System and method for performing and evaluating a procedure

Disclosed is a method and system for performing a procedure. The system may include a navigation system to be used to at least assist in the procedure. The system may assist in delineating objects and/or determining physical characteristics of subject portions. The system may assist in performing and/or a workflow of the procedure.

FIELD

The subject disclosure relates generally to a system and method for determining a position, including location and orientation, of a member in space relative to a subject.

BACKGROUND

Various procedures may be selected to repair or replace portions of selected subjects. For example, in a human subject a portion of the human anatomy may be selected to be repaired or replaced. During the procedure, a minimally or low invasive procedure may be selected. The low invasive procedure may limit direct viewing of a work area within the subject, but may decrease recovery time and/or discomfort to the subject.

A navigation system for various procedures, such as surgical procedures, assembling procedures, and the like, allow an instrument or object to be tracked. Tracking systems may include appropriate tracking systems, such as optical, acoustic, electro-magnetic (EM), etc. EM tracking or navigation systems include the AxiEM™ electro-magnetic navigation system sold by Medtronic Navigation, Inc., having a place of business in Louisville, Colo. The AxiEM™ electro-magnetic navigation system may include a plurality of coils that are used to generate an electro-magnetic field that is sensed by a tracking device, which may be the sensor coil, to allow a navigation system, such as a StealthStation® surgical navigation system, to be used to track and/or illustrate a tracked position of an instrument. Optical tracking systems include those such as the StealthStation® S7® tracking system. The optical tracking system includes a set of cameras with a field of vision to triangulate a position of the instrument.

SUMMARY

A tracking device connected to an instrument is generally required to allow tracking and navigation of the instrument. The instrument, therefore, is generally specific to a tracking or navigation system. A user specific instrument, such as surgeon specific instrument may not include a tracking device. Disclosed is an auxiliary instrument that may be tracked and a tracking and/or navigation system that may be used with the auxiliary system to track a progress or extent of a procedure.

A system for performing a procedure is disclosed. The procedure may also be performed on a living subject such as an animal, human, or other selected patient. The procedure may include any appropriate type of procedure, such as one being performed on an inanimate object (e.g. an enclosed structure, airframe, chassis, etc.). Nevertheless, the procedure may be performed using a navigation system where a tracking system is able to track a selected one or more items.

A navigation system may be used to navigate an instrument relative to a subject during a selected portion of a procedure. In various embodiments, the procedure may include a procedure on a spine such as a spinal fusion (i.e. two or more vertebrae are connected together with a selected implant system or assembly) and/or discectomy. During a discectomy portion of the procedure, the removal tool (e.g. a curette) may not include a tracking device. Thus, the cutting or removal instrument may not be directly tracked and/or navigated. An auxiliary or volume checking tool may include a tracking device to allow the auxiliary instrument to be tracked and/or navigated.

DETAILED DESCRIPTION

With initial reference toFIG. 1, a navigation system10is illustrated. The navigation system10may be used for various purposes or procedures by one or more users, such as a user12. The navigation system10may be used to determine or track a position of an instrument16in a volume. The position may include both a three dimensional X,Y,Z location and orientation. Orientation may include one or more degree of freedom, such as three degrees of freedom. It is understood, however, that any appropriate degree of freedom position information, such as up to or less than six-degree of freedom position information, may be determined and/or presented to the user12.

Tracking the position of the instrument16may assist the user12in determining a position of the instrument16, even if the instrument16is not directly viewable by the user12. Various procedures may block the view of the user12, such as performing a repair or assembling an inanimate system, such as a robotic system, assembling portions of an airframe or an automobile, or the like. Various other procedures may include a surgical procedure, such as performing a spinal procedure, neurological procedure, positioning a deep brain simulation probe, or other surgical procedures on a living subject. In various embodiments, for example, the living subject may be a human subject20and the procedure may be performed on the human subject20.

It is understood, however, that the instrument16may be tracked and/or navigated relative to any subject for any appropriate procedure. Tracking or navigating an instrument for a procedure, such as a surgical procedure, on a human or living subject is merely exemplary. Further, an initial or selected portion of the procedure may occur with an instrument, such as a first instrument15that is not tracked or may not be navigated. The non-tracked instrument15may be used for selected portions of the procedure, such as a resection or cutting. Thus, in various embodiments only the instrument16, which may be referred to as a second or auxiliary instrument, may be tracked and have a tracked device associated (e.g. attached) therewith. The first instrument15may not be tracked or navigated and may not have a tracking device associated therewith.

Nevertheless, in various embodiments, the surgical navigation system10, as discussed further herein, may incorporate various portions or systems, such as those disclosed in U.S. Pat. Nos. RE44,305; 7,697,972; 8,644,907; and 8,842,893; and U.S. Pat. App. Pub. No. 2004/0199072, all incorporated herein by reference. Various components that may be used with or as a component of the surgical navigation system10may include an imaging system24that is operable to image the subject20, such as an O-arm® imaging system, magnetic resonance imaging (MRI) system, computed tomography system, etc. A subject support26may be used to support or hold the subject20during imaging and/or during a procedure. The same or different supports may be used for different portions of a procedure.

In various embodiments, the imaging system24may include a source24s. The source24smay emit and/or generate X-rays. The X-rays may form a cone24c, such as in a cone beam, that impinge on the subject20. Some of the X-rays pass though and some are attenuated by the subject20. The imaging system24may further include a detector24dto detect the X-rays that are not completely attenuated, or blocked, by the subject20. Thus, the image data may include X-ray image data. Further, the image data may be two-dimensional (2D) image data.

Image data may be acquired, such as with one or more of the imaging systems discussed above, during a surgical procedure or acquired prior to a surgical procedure for displaying an image30on a display device32. In various embodiments, the acquired image data may also be used to form or reconstruct selected types of image data, such as three-dimensional volumes, even if the image data is 2D image data.

The trackable instrument16may be tracked in a trackable volume or a navigational volume by one or more tracking systems. Tracking systems may include one or more tracking systems that operate in an identical manner or more and/or different manner or mode. For example, the tracking system may include an electro-magnetic (EM) localizer40, as illustrated inFIG. 1. In various embodiments, it is understood by one skilled in the art, that other appropriate tracking systems may be used including optical, radar, ultrasonic, etc. For example, an optical localizer82may be used to track the instrument16.

The discussion herein of the EM localizer40and tracking system is merely exemplary of tracking systems operable with the navigation system10. The position of the instrument16may be tracked in the tracking volume relative to the subject20. The position, or selected portion of the instrument16, may then be illustrated as a graphical representation, also referred to as an icon,16iwith the display device32. In various embodiments, the icon16imay be superimposed on the image30and/or adjacent to the image30. As discussed herein, the navigation system10may incorporate the display device32and operate to render the image30from selected image data, display the image30, determine the position of the instrument16, determine the position of the icon16i, etc.

With reference toFIG. 1, the EM localizer40is operable to generate electro-magnetic fields with a transmitting coil array (TCA)42which is incorporated into the localizer40. The TCA42may include one or more coil groupings or arrays. In various embodiments, more than one group is included and each of the groupings may include three coils, also referred to as trios or triplets. The coils may be powered to generate or form an electro-magnetic field by driving current through the coils of the coil groupings. As the current is driven through the coils, the electro-magnetic fields generated will extend away from the coils42and form a navigation domain or volume50, such as encompassing all or a portion of a head20h, spinal vertebrae20v, or other appropriate portion. The coils may be powered through a TCA controller and/or power supply52. It is understood, however, that more than one of the EM localizers40may be provided and each may be placed at different and selected locations.

The navigation domain or volume50generally defines a navigation space or patient space. As is generally understood in the art, the instrument16, such as a probe, may be tracked in the navigation space that is defined by a navigation domain relative to a patient or subject20with an instrument tracking device56. For example, the instrument16may be freely moveable, such as by the user12, relative to a dynamic reference frame (DRF) or patient reference frame tracker60that is fixed relative to the subject20. Both the tracking devices56,60may include tracking portions that are tracked with appropriate tracking systems, such as sensing coils (e.g. conductive material formed or placed in a coil) that senses and are used to measure a magnetic field strength, optical reflectors, ultrasonic emitters, etc. Due to the tracking device56connected or associated with the instrument16, relative to the DRF60, the navigation system10may be used to determine the position of the instrument16relative to the DRF60.

The navigation volume or patient space may be registered to an image space defined by the image30of the subject20and the icon16irepresenting the instrument16may be illustrated at a navigated (e.g. determined) and tracked position with the display device32, such as superimposed on the image30. Registration of the patient space to the image space and determining a position of a tracking device, such as with the tracking device56, relative to a DRF, such as the DRF60, may be performed as generally known in the art, including as disclosed in U.S. Pat. Nos. RE44,305; 7,697,972; 8,644,907; and 8,842,893; and U.S. Pat. App. Pub. No. 2004/0199072, all incorporated herein by reference.

The navigation system10may further include and or be in communication with a navigation processor system66. The navigation processor system66may include connections to the display device32, the TCA40, the TCA controller52, and other portions and/or connections thereto. For example, a wire connection may be provided between the TCA controller52and a navigation processing unit70. It is understood that the navigation processing unit70may include one or more processors of various types (e.g. general purpose processors executing accessed instructions and/or specific processors (e.g. ASIC)). Further, the navigation processor system66may have one or more user control inputs, such as a keyboard72, and/or have additional inputs such as from communication with one or more memory systems74, either integrated or via a communication system. The navigation processor system66may, according to various embodiments include those disclosed in U.S. Pat. Nos. RE44,305; 7,697,972; 8,644,907; and 8,842,893; and U.S. Pat. App. Pub. No. 2004/0199072, all incorporated herein by reference, or may also include the commercially available StealthStation® or Fusion™ surgical navigation systems sold by Medtronic Navigation, Inc. having a place of business in Louisville, Colo.

Tracking information, including information regarding the magnetic fields sensed with the tracking devices56,60, may be delivered via a communication system, such as the TCA controller, which also may be a tracking device controller52, to the navigation processor system66including the navigation processor70. Thus, the tracked position of the instrument16may be illustrated as the icon16irelative to the image30. Various other memory and processing systems may also be provided with and/or in communication with the processor system66, including the memory system72that is in communication with the navigation processor70and/or an imaging processing unit76.

The image processing unit76may be incorporated into the imaging system24, such as the O-arm® imaging system, as discussed above. The imaging system24may, therefore, including the various portions such as a source and a x-ray detector that are moveable within a gantry78. The imaging system24may also be tracked with a tracking device80. It is understood, however, that the imaging system24need not be present while tracking the tracking devices, including the instrument tracking device56. Also, the imaging system24may be any appropriate imaging system including a MRI, CT, etc.

In various embodiments, the tracking system may include an optical localizer82. The optical localizer82may include one or more cameras that view or have a field of view that defines or encompasses the navigation volume50. The optical localizer82may receive light (e.g. infrared or ultraviolet) input to determine a position or track the tracking device, such as the instrument tracking device56. For example, at least two cameras at a fixed position relative to one another may view both the tracking device56of the instrument16and the DRF60on the patient20. Due to registration, the tracking system and the navigation system10may then determine the position of the instrument16(including at least a portion thereof) relative to the subject20. Generally, the position may be triangulated using the view of the volume50. It is understood that the optical localizer82may be used in conjunction with and/or alternatively to the EM localizer40for tracking the instrument16and may also have a communication line83with the navigation processor system66.

Information from all of the tracking devices may be communicated to the navigation processor70for determining a position of the tracked portions relative to each other and/or for localizing the instrument16relative to the image30. The processor70may execute instructions or be designed to analyze the incoming navigation signals to determine the position of the instrument16, as is generally understood in the art as discussed above. The determined position of the instrument16, however, may be displayed with the display device32in various manners and with various indications, as discussed herein. The imaging system24may be used to acquire image data to generate or produce the image30of the subject20. It is understood, however, that other appropriate imaging systems may also be used. The TCA controller52may be used to operate and power the EM localizer40, as discussed above.

The image30that is displayed with the display device32may be based upon image data that is acquired of the subject20in various manners. For example, the imaging system24may be used to acquire image data that is used to generate the image30. It is understood, however, that other appropriate imaging systems may be used to generate the image30using image data acquired with the selected imaging system. Imaging systems may include magnetic resonance imagers, computed tomography imagers, and other appropriate imaging systems. Further, the image data acquired may be two dimensional or three dimensional data and may have a time varying component, such as imaging the patient during a heart rhythm and/or breathing cycle.

In various embodiments, the image data is a 2D image data that is generated with a cone beam. The cone beam that is used to generate the 2D image data may be part of an imaging system, such as the O-arm® imaging system. The 2D image data may then be used to reconstruct a 3D image or model of the imaged subject, such as the patient20. The reconstructed 3D image and/or an image based on the 2D image data may be displayed. Thus, it is understood by one skilled in the art that the image30may be generated using the selected image data.

Further, the icon16i, determined as a tracked position of the instrument16, may be displayed on the display device32relative to the image30. In addition, the image30may be segmented, for various purposes, including those discussed further herein. Segmentation of the image30may be used to determine and/or delineate objects or portions in the image. In various embodiments, the delineation may be used to identify boundaries of various portions within the image30, such as boundaries of one or more structures of the patient that is imaged, such as the vertebrae20v. Accordingly, the image30may include an image of one or more of the vertebrae20v, such as a first vertebra20viand a second vertebra20vii. In various embodiments, the delineation may be represented, such as with selected icons, such as an icon20vi′ or a second icon20vii′. The boundaries20vi′,20vii′ may be determined in an appropriate manner and for various purposes, as also discussed further herein. Selected anatomical portions may include displaying a disc between vertebrae and or determining that a disc is between determined vertebrae. For example, in various imaging modalities, soft tissue of a disc may not be easily or directly viewable, while the bone of the vertebrae is easily viewed by the user12.

With continuing reference toFIG. 1, the subject20may include a plurality of vertebrae, such as a first vertebra20v1and a second vertebra20v2. The vertebrae20vmay be surrounded or covered by soft tissue, such as a dermis, muscle, and the like. In performing a selected procedure, such as in a spinal fusion, discectomy, or other procedures, a small incision230(FIG. 2) may be made. A small incision may allow for a substantially minimal or low invasive procedure. For example, the incision may generally be about 1 millimeter (mm) to about 3 centimeters (cm) in length. Generally the incision allows access for instruments, such as the first instrument15or the second or auxiliary instrument16to a selected area while minimizing the incision size, which may also limit the view of the user12of the area where a procedure is occurring. In various procedures, such as in a spinal fusion, a discectomy may occur. A discectomy may include removing a portion or all of a disc. The disc may generally be the tissue between two vertebrae, such as the vertebrae20v1and20v2. The two vertebrae may be any appropriate vertebrae, such as a third lumbar vertebra (L3) and a fourth lumbar vertebra (L4).

As illustrated inFIG. 1, the image30may include the vertebrae of the subject, along with other tissue of the subject20. As discussed further herein, an illustration of the vertebrae may include the image acquired with the imaging system24, or any appropriate imaging system, or a selected reconstruction thereof, such as a three-dimensional reconstruction.

In various embodiments, the imaging system24, or any appropriate imaging system, may include an image processing unit76that may be used to analyze and allow for manipulation of selected images. The images may be stored with the imaging system24and/or stored in a selected image memory112. Further, various instructions such as tracking, registration, and the like may be stored in the navigation memory74.

According to various embodiments, the user12may plan or select a selected procedure for the subject20. In planning the procedure, the user12may predetermine or preselect a volume of the anatomy to be manipulated. In various embodiments the user12may predetermine a volume of the disc to be removed between the vertebrae20v1and20v2. For example, the user12may select to remove about 10% to about 90%, including further about 30% to about 80%, and further including about 60% to about 80%. Generally, the user12may select to remove a substantially central or middle portion of the disc between adjacent vertebrae. The user12may select to maintain a selected portion of the disc, such as an annulus of the disc, to assist in maintaining an implant (e.g. intervertebral implant and/or bone graph). Accordingly, the user may predetermine an amount of volume to be removed.

With use of the image30and the display device32, the user12may also specifically identify a region or volume to be removed. As discussed above, selected vertebrae may be displayed20viand20vii. Icons may be used to represent the vertebrae, such as being delineated or identified by the user12. The vertebrae icons20vi′ and20vii′ may be used by the navigation processing unit70, or any appropriate processing unit, such as a planning processing unit, to assist in determining a volume between the two vertebrae20v1and20v2displayed in the image30. The user12may specifically define a volume or portion of the volume of the disc to be removed between the selected vertebrae in the image30. For example, the user12may use selected inputs, such as the input72, to identify the volume to be removed. In various embodiments, the user12may identify a selected volume such as about 2 cubic centimeters (cc) to about 8 cc, and further including about 4 cc to about 6 cc.

The user may define a volume, such as with an icon or template, and place the template adjacent to the image30. The navigation system66may then determine a position of the tracked instrument16relative to the predetermined volume displayed with the display device32relative to the image30. Moreover, as discussed further herein, the navigation system66may be used to determine a volume identified by the tracked instrument16when the tracked instrument16is moved within the navigated volume50.

With continuing reference toFIG. 1and further reference toFIG. 2, the display device32may display one or more images of the subject20. For example, the display device32may display a plurality of windows including an axial view window200, a sagittal view window210and a 3D view window218. Each of the views in the windows200,210,218may be viewed by the user12substantially simultaneously with the display device32. The user12may also select which views to be viewed on the display device32and the view windows200,210,218are merely exemplary. Further, additional information may also be displayed for view by the user12such as a volume removed window226. The volume removed window226may include a title228, such as Volume Remove (or any appropriate title), an absolute numerical volume box232, and/or a percentage removed box254. At the initiation of a procedure the numerical value box232may illustrate or identify 0.0 cc and 0%. Accordingly, the user12may view the indication that no determined volume has been removed from the subject20.

Turning reference toFIG. 3AandFIG. 3B, the display device32may display a tracked or navigated location of the instrument16as the icon16i. The instrument16may be tracked as it is moved relative to the subject20. For example, the user12may position the instrument16through an incision230. The incision230may be initially produced to allow positioning the instrument15into the subject20for performing an initial portion of the procedure. The instrument15may be a non-navigated or non-tracked instrument that may be used to cut or resect tissue. For example, during a discectomy, tissue may be removed from the disc between the vertebrae20v1and20v2. A disc or disc space20dmay be the disc of the subject20between the two vertebrae20v1and20v2. During removal of tissue from the disc20d, a void may be formed in the disc space20d. A cutting or tissue removal instrument may not be tracked or navigated to allow for viewing or determining the position of the resected material. Resecting material with a navigated instrument, however, is disclosed in U.S. Pat. No. 7,542,791, issued Jun. 2, 2009, incorporated herein by reference.

When the instrument15is not navigated or tracked and the incision230is of a selected size such that the user12does not have direct view of the disc space20d, the tracked instrument16may be moved into the disc space20d. The instrument15that is not tracked, in various embodiments, may be the only instrument that cuts or removes material form the subject20. Moving the tracked instrument16into the disc space20dallows for a determination or visualization of the volume resected with the instrument15using the display device32. The tracked instrument16, therefore, may only be moved and not cut or remove tissue or material from the subject20. As discussed herein, the instrument16may be moved within the disc space20dto indicate the volume resected or removed with the instrument15.

The instrument16may include the trackable member56that is tracked with a selected tracking system, such as the optical localizer82. The instrument16may further include a shaft or elongated member240that ends in a distal end or tip244. The distal tip244may include a selected geometry, such as a substantially spherical member positioned at the end of the elongated member240. The distal end244, however, may be any appropriate shape or geometry such as ovoid, curved, cylindrical, ellipsoid, etc. In various embodiments, for example when the distal end is substantially spherical or forms at least a portion of a sphere, the distal end244may have a selected radius244rthat extends from a center to a surface244s(FIG. 4B). The surface244smay be a substantially smooth or non-abrasive or non-cutting surface, such that it may contact a resected surface within the disc space20d. Further, the geometry or volume of the distal end244may be known, such as saved in the memory74so that its tracked movement within the disc space20dmay be used to determine a volume of a void within the disc space20d. Again the void into which the instrument16is placed may be formed by the instrument15that is not tracked.

The tracked instrument16may be moved through the void and a painted or illustrated volume or area250may be illustrated on the display device32relative to the different view windows200,210,218. In each of the view windows the volume250may be illustrated to display the volume through which the tracked instrument16, including the distal end244thereof, has moved. Accordingly, the display device32may display graphical illustration of a volume through which the distal end244has moved. As discussed herein, the volume250is “painted”, substantially or only, as selected, by tracking movement of the tracking device56and the known position of the distal end244relative thereto. Further, the icon16imay illustrate the instrument, including the distal end244i.

The information window may illustrate the volume removed by a numerical value232, such as 1.3 cc. Further, as discussed above, a predetermined or preselected volume may be made by the user12to be resected. The predetermined volume may be saved in the navigation memory74. Accordingly, the processor system66, including the processor70, may determine the percentage or fraction of the determined volume as a portion of the hole. Accordingly, the portion of the whole predetermined volume may also be displayed, such as 29%.

The user12may view the determined volume graphically, numerically as an absolute value, or numerically as a percent, or any other appropriate manner in determining whether more resection is selected. If more resection is selected, the user12may withdraw the tracked instrument16and position the non-tracked instrument15within the disc space20dto continue resection and removal of tissue therefrom. After a selected amount of time or movement of the instrument15, the user12may then reinsert the tracked instrument16to move within the void formed by removing of tissue. This process may continue until the user has determined that a selected amount of tissue has been removed. Generally, the instrument15is first removed prior to placing the tracked instrument through the incision230into the created void.

With reference toFIG. 4AandFIG. 4B, the display device32may display the tracked instrument icon16iincluding the tip24ithereof and a second volume260. The second volume260may also be viewed or displayed in each of the view windows200,210,218. The second volume260may be based upon further movement of the tracked instrument16within the disc space20d. As illustrated inFIG. 4B, the tracked instrument16may be moved from a first position to a second position244′ (illustrated in phantom). Movement of the tracked instrument16may allow for a real time display of the volume260, such as if the user12were paining the volume.

When moving the tracked instrument16, which may only include a smooth surface244s, the painting of the volume260may occur. In painting the display32may display the volume260with a selected color. The color may change from a first to a second color to indicate that the distal end244has already been tracked in an area or volume. Thus, the user12may more efficiently move the distal end244to all portions or areas of the void. Generally, the determined volume may only be of the volume in which the instrument16, which is tracked, is moved. Thus, the user12may also be prompted to confirm movement to all areas in the void of the disc space20d. Further, the user12may ensure that the void is all a second color to confirm that the instrument16has moved within the area or volume at least twice for a confirmation.

The second volume260may be any appropriate volume following the first volume measured with the tracked instrument16. As illustrated inFIG. 4A, for example, the volume removed may be identified as the absolute value 4.5 cc in the value box232. Further in the percent or portion box254, 100% may be displayed. Accordingly, the user may be notified that the volume removed is equal to the predetermined volume to be removed, such as by comparison to a recalled predetermined volume from the navigation memory74.

With reference toFIG. 4B, during movement of the instrument16within the disc space20d, the display device32may, in real time, such as substantially with movement or in time with movement of the tracked instrument16, illustrate the second volume260, or any selected series of volume. Accordingly, the user16may move the tracked instrument16within the disc space20dand view a real time movement or painting of the volume determined or measured by a tracking instrument16within the disc space20d. Thus, the user12may view in real time the volume of a void created within the disc space20dduring a selected procedure, such as a discectomy.

The volume is determined by tracking the distal end244throughout its movement within the disc space20d. Generally, the user12moves the distal end along all of the surfaces within the disc space20dand within the open volume in the disc space20d. By adding the non-overlapping positions of the distal end244, a volume is determined. The volume of the distal end244is known based on its geometry and dimensions, such as the radius of the sphere.

The volume may be determined by the navigation system10, such as by the processor unit70executing instructions to add the non-overlapping volumes together. The navigation system10may, therefore, substantially automatically determine the volume250,260or any appropriate volume with the tracked instrument16. The determined volume is then displayed, as discussed above.

Once the user12has determined an appropriate amount of disc has been removed and a selected volume of space when the disc has been created the user12may perform additional procedural steps. For example, the user12may pack the void with a selected material, such as a bone graft. In various embodiments, a cage may also be positioned within the volume that is either filled or packed with a selected graph or bone graph. The cage may include a cage such as an Inter Fix™ Threaded spinal Fusion Device, sold by Medtronic, Inc. It is understood, however, that any appropriate procedure may follow.

Further, it is understood that the instrument16may be used to track or determine a volume in any appropriate portion of a subject. For example, during a tumor removal, such as a resection of a cancerous tumor in various portions of the anatomy including the brain, near a spinal column, or the like, a non-navigated instrument may be used during resection or removal. Further, other selected portions of the anatomy may be analyzed for volume, such as a sinus cavity, nasal passage, ear canal, etc.

The tracked instrument16may be positioned within the subject using the same incision for the resection instrument and the tracked instrument may be moved within the created void. Tracking the tracked instrument in the created void may be used to determine the volume of the created void even if the resection instrument is not tracked. Accordingly the second or auxiliary instrument16that is tracked may be used to determine a volume or an area that is resected with a non-navigated instrument. Thus the user12may use selected instruments, such as procedure specific instruments, user specific instruments, or other appropriate instruments for performing a procedure while allowing for determination of a volume or area based upon a tracked location of an auxiliary or secondary instrument.

Further, it is understood that the user12may determine and/or the navigation system10may automatically determine when and/or where to begin or include in the volume determination. For example, the user12may provide an input to begin volume determination and/or painting once the user12views that the distal end244is within the volume of the disc space20ddue to registration of the image30to the subject20. Alternatively, or in addition thereto, the navigation system10may determine automatically to initiate volume determination based on the tracked position of the distal end244at or near the disc space20d.

Similarly, the painting of the volume determination may be substantially coincident with the initiation of the volume determination or at some other time. Generally, however, the painting of the volume for viewing by the user20will be initiated with volume determination initiation to determine and illustrate a selected volume or space, such as a resected disc space. Generally, however, the instrument16and the distal end244thereof is tracked and navigated, whether or not the determination of a volume or space has been initiated and/or painting of the determined volume and/or area.

It is further understood that the user12may select to operate the navigation system10for various purposes. For example, the user12may view a calculated volume based on the tracked position of the distal end244, for example a discrete calculated volume such as 4 cc. The user12may also, or alternatively, select to have displayed and/or determined a percentage of a predetermined volume, such as 45%. The user12may also or alternatively selected to display the painted volume, such as the volume260or any volume through which the distal end244has been moved and tracked. The user12may selected to have only one, only two, or all three of the above or any appropriate representation of the volume through which the tracked instrument16, including the distal end244, has been tracked.