Patent Publication Number: US-11045226-B2

Title: Screw element for use in spinal, orthopedic or trauma surgery and a system of such a screw element and a screw driver adapted thereto

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 15/830,858, filed Dec. 4, 2017, which is a continuation of U.S. patent application Ser. No. 14/685,433, filed on Apr. 13, 2015, now. U.S. Pat. No. 9,867,639, which claims the benefit of U.S. Provisional Patent Application Ser. No. 61/979,818, filed on Apr. 15, 2014, the contents of which are hereby incorporated by reference in their entirety, and claims priority from European Patent Application EP 14164692.7, filed on Apr. 15, 2014, the contents of which are hereby incorporated by reference if their entirety. 
    
    
     BACKGROUND 
     Field of the Invention 
     The invention relates to a screw element for use in spinal, orthopedic or trauma surgery, and to a screw driver adapted for use with the screw element. The screw element includes a drive portion for engagement with a screw driver, wherein the drive portion includes drive grooves for engagement with corresponding engagement protrusions of the screw driver, and guide grooves that are configured to guide the engagement protrusions of the screw driver into the drive grooves. The screw element can be used in particular in minimally invasive surgery and other procedures, such as minimal access surgery, where the visibility of and/or access to the operation site is reduced. 
     Description of the Related Art 
     In spinal surgery, surgical techniques are known that include a step of mounting a receiving part of a polyaxial pedicle screw onto the screw element in situ after placement of the screw element into the pedicle of a vertebra. For example, in a surgical technique known as interpedicular minimal access surgery, a small incision is made and several motion segments of the spine are treated through the small incision. First, the screw elements with ball-shaped heads are inserted into the pedicles using an instrument that holds the screw elements so that they do not accidentally detach from the instrument, and where the instrument also acts as a screw driver to insert the screw elements. The screw elements are inserted into the pedicles to a certain depth that might not be the final insertion depth for the screw elements. Then, the actual insertion depths are determined with the aid of, for example, an X-ray image, and thereafter the screw elements are more precisely adjusted to a final desired insertion depth on the basis of the X-ray image. Finally, the receiving parts are mounted onto the screw elements and a stabilization rod is connected to the receiving parts. 
     During the step of adjusting the insertion depth of the respective screw elements, a screw driver that is configured to engage a drive portion of the screw element is used. With known screw elements and drivers, locating the drive portion of the screw element may be difficult if visibility of the operation site is restricted or if the respective screw element is not visible at all. 
     SUMMARY 
     Embodiments of the present invention provide a screw element and a system of a screw element and a corresponding screw driver adapted thereto that allows for adjustment of an insertion depth of the screw element in a quick and safe manner. 
     The screw element permits the screw driver to more easily locate the corresponding drive portion on the screw element. In addition, the screw element facilitates insertion of the engagement portion of the screw driver into the drive portion of the screw element. Therefore, even when the screw driver is inserted at a slight incline relative to the screw element, the design of the drive portion of the screw element helps align the screw axis and the axis of the screw driver. Further, operation of the screw driver does not require any complex functions, which allows for easy and convenient handling. 
     The screw element may be a bone screw with a head that includes the drive portion. However, the screw element may also be a set screw that is used as a locking element in a receiving part of a polyaxial bone screw or in a bone plate. More generally, the screw element may be used to adjust the position of a screw that has already been placed or implanted when there is limited or no visibility at the operation site. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further features and advantages of the invention will become apparent from the description of embodiments by means of the accompanying drawings. In the drawings: 
         FIG. 1  shows a perspective view of a screw element and a portion of a screw driver adapted to a drive portion of the screw element according to a first embodiment of the present invention. 
         FIG. 2  shows an enlarged view of a detail of  FIG. 1 . 
         FIG. 3  shows a perspective view from a top of the screw element of  FIGS. 1 and 2 . 
         FIG. 4  shows a top view of the screw element of  FIGS. 1-3 . 
         FIG. 5  shows a cross-sectional view of the screw element of  FIGS. 1-4  along line A-A in  FIG. 4 . 
         FIG. 6  shows a side view of a screw driver with an engagement portion adapted to the drive portion of the screw element of  FIGS. 1-5 . 
         FIG. 7  shows an enlarged perspective view of the engagement portion of the screw driver of  FIG. 6 . 
         FIG. 8  shows a cross-sectional view of a screw element according to a modified embodiment of the present invention. 
         FIG. 9  shows an enlarged perspective view of a step of using the screw element and the screw driver according to the first embodiment. 
         FIG. 10  shows a perspective view of a step of adjusting an insertion depth of the screw element according to the first embodiment. 
         FIGS. 11 a -11 c    show cross-sectional views of steps of engaging the drive portion of the screw element with the engagement portion of the screw driver according to the first embodiment. 
         FIG. 12  shows a perspective view of a second embodiment of the screw element as part of a polyaxial bone anchor. 
         FIG. 13  shows a perspective view of a further application of the screw element in connection with a bone plate. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIGS. 1 to 5 , a screw element  1  according to a first embodiment includes a shank  2  with a bone thread (or a screw thread)  3  on at least a portion of the shank  2  and a head  4 . The shank  2  is configured to be inserted into a bone, for example, into a pedicle of a vertebra. A screw axis S is defined by the axis of the bone thread  3 . The head  4  has a spherical segment shape and a free end  5  on a side that is opposite to the shank  2 . A drive portion  6  that is configured to engage with an engagement portion of a screw driver is provided at the free end  5 . The drive portion  6  is explained in more detail below. 
     A system according to an embodiment of the invention includes the screw element  1  with the drive portion  6  and a screw driver  20  that has an engagement portion  30  adapted for engagement with the drive portion  6  of the screw element  1 . 
     As depicted in  FIGS. 3 to 5 , the drive portion  6  of the screw element  1  defines a first recess  7  that is located at a distance from the free end  5  and that has an inner wall with a substantially cylindrical main contour with a main inner diameter and with a cylinder axis coaxial with the screw axis S. A plurality of longitudinal drive grooves  8  are formed on the inner wall of the substantially cylindrical first recess  7 . The drive grooves  8  each has a bottom defining or extending along a longitudinal bottom line B d  that is parallel to the screw axis S (see  FIG. 5 ). A cross-section of each of the drive grooves  8 , taken along a plane perpendicular to the screw axis S, is substantially circular segment-shaped. From a top view, the drive grooves  8  are arranged circumferentially around the first recess  7  in a star-like manner, as shown in  FIG. 4 . In one embodiment, the first recess  7  and the drive grooves  8  together forma torx-shaped drive structure that is configured to be engaged by a torx-shaped engagement portion of the screw driver. An upper end  7   a  of the recess  7  is positioned at a distance from the free end  5  of the head  4 . An axial depth from the upper end  7   a  to a lower end  7   b  of the first recess  7  substantially corresponds to a depth of usual drive recesses for screw elements of this type. In other words, the size of the first recess  7  with the drive grooves  8  is sufficient for applying a necessary torque for inserting or advancing the screw element  1 . 
     Between the first recess  7  and the free end  5  is a second recess  9  that conically tapers and narrows from the free end  5  towards the first recess  7 . A lower diameter of the second recess  9  may be slightly larger than the main diameter of the first recess  7  and an upper diameter of the second recess  9  is greater than the lower diameter of the second recess  9 . The depth of the second recess  9  in the axial direction corresponds to approximately one fifth to one third of the depth of the first recess  7 , preferably between one fourth and one third of the depth of the first recess  7 . The second recess  9  provides an enlarged bevelled surface that facilitates insertion of the engagement portion  30  of the screw driver  20  into the drive portion  6 . 
     A plurality of guide grooves  10  are provided in the wall defining the second recess  9  at positions corresponding to the positions of the drive grooves  8  in the first recess  7 . Each of the guide grooves  10  has a bottom defining or extending along a longitudinal bottom line B g  that is parallel to the screw axis S and also parallel to the bottom line B d  of the corresponding drive groove  8 . The bottom lines B g  of the guide grooves  10  are farther away from the screw axis S than the bottom lines B d  of the drive grooves  8  are from the screw axis S in a radial direction. Hence, the guide groove  10  is arranged at an axial position that is closer to the free end  5  and also extends farther from the screw axis S in the radial direction than the corresponding drive groove  8 . Due to the bevelled surface of the second recess  9 , the depth of the guide grooves  10  gradually increases from the free end  5  towards the guide groove  8  relative to the second recess  9 . This allows for more precise guiding of an engagement protrusion  31  of the screw driver  20  into the first recess  7  while simultaneously facilitating the engagement of the engagement protrusion  31  with the outermost portion of the guide groove  10  at or near the free end  5 . 
     As can be seen from the top view of  FIG. 4 , each of the guide grooves  10  has a greater width than each of the drive grooves  8 . A transverse width of each of the guide grooves  10  decreases along a radial direction from the screw axis S towards the bottom line B g , and due to the tapering of the second recess  9 , a maximum width of each of the guide grooves  10  also decreases in a direction towards the free end  5 . 
     The guide grooves  10  connect to (or are in communication with) the drive grooves  8  through an intermediate section (or an inclined shoulder)  11  with a bevelled wall  11   a  that conically narrows towards the drive grooves  8 . The intermediate section  11  may have a considerably smaller axial height than the axial heights of the first recess  7  and the second recess  9 . Accordingly, the intermediate section  11  and the guide grooves  10  form pocket-like recesses that catch and guide the engagement protrusions  31  of the screw driver  20  into the guide grooves  8 . 
     As depicted in  FIGS. 6 and 7 , the screw driver  20  includes a drive shaft  21 , a handle  22  at one end of the drive shaft  21  and the engagement portion  30  at the opposite end of the drive shaft  21 . The engagement portion  30  has a substantially cylindrical main contour that fits into the first recess  7 , and longitudinally extending rib-like engagement protrusions  31  that are sized to engage the drive grooves  8  to apply torque onto the screw element  1 . The engagement portion  30  is bevelled towards a free end surface  32  of the engagement portion  30 . The free end surface  32  is substantially circular. In addition, the engagement protrusions  31  each have a bevelled front end surface  31   a . The length of the bevelled front end surface  31   a  of the engagement projections  31  corresponds substantially to the length of the conical surface of the second recess  9  of the drive portion  6  of the screw element  1 , between the free end  5  and the intermediate portion  11 . The bevelled front end surface  31   a  may have the same angle of inclination as the conical recess  9  or the slanted wall  11   a  of the intermediate portion  11 . Such an enlarged bevelled surface facilitates easier location of the drive portion  6  of the screw element  1  even in instances where there is limited visibility or no visibility at the operation site. 
     A modified embodiment of the screw element with a modified drive portion  6  is shown in  FIG. 8 . All parts and portions that are identical to the first embodiment are marked with the same reference numerals and the descriptions thereof will not be repeated. The modified embodiment of the screw element differs in the shape of the intermediate portion. In this embodiment, the intermediate portion  11 ′ is formed by a rounded wall  11   a′.    
     Referring now to  FIGS. 9 and 10 , the application of the screw element and the screw driver according to the first embodiment will be explained. In  FIG. 9 , two screw elements  1  have already been inserted into the pedicles of two vertebrae  100 . Each of the screw elements  1  includes the drive portion  6  as described above. The insertion depths of the screw elements  1  are further adjusted with the screw driver  20  by engaging the engagement portion  30  with the corresponding drive portions  6  of the screw elements  1 . Due to the design of the drive portion  6  of the screw element  1  and the engagement portion  30  of the screw driver  20 , the engagement portion  30  and the drive portion  6  can be quickly and easily engaged, even if there is limited or no visibility at the operation site. Therefore, it is possible to adjust multiple pedicle screws in a short time. 
     Referring now to  FIGS. 11 a , 11 b , and 11 c   , the interaction between the engagement portion  30  of the screw driver  20  and the drive portion  6  of the screw element  1  is shown in more detail. As depicted in  FIG. 11 a   , the screw driver  20  may approach the screw element  1  at an incline relative to the screw axis S. As further shown in  FIGS. 11 a  and 11 b   , the engagement portion  30  of the screw driver  20  may first engage the conical second recess  9 . When the engagement protrusions  31  of the engagement portion  30  of the screw driver  20  begin to engage the guide grooves  10 , the screw driver  20  is automatically aligned with the screw element  1  while penetrating or advancing further into the drive portion  6 . The guide grooves  10  and the intermediate portion  11  guide the engagement portion  30  into the drive grooves  8 , so that the screw element  1  and the screw driver  20  become aligned and connected in a form-fit manner to each other. Then, torque can be applied with the screw driver  20  onto the screw element  1 . Due to the decreasing depth and width of the guide grooves  10  towards the free end  5  and the bottom lines B g , respectively, the engagement portion  30  can be easily rotated until the engagement protrusions  31  locate and engage the engagement grooves  10 . 
     A second embodiment of a screw element is explained with reference to  FIG. 12 . Parts and portions that are the same or substantially the same as the previous embodiments have the same reference numerals and the descriptions thereof will not be repeated. In the embodiment of  FIG. 12 , the screw element is a set screw  40  that is used in a polyaxial bone anchoring device  50 . The polyaxial bone anchoring device  50  is shown only in an exemplary manner; many different designs of such polyaxial bone anchoring device may be contemplated. The polyaxial bone anchoring device  50  includes a screw element  1 ′ that has a spherical segment-shaped head (not shown) and a drive portion. The drive portion may be a known drive portion, such as, for example, a known torx-shaped drive portion or a polygon-shaped drive portion, or may be a drive portion  6  according to the previously described embodiments. The screw element  1 ′ is pivotably connected to a receiving part  51  that includes a seat to hold the head of the screw element  1 ′ in a ball and socket manner. A pressure element (not shown) may also be provided to exert pressure onto the head. The receiving part  51  also includes a substantially U-shaped recess  52  that is configured to receive a rod  200  therein. The rod  200  may be connected to a plurality of bone anchoring devices. To lock the rod  200  in the receiving part  51  and a pivot position of the head relative to the receiving part  51 , a locking element in the form of a set screw  40  is used that cooperates with a thread provided in the receiving part  51 . Once the head and the rod are locked, further adjustments may become necessary. To make such adjustments, the set screw  40  has to be loosened and tightened again after correcting the angular position of the receiving part  51  relative to the head or after correcting the position of the rod  200 . For such adjustments, the screw driver  20  that cooperates with the drive portion  6  in the set screw  40  may be used. Hence, the adjustments can be performed more quickly and easily. 
     It should be noted that a set screw having the engagement portion  6  could also be used for other types of bone anchoring devices, for example, for a monoaxial bone anchor in which the screw element and the receiving part are fixed relative to each other. 
     A further application is shown in  FIG. 13 .  FIG. 13  depicts a bone plate  60  that may be used with the screw elements  1 , for example, in orthopedic and trauma surgery to immobilize broken bone parts. The screw elements  1  can be the same or similar to those discussed with respect to  FIGS. 1 to 5 and 8 , where the head of each screw element  1  includes the drive portion  6 . The head may have a spherical segment shape so that the screw element  1  can be placed and positioned within a hole of the bone plate  60  at various angles. Alternatively, the head may have a shape that limits positioning of the screw element  1 , for example, to a fixed angle with respect to the bone plate  60 . When implanting the bone plate  60 , the insertion depth of the screw elements  1  may need to be adjusted. These adjustments may be made by using the screw element  1  with the drive portion  6  and a corresponding screw driver  20 . In a still further modification, a locking element may be provided in the holes of the bone plate  60  to prevent pull-out of the screw elements, where the drive portion  6  is formed on the locking elements. 
     Further embodiments and modifications of the previously described embodiments may also be contemplated. For example, the sizes and the angles of the bevelled surface of the second recess  9 , of the guide grooves  8 , as well as of the intermediate portion  11 ,  11 ′ can be varied. The wall  11   a ,  11   a ′ of the intermediate portion  11 ,  11 ′ may also have any shape that is configured to guide the engagement portion  30  of the screw driver  20  into the first recess  7 . 
     In the embodiments shown, an even number of drive grooves  8  are shown, and each drive groove  8  is positioned opposite to another drive groove  8  in the drive portion  6 . However, an odd number of drive grooves may also be contemplated, and one drive groove may not be opposite to another drive groove in the drive portion. This may also apply to the corresponding guide grooves. 
     In addition, instead of the torx-shape of the drive grooves, a polygonal shape of the first recess may also be contemplated. In such a case, the corners of the polygon may be considered the drive grooves. 
     In some embodiments, the respective bottom lines of the drive grooves and the guide grooves may not align and instead may be arranged in a twisted configuration around the screw axis. Also, the respective bottom lines may not be exactly parallel to the screw axis in some embodiments. 
     While the present invention has been described in connection with certain exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but is instead intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims, and equivalents thereof.