WO2012107875A1

WO2012107875A1 - Device for the location of the position of fastening holes of endomedullary nail

Info

Publication number: WO2012107875A1
Application number: PCT/IB2012/050542
Authority: WO
Inventors: Francesco SOMMAVILLA
Original assignee: Asso Srl
Priority date: 2011-02-07
Filing date: 2012-02-07
Publication date: 2012-08-16
Also published as: ITTV20110015A1; IT1403826B1

Abstract

The present invention relates to a device 10 for the position of the axis of a transversal fastening hole 14 of a hollow endomedullary nail 12 positioned inside a medullary canal of a bone 5. Said device 10 comprises a flexible detection probe 20 suitable to be axially inserted with a head end 30 inside the endomedullary nail 12 to slide therein. On the head end 30 of said detection probe 20, an alignment or location sensor is placed. Said alignment or location sensor is suitable to signal an alignment condition between the transversal fastening hole 14 of the endomedullary nail 12 and the sensor itself 32. The device 10 further comprises detecting means 40, 50. Said detecting means 40, 50 are connected to the detection probe 20 and they are suitable to provide data on the space position of the head end 30 of the detection probe 20 with respect to a preset reference system. The device 10 also comprises computing means 70 which are suitable to receive data detected by the detecting means 40, 50. On the basis of data received from the detecting means 40, 50 and at the alignment condition signalled by the alignment sensor 32, computing means 70 allow to compute the position coordinates in the space of the axis of the transversal fastening hole 14 of the endomedullary nail 12 with respect to an external reference system. Finally, the present invention relates to an alignment equipment 80 of a drill 104 comprising said position locating device 10 and pointing means 90, comprising themselves a drill guiding device 95. Said pointing means are suitable to align, on the basis of the position coordinates provided by the device 10, a longitudinal axis K of the drill guiding device 95 with the axis of the fastening hole of the endomedullary nail 12.

Description

" Device for the location of the position of fastening holes o endomeduUary nail"

Description

The present invention relates to a device for the location of the position of fastening holes of an endomeduUary nail, once that said nail has been inserted inside the meduUary canal of a bone.

The present invention also relates to pointing and guiding equipment for a drilling tool having a driU suitable to drill a bone inside which an endomeduUary nail has been introduced.

It is known that the reduction and the stabilization of several types of fractures of long bones, as for example the fractures of the femur, tibia, humerus and fibula, are surgicaUy resolved through surgical techniques which involve the use of an endomeduUary nail.

Said endomeduUary nails, whose length can vary depending on the age of the patient and on the type of the limb inside which they must be inserted, are provided, at the two ends, with proper transversal fastening holes.

SpecificaUy, the fastening holes positioned near the head of the endomeduUary naU are named proximal holes, whereas the fastening holes positioned on the terminal end of the endomeduUary nail are named distal holes.

In order to guarantee the fuU healing of the fractured bone, the endomeduUary naU, after having been inserted inside the meduUary canal of the fractured bone, must be properly fastened to the bone itself, so that to fix and stabiUze to each other the parts of the fractured bone.

The techniques in use require that the insertion of the endomeduUary nail inside the medullary canal can be done either with antegrade or retrograde endomeduUary nailing.

The surgical access to the medullary canal with antegrade endomeduUary nailing requires, for fractures of the femoral bone, the insertion of the endomeduUary nail from the nearest part of the femur to the hip, whereas, always for fractures of the femoral bone, the access to the endomeduUary canal with retrograde endomeduUary nailing, requires the insertion of the endomeduUary nail from the nearest part of the femur to the knee.

Likewise, for fractures of the humerus, the access to the endomeduUary canal with antegrade endomeduUary nailing requires the insertion of the endomeduUary nail from the nearest part of the humerus to the clavicle, whereas, always for fractures of the humerus, the surgical access to the meduUary canal with retrograde endomeduUary nailing requires that the insertion of the endomeduUary naU is done from the nearest part of the humerus to the elbow. The endomedullary nail insertion inside the medullar canal, either with antegrade or retrograde endomeduUary nailing, is done by using a device named 'guide-wire'.

In detail, the surgeon first prepares the area on which he must intervene, setting, through an incision of the tissues surrounding the fractured bone, an access way to the bone itself.

Later, after having provided, if necessary, for the reaming of the medullary canal, the surgeon proceeds to the insertion inside the medullary canal of said guide-wire.

Said guiding device has the function of directing inside the medullary canal the endomedullary nail and consequentiy of guiding the surgeon during the insertion operation inside the medullary canal.

The guide-wire generally consists of a steel rood of a diameter about 3 mm and has at its head a bulge named olive. Said bulge allows easier entry of the guide-wire inside the medullary canal. The nail is axially perforated for running on the guide-wire until it reaches its final position in the medullary canal.

The surgeon extracts the guide-wire once the endomedullary nail has been positioned in its operative position inside the fractured bone.

As mentioned above, the endomedullary nail, after having been inserted inside the medullary canal, must be fastened to the fractured bone in order to stabilize the fracture.

The endomedullary nail fastening is performed by means of fastening screws which, passing through the surrounding tissues of the fractured bone along a direction substantiaUy transversal to the axis of the nail, are inserted inside the fixing holes of the endomedullary nail.

The procedure used for the insertion of the fastening screws into the fastening holes of the endomedullary nail requires a precise location of the position of the fastening holes in order to properly insert the screw into the corresponding hole.

Besides, it must be avoided that the fastening screw may hit, even if only slightly, against the end of the endomedullary nail, so that making it divert from its correct operative position and thus jeopardizing the correct result of the surgical operation.

The fastening of the fastening screws inside the proximal holes of the endomedullary nail has no particular difficulty as the proximal end of the nail does not undergo any deformation during its insertion and it is easily identified by the surgeon with the aid of proper centering jigs which allow to easily obtain a proper alignment of the fastening screw with the axis of the proximal hole of the endomedullary nail.

On the contrary, the fastening of the fastening screws inside the distal holes of the endomedullary nail represents a rather complex operation to perform. The terminal end of the endomedullary nail, in fact, during its insertion into the medullary canal of the fractured bone, inevitably undergoes a slight bending and/ or torsion.

Therefore, the endomedullay nail, considered in its whole, after having been inserted inside the medullary canal, presents a different geometry compared to its original shape.

As a result of such deformation, the relative position of the distal fastening holes compared to the position of the proximal fastening holes is varied.

Consequently, for the fastening of the fastening screws inside the distal holes of the endomedullary nail, it is no longer possible to use only centering jigs similar to those used for the fastening of the fastening screws into the proximal holes of the endomedullary nail.

The references on the centering jigs allow, in fact, to locate the position of the distal holes of the endomedullary nail only if the endomedullary nail does not present any variation with respect to its own shape and initial configuration.

On the other hand, the surgeon is not able to establish exactly how much the relative position of the distal fastening holes of the endomedullary nail has changed due to the deformation undergone by the endomedullary nail during the insertion inside the medullar canal.

Consequently, the surgeon is not even autonomously able to restore 'a posteriori' the correct alignment between the references of the centering jig and the distal holes by changing, according to the deformation undergone by the endomedullary nail, the mutual position of the centering jig with respect to the deformed endomedullary nail.

To overcome this problem, a series of x-rays are taken, an average of 5/ 6 x-rays per implant, with the aim to assist and to guide the surgeon in the process of restoring the proper alignment between the external centering jig and the endomedullary nail (deformed) inserted inside the medullar canal.

Essentially, the surgeon, according to the information received from the x-rays, proceeds by trial and error to change the position of the external centering jig as long as the latter is positioned in such a way to align itself with the holes of the distal end of the nail and to allow the collimation of the drill, by means of which the bone is drilled, and the axis of the distal hole inside which the fastening screw must be inserted.

The use of jigs and the need for an x-ray monitoring of the positions for the slots of the fastening screws are not free from defects.

On the one hand, the timing of the implant is rather long. As mentioned above, the surgeon is forced to proceed by trial and error to achieve the correct alignment of the external centering jig with respect to the endomedullary nail.

Besides, to the indispensable technical timing needed to perform the insertion of the endomedullary nail into the medullar canal and to perform the subsequent fastening to the bone, the necessary timing for the x-rays and the reading of themselves must be added, causing a consequent prolonged duration of surgery.

Furthermore, the need for a series of x-rays to locate the correct position of the distal nails of the endomedullary nail, can submit the patient and the whole surgical team to an exposure to ionizing radiation with the consequent health risks that this involves.

Finally, even if the surgeon performing the implant is particularly skilled and experienced, the alignment between external centering jig and endomedullary nail is always subject to a certain degree of imprecision and consequently it may affect the correct fastening of the endomedullary nail and the patient's recovery.

The object of the present invention is therefore to substantially overcome the disadvantages of the prior art.

In particular, an aim of the present invention is to provide a device suitable for accurately and quickly identifying the position of the fastening holes of an endomedullary nail, even if deformed, once said nail has been inserted inside the medullary canal of a bone

An other aim of the present invention is to provide a device suitable for simplifying the procedure of the location of the position of the fastening holes of an endomedullary nail.

A further aim of the present invention is to provide a pointing and guiding equipment for a drilling tool which can align the drill of the tool with the fastening hole of the endomedullary nail without having to use x-rays.

The object and aims mentioned above are achieved by a device according to what is claimed in claim 1 and by a guiding equipment according to what is claimed in claim 9.

The features and the additional advantages of the invention will emerge from the description made below of some embodiments, given as indicative and not exhaustive example with reference to the attached drawings in which:

figure 1 schematically shows a perspective view of the device and the equipment according to the invention;

figure 2 schematically shows a top view, partially in section, of the device inserted inside an endomedullary nail, according to the invention; figure 2a schematically shows a larger exploded view of the detail of figure 1 referenced by B;

figure 3 schematically shows a side view, partially in section, of the device inserted inside an endomeduUary nail, according to the invention;

figure 4 schematically shows view, partiaUy in section, of an end of a probe of the device according to the invention, in a first operative condition;

figure 5 schematicaUy shows a sectional view taken along the plane of trace V-V of figure 4; figure 6 schematicaUy shows a sectional view, similar to figure 4, of the device in a second operative condition;

figure 7 schematicaUy shows a sectional view taken along the plane of trace VII-VII of figure 6;

figure 8 schematicaUy shows a top view of the detaU of figure 6;

figure 9 schematicaUy shows a larger view of the detail of figure 1 referenced by A;

figure 10 schematicaUy shows a sectional view of the detail of figure 9 along the plane of trace X-X;

figure 11 schematicaUy shows a view, partiaUy in section, of a second component of the device according to the invention;

figure 12 schematicaUy shows the section of a component of the device according to the invention, taken along the plane of trace XII-XX of figure 2;

figure 13 schematicaUy shows the section of the component of figure 12, in a second operative condition;

figure 14 schematicaUy shows a perspective view of a component of the equipment according to the invention, in a first operative condition;

figure 15 schematicaUy shows a perspective view of the component of figure 14 in a second operative condition.

With reference to the attached figures, the present invention refers to a device 10 for the location of the position of the axis of a transversal fastening hole 14 of a hoUow endomeduUary nail 12 positioned inside a meduUary canal of a bone 5.

Said device 10 comprises a flexible detection probe 20 suitable to be axiaUy inserted with a head end 30 inside the endomeduUary 12 to sHde therein. On the head end 30 of said detection probe 20, an alignment or location sensor 32 is placed. Said alignment or location sensor 32 is suitable to signal an alignment condition between the transversal fastening hole 1 of the endomedullary nail 12 and the sensor itself 32.

Device 10 further comprises detecting means 40, 50. Said detecting means 40, 50 are connected to the detection probe 20 and suitable to provide data on the space position (for example, xs, ys, zs, 6xs, 9ys, dzs) of the head end 30 of the detection probe 20 with respect to a preset reference system. Herein as space position there will be genetically indicate either the spatial coordinates or the orientation (at least due to an axial rotation of the probe).

Device 10 further comprises computing means 70 which are suitable to receive the data detected by the detecting means 40, 50.

On the basis of the data received from the detecting means 40, 50 and of the alignment condition signalled by the alignment or location sensor 32, computing means 70 allow to compute position coordinates (for example x_r, y_f, z_f Gx_f 6y_f,

in the space of the transversal fastening hole 14 of the endomedullary nail 12 with respect to an external reference system Xp, Yp, Zp.

Advantageously, the axis Yp of said external reference system substantially coincides with the insertion direction of the probe inside the nail 12, while the axis Xp coincides with an axis perpendicular to the insertion direction of the detection probe 20.

The axis Zp extends perpendicularly to plane Xp, Yp.

With reference to figures 9 and 10, the detection probe 20 comprises a probe body 22 of elongated shape, made of polymeric material, preferably in glass fibres reinforced technopolymer .

As a matter of fact, the probe 20on the one hand must be flexible, to adapt itself to the deformed shape of the endomedullary nail 12, once that the latter has been inserted inside the endomedullary canal of the fractured bone, on the other hand it must be able to slide easily inside the endomedullary nail itself 12, avoiding to deform itself uncontrollably as a result of push action performed by the operator during the insertion inside the longitudinal hole of the endomedullary nail 12. Moreover, the probe itself, as it will be clear from below, must have adequate torsional stiffness.

The probe body 22 is provided with a first end, the head end 30, suitable to be inserted and to slide inside the longitudinal hole of the endomedullary naill2, and with a second end, tail end 33, opposite to said head end 30 (see figure 1). The tail end 33 is not inserted inside the endomedullary nail and being suitable to remain integral to the external reference system Xp, Yp and Zp, it serves, as it will be described in detail below, as a reference to determine the position in the space of the head end 30 once the probe has been inserted inside the endomedullary nail 12.

The probe body 22 preferably presents a substantially elongated cylindrical form. In the preferred embodiment, the outer profile of the probe body 22 can be assimilated to a circumference missing two circular segments positioned in a symmetrical position with respect to one another.

From each secant of these circular segments, a element 24 protrudes being suitable, as it will be explained in detail below, to act as a connection means to the detecting means 40 and the detecting means 50 (see figures 10, 12 and 3).

The length of the detection probe 20 depends on the length of the endomedullary nail 12 inside which it must be inserted. At the head end 30 of the detection probe 20 the alignment sensor 32 is placed.

Said alignment sensor 32 has the function to signal the occurred alignment between the sensor itself 32 and the axis of the transversal fastening hole 14.

In a first embodiment, the alignment sensor 32 comprises a feeler member 34 which may radially protrude from the probe 20 and it is suitable to engage in a removable way the inside of the transversal fastening hole 14 of the endomedullary nail 12, as it will be clearified below.

In this way, the head end 30 of the probe 20, which after the insertion of the probe 20 inside the endomedullary nail 12 is closer to said fastening hole 14, is made integral to said fastening hole 14.

Following to the engagement of the feeler member 34 with the transversal hole 14 it is possible to detect, by means of the detection of the space-oriented position of the head end 30 of the probe 20, the space-oriented position of the axis of the transversal hole 14.

As a matter of fact, being either flexible or able to rotate around an own longitudinal axis, the probe 20 allows, as it will be explained below, to detect also the deformations undergone by the endomedullary nail 12 as a result of the insertion of the nail itself inside the medullary canal of the fractured bone 5.

As schematically shown in figures 4-8, the feeler element 34 in the preferred embodiment comprises an element with a rounded end 36 connected to the body of the alignment sensor 32 by means of elastic supports 38 that push the element 36 radially towards the outside of the probe. Preferably, the rounded end 36 has a hemispherical shape.

As shown in figure 4, the rounded or hemispherical element 36 is suitable to remain inside the body of the alignment sensor 32 during the insertion of the probe along the axial hole of the endomedullary body 12.

The elastic supports 38 keep it in contact with the inner surface of the axial hole of the endomedullary nail 12 as long as a discontinuity in said surface is not met, for example a transversal fastening hole 14.

In this case, in fact, the element of rounded or hemispherical shape 36, as a result of the push received from the elastic supports 38, moves toward the outside of the body of the alignment sensor 32 thus engaging the fastening hole 14, as it is well shown in figures 6 and 7.

The rounded or hemispherical shape of the protruding part of the element 36 helps the release of the feeler element 34 from the inside of the transversal hole 14 once the position detection of the axis of the hole is completed.

iAs a matter of fact, when the probe is pulled for being extracted from inside the endomedullary nail, the hemispherical element 36 is forced by the contact with the inner surface of the axial hole of the endomedullary nail to return inside the body of the alignment sensor 32. Such movement is allowed by the provision of the elastic supports 38.

In a second embodiment, the alignment or location sensor 32 comprises a proximity sensor (not shown in the attached figures) with detecting axis transversally directed with respect to the axis of the head 30 of the probe 20.

Said proximity sensor is suitable to detect the fastening hole 14 when the end 30 of the probe 20 is near to said fastening hole 14.

Such a sensor for the detection of a hole is in itself known and therefore easy to be conceived for a skilled operator on the basis of the description of the invention made here. For example, the sensor can be a known reflex optical sensor, a hall effect proximity sensor, etc..

The device 10 comprises, as above mentioned, detection means 40, 50.

Said detecting means 40, 50 are connected to the detection probe 20 and are suitable to provide data on the space position of the head end 30 of the detection probe 20, with respect to the external reference system Xp, Yp, Zp, once said probe has been inserted inside the endomedullary nail 12. The detecting means 40, 50 comprise sensor means 40 for the bending of the probe with respect to a straight condition and sensor means 50 for the rotation of the probe 20 around its own longitudinal axis Yp.

In particular, said sensor means for the bending 40 allo to detect possible deviations of the probe body 22 with respect to its original shape respectively in the planes XpYp, XpZp and YpZp.

The sensor means for the bending 40 preferably comprise at least three linear transducers 44 that are housed in a body of support 46 provided on the tail end 33 of the probe 20 and each of these transducers being connected to a flexible tie -rod 42 substantially inextensible, advantageously made of stainless (see figure 11).

The linear transducers 44 can be of any known type. For example, they can be at induction, with a ferromagnetic core that slides, against the action of a spring, as a result of the traction exerted by the corresponding tie-rod.

The probe body 22, preferably, has three longitudinal canals 26 of circular section.

The longitudinal axes of said canals 26, substantially parallel to the axis Yp of reference when the probe is not bent, are arranged along a circle of smaller radius than the outer radius of the probe body 22 and they intersect three radii of the probe body 22 arranged to each other at 120° (see figure 10).

In the preferred embodiment, the flexible tie-rods 42 of each linear transducer are arranged inside the longitudinal canals 26 of the probe body 22.

The free ends of the flexible tie-rods 42 are fastened in a known way at the tip of the probe (near the alignment sensor 32 of the detection probe 20) whereas the transducers 44 are mounted in proper cavities 47, inside the housing or body 46, as best seen in figure 11.

The housing 46 for the sensor means 40 has preferably conical shape and it is provided with a mobile head 48 on which the connectors suitable for transmitting to the computing means 70 the data detected from the detecting means 40 of device 10 are positioned.

The housing or body 46 is in its turn mounted (as to rotate around the axis Yp of reference) on a support truck 49 suitable to slide along a linear guide 60, having its own longitudinal axes parallel to the Yp axis of reference.

To a linear distortion of the probe (that is, to a transversal bending of the probe body with respect to its not bent stand-by position) it will correspond proportional signals of Hnear displacement or traction of the three linear transducers 44 because of the traction, produced by the probe bending, that their corresponding tie-rods 42 transmit them.

From these signals it is possible to know the position of the head 30 of the probe 20 following to the distortion.

The sensor means for the rotation 50 in the preferred embodiment consist of an angular position transducer 50 housed inside a substantially cylindrical housing/ slot, whose longitudinal axis coincides with the axis of reference Yp.

Said housing 56 is fastened to an end of the linear guide 60.

The angular position transducer 50 preferably is composed bya rotary encoder which comprises in a known way a stationary body 52, integral to the housing 56, inside which various electronic elements of the transducer are housed, and of a hollow mobile part 54, coaxial with the stationary body 52 and suitable to be coupled to the probe body 22 of the detection probe 20.

As it will be clear for the skilled man, the rotary encoder can be an absolute rotary encoder or an incremental rotary encoder with a proper detection device for detecting a predetermined 'zero' position.

The mobile part 54 is suitable for being crossed by the probe body 22 of the detection probe 20 and it has an inner section corresponding to the outer section of the probe body 22. In particular, the mobile part 54 of the transducer has along its own inner section some cavities 55 adapted to be easily engaged by the mating means 24 of the probe body 22.

As it can be seen from figures 12 and 13, where for sake of clarity the housing 56, external and integral with the mobile part 54,is not shown, a possible rotation of the probe body 22 around the axis Yp causes a corresponding rotation of the mobile part 54 of the transducer 50, allowing the detection of the rotation or angular displacement ΘΥρ of the probe body 22 of the detection probe 20 with respect to the reference system.

The detection of such angular displacement ΘΥρ, if carried out after the signalling by the alignment sensor 32 has of the alignment between the sensor itself and the transversal axis of the fastening hole of the endomedullary naill4, allows to detect how much the fastening hole has varied its angular position with respect to the external reference system Xp, Yp, Zp.

The detection of said angular displacement ΘΥρ, together with the detection of the transversal distortions of the probe body 22 detected by the linear transducers 44 relatively to the reference planes pYp, XpZp and YpZp, is acquired by the computing means 70. As anticipated, said computing means 70 are suitable for calculating, on the basis of data received by the detecting means 40, 50, by means of known mathematical transformations which are obvious to the skilled man in the art, the position coordinates in the space of the transversal axis x_f, y_f, z_f of the fastening hole 14 of the endomeduUary hole 12.

For obtaining the coordinates of the probe tip with respect to an external absolute reference, it is necessary to know the position of the base of the probe with respect to which the bending of the probe are measured.

For this purpose, if the probe is chosen according to the length of the nail, it is possible to establish a fixed stop position of the truck 49 so as when the truck reaches said stop position, the alignment device on the probe head is situated on the plane, transversal to the probe, that contains the hole.

To locate the hole, after having reached said stop position, it is enough to axially rotate the probe until the alignment device signals the alignment with the hole.

In this way, the location of the hole (especially in the case of a mechanical feeler alignment sensor) is simplified and the computations are reduced.

The stop position can advantageously coincide with the coupling of the front portion of the body support 46 with the rear portion of the housing 56, as shown in figures 2 and 3.

Alternatively, for providing to the computing system the position of the truck along the guide with respect to the zero of the reference coordinate system, other known sliding transducers (not shown) can be envisaged.

In this way, when the alignment sensor signals the hole, the computing means can correct the position of the reference system of the probe base along the guide 60 with respect to the chosen absolute reference system.

The computing means 70 are means known per se and herein they will not be described in detail. Said computing means 70 comprise a microprocessor computing unit (for example a personal computer properly programmed and provided with a known acquisition interface of sensors signals ) that on the basis of the bending signals received by the detecting means 40 calculates the corresponding position of the head end 30 of the probe 20 with respect to the tail end, opposite to said head end 30, and integral to the chosen reference system, except for the rotation detected by the sensor 50 (and for the possible sliding detected by the possible further sliding transducers, if a reference given by a stop position is not used). Likewise, the computing unit of the computing means 70 is suitable for calculating on the basis of the rotation signals detected by the detecting means 50 the orientation of the head end 30 of the probe 20 around the longitudinal axis Yp, said orientation being function of the rotation signals detected by the detecting means 50.

The computing means 70 are therefore able to provide, with respect to the external reference Xp, Yp, Zp, the coordinates x_f, y_f, z_f, 6x_f, 6y_f, 6z_f assumed in the space by the axis of the transversal hole of the endomedullary 12 inserted inside the bone 5 and they are therefore able to lead the surgeon in the realization in the fractured bone 5 of a hole aligned with the axis of said transversal fastening hole 14 without having to use x-rays and in less time.

If an alignment 'feeler' sensor is used, as described above, for greater accuracy it can be envisaged to engage the feeler element in the hole by means of a first axial rotation of the probe and then to slightly rotate the probe in both directions so as to locate the opposite edges of the hole.

In this way the system can calculate the midpoint of the rotation movement in both directions, said midpoint corresponding to centre of the hole.

The computed coordinates can be displayed by means of a displaying unit 100, as for example a monitor connected to the computing unit 70.

Advantageously, the above-mentioned device 10 can be used together with a proper alignment equipment 80 of a drill 104 suitable for producing in a bone 5 a hole aligned with a transversal fastening hole 14 of a hollow endomedullary bone 12 inserted in the bone 5.

The device 10 and the alignment equipment 80 achieve in this way a complete collimation system for bone drilling.

Said alignment equipment 80 comprises pointing devices 90 which comprise, in turn, a drill guiding device 95 suitable to guide the drill 104 during the drilling.

Said pointing devices 90 are suitable for augning, on the basis of the position coordinates detected by the device 10, a longitudinal axis K of the drill guiding device 95, so that the drill 104 is in turn aligned with the axis of the fastening hole of the endomedullary naill2.

In a first form embodiment of the alignment equipment 80 the pointing devices 90 comprise a pointing turret 90 arranged with a drill guide device 95 mounted on the turret itself 90 to be oriented by it. The position and the inclination of said drill guide device 95 is adjustable by acting on four control elements 91, 92, 93, 94 of the turret 90, said elements being movably connected to each other (see figure 14 and 15).

Advantageously, being mainly necessary to align axis K of the drill guiding device 95 with the axis of the hole, it takes only two position adjustments and two inclination adjustments with respect to the fixed reference system.

The pointing devices 90 are preferably mounted, in a mobile way, on a support 81 provided with a linear guide 82.

Advantageously, at the pointing turret 90 a second external reference system Xt, Yt and Zt can be defined (see figure 1).

The axis Yt of said external reference system coincides with the longitudinal axis of the guide 82 of the support 81, whereas the axis Xt coincides with an axis perpendicular to the longitudinal axis of the linear guide 82.

The axis Zt extends perpendicularly to the plane Xt, Yt.

If the linear guide 82 is positioned with its own longitudinal axis parallel to the reference axis Yp, the position coordinates (x_f, y_f, z_f, 6x_f, 6y_f, θζ,) of the axis of the transversal fastening hole 14 can be advantageously computed no longer with respect to the external reference system Xp, Yp and Zp, as defined above, but with respect to the reference system Xt, Yt and Zt.

Furthermore, by aligning manually or automatically, as it will explained in detail below, the axis Xt of the reference system integral with the pointing turret 90 with the axis of the transversal fastening hole in the not deformed position (known), the algorithm used by the computing means 70 is simplified.

The position of the turret 90, and consequently of the external reference system Xt, Yt, Zt, can be easily detected once the alignment equipment 80 is properly made integral with the endomedullary nail 12 inserted inside the bone 5.

As anticipated, by acting on the four control elements 91, 92, 93, 94 of the turret 90, the position and the inclination of the drill guiding device 95 are adjusted, based on data provided by the computing means 70 of the device 10.

Advantageously, said data can be provided by the means to the displaying unit 100 as setting data of the four control elements of the turret, so as to simplify the setting thereof by the surgeon. Naturally, when the whole device is positioned on the surgical field, it is chosen a position which already approaches the turret 90 where the hole 14 will be presumably positioned.

As a matter of fact, the deformation of the nail will not however exceed a certain value. Especially the rotating twist around the axis will presumably be comprised between—2° and +2°, so that the hole will still remain on the side of the device where the turret 90 is.

Advantageously, as clearly shown in figure 14, the first control element 91 is suitable to regulate the translation of the drill guiding device 95 along the guide 82. Said guide 82 is advantageously positioned integral and parallel to guide 60.

The translation of the drill guiding device 95 is shown in figure 14 by arrow Fl .

The second control element 92 is suitable to regulate the rotation of the drill guiding device 95 around axis Zt. Said rotation of the drill guiding device 95 is shown in figure 14 by arrow F2.

The third control element 93 is suitable to regulate the translation of the drill guiding device 95 along an axis parallel to axis Zt.

Said translation of the drill guiding device 95 is shown in figure 14 by arrow F3.

The fourth control element 94 is suitable to regulate the rotation of the drill guiding device 95 around axis Yt. Said rotation of the drill guiding device 95 is shown in figure 14 by arrow F4.

In figure 15, by way of example, it is shown one of the possible settings of the pointing turret 90 in order to align axis K of the drill guiding device 95 with the axis of the transversal fastening hole of the endomedullary nail 12.

In this specific case, it is depicted the hypothesis in which, by acting on the second control element 92 of the turret 90, it is given to axis K of the drill guiding device 95 a rotation around axis Zt equal to an angle ΘΖΐ and in which, by acting on the fourth control element 94 of the turret 90, it is given to axis K of the drill guiding device a rotation around axis Yt equal to an angle 6Yt.

Following the implementation of these settings, it is therefore possible to align, on the basis of the position data detected by the device 10, the drill guiding device 95 with the axis of the fastening hole 14.

The control devices can be manual, for example provided with graduated knobs for micrometric adjusting. In figures 14 and 15 the graduated knobs used for carrying out the rnicrometric adjustments of the control elements 91, 92, 93 and 94 are indicated by the references 91A, 92A, 93A and 94A respectively.

In the preferred embodiment of the pointing turret 90 the control devices comprise electric engines adjusted with feedback directly by the device 70 for moving automatically said pointing turret 90.

In this way it is possible to align the longitudinal axis K of the drill guiding device 95 with the axis of the fastening hole 14 of the endomedullary nail 12 without carrying out any manual operation, except the insertion of the detecting probe inside the nail 12 and the start of the pointing procedure.

Advantageously, the alignment equipment 80 can comprise a support 81, provided with a guide 82 on which the pointing means 90, a fastening bracket 83 and a cannular screw 87 are mounted.

The fastening bracket in its turn comprises a hollow tubular element 88, suitable for being crossed by a cannular screw 87, and a fastening arm 84 by means of which the bracket is fixed to the support 81.

By means of this fastening bracket 83, the endomedullary nail 12, once said nail 12 has been inserted inside the fractured bone 5, the device for the location of the position 10 and the support 81, on which the pointing means 90 are mounted, are firmly connected to each other.

In detail, as schematically shown in figure 2a, the cannular screw 87 is suitable to be fastened on the head of the nail 12 so that the longitudinal axis of the cannular screw 87 coincides with the axis of reference Yp.

The cannular screw 87 is generally fastened to the endomedullary nail 12 via a screw-nut screw coupling.

As a matter of fact, as shown in figure 2a, the cannular screw 87 has; at one end an outer thread 89 suitable for being engaged with the inner thread of the longitudinal hole of the nail 12 (not shown for sake of clarity).

As anticipated, the fastening bracket 83 comprises a hollow tubular element 88 and a fastening arm 84 which are orthogonal to each other.

The tubular element 88 has along its whole length a longitudinal hole 88a with a diameter equal to the outer diameter of the cannular screw 87. The fastening bracket 83 is made integral to the cannular screw 87, before the latter is locked to the endomedullary nail, by means of the insertion of the cannular screw 87 inside the longitudinal hole 88a of the tubular element 88 of the fastening bracket 83.

The following fastening of the cannular screw 87 to the endomedullary nail consequendy causes also the fastening of the fastening bracket 83 to the nail itself. As it can be seen in figure 2a, the end portion 87a of the cannular screw 87, once that this latter has been fastened to endomedullary nail 12, goes against the end 88b of the tubular element 88, thus making the fastening bracket 83 and the cannular screw integral to each other.

Advantageously, in correspondence of the cannular screw 87 and the tubular element 88 of the fastening bracket 83, a reference suitable for defining the preset 'zero' position of the rotating encoder can be provided.

As a matter of fact, as shown in figure 2a, on the outer surface of the tubular element 88 of the bracket 83 it can be advantageously arranged a hole 85 suitable for being engaged by the alignment sensor 32 of the probe 20 while this latter is inserted inside the cannular screw - bracket assembly.

Obviously, in this case, the cannular screw 87 will have a corresponding hole 85a suitable for collimating with the hole 85 once that the cannular screw 87 and the tubular element 88 are assembled together.

Advantageously, the engagement by the alignment sensor of such zero reference 85, allows to detect a zero reference position with respect to which it can be computed, once occurred the alignment between the alignment sensor and the transversal axis of the hole, of how much the fastening hole has changed its angular position with respect to the reference system.

The cannular screw 87— fastening bracket 83 coupling is made to ensure that the tubular element 88 of the bracket 83 coincides with the reference axis Xp.

The support 81 is coupled orthogonally to the fastening arm 84 of the bracket 93, preferably with a bayonet joint, so that its own longitudinal axis is parallel to the reference axis Yp and is consequendy parallel to the longitudinal axis of the cannular screw 87 and to the direction of the probe insertion 20.

The support 81 is afterwards fixed to a bearing plane by means of proper supporting means (not shown in the figures) so as to be able to support the whole equipment. The detection probe is suitable to slide inside the cannular screw 87 and therefore the device for the location 10 is coupled to the support 81 with the probe axis coincident with the reference axis Yp.

On the support 81 the linear guide 82 is provided, whose axis being parallel to the reference axis Yp, along which the pointing devices 90 can slide.

Close to the guide 82 some references showing the lengths of the various endomedullary nails usable for the reduction of various types of fractures can be arranged.

In this way, if the pointing means 90 are manually moved by the surgical staff, the positioning of the drill guiding device 95 is easier.

For the same reason, the guide 82 can also be provided, along its extension, with a plurality of clutches for the turret, with a predefined step along the support, for the easy positioning of the turret.

The support 81 is generally made of composite material, for example carbon fiber, assuring a high stiffness and a limited weight.

In the preferred embodiment, the support 81 has an anatomic shape so that it can be easily handled and used by both limbs.

Below, it will be briefly described the functioning of device 10 and equipment 80, with reference to the preferred embodiment.

After the insertion of the endomedullary nail 12 inside the medullar canal of the fractured bone, the tubular element 88 of the bracket 83 is fastened to the cannular screw 87.

Successively, in accordance with what above described, the fastening of the cannular screw 87 to the endomedullary nail 12 and the fastening of the support 81 for the pointing means 90 to the locking arm 84 of the bracket are carried out.

The coupling between the endomedullary nail 12 and the cannular screw 87 and the bracket 83 allows to define the axis of the external reference system Xp, Yp, Zp.

Said reference system has the first reference axis Xp directed according to the longitudinal axis of the fastening arm 84 of the bracket 83, the second reference axis Yp directed according to the longitudinal axis of the cannular screw 87 and the third reference axis directed orthogonally to the plane identified by Xp, Yp.

Successively the conic housing is rigidly coupled to the bracket 83 so that its own longitudinal axis is parallel to the second reference axis Yp. Consequently, the linear guide 60, on which the conic housing 46 for the sensor means for the bending 40 and the cylindrical housing 56 for the sensor means for teh rotation 50 are connected, is fixed to the cannular screw 87 with its own axis coinciding with the direction of insertion of the probe inside the endomedullary nail .

Furthermore the linear guide 60 is suitable for being locked on a support plan with proper fastening means.

By moving the conic housing 46 along the linear guide 60 towards the endomedullary nail 12, it is possible to insert the head end 30 of the detection probe 20 inside the cannular screw 87 thus assuring that the direction of insertion of the probe coincides with the second reference axis Yp.

The head end 30, after having been passed through the cannular screw 87, detects the preset '2ero' position of the rotating encoder by the engagement of the alignment sensor with the hole 85.

The condition of insertion can be detected by a suitable electric or electronic sensor, or directly by the surgeon through the resistance felt during the rotation of the probe due to the mechanic engagement of the feeler inside the hole.

After the detection of the 'zero' position of the encoder, the probe slides inside the axial hole of the endomedullary nail 12. The probe, being flexible, is suitable to adjust itself to the new shape of the endomedullary nail, the shape of the nail being varied with respect to its original shape due to the deformations undergone during the insertion inside the medullary canal.

The head end 30 slides inside the endomedullary nail 12 as far as it does not reach the transversal plane which includes the transversal hole 14. Reached this position, the rotation of the probe leads the feeler element 34 of the alignment sensor 32, provided at the head end 30 of the probe, to removably engage itself inside the fastening hole 14.

Also in this case the engagement cond tion can be detected by a suitable electric or electronic sensor, or direcdy by the surgeon through the resistance felt on the rotation of the probe due to the mechanic engagement of the feeler inside the hole.

After the detection of the occurred alignment, the detection of the spatial position assumed by the probe head 20 can be detected by means of sensor means for the bending (40) and sensor means for the rotation (50). The tie-rods housed inside the probe body 22, in fact, following to the insertion and the deformation of the probe 20 inside the endomedullary nail 12, undergo tractions or releases. The resulting modifications of the pull action of each tie-rod are detected by the transducers 44.

Said modifications, being proportional to the deformation of the probe, allows to obtain information about the displacement of the head end of the probe once it has been inserted inside the endomedullary nail.

Likewise, the sensor means for the rotation 50 detect how much the head end of the probe has rotated with respect to its initial configuration to reach the alignment of the alignment sensor with the hole.

The data detected by the sensor means for the bending 40 or by the sensor means for the rotation 50 are sent to the computing means 70.

The computing means convert the data received by the detecting means into coordinates calculated with respect to the reference system which will be set in the pointing means 90 so to allow an easy alignment of the longitudinal axis of the drill guiding device 95 with the axis of the transversal hole of the nail 12.

The shifting from the coordinates, calculated with respect to the main reference system (Xp, Yp, Zp), of the position in the space of the hole to the pointing coordinates of the drill guiding device 95 is easy since the computing means know the geometrical dimensions of the system, as for example the dimensions of the cannular screw 87, of the fastening bracket 83 and of the support 81.

Likewise, as anticipated, if the support 81 on which the pointing means 90 are provided, is positioned with the longitudinal axis of the guide 92 parallel to the insertion direction of the probe and if axis K of the drill guiding device 95 is aligned with the axis of the transversal fastening hole in the not deformed position, the pointing coordinates of the drill guiding device 95 can be calculated directly with respect to the reference system Xt, Yt and Zt.

In this latter case, the computation algorithm can operate without needing to set the dimensions of the cannular screw 87 and of the support 81. In this case, in fact, it is only necessary to set the dimensions of the distance between the axis of the probe and the longitudinal axis of the guide to detected, if it is need, how much the fastening hole has moved with respect to its not deformed position.

Once known the coordinates that the longitudinal axis K of the drill guiding device 95 must assumed, it will be possible to align the longitudinal axis of the drill guiding device 95 with the transversal axis of the fastening hole by carrying out (manually or with motorized systems) on the control devices 91, 92, 93, 94 of the pointing means 90 and by sliding the pointing means along the linear guide 82 of the support 81.

Once carried out the pointing, y the drill 104 can be inserted into the drill guiding device 95 and the hole in the bone for the transversal fastening screw can be correctly made.

From what has been described above, it is clear how both the device and the equipment according to the invention allow to solve the problems of the prior art.

To the embodiments of the device and the equipment described above, the skilled man in the art may, to meet specific needs, make changes and/or replacements of the described elements with equivalent elements, without however falling outside of the scope of protection of the attached claims.

For example, the motorized alignment system can be also made with a robotized arm provided with a drill and that receives from the computing system 70 the data regarding the calculated position of the hole in the nail and that directiy drills and, if necessary, carries out the positioning of the screw.

It can also be envisaged the use of an electronic alignment sensor having a detection range of 360° on a plane transversal to the axis of the probe and directly providing the angular position of the hole around the probe tip. In this case the rotation of the probe and the correspondent detecting sensor 50 can be avoided.

The guide 60 can also be different from what it has been shown or also be lacking. Obviously, if it is needed, the turret can also be provided with more than one drill guiding device (for example two) for the fast carrying out of more correlated holes.

The sensors means for the bending of the probe can also be of another known type, for example of the known optic-fiber optoelectronic type, with the fiber housed in the canals 26 and the corresponding optic sensor housed in the seat 47.

Claims

1. Device (10) for the location of the position of the axis of a transversal fastening hole (14) of a hollow endomedullary nail (12) positioned inside a medullary canal of a bone (5), comprising:

- a flexible detection probe (20) suitable to be axially inserted with a head end (30) inside the endomedullary nail (12) to slide therein;

- an alignment or location sensor (32) placed on the head end (30) of said detection probe (20); said alignment or location sensor (32) being suitable to signal an alignment condition between it and said transversal fastening hole (14) of the endomedullary nail (12);

- detecting means (40, 50) connected to said detection probe (20) and suitable to provide data on the space position of said head end (30) of the detection probe (20);

- computing means (70) receiving data from the detecting means (40, 50) and suited to compute, on the basis of the data received from the detecting means (40, 50) and of the alignment condition signalled by the alignment or location sensor (32), position coordinates in the space of the axis of the transversal fastening hole (14) of the endomedullary nail (12) with respect to a preset reference system, characterized in that the detecting means (40, 50) comprise sensor means (40) for the bending of the probe (20) with respect to a straight condition and sensor means (50) for the rotation of the probe (20) around its own longitudinal axis.

2. Device according to claim 1, characterized in that the bending sensor means (40) comprise at least three linear transducers (44); each of said linear transducers (44) being connected to a first end of a corresponding tie-rod (42) running inside the probe (20), the tie-rod (42) having an end, opposite to the first end, which is fastened near the tip of the probe.

3. Device according to claim 1, characterized in that the rotation sensor means (50) comprise an angular position transducer.

4. Device according to claim 1, characterized in that the alignment sensor (32) comprises a feeler member (34) suitable to be removably engaged in the fastening hole (14); said feeler member (34) protruding radially from the detection probe (20).

5. Device according to claim 4, characterized in that the feeler member (34) comprises at least one member (36) with a rounded end elastically protruding in radial direction from the probe.

6. Device according to claim 1 , characterized in that the alignment sensor (32) comprises a proximity sensor with sensing axis transversally directed with respect to the axis of the head (30) of the probe (20), suitable to detect the presence of the fastening hole (14) when the end (30) of the probe (20) is axially near said fastening hole (1 ).

7. Device according to claim 1, characterized in that the computing means (70) comprise a

microprocessor computing unit receiving bending signals from the sensors means for bending (40) of the probe (20) and compute, as a function of said bending signals, the corresponding position of the head end (30) of the probe (20) with respect to its own tail end (33) opposed to said head end (30).

8. Device according to claim 7, characterized in that the microprocessor computing unit also receives rotation signals from said sensor means for the rotation (50) and computes the corresponding orientation of the head end (30) of the probe (20) around its longitudinal axis as a function of said rotation signals.

9. Alignment equipment (80) of a drill, to produce in a bone (5) a hole aligned with a transversal fastening hole ( 4) of a hollow endomedullary nail (12) inserted in the bone (5), comprising: - a position locating device (10) of the axis of the transversal fastening hole (14) according to any one of the preceding claims and

- pointing means (90) comprising a drill guiding device (95) suitable to guide the drill (104), said pointing means (90) being suitable to align, on the basis of the position coordinates provided by the position locating device (10), a longitudinal axis (K) of the drill guiding device. (95) with the axis of the fastening hole (14) of endomedullary nail (12).

10. Equipment according to claim 9, characterized in that the pointing means (90) comprise a pointing turret (90) supporting the guiding device (95) of the drill (104), the turret (90) being movable by means of first driven control means (91) along a first axis having a direction parallel to the insertion axis of the probe in the nail and comprises second driven control means (93) of the position of the guiding device along a second axis having a transversal direction with respect to said first axis and driven control means (92, 94) of the rotation of the guiding device around said first and second axis.

11. Equipment according to claim 10, characterized in that the first and second driven control means (91 , 93) of the translation and the driven control means (92, 94) of the rotation of the pointing turret (90) are motorized means receiving controls from the computing means (70) to move automatically said pointing turret (90), on the basis of position coordinates provided by the position locating device (10), so that the longitudinal axis (K) of the drill guiding device (95) is autonomously aligned with the axis of the fastening hole (14) of the endomedullary nail (12) as located by the position locating device (10).

12. Equipment according to claim 11 , characteri2ed in that the first and second driven control means (91, 93) of the translation and the driven control means of the rotation of the pointing turret (90) are manual control means to align, on the basis of alignment information displayed by the computing means (70) on a displaying unit (100), the longitudinal axis (K) of the drill guiding device (95) with the axis of the fastening hole (14) of the endomedullary nail (12) as located by the position locating device (10).

13. Equipment according to claim 9, characterized by comprising a support (81) on which the pointing means (90) are mounted, a fastening bracket (83) and a cannular screw (87); the support (81), the fastening bracket (83) and the cannular screw (87) being each other orthogonally connected and allowing to stiffly connect the endomedullary nail (12), the position locating device (10) and the aiming means (90) to each other.

14. Equipment according to claim 13, wherein on said support (81) is prearranged a straight track (82), whose axis is parallel to the second reference axis (Yp), along which the pointing means (90) can slide.

15. Equipment according to claim 14, wherein the position locating device (10) is connected to the support (81) with the axis of the probe coincident with the second reference axis (Yp).