WO2003065907A1

WO2003065907A1 - Adjustable drilling jib for targeting locking screws for intramedullary nails

Info

Publication number: WO2003065907A1
Application number: PCT/IL2003/000095
Authority: WO
Inventors: Charles Milgrom; Ariel Simkin; Leo Joskowicz
Original assignee: Hadasit Medical Research Services and Development Co; Yissum Research Development Co of Hebrew University of Jerusalem
Current assignee: Hadasit Medical Research Services and Development Co; Yissum Research Development Co of Hebrew University of Jerusalem
Priority date: 2002-02-10
Filing date: 2003-02-06
Publication date: 2003-08-14
Anticipated expiration: 2004-08-10
Also published as: IL148074A0; AU2003209620A1

Abstract

There is provided an adjustable, radio-translucent drilling jig for targeting locking screws into an intramedullary nail (2) having proximal and distal holes, and provided with handle means (4) to which the nail is temporarily attachable, the jig comprising a guide rail (18) fixedly attachable to a free end portion (6) of the handle means and extending in a direction substantially parallel to the proximal end portion of the nail; a bar member (24) slidingly movable in translation within the guide rail (18) and having a distal end portion (26) provided with an internal thread (28) and an opening (30) passing through the end portion (26); a manually rotatable lead screw (36) mounted between end plates (38) of a base member (40) and engaging the internal thread (28) in the distal end portion (26) of the bar member, thereby enabling the bar member (24) to perform a translational movement in the ventral-dorsal direction along the lead screw (36) and a rotational movement in the varus-valgus direction about the lead screw (36); a locking plate (44) accommodated in the slot (32) and allowing the bar member (24) to perform the rotational movement when the first thumbscrew (50) is loose, but preventing the rotational movement when the first thumbscrew (42) is tightened, and a disk-like plate (62) mounted in a frame (60) fixedly attached to an element of the base member and provided with at least one off-center bore (64), the plate (62) being rotatable within the frame (60) in an extension-flexion direction and being lockable by means of a second thumbscrew (66).

Description

ADJUSTABLE DRILLING JIG FOR TARGETING LOCKING SCREWS FOR INTRAMEDULLARY NAILS Field of the Invention

The present invention relates to an adjustable drilling jig for targeting locking screws for intramedullary nails. Background of the Invention

Intramedullary nailing is currently the routine procedure of choice for internally fixing long-bone fractures such as, e.g., fractures of the femur. It restores the integrity of the fractured bone by means of a nail inserted in the medullary canal of the bone. The nail is inserted, without surgically exposing the fracture, through a small opening at the edge of the bone. The surgeon manually aligns the bone fragments by manipulating them through the tissues surrounding the bone and inserts a guide wire, followed by the intramedullary nail, through the small opening in the bone. Lateral interlocking screws for the nail, proximal and distal to the fracture site, are inserted as needed to prevent fragment rotation and bone shortening. All of these steps are performed under fluoroscopic guidance.

The above-described procedure, although having many benefits compared to open reduction of fractures, is difficult and time-consuming. The most common errors and complications in closed intramedullary nailing occur because of the lack of a direct view of the fracture site and bone fragments. The surgeon must mentally reconstruct the location of the bone segments and the nail in space and time, manipulate the tools and bone fragments without direct visual feedback, and repeatedly confirm their positions by fluoroscopic imaging. This slow and tedious procedure can cause improper positioning and alignment, inadequate fixation, bone cracking, cortical bone penetration and bone weakening by multiple or enlarged screw holes, in addition to the exposure of both surgeon and patient to radiation. These difficulties are even more pronounced when the nail is of the open cross-section type, which is flexible and deforms more than the rigid, closed section nail. U.S. Patent No. 5,474,561 discloses a guiding device for interlocking intramedullary nails without the use of fluoroscopy, claiming to overcome the above-mentioned difficulties and risks. Perusal of this Patent, however, shows the disclosed device to be of extreme complexity and intricacy, which already emerges from the fact that the device embodies altogether nine degrees of freedom (five rotational and four translational) and is therefore very cumbersome. In addition, rotational adjustment can be carried out only in discrete, i.e., non-continuous steps. The absence of the need for fluoroscopy is based on the assumption that the nail is totally rigid, with no deformation during its insertion. Nails used today are not completely rigid; studies have indicated motions of several millimeters, as well as torsional deformation of the distal end of the nail. These movements have to be monitored in order to facilitate proper insertion of the distal locking screws.

U.S. Patent No. 6,039,742 discloses an alignment device for locking the base portions of intramedullary nails. This device is used with a different type of nail, which has two sets of distal holes having mutually perpendicular anteroposterior and mediolateral axes. The nail itself has a non-circular cross-section, which is oval and has a sharp edge. For the mediolateral holes, the device provides two degrees of freedom, one in translation and one in ventral-dorsal rotation around a mediolateral axis. For the anteroposterior holes, an additional mediolateral translational movement is provided. Adjustment is performed without recourse to x-rays, by using mechano-acoustical or electromechanical space sensors.

Another U.S. Patent, No. 6,027,506, discloses an all-mechanical system for bone-drilling alignment of blind distal bone-screw holes in an intramedullary nail, without the use of x-rays. This system, however, provides only one degree of freedom and is suitable only for comparatively rigid nails, with only small bending deflections in one plane.

U.S. Patent No. 5,178,621 teaches a radio-transparent targeting device for locking intramedullary nails. This device is designed, however, only for the insertion of proximal interlocking screws, and does not provide an adjustment mechanism for the location and direction of the screw holes when the nail is distorted. Another type of instrumentation for distal targeting of locking screws in intramedullary nails is described in U.S. Patent No. 5,411,503. This device relies on an electromagnetic probe within the nail and an external electromagnetic device for locating the placement and direction of the holes for the locking screws in the nail. This instrument, however, does not rely on mechanical adjustments or x-ray images to target the locking screws, and is therefore not related to the present invention. Disclosure of the Invention

It is therefore one of the objects of the present invention to provide an adjustable drilling jig for targeting locking screws into intramedullary nails that is mechanically simple and has practically no loose components, while providing all required degrees of freedom of movement, both in translation and in rotation, which can be fully and rapidly adjusted prior to the insertion of the nail and that are easily readjusted after insertion and possible deflection or distortion of the distal portion of the nail.

It is a further object of the present invention to provide such a device that can be used with a minimal amount of fluoroscopy, as well as in conjunction with the per-se known, computer-integrated system for long-bone reduction.

According to the invention, these objects are achieved by providing an adjustable, radio-translucent drilling jig for targeting locking screws into an intramedullary nail having proximal and distal holes, and provided with handle means to which the nail is temporarily attachable, the jig comprising a guide rail fixedly attachable to a free end portion of the handle means and extending in a direction substantially parallel to the proximal end portion of the nail; a bar member slidingly movable in translation within the guide rail and having a distal end portion provided with an internal thread and an opening passing through the end portion; a manually rotatable lead screw mounted between end plates of a base member and engaging the internal thread in the distal end portion of the bar member, thereby enabling the bar member to perform a translational movement in the ventral-dorsal direction along the lead screw and a rotational movement in the varus-valgus direction about the lead screw; a locking plate accommodated in the slot and allowing the bar member to perform rotational movement when the first thumbscrew is loose, but preventing rotational movement when the first thumbscrew is tightened, and a disk-like plate mounted in a frame fixedly attached to an element of the base member and provided with at least one off-center bore, the plate being rotatable within the frame in an extension- flexion direction and being lockable by means of a second thumbscrew.

The invention further provides an adjustable, radio-translucent drilling jig for targeting locking screws into an intramedullary nail having proximal and distal holes, and provided with handle means to which the nail is temporarily attachable, the jig comprising a connector member attachable to the handle means and including drilling bushings which, when the connector member is thus attached, are aligned with proximal holes in the nail; a bar member at least indirectly linked to the connector member and movable relative to the nail in translation in a direction parallel to the upper portion of the nail; a cross member fixedly attached to the distal end of the bar member and extending in a direction substantially perpendicular thereto; a plate member at least indirectly linked at one of its ends to the cross member and connected at the other one of its ends to a guide block, the plate member and the guide block being adapted to move in translation along the cross member; a beam disposed in the guide block and slidably movable therein in translation in a plane substantially perpendicular to the direction of translation of the bar member and in a direction substantially perpendicular to the plane containing the nail; a base member fixedly attached to the proximal end of the beam and provided with a circular slot in which an annular segment is slidingly movable and lockable, and a disk-like plate member in a frame fixedly attached to the annular segment and provided with at least one off-center bore, the plate being rotatable and lockable within the frame. Brief Description of the Drawings

The invention will now be described in connection with certain preferred embodiments with reference to the following illustrative figures so that it may be more fully understood.

With specific reference now to the figures in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of the preferred embodiments of the present invention only, and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the invention may be embodied in practice.

In the drawings: Fig. 1 is a schematic representation of the degrees of freedom afforded by a first embodiment of the drilling jig according to the present invention; Fig. 2 is an elevational view of a first embodiment of the drilling jig of the present invention; Fig. 3 is a side view of the device of Fig. 2; Fig. 4 is a perspective view of the end portion of the bar member of the device of

Fig. 2; Fig. 5 is a cross-sectional view along plane V-V of Fig. 3; Fig. 6 is a cross-sectional view along plane VI- VI of Fig. 2; Fig. 7 is a perspective view of the friction plate; Fig. 8 is a cross-sectional view along plane VIII- VIII of Fig. 2; Fig. 9 is a cross-sectional view along plane IX-IX of Fig. 2; Fig. 10 is a cross-sectional view of the device for coarse sighting; Fig. 11 is a top view of the device of Fig. 10; Fig. 12 is an elevational view of the device for final sighting; Fig. 13 is a top view of the device of Fig. 12; Fig. 14 is a schematic representation of the degrees of freedom of a second embodiment of the drilling jig according to the invention; Fig. 15 is an elevational view of the drilling jig of Fig. 14; Fig. 16 is a cross-sectional view along plane XVI-XVI of Fig. 15; Fig. 17 is a side view of the jig of Fig. 15, in the direction of arrow A; Fig. 18 illustrates an accessory serving to support and stabilize the drilling jig during adjustments and drilling operations; Fig. 19 shows a punch used to clear the way to the bone before the insertion of the drill bushing; Fig. 20 shows several small, radio-opaque spheres to serve for coarse sighting and inserted into the disk-like plate along circles concentric with the bores accommodating the drill bushings, and Fig. 21 represents a variant of the rod of Fig. 12 for final sighting. Detailed Description

Referring now to the drawings, there is seen in Fig. 1 a schematic representation of the five degrees of freedom afforded by the drilling jig according to the present invention, as indicated by Roman numerals. It will be appreciated that, apart from^' the translational movement I, which serves to adapt the device to intramedullary nails of different lengths, movements II- V are listed using the following anatomical terminology to indicate the adjustment direction taken by what can be defined as end effectors of the device, namely, the drill bushing for drillling the holes for the distal locking screws:

II ventral-dorsal (translation)

III varus-valgus (rotation)

IV flexion-extension (rotation)

V external- internal (rotation).

Figs. 2 and 3, respectively, present an elevational view and a side view of the drilling jig, showing the commercially available nail 2, which, as can be seen in Fig. 3, is slightly curved. Equally supplied by the manufacturer is a handle 4, the lower end. portion 6 of which is of a rectangular cross-section, whereby, as will be explained further below, it connects to the device proper. To the upper end 8 of handle 4 is welded a socket 10. The latter accommodates a bolt 12, also supplied by the manufacturer and therefore not described herein in detail. Bolt 12 is tightly screwed into the upper end of nail 2 which, with the aid of knurled nut 14, is then pulled up against socket 10. The flared and flanged end of nail 2 has two tabs 16 which index into two slots in socket 10, allowing nail 2 to assume two positions relative to the device, one for use on the left femur, and one for the right.

Connected to end portion 6 of handle 4, there is seen a guide rail 18. Connection is effected by screws 20 which have threaded ends and knurled heads for manual application and fit bores in end portion 6, and are thus aligned with the holes in nail 2 that are designed to allow the proximal locking screws to pass.

Slidingly movable in translation inside guide rail 18 and lockable by means of a thumbscrew 22 (Fig. 8), there is seen a bar member 24 of the drilling jig. As already mentioned, the purpose of this translational movement is to adapt the drilling jig to nails of different lengths. The distal end portion 26 of bar member 24, shown to better effect in Fig. 4, is widened and is seen to comprise an internal thread 28, a curved slot 30, and a plane slot 32 entering end portion 26 in a direction substantially perpendicular to the axis of internal thread 28 and dividing end portion 26 into two sections, one thin and thus flexible, the other heavier. Further seen is a hole 34 passing through the thin section of end portion 26 and continuing as a threaded hole (Fig. 6) in the heavier section. The purpose of these features will be explained further below.

Bar member 24 is supported by a lead screw 36 which engages its internal thread 28 and is mounted in two end plates 38 (Figs. 5 and 6) fixedly attached to a base member 40 that, in a manner to be discussed further below, also carries the units controlling the flexion-extension movement and the external-internal movement. The varus-valgus movement of these units relative to bar member 24 is controlled by a friction plate 44, seen to best effect in Fig. 7. Plate 44, slidably articulated to guide rod 46, is located inside slot 32 in end portion 26 of bar member 24 and is provided with a slot 48, through which the shaft of a thumbscrew 50 can freely pass. Guide rod 46 passes through curved slot 30 in end portion 26 and, as long as thumbscrew 50 is not tightened, a relative tilting movement - the varus-valgus movement - is possible between bar member 24 and the above units. As soon as thumbscrew 50 is tightened, friction plate 44 is clamped between the surfaces of slot 32 and no further varus-valgus movement is possible. In the tightened state of thumbscrew 50, lead screw knob 42, when turned, causes the above units to move ventrally or dorsally, depending on the sense of rotation of knob 42. During this movement, friction plate 44, clamped tight between the surfaces of slot 32, slides along guide rod 46.

Fig. 9 is a view in cross-section along plane IX-IX of Fig. 2. Base member 40 is seen to be provided with a circular groove 52 having a T-slot-like cross-section, in which an annular segment 54 is slidingly accommodated. The angular position of segment 54 relative to base member 40 can be adjusted by sliding thumbscrew 56 along a slot 58 provided in base member 40 and shown in Fig. 3. This is the mechanical realization of the external-internal movement (V, Fig. 1) which is important in cases where, upon implantation, the intramedullary nail 2 is strained not only in flexure, but also in torsion. Tightening thumbscrew 56 locks this mechanism.

Frame 60 (Fig. 3) accommodates a rotatable, disk-like plate 62, which is provided with two off-center bores 64. The center distance between bores 64 is substantially equal to the distance between the pair of distal holes in nail 2. Plate 62 can be locked by tightening thumbscrews 66. Bores 64 accommodate, in succession, a trocar sleeve 68 (Fig. 2), into which fits a drill bushing 70, to prepare the holes for the distal locking screws. Frame 60 and disk-like plate 62 thus constitute the mechanical realization of the flexion-extension movement (IV, Fig. 1) required for the final alignment of the drilling jig prior to the drilling of the holes for the two distal locking screws. To facilitate this alignment, the present invention provides two sighting devices, one for preliminary, coarse alignment, and one for final alignment.

Figs. 10 and 11 represent the sighting device for coarse alignment, which is seen to consist of a cap 72 made of a radio-opaque material, to be slipped over the end of drill bushing 70. Cap 72 is provided with a hole 73 and with a number of radial barbs 74, also made of a radio-opaque material. The purpose of these barbs is to enhance visual perception of the target location.

The sighting device for final alignment is shown in Figs. 12 and 13, and consists of a rod 76, made of radio-translucent material, to be introduced into drill bushing 70. Each of the ends of rod 76 is provided with two wires 78 and 80 made of a radio-opaque material, so oriented as to constitute cross-hairs visually intersecting at the axis of rod 76. When, upon sighting, the cross-hairs of both ends and the hole for the insertion of the locking screw in the nail register, rod 76, and therefore, the drill going to prepare the hole for the locking screw, are precisely on target.

Except for guide rail 18, the drilling jig according to the present invention is made of a radio-translucent, rigid material, advantageously one of the engineering plastics, such as acetal, e.g., Delrin®.

The basic targeting procedure for the accurate drilling of holes for the proximal, and especially for the distal, locking screws, is as follows:

In a "dry run," i.e., prior to the implantation of intramedullary nail 2, the surgeon connects the assembled jig to end portion 6 of handle 4 with the aid of the knurled-head screws 20. Then nail 2 is locked into socket 10 of handle 4 in the proper position, as the case may be, for the right or left femur, using bolt 12 and knurled nut 14. The surgeon then makes use of the five degrees of freedom of the device by matching its length to the length of nail 2, sliding bar member 24 inside guide rail 18 and tightening thumbscrew 22; setting the ventral-dorsal position by turning lead-screw knob 42; determining the varus-valgus position by setting the proper tilt of the device relative to bar member 24 and tightening thumbscrew 50; setting the external-internal rotational position by swivelling and locking frame 60, and adjusting the flexion-extension position by rotating and locking disk-like plate 62, until a drill inserted into drill bushing 70 is in alignment with, i.e., fits easily into, one of the holes provided in nail 2 for the distal locking screws. Clearly, this procedure may also involve some trial-and-error, as in these sequential settings some later adjustments are liable to interfere with previous ones.

Then the nail, as attached to handle 4 and the drilling jig, is inserted into the femur by the usual surgical procedure, or as assisted by the computer-integrated system for closed, long-bone fracture reduction. During this procedure, the nail is usually distorted within the bone, especially that nail portion carrying the holes for the distal locking screws, so that the adjustments performed during the "dry run" are no longer valid. After insertion of the nail, re-adjustment is carried out, when necessary, with the help of fluoroscopic images, until drill bushing 70 is aligned with the hole for one of the distal screws in nail 2. This may be done manually, using the coarse sighting device of Fig. 9 and the final sighting device of Fig. 11, or with the guidance of the computer-integrated system mentioned above. After the insertion of the first distal locking screw, the procedure is repeated for the second screw.

Subsequently, the drilling jig is removed and the holes for the proximal screws are drilled, making use of a trocar and drilling sleeve prepared by the manufacturer of the nail and fitting the above-mentioned bores in the end portion 6 of handle 4. It is, however, also possible to reverse this order, i.e., to drill the holes for the proximal screws first, then for the distal screws.

Another embodiment of the drilling jig according to the present invention is illustrated in Figs. 14-17.

A basic difference between the first and second embodiments is apparent in Fig. 14, which, in analogy to Fig. 1, indicates the degrees of freedom available to the device. While the two embodiments have the same number of degrees of freedom, namely, five,, the embodiment of Figs. 14-17 has three degrees of freedom in translation, compared to two degrees of freedom in translation in the embodiment of Figs. 1-13; the rotary varus-valgus movement has been replaced by a translational medial-lateral movement. As seen in Fig. 14, apart from the translational movement I, which serves to adapt the device to intramedullary nails of different lengths, the movements indicated are:

II ventral-dorsal (translation)

III medial-lateral (translation)

IV flexion-extension (rotation)

V external-internal (rotation).

Referring now to Fig. 15, shown are nail 2 and handle 4, the lower end portion 6 of which has a rectangular cross-section, and its upper end 8, to which socket 10 is welded. Also seen are bolt 12, knurled nut 14 and tabs 16, the purpose of which is explained above in conjunction with Fig. 2. Lower end portion 6 of the handle/nail unit is seen to be attached to a connector member 82 by means of two knurled-head screws 84 that fit bores in end portion 6 and are aligned with the holes in nail 2 that are designed to allow the proximal locking screws to pass through. Screws 84, having holes of the appropriate diameter, also serve as drill bushings for the drill preparing the holes for the locking screws. In turn, connector member 82 is fixedly attached to a distance piece 86, the purpose of which is to increase the distance between base member 40 and its appendages and the patient's thigh. Fixeldy attached to distance piece 86 is the base 88 of a rack-and-pinion mechanism (Edmund Scientific Large Movement Stage L52-109/C) in which base a shafted pinion 90 (Fig. 16) is rotatably mounted. Pinion 90 engages a rack 92 attached to a slider 94, provided with a male dovetail moving in a female dovetail cut in base 88. When knobs 96 are turned, slider 94 moves along base 88 in a direction depending on the sense of rotation of the knobs.

Attached to slider 94 is the base 98 of a male dovetail 100, slidable in a female dovetail 101 provided along bar member 102 which caries the rest of the drilling jig at its end. This arrangement facilitates rapid, coarse adjustment by hand, in the direction of movement I of Fig. 14. Coarse adjustment having been achieved, bar member 102 is locked by tightening thumbscrew 104, acting on plate 105. Fine adjustment is effected with the aid of the above-described rack-and-pinion mechanism.

Fixedly attached to the end of bar member 102 is a cross member 106, which defines the ventral-dorsal movement II of Fig. 14. Coarse adjustment is facilitated by the male-female dovetail arrangement explained above in conjunction with movement I, involving female dovetail 101' (Fig. 15) in cross member 106, and male dovetail 100' and its base 98'. Coarse adjustment having been achieved, base 98' is locked by tightening one of two screws 108. The total movement is long enough to allow the same device to be used for both the left and the right limbs. As in the arrangement of movement I, base 98' is mounted on slider 94' of the already described rack-and-pinion mechanism actuated by means of knob 96', effecting fine adjustment. Medial-lateral movement III of Fig. 14 is effected by a T-profile beam 1 10, slidably mounted in a guide block 112 provided with a T-slot of the appropriate size, the guide block, in turn, being suspended from base 88' by a plate 114 to which guide block 112 is fixedly attached. The position of beam 110 inside guide block 112 can be locked by means of a thumbscrew 116.

A base member 40 is attached to the proximal end of beam 110 by means of two screws 118 (Fig. 15). Base member 40 is essentially the same as that used in the embodiment of Figs. 2-13, as are the rest of the components used to control flexion-extension movement IV and external-internal movement V. Their structure, interaction and specific purposes are described above in conjunction with Figs. 2, 3, 9 and 10-13.

An accessory for supporting and stabilizing the drilling jig during adjustments and drilling operations is illustrated in Fig. 18. There is seen a base 120 carrying an upright 122 with an axial bore 124 in which is slidingly inserted a rod 126 provided with a keyslot 128 in which engages the end of a thumbscrew 130, constraining rod 126 to one degree of freedom in translation. The end of rod 126 is designed as a joint 132, the mating part of which is a bar 134 on which is mounted a clamp-like member 136 to which can be clamped, by means of thumbscrew 138, a suitable part of the jig, such as beam 110 (Fig. 15). The drilling jig is thereby supported and stabilized. Joint 132 permits member 136 to be tilted about the axis of the joint, a thumbscrew 140 permitting the angle of tilt to be fixed. The device is intended to be mounted on the operating table.

In a slight modification of the above-described procedure, a punch-like device 142 (Fig. 19) made of a radio-translucent material, is introduced into trocar sleeve 68 (Fig. 15), prior to the introduction of drill bushing 70. Punch 142, slidingly fitting trocar sleeve 68, has a pointed end 144 and a head 146 for handling. Pushing in punch 142 clears the way to the bone between the soft tissues surrounding it. After punch 142 has reached the bone, it is withdrawn and replaced by drill bushing 70.

Under certain circumstances, the sighting devices of Figs. 10 to 13 were found hard to identify in the fluoroscopic images, for which reason the invention provides variants both for the coarse sighting device shown in Figs. 10 and 11, and for the final sighting device shown in Figs. 12 and 13.

Fig. 20 represents the disk-like plate 62 with its two bores 64 around both of which, along circles concentric with bores 64, several small, radio-opaque spheres 148 are pressed into the surface of plate 62. These relatively massive spheres are meant to replace the thin barbs 74 of Figs. 10 and 11. To reduce parallax, spheres 148 should be close to the disk surface facing the bone.

Fig. 21 represents the variant of the final sighting device of Figs. 12 and 13. Here, the cross-wires 78, 80 have been replaced by radio-opaque bodies 150 pressed into the ends of rod 152.

It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrated embodiments and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

Claims

1. An adjustable, radio-translucent drilling jig for targeting locking screws into an intramedullary nail having proximal and distal holes, and provided with handle means to which said nail is temporarily attachable, said jig comprising: a guide rail fixedly attachable to a free end portion of said handle means and extending in a direction substantially parallel to the proximal end portion of said nail; a bar member slidingly movable in translation within said guide rail and having a distal end portion provided with an internal thread and an opening passing through said end portion; a manually rotatable lead screw mounted between end plates of a base member and engaging the internal thread in the distal end portion of said bar member, thereby enabling said bar member to perform a translational movement in the ventral-dorsal direction along said lead screw and a rotational movement in the varus-valgus direction about said lead screw; a locking plate accommodated in said slot and allowing said bar member to perform said rotational movement when said first thumbscrew is loose, but preventing said rotational movement when said first thumbscrew is tightened, and a disk-like plate mounted in a frame fixedly attached to an element of said base member and provided with at least one off-center bore, said plate being rotatable within said frame in an extension-flexion direction and^' being lockable by means of a second thumbscrew.

2. The drilling jig as claimed in claim 1, wherein said distal end portion is widened and is further provided with a slot passing through said end portion in a direction substantially perpendicular to the axis of said internal thread and extending beyond at least part of said opening, the width of said slot being reducible by means of a first thumbscrew.

3. The drilling jig as claimed in claim 1, further comprising a guide bar extending between, and attached to, said end plates and passing through the opening in said distal end portion.

4. The drilling jig as claimed in claim 1, further comprising an annular segment to which said frame is fixedly attached, said segment being slidably accommodated in a circular groove provided in said base member and permitting said disk-like plate to perform an external-internal rotational movement about an axis passing through the center of curvature of said circular groove, said annular segment being lockable by a third thumbscrew.

5. The drilling jig as claimed in claim 1, wherein said guide rail is attachable to said handle means with the aid of screws aligned with said pair of proximal holes in said intramedullary nail.

6. The drilling jig as claimed in claim 1, wherein said opening in the distal end portion of said bar member has the form of a curved slot, the center of curvature of said slot being located in the axis of said internal thread.

7. An adjustable, radio-translucent drilling jig for targeting locking screws into an intramedullary nail having proximal and distal holes, and provided with handle means to which the nail is temporarily attachable, said jig comprising: a connector member attachable to said handle means and including drilling bushings which, when the connector member is thus attached, are aligned with proximal holes in said nail; a bar member at least indirectly linked to said connector member and movable relative to said nail in translation in a direction parallel to the upper portion of the nail; a cross member fixedly attached to the distal end of said bar member and extending in a direction substantially perpendicular thereto; a plate member at least indirectly linked at one of its ends to said cross member and connected at the other one of its ends to a guide block, said plate member and said guide block being adapted to move in translation along said cross member; a beam disposed in said guide block and slidably movable therein in translation in a plane substantially perpendicular to the direction of translation of said bar member and in a direction substantially perpendicular to the plane containing said nail; a base member fixedly attached to the proximal end of said beam and provided with a circular slot in which an annular segment is slidingly movable and lockable, and a disk-like plate member in a frame fixedly attached to said annular segment and provided with at least one off-center bore, the plate being rotatable and lockable within the frame.

8. The drilling jig as claimed in claim 7, further comprising a distance piece fixedly attached to the free end of said connector member and carrying, at its free end, a first rack-and-pinion mechanism comprising a slider movable in translation by rotation of a knob.

9. The drilling jig as claimed in claim 8, further comprising a first base of a male dovetail means fitting matching female dovetail means in said bar member, said base being fixedly attached to said slider.

10. The drilling jig as claimed in claim 9, further comprising locking means mounted on said base, whereby said bar member is lockable.

11. The drilling jig as claimed in claim 7, further comprising a second base of a mail dovetail means fitting matching female dovetail means in said cross member, said base being fixedly attached to a slider of a second rack-and-pinion mechanism fixedly attached to said plate member.

12. The drilling jig as claimed in claims 1 or 7, wherein said disk-like plate is provided with two off-center bores.

13. The drilling jig as claimed in claims 1 or 7, further comprising trocar means slidingly fitting the bores of said disk-like plate.

14. The drilling jig as claimed in claim 13, further comprising a drill bushing slidingly fitting the bore of said trocar means.

15. The drilling jig as claimed in claims 1 or 7, further comprising a sighting device for coarse alignment of a bore in said disk-like plate with said at least one distal hole in said nail, said sighting device having the form of a number of small, radio-opaque bodies inserted into the surface of said disk-like plate along a circle concentric with said bore.

16. The drilling jig as claimed in claim 14, ftirther comprising a sighting device for final alignment of a bore in said disk-like plate with said at least one distal hole in said nail, said sighting device consisting of a rod of radio-translucent material slidingly fitting said drill bushing, each end of said rod being provided with two bodies made of a radio-opaque material, the axes of said bodies being aligned with the axis of said rod.

17. The drilling jig as claimed in claims 1 or 7, further including a supporting and stabilizing accessory comprising a base mountable on an operating table, an upright having an axial bore in which is slidingly insertable and arrestable in selectable position a rod the upper end of which is in the form of a joint, the mating part of which joint is a tillable bar on which is mounted a clamp-like member to which is attachable a selected part of said drilling jig, thereby to be supported and stabilized.