FR2800987A1 - Artificial locking support, for immobilizing a knee, comprises first rod which is implanted within the femur, second rod implanted within the tibia and a screwed joint at the knee which allows for the set of the leg - Google Patents

Abstract

A first rod (10) is inserted into the femur and a second rod (12) is inserted into the tibia. The first and second rods are then joined rigidly by a fitting (14) which is pinned to the second rod and screwed to the first rod and allows for the difference in angle of the femur and tibia. The first rod has grooves in the upper section to improve stability and reduce pressure and the second rod has locking pins in the lower section

Description

 The present invention relates to an endoprosthesis for femoro-tibial arthrodesis.

In the case of some elderly patients, it is necessary to proceed to an arthrodesis, particularly after several interventions performed during the time on the knee joint for the implantation of articulated prostheses. The need may also be met with after the severe destruction of this knee joint following an accidental trauma <B>.

Indeed, only the immobilization of the joint allows the patient to maintain a member reached in satisfactory conditions to consider resumption of movement in support of this member.

Arthrodesis devices are known which are external, in the form of fixators, and immobilize the tibia relative to the femur until bone calcification allows the development of a callus and colonizes reinforcement implants.

Such interventions are on the one hand heavy in the operating room and on the other hand very long postoperatively to obtain such bone developments, especially in the case of elderly people. The risks of infection are high and the failure rate remains high.

The discomfort is obvious and the multiplication of interventions, at least two, as the problems of tolerance and surveillance have led industrial concerned and the medical profession to look for solutions to overcome these disadvantages. Thus a known alternative is the installation of a centro-medullary nail, femoro-tibial.

This nail of considerable length, substantially that of the patient leg is implanted by introduction into the medullary canal of the femur impaction. This introduction is performed <B> to </ B> from the area between the femoral head and the greater trochanter then by consecutive penetration of the corresponding part of the same nail in the medullary canal of the tibia, thus ensuring the immobilization of the shin and femur. This nail poses problems during the introduction in the introduction phase because it is very long and it is necessary to avoid causing the bursting of the bone material. Now it is impossible to respect with the same nail, the sagittal femoral curvature and simultaneously the straightness of the tibia.

In addition, once placed, the femoro-tibial nail, necessarily rectilinear for its introduction, leads <B> to </ B> a relative position of the femur and tibia is not satisfactory because the mechanical axis according to which the head Femoral in the alignment of the tibia axis is not respected. Obtaining an overall <I> varus </ I> axis does not correspond to the <b> the </ i> the correspondingly sought-after small-valued axis <B> to the mechanical axis of the member.

The tibia, in sagittal view, is found in advanced position relative to femur.

It is also known that such nails cause femoro-tibial hypertension, particularly aggravating in the case of elderly people or already suffering from hypertension.

The present invention provides a bi-element implant which overcomes disadvantages and which finds a particular indication after successive failures of joint prostheses or after an articular destruction allowing not to implant or reimplant a joint prosthesis. This implant allows immediate ambulation in full support immediately, while allowing a satisfactory arthrodesis. The implant according to the invention, made to measure, requires surgery in the operating room, limited in time as postoperative trauma. This bi-component implant does not require any additional intervention for removal of fixatives. In addition, this implant can be placed notwithstanding the presence of a hip prosthesis rod in the femur.

<B> A </ B> this effect the stent for arthrodesis according to the invention, in particular the knee joint, is characterized in that it comprises a femoral implant intended to be introduced into the medullary canal of the femur, a tibial implant intended to be introduced into the medullary canal of the tibia and means rigid connection of the two implants, to the right of the joint.

This femoral implant is a profile rod conjugated to that of the femur with a sagittal plane in the plane and comprises a connecting head constituting part of the rigid connection means.

The one head is attached and includes a bearing face with the proximal face of the femoral stem which is inclined at an angle <B> <U> a </ U> </ B> relative <B> to </ B> the longitudinal axis (X) of said endoprosthesis and an opposite face provided with a tip perpendicular <B> to </ B> this face and coaxial <B> to </ B> the axis (X).

This head comprises anti-rotation means relative to the femur carries the femoral stem, especially in the form of fins.

The tibial implant is a rectilinear tibial shaft whose proximal end includes a blind housing which constitutes another part of the rigid connection means.

 The stent includes conical areas with at least one portion having undergone a surface treatment to facilitate bone healing.

The present invention is now described in detail according to a particular embodiment, not limiting, with reference to the accompanying drawings in which different figures represent <B>: </ B> <B> - </ B> figures <B> 1 A < / B> and <B> 1 </ B> B, two schematic views of the stent according to the present invention, in place in the femur and the tibia, respectively patient face and patient in profile, <B> - </ B> Figures <B> 2A </ B> and 2B, views respectively patient front and patient profile, bare femoral stem, <B> - </ B> figures <B> 3A </ B> and 3B, views respectively front patient and patient profile of the femoral stem equipped with its connecting head <B> to angular offset, FIGS. 4A and 4B, patient respectively front and patient views of the tibial stem, FIG. B> 5, </ B> a section following the line <B> 5-5 </ B> of Figure 4A, figure <B> 6, </ B> a section following the line <B> 6-6 < / B> of Figure 4B, Figures <B> 7A </ B> and <B> 7B, </ B> Detail Views of the a femoral stem connecting head, figures <B> 8A </ B> and 8B, detailed views of the connecting head the tibial stem, at another angle and in perspective, and <B> - </ B> figure <B> 9, </ B> a view of a tibial stem fixation key.

Figure <B> 1A, </ B> the stent is shown in place. It includes a femoral implant and a tibial implant with rigid linkage means. Rigid connection means are located at the knee level, the right articulation.

The femoral implant is shown in more detail in the following figures, <B> 2A to </ B> as well as in Figures <B> 2A </ B> and 2B. The implant includes a stem <B> 16 </ B> with a distal <B> 18 </ B> end, <B> end round, intended to penetrate the medullary canal and whose the proximal end 20 comprises a seat adapted to receive a rigid connecting head 24, shown in the figures and 3B in particular.

The rod itself preferably has a variable section. A first zone I of the rod has a diameter <B> to </ B> constant circular section, adapted to the diameter of the medullary canal that receives said rod. A second zone 11F is of frustoconical shape, substantially in line with the proximal zone of <B>. The third zone 111F, when <B> to </ B> it, is of a larger diameter, this only for the purpose of giving <B> to </ B> the implant a sufficient mechanical rigidity <B> to </ B> near the means 14 of connection, thus ensuring the recovery of efforts.

note the peculiarities of this femoral stem which has a sagittal curvature adapted <B> to </ B> that of the femur of the patient.

Another particularity of this rod is that of being provided with at least one distal groove which improves the stability in rotation and reduces the endomedullary hyperpressure, source of fat embolism. Similarly, the rod has in the second zone of frustoconical shape a surface state for example micro-blasted, also to allow good bone reconstitution. This microblasted area can be increased or decreased in area as needed or even moved to areas <B> 1 </ B> and <B> il. </ B>

A double flat <B> 28 </ B> is machined in the zone of the proximal end, so as to immobilize in rotation the rod during the mounting of the head 24. This head 24 is shown in detail in the figures and <B> 8A. </ B> It comprises a body <B> 30 </ B> of substantially cylindrical shape, provided with fins <B> 32 </ B> radial, anti-rotation.

The body <B> 30 </ B> has a face 34 facing vis-à-vis seat 22. <B> A </ B> from this face, there is provided a housing <B> 36 </ B> blind, adapted to cooperate with a connecting piece <B> 38 </ B> secured to the rod <B> 16. </ B> thread with shoulder is a particularly suitable solution for connection. Note that this face 34 and the axis of the housing <B> 36 </ B> make an angle <B> <U> a </ U> </ B> with the perpendicular <B> to </ B> l X axis of connection.

Opposite face <B> 39 </ B>, protrudes a tip 40 <B> to </ B> conical range while two grooves 41 are recessed relative to <B> to </ B> this face < B> 39. </ B> A groove 42 of keying is machined in this mouthpiece, perpendicular <B> to </ B> a generatrix of the tip 40, parallel <B> to </ B> the face <B> 39. </ B>

This femoral stem has a curvature that respects the <I> valgus </ I> anatomical and a flexum that causes a slight folding of the leg allows an easier approach of the patient carrying such a stent.

The tibial implant 1 comprises a rectilinear rod 44 intended to be introduced into the medullary canal of the tibia. This stem also includes three zones <B> 1, 11, </ B> and <B> III, </ B>. The first zone is adapted in diameter to penetrate the medullary canal of the tibia. This zone may carry at least one transverse bore 46, a section of which is shown in FIG. 5. Each bore receives, after placement of the rod, an axis 48 of immobilization in rotation. as in translation, such an axis being shown in Figure <B> 9. </ B> Advantageously, an end depression allows introduction by impact avoiding skidding the percussion tool.

groove <B> 50 </ B> at least is machined in the longitudinal direction along a generatrix of the rod 44, groove which also improves, as for the femoral stem, rotational stability and revascularization, as will be explained in detail later.

second zone 11T is of frustoconical shape so as to limit the penetration of the implant into the bone and resume some of the compressive forces generated by the load. This zone may advantageously receive a surface treatment such as microbilling to facilitate colonization by the bone material. This area can be increased or decreased in area or moved to another area.

Part 111T is of constant diameter greater than the area T to ensure recovery of mechanical forces.

This zone 111 is shown in detail in FIG. <B> A </ B> from the surface a blind housing 54 is machined which is conical in profile to receive, with a soft wedging, the conical tip 40, said housing being coaxial with the X axis.

This housing is suralésé to allow a good range and includes two tabs <B> 56 </ B> adapted to cooperate with the grooves of the head 24. A hole <B> 58 </ B> opening is formed perpendicularly <B> to The <U> X </ U> axis to allow the introduction of a latch key <B> 60 </ B>.

The placement of the two implants of such an arthrodesis is generally carried out as will be described, while disregarding the general conditions of surgical intervention.

For the intervention, it is advisable beforehand <B> to </ B> the placement of implants to provide for the removal of any other joint prosthesis and it is also necessary the joint is dry.

<B> It </ B> agrees to prepare the implants before <B> to </ B> the intervention because it can only be made to measure. The two implants are manufactured from two orthopantograms of the face and the profile. We then note <B>: </ B> <B> - </ B> the length of the femoral stem desired and / or possible, <B> - </ B> the front and femoral cut preview of the femoral and tibial profile, <B> - </ B> the length of the desired tibial stem and / or possible, <B> - </ B> the sagittal femoral mean curvature, <b> - </ b> the femoral and tibial calibers, and <b> - </ b> <i> the valgus </ i> considered of all the two implants once assembled.

Overlay tests of the implant and radiotherapy fabrication plans allow a priori control.

For the procedure, the patient is placed in a simple supine position.

Proximal resection considered both femoral and tibial should reveal the living bone and be <B> at </ B> the expected dimension during the manufacture of implants.

The femur and tibia are bored with a suitable ancillary which allows femoral and tibial shaft lining, <b> to </ b> from the joint.

The bone surface of the proximal end is flat. Each implant is then implanted by impaction.

The femoral implant is equipped with its head and its introduction is facilitated by the curvature in the sagittal plane which guides the implant and avoids any pressure of the bone.

This curvature also allows a virtually automatic orientation of this implant relative to the bone.

The adjustment in position is provided by the practitioner who, especially with the fins, can rotate the implant.

The tibial implant is also introduced by impaction into the medullary canal, easily since this channel has been reamed and rectilinear. If necessary, one or more pins 48 of immobilization and locking should be provided in the corresponding holes of the tibial implant. An access window must be provided to the right of each hole 46 envisaged to receive said axis. The two implants are then nested by a movement reducing the limb in full extension.

The interlock ensures immobilization in rotation of the two implants by the cooperation of the grooves 41 of the femoral implant with the tabs <B> 56 </ B> of the tibial implant.

note that the tip 40 <B> to </ B> conical reach enters the housing 54 and gets stuck. A complementary impaction of the entire percussion assembly under the heel ensures a final fit and the confrontation of the femoro-tibial cuts.

then key <B> 60 </ B> must be placed in the hole to immobilize both implants in relation to each other. This key ensures immobilization in translation but also completes the immobilization in rotation <B> already </ B> performed. Anterior femoral access window may be required.

The femoral implant makes an angle with the tibial implant and respects the initial <I> valgus </ I> patient.

such a stent allows a recovery of total support 2 <B> to 3 </ B> days after the intervention under cover of a removable extension splint.

It is then sufficient to carry out all the medical checks linked to such an intervention.

Advantages of such an endoprosthesis arise from the foregoing description.

notes the ease of implementation of the two implants that are independent at the time of implementation. Negative effects of impaction are limited because the introductory efforts in the medullary canal are diminished due to the reduced length of each piece.

Orientation possibilities such as compliance with the patient's morphology allow a better stent / patient adequacy and therefore facilitate the fusion of arthrodesis, especially on deficient organisms.

repeated efforts are distributed to avoid asking too punctually certain areas. note that a preferred embodiment has <B> '' </ B> described which is particularly well in terms of mechanical rigidity and angulation avoiding micromouvements possible at the level of the connecting means. This arrangement is therefore all <B> to </ B> made judicious, nevertheless other means of connection that a Morse taper can be used as a clevis with locking or a nesting tenon / mortise without changing the spirit of the present invention, these connecting means being technical equivalents in the function even if they are more difficult to implement.

Claims (1)

R <B> E </ B> V <B> END 1 CA </ B> 1 0 NS </ B> <B>. </ B> Endoprosthesis for arthrodesis, including the knee joint , characterized in that it comprises a femoral <B> (10) </ B> implant intended to be introduced into the medullary canal of the femur, a tibial <B> (1 </ B> 2) implant intended to be introduced in the medullary canal of the tibia and means <B> (Il </ B> 4) of rigid connection two implants, to the right of the articulation. Endoprosthesis according to claim <B> 1, </ B> characterized in that the implant <B> (10) </ B> femoral is a stem <B> (16) </ B> conjugated profile of that of the femur with a curvature in the sagittal plane. Endoprosthesis according to any one of the preceding claims, characterized in that the femoral <B> (10) </ B> implant comprises a connecting head (24) forming part of the rigid connection means. Endoprosthesis according to claim 3, characterized in that the head is an attached head (24) which comprises a bearing face (34) with the proximal face of the femoral stem which is inclined by a angle <B> <U> a </ U> </ B> relative <B> to </ B> the longitudinal axis (X) of said stent and an opposite face <B> (39) </ B> equipped with a tip (40) perpendicular <B> to </ B> this face and coaxial <B> to </ B> the axis (X). <B> 5. </ B> Endoprosthesis according to claim 4, characterized in that the head (24) comprises means <B> (32) </ B> anti-rotation relative to the femur which carries the femoral stem. Endoprosthesis according to claim 5, characterized in that the anti-rotation means comprise fins <B> (32). </ B> <B>. </ B> Endoprosthesis according to any one of the preceding claims, characterized in that the tibial implant <B> (1 </ B> 2) is a straight tibial shaft (44) <B>. </ B> Endoprosthesis according to claim <B> 7, </ Characterized in that the proximal end (52) of the tibial stem comprises a blind housing (54) which constitutes another part of the rigid connection means. Endoprosthesis according to claim 7, characterized in that the rod (44) comprises at least one transverse bore immobilization. <B> 0. </ B> Endoprosthesis according to any one of the preceding claims, characterized in that at least one of the stems of the femoral and tibial implants comprises a conical zone (11F and 11T) taking up stresses at the right zone. proximal of the bone concerned. <B> 1. </ B> Endoprosthesis according to any one of the preceding claims, characterized in that one of the zones less than at least one of the stems of the femoral and libial implants comprises part having undergone a surface treatment provided for to facilitate bone reconstitution. Endoprosthesis according to any one of the preceding claims, characterized in that at least one of the rods of the femoral and tibial <B> (10,1 </ B>) implants has at least one groove <B> (50) </ B> longitudinal endoprosthesis according to claims 4 and <B> 8, </ B> characterized in that the tip (40) and the housing (54) blind form a <B> conical bearing assembly. according to claim 13, characterized in that the blind housing comprises a hole (B) for passing a locking key (60). and setting the link voltage.