Patent Description:
Spinal pathologies and disorders such as scoliosis, kyphosis and other curvature abnormalities, degenerative disc disease, disc herniation, osteoporosis, spondylolisthesis, stenosis, tumor and fracture may result from factors including trauma, disease and degenerative conditions caused by injury and aging. Spinal disorders typically result in symptoms including deformity, pain, nerve damage, and partial or complete loss of mobility.

Non-surgical treatments, such as medication, rehabilitation and exercise can be effective, however, may fail to relieve the symptoms associated with these disorders. Surgical treatment of these spinal disorders includes fusion, fixation, corpectomy, discectomy, laminectomy and implantable prosthetics. In procedures, such as, for example, corpectomy and discectomy, fusion and fixation treatments may be performed that employ implants to restore the mechanical support function of vertebrae. From <CIT> a surgical system according to the preamble of claim <NUM> is known. From <CIT> an attachable image guide is known.

The object of this disclosure is to provide an improvement over the above-mentioned prior art technologies in form of a surgical system allowing better surgery results.

This object is solved by a surgical system according to claim <NUM>. Further embodiments are subject of the dependent claims.

The exemplary embodiments of the inventive surgical system disclosed are discussed in terms of medical devices for the treatment of musculoskeletal disorders and more particularly, in terms of a spinal implant system. Furthermore, exemplary embodiments of the inventive surgical system are also discussed in terms of methods of use thereof and of methods for treating a spine to enable a better understanding of the technical aspects of the inventive surgical system. In some embodiments, the surgical system of the present disclosure comprises medical devices including surgical instruments and implants that are configured to be employed with a surgical treatment, as described herein, for example, with a cervical, thoracic, lumbar and/or sacral region of a spine.

The present surgical system includes a plurality of distinct navigated templates, such as, for example, four navigated templates. The templates include features compatible with an image guide, such as, for example, a navigation component, to connect the navigation component with the templates. The templates can be used in two separate approaches, such as, for example, a posterior approach and a lateral approach. The templates can be used in three separate approaches, such as, for example, an anterior approach, a lateral approach and a posterior approach.

In the posterior approach, an inventive surgical system with three templates is preferably used. The three templates have varying size cylindrical geometries that are each representative of a spinal implant, such as, for example, a corpectomy implant or cage. In some embodiments, the templates are relatively short templates. At least one of the templates includes angulation proximal to a cylindrical sizing feature to allow for insertion of the cylindrical sizing feature into a defect space, such as, for example, a corpectomy defect, while facilitating ease of entry around the spinal cord. The templates are configured to be moved against the adjacent vertebral body end plates, as well as throughout the defect space, to ensure enough bone and/or disc material is removed so that the representative cage size could fit into the defect space with the cage in a selected trajectory. The navigated templates can be used to identify key landmarks within the corpectomy defect, provide tactile feedback, and confirm the amount of resection.

In the lateral approach, either an inventive surgical system with three angled templates, or an extended length template with a rectangular geometry representative of additional end cap options of the cage, is preferably used in a lateral trajectory. The extended length template is configured to be moved against the adjacent vertebral endcaps, and up against the lateral annulus, to ensure bone and/or disc is removed for intended final placement of the representative endcap size.

In some embodiments, the templates include features to interface with the image guide, such as for example, NAVLOCK™ interface features sold by Medtronic Navigation, Inc. having a place of business in Louisville, Colo. , that are oriented such that the image guide is parallel to the plane created by the top or bottom of the instruments, allowing for proper insertion of the templates into the defect space, with the top/bottom faces parallel to the vertebral body endcaps, and easy to view from a camera system connected with the image guide.

For navigating the angled templates, the orientation of the angle of the inventive system can be selectable for a surgeon's need via a software menu, allowing for <NUM> degree rotation of the instrument being visualized.

The navigated templates have verification features of varying geometries and non-symmetric cross-sections that allow for verification with the navigated software. For example, in some embodiments, the navigated templates can include one or more verification features, such as, for example, bosses that are configured to be seated in a navigation verification divot of an implanted navigated component to allow for verification of the navigated templates with the navigation software. In some embodiments, the verification features are rectangular in a fashion that allows for seating within the navigation verification divot. In some embodiments, the verification features maintain a circular arc length from the cylindrical implant sizing geometry.

The navigation of the templates allows for visual representation of the templates within the patient's anatomy. The image guide can be configured to interface with a computer having software features that include estimation of appropriate final implant sizing, defect height sizing, estimation of implant position and trajectory in fully collapsed and fully expanded states and/or intermediate states between the fully collapsed and fully expanded states. Such software can also allow for visualization of anatomy during implant sizing estimation by allowing the user the ability to save plans of the implant position and trajectory.

Such software can allow for estimation of appropriate final implant sizing through two methods. The first method includes manual implant size estimation using the cylindrical sizing feature of the template. The cylindrical sizing feature can be representative of an implant size, chosen by diameter and height, either in a collapsed or expanded state through use of a toggle button, for example. Toggling of the collapsed and expanded states of the implant allows the surgeon to see if the largest expanded state of the implant or cage can span the corpectomy defect space. The defect space is represented by the vertebral body height if a post-corpectomy image scan is not performed. The virtual implant and additional implants can be toggled on or off, different sizes can be selected, and the direction of the projections can be flipped <NUM> degrees.

In the second method, two separate projections can be saved at each of the opposite ends of the defect space. The software will then measure the resultant defect height, the angulation between coronal and sagittal planes, and the appropriate implant size for use in the defect. Angulation data from the software feature can be used to select a corresponding implant addition of a similar angle from the system offerings. The projections and navigated representations of the templates allow for ease of visualization through projections with a central cavity. The saved projections representing the cylindrical and rectangular implant can be used to plan ideal placement and trajectory during actual implant insertion. Additionally, the implant can be combined with multiple types of implant additions in varying geometries and sizes.

The template virtual geometry can be configured to be used within the software to erase the resected vertebral body by moving the physical template within the resected space and removing the material from the visual representation of the patient's anatomy.

The implant can be inserted into the defect space using a surgical instrument, such as, for example, one or a plurality of inserters. In some embodiments, the surgical system includes three distinct navigated inserters of varying lengths, sizes and angularity. These inserters are intended for use with two separate approaches, with varying size implants. The navigated inserters have a fixed tracker geometry extended from bodies of the inserters and perpendicular to the plane of attachment of the varying implants. The perpendicularity allows for proper placement of the implant or cage while maintaining optimal visibility to a camera of the surgical system. On the navigated inserter, the geometry of the image guide can be oriented at a <NUM> degree offset angle from the implant attachment plane.

One of the inserters can be an angled inserter and one of the inserters can be a longer length straight inserter. These inserters can share verification features at the implant interface tip. The tip geometry, with a round on one edge of the instrument, allows for seating into the navigated verification divot. The third inserter can be a shorter navigated inserter and is straight. The tip geometry of the third inserter can be less wide and also allows the instrument to sit within the navigated verification slot. All three navigated inserters can also have specific markings to indicate use of proper tip geometry for interface with the navigated verification divot. Additionally, the implant tip geometry and software angular verification threshold on the angled inserter, and the straight inserters, allow for verification when the inserter body is parallel to the verification divot central axis, or when the inserter body is offset from the verification divot central axis.

The posterior approach uses any of the three navigated inserters. The two straight inserters allow for direct insertion of an implant into the corpectomy defect space. The navigated angled inserter, with an angulation proximal to the implant attachment interface, allows for insertion into the defect space while facilitating ease of entry around the spinal cord. The lateral approach utilizes the longest navigated straight inserter. It allows for direct insertion of the implant into the corpectomy defect space from a lateral trajectory.

The navigation of the inserters allows for visual representation in posterior and lateral approaches in multiple anatomical views of the inserters, implants and projections relative to the patient's anatomy. The software features can include estimation of appropriate final implant sizing, estimation of appropriate implant placement and trajectory, and visualization of expansion direction of the implant. It also allows easy visualization and distinction of implants and projections while estimating size, position, and trajectory with multiple implant and implant additions in multiple states of representation.

The software can allow for estimation of appropriate final implant sizing through representation of the implant in a collapsed or expanded state. The intended direction of expansion of the implant can be represented by a colored portion different than the main body of the implant. Geometries of varying color and/or transparency allow for easy visualization of anatomy while navigating. Varying transparency and coloration also provide a visual way to communicate to surgeons hardware components that are only being provided for trajectory and sizing guidance, not accurately navigated.

The inserter, the implant and implant additions can be navigated where multiple planes in a similar anatomical view are visible at once. This allows the surgeon to visualize where the implant is within the defect space. In addition to navigating the inserter and the implants of varying sizes, projections may show implant additions of varying cylindrical and rectangular geometries and of varying degrees of geometric and/or mechanical detail. The navigation software can also allow for visualization in the lateral approach of the implant and varying sizes of implant additions across the vertebral body in order to get appropriate placement and ensure the implant additions do not protrude out of the lateral annulus or lateral border of the vertebral body.

The surgical system of the present disclosure may be employed to treat spinal disorders such as, for example, degenerative disc disease, disc herniation, osteoporosis, spondylolisthesis, stenosis, scoliosis and other curvature abnormalities, kyphosis, tumor and fractures. The surgical system of the present disclosure may be employed with other osteal and bone related applications, including those associated with diagnostics and therapeutics. The disclosed surgical system may be alternatively employed in a surgical treatment with a patient in a prone or supine position, and/or employ various surgical approaches to the spine, including anterior, posterior, posterior mid-line, direct lateral, postero-lateral, and/or antero-lateral approaches, and in other body regions. The surgical system of the present disclosure may also be alternatively employed with procedures for treating the lumbar, cervical, thoracic, sacral and pelvic regions of a spinal column. The surgical system of the present disclosure may also be used on animals, bone models and other non-living substrates, such as, for example, in training, testing and demonstration.

The surgical system of the present disclosure may be understood more readily by reference to the following detailed description of the embodiments taken in connection with the accompanying drawing figures, which form a part of this disclosure, wherein some figures show methods, steps and representations of applying/using the inventive surgical system for explaining technical aspects of the inventive surgical system. It is to be understood that this application is not limited to the specific devices, conditions or parameters described and/or shown herein, and that the terminology used herein is for the purpose of describing particular embodiments by way of example only and is not intended to be limiting. In some embodiments, as used in the specification and including the appended claims, the singular forms "a," "an," and "the" include the plural, and reference to a particular numerical value includes at least that particular value, unless the context clearly dictates otherwise. Ranges may be expressed herein as from "about" or "approximately" one particular value and/or to "about" or "approximately" another particular value. Similarly, when values are expressed as approximations, by use of the antecedent "about," it will be understood that the particular value forms another embodiment. It is also understood that all spatial references, such as, for example, horizontal, vertical, top, upper, lower, bottom, left and right, are for illustrative purposes only and can be varied within the scope of the disclosure. For example, the references "upper" and "lower" are relative and used only in the context to the other, and are not necessarily "superior" and "inferior".

As used in the specification, "treating" or "treatment" of a disease or condition refers to performing a procedure that may include administering one or more drugs to a patient (human, normal or otherwise or other mammal), employing implantable devices, and/or employing instruments that treat the disease, such as, for example, microdiscectomy instruments used to remove portions bulging or herniated discs and/or bone spurs, in an effort to alleviate signs or symptoms of the disease or condition. Alleviation can occur prior to signs or symptoms of the disease or condition appearing, as well as after their appearance. Thus, treating or treatment includes preventing or prevention of disease or undesirable condition (e.g., preventing the disease from occurring in a patient, who may be predisposed to the disease but has not yet been diagnosed as having it). In addition, treating or treatment does not require complete alleviation of signs or symptoms, does not require a cure, and specifically includes procedures that have only a marginal effect on the patient. Treatment can include inhibiting the disease, e.g., arresting its development, or relieving the disease, e.g., causing regression of the disease. For example, treatment can include reducing acute or chronic inflammation; alleviating pain and mitigating and inducing re-growth of new ligament, bone and other tissues; as an adjunct in surgery; and/or any repair procedure. As used in the specification and including the appended claims, the term "tissue" includes soft tissue, ligaments, tendons, cartilage and/or bone unless specifically referred to otherwise.

The following discussion includes a description of a surgical system including a surgical instrument and related components in accordance with the principles of the present disclosure, wherein methods of employing the inventive surgical system are described to allow a better understanding of technical aspects of the inventive surgical system. Alternate embodiments are also disclosed. Reference is made in detail to the exemplary embodiments of the present disclosure, which are illustrated in the accompanying figures. Turning to <FIG>, there are illustrated components of a surgical system, such as, for example, a surgical system <NUM>.

The components of surgical system <NUM> can be fabricated from biologically acceptable materials suitable for medical applications, including metals, synthetic polymers, ceramics and bone material and/or their composites. For example, the components of surgical system <NUM>, individually or collectively, can be fabricated from materials such as stainless steel alloys, aluminum, commercially pure titanium, titanium alloys, Grade <NUM> titanium, super-elastic titanium alloys, cobalt-chrome alloys, superelastic metallic alloys (e.g., Nitinol, super elasto-plastic metals, such as GUM METAL®), ceramics and composites thereof such as calcium phosphate (e.g., SKELITE™), thermoplastics such as polyaryletherketone (PAEK) including polyetheretherketone (PEEK), polyetherketoneketone (PEKK) and polyetherketone (PEK), carbon-PEEK composites, PEEK-BaSO<NUM> polymeric rubbers, polyethylene terephthalate (PET), fabric, silicone, polyurethane, silicone-polyurethane copolymers, polymeric rubbers, polyolefin rubbers, hydrogels, semi-rigid and rigid materials, elastomers, rubbers, thermoplastic elastomers, thermoset elastomers, elastomeric composites, rigid polymers including polyphenylene, polyamide, polyimide, polyetherimide, polyethylene, epoxy, bone material including autograft, allograft, xenograft or transgenic cortical and/or corticocancellous bone, and tissue growth or differentiation factors, partially resorbable materials, such as, for example, composites of metals and calcium-based ceramics, composites of PEEK and calcium based ceramics, composites of PEEK with resorbable polymers, totally resorbable materials, such as, for example, calcium based ceramics such as calcium phosphate, tri-calcium phosphate (TCP), hydroxyapatite (HA)-TCP, calcium sulfate, or other resorbable polymers such as polyaetide, polyglycolide, polytyrosine carbonate, polycaroplaetohe and their combinations.

Surgical system <NUM> is employed, for example, with a fully open surgical procedure, a minimally invasive procedure including percutaneous techniques, and mini-open surgical techniques to deliver and introduce instrumentation and/or a spinal implant, such as, for example, a corpectomy cage, at a surgical site of a patient, which includes, for example, a spine. In some embodiments, the spinal implant can include one or more components of one or more spinal constructs, such as, for example, interbody devices, interbody cages, bone fasteners, spinal rods, tethers, connectors, plates and/or bone graft, and can be employed with various surgical procedures including surgical treatment of a cervical, thoracic, lumbar and/or sacral region of a spine.

System <NUM> includes a plurality of surgical instruments, such as a template <NUM> (e.g., <FIG>), a template <NUM> (e.g., <FIG>) and a template <NUM> (e.g., <FIG>) and preferably an image guide, such as, for example, a navigation component <NUM> that is removably attachable with templates <NUM>, <NUM>, <NUM>, as discussed herein. Navigation component <NUM> is configured to allow for visualization of templates <NUM>, <NUM>, <NUM> within a patient's anatomy. Navigation component <NUM> interfaces with a computer having software configured to estimate the appropriate final implant sizing, defect height sizing, and estimation of implant position and trajectory in full and collapsed states, as discussed herein. In some embodiments, system <NUM> includes other templates in place of or in addition to templates <NUM>, <NUM>, <NUM>, such as, for example, templates having different sizes and/or geometries than templates <NUM>, <NUM>, <NUM>.

Template <NUM> includes a shaft <NUM> extending along a longitudinal axis X1 between a proximal end <NUM> and an opposite distal end <NUM>. Shaft <NUM> is coaxial with axis X1 along the entire length of shaft <NUM>. Shaft <NUM> includes a body <NUM> extending from end <NUM> to an end <NUM> between end <NUM> and end <NUM>. Body <NUM> may include one or a plurality of recesses <NUM> along the length of body <NUM> to facilitate gripping of shaft <NUM>. Shaft <NUM> includes a stem <NUM> that is connected to body <NUM> by a section <NUM> in various embodiments. Section <NUM> extends from end <NUM> to an end <NUM> and stem <NUM> extends from end <NUM> to end <NUM>. Section <NUM> can be tapered from end <NUM> to end <NUM>, as shown in <FIG>. In some embodiments, section is continuously tapered from end <NUM> to end <NUM> such that stem <NUM> has a diameter that is less than a diameter of body <NUM> to facilitate insertion of stem <NUM> into a surgical site, such as, for example, a corpectomy defect. For example, in some embodiments, body <NUM> has a maximum diameter D1 that is greater than a maximum diameter D2 of stem <NUM>, as shown in <FIG>. This allows body <NUM> to be large enough to facilitate gripping by a medical practitioner, while a permitting stem <NUM> to be small enough to be inserted into a corpectomy defect. In some embodiments, stem <NUM> has a uniform diameter along the entire length of stem <NUM>. In some embodiments, stem <NUM> is tapered and has a diameter adjacent to end <NUM> that is less than a diameter adjacent to end <NUM>. In some embodiments, stem <NUM> is continuously tapered from end <NUM> to end <NUM>. In some embodiments, shaft <NUM> has a solid configuration that is free of any cavities or openings to provide strength and/or rigidity to shaft <NUM>.

Template <NUM> includes an engagement portion <NUM> adjacent to end <NUM>. Portion <NUM> is configured for insertion between adjacent vertebrae of a patient, or insertion within a corpectomy defect. Portion <NUM> includes a rod <NUM> that extends from end <NUM> to an end <NUM> along a longitudinal axis X2. Axis X2 extends at an angle α relative to axis X1 to facilitate insertion of portion <NUM> around a spinal cord of a patient, as discussed herein. In some embodiments, angle α is greater than <NUM>°. In some embodiments, angle α is an acute angle. In some embodiments, angle α is an oblique angle. In some embodiments, angle α is between about <NUM>° and about <NUM>°. In some embodiments, angle α is between about <NUM>° and about <NUM>°. In some embodiments, angle α is between about <NUM>° and about <NUM>°.

Portion <NUM> includes a head <NUM> that extends from end <NUM>. Head <NUM> is configured to be positioned in the corpectomy defect to represent sizing of an implant to be inserted into the corpectomy defect, as discussed herein. Head <NUM> includes a wall <NUM> having a top surface <NUM> and an opposite bottom surface <NUM>, as best shown in <FIG> and <FIG>. The distance between surface <NUM> and surface <NUM> defines a height H1 of head <NUM>. Wall <NUM> has a cylindrical configuration and defines an opening <NUM> that extends through the thickness of head <NUM>. That is opening <NUM> extends continuously between and through surface <NUM> and surface <NUM>. In some embodiments, height H1 is greater than diameter D2. In some embodiments, height H1 is greater than or equal to diameter D1. In some embodiments, height H1 is less than diameter D1. The size and shape of wall <NUM> and/or opening <NUM> are configured to correspond to the size and shape of an implant to be inserted into the corpectomy defect to determine if the implant is suitable for implantation into the corpectomy defect, or if an implant of a different size and shape would be more suitable for implantation into the corpectomy defect, as discussed herein. Wall <NUM> has a maximum outer diameter D3, as shown in <FIG>, and a maximum inner diameter D4, as shown in <FIG>. In some embodiments, opening <NUM> can be variously shaped, such as, for example, circular, oval, oblong, triangular, square, polygonal, irregular, uniform, nonuniform, offset, staggered, undulating, arcuate, variable and/or tapered.

In some embodiments, head <NUM> is monolithically and/or integrally formed with shaft <NUM> to provide increased strength and/or rigidity to template <NUM>. In some embodiments, head <NUM> is removably coupled to shaft <NUM> to allow different heads, such as, for example, heads having different sizes or shapes to be coupled to shaft <NUM>. It is envisioned that allowing different heads to be coupled to shaft <NUM> will reduce the number of instruments needed to perform a given procedure. Indeed, rather than having a plurality of shafts, with each of the shafts having a different head coupled thereto, there could be only one shaft and a plurality of heads that can be removably coupled to the shaft.

Shaft <NUM> includes a hub <NUM> positioned between end <NUM> and end <NUM>. Hub <NUM> includes a flange <NUM> and a flange <NUM> that is spaced apart from flange <NUM>. Hub <NUM> includes a recess <NUM> between flanges <NUM>, <NUM>. Recess <NUM> is defined by an outer surface <NUM> of shaft <NUM>, a surface <NUM> of flange <NUM> and a surface <NUM> of flange <NUM>, as best shown in <FIG>. In various embodiments, surface <NUM> extends parallel to axis X1 and surfaces <NUM>, <NUM> extend perpendicular to axis X1. Flange <NUM> includes a surface <NUM> positioned between surface <NUM> and a surface <NUM> of hub <NUM>. Surface <NUM> extends parallel to axis X1 and surface <NUM> extends perpendicular to axis X1. Flange <NUM> includes a surface <NUM> positioned between surface <NUM> and a surface <NUM> of flange <NUM>. Surface <NUM> extends parallel to axis X1 and surface <NUM> extends perpendicular to axis X1. In some embodiments, surface <NUM> is configured to act as a ramp to connect navigation component <NUM> with shaft <NUM>, as discussed herein. In some embodiments, surface <NUM>, surface <NUM>, surface <NUM>, surface <NUM>, surface <NUM> and/or surface <NUM> may be disposed at alternate orientations, relative to axis X1, such as, for example, parallel, transverse, perpendicular and/or other angular orientations such as acute or obtuse, co-axial and/or may be offset or staggered.

Template <NUM> is similar to template <NUM> and includes shaft <NUM> with hub <NUM> positioned between end <NUM> and end <NUM>, as shown in <FIG>. Template <NUM> includes an engagement portion <NUM> having a rod <NUM> that is similar to rod <NUM> extending from end <NUM>. Rod <NUM> extends from end <NUM> to an end <NUM> along a longitudinal axis X3. Axis X3 extends at an angle β relative to axis X1 to facilitate insertion of portion <NUM> around a spinal cord of a patient, as discussed herein. In some embodiments, angle β is greater than <NUM>°. In some embodiments, angle β is an acute angle. In some embodiments, angle β is an oblique angle. In some embodiments, angle β is between about <NUM>° and about <NUM>°. In some embodiments, angle β is between about <NUM>° and about <NUM>°. In some embodiments, angle β is between about <NUM>° and about <NUM>°. In some embodiments, angle β is less than or equal to angle α. In some embodiments, angle β is greater than or equal to angle α. In some embodiments, angle β is different than angle α. In some embodiments, the maximum length of rod <NUM> is less than the maximum length of rod <NUM>. It is envisioned that the differences between the lengths of rod <NUM> and rod <NUM> and the difference between angle α and angle β provides a medical practitioner with options regarding which instrument to use for a given procedure. For example, the medical practitioner can choose either template <NUM> or template <NUM> depending on which has the greater angulation, where increased angulation is required to facilitate insertion around the spinal cord of a patient.

Portion <NUM> includes a head <NUM> that extends from end <NUM>. Head <NUM> is similar to head <NUM> and is configured to be positioned in the corpectomy defect to represent sizing of an implant to be inserted into the corpectomy defect, as discussed herein. Head <NUM> includes a wall <NUM> having a cylindrical configuration and defines an opening <NUM> that extends through the thickness of head <NUM>. That is, opening <NUM> extends continuously between and through opposite top and bottom surfaces of head <NUM>. The size and shape of wall <NUM> and/or opening <NUM> are configured to correspond to the size and shape of an implant to be inserted into the corpectomy defect to determine if the implant is suitable for implantation into the corpectomy defect, or if an implant of a different size and shape would be more suitable for implantation into the corpectomy defect, as discussed herein. Wall <NUM> has a maximum outer diameter D5 and a maximum inner diameter D6. In some embodiments, diameter D3 is less than diameter D5 and diameter D4 is less than diameter D6. Template <NUM> may therefore be used to approximate the positioning of larger implants, while template <NUM> may be used to approximate the positioning of smaller implants. However, it is envisioned that the length of rod <NUM> or rod <NUM>, the inner diameter of head <NUM> or head <NUM> and/or the outer diameter of head <NUM> or head <NUM> can be selected based on the size and configuration of the implant to be positioned in the corpectomy defect. In some embodiments, opening <NUM> can be variously shaped, such as, for example, oval, oblong, triangular, square, polygonal, irregular, uniform. In some embodiments, head <NUM> is monolithically and/or integrally formed with shaft <NUM> to provide increased strength and/or rigidity to template <NUM>. In some embodiments, head <NUM> is removably coupled to shaft <NUM> to allow different heads, such as, for example, head <NUM> or head <NUM> to be coupled to shaft <NUM> depending upon the preference of a medical practitioner.

Template <NUM> is similar to template <NUM> and template <NUM> and includes shaft <NUM> with hub <NUM> positioned between end <NUM> and end <NUM>, as shown in <FIG>. Template <NUM> includes an engagement portion <NUM> having a rod <NUM> that is similar to rods <NUM>, <NUM> extending from end <NUM>. Rod <NUM> extends from end <NUM> to an end <NUM> along axis X1. In some embodiments, the maximum length of rod <NUM> is less than or equal the maximum length of rod <NUM> and/or rod <NUM>. In some embodiments, the maximum length of rod <NUM> is greater than or equal the maximum length of rod <NUM> and/or rod <NUM>. Portion <NUM> includes a head <NUM> that extends from end <NUM>. Head <NUM> is configured to be positioned in the corpectomy defect to represent sizing of an implant to be inserted into the corpectomy defect, as discussed herein. Head <NUM> has a solid wall configuration with the shape of a rounded rectangle. That is, head <NUM> is free of any recesses, holes or apertures. It is envisioned that the size and shape of head <NUM> can be adapted to match or approximate the size and shape of an implant to be implanted in the corpectomy defect. In some embodiments, head <NUM> is monolithically and/or integrally formed with shaft <NUM> to provide increased strength and/or rigidity to template <NUM>. In some embodiments, head <NUM> is removably coupled to shaft <NUM> to allow different heads, such as, for example, head <NUM>, head <NUM> or head <NUM> to be coupled to shaft <NUM> depending upon the preference of a medical practitioner.

Navigation component <NUM> is configured to be coupled to hub <NUM> to connect navigation component <NUM> with template <NUM>, template <NUM>, or template <NUM>. Navigation component <NUM> includes a collar <NUM> having an inner surface <NUM> and an outer surface <NUM>, as best shown in <FIG>. Surface <NUM> defines a passageway <NUM>. Surface <NUM> is configured for releasable engagement with hub <NUM>. Passageway <NUM> is configured to receive shaft <NUM> and a portion of hub <NUM>. Surface <NUM> defines a lock, such as, for example, at least one resilient prong or tab <NUM>. In one embodiment, collar <NUM> includes a plurality of tabs <NUM>, as shown in <FIG>. Each tab <NUM> includes an inner surface <NUM> that defines a cutout <NUM> and an outer surface <NUM>. Each cutout <NUM> includes raised portions <NUM> that define edges of cutout <NUM>. Cutout <NUM> is configured to receive flange <NUM>. In its initial position, surface <NUM> is aligned with surface <NUM> of collar <NUM>.

To connect navigation component <NUM> with template <NUM>, template <NUM> or template <NUM>, collar <NUM> is translated over shaft <NUM> such that flange <NUM> engages portions <NUM> and applies a force to tabs <NUM> to move tabs <NUM> outwardly, in the direction shown by arrows A in <FIG>, such that surface <NUM> is deflected from surface <NUM>. As flange <NUM> translates over portions <NUM>, flange <NUM> moves into cutouts <NUM> allowing tabs <NUM> to move back to their initial position. In some embodiments, navigation component <NUM> is configured for removable engagement with template <NUM>, template <NUM> and template <NUM>. In some embodiments, navigation component <NUM> may be integrally formed with template <NUM>, template <NUM>, or template <NUM>. In one embodiment, flange <NUM> is configured to engage collar <NUM> to reduce vibrations resulting from the torque of an actuator. In some embodiments, an end surface <NUM> of collar <NUM> directly engages surface <NUM> of hub <NUM> when flange <NUM> is positioned in cutouts <NUM> to prevent and/or reduce the amount of movement between navigation component <NUM> and shaft <NUM>.

Navigation component <NUM> includes an emitter array <NUM>, as shown in <FIG>. Emitter array <NUM> is configured for generating a signal to sensor array <NUM> of a surgical navigation system <NUM>, as shown in <FIG>. In some embodiments, the signal generated by emitter array <NUM> represents a position of an instrument, such as, for example, template <NUM>, template <NUM>, or template <NUM> relative to tissue, such as, for example, bone. In some embodiments, the signal generated by emitter array <NUM> represents a three-dimensional position of template <NUM>, template <NUM>, or template <NUM> relative to tissue. In some embodiments, emitter array <NUM> includes a reflectance array and/or is configured to reflect a signal to sensor array <NUM>.

In some embodiments, sensor array <NUM> receives signals from emitter array <NUM> to provide a three-dimensional spatial position and/or a trajectory of a template <NUM>, template <NUM> or template <NUM> relative to tissue. Emitter array <NUM> communicates with a processor of a computer <NUM> of navigation system <NUM> to generate data for display of an image on a monitor <NUM>. In some embodiments, sensor array <NUM> receives signals from emitter array <NUM> to provide a visual representation of a position of template <NUM>, template <NUM> or template <NUM> relative to and/or tissue. See, for example, similar surgical navigation components and their use as described in US Patent Nos.

Surgical navigation system <NUM> is configured for acquiring and displaying medical imaging, such as, for example, x-ray images appropriate for a given surgical procedure. Pre-acquired images of a patient can be collected. Surgical navigation system <NUM> can include an O-ARM® imaging device <NUM> sold by Medtronic Navigation, Inc. having a place of business in Louisville, Colo. Imaging device <NUM> may have a generally annular gantry housing that encloses an image capturing portion <NUM>.

Navigation system <NUM> can comprise an image capturing portion <NUM> that may include an x-ray source or emission portion and an x-ray receiving or image receiving portion located generally or as practically possible <NUM> degrees from each other and mounted on a rotor (not shown) relative to a track of image capturing portion <NUM>. Image capturing portion <NUM> can be operable to rotate <NUM> degrees during image acquisition. Image capturing portion <NUM> may rotate around a central point or axis, allowing image data of the patient to be acquired from multiple directions or in multiple planes. Surgical navigation system <NUM> can include those disclosed in <CIT>, <CIT>; <CIT>; <CIT>; <CIT>; and <CIT>.

Surgical navigation system <NUM> can include C-arm fluoroscopic imaging systems, which can generate three-dimensional views of a patient. The position of image capturing portion <NUM> can be precisely known relative to any other portion of an imaging device of navigation system <NUM>. A precise knowledge of the position of image capturing portion <NUM> can be used in conjunction with a tracking system <NUM> to determine the position of image capturing portion <NUM> and the image data relative to the patient.

Tracking system <NUM> can include various portions that are associated or included with surgical navigation system <NUM>. Tracking system <NUM> can also include a plurality of types of tracking systems, such as, for example, an optical tracking system that includes an optical localizer, such as, for example, sensor array <NUM> and/or an EM tracking system that can include an EM localizer. Various tracking devices can be tracked with tracking system <NUM> and the information can be used by surgical navigation system <NUM> to allow for a display of a position of an item, such as, for example, a patient tracking device, an imaging device tracking device <NUM>, and an instrument tracking device, such as, for example, emitter array <NUM>, to allow selected portions to be tracked relative to one another with the appropriate tracking system.

The EM tracking system can include the STEALTHSTATION® AXIEM™ Navigation System, sold by Medtronic Navigation, Inc. having a place of business in Louisville, Colo. Exemplary tracking systems are also disclosed in <CIT>,<CIT>, <CIT>.

Fluoroscopic images taken are transmitted to a computer <NUM> where they may be forwarded to computer <NUM>. Image transfer may be performed over a standard video connection or a digital link including wired and wireless. Computer <NUM> provides the ability to display, via monitor <NUM>, as well as save, digitally manipulate, or print a hard copy of the received images. Images may also be displayed to the surgeon through a heads-up display.

Surgical navigation system <NUM> can provide for real-time tracking of the position of template <NUM>, template <NUM>, or template <NUM> relative to tissue. Sensor array <NUM> can be located in such a manner to provide a clear line of sight with emitter array <NUM>, as described herein. Fiducial markers of emitter array <NUM> can communicate with sensor array <NUM> via infrared technology. Sensor array <NUM> can be coupled to computer <NUM>, which may be programmed with software modules that analyze signals transmitted by sensor array <NUM> to determine the position of each object in a detector space.

In some embodiments, template <NUM>, template <NUM>, or template <NUM> are configured for use with a guide member, such as, for example, an end effector <NUM> of a robotic arm R. End effector <NUM> defines a channel configured for disposal of template <NUM>, template <NUM>, or template <NUM>. Robotic arm R includes position sensors (not shown), similar to those referenced herein, which measure, sample, capture and/or identify positional data points of end effector <NUM> in three-dimensional space for a guide-wireless insertion of template <NUM>, template <NUM>, or template <NUM>. The position sensors of robotic arm R can be employed in connection with surgical navigation system <NUM> to measure, sample, capture and/or identify positional data points of end effector <NUM> in connection with surgical treatment, as described herein. The position sensors are mounted with robotic arm R and calibrated to measure positional data points of end effector <NUM> in three dimensional space, which are communicated to computer <NUM>.

In assembly, operation and use, navigation component <NUM> is connected with template <NUM>, as discussed herein, and template <NUM> is inserted into a corpectomy defect space S of a vertebra V using a posterior approach such that engagement portion <NUM> moves around a spinal cord SC for positioning in space S and stem <NUM> is positioned between a spinous process SP of vertebra V and a transverse process TP of vertebra V, as shown in <FIG>. Navigation component <NUM> has been omitted from <FIG>, for clarity. Shaft <NUM> is manipulated to move head <NUM> such that surface <NUM> moves against an end plate EP of vertebra V. In some embodiments, shaft <NUM> is configured to be manipulated to move head <NUM> such that surface <NUM> moves against an end plate of a vertebra that is superior to vertebra V and defines a portion of space S. Head <NUM> is moved against the end plates and/or the lateral annuluses of the vertebrae as well as throughout space S to remove bone and/or disc material within space S. In some embodiments, head <NUM> is configured to be moved throughout space S to remove enough bone and/or disc material within space S to fit an implant, such as, for example, implant I within space S in an intended position and an intended trajectory. For example, in some embodiments, implant I is configured to be movable between a collapsed state, as shown in <FIG>, and an expanded state, as shown in <FIG>. Implant has a height H2 when implant I is in the collapsed state and an increased height H3 when implant I is in the expanded state. As such, head <NUM> is moved throughout space S to remove enough bone and/or disc material within space S to fit implant I in space S when implant I is in the collapsed state, the expanded state, or a state in between the collapsed state and the expanded state wherein implant I has a height between height H2 and height H3. In some embodiments, head <NUM> includes a blade or other sharpened surface to facilitate cutting and/or scraping of tissue, such as, for example, bone and/or disc material. In some embodiments, template <NUM> is configured to be used to identify key landmarks within space S, provide tactile feedback, and confirm the amount of resection via navigation component <NUM> and surgical navigation system <NUM>, as discussed herein. Implant I is the same or similar to one or more of the implants disclosed in <CIT>.

In some embodiments, navigation component <NUM> is connected with template <NUM>, as discussed herein, and template <NUM> is inserted into space S of vertebra V using a lateral approach such that engagement portion <NUM> is positioned in space S, as shown in <FIG>. Navigation component <NUM> has been omitted from <FIG>, for clarity. Shaft <NUM> is manipulated to move head <NUM> such that surface <NUM> moves against an end plate EP of vertebra V. In some embodiments, shaft <NUM> is configured to be manipulated to move head <NUM> such that surface <NUM> moves against an end plate of the vertebra that is superior to vertebra V and defines a portion of space S. Head <NUM> is moved against the end plates and/or the lateral annuluses of the vertebrae as well as throughout space S to remove bone and/or disc material within space S. In some embodiments, head <NUM> is configured to be moved throughout space S to remove enough bone and/or disc material within space S to fit an implant, such as, for example, implant I within space S in an intended position and an intended trajectory.

In some embodiments, navigation component <NUM> is connected with template <NUM>, as discussed herein, and template <NUM> is inserted into space S of vertebra V using a lateral approach such that engagement portion <NUM> is positioned in space S, as shown in <FIG>. Navigation component <NUM> has been omitted from <FIG>, for clarity. Shaft <NUM> is manipulated to move head <NUM> such that head <NUM> moves against end plate EP of vertebra V. In some embodiments, shaft <NUM> is configured to be manipulated to move head <NUM> against the end plates and the lateral annuluses of the vertebrae as well as throughout space S to remove bone and/or disc material within space S. In some embodiments, head <NUM> is configured to be moved throughout space S to remove enough bone and/or disc material within space S to fit an implant, such as, for example, implant I within space S in an intended position and an intended trajectory. Head <NUM> has rectangular geometry that is representative of end plate options of implant I. For example, one or more end plates can be used in connection with implant I. The end plates of implant I can have different geometries, such as, for example, rectangular, oval, circular, square, etc. Head <NUM> can thus be adapted to have a geometry that matches the geometry of the end plates of implant I to approximate the position of the end plates within space S.

In some embodiments, navigation component <NUM> is connected with template <NUM>, as discussed herein, and template <NUM> is inserted into space S of vertebra V using a lateral approach such that engagement portion <NUM> is positioned in space S, as shown in <FIG>. Navigation component <NUM> has been omitted from <FIG>, for clarity. Shaft <NUM> is manipulated to move head <NUM> such that head <NUM> moves against end plate EP of vertebra V. In some embodiments, shaft <NUM> is configured to be manipulated to move head <NUM> such that head <NUM> moves against an end plate of the vertebra that is superior to vertebra V and defines a portion of space S. Head <NUM> is moved against the end plates and the lateral annuluses of the vertebrae as well as throughout space S to remove bone and/or disc material within space S. In some embodiments, head <NUM> is configured to be moved throughout space S to remove enough bone and/or disc material within space S to fit an implant, such as, for example, implant I within space S in an intended position and an intended trajectory.

Navigation component <NUM> is connected with template <NUM>, template <NUM> and/or template <NUM> such that an axis X4 defined by emitter array <NUM> such that axis X4 is parallel with axis X1, as shown in <FIG>, for example. This allows for proper insertion of template <NUM>, template <NUM> and/or template <NUM> into space S, with the top and bottom surfaces of heads <NUM>, <NUM>, <NUM> parallel to the end caps of the vertebrae. It is envisioned that having axis X4 parallel to axis X1 facilitates viewing from a camera system of surgical navigation system <NUM>.

In some embodiments, the orientation of angles α of template <NUM> and/or the orientation of angle β of template <NUM> are selectable, for example by using a software menu of surgical navigation system <NUM>, such as, for example, a software menu <NUM> of computer <NUM>, as shown in <FIG>. Menu <NUM> can be displayed on monitor <NUM>. Menu <NUM> can provide instructions <NUM> to a medical practitioner concerning how he or she should hold template <NUM> and/or template <NUM>. The medical practitioner can then select either a first window <NUM>, which orients rod <NUM> and/or rod <NUM> in a first orientation, or a second window <NUM>, which orients rod <NUM> and/or rod <NUM> in a second orientation. This allows for <NUM> degree rotation of template <NUM> and/or template <NUM>.

In some embodiments, template <NUM>, template <NUM> and/or template <NUM> can include one or more verification features, such as, for example, one or more bosses <NUM> configured to be seated in a verification divot <NUM> of an implanted navigation component <NUM> to allow for verification with the navigation software, as shown in <FIG>. Boss <NUM> of template <NUM> extends outwardly from wall <NUM> of head <NUM>, as shown in <FIG>. It is envisioned that bosses <NUM> of templates <NUM>, <NUM> can be similarly positioned on head <NUM> of template <NUM> and head <NUM> of template <NUM>. For example, boss <NUM> of template <NUM> can extend outwardly from wall <NUM> and boss <NUM> of template <NUM> can extend outwardly from an outer surface of head <NUM> of template <NUM>. Component <NUM> is implanted in or adjacent to an intervertebral disc space prior to inserting head <NUM> of template <NUM>, head <NUM> of template <NUM> or head <NUM> of template <NUM> into the intervertebral disc space. After component <NUM> is implanted in or adjacent to an intervertebral disc space, head <NUM> of template <NUM>, head <NUM> of template <NUM>, or head <NUM> of template <NUM> is guided into the intervertebral disc space such that boss <NUM> is seated within divot <NUM> to allow for verification with the navigation software. Boss <NUM> can have varying geometries and/or non-concentric cross-sections. In one embodiment, boss <NUM> is rectangular to allow for seating within divot <NUM> in a manner that prevents movement of boss <NUM> within divot <NUM>, as shown in <FIG>. In one embodiment, boss <NUM> is arcuate to allow for seating within divot <NUM> in a manner that allows boss <NUM> to move within divot <NUM>, as shown in <FIG>.

In some embodiments, navigation component <NUM> in configured to communicate with surgical navigation system <NUM> to provide visual representations of template <NUM>, template <NUM> and/or template <NUM> within a patient's anatomy. Computer <NUM> can include software that provides an estimation of appropriate full implant sizing, defect height sizing, and estimation of implant position and trajectory in both fully collapsed or fully expanded states. The software can be configured to determine the size of an area, such as, for example, space S, and the size of an implant, such as, for example, implant I. For example, the software can determine height H2 and/or height H3. The software can create an image of space S and a representation of implant I within space S so a medical practitioner can visualize whether there is sufficient room within space S for implant I. The image created by the software can show the trajectory of implant I within space S. The software can adjust the trajectory of implant I within space S and provide an image representing the same so that the medical practitioner can determine the optimal trajectory of implant I within space S. The software can allow visualization of anatomy during implant sizing estimation by allowing the user the ability to save plans of the implant position and trajectory.

Computer <NUM> can include software that estimates final implant system using head <NUM> and/or head <NUM>. For example, head <NUM> and/or head <NUM> can be used to generate a cylindrical representation <NUM> that is representative of the size of implant I, as shown in <FIG>. The software can be configured to generate a toggle button <NUM> that is viewable on monitor <NUM>. Toggle button <NUM> switches representation <NUM> between a view having implant I in the collapsed and a view having implant I in the expanded state. This allows a medical practitioner to quickly visualize implant I within space S with implant I in both the collapsed state (<FIG>) and the expanded state (<FIG>) via representation <NUM>. That is, toggling of representation <NUM> allows the medical practitioner to see if the largest expanded state of implant I can span the space between adjacent vertebrae.

The software can be configured to flip the orientation of representation <NUM><NUM> degrees. The software can be configured to turn representation <NUM> on and off. That is, the software can be configured to provide an image of template <NUM> within space without representation <NUM>. If the medical practitioner then wishes to visualize how an implant, such as, for example, implant I would fit within space S, he or she can use toggle button <NUM> to provide an image of template <NUM> within space via representation <NUM>.

Computer <NUM> can include software that estimates final implant system using a projection <NUM> and a projection <NUM> that can be saved at each of the opposite ends of space S, as shown in <FIG>. Projections <NUM>, <NUM> represent the cylindrical geometry of an implant, such as, for example, implant I. Projection <NUM> represents the cylindrical geometry of implant I with implant I in the collapsed state and projection <NUM> represents the cylindrical geometry of implant I with implant I in the expanded state. The software will then measure the resultant defect height, angulation between coronal and sagittal planes, and appropriate implant size for use in space S. Angulation data from the software can be used to select a corresponding implant addition, such as, for example, one or more end plates of an implant, such as, for example, implant I. The visual representation of template <NUM> allows for ease of visualizations through opening <NUM>, as shown in <FIG>.

The software can generate one or more projections <NUM> that correspond to the polygonal or rectangular geometry an implant addition, such as, for example, one or more end plates of an implant, such as, for example, implant I, as shown in <FIG>. Projections <NUM>, <NUM>, <NUM> are saved, representing the cylindrical and rectangular geometries of implant I. Projections <NUM>, <NUM>, <NUM> are used to plan optimal placement and trajectory of implant I during actual implant insertion. It is envisioned that projections <NUM> can be used to provide representations of variously shaped and sized implant additions. The software can be configured to erase the resected vertebral body by moving template <NUM> within space S and removing the material from the visual representation of the patient's anatomy, as shown in <FIG>. While using template <NUM> for estimation of implant size, position and trajectory, it is contemplated that template <NUM> and/or template <NUM> can be used in place of, or in addition to, template <NUM>.

After the optimal implant size, position and trajectory is determined, an implant, such as, for example, implant I is selected from a plurality of implants having different sizes and/or geometries. In some embodiments, implant I is configured to be inserted into space S using a posterior approach. In some embodiments, an image guide, such as, for example, navigation component <NUM> is configured to be coupled to a surgical instrument, such as, for example, a straight inserter <NUM>, as shown in <FIG>. Implant I is coupled to inserter <NUM> and inserter <NUM> is manipulated to position implant I within space S using a posterior approach. In some embodiments, an image guide, such as, for example, navigation component <NUM> is coupled to a surgical instrument, such as, for example, an angled inserter <NUM>, as shown in <FIG>. Implant I is coupled to inserter <NUM> and inserter <NUM> can be manipulated to position implant I within space S using a posterior approach, while facilitating ease of entry around spinal cord SC.

In some embodiments, implant I is configured to be inserted into space S using a lateral approach. For example, in some embodiments, an image guide, such as, for example, navigation component <NUM> is coupled to inserter <NUM> and inserter <NUM> can be manipulated to position implant I within space S using a lateral approach, as shown in <FIG>.

In some embodiments, implant I is configured to be inserted into space S using an anterior approach. For example, in some embodiments, an image guide, such as, for example, navigation component <NUM> is coupled to inserter <NUM> and inserter <NUM> can be manipulated to position implant I within space S using an anterior approach, as shown in <FIG>.

Navigation component <NUM> allows for visual representation of inserters <NUM>, <NUM> in posterior, lateral and anterior approaches in multiple anatomical views of inserters <NUM>, <NUM>, implants and projections relative to the patient's anatomy. Computer <NUM> can include software configured to estimate appropriate final implant sizing, estimate appropriate implant placement and trajectory, and provide visualization of implant expansion. The software provides visualization and distinction of implants and projections while estimating size, position, and trajectory with multiple implants and/or multiple implant additions in multiple states of representation. For example, the software provides estimation of appropriate implant sizing through representations of an implant, such as, for example, implant I in the expanded state (<FIG>) and the collapsed state (<FIG>). The intended direction of expansion of implant I is represented by a colored portion <NUM> that is a different color than a main body portion <NUM> of implant I. Implant additions, such as, for example, end plates <NUM> can be represented by a color that is different than the colors that represent portion <NUM> or portion <NUM>, as shown in <FIG>. Geometries of varying color and/or transparency allow for easy visualization of anatomy while navigating. Varying transparency and coloration also provides a visual way to communicate to surgeons hardware components that are only being represented, but not navigated. The software provides visualization of inserter <NUM>, inserter <NUM>, implant I and/or end plates <NUM> where multiple planes in a similar anatomical view are visible at once, as shown in <FIG>. This allows the surgeon to visualize where implant I is within space S. As shown in <FIG>, implant I is shown without any implant additions, such as, for example, end plates <NUM>. Implant I is then shown in <FIG> with end plates <NUM> attached. The software is configured to allow for visualization of implant I in a lateral approach, as shown in <FIG>, to ensure that end plates do not protrude out of the lateral annulus or lateral border of vertebra V, for example.

Claim 1:
A surgical system (<NUM>) comprising:
a first template (<NUM>) comprising a first shaft (<NUM>) extending along a first axis (X1) between a first proximal end (<NUM>) and a first distal end (<NUM>), the first template (<NUM>) comprising a first engagement portion (<NUM>) configured for insertion between vertebrae of a patient, the first engagement portion (<NUM>) comprising a first rod (<NUM>) extending from the first distal end (<NUM>) at an acute angle (α) relative to the first axis (X1) and a first head (<NUM>) coupled to the first rod (<NUM>), the first head (<NUM>) comprising a first cylindrical wall (<NUM>) having a first diameter (D3); and
a second template (<NUM>) comprising a second shaft (<NUM>) extending along a second axis (X1) between a second proximal end (<NUM>) and a second distal end (<NUM>), the second template (<NUM>) comprising a second engagement portion (<NUM>) configured for insertion between the vertebrae, the second engagement portion (<NUM>) comprising a second rod (<NUM>) extending from the second distal end (<NUM>) at an acute angle (β) relative to the second axis (X1) and a second head (<NUM>) coupled to the second rod (<NUM>), the second head (<NUM>) comprising a second cylindrical wall (<NUM>) having a second diameter (D5),
wherein the first diameter (D3) is different than the second diameter (D5), characterized in that
the surgical system (<NUM>) further comprises a third template (<NUM>) comprising a third shaft (<NUM>) extending along a third axis (X1) between a third proximal end (<NUM>) and a third distal end (<NUM>), the third template (<NUM>) comprising a third engagement portion (<NUM>) configured for insertion between the vertebrae, the third engagement portion (<NUM>) comprising a third rod (<NUM>) extending from the third distal end (<NUM>) such that the third rod (<NUM>) is parallel to the third axis (X1) and a third head (<NUM>) coupled to the third rod (<NUM>), the third head (<NUM>) comprising a rectangular geometry.