Abstract:
A bone screw apparatus, system, and method for assisting in the placement and alignment of a bone screw and for aligning bone are described. The present invention allows a surgeon to position a bone screw in a desired position and adjust a coupling element in a variety of positions and angles with respect to the bone screw.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an orthopedic implant. In particular, the present invention relates to a bone screw apparatus, system, and method. 
     2. Description of Related Art 
     Conventional bone screws and precursory polyaxial screws have found wide usage in orthopedic spinal surgery. Such devices are routinely used to address spinal instability and displacement, genetic or developmental irregularities, trauma, chronic stress, tumors, and disease. However, such designs are not without limitation. For example, conventional bone screws used with fixation rods , provide for minimal, if any variability in the placement of these rods relative to the position of the bone screw. Specifically, such conventional designs limit the positioning of the rod such that it is aligned with and/or above the screw. The rod itself makes direct contact with the screw head and is used to secure the screw into a coupling element in order to lock or secure the entire assembly into place. As a result, a surgeon is forced to try and position the screw taking into account the position of the rod and being generally unable to move the screw into the most optimal or strategic position. These limitations may cause the surgeon to reposition the bone screw in order to correctly align the system and as a result cause additional and unnecessary weakening of the bone due to, for example, additional screw holes created by the repositioning and/or stress on the bone screw interface by forcible repositioning. Further, while some bone screws allow for limited radial movement of the coupling element, medial-lateral variability of the placement of these rods relative to the screw is curtailed. 
     Accordingly, there exists a need for an improved bone screw alignment system that provides ease of use and modularity of assembly and that eliminates the problems set forth above. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention provides for an apparatus for coupling a bone screw to a connector, comprising; a housing that includes; an aperture for receiving a connector, a base having a slot configured for receiving at least one bone screw, and wherein the housing is configured to receive a fixation element. 
     The present invention also provides for a bone screw apparatus comprising; a coupling element that includes; a housing having; an aperture and a base having a slot; a connector extending through the aperture; a bone screw positioned within the slot; and a fixation element configured to secure the coupling element, connector, and bone screw in a fixed position. 
     The present invention further provides for a bone screw system comprising; a connector; and at least two bone screw apparatuses each comprising; a coupling element that includes; an aperture, wherein the connector extends through the aperture, and a base having slot; a bone screw positioned within the slot; and a fixation element configured to secure the coupling element, connector, and bone screw in a fixed position. 
     The present invention furthermore provides for a method for aligning and placing a bone screw system in bone, wherein the bone screw system includes; a connector; and at least a first and a second bone screw apparatus, wherein each bone screw apparatus has a coupling element having an aperture; and a base having a slot; a bone screw positioned within the slot; and a fixation element, wherein the connector extends through the aperture and wherein the fixation element is configured to secure the coupling element, connector, and bone screw in a fixed position, comprising; (a) positioning the first bone screw of the first bone screw apparatus in the slot of the first coupling element, (b) screwing the first bone screw into bone, (c) positioning the second bone screw of the second bone screw apparatus in the slot of the second coupling element, (d) screwing the second bone screw into a second bone, (e) aligning the coupling elements relative to the first and second bone screws, (f) extending the connector through each of the aligned coupling elements, and (g) securing the alignment of the first and second bone screw apparatuses in a fixed position. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       The foregoing summary, as well as the following detailed description of the embodiments of the invention, will be better understood when read in conjunction with the appended drawings. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown. In the drawings: 
         FIG. 1  is a perspective view of a bone screw apparatus embodiment of the present invention; 
         FIG. 2  is a perspective view of a coupling element of the bone screw apparatus of  FIG. 1 ; 
         FIG. 3  is an anterior perspective view of the coupling element of  FIG. 2 ; 
         FIG. 4  is a perspective view of an optional locking wedge for use with the bone screw apparatus of  FIG. 1 ; 
         FIG. 5  is a plan view of a polyaxial screw of the bone screw apparatus of  FIG. 1 ; 
         FIG. 6  is an anterior perspective view of a another embodiment of a bone screw apparatus of the present invention; 
         FIG. 7  is a perspective view of a further embodiment of the present invention; 
         FIG. 8  is an anterior perspective view of yet another embodiment of a bone screw apparatus of the present invention; and 
         FIG. 9  is an illustration of a bone screw system of the present invention affixed to bone. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As used herein, the following definitional terms apply. The term “anterior” and “posterior” mean nearer to the front or the back of the body respectively. “Proximal” and “distal” mean nearer and farther from the center of the body respectively. “Medial” and “lateral” mean nearer or farther from the median plane respectively. The median plane is an imaginary, vertical plane that divides the body into a right and left half. A coronal plane is an imaginary, vertical plane that divides the body into a front half and a back half. “Superior” and “inferior” mean above or below respectively. “Sagittal” means a side profile. 
     The present invention provides for a bone screw apparatus, system, and method for attaching a connector to a vertebra. 
     In an embodiment, as illustrated in  FIGS. 1-5 , the present invention provides for a bone screw apparatus  1  that includes a coupling element  2 , a fixation element  8 , a connector  30 , a locking wedge  40 , and a bone screw  50 . 
     As illustrated in  FIG. 2 , the coupling element  2  includes an upper housing  4  and a lower housing  6 . A fixation element  8  as shown in  FIG. 1  is inserted into the apparatus  1 . The coupling element  2 , can optionally be configured as a single housing only. In the present embodiment the fixation element is a locking screw  8  and the coupling element  2  has a connector  30  therethrough as shown in  FIG. 1 . 
     The upper housing  4  and lower housing  6  units can be an integral one-piece unit or separate units connected together by any acceptable means (e.g., taper lock, mechanical locking mechanism, screw, dovetail, bonding, and the like). The upper housing  4  has a cross-sectional shape perpendicular to axis A that is generally circular in shape but can also be any shape consistent with the intended use, such as a square, rectangle, oval, or the like. Further, the outer cross-sectional shape can vary from the cross-sectional shape of hole  10  extending therethrough. The upper housing  4  is configured to accommodate the fixation element  8 . In this embodiment, the upper housing  4  is configured to have a hole  10  that can receive and accommodate a locking screw  8  (e.g., a set screw). It is preferred that the interior surface  11  defining the hole  10  is threaded, but other embodiments such as snap-fit, cross-threading, interlocking, and dovetailing can also be used. 
     The lower housing  6  can be wider or narrower measured perpendicular to axis A in the longest dimension of the device than the upper housing  4 . In the present embodiment, the lower housing  6  is wider than the upper housing  4  and is generally configured as illustrated in  FIG. 2 and 3 . However, the shape of the lower housing  6  can be any other shape consistent with the intended use, such as a cross-sectional shape perpendicular to axis A that is circular, oval, or square so long as it can accommodate a slot  12 . 
     The lower housing  6  includes a slot  12  as illustrated in  FIG. 3 . The slot  12  can be positioned at the base  14  of the lower housing  6 . The base  14  can be integrally formed as part of the lower housing  14 , a separately formed and attached piece, or a prefabricated interchangeable insert having a slot  12 . 
     The base  14  has a posterior surface  16  (as shown in  FIG. 2 ) and an anterior surface  18 . The slot  12  is formed so as to extend between surfaces  16  and  18  and includes a plurality of slot positions  20 , including a center slot position  20   a . The slot  12  can alternatively include at least two slot positions, or a smooth peripheral, oval shaped or capsule shaped slot (i.e., a continuous slot). The slot  12  allows the coupling element  2  to be positioned more medially, laterally, superiorly, or inferiorly relative to the position of the bone screw  50 . This advantageously allows the surgeon to optimally position the bone screw  50  without being limited by the constraints of a connector&#39;s position. 
     In the present embodiment, the slot  12  includes five slot positions  20  and a center slot position  20   a  positioned directly below the threaded hole  10 . The slot positions  20  are circular in shape but can be any other shape consistent with the intended use. As illustrated in  FIG. 2 , the slot positions are overlapping and form notches  22 . The notches  22  facilitate positioning of the bone screw  50  into a bone by helping to prevent the bone screw  50  from moving to another slot position and guiding the bone screw  50  as the screw is being drilled into the bone. The notches  22  further provide for greater contact area between the bone screw  50  and the coupling element  2 , which improves the overall structural integrity of the bone screw apparatus  1  when in use. 
     The slot positions  20  and generally the edge of the slot  20  can optionally be configured to have or be contoured with a beveled edge  24  as shown in  FIG. 3  or a round edge (not shown). The edge  24  can be complementary in shape to that of the screw head  52 . The contoured edge facilitates movement (e.g., polyaxial movement) of the bone screw  50  within the coupling element  2  due to its generally complementary configuration to that of the curvate polyaxial screw head  52  (as shown in  FIG. 5 ) of the bone screw  50 . 
     The lower housing  6  can include an aperture  26  as shown in  FIG. 1 . The aperture  26  allows the placement of a connector, such as rod  30 , within the coupling element  2  such that the connector (e.g., rod  30 ) is generally centered within the coupling element  2 , allowing for greater stability when fastening the locking screw  8  into place. The aperture  26  can be configured so as to allow the connector to be perpendicular to plane B or at an angle relative to plane B, as illustrated in  FIG. 1 . The lower housing  6  can also include a visibility hole  28 . The visibility hole  28  advantageously allows the surgeon to be able to see the polyaxial screw  50  during assembly of the bone screw apparatus  1 . 
     As illustrated in  FIG. 2 , the lower housing  6  can optionally include angled ridges  32   a ,  32   b  positioned on the interior surface of the lower housing  6  of coupling element  2  for mating with angled flats  49   a ,  49   b  of an optional locking wedge  40  (as shown in  FIG. 4  and described below). Together, the angled flats  49   a ,  49   b  of the locking wedge  40  and angled ridges  32   a ,  32   b  form a wedge for mating and securing locking wedge  40  into place. The angled ridges  32   a ,  32   b  can be slightly steeper than the angled flats  49   a ,  49   b . The angled flats  49   a ,  49   b  help locking wedge  40  remain level and parallel with the base  14  of the coupling element  2 , to facilitate maintaining the alignment of the rod  30 . 
     In the present embodiment, the fixation element is configured to be a locking screw  8  as shown in  FIG. 1 . The fixation element, without limitation, can also be a cam lock, a taper lock, an interference fit, a locking tab, a tapered wedge, a locking collar, a dovetail, or any other configuration consistent with the intended use. The fixation element can be positioned anywhere within the coupling element  2  such that the fixation element provides a securing force to the bone screw apparatus  1  (e.g., secures the coupling element  2 , rod  30 , and the bone screw  50  in a fixed position). For example, the fixation element can be in an upper housing  4  or the lower housing  2  of the coupling element. Examples of such fixation elements are readily known in the art and a detailed explanation of such fixation elements is not necessary for a complete understanding of the present invention. 
     The present embodiment further includes a connector. In the present embodiment the connector is configured as a rod  30 . The connector, without limitation, can also be a cylindrical rod, a square rod, an oval rod, a rectangular rod, a hollow rod, or any other longitudinal member consistent with the intended use. 
     The present embodiment can optionally include a locking wedge  40  as configured and illustrated in  FIG. 4 . The locking wedge  40  includes an optional connector channel  42 , a tool hole  44 , and a concave channel  46  defined by the downwardly extending sides  48  of the locking wedge  40 . The locking wedge  40  can optionally include angled flats  49   a ,  49   b  to mate with angled ridges  32   a ,  32   b  on the lower housing  6  of the coupling element as discussed above. The angle of the angled flats  49   a ,  49   b  can be from 0 to about 89 degrees, and preferably about 35 to about 55 degrees. The locking wedge  40  can be made from a metal, alloy, polymer, or any combination thereof. 
     The connector channel  42  is formed on the posterior side of the locking wedge  40  and is configured to cradle or support and preferably mate with the surfaces of the rod  30  as it extends or passes through the device. The connector channel  42  can be indented into the locking wedge  40  as illustrated in  FIG. 4 . The configuration of the connector channel  42  allows the rod  30  to be positioned perpendicular to or at an angle relative to plane B, as shown in  FIG. 1 . The tool hole  44  is configured to be a circular through hole but can, without limitation, be any shaped through hole. The tool hole  44  can be positioned at the center of the locking wedge  40 , which helps a surgeon better manipulate the bone screw  50 . The size of the tool hole  44  is configured to accommodate a range of motion for a surgical tool, such as a screwdriver or drill (not shown), such that the screw head  52  (as shown in  FIG. 5 ) can be accessed by the surgical tool even when the bone screw  50  is at its maximum angulation. 
     The bone screw  50  of the present embodiment is illustrated in  FIG. 5 . Bone screw designs, like the surgical tools discussed above, are readily known in the art and a detailed explanation of them are not necessary for a complete understanding of the present invention. The present embodiment of the invention is not limited to polyaxial screws but can alternatively include non-polyaxial screws such as a posted bone screws or posted/polyaxial bone screws. 
     In the present embodiment, the bone screw  50  includes a head  52  and a threaded shaft  54 . The head  52  is configured to have a predominately curvate shape such as a spherical outer surface or a hemispherical shape. The head  52  further includes at least one recess  56  positioned on the top of the bone screw  50  to receive the application of a torque driving tool, such as a screw driver or drill. The recess  56  can alternatively be any configuration that cooperates with any suitable torque driving tool, such as a phillips head configuration, allen wrench, or the like. It is noted that the size of the head  52  and diameter of the threaded shaft can vary depending upon the individual circumstances and size requirements for a particular use or patient. As the size of the bone screw  50  changes, the size of other corresponding components of the bone screw apparatus  1  should change accordingly. 
     In an assembled state, the bone screw  50  is adjustably positioned within the lower housing  6  with its head  52  positioned within the lower housing  6  and in one of the slot positions  20 . The spherical shape of the screw head  52  allows the bone screw  50  to be angled relative to axis A. The locking wedge  40  is positioned within the lower housing  6  such that the concave channel  46  contacts the screw head  52 . The rod  30  is then positioned to extend through the coupling element  2  and in contact with or on the connector channel  42 . The shape of the connector channel  42  allows the rod  30  to be either perpendicular to or at an angle relative to the direction of the concave channel  46 . The locking screw  8  is then screwed (i.e. torqued down) into the threaded hole  10  of the upper housing  4  until sufficient contact is made with the rod  30 . As the locking screw  8  is screwed down, it pulls the coupling element  2  posteriorly. As the locking screw  8  is screwed down, it pushes anteriorly onto the rod  30  transmitting a securing force (e.g., an anteriorly directed force) onto the rod  30 . Thus, the locking screw  8  supplies an anterior force (i.e., a securing force) to the rod  30  which further transmits a securing force onto the locking wedge  40  which, as a result, secures the coupling element  2  and the bone screw  50  in a fixed position. Overall, the anterior force of the locking screw  8  and the resulting posterior force of the coupling element assembles the bone screw apparatus  1  into a secure and stable position regardless of which slot position  20  the bone screw  50  is located. 
     In operation, the coupling element  2  can be preassembled with the bone screw  50 , which is positioned loosely in a center slot position or the center of the slot  12 . Locking wedge  40  can be positioned inside the coupling element  2  such that angled flats  49   a ,  49   b  lie loosely on top of angled ridges  32   a ,  32   b  of coupling element  2 . The concave channel  46  of locking wedge  48  can contact the screw&#39;s head  52  as it is positioned in the coupling element  2 . A screw-driving tool (not shown) is then inserted through the coupling element  2  from above such that it passes through the upper housing  4  and through tool hole  44  of locking wedge  40 . The driving tool then secures bone screw  50  into the bone at a strategic place as determined by the surgeon. Once bone screw  50  is secured into the bone, coupling element  2  is able to move along a plane of the bone surface. That is, coupling element  2  is able to travel along the length of the slot  12  relative to the position of the bone screw  50 , and is able to rotate a full 360 degrees around the screw head  52 . Coupling element  2  can then be slid medio-laterally for optimal positioning, or rotated in the same plane if needed, so that upper housing  4  lines up with the rod  30  and the screw head  52  is positioned in one of the slot positions  20 . 
     Once screw head  52  is located in the proper slot position  20 , the surgeon then inserts rod  30  into the coupling element  2  via through hole  26 , wherein the rod  30  is positioned on connector channel  42  of locking wedge  40 . The surgeon can then use the screw-driving tool to fasten locking screw  8  onto the upper housing  4  of coupling element  2 . Locking screw  8  is then tightened or screwed down until locking wedge  40  engages the screw head  52  (e.g., by being compressed between rod  30  and the screw head  52 ). Coupling element  2  is pulled upwards as locking screw  8  is tightened so that screw head  52  is secured inside slot position  20  of slot  12 . 
     To remove the bone screw apparatus  1 , locking screw  8  can be unfastened and rod  30  removed. Locking wedge  40  is loosened by insertion of a tool (not shown) through tool hole  44 . A gripping tool (not shown) may then be used to push down on coupling element  2  and the coupling element  2  slid such that screw head  52  can be located in a center slot position, allowing for the screw driving tool to access and loosen the bone screw  50 . 
       FIG. 6  illustrates another embodiment of the present invention. In this embodiment the bone screw apparatus  100  includes a coupling element  102  having a continuous slot  104 . 
       FIG. 7  illustrates a further embodiment of the present invention. In this embodiment, the bone screw apparatus  200  includes a coupling element  202  having two bone screws  204   a ,  204   b  for screwing into a bone. 
       FIG. 8  illustrates yet another embodiment of the present invention. In this embodiment, bone screw apparatus  300  includes a coupling element  302  having a slot  304  with an anterior surface  306  and a posterior surface  308  (not shown). The slot  304  includes five slot positions  310 . The slot  304  includes a continuous beveled edge  312  configured to have three diameters D 1 , D 2 , and D 3  positioned along the edge between surfaces  306 ,  308 . D 1  is the largest diameter adjacent the posterior surface  308 . For illustrative purposes only, for a bone screw head having a 3.5 mm diameter head, D 1  can be 3.6 mm, which is larger than the diameter of the polyaxial screw head and allows the maximum amount of motion for the bone screw before it is secured into the bone. The beveled edge  312  then tapers down into a second diameter D 2  that measures, for example, 3.4 mm. This diameter D 2 , which is slightly smaller than that of the diameter of the polyaxial screw head, helps prevents the screw head from slipping through the slot positions  310 . Located below diameter D 2  is diameter D 3 . The diameter D 3 , for illustrative purposes only, is 3.5 mm that allows the screw to retain about 30 degrees angulation relative to the vertical. To increase this angulation, the diameter D 3  can be increased. 
     The present invention also provides for a bone screw system  400  as shown in  FIG. 9 . The bone screw system  400  includes a least two bone screw apparatuses  402   a ,  402   b  and a connector  404 . Each bone screw apparatus, for example  402   a , includes a coupling element having an aperture, a fixation element, an optional locking wedge, and at least one bone screw  406 . In operation, as shown in  FIG. 9 , the connector  404 , is attached to and extends through at least two bone screw apparatuses  402   a ,  402   b  that are each independently affixed to a bone. 
     The present invention further provides for a method for placing and aligning a bone screw system (as describe above) in bone. The method includes positioning a bone screw in a slot of a coupling element (as described in any of the above embodiments), inserting the bone screw into the bone, repositioning the coupling element relative to the bone screw, and securing the alignment and position of the coupling element, and bone screw. The method can further include positioning a connector (as described in any of the above embodiments) through the coupling element, and securing the alignment and position of the connector, coupling element, and bone screw. 
     The present invention also provides for a method for aligning bones. The method includes providing a bone screw system. The bone screw system includes at least two bone screw apparatuses that each include a coupling element having a connector therethrough and a slot, and a bone screw positioned within the slot, wherein the connector transmits a securing force securing the coupling element and bone screw in a fixed position. 
     The present invention advantageously allows for additional positioning freedom between a bone screw and a connector in multiple degrees of freedom including the medial, lateral, superior, and inferior directions. 
     It will be appreciated by those skilled in the art that changes can be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as defined by the appended claims.