WO2001082809A1

WO2001082809A1 - Contoured bone plate

Info

Publication number: WO2001082809A1
Application number: PCT/CH2001/000264
Authority: WO
Inventors: Joachim Pfefferle; Peter Scheuble; Hermann Zeuner
Original assignee: Medartis Ag
Priority date: 2000-05-03
Filing date: 2001-04-26
Publication date: 2001-11-08
Also published as: AU4821601A; DE20007908U1

Abstract

The invention relates to a contoured bone plate (1, 1'), comprising several plate members (2) which are interconnected by thin links (3) and which lie on a plate plane (Y) in their unbent state. A screw hole (4) is provided in at least some plate members (2) and bone screws (9) can be inserted into or through said screw holes (4) in order to fix the bone plate (1'). The longitudinal axis (Z) of the bone plate (1') as it extends in the plate plane (Y) is at least considerably circular in shape.

Description

Contoured bone plate

Field of application of the invention

The present invention relates to a bone plate, which means

Bone screws are to be fastened and in particular as a reconstruction system for the maxillofacial area of the human skull, e.g. for the lower jaw. In a special embodiment, the bone plate and screws are blocked together. For the time being, the terms "plate", "screw" and "plate-screw connection" will be used in abbreviated form. Such plates are used, for example, to reinforce weakened, regressed bone structures. In the case of large continuity defects, the plates have to provide stability over long periods of time and absorb the loads that the missing bone would have to bear. In its simplest form, plates of this type consist of a straight, elongated branch with a multiplicity of plate members, in each of which there is a screw hole for receiving a screw. An angled side branch is used as bridging plates on the left or right. In the case of total bridging plates, side branches angled on both sides extend from the elongated branch. The plates can be cut to the required length, which is done by removing excess plate members, and bent to adapt to the patient's anatomy.

The following requirements are placed on such bone plates or the plate-screw connections constructed with them:

- high strength and stability of the bone plate; - high rigidity of the plate-screw connection;

- Flexibility of the slab in all levels with little loss of strength both in the slab level and around the slab level, including as torsion;

- Possibility of applying various types of biological tissue to the plate;

- the lowest possible surface pressure of the plate on the periosteum; - Often, additional securing (so-called blocking) of the screws penetrating the plate in order to more reliably rule out an independent loosening of the screws; and

- Favorable applicability by the surgeon.

State of the art

Plates of the type relevant here as straight, elongated branches, as bridging plates with side branches angled to the right or left of the main branch or as total bridging plates with side branches angled to the main branch (double angled) have long been described in the literature , from many suppliers on the market and in widespread clinical use. Examples of this include the company

(R) ten from LEIBINGER, Freiburg / Germany, with the titles "Titanium -

Locking Screw Mandibular Reconstruction Plating System ", 90-01680,10 / 95; and" MARX® - Titan Mandibular Bridging Plate System ", 90-01637,

05/94. In some brands, a reinforced angle segment is provided at the transition between the main branch and the angled side branches, see

® SYNTHES "The Locking Reconstruction Plate,

Technique Guide, Maxillofacial "; and" COMPACT 2.4 Recon ", 3/96.

When applied, these plates must be bent to a relatively large extent to the patient's anatomy. In principle, the plates used in the patient are constantly changing bending stress due to their activities, e.g. by swallowing and chewing. Depending on the intensity of the bending process, the long-term bending fatigue strength of the plates, which are mostly made of titanium, is reduced by the operative bending during insertion, thus reducing their fracture resistance and service life in the patient. This is an essential aspect of the imperfection of the bone plates of the type known to date.

Another problem is the blocking between the inserted plate and the fastening screws. In order to keep the surface pressure of the plate against the periosteum low, US 5,810,823 proposes Arrange insertable or fixed spacer elements with an internal thread on the underside of the plate, which sit on the bone and are penetrated by the threaded shanks of the screws. Spacers that can be positioned variably also allow the screws to be aligned differently from the vertical. With this construction, the large-area pressing of the plate onto the periosteum is avoided, but increased pressure arises at the attachment points of the spacer elements. The relatively small insertable spacing elements complicate the surgical procedure. Regardless of whether the spacer elements are fixed or can be used, they do not provide improved protection against unintentional loosening of the screws.

WO 96/39975 describes a blocked plate-screw connection, where recessed securing elements are provided on the underside of the plate in the area of the screw holes. The threadless neck portion of the screw shaft, which has a smaller diameter than the threaded part, projects through the individual securing element. First, the threaded part can be inserted through the securing element and screwed into the bone, the screw head coming to rest on the top of the plate. After a heat treatment, the securing element shrinks so that the plate is held at a distance from the periosteum and the screw is secured against unscrewing. This system requires the special security elements and devices and is therefore complex to handle and manufacture.

In the company publication "SYNTHES ^® - THORP reconstruction set" from STRATEC Medical, Waidenburg / Switzerland, a plate system is disclosed, in which the screw holes of the plate are first used to screw anchor screws into the bone. An expansion screw is screwed into the slotted head of the anchoring screw, which sits in the screw hole. As a result, the head of the anchoring screw presses against the wall of the screw hole in the plate. Thus the anchoring screw is secured against unscrewing and the plate is held at a distance from the periosteum. So that the screw holes in the plate do not narrow when bending, bending inserts are provided as insertable cores. The higher number of parts len requires more time and instrumental effort during the operation and is more difficult overall.

A further development of a lockable plate-screw connection is known from US 5,709,686. The bone plate has a plurality of holes provided in the direction of the longitudinal axis of the plate for the passage of screws. The screw hole is oval, with its main axis lying in the longitudinal axis of the plate. The screw hole is surrounded by a spherical countersink on the top of the plate. There is a partial internal thread along the shorter minor axis of the screw hole, the threads of which each run out towards the main axis of the oval screw hole. The internal thread serves to accommodate a thread section located on the screw under its head, which is expanded in diameter compared to the threaded shaft of the screw. The screw hole opens towards the underside of the plate in the area of the two ends of the main axis, i.e. outside the internal thread on the longitudinal axis of the plate.

In the clinical application of the plate, the threaded shaft of the screw protrudes into the bone, while the threaded part engages with the internal thread in the screw hole. This supports the plate and does not force the screw onto the periosteum. The screw is secured against unintentional removal by the threaded connection between the internal thread in the screw hole and the threaded part of the screw. The plate and screw are interlocked. The countersink around the screw hole allows a screw without a threaded part to be eccentrically created to produce compression between bone compartments. Screws without a thread section for blocking can also be screwed in differently from the vertical. There is more space for this in the direction of the longitudinal axis of the plate due to the oval hole shape and the only partial internal thread in the screw hole.

With the plate-screw connection according to US Pat. No. 5,709,686, perfect blocking and additional securing of the screws is possible, but significant disadvantages remain, such as: - In order to prevent deformation of the internal thread in the screw holes when bending the plate, bending inserts must still be used.

- Even at low torques while the screw is being screwed in, the internal thread in the screw hole can be over-tightened. With standard screwdrivers, such critical torques can be easily applied. A damaged plate is unusable; you have to use a new plate and possibly also a new screw.

- In the case of a blocked plate-screw connection, the screwed-in screws can only be positioned vertically, which necessitates the use of drill guides that are exactly vertical.

- Due to the entire geometry of the plate holes, machining must be done in two directions, which makes plate production more complex.

Object of the invention

In view of the imperfections shown in the previously known bone plates, the object of the invention is to propose a bone plate of the type relevant here, where the number and intensity of the required bends are significantly reduced during the surgical adaptation to the patient's anatomy. This is primarily to increase the long-term fatigue strength of the plates and, as a synergy effect, to reduce the surgical effort for the surgeon.

In addition, the object of the invention is to propose an improved blockable plate-screw connection for the plates to be improved with regard to the adaptation. It is particularly important here to get by without third parts, such as inserts or expansion screws for locking and bending inserts. The connections should be less sensitive to overtightening and angular misalignment of the screws in relation to the vertical and the longitudinal axis of the plate. It is desirable to achieve a high loosening torque within the plate-screw connection for the screws, in order to thus strictly avoid automatic loosening of the screws. The clinical application for the surgeon should be as simple as possible. The possibilities of an osteosynthetic must be preserved Bring bone compression and use the connection with conventional screws unblocked. Finally, the parts of the connection must be able to be mass-produced efficiently.

Overview of the invention

To solve the problem, osteosynthesis of fractures on arched or arched bones, e.g. proposed a lower jaw, a contoured bone plate, which extends in a plane of the plate and whose longitudinal axis of the plate extends at least essentially in the form of a circular arc. The circular longitudinal axis of the plate between the central axes of the webs and the central axis of the adjacent screw hole results in an offset with e.g. 1 ° to 10 °, preferably 2.5 °. The plate has several plate members, which are connected to one another by webs. At least in some plate members, preferably in each plate member, there is a screw hole.

The bone plate consists at least of an arcuate main segment. For special tasks, the main segment is provided with a lateral segment attached to it on one or both sides and lying in the plate level, which extends straight or curved. Some screw holes on the bone plate may not be designed for blocking, but as standard cylindrical screw holes or as direction-oriented compression holes. Preferably the arcuate bone plate is given its shape without reshaping, i.e. the plate is made from the material during manufacture, so that the plates produced in this way reach the surgeon without first being weakened by bending stresses.

The further development of the interlocking according to the invention is based on a bone plate and screws with an interlocking thread according to the genus from US Pat. No. 5,709,686. The screw holes in the plate links are surrounded by a spherical countersink on the top of the plate. Internally, an engagement contour is present in the screw hole, which consists partly of horizontal and radial circumferential valley troughs on the wall of the screw hole and adjacent remaining contour tips. The diameter the countersink for receiving the screw head is greater than the clear width of the engagement contour. It runs out towards the edges of the engagement contour, so that smooth, non-contoured wall areas remain in the screw hole. In relation to the threaded shaft of the screw, the screw hole is an elongated hole. The engagement contour is preferably produced by milling and has, for example, a pointed, round, trapezoidal or sawtooth-shaped shape.

On the screw suitable for blocking, there is a blocking thread below the screw head, which has a diameter of the same size or larger than the thread on the threaded shaft intended for engagement in the bone. When the plate is fixed to the bone, the screw with its threaded shaft protrudes through the screw hole and the thread of the threaded shaft rotates into the bone. In the final phase of screwing in the screw, the locking thread below the screw head enters the engagement contour in the screw hole. Since the interlocking thread, with its helical shape and its pitch, is not complementary to the engagement contour, deformation occurs on both and thus a more resistant connection to loosening. Blocking of reduced thickness can still be achieved if there is a continuous thread on the screw, the uppermost threads of which undermine the engagement contour.

The bone plate according to the invention with an arcuate plate longitudinal axis - at least in the main segment, if the bone plate is provided with a lateral segment attached to it on one or both sides - provides the following advantages:

- After bending in the webs, one achieves from the plane of the plate, almost over the surface, often in principle a perfect fit of the bone plate to the bone. The result is an ideal adaptation of the bone plate in its longitudinal course and the inclination across the plate width.

- There is no additional bending in the plate level, quasi twisting or twisting over the edge. - Due to the arcuate starting geometry, the bone plate takes up the inclination of a circular section of the lateral surface of a cone.

- This reduces the operational effort when adapting the plate and its loss of strength due to less deformation.

The improved blocking also has the following advantages:

- The plate-screw connection is efficient in clinical use since no third parts are required for blocking. No bending inserts are required even when bending the plate. Even with a deformation within the screw hole, the functionality of the blocking is not impaired.

- When blocking, no forces act on the periosteum, so that it is protected. Similar to a fixator, the plate can be positioned at a distance from the bone. - The internal engagement contour in the screw hole also allows a slight angular misalignment of the screw in relation to the vertical and longitudinal axis of the plate. This without loss of functionality of the blocking.

- When generating a compression, the screws are not subjected to tensile stress, since the screw is not blocked in the plate, which means that no axial movement between the plate and the bone is permitted.

- The screwed-in screws are better secured against unintentional loosening since a high torque has to be applied. This is due to the deformations in the blocking on the internal engagement contour on the screw hole and on the thread of the screw involved. - The risk of overturning and thus damaging the plate is reduced. With conventional plates, the screws overtighten at low screwing torques, which can be effortlessly applied with standard screwdrivers.

- The internally arranged engagement contour in the screw holes causes a significantly lower notch effect than conventional internal threads, which reduces the risk of breaking the plate.

- The plate can be equipped with different screws, namely those with which locking occurs and those without locking. In the latter case, the screw holes act as neutral Compression holes to accommodate the screw head. This is the case, for example, when applying small screws to staple a bone compartment. The screw can also be set at an angle. - Since the complete geometry of the screw holes in the plate can be machined from one side, there is no need for reclamping during machining, so that overall there is a cost-effective production that can also be carried out precisely with reasonable effort.

Brief description of the accompanying drawings.

Figure 1A - a bone plate with an arcuate plate longitudinal axis Z and 16 screw holes;

Figure 1 B - an enlarged view of three plate members according to Figure 1A; 1C - a schematic diagram of a human lower jaw with the adapting circular-arch-shaped bone plate according to FIG. 1A and a straight bone plate drifting from the lower jaw according to FIG. 5A;

Figure 2 - a bone plate with an arcuate plate longitudinal axis Z and 8 screw holes of different types;

FIG. 3A - a bone plate for the left jaw branch with an arc-shaped main segment according to FIG. 1A, a straight, rising lateral segment and a reinforced angular area with an additional screw hole;

Figure 3B - the bone plate according to Figure 3A with a curved lateral segment and reinforced angular range without an additional screw hole;

FIG. 3C - the bone plate according to FIG. 3B with an additional screw hole in the reinforced angular range;

Figure 3D - the bone plate according to Figure 3A without additional screw hole in the reinforced angular range;

Figure 3E - the bone plate according to Figure 3A with reduced spacing of the screw holes in the lateral segment; FIG. 4A - a bone plate screwed onto a fractured lower jaw;

FIG. 4B - a bone plate screwed onto the lower jaw to bridge a continuity defect;

Figure 5A - a straight bone plate with uniformly aligned screw holes in plan view;

Figure 5B - the representation according to Figure 5A with differently oriented screw holes; Figure 5C - the bone plate according to Figure 5A in section on the line A-A with the engaging contour of the first embodiment, schematic diagram;

FIG. 5D - the representation according to FIG. 5C with the engagement contour, real contour;

Figure 5E - the bone plate according to Figure 5A in section on the line B-B;

Figure 6A - a two-start bone screw with locking thread in the

Neck; Figure 6B - the two-start bone screw according to Figure 6A with locking thread in the neck area and thick screw shaft; Figure 6C - a bone screw with blocking thread in the neck area and self-drilling and self-tapping thread on

Screw shaft; Figure 6D - the bone screw according to Figure 6C with blocking thread in the neck area and self-drilling and self-tapping thread on the screw shaft and additional cutting groove;

Figure 6E - a catchy self-tapping bone screw with pointed

Thread flanks; Figure 6F - a two-start self-tapping bone screw with pointed

Thread flanks and thicker screw shank; Figure 6G - the two-start self-tapping bone screw according to

Figure 6F with round thread in the neck area; Figure 6H - the catchy self-tapping bone screw according to figure

6E with pointed thread flanks, larger pitch and larger

Outside diameter at screw shaft; FIG. 7A - the bone screw according to FIG. 6A screwed vertically into a screw hole from FIG. 5E;

FIG. 7B - the view according to FIG. 7A with the bone screw screwed in at an angle;

FIG. 7C - bone screws according to FIG. 6A screwed into screw holes with engagement contours of the first embodiment according to FIG. 5E, blocked in a bent bone plate;

FIG. 7D - bone screws screwed into a bent and twisted bone plate according to FIG. 5A;

Figure 8A - the bone screw according to Figure 6A with locking thread, deformed after locking; FIG. 8B - a screw hole with an engagement contour of the first embodiment from FIG. 5E, deformed after the blocking;

Figure 9A shows a screw hole with an engagement contour of the second embodiment in plan view;

FIG. 9B shows the representation according to FIG. 9A as a section on the line C-C;

FIG. 9C shows the representation according to FIG. 9A as a section on the line D-D;

FIG. 9D, the bone screw according to FIG. 6E screwed into the screw hole from FIG. 9B, blocked;

Figure 10A - a screw hole with an engagement contour of the third embodiment in plan view; Figure 10B - the representation of Figure 10A as a section on the line E-E;

Figure 10C - the bone screw according to Figure 6F in the screw hole

FIG. 10B screwed in in a blocked manner;

Figure 11A - a screw hole with an engagement contour fourth embodiment in plan view;

Figure 11 B - the representation according to Figure 11 A as a section on the line F-F; Figure 11 C - the bone screw according to Figure 6G screwed into the screw hole of Figure 11 B blocked;

Figure 12A - a screw hole with an engagement contour fifth embodiment in plan view; Figure 12B - the representation of Figure 12A as a section on the line GG; Figure 12C - the bone screw according to Figure 6H screwed into the screw hole of Figure 12B blocked;

FIG. 13A - the situation before a fracture is closed by means of compression osteosynthesis; Figure 13B - the situation during closure of the fracture; Figure 13C - the situation after the fracture has closed;

Figure 14A - a bone screw without locking thread;

Figure 14B - the bone screw without locking thread according to figure

14A with thicker screw shaft; FIG. 14C - the bone screw according to FIG. 14A is screwed into a screw hole from FIG. 5E unblocked and vertically; FIG. 14D - the representation according to FIG. 14C with the bone screw unblocked and screwed in at an angle; 14E - the situation in a lag screw osteosynthesis with a bone screw without locking thread according to FIG. 14A screwed into a screw hole with engagement contours of the first embodiment according to FIG. 5E without being locked;

Figure 15A - the bone screw according to Figure 6E from a screw hole

Figure 5C unblocked and screwed vertically; and FIG. 15B — the representation according to FIG. 15A with the bone screw screwed in unblocked and at an angle.

embodiments

The detailed description of exemplary embodiments of the osteosynthetic bone plate according to the invention is given below with reference to the accompanying drawings. A special variant of the bone plate with lockable bone screws can be found in the second part of the description, starting with FIG. 4A.

The following definition applies to the entire further description. Are reference numerals in a figure for the sake of graphic clarity, but in the immediately associated description text is not explained, reference is made to their mention in the preceding or following figure descriptions. In the interest of clarity, the repeated designation of components in other figures is mostly dispensed with, provided that it can be clearly seen in the drawing that the components are "recurring".

Figures 1A, 1 B and 2

The bone plate 1 "has an arcuate plate longitudinal axis Z with a multiplicity of plate members 2, which are connected to one another by webs 3. The plate V extends in the unbent initial state in the plate plane Y. A screw hole 4 is provided in each of the plate members 2. Depending on If required, all or individual screw holes 4 can be designed as cylindrical standard screw holes 40 or as known direction-oriented compression holes 41. Alternatively, all or individual screw holes 4 can be provided with a special engagement contour 8 to be described later for the blocking.

The combination pattern of screw holes 4 shown in FIG. 2 is only intended to illustrate the variety of designs without being relevant in practice. The outer screw holes 4 have the shape of standard cylindrical screw holes 40, while the three screw holes 4 in front are compression holes 41 acting in different directions or have engagement contours 8 intended for blocking. Depending on the intended use, the plate 1 'is produced in the required length or is brought to the desired length by separating plate members 2 and webs 3. The number, the positioning, the distance and the type of screw holes 4 can also be selected depending on the intended use. The circular arc-shaped longitudinal axis Z of the plate results between the central axes Zi of the webs 3 and the central axis ∑ _{2 of} the respectively adjacent screw hole 4, an offset β with, for example, 1 ° <β> 10 ° and preferably β = 2.5 °. Between two adjacent screw holes 4 there is an offset of 2ß with, for example, 2 ° <ß> 20 ° and preferably ß = 5 °. Preferably receives the arcuate plate 1 'its shape without forming, but is elaborated from the material during manufacture.

FIG. 1C This figure illustrates a basic illustration of the direction of extension and the geometrical adaptation of a plate 1 'contoured according to the invention with a plate longitudinal axis Z which runs in a circular arc or a plate 1 with a conventionally straight plate longitudinal axis Z, both plates 1', 1 being attached to a human lower jaw and facing each other In the fully bent state, stretching the lower jaw, extend between the ascending jaw branches.

After bending in the webs 3, the straight plate 1 attached to the left branch of the jaw drifts out of the plate plane Y - virtually over the surface - from the lower jaw. In order for this plate 1 to encompass the lower jaw, an additional bending in the plate plane Y must be carried out in each bar 3 - virtually over the edge. Only then does plate 1 follow the course of the lower jaw. Since this in principle has no vertical surfaces, but rather extends apically, in order to ensure that the plate 1 fits snugly against the jawbone, a subsequent setting or twisting of the plate members 2 is necessary. Due to the greater bending of the plate 1 required to adapt to the patient's anatomy, the flexural fatigue strength is reduced and thus the service life of the plate 1 used for the patient, which is subjected to constantly changing bending with the movements of the patient.

The conforming of the plate 1 'contoured according to the invention to the jawbone with the longitudinal axis Z of the plate running in a circular arc is achieved much more favorably. It is only necessary to bend the plate 1 'in the webs 3 out of the plate plane Y, quasi over the surface, in order to bring the plate into the U-shape encompassing the lower jaw. The bending generally takes place essentially in the area of the webs 3. The additional bending in the plate plane Y, quasi over the edge, and the setting or twisting omitted here. This plate 1 'is thus considerably less stressed by the adaptation, that is to say it is significantly less weakened by a substantially reduced preload.

Due to the arc-shaped initial geometry, the plate 1 ', after bending out of the plate plane Y, assumes the inclination of a circular section of the lateral surface of a cone. In this way, both the basically horizontal, U-shaped encirclement of the lower jaw in the longitudinal course of the plate V and the close fitting of the plate 1 "over its width to the apically pre-stretched bone are realized. The circular arc-shaped initial geometry reduces the surgical effort for the surgeon considerably when fitting the plate 1 ', the plate 1' fits snugly against the lower jaw and the loss of strength is reduced as a result of less deformation - only from the plate plane Y. The positive effects occur essentially when the arcuate plate 1 ' is produced without reshaping, so that the plates 1 'reach the surgeon in the arcuate geometry, but without prior bending.

FIGS. 3A to 3E In this series of figures, variously modified plates 1 'with an arcuate plate longitudinal axis Z are shown. All of the plates 1 'have a main segment 10' in the form of a circular arc, to which a lateral segment 11 'extends on the right or left or on both sides. The main segment 10 'is provided here, for example, uniformly with 16 screw holes 4 suitable for blocking. In the transition between the main segment 10 'and the lateral segment 11 "there is an angle segment 12', which is preferably reinforced in width in relation to the webs 3. The angle segment 12 'can be hole-free (see FIGS. 3B and 3D) or at least have a screw hole 4 (see FIGS. 3A, 3C and 3E). The lateral segment 11 'can extend straight (see FIGS. 3A, 13D and 3E) or curved (see FIGS. 3B and 3C) in the plane of the plate Y. The modification 3E shows a plate 1 'with an arc-shaped main segment 10' and a straight lateral segment 11 'with a reduced spacing of the 5 screw holes 4 shown, the intermediate angle segment 12 'has a screw hole 4. If a curved lateral segment 11 'is provided on one or both sides of the circular-arc-shaped main segment 10', the latter can have a bending radius which differs from the main segment 10 '.

The further sequence of figures 4A to 15B serves primarily to explain the special inventive engagement contour 8 for the blocking, which is optionally present in the screw holes 4.

Figures 4A and 4B

The pair of figures shows two typical applications of the bone plate 1 which can be blocked according to the invention, which together with bone screws 9 results in a plate-screw connection. Plate 1 is particularly suitable for osteosynthesis of a lower jaw fractured in bone compartments (see FIG. 4A). Another main application is in bridging a continuity defect, i.e. in the case of a missing piece of bone, the load must be permanently absorbed by plate 1 and stability must be established on the lower jaw (see FIG. 4B). Both pressing the plate 1 onto the periosteum and unintentional loosening of the screwed-in screws are to be avoided, so that solid blocking is particularly relevant here.

Figures 5A to 5E

To explain the function of the interlocking, the simplest form of the plate 1 is initially assumed schematically as an elongated, unbranched branch through which the plate longitudinal axis Z extends in a straight line. The plate 1 is composed of a plurality of plate members 2, which are each connected by webs 3. The webs 3 form waisted transitions between adjacent plate members. At least in some plate links 2, but preferably in each plate link, there is a screw hole 4. The screw holes 4 emerging on the underside of the plate 6 are surrounded by a spherical countersink 7 on the top side 5 of the plate. Inside screw hole 4 is the one that is now to be shown in detail Engagement contour 8.

The engagement contour 8 resembles a partial thread only at first glance; in fact the engagement contour 8 consists of contour valleys 80 extending on the wall of the screw hole 4 parallel to the plate plane Y and adjacent contour tips 81 alternating therewith. The contour valleys 80 and tips 81 ^″ run partially in the screw hole 4, that is to say to the edges of the engagement contour 8 so that there are uncontoured wall areas 82 in the screw hole 4. The countersink 7 has a depth in order to receive the screw heads countersunk. The diameter of the countersink 7 is larger than the clear width of the engagement contour 8. The distance between opposite contour troughs 80 and contour tips 81 is less than the distance between the opposite, non-contoured wall areas 82, so that the outlet 83 of the screw hole 4 on the underside of the plate 6 shows an elongated hole shape to this it be arranged so that the longitudinal extent of the outlet 83 lies on the longitudinal axis Z of the plate (see FIG. 5A) or assumes different angles to the longitudinal axis Z of the plate (see FIG. 5B). Correspondingly, the non-contoured wall regions 82 are distributed along the longitudinal axis Z of the plate or offset to it. In the first embodiment of the engagement contour 8 here, the contour valleys 80 and contour tips 81 form trapezoidal passages.

FIG. 6A At the top, the bone screw 9 has the screw head 90, which at the bottom is shaped like a box, complementary to the countersink 7 in the plate 1. In the screw head 90 there is a recess 91 that can be grasped from above with a screwing tool, for example a cross recess. Below the screw head 90 there is an interlocking thread 92, here designed as a trapezoidal thread - corresponding to the engagement contour 8. The two-start bone thread 94 is arranged along the screw shaft 93. The bone thread 94 has, for example, an outer diameter of 2.5 mm, while the outer diameter of the blocking thread 92 is significantly larger and is, for example, 3.2 mm. Figure 6B

Is the diameter of e.g. 2.5 mm on the bone thread 94 too small according to the previous screw 9, since the screw hole in the bone was drilled too large or the strength is insufficient, a modified screw 9 with a larger diameter can be used on the bone thread 94, which e.g. Is 3.2 mm. With this diameter, too, the bone thread 94 can be moved effortlessly through the engagement contour 8 in the plate 1. The wide trapezoidal flanks of the interlocking thread 92, on the other hand, lead to an interlocking with the engagement contour 8.

Figures 6C and 6D

Alternatively, the self-drilling screw 9 shown can be used for a lockable plate-screw connection, which also has a trapezoidal locking thread 92 below the screw head 90, from which the bone thread 94 extends. For example, the bone thread 94 has a maximum outside diameter of 2.5 mm and the blocking thread 92 has an outside diameter of 3.2 mm. The screw 9 according to FIG. 6D is additionally provided with a cutting groove 96 on the shaft tip 95.

Figures 6E. 6F and 6H

These screws 9 have a thread with pointed thread flanks which is uniform across the screw shaft 93 and which is used with the appropriately contoured engagement contours 8 in the plates 1 in the upper part as a blocking thread 92 and in the lower part as a bone thread 94. The screws 9 according to FIGS. 6E and 6H are single-start, the screw 9 to FIG. 6F is double-start.

Figure 6G

Here, a two-start screw 9 with round thread flanks on the blocking thread 92 and pointed thread flanks on the bone thread 94 is shown. Figures 7A to 7D

The engagement contour 8 in the plate 1 allows the screw 9 with the locking thread 92 to be screwed into the screw hole 4 both vertically (see FIG. 7A) and with an angular offset α in relation to the longitudinal axis Z (see FIG. 7B). A fully effective blocking occurs even when the screw 9 is positioned at an angle; the interlocking thread 92 also moves into the engagement contour 8. The non-contoured wall areas 82 at the ends of the engagement contour 8 with the longitudinal extent of the outlet 83 offer space for the inclined blocking thread 92 to approach. The screw head 90 comes to lie obliquely in the countersink 7 due to the inclined position of the screw 9. The practically full and seamless support of the screw head 90 in the countersink 7 results from the complementary spherical surfaces lying one on top of the other.

Bending plate 1 out of plate plane Y - i.e. over the surface (see FIG. 7C) - or in the plate plane Y - i.e. over the edge -, or twisting the plate 1 (see FIG. 7D), does not impair the functionality of the blocking. On the one hand, the substantial change in shape of the plate 1 takes place in the area of the webs 3 and, on the other hand, the engagement contour 8 does not lose its effectiveness due to a limited deformation.

Figures 8A and 8B

Here, the deformation caused by the interlocking between the engagement contour 8 and the interlocking thread 92 entering the latter is shown, which very effectively secures the screw 9 against unintentional loosening. Engagement contour 8 and interlocking thread 92 are not complementary to one another. The interlocking thread 92 has a helically extending thread tooth; with a two-start thread, two teeth. The engagement contour 8, on the other hand, consists of the contour valleys 80 and contour tips 81, which do not run at a pitch angle, as in the case of a thread as a helix. When the interlocking thread 92 is inserted between the contour tips 81, there is an intentional collision and mutual deformation. The interlocking thread 92 requires an additional helical internal thread and the horizontally running contour tips 81 brace against the retracting interlocking thread 92. As a result of this contrast, the interlocking thread 92 and the engagement contour 8 are deformed, that is to say, bending edges 920, 810, which are directed towards each other, occur on both of them, which when turning out Butt screw 9 against each other and thus form a significant resistance to unwanted loosening. When the screw 9 is unscrewed, a strong torque must be exerted in order to partially deform the bending edges 920, 810 and to overcome the increased frictional resistance. For the engagement contour 8, the preferred range of the vertical distance between repeating structures - the contour valleys 80 or the contour tips 81 - is between 0.5 mm and 1.0 mm. The contour valleys 80 can expediently be produced by milling so that the contour tips 81 remain between the milled contour valleys 80.

Figures 9A to 9D

The second embodiment of the engagement contour 8 is likewise formed from contour valleys 80 and contour tips 81, which are worked into the wall of the screw hole 4 parallel to the longitudinal axis Z of the plate and terminate at their ends in non-contoured wall areas 82. The special feature here is that on both sides of the longitudinal axis Z of the contour troughs 80 and contour peaks 81 lie opposite each other offset. In this way, the thread, which is uniform on the screw shaft 93, acts in the upper part as a blocking thread 92, the thread teeth of which engage behind the contour tips 81, while the lower part serves as a bone thread 94 for screwing into the bone. The dome-shaped screw head 90 sits in the spherical countersink 7.

Figures I QA to 10C

The third embodiment of the engagement contour 8 is composed of contour valleys 80 and contour tips 81 which extend within the screw hole 4 parallel to the longitudinal axis Z of the plate and are saw-shaped. Lay here the contour valleys 80 and contour peaks 81 on both sides of the longitudinal axis Z of the plate at the same height and terminate at the ends of the engagement contour 8 in non-contoured wall areas 82. The two-start screw 9 used in the local plate-screw connection also has a uniform thread through its screw shaft 93, the upper part of which engages under the contour tips 81 as a blocking thread 92 and whose lower part is provided as a bone thread 94 for screwing into the bone , The screw head 90 is in turn embedded in the spherical countersink 7.

Figures 11A to 11C

In this fourth embodiment of the engagement contour 8, the contour valleys 80 and the contour tips 81 have a rounded shape. Complementary to the rounded shape of the engagement contour 8, a screw 9 with a two-start locking thread 92, which is designed as a round thread, is used. The pointed, double-start bone thread 94 extends below the blocking thread 92. The rounded contour valleys 80 and contour tips 81 lie on both sides of the longitudinal axis Z of the plate at the same height with wall regions 82 which are uncontoured at the ends of the engagement contour 8. The blocking thread 92 comes with the contour valleys 80 and -peaks 80.81 in blocked engagement. The screw head 90 is 7 in the counterbore.

Figures 12A to 12C

The special feature of the fifth embodiment of the engagement contour 8 is that the contour tips 81 in the screw hole 4 are offset from one another by 120 ° each in the plate plane Y and are located in a step-like manner in relation to one another in relation to the plate plane Y. Contour valleys and peaks 80.81 have an angular shape. Corresponding to the engagement contour 8, the screw 9 used has a uniform thread running over its screw shaft 93, the upper part of which engages under the contour tips 81 as a blocking thread 92 and the lower part of which represents the bone thread 94. The spherical countersink offers 7 space for the screw head 90. Figures 13A to 13C

The clinical application of the plate-screw connection is shown using the example of a compression osteosynthesis. In the initial situation (see FIG. 13A), ie before the fracture is closed, eccentric bores 100 are made in the two bone compartments K1, K2 to be connected - in relation to the screw holes 4 in the plate 1. The distance between the bores 100 is greater than the distance between the screw holes 4 in the plate 1, which is brought into position with the bone gap X above the breaking point. The screw holes 4 have the engagement contours 8 and the counterbores 7.

To close the fracture (see FIG. 13B), screws 9 are introduced into the holes 100 through the screw holes 4 in the plate 1. First, still with protruding screw heads 90, the screws 9 are eccentrically fresh in the screw holes 4. As the screws 9 are screwed in deeper, the bone thread 94 penetrates deeper into the bores 100 and the spherical surfaces at the bottom of the screw head 90, in cooperation with the spherical shaped countersinks 7 in the screw holes 4, bring about the successive centering of the screws 9. At the same time, the locking thread 92 of the screws 9 begins to move into the engagement contour 8. When the screws 9 are centered, they are moved towards one another and take the bone compartments K1.K2 with them; the bone gap X begins to close.

In the end position (see FIG. 13C), the screw heads 90 are maximally embedded in the counterbores 7 and the screws 9 are centered to such an extent that the bone gap X is completely closed. The bone compartments K1.K2 are now pressed together. The blocking is produced between the blocking thread 92 of the screws 9 and the engagement contours 8; the screws 9 are thus secured against unintentional loosening.

Figures 14A to 14D

The two screws 19 shown (see FIGS. 14A and 14B) have no locking blocking thread 92. The screw 19 from FIG. 14A, for example with an external thread diameter of 2.5 mm, is too weak to block with the engagement contour 8. In the case of the screw 19 from FIG. 14B, with a larger external thread diameter of, for example, 3.0 mm, an undercut 97 is provided below the screw head 90, so that there is no locking thread 92 here either. These screws 19 without interlocking thread 92, ie only with the bone thread 94, can also be used together with the plate 1, which has engagement contours 8 in its screw holes. Blocking does not occur here, as may be desired in the specific application (see FIG. 14C). Without problems, the screw 19 can also be inserted at an angle without the blocking thread 92, together with the plate 1 (see FIG. 14D).

FIG. 14E This illustration shows a lag screw osteosynthesis with the plate 1 which can be locked according to the invention and a conventional screw 19 without locking thread 92. The screw head 90 is supported obliquely in the screw hole 4 and the screw shaft 93 projects through the two bone compartments K1, K2, which are pressed against one another should. In the upper bone compartment K1 there is a through hole 101 with the width that the bone thread 94 cannot grip. A bore 100 with a reduced diameter has been provided in the lower bone compartment K2, where the bone thread 94 engages. When screw 19 is screwed in, lower bone compartment K2 is pulled towards upper bone compartment K1. The engagement contour 8 does not come into play here; the thin screw shaft 93 projects through the engagement contour 8 without entering into a blockage.

FIGS. 15A and 15B. For the sake of completeness, the two figures are intended to illustrate that small fragment screws 29, for example with an external thread diameter of 2.0 mm, can also be inserted vertically or obliquely into the plate 1. The small screw head 90 is deeply supported in the screw hole 4 and the engagement contour 8 remains without function. Such small fragment screws 29 with a screw shaft 93 protruding from the outlet 83 and the bone thread 94 serve for attaching smaller bone fragments.

Claims

claims

1. Contoured bone plate (1 ') with: a) a plurality of plate members (2) which are connected to one another by waist-shaped webs (3) and lie in the unbent state on a plate plane (Y); b) at least in some plate members (2) each have a screw hole (4); and c) through the screw holes (4) insertable bone screws (9) for fastening the bone plate (1 '), characterized in that. d) the longitudinal axis (Z) of the bone plate (1 ") extending in the plane of the plate (Y) is at least substantially circular.

2. Contoured bone plate (1 ") according to claim 1, characterized in that through the circular arc-shaped plate longitudinal axis (Z) between the central axes (Z-) of the webs (3) and the central axis (Z ₂ ) of the adjacent screw hole ( 4) a dislocation (β) with, for example, 1 ° <β> 10 ° and preferably β = 2.5 ° results.

3. Contoured bone plate (1 ') according to claim 1 or 2, characterized in that a) all or individual screw holes (4) are designed as cylindrical standard screw holes (40) or as directionally oriented compression holes (41); wherein b) alternatively all or individual remaining screw holes (4) have an engagement contour (8) for blocking the bone plate (1 ') by means of a blocking thread (92) provided on the bone screw (9); and c) the individual bone screw (9) has a screw head (90) which is thickened in diameter, which has interlocking threads (92) underneath and a bone thread (94) which is at least partially over the

Screw shaft (93) extends, which has a smaller cross-sectional diameter than the screw head (90).

4. Contoured bone plate (1 ') according to one of claims 1 to 3, characterized in that the bone plate (1') a) consists of a main segment (10 ') with an arcuate plate longitudinal axis (Z); and b) one or both sides of the main segment (10 ') attaches a lateral segment (11'), which also extends in the plate plane (Y) and is straight or curved; wherein c) the transition between the main segment (10 ') and the lateral segment (11') is formed by an angle segment (12 ') extending in the plate plane (Y).

5. Contoured bone plate (1 ') according to claim 4, characterized in that a) the angle segment (12 ") aa) is hole-free; or ab) has at least one screw hole (4) which has a standard cylindrical screw hole (40) or is a directionally oriented compression hole (41) or has the engagement contour (8) for blocking; and ac) is preferably reinforced compared to the webs (3) connecting the plate members (2); and b) the lateral segment (11 ') with screw holes (4) is provided, alternatively here: ba) all or individual remaining screw holes (4) as cylindrical

Standard screw holes (40) are formed; or bb) all or individual remaining screw holes (4) as directional

Compression holes (41) are formed; or bc) all or individual remaining screw holes (4) have the engagement contour (8) for blocking.

6. Contoured bone plate (1 ') according to one of claims 1 to 5, characterized in that the arcuate shape of the bone plate (1') is produced without reshaping.

7. Contoured bone plate (1 ') according to one of claims 1 to 6, characterized in that a) the bone plate (1') is configured for substantially horizontal, U-shaped encirclement of the human jawbone, in particular the lower jaw; wherein b) the ends of the bone plate (1 '), which consists only of a main segment (10') or one or two additional lateral segments (11 '), are dimensioned to reach over at least one ascending jaw branch.

8. Contoured bone plate (1 ', 1) according to claim 3 or 5, characterized in that a) the engagement contour (8) consists of contour valleys (80) and adjacent contour tips (81) which are arranged at least substantially horizontally and partially circulate around the wall of the screw hole (4); where b) related to the height to the plate plane (Y), it between a contour valley

(80) and the next contour valley (80) and between a contour tip

(81) and the next contour tip (81) there is no alignment in the sense of a thread.

9. Contoured bone plate (1 ', 1) according to claim 3, 5 or 8, characterized in that the screw hole (4) a) on the plate top (5) a dome-shaped countersink (7) for partially receiving the lower part of the screw head ( 90) and the centering of the bone screw (9); and b) is slot-shaped on the underside of the plate (6) at its outlet (83).

10. Contoured bone plate (1 ', 1) according to claim 3, characterized in that the blocking thread (92) of the bone screw (9) a) one or more threads; and b) has a different or the same geometry as the bone thread (94); wherein c) the bone thread (94) is self-drilling and / or self-tapping can.

11. Contoured bone plate (1 ', 1) according to claim 8, characterized in that the contour valleys (80) and the contour tips (81) are in the direction of the longitudinal axis of the plate (Z) or at an angle thereto.

12. Contoured bone plate (1 ', 1) according to one of claims 3, 5 or 8, characterized in that the engagement contour (8) a) is similar to a pointed, round, trapezoidal or saw thread; and b) is preferably generated by milling.

13. Contoured bone plate (1 ', 1) according to one of claims 3, 5, 8 or 12, characterized in that the engagement contour (8) a) runs out at the horizontally located ends, whereby there in the screw hole (4) uncontoured Wall areas (82) remain; and b) the non-contoured wall areas (82) preferably lie on the theoretical main axis of the screw hole (4) which is elongated in the area of the engagement contour (8).

14. Contoured bone plate (1 ', 1) according to one of claims 1, 3 or 9, characterized in that in the screw holes (4) the bone screws (9) vertically or with an angular offset (α) in relation to the longitudinal axis of the plate (Z) and plate level (Y) can be used.

15. Contoured bone plate (1 ', 1) according to claim 3, characterized in that during the blocking on the blocking thread (92) and on the engagement contour (8) by bending edges (920, 810) are created, which provide increased protection against the loosening of the bone screw (9) effect.

16. Contoured bone plate (1 ', 1) according to claim 8 or 11, characterized in that the vertical distance between adjacent contour valleys (80) and contour tips (81) is preferably in the range between 0.5 mm and 1.0 mm.

17. Contoured bone plate (1 ', 1) according to one of claims 3, 5, 8, 9, 11, 12 or 13, characterized in that in the screw holes (4) with the engagement contour (8) for blocking also bone screws (19 , 29) can be used vertically or at an angle without an interlocking thread (92).