Optical Tracker And Surgical Device With An Optical Tracker

Abstract

An optical tracker and a surgical device. The surgical device includes a shaft defining a longitudinal axis. The shaft has a first shaft portion configured to be inserted into a patient, and a second shaft portion configured to be located outside the patient when the first shaft portion is inserted in the patient. The surgical device further includes an actuation member actuatable relative to the first shaft portion, and an operation member operable relative to the second shaft portion. The operation member is configured to actuate the actuation member when being operated. Further, the surgical device includes a tracker coupled with the operation member so that operation of the operation member causes the tracker to move relative to the shaft, such as to rotate around the longitudinal axis.

Claims

1. An optical tracker comprising: a body; a cover layer for the body; and one or more optically detectable markers arranged between the body and the cover layer, wherein the cover layer is optically transparent at least in one or more regions where the one or more optically-detectable markers are located.

2. The optical tracker according to claim 1, wherein the cover layer is detachably attached to the body.

3. The optical tracker according to claim 1, wherein the markers of the optical tracker are arranged in a pattern that defines, from a given viewing direction, distinctive arrangements of the markers in different rotational states of the optical tracker relative to a longitudinal axis of the optical tracker.

4. The optical tracker according to claim 1, wherein the one or more optically detectable markers are optically-passive markers.

5. The optical tracker according to claim 1, wherein the one or more optically detectable markers are optically-active markers.

6. The optical tracker according to claim 1, wherein the body has a substantially cylindrical shape.

7. The optical tracker according to claim 6, wherein the body has a drum shape with a central opening.

8. The optical tracker according to claim 1, wherein the body has a plurality of distinct sides.

9. The optical tracker according to claim 1, wherein the optical tracker is configured to be coupled to a surgical device in a detachable manner.

10. A surgical device comprising: a shaft defining a longitudinal axis, the shaft having a first shaft portion configured to be inserted into a patient and a second shaft portion configured to be located outside the patient when the first shaft portion is inserted in the patient; an actuation member actuatable relative to the first shaft portion; an operation member operable relative to the second shaft portion, the operation member being configured to actuate the actuation member when being operated; and an optical tracker coupled with the operation member so that operation of the operation member causes the optical tracker to rotate relative to the shaft, wherein the optical tracker comprises a plurality of markers arranged in a pattern that defines, from a given viewing direction, distinctive arrangements of the markers in different rotational states of the optical tracker relative to a longitudinal axis of the optical tracker.

11. The surgical device according to claim 10, wherein the optical tracker is coupled to the surgical device in a detachable manner.

12. The surgical device according to claim 10, wherein operation of the operation member is configured to cause the optical tracker to rotate relative to the longitudinal axis.

13. The surgical device according to claim 10, wherein there exists a predefined relationship between (i) a movement of the optical and (ii) an actuation movement of one of the actuation member and an actuatable implant detachably coupled to the actuation member.

14. The surgical device according to claim 13, wherein the predefined relationship associates a change of a position of the optical tracker resulting from its movement with a change of a dimension or state of one of the actuation member and the actuatable implant detachably coupled to the actuation member resulting from the actuation movement.

15. The surgical device according to claim 10, wherein the operation member is rotatable around the longitudinal axis.

16. The surgical device according to claim 10, wherein the optical tracker is rigidly coupled or configured to be rigidly coupled to the operation member.

17. The surgical device according to claim 10, wherein the optical tracker is arranged or configured to be arranged co-axially to the longitudinal axis of the shaft.

18. A system comprising: a shaft defining a longitudinal axis, the shaft having a first shaft portion configured to be inserted into a patient and a second shaft portion configured to be located outside the patient when the first shaft portion is inserted in the patient; an actuation member actuatable relative to the first shaft portion; an operation member operable relative to the second shaft portion, the operation member being configured to actuate the actuation member when being operated; an optical tracker coupled with the operation member so that operation of the operation member causes the optical tracker to rotate relative to the shaft; and an implant configured to be actuated by the actuation member from a first actuation state to a second actuation state, wherein the optical tracker comprises a plurality of markers arranged in a pattern that defines, from a given viewing direction, distinctive arrangements of the markers in different rotational states of the optical tracker relative to a longitudinal axis of the optical tracker.

19. A computer-implemented method for determining an actuation performed with a surgical device including a shaft defining a longitudinal axis and having a first shaft portion configured to be inserted into a patient and a second shaft portion configured to be located outside the patient when the first shaft portion is inserted in the patient, an actuation member actuatable relative to the first shaft portion, an operation member operable relative to the second shaft portion and being configured to actuate the actuation member when being operated, and an optical tracker coupled with the operation member so that operation of the operation member causes the optical tracker to rotate relative to the shaft, wherein the optical tracker includes a plurality of markers arranged in a pattern that defines, from a given viewing direction, distinctive arrangements of the markers in different rotational states of the optical tracker relative to a longitudinal axis of the optical tracker, the method comprising: determining a rotational state of the optical tracker; and determining, from at least the rotational state of the optical tracker, an actuation of at least one of the actuation member and an implant detachably coupled to the actuation member.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Further details, advantages and aspects of the present disclosure will become apparent from the following embodiments taken in conjunction with the drawings, wherein:

[0048] FIG. 1A shows a perspective view of an embodiment of a surgical device according to the present disclosure, comprising a first and a second part of the device in a decoupled state;

[0049] FIG. 1B shows a perspective view of the embodiment of FIG. 1A, wherein the two parts are in a coupled state;

[0050] FIG. 2A shows the first device part of the embodiment of FIGS. 1A and 1B;

[0051] FIG. 2B shows an embodiment of an optical tracker comprising a body and a cover layer in an exploded view;

[0052] FIG. 2C shows the optical tracker of FIG. 2B in an assembled state;

[0053] FIG. 2D shows an embodiment of the first device part with an alternative arrangement of the operation member and the optical tracker;

[0054] FIG. 2E shows an embodiment of the first device part with a drive member and a coupling section comprising an inner and outer driver;

[0055] FIG. 3A shows a front view of an outer driver of a coupling section of the first part of the surgical device presented herein;

[0056] FIG. 3B shows a front view of the outer driver and an inner driver of the coupling section of the first part of the surgical device;

[0057] FIG. 4 shows a perspective view of the second device part of the embodiment of FIGS. 1A and 1B;

[0058] FIG. 5A shows a perspective view of a system embodiment comprising the surgical device in its coupled state as shown in FIG. 1B and an actuatable implant;

[0059] FIG. 5B shows a side view of a system embodiment comprising the surgical device in its coupled state as shown in FIG. 1B and an actuatable implant;

[0060] FIGS. 6A-6C show different views of an actuatable implant;

[0061] FIG. 6D shows a schematic representation of a drive member in a first position and an implant actuated for posterior expansion or retraction;

[0062] FIG. 6E shows a schematic representation of a drive member in a second position and an implant actuated for lordotical expansion or retraction;

[0063] FIG. 6F shows a schematic representation of a drive member in a third position and an implant actuated for a symmetric height expansion or retraction;

[0064] FIG. 7 shows a flow diagram of a method embodiment for determining an actuation of an actuation member of a surgical device;

[0065] FIG. 8 shows a schematic representation of a computer program product with code executable by a processor;

[0066] FIG. 9 shows a schematic representation of a surgical navigation system embodiment with an optical sensor used for tracking actuation of the actuation member and implant;

[0067] FIG. 10 shows an example visualization of a part of the surgical device and of the implant during a spinal treatment surgery;

[0068] FIG. 11A shows a schematic representation of a visualization of a part of the surgical device and the actuatable implant during a spinal surgery; and

[0069] FIG. 11B shows a schematic representation of a visualization of a part of the surgical device and the actuatable implant during a spinal surgery.

DETAILED DESCRIPTION

[0070] In the following description, exemplary embodiments will be explained with reference to the drawings. The same reference numerals will be used to denote the same or similar structural features.

[0071] FIGS. 1A and 1B show an embodiment of a surgical device 10 according to the present disclosure. The surgical device 10 comprises two device parts 100, 102 that can be coupled with each other. FIG. 1A, shows the two device parts 100, 102 in a decoupled state, and FIG. 1B shows the two device parts 100, 102 in a coupled state. The two device parts 100, 102 each have a longitudinal extension along a longitudinal axis AL. The second device part 102 has a generally tubular configuration and is configured to coaxially receive the first device part 100. The individual components of the surgical device 10 and their functions will be described in greater detail below with reference to FIGS. 2A to 2E and 3.

[0072] FIG. 2A illustrates the first device part 100 of the embodiment shown in FIGS. 1A and 1B. The first device part 100 has a rod-like shape and comprises a operation member 110 at its proximal end. In the present embodiment, the operation member 110 is a handle exemplarily having a knob-like configuration.

[0073] The operation member 110 is rigidly coupled to an actuation member 120 provided at a distal end of the first device part 100. In more detail, a rigid coupling section 130 extends between and interconnects the operation member 110 and the actuation member 120. The operation member 110 is operable to actuate the actuation member 120. Rotation of the operation member 110 around the longitudinal axis A.sub.L leads to a corresponding rotation of the actuation member 120. The rotation around the longitudinal axis A.sub.L can be clockwise or counter-clockwise.

[0074] In other examples a gear mechanism may functionally be provided between the operation member 110 and the actuation member 120. The gear mechanism may enable that a given rotational speed of the operation member 110 results in a different rotational speed of the actuation member 120. In one example, the gear mechanism may function as a reduction gear for fine adjustments. For example, the rotational speeds of the operation member 110 and the actuation member 120 have a ratio of 2:1 (e.g., a rotation of the operation member 110 of 2° results in an rotation of the actuation member of 1°).

[0075] The first device part 100 of the surgical device 10 further comprises a first tracker 140. The first tracker is an optical tracker 140 that can be tracked in the infrared or visible spectrum by a suitable optical tracking system. Also the further trackers described herein are configured as such optical trackers. It will be appreciated that the present disclosure is not limited to optical trackers and an optical tracking system. Rather, one or more of the trackers described herein could also be configured as electromagnetic trackers (each including, e.g., one or more tracking coils) or as ultrasound trackers to be tracked by a suitable electromagnetic or ultrasound tracking system.

[0076] With continued reference to FIG. 2A, optical tracker 140 is detachably coupled to the first device part 100 in a rotationally fixed manner, for example via a plug-in connection. In other examples, the optical tracker 140 may be clamped to the first device part 100. The optical tracker 140 is rigidly (but detachably) coupled to the operation member 110 so that a rotation of the operation member 110 around the longitudinal axis A.sub.L results in a corresponding rotation of the optical tracker 140. Referring to the example wherein the coupling section 130 comprises a gear, the optical tracker 140 may be located on either functional side of the gear.

[0077] The optical tracker 140 shown in FIG. 2A is also shown in FIGS. 2B and 2C in greater detail. As illustrated therein, the optical tracker 140 comprises a body 150, which has a substantially hollow-cylindrical shape with a cylinder axis that is arranged co-axial to the longitudinal axis AL when attached to the coupling section 130. The body 150 comprises a plurality of optically-detectable markers 152 at its outer surface. The optically-detectable markers 152 are located on the body 150 and circumferentially arranged in a pattern that defines, from a given viewing direction, distinctive arrangements of the optically-detectable markers 152 in different rotational states relative to the longitudinal axis AL. The optically-detectable markers 152 are flat passive markers and comprise a reflective coating configured to reflect a specific wavelength, e.g., infrared-(IR-) light.

[0078] The optical tracker 140 further comprises a cover layer 154. The cover layer 154 is transparent (e.g., in the infrared spectrum and/or in the visible spectrum), so that the optically-detectable markers 152 are protected against damages while still being optically-detectable when the tracker body 150 is covered by the cover layer 154, as shown in FIG. 2C. In other examples, the cover layer 154 is transparent only in regions where the optically-detectable markers are located. The cover layer 154 shown in FIG. 2B is configured to be detachably attached to the tracker body 150. A detachable cover layer 154 enables, for example, cleaning, sterilization and maintenance of the body and the optically-detectable markers 152 located on the body 150. In other examples, the cover layer 154 is fixedly attached to the body 150.

[0079] In another variant not illustrated in the drawings, the optically-detectable markers 152 may be located on an inner surface of the cover layer 154. For example, the cover layer 154 may have recesses on its inner surface in which the optically-detectable markers 152 are located.

[0080] FIG. 2D shows an embodiment of the first device part 100 with an alternative arrangement of the operation member 110 and the first optical tracker 140. In this embodiment, the operation member 110 extends perpendicularly to the longitudinal axis A.sub.L and the first optical tracker 140 is rigidly attached to the first device part 100 and located opposite to the operation member with regard to the longitudinal axis A.sub.L. The first optical tracker 140 comprises four optical tracking elements 144 arranged on a cross-shaped mount 146 at the end of each arm. The optical tracking elements 144 are realized as passive tracking elements in the form of spheres having a reflective coating. An optical sensor (e.g., a mono camera or stereo camera, not shown in FIG. 2D) may track the movement of the optical tracking elements 144, and a corresponding rotation of the surgical device 10 can be derived computationally based on the tracked movement.

[0081] FIG. 2E shows a variant of an embodiment of the first device part 100 with a drive member 160 and the coupling section 130. The coupling section 130 comprises a radially inner and a radially outer driver 170, 180 (see also FIG. 3B). The radial direction is defined relative to the longitudinal axis A.sub.L. The drive member 160 is coupled to the radially inner driver 170 and movable relative to the radially outer driver 180 such that a movement of the drive member 160 results in a corresponding movement of the inner driver 170 relative to the outer driver 180. The operation member 110 is coupled to the inner driver 170 and the outer driver 180 in a rotationally fixed manner. It should be noted that in some embodiments, the axial positions of the drive member 160 and the optical tracker 140 may be switched such that the drive member 160 is closer to the operation member 110 than the optical tracker 140.

[0082] The drive member 160 has at least two, in particular three predefined positions along the longitudinal axis A.sub.L. Consequently, also the inner driver 170 has at least two, in particular three predefined positions relative to the outer driver 180. In this embodiment, the actuation member 120 is provided by a combination of an end region of the inner driver 170 and an end region of the outer driver 180.

[0083] An axial movement of the inner driver 170 selectively controls an engagement of an implant part by the actuation member 120 as schematically shown in FIGS. 3A and 3B. For example, in a first, or retracted, axial position (as shown in FIG. 3A) the inner driver 170 may be disengaged from the implant part. In this first position, an operation of the operation member 110 may cause an implant comprising the implant part to expand posteriorly. In a second, or extended, axial position (not shown) the outer driver 180 may be disengaged from the implant part. In this second position, an operation of the operation member 110 may cause the implant comprising the implant part to expand lordotically. In the retracted axial position, the drive member 160 may be closer to the operation member 110 than in the extended axial position. In a third predefined position (as shown in FIG. 3B), both the inner driver 170 and the outer driver 180 may be in engagement with the implant part. In this third position, an operation of the operation member 110 may cause the implant comprising the implant part to expand its height symmetrically.

[0084] In one embodiment, the functions of the drive member 160 and the first optical tracker 140 may be combined in one component (not shown) so as to reduce the number of components of the surgical device 10 while maintaining the functionality as described herein. For example, the drive member 160 may be configured to additionally function as the first optical tracker 140. In this embodiment, the drive member 160 may comprise a body, a cover layer for the body and one or more optically-detectable markers arranged between the body and the cover layer.

[0085] Further, the drive member 160 may be coupled to the operation member 110 in such a way that operation of the operation member 110 may cause the drive member 160 to rotate relative to the shaft around the longitudinal axis A.sub.L.

[0086] FIG. 3A shows a front view of the outer driver 180. The tip of the outer driver 180 is configured as an outer part of the actuation member 120 to cooperate with an implant that is to be actuated by the surgical device 10. The implant will be described in greater detail with reference to FIGS. 6A to C below.

[0087] The tip of the outer driver 180 shown in FIG. 3A has a substantially cylindrical shape, wherein the inner surface of the tip has an actuation profile configured to cooperate in a torque proof manner with a first portion of the implant (i.e., such that the first implant portion cannot rotate relative to the outer driver 180). In more detail, the inner tip surface has an undulating profile in a circumferential direction, but other profiles such as an inner square would serve the same purpose.

[0088] FIG. 3B shows a front view of the outer driver 180 and the inner driver 170. As becomes apparent from FIG. 3B, a tip of the inner driver 170 is configured as an inner part of the actuation member 120 and comprises an actuation profile configured to cooperate in a torque proof manner with a second portion of the implant (i.e., such that the second implant portion can rotate relative to the outer driver 180 when the actuation member 120 is rotated). In more detail, the tip of the inner driver 170 has an outer surface with an undulating profile in a circumferential direction, but other profiles such as an outer square would serve the same purpose.

[0089] FIG. 4 shows the second device part 102 of the surgical device 10 of FIGS. 1A and 1B. The second device part 102 comprises a shaft 210 having a distal first shaft portion 212 configured to be inserted into a patient and a proximal second shaft portion 214 configured to be located outside the patient when the first shaft portion 212 is inserted in the patient. The shaft 210 has a generally tubular configuration such that it defines a passage through the first shaft portion 212 and the second shaft portion 214 to coaxially receive the first device part 100 (see FIG. 1B).

[0090] The first shaft portion 212 comprises two actuatable claws 216 located on opposite sides at its distal tip and configured to detachably grip an implant (not shown in FIG. 4, see FIGS. 6A to 6C below) for temporarily coupling the implant to the first shaft portion 212. The claws 216 are configured to be movable substantially perpendicularly relative to the longitudinal axis AL between a closed position in which the implant is gripped and an opened position in which the implant is not gripped. The claws 216 may be coupled to an operating mechanism. A movement of the operating mechanism in a direction towards the implant opens the claws 216 and the gripped implant is released. A movement in the opposite direction closes the claws 216 and the implant is gripped by the claws 216.

[0091] The second device part 102 further comprises a handle portion at its proximal end. A second optical tracker 220 is rigidly but detachably coupled to the second shaft portion 214 in the region of this handle portion. Due to the rigid coupling of the second optical tracker 220 to the second shaft portion 214 of the second device 123 102 and the rigid coupling of the first optical tracker 140 to the first device part 100, both trackers 140, 220 move relative to each other when the two device parts 100, 102 move to each other. As such, the two trackers 140, 220 permit a determination of a relative movement between the two device parts 100, 102 by a surgical navigation system with optical tracking capabilities.

[0092] In the example of FIG. 4, the optical tracker 220 comprises four optical tracking elements 222 arranged on a cross-shaped mount 224 at the end of each arm. The optical tracking elements 222 are realized as passive tracking elements in the form of spheres having a reflective coating.

[0093] FIGS. 5A and 5B show two different views of a system comprising the surgical device 10 in the coupled state as shown in FIG. 1B and an actuatable implant 300 detachably coupled thereto. In more detail, the implant 300 is held by the claws 216 to the distal end of the second shaft portion 214. The implant 300 is configured to be actuated by the actuation member 120 (as will be described in greater detail below) when the operation member 110 is operated by one hand while the shaft 210 is held stationary by the other hand.

[0094] As will be appreciated, a rotation of the operation member 110 around the longitudinal axis A.sub.L results in a corresponding rotation of the actuation member 120 and the first optical tracker 140. Since the shaft 210 with the second optical tracker 220 is kept stationary, the first optical tracker 140 rotates relative to the second optical tracker 220, so that this relative rotation is detectable by an optical sensor of a surgical navigation system. Since the rotation of the actuation member 120 around the longitudinal axis A.sub.L actuates the actuatable implant 300 coupled to the actuation member 120, and since the rotation of the actuation member 120 corresponds to the rotation of the first optical tracker 140, the rotational movement of the first optical tracker 140 has a predefined relationship with an actuation movement of the actuatable implant 300. In one example, this predefined relationship is given by a change of a dimension of the actuatable implant 300 in relation to an rotation angle covered by the rotational movement of the first optical tracker 140 (e.g., mm/°). The relationship could also be given in relation to a change of a discrete (e.g., binary) actuation state of the implant 300 (e.g., retracted/extended) or any combination of a dimensional change and a state change of the implant 300 in relation to the rotation angle covered by the rotational movement of the operation member 110 and, thus, first optical tracker 140.

[0095] In one example, if the rotation angle covered is greater than 359°, the number of full turns can be counted automatically (e.g., by a computing system connected to the optical sensor of the surgical navigation system). In another example, the first optical tracker 140 is configured to change its position along the longitudinal axis A.sub.L every full turn, so that the number of full turns can be measured (e.g., derived by the distance between the first optical tracker 140 and the second optical tracker 220).

[0096] FIGS. 6A to 6C show detailed views of the actuatable implant 300. In FIG. 6A, the actuatable implant 300 is shown in a rear view with a focus on first and second portions 310, 320 of the implant 300 configured to cooperate with the first shaft portion 212 and the actuation member 120, respectively.

[0097] The first portion 310 of the implant 300 comprises two notches 312 on opposite sides of the first portion 310. The notches 312 are configured to cooperate with corresponding claws 216 of the surgical device 10 (not shown in FIGS. 6A to 6C; see for example FIG. 4) to rigidly and releasably couple the first portion 310 of the implant 300 to the first shaft portion 212.

[0098] The center of the first portion 310 of the implant 300 comprises a substantially cylindrical shaped cavity configured to receive the substantially cylindrically shaped tip of the first shaft portion 212 and having a matching undulating outer profile. The second portion 320 of the implant 300 is located in the center of the substantially cylindrical shaped cavity of the first portion 310 of the implant 300 and configured to cooperate with the actuation member 120 via a matching undulating inner profile. In this example, an actuation of the actuation member 120 rotates the second portion 320 relative to the first portion 310 of the implant 300. The rotation of the second portion 320 further leads to a change of an actuation state of the implant 300, in particular to a change of dimensions (here: a height of the implant 300).

[0099] FIG. 6B shows a side view of the implant 300 with a focus on a mechanism configured to actuate (here: expand or retract) at least a part of the implant 300 relative to the first shaft portion 212 when the second portion 320 of the implant 300 is actuated by the actuation member 120. In the view of FIG. 6B, the implant 300 comprises an actuatable upper implant part 330 and an actuatable lower implant part 340 each comprising a guiding portion configured to define the direction of the actuation movement of the implant parts 330, 340 either away from each other (expansion) or towards each other (retraction). Each guiding portion comprises a slit-like guiding opening 350, 360. The guiding openings 350, 360 cooperate with a guide pin 370 extending into the guiding openings 350, 360 for guiding movements of the implant parts 330, 340.

[0100] FIGS. 6D to 6F each show a schematical side view of the implant 300 with a corresponding position of the drive member 160 along the longitudinal axis A.sub.L. Each side view refers to a different engagement of the implant 300 with the actuation member 120 exemplarily as shown in FIGS. 3A and 3B. The engagement of the implant 300 and the actuation member 120 is in each case dependent on the position of the drive member 160 along the longitudinal axis A.sub.L.

[0101] In FIG. 6D, the drive member 160 is located in a first position along the longitudinal axis A.sub.L and the implant 300 is configured for posterior expansion or retraction. In FIG. 6E, the drive member 160 is located in a second position along the longitudinal axis A.sub.L and the implant 300 is configured for lordotical expansion or retraction. In

[0102] FIG. 6F, the drive member 160 is located in a third position along the longitudinal axis A.sub.L and the implant 300 is configured for a symmetric height expansion or retraction.

[0103] FIG. 7 illustrates in a block diagram 400 a computer-implemented method embodiment for determining an actuation of the actuation member 120 of the surgical device 10 described above. The method embodiment will be explained with reference to FIGS. 8 and 9.

[0104] FIG. 8 shows a schematic representation of a computer program product 500 with code 510 executable by a processor of a computer 520. The code is configured to cause the processor to carry out the method embodiment when executed by the processor. The computer 520 may belong to a surgical navigation system as commonly used for computer assisted surgery.

[0105] FIG. 9 shows a schematic representation of such a surgical navigation system with an additional optical sensor 415 connected to a computer 520 (see FIG. 8) and a display 600 also connected to the computer 520. The surgical navigation system is configured for visualizing at least the actuatable implant 300 and, optionally, at least a part of the first shaft portion 212 on the display 600.

[0106] Referring now to FIG. 7 again, in step 410, the computer 520 determines a position of the first optical tracker 140 around the longitudinal axis A.sub.L defined by the shaft 210 of the surgical device 10. In one example, determining the position may be performed automatically via the optical sensor 415 and the computer 520. Based on data from the optical sensor 415, the computer 520 in some scenarios tracks a change of the distinctive arrangement of the optically-detectable markers 152 of the first optical tracker 140 from a given viewing direction (e.g., relative to the second optical tracker 220). In this way, a positional change of the first optical tracker 140 around the longitudinal axis A.sub.L is determined.

[0107] In step 420, the computer 520 determines, from at least the position of the first optical tracker 140 and optionally further information, an actuation of the actuation member 120. As an example, based on data from the optical sensor 415, the computer 520 may continuously track the distinctive arrangement of the optically-detectable markers 152 of the first optical tracker 140. Any newly received data are compared with previously received ones. The comparison may be done in real-time. If a difference between the data is determined, the first optical tracker 140 was rotated around the longitudinal axis A.sub.L and consequently, the actuation member 120 was actuated. If no difference between the data can be determined, the first optical tracker 140 was not or no longer rotated and thus, the actuation member 120 was not or no longer actuated. A continuous comparison of received results therefore enables determining a start and an end of an actuation as well as determining a rotation angle covered by the first optical tracker 140 during the determined actuation (e.g., relative to the second optical tracker 220).

[0108] Additionally, an actuation state of the implant 300 resulting from the actuation can be determined by the computer 520 based on the determined angle of rotation. In particular, the resulting actuation state can be determined relative to a known initial state prior to the actuation. Therefore, the known initial actuation state can be combined with the determined angle of rotation to determine a later actuation state of the implant 300. In particular, a dimensional change of the implant 300 can be determined based on a predefined (e.g., functional) relationship between the first optical tracker 140 and the actuatable implant 300 as pre-stored by the computer 520.

[0109] For the visualization, image data of the surgical device 10 and the implant 300 may be pre-stored by the computer 520. The optical sensor 415 may track the movements of the first and the second optical trackers 140, 220 and send tracking related data to the computer 520. The computer 520 receives and processes these data and correspondingly visualizes models of the surgical device 10 and the implant 300 on the display 600.

[0110] In the exemplary display view shown in FIG. 10, the visualization comprises visualizing the implant 300 in relation to registered three dimensional image data of a patient to assist a surgeon during a surgery. The image data of the patient may also be pre-stored by the computer 520. Additionally, the position of the patient may be tracked via additional optical patient trackers. A visualization in real-time may comprise tracking movement of both, the patient and the surgical device 10 and converting the tracked movement into a visualization on the display 600.

[0111] FIGS. 11A and 11B show schematic representations of the visualization of the actuatable implant 300 (and, optionally, at least a part of the first shaft portion 212) with registered three dimensional image data of a patient on the display 600 for a spinal intervention. A change of a dimension of the actuatable implant 300 is also visualized in real time. For visualizing the dimensional change of the implant 300, the rotation of the optical tracker 140 is tracked by the optical sensor 415 and translated by the computer 520 according to the relationship between the rotational movement of the optical tracker 140 and the actuation of the implant 300 as described above.

[0112] Further, assuming that the drive member 160 can be tracked also (e.g., because its function is assumed by the first optical tracker 140, or because the first optical tracker 140 is rigidly attached to the drive member 160, or because a separate third optical tracker is rigidly attached thereto), the position of the drive member 160 along the longitudinal axis A.sub.L may be tracked by the optical sensor 415, for example by tracking an axial distance between the first optical tracker 140 and the second optical tracker 220. The tracked position may be translated by the computer 520 into a particular engagement of the implant 300 and the actuation member 120, so as to determine the type of expansion or retraction of the implant 300 (e.g., posteriorly, lordotically or symmetric height expansion or retraction, as described above) for later visualization. Alternatively to tracking the position of the drive member 160 with the optical sensor 415, the position of the drive member 160 may be entered manually into the computer 520, for example via a graphical user interface (GUI).

[0113] Based on the results of the translation of the rotation of the optical tracker 140 and, optionally, based on the position of the drive member 160 along the longitudinal axis A.sub.L, the computing system determines and applies the dimensional change on the implant model visualized on the display 600. All visualizations described above may be done in real-time.

[0114] As has become apparent from the above description of exemplary embodiments, the surgical device presented herein comprises an optical tracker that rotates relative to a longitudinal axis when the surgical device is operated. This rotation can be translated into an actuation movement of, for example, an implant. The actuation movement, in turn, can be visualized despite not being observable as such.

[0115] It will be appreciated that the present disclosure is not limited to detecting an actuation movement of an implant. Rather, the surgical device may have an actuation member that harvests tissue, or performs any other surgical task, and the state of that task can also be visualized as described above.