WO2003059210A2

WO2003059210A2 - Steady shaft for prostheses

Info

Publication number: WO2003059210A2
Application number: PCT/IT2002/000828
Authority: WO
Inventors: Pierluigi Versari
Original assignee: Pierluigi Versari
Priority date: 2002-01-04
Filing date: 2002-12-24
Publication date: 2003-07-24
Also published as: AU2002366979A1; WO2003059210A3; ITPI20020002A1; AU2002366979A8

Abstract

The present invention consists of a prosthesis with the intention to mend fractures of the upper end part of the femur bone and in particular for the reconstruction of the joint of the femur with the pelvis. It comprises two flaps (3, 4) held in suitable portions (3a, 2a, 4a) and connected each other by a pivot (2) that makes them open by means of an appropriate tool. Once open, they permit a better reconstruction of the fracture.

Description

Description Technical Field

The present invention concerns the technical sector relative to the production of prostheses with the intention to mend fractures of the upper end part of the femur bone and in particular for the reconstruction of the joins of the femur with the pelvis. Background Art Nowadays, various systems are used in orthopaedic surgery, which are generally based on the use of a prosthesis made of two elements: an upper acetabulum, fixed at the pelvis, and a lower part, the "stalk", inserted in the femur proximal epiphysis. These operations, at present, even if technologically adjusted to the physical structural sizes of the patient, have the drawback of permitting, during some movements of the joins, a minimum rotation of the prosthesis round the bone where it's inserted. Said rotation may occur relating to the one's vertical axis as well as to the upper acetabulum fixed at the pelvis. This further movement of "intrarotation" is particularly facilitated by the patient's natural movement when he stands up from sitting, which is essentially due to the gap existing between the stalk of the prosthesis and the inside of the bone-cavity. Disclosure of invention

The present invention aims at avoiding these and other drawbacks, supplying a prosthesis equipped with an internal device that, once inserted in the femur proximal epiphysis, allows two flaps to extend and rest on two diametrically opposed points inside the bone-cavity, placed at different levels. In this way the prosthesis, once inserted, is connected to the same bone, in fact preventing any relative movement and, consequently, facilitating its osteointegration. The advantages resulting from the present invention essentially consist of the fact that it permits to have a solid join with the bone and consequently it facilitates the osteointegration; that the prosthesis intrarotation stability, during the phase of the passage from sitting to the upright position, is possible thanks to two removable flaps placed in the stalk of the femur prosthesis that can attach to the bone; that said flaps are simultaneously activated by a rotation pivot connected to them; that the stalk can be removed from its medullary portion; that the rotation of the pivot, in its turn, can be performed with a screwdriver or other tool to be fitted in the track located in the upper end of the same pivot; that this object has an long rectangular shape, only just belled, in order to suit the sinuous shape of the femur. Reduced to its essential structure and with reference to the figures of the enclosed drawings, a prosthesis for femur fractures, according to the present invention, comprises: means to steadily fix the stalk to the internal surfaces of the bone, with two or more removable flaps, placed at the opposite ends of the stalk, opposite equivalent at different heights; - means to hold the flaps (3, 4) in corresponding places {3a, 4a) created on the external surfaces (5, 8) at different heights; means to activate and simultaneously remove said flaps, with an internal pivot (2) , connected to both; from its rotation, once the prosthesis has entered the medullary portion, said flaps come out until they touch the internal surfaces of the bone; means to rotate the pivot (2), by an incision made on its upper surface, where a screwdriver or a suitable key works. Conveniently, the prosthesis comprises an upper acetabulum (1) for the traditional join with the hip, which is connected to the lower stalk consisting of a metal prod, of such a size as to suit the physical structure of the patient, which, inserted and well fitted inside the medullary bone canal, has an internal mechanism permitting the extension of two flaps that rest on the internal parts of the bone.

Conveniently, the different angle of the upper part of the prosthesis with the stalk, lets the upper end of the same stalk accessible. Conveniently, the stalk has a long rectangular shape, linked at the corners and only just belled, in order to better suit the sinuous shape of the femur, and has an internal portion for a metal pivot that is blocked in the axes but free in rotation.

Conveniently, the stalk consists of two external parts (5, 8) and an internal portion (7) connected each other by pins (6) and steadily fixed one to the other by welding or any other means for ensuring stability to the structure.

Conveniently, along the longitudinal axis of the internal pivot (2) there are two extending flaps, connected to it, placed at different levels, which find suitable place in equivalent spaces on the inner diametrically opposite surfaces of the prosthesis so that, rotating the pivot, the flaps rotate simultaneously. Conveniently, the flaps have a rounded external shape in order to avoid poking the internal bone tissue.

Conveniently, on the central surface (7) of the stalk there is a portion (2a) where the pivot (2) and the flaps (3, 4) enter, filling this surface when not open, while the lower part of the pivot enters a cylindrical portion that permits its rotation.

Conveniently, the upper end of the pivot, fitted inside the stalk, has a track for a blade screwdriver or a portion for a Torz key, anyway permitting to make the pivot rotate of 90 degrees after the insertion in the femur bone-cavity. Conveniently, this rotation, made after the prosthesis has been inserted and centred perfectly in the medullary canal, allows the two flaps connected to the pivot to come out equally and simultaneously, so filling the gap between prosthesis and bone and making them connected, avoiding relative movements of rotation and intrarotation. Conveniently, in order to block the central pivot outbound in the axes, once the flaps have been removed, an elastic washer is inserted inside the upper part of the same pivot. Conveniently, the join of the prosthesis with the bone is much more stable as the insertion in the bone medullary canal, previously prepared, is much more exact and minor cutting forces between the bone and the prosthesis structure are raised during movement.

Conveniently, if it's necessary to remove the stalk from its medullary portion - inevitable operation in case of pre-adults patients - it will be sufficient to make the pivot rotate backwards, recalling the flaps in their original portions, so as not to make resistance to the traction of the prosthesis. Conveniently, this prosthesis, as already tested for other modern prosthesis, can be entirely made of steel alloy, an extremely strong material, biologically compatible, holding reduced nickel: Fe, Cr, Ni, Mn, Mo, NbN.

In practice, the manufacturing details may, however, equally vary as regards shape, size, position of elements, and type of materials used, but still remain within the range of the idea proposed as a solution and, consequently, within the limits of the protection granted by this patent for invention. Brief description of drawings

The inventiveness and industriability of the present invention can be better understood by every expert in this field, reading the following description and referring to the enclosed drawings, given as practical examples of the invention, but not to be considered restrictive.

Fig. 1 shows a side surface (8) of the invention, with the upper acetabulum (1), whose angle, following the anatomic structure, permits the access to the upper part of the stalk, which holds inside the pivot (2), connected to the flap (3) embodied in this side in the surface (8) . Fig. 2 shows the side view of the prosthesis that consists of three components: two external surfaces (8, 5), with the corresponding portions for the flaps (3, 4), and a central part (7) that is place and guide of the rotation pivot (2) . Fig. 3 is the opposite side surface (5) of Fig. 1, showing the different height where the mirror flap (4) is placed, connected to the pivot (2) too, and directed backwards, so that the same rotation of the pivot causes the equivalent extension of the flaps.

Fig. 4 is the top view of the invention, showing the head of the pivot with the portion for the screwdriver making the system rotate.

Fig. 5 is a section made from Fig. 2, as indicated, showing the pivot (2) inside the stalk during insertion, with the flaps (3, 4) inside. In this figure it's possible to notice the suitable portion created inside the central part of the invention, that acts as axis guide for the pivot (2) thanks to the similar shape of the central body and the position blocked in the axes by the washer (9) . Fig. 6 shows an exploded view of the invention, with the external bodies (8, 5) holding at different heights the portions (3a, 4a) for the flaps (3, 4), and the central body (7) with the space (2a) for the insertion and the guide of the pivot (2) finally blocked in the axes by the washer (9) . The different parts of the prosthesis are locked with precision pins (6) .

Fig. 7 shows a side view of the invention during use, with the flaps (3) rotated outwards of 90 degrees. Fig. 8 shows the corresponding extension at different heights of the flaps (3, 4), inside the medullary bone- cavity, until they reach the internal surfaces, filling the gaps and so connecting the prosthesis with the same bone. Figs. 9 and 10 show the top views of the same situation.

Claims

1) Prosthesis for femur fractures, characterized in that it comprises: means to steadily fix the stalk to the internal surfaces of the bone, with two or more removable flaps, placed at the opposite ends of the stalk, opposite equivalent at different heights; means to hold the flaps (3, 4) in corresponding places (3a, 4a) created on the external surfaces (5, 8) at different heights; means to activate and simultaneously remove said flaps, with an internal pivot (2), connected to both; from its rotation, once the prosthesis has entered the medullary portion, said flaps come out until they touch the internal surfaces of the bone; means to rotate the pivot (2), by an incision made on its upper surface, where a screwdriver or a suitable key works.

2) Prosthesis as claimed in claim 1, characterized in that it comprises an upper acetabulum (1) for the traditional join with the hip, which is connected to the lower stalk consisting of a metal prod, of such a size as to suit the physical structure of the patient, which, inserted and well fitted inside the medullary bone canal, has an internal mechanism permitting the extension of two flaps that rest on the internal parts of the bone. 3) Prosthesis as claimed in claim 1, characterized in that the upper part of the prosthesis has a different angle with the stalk.

4) Prosthesis as claimed in claim 1, characterized in that the stalk has a long rectangular shape, linked at the corners and only just belled, in order to better suit the sinuous shape of the femur, and has an internal portion for a metal pivot that is blocked in the axes but free in rotation.

5) Prosthesis as claimed in claim 1, characterized in that the stalk consists of two external parts (5, 8) and an internal portion (7) connected each other by pins (6) and steadily fixed one to the other by welding or any other means for ensuring stability to the structure.

6) Prosthesis as claimed in claim 1, characterized in that, along the longitudinal axis of the internal pivot (2), there are two extending flaps, connected to it, placed at different levels, which find suitable place in equivalent spaces on the inner diametrically opposite surfaces of the prosthesis so that, rotating the pivot, the flaps rotate simultaneously.

7) Prosthesis as claimed in claim 1, characterized in that the flaps have a rounded external shape in order to avoid poking the internal bone tissue.

8) Prosthesis as claimed in claim 1, characterized in that, on the central surface (7) of the stalk, there is a portion

(2a) where the pivot (2) and the flaps (3, 4) enter, filling this surface when not open, while the lower part of the pivot enters a cylindrical portion that permits its rotation.

9) Prosthesis as claimed in claim 1, characterized in that the upper end of the pivot, fitted inside the stalk, has a track for a blade screwdriver or a portion for a Torz key, anyway permitting to make the pivot rotate of 90 degrees after the insertion in the femur bone-cavity.

10) Prosthesis as claimed in claim 9, characterized in that this rotation, made after the prosthesis has been inserted and centred perfectly in the medullary canal, allows the two flaps connected to the pivot to come out equally and simultaneously, so filling the gap between prosthesis and bone and making them connected, avoiding relative movements of rotation and intrarotation.

11) Prosthesis as claimed in claim 1, characterized in that, in order to block the central pivot outbound in the axes, once the flaps have been removed, an elastic washer is inserted inside the upper part of the same pivot. 12) Prosthesis as claimed in claim 1, characterized in that it can be entirely made of steel alloy, an extremely strong material, biologically compatible, holding reduced nickel: Fe, Cr, N^'i, Mn, Mo, NbN.