US20100249581A1 - Surgical Navigation System Component Fault Interfaces and Related Processes - Google Patents

Abstract

Devices and processes for use in computer aided or computer navigated surgery include one or more fault interfaces interposed between an indicium and an item to be used during surgery such as a body part, tool, implant, trial or other structure or component. After the indicia have been registered into the system and surgery begun, it is sometimes the case that indicia can be inadvertently moved or dislodged in position and/or orientation relative to the body part. Fault interfaces according to various embodiments are designed to fail first, so that the indicia can be repositioned relative to the item without the need to reregister the indicia into the system relative to the item. The fault interfaces preferably include structure that allows the indicium to be repositioned relative to the item so that it does not need to be reregistered into the system. Frame attachments which can by easily manufactured at relatively low cost, are disposable, and which are manufactured for single use are disclosed.

Description

CROSS REFERENCE TO RELATED APPLICATION
• This application is a continuation-in-part application of, and claims priority to U.S. patent application Ser. No. 10/689,103 filed on Oct. 20, 2003.
FIELD OF THE INVENTION
• The present invention relates to frame attachments for use in surgical navigation, and methods for their use. More specifically, the invention relates to frame attachments comprising fiducials or other reference structures which are designed to be accurately reinstalled into correct position if inadvertently or otherwise moved or altered with respect to their original registration in a surgical navigation system. The invention further relates to frame attachments which are disposable.
BACKGROUND
• A major concern during surgical procedures as well as other medical operations is carrying out the procedures with as much precision as possible. For example, in orthopedic procedures, less than optimum alignment of implanted prosthetic components may cause undesired wear and revision, which may eventually lead to the failure of the implanted prosthesis. Other general surgical procedures also require precision in their execution.
• With orthopedic procedures, for example, previous practices have not allowed for precise alignment of prosthetic components. For example, in a total knee arthroplasty, previous instrument design for resection of bone limited the alignment of the femoral and tibial resections to average value for varus/valgus, flexion/extension and external/internal rotation. Additionally, surgeons often use visual landmarks or “rules of thumb” for alignment which can be misleading due to anatomical variability. Intramedullary referencing instruments also violate the femoral and tibial canal. This intrusion increases the risk of fat embolism and unnecessary blood loss in the patient.
• Devices and processes according to various embodiments of the present invention are applicable not only for knee repair, reconstruction or replacement surgery, but also repair, reconstruction or replacement surgery in connection with any other joint of the body as well as any other surgical or other operation where it is useful to track position and orientation of body parts, non-body components and/or virtual references such as rotational axes, and to display and output data regarding positioning and orientation of them relative to each other for use in navigation and performance of the operation.
• Several manufacturers currently produce image-guided surgical navigation systems that are used to assist in performing surgical procedures with greater precision. The TREON™ and iON™ systems with FLUORONAV™ software manufactured by Medtronic Surgical Navigation Technologies, Inc. are examples of such systems. The BrainLAB VECTORVISION™ system is another example of such a surgical navigation system. Systems and methods for accomplishing image-guided surgery are also disclosed in U.S. Ser. No. 10/364,859, filed Feb. 11, 2003 and entitled “Image Guided Fracture Reduction,” which claims priority to U.S. Ser. No. 60/355,886, filed Feb. 11, 2002 and entitled “Image Guided Fracture Reduction”; U.S. Ser. No. 60/271,818, filed Feb. 27, 2001 and entitled “Image Guided System for Arthroplasty”; U.S. Ser. No. 10/229,372, filed Aug. 27, 2002 and entitled “Image Computer Assisted Knee Arthroplasty”; U.S. Ser. No. 10/084,278 filed Feb. 27, 2002 and entitled “Total Knee Arthroplasty Systems and Processes,” which claims priority to provisional application entitled “Surgical Navigation Systems and Processes,” Ser. No. 60/355,899, filed Feb. 11, 2002; U.S. Ser. No. 10/084,278 filed Feb. 27, 2002 and entitled “Surgical Navigation Systems and Processes for Unicompartmental Knee Arthroplasty,” which claims priority to provisional application entitled “Surgical Navigation Systems and Processes,” Ser. No. 60/355,899, filed Feb. 11, 2002; U.S. Ser. No. 10/084,291 entitled Surgical Navigation Systems and Processes for High Tibial Osteotomy,” which claims priority to provisional application entitled “Surgical Navigation Systems and Processes,” Ser. No. 60/355,899, filed Feb. 11, 2002; provisional application entitled “Image-guided Navigated Precisions Reamers,” Ser. No. 60/474,178, filed May 29, 2003; and nonprovisional application entitled “Surgical Positioners,” T. Russell, P. Culley, T. Ruffice, K. Raburn and L. Grisoni, inventors, filed Oct. 3, 2003, the entire contents of each of which are incorporated herein by reference as are all documents incorporated by reference therein.
• These systems and processes use position and/or orientation tracking sensors such as infrared sensors acting stereoscopically or other sensors acting in conjunction with reference structures or reference transmitters to track positions of body parts, surgery-related items such as implements, instrumentation, trial prosthetics, prosthetic components, and virtual constructs or references such as rotational axes which have been calculated and stored based on designation of bone landmarks. Processing capability such as any desired form of computer functionality, whether standalone, networked, or otherwise, takes into account the position and orientation information as to various items in the position sensing field (which may correspond generally or specifically to all or portions or more than all of the surgical field) based on sensed position and orientation of their associated reference structures such as fiducials, reference transmitters, or based on stored position and/or orientation information. The processing functionality correlates this position and orientation information for each object with stored information, such as a computerized fluoroscopic imaged file, a wire frame data file for rendering a representation of an instrument component, trial prosthesis or actual prosthesis, or a computer generated file relating to a rotational axis or other virtual construct or reference. The processing functionality then displays position and orientation of these objects on a screen or monitor, or otherwise. Thus, systems or processes, by sensing the position of reference structures or transmitters, can display or otherwise output useful data relating to predicted or actual position and orientation of body parts, surgically related items, implants, and virtual constructs for use in navigation, assessment, and otherwise performing surgery or other operations.
• Some of these reference structures or reference transmitters may emit or reflect infrared light that is then detected by an infrared camera. The references may be sensed actively or passively by infrared, visual, sound, magnetic, electromagnetic, x-ray or any other desired technique. An active reference emits energy, and a passive reference merely reflects energy. Reference structures may have at least three, but usually four, markers or fiducials that are traced by an infrared sensor to determine the position and orientation of the reference and thus the position and orientation of the associated instrument, implant component or other object to which the reference is attached.
• In addition to reference structures with fixed fiducials, modular fiducials, which may be positioned independent of each other, may be used to reference points in the coordinate system. Modular fiducials may include reflective elements which may be tracked by two, sometimes more sensors whose output may be processed in concert by associated processing functionality to geometrically calculate the position and orientation of the item to which the modular fiducial is attached. Like fixed fiducial reference structures, modular fiducials and the sensors need not be confined to the infrared spectrum—any electromagnetic, electrostatic, light, sound, radio frequently or other desired technique may be used. Similarly, modular fiducials may “actively” transmit reference information to a tracking system, as opposed to “passively” reflecting infrared or other forms of energy.
• Some image-guided surgical navigation systems allow reference structures to be detected at the same time the fluoroscopy imaging is occurring. This allows the position and orientation of the reference structure to be coordinated with the fluoroscope imaging. Then, after processing position and orientation data, the reference structures may be used to track the position and orientation of anatomical features that were recorded fluoroscopically. Computer-generated images of instruments, components, or other structures that are fitted with reference structures may be superimposed on the fluoroscopic images. The instruments, trial, implant or other structure or geometry can be displayed as 3-D models, outline models, or bone-implant interface surfaces.
• Some image-guided surgical navigation systems monitor the location and orientation of the reference structures and consequently the portion of the anatomy or instruments secured to the reference structure by either actively or passively detecting the position of fiducials associated with the reference structure. Because the fiducials may be arranged in particular patterns, the system can determine the exact orientation and location of the reference structure associated with the fiducials. In other words, depending upon the particular location of the individual fiducials, the system will “see” the reference structure in a particular way and will be able to calculate the location and orientation of the reference structure based upon that data. Consequently, the system can determine the exact orientation and location of the portion of the anatomy or instrument associated with the reference structure.
• The exact spatial relationship of the individual fiducials with respect to each other and the associated anatomy or instrument forms the basis of how a fiducial-based system calculates the position and orientation of the associated items. Similarly, the exact spatial relationship of a reference transmitter with respect to its associated anatomy or instrument forms the basis of how a transmitter-based system calculates the position and orientation of the associated anatomy or instruments. Consequently, once the spatial relationship of the fiducials or reference transmitter with respect to the associated item to be tracked has been registered in the system, subsequent changes in the position and/or orientation of the fiducials or reference transmitter may cause the system to erroneously calculate the position and orientation of the anatomy or instruments associated with the fiducials or reference transmitter. Even minor changes in orientation and/or position of the references may lead to dramatic differences in how the system detects the orientation and/or location of the associated anatomy or instruments. Such changes may require the system to be recalibrated, requiring additional fluoroscopy or other imaging to be obtained, increasing the time and the expense of the procedure. Failure to recalibrate the system may lead to imprecision in the execution of the desired surgical procedure.
• In a busy operating room, there is a possibility that reference structures, or one or more fiducials on a reference structure, will be inadvertently deformed or displaced in position or orientation, such as by a surgeon or nurse's arm or elbow, after calibration. When this happens, the reference structures and/or fiducials will provide inaccurate information about the location, position, and orientation of the body parts, non-body components and other reference points previously placed in the coordinate system and the accuracy and safety of the surgical procedure may be jeopardized. Even where a surgeon or other surgery attendant tries to place the reference structure back in its original position, it is virtually impossible to relocate the original location, position and orientation with precision. And as discussed above, even the slightest change can have dramatic results.
• As a result, when a reference structure or fiducial loses its original position in the reference system, the entire coordinate system must be recalibrated or reregistered. To continue with the image guided surgery, the surgeon must reregister each instrument that will be used in the procedure and each reference structure and fiducial that is on the patient or otherwise in the coordinate system. This process lengthens the time necessary to complete the surgical procedure and can result in unnecessary complications resulting from the additional length of time the patient is in surgery.
• Adding to this concern is the tendency of some surgeons to not take the time necessary to recalibrate the entire system when a reference structure or fiducial is dislocated as described above. When this occurs, the virtual image created by the imaging system is not a true reflection of the actual position, orientation and relationship of the body parts, non-body components and other reference points. Proceeding with surgical procedures with a coordinate system under these conditions can lead to obvious dangers.
SUMMARY
• Various aspects and embodiments of the present invention include frame attachments with portions that, when displaced or dislodged, will readily disconnect from a base secured to the reference point in the coordinate system and be able to be precisely repositioned.
• According to one aspect of the present invention, a frame attachment includes a connecting portion with an interface designed to complement the receiving portion of a base secured in the coordinate system. The attachment device creates a stable connection with the base but, when displaced or dislodged, separates from the base without resulting in a change of location of the base within the coordinate system. The attachment can therefore be replaced without having to recalibrate the entire system.
• According to another aspect, a frame attachment includes a connecting portion with an interface which is designed to complement a receiving portion of a base. The attachment device creates a stable connection with the base through the use of an additional connection aid, such as magnetic attraction, adhesive, hook and pile connectors, or any other material or force which creates a bond between the attachment device and base. The failure strength of the bond is preferably smaller than the failure strength of any portion of the attachment or the base. When the attachment device is displaced or dislodged, it separates from the base without resulting in a change of location of the base within the coordinate system. As such, the attachment device can be replaced without having to recalibrate the entire system.
• According to other aspects of the present invention, the attachment device comprises fiducials, reference transmitters and/or other reference devices.
• According to other aspects of the present invention, the base comprises a bone screw and/or other devices connected to a human body.
• According to other aspects of the present invention, attachment devices and modular fiducials exhibit modularity such that they may be moved within a coordinate system without the disruption of the base secured within the coordinate system.
• According to other aspects of the present invention, the fiducials are adapted for single use and are, thus, disposable. According to certain aspects of this embodiment, the fiducials are comprised of plastic.
BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1 shows a schematic side view of a modular fiducial according to one embodiment of the present invention.
• FIG. 2 shows a schematic top view of the portion of a base having the fault interface for connection with the modular fiducial ofFIG. 1.
• FIG. 3 shows a perspective view of the modular fiducial ofFIG. 1.
• FIG. 4 shows a perspective view of the portion of the base having the fault interface ofFIG. 2.
• FIG. 5 shows a schematic view of the modular fiducial ofFIG. 1 positioned for placement within the portion of the base having the fault interface ofFIG. 2.
• FIG. 6 shows a perspective view of an attachment device positioned for placement on top of a base according to another embodiment of the invention.
• FIG. 7 shows a perspective view of an attachment device connected to a base according to another embodiment of the invention.
• FIG. 8 shows a perspective view of an attachment device connected to a base according to still another embodiment of the present invention.
• FIG. 9 shows a perspective view of a drill attachment according to another embodiment of the present invention positioned for connection to a bone screw.
• FIG. 10 shows another perspective view of a drill attachment device ofFIG. 9 positioned for placement in a bone screw.
• FIG. 11 shows a perspective view of an attachment device according to another aspect of the present invention connected to a bone screw.
• FIG. 12 shows a schematic view of a tracking system according to another embodiment of the present invention.
• FIG. 13 shows a perspective view of an attachment device of unitary construction, according to one embodiment of the present invention.
• FIG. 14 shows a perspective view of an attachment device with four fiducials according to a certain aspect of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
• FIGS. 1-5 illustrate one form of device according to one embodiment of the present invention.FIGS. 1 and 3 show amodular indicium20 that includes a fiducial orreflective element78, astem80, and a key210. Theindicium20 can instead be a transponder using any energy within the energy spectrum as desired, or any other active or passive device which is able to impart position information to another device so that, when that device senses position of three ormore indicia20 rigidly attached to a body part, tool, implant, trial or other thing in the operating room, the device is able to generate position and orientation information about the thing. The indicium can be of any desired shape, size, structure, material, circuitry such as RFID, or any other physical instantiation. The device which senses theindicium20 can be any of the conventional or unconventional computer aided surgery systems mentioned above or otherwise, which include an imager for sensing the position and location of theindicium20, computer functionality for generating position and orientation information about the thing to which the indicium is attached, and a display device which can render the thing correctly located and oriented according to position of theindicia20.
• In the embodiment shown in these figures, the key210 protrudes from the lower portion of thestem80. Any structure can be used to create a fault interface that has a failure strength less than the failure strength of the indicium to reference frame connection, or the reference frame to body part or other thing connection, or the failure strength of any part of these components or relevant parts of them. Preferably, the fault interface permits the indicium to be repositioned with respect to the thing or item in only one position and orientation if inadvertently or otherwise dislodged. That position is the position in which the indicium was originally registered into the computer aided surgery system. The present invention includes, however, any fault interface that permits the indicium to be repositioned without the need to reregister the indicium in the system.
• FIGS. 2 and 4 show a base140awith afault interface120 for the modular fiducial20. The base may include, without limitation, a pin, a plate, a platform, or any other device which is secured within a reference system. Thefault interface120 has agroove310 for placement of the key210. This key/groove arrangement requires that the fiducial20 be positioned in only one orientation in order to fit correctly. As a result, when the fiducial is dislodged or displaced relative to the base, either by purpose or accident, it may be replaced within the base in the precise location, position and orientation as its original placement in the coordinate system thus removing the necessity for the recalibration of the entire reference system. Placement of the fiducial20 onto the base140ais depicted inFIG. 5.
• WhileFIGS. 1-5 depict one embodiment of the present invention, the invention includes any interface that allows registration of indicium or an attachment device with a base which allows the indicium or attachment device to be repositioned without the need to reregister the indicium in the system. For instance,FIGS. 6-8 depict other structures according to other embodiments of the present invention.
• FIG. 6 shows an embodiment of the present invention in which thebase140bis in the form of a plate. The plate is securely attached to a body part or other reference point through the use ofpins410. In this embodiment, the base140bincludes twoprotrusions402,404 at the fault interface—afirst protrusion402 and asecond protrusion404. The protrusions are preferably of different size and/or shape, in order to allow another component to be attached in only one orientation. Anattachment device420 is included in this particular structure, which is designed to accept anadditional element400 for placement of a reference frame, fiducial or fiducials or other reference device or devices whether active or passive. Thereference structure420 includes twoapertures412,414 which correspond in size and shape toprotrusions402,404, whether or not those protrusions are of different size and/or shape. The design and placement of the protrusions and apertures preferably mandates that theattachment device420 connects with the base140bin only one position and orientation. Preferably, there is a friction fit at the fault interface which has a failure strength less than the failure strength of any part of, or relevant parts of any ofcomponents140b,400, or420, and also less than the deformation limit or failure strength of the connection between the base140band the patient. Accordingly, when a fiducial, reference frame or other structure attached or connected, directly or indirectly tocomponent400 or420 is dislodged or displaced, theattachment device420 dislocates at the fault interface, but the base140bremains securely in place. Because the design of theattachment device420 and the base140 allow connection in only position and orientation, however, theattachment device420 may be precisely replaced on the base140band no further calibration is necessary before proceeding with surgery.
• FIG. 7 shows a variation of the embodiment ofFIG. 6 in which theattachment device420 has been placed upon the base140b. This embodiment includes anelement400 which can feature an active position indicating device or fiducial projecting above the surface of theelement400.
• FIG. 8 shows yet another embodiment of the present invention. In this embodiment, the fiducial-acceptingelement400 places the indicating device or fiducial outside the perimeter of theattachment device420. However, the design of theattachment device420 and the base140bare such that, when sufficient force is exerted, theattachment device420 dislodges while the base140bremains securely in place allowing theattachment device420 to be replaced in the same position and orientation. Therefore, the recalibration of the coordinate system is not necessary.
• FIGS. 9 and 10 show another embodiment of the present invention in which the base140cis in the form of a bone screw. The bone screw contains afault interface434 which corresponds to apattern432 on adrill attachment440. This pattern is also present on the portion of the fiducial or other reference structure which attaches to the bone screw140c. The interface on thebone screw434 andcorresponding pattern432 require that thedrill attachment440 be positioned in only on orientation in order to fit correctly. Thedrill attachment440 is connected to the bone screw140cand the drill is used to secure the bone screw140cto thebone300.
• FIG. 11 shows a variation of the embodiment ofFIGS. 9 and 10 in whichattachment devices320 have been placed on the bone screws140cwhich are connected to abone300. The design of theattachment device320 and the base140care such that, when sufficient force is exerted, theattachment device320 dislodges while the bone screw140cremains securely in place allowing theattachment device320 to be replaced in the same position and orientation. Therefore, the recalibration of the coordinate system is not necessary.
• According to certain embodiments of the present invention, a connection aid provides further support for the connection between the fiducial20 and the base140a,b,c. The connection aid may be located near the bottom portion of the fiducial20, within thefault interface120, both, or otherwise, and can include magnetic attraction, adhesives, hook and pile connectors, or any other materials or forces which result in a bond between the fiducial20 andbase140a,b,cwhich features a smaller failure strength than relevant portions of either the fiducial or base. Accordingly, when sufficient force is placed on the fiducial20, the connection aid allows the base to be displaced or dislodged in a manner that allows ready replacement into correct position and orientation.
• In use,attachment devices20,320, or420 bearing fiducials and/or active devices are connected to relevant body parts or part of tools, trials, implant components, tables, or other tangible things in the operating room. The fiducials and/or active devices are then registered into the computer aided surgery system in accordance with techniques discussed at length in the documents cited and incorporated by reference above. During surgery, the fiducials and/or active devices allow images of the thing to which they are attached to be represented in accurate position and orientation on a monitor with the aid of computer processing. However, when a fiducial or active device is inadvertently struck with an elbow or implement in a manner that would otherwise deform it in position or orientation or both, or dislodge it the thing to which was attached, instead the fault interface fails and allows the fidicial or active device or reference frame to be dislodged in a manner that permits its ready replacement in a manner that eliminates the necessity to reregister the indicium or the reference frame into the system. For example, the fiducial20 may be replaced in its correct position, location and orientation with respect to the thing to which it was attached.
• FIG. 12 shows atracking system102 that may utilizemodular indicium20 to track the orientation and/or position of desireditems104 within the tracking sensor's106 field of vision.Modular indicium20 or other reference structures8 may be placed onitems104 to be tracked such that atracking system102 can track the position and/or orientation of any desired item in the field of view of thetracking sensor106. The trackingsensor106 may relay the position and/or orientation data to aprocessing functionality112 which can correlate the data with data obtained from animaging device108 and output that data to asuitable output device110.
• FIG. 13 shows yet another embodiment of the present invention in which theattachment device460 may be of unitary construction. Among other materials and methods of manufacture, this embodiment of the attachment device may be comprised of plastic and may be manufactured by the injection of plastic into a suitable mold. In a particular embodiment, the attachment device contains a set of twoprotrusions462a,462bwhich correspond to ahole464band aslot464aon anarray base140d. Theattachment device460 in this particular structure is designed to acceptadditional elements480a,480b, and480cfor placement on theextensions470a,470b, and470con theattachment device460. These additional elements may comprises active or passive position indicating devices. As with other devices, an additional connection aid may be utilized in this embodiment.
• Certain embodiments of the present invention may be comprised of plastic or another material which results in production costs which are relatively low compared to other manufacturing materials. Because of this, the attachment devices and bases may be disposed of after each use. Disposal of used devices and bases eliminates the time and expense necessary for sterilization between uses. It is not necessary that the present invention be comprised of plastic; any device or position indicator which can be manufactured for less expense than it costs to sterilize a used device is contemplated.
• The active or passive position indicating devices may be often more expensive, however. To account for such, according to certain embodiments of the present invention, the position indicating devices are manufactured separately from the attachment device. After use, they may be disposed of or easily removed and stored for re-use while the attachment device itself may be disposed.
• FIG. 14 shows a variation of the embodiment ofFIG. 13 in which fourextensions480a,480b,480c, and480d, are present on the attachment device. This provides for the use of a further position indicating device that may be registered into the coordinate system.
• The foregoing is provided for purposes of disclosure of various aspects and embodiments of the present invention. Changes, deletions, additions or and substitutions may be made to components, combinations, processes, and embodiments disclosed in this document without departing from the scope or spirit of the invention.

Claims (21)

1-40. (canceled)

41. A surgical navigation system comprising:

sensors adapted to sense position of a plurality of indicia attached by a reference frame to a patient's body part involved in surgery, the reference frame including a reference frame attachment member;

a computer adapted to receive information from the sensor about position of the indicia and generate information corresponding to position and location of the body part to which the indicia are attached;

a base plate configured to attach by way of one or more attachment devices to a bone portion of the body part involved in surgery, the base plate having a bottom portion including one or more openings for the one or more attachment devices, and further having a first mating portion configured to mate with a second mating portion of the reference frame attachment member;

wherein one of the first mating portion and second mating portion comprises a receiving slot and the other of the first mating portion and said second mating portion comprises a key portion configured to mate with the receiving slot in only a single predetermined orientation, and such that movement of the key portion within the slot is substantially limited to back and forth movement along a single sliding direction within the receiving slot;

wherein one of the first mating portion and second mating portion further comprises a connection aid protrusion configured to engage a retaining portion in the other of the first mating portion and second mating portion, the connection aid protrusion configured to secure the key portion in a single predetermined position in the receiving slot.

42. The system ofclaim 41, wherein the connection aid protrusion is a set screw and the retaining portion in the receiving slot is a conical shape opening in a bottom portion of the receiving slot.

43. The system ofclaim 41, wherein the connection aid protrusion is a biased member configured to engage a groove within the receiving slot.

44. The system ofclaim 43, further comprising an additional magnetic connection aid to assist securing the reference frame attachment member within the receiving slot.

45. The system ofclaim 41, wherein the attachment devices are bone screws.

46. The system ofclaim 41, wherein the reference frame comprises openings for receiving removable indicia.

47. The system ofclaim 41, wherein the second mating portion of the reference frame attachment member and reference frame are molded as a single piece unitary reference frame.

48. A method for performing a computer assisted surgical procedure comprising:

providing sensors adapted to sense position of a plurality of indicia attached by a reference frame to a patient's body part involved in surgery, the reference frame including a reference frame attachment member;

providing a computer adapted to receive information from the sensor about position of the indicia and generate information corresponding to position and location of the body part to which the indicia are attached;

providing a base plate configured to attach by way of one or more attachment devices to a bone portion of the body part involved in surgery, the base plate having a bottom portion including one or more openings for the one or more attachment devices, and further having a first mating portion configured to mate with a second mating portion of the reference frame attachment member, wherein one of the first mating portion and second mating portion comprises a receiving slot and the other of the first mating portion and second mating portion comprises a key portion configured to mate with the receiving slot in only a single predetermined orientation, and such that movement of the key portion within the slot is substantially limited to back and forth movement along a single sliding direction within the receiving slot, and wherein one of the first mating portion and second mating portion further comprising a connection aid protrusion configured to engage a retaining portion in the other of the first mating portion and second mating portion, the connection aid protrusion configured to secure the key portion in a single predetermined position in the receiving slot;

attaching the base plate to a bone portion of the body part involved in surgery;

sliding the key portion into the receiving slot to attach the plurality of indicia to the body part involved in surgery in a predetermined orientation and securing the key portion in a predetermined position by use of the connection aid protrusion; and

performing the computer assisted surgical procedure based at least in part on information obtained from the position of the plurality of indicia.

49. The method ofclaim 48, wherein the provided connection aid protrusion is a set screw and the retaining portion in the receiving slot is a conical shape opening in a bottom portion of the receiving slot, the method further comprising securing the key portion into the receiving slot by tightening the set screw.

50. The method ofclaim 48, wherein the provided connection aid protrusion is a biased member configured to engage a groove within the receiving slot.

51. The method ofclaim 50, wherein the provided key portion further comprises an additional magnetic connection aid to assist in securing the reference frame attachment member within the receiving slot.

52. The method ofclaim 48, wherein the provided attachment devices are bone screws.

53. The method ofclaim 48, wherein the provided reference frame comprises openings for receiving removable indicia, the method further comprising attaching the removable indicia to the reference frame.

54. The method ofclaim 48, wherein the provided second mating portion of the reference frame attachment member and reference frame are molded as a single piece unitary reference frame.

55. A surgical navigation device comprising:

a reference frame for attaching a plurality of indicia to a patient's body part involved in surgery, the reference frame including a reference frame attachment member;

a base plate configured to attach by way of one or more attachment devices to a bone portion of the body part involved in surgery, the base plate having a bottom portion including one or more openings for the one or more attachment devices, and further having a first mating portion configured to mate with a second mating portion of the reference frame attachment member, wherein one of the first mating portion and second mating portion comprises a receiving slot and the other of the first mating portion and second mating portion comprises a key portion configured to mate with the receiving slot in only a single predetermined orientation, and such that movement of the key portion within the slot is substantially limited to back and forth movement along a single sliding direction within the receiving slot;

wherein one of the first mating portion and second mating portion further comprises a connection aid protrusion configured to engage a retaining portion in the other of the first mating portion and second mating portion, the connection aid protrusion configured to secure the key portion in a single predetermined position in the receiving slot.

56. The device ofclaim 55, wherein the connection aid protrusion is a set screw and the retaining portion in the receiving slot is a conical shape opening in a bottom portion of the receiving slot.

57. The device ofclaim 55, wherein the attachment devices are bone screws.

58. The device ofclaim 55, wherein the second mating portion of the reference frame attachment member and reference frame are molded as a single piece unitary reference frame.

59. The device ofclaim 55, wherein the reference frame comprises openings for receiving removable indicia.

60. The device ofclaim 55, wherein the connection aid protrusion is a biased member configured to engage a groove within the receiving slot and further comprises a magnetic attraction aid to assist securing the reference frame attachment member within the receiving slot.

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