Tracker for surgical instrument

Abstract

An optical tracker for use with a handheld surgical instrument, the optical tracker comprising a tracker frame including a mounting body, the tracker frame defining an instrument engagement hole having a longitudinal axis, and a biasing body projecting proximally from the mounting body. The instrument engagement hole is configured to receive a proximal region of a surgical instrument such that the longitudinal axis of the tracker is aligned with an axis of the surgical instrument. Three radially equidistant segments are defined about the longitudinal axis and collectively encircle the longitudinal axis. The tracker further comprises at least six markers arranged to form at least two arrays, coupled to the tracker frame and positioned such that at least one marker is positioned within each radial segment. A portion of each array is coupled to the biasing body and positioned proximally of the mounting body.

Description

[0001] Related applications

[0002] This application claims priority and benefit to U.S. Provisional Patent Application No. 62 / 906,629, filed September 26, 2019, the entire contents of which are incorporated herein by reference. Background Technology

[0003] During surgery, surgeons frequently use instruments that must be inserted into the patient's body. Once inside, the surgeon cannot see the end of the instrument. In such cases, to assist the surgeon in navigating the instrument, a surgical navigation system can be used to track it and provide visual or auditory guidance.

[0004] One method for tracking the device is to attach a tracker to it. A camera in the operating room senses the tracker and generates data to calculate the tracker's position and, consequently, the device's position. Typically, the patient is also tracked, which allows the device's position relative to the patient to be calculated.

[0005] Further improvements to the tracker are needed. Attached Figure Description

[0006] The advantages of this disclosure will be readily understood when considered in conjunction with the accompanying drawings, as these advantages can be better understood by referring to the following detailed description.

[0007] Figure 1 This is an exemplary surgical kit illustrating a surgical navigation system.

[0008] Figure 2 This is an environmental view of a first embodiment of the tracker and the surgical instruments held by the user.

[0009] Figure 3 yes Figure 2 A perspective view of a tracker having a tracker frame attached to a surgical instrument and three radial segments arranged around the longitudinal axis of the tracker.

[0010] Figure 4 yes Figure 2 Another perspective view of the tracker, in which the tracker frame is shown as being attached to a surgical instrument.

[0011] Figure 5 yes Figure 2 The side view of the tracker shows the tetrahedral shape of the tracker frame and the two lines of sight between the tracker and the surgical instruments.

[0012] Figure 6 yes Figure 2 A top view of the tracker and surgical instruments, showing the marker array and areas.

[0013] Figure 7 yes Figure 2 The proximal view of the tracker and surgical instruments shows the emission patterns of three radial segments, a first region and a second region, and several markers.

[0014] Figure 8 yes Figure 2 A perspective view of the tracker, showing the tetrahedral shape of the tracker frame as well as the marker array and regions.

[0015] Figure 9 yes Figure 2 A perspective view of the tracker, showing the instrument engagement hole and the relief area.

[0016] Figure 10 yes Figure 2 The distal perspective view of the tracker shows the instrument engagement hole and retaining assembly.

[0017] Figure 11 yes Figure 2 An exploded view of the tracker, showing the interior of the tracker frame and the marker array.

[0018] Figure 12 This is a perspective view showing another embodiment of a tracker attached to a surgical instrument.

[0019] Figure 13 yes Figure 12 Another perspective of the tracker.

[0020] Figure 14 yes Figure 12 A side view of the tracker.

[0021] Figure 15 yes Figure 12 A top view of the tracker.

[0022] Figure 16 yes Figure 12 A close-up view of the tracker.

[0023] Figure 17 This is a perspective view showing yet another embodiment of a tracker attached to a surgical instrument.

[0024] Figure 18 yes Figure 17 Another perspective of the tracker.

[0025] Figure 19 yes Figure 17 A side view of the tracker.

[0026] Figure 20 yes Figure 17is a top view of the tracker.

[0027] Figure 21 is Figure 17 is a proximal view of the tracker.

[0028] Figure 22 is a perspective view of another embodiment of the tracker.

[0029] Figure 23 is Figure 22 is a perspective view of the tracker.

[0030] Figure 24 is a proximal view of the tracker. Figure 22

[0031] Figure 25 is a side view of the tracker coupled to a surgical instrument. Figure 22

[0032] Figure 26 is a perspective view of the tracker and a surgical navigation cart. DETAILED DESCRIPTION

[0033] Referring to the drawings wherein identical numerals indicate the same elements in the several views, the present disclosure includes a tracker 100 for a handheld surgical instrument 34, a surgical navigation system 12, and a method for operating the tracker 100. Figure 1 An exemplary surgical system 10 is shown that can include a surgical navigation system 12 for tracking one or more surgical instrument assemblies 30 that include a surgical instrument 34 and a tracker 100 to assist a medical professional, such as a surgeon, in performing a medical procedure.

[0034] ​​The surgical navigation system 12 can include a navigation interface that includes one or more display units 14 and one or more user input terminals 16. The display units 14 of the surgical navigation system 12 can be configured to display various prompts or data entry boxes. For example, the display units 14 can be configured to display a text box or prompt that allows the surgeon to manually enter or select the type of surgical procedure to be performed. The display units 14 can also be configured to display patient data, such as preoperative images or scans. As noted above, the preoperative images can be based on MRI scans, radiological scans, or computed tomography (CT) scans of the patient’s anatomy. The preoperative images can be uploaded to the surgical navigation system 12 and displayed on the display units 14. The display units 14 can be further configured to display a surgical plan for the medical procedure overlaid on the patient data or images. The surgical plan can include a surgical path for performing the medical procedure or a planned trajectory or orientation of a medical instrument during the medical procedure. The surgical plan can also include a location and / or orientation of an implant or medical device to be inserted during the medical procedure overlaid on the patient data or images. It is contemplated that the surgical navigation system 12 can include display units 14 configured to display and / or project a holographic image of the surgical path for performing the medical procedure or the planned trajectory or orientation of a medical instrument during the medical procedure. This can include projecting the surgical path onto the patient or other surface in the operating room. It can also include projecting the surgical path onto a head unit (such as the lenses, visor, or glasses of a head unit) worn by the surgeon. An exemplary configuration of a surgical navigation system 12 that includes a display unit worn by a surgeon to display a target trajectory and / or target location is disclosed in International Patent Application No. PCT / IB2018 / 053130, the entire contents of which are hereby incorporated by reference in their entirety.

[0035] The user input terminals 16 can be configured to allow the surgeon to input or key in patient data or modify the surgical plan. The patient data can include patient images, such as preoperative images of the patient’s anatomy. These images can be based on MRI scans, radiological scans, or computed tomography (CT) scans of the patient’s anatomy. The patient data can also include additional information related to the type of medical procedure being performed, anatomical features of the patient, the patient’s specific medical condition, and / or operational settings for the surgical navigation setup. For example, in performing a spinal surgery, the surgeon can input information related to the specific vertebrae on which the medical procedure is being performed via the user input terminals 16. The surgeon can also input various anatomical dimensions related to the size and shape of the vertebrae and / or medical devices or implants to be inserted during the medical procedure. The user input terminals 16 can also be configured to allow the surgeon to select, edit, or manipulate the patient data. For example, the surgeon can identify and / or select anatomical features from the patient data. This can include selecting a surgical site, such as selecting a vertebra and / or a particular region on the vertebra on which the medical procedure is to be performed.

[0036] The surgical navigation system 12 can further include a navigation processor 18. The navigation processor 18 can be located on a personal computer or laptop computer. The navigation processor 18 can be in communication with the user input 16, the display unit 14, a central processing unit (CPU) and / or other processors, a memory (not shown), and a storage (not shown). The navigation processor 18 can further include software and / or operating instructions related to the operation of the surgical navigation system 12 and to implementing the various routines and / or methods disclosed herein. The software and / or operating instructions can include a planning system configured to find an accurate position and / or angular alignment of the surgical instrument 34 relative to the patient 20. The navigation processor 18 can be in direct or indirect wired or wireless communication with the surgical instrument assembly 30.

[0037] The surgical navigation system 12 can further include a tracking unit 22 or localizer that includes one or more sensors 24. The sensors can include a video camera, such as a CCD video camera, a CMOS video camera, and / or an optical image camera, a magnetic sensor, a radio frequency sensor, or any other sensor suitable for detecting and / or sensing the position of the tracking device 100 of the surgical instrument assembly 30. The localizer 22 is capable of detecting radiation or light from a plurality of markers 128 and is capable of producing a localizer signal representative of the detected radiation or light. An exemplary surgical navigation system 12 can be configured to use a tracker 100 having a fixed spatial relationship between the markers 128. Descriptions of various suitable localizers that can be used are found in U.S. Patent No. 10,531,926 B2, which is incorporated by reference herein in its entirety.

[0038] The processor 18 can be capable of receiving the localizer signal. The processor 18 can further be capable of registering and tracking the tracker 100 based on the received sensor signal. Based on the localizer signal, the processor is further capable of calculating the orientation and / or position of the tracker 100 relative to the localizer 22. The processor 18 can have access to information about the spatial relationship. In this case, a three-dimensional image captured by a stereo camera will not be required, and the camera can include only a single two-dimensional image sensor.

[0039] The processor 18 can further be configured to receive and / or store information of the patient body 20 (e.g., a computed tomography scan of the patient body and / or a tracking signal). The processor 18 can then calculate the position and / or orientation of the surgical instrument 34 relative to the patient body 20. The processor 18 can be configured to generate a visual or audible signal indicative of the tracking of the surgical instrument 34. The visual signal can be displayed on a display unit. The processor 18 can be part of a computing device separate from the localizer. Alternatively, the localizer can include the processor.

[0040] Figure 2A perspective view of the first configuration of tracker 100 and surgical instrument 34 is shown. Surgical instrument 34 has a proximal end 36 and a distal end 38 spaced apart along an instrument axis 40. In many cases, such as shown in Figure 2 surgical instrument 34 transmits mechanical energy from a source (e.g., a motor or an ultrasonic transducer) disposed near proximal end 36 along instrument axis 40 to an accessory 42 coupled to distal end 38 of surgical instrument 34. One example of such an arrangement is shown in Figures 2-7 surgical instrument 34 is shown as a high-speed drill. Here, surgical instrument 34 can include a housing 46, a motor (not shown) disposed in housing 46, a flexible power cable 48 that emerges from housing 46 in a proximal region, and an attachment interface 50 located near distal end 38 of surgical instrument 34. Exemplary surgical instruments can be found in U.S. Patent No. 8,597,316 and U.S. Patent Publication No. 2017 / 0319217, which are incorporated by reference herein in their entireties.

[0041] Tracker 100 can operate with surgical instrument 34 and a surgical navigation system to determine the position and / or orientation of surgical instrument 34 within the operating room. In order to accurately determine the position of surgical instrument 34, tracker 100 is coupled to surgical instrument 34 and configured to prevent relative motion between them during surgery. In addition, tracker 100 should be coupled to surgical instrument 34 so as to maximize the visibility of tracker 100 by the surgical navigation system.

[0042] While surgical instrument 34 is shown as a high-speed drill in all of the figures, tracker 100 can be used with surgical instruments 34 other than a high-speed drill. For example, tracker 100 can be coupled to a handheld ultrasonic ablation tool or a biopsy needle or a portion of a robotic device (e.g., a robotic end effector). Likewise, tracker 100 can be adapted to be coupled to other surgical instruments (not shown), such as a handheld drill, saw, or burr. Still further, likewise, accessory 42 coupled to distal end 38 of surgical instrument 34 is shown in Figure 2 as an angled accessory that drives a rotary tool on an axis (not shown) different from instrument axis 40. For example, the accessory can be straight, angled 15 degrees, 45 degrees, etc.; the accessory can have various lengths, such as 30 mm, 50 mm, etc.

[0043] The quality of surgical instruments can be small and the structure can be weak. When attaching a heavy tracker to such a handheld surgical instrument 34, the tracker 100 displaces the center of mass, which can be annoying (e.g., due to the torque exerted on the holding hand). Furthermore, the surgical instrument 34 can be deformed (elastically or plastically) or even damaged due to the weight of the attached heavy tracker 100. The tracker 100 shown throughout the drawings generally has a reduced weight. Thus, the above-mentioned drawbacks are reduced or eliminated. The handheld surgical instrument 34 can be less tiring to hold by hand and is less likely to deform due to the weight of the tracker 100.

[0044] To facilitate the detachable coupling of the tracker 100 to the surgical instrument 34, the tracker 100 includes a tracker frame 102 that includes a mounting body 104 defining an instrument engagement hole 106 extending therethrough along a longitudinal axis 108. As will be discussed in greater detail below, the instrument engagement hole 106 is configured to receive the surgical instrument 34 such that the instrument axis 40 is aligned with the longitudinal axis 108 of the mounting body 104. In other words, the mounting body 104 can be concentric with the body of the surgical instrument 34. The tracker frame 102 can further include a biasing body 110 supported on the mounting body 104 and extending proximally and generally parallel to the longitudinal axis 108. The biasing body 110 can define a cutout 118 extending therethrough along a direction generally perpendicular to the longitudinal axis 108. The tracker frame 102 can comprise metal (e.g., titanium), polymer (e.g., nylon), or epoxy (e.g., aromatic epoxy amine resin). The tracker frame can comprise any other suitable material for use in a medical environment to provide the necessary rigid structure for the tracker 100. The tracker frame can be composed of a polymer and can be manufactured using additive manufacturing techniques.

[0045] Alternatively, the tracker 100 and the surgical instrument 34 can be mechanically connected for single use. The tracker 100 and the surgical instrument 34 can be integrally formed (e.g., during injection molding). For example, the tracker 100 can be integrally formed with the handle of the surgical instrument 34. With the tracker 100 attached to the instrument 34, the surgeon can immediately use the surgical instrument 34 without having to attach the tracker 100 thereto. The surgeon can discard the tracker 100 and the surgical instrument 34 after single use.

[0046] To track the position and orientation of the surgical instrument 34, the tracker 100 includes a plurality of markers 128 that are selectively arranged into one or more arrays 162, 164, 166 and coupled to the tracker frame 102. The tracker frame 102 can have three sides each aligned with a respective radial segment 112, 114, 116, each oriented about 120 degrees from the other sides. The plurality of arrays 162, 164, 166 are positioned such that each array 162, 164, 166 is arranged on one of the three sides and oriented in a different direction from the other arrays 162, 164, 166. The first array 162 is arranged on a side aligned with the first radial segment 112, the second array 164 is arranged on a side aligned with the second radial segment 114, and the third array 166 is arranged on a side aligned with the third radial segment 116. The side aligned with the first radial segment 112 is positioned on the offset body 110. The offset body 110 and the mounting body 104 cooperate to define two sides aligned with the second radial segment 114 and the third radial segment 116. Other numbers of arrays and / or other numbers of sides are also contemplated.

[0047] While each side has a particular radial arrangement, the angles of the sides can be configured such that they are tilted toward a common apex such that they will converge at a point beyond the proximal end 152 of the offset body 110. The offset body 110 and / or the first array 162 can define a tilt axis such that the offset body 110 extends from the mounting body 104 along the tilt axis. The tilt axis can also define three tilt segments (similar to the radial segments not discussed herein) that are equidistant about the tilt axis. Here, at least six markers 128 are arranged radially about the longitudinal axis and at least three markers 128 are arranged radially about the tilt axis and on the offset body 110 such that one of the at least three markers 128 is in each of the three tilt segments and spaced apart from the longitudinal axis 108 to provide clearance for the flexible power cable 48.

[0048] A method for improving the accuracy of a surgical navigation system includes maximizing the visibility of the tracker 100. Improving the accuracy of the tracker 100 can be improved in several ways, for example, the size of the tracker 100 can be increased, the number of markers 128 can be increased, the brightness of the markers 128 can be increased, etc. However, these methods can result in increasing the size and / or mass of the tracker 100, for example, increasing the brightness of the markers 128 will come at the expense of power consumption, thereby shortening the duration that the tracker 100 can be operated, or heavier batteries with increased capacity.

[0049] The visibility of the tracker 100 can also be improved by the strategic arrangement of the markers 128 on the tracker frame 102. In Figure 3 andFigure 7 As best shown, three radial segments 112, 114, and 116 are defined around the longitudinal axis 108. Each radial segment 112, 114, and 116 has a volume corresponding to a respective portion of the tracker 100 and the arrangement of components of the tracker 100. As shown, the first radial segment 112 may generally be defined to be aligned with the bias body 110. The second radial segment 114 and the third radial segment 116 are aligned across the longitudinal axis 108 in a manner opposite to the bias body 110. For example, as Figure 3 As shown, each radial segment 112, 114, 116 extends 120 degrees around the periphery of tracker 100. Radial segments 112, 114, 116 are defined such that all three radial segments are equal in size.

[0050] In some configurations, tracker 100 may include a body housing 120, for example Figures 2-11 The first configuration shown and Figures 12-16 The second configuration is shown. The body housing 120 covers multiple portions of the tracker frame 102 and surrounds the inner 122 and outer 124 of the tracker frame 102 (see...). Figure 11 As will be discussed in more detail below, certain components of tracker 100 may be arranged within the interior 122 of tracker frame 102. The body housing 120 may be constructed of polymeric material, titanium, or other suitable materials. Tracker frame 102 may be a monolithic or integral structure, such that there are no separate mounting bodies 104 and / or biasing bodies 110. Suitable manufacturing processes for forming tracker frame 102 and body housing 120 may include injection molding, additive manufacturing (3D printing), computer numerical control (CNC) machining, polymer casting, vacuum forming, and blow molding, etc.

[0051] Tube guide 126 may be defined on tracker frame 102 within mounting body 104 and configured to receive surgical irrigation tube 52. Tube guide 126 receives irrigation tube 52 and neatly arranges it around tracker frame 102 in a manner that avoids the surgeon, such that the irrigation tube does not interfere with the tracker frame in unpredictable ways. Tracker 100 may include two tube guides 126 configured to receive irrigation tubes 52 with different diameters. These tube guides 126 may be identical in size or sized differently to accommodate irrigation tubes 52 of various sizes. Figure 2 As shown, the tube guide 126 is configured to guide the irrigation tube 52 through a bend of approximately 90 degrees so that it is substantially parallel to the longitudinal axis 108 when it encounters the surgical instrument 34. The tube guide can also be configured as a guide for other elongated components, such as cables for powering trackers and suction cannulas.

[0052] When in perspective (e.g. in)Figure 8 When viewed in the image, the tracker frame 102 may have a generally tetrahedral shape due to the arrangement of three sides aligned with radial segments 112, 114, and 116. Each of these sides forms one of the four faces of a tetrahedron 154, and the edges are defined at the intersection of each side. The fourth face of the tetrahedron is formed by a distal guide surface 184 on the mounting body 104. This distal guide surface 184 is generally perpendicular to the longitudinal axis 108 and defines a portion of the instrument engagement hole 106. The distal guide surface 184 is arranged opposite to the proximal guide surface 185 of the mounting body 104. The distal guide surface 184 and the proximal guide surface 185 generally form the corresponding distal and proximal ends of the mounting body 104. The tetrahedral shape may be implemented as a regular tetrahedron (having all four identical faces) or an irregular tetrahedron (where some faces are sized differently and intersect at different angles).

[0053] In some embodiments, tracker 100 may include as few as four markers 128 to track surgical instruments 34. In these embodiments, each marker 128 is coupled to tracker frame 102 and arranged at the vertices of a tetrahedral shape. Each marker 128 forms an array with two other markers 128 visible to the navigation system. Each marker 128 may be oriented differently from the other markers to maximize radial emission of light around longitudinal axis 108.

[0054] As described above, the bias body 110 is supported on the mounting body 104 and extends in the proximal direction. The bias body 110 extends from its attachment to the mounting body 104 and adjacent to the distal guide surface 184 to a proximal end 152. The length 156 of the bias body 110 is defined between the distal end 150 and the proximal end 152, corresponding to the distance between the proximal end 152 and the mounting body 104. The proximal end 152 is adjacent to a vertex of the tetrahedron 154 defined by the tracker frame 102. Figure 6 , Figure 8 and Figure 10 As best shown, the bias body 110 tapers from the distal end 150 to the proximal end 152; in other words, the proximal end 152 has a smaller profile than the distal end 150.

[0055] As also described above, the bias body 110 is typically arranged in the first radial segment 112, and further, as Figure 5 As best shown, the tracker frame 102 is spaced at a height 158 ​​from the longitudinal axis 108. Partly due to the smaller profile of the proximal end 152 and the height 158 ​​at which it is spaced, the tracker frame 102 provides a release area 160 for the flexible power cable 48 of the surgical instrument 34. Figure 5As best shown in the side view, the release area 160 is generally centered on the flexible power cable 48 and minimizes potential contact between the flexible power cable 48 and the tracker frame 102. For example, when a user such as a surgeon uses a similar... Figure 2 When the pencil gripper is used with the surgical instrument 34 as shown, the flexible power cable 48 will typically bend towards the floor and away from the surgeon. Because the flexible power cable 48 has mass, it exerts a force on the proximal end 36 of the surgical instrument 34, which becomes a torque centered on the position where the surgeon is gripping the surgical instrument 34. As the surgical instrument 34 moves during the surgical procedure, the surgeon typically becomes familiar with the forces naturally associated with the flexible power cable 48 after that movement. If the flexible power cable 48 accidentally comes into contact with something, the balance of the surgical instrument 34 is affected. When the instrument 34 is not balanced, the surgeon's fine movements may be affected, potentially leading to undesirable movement at the distal end 38 of the surgical instrument 34. By providing a large release area 160 below the bias body 110, the surgeon can move the surgical instrument 34 with confidence and an increased range of motion, while reducing the chance that the flexible power cable 48 will come into contact with the tracker frame 102. Release area 160 provides a gap for flexible power cable 48 to bend freely with a small bending radius (i.e., at a large angle to the instrument axis 40) without contacting tracker frame 102.

[0056] In addition to reducing the quality of tracker 100, it is also desirable to reduce any interference with the surgeon's visibility of the surgical site. In some cases, the surgeon may want to observe the surgical site along line of sight 188, such as... Figure 5As shown schematically, the line of sight 188 is approximately aligned with the instrument axis 40. If a large tracker is used with the surgical instrument 34, it can obstruct the surgeon's line of sight or require the surgeon to hold the surgical instrument 34 in a less preferred manner, increasing the angle from the longitudinal axis in which the surgeon views the surgical site. The angle of the line of sight 188 is affected by both the length of the surgical instrument 34 and the height 158 of the offset body 110 relative to the longitudinal axis 108. It is therefore desirable to reduce the height 158 of the offset body 110 to minimize the angle of the line of sight 188. However, because the proximal end 152 of the offset body 110 extends proximally from the distal end 150 of the offset body 110 a distance (i.e., length 156) that is greater than the distance (i.e., height 158) by which the offset body 110 is spaced from the longitudinal axis 108, the area of each array 162, 164, 166 is still maximized, maximizing the accuracy of the tracker 100. The reduced height 158 of the offset body 110 allows the angle of the line of sight 188 to be less than 40 degrees. Depending on the accessory 42 coupled to the surgical instrument 34, the line of sight can be further reduced to less than 30 degrees, or further reduced to less than 20 degrees. In certain configurations, no part of the tracker 100 extends more than 1, 2, 3, or 4 cm from the longitudinal axis.

[0057] As described above, the tracker 100 is coupled to the surgical instrument 34 via the instrument engagement hole 106 such that the instrument axis 40 and the longitudinal axis 108 are aligned. Because the determined relationship between the tracker 100 and the surgical instrument 34 facilitates accurate determination of the position of the surgical instrument 34, their coupling should be secure, while being removable. As shown in Figure 4 and Figure 9 The tracker 100 can also include a retention assembly 132 configured to secure the surgical instrument 34 within the instrument engagement hole 106, as shown. The retention assembly 132 can be implemented in several different ways depending on the particular surgical instrument 34 to be tracked and the structure of the tracker frame 102. In particular, some retention assemblies 132 can be more suitable for tracker frames 102 that include a metal structure, while others can be more suitable for polymer structures. Suitability can be determined in part by the physical characteristics of the surgical instrument 34 (e.g., weight or diameter) or cost (e.g., whether the tracker 100 is single-use or durable, as the case can be). In certain cases, the tracker 100 can include more than one retention assembly 132 in order to improve compatibility across a variety of surgical instruments 34.

[0058] The housing 46 of the surgical instrument 34 is slidably engaged with the tracker frame 102 to securely connect the tracker 100 and the surgical instrument 34. More specifically, by aligning the instrument axis 40 and the longitudinal axis 108 and inserting the distal end 38 of the surgical instrument 34 through the proximal side of the instrument engagement hole 106.

[0059] A first alternative of the retention assembly 132 is implemented as a friction clamp 134, which is best shown in Figure 8 and Figure 10 Here, a clamp channel 138 is defined in the mounting body 104 in a through-going manner. Two resilient arms 140A, 140B are disposed in the clamp channel 138, each having a reference end 142A, 142B and a movable end 144A, 144B. The reference ends 142A, 142B are both coupled to the mounting body 104 on one side of the clamp channel 138 and extend into the clamp channel 138 and to the respective movable ends 144A, 144B. As best shown in Figure 10 , the instrument engagement hole 106 is positioned in alignment with the resilient arms 140A, 140B, allowing the resilient arms 140A, 140B to contact opposite sides of the housing 46 of the surgical instrument 34 during use. In the vicinity of each movable end 144A, 144B, each resilient arm 140A, 140B has an overlapping portion 146A, 146B of reduced width. The overlapping portion 146A of the distal resilient arm 140A has a reduced width in the distal direction, and the overlapping portion 146B of the proximal resilient arm 140B has a reduced width in the proximal direction. The reduced width of the overlapping portions 146A, 146B allows each resilient arm 140A, 140B to wrap around the housing 46 of the surgical instrument 34 in a manner greater than 180 degrees (here, greater than 180 degrees) than it would if abutting at the movable ends 144A, 144B.

[0060] Here, to securely couple the surgical instrument 34 and the tracker 100, the diameter of the instrument engagement hole 106 is less than the diameter of the housing 46. When the housing 46 is slidably engaged with the mounting body 104, the movable end 144A of the resilient arm 140A and the movable end 144B of the resilient arm 140B splay open to increase the diameter of the instrument engagement hole 106 to match the housing 46. The force from the deformation causes the resilient arms 140A, 140B to exert a clamping force on the housing 46. Due to the friction and contact between the resilient arms 140A, 140B and the housing 46, the tracker 100 is thereby securely retained to the surgical instrument 34.

[0061] In addition to the resilient arms 140A, 140B, the retention assembly can also include an attachment protrusion 148, which is shown disposed on the proximal side of the instrument engagement hole 106, as Figure 9An exemplary attachment protrusion 148 is radially disposed about the longitudinal axis 108 and is configured for indexing engagement with the surgical instrument 34 along the instrument axis 40. In particular, the attachment protrusion 148 engages a complementarily shaped notch in the housing 46 of the surgical instrument 34 to index the tracker frame 102 into rotational alignment about the instrument axis 40. Here, the attachment protrusion 148 has a generally rectangular profile that is proximate the instrument engagement hole 106 and is asymmetrically positioned such that full engagement of the surgical instrument 34 and the tracker 100 can only be achieved in a single position. Indexing engagement of the surgical instrument 34 and the tracker 100 can be achieved using one or more attachment protrusions 148, which can provide redundancy or further retention to securely couple the tracker 100.

[0062] A second alternative to the retention assembly 132 is implemented as a cam lock 136', 136" as shown in FIGS. Figures 12-16 and Figures 17-21 .

[0063] As noted above, the tracker 100 can include a plurality of markers 128 arranged in a plurality of arrays 162, 164, 166 coupled to the tracker frame 102. Figure 3 , Figure 7 and Figure 11 shows that the tracker 100 can be configured such that the plurality of markers 128 is further defined as at least six markers 128, wherein, Figure 7 shows that at least one of the at least six markers 128 is positioned on the tracker frame 102 in each radial segment 112, 114, 116. In other words, each radial segment 112, 114, 116 contains one of the markers 128, wherein some radial segments 112, 114, 116 can have more than one marker 128.

[0064] While the above-described tracker 100 includes at least six markers 128, a greater number of markers 128 can be desired. For example, the tracker 100 can include nine markers 128 for higher three-dimensional accuracy. Power consumption of the tracker 100 can be reduced by reducing the number of markers 128, which can be desirable in trackers 100 used to track motion having limited degrees of freedom (e.g., five degrees of freedom) or, for example, surgical instruments 34. The tracker 100 can include more than nine markers 128 for increased redundancy. Alternatively, the tracker can include exactly nine, ten, eleven, or twelve markers to minimize energy consumption, maximize line-of-sight, and maintain tracking accuracy. Still alternatively, the tracker can include fewer than twelve markers.

[0065] Additionally or as an alternative to the above-described arrangement of markers 128 in each of the radial segments 112, 114, 116, the tracker 100 can be configured such that a plurality of markers 128 are coupled to the tracker frame 102 and are arranged radially asymmetrically about the longitudinal axis 108. Figure 5 and Figure 7 An edge of a longitudinal plane 168 is shown that is parallel to the longitudinal axis 108 and bisects the instrument engagement hole 106 to define a first region 170 and a second region 172. The arrangement of markers 128 is further defined with respect to the first region 170 and the second region 172. A first number of the plurality of markers 128 is located in the first region 170, and a second number of the plurality of markers 128 is located in the second region 172, the first number being greater than the second number. For example, one configuration of the tracker 100 can include nine markers 128, a first number of seven markers 128 can be positioned on the tracker frame 102 such that they are located in the first region 170 or above the longitudinal plane 168, and a second number of two markers 128 can be positioned on the tracker frame 102 such that they are located in the second region 172 or below the longitudinal plane 168. According to this example, there can be more or fewer markers 128 in either region 170, 172, such that the first number of markers 128 in the first region 170 is greater than the second number of markers 128 in the second region 172.

[0066] The tracker 100 can be adapted to be compatible with a variety of different surgical navigation systems and position tracking technologies. For example, the tracker 100 can employ passive tracking markers that reflect infrared light or radiation that has been emitted from a camera unit or another light source. Although one embodiment of a navigation system is described herein, the navigation system can have any other configuration that is suitable for monitoring the tracker 100, which can have various types and configurations. For example, the navigation system can include other types of cameras and / or markers 128.

[0067] In some embodiments, the navigation system can be radio frequency (RF) based. For example, the tracker 100 can include RF transmitters or transponders, which can be passive or can be actively energized. Alternatively, in some embodiments, the navigation system can be electromagnetic (EM) based. For example, the navigation system can include an EM transceiver coupled to a computing device, controller, or the like. Here, the tracker 100 can include EM components (e.g., various types of magnetic trackers, electromagnetic trackers, inductive trackers, or the like) attached thereto, which can be passive or can be actively energized.

[0068] As shown throughout the drawings and particularly with reference to Figure 7The markers 128 are infrared emitters capable of emitting infrared radiation or light that can be sensed by a surgical navigation system. Infrared wavelengths are preferred because the ambient lighting used by surgeons emits in the visible spectrum, but the wavelengths of infrared light enable the brightness of the markers 128 to be detected by the surgical navigation system substantially independent of the brightness of the ambient lighting. Thus, because the markers 128 emit infrared light, the markers 128 can be operated at a lower brightness, which reduces the current required to power the markers 128. The current required to power the markers can be as low as 15 mA or lower.

[0069] Here, the infrared emitters are infrared light emitting diodes (IR-LEDs) that can emit infrared radiation and light at a relatively low power level. The current of at least one of the IR-LEDs can be limited by the internal resistance of the IR-LED and the resistance of at least one resistor electrically connected in series with the at least one IR-LED. The current of the at least one IR-LED can be limited by one or more resistors electrically connected in series to the at least one IR-LED.

[0070] The tracker 100 includes circuitry placed in the tracker frame 102, which will be discussed further below. The circuitry includes IR-LEDs (shown as markers 128), a battery 182, and resistors (not shown). The circuitry includes electrical wires (not shown) that electrically connect the battery 182 to each of the IR-LEDs. The IR-LEDs, the battery 182, and the resistors are electrically connected in series. Thus, the resistance of the resistors limits the current of the IR-LEDs. The resistors have a resistance such that the current of the IR-LEDs does not exceed about 15 mA. In one embodiment, the IR-LEDs are electrically connected to each other in parallel. Thus, if one of the IR-LEDs fails, the electrical connection of the battery 182 to the remaining IR-LEDs is not interrupted. Each resistor forms a series electrical circuit with its corresponding IR-LED. Furthermore, each IR-LED contributes its own resistance to the resistance of the resulting series electrical circuit. According to Ohm’s Law, current is inversely proportional to resistance. Thus, by adjusting the resistance of each resistor, the current through that resistor and through its corresponding IR-LED can be adjusted. An example circuit configuration can be found in U.S. Patent Publication No. 2019 / 0321108, which is incorporated by reference herein.

[0071] In one configuration, the tracker 100 includes four resistors, which equals the number of IR-LEDs. Alternatively, the tracker 100 can include a different number of resistors. Each resistor is disposed between the battery 182 and its corresponding IR-LED. The resistors are disposed within the tracker frame 102, and each resistor is electrically connected in series to its corresponding IR-LED. The resistors are electrically connected between the IR-LEDs and the positive terminal of the battery 182. Alternatively, at least one resistor can be electrically connected between the respective IR-LEDs and the negative terminal of the battery 182. This embodiment includes a lower number of resistors, and thus has a lower material cost. Alternatively, more than one resistor can each be electrically connected in series to multiple IR-LEDs. For example, two resistors can each be electrically connected in series to an IR-LED.

[0072] The circuit can further include a switch 186 that is operable by a user and configured to electrically open and close the circuit. Thus, the IR-LEDs can be operated by operating the switch 186, which opens and closes the circuit connecting the battery 182 to the IR-LEDs. Alternatively, multiple switches can be provided that are configured to individually control the power to each IR-LED. As another alternative, the tracker 100 can include at least one switch that is one-time or one-shot. Such one-time use can be implemented by the switch 186 including a removable barrier material (e.g., a paper or polymer strip, such as Mylar or Kapton), where the switch 186 is configured to close the circuit once the barrier material is removed. Alternatively, the one-shot switch can be implemented as exposed contacts that are shorted together when the tracker 100 is assembled.

[0073] The circuit can be configured to limit the radiance of at least one IR-LED to no more than 40 microwatts per steradian (μW / sr), preferably 20 μW / sr, more preferably 10 μW / sr. The circuit can be configured to limit the maximum or average radiance of at least one IR-LED to be in a range between 0.1 μW / sr and 40 μW / sr, such as between 0.5 μW / sr and 20 μW / sr, or between 1 μW / sr and 10 μW / sr. The circuit can be configured to limit the radiance of some or all of the plurality of IR-LEDs to 40 μW / sr or less, as described above.

[0074] The battery 182 can be implemented as a single coin cell battery unit (also referred to as a button cell battery unit). However, the battery 182 can also include multiple battery units. Coin cells are lightweight batteries, resulting in a reduced weight of the tracker 100. The battery 182 can have a mass of less than 5 grams, for example 3 grams. The battery 182 can be a non-rechargeable primary battery, or alternatively, a rechargeable secondary battery. The battery 182 can use an anode material including zinc or lithium. The battery 182 can be an alkaline battery or a lithium battery, for example a CR2032 or CR2025 battery that is commonly used and has a circular or cylindrical shape. Alternatively, the battery 182 can be a zinc-air battery. The capacity of the battery 182 can be between 100 milliampere-hours (mAh) and 1000 mAh, for example between 200 mAh and 400 mAh.

[0075] In Figure 3 and Figures 5-6 the battery 182 is shown in dashed lines to surface that the battery 182 is placed in the interior 122 of the tracker 100 to protect the battery 182 from contaminants (e.g., blood, water, and sterilizing agents) that can occur during surgery. In various embodiments shown throughout the drawings, the battery 182 can be removable by a user from the tracker 100. Alternatively, the battery 182 can be non-removable by a user from the tracker 100 (e.g., when the tracker 100 is configured as a disposable item). Since the current of at least one of the plurality of markers 128 is limited, the battery 182 can be sufficient as a power source and can not require an external power source. The tracker 100 can not include a power cord that is connected to an external power source.

[0076] The battery 182 provides a direct current voltage of, for example, 3 V. Each IR-LED has an operating voltage of, for example, 1.5 V. Therefore, the battery voltage of 3 V - 1.5 V = 1.5 V drops at each resistor. The resistance of each resistor is 150 Ω. Therefore, the current through each resistor and thus through each IR-LED is 1.5 V / 150 Ω = 10 mA. Since the resistors are provided, the circuit is configured to limit the current of each IR-LED to no more than 15 mA. In this way, the circuit also limits the radiant intensity of at least one IR-LED to no more than 40 μW / sr lumens.

[0077] The battery 182 is a coin cell unit that is lightweight and has a small capacity (e.g., 520 mAh). Because the circuit is selectively configured to limit the current to each IR-LED to no more than 15 mA or 20 mA, the capacity of the coin cell unit is still sufficient to safely operate the tracker 100 during a typical surgical navigation procedure. For example, where a CR2032 type battery has a capacity of 520 mAh and the four IR-LEDs are each powered at a current of 10 mA, the tracker 100 can last 520 mAh / (4 x 10 mA) = 5.5 h. The tracker 100 can be configured to house additional batteries to extend the duration that the tracker 100 can operate. For example, a tracker with two 520 mAh batteries can operate for more than 10 hours.

[0078] Because the current load is reduced, the tracker 100 is configured for continuous operation of the markers 128. The tracker 100 can be configured to simultaneously operate at least two of the plurality of markers 128. The tracker 100 can also be configured to simultaneously operate all of the markers 128. Alternatively, the tracker 100 can be configured to sequentially operate the plurality of markers 128.

[0079] Alternatively, the tracker 100 can be configured for quasi-continuous or pulsed operation. Quasi-continuous operation can also include circuitry capable of adjusting the brightness of the markers 128, for example, via a pulse width modulation (PWM) circuit, where the duty cycle of the electrical signal provided to the markers 128 is modified to have more time on than off, thereby increasing the brightness, or vice versa. Quasi-continuous operation can be performed at an operating frequency of more than 0.5 kHz. Such quasi-continuous operation reduces the power consumption of the tracker 100.

[0080] In addition to the IR-LEDs mentioned above, the tracker 100 can also include circuitry for a status indicator electrically coupled to at least one of the IR-LEDs, the battery, and the resistor. In one implementation, the status indicator can include an LED that emits visible light (i.e., not infrared light) so that the surgeon can easily verify that the tracker 100 has been activated and is operating. The status indicator can be configured to provide additional diagnostic or operational information to the surgeon, such as the remaining battery capacity. For example, the status indicator can flash or blink when the battery voltage corresponds to a first level, and the status indicator can be off when the battery voltage corresponds to a second level. The status indicator can also be implemented with more than one LED or an LED capable of emitting light in more than one color. If more than one LED is used, the voltage level of the battery can correspond to the number of LEDs that are lit at the same time. If a multi-color LED is used, the color can correspond to the voltage level of the battery.

[0081] As noted above, the markers 128 are positioned about the longitudinal axis 108 either by being disposed in each radial segment 112, 114, 116 or in a number on one side of the longitudinal plane 168. These configurations increase the visibility of the tracker 100 and, thus, the ability of the surgical navigation system to accurately determine the position and orientation of the surgical instrument 34. Moreover, these configurations position the markers 128 at a plurality of angular positions about the longitudinal axis 108 such that the markers 128 are capable of radially emitting infrared radiation or light over at least 260 degrees about the longitudinal axis 108. This radial emission is shown in Figure 7 , where an exemplary emission pattern for each of the plurality of markers 128 is shown relative to the tracker 100 and the surgical instrument 34. The radial emission shown here is 360 degrees about the longitudinal axis 108. Here again, the markers 128 are IR-LEDs having an assumed total emission angle 174 of about 150 degrees. In other words, each IR-LED is capable of emitting at least 50% of its peak intensity at an angle of 75 degrees from the normal 175 (see Figure 25 ) or centerline of peak intensity, which angle is commonly referred to as the half angle. The normal 175 of an IR-LED is generally orthogonal to the mounting plane of the IR-LED and defines the centerline of peak intensity. IR-LEDs having greater or lesser half angle values can be implemented in alternatives, such as 65 degrees or 85 degrees. The configuration of the IR-LEDs having an exemplary emission angle 174 of 150 degrees allows the radiation or light emitted from the IR-LEDs to be visible to the navigation system by a rotation of about 360 degrees of the tracker 100 over the longitudinal axis 108, as can occur during a procedure as the surgeon operates the surgical instrument 34 as needed.

[0082] In some embodiments, a distance between at least two of the plurality of markers 128 can be less than 70 millimeters (mm). A distance between at least two of the plurality of markers 128 can be in a range between 1 mm and 70 mm, such as between 3 mm and 35 mm or between 5 mm and 30 mm. As will be discussed below, the markers 128 can be placed in a common plane. Alternatively, the markers 128 can be configured such that they are not disposed in a common plane.

[0083] Turning to Figure 11Each circuit includes an IR-LED (i.e., marker 128), which is attached (e.g., via soldering) to printed circuit boards (PCBs) 176, 178, and 180, which are in turn coupled to tracker frame 102. Three PCBs 176, 178, and 180 are shown here, with three markers 128 coupled to each PCB. Each of the PCBs 176, 178, and 180 is electrically connected to a voltage source (shown here as battery 182) that provides power to the multiple markers 128. PCBs 176, 178, and 180 have a generally flat and planar configuration to which the markers 128 and other components (e.g., resistors discussed herein) are attached. More specifically, each PCB 176, 178, 180 defines a plane 176A, 178A, 180A, which is generally perpendicular to the direction of radiation emitted by the corresponding marker 128. Two or more, or three or more, PCBs 176, 178, 180 are arranged such that they are not parallel to each other. In some configurations, a battery 182 may be connected to circuitry on only one of the PCBs 176, 178, 180. Here, the battery 182 is electrically connected to the upper PCB 176. Each of the other PCBs 178, 180 is electrically connected to the upper PCB 176 via wiring to power all markers 128. Alternatively, all markers 128 may be connected to a single flexible PCB configured with flexible portions, thereby allowing the PCB to have a single surface oriented along at least three different directions.

[0084] The following text will combine Figure 22 As discussed in the fourth embodiment of tracker 100”' shown, some embodiments may include a battery socket (e.g., tray 183”') that holds the battery 182 and can be slidably engaged with tracker frame 102”' to position the battery 182 in electrical communication with an IR-LED. In some configurations, the battery 182 and battery tray 183 are arranged to directly engage the PCB in a low-profile configuration. When the battery 182 is configured as a coin cell battery (e.g., CR2032, as described above), one of the circular faces of the battery contacts a conductive element of the PCB. By positioning the battery 182 in contact with the PCB, the overall height of the PCB assembly is minimized. As described above, reducing the height of tracker 100 advantageously reduces the angle of view 188 during use.

[0085] Since the markers 128, when configured as infrared emitters or IR-LEDs, are coupled to respective non-parallel PCBs 176, 178, 180, each marker 128 emits radiation in a manner that is perpendicular to the plane 176A, 178A, 180A on which it is disposed. Thus, the markers 128 collectively emit radiation in at least as many directions as the non-parallel planes 176A, 178A, 180A. Referring again to Figure 7 where three different directions are shown.

[0086] To take advantage of the radial emission characteristics provided by the configuration of the markers 128, the surgical navigation system can be able to determine which markers 128 correspond to a particular arrangement on the tracker frame 102. As noted above, the plurality of markers 128 are arranged to form at least two arrays, each array having at least three markers 128, a portion of each array being coupled to the offset body 110. More specifically, Figure 11 The tracker 100 shown in FIG. 16 includes three arrays 162, 164, 166 coupled to the tracker frame 102. The first array 162 is coupled to the offset body 110 and faces the top of Figure 11 The second array 164 is coupled to the mounting body 104 and the offset body 110 and faces the lower left of Figure 11 The third array 166 is also coupled to the mounting body 104 and the offset body 110 and faces the lower right of Figure 11 However, other array arrangements are contemplated.

[0087] In addition to a portion of each of the at least two arrays 162, 164, 166 being coupled to the offset body 110, a portion of each of the at least two arrays 162, 164, 166 is positioned proximal to the mounting body 104, and the portion of the at least two arrays 162, 164, 166 that is proximal to the mounting body 104 includes exactly one marker 128. As noted above, a portion of the offset body 110 extends in a proximal direction from the mounting body 104 and terminates at the proximal end 152. This proximal end 152 of the offset body 110, and likewise the tracker frame 102, is positioned proximal to the proximal end 36 of the surgical instrument 34. In Figure 7 Best shown in FIG. 16, three markers 128 from the first array 162, the second array 164, and the third array 166, respectively, are arranged on the tracker frame 102 proximal to the proximal end 36 of the surgical instrument 34, near a location of the proximal end 152 of the offset body 110.

[0088] The camera comprises two lenses for focusing the infrared light emitted by the plurality of IR-LEDs. In contrast to a non-focusing aperture like a slit hole, these lenses allow more light to enter the camera. Thus, the camera is able to detect low-brightness light sources, e.g. IR-LEDs running with limited current.

[0089] The camera further comprises two two-dimensional image sensors 66. The two- dimensional image sensors 66 are able to sense a solid angle, i.e. a two-dimensional angle. In contrast, a conventional one-dimensional sensor row usually needs to be synchronized with the detected light source and can only allow tracking a single light source per scan. Since the two-dimensional image sensors 66 can detect all IR-LEDs at once, the tracker 100 can be configured to operate at least two and in particular all of the plurality of IR-LEDs simultaneously. This simultaneous operation does not require the camera to be synchronized with the tracker 100. Thus, the tracker 100 does not need a communication interface, e.g. a wireless transceiver, for communicating with the camera, which further reduces the weight of the tracker 100. Other advantages of the tracker 100 without a transceiver include preventing unwanted interference of emitted signals with external systems, preventing unwanted signal interference in received signals, reducing costs and reducing complexity.

[0090] The surgical navigation system can comprise two two-dimensional image sensors which are part of a stereo camera. Such a stereo camera is able to capture three- dimensional image data. Thus, a known spatial relationship between the IR-LEDs is not necessary. Thus, a stereo camera can be used when a plurality of single IR-LEDs is attached to a patient. Since the attachment is done manually, the spatial relationship between the IR-LEDs is unknown. However, since the stereo camera is able to capture three-dimensional image data, the stereo camera can track the IR-LEDs.

[0091] In one configuration, the identification of each of the arrays 162, 164, 166 is performed by the surgical navigation system by determining the distance to each of the markers 128 and triangulating the position relative to the camera, as described above. The configuration of the arrays 162, 164, 166 with more than one marker 128 enables independent tracking of each array 162, 164, 166 in more than one dimension, e.g. 2D or 3D. As shown throughout the figures, each array 162, 164, 166 is defined by three markers 128, for a total of nine markers 128. To accurately distinguish each array 162, 164, 166, the specific arrangement of the markers 128 can vary between each array 162, 164, 166. In one example, the first array 162 can define a first region 162A Figure 6 ), which is the region of a triangle with its vertices at the common reference of each of the respective markers 128. Likewise, the second array 164 can define a second region 164AFigure 8 ) and the third array 166 can define a third area 166A Figure 5 ), the second area 164A and the third area 166A are both based on the area of a triangle with vertices at the common reference on each of the respective markers 128. Here, the first area 162A can be larger than the second area 162A, and the second area 164A can be larger than the third area 166A.

[0092] In another example, particularly Figures 22-26 shown in the tracker 100”’ (to be discussed in further detail below), the second area 164A”’ and the third area 166A”’ can be equal. Here, the second array 164”’ and the third array 166”’ can be configured with markers 128”’ in the same locations on the respective arrays. The second array 164”’ and the third array 166”’ can be identical (or substantially identical) in size in opposite or mirrored configurations. This can provide a pleasing appearance and reduced manufacturing costs.

[0093] Reference is now made to Figures 12-16 , another embodiment of a tracker 100’ is shown, wherein the tracker frame 102’ includes a cam lock retention mechanism 136’. In many respects, the tracker 100’ can be similar to the previously described trackers, wherein like numbers (plus an apostrophe (’)) correspond to like components, and any disclosure common to the corresponding components that can be omitted for brevity should not be understood as limiting. It should be understood that the corresponding components on the tracker frame 102’ can be modified in an appropriate manner to allow for insertion and removal of the surgical instrument 34 into and from the instrument engagement hole 106’ in the manner previously described. Further, it should be understood that while discussed in the context of the retention mechanism 132’, which can be integrated with or coupled to any mounting body 104’ (such as the previously described mounting bodies 104), in general, the present disclosure can be applicable to the tracker 100’ and / or the tracker frame 102’.

[0094] In Figures 12-16In this embodiment, the tracker 100' is shown to include a tracker frame 102' having a mounting body 104' and a biasing body 110' supported thereon. Similar to the above, the mounting body 104' defines an instrument engagement hole 106' configured to slidably engage the surgical instrument 34 at the proximal end 36. The distal end 38 of the surgical instrument 34 is inserted into the proximal side of the instrument engagement hole 106' and slid along the distal direction until a collar coupled to the proximal end 36 of the surgical instrument 34 and having a diameter greater than the instrument engagement hole 106' abuts the mounting body 104'. The collar defines a complementarily shaped recess in the housing 46 of the surgical instrument 34 configured to engage the attachment protrusion 148' adjacent to the instrument engagement hole 106'. Here, the retention mechanism 132' has a release knob having a ramped cam surface that engages the collar of the surgical instrument 34 that biases the surgical instrument 34 toward engagement with the instrument engagement hole 106'. Moving the knob to a release position disengages the collar and allows the surgical instrument 34 to be removed from the tracker 100'.

[0095] Figure 16 The radial segments 112', 114', 116' are shown as they are arranged about the longitudinal axis 108'. The asymmetric arrangement of markers 128' on the tracker body 102' facilitates improved visibility of the tracker 100' to a surgical navigation system by emitting infrared radiation or light about at least 260 degrees around the longitudinal axis 108'. Some arrangements of markers 128' can emit light about 360 degrees around the longitudinal axis 108'.

[0096] Reference is now made to Figures 17-21 , showing another embodiment of the tracker 100" in which the tracker frame 102" is a space frame structure. Here, the tracker 100" also includes a cam lock retention mechanism 136". In many respects, the tracker 100" can be similar to the previously described trackers in which like numbers (plus double prime (")) correspond to like parts and any disclosure common to the corresponding parts that is omitted for brevity should not be understood as limiting. It should be appreciated that the corresponding parts on the tracker frame 102" can be modified in an appropriate manner to allow the surgical instrument 34 to be inserted into and removed from the instrument engagement hole 106" in the manner previously described. Further, it should be appreciated that while discussed in the context of the tracker frame 102", the present disclosure can apply generally to the tracker 100" and / or the tracker frame 102".

[0097] In Figures 17-21In this embodiment, the tracker 100" is shown to include a tracker frame 102" having a mounting body 104" and a biasing body 110" supported thereon. Similar to the above, the mounting body 104" defines an instrument engagement hole 106" configured to slidably engage the surgical instrument 34 at the proximal end 36. The distal end 38 of the surgical instrument 34 is inserted into the proximal side of the instrument engagement hole 106" and slid along the distal direction until the proximal end 36 of the surgical instrument 34 is coupled and a collar having a diameter greater than the instrument engagement hole 106" abuts the mounting body 104".

[0098] In this embodiment, the tracker frame 102" is formed from a curved sheet, forming each of the three sides. The tracker frame 102" is curved such that each side is aligned with the three radial segments 112", 114", 116" shown. The tracker frame 102" is made from a lightweight, durable metal material, such as titanium. Since the tracker 100" is intended to be reusable, this structure allows for repair or replacement of certain components. For example, the at least two arrays 162", 164", 166" are coupled to the tracker frame 102" with threaded fasteners. Again, this allows for removal of the at least two arrays 162", 164", 166" for cleaning. Figure 21 As previously mentioned, a plurality of markers 128" are arranged on the tracker frame 102" such that at least one marker 128" is positioned in each of the radial segments 112", 114", 116". Furthermore, the plurality of markers 128" are arranged in a pattern such that the at least one marker 128" in each of the radial segments 112", 114", 116" is spaced apart from the at least one marker 128" in each of the other radial segments 112", 114", 116".

[0099] Figure 21 An edge of a longitudinal plane 168" is shown, which is parallel to the longitudinal axis 108" and bisects the instrument engagement hole 106" to define a first region 170" and a second region 172". The arrangement of the markers 128" is further defined with respect to the first region 170" and the second region 172", wherein a first number of the plurality of markers 128" are positioned in the first region 170" and a second number of the plurality of markers 128" are positioned in the second region 172", the first number being greater than the second number.

[0100] Figure 18 A proximal end 152" of the biasing body 110" is shown, which is spaced apart about the longitudinal axis 108" to define a release region 160" that provides clearance for the flexible power cable 48. Here, a portion of the at least two arrays 162", 164", 166" are positioned proximal to the mounting body 104" and this portion includes exactly one marker 128".

[0101] ​Some embodiments of the trackers 100 can be configured with PCBs as the outer facing exterior surfaces, where these exterior surfaces can be exposed and susceptible to contact with debris or fluids. Shorting can cause damage to components coupled to the PCBs, such as the markers 128 or resistors, which can result in poor operation of the trackers 100. The components and PCBs forming each tracker array can be protected by applying a conformal coating that forms a barrier on the PCBs, preventing debris and liquids from entering. An exemplary conformal coating can include a parylene film applied to the assembled PCBs.

[0102] Referring now to Figures 22-26 , another alternative embodiment of the optical tracker 100”’ is shown without the handheld surgical instrument 34. In this embodiment of the tracker 100”’, the retention mechanism 132 takes the form of a lever clamp 192”’. As described above, the tracker 100’ can be similar in many respects to the previously described embodiments, where like numbers (plus triple prime (”’)) correspond to like components, and any disclosure common to the corresponding components can be considered omitted for brevity without being understood as limiting. Here, the lever clamp 192”’ includes two resilient arms 194”’ coupled at first ends to the tracker frame 102”’ and spaced apart from each other at second ends, and a lever 196”’ pivotably coupled to the second ends of the resilient arms 194”’. The resilient arms 194”’ cooperate to define the instrument engagement hole 106”’ extending along the longitudinal axis 108”’ within the mounting body 104”’.

[0103] The biasing body 110”’ is supported on the mounting body 104”’ and extends in the proximal direction. The biasing body 110”’ is spaced apart from the longitudinal axis 108”’ and defines a cutout 118”’ extending through the biasing body 110”’ in a direction generally perpendicular to the longitudinal axis 108”’. Within the biasing body 110”’, here shown is the lever 196”’ having a triangular shape corresponding to one face of the generally tetrahedral shape of the tracker frame 102”’. The lever 196”’ is pivotable between a clamped position and an unclamped position (not shown) to secure the tracker frame 102”’ to the surgical instrument 34.

[0104] Each elastic arm 194"' has an ear 198"' at one end. A lever 196"' is engaged with each ear 198"' and is pivotable about a lever axis that is generally perpendicular to the longitudinal axis 108"' of the tracker frame 102"'. In one case, each ear 198"' can define a lever support hole that extends through the ear 198"' along the lever axis. The lever 196"' can include two pins that are disposed on the lever axis and are engageable with the lever support hole. Engagement between the pins and the lever support hole facilitates pivotal movement of the lever 196"' between the clamped position and the unclamped position. In another case, the lever 196"' and the ear 198"' can be configured with a pin that protrudes from the ear 198"' and a lever support hole that is defined in the lever 196"'. The elastic arms 194"' can be formed of a resilient material, such as a polymer or a plastic. In one case, the elastic arms 194"' can be formed of a polymer or a plastic that is capable of being stretched to a length that is greater than the length of the elastic arms 194"' in the unclamped position. In another case, the elastic arms 194"' can be formed of a polymer or a plastic that is capable of being stretched to a length that is greater than the length of the elastic arms 194"' in the clamped position. In one case, the elastic arms 194"' can be formed of a polymer or a plastic that is capable of being stretched to a length that is greater than the length of the elastic arms 194"' in the unclamped position and in the clamped position. In another case, the elastic arms 194"' can be formed of a polymer or a plastic that is capable of being stretched to a length that is greater than the length of the elastic arms 194"' in the unclamped position and in the clamped position.

[0105] As described above, the tracker frame 102"' can include a plastic or a polymer material. Accordingly, the tracker frame 102"' can be formed using an injection molding or an additive manufacturing process that forms the tracker frame 102"' as a single unitary body. By forming the tracker frame 102"' as a single unitary body, steps such as assembly of the clamp 192"' to the tracker frame 102"' can be eliminated. Moreover, dimensional accuracy of the tracker frame 102"' can be improved by reducing tolerance stack-ups. Furthermore, by eliminating any joints between components, stiffness of the tracker frame 102"' can be improved. Geometry that would be created by joining multiple components together can be eliminated, further reducing weight of the tracker frame 102"' and the need for precision of mating surfaces. When formed from a plastic or a polymer material, the elastic arms 194"' can be slightly flexible, which allows the ears 198"' to be displaced relative to one another, allowing the distance defined therebetween to be shortened. When a user pivots the lever 196"' from the unclamped position to the clamped position, the ears 198"' are moved closer together, which reduces the diameter of the instrument engagement hole 106"'. When a surgical instrument 34 is inserted into the instrument engagement hole 106"' and the lever 196"' is pivoted into the clamped position, the elastic arms 194"' are tightened against the outer surface of the surgical instrument 32 and prevent relative motion therebetween.

[0106] The structure of the trackers 100, 100', 100", 100"' described herein is optimized to reduce mass and size to facilitate the formation of a low cost, disposable tracker. In some embodiments, the mass of a tracker including a battery can be 40 g. Some embodiments of a tracker including a power source can have a mass of less than 50 g, 40 g, or less than 35 g.

[0107] A method for calibrating and registering a tracker 100 and a tracking array for use in surgical procedures using a localizer is also disclosed. Turning to Figures 24-26FIG. 6 shows steps for calibrating and registering a tracking array having a first tracking face TF1 and a second tracking face TF2 coupled to one another. The tracking array can further include a third tracking face TF3 coupled to the first tracking face TF1 and the second tracking face TF2. The method steps are illustrated in the context of the fourth embodiment of the tracker 100"'described above, however, these steps can be applicable to each of the trackers 100, 100', 100", 100"'described herein. Thus, any of the trackers 100, 100', 100", 100"'can be calibrated according to the method described below. The elements described in connection with the method are generally similar in each of the four embodiments, with like numbers corresponding to like parts and any apostrophes being omitted for clarity.

[0108] The tracker is calibrated in the operating room to achieve high tracking accuracy. High tracking accuracy can correspond to an accurate and precise measurement of the relative position of each optical tracking element. By calibrating the tracker in situ, the navigation system can accurately measure the position of each optical tracking element to compensate for high manufacturing tolerances. As a result of the high accuracy that can be achieved through the calibration procedure, the tracker can be manufactured in a cost-reduced and weight-reduced manner. In an exemplary embodiment of the tracker, the tracker frame can be formed using a stereolithography process and epoxy.

[0109] Calibration and registration of the tracking array can be initiated by a user (e.g., a surgeon) prior to or at the beginning of a surgical procedure by coupling the tracker 100 to the medical instrument 34 or the patient and activating the tracker 100 (e.g., by actuating a one-time switch). Alternatively, the calibration and registration procedure can be automatically initiated by the surgical navigation system 12 upon recognizing the tracker or via user input 16. Upon initiating calibration and registration, the navigation processor 18 can provide a first set of instructions to the user on the display unit 14. These instructions can be a static list of steps or can be dynamically updated as discussed below.

[0110] Some embodiments of the surgical navigation system 12 include a storage device (not shown) on which can be stored manufacturing dimensions of the tracking array. The manufacturing dimensions can include a first set of geometric data including first tracking face TF1 geometric data, second tracking face TF2 geometric data, and third tracking face TF3 geometric data. The first tracking face geometric data can include data indicative of the expected relative positions of the plurality of optical tracking elements 128 on the first tracking face TF1, their positions relative to one another, and the expected orientation of the plurality of optical tracking elements 128 on the first tracking face. The second tracking face geometric data can include data indicative of the expected relative positions of the plurality of optical tracking elements 128 on the second tracking face TF2, their positions relative to one another, and the expected orientation of the plurality of optical tracking elements 128 on the second tracking face. The third tracking face geometric data can include data indicative of the expected relative positions of the plurality of optical tracking elements 128 on the third tracking face TF3, their positions relative to one another, and the expected orientation of the plurality of optical tracking elements on the third tracking face TF3. These data can also include distances between individual optical tracking elements 128, angles of the normal 175, expected manufacturing position tolerances, and other data that can characterize the tracking array.

[0111] The first tracking face TF1, the second tracking face TF2, and the third tracking face TF3 can each include a plurality of optical tracking elements 128 that are detectable by the navigation system 12. Calibration of the tracker 100 can be initiated by positioning the tracking array such that the plurality of optical tracking elements 128 of at least two of the first tracking face TF1, the second tracking face TF2, and / or the third tracking face TF3 are at least partially visible to the localizer 22. In a next step, the relative positions of the plurality of optical tracking elements 128 are measured while the plurality of optical tracking elements 128 are visible to the localizer 22.

[0112] As mentioned above, the optical tracking elements 128 (or markers) can be infrared light emitting diodes (IR-LEDs) that emit light in the infrared spectrum in the form of a generally conical beam of light along the normal 175. However, the optical tracking elements 128 can be implemented as reflective tracking elements or retro-reflectors that reflect light from an infrared light source in the vicinity of the localizer 22 in a direction that is closely aligned with the source.

[0113] As mentioned previously, each tracking element 128 has a normal 175 that is generally orthogonal to the respective tracking face and that defines a centerline of peak intensity. In other words, the orientation of the normal 175 represents the orientation of the optical tracking element 128. In addition to measuring the relative positions of the plurality of optical tracking elements 128, the navigation system 12 can detect the normals 175 of the plurality of optical tracking elements 128 while the plurality of optical tracking elements 128 are visible to the localizer 22 of each tracking face. For certain tracker configurations, such as when the tracker includes an array that defines three different regions, the detection step can be omitted.

[0114] Some embodiments of the tracker 100 can be configured such that the tracking array has two tracking faces, where the optical tracking elements 128 are arranged in the same geometric arrangement. In other words, the optical tracking elements 128 are arranged on one tracking face in the same relative position as the optical tracking elements 128 on the other tracking face. In Figure 24 In the illustrative example shown in FIG. 3, the second tracking face TF2 is one tracking face and the third tracking face TF3 is the other tracking face. The distance between each optical tracking element 128 on the second tracking face TF2 and the third tracking face TF3 or their relative position is the same. Furthermore, the optical tracking elements 128 on each of those tracking faces define the same triangular area. However, as can be seen in Figure 24 As can be seen in FIG. 3, the second tracking face TF2 and the third tracking face TF3 are mirror image arrangements, where the normal 175 of the respective optical tracking elements 128 face away from each other. By determining the normal 175 / orientation of each visible optical tracking element 128 or at least one optical tracking element 128 on each face, the navigation processor can distinguish between two or more tracking faces.

[0115] Once the normal 175 of a visible optical tracking element 128 has been detected, the optical tracking elements 128 can be grouped into a first rigid body and a second rigid body based on the measured relative position and orientation, each of the first rigid body and the second rigid body comprising at least one tracking element 128. Based on the measured relative position and orientation of the plurality of optical tracking elements 128 of the third tracking face TF3, the plurality of visible optical tracking elements 128 can be further grouped into a third rigid body.

[0116] The method further includes the step of positioning the tracking array such that at least one of the optical tracking elements 128 of the first tracking face TF1, at least one of the optical tracking elements 128 of the second tracking face TF2, or at least one of the optical tracking elements 128 of the third tracking face TF3 is simultaneously visible to the localizer 22. The relative positions are measured using the localizer 22 when at least one optical tracking element 128 belonging to the respective first tracking face TF1, second tracking face TF2, or third tracking face TF3 is simultaneously visible. In certain configurations, the positioning step can require that at least three optical tracking elements 128 of the first tracking face TF1 be simultaneously visible while at least one optical tracking element 128 of the second tracking face TF2 or third tracking face TF3 is visible. Likewise, to establish a correspondence between the second tracking face TF2 and the third tracking face TF3, at least three optical tracking elements 128 of the second tracking face TF2 can need to be simultaneously visible with at least one optical tracking element 128 of the third tracking face TF3. It should be understood that it is not limited to three tracking faces and that this embodiment is useful for trackers having only two faces or four or more faces.

[0117] Using the navigation processor 18, a composite rigid body can be created based on the first rigid body, the second rigid body, and the third rigid body; and the measured relative positions of the at least one optical tracking element 128 of the first tracking face TF1, the at least one optical tracking element 128 of the second tracking face TF2, and the at least one optical tracking element 128 of the third tracking face TF3. Alternatively, the composite rigid body can be created based only on the measured relative positions of the at least one optical tracking element 128 of the first tracking face TF1, the at least one optical tracking element 128 of the second tracking face TF2, and the at least one optical tracking element 128 of the third tracking face TF3.

[0118] Using the measured relative positions of the plurality of optical tracking elements 128 of the at least three optical tracking elements of a single tracking face, the tracker can be identified. In some embodiments, the identification step can be further based on the detected orientation data of the plurality of optical tracking elements.

[0119] The navigation processor can identify the tracking array by comparing the positions and / or detected orientations of at least three optical tracking elements on the tracking surface with a first set of geometric data. This identification can be based on the expected orientations of multiple optical tracking elements 128 on the first tracking surface TF1, the expected orientations of multiple optical tracking elements 128 on the second tracking surface TF2, and / or the expected orientations of multiple optical tracking elements 128 on the third tracking surface TF3. Despite the fact that the visibility of the optical tracking elements may be limited to avoid reducing measurement accuracy at wide angles, the positioner 22 may be able to identify the tracker by utilizing this orientation. This identification step can trigger the calibration workflow.

[0120] As described above and as Figure 26 As shown, to facilitate accurate calibration, the navigation system 12 can display calibration instructions to the user via the display unit 14. These displayed instructions can be updated based on which calibration step the user is currently performing or which calibration step has just been completed. The instructions may include graphics indicating to the user that the tracking array is rotated relative to the locator 22 such that at least one optical tracking element 128 of the first tracking surface TF1 and at least one optical tracking element 128 of the second tracking surface TF2 are simultaneously visible to the locator 22. The instructions may also include graphics indicating to the user that the tracking array is rotated relative to the locator 22 such that at least one optical tracking element 128 of the first tracking surface TF1 and at least one optical tracking element 128 of the third tracking surface TF3 are simultaneously visible to the locator 22. Furthermore, the instructions may subsequently include graphics indicating to the user that the tracking array is rotated relative to the locator 22 such that at least one optical tracking element 128 of the second tracking surface TF2 and at least one optical tracking element 128 of the third tracking surface TF3 are simultaneously visible to the locator 22. The same step can be indicated for both the third tracking surface TF3 and the first tracking surface TF1.

[0121] The calibration and registration method may also include the step of identifying a medical device 34 associated with tracker 100. Identification of the medical device 34 is based on associating a composite rigid body of a tracker array formed by a navigation processor with the medical device 34, which can be used in surgical procedures. By associating the composite rigid body with the medical device 34, the tracking array can be further assigned to a specific medical device 34 in the same manner. The method may also include determining the positional relationship between a portion of the medical device 34 and the composite rigid body by positioning a portion of the medical device 34 at a known reference location. Various techniques can be used to calibrate to the medical device, such as by triggering a reference location being tracked by locator 22. In one example, the reference location is a known location on a trackable calibration device.

[0122] Terms:

[0123] I. A method of operating a tracker, wherein the tracker comprises a tracker frame 102 and a circuit supported by the tracker frame 102, wherein the circuit comprises at least one infrared light emitting diode (IR-LED), wherein the circuit further comprises a battery or a wireless power receiving device configured to receive power wirelessly, the method comprising: providing power by the battery or the wireless power receiving device to operate the at least one IR-LED; and limiting a current of at least one of the at least one IR-LED to no more than 15 milliampere (mA) by the circuit.

[0124] II. A method of tracking a position and orientation of a tracker coupled to a surgical instrument within a surgical navigation system, the tracker defining a longitudinal axis and comprising at least three arrays each having at least three infrared emitters, the at least three arrays being arranged radially around the longitudinal axis, the method comprising: measuring a position of each of the at least three infrared emitters to determine a position and orientation of each array; calculating a correction factor corresponding to a position of at least one marker of each array relative to other arrays; determining a relative position and orientation of the at least one marker of each array visible to the surgical navigation system; and determining the position and orientation of the tracker by correlating the relative position and orientation of the at least one marker of each array with an absolute position of the tracker using the correction factor.

[0125] III. A method for calibrating a tracking array for surgical use using a localizer, the tracking array having a first tracking face and a second tracking face coupled to one another, the first tracking face and the second tracking face collectively comprising a plurality of optical tracking elements, the method comprising: positioning the tracking array such that the plurality of optical tracking elements of the first tracking face and the second tracking face are visible to the localizer; measuring relative positions of the plurality of optical tracking elements while the plurality of optical tracking elements are visible to the localizer; detecting orientations of the plurality of optical tracking elements while the plurality of optical tracking elements are visible to the localizer; grouping the plurality of optical tracking elements into a first rigid body and a second rigid body based on the measured relative positions and orientations of the plurality of optical tracking elements, each of the first rigid body and the second rigid body comprising at least one tracking element; positioning the tracking array such that at least one optical tracking element of the first rigid body and at least one optical tracking element of the second tracking face are simultaneously visible to the localizer; measuring relative positions of the at least one optical tracking element of the first tracking face and the at least one optical tracking element of the second tracking face while the at least one optical tracking element of the first tracking face and the at least one optical tracking element of the second tracking face are visible to the localizer; and forming a composite rigid body based on the first rigid body, the second rigid body, and the measured relative positions of the at least one optical tracking element of the first tracking face and the at least one optical tracking element of the second tracking face when simultaneously visible.

[0126] IV. A method for calibrating a tracking array for surgical use using a localizer, the tracking array having a first tracking face and a second tracking face coupled to one another, the first tracking face and the second tracking face collectively comprising a plurality of optical tracking elements, the method comprising: positioning the tracking array such that the plurality of optical tracking elements of the first tracking face and the second tracking face are visible to the localizer; measuring relative positions of the plurality of optical tracking elements while the plurality of optical tracking elements are visible to the localizer; positioning the tracking array such that at least one optical tracking element of the first tracking face and at least one optical tracking element of the second tracking face are simultaneously visible to the localizer; measuring relative positions of the at least one optical tracking element of the first tracking face and the at least one optical tracking element of the second tracking face while the at least one optical tracking element of the first tracking face and the at least one optical tracking element of the second tracking face are simultaneously visible to the localizer; and forming a composite rigid body based on the measured relative positions of the at least one optical tracking element of the first tracking face and the at least one optical tracking element of the second tracking face while the at least one optical tracking element of the first tracking face and the at least one optical tracking element of the second tracking face are simultaneously visible.

[0127] V. A disposable optical tracker for tracking a surgical instrument, the optical tracker comprising: a circuit board having a planar configuration; an arrangement of at least three IR-LEDs coupled to the circuit board and placed within a common plane, wherein a distance between any two IR-LEDs is unique; a circuit configured to limit a current of the at least three IR-LEDs to no more than 15 mA; a battery in electrical communication with the at least three IR-LEDs; and wherein the disposable optical tracker does not include a communication interface and does not include a power cord.

[0128] VI. The disposable optical tracker of clause V, wherein the arrangement of at least three IR-LEDs is configured for continuous or quasi-continuous operation.

[0129] VII. The disposable optical tracker of clause V, wherein the circuit includes at least one resistor configured to limit a current of at least one of the at least three IR-LEDs.

[0130] VIII. The disposable optical tracker of clause VII, wherein the current of at least one of the at least three IR-LEDs is limited by an internal resistance of the at least one of the at least three IR-LEDs and a resistance of the at least one resistor electrically connected in series to the at least one of the at least three IR-LEDs.

[0131] IX. The disposable optical tracker of clause VII, wherein the circuitry is configured to limit the radiated intensity of at least one of the at least three IR-LEDs to no more than 40 microwatts per steradian (pW / sr).

[0132] X. The disposable optical tracker of clause VII, wherein a distance between two of the at least three IR-LEDs is less than 70 mm.

[0133] XI. The disposable optical tracker of clause VII, wherein the circuitry is configured to operate the at least three IR-LEDs simultaneously.

[0134] XII. The disposable optical tracker of clause VII, wherein a mass of the disposable optical tracker is no more than 40 g.

[0135] XIII. The disposable optical tracker of clause V, wherein the disposable optical tracker further comprises a battery receptacle configured to engage the battery, and wherein the battery is further defined as a coin cell battery.

[0136] XIV. The disposable optical tracker of clause V, wherein the disposable optical tracker further comprises a disposable switch in electrical communication with the at least three IR-LEDs.

[0137] XV. A surgical navigation system comprising the tracker of clause V and a camera capable of detecting light of at least one IR-LED and generating a camera signal indicative of the detected light.

[0138] Several examples have been discussed in the foregoing description. However, the examples discussed herein are not intended to be exhaustive or to limit the application to any particular form. The terms used are intended to be descriptive, not limiting. Many modifications and variations are possible in light of the above teachings, and the application can be implemented differently than specifically described.

Claims

1. An optical tracker for a handheld surgical instrument, the handheld surgical instrument having a proximal end spaced apart from a distal end along an instrument axis, the optical tracker comprising: a tracker frame, the tracker frame comprising: a mounting body configured for coupling to the surgical instrument such that a longitudinal axis of the mounting body is aligned with the instrument axis; and a biasing body supported on the mounting body and projecting proximally from the mounting body and parallel to the instrument axis when the surgical instrument is coupled to the mounting body so as to provide a large relief area for a flexible power cable of the surgical instrument beneath the biasing body; at least two circuit boards coupled to the tracker frame such that the at least two circuit boards are oriented to be non-parallel to each other; at least six optical markers coupled to the at least two circuit boards and arranged to form at least two arrays, each of the at least two arrays comprising at least three of the at least six optical markers; and wherein a portion of each of the at least two arrays is positioned proximally of the mounting body such that at least two of the at least six optical markers are positioned proximally of the mounting body.

2. The optical tracker of claim 1, wherein, the biasing body extends from a distal end coupled to the mounting body to a proximal end.

3. The optical tracker of claim 2, wherein, the proximal end of the biasing body is spaced apart from the distal end by a distance greater than a distance the biasing body is spaced apart from the instrument axis.

4. The optical tracker of any of claims 2-3, wherein, the biasing body tapers from the distal end to the proximal end.

5. The optical tracker of any of claims 1-3, wherein, the at least six optical markers are infrared LEDs.

6. The optical tracker of claim 5, wherein, the at least six infrared LEDs emit light in a continuous and simultaneous manner.

7. The optical tracker of any of claims 1-3, wherein, the at least three optical markers arranged to form one array are oriented in a different direction than other at least three optical markers forming other arrays.

8. The optical tracker of claim 7, wherein, each circuit board defines a plane orthogonal to a direction in which a respective optical marker emits radiation.

9. The optical tracker of claim 8, wherein, the at least six optical markers are further defined as at least nine optical markers.

10. The optical tracker of claim 9, wherein, the at least two arrays are further defined as at least three arrays and the at least three arrays are arranged radially about a tool axis of the tool such that the at least nine optical markers emit infrared light radially about the tool axis 360 degrees.

11. The optical tracker of any of claims 8-10, wherein, the portion of each of the at least two arrays positioned proximally of the mounting body comprises exactly one optical marker.

12. The optical tracker of any of claims 1-3, wherein, the tracker frame comprises a polymer.

13. The optical tracker of any one of claims 1-3, wherein, the optical tracker further comprises a disposable switch coupled to the tracker frame and in electrical communication with the optical markers, the disposable switch comprising a removable barrier material.

14. The optical tracker of any one of claims 1-3, wherein, a line of sight defined between the tracker frame and the surgical instrument is less than 30 degrees.

15. A handheld surgical instrument having an instrument axis and coupled to the optical tracker of any of claims 1-3.

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