Double rod implant cutter

Abstract

The present invention relates to a cutter (100) for cutting an implant (800). The cutter comprises a gearbox (105); a primary milling drill bit (110), a secondary milling drill bit (110') and a lead screw (120) operably connected to the gearbox; an input coupling (125) rigidly connected to the primary milling drill bit; and an implant coupling (14) rigidly connected to the lead screw, wherein the gearbox is operable to translate relative to the lead screw and drive the secondary milling drill bit in response to a driving force applied to the input coupling.

Description

Background Art

[0001] Various types of surgical procedures involve placing implants, such as spinal rods, in a patient's body. It is often necessary or desirable to adjust the length of the spinal rod after implantation, because it is often difficult or impossible to accurately determine the exact length of the spinal rod before surgery. Standard procedures for certain surgical procedures may also require cutting the spinal rod after implantation to best provide the desired customized length for each patient. In order to adjust the length, the spinal rod can be removed from the patient's body, cut to the required length outside the site, and re-implanted into the patient's body later. However, this method is time-consuming, expensive, and may require the patient to undergo multiple surgeries. Typical spinal rod cutters are also difficult to align and use, and often require the user to devote a lot of attention to ensure that the cutter remains aligned and engaged with the spinal rod during the cutting operation. Therefore, there is a need for an efficient and effective implant cutter that can be used in situ.

[0002] In addition, during the revision surgery when the spinal rod is removed, it is advantageous for the surgeon to cut the spinal rod so as to more easily remove it. In addition, the surgeon may not have a suitable driver to unscrew the locking cap that the spinal rod is mounted on the pedicle screw. In this scenario, it is also advantageous to have a device that can cut the rod on either side of the pedicle screw. Then, the section of the rod between the screws can be easily taken out. The remaining small section of the rod still attached to the pedicle screw can be taken out by "helicoptered" then. Summary of the invention

[0003] According to an exemplary embodiment of the present disclosure, a cutter for cutting implants is provided. The cutter includes a gearbox; a main milling drill bit, a secondary milling drill bit and a lead screw operably connected to the gearbox; an input coupling coupled to the main milling drill bit; and an implant coupling coupled to the lead screw, wherein the gearbox is operable to translate relative to the lead screw and drive the secondary milling drill bit in response to a driving force applied to the input coupling.

[0004] According to another aspect of the subject disclosure, the gearbox includes a translation drive assembly operable to translate the gearbox relative to the lead screw in response to a drive force applied to an input coupling, and a milling drive assembly operable to drive a secondary milling bit in response to the drive force applied to the input coupling.

[0005] According to yet another aspect of the subject disclosure, a translation drive assembly includes a first worm screw surrounding and coupled to a main milling drill bit; a first worm wheel operatively coupled to the first worm screw; a second worm screw rigidly coupled to the first worm wheel; a second worm wheel operatively coupled to the second worm screw, the second worm wheel surrounding a lead screw and having a socket; and a nut threadably engaged with the lead screw in the socket of the second worm wheel.

[0006] According to yet another aspect of the subject disclosure, a mill drive assembly includes a first spur gear surrounding and rigidly coupled to a primary mill bit; a second spur gear operatively coupled to the first spur gear; and a third spur gear operatively coupled to the second spur gear and coupled to the secondary mill bit.

[0007] According to other aspects of the subject disclosure, the first spur gear, the second spur gear and the third spur gear each include the same number of teeth. The input coupling includes a Hudson connector. The cutter further includes a first and a second chip collector, which are connected to the gearbox and surround the main milling drill bit and the auxiliary milling drill bit, respectively. Each of the first and second chip collectors includes a cutout for receiving the implant and a chip collection cavity for retaining chips and debris milled from the implant. Each of the first and second chip collectors includes a longitudinal guide rail to slidably engage with a corresponding groove on the implant connector.

[0008] According to other aspects of the present subject disclosure, the implant connector includes a threaded receiving portion connected to the distal end of the lead screw and a straight-up socket releasably connected to the implant. The implant connector includes a recess for receiving the nail head (tulip) of the screw. Each of the main milling drill bit and the auxiliary milling drill bit includes a distal cutting end with a spiral groove for cutting the implant and a proximal driving end operatively connected to the gear box. Each distal cutting end includes a circular edge. Each of the main milling drill bit and the auxiliary milling drill bit includes tungsten carbide. The main milling drill bit, the auxiliary milling drill bit and the lead screw are spaced apart along a substantially straight path, and the longitudinal axis of the main milling drill bit and the longitudinal axis of the auxiliary milling drill bit are substantially parallel to the longitudinal axis of the lead screw. The implant connector is configured to be connected to a spinal rod. The input coupling is operable to receive a rotational drive force.

[0009] According to other aspects of the present subject disclosure, the implant cutter further includes a clamping mechanism for applying a clamping force to the implant during cutting the implant. According to one aspect, the clamping mechanism includes an axially extending shaft engaging an implant connector, the shaft having a proximal end and an implant engageable end at its distal end, the implant engageable end being operable to clampingly engage the implant. According to another aspect, the clamping mechanism includes a set screw extending through the implant connector. According to another aspect, the clamping mechanism includes an internal thread operable to threadably engage the implant connector and a distal edge for clampingly engaging the implant.

[0010] According to another exemplary embodiment of the present disclosure, a cutter for cutting a spinal rod fixed to a spine is provided. The cutter includes a gear box having a distal end, a translation drive assembly, and a milling drive assembly; a main milling drill bit having a proximal drive end and a distal cutting end, the proximal drive end being operatively connected to the translation drive assembly and the milling drive assembly; an auxiliary milling drill bit having a proximal drive end operatively connected to the milling drive assembly and a distal cutting end for cutting a spinal rod; a lead screw operatively connected to the translation drive assembly and having a proximal end and a distal end; an input coupling connected to the proximal drive end of the main milling drill bit; a knob connected to the proximal end of the lead screw; first and second Two chip collectors, which are connected to the distal end of the gear box and surround the main milling drill bit and the auxiliary milling drill bit respectively, each chip collector includes a cutout for receiving the spinal rod, a chip collection cavity for retaining chips and debris cut from the spinal rod, and an outer surface provided with a longitudinally arranged guide rail; and an implant connector, which has a proximal receiving portion connected to the distal end of the lead screw, a first and a second groove, and a distal end, the first and second grooves are sized to be slidably engaged with the guide rails of the first and second chip collectors, respectively, and the distal end has a socket configured to be releasably connected to the spinal rod.

[0011] According to another aspect of the subject disclosure, the socket includes at least one receiving channel and at least one locking channel. According to yet another aspect of the subject disclosure, the input coupling is configured to releasably couple to a drilling rig. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The following detailed description of exemplary embodiments of the subject disclosure will be better understood when read in conjunction with the accompanying drawings. For the purpose of illustrating the present disclosure, exemplary embodiments are shown in the accompanying drawings. However, it should be understood that the subject application is not limited to the precise arrangements and instruments shown.

[0013] Figure 1 is a perspective view of a cutter for cutting an implant, coupled to a drill and positioned to cut a spinal rod, according to an exemplary embodiment of the subject disclosure;

[0014] Figure 2 yes Figure 1 A perspective view of a cutter;

[0015] Figure 3 and Figure 4 yes Figure 1 A perspective view of a main milling drill bit and an auxiliary milling drill bit of a cutter;

[0016] Figure 5 yes Figure 1 A partial perspective view of a cutter, wherein the housing is shown in phantom for illustrative purposes;

[0017] Figure 6 yes Figure 1 A partially exploded perspective view of a cutter;

[0018] Figure 7 yes Figure 1 An exploded perspective view of a translation drive assembly of a cutter;

[0019] Fig. 8A yes Figure 1 A side view of a chip collector of a cutter;

[0020] Figure 8B yes Fig. 8A A longitudinal cross-sectional view of a chip collector surrounding a milling drill bit;

[0021] Figure 8C yes Fig. 8A A perspective view of a chip collector;

[0022] Fig.9A yes Figure 1 A perspective view of an implant connector of a cutter;

[0023] Fig. 9B yes Fig.9A Another perspective view of the implant connector;

[0024] Fig. 10A It is aligned above the spinal rod Figure 1 A perspective view of a cutter;

[0025] Fig. 10B It is connected to the spinal rod Figure 1 A perspective view of a cutter;

[0026] Fig. 10C is engaged with and releasably coupled to the spinal rod Figure 1 A perspective view of a cutter;

[0027] Fig. 10D yes Figure 1 A perspective view of a cutter cutting a spinal rod;

[0028] Fig.11 is a front cross-sectional view of another exemplary embodiment of a cutter for cutting an implant according to the subject disclosure;

[0029] Fig.12 is a perspective view of a lower portion of another exemplary embodiment of a cutter for cutting an implant according to the subject disclosure;

[0030] Fig.13A is a front view of another exemplary embodiment of a cutter for cutting an implant according to the subject disclosure; and

[0031] Fig. 13B It is used for cutting implants Fig.13A A front cross-sectional view of a cutter. DETAILED DESCRIPTION

[0032] Reference will now be made in detail to the exemplary embodiments of the present subject disclosure shown in the accompanying drawings. Whenever possible, the same or similar reference numerals will be used to refer to the same or similar features in all drawings. It should be noted that the drawings are in simplified form and are not drawn to exact proportions. With reference to the disclosure herein, directional terms such as upper, lower, top, bottom, above, below and diagonal are used relative to the drawings for convenience and clarity only. These directional terms used in conjunction with the following description of the drawings should not be interpreted as limiting the scope of the present subject disclosure in any manner not explicitly set forth. In addition, the term "one" used in this specification means "at least one". The term includes the words specifically mentioned above, their derivatives and words of similar meanings.

[0033] As used herein, "about" when referring to a measurable value (eg, an amount, a duration, etc.) is meant to encompass variations of ±20%, ±10%, ±5%, ±1%, or ±0.1% of the particular value, as such variations are appropriate.

[0034] As used herein, "substantially" means to a considerable extent, to a large extent but not entirely as specified, or to a suitable variation acceptable in the art. "Exemplary" is used herein to mean "serving as an example or illustration."

[0035] Throughout this subject application, its various aspects can be presented in the form of range.It should be understood that the description of range form is only convenient and concise, and should not be interpreted as an inflexible limitation to the scope of the present disclosure.Therefore, the description of the scope should be deemed to have clearly disclosed all possible subranges and single numerical values ​​in the scope.For example, the description of the scope (for example, from 1 to 6) should be deemed to have a specifically disclosed subrange (for example, 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.), and a single number in the scope, for example, 1, 2, 2.7, 3, 4, 5, 5.3 and 6.This is applicable to the width of any scope.

[0036] In addition, the features, advantages and characteristics of the exemplary embodiments of the present disclosure may be combined in one or more exemplary embodiments in any suitable manner. Those skilled in the relevant art will recognize that, based on the description herein, the subject disclosure may be practiced without one or more specific features or advantages of a particular exemplary embodiment. In other cases, additional features and advantages that may be identified in certain exemplary embodiments may not be present in all exemplary embodiments of the present disclosure.

[0037] Referring now to the drawings, a cutter 100 is shown in accordance with an exemplary embodiment of the subject disclosure. The cutter 100 can be used to cut / mill a spinal rod, including, for example, a spinal rod 800 secured to a patient's spine 805 using a spinal rod screw 810 having a proximally attached nail head 815 (see FIG. Figure 1 and Figures 10A to 10D ). Cutter 100 can be used, for example, to cut implanted spinal rods of varying lengths and diameters (e.g., 2, 4, 6, 8, 10 mm, etc.), as well as those spinal rods that are fixed to the spine using structures other than screws 810, and those spinal rods that are constructed of various materials, such as stainless steel, titanium, or cobalt-chromium alloys. Although cutter 100 is described herein and shown in the accompanying drawings as being operable to cut spinal rods (e.g., spinal rod 800), it should be understood that cutter 100 and other embodiments of the subject disclosure concept can be used to cut / mill other types of implants, and the various embodiments of the subject disclosure are not intended to be limited to any particular size, type, or type of implant(s).

[0038] like Figures 2 to 5 and FIG. 10A to FIG. 10D As best shown in the figure, the cutter 100 includes a gear box 105, a primary milling drill bit 110 and a secondary milling drill bit 110', and an axis, such as a threaded lead screw 120 operably connected to the gear box 105 and extending through the gear box, an input connector 125 rigidly connected to the proximal end of the main milling drill bit 110 (which may, for example, include a Hudson connector or a similar connector for connecting to a drive source), a knob 130 connected to the proximal end of the lead screw 120, a chip collector 135, 135' connected to the distal end of the gear box 105 and surrounding the primary milling drill bit 110 and the secondary milling drill bit 110', respectively, and an implant connector 140 connected to the distal end of the lead screw 120 and guided in longitudinal translation by the chip collectors 135, 135', for example via guide rails 625, 625'. In the illustrated exemplary embodiment, the primary mill bit, secondary mill bit and lead screw are spaced apart along a substantially linear path, and the longitudinal axes of the primary mill bit and the secondary mill bit are substantially parallel to the longitudinal axis of the lead screw.

[0039] like Figure 3 and Figure 4As best shown in FIG. 1 , the primary and secondary milling drill bits 110, 110', respectively, include distal cutting ends 305, 305' for cutting implants such as spinal rods 800 and proximal drive ends 310, 310' having respective drive grooves 315, 315' for operably coupling to the gearbox 105. The cutting ends 305, 305' include notches or rounded edges 325, 325' for reducing chips, and spiral grooves 320, 320' for conveying chips and other debris cut / milled from the spinal rod 800 proximally toward a central region 330, 330' of the drill bits 110, 110'. In an exemplary embodiment, at least the cutting ends 305, 305' of the primary milling drill 110 and the secondary milling drill 110' are made of tungsten carbide, but it should be understood that other parts of the milling drill 110, 110' may also be made of tungsten carbide, or any or all parts of the milling drill may be constructed using alternative materials. It should also be understood that the cutting ends 305, 305' may be center-cut or edge-cut and / or have rounded edges 325, 325', and the various exemplary embodiments disclosed in the subject matter are not intended to be limited to any particular type of cutting end or cutting method of cutting the spinal rod 800 or other implant.

[0040] refer to Figure 2 and Figures 5 to 7 The gearbox 105 includes a housing 205 having a distal plate 207, which encloses a translation drive assembly 210 and a milling drive assembly 215, which can be respectively operated to translate the gearbox 105 distally relative to the lead screw 120 or along the longitudinal extent of the lead screw, and drive the auxiliary milling drill bit 110' in response to the rotational drive force applied to the input connecting member 125; and various washers 270 and bushings 275a, 275b, 275c, 275d, 275e and 275f to protect the various components of the drive assemblies 210, 215 from wear and properly position, align and space the components within the housing 205. In the exemplary embodiment shown in the figures, the driving force is provided, for example, by a drill 500 having a flexible drive shaft 505, but it should be understood that the rotational driving force can be applied to the input coupling 125 in other ways, for example, via a rigid drive shaft, and the various exemplary embodiments disclosed in the subject matter are not intended to be limited to any particular manner of applying the driving force to the input coupling 125.

[0041] like Figures 5 to 7As shown, the translation drive assembly 210 includes a first worm 220 having a longitudinal hole 225 for receiving the proximal drive end 310 of the main milling drill bit 110 and a longitudinally extending drive rib 230 for engaging the drive groove 315 of the main milling drill bit 110; a first worm wheel 235 operably coupled to the first worm 220; a shaft 245 extending longitudinally through the first worm wheel 235, one end of the shaft being defined by an end cap 280 and a circlip (not shown) within the housing 205, and the other end being defined by an alignment receiving portion 285 (not shown) within the housing 205. Fig. 10D ) is defined as follows; a second worm 250, which is rotatably disposed on the shaft 245 and surrounds the shaft and is rigidly connected to the first worm wheel 235; a second worm wheel 255, which is operably connected to the second worm 250 and has a hexagonal socket 260 and a longitudinal through hole 265 surrounding the lead screw 120; and a hexagonal guide nut 272 located in the hexagonal socket 260 and threadedly engaged with the lead screw 120.

[0042] like Figure 5 and Figure 6 As best shown in the figure, the milling drive assembly 215 includes a first spur gear 405, which surrounds the main milling drill bit 110 distally of the first worm gear 220 and has a longitudinally extending drive rib 410 that engages the drive groove 315 of the main milling drill bit 110; a freely rotating second spur gear 415, which is operably engaged with the first spur gear 405 and rotatably surrounds the lead screw 120 distally of the second worm gear 255; and a third spur gear 420, which is operably engaged with the second spur gear 415, surrounds the auxiliary milling drill bit 110', and has a longitudinally extending drive rib 425 that engages the drive groove 315' of the auxiliary milling drill bit 110'.

[0043] Although the components of the translation drive assembly 210 and the mill drive assembly 215 described herein and shown in the accompanying drawings operate together to translate the gearbox 105 distally relative to the lead screw 120 and drive the secondary mill drill bit 110', it should be understood that the translation drive assembly 210 and the mill drive assembly 215 can include other arrangements of the same or different components to achieve these functions, and the various embodiments of the subject disclosure are not intended to be limited to any particular components or arrangements of components for translating the gearbox 105 or driving the secondary mill drill bit 110'. It should also be understood that the translation drive assembly 210 and the mill drive assembly 215 can include non-gear components, such as hydraulic and / or electrical components, and the various embodiments of the subject disclosure are not intended to be limited to any type or kind of components.

[0044] like Figure 2 , Figures 8A to 8C and Figures 10A to 10DAs shown, the chip collectors 135, 135' surround the main milling drill bit 110 and the auxiliary milling drill bit 110' and respectively include proximal funnel-shaped ends 605, 605' connected to the distal plate 207 of the housing 205; a generally cylindrical main body portion 610, which has an internal chip collection chamber 620 connected to the milling drill bit 110, 110' and an outer surface provided with longitudinally extending guide rails 625, 625'; a longitudinal hole 630 extending from the distal bottom of the chip collection chamber 620 to the distal end of the main body portion 610, 610'; and a cutout 635 shaped to receive the spinal rod 800 and laterally facing the longitudinal hole 630 at the distal end of the main body portion 610, 610' and intersecting the longitudinal hole. The inner diameter of the hole 630 at the distal end of the chip collector is equal to or slightly larger than the outer diameter of the primary milling drill 110 and the secondary milling drill 110' to effectively retain or seal the chip collection cavity 620 and prevent the chips and other debris removed from the spinal rod 800 from escaping from the cavity 620. In the exemplary embodiment shown in the drawings, the cutout 635 is U-shaped to receive the spinal rod 800, but it should be understood that the cutout 635 can have a different shape to receive other types of implants.

[0045] like Figure 2 and 9A to 10D As best shown, the implant coupler 140 includes a proximal threaded receiving portion 705 coupled to the distal end of the lead screw 120 and a generally cylindrical coupling body 710, the outer surface of the coupling body is provided with longitudinally extending grooves 720, 720', respectively, and is slidably engaged with the guide rails 625, 625' of the chip collector 135, 135', and the distal end 725 is provided with a socket 730, such as a helicopter socket, and a hollow receiving portion 732, which is shaped to receive, for example, the nail head 815 of the spinal rod screw 810 for correctly orienting and aligning the cutter 100 during the cutting / milling operation. In an alternative exemplary embodiment, the implant coupler may or may not include a hollow receiving portion, for example, the implant coupler may have a smaller diameter or a column with a socket (similar to the socket 730) for engaging the rod. In this alternative embodiment, the coupler does not receive the nail head 815 and is only engaged with the spinal rod 800.

[0046] The socket 730 is shaped to releasably receive the spinal rod 800 and includes a straight rise cutout having corresponding and radially aligned or diametrically opposite receiving channels 740, 740' and locking channels 745, 745'. The locking channels 745, 745' are also configured to align in a plane with the cutout 635 of the chip collector 135, 135' so that the primary milling drill 110 and the secondary milling drill 110' can be correctly aligned with the spinal rod 800 during the operation of the cutter 100. It should be understood that the receiving channels 740, 740' and the locking channels 745, 745' can have different shapes to receive rods and other implants of different shapes. It should also be understood that in addition to or in place of the socket 730, the implant coupler 140 can include a structure for releasably receiving the spinal rod 800 or other implants.

[0047] To operate the cutter 100 to cut / mill the spinal rod 800, the user first aligns the cutter 100 (see Fig. 10A ) and the hollow receiving portion 732 of the implant connector is engaged with the nail head 815 of the spinal rod screw 810, while the receiving channels 740, 740' of the implant connector 140 are aligned with the spinal rod 800 (see Fig. 10B Once the spinal rod 800 is fully received within the receiving channels 740, 740' of the implant coupler 140, the user rotates the cutter 100 counterclockwise (when viewed from the proximal side to the distal side of the cutter 100) to fully position the spinal rod 800 within the locking channel (see FIG. Fig. 10C), thereby rigidly locking the spinal rod 800 in place relative to the cutter 100 and aligning the primary milling drill bit 110 and the secondary milling drill bit 110' with the spinal rod 800. The user then applies a clockwise drive force to the input coupling 125. The clockwise rotation of the input coupling 125 drives the primary milling drill bit 110, which in turn causes the drive groove 315 of the primary milling drill bit 110 to engage the drive rib 410 of the first spur gear 405 and causes the gear 405 to rotate clockwise with the primary milling drill bit 110. The rotation of the first spur gear 405 causes the freely rotating second spur gear 415 to rotate counterclockwise about the lead screw 120, which in turn causes the third spur gear 420 to rotate clockwise. As the third spur gear 420 rotates, the drive rib 425 of the third spur gear 420 engages the drive groove 315' of the secondary milling drill bit 110', causing the drill bit 110' to also rotate clockwise with the third spur gear 420. Because the first, second and third spur gears 405, 415, 420 have similar sizes and include the same number of teeth, the third spur gear 420 rotates at the same speed and in the same clockwise direction as the first spur gear 405 to ensure that the main milling drill bit 110 and the auxiliary milling drill bit 110' rotate clockwise at the same speed. However, it should be understood that the spur gears 405, 415, 420 can have different sizes and / or include different numbers of teeth, and the auxiliary milling drill bit 110' can rotate at a different speed or a different rotation direction compared to the main milling drill bit 110.

[0048] The rotation of the main milling bit 110 also causes the drive groove 315 of the main milling bit 110 to engage with the drive rib 230 of the first worm 220, thereby causing the first worm to rotate clockwise with the main milling bit 110. The rotation of the first worm 220 causes the first worm gear 235 and the second worm 250 to rotate about the shaft 245, which in turn causes the second worm gear 255 and the hexagonal lead nut 272 to rotate clockwise about the lead screw 120. Because the lead nut 272 is threadedly engaged with the lead screw 120, and because the engagement of the implant coupler 140 with the spinal rod 800 prevents longitudinal displacement of the lead screw 120, clockwise rotation of the hexagonal lead nut 272 causes the lead screw 120 to generate a distal force on the lead nut 272, thereby causing the gearbox 105 (with the coupled milling drill bit 110, 110' and the chip collector 135, 135') to be guided to translate distally along the lead screw 120 through the engagement of the guide rails 625, 625' of the chip collector 135, 135' with the grooves 720, 720' of the implant coupler 140. In another embodiment, the device may use a compound gear set instead of a worm drive gear.

[0049] The gearbox 105 is translated distally until the distal cutting ends 305, 305' of the primary and secondary milling bits 110, 110' contact the spinal rod 800, at which point cutting / milling of the spinal rod 800 begins. The cutouts 635 of the chip collectors 135, 135' engage the spinal rod 800 and help guide the milling bits 110, 110' as they advance through. Chips and other debris removed from the spinal rod 800 are transported proximally by the spiral grooves 320, 320' of the primary and secondary milling bits 110, 110' into the chip collection chamber 620 of the chip collectors 135, 135' where they are deposited and retained during the cutting / milling operation. The primary milling drill bit 110 and the secondary milling drill bit 110' continue to translate distally until they cut through the spinal rod 800, at which point the cutting / milling operation is complete ( Fig. 10D ), the cutter 100 is removed from the patient's body.

[0050] The proximal top surface of the cutout 635 prevents overcutting, and the cutout engages with the spinal rod 800 to prevent the distal center cutting ends 305, 305' of the main milling drill 110 and the auxiliary milling drill 110' from translating too far distally and entering the patient's body. In other words, since the proximal top surface of the cutout of the chip collector abuts the spinal rod, once the spinal rod is cut, the proximal top surface of the cutout of the chip collector prevents the cutting ends of the main milling drill and the auxiliary milling drill from further penetrating distally. For example, the maximum diameter of the spinal rod is currently 6mm. Therefore, at a distance slightly greater than 6mm, the travel of the cutter will have a hard stop. The cylindrical guide concentric with the cutter has a cutout for receiving the spinal rod. The farthest travel of the cutter is limited to not extending beyond these guides.

[0051] After the cutting / milling operation is completed, the chip collector 135, 135' is removed from the cutter 100, so that the chips and other debris cut / milled from the spinal rod 800 and any chips and debris remaining in the spiral grooves 320, 320' of the main milling drill 110 and the auxiliary milling drill 110' can be approached and discarded. In at least some exemplary embodiments, the removal of the chip collector 135, 135' can be facilitated by first removing the implant coupler 140 from the cutter 100. This can be achieved by first rotating the knob 130 counterclockwise to retract the distal end of the lead screw 120 from the threaded receiving portion 705 of the implant coupler 140, and then sliding the coupler 140 to the far side to disengage the guide rails 625, 625' of the chip collector 135, 135' from the grooves 720, 720' of the implant coupler 140. The cutter 100 can then be reset to perform a new cutting / milling operation by first reattaching the chip collectors 135, 135' and implant coupler 140 and then translating the gearbox 105 proximally to its initial position, either manually or by using a drill 500 or other mechanism, by applying a counterclockwise rotational force to the input coupling 125.

[0052] Fig.11 , Fig.12 , Fig.13A and 13B Further exemplary embodiments of the subject disclosure are disclosed that include a clamping mechanism for applying a clamping force to an implant during cutting of the implant. The various clamping mechanisms of these embodiments hold the implant firmly and stably in place to prevent vibration of the implant, i.e., to resist vibration of the implant caused by milling. For the sake of brevity, only the following will be described in detail. Fig.11 , Fig.12 , Fig.13A and 13B The implant cutters shown in FIG. 1 are structurally and / or functionally similar to those of FIG. Figure 1-10D Elements that are substantially different from their counterparts shown in, or are essential to a proper understanding of the subject disclosure.

[0053] Reference Fig.11, an exemplary embodiment of a clamping mechanism 900 is shown, which is operably connected to an implant coupler 140' for applying a clamping force to an implant 800 during cutting of the implant. The clamping mechanism 900 includes an axially extending elongated shaft 902 having threads (e.g., around its proximal end 902a) that threadably engage the implant coupler. The threaded shaft includes a handle 904 at its proximal end and an implant engageable end 906 at its distal end, which is operable to clampingly engage an implant, such as a spinal rod 800. Although the elongated threaded shaft 902 is threadedly engaged with at least the implant coupler 140', it should be understood that one or both of the knob 130' and the threaded lead screw 120' can have internal threads to engage with the external threads of the shaft 902, respectively. That is, the lead screw 120' and / or the knob 130' can include a longitudinal through hole having internal threads. However, in order to minimize the resistance of the handle 904 to turning the threaded shaft, the knob 130' and the threaded lead screw 120' are provided with smooth-walled internal bores having a diameter slightly larger than the diameter of the threaded shaft.

[0054] Reference Fig.12 , shows an exemplary embodiment of a clamping mechanism 1000 that is operably connected to an implant coupler 140″ for applying a clamping force to an implant 800 during cutting of the implant. The clamping mechanism 1000 includes a set screw receiver 1002 that extends radially or laterally from the implant coupler 140″ and a laterally extending set screw 1004 that threadably engages the implant coupler at the set screw receiver and is operable to clamp the engaged implant. The set screw has a socket 1006 or other tool-engageable structure that allows the set screw to be advanced into the implant coupler until the set screw securely engages the implant. Milling can then be performed with minimal or no vibration of the implant during milling.

[0055] Reference Fig.13A and 13B , shows an exemplary embodiment of a clamping mechanism 1100 that is operably connected to an implant coupler 140"' for applying a clamping force to an implant (not shown) during cutting of the implant. Fig. 13B As shown, the circumferential surface of the implant coupler has external threads at 1102. The clamping mechanism includes a substantially cylindrical sleeve 1104 that surrounds the implant coupler and has internal threads 1106 that are configured to threadably engage the external threads of the implant coupler. In addition, the internally threaded sleeve 1104 includes a distal edge 1108 that is operable to clampingly engage the implant. Fig.13AAs shown, the outer surface of sleeve 1104 can be provided with structure 1110, for strengthening the grip of the user when rotating the sleeve relative to the implant coupler. Such structure may include grooves, raised ridges, knurling, etc. Once the implant coupler engages with an implant (not shown), the user rotates sleeve 1104 in one direction so that the distal edge 1108 of the sleeve advances into the firm extrusion engagement with the implant. When the implant is firmly engaged, the milling operation is carried out during milling when the implant vibrates minimally or without vibration, so that the implant is easily and accurately cut by implant cutter 100 ".

[0056] Those skilled in the art will appreciate that changes may be made to the exemplary embodiments described above without departing from the broad inventive concept of the present invention. Therefore, it should be understood that this disclosure is not limited to the specific exemplary embodiments disclosed, but is intended to cover modifications within the spirit and scope of the claims defined herein.

Claims

1. A cutter (100) for cutting an implant (800), characterized in that: Gear box (105); a primary milling drill bit (110), a secondary milling drill bit (110') and a lead screw (120) spaced apart along a linear path and operably coupled to the gearbox; an input coupling (125) coupled to the main milling drill bit; and an implant coupler (140) coupled to the lead screw, wherein the gearbox is operable to translate relative to the lead screw and to drive the secondary milling drill bit in response to a driving force applied to an input coupling, Wherein, the gear box comprises: a translation drive assembly (210) operable to translate the gearbox relative to the lead screw in response to a drive force applied to the input coupling; and A milling drive assembly (215) is operable to drive the secondary milling bit in response to a driving force applied to the input coupling.

2. The cutter according to claim 1, wherein: The translation drive assembly comprises: a first worm (220) surrounding and coupled to the main milling drill bit; a first worm gear (235) operatively coupled to the first worm; a second worm (250) rigidly coupled to the first worm gear; and A second worm gear (255) is operatively coupled to the second worm, the second worm gear surrounding the lead screw and having a socket (260).

3. The cutter according to claim 2, wherein: The translation drive assembly further includes a nut (272) positioned in the socket of the second worm gear and threadably engaged with the lead screw.

4. The cutter according to claim 1, wherein: The milling drive assembly comprises: a first spur gear (405) surrounding and rigidly coupled to the main milling drill bit; a second spur gear (415) operatively coupled to the first spur gear; and A third spur gear (420) is operatively coupled to the second spur gear and surrounds and is rigidly coupled to the secondary milling bit.

5. The cutter according to claim 4, wherein: Each of the first spur gear, the second spur gear, and the third spur gear includes the same number of teeth.

6. The cutter of claim 1, further comprising first and second chip collectors (135', 135) coupled to the gearbox and surrounding the primary and secondary milling bits, respectively.

7. The cutter according to claim 6, wherein: Each of the first and second chip collectors includes a cutout (635) for receiving the implant and a chip collection cavity (620) for retaining chips and debris milled from the implant.

8. The cutter according to claim 7, wherein: Each of the first and second chip collectors includes a longitudinal rail (625, 625') for slidably engaging a corresponding groove (720, 720') on the implant coupler.

9. The cutter according to claim 1, wherein: The implant coupler includes a receiver (705) coupled to a distal end of the lead screw and a straight-up socket (730) configured to releasably couple to the implant.

10. The cutter according to claim 9, wherein: The implant coupler includes a recess (732) for receiving a nail head (815) of a screw (810).

11. The cutter according to claim 1, wherein: Each of the primary and secondary milling drill bits includes a distal cutting end (305, 305') having a spiral groove (320, 320') for cutting the implant and a proximal driving end (310, 310') operatively coupled to the gear box.

12. The cutter according to claim 11, wherein Each of the distal cutting ends includes a rounded edge (325, 325').

13. The cutter according to claim 1, wherein: Each of the primary milling bit and the secondary milling bit includes tungsten carbide.

14. The cutter according to claim 1, wherein: The implant coupler is configured to couple to an implant (800).

15. The cutter according to claim 1, wherein: The input coupling is operable to receive a rotational drive force.

16. The cutter according to claim 1, further comprising a clamping mechanism (900, 1000, 1100) for applying a clamping force to the implant during cutting of the implant.

17. The cutter according to claim 16, wherein: The clamping mechanism (900) includes an axially extending shaft (902) engaging the implant coupler, the shaft including a proximal end and an implant engageable tip (906) at its distal end operable to clampingly engage the implant.

18. The cutter according to claim 16, wherein: The clamping mechanism (1000) includes a set screw (1004) extending through the implant coupler.

19. The cutter according to claim 16, wherein: The clamping mechanism (1100) includes internal threads (1106) operable to threadingly engage the implant coupler and a distal edge (1108) for clampingly engaging the implant.

20. A cutter (100) for cutting a spinal rod fixed to a spine (805), the cutter being characterized by: a gear box (105) having a distal end, a translation drive assembly (210), and a milling drive assembly (215); a main milling drill bit (110) having a proximal drive end (310) and a distal cutting end (305), the proximal drive end being operatively coupled to the translation drive assembly and the milling drive assembly; an auxiliary milling drill bit (110') having a proximal drive end (310') operatively coupled to the milling drive assembly and a distal cutting end (305') for cutting the spinal rod; a lead screw (120) operably coupled to the translation drive assembly and having a proximal end and a distal end; an input coupling (125) rigidly coupled to the proximal drive end of the main milling drill bit; first and second chip collectors (135, 135') coupled to the distal end of the gearbox and surrounding the primary and secondary milling drill bits, respectively, each chip collector comprising a cutout (635) for receiving the spinal rod, a chip collection cavity (620) for retaining chips and debris cut from the spinal rod, and an outer surface having a longitudinally disposed guide rail (625, 625'); and An implant connector (140) having a proximal receiving portion (705) rigidly coupled to the distal end of the lead screw, first and second grooves (720, 720') sized to slidably engage the guide rails of the first and second chip collectors, respectively, and a distal end having a straightening socket (730) configured to releasably couple to the spinal rod.

21. The cutter according to claim 20, wherein: The direct riser socket includes at least one receiving channel (740, 740') and at least one locking channel (745, 745').

22. The cutter according to claim 20, wherein: The longitudinal axis of the primary milling bit and the longitudinal axis of the secondary milling bit are parallel to the longitudinal axis of the lead screw.

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