Abstract:
Equipment for the positioning of a proximal extremity of a tibia against a cutting guide ( 1 ), including a support bracket is shown. Devices are provided for distally immobilizing a tibia, which will immobilize the distal extremity of a tibia in a given position. These devices are mounted on the support bracket and can slide and be blocked in position following two directions perpendicular to the support bracket. It also includes devices ( 8, 9, 10, 11, 12, 13, 14 ) for proximally immobilizing a tibia which are mounted and can slide along the support bracket, a cutting guide ( 1 ) mounted on the support bracket frame, a gun handle ( 32 ) fixed to the support bracket, the hammer of which acts on devices ( 6 ) that enable the adjustment of the relative position of devices ( 8, 9, 10, 11, 12, 13, 14 ). This provides proximal immobilization with regard to the support bracket, the trigger of which acts on devices that enable the adjustment of the angle (posterior slope) between the support bracket and the tibia in the sagittal plane.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a device for the positioning of a proximal extremity of a tibia against a cutting guide, so that the cutting guide can guide a saw blade in cutting the tibia following a given resection plan, in order to install a knee prosthetic. 
     2. Description of the Related Art 
     Devices for positioning of this type are already known from the former art. They generally include a support bracket and means of distally immobilising a tibia In a given position, where those means are implemented so that they may slide along the support bracket and be securely held in place, following at least one direction, preferably two perpendicular directions, within a perpendicular plane. They also generally include means of proximally immobilising a tibia in a given position, where those means are implemented so that they may slide longitudinally along the support bracket Finally, they also include a cutting guide implemented on the support bracket. 
     These devices known from the former art feature several inconveniences, 
     The chosen resection plan takes into account the inclination of the tibia in both the ante-posterior plane as well as the inclination of the tibia in the frontal plane. When positioning the cutting guide with regard to the immobilised tibia, it is therefore necessary to be able to adjust the angle between the support bracket and the tibia within the sagittal plane (posterior slope) and also the angle between the support bracket and the tibia within the frontal plane (varus valgus). However, in order for these adjustments, as well as adjusting the height of the cutting guide to take place, these devices known from the former art consist of a great number of assembling components, complicated and difficult to manipulate. 
     BRIEF SUMMARY OF THE INVENTION 
     The invention aims to remedy those inconveniences, notably with a positioning device of the type described previously, which would be easier to grasp and manipulate, especially when adjusting the inclination of the tibia within the frontal and posterior planes and also when adjusting the height of the cutting guide with regard to the tibia. 
     The device for positioning the proximal extremity of a tibia with regard to a cutting guide according to the invention, is characterised in that it includes a gun handle with a hammer and a trigger fixed to the support bracket. The hammer acts on devices that allow the adjustment of the relative position of the immobilising devices with regard to the support bracket, with the possibility of blocking. The trigger acts on devices that allow the adjustment of the angle (posterior slope) between the support bracket and the tibia within the sagittal plane. 
     As a gun handle with a-hammer and a trigger is implemented, the device enables the surgeon to position the tibia with regard to the cutting guide in a simple manner. The positioning of proximal immobilising devices is simply done by the use of the hammer and sliding those devices along the support bracket, once the appropriate position has been reached, the hammer is released, which then blocks the proximal immobilising devices in place with the chosen resection plan facing the cutting guide. The trigger is depressed next which enables the adjustment of the posterior slope of the tibia and then released to block the adjusted value of the posterior slope. Finally, without using neither the hammer nor the trigger, the handle is used to adjust the angle of (varus valgus) by sliding within the frontal plane. 
     According to an aspect of the present invention, the devices that adjust the angle between the tibia and the support bracket in the sagittal plane consist of a lever, an extremity of which co-operates with a pushing component, the inferior extremity of which features gears which themselves couple with the gears of a supporting arm. The action of depressing the trigger de-couples the gears of the pushing component from the gears of the supporting arm and by releasing the trigger, couples those same gears in order to adjust the angle between the support bracket and the tibia in the sagittal plane. The device according to this improvement is of a simple assembly. 
     According to a further aspect of the present invention, the supporting arm includes a plate which slides within a rail that is formed within a support of the distal immobilising devices of the tibia. The sliding action takes place with the possibility of blocking by way of the co-operation between an ergot and regularly spaced notches that have been implemented on the guiding rail. The notches successively receive the ergot to enable the blocking of the plate with regard to the distal immobilising devices in order to adjust the angle between the tibia and the support bracket within the frontal plane (angle of varus/valgus). 
     According to a further aspect of the present invention, the proximal immobilising devices of the tibia include a stem which can slide within the support bracket, and which includes notches that couple with gears of a first pushing piece, the moving of which is acted by the hammer. Depressing of the hammer de-couples the gears of the piece from the notches of the stem, so that the stem may slide with regard to the support bracket. Suspending the action of depressing the hammer couples the gears of the piece with the notches, so that the stem is blocked in place with regard to the support bracket, therefore the proximal immobilising devices with regard to the tibia is blocked into place. 
     According to a further aspect of the present invention, the number of notches on the supporting arm relates to a pre-determined bracket of adjustment, based on the angle of the posterior slope, ie between zero degrees and eight degrees. 
     According to a further aspect of the present invention, the number of notches on the guiding rail relates to a predetermined bracket of adjustment, based on the angle of varus valgus, ie between three degrees and minus three degrees. 
     According to a further aspect of the present invention, the cutting guide may slide vertically with regard to the support bracket and, being blocked as for rotation, do so independently from the proximal immobilising devices. This enables an even finer adjustment of the position of the cutting guide, therefore a finer adjustment of the position is obtained for the resection of the tibia. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     FIG. 1 is a side representation of a device according to the present invention; 
     FIG. 2 is a representation in perspective of a device according to the present invention; 
     FIG. 3 is a representation in perspective of the device according to FIG. 1, with the various elements the device consists of being disassembled to allow for a better comprehension of the Figure. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In FIG. 1, the device for the positioning of a proximal extremity of a tibia (not represented) against a cutting guide I includes an oblong, cylindrical support bracket  2 . A claw  3  consists of two forks  3 A and  3 B, which clamp the tibia (malleol), two springs  4 A and  4 B which co-operate with the two forks to grip the tibia and is articulated on a support  55 . The claw  3  is mounted on the support bracket  2  so that it may slide perpendicularly to the plane including the tibia and the support bracket (the sagittal plane). The support bracket which is hollow and of oblong shape  2  features a stem  5 , which slides in the upper part of the support bracket  2 . This sliding stem  5  includes notches  6  on its lower extremity, which enable the positioning of stem  5  with regard to support bracket  2  and blocking in position, as will be explained later. The upper part of stem  5  includes a bore  7  with a rectangular transversal section, which accommodates a fixating rod  8  sliding within this bore  7  and which can be blocked in any chosen position by a screw  9 . The fixating rod  8  Includes a cylindrical bore  10 , which accommodates a pin  11  that will be punched to the proximal part of the tibia, notably to the tibia needles, in order to fix it. Another bore  12  is also included for another broach or pin. Two hollow notches  13  and  14  are implemented within the rod  8  to lighten it and therefore lightens the weight of the entire device. A support  15  for the cutting guide can slide on the upper part of stem  5 . This sliding action takes place independently from the sliding action of stem  5  within support bracket  2 . The support  15  features a bore  16  through which stem  5  passes and through which support  15  can slide on stem  5 . A screw  17  enables the blocking of support  15  of the cutting guide on stem  5  in the appropriate position. The rotation of support  15  with regard to the longitudinal axis of stem  5  is prevented by the implementation of a longitudinal slot  25  on stem  5 , through which support  15  can slide, and an ergot in support  15 , so that support  15  may not rotate on stem  5 . The cutting guide  1  is fixated to support  15  in a simple manner, for instance by way of the co-operation of a small plate  19  and a bore  20  of the cutting guide, which features a complementary transversal section, with separable coupling. To this effect the small plate  19  features a transversal orifice  21  for the reception of a hollow stem which contains a spring that pushes a retaining ball outward. This ball lodges itself in a corresponding notch implemented in the surface of the bore  20  of the cutting guide Therefore, in order to mount the cutting guide onto the small plate or dismount it from the small plate, the two elements may simply be manually moved away from one another so that the ball is forced inside the orifice  21 , as the ball juts outward either when both elements are separate or when the cutting guide is coupled to the small plate  19 . The cutting guide includes, in its upper part, a removable palpating device including a body  22 , a palpating rod  23  and a column  24 . The column  24  inserts in the cutting guide  1  in a left-hand bore  26  or a right-hand bore  27 . A ball-based coupling system can be implemented. The body  22  slides on column  24  by way of a bore  28 , whereas the palpating rod  23  slides in a bore  29  transversal to bore  28 . 
     The sliding action of the body  22  on column  24  can take place without a mutual rotation. The transversal section of bore  28  may indeed be circular and complementary to that of column  24 , but the co-operation of the rod  23  with the opening  30  prevents any rotation of the body  22 . Similarly, the sliding action of the rod  23  takes place without any possible rotation as the transversal section of bore  29  Is square, as is that of rod  23 . An opening  30  is implemented in column  24  that will allow rod  23  to pass through it. Both the rod  23  and the body  22  are blocked onto column  24  by pressing part of body  22  onto column  24 . This is achieved by way of a spring positioned inside the body  22 . The palpating rod can therefore materialise a height for the resection of the tibia. 
     The cutting guide  1  includes a slot or guide  31  implemented for the passing of a saw blade, 
     A gun handle  32  is implemented on support bracket  2 . In its upper part, this gun handle  32  includes a hammer  33  articulated to a rotational axis  34  and which cooperates with a spring  35 , which itself actions a first pushing piece  36 . The extremity of the piece  36  proximal to the spring  35  includes gears that can couple with the notches  6  of stem  5 . The gun handle  32  also include a trigger  37  articulated to a rotational axis  38 . A spring  39  exerts a rappelling action on the trigger  37  with regard to the rotational axis  38 . The trigger  37  co-operates with a lever  40  placed inside the gun handle  32 . This lever  40  is bent and incorporates two branches, a first branch which co-operates with the trigger  37  and a second branch  41 , which penetrates a transversal bore  43  of support bracket  2  in its lower part, by way of its extremity  42 . The lever  40  is permanently mounted inside the handle  32  and is articulated to an axis  44 , itself situated at the junction where both branches of lever  40  meet. Within the lower part of support bracket  2 , the extremity  42  of lever  40  co-operates with a second pushing piece  45  and a rappelling spring  46 , which are both situated and can slide inside support bracket  2 . The lower extremity of the second pushing piece  45  features gears which can couple with notches  47  of an oblong supporting arm  48 . Itself of a square transversal section and which can slide In a bare  49  of support bracket  2  in its lower part. The bore  49  has a square transversal section, complementary to the square transversal section of supporting arm  48 . The sliding action takes place in the mid-lateral plane. This supporting arm  48  includes a guiding plate  50  at one of its extremities, which can slide on a guiding rail  51  formed within the support of claws  3 A and  3 B. The sliding action of the guiding plate  50  takes place perpendicularly to support bracket  2  and perpendicularly to the sliding direction of the supporting arm  48  in the bore  49 . The outside of plate  50  (away from support bracket  2 ) includes an ergot  52 , which can couple to a row of notches  53  which are implemented on the side of the guiding rail  51  onto which plate  50  is guided. The ergot  52  can couple to each notch  53  by being pushed into place by way of a spring inside supporting arm  48 . The position of the support of claws  3 A and  3 B varies for each position of the ergot  52  in a notch  53  and therefore the relative angle between the tibia held by the claws and the support bracket also varies in the frontal plane. 
     The adjustment of the position of the tibia with regard to the cutting guide takes place in following manner: 
     The user holds the positioning system by its gun handle  32  and grasps the bones of the tibia with the claws  3 A and  3 B, which tightly adapt by way of the springs  4 A and  40 . The user next depresses the hammer  33  with his thumb. As the hammer  33  rotates clockwise it relaxes the spring  35 , which exerts its action on the first pushing piece  36 , the gears of which de-couple from the notches  6 . With his other hand, the user can then adjust the height of stem  5  by sliding it within support bracket  2 . Once the appropriate height for the fixating rod  8  is reached, the user then releases the hammer  33  which, through spring  35 , couples the pushing piece  36  back by way of coupling its gears to notches  6  of stem  5 . The stem  5  is then blocked in place and cannot slide within support bracket  2  any further. After releasing the hammer, the user then fixes the upper part of the tibia (needles) by way of the pin  11 , at the level of the centre of the tibia. He then depresses the trigger  37 . The pushing action on this trigger  37  acts on the first branch of lever  40  linked to trigger  37  and makes the second branch  41  of lever  40  lift up. The extremity  42  of the second branch  41  of lever  40  therefore pulls the second pushing piece  45  upwards, the gears at the lower extremity of which de-couple from gears  47  of the supporting arm  48 . The supporting arm  48  can now slide in bore  49  perpendicularly to support bracket  2 . When the appropriate value setting for the angle in the sagittal plane between the tibia, held in place by its bones in claws  3 A and  3 B, and support bracket  2  is reached, the user then release the trigger  37 . The trigger  37  is then brought back to its free position by the rappelling action of spring  39 . The extremity  42  of the second branch  41  of lever  40  then lowers and the gears of the pushing piece  45  couple again with the gears  47  of the supporting arm  48 . The posterior slope of the tibia is therefore set with regard to the support bracket. The angle may be chosen between zero degrees and eight degrees, so an appropriate number of gears  47  should be planned to accommodate this range. The angle of varus valgus (in the frontal plane) is then set by way of sliding the plate  50  on its guiding rail  51 , by way of moving the support bracket  2  by the handle  32  perpendicularly to FIG. 1 (frontal plane). Once the appropriate angle has been chosen, the ergot  52  is placed in the notch  53  within which it should rest by now, by way of a lever  54 . The varus valgus is then set. The number of notches  53  is planned to allow for adjustments of ±three degrees of the varus valgus angle (frontal plane). As the height, posterior slope and varus valgus angle have all been set, the palpating rod  23  is set next. The palpating rod slides along the column  24  to define the height of the resection plan exactly. The resection can then take place. The support  15  of the cutting guide can be slid to bring the palpating rod  23  in contact with the bone so as to precisely materialise the resection plan and block the support  15  in position by way of the screw  17 . 
     The hammer and the trigger are both integrated to the handle. The user can easily depress the hammer with his thumb and the trigger with his index for all the relative positions of the proximal immobilising devices with regard to the support bracket. 
     In the former art, notably in French patent 2.720.629, the trigger is independent of the handle and, for certain relative positions of the proximal immobilising devices with regard to the support bracket, the user will not have an index finger long enough to use the trigger and simultaneously use the hammer with his thumb. 
     According to a preferred implementation of the invention, devices to transmit the action of the finger on the trigger to the adjusting devices of the angle between the support bracket and the tibia are planned, but those devices do not form part of the support bracket. 
     According to a preferred implementation of the invention, these devices consist of at least one lever, which is situated outside the support bracket and inside the gun handle.