Patent ID: 12256963

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to an exemplary embodiment of the subject disclosure illustrated in the accompanying drawings. Wherever possible, the same or like reference numbers will be used throughout the drawings to refer to the same or like features. It should be noted that the drawings are in simplified form and are not drawn to precise scale. In reference to the disclosure herein, for purposes of convenience and clarity only, directional terms such as upper, lower, top, bottom, above, below and diagonal, are used with respect to the accompanying drawings. Such directional terms used in conjunction with the following description of the drawings should not be construed to limit the scope of the subject disclosure in any manner not explicitly set forth. Additionally, the term “a,” as used in the specification, means “at least one.” The terminology includes the words above specifically mentioned, derivatives thereof, and words of similar import.

“About” as used herein when referring to a measurable value such as an amount, a temporal duration, and the like, is meant to encompass variations of ±20%, ±10%, ±5%, ±1%, or ±0.1% from the specified value, as such variations are appropriate.

“Substantially” as used herein shall mean considerable in extent, largely but not wholly that which is specified, or an appropriate variation therefrom as is acceptable within the field of art. “Exemplary” as used herein shall mean serving as an example.

Throughout the subject application, various aspects thereof can be presented in a range format. It should be understood that the description in range format is merely for convenience and brevity and should not be construed as an inflexible limitation on the scope of the subject disclosure. Accordingly, the description of a range should be considered to have specifically disclosed all the possible subranges as well as individual numerical values within that range. For example, description of a range such as from 1 to 6 should be considered to have specifically disclosed subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6 etc., as well as individual numbers within that range, for example, 1, 2, 2.7, 3, 4, 5, 5.3, and 6. This applies regardless of the breadth of the range.

Furthermore, the described features, advantages and characteristics of the exemplary embodiments of the subject disclosure may be combined in any suitable manner in one or more exemplary embodiments. One skilled in the relevant art will recognize, in light of the description herein, that the subject disclosure can be practiced without one or more of the specific features or advantages of a particular exemplary embodiment. In other instances, additional features and advantages may be recognized in certain exemplary embodiments that may not be present in all exemplary embodiments of the present disclosure.

Referring now to the Figures, there is shown a cutter100in accordance with an exemplary embodiment of the subject disclosure. The cutter100may be used to cut/mill spine rods, including, for example, a spine rod800affixed to a spine805of a patient using spine rod screws810having proximally attached tulips815(seeFIGS.1and10A through10D). The cutter100may be employed, for example, to cut implanted spine rods of varying lengths and diameters (e.g., 2, 4, 6, 8, 10 mm, etc.), as well as those affixed to a spine using structures other than screws810and those constructed from various materials, such as, for example, stainless steel, titanium, or cobalt chrome. Although the cutter100is described herein and shown in the Figures as operable to cut spine rods (such as spine rod800), it should be appreciated that the cutter100and other embodiments contemplated by the subject disclosure may be used to cut/mill other types of implants, and that various embodiments of the subject disclosure are not intended to be limited for use with any particular size, type or category of implant(s).

As best shown inFIGS.2through5and10A through10D, the cutter100includes a gearbox105, primary and secondary milling bits110,110′, and a shaft e.g., a threaded lead screw120operatively coupled to and extending through the gearbox105, an input coupling125(which e.g., may include a Hudson connector or similar connector for coupling to a driving source) coupled rigidly to the proximal end of the primary milling bit110, a knob130coupled to the proximal end of the lead screw120, chip collectors135,135′ coupled to the distal end of the gearbox105and respectively circumscribing the primary and secondary milling bits110,110′, and an implant coupler140coupled to the distal end of the lead screw120and guided for longitudinal translation by the chip collectors135,135′, e.g., via guide rails625,625′. In the illustrated exemplary embodiment, the primary milling bit, the secondary milling bit and the lead screw are spaced apart along a substantially linear path, and a longitudinal axis of the primary milling bit and a longitudinal axis of the secondary milling bit are substantially parallel to a longitudinal axis of the lead screw.

As best shown inFIGS.3and4, the primary and secondary milling bits110,110′ respectively include distal cutting ends305,305′ for cutting implants e.g., the spine rod800, and proximal drive ends310,310′ with respective drive grooves315,315′ for operatively coupling to the gearbox105. The cutting ends305,305′ include notched or rounded edges325,325′ to reduce chipping and spiral flutes320,320′ for transporting chips and other fragments cut/milled from the spine rod800proximally toward center regions330,330′ of the bits110,110′. In one exemplary embodiment, at least the cutting ends305,305′ of the primary and secondary milling bits110,110′ are made from tungsten carbide, though it should be appreciated that other portions of the milling bits110,110′ may also be made of tungsten carbide, or that any or all portions thereof may be constructed using alternative materials. It should also be appreciated that the cutting ends305,305′ may be center or edge cutting and/or or have rounded edges325,325′, and that various exemplary embodiments of the subject disclosure are not intended to be limited to any particular type of cutting end or manner of cutting the spine rod800or other implant.

With reference toFIGS.2and5through7, the gearbox105includes a housing205with a distal plate207enclosing translation and milling drive assemblies210,215operable respectively to translate the gearbox105distally with respect to the lead screw120or along a longitudinal extent of the lead screw and to drive the secondary milling bit110′ in response to a rotational driving force applied to the input coupling125, as well as various washers270and bushings275a,275b,275c,275d,275eand275fto protect the various components of the drive assemblies210,215from wear and to properly position, align and space the components within the housing205. In the exemplary embodiment depicted in the Figures, the driving force is supplied e.g., by a drill500with a flexible drive shaft505, though it should be appreciated that the rotational driving force may be applied to the input coupling125in other ways, such as, for example, via a rigid drive shaft, and that various exemplary embodiments of the subject disclosure are not intended to be limited to any particular manner of applying a driving force to the input coupling125.

As best shown inFIGS.5through7, the translation drive assembly210includes a first worm screw220having a longitudinal bore225receiving the proximal drive end310of the primary milling bit110and a longitudinally extending drive rib230engaging the drive groove315of the primary milling bit110, a first worm gear235operatively coupled to the first worm screw220, a shaft245extending longitudinally through the first worm gear235and bounded at one end by an end cap280and circlip (not shown) inside the housing205and on the other end by an alignment receptacle285(FIG.10D) on the inside of the housing205, a second worm screw250disposed rotatably on and circumscribing the shaft245and coupled rigidly to the first worm gear235, a second worm gear255operatively coupled to the second worm screw250and having a hexagonal socket260and a longitudinal through bore265circumscribing the lead screw120, and a hexagonal lead nut272positioned within the hexagonal socket260and threadedly engaged with the lead screw120.

As best shown inFIGS.5and6, the milling drive assembly215includes a first spur gear405circumscribing the primary milling bit110distally of the first worm screw220and having a longitudinally extending drive rib410engaging the drive groove315of the primary milling bit110, a free-spinning second spur gear415operatively engaging the first spur gear405and rotatably circumscribing the lead screw120distally of the second worm gear255, and a third spur gear420operatively engaging the second spur gear415, circumscribing the secondary milling bit110′ and having a longitudinally extending drive rib425engaging the drive groove315′ of the secondary milling bit110′.

Although the components of the translation and milling drive assemblies210,215described herein and illustrated in the Figures operate together to translate the gearbox105distally with respect to the lead screw120and to drive the secondary milling bit110′, it should be appreciated that the translation and milling drive assemblies210,215may include other arrangements of the same or different components to effectuate these functions, and that various embodiments of the subject disclosure are not intended to be limited to any specific components or arrangement of components for translating the gearbox105or driving the secondary milling bit110′. It should also be appreciated that the translation and milling drive assemblies210,215may include non-gear components, such as hydraulic and/or electrical components, and that various embodiments of the subject disclosure are not intended to be limited to any type or class of components.

As best shown inFIGS.2,8A through8C, and10A through10D, the chip collectors135,135′ circumscribe the primary and secondary milling bits110,110′ and respectively include proximal funnel-shaped ends605,605′ coupled to the distal plate207of the housing205, generally cylindrical body portions610having internal chip collection cavities620in communication with the milling bits110,110′ and outer surfaces provided with longitudinally extending guide rails625,625′, longitudinal bores630extending from the distal bottoms of chip collection cavities620to the distal ends of the body portions610,610′, and cutouts635shaped to receive the spine rod800and facing transversely to and intersecting the longitudinal bores630at the distal ends of the body portions610,610′. The internal diameters of bores630at the distal ends of the chip collectors are equal to or slightly larger than the external diameters of the primary and secondary milling bits110,110′ to effectively retain or seal the chip collection cavities620and prevent chips and other fragments removed from the spine rod800from escaping the cavities620. In the exemplary embodiment depicted in the Figures, the cutouts635are U-shaped to receive the spine rod800, though it should be appreciated that the cutouts635may be shaped differently to receive other types of implants.

As best shown inFIGS.2and9A through10D, the implant coupler140includes a proximal threaded receptacle705coupled to the distal end of the lead screw120and a generally cylindrical coupling body710having an outer surface provided with longitudinally extending grooves720,720′ respectively and slidably engaging with the guide rails625,625′ of the chip collectors135,135′ and a distal end725provided with a socket730e.g., a helicopter socket and a hollow receptacle732shaped e.g., to receive a tulip815of a spine rod screw810for properly orientating and aligning the cutter100during a cutting/milling operation. In alternative exemplary embodiments, the implant coupler may or may not include a hollow receptacle e.g., the implant coupler may be of smaller diameter or a cylinder having a socket for engaging a rod similar to socket730. In this alternative embodiment, the coupler does not receive the tulip815and engages only with the spine rod800.

The socket730is shaped to releasably receive the spine rod800and includes helicopter cutouts having respective and radially aligned or diametrically opposed receipt channels740,740′ and locking channels745,745′. The locking channels745,745′ are also configured to align planarly with the cutouts635of the chip collectors135,135′ so that the primary and secondary milling bits110,110′ can properly align with the spine rod800during operation of the cutter100. It should be appreciated that the receipt channels740,740′ and locking channels745,745′ may be shaped differently to receive differently shaped rods and other implants. It should also be appreciated that the implant coupler140may include structures in addition to or in lieu of the socket730for releasably receiving the spine rod800or other implant.

To operate the cutter100to cut/mill the spine rod800, a user first aligns the cutter100(seeFIG.10A) and engages the hollow receptacle732of the implant coupler with a tulip815of a spine rod screw810, while at the same time aligning the receipt channels740,740′ of the implant coupler140with the spine rod800(seeFIG.10B). Once the spine rod800is received completely within the receipt channels740,740′ of the implant coupler140, the user rotates the cutter100counterclockwise (when viewed distally from the proximal side of the cutter100) to position the spine rod800fully within the locking channels (seeFIG.10C), thereby locking the spine rod800rigidly in position with respect to the cutter100and aligning the primary and secondary milling bits110,110′ with the spine rod800. The user then applies a clockwise driving force to the input coupling125. Clockwise rotation of the input coupling125drives the primary milling bit110, which in turn causes the drive groove315of the primary milling bit110to engage the drive rib410of the first spur gear405and rotate the gear405clockwise with the primary milling bit110. Rotation of the first spur gear405causes the free-spinning second spur gear415to rotate counterclockwise about the lead screw120which, in turn, causes the third spur gear420to rotate clockwise. As the third spur gear420rotates, the drive rib425of the third spur gear420engages the drive groove315′ of the secondary milling bit110′ causing the bit110′ to also rotate clockwise with the third spur gear420. Since the first, second and third spur gears405,415,420are similarly sized and include the same number of teeth, the third spur gear420rotates at the same speed and in the same clockwise direction as first spur gear405to ensure that the primary and secondary milling bits110,110′ rotate clockwise at the same speed. It should be appreciated, however, that the spur gears405,415,420may be sized differently and/or include different numbers of teeth, and that the secondary milling bit110′ may rotate at a different speed or in a different rotational direction compared to the primary milling bit110.

Rotation of the primary milling bit110also causes the drive groove315of the primary milling bit110to engage the drive rib230of the first worm screw220causing it to rotate clockwise with the primary milling bit110. Rotation of the first worm screw220causes rotation of the first worm gear235and second worm screw250about the shaft245which, in turn, causes clockwise rotation of the second worm gear255and hexagonal lead nut272about the lead screw120. Since the lead nut272threadedly engages with the lead screw120and because engagement of the implant coupler140with the spine rod800prevents longitudinal displacement of the lead screw120, the clockwise rotation of the hexagonal lead nut272causes the lead screw120to produce a distal force on the lead nut272, thereby causing the gearbox105(with coupled milling bits110,110′ and chip collectors135,135′) to translate distally along the lead screw120guided by engagement of the guide rails625,625′ of the chip collectors135,135′ with the grooves720,720′ of the implant coupler140. In another embodiment, the device may use a compound gear set instead of worm drive gears.

The gearbox105translates distally until the distal cutting ends305,305′ of the primary and secondary milling bits110,110′ contact the spine rod800, at which point cutting/milling of the spine rod800begins. The cutouts635of the chip collectors135,135′ engage with the spine rod800and help guide the milling bits110,110′ as they advance therethrough. Chips and other fragments removed from the spine rod800are transported proximally by the spiral flutes320,320′ of the primary and secondary milling bits110,110′ into the chip collection cavities620of the chip collectors135,135′, where they are deposited and maintained during the cutting/milling operation. The primary and secondary milling bits110,110′ continue to translate distally until they cut through the spine rod800, at which point the cutting/milling operation ends (FIG.10D) and the cutter100is removed from the patient.

Over cutting is prevented by the proximal top surfaces of cutouts635which engage with the spine rod800to prevent the distal center-cutting ends305,305′ of the primary and secondary milling bits110,110′ from translating too far distally into the patient. In other words, owing to their abutment with the spine rod, the proximal top surfaces of cutouts of the chip collectors prevent further distal penetration of the cutting ends of the primary and secondary milling bits once the spine rod is cut thereby. For example, the largest diameter of spine rods is currently 6 mm. Therefore, there will be a hard stop on the travel of the cutters at a distance slightly greater than 6 mm. The cylindrical guides concentric to the cutters have a cutout that accepts the spine rod. The furthest travel of the cutters is limited to not extend past these guides.

After completion of the cutting/milling operation, the chip collectors135,135′ are removed from the cutter100so that the chips and other fragments cut/milled from the spine rod800, as well as any chips and fragments remaining in the spiral flutes320,320′ of the primary and secondary milling bits110,110′, may be accessed and discarded. In at least some exemplary embodiments, removal of the chip collectors135,135′ may be facilitated by first detaching the implant coupler140from the cutter100. This may be effectuated by first rotating the knob130counterclockwise to retract the distal end of the lead screw120from the threaded receptacle705of the implant coupler140and then sliding the coupler140distally to disengage the guide rails625,625′ of the chip collectors135,135′ from the grooves720,720′ of the implant coupler140. The cutter100may then be reset to perform a new cutting/milling operation by first reattaching the chip collectors135,135′ and the implant coupler140and then translating the gearbox105proximally into its initial position by applying a counterclockwise rotational force to the input coupling125manually or by using the drill500or other mechanism.

FIGS.11,12,13A and13Bdisclose further exemplary embodiments of the subject disclosure, which include a clamping mechanism for applying clamping force to an implant during cutting of the implant. The various clamping mechanisms of these embodiments hold the implant firmly and steady in place to prevent chattering of the implant, i.e., resist vibrations of the implant, caused by milling. For brevity, only those elements of the implant cutters shown inFIGS.11,12,13A and13Bthat materially depart in structure and/or function from their counterparts shown inFIGS.1-10D, or are otherwise necessary for a proper understanding of the subject disclosure, will be described in detail.

Referring toFIG.11, there is shown an exemplary embodiment of a clamping mechanism900operatively connected to the implant coupler140′ for applying a clamping force to an implant800during cutting of the implant. The clamping mechanism900comprises an axially extending elongated shaft902have threads threadedly engaging the implant coupler e.g., about its proximal end902a. The threaded shaft includes a handle904at a proximal end thereof and an implant engageable tip906at a distal end thereof operable to clampingly engage the implant, e.g., spine rod800. While the elongated threaded shaft902threadedly engages at least the implant coupler140′, it is understood that one or both of knob130′ and threaded lead screw120′ may be correspondingly internally threaded to engage with the external threading of the shaft902. That is the lead screw120′ and/or knob130′ can include a longitudinal through hole having internal threads. However, to minimize resistance to turning of the threaded shaft by the handle904, the knob130′ and the threaded lead screw120′ are provided with smooth-walled internal bores of slightly larger diameter than the diameter of the threaded shaft.

In operation, and prior to milling of the implant800, the implant coupler is engaged with the implant as described above. Thereafter, the handle904is turned in a direction to advance the threaded shaft and tip906towards the implant800until the tip comes into firm direct engagement with the implant. With the implant firmly engaged, the above-described milling operation is performed with minimal or no vibration of the implant occurring during milling, whereby the implant is easily and precisely cut by the implant cutter100′.

Referring toFIG.12, there is shown another exemplary embodiment of a clamping mechanism1000operatively connected to the implant coupler140″ for applying a clamping force to an implant800during cutting of the implant. The clamping mechanism1000comprises a set screw receiver1002radially or laterally projecting from the implant coupler140″ and a laterally extending set screw1004threadedly engaging the implant coupler at the set screw receiver and operable to clampingly engage the implant. The set screw has a socket1006or other tool engageable structure that permits the set screw to be advanced into the implant coupler until it firmly engages the implant. Milling of the implant can then be performed with minimal or no vibration of the implant occurring during milling.

Referring toFIGS.13A and13B, there is shown another exemplary embodiment of a clamping mechanism1100operatively connected to the implant coupler140′″ for applying a clamping force to an unillustrated implant during cutting thereof. As shown inFIG.13B, a circumferential surface of the implant coupler is externally threaded1102. The clamping mechanism includes a substantially cylindrical sleeve1104surrounding the implant coupler and having internal threading1106configured to threadedly engage the external threading of the implant coupler. In addition, the internally threaded sleeve1104includes a distal edge1108operable to clampingly engage the implant. As shown inFIG.13A, the external surface of the sleeve1104can be provided with structure1110for enhancing a user's grip when turning the sleeve relative to the implant coupler. Such structure can include recesses, raised ridges, knurling, and the like. Once the implant coupler is engaged with an implant (not illustrated), a user turns the sleeve1104in a direction to advance the distal edge1108of the sleeve into firm compressive engagement with the implant. The sleeve is locked in position by the application of sufficient torque upon engagement with the implant. With the implant firmly engaged, the milling operation is performed with minimal or no vibration of the implant occurring during milling, whereby the implant is easily and precisely cut by the implant cutter100″.

It will be appreciated by those skilled in the art that changes could be made to the exemplary embodiments described above without departing from the broad inventive concept thereof. It is to be understood, therefore, that this disclosure is not limited to the particular exemplary embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the claims defined herein.