AU2008353332B2

AU2008353332B2 - Arthrodesis system for the ankle of a human patient

Info

Publication number: AU2008353332B2
Application number: AU2008353332A
Authority: AU
Inventors: Beat Hintermann
Original assignee: Smith and Nephew Asia Pacific Pte Ltd
Current assignee: Smith and Nephew Asia Pacific Pte Ltd
Priority date: 2008-03-27
Filing date: 2008-03-27
Publication date: 2015-04-16
Anticipated expiration: 2028-03-27
Also published as: AU2008353332A1; EP2273943A1; JP2011515172A; JP5449316B2; WO2009118461A1; EP2273943B1

Abstract

The invention relates to a system for immobilising the articulation of the tibia (1) and the talus (2) of a human patient, wherein said system is characterised in that the same comprises at least one anterolateral plate (3) and one anetromedial plate (7). The invention can be used for surgical tools.

Description

1 ARTHRODESIS SYSTEM FOR THE ANKLE OF A HUMAN PATIENT TECHNICAL FIELD The present invention relates to the general 5 technical field of surgical devices designed to secure together two bone portions of a joint, e.g. with a view to performing arthrodesis. The present invention relates more precisely to a system for immobilizing the joint between the tibia and 10 the talus of a human patient. PRIOR ART In certain pathologies that occur at the joint between the tibia and the talus (primary osteoarthritis, 15 post-traumatic osteoarthritis, or ankle arthritis) or after failure of total ankle replacement, it can be necessary to perform arthrodesis in order to fuse the two bones (talus and tibia) together. In general arthrodesis operations are delicate because they lock a joint 20 irreversibly in a defined position. Arthrodesis of the joint between the tibia and the talus is highly important insofar as that joint plays an essential part in the walking cycle of a human being. It can thus be understood that it is essential, in particular in view of the load 25 cycles to which the joint between the tibia and the talus is subjected, that the arthrodesis of that joint be performed in the least invasive and most precise manner possible, so as to avoid any subsequent discomfort. Currently, ankle arthrodesis is usually performed by 30 means of bone fastener plates provided with holes designed to receive fastener screws for securing the plate to the bone to be fused. Plates are thus known that are designed to be fastened to the lateral side of the tibia or of the 35 talus. Unfortunately, those plates are generally difficult to fit in particular because of the operating difficulty caused by the presence of the fibula. In 2 addition, those known plates have a shape that does not enable them fit snugly over the bone outlines, which gives rise to a risk of subsequent discomfort and complications for the patient, and does not facilitate surgical intervention. In order to remedy that problem, the surgeon can be obliged to perform steps of shaping the plate during the operation, by folding it manually (using pliers) . Such folding steps constitute a significant additional constraint in surgical intervention, and can also weaken the metal at the foldzone, thereby constituting a major drawback in terms of strength. In addition, the need to provide openings for allowing the fastener screws to pass through the plate complicates the plate-folding step precisely because of the presence of said openings. Thus, known plates do not make it possible to perform tibia/talus arthrodesis under good operating conditions, and with minimized risk of subsequent discomfort and complications for the patient. Any discussion of the prior art throughout the specification should in, no way be considered as an admission that such prior art is widely known or forms part of common general knowledge in the field. SUMMARY OF THE INVENTION An object of the invention is therefore to remedy the various above-listed drawbacks and to propose a novel system for immobilizing the joint between the tibia and the talus of a human patient that makes it possible to perform arthrodesis under good operating conditions while also making it possible to obtain bone fusion that is particularly stable, strong, precise, and comfortable for the patient. Another object of the invention is to propose a novel system for immobilizing the joint between the tibia and the talus of a human patient that is particularly comfortable for the patient, under all circumstances. Another object of the invention is to propose a novel system for immobilizing the joint between the tibia and the talus of a human patient that is particularly easy and quick to put in place, and that procures particularly reliable bone fusion.

3 Another object of the invention is to propose a novel system for immobilizing the joint between the tibia and the talus of a human patient that facilitates the process of osteosynthesis between the tibia and the talus. Another object of the invention is to propose a novel system for immobilizing the joint between the tibia and the talus of a human patient that makes it possible to facilitate osteosynthesis in a manner that is particularly simple, quick, and reliable. The objects assigned to the invention are achieved by means of a system for immobilizing the joint between the tibia and the talus of a human patient, said system including: an antero-lateral plate, itself including a tibio lateral strip and a talo-lateral tab interconnected by a link zone, said tibio-lateral strip, said talo-lateral tab, and said link zone being shaped both so that: at least one portion of the tibio-lateral strip rests substantially against the anterior lateral face of the tibia that is situated towards the outside of the body of the patient relative to the anterior tibial crest ; and also so that the talo-lateral tab rests substantially against the talus; and an antero-medial plate, itself including a tibio medial strip and a talo-medial tab interconnected by a link zone, said tibio-medial strip, said talo-medial tab, and said link zone being shaped both so that: at least one portion of the tibio-medial strip rests substantially against the anterior medial face of the tibia that is situated towards the inside of the body of the patient relative to the anterior tibial crest; and also so that the talo-medial tab rests substantially against the talus, said link zone of the antero-medial plate being designed to come into register with at least a portion of the tibial pilon, said link zone having a shape that is substantially complementary to the shape of said portion of the tibial pilon.

4 The objects assigned to the invention are also achieved by means of an antero-lateral plate designed to be part of a system of the invention. The objects assigned to the invention are also 5 achieved by means of an antero-medial plate designed to be part of a system of the invention. BRIEF DESCRIPTION OF THE DRAWINGS Other advantages and objects of the invention appear 10 in more detail on reading the following description and on examining the accompanying drawings that are given merely by way of explanatory and non-limiting example, and in which - Figure 1 is a front view (ventral view) of the 15 antero-lateral and antero-medial plates of the system of the invention, as positioned on the right tibia and the right talus of a human patient so as to immobilize the joint between the tibia and the talus; - Figure 2 is identical to Figure 1, except that it 20 is a lateral side view rather than a front view (ventral view); - Figure 3 is identical to Figures 1 and 2 except that it is a medial side view; - Figure 4 is a lateral side view of the antero 25 lateral plate of Figures 1 to 3; - Figure 5 is a medial side view of the antero lateral plate of Figure 4; - Figure 6 is a rear view (dorsal view) of the antero-lateral plate of Figures 4 and 5; 30 - Figure 7 is a front view (ventral view) of the antero-lateral plate of Figures 4 to 6; - Figure 8 is a front view (ventral view) of the antero-medial plate of Figures 1 to 3; - Figure 9 is a rear profile view of the antero 35 medial plate of Figure 8; - Figure 10 is a lateral view of the antero-medial plate of Figures 8 and 9; 5 - Figure 11 is a medial view of the antero-medial plate of Figures 8 and 10; - Figure 12 is a rear view (dorsal view) of the antero-medial plate of Figures 8 to 11; 5 - Figure 13 shows a pair of plates made up of an antero-lateral plate and of an antero-medial plate that are part of a system of the invention for immobilizing the joint between the right tibia and the right talus of a human patient; 10 - Figure 14 shows a front view of a pair of plates made up of an antero-lateral plate and of an antero medial plate that are part of the system of the invention and that are designed to immobilize the joint between the left tibia and the left talus of a human patient; 15 - Figure 15 is a side view showing the antero lateral plate of Figure 14 co-operating with bone anchor screws; - Figure 16 is a plan view of pliers forming compression means for compressing the joint between the 20 tibia and the talus. - Figure 17 is a perspective view of a fastener and guide bush designed to be associated with a first jaw of the pliers of Figure 16; - Figure 18 is a perspective view of a fastener 25 screw designed to be associated with the second jaw of pliers of Figure 16; - Figure 19 shows how the pliers of Figure 16 co operate firstly with the bush of Figure 17 and secondly with the screw of Figure 18; 30 - Figure 20 shows how the compression means of Figure 19 are implemented in co-operation with the antero-medial plate of Figure 14; - Figures 21 and 22 show two examples of screws (with heads that are respectively frustoconical and 35 spherical) and of corresponding lock screws (systems of the Surfix@ type) suitable for fastening the antero lateral and antero-medial plates to the bone.

6 BEST MANNER OF IMPLEMENTING THE INVENTION The invention relates to a system for immobilizing the joint between the tibia 1 and the talus 2 of a human 5 patient, with a view to performing arthrodesis of the ankle. The system of the invention thus advantageously constitutes an ankle arthrodesis system. The system of the invention comprises at least an 10 antero-lateral plate 3 designed to be fastened both to the anterior (ventral) face of the tibia 1 and to the anterior face of the talus 2. The antero-lateral plate 3 is a plate designed to be implanted surgically. 15 It presents the characteristic of being rigid, and it is preferably made of a hard and rigid material such as stainless steel, titanium, or any other metal material of surgical grade. The antero-lateral plate 3 itself comprises a tibio 20 lateral strip and a talo-lateral tab 5 that are interconnected by a link zone 6. In other words, the tibio-lateral strip 4 is extended by the link zone 6, which is itself extended by the talo-lateral tab 5. The antero-lateral plate 3 preferably has an elongate overall 25 shape, as shown in the figures, i.e. the overall length of the antero-lateral plate 3 is significantly greater both than its width and than its thickness. In accordance with the invention, said tibio-lateral strip 4, said talo-lateral tab 5, and said link zone 6 30 are shaped both so that: - at least one portion of the tibio-lateral strip 4 rests substantially against the anterior lateral face 1A of the tibia 1 that is situated towards the outside of the body of the patient relative to the anterior tibial 35 crest 1B; and also so that 7 the talo-lateral tab 5 rests substantially against the talus 2, and preferably against the neck 2A of the talus 2. In other words, the tibio-lateral strip 4, the talo 5 lateral tab 5, and the link zone 6 are positioned, oriented, and dimensioned relative to one another so that when the antero-lateral plate 3 is installed in its final implantation position, inside the body of the patient, the tibio-lateral strip 4 substantially snugly fits the 10 anterior lateral face 1A of the tibia 1, while the talo lateral tab 5 is substantially pressed against the talus 2, and preferably against the neck 2A of the talus 2. The antero-lateral plate 3 is thus designed to be positioned in register with the distal end of the tibia 15 1, and to be pressed against the lateral anterior face 1A thereof. Advantageously, as shown in the figures, the antero lateral plate 3 is shaped so that, when it finds itself in its final implantation position, its tibio-lateral 20 strip 4 extends substantially against the anterior tibial crest 1B, and parallel thereto. The tibio-lateral strip 4 thus finds itself pressed against the portion of the anterior lateral face 1A that finds itself in the immediate vicinity of the anterior tibial crest 1E, the 25 portion in question of the anterior lateral face 1A presenting the characteristic of being substantially flat, which makes it possible for the tibio-lateral strip 4 to be fastened stably and effectively to the tibia 1, by means that are described in more detail below. 30 Preferably, the link zone 6 of the antero-lateral plate 3 is designed to come into register with at least a portion of the tibial pilon 1C, which forms a bulge of bone at the distal end of the tibia 1. In order to make the antero-lateral plate 3 easier for the patient to 35 tolerate and thus more comfortable for said patient, the link zone 6 of the antero-lateral plate 3 preferably has 8 a shape that is substantially complementary to the shape of the portion of the tibial pilon 1C that it covers. Preferably, the link zone 6 of the antero-lateral plate 3 has a shape that is curved significantly so as to 5 match the outline of the tibial pilon 1C, as shown in the figures. Thus, the antero-lateral plate 3 of the invention is anatomical in general shape, i.e. it is shaped to match as closely as possible the anatomy of the bone structures to which it is designed to be fastened. 10 By means of this characteristic, the antero-lateral plate 3 is easier for the patient to tolerate and easier for the surgeon to fit. Surgically putting the antero-lateral plate 3 into place is also greatly facilitated by the specific 15 positioning chosen, i.e. the positioning on the anterior lateral face 1A of the tibia 1. This positioning facilitates the work of the surgeon because it requires only an anterior approach. Such an anterior approach procures better visibility 20 than lateral, posterior, or medial approaches, and it requires only a short incision in comparison with the incisions that are required for the other above-mentioned approaches, and fitting the plate is facilitated because the anterior approach is not obstructed by anatomical 25 obstacles such as the fibula (an obstacle for the lateral approach), the Achilles tendon (an obstacle for the posterior approach), or the malleolus (an obstacle for the medial approach). In addition, it is already known that the anterior surgical approach can be used for 30 fitting total ankle prostheses. It is thus very advantageous to propose for the same surgeons to use an anterior approach for performing talo-tibial arthrodesis, in particular since said arthrodesis can take place after fitting a total ankle prosthesis has failed. The 35 invention has identified a very precise anatomical positioning for the antero-lateral plate 3, and proposes a very specific geometrical shape for the antero-lateral 9 plate 3, which makes it possible to match as closely as possible the anatomy of the particular implantation site, thereby procuring fastening that is reliable, effective, and comfortable. 5 The system of the invention further comprises an antero-medial plate 7. The antero-medial plate 7 is a plate that is also designed to be implanted surgically, preferably via the same anterior approach as the antero lateral plate 3. The antero-medial plate 7 also has the 10 characteristic of being rigid and is also preferably made of a hard and rigid material such as stainless steel, titanium, or any other metal material of surgical grade. The antero-medial plate 7 itself comprises a tibio medial strip 8 and a talo-medial tab 9 interconnected by 15 a link zone 10. In other words, the tibio-medial strip 8 is extended by the link zone 10, which is itself extended by the talo-medial tab 9. Preferably, the antero-medial plate 7 has an elongate overall shape, i.e. its overall length is significantly greater both than its width and 20 than its thickness. Said tibio-medial strip 8, said talo-medial tab 9, and said link zone 10 of the antero-medial plate 7 are shaped both so that: - at least one portion of the tibio-medial strip 8 25 rests substantially against the anterior medial face ID of the tibia 1 that is situated towards the inside of the body of the patient relative to the anterior tibial crest 1B; and also so that the talo-lateral tab 9 rests substantially against 30 the talus 2, and preferably against the neck 2A of the talus 2. Thus, one of the particularly advantageous technical characteristics of the system of the invention lies in the implementation of two plates 3, 7 disposed towards 35 the distal portion of the tibia 1, at least partially on either side of the anterior tibial crest 1B, said antero lateral plate 3 and said antero-medial plate 7 being 10 designed to be secured both to the distal portion of the tibia 1 and to the talus 2. Such an arrangement procures fastening that is particularly stable and effective, while also being particularly well tolerated by the 5 patient because the antero-medial plate 7, like the antero-lateral plate 3, matches as closely as possible the outline of the bone structure against which it is mounted and to which it is designed to be fastened. The system of the invention is particularly easy to 10 fit because the antero-medial plate 7, like the antero lateral plate 3, can be fitted via the anterior approach, with the above-described ensuing advantages. Both plates, i.e. the antero-lateral plate 3 and the antero-medial plate 7, can also be fitted via the same anterior 15 incision. Preferably, the link zone 10 of the antero-medial plate 7 is designed to come into register with at least a portion of the tibial pilon 1C, said link zone 10 of the antero-medial plate 7 having, for this purpose, a shape 20 that is substantially complementary to the shape of said portion of the tibial pilon 1C; The antero-medial plate 7 thus advantageously snugly fits the outline of the anatomical structures that it covers and to which it is designed to be secured, thereby 25 contributing not only to the reliability and to the stability of the fastening, but also to the comfort of the patient. Advantageously, and as shown in the figures, the antero-medial plate 7 is thus shaped so that, when it 30 finds itself in its final implantation position, its tibio-medial strip 8 extends at least in part substantially against the anterior tibial crest 1B, and parallel thereto, on the medial side. The tibio-medial strip 8 thus finds itself at least in part pressed 35 against the portion of the anterior medial face 1D that finds itself in the immediate vicinity of the anterior tibial crest 1B, the portion in question of the anterior 11 medial face ID having the characteristic of being substantially flat, which makes it possible for the tibio-medial strip 8 to be fastened stably and effectively to the tibia 1, by means that are described 5 in more detail below. More precisely, and as shown in the figures, the antero-medial plate 7 is designed to be positioned in part straddling the anterior tibial crest 1B. As is well known, and as shown in the figures, the anterior tibial 10 crest 1B is not rectilinear over the entire length of the tibia 1 and it is inclined towards the internal malleolus 11 in the vicinity of the distal end of the tibia 1. The antero-medial plate 7 is thus advantageously designed so that only an end portion of its tibio-medial strip 8 that 15 is situated towards the free end thereof is disposed medially relative to the anterior tibial crest 1B. In other words, the antero-medial plate 7 is preferably designed so that its talo-medial tab 9 substantially snugly fits the neck 2A of the talus 2, and is extended 20 by the link zone 10 that snugly fits most of the bulge formed by the tibial pilon 1C. The link zone 10 is then extended by a first portion (or distal portion) of the tibio-medial strip 8, said first portion being situated under the anterior tibial crest 1B, said distal portion 25 itself being extended by a second portion (or end portion) which preferably extends substantially parallel to and against the anterior tibial crest 1B (see Figure 1). The invention has identified very precise anatomical 30 positioning for the antero-medial plate 7, and proposes a very specific geometrical shape for the antero-medial plate 7, which makes it possible to match as closely as possible the anatomy of the particular implantation site, thereby procuring fastening that is reliable, effective, 35 and comfortable. Advantageously, and as can be seen in particular in Figures 9 and 10, the antero-medial plate 7 has a 12 significantly twisted shape so as to match both the outline of the anterior medial face ID of the tibia 1 and also the outline of the talus 2 and more precisely of the neck 2A of the talus 2. 5 Preferably, the antero-lateral plate 3 also has such a significantly twisted shape, so as to match both the outline of the anterior side face 1A and the outline of the neck 2A of the talus 2. Advantageously, the tibio-medial strip 8 of the 10 antero-medial plate 7 has a substantially arcuate shape, as can be seen in particular in Figures 2, 3, and 10, so as to match both the outline of the anterior medial face ID of the tibia 1 and also the outline of at least a portion of the tibial pilon 1C. In other words, the 15 tibio-medial strip 8 is preferably shaped and dimensioned so as not only to extend over the anterior medial face 1D but also to fit snugly over the beginning of the bulge formed by the pilon IC, the remainder of the bulge fitting snugly into the link zone 10, which is extended 20 by the talo-medial tab 9. By means of the very particular positioning of the antero-lateral plate 3 and of the antero-medial plate 7 as identified within the ambit of the invention, it is possible, with only two plates that are small in size and 25 easy to fit, to obtain fastening that is extremely robust, stable, and comfortable, and that is, in addition, easy for the surgeon to perform, in particular in view of the techniques known from the prior art. Advantageously, and as can be seen more particularly 30 in Figures 10 and 11, the antero-medial plate 7 (preferably like the antero-lateral plate 3) has, as seen in profile, substantially the shape of a spoon, the tibio-medial strip 8 corresponding to the handle of the spoon, while the link zone 10 and the talo-medial tab 9 35 form the concave portion (receptacle) of the spoon. Advantageously, the talo-medial tab 9 extends in a main longitudinal direction X-X' that is inclined laterally, 13 i.e. towards the outside of the body of the patient, relative to the main longitudinal direction Y-Y' in which the tibio-medial strip 8 extends. In other words, as seen from the front (Figure 8), 5 the antero-medial plate 5 presents a main body that is substantially rectilinear, corresponding substantially to the tibio-medial strip 8 and to the link zone 10, which main body is provided with a spatulate element that forms a non-zero angle with the main body, the spatulate 10 element in question corresponding to the talo-medial tab 9. Preferably, the antero-lateral plate 3 presents a shape that is substantially symmetrical, about the anterior tibial crest 1, to the shape of the antero 15 medial plate 7, i.e. the talo-lateral tab 5 is advantageously inclined towards the inside of the body of the patient relative to the tibia-lateral strip 4. By means of this characteristic, the tabs 5, 9 converge towards the middle of the neck 2A of the talus 20 2, thereby making it possible to take advantage of a bone surface that is not only effective for fastening (because it has the characteristic of being generally flat in that region) but that is also easy for the surgeon to reach and to identify. 25 Advantageously, the system of the invention further comprises at least one first anchor member 12 provided with a head 12A and with a bone-anchor shank 12B that extends from the head 12A, the tibio-medial strip 8 being provided at least a first orifice 8A provided with a 30 first bearing surface 8B against which said head 12A is designed to come into abutment, said first bearing surface 8B advantageously being shaped so that the anchor shank 12B can extend in a direction enabling it to pass through both the tibia 1 and the talus 2 (as shown in 35 dashed lines in Figure 3), the shank 12E thus forming a trans-articular anchor shank. In another particularly advantageous embodiment, the first bearing surface 8B of 14 the first orifice 6A is advantageously shaped so that the anchor shank 12E can extend through the tibia 1, through the talus 2, and through the calcaneum (not shown). Thus, by combining an adapted orientation of the first bearing 5 surface 8B of the first orifice 8A and a sufficient length for the shank 12B of the corresponding first anchor member 12, it is possible to achieve trans articular fastening that secures together the antero medial plate 7, the tibia 1, the talus 2, and optionally 10 the calcaneum. Preferably the first anchor member 12 is constituted by a bone screw designed to be screwed both into the tibia 1 and into the talus 2, and its length is thus appropriate for this purpose. 15 Advantageously, as shown in the figures, the tibio medial strip 8 is provided with a plurality of orifices 8A, 8C, 8D, each of which is designed to be associated with a corresponding anchor member. Advantageously, the first orifice 8A is positioned as close as possible to 20 the link zone 10 of the tibio-medial strip 5, i.e. it constitutes the orifice that is furthest away from the tibio-medial strip 8. In other words, the orifice that is closest to the link zone 10 corresponds to the first orifice 8A. 25 Thus, in the example shown in the figures, the tibio-medial strip 8 is provided with three orifices 8A, 8C, 8D, namely a proximal orifice 8D, an intermediate orifice 8C, and a distal orifice that corresponds to the first orifice 8A. 30 Preferably, in order to facilitate positioning the shank 12B of the first anchor member 12 forming the trans-articular fastening member, the first orifice 8A is positioned on the tibio-medial strip 8 in a manner such as to find itself substantially in the vicinity of the 35 beginning of the bulge of bone formed by the pilon 1C. The applicant has established that this position is particularly conducive to easily obtaining stable and 15 robust fastening by transpiercing the tibia 1 and the talus 2 with the same shank 12B. In order to facilitate fitting the first trans articular anchor member 12, the first bearing surface 8B 5 of the first orifice 8A advantageously extends in a midplane P disposed slantingly relative to the main longitudinal direction Y-Y' in which the tibio-medial strip 8 extends. In other words, and as shown in the figures, the first orifice 8A extends through the 10 thickness of the tibio-medial strip 8 between the inside face 13 of the strip 8 that is designed to find itself in contact with the bone and the opposite outside face 14, the first bearing surface 8B being disposed slantingly relative to the inside face 13 and/or to the outside face 15 14. Preferably, the first bearing surface 8B of the first orifice 8A has a substantially rounded shape, preferably in the shape of a sphere portion, so as to enable the orientation of the first anchor member 12 20 relative to the tibio-medial strip 8 to be adjusted. For this purpose, the head 12A of the first anchor member 12, or at least the portion of the head 12A that is designed to come into contact with the first bearing surface 8B, has a complementary spherical shape (cf. Figure 22). 25 The surgeon can thus finely adjust the orientation of the first anchor member 12 relative to the tibio medial strip 8 so as to make sure, e.g. by X-ray checking, that the shank 12B does indeed extend both through the tibia 1 and through the talus 2. 30 Preferably, in order to facilitate good fastening to the bone, the shank 12B of the first anchor member 12 has a diameter (e.g. a diameter of 3.5 millimeters (mm)) that is significantly greater than the diameter (e.g. 3 mm) of the shanks of the other anchor members used in co 35 operation with the other orifices 8C, 8D provided through the tibio-medial strip 6.

16 Advantageously, the talo-medial strip 9 is also provided with orifices, and preferably with three such orifices disposed in a triangle configuration, the talo medial tab advantageously presenting a shape that is 5 wider than the shape of the tibio-medial strip 8 and than the shape of the link zone 10. Preferably, said link zone 8 is not provided with any orifices, thereby facilitating any plate-folding steps that the surgeon might wish to perform during the operation, so as to adapt to 10 accommodate specific anatomical conditions. The antero-medial plate 7 is thus preferably provided with three fastening orifices in line that are provided in its tibio-medial strip 8, and with three fastening orifices not in line that are provided in its 15 talo-medial tab 9. As explained above, the first orifice 8A advantageously has a spherical bearing surface 8B making it possible to adjust the angulation of the screw with which it is designed to co-operate, said spherical 20 bearing surface 8B further being oriented specifically to direct the screw both towards the tibia 1 and towards the talus 2, the screw in question (which corresponds to the first anchor member 12) thus forming a trans-articular screw. 25 Preferably, each of the other orifices is provided with a frustoconical bearing surface surmounted by an inside thread designed to receive a lock screw making it possible to lock the screw head (system of the Surfix@ type described in particular in French Patent Application 30 FR-07 04449 filed on June 21, 2007, and in European Patent Application EP-0 345 133 filed on May 26, 1989, the contents of those applications being incorporated into the present description). Advantageously, as described in above-mentioned 35 Patent Application FR-07 04449, each orifice provided in the antero-medial plate 7, preferably except for the first orifice 8A, can be used equally well either with a 17 screw having a frustoconical head as shown in Figure 21 (for particularly firm and stable fastening, or with a screw having a spherical head as shown in Figure 22 (for fastening making it possible to adjust the angulation of 5 the screw relative to the plate), a lock nut always being used, making it possible to secure the screws effectively to the plate. Preferably, the antero-lateral plate 3 is of design substantially similar to the design of the antero-medial 10 plate 5, except that the tibio-lateral strip 4 is preferably longer than the tibic-medial strip 6, and is provided with more orifices (five orifices, each of which is designed to receive a fastener member, of the screw type, the distal orifice, situated closest to the link 15 zone 6, having a bearing surface disposed slantingly so as to enable a screw 15 that is longer and of larger diameter than the other screws to pass both through the tibia 1 and through the talus 2. Advantageously, the system of the invention further 20 comprises compression means 16 for compressing the joint between the tibia 1 and the talus 2, said compression means 16 comprising: - a first jaw iA designed to be fastened temporarily to the tibia 1; 25 - a second jaw 16B designed to be fastened temporarily to either one of the plates, namely the antero-lateral plate 3 or the antero-medial plate 7; and - closure means (preferably manual means) for bringing the first and second jaws 16A, 16B closer 30 together. Preferably, one or both of the antero-lateral plate 3 and the antero-medial plate 7 is/are provided with a tapped hole into which the second jaw 16B itself or an independent piece 17 mounted on said second jaw 16B is 35 designed to be screwed. Advantageously, said tapped hole is provided in the tibio-lateral strip 4 or in the tibio medial strip 8 (preferably in the tibio-lateral strip 4) 18 and even more preferably towards the free end of the strip in question. Preferably, and as shown in the figures, the compression means 16 are in the form of a pair of pliers, the second jaw 16B being provided with a 5 sleeve into which a bush 17A is engaged, which bush is provided with an outside thread 17B, said outside thread 17B preferably being designed to be screwed either into the inside thread of the proximal orifice 4D provided in the tibio-lateral strip 4, closest to the free end 10 thereof, or into the inside thread of the proximal orifice 8D provided in the tibio-medial strip 8, closest to the free end thereof (as shown in Figure 20). The second jaw is thus fastened to the tibio-lateral strip 4 or to the tibio-medial strip 8 by being screwed into the 15 orifice 4D, 8D in question. The tapping of the orifice in question thus performs two functions because it makes it possible firstly to secure the second jaw 16B of the compression means 16 to the plate in question, and secondly, once the compression has been performed, to co 20 operate with a lock screw to lock the head of the fastener screw inserted into the orifice in question (Surfix@ system described in above-mentioned Applications FR-07 04449 and EP-0 345 133). Naturally, the invention also relates independently 25 to the compression means in question per se, and similarly relates independently to the antero-lateral plate 3 on its own and to the antero-medial plate 5 on its own. Each of the plates in question also constitutes an 30 independent invention per se. Use of the system of the invention is described below in more detail. Firstly, the patient is installed in the supine position on an X-ray operating table. A longitudinal 35 anterior incision of in the range 10 centimeters (cm) to 12 cm is formed laterally directly in the anterior tendon of the tibia. The surgeon then performs surgical cleaning 19 in order to uncover both the anterior face of the tibia 1 and the anterior face of the talus 2. In particular, the surgeon removes the cartilage from the dome of the talus and from the tibial plafond. Bone grafts can be inserted 5 into the talo-tibial joint. The surgeon then fits the antero-lateral plate 4 preferably first. For this purpose, the surgeon firstly fastens the talo-lateral tab 5 to the neck 2A of the talus 2, by means of three screw & lock-screw sets of the 10 Surfix@ type, as shown in Figures 21 and 22. The talo lateral tab 5 is positioned on the lateral side of the neck of the talus 2, and is fastened by means of three screws that are inserted into respective ones of the three fastener orifices provided in the talo-lateral 15 tab 5. The surgeon then compresses the joint between the tibia 1 and the talus 2. For this purpose, the first jaw 16A of the pliers constituting the compression means 16 is fastened to the 20 tibia 1, by means of a temporary screw 18, while the second jaw 16B is screwed, via the bush 12A, into the tibia 1, in alignment with the fastening orifices provided in the tibio-lateral strip 4. The compression pliers are thus fastened, in the 25 open position, both to the tibio-lateral strip 4 and to the heel 2. The surgeon then exerts a force on the arms 16C of the pliers, thereby causing the first and second jaws 16A, 16B to move closer together. More precisely, the first jaw 16A remains stationary while the second jaw 30 16B moves towards the first jaw iGA, entraining with it upwards the antero-lateral plate 4 and the talus 2 to which said plate 4 is fastened. The talus 2 is thus compressed against the distal base of the tibia 1. With the joint being held thus in compression, the tibio 35 lateral strip 4 is fastened permanently to the tibia 1 by means of screws inserted into the orifices provided in the tibio-lateral strip 4.

20 Once the antero-lateral plate 3 is fastened in this way, the surgeon inserts and fastens the antero-medial plate 5 in similar manner. 5 SUSCEPTIBILITY OF INDUSTRIAL APPLICATION The invention finds its industrial application in developing, manufacturing, and using systems for immobilizing the talo-tibial joint.

Claims

1. A system for immobilizing the joint between the tibia and the talus of a human patient, said system including: an antero-lateral plate, itself including a tibio-lateral strip and a talo-lateral tab interconnected by a link zone said tibio-lateral strip, said talo-lateral tab, and said link zone being shaped both so that: at least one portion of the tibio-lateral strip rests substantially against the anterior lateral face of the tibia that is situated towards the outside of the body of the patient relative to the anterior tibial crest ; and also so that the talo-lateral tab rests substantially against the talus; and an antero-medial plate, itself including a tibio medial strip and a talo-medial tab interconnected by a link zone , said tibio-medial strip, said talo-medial tab, and said link zone being shaped both so that: at least one portion of the tibio-medial strip rests substantially against the anterior medial face of the tibia that is situated towards the inside of the body of the patient relative to the anterior tibial crest; and also so that the talo-medial tab rests substantially against the talus, said link zone of the antero-medial plate is designed to come into register with at least a portion of the tibial pilon, said link zone having a shape that is substantially complementary to the shape of said portion of the tibial pilon.

2. A system according to claim 1, wherein the antero-medial plate has a shape that is significantly twisted so as to match the outline of said anterior medial face (1 of the tibia and of the talus.

3. A system according to claim 1 or claim 2, wherein the tibio-medial strip has a shape that is substantially arcuate so as to match both the outline of said anterior medial face of the tibia and the outline of at least one portion of the tibial pilon.

4. A system according to any one of claims 1 to 3, wherein the antero-medial plate has, as seen in profile, substantially the shape of a spoon.

5. A system according to any one of claims 1 to 4, wherein the talo-medial tab extends in a main longitudinal direction(X-X') that is inclined towards the outside of the body of the patient relative to the main longitudinal direction(Y-Y') in which the tibio-medial strip extends.

6. A system according to any one of claims 1 to 5, further including at least a first anchor member provided with a head and with a bone anchor shank that extends from said head, the tibio-medial strip being provided with at least a first orifice provided with a first bearing surface against which said head is designed to come into abutment, the bearing surface being shaped so that the anchor shank can extend in a direction enabling it to pass both through the tibia(1) and through the talus(2).

7. A system according to claim 6, wherein said first bearing surface extends in a midplane (disposed slantingly relative to the main longitudinal direction(Y-Y') in which the tibio-medial strip extends.

8. A system according to claim 6 or claim 7, wherein the first bearing surface has a substantially rounded shape so as to make it possible to adjust the orientation of the first anchor member relative to the tibio-medial strip.

9. A system according to any one of claims 6 to 8, wherein the tibio-medial strip is provided with a plurality of orifices, each of which is designed to be associated with a corresponding anchor member, the orifice that is closest to the link zone of the antero-medial plate corresponding to said first orifice.

10. A system according to claim 9, wherein the shank of the first anchor member has a diameter that is significantly greater than the diameter of the shanks of the other anchor members.

11. A system according to any one of claims 1 to 10, further including compression means for compressing the joint between the tibia and the talus, said compression means including: - a first jaw designed to be fastened temporarily to the tibia; - a second jaw designed to be fastened temporarily to either one of the plates, namely to the antero-lateral plate or to the antero-medial plate; and closure means, which are preferably manual means, for bringing the first and second jaws closer together.

12. A system according to claim 11, wherein one or both of the antero-lateral plate and the antero-medial plate is/are provided with a tapped hole into which either the second jaw itself or apiece mounted on the second jaw is designed to be screwed.

13. A system according to claim 11 or claim 12, wherein said tapped hole is provided in the tibia-lateral strip or in the tibio-medial strip, preferably towards the free end of said strip.