DE29913390U1 - Plastic bone plate - Google Patents

Description

A 55 045 and AESCULAP AG & Co. KG

u - 223/248 Am Aesculap Platz

30 July 1999 78532 Tuttlingen

PLASTIC BONE PLATE

The invention relates to a bone plate made of plastic, a set of such bone plates and a drilling tool for preparing such bone plates.

Bone plates are used to connect bone fragments together. Bone screws or other pin-shaped fixation elements are inserted through openings in the bone plate and into the bone fragments, creating a firm connection between the bone plate and the bone fragments.

Bone plates with relatively small dimensions have been used, particularly in facial surgery; these are usually bone plates made of a metal that is compatible with the body, for example titanium or a titanium alloy.

It is also known to manufacture these bone plates from plastic, in particular from a resorbable plastic. However, difficulties have arisen in this regard because the holes in the bone plate mean that they do not have the desired strength, particularly in the case of small dimensions.

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This is due, on the one hand, to the weakening of the cross-section caused by the perforations, but, on the other hand, to the fact that when such bone plates are manufactured by injection molding or similar processes, the perforations create weld lines, i.e. areas where the flow of the liquid plastic material is divided and reunited, and in these areas weakening of the material occurs.

It is the object of the invention to design generic bone plates made of plastic in such a way that a high strength of these bone plates can be achieved even with small dimensions.

This object is achieved according to the invention in a bone plate made of plastic in that it has at least two centering recesses for a drilling instrument, which do not completely penetrate the bone plate, at a distance from one another. In contrast to known bone plates, the new bone plate is thus closed in the area in which a bone screw or another fastening pin is to be inserted through it and has only one centering recess in this area, which enables the insertion of a drilling instrument and thus the creation of a hole through which the bone screw or fastening pin can then be inserted. This has the great advantage that closed surfaces are present when producing such a bone plate, and the difficulties described with separating surfaces are therefore eliminated. In addition, it remains

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It is up to the surgeon to decide in which area of the bone plate he will drill a hole using the centering recesses provided there. The bone plate is only broken through in the places where a bone screw or a fixing pin is required, but in the other areas it remains closed and therefore retains its original higher strength in these areas.

In particular, it can be provided that the bone plate does not have an opening that completely penetrates it, so that it reaches the surgeon as a completely closed plate in which only centering recesses are provided.

It is advantageous if a large number of centering recesses are arranged in the bone plate so that the surgeon has the option of selecting from this large number of centering recesses those that he actually needs to create an opening.

In a particularly preferred embodiment, each centering recess is concentrically surrounded by a contact recess for receiving a head-shaped thickening of a pin-shaped fixing element. This contact recess receives the head of a bone screw or a corresponding thickening of a fixing pin if the surgeon has actually drilled a hole in the bone plate with the help of the centering recess, the diameter of this hole being smaller than the diameter of the

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Installation recess so that the installation recess surrounds the hole in a ring shape after it has been drilled.

It is advantageous if the centering recess is arranged in the bottom of the installation recess.

In particular, the installation recess can have a flat central area and a sloping edge area. After the hole has been drilled, the sloping edge area surrounds it in the manner of an oblique countersink and thus centers the head of a bone screw or a threaded pin relative to the hole, which can then also have a diameter that is larger than the diameter of the bone screw or the fastening pin.

It is advantageous if the depth of the installation depression is 25% to 80% of the thickness of the bone plate, especially 25% to 50%.

Furthermore, it can be provided that the centering recess extends up to a maximum of 90% of the thickness of the bone plate, so that in any case a continuous plastic area with a thickness of at least 10% of the bone plate remains if no opening is made in the area of a centering recess. Preferably, this centering recess extends up to a maximum of 60% of the thickness of the bone plate.

The bone plate can in particular be made of resorbable plastic.

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It is particularly advantageous if the bone plate consists of a substantially amorphous plastic. With conventional plastic plates, it is usually necessary for reasons of strength to strengthen the bone plate substance by structuring it, for example by stretching it or by using fiber reinforcement. This does improve the strength, but the manufacturing effort is significantly increased and great difficulties arise when fiber-reinforced bone plates are to be processed, for example when cutting such bone plates to length, since fraying then occurs at the cut edges, which can lead to a loss of strength. Due to the advantageous structure of the new bone plates, their strength is intrinsically greater than that of perforated bone plates, and therefore the bone plates can consist of amorphous plastic that is not reinforced in the manner described. Such a plastic material can be processed in a simple manner, for example by cutting, without fraying or other damage occurring at the edge areas, and in particular without crushing.

In a preferred embodiment of the invention, the bone plate is designed as a flat band with a series of centering recesses arranged one behind the other. Such a bone plate can be made available in a longer length and is then cut by the surgeon to the required length as required.

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The implant is cut to the desired length, using only the centering recesses to create the opening that the surgeon actually needs.

The flat strip can be straight, but it is also possible to use curved flat strips, especially those curved in a circular arc.

In another embodiment, the bone plate has a central web and at each end two legs which protrude symmetrically from the web on opposite sides at an angle to the web and lie in the same plane as the web, and a series of centering recesses are arranged in the web and/or in the legs. Such a bone plate therefore has essentially a cross-shaped or X-shaped form, with the two legs being laterally offset from one another by the interposition of the web. Such a bone plate can be used by the surgeon as it is, but the surgeon can also transform it into bone plates that meet the respective requirements by cutting off certain parts, for example the legs can be shortened or legs can be removed completely, so that crosses with long and short legs, flat strips with end regions offset from one another, Y-shaped plates or angles can be formed in this way.

It is advantageous if embodiments are provided in which the web forms an angle with the legs

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between 75° and 90°, in another embodiment the angle is 40° to 50°.

In other embodiments of the bone plate, it is provided that it is rectangular and has several rows of centering recesses next to each other. Such a flat bone plate can be used in the form supplied, but the surgeon can at any time cut out the plate geometry that is most suitable for him from this bone plate and then use the centering recesses to drill holes in the places where the bone plate is to be fixed using a bone screw or a fixing pin.

In a particularly preferred embodiment, the differently designed bone plates described above are combined to form a set that enables the surgeon to produce a wide variety of shapes using only flat strips, cross-shaped bone plates and/or rectangular bone plates. To do this, the surgeon only needs a cutting tool and a drilling tool.

Such a drilling tool for preparing the bone plates can preferably be designed in such a way that it has two adjoining sections with different outer diameters. The front section, which has a smaller outer diameter, is then used to drill a hole in the

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Bone fragment, the adjoining section with a larger outer diameter, on the other hand, creates the hole in the bone plate through which a bone screw or a fixation pin is then to be inserted.

It is advantageous if the drilling tool has a depth stop so that the section with the larger outer diameter does not reach the bone fragment.

This depth stop can in particular have a stop surface arranged transversely to the axis of rotation of the drilling tool, the outer diameter of which is larger than the outer diameter of a contact recess surrounding the centering recess. Such a contact recess is thus completely covered by the stop surface, and the depth stop is thus supported on the outer surface of the bone plate.

The section with the smaller outer diameter of the drilling tool can be designed as a twist drill and thus serves to create a hole in the bone fragment. In another embodiment, however, this section with a smaller outer diameter is designed as a tap, which cuts a thread in the bone fragment in one operation and creates the hole in the bone plate through which a bone screw is then screwed into the threaded hole in the bone fragment.

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The following description of preferred embodiments of the invention serves to explain in more detail in conjunction with the drawing. They show:

Fig. 1: a plan view of a preferred embodiment of a cross-shaped bone plate with centering recesses and contact recesses;

Fig. 2: a sectional view along line 2-2 in Figure 1;

Fig. 3: an enlarged detailed view of area A in Figure 2;

Fig. 4: a bone plate in the form of a flat band;

Fig. 5: a bone plate similar to Figure 4 after a part of it has been cut off at one end;

Fig. 6: a bone plate similar to Figure 4 with centering recesses only in the two end areas;

Fig. 7: a view similar to Figure 6 with a bone plate shortened at both ends compared to the bone plate of Figure 6;

Fig. 8: a curved flat ligament bone plate;

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Figure 9: a view similar to Figure 8 after shortening of the bone plate;

Fig. 10: a top view of a very long, straight flat ligament bone plate;

Fig. 11: a view similar to Figure 10 after shortening of the bone plate;

Fig. 12: a plan view of a first preferred embodiment of a cross-shaped bone plate;

Fig. 13: a view of the bone plate of Figure 12 after removal of two legs and after shortening of two legs;

Fig. 14: a view similar to Figure 12 after shortening of all four legs;

Fig. 15: a view similar to Figure 12 with modified angles between the bar and the legs of the bone plate;

Fig. 16: a view similar to Figure 15 after removal of three legs;

Fig. 17: a view similar to Figure 14 of the bone plate of Figure 15;

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Fig. 18: a rectangular bone plate with a plurality of centering recesses arranged in rows next to one another;

Fig. 19: a square bone plate similar to that of Figure 18;

Fig. 20: a schematic side view of a first preferred embodiment of a drilling tool with a twist drill of small outer diameter and a twist drill of larger outer diameter;

Fig. 21: a view similar to Fig. 20 with a tap of small outside diameter and a twist drill of larger outside diameter and

Fig. 22: a drilling tool with a twist drill of small outer diameter and a milling head of larger outer diameter.

The bone plates 1 shown in the drawing are plate-shaped, essentially flat components made of plastic, in particular of a resorbable amorphous plastic, as is already known for the production of pin-shaped implants (company brochure "Scientific Information 26 of the company Aesculap AG & Co. KG., Tuttlingen, November 1997, "ISOSORB - The first resorbable polymer blend with clinical application").

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In the embodiment shown in Figures 1 to 3, the bone plate is cross-shaped and has an elongated central web 2 with parallel edges 3, at the ends of which two legs 4, 5 protrude at an angle and symmetrically, the edges 6 of which also run parallel to one another. This results in an H-shaped course, with the two legs of the H forming an angle with one another. In the embodiment shown in Figure 1, the angle between the legs 4 on the one hand and the web on the other hand is approximately 75°, but of course a different angle can also be used here.

The bone plate 1 has no perforations, i.e. the material is continuously distributed over the entire cross-sectional area.

A number of circular support recesses 7 are incorporated along the center lines of the web 2 and the legs 4, 5, which have a flat, central base 8 and an edge strip 9 that rises diagonally from this to the outside of the bone plate 1 (Figure 3). The depth of this support recess 7 is approximately 25% of the thickness of the bone plate. At the center of the base 8 of the support recess 7 there is a centering recess 10, the diameter of which is significantly smaller than the diameter of the base 8 and the depth of which also amounts to approximately 25% of the thickness of the bone plate 1, so that the centering recess 10

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only reaches about half the thickness of bone plate 1.

To use this bone plate, the surgeon must drill a hole at the point where he wants to insert a bone screw or other fixing pin through the bone plate 1. This is done using a suitable drilling tool that is inserted into a centering recess 10 at the desired point and that drills a hole through the bone plate 1 in the area of the base 8 of the attachment recess 7. This hole preferably extends approximately to the inner edge of the edge strip 9 so that a through-hole for a bone screw is formed in the bone plate 1, which is surrounded laterally by the sloping edge strip 9. The outer diameter of the hole can also be larger than the inner diameter of the attachment recess 7 so that the entire base 8 is then removed through the hole.

The surgeon will only make such a hole in the place where it is actually needed, so in all other areas the bone plate will remain closed and free of perforations.

The hole can be made by means of a simple twist drill, but it is advantageous to use special drilling tools, such as those shown in Figures 20 to 22.

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The drilling tool 11 of Figure 20 carries a twist drill 12 with a first section 13 with a small outer diameter and an adjoining second section 14 with a larger outer diameter, wherein the first section 13 merges into the second section 14 to form a straight or oblique cutting edge 15.

The second section 14 is closed off by a plate-shaped depth stop 16, which has a front surface 17 perpendicular to the axis of rotation of the twist drill 12 and is selected to be so large that this front surface 17 completely covers the contact recess 7, the front surface 17 thus rests against the outer surface of the bone plate 1 when the hole is made and thus limits the penetration depth of the drilling tool 11.

Since the length of the section 14 with a larger outer diameter corresponds approximately to the thickness of the bone plate 1, a hole is made in a bone fragment by means of the section 13 with a smaller outer diameter, to which the bone plate 1 is applied, while at the same time a hole is made in the bone plate 1 at the desired location, which hole is sufficient for the insertion of a bone screw.

The drilling tool 11 of Figure 21 is constructed in a similar manner, corresponding parts therefore have the same

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It differs only in that section 13 is designed as a tap and can therefore form a threaded hole in the adjacent bone fragment.

The drilling tool 11 of Figure 22 is again constructed in a similar way, and corresponding parts therefore have the same reference numerals. In this drilling tool, the section 14 with a larger outer diameter is designed as a milling tool, and this milling tool also creates a hole in the bone plate 1 at the desired location.

The bone plate 1 shown in Figure 1 is constructed in a cross shape; Figures 4 to 19 show other configurations of such bone plates, all of which are essentially constructed in the same way in terms of their closedness, the centering recesses 10 and the contact recesses 7, but which have different outer contours. The bone plates 1 in Figures 4, 6 and 10 are designed as straight flat strips, the bone plate in Figure 8 as a curved flat strip, the bone plate in Figure 15 corresponds to the bone plate in Figure 1 and the bone plate in Figure 12 is constructed similarly to that in Figure 1, but the legs 4 and 5 protruding from the web 2 form an angle of approximately 90° with one another.

Finally, in Figures 18 and 19, flat bone plates with several adjacent rows

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of centering recesses 10 and contact recesses 7, in the embodiment of Figure 18 a rectangular plate, in the embodiment of the figure a square plate.

Based on the described shapes of the bone plates 1, it is possible for the surgeon to create geometries adapted to a particular application by removing parts from the described bone plates. This can be done using a simple cutting tool, but in principle it would also be possible to use a thermal cutter, a band saw or similar tools for this purpose.

In Figures 5, 7, 9, 11, 13, 14, 16 and 17, the parts of the adjacent bone plates 1 are shown in dotted lines, which are separated in this way, so that shortened flat bands, flat bands offset at their ends, cross-shaped implants with shortened legs or angles can be produced.

In this way, the surgeon has the possibility to work with a set of bone plates that are limited to a few prototypes. For example, it is sufficient if such a set contains implants according to Figure 8, Figure 10, Figure 12, Figure 15 and Figure 18, then all other configurations can be produced simply by removing parts of these bone plates. The variety of production and storage

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This significantly reduces the maintenance costs and also gives the surgeon the opportunity to decide during the operation
must know which configuration is needed, a universal set with a few prototypes offers him every
the necessary opportunity for this.

Claims (23)

1. Bone plate made of plastic, characterized in that it has at least two centering recesses ( 10 ) for a drilling instrument ( 11 ) at a distance from one another, which do not completely penetrate the bone plate ( 1 ). 2. Bone plate according to claim 1, characterized in that the bone plate ( 1 ) does not have an opening completely penetrating it. 3. Bone plate according to claim 1 or 2, characterized in that a plurality of centering recesses ( 10 ) are arranged in the bone plate ( 1 ). 4. Bone plate according to one of the preceding claims, characterized in that each centering recess ( 10 ) is concentrically surrounded by a support recess ( 7 ) for receiving a head-shaped thickening of a pin-shaped fixing element. 5. Bone plate according to claim 4, characterized in that the centering recess ( 10 ) is arranged in the bottom ( 8 ) of the contact recess ( 7 ). 6. Bone plate according to one of claims 4 or 5, characterized in that the contact recess ( 7 ) has a flat central region ( 8 ) and an obliquely rising edge region ( 9 ). 7. Bone plate according to one of claims 4 to 6, characterized in that the depth of the contact recess ( 7 ) is 25% to 80% of the thickness of the bone plate ( 1 ), in particular 25% to 50%. 8. Bone plate according to one of the preceding claims, characterized in that the centering recess ( 10 ) extends up to a maximum of 90% of the thickness of the bone plate ( 1 ), preferably up to 60%. 9. Bone plate according to one of the preceding claims, characterized in that the bone plate ( 1 ) consists of a resorbable plastic. 10. Bone plate according to one of the preceding claims, characterized in that the bone plate ( 1 ) consists of a substantially amorphous plastic. 11. Bone plate according to one of the preceding claims, characterized in that the bone plate ( 1 ) is made of flat strip with a series of centering recesses ( 10 ) arranged one behind the other. 12. Bone plate according to claim 11, characterized in that it is designed as a straight flat band. 13. Bone plate according to claim 11, characterized in that it is designed as a curved flat band. 14. Bone plate according to one of claims 1 to 10, characterized in that it has a central web ( 2 ) and at each end thereof two legs ( 4 , 5 ) projecting symmetrically from the web ( 2 ) at an angle to the latter and lying in the same plane as the web ( 2 ), and that a series of centering recesses ( 10 ) are arranged in the web ( 2 ) and/or in the legs ( 4 , 5 ). 15. Bone plate according to claim 14, characterized in that the legs ( 4 , 5 ) enclose an angle between 75° and 90° with the web ( 2 ). 16. Bone plate according to claim 14, characterized in that the legs ( 4 , 5 ) enclose an angle of between 40° and 50° with the web ( 2 ). 17. Bone plate according to one of claims 1 to 10, characterized in that it is rectangular and has several rows of centering recesses ( 10 ) next to one another. 18. Set of bone plates, characterized in that it comprises bone plates ( 1 ) according to at least one of claims 11 to 13, according to at least one of claims 14 to 16 and bone plates according to claim 17. 19. Drilling tool for preparing the bone plate ( 1 ) of claims 1 to 18 for implantation, characterized in that it has two adjoining sections ( 13 , 14 ) with different outer diameters. 20. Drilling tool according to claim 19, characterized in that it has a depth stop ( 16 ). 21. Drilling tool according to claim 20, characterized in that the depth stop ( 16 ) forms a stop surface ( 17 ) arranged transversely to the axis of rotation of the drilling tool ( 11 ), the outer diameter of which is larger than the outer diameter of a contact recess ( 7 ) surrounding the centering recess ( 10 ). 22. Drilling tool according to one of claims 19 to 21, characterized in that the section ( 13 ) with the smaller outer diameter is designed as a twist drill. 23. Drilling tool according to one of claims 19 to 21, characterized in that the section ( 13 ) with the smaller outer diameter is designed as a tap.