Patent Publication Number: US-2023149116-A1

Title: Fiducial marker devices

Description:
This application claims the benefit of U.S. Provisional Application Ser. No. 63/012,526, filed on Apr. 20, 2020, the contents of which are incorporated herein by reference in their entirety. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates generally to methods, systems, and apparatuses related to a computer-assisted surgical system that includes various hardware and software components that work together to enhance surgical workflows. The disclosed techniques may be applied to, for example, shoulder, hip, and knee arthroplasties, as well as other surgical interventions such as arthroscopic procedures, spinal procedures, maxillofacial procedures, rotator cuff procedures, ligament repair and replacement procedures. 
     BACKGROUND 
     An arthroscopic procedure using augmented reality (AR) and/or robotics generally involves an arthroscope, the surgical instruments necessary for the procedure, a tracking system, a robot (if applicable), and a display, which may be a traditional arthroscopic tower or a head-mounted display (HMD). The tracking system tracks the position of the arthroscope, the surgical instruments, the bones, the robot (if applicable), and potentially also the HMD. In orthopedic and some sports medicine procedures, the tracking is accomplished by means of infrared cameras that track fiducial markers attached to the arthroscope, bones, and surgical instruments, for example. 
     The surgical workflow with respect to the anatomical tracking includes attaching fiducial markers that can be recognized by the tracking system into the bone or other anatomical structure(s), then registering the contours of the bone so that the system knows the location of the fiducial markers. Typically, the registration step involves a “random walk” in which the surgeon moves a touch probe over the surface of the bone. After the positions of the bones are known, they can be matched with a three dimensional (3D) bone model generated from the patient&#39;s preoperative computed tomography (CT) or magnetic resonance imaging (MRI) scan and the surgeon&#39;s surgical plan. A display can then show an overlay of the preoperative scan or three dimensional (3D) bone model and the projected area of bone to resect or that are otherwise part of the surgical procedure. 
     The current state of the art for bone tracking is to drill a hole into the bone and place a fiducial marker assembly within the drilled hole, which creates more bone lesions than is strictly necessary for the procedure. In arthroscopic surgery, there is little room to maneuver inside the joint, and there are few accessible locations for inserting trackers. Further, many fiducial markers are susceptible to “line-of-sight” issues that render the tracking devices ineffective when obscured. Even further, trackers that protrude from the bone could potentially impede the surgeon from maneuvering in the joint or damage sensitive anatomy when the surgeon takes the joint through its range of motion during the surgical procedure. 
     SUMMARY 
     Fiducial marker devices, systems and methods thereof are illustrated that more efficiently facilitate tracking in surgical environments. According to some embodiments, a fiducial marker device is disclosed that includes a first portion including one or more beacons or a top surface comprising a printed visual pattern comprising a plurality of shapes having different reflective properties. The fiducial marker device in these embodiments includes a second portion including an adhesive material, wherein the second portion has a composition coated or embedded with the adhesive material to facilitate adhesion of the fiducial marker device when the second portion contacts fluid associated with an anatomical structure of a patient. 
     According to some embodiments, at least a portion of the first portion is integral with at least another portion of the second portion. Alternatively, in other embodiments, the first portion includes a backing layer, and the second portion comprises an adhesive layer coupled to the backing layer. 
     According to some embodiments, the one or more beacons comprise an array of a plurality of passive electromagnetic (EM) or radio frequency (RF) beacons configured to facilitate a depth determination. 
     According to some embodiments, the one or more beacons comprise an RF identification (RFID) inlay. 
     According to some embodiments, the first portion further includes a grasping tab that extends beyond an interface of the first portion and the second portion. 
     According to some embodiments, the adhesive material includes one or more of thrombin, fibrinogen, a synthetic surgical adhesive, or a clotting factor XIII 
     According to some embodiments, the first and second portions are pre-rolled and dried. 
     According to some embodiments, the composition includes one or more of a plurality of fibers, a fleece, or a sponge. 
     According to some embodiments, the first portion and second portion are flexible and configured to conform to a contour of the anatomical structure when adhered to the anatomical structure to facilitate a depth determination. 
     According to some embodiments, one or more of the first portion or the second portion further comprises one or more of collagen, a synthetic material, poly lactic-co-glycolic (PLG), or PLG acid (PLGA). 
     According to some embodiments, a method for utilizing a fiducial marker to facilitate tracking during an arthroscopic procedure is disclosed. In these embodiments, the method includes engaging a fiducial marker device with a surgical tool and introducing the fiducial marker device into a cannula. The cannula is inserted into an opening proximate the anatomical structure, and the fiducial marker device is released with the surgical tool, when the fiducial marker device contacts a desired location on the anatomical structure, in order to affix the fiducial marker device to the anatomical structure at the desired location. The surgical tool is removed from the cannula, and the cannula is removed from the opening. 
     According to some embodiments, the method includes grasping a grasping tab of the fiducial marker device with an arthroscopic grasper to engage the fiducial marker device. The fiducial marker device is adhered to the anatomical structure at the desired location to affix the fiducial marker device. Additionally, the grasping tab is released with the arthroscopic grasper when the fiducial marker device contacts the desired location on the anatomical structure. 
     According to some embodiments, the method includes identifying the fiducial marker device during the arthroscopic procedure. A distortion of the fiducial marker device is correlated to determine a depth of a plurality of portions of the fiducial marker device. The fiducial marker device is flexible and conforms to a shape of the desired location of the anatomical structure when the fiducial marker device is adhered to the desired location of the anatomical structure in these embodiments. A topology of the anatomical structure is determined based on the determined depth of the plurality of portions. 
     According to some embodiments, the topology is determined via a computer-aided surgical system including a tracking system configured to identify the fiducial marker device during the arthroscopic procedure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and form a part of the specification, illustrate the embodiments of the invention and together with the written description serve to explain the principles, characteristics, and features of the invention. In the drawings: 
         FIG.  1    depicts an operating theatre including an illustrative computer-assisted surgical system (CASS) in accordance with an embodiment. 
         FIG.  2    depicts an example of an electromagnetic sensor device according to some embodiments. 
         FIG.  3 A  depicts an alternative example of an electromagnetic sensor device, with three perpendicular coils, according to some embodiments. 
         FIG.  3 B  depicts an alternative example of an electromagnetic sensor device, with two nonparallel, affixed coils, according to some embodiments. 
         FIG.  3 C  depicts an alternative example of an electromagnetic sensor device, with two nonparallel, separate coils, according to some embodiments. 
         FIG.  4    depicts an example of electromagnetic sensor devices and a patient bone according to some embodiments. 
         FIG.  5 A  depicts illustrative control instructions that a surgical computer provides to other components of a CASS in accordance with an embodiment. 
         FIG.  5 B  depicts illustrative control instructions that components of a CASS provide to a surgical computer in accordance with an embodiment. 
         FIG.  5 C  depicts an illustrative implementation in which a surgical computer is connected to a surgical data server via a network in accordance with an embodiment. 
         FIG.  6    depicts an operative patient care system and illustrative data sources in accordance with an embodiment. 
         FIG.  7 A  depicts an illustrative flow diagram for determining a pre-operative surgical plan in accordance with an embodiment. 
         FIG.  7 B  depicts an illustrative flow diagram for determining an episode of care including pre-operative, intraoperative, and post-operative actions in accordance with an embodiment. 
         FIG.  7 C  depicts illustrative graphical user interfaces including images depicting an implant placement in accordance with an embodiment. 
         FIGS.  8 A-B  depict an illustrative bilayer fiducial marker with a visual pattern and illustrative adhesive layer compositions, respectively, in accordance with an embodiment. 
         FIGS.  9 A-B  depict illustrative bilayer fiducial markers with embedded beacon(s) in accordance with an embodiment. 
         FIG.  10    depicts a flow diagram of an illustrative method for fiducial marker fixation in accordance with an embodiment. 
         FIG.  11    depicts an illustrative die-based fiducial marker stamp pen in accordance with an embodiment. 
         FIG.  12    depicts an illustrative pre-inked fiducial marker stamp pen in accordance with an embodiment. 
         FIG.  13 A  depicts an illustrative fiducial marker stamp pen comprising a selectable visual pattern in accordance with an embodiment. 
         FIG.  13 B  depicts a sectional view of the fiducial marker stamp pen of  FIG.  13 A  in accordance with an embodiment. 
         FIG.  13 C  depicts the fiducial marker stamp pen of  FIG.  13 A  with the applicator tips extended in accordance with an embodiment. 
         FIG.  14    depicts an illustrative fiducial marker deformable applicator assembly in accordance with an embodiment. 
         FIG.  15 A  depicts a fiducial marker with no distortion in accordance with an embodiment. 
         FIG.  15 B  depicts a fiducial marker with positive radial distortion in accordance with an embodiment. 
         FIG.  15 C  depicts a fiducial marker with negative radial distortion in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     This disclosure is not limited to the particular systems, devices and methods described, as these may vary. The terminology used in the description is for the purpose of describing the particular versions or embodiments only and is not intended to limit the scope. 
     As used in this document, the singular forms “a,” “an,” and “the” include plural references unless the context clearly dictates otherwise. Unless defined otherwise, all technical and scientific terms used herein have the same meanings as commonly understood by one of ordinary skill in the art. Nothing in this disclosure is to be construed as an admission that the embodiments described in this disclosure are not entitled to antedate such disclosure by virtue of prior invention. As used in this document, the term “comprising” means “including, but not limited to.” 
     Definitions 
     For the purposes of this disclosure, the term “implant” is used to refer to a prosthetic device or structure manufactured to replace or enhance a biological structure. For example, in a total hip replacement procedure a prosthetic acetabular cup (implant) is used to replace or enhance a patients worn or damaged acetabulum. While the term “implant” is generally considered to denote a man-made structure (as contrasted with a transplant), for the purposes of this specification an implant can include a biological tissue or material transplanted to replace or enhance a biological structure. 
     For the purposes of this disclosure, the term “real-time” is used to refer to calculations or operations performed on-the-fly as events occur or input is received by the operable system. However, the use of the term “real-time” is not intended to preclude operations that cause some latency between input and response, so long as the latency is an unintended consequence induced by the performance characteristics of the machine. 
     Although much of this disclosure refers to surgeons or other medical professionals by specific job title or role, nothing in this disclosure is intended to be limited to a specific job title or function. Surgeons or medical professionals can include any doctor, nurse, medical professional, or technician. Any of these terms or job titles can be used interchangeably with the user of the systems disclosed herein unless otherwise explicitly demarcated. For example, a reference to a surgeon also could apply, in some embodiments to a technician or nurse. 
     The systems, methods, and devices disclosed herein are particularly well adapted for surgical procedures that utilize surgical navigation systems, such as the NAVIO® surgical navigation system. NAVIO is a registered trademark of BLUE BELT TECHNOLOGIES, INC. of Pittsburgh, Pa., which is a subsidiary of SMITH &amp; NEPHEW, INC. of Memphis, Tenn. 
     CASS Ecosystem Overview 
       FIG.  1    provides an illustration of an example computer-assisted surgical system (CASS)  100 , according to some embodiments. As described in further detail in the sections that follow, the CASS uses computers, robotics, and imaging technology to aid surgeons in performing orthopedic surgery procedures such as total knee arthroplasty (TKA) or total hip arthroplasty (THA). For example, surgical navigation systems can aid surgeons in locating patient anatomical structures, guiding surgical instruments, and implanting medical devices with a high degree of accuracy. Surgical navigation systems such as the CASS  100  often employ various forms of computing technology to perform a wide variety of standard and minimally invasive surgical procedures and techniques. Moreover, these systems allow surgeons to more accurately plan, track and navigate the placement of instruments and implants relative to the body of a patient, as well as conduct pre-operative and intra-operative body imaging. 
     An Effector Platform  105  positions surgical tools relative to a patient during surgery. The exact components of the Effector Platform  105  will vary, depending on the embodiment employed. For example, for a knee surgery, the Effector Platform  105  may include an End Effector  105 B that holds surgical tools or instruments during their use. The End Effector  105 B may be a handheld device or instrument used by the surgeon (e.g., a NAVIO® hand piece or a cutting guide or jig) or, alternatively, the End Effector  105 B can include a device or instrument held or positioned by a Robotic Arm  105 A. While one Robotic Arm  105 A is illustrated in  FIG.  1   , in some embodiments there may be multiple devices. As examples, there may be one Robotic Arm  105 A on each side of an operating table T or two devices on one side of the table T. The Robotic Arm  105 A may be mounted directly to the table T, be located next to the table T on a floor platform (not shown), mounted on a floor-to-ceiling pole, or mounted on a wall or ceiling of an operating room. The floor platform may be fixed or moveable. In one particular embodiment, the robotic arm  105 A is mounted on a floor-to-ceiling pole located between the patient&#39;s legs or feet. In some embodiments, the End Effector  105 B may include a suture holder or a stapler to assist in closing wounds. Further, in the case of two robotic arms  105 A, the surgical computer  150  can drive the robotic arms  105 A to work together to suture the wound at closure. Alternatively, the surgical computer  150  can drive one or more robotic arms  105 A to staple the wound at closure. 
     The Effector Platform  105  can include a Limb Positioner  105 C for positioning the patient&#39;s limbs during surgery. One example of a Limb Positioner  105 C is the SMITH AND NEPHEW SPIDER2 system. The Limb Positioner  105 C may be operated manually by the surgeon or alternatively change limb positions based on instructions received from the Surgical Computer  150  (described below). While one Limb Positioner  105 C is illustrated in  FIG.  1   , in some embodiments there may be multiple devices. As examples, there may be one Limb Positioner  105 C on each side of the operating table T or two devices on one side of the table T. The Limb Positioner  105 C may be mounted directly to the table T, be located next to the table T on a floor platform (not shown), mounted on a pole, or mounted on a wall or ceiling of an operating room. In some embodiments, the Limb Positioner  105 C can be used in non-conventional ways, such as a retractor or specific bone holder. The Limb Positioner  105 C may include, as examples, an ankle boot, a soft tissue clamp, a bone clamp, or a soft-tissue retractor spoon, such as a hooked, curved, or angled blade. In some embodiments, the Limb Positioner  105 C may include a suture holder to assist in closing wounds. 
     The Effector Platform  105  may include tools, such as a screwdriver, light or laser, to indicate an axis or plane, bubble level, pin driver, pin puller, plane checker, pointer, finger, or some combination thereof. 
     Resection Equipment  110  (not shown in  FIG.  1   ) performs bone or tissue resection using, for example, mechanical, ultrasonic, or laser techniques. Examples of Resection Equipment  110  include drilling devices, burring devices, oscillatory sawing devices, vibratory impaction devices, reamers, ultrasonic bone cutting devices, radio frequency ablation devices, reciprocating devices (such as a rasp or broach), and laser ablation systems. In some embodiments, the Resection Equipment  110  is held and operated by the surgeon during surgery. In other embodiments, the Effector Platform  105  may be used to hold the Resection Equipment  110  during use. 
     The Effector Platform  105  also can include a cutting guide or jig  105 D that is used to guide saws or drills used to resect tissue during surgery. Such cutting guides  105 D can be formed integrally as part of the Effector Platform  105  or Robotic Arm  105 A, or cutting guides can be separate structures that can be matingly and/or removably attached to the Effector Platform  105  or Robotic Arm  105 A. The Effector Platform  105  or Robotic Arm  105 A can be controlled by the CASS  100  to position a cutting guide or jig  105 D adjacent to the patient&#39;s anatomy in accordance with a pre-operatively or intraoperatively developed surgical plan such that the cutting guide or jig will produce a precise bone cut in accordance with the surgical plan. 
     The Tracking System  115  uses one or more sensors to collect real-time position data that locates the patient&#39;s anatomy and surgical instruments. For example, for TKA procedures, the Tracking System may provide a location and orientation of the End Effector  105 B during the procedure. In addition to positional data, data from the Tracking System  115  also can be used to infer velocity/acceleration of anatomy/instrumentation, which can be used for tool control. In some embodiments, the Tracking System  115  may use a tracker array attached to the End Effector  105 B to determine the location and orientation of the End Effector  105 B. The position of the End Effector  105 B may be inferred based on the position and orientation of the Tracking System  115  and a known relationship in three-dimensional space between the Tracking System  115  and the End Effector  105 B. Various types of tracking systems may be used in various embodiments of the present invention including, without limitation, Infrared (IR) tracking systems, electromagnetic (EM) tracking systems, video or image based tracking systems, and ultrasound registration and tracking systems. Using the data provided by the tracking system  115 , the surgical computer  150  can detect objects and prevent collision. For example, the surgical computer  150  can prevent the Robotic Arm  105 A and/or the End Effector  105 B from colliding with soft tissue. 
     Any suitable tracking system can be used for tracking surgical objects and patient anatomy in the surgical theatre. For example, a combination of IR and visible light cameras can be used in an array. Various illumination sources, such as an IR LED light source, can illuminate the scene allowing three-dimensional imaging to occur. In some embodiments, this can include stereoscopic, tri-scopic, quad-scopic, etc. imaging. In addition to the camera array, which in some embodiments is affixed to a cart, additional cameras can be placed throughout the surgical theatre. For example, handheld tools or headsets worn by operators/surgeons can include imaging capability that communicates images back to a central processor to correlate those images with images captured by the camera array. This can give a more robust image of the environment for modeling using multiple perspectives. Furthermore, some imaging devices may be of suitable resolution or have a suitable perspective on the scene to pick up information stored in quick response (QR) codes or barcodes. This can be helpful in identifying specific objects not manually registered with the system. In some embodiments, the camera may be mounted on the Robotic Arm  105 A. 
     Although, as discussed herein, the majority of tracking and/or navigation techniques utilize image-based tracking systems (e.g., IR tracking systems, video or image based tracking systems, etc.). However, electromagnetic (EM) based tracking systems are becoming more common for a variety of reasons. For example, implantation of standard optical trackers requires tissue resection (e.g., down to the cortex) as well as subsequent drilling and driving of cortical pins. Additionally, because optical trackers require a direct line of sight with a tracking system, the placement of such trackers may need to be far from the surgical site to ensure they do not restrict the movement of a surgeon or medical professional. 
     Generally, EM based tracking devices include one or more wire coils and a reference field generator. The one or more wire coils may be energized (e.g., via a wired or wireless power supply). Once energized, the coil creates an electromagnetic field that can be detected and measured (e.g., by the reference field generator or an additional device) in a manner that allows for the location and orientation of the one or more wire coils to be determined. As should be understood by someone of ordinary skill in the art, a single coil, such as is shown in  FIG.  2   , is limited to detecting five (5) total degrees-of-freedom (DOF). For example, sensor  200  may be able to track/determine movement in the X, Y, or Z direction, as well as rotation around the Y-axis  202  or Z-axis  201 . However, because of the electromagnetic properties of a coil, it is not possible to properly track rotational movement around the X axis. 
     Accordingly, in most electromagnetic tracking applications, a three coil system, such as that shown in  FIG.  3 A  is used to enable tracking in all six degrees of freedom that are possible for a rigid body moving in a three-dimensional space (i.e., forward/backward  310 , up/down  320 , left/right  330 , roll  340 , pitch  350 , and yaw  360 ). However, the inclusion of two additional coils and the 90° offset angles at which they are positioned may require the tracking device to be much larger. Alternatively, as one of skill in the art would know, less than three full coils may be used to track all 6DOF. In some EM based tracking devices, two coils may be affixed to each other, such as is shown in  FIG.  3 B . Because the two coils  301 B and  302 B are rigidly affixed to each other, not perfectly parallel, and have locations that are known relative to each other, it is possible to determine the sixth degree of freedom  303 B with this arrangement. 
     Although the use of two affixed coils (e.g.,  301 B and  302 B) allows for EM based tracking in 6DOF, the sensor device is substantially larger in diameter than a single coil because of the additional coil. Thus, the practical application of using an EM based tracking system in a surgical environment may require tissue resection and drilling of a portion of the patient bone to allow for insertion of a EM tracker. Alternatively, in some embodiments, it may be possible to implant/insert a single coil, or 5DOF EM tracking device, into a patient bone using only a pin (e.g., without the need to drill or carve out substantial bone). 
     Thus, as described herein, a solution is needed for which the use of an EM tracking system can be restricted to devices small enough to be inserted/embedded using a small diameter needle or pin (i.e., without the need to create a new incision or large diameter opening in the bone). Accordingly, in some embodiments, a second 5DOF sensor, which is not attached to the first, and thus has a small diameter, may be used to track all 6DOF. Referring now to  FIG.  3 C , in some embodiments, two 5DOF EM sensors (e.g.,  301 C and  302 C) may be inserted into the patient (e.g., in a patient bone) at different locations and with different angular orientations (e.g., angle  303 C is non-zero). 
     Referring now to  FIG.  4   , an example embodiment is shown in which a first 5DOF EM sensor  401  and a second 5DOF EM sensor  402  are inserted into the patient bone  403  using a standard hollow needle  405  that is typical in most OR(s). In a further embodiment, the first sensor  401  and the second sensor  402  may have an angle offset of “α”  404 . In some embodiments, it may be necessary for the offset angle “α”  404  to be greater than a predetermined value (e.g., a minimum angle of 0.50°, 0.75°, etc.). This minimum value may, in some embodiments, be determined by the CASS and provided to the surgeon or medical professional during the surgical plan. In some embodiments, a minimum value may be based on one or more factors, such as, for example, the orientation accuracy of the tracking system, a distance between the first and second EM sensors. The location of the field generator, a location of the field detector, a type of EM sensor, a quality of the EM sensor, patient anatomy, and the like. 
     Accordingly, as discussed herein, in some embodiments, a pin/needle (e.g., a cannulated mounting needle, etc.) may be used to insert one or more EM sensors. Generally, the pin/needle would be a disposable component, while the sensors themselves may be reusable. However, it should be understood that this is only one potential system, and that various other systems may be used in which the pin/needle and/or EM sensors are independently disposable or reusable. In a further embodiment, the EM sensors may be affixed to the mounting needle/pin (e.g., using a luer-lock fitting or the like), which can allow for quick assembly and disassembly. In additional embodiments, the EM sensors may utilize an alternative sleeve and/or anchor system that allows for minimally invasive placement of the sensors. 
     In another embodiment, the above systems may allow for a multi-sensor navigation system that can detect and correct for field distortions that plague electromagnetic tracking systems. It should be understood that field distortions may result from movement of any ferromagnetic materials within the reference field. Thus, as one of ordinary skill in the art would know, a typical OR has a large number of devices (e.g., an operating table, LCD displays, lighting equipment, imaging systems, surgical instruments, etc.) that may cause interference. Furthermore, field distortions are notoriously difficult to detect. The use of multiple EM sensors enables the system to detect field distortions accurately, and/or to warn a user that the current position measurements may not be accurate. Because the sensors are rigidly fixed to the bony anatomy (e.g., via the pin/needle), relative measurement of sensor positions (X, Y, Z) may be used to detect field distortions. By way of non-limiting example, in some embodiments, after the EM sensors are fixed to the bone, the relative distance between the two sensors is known and should remain constant. Thus, any change in this distance could indicate the presence of a field distortion. 
     In some embodiments, specific objects can be manually registered by a surgeon with the system preoperatively or intraoperatively. For example, by interacting with a user interface, a surgeon may identify the starting location for a tool or a bone structure. By tracking fiducial marks associated with that tool or bone structure, or by using other conventional image tracking modalities, a processor may track that tool or bone as it moves through the environment in a three-dimensional model. 
     In some embodiments, certain markers, such as fiducial marks that identify individuals, important tools, or bones in the theater may include passive or active identifiers that can be picked up by a camera or camera array associated with the tracking system. For example, an IR LED can flash a pattern that conveys a unique identifier to the source of that pattern, providing a dynamic identification mark. Similarly, one or two dimensional optical codes (barcode, QR code, etc.) can be affixed to objects in the theater to provide passive identification that can occur based on image analysis. If these codes are placed asymmetrically on an object, they also can be used to determine an orientation of an object by comparing the location of the identifier with the extents of an object in an image. For example, a QR code may be placed in a corner of a tool tray, allowing the orientation and identity of that tray to be tracked. Other tracking modalities are explained throughout. For example, in some embodiments, augmented reality headsets can be worn by surgeons and other staff to provide additional camera angles and tracking capabilities. 
     In addition to optical tracking, certain features of objects can be tracked by registering physical properties of the object and associating them with objects that can be tracked, such as fiducial marks fixed to a tool or bone. For example, a surgeon may perform a manual registration process whereby a tracked tool and a tracked bone can be manipulated relative to one another. By impinging the tip of the tool against the surface of the bone, a three-dimensional surface can be mapped for that bone that is associated with a position and orientation relative to the frame of reference of that fiducial mark. By optically tracking the position and orientation (pose) of the fiducial mark associated with that bone, a model of that surface can be tracked with an environment through extrapolation. 
     The registration process that registers the CASS  100  to the relevant anatomy of the patient also can involve the use of anatomical landmarks, such as landmarks on a bone or cartilage. For example, the CASS  100  can include a 3D model of the relevant bone or joint and the surgeon can intraoperatively collect data regarding the location of bony landmarks on the patient&#39;s actual bone using a probe that is connected to the CASS. Bony landmarks can include, for example, the medial malleolus and lateral malleolus, the ends of the proximal femur and distal tibia, and the center of the hip joint. The CASS  100  can compare and register the location data of bony landmarks collected by the surgeon with the probe with the location data of the same landmarks in the 3D model. Alternatively, the CASS  100  can construct a 3D model of the bone or joint without pre-operative image data by using location data of bony landmarks and the bone surface that are collected by the surgeon using a CASS probe or other means. The registration process also can include determining various axes of a joint. For example, for a TKA the surgeon can use the CASS  100  to determine the anatomical and mechanical axes of the femur and tibia. The surgeon and the CASS  100  can identify the center of the hip joint by moving the patient&#39;s leg in a spiral direction (i.e., circumduction) so the CASS can determine where the center of the hip joint is located. 
     A Tissue Navigation System  120  (not shown in  FIG.  1   ) provides the surgeon with intraoperative, real-time visualization for the patient&#39;s bone, cartilage, muscle, nervous, and/or vascular tissues surrounding the surgical area. Examples of systems that may be employed for tissue navigation include fluorescent imaging systems and ultrasound systems. 
     The Display  125  provides graphical user interfaces (GUIs) that display images collected by the Tissue Navigation System  120  as well other information relevant to the surgery. For example, in one embodiment, the Display  125  overlays image information collected from various modalities (e.g., CT, MRI, X-ray, fluorescent, ultrasound, etc.) collected pre-operatively or intra-operatively to give the surgeon various views of the patient&#39;s anatomy as well as real-time conditions. The Display  125  may include, for example, one or more computer monitors. As an alternative or supplement to the Display  125 , one or more members of the surgical staff may wear an Augmented Reality (AR) Head Mounted Device (HMD). For example, in  FIG.  1    the Surgeon  111  is wearing an AR HMD  155  that may, for example, overlay pre-operative image data on the patient or provide surgical planning suggestions. Various example uses of the AR HMD  155  in surgical procedures are detailed in the sections that follow. 
     Surgical Computer  150  provides control instructions to various components of the CASS  100 , collects data from those components, and provides general processing for various data needed during surgery. In some embodiments, the Surgical Computer  150  is a general purpose computer. In other embodiments, the Surgical Computer  150  may be a parallel computing platform that uses multiple central processing units (CPUs) or graphics processing units (GPU) to perform processing. In some embodiments, the Surgical Computer  150  is connected to a remote server over one or more computer networks (e.g., the Internet). The remote server can be used, for example, for storage of data or execution of computationally intensive processing tasks. 
     Various techniques generally known in the art can be used for connecting the Surgical Computer  150  to the other components of the CASS  100 . Moreover, the computers can connect to the Surgical Computer  150  using a mix of technologies. For example, the End Effector  105 B may connect to the Surgical Computer  150  over a wired (i.e., serial) connection. The Tracking System  115 , Tissue Navigation System  120 , and Display  125  can similarly be connected to the Surgical Computer  150  using wired connections. Alternatively, the Tracking System  115 , Tissue Navigation System  120 , and Display  125  may connect to the Surgical Computer  150  using wireless technologies such as, without limitation, Wi-Fi, Bluetooth, Near Field Communication (NFC), or ZigBee. 
     Powered Impaction and Acetabular Reamer Devices 
     Part of the flexibility of the CASS design described above with respect to  FIG.  1    is that additional or alternative devices can be added to the CASS  100  as necessary to support particular surgical procedures. For example, in the context of hip surgeries, the CASS  100  may include a powered impaction device. Impaction devices are designed to repeatedly apply an impaction force that the surgeon can use to perform activities such as implant alignment. For example, within a total hip arthroplasty (THA), a surgeon will often insert a prosthetic acetabular cup into the implant host&#39;s acetabulum using an impaction device. Although impaction devices can be manual in nature (e.g., operated by the surgeon striking an impactor with a mallet), powered impaction devices are generally easier and quicker to use in the surgical setting. Powered impaction devices may be powered, for example, using a battery attached to the device. Various attachment pieces may be connected to the powered impaction device to allow the impaction force to be directed in various ways as needed during surgery. Also, in the context of hip surgeries, the CASS  100  may include a powered, robotically controlled end effector to ream the acetabulum to accommodate an acetabular cup implant. 
     In a robotically-assisted THA, the patient&#39;s anatomy can be registered to the CASS  100  using CT or other image data, the identification of anatomical landmarks, tracker arrays attached to the patient&#39;s bones, and one or more cameras. Tracker arrays can be mounted on the iliac crest using clamps and/or bone pins and such trackers can be mounted externally through the skin or internally (either posterolaterally or anterolaterally) through the incision made to perform the THA. For a THA, the CASS  100  can utilize one or more femoral cortical screws inserted into the proximal femur as checkpoints to aid in the registration process. The CASS  100  also can utilize one or more checkpoint screws inserted into the pelvis as additional checkpoints to aid in the registration process. Femoral tracker arrays can be secured to or mounted in the femoral cortical screws. The CASS  100  can employ steps where the registration is verified using a probe that the surgeon precisely places on key areas of the proximal femur and pelvis identified for the surgeon on the display  125 . Trackers can be located on the robotic arm  105 A or end effector  105 B to register the arm and/or end effector to the CASS  100 . The verification step also can utilize proximal and distal femoral checkpoints. The CASS  100  can utilize color prompts or other prompts to inform the surgeon that the registration process for the relevant bones and the robotic arm  105 A or end effector  105 B has been verified to a certain degree of accuracy (e.g., within 1 mm). 
     For a THA, the CASS  100  can include a broach tracking option using femoral arrays to allow the surgeon to intraoperatively capture the broach position and orientation and calculate hip length and offset values for the patient. Based on information provided about the patient&#39;s hip joint and the planned implant position and orientation after broach tracking is completed, the surgeon can make modifications or adjustments to the surgical plan. 
     For a robotically-assisted THA, the CASS  100  can include one or more powered reamers connected or attached to a robotic arm  105 A or end effector  105 B that prepares the pelvic bone to receive an acetabular implant according to a surgical plan. The robotic arm  105 A and/or end effector  105 B can inform the surgeon and/or control the power of the reamer to ensure that the acetabulum is being resected (reamed) in accordance with the surgical plan. For example, if the surgeon attempts to resect bone outside of the boundary of the bone to be resected in accordance with the surgical plan, the CASS  100  can power off the reamer or instruct the surgeon to power off the reamer. The CASS  100  can provide the surgeon with an option to turn off or disengage the robotic control of the reamer. The display  125  can depict the progress of the bone being resected (reamed) as compared to the surgical plan using different colors. The surgeon can view the display of the bone being resected (reamed) to guide the reamer to complete the reaming in accordance with the surgical plan. The CASS  100  can provide visual or audible prompts to the surgeon to warn the surgeon that resections are being made that are not in accordance with the surgical plan. 
     Following reaming, the CASS  100  can employ a manual or powered impactor that is attached or connected to the robotic arm  105 A or end effector  105 B to impact trial implants and final implants into the acetabulum. The robotic arm  105 A and/or end effector  105 B can be used to guide the impactor to impact the trial and final implants into the acetabulum in accordance with the surgical plan. The CASS  100  can cause the position and orientation of the trial and final implants vis-à-vis the bone to be displayed to inform the surgeon as to how the trial and final implant&#39;s orientation and position compare to the surgical plan, and the display  125  can show the implant&#39;s position and orientation as the surgeon manipulates the leg and hip. The CASS  100  can provide the surgeon with the option of re-planning and re-doing the reaming and implant impaction by preparing a new surgical plan if the surgeon is not satisfied with the original implant position and orientation. 
     Preoperatively, the CASS  100  can develop a proposed surgical plan based on a three dimensional model of the hip joint and other information specific to the patient, such as the mechanical and anatomical axes of the leg bones, the epicondylar axis, the femoral neck axis, the dimensions (e.g., length) of the femur and hip, the midline axis of the hip joint, the ASIS axis of the hip joint, and the location of anatomical landmarks such as the lesser trochanter landmarks, the distal landmark, and the center of rotation of the hip joint. The CASS-developed surgical plan can provide a recommended optimal implant size and implant position and orientation based on the three dimensional model of the hip joint and other information specific to the patient. The CASS-developed surgical plan can include proposed details on offset values, inclination and anteversion values, center of rotation, cup size, medialization values, superior-inferior fit values, femoral stem sizing and length. 
     For a THA, the CASS-developed surgical plan can be viewed preoperatively and intraoperatively, and the surgeon can modify CASS-developed surgical plan preoperatively or intraoperatively. The CASS-developed surgical plan can display the planned resection to the hip joint and superimpose the planned implants onto the hip joint based on the planned resections. The CASS  100  can provide the surgeon with options for different surgical workflows that will be displayed to the surgeon based on a surgeon&#39;s preference. For example, the surgeon can choose from different workflows based on the number and types of anatomical landmarks that are checked and captured and/or the location and number of tracker arrays used in the registration process. 
     According to some embodiments, a powered impaction device used with the CASS  100  may operate with a variety of different settings. In some embodiments, the surgeon adjusts settings through a manual switch or other physical mechanism on the powered impaction device. In other embodiments, a digital interface may be used that allows setting entry, for example, via a touchscreen on the powered impaction device. Such a digital interface may allow the available settings to vary based, for example, on the type of attachment piece connected to the power attachment device. In some embodiments, rather than adjusting the settings on the powered impaction device itself, the settings can be changed through communication with a robot or other computer system within the CASS  100 . Such connections may be established using, for example, a Bluetooth or Wi-Fi networking module on the powered impaction device. In another embodiment, the impaction device and end pieces may contain features that allow the impaction device to be aware of what end piece (cup impactor, broach handle, etc.) is attached with no action required by the surgeon, and adjust the settings accordingly. This may be achieved, for example, through a QR code, barcode, RFID tag, or other method. 
     Examples of the settings that may be used include cup impaction settings (e.g., single direction, specified frequency range, specified force and/or energy range); broach impaction settings (e.g., dual direction/oscillating at a specified frequency range, specified force and/or energy range); femoral head impaction settings (e.g., single direction/single blow at a specified force or energy); and stem impaction settings (e.g., single direction at specified frequency with a specified force or energy). Additionally, in some embodiments, the powered impaction device includes settings related to acetabular liner impaction (e.g., single direction/single blow at a specified force or energy). There may be a plurality of settings for each type of liner such as poly, ceramic, oxinium, or other materials. Furthermore, the powered impaction device may offer settings for different bone quality based on preoperative testing/imaging/knowledge and/or intraoperative assessment by surgeon. In some embodiments, the powered impactor device may have a dual function. For example, the powered impactor device not only could provide reciprocating motion to provide an impact force, but also could provide reciprocating motion for a broach or rasp. 
     In some embodiments, the powered impaction device includes feedback sensors that gather data during instrument use and send data to a computing device, such as a controller within the device or the Surgical Computer  150 . This computing device can then record the data for later analysis and use. Examples of the data that may be collected include, without limitation, sound waves, the predetermined resonance frequency of each instrument, reaction force or rebound energy from patient bone, location of the device with respect to imaging (e.g., fluoro, CT, ultrasound, MRI, etc.) registered bony anatomy, and/or external strain gauges on bones. 
     Once the data is collected, the computing device may execute one or more algorithms in real-time or near real-time to aid the surgeon in performing the surgical procedure. For example, in some embodiments, the computing device uses the collected data to derive information such as the proper final broach size (femur); when the stem is fully seated (femur side); or when the cup is seated (depth and/or orientation) for a THA. Once the information is known, it may be displayed for the surgeon&#39;s review, or it may be used to activate haptics or other feedback mechanisms to guide the surgical procedure. 
     Additionally, the data derived from the aforementioned algorithms may be used to drive operation of the device. For example, during insertion of a prosthetic acetabular cup with a powered impaction device, the device may automatically extend an impaction head (e.g., an end effector) moving the implant into the proper location, or turn the power off to the device once the implant is fully seated. In one embodiment, the derived information may be used to automatically adjust settings for quality of bone where the powered impaction device should use less power to mitigate femoral/acetabular/pelvic fracture or damage to surrounding tissues. 
     Robotic Arm 
     In some embodiments, the CASS  100  includes a robotic arm  105 A that serves as an interface to stabilize and hold a variety of instruments used during the surgical procedure. For example, in the context of a hip surgery, these instruments may include, without limitation, retractors, a sagittal or reciprocating saw, the reamer handle, the cup impactor, the broach handle, and the stem inserter. The robotic arm  105 A may have multiple degrees of freedom (like a Spider device), and have the ability to be locked in place (e.g., by a press of a button, voice activation, a surgeon removing a hand from the robotic arm, or other method). 
     In some embodiments, movement of the robotic arm  105 A may be effectuated by use of a control panel built into the robotic arm system. For example, a display screen may include one or more input sources, such as physical buttons or a user interface having one or more icons, that direct movement of the robotic arm  105 A. The surgeon or other healthcare professional may engage with the one or more input sources to position the robotic arm  105 A when performing a surgical procedure. 
     A tool or an end effector  105 B attached or integrated into a robotic arm  105 A may include, without limitation, a burring device, a scalpel, a cutting device, a retractor, a joint tensioning device, or the like. In embodiments in which an end effector  105 B is used, the end effector may be positioned at the end of the robotic arm  105 A such that any motor control operations are performed within the robotic arm system. In embodiments in which a tool is used, the tool may be secured at a distal end of the robotic arm  105 A, but motor control operation may reside within the tool itself. 
     The robotic arm  105 A may be motorized internally to both stabilize the robotic arm, thereby preventing it from falling and hitting the patient, surgical table, surgical staff, etc., and to allow the surgeon to move the robotic arm without having to fully support its weight. While the surgeon is moving the robotic arm  105 A, the robotic arm may provide some resistance to prevent the robotic arm from moving too fast or having too many degrees of freedom active at once. The position and the lock status of the robotic arm  105 A may be tracked, for example, by a controller or the Surgical Computer  150 . 
     In some embodiments, the robotic arm  105 A can be moved by hand (e.g., by the surgeon) or with internal motors into its ideal position and orientation for the task being performed. In some embodiments, the robotic arm  105 A may be enabled to operate in a “free” mode that allows the surgeon to position the arm into a desired position without being restricted. While in the free mode, the position and orientation of the robotic arm  105 A may still be tracked as described above. In one embodiment, certain degrees of freedom can be selectively released upon input from user (e.g., surgeon) during specified portions of the surgical plan tracked by the Surgical Computer  150 . Designs in which a robotic arm  105 A is internally powered through hydraulics or motors or provides resistance to external manual motion through similar means can be described as powered robotic arms, while arms that are manually manipulated without power feedback, but which may be manually or automatically locked in place, may be described as passive robotic arms. 
     A robotic arm  105 A or end effector  105 B can include a trigger or other means to control the power of a saw or drill. Engagement of the trigger or other means by the surgeon can cause the robotic arm  105 A or end effector  105 B to transition from a motorized alignment mode to a mode where the saw or drill is engaged and powered on. Additionally, the CASS  100  can include a foot pedal (not shown) that causes the system to perform certain functions when activated. For example, the surgeon can activate the foot pedal to instruct the CASS  100  to place the robotic arm  105 A or end effector  105 B in an automatic mode that brings the robotic arm or end effector into the proper position with respect to the patient&#39;s anatomy in order to perform the necessary resections. The CASS  100  also can place the robotic arm  105 A or end effector  105 B in a collaborative mode that allows the surgeon to manually manipulate and position the robotic arm or end effector into a particular location. The collaborative mode can be configured to allow the surgeon to move the robotic arm  105 A or end effector  105 B medially or laterally, while restricting movement in other directions. As discussed, the robotic arm  105 A or end effector  105 B can include a cutting device (saw, drill, and burr) or a cutting guide or jig  105 D that will guide a cutting device. In other embodiments, movement of the robotic arm  105 A or robotically controlled end effector  105 B can be controlled entirely by the CASS  100  without any, or with only minimal, assistance or input from a surgeon or other medical professional. In still other embodiments, the movement of the robotic arm  105 A or robotically controlled end effector  105 B can be controlled remotely by a surgeon or other medical professional using a control mechanism separate from the robotic arm or robotically controlled end effector device, for example using a joystick or interactive monitor or display control device. 
     The examples below describe uses of the robotic device in the context of a hip surgery; however, it should be understood that the robotic arm may have other applications for surgical procedures involving knees, shoulders, etc. One example of use of a robotic arm in the context of forming an anterior cruciate ligament (ACL) graft tunnel is described in WIPO Publication No. WO 2020/047051, filed Aug. 28, 2019, entitled “Robotic Assisted Ligament Graft Placement and Tensioning,” the entirety of which is incorporated herein by reference. 
     A robotic arm  105 A may be used for holding the retractor. For example in one embodiment, the robotic arm  105 A may be moved into the desired position by the surgeon. At that point, the robotic arm  105 A may lock into place. In some embodiments, the robotic arm  105 A is provided with data regarding the patient&#39;s position, such that if the patient moves, the robotic arm can adjust the retractor position accordingly. In some embodiments, multiple robotic arms may be used, thereby allowing multiple retractors to be held or for more than one activity to be performed simultaneously (e.g., retractor holding &amp; reaming). 
     The robotic arm  105 A may also be used to help stabilize the surgeon&#39;s hand while making a femoral neck cut. In this application, control of the robotic arm  105 A may impose certain restrictions to prevent soft tissue damage from occurring. For example, in one embodiment, the Surgical Computer  150  tracks the position of the robotic arm  105 A as it operates. If the tracked location approaches an area where tissue damage is predicted, a command may be sent to the robotic arm  105 A causing it to stop. Alternatively, where the robotic arm  105 A is automatically controlled by the Surgical Computer  150 , the Surgical Computer may ensure that the robotic arm is not provided with any instructions that cause it to enter areas where soft tissue damage is likely to occur. The Surgical Computer  150  may impose certain restrictions on the surgeon to prevent the surgeon from reaming too far into the medial wall of the acetabulum or reaming at an incorrect angle or orientation. 
     In some embodiments, the robotic arm  105 A may be used to hold a cup impactor at a desired angle or orientation during cup impaction. When the final position has been achieved, the robotic arm  105 A may prevent any further seating to prevent damage to the pelvis. 
     The surgeon may use the robotic arm  105 A to position the broach handle at the desired position and allow the surgeon to impact the broach into the femoral canal at the desired orientation. In some embodiments, once the Surgical Computer  150  receives feedback that the broach is fully seated, the robotic arm  105 A may restrict the handle to prevent further advancement of the broach. 
     The robotic arm  105 A may also be used for resurfacing applications. For example, the robotic arm  105 A may stabilize the surgeon while using traditional instrumentation and provide certain restrictions or limitations to allow for proper placement of implant components (e.g., guide wire placement, chamfer cutter, sleeve cutter, plan cutter, etc.). Where only a burr is employed, the robotic arm  105 A may stabilize the surgeon&#39;s handpiece and may impose restrictions on the handpiece to prevent the surgeon from removing unintended bone in contravention of the surgical plan. 
     The robotic arm  105 A may be a passive arm. As an example, the robotic arm  105 A may be a CIRQ robot arm available from Brainlab AG. CIRQ is a registered trademark of Brainlab AG, Olof-Palme-Str. 9 81829, Munchen, FED REP of GERMANY. In one particular embodiment, the robotic arm  105 A is an intelligent holding arm as disclosed in U.S. patent application Ser. No. 15/525,585 to Krinninger et al., U.S. patent application Ser. No. 15/561,042 to Nowatschin et al., U.S. patent application Ser. No. 15/561,048 to Nowatschin et al., and U.S. Pat. No. 10,342,636 to Nowatschin et al., the entire contents of each of which is herein incorporated by reference. 
     Surgical Procedure Data Generation and Collection 
     The various services that are provided by medical professionals to treat a clinical condition are collectively referred to as an “episode of care.” For a particular surgical intervention the episode of care can include three phases: pre-operative, intra-operative, and post-operative. During each phase, data is collected or generated that can be used to analyze the episode of care in order to understand various features of the procedure and identify patterns that may be used, for example, in training models to make decisions with minimal human intervention. The data collected over the episode of care may be stored at the Surgical Computer  150  or the Surgical Data Server  180  as a complete dataset. Thus, for each episode of care, a dataset exists that comprises all of the data collectively pre-operatively about the patient, all of the data collected or stored by the CASS  100  intra-operatively, and any post-operative data provided by the patient or by a healthcare professional monitoring the patient. 
     As explained in further detail, the data collected during the episode of care may be used to enhance performance of the surgical procedure or to provide a holistic understanding of the surgical procedure and the patient outcomes. For example, in some embodiments, the data collected over the episode of care may be used to generate a surgical plan. In one embodiment, a high-level, pre-operative plan is refined intra-operatively as data is collected during surgery. In this way, the surgical plan can be viewed as dynamically changing in real-time or near real-time as new data is collected by the components of the CASS  100 . In other embodiments, pre-operative images or other input data may be used to develop a robust plan preoperatively that is simply executed during surgery. In this case, the data collected by the CASS  100  during surgery may be used to make recommendations that ensure that the surgeon stays within the pre-operative surgical plan. For example, if the surgeon is unsure how to achieve a certain prescribed cut or implant alignment, the Surgical Computer  150  can be queried for a recommendation. In still other embodiments, the pre-operative and intra-operative planning approaches can be combined such that a robust pre-operative plan can be dynamically modified, as necessary or desired, during the surgical procedure. In some embodiments, a biomechanics-based model of patient anatomy contributes simulation data to be considered by the CASS  100  in developing preoperative, intraoperative, and post-operative/rehabilitation procedures to optimize implant performance outcomes for the patient. 
     Aside from changing the surgical procedure itself, the data gathered during the episode of care may be used as an input to other procedures ancillary to the surgery. For example, in some embodiments, implants can be designed using episode of care data. Example data-driven techniques for designing, sizing, and fitting implants are described in U.S. patent application Ser. No. 13/814,531 filed Aug. 15, 2011 and entitled “Systems and Methods for Optimizing Parameters for Orthopaedic Procedures”; U.S. patent application Ser. No. 14/232,958 filed Jul. 20, 2012 and entitled “Systems and Methods for Optimizing Fit of an Implant to Anatomy”; and U.S. patent application Ser. No. 12/234,444 filed Sep. 19, 2008 and entitled “Operatively Tuning Implants for Increased Performance,” the entire contents of each of which are hereby incorporated by reference into this patent application. 
     Furthermore, the data can be used for educational, training, or research purposes. For example, using the network-based approach described below in  FIG.  5 C , other doctors or students can remotely view surgeries in interfaces that allow them to selectively view data as it is collected from the various components of the CASS  100 . After the surgical procedure, similar interfaces may be used to “playback” a surgery for training or other educational purposes, or to identify the source of any issues or complications with the procedure. 
     Data acquired during the pre-operative phase generally includes all information collected or generated prior to the surgery. Thus, for example, information about the patient may be acquired from a patient intake form or electronic medical record (EMR). Examples of patient information that may be collected include, without limitation, patient demographics, diagnoses, medical histories, progress notes, vital signs, medical history information, allergies, and lab results. The pre-operative data may also include images related to the anatomical area of interest. These images may be captured, for example, using Magnetic Resonance Imaging (MRI), Computed Tomography (CT), X-ray, ultrasound, or any other modality known in the art. The pre-operative data may also comprise quality of life data captured from the patient. For example, in one embodiment, pre-surgery patients use a mobile application (“app”) to answer questionnaires regarding their current quality of life. In some embodiments, preoperative data used by the CASS  100  includes demographic, anthropometric, cultural, or other specific traits about a patient that can coincide with activity levels and specific patient activities to customize the surgical plan to the patient. For example, certain cultures or demographics may be more likely to use a toilet that requires squatting on a daily basis. 
       FIGS.  5 A and  5 B  provide examples of data that may be acquired during the intra-operative phase of an episode of care. These examples are based on the various components of the CASS  100  described above with reference to  FIG.  1   ; however, it should be understood that other types of data may be used based on the types of equipment used during surgery and their use. 
       FIG.  5 A  shows examples of some of the control instructions that the Surgical Computer  150  provides to other components of the CASS  100 , according to some embodiments. Note that the example of  FIG.  5 A  assumes that the components of the Effector Platform  105  are each controlled directly by the Surgical Computer  150 . In embodiments where a component is manually controlled by the Surgeon  111 , instructions may be provided on the Display  125  or AR HMD  155  instructing the Surgeon  111  how to move the component. 
     The various components included in the Effector Platform  105  are controlled by the Surgical Computer  150  providing position commands that instruct the component where to move within a coordinate system. In some embodiments, the Surgical Computer  150  provides the Effector Platform  105  with instructions defining how to react when a component of the Effector Platform  105  deviates from a surgical plan. These commands are referenced in  FIG.  5 A  as “haptic” commands. For example, the End Effector  105 B may provide a force to resist movement outside of an area where resection is planned. Other commands that may be used by the Effector Platform  105  include vibration and audio cues. 
     In some embodiments, the end effectors  105 B of the robotic arm  105 A are operatively coupled with cutting guide  105 D. In response to an anatomical model of the surgical scene, the robotic arm  105 A can move the end effectors  105 B and the cutting guide  105 D into position to match the location of the femoral or tibial cut to be performed in accordance with the surgical plan. This can reduce the likelihood of error, allowing the vision system and a processor utilizing that vision system to implement the surgical plan to place a cutting guide  105 D at the precise location and orientation relative to the tibia or femur to align a cutting slot of the cutting guide with the cut to be performed according to the surgical plan. Then, a surgeon can use any suitable tool, such as an oscillating or rotating saw or drill to perform the cut (or drill a hole) with perfect placement and orientation because the tool is mechanically limited by the features of the cutting guide  105 D. In some embodiments, the cutting guide  105 D may include one or more pin holes that are used by a surgeon to drill and screw or pin the cutting guide into place before performing a resection of the patient tissue using the cutting guide. This can free the robotic arm  105 A or ensure that the cutting guide  105 D is fully affixed without moving relative to the bone to be resected. For example, this procedure can be used to make the first distal cut of the femur during a total knee arthroplasty. In some embodiments, where the arthroplasty is a hip arthroplasty, cutting guide  105 D can be fixed to the femoral head or the acetabulum for the respective hip arthroplasty resection. It should be understood that any arthroplasty that utilizes precise cuts can use the robotic arm  105 A and/or cutting guide  105 D in this manner. 
     The Resection Equipment  110  is provided with a variety of commands to perform bone or tissue operations. As with the Effector Platform  105 , position information may be provided to the Resection Equipment  110  to specify where it should be located when performing resection. Other commands provided to the Resection Equipment  110  may be dependent on the type of resection equipment. For example, for a mechanical or ultrasonic resection tool, the commands may specify the speed and frequency of the tool. For Radiofrequency Ablation (RFA) and other laser ablation tools, the commands may specify intensity and pulse duration. 
     Some components of the CASS  100  do not need to be directly controlled by the Surgical Computer  150 ; rather, the Surgical Computer  150  only needs to activate the component, which then executes software locally specifying the manner in which to collect data and provide it to the Surgical Computer  150 . In the example of  FIG.  5 A , there are two components that are operated in this manner: the Tracking System  115  and the Tissue Navigation System  120 . 
     The Surgical Computer  150  provides the Display  125  with any visualization that is needed by the Surgeon  111  during surgery. For monitors, the Surgical Computer  150  may provide instructions for displaying images, GUIs, etc. using techniques known in the art. The display  125  can include various portions of the workflow of a surgical plan. During the registration process, for example, the display  125  can show a preoperatively constructed 3D bone model and depict the locations of the probe as the surgeon uses the probe to collect locations of anatomical landmarks on the patient. The display  125  can include information about the surgical target area. For example, in connection with a TKA, the display  125  can depict the mechanical and anatomical axes of the femur and tibia. The display  125  can depict  varus  and valgus angles for the knee joint based on a surgical plan, and the CASS  100  can depict how such angles will be affected if contemplated revisions to the surgical plan are made. Accordingly, the display  125  is an interactive interface that can dynamically update and display how changes to the surgical plan would impact the procedure and the final position and orientation of implants installed on bone. 
     As the workflow progresses to preparation of bone cuts or resections, the display  125  can depict the planned or recommended bone cuts before any cuts are performed. The surgeon  111  can manipulate the image display to provide different anatomical perspectives of the target area and can have the option to alter or revise the planned bone cuts based on intraoperative evaluation of the patient. The display  125  can depict how the chosen implants would be installed on the bone if the planned bone cuts are performed. If the surgeon  111  choses to change the previously planned bone cuts, the display  125  can depict how the revised bone cuts would change the position and orientation of the implant when installed on the bone. 
     The display  125  can provide the surgeon  111  with a variety of data and information about the patient, the planned surgical intervention, and the implants. Various patient-specific information can be displayed, including real-time data concerning the patient&#39;s health such as heart rate, blood pressure, etc. The display  125  also can include information about the anatomy of the surgical target region including the location of landmarks, the current state of the anatomy (e.g., whether any resections have been made, the depth and angles of planned and executed bone cuts), and future states of the anatomy as the surgical plan progresses. The display  125  also can provide or depict additional information about the surgical target region. For a TKA, the display  125  can provide information about the gaps (e.g., gap balancing) between the femur and tibia and how such gaps will change if the planned surgical plan is carried out. For a TKA, the display  125  can provide additional relevant information about the knee joint such as data about the joint&#39;s tension (e.g., ligament laxity) and information concerning rotation and alignment of the joint. The display  125  can depict how the planned implants&#39; locations and positions will affect the patient as the knee joint is flexed. The display  125  can depict how the use of different implants or the use of different sizes of the same implant will affect the surgical plan and preview how such implants will be positioned on the bone. The CASS  100  can provide such information for each of the planned bone resections in a TKA or THA. In a TKA, the CASS  100  can provide robotic control for one or more of the planned bone resections. For example, the CASS  100  can provide robotic control only for the initial distal femur cut, and the surgeon  111  can manually perform other resections (anterior, posterior and chamfer cuts) using conventional means, such as a 4-in-1 cutting guide or jig  105 D. 
     The display  125  can employ different colors to inform the surgeon of the status of the surgical plan. For example, un-resected bone can be displayed in a first color, resected bone can be displayed in a second color, and planned resections can be displayed in a third color. Implants can be superimposed onto the bone in the display  125 , and implant colors can change or correspond to different types or sizes of implants. 
     The information and options depicted on the display  125  can vary depending on the type of surgical procedure being performed. Further, the surgeon  111  can request or select a particular surgical workflow display that matches or is consistent with his or her surgical plan preferences. For example, for a surgeon  111  who typically performs the tibial cuts before the femoral cuts in a TKA, the display  125  and associated workflow can be adapted to take this preference into account. The surgeon  111  also can preselect that certain steps be included or deleted from the standard surgical workflow display. For example, if a surgeon  111  uses resection measurements to finalize an implant plan but does not analyze ligament gap balancing when finalizing the implant plan, the surgical workflow display can be organized into modules, and the surgeon can select which modules to display and the order in which the modules are provided based on the surgeon&#39;s preferences or the circumstances of a particular surgery. Modules directed to ligament and gap balancing, for example, can include pre- and post-resection ligament/gap balancing, and the surgeon  111  can select which modules to include in their default surgical plan workflow depending on whether they perform such ligament and gap balancing before or after (or both) bone resections are performed. 
     For more specialized display equipment, such as AR HMDs, the Surgical Computer  150  may provide images, text, etc. using the data format supported by the equipment. For example, if the Display  125  is a holography device such as the Microsoft HoloLens™ or Magic Leap One™, the Surgical Computer  150  may use the HoloLens Application Program Interface (API) to send commands specifying the position and content of holograms displayed in the field of view of the Surgeon  111 . 
     In some embodiments, one or more surgical planning models may be incorporated into the CASS  100  and used in the development of the surgical plans provided to the surgeon  111 . The term “surgical planning model” refers to software that simulates the biomechanics performance of anatomy under various scenarios to determine the optimal way to perform cutting and other surgical activities. For example, for knee replacement surgeries, the surgical planning model can measure parameters for functional activities, such as deep knee bends, gait, etc., and select cut locations on the knee to optimize implant placement. One example of a surgical planning model is the LIFEMOD™ simulation software from SMITH AND NEPHEW, INC. In some embodiments, the Surgical Computer  150  includes computing architecture that allows full execution of the surgical planning model during surgery (e.g., a GPU-based parallel processing environment). In other embodiments, the Surgical Computer  150  may be connected over a network to a remote computer that allows such execution, such as a Surgical Data Server  180  (see  FIG.  5 C ). As an alternative to full execution of the surgical planning model, in some embodiments, a set of transfer functions are derived that simplify the mathematical operations captured by the model into one or more predictor equations. Then, rather than execute the full simulation during surgery, the predictor equations are used. Further details on the use of transfer functions are described in WIPO Publication No. 2020/037308, filed Aug. 19, 2019, entitled “Patient Specific Surgical Method and System,” the entirety of which is incorporated herein by reference. 
       FIG.  5 B  shows examples of some of the types of data that can be provided to the Surgical Computer  150  from the various components of the CASS  100 . In some embodiments, the components may stream data to the Surgical Computer  150  in real-time or near real-time during surgery. In other embodiments, the components may queue data and send it to the Surgical Computer  150  at set intervals (e.g., every second). Data may be communicated using any format known in the art. Thus, in some embodiments, the components all transmit data to the Surgical Computer  150  in a common format. In other embodiments, each component may use a different data format, and the Surgical Computer  150  is configured with one or more software applications that enable translation of the data. 
     In general, the Surgical Computer  150  may serve as the central point where CASS data is collected. The exact content of the data will vary depending on the source. For example, each component of the Effector Platform  105  provides a measured position to the Surgical Computer  150 . Thus, by comparing the measured position to a position originally specified by the Surgical Computer  150  (see  FIG.  5 B ), the Surgical Computer can identify deviations that take place during surgery. 
     The Resection Equipment  110  can send various types of data to the Surgical Computer  150  depending on the type of equipment used. Example data types that may be sent include the measured torque, audio signatures, and measured displacement values. Similarly, the Tracking Technology  115  can provide different types of data depending on the tracking methodology employed. Example tracking data types include position values for tracked items (e.g., anatomy, tools, etc.), ultrasound images, and surface or landmark collection points or axes. The Tissue Navigation System  120  provides the Surgical Computer  150  with anatomic locations, shapes, etc. as the system operates. 
     Although the Display  125  generally is used for outputting data for presentation to the user, it may also provide data to the Surgical Computer  150 . For example, for embodiments where a monitor is used as part of the Display  125 , the Surgeon  111  may interact with a GUI to provide inputs which are sent to the Surgical Computer  150  for further processing. For AR applications, the measured position and displacement of the HMD may be sent to the Surgical Computer  150  so that it can update the presented view as needed. 
     During the post-operative phase of the episode of care, various types of data can be collected to quantify the overall improvement or deterioration in the patient&#39;s condition as a result of the surgery. The data can take the form of, for example, self-reported information reported by patients via questionnaires. For example, in the context of a knee replacement surgery, functional status can be measured with an Oxford Knee Score questionnaire, and the post-operative quality of life can be measured with a EQSD-5L questionnaire. Other examples in the context of a hip replacement surgery may include the Oxford Hip Score, Harris Hip Score, and WOMAC (Western Ontario and McMaster Universities Osteoarthritis index). Such questionnaires can be administered, for example, by a healthcare professional directly in a clinical setting or using a mobile app that allows the patient to respond to questions directly. In some embodiments, the patient may be outfitted with one or more wearable devices that collect data relevant to the surgery. For example, following a knee surgery, the patient may be outfitted with a knee brace that includes sensors that monitor knee positioning, flexibility, etc. This information can be collected and transferred to the patient&#39;s mobile device for review by the surgeon to evaluate the outcome of the surgery and address any issues. In some embodiments, one or more cameras can capture and record the motion of a patient&#39;s body segments during specified activities postoperatively. This motion capture can be compared to a biomechanics model to better understand the functionality of the patient&#39;s joints and better predict progress in recovery and identify any possible revisions that may be needed. 
     The post-operative stage of the episode of care can continue over the entire life of a patient. For example, in some embodiments, the Surgical Computer  150  or other components comprising the CASS  100  can continue to receive and collect data relevant to a surgical procedure after the procedure has been performed. This data may include, for example, images, answers to questions, “normal” patient data (e.g., blood type, blood pressure, conditions, medications, etc.), biometric data (e.g., gait, etc.), and objective and subjective data about specific issues (e.g., knee or hip joint pain). This data may be explicitly provided to the Surgical Computer  150  or other CASS component by the patient or the patient&#39;s physician(s). Alternatively or additionally, the Surgical Computer  150  or other CASS component can monitor the patient&#39;s EMR and retrieve relevant information as it becomes available. This longitudinal view of the patient&#39;s recovery allows the Surgical Computer  150  or other CASS component to provide a more objective analysis of the patient&#39;s outcome to measure and track success or lack of success for a given procedure. For example, a condition experienced by a patient long after the surgical procedure can be linked back to the surgery through a regression analysis of various data items collected during the episode of care. This analysis can be further enhanced by performing the analysis on groups of patients that had similar procedures and/or have similar anatomies. 
     In some embodiments, data is collected at a central location to provide for easier analysis and use. Data can be manually collected from various CASS components in some instances. For example, a portable storage device (e.g., USB stick) can be attached to the Surgical Computer  150  into order to retrieve data collected during surgery. The data can then be transferred, for example, via a desktop computer to the centralized storage. Alternatively, in some embodiments, the Surgical Computer  150  is connected directly to the centralized storage via a Network  175  as shown in  FIG.  5 C . 
       FIG.  5 C  illustrates a “cloud-based” implementation in which the Surgical Computer  150  is connected to a Surgical Data Server  180  via a Network  175 . This Network  175  may be, for example, a private intranet or the Internet. In addition to the data from the Surgical Computer  150 , other sources can transfer relevant data to the Surgical Data Server  180 . The example of  FIG.  5 C  shows 3 additional data sources: the Patient  160 , Healthcare Professional(s)  165 , and an EMR Database  170 . Thus, the Patient  160  can send pre-operative and post-operative data to the Surgical Data Server  180 , for example, using a mobile app. The Healthcare Professional(s)  165  includes the surgeon and his or her staff as well as any other professionals working with Patient  160  (e.g., a personal physician, a rehabilitation specialist, etc.). It should also be noted that the EMR Database  170  may be used for both pre-operative and post-operative data. For example, assuming that the Patient  160  has given adequate permissions, the Surgical Data Server  180  may collect the EMR of the Patient pre-surgery. Then, the Surgical Data Server  180  may continue to monitor the EMR for any updates post-surgery. 
     At the Surgical Data Server  180 , an Episode of Care Database  185  is used to store the various data collected over a patient&#39;s episode of care. The Episode of Care Database  185  may be implemented using any technique known in the art. For example, in some embodiments, a SQL-based database may be used where all of the various data items are structured in a manner that allows them to be readily incorporated in two SQL&#39;s collection of rows and columns. However, in other embodiments a No-SQL database may be employed to allow for unstructured data, while providing the ability to rapidly process and respond to queries. As is understood in the art, the term “No-SQL” is used to define a class of data stores that are non-relational in their design. Various types of No-SQL databases may generally be grouped according to their underlying data model. These groupings may include databases that use column-based data models (e.g., Cassandra), document-based data models (e.g., MongoDB), key-value based data models (e.g., Redis), and/or graph-based data models (e.g., Allego). Any type of No-SQL database may be used to implement the various embodiments described herein and, in some embodiments, the different types of databases may support the Episode of Care Database  185 . 
     Data can be transferred between the various data sources and the Surgical Data Server  180  using any data format and transfer technique known in the art. It should be noted that the architecture shown in  FIG.  5 C  allows transmission from the data source to the Surgical Data Server  180 , as well as retrieval of data from the Surgical Data Server  180  by the data sources. For example, as explained in detail below, in some embodiments, the Surgical Computer  150  may use data from past surgeries, machine learning models, etc. to help guide the surgical procedure. 
     In some embodiments, the Surgical Computer  150  or the Surgical Data Server  180  may execute a de-identification process to ensure that data stored in the Episode of Care Database  185  meets Health Insurance Portability and Accountability Act (HIPAA) standards or other requirements mandated by law. HIPAA provides a list of certain identifiers that must be removed from data during de-identification. The aforementioned de-identification process can scan for these identifiers in data that is transferred to the Episode of Care Database  185  for storage. For example, in one embodiment, the Surgical Computer  150  executes the de-identification process just prior to initiating transfer of a particular data item or set of data items to the Surgical Data Server  180 . In some embodiments, a unique identifier is assigned to data from a particular episode of care to allow for re-identification of the data if necessary. 
     Although  FIGS.  5 A- 5 C  discuss data collection in the context of a single episode of care, it should be understood that the general concept can be extended to data collection from multiple episodes of care. For example, surgical data may be collected over an entire episode of care each time a surgery is performed with the CASS  100  and stored at the Surgical Computer  150  or at the Surgical Data Server  180 . As explained in further detail below, a robust database of episode of care data allows the generation of optimized values, measurements, distances, or other parameters and other recommendations related to the surgical procedure. In some embodiments, the various datasets are indexed in the database or other storage medium in a manner that allows for rapid retrieval of relevant information during the surgical procedure. For example, in one embodiment, a patient-centric set of indices may be used so that data pertaining to a particular patient or a set of patients similar to a particular patient can be readily extracted. This concept can be similarly applied to surgeons, implant characteristics, CASS component versions, etc. 
     Further details of the management of episode of care data is described in U.S. Patent Application No. 62/783,858 filed Dec. 21, 2018 and entitled “Methods and Systems for Providing an Episode of Care,” the entirety of which is incorporated herein by reference. 
     Open Versus Closed Digital Ecosystems 
     In some embodiments, the CASS  100  is designed to operate as a self-contained or “closed” digital ecosystem. Each component of the CASS  100  is specifically designed to be used in the closed ecosystem, and data is generally not accessible to devices outside of the digital ecosystem. For example, in some embodiments, each component includes software or firmware that implements proprietary protocols for activities such as communication, storage, security, etc. The concept of a closed digital ecosystem may be desirable for a company that wants to control all components of the CASS  100  to ensure that certain compatibility, security, and reliability standards are met. For example, the CASS  100  can be designed such that a new component cannot be used with the CASS unless it is certified by the company. 
     In other embodiments, the CASS  100  is designed to operate as an “open” digital ecosystem. In these embodiments, components may be produced by a variety of different companies according to standards for activities, such as communication, storage, and security. Thus, by using these standards, any company can freely build an independent, compliant component of the CASS platform. Data may be transferred between components using publicly available application programming interfaces (APIs) and open, shareable data formats. 
     To illustrate one type of recommendation that may be performed with the CASS  100 , a technique for optimizing surgical parameters is disclosed below. The term “optimization” in this context means selection of parameters that are optimal based on certain specified criteria. In an extreme case, optimization can refer to selecting optimal parameter(s) based on data from the entire episode of care, including any pre-operative data, the state of CASS data at a given point in time, and post-operative goals. Moreover, optimization may be performed using historical data, such as data generated during past surgeries involving, for example, the same surgeon, past patients with physical characteristics similar to the current patient, or the like. 
     The optimized parameters may depend on the portion of the patient&#39;s anatomy to be operated on. For example, for knee surgeries, the surgical parameters may include positioning information for the femoral and tibial component including, without limitation, rotational alignment (e.g., varus/valgus rotation, external rotation, flexion rotation for the femoral component, posterior slope of the tibial component), resection depths (e.g., varus knee, valgus knee), and implant type, size and position. The positioning information may further include surgical parameters for the combined implant, such as overall limb alignment, combined tibiofemoral hyperextension, and combined tibiofemoral resection. Additional examples of parameters that could be optimized for a given TKA femoral implant by the CASS  100  include the following: 
     
       
         
           
               
               
               
             
               
                   
               
               
                 Parameter 
                 Reference 
                 Exemplary Recommendation (s) 
               
               
                   
               
             
            
               
                 Size 
                 Posterior 
                 The largest sized implant that 
               
               
                   
                   
                 does not overhang medial/ 
               
               
                   
                   
                 lateral bone edges or overhang 
               
               
                   
                   
                 the anterior femur. 
               
               
                   
                   
                 A size that does not result in 
               
               
                   
                   
                 overstuffing the patella femoral 
               
               
                   
                   
                 joint 
               
               
                 Implant Position - 
                 Medial/lateral 
                 Center the implant evenly 
               
               
                 Medial Lateral 
                 cortical bone edges 
                 between the medial/lateral 
               
               
                   
                   
                 cortical bone edges 
               
               
                 Resection Depth - 
                 Distal and 
                 6 mm of bone 
               
               
                 Varus Knee 
                 posterior lateral 
               
               
                 Resection Depth - 
                 Distal and 
                 7 mm of bone 
               
               
                 Valgus Knee 
                 posterior medial 
               
               
                 Rotation - 
                 Mechanical Axis 
                 1° varus 
               
               
                 Varus/Valgus 
               
               
                 Rotation - 
                 Transepicondylar 
                 1° external from the 
               
               
                 External 
                 Axis 
                 transepicondylar axis 
               
               
                 Rotation - 
                 Mechanical Axis 
                 3° flexed 
               
               
                 Flexion 
               
               
                   
               
            
           
         
       
     
     Additional examples of parameters that could be optimized for a given TKA tibial implant by the CASS  100  include the following: 
     
       
         
           
               
               
               
             
               
                   
               
               
                 Parameter 
                 Reference 
                 Exemplary Recommendation (s) 
               
               
                   
               
             
            
               
                 Size 
                 Posterior 
                 The largest sized implant that 
               
               
                   
                   
                 does not overhang the medial, 
               
               
                   
                   
                 lateral, anterior, and posterior 
               
               
                   
                   
                 tibial edges 
               
               
                 Implant Position 
                 Medial/lateral and 
                 Center the implant evenly 
               
               
                   
                 anterior/posterior 
                 between the medial/lateral and 
               
               
                   
                 cortical bone edges 
                 anterior/posterior cortical 
               
               
                   
                   
                 bone edges 
               
               
                 Resection Depth - 
                 Lateral/Medial 
                 4 mm of bone 
               
               
                 Varus Knee 
               
               
                 Resection Depth - 
                 Lateral/Medial 
                 5 mm of bone 
               
               
                 Valgus Knee 
               
               
                 Rotation - 
                 Mechanical Axis 
                 1° valgus 
               
               
                 Varus/Valgus 
               
               
                 Rotation - 
                 Tibial Anterior 
                 1° external from the tibial 
               
               
                 External 
                 Posterior Axis 
                 anterior paxis 
               
               
                 Posterior Slope 
                 Mechanical Axis 
                 3° posterior slope 
               
               
                   
               
            
           
         
       
     
     For hip surgeries, the surgical parameters may comprise femoral neck resection location and angle, cup inclination angle, cup anteversion angle, cup depth, femoral stem design, femoral stem size, fit of the femoral stem within the canal, femoral offset, leg length, and femoral version of the implant. 
     Shoulder parameters may include, without limitation, humeral resection depth/angle, humeral stem version, humeral offset, glenoid version and inclination, as well as reverse shoulder parameters such as humeral resection depth/angle, humeral stem version, Glenoid tilt/version, glenosphere orientation, glenosphere offset and offset direction. 
     Various conventional techniques exist for optimizing surgical parameters. However, these techniques are typically computationally intensive and, thus, parameters often need to be determined pre-operatively. As a result, the surgeon is limited in his or her ability to make modifications to optimized parameters based on issues that may arise during surgery. Moreover, conventional optimization techniques typically operate in a “black box” manner with little or no explanation regarding recommended parameter values. Thus, if the surgeon decides to deviate from a recommended parameter value, the surgeon typically does so without a full understanding of the effect of that deviation on the rest of the surgical workflow, or the impact of the deviation on the patient&#39;s post-surgery quality of life. 
     Operative Patient Care System 
     The general concepts of optimization may be extended to the entire episode of care using an Operative Patient Care System  620  that uses the surgical data, and other data from the Patient  605  and Healthcare Professionals  630  to optimize outcomes and patient satisfaction as depicted in  FIG.  6   . 
     Conventionally, pre-operative diagnosis, pre-operative surgical planning, intra-operative execution of a prescribed plan, and post-operative management of total joint arthroplasty are based on individual experience, published literature, and training knowledge bases of surgeons (ultimately, tribal knowledge of individual surgeons and their ‘network’ of peers and journal publications) and their native ability to make accurate intra-operative tactile discernment of “balance” and accurate manual execution of planar resections using guides and visual cues. This existing knowledge base and execution is limited with respect to the outcomes optimization offered to patients needing care. For example, limits exist with respect to accurately diagnosing a patient to the proper, least-invasive prescribed care; aligning dynamic patient, healthcare economic, and surgeon preferences with patient-desired outcomes; executing a surgical plan resulting in proper bone alignment and balance, etc.; and receiving data from disconnected sources having different biases that are difficult to reconcile into a holistic patient framework. Accordingly, a data-driven tool that more accurately models anatomical response and guides the surgical plan can improve the existing approach. 
     The Operative Patient Care System  620  is designed to utilize patient specific data, surgeon data, healthcare facility data, and historical outcome data to develop an algorithm that suggests or recommends an optimal overall treatment plan for the patient&#39;s entire episode of care (preoperative, operative, and postoperative) based on a desired clinical outcome. For example, in one embodiment, the Operative Patient Care System  620  tracks adherence to the suggested or recommended plan, and adapts the plan based on patient/care provider performance. Once the surgical treatment plan is complete, collected data is logged by the Operative Patient Care System  620  in a historical database. This database is accessible for future patients and the development of future treatment plans. In addition to utilizing statistical and mathematical models, simulation tools (e.g., LIFEMOD®) can be used to simulate outcomes, alignment, kinematics, etc. based on a preliminary or proposed surgical plan, and reconfigure the preliminary or proposed plan to achieve desired or optimal results according to a patient&#39;s profile or a surgeon&#39;s preferences. The Operative Patient Care System  620  ensures that each patient is receiving personalized surgical and rehabilitative care, thereby improving the chance of successful clinical outcomes and lessening the economic burden on the facility associated with near-term revision. 
     In some embodiments, the Operative Patient Care System  620  employs a data collecting and management method to provide a detailed surgical case plan with distinct steps that are monitored and/or executed using a CASS  100 . The performance of the user(s) is calculated at the completion of each step and can be used to suggest changes to the subsequent steps of the case plan. Case plan generation relies on a series of input data that is stored on a local or cloud-storage database. Input data can be related to both the current patient undergoing treatment and historical data from patients who have received similar treatment(s). 
     A Patient  605  provides inputs such as Current Patient Data  610  and Historical Patient Data  615  to the Operative Patient Care System  620 . Various methods generally known in the art may be used to gather such inputs from the Patient  605 . For example, in some embodiments, the Patient  605  fills out a paper or digital survey that is parsed by the Operative Patient Care System  620  to extract patient data. In other embodiments, the Operative Patient Care System  620  may extract patient data from existing information sources, such as electronic medical records (EMRs), health history files, and payer/provider historical files. In still other embodiments, the Operative Patient Care System  620  may provide an application program interface (API) that allows the external data source to push data to the Operative Patient Care System. For example, the Patient  605  may have a mobile phone, wearable device, or other mobile device that collects data (e.g., heart rate, pain or discomfort levels, exercise or activity levels, or patient-submitted responses to the patient&#39;s adherence with any number of pre-operative plan criteria or conditions) and provides that data to the Operative Patient Care System  620 . Similarly, the Patient  605  may have a digital application on his or her mobile or wearable device that enables data to be collected and transmitted to the Operative Patient Care System  620 . 
     Current Patient Data  610  can include, but is not limited to, activity level, preexisting conditions, comorbidities, prehab performance, health and fitness level, pre-operative expectation level (relating to hospital, surgery, and recovery), a Metropolitan Statistical Area (MSA) driven score, genetic background, prior injuries (sports, trauma, etc.), previous joint arthroplasty, previous trauma procedures, previous sports medicine procedures, treatment of the contralateral joint or limb, gait or biomechanical information (back and ankle issues), levels of pain or discomfort, care infrastructure information (payer coverage type, home health care infrastructure level, etc.), and an indication of the expected ideal outcome of the procedure. 
     Historical Patient Data  615  can include, but is not limited to, activity level, preexisting conditions, comorbidities, prehab performance, health and fitness level, pre-operative expectation level (relating to hospital, surgery, and recovery), a MSA driven score, genetic background, prior injuries (sports, trauma, etc.), previous joint arthroplasty, previous trauma procedures, previous sports medicine procedures, treatment of the contralateral joint or limb, gait or biomechanical information (back and ankle issues), levels or pain or discomfort, care infrastructure information (payer coverage type, home health care infrastructure level, etc.), expected ideal outcome of the procedure, actual outcome of the procedure (patient reported outcomes [PROs], survivorship of implants, pain levels, activity levels, etc.), sizes of implants used, position/orientation/alignment of implants used, soft-tissue balance achieved, etc. 
     Healthcare Professional(s)  630  conducting the procedure or treatment may provide various types of data  625  to the Operative Patient Care System  620 . This Healthcare Professional Data  625  may include, for example, a description of a known or preferred surgical technique (e.g., Cruciate Retaining (CR) vs Posterior Stabilized (PS), up- vs down-sizing, tourniquet vs tourniquet-less, femoral stem style, preferred approach for THA, etc.), the level of training of the Healthcare Professional(s)  630  (e.g., years in practice, fellowship trained, where they trained, whose techniques they emulate), previous success level including historical data (outcomes, patient satisfaction), and the expected ideal outcome with respect to range of motion, days of recovery, and survivorship of the device. The Healthcare Professional Data  625  can be captured, for example, with paper or digital surveys provided to the Healthcare Professional  630 , via inputs to a mobile application by the Healthcare Professional, or by extracting relevant data from EMRs. In addition, the CASS  100  may provide data such as profile data (e.g., a Patient Specific Knee Instrument Profile) or historical logs describing use of the CASS during surgery. 
     Information pertaining to the facility where the procedure or treatment will be conducted may be included in the input data. This data can include, without limitation, the following: Ambulatory Surgery Center (ASC) vs hospital, facility trauma level, Comprehensive Care for Joint Replacement Program (CJR) or bundle candidacy, a MSA driven score, community vs metro, academic vs non-academic, postoperative network access (Skilled Nursing Facility [SNF] only, Home Health, etc.), availability of medical professionals, implant availability, and availability of surgical equipment. 
     These facility inputs can be captured by, for example and without limitation, Surveys (Paper/Digital), Surgery Scheduling Tools (e.g., apps, Websites, Electronic Medical Records [EMRs], etc.), Databases of Hospital Information (on the Internet), etc. Input data relating to the associated healthcare economy including, but not limited to, the socioeconomic profile of the patient, the expected level of reimbursement the patient will receive, and if the treatment is patient specific may also be captured. 
     These healthcare economic inputs can be captured by, for example and without limitation, Surveys (Paper/Digital), Direct Payer Information, Databases of Socioeconomic status (on the Internet with zip code), etc. Finally, data derived from simulation of the procedure is captured. Simulation inputs include implant size, position, and orientation. Simulation can be conducted with custom or commercially available anatomical modeling software programs (e.g., LIFEMOD®, AnyBody, or OpenSIM). It is noted that the data inputs described above may not be available for every patient, and the treatment plan will be generated using the data that is available. 
     Prior to surgery, the Patient Data  610 ,  615  and Healthcare Professional Data  625  may be captured and stored in a cloud-based or online database (e.g., the Surgical Data Server  180  shown in  FIG.  5 C ). Information relevant to the procedure is supplied to a computing system via wireless data transfer or manually with the use of portable media storage. The computing system is configured to generate a case plan for use with a CASS  100 . Case plan generation will be described hereinafter. It is noted that the system has access to historical data from previous patients undergoing treatment, including implant size, placement, and orientation as generated by a computer-assisted, patient-specific knee instrument (PSKI) selection system, or automatically by the CASS  100  itself. To achieve this, case log data is uploaded to the historical database by a surgical sales rep or case engineer using an online portal. In some embodiments, data transfer to the online database is wireless and automated. 
     Historical data sets from the online database are used as inputs to a machine learning model such as, for example, a recurrent neural network (RNN) or other form of artificial neural network. As is generally understood in the art, an artificial neural network functions similar to a biologic neural network and is comprised of a series of nodes and connections. The machine learning model is trained to predict one or more values based on the input data. For the sections that follow, it is assumed that the machine learning model is trained to generate predictor equations. These predictor equations may be optimized to determine the optimal size, position, and orientation of the implants to achieve the best outcome or satisfaction level. 
     Once the procedure is complete, all patient data and available outcome data, including the implant size, position and orientation determined by the CASS  100 , are collected and stored in the historical database. Any subsequent calculation of the target equation via the RNN will include the data from the previous patient in this manner, allowing for continuous improvement of the system. 
     In addition to, or as an alternative to determining implant positioning, in some embodiments, the predictor equation and associated optimization can be used to generate the resection planes for use with a PSKI system. When used with a PSKI system, the predictor equation computation and optimization are completed prior to surgery. Patient anatomy is estimated using medical image data (x-ray, CT, MRI). Global optimization of the predictor equation can provide an ideal size and position of the implant components. Boolean intersection of the implant components and patient anatomy is defined as the resection volume. PSKI can be produced to remove the optimized resection envelope. In this embodiment, the surgeon cannot alter the surgical plan intraoperatively. 
     The surgeon may choose to alter the surgical case plan at any time prior to or during the procedure. If the surgeon elects to deviate from the surgical case plan, the altered size, position, and/or orientation of the component(s) is locked, and the global optimization is refreshed based on the new size, position, and/or orientation of the component(s) (using the techniques previously described) to find the new ideal position of the other component(s) and the corresponding resections needed to be performed to achieve the newly optimized size, position and/or orientation of the component(s). For example, if the surgeon determines that the size, position and/or orientation of the femoral implant in a TKA needs to be updated or modified intraoperatively, the femoral implant position is locked relative to the anatomy, and the new optimal position of the tibia will be calculated (via global optimization) considering the surgeon&#39;s changes to the femoral implant size, position and/or orientation. Furthermore, if the surgical system used to implement the case plan is robotically assisted (e.g., as with NAVIO® or the MAKO Rio), bone removal and bone morphology during the surgery can be monitored in real time. If the resections made during the procedure deviate from the surgical plan, the subsequent placement of additional components may be optimized by the processor taking into account the actual resections that have already been made. 
       FIG.  7 A  illustrates how the Operative Patient Care System  620  may be adapted for performing case plan matching services. In this example, data is captured relating to the current patient  610  and is compared to all or portions of a historical database of patient data and associated outcomes  615 . For example, the surgeon may elect to compare the plan for the current patient against a subset of the historical database. Data in the historical database can be filtered to include, for example, only data sets with favorable outcomes, data sets corresponding to historical surgeries of patients with profiles that are the same or similar to the current patient profile, data sets corresponding to a particular surgeon, data sets corresponding to a particular element of the surgical plan (e.g., only surgeries where a particular ligament is retained), or any other criteria selected by the surgeon or medical professional. If, for example, the current patient data matches or is correlated with that of a previous patient who experienced a good outcome, the case plan from the previous patient can be accessed and adapted or adopted for use with the current patient. The predictor equation may be used in conjunction with an intra-operative algorithm that identifies or determines the actions associated with the case plan. Based on the relevant and/or preselected information from the historical database, the intra-operative algorithm determines a series of recommended actions for the surgeon to perform. Each execution of the algorithm produces the next action in the case plan. If the surgeon performs the action, the results are evaluated. The results of the surgeon&#39;s performing the action are used to refine and update inputs to the intra-operative algorithm for generating the next step in the case plan. Once the case plan has been fully executed all data associated with the case plan, including any deviations performed from the recommended actions by the surgeon, are stored in the database of historical data. In some embodiments, the system utilizes preoperative, intraoperative, or postoperative modules in a piecewise fashion, as opposed to the entire continuum of care. In other words, caregivers can prescribe any permutation or combination of treatment modules including the use of a single module. These concepts are illustrated in  FIG.  7 B  and can be applied to any type of surgery utilizing the CASS  100 . 
     Surgery Process Display 
     As noted above with respect to  FIGS.  1  and  5 A- 5 C , the various components of the CASS  100  generate detailed data records during surgery. The CASS  100  can track and record various actions and activities of the surgeon during each step of the surgery and compare actual activity to the pre-operative or intraoperative surgical plan. In some embodiments, a software tool may be employed to process this data into a format where the surgery can be effectively “played-back.” For example, in one embodiment, one or more GUIs may be used that depict all of the information presented on the Display  125  during surgery. This can be supplemented with graphs and images that depict the data collected by different tools. For example, a GUI that provides a visual depiction of the knee during tissue resection may provide the measured torque and displacement of the resection equipment adjacent to the visual depiction to better provide an understanding of any deviations that occurred from the planned resection area. The ability to review a playback of the surgical plan or toggle between different phases of the actual surgery vs. the surgical plan could provide benefits to the surgeon and/or surgical staff, allowing such persons to identify any deficiencies or challenging phases of a surgery so that they can be modified in future surgeries. Similarly, in academic settings, the aforementioned GUIs can be used as a teaching tool for training future surgeons and/or surgical staff. Additionally, because the data set effectively records many elements of the surgeon&#39;s activity, it may also be used for other reasons (e.g., legal or compliance reasons) as evidence of correct or incorrect performance of a particular surgical procedure. 
     Over time, as more and more surgical data is collected, a rich library of data may be acquired that describes surgical procedures performed for various types of anatomy (knee, shoulder, hip, etc.) by different surgeons for different patients. Moreover, information such as implant type and dimension, patient demographics, etc. can further be used to enhance the overall dataset. Once the dataset has been established, it may be used to train a machine learning model (e.g., RNN) to make predictions of how surgery will proceed based on the current state of the CASS  100 . 
     Training of the machine learning model can be performed as follows. The overall state of the CASS  100  can be sampled over a plurality of time periods for the duration of the surgery. The machine learning model can then be trained to translate a current state at a first time period to a future state at a different time period. By analyzing the entire state of the CASS  100  rather than the individual data items, any causal effects of interactions between different components of the CASS  100  can be captured. In some embodiments, a plurality of machine learning models may be used rather than a single model. In some embodiments, the machine learning model may be trained not only with the state of the CASS  100 , but also with patient data (e.g., captured from an EMR) and an identification of members of the surgical staff. This allows the model to make predictions with even greater specificity. Moreover, it allows surgeons to selectively make predictions based only on their own surgical experiences if desired. 
     In some embodiments, predictions or recommendations made by the aforementioned machine learning models can be directly integrated into the surgical workflow. For example, in some embodiments, the Surgical Computer  150  may execute the machine learning model in the background making predictions or recommendations for upcoming actions or surgical conditions. A plurality of states can thus be predicted or recommended for each period. For example, the Surgical Computer  150  may predict or recommend the state for the next 5 minutes in 30 second increments. Using this information, the surgeon can utilize a “process display” view of the surgery that allows visualization of the future state. For example,  FIG.  7 C  depicts a series of images that may be displayed to the surgeon depicting the implant placement interface. The surgeon can cycle through these images, for example, by entering a particular time into the display  125  of the CASS  100  or instructing the system to advance or rewind the display in a specific time increment using a tactile, oral, or other instruction. In one embodiment, the process display can be presented in the upper portion of the surgeon&#39;s field of view in the AR HMD. In some embodiments, the process display can be updated in real-time. For example, as the surgeon moves resection tools around the planned resection area, the process display can be updated so that the surgeon can see how his or her actions are affecting the other factors of the surgery. 
     In some embodiments, rather than simply using the current state of the CASS  100  as an input to the machine learning model, the inputs to the model may include a planned future state. For example, the surgeon may indicate that he or she is planning to make a particular bone resection of the knee joint. This indication may be entered manually into the Surgical Computer  150  or the surgeon may verbally provide the indication. The Surgical Computer  150  can then produce a film strip showing the predicted effect of the cut on the surgery. Such a film strip can depict over specific time increments how the surgery will be affected, including, for example, changes in the patient&#39;s anatomy, changes to implant position and orientation, and changes regarding surgical intervention and instrumentation, if the contemplated course of action were to be performed. A surgeon or medical professional can invoke or request this type of film strip at any point in the surgery to preview how a contemplated course of action would affect the surgical plan if the contemplated action were to be carried out. 
     It should be further noted that, with a sufficiently trained machine learning model and robotic CASS, various elements of the surgery can be automated such that the surgeon only needs to be minimally involved, for example, by only providing approval for various steps of the surgery. For example, robotic control using arms or other means can be gradually integrated into the surgical workflow over time with the surgeon slowly becoming less and less involved with manual interaction versus robot operation. The machine learning model in this case can learn what robotic commands are required to achieve certain states of the CASS-implemented plan. Eventually, the machine learning model may be used to produce a film strip or similar view or display that predicts and can preview the entire surgery from an initial state. For example, an initial state may be defined that includes the patient information, the surgical plan, implant characteristics, and surgeon preferences. Based on this information, the surgeon could preview an entire surgery to confirm that the CASS-recommended plan meets the surgeon&#39;s expectations and/or requirements. Moreover, because the output of the machine learning model is the state of the CASS  100  itself, commands can be derived to control the components of the CASS to achieve each predicted state. In the extreme case, the entire surgery could thus be automated based on just the initial state information. 
     Using the Point Probe to Acquire High-Resolution of Key Areas During Hip Surgeries 
     Use of the point probe is described in U.S. patent application Ser. No. 14/955,742 entitled “Systems and Methods for Planning and Performing Image Free Implant Revision Surgery,” the entirety of which is incorporated herein by reference. Briefly, an optically tracked point probe may be used to map the actual surface of the target bone that needs a new implant. Mapping is performed after removal of the defective or worn-out implant, as well as after removal of any diseased or otherwise unwanted bone. A plurality of points is collected on the bone surfaces by brushing or scraping the entirety of the remaining bone with the tip of the point probe. This is referred to as tracing or “painting” the bone. The collected points are used to create a three-dimensional model or surface map of the bone surfaces in the computerized planning system. The created 3D model of the remaining bone is then used as the basis for planning the procedure and necessary implant sizes. An alternative technique that uses X-rays to determine a 3D model is described in U.S. patent application Ser. No. 16/387,151, filed Apr. 17, 2019 and entitled “Three-Dimensional Selective Bone Matching” and U.S. patent application Ser. No. 16/789,930, filed Feb. 13, 2020 and entitled “Three-Dimensional Selective Bone Matching,” the entirety of each of which is incorporated herein by reference. 
     For hip applications, the point probe painting can be used to acquire high resolution data in key areas such as the acetabular rim and acetabular fossa. This can allow a surgeon to obtain a detailed view before beginning to ream. For example, in one embodiment, the point probe may be used to identify the floor (fossa) of the acetabulum. As is well understood in the art, in hip surgeries, it is important to ensure that the floor of the acetabulum is not compromised during reaming so as to avoid destruction of the medial wall. If the medial wall were inadvertently destroyed, the surgery would require the additional step of bone grafting. With this in mind, the information from the point probe can be used to provide operating guidelines to the acetabular reamer during surgical procedures. For example, the acetabular reamer may be configured to provide haptic feedback to the surgeon when he or she reaches the floor or otherwise deviates from the surgical plan. Alternatively, the CASS  100  may automatically stop the reamer when the floor is reached or when the reamer is within a threshold distance. 
     As an additional safeguard, the thickness of the area between the acetabulum and the medial wall could be estimated. For example, once the acetabular rim and acetabular fossa has been painted and registered to the pre-operative 3D model, the thickness can readily be estimated by comparing the location of the surface of the acetabulum to the location of the medial wall. Using this knowledge, the CASS  100  may provide alerts or other responses in the event that any surgical activity is predicted to protrude through the acetabular wall while reaming. 
     The point probe may also be used to collect high resolution data of common reference points used in orienting the 3D model to the patient. For example, for pelvic plane landmarks like the ASIS and the pubic symphysis, the surgeon may use the point probe to paint the bone to represent a true pelvic plane. Given a more complete view of these landmarks, the registration software has more information to orient the 3D model. 
     The point probe may also be used to collect high-resolution data describing the proximal femoral reference point that could be used to increase the accuracy of implant placement. For example, the relationship between the tip of the Greater Trochanter (GT) and the center of the femoral head is commonly used as reference point to align the femoral component during hip arthroplasty. The alignment is highly dependent on proper location of the GT; thus, in some embodiments, the point probe is used to paint the GT to provide a high-resolution view of the area. Similarly, in some embodiments, it may be useful to have a high-resolution view of the Lesser Trochanter (LT). For example, during hip arthroplasty, the Don Classification helps to select a stem that will maximize the ability of achieving a press-fit during surgery to prevent micromotion of femoral components post-surgery and ensure optimal bony ingrowth. As is generated understood in the art, the Don Classification measures the ratio between the canal width at the LT and the canal width 10 cm below the LT. The accuracy of the classification is highly dependent on the correct location of the relevant anatomy. Thus, it may be advantageous to paint the LT to provide a high-resolution view of the area. 
     In some embodiments, the point probe is used to paint the femoral neck to provide high-resolution data that allows the surgeon to better understand where to make the neck cut. The navigation system can then guide the surgeon as they perform the neck cut. For example, as understood in the art, the femoral neck angle is measured by placing one line down the center of the femoral shaft and a second line down the center of the femoral neck. Thus, a high-resolution view of the femoral neck (and possibly the femoral shaft as well) would provide a more accurate calculation of the femoral neck angle. 
     High-resolution femoral head neck data also could be used for a navigated resurfacing procedure where the software/hardware aids the surgeon in preparing the proximal femur and placing the femoral component. As is generally understood in the art, during hip resurfacing, the femoral head and neck are not removed; rather, the head is trimmed and capped with a smooth metal covering. In this case, it would be advantageous for the surgeon to paint the femoral head and cap so that an accurate assessment of their respective geometries can be understood and used to guide trimming and placement of the femoral component. 
     Registration of Pre-Operative Data to Patient Anatomy Using the Point Probe 
     As noted above, in some embodiments, a 3D model is developed during the pre-operative stage based on 2D or 3D images of the anatomical area of interest. In such embodiments, registration between the 3D model and the surgical site is performed prior to the surgical procedure. The registered 3D model may be used to track and measure the patient&#39;s anatomy and surgical tools intraoperatively. 
     During the surgical procedure, landmarks are acquired to facilitate registration of this pre-operative 3D model to the patient&#39;s anatomy. For knee procedures, these points could comprise the femoral head center, distal femoral axis point, medial and lateral epicondyles, medial and lateral malleolus, proximal tibial mechanical axis point, and tibial A/P direction. For hip procedures these points could comprise the anterior superior iliac spine (ASIS), the pubic symphysis, points along the acetabular rim and within the hemisphere, the greater trochanter (GT), and the lesser trochanter (LT). 
     In a revision surgery, the surgeon may paint certain areas that contain anatomical defects to allow for better visualization and navigation of implant insertion. These defects can be identified based on analysis of the pre-operative images. For example, in one embodiment, each pre-operative image is compared to a library of images showing “healthy” anatomy (i.e., without defects). Any significant deviations between the patient&#39;s images and the healthy images can be flagged as a potential defect. Then, during surgery, the surgeon can be warned of the possible defect via a visual alert on the display  125  of the CASS  100 . The surgeon can then paint the area to provide further detail regarding the potential defect to the Surgical Computer  150 . 
     In some embodiments, the surgeon may use a non-contact method for registration of bony anatomy intra-incision. For example, in one embodiment, laser scanning is employed for registration. A laser stripe is projected over the anatomical area of interest and the height variations of the area are detected as changes in the line. Other non-contact optical methods, such as white light interferometry or ultrasound, may alternatively be used for surface height measurement or to register the anatomy. For example, ultrasound technology may be beneficial where there is soft tissue between the registration point and the bone being registered (e.g., ASIS, pubic symphysis in hip surgeries), thereby providing for a more accurate definition of anatomic planes. 
     Bilayer Fiducial Marker with Visual Pattern 
       FIGS.  8 A-B  illustrate an illustrative bilayer fiducial marker  800 A with a visual pattern  802  and illustrative adhesive layer compositions  804 A-C, respectively, that can be used to facilitate surgical tracking. In this example, the bilayer fiducial marker  800 A includes a backing layer  806  coupled to, or having portion(s) integral with, an adhesive layer  808  that is configured to attach to an anatomical structure (e.g., bone). Accordingly, while an illustrative bilayer fiducial marker  800 A is illustrated in  FIGS.  8 A-B  as including two layers (i.e. a backing layer  806  and an adhesive layer  808 ), the fiducial marker of this technology can include only one layer or more than two layers in other examples. 
     The backing layer  806  of the bilayer fiducial marker  800 A in this example has a top surface  810  on which the visual pattern  802  is printed in this example, although other deposition methods of the visual pattern  802  can also be used. The visual pattern  802  can appear as a quick response (QR) code or other type of two dimensional (2D) barcode, although any other type of visual pattern having any type(s) or number of shape(s) having different contrast, brightness, color, light reflection, or other characteristic(s) can also be used in other examples. 
     The backing layer  806  and/or the adhesive layer  808  can be made of collagen and/or a synthetic material (e.g. poly lactic-co-glycolic acid (PLGA)), although the backing layer  806  and/or the adhesive layer  808  can include other and/or additional materials in other examples. The adhesive layer  808  further optionally includes, is coated with, or has embedded, one or more of thrombin, fibrinogen, and/or clotting factor XIII in some examples. The composition  804 A-C of the material in the adhesive layer  808  can include fibers  804 A, fleece  804 B, and/or a sponge/random  804 C, although other types of material compositions can also be used. 
     The thrombin and fibrinogen coating of the adhesive layer  808  functions as an adhesive when the bilayer fiducial marker  800 A comes into contact with fluid in a joint space, for example. In particular, the thrombin activates and cleaves the fibrinogen into fibrin molecules, which cross-link to form a fibrin clot that attaches the bilayer fiducial marker  800 A to a tissue or other anatomical structure surface. In other examples, a synthetic surgical adhesive (e.g., TissuGlu™ available from Cohera Medical, Inc. of Raleigh, N.C.) can be used in place of, or in addition to, the fibrinogen in the adhesive layer  808 , and other types of adhesives can also be used. 
     The concentration of the thrombin in the adhesive layer  808  can be varied based on a desired bonding time, such that an increased concentration of thrombin will result in faster bonding. Additionally, the concentration of the fibrinogen in the adhesive layer  808  can be varied based on a desired adhesive strength, such that an increased concentration of fibrinogen will result in a corresponding increase in adhesive strength. Accordingly, any amount, concentration, and/or ratio of thrombin and/or fibrinogen can be used based on the desired adhesive properties of the bilayer fiducial marker  800 A 
     A grasping tab  812  is attached to, or has portion(s) integral with, the backing layer  806 , and is not configured to be adhesive. Accordingly, the grasping tab  812  facilitates insertion and removal of the bilayer fiducial marker  800 A from a bone or other anatomical structure with an arthroscopic grasper, as described and illustrated in more detail below with reference to  FIG.  10   , for example. Once inserted and attached to an anatomical structure of a patient, the visual pattern  802  of the bilayer fiducial marker  800 A can be recognized and tracked through an arthroscopic video feed, for example, although other methods of tracking the bilayer fiducial marker can also be used in other examples. 
     Bilayer Fiducial Marker with Embedded Beacon(s) 
       FIGS.  9 A-B  depict illustrative bilayer fiducial markers  800 B-C with embedded beacon(s)  900  and  902 A-H that can be used to facilitate surgical tracking without requiring line-of-sight with an image sensor or other tracking device. In this example, the bilayer fiducial marker  800 B includes a radio frequency (RF) identification (RFID) inlay  900  instead of the visual pattern  802 . The RFID inlay  900  is attached to, or incorporated or embedded into, the backing layer  806 , such as at the top surface  810  for example. In other examples, an RFID tag, other passive electromagnetic (EM) beacon(s), or one or more active beacon(s) can also be used in place of, or in combination with, the RFID inlay  900 . 
     In the illustrative bilayer fiducial maker  800 C, an array of passive EM/RF beacons  902 A-H are attached to, or incorporated or embedded into, the backing layer  806 , such as at the top surface  810  for example. While eight passive EM/RF beacons  902 A-H are illustrated in  FIG.  9 B , another number of passive EM/RF beacons, and/or other type(s) of passive beacons, can also be used in other examples. 
     In the examples illustrated in  FIGS.  9 A-B , an external tracking device transmits signal(s) exciting the passive beacon(s)  900  and/or  902 A-H and receives position information in response to the signal(s), which can be used to track the bilayer fiducial markers  800 B-C and associated anatomical structures. In examples in which EM or RF beacon(s) are used, line-of-sight between the bilayer fiducial markers  800 B-C and the external tracking device is advantageously not required to facilitate the tracking. 
     Bilayer Fiducial Marker Fixation 
       FIG.  10    illustrates a flow diagram of an illustrative method for bilayer fiducial marker fixation to an anatomical structure of a patient, for example. In a first step  1000  in this example, the bilayer fiducial marker  800  is grasped by an arthroscopic grasper  1002  at the grasping tab  812 . Any of the illustrative bilayer fiducial markers  800 A-C that are described and illustrated herein with reference to  FIGS.  8 A-B  and  9 A-B, for example, and that include the optional grasping tab, can be placed or attached using the method described and illustrated with reference to  FIG.  10   . 
     In a second step  1004 A-B, a user of the arthroscopic grasper  1002  introduces the bilayer fiducial marker  800  into a cannula  1006 . The cannula  1006  is inserted via an opening  1008  in the patient&#39;s skin (e.g., at a joint space) and disposed proximate a location of an anatomical structure at which the bilayer fiducial marker  800  is to be fixed. The cannula  1006  is funnel-shaped in this example, although other shapes (e.g., tubular) and/or types of cannulas or insertion mechanisms that direct the placement of the bilayer fiducial marker  800  can also be used in other examples. 
     Optionally, as reflected in step  1004 B, the bilayer fiducial marker  800  can be pre-rolled (e.g., dried on a mandrel) for ease of passage through the cannula  1006 . Upon hydration inside the joint space, for example, the relatively stiff, dry, bilayer fiducial marker  800  would become flexible and unfurl. Other configurations of the bilayer fiducial marker  800  can also be used in other examples. 
     In step  1010 , a user of the arthroscopic grasper  1002  places the bilayer fiducial marker  800  at the desired location on the anatomical structure by releasing the grasping tab  812  when the bilayer fiducial marker contacts the desired location. The user then removes the arthroscopic grasper  812  from the cannula  1006  and subsequently removes the cannula  1006  from the opening  1008 . Other types of tools can also be used to place and/or releasably engage the bilayer fiducial marker  800  in other examples. Subsequent to fixation of the bilayer fiducial marker  800  on the anatomical structure at a particular location, a tracking device, such as an image sensor, can track the location of the bilayer fiducial marker  800 , as described in more detail above. 
     Die-Based Fiducial Marker Stamp Pen 
       FIG.  11    depicts an illustrative fiducial marker stamp pen  1100 A that is die-based and is configured to stamp or deposit a pattern that can represent a fiducial marker capable of being tracked by a tracking device. The fiducial marker stamp pen  1100 A has a body  1102  with a proximal end  1104 , a distal end  1106 , an inner lumen  1107  or cavity within which a shaft  1108 A is disposed and is configured to move translationally upon user engagement with a slider  1110  coupled to, or integral with, the shaft. The body  1102  further includes a proximal aperture  1112  in this example configured to allow movement of the slider  1110  toward the distal end  1106  when engaged by a user, although other methods for moving the shaft  1108 A toward the distal end can also be used in other examples. 
     The body  1102  of the fiducial marker stamp pen  1100 A also includes a distal tip  1114 A that includes a die  1116  having cutouts  1118 A-D or apertures that collectively form a fiducial marker pattern. While the cutouts  1118 A-E are illustrated in  FIG.  11    as having square or linear shapes, other types of shapes can also be used. Disposed between the distal tip  1114 A and a shaft tip  1120 A of the shaft  1108 A, and within the lumen  1107 , is a pad  1122  that includes a spongy or felt-like material, for example, that is configured to retain or absorb deposition material and is compressible to thereby release the deposition material through the cutouts  1118 A-D. 
     Optionally, the fiducial marker stamp pen  1100 A can include a reservoir (not shown), such as within a cavity of the shaft  1108 A, that is configured to receive the deposition material and is in fluid material with the pad  1122  (e.g., via an aperture (not shown) in the shaft tip  1120 A. The deposition material can be India ink or Lugol&#39;s iodine, for example, although other types of ink and/or deposition materials can also be used in other examples. 
     In use, the slider  1110  is advanced within the proximal aperture  1112  in the body  1102 , which advances the shaft  1108 A toward the distal end  1106  and thereby compresses the ink pad  1122  between the distal tip  1114 A and the shaft tip  1120 A. Upon compression, the pad  1122  is forced to release the deposition material through the cutouts  1118 A-D in the die  1116  at the distal tip  1114 A. When the distal tip  1114 A of the fiducial marker stamp pen  1100 A is placed against an anatomical structure (e.g., bone surface), the deposition material released through the cutouts  1118 A-D in the die  1116  at the distal tip  1114 A is deposited on the anatomical structure to render a visual fiducial marker pattern that corresponds to the cutouts  1118 A-E and can be tracked by a tracking device. 
     Pre-Inked Fiducial Marker Stamp Pen 
       FIG.  12    depicts another illustrative fiducial marker stamp pen  1100 B that is pre-inked and is configured to stamp or deposit a pattern that can represent a fiducial marker capable of being tracked by a tracking device. In this example, the fiducial marker stamp pen  1100 B includes a shaft  1108 B having a shaft tip  1120 B with embossed features  1200 A-D extending therefrom to form a pattern. The embossed features  1200 A-E are configured to receive and deposit deposition material (e.g., ink) and therefore can be composed at least in part of a material (e.g., rubber or silicone) to which the deposition material will releasably adhere. 
     While the embossed features  1200 A-D are illustrated in  FIG.  12    as having square or linear shapes, other types of shapes can also be used. The distal tip  1114 B disposed toward the distal end  1106  of the body  1102  of the fiducial marker stamp pen  1100 B in this example includes a distal aperture  1202  that is configured to receive the shaft  1108 B, and in particular the shaft tip  1120 B and embossed features  1200 A-D that extend from the shaft tip  1120 B. In some examples, the distal aperture  1202  is part of the inner lumen  1107 . 
     Accordingly, in use, the slider  1110  is advanced within the proximal aperture  1112  in the body  1102 , which advanced the shaft  1108 B toward the distal end  1106  and thereby moves the embossed features  1200 A-E within the distal aperture  1202 . The slider  1110  is advanced in a first step to cause the embossed features  1200 A-D to engage and adhere deposition material (e.g., by contacting an ink pad). Accordingly, the embossed features  1200 A-E can be advanced beyond a plane formed by the distal tip  1114 B in the first step. 
     In a second step, the slider  1110  is advanced subsequent to placement of the distal tip  1114 B of the fiducial marker stamp pen  1100 B against an anatomical structure (e.g., bone surface). In this step, the embossed features  1200 A-D can be advanced at least until they reach the plane formed by the distal tip  1114 B, at which point the embossed features engage the anatomical structure and, as a result of the engagement, deposit the deposition material adhered to the embossed features as a result of the first step. The deposition of the deposition material as a result of the second step renders a visual fiducial marker pattern that corresponds to the embossed features  1200 A-D on the anatomical structure, which can be tracked by a tracking device. 
     While the slider  1110  is illustrated as disposed toward the proximal end  1104  of the fiducial marker stamp pen  1100 A-B in the examples described and illustrated with reference to  FIGS.  11 - 12   , the slider can be located elsewhere and/or other methods for advancing the shaft  1108 A-B can be used in other examples. Additionally, while the body  1102  of the fiducial marker stamp pen  1100 A-B is described and illustrated with reference to  FIGS.  11 - 12    as having a substantially tubular shape, other types of shapes can be used for the body in other examples. 
     Fiducial Marker Stamp Pen with Selectable Visual Pattern 
       FIGS.  13 A-C  depict another illustrative fiducial marker stamp pen  1100 C that is configured to stamp or deposit a selectable or customizable pattern that can represent a fiducial marker capable of being tracked by a tracking device. In this example, the fiducial marker stamp pen  1100 C includes a body  1102  with a proximal end  1104 , a distal end  1106 , an inner lumen  1107  or cavity, and a plurality of selectably deployable members  1252  located within the lumen  1107 . In one embodiment, the members  1252  are configured to move longitudinally within the lumen  1107  independently from each other. In one embodiment, the members  1252  are coupled to an actuator (not shown), such as a slider  1110  as is shown in  FIG.  12   , that is configured to translate the members  1252  longitudinally to selectably deploy the tip  1254  of each of the members  1252  from the distal end  1106  (as shown in  FIG.  13 C ) to form a customizable pattern  1250  (as shown in  FIG.  13 A ). In use, the pattern  1250  can be customized by controlling which of the members  1252  are deployed (i.e., have their tips  1254  exposed from the lumen  1107 ) or stowed (i.e., have their tips retracted within the lumen). Accordingly, the pattern  1250  is defined by the particular combination and arrangement of which tips  1254  are exposed or deployed. In another embodiment, each of the tips  1254  of the members  1252  can include a pattern corresponding to a fiducial marker and the tips can be independently deployable for depositing each individual pattern. 
     In one embodiment, the members  1252  can include or be fluidically coupled to a reservoir (not shown) that can hold a deposition material, and the tips  1254  can be configured to extrude or release the deposition material when the tips  1254  are extended from the body  1102 . For example, the fiducial marker stamp pen  1100 C can include an actuator (not shown), such as a slider, that is configured to compress a shaft (not shown) located within each of the members  1252  and thereby compresses an ink pad (not shown) located at the tips  1254 . Upon compression, the pad is forced to release the deposition material through the tips  1254 , similarly to the embodiment shown in  FIG.  11   . In another embodiment, the tips  1254  are configured to receive and deposit deposition material (e.g., ink) and therefore can be composed at least in part of a material (e.g., rubber or silicone) to which the deposition material will releasably adhere, similarly to the embodiment shown in  FIG.  12   . Further, while the tips  1254  are illustrated in  FIG.  13 A  as having square shapes, other types of shapes can also be used. 
     In use, the members  1252  can be selectively deployed from the body  1102  of the fiducial marker stamp pen  1100 C to form a pattern  1250  desired by the user. Accordingly, the pattern  1250  defined by the tips  1254  can be placed against an anatomical structure (e.g., bone surface) to deposit the deposition material thereon. The deposition of the deposition material renders a visual fiducial marker pattern on the anatomical structure that corresponds to the pattern  1250 . The fiducial marker pattern can be tracked by a tracking device. 
     Fiducial Marker Deformable Applicator 
       FIG.  14    depicts an illustrative fiducial marker deformable applicator assembly  1300  that is configured to stamp or deposit a pattern that can represent a fiducial marker capable of being tracked by a tracking device. In this example, the fiducial marker deformable applicator assembly  1300  includes a deformable member  1302  and an arthroscopic tool  1304  (e.g., an arthroscopic grasper). The deformable member  1302  can include an inflatable balloon, a compressible elastic dome (e.g., a structure configured to deform under sufficient force and reversibly/elastically return to its original, undeformed shape upon removal of the force), or another device having a structure that can be controllably deformed and is suitable for an arthroscopic surgical application. The arthroscopic tool  1304  includes a distal end  1306  that is configured to grasp or manipulate the deformable member  1302 . In one embodiment, the deformable member  1302  can be constructed from silicone or other materials having sufficient physical properties that allow the deformable member  1302  to, during an arthroscopic surgical procedure, be inflated/deflated, compressed/decompressed, or otherwise reliably deform under the application of a force and return to its original shape when the application of force is absent. In one embodiment, the fiducial marker deformable applicator assembly  1300  is configured to be inserted through a cannula (e.g., the cannula  1006  shown in  FIG.  10   ) so that the deformable member  1302  can be arthroscopically deployed within or at a surgical site. 
     In use, the fiducial marker deformable applicator assembly  1300  can be used to transfer a pattern  1310  from an exterior source onto an anatomical structure (e.g., a bone  1320 ) in the form of a fiducial marker  1312  that is capable of being tracked by a tracking device. An example process of using the fiducial marker deformable applicator assembly  1300  is shown in  FIG.  14   . For example, in a first step  1350 , the deformable member  1302  can be grasped or removably affixed to the arthroscopic tool  1304 . In a second step  1352 , the undeformed (e.g., non-inflated or uncompressed) deformable member  1302  can be placed against a pattern  1310  of a deposition material (e.g., a bioadhesive ink) that is configured to releasably adhere to the surface of the deformable member  1302 . In one embodiment, the pattern  1310  can be arranged such that it forms the desired fiducial marker  1312  when the deformable member  1302  is deformed (e.g., inflated or compressed). In other words, the pattern  1310  can be arranged such that it forms the desired shape or configuration of the fiducial marker  1312  when stretched or otherwise altered by the deformation of the deformable member  1302 . In one embodiment, the user can place the deformable member  1302  against the deposition material multiple different times in different orientations to generate different patterns that are adhered to the deformable member. In a third step  1354 , the fiducial marker deformable applicator assembly  1300  is arthroscopically inserted into the surgical site, the deformable member  1302  is deformed (e.g., inflated or compressed), and the deformable member is pressed against the surface of the anatomical structure (e.g., a bone  1320 ) that the user wishes to mark or track. Placing the deformable member  1302  against the anatomical structures transfers the deposition material from the surface of the deformable member to the anatomical structure. In a fourth step  1356 , the fiducial marker deformable applicator assembly  1300  is removed from the surgical site (and, optionally, the deformable member  1302  is deflated), leaving the fiducial marker  1312  deposited on the anatomical structure such that the fiducial marker can be tracked by a tracking device throughout the course of the surgical procedure. In one embodiment, the deposition material can be a material that is configured to degrade over time so that the fiducial marker is not permanently deposited on the anatomical structure, as shown in a fifth step  1358 . 
     In one embodiment, the deformable member  1302  can be configured to have a smooth surface when deformed. In this embodiment, the entire surface of the deformable member  1302  can be available to transfer the deposition material to form the fiducial marker  1312 . In another embodiment, the deformable member  1302  can be configured to have a protruding portion when deformed. In this embodiment, the protruding portion can be used to transfer the deposition material to form the fiducial marker  1312 . In one embodiment, the deformable member  1302  can include a coating that is configured to facilitate the release of the deposition material from the deformable member to the anatomical structure. 
     Fiducial Marker Characteristics 
     In one embodiment, the deposition material(s) described in connection with  FIGS.  11 - 14    that is used to form the fiducial marker can include a biocompatible adhesive, a biocompatible stain or ink (e.g., a bioink), and other such materials. In one embodiment, the deposition material can include a biocompatible adhesive that is configured to adhere to biological tissues in an arthroscopic environment and degrade on a timeframe that allows for completion of the surgical procedure without delaminating or distorting the fiducial marker (e.g., six or more hours). In one embodiment, the deposition material can be configured to have minimal bleed when deposited so that the deposition material is transferred from the applicator to the anatomical structure with high fidelity to form the desired fiducial marker. 
     Advantageously, depth information can be obtained by the tracking device since the bilayer fiducial marker  800  and the fiducial markers deposited from the application of the various fiducial marker applicators shown in  FIGS.  11 - 14    are flexible and/or can conform to anatomical structure (e.g., bone) contour, which can render a “random walk” registration procedure unnecessary and facilitate direct matching of the bilayer fiducial marker to the preoperative scan or 3D model. Additionally, this technology provides a relatively low profile or planar fiducial marker that does not interfere with surgical instruments or other objects in the operating environment. 
     The fiducial markers of this technology also adhere to the surface of anatomical structures to be tracked in a non-destructive manner that does not damage intra-articular anatomy. Because the application of the fiducial markers is non-destructive, a plurality of fiducial markers can be placed in order to advantageously mitigate or prevent occlusion issues and improve the effectiveness and/or accuracy of the tracking and/or depth determination. 
     The fiducial markers described herein can be used intraoperatively for a variety of different purposes during a surgical procedure, including as anchors for an AR system or for topographical analyses of the anatomical structure on which the fiducial markers are located. As noted above, the CASS  100  can include a scope (e.g., an arthroscope) through which a video feed of the surgical site can be obtained (e.g., and displayed to the users via a display  125 ). Further, the CASS  100  can utilize image recognition and processing techniques on the obtained video feed to identify fiducial markers visualized within the video feed and take corresponding actions, such as displaying AR elements to the users or determining characteristics of the anatomical structures.  FIGS.  15 A-C  demonstrate how fiducial markers can be analyzed to determine the topography of the underlying anatomical surface. For example,  FIG.  15 A  shows an illustrative undistorted fiducial marker  1400 . The illustrated pattern of the undistorted fiducial marker  1400  could represent the “base” or “expected” pattern for the fiducial marker. Accordingly, a tracking system  115 , surgical computer  150 , and/or another component of a CASS  100  can be configured to determine that the portion of the anatomical structure on which the undistorted fiducial marker  1400  is deposited is substantially planar when the fiducial marker in  FIG.  15 A  is visualized by the CASS. Alternatively,  FIGS.  15 B and  15 C  show fiducial markers  1402 ,  1404  corresponding to the fiducial marker  1400  shown in  FIG.  15 A  subject to positive and negative radial distortion, respectively. Accordingly, a tracking system  115 , surgical computer  150 , and/or another component of a CASS  100  can be configured to determine that the portion of the anatomical structure on which the fiducial marker  1402  in  FIG.  15 B  is deposited is substantially convex. Similarly, a tracking system  115 , surgical computer  150 , and/or another component of a CASS  100  can be configured to determine that the portion of the anatomical structure on which the fiducial marker  1404  in  FIG.  15 C  is deposited is substantially concave, for example. The component of the CASS  100  can make these determinations by comparing the pattern of the fiducial marker as visualized to the base or expected pattern (e.g., as shown in  FIG.  15 A ) using known image processing algorithms to determine whether the visualized fiducial marker pattern has been distorted relative to the expected pattern and, further, the type of distortion that the pattern has been subjected to. 
     In various embodiments, the fiducial markers described herein can be applied to a surgical site using the variety of different applicators described herein and can be used for a variety of different purposes. In one embodiment, the CASS  100  can be configured to use the fiducial markers for multiple simultaneous purposes. For example, the CASS  100  can be configured to simultaneously use the fiducial markers as anchors for an AR system and for topographical analyses of the anatomical structures on which the fiducial markers are deposited. 
     While various illustrative embodiments incorporating the principles of the present teachings have been disclosed, the present teachings are not limited to the disclosed embodiments. Instead, this application is intended to cover any variations, uses, or adaptations of the present teachings and use its general principles. Further, this application is intended to cover such departures from the present disclosure that are within known or customary practice in the art to which these teachings pertain. 
     In the above detailed description, reference is made to the accompanying drawings, which form a part hereof. In the drawings, similar symbols typically identify similar components, unless context dictates otherwise. The illustrative embodiments described in the present disclosure are not meant to be limiting. Other embodiments may be used, and other changes may be made, without departing from the spirit or scope of the subject matter presented herein. It will be readily understood that various features of the present disclosure, as generally described herein, and illustrated in the Figures, can be arranged, substituted, combined, separated, and designed in a wide variety of different configurations, all of which are explicitly contemplated herein. 
     The present disclosure is not to be limited in terms of the particular embodiments described in this application, which are intended as illustrations of various features. Many modifications and variations can be made without departing from its spirit and scope, as will be apparent to those skilled in the art. Functionally equivalent methods and apparatuses within the scope of the disclosure, in addition to those enumerated herein, will be apparent to those skilled in the art from the foregoing descriptions. It is to be understood that this disclosure is not limited to particular methods, reagents, compounds, compositions or biological systems, which can, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting. 
     With respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. The various singular/plural permutations may be expressly set forth herein for sake of clarity. 
     It will be understood by those within the art that, in general, terms used herein are generally intended as “open” terms (for example, the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” et cetera). While various compositions, methods, and devices are described in terms of “comprising” various components or steps (interpreted as meaning “including, but not limited to”), the compositions, methods, and devices can also “consist essentially of” or “consist of” the various components and steps, and such terminology should be interpreted as defining essentially closed-member groups. 
     In addition, even if a specific number is explicitly recited, those skilled in the art will recognize that such recitation should be interpreted to mean at least the recited number (for example, the bare recitation of “two recitations,” without other modifiers, means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogous to “at least one of A, B, and C, et cetera” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (for example, “a system having at least one of A, B, and C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, et cetera). In those instances where a convention analogous to “at least one of A, B, or C, et cetera” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (for example, “a system having at least one of A, B, or C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, et cetera). It will be further understood by those within the art that virtually any disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, sample embodiments, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase “A or B” will be understood to include the possibilities of “A” or “B” or “A and B.” 
     In addition, where features of the disclosure are described in terms of Markush groups, those skilled in the art will recognize that the disclosure is also thereby described in terms of any individual member or subgroup of members of the Markush group. 
     As will be understood by one skilled in the art, for any and all purposes, such as in terms of providing a written description, all ranges disclosed herein also encompass any and all possible subranges and combinations of subranges thereof. Any listed range can be easily recognized as sufficiently describing and enabling the same range being broken down into at least equal halves, thirds, quarters, fifths, tenths, et cetera. As a non-limiting example, each range discussed herein can be readily broken down into a lower third, middle third and upper third, et cetera. As will also be understood by one skilled in the art all language such as “up to,” “at least,” and the like include the number recited and refer to ranges that can be subsequently broken down into subranges as discussed above. Finally, as will be understood by one skilled in the art, a range includes each individual member. Thus, for example, a group having 1-3 components refers to groups having 1, 2, or 3 components. Similarly, a group having 1-5 components refers to groups having 1, 2, 3, 4, or 5 components, and so forth. 
     The term “about,” as used herein, refers to variations in a numerical quantity that can occur, for example, through measuring or handling procedures in the real world; through inadvertent error in these procedures; through differences in the manufacture, source, or purity of compositions or reagents; and the like. Typically, the term “about” as used herein means greater or lesser than the value or range of values stated by 1/10 of the stated values, e.g., ±10%. The term “about” also refers to variations that would be recognized by one skilled in the art as being equivalent so long as such variations do not encompass known values practiced by the prior art. Each value or range of values preceded by the term “about” is also intended to encompass the embodiment of the stated absolute value or range of values. Whether or not modified by the term “about,” quantitative values recited in the present disclosure include equivalents to the recited values, e.g., variations in the numerical quantity of such values that can occur, but would be recognized to be equivalents by a person skilled in the art. 
     Various of the above-disclosed and other features and functions, or alternatives thereof, may be combined into many other different systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art, each of which is also intended to be encompassed by the disclosed embodiments.