Robotic system for removing bone material from anatomical structures

Abstract

The present disclosure relates to a robotic system for removing bone material from an anatomical structure of a patient, comprising: a base (4), an end effector (2), the end effector being configured to hold a surgical tool (1), an actuation unit (3), the actuation unit being configured to translate the end effector relative to the base at least along one feed axis (A), a control unit, the control unit being connected to the actuation unit (3) and being configured to close the tool (1) and to command the actuation unit (3) to translate the end effector (2) along the feed axis (A) when the tool is closed, the control unit comprising a feedback unit, the feedback unit being configured to measure the force applied by the surgical tool (1) to the anatomical structure during the translation of the end effector (2) and, based on the measured force, to detect contact of the tool with the bone material of the anatomical structure.

Description

Technical Field

[0001] The present invention relates to a robotic system for removing bone material from an anatomical structure. Background of the Invention

[0003] During knee arthroplasty, the surgeon must remove bone material from the femur and tibia to replace the bone material with the prosthesis.

[0004] To do this, the surgeon uses a surgical tool, such as a drill.

[0005] However, cutting the posterior portion of the tibia is a delicate operation because the area of ​​the knee adjacent to the posterior portion of the tibia T specifically includes the femoral artery FA and the joint capsule AC, which contains synovial fluid (see Figure 1 ), which must not be damaged by the tool. The arrow shows the approximate cutting direction.

[0006] Therefore, the surgeon must ensure that he or she is only removing bone and that the cutting operation is stopped before impacting other structures in the area.

[0007] However, this may be a challenging task because the surgeon does not directly see the rear portion of the bone during cutting. In fact, other bone parts, soft tissues, various fluids, or the cutting tool itself will generally hide the rear portion.

[0008] In the case of navigated image-based surgery, the surgeon is able to visualize the position of the cutting tool relative to the bone model thanks to a 3D image of the area acquired before surgery. Such preoperative images only provide a model of the bone, but not a model of the soft structures that surround the bone and can deform during surgical intervention. Such a model can help the surgeon stop the cutting tool at the appropriate depth, but it assumes that the bone model and its registration with the real anatomy is accurate.

[0009] In the case of navigated imageless surgery, only the bone portion can be visualized, which the surgeon can digitize before cutting (usually with a local pointer tool).

[0010] At the beginning of a surgical intervention, the posterior part of the bone is not easily accessible: therefore digitization is often difficult and modeling of the area may not be accurate. Later, it may not be appropriate to ask the surgeon to repeatedly palpate the area to detect whether all bone material has been removed. Frequent palpation may significantly increase the duration of the surgical intervention.

[0011] Another problem may arise from the fact that the tool may not be held in the surgeon's hand, but may be held by an active robotic system, meaning that the surgeon does not directly control the operation of the tool. Summary of the invention

[0012] The present disclosure seeks to remedy the above-mentioned problem by finding a solution that can easily detect whether bone material remains in the anatomical structure being cut by a surgical tool, even if the anatomical structure is not accessible to visual inspection or palpation.

[0013] To this end, the purpose of the systems and methods disclosed herein is to design a robotic system for removing bone material from a patient's anatomical structure, the robotic system comprising:

[0014] - base,

[0015] - an end effector configured to hold a surgical tool,

[0016] an actuation unit configured to translate the end effector relative to the base at least along one feed axis,

[0017] a control unit coupled to the actuation unit and configured to close the tool and to command the actuation unit to translate the end effector along the feed axis when the tool is closed,

[0018] The control unit comprises a feedback unit configured to measure a force applied by the surgical tool to the anatomical structure during the translation of the end effector and to detect contact of the tool with a bone material of the anatomical structure based on the measured force.

[0019] According to one embodiment, the robotic system further comprises a user interface configured to display information related to the presence of bone material in the anatomical structure along the feed axis.

[0020] According to an embodiment, the control unit is configured to prevent activation of the surgical tool if the feedback unit does not detect any contact of the tool with bone material.

[0021] The control unit may further be configured to generate an alert if the feedback unit does not detect any contact of the tool with the bone material.

[0022] According to one embodiment, the control unit is configured to close the tool and to command the actuation unit to move the end effector along the feed axis at predetermined time or distance intervals.

[0023] According to one embodiment, the feedback unit comprises at least one sensor configured to measure the intensity of an electric current supplying power to the actuation unit, the feedback unit being configured to monitor changes in the intensity over time during the translation of the end effector and to detect contact of the tool with bone material of the anatomical structure if the intensity exceeds a predetermined threshold.

[0024] The robotic system may further comprise a support unit connected to the base, comprising at least one element designed to contact the anatomical structure or an area of ​​the patient's body adjacent to the anatomical structure so as to provide a local mechanical link between the tool and the anatomical structure.

[0025] The robotic system may also include a grasping arm having one end rigidly attached to the base and an opposite end configured to be attached to a structure fixed relative to the patient.

[0026] According to one embodiment, the robotic system further comprises a tracker rigidly attached to the end effector and adapted to be positioned by a positioning system, and the feedback unit is configured to take into account positioning data of the tracker to detect contact between the tool and bone material of the anatomical structure.

[0027] The robotic system may also include a surgical tool configured to remove bone material from the anatomical structure rigidly attached to the end effector.

[0028] Advantageously, the surgical tool is a bone drill, preferably a round bone drill.

[0029] According to an embodiment, wherein the control unit is configured to record at least one physical parameter of the robotic system associated with bone mineral density.

[0030] The robot system can be operated according to the following procedures:

[0031] - Mounting the tool on the end effector;

[0032] - opening the tool and moving the tool by means of the actuation unit to partially cut the anatomical structure;

[0033] - The tool is then closed and the end effector is translated along the feed axis;

[0034] - measuring, by means of a feedback unit, the force exerted by the surgical tool on the anatomical structure during said translation of the end effector;

[0035] - Based on the measured forces, contact of the tool with the bone material of the anatomical structure can be detected.

[0036] Then, if bone material is detected, the tool can be switched on again and moved by the actuation unit to continue cutting the anatomical structure.

[0037] Conversely, if no bone material is detected, opening of the tool may be prevented by the control unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Additional features and advantages of the systems and methods disclosed herein will appear in the following detailed description with reference to the accompanying drawings, in which:

[0039] - Figure 1 shows a schematic side cross-sectional view of a knee joint,

[0040] - Figure 2 An embodiment of the principle of detecting the presence of residual bone is schematically shown;

[0041] - FIG. 3A to FIG. 3C Different steps of using the robotic system are shown;

[0042] - Figure 4 An embodiment of a robotic system comprising a support unit forming a local mechanical link with a bone to be cut is shown;

[0043] - Figure 5 An embodiment of a robotic system is shown with its base held by a holding arm. DETAILED DESCRIPTION

[0044] Although the following description relates to milling the posterior portion of the tibia using a surgical bone drill, the description may also be applicable to other surgical interventions, such as spinal surgery (e.g., decompression, laminectomy, etc.). The cutting process preferably includes (but is not limited to) milling the bone; the cutting process may include drilling or sawing the bone.

[0045] The robotic system can be configured to perform the cutting process. Figures 2 to 5 Detailed Description of the Invention In the present invention, the same reference numerals are used to denote the same elements.

[0046] The robotic system comprises an end effector 2 configured to hold a surgical tool 1, such as a bone drill, a bur or a saw. The surgical tool may be an off-the-shelf tool and will therefore not be described in further detail.

[0047] According to a preferred embodiment, the surgical tool is a bone drill.

[0048] The robotic system comprises a base 4 which can be held by a user. As explained in further detail below, the base may not only be held by hand, but may also be held by an articulated holding arm and / or connected to the tibia via a support unit.

[0049] The robotic system further comprises an actuation unit 3 configured to move the end effector 2 relative to the base 4. To this end, the actuation unit may comprise one or several motors capable of moving the end effector according to at least one degree of freedom. The at least one degree of freedom consists of a translation of the end effector along the feed axis.

[0050] During the cutting operation, the bone drill is rotated along its own longitudinal axis.

[0051] The robotic system further comprises a control unit coupled to the actuation unit. The control unit is configured to switch the tool on and off (ie, to cause or not cause the bone drill to rotate). Furthermore, the control unit is configured to command the actuation unit to move the end effector.

[0052] In accordance with the present disclosure, a robotic system is configured to detect the presence of bone material in front of a bone drill, specifically in the posterior region of the tibia.

[0053] To this end, the control unit comprises a feedback unit implementing a test procedure involving the translation of the tool in the closed state and the evaluation of the mechanical resistance of any material encountered by the end of the tool during this translation.

[0054] If the feed axis is substantially parallel to the surface (usually a plane) of the bone that has been cut, such translation may involve only one motor of the actuation unit. However, if this is not the case, several motors of the actuation unit may be combined to orient the tool substantially parallel to the cutting plane.

[0055] The detection is performed by measuring the force applied by the tool during translation of the end effector (the tool is closed), and by determining whether the tool is in contact with the bone material based on the measured force.

[0056] This force is specifically associated with the intensity of the current supplied to the motor to translate the tool along the feed axis towards the bone. In fact, if the tool is in contact with anatomical tissue, the intensity of the current required to push the tool further along the feed axis will increase.

[0057] To this end, the robotic system comprises at least one sensor configured to measure the intensity, and the feedback unit is configured to monitor changes in the current measured by the sensor and to compare the measured intensity with a predetermined threshold value.

[0058] The threshold value may be arbitrarily fixed, for example based on an average value which may have been measured prior to configuration of the robotic system.

[0059] Alternatively, the threshold value may be determined in situ and thus specific to the patient to be treated. In this way, the feedback will more accurately take into account the bone density variations from one patient to another, in particular in the case of osteoporosis. To this end, the current intensity measured during the cutting process before the test procedure can be used to infer the threshold value suitable for the patient. Otherwise, the surgeon may need to calibrate the system by carrying out a test procedure on one or several bone areas of the patient before starting the surgical intervention.

[0060] Optionally, the robotic system may comprise a user interface (not shown) configured to display information about the measured forces and / or the presence of bone material. The user interface may, for example, comprise a screen coupled to the control unit.

[0061] Optionally, the control unit may be configured to generate an alert (eg, a visual alert or an audible alert) to warn the user if no bone material is detected.

[0062] The control unit may be programmed to start the test procedure at determined time intervals or distance intervals (e.g. every centimeter) during the cutting step. Otherwise, the control unit may be configured to start the test procedure at the end of the cutting step. Alternatively, the test procedure may be started by the user himself, for example by means of a dedicated switch on the robot system.

[0063] Figure 2 An embodiment of the principle of detecting the presence of remaining bone on the posterior tibia is schematically shown.

[0064] The head 10 of the bone drill 1 advantageously presents a spherical shape or any other rounded shape. Preferably, the head does not have a pointed shape so as to avoid the head penetrating into the bone when pressure is applied to the bone by the drill, rather than increasing this pressure. In the case where the tool comprises a tip or teeth that may penetrate into the bone (e.g. a drill or a saw), the feed axis advantageously does not coincide with the direction of said tip or teeth.

[0065] The bone drill 1 is mounted on the end effector 2 .

[0066] The actuation unit 3 is represented in a simplified manner, wherein a motor 30 is coupled to the end effector 2 by a mechanical connection 31, causing the end effector to translate along the feed axis A when the motor rotates. It should be noted that the actuation unit can be more complex and in particular comprise more than one motor, with different types of mechanical connections to the end effector. The sensor is arranged to measure the current supplied to each associated motor. In the following description, it is assumed that one motor is sufficient to translate the tool, and only the current supplied to this motor is measured. However, in the case of several motors involved, the current supplied to each motor can be measured and the measurements combined to determine the force applied by the tool end.

[0067] Figure 2The bottom curve shows the intensity I of the electric current supplied to the motor of the actuation unit as a function of the time t.

[0068] During surgical intervention, the bone drill 10 is rotated and moved by the actuation unit 3 to adjust the cutting plane ( Figure 2 (not shown) cutting the tibia.

[0069] When it is desired to check whether there is still bone material left in the tibia posterior, the control unit turns off the drill and stops the actuation unit. Alternatively, the user himself can turn off the drill and start the test program.

[0070] At the beginning of the test procedure, the actuation unit 3 is stopped so that no current is supplied to the motor 30 ( Figure 2 ). Therefore, the intensity I measured by the sensor is zero.

[0071] Once the test procedure has been initiated, the motor 30 is supplied with a current of substantially constant intensity, which remains constant as long as the bone drill head 10 is not in contact with any anatomical structure ( Figure 2 (center view).

[0072] When the bone drill head 10 contacts the surface of the anatomical structure B, the intensity of the current supplied to the motor increases significantly ( Figure 2 ). In the case of soft tissue, the strength will increase more slowly than in the case of bone material. If the strength reaches a predetermined threshold, the control unit determines that bone material is present and stops the operation of the actuation unit.

[0073] The control unit may then allow the robotic system to turn the bone drill on again to continue the cutting operation.

[0074] If the strength does not reach a predetermined threshold after the bone drill has traveled a specified distance, the control unit determines that there is no bone material in the posterior region of the tibia. Therefore, the control unit can prevent further operation of the cutting tool in this region to reduce the possibility of damaging the femoral artery and / or joint capsule.

[0075] FIG. 3A to FIG. 3C Different steps of using the robotic system are shown.

[0076] Figure 3A It is a side cross-sectional view of the tibia T to be cut. The front part of the tibia is located on the right side of the figure; the back part of the tibia is located on the left side of the figure.

[0077] Figure 3B Schematically illustrates the tibial plateau defining the cutting plane P after a significant portion of the tibial plateau has been removed. Figure 3AHowever, a certain amount of bone B remains in the posterior region of the tibia. In order to detect this remaining amount, the above-described test procedure is implemented. To this end, the bone drill 1 with a spherical head 10 is translated in the direction indicated by the arrow, substantially parallel to the cutting plane P, until contact between the head and the surface of the bone B is detected.

[0078] Figure 3C FIG. 2 shows another situation that may occur after a significant portion of the tibial plateau has been cut. In some cases, the amount of bone B remaining in the posterior region of the tibia is of a shape that does not ensure that the bone drill head will abut the surface. For example, in Figure 3C In the case shown, the height of the bone material extending above the cutting plane P is too small to block the bone drill head. As a result, the bone drill head can slide along the surface and thus pass over the remaining bone material (the trajectory represented by the twisted arrow). In such cases, the test procedure may not provide accurate results.

[0079] To improve the accuracy of the detection, a navigation system can be used. To this end, a tracker 70 is rigidly attached to the end effector 2. The tracker is positioned by the positioning system 7, allowing the position of the bone drill head to be determined.

[0080] By comparing the position of the drill head determined by the positioning system with the position of the expected remaining bone material, it is possible to determine whether the drill head has reached the remaining bone along the predetermined path, and thereby infer the presence or absence of bone material, or infer the validity of the test procedure and its results.

[0081] The positioning data may be used alone (ie without any measure of the strength of the current supplied to the motor) or in combination with such measurements to provide redundant information.

[0082] The embodiments disclosed herein can provide more accurate results when there is a mechanical link between the bone and the end effector. The mechanical link can be a support unit connecting the base of the robotic device to the tibia (see Figure 4 ) and / or by an articulated gripping arm that rigidly connects the base of the robotic device to a fixed element in the operating room (see Figure 5 )supply.

[0083] refer to Figure 4 , a strip 50 is placed around a portion of the leg to compress the soft tissue around the bone. Two V-shaped pins 5 extend from the base 4 of the robotic system and the strip 50, thereby forming a local mechanical link between the tool and the bone. Of course, other support units may be used, as described in particular in documents WO 2014 / 198784 and WO 2014 / 198796.

[0084] refer to Figure 5, the robotic system can be held by a holding arm 6. The arm comprises one end rigidly attached to a fixed structure such as an operating table 8 and an opposite end 60 rigidly connected to the base 4. The holding arm articulates with several degrees of freedom and comprises a switch that allows braking or freezing its position once the base 4 is in a position suitable for surgical intervention. Various technologies can be used (pneumatic arms, hydraulic arms, mechanical arms, arms with brakes, etc.).

[0085] The above detection procedure can also be advantageously used with another objective. During a surgical intervention, at least one first tracker is fixed to the patient (e.g., to the bone to be cut or to an adjacent bone), and at least one second tracker is fixed to the robotic system, e.g., to the end effector, in order to position the end effector relative to the patient. The first tracker should be rigidly fixed to the patient during the entire surgical intervention; however, in some cases, in particular when vibrations are applied to the tracker, the tracker may move relative to the patient, resulting in an incorrect positioning of the end effector relative to the bone to be cut. In order to detect such a situation, the user may be required to place the robotic system in an initial position before starting the cutting process, and the control unit may initiate the bone detection procedure by commanding the actuation unit to bring the surgical tool to several areas that should include bone material (based on the numerical model of the bone). If the feedback unit detects the presence of bone material at each expected position, one may consider that the numerical model of the bone is correct and the relative position of the robotic system and the bone is correct. On the contrary, if the feedback unit detects bone material in an area where such bone material is not expected, or if the feedback unit does not detect bone material in an area where bone material should be present, one may conclude that the numerical model of the bone is inaccurate or that the position of the robotic system relative to the bone is wrong. In such circumstances, the control unit may generate an alert and / or prevent any actuation of the surgical tool.

[0086] According to one embodiment, the control unit may record at least one physical parameter of the robotic system associated with bone mineral density (BMD). Such parameters may be the current used for the displacement of the cutting tool as described above, or the current level (e.g., the current required for the rotation of the bone drill) used to actuate the cutting tool itself. The recording may be performed continuously during the normal bone cutting process, or after the cutting, by pressing the cutting surface with the tool at different points. Therefore, the control unit may create and display a map of the value of the recorded current or a map of the calculation results based on several current levels, so that the recording can be visualized at various locations on the cutting surface. The map can then be interpreted as a "bone density map", which can be used as an input for another application. Algorithms may be needed to interpret and correct the data, for example, taking into account that the displacement load may be different in one direction and the opposite direction when the bone drill is always rotating in the same direction, or taking into account that the cutting tool may also be worn during surgery, which may affect the current level.

Claims

1. A robotic system for removing bone material from an anatomical structure of a patient, comprising: - a base (4), - an end effector (2) configured to hold the surgical tool (1), an actuation unit (3) configured to translate the end effector relative to the base at least along one feed axis (A), a control unit coupled to the actuation unit (3) and configured to close the surgical tool (1) and to command the actuation unit (3) to translate the end effector (2) along the feed axis (A) when the surgical tool is closed so as not to rotate, The control unit includes a feedback unit configured to measure the force applied by the surgical tool (1) to the anatomical structure when the surgical tool is not rotating during the translation of the end actuator (2), and to determine the presence or absence of residual bone material of the anatomical structure in front of the surgical tool based on the measured force.

2. The robotic system of claim 1, further comprising a user interface configured to display information related to the presence of bone material in the anatomical structure along the feed axis.

3. The robotic system according to claim 1 or claim 2, wherein the control unit is configured to prevent activation of the surgical tool if the feedback unit does not detect any contact of the surgical tool with bone material.

4. The robotic system according to one of claims 1 to 2, wherein the control unit is configured to generate a warning if the feedback unit does not detect any contact of the surgical tool with bone material.

5. The robotic system according to one of claims 1 to 2, wherein the control unit is configured to close the surgical tool and to command the actuation unit to move the end effector along the feed axis at predetermined time or distance intervals.

6. A robotic system according to one of claims 1 to 2, wherein the feedback unit comprises at least one sensor, the at least one sensor being configured to measure the intensity of an electric current supplied to the actuation unit, the feedback unit being configured to monitor changes in the intensity over time during the translation of the end effector (2), and to detect contact of the surgical tool (1) with the bone material of the anatomical structure if the intensity exceeds a predetermined threshold.

7. The robotic system according to one of claims 1 to 2, further comprising a support unit (5) connected to the base (4) and comprising at least one element designed to contact the anatomical structure or an area of ​​the patient's body adjacent to the anatomical structure so as to provide a local mechanical link between the surgical tool (1) and the anatomical structure.

8. The robotic system according to one of claims 1 to 2, further comprising a holding arm (6) having one end (60) rigidly attached to the base (4) and an opposite end configured to be attached to a structure (8) fixed relative to the patient.

9. The robotic system according to one of claims 1 to 2, further comprising a tracker (70) rigidly attached to the end effector and suitable for being positioned by a positioning system (7), wherein the feedback unit is configured to take into account the positioning data of the tracker (70) to detect contact between the surgical tool (1) and the bone material of the anatomical structure.

10. The robotic system according to one of claims 1 to 2, further comprising a surgical tool (1) configured to remove bone material from the anatomical structure rigidly attached to the end effector.

11. The robotic system according to claim 10, wherein the surgical tool (1) is a bone drill.

12. The robotic system according to claim 10, wherein the surgical tool (1) is a round bone drill.

13. The robotic system according to one of claims 1 to 2, wherein the control unit is configured to record at least one physical parameter of the robotic system associated with bone mineral density.

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