Abstract:
An exemplary bone screw includes a proximal section including a first outer thread, a center section including a second outer thread, an unthreaded distal section on an opposite side of the center section from the proximal section, a channel extending from the proximal section to a distal opening of the unthreaded distal section, and at least one side opening extending from the channel to an outer surface of the unthreaded distal section. In some embodiments, the at least one side opening includes a cutting edge configured to cut a material as the bone screw is rotated in a direction for removing the bone screw. In other embodiments, the side opening is formed in at least one of the center section and the unthreaded distal section and includes a diameter that increases in a direction from the channel toward an outer surface of the center section or the unthread distal section. The exemplary bone screws may be used to treat bone fractures with or without a bone plate.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of pending International Application No. PCT/EP2014/071458, filed on Oct. 7, 2014, which designates the United States and claims priority to European Application No. 13187609.6, filed on Oct. 7, 2013. 
         [0002]    The entire disclosures of all of the above priority applications are incorporated herein by reference. 
     
    
     BACKGROUND 
       [0003]    1. Field of the Disclosure 
         [0004]    The disclosure relates to orthopedic devices used to reinforce bones in mammals and to a method of treating a humerus fracture. It specifically relates to cannulated bone screws and a method for using them. 
         [0005]    2. Description of Relevant Art 
         [0006]    Bone screws are used to reinforce bones by connecting at least two sections of a bone and/or by holding bone plates or other parts to a bone. It is often desirable to deliver medication and/or reinforcing material into the bone. A reinforcing material may be any kind of bone cement or bone graft or any other similar material. Specifically, delivery of bone cement into a bone material in close proximity of a bone screw may increase the mechanical retention of the bone screw within the bone material. 
         [0007]    Cannulated bone screws are known from U.S. Pat. No. 6,048,343. The screw has a bore forming a central channel connected to sideward channels for delivering of bone cement into the bone surrounding the screw. A sealed adaptor is provided for connecting the screw to a dispensing device. 
         [0008]    A further bone screw having a central channel is disclosed in U.S. Pat. No. 7,608,097 B2. A sleeve including a closed distal end can be inserted into the screw for selectively delivering a fluid to individual side holes connected to the central channel. 
         [0009]    A further bone screw is disclosed in EP 1 210 019 B2. The screw has an inner bore connected to at least one sideward channel. The bore has a closed end so that no bone cement can penetrate through the tip of the screw. 
         [0010]    A bone screw with a through hole and sideward openings for delivering a growth promoting agent is disclosed in US 2008/0269893. The screw is not intended to be removed from the bone. After the bone has grown into the structure of the screw, removal is impossible. 
         [0011]    U.S. Pat. No. 8,197,517 discloses a bone screw with a blind hole and sideward openings. If cement has been introduced into the screw, removal is no longer possible. 
         [0012]    In WO 2011/054122, a further bone screw having a blind hole and sideward openings is disclosed. The hole has inner structures or a slider to reduce the cross section and to improve distribution of material. Once cement has been introduced into the screw, removal is no longer possible. 
       SUMMARY 
       [0013]    The embodiments of this disclosure are based on the object of providing a bone screw, which has a channel or lumen for the delivery of a material like medication, therapeutic fluid, or any kind of bone cement or strengthening material. The bone screw should provide an increased retention force and a decreased removal torque, which allows a removal of the screw without further damaging the bone structure. Particularly, removal of the screw should be possible after the screw has been fixed to a bone by injecting cement or a similar material through the screw into the bone or after ingrowth of bone into the screw. Another object is to provide a bone screw, which allows a selective delivery of material at selected positions of the screw. For simplifying the selective application, a specific tool is provided. Another problem to be solved is to improve a method for fastening a bone plate to a bone and/or to reinforce a bone by using a bone screw. 
         [0014]    In a first embodiment, a bone screw has a proximal section, a center section, and an unthreaded distal section. The proximal section has an approximately cylindrical shape with a first outer thread. An outer thread is considered as a thread at the outside of the screw, basically for interfacing with a bone. In an alternate embodiment, the proximal section may have a conical shape having a first outer thread. This proximal section is intended for interfacing with a bone plate, which can be attached by means of the screw to the surface of a bone. The screw has a channel from the proximal section to the distal section, the channel defining a center axis. The screw may go through the distal section and end in a distal opening. The hollow channel is cylindrical and has a constant diameter at the center and the distal section. The diameter may be enlarged at the proximal section. The screw may also be used for fixing or holding bone parts together, without using a bone plate. Furthermore, the proximal section has at least one means for driving the screw. 
         [0015]    Next to the proximal section is a center section. The center section has a roughly cylindrical shape and includes a second thread. The diameter of the center section is smaller than the diameter of the proximal threaded section. The pitch of the second outer thread of the center section is larger than the pitch of the first outer thread of the proximal threaded section. This difference in pitches allows for tightly fixing a bone plate to a bone or for tying at least two bone fragments together. Alternatively, both pitches may be similar. At the distal side of the second outer thread, there may be at least one cutout for simplifying cutting of the outer thread into the bone. The center section may bear at least one or a plurality of sideward holes, which allow the flow of material from the channel or lumen into the bone. 
         [0016]    Next to the center section is a distal section. This distal section is unthreaded, has an approximately cylindrical shape, and has a centered distal opening connected to the channel of the screw for delivering material into the bone at the distal side. It may have further sideward oriented holes for delivering material into the bone. The distal section has the same diameter as the center section. It may be unthreaded. The distal section may have a closed end without a distal opening. 
         [0017]    Within the proximal threaded section, the center section, and the distal section, a channel or lumen is provided. This channel has a circular cross section. It has a constant diameter. This channel is connected to the sideward openings and to the distal opening of the distal section. It is further connected to a proximal opening at the proximal end of the screw. The channel may be used to deliver any material, for example a bone cement (permanent or bioresorbable), or a medication into the surrounding bone material. 
         [0018]    The side openings, which are provided in the center section and/or distal section, are provided by pairs resulting in through-holes through the screw. Therefore, two side openings are oriented at a 180° angle with respect to each other in a plane perpendicular to the center axis of the screw. In an alternative embodiment, there may be three or more side openings in the same plane. At least one opening has an elongated shape with respect to the center axis. The at least one opening may have an elliptical shape. Due to the larger extension or size of the opening parallel to the center axis, a larger total cross section of the opening can be achieved without significantly weakening the structure of the screw. There may be at least one cutting edge at at least one of the side openings. This cutting edge allows cutting of the material or bone cement when removing the screw by rotating counter-clockwise. The angle of the cutting edge is, in one embodiment, less than 90°. At least one of the side openings has a conical shape with increasing diameter towards the outside of the screw. This allows to form a cutting edge and to further increase the cross section for delivery of material into the bone. Here, the term cross section relates to the cross section available for delivery of material. 
         [0019]    The openings may be oriented into specific directions for directing the flow of material into the bone. They are oriented orthogonally to the center axis or towards the distal end to direct the flow of material into a distal direction. 
         [0020]    A further embodiment relates to a tool, such as a sleeve, which allows selective delivery of material into the bone surrounding the screw. The tool has a hollow shaft and a cylindrical shaft defining an inner channel for delivery of material. The outer diameter of the sleeve is adapted to fit into the channel of the bone screw. The sleeve may be inserted into different positions, which are in proximity to the distal opening or to any specific side opening to allow selective delivery of material into the surrounding bone. For precise adjustment of the insertion depth of the sleeve into the bone screw, there may be markers at the outside of the sleeve. There may be any other measuring tool for indicating the depth and/or the position of the sleeve inserted into the bone screw. The markers indicate the positions of the sleeve close to specific openings for delivering material through these openings. As there may be two openings at opposite sides of the lumen of the bone screw, the cross-section pointing outwards into the bone through the side opening is larger than the cross-section through the lumen of the bone screw. This will result in a significantly larger side flow, sideward through the side openings compared to the center flow through the remaining channel of the bone screw. This allows selective application of material to the bone. For example, material may be supplied through openings in the center section without filling the openings in the distal section. This allows the application of bone cement where needed. Such a selective application of bone cement simplifies later removal of the screw. 
         [0021]    Another embodiment relates to a tool kit comprising at least one bone screw as described herein and at least one tool which may be a sleeve as described herein. At least one sleeve is adapted to fit into the channel of at least one screw. Furthermore, the markers at the outside of the at least one sleeve are adapted to the at least one screw. 
         [0022]    A further embodiment relates to a method for fixing a bone screw as described herein to a bone. It includes the steps of drilling a hole into the bone, screwing the screw by rotation of the screw into the hole, inserting a sleeve into the channel of the screw, positioning of the sleeve into close proximity to at least one desired opening, and feeding a material through the sleeve via the screw into the bone. Another embodiment relates to an improved method for selectively supplying material like bone cement through a bone screw. It includes the steps of inserting a sleeve into the channel of the screw, positioning of the sleeve into close proximity to at least one desired opening, and feeding a material through the sleeve via the screw into the bone. Another embodiment relates to improving a method for fixing bone fragments and/or fixing a bone plate to a bone, such as a humerus, by fixing a screw as disclosed herein to the bone and/or the bone fragments and/or the bone plate. The process of delivering material may include the steps of delivering contrast agent for X-ray imaging, delivering of a rinsing solution, which may comprise NaCl, and finally delivering a bone cement. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]      FIG. 1  shows a first embodiment of a bone screw. 
           [0024]      FIG. 2  shows a sectional view of the first embodiment. 
           [0025]      FIG. 3  shows a further embodiment of the bone screw. 
           [0026]      FIG. 4  shows a sectional view of the further embodiment. 
           [0027]      FIG. 5  shows a sectional view of the distal section of an embodiment. 
           [0028]      FIG. 6  shows a further sectional view of the embodiment of  FIG. 5 . 
           [0029]      FIG. 7  shows a sectional view of the distal section of another embodiment. 
           [0030]      FIG. 8  shows the flow of material through the openings of the bone screw. 
           [0031]      FIG. 9  shows a top view of the bone penetration areas. 
           [0032]      FIG. 10  shows a material feeding sleeve. 
           [0033]      FIG. 11  shows a sleeve inserted into a bone screw. 
           [0034]      FIG. 12  shows a further embodiment of a bone screw with a plurality of side openings. 
           [0035]      FIG. 13  shows a sectional view of the previous embodiment. 
           [0036]      FIG. 14  shows another embodiment of a bone screw with a plurality of side openings. 
           [0037]      FIG. 15  shows a sectional view of the previous embodiment. 
           [0038]      FIG. 16  shows a humerus head with a bone plate attached by the bone screws. 
       
    
    
       [0039]    While the disclosure is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that the drawings and detailed description thereto are not intended to limit the disclosure to the particular form disclosed, but on the contrary, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims. 
       DETAILED DESCRIPTION 
       [0040]    In  FIG. 1 , a first embodiment of a bone screw  10  is shown. The bone screw  10  has a threaded proximal section  11 , a center section  12 , and a distal section  13 . The bone screw  10  further has a hollow channel  30  from the proximal section  11  through the distal section  13 , defining a center axis  19 . The proximal section  11  is approximately cylindrical shaped. It may also have a conical shape to simplify insertion. The proximal section  11  has a first outer thread  40 , which is designed to interface with a bone plate  150  as shown in  FIG. 16 . The center section  12  has a cylindrical shape and is at least partially threaded with a second outer thread  41 . The second outer thread  41  may have at least one cutout  44  to improve cutting of the outer thread into the bone material when inserting the screw. The pitch of the first outer thread  40  is less than the pitch of the second outer thread  41  to allow pressing of a bone plate  150  interfacing with the first outer thread  40  to a bone interfacing with the second outer thread  41 . The distal section  13  is unthreaded and has at least one side opening  33 ,  34 ,  35 . The side openings  33 ,  34 ,  35  have a conical shape with increasing diameters toward the outside of the bone screw  10 . 
         [0041]    In  FIG. 2 , a sectional view of the first embodiment is shown. The bone screw  10  has a channel or lumen  30 , which proximately is centered to the center axis  19 . The channel  30  passes through the proximal section  11 , the center section  12 , and the distal section  13 . It ends with a distal opening  31  at the distal section  13 . Furthermore, it is connected to at least one side opening  32 ,  33 ,  35 , which may be provided in the distal section  13  or the center section  12 . For rotating the screw, a means  42  for attaching a driving tool is provided for interfacing with a screwdriver, a wrench or any other tool. 
         [0042]    In  FIG. 3 , a further embodiment of the bone screw  20  is shown. This screw  20  has differently shaped side openings  36 ,  37 ,  39  compared to the embodiment of  FIG. 1 . Here, the openings are oriented towards the distal end to direct the flow of material in a distal direction. Furthermore, the length of the second outer thread  41  is shorter than the outer thread shown in  FIG. 1 . Although there are preferred embodiments, any of the parts like threads or side openings shown in this document can be combined without any limitation. 
         [0043]    In  FIG. 4 , a sectional view of a further embodiment of the bone screw  20  is shown. Here, the different structure of the side openings  36 ,  37  can be seen compared to the side openings  32 ,  33  of  FIG. 2 . The side openings shown in this figure provide a flow of material in a slightly more distal direction compared to the previous embodiment. Here a further side opening  38 , which is opposing side opening  39 , is shown. 
         [0044]    In  FIG. 5 , a sectional view of the distal section  13  of another embodiment is shown. The first side opening  32  is located opposite to a second side opening  33 . Above the side openings  32 ,  33 , there is a further side opening  34 , which basically has the same size as the other side openings, although it may have any different size. 
         [0045]    The side openings  32 ,  33  have heights  61 ,  62 . Reference sign  63  denotes the width of the channel  30 , which is identical to the diameter of the distal opening  31  in this embodiment. The cross-section of two opposing side openings  32 ,  33  given by the heights  61 ,  62  and the width  63  is significantly larger than the cross-section of the channel  30  in a distal direction given by its diameter  64 . This allows controlled sideward flow through the side openings  32 ,  33  and a minimal flow of material through the lumen  30 , as will be shown later in detail. 
         [0046]    In  FIG. 6 , a further detail of section A-A of  FIG. 5  is shown. The outer sides of the side openings  32 ,  33  form cutting edges  71 ,  72  which cut off the bone cement when rotating the bone screw for example for removal. These cutting edges  71 ,  72  significantly reduce the removal torque of the screw and help to avoid severe damage of the bone material. The angles  73 ,  74  of the cutting edges are less than 90° to achieve maximum cutting efficiency. In this embodiment, the cutting edges  71  and  72  are most important, as these have the first contact with the material inside the opening when rotating the screw counterclockwise for removal. Angles of less than 90 degrees may be obtained by offsetting the center axes  75 ,  76  of the openings  32 ,  33  to the center axis  19  of the screw, so that the axes do not cross. The angles  73 ,  74  can be defined between the tangents  77 ,  78  to the inner wall of the channel  30  and the leading edges of the body of the screw intersecting at the points  71 ,  72 . This embodiment applies to a screw which has to be turned counterclockwise for removal. 
         [0047]    In  FIG. 7 , a sectional view of the distal section  13  of a further embodiment is shown. Here, the side openings  35 ,  36 ,  38  have a slightly different direction. As shown before, here again, the cross-sections determined by the dimensions  61 ,  62 ,  63  of the side openings are larger than the cross-section  64  of the channel  30 . 
         [0048]    In  FIG. 8 , an example of the flow of material, like bone cement, into the bone  100  is shown. Due to the shape of the side openings  32 ,  33  of bone screw  10 , certain areas of the bone  100  are penetrated by a material like bone cement. There is a first penetration area  81 , which is supplied by the distal opening  31 . A second and third penetration area  82  and  83  is supplied by the side openings  32  and  33 , respectively. The penetration areas  81 ,  82 ,  83  overlap to achieve additional solidification. Due to the distal opening  31 , for achieving a first central penetration area  81 , an additional retention force of the bone screw can be obtained. This is significantly enlarged by connecting the penetration areas  82  and  83 . It is essential that there is no outer threaded area or even a single outer thread between the side openings  32 ,  33  close to the distal opening and the distal opening  31  itself, as this can prevent a smooth flow of the material over the surface of the screw, specifically in a high density of the bone material. Therefore, by avoiding any outer thread, a complete enclosure of the end of the distal section and therefore a better connection to be bone  100  can be achieved. For optimized filling with material, a first material is injected through the distal opening  31  by placing a sleeve  50  as shown later in close proximity to the distal opening  31 . In the next step, the sleeve  50  is slightly retracted for delivery of material through the side openings  32 ,  33  close to the distal opening  31 . 
         [0049]    In  FIG. 9 , a top view of the bone penetration areas  81 ,  82 ,  83  is shown. Here, the enhanced bone penetration and the connection of the penetration areas  82  and  83  by the central penetration area  81  can clearly be seen. 
         [0050]    In  FIG. 10 , a material feeding tool like a sleeve  50  is shown. This sleeve  50  may be inserted into bone screw  10  or  20 . It may bear at least one marker  52  for indicating the position of the sleeve  50  relative to the screw  10 ,  20  when inserted into the screw and therefore positioning the sleeve into the channel  30  of the bone screw. 
         [0051]    In  FIG. 11 , a sleeve  50  inserted into a bone screw  10  is shown. The sleeve  50  may be moved into the direction indicated by arrow  51  and pushed into the lumen or pulled outside to place the end of the sleeve  50  at any desired position, such as close to any desired opening. By this, the flow of material may be directed through the distal opening or any side openings. The indication of the height may be given by the markers  52 . Any material, such as a bone cement, may be supplied through the sleeve  50  into the bone screw  10 . The flow is indicated by arrows  53 ,  54 ,  55 . There are side flows  53 ,  54  through the side openings and a further center flow  55  into the direction of the channel  30 . Due to the larger cross-section of the side openings, side flows  53  and  54  are significantly larger than the center flow  55 . This allows a selective supply of material through individual side holes, where needed. An exemplary method may include first supplying bone cement through the distal section holes, and later supplying materials to remote holes in the center section. Here, other holes lying between the holes being used for supplying material to the bone may be unused. This may be the case, if there are solid bone segments and no fractured segments around the screw. 
         [0052]    In  FIG. 12 , an embodiment with a plurality of side openings is shown. The proximal section  11  and the distal section  13  are similar to the embodiment of  FIG. 3 . The center section  12  has further side openings  90 ,  91  and  92 . There is a further outer threaded section  93  between the side openings  92  and the side openings  90 ,  91 . Below the latter side openings is another outer threaded section  94 . There may be any combination of any one of the side openings shown in here with or without outer threaded sections in between. In general, there are only openings in unthreaded sections. 
         [0053]    In  FIG. 13 , the above embodiment is shown in a sectional view. Here, a further side opening  94 , which opposes side opening  92 , is shown. 
         [0054]    In  FIG. 14 , another embodiment with a plurality of side openings in the distal section  13  is shown. The side openings ( 101 - 106 ) are oriented into varying directions to allow for complete surrounding penetration of the material into the bone. 
         [0055]    In  FIG. 15 , the above embodiment is shown in a sectional view. Here some pairs of opposing side openings ( 35 ,  46 ;  105 ,  104 ) are shown. 
         [0056]    In  FIG. 16 , a humerus head  100  is shown with a bone plate  150  attached by the bone screws  10  and standard bone screws  110 . 
         [0057]    In this example, there is a fracture of the humerus head, which requires the use of bone screws  10 , having a lumen and delivering cement through the lumen of the bone screws  10  to further stabilize the fractured humerus head. The bone shaft is not fractured, therefore regular screws  110  may be used to further hold the bone plate  150  to the bone  100 . 
         [0058]    It will be appreciated to those skilled in the art having the benefit of this disclosure that this disclosure is believed to provide bone screws and a method for treating a humerus fracture. Further modifications and alternative embodiments of various aspects of the disclosure will be apparent to those skilled in the art in view of this description. Accordingly, this description is to be construed as illustrative only and is for the purpose of teaching those skilled in the art the general manner of carrying out the disclosure. It is to be understood that the forms of the disclosure shown and described herein are to be taken as the presently preferred embodiments. Elements and materials may be substituted for those illustrated and described herein, parts and processes may be reversed, and certain features of the disclosure may be utilized independently, all as would be apparent to one skilled in the art after having the benefit of this description of the disclosure. Changes may be made in the elements described herein without departing from the spirit and scope of the disclosure as described in the following claims.