Device for use in computer-assisted surgery

Abstract

A device for computer-assisted surgery, the device comprising: a body; an optical element coupled to the body; a reference portion coupled to the main body; and a calibration element. The calibration element, alone or in combination, is a pointer tip or dimple.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of U.S. Nonprovisional Application Serial No. 18 / 047,553, filed October 18, 2022, the contents of which are incorporated herein in their entirety by this reference. TECHNICAL FIELD

[0003] Various exemplary embodiments disclosed herein relate generally to devices used in computer-assisted surgery (CAS). BACKGROUND

[0004] Registration and calibration processes in computer-assisted surgery often use multiple separate, discrete components. SUMMARY

[0005] A summary of various exemplary embodiments is presented below. Some simplifications and omissions can be made in the following summary in the interest of conciseness and lucidity, as these particular embodiments are intended to be illustrative only and not limiting in any way. Detailed descriptions of well-known devices, methods, procedures, components, and modes of operation are omitted so as not to unnecessarily obscure implementations of the embodiments. The detailed description should be taken in conjunction with the appended drawings to illustrate a number of exemplary embodiments.

[0006] Various embodiments relate to a device for computer-assisted surgery, the device comprising: a body; an optical element coupled to the body; a fiducial coupled to the body; and a calibration element.

[0007] Various embodiments are described in which the device comprises at least three optical elements.

[0008] Various embodiments are described in which the device comprises at least three fiducials.

[0009] Various embodiments are described in which the calibration element is a calibration dimple forming a recess on the body, the recess configured to receive a surgical instrument.

[0010] Various embodiments are described in which the calibration dimple further comprises a flat, cylindrical positioning dimple.

[0011] Various embodiments are described in which the calibration dimple further comprises a tapered positioning dimple.

[0012] Various embodiments are described in which the calibration element is a pointer tip extending from the body.

[0013] Various embodiments are described in which the pointer tip is adapted to receive a first pointer extension.

[0014] Various embodiments are described in which the pointer tip is removable from the body.

[0015] Various embodiments are described in which a pointer tip is attached to a pointer extension on the body.

[0016] Various embodiments are described in which the device further comprises a second pointer extension having a different length than the first pointer extension.

[0017] Various embodiments are described in which the device further comprises data representing dimensions of the device as manufactured.

[0018] Various embodiments are described in which the device further comprises a second pointer extension having a different length than the first pointer extension.

[0019] Various embodiments are described in which the calibration element is a calibration dimple forming a recess on the body, the recess configured to receive a surgical instrument.

[0020] Various embodiments are described in which the calibration dimple further comprises a flat cylindrical positioning dimple.

[0021] Various embodiments are described in which the calibration dimple further comprises a tapered positioning dimple.

[0022] Various embodiments are described in which the calibration element is a pointer tip mounted to the body.

[0023] Various embodiments are described in which the pointer tip is configured to receive a first pointer extension.

[0024] Various embodiments are described in which the pointer tip is removable from the body.

[0025] Various embodiments are described in which a pointer tip is attached to a pointer extension on the body.

[0026] Various embodiments are described in which the device further comprises a second pointer extension having a different length than the first pointer extension.

[0027] Various embodiments are described in which the device further comprises data representing dimensions of the device as manufactured. BRIEF DESCRIPTION OF DRAWINGS

[0028] For a better understanding of various exemplary embodiments, reference will be made to the accompanying drawings, which illustrate embodiments of a device for use in computer-assisted surgery:

[0029] Figure 1 is a front perspective view of a device for use in computer-assisted surgery;

[0030] is a front perspective view of a device for use in computer-assisted surgery; Figure 2 for Figure 1 A rear perspective view of the device;

[0031] Figure 3 for Figure 1 Exploded view of the device;

[0032] Figure 4 for Figure 1 A top view of the device;

[0033] Figure 5 for Figure 1 A right side view of the device;

[0034] Figure 6 for Figure 1 A bottom view of the device;

[0035] Figure 7 for Figure 1 A front view of the device;

[0036] Figure 8 for Figure 1 A rear view of the device;

[0037] Figure 9 for Figure 1 A bottom perspective view of the device;

[0038] Figure 10 is a top view of another device for use in computer-assisted surgery;

[0039] Figure 11 for Figure 10 A right side view of the device;

[0040] Figure 12 for Figure 10 A rear side view of the device;

[0041] Figure 13 for Figure 10 a top perspective view of the device; and

[0042] Figure 14 for Figure 10 A top perspective view of the device.

[0043] To facilitate understanding, the same reference numerals are used to designate elements having substantially the same or similar structures and / or substantially the same or similar functions. DETAILED DESCRIPTION

[0044] The description and drawings illustrate the principles of the application. It should be understood, however, that those skilled in the art could devise various arrangements that, although not explicitly described or shown herein, embody the principles of the application and are included within its scope. Furthermore, all examples shown and described herein are to be considered illustrative and not restrictive, and the scope of the application is to be determined not by the Examples, but by the appended claims. Additionally, the term, “or,” as used herein, refers to a non-exclusive or, unless otherwise indicated (e.g., “or else” or “or in the alternative”). Additionally, the various embodiments described herein are not necessarily mutually exclusive, as some embodiments can be combined with one or more other embodiments to form new embodiments.

[0045] Prior to a computer-assisted surgery (CAS) surgery taking place, the CAS system learns the positions and relationships of various elements, such as the patient (based on images of the patient that can be obtained through fluoroscopy, x-rays, CT, MRI, etc.) and medical instruments (e.g., surgical knives, saws, drills, bone screws, implants, robots, etc.). In order for the CAS to be able to position the patient, the patient typically has to attach a navigation array somewhere on their body, often to a bone for stability. These navigation arrays can be monitored by a positioning device or system such as a spatial camera, one of which is commercially available from Northern Digital Inc. The spatial camera typically uses an internal coordinate system that is defined by the camera, rather than by the position of the patient (the spatial camera can be placed in various positions relative to the patient). The navigation array can be an array of reflective spheres that reflect light back to the spatial camera (the spatial camera or other light source can emit infrared (IR) light, which is then sensed from the spheres using a stereo camera, enabling the spheres to be spatially located). Alternatively, the navigation array can be an LED (or other point light source) that emits light that is sensed by the spatial camera (no reflection is needed). Further, instead of a navigation array and spatial camera, the spatial system can use electromagnetic devices that emit signals that can be used to determine their spatial position using receivers or other known systems for device navigation.

[0046] Many surgical procedures use imaging devices (e.g., fluoroscope, x-ray, CT, MRI) that take pictures of the patient, which can be helpful to the surgeon during the surgical procedure. Before imaging takes place, fiducials such as radiopaque markers can be attached to the patient. These fiducials form relatively distinct landmarks in the image, which can be used later to transform between the patient coordinate system and the camera coordinate system. The imaging device typically has its own internal coordinate system, which is defined by the imaging device itself, and has no fixed relationship to the coordinate system of the spatial camera (the camera can typically be placed in various positions relative to the imaging device).

[0047] A navigation array can also be attached to the surgical instrument, so that the CAS system can track the spatial position of the instrument. The spatial camera tracks the position of the navigation array, and thus the position of the surgical instrument in the coordinate system of the camera. But knowing the position of the surgical instrument in the camera coordinate system is only part of the picture for the spatial camera. It is helpful for the CAS system to be able to know the position of the instrument relative to the patient.

[0048] To accomplish this, various processes are used when the CAS system is set up before the surgical procedure. One process is used to allow the CAS system to coordinate between the spatial camera coordinate system, the patient coordinate system, and the image device coordinate system - this process is often referred to as registration. In registration, the CAS system determines the relationship between the various coordinate systems. That is, if the CAS system knows the spatial relationship between the navigation array attached to the patient (which is monitored by the spatial camera) and the fiducials attached to the patient (which appear in the images created by the imaging device), then the CAS system can mathematically / spatially correlate that information so that the images of the patient can be properly aligned or overlaid onto the patient in 3D space.

[0049] The CAS system also needs to know the spatial relationship between the navigation array and the tip of the surgical instrument, because the tip is the part that can change the patient's tissue. Another process is used to allow the CAS to obtain this relationship - this is often referred to as calibration. The term calibration can be used to describe the scenario where the CAS system learns the distance or geometric relationship between the array and the tool tip, for example when the CAS system does not know the exact geometry of the surgical instrument. If the CAS system allows the use of a saw blade of any length, then the user can need to calibrate the tip of the saw blade. To accomplish this, the CAS system can use a "pointer", which is another surgical instrument that has a pointed tip, a shaft, and a navigation array attached to the shaft, so that the tip is at a fixed position relative to the array. The CAS system is programmed to know this fixed geometric relationship, and thus can use the pointer to obtain a geometric point in 3D space, such as the tip of the saw blade (other points on the saw blade can be used, such as a dimple on the saw blade that has a known relationship to the tip of the saw blade), and then can infer the relationship between the tip of the saw blade and the navigation array.

[0050] In some scenarios, the CAS system may require that only saw blades of a certain length be used (and may know the length and geometry of the intended saw blade (sometimes referred to as a pre-calibrated instrument)). In such cases, the CAS system may perform an operation commonly referred to as a calibration verification. During a calibration verification, the user touches the tip of a pointer to the tip of a saw blade (or dimple as described above), and the CAS system determines whether the tip of the pointer is in the position in space where it expects the tip (or dimple) of the saw blade to be located.

[0051] These processes coordinate the spatial relationships between the various elements of the CAS system. This allows the CAS system to understand the position of the saw blade tip relative to the patient, not just relative to the camera system, and the image can be correlated with the patient's actual position, providing the surgeon with information not available to the eye, such as the location of bones or even nerves that are obscured by the patient's skin. Conventional systems typically use separate devices for the navigation array, fiducials, and pointers. Such systems create additional inaccuracies and complications during the surgical procedure, for example, when multiple elements need to be grasped during various stages of the surgical process.

[0052] An exemplary embodiment of a device for use in computer-assisted surgery will be described that combines some or all of a reflective sphere, a radiopaque fiducial, a pointer, and a dimple into a single device. This reduces the number of devices required for registration and / or calibration, and thus can streamline these processes and simplify surgical workflows. The pointer and dimple may be referred to individually or in combination as calibration elements.

[0053] Figures 1 to 9 An exemplary embodiment of an apparatus for use in computer-assisted surgery is shown.

[0054] Figures 1 to 9 The device 10 is shown comprising a body 12. The body 12 has four posts 14, wherein each respective post supports a reflective sphere 16. The reflective spheres 16 are optically visible to the camera. Thus, the reflective spheres provide an optical element.

[0055] Although the posts 14 are shown as elongated tapered cylinders, they can be of any shape and have different lengths from one another. The posts 14 can simply be mounting locations on the body 12.

[0056] The posts 14 are injection molded with the body 12. Although shown as being integrally molded with the body 12, the posts 14 can be separate components that are mounted by any method, including attachment by snap-fit, threaded, separate fasteners, or clamp features. Although the posts 14 are shown as elongated tapered cylinders, they can be of any shape. Moreover, different posts 14 can have different lengths from one another or the same length. In this embodiment, the posts 14 have the same length so that the reflective spheres 16 are in a horizontal plane. The reflective spheres 16 form an optically visible array. The reflective spheres 16 can be attached to the posts 14 by snap-fit ​​features 17, but other attachment mechanisms and methods can also be used. The reflective spheres 16 provide an optical element. Although the reflective spheres 16 are used as an example of an optical element, optical elements can also take other shapes. The reflective spheres 16 are an example of a passive optical element. In other embodiments, the optical elements may instead be active optical elements, which may include precise light sources, such as light emitting diodes (LEDs), that emit light that is captured by the camera and then used to determine the position of the optical element. With knowledge of the spatial position of the optical element, the CAS system can then use a priori knowledge of the spatial relationship of various features of the device 10 to each other to determine the spatial position of those features, such as the fiducial 18, which will be described in more detail below.

[0057] The posts 14 each support a corresponding optical reflective sphere 16. The reflective spheres 16 form an optically visible array. These are shown as being connected to the ends of the posts 14 by snap features. The purpose of the corresponding spheres 16 is to be visible to a positioning device such as a space camera. The reference portion 18 provides a mark that appears on an image taken by an imaging device (such as a fluoroscope or X-ray). The mark can be used to determine positional information relative to the patient. In addition, the device may include pits that can be used to calibrate instruments as described above. The device 10 holds the reflective spheres 16, the reference portion 18, the pointer extension column 22 with the pointer tip 23, and the pits 28, 29 in a fixed spatial relationship. The CAS system will be programmed to understand this fixed geometric relationship and can therefore use this information beneficially during alignment and / or calibration.

[0058] Body 12 is shown with four reflective spheres (or optical elements). However, it should be noted that more than four spheres can be used, and three spheres are generally sufficient. Reflective spheres 16 can be optical elements having other shapes (e.g., having a cube, an elongated tip, or a paddle shape). The reflectivity of the optical element can be partially reflective or fully reflective. Reflectivity can be achieved during manufacturing using paint, coating, impregnation, or other techniques. Furthermore, the optical element can be molded as an integral part of column 14.

[0059] The reference portion 18 is typically molded into the body 12, but can also be attached to the body 12 using a snap fit or fasteners. The reference portion 18 is radiopaque and is visible, for example, during a C-arm X-ray (CBCT) scan of the patient when the device 10 is placed on or attached to the patient. The reference portion 18 can be a separate component that is mounted by any method, including attachment by a snap fit, a threaded fit, a separate fastener, a clamp feature, or an overmold. Radiopaque is intended to mean that the reference portion 18 can be detected from the surrounding material by X-ray (for other imaging devices, the reference portion can be any other material that is clearly shown in the image taken). Thus, the reference portion 18 can be partially transparent and partially translucent to X-rays so that after an X-ray scan of the patient is performed with the device 10 placed on or attached to the patient, the position of the reference portion 18 can be obtained by processing the X-ray image.

[0060] Because the CAS system knows the spatial relationship of the reflective sphere 16, fiducial 18, pointer tip 23, and dimples 28, 29, the CAS system can then calculate the position and orientation of the fiducial 18, pointer tip 23, and dimples 28, 29. The fixed relationship between the reflective sphere 16 and the fiducial 18 can be used in the registration process described above.

[0061] The device 10 also includes a pointer extension post 22. The pointer extension post 22 can be formed integrally with the body 12 or can be attached to the body 12. The CAS system needs to understand the spatial relationship of the features of the device relative to the tip 27. Therefore, the CAS system must understand whether the pointer extension has been attached to the device 10. This understanding can be achieved via a configuration GUI screen, or it can be achieved by a machine vision system that evaluates an image of the device 10 and determines whether the pointer extension is attached based on image analysis. Alternatively, the device 10 may include electronic devices such as RFID sensors, proximity sensors, to determine whether the pointer extension has been attached and what length of pointer extension may have been attached. The device 10 may include wireless communications to transmit this information to the CAS system.

[0062] like Figure 1 As shown, a pointer extension 26 terminating in a pointer tip 27 can be attached to the device 10 via a pointer extension post 22. The pointer extension 26 can be any length required to perform the desired calibration. The pointer extension post 22 can be integral with the body 12 or can be one or more separate components that are mounted by any method, including attachment by snap-fit ​​engagement, threaded engagement, separate fasteners, or a clamping feature. The pointer extension post 22 can have any length and cross-section and can be located at various locations on the body 12, including, for example, any of the arrow positions A, B, and C (as shown in FIG. Figure 10). The pointer extension post 22 terminates in a tip 23. When the device 10 is used without the pointer extension 26, this allows for a relatively short pointer so that it does not interfere with imaging. When the device 10 is used with the pointer extension 26, this allows for a longer pointer, which may be more convenient for the surgeon during registration, for example, when touching the tip 27 to a surgical instrument. The pointer extension 26 can be mounted to the pointer extension post 22 by any method, including attachment by a snap fit, a threaded fit, a separate fastener, or a clamp feature. The pointer extension 26 can have any shape or size and any length. Multiple pointer extensions 26 can be provided with different lengths. In this case, the CAS system will be configured with the size of the extension and provisions will be provided for informing the CAS system which extension is being used. A variety of pointer tip shapes and types can be used.

[0063] The body 12 forms a conical recess 28 that terminates at a point and a cylindrical recess 29 that terminates at a plane. The conical recess 28 provides a point for complementary surgical instrument features to engage during calibration (or calibration verification). The cylindrical recess 29 provides a flat, planar surface for complementary instrument features to engage during calibration (or calibration verification). For example, the end of a medical instrument with its own navigation array can contact the conical recess 28 or the flat recess 29. The position and orientation of the conical recess 28 and the flat recess 29 relative to the reflective sphere 16, the reference portion 18, and the pointer tip 27 are known, and therefore the CAS system can use this known relationship in the calibration (or calibration verification) of the surgical instrument.

[0064] A plurality of mounting holes 34 may be provided for attachment to an arm or other component of a medical device. The device 10 may be attached to the patient using double-sided tape or other securing methods.

[0065] Ears 35 are shown on the sides of the body 12 to aid in operating the device 10. Although the ears 35 are shown as flat structures extending away from the sides of the body 12, the ears 35 may take other shapes and sizes.

[0066] The reflective sphere 16, fiducial 18, pointer tip 27 (possibly extended by a pointer extension) and / or dimples 28, 29 are fixedly held in relative position to one another by the body 12. The system 10 accordingly provides a multi-feature device 10. Any combination of these features may be used.

[0067] The body 12 can be made of injection molded plastic, preferably at least partially of a radiolucent material such as, for example, injection molded plastic or a machined polymer. The posts 14 can be integral with the body 12 or separate from the body 12 and also made of injection molded plastic, such as a machined polymer. If the posts 14 are manufactured separately from the body 12, they can be made of a metal such as stainless steel, titanium, aluminum, etc. The reflective sphere 16 can be injection molded plastic or machined plastic with a reflective coating, paint, or tape. The pointer extension post 22 can be manufactured integrally with the body 12 or separate from the body 12 and can also be made of, for example, injection molded plastic, machined plastic, stainless steel, titanium, etc. The pointer extension 26 can be made of injection molded plastic, machined plastic, stainless steel, titanium, etc. The reference portion 18 can be made of stainless steel, titanium, ceramic, and / or tantalum, or any other radiopaque material.

[0068] The CAS system can use manufacturing specifications for the positions of the reflective sphere 16, the reference 18, the pointer tip 27, and the conical and flat recesses 28 and 29. However, due to manufacturing tolerances, the actual as-manufactured positions of the reflective sphere 16, the reference 18, the pointer tip 27, the conical and flat recesses 28, and the flat recesses 29 will vary. Therefore, after manufacturing, the device 10 can be accurately measured to determine the actual positions of the reflective sphere 16, the reference 18, the pointer extension 22, the tip 27, the flat recesses 29, and the conical and flat recesses 28. The CAS system can use this as-manufactured measurement data rather than the manufacturing specifications to achieve improved accuracy.

[0069] Figures 10 to 14 Another embodiment of an apparatus for use in computer-assisted surgery is shown.

[0070] Figures 10 to 14 The device 110 is shown as including a body 112. The body 112 has four posts 114, wherein each respective post supports a reflective sphere 116. The reflective sphere 116 is optically visible to the space camera. Thus, the reflective sphere 116 provides an optical element. As described above, the number of optical elements may vary, and the type of optical element may vary.

[0071] Although the posts 114 are shown as elongated tapered cylinders, they can be of any shape and have different lengths from one another. The posts 114 can simply be mounting locations on the body 112.

[0072] The posts are injection molded with the body 112. Although shown as being integrally molded with the posts 114, the posts 114 can be a separate component that is mounted by any method, including attachment by snap-fit, threaded, separate fasteners, or a clamping feature. If the posts 114 are manufactured separately from the body 112, they can be made of a metal such as stainless steel, titanium, aluminum, etc. Although the posts 114 are shown as elongated tapered cylinders, they can be of any shape and have different lengths from one another. The posts 114 can simply be a mounting location on the body 112.

[0073] The columns 114 each support a respective optical reflective sphere 116. The reflective spheres 116 are optically visible to a space camera.

[0074] The reflective spheres 116 form an optically visible array. The reflective spheres 116 are shown as being threadedly connected to the ends of the respective posts 114, but other attachment mechanisms and methods may also be used. As described above, the purpose of the respective reflective spheres 116 is to be visible to a camera using visible light or infrared light. As described above, the reflective spheres 116 may alternatively be replaced by LEDs. The purpose of the reflective spheres 116 is to be visible to a positioning device such as a space camera to determine the position of the optical array, and the CAS system can then determine the position of the various features of the device (as an alternative, the CAS system and the camera system can be a single computing device, or they can be separate devices that communicate with each other). Any or all of the different posts 114 may have different lengths from each other or the same length. Figure 1 The embodiment shown shows the posts 14 lying in a common plane, ie the posts 14 have the same length so that they lie substantially in one plane. Figure 11 The embodiment shows pillars of different heights that position the spheres so that they do not lie in a common plane.

[0075] A plurality of fiducials 118 are also mounted to the body 112. These are attached to the body using snap-fit ​​connections, fasteners, or may be molded into the body 112. The fiducials 118 are radiopaque and are visible during a C-arm X-ray scan of the body 112 and the patient. The fiducials 118 may be separate components that are mounted by any method, including attachment by snap-fit ​​connections, threaded connections, separate fasteners, or a clamping feature. The fiducials 118 may be made of stainless steel, titanium, ceramic, and / or tantalum, or any other radiopaque material.

[0076] The main body 112 also supports a pointer extension 122 having a pointer tip 123. The pointer extension 122 can be integral with the main body 112 or can be one or more separate components mounted by any method, including snap-fit, threaded, separate fasteners, or a collet feature. The pointer extension 122 can have any length and cross-section and can be located at various locations on the main body 112, including, for example, any of the arrow positions A, B, and C. Different pointer extensions 126 can have different lengths, each terminating in a tip 127. This allows for a relatively short pointer extension 122 that does not obstruct imaging, while supporting a longer pointer for accuracy checks. The pointer extension 126 can be mounted by any method, including snap-fit, threaded, separate fasteners, or a collet feature. The pointer extension 122 can support a measurement extension 126 that snaps, threads, attaches via a fastener, or the like to the pointer extension 122. If a pointer extension 126 is used in the procedure, the user can specify to the CAS system that a pointer extension is being used (in which case only one length of extension is provided), or the user can specify to the CAS system which pointer extension is being used (in which case multiple lengths of extension are available) using various methods (i.e., indicating the length and position of the measuring tip). One method is for the user to input information about the measuring tip 126 being used via a graphical user interface (GUI). Another method is to place the tip 127 of the measuring tip 126 in a well with a known position on another instrument or navigation array. In addition, machine vision recognition or other techniques as described above can be utilized.

[0077] Body 112 forms a conical recess 128 and / or a cylindrical or flat recess 129. Conical recess 128 terminates at a point. The cylindrical recess terminates at a flat surface. The point and / or flat surface provide a surface for complementary instrument features to engage during calibration. Recesses 128 and 129 have the same functionality as described above with respect to body 112.

[0078] The rear side or the other side of the body 112 may be partially hollow and supported by the web 130 .

[0079] A plurality of mounting holes 134 may be provided on the body 112 for attachment to an arm or other component of a medical device. The system 110 may be attached to the patient using double-sided tape or other securing methods.

[0080] Ears 135 are shown on the sides of the body 112 to aid in operating the device 110. The body 132 is shown attached to the patient using double-sided tape or other adhesive method.

[0081] The reflective sphere 116, the reference portion 118, and the extension post 122 are fixedly held in position relative to one another by the body 112. The system 110 accordingly provides a multi-feature device. Any of these features may be used in any combination.

[0082] Although each of the various embodiments is described above in terms of its structural arrangement, it should be understood that the present invention also encompasses associated methods of using the above-described embodiments.

[0083] Although various exemplary embodiments have been described in detail with particular reference to certain exemplary aspects, it will be understood that the invention is capable of other embodiments and that its details are capable of modification in various obvious respects. It will be apparent to those skilled in the art that various variations and modifications, as well as combinations of the various embodiments, can be implemented while remaining within the spirit and scope of the invention. Accordingly, the foregoing disclosure, description, and drawings are for illustrative purposes only and do not in any way limit the invention, which is defined solely by the claims.

Claims

1. An apparatus for computer-assisted surgery, comprising: main body; an optical element coupled to the body; a reference portion coupled to the main body; as well as Calibration element.

2. The device of claim 1, wherein the device comprises at least three optical elements. The device of claim 1 , wherein the device comprises at least three reference portions.

4. The device of claim 1, wherein the calibration element is a calibration dimple forming a recess on the body, the recess configured to receive a surgical instrument.

5. The device of claim 4, wherein the calibration pit further comprises a flat cylindrical positioning pit.

6. The device of claim 4, wherein the calibration pit further comprises a conical positioning pit.

7. The device of claim 1, wherein the calibration element is a pointer tip extending from the body.

8. The device of claim 7, wherein the pointer tip is adapted to receive a first pointer extension.

9. The device of claim 7, wherein the pointer tip is removable from the body.

10. The device of claim 7, wherein the pointer tip is attached to a pointer extension on the body.

11. A system comprising the apparatus of claim 8 and further comprising a second pointer extension having a different length than the first pointer extension.

12. A system comprising the apparatus of claim 1 and further comprising data representing as-manufactured dimensions of the apparatus.

13. An apparatus for computer-assisted surgery, comprising: main body; an optical element, wherein the optical element is configured to be visible to a positioning camera; as well as a reference portion, wherein the reference portion is radiopaque; as well as Calibration components, wherein the optical element, the reference portion, the body and the calibration element are held in fixed positions relative to each other.

14. The device of claim 13, wherein the calibration element is a calibration dimple forming a recess on the body, the recess configured to receive a surgical instrument.

15. The apparatus of claim 14, wherein the calibration recess further comprises a flat cylindrical positioning recess.

16. The apparatus of claim 14, wherein the calibration pit further comprises a tapered positioning pit.

17. The device of claim 13, wherein the calibration element is a pointer tip mounted to the body.

18. The apparatus of claim 17, wherein the pointer tip is configured to receive a first pointer extension.

19. The device of claim 17, wherein the pointer tip is removable from the body.

20. The device of claim 17, wherein the pointer tip is attached to a pointer extension on the body.

21. A system comprising the apparatus of claim 17 and further comprising a second pointer extension having a different length than the pointer extension.

22. A system comprising the apparatus of claim 13 and further comprising data representing as-manufactured dimensions of the apparatus.

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