MX2013014192A - Self-lockable intramedullary nail. - Google Patents

Abstract

The present invention is an alternative to the process for the inner stabilization of femoral diaphysis fractures, which consists in a self-lockable nail with an anti-rotational effect design. This fixer has the particularity of having four or more flanges previously deformed, which act as a spring and are fixed to the inner wall of the bone. The flanges have an acute geometry, which is fixed by lightly penetrating into the wall of the bone and limiting the rotation of the fixer. As a consequence, the invention provides an improved immobilization compared to that provided by the intramedullary nail with locking holes. The self-lockable intramedullary nail is made of a bio-compatible material, which may be an alloy based on titanium, stainless steel or cobalt.

Description

INTRAMEDULAR NAIL AUTO-BLOCKABLE DESCRIPTION OBJECT OF THE INVENTION The object of the present invention is to provide an alternative for the process of internal stabilization of fractures of the femoral shaft, which consists of a self-locking nail with an anti-rotational design. This fixator has the particularity of having four previously deformed fins which act as a spring fixing to the inner wall of the bone. The fins have a sharp geometry which is fixed by slightly penetrating the bone wall and limiting the rotation of the fixator. As a consequence, it generates a better immobilization than the typical intramedullary nail with blockade of holes.

BACKGROUND Currently the intramedullary nails that are used to stabilize fractures in long bones such as the femur; They are designed to be fixed on both ends with screws.

This fixation is made by the orthopedist in the operating room with the typical instruments used in this operation; however, in the lower part of the bone, the guide instrument for placing the screws does not work with the precision required especially for patients with large soft tissue. This results in cross-cutaneous screws and holes hardly matching the nail holes. As a result of this; The orthopedic surgeon uses real-time X-ray instrumentation to help and drill in the right place so that the lower or distal block screw can be placed. This results in high exposure of X-rays to medical personnel as well as possible damage to the mechanical integrity of the bone.

Thus, specific mechanical devices have been studied and made, such as, for example, the one described in this patent. This device requires the use of X-rays in a limited way, which considerably reduces the exposure of medical personnel, increasing their safety.

Several kinds of intramedullary nails designed to solve these difficulties are already known in this technique, which are expandable in a limited section of the nail to allow its fixation against the bone cortex, for example, by means of the radial deployment of several cutting blades in the distal part of the intramedullary nail as shown in documents US4227518, US4262665, US4519100, ES2323273, where some kind of fins are deployed by some mechanism, this type of designs transmit the total load axially to the bone over small areas, causing fractures of bone caused by a concentration of efforts almost punctual in the contact area of the fins and bone. The design disclosed in the present invention shows a new way of axial load transmission with a greater bone-metal contact area, which reduces stress concentrations that can cause severe fractures. Other types of designs with larger contact areas have been disclosed, as are those described in documents ES2241331, US20060142764A1 and ES2048080. These intramedullary nails of the prior art are provided with two radially expandable sections. The disadvantage of this type of intramedullary nail is its sections with expansion, a limited expansion reduces the area of action of the nail so it is necessary to increase the areas of expansion, which could cause bad bone integration in comminuted fractures and even the detachment of small fragments of bones caused by the axial force of the expansion of such nails.

The invention, as claimed, has the objective of solving the problems and drawbacks described above.

BRIEF DESCRIPTION OF THE FIGURES The Figure shows a machined design before deformation.

Figure 2 presents complete self-locking intramedullary nail after deformed.

Figure 3 displays a detailed view of the anti-rotation system.

DETAILED DESCRIPTION OF THE INVENTION In Figure 1, the self-locking intramedullary nail (10) is indicated in a generalized manner, suitable for insertion into an elongated fractured bone (20), such as a femur or tibia. The nail (10) which is presented in greater detail in Figure 2 allows to obtain the following advantages: 1. Reduces exposure to radiation due to the use of image intensifiers. 2. The nail (10) comprises a solid with two attachment zones, one proximal (30) and another distal (40). 3. The fixation parts (30 and 40) of the nail, which consist of a deformed area of 4 fins (50) for the distal locking (40) and a proximal locking (30) of axial bolts to the bone, are located in a extra focal position (60), leaving the fracture zone minimally affected by radial forces, this allows a greater area of work as well as its use in the treatment of comminuted fractures. 4. The nail is composed of a single cylindrical piece (70) which increases its strength while reducing the threaded areas prone to corrosion due to the saline medium inside the body. 5. Longitudinally, the nail is designed to deviate from its straight following a predicted curve (90) of radius R1 that coincides with the natural curvature of the patient's bone, which is well known to involve a medullary canal not perfectly straight, this modality allows us to Its insertion in various types of long and straight bones is specific to each patient. 6. The treated intramedullary nail consists of a termination at a distal end (40) that acts like a spring and is axially fixed to the inner wall of the bone. This fixation is made by means of 4 fins (50) previously axially deformed at an angle in Q (100) forming a kind of four-pointed flower (110). The angle Q is previously calculated for each patient, in order that the deformation force produced by the opening of the fins is necessary to maintain longitudinal fixation in compression and tension until bone consolidation without causing axial fractures. 7. As is well known, the natural movement of the body subjects its osseous members to tensile, compression and especially torsional forces. To specifically reduce the latter the nail treated in this invention has an anti-rotation system in its fins (110). The fins have a sharp geometry as can be seen in Figure 3 (120) which is fixed to the bone by the axial force of the deformation produced by the weight of the body under compression, which in turn cause a slight penetration in the bone wall producing an anchor and thus limiting its rotation. 8. This geometry is performed by ravaging at an angle of 45 ° on the distal clamping end of the nail until obtaining a flat face (130) square at the base and 4 flat edges (140) at an angle. This base is subjected to a cross cut (150) just in the center of the flat square at a calculated depth that will coincide with the calculation of the deformation of the fins. 9. The proximal fixation (30) is made by axial bolts, the treated nail has transverse holes in its proximal area where said bolts must be fixed. Although this proximal fixation seems to fall on the fixation method that is intended to be replaced, it is important to emphasize that it is intended to reduce the complexity of the fixation produced by the distal fixation, due to the proximity to the focus of the nail the proximal fixation results in a easy and simple procedure without great complications compared to distal fixation using the same method of bolts, so replacing this distal fixation would cause a significant reduction in risks in the patient and the medical personnel involved.

The characteristic details of the process of elaborating this innovation are clearly shown in the following description and in the section of accompanying drawings.

The final measurements of the nail are calculated taking into account weight, height and diameter of the medullary canal. Said calculation is carried out by means of tables specifying the variation of diameter in a range of 6 to 55 mm, length of the nail and length and opening of fins that are deformed axially at an angle in the range of 5o to 80 °.

The nail is machined until obtaining the desired shape (Figure 1), the first step is the diameter reduction using a conventional lathe machine, using a polishing machine, four sides are devaded at a 45 ° angle from one end of the cylinder until obtaining a square shape on the underside, an orthogonal (cross) cut is made up to the depth previously calculated in the range of 1 to 500 mm using a cutting disc and finally the upper holes that will be the nails channel are machined of the proximal block.

The machined part is subjected to hot deformation at a temperature of 0 to 1250 ° C up to the desired angle according to the needs of the patient, have a geometry with an angle of attack of a range of 1 to 165 ° which slightly penetrates the bone causing a resistive anti-rotation force. The self-locking intramedullary nail is made of a bio-compatible material which can be a titanium base alloy, stainless steel or cobalt base.

Claims (10)

CLAIMS Having described my invention enough, I consider it as a novelty and therefore claim as my exclusive property, what is contained in the following clauses:

1. Self-locking intramedullary nail for the reduction of bone fractures characterized by being formed by a metal rod that is comprised of a first radially expanded distal section defined by a mechanism of pre-deformed fins that provide the nail with some elasticity in the transverse direction. allows fixation in the bone; a non-expanded mid section determined by the solid non-hollow cylindrical shape; and a third proximal section characterized by containing transverse holes for fixation to the bone by means of pins.

2. Self-locking intramedullary nail according to claim 1, characterized in that the distal section is provided with a distraction mechanism in the form of fins, by means of which said fins are expanded radially to the longitudinal axis.

3. Self-locking intramedullary nail according to claim 2, characterized in that said expanded section of the intramedullary nail has a diameter in a range of 6 to 55 mm.

4. Self-locking intramedullary nail according to claim 1, characterized in that said non-expanding section of the intramedullary nail has a diameter in the range of 6 to 55 mm.

5. Self-locking intramedullary nail according to claim 1, characterized in that the distal fixation is carried out by means of fins.

6. Self-locking intramedullary nail according to claim 5, characterized in that said fins are part of a same solid which is subjected to a cross-sectional longitudinal cutting process with a length in the range of 1 to 500 mm.

7. Self-locking intramedullary nail according to claim 5, characterized in that said fins are deformed axially at an angle in the range of 5 ° to 80 °.

8. Self-locking intramedullary nail according to claim 7, characterized in that said fins are hot deformed at a temperature of a range of 0 to 1250 ° C.

9. Self-locking intramedullary nail according to claim 5, characterized in that said fins have a geometry with an angle of attack of a range of 1 to 165 ° which slightly penetrates the bone causing a resistive anti-rotation force.

10. Self-locking intramedullary nail according to claim 1, characterized by being of a bio-compatible material which can be a titanium base alloy, stainless steel or cobalt base.