Patent Description:
The present invention relates generally to a system and computer program product for manipulating an anatomy with a tool of a surgical system, and more specifically, constraining the tool using virtual boundaries.

Recently, operators have found it useful to use robotic devices to assist in the performance of surgical procedures. A robotic device typically includes a moveable arm having a free, distal end, which may be placed with a high degree of accuracy. A tool that is applied to the surgical site attaches to the free end of the arm. The operator is able to move the arm and thereby precisely position the tool at the surgical site to perform the procedure.

In robotic surgery, virtual boundaries are created prior to surgery using computer aided design software to delineate areas in which the tool may maneuver from areas in which the tool is restricted. For instance, in orthopedic surgery a virtual cutting boundary may be created to delineate sections of bone to be removed by the tool during the surgery from sections of bone that are to remain after the surgery.

A navigation system tracks movement of the tool to determine a position and/or orientation of the tool relative to the virtual boundary. The robotic system cooperates with the navigation system to guide movement of the tool so that the tool does not move beyond the virtual boundary. Virtual boundaries are often created in a model of a patient's bone and fixed with respect to the bone so that when the model is loaded into the navigation system, the navigation system may track movement of the virtual boundary by tracking movement of the bone.

Operators often desire dynamic control of the tool in different cutting modes during a surgical operation. For example, in some instances, the operator may desire a manual mode to control the tool manually for bulk cutting of the anatomy. In other instances, the operator may desire to control the tool in an autonomous mode for automated and highly accurate cutting of the anatomy. In conventional systems, a virtual boundary associated with a target surface of the anatomy remains active regardless of the mode of control. In other words, the same virtual boundary is on whether the tool is controlled in the autonomous mode or manual mode, for example. The manipulator generally does not allow advancement of the tool beyond the boundary in either mode. However, in some cases, the manipulator may inadvertently allow movement of the tool beyond the boundary. For instance, in the manual mode, the operator may apply such a large amount of force on the tool that exceeds the ability of the manipulator to prevent movement of the tool beyond the boundary. In this case, cutting of the anatomy may occur beyond the virtual boundary thereby deviating from the desired target surface.

There is a need in the art for systems and methods for solving at least the aforementioned problems.

Document <CIT> discloses a method for activating a virtual haptic geometry based on a position of a portion of an instrument relative to a target feature. The method comprises detecting a presence of a reference point of an instrument within a threshold distance of a target feature. A virtual haptic geometry corresponding to the target featureis activated in response to the detected presence of the reference point of the instrument within the threshold distance. <CIT> discloses another system of the prior art of using virtual boundaries with a surgical tool.

According to aspects of the present disclosure, a surgical system and a computer program product are provided according to the independent claims. Preferred embodiments are recited in the dependent claims. Surgical methods described herein are not part of the claimed invention. One embodiment of a system for manipulating an anatomy is provided. The system includes a manipulator having a base and a linkage. A tool is coupled to the manipulator and movable relative to the base to interact with the anatomy. A controller is configured to generate a first virtual boundary associated with the anatomy and a second virtual boundary associated with the anatomy. The controller is configured to control movement of the tool in a first mode and a second mode. The controller activates the first virtual boundary in the first mode to constrain the tool in relation to the first virtual boundary. The controller deactivates the first virtual boundary in the second mode to constrain the tool in relation to the second virtual boundary.

One example of a method of operating a surgical system for manipulating an anatomy with a tool is provided. The method includes defining a first virtual boundary associated with the anatomy and a second virtual boundary associated with the anatomy. The first virtual boundary is activated in a first mode. Movement of the tool is constrained in relation to the first virtual boundary in the first mode. The first virtual boundary is deactivated in a second mode. Movement of the tool is constrained in relation to the second virtual boundary in the second mode.

The system and method advantageously provide the opportunity to selectively control activation of the intermediate virtual boundary between the first and second modes. By doing so, the system and method provide a different virtual boundary configuration for each of the first and second modes thereby increasing versatility and performance of the surgical system.

Referring to the Figures, wherein like numerals indicate like or corresponding parts throughout the several views, a system <NUM> and method for manipulating an anatomy of a patient <NUM> are shown throughout. As shown in <FIG>, the system <NUM> is a robotic surgical cutting system for cutting away material from the anatomy of the patient <NUM>, such as bone or soft tissue. In <FIG>, the patient <NUM> is undergoing a surgical procedure. The anatomy in <FIG> includes a femur (F) and a tibia (T) of the patient <NUM>. The surgical procedure may involve tissue removal. In other examples, the surgical procedure involves partial or total knee or hip replacement surgery. The system <NUM> is designed to cut away material to be replaced by surgical implants such as hip and knee implants, including unicompartmental, bicompartmental, or total knee implants. Some of these types of implants are shown in <CIT>, entitled, "Prosthetic Implant and Method of Implantation,". Those skilled in the art appreciate that the system and method disclosed herein may be used to perform other procedures, surgical or non-surgical, or may be used in industrial applications or other applications where robotic systems are utilized.

The system <NUM> includes a manipulator <NUM>. The manipulator <NUM> has a base <NUM> and a linkage <NUM>. The linkage <NUM> may comprise links forming a serial arm or parallel arm configuration. A tool <NUM> couples to the manipulator <NUM> and is movable relative to the base <NUM> to interact with the anatomy. The tool <NUM> forms part of an end effector <NUM> attached to the manipulator <NUM>. The tool <NUM> is grasped by the operator. One exemplary arrangement of the manipulator <NUM> and the tool <NUM> is described in <CIT>, entitled, "Surgical Manipulator Capable of Controlling a Surgical Instrument in Multiple Modes,". The manipulator <NUM> and the tool <NUM> may be arranged in alternative configurations. The tool <NUM> can be like that shown in <CIT>, entitled, "End Effector of a Surgical Robotic Manipulator,". The tool <NUM> includes an energy applicator <NUM> designed to contact the tissue of the patient <NUM> at the surgical site. The energy applicator <NUM> may be a drill, a saw blade, a bur, an ultrasonic vibrating tip, or the like. The manipulator <NUM> also houses a manipulator computer <NUM>, or other type of control unit.

Referring to <FIG>, the system <NUM> includes a controller <NUM>. The controller <NUM> includes software and/or hardware for controlling the manipulator <NUM>. The controller <NUM> directs the motion of the manipulator <NUM> and controls an orientation of the tool <NUM> with respect to a coordinate system. In one embodiment, the coordinate system is a manipulator coordinate system MNPL (see <FIG>). The manipulator coordinate system MNPL has an origin, and the origin is located at a point on the manipulator <NUM>. One example of the manipulator coordinate system MNPL is described in <CIT>, entitled, "Surgical Manipulator Capable of Controlling a Surgical Instrument in Multiple Modes,".

The system <NUM> further includes a navigation system <NUM>. One example of the navigation system <NUM> is described in <CIT>, entitled, "Navigation System Including Optical and Non-Optical Sensors,". The navigation system <NUM> is set up to track movement of various objects. Such objects include, for example, the tool <NUM>, and the anatomy, e.g., femur F and tibia T. The navigation system <NUM> tracks these objects to gather position information of each object in a localizer coordinate system LCLZ. Coordinates in the localizer coordinate system LCLZ may be transformed to the manipulator coordinate system MNPL using conventional transformation techniques. The navigation system <NUM> is also capable of displaying a virtual representation of their relative positions and orientations to the operator.

The navigation system <NUM> includes a computer cart assembly <NUM> that houses a navigation computer <NUM>, and/or other types of control units. A navigation interface is in operative communication with the navigation computer <NUM>. The navigation interface includes one or more displays <NUM>. First and second input devices <NUM>, <NUM> such as a keyboard and mouse may be used to input information into the navigation computer <NUM> or otherwise select/control certain aspects of the navigation computer <NUM>. Other input devices <NUM>, <NUM> are contemplated including a touch screen (not shown) or voice-activation. The controller <NUM> may be implemented on any suitable device or devices in the system <NUM>, including, but not limited to, the manipulator computer <NUM>, the navigation computer <NUM>, and any combination thereof.

The navigation system <NUM> also includes a localizer <NUM> that communicates with the navigation computer <NUM>. In one embodiment, the localizer <NUM> is an optical localizer and includes a camera unit <NUM>. The camera unit <NUM> has an outer casing <NUM> that houses one or more optical position sensors <NUM>. The system <NUM> includes one or more trackers. The trackers may include a pointer tracker PT, a tool tracker <NUM>, a first patient tracker <NUM>, and a second patient tracker <NUM>. The trackers include active markers <NUM>. The active markers <NUM> may be light emitting diodes or LEDs. In other embodiments, the trackers <NUM>, <NUM>, <NUM> may have passive markers, such as reflectors, which reflect light emitted from the camera unit <NUM>. Those skilled in the art appreciate that the other suitable tracking systems and methods not specifically described herein may be utilized.

In the illustrated embodiment of <FIG>, the first patient tracker <NUM> is firmly affixed to the femur F of the patient <NUM> and the second patient tracker <NUM> is firmly affixed to the tibia T of the patient <NUM>. The patient trackers <NUM>, <NUM> are firmly affixed to sections of bone. The tool tracker <NUM> is firmly attached to the tool <NUM>. It should be appreciated that the trackers <NUM>, <NUM>, <NUM> may be fixed to their respective components in any suitable manner.

The trackers <NUM>, <NUM>, <NUM> communicate with the camera unit <NUM> to provide position data to the camera unit <NUM>. The camera unit <NUM> provides the position data of the trackers <NUM>, <NUM>, <NUM> to the navigation computer <NUM>. In one embodiment, the navigation computer <NUM> determines and communicates position data of the femur F and tibia T and position data of the tool <NUM> to the manipulator computer <NUM>. Position data for the femur F, tibia T, and tool <NUM> may be determined by the tracker position data using conventional registration/navigation techniques. The position data includes position information corresponding to the position and/or orientation of the femur F, tibia T, tool <NUM> and any other objects being tracked. The position data described herein may be position data, orientation data, or a combination of position data and orientation data.

The manipulator computer <NUM> transforms the position data from the localizer coordinate system LCLZ into the manipulator coordinate system MNPL by determining a transformation matrix using the navigation-based data for the tool <NUM> and encoder-based position data for the tool <NUM>. Encoders (not shown) located at joints of the manipulator <NUM> are used to determine the encoder-based position data. The manipulator computer <NUM> uses the encoders to calculate an encoder-based position and orientation of the tool <NUM> in the manipulator coordinate system MNPL. Since the position and orientation of the tool <NUM> are also known in the localizer coordinate system LCLZ, the transformation matrix may be generated.

As shown in <FIG>, the controller <NUM> further includes software modules. The software modules may be part of a computer program or programs that operate on the manipulator computer <NUM>, navigation computer <NUM>, or a combination thereof, to process data to assist with control of the system <NUM>. The software modules include sets of instructions stored in memory on the manipulator computer <NUM>, navigation computer <NUM>, or a combination thereof, to be executed by one or more processors of the computers <NUM>, <NUM>. Additionally, software modules for prompting and/or communicating with the operator may form part of the program or programs and may include instructions stored in memory on the manipulator computer <NUM>, navigation computer <NUM>, or a combination thereof. The operator interacts with the first and second input devices <NUM>, <NUM> and the one or more displays <NUM> to communicate with the software modules.

In one embodiment, the controller <NUM> includes a manipulator controller <NUM> for processing data to direct motion of the manipulator <NUM>. The manipulator controller <NUM> may receive and process data from a single source or multiple sources.

The controller <NUM> further includes a navigation controller <NUM> for communicating the position data relating to the femur F, tibia T, and tool <NUM> to the manipulator controller <NUM>. The manipulator controller <NUM> receives and processes the position data provided by the navigation controller <NUM> to direct movement of the manipulator <NUM>. In one embodiment, as shown in <FIG>, the navigation controller <NUM> is implemented on the navigation computer <NUM>.

The manipulator controller <NUM> or navigation controller <NUM> may also communicate positions of the patient <NUM> and tool <NUM> to the operator by displaying an image of the femur F and/or tibia T and the tool <NUM> on the display <NUM>. The manipulator computer <NUM> or navigation computer <NUM> may also display instructions or request information on the display <NUM> such that the operator may interact with the manipulator computer <NUM> for directing the manipulator <NUM>.

As shown in <FIG>, the controller <NUM> includes a boundary generator <NUM>. The boundary generator <NUM> is a software module that may be implemented on the manipulator controller <NUM>, as shown in <FIG>. Alternatively, the boundary generator <NUM> may be implemented on other components, such as the navigation controller <NUM>. As described in detail below, the boundary generator <NUM> generates the virtual boundaries for constraining the tool <NUM>.

A tool path generator <NUM> is another software module run by the controller <NUM>, and more specifically, the manipulator controller <NUM>. The tool path generator <NUM> generates a tool path <NUM> as shown in <FIG>, which represents a bone, a section of which is to be removed to receive an implant. In <FIG>, the tool path <NUM> is represented by the back and forth line. The smoothness and quality of the finished surface depends in part of the relative positioning of the back and forth line. More specifically, the closer together each back and forth pass of the line, the more precise and smooth is the finished surface. Dashed line <NUM> represents the perimeter of the bone that is to be removed using manipulator <NUM>. One exemplary system and method for generating the tool path <NUM> is explained in <CIT>, entitled, "Surgical Manipulator Capable of Controlling a Surgical Instrument in Multiple Modes,".

The system <NUM> and method for manipulating the anatomy with the tool <NUM> include defining with the controller <NUM>, a first, or intermediate virtual boundary <NUM> and a second, or target virtual boundary <NUM> associated with the anatomy, as shown in <FIG>. The intermediate virtual boundary <NUM> is spaced apart from the target virtual boundary <NUM>. The intermediate virtual boundary <NUM> is activated in a first mode as shown in <FIG>. Movement of the tool <NUM> is constrained in relation to the intermediate virtual boundary <NUM> in the first mode. The intermediate virtual boundary <NUM> is deactivated in a second mode, as shown in <FIG>. Movement of the tool <NUM> is constrained in relation to the target virtual boundary <NUM> in the second mode.

One exemplary system and method for generating the virtual boundaries <NUM>, <NUM> is explained in <CIT>, entitled, "Surgical Manipulator Capable of Controlling a Surgical Instrument in Multiple Modes,". The boundary generator <NUM> generates maps that define the target and intermediate virtual boundaries <NUM>, <NUM>. These boundaries <NUM>, <NUM> delineate between tissue the tool <NUM> should remove and tissue the tool <NUM> should not remove. Alternatively, these boundaries <NUM>, <NUM> delineate between tissue to which the tool <NUM> energy applicator <NUM> should be applied and tissue to which the energy applicator <NUM> should not be applied. As such, the target and intermediate virtual boundaries <NUM>, <NUM> are cutting or manipulation boundaries, which limit movement of the tool <NUM>. Often, but not always, the virtual boundaries <NUM>, <NUM> are defined within the patient <NUM>.

As shown throughout, the target and intermediate virtual boundaries <NUM>, <NUM> independently constrain movement of the tool <NUM> between the first and second modes. That is, the tool <NUM> is constrained by either the intermediate virtual boundary <NUM> in the first mode or the target virtual boundary <NUM> in the second mode. Methods for constraining movement of the tool <NUM> are explained in <CIT>, entitled, "Surgical Manipulator Capable of Controlling a Surgical Instrument in Multiple Modes,".

The surgical system <NUM> allows switching between the first and second modes to provide different constraint configurations for the tool <NUM>. When the first mode is switched to the second mode, as shown in <FIG> the intermediate virtual boundary <NUM> is deactivated, leaving the target virtual boundary <NUM>. Thus, in the second mode, the tool <NUM> is permitted to reach the target virtual boundary <NUM> because the intermediate virtual boundary <NUM> is not constraining the tool <NUM>. The tool <NUM> is constrained in relation to the target virtual boundary <NUM> when the intermediate virtual boundary <NUM> is inactivated.

When the second mode is switched to the first mode, as shown in <FIG>, the intermediate virtual boundary <NUM> is activated or re-activated. The tool <NUM> is constrained in relation to the intermediate virtual boundary <NUM> when the intermediate virtual boundary <NUM> is activated. Thus, in the first mode, the intermediate virtual boundary <NUM> prevents the tool <NUM> from reaching the target virtual boundary <NUM>.

The manipulator <NUM> is configured to receive instructions from the controller <NUM> and move the tool <NUM> in relation to the intermediate virtual boundary <NUM> in the first mode and/or the target virtual boundary <NUM> in the second mode. The navigation system <NUM> tracks movement of the tool <NUM> in relation to the intermediate virtual boundary <NUM> in the first mode and/or the target virtual boundary <NUM> in the second mode. As the tool <NUM> moves, the manipulator <NUM> and navigation system <NUM> cooperate to determine if the tool <NUM> is inside the intermediate virtual boundary <NUM> in the first mode and/or the target virtual boundary <NUM> in the second mode. The manipulator <NUM> selectively limits the extent to which the tool <NUM> moves. Specifically, the controller <NUM> constrains the manipulator <NUM> from movement that would otherwise result in the application of the tool <NUM> outside of the intermediate virtual boundary <NUM> in the first mode and/or the target virtual boundary <NUM> in the second mode. If the operator applies forces and torques that would result in the advancement of the tool <NUM> beyond the intermediate virtual boundary <NUM> in the first mode and/or target virtual boundary <NUM> in the second mode, the manipulator <NUM> does not emulate this intended positioning of the tool <NUM>.

As shown in <FIG>, the target virtual boundary <NUM> is associated with the anatomy, and more specifically a target surface <NUM> of the anatomy. The target virtual boundary <NUM> is defined in relation to the target surface <NUM>. Target surface <NUM> is also the outline of the bone remaining after the removal procedure and is the surface to which the implant is to be mounted. In other words, the target surface <NUM> is a contiguous defined surface area of the tissue that is to remain after cutting has completed.

As shown in <FIG>, during the procedure, the target virtual boundary <NUM> may be slightly offset or spaced apart from the target surface <NUM>. In one embodiment, this is done to account for the size and manipulation characteristics of the tool <NUM>. The manipulation characteristics of the tool <NUM> may cause the tool <NUM> to breach the target virtual boundary <NUM>. To account for this overreaching, the target virtual boundary <NUM> may be translated from target surfaces <NUM> by a predetermined distance defined between the target surface <NUM> and the target virtual boundary <NUM>. In one example, the distance is equivalent to half of the thickness of the tool <NUM>. In another embodiment, the target virtual boundary <NUM> may be slightly offset or spaced apart from the target surface <NUM> depending on how the tool <NUM> and energy applicator <NUM> are tracked. For example, the energy applicator <NUM> may be tracked based on points based on a center of the energy applicator <NUM> rather than points based on an exterior cutting surface of the energy applicator <NUM>. In such instances, offsetting the target virtual boundary <NUM> from the target surface <NUM> provides accommodates the center tracking to prevent overshooting of the target surface <NUM>. For instance, when the energy applicator of the tool <NUM> is a spherical bur, the target virtual boundary is offset by half the diameter of the bur when the tool center point (TCP) of the bur is being tracked. As a result, when the TCP is on the target virtual boundary <NUM>, the outer surface of the bur is at the target surface <NUM>.

The intermediate virtual boundary <NUM> is spaced apart from the target virtual boundary <NUM>. As shown in <FIG>, the intermediate virtual boundary <NUM> is spaced further from the target surface <NUM> than the target virtual boundary <NUM> is spaced from the target surface <NUM>. In essence, the target virtual boundary <NUM> is located between the target surface <NUM> and the intermediate virtual boundary <NUM>. Since the intermediate virtual boundary <NUM> is spaced further from the target surface <NUM>, movement of the tool <NUM> is generally more restricted in relation to the intermediate virtual boundary <NUM> as compared in relation to the target virtual boundary <NUM>. Said differently, movement of the tool <NUM> is more restricted in the first mode as compared with the second mode.

A zone <NUM> is defined between the target and intermediate virtual boundaries <NUM>, <NUM>, as shown in <FIG>. The boundaries <NUM>, <NUM> may be spaced according to any suitable distance. In one example, the target and intermediate virtual boundaries <NUM>, <NUM> are spaced by approximately one half millimeter such that the zone <NUM> has a thickness of one half millimeter. In one sense, the intermediate virtual boundary <NUM> may be considered an offset boundary in relation to the target virtual boundary <NUM>. In general, the controller <NUM> prevents the tool <NUM> from penetrating the zone <NUM> in the first mode. Preventing the tool <NUM> from penetrating the zone <NUM> in the first mode may occur regardless of whether or not the target virtual boundary <NUM> is active. The controller <NUM> allows the tool <NUM> to penetrate the zone <NUM> in the second mode. The zone <NUM> may be defined independent of whether the target and/or intermediate virtual boundaries <NUM>, <NUM> are active or inactive.

The target and intermediate virtual boundaries <NUM>, <NUM> may have the same profile has shown in <FIG>. Specifically, the target and intermediate virtual boundaries <NUM>, <NUM> have profiles that are similar to the target surface <NUM>. Having similar profiles may be useful to promote gradual formation of the target surface <NUM>.

Displays <NUM> may show representations of the target and intermediate virtual boundaries <NUM>, <NUM> and the anatomy being treated. Additionally, information relating to the target and intermediate virtual boundaries <NUM>, <NUM> may be forwarded to the manipulator controller <NUM> to guide the manipulator <NUM> and corresponding movement of the tool <NUM> relative to these virtual boundaries <NUM>, <NUM> so that the tool <NUM> does not intrude on such.

The manipulator controller <NUM> may continuously track movement of the target and intermediate virtual boundaries <NUM>, <NUM>. In some instances, the anatomy may move from a first position to a second position during the procedure. In such instances, the manipulator controller <NUM> updates the position of the virtual boundaries <NUM>, <NUM> consistent with the second position of the anatomy.

In one embodiment, the first mode and/or second mode is/are an autonomous mode or a manual mode. Examples of the autonomous mode and manual mode are described in <CIT>, entitled, "Surgical Manipulator Capable of Controlling a Surgical Instrument in Multiple Modes,".

In one embodiment, in the first mode, the system <NUM> operates in the manual mode. The operator manually directs, and the manipulator <NUM> controls, movement of the tool <NUM> and, in turn, the energy applicator <NUM> at the surgical site. The operator physically contacts the tool <NUM> to cause movement of the tool <NUM>. The manipulator <NUM> monitors the forces and torques placed on the tool <NUM> by the operator in order to position the tool <NUM>. These forces and torques are measured by a sensor that is part of the manipulator <NUM>. In response to the applied forces and torques, the manipulator <NUM> mechanically moves the tool <NUM> in a manner that emulates the movement that would have occurred based on the forces and torques applied by the operator. Movement of the tool <NUM> in the first mode is constrained in relation to the intermediate virtual boundary <NUM>. In this case, the intermediate virtual boundary <NUM> acts as a haptic boundary and the manipulator <NUM> provides the operator with haptic feedback to indicate the location of the intermediate virtual boundary <NUM> to the operator. For instance, by virtue of the manipulator <NUM> preventing or resisting movement of the tool <NUM> beyond the intermediate virtual boundary <NUM>, the operator haptically senses a virtual wall when reaching the intermediate virtual boundary <NUM>.

At any time during manual manipulation in the first mode, or after manipulation in the first mode is complete, the system <NUM> allows switching from the first mode to the second mode. In one embodiment, switching between the first and second modes occurs in response to manual input. For example, the operator may use some form of control to manage remotely which of the first and second modes should be active. Alternatively, switching may be implemented autonomously in response to certain events or conditions. For example, the system <NUM> may determine that the requisite amount of tissue has been removed in the first mode and switch to the second mode in response. Those skilled in the art appreciate that switching between first and second modes may be performed according to other methods not explicitly described herein.

In the second mode, in one embodiment, the manipulator <NUM> directs autonomous movement of the tool <NUM> and, in turn, the energy applicator <NUM> at the surgical site. The manipulator <NUM> is capable of moving the tool <NUM> free of operator assistance. Free of operator assistance may mean that an operator does not physically contact the tool <NUM> to apply force to move the tool <NUM>. Instead, the operator may use some form of control to remotely manage starting and stopping of movement. For example, the operator may hold down a button of a remote control to start movement of the tool <NUM> and release the button to stop movement of the tool <NUM>. Alternatively, the operator may press a button to start movement of the tool <NUM> and press a button to stop movement of the tool <NUM>. Movement of the tool <NUM> in the second mode is constrained in relation to the target virtual boundary <NUM>.

The system <NUM> and method advantageously provide the opportunity to selectively control activation of the intermediate virtual boundary <NUM> between the first and second modes. By doing so, the system <NUM> and method provide different virtual boundary configurations for each of the first and second modes. This increases versatility of the surgical system and performance of the operator. In some embodiments, this advantageously provides the opportunity for the operator to use the manipulator <NUM> in a bulk-manipulation fashion in the first mode. The operator may initially operate the tool <NUM> manually in order to remove a large mass of tissue. This part of the procedure is sometimes referred to as debulking. The operator, knowing that the intermediate virtual boundary <NUM> is constraining the tool <NUM> away from the target surface <NUM>, may take measures to perform bulk-manipulation that is much faster than otherwise possible during autonomous manipulation. Once the bulk of the tissue is removed manually, the system <NUM> may be switched to the second mode to provide autonomous manipulation of the remaining portion of the tissue in a highly accurate and controlled manner. Said differently, in the second mode, the operator may require fine positioning of the instrument to define the surfaces of the remaining tissue. This part of the procedure is sometimes known as the finishing cut, and is possible because the intermediate virtual boundary <NUM> is inactive and the target virtual boundary <NUM> is active.

The target and virtual boundaries <NUM>, <NUM> may be derived from various inputs to the manipulator <NUM>, and more specifically, the boundary generator <NUM>. One input into the boundary generator <NUM> includes preoperative images of the site on which the procedure is to be performed. If the manipulator <NUM> selectively removes tissue so the patient <NUM> may be fitted with an implant, a second input into the boundary generator <NUM> is a map of the shape of the implant. The initial version of this map may come from an implant database. The shape of the implant defines the boundaries of the tissue that should be removed to receive the implant. This relationship is especially true if the implant is an orthopedic implant intended to be fitted to the bone of the patient <NUM>.

Another input into boundary generator <NUM> is the operator settings. These settings may indicate to which tissue the energy applicator <NUM> should be applied. If the energy applicator <NUM> removes tissues, the settings may identify the boundaries between the tissue to be removed and the tissue that remains after application of the energy applicator <NUM>. If the manipulator <NUM> assists in the fitting of an orthopedic implant, these settings may define where over the tissue the implant should be positioned. These settings may be entered preoperatively using a data processing unit. Alternatively, these settings may be entered through an input/output unit associated with one of the components of the system <NUM> such as with navigation interface <NUM>, <NUM>.

Based on the above input data and instructions, boundary generator <NUM> may generate the target and intermediate virtual boundaries <NUM>, <NUM>. The boundaries <NUM>, <NUM> may be two-dimensional or three-dimensional. For example, the target and intermediate virtual boundaries <NUM>, <NUM> may be generated as a virtual map or other three-dimensional model, as shown in the Figures. The created maps or models guide movement of the tool <NUM>. The models may be displayed on displays <NUM> to show the locations of the objects. Additionally, information relating to the models may be forwarded to the manipulator controller <NUM> to guide the manipulator <NUM> and corresponding movement of the tool <NUM> relative to the target and intermediate virtual boundaries <NUM>, <NUM>.

In practice, prior to the start of the procedure the operator at the surgical site may set an initial version of the virtual target and intermediate virtual boundaries <NUM>, <NUM>. At the start of the procedure, data that more precisely defines the implant that is to be actually fitted to the patient <NUM> may be loaded into the boundary generator <NUM>. Such data may come from a storage device associated with the implant such as a memory stick or an RFID tag. Such data may be a component of the implant database data supplied to the boundary generator <NUM>. These data are based on post manufacture measurements of the specific implant. These data provide a definition of the shape of the specific implant that, due to manufacturing variations, may be slightly different than the previously available stock definition of implant shape. Based on this implant-specific data, the boundary generator <NUM> may update the target and intermediate virtual boundaries <NUM>, <NUM> to reflect the boundaries between the tissue to be removed and the tissue that should remain in place. Implants that could be implanted into the patient <NUM> include those shown in <CIT> and entitled, "Prosthetic Implant and Method of Implantation",. The implants disclosed herein could be implanted in the patient <NUM> after the appropriate amount of material, such as bone, is removed. Other implants are also contemplated.

In one embodiment, the target virtual boundary <NUM> is derived from points in a coordinate system associated with the anatomy. The target virtual boundary <NUM> may be interpolated by connecting each of the captured points together. This creates a web or mesh that defines the target virtual boundary <NUM>. If only two points are captured, the target virtual boundary <NUM> may be a line between the points. If three points are captured, the target virtual boundary <NUM> may be formed by lines connecting adjacent points. The displays <NUM> may provide visual feedback of the shape of the target virtual boundary <NUM> created. The input devices <NUM>, <NUM> may be utilized to control and modify the target virtual boundary <NUM> such as by shifting the boundary, enlarging or shrinking the boundary, changing the shape of the target virtual boundary <NUM>, etc. Those skilled in the art understand that the target virtual boundary <NUM> may be created according to other methods not specifically described herein.

Alternative arrangements and configurations of the target virtual boundary <NUM> are shown in <FIG> and <FIG>. In some instances, as shown in <FIG>, it may be suitable to align the target virtual boundary <NUM> directly with the target surface <NUM> of the anatomy rather than to have an offset between the two. For example, the manipulation characteristics of the tool <NUM> may not extend beyond the target virtual boundary <NUM>. Additionally or alternatively, the tool <NUM> may be tracked based on points that are on an exterior surface of the energy applicator <NUM> rather than points that are in the center of the energy applicator <NUM>. In such instances, aligning the target virtual boundary <NUM> with the target surface <NUM> provides accurate manipulation to create the target surface <NUM>. In yet another embodiment, the tool <NUM> may be tracked based on an envelope outlining a range of movement of the exterior surface of the tool <NUM>. For instance, when the tool <NUM> is a saw blade, the envelope encompasses the range of movement of the exterior surface of the saw blade such that movement of the exterior surface of the saw blade during oscillations of the saw blade is captured within the envelope. Positioning of the target virtual boundary <NUM> may take into account the envelope.

In other examples, as shown in <FIG>, the target virtual boundary <NUM> is generally un-aligned with the target surface <NUM>. Instead, the target virtual boundary <NUM> is spaced apart from and rests beyond the target surface <NUM>. Those skilled in the art appreciate that the target virtual boundary <NUM> may have other configurations not specifically recited herein.

The intermediate virtual boundary <NUM> may be formed in a similar manner as the target virtual boundary <NUM>. Alternatively, the controller <NUM> may derive the intermediate virtual boundary <NUM> from the target virtual boundary <NUM>. For example, the controller <NUM> may copy the target virtual boundary <NUM> to form the intermediate virtual boundary <NUM>. The copy of the target virtual boundary <NUM> may be modified or transformed according to any suitable method to form the intermediate virtual boundary <NUM>. For example, the copy of the target virtual boundary <NUM> may be translated, shifted, skewed, resized, rotated, reflected, and the like. Those skilled in the art understand that the intermediate virtual boundary <NUM> may be derived from the target virtual boundary <NUM> according to other methods not specifically described herein.

The target virtual boundary <NUM> and the intermediate virtual boundary <NUM> may have any suitable profile. For example, as shown in <FIG>, the target virtual boundary <NUM> has a profile that is similar to the profile of the target surface <NUM>. In <FIG>, the target virtual boundary <NUM> has a profile that is planar or flat. In <FIG>, the intermediate virtual boundary <NUM> has a profile that is similar to the profile of the target surface <NUM>. In <FIG>, the intermediate virtual boundary <NUM> has a profile that is planar or flat. Those skilled in the art appreciate that the target virtual boundary <NUM> and the intermediate virtual boundary <NUM> may have other profiles not specifically recited herein.

The target and intermediate virtual boundaries <NUM>, <NUM> need not have the same profile, as shown in <FIG>. Instead, the boundaries <NUM>, <NUM> may have the different profiles with respect to one another, as shown in <FIG>. In <FIG>, the profile of the target virtual boundary <NUM> is similar to the profile of the target surface <NUM> whereas the profile of the intermediate virtual boundary <NUM> is planar. Of course, those skilled in the art appreciate that either profile of the boundaries <NUM>, <NUM> may differ from those illustrated in <FIG>. The profiles of each of the boundaries <NUM>, <NUM> may be generated manually or automatically in accordance with any suitable technique. Having different profiles may be useful depending on several factors, including, but not limited to, the tool <NUM> and/or mode being used.

Several different embodiments are possible for the target virtual boundary <NUM> in view of the first mode. As described, in the first mode, the intermediate virtual boundary <NUM> is active and the tool <NUM> is constrained in relation to the intermediate virtual boundary <NUM>. However, activation and deactivation of the target virtual boundary <NUM> may be controlled in the first mode. For example, as shown in <FIG>, and <FIG>, the target virtual boundary <NUM> may be activated in the first mode simultaneously while the intermediate boundary <NUM> is active. In one example, this may be done for redundancy purposes. As described, the intermediate boundary <NUM> is an important feature of the system <NUM> because it operates as a cutting boundary. Any errors in implementation of the intermediate boundary <NUM> may, in turn, leave the target surface <NUM> exposed to error. By simultaneously activating the target virtual boundary <NUM>, the system <NUM> increases reliability by having the target virtual boundary <NUM> as a back up to the intermediate virtual boundary <NUM>. This may also allow the manipulator <NUM> to operate at higher speeds knowing that the target virtual boundary <NUM> is provided as a redundancy. Alternatively, as shown in <FIG>, the target virtual boundary <NUM> may be deactivated in the first mode. This may be done to preserve computing resources, reduce complexity in implementation, and the like.

Control of the target virtual boundary <NUM> in the first mode may be automatic or manual. For example, the operator may manually activate or deactivate the target virtual boundary <NUM> in the first mode. Alternatively, the system <NUM> may automatically determine whether it is appropriate to activate the target virtual boundary <NUM> depending on certain events or conditions. For example, detection of instability of the system <NUM> may trigger automatic activation of the target virtual boundary <NUM> in the first mode.

The first mode and the second mode may be different type (i.e., manual/autonomous) or the same type depending on the application and a variety of other factors. One such factor is duration of the operating procedure, which is largely affected by a feed rate of the tool <NUM>. The feed rate is the velocity at which a distal end of the energy applicator <NUM> advances along a path segment. In general, in the autonomous mode, the manipulator <NUM> may be more accurate but provides a slower feed rate than in the manual mode. In the manual mode, the manipulator <NUM> may be less accurate but is capable of providing a faster feed rate than in the autonomous mode. This trade-off between accuracy and feed rate is one factor dictating what type of control is implemented during the first and second modes.

A frequency of back-and-forth oscillations of the tool <NUM> along the cutting path <NUM> may differ between the first and second modes. Generally, the greater the frequency of the oscillations, the closer together the cutting path <NUM> oscillations and the "finer" the cut provided by the tool <NUM>. On the other hand, the lesser the frequency of the oscillations, the more spaced apart the cutting path <NUM> oscillations and the "bulkier" the cut provided by the tool <NUM>.

Generally, as the tool <NUM> traverses the cutting path <NUM>, the tool <NUM> forms ribs <NUM> in the anatomy (distal femur), as shown in <FIG> and <FIG>. Examples of such ribs are shown in <CIT>, entitled, "Bone Pads,". The specific three-dimensional geometry of the ribs <NUM> is the result of a rotational cutting tool, such as a burr for example, making a plurality of channeled preparations <NUM>. In the embodiments shown, the plurality of channeled preparations <NUM> follow a substantially linear path resulting from back and forth movement of the tool <NUM> along the cutting path <NUM>. The ribs <NUM> have a height <NUM>, a width <NUM> and a plurality of protrusions <NUM>. When the first and second modes exhibit different cutting path <NUM> oscillation frequencies, the first and second modes produce ribs <NUM> having different configurations.

In one example, the oscillations are more frequent in the second mode than the first mode. For example, <FIG> illustrate ribs <NUM> resulting from bulk-cutting in the first mode and <FIG> illustrate ribs <NUM> resulting from fine-cutting in the second mode. Consequently, the ribs <NUM> are formed differently between the first and second modes. Specifically, the ribs <NUM> formed in the first mode (<FIG>) exhibit a larger peak-to-peak distance between adjacent ribs <NUM> as compared with ribs <NUM> formed in the second mode (<FIG>), which are closer together. The height and/or width of the ribs <NUM> may also be different between the first and second modes. For example, the width <NUM> of the ribs <NUM> in the bulk-cutting mode (<FIG>) is greater than the width <NUM> of the ribs <NUM> in the fine-cutting mode (<FIG>). Conversely, the height <NUM> of the ribs <NUM> in the bulk-cutting mode (<FIG>) is less than the height <NUM> of the ribs <NUM> in the fine-cutting mode (<FIG>). Additionally, the geometry of the protrusions <NUM> formed in the first mode may differ from those formed in the second mode. The first and second modes advantageously provide different surface finishes appropriate for the specific application. Those skilled in the art recognize that the first and second modes may cause differences in characteristics of the anatomy other than those described herein with respect to the ribs.

In one embodiment, the first mode is the autonomous mode and the second mode is the manual mode. Movement of the tool <NUM> occurs autonomously in the first mode and is constrained in relation to the intermediate virtual boundary <NUM>. Autonomous manipulation in the first mode is switched to manual manipulation in the second mode. Movement of the tool <NUM> occurs manually in the second mode and is constrained in relation to the target virtual boundary <NUM>. Specifically, the operator may rely on the surgical system <NUM> to perform a majority of the manipulation of the tissue autonomously in the first mode. As needed, the operator may switch to manual manipulation in the second mode to interface directly with the target virtual boundary <NUM>, which is closer to the target surface <NUM>. By doing so, the operator can perform versatile procedures, such as creating irregular surface finishes on the target surface <NUM>. The system <NUM> and method allow the operator to make final cuts in the target surface <NUM> that secure the implant better than may be planned with autonomous manipulation. Moreover, operators may prefer not to allow the system <NUM> to autonomously cut tissue entirely up to the target surface <NUM>. Having the intermediate virtual boundary <NUM> activated in the first mode provides added comfort for operators during autonomous manipulation because the intermediate virtual boundary <NUM> is spaced from the target virtual boundary <NUM>.

In another embodiment, the first mode and the second mode are both manual modes. Movement of the tool <NUM> occurs manually in the first mode and is constrained in relation to the intermediate virtual boundary <NUM>. Manual manipulation in the first mode is switched to manual manipulation in the second mode. Although manual manipulation is preserved in the second mode, the boundary configuration changes because the intermediate virtual boundary <NUM> is deactivated. In the second mode, movement of the tool <NUM> occurs manually and is constrained in relation to the target virtual boundary <NUM>. This embodiment advantageously provides the opportunity for the operator to use the manipulator <NUM> in a bulk-manipulation fashion in both the first and second modes. The operator, knowing that the intermediate virtual boundary <NUM> is constraining the tool <NUM> away from the target surface <NUM>, may take measures to perform bulk manipulation that is much faster and more aggressive than otherwise possible during autonomous manipulation. Once the bulk of the tissue is removed manually in the first mode, the system <NUM> may be switched to the second mode for allowing manual manipulation of the remaining portion of the tissue. In the second mode, the operator may manually create irregular or fine surface finishes on the target surface <NUM> in relation to the target virtual boundary <NUM>.

In yet embodiment, the first mode and the second mode are both autonomous modes. Movement of the tool <NUM> occurs autonomously in the first mode and is constrained in relation to the intermediate virtual boundary <NUM>. Autonomous manipulation in the first mode is switched to autonomous manipulation in the second mode. Although switching to the second mode maintains autonomous manipulation, the boundary configuration changes by deactivating the intermediate virtual boundary <NUM>. In the second mode, movement of the tool <NUM> occurs autonomously and is constrained in relation to the target virtual boundary <NUM>. This embodiment advantageously provides the opportunity to manipulate the tissue autonomously in a highly accurate and controlled manner throughout the first and second modes. Additionally, the operator may examine the tissue after autonomous manipulation in the first mode. In other words, rather than having the surgical device <NUM> autonomously manipulate the tissue entirely up to the target surface <NUM>, the first mode may be used as a first-phase whereby the operator checks the progress and accuracy of the autonomous cutting before deactivating the intermediate virtual boundary <NUM> in the second mode.

In one embodiment, the system implement "n" modes. For example, the system may implement three or more modes. The first mode may be a manual mode. The second mode may be an autonomous mode exhibiting autonomous bulk-cutting, as shown in <FIG>, for example. The third mode may be an autonomous mode exhibiting autonomous fine-cutting, as shown in <FIG>, for example. Those skilled in the art appreciate that any of the "n" modes may be a mode other than an autonomous or manual mode described herein.

The system and method may implement "n" virtual boundaries. For example, the system and method may implement three or more virtual boundaries. The "n" virtual boundaries may be implemented for the "n" modes. One example of a three- virtual boundary implementation is illustrated in <FIG>. In <FIG>, the first virtual boundary <NUM>, the second virtual boundary <NUM>, and a third virtual boundary <NUM> are associated with the anatomy. Here, first virtual boundary <NUM> is provided to promote removal of cartilage and a superficial layer of bone, the second virtual boundary <NUM> is provided to promote removal of a deeper layer of bone for placement of an implant, and the third virtual boundary <NUM> is provided to promote formation of a hole in preparation for insertion of a peg/tail to secure the implant. The first virtual boundary <NUM> is activated in the first mode. Movement of the tool is constrained in relation to the first virtual boundary <NUM> in the first mode. The first virtual boundary <NUM> is deactivated in the second mode. The third virtual boundary <NUM> may remain active in the second mode. Movement of the tool is constrained in relation to the second virtual boundary <NUM> in the second mode. The second virtual boundary <NUM> is deactivated in a third mode. Movement of the tool is constrained in relation to the third virtual boundary <NUM> in the third mode.

In some embodiments, the "n" virtual boundaries are tissue specific. That is, the virtual boundaries are configured to constrain the tool <NUM> in relation to different types of tissue. For example, the "n" virtual boundaries may constrain the tool <NUM> in relation to soft tissue, cartilage, bone, ligaments, and the like. This may be done to protect the specific tissue from manipulation by the tool <NUM>.

Additionally or alternatively, the "n" virtual boundaries are area/location specific. That is, the virtual boundaries are configured to constrain the tool <NUM> in relation to different areas or locations. For example, the "n" virtual boundaries may constrain the tool <NUM> in relation to other objects at the surgical site, such as retractors, other tools, trackers, and the like. Additionally, any one of the "n" virtual boundaries may serve as an irrigation boundary preventing the tool <NUM> from accessing a wet location in which the anatomy is undergoing irrigation. Those skilled in the art recognize that the "n" virtual boundaries and "n" modes may be implemented according to various other techniques not specifically recited herein.

In other embodiments, the "n" virtual boundaries may be used in conjunction with more than one surgical tool <NUM>. For example, as shown in <FIG>, a first surgical tool 20a and a second surgical tool 20b are provided. The tools 20a, 20b move in a coordinated and/or synchronized fashion. The first virtual boundary <NUM> is defined with relation to an upper surface of the anatomy and the second and third virtual boundaries <NUM>, <NUM> are defined along respective right and left surfaces of the anatomy. Here, the virtual boundaries <NUM>, <NUM>, <NUM> may be simultaneously active. Moreover, the virtual boundaries <NUM>, <NUM>, <NUM> may intersect, or touch, one another. In other examples, one tool <NUM> is used for manipulation while another tool is used for tissue retraction. In such instances, one virtual boundary may function as a manipulation constraining boundary while another virtual boundary functions as a tissue retraction boundary to prevent the retraction tool from leaving the intended area of retraction.

Any of the "n" virtual boundaries may be defined with respect to the anatomy such that virtual boundaries move as the anatomy position changes. This may be accomplished using the navigation and control techniques described herein.

The "n" virtual boundaries may be defined with respect to the same anatomy, as shown throughout the Figures, for example. In such instances, each of the "n" virtual boundaries follows the anatomy as the anatomy moves. Alternatively, the "n" virtual boundaries may be defined with respect to the different anatomy. For example, some "n" virtual boundaries may be defined with respect to the femur while other "n" virtual boundaries are defined with respect to the tibia. This may be done to protect the tibia from inadvertent manipulation. In such instances, spacing between the virtual boundaries may vary depending upon respective movement between the femur and tibia.

The controller <NUM> detects when the first mode is switched to the second mode, and vice-versa. The controller <NUM> may produce an alert to the operator to inform the operator whether constraint of the tool <NUM> is occurring in relation to the target virtual boundary <NUM> or intermediate virtual boundary <NUM>. The alert may be visual, haptic, audible, and the like. Those skilled in the art recognize that the alert may be implemented according to various other ways not specifically described herein.

In some instances, the tool <NUM> may be within the zone <NUM> in the second mode at a moment when the system <NUM> is switched to the first mode. In such instances, the tool <NUM> may become trapped between the intermediate virtual boundary <NUM> and the target virtual boundary <NUM> or target surface <NUM>. In one example, as shown in <FIG>, the target virtual boundary <NUM> remains active in the first mode such that the tool <NUM> is trapped between the intermediate virtual boundary <NUM> and the target virtual boundary <NUM>. In another example, as shown in <FIG>, the target virtual boundary <NUM> is deactivated in the first mode such that the tool <NUM> is trapped between the intermediate virtual boundary <NUM> and the target surface <NUM>.

Trapping the tool <NUM> in this manner may be deliberate or unintentional. When unintentional, the controller <NUM> may evaluate the position of the tool <NUM> when the second mode is switched to the first mode to prevent trapping the tool <NUM>. For example, if the tool <NUM> is in the zone <NUM> at the time of switching to the first mode, the controller <NUM> may instruct the manipulator <NUM> to withdraw the tool <NUM> from the zone <NUM> such that the tool <NUM> is pulled beyond the intermediate virtual boundary <NUM>. This may entail temporarily deactivating the intermediate virtual boundary <NUM> to allow exit of the tool <NUM>. In other instances, it may be intended to trap the tool <NUM> within the zone <NUM> in the first mode. Trapping the tool <NUM> may be done to use the intermediate virtual boundary <NUM> as an upper constraining or cutting boundary. To illustrate, in the second mode, the tool <NUM> may penetrate tissue in the zone <NUM> with a narrow incision. Thereafter, the first mode may be re-activated to trap the tool <NUM> within the zone <NUM> with the intermediate virtual boundary <NUM>. The operator may then remove tissue in the zone <NUM> manually or autonomously knowing that the tool <NUM> is constrained from above. This configuration may be useful for creating burrows in the tissue, and the like.

Several embodiments have been discussed in the foregoing description. However, the embodiments discussed herein are not intended to be exhaustive or limit the invention to any particular form. The terminology which has been used is intended to be in the nature of words of description rather than of limitation.

The many features and advantages of the invention are apparent from the detailed specification, and thus, it is intended by the appended claims to cover all such features and advantages of the invention which fall within the scope of the invention as defined by the appended claims.

Claim 1:
A surgical system (<NUM>) for manipulating an anatomy, said surgical system (<NUM>) comprising:
a manipulator (<NUM>) having a base (<NUM>) and a linkage (<NUM>);
a tool (<NUM>) coupled to said manipulator (<NUM>) and movable relative to said base (<NUM>) to interact with the anatomy; and
a controller (<NUM>) configured to:
generate a first virtual boundary (<NUM>) associated with the anatomy;
generate a second virtual boundary (<NUM>) associated with the anatomy and being spaced apart from the first virtual boundary (<NUM>);
define a zone (<NUM>) between said first and second virtual boundaries (<NUM>, <NUM>);
control movement of said tool (<NUM>) in a first mode and a second mode,
characterized in that said controller (<NUM>) is configured to prevent said tool (<NUM>) from penetrating said zone (<NUM>) in said first mode and to allow said tool (<NUM>) to penetrate said zone (<NUM>) in said second mode.