Patent Publication Number: US-2021186582-A1

Title: Removable Orthopedic Screws

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 16/387,799, filed on Apr. 18, 2019, and which claims priority to U.S. provisional application No. 62/659,340, filed on Apr. 18, 2018. Each of these related applications is incorporated by reference, in its entirety, into this disclosure. 
    
    
     FIELD 
     The disclosure relates to the field of medical devices. More particularly, the disclosure relates to orthopedic screws. The disclosure also relates to methods of manufacturing orthopedic screws. 
     BACKGROUND 
     Orthopedic screws, also referred to as bone screws, are implantable medical devices that are commonly used for fracture stabilization and fixation. These devices can be made from a variety of materials and can include structural adaptations that facilitate their use and/or enhance their performance. For example, orthopedic screws having a variety of sizes, shapes, thread patterns, and head geometries are available. 
     It can be desirable or even necessary to remove an orthopedic screw after implantation, such as after bone consolidation has occurred. Changes in bony structures over time can make removal difficult; it is not uncommon for implanted bone screws that were clearly accessible at the time of implantation to have bone grown into the thread. Screws can even become completely overgrown with bone, making explantation extremely difficult. Use of accessory tools, such as coring bits and even impact drivers, can be necessary to initiate removal of screws in these situations. 
     A need remains, therefore, for improved removable orthopedic screws and methods of manufacturing orthopedic screws. 
     BRIEF SUMMARY OF SELECTED EXAMPLES 
     Various example orthopedic screws are described and illustrated herein. 
     An example orthopedic screw comprises a head portion defining a proximal end, a tip portion defining a cutting edge and a distal end, and a body extending between the proximal end and the distal end along a longitudinal axis and defining a distal thread extending around the longitudinal axis. The head portion defines a series of cutting teeth on a plane that is perpendicular to the longitudinal axis. 
     Another example orthopedic screw comprises a shaft having a proximal end, a distal end, and a body extending between the proximal end and the distal end along a longitudinal axis. The shaft has a shaft external surface that defines a distal thread extending around the longitudinal axis. A head portion is disposed on the shaft and defines a proximal thread and a series of cutting teeth lying on a plane that is perpendicular to the longitudinal axis of the shaft. The proximal thread is disposed between the distal thread and the series of cutting teeth and extends around the longitudinal axis. A tip portion is disposed on the shaft and defines a cutting edge. The proximal thread has a first outer diameter and the proximal end has a second outer diameter that is less than the first outer diameter. 
     Another example orthopedic screw comprises an inner core member defining a proximal end, a distal end, and a body extending between the proximal end and the distal end along a longitudinal axis. The proximal end defines a series of cutting teeth on a plane that is perpendicular to the longitudinal axis and the distal end defines a cutting edge. An outer body member is disposed circumferentially around the inner core member and defines a distal thread extending around the longitudinal axis. 
     Another example orthopedic screw comprises a shaft having a proximal end, a distal end, a body extending between the proximal end and the distal end, and a longitudinal axis, the shaft having a shaft external surface defining a distal thread that extends around the longitudinal axis; a head portion on the shaft, the head portion defining a proximal end defining a series of cutting teeth on a plane that is perpendicular to the longitudinal axis of the shaft; and a tip portion on the shaft, the tip portion defining a cutting edge. 
     Another example orthopedic screw comprises a shaft having a proximal end, a distal end, a body extending between the proximal end and the distal end, and a longitudinal axis, the shaft having a shaft external surface defining a distal thread that extends around the longitudinal axis; a head portion on the shaft, the head portion defining a proximal thread and a series of cutting teeth lying a on a plane that is perpendicular to the longitudinal axis of the shaft, the proximal thread disposed between the distal thread and the series of cutting teeth and extending around the longitudinal axis; and a tip portion on the shaft, the tip portion defining a cutting edge. The proximal thread has a first outer diameter and the proximal end has a second outer diameter that is less than the first outer diameter. 
     Another example orthopedic screw comprises a shaft having a proximal end, a distal end, a body extending between the proximal end and the distal end, and a longitudinal axis, the shaft having a shaft external surface defining a distal thread that extends around the longitudinal axis; a head portion on the shaft, the head portion defining a proximal thread and a series of cutting teeth lying on a plane that is perpendicular to the longitudinal axis of the shaft, the proximal thread disposed between the distal thread and the series of cutting teeth and defining a series of reverse cutting teeth in the first rotation of the proximal thread relative to the proximal end; and a tip portion on the shaft, the tip portion defining a cutting edge. The proximal thread has a first outer diameter and the proximal end has a second outer diameter that is less than the first outer diameter 
     Various example methods of manufacturing an orthopedic screw are described. 
     An example method of manufacturing an orthopedic screw comprises machining a member from a precursor to form a distal thread on an external surface of the member between proximal and distal ends of the member and forming a series of cutting teeth on the proximal end of the member such that the series of cutting teeth lies on a plane that is parallel to the longitudinal axis of the member. 
     Another example method of manufacturing an orthopedic screw comprises machining a member from a precursor to form a distal thread on an external surface of the member between proximal and distal ends of the member; forming a series of cutting teeth on the proximal end of the member such that the series of cutting teeth lies on a plane that is parallel to the longitudinal axis of the member; and forming a proximal thread on the external surface of the member at an axial position between the distal thread and the proximal end of the member. 
     Another example method of manufacturing an orthopedic screw comprises machining a member from a precursor to form a distal thread on an external surface of the member between proximal and distal ends of the member and forming a proximal thread on the external surface of the member at an axial position between the distal thread and the proximal end of the member such that the proximal thread includes a reverse cutting tooth in the first rotation of the proximal thread. 
     Another example method of manufacturing an orthopedic screw comprises machining a member from a precursor to form a distal thread on an external surface of the member between proximal and distal ends of the member; forming a proximal thread on the external surface of the member at an axial position between the distal thread and the proximal end of the member such that the proximal thread includes a reverse cutting tooth in the first rotation of the proximal thread; and forming a series of cutting teeth on the proximal end of the member such that the series of cutting teeth lies on a plane that is parallel to the longitudinal axis of the member. 
     Additional understanding of the claimed devices and methods can be obtained by reviewing the detailed description of selected examples, below, with reference to the appended drawings. 
    
    
     
       DESCRIPTION OF FIGURES 
         FIG. 1  is a side view of a first example orthopedic screw. 
         FIG. 2  is a magnified partial perspective view of the first example orthopedic screw. The head portion of the orthopedic screw is illustrated. 
         FIG. 3  is a partial perspective view of a second example orthopedic screw. The head portion of the orthopedic screw is illustrated. 
         FIG. 4  is a partial perspective view of a third example orthopedic screw. The head portion of the orthopedic screw is illustrated. 
         FIG. 5  is a partial perspective view of a fourth example orthopedic screw. The head portion of the orthopedic screw is illustrated. 
         FIG. 6  is a flowchart representation of a first example method of manufacturing an orthopedic screw. 
         FIG. 7  is a flowchart representation of a second example method of manufacturing an orthopedic screw. 
     
    
    
     DETAILED DESCRIPTION OF SELECTED EXAMPLES 
     The following detailed description and the appended drawings describe and illustrate various example medical devices and methods individually selected by the inventors for the purpose of enabling one skilled in the art to make and use examples of the inventive medical devices and to perform examples of the inventive methods. The examples do not limit the scope of the claims in any manner. 
     As used herein, the term “lumen,” and grammatically related terms, refers to the inside space of a tubular structure. The term does not require any specific dimensions, relative dimensions, configuration, or regularity. 
       FIGS. 1 and 2  illustrate a first example orthopedic screw  1000 . The orthopedic screw  1000  has a proximal end  1002 , a distal end  1004 , and a body  1006  extending between the proximal end  1002  and the distal end  1004  along a longitudinal axis  1008 . The orthopedic screw  1000  includes a head portion  1010  that terminates with the proximal end  1002 , a tip portion  1012  that terminates with the distal end  1004 , and a shaft  1014  extending between the head portion  1010  and the tip portion  1012  and comprising the body  1006 . As described in detail below, the tip portion  1012  provides structure for cutting into tissue, such as bone and/or cartilage, and the head portion  1010  provides structure for interacting with one or more tools for placing or implanting the orthopedic screw  1000  into tissue, such as a driver. In this example, the orthopedic screw  1000  defines an inner lumen  1016 , allowing it to be passed over a separate member, such as a wire, to facilitate placement and/or positioning during implantation. Accordingly, the orthopedic screw  1000  according to this example is a cannulated screw. It is noted that, while the illustrated example orthopedic screw  1000  is a cannulated screw, orthopedic screws according to other embodiments do not include a lumen, such as solid body orthopedic screws. 
     In the illustrated example, the proximal end  1002  defines a proximal opening  1018  and the distal end  1004  defines a distal opening  1020 . The lumen  1016  extends between the proximal opening  1018  and the distal opening  1020 . Thus, each of the proximal opening  1018  and the distal opening  1020  provides access to the lumen  1016  from the environment external to the orthopedic screw  1000 . In use, the orthopedic screw  1000  can be passed over a previously-placed wire such that the wire extends through the lumen  1016 . The orthopedic screw  1000  can then be advanced over the wire to achieve a desired placement and/or positioning before initiating driving of the orthopedic screw  1000  into tissue. Similarly, a wire can be used during removal of the orthopedic screw  1000  from tissue into which the orthopedic screw  1000  has been implanted. For example, a wire can be placed into the lumen  1016  of the orthopedic screw and advanced distally toward the distal end  1004 . A removal tool, such as a driver or other tool, can then be passed over the wire and guided toward to the head portion  1010  to facilitate alignment of the tool and the head portion  1010  prior to application of a removal force. 
     As best illustrated in  FIG. 2 , the head portion  1010  has a head core  1030  that defines a cavity  1032  that is bounded by a circumferential wall  1034  and a transverse wall  1036 . The circumferential wall  1034  extends around the longitudinal axis  1008  of the orthopedic screw  1000 . The transverse wall  1036  transitions the inner diameter of the lumen  1016  from a larger inner diameter of the cavity  1032  to a smaller inner diameter within the body  1006  of the orthopedic screw  1000 . 
     The circumferential wall  1034  defines structure that facilitates interaction with a tool, such as a driver, that can be used to drive the orthopedic screw  1000  into, and remove the screw  1000  from, tissue, such as cartilage and/or bone. The transverse wall  1036  may also define structure that facilitates such interaction. As such, the circumferential wall  1034 , the transverse wall  1036 , and, as a result, the cavity  1032  may have any suitable configuration and a skilled artisan will be able to select an appropriate configuration for each of these structures in an orthopedic screw according to a particular embodiment based on various considerations, including the configuration and nature of any driver with which the orthopedic screw is intended to be used. Examples of suitable configurations include conventional configurations for screw heads, including hex, star-shaped configurations, such as configurations compatible with TORX brand drivers, and other configurations. In this example, the head  1030  is an enlarged structure relative to the tip portion  1012  and body  1006  of the orthopedic screw. 
     The external surface  1038  of the head portion  1010  defines head thread  1040 . In this example, the head thread  1040  is oriented such that the head thread  1040  cuts into bone into which the orthopedic screw  1000  is being implanted upon application of a clockwise rotational force to the orthopedic screw  1000 . 
     In this example, the circumferential wall  1034  of the head core  1030  defines a series of cutting teeth  1050 . The series of cutting teeth  1050  lies on a plane that is perpendicular to the longitudinal axis  1008  of the orthopedic screw  1000 . Also, the series of cutting teeth  1050  is oriented in the opposite direction relative to the head thread  1040 . Thus, in this example, the series of cutting teeth  1050  is oriented such that the series of cutting teeth  1050  cuts into bone upon application of a counter-clockwise rotational force to the orthopedic screw  1000 . The arrangement of the series of cutting teeth  1050  on a plane perpendicular to the longitudinal axis  1008  and in an orientation opposite to that of the head thread  1040  is considered advantageous at least because it places the series of cutting teeth  1050  in a position and orientation suitable for cutting through bone that has grown over the head core  1030  after the orthopedic screw  1000  has been implanted and left in place. As such, this arrangement and orientation facilitates removal of the orthopedic screw  1000 . 
     While the illustrated example includes a head thread  1040  oriented for cutting into bone upon application of a clockwise rotational force and a series of cutting teeth oriented for cutting into bone upon application of a counter-clockwise rotational force, it is noted that, in an embodiment, the orientations of the head thread and series of cutting teeth can be reversed if desired, so long as the opposite nature of these orientations is maintained. Thus, in an embodiment, the head thread can be oriented such that the head thread cuts into bone into which an orthopedic screw according to the embodiment is being implanted upon application of a counter-clockwise rotational force to the orthopedic screw. In this embodiment, the series of cutting teeth would be oriented such that the series of cutting teeth cuts into bone into which an orthopedic screw according to the embodiment is being implanted upon application of a clockwise rotational force to the orthopedic screw. 
     In the illustrated embodiment, the series of cutting teeth  1050  on the head core  1030  includes five individual cutting teeth  1050   a ,  1050   b ,  1050   c ,  1050   d , and  1050   e . Each cutting tooth  1050   a ,  1050   b ,  1050   c ,  1050   d , and  1050   e  of the series of cutting teeth  1050  has a curvilinear inclined planar surface  1052   a ,  1052   b ,  1052   c ,  1052   d ,  1052   e  that extends from a first end  1054   a ,  1054   b ,  1054   c ,  1054   d ,  1054   e  having a first height to a second end  1056   a ,  1056   b ,  1056   c ,  1056   d ,  1056   e  having a second height that is greater than the first height. Each cutting tooth  1050   a ,  1050   b ,  1050   c ,  1050   d ,  1050   e  of the series of cutting teeth  1050  also has an impact surface  1058   a ,  1058   b ,  1058   c ,  1058   d ,  1058   e  that is planar or substantially planar and that extends from the second end  1056   a ,  1056   b ,  1056   c ,  1056   d ,  1056   e  of the cutting tooth  1050   a ,  1050   b ,  1050   c ,  1050   d ,  1050   e  to the first end  1054   a ,  1054   b ,  1054   c ,  1054   d ,  1054   e  of the curvilinear inclined planar surface  1052   a ,  1052   b ,  1052   c ,  1052   d ,  1052   e  of the immediately adjacent cutting tooth  1050   a ,  1050   b ,  1050   c ,  1050   d ,  1050   e  of the series of cutting teeth  1050 . As such, the impact surface  1058   a ,  1058   b ,  1058   c ,  1058   d ,  1058   e  of each cutting tooth  1050   a ,  1050   b ,  1050   c ,  1050   d ,  1050   e  of the series of cutting teeth  1050  extends from the second end  1056   a ,  1056   b ,  1056   c ,  1056   d ,  1056   e  of one cutting tooth  1050   a ,  1050   b ,  1050   c ,  1050   d ,  1050   e  of the series of cutting teeth  1050  to the first end  1054   a ,  1054   b ,  1054   c ,  1054   d ,  1054   e  of another, immediately adjacent cutting tooth  1050   a ,  1050   b ,  1050   c ,  1050   d ,  1050   e  of the series of cutting teeth  1050 . Furthermore, the impact surface  1058   a ,  1058   b ,  1058   c ,  1058   d ,  1058   e  of each cutting tooth  1050   a ,  1050   b ,  1050   c ,  1050   d ,  1050   e  of the series of cutting teeth  1050  transitions from the second height of one cutting tooth  1050   a ,  1050   b ,  1050   c ,  1050   d ,  1050   e  of the series of cutting teeth  1050  to the first height of another, immediately adjacent cutting tooth  1050   a ,  1050   b ,  1050   c ,  1050   d ,  1050   e  of the series of cutting teeth  1050 . In the illustrated embodiment, the impact surface  1058   a ,  1058   b ,  1058   c ,  1058   d ,  1058   e  of each cutting tooth  1050   a ,  1050   b ,  1050   c ,  1050   d ,  1050   e  of the series of cutting teeth  1050  lies on a plane that contains the longitudinal axis  1008  of the orthopedic screw  1000 . It is noted, though, that an orthopedic screw according to a particular embodiment can include one or more cutting teeth that has an impact surface that lies in a plane disposed at an angle to the longitudinal axis of the particular orthopedic screw. 
     In this embodiment, each cutting tooth  1050   a ,  1050   b ,  1050   c ,  1050   d ,  1050   e  of the series of cutting teeth  1050  has the same size and configuration. This number and structural configuration of the cutting teeth in the series of cutting teeth is considered advantageous at least because it provides a desirable number of positions at which cutting action can be initiated along with a regularity to the cutting performance of the series of cutting teeth  1050 . It is noted, though, that an orthopedic screw according to a particular embodiment can include any suitable number of individual cutting teeth in a series of cutting teeth, and a skilled artisan will be able select an appropriate number of individual cutting teeth based on various considerations, including the nature of the bone or other tissue into which the orthopedic screw is intended to be implanted, the intended, expected, or potential duration of any implantation period, and any expected likelihood that the orthopedic screw will need to be removed from tissue at a point in time after implantation. The inclusion of five or fewer individual cutting teeth is considered advantageous at least because this number provides an aggressive cutting ability but does not negatively impact the handling characteristics of the orthopedic screw. Examples of numbers of cutting teeth considered suitable for inclusion in an orthopedic screw according to an embodiment include, but are not limited to, one, more than one, multiple, a plurality, two, three, four, five, six, seven, eight, nine, ten, more than ten, a dozen, and multiples of these numbers. It is also noted that an orthopedic screw according to a particular embodiment can include a series of cutting teeth in which at least two individual cutting teeth have different structural configurations. For example, one cutting tooth of the series of cutting teeth can have a curvilinear inclined planar surface that has a first length and a second cutting tooth of the series of cutting teeth can have a curvilinear inclined planar surface that has a second length that is different from the first length. As another example, one cutting tooth of the series of cutting teeth can have a second height at the second end of its curvilinear inclined planar surface, using the identifying terms from the orthopedic screw  1000 , that is different from the second height at the second end of the curvilinear inclined planar surface of another cutting tooth of the series of cutting teeth. 
     As best illustrated in  FIG. 1 , head thread  1040  has a first outer diameter  1060  at the widest point of the head thread, measured on a plane perpendicular to the longitudinal axis  1008  of the orthopedic screw  1000 . The series of cutting teeth  1060  has a second outer diameter  1062 , also measured on a plane perpendicular to the longitudinal axis  1008  of the orthopedic screw  1000 . The first outer diameter  1060  is different from the second outer diameter  1062 . Also as best illustrated in  FIG. 1 , the first outer diameter  1060  is greater than the second outer diameter  1062 ; the second outer diameter  1062  is less than the first outer diameter  1060 . This structural arrangement is considered advantageous at least because it provides the functional advantage of the series of cutting teeth  1050  but ensures the cutting teeth of the series of cutting teeth  1050  do not interfere with initial insertion of the orthopedic screw  1000  into bone. 
     The tip portion  1012  defines a tip  1070  at the distal end  1004 . The tip  1070  defines cutting edge  1072 . Cutting edge  1072  defines structure for cutting into tissue, such as bone and/or cartilage. Cutting edge  1072  may have any suitable configuration and a skilled artisan will be able to select an appropriate configuration for the cutting edge in an orthopedic screw according to a particular embodiment based on various considerations, including the nature of any particular tissue with which the orthopedic screw is intended to be used. Examples of suitable configurations include conventional configurations for bone screw cutting edges. Different configurations may be appropriate for orthopedic screws intended for use in different tissues and/or applications. For example, an orthopedic screw intended for use in fracture fixation in the foot and/or ankle may have one cutting edge configuration while an orthopedic screw intended for us in fracture fixation in the upper extremities may have another, different cutting edge configuration. Orthopedic screws intended for other uses, such as spinal or trauma applications, may have yet other cutting edge configurations. 
     The shaft  1014  defines external surface  1080  that extends entirely around the longitudinal axis  1008  of the orthopedic screw  1000 . As best illustrated in  FIG. 1 , external surface  1080  defines distal thread  1082 . In this example, the distal thread  1080  extends along only a first axial portion  1084  of the shaft  1014 , leaving another axial portion  1086  of the shaft  1014  free of the distal thread  1082 . It is noted, though, that the distal thread in an orthopedic screw according to a particular embodiment can extend along any suitable axial length of the shaft of the orthopedic screw. A skilled artisan will be able to select a suitable axial length for an orthopedic screw according to an embodiment based on various considerations, including the nature of the bone or other tissue into which the orthopedic screw is intended to be implanted. 
     The distal thread  1080  can have any suitable structural configuration, and a skilled artisan will be able to select an appropriate configuration for the distal thread in an orthopedic screw according to a particular embodiment based on various considerations, including the nature of any tissue with which the orthopedic screw is intended to be used. One example embodiment, not illustrated, includes sawing teeth which are considered particularly advantageous at least because they provide additional cutting functionality. 
       FIG. 3  illustrates a second example orthopedic screw  2000 . For simplicity,  FIG. 3 , only illustrates the head portion  2010  and a portion of the shaft  2014  of the orthopedic screw  2000 . The orthopedic screw  2000  is identical to the orthopedic screw  1000  described above and illustrated in  FIGS. 1 and 2 , except as detailed below. Thus, orthopedic screw  2000  has a proximal end  2002 , a distal end, and a body extending between the proximal end  2002  and the distal end along a longitudinal axis  2008 . The orthopedic screw  2000  includes a head portion  2010  located at the proximal end  2002 , a tip portion located at the distal end, and a shaft  2014  extending between the head portion  2010  and the tip portion and comprising the body. The shaft  2014  defines an external surface  2080  that defines a distal thread. The head portion  2010  has a head core  2030  that defines a cavity  2032  that is bounded by a circumferential wall  2034  and a transverse wall  2036 . The circumferential wall  2034  extends around the longitudinal axis  2008  of the orthopedic screw  2000 . The transverse wall  2036  transitions the inner diameter of the inner lumen  2016  from a larger inner diameter of the cavity  2032  to a smaller inner diameter within the body  2006  of the orthopedic screw  2000 . The external surface  2038  of the head portion  2010  defines head thread  2040 . In this example, the head thread  2040  is oriented such that the head thread  2040  cuts into bone into which the orthopedic screw  2000  is being implanted upon application of a clockwise rotational force to the orthopedic screw  3000 . 
     In this example, the head thread  2040  defines reverse cutting teeth  2090   a ,  2090   b  in the first rotation of the head thread  2040  from the proximal end  2002  of the orthopedic screw  2000 . Each of the reverse cutting teeth  2090   a ,  2090   b  comprises a step in the flank of the head thread  2040  from the crest of the head thread  2040  to a height between the root of the head thread  2040  and the crest of the head thread  2040 . 
     In the illustrated embodiment, the head thread  2040  includes two individual reverse cutting teeth  2090   a ,  2090   b , each of the same size and configuration. An orthopedic screw according to a particular embodiment can include any suitable number of individual reverse cutting teeth in a series of reverse cutting teeth on the head thread, and a skilled artisan will be able select an appropriate number of individual reverse cutting teeth based on various considerations, including the nature of the bone or other tissue into which the orthopedic screw is intended to be implanted, the intended, expected, or potential duration of any implantation period, and any expected likelihood that the orthopedic screw will need to be removed. The inclusion of two or fewer individual reverse cutting teeth is considered advantageous at least because this number provides an aggressive cutting ability but does not negatively impact the ability of the head thread to cut into bone upon initial implantation. 
     Also in this embodiment, the circumferential wall  2034  of the head core  2030  comprises a continuous circumferential flange that forms the proximal end  2002  of the orthopedic screw  2000 . As such, and in contrast to the first example orthopedic screw  1000  described above and illustrated in  FIGS. 1 and 2 , the circumferential wall  2034  of the head core  2030  in this embodiment does not define any cutting teeth. 
       FIG. 4  illustrates a third example orthopedic screw  3000 . For simplicity,  FIG. 4 , only illustrates the head portion  3010  and a portion of the shaft  3014  of the orthopedic screw  3000 . The orthopedic screw  3000  is similar to the orthopedic screw  2000  described above and illustrated in  FIGS. 1 and 2 , except as detailed below. Thus, orthopedic screw  3000  has a proximal end  3002 , a distal end, and a body extending between the proximal end  3002  and the distal end along a longitudinal axis  3008 . The orthopedic screw  3000  includes a head portion  3010  located at the proximal end  3002 , a tip portion located at the distal end, and a shaft  3014  extending between the head portion  3010  and the tip portion and comprising the body. The shaft  3014  defines an external surface  3080  that defines a distal thread. The head portion  3010  has a head core  3030  that defines a cavity  3032  that is bounded by a circumferential wall  3034  and a transverse wall. The circumferential wall  3034  extends around the longitudinal axis  3008  of the orthopedic screw  3000 . The transverse wall transitions the inner diameter of the lumen  3016  from a larger inner diameter of the cavity  3032  to a smaller inner diameter within the body  3006  of the orthopedic screw  3000 . The external surface  3038  of the head portion  3010  defines head thread  3040 . In this example, the head thread  3040  is oriented such that the head thread  3040  cuts into bone into which the orthopedic screw  3000  is being implanted upon application of a clockwise rotational force to the orthopedic screw  3000 . 
     In this example, the head thread  3040  defines a single reverse cutting tooth  3090  in the first rotation of the head thread  3040  from the proximal end  3002  of the orthopedic screw  3000 . The reverse cutting tooth  3090  comprises a step in the flank of the head thread  3040  from the crest of the head thread  3040  to the root of the head thread  3040  and the crest of the head thread  3040 . 
     The orthopedic screw  3000  also includes a series of cutting teeth  3050  on the circumferential wall  3034  of the head core  3030 . The series of cutting teeth  3050  lies on a plane that is perpendicular to the longitudinal axis  3008  of the orthopedic screw  3000 . Also, the series of cutting teeth  3050  is oriented in the opposite direction relative to the head thread  3040 . Thus, in this example, the series of cutting teeth  3050  is oriented such that the series of cutting teeth  3050  cuts into bone upon application of a counter-clockwise rotational force to the orthopedic screw  3000 . In this example, the series of cutting teeth  3050  is similar to the series of cutting teeth  1050  described above and illustrated in  FIGS. 1 and 2  in connection with the first example orthopedic screw  1000 . 
     In the illustrated embodiment, reverse cutting tooth  3090  includes an impact surface  3090   a  that lies on a plane disposed between first and second planes on which first and second impact surfaces of first and second teeth of the series of cutting teeth  3050 . This structural configuration is considered advantageous at least because it ensures a distance between impact surfaces of the reverse cutting tooth  3090  and the impact surfaces of the cutting teeth of the series of cutting teeth  3050 . It is noted, though, that an orthopedic screw according to a particular embodiment can include a reverse cutting tooth having an impact surface that lies on a plane on which an impact surface of a cutting tooth of the series of cutting teeth also lies. 
     The inclusion of both the reverse cutting tooth  3090  in the head thread  3040  and the series of cutting teeth  3050  on the circumferential wall  3034  of the head core  3030  is considered advantageous at least because it provides multiple structures to interface with and disrupt bone overgrowth to facilitate removal of the orthopedic screw  3000  from bone after implantation. Furthermore, the inclusion of both a cutting tooth, or multiple cutting teeth, that is or are defined by a thread that extends along a spiral path around the longitudinal axis of the orthopedic screw, such as cutting tooth  3090  in the head thread  3040 , and a series of cutting teeth that lies on a plane that is perpendicular to the longitudinal axis the orthopedic screw, such as series of cutting teeth  3050 , is considered advantageous at least because it provides multiple modes of action for interfacing with and disrupting bone overgrowth to facilitate removal of the orthopedic screw from bone after implantation. 
       FIG. 5  illustrates a fourth example orthopedic screw  4000 . For simplicity,  FIG. 5 , only illustrates the head portion  4010  and a portion of the shaft  4014  of the orthopedic screw  4000 . The orthopedic screw  4000  is similar to the orthopedic screw  1000  described above and illustrated in  FIGS. 1 and 2 , except as detailed below. Thus, orthopedic screw  4000  has a proximal end  4002 , a distal end, and a body extending between the proximal end  4002  and the distal end along a longitudinal axis  4008 . The orthopedic screw  4000  includes a head portion  4010  located at the proximal end  4002 , a tip portion located at the distal end, and a shaft  4014  extending between the head portion  4010  and the tip portion and comprising the body. The shaft  4014  defines an external surface  4080  that defines a distal thread. The head portion  4010  has a head core  4030  that defines a cavity  4032  that is bounded by a circumferential wall  4034  and a transverse wall. The circumferential wall  4034  extends around the longitudinal axis  4008  of the orthopedic screw  4000 . The transverse wall transitions the inner diameter of the inner lumen  4016  from a larger inner diameter of the cavity  4032  to a smaller inner diameter within the body  4006  of the orthopedic screw  4000 . 
     In this example, the orthopedic screw  4000  also includes a series of cutting teeth  4050  on the circumferential wall  4034  of the head core  4030 . The series of cutting teeth  4050  lies on a plane that is perpendicular to the longitudinal axis  4008  of the orthopedic screw  4000 . Also, the series of cutting teeth  4050  is oriented such that the series of cutting teeth  4050  cuts into bone upon application of a counter-clockwise rotational force to the orthopedic screw  4000 . 
     In this example, the external surface  4038  of the head portion  4010  defines a smooth surface that is free of a thread. Indeed, in this example, the orthopedic screw  4000  only includes a single thread on the distal end. 
     In all embodiments, the orthopedic screw can be made of any material suitable for use in medical devices intended for orthopedic use, including use as a long-term implant. Examples of suitable materials include metals, metal alloys, and polymeric materials. Examples of suitable metals include, but are not limited to, Titanium, Magnesium, and other metals. Examples of suitable metal alloys include, but are not limited to, Ti6Al4V, 316 LVM, 1.4441Ti-13Nb-13Zr, Ti-12Mo-6Zr-2Fe, Ti-15Mo-5Zr-3Al, Ti-15Mo, Ti-35Nb-7Zr-5Ta and Ti-29Nb-13Ta-4.6Zr Ti-6Al-7Nb and Ti-15Sn-4Nb-2Ta-0.2Pd Co—Cr—Mo alloys. Examples of suitable polymeric materials include, but are not limited to, polyaryletherketone (PAEK), polyether ether ketone (PEEK), PEEK (90G, 450G, 12, 14), Polyamide, PA66, carbon fiber reinforced polyaryletherketone (CFR PAEK), polyether ketone ketone (PEKK), carbon fiber reinforced polyether ketone ketone (CFR PEKK), carbon fiber reinforced polyether ether ketone (CFR PEEK), CFR PEEK (90G CA30, 90G CA20, 450G CA30, 450G CA20, I2 CF20, 12 CF30, 14 CF30, 14 CF20), Polyamide CFR, and PA66 CFR. 
     Orthopedic screws according to some embodiments include multiple components, such as an inner core member and an outer body member. In these embodiments, the components can be formed of the same or different materials. For example, an orthopedic screw according to an embodiment can include an inner core member that defines a distal tip, head core, and a series of cutting teeth on the head core as described above, and an outer body member that circumferentially surrounds the inner core member and defines a distal thread and a head thread. In this embodiment, it is considered advantageous to include an inner core member formed of a first metallic material, such as a metal or a metal alloy, and an outer body member formed of a second, different material, such as a polymeric material, a blended material such as a carbon fiber reinforced polymer, or another non-metallic material. It is considered particularly advantageous to include an inner core member formed of a Titanium alloy, such as Ti6Al4V, and an outer body member formed of a second, different material, such as CFR PEEK at least because this combination of materials provides desirable characteristics and a favorable balance between manufacturability and strength considerations. In these embodiments, the outer body member can be made of any material suitable for use in medical devices intended for orthopedic use, including use as a long-term implant. Examples of suitable types of materials include, but are not limited to, polymeric materials, blended materials such as carbon fiber reinforced polymers, and other materials. Examples of suitable polymeric materials include, but are not limited to, PAEK, CFR PAEK, PEKK, CFR PEKK, PEEK, CFR-PEEK, PEEK (90G, 450G, 12, 14), Polyamide, and PA66. Examples of suitable blended materials include, but are not limited to, PEEK-Carbon materials, CFR PAEK, CFR PEKK, CFR PEEK (90G CA30, 90G CA20, 450G CA30, 450G CA20, 12 CF20, 12 CF30, 14 CF30, 14 CF20), Polyamide CFR, PA66 CFR. 
     It is noted that the materials used in an orthopedic screw according to a particular embodiment can include additives, coatings, fillers, and/or other elements if desired. For example, antibiotics, bioactive glass, silver, copper, or another material that can reduce bacterial colonization of the orthopedic screw following implantation can be included in the material of the inner core member, the outer body member, or both. 
       FIG. 6  is a schematic representation of a method  5000  of manufacturing an orthopedic screw. A step  5010  comprises machining a member from a suitable precursor, such as a solid rod or cannula to form a distal thread on an external surface of the member between proximal and distal ends of the member. Another step  5012  comprises forming a series of cutting teeth on the proximal end of the member such that the series of cutting teeth lies on a plane that is parallel to the longitudinal axis of the member. An optional step  5014  comprises forming a proximal thread on the external surface of the member at an axial position between the distal thread and the proximal end of the member. Additional steps, such as step  5016 , which comprises finishing the medical device using suitable techniques or processes, can also be included. Another additional step  5018  comprises performing one or more surface treatments on the medical device, such as roughening, coating, and the like. 
       FIG. 7  is a schematic representation of another method  6000  of manufacturing an orthopedic screw. A step  6010  comprises machining a member from a suitable precursor, such as a solid rod or cannula to form a distal thread on an external surface of the member between proximal and distal ends of the member. Another step  6012  comprises forming a proximal thread on the external surface of the member at an axial position between the distal thread and the proximal end of the member such that the proximal thread includes a reverse cutting tooth in the first rotation of the proximal thread. An optional step  6014  comprises forming a series of cutting teeth on the proximal end of the member such that the series of cutting teeth lies on a plane that is parallel to the longitudinal axis of the member. Additional steps, such as step  6016 , which comprises finishing the medical device using suitable techniques or processes, can also be included. Another additional step  6018  comprises performing one or more surface treatments on the medical device, such as roughening, coating, and the like. 
     Those with ordinary skill in the art will appreciate that various modifications and alternatives for the described and illustrated examples can be developed in light of the overall teachings of the disclosure, and that the various elements and features of one example described and illustrated herein can be combined with various elements and features of another example without departing from the scope of the invention. Accordingly, the particular examples disclosed herein have been selected by the inventors simply to describe and illustrate examples of the invention are not intended to limit the scope of the invention or its protection, which is to be given the full breadth of the appended claims and any and all equivalents thereof.