WO2013018026A1

WO2013018026A1 - Positioning device for screws used to fasten an endomedullary nail

Info

Publication number: WO2013018026A1
Application number: PCT/IB2012/053900
Authority: WO
Inventors: Franco Mingozzi; Alan Dovesi; Alberto Scoccianti
Original assignee: Citieffe S.R.L.
Priority date: 2011-08-01
Filing date: 2012-07-31
Publication date: 2013-02-07
Also published as: ITBO20110481A1; BR112014002507B1; MX2014000820A; CO6862120A2; BR112014002507A2; MX343313B

Abstract

A positioning device for screws used to fasten an endomedullary nail (2) having a principal direction of extension (A2) and presenting at least one hole (DH1, DH2) for the passage of the screws, comprises an arm (5) which is connectable to the nail (2), a bar (6) mounted at a first end of it (6a) to the arm (5) and extending substantially parallel to the principal direction of extension (A2) of the nail (2), an alignment head (7) mounted in the vicinity of a second end (6b) of the bar (6) opposite the first end (6a), the head (7) being made at least partly of a radio-transparent material, having at least one hole (13, 13', 14, 14') for guiding the fastening screws and being movable relative to the nail (2) through the agency of respective adjustment means (8) in order to bring the at least one guide hole (13, 13', 14, 14') into alignment with the at least one passage hole (DH1, DH2).

Description

POSITIONING DEVICE FOR SCREWS USED TO FASTEN AN ENDOMEDULLARY NAIL

Technical Field

This invention relates to a positioning device for screws used to fasten endomedullary nails.

Background Art

The use of endomedullary or intramedullary nails to support fractures in long bones is known in the surgical field.

These nails must be locked in place relative to the bone parts in which they are inserted. This is done by means of screws which pass through the nail at different points along its length.

Although fastening the proximal screws (these usually are the screws closest to the insertion end of the nail) is relatively simple, inserting the distal screws - those used to fasten the part of the nail which is most deeply inserted in the bone - is a much more complex operation.

To be able to centre the distal screws inside the holes made for them in the nail, the prior art teaches the use of positioning devices which normally comprise a plurality of parts which can be adjusted in such a way that they can be set to a configuration of substantial centring relative to the holes.

In other words, using these positioning devices, the surgeon is able to identify with a good degree of precision the position of the nail and of the respective holes in the bone and can therefore insert the screw more easily.

In practice, the positioning devices have markings or holes which must be aligned with the hole in the nail inserted in the bone because, on account of the inherent flexibility of the nail, the holes which would have been aligned before the nail is inserted, often become misaligned upon actual insertion, when the nail tends to bend.

For the purpose, devices known as brightness amplifiers (image intensifiers) are commonly used.

A brightness amplifier is a direct, real-time viewing X-ray instrument and is therefore located in the operating room. It provides one or more substantially instantaneous images making it possible for the surgeon to align the positioning device relative to the nail in step-by-step fashion.

Prior patent documents EP 1499249 and EP 1719465, the latter being in the name of the same applicant as this invention, both teach the use of positioning devices where an external arm is fixed to the nail to be inserted into the bone and where the selfsame arm mounts a bar which, in use, extends substantially parallel to the bone and to the nail inserted in the bone.

At the distal end of it, the bar has a head in which there are guiding holes for the distal screws to be inserted and which can be adjusted in order to allow the holes to be aligned with the matching holes in the nail.

The head is made of a radio-transparent material.

Both of the above mentioned prior patent documents describe the presence, on the positioning head, of radio-opaque markings adapted to allow initial alignment between the beam emitted by the brightness amplifier and the guide holes made in the head.

Both of the devices described in the prior patent documents EP 1499249 and EP 1719465 are not, however, free of disadvantages.

In particular, by the very nature of their structure, these solutions cannot guarantee either error-free or particularly rapid alignment. Indeed, alignment may involve often repeated exposure to radiation (emitted by the brightness amplifier) which is harmful to both patient and medical staff.

Disclosure of the Invention

According to the invention, the aim to overcome the drawbacks of the known prior art, is achieved by a positioning device comprising the technical features described in one or more of the appended claims.

The technical features of the invention, in accordance with the above mentioned aim, may be clearly inferred from the contents of the appended claims, in particular from claim 1 and, preferably, from any of the claims directly or indirectly dependent on claim 1.

Brief Description of the Drawings

The advantages of the invention are more apparent from the detailed description which follows, with reference to the accompanying drawings which illustrate a preferred, non-limiting example embodiment of the invention and in which:

- Figure 1 is a schematic perspective view showing the positioning device according to the invention, in combination with a long bone such as a femur, for example;

- Figure 2 is a schematic front view, with some parts transparent in order to better illustrate others, of the positioning device of Figure 1, combined with a femur, also shown as transparent;

- Figure 3 is a schematic perspective view of a detail of the positioning device of the previous figures;

- Figure 4 is a schematic side view of the detail of Figure 3;

- Figure 5 is a cross section view of the detail of Figure 4 through the line

V-V;

- Figures 6 and 7 are two plan views, from above and below, respectively, showing the detail of Figures 3 to 5;

- Figures 8 to 10 illustrate, in respective schematic views with some parts cut away for clarity, three different steps in the use of the device according to the invention. Detailed Description of the Preferred Embodiments of the Invention

With reference to the accompanying drawings, the numeral 1 denotes in its entirety a positioning device according to the invention, combined with an endomedullary nail 2 of known type.

By way of an example, the nail 2 is inserted in a femur 3.

The nail 2 is inserted into the femur 3 in a substantially known anterograde manner, for example to support a femur fracture and, as illustrated in Figure 2, has two proximal fastening screws 4, that is, two screws close to the head 3a of the femur 3, already applied to it.

As illustrated in Figure 2, the two proximal fastening screws 4 are inserted in holes PH especially made in the nail 2 for the passage of the screws themselves.

The nail 2 has a principal longitudinal direction of extension A2.

The positioning device 1 comprises an arm 5 connectable to the nail 2 and a bar 6 mounted at a first end of it 6a to the arm 5.

The bar 6 extends substantially parallel to the principal direction of extension A2 of the nail 2. The bar 6 has a second end 6b longitudinally opposite the first end 6a.

At the second end of it 6b the bar 6 mounts a head 7 for aligning and guiding the distal fastening screws.

The distal fastening screws, not illustrated in the accompanying drawings, are designed to secure the end of the nail 2 to the distal part 3b of the femur 3, passing through respective passage holes DHl, DH2 made in the nail 2, shown in Figure 2.

The head 7 is connected to the bar 6 by a slider device 8 designed to slide the head 7 relative to the bar 6 along a direction A7 substantially perpendicular to the direction of extension of the bar 6 itself.

The slider device 8 comprises a screw actuation element 9 by which the head 7 is made to slide along the direction A7.

For a full description, both structural and functional, of the slider device 8, the reader is referred to the above mentioned document EP 1719465 in the name of the same applicant as this invention.

The head 7 is made of a radio-transparent material and has a substantially cylindrical body 10 and an eyelet 11 projecting from the body 10.

By means of the eyelet 11 the head 7 is connected through a screw element 12 to the bar 6 and, more precisely, to the slider device 8.

On the body 10 of the head 7 there are two pairs of holes 13, 14 and 13',

14', hereinafter referred to as guide holes because of their twofold function both of guiding the distal screws during their application and of guiding and/or housing the instruments used to position and insert them correctly.

The guide holes 13, 14 and 13', 14' are through holes and their longitudinal extension is interrupted by a lightening cavity 10a made in the body 10.

The guide holes 13, 14 and 13', 14' are advantageously arranged mirror- symmetrically about a midplane (not illustrated) common to both the head 7 and to the bar 6 and perpendicular to the direction A7.

More specifically, advantageously, the pairs of holes 13, 14 and 13', 14' are arranged on two lines L, L' which are slightly divergent from each other by an angle equal to the angle of deviation of the distal portion of the nail 2 relative to the aforementioned plane.

Further, the distance between the holes 13 and 14 and between the holes 13' and 14' is equal to the distance between the passage holes DHl, DH2 made in the nail 2. In practice, the choice to use the pair of holes 13, 14 or 13', 14' to guide the screws depends on the direction of the nail deviation angle, according to whether the nail has to be inserted into a right-hand bone or a left-hand bone.

As illustrated in Figures 1 and 2, inserted in one of the guide holes 13, 13', 14, 14' there is a removable member 15 which is designed, as described in detail below, to facilitate correctly aligning the guide holes 13, 13', 14, 14' themselves relative to the corresponding passage holes DH1, DH2 made in the nail 2.

The removable member 15, clearly illustrated in Figures 3-7, comprises a substantially cylindrical central body 16 made of a radio-transparent material and having a central axis A 16.

The removable member 15 has a first and a second flange, labelled 17 and 18 respectively, extending radially from the central body 16 and spaced from each other along the direction defined by the axis A 16.

The first flange 17 is located at an intermediate position between two longitudinally opposite ends 15a, 15b of the removable member 15 and is designed to define a reference stop against the alignment head 7, as clearly illustrated in Figures 1 and 2.

The second flange 18, on the other hand, is located at the end 15a of the member 15 furthest from the bone 3 and from the nail 2.

Advantageously, at the end of it 15b closest to the bone 3, the removable member 15 has a rounded tip adapted to come into contact with the patient's skin, if necessary, without causing abrasions or lesions of any kind.

Advantageously, but not necessarily, to facilitate its production, the removable member 15 is made in two parts connected to each other for example by screwing, as clearly shown in Figure 5.

Cavities filled with radio-opaque material in the removable member 15 make a plurality of radio-opaque portions defining markings which are visible through the images obtained from the brightness amplifier.

More in detail, a first radio-opaque portion 19 is made in the vicinity of the end 15b with the rounded tip.

Advantageously, the shape of the first radio-opaque portion 19, and hence of the respective image visible through the brightness amplifier, is substantially punctiform.

A second radio-opaque portion 20 is made on the first flange 17. Advantageously, the shape of the second radio-opaque portion 20, and hence of the respective image visible through the brightness amplifier, is approximately circular, with a plurality of ears projecting from the respective circumference.

A third radio-opaque portion 21 is made on the second flange 18.

Advantageously, the shape of the third radio-opaque portion 21, and hence of the respective image visible through the brightness amplifier, is substantially circular.

The three radio-opaque portions 19, 20 and 21 have a single central axis, the axis A 16, common to the three of them, and therefore appear concentric to an observer at a point in line with the selfsame axis A16.

In use, thanks to the positioning device 1 according to the invention, a guide hole 13, 13', 14, 14' for the distal screws can be aligned rapidly and effectively with the matching passage hole DH1, DH2 made in the nail 2.

More in detail, once the nail 2 has been inserted into the femur 3 and the proximal screws 4 have also been inserted, it is necessary to proceed to aligning the brightness amplifier (not illustrated) relative to the removable member 15 which has already been inserted into one of the guide holes 13, 13', 14, 14' in the head 7.

In the example shown in the accompanying drawings, it is the guide holes

13, 14 which need to be aligned with the matching passage holes DH1, DH2.

As shown for example in Figure 8, which schematically represents a first image obtained from the brightness amplifier, the removable member 15 is located at a random position, misaligned with the principal direction of emission of the brightness amplifier.

For that reson, the three radio-opaque portions 19, 20, 21 present at different points of the removable member 15 are not concentric.

By suitably adjusting the position of the emission head (not illustrated) of the brightness amplifier, it is possible to adjust the image (Figure 9) so the three radio-opaque portions 19, 20, 21 are in a concentric configuration. This image represents the position where the direction of emission of the brightness amplifier rays is aligned with the central axis A16 of the removable member, the axis relative to which the three radio-opaque portions 19, 20, 21 are concentric.

Figure 9 thus shows a condition of substantial parallelism between the direction of emission of the brightness amplifier rays and the guide holes 13, 13', 14, 14' present on the head 7. This situation minimizes problems in positioning the distal screws due to the parallax error, that is to say, in other terms, the measuring error due in the specific case to the non-coplanar position of the holes to be aligned.

Starting from the aligned configuration illustrated in Figure 9, the operator

(in practice, the surgeon) must adjust the slider device 8 to set the head 7 so that the three radio-opaque portions, now concentric with each other, are brought into alignment with, for example, the passage hole DHL

More specifically, in the embodiment described, in order to position the distal screws correctly, the punctiform radio-opaque portion 19 should be aligned with the centre of the passage hole DHL This configuration is illustrated in Figure 10.

Thus, for the positioning device 1, the slider device 8 constitutes adjustment means for bringing at least one guide hole 13, 13', 14, 14' into alignment with at least one matching passage hole DH1, DH2.

At this point, the removable member 15 can be extracted from the guide hole 13 it was inserted in. The hole 13 itself is thus made free so it can suitably guide and house the surgical instruments needed to prepare for the insertion of the distal screw (not illustrated) into the hole DHL

Once the distal screw has been inserted into the hole DH1, a second distal screw can, if necessary, be inserted into the hole DH2 by simply using the hole 14 as a guide for the surgical instruments and for the distal screw itself, obviously provided always that the centre distance between the holes 13 and 14 on the head 7 is compatible with the actual distance between the holes DH1, DH2.

The invention described has important advantages.

A first advantage is due to the fact that since the removable member 15 extends well beyond the head 7, both towards and away from the patient's body (see Figure 1), the precision obtained in aligning the guide hole with the brightness amplifier is greater than that obtainable with the prior art devices, where the radio-opaque portions are located exclusively on the head.

Another advantage inherent in the device 1 according to the invention is due to the presence, in the removable member 15, of an extension towards the patient's body. This extension enables the position of the radio-opaque portions - at least of the first portion 19 - to be moved considerably closer to the actual position of the nail 2 (and of the holes DH1, DH2 therein). This circumstance, too, contributes to increasing the positioning precision of the guide hole relative to the passage holes in the nail.

Advantageously, moreover, the removable member 15 can also be used, as a function also of the size of the individual patient's limb, to apply a certain amount of pressure on the patient's skin - thanks also to its rounded tip - so as to get very close to the bone in which the nail is positioned.

Advantageously, the positioning device 1 has removable members 15 of different lengths so it can adapt to different patient body structures. In other words, depending on the amount of soft tissue on the limb subjected to the surgical operation, the removable member 15 of the most suitable length can be selected to get as near as possible to the bone.

In this description, the term "flange" is used exclusively to mean a zone of larger diameter protruding from the central body of the removable member and substantially coaxial therewith, that is to say, without any reference to the possible connection between two or more flanges, as might be inferred considering the term "flange" in its broadest sense.

The invention described has evident industrial applications and can be modified and adapted in several ways without thereby departing from the scope of the inventive concept. Moreover, all the details of the invention may be substituted for technically equivalent elements.

Claims

1. A positioning device for screws used to fasten an endomedullary nail (2) having a principal direction of extension (A2) and presenting at least one hole (DH1, DH2) for the passage of the screws, comprising an arm (5) which is connectable to the nail (2), a bar (6) mounted at a first end of it (6a) to the arm (5) and extending substantially parallel to the principal direction of extension (A2) of the nail (2), an alignment head (7) mounted in the vicinity of a second end (6b) of the bar (6) opposite the first end (6a), the head (7) being made at least partly of a radio-transparent material, having at least one hole (13, 13', 14, 14') for guiding the fastening screws and being movable relative to the nail (2) through the agency of respective adjustment means (8) in order to bring the at least one guide hole (13, 13', 14, 14') into alignment with the at least one passage hole (DH1, DH2), characterized in that it comprises a removable member (15) extending longitudinally along its central axis (A 16), adapted to be inserted into the guide hole (13, 13', 14, 14') and to emerge from the alignment head (7) towards the nail (2), the removable member (15) having at least two radio-opaque concentric portions (19, 20, 21) positioned at different points along the central axis (A16), at least one of the portions (19, 20, 21) being external of the head (7).

2. The positioning device according to claim 1, characterized in that the removable member (15) comprises a central body (16) and a first flange (17) extending from the central body (16) and adapted to define an abutment for the head (7).

3. The positioning device according to claim 2, characterized in that one of the radio-opaque concentric portions (19, 20, 21) is formed on the first flange (17).

4. The positioning device according to any of the claims from 1 to 3, characterized in that one of the radio-opaque portions (19, 20, 21) is pointed in shape and is located at the end (15b) of the member (15) closest to the nail (2).

5. The positioning device according to any of the claims from 1 to 4, characterized in that the removable member (15) comprises, near the end of it (15a) which is furthest from nail (2), a second flange (18).

6. The positioning device according to claims 3, 4 and 5, characterized in that the three radio-opaque portions (19, 20, 21) present on the removable member (15), respectively on the two flanges (17, 18) and near the end of it (15b), are shaped in such a way as to be concentric for an observer in line with the central axis (A16) of the selfsame removable member (15).

7. The positioning device according to any of the claims from 1 to 6, characterized in that it comprises a plurality of removable members (15) of different lengths.