Mounting device especially for the tibial and/or femoral part of a two-piece knee joint prosthesis.

p0001The invention relates to a particular hardware or instrumentation of implant placement, a bi-compartmental knee prosthesis comprising femoral implants of the type which the section profile is the average radius of curvature of the condyle and tibial implants like those formed with a pad or supporting platform capable of cooperating with the resséquée part of massive tibial spines.

p0002The materials used to date do not entirely satisfactory.

p0003Regarding the implementation of the tibial implant, it is known to use, having obviously different radiographs and necessary, a device called tibial viewfinder which comprises a support designed to be positioned on the ridge of the general axis of the diaphysis of the tibia. In this holder is slidably mounted the actual viewfinder which occupies a large volume so that in an open knee, it appears important problems of implementation of such an apparatus.

p0004Another very important problem is that the viewfinder for receiving a saw blade or other must be held in position manually, usually by a practitioner's assistant. It is understandable that this way of working is very rational and very random may harm the quality and outcome of implant placement.

p0005To overcome these disadvantages and solve the problems, according to the invention, the support of the tibial viewfinder gets to slide freely with blocking ability in position, a rod end of which is fixed a guide rail curve to match the tibia Profile , said guide forming a horizontal support plane, said rod being arranged to be temporarily fixed on a part of the tibia.

p0006In addition, another problem to be solved by the invention is to respect the maximum tibial cutting plane initially determined, which is not allowed with the current means used that force to operate in a way approximate and in stages.

p0007This problem is solved according to the invention, in that the tibial guide has a slot for passage of pin-type bodies can cooperate with the tibia to specify and maintain the tibial cutting plane initially calculated, said pin being capable of receive, after removal of the entire tibial guide, a reversible cutting jig.

p0008errors to have also wanted to address made at the cutting plane to take account of differences that may exist between the front and the rear part. Such a problem is solved according to the invention taking into account the fact that the cutting jig is engaged on the pin by means of a slot disposed asymmetrically in the thickness of said template while in correspondence of one side with the slot of the tibial jig.

p0009It also appears that the ancillary equipment installation, it is not given the rotary components of the knee, that is to say of the frontal section of the massive spirals thorns.

p0010To resolve this problem according to the invention, the cutting jig receives in a plane perpendiculiare a vertical support pin cooperating with a pin suitably oriented to indicate the mass of the cutting angle of the tibial spines depending on the rotation of the knee, said stud constitutes a means for guiding and supporting the cutting member.

p0011As regards the placement of the femoral implant to take account of rotational constraints at the time of knee flexion, it is necessary that the positioning of the implant to be perfect in all three planes of space. The frontal plane of curvature must watch the load.

p0012To resolve this issue and achieving the aim of the invention, using a posterior femoral cutting guide comprises a rod receiving end a bearing pad curve whose radius corresponds to the condylar pad is remarkable in that the rod is positioned, relative to the bearing block, so as to be disposed in correspondence and in axial alignment with the anchoring pin that normally present the tibial implant to be placed, said rod being axially pierced to allow the commitment of a wick.

p0013The invention is described below in more detail using the appended drawings, in which:<ul><li>- Figure 1 is a perspective view showing the main installation equipment elements to the tibial implant,</li><li>- Figures 2, 3, 4, 5 and 6 are purely schematic views showing major process steps for the preparation of the tibial compartment,</li><li>- Figures 7 and 8 are views respectively of the tibial cutting guide and tibial cutting jig,</li><li>- Figure 9 is a perspective view of the femoral cutting guide</li><li>- Figure 10 is a longitudinal sectional view of the femoral cutting guide, placed on the condyle of the knee flexion in combination with the tibial cutting plane,</li><li>- Figure 11 is a plan view in schematic showing the positioning of the femoral guide.</li></ul>

p0014To make it more concrete object of the invention, it is now described in a nonlimiting way with reference to the embodiments of the drawings.

p0015The viewfinder of tibial cut comprises a support (1) whose cross-section is profiled V over the whole of its height, to be applied, positioned and centered in combination with the general axis of the diaphysis of the tibia. This type of support is known.

p0016According to the invention, the support (1) is free to slide a rod (2) mounted with blocking ability in a vertical position according to different heights. For example, blocking may be effected by means of a screw (3) engaged in an oblong slot (2a) of the rod and screwed into the support (1). This rod (2) receives the end, in particular a removable manner, a profiled track (4) forming a horizontal supporting plane. The guide (4) has a radius of curvature internal (4a) corresponding very substantially to the internal or external profile of the tibia. So there are two guides (4) to match the right profile and left profile, as the case (Figure 2).

p0017The upper part of the rod (2) shown in overflow of the support (1) has holes for fixing pins engaging member (5) to ensure the holding in position of the entire guide (4 ) and the rod (2). In those circumstances, the support (1) can be removed (Figure 3).

p0018In addition, the tibial guide (4) has, in a horizontal plane, a longitudinal slot (4b) through which can be engaged pins (6). These pins (6), including three in number, primary function of maintaining and indicate the tibial cutting plan initially calculated, in a conventional manner, after the various X-rays and measurements. Indeed, after the establishment of these pins (6) (4), it is possible to remove the entire tibial guide (4) and upper (2) the level of the cutting plane to perform still being reported by said pins.

p0019These pins (6) are the support to a cutting jig (7) of reduced size (Figure 5). For this purpose, the template (7) has in a horizontal plane, a slot (7a) adapted to cooperate with all of the pins.

p0020Importantly, the slot (7a) is set asymmetrically with respect to the thickness of the template (7) to make it reversible and usable in two different horizontal planes.

p0021This slit (7a) is set to a distance (a) of one edge thereof and at a distance (b) relative to its other edge, the distance (a) being greater than the distance (b). In addition, the distance (a) corresponds exactly to the distance (a ') between the slot (4b) of the edge of the tibial guide (4). It thus appears that after positioning of the cutting jig (7) on pins (6) in an identical manner to the tibial guide (4), (according to the distance (a)), if the cut is made is not sufficient , simply return the template to change accordingly the level of the tibial cut.

p0022Regarding the problem of assessing the knee rotation, that is to say of the frontal section of the massive spirals thorns, according to an angular orientation, using a vertical contact area (8) . This stud (8) is arranged to cooperate with a locating pin (9) for indicating the cutting angle () of the tibial spine Angular positioning of the pin (9) has been shown and described in the patent application 87.06043, which the applicant of this also holds. Briefly, it is recalled that this pin engages the inner edge of the lateral condyle (E) 90 degrees of knee flexion to indicate the angular cut to be made on the massif of the corresponding side of the tibial spines according to the rotation of the knee.

p0023Just under these conditions, to engage the stud (8) on the spindle (9), prop on the cutting jig (7) in a perpendicular plane (Figure 6). The stud (8) acts against-guide support to the cutting member.

p0024The femur, the equipment used includes a femoral cutting guide generally designated by (10).

p0025The cutting guide comprises a rod (10a) integral with a curved bearing pad (10b), whose radius of curvature is determined to correspond very substantially condyles profile.

p0026One way imports nte, the rod (10a) is disposed relative to the support pad-curve (10b) so as to be positioned in correspondence and in axial alignment with the anchoring pin that normally present the tibial implant to be asked.

p0027This rod (10a) whose length is at least 10 cm, and very important and can be positioned very exactly in the optimum bio-mechanical conditions, the curved support pad (10b), in particular in the middle of the tibial plateau corresponding . The rod (10a) is hollow to allow passage of a wick (11) intended to mask the implantation of the anchoring pin.

p0028In addition, it is necessary to take into account the rotational constraints at the time of knee flexion so that the positioning of future implant must be perfect in all three planes of space while respecting the condylar curvature, asymmetry of the condyle and considering that the frontal plane of curvature must watch the dynamic load and / or static (Figure 11). Accordingly, the stem allows to visualize how it must plane so as to have immediately the correct orientation for the implant and indicates how much to grind condyle for a good tackle on condyle according to the axis load we want to give it.

p0029Bending, it is also necessary to position the implant strictly perpendicular to the tibial cutting plane. For this purpose the lower end of the pad support curve (10b) has a supporting squared edge (10c) to check that the posterior condylar cutting plane is perfectly parallel to the tibial cutting plane to avoid overhang and additional load (Figure 9)

p0030The pad support curve (10b) has, on either side of the rod (10a) and along its median axis, two slots (10d) and (10e) to make, by means of a scalpel, for example, the angular positioning determined. It is then enough to match the final implant with the marking lines, the anchoring pin of the implant being placed next to the hole location determined by the hollow rod (10a).

p0031Note that is provided to ensure the anti-rotational positioning of the implant (10), fixed in the upper part of the support block (10b) a pin (12).