DESCRIPTION
REPOSITIONING JIG
Field of the invention
This invention relates generally to a surgical device and associated methods, and, more particularly, to a repositioning jig, which is intended for accurate repositioning of vertebrae.
Background of the invention
Degenerative, neoplastic, and traumatic conditions of the spine can lead to compromised alignment of spinal segments. The importance of restoring alignment is well recognised. A surgical plan for repositioning vertebrae can be facilitated by imaging for determining the position of translation and/or rotation correction axes relative to the distorted vertebrae and calculating the associated repositioning parameters (axial, coronal, and sagittal plane translation/rotation). Three-dimensional surgical planning software has been developed as a means of integrating spinerelated measurements to pre-operative planning. Furthermore, real-time assessment during an operation is readily available. While three-dimensional planning software helps improve accuracy, final alignment can be affected by the limitations of the chosen repositioning/fixation system.
Spinal repositioning/fixation systems used to restore alignment of vertebrae typically comprise rods secured to vertebrae by anchoring devices such as bone screws. Rods are inserted and connected to screws by spinal rod reduction devices. Spinal rod reduction devices can grasp the rod-receiving head of the screws and reduce the rod into it. This repositioning method relies on a pre-contoured or in situcontoured connecting rod. However, the rod contour partially determines the final position of the vertebrae. Very often additional repositioning instruments may be used for accomplishing the required (six or fewer) degrees of freedom repositioning of the vertebrae.
Repositioning instruments applied to spinal rod reduction devices can be holder-like devices such as the apparatus described in US20070213715 issued Sep. 13, 2007 to Bridwell, Young, Burd and Kave. They generally comprise multiple clamps and bars. Each bar can be attached to a pair of spinal rod reduction devices by clamps for manual manipulation of a vertebra. Two or more vertebrae can be repositioned by single or multiple manual maneuvers. The spinal surgeons must be mindful how they bent/rotate to avoid excessive pressure to the nerves. The actual magnitude of manual rotation cannot be measured accurately when using holder-like devices.
Other instruments applied to spinal rod reduction devices are based on a single or dual sliding kinematic mechanism such as the apparatus described in US20080077155 issued Mar. 27, 2008 to Diederich, Colleran and Dye. This type of repositioning instruments usually comprises one or two sliding kinematic joints for generating translation and/or rotation along or about a functional translation/rotation axis respectively. A functional axis of a kinematic joint is a virtual axis that shows the direction along or about which the main function of the kinematic joint (translation/rotation) is performed.
Rotation can be generated when actuating a first sliding joint, while a second sliding joint or any other constraining mechanisms simultaneously restrict the relative motion of the spinal rod reduction devices. The sliding joints and/or any other mechanisms of these repositioning instruments are attached to predetermined positions along the spinal rod reduction devices. Customizing the position/orientation of their central functional axes by adjusting the position/orientation of the instruments relative to the spinal rod reduction devices is not always possible. Furthermore, the spinal surgeon cannot customize their kinematic mechanism by adjusting the position/orientation of the functional axis of one kinematic joint relative to another. Hence, they cannot always facilitate six degrees of freedom repositioning of vertebrae.
Currently, minimally invasive or open surgery requires numerous instruments for reducing vertebrae, all of which contribute to procedural complexity. Hence, there is a need for a repositioning device that combines many of these instruments into one single tool, and thus shortening the overall time of repositioning and enhancing surgical workflow.
Furthermore, in order to ensure accurate alignment of vertebrae, multiple intra-operative radiographic images are used to guide the surgeon and confirm that every maneuver has been executed in the desired way, exposing the patient, surgeon, and staff to increased radiation. There is a need for a spine repositioning device compatible with a predetermined repositioning plan translated into clear intraoperative instructions for manipulating vertebrae avoiding a series of radiographically confirmed “trial and error” repositioning maneuvers.
Repositioning of vertebrae is still often regarded as an “art” in which the preoperatively determined repositioning parameters based on the relevant translation/rotation correction axes cannot be corrected intra-operatively in an accurate way relative to the functional translation/rotation axes of the applied repositioning devices, and thus the personal experience of the surgeon still plays a vital role. Hence, there is a need for a repositioning device that can be easily customized such that the spinal surgeon can accurately set the position and orientation of the functional translation/rotation axes of the device relative to the distorted vertebrae according to the surgical plan for accomplishing the required (six or fewer) degrees of freedom repositioning of the vertebrae.
Summary of the invention
The present invention provides methods and apparatuses to alleviate the aforementioned drawbacks. This invention is a repositioning jig (RJ) adaptable at any operated anatomic site. The RJ is a surgical device for repositioning a first generally tubular screw extension of a first screw attached to a first vertebra and a second generally tubular screw extension of a second screw attached to a second vertebra in order to restore alignment of the vertebrae and facilitate placement of any spinal implants. The term “generally tubular screw extension” (GTSE) as used herein refers to any type of elongated post attached to a bone screw such as a shaft of a spinal rod reduction device, a shaft of a Schanz screw, a shaft of a screwdriver-like instrument and the like.
The first and/or the second vertebra may be rigidly coupled to one or more vertebrae by connecting rods, bone screws, GTSEs, clamps or any combination thereof comprising a first and/or a second cluster of vertebrae respectively.
A main object of this invention is to provide an RJ for accomplishing the required (six or fewer) degrees of freedom repositioning of vertebrae with reference to a Cartesian RJ-based coordinate system (RJ-coordinate system). The term “degrees of freedom” refers to any required translations and/or rotations accomplished relative to three mutually perpendicular reference axes of the RJcoordinate system.
The RJ comprises a registration unit, a first clamp, a kinematic unit, a coupling unit, and a second clamp. The first clamp defines the position of the registration unit relative to the first GTSE. The second clamp defines the position of the coupling unit relative to the second GTSE.
It is another object of this invention to provide an RJ that comprises a registration unit for coupling the repositioning jig to the first GTSE and setting the position and orientation of the three mutually perpendicular reference axes of the RJcoordinate system relative to the first GTSE. The registration unit comprises a directional washer, an ωΐ direction hinge, an ω2 direction hinge, and an ω3 direction hinge.
It is yet another object of this invention to provide an RJ that comprises a kinematic unit for repositioning the first and second GTSEs with reference to the RJcoordinate system. The kinematic unit comprises a first stage, a second stage, a third stage, an ω4 direction hinge, an ω5 direction hinge, and a rotating ring.
The rotating ring can rotate the first and second GTSEs about a functional rotation axis. The rotating ring comprises an arc scale for indicating a magnitude of the performed rotation.
A functional axis of a kinematic joint will be defined hereafter as a virtual axis that shows the direction along or about which the main function of the kinematic joint (translation/rotation) is performed.
Each stage provides a sliding joint for translating the first and second GTSEs along a functional translation axis. Each stage comprises a ruler for indicating a magnitude of the performed translation.
The ω4 and ω5 direction hinges determine the orientation of the functional rotation axis relative to the RJ-coordinate system. The indicated translation along the functional translation axis of each stage specifies the position of the functional rotation axis relative to the RJ-coordinate system.
It is another object of this invention to provide an RJ that comprises a coupling unit for connecting the repositioning jig to the second GTSE. The coupling unit comprises a rotating ring-to-rod clamp and a coupling hinge.
Each direction hinge ω1,ω2,ω3,ω4, and ω5 comprises a pair of recesses for receiving a protractor. The directional washer, the ωΐ direction hinge, the ω2 direction hinge, the third stage, and the rotating ring comprise a directional bore for receiving an angle indicator.
According to another aspect of the present invention, there is provided a method whereby the spinal surgeon can set the position and orientation of three mutually perpendicular reference axes of an RJ-coordinate system relative to a first GTSE of a first screw attached to a first vertebra, each having a known position, by means of a first clamp and a registration unit comprising a directional washer, an ωΐ direction hinge, an ω2 direction hinge, and an ω3 direction hinge, said method comprising the following steps:
The spinal surgeon can engage a protractor with the ω1,ω2, and ω3 direction hinges and an angle indicator with the directional washer, the ωΐ direction hinge, and the ω2 direction hinge for rigidly coupling the directional washer to the ωΐ direction hinge, the ωΐ direction hinge to the ω2 direction hinge, and the ω2 direction hinge to the ω3 direction hinge such that they form a first, a second, and a third angle therebetween respectively.
The spinal surgeon can adjust said first, second, and third angle for setting the orientation of the reference axes of the RJ-coordinate system relative to the first GTSE. The spinal surgeon can engage the first clamp with the first GTSE, and adjust the position of said first clamp along the first GTSE for setting the position of the reference axes of the RJ-coordinate system relative to the first GTSE.
The spinal surgeon can advance the registration unit along the first GTSE up to the first clamp, re-engage the angle indicator with the directional washer, and rotate the registration unit such that the angle indicator indicates a predetermined reference landmark of the first vertebra, said landmark can be visually or radiographically discernible or identifiable by its known position, density or geometric properties. Subsequently, the spinal surgeon can rigidly couple the registration unit to the first GTSE.
According to another aspect of the present invention, there is provided an alternative method whereby the spinal surgeon can set the position and orientation of three mutually perpendicular reference axes of an RJ-coordinate system relative to a first GTSE of a first screw attached to a first vertebra, each having a known position, and an interacting GTSE of an interacting screw attached to the first vertebra, each having a known position, by means of a first clamp and a registration unit comprising a directional washer, an ωΐ direction hinge, an ω2 direction hinge, and an ω3 direction hinge, said method comprising the following steps:
The steps of this method differ from the steps of the earlier method in that the spinal surgeon can advance the registration unit along the first GTSE up to the first clamp, re-engage the angle indicator with the directional washer, and rotate the registration unit such that the angle indicator engages with the interacting GTSE. Subsequently, the spinal surgeon can rigidly couple the registration unit to the first GTSE.
According to another aspect of the present invention, there is provided a method whereby the spinal surgeon can set the position and orientation of a functional rotation axis of a kinematic unit comprising a first stage, a second stage, a third stage, an ω4 direction hinge, an ω5 direction hinge, and a rotating ring with reference to an RJ-coordinate system, said method comprising the following steps:
The spinal surgeon can set the position and orientation of the reference axes of the RJ-coordinate system relative to the first GTSE of the first screw attached to the first vertebra, each having a known position, according to one of the above methods.
The spinal surgeon can engage a protractor with the ω4 and the ω5 direction hinges, and an angle indicator with the third stage and the rotating ring for rigidly coupling the ω4 direction hinge to the third stage, and the third stage to the rotating ring, such that they form a fourth and a fifth angle therebetween respectively.
The spinal surgeon can adjust said fourth and fifth angle for setting the orientation of the functional rotation axis relative to the RJ-coordinate system, and adjust the indicated translation along the functional translation axes of the first, second, and third stage of the kinematic unit for setting the position of the functional rotation axis relative to the RJ-coordinate system. Subsequently, the spinal surgeon can rigidly couple the kinematic unit to the registration unit.
According to another aspect of the present invention, there is provided a method whereby the spinal surgeon can reposition a first GTSE of a first screw attached to a first vertebra and a second GTSE of a second screw attached to a second vertebra, each having a known position, by means of a second clamp and a coupling unit, said method comprising the following steps:
The spinal surgeon can set the position and orientation of the functional rotation axis of the kinematic unit with reference to the RJ-coordinate system according to the above method.
The spinal surgeon can engage the second clamp with the second GTSE, adjust the position of said second clamp along the second GTSE for setting the position of the coupling unit relative to the second GTSE, advance the coupling unit along the second GTSE up to the second clamp, and connect the coupling unit to the kinematic unit.
The spinal surgeon can actuate the rotating ring for rotating the first and the second GTSEs about the functional rotation axis, and actuate one or more of the first, second, and third stage for translating the first and the second GTSEs along one or more of the functional translation axes of the first, second, and third stage.
These and other object features and advantages of one or more aspects will become apparent from a consideration of the ensuing description and accompanying drawings. Aspects and embodiments of the present invention are defined in the appended claims.
Brief description of the drawings
FIG. 1 is a perspective view of one embodiment of the present invention.
FIG. 2 is a perspective view of one embodiment of a registration unit of the present invention comprising a directional washer, a first direction hinge, a second direction hinge, and a third direction hinge.
FIG. 3 is an exploded view of the registration unit of the present invention depicted in FIG 2.
FIG. 4 is a perspective view of the first direction hinge in cross-section along plane a-a of FIG. 3
FIG. 5 is a perspective view of the third direction hinge in cross-section along plane b-b of FIG. 3
FIG. 6 is an exploded view of the directional washer, the first direction hinge, a protractor, and an angle indicator.
FIG. 7 is a perspective view of the directional washer, the first direction hinge, the protractor, and the angle indicator assembled such that the directional washer and the first direction hinge form a first angle therebetween.
FIG. 8 is an exploded view of the first and second direction hinge, the protractor, and the angle indicator.
FIG. 9 is a perspective view of the first and second direction hinge, the protractor and the angle indicator assembled such that the second direction hinge and the first direction hinge form a second angle therebetween.
FIG. 10 is an exploded view of the first and second direction hinge, the third direction hinge, the protractor, and the angle indicator.
FIG. 11 is a perspective view of the first, second and third direction hinge, the protractor, and the angle indicator assembled such that the second direction hinge and the third direction hinge form a third angle therebetween.
FIG. 12 is a perspective view of the registration unit coupled to a first generally tubular screw extension of a first screw attached to a first vertebra.
FIG. 13 is a perspective view of one embodiment of a kinematic unit of the present invention.
FIG. 14 is another perspective view of the kinematic unit and one embodiment of a coupling unit of the present invention
FIG. 15 is an exploded view of one embodiment of a first stage, a second stage, a third stage, a fourth direction hinge, and a fifth direction hinge of the kinematic unit of the present invention.
FIG. 16 is an exploded view of one embodiment of a rotating ring of the kinematic unit and an exploded view of the coupling unit of the present invention.
FIG. 17 is a perspective view of one embodiment of a housing unit of the rotating ring in cross-section along plane c-c of FIG. 16
FIG. 18 is an exploded view of the fourth direction hinge, the third stage, a protractor and an angle indicator.
FIG. 19 is a perspective view of the fourth direction hinge, the third stage, the protractor, and the angle indicator assembled such that the fourth direction hinge and the third stage form a fourth angle therebetween.
FIG. 20 is an exploded view of the rotating ring, the fifth direction hinge, a protractor and an angle indicator.
FIG. 21 is a perspective view of the rotating ring, the fifth direction hinge, the protractor, and the angle indicator assembled such that the fifth direction hinge and the rotating ring form a fifth angle therebetween.
FIG 22 is a diagram of a Cartesian coordinate system related to the present invention for defining the position and orientation of the kinematic unit.
FIG. 23 is a perspective view of one embodiment of a first generally tubular screw extension of a first screw attached to a first vertebra, and a first clamp of the present invention attached thereto.
FIG. 24 is an exploded view of an angle indicator, the first clamp and the registration unit attached to the first generally tubular screw extension depicted in FIG 23.
FIG. 25 is a perspective view of the registration unit and the angle indicator rotated about the first generally tubular screw extension, depicted in FIG 24, such that the angle indicator engages with an interacting generally tubular screw extension.
FIG. 26 is a perspective view of the registration unit and the angle indicator rotated about the first generally tubular screw extension, depicted in FIG 24, such that the angle indicator indicates a landmark of the first vertebra.
FIG. 27 is an exploded view of the kinematic unit, the first clamp and the registration unit attached to the first generally tubular extension, the coupling unit and a second clamp coupled to a second generally tubular extension of a second screw attached to a second vertebra.
FIG. 28 is another perspective view of the present invention attached to a first and a second generally tubular screw extension.
FIG. 29 is another perspective view of the present invention depicted in FIG 28 after repositioning the first and second generally tubular screw extensions.
Detailed description
Throughout the description and claims of this invention, the word “ comprise” and variations of the word, such as “comprising” and “comprises”, means “including but not limited to” and it does not exclude other components, integers or steps.
FIG 1 shows an overview of one embodiment of a repositioning jig (RJ) designated generally by the arrow 10. The RJ 10 is a surgical device for repositioning a first generally tubular screw extension 15a of a first screw 12a attached to a first vertebra 1 and a second generally tubular screw extension 15b of a second screw 12b attached to a second vertebra 2 in order to restore alignment and facilitate placement of any spinal implants such as cages and the like.
The term “generally tubular screw extension” (GTSE) as used herein refers to any type of elongated post attached to a bone screw such as a shaft of a spinal rod reduction device, a shaft of a Schanz screw, a shaft of a screwdriver-like instrument and the like.
It is to be emphasised that in some cases the first vertebra 1 and/or the second vertebra 2 can be connected to one or more vertebrae by connecting rods, bone screws, GTSEs, clamps or any combination thereof forming a first and/or a second cluster of vertebrae. The RJ 10 can be used for repositioning the first and/or the second cluster of vertebrae of a distorted spinal segment by coupling a GTSE of each cluster of vertebrae to the RJ 10. This case is not illustrated.
The RJ 10 comprises a first clamp 400a, a registration unit 100, a kinematic unit 200, a coupling unit 300, and a second clamp 400b.
FIG 2 shows an overview of one embodiment of a registration unit 100 of the RJ 10. The registration unit 100 comprises a directional washer 127, an ωΐ direction hinge 120, an ω2 direction hinge 140, and an ω3 direction hinge 160.
The wldirection hinge 120 comprises a base member 125, a directional post 128 and a directional shaft 130, as shown in FIG 3. The base member 125 comprises a central bore 125a for receiving the first GTSE 15a and a pair of recesses 125b on its sidewall. A protractor 60 can be slidably mounted on the recesses 125b of the base member 125 as will become hereinafter apparent.
The first GTSE 15a can be rigidly coupled to the ωΐ direction hinge 120 by a clamp mechanism (CM). The CM comprises a cut section 7a along the sidewall of the central bore 125a and a cut section 7b perpendicular to 7a, as shown in FIG 4. These cut sections define a block that comprises a partially threaded bore 8 for receiving a bolt fastener 135. When said fastener 135 is tightened, the cut sections are compressed, and thus the sidewall of the bore 8 is urged against the first GTSE 15a.
One embodiment of a directional post 128 of the ωΐ direction hinge 120 is a preferably cylindrical partially threaded elongated member of the ωΐ direction hinge 120. The directional post 128 comprises a central bore 128a aligned with the central bore 125a for receiving the first GTSE 15a.
The directional post 128 can receive a directional washer 127. The directional washer 127 can be rigidly coupled to the directional post by a nut 126. The directional washer 127 comprises a directional bore 127b orientated perpendicular to a flat sidewall 127a for receiving an angle indicator 50 as will become hereinafter apparent.
One embodiment of a directional shaft 130 of the ωΐ direction hinge 120 comprises a rod-like member 130b and a directional bore 130a for receiving an angle indicator 50. The directional bore 130a is illustrated in FIG 8.
One embodiment of an ω2 direction hinge 140 can be generally constructed in a similar way to the ωΐ direction hinge 120. However, the ω2 direction hinge 140 does not comprise a structure similar to the directional post 128. A central bore 140a of the ω2 direction hinge 140 has an inner diameter corresponding to the outer diameter of the rod-like member 130b of the ωΐ direction hinge 120. A CM can rigidly couple the rod-like member 130b to the ω2 direction hinge 140.
One embodiment of a directional shaft 150 of the ω2 direction hinge 140 comprises a rod-like member 150b and a directional bore 150a for receiving an angle indicator 50.
One embodiment of an ω3 direction hinge 160 comprises a first CM (CM A) for rigidly coupling the ω3 direction hinge 160 to the rod-like member 150b of the ω2 direction hinge 140 and a second CM (CM B) for rigidly coupling the third direction hinge 160 to the kinematic unit 200, as shown in FIGS 3 and 5. The CM A is associated with a central bore 160a, which can receive the rod-like member 150b of the ω2 direction hinge 140. The CM B is associated with a bayonet-like bore 160b, which can receive a bayonet-like insert 220e of a first stage 220 of the kinematic unit 200. The bayonet-like insert 220e can be better appreciated in FIG 15. The central bore 160a and the bayonet-like bore 160b terminate within the ω3 direction hinge 160.
FIGS 6 and 7 show the assembly of the ωΐ direction hinge 120 with the directional washer 127 such that they form a first angle therebetween. The first angle will be defined hereafter as ωΐ angle. The preferred ωΐ angle can be determined by a protractor 60 and an angle indicator 50. The angle indicator 50 can be threadably engaged with the directional bore 127b of the directional washer 127. The protractor 60 can be removably coupled to a pair of recesses 125b of the first direction hinge 120.
As shown in FIG 7, the angle indicator 50 along with the directional washer 127 can be manually rotated about the directional post 128 such that the angle indicator 50 indicates an ωΐ angle. The spinal surgeon can rigidly couple the directional washer 127 to the ωΐ direction hinge 120 at the ωΐ angle by tightening the nut 126. Subsequently, the protractor 60 and the angle indicator 50 can be removed. It is to be emphasised that any other type of goniometer can be adapted and/or incorporated to the configuration of the ωΐ direction hinge 120 to allow the spinal surgeon to select a predetermined desired ωΐ angle.
FIGS 8 and 9 show the assembly of the ω2 direction hinge 140 with the ωΐ direction hinge 120 such that they form a second angle therebetween. The second angle will be defined hereafter as ω2 angle. The ω2 direction hinge 140 comprises a pair of recesses 140b for receiving a protractor 60. An angle indicator 50 can be engaged with the ωΐ direction hinge 120. The rod-like member 130b of the ω1 direction hinge 120 can be inserted into the central bore 140a of the ω2 direction hinge 140, rotated at the ω2 angle, and secured by the CM mechanism of the ω2 direction hinge 140. The ω2 angle can be determined by a protractor 60 and an angle indicator 50 in a similar way as described in FIG 7.
FIGS 10 and 11 show the assembly of the ω2 direction hinge 140 with the ω3 direction hinge 160 such that they form a third angle therebetween. The third angle will be defined hereafter as ω3 angle. The ω3 direction hinge 160 comprises a pair of recesses 160c for receiving a protractor 60. An angle indicator 50 can be engaged with the ω2 direction hinge 140. The directional shaft 150 of the ω2 direction hinge 140 can be inserted into the central bore 160a of the<u3 direction hinge 160, rotated at the ω3 angle, and secured by the associated CM A mechanism. The ω3 angle can be determined by the protractor 60 and an angle indicator 50 in a similar way as described in FIG 7.
The position and orientation of a first GTSE 15a of a first screw 12a attached to a first vertebra 1 can be defined by a Cartesian coordinate system (XYZ 1), as shown in FIG 12. The ωΐ, ω2 and ω3 angles are selected such that they define the orientation of an RJ-coordinate system (XYZ 2) relative to the first GTSE 15a. The RJ-coordinate system defines the position and orientation of a kinematic unit 200 of the RJ 10.
FIGS 13 and 14 show an overview of one embodiment of a kinematic unit 200. The main object of the kinematic unit 200 is the accurate accomplishment of the required (six or fewer) degrees of freedom repositioning of a first GTSE 15a of a first screw 12a attached to a first vertebra 1 and a second GTSE 15b of a second screw 12b attached to a second vertebra 2. The “degrees of freedom” (DOF) refers to any required translation and/or rotation performed relative to the reference axes of the RJ-coordinate system for restoring alignment of the vertebrae 1, 2, and placement of any spinal implants such as cages and the like. The kinematic unit 200 comprises a first stage 220, a second stage 240, a third stage 260, an ω4 direction hinge 270, an ω5 direction hinge 280, and a rotating ring 290.
One embodiment of a first stage 220 comprises an open platform-like base member 221, as shown in FIG 15. The platform-like base member 221 comprises bores 220a, 220b on its sidewalls for receiving a pair of bearings 222. Each bearing 222 has a central bore, through which a leadscrew 225 is pivotally connected to the platform-like base member 221. The first stage 220 also comprises a bayonet-like insert 220e forming a detachable bayonet-like coupling with the bayonet-like bore 160b of the ω3 direction hinge 160. The CM B can lock the bayonet-like coupling when tightened. However, it can be appreciated that any type of coupling mechanisms such as self-locking coupling mechanisms and the like can also be adopted.
One embodiment of a second stage 240 and a third stage 260 can be telescopic-like stages that comprise an outer tube 245, 265, a translating shaft 246, 266, and a leadscrew 247, 267 respectively. Each outer tube 245, 265 comprises a central square bore configured to receive the translating shafts 246, 266. The leadscrews 247, 267 are pivotally connected to the outer tube 245, 265 via bearings 224. The translating shafts 246, 266 comprise a central threaded bore 246a, 266a for receiving the leadscrews 247, 267 respectively.
The translating shaft 246 comprises a threaded bore 246b for engaging with the leadscrew 225 of the first stage 220. The first stage 220 also comprises a pair of longitudinally extending guide rails 220c, 220d that correspond to a pair of grooves 246c, 246d of the translating shaft 246.
The second and third stage 240, 260 can be rigidly connected via one embodiment of an ω4 direction hinge 270. The ω4 direction hinge 270 comprises a lower base member 271 and an upper base member 272 for accommodating the second stage 240 within a cutaway channel 271a. A pair of bolts 273 urges the lower base member 271 against the upper base member 272, and thus secures the second stage 240 within the cutaway channel 271a.
The upper base member 272 comprises a central bore 272a for receiving the third stage 260. A CM of the upper base member 272 can rigidly couple the third stage 260 to the second stage 240. The translating shaft 266 of the third stage 260 is rigidly attached to an ω5 direction hinge designated by arrow 280. Theo>5 direction hinge 280 couples the third stage 260 to a rotating ring 290.
Each stage 220, 240, 260 of the kinematic unit 200 provides a sliding joint orientated such that it generates translation along a reference axis XX’, YY’, ZZ’ of the RJ-coordinate system, as shown in FIGS 12, 15, and 21. The actuators of each stage 220, 240, 260 (i.e. the leadscrews 225, 247, 267) are provided with a leadscrew head 225a, 247a, 267a respectively. Rotation of the leadscrew head 225a, 247a, 267a can be performed either manually or by a corresponding instrument applied thereto (not illustrated). This allows a precise degree of translation of the vertebrae along the associated RJ-reference axes by means of rulers designated by arrows R1, R2, and R3, which are depicted on the sidewalls of the platform-like base member 221 and the translating shafts 246, 266. The rulers R1, R2, and R3 indicate a magnitude of the accomplished translation along the RJ-reference axes.
FIG 16 shows one embodiment of a rotating ring 290 of the kinematic unit 200. The rotating ring 290 comprises a ring plate 291 and a housing unit 292. In particular, the ring plate 291 comprises a shaft 291c and a serrated surface 291a about its periphery that forms a rack. A groove 291b and an arc scale R4 extend around the circumference on each sidewall of the ring plate 360.
One embodiment of a housing unit 292 comprises flattened parallelepiped sides advantageously shaped to accommodate a worm gear 293 within its cutaway interior. The housing unit 292 is rotatable about the serrated surface 291a of the ring plate 291a via the worm gear 293. The worm gear 293 is pivotally connected to the housing unit 292 by a pair of bearings 294. The housing unit 292 comprises a directional shaft 292a and a pair of protrusions 292b, which engage with the pair of grooves 291b of the ring plate 291.
The housing unit 292 comprises a bore 292c for receiving a leadscrew 295 via a bearing 296. The leadscrew 295 can extend generally perpendicular to the worm gear 293. A bevelled serrated edge of the leadscrew 295b is pivotally connected to a bevelled serrated edge of the worm gear 293b, as shown in FIG 17. Actuation of the leadscrew head 295a either manually or by a corresponding instrument (not illustrated) can rotate a first GTSE 15a and a second GTSE 15b.
FIGS 14 and 16 show one embodiment of a coupling unit 300. The coupling unit 300 comprises a rotating ring-to-rod clamp 350 and a coupling hinge 380.
One embodiment of a coupling hinge 380 comprises a first hinge member 385 and a second hinge member 390 connected by a latch 395. The first hinge member 385 comprises a connecting rod 385a and a first pivot lobe 385b. The second hinge member 390 comprises a clamping coupling head 390a and a second pivot lobe 390b. Each pivot lobe 385b, 390b has a central bore for receiving a latch 395.
The first and second pivot lobes 385b, 390b are rotatably connected by the latch 395. The latch 395 comprises a preferably flange-head screw 395a threadably engaged with a press tab 395b. When the flange head screw 395a is tightened, the spinal surgeon can lock the first and second hinge members 385, 390 together. Although, it can be appreciated that any other locking mechanism can be adopted such as a self-locking latch and the like.
The clamping coupling head 390a of the second hinge member 390 comprises a central bore 390b for receiving a second GTSE 15b. A CM of the clamping coupling head 390a can rigidly connect the coupling unit 300 to the second GTSE 15b. Tightening the rotating ring-to-rod clamp 350 rigidly couples the connecting rod 385a to the shaft 291c of the ring plate 291.
FIGS 18 and 19 show the assembly of the ω4 direction hinge 270 with the third stage 260 such that they form a fourth angle therebetween. The fourth angle will be defined hereafter as ω4 angle. The diameter of the outer tube 265 of the third stage 260 corresponds to the inner diameter of the central bore 272a of the ω4 direction hinge 270. The ω4 direction hinge 270 comprises a pair of recesses 272b on its sidewalls for receiving a protractor 60. An angle indicator 50 can be engaged with a directional bore 265a of the outer tube 265 of the third stage 260. The ω4 direction hinge 270 can rigidly lock the third stage 260 by an associated CM at the ω4 angle. The ω4 angle can be determined by the protractor 60 and the angle indicator 50 in a similar way as described in FIG 7.
FIGS 20 and 21 show the assembly of the rotating ring 290 with the ω5 direction hinge 280 such that they form a fifth angle therebetween. The fifth angle will be defined hereafter as ω5 angle. The directional shaft 292a of the housing unit 292 can be inserted into a central bore 280a of the ω5 direction hinge 280. The ω5 direction hinge 280 comprises a pair of recesses 280b for receiving a protractor 60. An angle indicator 50 can be threadably engaged with a directional bore 292b of the directional shaft 292a. The ω5 angle can be determined by the protractor 60 and the angle indicator 50 in a similar way as described in FIG 7. Subsequently, an associated CM mechanism of the ω5 direction hinge 280 can rigidly couple the ω5 direction hinge to the rotating ring 290.
The rotating ring 290 defines a functional rotation axis OA, as shown in FIG 21. A functional axis of a kinematic joint will be defined hereafter as a virtual axis that shows the direction along or about which the main function of the kinematic joint (translation/rotation) is performed. Each stage 220, 240, and 260 of the kinematic unit 200 provides a prismatic joint that defines a functional translation axis along a reference axis (XX’, YY’, ZZ’) of the RJ-coordinate system.
The indicated translation (x, y, z) along the functional translation axes/reference axes of the RJ-coordinate system specifies the position of the functional rotation axis OA. The orientation of the functional rotation axis OA can be defined by theo>4 and ω5 angles, as shown in FIG 22. In particular, the XX’ and YY’ reference axes of the RJ-coordinate system define a horizontal plane (YOX). The ZZ’ and YY’ reference axes define a vertical plane (YOZ). The ω4 angle is the angle between the functional rotation axis OA and the horizontal plane YOX. The ω5 angle is the angle between the projection OA’ of the functional rotation axis OA on the horizontal plane YOX and the vertical plane YOZ.
The spinal surgeon can set the position and orientation of the reference axes of the RJ-coordinate system relative to a first GTSE 15a of a first screw 12a attached to a first vertebra 1 and an interacting GTSE 15i of an interacting screw 12i attached to the first vertebral, each having a know position defined by the preferred imaging method.
As shown in FIG 23, the spinal surgeon can engage one embodiment of a first clamp 400a with the first GTSE 15a, and adjust the position of the first clamp 400a along the first GTSE 15a for defining the position of the registration unit 100 relative to the first GTSE 15a. In this exemplary embodiment, the first clamp 400a is placed at hi distance from the top of the first GTSE 15a. It is to be emphasised that numerous modifications of the first clamp 400a may be adopted for determining the particular position of the registration unit 100 relative to the first GTSE 15a.
The spinal surgeon can assemble the registration unit 100 according to the method described in FIGS 6, 7, 8, 9, 10, and 11. The particular orientation of the registration unit 100 relative to the first GTSE 15a can be defined by the ωΐ, ω2 and ω3 angles preferably pre-operatively. As shown in FIG 24, the spinal surgeon can advance the registration unit 100 up to the first clamp 400a. The spinal surgeon can re-engage the angle indicator 50 with the directional washer 127 of the registration unit 100. As shown in FIG 25, the spinal surgeon can rotate the registration unit 100 such that the angle indicator 50 engages with the interacting GTSE 15i.
It is to be appreciated by those skilled in the art that the angle indicator 50 may be additionally used with appropriate adaptation for rigidly connecting the first GTSE 15a to the interacting GTSE 15i.
According to an alternative method, as shown in FIG 26, the spinal surgeon can set the position and orientation of the reference axes of the RJ-coordinate system relative to a first GTSE 15a of a first screw 12a attached to a first vertebra 1, each having a know position defined by the preferred imaging method, without an interacting GTSE 15i.
This method differs from the above method in that the spinal surgeon can engage the angle indicator 50 with the directional washer 127 of the registration unit 100 and rotate the angle indicator 50 about the first GTSE 15a such that, under visual or imaging guidance, the angle indicator 50 indicates a predetermined reference landmark A of the first vertebra 1.
A reference landmark A of a vertebra can be visually or radiographically discernible or identifiable by its known position, density or geometric properties (e.g. vertebra centroid). The angle indicator 50 can be radiopaque for showing up as a discernable line in images such as radiographs. After rotation of the angle indicator 50, the projection of the angle indicator 50 onto a visual or imaging plane can pass through the projected landmark A onto the same plane.
The interacting GTSE 15i or the reference landmark A helps determine the orientation of the registration unit 100 about the first GTSE 15a. After placing the registration unit 100 at a predetermined position/orientation, the spinal surgeon can rigidly couple the registration unit 100 to the first GTSE 15a.
Subsequently, the registration unit 100 can be coupled to the kinematic unit 200 for repositioning the first GTSE 15a of the first screw 12a attached to the first vertebra 1 and a second GTSE 15b of a second screw 12b attached to a second vertebra 2, each having a known position defined by the preferred imaging method, by means of one embodiment of a second clamp 400b and a coupling unit 300.
As shown in FIG 27, the spinal surgeon can engage the second clamp 400b with the second GTSE 15b and adjust the position of the second clamp 400b along the second GTSE 15b for defining the position of the coupling unit 300 relative to the second GTSE 15b. It is to be emphasised that numerous modifications of the second clamp 400b may be adopted for determining the particular position of the coupling unit 300 along the second GTSE 15b. In this exemplary embodiment, the second clamp 400b is placed at h2 distance from the top of the second GTSE 15b. The spinal surgeon can advance the coupling hinge 380 of the coupling unit 300 along the second GTSE 15b up to the second clamp 400b and connect the coupling hinge 380 to the kinematic unit 200 by the rotating ring-to-rod clamp 350.
The kinematic mechanism of the kinematic unit 200 can be customized prior to placement such that it facilitates the required (six or fewer) DOF repositioning of a first vertebra 1 and a second vertebra 2.
According to one method, the first vertebra 1 and the second vertebra 2 can be repositioned from their original position to their repositioned position by translating along three mutually perpendicular reference axes of a Cartesian coordinate system and/or by rotating about the reference axes of the Cartesian coordinate system. An exemplary embodiment of a Cartesian coordinate system can be the XYZ 1 coordinate system depicted in FIG 12, and it will be used hereinafter as a reference coordinate system.
According to an alternative preferred method, the first vertebra 1 and the second vertebra 2 can be repositioned from their original position to their repositioned position by three or fewer translations along the XYZ 1 reference axes and/or a single rotation about a rotation correction axis. The position and orientation of the rotation correction axis can be customized such that it can express the total rotation equivalent to three or fewer rotations about the XYZ 1 reference axes.
The position and orientation of the RJ-coordinate system relative to the XYZ 1 can be defined by the position h and the interconnecting angles ωΐ, ω2, and ω3 of the registration unit 100 relative to the first GTSE 15a of the first screw 12a attached to the first vertebra 1 such as: RJ-coordinate system= f (ω1,ω2, ω3, h)
Thus, any translations performed intra-operatively along the RJ-reference axes can correspond to the required translations along the XYZ 1 reference axes. The translations can be equivalent to the required (three or fewer) DOF.
FIG 28 shows a custom position and orientation of a functional rotation axis OA of the rotating ring 290 designated by a cross sign x. The spinal surgeon can set the position and orientation of the functional rotation axis OA with reference to the RJ-coordinate system by the indicated translation (x, y, z) along the functional translation axes of the kinematic unit 200, and the interconnecting angles ω4,ω5. Hence, OA = f(x, y, z, ω4, ω5)
The above parameters (ωΐ, ω2, ω3,/ι, x,y, z, ω4, ω5) can be adjusted such that the functional rotation axis OA can preferably coincide with the rotation correction axis. Thus, a single rotation about the functional rotation axis OA can be equivalent to the required (three or fewer) DOF. Therefore, the RJ 10 can be customized for substantially fully accomplishing the required (six or fewer) DOF repositioning of the first vertebra 1 and the second vertebra 2.
It is to be appreciated that a plurality of embodiments of GTSEs may incorporate technical features of the present invention rendering parts of the present invention not necessary. In some embodiments of GTSEs, there may be an incorporated positioning apparatus wherein the position of the registration unit 100 5 along the first GTSE 15a and the position of the coupling hinge 380 along the second GTSE 15b may be determined without the associated first and second clamp 400a, 400b.
It is also to be appreciated that the present invention may be additionally used with appropriate adaptation in any situation in which immobilization, manipulation and 10 reduction of a bone segment is important such as long bone deformity correction or fracture repair and the like. Furthermore, numerous modifications may be made to the illustrative embodiments and other arrangements may be devised without departing from the scope of the present invention as defined by the appended claims.