Patent Publication Number: US-2023149082-A1

Title: Systems, methods, and devices for performing a surgical procedure using a virtual guide

Description:
BACKGROUND 
     The present disclosure is generally directed to performing a surgical procedure, and relates more particularly to performing a surgical procedure using a virtual guide. 
     Displays providing information about a surgical procedure may assist a surgeon or other medical provider in carrying out the surgical procedure. The information provided may include positioning of a patient. Patient anatomy can change over time, particularly following placement of a medical implant in the patient anatomy or after a surgical step is performed to move one or more anatomical elements. 
     BRIEF SUMMARY 
     Example aspects of the present disclosure include: 
     A system for performing a surgical procedure using a virtual guide according to at least one embodiment of the present disclosure comprises a display configured to display an augmented image in an environment; a processor; and a memory storing data for processing by the processor, the data, when processed, causes the processor to: track a surgical landmark; determine a parameter of the surgical landmark; generate a virtual guide for presentation within the augmented image based on the parameter of the surgical landmark; and cause the display to present the virtual guide within the augmented image. 
     Any of the aspects herein, wherein the virtual guide is related to minimizing at least one of a force and a pressure applied to the surgical landmark. 
     Any of the aspects herein, wherein the surgical landmark comprises at least one of an anatomical element, an implant, and a marker. 
     Any of the aspects herein, wherein the parameter comprises at least one of an angle, a pose, a position, an orientation, a size, a trajectory, and a shape of the surgical landmark. 
     Any of the aspects herein, wherein the memory stores further data for processing by the processor that, when processed, causes the processor to: detect movement of the surgical landmark. 
     Any of the aspects herein, wherein the memory stores further data for processing by the processor that, when processed, causes the processor to: update a presentation of the virtual guide based on the movement of the surgical landmark; and cause the display to present the updated virtual guide within the augmented image. 
     Any of the aspects herein, wherein the memory stores further data for processing by the processor that, when processed, causes the processor to: generate a notification when the surgical landmark meets or exceeds one or more thresholds during the detected movement. 
     Any of the aspects herein, wherein the memory stores further data for processing by the processor that, when processed, causes the processor to: receive a surgical plan comprising one or more expected thresholds; and update the one or more expected thresholds based on the detected movement. 
     Any of the aspects herein, wherein the one or more expected thresholds comprises at least one of a force threshold, a positional threshold, a pressure threshold, an orientation threshold, and an acceleration threshold. 
     Any of the aspects herein, wherein determining the parameter is based on at least one of the one or more expected parameters, a surgical landmark within a field of view of the display, and a surgical step to be performed. 
     Any of the aspects herein, wherein the display comprises a headset. 
     Any of the aspects herein, wherein the surgical landmark comprises a plurality of vertebrae and the surgical plan comprises one or more surgical steps for moving the plurality of vertebrae to a predetermined alignment. 
     A system for performing a surgical procedure using a virtual guide according to at least one embodiment of the present disclosure comprises a display configured to display an augmented image in an environment; a processor; and a memory storing data for processing by the processor, the data, when processed, causes the processor to: detect a first surgical landmark in the environment and within a first field of view of the display; determine a first parameter of the first surgical landmark; generate a first virtual guide based on the first parameter of the first surgical landmark; detect a second surgical landmark in the environment and within a second field of view of the display; determine a second parameter of the second surgical landmark; generate a second virtual guide based on the second parameter of the second surgical landmark; and cause the display to present the augmented image such that at least one of the first virtual guide is presented on the first surgical landmark, the second virtual guide is presented on the second surgical landmark, and the first virtual guide is presented on the first surgical landmark and the second virtual guide is presented on the second surgical landmark. 
     Any of the aspects herein, wherein the first field of view and the second field of view are at least partially overlapping. 
     Any of the aspects herein, wherein the display comprises a headset. 
     Any of the aspects herein, wherein each of the first surgical landmark and the second surgical landmark comprises at least one of an anatomical element, an implant, and a marker. 
     Any of the aspects herein, wherein each of the first parameter and the second parameter comprises at least one of an angle, a pose, a position, an orientation, a size, a trajectory, and a shape of the first surgical landmark and the second surgical landmark. 
     Any of the aspects herein, wherein the memory stores further data for processing by the processor that, when processed, causes the processor to: detect movement of at least one of the first surgical landmark and the second surgical landmark. 
     Any of the aspects herein, wherein the memory stores further data for processing by the processor that, when processed, causes the processor to: update a presentation of at least one the first virtual guide and the second virtual guide based on the movement of the first surgical landmark and/or the second surgical landmark; and cause the display to present the updated at least one of the first virtual guide and the second virtual guide within the augmented image. 
     A device for performing a surgical procedure using a virtual guide according to at least one embodiment of the present disclosure comprises a processor; and a memory storing data for processing by the processor, the data, when processed, causes the processor to: track a surgical landmark visible in a field of vision of a display configured to display an augmented image of an environment; determine a parameter of the surgical landmark; generate a virtual guide based on the parameter of the surgical landmark; and cause the display to present the virtual guide overlapping with the surgical landmark as part of the augmented image of the environment. 
     Any aspect in combination with any one or more other aspects. 
     Any one or more of the features disclosed herein. 
     Any one or more of the features as substantially disclosed herein. 
     Any one or more of the features as substantially disclosed herein in combination with any one or more other features as substantially disclosed herein. 
     Any one of the aspects/features/embodiments in combination with any one or more other aspects/features/embodiments. 
     Use of any one or more of the aspects or features as disclosed herein. 
     It is to be appreciated that any feature described herein can be claimed in combination with any other feature(s) as described herein, regardless of whether the features come from the same described embodiment. 
     The details of one or more aspects of the disclosure are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the techniques described in this disclosure will be apparent from the description and drawings, and from the claims. 
     The phrases “at least one”, “one or more”, and “and/or” are open-ended expressions that are both conjunctive and disjunctive in operation. For example, each of the expressions “at least one of A, B and C”, “at least one of A, B, or C”, “one or more of A, B, and C”, “one or more of A, B, or C” and “A, B, and/or C” means A alone, B alone, C alone, A and B together, A and C together, B and C together, or A, B and C together. When each one of A, B, and C in the above expressions refers to an element, such as X, Y, and Z, or class of elements, such as X1-Xn, Y1-Ym, and Z1-Zo, the phrase is intended to refer to a single element selected from X, Y, and Z, a combination of elements selected from the same class (e.g., X1 and X2) as well as a combination of elements selected from two or more classes (e.g., Y1 and Zo). 
     The term “a” or “an” entity refers to one or more of that entity. As such, the terms “a” (or “an”), “one or more” and “at least one” can be used interchangeably herein. It is also to be noted that the terms “comprising”, “including”, and “having” can be used interchangeably. 
     The preceding is a simplified summary of the disclosure to provide an understanding of some aspects of the disclosure. This summary is neither an extensive nor exhaustive overview of the disclosure and its various aspects, embodiments, and configurations. It is intended neither to identify key or critical elements of the disclosure nor to delineate the scope of the disclosure but to present selected concepts of the disclosure in a simplified form as an introduction to the more detailed description presented below. As will be appreciated, other aspects, embodiments, and configurations of the disclosure are possible utilizing, alone or in combination, one or more of the features set forth above or described in detail below. 
     Numerous additional features and advantages of the present disclosure will become apparent to those skilled in the art upon consideration of the embodiment descriptions provided hereinbelow. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       The accompanying drawings are incorporated into and form a part of the specification to illustrate several examples of the present disclosure. These drawings, together with the description, explain the principles of the disclosure. The drawings simply illustrate preferred and alternative examples of how the disclosure can be made and used and are not to be construed as limiting the disclosure to only the illustrated and described examples. Further features and advantages will become apparent from the following, more detailed, description of the various aspects, embodiments, and configurations of the disclosure, as illustrated by the drawings referenced below. 
         FIG.  1    is a block diagram of a system according to at least one embodiment of the present disclosure; 
         FIG.  2    is a flowchart according to at least one embodiment of the present disclosure; 
         FIG.  3    is a flowchart according to at least one embodiment of the present disclosure; 
         FIG.  4    is a flowchart according to at least one embodiment of the present disclosure; and 
         FIG.  5    is a flowchart according to at least one embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     It should be understood that various aspects disclosed herein may be combined in different combinations than the combinations specifically presented in the description and accompanying drawings. It should also be understood that, depending on the example or embodiment, certain acts or events of any of the processes or methods described herein may be performed in a different sequence, and/or may be added, merged, or left out altogether (e.g., all described acts or events may not be necessary to carry out the disclosed techniques according to different embodiments of the present disclosure). In addition, while certain aspects of this disclosure are described as being performed by a single module or unit for purposes of clarity, it should be understood that the techniques of this disclosure may be performed by a combination of units or modules associated with, for example, a computing device and/or a medical device. 
     In one or more examples, the described methods, processes, and techniques may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored as one or more instructions or code on a computer-readable medium and executed by a hardware-based processing unit. Alternatively or additionally, functions may be implemented using machine learning models, neural networks, artificial neural networks, or combinations thereof (alone or in combination with instructions). Computer-readable media may include non-transitory computer-readable media, which corresponds to a tangible medium such as data storage media (e.g., RAM, ROM, EEPROM, flash memory, or any other medium that can be used to store desired program code in the form of instructions or data structures and that can be accessed by a computer). 
     Instructions may be executed by one or more processors, such as one or more digital signal processors (DSPs), general purpose microprocessors (e.g., Intel Core i3, i5, i7, or i9 processors; Intel Celeron processors; Intel Xeon processors; Intel Pentium processors; AMD Ryzen processors; AMD Athlon processors; AMD Phenom processors; Apple A10 or 10X Fusion processors; Apple A11, A12, A12X, A12Z, or A13 Bionic processors; or any other general purpose microprocessors), graphics processing units (e.g., Nvidia GeForce RTX 2000-series processors, Nvidia GeForce RTX 3000-series processors, AMD Radeon RX 5000-series processors, AMD Radeon RX 6000-series processors, or any other graphics processing units), application specific integrated circuits (ASICs), field programmable logic arrays (FPGAs), or other equivalent integrated or discrete logic circuitry. Accordingly, the term “processor” as used herein may refer to any of the foregoing structure or any other physical structure suitable for implementation of the described techniques. Also, the techniques could be fully implemented in one or more circuits or logic elements. 
     Before any embodiments of the disclosure are explained in detail, it is to be understood that the disclosure is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. The disclosure is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Further, the present disclosure may use examples to illustrate one or more aspects thereof. Unless explicitly stated otherwise, the use or listing of one or more examples (which may be denoted by “for example,” “by way of example,” “e.g.,” “such as,” or similar language) is not intended to and does not limit the scope of the present disclosure. 
     The terms proximal and distal are used in this disclosure with their conventional medical meanings, proximal being closer to the operator or user of the system, and further from the region of surgical interest in or on the patient, and distal being closer to the region of surgical interest in or on the patient, and further from the operator or user of the system. 
     A patient may have a deformity such as a spinal deformity, which may be an abnormal alignment or curve of the bony vertebral column. Adult scoliosis and kyphosis can be caused by age-related wear and tear on the back and/or complications from past surgeries. A moderate deformity of a patient&#39;s spine may occur when the facet joints and discs deteriorate over time and are no long able to support the spine&#39;s normal posture. Pain may result from stressed joints and pinched nerves caused by the abnormal alignment. Conventional treatment may include medications, physical therapy, injections, or surgery. 
     Surgical options to correct a spinal deformity may vary depending on the severity of the symptoms, the number of spinal levels affected, and the type of deformity. A combination of different fusion and instrumentation techniques may be used to treat the patient&#39;s specific condition. Complex deformities such as, for example, kyphosis, often require the cutting of bone (osteotomy) and stabilization of the spine with long rods and screws in staged operations. The alignment is conventionally performed based on a surgeon&#39;s perception of the alignment without any substantial feedback as to whether the alignment was performed properly. 
     In at least one embodiment of the present disclosure, an augmented reality display is used to guide a surgeon on a surgical procedure such as a spinal alignment and provides the surgeon with virtual guides such as virtual lines and angles on top of the anatomy when the patient is lying on a surgery table. By seeing the virtual guides, the surgeon can use the additional information to perform the alignment safely and accurately. In addition to virtual guides such as virtual lines and angles, virtual recommendations may be provided for the execution of the procedure itself to minimize forces and pressures applied on the spine. Such embodiments provide crucial information to the surgeon to increase an accuracy of the procedure during the procedure and to reduce the surgeon&#39;s uncertainty of whether the procedure was performed accurately. 
     Embodiments of the present disclosure provide technical solutions to one or more of the problems of (1) providing virtual information about one or more anatomical elements during a surgical procedure, (2) effectively displaying virtual information during a surgical procedure, and (3) increasing an accuracy and safety of a surgical procedure. 
     Turning first to  FIG.  1   , a block diagram of a system  100  according to at least one embodiment of the present disclosure is shown. The system  100  may be used to generate and present a virtual guide during a surgical procedure and/or carry out one or more other aspects of one or more of the methods disclosed herein. The system  100  comprises a computing device  102 , one or more imaging devices  112 , a robot  114 , a navigation system  118 , a display  126 , a database  130 , and/or a cloud or other network  134 . Systems according to other embodiments of the present disclosure may comprise more or fewer components than the system  100 . For example, the system  100  may not include the imaging device  112 , the robot  114 , the display  126 , the navigation system  118 , one or more components of the computing device  102 , the database  130 , and/or the cloud  134 . 
     The computing device  102  comprises a processor  104 , a memory  106 , a communication interface  108 , and a user interface  110 . Computing devices according to other embodiments of the present disclosure may comprise more or fewer components than the computing device  102 . 
     The processor  104  of the computing device  102  may be any processor described herein or any similar processor. The processor  104  may be configured to execute instructions stored in the memory  106 , which instructions may cause the processor  104  to carry out one or more computing steps utilizing or based on data received from the imaging device  112 , the robot  114 , the navigation system  118 , the display  126 , the database  130 , and/or the cloud  134 . 
     The memory  106  may be or comprise RAM, DRAM, SDRAM, other solid-state memory, any memory described herein, or any other tangible, non-transitory memory for storing computer-readable data and/or instructions. The memory  106  may store information or data useful for completing, for example, any step of the methods  200 ,  300 ,  400 , and/or  500  described herein, or of any other methods. The memory  106  may store, for example, instructions and/or machine learning models that support one or more functions of the robot  114 . For instance, the memory  106  may store content (e.g., instructions and/or machine learning models) that, when executed by the processor  104 , enable a registration  120 , tracking  122 , and/or virtual guide generation  124 . 
     The registration  120  enables the processor  104  to register or correlate a patient coordinate space with, for example, a display coordinate space of the display  126 . The registration  120  may also enable the processor  104  to register or correlate any coordinate space with another coordinate space (e.g., a patient coordinate space to a robotic coordinate space, the patient coordinate space to a navigation coordinate space, the robotic coordinate space to the navigation coordinate space, etc.). The registration  120  may also enable the processor  104  to perform more than one registration or correlation of coordinate spaces. For example, the patient coordinate space may be correlated or registered with the navigation coordinate space and the navigation coordinate space may be correlated or registered with the display coordinate space. The registration  120  may be based on, for example, information about a pose of a patient during a surgical procedure. The information may be obtained from an imaging device such as the imaging device  112 , sensors, and/or tracking devices affixed or placed on the patient. The information may also be obtained from an accurate robotic arm such as the robotic arm  116  or a navigated probe touching one or more points on the patient to obtain the pose of each point on the patient. 
     The tracking  122  enables the processor  104  (or a processor of the navigation system  118 ) to detect and track one or more surgical landmarks of the registered patient. The surgical landmark may comprise, for example, a reference marker, an implant implanted on an anatomical element, an anatomical element, and/or any other landmark in any combination thereof. The tracking  122  may enable the processor  104  to detect the surgical landmark by, for example, using image processing to process an image received from, for example, an imaging device such as the imaging device  112  to detect the surgical landmark depicted in the image and/or by using the navigation system  118  to detect the surgical landmark. The tracking  122  may, for example, also enable the processor  104  to track the surgical landmark for movement by comparing the surgical landmark at a first time period and a second time period to determine if movement of the surgical landmark has occurred. In other embodiments, the tracking  122  may, for example, enable the processor  104  to compare a pose of the surgical landmark at a first time period and a second time period to determine a change in the pose (and thus, movement of the surgical landmark). 
     The virtual guide generation  124  enables the processor  104  to generate a virtual guide  138  corresponding to a parameter associated with the surgical landmark. As will be described in more detail in  FIG.  2   , the parameter may comprise at least one of an angle, a pose, a position, an orientation, a size, a trajectory, and/or a shape of the surgical landmark. As will also be described in more detail below, the virtual guide  138  may be a visual aid to visualize the parameter. For example, an angle of a vertebra may be represented by a virtual line or rod extending from one end of the vertebra to another end of the vertebra and may include a number indicating the value of the angle. In such examples, the angle may be relative to, for example, an axis extending across a pelvic bone or shoulders of a patient. In some embodiments, the processor  104  may simply retrieve a corresponding virtual guide  138  from, for example, the memory  106 , the database  130 , or any other component in which the virtual guide  138  may be stored within. In other embodiments, the processor  104  may also automatically generate the virtual guide  138  based on preexisting or historical virtual guides  138  and historical parameters. 
     The content stored in the memory  106 , if provided as in instruction, may, in some embodiments, be organized into one or more applications, modules, packages, layers, or engines. Alternatively or additionally, the memory  106  may store other types of content or data (e.g., machine learning models, artificial neural networks, deep neural networks, etc.) that can be processed by the processor  104  to carry out the various method and features described herein. Thus, although various contents of memory  106  may be described as instructions, it should be appreciated that functionality described herein can be achieved through use of instructions, algorithms, and/or machine learning models. The data, algorithms, and/or instructions may cause the processor  104  to manipulate data stored in the memory  106  and/or received from or via the imaging device  112 , the robot  114 , the database  130 , the display  126 , and/or the cloud  134 . 
     The memory  106  may also store a surgical plan  128 . The surgical plan  128  may comprise, for example, one or more steps for performing a surgical procedure and/or one or more expected thresholds for monitoring one or more parameters during the surgical procedure. In some embodiments, the surgical procedure may be a spinal procedure (e.g., a spinal alignment, installing implants, osteotomy, fusion, and/or any other spinal procedure) to correct a spinal deformity. For example, the surgical plan  128  may comprise one or more surgical steps for moving a plurality of vertebrae to a predetermined alignment. In such embodiments, the surgical landmark may comprise the plurality of vertebrae and the surgical plan  128  may include, for example, desired angles for one or more vertebrae, a desired shape of a patient&#39;s spine, and/or maximum force thresholds for an anatomical element such as, for example, a nerve. The surgical plan  128  may also be stored in the database  130 . 
     The computing device  102  may also comprise a communication interface  108 . The communication interface  108  may be used for receiving image data or other information from an external source (such as the imaging device  112 , the robot  114 , the navigation system  118 , the database  130 , the display  126 , the cloud  134 , and/or any other system or component not part of the system  100 ), and/or for transmitting instructions, images, or other information to an external system or device (e.g., another computing device  102 , the imaging device  112 , the robot  114 , the navigation system  118 , the database  130 , the display  126 , the cloud  134 , and/or any other system or component not part of the system  100 ). The communication interface  108  may comprise one or more wired interfaces (e.g., a USB port, an Ethernet port, a Firewire port) and/or one or more wireless transceivers or interfaces (configured, for example, to transmit and/or receive information via one or more wireless communication protocols such as 802.11a/b/g/n, Bluetooth, NFC, ZigBee, and so forth). In some embodiments, the communication interface  108  may be useful for enabling the device  102  to communicate with one or more other processors  104  or computing devices  102 , whether to reduce the time needed to accomplish a computing-intensive task or for any other reason. 
     The computing device  102  may also comprise one or more user interfaces  110 . The user interface  110  may be or comprise a keyboard, mouse, trackball, monitor, television, screen, touchscreen, and/or any other device for receiving information from a user and/or for providing information to a user. The user interface  110  may be used, for example, to receive a user selection or other user input regarding any step of any method described herein. Notwithstanding the foregoing, any required input for any step of any method described herein may be generated automatically by the system  100  (e.g., by the processor  104  or another component of the system  100 ) or received by the system  100  from a source external to the system  100 . In some embodiments, the user interface  110  may be useful to allow a surgeon or other user to modify instructions to be executed by the processor  104  according to one or more embodiments of the present disclosure, and/or to modify or adjust a setting of other information displayed on the user interface  110  or corresponding thereto. 
     Although the user interface  110  is shown as part of the computing device  102 , in some embodiments, the computing device  102  may utilize a user interface  110  that is housed separately from one or more remaining components of the computing device  102 . In some embodiments, the user interface  110  may be located proximate one or more other components of the computing device  102 , while in other embodiments, the user interface  110  may be located remotely from one or more other components of the computer device  102 . 
     The system  100  may also comprise the display  126 . The display  126  may communicate with the computing device  102  or the processor  104  of the computing device to receive and present a virtual guide  138 . It will be appreciated that in some embodiments, the display  126  can communicate with any component of the system  100  or any component external to the system  100 . In some embodiments, the display  126  is an augmented display configured to display an augmented image  136  in which an environment is visible through at least a portion of the display  126  and the virtual guide  138  may be presented within the augmented image  136 . In some embodiments, the virtual guide  138  may be visible as an overlay on the environment. In such embodiments, the display  126  may comprise a headset worn by a user. The headset may comprise a screen through which the environment is visible to the user and on which the virtual guide  138  may be displayed on. In some embodiments, the headset may display at least one virtual guide  138  corresponding to an object, anatomical element, portion of a patient, tool, and/or an instrument in a field of view of the headset. The headset may be beneficial in, for example, providing information to a user such as a surgeon during a surgical procedure. For example, the headset may display a presentation of one or more virtual guide(s)  138  corresponding to one or more surgical landmarks visible through the display  126 . In such examples, the presentation of the virtual guide  138  may be updated as the surgical procedure progresses. 
     The augmented image  136  comprises one or more virtual representations that are visible to a user when presented in the display  126 . The augmented image  136  (and thus, the virtual representation(s)) may appear as an overlay on the environment. Each virtual representation may appear as semi-transparent or opaque in the environment. The virtual representation may be two-dimensional or three-dimensional. The virtual representation may comprise, for example, the virtual guide  138 . The augmented image  136  may comprise a first virtual guide  138  in a first field of view of the display  126  and a second virtual guide  138  in a second field of view of the display  126 . In other words, the augmented image  136  may comprise different virtual guides  138  based on the field of view of the display  126 . For example, the corresponding virtual guides  138  may change as the display  126  moves and views different portions of the environment. 
     The virtual guide  138  may be based on, for example, a parameter of a corresponding surgical landmark. The parameter may comprise, for example, an angle, a pose, a position, an orientation, a size, a trajectory, and/or a shape of the surgical landmark. For example, the parameter may comprise an angle, the surgical landmark may comprise a vertebra, and the virtual guide  138  may comprise a virtual line representing the angle of the vertebra overlaid onto the vertebra. In some embodiments, the virtual guide  128  may be a three-dimensional model of the surgical landmark. For example, image data may be received from the imaging device  112 , as described below, and used to generate a three-dimensional model of the surgical landmark (which may be, for example, an anatomical element). The three-dimensional model may be updated to show changes to the surgical landmark(s), which may be advantageous when, for example, the entire surgical landmark is not visible. In other examples, the three-dimensional model may be used to visualize a global change. For example, a three-dimensional model of a spine may be updated to reflect changes resulting from movement of a vertebra. 
     The imaging device  112  may be operable to image anatomical feature(s) (e.g., a bone, veins, tissue, etc.) and/or other aspects of patient anatomy to yield image data (e.g., image data depicting or corresponding to a bone, veins, tissue, etc.). “Image data” as used herein refers to the data generated or captured by an imaging device  112 , including in a machine-readable form, a graphical/visual form, and in any other form. In various examples, the image data may comprise data corresponding to an anatomical feature of a patient, or to a portion thereof. The image data may be or comprise a preoperative image, an intraoperative image, a postoperative image, or an image taken independently of any surgical procedure. In some embodiments, a first imaging device  112  may be used to obtain first image data (e.g., a first image) at a first time, and a second imaging device  112  may be used to obtain second image data (e.g., a second image) at a second time after the first time. The imaging device  112  may be capable of taking a 2D image or a 3D image to yield the image data. The imaging device  112  may be or comprise, for example, an ultrasound scanner (which may comprise, for example, a physically separate transducer and receiver, or a single ultrasound transceiver), an O-arm, a C-arm, a G-arm, or any other device utilizing X-ray-based imaging (e.g., a fluoroscope, a CT scanner, or other X-ray machine), a magnetic resonance imaging (MM) scanner, an optical coherence tomography (OCT) scanner, an endoscope, a microscope, an optical camera, a thermographic camera (e.g., an infrared camera), a radar system (which may comprise, for example, a transmitter, a receiver, a processor, and one or more antennae), or any other imaging device  112  suitable for obtaining images of an anatomical feature of a patient. The imaging device  112  may be contained entirely within a single housing, or may comprise a transmitter/emitter and a receiver/detector that are in separate housings or are otherwise physically separated. 
     In some embodiments, the imaging device  112  may comprise more than one imaging device  112 . For example, a first imaging device may provide first image data and/or a first image, and a second imaging device may provide second image data and/or a second image. In still other embodiments, the same imaging device may be used to provide both the first image data and the second image data, and/or any other image data described herein. The imaging device  112  may be operable to generate a stream of image data. For example, the imaging device  112  may be configured to operate with an open shutter, or with a shutter that continuously alternates between open and shut so as to capture successive images. For purposes of the present disclosure, unless specified otherwise, image data may be considered to be continuous and/or provided as an image data stream if the image data represents two or more frames per second. 
     The robot  114  may be any surgical robot or surgical robotic system. The robot  114  may be or comprise, for example, the Mazor X™ Stealth Edition robotic guidance system. The robot  114  may be configured to position the imaging device  112  at one or more precise position(s) and orientation(s), and/or to return the imaging device  112  to the same position(s) and orientation(s) at a later point in time. The robot  114  may additionally or alternatively be configured to manipulate a surgical tool (whether based on guidance from the navigation system  118  or not) to accomplish or to assist with a surgical task. In some embodiments, the robot  114  may be configured to hold and/or manipulate an anatomical element during or in connection with a surgical procedure. The robot  114  may comprise one or more robotic arms  116 . In some embodiments, the robotic arm  116  may comprise a first robotic arm and a second robotic arm, though the robot  114  may comprise more than two robotic arms. In some embodiments, one or more of the robotic arms  116  may be used to hold and/or maneuver the imaging device  112 . In embodiments where the imaging device  112  comprises two or more physically separate components (e.g., a transmitter and receiver), one robotic arm  116  may hold one such component, and another robotic arm  116  may hold another such component. Each robotic arm  116  may be positionable independently of the other robotic arm. The robotic arms  116  may be controlled in a single, shared coordinate space, or in separate coordinate spaces. 
     The robot  114 , together with the robotic arm  116 , may have, for example, one, two, three, four, five, six, seven, or more degrees of freedom. Further, the robotic arm  116  may be positioned or positionable in any pose, plane, and/or focal point. The pose includes a position and an orientation. As a result, an imaging device  112 , surgical tool, or other object held by the robot  114  (or, more specifically, by the robotic arm  116 ) may be precisely positionable in one or more needed and specific positions and orientations. 
     The robotic arm(s)  116  may comprise one or more sensors that enable the processor  104  (or a processor of the robot  114 ) to determine a precise pose in space of the robotic arm (as well as any object or element held by or secured to the robotic arm). 
     In some embodiments, reference markers (e.g., navigation markers) may be placed on the robot  114  (including, e.g., on the robotic arm  116 ), the imaging device  112 , or any other object in the surgical space. The reference markers may be tracked by the navigation system  118 , and the results of the tracking may be used by the robot  114  and/or by an operator of the system  100  or any component thereof. In some embodiments, the navigation system  118  can be used to track other components of the system (e.g., imaging device  112 ) and the system can operate without the use of the robot  114  (e.g., with the surgeon manually manipulating the imaging device  112  and/or one or more surgical tools, based on information and/or instructions generated by the navigation system  118 , for example). 
     The navigation system  118  may provide navigation for a surgeon and/or a surgical robot during an operation. The navigation system  118  may be any now-known or future-developed navigation system, including, for example, the Medtronic StealthStation™ S8 surgical navigation system or any successor thereof. The navigation system  118  may include one or more cameras or other sensor(s) for tracking one or more reference markers, navigated trackers, or other objects within the operating room or other room in which some or all of the system  100  is located. The one or more cameras may be optical cameras, infrared cameras, or other cameras. In some embodiments, the navigation system  118  may comprise one or more electromagnetic sensors. In various embodiments, the navigation system  118  may be used to track a position and orientation (e.g., a pose) of the imaging device  112 , the robot  114  and/or robotic arm  116 , the display  126 , and/or one or more surgical tools (or, more particularly, to track a pose of a navigated tracker attached, directly or indirectly, in fixed relation to the one or more of the foregoing). The navigation system  118  may include a display for displaying one or more images from an external source (e.g., the computing device  102 , imaging device  112 , or other source) or for displaying an image and/or video stream from the one or more cameras or other sensors of the navigation system  118 . In some embodiments, the system  100  can operate without the use of the navigation system  118 . The navigation system  118  may be configured to provide guidance to a surgeon or other user of the system  100  or a component thereof, to the robot  114 , or to any other element of the system  100  regarding, for example, a pose of one or more anatomical elements, whether or not a tool is in the proper trajectory, and/or how to move a tool into the proper trajectory to carry out a surgical task according to a preoperative or other surgical plan. 
     The database  130  may store information that correlates one coordinate system to another (e.g., one or more robotic coordinate systems to a patient coordinate system and/or to a navigation coordinate system). The database  130  may additionally or alternatively store, for example, one or more surgical plans  128  (including, for example, pose information about a target and/or image information about a patient&#39;s anatomy at and/or proximate the surgical site, for use by the robot  114 , the navigation system  118 , and/or a user of the computing device  102  or of the system  100 ); one or more images useful in connection with a surgery to be completed by or with the assistance of one or more other components of the system  100 ; and/or any other useful information. The database  130  may be configured to provide any such information to the computing device  102  or to any other device of the system  100  or external to the system  100 , whether directly or via the cloud  134 . In some embodiments, the database  130  may be or comprise part of a hospital image storage system, such as a picture archiving and communication system (PACS), a health information system (HIS), and/or another system for collecting, storing, managing, and/or transmitting electronic medical records including image data. 
     The cloud  134  may be or represent the Internet or any other wide area network. The computing device  102  may be connected to the cloud  134  via the communication interface  108 , using a wired connection, a wireless connection, or both. In some embodiments, the computing device  102  may communicate with the database  130  and/or an external device (e.g., a computing device) via the cloud  134 . 
     The system  100  or similar systems may be used, for example, to carry out one or more aspects of any of the methods  200 ,  300 ,  400 , and/or  500  described herein. The system  100  or similar systems may also be used for other purposes. 
       FIG.  2    depicts a method  200  that may be used, for example, for generating and presenting a virtual guide during a surgical procedure. 
     The method  200  (and/or one or more steps thereof) may be carried out or otherwise performed, for example, by at least one processor. The at least one processor may be the same as or similar to the processor(s)  104  of the computing device  102  described above. The at least one processor may be part of a robot (such as a robot  114 ) or part of a navigation system (such as a navigation system  118 ). A processor other than any processor described herein may also be used to execute the method  200 . The at least one processor may perform the method  200  by executing elements stored in a memory such as the memory  106 . The elements stored in the memory and executed by the processor may cause the processor to execute one or more steps of a function as shown in method  200 . One or more portions of a method  200  may be performed by the processor executing any of the contents of memory, such as a registration  120 , tracking  122 , and/or virtual guide generation  124 . 
     The method  200  comprises tracking a surgical landmark (step  204 ). The surgical landmark may comprise, for example, a reference marker, an implant implanted on an anatomical element, an anatomical element, and/or any other landmark in any combination thereof. Tracking the surgical landmark may comprise a processor such as the processor  104  using a tracking such as the tracking  122  to detect and track the surgical landmark. The tracking may enable the processor to detect the surgical landmark in a field of view of, for example, a display such as the display  126 . The surgical landmark may be detected by, for example, using image processing to process an image to identify the surgical landmark in the image and/or by using a navigation system such as the navigation system  118  to identify the surgical landmark. 
     The tracking may also enable the processor to detect track and movement of the surgical landmark by comparing the surgical landmark at a first time period and a second time period to determine if movement of the surgical landmark has occurred. In other embodiments, the tracking may, for example, enable the processor to compare a pose of the surgical landmark (whether determined from an image received from an imaging device such as the imaging device  112 , receiving pose information about a reference marker tracked by a navigation system such as the navigation system  118 , receiving pose information from a robotic arm such as the robotic arm  116  supporting or in contact with the surgical landmark, or otherwise) at a first time period and a second time period to determine a change in the pose (and thus, movement of the surgical landmark). 
     The method  200  also comprises determining a parameter of the surgical landmark (step  208 ). The parameter may be a feature of the surgical landmark. For example, the parameter may comprise an angle, a pose, a position, an orientation, a size, a trajectory, and/or a shape of the surgical landmark. Determining the parameter may be based on at least one factor. The at least one factor may comprise, for example, a step of a surgical procedure about to be performed or is being performed, a surgical landmark within a field of view of a display, and/or input from a user such as a surgeon or other medical provider. Some parameter(s) may provide desirable information to the user prior to or during the step of the surgical procedure. For example, an orientation and/or a position of one or more vertebrae may be helpful to view during tightening of one or more screws onto a rod to view. In another example, it may be desirable to monitor the change in orientation and/or position of the one or more vertebrae. In other instances, the user may select parameters that the user desires to view during a surgical step or surgical procedure. 
     The method  200  also comprises generating a virtual guide (step  212 ). The virtual guide may be the same as or similar to the virtual guide  138 . Generating the virtual guide may comprise the processor using a virtual guide generation such as the virtual guide generation  124  to generate the virtual guide. Generating the virtual guide may be based on, for example, the parameter determined in step  208 . In other instances, generating the virtual guide may be based on input received from a user such as a surgeon or other medical personnel. The processor may simply retrieve a corresponding virtual guide from, for example, a memory such as the memory  106 , a database such as the database  130 , or any other component in which the virtual guide may be stored within. In other instances, the processor may also automatically generate the virtual guide based on preexisting or historical virtual guides and historical parameters. 
     In some embodiments, the virtual guide may be a guide to visually display the parameter such as, for example, an angle of a surgical landmark or a position and/or orientation of the surgical landmark. For example, the virtual guide may comprise a virtual line or rod to visually show the angle of the surgical landmark. In other embodiments, the virtual guide may be predetermined based on, for example, a surgical plan such as the surgical plan  128 . For example, the virtual guide may comprise text regarding a step in the surgical plan. In still other examples, the virtual guide may comprise a numerical coordinate of the surgical landmark. In other embodiments, the virtual guide may be related to minimizing at least one of a force and/or pressure applied to the surgical landmark. For example, the virtual guide may show a force and/or pressure applied to the surgical landmark by, for example, a robotic arm such as the robotic arm  116 . Such force and/or pressure may be monitored by the user to prevent damage to the surgical landmark. 
     The method  200  also comprises causing a display to present the virtual guide (step  216 ). The virtual guide may be received from the step  212 . In other instances, the virtual guide may be received from, for example, a database such as the database  130  or any other component. The display may be the same as or similar to the display  126  and may be configured to display an augmented image such as the augmented image  136 . The display may be configured to present the virtual guide in the augmented image. In some embodiments, an environment is visible through the display and one or more surgical landmarks may be visible in the environment. In some embodiments, a display coordinate system of the display may be correlated or registered with a patient coordinate space by a processor such as the processor  104  using a registration such as the registration  120 . In other embodiments, the display coordinate system may be correlated or registered with a navigation coordinate system of a navigation system such as the navigation system  118 , which may be correlated or registered with a patient coordinate space. Such registration may enable the processor to detect which surgical landmarks are visible within the environment and a field of view of the display. 
     In some embodiments, the virtual guide may be displayed as an overlay on the environment visible in the display. The virtual guide may be displayed as opaque or semi-transparent and may be two-dimensional or three-dimensional. In some embodiments, the virtual guide may be displayed on a corresponding surgical landmark detected within the field of view of the display. For example, a virtual guide representing an angle of a vertebrae visible in the display may be displayed on the vertebrae. In such embodiments, and as will explained in detail in  FIGS.  3  and  4   , different virtual guide(s) and/or multiple virtual guide(s) may be presented based on a corresponding surgical landmark visible in a field of view of the display. In other embodiments, the virtual guide may be displayed anywhere in the augmented image and may remain visible regardless of a field of view of the display. 
     It will be appreciated that more than one virtual guide may be presented at a time. For example, the display may present a virtual guide corresponding to and overlaid on the surgical landmark and another virtual guide displaying other information positioned anywhere in the augmented image. It will also be appreciated that more than one virtual guide may be presented for a corresponding surgical landmark. For example, a virtual line or rod representing an angle of the surgical landmark and a label identifying the surgical landmark may be presented on the surgical landmark. 
     The method  200  also comprises detecting movement of the surgical landmark (step  220 ). Detecting movement of the surgical landmark may be based on a comparison of a first image with a second image. The first image and the second image may be obtained from one or more imaging devices such as the imaging devices  112 . More specifically, detecting the movement may comprise comparing a position of the surgical landmark in the first image to the position of the surgical landmark in the second image. In some embodiments, detecting movement of the at least one surgical landmark may comprise superimposing the second image over the first image and comparing differences between the surgical landmark depicted in the first image and the second image. The differences may be determined by visually detecting the differences between the first image and the second image. In other instances, the differences may be determined automatically by, for example, a processor such as the processor  104 . For example, the processor may compare each pixel of the first image to each corresponding pixel of the second image and differences in pixels may indicate a difference between the first image and the second image. 
     In other embodiments, detecting the movement of the surgical landmark may be based on a comparison of pose information of the surgical landmark at a first timestamp and pose information of the surgical landmark at a second landmark. The pose information may be obtained from, for example, a navigation system such as the navigation system  118  tracking the surgical landmark, the navigation system tracking a marker affixed to the surgical landmark, a sensor disposed on the surgical landmark, a robotic arm such as the robotic arm  116  or a navigated probe touching the surgical landmark, and/or the robotic arm supporting the surgical landmark. A change in the pose information between the first timestamp and the second timestamp may indicate movement of the surgical landmark. 
     The method  200  also comprises updating a presentation of the virtual guide (step  224 ). The presentation of the virtual guide may be updated based on the movement detected in step  220 . Updating the presentation of the virtual guide may comprise regenerating the virtual guide by, for example, repeating step  212 . In other instances, updating the presentation of the virtual guide may comprise adjusting corresponding pixels of the virtual guide to reflect a change in the virtual guide based on the movement of the surgical landmark. For example, if the surgical landmark has tilted and the virtual guide is a virtual line or rod representing an angle of the surgical landmark, then the virtual line or rod may be tilted to match a new angle of the surgical landmark. In other examples, the virtual guide may be a representation of a spine of a patient the movement detected may be a vertebra that has moved or multiple vertebrae that have moved. In such examples, the representation of the spine may be updated to reflect the movement of the vertebrae (and may, in some instances, update one or more adjacent vertebra that may have moved as a result of the movement of the vertebrae). 
     The method  200  also comprises causing the display to present the updated virtual guide (step  228 ). The step  228  may be the same as or similar to the step  216  described above and with respect to presenting the updated virtual guide. 
     It will be appreciated that the steps  220 - 228  may be repeated continuously. In some embodiments, the virtual guide may be updated in real-time. In other embodiments, the steps  220 - 228  may be repeated incrementally or after a surgical step to view the updated virtual guide resulting from the surgical step. 
     The present disclosure encompasses embodiments of the method  200  that comprise more or fewer steps than those described above, and/or one or more steps that are different than the steps described above. 
       FIG.  3    depicts a method  300  that may be used, for example, for generating a notification or updating one or more expected thresholds based on a detected movement of a surgical landmark. 
     The method  300  (and/or one or more steps thereof) may be carried out or otherwise performed, for example, by at least one processor. The at least one processor may be the same as or similar to the processor(s)  104  of the computing device  102  described above. The at least one processor may be part of a robot (such as a robot  114 ) or part of a navigation system (such as a navigation system  118 ). A processor other than any processor described herein may also be used to execute the method  300 . The at least one processor may perform the method  300  by executing elements stored in a memory such as the memory  106 . The elements stored in memory and executed by the processor may cause the processor to execute one or more steps of a function as shown in method  300 . One or more portions of a method  300  may be performed by the processor executing any of the contents of memory, such as a registration  120 , tracking  122 , and/or virtual guide generation  124 . 
     The method  300  comprises detecting movement of a surgical landmark (step  304 ). The step  304  may be the same as or similar to the step  220  of the method  200  described above. 
     The method  300  also comprises generating a notification when the surgical landmark meets or exceeds one or more thresholds (step  308 ). The notification may be a visual notification, an audible notification, or any type of notification communicated to a user. The notification may be communicated to the user via a user interface such as the user interface  110  or in the display. In some embodiments, the notification may be automatically generated by the processor  104 . In other embodiments, the notification may be automatically generated by any component of a system such as the system  100 . 
     The one or more thresholds may comprise, for example, a force threshold, a positional threshold, a pressure threshold, an orientation threshold, and/or an acceleration threshold. The one or more thresholds may be beneficial to monitor a surgical step and to, for example, prevent excessive force or pressure from being applied to an anatomical element or to ensure that an anatomical element has not moved outside of a desired range of movement. The one or more thresholds may be received as input from a user such as a surgeon or other medical provider. In other instances, the one or more thresholds may be based on the parameters determined in, for example, the step  208  of the method  200  above and/or received from a surgical plan such as the surgical plan  128 . In such embodiments, the one or more thresholds may be generated automatically by a processor such as the processor  104  based on historical thresholds and historical parameters. 
     The method  300  also comprises receiving a surgical plan comprising one or more expected thresholds (step  312 ). The surgical plan may be the same as or similar to the surgical plan  128 . The one or more thresholds described in step  308  above may be defined by the one or more expected thresholds provided in the surgical plan. The one or more expected thresholds may be received as input from a user such as a surgeon or other medical provider. In other embodiments, the one or more thresholds may be generated automatically by a processor such as the processor  104  based on historical thresholds and historical parameters. 
     The method  300  also comprises updating the one or more expected thresholds (step  316 ). The one or more expected thresholds may be updated, for example, in real-time prior to a start of or during a surgical procedure. For example, the one or more expected thresholds may have been generated based on one or more expected parameters. In such embodiments, prior to a start of the surgical procedure, or during the surgical procedure, actual parameters may be obtained. The actual parameters may be used to regenerate or update the expected thresholds. 
     The present disclosure encompasses embodiments of the method  300  that comprise more or fewer steps than those described above, and/or one or more steps that are different than the steps described above. 
       FIG.  4    depicts a method  400  that may be used, for example, for generating and displaying a presentation of a virtual guide during a surgical procedure. 
     The method  400  (and/or one or more steps thereof) may be carried out or otherwise performed, for example, by at least one processor. The at least one processor may be the same as or similar to the processor(s)  104  of the computing device  102  described above. The at least one processor may be part of a robot (such as a robot  114 ) or part of a navigation system (such as a navigation system  118 ). A processor other than any processor described herein may also be used to execute the method  400 . The at least one processor may perform the method  400  by executing elements stored in a memory such as the memory  106 . The elements stored in memory and executed by the processor may cause the processor to execute one or more steps of a function as shown in method  400 . One or more portions of a method  400  may be performed by the processor executing any of the contents of memory, such as a registration  120 , tracking  122 , and/or virtual guide generation  124 . 
     The method  400  comprises detecting a first surgical landmark within an environment and a first field of view of a display (step  404 ). The display may be the same as or similar to the display  126 . The environment may be visible through the display. In some embodiments, the environment is a surgical site. The first surgical landmark may comprise, for example, a reference marker, an implant implanted on an anatomical element, an anatomical element, and/or any other landmark in any combination thereof. Detecting the first surgical landmark may comprise a processor such as the processor  104  using a tracking such as the tracking  122  to detect and track the first surgical landmark. The tracking may, for example, enable the processor to detect the first surgical landmark in a first field of view of the display. The first surgical landmark may be detected by, for example, using image processing to process an image to identify the landmark in the image and/or by using a navigation system such as the navigation system  118  to identify the surgical landmark. 
     The method  400  also comprises determining a first parameter (step  408 ). The step  408  is the same as or similar to the step  208  of the method  200  above. 
     The method  400  also comprises generating a first visual guide (step  412 ). The step  412  is the same as or similar to the step  212  of the method  200  above. 
     The method  400  also comprises detecting a second surgical landmark within the environment and a second field of view of the display (step  416 ). The step  416  may be the same as or similar to the step  416  with respect to detecting the second surgical landmark within the second field of view. The second field of view may be the same as, overlap, or not overlap the first field of view. In other words, in some embodiments the first surgical landmark is visible at the same time as the second surgical landmark. In other embodiments, the display may move and the first surgical landmark may still be visible at the same time as the second surgical landmark. In still other embodiments, the display may move such that the first surgical landmark is not visible and the second surgical landmark is visible. 
     The method  400  also comprises determining a second parameter (step  420 ). The step  420  is the same as or similar to the step  208  of the method  200  above. The second parameter may be the same as the first parameter. For example, the first parameter may be a first angle for a first vertebrae and the second parameter may be a second angle for a second vertebrae. In other instances, the second parameter may be different from the first parameter. For example, the first parameter may be an angle for a first vertebra and the second parameter may be a pose of a second vertebra. 
     The method  400  also comprises generating a second virtual guide (step  424 ). The step  424  is the same as or similar to the step  212  of the method  200  above. The second virtual guide may be the same as the first virtual guide. For example, the first virtual guide may be a first rod representing a first angle for a first vertebrae and the second virtual guide may be a second rod representing a second angle for a second vertebrae. In other instances, the second virtual guide may be different from the first virtual guide. For example, the first virtual guide may be a rod representing an angle for a first vertebra and the second virtual guide may be a set of coordinates representing a pose of a second vertebra. 
     The method  400  also comprises causing the display to present an augmented image such that at least one of the first virtual guide and/or the second virtual guide is presented (step  428 ). The step  428  is the same as or similar to the step  216  of the method  200  above. In some embodiments, the first virtual guide is presented on the first surgical landmark when the first field of view is visible through the display and the second virtual guide is presented on the second surgical landmark with the second field of view is visible through the display. In other embodiments, the first virtual guide is presented on the first surgical landmark and the second virtual guide is presented on the second surgical landmark when the first field of view and the second field of view are the same or overlapping. In other words, as the display moves and the field of view changes, one or more surgical landmarks (whether the first surgical landmark and/or the second surgical landmark) are detected and the corresponding virtual guide is presented. 
     It will be appreciated that one, two, or more than two surgical landmarks may be detected and one, two, or more than two corresponding visual guides may be generated. In other words, any number of surgical landmarks may be detected, any number of corresponding visual guides may be generated, and any number of visual guides may be presented by the display. 
     The present disclosure encompasses embodiments of the method  400  that comprise more or fewer steps than those described above, and/or one or more steps that are different than the steps described above. 
       FIG.  5    depicts a method  500  that may be used, for example, for updating one or more virtual guides based on a detected movement of one or more surgical landmarks. 
     The method  500  (and/or one or more steps thereof) may be carried out or otherwise performed, for example, by at least one processor. The at least one processor may be the same as or similar to the processor(s)  104  of the computing device  102  described above. The at least one processor may be part of a robot (such as a robot  114 ) or part of a navigation system (such as a navigation system  118 ). A processor other than any processor described herein may also be used to execute the method  500 . The at least one processor may perform the method  500  by executing elements stored in a memory such as the memory  106 . The elements stored in memory and executed by the processor may cause the processor to execute one or more steps of a function as shown in method  500 . One or more portions of a method  500  may be performed by the processor executing any of the contents of memory, such as a registration  120 , tracking  122 , and/or virtual guide generation  124 . 
     The method  500  comprises detecting movement of at least one of a first surgical landmark and/or a second surgical landmark (step  504 ). The step  504  may be the same as or similar to the step  220  of the method  200  described above. In some embodiments, the first surgical landmark may be visible within the same field of view as the second surgical landmark. In other embodiments, the first surgical landmark may not be visible at the same time as the second surgical landmark. 
     The method  500  also comprises updating at least one of a first virtual guide and/or a second virtual guide (step  508 ). The step  508  may be the same as or similar to the step  224  of the method  200  described above. The first virtual guide and/or the second virtual guide may be received from the steps  412  and  424  of the method  400  described above. 
     The method  500  also comprises causing a display to present the updated first virtual guide and/or the second virtual guide (step  512 ). The step  512  may be the same as or similar to the step  228  of the method  200  described above. 
     It will be appreciated that the steps  504 - 512  may be repeated continuously. In some embodiments, the first virtual guide, the second virtual guide, or any virtual guide may be updated in real-time. In other embodiments, the steps  504 - 512  may be repeated incrementally or after a surgical step to view the updated virtual guide resulting from the surgical step. 
     The present disclosure encompasses embodiments of the method  500  that comprise more or fewer steps than those described above, and/or one or more steps that are different than the steps described above. 
     As noted above, the present disclosure encompasses methods with fewer than all of the steps identified in  FIGS.  2 ,  3 ,  4 , and  5    (and the corresponding description of the methods  200 ,  300 ,  400 , and  500 ), as well as methods that include additional steps beyond those identified in  FIGS.  2 ,  3 ,  4 , and  5    (and the corresponding description of the methods  200 ,  300 ,  400 , and  500 ). The present disclosure also encompasses methods that comprise one or more steps from one method described herein, and one or more steps from another method described herein. Any correlation described herein may be or comprise a registration or any other correlation. 
     The foregoing is not intended to limit the disclosure to the form or forms disclosed herein. In the foregoing Detailed Description, for example, various features of the disclosure are grouped together in one or more aspects, embodiments, and/or configurations for the purpose of streamlining the disclosure. The features of the aspects, embodiments, and/or configurations of the disclosure may be combined in alternate aspects, embodiments, and/or configurations other than those discussed above. This method of disclosure is not to be interpreted as reflecting an intention that the claims require more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed aspect, embodiment, and/or configuration. Thus, the following claims are hereby incorporated into this Detailed Description, with each claim standing on its own as a separate preferred embodiment of the disclosure. 
     Moreover, though the foregoing has included description of one or more aspects, embodiments, and/or configurations and certain variations and modifications, other variations, combinations, and modifications are within the scope of the disclosure, e.g., as may be within the skill and knowledge of those in the art, after understanding the present disclosure. It is intended to obtain rights which include alternative aspects, embodiments, and/or configurations to the extent permitted, including alternate, interchangeable and/or equivalent structures, functions, ranges or steps to those claimed, whether or not such alternate, interchangeable and/or equivalent structures, functions, ranges or steps are disclosed herein, and without intending to publicly dedicate any patentable subject matter.