Abstract:
A method of automatically registering a surgical navigation system to a patient&#39;s anatomy is provided. The method comprises programming a surgical navigation system with a first spatial relationship between a surgical component and a reference array connected to the surgical component, programming the surgical navigation system with a second spatial relationship between an anatomical feature of a patient and the surgical component, installing the surgical component on the patient such that the surgical component engages the anatomical feature in the second spatial relationship, and locating the reference array with the surgical navigation system. The navigation system automatically recognizes the position of the reference array relative to the patient&#39;s anatomy.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Patent Application Ser. No. 60/944,817, filed Jun. 19, 2007, the complete disclosure of which is expressly incorporated herein by this reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present teachings relate generally to surgical navigation, and more particularly to patient-matched surgical components that are adapted to conform to a patient&#39;s anatomy, as well as to methods for using such surgical components during a surgical navigation procedure. 
       BACKGROUND 
       [0003]    Surgical navigation systems, also known as computer assisted surgery systems and image guided surgery systems, aid surgeons in locating patient anatomical structures, guiding surgical instruments, and implanting medical devices with a high degree of accuracy. Surgical navigation has been compared to a global positioning system that aids vehicle operators to navigate the earth. A surgical navigation system typically includes a computer, a tracking system, and patient anatomical information. The patient anatomical information can be obtained by using an imaging mode such as fluoroscopy, magnetic resonance imaging (MRI), computer tomography (CT) or by simply defining the location of patient anatomy with the surgical navigation system. Surgical navigation systems can be used for a wide variety of surgeries to improve patient outcomes. 
         [0004]    To successfully implant a medical device, surgical navigation systems often employ various forms of computing technology, as well as utilize intelligent instruments, digital touch devices, and advanced 3-D visualization software programs. All of these components enable surgeons 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 a patient&#39;s body, as well as conduct preoperative and intra-operative body imaging. 
         [0005]    To accomplish the accurate planning, tracking and navigation of surgical instruments, tools and/or medical devices during a surgical procedure utilizing surgical navigation, surgeons often couple “tracking arrays” to the surgical components. These tracking arrays allow the surgeons to track the physical location of these surgical components, as well as the patient&#39;s bones during the surgery. By knowing the physical location of the tracking array, software associated with the tracking system can accurately calculate the position of the tracked component relative to a surgical plan image. 
         [0006]    It is known to use surgical navigation instruments to measure the size and general contour of a bone before selecting and/or manufacturing a prosthetic implant. This process allows the surgeon to choose a prosthetic component that generally resembles the shape and size of the patient&#39;s anatomy, thereby achieving a more customized fit during the implantation process. Despite such customization efforts, most orthopaedic procedures still require the use of adjustable components or guides during the surgical procedure, particularly as such instruments are needed to fit the prosthetic components to the patient&#39;s anatomy. However, this process is time consuming, as well as subject to error during the placement and registration of the surgical components. As such, it would be desirable to improve this process to reduce surgery time and improve prosthetic fit and/or function. 
       SUMMARY OF THE INVENTION 
       [0007]    The present teachings provide a patient matched surgical component that is custom manufactured to fit a patient&#39;s anatomy in a precise manner. To achieve such customization, the patient&#39;s anatomy is preoperatively scanned and uploaded to a software program, which then recreates a three-dimensional model of the patient&#39;s anatomy from the scanned image. The three-dimensional model is then used by the software program to identify and locate on the image specific known anatomical landmarks of the patient&#39;s anatomy. Planning software then analyzes the identified anatomical landmarks together with any specific surgical instructions needed to develop and plan a surgical protocol for the patient. Once the surgical protocol has been approved by the surgeon, the protocol is presented to a software program, which then uses the protocol, as well as the preoperative scan images, to create a virtual patient matched surgical component. The virtual component is then sent to a rapid prototyping machine or a standard machining process, which in turn manufactures the surgical component for use during the surgical procedure. Because the surgical component is custom manufactured to fit the patient&#39;s anatomy relative to specific anatomical landmarks, it can be manufactured with a reference array positioned on its surface in a predefined spatial relationship with respect to the patient&#39;s anatomy. By having a predefined spatial relationship between the reference array and the patient&#39;s anatomy, the need for intra-operative registration during the surgical procedure is minimized or even eliminated altogether. Furthermore, since the patient matched component is fixable to the patient&#39;s anatomy with pins, the reference array can act as an automatically registered rigid bone reference marker that can be used throughout the surgical navigation procedure. 
         [0008]    According to one aspect of the present teachings, a method of automatically registering a surgical navigation system to a patient&#39;s anatomy is provided. The method comprises programming a surgical navigation system with a first spatial relationship between a surgical component and a reference array connected to the surgical component, programming the surgical navigation system with a second spatial relationship between an anatomical feature of a patient and the surgical component, installing the surgical component on the patient such that the surgical component engages the anatomical feature in the second spatial relationship, and locating the reference array with the surgical navigation system. The navigation system automatically recognizes the position of the reference array relative to the patient&#39;s anatomy. 
         [0009]    According to another exemplary embodiment herein, a method of performing a surgical procedure aided by a surgical navigation system is provided. The method comprises generating a representative model of an anatomical feature from an image of a patient&#39;s anatomy, using the model to make a surgical component, installing the surgical component on the anatomical feature by mating the surface of the component with the anatomical feature in the predefined spatial relationship, and tracking movement of the anatomical feature with a tracking system when the installed surgical component is moved within a measurement field of the tracking system. According to this embodiment, the surgical component has a surface that is shaped to substantially mate with the anatomical feature in a predefined spatial relationship. 
         [0010]    According to yet another exemplary embodiment herein, a patient matched surgical component is provided. The surgical component comprises a body having a surface that is shaped to substantially mate with the shape of an anatomical feature of a patient in a predefined spatial relationship, and a reference array connected to the body, the reference array being trackable by a tracking system when exposed to a measurement field of the tracking system. 
         [0011]    In still another exemplary embodiment, a method of performing a surgical procedure aided by a surgical navigation system is provided. According to this exemplary embodiment, the method comprises generating a representative model of an anatomical feature from an image of a patient&#39;s anatomy, using the model to make a surgical component, the surgical component having a reference array associated therewith and a surface that is shaped to substantially mate with an anatomical feature in a predefined spatial relationship, installing the surgical component on the anatomical feature by mating the surface of the component with the anatomical feature in the predefined spatial relationship, tracking movement of the anatomical feature with the tracking system when the installed surgical component is moved within a measurement field of the tracking system, removing a portion of the anatomical feature, the removed portion also including a portion of the installed surgical component, and tracking a remaining portion of the anatomical feature with the tracking system, the remaining portion of the anatomical feature including a portion of the installed surgical component, the remaining portion of the installed surgical component including the reference array. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    The above-mentioned aspects of the present teachings and the manner of obtaining them will become more apparent and the invention itself will be better understood by reference to the following description of the embodiments of the invention taken in conjunction with the accompanying drawings, wherein: 
           [0013]      FIG. 1  is a perspective view of an exemplary operating room setup in a surgical navigation embodiment in accordance with the present teachings; 
           [0014]      FIG. 2  is a patient-matched surgical component created from a preoperative scan image of the patient&#39;s bone; 
           [0015]      FIG. 3A  is a fragmentary perspective view of a surgeon aligning the patient-matched surgical component of  FIG. 2  with a bone; 
           [0016]      FIG. 3B  is a fragmentary perspective view of the backside of the surgical component of  FIG. 3A , the component being shown aligned with a bone; 
           [0017]      FIG. 4  is a fragmentary perspective view of the patient-matched surgical component of  FIG. 2  being attached to the bone by the surgeon; 
           [0018]      FIG. 5  is a fragmentary perspective view of the patient-matched surgical component of  FIG. 4  attached to the bone and its corresponding reference array, which is connectable thereto; 
           [0019]      FIGS. 6 and 7  are fragmentary perspective views illustrating the bone of  FIG. 5  undergoing an exemplary resection process in accordance with the present teachings; 
           [0020]      FIG. 8  is a fragmentary perspective view of a surgeon aligning a patient-matched surgical component with a patient&#39;s pelvis in accordance with the present teachings; 
           [0021]      FIG. 9  is a fragmentary perspective view of the patient-matched surgical component of  FIG. 8  being attached to the pelvis by the surgeon; and 
           [0022]      FIG. 10  is a fragmentary perspective view of the patient-matched surgical component of  FIG. 8  and its corresponding reference array connected thereto. 
       
    
    
       [0023]    Corresponding reference characters indicate corresponding parts throughout the several views. 
       DETAILED DESCRIPTION 
       [0024]    The embodiments of the present teachings described below are not intended to be exhaustive or to limit the invention to the precise forms disclosed in the following detailed description. Rather, the embodiments are chosen and described so that others skilled in the art may appreciate and understand the principles and practices of the present teachings. 
         [0025]      FIG. 1  shows a perspective view of an operating room with surgical navigation system  20 . Surgeon  21  is aided by surgical navigation system  20  in performing knee arthroplasty, also known as knee replacement surgery, on patient  22  shown lying on operating table  24 . Surgical navigation system  20  has a tracking system that locates arrays and tracks them in real-time. To accomplish this, the surgical navigation system includes optical locator  23 , which has two CCD (charge couple device) cameras  25  that detect the positions of the arrays in space by using triangulation methods. The relative location of the tracked arrays, including the patient&#39;s anatomy, can then be shown on a computer display (such as computer display  27  for instance) to assist the surgeon during the surgical procedure. The arrays that are typically used include probe arrays, instrument arrays, reference arrays, and calibrator arrays. The tracking system also detects the location of reference array  36 , which is attached to patient matched surgical component  34 . The relative location of patient matched surgical component  34  with respect to the patient&#39;s anatomy can then be shown on computer display image  38  of computer monitor  42 . The operating room also includes instrument cart  45  having tray  44  for holding a variety of surgical instruments and arrays  46 . Instrument cart  45  is also draped in sterile cover  48  to eliminate contamination risks within the sterile field. 
         [0026]    The surgery is performed within a sterile field, adhering to the principles of asepsis by all scrubbed persons in the operating room. Patient  22 , surgeon  21  and assisting clinician  50  are prepared for the sterile field through appropriate scrubbing and clothing. The sterile field will typically extend from operating table  24  upward in the operating room. Typically, the computer display is located outside of the sterile field. 
         [0027]    A representation of the patient&#39;s anatomy  52  can be acquired with an imaging system, a virtual image, a morphed image, or a combination of imaging techniques. The imaging system can be any system capable of producing images that represent the patient&#39;s anatomy such as a fluoroscope producing x-ray two-dimensional images, computer tomography (CT) producing a three-dimensional image, magnetic resonance imaging (MRI) producing a three-dimensional image, ultrasound imaging producing a two-dimensional image, and the like. A virtual image of the patient&#39;s anatomy can be created by defining anatomical points with the surgical navigation system  20  or by applying a statistical anatomical model. A morphed image of the patient&#39;s anatomy can be created by combining an image of the patient&#39;s anatomy with a data set, such as a virtual image of the patient&#39;s anatomy. 
         [0028]    The tracking system of the present invention can be any system that can determine the three-dimensional location of devices carrying or incorporating markers that serve as tracking indicia. More particularly, the tracking system may be an active tracking system that has a collection of infrared light emitting diode (ILEDs) illuminators surrounding the position sensor lenses to flood a measurement field of view with infrared light. Alternatively, the system may be a passive tracking system, which incorporates retro-reflective markers that reflect infrared light back to the position sensor, and the system triangulates the real-time position (x, y, and z location) and orientation (rotation around x, y, and z axes). In yet other embodiments, the tracking system may be a hybrid tracking system that detects active and active wireless markers in addition to passive markers. Active marker based instruments enable automatic tool identification, program control of visible LEDs, and input via tool buttons. Finally, in yet other exemplary embodiments, the tracking system may utilize electromagnetic tracking techniques. These systems locate and track devices and produce a real-time, three-dimensional video display of the surgical procedure by using electromagnetic field transmitters that generate a local magnetic field around the patient&#39;s anatomy. 
         [0029]    The present teachings enhance surgical navigation system  20  by incorporating into the system a process for custom manufacturing patient-matched surgical component  34  so that it fits the anatomy of patient  22  in a precise manner. Particularly, in addition to tracking surgical components, the navigation system can also generate preoperative images of the patient&#39;s anatomy and then use such images to manufacture a surgical component that is custom matched to the patient&#39;s anatomy. More specifically, the patient&#39;s anatomy is preoperatively scanned and uploaded to a software program, which then recreates a three-dimensional virtual model of the patient&#39;s anatomy from the scanned image. The virtual model is then used by the software program to identify and locate known bony anatomical landmarks or predefined points of the patient&#39;s anatomy. For a further description about the acquisition and registration of bony landmarks, see U.S. patent application Ser. No. 11/689,711, entitled “Modeling Method and Apparatus for use in Surgical Navigation,” filed Mar. 22, 2007, which is incorporated by reference herein in its entirety. 
         [0030]    As is appreciated by those of skill within the art, bony anatomical landmarks are visible points or locations on a patient&#39;s anatomy, which axe identifiable by referencing known locations on the surface of the bone. For instance, known bony landmarks on the femur include, but are not limited to, a femoral head landmark, a central knee landmark, a medial femoral condyle landmark, a lateral femoral condyle landmark, a medial epicondyle landmark, a lateral epicondyle landmark, a medial posterior condyle landmark, a lateral posterior condyle landmark and an anterior cortex point landmark. Similar bony landmarks are also found on other bones (such as the tibia, fibula, patella and pelvis, for instance), however, for simplicity purposes, the exemplary illustrations provided here are specifically directed to the femur. As the present teachings are not intended to be limiting, it should be understood and appreciated that these teachings are also applicable to bony landmark structures other than the femur. 
         [0031]    Planning software analyzes the identified anatomical landmarks together with any specific surgical instructions received from the surgeon and develops a surgical procedure or protocol for the patient. After its approval, the protocol is then entered into a software program, which uses the protocol together with the preoperative scan images to create a virtual representation of a patient matched surgical component. The virtual representation of the surgical component is then sent to a rapid prototyping machine or a standard machining process, which in turn manufactures a physical prototype of the surgical component. Because the surgical component is custom manufactured to fit the patient&#39;s anatomy relative to known anatomical landmarks, it can be manufactured to include a reference array that extends from its surface in a predefined manner. By having the reference array positioned in a predefined spatial orientation with respect to the patient&#39;s anatomy, the need to further register the component intraoperatively is unnecessary; particularly as the registration of the reference array is completed preoperatively during the surgical planning stages. Furthermore, since the patient matched component can be secured to the patient&#39;s anatomy, the reference array can also function as an automatically registered and trackable bone reference array during the surgical procedure. 
         [0032]    The principles upon which exemplary embodiments of the present invention rely can be understood with reference to FIG,  2 , which illustrates three-dimensional bone model  301  on surgical display image or user interface screen  303  of monitor  305 . Model  301  is based on an image of the patient&#39;s anatomy, which was obtained from a preoperative diagnostic imaging procedure, such as by magnetic resonance imaging (MRI), computer assisted tomography (CT), fluoroscopy, ultrasound or positron emission tomography (PET). It should be understood that model  301  is intended to illustrate general principles of the present teachings and is not representative of any particular screen shot that a surgeon may observe during a surgical navigation procedure. Moreover, it should be understood and appreciated herein that processes for generating three-dimensional models from preoperative images of anatomical features are well known by those within the surgical navigation field and therefore not discussed in detail herein. 
         [0033]    Once three-dimensional model  301  has been created, it is then used by the software program to identify and locate specific known anatomical landmarks characteristic of the anatomical feature. The number of anatomical landmarks identified on the model will depend on the bony anatomy that is being characterized, as well as what type of surgical procedure is being performed on the patient undergoing the operation. In some exemplary embodiments, however, less than about ten anatomical landmarks are identified by the software program and represented on the three-dimensional model. In other exemplary embodiments, less than about seven anatomical landmarks are identified, while in still other exemplary embodiments, less than about three landmarks are identified. 
         [0034]    In  FIG. 2 , model  301  depicts five bony anatomical landmarks common to a typical femur. These bony landmarks include the distal most point of the medial femoral condyle  307 , the distal most point of the lateral femoral condyle  309 , the medial epicondyle  311 , the lateral epicondyle  313  and the anterior cortex point of the femur  315 . By acquiring such bony landmarks, the surgeon can use such information to assist in planning the surgical protocol to be performed on the patient. For instance, by acquiring the epicondyles ( 311 ,  313 ), the transepicondylar axis of the femur can be determined to assist with the rotation and positioning of a femoral implant component. Moreover, by acquiring the anterior cortex point of the femur  315 , proper implant sizing techniques can be utilized. 
         [0035]    Once model  301  has been created and the bony anatomical landmarks identified, the surgeon can use the model as a visual aid and manipulate it to gather important surgical information, such as gap analysis data, resection plane details and bone alignment angles. Furthermore, if the surgeon desires, he can rotate or manipulate model  301  so that he can visually appreciate the general shape and characteristics of the patient&#39;s femur, particularly as the acquired bony anatomical landmark points shown on the model remain accurate as it is manipulated by the surgeon. In addition to displaying the acquired femoral landmark points (i.e. points  307 ,  309 ,  311 ,  313  and  315 ), model  301  can also depict a representation of the implant component that will be implanted onto the patient during the surgical procedure. By displaying a representation of the implant on the bone model, the system can gather additional information useful for finalizing the surgical protocol, particularly implant sizing and rotation information. The representation of the implant can also be rotated and aligned preoperatively, particularly so that the navigation system can calculate the location of necessary bone cuts and/or resection planes to be used during the surgical procedure. Some resection planes that can be determined preoperatively include, but are not limited to, the tibial proximal cut, the femoral distal cut, the femoral anterior cut, as well as the chamfer cuts made by a 4-in-1 resection block. 
         [0036]    After the surgical protocol has been planned and is approved, the software then creates a virtual surgical component that is custom-shaped to effect implementation of the surgical specifications (e.g., bone cuts, resection planes, drill holes, etc.) that were determined by the planning software. In some exemplary embodiments, the surgical component may function as a patient-matched reference array and not include any cut slots in its body design. More particularly, in certain embodiments, the surgical component may replace one or more rigid bone reference arrays or markers typically attached to the patient&#39;s anatomy during a surgical procedure. By eliminating the use of such rigid bone reference arrays, the surgical procedure can be performed in a minimally invasive manner, particularly as fewer incisions would be required of the patient&#39;s anatomy. Reducing the number of required incisions during a surgical procedure is advantageous, particularly in terms of reducing associated scarring and/or complications typically caused from such incisions. 
         [0037]    Once the component has been virtually designed, the virtual representation is then sent to a rapid prototyping machine or a standard machining process, which in turn manufactures a physical component that corresponds to the dimensional parameters of the virtual component. For instance, as shown in  FIGS. 2, 3A and 3B , surgical component  320  has been created having an interior surface  322 , which matches the topography of model  301 . Surgical component  320  also includes one or more cutting slots or guides  324 , which are specifically designed to accommodate cutting devices (e.g., saw blades) during a bone resection process. It should be understood and appreciated herein that the position, shape and directional orientation of the cutting slot(s) on the surgical component will depend particularly on the surgical procedure that is to be performed on the given patient. For instance, if the surgeon will be performing a total knee arthroplasty, a cutting slot to accommodate the distal femur cut, such as slot  324  shown in  FIG. 2 , may be included. Surgical component  320  may also include one or more holes  328  to accommodate drilling into the patient&#39;s bone and/or attaching the component to the patient&#39;s bone during a surgical procedure. 
         [0038]      FIGS. 3A and 3B  show surgeon  402  positioning surgical component  320  relative to bone  404  during a surgical procedure. As the interior surface of the surgical component is shaped to substantially match the general topographic landscape and contour of bone  404 , the surgeon is able to align the component with the bone in such a manner that the component mates with the bone in a position predefined by the software. In other words, surgeon  402  is able to press inner surface  322  of surgical component  320  against outer surface  406  of bone  404  until a tactile sensation is felt by the surgeon indicating that the component has mated with or “matched” its corresponding surface of the bone. Because surgical component  320  is patient-matched to the shape of hone  404 , surgeon  402  can position surgical component  320  by feel with a high degree of precision. More particularly, the body of the surgical component is shaped in such a manner that it interfits or interlocks to the shape of the anatomical feature during installation. This interfitting or interlocking relationship allows the surgeon to achieve the tactile sensation when the surgical component is correctly installed onto the anatomical feature. When the surgical component  320  is properly or correctly installed, it sits substantially flush against the surface of bone  404 , i.e., there will not be significant gaps around the edge of the component as it sits against the patient&#39;s anatomical feature or bone. 
         [0039]    As explained above, surgical component  320  further includes one or more holes  328  for drilling into the bone and/or for attaching the component to the bone&#39;s surface during a surgical procedure, as well as one or more cutting slots  324  to accommodate cutting devices during a bone resection process. According to one exemplary embodiment, holes  328  are configured to function as anchoring holes, which can be used for inserting temporary pins or screws into the hone to hold the surgical component into place during a surgical procedure. Holes  328  may also be configured into various dimensional patterns and arrangements to accommodate the surgical plan and/or to accommodate the anatomical shape of the bony structure or anatomical feature to which the component is to be affixed. Moreover, in certain exemplary embodiments, the same surgical component may be used in multiple resection procedures, whereby the holes are arranged such that the remaining portion of surgical component  320  remains securely fastened to the bone after the initial resection is completed. Holes  328  may also be configured to use previously placed reference markers or anchors already attached to the surface of the bone. More particularly, according to this embodiment, the arrangement of the holes can be positioned such that the surgeon places the surgical component over one or more reference markers or anchor devices previously placed into the bone. Such reference markers or anchor devices may have been placed during prior diagnostic or therapeutic surgeries, or may have been placed preoperatively for use in future diagnostic or therapeutic procedures. 
         [0040]      FIG. 4  shows surgical component  320  aligned with and positioned substantially flush against bone  404 . Once positioned, surgical component  320  can be affixed to bone  404  by inserting one or more pins  502  into the bone through holes  328 . Affixing surgical component  320  to bone  404  with pins, screws, or other attachment means insures that the surgical component is securely held in place during the surgical procedure. In  FIG. 4 , surgeon  402  is shown using a pin insertion device  504  to insert pin  502  into bone  404  through one of holes  328 . Such surgical pin insertion techniques and instrumentation are known by those of skill within the art and therefore not discussed in detail herein. 
         [0041]      FIG. 5  shows surgical component  320  positioned against bone  404  and secured into place with attachment pins  502 . Surgical component  320  also includes a quick connect receptacle  602 , which is configured to connect to a tracking device, such as a reference array. According to this embodiment, tracking or reference array  604  is provided with a quick connect base  606  that dimensionally corresponds with receptacle  602  such that a removable snap-fit connection can be achieved between the two components. While  FIG. 5  illustrates a snap-fit attachment means between the reference array and the component, it should be understood that in other embodiments, reference array  604  may be “pre-installed” onto surgical component  320 , whereby no additional attachment means is required after the component is attached to the bone. It should also be understood and appreciated that any attachment means known within the art may be used to secure reference array  604  to surgical component  320 . Such attachment means include, but are not limited to, welding, fusing, molding, gluing, threading, snap-connections, quick disconnect connections and the like. 
         [0042]    Once reference array  604  is attached to surgical component  320 , navigation system  20  is able to locate and track its position in real-time and display its tracked position on a surgical plan image. In other words, once the navigation system locates the array, the system automatically knows its position with respect to the landmarks identified on the model image, as well as where it has been pre-registered with respect to the image. To accomplish this, and with reference to  FIG. 6 , cameras  702  of optical locator  704  detect in space the position of markers  706 , which extend from the surface of reference array  604 . It should be understood and appreciated herein that while this embodiment shows four markers  706  attached to the frame of reference array  604 , in other embodiments less than four markers may be used, while in yet other embodiments, more than four markers may be used. For instance, in some embodiments using electromagnetic tracking technology, only one marker is needed to track the position of the surgical component in space. In yet other embodiments, three markers may be used to triangulate the position of the surgical component in space. As such, it should be fully appreciated that the present teachings are not intended. to be limited herein. 
         [0043]    To detect the position of the markers in space, known triangulation methods are used. These triangulation methods allow the navigation system to determine the relative location of the reference array and its markers with respect to the patient&#39;s anatomy, and then display the same on a surgical plan image. As reference array  604  is trackable in real-time, the position of bone  404  can also be tracked in real-time, particularly since reference array  604  is fixably attached to its surface by way of surgical component  320 . As explained above, by having reference array  604  positioned relative to the surgical component  320  in a predefined spatial manner, the need for intra-operative registration during the surgical procedure is substantially minimized. 
         [0044]    As used herein, “predefined” refers to a preoperatively planned spatial relationship between the surgical component and the anatomical feature of the patient to which the component is to be attached. In other words, once the component is installed onto the anatomical feature in its predefined spatial orientation, it is automatically registered with the system and can be tracked by the navigation system for the remainder of the procedure without further registration techniques. Moreover, since the patient matched component is fixably secured to the patient&#39;s anatomy throughout the surgical procedure, reference array  604  is able to function as a rigid reference bone marker to track bone  404  during the surgical procedure. Such rigid bone reference arrays are commonly used in orthopaedic surgical procedures and are able to track a patient&#39;s bones with respect to various surgical instruments during a surgical navigation procedure. Because the presently disclosed reference arrays are preoperatively registered with the navigation system in a predefined manner with respect to the patient&#39;s anatomy, these components can be used to track the patient&#39;s anatomy without the need to insert additional rigid array markers into the patient during the procedure. Moreover, because such surgical components are registered with the navigation system during the preoperative planning steps of the surgical procedure, timely intraoperative registration processes are also unnecessary. 
         [0045]    An exemplary illustration of a bone undergoing a resection process in accordance with the present teachings is depicted in  FIGS. 6-7 . Surgical instrument  714  may optionally include a marker array  715 , which can be further identified and tracked by cameras  702  of optical locator  704 , However, since surgical component  320  was custom designed to match and mate with the specific shape of bone  404 , the surgeon does not need to track the position of the surgical instrument relative to the bone during the surgical procedure. More particularly, the position of cutting slot  324  on surgical component  320  was previously registered with the tracking system during the preoperative planning stages of the surgical procedure. As such, once the surgeon attaches the component to the bone in its predetermined position, he can proceed directly to resecting the bone with the surgical instrument without further tracking or registering of the surgical instrument. As such, it should be understood that the depiction of marker array  715  on surgical instrument  714  is optional and is not intended to limit the scope of the present teachings. 
         [0046]    Referring still to  FIGS. 6 and 7 , as surgeon  716  moves instrument  714  relative to bone  404 , the tracking system locates and tracks marker array  715  in real-time. The relative location of marker array  715  is then shown on surgical plan image  708  of computer display  710 . The tracking system detects the location of surgical instrument  714  relative to bone  404  by referencing the position of marker array  715  as it moves with respect to reference array  604 , which is fixably attached to bone  404  by way of surgical component  320 . The position of saw blade  712  of surgical instrument  714  is displayed on surgical plan image  708  as cut plane  713 . By viewing cut plane  713  on surgical plan image  708 , surgeon  716  can confirm that the surgical component is positioned properly, although as just noted, this step is optional since the component can be properly positioned by the surgeon by feel alone. 
         [0047]      FIG. 7  shows a portion of bone  404  removed after surgeon  716  has inserted saw blade  712  into cut slot  324  of surgical component  320 . A portion of the surgical component  321  remains affixed to the removed bone by attachment pin  329 . Because reference array  604  is still attached to bone  404  by way of surgical component  320 , the surgical navigation system continues to recognize and track the position of bone  404  and the remaining portion of the attached surgical component  320  in real-time throughout the remainder of the surgical procedure. As such, the remaining portion of surgical component  320 , and its reference array  604 , can be used for additional steps in the surgical procedure, such as the removal or modification of a second predefined part of the bone after the initial resection, or the placement and use of additional surgical components. The tracked remaining portion of surgical component  320  can also be used to perform other surgical procedures that require tracking, such as ligament balancing, range of motion and impingement analyses. 
         [0048]    It should be understood and appreciated herein that while  FIG. 7  depicts portion  321  of surgical component  320  being removed with saw blade  712 , in other exemplary embodiments, portion  321  may be removed by being snapped, broken or cleaved away from surgical component  320 . For instance, cut slot  324  could be replaced by a groove or cleave that is designed to be physically broken or torn away from the surgical component after it has been attached to the patient&#39;s anatomy. As such, the attachment means useful for the present teachings are not intended to be limited herein. 
         [0049]    While the above-described embodiments illustrate the presently disclosed surgical components as being useful for knee related applications, it should be appreciated and understood herein that the exemplary components disclosed herein may also be used together with any other anatomical features without straying from the present teachings. For instance, in certain exemplary embodiments, the surgical components may also be used together with hip-related navigation applications. More particularly, as is known within the surgical navigation field, registration processes for the hip can be quite challenging, particularly as the surgeon must register both sides of the patient&#39;s pelvis, including rolling the patient onto their side to collect data points and then re-draping and re-scrubbing the patient between such registration steps. By using the presently disclosed surgical components, navigating the hip during a surgical procedure is significantly simplified, particularly as the need to register the hip intraoperatively is eliminated. 
         [0050]    Further principles upon which exemplary embodiments of the present invention rely can be understood with reference to  FIG. 8 .  FIG. 8  depicts surgical component  802 , which has been created by a rapid prototyping machine or a standard machining process to match the dimensional parameters of a virtual representation of a patient&#39;s pelvis according to the process described above. More particularly, surgical component  802  has an interior surface that matches the topographic landscape of pelvis  803 . According to this embodiment, surgeon  806  positions surgical component  802  relative to pelvis  803  during a hip procedure. As the interior surface of the surgical component is shaped to substantially match the general topographic landscape and contour of pelvis  803 , the surgeon is able to align the component with the pelvis in such a manner that the component mates with the pelvis in a position predefined by the software. In other words, surgeon  806  is able to press the inner surface of surgical component  802  against outer surface  804  of pelvis  803  until a tactile sensation is felt by the surgeon indicating that the component has mated with or “matched” its corresponding surface of the pelvis. Because surgical component  802  is patient-matched to the shape of pelvis  803 , surgeon  806  can position surgical component  802  by feel with a high degree of precision. When properly positioned, surgical component  802  will. sit substantially flush against the surface of pelvis  803 , i.e., there will not be significant gaps around the edge of the component as it sits against the patient&#39;s pelvic bone. 
         [0051]    Surgical component  802  also includes one or more holes  808  for drilling into the pelvis and/or for attaching the component to the pelvis&#39;s surface during a hip procedure. According to one exemplary embodiment, holes  808  are configured to function as anchoring holes, which can be used for inserting temporary pins or screws into the pelvis, thereby holding the surgical component into place during a surgical procedure. For instance,  FIG. 9  shows surgical component  802  aligned with and positioned substantially flush against pelvis  803 . Once positioned, surgical component  802  can be affixed to pelvis  803  by inserting one or more pins  810  into the pelvis through holes  808 . Affixing surgical component  802  to pelvis  803  with pins, screws, or other attachment means insures that the surgical component is securely held in place during the surgical procedure. In  FIG. 9 , surgeon  806  is shown using a pin insertion device  812  to insert pin  810  into pelvis  803  through one of holes  808 . 
         [0052]      FIG. 10  shows surgical component  802  positioned against pelvis  803  and secured into place with attachment pins  810 . Surgical component  802  also includes a quick connect receptacle  814 , which is configured to connect to a tracking device, such as reference array  816 . Once reference array  816  is attached to surgical component  802 , navigation system  20  is able to locate and track its position in real-time and display its tracked position on a surgical plan image. In other words, once the navigation system locates the array, the system automatically knows its position with respect to the landmarks identified on the model image, as well as where it has been pre-registered with respect to the image. To accomplish this, cameras  818  of optical locator  820  detect in space the position of markers  817 , which extend from the surface of reference array  816 . To detect the position of the markers in space, known triangulation methods are used. These triangulation methods allow the navigation system to determine the relative location of the reference array and its markers with respect to the patient&#39;s anatomy, and then display the same on a surgical plan image. As reference array  816  is trackable in real-time, the position of pelvis  803  can also be tracked in real-time, particularly since reference array  816  is fixably attached to its surface by way of surgical component  802 . As explained above, by having reference array  816  positioned relative to the surgical component  802  in a predefined spatial manner, the need for intra-operative registration during the surgical procedure is substantially minimized. 
         [0053]    In additional to navigating knees and hips, the present teachings can also be used with surgical procedures involving the shoulder, spine, ankle, elbow, skull or any other type of bony structure found within the human anatomy. As such, the present teachings are not intended to be limited herein. 
         [0054]    While an exemplary embodiment incorporating the principles of the present invention has been disclosed hereinabove, the present invention is not limited to the disclosed embodiments. Instead, this application is intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.