Patent Description:
A first family of mechanical guide solutions for machining tools for bone cutting is known from the state of the art. Patent <CIT> describes a device for the preparation of bone cuts for the establishment of a knee prosthesis without conservation of the cruciate ligaments, comprising a femoral cutting guide and a tibial cutting guide made to measure. Said device is based on scan data of the patient's joint which is transmitted to a planning software. Each guide has supporting means on the distal femoral epiphysis and on the proximal tibia I epiphysis, in two substantially orthogonal planes, and arrangements for the passage of drill guides, and at least one cutting blade. According to this solution, the cutting planes are determined digitally in the femur and tibia reference systems. These cutting planes then determine the configuration of the two guides, which are used after being firmly attached to the bone to be machined. It is necessary to screw the guide to the bone to allow effective guidance of the tool. This solution is very invasive due to the requirement of mechanical coupling of the bone with the guide, and requires the manufacture of a specific guide for each operation. Such a solution also leads the surgeon to spend a lot of time to mechanically couple the bone with the guide in several successive positions to perform the various cuts.

Patents No. <CIT> and <CIT> describe a positioning device with a base that attaches to the bone. This positioning device is driven by computer-controlled motors. In the European patent <CIT> the position of the device is determined by a navigation system. A tracking system is used in combination with the navigation system, allowing the correct positioning and orientation of the implants. The main disadvantage of the positioning devices described above is that they are based on an anchoring element or a base component that must first be attached to the bone. Said devices also comprise an important amount of positioning elements that connect the cutting guide to the base to adjust the angle and/or position the cutting guide relative to the base with at least <NUM> and up to <NUM> degrees of freedom. These types of devices therefore generally take up significant space in the vicinity of the bone and are invasive to the patient. In addition, since an anchor or a base component is first attached to the bone, such positioning devices can cause unnecessary damage or even fracture the bone. In addition, the installation of such positioning devices is usually time-consuming because it must be carried out very precisely and repeatedly for each guide.

Another family of solutions consists in using markers fixed both to the bone and to the guide. The position of the guide relative to the bone is then tracked in real-time from the position and orientation of these markers determined by a stationary sensor. The European patent <CIT> describes an example of the use of such a device for positioning a bone cutting guide. However, locating the effective position of the device requires uninterrupted acquisition of the position and orientation of markers associated with the device. This is very time and energy consuming, not least because the physician must constantly be aware of his movements in order to not block the necessary "line of sight" from the stationary sensor to the markers.

Patent <CIT> describes another solution for a guiding device for bone cutting adapted to cut bone portions at the level of the head of a bone, comprising: a device with a seat intended to be screwed to the bone at the level of said head, means for adjusting the inclination of a first axis of rotation with respect to said seat around two perpendicular axes OX,OY, an arm, one end of said arm being pivotally assembled on said seat according to the first axis of rotation; and a guide intended to support the tool. This guide is pivotally assembled on the arm according to a second axis of rotation.

A major drawback of such a system is that the fixation of the seat to the femur is quite invasive since it requires implanting large pins into the bone to bear the weight of the robot and compensate for forces exerted during sawing by the saw inserted in the cutting block carried by the robot. Large pins used to carry an important weight and react to important forces can potentially generate bone fracture. In addition, weight and efforts can lead to motion of the pins in the bone, which will impact significantly the accuracy of the system. Besides, the rotational axes have to be adjusted very precisely in order to achieve all the target planes. However, this adjustment is difficult and prone to errors or inaccuracies because it is done manually and is guided through visual feedback provided by the navigation system. If the cutting plane slightly moves during sawing because of the forces exerted by the operator or the saw, it would be very difficult for the operator to detect it and to correct these adjustments manually. Moreover, if the pins are not placed in a correct location because of surgical constraints, anatomical constraints or misuse, the robot will not be able to position the cutting block so that all the cuts can actually be reached, and it will be necessary to reposition the pins in the bone at slightly different locations, which is a difficult task. In addition, this system does not allow carrying out the tibial cut while the seat is fixed to the femur, and therefore another specific device is necessary to perform cuts on the tibia, which takes additional time, pins, systems and efforts.

The reference system of a bone element is usually determined in an invasive and approximate manner. The medullar canal is sometimes used in prior art solutions to provide a reliable reference system, but these solutions require the highly invasive insertion of a rod into the bone canal. Other reference systems are theoretically known, but are generally not accessible on the patient, for whom the amplitude of the incision and therefore of the exposed area is minimized. Finally, orthopedics applications require high precision machining on complex surfaces. An error of a fraction of a millimeter or a degree of inclination of the cutting plane for the installation of a knee prosthesis can lead to instability, severe residual pain, walking difficulties and/or prosthesis revision surgery.

As outlined above, there is a need for a less invasive, more compact and surgeon-friendly device, that can be smoothly integrated to the surgical workflow and thus become a standard surgical technique. The present disclosure addresses the aforementioned limitations of the existing surgical robots through a new design that will be described hereafter.

In order to remedy the disadvantages of the prior art, most notably to offer a less invasive more compact and more intuitive solution, the present disclosure relates to a surgical system for machining an anatomical structure of a patient positioned on an operation table, said anatomical structure being part of an anatomical reference system of the surgical system, said surgical system comprising:.

where the at least two elements of the lockable unit are linked to each other by at least one degree of freedom aimed at cooperating with lockable means, said lockable means being configured to be activated by the control unit when the real time configuration of the lockable unit corresponds to the at least one locked configuration recorded inside the control unit, in order to lock the constraining device in a determined position which constrains the machining tool within a determined machining plane. Constraining the movement of the lockable unit and therefore the surgical machining tool within a manually induced trajectory improves the accuracy and safety of the procedure.

The system being manually moved is not motorized or automatically actuated and this allows:.

According to alternative embodiments taken alone or in any technically feasible combination, the system also has several of the following characteristics:.

In the present disclosure, the following terms have the following meanings:
"Machining" refers to the mechanical process of cutting or other methods for removing material. The purpose of machining is to modify the dimensions, precision, geometry and surface state of all the surfaces of the finished element, in order to move from a raw original state to a final state in accordance with a predefined model.

"Pose estimation" refers to the estimation of the position and orientation of the device relative to the anatomical structure to be machined. This determination can be carried out either by acquiring an image or a point cloud followed by a digital processing, or by knowing the a priori geometry of the grasping element base and the morphology of the surface of the element to be machined.

"Reference position" refers to a position and orientation of the machining tool in the reference system of the element to be machined and from which the machining head of this tool must move. In other words, the tool is placed in a position and orientation known as the reference position and held in this position for subsequent machining by moving the machining head.

The following detailed description will be better understood when read in conjunction with the drawings. For the purpose of illustrating, the surgical system is shown in the preferred embodiments. It should be understood, however that the application is not limited to the precise arrangements, structures, features, embodiments, and aspect shown. The drawings are not drawn to scale and are not intended to limit the scope of the claims to the embodiments depicted. Accordingly, it should be understood that where features mentioned in the appended claims are followed by reference signs, such signs are included solely for the purpose of enhancing the intelligibility of the claims and are in no way limiting on the scope of the claims.

Features and advantages of the disclosure will become apparent from the following description of embodiments of a system, this description being given merely by way of example and with reference to the appended drawings in which:.

While various embodiments have been described and illustrated, the detailed description is not to be construed as being limited hereto. Various modifications can be made to the embodiments by those skilled in the art without departing from the scope of the disclosure as defined by the claims.

As shown in <FIG>, an anatomical structure A which is classically well known for regularly needing surgery, is the knee j oint. As known per se, the knee joint includes three bones, the femur F and the tibia T and the patella. (We willfully exclude the patella, from this description for it adds no explanatory value). The examples described in the present specification relate therefore to the field of orthopedic surgery and more specifically to the preparation of a femur F and a tibia T for the implantation of a femoral and tibial knee implants I (see <FIG>).

This preparation includes a succession of well-known steps, each step being the machining of one of the bones F, T according to a given pre-determined machining plane P<NUM>, P<NUM>, P<NUM>, P<NUM>, P<NUM>, P<NUM> (see <FIG>). Those machining steps are well-known per se and they usually take place in the same order, depending on the strategy adopted by the operator (surgeon). On <FIG>, each machining plane P<NUM>, P<NUM>, P<NUM>, P<NUM>, P<NUM>, P<NUM> is numbered in the generally admitted chronological sequence. Those machining planes P<NUM>, P<NUM>, P<NUM>, P<NUM>, P<NUM>, P<NUM> are classically determined by a pre-operative surgical planning. A pre-operative surgical planning is only valid for one given patient for one given surgery for one given type of implant (size, design, brand, etc.). Each patient (and each surgery) gets a personalized surgical planning. Therefore, the machining planes P<NUM>, P<NUM>, P<NUM>, P<NUM>, P<NUM>, P<NUM> slightly change for each surgery. The usual first step of the pre-operative surgical planning, is the establishing of a three-dimensional bones F, T model. One way to obtain such a three-dimensional bones F, T model is to use medical imaging such as computed tomography, X-rays, MRI, fluoroscopy, ultrasound or other imaging means. X-ray or scanner, or even MRI, acquisitions are usually made during full weight-bearing , with typically a frontal (also named coronal or anteroposterior) view, a lateral (or profile) view with the knee in full extension and/or at <NUM>°-<NUM>° of flexion, a long-leg view, including the lower limb from the femoral head to the ankle joint and lastly a view of the kneecap at <NUM>° flexion, also called skyline view. From these acquisitions it is possible to build a digital model of the bones F, T to be machined during the operation. A particular knee set of implants I is then selected based on an analysis of the three-dimensional bones F, T model.

The present disclosure aims at allowing an accurate and safe machining of the bones F, T by means of a surgical system <NUM> which will be described here-after.

After being established, the bones F, T model is stored in a memory of a control unit <NUM> of said surgical system <NUM>.

The surgical system <NUM> includes a 3D imaging sensor <NUM> which position is well known within the surgical system <NUM>. More precisely, the 3D imaging sensor <NUM> is placed at a known geometrical position of the lockable unit <NUM>. This 3D imaging sensor <NUM> allows the operator, in cooperation with the bones F, T model stored in the memory of the control unit <NUM>, to reset the anatomical reference system for each new operation. Once a bones F, T model has been determined for a given patient, and stored inside the memory of the control unit <NUM>, the surgical system <NUM> can be used for surgery. Once the patient is correctly installed, the anatomical structure A to be seen and the surgery system correctly put in place with regards to the patient, an acquisition of the anatomical structure A is taken. This acquisition is taken with the 3D imaging sensor <NUM>. The control unit <NUM> analyses the taken acquisition and merges it with the bones F, T model. This enables the control unit <NUM> to position the anatomical structure A with regards to the 3D imaging sensor <NUM> and therefore to the surgery system <NUM>. This then enables the control unit <NUM> to define an anatomical reference system and set the precise machining planes P<NUM>, P<NUM>, P<NUM>, P<NUM>, P<NUM>, P<NUM> for this specific surgery within this anatomical reference system.

After the machining steps, the bones F, T display clean ends with sharp edges in order to facilitate the fitting and fixation of the implant I (see <FIG> and <FIG>).

The free surface of the bones F, T to be machined (see <FIG>) is limited and there are therefore only a few areas where a machining tool <NUM> can be put in contact with the bones F, T. This contact has to be as minimally invasive as possible in order to neither damage the bones F, T nor the surrounding soft tissue, while ensuring a precise relative positioning of the machining tool <NUM> relative to the bones F, T.

The surgical system <NUM> is to be seen on <FIG>. As can be seen, said surgical system <NUM> aims at machining an anatomical structure A (in this case, a knee) of a patient positioned on an operation table. The patient is usually anesthetized and maintained on the operation table by means of specific and well-known fixation means. In addition, the patient's limb in its whole is secured to the surgical system <NUM>.

The control unit <NUM> can for example be a computer. This control unit <NUM> comprises a memory, a real time computing processor, power supply, power converters, fuses, actuators and locking means drivers. The control unit <NUM> further comprises an operator interface <NUM> allowing an interaction between the control unit <NUM> and the operator. This operator interface <NUM> allows to.

As can be seen on <FIG>, the lockable unit <NUM> and the grasping element <NUM> are carried by the base unit <NUM>. The base unit <NUM> is static with regards to the patient. The base unit <NUM> comprises for example a base secured on the floor or attached to the operation table on which the patient is secured.

In some embodiment (not shown), the base unit <NUM> is a motorized actuation unit securing the patient's limb. This actuation unit is aimed at enabling a motorized flexion-extension movement of the patient's knee. This actuation unit allows the operator to mobilize the patient's limb and expose the operating field according to the surgical steps.

As can be seen on <FIG>, the grasping element <NUM> includes three parts, a first part 22a configured to be rigidly secured to the anatomical structure A, a second part 22b being carried by the base unit <NUM> and a third part 22c also being configured to be rigidly secured to the anatomical structure A. The first and second parts 22a, 22c are two mobile parts, each aimed at being attached and detached at least two times to the second part 22b. More precisely, each of the first and third parts 22a, 22c of the grasping element <NUM> parts, is a base plate aimed at being screwed to one bone F, T: each base plate is screwed to one different bone F, T of the anatomical structure A. The second part 22b of the grasping element <NUM> connects either the first part 22a or the third part 22c. The connection depends on which bone F, T the operator wants to secure. As shown on <FIG>, the second part is a rod 22b. The grasping element <NUM> ensures therefore the positioning of the lockable unit <NUM> with regards to the anatomical structure A while the operator is using the machining tool <NUM>. Particularly, the grasping element <NUM> secures the femur F while it is machined and secures the tibia T while it is machined. The grasping element <NUM> enables, while the anatomical structure A is machined, to maintain the machined bone F, T immobile within the patient's flesh. The connection and disconnection of the second part 22b with the first or third part 22a, 22c is enabled by a quick-release system.

As can be seen on <FIG>, the lockable unit <NUM> comprises at least two linked and manually displaceable elements <NUM>, <NUM>, <NUM>, <NUM> aimed at being manually moved by an operator's hand H. The manually displaceable elements <NUM>, <NUM>, <NUM>, <NUM> have to be moved around by the operator. Without the movement induced by the operator, said manually displaceable elements <NUM>, <NUM>, <NUM>, <NUM> remain motionless. When moved around by an operator, the manually displaceable elements <NUM>, <NUM>, <NUM>, <NUM> can be arranged according to at least one, relatively to the anatomical structure A, calculated locked configuration L<NUM>, L<NUM>, L<NUM>, L<NUM>, L<NUM>, L<NUM>. The configuration L<NUM>, L<NUM>, L<NUM>, L<NUM>, L<NUM>, L<NUM> is calculated by the control unit <NUM>.

Each manually displaceable element <NUM>, <NUM>, <NUM>, <NUM> of the lockable <NUM> unit has therefore a determined position within the calculated locked configuration L<NUM>, L<NUM>, L<NUM>, L<NUM>, L<NUM>, L<NUM> of the lockable unit <NUM>.

As already mentioned, different machining planes P<NUM>, P<NUM>, P<NUM>, P<NUM>, P<NUM>, P<NUM> are determined computer wise during a pre-operative surgical planning. Therefore, the corresponding ideal relative position of the machining tool <NUM> is also determined computer wise. Each machining plane P<NUM>, P<NUM>, P<NUM>, P<NUM>, P<NUM>, P<NUM> thus represents a target position of the machining tool <NUM> in the anatomical reference system and each machining plane P<NUM>, P<NUM>, P<NUM>, P<NUM>, P<NUM>, P<NUM> corresponds to a specific calculated locked configuration L<NUM>, L<NUM>, L<NUM>, L<NUM>, L<NUM>, L<NUM> of the lockable unit <NUM>. Each plan P<NUM>, P<NUM>, P<NUM>, P<NUM>, P<NUM>, P<NUM> represents a target position of the machining tool <NUM> in the anatomical reference system and to each plan P<NUM>, P<NUM>, P<NUM>, P<NUM>, P<NUM>, P<NUM> corresponds a specific calculated locked configuration L<NUM>, L<NUM>, L<NUM>, L<NUM>, L<NUM>, L<NUM>.

The lockable unit <NUM> further comprises a constraining device <NUM> aimed at supporting and guiding the machining tool <NUM>. The constraining device <NUM> sets the machining plane P<NUM>, P<NUM>, P<NUM>, P<NUM>, P<NUM>, P<NUM> within which the tool <NUM> can be moved by the operator. Regarding the current disclosure, the constraining device <NUM> can carry or guide any kind of tool <NUM>, for example a saw, a drill or a burr. In the example of <FIG>, the carried machining tool <NUM> is an oscillating saw. This constraining device <NUM> is linked to the lockable unit <NUM> by means of an articulated connection <NUM>. This articulated connection <NUM> can be a quick fastener.

In the embodiment of <FIG>, <FIG>, <FIG>, <FIG>, <FIG>, this constraining device <NUM> is a planar mechanism.

It is well known by any person skilled in the art that, according to the relative motion of the rigid bodies, mechanisms can be divided into planar mechanisms and spatial mechanisms. In a planar mechanism, all of the relative motions of the rigid bodies are in one plane or in parallel planes. If there is any relative motion that is not in the same plane or in parallel planes, the mechanism is called spatial mechanism. In other words, planar mechanisms are essentially two dimensional while spatial mechanisms are three dimensional.

The planar mechanism as illustrated on <FIG>, <FIG>, <FIG> and <FIG> is a passive mechanism that needs to be actuated by the operator's hand H. The planar mechanism defines the machining plane P<NUM>, P<NUM>, P<NUM>, P<NUM>, P<NUM>, P<NUM> by blocking the machining tool <NUM> within a determined orientation. Once blocked, the machining tool <NUM> can only be moved according to three degrees of freedom within he machining plane P<NUM>, P<NUM>, P<NUM>, P<NUM>, P<NUM>, P<NUM>. The planar mechanism might include encoders linked to the control unit <NUM>. This would allow the control unit <NUM> to precisely know the configuration of the planar mechanism. The control unit <NUM> might be able to help the operator to operate the machining tool <NUM> by means of haptic, visual or audio signals.

On another embodiment illustrated on <FIG>, the constraining device <NUM> is a guiding element comprising a slit or a sleeve 30a forming a cutting guide through which an active and elongated part of the machining tool <NUM>, for example the blade, can be inserted. This slit or sleeve 30a orientates the machining tool <NUM> and confines it within the predetermined machining plane P<NUM>, P<NUM>, P<NUM>, P<NUM>, P<NUM>, P<NUM>. In another embodiment (not shown), the constraining device <NUM> can be tracked. The machining tool <NUM> can be secured in a removable or unremovable way to the constraining device <NUM>. The constraining device <NUM> is linked to the lockable unit <NUM> by means of an articulated connection <NUM>. As already mentioned, this articulated connection <NUM> can be a quick fastener. The lockable unit <NUM> of the surgical system <NUM> comprises six locked configurations L<NUM>, L<NUM>, L<NUM>, L<NUM>, L<NUM>, L<NUM>. The memory of the control unit <NUM> contains a recording of each of the calculated locked configurations L<NUM>, L<NUM>, L<NUM>, L<NUM>, L<NUM>, L<NUM> of the lockable unit <NUM>. In short, the lockable unit <NUM> aims at positioning the constraining device <NUM> relatively to the anatomical structure A to enable the machining tool <NUM> to machine said anatomical structure A. Each calculated locked configuration L<NUM>, L<NUM>, L<NUM>, L<NUM>, L<NUM>, L<NUM> of the lockable unit <NUM> corresponds to a unique machining plane P<NUM>, P<NUM>, P<NUM>, P<NUM>, P<NUM>, P<NUM>. Each locked configuration L<NUM>, L<NUM>, L<NUM>, L<NUM>, L<NUM>, L<NUM> constraining the machining tool <NUM> within said corresponding unique machining plane P<NUM>, P<NUM>, P<NUM>, P<NUM>, P<NUM>, P<NUM>.

Each calculated locked configuration L<NUM>, L<NUM>, L<NUM>, L<NUM>, L<NUM>, L<NUM> of the lockable unit <NUM> is defined within an anatomical reference system (re)set by means of the 3D imaging sensor <NUM>. However, each time the grasping element <NUM> is secured to the anatomical structure A, the 3D imaging sensor <NUM> makes new acquisitions of the anatomical structure A in order to verify that the anatomical structure is still in place. If the anatomical structure A has moved the control unit <NUM> recalculates the remaining locked configurations L<NUM>, L<NUM>, L<NUM>, L<NUM>, L<NUM>, L<NUM>, in order to fit the machining planes P<NUM>, P<NUM>, P<NUM>, P<NUM>, P<NUM>, P<NUM> to the position of the anatomical structure A.

As can be seen on <FIG>, the manually displaceable elements <NUM>, <NUM>, <NUM>, <NUM> of the lockable unit <NUM> are linked to each other by at least one degree of freedom. In the embodiment shown on <FIG>, <FIG>, <FIG>, <FIG>, there are four manually displaceable elements <NUM>, <NUM>, <NUM>, <NUM> to be counted. On the embodiment illustrated by <FIG>, there are three manually displaceable elements <NUM>, <NUM>, <NUM> to be counted. On the embodiments illustrated on <FIG>, <FIG>, <FIG>, <FIG>, <FIG> the manually displaceable elements <NUM>, <NUM>, <NUM>, <NUM> are all linked to each other by means of articulated connections <NUM>, <NUM>, <NUM>. In the embodiment illustrated on <FIG>, the second and third manually displaceable elements <NUM>, <NUM> are linked to each other by a sliding connection while the other manually displaceable elements <NUM>, <NUM>, <NUM>, <NUM> are linked of each other by means of an articulated connection <NUM>, <NUM>. In each embodiment, the combination of the manually displaceable elements <NUM>, <NUM>, <NUM>, <NUM> and the connecting degrees of freedom (articulated connections <NUM>, <NUM>, <NUM> or sliding connections) forms a planar linkage mechanism. The three (as on <FIG>) or four (as on <FIG>, <FIG>, <FIG>, <FIG>) manually displaceable elements <NUM>, <NUM>, <NUM>, <NUM> are all oriented in the same direction and this orientation does not change during the manually induced motion: said manually displaceable elements <NUM>, <NUM>, <NUM>, <NUM> remain within a plan substantially parallel to the operation table edge and therefore parallel to the patient's limb.

As previously mentioned, the different degrees of freedom (sliding or articulated connections <NUM>, <NUM>, <NUM>) allow the operator to displace the manually displacing elements <NUM>, <NUM>, <NUM>, <NUM> and bring the lockable unit <NUM> into the calculated locked configuration L<NUM>, L<NUM>, L<NUM>, L<NUM>, L<NUM>, L<NUM> corresponding to the pre-determined machining plane P<NUM>, P<NUM>, P<NUM>, P<NUM>, P<NUM>, P<NUM> needed by the operator.

The rotation axis of the articulated connection <NUM> of the constraining device <NUM> is extending sensibly perpendicularly to the rotation axes of the sliding or articulated connections <NUM>, <NUM>, <NUM> of the lockable unit <NUM>.

The surgical system <NUM> further comprises a sensor unit <NUM>. The sensor unit <NUM> includes at least one sensor <NUM>, <NUM>, <NUM>, <NUM> aimed at following, in real time, a real time configuration of the lockable unit <NUM> within the anatomical reference system. The sensor unit <NUM> is connected to the control unit <NUM> and aims at estimating the configuration of the lockable unit <NUM> relative to the femur F or the tibia T. In the embodiment shown on figure , the sensor unit <NUM> comprises several mechanical sensors <NUM>, <NUM>, <NUM>, <NUM> mounted within the sliding or articulated connections <NUM>, <NUM>, <NUM>, <NUM> and enabling the control unit <NUM> to follow the position of each manually displaceable element <NUM>, <NUM>, <NUM>, <NUM>. When the detected angular position of the articulated connections <NUM>, <NUM>, <NUM>, <NUM> or the relative position of the manually displaceable elements <NUM>, <NUM>, <NUM>, <NUM> corresponds to a calculated locked configuration L<NUM>, L<NUM>, L<NUM>, L<NUM>, L<NUM>, L<NUM> stored in the memory of the control unit <NUM>, the control unit <NUM> outputs a signal. This signal can be an acoustic, visual or vibrating signal informing the operator about the reaching of a calculated locked configuration L<NUM>, L<NUM>, L<NUM>, L<NUM>, L<NUM>, L<NUM>. Based on this signal, the operator may perform a manual lock of the articulated connections <NUM>, <NUM>, <NUM>, <NUM> and lock the lockable unit <NUM>. However, in a preferred embodiment illustrated on <FIG>, <FIG>, the signal emitted by the control signal is an electrical signal. This electric signal communicates directly with the sliding or articulated connections <NUM>, <NUM>, <NUM>, <NUM> by means of locking means <NUM>, <NUM>, <NUM>, <NUM>.

Each sliding or articulated connection <NUM>, <NUM>, <NUM>, <NUM> is cooperating with locking means <NUM>, <NUM>, <NUM>, <NUM>. In the present embodiment those locking means <NUM>, <NUM>, <NUM>, <NUM>. are locking joints or brakes. Each locking means <NUM>, <NUM>, <NUM>, <NUM> is connected to the control unit <NUM> and is configured to be activated by the control unit <NUM>. This activation takes place when the control unit <NUM> sense, through the sensor unit <NUM>, that the real time configuration of the lockable unit <NUM> corresponds one of the predetermined calculated locked configuration L<NUM>, L<NUM>, L<NUM>, L<NUM>, L<NUM>, L<NUM> recorded inside the memory of the control unit <NUM>.

This activation locks the sliding or articulated connections <NUM>, <NUM>, <NUM>, <NUM> and therefore locks the constraining device <NUM> in a predetermined position which constrains the machining tool <NUM> within one of the predetermined corresponding machining planes P<NUM>, P<NUM>, P<NUM>, P<NUM>, P<NUM>, P<NUM>. This way, the operator is informed when the right locked configuration L<NUM>, L<NUM>, L<NUM>, L<NUM>, L<NUM>, L<NUM> of the lockable device <NUM> is reached and is informed that there is no need to further try to move the manually displaceable elements <NUM>, <NUM>, <NUM>, <NUM>. The operator then knows that the bone F, T machining according to the corresponding machining plane P<NUM>, P<NUM>, P<NUM>, P<NUM>, P<NUM>, P<NUM> can begin. In one embodiment, the locking means remain manually lockable in case of an emergency. The signal emitted by the control unit <NUM> can be a double signal: a visual or acoustic or vibrating signal aimed at the operator and an electric signal directed to the locking means <NUM>, <NUM>, <NUM>, <NUM>. Therefore, the operator gets some information about when the calculated locked configuration L<NUM>, L<NUM>, L<NUM>, L<NUM>, L<NUM>, L<NUM> is about to be reached. For this purpose, the signal may have a frequency and/or modulation and/or intensity varying according to the discrepancy to the locked configuration L<NUM>, L<NUM>, L<NUM>, L<NUM>, L<NUM>, L<NUM>. The signal may be a haptic signal, a sound signal or a visual signal.

In an embodiment, the control unit <NUM> activates each lockable means in a progressive way: the activation of each locking means <NUM>, <NUM>, <NUM>, <NUM> is reversely proportional to the distance separating each manually displaceable element <NUM>, <NUM>, <NUM>, <NUM> from its predetermined position within the locked configuration L<NUM>, L<NUM>, L<NUM>, L<NUM>, L<NUM>, L<NUM>. This allows the operator to feel when the locked configuration L<NUM>, L<NUM>, L<NUM>, L<NUM>, L<NUM>, L<NUM> is soon to be reached and allows to secure the moving of the lockable unit <NUM>. Regarding another aspect of the locking, the control unit <NUM> may activate the locking means <NUM>, <NUM>, <NUM>, <NUM> one by one according to an order recorded inside the memory of control unit <NUM>. The first locking means <NUM>, <NUM>, <NUM>, <NUM> to be activated is the locking means <NUM>, <NUM>, <NUM>, <NUM> cooperating with the articulated connection <NUM> the closest to the base unit <NUM>. Once this first articulated connection <NUM> is locked, the control unit activates the second closest to the base unit <NUM> articulated connection <NUM>. The last articulated connection to be activated is the connection <NUM> which connects the constraining device <NUM> to the lockable unit <NUM>. Further, the control unit <NUM> contains at least two locked configurations L<NUM>, L<NUM>, L<NUM>, L<NUM>, L<NUM>, L<NUM> recordings. In the current disclosure, the control unit <NUM> contains six different locked configurations L<NUM>, L<NUM>, L<NUM>, L<NUM>, L<NUM>, L<NUM> recordings. Those calculated locked configurations L<NUM>, L<NUM>, L<NUM>, L<NUM>, L<NUM>, L<NUM> are recorded inside the control unit <NUM> following a given chronological order. This chronological order is determined by the operator, during the pre-operative phase. The control unit <NUM> is configured to activate the locking means <NUM>, <NUM>, <NUM>, <NUM> according to each calculated locked configuration L<NUM>, L<NUM>, L<NUM>, L<NUM>, L<NUM>, L<NUM> following this chronological order.

<FIG> is a flowchart of a complete surgical intervention intended to machine an anatomical structure A using the surgical system <NUM> in order to perform a total knee arthroplasty:.

Claim 1:
A surgical system (<NUM>) for machining an anatomical structure (A) of a patient positioned on an operation table, said anatomical structure (A) being part of an anatomical reference system of the surgical system (<NUM>), said surgical system (<NUM>) comprising:
- a base unit (<NUM>) configured to be secured to the operation table,
- a machining tool (<NUM>) configured to be manually displaced by an operator,
- a lockable unit (<NUM>) carried by the base unit (<NUM>), said lockable unit (<NUM>) including:
o at least two linked and manually displaceable elements (<NUM>, <NUM>, <NUM>, <NUM>) configured to be manually arranged according to a least one, relatively to the anatomical structure (A), calculated locked configuration (L<NUM>, L<NUM>, L<NUM>, L<NUM>, L<NUM>, L<NUM>), said locked configuration (L<NUM>, L<NUM>, L<NUM>, L<NUM>, L<NUM>, L<NUM>) being defined within the anatomical reference system, and
o a constraining device (<NUM>) configured to support and guiding the machining tool (<NUM>),
- a grasping element (<NUM>) carried by the base unit (<NUM>), said grasping element being designed to secure the anatomical structure (A),
- a sensor unit (<NUM>) including at least one sensor configured to follow, in real time, a real time configuration of the lockable unit (<NUM>) within the anatomical reference system,
- a control unit (<NUM>) containing a recording of the at least one locked configuration (L<NUM>, L<NUM>, L<NUM>, L<NUM>, L<NUM>, L<NUM>) of the lockable unit (<NUM>),
wherein the at least two elements (<NUM>, <NUM>, <NUM>, <NUM>) of the lockable unit (<NUM>) are linked to each other by at least one degree of freedom configured to cooperate with lockable means, said lockable means being configured to be activated by the control unit (<NUM>) when the real time configuration of the lockable unit (<NUM>) corresponds to the at least one locked configuration (L<NUM>, L<NUM>, L<NUM>, L<NUM>, L<NUM>, L<NUM>) recorded inside the control unit (<NUM>), in order to lock the constraining device (<NUM>) in a predetermined position which constrains the machining tool (<NUM>) within a determined machining plane (P<NUM>, P<NUM>, P<NUM>, P<NUM>, P<NUM>, P<NUM>).