Patent Description:
Various medical procedures require the accurate localization of a three-dimensional position of a surgical instrument within the body in order to effect optimized treatment. A robotic surgical system may have five degrees of freedom to facilitate accurate positioning of the surgical instrument in relation to the body. These five degrees of freedom from a base of the robotic surgical system to an end effector include: (<NUM>) vertical linear motion, (<NUM>) shoulder rotation in the horizontal plane, (<NUM>) elbow rotation in the horizontal plane, (<NUM>) roll of the forearm, and (<NUM>) pitch of the end effector. With these five degrees of freedom, it is possible to move the robotic surgical system into a range of positions and angles where it can hold a guide tube to facilitate placement of screws and other straight line trajectories into the body.

These five degrees of freedom allow the guide tube of the end effector to be aligned with a trajectory vector, but the rotational position of the guide tube about the trajectory vector may not be independently selected and is dependent on the positions of these other joints. When using five degrees of freedom in this configuration, the movement of the robot along a straight line approaching the patient is usually associated with some residual rotation of the guide tube during the movement.

Shortcomings of a five degree of freedom robotic system may include an inability of the robot to move the guide tube along a fixed trajectory without residual rotation about the guide tube, an inability to provide active rotational motion to perform surgical tasks such as drilling or inserting screws, and inability to automatically orient a cutting blade while holding the guide tube perpendicular to a surface.

Examples of system and approach for controlling insertion paths of needles with asymmetric tips for therapeutic and diagnostic medical interventions are disclosed in <CIT>. Another example of a prior art system is disclosed in <CIT>.

Thus, there is a need to provide an additional degree of freedom for a guide tube associated with a five degree of freedom surgical robotic system. This may be accomplished as noted in the present disclosure using robot-assisted surgical techniques.

To meet these and other needs, device, systems, and methods for automatically rotating a guide tube are provided.

Methods described herein are not claimed but are useful for the understanding of the invention.

The invention and the following detailed description of certain embodiments thereof may be understood by reference to the following figures:.

It is to be understood that the present disclosure is not limited in its application to the details of construction and the arrangement of components set forth in the description herein or illustrated in the drawings. The teachings of the present disclosure may be used and practiced in other embodiments and practiced or carried out in various ways.

The following discussion is presented to enable a person skilled in the art to make and use embodiments of the present disclosure. The following detailed description is to be read with reference to the figures, in which like elements in different figures have like reference numerals. The figures, which are not necessarily to scale, depict selected embodiments and are not intended to limit the scope of the embodiments. Skilled artisans will recognize the examples provided herein have many useful alternatives and fall within the scope of the embodiments.

Turning now to the drawing, <FIG> and <FIG> illustrate a surgical robot system <NUM> in accordance with an exemplary embodiment. Surgical robot system <NUM> may include, for example, a surgical robot <NUM>, one or more robot arms <NUM>, a base <NUM>, a display <NUM>, an end effector <NUM>, for example, including a guide tube <NUM>, and one or more tracking markers <NUM>. The surgical robot system <NUM> may include a patient tracking device <NUM> also including one or more tracking markers <NUM>, which is adapted to be secured directly to the patient <NUM> (e.g., to the bone of the patient <NUM>). The surgical robot system <NUM> may also utilize a camera <NUM>, for example, positioned on a camera stand <NUM>. The camera stand <NUM> can have any suitable configuration to move, orient, and support the camera <NUM> in a desired position. The camera <NUM> may include any suitable camera or cameras, such as one or more infrared cameras (e.g., bifocal or stereophotogrammetric cameras), able to identify, for example, active and passive tracking markers <NUM> in a given measurement volume viewable from the perspective of the camera <NUM>. The camera <NUM> may scan the given measurement volume and detect the light that comes from the markers <NUM> in order to identify and determine the position of the markers <NUM> in three dimensions. For example, active markers <NUM> may include infrared-emitting markers that are activated by an electrical signal (e.g., infrared light emitting diodes (LEDs)), and passive markers <NUM> may include retro-reflective markers that reflect infrared light (e.g., they reflect incoming IR radiation into the direction of the incoming light), for example, emitted by illuminators on the camera <NUM> or other suitable device.

<FIG> and <FIG> illustrate a potential configuration for the placement of the surgical robot system <NUM> in an operating room environment. For example, the robot <NUM> may be positioned near or next to patient <NUM>. Although depicted near the head of the patient <NUM>, it will be appreciated that the robot <NUM> can be positioned at any suitable location near the patient <NUM> depending on the area of the patient <NUM> undergoing the operation. The camera <NUM> may be separated from the robot system <NUM> and positioned at the foot of patient <NUM>. This location allows the camera <NUM> to have a direct visual line of sight to the surgical field <NUM>. Again, it is contemplated that the camera <NUM> may be located at any suitable position having line of sight to the surgical field <NUM>. In the configuration shown, the surgeon <NUM> may be positioned across from the robot <NUM>, but is still able to manipulate the end effector <NUM> and the display <NUM>. A surgical assistant <NUM> may be positioned across from the surgeon <NUM> again with access to both the end effector <NUM> and the display <NUM>. If desired, the locations of the surgeon <NUM> and the assistant <NUM> may be reversed. The traditional areas for the anesthesiologist <NUM> and the nurse or scrub tech <NUM> remain unimpeded by the locations of the robot <NUM> and camera <NUM>.

With respect to the other components of the robot <NUM>, the display <NUM> can be attached to the surgical robot <NUM> and in other exemplary embodiments, display <NUM> can be detached from surgical robot <NUM>, either within a surgical room with the surgical robot <NUM>, or in a remote location. End effector <NUM> may be coupled to the robot arm <NUM> and controlled by at least one motor. In exemplary embodiments, end effector <NUM> can comprise a guide tube <NUM>, which is able to receive and orient a surgical instrument <NUM> (described further herein) used to perform surgery on the patient <NUM>. As used herein, the term "end effector" is used interchangeably with the terms "end-effectuator" and "effectuator element. " Although generally shown with a guide tube <NUM>, it will be appreciated that the end effector <NUM> may be replaced with any suitable instrumentation suitable for use in surgery. In some embodiments, end effector <NUM> can comprise any known structure for effecting the movement of the surgical instrument <NUM> in a desired manner.

The surgical robot <NUM> is able to control the translation and orientation of the end effector <NUM>. The robot <NUM> is able to move end effector <NUM> along x-, y-, and z-axes, for example. The end effector <NUM> can be configured for selective rotation about one or more of the x-, y-, and z- axis, and a Z Frame axis (such that one or more of the Euler Angles (e.g., roll, pitch, and/or yaw) associated with end effector <NUM> can be selectively controlled). In some exemplary embodiments, selective control of the translation and orientation of end effector <NUM> can permit performance of medical procedures with significantly improved accuracy compared to conventional robots that utilize, for example, a six degree of freedom robot arm comprising only rotational axes. For example, the surgical robot system <NUM> may be used to operate on patient <NUM>, and robot arm <NUM> can be positioned above the body of patient <NUM>, with end effector <NUM> selectively angled relative to the z-axis toward the body of patient <NUM>.

In some exemplary embodiments, the position of the surgical instrument <NUM> can be dynamically updated so that surgical robot <NUM> can be aware of the location of the surgical instrument <NUM> at all times during the procedure. Consequently, in some exemplary embodiments, surgical robot <NUM> can move the surgical instrument <NUM> to the desired position quickly without any further assistance from a physician (unless the physician so desires). In some further embodiments, surgical robot <NUM> can be configured to correct the path of the surgical instrument <NUM> if the surgical instrument <NUM> strays from the selected, preplanned trajectory. In some exemplary embodiments, surgical robot <NUM> can be configured to permit stoppage, modification, and/or manual control of the movement of end effector <NUM> and/or the surgical instrument <NUM>. Thus, in use, in exemplary embodiments, a physician or other user can operate the system <NUM>, and has the option to stop, modify, or manually control the autonomous movement of end effector <NUM> and/or the surgical instrument <NUM>. Further details of surgical robot system <NUM> including the control and movement of a surgical instrument <NUM> by surgical robot <NUM> can be found in co-pending <CIT>.

The robotic surgical system <NUM> can comprise one or more tracking markers <NUM> configured to track the movement of robot arm <NUM>, end effector <NUM>, patient <NUM>, and/or the surgical instrument <NUM> in three dimensions. In exemplary embodiments, a plurality of tracking markers <NUM> can be mounted (or otherwise secured) thereon to an outer surface of the robot <NUM>, such as, for example and without limitation, on base <NUM> of robot <NUM>, on robot arm <NUM>, or on the end effector <NUM>. In exemplary embodiments, at least one tracking marker <NUM> of the plurality of tracking markers <NUM> can be mounted or otherwise secured to the end effector <NUM>. One or more tracking markers <NUM> can further be mounted (or otherwise secured) to the patient <NUM>. In exemplary embodiments, the plurality of tracking markers <NUM> can be positioned on the patient <NUM> spaced apart from the surgical field <NUM> to reduce the likelihood of being obscured by the surgeon, surgical tools, or other parts of the robot <NUM>. Further, one or more tracking markers <NUM> can be further mounted (or otherwise secured) to the surgical tools <NUM> (e.g., a screw driver, dilator, implant inserter, or the like). Thus, the tracking markers <NUM> enable each of the marked objects (e.g., the end effector <NUM>, the patient <NUM>, and the surgical tools <NUM>) to be tracked by the robot <NUM>. In exemplary embodiments, system <NUM> can use tracking information collected from each of the marked objects to calculate the orientation and location, for example, of the end effector <NUM>, the surgical instrument <NUM> (e.g., positioned in the tube <NUM> of the end effector <NUM>), and the relative position of the patient <NUM>.

In exemplary embodiments, one or more of markers <NUM> may be optical markers. In some embodiments, the positioning of one or more tracking markers <NUM> on end effector <NUM> can maximize the accuracy of the positional measurements by serving to check or verify the position of end effector <NUM>. Further details of surgical robot system <NUM> including the control, movement and tracking of surgical robot <NUM> and of a surgical instrument <NUM> can be found in co-pending <CIT>.

Exemplary embodiments include one or more markers <NUM> coupled to the surgical instrument <NUM>. In exemplary embodiments, these markers <NUM>, for example, coupled to the patient <NUM> and surgical instruments <NUM>, as well as markers <NUM> coupled to the end effector <NUM> of the robot <NUM> can comprise conventional infrared light-emitting diodes (LEDs) or an Optotrak® diode capable of being tracked using a commercially available infrared optical tracking system such as Optotrak®. Optotrak® is a registered trademark of Northern Digital Inc. , Waterloo, Ontario, Canada. In other embodiments, markers <NUM> can comprise conventional reflective spheres capable of being tracked using a commercially available optical tracking system such as Polaris Spectra. Polaris Spectra is also a registered trademark of Northern Digital, Inc. In an exemplary embodiment, the markers <NUM> coupled to the end effector <NUM> are active markers which comprise infrared light-emitting diodes which may be turned on and off, and the markers <NUM> coupled to the patient <NUM> and the surgical instruments <NUM> comprise passive reflective spheres.

In exemplary embodiments, light emitted from and/or reflected by markers <NUM> can be detected by camera <NUM> and can be used to monitor the location and movement of the marked objects. In alternative embodiments, markers <NUM> can comprise a radio-frequency and/or electromagnetic reflector or transceiver and the camera <NUM> can include or be replaced by a radio-frequency and/or electromagnetic transceiver.

Similar to surgical robot system <NUM>, <FIG> illustrates a surgical robot system <NUM> and camera stand <NUM>, in a docked configuration, consistent with an exemplary embodiment of the present disclosure. Surgical robot system <NUM> may comprise a robot <NUM> including a display <NUM>, upper arm <NUM>, lower arm <NUM>, end effector <NUM>, vertical column <NUM>, casters <NUM>, cabinet <NUM>, tablet drawer <NUM>, connector panel <NUM>, control panel <NUM>, and ring of information <NUM>. Camera stand <NUM> may comprise camera <NUM>. These components are described in greater with respect to <FIG>. <FIG> illustrates the surgical robot system <NUM> in a docked configuration where the camera stand <NUM> is nested with the robot <NUM>, for example, when not in use. It will be appreciated by those skilled in the art that the camera <NUM> and robot <NUM> may be separated from one another and positioned at any appropriate location during the surgical procedure, for example, as shown in <FIG> and <FIG>. <FIG> illustrates a base <NUM> consistent with an exemplary embodiment of the present disclosure. Base <NUM> may be a portion of surgical robot system <NUM> and comprise cabinet <NUM>. Cabinet <NUM> may house certain components of surgical robot system <NUM> including but not limited to a battery <NUM>, a power distribution module <NUM>, a platform interface board module <NUM>, a computer <NUM>, a handle <NUM>, and a tablet drawer <NUM>. The connections and relationship between these components is described in greater detail with respect to <FIG>.

<FIG> illustrates a block diagram of certain components of an exemplary embodiment of surgical robot system <NUM>. Surgical robot system <NUM> may comprise platform subsystem <NUM>, computer subsystem <NUM>, motion control subsystem <NUM>, and tracking subsystem <NUM>. Platform subsystem <NUM> may further comprise battery <NUM>, power distribution module <NUM>, platform interface board module <NUM>, and tablet charging station <NUM>. Computer subsystem <NUM> may further comprise computer <NUM>, display <NUM>, and speaker <NUM>. Motion control subsystem <NUM> may further comprise driver circuit <NUM>, motors <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, stabilizers <NUM>, <NUM>, <NUM>, <NUM>, end effector <NUM>, and controller <NUM>. Tracking subsystem <NUM> may further comprise position sensor <NUM> and camera converter <NUM>. System <NUM> may also comprise a foot pedal <NUM> and tablet <NUM>.

Input power is supplied to system <NUM> via a power source <NUM> which may be provided to power distribution module <NUM>. Power distribution module <NUM> receives input power and is configured to generate different power supply voltages that are provided to other modules, components, and subsystems of system <NUM>. Power distribution module <NUM> may be configured to provide different voltage supplies to platform interface module <NUM>, which may be provided to other components such as computer <NUM>, display <NUM>, speaker <NUM>, driver <NUM> to, for example, power motors <NUM>, <NUM>, <NUM>, <NUM> and end effector <NUM>, motor <NUM>, ring <NUM>, camera converter <NUM>, and other components for system <NUM> for example, fans for cooling the electrical components within cabinet <NUM>.

Power distribution module <NUM> may also provide power to other components such as tablet charging station <NUM> that may be located within tablet drawer <NUM>. Tablet charging station <NUM> may be in wireless or wired communication with tablet <NUM> for charging table <NUM>. Tablet <NUM> may be used by a surgeon consistent with the present disclosure and described herein. Power distribution module <NUM> may also be connected to battery <NUM>, which serves as temporary power source in the event that power distribution module <NUM> does not receive power from input power <NUM>. At other times, power distribution module <NUM> may serve to charge battery <NUM> if necessary.

Other components of platform subsystem <NUM> may also include connector panel <NUM>, control panel <NUM>, and ring <NUM>. Connector panel <NUM> may serve to connect different devices and components to system <NUM> and/or associated components and modules. Connector panel <NUM> may contain one or more ports that receive lines or connections from different components. For example, connector panel <NUM> may have a ground terminal port that may ground system <NUM> to other equipment, a port to connect foot pedal <NUM> to system <NUM>, a port to connect to tracking subsystem <NUM>, which may comprise position sensor <NUM>, camera converter <NUM>, and cameras <NUM> associated with camera stand <NUM>. Connector panel <NUM> may also include other ports to allow USB, Ethernet, HDMI communications to other components, such as computer <NUM>.

Control panel <NUM> may provide various buttons or indicators that control operation of system <NUM> and/or provide information regarding system <NUM>. For example, control panel <NUM> may include buttons to power on or off system <NUM>, lift or lower vertical column <NUM>, and lift or lower stabilizers <NUM>-<NUM> that may be designed to engage casters <NUM> to lock system <NUM> from physically moving. Other buttons may stop system <NUM> in the event of an emergency, which may remove all motor power and apply mechanical brakes to stop all motion from occurring. Control panel <NUM> may also have indicators notifying the user of certain system conditions such as a line power indicator or status of charge for battery <NUM>.

Ring <NUM> may be a visual indicator to notify the user of system <NUM> of different modes that system <NUM> is operating under and certain warnings to the user.

Computer subsystem <NUM> includes computer <NUM>, display <NUM>, and speaker <NUM>. Computer <NUM> includes an operating system and software to operate system <NUM>. Computer <NUM> may receive and process information from other components (for example, tracking subsystem <NUM>, platform subsystem <NUM>, and/or motion control subsystem <NUM>) in order to display information to the user. Further, computer subsystem <NUM> may also include speaker <NUM> to provide audio to the user.

Tracking subsystem <NUM> may include position sensor <NUM> and converter <NUM>. Tracking subsystem <NUM> may correspond to camera stand <NUM> including camera <NUM> as described with respect to <FIG>. Position sensor <NUM> may be camera <NUM>. Tracking subsystem may track the location of certain markers that are located on the different components of system <NUM> and/or instruments used by a user during a surgical procedure. This tracking may be conducted in a manner consistent with the present disclosure including the use of infrared technology that tracks the location of active or passive elements, such as LEDs or reflective markers, respectively. The location, orientation, and position of structures having these types of markers may be provided to computer <NUM> which may be shown to a user on display <NUM>. For example, a surgical instrument <NUM> having these types of markers and tracked in this manner (which may be referred to as a navigational space) may be shown to a user in relation to a three dimensional image of a patient's anatomical structure. Motion control subsystem <NUM> may be configured to physically move vertical column <NUM>, upper arm <NUM>, lower arm <NUM>, or rotate end effector <NUM>. The physical movement may be conducted through the use of one or more motors <NUM>-<NUM>. For example, motor <NUM> may be configured to vertically lift or lower vertical column <NUM>. Motor <NUM> may be configured to laterally move upper arm <NUM> around a point of engagement with vertical column <NUM> as shown in <FIG>. Motor <NUM> may be configured to laterally move lower arm <NUM> around a point of engagement with upper arm <NUM> as shown in <FIG>. Motors <NUM> and <NUM> may be configured to move end effector <NUM> in a manner such that one may control the roll and one may control the tilt, thereby providing multiple angles that end effector <NUM> may be moved. These movements may be achieved by controller <NUM> which may control these movements through load cells disposed on end effector <NUM> and activated by a user engaging these load cells to move system <NUM> in a desired manner.

Moreover, system <NUM> may provide for automatic movement of vertical column <NUM>, upper arm <NUM>, and lower arm <NUM> through a user indicating on display <NUM> (which may be a touchscreen input device) the location of a surgical instrument or component on three dimensional image of the patient's anatomy on display <NUM>. The user may initiate this automatic movement by stepping on foot pedal <NUM> or some other input means.

<FIG> illustrates a surgical robot system <NUM> consistent with an exemplary embodiment. Surgical robot system <NUM> may comprise end effector <NUM>, robot arm <NUM>, guide tube <NUM>, instrument <NUM>, and robot base <NUM>. Instrument tool <NUM> may be attached to a tracking array <NUM> including one or more tracking markers (such as markers <NUM>) and have an associated trajectory <NUM>. Trajectory <NUM> may represent a path of movement that instrument tool <NUM> is configured to travel once it is positioned through or secured in guide tube <NUM>, for example, a path of insertion of instrument tool <NUM> into a patient. In an exemplary operation, robot base <NUM> may be configured to be in electronic communication with robot arm <NUM> and end effector <NUM> so that surgical robot system <NUM> may assist a user (for example, a surgeon) in operating on the patient <NUM>. Surgical robot system <NUM> may be consistent with previously described surgical robot system <NUM> and <NUM>.

A tracking array <NUM> may be mounted on instrument <NUM> to monitor the location and orientation of instrument tool <NUM>. The tracking array <NUM> may be attached to an instrument <NUM> and may comprise tracking markers <NUM>. As best seen in <FIG>, tracking markers <NUM> may be, for example, light emitting diodes and/or other types of reflective markers (e.g., markers <NUM> as described elsewhere herein). The tracking devices may be one or more line of sight devices associated with the surgical robot system. As an example, the tracking devices may be one or more cameras <NUM>, <NUM> associated with the surgical robot system <NUM>, <NUM> and may also track tracking array <NUM> for a defined domain or relative orientations of the instrument <NUM> in relation to the robot arm <NUM>, the robot base <NUM>, end effector <NUM>, and/or the patient <NUM>. The tracking devices may be consistent with those structures described in connection with camera stand <NUM> and tracking subsystem <NUM>.

<FIG> illustrate a top view, front view, and side view, respectively, of end effector <NUM> consistent with an exemplary embodiment. End effector <NUM> may comprise one or more tracking markers <NUM>. Tracking markers <NUM> may be light emitting diodes or other types of active and passive markers, such as tracking markers <NUM> that have been previously described. In an exemplary embodiment, the tracking markers <NUM> are active infrared-emitting markers that are activated by an electrical signal (e.g., infrared light emitting diodes (LEDs)). Thus, tracking markers <NUM> may be activated such that the infrared markers <NUM> are visible to the camera <NUM>, <NUM> or may be deactivated such that the infrared markers <NUM> are not visible to the camera <NUM>, <NUM>. Thus, when the markers <NUM> are active, the end effector <NUM> may be controlled by the system <NUM>, <NUM>, <NUM>, and when the markers <NUM> are deactivated, the end effector <NUM> may be locked in position and unable to be moved by the system <NUM>, <NUM>, <NUM>.

Markers <NUM> may be disposed on or within end effector <NUM> in a manner such that the markers <NUM> are visible by one or more cameras <NUM>, <NUM> or other tracking devices associated with the surgical robot system <NUM>, <NUM>, <NUM>. The camera <NUM>, <NUM> or other tracking devices may track end effector <NUM> as it moves to different positions and viewing angles by following the movement of tracking markers <NUM>. The location of markers <NUM> and/or end effector <NUM> may be shown on a display <NUM>, <NUM> associated with the surgical robot system <NUM>, <NUM>, <NUM>, for example, display <NUM> as shown in <FIG> and/or display <NUM> shown in <FIG>. This display <NUM>, <NUM> may allow a user to ensure that end effector <NUM> is in a desirable position in relation to robot arm <NUM>, robot base <NUM>, the patient <NUM>, and/or the user.

For example, as shown in <FIG>, markers <NUM> may be placed around the surface of end effector <NUM> so that a tracking device placed away from the surgical field <NUM> and facing toward the robot <NUM>, <NUM> and the camera <NUM>, <NUM> is able to view at least <NUM> of the markers <NUM> through a range of common orientations of the end effector <NUM> relative to the tracking device <NUM>, <NUM>, <NUM>. For example, distribution of markers <NUM> in this way allows end effector <NUM> to be monitored by the tracking devices when end effector <NUM> is translated and rotated in the surgical field <NUM>.

In addition, in exemplary embodiments, end effector <NUM> may be equipped with infrared (IR) receivers that can detect when an external camera <NUM>, <NUM> is getting ready to read markers <NUM>. Upon this detection, end effector <NUM> may then illuminate markers <NUM>. The detection by the IR receivers that the external camera200, <NUM> is ready to read markers <NUM> may signal the need to synchronize a duty cycle of markers <NUM>, which may be light emitting diodes, to an external camera200, <NUM>. This may also allow for lower power consumption by the robotic system as a whole, whereby markers <NUM> would only be illuminated at the appropriate time instead of being illuminated continuously. Further, in exemplary embodiments, markers <NUM> may be powered off to prevent interference with other navigation tools, such as different types of surgical instruments <NUM>.

<FIG> depicts one type of surgical instrument <NUM> including a tracking array <NUM> and tracking markers <NUM>. Tracking markers <NUM> may be of any type described herein including but not limited to light emitting diodes or reflective spheres. Markers <NUM> are monitored by tracking devices associated with the surgical robot system <NUM>, <NUM>, <NUM> and may be one or more of the line of sight cameras <NUM>, <NUM>. The cameras <NUM>, <NUM> may track the location of instrument <NUM> based on the position and orientation of tracking array <NUM> and markers <NUM>. A user, such as a surgeon <NUM>, may orient instrument <NUM> in a manner so that tracking array <NUM> and markers <NUM> are sufficiently recognized by the tracking device or camera <NUM>, <NUM> to display instrument <NUM> and markers <NUM> on, for example, display <NUM> of the exemplary surgical robot system.

The manner in which a surgeon <NUM> may place instrument <NUM> into guide tube <NUM> of the end effector <NUM> and adjust the instrument <NUM> is evident in <FIG>. The hollow tube or guide tube <NUM>, <NUM> of the end effector <NUM>, <NUM>, <NUM> is sized and configured to receive at least a portion of the surgical instrument <NUM>. The guide tube <NUM>, <NUM> is configured to be oriented by the robot arm <NUM> such that insertion and trajectory for the surgical instrument <NUM> is able to reach a desired anatomical target within or upon the body of the patient <NUM>. The surgical instrument <NUM> may include at least a portion of a generally cylindrical instrument. Although a screw driver is exemplified as the surgical tool <NUM>, it will be appreciated that any suitable surgical tool <NUM> may be positioned by the end effector <NUM>. By way of example, the surgical instrument <NUM> may include one or more of a guide wire, cannula, a retractor, a drill, a reamer, a screw driver, an insertion tool, a removal tool, or the like. Although the hollow tube <NUM>, <NUM> is generally shown as having a cylindrical configuration, it will be appreciated by those of skill in the art that the guide tube <NUM>, <NUM> may have any suitable shape, size and configuration desired to accommodate the surgical instrument <NUM> and access the surgical site.

<FIG> illustrate end effector <NUM> and a portion of robot arm <NUM> consistent with an exemplary embodiment. End effector <NUM> may further comprise body <NUM> and clamp <NUM>. Clamp <NUM> may comprise handle <NUM>, balls <NUM>, spring <NUM>, and lip <NUM>. Robot arm <NUM> may further comprise depressions <NUM>, mounting plate <NUM>, lip <NUM>, and magnets <NUM>.

End effector <NUM> may mechanically interface and/or engage with the surgical robot system and robot arm <NUM> through one or more couplings. For example, end effector <NUM> may engage with robot arm <NUM> through a locating coupling and/or a reinforcing coupling. Through these couplings, end effector <NUM> may fasten with robot arm <NUM> outside a flexible and sterile barrier. In an exemplary embodiment, the locating coupling may be a magnetically kinematic mount and the reinforcing coupling may be a five bar over center clamping linkage.

With respect to the locating coupling, robot arm <NUM> may comprise mounting plate <NUM>, which may be non-magnetic material, one or more depressions <NUM>, lip <NUM>, and magnets <NUM>. Magnet <NUM> is mounted below each of depressions <NUM>. Portions of clamp <NUM> may comprise magnetic material and be attracted by one or more magnets <NUM>. Through the magnetic attraction of clamp <NUM> and robot arm <NUM>, balls <NUM> become seated into respective depressions <NUM>. For example, balls <NUM> as shown in <FIG> would be seated in depressions <NUM> as shown in <FIG>. This seating may be considered a magnetically-assisted kinematic coupling. Magnets <NUM> may be configured to be strong enough to support the entire weight of end effector <NUM> regardless of the orientation of end effector <NUM>. The locating coupling may be any style of kinematic mount that uniquely restrains six degrees of freedom.

With respect to the reinforcing coupling, portions of clamp <NUM> may be configured to be a fixed ground link and as such clamp <NUM> may serve as a five bar linkage. Closing clamp handle <NUM> may fasten end effector <NUM> to robot arm <NUM> as lip <NUM> and lip <NUM> engage clamp <NUM> in a manner to secure end effector <NUM> and robot arm <NUM>. When clamp handle <NUM> is closed, spring <NUM> may be stretched or stressed while clamp <NUM> is in a locked position. The locked position may be a position that provides for linkage past center. Because of a closed position that is past center, the linkage will not open absent a force applied to clamp handle <NUM> to release clamp <NUM>. Thus, in a locked position end effector <NUM> may be robustly secured to robot arm <NUM>.

Spring <NUM> may be a curved beam in tension. Spring <NUM> may be comprised of a material that exhibits high stiffness and high yield strain such as virgin PEEK (poly-ether-etherketone). The linkage between end effector <NUM> and robot arm <NUM> may provide for a sterile barrier between end effector <NUM> and robot arm <NUM> without impeding fastening of the two couplings.

The reinforcing coupling may be a linkage with multiple spring members. The reinforcing coupling may latch with a cam or friction based mechanism. The reinforcing coupling may also be a sufficiently powerful electromagnet that will support fastening end-effector <NUM> to robot arm <NUM>. The reinforcing coupling may be a multi-piece collar completely separate from either end effector <NUM> and/or robot arm <NUM> that slips over an interface between end effector <NUM> and robot arm <NUM> and tightens with a screw mechanism, an over center linkage, or a cam mechanism.

Referring to <FIG> and <FIG>, prior to or during a surgical procedure, certain registration procedures may be conducted in order to track objects and a target anatomical structure of the patient <NUM> both in a navigation space and an image space. In order to conduct such registration, a registration system <NUM> may be used as illustrated in <FIG>.

In order to track the position of the patient <NUM>, a patient tracking device <NUM> may include a patient fixation instrument <NUM> to be secured to a rigid anatomical structure of the patient <NUM> and a dynamic reference base (DRB) <NUM> may be securely attached to the patient fixation instrument <NUM>. For example, patient fixation instrument <NUM> may be inserted into opening <NUM> of dynamic reference base <NUM>. Dynamic reference base <NUM> may contain markers <NUM> that are visible to tracking devices, such as tracking subsystem <NUM>. These markers <NUM> may be optical markers or reflective spheres, such as tracking markers <NUM>, as previously discussed herein.

Patient fixation instrument <NUM> is attached to a rigid anatomy of the patient <NUM> and may remain attached throughout the surgical procedure. In an exemplary embodiment, patient fixation instrument <NUM> is attached to a rigid area of the patient <NUM>, for example, a bone that is located away from the targeted anatomical structure subject to the surgical procedure. In order to track the targeted anatomical structure, dynamic reference base <NUM> is associated with the targeted anatomical structure through the use of a registration fixture that is temporarily placed on or near the targeted anatomical structure in order to register the dynamic reference base <NUM> with the location of the targeted anatomical structure.

A registration fixture <NUM> is attached to patient fixation instrument <NUM> through the use of a pivot arm <NUM>. Pivot arm <NUM> is attached to patient fixation instrument <NUM> by inserting patient fixation instrument <NUM> through an opening <NUM> of registration fixture <NUM>. Pivot arm <NUM> is attached to registration fixture <NUM> by, for example, inserting a knob <NUM> through an opening <NUM> of pivot arm <NUM>.

Using pivot arm <NUM>, registration fixture <NUM> may be placed over the targeted anatomical structure and its location may be determined in an image space and navigation space using tracking markers <NUM> and/or fiducials <NUM> on registration fixture <NUM>. Registration fixture <NUM> may contain a collection of markers <NUM> that are visible in a navigational space (for example, markers <NUM> may be detectable by tracking subsystem <NUM>). Tracking markers <NUM> may be optical markers visible in infrared light as previously described herein. Registration fixture <NUM> may also contain a collection of fiducials <NUM>, for example, such as bearing balls, that are visible in an imaging space (for example, a three dimension CT image). As described in greater detail with respect to <FIG>, using registration fixture <NUM>, the targeted anatomical structure may be associated with dynamic reference base <NUM> thereby allowing depictions of objects in the navigational space to be overlaid on images of the anatomical structure. Dynamic reference base <NUM>, located at a position away from the targeted anatomical structure, may become a reference point thereby allowing removal of registration fixture <NUM> and/or pivot arm <NUM> from the surgical area.

<FIG> provides an exemplary method <NUM> for registration consistent with the present disclosure. Method <NUM> begins at step <NUM> wherein a graphical representation (or image(s)) of the targeted anatomical structure may be imported into system <NUM>, <NUM><NUM>, for example computer <NUM>. The graphical representation may be three dimensional CT or a fluoroscope scan of the targeted anatomical structure of the patient <NUM> which includes registration fixture <NUM> and a detectable imaging pattern of fiducials <NUM>.

At step <NUM>, an imaging pattern of fiducials <NUM> is detected and registered in the imaging space and stored in computer <NUM>. Optionally, at this time at step <NUM>, a graphical representation of the registration fixture <NUM> may be overlaid on the images of the targeted anatomical structure.

At step <NUM>, a navigational pattern of registration fixture <NUM> is detected and registered by recognizing markers <NUM>. Markers <NUM> may be optical markers that are recognized in the navigation space through infrared light by tracking subsystem <NUM> via position sensor <NUM>. Thus, the location, orientation, and other information of the targeted anatomical structure is registered in the navigation space. Therefore, registration fixture <NUM> may be recognized in both the image space through the use of fiducials <NUM> and the navigation space through the use of markers <NUM>. At step <NUM>, the registration of registration fixture <NUM> in the image space is transferred to the navigation space. This transferal is done, for example, by using the relative position of the imaging pattern of fiducials <NUM> compared to the position of the navigation pattern of markers <NUM>.

At step <NUM>, registration of the navigation space of registration fixture <NUM> (having been registered with the image space) is further transferred to the navigation space of dynamic registration array <NUM> attached to patient fixture instrument <NUM>. Thus, registration fixture <NUM> may be removed and dynamic reference base <NUM> may be used to track the targeted anatomical structure in both the navigation and image space because the navigation space is associated with the image space.

At steps <NUM> and <NUM>, the navigation space may be overlaid on the image space and objects with markers visible in the navigation space (for example, surgical instruments <NUM> with optical markers <NUM>). The objects may be tracked through graphical representations of the surgical instrument <NUM> on the images of the targeted anatomical structure.

<FIG> illustrate imaging devices <NUM> that may be used in conjunction with robot systems <NUM>, <NUM>, <NUM> to acquire pre-operative, intra-operative, post-operative, and/or real-time image data of patient <NUM>. Any appropriate subject matter may be imaged for any appropriate procedure using the imaging system <NUM>. The imaging system <NUM> may be any imaging device such as imaging device <NUM> and/or a C-arm <NUM> device. It may be desirable to take x-rays of patient <NUM> from a number of different positions, without the need for frequent manual repositioning of patient <NUM> which may be required in an x-ray system. As illustrated in <FIG>, the imaging system <NUM> may be in the form of a C-arm <NUM> that includes an elongated C-shaped member terminating in opposing distal ends <NUM> of the "C" shape. C-shaped member <NUM> may further comprise an x-ray source <NUM> and an image receptor <NUM>. The space within C-arm <NUM> of the arm may provide room for the physician to attend to the patient substantially free of interference from x-ray support structure <NUM>. As illustrated in <FIG>, the imaging system may include imaging device <NUM> having a gantry housing <NUM> attached to a support structure imaging device support structure <NUM>, such as a wheeled mobile cart <NUM> with wheels <NUM>, which may enclose an image capturing portion, not illustrated. The image capturing portion may include an x-ray source and/or emission portion and an x-ray receiving and/or image receiving portion, which may be disposed about one hundred and eighty degrees from each other and mounted on a rotor (not illustrated) relative to a track of the image capturing portion. The image capturing portion may be operable to rotate three hundred and sixty degrees during image acquisition. The image capturing portion may rotate around a central point and/or axis, allowing image data of patient <NUM> to be acquired from multiple directions or in multiple planes. Although certain imaging systems <NUM> are exemplified herein, it will be appreciated that any suitable imaging system may be selected by one of ordinary skill in the art.

Referring now to <FIG> of the present disclosure, <FIG> illustrates surgical tool <NUM> with tip <NUM> and bone <NUM>, which may be target bone of a patient during a surgical procedure. Also illustrated are three forces (Finsertion, Fp, and Fn) associated with tool <NUM> as it penetrates bone <NUM>, for example during a medical procedure where a surgeon drills into a patient's bone. Surgical tool <NUM> may be any surgical instrument or tool associated with surgical applications including but not limited to a drill, an awl, a tap, a screwdriver, or other types of surgical tools. These forces may be referred to as reactive forces at the tool-bone interface when a force intended to penetrate bone is applied to a tool. The force of insertion (Finsertion) can be resolved into a component force normal to the surface (FN) and a component force parallel to the surface (FP).

While tip <NUM> of instrument <NUM> is disposed and poised at the surface of bone <NUM>, physical mechanisms resulting from the aforementioned forces include the following: (<NUM>) bone <NUM> may move away from the insertion force (Finsertion) en masse, (<NUM>) frictional resistance preventing slippage of tip <NUM> may be overcome resulting in tip <NUM> to travel laterally in direction parallel to bone surface <NUM> in the direction of Fp, or (<NUM>) the tip may penetrate the bone in an intended direction such as Finsertion.

The present disclosure seeks to keep instrument <NUM> aligned where desired and prevent tip <NUM> from wandering or "skiving" due to the force parallel (Fp) to the surface of bone <NUM>. Instrument <NUM> may be operated through a rigidly held guide tube with close tolerance between the tube's inner diameter and the tool's outer diameter. Such guide tube has been described previously herein. In order for the guide tube to be completely effective in driving instrument <NUM> or another piece of hardware into bone <NUM>, the tube should not move relative to bone <NUM> and instrument <NUM> or other hardware should not bend relative to the tube or bone <NUM>.

As previously described herein, a surgical robot capable of being rigidly locked to the floor can be effective in maintaining a stationary, rigid position of a guide tube (for example, robot system <NUM>). Skiving may result in multiple scenarios in the context of robot-assisted surgery. For example, during insertion of instrument <NUM> at an angle through the guide tube and into contact with bone <NUM>, the force generated parallel to the surface of bone <NUM>, which may depend, at least in part or in total, on the instrument insertion force and insertion angle, may lead to bending of the instrument and/or movement of the patient.

As another example, inserting instrument <NUM> through a guide tube, either at an angle to bone <NUM> or perpendicular to bone <NUM>, may result in instrument <NUM> reaching a depth or point where instrument <NUM> is fully within the guide tube or the instrument's handle bottoms out (i.e., is fully on the top entry of the guide tube, at which point the tool can no longer be inserted any further unless the tube is advanced longitudinally). If a surgeon applies additional downward force after instrument <NUM> is bottomed out, that force is absorbed by the guide tube, not transferred to instrument <NUM> for further penetrating bone <NUM>. This example may lead to several unintended results. One unintended result may be that if the surgeon does not realize that instrument <NUM> is bottomed out, addition force may damage or strip the screw hole in the patient bone by rotating a screwdriver or tap while screw or tap cannot move forward. Another unintended result may be that the surgeon may not achieve the desired or expected penetration of the instrument or tool that the surgeon is attempting to advance.

As previously described, robot system <NUM> may include load cells (which control multiaxial movement of the robot arm) disposed on end effector <NUM>. Using a multi-axis load cell mounted to the guide tube and/or end effector, one may quantify the lateral deflection and longitudinal bottoming out forces/torques described above in real time during surgery. Consistent with the present disclosure, robot system <NUM> may use the forces and moments monitored by a multi-axis load cell on the robot's guide tube to provide specific feedback to the surgeon to help prevent the instrument or tool from being inserted inaccurately, incompletely or poorly.

<FIG> illustrates an exemplary embodiment of a robot arm <NUM> consistent with the present disclosure. Robot arm <NUM> may include end-effector <NUM>, guide tube <NUM>, and bracelet <NUM> mounted to end-effector <NUM>. Bracelet <NUM> may further include one or more multi-axis load cells <NUM>.

Multi-axis load cell <NUM> mounted to end effector <NUM> via bracelet <NUM> may be capable of providing measurements of torques and forces along, about, and across an axis of the guide tube (for example, a longitudinal axis of guide tube <NUM>). Multi-axis load cells <NUM> may comprise strain gauges applied across appropriately oriented rigid internal members such that they may accurately measure forces and torques while elastically deforming by a negligible amount.

Multi-axis load cell <NUM> may support end-effector <NUM> and guide tube <NUM> in a manner such that the forces and moments applied to guide tube <NUM> may be detected by one or more of load cells <NUM>. As shown in <FIG>, directions of forces and moments sensed by the one or more load cells <NUM> are depicted with arrows Mx, My, and Mz and arrows labeled X, Y, and Z.

In a case where a surgeon is inserting instrument <NUM> (for example, a drill) through guide tube <NUM> and penetrating bone <NUM> with instrument <NUM> at a position normal to a flat surface, the majority of the force applied by the surgeon may be transferred to the drill as longitudinal force down the axis of the drill bit. It may be that a relatively small lateral force (in the X or Y direction as shown in <FIG>) or torque across the axis of the guide tube (Mx or My as shown in <FIG>) would be expected, and a relatively small longitudinal force applied to guide tube <NUM> would be expected (for example in the Z direction as shown in <FIG>).

Continuing with the last example, as the surgeon torques the tool, a relatively small amount of that torque should be transferred to the load cell (shown as Mz in <FIG>) since the tool should rotate freely inside guide tube <NUM>. It may be possible that the surgeon may misalign the applied force, in which case the rigidly held guide tube <NUM> may act to prevent the tool from moving laterally. This lateral force may be monitored by one or more of the multi-axis load cells <NUM> as a moderate lateral (X, Y or combined XY) force.

In cases where instrument <NUM> (e.g., a drill or tool) is inserted under conditions where instrument <NUM> strikes bone <NUM> at a steep angle causing tip <NUM> to skive, the forces detected by one or more multi-axis load cells <NUM> may change in certain predictable ways. For example, the moment across guide tube <NUM> (Mx or My as shown in <FIG>) may increase and the force lateral to guide tube <NUM> (X or Y direction in <FIG>) may increase. The X-Y orientation of this increased moment may be perpendicular to the direction of slope of bone <NUM> as shown in <FIG>. Similarly, the orientation of the force would be in the direction of the downhill slope of bone <NUM>, as shown in <FIG>, and perpendicular to the increased moment. Due to the lateral force that may instrument <NUM> to press against the side of guide tube <NUM> and slightly bend, a slightly increased downward force on guide tube <NUM> (Z direction as shown in <FIG>) may be expected. In this example, it may be that the prominent increased values should be in this bending moment and lateral force.

In another example, in cases where instrument <NUM> (for example, a drill or tool) bottoms out within guide tube <NUM>, a sudden spike in the downward longitudinal force in the direction of guide tube <NUM> (Z direction shown in <FIG>) may be expected without any substantial increase in any other detected moment or force as the surgeon applies additional downward force. Additionally, if the surgeon were to release instrument <NUM>, some residual downward force (Z) may be expected since instrument <NUM> may still interact with guide tube <NUM>. For example, if the surgeon were inserting a screw using a locking screwdriver but the screwdriver bottomed out, after releasing the screwdriver, its handle under tension against the top of the guide tube would cause a downward force to remain.

The robot system via software may continuously monitor forces and moments and check whether each force and moment remains within the normal expected range or threshold. Software could react with messaging when a force/moment pattern that meets the above expected undesirable conditions is encountered. Examples of messages could be "caution - possible skiving of the tool may be occurring" or "caution - the tool may have reached its depth stop".

<FIG> illustrates and an exemplary method 1800for detecting the presence of skiving of an instrument during a surgical procedure. Method <NUM> begins at step <NUM> where, as previously discussed herein, the end-effector and guide may be automatically or manually positioned to a location relative to a patient undergoing a surgical procedure. At step <NUM>, an instrument or tool (for example, instrument <NUM>) may be inserted into the guide tube of the robot system. At step <NUM>, the instrument may be inserted into the patient and advanced to contact a target bone of the patient for the surgical procedure. For example, instrument may be advanced to contact the target bone in order to drill screw holes for pedicle screws, as previously described. At step <NUM>, robot system may monitor the forces and moments measured by one or more load cells present on the robot system, for example, disposed on the end-effector. At step <NUM> the monitored forces and moments may be compared against the expected forces and moments that would be consistent with the surgical procedure. At step <NUM>, if the monitored forces and moments fall within an expected range or predetermined threshold, the surgical procedure is continued at step <NUM> and method <NUM> continues to step <NUM> as previously described. If the monitored forces and moments do not fall within an expected range or predetermined threshold, an alert or notification is provided by the robot system to indicate the presence of skiving.

In another embodiment, there is provided a method to quantify the number of millimeters of skiving that occurs and a method to overcome any skiving that does occur.

As described above, a <NUM>-axis load cell mounted to a robot arm is configured to detect forces that are oriented laterally relative to a guide tube. In an optimal procedure, the lateral forces are applied on the guide tube should generally be minimal. The main force detected and applied in one embodiment should be along the axis of the guide tube. In embodiments, where there are lateral forces that occur, these forces can cause skiving or movement of a surgical instrument along a bone surface without penetrating bone, or if the forces excessive lateral skiving or movement of the bone away from the surgical instrument. In some embodiments, lateral forces may cause the tip of the tool, to bend and deflect laterally away from the central axis of the surgical instrument shaft and guide tube.

In certain embodiments, a robotic arm may hold the guide tube in an immobile position even in the presence of lateral forces. As lateral forces push on bone and cause the bone to move away from the rigid guide tube, in one embodiment, the amount of bone movement that occurs can be tracked with a DRB (dynamic reference base) attached to the patient. The DRB comprises an array of tracking markers such as reflective spheres, the positions of which are tracked using a tracking system such as the Polaris Spectra optical tracking system (Northern Digital, Inc. ) Since the amount of bone movement is monitored, any offset can be reported by the system to the user, and automatic robotic adjustment of the guide tube position can offset additional movement caused by the lateral forces.

Now turning to <FIG>, in some embodiments, if the instrument tip bends relative to the instrument's tracking array as a result of lateral forces, the amount of deflection of the instrument relative to its tracking array may be measured. In one embodiment, strain gauges may be used to measure the instrument tip deflection caused by lateral forces. Strain gauges are typically resistance-based and are configured to detect slight increases or decreases in length of a surface. In one embodiment, a pair of strain gauges oriented parallel, along the axis of the instrument, and attached to the surface of the instrument on opposite sides of the shaft may measure the deflection toward or away from either strain gauge. In another embodiment, three or more gauges may be mounted in parallel around the perimeter of the instrument at a given longitudinal position and configured to provide estimates of the magnitude of longitudinal shortening or lengthening around the perimeter of an instrument at the location where the strain gauges are attached.

<FIG> illustrates an exaggerated lateral deflection of an instrument <NUM> due to lateral forces, indicated by the arrow. Strain gauges <NUM> mounted on opposing sides of the instrument <NUM> measure the elongation of the instrument <NUM> on the side the force is measured and shortening of the instrument <NUM> on the side opposite to the force. If an instrument <NUM> or guide tube is deflected, the side of the shaft toward which it is deflected decreases in length and the opposite side of the shaft increases in length. The deflection of cylinders, which comprise the shaft of an instrument or guide tube, utilizes the following equations in response to applied lateral forces: deflection = FL<NUM>/ 3EI where F is the applied lateral force at the tip; L is the length from tip to the fulcrum (assumed to be cantilevered); E is the modulus of elasticity of the shaft material, such as cobalt chrome or stainless steel; I is the moment of inertia, which is a geometric property related to the cross section of the tool. In one embodiment, when the instrument is configured as a cylinder, I = □ d<NUM>/<NUM>, where d is the diameter of the cylinder.

If the instrument is a uniform cylinder, the tip deflection can be estimated by knowing the lateral force and the contact points of the instrument in the guide tube. In some embodiments if the instrument is tapered toward the tip or is otherwise non-uniform, the exact point of contact within the guide tube may be difficult to determine since it would be within the tube at the point where the instrument starts tapering and is no longer in tight contact with the tube. In this case calibrating the tip deflection is based on the strain gauges mounted to the instrument, specifically the attachment points of the strain gauges, and the geometry of the internal portion of the guide tube. This data is then used to calculate the estimated deflection of the instrument <NUM>.

In another embodiment for calibrating the tip deflection, strain measurements from a set of strain gauges attached around the shaft of the instrument maybe used with a neural network. A neural network is a mathematical method in which patterns of responses of nodes (in this case, the output from the array of strain gauges) are used as inputs to produce well-defined outputs (in this case, lateral deflection) if the outputs are distinctive enough for different sets of inputs. In some embodiments, the neural network for instrument deflection measurement is used by applying known test loads laterally at different approach angles and contact locations around the tool tip while measuring deflection using optical tracking, coordinate measurement machine (CMM) or other means. Once this data is a part of the neural network, the output of the strain gauges would be fed continuously into the neural network computer model and deflection data may be streamed out and displayed by the system.

In another embodiment, a neural network or physical modeling may be used by applying data from the instrument <NUM> and guide tube <NUM> interaction in two zones, as illustrated in <FIG>. In the first zone, the instrument's <NUM> taper ends within the guide tube <NUM> and so a lever arm for deflection is the point of application of force to the point where the largest diameter of the instrument touches the guide tube. The lever arm remains fixed for a fixed point of load application as long as the instrument <NUM> remains in this zone. In the second zone, the instrument's <NUM> taper ends outside the guide tube <NUM> and so the lever arm for deflection is the point of application of force to the point where the instrument <NUM> exits the guide tube <NUM>. The lever arm continuously increases as more of the instrument <NUM> protrudes. Based on the instrument's tracking array location relative to the guide tube's tracking array location, the system can keep track of the current zone and appropriately interpret the neural network model or physical model of the tool to calculate tip force and displacement.

In one embodiment, a <NUM>-axis load cell mounted to a robot arm can assess forces and moments caused by the interaction of the tip of the instrument with a bone. If skiving occurs due to lateral forces being applied to the instrument, the following method may be utilized to overcome or mitigate any skiving that may occur. In one embodiment, the instrument tip can be configured to be sharp and capable of penetrating the bone with axial cutting capabilities as well as side-cutting capabilities. The sharpened tip of the instrument when lateral forces are applied may be similar to drilling a surface at a <NUM>° angle relative to the drill as shown in <FIG>. Specifically, <FIG> illustrates an instrument <NUM> having axial cutting capabilities and instrument <NUM> illustrates an axial and lateral side-cutting capabilities striking an inclined surface.

In the preferred embodiment, an instrument with a sharpened tip will cut through the surface of bone before skiving. In some cases, even if the instrument is provided with a greater cutting surface, skiving may still be possible. In these cases, in one embodiment, a repetitive puncturing action may be used to insert the instrument through the surface of the bone without moving the bone. This tapping motion may be applied by a surgeon, and a tactile response to the penetration is signaled when the instrument has advanced through the surface of the bone as illustrated in <FIG>. The stepwise or tapping motion as shown in <FIG>, prevents skiving from occurring.

Turning now to <FIG>, a robotic surgical system having five degrees of freedom is illustrated. These five degrees of freedom from base of the robotic surgical system to the end effector include: (<NUM>) vertical linear motion (<FIG>), (<NUM>) shoulder rotation in the horizontal plane (<FIG>), (<NUM>) elbow rotation in the horizontal plane (<FIG>), (<NUM>) roll of the forearm (<FIG>), and (<FIG>) pitch of the end effector (<FIG>). With these five degrees of freedom, it is possible to move the robotic surgical system into a range of positions and angles where it can hold a guide tube to facilitate placement of screws and other straight line trajectories into the body.

These five degrees of freedom allow the guide tube of the end effector to be aligned with a trajectory vector, but the rotational position of the guide tube about the trajectory vector may not be independently selected and is dependent on the positions of these other joints. When using five degrees of freedom in this configuration, the movement of the robot along a straight line approaching the patient is usually associated with some residual rotation of the guide tube during the movement (<FIG>).

<FIG> illustrate a robotic surgical system <NUM>, including robot arm <NUM>, base <NUM>, and guide tube <NUM>. Together, <FIG> show movement of robot arm <NUM> along a straight line. As coordinated movement of the joints illustrated in <FIG> occurs, constraining motion to keep guide tube <NUM> centered along the line, the rotational position of guide tube <NUM> relative to the line and the room varies.

According to principles of the present disclosure, instead of fixing the rotational orientation of the guide tube relative to proximal joints and allowing the rotational position of the guide tube to be dictated by the kinematics of these other joints, an additional degree of freedom may be added to the robotic system. This additional degree of freedom would include automatic rotation about the central axis of the guide tube. Referring to <FIG>, a motorized end effector <NUM>, a motor <NUM>, a rotational bearing <NUM>, and a guide tube <NUM> may be used to provide automatic rotation. Automatic rotation may be accomplished by connecting guide tube <NUM> to end effector <NUM> with rotational bearing <NUM> and driving the rotational position of guide tube <NUM> with a rotational motor <NUM>, such as a servo motor. The position to which to drive the rotational motion of guide tube <NUM> could be based on feedback from various types of sensors or from user input through software, as discussed in greater detail below.

There are several advantages to maintaining a desired orientation while moving down a trajectory line. For example, some types of surgical implants such as interbody cages are inserted in a particular orientation. A system to set and maintain the orientation of an implant at all points along the insertion trajectory would ensure that the implant was inserted in the proper final orientation and did not bind or seize on tissue or other instruments during insertion.

Another example of a situation in which a particular orientation is required while moving along a path other than a straight line is if the surgeon wants to trace or cut tissue at a particular orientation. For example, and as shown in <FIG>, when cutting soft tissue with a scalpel or cutting bone with a bone scalpel, if a flat blade <NUM> is perpendicular to the axis of the guide tube, it would be desirable to keep the flat cutting blade oriented in a certain way (i.e., tangent to the cut line).

The extra degree of freedom that rotates blade <NUM> within the guide tube could automatically keep blade <NUM> orientated as desired as the robot arm moves through the path of the intended cut. As illustrated in the figures, <FIG> show an orientation of blade <NUM> in a first position. <FIG> show blade <NUM> moving to a second position and <FIG> show blade <NUM> moving to a third position along the path.

As noted above, the robot system could operate to control this additional degree of freedom through several methods. A software input may fix the guide tube rotation at a particular position relative to the robot base, for example, <NUM>°, <NUM>°, <NUM>°, <NUM>° or any value from <NUM>-<NUM>°. Through forward kinematics, the actual position of the guide tube relative to the robot base could be determined for any set of joint positions, and the rotational position of the guide tube then adjusted so that the rotational orientation of the guide tube remained fixed relative to the base at the value specified. Alternately, the rotational position that will be necessary to correctly orient a surgical implant when the guide tube is positioned where needed for a planned trajectory can be specified manually or automatically in software. Through inverse kinematics, the rotational position that the guide tube will be in at that position can be predicted. Then, the rotational position of the guide tube can be adjusted so that this target rotational position will be achieved once the robot arm has moved in place.

The additional rotational degree of freedom could also make use of feedback from tracking, such as the optical tracking of reflective spheres as described above. If the tracking system is registered to patient anatomy such as a CT scan, then through tracking of the patient and robot, software may automatically determine the necessary rotational position of the guide tube relative to the anatomy at any position of the robot to ensure that an implant is rotationally oriented as needed for implantation. For example, for an interbody implant, which is inserted in the disc space between two vertebral bodies, the angle of placement could be determined from drawing or automatically detecting from medical images the orientation of the disc space. This position would be set relative to the reference array on the patient and the guide tube rotation automatically updates to keep this angle fixed regardless of the position of the arm to ensure that the implant is inserted at the correct orientation.

Feedback from the tracking system may also use camera-based tracking of visible light patterns located on the guide tube. Trackable patterns could be artificially added to the guide tube, for example, by etching or printing lines on the guide tube, or patterns could be natural edges of the guide tube itself or extensions from the guide tube. Using tracked position feedback of the guide tube's orientation and location, the system could drive the rotational position of the guide tube into the desired rotation. For example, the system could ensure that the guide tube was properly aligned with the disc space for insertion of an interbody implant.

Referring <FIG>, end effector <NUM> may include an inertial sensor <NUM>. Another feedback method to maintain a fixed rotational orientation of the guide tube relative to the patient or the room is to use inertial or tilt sensor <NUM>. Such a sensor could detect the direction of gravity and direct the robot system to orient the guide tube to maintain a particular alignment relative to the gravity vector. For example, an inertial sensor that is offset radially from the centerline of the guide tube could provide feedback that directs the guide tube to always rotate into a position where the radial vector from the centerline of the guide tube through the sensor is oriented as closely with the line of gravity as is possible in the rotational degree of freedom. That is, there is a solution in the range of <NUM>-<NUM>° of rotation of the guide tube where the angular difference between the gravity vector and the radial vector from guide tube center through the inertial sensor is smallest.

However, most straight-line trajectories into the body for surgical purposes have some angulation, and this method would be a simple way to keep the guide tube's rotational orientation fixed relative to the robot base while traveling along a straight line despite the normal rotation that would occur due to joint positions more proximal to the base.

Referring to <FIG>, end effector <NUM> may include a force sensor <NUM>. Another feedback method to set a rotational orientation of the guide tube is force sensor <NUM>. Such a sensor would be effective in situations where the robot is used to perform some action perpendicular to the central axis of the guide tube, for example, cutting. Force magnitude and direction sensed from a force sensor that is embedded in the guide tube could be used to alter the rotational orientation of the guide tube to facilitate the procedure. For example, if the robot is moving laterally to cut or push through tissue, the direction of force could be sensed and the robot system could send an instruction to rotate the guide tube so that the sharpest edge is toward the direction of highest force.

Although several embodiments of the invention have been disclosed in the foregoing specification, it is understood that many modifications and other embodiments of the invention will come to mind to which the invention pertains, having the benefit of the teaching presented in the foregoing description and associated drawings. It is thus understood that the invention is not limited to the specific embodiments disclosed hereinabove, and that many modifications and other embodiments are intended to be included within the scope of the appended claims. Moreover, although specific terms are employed herein, as well as in the claims which follow, they are used only in a generic and descriptive sense, and not for the purposes of limiting the described invention, nor the claims which follow.

Claim 1:
A surgical robot system comprising:
a robot base (<NUM>);
a robot arm (<NUM>) connected to and in electronic communication with the robot base;
an end-effector (<NUM>) connected to the robot arm and in electronic communication with the robot base, wherein the end-effector comprises a guide tube (<NUM>) defining a central axis and which is configured to receive a surgical instrument,
wherein the guide tube is connected to the end-effector via a rotational bearing (<NUM>),
wherein the end-effector includes a motor (<NUM>) adapted to automatically rotate the guide tube around the central axis of the guide tube, and
characterized in that
the guide tube is configured to be automatically rotated about the central axis of the guide tube so as to preserve a fixed rotational angle of the guide tube relative to the robot base as the robot arm and end-effector are moved along a trajectory to a surgical site.