ANATOMIC SURFACE AND FIDUCIAL REGISTRATION WITH AN INTRA-OPERATIVE 3D SCANNER

Aspects of the present disclosure include surgical systems and methods for modifying an existing 3D model of a region of anatomic interest to include features intra-operatively scanned by a 3D scanner. In one aspect, the systems and methods include operations for: receiving scan data from an intra-operative scan of a bone surface in the region of anatomic interest, where the scan data includes a fiducial placed by a surgeon; generating an intra-operative 3D model that includes a 3D representation of the fiducial; registering the intra-operative 3D model with a pre-operative 3D model of the region of anatomic interest; modifying the pre-operative 3D model to include the fiducial at a location according to the intra-operative 3D model; and providing the modified pre-operative 3D model to a surgical navigation system that tracks objects in the region of anatomic interest based on the location of the fiducial.

FIELD OF THE INVENTION

The present invention generally relates to the field of surgical systems. In particular, the disclosure is directed to surgical systems with intra-operative 3d scanners and surgical methods using the same, for example, for intra-operative registration and subsequent tracking of a surgeon-placed fiducial.

BACKGROUND

Joint replacement surgery has become an ever-increasing area of surgical procedures. It has been reported that more than 7 million Americans living with a hip or knee replacement. A 2017 report of American Joint Registry shows 860,080 procedures from 654 institutions and 4,755 surgeons, representing a 101% increase in procedures from the year prior. Kurt et al in an article in the Journal of Bone and Joint Surgery estimate that 700,000 knee replacement procedures are performed annually in the US, and this number is projected to increase to 3.48 million procedures per year by 2030. The current annual economic burden of revision knee surgery is $2.7 billion for hospital charges alone, according to Bhandari et al in Clinical Medical Insights: Arthritis and Musculoskeletal Disorders (2012). By 2030, assuming a 5-fold increase in the number of revision procedures, this economic burden will exceed $13 billion annually (Bhandari et al). Adding to the number of the procedures and the economic burden is the fact that of the total knee replacements per annum, around 3% need to be revised for malposition/malalignment. This constitutes more than 21,000 cases a year of suffering patients who need to undergo a revision surgery.

Currently there are two ways of performing a knee replacement, either with conventional instruments or computer aided surgery. Most cases in the United States are performed using conventional instruments. This technique involves using intra- or extra-medullary rods to reproduce the anatomic axes. For the proximal tibial cut, an extramedullary rod is conventionally used. The distal portion of the rod is clamped around the ankle and the tibia is cut perpendicular to the anatomical axis. For the distal femoral cut, an intra-medullary rod is also conventionally used. The femur is drilled to accept the rod and then the distal femur is arbitrarily cut at 5 degrees, with a range of 3 to 7 degrees. The rotational position of the femur and tibia is mostly achieved by visually identifying anatomical landmarks or some form of gap balancing methods. The drawbacks to conventional alignment systems include difficulty with identifying the anatomic landmarks, (e.g., the lateral epicondyle, lateral condyle, medial epicondyle, medial condyle, or the intercondylar fossa, etc., of a femur), intra-operatively as well as the assumption of standard anatomic relationships, which may not always be consistent or accurate across all patients.

Computer-assisted surgery (CAS) was developed to help achieve more customized, precise, and repeatable techniques. CAS, and especially orthopedic CAS, typically employs an image-based navigation system (a.k.a. an optical tracking system) that requires intra-operative registration of anatomical landmarks to a pre-operative three-dimensional (3D) model of the region or area of anatomical interest (e.g., the bones of a knee joint), where the pre-operative 3D model is created from pre-operative images, such as pre-operative MRI images. Typically, this registering process is long, tedious, and involves multiple steps with a handheld pointer probe that is optically tracked by the navigation system as it is positioned by the surgeon to identify anatomic landmarks.

For example, typical conventional computer-assisted orthopedic surgery requires manual acquisition and registration of bony landmarks using a CAS pointer probe or the like, and the attachment of optical trackers to bones for calibration and tracking. The trackers are usually outside of the incision and must be well fixed to the bone because any movement can lead to errors in the acquisition of data for the CAS navigation system. Among other drawbacks, the manual acquisition of anatomic landmarks by palpation is time-consuming, error-prone—its accuracy is surgeon-dependent, and it is not consistently reproducible.

Other drawbacks include that the surgeons must be specially trained in multiple manual registration techniques using different probes so to be able to employ the manual registration techniques required by each different CAS system. These drawbacks detrimentally prolong the time in surgery, increase the incidents of malpositioning of implants (e.g., knee joint implants), (which can lead to instability, pain, decreased range of motion, and implant loosening), and increase the cost of orthopedic operations.

SUMMARY OF THE DISCLOSURE

In one aspect, the present disclosure is directed to systems, methods, and computer program products for modifying a 3D model of an area of anatomic interest. The systems, methods, and computer program products may have features that include: a fiducial that is attached to a bone surface in the area of anatomic interest; an intra-operative three-dimensional (3D) scanner; and a computer that is connected to the intra-operative 3D scanner. The computer may perform a process or operations that may include: receiving, from the intra-operative 3D scanner, scan data from an intra-operative scan of the bone surface, wherein the scan data includes data representing the fiducial; generating, from the scan data, an intra-operative 3D model that includes a 3D representation of the fiducial; registering the intra-operative 3D model with a pre-operative 3D model of the area of anatomic interest; modifying the pre-operative 3D model to include the fiducial at a location according to the intra-operative 3D model; and providing the modified pre-operative 3D model to a surgical navigation system that tracks objects in the area of anatomic interest based on the location of the fiducial.

In another aspect, the present disclosure is directed to systems, methods, and computer program products in which the intra-operative 3D scanner may be a handheld laser 3D scanner. In another aspect, the present disclosure is directed to systems, methods, and computer program products in which the pre-operative 3D model may be created from MRI scan data.

In another aspect, the operations may include employing a machine learning model to identify an anatomical landmark in the intra-operative 3D model.

In another aspect, the fiducial is a plate or an anchor. In such aspects, the fiducial may also be attached to the bone surface at a predetermined location. In further such aspects, the predetermined location may be based on a preoperative image of the bone surface. In further such aspects, the preoperative image may be any of a computer tomography image, an ultrasound image, and/or a magnetic resonance image. In another aspect where the fiducial is a plate, the plate may include a bar code the encodes surgery-assisting information.

In another aspect, the operations may include analyzing the intra-operative 3D model to differentiate between different types of tissue. In such aspects, the analyzing may employ machine learning methods. In further aspects, the different types of tissue may include bone tissue and cartilage tissue.

In another aspect, fiducial may be attached intra-operatively without using a predetermined location on the bone surface, and the operations may further include analyzing the intra-operative 3D model to detect the location of the fiducial.

In yet another aspect, the operation for registering the intra-operative 3D model with a pre-operative 3D model may include aligning the intra-operative 3D model with the pre-operative 3D model using an iterative closest point (ICP) algorithm.

In yet another aspect, the operation for modifying the pre-operative 3D model to include the fiducial at a location according to the intra-operative 3D model may include combining the intra-operative 3D model with the pre-operative 3D model to produce the modified pre-operative 3D model. In such aspects, the modified pre-operative 3D model may include the fiducial from the intra-operative 3D model.

DETAILED DESCRIPTION

Aspects of the present disclosure include surgical systems that provide a cost-effective, accurate, and efficient system for performing surgical procedures.

In one aspect of the disclosure, a surgical system utilizes an intra-operative laser, white light or blue light 3D scanner. This 3D scanner is used to determine anatomical landmarks and calculate surgical positions based on such anatomical landmarks. Utilizing well-defined focused light, e.g., laser light lines, onto a bony and/or a cartilage surface, the 3D scanner can be used to generate a complete or partial scan of the surgical surface, which can then be superimposed on pre-operative images to instantly register the bone. Such instant registration can be based on pre-operative imaging such as computerized tomography, magnetic resonance imaging, or plane radiographs of the limb or organ. In another aspect, the instant registration can be achieved with machine learning algorithms incorporating artificial intelligence technology.

In another aspect of the disclosure, a surgical system is provided that is useful in performing orthopedic procedures in the absence of trackers. In another aspect of the disclosure, a surgical system is provided that is useful in sizing orthopedic implants in the absence of an implant representative. In another aspect of the disclosure, an artificial intelligence system is used that utilizes machine learning to provide improvements in surgical efficiency. In another aspect of the disclosure, a surgical software system may be used to recognize and track implants, instruments or the like. In another aspect of the disclosure, a specific instrument can be used for calibration and aid in navigation or robotic assistance without trackers.

The present disclosure includes surgical systems that include one or more intra-operative 3D scanners. Although the surgical system is illustrated and described in the context of being useful for orthopedic surgical procedures, the present disclosure can be useful in other instances. Accordingly, the present disclosure is not intended to be limited to the examples and embodiments described herein.

FIG.1Ashows a surgical system100, which can be used to perform a computer-assisted surgery utilizing an intra-operative 3D scanner110. The surgical system100ofFIG.1Ais shown in use in an operating room105and includes a 3D scanner110capable of producing an intra-operative 3D scan of a body part of interest. In the context ofFIG.1A, a patient115is undergoing a knee replacement operation. The soft tissue around the knee120has been incised to expose the femur125and the tibia130.

The 3D scanner110projects a light or other wave135onto the region of anatomical interest140and monitors the reflection of the light135so as produce a 3D scan of the region of interest140. The 3D scan is transmitted to a computer150by cable155or by wireless connection. The computer150processes and analyzes the 3D scan and controls or assists the surgical procedure based on the analysis, as described below. For example, the computer150may control or operate or provide information to an optional robotics unit160. The robotics unit160may perform a computer-guided surgical procedure. Alternatively, the computer150may provide information to a surgeon and/or may provide information to the robotics unit160that will allow the robotics unit160to aid the surgeon during the procedure.

Referring to bothFIGS.1A and1D, the computer150can be any device capable of receiving input, performing calculations based on the input, and producing output as a result of the calculations. The computer150may include a central processor102that is capable of interacting with a user via a keyboard, a graphical user interface, wireless communication, voice command, or any other manner. The computer150may be a personal computer, a laptop, a handheld device, a server, a network of servers, a cloud network, or the like. The user, such as a surgeon or surgeon's assistant, may interact with the computer150before, during, or after the surgical procedure. The computer150may include a memory104or may be otherwise communicatively coupled to a memory that contains various software applications106for performing calculations, and executing algorithms, routines, and/or subroutines, for example, to process information and/or make determinations. For example, the computer150may include one or more software applications configured to analyze information (e.g. scan data) obtained from 3D scanner110, generate a 3D model or 3D scan image, and analyze the 3D model. In one example, software applications106include an object recognition module108configured to recognize various objects or features in an image, such as the 3D scanned image. Facial recognition, fingerprint recognition, and iris recognition software systems are examples of object recognition technology. Each of these software systems make comparisons of anatomical features of an image with features in a database that is either stored in the computer150or is accessible by the computer by wired or wireless connection. The computer150may further include a robotics control module109for controlling and communicating with the robotics unit160. The computer150may further include other optional modules, such as an artificial intelligence or also referred to herein as a machine learning module112that are configured to apply one or more machine learning algorithms to identify anatomical landmarks of interest, among other functions.

In examples, the 3D scanner110may be a laser, white light or blue light scanner. In various embodiments, the 3D scanner may be a device that generates 3D scan date that can be used to generate a virtual 3D model of a scanned object, which may include 3D scanner devices that perform surface height measurements of an object using coherence scanning interferometry with broadband light illumination. Commercially available 3D scanners that incorporate 3D scanning technology that may be used or modified for applications of the present disclosure include the AICON PrimeScan and the WLS400M from Hexagon Manufacturing Intelligence in Surrey, Great Britain; the Go!SCAN 3D from Advanced Measurements Labs in Tustin, California; the HandySCAN 3D TM from Creaform Inc. in Levis, Canada; and 3D scanners produced by E4D Technologies in Dallas, Texas.

As shown inFIG.1B, in one example, the 3D scanner110is incorporated into handle170of medical light175. Medical light also includes an array of lights180that are used to illuminate the operating room105as is known in the art. The 3D scanner110also includes one or more light emitting modules that may emit a laser, white light or blue light, which can be projected onto the patient115and the area of interest140. 3D scanner110captures reflections of the light emitted by the scanner and which can be used to generate a 3D image using imaging software executed, e.g., by computer150. As described herein, the term 3D model is often used interchangeably with the term 3D image. In the example shown inFIG.1B, the 3D scanner110is mounted at the center portion of the medical light175at or near the handle170or in the peripheral aspect of the light175so that it may be easily manipulated and directed by a user, such as a surgeon or surgeon's assistant. The user directs the 3D scanner110at a region of anatomical interest140, such as an exposed knee120, and a 3D scan can be performed to generate a 3D image or model of the anatomy, such as the 3D image/model185shown inFIG.1C.

FIG.1Cshows an example of a 3D image or 3D model generated from a 3D scan of an anterior view of the distal end of the femur125. In one example, such 3D images or models are accurate up to less than 0.001 inches, with up to five million data points generated, e.g., in a few seconds, generating a nearly exact virtual model of the scanned object. The scan data generated by scanner110can be collected efficiently with minimal setups, and generated into a 3D image or model using, for example, one or more software modules executed by or accessible by computer150as described more below. System100may also include a hologram projector116for projecting a hologram of an object during surgery, which can be used for a variety of purposes, including projecting a proper position and orientation of a bone cutting jig in a surgical field.

FIG.2illustrates an example of a surgical procedure200that may be performed using surgical systems of the present disclosure, e.g., surgical system100. At step210, a patient is prepped for surgery. At step220, the anatomical area of interest140is cleaned, excised, or otherwise exposed so that it is visible from the point of view of the 3D scanner110. Light135or other scanning medium is directed onto the anatomical area of interest140so that the 3D scanner110and/or computer150can generate, at step230, a 3D image of the anatomical area of interest140. The optical camera of the 3D scanner that is attached to the light handle is communicatively connected to the computer for transmitting images (e.g., scan data) for processing by the object recognition module108. 3D scanner110and object recognition module108may be configured to constantly scan a field of view of the 3D scanner camera and automatically detect a scanned surface and anatomical landmarks located thereon. Object recognition module108can then automatically match or register the 3D scanner image to a preoperative image of the same anatomical area. If the 3D scanner includes separate processors and software for generating a 3D model or 3D image, then at step240, the 3D image/model is sent to the computer150by cable connection155, by wireless connection, or the like. At step250, the computer150analyses the 3D image, for example, with object recognition module108, and identifies one or more anatomical landmarks in the image.

The object recognition module108can be programmed or configured via a user interface to identify one or more particular anatomical landmarks. Once the one or more anatomical landmarks are identified, at step260, surgery planning module114may be executed to perform calculations and/or make determinations based on the one or more identified anatomical landmarks. For example, surgery planning module114can determine the optimal location to make a cut or a drill a hole relative to the anatomical landmark. At step270the computer150, e.g., with surgery planning module114can then generate an output signal related to the calculations or determinations. The output signal can be in any of various forms. For example, the output signal can be information that is delivered to the surgeon for the surgeon to consider during performance of the procedure. Alternatively or additionally, the output can be in the form of computer-assisted surgery signals or data, and the output can be used to guide pointers, instruments, and the like and/or can be in communication with a robotics module or a robotics unit160. Alternatively or additionally, the output can be in the form of computer-aided design (CAD) files for use in computer assisted surgery, and the output can be used for providing visual aid on a monitor or via projecting, such as using hologram projector116, onto the surgical field or on the skin or bony surface. The output can be used to guide pointers, instruments, robotic arms, and the like and/or can be in communication with a robotics module or robotics unit160.

The surgical system100of the present disclosure is useful in a wide variety of surgical procedures where precise movements and/or placement of components relative to an anatomical landmark is important. For example, the surgical system100is particularly useful in orthopedic procedures where precise cuts and placement of devices is important for the success of the procedure. Joint replacement procedures, such as knee replacement and hip replacement procedures, are examples of such orthopedic procedures. The surgical system100is also useful in other surgical arenas, such as guidance of any cutting device. For example, the surgical system100can be used for fracture fixation with a plate or other fixation device. The 3D scan can help with superimposing an image onto intra-operative radiographs or fluoroscopic images. The surgical system100can also be useful in dental and maxillofacial surgical procedures; in spinal procedures especially when pedicle screws are to be placed by scanning the area and correlating with pre-operative and intra-operative MRI; hand, foot, and ankle procedures, shoulder replacement and fracture treatment procedures. In addition, the surgical system100can be useful in general surgical procedures where an organ is scanned by endoscopy and/or laparoscopy, and images are used to guide surgical tools for accurate cut or suture placement and the like.

The surgical system100will now be described in the context of a knee replacement procedure. The present examples and the specifics involved are not intended to limit the scope or usefulness of the surgical system100but merely to demonstrate its applicability in a particular field. One of ordinary skill in the art will understand that this exemplified use can be modified and extended to other fields, such as any of those mentioned above.

An important factor for a successful knee replacement procedure is the appropriate alignment and placement of implants to reproduce the biomechanical properties of the joint. Determination of proper alignment includes positioning the femur and tibia at a defined angle, typically 90 degrees, to the mechanical axes of the femur and tibia and typically within 3 degrees of error. As such, a cause for a malposition of an implant can be a 3-degree deviation from the 90-degree positioning to the mechanical axis or inappropriate rotation of femoral and/or tibial components. Accordingly, in one example, surgical system100may be designed and configured to aid in making the cuts associated with and placement of an artificial knee joint so as to be within the 3 degrees of the desired 90-degree positioning of the implant relative to the mechanical axes of the femur and tibia.

Memory104may include information related to the knee joint and the instruments associated with knee joint replacement, with such information accessible by object recognition module108and surgery planning module114.

For example, the computer150may execute object recognition module108and recognize a pre-defined bone jig configured for use in the procedure, as well the anatomy of the knee120. After the surgical approach is performed and the knee exposed, the medical lights175equipped with a 3D scanner110like the one inFIG.1Bmay be brought closer to the knee region120, a 3D scan of the exposed bone can be performed, and a 3D image is generated. In one example, a plurality, e.g., two, 3D scanners110can be utilized. The plurality of 3D scanners110can be positioned at different locations around knee region120so that they generate a corresponding plurality of different simultaneous views of the exposed surgical area. The 3D image can then be delivered to the computer150by Wi-Fi technology or the like, or scan data generated by the scanners can be transmitted to the computer to generate a 3D image or model. Object recognition module108can be configured to recognize and detect different surface textures and colors and can distinguish between bone, cartilage, instruments, and soft tissue. The 3D image can be analyzed by object recognition module108to identify pre-determined anatomical landmarks.

For the knee replacement surgery, the object recognition module108may be configured to identify certain predetermined anatomical landmarks. For example, one or more of bony landmarks, surfaces, limb axes, and dimensions can be identified and defined or recorded by the object recognition module108and stored in the memory104.

FIGS.3Athrough 3D illustrate examples of the anatomical landmarks that object recognition module108may be configured to identify and locate.FIG.3Ais a representative 3D image185of an anterior view of the distal femur125generated from a 3D scan of the distal femur.FIG.3Bis an enlarged anterior view of a portion of the distal femur 3D image185.FIG.3Cis a representative 3D image185of a top view of the proximal tibia130.FIG.3Dis a representative 3D image185of an anterior view of the proximal tibia130. On the femur125, object recognition module108may be configured to identify one or more of the trochlea groove310, the trochlea notch315, the medial epicondyle320, the lateral epicondyle325, and the distal femur articulating surface330. On the tibia130, object recognition module108may be configured to identify one or more of the medial tibial plateau360, the lateral tibial plateau365, and the tibial tubercle370. In another example, object recognition module108may be configured to identify one or more predetermined bone-cartilage junctions as one of the anatomical landmarks. In one example, the computer150may be used to identify and locate all of the above landmarks on the femur125and the tibia130.

After identifying and locating the anatomical landmarks, surgery planning module114may be executed to perform calculations based on the landmarks. For example,FIGS.4A through4Dshow the representative 3D images185fromFIGS.3Athrough 3D respectively, and also illustrate pre-established axes calculated by surgery planning module114for implant positioning. On the distal femur125, surgery planning module114may calculate the transepicondylar axis (TEA)410, the patetllofemoral axis (PFA)415, and the posterior condylar axis (PCA)420. On the proximal tibia130, surgery planning module114may calculate the tibial rotation axis (TRA)460.

In one example, surgical system100further includes a bone jig500(FIG.5A). In the illustrated example, bone jig500is a bone cutting guide and memory104may contain one or more dimensions of the jig. The bone jig has a body505with pin holes510for fixation to the bone. A saw blade protector515helps define a guide slot for a saw blade. Bone jig500also includes an initial fixation pin hole525coupled to body505by a hinged connection530, which as described below, can be used for fine adjustments of the bone jig500prior to fixation of the jig t bone with pin holes510. The bone jig500is relatively small and is user friendly. The bone jig500is positioned over the femur125inFIG.5Band over the tibia130inFIG.5Cat precisely determined positions as will be described.FIGS.5B and5Calso illustrate a hologram projection502projected onto the bony surface from hologram projector116and show the jib aligned with the projection. In the illustrated example, the projection is a projection of a portion of an outer perimeter of the bone jig. In other examples, other types of projections may be used, such as the projection of one or more points. The jig position can, therefore, be projected onto the bony surface, so that the surgeon can position the jig with the projected hologram. As will be appreciated, hologram projector116can also be configured to project other holograms, for example, one or more targets or a portion of an outer perimeter of other jigs. In other example, rather than aligning a bone cutting jig, such as jig500, with a hologram, such as hologram502, a hologram projection may be directly used as an augmented reality cutting guide and a surgeon may use a surgical instrument, such as a saw in a plane of cut that is projected by the hologram.

Since the bone jig500has exact pre-determined dimensions, it can also be used by the computer150, e.g., surgery planning module114, to calibrate images (for example, in cases where there are no pre-operative images) of the bone jig captured by 3D scanner110. The bone jig500parameters and dimensions are loaded into the computer150and stored in Memory104prior to surgery. Then, during surgery, object recognition module108can be configured to detect the unique shape and dimensions of bone jig500and, in some examples, since the dimensions are already defined, the dimensions can be used to calibrate the image of the scanned bone adjacent to the bone jig. With the jig500roughly positioned in a region of interest, a pin can be inserted through the initial fixation pin hole525and the bone jig500is placed over the bone and the bone jig500can be provisionally fixed by this pin to the bone (as shown inFIG.6A). The computer150recognizes the bone jig500, the 3D image of the bone, and the calibrated bone.

The mechanical axis610of the femur and the mechanical axis620of the tibia are determined as shown inFIGS.6A through6C. With jig500provisionally fixed to the bone, the knee can be placed in different positions, moved around in a triangle630until the mechanical axis of the bone is identified from this triangular positioning. This is done based on the shape of the cutting jig, distance and position as referenced to the optical camera of 3D scanner110, e.g., on the light handle170. Bone jig position data can be determined from the image data captured by the camera of the 3D scanner110with, e.g., surgery planning module114, and stored in Memory104. Surgery planning module114may also be configured to calculate the femur mechanical axis from the bone jib position data. The rotational axis of the femur can also be calculated based on transepicondylar axis or gap balancing principles, which are previously described and well-known in the art. Since the mechanical axis of the femur125goes through the femoral head, by rotating the distal aspect of the femur in various positions, the position and orientation of the bone jig500and the bony surface can be determined from images of the jig and bone surface captured by the camera of the 3D scanner110, and the computer150, with, e.g., surgery planning module114, can generate a model that defines the femur mechanical axis. This axis is used for cutting the distal femur125. Similarly, the tibial mechanical axis is defined based on the change in position and orientation of the jig500fixed to the proximal tibia, determined from analysis of images of the jig captured by the optical camera of the 3D scanner while the tibia is rotated around the ankle axis.

These axes are important for proper implant positioning as the bony cuts and thus the implants are desirably placed 90 degrees to the mechanical axes610,620. After the mechanical axis of the femur610and the mechanical axis of the tibia620are defined, surgery planning module114can determine the proper positions of the bone jig500over the bony surface. Surgery planning module114can also be configured to generate an image of the proper position of the jig on the bone that can be overlaid with a live image of the bone surface displayed on a monitor of computer150. The surgeon can adjust the position and orientation of the jig on the bone surface while watching the monitor until the live image of the jig is aligned with the properly positioned image generated by the surgery planning module114. In some examples, hologram projector116may also be used to project a hologram of a properly positioned jig on the bone surface, which the surgeon can use to align jig500. The calculated jig position and orientation can be modified based on the surgeon's preferences and techniques and can also be modified pre-and intra-operatively to accommodate different bony resection methods (measured resection, gap balancing and kinematic or a combination thereof). The jig position and orientation can also be pre-defined based on the surgeon's preferences and techniques.

As shown inFIGS.7A through7C, surgery planning module114can be executed to calculate the optimum position of the bone jig500for restoration of bony cut in three planes: Medial-lateral, anterior-posterior, and superior-inferior planes. For the femoral cut, as shown inFIG.7A, surgery planning module114may determine the perpendicular axis to the mechanical axis of the femur and calculate the position of the jig to obtain appropriate depth of bony resection, as well as alignment in three planes. The bone jig500can then be fixed to the femur125with multiple pins using the methods described above, e.g., when the bone jig500is superimposed accurately on a projected hologram from hologram projector116and the surgeon has achieved all the qualifying criteria for the bony cut (which are based on principles of knee arthroplasty), including depth of the cut and the location of the cut in the three planes. Alternatively, the surgeon can watch a live image of the knee region that includes a computer-generated cutting jig in the proper position and orientation.

FIG.7Bshows the jig positioned for the tibial cuts. After the proximal tibia and distal femoral cuts, the bone cutting jig(s)500are removed but the initial pins can be left in place. Then a spacer block (not illustrated) can be placed in the knee120in extension. The soft tissue balance of knee is assessed in extension with varus/valgus forces manually applied. Scanner110can continuously monitor the movement of the pins during the varus/valgus test and the change in position of the pins can be calculated by the computer150, e.g., surgery planning module114, which can be used to determine the medial and lateral opening in extension. This opening is usually 2-4 mm. If the extension gap is not balanced, the surgeon can perform various methods known in the art to achieve a balanced extension gap. Then the knee is placed in 90 degrees of flexion and distracted by manual means or use of lamina spreaders. The femoral 4-in-1 cutting jig700, which is typically provided by the implant manufacturing company and specific to the size of the implant is placed over the distal femoral cut. The rotational orientation of the femoral 4-in-1 cutting jig700can be determined based on anatomic landmarks identified by object recognition module108and re-creation of a rectangular flexion gap. The computer150has the ability to identify this instrument and communicate with the surgeon as displayed on the monitor or hologram projector, as what the appropriate position should be to achieve a balanced flexion gap. Femoral sizing can be performed by surgery planning module114based on implant dimensions stored in Memory104for femoral implants810, such as the one shown inFIG.8B, bony landmarks that were identified previously and stored in memory and the calculated flexion gap. In one example, the flexion gap is achieved by “parallel to the tibial cut” technique, distracting the femur in 90 degrees of flexion. Femoral sizing and rotation can be adjusted intra-operatively if the surgeon needs to up or downsize the implant to achieve accurate flexion and extension gaps. The tibial implant820(FIG.8A) is then similarly sized. After cutting the anterior, posterior, chamfers using a bone saw705inserted into the cutting slots710in the 4-in-1 cutting jig700as shown inFIG.7C(the alignment of the 4-in-1 cutting jig700being guided by hologram702), trial implants are used to assess the gaps and alignment prior to opening the final implants. Surgery planning module114can determine the correct size of the trial implants and communicate with an implant dispensing machine830, as shown inFIG.8C, to open the appropriate door for the proper implant and reduce errors. Computer150can also send an email for replenishment and a bill after the implant is used.

The implant dispensing machine830can be operated by, e.g., nurses in an operating room and can eliminate the need to have an implant representative present in the operating room for routine cases. The ability to integrate the surgical system100and a facility's billing department can also be beneficial.

In the illustrated example, the implant dispensing machine830includes actual implants provided by one or more manufacturing companies and the machine is replenished by the corresponding companies. Implant dispensing machine830can also store disposable items such as instruments and jigs.

Although described in this example in the context of a knee replacement operation, the surgical system100can be similarly used in hip replacement and shoulder replacement procedures, as well as other procedures mentioned above.

In hip replacement procedures, the surgical system100can calculate functional anteversion and abduction angles in adjusted zone. The computer150can feature broach recognition, femoral anteversion and depth of broach based on pin location. The surgical system100allows for only one reamer to be necessary during pelvic preparation, provides depth of ream, anteversion and abduction angles for final cup positioning. Lastly, the surgical system100can capture the final data and store it on the patient's file and generate operative reports for better documentation.

In one example, system100can be used to perform a surgery without conventional instruments, traditional manual alignment jigs, pre-operative CT scans, trays, or sterilization of multiple trays during surgery, which can significantly increase OR efficiencies and thus simplify knee and hip surgeries. In other examples, system100can be used in combination with one or more of the above to improve the accuracy and efficiency of a surgery.

The surgical system100of the present disclosure provides an accurate, affordable, easy to use open-platform navigation system for reproducible and correctly-performed hip and knee replacement or other surgical procedures. The surgical system100can be used to eliminate one or more of current traditional instruments, can make a surgery less complicated, eliminate trays, sterilization processes and reduce costs while improving outcomes. The surgical system100can also be used to improve the surgical flow and make a surgery faster with less errors. In addition, implant dispensing machines830can reduce errors in implant utilization by eliminating human errors, improve billing processes and provide for auto-replenishment of implants.

The surgical system100uses 3D intra-operative laser, white, or blue light scanner(s), which may be attached to a medical light above a patient. In one example, the system obviates the need for trackers, which are typically used in prior art computer-aided navigation to aid with registration as a fixed point on the bone.

Aspects of the present disclosure also include, in one example, a method of performing a surgical procedure, comprising: scanning, with a 3D scanner, a region of anatomical interest; generating, with a processor, from data generated by the 3D scanner during the scanning step, a 3D image; identifying, with the processor, in the 3D image, one or more anatomical landmarks; calculating, with the processor, according to the identified anatomical landmarks, a plurality of surgical positions; and generating, with the processor, guidance information, according to the surgical positions, for guiding a surgical procedure.

Aspects of the present disclosure also include a computing device, comprising: a 3D scanner and; a processor configured to: receive, from the 3D scanner, scan data from a scan of a region of anatomical interest; generate, from the scan data, a 3D image; identify, in the 3D image, one or more anatomical landmarks; calculate, according to the identified anatomical landmarks, a plurality of surgical positions; and generate guidance information, according to the surgical positions, for guiding a surgical procedure.

Aspects of the present disclosure also include: a surgical system useful in performing orthopedic procedures in the absence of trackers; a surgical system utilizing an intra-operative laser 3D scanner, wherein the 3D laser scanner is used to determine anatomical landmarks and/or calculates surgical positions based on the anatomical landmarks; “instant registration” that can be based on pre-operative imaging such as computerized tomography, magnetic resonance imaging, or plane radiographs of the limb or organ; instant registration based on machine learning and artificial intelligence; an object recognition module that includes code, algorithms and/or routines, that allow for identification of the actual surfaced area based on the 3D scan; software that recognizes the scanned bone and determines a proper placement of a pin for which all calculations are based on, for example one pin is placed on the femur and one on the tibia during a knee replacement; software that can recognize the distance change between two pins, which is used for soft-tissue assessment; software that can recognize and track the implants, instruments or the like; an object recognition module can also recognize the cutting jigs/instruments; a computer screen that can show the plane of the bony cut so the surgeon can align the jig and the cutting planes; an implant dispensing machine that can store multiple sizes of an implant; and a computer that can identify the size of implant trials and communicate with an implant dispensing machine to open an appropriate door for a specified implant and reduce errors.

As noted to some degree above, various implementations consistent with this disclosure provide systems, methods, devices, and computer products for new intra-operative registration techniques that may be used with image-based CAS systems, such as image-based surgical navigation systems, and the like, e.g., for orthopedic procedures. Such implementations involve the superimposition, alignment, or registration of a virtual 3D model of an area of anatomical interest that is built from scan data gathered during surgery (intra-operatively) using a 3D scanner device with pre-operative images of the area of anatomical interest so as to accurately identify and track the position of a fiducial that is attached in the area of anatomical interest by the surgeon during surgery. Registration is required to orient the CAS system's coordinate system to the real-life surgical coordinate system and thereby enable accurate real-time tracking of the patient anatomy using an image-based CAS navigation system. The accuracy of the registration of the anatomic landmarks (e.g., bone features) directly affects the overall accuracy of the CAS navigation system. In many embodiments, the CAS navigation system may an optical tracking system that uses cameras and optical trackers affixed to bones etc., while in other embodiments, the CAS navigation system may be a radar tracking system that uses radar transceivers and radar-beacon trackers affixed to bones, etc. (e.g., as described in U.S. Pat. No. 11,896,319 and its family members).

In various implementations, the present disclosure is directed to systems, methods, devices, and computer products for CAS that intra-operatively utilize a handheld scanner (e.g., a 3D laser scanner) to captures and create and intra-operative 3D model of medical surfaces, (e.g., bone and cartilage surfaces, the surfaces of a surgeon-attached fiducial, etc.) and register the intra-operative 3D model with the pre-operative 3D images/models, (such as MRI, CT, or similar pre-operative 3D images/models), utilized by a CAS navigation system such that the fiducial surfaces become part of the 3D model used by the CAS navigation system, and such that the CAS navigation system can track the location of the fiducial and the medical object (e.g., bone) to which the fiducial is attached.

FIG.9is a diagram of an example of a surgical system100, such as a CAS system, that includes a handheld 3D scanner110in accordance with the present disclosure. The system100can be used to perform a computer-assisted surgery utilizing the intra-operative 3D scanner110. The surgical system100ofFIG.1is shown in use in an operating room105and the handheld 3D scanner110is capable of intra-operatively producing scan data for an intra-operative 3D model of a region of anatomic interest140, such as a body part of interest. In the context ofFIG.9, a patient115is undergoing a knee replacement operation and the leg of the patient115in the knee area is the relevant region of anatomical interest140. The soft tissue around the knee120has been incised to expose the femur125and the tibia130. For clarity in the drawing, the surgeon (or other user) that is holding the scanner110in their hand is not shown inFIG.1. It should be noted, nonetheless, that the scanner110may be easily moved, positioned, and pointed by the user (not shown) that is holding it. Thus, the user can move the 3D scanner110all around the exposed femur125and tibia130so as to gather enough scan data to create a good intra-operative 3D model of the tibio-femoral joint, including the relevant portions of the femur125and the tibia130. It should also be noted that the surgeon can attach fiducials, such as are described below, to the femur125and/or to the tibia130before scanning, so that the fiducials are included in the intra-operative 3D model of the femur125and the tibia130.

The 3D scanner110projects a light (e.g., laser)135onto the region of anatomical interest140that the user points it at and monitors, captures, and/or processes the reflection of the light135so as produce scan data, which is used to form a 3D model of the region of interest140. In various embodiments, the 3D scan data is transmitted to a computer150. In one embodiment, the 3D scanner110transmits the scan data via a wire or cable155as shown in the example ofFIG.1, and the wire155should be long enough to easily reach all around the region of interest140. In other embodiments, the transmission may be via a wireless connection, (e.g., Bluetooth, or the like). In various embodiments, the computer150processes the 3D scan data to produce an intra-operative 3D model, which, as noted, includes a representation of any fiducial(s) attached to the bones by the surgeon.

In various implementations, the surgeon or other user may position the handheld 3D scanner110to start the scanning process from a known point, feature, or landmark on a bone that is used as an initial fixed reference basis. As noted, the surgeon can affix a fiducial to a bone prior to scanning and in some implementations the fiducial may be used as the scan starting point.

In some general implementations, a fiducial may be an object with a known topology that is easily distinguishable from bone surfaces, skin surfaces, etc. in a scanned 3D model, such as a pyramidal topology. In some embodiments, the fiducial may be a plate shaped object, which may be metal or polymer. Some plate fiducials may have an easily identifiable top surface topography, so as to make them easy to distinguish from bone and cartilage surfaces, and plate fiducials may also be designed for a tracking device (a.k.a. a navigation marker) to attach to them. In other embodiments, the fiducial may be a non-plate-shaped anchoring device that is configured such that an additional device(s) may be easily and securely attached to it, such as a tracker device. Examples include an optical tracker device used with a CAS optical navigation system160or a radar beacon tracker device used with a CAS RF-based navigation system160. In some instances, an extension arm may attach to the anchor fiducial, and the tracker device may in turn attach to the extension arm, such that the arm raises the tracker device above the patient's soft tissue. One example of an anchor fiducial is a metal anchor that mounts to a bone using teeth and a screw and that includes attachment features for tracking devices, etc. to mount on it, as described (e.g.,FIG.20A) in U.S. patent application Ser. No. 18/124,554, filed on 21 Mar. 2023, which is hereby incorporated by reference in its entirety. In some other embodiments, the fiducial may be or include a complete tracker device, such as an optical tracker device featuring four reflector spheres arranged in a specific configuration.

In some implementations, the fiducial may be secured to a bone at a specific location, which may be determined in advance. In some such implementations, the predetermined location may be identified using a pre-operative 3D model or pre-operative image(s), such as a computer tomography image, an ultrasound image, a magnetic resonance image, or the like. In some embodiments, a bone-affixed fiducial (e.g., a metal plate) can include a bar code (e.g., QR code) or the like that includes, or provides a reference to, pre-determined surgery-assisting data or information, such as: surgical steps, a surgeon's preferences (e.g., preferences for cuts, angles, equipment settings, etc.), patient data, etc. In various implementations, this surgery-assisting data may be detected and relayed to the computer150by the scanner110, or by a separate bar code scanner/reader (not shown). In other implementations, the surgeon may attach a fiducial to a bone at a location that the surgeon determines intra-operatively—i.e., without using a predetermined location.

In either implementation, the 3D scanner110may be used to scan the fiducial after the surgeon affixes it to the bone, and the computer system150may analyze the intra-operative 3D model to intra-operatively determine and/or record the location of the affixed fiducial. The computer system150may also provide the location of the affixed fiducial to a CAS navigation system160, for example, by recording or registering the fiducial's location in the 3d model used by the CAS navigation system160.

As shown, the surgical system100includes a CAS unit160, such as a CAS navigation (e.g., tracking) system, a surgical robot unit, or the like, which may be communicatively connected to the computer150, as shown. In some typical embodiments, the CAS unit160includes and/or uses a pre-operative 3D model that was created from pre-operative imaging data, including non-optical imaging data, such as MRI scan data, CT scan data, X-ray imaging data, or other imaging techniques from which a 3D model of anatomy can be constructed. In various embodiments, a pre-operative 3D model created from pre-operative MRI scan data may be preferred, especially for orthopedic surgery, because the MRI model may better represent the cartilage in comparison to a CT-based model. The CAS unit160uses the pre-operative 3D model in order to perform its functions, such as real-time tracking of optical tracker devices, or the like, that are affixed to the bones (e.g., using an anchor fiducial). In various implementations, the pre-operative 3D model, or a copy thereof, may be stored by the computer150. It also may be stored by the CAS unit160. In various embodiments, the pre-operative 3D model and/or the intra-operative 3D model may be produced using commercial software, such as the MIMICS software by the Materialise company of Leuven, Belgium.

In various implementations, the computer150may register the intra-operative 3D model associated with the 3D scanner110with the pre-operative 3D model associated with (e.g., used by) the CAS unit160. In general, this may be done by scaling and turning the intra-operative 3D model until its virtual surface nearly matches the virtual surface and orientation of the pre-operative 3D model. In some implementations, an iterative closest point (ICP) algorithm may be used to align, match or register the scan-based intra-operative 3D model with the MRI-based pre-operative 3D model. The ICP algorithm identifies the rigid transformation that best fits a cloud of points with a model. The algorithm uses a least-squares method to minimize the sum of the squared differences between both sets of points. In some embodiments, the algorithm may be preset to use 85% of the point cloud for matching to allow for surface variations and outliers, including variations caused by the fiducials that are included in the intra-operative 3D model but not in the pre-operative 3D model. Other percentages may also be used. In some embodiments, the computer150may determine the accuracy of the registration fit based on the Root Mean Square (RMS) difference between the two surfaces.

In various implementations, the registration function may perform a spatial alignment of the coordinate frame of the CAS navigation system160(e.g., the pre-operative 3D model) with the coordinate frame of the real-world patient115as represented by the scanned-in intra-operative 3D model. The spatial alignment process may utilize anatomic objects (e.g., landmarks on bones) to aid in, and increase the accuracy of, the alignment.

In some embodiments, in aligning the two models, the computer150may create a combined 3D model, or the like, that includes features from both models, which features may include the fiducial(s) represented in the intra-operative 3D model. In such embodiments, the computer150, in effect, adds the 3D representation(s) of the fiducial(s) to the pre-operative 3D model, based on the location of the fiducial(s) as recorded by the 3D scanner110. In some embodiments, this combining may be done, for example, by overlaying or superimposing the intra-operative 3D model and the pre-operative 3D model. A CAS navigation system160may use the combined 3D model with the fiducial representation(s) to track the location of the fiducial(s), and thus also track the bone(s) to which the fiducial(s) are attached. This is in contrast to the pre-operative 3D model which had no information about the location of the fiducial(s) in relation to the bones (or anything else), such that a CAS navigation system160would not be able to identify or track the fiducial(s) or the bones using just the pre-operative 3D model.

Expressed another way, the herein described techniques associated with using the 3D scanner110to create an intra-operative 3D model after a fiducial is attached to a bone provides a novel, fast, low-error, technical solution to the problem of how to add the location of a fiducial to an existing pre-operative 3D model that is used by a CAS navigation system160or the like.

In operation, the CAS navigation system160, e.g. an optical navigation system160, may locate and track the tracking device (e.g., a navigation marker featuring four reflector spheres arranged in a specific configuration) in its detection space in the operating room105. And using the known spatial relationship between the tracker device and the anchor fiducial to which it is attached, as well as the known position of the anchor fiducial on a bone as represented in the pre-operative 3D model as modified by the intra-operative 3D model which includes the anchor fiducial, the optical navigation system160can determine and display the current position of the bone to which the anchor fiducial is attached. This is rather similar to the tracking of the bone jig500described above.

Additionally or alternatively, the computer150may control, assist, or provide directions or steps for surgical procedure(s), as described herein. For example, the computer150may control or operate or provide information to the CAS unit160. In some embodiments that use a surgical robot unit160, the surgical robot unit160may perform a computer-guided surgical procedure using, for example, the fiducial locations from the intra-operative 3D model. Additionally or alternatively, the computer150may provide information to a surgeon, such as a workflow, which may include multiple steps for a surgical procedure. Additionally or alternatively, the computer150may provide information to a CAS navigation unit160that presents displays (e.g., 3D model displays), suggestions, directions, etc., using, for example, the fiducial locations from the intra-operative 3D model, to aid the surgeon during an operation, such as a total knee arthroplasty (TKA), among others.

In various implementations, the computer150may be a device as described above with respect toFIGS.1A and1D. In various implementations, the handheld 3D scanner110may be a device as described above with respect toFIG.1A. In some implementations, the 3D scanner110may obtain or utilize a series of snapshot images, and the computer150may analyze and stitch together the scan data representing the snapshot images of the scanned surfaces by overlapping the edges of each scanned surface image with each other, so as to form a more complete 3D model of the region of interest.

In some implementations, the intra-operative 3D scanner110may be mounted and set to continuously scan the fiducial, and the system100may process the continuous scan data to track the fiducial in real time or near real time; e.g., to provide live tracking of the fiducial. In some implementations, the scanner110may calculate or measure the distance from the 3D scanner110to the region of interest (e.g., to a bone surface, landmark, etc.) during the course of an operation, e.g. at short intervals, and the computer system150may use the distance measurements for tracking the area of interest. Additionally or alternatively, the distance measurements may be provided to a CAS navigation system160, which may perform the tracking function. In such variants, the CAS navigation system160may use the distance measurements from the 3D scanner110to supplement its own independent distance measurements. In other similar variants, the CAS navigation system160may use only the distance measurements from the scanner110to perform its tracking function. In implementations that are configured for scanner tracking, the scanner110may be mounted at a fixed location known to the system100, for example, it may be placed in a wall-mounted cradle or stand-mounted cradle, while the surgeon performs the surgery. In some embodiments, the scanner110may be configured to ignore erroneous data and images related to temporary obstructions, such as the surgeon moving their hand between the scanner110and the region of interest140that is being tracked.

In some embodiments, a pre-determined workflow may be displayed or otherwise provided by the computer system150(e.g., via its graphical user interface screen) to indicate to the surgeon where to start the initial scan using the handheld scanner110and to indicate each step of the surface scan procedure, so as to produce a satisfactory intra-operative 3D model. For example, the computer150may display steps indicating which separate anatomical features or landmarks to scan and the order in which to scan them. In such embodiments, the surgeon may position and then activate the handheld 3D scanner110according to the steps provided by the computer system150. In such embodiments, the system150may identify or tag different image(s) as being associated with specific bony landmarks, based at least partially on which step of the pre-determined workflow has gathered or produced each set of scanned images.

In some implementations, the light output135of the 3D scanner110(e.g., the laser light) may be set, modified, or changed by the user, e.g., based on the anatomical area of interest140that the user is going to scan, the desired amount of detail or area coverage, and/or e.g., based on instructions from the pre-determined workflow provided by the computer system150. The scanner110may employ lenses, apertures, multiple emitters, or other optical devices or techniques to change its light output135. For example, the light beam or laser beam135may be widened so as to scan a larger area in one step (e.g., in one image) rather than taking multiple, smaller, snapshot images to cover the same area. For another similar example, additional light emitters (e.g., lasers) of the scanner110may be activated to emit more beams135and scan a larger area in one step (e.g., in one image).

In various implementations, the computer system150may analyze the scan data gathered by the handheld 3D scanner110and/or the intra-operative 3D model using machine learning models and artificial intelligence, for example, to identify anatomical features or landmarks (e.g., bony landmarks). In some embodiments, the computer system150may employ predictive modeling to perform such identification. The identifications may be used to aid in the registration process and/or to identify the location of fiducials that are attached to the bone that includes the landmarks.

In various implementations, the computer system150may analyze the scan date and/or 3D models in order to differentiate between different types of tissue, for example, between bone tissue and cartilage tissue. In some implementations, the computer system150may analyze the color and/or texture of a bone surface image in order to identify features, such as anatomical landmark features or the like.

Other variants may be used for imageless CAS navigation systems160. In imageless systems, there are no prior advanced images and thus no pre-operative 3D model, and the surgeon is required to either “paint” the surfaces of the region of interest140with a pointer probe to obtain the data needed by the CAS navigation system to build an fairly accurate 3D model, including the joint surfaces, or manually choose the most important anatomical landmarks in the region of interest140using the pointer probe, which typically results in a less accurate 3D model. In either case, the manual use of a pointer probe to create a 3D model introduces user error and variability when recording bone morphology for the 3D model. Using a 3D laser scanner as disclosed herein is an easy and accurate method of acquiring bone morphology to create the 3D model and it requires much less time than painting a joint surface during surgery with a pointer probe.

In such variants, the computer150may provide a scanning workflow, e.g., via directions on a monitor, that direct the user of the 3D scanner110as to where to start to scan, what direction to scan in, etc., so as to gather the scan data for building the 3D model in a specific order and manner. The system100can then employ AI models or the like to recognize bony landmarks, fiducials, and other features to help orient and build the 3D model. Once the 3D model is built, including the fiducials, the imageless CAS navigation systems160can use the model to track the fiducials, e.g., via their attached tracking devices.

FIG.10is an example of a process1000for modifying a 3D model of a region of anatomical interest to include a fiducial in accordance with the present disclosure. In various embodiments, the process1000may be implemented by a computer150that is part of a surgical system100, as described herein.

The process1000starts at block1010with receiving scan data from an intra-operative scan of a bone surface, where the scan data includes data representing a fiducial. In various implementations, the scan data may be intra-operatively generated by intra-operative 3D scanner, and the fiducial may have been affixed to an object, e.g., a bone, in an area of anatomic interest that is involved in a surgical operation.

At block1020, the process1000continues with generating, from the scan data, an intra-operative 3D model that includes a 3D representation of the fiducial. As noted above with regard toFIG.9, there is commercial software that may be used to generate a 3D model from scan data, including software that is associated with or comes with 3D laser scanners.

At block1030, the process1000continues by registering the intra-operative 3D model with a pre-operative 3D model of the area of anatomic interest. In various implementations, this may involve overlaying and/or aligning the surfaces/features of the two models in a close manner, such as may be achieved using an iterative closest point (ICP) algorithm.

The process1000next modifies the pre-operative 3D model to include the fiducial at a location indicated or specified by the intra-operative 3D model, at block1040. Thus, the pre-operative 3D model which did not include the fiducial because the fiducial was not in place prior to the surgical operation is changed to now include a representation of the fiducial. In some alternative embodiments, instead of modifying the pre-operative 3D model, the computer150is programmed to create a new 3D model that is a combination of the pre-operative 3D model and the intra-operative 3D model and that includes a representation of the fiducial, leaving an unchanged copy of the pre-operative 3D model stored in the system100.

At block1050, the process1000continues providing the modified pre-operative 3D model to a surgical navigation system that tracks objects, e.g., during the surgical operation. As explained above with respect toFIG.9, the tracking is done based on the location of the fiducial, as the tracking device (e.g., tracking marker) that is attached to the fiducial using a known fixed geometry, such that tracking the location of the tracking marker reveals the location of the fiducial, which reveals the location of the object (e.g., bone, medical instrument, etc.) to which the fiducial is attached. Generally, the tracked objects are in the area of anatomic interest140that the surgical navigation system covers.

One of ordinary skill will recognize that the blocks, operations, functions, and details shown inFIG.10are examples presented for conciseness and clarity of explanation. Other blocks, operations, functions, details, and variations may be used without departing from the principles of the invention, as these examples are not intended to be limiting, and many different implementations are possible. For example, the order of the blocks may be varied, some blocks may be executed in parallel with others, the functionality of two more blocks may be combined into a single block, and/or blocks could be eliminated.

The foregoing has been a detailed description of illustrative embodiments of the invention. It is noted that in the present specification and claims appended hereto, conjunctive language such as is used in the phrases “at least one of X, Y and Z” and “one or more of X, Y, and Z,” unless specifically stated or indicated otherwise, shall be taken to mean that each item in the conjunctive list can be present in any number exclusive of every other item in the list or in any number in combination with any or all other item(s) in the conjunctive list, each of which may also be present in any number. Applying this general rule, the conjunctive phrases in the foregoing examples in which the conjunctive list consists of X, Y, and Z shall each encompass: one or more of X; one or more of Y; one or more of Z; one or more of X and one or more of Y; one or more of Y and one or more of Z; one or more of X and one or more of Z; and one or more of X, one or more of Y and one or more of Z.