WO2009109669A1 - System for the resection of the tibial plateau and/or the femoral condyles in order to implant a prosthesis - Google Patents

Abstract

The invention relates to a system which can be used to perform a preoperative evaluation in which the tibia and/or the femur are modelled on a computer (6) in 3D, the ideal cutting plane is defined and the position of the resection instrument (1, 2, 3) for cutting the bone is modelled. According to the invention, the system can be used to redefine the ideal cutting plane, as well as the positioning and orientation of the resection instrument (1, 2, 3) on the tibia and/or the femur, such that the plane of the groove (4) of the cutting guide (3) which receives the cutting tool matches the ideal cutting plane.

Description

 SYSTEM FOR THE RESECTION OF THE TIBIAL TABLE AND / OR THE FEMUR CONDOMES TO IMPLEMENT A PROSTHESIS

D E S C R I P C I Ó N

OBJECT OF THE INVENTION

The present invention belongs to the field of knee prostheses and more specifically proposes a method and system for carrying out the resection of the tibial plateau and / or the condyles of the femur for the implantation of the prosthesis.

The object of the invention consists of a system by means of which a preoperative study is carried out that models the tibia and the femur of the patient in 3D to define the ideal cutting plane and models the position of the instruments to cut the bone, and then, in The stage of surgery, translates and redefines on the tibia and the patient's femur the data of the position and real orientation of the instruments to practice the resection according to said cutting plane.

It is also the object of the invention the method used to model the tibia and / or the femur and determine the plane of cut or resection in a preoperative study, as well as in the subsequent phase of surgery to perform adjustments in the orientation of the cutting instruments according to the determined cutting plane.

Another object of the invention relates to the program that executes the described modeling method.

BACKGROUND OF THE INVENTION An intervention of total knee replacement consists in the implantation of a prosthesis that acts as a prosthesis.

The intervention consists first of all in cutting the lower end of the femur and the upper end of the tibia to leave a surface where the elements of the prosthesis can be implanted. Then, between these two elements, a separation of polyethylene is placed that allows rotation and compensation of the tibial cut.

An important factor in the success of these interventions, in relation to the life of the prosthesis, for example, is the correct placement of the prosthesis with respect to the patient's anatomy. To achieve this implantation correctly, a preoperative study is made based on a pair of radiographs of the knee taken from two perpendicular points of view (frontal and lateral). Having noted the position and / or the angles between certain anatomical characteristics, the surgeon can perform some calculations to determine the desirable position and spatial orientation of the prosthesis (in three dimensions or, rather, in two dimensions, one for each view).

The spatial orientation refers to the orientation of the cutting plane of the tibia and / or the femur. In effect, the surgeon has to resect the tibia and / or the femur in a plane with a spatial orientation defined by two angles with respect to an imaginary axis that passes through the mechanical axis thereof.

This imaginary axis is mentally constructed by the surgeon from direct visual information or images of X-ray fluoroscopy. Since it is a qualitative estimate, sometimes the prosthesis cannot be placed in the desired alignment. Thus, the difficulty of this process is to transport in the most precise way possible the orientation of the cutting plane with respect to the mechanical axis of the bone, decided from the preoperative images, to the "patient coordinates" during the surgical intervention.

The solutions used during the intervention include the use of surgery, the use of navigators or robotic systems.

The use of surgery means that during the intervention intra or extramedullary guides are used, in which instruments are attached to cut the bone in the desired 3D orientation. In relation to this orientation, the surgeon can, using the appropriate instruments, act according to a cutting plane. However, if the guide is slightly offset, the orientation of the cut, and therefore that of a part of the prosthesis, would not be desired.

Another solution includes the use of commercial browsers consisting of computer vision systems based on a stereoscopic pair of infrared cameras. Once the cameras are calibrated, it is possible to determine by triangulation the 3D coordinates of a visible point by two cameras at the same time.

Through navigation, the surgeon creates an individual anatomical map for each patient. Prior to the intervention, markers are fixed to the bone (tibia and / or femur) of the patient. Then, diodes (LEDs) that emit infrared light are fixed so that they are easily visible by the cameras. In this way, the computer can deduce the 3D (patient) coordinates of the markers from the 2D coordinates of the diodes captured in each camera. As the emitting diodes are fixed to the patient, it does not matter if the leg moves as its position is recalculated constantly. In this way, movements and reference points can be recorded and, from these data, the navigation system shows the position of the instruments in relation to the available information of the patient on the computer screen. In this way, the surgeon is assisted in the alignment of the instruments during the intervention to ensure the correct implantation of the prosthesis.

The use of browsers is probably the best solution from a technical point of view, but on the one hand they have the problem that their economic cost makes them difficult for small and medium hospitals, and on the other the calibration process is long and should be performed by the same surgeon with the consequent duration of the interventions.

Another solution consists in the use of robotic arms, commanded by computer, which can perform bone resection automatically with the help of a navigator and / or preoperative images. Therefore they turn out to be even more complex systems than those of browsers.

DESCRIPTION OF THE INVENTION

In accordance with the method proposed in this invention, it is a question of practicing the resection of the tibial plateau and / or of the femoral condyles in a cut plane established as ideal by the doctor in a preoperative study, so as to minimize the possibilities of error and of causing damage to the tibia and / or the femoral condyles when making the cuts.

The preoperative study tries to obtain all the geometric data of the tibia and / or the femur by means of exploration that can consist of devices designed to perform scanning operations, MRI, radiography or computed tomography, for example.

These data are treated with the help of a computer, according to a program developed for this purpose, to reconstruct the tibia and / or the femur generating a virtual 3D model. In view of this model, the surgeon decides which is the ideal cutting plane and thus a first virtual model is defined.

Also on these images, and more specifically on this first virtual model, a virtual reproduction of the instruments used for bone resection is introduced, with measures and shapes coinciding with those shown by physical objects.

In general, the instruments used for resection include a support that is embedded in the bone, a guide holder that is mounted on the support that at its end has the positioning support of the cutting guide and a cutting guide.

In this first virtual model of the tibia and the femur, the set consisting of virtual support, virtual guide and virtual cutting guide is fixed, establishing the position and orientation of the virtual support on the bone, so that the plane of the groove of the The cutting guide coincides with the ideal cutting plane selected by the surgeon.

The phases described are performed in the preoperative study, then, in the stage of surgery, the support is placed in the tibia or in the patient's femur at a point and in a position approximately coincident with those obtained for virtual support.

To determine the exact position in which the support has been placed on the tibia or in the femur, a plaque is mounted on it reference that is preferably formed by translucent material to an x-ray and opaque radio elements. Next, scanning means are applied on the reference plate, preferably approximately orthogonal fluoroscopies are performed, which are loaded to the program, where a second virtual model is obtained in which the upper profile of the tibia or the femur, the support is appreciated and the reference plate.

In this way, the position and orientation of the virtual model can be compared with the position and orientation of the real model, and as a result the program presents the correction data.

By means of the calibration tool, the position of the guide holder is made relative to the place of the guide holder that is fixed to the support.

Once the guide holder configuration is adjusted, it is positioned on the support and the cutting guide in the guide, then proceeding to introduce the cutting tool through the groove to perform bone resection.

In summary and in accordance with one of the objects of the invention, a method of modeling the tibia or femur and positional configuration of the resection instrument that runs according to the following phases is also proposed:

- image capture of the tibia or femur and generation of a first virtual model of the tibia in 3D to select the ideal cutting plane of the tibial plateau and / or the condyles of the femur, - determination in the virtual model of the tibia and / or the femur, of the position of the cutting instruments according to the ideal cutting plane, - image capture of the tibia and / or the femur and generation of a second virtual model, - Determination of the gap between the first virtual model and the second virtual model and presentation of correction data for the positional configuration of the instruments for performing the cut.

Unlike other systems, the determination of the cutting plane and

The execution of the cut or resection is carried out according to this modeling method oriented to the tibia and / or femur of the patient to be treated and without the need to use intra or extramedullary guides.

DESCRIPTION OF THE DRAWINGS

To complement the description that is being made and in order to help a better understanding of the characteristics of the invention, according to a preferred example of practical implementation thereof, a set of drawings is attached as an integral part of said description. Where illustrative and non-limiting, the following has been represented, referring to the resection of the tibial plateau although it would also serve to resect the condyles of the femur:

Figure 1.- Shows a schematic representation of the system for the resection of the tibial plateau.

Figure 2.- Shows a perspective view of the support.

Figure 3.- Shows a perspective view from below of the reference plate.

Figure 4.- Shows a perspective view from above of the reference plate. Figure 5.- Shows a perspective view from below of the guide. Figure 6.- Shows a perspective view from the top of the guide.

Figure 7.- Shows a view of the guide holder according to section A-A practiced in Figure 6.

Figure 8.- Shows a previous perspective view of the cutting guide.

Figure 9.- Shows a rear perspective view of the cutting guide.

Figure 10.- Shows a perspective view of the calibration tool.

PREFERRED EMBODIMENT OF THE INVENTION

In view of the figures, a preferred embodiment of the system for the resection of the tibial plateau is described below.

The system for resection of the tibial plateau proposed by this invention is based on the basic incorporation of:

• Software that models the tibia and the cutting plane, and calculates the configuration parameters to adapt the cutting instruments (1, 2, 3) and perform the defined cut. The software includes two differentiated parts, a program for the preoperative study that models the tibia of the patient where the surgeon defines, based on the physical characteristics of the tibia, the ideal cut plane and, another program for surgery that calculates the parameters of Instrument configuration to perform the cut defined in the preoperative study. • Instrumentation of cut or resection (1, 2, 3) composed of a fixing support (1) represented in Figure 2, intended for interlocking on the tibia, a guide (2) represented in Figures 5 and 6, which it is mounted on the fixing support (1), and a cutting guide (3) shown in figures 8 and 9, which is provided with a groove (4) for the passage of

The cutting tool (36), such as a saw, chisel, blade, ... with which the resection is practiced, which in turn is mounted on the holder (2).

As can be seen in Figure 1, the system additionally comprises the following elements:

- scanning means (5) that capture images of the tibia,

- a computer (6) to which those images arrive from which it models the tibia in 3D by means of the software that also defines the virtual position of the resection instruments with respect to the tibia according to a cut or resection plane,

- a removable reference plate (7) that is mounted on the fixing support (1) to, through the scanning means (5), send images of the position and orientation of the fixing support (1) to the computer ( 6), in which they are compared with the virtual positions of the instruments to redefine the cutting plane and consequently the relative position of the cutting instruments (1, 2, 3),

- a calibration tool (8) in which the guideline configuration is adjusted according to the data given by the program.

Adjusting the configuration of the guide holder (2) in the calibration tool, it is mounted on the fixed support (1) previously interlocked in the tibia, and on the holder (2) the cutting guide (3) is mounted, proceeding next to the resection of the tibia by means of the cutting tool (36) that penetrates through the cutting guide (3). As can be seen in Figure 2, the fixing support (1) comprises a nail (5), a cylindrical central section (6) and a quasi-cylindrical upper section (37) topped by a vertical plane, inside the which is a longitudinal drill (8).

On the other hand, the reference plate (7), as seen in Figures 3 and 4, consists of a central body (9) provided with a cavity (10) of configuration adaptable to the upper section (37) of the fixing support ( 1), a transparent body to the radiographs (11) that surrounds the central body (9) and opaque radio spheres (12) integrated in the transparent body to the radiographs (11). Through the cavity (10) a screw (13) can be penetrated, which screws into the longitudinal hole (8) of the fixing support (1), linking the reference plate (7) with said fixing support (1).

In figures 5 and 6 it can be seen that the guide (2) incorporates a positioning support of the cutting guide (14) in which a groove (24) is defined to receive the cutting guide (3), represented in Figure 8. The positioning support of the cutting guide (14) is integral with parallel shafts (15) connected in turn by their opposite ends, on which a carriage (16) is constituted consisting of two plates ( 17), upper and lower, joined together by thymes (18), which slide with respect to the axes (15), and have corresponding central openings (19), as shown in Figures 6 and 7 , in which a ball joint (20) is located with respect to which the carriage (16) can rotate in the horizontal plane and in the vertical plane. About this kneecap

(20) there is a central screw (21) that links the guide (2) to the fixing support (1), also counting in the lower face of the kneecap (20) with a fitting (25) of configuration configurable to the upper section (7) of the fixing bracket (1).

Based on the above, the relative position of the guide of cutting (3), or rather of the guide holder (2) that at its end has the positioning support of the cutting guide (14) in which the cutting guide (3) is housed, with respect to the fixing support ( 1), it will be adjusted by means of the calibration tool (8), represented in figure 10- By means of the calibration tool (8) the distance between the positioning support of the cutting guide (14) and the center of The ball joint (20) by displacement of the assembly formed by said positioning support of the cutting guide (14) and axes (15) with respect to the carriage (16). On the other hand, the assembly formed by the positioning support of the cutting guide (14), carriage (16) and axles (15) can rotate with respect to the ball joint (20) in the horizontal and vertical plane, establishing the fixing of this set with respect to the kneecap (20) by means of a fixing screw (22), as seen in figures 6 and 7, which hugs the plates (17) against the ball joint (20) and against one of the axes (15 ) leaving all the elements of the carrier (2) in solidarity. In this position the cutting guide (3), which is mounted the positioning support of the cutting guide (14) of the guide (2), is oriented so that the plane of its groove (4) coincides with the ideal plane cutting

The cutting guide (3) represented in figures 8 and 9, consists of a flat body (23) in which the aforementioned groove (4) is defined, finished at its ends in some lateral stops (26), counting in one of the faces of the flat body (23) with a circular headland (27) that fits into the groove (24) of the positioning support of the cutting guide (14) during the assembly of the cutting guide (3) on the guide holder (2). Positioned the cutting guide (3) is fixed to the tibia by using pins that are inserted through the holes (36).

As can be seen in Figure 10, the calibration tool (8) fundamentally incorporates a coupling shaft (28) of the same shape and dimensions as the upper section (7) of the fixed support (1), on which the Ia ball joint (20) of the guide holder (2) and a support (29) distant from the axis of coupling (28) on which the guide support positioning bracket (14) fits.

This support (29) is mounted on a first block (30) provided with linear displacement with respect to the coupling shaft (28), in order to adjust the distance between the positioning support of the cutting guide (14) and the ball joint ( 20), as seen in Figure 1, operation that is performed with a first command (31).

On the other hand, the coupling shaft (28) of the calibration tool (8) is linked to a second block (32) that moves with rotational movement in the vertical plane with respect to a third block (33) to adjust the relative inclination, in this vertical plane of the positioning support of the cutting guide (14), with respect to the kneecap (20), operation that is performed with a second command (34).

The third block (33) is provided with rotating movement in the horizontal plane to adjust the angular position of the positioning support of the cutting guide (14) with respect to the ball joint (20), an operation that is performed with a third control (35 ).

Claims

1.- System for the resection of the tibial plateau and / or the condyles of the femur to implant a prosthesis that incorporates a cutting or resection instrument (1, 2, 3) composed of a fixation support (1) for its fixing on Ia tibia and / or on the femur, a guide holder (2) that is mounted on the fixing support (1), and a cutting guide (3), which is provided with a slot (4) for the passage of the tool of cut (36) with which it practices the resection, which in turn is mounted on the holder (2), characterized in that it additionally comprises: - scanning means (5) that capture images of the tibia, and / or the femur - a computer (6) to which those images arrive from which it models the tibia and / or the femur in 3D by means of software that also defines the virtual position of the resection instruments according to a cutting plane, - a removable reference plate (7) that is mounted on the fixing support (1) to, through the scanning means (5), send images of the position and orientation of the fixing support (1) to the computer ( 6) to redefine the cutting plane and the position of the cutting instruments (1, 2, 3), - a calibration tool (8) in which the cutting instruments (1, 2, 3) are adjusted. 2. System for the resection of the tibial plateau and / or the condyles of the femur to implant a prosthesis according to claim 1 characterized in that the fixing support (1) comprises a nail (5), a cylindrical central section (6) and an upper section (37) quasi-cylindrical topped by a vertical plane, inside which is a longitudinal bore (8). 3.- System for the resection of the tibial plateau and / or the condyles of the femur to implant a prosthesis according to previous claims characterized in that the reference plate (7) comprises: - a central body (9) provided with a perforation (10) of configuration adaptable to the upper section (7) of the fixing support (1), - a transparent body to the radiographs (11) that surrounds the central body (9) and opaque radio spheres (12) integrated in the transparent body to the radiographs (11), and - a screw (13) that passes through the perforation (10) and bolts in the longitudinal bore (8) of the fixing support (1) linking the reference plate (7) with said fixing support (1). 4. System for the resection of the tibial plateau and / or the condyles of the femur to implant a prosthesis according to previous claims characterized in that the guide holder (2) comprises: - a positioning support of the cutting guide (14) in which a groove (24) is defined to receive the cutting guide (3), - parallel axes (15) integral to the positioning support of the cutting guide (14) in turn joined by their opposite ends, - a carriage (16) mounted on the parallel axes constituted by two plates (17), upper and lower, joined together by thymes (18), which slide with respect to the axes (15), and have corresponding central openings (19), - a ball joint (20) located between the central openings (19) of the plates (17), with respect to which the carriage (16) can rotate in the horizontal plane and in the vertical plane, in which a central screw is located (21) that links the guide holder (2) to the fixing support (1), and which has on its lower face a fitting (25) that can be attached to the upper section (7) of the fixing support (1), and - a fixing screw (22) used to hug the plates (17) against the kneecap (20) and against one of the axes (15) to fix the relative orientation of the guide (2) with respect to the central thyme (21). 5. System for the resection of the tibial plateau and / or the condyles of the femur to implant a prosthesis according to previous claims characterized in that the calibration tool (8) comprises: -a coupling shaft (28) of the same shape and dimensions as the upper section (7) of the fixed support (1), on which the ball joint (20) of the guide holder (2) is coupled, - a support (29) distant from the coupling shaft (28) on which the positioning support of the cutting guide (14) fits, - a first block (30) on which the support (29) is mounted which is operated by a first control (31) for its linear displacement with respect to the coupling shaft (28) in order to adjust the distance between the positioning support of the cutting guide (14) and the ball joint (20), - a second block (32) to which the coupling shaft (28) of the calibration tool (8) is linked, which is operated by a second knob (34) for its rotational displacement in the vertical plane to adjust the relative inclination, in this vertical plane of the positioning support of the cutting guide (14) with respect to the ball joint (20), - a third block (33), with respect to which the second block (32) rotates, which is operated by a third knob (35) for its rotation in the horizontal plane to adjust the angular position of the positioning support of the cutting guide (14) with respect to the kneecap (20). 6. System for the resection of the tibial plateau and / or the condyles of the femur to implant a prosthesis according to claim 1 characterized in that the scanning means (5) are selected among devices designed to perform scanning, magnetic resonance, radiography operations , computerized tomography and any other means of image capture. 7.- Modeling method of the tibia and / or femur and positional configuration of the resection instruments characterized in that it comprises the phases of: - image capture of the tibia and / or femur and generation of a first virtual model of the tibia in 3D to select the ideal plane of cut or resection of the tibial plateau, and / or the condyles of the femur - determination in the virtual model of the tibia and / or femur of the position of the cutting instruments according to the ideal cutting plane, - image capture of the tibia and / or femur and generation of a second virtual model, - Determination of the gap between the first virtual model and the second virtual model and presentation of correction data for the configuration of the instruments for performing the cut. 8. Method of modeling the tibia and / or femur and positional configuration of the resection instruments according to claim 7, characterized in that it does not require the use of intra or extramedullary guides. 9. Computer program comprising code means adapted to perform all phases of the method defined according to claims 7 and 8 when said program is run on a computer.