WO2015117207A1

WO2015117207A1 - Tightening joints for versatile modular systems for osteosynthesis

Info

Publication number: WO2015117207A1
Application number: PCT/BG2014/000006
Authority: WO
Inventors: Stanislav Georgiev Nestorov
Original assignee: Stanislav Georgiev Nestorov
Priority date: 2014-02-06
Filing date: 2014-02-06
Publication date: 2015-08-13
Also published as: BG112250A

Abstract

The invention provides improved tightening joints for elements of versatile modular systems for osteosynthesis designed for orthopedics and traumatology as well their application. The tightening joints of the invention are three as the second and third are embodiments of the first joint. In the first tightening joint (Fig. 4) a rotational wedge-shaped body called clamp is moved along the hole in the other body and pressed against a rod inserted in a cross hole, which intersects the first hole. In the second tightening joint, the clamp is formed as a hemispherical nut in which is screwed the threaded shank of the bone screw, previously screwed in a bone fragment (Fig. 6). In the third tightening joint, the clamp is formed as a sphere having slots (Fig. 7). The versatile modular system for internal osteosynthesis includes bone screws, rods and plates which can be mounted on the rods. The versatile modular system for external osteosynthesis includes bone screws (pins), rods, screwholders and connection modules.

Description

TIGHTENING JOINTS

FOR VERSATILE MODULAR SYSTEMS FOR OSTEOSYNTHESIS

TECHNICAL FIELD

5 The invention refers to the field of medical inactive implantable devices category 7 by ISO 15225, used in orthopaedics and traumatology and particularly to tightening joints for elements of versatile modular systems for osteosynthesis. On the basis of the proposed technical solutions for tightening are designed versatile modular systems for internal osteosynthesis and for lOexternal osteosynthesis.

These systems allow the construction of frames that are mounted inside the body or outside of it. By means of these frames one can reduce and fix the bone fragments in fractures. Furthermore, the systems allow construction of composite frames for both external and internal fixation as well as frames

I5which combine supraperiostal and intramedullary mounting of the fixing elements.

BACKGROUND ART

In surgical treatment in orthopedics and traumatology usually are used devices that connect bone fragments in proper alignment and help the healing 0or correcting of injured bone tissue. This method of treatment is referred to as osteosynthesis. There are two main types of systems for osteosynthesis - internal (implantable) and external fixators.

I. Systems for internal osteosynthesis

In the theory of internal osteosynthesis are formulated four basic 5principles which are still considered valid and taken into account in the design of osteosynthesis means: anatomic reduction; stable fixation; preservation of blood supply; early active mobilization. A variety of different means and methods of internal fixation exists, among which the most similar in features to the system of internal osteosynthesis of the invention are plates and rod (bridge) modular systems.

Plates are widely used in osteosynthesis. A plate is a strip of 5biocompatible metal in which at least 4 holes are made. In the holes are placed screws with spherical head that are screwed into the bone tightening the plate to the bone corticalis. A steady structure is created that keeps bone fragments in proper position until the fracture heals.

To better conform to the principles of osteosynthesis, the plates have lObeen enhanced resulting in different types of plates:

• Traditional plates also called Dynamic-Compression Plates (DCP) because they can perform compression along the axis due to the special geometry of its holes.

• Limited Contact Plates (LC plates) on whose lower side (to the bone) l5grooves or holes are made formed in different ways by different companies.

The objective of this design is to provide minimal contact between the plate and the underlying bone so as to reduce trauma of the vascular system and to provide fast indirect healing through the callus. A variant of this embodiment are supraperiosteal plates which are arranged above the periosteum (the veil 0of the bone).

• Reconstruction plates have deep notches on the edge of the plate. These notches are situated between the holes and allow accurate contouring of the plate in all planes. These plates are especially useful in in case of bone fractures with complex 3-D geometry, such as the pelvis, acetabulum, distal 5humerus, distal tibia, and clavicle.

^• Locking plates (LCP - Locking Compression Plate). Conically threaded undersurfaces of the screw heads fit matching threads in the plate, allowing the screws to be mounted obliquely and effectively bolt into the plate and bone. As a result these plates provide stability against twisting of the bone 0fragments, and also allow load to be more evenly distributed along the entire construction rather than being concentrated at a single bone-screw interface, with an increased risk of fracture as with traditional plates. In some recent designs of piates (LC-DCP) all the positive features of the described types of plates are combined: dynamic compression, limited contact and locking screws as in the plates are made combined holes.

Despite all the improvements, the plates have a number ofdisadvantages:

• DCP plates have not limited contact, can not easily adapt their shape to the bone and do not provide good angle stability;

• LC plates still have a relatively large contact with the bone;

• reconstructive plates have limited options to change their shape, as their strength decreases at sharp curves;

• The head of bone screw and plate holes of LCP plates have complicated design, which makes them expensive. The angle of inclination of the screw is limited. Operational technology of mounting of the locking plate is complicated and difficult to implement: one has to use special guiding tools to insert bone screws; proper screwing the screw heads into the plate is difficult and sometimes impossible task;

• a huge collection of different plates is created to match the shape and dimensions of the wide variety of bone fragments, which further increased by the individual anatomical differences; hospitals must keep all these plates in sets;

• because the screw holes in the plates are prefabricated, it imposes a restriction on locations of mounting of the screws in the bone, which may sometimes be unsuccessful, particularly in unstable, spiral and other complex fractures.

To overcome the shortcomings of the plates rod (bridge) osteosynthesis systems are designed which include the system of the invention. The idea of the rod system is the monolithic plate to be substituted with modular elements (also called holders or screwholders) connected on the one hand with thesupporting rods, and on the other side - with the bone by means of screws (Fig. 1 ). An osteosynthesis rod system is known [1], in which the plate is fixed by means of bone screws whose heads are spherical and have tapered threaded section ( Fig. 2). In the final stage of screwing the screw's head starts to be screwed into the threaded hole in the bottom of the plate. Accordingly, the 5spherical part of the screw head contacts the bed in the upper part of the plate's hole and to the rods in the cross holes of the plate. As a result of screwing of the screw head in the plate, the upper side of the plate is comes near to the bottom side, clamping the rod (rods). At the same time, the head of the screw abuts the rods tightening them further. In one embodiment, the plate lOhas an extension with additional holes for bone screws aimed at fixation of fragments in the distal part of the bone. The system under consideration has the following disadvantages: nonstandard screws with considerably complicated structure and manufacturing technology are used; the screws can not be screwed obliquely; the thickness of the plate is increased because of

I5the threading into the lower part of the plate, the versatility of the system is reduced due to using of the special plates for distal sides of the bone.

It is known also the rod system for the internal fixation from [2]. It uses screwholders, which are formed as clamps tightened on a single rod. They use a clamping force of the screw to the bone. When screwing the bone screw into 0the bone fragment, the lower part of the bracket abuts against the bone, while the upper side comes near to the bottom side under the influence of the screw head. Consequently, the clamp is clamped to the shaft. In order to achieve axial fixing, the end of the rod has a protrusion, which grips the dedicated notch of the end clamp. Disadvantages of this system are: it can only work 5with one rod; it does not allow the construction of more complex spatial structures; bracket has a complex shape hampering technology of manufacturing; installation and moving of the clamp on rod requires a special tool to hold it open; restricted angle of tilt of bone screw (up to 5°).

II. Systems for external fixation (external osteosynthesis) 0 The external fixation is a method of remote osteosynthesis, which is realized by placing the pins or screws into the bone above and below the fracture line, connected together outside of the human body through the support structure, referred to as an external frame.

In orthopedic practice are known many systems for external fixation with various designs. One widely used class of fixators in this area represents rod 5(bridge) systems joined by a common feature that have screw holders connected by carrying rods. This class refers to the external system for osteosynthesis of the present invention.

It is known an external rod fixator of [3], including the following modules: rods, compressor-distractor tube, dynamical tube, connector "pin to rod", lOconnector "rod to rod", and connector "tube to rod". Similar in function to the system of the invention are connectors "pin to rod". In the fixation system there are two types of such connectors. One type consists of two plates, which are tightened to each other by pins at both ends. In the two plates are made semicircular grooves, which form 5 or 10 openings for the bone pins when the l5parts are coupled together. Upon tightening of the two parts the pins are pressed between them. Perpendicular to the pin holes there is a clamping joint for the rod, which is generally similar in the principle and design to the joint for tightening the pins. The other type of connectors "pin to rod" is composed of 4 parts, which have a central hole in which a screw is placed. One pair of the 0parts has a transverse hole consisting of two halves, in which the bone pin is tightened, and the other pair has a hole of two halves, in which the rod is tightened. The principle of tightening of this connector is similar to the first type connectors, but in contrast to it tightening is done by the central screw. Each pair of parts has a joint formed as a notch and a protrusion which prevents the 5rotation of the two parts relative to each other while maintaining the mutual arrangement of the two halves of the hole. The two pairs may be rotated about the center pivot to any angle relative to each other, providing a variety of angles between the rod and the bone screw. Furthermore, around the central axis there is a spring which creates a pre-tightness in the jaws so that the rod 0and the pins can not slip out of the openings.

This system of external fixation has the following disadvantages: the connecting modules and the frames constructed with the help of these modules are bulky; the complex design of the modules, which increases their cost; for tightening of bone pins and rods in modules with 5 or 10 holes are used as many as 4 screws which slows down and makes difficult their installation and final fixing as well their disassembly; the pins cannot be tilted 5in different directions relative to a screwholder.

It is known also a fixation system of [4]. The module for connection of the screw and the rod consists of two pairs of jaws, one of which clamps bone screw (screws), and the other - the rod. Parts of each of the two pairs are provided by protrusion and notch against mutual rotation. The two pairs of lOjaws can be rotated relative to one another round the central axis, providing a variety of angles between the rod and the bone screw. Differences compared to the design of abovementioned system [3] are: tightening is carried out by eccentric rather than a screw; the screwholder has openings for two screws, not just one. The disadvantages of the system of [4] are as follows: l5complicated and bulky components; it doesn't allow installation of angled bone screws. Furthermore, since the screwholder can be connected with only one rod, the use of thicker rods is required (12 mm for the lower limbs, 9 and 6 mm for the upper limbs). The system has insufficient reliability of fixation, as clamping joints with eccentric come loose during cyclic loading.

20 It is also known a bridging external fixation system of [5] and [6]. In one embodiment (Fig. 3) in the central hole of the screwholder body a plastic sphere with slots is mounted, on which the clamping screw leans. There is a central hole in the sphere, which has a diameter greater than the diameter of the bone screw. The bone screw is placed in the central hole of the sphere.

25The slots of the sphere are parallel to the axis of the hole and reach the middle of the sphere and their bottoms are cross and perpendicular to the axis. Upon tightening the clamping screw in the body of the screwholder, the screw presses the sphere by the (its) screw's inner conical surface to the spherical bed of the body. This tightens the sphere and makes it to shrink due to the 0slots tightening the bone screw. Simultaneously, the clamping screw presses with its outer conical portion the two rods. An important advantage of this solution is the possibility of spatial tilting of the bone screw in all directions. One disadvantage is its unreliable tightening because the surface of the clamping screw cannot press simultaneously each of the two rods and the sphere and at the same time the sphere to tighten the bone screw.

It is known [7] external fixator for trochanter-lateral fractures. This fixator 5includes a plate with at least four through elongated slots, screwholders connected to the plate and bone implants (screws or pins). The screwholder comprises a body, a nut for tightening the body to the rod, a sphere mounted in the body, pressing washer with a spherical bed and a threaded bush for the clamping of the washer. The sphere has a central hole for implant screw and lOslots which allow it to shrink. When screwing the threaded bush clamping of the sphere is performed between the spherical beds of the body and the washer. As a result, under the action of wedge forces the sphere shrinks due to the slots on the periphery and tightens the pin. A disadvantage of this construction is that the change of location of screwholders is limited by the

I5size of the plate and slots in it. This restriction determines the specialized use of this fixator for a certain type of fractures.

Reference:

1. http://www.walkman.com.cn

2. http://sites.synthes.com/MediaBin/lnternational%20DATA/036.000.550.pdf 0 3. http://www.osteosynthesis.stryker.com/medias/pdf/

hoffmann2_brochure_50751000c2109.pdf

4. http://intl.orthofix.com/uploads/contentUpload/GF-1101-OPT-E0.pdf

5. Patent DE 3611319 C2 /1 1.02.1988.

6. US patent 4,920,959 /1.05.1990.

5 7. Patent BG 66193

DISCLOSURE OF INVENTION

The main objective of this invention is to provide reliable, compact, technological and easy to use joints for tightening of elements of the versatile modular internal and external system for osteosynthesis used in orthopaedics 0and traumatology. The further object of the invention is to propose design of novel versatile modular rod system for internal and external osteosynthesis based on the proposed tightening joints. The systems are meant to possess better qualities than those of cited similar systems, to add new functionalities and to improve 5some important features such as: manufacturability; low cost; versatility; ability to use all standard bone screws; reliability; ease in installation; abatement of trauma patients.

1. Tightening Joints

The first tightening joint, proposed for use in osteosynthesis systems lO(Fig. 4) includes a main body 1 , in which there are at least two cross holes which intersect, so that they have a common part. At the hole A of the main body is placed with a small clearance second body 2 with a cylindrical or prismatic shape (which will be provisionally called "Rod"), in the other hole B - third body 3 (which will be provisionally called "Clamp") having rotational isshape which is wedge-shaped in the area C, which contacts to the second body. The body 3 can be moved along the hole B with a small clearance. The second and third body are able to touch each other, whereas contact surfaces may be smooth or have a surface that has been treated in a special way in order to improve the cohesion and retention: nurling, furrowing, faceting, etc. 0 Upon compression of the Clamp to the Rod, because of the wedge shape of the Clamp, it pushes Rod towards the walls of the hole and jams it. Thus the simultaneous tightening of all three bodies is carried out. If the wedge portion C has a spherical shape, the Clamp is able to be inclined relative to the axis of the hole in which it is moved, before final tightening. It is an essential 5feature of the proposed joint in terms of its application in systems for osteosynthesis.

An example for the application of the first tightening joint is a plate, involved in system for internal fixation (Fig. 5).

The second tightening joint used in the invention (Figure 6), 0represents an embodiment of the first tightening joint, where the Clamp 3 has at least one threaded hole E, in which is screwed the threaded shank C of the bone screw 4 previously screwed into the bone fragment 6. The screw is provided against rotation relative to the main body B. When the Clamp 3 is rotated in an appropriate direction, the screw moves linearly, and pulls the bone fragment 6 till it contacts to the other bone fragment 5, which supports 5the base body 1 , wherein the clamping is carried out simultaneously on all objects including bone fragments.

An example for application of the second tightening joint is a plate used in the system for internal fixation of condylar fractures (Fig. 6).

The third tightening joint used in the present invention (Fig. 7), lOrepresents a further embodiment of the first tightening joint, wherein the Clamp is made of a resilient material and has a wedge shape at least at one end, which is faced towards rods. There is at least one hole in the Clamp and one radial slot just reaching the hole and located in a plane passing through the axis of the opening. The purpose of the slot is to allow an elastic compression l5of the body and respectively - of the hole under the action of the opposite radial compressive forces perpendicular to the slot. To improve the shrinkage there is an embodiment in which the body has at least one additional slot, which is also located in a plane passing through the axis of the hole, but it is blind, i.e. a thin wall remains between the hole and the slot. In the hole of the 0Clamp fourth body is closely inserted. Upon compression of the Clamp to the Rod, the Clamp shrinks under the action of forces of the wedge and acts as a collet body toward the fourth, whereupon all the other units are tightened simultaneously.

If the Clamp is made with spherical shape it is able to be inclined 5relative to the axis of the hole, in which moves, before final tightening.

An example of the application of the third tightening joint is the screwholder used in the system of external fixation.

On the basis of the disclosed in the invention three types of tightening0joints and the used therein principles of clamping elements, in the present invention are implemented versatile modular system for internal osteosynthesis and versatile modular system for external osteosynthesis. 2. Versatile Modular System for Internal Osteosynthesis

In one embodiment of the above-mentioned tightening joints a versatile modular rod system for internal osteosynthesis is created (Fig. 5), which includes a bone screw 3, at least one carrying rod 2, and at least one plate 5(screwholder) 1 capable to move along the rod, in which can be positioned at least one bone screw (in practice usually at least 4 plates have to be used). According to the invention, bone screws can be all kinds of standard bone screws with a hemispherical head which can be in accordance with the functional purpose: cortical, cancellous, malleolar, etc. Some of them can be lOcannulated. Non-standard screws with hemispherical, conical or other rotational body heads, as well bone screws with coupling nuts. Standard bone screws, regardless of their type, have an element that unites them - the hemispherical head. The use of screws with spherical heads allows the screws to be fixed in the screwholder angled, which is an important advantage of the

I5system. According to the standard ISO 5835-1991 heads of the bone screws are only 5 sizes with diameters 3, 4, 5, 6 and 8 mm. This allows you to create limited nomenclature of plates consistent with these diameters.

The carriers are rods with any cross section (usually circular). The axis of the rods may be in the form of any 3-D curve, and is usually contoured for 0optimal anatomic fit prior to and/or during surgical operation. In one embodiment the rod is U-shaped with a center distance of the parallel arms equal to the center distance of the holes in the plates (Figure 10 and Figure 1 ). In another embodiment, the bar is furrowed with annular grooves of semicircular cross-section (Fig. 9). The bone screw head is supported by 5these channels and thus axially fixing of the rod is carried out.

According to the invention (Fig. 5) each plate 1 is a monolithic body (usually in rotational or prismatic shape) having a central hole A for insertion of the bone screw 3, and at least one hole D for receiving the carrying rod 2, which intersects the central hole so that they have a common part. In the 0operational state, the rods and bone screw are placed in the plate and rods contact with the screw head B. In one embodiment (Fig. 6) an extension A of the Dlate ir> formed along the axis of the bone screw 4, which guiding the screw. At the hole B of the extension a feature is formed preventing rotation of the screw relative to the extension. The screw 4, for use in this type of plates is cancellous, and its

5shaft C has a design which ensures the screw against rotation. In one embodiment, the element which prevents rotation of the bone screw is at least one bevel along the shaft of the bone screw and the screw hole in the extension of the plate has a profile which corresponds to the profile of the shaft of the screw. The shank E of the screw is threaded. On the shcirik is screwed lOnut 3 with a hemispherical surface F faced to the plate. The nut 3 contacts through the common part of the holes G and H with rods 2. The bone screw is pre-screwed into the bone fragment 6, the shank, which hcis a smaller diameter than the screw part, passes freely through the opening of the fragment 5. When tightening the nut 3, it abuts against the rod and pulls the

I5screw together with bone fragment 6 until the two fragments 5 and 6 contact. Simultaneously the rods are tightened in the holes of the plate and the face I of the plate abuts against the surface of fragment 5.

Advantages of the system for osteosynthesis of the present invention

System complies fully with the four basic principles of osteosynthesis 0and can perform all the functions of known types of osteosynthesis plates and rod systems for internal osteosynthesis introducing the following improvements:

^• high reliability - the principle of tightening proposed in the invention provides firmly fixing of the bone fragments and elements of the system, 5without risk of loosening the connections, scroll or slip of the components throughout the entire treatment period; it is proved by the corresponding mechanical testing of the invention;

^• a small number of types of versatile modules with simple design and manufacturability;

0 · utilizes all kinds of standard bone screws with a hemispherical head; • versatile system requires less inventory - it is not necessary to maintain a large stock with several sets of all of the numerous types of plates;

• the plates (screwholders) and the bone screws can be positioned anywhere on the rods, for optimal anatomic and fracture fit; simplified

5installation and moving of the screwholders which does not require special tool;

• modeling of the right frame for the right indication my means of cutting and unlimited bending of the rods according to the bone before or during surgery;

10 · opportunity to build stable and reliable frames when using U- shaped rods, on which are mounted plates with two holes;

• the possibility of creating multiplane locking frames where some of the plates are mounted only on one arm of the paired rod or mounted on a single rod; it enables a local strengthening of the bone fragments by the addition of l5the lateral rod and place aside of a portion of the screws in the additional plane; that frames are applied in the treatment of loaded bones and complex fractures;

• in comparison with interlocking plates larger angles of tilt of bone screw (cone angle of 40 ° against the plates - 25-30°);

0 · due to the possibility of tilt screws the frame provides: stability of the structure against rotation (self-locking); stability, because the screws can come very close to the fracture; fixation of more complex fractures;

^• the built devices are supraperiostal with much smaller contact area than LC plates, because contact with bone is only a narrow area of the plates 5while rods are over the bone;

^• between each 2 plates can be produced not only the compression (compare DCP plates), but the distraction;

^• compression in another plane can be done - by means of special screwholder with extension, in which screw with threaded shank and 0hemispherical nut is placed;

^• possibility to create devices that combine supracortical and intramedullary osteosynthesis; • using furrowed rod with annular grooves ensures reliable axial fixation;

• easy building and mounting of various osteosynthesis devices; operational technology is similar in complexity to plates, while no restrictions on the freedom of choice of the surgeon caused by limitations of technical

5means;

• can be used with both open and with minimal invasive techniques. The possibility exists to install the devices through small partial sections in the places where the plates with screws are mounted, not by a complete cut.

• reducing the trauma of the surrounding soft tissue, since the lOdimensions of the members can be smaller at the same strength of the structure; the dimensions are comparable with those of the plates of a similar purpose.

The above and other features and advantages of the invention are disclosed in the examples of embodiment, with reference to the enclosed I5drawings.

3. Versatile modular system for external osteosynthesis

In one embodiment of the use of the disclosed tightening joints a modular rod system for external fixation of bone fractures is created, which allows the building of a wide variety of devices having versatility as regards the

20shape and configuration of the device, the number and mutual positions of building modules and bone screws.

These problems are solved by means of a modular system comprising at least one carrying rod or a pair of rods, at least one holder of bone screws (pins), which can be mounted on rods (Fig. 7), bone screws, corresponding in

25number of holders, modules for connecting rods in different planes and angles, modules using ball-and-socket joint to connect rods to other systems for external fixation.

The holder of the bone screws (Fig. 7) includes a body 1 with at least one stepped hole A, whose wide portion ends with thread C, and at least one 0cross hole B for a rod, located near the narrow end of the stepped hole. The stepped hole and the rod hole intersect, so as to have a common part. At the wide end of the stepped hole of the body 1 are mounted washer 7, which abuts against the rods, a sphere with slots 3, washer 6, which presses the sphere, and the clamping screw 5.

The clamping screw 5 has a thread corresponding to the thread of the stapped hole of the body, a central hole G, through which bone screw passes and can be tilted and the features, allowing to be rotated and screwed by means of a wrench. Clamping washers 6 and 7 have a spherical or conical bed H. The beds are oriented to the sphere and touch it. Clamping washer 7 has a bevel I, touching the rods.

10 Sphere with slots 3 has a central hole for the attachment of a bone screw or pin 4. The hole has a diameter slightly larger than that of the shank of the bone screw (pin), allowing ease of insertion into the hole, but with a minimum clearance. There is a slot F in the sphere, which reaches its central hole. The slot lies in a plane passing through the hole. There may be other isslots E, which are placed in similar way, but between each of them and the central hole F remains a thin wall. These slots provide an elastic shrinking of the sphere under pressure from outside. Because the sphere works as a collet, further somewhere in the statement it will be referred to as a spherical collet.

0 When tightening the screw 5, it presses by means of the washer 6 the sphere with slots 3 to the washer 7, and through it - the rods 2 in the holes B of the body 1. Since the sphere is located between the two openings, formed as a slant -bed, under the action of forces of the wedge, it shrinks and tightens firmly inserted bone screw 4. When the screw 5 is loose, the spherical collet 3 5can rotate freely, allowing the mounted implant screw 4 to tilt in all directions. Besides, the screw holder can be slid on the supporting rod (rods) 2 so as to take up the required position.

The carrying rod can be of various profiles and have different spatial shapes of its axis. In one preferred embodiment, the axis is U-shaped, with the0center distance of the arms corresponding to the position of the holes in screwholder. In another embodiment (Fig. 6), on the ends of the rods 2 a brace 1 is placed. The purpose of this brace is to strengthen construction, to make safe the protruding ends of the rods and to give aesthetic appearance of the device. In brace are made 2 holes whose center distance is equal to the distance 5between the rods. To hold the brace, at the ends of the rods is shaped groove B, and within the bracket are mounted ball 3 and spring 4. When the brace is installed on the rods, under the pressure of the spring 4 the balls 3 enter in the grooves B of the rods 2, to provide retaining of the brace. To be easy to insert the rods 2 in the holes of the brace 1 while pushing the balls 3, the ends of the lOrods are formed with a chamfer A. This arrangement ensures the easy and fast assembly and disassembly of the brace, so that on the rods to be placed or removed screwholders or connecting modules.

In another embodiment, the system uses a pair of rods 1 fixed in the holes of the connecting module with the ball 6 and nut 3 with a spherical bed l5(Fig. 17). This module allows the system to be connected to other systems which include modules with spheres and spherical beds, as the ones mentioned in patents BG 61553 B1 / 08.04.94 and BG 100 328 / 31.01.96.

In another embodiment of the system (Fig. 21 ) the connection module is used for connecting of rods with other rods or implant screws/pins. This 0module consists of two bodies 1 and 4, which are connected with screw 3 and the nut 6. Each body has at least one hole located crosswise in relation to the hole of the connecting screw. In this hole a rod or implant screw/pin is placed. The holes are situated in such a way that the hemispherical head of the screw 3 and the hemispherical surface of the nut 6 can touch the surface A of the 5bone screws or rods placed in the cross hole (holes). The nut is secured against rotation when tightening. In a loosened condition of the screw 3 the bodies can be rotated relative to one another, changing the angle between the rods placed in the holes. When tightening the screw into the nut, the spherical surfaces of the nut and the screw head press the rods in the holes, at the 0same time are pressed against the two bodies. Thus all the parts are simultaneously tighten.

The advantages of this module are possibilities for: • fixing of the rods to one another at any angle

• create different combinations of rods and screws, or simply by rods;

• combining the rods and screws of different diameters.

In another embodiment of the system, the supporting rod is placed in the Scentral hole of the spherical collet, and in two transverse holes are placed bone screws or pins (Fig. 22).

The disclosed embodiments of the elements of the system in the present invention allow devices to be constructed similar to known external systems, as well devices with a novel functionality.

0 The system provides versatility that makes it applicable for fixation of fractures of all types of bones, including complex fractures that are difficult or impossible to be fixed with other similar devices. Moreover, the devices built with the elements of the system have important for operational technology qualities like easy assembly of the appropriate device, easy and quick5installation of the device on the bone, reliable fixture, less weight and more.

The positive features of the proposed system for external fixation are:

• the rods may be bent to the required shape and be cut to the required length before or during surgery;

• the screwholders and the bone screws can be positioned anywhere on0the rods, for optimal anatomic and fracture fit;

^• prior to final tightening of the screwholders to the carriers it is possible to perform compression or distraction between two fragments of the bone;

^• screw can be angled up to 20° independently of the other screws;

^• fast and reliable simultaneous tightening of the pin, screwholder and5rods, guaranteed by the consecutive chain of all the tightened details;

^• screwholder can be rotated at any angle (0 to 360°) round the axis of rod when it is mounted on the one rod only;

^• ability to implement different types monofixators: single arm; two arms and rigid spherical connection between them; two arms and compressor- distractor connected them using ball-and-socket join; • ability to build complex spatial structures of external fixators made of screwholders, rods and connecting modules, including modules with spherical connection,

• ability to implement a device for combined internal and external 5fixation;

Other features and advantages of the invention are disclosed in the examples of embodiment, with reference to the enclosed drawings.

BRIEF DESCRIPTION OF DRAWINGS

10 The enclosed drawings in Figures 1 to 3 show the constructions of the background art, where:

- Figure 1 shows the concept of transition from plate to rod system;

- Figure 2 shows a prior design of a bridged system for internal fixation;

- Figure 3 shows the construction of the screwholder from prior bridging l5external fixation system - US Patent 4,920,959;

Figures 4 to 7 show exemplary embodiments of the types of tightening joints of the invention where:

- Figure 4 shows a sectional view of the tightening joint of a first type;

- Figure 5 shows a sectional view of the assembly of an internal system 0for osteosynthesis, which is an embodiment of the tightening joint of the first type;

- Figure 6 shows a sectional view of the tightening joint of the second type;

- Figure 7 shows a sectional view of the tightening joint of the third type; 5 Figures 8 to 12 show embodiments of frames for internal fixation using modules from system for internal fixation of the invention.

- Figure 8 shows a sectional view, which illustrates the limited contact of the plates and rods with the bone shown in the transverse and longitudinal direction;

0 - Figure 9 shows a 3-D drawing of the device for internal fixation with one furrowed rod; - Figure 10 shows a 3-D drawing of multiplane device for internal fixation with a U-shaped rod, carried off additional single rod ???? and additional strengthening by plate with one hole;

- Figure 11 shows a 3-D drawing of the device for internal fixation of the 5trochanter-lateral fractures of the femur, with additional cancellous cannulated screw in the distal part;

- Figure 12 shows a 3-D drawing of a device for osteosynthesis with a U-shaped rod and a single rod, in which one arm of the U-shaped rod is used as an intramedullary fixator;

10 Figures 13 to 23 show embodiments of modules of external fixation system and its utilization in the building of the osteosynthesis devices, where:

- Figure 3 shows a sectional view of the module serving to tighten two Kirschner wires or two rods;

- Figure 4 shows a perspective view of an osteosynthesis device using I5the module for fastening two Kirschner wires from the above figure;

- Figure 15 shows a perspective view of a hybrid drive for internal and external osteosynthesis, mounted on the bone, in which Kirschner wires are inserted in the bone intramedullary; the ends of the wires, which are outside of the bone, are fixed in the holes for rods of the two screwholders for external 0fixation;

- Figure 16 shows a sectional view of a brace for strengthening rod system;

- Figure 17 shows a section of a connecting module with rods and sphere;

5 - Figure 18 shows a sectional view of the device for external fixation of the type "monofixator", comprising a compressor-distractor with spherical beds at both ends (from an other system) and two pairs of rods with a spherical connection, connected through the modules from Fig. 16 and 17;

- Figure 19 shows a 3-D drawing of the device for fixation of the 0trochanter-lateral fractures of the femur;

- Figure 20 shows a 3-D drawing of the device for fixation of a fractured humerus, in which one of the implant screws is inserted intramedullary; - Figure 21 shows a sectional view of a module which can connect at any angle rods with rods or rods with implant screws (pins);

- Figure 22 shows a perspective view of an osteosynthesis device, wherein the rod is inserted in the central hole of each screwholder, while the

Spins are placed in the transverse holes;

- Figure 23 shows a perspective view of an osteosynthesis device, with options for compression and distraction of the bone fragments comprising screwholders for external fixation as well an additional mechanism actuated by screws;

10DESCRIPTION OF EMBODIMENTS

The present invention is visualized in the enclosed drawings and demonstrated by the examples below, which are for illustration only.

System for internal osteosynthesis

Fig. 5 illustrates an exemplary module using tightening joint of the first

I5type according to the invention. The module is a plate 1 , which is attached to the bone 4 by bone screw with hemispherical head 3 and is connected to other plates by means of two rods. Each plate is a monolithic body with rotational form, which provides good manufacturability.

The central hole of the plate is cylindrical whereas in the lower part it is 0bevelled to provide a greater angle of inclination of the screw. In the plate are made cross holes for carrying rods. The dimensions of the plate and the holes are defined suitably so that the plate can be combined with bone screws with standard hemispherical head. Due to spherical head the screw 3 can be angled spatially up to ± 20°. In one embodiment of the invention, the plate has 5two holes for the carrying bars. In another embodiment of the invention used in single rod frames the plate has one hole for a rod, while in the opposite wall of the central hole a spherical bed is formed, which supports the head of the bone screw, replacing the second rod. Alternatively of that solution, a plate with two holes can be used, placing in the second hole a short rod. In another 0embodiment, the plate is made with a groove on the lower surface, thereby reducing the contact area with the periosteum. This is clearly shown in Fig. 8, 9 and 10.

Figure 6 shows an exemplary module using ightening joint of the second type according to the invention. This module is used in condylar and 5trochanter-lateral fractures. The module includes a plate with extension 1 , two rods 2, bone screw 4 and nut with a hemispherical surface 3. The plate extension can be angled in 90° when the plate is applied to the condylar fractures, or - 130 ° (Fig. 1 1 ), when it is applied to the lateral-trochanter fractures. The plate has a central cylindrical hole, which at its upper end is lOformed with a spherical bed, and at the end of the elongation of the plate transforms into dihedron B. In this hole is placed bone screw whose shank C is also formed as a dihedron. Dihedron joint provides ability to move the screw linearly without rotating relative to the plate. The plate also has two holes H, which intersect the central hole so that they having a common portion. The l5rods are placed in these holes. On the threaded shank E of the bone screw 4 is screwed nut with its hemispherical surface F to the side of the body. On the reverse side of the nut has a thin zone D, which can be flattened round the screw shank after final assembly in order to prevent loosing of the nut 3.

All modules of the system for an internal osteosynthesis are made of 0biocompatible materials, since they are implanted in the human body.

Figures 9 to 12 show examples of the application of the modules for internal osteosynthesis in the building of internal fixation devices.

Fig. 9 illustrates a device for internal fixation with one furrowed rod.

Figure 10 reveals the advantage of the present invention which allows 5multiplane devices to be created. In the device shown some of the plates are placed on the arms of the U-shaped rod, which provides them an angular stability. Another part of the plates are placed only on one side of the U- rod and in their second holes a single rod is placed, which allows the inclination in another plane. Some of the plates that have one hole are inclined 0considerably. They serve for lateral stabilization.

Figure 1 1 shows a construction for internal fixation of the trochanter- lateral fractures of the femur using the plate with extension and cancellous screw with nut. The structure is strengthened with an additional cancellous screw with a hemispherical head which is inserted directly between the rods, without the plate, to provide a greater angle of inclination. In the distal part additional cancellous cannulated screw is placed, guided at screwing by a SKirschner wire. Additional lateral strengthening of the construction is provided by means of plates with one hole.

Figure 12 shows a device for osteosynthesis using U-shaped rod and a single rod, in which one arm of the U-shaped rod is used as an intramedullary fixator.

10 System for external osteosynthesis

Figure 7 shows an exemplary screwholder used in the external fixation system according to the invention. It includes body 1 , clamping screw 5 with a central hole G, spherical collet 3 with slots E and F.

The body 1 has a central stepped hole A, whose wide portion ends with isthread C, and at least one cross hole B for a rod, located near the narrow end of the stepped hole. The stepped hole and the rod hole intersect, so as to have a common part. On the body are made faces J, so that it can be held with a wrench during the tightening. Besides the bevels enable screwholders to be placed more closely to each other.

0 The clamping screw 5 has a thread corresponding to the thread of the tapped hole of the body, a central hole G, through which bone screw passes and can be tilted and notches on the face D, making it possible to be screwed by means of a wrench. Inside the body there is a spherical or conical bed H, given the wide part to the field that touches it.

5 The spherical collet 3, washers 6 and 7, displayed in the drawing, are described in details in section 'Disclosure of Invention'.

In another embodiment of the screwholder the clamping screw 5 and washer 6, which presses the sphere can be made as a monolithic unit. In another embodiment, a washer 7 is not used; instead the sphere directly abuts 0on the rods 2. This allows a more compact design and a larger tilt angle of the implant screw. In another embodiment, the body 1 has an external thread on which is screwed a screw cap, which presses the sphere, performing the functions of the screw 5.

Bone screws used in external fixation system are made of biocompatible 5materials, and other modules of the system - metal or non-metallic materials. The materials used must have mechanical properties that provide the necessary strength and stability of the built devices in operating conditions. When the modules are made of plastic, it provides X-ray pellucidity of the constructed devices. This facilitates the X-ray control during the operation and loafter.

Figures 13 to 23 show embodiments of modules for external fixation system and its use in the construction of devices for external osteosynthesis.

Figure 13 shows a module serving to tighten the two Kirschner wires. The screw 3 is screwed into the threaded hole C of the body 1 and through the lscone (or spherical) lower part of its head presses wires to the holes. Screw has countersunk head and hexagon socket for wrench. Figure 14 illustrates the use of this module in a device for osteosynthesis using two Kirschner wires. The wires are inserted intramedullary in the bone and the ends, which are out of the bone, are fixed in the clamping module.

0 Figure 15 shows a device that combines internal and external osteosynthesis. Kirschner wires are inserted intramedullary into the bone like the preceding example. The difference is that the ends of the wires, which are outside of the bone, are fixed in the holes for the rods of the two screwholders for external fixation.

5 Fig. 16 shows a brace for strengthening the construction, which uses two rods. Another purpose of this brace is to make safe the protruding ends of the rods. Fig. 17 shows the design of the connecting module with sphere intended to interconnect External fixation system of invention with other systems, which use ball-and-socket join. The brace and connecting module 0with sphere are described in details in section 'Disclosure of Invention'.

One of the applications of the above modules is shown in Fig. 18 - to build a monofixator. To the both spherical sockets of a compressor-distractor 5, two connectors with sphere 4 are attached with assembled pairs of rods 2,

Sending with braces 1. On the rods are installed the screwholders 3. In another embodiment, instead of a compressor-distractor a rigid coupling module with spherical sockets is placed (not shown in the drawing).

Figure 19 shows the application of the modules of the external system in a device for fixing the lateral-trochanter fracture of the femur. The frame lOcomprises screwholders and two U-shaped rods, curved in the shape of the letter 'S\

Figure 20 shows the application of the external system in a device for external fixation of a fractured humerus, wherein the rods are contoured in accordance with the bone anatomy. Note that one of the screws is inserted ^intramedullary.

Figure 21 shows an embodiment of a module which can connect at any angle rods with rods or rods with implant screws. For further details on that module, refer to section 'Disclosure of Invention'.

Figure 22 shows a variant for using screwholders of external fixation 0system, wherein the implant screw and the carriers have exchanged places - in the central hole of screwholders the supporting rod is inserted, while in the two transverse holes - Kirschner wires are placed. This allows to build a device operating as monofixator whereas screwholders can be tilted in all three axes because of the spherical joint and the ability to pivot about the axis 5of the rod.

Figure 23 shows the device for osteosynthesis, with options for compression and distraction of the bone fragments. The device includes screwholders for external fixation 1 , screw mechanism and U- shaped rod 3.

Claims

The screw mechanism consists of four screws 2, two pairs of plates 6 and 7, which can slide along the arms of the U-shaped rod 3. Plate 6 has threaded through hole and plate 7 - blind smooth hole. Screw 2 has at its end a smooth part with the annular groove. In the groove enters tangentially a pin 8, which 5restricts translational movement of the plate along the screw axis, but allows rotation of the screw relative to the plate. The screwholders 1 are used in a similar manner to the device of Fig. 22, but instead of rod in their central hole a shaft 4 is inserted connected immovably to the two opposite plates. When you turn simultaneously screws 2 using lined handles A, the plates 6 and 7 come lOnear or move away depending on the direction of rotation. Such device can be used as a Limb Reconstruction System (LRS).

Claim 1. A tightening joint of the elements of the versatile modular systems for internal and external osteosynthesis, intended for orthopedics and l5traumatology, comprising at least one base body, with at least two cross holes, in which are placed with a small clearance, two other bodies, so as to come into contact, characterized in that:

- Cross holes on the main body partially intersect;

- Holes can be of different size and shape, one hole of the main body is 0cylindrical or prismatic and has a constant section, and the other hole has a rotational shape and may have a different cross-section along its length;

- The second body has a cylindrical or prismatic shape corresponding to the shape and dimensions of the hole in which it is placed, so that there is a small play;

5 - The third body has a rotational form in which the portion, which contacts the second body has a slope, so that the body can act as a wedge; the body can be moved along the length of the hole intended for it, with a small clearance;

- The contact surfaces of the second and the third body are flat or have 0a surface which is treated in a special way in order to increase friction and to improve the fixation: nurling, furrowing or faceting. Claim 2. The tightening joint of claim 1 , characterized in that the third body has at least one threaded opening, in which the threaded shank of the bone screw is screwed; besides the screw is secured against rotation relative to the base body.

5 Claim 3. The tightening joint of claim 1 , characterized in that the third body is made of an elastic material and has at least one smooth hole, and just one radial slot reaching the opening and located in a plane passing through the axis of the hole and in the hole of the third body the fourth body is closely inserted.

10 Claim 4. The tightening joint of claim 3, characterized in that the third body has at least one additional slot which is arranged in a plane passing through the axis of the hole, but not through, so that a thin wall remains between the hole and the slot.

Claim 5. Versatile modular system for internal osteosynthesis using the l5tightening joint of claim 1 , comprising at least one carrier in the form of a rod, bone screw, and at least one plate movable along a rod, in which plate can be positioned at least one bone screw, characterized in that:

- The plate is an implementation of the base body of claim 1 and represents (Fig. 5) a monolithic body ( 1 ) having a central opening (A) for 0positioning the member for attachment to the bone and at least one opening (D) for receiving a carrying rod ( 2 ) located in relation to the central hole (A) such that their axes are crossed, as in the area of crossing the holes intersect;

- The central hole (A) of the plate is cylindrical whereas in the lower part it is bevelled to provide a greater angle of inclination of the screw.

5 - The rods are implementation of a second body of claim 1 , and may have different cross-section, shape of the axis and length;

- The heads of the bone screws are implementation of the third body of claim 1 ;

- When the carriers (2) are installed in the plate and the bone screw (3), 0is in the operating position, carriers must contact with the screw head so that the carriers to serve as a support for the head and in its turn head has to press the carrier to holes of the body. Claim 6. The system of claim 5, characterized in that the screw head (3) is a part of sphere oriented toward screw threading.

Claim 7. The system of claim 5, wherein at least one of the plates and at least one of the bone screws are involved in the tightening joint of claim 2, 5characterized in that:

- Plate has an extension that serves as a guide for the bone screw; in the operating position the extension is oriented to the bone;

- The elongation of the plate has a feature which prevents rotation of the bone screw;

10 - Bone screw ends with a cylindrical shaft that has a thread;

- The third body of claim 2 is implemented as a nut, with a hemispherical surface at one side, which is screwed onto the shank of the screw so that the hemispherical surface is facing to the plate;

Claim 8. The system of claim 6, characterized in that the element which isprevents rotation of the bone screw is at least one bevel along the shank of the bone screw and the screw hole in the extension of the plate has a profile which corresponds to the profile of the screw shank.

Claim 9. The system of claim 8, characterized in that the clamping nut (3) is formed at its upper end with a thin zone (D), which can be plastically 20deformed until it stops at the bevels of the bone screw ( Fig. 6 ).

Claim 10. The system of claim 5, characterized in that:

- The plate (1 ) has two holes for the carriers, disposed symmetrically about the axis of the central hole;

- The form of the axis of the rod is U-shaped with a center distance of 5the parallel arms equal to the center distance of the holes in the plate;

Claim 11. The system of claim 5, characterized in that the rod can be furrowed with annular grooves of semicircular cross-section.

Claim 12. The system of claim 5, characterized in that the plate ( 1 ) has an opening for a carrier ( 2 ) and in the wall of the central hole (A) opposite to 0the hole (D) for a carrier, a spherical bed is formed for convex spherical part (B) of the element for attachment to the bone (bone screw or pin). Claim 13. Versatile modular system for external osteosynthesis using the tightening joint of claim 3 or claim 4 comprising at least one carrier in the form of a rod, holders for fixture the bone screw (pin) and the connecting components, characterized in that:

5 - Carriers are single rod or a pair of rods that can be of different sizes and shapes: straight, arcs, circles, or any shape bent by an orthopedic surgeon according to the specific clinical case.

- Holder of the bone screws (pins) (Fig.7) is an implementation of the tightening joint of claim 3 or claim 4, including a monolithic body (1 ) which has

10a central stepped hole (C) and at least one opening (B) for receiving a carrier (2) disposed crosswise in relation to the central opening (C), so as to partially intersect; in the central opening is mounted a washer ( 6 ) for clamping the carriers and having a spherical bed facing towards the sphere, a sphere with slots (3) for fastening the bone screw, clamping washer (7) with a bed for issphere, oriented to the sphere and tightening threaded part (5) with center hole.

- The dimensions of the parts and location of the holes of the screwholder are so defined that when screwing the clamping member ( 5 ) relative to the body (1 ) to ensure a clamping of the sphere between the two

20clamping washers, pressing of the carriers (2) by pressing washer (7) and contraction of the sphere with slots (3), which tightens the bone screw (4); when the clamping member (5) is not tight, free rotation of the sphere is possible as well free insertion and removal of the bone screw (pin) into the hole of the sphere.

25 - connecting modules are: connecting modules to connect carrying rods with other carrying rods or pins and connecting modules to connect carrying rods with modules having spherical connection.

Claim 14. The system of claim 13, characterized in that on the portion of the screwholder body is cut external thread; the clamping part has a 0corresponding internal thread and some elements at its periphery or face, which allow its tightening with a wrench. Claim 15. The system of claim 13, characterized in that alternatively of claim 14 in the central hole of the screwholder body is cut internal thread; the clamping part has a corresponding outer thread, and some elements at its periphery or face, which allow its tightening with a wrench.

5 Claim 16. The system of claim 13, characterized in that there is an embodiment that does not use a pressure washer for clamping the carriers, but the sphere contacts directly with rods.

Claim 17. The system of claim 13, characterized in that there is an embodiment, wherein the pressure washer for clamping the sphere is made lOmonolithically with the clamping part of claim 14 or claim 15.

Claim 18. The system of claim 13, characterized in that the connecting module for connection rods to other rods or pins at any angle (Fig. 21 ) includes two bodies which are connected by screw and nut:

- Each body has at least one hole located crosswise in relation to the l 5hole of the connecting screw. The holes are situated in such a way that the hemispherical head of the screw (3) and the hemispherical surface of the nut (6) can touch the surface (A) of the bone screws or rods placed in the cross hole (holes).

- The nut is secured against rotation during tightening, but can move 0axially;

Claim 19. The system of claim 13, characterized in that the connecting module for the connection of rods with modules having a ball joint comprises a body to which a sphere and a nut are mounted; the nut has a spherical bed inside, which abuts on the sphere:

5 - The sphere and the nut have dimensions that correspond to the spherical bed of the unit, which need to establish a connection;

- The body has at least one hole in which is affixed a rod by thread connection; pressing or other known method for establishing a fixed joint.

Claim 20. The system of claim 13, characterized in that when using a 0pair of rods, in order to strengthen and secure the construction a brace is attached to rods; brace has two holes, into which enter the rods (Figure 16): - The end of the rod is formed with a chamfer (A); the slope of chamfer makes it easy to mount the rod in the hole; near the end of the rod is shaped groove (B) serving as a lock;

- The body has a hole which is perpendicular to the holes of the carriers,and reaches them, in the hole are mounted a spring (4) and balls (3) on both sides of the spring;

- In operating position under spring pressure the balls come into the grooves of the rods;