WO2025096361A1

WO2025096361A1 - Devices and methods for anterior transpedicular fixation and posterior revision

Info

Publication number: WO2025096361A1
Application number: PCT/US2024/053301
Authority: WO
Inventors: Joshua Michael AMMERMAN; Spencer Austin JONES; Laurent Schaller; James P. Duncan
Original assignee: Combination Spine Inc
Current assignee: Combination Spine Inc
Priority date: 2023-10-30
Filing date: 2024-10-28
Publication date: 2025-05-08
Anticipated expiration: 2026-04-30

Abstract

Devices and methods for anterior transpedicular fixation and posterior revision including one or more transpedicular screws configured for insertion into a vertebra from an anterior approach and/or one or more revision screws.

Description

Devices And Methods For Anterior Transpedicular Fixation And Posterior Revision

The Present Application claims the benefit of and priority to U.S. Provisional Patent Application No. 63/594,359, filed October 30, 2023, which is hereby incorporated herein by reference.

FIELD OF DISCLOSURE

[0001] This Application generally relates to devices and methods for spinal fixation and/or revisions. More particularly, this application generally relates to devices and methods for spinal fixation using an anterior approach following the placement of an anterior cage. This application also generally relates to devices and methods for revisions to previous implantations that employ additional fixation from a posterior approach.

BACKGROUND

[0002] There currently exist multiple techniques to stabilize adjacent spinal vertebrae (cervical, thoracic, lumbar, sacral), including plates, clamps, screws, wires, etc. One of the most rigid options is the placement of screws via a posterior approach across the pedicles terminating in the body of a given vertebrae and connecting these screws via rods/plates affixed between adjacent vertebrae. Surgical approaches, such as the anterior spinal approach, offer certain advantages over a posterior spinal approach but require repositioning of the patient from supine to prone (which takes significant time) to place posterior screws for immobilization of the spinal segment of interest. An anterior approach also requires dissection of the posterior spinal muscles, increasing the risks of pain, bleeding, nerve injury, and infection. Standalone anterior devices that do not require posterior implant placement exist, but they are not as rigid as those constructs incorporating transpedicular screw placement.

[0003] There are also concerns when a revision is required. Revision of a posterior level or the addition of another segmental fusion from a posterior approach normally requires the removal of the existing hardware, which might increase risks of pain, bleeding, nerve injury, and infection, as well as the potential for complication if existing hardware is difficult to remove and might break during such attempt.

[0004] Therefore, there remains a need for improved spinal stabilization devices and methods for spinal fixation and revisions to previously implanted spinal fixation devices.

SUMMARY

[0005] In one aspect, vertebral fixation system includes first transpedicular screw sized and configured for insertion into a vertebral body of a first vertebra from an anterior approach. The first transpedicular screw having a head, a shank, and a longitudinal length, wherein when the head is positioned against an anterior wall of the vertebral body the length of the first transpedicular screw is sized so that a terminal end of the shank terminates at a posterior limit of a pedicle of the vertebra. The system also includes a first posterior revision screw sized, which is configured to be inserted into the first vertebra from a posterior approach. The first posterior revision screw having a shank that engages with the shank of the first transpedicular screw.

[0006] In another aspect, a revision screw adapted to engage a screw implanted in a vertebra. The revision screw includes a shank having an external thread. The revisions screw includes an internal passageway in the shank defined by an interior surface. The interior surface included at least one threaded portion. The passageway is configured to accept the screw implanted in the vertebra and the at least one threaded portion is configured to engage an external thread of the screw implanted in the vertebra.

[0007] In yet another aspect, a vertebral fixation system includes a vertebral implant screw having a head and a shank, wherein the head includes external thread. The system includes a revision screw positioned over the implanted screw.

BRIEF DESCRIPTION OF DRAWINGS

[0008] Fig. 1 is a top view of a vertebral body showing a schematic representation of an anterior approach for transpedicular fixation.

[0009] Fig. 2 is a side view of adjacent vertebral bodies showing a schematic representation of the anterior approach for transpedicular fixation.

[00010] Fig. 3 is a top view of a vertebral body with a guide pin placed therein according to the trajectory of transpedicular fixation for an anterior approach. [00011 ] Fig. 4 is a side view of adjacent vertebral bodies with a guide pin placed therein according to the trajectory of transpedicular fixation for an anterior approach.

[00012] Fig. 5 is a top view of a vertebral body showing the placement of screws and a fixation plate for transpedicular fixation employing an anterior approach.

[00013] Fig. 6 is a side view of adjacent vertebral bodies showing the placement of screws and a fixation plate for transpedicular fixation of an anterior approach.

[00014] Fig. 7a is a cross-sectional view of a cannulated screw with cortical and cancellous thread patterns.

[00015] Fig. 7b is a cross-sectional view of an alternative cannulated screw with a uniform thread pattern.

[00016] Fig. 7c is a cross-sectional view of another alternative cannulated screw with a uniform outer thread pattern and an internal thread, the screw is shown with a plate connection for anterior fixation.

[00017] Fig. 7d is a cross-sectional view of another alternative cannulated screw with a uniform outer thread pattern and a double internal thread configuration, the screw is shown with a plate connection for anterior fixation. [00018] Fig. 8 is an isometric view of adjacent vertebral bodies shown with an anterior fixation system having an anterior plate and four transpedicular screws for anterior fixation.

[00019] Fig. 9 is a side view of adjacent vertebral bodies shown with a front-to- back fixation system that has transpedicular screws from an anterior approach and posterior hollow fixation screws from a posterior approach.

[00020] Fig. 10a is a cross-sectional view of one embodiment of a screw combination in a position before being assembled.

[00021 ] Fig. 10b is a cross-sectional view of the screw combination of Fig. 10a in an assembled position.

[00022] Fig. 11 a is a side view of adjacent vertebral bodies shown with an implemented fixation system.

[00023] Fig. 11 b is an anterior view of the adjacent vertebral bodies of Fig. 1 1a, shown with the implemented fixation system. [00024] Fig. 11 c is a posterior view of the adjacent vertebral bodies of Fig. 1 1a, shown with the implemented fixation system.

[00025] Fig. 12 is a side view of adjacent vertebral bodies shown with a previously placed, existing posterior fixation system.

[00026] Figs. 13-17 illustrate one embodiment of a method for preparation for an additional segment to be fused.

[00027] Fig. 13a is a cross-sectional view of a vertebral body showing a schematic illustration of a cutting tool being used to cut a rod below the superior screw.

[00028] Fig. 13b is a cross-sectional view of the vertebral body of Fig. 13a, showing a system with an extractor tool being inserted into an existing tulip of the screw.

[00029] Fig. 13c is a side cross-sectional view of the insertion of the extractor tool into the existing tulip of the screw.

[00030] Fig. 14 is a cross-sectional view of the vertebral body of Fig. 13a with the extractor tool within the system and being advanced to break up the tulip.

[00031 ] Fig. 15 is a cross-sectional view of the vertebral body of Fig. 13a, showing a broken-up tulip and the original screw.

[00032] Fig. 16a is a cross-sectional view of the vertebral body of Fig. 13a, showing a thread die being used to create a threaded path over the spherical head of the original screw.

[00033] Fig. 16b is a front-end view of the thread die tool.

[00034] Fig. 17 is a cross-sectional view of the vertebral body of Fig. 13a, showing the original screw with the newly threaded head.

[00035] Fig. 18 is a cross-sectional view of the vertebral body of Fig. 13a, showing the original screw and the advancement of the one embodiment of a screw-over-screw system using a single-threaded hollow revision screw.

[00036] Fig. 19 is a cross-sectional view of the vertebral body of Fig. 13a, showing the original screw and the advancement of another embodiment of a screw-over-screw system using a double-threaded hollow revision screw.

[00037] Fig. 20 is a side view of adjacent vertebral bodies showing the fixation assembly of the new segment using the system and methods disclosed herein.

[00038] Fig. 21 a is a side view of one embodiment of the tulip head.

[00039] Fig. 21 b is an isometric view of a snap ring used with the tulip head of Fig. 21 a.

[00040] Fig. 22 is a cross-sectional view of one embodiment of a tulip head once mounted over the screw.

[00041] Fig. 23 is a side view of the tulip head of Fig. 22, shown mounted over the screw and with extended arms.

DETAILED DESCRIPTION

[00042] While the subject matter of the present disclosure is susceptible to embodiments in various forms, there will hereinafter be described presently preferred embodiments with the understanding that the present disclosure is to be considered an exemplification and is not intended to limit the disclosure to the specific embodiments illustrated. The words "a" or "an" are to be taken to include both the singular and the plural. Conversely, any reference to plural items shall, where appropriate, include the singular.

[00043] The devices and methods disclosed herein generally relate to the deployment of screw fixation systems for the fusion of one or several spinal segments. The fixation screw systems can have an application from an anterior approach for spinal surgery in which the screws are positioned transpedicularly. [00044] In some embodiments, the screw fixation system can supplement an anterior system by being adapted to dock from the posterior side of the transpedicular screws. The screw fixation system can be used in the same procedure when a second level is needed to be fused but cannot be accomplished via the anterior approach, and therefore, a posterior access is needed.

[00045] In alternative embodiments, a revision screw system is configured for and employed in the revision of a failed fusion or an expansion to another segment in an implanted fusion device. One feature of the revision system is to be able to leave the existing implanted screws of a previously implanted fixation system in place and use the previously implanted screws as part of the revision system. For example, and as described in more detail below, the revision screw system may include hollow single- threaded revision screws or double-threaded revision screws.

[00046] Now, turning to Fig. 1 and Fig. 2, these figures show the trajectory (3) for the placement of transpedicular implants from an anterior approach, with the device trajectory beginning in the anterior vertebral body cortex (1) and terminating at the posterior limit of the pedicle (2). The screws of the present system follow an anterior- medial to posterior-lateral trajectory (3) shown in Figs. 1 and 2. This trajectory and placement of the screws can provide rigid fixation of the spinal segment of interest. In some instances, this trajectory and placement of the screws can provide improvement in fixation over a standalone anterior approach.

[00047] Turning to Fig. 3 and Fig. 4, a Jamshidi needle (1 10) is inserted into the vertebral body (5) at the anterior vertebral body cortex (4). The Jamshidi needle (110) is advanced through the vertebral body (5) and exits at the posterior limit of the pedicle (6). The Jamshidi needle (5) can be inserted manually or with the assistance of a robotic guidance or other suitable machine-aided system. Furthermore, the insertion can be added by a computer system, which may be adapted to use imaging such as CT scan, MRI, or other imaging. The computer system may be used to plan and execute the desired trajectory and placement of the screws and avoid a breach at the pedicle level in the area of the vertebral foramen (7).

[00048] Figs. 5 and 6 are illustrations showing the trajectory and placement of the transpedicular screws (8') and (8”). There are four transpedicular screws - a first transpedicular screw (8’) and a second transpedicular screw (8”) in a superior vertebra (11a) and a third screw (8”) and a four transpedicular screw (not shown) in the inferior vertebra (11 b). Fig. 5 shows the placement of the transpedicular screws (8’) and (8”) following the removal of the Jamshidi needles but leaving a guidewire in place for placement of the transpedicular screws (8’) and (8”). The transpedicular screws (8’) and (8”) are cannulated to follow the guidewires along the desired trajectory and to be placed in the desired position in vertebras (11 a) and (11b). Turning to Fig. 6, screws (8’) (not shown in Fig. 6) and (8”) are placed in adjacent vertebras (11 a) and (11 b). An anterior locking plate (9) is attached to screws (8’) and (8”) and spans between the vertebral bodies (1 1 ’ and 11 ”), providing support to the vertebras after a fusion cage (12) (Fig. 6) has been positioned in the disc space. In one example, an anterior approach is used to place fusion cage (12) between the vertebral bodies (11 ’ and 11 ”).

[00049] Fig. 7a illustrates one embodiment of a transpedicular screw (26), which has a length “L” of about 20 mm to about 100 mm. Preferably, but not necessarily, screw (26) is longer than known pedicle screws that would be employed for a particular vertebral body. Furthermore, screw (26) has a shank (26a) with at least a dual-thread configuration with different sized pitches. For example, a coarse thread pitch and a finer pitch. The pitch “P” is measured along the thread's length from the crest (peak) of one thread to an adjacent crest. The dual-thread configuration assists in providing holding strength, which reduces the risk of pullout. For example, the dual-thread configuration may provide a screw with a greater pull-out strength. In the illustrated embodiment, the distal portion of the screw (26) has a finer thread (13) that can have better holding power and greater pull-out force in a cortical bone setting which is found in the pedicle. The second half or a segment of the screw (26) extending from a middle portion of the screw (26) distally has a coarser thread pitch (14) that can have better hold power and greater pull-out strength in a more cancellous bone structure, such as it is found in the vertebral body. Also, in some embodiments, the outer or major thread diameter, the minor thread diameter, and the outer diameter of screw (2) may vary along the longitudinal length of the screw. For example, the outer diameter between the finer pitch threaded portion (13) and the coarse pitch threaded portion (14) is different, with the smaller outer diameter in the distal portion of the screw (26) and the large diameter in the more proximal portion of the screw (26), allowing for a stronger holding force in the two different bone structures that the screw will be placed into. The transition between the finer pitch thread (13) and the coarse pitch (14) may be tapered or stepped.

[00050] In some embodiments, screw (26) is fully cannulated and includes a guidance passageway (15) for guidance over a guidewire. In other alternatives, screw (26) may not be cannulated, be partially cannulated, and/or be guided during implantation in some other manner. In some embodiments, the distal tip (16) of screw (26) is tapered to facilitate penetration into the bone. The thread design could also include a dual start pitch, be greater, be tapered and/or fenestrated in any suitable manner.

[00051 ] On the proximal end of the screw (26), there is a head (17) that a suitable driver can engage to advance the screw into the bone. In one embodiment, the head (17) may have a square or hexagonal shape configured for engagement with the driver. The screw (26) may include an internal passageway (18a) with an inner surface having a thread (18b) that engages a locking plate screw (9a) for attaching a locking plate (9) to screw (26) (see, Figs. 5 and 6). Adjacent to the head (17) screw (26) also may include a small recess (19) between the threaded portion and the drive portion. This recess (19) may be added in the facilitation of manufacturing of the screw.

[00052] Fig. 7b illustrates another embodiment of a transpedicular screw (27) having a shank (27a). The shank (27a) has a thread (20) that has a single or uniform pitch or pitch size along the length of screw shank (27a). In some embodiments, the pitch may be a relatively finer pitch. The pitch also could be coarser or finer depending on the desired use. For example, the pitch and other configurations of the thread could vary based on bone condition and user preferences. It is also understood that the proximal end of screws (26) and (27) could have variations of the head, such as having a spherical head to adapt a fixation tulip as it is known in a polyaxial screw. The screw (27) may have an outer/major thread diameter as measured about the thread crest from about 4.5 mm to about 10 mm and an outer diameter of the wall of the shank/ from which the thread extends and/or minor thread diameter from about 3 mm to about 8 mm. [00053] Turning to Figs. 7c and 7d, these screws (24 and 28) may be for, but are not necessarily limited to, revision or additional deployment for two or multiple fusion segments, as will be further described herein. These screws (24 and 28) may be inserted from a posterior approach. In one alternative, screws (24 and 28) may be posterior revision screws. In some embodiments, the systems disclosed herein include one or more posterior revision screws (24 and 28). For example, the systems may include a first posterior revision screw and a second postern revision screw.

[00054] Turning first to Fig. 7c, the outer portion of the screw (24), which may be a first or second posterior revision screw, is similar to the screw (27) in Fig. 7b with a uniform pitched thread (20). In some embodiments, screw (24) has a larger outer diameter than screw (27). For example, screw (24) may have an outer/major thread diameter, as measured at the thread crest, from about 4.5 mm to about 10 mm and an outer diameter of the wall of the shank from which the thread extends/minor thread diameter from about 3.5 mm to about 8 mm. Screw

(24) may be cannulated and include an internal passageway (25). Passageway

(25) may include a non- threaded portion (21 ) and a threaded portion (22). Threaded portion (22) includes threads that match or are configured to engage the external threads of a screw, such as screw (27) shown in Fig. 7b. Passageway (25) may also include a guiding hole (23) at the distal end of the screw (27) that fits over a previously implanted screw shank.

[00055] Fig. 7d illustrates another embodiment of a posterior revision screw or hollow revision screw (28) having a similar external thread design (20) as previously described with regard to screw (24), a similar cannulated section having a passageway (25), a first internal threaded portion (22) and a secondary internal thread (29). The second internal (29) is positioned at the distal section of the screw (28). A larger guiding hole (30) is also provided at the distal end section of screw (28), and the screw (28) may have a similar tapered distal tip as that of tip (16) of the previously described screw (24).

[00056] The proximal portions (31 ) of each screw (24) and (28) are shown with a screw (32) and (33), respectively, for attaching a locking plate (9’). Screw (24) is shown with a taper locking screw (32) to hold the anterior locking plate (9’), as can be seen in Fig. 7c. Fig. 7d shows a pan head screw (33) holding the anterior locking plate (9’) in place relative to screw (28). It is also understood that these types of screws could also have a polyaxial head type with a spherical head to be used with a rod fixation system, as will be described later.

[00057] Turning to Fig. 8, this figure shows an isometric view of one embodiment of an anterior fixation system (35) implanted in the vertebrae or spine. The anterior fixation system (35) includes transpedicular screws (27) and an anterior locking plate (9) attached using tapered holding screws (32). The distal ends of the transpedicular screws (27) may extend to the posterior limit of the pedicle (34) for easy access if an additional fused level is required via a posterior access or a future posterior revision is desired. Anterior fixation system (35), using transpedicular screws, can provide for a very rigid construct that may have advantages over those using only short anterior screws for the locking plate. A spinal cage implant may be in the disc space between the adjacent vertebral bodies, but the spinal cage implant is not shown in Fig. 8.

[00058] It is understood a transpedicular screw system, such as the ones illustrated in Figs. 7a and 7b (26 or 27), may provide benefits in a situation where an anterior disc fusion is desired for an L5-S1 level, especially when followed by a secondary level to be fused (L4-L5 in this instance) but not possible from an anterior approach due to anatomy of the great vessels (as an example) not allowing to reach the desired level, therefore a posterior approach would be required.

[00059] Fig. 9 illustrates one embodiment of the anterior fixation system (35) being implanted in the vertebrae. The anterior fixation system (35) includes transpedicular screws (26) and (26’) and at least one locking anterior plate (9). It should be understood that Fig. 9 illustrates a side view and that there are second screws (26) and (26’) on the other side of each vertebra. That is, there are two screws in the upper vertebra and two screws in the lower vertebra. The anterior fixation system (35) and fusion implant (36) are deployed using an anterior approach.

[00060] To perform second-level fusion, add additional fixation to an adjacent vertebral body, or reinforce transpedicular screws (26 or 26’), the patient is repositioned from supine to prone to place the posterior screws (24). When the procedure is for reinforcing transpedicular screws (26 or 26’), screw(s) (24) is inserted and engaged with the transpedicular screw(s) (26 or 26’) needing reinforcement. For example, a screw (25) can be inserted to engage one or more of the transpedicular screws as desired.

[00061] In another alternative, to perform second level fusion, posterior screws (24) and (40) of the posterior fixation system (38) are placed for immobilization of the spinal segment having fusion implant (37) placed therein. It will be understood that the system (38) includes two revision screws (24) and two fixation screws (40). As the physician is getting ready to add posterior revision screws (24) for reinforcement or add the posterior fixation system (38), the transpedicular screws (26 or 26’) that were implanted during the anterior approach will be showing at the posterior portion of the pedicle (34), preferably the most posterior portion, as previously described. With the distal end of the transpedicular screws (26 or 26’) showing, a guidewire (not shown) can be placed within the passageway (15) (Fig. 7a) of transpedicular screws (26 or 26’). Once the guidewires are in place, hollow screw (24) (shown here in partial cross section) is slid over the guidewire. The thread (20) of the outer portion of screw (24) engages the bone of the pedicle (34), and the threaded inner section (22) of screw (24) accepts and engages over the threaded portion (39) of the already implanted transpedicular screw (26 or 26’). This arrangement provides a strong reinforcement for transpedicular screws (26 or 26'). When second level fusion is being performed, this arrangement provides a strong anchor for the posterior fixation that will also be connected to the anterior fixation system. In the illustrated embodiment, the hollow screw (24) has a tulip-type head (41 ), similar to the head of polyaxial systems. It may have other head configurations as well.

[00062] To complete the second level fusion, the physician will place another set of fixation screws, such as pedicle or second level fixation screws (40), at the level above the fused disc. For example, the pedicle screws (40) are placed at a vertebra adjacent to the vertebra containing the transpedicular screws. To create a rigid segment with the placement of a pedicle screw (40), such as a standard polyaxial screw, which can be connected to the level below via a connecting member, such as a fixation rod (42). In the illustrated embodiment, rod (42) is connected to screw (24).

[00063] Figs. 10a and 10b are cross-sectional views looking down from the top, which shows the connected of rod (42) to screw (24). These figures illustrate the engagement of transpedicular screw (26') and the hollow screw (24). Turning to Fig. 10a, this figure shows a pre-engagement view of the screws (24) and (26’) before the screws are engaged or mated. A guidewire (not shown) may be located in the passageways of the screws along dotted line (43). In some embodiments, the guidewire would engage only the distal section (44) of transpedicular screw (26’). The hollow screw (24) would be slid over the guidewire (not shown) and moved toward the transpedicular screw (26’) in the direction indicated by arrow (45a). Turning to Fig. 10b, the hollow screw (24) engages screw (26’). In particular, hollow screw (24) is placed over screw (26’) wherein the outer threads of external threaded portion (39) of screw (26’) engage the inner threads of hollow screw (24) to form a well-connected, solid union. To complete the posterior portion of the polyaxial system, the tulip (41 ) will receive the rod (42) and be locked in place by locknut (45). It is also understood and apparent to those skilled in the art that the system could be inverted so as to use the hollow screws (24 from the anterior approach and the transpedicular screws (26 engaged from the posterior approach. It is also understood that in this configuration, the proximal portion of the screws would be adapted to the tulip head configuration on the posterior side and the anterior locking plate configuration on the anterior side.

[00064] Fig. 11 a shows a side view of a spine with the anterior fused disc with its implant (36) and the anterior fixation system (35), which includes transpedicular screws (26) and (26’). The posterior fixation system (38) includes polyaxial hollow screw (24) and standard polyaxial screw (40) that are used to stabilize implant (37) in the level two fusion. The system uses an anterior approach at the lower level and a posterior approach at the superior level, which provides a rigid system. Similar to Fig. 9, there are two screws in each of the upper and lower vertebral bodies. In the posterior system (38), there are also two screws (24) and two screws (40).

[00065] Fig. 11 b shows the same system but for a frontal view where the anterior fixation system (35) is visible. Fig. 11c shows the same system but from a posterior view, with the novel posterior fixation system (38) visible.

[00066] The hollow screws (24) and (28) also may be used in revision systems for treating a failed fused disc, a loosened screw fixation, or for the addition of another segment to be fused. The method of using the revision system would be fairly similar to current revision surgeries but would vary in how much tissue would have to be exposed depending on the type of revision.

[00067] Fig. 12 illustrates a situation where the addition of another level of fusion (46) is desired. For example, in situations where the back pain has progressed to the superior level of the prior fused level (47). The approach would be via a posterior incision, as indicated by arrow (48). Preferably, only the top level (49) of the prior fused segment needs to be exposed. Figs. 13a-13c illustrate additional steps of the method of performing a revision. Access to the superior polyaxial screw (54) is obtained by removing the locknut (52) from the tulip head (51 ), which was holding a fixation rod (50). In some instances, the rod (50) is no longer necessary as the fused level (47) is now solid, and therefore the rod (50) is redundant.

[00068] Rod (50) is cut below the tulip (51) by using a rod cutter (53), as is well known in the art. Fig. 13b shows a side view of the tulip (51). A pair of fingers (55) and (55’) hold the tulip portion (51 ) of spherical head (57) of polyaxial screw (54). As fingers (55) and (55’) are holding the tulip head in place, a conical extraction tool (56) is positioned on top of the tulip portion (51) of the head. The extraction tool (56) is advanced in the direction of the arrow (58). Fig. 13c shows a side view illustrating the position of the extraction tool (56) inside the tulip portion (51 ) and surrounded by the holding fingers (55) and (55’).

[00069] Fig. 14 illustrates the shearing of tulip portion (51 ). The conical extraction tool (56) is advanced distally to bend and shear the tulip portion (51), which is retained by the holding fingers (55) and (55’). In one embodiment, the holding fingers (55) and (55’) are attached to a supporting guide frame (59). The attachment may be by standard methods, such as lock-screws or similar (not shown). The supporting guide frame (59) also holds or supports an advancing threaded rod (60) that is connected to the conical extractor head (56). In some embodiments, the threaded rod (60) and conical extractor head (56) can be advanced by manually turning the handle (61 ). This allows the physician to determine the amount of force needed to break open the tulip portion (51). Now it is understood that other means could be used to remove the tulip head as sometimes the polyaxial screw manufacturer will provide such a tool in case of revision to facilitate the removal of such tulip head.

[00070] With the tulip portion (51 ) removed, the screw shank of polyaxial screw (54) may be used as a base for the placement of either a new revision tulip portion or the placement of the revision hollow screws.

[00071] One option is to place a new custom tulip section and possibly an extended tulip or a custom tulip with a connector/rod integrated to facilitate attaching to an adjacent screw over the existing screw shank for the purposes of connection to an adjacent screw. This would allow the recapture and reuse of the existing implanted shank now with a new custom tulip. Another option is to place the hollow revision screw over the existing implanted screw shank.

[00072] Fig. 15 shows the intact screw shank (54) with its spherical head (57) and the removed broken tulip portion (51 ). After the tulip portion (51 ) is removed, a path over the spherical head (57) is made or formed to be able to mount a revision hollow screw onto the spherical head (57). The pathway created can be in the form of removing some material by sending or grinding with suction so that the diameter of the spherical head is smaller than the screw shank. Another way to create such a pathway may be to deform the spherical head into a cylinder by applying dies around it to compress the spherical head into a smaller diameter cylinder. For example, the tool could be similar to a rod cutter, but instead of cutting jaws, the tool would have a die to deform that spherical head.

[00073] Fig. 16a illustrates another method that includes creating the pathway by rolling or cutting a thread path into the spherical head (57). For example, a forming thread die (62) with an internal recess (64) (shown in partial cross section for illustration) includes cutting or forming teeth (63) at the distal end of the forming die. The forming die (62) is advanced over the spherical head (57) of the screw (54) using saline fluid and vacuum to remove any potential debris. Fig. 16b shows the end section of the forming die head, with the cutting teeth (63) and the recess (64).

[00074] Fig. 17 shows a screw head (65) of implanted screw (54) with the newly formed thread (66) formed by the above process. Fig. 18 shows the insertion of the revision hollow screw (24) onto the implanted screw (54). It can be seen here that the diameter of the threaded spherical head is of similar diameter as of the shank of screw (54). Because screw head (65) has a similar diameter to the shank of screw (54), revision hollow screw (24) may have a uniform internal threaded portion. In other embodiments, the internal threaded portion of the hollow screw may vary to be commensurate or match with an implanted screw that has varying outer threads on an external threaded portion. A surgical hex driver (67) may engage head (68) and be used to advance the revision hollow screw (24) on the already implanted screw (54) until it is solidly seated.

[00075] Another embodiment of the system is illustrated in Fig. 19. This figure shows a revision screw (28) that has at least two different thread configurations or a dual-thread configuration. Revision screw (28) can be used wherein the previously implanted screw (54) includes an external thread (29’) having a diameter larger than the diameter of the thread (22’) formed on the head (65’) of the already implanted screw (54). For example, revision hollow screw (28) may be used where first internal threaded portion (22) matches the formed thread (22’) on the head of screw (54) and a second internal threaded portion (29) matches the larger thread (29’) on the shank of screw (54). A tulip head (69) may be mounted at the proximal end of the revision hollow screw (28) to accept a rod fixation system.

[00076] Fig. 20 shows a completed arrangement of a fused segment with the new implant (70) that is rigidly fixed with the combination of a polyaxial screw (71) and a newly formed fixation (72) as described in Fig. 18 or Fig. 19. The newly implanted fixation system (76) includes a polyaxial screw (71 ), revision screw (54) and a connecting/fixation rod (75). The figure also illustrates the already fused level (74) and the remaining screw system (73) from the previous surgery still intact. Additionally, it is possible that the lower portion of the previously used rod (50) is to remain in place or could be removed as the physician might choose, depending on how much tissue exposure is needed to access the lower screw to unsecure the rod from the tulip.

[00077] In Fig. 21 a, screw (54) includes the spherical screw head (57) that was described in Fig. 15 and a tulip head (77) that can be snapped over the spherical screw head (57). A snap ring (78) is held open by a polymer shaft (80), which is a slightly greater size than the spherical head of the screw (54). The snap ring (78) has an internal lip (79) that will provide containment and restriction once inserted over the spherical head (57) to retain the tulip head (77) in place on head (57). Fig. 21 b shows an isometric view of the snap ring (78), which is cylindrical in shape with the internal lip (79) and the split cut (81), allowing for expansion or compression into a small diameter or a larger diameter, as the case might be. Once the tulip (77) has been inserted over the spherical head (57), the polymer shaft (80) can be removed, and the snap ring will take its relaxed position, which has a smaller diameter, and will trap the tulip over the spherical head.

[00078] The snap ring (78) material may be a material of high strength but also of flexibility so as to not break when compressed or expanded. For example, snap ring (78) may be made from a nitinol material, which is biocompatible and has a greater elasticity than steel, making it a desirable material for such applications. However, other materials could be used as known in the art.

[00079] Fig. 22 shows the assembly (82) with the screw (54), the tulip head (77) in its assembled position, which now includes a rod (84) that is attached via a locknut (83). In such a configuration, the already implanted screw can be reused with a tulip head (77) and reconnected to another set of screws and rods to create a solid construct.

[00080] Fig. 23 shows another embodiment of such tulip assembly (82), but this time with extended tulip arms (85), as it is commonly used in minimally invasive surgeries. Those extended arms can be snapped off at the recess (86) located just above the location of the locknut (83).

[00081] As for the benefits of such novel method with such system and devices, there are multiple as it would save time not to remove the existing already implanted screw shank. Another benefit would reduce the risk of fracturing the existing screw shank during extraction and leaving behind a portion of the shank blocking access to the pedicle tract for a new screw. Many of these screws become deeply integrated into the bone making removal challenging. In addition, there is a potential to reduce morbidity (infection, pain and associated narcotic use) for the patient due to a reduction in OR time, reduced blood loss and smaller surgical exposure as well as the ability for the surgeon to mate together different screw systems and not be forced to do revision with the same system that is currently in the patient which may not be the best choice for their pathology. [00082] Therefore, the above benefits make it advantageous for the use of the novel system, devices, and methods.

[00083] It is understood that the foregoing merely illustrates the principles of the various embodiments of the systems, device and methods disclosed herein.

Various modifications and alterations to the described embodiments will be apparent to those skilled in the art in view of the teachings herein.

Claims

1 . A vertebral fixation system, comprising: a first transpedicular screw sized and configured for insertion into a vertebral body of a first vertebra from an anterior approach, the first transpedicular screw having a head, a shank and a longitudinal length, wherein when the head is positioned against an anterior wall of the vertebral body the length of the first transpedicular screw is sized so that a terminal end of the shank terminates at a posterior limit of a pedicle of the vertebra; and a first posterior revision screw sized and configured to be inserted into the first vertebra from a posterior approach, the first posterior revision screw having a shank that engages with the shank of the first transpedicular screw.

2. The vertebral fixation system of claim 1 , wherein the shank of the first posterior revision screw includes an internal passageway that accepts the shank of the first transpedicular screw.

3. The vertebral fixation system of claim 2, wherein the shank of the first transpedicular screw include an external threaded portion and the shank of the first posterior revision screw has an internal threaded portion, and wherein the external threaded portion of the first transpedicular screw and internal threaded portion of the first posterior revision screw mate.

4. The vertebral fixation system of any one of claims 1 -3, further including a posterior second level fixation screw configured to be inserted into a second vertebra above or below the first vertebra, wherein the posterior second level fixation screw and the first posterior revision screw are connected by a connecting member.

5. The vertebral fixation system of claim 4, wherein the connecting member comprises a rod.

6. The vertebral fixation system of any one of claims 1 -5, further including a second transpedicular screw and a second posterior revision screw configured for insertion into the vertebral body of the first vertebra, wherein the second transpedicular screw and second posterior revision screw are mated.

7. The vertebral fixation system of claim 6, wherein a shank of the second transpedicular screw includes an external threaded portion and a shank of the second posterior revision screw has an internal threaded portion, and wherein the external threaded portion of the second transpedicular screw and internal threaded portion of the second posterior revision screw mate.

8. The vertebral fixation system of any one of claim 6 and 7, further including a locking plate attached to the first transpedicular screw and second transpedicular screw are attached to the locking plate.

9. The vertebral fixation system of any one of claims 6-8, furthering including a posterior second level fixation screw, wherein the second posterior revision screw and the level fixation screw are connected by a connecting member.

10. The vertebral fixation system of claim 9, wherein the connecting member is a rod.

1 1 . The vertebral fixation system of any one of claim 8-10, further including a third and fourth transpedicular screws configured to be inserted into a third vertebral body.

12. The vertebral fixation system of claim 11 , wherein the third and fourth transpedicular screws are attached to the locking plate.

13. A revision screw adapted to engage a screw implanted in a vertebra, the revision screw comprising: a shank having an external thread; an internal passageway in the shank defined by an interior surface, the interior surface comprising at least one threaded portion; and wherein the passageway is configured to accept the screw implanted in the vertebra and the at least one threaded portion is configured to engage an external thread of the screw implanted in the vertebra.

14. The revision screw of claim 13, wherein the at least one threaded portion of the interior surface comprises a first threaded portion and a second threaded portion, wherein the first and second threaded portions have thread pitches of differing size relative to each other.

15. The revisions screw of claim 13, wherein the at least one threaded portion has a uniform pitch.

16. The revision screw of any one of claims 13-15, further including a head configured to be attached to a connecting member.

17. The revision screw of the claim 16, wherein the connecting member comprises a rod.

18. A vertebral fixation system, comprising; a vertebral implant screw having a head and a shank, wherein the head includes external threads; and a revision screw positioned over the implanted screw.

19. The system of claim 9, wherein the shank of the vertebral implant screw has at least one external threaded portion.

20. The fixation system of claim 19, wherein the at least one external threaded portion includes a first threaded portion and a second threaded portion, wherein the first threaded portion and the second threaded portion have different pitch sizes.

21 . The fixation system of claim 19, wherein the at least one external threaded portion comprises one threaded portion having a uniform pitch size.

22. The fixation system of any one of claims 19-22, wherein the revision screw has an internal passageway and at least one threaded portion within the internal passageway.

23. The fixation system of claim 22, wherein the at least one threaded portion within the internal passageway of the revision screw is configured to mate with the external threaded portion of the shank of the implant screw.

24. The system of any one of claims 18-23, wherein the revision screw includes a head configured for attachment to a fixation rod.