FR2770128A1 - Hip joint prosthesis and fitting tool - Google Patents

Abstract

The prosthesis, comprising a femoral implant with a shank (1) and a cone (4) for a femoral head, is fitted with the aid of a clamp tool (2) with jaws (10, 11) recessed to form a socket (12) for the cone when closed. One of the jaws also has a projecting lug (16) which fits into a cavity in a collar (6) at the upper end of the implant. The lug can be adjusted to suit implants of different sizes.

Description

 The invention relates to hip prosthesis systems.

 These systems are intended to replace the natural hip joint, which has a femoral head that is lodged in an acetabulum of the iliac bone, so as to form a ball joint type.

 These prosthesis systems comprise, on the one hand, a femoral implant comprising a penetrating tail in the bored femoral medullary canal and a cone for receiving a prosthetic femoral head and, on the other hand, an acetabular implant defining a spherical cavity. of receiving the prosthetic femoral head, so as to reconstruct the natural joint.

 According to a first aspect, the invention relates to such a system which further comprises, for the introduction of the femoral implant, a gripper with two jaws for inserting the tail of the femoral implant into the canal. medulla. According to this first aspect, the invention is characterized in that: said jaws are arranged to define, for the closed position of the clamp, a housing for cooperation with the cone for clamping thereof; one of said jaws carries a lug, beyond its free end; and the femoral implant has, between the tail and the cone, a cavity intended to cooperate with said pin.

 Preferably, this cavity is located at a collar that includes the femoral implant for support on the resection plan of the femur. This cavity is for example elongated in the peripheral direction, and the end of the lug has a complementary shape, with the game.

 The lug is preferably movable relative to the jaw which carries it for the adaptation of the clamp to implants of different sizes for which the distance between the cone and the cavity is variable. This pin is for example movable in a direction having a component parallel to the common axis of the cone of the implant and the housing defined by the jaws of the clamp in the closed position on the cone, this direction is preferably oblique with respect to this common axis, and it is parallel to a line on which are located the respective cavities of implants of different sizes.

 According to one embodiment, the lug is carried by a clean rod to slide axially in the jaw which carries it, this rod being biased by a spring towards one of its extreme retracted and deployed positions, preferably the extended position. This rod slides in a bore formed in the jaw which carries it, this bore and the rod being arranged so that the rod can not rotate about its axis, for example because the bore and the rod have a polygonal cross section. , especially square.

 In general, to protect the cone and reinforce the friction, there is provided a mordache, in particular plastic, and for example polyethylene or polytetrafluoroethylene, disposed between the cone of the implant and the jaws of the clamp. According to one embodiment, each jaw defines a U-shaped housing of constant section and open towards the other jaw; each mordache is also U-shaped, of constant outer cross-section, complementary to that of the associated jaw, and of an isosceles trapezoidal inner cross-section tapering for adaptation to the cone of the implant. The cone is thus tightened along four generators.

 According to a second aspect, the invention relates to such a hip prosthesis system which also comprises a first device for the prior verification of the selected future position of the femoral implant on the prepared femur, and in particular the prior checking of the position selected future of the center of the prosthetic femoral head.

 According to one embodiment of this first prior checking device, this device comprises a block adapted to be inserted into a predetermined position on the tail of a preparation rasp of the medullary canal, this block having a plurality of orifices, for example four, of which a predetermined one receives a probe which, for a correct preparation of the medullary canal, occupies a predetermined position with respect to an anatomical landmark, for example the top of the greater trochanter.

 These orifices of the block are at different levels in the direction of the axis of the cone of the implant to show the various possible axial positions of the center of the femoral prosthetic head with respect to the cone of the implant, one of these positions that have been previously selected to coincide with the center of the cotyloid implant, which usually coincides with the center of the natural acetabulum.

 According to a third aspect, the invention relates to such a hip prosthesis system which also includes a second device for the prior checking of the selected future position of the cotyloid implant in the prepared pelvic bone.

 According to a preferred embodiment of this second verification device, it comprises a spherical test head showing, by its external surface, the prosthetic and integral acetabular housing, on the one hand, a maneuvering and support handle, and on the other hand, a slide, preferably graduated, on which can slide a slider provided with a probe which, for a correct preparation of the pelvic bone, occupies a predetermined position relative to the spherical head of test and at an anatomical landmark, for example the junction line between the tops of the obturator holes of the iliac bones and the lower edges of the natural acetabulum.

The invention will be clearly understood on reading the additional description which will follow and with reference to the appended drawings which form part of the description and in which
Fig. 1 is a diagrammatic elevational view, partially in section and severed, of a grasping forceps and a femoral implant made according to the first aspect of the invention, this Figure also showing another femoral implant of a different size.
Fig. 2 is a perspective view of the upper portion of one of the femoral implants of FIG. 1;
Fig. 3 shows, in a, b, c and d, for the same femoral implant, and in a tearing manner, various possible positions of the femoral prosthetic head on the cone of the femoral implant
Fig. 4 is a diagram, from a radiography, of preparatory work for implantation and allowing, before implantation but after the preparation of the femur and the iliac bone, to verify the positions that will effectively occupy the femoral implants and cotyloid selected
Fig. 5 is a schematic view illustrating, according to the second aspect of the invention, a device for checking the accuracy of the preparation of the femur
Fig. 6 is a perspective view of the device of
FIG. 5
Fig. 7 is an external side view of the device of FIG. 6 according to arrow VII
Fig. 8 is a median section along VITI-VITI of the device of FIG. 7
Fig. 9 is a perspective view illustrating, according to the third aspect of the invention, a device for verifying the accuracy of the preparation of the pelvic bone; and
Fig. 10 shows the use of the device of the
Fig. 9.

 There is shown in Figs 1 and 2 a hip prosthesis system according to a preferred embodiment of the first aspect of the invention.

 The system comprises a femoral implant 1 and a grasper 2 for the placement of the implant 1 in the femur 21 (Figs 4 and 5), after resection and preparation thereof.

 Usually, the femoral implant 1 comprises a substantially rectilinear tail 3 which tapers towards its free end and which is intended to penetrate into the bored femoral medullary canal 29 (FIG 5), and a cone 4 intended to penetrate into the bored femoral medullary canal 29 (FIG. to receive a prosthetic femoral head 44 (Fig. 3), replacing the natural head 49 of the femur 21 and intended to cooperate with an acetabular implant (not shown) .Anatomically, the axis of the cone 4 is inclined on the axis of the tail 3 of an angle of the order of 135.

 Between the shank 3 and the cone 4, the femoral implant 1 has a narrowed neck 5, showing the natural femoral neck 50, and a support collar 6 of the implant on the resection plane of the femur.

 The clamp 2 comprises two handles 7 and 8 which are articulated one on the other around a pivot 9 and which are extended, beyond the pivot 9, by respective jaws 10 and 11.

 On their opposite inner end faces, the jaws 10 and 11 are recessed to define a housing 12 for cooperation with the cone 4 for clamping thereof. Preferably, this clamping of the cone by the jaws 10 and 11 is via the jaws 13 for protecting the cone 4 and / or friction reinforcement. These jaws 13 are for example plastic, especially polyethylene or polytetrafluoroethylene. For example, each housing 12 is U-shaped of constant section and open to the other jaw. Each mordache is also U-shaped and has an outer surface 15 of constant section, complementary to the shape of the associated housing 12, and an inner surface 14 in the shape of an isosceles trapezium tapered towards the joint 9 for the adaptation to the shape of the cone 4 of the implant 1. The cone 4 is tight, by each mordache 13, along two of its generators.

 The jaw 10 carries, beyond its free end, a lug 16 intended to cooperate with a cavity 17 formed in the femoral implant 1, between the shank 3 and the cone 4, preferably at the level of the collar 6.

 As shown in FIG. 2, the cavity 17 is preferably elongated in the peripheral direction, that is to say transversely to the axis A of the cone 4. The free end of the lug 16 has a shape complementary to that of the cavity 17 , with the game.

 Preferably, the lug 16 is movable relative to the jaw 10 to allow the adaptation of the clamp 2 to femoral implants of different sizes, the distance between the cone 4 and the cavity 17 is variable.

 By way of illustration, it is shown in phantom in FIG. 1 femoral implant much larger than that shown in solid lines. Both implants 1 comprise a cone of the same dimensions, but the position of their cavity 17 and their collar 6 is different. Because the lug 16 is movable relative to the jaw 10, it can cooperate selectively with the cavity 17 of the two implants, without it being necessary to have a clamp 2 for each dimension of femoral implant.

 The lug 16 is movable in a direction that has a component parallel to the common axis A of the cone 4 and the housing 12. Because, due to its dimensions, the femoral implant shown in phantom lines has a cavity 17 which is farther away from the axis A of the cone 4 than the cavity 17 of the femoral implant represented in solid lines, the imaginary line joining the two cavities 17 is oblique with respect to the axis of the cone. The lug 16 is also movable along the same oblique direction so as to come selectively to cooperate with one or the other of these two cavities.

 According to a preferred embodiment, the lug 16 is carried by a rod 18 adapted to slide axially in the jaw 10, in the manner of a piston. At its free end, the rod 18 is bent towards the common axis A of the cone 4 and the housing 12. Preferably, the rod 18 is biased by a spring 19 towards one of its extreme positions retracted and deployed, preferably the deployed position, the spring 19 then being a compression spring.

 The rod 18 slides in a bore 20 formed in the jaw 10 and, to prevent rotation of the rod 18 about its axis relative to the jaw 10, this rotation being such as to cause an escape of the lug 16 relative to at the cavity 17, the bore 20 and the rod 18 have a non-circular cross section, this cross section being for example polygonal, and in particular square.

 The cooperation of the lug 16 with the cavity 17 allows a better cooperation of the clamp 2 with the implant 1, both for the handling of the implant for its introduction and extraction.

 For the following description of the other two aspects of the present invention, there is shown in FIG. 3, in a, b, c and d, by way of example, four possible positions that can occupy a prosthetic femoral head 44 of a given diameter relative to the cone 4 of the femoral implant 1, these different positions of the head being translated by as many different positions of the center 45 of the spherical head 44 on the axis A of the cone, after the mounting of the head thereon.

It should first be pointed out that, for reasons of simplicity of manufacture and stock reduction, the cones 4 have an identical shape for all the implants and that, in general, for the same reasons, the angle between the axis
A cone and the axis B of the tail 3, regardless of the size of the implant, is the same for all femoral implants, for example 135 ".

 Because cone 4 is identical for all femoral implants, it can receive any of a plurality of prosthetic femoral heads 44. These heads differ from each other not only in diameter but also in diameter. the position of their center 45 on the axis A which is also that of their conical bore 46, that is to say with respect to the cone 4, after mounting thereon. For each head diameter 44, there are several heads whose centers 45 have different positions on the axis A relative to the cone. As will be described later, the practitioner can, for a given position of the cone, choose, for the same head diameter, between several positions for the center of the head relative to the cone.

 As shown by way of example in FIG. 3 for four heads 44 having the same diameter, for example 28 mm, the heads 44 comprise a blind frustoconical bore 46 complementary to the cone 4, but having a small inner base smaller than that of the cone 4 so that the cooperation between the head 44 and the cone 4 is made only by complementary conical surfaces. The bores 46 are more or less deep, which determines the depth of engagement of the heads on the cone 4. In FIG. 3a, the cone 4 is totally embedded in the head, in FIGS. 3b and 3c the cone is less engaged in the head and in FIG. 3d, showing an extreme position, the cone 4 is almost completely outside the outer spherical surface of the head 44 which, for this reason, comprises a cylindrical extension 47 in which is formed, at least partially, the frustoconical bore one-eyed 46.

 It emerges from the example of FIG. 3 that, for a selected head diameter, the practitioner can therefore choose the position of the center 45 thereof after it has been mounted on the femoral cone.

 There are shown in Figures 4 to 10 two other aspects of the invention. According to these two aspects, two devices for pre-checking the selected future position of the femoral implant 1 with respect to the femur 21 and the cotyloid implant respectively with respect to the pelvic bone 48 (FIG. predetermination of these positions from a radiograph of the natural joint, before surgery, and pre-implantation verification after preparation of the femur for the femoral implant and the bone respectively iliac for the reception of the cotyloid implant, but before actual implantation.

 Schematically illustrated in FIG. 4 these two geometric predeterminations from a radiograph of the patient's joint, before intervention.

 With regard firstly to the femoral implant, the X-ray shown in FIG. 4 a layer of the femoral implant 1 whose silhouette, with its tail 3, its neck 5 and its cone 4, seems most suited to the morphology of the femur 21.

 The choice of the femoral implant is made according to the adaptation to the latter. As for its position, it is defined by the coincidence, by superposition of the layer of the implant with the radiograph <Fig. 4), of one of the possible positions of the center 45 of the prosthetic head 44 (Fig. 3) with the position of the common center 22 of the natural head 49 and the natural cup 28. This coincidence is obtained by moving the layer on the radiography, the visualization of this coincidence being done for example by four markers, including crosses, worn by the layer and the four possible positions of the center of the prosthetic head.

 The femoral implant to be put in place and its future position being thus selected, and its layer being superimposed on the radiography at the location where the implant will occupy, the practitioner traces on the radiograph a line representing the resection plane 23 of the implant. Femur at the neck 50. This drawing of the resection plane 23 on the radiography is through a slot in the layer at the location of the bearing surface of the flange 6 of the selected femoral implant.

 He also traces on the radiography, through another slot of this layer representative of the selected femoral implant, a line corresponding to the location of each natural center 22, and then a line 22 'joining the centers 22.

 For subsequent verification after preparation of the femur, the practitioner measures the height between the line 22 'and the top of the greater trochanter 24.

 To increase the accuracy of the resection, he can also measure the distance of the line 23 from the small trochanter 25.

 With regard to the future implantation of the prosthetic acetabulum and the choice of the diameter of the prosthetic head 44, the practitioner traces on the X-ray a line 26, called the radiological U-line, joining the apices of the two obturator holes 27 and the lower edges. 28. He then places on the radiograph a prosthetic acetabular layer whose diameter, defining that of the prosthetic head, seems best adapted to the natural acetabulum 28. It then measures the distance 6 'between the center line 22'. and line 26.

 FIGS. 5 to 8 show a first verification device making it possible to verify, after preparation of the femur and before implantation of the femoral implant, the future position that the implant will occupy, this position being physically defined. by the effective position of the resection plane 23 and the geometry of the tapered housing 29 formed in the body of the femur 21, from the resection plane 23, using a rasp 30 having a rough working portion 31 and a pin 32 for removable reception, on the one hand, an operating handle (not shown) for the realization by the practitioner housing 29 and, secondly, a block 33 forming part of the verification device.

 When the practitioner thinks to have correctly realized the housing 29, as to the predetermined final shape thereof and to the position of the resection plane 23, and the rasp 30 being in an extreme driving position, as shown in FIG. 5, that is to say that the junction between the rough working portion 31 and the pin 32 coincides with the resection plane 23 and that the pin 32 is coaxial with the position occupied by the cone 4, it proceeds to a first geometric verification for the housing 29, and therefore the future position of the selected femoral implant 1, and more specifically the final position of the cone 4 and therefore that of the center 45 of the prosthetic femoral head 44.

 This verification is done using the block 33 which has a central bore 34 receiving no play of the pin 32, the lower surface 35 of the block bearing against a shoulder 32 'of the pin 32. The angular positioning of the block 33 on the pin 32 is obtained thanks to a flat portion 36 of the bore 34 cooperating with a conjugate profile of the pin 32.

 On either side of the bore 34, the block 33 has a plurality of orifices 37 whose axis is substantially perpendicular to the general direction of the femur 21, that is to say substantially 135 relative to the axis of the bore 34, and which converge slightly in pairs towards the median plane P of the block 33. The orifices 37 are at different levels in the direction of the axis of the bore 34 and each of them is representative of one of the possible positions of the center of the prosthetic femoral head to be implanted, as described above.

 The block 33 cooperates with a feeler 38 which is constituted by a rectilinear rod intended to be threaded into that of the orifices 37 which corresponds to the predetermined final position of the center 45 of the prosthetic head 44 chosen.

 If the preparation of the femur is correct, the stem 38 is at the height 6 above determined between the line 22 'of the natural centers 22 and the top of the greater trochanter 24, which corresponds to a coincidence between the natural center 22 and the future prosthetic center 45. In the opposite case, the practitioner may for example choose another femoral implant which differs from the previous one only by the length of the neck 5.

 FIGS. 9 and 10 show the second device according to the invention enabling the practitioner, after the preparation of the acetabulum cavity 28 'and before implantation of the prosthetic acetabulum, to verify that the geometry of this cavity 28' obtained by Milling corresponds, with regard to its center and its diameter, to the predetermined geometry sought.

 This device comprises a handle 39 of support and maneuvering which, at one end, carries a test spherical head 40 appearing by its outer surface the selected acetabular implant and defining by its center the center thereof. The head 40 fixedly carries a graduated ruler 41 on which can slide a slider 42 provided with a probe 43 constituted by a finger. The graduation carried by the slide 41 represents the distance between the center of the test head 40 and the probe 43.

 If the preparation of the acetabular cavity 28 'is correct, the value read by the practitioner on this graduation, when the test head 40 is in place in the acetabular cavity and the probe 43 is placed by the practitioner at the level of the radiological U line above, must coincide with the 6 'value defined above.

If this coincidence does not exist, the practitioner must intervene again on the acetabulum.

 Of course, the invention is not limited to the embodiments that have been described; on the contrary, we could design various variants without departing from its scope.

Claims (16)

 1. Hip prosthesis system, comprising, in particular, on the one hand, a femoral implant (1) comprising a tail (3) for penetration into the bored femoral medullary canal (29) and a cone (4) for receiving a prosthetic femoral head (44) intended to cooperate with an acetabular implant, and secondly a gripper (2) with two jaws (10, 11) for insertion of the tail (3) into the medullary canal , characterized in that said jaws (10, 11) are arranged to define, for the closed position of the clamp (2), a housing (12) for cooperation with the cone (4) for clamping thereof; one of said jaws (10, 11) carries a lug (16) beyond its free end; and the femoral implant (1) has, between the shank (3) and the cone (4), a cavity (17) intended to cooperate with said lug (16).  2. System according to claim 1, characterized in that said cavity (17) is located at a flange (6) that includes the femoral implant (1) for bearing on the plane (23) of resection of the femur (21).  3. System according to one of claims 1 and 2, characterized in that a mordache (13) of protection and / or friction, in particular plastic, and for example polyethylene or polytetrafluoroethylene, is disposed between the cone (4) of the implant and each jaw (10, 11) of the forceps.  4. System according to one of claims 1 to 3, characterized in that said cavity (17) is elongated in the peripheral direction, and the free end of the lug (16) has a shape complementary to that of the cavity , with the game.  5. System according to one of claims 1 to 4, characterized in that the lug (16) is movable on the jaw (10) which carries it for the adaptation of the clamp (2) to femoral implants (1). ) of different sizes for which the distance between the cone (4) and the cavity (17) is variable.  6. System according to claim 5, characterized in that the lug (16) is movable in a direction having a component parallel to the common axis (A) of the cone (4) of the implant and the housing (12). defined by the jaws (10, 11) of the clamp in the closed position on the cone.  7. System according to claim 6, characterized in that the lug (16) is movable in a direction oblique with respect to said common axis (A).  8. System according to one of claims 5 to 7, characterized in that the direction of movement of the lug (16) is parallel to a line on which are located the respective cavities (17) of the femoral implants (1) of different sizes.  9. System according to one of claims 5 to 8, characterized in that the lug (16) is carried by a rod (18) adapted to slide axially in the jaw (lo) which carries it.  10. System according to claim 9, characterized in that the rod (18) is biased by a spring (19) towards one of its extreme retracted and deployed positions, preferably the extended position.  11. System according to one of claims 9 and 10, characterized in that the rod (18) slides in a bore (20) formed in the jaw (10) which carries it, said bore and the rod being arranged so that the rod can not rotate about its axis, for example because the bore and the rod have a polygonal cross section, including square.  12. System according to one of claims 1 to 11, characterized in that it comprises a first device (3338) for prior verification of the selected future position of the femoral implant (1) on the prepared femur (21), and in particular the position of the center (45) of the prosthetic femoral head (44).  13. System according to claim 12, characterized in that said first device (33-38) verification includes a block (33) adapted to be threaded in predetermined position on the operating pin (32) of a rasp (30). for preparing the medullary canal (29), this block (33) having a plurality of orifices (37), for example four, one of which, selected, receives a probe (38) which, for a correct preparation of the medullary canal, occupies a predetermined position relative to an anatomical landmark, for example the top of the greater trochanter (24).  14. System according to claim 13, characterized in that said orifices (37) of the block (33) are at different levels in the direction of the axis (A) of the cone (4) of the implant to show the various possible axial positions of the center (45) of the prosthetic femoral head (44) relative to the cone (4) of the implant.  15. System according to one of claims 1 to 14, characterized in that it comprises a second device (39-43) for pre-checking the selected future position of the cotyloid implant in the prepared pelvic bone (48). .  16. The system of claim 15, characterized in that said second device (39-43) of verification comprises a test spherical head (40) with its outer surface prosthetic acetabular cavity (28 ') selected and prepared and secured on the one hand, a handle (39) maneuvering and support and on the other hand, a slider (41), preferably graduated, on which can slide a slider (42) provided with a probe ( 43) which, for correct preparation of the pelvic bone, occupies a predetermined position with respect to the spherical test head (40) and an anatomical landmark, for example the line (26) connecting the apices of the holes shutters (27) and the lower edges of the natural cups (28).