Spinal decompression planning

Abstract

Disclosed is a method for assisting a user in planning a surgical procedure for spinal decompression. Medical patient image data is obtained and a critical area is identified. A planned cutting shape and / or a planned volume to be removed is obtained. User input is obtained that indicates an update of the cutting shape and / or volume. It is then determined whether the updated cutting shape and / or the updated volume to be removed intersect the critical area. A computer program, a carrier and a surgical planning system are also disclosed.

Description

[0001] Stryker European Operations Limited 30A-162 411

[0002] - 1 -

[0003] Spinal Decompression Planning

[0004] Technical Field

[0005] The present disclosure relates to a method for assisting a user in planning a surgical procedure for spinal decompression. A corresponding computer program, carrier and surgical planning system are also disclosed.

[0006] Background

[0007] Spinal stenosis is a medical condition in which the spinal canal is narrowed, putting pressure on the spinal cord or nerves. This pressure may lead to pain or other implications. Common treatment techniques of spinal stenosis include spinal decompression techniques such as Laminectomy, Laminotomy or Foraminotomy.

[0008] These types of surgeries are difficult for a variety of reasons. For example, the proximity to the spinal cord generally requires a high level of precision, the treatments as such are quite complex and, due to the required length of surgery, may lead to surgeon fatigue, etc.

[0009] Is may be desirable to provide a technique that supports users such as surgeons in (e.g., pre-) planning a surgical procedure for spinal decompression.

[0010] Summary of the invention

[0011] The solution to the above and other problems is provided the followings aspects.

[0012] According to a first aspect, a computer-implemented method for assisting a user in planning a surgical procedure for spinal decompression is provided. The method comprises: obtaining medical patient image data representing at least a portion of a patient's spine; identifying at least one (e.g., two-dimensional) critical area and / or at least one (e.g., three-dimensional) critical volume based on the medical patient image data; obtaining planning data indicative of at least one planned cutting shape associated with spinal decompression and / or at least one (e.g., three-dimensional) planned volume to be removed for spinal decompression; obtaining a user input Stryker European Operations Limited 30A-162 411

[0013] - 2 - indicating an update of one or more of the at least one planned cutting shape and / or one or more of the at least one planned volume to be removed; and determining whether the updated cutting shape(s) and / or the updated volume(s) to be removed intersect one or more of the at least one critical area and / or one or more of the at least one critical volume.

[0014] According to the present disclosure, the at least one cutting shape may comprise or consist of: {i} one or more (e.g., flat and / or two-dimensional) cutting planes; {ii} one or more (e.g., linear or curved) cutting paths that, optionally, each lie within one or more (e.g., flat and / or two-dimensional) cutting planes; {iii} one or more (e.g., non-planar) cutting surfaces. The (e.g., each) cutting shape associated with spinal decompression may define a geometrical shape along which a cut shall be performed (e.g., using a surgical instrument such as a saw, a drill or a cutter) for spinal decompression. The at least one volume to be removed may comprise (e.g., be entirely filled with) bone tissue of the patient's spine. The at least one volume to be removed may be defined and / or bounded by one or more cutting shapes. For example, a volume to be removed may comprise a part of a patient's vertebra that is defined by a curved cutting surface intersecting said vertebra.

[0015] Regarding obtaining medical patient image data:

[0016] For example, a set of levels, i.e. cross-sectional images of the spine, may be provided as medical patient image data. This set of levels forms a virtual reconstruction of the spine. A portion of the full set of levels or the full set of levels may be used for the further procedure. So, if it is determined that a spinal decompression shall be performed on a vertebra, the portion of the set of levels may only include the levels showing the vertebra. Additionally, the portion of the set of levels may include levels showing vertebrae above and / or below the vertebra determined for spinal decompression. In doing so, either all of the levels showing the above and / or below vertebrae may be included in the portion of the set of levels or only a portion of the levels of the above and / or below vertebrae, e.g. half and / or less than half of the levels of the above and / or below vertebrae, closest to the vertebra determined for spinal decompression may be included in the portion of the set of levels.

[0017] Regarding the identifying at least one critical area and / or volume:

[0018] A critical area and / or volume may be identified by the user and / or automatically by (computer-aided) image processing of the medical patient image data. The latter Stryker European Operations Limited 30A-162 411

[0019] - 3 - may include determining a set of meshes and anatomical key points via one or more segmentation algorithms.

[0020] Regarding obtaining a user input:

[0021] For example, the user may add to or subtract from the cutting shape(s) and / or the volume(s). For such addition or subtraction an algorithm may be provided to take a (virtual) seed point placed by the user as input and to then generate a spherical volume around this seed point. The user may control the volumetric size of the spherical volume by changing the radius. The volumetric expansion of the spherical volume may be limited either through a plane set by the user or by boundaries of the segmented vertebra(e).

[0022] If it is determined that the updated cutting shape(s) and / or the updated volume(s) to be removed intersect one or more of the at least one critical area and / or one or more of the at least one critical volume, a warning may be output to the user. The warning may include at least one suggestion for further updated cutting shape(s) and / or further updated volume(s) to be removed, which avoid intersecting the one or more of the at least one critical area and / or volume.

[0023] Obtaining planning data may comprise: determining a stenosis region based on the medical patient image data; and determining a planned cutting shape associated with spinal decompression and / or a planned volume to be removed for spinal decompression based on the determined stenosis region.

[0024] Determining the stenosis region may comprise: segmenting the stenosis region based on the medical patient image data using a trained machine learning model and / or identifying the stenosis region based on the segmented medical patient image data using a trained machine learning model.

[0025] The planned cutting shape and / or the planned volume to be removed may be determined based on the medical image data and the determined stenosis region using a trained machine learning model.

[0026] The stenosis may be determined by the user and / or automatically by image processing of the medical patient image data, such as stenosis segmentation by machine learning (ML). The user may determine the stenosis in the levels based on his experience. Additionally, or alternatively, the stenosis may be automatically Stryker European Operations Limited 30A-162 411

[0027] - 4 - determined by comparison of the left and right half of the vertebra, by comparison of the vertebra with adjacent vertebrae, and / or by comparison of the vertebra with a vertebra from a database of vertebrae, which may include a statistical and / or an ideal vertebra. Based on this comparison, structures in a portion of the vertebra, which portion is provided for the spinal cord, the nerves and / or the facet joints may be determined as the stenosis region. The user may then update the automatically determined stenosis region by adding or subtracting regions from it manually. The machine learning model may be trained based on stenosis regions entirely determined by the user, and / or based on the user input or lack thereof for modifying an automatically determined stenosis region. To reduce input by the user, the machine learning may be based on initial user input and / or based on user input updating automatically computer-generated data.

[0028] The volume to be removed may be determined al) based on the user marking a few points across one level or several levels, e.g. across 1 to 3 levels, and executing an algorithm configured to extend I connect these points to create a volume to be removed, and / or a2) based on the user highlighting I drawing every area to be removed on a level, and / or b) based on image processing of a set of images, e.g. images obtained by Computed Tomography (CT) or Magnetic Resonance Imaging (MRI), automatically determining an area to be removed across one level or several levels, e.g. across 1 to 3 levels, wherein the user may modify the determined volume to be removed.

[0029] Instead of or in addition to a volume to be removed, a cutting shape can be determined in a similar manner.

[0030] The method may further comprise: determining, for each of at least one surgical instrument, whether the surgical instrument is suitable to perform the spinal decompression procedure associated with the planned and / or updated cutting shape(s) and / or the planned and / or updated volume(s) to be removed. An indication (e.g., a visualization) may be output that indicates whether the surgical instrument (e.g., selected by a user) is determined to be suitable to perform the spinal decompression procedure.

[0031] Determining whether the surgical instrument is suitable to perform the spinal decompression procedure may comprise determining whether the surgical instrument Stryker European Operations Limited 30A-162 411

[0032] - 5 - is capable of reaching the planned and / or updated cutting shape(s) and / or the planned and / or updated volume(s) to be removed without traversing the at least one critical area and / or the at least one critical volume.

[0033] The method may further comprise: determining, for each of at least one surgical instrument, {i} which part(s) of the planned and / or updated cutting shape(s) and / or the planned and / or updated volume(s) to be removed can be reached by the surgical instrument without traversing the at least one critical area and / or the at least one critical volume and / or {ii} which part(s) of the planned and / or updated cutting shape(s) and / or the planned and / or updated volume(s) to be removed cannot be reached by the surgical instrument without traversing the at least one critical area and / or the at least one critical volume.

[0034] The method may further comprise: triggering output of a visualization indicating {i} the part(s) of the planned and / or updated cutting shape(s) and / or the planned and / or updated volume(s) to be removed that can be reached by the surgical instrument without traversing the at least one critical area and / or the at least one critical volume in a different manner than {ii} the part(s) of the planned and / or updated cutting shape(s) and / or the planned and / or updated volume(s) to be removed that cannot be reached by the surgical instrument without traversing the at least one critical area and / or the at least one critical volume.

[0035] It may be determined whether the surgical instrument is capable of reaching a given part of the planned and / or updated cutting shape(s) and / or a given part of the planned and / or updated volume(s) to be removed without traversing the at least one critical area and / or the at least one critical volume by: determining an entry path of the surgical instrument; and determining whether the entry path intersects the at least one critical area and / or the at least one critical volume.

[0036] The entry path may be determined based on a planned or tracked pose of the surgical instrument. The tracked pose may be obtained from a tracking device configured to track one or more tracking markers associated with the surgical instrument. The warning may include at least one suggestion for at least one updated entry path, which avoids intersecting the one or more of the at least one critical area and / or volume. Stryker European Operations Limited 30A-162 411

[0037] - 6 -

[0038] The method may further comprise: obtaining a user input indicating a selection of a surgical instrument from the at least one surgical instrument; and triggering feedback for the user to inform the user whether the selected surgical instrument is determined to be suitable to perform the spinal decompression procedure.

[0039] Triggering feedback may comprise: displaying a visualization of the selected surgical instrument and visualizing the selected surgical instrument in a different manner depending on whether the selected surgical instrument can be used to perform the surgical procedure or not.

[0040] The method may further comprise: displaying a visualization of {i} at least a part of the medical patient image data and {ii} one or more of the at least one planned cutting shape and / or one or more of the at least one planned volume to be removed, wherein the user input indicating the update relates to an update of one or more displayed planned cutting shapes and / or one or more displayed volumes to be removed.

[0041] The user input relating to an update of one or more displayed volumes to be removed may be based on a seed growing algorithm that automatically selects pixels or voxels around a user-selected starting point in the medical image data.

[0042] The visualization(s) may use one color for the cutting shape(s) and another color for the volume(s) to be removed. Depending on the surgical instrument selected by the user for the surgical procedure, the visualization(s) may include a colored indication of the cutting shape(s) and / or volume(s) to be removed being unreachable in their entirety or of the portions of the cutting shape(s) and / or volume(s) to be removed being unreachable. Further, the visualization(s) may include a list of surgical instruments capable of reaching the cutting shape(s) and / or volume(s) to be removed in their entirety. Also, this list may be ordered by reachability of the respective surgical instrument. Further, if a user selects a surgical instrument that cannot reach the cutting shape(s) and / or volume(s) to be removed, a color change in the graphics, e.g. of the surgical instrument, or a warning may be displayed to indicate that the surgical instrument is not suitable for the procedure. It is possible that the selection of a surgical instrument displays a zone that is reachable by the surgical instrument. Upon selection of another surgical instrument the zone is updated to visualize its reachability. The surgical instrument may be a robotic or manually navigated surgical instrument (tool). Stryker European Operations Limited 30A-162 411

[0043] - 7 -

[0044] The at least one critical area and / or the at least one critical volume may comprise one or more of the following: at least a part of a facet joint; at least a part of the spinal canal; at least a part of an intervertebral disk.

[0045] The method may further comprise setting virtual boundaries based on at least one of the at least one critical area and / or volume, patient specific anatomy, the cutting shape(s) and / or the volume(s) to be removed, and / or an entry path for a surgical instrument into a patient's body.

[0046] These virtual boundaries may be used for providing a surgical plan, including a surgical instrument and a surgical path of the surgical instrument. The virtual boundaries may be used as guidance for the surgical path and may further be used during navigation of the surgical instrument following the surgical path.

[0047] According to a second aspect, a computer program is provided. The computer program comprises instructions that when executed by at least one processor cause the at least one processor to perform the method according to the first aspect.

[0048] According to a third aspect, a carrier is provided. The carrier carries the computer program according to the second aspect. The carrier may be one of a data stream, a computer program product or a non-transitory computer storage medium.

[0049] According to a fourth aspect, a surgical planning system is provided. The surgical planning system comprises at least one processor, the at least one processor configured to perform the method according to the first aspect. The surgical planning system may further comprise at least one of the following entities: a tracking device configured to track one or more tracking markers associated with a surgical instrument or a patient; a user input unit configured to receive a user input from the user; a display unit configured to display one or more visualizations to the user.

[0050] Description of the Drawings

[0051] Fig. 1 shows a lateral view of a vertebra on the left and a superior crosssection of the vertebra on the right. Stryker European Operations Limited 30A-162 411

[0052] - 8 -

[0053] Fig. 2 shows a simplified illustration of a laminectomy (I), a laminotomy (II) and a foraminotomy (III) in the superior cross-section of the vertebrae shown in Fig. 1.

[0054] Fig. 3 shows an exemplary critical area and volume to be removed with regard to the vertebra shown in Fig. 1.

[0055] Fig. 4 shows various ways (al, a2, b) of determining a region of stenosis in an exemplary preparation for the foraminotomy (III) shown in Fig. 2.

[0056] Fig. 5 indicates the reachability of the volume to be removed shown in Fig. 4 as III b) depending on the surgical instrument used.

[0057] Fig. 6 is a flow diagram of a method in accordance with the present disclosure.

[0058] Detailed Description

[0059] Fig. 1 shows a lateral view of a vertebra 1 on the left and a superior cross-section of the vertebra 1 on the right.

[0060] The vertebra 1, which in this case is a lumbar vertebra but could alternatively be a thoracic or cervical vertebra, comprises a spinal canal 3 with a spinal cord 5 and nerves 7 in it. The spinal cord 5 and / or nerves 7 can be defined as critical volumes. The vertebra 1 further comprises a back part called lamina 9 and openings called foramen 11 through which nerves 7 exit the vertebra 1. Facet joints 13 are located between the spinous process 15 of the lamina 9 of two adjacent vertebrae 1. The facet joints 13 can also be defined as critical volumes.

[0061] Fig. 2 shows a simplified illustration of a laminectomy (I), a laminotomy (II) and a foraminotomy (III) in the superior cross-section of the vertebra 1 shown in Fig. 1.

[0062] Spinal stenosis is a condition in which pressure is put on the spinal cord 5 and / or nerves 7 due to a narrow spinal canal 3 and / or foramen 11. A decompression surgery has the goal to relieve this pressure on the spinal cord 5 and / or nerves 7. The following procedures, i.e. a laminectomy (I), a laminotomy (II) and a foraminotomy (III), all have in common that they include removing a portion of the Stryker European Operations Limited 30A-162 411

[0063] - 9 - vertebra 1 to enlarge the spinal canal 3 or foramen 11 and, thereby, to relieve pressure on the spinal cord 5 or nerves 7. One may say that cutting planes, cutting surfaces and cutting paths are examples of cutting shapes that define geometrical shapes along which a cut is to be performed for spinal decompression.

[0064] A laminectomy (I) involves removing a cutting volume 17 of the lamina 9, e.g. removing the spinous process 15, for example by cutting along cutting planes 17-1 and 17-2, which in this case are oblique to each other. Rather than cutting along such flat planes 17-1, 17-2, it is also possible to remove a cutting volume by cutting along a non-planar cutting surface.

[0065] A laminotomy (II) involves removing a smaller cutting volume 19 of the lamina 9 compared to the laminectomy (I), e.g. by creating an opening next to the spinous process 15. This smaller cutting volume 19 being an opening can be created by drilling along a cutting path 19-1, which can extend in a cutting plane and / or cutting surface.

[0066] A foraminotomy (III) enlarges the foramen 11 by removing a cutting volume 21, e.g. removing walls of the foramen 11 to enlarge the opening provided by the foramen 11.

[0067] A surgical procedure for spinal decompression, such as one of the above (I-III), requires careful planning. Therefore, a computer-implemented method may assist a user in planning a surgical procedure for spinal decompression. A flow-chart of such a method is shown in Fig. 6 and will be described below with reference to Figs. 2 to 5.

[0068] In a first step 602, medical patient image data representing at least a portion of a patient's spine is obtained.

[0069] For example, a set of levels, i.e. cross-sectional images of the spine, may be provided as medical patient image data. This set of levels forms a virtual reconstruction of the spine. A portion of the full set of levels or the full set of levels may be used for the further procedure. So, if it is determined that a spinal decompression shall be performed on a vertebra 1, e.g. L4, the portion of the set of levels may only include the levels showing the vertebra 1, e.g. L4. Additionally, the portion of the set of levels may include levels showing vertebrae above and / or Stryker European Operations Limited 30A-162 411

[0070] - 10 - below, e.g. L3 and / or L5, the vertebra 1 determined for spinal decompression, e.g. L4. In doing so, either all of the levels showing the above and / or below vertebrae may be included in the portion of the set of levels or only a portion of the levels of the above and / or below vertebrae, e.g. half and / or less than half of the levels of the above and / or below vertebrae, closest to the vertebra 1 determined for spinal decompression may be included in the portion of the set of levels.

[0071] In a second step 604, at least one critical area and / or at least one critical volume is identified based on the medical patient image data.

[0072] A critical area and / or volume may be identified by the user and / or automatically by image processing of the medical patient image data. The latter may include determining a set of meshes and anatomical key points via segmentation algorithms.

[0073] Fig. 3 shows a critical area 23 and a critical volume 25 with regard to the vertebra 1 shown in Fig. 1.

[0074] Here, the critical area 23 is a plane, which can be limited to have a specific length and width. Such limitation can be set by the user and / or automatically by image processing of the medical patient image data. The critical volume 25 in the illustrated example is a sphere with a center that is set by the user and / or automatically by image processing of the medical patient image data, wherein a radius r is defined around the center by the user and / or automatically by image processing of the medical patient image data to form the sphere. The center 27 may also be referred to as a seed point. Further, the critical area 23 may form one end of another critical volume extending in one direction orthogonal to the here plane-like critical area 23. The volumetric extension of the sphere or of the aforementioned another critical volume may be limited by planes set by the user or by boundaries of the segmented vertebra(e). The critical volume 25 may also be referred to as a safety zone.

[0075] Thereby, the spinal cord 5, the nerves 7, the facet joints 13 and, optionally, portions of the vertebra 1 (e.g., in close proximity to these important elements) may be identified as being critical.

[0076] In a third step 606, planning data indicative of at least one cutting shape associated with spinal decompression (e.g., a cutting plane or a non-planar cutting surface) and / or at least one volume to be removed for spinal decompression is obtained. Stryker European Operations Limited 30A-162 411

[0077] - 11 -

[0078] This step 606 may include a first sub-step of determining a stenosis region, which may be done in various ways.

[0079] The stenosis may be determined by the user and / or automatically by image processing of the medical patient image data, such as stenosis segmentation by machine learning (ML). The user may determine the stenosis in the levels based on his experience. Additionally, or alternatively, the stenosis may be automatically determined by comparison of the left and right half of the vertebra, by comparison of the vertebra with adjacent vertebrae, and / or by comparison of the vertebra with a vertebra from a database of vertebrae, which may include a statistical and / or an ideal vertebra. Based on this comparison, structures in a portion of the vertebra, which portion is provided for the spinal cord 5, the nerves 7 and / or the facet joints 13 may be determined as the stenosis region. The user may then update the automatically determined stenosis region by adding or subtracting regions from it manually. The machine learning may be based on stenosis regions entirely determined by the user, and / or based on the user input or lack thereof for modifying an automatically determined stenosis region.

[0080] The third step 606 may include a second sub-step of obtaining planning data indicative of at least one cutting shape and / or at least one volume to be removed for spinal decompression based on the stenosis region determined in the first sub-step of step 606.

[0081] Fig. 4 shows various ways of determining a volume to be removed for spinal decompression in an exemplary preparation for the foraminotomy (III) shown in Fig. 2.

[0082] The volume to be removed may be determined al) based on the user marking a few points 31 across one level, as shown here, or several levels, e.g. across 1 to 3 levels, and executing an algorithm configured to extend I connect these points 31 to create a volume to be removed, and / or a2) based on the user highlighting I drawing every area or volume to be removed 29 on a level, and / or b) based on image processing of a set of images, e.g. images obtained by Computed Tomography (CT) or Magnetic Resonance Imaging (MRI), automatically determining an area or volume to be removed 29 across one Stryker European Operations Limited 30A-162 411

[0083] - 12 - level, as shown here, or several levels, e.g. across 1 to 3 levels, wherein the user may modify the determined volume to be removed.

[0084] Instead of or in addition to a volume to be removed, a cutting shape as described above with regard to the laminectomy (I) and the laminotomy (II) shown in Fig. 2 may be determined.

[0085] A visualization of the medical patient image data and the cutting shape(s) and / or volume(s) to be removed may be displayed. The visualization may include using one color for the cutting shape(s) and another color for the volume(s) to be removed. Depending on the surgical instrument selected by the user for the surgical procedure, the visualization may include a colored indication of the cutting shape(s) and / or volume(s) to be removed being unreachable in their entirety or of the portions of the cutting shape(s) and / or volume(s) to be removed being unreachable. Further, the visualization may include a list of surgical instruments capable of reaching the cutting shape(s) and / or volume(s) to be removed in their entirety. Also, this list may be ordered by reachability of the respective surgical instrument. Further, if a user selects a surgical instrument that cannot reach the cutting shape(s) and / or volume(s) to be removed, a color change in the graphics, e.g. of the surgical instrument, or a warning may be displayed to indicate that the surgical instrument is not suitable for the procedure. It is possible that the selection of a surgical instrument displays a zone that is reachable by the surgical instrument. Upon selection of another surgical instrument the zone is updated to visualize its reachability. The surgical instrument may be a robotic or manually navigated surgical instrument (tool).

[0086] Fig. 5 indicates the reachability of the volume to be removed shown in Fig. 4 as III b), depending on the surgical instrument (i-iii) used.

[0087] Each of the exemplary surgical instruments i-iii on the right of Fig. 5 has a tip with a different length, which length increases from the top surgical instrument i to the bottom surgical instrument iii in Fig. 5. On the left of each surgical instrument i-iii there is a representation of Fig. 4 III b) with the volume to be removed 29 divided into a reachable portion 29-1, indicated as a rectangle filled with black, and an unreachable portion 29-2, indicated as a rectangle filled with white, for the corresponding surgical instrument i-iii. It is evident from Fig. 5 that surgical instrument ii reaches further into the volume to be removed 29 than surgical Stryker European Operations Limited 30A-162 411

[0088] - 13 - instrument i, and surgical instrument iii reaches the entire volume to be removed 29. Of course, the same applies to a cutting shape such as a cutting plane or a curved cutting surface. A volume to be removed and / or a cutting shape may also be referred to as a target. Each surgical instrument i-iii may be linked to virtual boundaries specific to the surgical instrument i-iii and / or the patient specific anatomy (for example, a geometry of the vertebra or a portion of the vertebra).

[0089] A fourth step 608 includes obtaining a user input indicating an update of one or more of the at least one planned cutting shape and / or one or more of the at least one planned volume to be removed.

[0090] For example, the user may add to or subtract from the cutting shape(s) and / or the volume(s). For such addition or subtraction an algorithm may be provided to take a (virtual) seed point placed by the user as input and to then generate a spherical volume around this seed point. The user may control the volumetric size of the spherical volume by changing the radius. The volumetric expansion of the spherical volume may be limited either through a plane set by the user or by boundaries of the segmented vertebra(e).

[0091] A fifth step 610 includes determining whether the updated cutting shape(s) and / or the updated volume(s) to be removed intersect one or more of the at least one critical area 23 and / or one or more of the at least one critical volume.

[0092] If so, a warning may be output to the user in a sixth step 612. The warning may include at least one suggestion for further updated cutting shape(s) and / or further updated volume(s) to be removed, which avoid intersecting the one or more of the at least one critical area and / or volume.

[0093] The method may further include providing a surgical plan, including a surgical path of a surgical instrument. The surgical plan may further include at least one of an indication of the surgical instrument, an entry point or entry path for the surgical instrument, a path for the surgical instrument, and a target for the surgical instrument. The surgical plan may be provided by the user. Alternatively, the surgical plan may be provided by being automatically computer-generated based at least on the provided set of levels or a portion thereof, the at least one critical area and / or volume, and the cutting shape(s) and / or the volume(s) to be removed. Stryker European Operations Limited 30A-162 411

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[0095] Further criteria for the surgical plan may be at least one of:

[0096] • a plane set by the user, e.g. for a preferred path or as a boundary not to be crossed by the (e.g., cutting, instrument or entry) path;

[0097] • boundaries of the segmented vertebra(e);

[0098] • a safety zone, which can be an area or a volume, e.g. a volume around a facet joint, which safety zone is not to be crossed by the (e.g., cutting, instrument or entry) path; and / or

[0099] • reachability of the target with a certain surgical instrument.

[0100] The method may include determining whether a path of a surgical instrument that is required for reaching the updated cutting shape(s) and / or updated volume(s) to be removed intersects one or more of the at least one critical area and / or volume, and if so, providing a warning to the user. The warning may include at least one suggestion for at least one updated path, which avoids intersecting the one or more of the at least one critical area and / or volume.

[0101] The method may include obtaining a user input indicating an update of the path of the surgical instrument (e.g., the surgical path included in the surgical plan) and optionally updating the warning and / or visualization(s) accordingly.

[0102] The above steps and provisions may be subject to computer-implemented machine learning (ML) configured to reduce input by the user in the above-described computer-implemented method, wherein the machine learning is based on initial user input and / or based on user input updating automatically computer-generated data. So, there may be a step of machine learning based on user input and / or lack thereof in or following one of the steps of the method, and a step of automatically performing the step based on a learning result.

[0103] To avoid repetition, additional features described in the Summary section are not repeated in verbatim here. It is to be understood, however, that the features and / or steps of the method described with reference to the figures can be combined with the features and / or steps of the method according to the first aspect described in the Summary section, and vice versa. The method disclosed herein may in particular not comprise a surgical step. The method may be performed by at least one processor of a surgical planning system comprising: a tracking device configured to track one or more tracking markers associated with a surgical instrument or a patient, a user input unit configured to receive the user input from the user; and a display unit Stryker European Operations Limited 30A-162 411

[0104] - 15 - configured to display the visualization(s) to the user. In one example, the warning may be an auditory warning rather than a visual warning in the form of a displayed visualization. Further modifications and advantages to the method disclosed herein will be apparent to those skilled in the art.

Claims

Stryker European Operations Limited 30A-162 411- 16 -Claims1. A computer-implemented method for assisting a user in planning a surgical procedure for spinal decompression, the method comprising: obtaining (602) medical patient image data representing at least a portion of a patient's spine; identifying (604) at least one critical area (23) and / or at least one critical volume (25) based on the medical patient image data; obtaining (606) planning data indicative of at least one planned cutting shape associated with spinal decompression and / or at least one planned volume to be removed for spinal decompression; obtaining (608) a user input indicating an update of one or more of the at least one planned cutting shape and / or one or more of the at least one planned volume to be removed; and determining (610) whether the updated cutting shape(s) and / or the updated volume(s) to be removed intersect one or more of the at least one critical area (23) and / or one or more of the at least one critical volume (25).

2. The method of claim 1, wherein if it is determined that the updated cutting shape(s) and / or the updated volume(s) to be removed intersect one or more of the at least one critical area (23) and / or one or more of the at least one critical volume (25), a warning is output to the user.

3. The method of claim 1 or 2, wherein obtaining planning data comprises: determining a stenosis region based on the medical patient image data; and determining a planned cutting shape associated with spinal decompression and / or a planned volume to be removed for spinal decompression based on the determined stenosis region.

4. The method of claim 3, wherein determining the stenosis region comprises: segmenting the stenosis region based on the medical patient image data using a trained machine learning model and / or identifying the stenosis region based on the segmented medical patient image data using a trained machine learning model.

5. The method of claim 3 or 4, wherein the planned cutting shape and / or the planned volume to be removed are determined based on the medical image data and the determined stenosis region using a trained machine learning model.Stryker European Operations Limited 30A-162 411- 17 -6. The method of any one of claims 1 to 5, further comprising: determining, for each of at least one surgical instrument, whether the surgical instrument (i-iii) is suitable to perform the spinal decompression procedure associated with the planned and / or updated cutting shape(s) and / or the planned and / or updated volume(s) to be removed.

7. The method of claim 6, wherein determining whether the surgical instrument (i-iii) is suitable to perform the spinal decompression procedure comprises determining whether the surgical instrument (i-iii) is capable of reaching the planned and / or updated cutting shape(s) and / or the planned and / or updated volume(s) to be removed without traversing the at least one critical area (23) and / or the at least one critical volume (25).

8. The method of any one of claims 1 to 7, further comprising: determining, for each of at least one surgical instrument,{i} which part(s) of the planned and / or updated cutting shape(s) and / or the planned and / or updated volume(s) to be removed can be reached by the surgical instrument without traversing the at least one critical area (23) and / or the at least one critical volume (25) and / or{ii} which part(s) of the planned and / or updated cutting shape(s) and / or the planned and / or updated volume(s) to be removed cannot be reached by the surgical instrument without traversing the at least one critical area (23) and / or the at least one critical volume (25).

9. The method of claim 8, further comprising: triggering output of a visualization indicating{i} the part(s) of the planned and / or updated cutting shape(s) and / or the planned and / or updated volume(s) to be removed that can be reached by the surgical instrument without traversing the at least one critical area (23) and / or the at least one critical volume (25) in a different manner than{ii} the part(s) of the planned and / or updated cutting shape(s) and / or the planned and / or updated volume(s) to be removed that cannot be reached by the surgical instrument without traversing the at least one critical area (23) and / or the at least one critical volume (25).Stryker European Operations Limited 30A-162 411- 18 -10. The method of any one of claims 7 to 9, wherein it is determined whether the surgical instrument (i-iii) is capable of reaching a given part of the planned and / or updated cutting shape(s) and / or a given part of the planned and / or updated volume(s) to be removed without traversing the at least one critical area (23) and / or the at least one critical volume (25) by: determining an entry path of the surgical instrument; and determining whether the entry path intersects the at least one critical area (23) and / or the at least one critical volume (25).

11. The method of claim 10, wherein the entry path is determined based on a planned or tracked pose of the surgical instrument.

12. The method of any one of claims 6 to 11, further comprising: obtaining a user input indicating a selection of a surgical instrument from the at least one surgical instrument; and triggering feedback for the user to inform the user whether the selected surgical instrument is determined to be suitable to perform the spinal decompression procedure.

13. The method of claim 12, wherein triggering feedback comprises: displaying a visualization of the selected surgical instrument (i-iii) and visualizing the selected surgical instrument (i-iii) in a different manner depending on whether the selected surgical instrument (i-iii) can be used to perform the surgical procedure or not.

14. The method of any one of claims 1 to 13, further comprising: displaying a visualization of {i} at least a part of the medical patient image data and {ii} one or more of the at least one planned cutting shape and / or one or more of the at least one planned volume to be removed, wherein the user input indicating the update relates to an update of one or more displayed planned cutting shapes and / or one or more displayed volumes to be removed.

15. The method of claim 14, wherein the user input relating to an update of one or more displayed volumes to be removed is based on a seed growing algorithm that automatically selects pixels or voxels around a user-selected starting point in the medical image data.Stryker European Operations Limited 30A-162 411- 19 -16. The method of any one of claims 1 to 15, wherein the at least one critical area and / or the at least one critical volume comprises one or more of the following: at least a part of a facet joint; at least a part of the spinal canal; at least a part of an intervertebral disk.

17. A computer program comprising instructions that when executed by at least one processor cause the at least one processor to perform the method according to any one of claims 1 to 16, the computer program being optionally carried by a carrier such as a data stream, a computer program product or a non-transitory computer storage medium.

18. A surgical planning system comprising at least one processor, the at least one processor configured to perform the method according to any one of claims 1 to 16.

19. The surgical planning system of claim 18, further comprising at least one of the following entities: a tracking device configured to track one or more tracking markers associated with a surgical instrument or a patient; a user input unit configured to receive a user input from the user; a display unit configured to display one or more visualizations to the user.

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