Patent Publication Number: US-2023134629-A1

Title: On-bone robotic system for computer-assisted surgery

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims the priority of U.S. Patent Application No. 63/274,554, filed on Nov. 2, 2021 and incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The application relates to computer-assisted surgery and, more particularly, to robotic tools, roboticized tools and implantable electronics used in surgical procedures. 
     BACKGROUND 
     In orthopedic surgery, robots are increasingly used to perform bone resection, to guide the positioning of implants, among other actions, in the context of computer-assisted surgery. Whether the robots are of collaborative nature or autonomous, the use of robots may contribute to increasing the precision and accuracy of bone-altering procedures. Robotic arms are tracked so as to navigate their various implements relative to the bone, i.e., obtain position and/or orientation data relating the robot implements to bone landmarks. 
     However, robots tend to have a non-negligible footprint in the operating room. Robotic systems typically have their own stand and/or station, and may consequently be an obstacle limiting personnel movement around the patient. Moreover, in some instances, robotic systems are used jointly with voluminous tracking systems, such as optical tracking devices, that also add to the space management concern in the operating room. It would be desirable to reduce the footprint of robots used in surgical procedures. 
     SUMMARY 
     In a first aspect, there is provided an on-bone robotic system comprising a bone anchor device configured to be received in a bone, the bone anchor device including at least one sensor for tracking an orientation of the bone; a robotic tool unit releasably connected to the bone anchor device, the robotic tool unit including at least one actuator for displacing a surgical implement of the robotic tool unit relative to the bone when the robotic tool unit is connected to the bone anchor device; wherein the on-bone robotic system includes at least one joint enabling at least one degree of freedom of movement of the surgical implement relative to the bone anchor device; and wherein the on-bone robotic system includes a processor for operating the at least one actuator as a function of the tracking of the bone by the sensor. 
     Further in accordance with the first aspect, for example, the bone anchor device has a receptacle configured to be received in the bone, the receptacle accommodating the at least one sensor. 
     Still further in accordance with the first aspect, for example, a leading end of the bone anchor device is flared. 
     Still further in accordance with the first aspect, for example, an anti-rotation feature projects laterally from the receptacly. 
     Still further in accordance with the first aspect, for example, the anti-rotation feature includes at least one fin. 
     Still further in accordance with the first aspect, for example, the at least one sensor includes an inertial sensor. 
     Still further in accordance with the first aspect, for example, the bone anchor device includes a battery. 
     Still further in accordance with the first aspect, for example, the bone anchor device is configured to be used as an implant to track movement of the bone post-operatively. 
     Still further in accordance with the first aspect, for example, the at least one actuator includes at least one motor. 
     Still further in accordance with the first aspect, for example, there may be two of the motor, the robotic tool unit displacing the surgical implement in at least two rotational degrees of freedom. 
     Still further in accordance with the first aspect, for example, the at least one actuator includes at least one linear actuator. 
     Still further in accordance with the first aspect, for example, the surgical implement has a cut slot. 
     Still further in accordance with the first aspect, for example, the robotic tool unit includes at least one sensor for tracking an orientation of the surgical implement. 
     Still further in accordance with the first aspect, for example, the robotic tool unit includes at least one camera oriented toward the bone and configured to capture images of the bone. 
     Still further in accordance with the first aspect, for example, a communication device may be connected to the processor and configured for wireless communication. 
     In accordance with a second aspect of the present disclosure, there is provided a method for performing an orthopedic procedure comprising: anchoring an on-bone robotic system to a bone via a bone anchor device inserted in the bone, the bone anchor device including at least one sensor for tracking an orientation of the bone; operating the on-bone robotic system for the on-bone robotic system to displace a surgical implement operatively connected to the bone anchor device, a movement of the surgical implement being guided as a function of the tracking of the bone by the sensor; and detaching at least the surgical implement from the bone anchor device to leave the bone anchor device as an implant post-operatively, the bone anchor device configured to track the bone post-operatively. 
     Further in accordance with the second aspect, for example, anchoring the on-bone robotic system to the bone including drilling a hole in the bone for insertion of the bone anchor device in the hole. 
     Still further in accordance with the second aspect, for example, insertion of the bone anchor device in the hole includes having an anti-rotation feature penetrate the bone. 
     Still further in accordance with the second aspect, for example, the movement in the operating includes moving the surgical implement in at least one rotational degree of freedom. 
     Still further in accordance with the second aspect, for example, moving the surgical implement includes actuating a rotational motor to move the surgical implement in the at least one rotational degree of freedom. 
     Still further in accordance with the second aspect, for example, the movement in the operating includes moving the surgical implement in two rotational degrees of freedom. 
     Still further in accordance with the second aspect, for example, the movement in the operating includes moving the surgical implement in one translational degree of freedom. 
     Still further in accordance with the second aspect, for example, the method may include imaging the bone from the on-bone robotic system. 
     Still further in accordance with the second aspect, for example, the method may include matching the imaging of the bone from the on-bone robotic system with a pre-operative virtual model of the bone for navigating a position and orientation of the surgical implement relative to the bone. 
     Still further in accordance with the second aspect, for example, the method may include wirelessly communicating data from the at least one sensor. 
     In accordance with a third aspect, there is provided a system for tracking a bone intraoperatively in a surgical procedure and post-operatively, comprising: a processing unit; and a non-transitory computer-readable memory communicatively coupled to the processing unit and comprising computer-readable program instructions executable by the processing unit for: obtaining orientation data of at least one sensor in a bone anchor device anchored to a bone, intraoperatively; actuating at least one actuator to displace a surgical implement operatively connected to the bone anchor device as a part of an on-bone robot, as a function of the orientation data; and after the surgical procedure, obtaining orientation data of at least one sensor in the bone anchor device remaining anchored to the bone, post-operatively. 
     Further in accordance with the third aspect, for example, actuating at least one actuator includes actuating at least one rotational motor to orient the surgical instrument relative to the bone in one rotational degree of freedom. 
     Still further in accordance with the third aspect, for example, actuating at least one actuator includes actuating a second rotational motor to orient the surgical instrument relative to the bone in a second rotational degree of freedom. 
     Still further in accordance with the third aspect, for example, actuating at least one actuator includes actuating at least one linear actuator to displace the surgical instrument relative to the bone in a translational degree of freedom. 
     Still further in accordance with the third aspect, for example, the method may include imaging the bone from the on-bone robot. 
     Still further in accordance with the third aspect, for example, the method may include matching the imaging of the bone from the on-bone robot with a pre-operative virtual model of the bone for navigating a position and orientation of the surgical implement relative to the bone. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       Reference is now made to the accompanying figures in which: 
         FIG.  1    is a schematic view of an on-bone robotic system in accordance with an aspect of the present disclosure; 
         FIGS.  2 A and  2 B  are schematic views showing the on-bone robotic system of  FIG.  1    relative to a distal femur; 
         FIGS.  3 A,  3 B and  3 C  are schematic views of the on-bone robotic system of  FIG.  1   , with an alignment plate implement; 
         FIGS.  4 A and  4 B  are a schematic views of the alignment plate implement with bone contacting actuators in accordance with an aspect of the present disclosure; 
         FIGS.  5 A to  5 D  are schematic illustrations of the robotic system of  FIG.  1    with a cutting guide implement; 
         FIGS.  6 A to  6 C  are a series of views showing the on-bone robotic system of  FIG.  1   , as used on a tibia in accordance with an aspect; 
         FIGS.  7 A to  7 C  are a series of views showing the on-bone robotic system of  FIG.  1   , as used on a tibia in accordance with another aspect; 
         FIGS.  8 A to  8 E  are schematic views of the on-bone robotic system of  FIG.  1    using a provisional implant surgical implement; 
         FIG.  9    is a perspective view of a variant of a cutting block surgical implement of the on-bone robotic system of  FIG.  1   ; 
         FIG.  10    is a schematic perspective view of another variant of a cutting block surgical implement of the on-bone robotic system of  FIG.  1   ; and 
         FIG.  11    is a schematic side view of another variant of a cutting block surgical implement of the on-bone robotic system of  FIG.  1   . 
     
    
    
     DETAILED DESCRIPTION 
     Referring to the drawings and more particularly to  FIG.  1   , there is illustrated an on-bone robotic system at  10 . The on-bone robotic system  10  is of the type used as part of computer-assisted surgery, to provide guidance to an operator in performing orthopedic surgery. Accordingly, the on-bone robotic system  10  may have electronic components and actuators so as to perform some automated functions described herein, and/or to guide an operator in performing alterations to a bone and placing implants (onboard electronics). Moreover, the on-bone robotic system  10  may include components that may be implanted in the patient&#39;s body (occasionally referred to as a wearable), that can provide navigation data intra-operatively and optionally post-operatively. In the following figures, the robotic system  10  is shown in a knee replacement surgical procedure that involves the resection of bone to define cut planes on a distal femur and at a tibial plateau. However, it is contemplated to use the on-bone robotic system  10  for other types of surgical procedures. 
     In  FIG.  1   , the on-bone robotic system  10  is shown in a schematic manner, as having a bone anchor device  20  and a robotic tool unit connectable to the bone anchor device  20 . The robotic tool unit may include a robotic base  30  and an exemplary surgical implement  40 , that may be integrally connected or releasably connected to one another. Other surgical implements that may be part of the robotic tool unit are shown as  50 ,  60 ,  70  and  80  and are described hereinbelow. The robotic base  30  and the surgical implement  40  are shown as being separated and interconnectable, but they may be as one component that may be connected to the bone anchor device  20 . Herein, for simplicity, components of the bone anchor device  20  will be in the  20   s,  such as receptacle  21 , etc. The same nomenclature is used for the robotic base  30  and for the surgical implements  40 ,  50 ,  60 ,  70  and  80 . The bone anchor device  20  may perform different functions. It may serve as an anchor or attachment for other components of the on-bone robotic system  10 . It may also be configured to track the bone to which it is connected, such as by providing orientation data related to the bone. For example, the bone anchor device  20  may produce data indicative of a location of a mechanical axis of a bone. The bone anchor device  20  may also be used as an implanted electronic device, to provide bone related data post-operatively, such as movements associated with a gait, e.g., range of motion, with flexion/extension, forces, step count, stride length, among others. The robotic tool unit attaches to the bone anchor device  20  with its robotic base  30  and is used intra-operatively to perform various functions associated for example with the surgical implement(s)  40  connected to the robotic base  30 . The robotic base  30  may be separated from the bone anchor device  20 , for embodiments in which the bone anchor device  20  becomes a post-operative implanted electronic device. 
     Referring concurrently to  FIGS.  1 ,  2 A and  2 B , the bone anchor device  20  is of the type that penetrates into a bone. In the embodiment of  FIGS.  2 A and  2 B , the bone anchor device  20  is anchored to a distal femur F, and may be used to track bone landmarks of the femur F, such as a mechanical axis, in three-dimensional space. Values such as varus/valgus and flexion/extension may be derived from the mechanical axis, whereby the tracking of the mechanical axis via the bone anchor device  20  may serve this purpose. 
     The bone anchor device  20  is configured to be received in a cavity in the bone. For example, as shown in  FIGS.  2 A and  2 B , the bone anchor device  20  is received in a cavity formed in the intercondylar fossa of the distal femur F, as one possible location for receiving the bone anchor device  20 .  FIGS.  6 A- 6 C and  7 A- 7 C  show the bone anchor device  20  in the proximal tibia. The bone anchor device  20  encloses electronic components and therefore defines a receptacle  21  or like body to accommodate the electronic components. The receptacle  21  in  FIG.  1    is schematically shown as being cylindrical in shape, but may have other shapes. In an embodiment, it is considered to drill a hole in the bone so as to introduce therein the bone anchor device  20 , with the cylindrical shape of the receptacle  21  being well suited to be received in a drilled hole. The receptacle  21  is configured to be connected to the robotic base  30  and therefore may have a connector  21 A. In the illustrated embodiment, the connector  21 A is shown as being a hole (e.g., threaded hole), but may have other forms, such as projecting members like a shaft, a rod, or may integrate a quick-connect system features, etc. The connector  21 A is complementary to a connector of the robotic base  30  and is selected for the connection between the bone anchor device  20  and the robotic base  30  to be geometrically determined, i.e., once the bone anchor device  20  and the robotic base  30  are connected to one another, some geometrical data is known, such as a distance between the bone anchor device  20  and the robotic base  30 , an orientation between coordinate system xyz 1  and xyz 2  associated respectively with the bone anchor device  20  and the robotic base  30 , if movement between the bone anchor device  20  and the robotic base  30  is possible after interconnection. Indeed, the connector  21 A may be part of a joint allowing relative movement between the bone anchor device  20  and the robotic base  30 . The joint(s) may include a spherical joint, a universal joint, and a telescopic joint, for example. 
     Electronic components  22  are received in the receptacle  21  of the bone anchor device  20 . In an embodiment, the bone anchor device  20  is autonomous in that it may operate in and of itself to produce signals. Therefore, as part of the electronic components  22 , there may be a processor/memory to execute particular functions. The memory may include non-transitory instructions executable by the processor to perform given functions detailed below. As the bone anchor device  20  may remain implanted in the bone post-surgery, a power source such as a battery may be part of the electronic components  22 . The bone anchor device  20  as set out above is tasked with tracking the bone in space. Therefore, an inertial sensor(s) is part of the electronic components. The inertial sensor may be known as a sourceless sensor, a micro-electromechanical sensor unit (MEMS unit), and has any appropriate set of inertial sensors (e.g., accelerometers, gyroscope) to produce tracking data in at least three degrees of rotation (i.e., the orientation about a set of three axes is tracked). The inertial sensor may include a processor, including a printed circuit board, and a non-transitory computer-readable memory communicatively coupled to the processor and comprising computer-readable program instructions executable by the processor, or may use the processor/memory described above. Moreover, the inertial sensor may be self-contained, in that they may be pre-calibrated for operation, have their own powering or may be connected to a power source, and may have an interface, such as in the form of a display thereon (e.g., LED indicators). 
     Further, as part of the electronic components, a communication device may be present for the bone anchor device  20  to issue signals indicative of the orientation of the bone. The communication device may be a wireless device that may use any appropriate wireless communication protocol, such as Bluetooth®, Wi-Fi, etc. 
     It is desired that the bone anchor device  20  remain anchored in a fixed position and orientation relative to the bone. In a variant, it may be possible to impact the bone anchor device  20  in the bone. Therefore, a spike  23 A or like flaring end (e.g., frusto-conical end) may project from a leading end of the bone anchor device  20 , as projecting from the receptacle  21 , the flaring shape being from the tip toward the trailing end. The spike  23 A is shown as having triangular fins that may facilitate the impacting of the bone anchor device  20  into the bone. However, if the bone anchor device is received in a drilled hole in the bone, the spike  23 A may be optional. Moreover, considering the penetration of the bone anchor device  20  into the bone, the spike  23 A may be received in cancellous bone, which may or may not provide sufficient purchase. Accordingly, one or more fins  23 B or like anchoring features may be at or near a trailing end of the receptacle  21 , for the fins  23 B to purchase into cortical bone. The fins  23 B may have a smaller profile than the spike  23 A, that may suffice in preventing rotation of the receptacle  21  in the bone, and ensure that the bone anchor device  20  does not move relative to the bone. Other anti-rotation features may be present as well. The fins  23 B may have a flaring profile from a leading to trailing direction to facilitate interaction with the surrounding bone. 
     For the inertial sensor within the electronic components  22  to perform a tracking of the axis of the bone receiving the bone anchor device  20 , appropriate calibration techniques may be used. In a variant, calibration is performed to create the axes or other landmarks. For example, the mechanical axis may be determined using the method described in U.S. Pat. No. 9,901,405, incorporated herein by reference. Other data that may be tracked by the bone anchor device  20  may include other axes, such as the medio-lateral axis of the femur, the frontal plane of the femur, a bone model of the femur, etc, in the context of the femur. In terms of pre-calibration, the position and orientation of the inertial sensor within the receptacle  21  may be known such that the inertial sensor may be associated to a given landmark of a bone upon insertion. For example, the bone anchor device may be calibrated relative to the entry point of a mechanical axis (e.g., tibia) by the its positioning in a drilled hole at the entry point in the tibia. 
     In order to accommodate the electronic components  22 , and to limit its invasiveness, the receptacle  21  has a given volumetric size. In an embodiment, a diameter of the receptacle  21  is between 8 mm and 10 mm, though other dimensions may be possible. A height of the receptacle  21  may be between 8 and 15 mm, though it may be smaller or larger than that. 
     Referring to  FIG.  1   , the robotic base  30  and the surgical implement  40  may form part of the robotic tool unit that is used with the bone anchor device  20 , to perform given tasks on the bone. The robotic tool unit may be available as a whole, i.e. integrating the robotic base  30  and the surgical implement  40  together, though it may be constituted of detachable components. i.e., the robotic base  30  and the surgical implement  40  being releasably connected. The releasable connection may allow the use of different surgical implements  40  with a same robotic base  30 , thereby reducing the cost of the robotic tool units as a common robotic base  30  with its electronic and mechanical components may be shared by the surgical implements  40 . During a surgical procedure, the robotic tool unit is moved relative to the bone and may be used by the user as a physical interface to perform functions on the bone, while the bone anchor device  20  is anchored to the bone and serves as a base for the robotic tool unit. 
     In  FIG.  1   , the robotic base  30  is in an exploded relation with the bone anchor device  20 . The robotic base  30  may be releasably connectable to the bone anchor device  20 . The robotic base  30  may also define a receptacle  31  so as to receive therein electronic, mechanical and/or electro-mechanical components  32 , 42 . The electronic, mechanical and/or electro-mechanical components  32 , 42  may also be within the surgical implement  40 , hence the use of reference numeral  42 . Stated differently, the electronic and/or mechanical components  32 , 42  may be part of the robotic tool unit, i.e., a combination of the robotic base  30  and the surgical implement  40 . The receptacle  31  has a connector  31 A that is configured to be connected to the connector  21 A of the bone anchor device  20 . For example, the connector  31 A is shown as being a shaft, as one possible means to be connected to the connector  21 A of the bone anchor device  20 . In an embodiment, the connectors  21 A and  31 A concurrently define one or more joints, to allow given movements of the robotic tool unit relative to the bone anchor device  20 . For example, with reference to xyz 1  in  FIG.  1   , i.e., the referential system of the bone anchor device  20  that is fixed to the bone, the robotic tool unit, including the robotic base  30  and/or the surgical implement  40 , may move in translation toward and away from the bone anchor device  20 , e.g., in a direction generally parallel to the mechanical axis of the femur F. The movement in translation may be limited to one degree of freedom (DOF). The robotic tool unit, including the robotic base  30  and/or the surgical implement  40 , may also rotate relative to the bone anchor device  20 , in two or three DOFs. One rotational DOF of a joint between the robotic tool unit and the bone anchor device  20  may be aligned with the femur for rotation about a medio-lateral axis of the femur F, for flexion-extension plane adjustment. Another rotational DOF of the joint between the robotic tool unit and the bone anchor device  20  may be aligned with the femur for rotation about an anterior-posterior axis of the femur F, for varus-valgus adjustment. A third rotational DOF may be aligned with the axis of the bone anchor device  20 , allowing a rotational adjustment about the posterior condyles or the epicondyles of the femur. This may allow an adjustment using the condyle abutment member described below. 
     Connectors  31 B may also be provided on the receptacle  31  for connection of the surgical implement(s)  40  to the robotic base  30 , if they are not integrally connected. The connectors  31 B are shown as being threaded holes, but other connection components may be present, for instance quick connect features such as clips, tongues, etc, or other types of complementary connections. In a variant, the robotic base  30  is fixed in movement relative to the bone anchor device  20 , while the surgical implement(s)  40  may move relative to the robotic base  30  and thus relative to the bone anchor device  20 , by one or more joints between the robotic base  30  and the surgical implement  40 . The robotic base  30  and the surgical implement  40  may be releasably connected, as shown in  FIG.  1   , with connector holes  41 B aligned with the holes  31 B in the robotic base  30 , for fastener connection, as a possibility. The movements may be as described above for a joint between the bone anchor device  20  and the robotic base  30 , i.e., one translational DOF, and two or more rotational DOFs.  FIGS.  3 A,  3 B and  3 C  show an exemplary spherical joint  33  and a translational joint  34  between the surgical implement  40  and the robotic base  30 , to illustrate one contemplated manner to move the surgical implement  40  relative to the femur F, in two or more rotational degrees of freedom. Other joint arrangements are possible to provide any suitable or desired degrees of freedom of movement. As an example, the surgical implement  40  has a cut slot  41 A, but may have different and/or other guiding features (e.g., drill guides, abutment features, etc). 
     Among the electronic and/or mechanical components  32 , 42 , the robotic base  30  may include a processor/memory having non-transitory instructions for the processor to perform given functions associated with the surgery. Rotational motors may be provided in the electronic and/or mechanical components  32 , 42  and may be used to control rotation of the robotic base  30  relative to the bone anchor device  20  or of the robotic base  30  relative to the surgical implement  40 . Movements of the robotic base  30  may be also be controlled using microgears, linear actuators or fluids (air, oil, water). An example thereof is provided below. In an embodiment, the rotational motors are controllable to cause movement of the receptacle  31  relative to the connector  31 A, with the connector  31 A being part of the joint between the bone anchor device  20  and the robotic base  30 . Therefore, with the surgical implement  40  connected to the robotic base  30 , movement of the robotic base  30  may cause movement of the surgical implement  40  relative to the bone. A linear actuator may be present as part of the components  32 , 42  and may actuate the translational movement between the robotic base  30  and the bone anchor device  20 . Stated differently, the robotic base  30  may move closer or farther from the bone anchor device  20 . Force sensors may also be present as part of the components  32 , 42  in the robotic base  30  or may be in the surgical implement  40 . Rotary encoders may be present to determine an orientation of the robotic base  30  relative to the bone anchor device  20  if one is moveable relative to the other by way of one or more joints. Alternatively, the rotary encoders may determine an orientation of the surgical implement  40  relative to the robotic base  30  if one may rotate relative to the other. Any appropriate power source is part of the components  32 , 42 . For example, the robotic tool unit may be wired to a power source, or may have a battery. A communication device may also be present for communication between the robotic tool unit and the bone anchor device  20  or with a processor separate from the on-bone robotic system  10 . While rotary encoders may determine the relative orientation between the robotic base  30  and the bone anchor device  20 , an inertial sensor may be present in the robotic base  30  or the surgical implement  40  to monitor an orientation of the robotic tool unit. It is also possible to use optical tracking technologies to observe a rotation of the robotic base  30  relative to the bone and/or bone anchor device. For example, the optical tracking technologies may include laser rangefinders that are part of the robotic base  30  and that project light, for instance on the bone. One or more cameras may also be provided as part of the components  32 , 42 , the expression “camera” encompassing the various hardware and software components necessary to perform imaging (e.g., lens(es), aperture, image sensor such as CCD, image processor). The cameras may come as a set to operate as a depth camera system. The cameras may be on the robotic base  30  and/or on the surgical implement  40 , with suitable distance given to the lenses of the camera(s) to observe the bone to which the on-bone robotic system  10  is mounted and/or to observe the environment of the bone—lenses shown at  42 A in  FIG.  1    being an example. For instance, the camera(s) may be used to image a bone surface. The imaging may then be used to match the imaged bone surface to a bone model (e.g., 3D virtual bone model) obtained via different preoperative or intraoperative imaging (e.g., CT scans, radiography in its various forms), and programmed into the memory of the on-bone robotic system  10  or accessible by the on-bone robotic system  10 . Hence, the presence of camera(s)  32 , 42 , on the on-bone robotic system  10  may contribute to the calibrating of the system relative to the bone, and to the subsequent navigation. The camera(s)  32 , 42  may for example have a unique perspective of voids, depressions on bones. As another possibility, a cutter actuator may be present as part of the robotic tool unit, if the surgical implement  40  is configured to perform cuts, as described hereinbelow. The cutter actuator may be a motor(s), an ultrasonic oscillator, a linear actuator, etc. 
     Now that the general configuration of the on-bone robotic system  10  has been described, a surgical procedure involving the system  10  is set forth, by which different types of surgical implements  40  may be used. The surgical procedure is a knee replacement procedure, in which a tibial plateau implant is installed on a tibia, and a femoral component is implanted on the distal femur. The on-bone robotic system  10  may be used in other types of surgery, for instance with a partial proximial tibia procedure, distal femur only, proximal tibia only, hip surgery (e.g., partial hip replacement, total hip replacement), hip resurfacing, shoulder surgery, etc. 
     As a starting point, the bone anchor device  20  is installed in the bone. For example, the bone anchor device  20  is in the intercondylar fossa (e.g., within the intramedullary canal, or medullar canal), and is tasked with tracking a landmark of the femur F, such as a referential system including a mechanical axis. Other locations on the femur F are also possible for the bone anchor device  20 . 
     Referring to  FIGS.  3 A,  3 B and  3 C , anterior and side views of the femur with the on-bone robotic system  10  are provided. The surgical implement  40  is shown as being an alignment plate that may be displaceable so as to contact the distal aspects of the condyles. Accordingly, the alignment plate has an abutment plane  40 A, and joint(s) in the robotic tool unit or between the robotic tool unit and the bone anchor device  20  may allow the abutment plane  40 A to be brought into contact with the condyles, by translation and/or rotation. Though  FIGS.  3 A and  3 B  show a single plane for abutment with the distal aspects of the condyles, the surgical implement  40  may also have another abutment plane for abutment with the posterior aspects of the condyles, such as shown in  FIG.  3 B . In  FIG.  3 B , a condyle abutment member  40 B may be connected to the abutment plane  40 A, though alternatively it may be possible to have the condyle abutment member  40 B integrally part of the abutment plane  40 A. A translation movement between the abutment plane  40 A and the condyle abutment member  40 B is possible in an embodiment, by way of a translation joint. In an embodiment, the bone contact surfaces of the abutment plane  40 A and of the condyle abutment member  40 B are perpendicular relative to one another. The abutment contact may be automated by the on-bone robotic system  10 , with the force sensors determining if contact is achieved. With the components  22  and  32 , 42 , the orientation of the surgical implement  40  relative to the bone anchor device  20  may be known by sharing of orientation data, such that additional bone landmarks may be tracked. In a variant, the alignment plate is used to locate the medio-lateral axis, a plane of the posterior aspects of the condyles, and/or a plane of the distal aspects of the condyles and/or a plane aligned with both epicondyles. Once the mechanical axis is known, the robotic base  30  can align itself parallel to the mechanical axis and, using the actuation means described herein, may touch the most distal part of the condyle with the abutment plane  40  and record that landmark (most distal point of the femur), Bone cuts can then be made relative to that landmark, e.g., resect a plane 9 mm from the most distal femoral point. Also, the orientation of the cutting plane for the distal cut may include the palpation of the distal condyles with an angle of flexion, e.g., 3°, relative to the mechanical axis. 
     Referring to  FIG.  4 A , a variant of the abutment plate surgical implement  40  is illustrated, in which bone-contacting actuators  43  are provided at the corners or sides of the abutment plane  40 A. The bone-contacting actuators  43  each have a piston or like movable component  43 A projecting out of the abutment plane  40 A. The movable components  43 A are configured to contact given landmarks of the bone, such as the distal features of the condyles. For example, the bone-contacting actuators  43  are stepper motors, ball-screw motors, or equivalents, that have an output rod defining the movable components  43 A. Rotation of the bone-contacting actuators  43 , may result in a projecting movement of the movable components  43 A, and may hence be performed for adjusting the orientation of the surgical implement  40  relative to the bone for instance via the spherical joint  33 . Concurrent rotation of the bone-contacting actuators  43  may also be performed to cause a spacing of the abutment plane  40 A from the bone, via the translational joint  34 . 
     For example, there may be four such bone-contacting actuators  43 , though only two are visible from the point of view of  FIG.  4 A . Therefore, as the abutment plate surgical implement  40  may have its orientation known relative to the bone axis via the bone anchor device  20  (e.g., inertial sensor in the electronic components  22 ), the bone-contacting actuators  43  may be controlled to orient the abutment plate surgical implement  40  to a desired orientation, relative to anatomical features of the femur, such as the mechanical axis, and/or to space the abutment plate surgical implement  40  from the femur F. It is therefore possible to allow a varus/valgus adjustment and/or flexion/extension slope adjustment of an eventual resection plane via the orientation of the surgical implement  40  relative to the femur F, notably by the degrees of freedom present in the robotic tool unit, or between the bone anchor device  20  and the robotic base  30 . The control of the bone-contacting actuators  43  may be used to set the abutment plate surgical implement  40  to a desired orientation and/or position, and hold the abutment plate surgical implement  40  in the desired orientation. If the bone-contacting actuators  43  are operated concurrently, it is also possible to move the surgical implement  40  axially relative to the bone, if a translational degree of freedom is present in the robotic tool unit or between the bone anchor device  20  and the robotic base  30 . The bone-contacting actuators  43  may be self-locking in that they may hold their length unless actuated. Therefore, once the bone-contacting actuators  43  hold their length and abut the bone, the abutment plate surgical implement  40  may be in a fixed position and orientation relative to the bone, for example as hovering over the bone, and can serve as a structure to support additional components. The desired position and/or orientation may be automated and/or effect on-bone, with the robotic system  10  operated to achieve the desired position and/or orientation for the abutment plate surgical implement  40 . 
     Referring to  FIG.  4 B , another embodiment is shown, in which the abutment plate surgical implement  40  has the movable components  43 A displaceable using cylinders, also known as pistons, shown as  43 B, whether there are two or more of the cylinders  43 B. The cylinders  43 B may be hydraulic or air powered cylinders, etc. As described in U.S. Patent Application Publication 2009/0018544A1 to Zimmer, Inc., which is incorporated herein by reference , each cylinder may have its own valve to control the length of the cylinder  43 B. The pressure source may be integrated, or may be separate from the on-bone robotic system  10 . 
     Referring to  FIGS.  5 A and  5 B , once the desired position and/or orientation is achieved for the abutment plate surgical implement  40  relative to the femur, another implement, such as a cutting guide  50 , may be secured to the abutment plate surgical implement  40 . The cutting guide  50  may have one or more cut slot(s)  51  and pinholes  52  for the cutting guide  50  to be secured to the bone. The exemplary embodiment is configured for the creation of a distal cut, but other cut slots may be present, for other cuts such as the anterior cut, the anterior chamfer, the posterior chamfer, and/or the posterior cut. The cut generated using the cut slot  51  may be a provisional cut, for instance to support a provisional implant. 
     The cutting guide  50  is in a known geometrical relation with respect to the abutment plate surgical implement  40  when attached to it, such that a cut plane machined via the cut slot  51  is in a desired position and orientation relative to the bone. The on-bone robotic system  10  may be operated to guide in the resection of cut planes in a navigated orientation relative to bone landmarks tracked by the bone anchor device  20 , such as the mechanical axis of the femur F, taking into consideration the geometry of the cutting guide  50  and the geometrical relation between the cutting guide  50  and the surgical implement  40  when displacing the surgical implement  40 . Therefore, following  FIG.  4 A  or  FIG.  4 B  in which an orientation of the abutment plate of the surgical implement  40  is adjusted via the electronic components  22  and  32 , and  FIGS.  5 A and  5 B  in which the cutting guide  50  is secured to the surgical implement  40  to having the cut slot(s)  51  at a desired location, the cutting guide  50  may be pinned to the bone, with pins  53  as in  FIG.  5 B , or attached to it in another other manner. The cameras  32  may be used to provide video imaging by which the cutting guide  50  may be positioned and oriented relative to the bone. The robotic tool unit (i.e., including the robotic base  30  and the surgical implement  40 ), may be removed to enable the distal cut. The bone anchor device  20  may remain in the bone after the cutting guide  50  is secured to the bone, and be used to track movements of the bone as described above. 
     Consequently, the on-bone robotic system  10  featuring the surgical implements  40  and/or  50  (the cutting guide  50  and the alignment plate surgical implement  40  may be a single device) may self-align relative to the femur F, by performing its femoral registration, and may guide femoral cuts. The self-alignment may also involve the imaging using the cameras  32 , for example using a 3D model of the bone. Moreover, the imaging from cameras or laser(s) from the components  32 , 42  may be used to determine the depth of resection relative to a landmark (e.g., malleoli for the tibia), such that laxity values can be calculated using virtual implant geometries. If the bone anchor device  20  is a implanted electronic device that is used post-operatively, the coordinates of the various planes resulting from the femoral registration may be transferred to the electronic components  22  of the bone anchor device  20 , as data used in the post-operative tracking. 
     Referring now to  FIGS.  6 A to  6 C , the on-bone robotic system  10  may also be used to create a cut plane on the proximal tibia T, to define a tibial plateau for receiving an implant. Accordingly, the on-bone robotic system  10  may have the bone anchor device  20 , and the robotic tool unit including the robotic base  30  and surgical implements of different types. In  FIGS.  6 A to  6 C , the cutting implement is defined by a cutting guide  60  having a cut slot  61 , and pinholes  62  for securing the cutting guide  60  to the tibia T. The pinholes  62  are one solution among others to secure the cutting guide  60  to the tibia T. An articulated mechanism  63  may mechanically connect the cutting guide  60  to the robotic base  30 . Appropriate joints may be present in the articulated mechanism  63  to allow a movement of the cutting guide  60  relative to the robotic base  30 , such as a sliding or telescopic joint  63 A, a first rotational joint  63 B (e.g., revolute joint), and a second rotational joint  63 C (e.g., revolute joint). The joints  63 A,  63 B and  63 C are shown being in a serial arrangement, but other arrangements are considered, such as by combining the joints  63 B and  63 C in a single rotational joint having two rotational degrees of freedom (e.g., spherical joint, universal joint). 
     Movements of the cutting guide  60  may be navigated in position and/or orientation through the appropriate electronics  22 ,  32  that are part of the robotic system  10 , so as to provide a desired orientation to the tibial plateau relative to a landmark of the tibia, such as the mechanical axis, the topmost point of the tibial plateau, or deepest point of the tibial plateau. If present, the cameras  32  may optionally be used to provide video imaging by which the cutting guide  60  may be positioned and oriented relative to the bone. A 3D virtual model of the tibial plateau may be used to be overlaid with the footage of the cameras  32  as a reference. Accordingly, in a variant, the positioning of the cutting guide  60  may be based on imaging, for example, with the imaging being used to determine the deepest point on the tibial plateau. Moreover, some or all of the various degrees of freedom in the articulated mechanism  63 , between the cutting guide  60  and the bone anchor device  20 , may be actuated by the actuators within the robotic tool unit to automate or control the position and/or orientation of the cut slot  61  relative to the tibia T. The bone anchor device  20  that is used in  FIGS.  6 A to  6 C  may navigate a mechanical axis of the tibia. Various techniques and tools may be used to calibrate the bone anchor device  20  and enable it to track tibial landmarks, such as those described in U.S. Pat. No. 10,729,452, incorporated herein by reference, according to which the mechanical axis of the tibia T may be digitized and tracked by an inertial sensor, such as the one present in the bone anchor device  20 . Thus the orientation of the cut slot  61  may be adjusted in relation to a varus-valgus (e.g., joint  63 B) and/or slope (e.g. joint  63 C). 
     Once the cutting guide  60  is appropriately placed relative to the tibia T, the cutting guide  60  may be anchored to the bone, for example by pins in the pinholes  62 . Components of the robotic tool unit may be removed, such as the robotic base  30  and the articulated mechanism  63 . The bone anchor device  20  may also be removed, or may remain in the tibia T, deep enough so as not to intersect the cut plane of the cut slot  61 . If it remains in the tibia T, the bone anchor device  20  may be used for post-operative motion tracking. Moreover, the bone anchor device  20  may be connected to a tibial plateau implant to receive force sensing data from force sensors in the implant. 
     Referring now to  FIGS.  7 A to  7 C , another approach is shown for creating a proximal tibial plane. The surgical implement of the robotic system  10  includes a milling tool or like cutting tool  70  that is translated onto the bone surface by the articulated mechanism  63 . Therefore, as part of  FIG.  7 A , an orientation of the cutting tool  70  is adjusted to achieve, for example, a desired orientation between the cutting implement  70  and the tibia. Again, various techniques and tools may be used to calibrate the bone anchor device  20  and enable it to track tibial landmarks, such as those described in U.S. Pat. No. 10,874,405, incorporated herein by reference, according to which the mechanical axis of the tibia T may be digitized and tracked by an inertial sensor, such as the one present in the bone anchor device  20 . Thus, the orientation of the cutting tool  70  may be adjusted in relation to a varus-valgus (e.g., joint  63 B) and/or slope (e.g. joint  63 C).The cutting implement  70  may then be translated onto a top surface of the tibial plateau, by way of joint  63 A, after having been properly oriented, to resurface the tibial plateau. The robotic system  10  may control the translational movement to achieve a desired resection depth of the tibial plateau. Hence, the articulated mechanism  63  may drive the movement of the cutting implement  70 , though manual assistance may be used as well. 
     The on-bone robotic system  10  featuring the surgical implements  60  and/or  70  may self-align relative to the tibia T, by performing its tibial registration, and may guide tibial cut, or perform the tibial cut itself. If the bone anchor device  20  is an implanted electronic device that is used post-operatively, the coordinates of the plane resulting from the tibial registration may be transferred to the electronic components  22  of the bone anchor device  20 , as data used in the post-operative tracking. 
     Referring to  FIGS.  8 A to  8 E , the on-bone robotic system  10  is shown using a provisional implant  80 , as surgical implement for the robotic tool unit, in conjuction with the robotic base  30 , and operating with the bone anchor device  20  described above. The provisional implant surgical implement  80  may be used intraoperatively, after a preliminary cut of the distal femur has been made. The provisional implant surgical implement  80  is used to assist in determining a desired position and/or orientation of the femoral implant relative the femur F, by providing data associated with soft tissue balancing of the bone. The provisional implant surgical implement  80  may therefore have a geometry emulating a shape of a femoral implant, with a distal surface  80 A and a posterior surface  80 B, the posterior surface  80 B having condyle-like formations. The provisional implant surgical implement  80  may have appropriate force sensors, as part of the electronics/mechanical components  42 , to gather force data for various flexion-extension and/or varus-valgus angles at the knee. Accordingly, in order to enable soft tissue balancing, the provisional implant surgical implement  80  must be adjustable andmovable relative to the femur F, as described in U.S. Pat. Nos. 7,442,196, 10,555,822, and 10,485,554, which are incorporated by reference herein. Therefore, the preliminary cut(s) made in the distal femur, such as a posterior cut and/or a distal cut, must take into consideration the size of the provisional implant surgical implement  80  to allow movement of the provisional implant surgical implement  80 . Moreover, the preliminary cut(s) must be minimal to allow additional bone removal for the final cut(s) to be made for the femoral implant to be installed. 
     In an embodiment, the provisional implant surgical implement  80  is connected to the robotic base  30  by the spherical joint  33  and/or the translational joint  34  ( FIGS.  3 A,  3 B and  3 C ), such that the actuators within the on-bone robotic system  10  may lock the provisional implant surgical implement  80  in a given position and orientation, relative to the femur F, the femur F having its landmarks tracked by the bone anchor device  20 . The position and/or orientation of the provisional implant surgical implement  80  is tracked relative to the femur F, via the various possible electronic/mechanical components  32 , 42 , such as the encoders, the motors, the linear actuator and/or the inertial sensor. These components may be used in conjunction with the data provided by the inertial sensor in the bone anchor device  20 . With the provisional implant surgical implement  80  in a fixed position and orientation relative to the femur, various knee manipulations may be made to gather force sensor data, the force sensor data being correlated to the instant position and orientation of the provisional implant surgical implement  80 . Dynamic adjustments may be performed by the on-bone robotic system  10 , for instance if the force sensor data is above given thresholds, that may be indicative of soft-tissue unbalance. The dynamic adjustements may be achieved by adjustments to the position and/or orientation of the provisional implant surgical implement  80 , such as to reproduce given varus-valgus angles, flexion-extension angles, femur rotation in flexion and/or femur length. Once sufficient data has been acquired by the force sensors of the provisional implant surgical implement  80  to select a target femoral implant position and orientation, the provisional implant surgical implement  80  may be detached. A cutting guide implement, such as that shown at  40  in  FIG.  4 A  or  FIG.  4 B , may be attached to the robotic base  30 , or to the provisional implant surgical implement  80  in another embodiment, to position cut slot(s) at a position and orientation corresponding to the target femoral implant position and orientation, with the geometrical relation and size of the cutting guide implement  40  are taken into consideration. 
     As part of the surgical workflow involving the provisional implant surgical implement  80 , the preliminary cut(s) may be made to the distal femur F to remove sufficient bone for the provisional implant cutting implement  80  to be secured to the femur. The resection of the tibial plateau as shown in  FIGS.  6 A to  6 C and  7 A to  7 C  may be achieved before or after the preliminary cut(s) to the distal femur F. The surgical workflow may thus conclude with resection of the femur to create the appropriate plane cuts, after the soft tissue balancing with the provisional implant surgical implement  80 . 
     Still referring to  FIGS.  8 A to  8 E , an alternative to the use of the joints  33  and  34  is shown, with the distal surface  80 A of the provisional implant surgical implement  80  having actuated pads  81 A. Likewise, the posterior surface  80 B of the provisional implant surgical implement  80  may have actuated pads  81 B. Each of the actuated pads  81 A,  81 B may be displaceable in translation relative to a remainder of the provisional implant surgical implement  80 , and may hold set positions relative to the remainder of the provisional implant surgical implement  80 . Any appropriate motor or linear actuator from the components  42  may be used to actuate the displacement. The movement to set positions may be used to emulate adjusted position and orientation of the provisional implant surgical implement  80  with respect to the femur F. Therefore, as shown in  FIGS.  8 A and  8 B , the flexion angle may be adjusted. As shown in  FIG.  8 B , the rotation of the femur in the AP plane may be adjusted for balance. As shown in  FIGS.  8 C and  8 D , the varus-valgus angle may be adjusted. Force sensors as described in U.S. Pat. No. 10,485,554 may be integrated into the actuated pads  81 A and/or  81 B to measure the forces in dynamic soft tissue balancing maneuvers for various degrees of varus-valgus and flexion-extension. In  FIG.  8 E , an optional cutting guide implement  82  may be positioned against the actuated pads  81 A, via abutment surface  82 A, to transfer their combined plane of contact to a cut slot  82 B. The cutting guide implement  82  may then be pinned to the bone, and the robotic base  30  may be removed, for the cut plane to be resected. In the embodiments of  FIGS.  8 A to  8 E , the robotic base  30  may be optional, though the robotic base  30  may be used to interface the bone anchor device  20  to the provisional implant surgical implement  80 . 
     The electronic components  42  on board the provisional implant surgical implement  80  may include range finders, such as optical sensors, that may be used to determine distances between the actuated pads  81 A and  81 B and a remainder of the provisional implant surgical implement  80 , or from the provisional implant surgical implement  80  to the bone, to determine position and/or orientation. For example, this may be an alternative to having an inertial sensor. These sensors may be used to determine a distance between the provisional implant surgical implement  80  and the tibial plateau during range of motion and laxity testing. The operator would then be given pressure readings as well as distance readings. 
     Referring to  FIG.  9   , another surgical implement is shown at  90 . The surgical implement is a cutting block  90  that may be used in various procedures. For instance, the cutting block  90  may be used in machining the distal plane of the femur in the embodiment of  FIG.  4   , or the tibial plateau in the embodiment of  FIGS.  7 A- 7 C , as the cutting block  90  can be used to prepare a planar bone surface. 
     A housing  91  may include a plurality of cutting heads  92 , in a milling tool arrangement, i.e., mill heads. In the example of  FIG.  9   , the housing  91  is shown having a generally trapezoidal perimeter around the plurality of cutting heads  92 . The perimeter can be shaped to complement the shape of a bone surface to be machined (e.g., femur, tibia). Other perimeter shapes can be provided, including generally triangular, parallelogram, rectangular or irregular shapes. The plurality of cutting heads  92  can be disposed within the housing  91  and can be exposable through the attacking surface of the cutting block  90 . 
     The cutting block  90  can be populated with the plurality of cutting heads  92  that are arranged to machine a planar surface. Together, the plurality of cutting heads  92  can form a two-dimensional cutting surface. In some examples, the cutting heads  92  can be extended or retracted with respect to the housing  91  such that the two-dimensional cutting surface can be exposed outside the housing  91 . The cutting heads  92  may be operated by motor(s) from the electronic/mechanical components  42 . Additional structure may be present oscillate or rotate the cutting heads  92 , that may be oscillated or rotated together as a whole. The oscillation or rotation of the cutting heads  92  (e.g., as a whole) can be in addition to rotational or oscillating movement provided to each of the plurality of cutting heads  92 . For example, ultrasonic actuation may be used to drive oscillations of the cutting block  90  and/or its displacement toward the bone. Irrigation and suction of bone debris is also planned in the cutting block  90 , as shown by suction hole  93 A, connected to a suction source S and irrigation jet  93 B in order to facilitate the milling operation. Only one suction hole  93 A is shown but others could be present, at various locations. Likewise, only one irrigation jet  93 B is shown, but others may be present, at various locations. 
     Referring to  FIG.  10   , another surgical implement is shown at  100 . The surgical implement  100  is another cutting block that may be used in various procedures. For instance, the cutting block  100  may also be used in machining the distal plane of the femur in the embodiment of  FIG.  4 A  or  FIG.  4 B , or the tibial plateau in the embodiment of  FIGS.  7 A- 7 C , as the cutting block  100  can be used to prepare a planar bone surface. 
     The cutting block  100  may include a cutting band  101 . The cutting block  100  can also include a first cylindrical drive member  102 A and a second cylindrical drive member  102 B disposed within housing  103 . The cutting band  101  can extend (e.g., be stretched) between the first cylindrical drive member  102 A and the second cylindrical drive member  102 B. One of the members  102 A and  102 B may be driven as another possibility. The cutting band  101  can form a closed loop (e.g., a flexible eternal band). The cutting band  101  can be rotated upon activation of a motor from the components  42 . In some examples, the rotators can reside inside of the first and/or second cylindrical drive members  102 A and/or  102 B. In some examples, instead of rotating or in addition to rotating the cutting band, the cutting band can be oscillated upon activation by an oscillator. The cutting band  101  may also be rotated by way of a transmission. Examples of transmissions include tendons and pulleys, chains and sprockets, gear drives, etc. The cutting band  101  can include abrasive elements. In some examples, the abrasive elements are a series of blades. Irrigation and suction of bone debris is also planned in the cutting block  100 , as shown by suction hole  104 A, connected to a suction source and irrigation jet  104 B in order to facilitate the milling operation. Only one suction hole  104 A is shown but others could be present, at various locations. Likewise, only one irrigation jet  104 B is shown, but others may be present, at various locations. 
     In  FIG.  11   , another surgical implement is shown at  110 . The surgical implement  110  is another cutting block that may be used in various procedures. For instance, the cutting block  110  may also be used in machining the distal plane of the femur in the embodiment of  FIG.  4   , or the tibial plateau in the embodiment of  FIGS.  7 A- 7 C , as the cutting block  110  can be used to prepare a planar bone surface. 
     The cutting block  110  may feature a plurality of blades  111 , that may oscillate when placed against a bone surface, to prepare a planar bone surface. In an embodiment, vertical oscillations of the blades  111 , i.e., in an axial direction of the blades  111 , are generated to perform a cutting action. Ultrasound actuation may be used to generate the oscillations, i.e., its displacement toward the bone. Irrigation and suction of bone debris is also planned in the cutting block  110 , as shown by suction holes  112 A, connected to a suction source S and irrigation jet  112 B in order to facilitate the milling operation. A pair of suction holes  112 A is shown but others could be present (or fewer), at various locations. Likewise, only one irrigation jet  112 B is shown, but others may be present, at various locations. 
     The above description is meant to be exemplary only, and one skilled in the art will recognize that changes may be made to the embodiments described without departing from the scope of the invention disclosed. Still other modifications which fall within the scope of the present invention will be apparent to those skilled in the art, in light of a review of this disclosure, and such modifications are intended to fall within the appended claims. While the on-bone robotic system  10  is described as being used for knee surgical, for femur and/or tibia resecton, similar procedure may be used for other bones, such as the the humerus, the spine, etc. For the tibia, an assembly as described in U.S. Pat. No. 10,729,452 may be used, the contents of U.S. Pat. No.  10 , 729 , 452  being incorporated herein by reference. 
     Claim Related Examples 
     Example 1 is an on-bone robotic system comprising a bone anchor device configured to be received in a bone, the bone anchor device including at least one sensor for tracking an orientation of the bone; a robotic tool unit releasably connected to the bone anchor device, the robotic tool unit including at least one actuator for displacing a surgical implement of the robotic tool unit relative to the bone when the robotic tool unit is connected to the bone anchor device; wherein the on-bone robotic system includes at least one joint enabling at least one degree of freedom of movement of the surgical implement relative to the bone anchor device; and wherein the on-bone robotic system includes a processor for operating the at least one actuator as a function of the tracking of the bone by the sensor. 
     Example 2 can include or may optionally be combined with the subject matter of Example 1, wherein the bone anchor device has a receptacle configured to be received in the bone, the receptacle accommodating the at least one sensor. 
     Example 3 can include or may optionally be combined with the subject matter of Example 2, wherein a leading end of the bone anchor device is flared. 
     Example 4 can include or may optionally be combined with the subject matter of Examples 2 and 3, wherein an anti-rotation feature projects laterally from the receptacly. 
     Example 5 can include or may optionally be combined with the subject matter of Example 4, wherein the anti-rotation feature includes at least one fin. 
     Example 6 can include or may optionally be combined with the subject matter of Examples 1 to 5, wherein the at least one sensor includes an inertial sensor. 
     Example 7 can include or may optionally be combined with the subject matter of Examples 1 to 6, wherein the bone anchor device includes a battery. 
     Example 8 can include or may optionally be combined with the subject matter of Example 7, wherein the bone anchor device is configured to be used as an implant to track movement of the bone post-operatively. 
     Example 9 can include or may optionally be combined with the subject matter of Examples 1 to 8, wherein the at least one actuator includes at least one motor. 
     Example 10 can include or may optionally be combined with the subject matter of Example 9, including two of the motor, the robotic tool unit displacing the surgical implement in at least two rotational degrees of freedom. 
     Example 11 can include or may optionally be combined with the subject matter of Examples 1 to 10, wherein the at least one actuator includes at least one linear actuator. 
     Example 12 can include or may optionally be combined with the subject matter of Examples 1 to 11, wherein the surgical implement has a cut slot. 
     Example 13 can include or may optionally be combined with the subject matter of Examples 1 to 12, wherein the robotic tool unit includes at least one sensor for tracking an orientation of the surgical implement. 
     Example 14 can include or may optionally be combined with the subject matter of Examples 1 to 13, wherein the robotic tool unit includes at least one camera oriented toward the bone and configured to capture images of the bone. 
     Example 15 can include or may optionally be combined with the subject matter of Examples 1 to 14, including a communication device connected to the processor and configured for wireless communication. 
     Example 16 is a method for performing an orthopedic procedure comprising: anchoring an on-bone robotic system to a bone via a bone anchor device inserted in the bone, the bone anchor device including at least one sensor for tracking an orientation of the bone; operating the on-bone robotic system for the on-bone robotic system to displace a surgical implement operatively connected to the bone anchor device, a movement of the surgical implement being guided as a function of the tracking of the bone by the sensor; and detaching at least the surgical implement from the bone anchor device to leave the bone anchor device as an implant post-operatively, the bone anchor device configured to track the bone post-operatively. 
     Example 17 can include or may optionally be combined with the subject matter of Example 16, wherein anchoring the on-bone robotic system to the bone including drilling a hole in the bone for insertion of the bone anchor device in the hole. 
     Example 18 can include or may optionally be combined with the subject matter of Example 17, wherein insertion of the bone anchor device in the hole includes having an anti-rotation feature penetrate the bone. 
     Example 19 can include or may optionally be combined with the subject matter of Examples 16 to 18, wherein the movement in the operating includes moving the surgical implement in at least one rotational degree of freedom. 
     Example 20 can include or may optionally be combined with the subject matter of Example 19, wherein moving the surgical implement includes actuating a rotational motor to move the surgical implement in the at least one rotational degree of freedom. 
     Example 21 can include or may optionally be combined with the subject matter of Examples 19 to 20, wherein the movement in the operating includes moving the surgical implement in two rotational degrees of freedom. 
     Example 22 can include or may optionally be combined with the subject matter of Examples 19 to 21, wherein the movement in the operating includes moving the surgical implement in one translational degree of freedom. 
     Example 23 can include or may optionally be combined with the subject matter of Examples 16 to 22, further including imaging the bone from the on-bone robotic system. 
     Example 24 can include or may optionally be combined with the subject matter of Example 23, further including matching the imaging of the bone from the on-bone robotic system with a pre-operative virtual model of the bone for navigating a position and orientation of the surgical implement relative to the bone. 
     Example 25 can include or may optionally be combined with the subject matter of Examples 16 to 24, further including wirelessly communicating data from the at least one sensor. 
     Example 26 is a system for tracking a bone intraoperatively in a surgical procedure and post-operatively, comprising: a processing unit; and a non-transitory computer-readable memory communicatively coupled to the processing unit and comprising computer-readable program instructions executable by the processing unit for: obtaining orientation data of at least one sensor in a bone anchor device anchored to a bone, intraoperatively; actuating at least one actuator to displace a surgical implement operatively connected to the bone anchor device as a part of an on-bone robot, as a function of the orientation data; and after the surgical procedure, obtaining orientation data of at least one sensor in the bone anchor device remaining anchored to the bone, post-operatively. 
     Example 27 can include or may optionally be combined with the subject matter of Example 26, wherein actuating at least one actuator includes actuating at least one rotational motor to orient the surgical instrument relative to the bone in one rotational degree of freedom. 
     Example 28 can include or may optionally be combined with the subject matter of Example 26, wherein actuating at least one actuator includes actuating a second rotational motor to orient the surgical instrument relative to the bone in a second rotational degree of freedom. 
     Example 29 can include or may optionally be combined with the subject matter of Examples 26 to 28, wherein actuating at least one actuator includes actuating at least one linear actuator to displace the surgical instrument relative to the bone in a translational degree of freedom. 
     Example 30 can include or may optionally be combined with the subject matter of Examples 26 to 29, further including imaging the bone from the on-bone robot. 
     Example 31 can include or may optionally be combined with the subject matter of Example 30, further including matching the imaging of the bone from the on-bone robot with a pre-operative virtual model of the bone for navigating a position and orientation of the surgical implement relative to the bone. 
     Each of these non-limiting examples can stand on its own, or can be combined in various permutations or combinations with one or more of the other examples.