Abstract:
A bone screw and method of inserting the same is disclosed. In one example, the bone screw includes an awl tip for creating a pilot hole in the pedicle of a vertebra without having to predrill a starter hole. One or more threads located adjacent to the awl tip engage the wall of the pilot hole and draw the screw into the bone, thereby eliminating the need to drill and tap a hole in the bone prior to implantation of the screw.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of and claims priority to co-pending U.S. patent application Ser. No. 14/011,052, which is a continuation-in-part of and claims priority to U.S. patent application Ser. No. 13/117,669 filed on May 27, 2011, which claims priority to U.S. Provisional Patent No. 61/396,564 filed on May 28, 2010. These applications are incorporated herein by reference, in their entireties. 
     
    
     TECHNICAL FIELD 
       [0002]    The claimed technology relates generally to medical devices and more particularly to bone screws and methods of implanting the same. 
       BACKGROUND 
       [0003]    A variety of threaded fasteners have been developed for use in orthopedic surgical procedures to secure bone fragments, reattach ligaments or soft tissue to bones, or to hold bones in relative position to one another. One variety of bone screws used in the vertebrae of the spine are called pedicle screws, so named because they are inserted into the pedicle of the vertebral body. Pedicle screws are commonly used along with rods and screws to immobilize a portion of the spinal column. In other applications, pedicle screws are inserted into a series of vertebrae and one or more metal rods are secured to the heads of the screws, typically using set screws or some other securing means. 
         [0004]    Current pedicle screw designs require multiple steps to insure proper implantation into the vertebral body. Typically, an entry point is made into the pedicle using a high speed drill bit or an awl to create a pilot hole. In some instances, the pilot hole is enlarged using larger diameter drill bits. The pilot hole may then be probed with an instrument to detect any breaches in the pedicle wall. After the integrity of the pilot hole wall is confirmed, the pilot is then tapped to create a track in the hole wall for the screw to follow using a tap. Finally, the screw may be implanted into the prepared hole. 
         [0005]    Every surgical procedure carries with it a risk of complications. Procedures which require multiple steps such as pedicle screw implantation create the potential for the patient to experience complications with each step. Additionally, the chances for a surgeon to make a mistake due to fatigue during long procedures involving multiple screws increases with the number of steps required for placement of each screw. Thus there is a need for an improved bone screw which reduces the number of steps required for implantation of the screw into bone. 
       SUMMARY 
       [0006]    In one embodiment, a bone screw is provided that comprises a tip portion comprising an awl tip. The awl tip has a pyramidal configuration capable of creating a hole in bone. The bone screw includes a shank portion proximate to said tip portion, a head portion proximate to said shank portion and at least one helical thread which begins at said tip portion and continues through said shank portion. In some embodiments, said awl tip comprises three flat surfaces that define said pyramidal configuration. In some embodiments, said flat surfaces intersecting at a common point 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    The present disclosure will become more readily apparent from the specific description accompanied by the following drawings, in which: 
           [0008]      FIG. 1  is a side view of a bone screw according to one embodiment of the present disclosure; 
           [0009]      FIG. 2  is a perspective view of the bone screw shown in  FIG. 1 ; 
           [0010]      FIG. 3  is a side view of a bone screw according to another embodiment of the present disclosure; 
           [0011]      FIG. 4  is a perspective view of the bone screw shown in  FIG. 3 ; 
           [0012]      FIG. 5  is a side and perspective view of the bone screw shown in  FIG. 3 ; 
           [0013]      FIG. 6  is a side view of the bone screw shown in  FIG. 3 ; 
           [0014]      FIG. 7  is a partial view of tips in accordance with the present disclosure; 
           [0015]      FIG. 7A  is a partial view of the tips shown in  FIG. 7 , with the tips shown in  FIG. 7  rotated 180 degrees about longitudinal axes defined by the bone screws; and 
           [0016]      FIG. 8  is a side, cross sectional view of a bone screw being inserted into the pedicle of a spine according to one embodiment of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0017]    For the purposes of promoting an understanding of the principles of the claimed technology and presenting its currently understood best mode of operation, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the claimed technology is thereby intended, with such alterations and further modifications in the illustrated device and such further applications of the principles of the claimed technology as illustrated therein being contemplated as would normally occur to one skilled in the art to which the claimed technology relates. 
         [0018]    A bone screw  10  according to one embodiment of the present disclosure is shown in  FIG. 1 . In the following description, the term “distal” will refer to the direction towards which a screw is designed to be advanced as the screw is engaged to bone and “proximal” will refer to the opposite direction. Bone screw  10  comprises several segments or portions which begin at a distal end  12  and extend along a longitudinal axis  20  to a proximal end  14 . Located at distal end  12  of bone screw  10  is a tip portion  40  comprising an awl tip  30  and a helical, radially outward-extending thread  80 . The awl tip is sized and configured so as to be capable of cutting, boring, or otherwise creating a pilot hole when placed against bone and torsional and/or downward force is applied to the screw, thereby eliminating the need for the separate steps for placing a pilot hole, drilling, probing, and tapping the hole during implantation. In some examples, the leading or distal edge  82  of the thread  80  begins at the proximal edge  32  of the awl tip  30 . In other examples, the thread actually overlaps a portion of the awl tip. Typically, the leading edge of the thread is positioned such that as the awl tip excavates a hole in the bone, the leading edge engages the walls of the hole and draws the screw body into the bone. A variety of different thread styles and patterns may be used, including self-tapping threads, dual threads, and other suitable thread designs known in the industry. Optionally, tip portion  40  further includes one or more flutes  70  for conveying bone material away from the awl tip  30  and/or thread  80  during insertion of the screw into bone. In some examples, the flute  70  may also include a cutting edge  75  for engaging and removing bone material. The flute show in  FIG. 1  is longitudinally disposed in the surface of the screw along axis  20 , however other shapes, styles, and configurations of fluting may be used. 
         [0019]    Adjacent to the proximal end of tip portion  40  is the distal end of a shank portion  50 . The thread  80  from tip portion  40  continues through shank portion  50  to approximately the head portion  60  in this particular example. In other examples, a part of shank portion  50  may be unthreaded. Optionally, flute  70  which begins in tip portion  40  may continue or extend through a portion or all of shank portion  50 . Adjacent to the proximal end of shank portion  50  and is the distal end of a head portion  60 . In this particular embodiment, head portion  60  is shown comprising a U-shaped rod fixation element having a cradle  100  for receiving and securing rods (not shown) such as those commonly used in spinal procedures. Cradle  100  may further include a locking portion  120  (as shown in  FIG. 2 ) for receiving and securing a locking member (not shown), such as a set screw, using a variety of locking means such as threads, bayonet style closure, and the like. Even though a fixed, U-shaped head assembly is shown in the present example, it is understood that other types and styles of head assemblies may also be used with the present disclosure such as a polyaxial head assembly, a hex head assembly, and any other mono-axial, mutli-axial, or fixed head design as known in the art. 
         [0020]    A bone screw  130  according to another embodiment of the present disclosure is shown in  FIGS. 3-6 . Bone screw  130  comprises several segments or portions which begin at a distal end  136  and extend along a longitudinal axis  132  to a proximal end  134 . Located at distal end  136  of bone screw  130  is a tip portion  140  comprising an awl tip  170  and a helical, radially outward-extending thread  200 . A variety of different thread styles and patterns may be used, including self-tapping threads, dual threads, and other suitable thread designs known in the industry. Optionally, tip portion  140  further includes one or more flutes  180  for conveying bone material away from the awl tip  170  and/or thread  200  during insertion of the screw into bone. In some examples, the flute  180  may also include a cutting edge  190  for engaging and removing bone material. The flute show in  FIG. 3  is an axially wound or spiral flute about the central body of screw  130  disposed along axis  132 . 
         [0021]    Adjacent to tip portion  140  is a shank portion  150 . The thread  200  from tip portion  140  continues through shank portion  150  to approximately the head portion  160  in this particular example. In other examples, a part of shank portion  150  may be unthreaded. Flute  180  which begins in tip portion  140  continues through a portion of shank portion  150 . Adjacent to shank portion  150  and continuing to the proximal end  134  of screw  130  is a head portion  210 . In this particular embodiment, head portion  210  is shown comprising a U-shaped rod fixation element having a cradle  220  for receiving and securing rods (not shown) such as those commonly used in spinal procedures. Cradle  220  may further include a locking portion  230  (as shown in  FIG. 4 ) for receiving and securing a locking member (not shown) using a variety of locking means such as threads, bayonet style closure, and the like. Even though only a U-shaped head assembly is shown in the present example, it is understood that other types and styles of head assemblies may also be used with the present disclosure such as a polyaxial head assembly, hex head assembly, and the like. 
         [0022]    In some embodiments, awl tip  170  has a pyramidal configuration, as shown in  FIGS. 7 and 7A . In some embodiments, awl tip  170  comprises a plurality of planar surfaces, such as, for example, planar surfaces  170   a ,  170   b ,  170   c . Planar surfaces  170   a ,  170   b ,  170   c  each extend at an angle relative to one another, such as, for example, an acute angle. That is, planar surface  170   b  extends at an acute angle relative to planar surface  170   a  and planar surface  170   c  and planar surface  170   c  extends at an acute angle relative to planar surface  170   a  and planar surface  170   c . In some embodiments, planar surfaces  170   a ,  170   b ,  170   c  intersect at a common point, such as, for example, a distalmost tip  172 . That is, planar surfaces  170   a ,  170   b ,  170   c  converge at tip  172 . In some embodiments, tip  172  is a sharp tip, as shown in  FIGS. 7 and 7A . In some embodiments, flute  180  extends parallel to a longitudinal axis defined by shank portion  150 . In some embodiments, flute  180  extends at an acute angle relative to a longitudinal axis defined by shank portion  150 . 
       Screw Implantation 
       [0023]    Placement of a bone screw according to the present disclosure does not require the multi-step procedure commonly used in the industry and previously described. 
         [0024]    One method of implanting a bone screw according to the present disclosure comprises placing the awl tip against the vertebra at the desired entry point, typically at the surface of a pedicle. Torsional force is applied to the bone screw using a driving tool engaged with the head of the screw. Typically the driving tool will be an image guided and navigated tool, such as a screw driver, to allow the surgeon to confirm the correct trajectory of the screw through the bone. In other examples, guidance techniques such as anatomic landmarks or fluoroscopy may also be used to insure proper screw placement. As torsional force is applied to the screw, the awl tip engages and begins to carve a hole into the bone. Once the awl has carved a hole of sufficient depth the threads will engage the bone. Typically, the thread (or threads if a multi-thread design is used) of the screw begin immediately adjacent to the awl tip so as to reduce the depth to which the screw must be driven before the screw engages the bone. 
         [0025]    Once the screw threads have engaged the bone, the threads act to draw the screw down into the vertebra while the awl tip continues to carve out bone at the tip of the screw. If the screw also includes one or more flutes, the flutes act to channel bone material away from the tip and thread so as to increase performance of the screw. As the threads act to pull the screw down into the bone less force will need to be applied by the surgeon. Proper placement of the screw can be confirmed using imaging. Additional confirmation may be provided using neuromonitoring to insure there is no nerve irritation. Once the desired implantation depth is reached, additional elements such as rods, plates, and the like, may be secured to the screw using appropriate means. 
         [0026]      FIG. 8  shows the implantation of a bone screw in a vertebra according to one embodiment of the present disclosure. In this particular example, a bone screw  250  such as those previously described is implanted in vertebra  240 . An awl tip  270  allows the screw  250  to be driven into the bone of the vertebra, specifically through the body of a pedicle  242  and into the vertebral body  244 . Bone screw  250  includes a head portion  260  which is configured and adapted to engage a suitable driving tool  280  which allows for implantation of the screw. Optionally, driving tool  280  is an image guided and navigated tool, such as a screw driver, to allow for confirmation of the trajectory of the screw through the pedicle. Image guided navigation allows a surgeon to confirm proper placement of the screw in the bone. Additionally, the harder cortical bone walls of the pedicle will encourage the screw to follow a trajectory through the softer, cancellous bone found in the center of the pedicle. Imaging may be used to confirm proper screw placement. Additionally, neuromonitoring may be used to confirm there is no nerve root irritation while the screw is being placed. Once placed, additional elements such as rods, plates, and the like, may be secured to the screw using appropriate means. 
         [0027]    Reducing the number of steps in the implantation procedure using the devices and methods previously described decreases the time required for a procedure. Less time in the operating room means less blood loss, decreased risk of infection and the patient spends less time sedated, thereby reducing the possibility of anesthesia-related complications. Elimination of preparatory steps required for the placement of current bone screw designs also decreases the opportunities for mistakes during implantation, especially during long procedures involving the implantation of multiple screws where surgeon fatigue can become a factor. 
         [0028]    While the claimed technology has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character. It is understood that the embodiments have been shown and described in the foregoing specification in satisfaction of the best mode and enablement requirements. It is understood that one of ordinary skill in the art could readily make a nigh-infinite number of insubstantial changes and modifications to the above-described embodiments and that it would be impractical to attempt to describe all such embodiment variations in the present specification. Accordingly, it is understood that all changes and modifications that come within the spirit of the claimed technology are desired to be protected.