CA2047521A1

CA2047521A1 - Osteosynthetic plate

Info

Publication number: CA2047521A1
Application number: CA002047521A
Authority: CA
Inventors: Robert Frigg
Original assignee: Robert Frigg; Synthes (U.S.A.) Partnership
Current assignee: Synthes USA LLC
Priority date: 1990-07-23
Filing date: 1991-07-22
Publication date: 1992-01-24
Also published as: EP0468192A2; CH681199A5; JP3176959B2; ATE142457T1; DE59108170D1; EP0468192A3; JPH04250156A; EP0468192B1

Abstract

Abstract of the Disclosure An osteosynthetic plate has an upper surface, a lower surface, a plurality of screw holes connecting the upper side with the lower side, two plate ends and two side plate walls.
One bone plate end is free, while the other plate end has a coupling means for effecting a detachable connection with an insertion and positioning device.

Description

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11598.A39 OSTEOSYNTHETIC PLATE

FIELD OF INVENTION

The invention relates to an osteosynthetic plate.

BACKGROUND OF THE INVENTION
So-called plate insertion has become established for the operative repair of broken bones. The shape and design of bone plates varies depending on the indication and the anatomy of the bone to be stabilized.
In contrast with so-called marrow or intramedullary nailing, the purpose of plate osteosynthesis is the repositioning, as exactly as possible, of the individual bone fragments, as well as an optimum stabilization of the fracture. Only when both of these factors are fulfilled can a primary healing of the fracture be achieved. This in turn protects the implant against overfatigue.
In the course of recent years, a trend to the use of intramedullary nailing to treat shaft fractures, rather than plate osteosynthesis, has been observed. There are two principal reasons for this trend. First, owing to the further development and improvement of X-ray operated image amplifiers, fractures can be repositioned and nailed without direct visual contact. The second reason resides in the~more biological nature of the procedure; i.e., the fracture zone is no longer exposed, and this 2 ~

contributes to a decreased disturbance of peripheral blood perfusion. Despite the initial enthusiasm, however, the disadvantages of intramedullary nailing are becoming more and more apparent. Along with the risky opening of the medulla, which places the soft tissue in danger, the central perfusion of the bone is destroyed for a sustained period of time, along its entire length.

OBJECTS AND SUMMARY OF THE INVENTION
It is an object of the invention to provide an osteosynthetic plate which can be implanted in a controlled manner and with the greatest possible protection of the bone as well as the soft parts.
This object is met by the present invention which provides an osteosynthetic plate and a device for insertion and positioning the plate with respect to the bone.
Specifically, the invention provides a bone plate for use in osteosynthesis comprising an upper surface, a lower surface, a plurality of screws holes connecting said upper and lower surfaces, said plate having a first end and a second end and means at said second end for coupling said plate to an insertion device.
The invention further comprises an insertion device for use with the novel plate and comprising a handle, a coupling element for connection to a bone.plate and a spacer element for connecting said handle to said coupling element.

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The invention further comprises a system for the treatment of bone fractures including the bone plate and insertion device as described.
The invention also includes a method for treating fractured bones which comprises inserting a bone plate having a plurality of screw holes through an incision in the soft tissue surrounding the bone by means of an insertion device, positioning the bone plate on the outside of the bone to bridge the fracturer securing the plate to the bone by means of screws inserted through the screw holes of the plate into the bone on either side of the fracture, detaching the insertion device and removing said device.
Briefly, the osteosynthetic plate in accordance with the invention corresponds to a locking nail, but one which is attached externally to the medulla. As with intramedullary nailing, the access is located at a distance from the fracture, but can be freely chosen, unlike intramedullary nailing, since it need not lie along the longitudinal axis of the bone. After a minimal incision at some distance from the fracture, a channel whose size corresponds to that of the plate is prepared through the soft tissue until the surface of the bone is reached. The osteosynthetic plate in accordance with the invention, which may be shaped like a flatiron, is now pushed with its point forward through this channel, along the surface of the bone and over the fracture. Depending on the anatomical situation, an additional channel may have to be prepared along the bone. This channel can be prepared basically in any suitable manner, even 2~ .,2~

arthroscopically if desired. Such additional preparation is, however, rarely necessary. Unlike conventional plates, the osteosynthetic plate in accordance with the invention need not be adapted to the bone, since it has the function of bridging over the fracture, in keeping with its length. That is, the fracture does not need to be positioned 100% anatomically, and no compression is exerted on the fracture.
After the placement of the osteosynthetic plate in accordance with the invention within the prepared channel, the plate is screwed onto the bone. This operation is performed as follows:
The handle mounted on the plate serves not only the function of guidance during insertion of the plate, but also the function of helping to position the screws when they are placed in the bone. The holes provided in the guide handle for this purpose correspond to the screw holes in the plate. The drilling, measurement of the necessary length of screws, possible tapping or thread cutting and setting of the screws is directed through the guide handle and through puncture incisions made in the soft tissue.
In accordance with a preferred embodiment of the invention, the holes in the plate have a conical shape and are preferably provided with an internal thread. The screws used for attaching the plate, correspondingly, have a conical head, preferably with a conical external thread. The screws are screwed through the holes in the plate and into-the bone. When the screw has been turned to its full extent, the conical screw head is tightly held ~?~7~
in the conical hole in the plate, an effect which is further enhanced by the pitch of the thread that is preferably used.
This tight holding is important if the screw is to be inserted only through the near cortex, and if the plate does not lie on the surface of the bone. With this kind of screwing, the angle between the plate and the screws is fixed. In a conventional osteosynthetic plate, on the other hand, a so-called plate-bone friction is needed in order to set a fracture.
The conical screw connection of the invention has a further advantage in that the screw threads are wedged together when the screw is fully tightened. This wedging decreases the danger of an unintended loosening of the rigid plate/screw connection due to cyclic stress.
The rigid plate/screw connection can also be achieved hy means of screws which make use of an expandable head, as disclosed, e.g., in WO 88/03781.
The preferred flatiron shape of the plate of the invention is preferably structured in such a way that the under, or lower, side of the plate, including the point of the plate, is flat.
The upper side of the plate, on the other hand, tapers downward to a point, in a sloping shape. Preferably, the side walls of the plate should also taper slightly to a point. The effect of this shape is that when the plate is pushed forward over the bone, it also automatically approaches the latter; i.e., it can be pushed forward along the bone in a controlled manner.
Alternatively, the under side of the plate, as well as the upper side, can be given a slightly sloping sled-like shape. In 2~ ~7;~2 -~

this embodiment, the point of the slope is located approximately at the central axis of the plate. The point of the plate, in this case, can push bluntly through the soft tissue but has no tendency to follow only the surface of the bone, since the soft tissue which stands in the way is displaced upwardly and downwardly uniformly. This embodiment is therefore suitable for those cases in which a channel must be formed for the insertion of the plate in any event (arthroscopically). It permits an anchoring screw to be fastened very close to the point of the plate, which is not possible in the case of a point shaped like a sled runner.

BRIEF DESCRIPTION OF THE DRAWINGS
An example of an embodiment of the invention, which at the same time elucidates the operating principle, is depicted in the drawings in which:
Figure 1 is a longitudinal cross section through an osteosynthetic plate in accordance with the invention, with an insertion and positioning device attached to it.
Figure 2 is a longitudinal cross section through a tibially implanted osteosynthetic plate in accordance with the invention, with an insertion and positioning device attached to it.
Figure 3 is a plan view of a femorally applied osteosynthetic plate in accordance with the invention, with the insertion and positioning device already removed.

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DET~ILED DESCRIPTION OF THE INVENTION
Referring to Fig. l, an osteosynthetic bone plate 10 according to the invention has an upper surface 1, a lower surface 2, and several screw holes 3 connecting the upper surface 1 with the lower surface 2, which serve to receive bone screws 30. The plate has a first end 5 and a second end 7. The first plate end 5 has a bevel 6 at the upper surface, like the point of a flatiron, so that when plate 10 is inserted through soft tissue, the lowest possible resistance, and thus the minimum degree of injury, occurs. For this purpose, the side walls 9 of the plate can also taper slightly to a point. The second end 7 of the plate has coupling means in the shape of a cylindrical threaded hole 8 by which an insertion device 20 can be fastened in a detachable manner by means of a fastening screw 21.
The screw holes 3 are conically shaped, tapering in the direction of lower surface 2, and are provided with internal threads 33 which correspond to the external threads 32 of the bone screws 30 which they are to receive. In this way, an absolutely rigid connection is achieved between plate 10 and screws 30, which is of utmost importance. The conical angle is advantageously between 2.0 and 4.0, preferably between 2.5 and 3.5. Especially preferred is a conical angle of 3.
The flatiron shaped insertion device 20 has at its end 22 a cylindrical hole 27 for coupling with plate 10. A fastening screw 21 can be guided through this hole in order to temporarily attach the insertion dev~ce 20 to the plate 10. A
perpendicularly arranged spacer element 23 is attached at end 22, 2~ 75~ ~
and connects the end 22 to a guide handle 24. The handle 24, when the guide 20 is joined to the plate 10 is parallel to plate 10. Handle 24 has cylindrical holes 25, whose axes 26 align exactly with axes 4 of the plate holes 3. In this way it is possible, by means of suitable instruments such as drill guide 40 (and also drills, length measuring devices, setting instruments, etc., not shown~, to insert screws 30 through coaxial holes 3 and 25, and to fasten the screws to the bone, rapidly and precisely, without an X-ray apparatus. The coupling and uncoupling of insertion device 20, by means of fastening screw 21, is accomplished through the corresponding hole 25 in guide handle 24, which aligns with hole 8 in plate 10, the hole 25 being of sufficient diameter to permit removal of screw 21.
The dimensions of plate 10 depend largely on the bone being set, or the fracture being treated. For use on the tibia, the width of the plate is about 12 mm, the height of the plate about 4 mm, and the length of the plate between 200 and 300 mm. For use on the femur, these dimensions would be somewhat larger.
Spacer element 23 is about 50 mm long when used on the tibia, or about 100 mm long when used on the femur.
Figure 2 represents the emplacement of a plate 10, according to the invention, implanted to bridge a fracture 51 of the tibia 50; insertion device 20 is still attached, and projects out through incision 52. ~late 10 is fastened to the bone with three screws located proximally to fracture 51 and three screws, such as 30, located distally to ~t, in such a way that a space 53 remains between bone 50 and plate 10, which permits revascularization.
Figure 3 represents the emplacement of a plate 10 according to the invention, to bridge a fracture 61 of femur 60. Here the insertion device used (not shown) has already been removed through incision 62. Just as is illustrated in Figure 2, the individual fragments 61 are not themselves fastened, in this operating technique~ but are bridged over by plate 10.
In addition to the advantages discussed above further advantages are achieved by the invention as follows:
- The osteosynthetic plate can be used as a bridging plate, so that the fracture need not be 100% repositioned.
- The osteosynthetic plate need not be adapted to the anatomy of the bone being treated.
- The implantation is performed through a minimal incision some distance from the fracture. This minimizes any additional disturbance of the biology around the fracture. The cosmetic advantage of a far shorter scar is appreciable.
- Simple, controlled insertion of the flatiron-shaped plate is made possible by the guide handle.
- The drilling, of holes in the bone, tapping of such holes, length measurement and setting of bone screws can be done in a planned manner by means of the guide handle.
- Owing to the firm anchoring of the screw heads in the bore holes of the plate, the plate can be positioned away from the surface of the bone, which is of extreme importance for maintaining the blood perfusion of the bone.

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- Since the anchorinq of the screws is necessary only in the near cortex, the range of screws needed can be reduced to about 3 screws per system dimension.
- The screws engaged in only one side of the cortex can have a self-cutting point, since they come to rest in the medulla.
There can be no damage to the soft tissue due to a self-cutting screw point.

Claims

1. An osteosynthetic plate having an upper surface, a lower surface, a plurality of holes connecting the upper and lower surfaces and adapted to receive screws, said plate having a first end and a second end, said second end having means for coupling said plate to an insertion device.

2. The plate claimed in claim 1 wherein the upper surface is bevelled at the first end.

3. The plate claimed in claim 1 wherein the plate has side walls which taper inwardly at the first end.

4. The plate claimed in claim 3 wherein the side walls taper to a point at the first end.

5. The plate claimed in claim 1 wherein the holes are shaped so that screws inserted in said holes may be rigidly connected to the plate.

6. The plate claimed in claim 1 wherein the holes are conically shaped, tapering toward the lower surface, and are threaded.

7. The osteosynthetic plate claimed in claim 6, in which the holes have a conical angle of from 2.0° to 4.0°.

8. The osteosynthetic plate claimed in claim 7, in which the holes have a conical angle of from 2.5° to 3.5°.

9. An insertion device for applying a bone plate to a bone comprising a handle, a coupling element for connection to a bone plate and a spacer element joining the handle to the coupling element.

10. An insertion device for use with the osteosynthetic plate claimed in claim 1, comprising a handle, a spacer element arranged on the handle, and coupling means connected to said spacer element for joining said device to the plate.

11. The insertion device claimed in claim 10, in which the coupling means is capable of detachably joining said insertion device to the plate.

12. The insertion device claimed in claim 11, in which the coupling means comprises a cylindrical socket.

13. The insertion device claimed in claim 10, in which holes are provided in the guide handle, the axes of said holes being adapted to be aligned with the axes of the holes in a plate, when joined to said insertion device by said coupling means.

14. A system for the treatment of bone fractures comprising a bone plate having a first end and a second end and a plurality of screw holes between said first and second ends, an insertion device, said insertion device having a handle, a coupling element, a spacer element joining said handle to said coupling element, and means connecting said coupling element to the second end of said plate

15. The system claimed in claim 14 wherein said handle comprises holes which are aligned with the screw holes in the plate.

16. The system claimed in claim 14 wherein the coupling element comprises a socket adapted to receive a pin or bolt.

17. The system claimed in claim 16 wherein the bone plate has a hole to receive a pin or bolt inserted through the socket in the coupling element.

18. The system claimed in claim 17 and comprising a pin or bolt for insertion through said socket and into the hole in the plate.

19. A method of treating a fractured bone which comprises inserting a hone plate having a plurality of screw holes through an incision in the soft tissue surrounding the bone by means of an insertion device detachably secured to the plate, positioning the plate on the outside of the bone to bridge the fracture, securing the plate to the bone by means of screws inserted through the screw holes into the bone on either side of the fracture, detaching the positioning device from the plate and removing said device.

20. The method claimed in claim 19 wherein the insertion device has a handle which extends parallel to the bone plate when the insertion device is attached to the plate, said handle having holes which are coaxial with the screw holes in the bone plate, said method fruther comprising the steps of inserting a drill guide through the holes in the handle of the insertion device and drilling holes in the bone through said drill guides and through the coaxial screw holes in the plate.