WO2012075128A2

WO2012075128A2 - Vertebral fixation system and methods of use

Info

Publication number: WO2012075128A2
Application number: PCT/US2011/062623
Authority: WO
Inventors: Lee W. Warren
Original assignee: Warren Lee W
Priority date: 2010-11-30
Filing date: 2011-11-30
Publication date: 2012-06-07
Also published as: WO2012075128A3

Abstract

Various assemblies for vertebral fixation are presented that include a minimally invasive tube port adapted for use as a dissector, retractor and tool guide. Also included are a removable insert sized to fit within the tube port, and a screw having a head sized to fit within the tube port.

Description

VERTEBRAL FIXATION SYSTEM AND METHODS OF USE

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This non-provisional application claims priority from U.S. Provisional

Patent Application serial number 61/418, 162, entitled VERTEBRAL FIXATION SYSTEM AND METHODS OF USE, filed on November 30, 2010, which is incorporated herein by reference.

BACKGROUND

[0002] Fractures of the vertebrae or spinal column commonly occur due to trauma such as a fall or an automobile accident, and can have consequences ranging from pain and sensation of instability, to paralysis and death. Cervical spine or C-spine fractures are typically considered among the most dangerous vertebral fractures because of the potential for serious symptoms and subsequent complications. The C-spine begins at the base of the skull and includes seven vertebrae, abbreviated C I , C2, C3, C4, C5, C6 and C7, with the C I vertebra being the topmost and forming the joint between the skull and spine. The C-spine contains and protects the spinal cord, supports the skull and enables movement of the head forward and backward, and side to, side. Injury to the C-spine in particular can result in serious or life-threatening conditions, with the danger increasing with proximity of injury to the base of the skull; that is, trauma to the C2 vertebra is generally more serious than trauma to the C6 vertebra. The C2 vertebra (also referred to as the axis) forms a pivot for the C I vertebra (also referred to as the atlas). The C2 vertebra has a vertical projection at the front called the odontoid (tooth-like) process, or dens (the tooth), from which ligaments are connected to the base of the skull, and which articulates with C I to restrain horizontal displacement of C I . The incidence of odontoid fractures in which the odontoid process or its connection to the body of the axis is fractured accounts for about 10% to 20% of all C-spine fractures.

[0003] Fractures to the vertebrae, including C-spine fractures and in particular odontoid fractures, may be treated by hard collar or halo fixation to immobilize the fractured vertebra and its neighbors. This type of treatment is very difficult to tolerate and has several other disadvantages, such as the need to maintain the immobilization for 12- 16 weeks and to assess alignment during the immobilization, and potentially a low rate of union or fusion, with up to 40%-50% non-union rates. Another type of treatment for an odontoid fracture and other fractures of the C I or C2 vertebra is a posterior occiput fusion or C I -C2 fusion, in which a posterior approach is taken to fuse the C2 vertebra to the occipital bone, thereby bypassing the C I vertebra. This treatment significantly reduces mobility in the region and has about a 30% non-union rate. Wiring techniques, such as Gaulle or Brooks methods, may also be used to wire fractures together and offer a high union rate of about 95%, although these are particularly invasive techniques and require postoperative halo fixation. Posterior transarticular screw fixation may be used to connect neighboring vertebrae such as the C 1-C2 pair, in which a transarticular screw is inserted from the rear through and between the vertebrae to be stabilized. Posterior transarticular screw fixation provides a high fusion rate, but results in up to about 50% loss of cervical rotation. Furthermore, these and other types of surgical approaches to vertebral fractures and other vertebral disorders are invasive, typically involving bulky retractors that require a large incision.

[0004] Hence, for at least the aforementioned reasons, there exists a need in the art for advanced systems and methods for fixing one vertebra relative to another and for fixing together fractured portions of a vertebra.

BRIEF SUMMARY

[0005] The present disclosure sets forth various implantable medical devices and systems for implanting medical devices, and more particularly, various vertebral fixation systems and methods for using such are described herein.

[0006] Various embodiments of a vertebral fixation system are disclosed that include a minimally invasive tube port, a removable insert sized to fit within the tube port, and screw having a head sized to fit within the tube port. The tube port is adapted for use as a dissector, retractor and tool guide. In some cases, the tube port has a blunt chisel tip. In various cases, the tube port has one or more spars or a roughened surface on the tip.

[0007] In instances of the aforementioned embodiments, the vertebral fixation system includes various types of screws, such as an odontoid lag screw, a transarticular lag screw, a self-tapping screw, a self-drilling screw, and/ or a screw having a partially threaded shank having an unthreaded proximal end adjacent the head and having a threaded distal end. In some instances, the screw is an odontoid screw and is driven through a portion of a C2 vertebra into a fractured odontoid process. In other instances, the screw is a transarticular screw and is driven through a portion of a C I vertebra and a portion of a C2 vertebra.

[0008] In various instances of the aforementioned embodiments, the system also includes a K wire, a non-canulated drill, and/ or a tap to form a screw hole. Some instances of the aforementioned embodiments also include a fluoroscopic imaging system which may be used to guide the tools during a fixation procedure.

[0009] Other disclosed embodiments provide methods for vertebral fixation. Such methods include forming an incision anterior to at least one vertebra, performing blunt instrument dissection through the incision to establish a prevertebral plane, inserting a soft tissue protection shield that is slightly larger than the head of a screw into the dissected incision, passing the screw into the incision along the soft tissue protection shield, and driving the screw through at least a portion of at least one vertebra.

[0010] In one or more instances of the embodiments of the methods for vertebral fixation, inserting a soft tissue protection shield involves inserting a tube port that is adapted for use as a dissector, retractor and tool guide, and the blunt instrument dissection is performed at least in part using the tube port. [0011] Various instances also include passing a K wire through a wire guide insert in the tube 20 port to create a drill path through the portion of the at least one vertebra, removing the K wire, drilling along the drill path through the tube port, and tapping along the drill path through the tube port, where the screw is driven into the drilled and tapped drill path through the tube port.

[0012] Yet other disclosed embodiments provide vertebral fixation kits. Such kits include a plurality of tube ports, removable wire guide inserts, K wires, screws, screw drivers, non-canulated drills and taps. Each of the tube ports has a blunt chisel tip with at least one spar. The wire guide inserts each have a cylindrical shape with a diameter sized to fit within the tube ports and each have an axial passage. The K wires each have a diameter sized to fit in the axial passages of the wire guide inserts. The screws each have a head, a shank, and male threads on at least a portion of the shanks opposite the heads. The non-canulated drills are adapted to be guided through the tube ports. The taps each have a diameter greater than a diameter of the non-canulated drills and are adapted to be guided through the tube ports. The taps are adapted to form female threads matched to the male threads on the screws.

[0013] This summary provides only a general outline of some embodiments according to the present invention. Many other objects, features, advantages and other embodiments of the present invention will become more fully apparent from the following detailed description, the appended claims and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] A further understanding of the various embodiments of the present invention may be realized by reference to the figures which are described in remaining portions of the specification. In the figures, like reference numerals may be used throughout several drawings to refer to similar components. [0015] Fig. 1 depicts a perspective view of a vertebral fixation system in use during an anterior vertebral surgical procedure;

[0016] Fig. 2 is a cross-sectional side view of a vertebral fixation system in use during an anterior vertebral surgical procedure to repair a fractured odontoid process, with a tube port approaching the vertebral column;

[0017] Fig. 3 is a cross-sectional side view of a vertebral fixation system in use during an anterior vertebral surgical procedure to repair a fractured odontoid process, with the tube port 10 being moved into place adjacent the C2 vertebra;

[0018] Fig. 4 is a cross-sectional side view of a vertebral fixation system in use during an anterior vertebral surgical procedure to repair a fractured odontoid process, with a spar on the tube port engaging the C3 vertebra;

[0019] Fig. 5 is a cross-sectional side view of a vertebral fixation system in use during an anterior vertebral surgical procedure to repair a fractured odontoid process, with the tube port also shown in cross-section to expose a removable insert;

[0020] Fig. 6 is a cross-sectional side view of a vertebral fixation system in use during an anterior vertebral surgical procedure to repair a fractured odontoid process, with the removable insert being withdrawn from the tube port;

[0021] Fig. 7 is a cross-sectional side view of a vertebral fixation system in use during an anterior vertebral surgical procedure to repair a fractured odontoid process, with a K wire in a wire guide insert creating a drill path;

[0022] Fig. 8 is a cross-sectional side view of a vertebral fixation system in use during an anterior vertebral surgical procedure to repair a fractured odontoid process, with a wire guide insert being withdrawn from the tube port; [0023] Fig. 9 is a cross-sectional side view of a vertebral fixation system in use during an anterior vertebral surgical procedure to repair a fractured odontoid process, with a drill entering the drill path;

[0024] Fig. 10 is a cross-sectional side view of a vertebral fixation system in use during an anterior vertebral surgical procedure to repair a fractured odontoid process, with a tap in the tube port approaching the drill path;

[0025] Fig. 1 1 is a cross-sectional side view of a vertebral fixation system in use during an anterior vertebral surgical procedure to repair a fractured odontoid process, with the tap cutting threads along the drill path;

[0026] Fig. 12 is a cross-sectional side view of a vertebral fixation system in use during an anterior vertebral surgical procedure to repair a fractured odontoid process, with an odontoid screw being driven along the drilled and tapped drill path;

[0027] Fig. 13 is a cross-sectional side view of a vertebral fixation system in use during an anterior vertebral surgical procedure to repair a fractured odontoid process, with the odontoid screw in place having approximated the fracture and with the driver being withdrawn through the tube port;

[0028] Fig. 14 is a cross-sectional side view of a vertebral fixation system in use during an anterior vertebral surgical procedure to repair a fractured odontoid process, with the odontoid screw in place having approximated the fracture and with the tube port removed; and

[0029] Fig. 15 is a flow diagram showing a method for vertebral fixation in accordance with various embodiments.

DETAILED DESCRIPTION

[0030] The present disclosure sets forth various implantable medical devices and systems for implanting medical devices, and more particularly, various vertebral fixation systems and methods for using such are described herein.

[0031] Vertebral fixation systems may be used to fix or fasten fractured pieces of a vertebra together, or to fix one vertebra to another vertebra, as part of a spinal fusion or other surgical procedure. Vertebral fixation systems disclosed herein involve minimally invasive techniques without requiring bulky retractors which would in turn require a large incision and would complicate and lengthen surgical procedures. Vertebral fixation systems may include the formation of a small incision anterior to the vertebrae or spinal column, blunt instrument dissection to establish the prevertebral plane, and the use of a minimally invasive tube port or shield in the dissected incision to protect soft tissue, with work performed through the tube port or along the shield. For example, in some embodiments, a small incision of around 15mm may be used to perform anterior screw fixation of a fractured odontoid process in the C2 vertebra. The incision may be dissected using finger dissection and/ or dissection using a blunt tipped tube port or other blunt instrument, gently separating tissue fibers along fascial planes or along natural lines of cleavage where possible rather than cutting them. In some cases, vertebrae to be fixed, or fractured portions of vertebrae, are positioned or aligned as desired prior to surgery by positioning of the patient. For example, a fractured odontoid process may be positioned appropriately adjacent the body of the C2 axis before surgery using patient positioning. Once the minimally invasive incision has been made and the prevertebral plane established using blunt instrument dissection, the tube port is angled through the dissected incision against one or more vertebrae, providing the appropriate angle for a screw to enter the vertebra or vertebrae. If using a self-drilling and/ or self- tapping screw, the screw can then be passed through the incision along the tube port and driven into and through the fractured pieces of a vertebra, approximating the fracture to close gaps, or through multiple vertebrae to fuse them, as the case may be. [0032] The vertebral fixation systems eliminate the need for bracing in many types of vertebral procedures, provide for odontoid screw fixation while preserving all motion of the C1-C2 vertebrae, and result in the highest fusion rate while maintaining short surgery times and hospitalization. A minimal incision is formed and the least invasive internal techniques are applied, with work being done through or along a soft tissue shield that is just larger than the screw.

[0033] In some cases, vertebral fixation systems include the use of one or more Kirschner wires or K wires to establish a drill path into and through the vertebra or vertebrae to be fixed. In these cases, a removable or retractable wire guide insert is placed inside the tube port, either during or after blunt dissection of the incision. A K wire is guided through the tube port through the wire guide and is tapped or drilled through the vertebra to form a drill path. The K wire and wire guide are then retracted from the tube port and incision, clearing the way for a screw or for further procedures.

[0034] In various cases, a drill is used to create a hole for the screw, with the drill passing through the tube port to protect soft tissue. Drilling and other procedures performed during the vertebral fixation may be performed using image guidance systems, such as under anterior-posterior (AP) and lateral fluoroscopy. If a K wire was used to establish a drill path, the drill is driven along the drill path to widen the drill path for the screw. A tap is used in some embodiments of a vertebral fixation system to create female threads along the drill path, substantially matching male threads on the screw. As with the drill, the tap passes through the tube port to protect soft tissue. Drilling and tapping may be used to reduce expansion forces created by the screw as it is driven into the vertebra.

[0035] Embodiments of a vertebral fixation system disclosed herein include a minimally invasive tube port that is adapted for use as a dissector, retractor and tool guide. The tube port provides a port into the surgical opening and a common path for all tools used in the procedure, while being only slightly larger than the screw head and tools. Some embodiments include a flat or curved shield rather than a tube port for soft tissue protection, with the flat or curved shield being inserted into the incision to expand the incision and allow tools to pass along a side of the flat or curved shield. As used herein, the term "shield" is used in its broadest sense to mean any device capable of protecting soft tissue from the other tools and devices used in the vertebral fixation system. Thus, a shield may be, but is not limited to, a tube having an enclosed passage therethrough (also referred to herein as a tube port), a flat or curved open structure, etc. One of ordinary skill in the art will appreciate that a variety of different configurations of shield may be used in relation to different embodiments, based on factors such as the particular fixation being performed, the angle at which the screw is to be placed, the physiology of the patient, etc. The shield may be rigid or flexible to some degree. The materials that may be used include, but are not limited to, titanium, stainless steel, and various plastics and other radiolucent materials. In some embodiments of a vertebral fixation system disclosed herein, the shield is a tube port in which a removable insert is placed as it is being positioned against one or more vertebrae, closing off the opening at the tip of the tube port as it is inserted. A removable insert can also facilitate the use of the tube port as a blunt dissection instrument when it is flush with the ends of the tube port walls, forming a substantially flat surface at the end of the tube port rather than leaving exposed tube port walls that could cut or tear soft tissue. In various embodiments, the tube port may have a blunt chisel tip, in which the end surface is angled rather than perpendicular to the longitudinal access of the tube port. The blunt chisel tip facilitates separation of tissue fibers, and can be adapted to match the angle at which the tube .port meets the vertebra for a snug joint. In various embodiments, the tube port or other type of shield may have one or more spars. As used herein, the term "spar" is used to refer to a spike or other protrusion adapted to engage with a vertebra or other surface and prevent or minimize slippage. In various embodiments, the tube port or other type of shield may have a roughened tip at the surface to engage with a vertebra or other surface and prevent or minimize slippage. As will be appreciated by one of ordinary skill in the art, the roughened surface may be realized using a wide variety of different textures, texture patterns and texture depths. The roughened surface may be formed in the material of the shield itself or may comprise a coating applied to the shield.

[0036] Embodiments of a vertebral fixation system also include a screw to be driven into and through a vertebra or vertebrae in order to fixate, or fuse or fasten together, portions of a vertebra or vertebrae. The screw may be left in place permanently, or may be eventually removed if desired. The screw may be made of any material suitable for implantation into a body. The materials that may be used include, but are not limited to, titanium and stainless steel. Various embodiments of the vertebral fixation system may include an odontoid lag screw for repairing a fractured odontoid process in the C2 vertebra, a transarticular lag screw for fusing vertebrae such as the CI and C2 vertebrae together, or other types of screws. Based upon the disclosure herein, one of ordinary skill in the art will recognize a variety of shapes and dimensions of screws that may be used in relation to different embodiments.

[0037] Turning now to Fig. 1, a perspective view of a tube port in accordance with various embodiments is illustrated in use during an anterior vertebral fixation procedure. The tube port 10 is shown at the entrance to a small incision 12, which may be opened using blunt instrument dissection either using the tube port 10 or another blunt instrument. For example, finger dissection may be used to gently separate tissue fibers along fascial planes or along natural lines of cleavage where possible rather than cutting them, reducing bleeding and enhancing healing and recovery. The blunt instrument dissection establishes the prevertebral plane, that is, it exposes or provides access to a plane anterior to the vertebral column. In some embodiments this refers to a fat stripe or thin layer of fat paralleling the anterior surface of the cervical vertebrae.

[0038] The vertebral fixation system disclosed herein, including the tube port 10, may be used in a number of vertebral surgical procedures, such as the repair of a fracture to the odontoid process 14. In Fig. 1 , the odontoid process 14 is partially hidden behind the axis, or body of the CI vertebra 16. The vertebral fixation system may be used for any type of odontoid fracture, including type I, involving a small oblique avulsion of the upper third of the odontoid process, type II, a fracture at the junction of the dens or odontoid process and the body of the atlas or vertebra C2 20, and type III, a fracture through the body of C2 vertebra 20. Other vertebral surgical procedures benefitting from the vertebral fixation system include anterior transarticular fixation or fusion of CI vertebra 16 and C2 vertebra 20, although the vertebral fixation system is not limited to use in any particular type of vertebral fixation. The incision 12 may be made at any suitable location, with the position based on factors such as the vertebra to be fixed, angle at which a screw is to be placed in the vertebra or vertebrae, size of patient, etc. The tube port 10 may be held in place during a surgical procedure manually using a handle 22, or using other positioning and clamping devices. During the procedure, tools used in the vertebral fixation procedure are passed through an opening 24 in the end of the tube port 10 to reach the vertebrae without damaging soft tissue in the incision 12. Thus, all work in a vertebral fixation procedure may be performed through the tube port 10, allowing the use of a small incision 12 without the need for bulky retractors. The diameter, length, and wall thickness, etc. of the tube port 10 may be adapted as desired based on the other tools used in the vertebral fixation system and based on the patient size. For example, smaller patients may require the use of smaller fixation screws, allowing a narrower tube port 10 and smaller incision to be used. Larger patients may require larger screws, leading to a wider tube port 10.

[0039] Turning now to Fig. 2, a cross-sectional side view of a vertebral fixation system is illustrated in use during an anterior vertebral surgical procedure to repair a fractured odontoid process. The tube port 10 is shown in side view in Fig. 2 rather than cross-sectional view to illustrate the outside of the tube port 10. The C I vertebra 16 is shown in two pieces due to the cross-section, with the brain stem and spinal cord 26 passing down through the central opening or vertebral foramen of the vertebrae. Similarly, the C2 vertebra 20, C3 vertebra 30 and C4 vertebra 32 are shown in two pieces, front and back, due to the cross-sectional view cutting through the central opening or vertebral foramen of the vertebrae. The skull 34 is also shown. The fractured odontoid process 14 is positioned adjacent the body of the C2 vertebra 20 before surgery by patient positioning or by any other suitable procedure. An incision is made at an appropriate location. For example, for an odontoid process fracture, the incision may be made near the C3 vertebra 30 and C4 vertebra 32, allowing the tube port 10 to approach the C2 vertebra 20 on a flattened trajectory to enable a screw to pass through the body of the C2 vertebra 20 and the odontoid process 14. The incision is dissected using a blunt instrument, and the tube port 10 is inserted into the dissected incision. As described above, some embodiments of the tube port 10 include a blunt chisel tip 36, in which the end surface is angled rather than perpendicular to the longitudinal access of the tube port. The blunt chisel tip facilitates separation of tissue fibers, and can be adapted to match the angle at which the tube port 10 meets the vertebra for a snug joint. In various embodiments, the tube port or other type of shield may have one or more spars 40 to engage with the vertebra or other surface and prevent or minimize slippage.

[0040] As illustrated in Fig. 3, the tube port 10 is moved in the incision until it is in place at the location appropriate for the fixation procedure being performed. In the case of the odontoid fracture illustrated in Fig. 3, the tube port 10 is moved into position between the C2 vertebra 20 and C3 vertebra 30 so that a screw can pass through the tube port 10 and through the body of the C2 20 and the odontoid process 14.

[0041] Turning to Fig. 4, the spar 40 on the tube port 10 is embedded in the C3 vertebra 30 by tapping on the tube port 10. Other embodiments of the tube port 10 have a roughened surface on the chisel tip 36 to engage with the C3 vertebra 30. The chisel tip 36 is angled until the correct angle is reached with respect to the vertebra (e.g., C2 vertebra 20) . In some embodiments, the face of the chisel tip 36 is angled with respect to the longitudinal axis of the tube port 10 such that the chisel tip 36 makes contact with the vertebra (e.g., C2 vertebra 20) substantially all around the tip opening, as illustrated in side view in Fig. 4.

[0042] Turning to Fig. 5, the tube port 10 is illustrated in cross- section, exposing a removable insert 42 that may be inserted in the tube port 10 as it enters the incision, optionally used to perform blunt dissection, and positioned against the vertebra (e.g., C2 vertebra 20). The removable insert 42 may be used to close off the opening at the tip 36 of the tube port 10 as it is inserted. The removable insert 42 also facilitates the use of the tube port 10 as a blunt dissection instrument when it is flush with the ends of the tube port walls, forming a substantially flat surface at the tip 36 of the tube port 10 rather than leaving exposed tube port walls that could cut or tear soft tissue. The removable insert 42 may further be used to stiffen the tube port 10 for use in blunt dissection, and may be formed of any suitable material, such as titanium, stainless steel, or plastic, etc. Once the tube port 10 is in place, the removable insert 42 may be removed from the tube port 10, as illustrated in Fig. 6. As tools such as the removable insert 42 are withdrawn from the tube port 10, the tube port 10 is held in place against the vertebra (e.g., C2 vertebra 20) and the spars (e.g., 40) or roughened surface helps in maintaining the position of the tube port 10.

[0043] Turning to Fig. 7, a Kirschner wire or K wire 44 is used in some embodiments to create a drill path in one or more vertebra (e.g., C2 20). The K wire 44 is a sharpened, smooth stainless steel pin that is used to start a drill path to center other tools such as drills and taps. The K wire 44 may be guided and supported in the tube port 1.0 by a retractable wire guide insert 46. The K wire 44 is sized to fit within a channel in the wire guide insert 46, or viewed another way, a channel is provided through the wire guide insert 46 sized to fit the K wire 44. The wire guide insert 46 and removable insert 42 may be separate elements, or the removable insert 42 may be adapted for use as a wire guide insert 46 by providing a channel through the removable insert 42. The K wire 44 is tapped or driven by a power or hand drill to push it through the vertebra (e.g., C2 vertebra 20). The K wire 44 may be used to form a shallow pilot hole or drill path in which a drill can be centered, or can be used to form a hole through the vertebrae at least as deep as a screw to be placed in that hole. Once the K wire 44 has been used to form the hole along the drill path 50, it and the wire guide insert 46 are withdrawn from the tube port 10. The wire guide insert 46 is illustrated in a partially withdrawn state in Fig. 8 to more clearly show the K wire 44.

[0044] Turning to Fig. 9, a drill 52 is used in some embodiments to form a hole along a drill path 50 in the vertebra (e.g., C2 vertebra 20) for a screw. The drill path may extend through multiple vertebrae or portions of a vertebra, such as through the body of the C2 vertebra 20 and the odontoid process 14. The term "drill" is used generically herein to refer to a tool for forming a hole, without distinguishing between a cutting bit and a driver for turning or otherwise operating the cutting bit. Thus, for example, the term "drill" as used herein may apply to a drill bit alone without a driver, or to a hole cutting device with cutting bit and driver. In some embodiments, the drill 52 is a non-canulated or solid-bodied drill for strength. The drill 52- may be operated while using an image guidance system (IGS), such as under anterior-posterior (AP) and lateral fluoroscopy, to ensure that the drill 52 is moving along the correct drill path 50 and to identify when it has reached the correct depth. The drill 52 may include a drill shaft 54 sized to fit and rotate within the tube port 10, centering the drill 52 within the tube port 10. The drill shaft 54 is sized and made of a material to minimize friction and heat buildup within the tube port 10.

[0045J Turning to Figs: 10 and 1 1, a tap 56 is used in some embodiments to cut threads in the drilled hole along the drill path 50. Generally, a drill 52 cuts a smooth sided hole along the drill path 50, and a tap 56 is used to cut a threaded hole, where the female threads cut by the tap 56 are matched to the male threads on the screw used to fixate the vertebra (e.g. C2 vertebra 20). When the vertebral fixation system includes the drill 52, the tap 56 has a diameter greater than that of the drill 52 to enable it to cut threads into the walls of the drilled hole along the drill path 50. The threads cut by the tap 56 substantially match the threads on the screw. As with the drill 52, the tap 56 passes through the tube port 10 to protect soft tissue. Drilling and tapping may be used to reduce expansion forces created by the screw as it is driven into the vertebra (e.g., C2 vertebra 20). As with the drill 52, the tap 56 is non-canulated in some embodiments. The tap 56 may include a tap shaft 60 to center the tap 56 within the tube port 10, sized to fit and rotate within the tube port 10. The tap shaft 60 is stepped in some embodiments to aid in insertion into the tube port 10 and to help in clearing material from the drilled and tapped drill path 50. In some embodiments, the drill 52 and tap 56 are combined into a single instrument, turning at a relatively low speed to drill and tap a hole along the drill path 50 in a single operation.

[0046] Turning to Fig. 12, a screw 62 is driven into the drill path 50 by a screw driver 64, such as a power screw driver. The screw 62 has a head .66 sized to fit within the tube port 10. The screw 62 may be adapted for use with a variety of drive systems, such as female hexagonal drive heads, male hexagonal heads, etc. The head 66 has a diameter greater than the body of the screw 62 and overhangs the body to provide a bearing surface that can be tightened against the vertebra (e.g., C2 vertebra 20) around the drill path 50. In other embodiments, the screw 62 is a set screw with a head 66 having the same diameter as the body of the screw 62. Some embodiments of the screw 62 have a straight bodied shank, with the head 66 at one end and a tapered, unthreaded tip 70 at the other end. In some embodiments, a partially threaded screw 62 is used, having threads 72 near the tip 70 and an unthreaded shank 74 near the head 66. This is particularly useful when vertebral structures at the tip 70 and head 66 of the screw 62 are to be approximated or pulled together. For example, in the odontoid process fracture fixation procedure, when the threads 72 are embedded in the fractured odontoid process 14 and the head 66 is driven against the body of the C2 vertebra 20, the smooth shank 74 of the screw 62 is allowed to slide with the body of the C2 vertebra 20 and the odontoid process 14 can be pulled against the C2 vertebra 20. In other, embodiments, the screw 62 is threaded from head 66 to tip 70. This is useful when the relative positions of vertebral structures along the screw 62 are to be maintained, for example in some transarticular fusion procedures. In these cases, the threads engage with vertebral structures all along the length of the screw 62. Thus, the screw 62 may comprise an odontoid lag screw for odontoid process fracture procedures, or a longer transarticular lag screw for anterior transarticular vertebral fusion procedures, or other types of screws. In a given vertebral fixation procedure, one or more screws (e.g., 62) may be placed within the vertebrae and other structures.

[0047] The drill path 50 may be prepared for the screw 62 as discussed above by one or more of the K wire 44, drill 52 and tap 56. In other embodiments, the screw 62 may be either or both self-drilling or self- tapping. In these embodiments, some or all of the K wire 44, drill 52 and tap 56 may be omitted. The self-drilling embodiment of the screw 62 includes a drill-shaped point to cut through the vertebra (e.g., C2 vertebra 20) to eliminate the need for forming a pilot hole along the drill path with a K wire 44 or otherwise. The self- tapping embodiment of the screw 62 includes sharp threads that cut female threads into the vertebra (e.g. , C2 vertebra 20) as it is driven.

[0048] As illustrated in Fig. 12, the screw 62 is driven along the drill path 50 through the vertebrae (e.g. , C2 vertebra 20) through the tube port 10. The screw 62 pulls the odontoid process 14 and the body of the C2 vertebra 20 together, approximating the fracture. The screw driver 64 may be removed from the tube port 10 as illustrated in Fig. 13, and the tube port 10 is removed from the incision as illustrated in Fig. 14, leaving the screw 62 in place to affix the vertebra (e.g., the C2 vertebra 20 with the odontoid process 14) or vertebrae and the incision is closed. The vertebral fixation system disclosed herein provides a common path for all tools used within the procedure while being only slightly larger than the screw head 66.

[0049] Turning to Fig. 15, a flow diagram 100 shows a method for vertebral fixation in accordance with various embodiments. Following flow diagram 100, an incision is formed anterior to at least one vertebra (block 102). Blunt instrument dissection is performed through the incision to establish a prevertebral plane, (block 104). This may include, but is not limited to, finger dissection and dissection using a blunt chisel tipped tube port. A soft tissue protection shield is inserted into the dissected incision (block 106). In some embodiments, the soft tissue protection shield comprises a cylindrical tube through which tools are applied during the vertebral fixation procedure. In other embodiments, the soft tissue protection shield comprises a flat or curved shield adjacent to which tools are applied. A screw is passed into the incision along the soft tissue protection shield (block 1 10), and the screw is driven through at least a portion of at least one vertebra, wherein the soft tissue protection shield is slightly larger than a head of the screw (block 1 12). Some embodiments of the method for vertebral fixation include passing a K wire through a wire guide insert in the tube port to create a drill path through the portion of the at least one vertebra, removing the K wire, drilling along the drill path through the tube port, tapping along the drill path through the tube port, and driving the screw into the drilled and tapped drill path through the tube port.

[0050] The method for vertebral fixation may be applied to repair a fractured odontoid process, in which case the screw is an odontoid lag screw that is driven through the body of the C2 vertebra and through the fractured odontoid process to approximate the fracture and fuse the odontoid process to the body of the C2 vertebra during bone healing. The method may also be applied in an anterior transarticular fusion, for example to fuse the CI and C2 vertebrae together to inhibit movement. In this case, a longer transarticular lag screw is used, driving it at a flatter angle to pass through a portion of the C 1 vertebra and a portion of the C2 vertebra.

[0051] In some cases, multiple instances of each of the elements of the described vertebral fixation systems are combined together in a kit. Such kits may include, but are not limited to, a number of screws. The screws may have different sizes, shapes, drive systems, thread patterns and extents, etc. This allows an installer to select a particular screw depending upon the particular circumstance that is presented. Each of the screws has a head and a shank, with male threads on at least a portion of the shanks opposite the heads. Also included are a number of tube ports, each having a blunt chisel tip with at least one spar. In some cases, the tube ports are all the same, and in other cases, the tube ports may have different sizes and shapes to accommodate differences in patients and different vertebral fixation procedures. The kits may also include a number of removable wire guide inserts, each having a cylindrical shape having a diameter sized to fit within the tube ports and each having an axial passage. Also included are a number of K wires each having a diameter sized to fit in the axial passages of the wire guide inserts. The K wires may all be of a uniform type, or may be provided in a variety of shapes and sizes. Also included are a number of non-canulated drills adapted to be guided through the tube ports and a number of taps each having a diameter greater than a diameter of the non- canulated drills and adapted to be guided through the tube ports. The taps are adapted to form female threads matched to the male threads on the screws. The kit may be incorporated into a case that maintains all of the elements conveniently together. The case and included elements may be capable of insertion into an autoclave allowing for convenient sterilization.

[0052] The vertebral fixation system disclosed herein minimize or eliminate the need for large 30 incisions, bulky retractors, and bracing in a number of vertebral fixation procedures, with short surgery times and hospitalizations. Odontoid screw fixation preserves all motion of the C1-C2 vertebrae while providing a high fusion rate. The vertebral fixation system enables simple surgery that is easily taught using the anterior cervical discectomy and fusion (ACDF) approach.

[0053] In conclusion, the present invention provides novel systems, devices, methods and arrangements for vertebral fixation. While detailed descriptions of one or more embodiments of the invention have been given above, various alternatives, modifications, and equivalents will be apparent to those skilled in the art without varying from the spirit of the invention. Therefore, the above description should not be taken as limiting the scope of the invention, which is defined by the appended claims.

Claims

What is claimed is:

1. A vertebral fixation system, the system comprising: a minimally invasive tube port, wherein the tube port is adapted for use as a dissector, retractor and tool guide; a removable insert sized to fit within the tube port; and a screw having a head sized to fit within the tube port.

2. The vertebral fixation system of claim 1, wherein the tube port comprises a blunt chisel tip.

3. The vertebral fixation system of claim 1, wherein the tube port comprises a tip having at least one spar.

4. The vertebral fixation system of claim 1, wherein at least a portion of the tip of the tube port has a roughened surface.

5. The vertebral' fixation system of claim 1, wherein the screw comprises a self-tapping screw.

6. The vertebral fixation system of claim 1, wherein the screw comprises a self-drilling screw.

7. The vertebral fixation system of claim 1 , wherein the screw comprises a partially threaded shank having an unthreaded proximal end adjacent the head and having a threaded distal end.

8. The vertebral fixation system of claim 1, wherein the screw comprises an odontoid lag screw.

9. The vertebral fixation system of claim 1, wherein the screw comprises a transarticular lag screw.

10. The vertebral fixation system of claim 1 , wherein the removable insert comprises a retractable wire guide insert, the system further comprising a K wire sized to fit within the wire guide insert.

1 1. The vertebral fixation system of claim 1 , further comprising a non- canulated drill adapted to be guided through the tube port.

12. The vertebral fixation system of claim 11 , the screw comprising male threads, wherein the non-canulated drill comprises a tap adapted to form female threads matched to the male threads on the screw.

13. The vertebral fixation system of claim 12, further comprising a tap having a diameter greater than a diameter of the non-Canulated drill, wherein the tap is adapted to form female threads matched to the male threads on the screw.

14. The vertebral fixation system of claim 1 , further comprising a fluoroscopic imaging system.

15. A method for vertebral fixation, the method comprising: forming an incision anterior to at least one vertebra; performing blunt instrument dissection through the incision to establish a prevertebral plane; inserting a soft tissue protection shield into the incision; passing a screw into the incision along the soft tissue protection shield; and driving the screw through at least a portion of the at least one vertebra, wherein the soft tissue protection shield is slightly larger than a head of the screw.

16. The method of claim 15, wherein the step of inserting the soft tissue protection shield comprises inserting a tube port that is adapted for use as a dissector, retractor and tool guide, and wherein the step of blunt instrument dissection is performed at least in part using the tube port.

17. The method of claim 16, further comprising: passing a K wire through a wire guide insert in the tube port to create a drill path through the portion of the at least one vertebra; removing the K wire; drilling along the drill path through the tube port; and tapping along the drill path through the tube port, wherein the screw is driven into the drilled and tapped drill path through the tube port.

18. The method of claim 15, wherein the screw comprises an odontoid screw, and wherein the odontoid screw is driven through a portion of a C2 vertebra into a fractured odontoid process.

19. The method of claim 15, wherein the screw comprises a transarticular screw, and wherein the transarticular screw is driven through a portion of a C 1 vertebra and a portion of a C2 vertebra.

20. A vertebral fixation kit, the kit comprising: a plurality of tube ports, wherein each tube port of the plurality of tube ports includes a blunt chisel tip with at least one spar; a plurality of removable wire guide inserts, wherein each wire guide insert of the plurality of removable wire guide inserts includes a cylindrical shape having a diameter sized to fit within the plurality of tube ports, and each wherein each wire guide insert of the plurality of removable wire guide inserts includes an axial passage; plurality of K wires, wherein each K wire of the plurality of K wires includes a diameter sized to fit in the axial passages of the plurality of removable wire guide inserts; plurality of screws, wherein each screw of the plurality of screws includes a head and a shank, wherein at least a portion of the shank opposite the head includes male threads thereon; plurality of screw drivers; plurality of non-canulated drills adapted to be guided through the plurality of tube ports; and plurality of taps, wherein each tap of the plurality of taps includes a diameter greater than a diameter of the plurality of non-canulated drills and adapted to be guided through the plurality of tube ports, wherein each tap of the plurality of taps is adapted to form female threads matched to the male threads on the plurality of screws.