out compressing displacements.

The invention is intended to provide a remedy for this. It is accordingly an object of the invention to create an apparatus permitting a distraction as well as a compression of bone fragments, vertebral bodies or implant parts which allows, in addition, a very precise and accurate adjustment of the distance between thc jaws.

According to the invention, this object is achieved by means of an apparatus for applying axial forces upon at least two bone fragments or vertebral bodies connectable tg the apparatus which shows the features of claim 1.

The apparatus of the invention comprises

A) a first connecting member with a longitudinal axis which is connectable to a bone fragment or a vertebral body;

B) a second, longitudinal connecting member with a longitudinal axis which is connectable to another bone fragment or vertebral body, said longitudinal axes forming a plane between them and the second connecting member being displaceable relative to the first connecting member in such a way that the movement of its longitudinal axis is coplanar to said plane;

C) a longitudinal carrier extending coaxially to the longitudinal axis of the first connecting member, including a longitudinal axis, a rear end portion, and a front end portion connectable to the first connecting member, said longitudinal axis extending parallel to said plane;

D) a tubular sleeve, extending coaxially to the longitudinal axis, which has a coaxial through bore in which the longitudinal carrier is displaceable parallel to its longitudinal axis, a front end portion facing the first connecting member, and a rear end portion;

E) at least one first lever connecting the front end portion and the second connecting member and having a longitudinal axis extending substantially parallel to said plane, rotatably connected to at least the end portion in such a way that said longitudinal axis may pivot substantially parallel to said plane; and

F) at least one second lever with a longitudinal axis extending substantially parallel to said plane, rotatably connected to the first connecting member and the second connecting member in such a way that its longitudinal axis may pivot substantially parallel to said plane; so that

G) a relative movement between the front end portion and the first connecting member parallel to said longitudinal axis will result in a relative movement between the first and the second connecting members along a line or a curve extending parallel to said plane and substantially vertically to said longitudinal axis. : The longitudinal axes of the two levers cross at a point of intersection and are rotatably connected to each other by means of a swivel Joint arranged at said point of oo intersection. The levers may also be arranged two by two, the first and second levers comprising in this case one lever each, arranged on opposed sides with respect to the sleeve and the connecting members. On the other hand, the first and second levers may comprise two or more levers each, which are situated on the same side of the sleeve or of the connecting members, respectively, and which may extend parallel to each other.

The longitudinal carrier may in a simple manner be axially displaceable within the sleeve, the manipulation of the longitudinal carrier and of the sleeve being possible by means of simple operating handles or levers attached to these elements. In another embodiment, the longitudinal carrier and the sleeve may bc displaceable paraliel to the longitudinal axis and relative to each other by means of a lever appliance. In this case, the longitudinal carrier and the sleeve are equipped with fixed levers, extending vertically to the longitudinal axis, which may be displaced towards or away from each other by means of a forceps-1like auxiliary device. The levers of the forceps are connected to the fixed levers by means of swivel joints and cross each other in a shared swivel joint, so that a compression of the levers of the forceps will cause the fixed levers to be displaced towards each other. For spreading apart the levers of the forceps, a spring is arranged between them.

In another embodiment of the apparatus of the invention, the longitudinal carrier is provided, in an area (B) corresponding to the position of the front end portion on the sleeve, with an external screw thread which corresponds to a complementary internal screw thread formed in the front end portion of the sleeve. In addition, the longitudinal carrier is mounted in the first connecting member in such a way that it is rotatable about the : longitudinal axis but axially fixed with respect to said longitudinal axis. The relative axial movement between the longitudinal carrier and the sleeve in the sense of the longitudinal axis is thus operated by means of a rotation of the longitudinal carrier within the sleeve.

On the other hand, the longitudinal carrier may be provided in an area (C), which is situated on its front end portion and is connectable with the first connecting member, with a second external screw thread and the first connecting member may be connected to the front end portion of the longitudinal carrier by means of an internal screw thread which is complementary to said second external Screw thread.

The threads may be of equal turn but have different pitches or may have opposite turns, in which case one external screw thread is shaped in the form of a right-hand thread,

whereas the other external screw thread is shaped in the form of a left-hand thread. The corresponding internal screw threads have matching turns. Multiple threads may also be used.

The levers may be rotatably connected to both connecting members. If, in addition, on a connecting member one pivot point of a lever is displaceable parallel to the longitudinal axis of said connecting member, a displacement of the connecting members relative to each other is enabled, with the longitudinal axes of the connecting members remaining parallel and the connecting members - moving along a straight line extending vertically to said longitudinal axes.

The first lever(s) may also be rigidly connected to its (their) respective connecting member, in which case the connecting members will move along a planar curve.

Further advantageous embodiments of the invention will be characterised in the dependent claims.

The advantages achieved by the invention reside basically in the fact that the apparatus according to the invention allows the processes of spreading apart and of compression to be carried out with the same apparatus disregarding the amount of required distracting or compressing displacement, that a parallel displacement of the bone fragments, vertebral bodies or implant parts is ensured, and that inp addition an implant-specific tool or instrument such as a screw driver may be inserted through the apparatus.

In the following, the invention and further developments of the invention will be illustrated in greater detail with reference to the partially diagrammatic representations of several embodiments.

In the drawings: : Fig. 1 is a view of one embodiment of the apparatus according to the invention;

Fig. 2 is a view of another embodiment of the apparatus according to the invention;

Fig. 3 shows a further embodiment of the apparatus according to the invention; and

Fig. 4 shows a forceps-like actuator attachment for the handling of the individual embodiments of the apparatus : according to the invention.

The embodiment of the apparatus according to the invention shown in Fig. 1 comprises a first connecting member 1 with a longitudinal axis 27 connectable to a bone fragment or a vertebral body and a second longitudinal connecting member 2 with a longitudinal axis 17 connectable to another bone fragment or vertebral body. The longitudinal axes 17;27 of the connecting members define a plane 18. Facing the bones or the implants, the connecting members 1;2 are equipped with pins 30 which are connectable to bone fragments, vertebral bodies or implant parts and move along a straight line 3 lying in the plane 18 and extending vertically to the longitudinal axes 17:27. In addition, the second connecting member 2 may be displaced relative to the first connecting member 1 in such a way that in the plane 18 the longitudinal axis 17 moves parallel to the longitudinal axis 27. For manipulation purposes, the apparatus of the invention is further equipped with a longitudinal carrier 4 extending coaxially to the longitudinal axis 27 of the first connecting member 1 and including a longitudinal axis extending concentrically to the ‘longitudinal axis 27, a rear end portion 7, and a front end portion 6 connectable with the first connecting member 1. In this embodiment, the longitudinal axis 5 lies in the plane 18. A tubular sleeve : 8 extends coaxially to the longitudinal axis 5 and is provided with a coaxial through bore 11 in such a way as to permit a displacement of said sleeve 8 relative to the longitudinal carrier 4 coaxially to the longitudinal axis 5. The sleeve 8 further comprises a front end portion 9 facing the connecting member 1 and a rear end portion 10.

The displacement of the two connecting members 1;2 relative to each other is operated by means of a first lever 12 connecting the front end portion 9 with the second connecting member 2 and having a longitudinal axis 16 extending substantially parallel to the plane 18, the lever 12 being rotatably connected to the front end portion 9 and to the second connecting member 2 in such a way that the lever 12 may pivot relative to the front end portion 9 and the connecting member 2, so that the longitudinal axis 16 moves parallel to the plane 18, and of a second lever 13 with a longitudinal axis 15 extending substantially parallel to the plane 18, the second lever 13 being rotatably connected to the first connecting member 1 and to the second connecting member 2 in such a way that the longitudinal axis 15 may pivot parallel to the plane 18.

The longitudinal axes 15;16 of the two levers 12;13 Cross at a point of intersection 19 and are connected to each other by means of a swivel joint 14 situated at the point of intersection 19. By means of the scissors-like arrangement of the levers 12;13, it can be achieved that a relative movement between the front end portion 9 and the first connecting member 1 parallel to the longitudinal axis

S causes a relative movement between the first and the : second connecting members 1;2 parallel to the longitudinal axes 17 and 27 and parallel to the straight line 3 which extends parallel to the plane 18 and vertically to the longitudinal axis 5.

The second connecting member 2 comprises a guide 22 assuring that the rotation of the second lever 13 relative - to the second connecting member 2 is executed about the longitudinal axis 28 of a bolt 21 which is freely movable along the guide 22. This guide 22 extends parallel to the longitudinal axis 17 and has a length A, thus permitting . the bolt 21 to be displaced in the guide 22 parallel to the longitudinal axis 17.

The longitudinal carrier 4 is provided in an area B corresponding to the position of the front end portion 9 with a first external screw thread 23, whereas the front end portion 9 has an internal screw thread 24 which is complementary to said first external screw thread 23. The longitudinal carrier 4 is further provided in an area Cc, which is situated on its front end portion 6 and connectable with the first connecting member 1, with a second external screw thread 25 and the first connecting member 1 is connected to the front end portion 6 of the longitudinal carrier 4 by means of an internal screw thread 26 which 1s complementary to said second external SCrew thread 25. The external screw threads 23 and 25 on the longitudinal carrier 4 have opposed thread pitches. The external screw thread 25 in the area C is a right-hand thread, whereas the external screw thread 23 in the area B is a left-hand thread. Analogously, the internal screw threads 24;26 in the front end portion 9 and in the first connecting member 1 have opposed thread pitches. Thus, it can be achieved that a rotation of the longitudinal carrier 4 about the longitudinal axis 5 will cause the front end portion 9 of the sleeve 8 and the first connecting member 1 to move towards or away from each other, depending on the sense of rotation of the longitudinal carrier 4. The relative movement of the front end portion 9 and the first connecting member 1 which is thus obtained results in a relative movement of the two connecting members 1;2 with respect to each other. For rotating the longitudinal carrier 4 and the sleeve 8 relative to each other, the longitudinal carrier 4 is equipped on its rear end portion 7 with a first operating handle 35 and the sleeve 8 is equally equipped on its rear end portion 10 with a second operating handle 36.

The longitudinal carrier 4 and the first connecting member 1 may each have a through bore extending coaxially to their respective longitudinal axes 5;27, so that a screw driver may be introduced through these bores. The second connecting member 2 may equally have a through bore extending coaxially to its longitudinal axis 17, so that a screw driver may be introduced through this bore.

The embodiment of the apparatus of the invention shown in

Fig. 2 differs from the embodiment shown in Fig. 1 only in so far as the longitudinal axes 15;16 of the two levers 12;13 cross at the extremities of the levers 12;13 which are distant from the front end portion 9 and from the first connecting member 1, respectively. The swivel joint 14 connecting the two levers 12;13 is accordingly situated on these extremities. The levers 12;13 are substantially of the same length and the second connecting member 2 is rigidly connected with the first lever 12, the longitudinal axis 16 of the lever 12 and the longitudinal axis 17 of the second connecting member 2 intersecting each other at a ~ specific angle. In this embodiment of the apparatus of the invention, the connecting members 1;2 on actuating the apparatus are no longer displaced in such a way that their longitudinal axes 17;27 move parallel to each other. Here, the movement of the connecting members 1;2 follows a curve

Co lying in the plane 18. Yet it is possible to define a point X on the second connecting member 2 which moves substantially along a straight line 3 extending parallel to the plane 18. The connecting members 1;2 are equipped with

U-shaped plates 32 which are attachable to implant parts.

The embodiment of the apparatus of the invention shown in

Fig. 3 differs from the embodiment shown in Fig. 2 only in so far as the longitudinal carrier 4 is displaceable within the sleeve 8 parallel to the longitudinal axis 5 and is connected on its front end portion 6 to the first connecting member 1 wherein it is lodged in an axially fixed manner relative to the longitudinal axis 27 while rotatable about said longitudinal axis 27. In this manner it is assurcd that the relative movemenls between the longitudinal carrier 4 and the sleeve 8 result in a purely axial displacement which may be achieved by moving the operating handles 35 and 36 towards or away from each other. The rotatable but axially fixed mounting of the longitudinal carrier 4 within the first connecting member 1 is achieved by means of a setscrew 34 which is screwed into the first connecting member 1 and protrudes into a corresponding groove 33 arranged in the longitudinal carrier 4.

The mechanism of movement working between the longitudinal carrier 4 and the sleeve 8 as shown in Fig. 3 can easily be transferred to the embodiment of the apparatus of the invention shown in Fig. 1.

Fig. 4 shows a detail of one embodiment of the apparatus of the invention, for example of the embodiment according to

Fig. 3, in which the longitudinal carrier 4 and the sleeve : 8 are displaceable parallel to the longitudinal axis 5 and relative to each other by means of a lever appliance 29.

The end portions 7 and 10 of the longitudinal carrier 4 and of the sleeve 8, respectively, are provided with fixed levers 37 and 38 which are displaceable towards or away from each other by means of a forceps. The levers 42 and 43 of the forceps are connected to the fixed levers 37 and 38 by means of swivel joints 39 and 40 and cross each other in a shared swivel joint 41, so that pressing together the levers 42 and 43 of the forceps results in a displacement of the fixed levers 37 and 38 towards each other. The levers 42 and 43 of the forceps are spread apart by means of a spring 44 arranged between them.

Claims

Claims

© 1. An apparatus for applying axial forces on at least two bone fragments or vertebral bodies connectable with said apparatus, including A) a first connecting member (1) with a longitudinal axis (27) which is connectable to a bone fragment or a vertebral body; and B) a second, longitudinal connecting member (2) with a longitudinal axis (17) which is connectable to another bone fragment or vertebral body, the longitudinal axes (17:27) forming a plane (18) between them and the second connecting member (2) being displaceable : relative to the first connecting member (1) in such a way that its longitudinal axis (17) will move in said plane (18); characterised in that the apparatus further comprises C) a longitudinal carrier (4) extending coaxially to the longitudinal axis (27) and including a longitudinal axis (5), a rear end portion (7), as well as a front end portion (6) connectable with the first connecting member (1), said longitudinal axis (5) extending parallel to said plane (18); D) a tubular sleeve (8) extending coaxially to the longitudinal axis (5) and including a coaxial through bore (11) in which the longitudinal carrier (4) is displaceable parallel to its longitudinal axis (5), a front end portion (Y) tacing the first connecting member (1), and a rear end portion (10); E) at least one first lever (12) connecting the front end portion (9) to the second connecting member (2) and having a longitudinal axis (16) extending substantially parallel to said plane (18), rotatably connected at oo 14 least to the end portion (9) in such a way that said longitudinal axis (16) may pivot substantially parallel to said plane (18); and : F) at least one second lever (13) with a longitudinal axis (15) extending substantially parallel to said plane (18), rotatably connected to the first connecting member (1) and the second connecting member (2) in such a way that the longitudinal axis (15) may pivot substantially parallel to said plane (18); so that G) a relative movement between the front end portion (9) and the first connecting member (1) parallel to said longitudinal axis (5) results in a relative movement between the first and the second connecting members : (1;2) along a line (20) extending parallel to said plane (18) and substantially vertically to said longitudinal axis (5). :
2. An apparatus as claimed in claim 1, characterised in that in the special case the expression 'parallel to the plane (18)' is to be understood as meaning 'coplanar to the plane (18)'.
3. An apparatus as claimed in claim 1 or 2, characterised in that the line (20) is a straight line (3).
4. An apparatus as claimed in any of the claims 1 to 3, characterised in that a point (X) may be defined on the second connecting member (2) which moves substantially along the straight line (3) extending parallel to the plane (18) as the front end portion (9) and the first connecting member (1) are displaced relative to each other.
5S. An apparatus as claimed in claim 3 or 4, characterised in that the straight line (3) extends vertically to the longitudinal axis (5).
6. An apparatus as claimed in any of the claims 1 to 5, characterised in that the longitudinal axes (15;16) cross at a point of intersection (19).
7. An apparatus as claimed in claim 6, characterised in “that the levers (12;13) are connected with each other by means of a swivel joint (14) arranged at their point of intersection (19). To
8. An apparatus as claimed in any of the claims 1 to 7, characterised in that the levers (12;13) are substantially of the same length.
9. An apparatus as claimed in any of the claims 1 to 8, characterised in that the second connecting member (2) is displaceable substantially parallel relative to the first connecting member (1).
10. An apparatus as claimed in claim 9, characterised in that the second connecting member (2) is displaceable substantially parallel to the longitudinal axis (5) relative to the first connecting member (1).
11. An apparatus as claimed in any of the claims 1 to 10, characterised in that the first lever (12) is rotatably connected to the second connecting member (2) in such a way that the longitudinal axis (16) may pivot substantially parallel to the plane (18).
12. An apparatus as claimed in any of the claims 1 to 11, characterised in that the second connecting member (2) comprises a guide (22) assuring that the rotation of the second lever (13) relative to the second connecting member (2) is executed about the longitudinal axis (28) of a bolt (21) which is freely movable along the guide (22).
13. An apparatus as claimed in claim 12, characterised in that the guide (22) has a length (A) extending parallel to the longitudinal axis (17) and enabling a displacement of the bolt (21) in the guide (22) parallel to the longitudinal axis (17).
14. An apparatus as claimed in any of the claims 1 to 8, characterised in that the second connecting member (2) and the first lever (12) are rigidly connected to each other.
15. An apparatus as claimed in claim 14, characterised in that the levers (12;13) form an isosceles triangle.
16. An apparatus as claimed in any of the claims 1 to 15, characterised in that A) the longitudinal carrier (4) is provided in an area (B) corresponding to the position of the front end portion (9) with an external screw thread (23); B) the front end portion (9) has an internal screw thread (24) which is complementary to said external screw thread (23); C) the longitudinal carrier (4) is mounted within the first connecting member (1) in such a way as to be rotatable about the longitudinal axis (5); and

D) the longitudinal carrier (4) is mounted within the first connecting member (1) in such a way as to be axially fixed relative to the longitudinal axis (5).
17. An apparatus as claimed in any of the claims 1 to 15, characterised in that A) the longitudinal carrier (4) is provided in an area (B) corresponding to the position of the front end portion (9) with a first external screw thread (23); B) the front end portion (9) has an internal screw thread (24) which is complementary to said external screw thread (23); C) the longitudinal carrier (4) is provided in an area : (C), which is situated on its front end portion (6) and is connectable to the first connecting member (1), with a second external screw thread (25); and D) the first connecting member (1) is connected to the front end portion (6) of the longitudinal carrier (4) by means of an internal screw thread (26) which is complementary to said second external screw thread (25).
18. An apparatus as claimed in claim 17, characterised in that the external screw threads (23;25) are of equal turn but have different pitches.
19. An apparatus as claimed in claim 17, characterised in that the external screw threads (23;25) have opposed turns.
20. An apparatus as claimed in claim 19, characterised in that the external screw thread (25) in the area (C) is a right-hand thread.
21. An apparatus as claimed in claim 19 or 20, characterised in that the external screw thread (23) in the area (B) is a left-hand thread.
22. An apparatus as claimed in any of the claims 17 to 21, characterised in that the external screw thread (23) in the area (B) is a multiple thread.
23. An apparatus as claimed in any of the claims 17 to 21, characterised in that the external screw thread (25) in the area (C) is a multiple thread.
24. An apparatus as claimed in any of the claims 1 to 16, ; characterised in that the longitudinal carrier (4) is mounted within the first connecting member (1) in such a way as to be at least axially fixed relative to the longitudinal axis (5).
25. An apparatus as claimed in any of the claims 1 to 16, and 24, characterised in that the longitudinal carrier (4) and the sleeve (8) are displaceable parallel to the longitudinal axis (5) and relative to each other by means of a lever appliance (29).
26. An apparatus as claimed in claim 25, characterised in that the lever appliance (29) is shaped in the form of a forceps and equipped with a spring (44) for flexibly spreading apart said lever appliance (29).
27. An apparatus as claimed in any of the claims 1 to 26, characterised in that both the longitudinal carrier (4) and the first connecting member (1) have a through bore extending coaxially to their longitudinal axes (5;27), so that a screw driver may be introduced through these bores.
28. An apparatus as claimed in any of the claims 1 to 27, characterised in that the second connecting member (2) has a through bore extending coaxially to its longitudinal axis (17), so that a screw driver may be introduced through this bore.
29. An apparatus as claimed in any of the claims 1 to 28, characterised in that the connecting members (1;2) are equipped with pins (30) which are connectable to bone fragments, vertebral bodies or implant parts. :
30. An apparatus as claimed in any of the claims ‘1 to 28, characterised in that the connecting members (1;2) are equipped with blades (31) which are attachable to bone fragments, vertebral bodies or implant parts.
31. An apparatus as claimed in any of the claims 1 to 28, characterised in that the connecting members (1;2) are equipped with U-shaped plates (32) which are attachable to implant parts.
32. An apparatus as claimed in any of the claims 1 to 28, characterised in that A) the connection between the connecting members (1;2) and the implants such as bone screws, which are fixedly connected to the vertebral bodies or bone fragments, is realised in the form of a ball-and-socket joint; and B) the ball joint-like connection is reversibly blockable in an angularly stable manner.