HRP990405A2 - System of intramedullary screw for the osteosynthesis of long bones - Google Patents

Description

The field to which the invention relates

This invention relates to the broad field (Int. Cl. A 61 B) of bone surgery in orthopedics and traumatology, for the surgical treatment of long bone fractures in humans and animals. Today, different types of implants are used in the world, which are surgically inserted into the body. This area includes bone screws (cortical, cancellous, malleolar, DHS, DCS, etc.), bone plates (flat, angular, etc.), various types of external fixators, and various types of intramedullary implants (Kuntcher's nail, Ender's nail , Rush's nail, Kirschner wires placed intramedullary, "gamma nail" and for the last fifteen years the anchored nail). The intramedullary screw system by indication covers a wide range of applications that includes almost all of the previously mentioned implants. and in many cases can be used instead of them.

Technical problem

The purpose of this implant, like all other osteosynthetic devices, is to surgically achieve relative stability between the fracture fragments, with the aim of enabling the conditions for bone growth between them. During the placement of any osteosynthetic device, some basic mechanical principles must be used in order for that type of osteosynthesis to be considered properly done and is usually characteristic of a certain type of osteosynthesis or anatomical area that requires it for biomechanical reasons. The basic mechanical principles used in osteosynthesis are:

1. Interfragmentary compression (static and dynamic) with a plate, external fixator, etc.

2. Guidance (with Kuntscher's, Ender's and Rush's nails),

3. Combination of the previous two principles - eg a tension screw and a neutralization plate over it.

4. Neutralization (unloading) - an example is an anchored intramedullary nail which, in case of a multifragmentary fracture of a long bone, takes over the forces and transfers them from the proximal part of the bone to the distal one, thus relieving the middle part where the unstable fragments are located. This is possible due to the transverse screws passing through the intramedullary (Kuntscher) nail, which prevent impaction and shortening of the bone as a whole.

The intramedullary screw system can be applied using all the previous principles depending on the type of fracture and the local biomechanical need.

Current situation and known solutions

It is logical to compare the intramedullary screw (IMV) with other intramedullary implants in osteosynthesis of long bones (humerus, radius, ulna, femur, tibia and fibula). I emphasize - long bones, because the joining of two smaller fragments with a single screw is known and widely used. For example, the Herbert screw (USP 4,175,555) is applied to the small scaphoid bone of the hand, which has a spongy structure and does not have a bone diaphysis (it does not have a tubular structure), and the principle of osteosynthesis is completely different from the IMV system, which is also bidirectional with the possibility anchoring of transverse screws. The same remark can be said for the difference to the Huebner screw (WO 94/16636) with variable thread pitch applicable also to small cancellous bones and to the compression screw (WO 94/20040) which compresses individual bone fragments or parts of bone, but is not placed intramedullary like Kuntscher's nail, or IMV. In addition, they are all too small (their size and diameter are the same as classic cortical screws) to be used in terms of intramedullary fixation of long bones.

Today's method of treating long bone fractures with intramedullary fixation uses two mechanical principles, and IMV should be compared with these implants, since its size, method of placement, mechanism of action, and indications are most similar to them:

1. Guidance - the fragments slide over the implant and are thus compressed (Kuntcher's nail, Ender's nail, Rush's nail, Kirschner wires placed intramedullary). One form of intramedullary screw guidance is described in patent application HR P921004A A2. Here, a combination of a classic anchored intramedullary nail and an intramedullary flexible threaded rod placed along it is used in the narrow limb of the narrowest diameter of the femur. This distractor serves to lengthen the femur, whereby the osteotomized fragments slide by classical guidance over a smooth Kuntcher nail, and axial stability is achieved by a centrally placed flexible winding shaft. However, it does not attach to the cortical part of the femur at all, as with the IMV described here, and that is why additional anchoring of the Kuntscher nail is necessary.

2. Anchoring with a transverse screw, in case of multifragmentary fractures of the diaphysis of long bones. This can achieve three possible actions and solutions:

a. Providing axial and rotatory stability - as in the case of an anchored Kuntscher nail (interlocking nail, verrigelungs Nagel)

b. The possibility of compression with an anchored transverse screw a through the intramedullary part. The best example is "gamma neil", which is described in various versions in several patent applications. Eg in EPO O 441 577 A3 and named "Intramedullary hip screw" or in EPO 0 321 170 B1, where "the intramedullary screw is actually a transverse cancellous screw that compresses the femoral head on the central femoral "short Kuntscher nail". These two features make it quite different from the variations of anchored intramedullary screws described later here.

c. The modular multi-part intramedullary nail is the latest solution in the group of new intramedullary implants characterized by a conical connection placed axially (WO 96/02202), but unlike the modular intramedullary screw described later here (Figure 12 - 16), it does not have transverse anchoring through the same connection, which would get additional rotatory stability.

Presentation of the essence of the invention

Unlike all previous intramedullary grafts, the intramedullary screw (IMV) does not achieve axial stability using the principle of guiding or anchoring with a transverse screw, but by neutralization over a very wide field of contact with the bone, its thread cuts into the cortex from the inside in the proximal and distal fragment. If a transverse anchored screw is placed, it is only to provide rotatory stability (FIGURE 1 - 1). Therefore, it can be used for multifragmentary and multi-level fractures with the same indications as an anchored (Kuntscher) nail. In addition, the IMV is very rigid in contrast to the Kuntscher nail and the anchored nail and other intramedullary implants, which are more elastic to adapt to the irregular shape of the bone, since they usually pass through it along its entire length. The IMV transmits forces to the bone almost along its entire circumference (thread), which gives it strength and does not need to extend the entire length of the bone.

IMV is placed intramedullary like other intramedullary implants. but unlike them, IMV is characterized by several features:

1. The IMV-screw is threaded to the inner rim of the compact tubular bone, not just the cancellous bone of the metaphyseal or epiphyseal region. This is precisely why a significantly higher degree of stability is achieved between fracture fragments connected with an IMV-screw than with other intramedullary implants. The IMV then transfers forces directly from the proximal to the distal fragment, without the risk of dislocation or impaction of the fragments in the middle part. The same principle is used with the anchored nail, but it is mechanically much weaker and the installation procedure is technically more demanding. Due to the precision of screw placement, the surgical set contains a collection of IMV screws of different thickness (0 from 1 - 18 mm), length, and thread height and pitch. In order to increase the surface of contact between the screw and the bone, in some cases pre-creasing can be done.

2. Bidirectionality of IMV is another important characteristic. The screw can be hollow in the middle (FIGURE 2 - 2) or not. with one-sided or double-sided self-tapping slots on the tips (FIG. 2. - 3). In addition, it also has a two-sided screwdriver connector (hex-sextant or cross connection or cross connection or Phylips or Torx). Due to its bidirectionality, it can be placed retrograde through the fracture crack itself, and then returned in the opposite direction to the back with the hollow screwdriver specified over the Kirschner wire from the outside.

3. The cavity through the middle of the screw (it can vary between 0.5 and 5.00 mm for different thicknesses of IMV-screws) allows for the mutual guidance of a screwdriver or a hollow drill over a Kirschner wire (or cable). In addition, it enables tightening - axial static compression between two broken parts of the bone if necessary. This is made possible by the use of a specially made tensioner that acts via a spring (PICTURE 3 - 4) guided around the threaded rod and connected to the handle of the screwdriver (PICTURE 3 - 5).

4. Thanks to the thread connection along the inside of the bone that transmits the force, anchoring with additional transverse screws is not necessary as in the case of the anchored Kuntscher nail. This achieves complete axial stability of the proximal and distal end of the bone.

5. However, it is possible to anchor one or more transverse screws at different angles to the radial and axial axis of the central screw. This achieves additional rotatory stabilization, especially for intra-articular fractures and those in the metaphyseal area.

6. In addition to the anti-rotational effect of the transverse screws, it is also possible to compress the free bone fragments in the middle part with the main central medullary screw (PICTURE 1 - 1). This effect cannot be achieved with any other intramedullary implant. This avoids the need for circular cerclage.

Joints with a transverse screw can be cylindrical (Figure 6 - 11), conical (Figure 8 - 12, Figure 9, Figure 12 - 17). threaded neutralization (Figure 10) and threaded compressive (Figure 11). Each of these cross screw approaches can be vertical or at an angle (Figure 8 - 13). Which compound will be applied depends on the local need. This significantly expands the operational possibilities of stabilizing free fragments.

Using the AO/ASIF division of fractures into ABC types - Comprehensive Classification of Fractures of Long Bones, M.E. Mueller; M. Allgower, R. Schneider, H. Willenegger; Manual of Internal Fixation, Third Edition. Spnnger Verlag 1991) we can easily see the practical correspondence and applicability with division and combinations in the IMV system.

Three groups of intramedullary screws can be used in practice:

1. SIMPLE - (Figures 2, Figure 3, Figure 5) They are suitable for almost all type A fractures (1, 2 and 3) in the area of the diaphysis of long bones (humerus, radius and ulna, femur, tibia and fibula).

2. ANCHORED:

a. unilateral - (Figure 9, Figure 10, Figure 11) when the transverse screw does not pass to the other side of the medullary screw. They are suitable for all type B fractures (1, 2 and 3) in the area of the diaphysis of long bones where a free bone fragment is fixed with a transverse screw for the central medullary screw in its middle part (Figure 1 - 1). They are also applicable for some cases of type B intra-articular fractures (1, 2 and 3).

b. bilateral - (Figure 4, Figure 6, Figure 7) when the transverse screw passes through the central medullary screw. They are suitable for almost all type A (1, 2 and 3) fractures in the distal parts of long bones and intra-articular type C (1, 2 and 3) fractures.

c. unipolar (Figure 6) when the transverse screw passes over only one end.

d. bipolar (Figure 7) when the transverse screws pass over both ends (proximal and distal). They are suitable for all type C diaphyseal fractures (1, 2 and 3). and in the distal parts of long bones for intra-articular fractures of type C (1, 2 and 3).

e. combined - multiple and multilateral (Figure 8) are the most variable and are made up of all the previously mentioned combinations for treating complex fractures, most often type C. The picture shows that the transverse screw can pass through the central screw at different sharp and obtuse angles (Figure 8 - 13).

3. MODULAR (double and triple), it is suitable especially on the smaller long bones of the metacarpus and metatarsus, but also elsewhere when the local need requires it. Each half of that screw has the ability to screw on both sides, depending on the possibilities of local access with a screwdriver. It is indicated by the fact that the forces are transferred from one half to the other through an axially placed conical joint (Figure 12 - 14), and the compression of bone parts with simultaneous anchoring through another conical transverse screw (Figure 12 - 15), which passes through the hole of the axial cone (Figure 12 - 16). The second transverse conical screw acts only derotationally (Figure 12 - 17).

Method of application of the invention

There are two ways to install the IMV screw:

1. Retrograde from the inside through the fracture crack itself. These are the screws described here without a head and with two threaded beginnings and an Allen key on each side of the screw

2. Antegrade placement identical to placement of a straight Kuntscher or Rush nail over the greater trochanter of the femur or the tuberculum maius of the humerus. These screws enter the bone from the outside and can have a head or be without one. that is, they can be hollow or not. In this case, classic cortical or cancellous screws with a head whose inner diameter corresponds to the inner diameter of the long bone can be used. Of course, this combination of bone sizes does not exist in humans, but only in smaller animals (cats, small dogs, etc.), and in that case it is necessary to make large screws (Ø 1-18 mm) with a length of 100 - 400 mm, with or without a head. whose shape may resemble classic cortical or spongy ones.

The operation begins with the usual procedure of open reposition of the fragments, with prior cleaning of the ends of the fractured bone from hematoma, displacement of the muscle interpositum, etc. (FIG. 3 - 6). This is followed by intramedullary placement of a screw thickness gauge intramedullary in the proximal and distal fragment. After that, the hole for the screwdriver and the internal guides (Kirschen wires or cables) of the IMV-screw is drilled in the proximal direction with a drill bit. The guide is inserted from the inside through the bone and exits through the skin in the proximal or distal part. According to it, the screwdriver is listed directly on IMV. A special hollow screw (mono or bicortical) is placed in the distal part through which the tension Kirschner wire or cable passes (FIG. 3 - 7). A flat screwdriver is used to tighten the screw. If we use a one-way IMV-screw, then immediately from the proximal side we introduce a screw that has a self-tapping thread and immediately fastens its entire circumference to the inside of the bone. When the screw reaches the fracture area, it is very important that we achieve a good reposition of the bone fragments, because later after the screw passes to the distal fragment, it remains fixed in the same position. Before we start screwing the screw over the fracture crack, we fix the tension cable at the end with the cable tensioner (PICTURE 3 - 8). Then we tighten the tension spring (PICTURE 3 - 4) above the handle using the tension nut (PICTURE 3 - 9) located on the threaded rod inside it. Then we can screw the screwdriver, since a strong compression has occurred between the fragments. At the same time, the tension cable also serves as a guide for the screwdriver. After the screw has passed halfway through the fracture crack, we can take out the screwdriver, the tension cable and the separate screw to which it is attached (PICTURE 3 - 10). This completes the osteosynthesis.

It should be noted that the IMV-screw can be made of steel bone implant ISO 5832/6 or 5832/IV or 5832-8 or of titanium or titanium alloy for implants ISO 5832-3. It is also possible to use a screw of the same shape but made of resorptive implantation material (polyglucoside, polylactide, PDS, etc.). In the case of placing this kind of intramedullary screw, the procedure is identical to the installation of a metal one, the only thing is that before installing the same, a slot is threaded from the inside of the bone with a slotted drill. This thread drill bit is identical in shape and installation method to the metal IMV-screw. After the thread is placed and cut from the inside of the bone, it is taken out, and a resorbable screw of the same size is placed in its place using the same procedure. The placement of all previously described anchored screws through the IMV is done with external guides and falls within the usual skill of the profession.

The IMV system is applicable to practically all types of fractures of all long bones in humans and animals, whether it is small pets (dogs, cats, birds) or large animals (horses, etc.) or wild animals in nature.

Claims (22)

1. Intramedullary bone screw for operative osteosynthesis of long bone fractures in human surgery and veterinary surgery (in small and large animals), characterized by the fact that the osteosynthetic effect is achieved through a thread cut through the inner rim of the cortical tubular diaphysis of long bones in their axial direction. 2. Intramedullary bone screw according to claim 1, characterized by the fact that it is bidirectional, i.e. that it has an initial thread and a connection point for the screw on both ends (hex-sextant, transverse or cross connection, Phylips or Torx.) 3. Intramedullary bone screw according to claim 1 and 2, characterized by the fact that it has an initial thread with self-tapping tips on both ends. 4. Intramedullary bone screw according to claim 1, 2 and 3, characterized in that it is hollow through the middle with a hole between 0.5 and 5.00 mm along its entire length. 5. Intramedullary bone screw according to claim 1, 2 and 3, characterized in that it is filled through the middle along its entire length. 6. Intramedullary bone screw according to claim 1, 4 and 5, characterized in that it is unidirectional, i.e. it has a screw head at one end. 7. Intramedullary bone screw according to claim 1, 2, 3, 4, 5 and 6, characterized in that it has a thread along its entire length. 8. Intramedullary bone screw according to claim 1, 2, 3, 4, 5 and 6, characterized in that it has a thread only in the initial and/or in the final part. 9. Intramedullary bone screw according to claim 1, 2, 3, 4, 5, 6, 7 and 8, characterized in that it has one or more transverse openings at different angles to the axial or radial axis of the screw and for the purpose anchoring of transverse screws. 10. Anchored intramedullary screw according to claim 9, characterized in that the transverse openings through it can be cylindrical. 11. Anchored intramedullary screw according to claim 9, characterized in that the transverse openings through it can be conical. 12. Anchored intramedullary screw according to claim 9, characterized in that the transverse openings through it can have a threaded hole of a cylindrical shape. 13. Anchored intramedullary screw according to claim 9, characterized in that the transverse openings through it can have a threaded hole of a cylindrical shape with a conical recess for the head or an extension of the transverse screw. 14. Transverse intramedullary screw according to claim 9, characterized in that it passes through the central IMV through its cylindrical smooth or threaded hole. 15. Transverse intramedullary screw according to claim 9, characterized in that its tip is conical and of the same shape for passage through the central IMV according to claim 11. 16. Transverse intramedullary screw according to claim 9, characterized in that its tip is cylindrical and with a thread of the same shape for passage through the central IMV according to claim 12. 17. Transverse intramedullary screw according to claim 9, characterized in that its tip is cylindrical and threaded and has a conical extension or a conical head for passage through the central IMV according to claim 13. 18. Modular (double and triple) intramedullary screw according to claim 9 characterized in that it has an axially placed conical joint through whose conical hole a transverse screw with the same conical tip passes. 19. Intramedullary bone screw according to claim 1, 2, 3, 4, 5, 6 and 7, and 9-18 characterized by the fact that it is made of stainless steel bone implant ISO 5832/6 or 5832/IV or 5832-8 or of titanium alloy for implants ISO 5832-3. 20. Intramedullary bone screw according to claim 1, 2, 3, 4, 5, 6 and 7 and 9-18, characterized in that it is made of resorbable material (polyglucuronide, polylactide, PDS, etc.) 21. Screwdriver for placing intramedullary bone graft according to claim 1, 2, 3, 4, 5, 6 and 7 and 9-18 with a solid and long flat body characterized by the fact that it has a cavity along its entire length. 22. Screwdriver for intramedullary bone placement 1st, 2nd, 3rd, 4th, 5th, 6th and 7th and 9-18 with a solid and long flat body characterized by having a tension spring above the holder.