Abstract:
A surgical assembly has a first section having a first hole with a smallest diameter and a second section having a threaded second hole with a minor thread diameter smaller than the smallest diameter of the first hole. The first hole encloses a center axis of the second hole and a clearance is provided between the first section and the second section. The assembly includes a screw member having a length for engaging the first hole and the second hole so as to bridge the clearance. The screw member has a first portion with a largest outer diameter smaller than or equal to the smallest diameter of the first hole, and a threaded second portion axially spaced from the first portion and configured to threadedly engage the second hole. A major thread diameter of the second portion is larger than the smallest diameter of the first hole.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims priority from European Patent Application No. 12003869.0 filed May 16, 2012, the disclosure of which is hereby incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     The present disclosure generally relates to an assembly for use in surgical procedures. In particular, a surgical assembly and a system comprising the surgical assembly are described. 
     When treating a bone fracture, bone fragments are typically aligned in a first step using, for example, a bone plate. The aligned bone fragments may then be tightened together by one or more surgical cables. To prevent sections of the one or more surgical cables from interfering with, for example, surgical instruments, a surgical assembly may be used to hold together the cable sections. 
     A conventional surgical assembly for this purpose comprises a C-shaped clamp with two clamping arms and a screw that is to be captively held by the clamp (see also  FIGS. 1   a  to  1   c ). The clamp has two coaxial threaded holes through its two arms. The screw is provided a cylindrical portion, a head at one end and a threaded portion at the other end. 
     In order to open the assembly for introducing cable sections, the screw needs to be unscrewed from the threaded lower hole so as to open a clearance between the two arms of the clamp. After screwing the screw again into the lower hole until its head abuts against the clamp, the clamp can be compressed by further screwing so that cable sections can be firmly held together. 
     The conventional assembly is bulky and requires a substantial space in the longitudinal direction of the screw. In order to overcome this drawback, the clearance of the clamp may be reduced. This in turn requires the threaded portion of the screw to be at least partly engaged with the threaded upper hole of the clamp in order for the clamping assembly to adopt the open position. As a consequence, a further drawback appears since the screw may unintentionally disengage from the assembly by movements or vibrations. 
     BRIEF SUMMARY OF THE INVENTION 
     Accordingly, there is a need for a surgical assembly which is small in size and where the screw does not easily disengage from the assembly unintentionally. 
     According to one aspect, a surgical assembly is provided, wherein the assembly comprises a first section having a first hole with a smallest diameter, a second section having a threaded second hole with a minor thread diameter smaller than the smallest diameter of the first hole, wherein the threaded second hole has a center axis enclosed by the first hole, a clearance between the first section and the second section, and a screw member having a length for simultaneous localization in the first hole and in the second hole so as to bridge the clearance, the screw member comprising a first portion with a largest diameter smaller than or equal to the smallest diameter of the first hole, and a threaded second portion axially spaced apart from the first portion along a longitudinal axis of the screw member and configured to threadely engage with the threaded second hole, wherein a major thread diameter of the second portion is larger than the smallest diameter of the first hole. As used herein, major and minor thread diameters may also be referred to as major and minor threads, respectively. 
     The first hole may be cylindrical or conical. The second hole may be cylindrical. The first and second holes may be through holes. Alternatively, the first hole may be a through hole and the second hole may be a blind hole. 
     The first hole may fully enclose the screw member around its circumference. Alternatively, the first hole may only partially enclose the screw member around its circumference but still prevent the screw member from laterally disengaging from the first hole. For example, the first hole may enclose the screw member around at least 200 degrees of its circumference (e.g., 270 or more degrees). 
     Furthermore, the threaded second portion may be located near a distal end of the screw member. A guiding structure may be provided at the distal end of the screw member for guiding the screw member into the first and/or second hole. Such a guiding structure may have a conical appearance with a largest outer diameter smaller than a minor thread diameter of the threaded second portion. 
     A length of the threaded second portion along the longitudinal axis of the screw member may be smaller than the clearance. The difference in length between the clearance and the extension of the threaded second portion may be (e.g., slightly) larger than the diameter of a surgical cable, for example, the difference may be 1 to 5 mm (e.g., 3 mm). The minimum clearance may be 1.5 thread pitch of the threaded second hole. The thread of the threaded second hole may extend over slightly less than the clearance. 
     The first portion may be unthreaded or threaded. In a threaded implementation, the major thread diameter of the first portion may be larger than the minor thread diameter of the second hole. The handedness and, optionally, the pitch of the threads of the first portion and of the second portion may be the same. In one implementation the threaded first portion is configured to threadedly engage with the threaded second hole. A major thread diameter of the threaded first portion may be smaller than the smallest diameter of the first hole. 
     The first hole may be unthreaded or threaded. In a threaded implementation, the handedness and, optionally, the pitch of the threads in the first section and second section may be the same. The threaded second portion may be configured to threadedly engage with the threaded first hole. In a threaded implementation, the smallest diameter of the first hole may be defined by a minor thread diameter of the threaded first hole. In a similar manner, the largest diameter of the first portion may be defined by a major thread diameter of the first portion (when threaded). The major thread diameter of the second portion may be larger than the minor thread diameter of the first hole. The largest diameter (e.g., the major thread diameter) of the first portion may be smaller than the minor thread diameter of the first hole. As an alternative to a thread, the first hole may be provided with structures which interfere, or engage, with the major thread diameter of the second portion but not with the largest outer diameter of the first section (the major thread diameter when threaded). 
     When the screw member bridges the clearance, a closed void may be defined by the first section, the second section, the screw member and a structure (e.g., a sidewall) connecting the first second and the second section. The closed void may be configured to accommodate one or more surgical cables. 
     In general, the surgical assembly may be configured to only serve holding purposes (e.g., for a surgical cable) or to further provide a clamping function. In the latter case the surgical assembly may thus constitute a clamping assembly wherein the first section and the second section may belong (e.g., constitute integral parts of) a clamp. The clamp may generally have a C-shape. 
     The first and second sections may be movable relative to each other so as to vary the clearance. This movability may be realized by a section of a flexible material and/or a pivot connection between the two sections. 
     A pivot connection may be realized as a springingly biased hinge which allows the two sections to be compressed or pulled apart to a certain degree defined by the spring. In the case a pivot connection is implemented, the clamp may or may not be of an elastically flexible material. Moreover, the hinge may constitute an integral part of the clamp. 
     The screw member may comprise a head. The head may have a radial extension larger than half of the smallest diameter of the first hole. The head can thereby prevent the screw member from moving longitudinally fully through the first hole. Alternative or additional structures for preventing the screw member from moving longitudinally relative to the first section may be realized. The head may be semi-spherical, cylindrical, polygonal, a cuboid or a wing-nut. Moreover, the head may comprise notches or any other structures at its outer circumference in order to provide a better grip to the operator. 
     As stated above, the first section and the second section may be relatively movable (e.g., with respect to the center axis of the second hole). Due to this, the clearance can be reduced or expanded. The clearance may be reduced by threadedly engaging the threaded second portion with the threaded second hole, contacting the head with the first section and screwing the screw member. This process may be referred to as clamping. Similarly, the clearance may be expanded to an unloaded position by screwing the screw member in an opposite direction. 
     Regarding the relationship of the first hole and the second hole, these two holes may be coaxial. Alternatively, the features of the surgical assembly may allow a certain offset and/or inclination between a center axis of the first hole and a center axis of the second hole. 
     According to a further aspect, there is provided a system comprising the surgical assembly and at least one surgical cable. The clearance may be configured to accommodate the surgical cable. The surgical assembly may be configured to enclose and/or clamp the at least one surgical cable around its circumference. 
     According to a further aspect, there is provided a manufacturing method for the surgical assembly. The method comprises the steps of tapping a temporary hole in the first section and the second hole with a first tap in one linear relative movement, tapping the first hole by machining the circumference of the temporary hole with a second tap, and cutting a thread in at least the second hole. The method may further comprise cutting a thread in the first hole in one linear relative movement when the cutting the thread in the second hole. Alternatively, or in addition, the method may comprise the steps of threading a temporary portion and the second portion of the screw member with a die in one linear relative movement, and machining the circumference of the temporary portion into the first portion (e.g., with a cutter) in one linear relative movement. 
     According to a further aspect, there is provided use of the assembly for clamping at least one surgical cable. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further details, advantages and aspects of the present disclosure will become apparent from the following example and embodiments taken in conjunction with the drawings, wherein: 
         FIGS. 1   a  to  1   c  show a clamping assembly according to an example useful for understanding the embodiments, wherein  FIG. 1   a  shows a side view of a screw member and  FIGS. 1   b  and  1   c  show a cross-sectional view of a clamping assembly comprising the screw member; 
         FIG. 2   a  shows a side view of a screw member according to an embodiment; 
         FIG. 2   b  shows a cross-sectional view of a clamp according to an embodiment; 
         FIGS. 3   a  to  3   c  show three different positions of the screw member relative to a first section and a second section of the clamp according to the embodiment; and 
         FIGS. 4   a  and  4   b  show a system comprising two surgical cables and the surgical assembly according to the embodiment in an open and closed position, respectively. 
     
    
    
     DETAILED DESCRIPTION 
     In the following, a surgical assembly and a system comprising the surgical assembly will be described. The same reference numerals will be used to denote the same or similar structural features. In the drawings the threads are only schematically shown, in particular with respect to their pitch, and do not correspond to actual realizations. 
       FIGS. 1   a  to  1   c  illustrate a conventional screw member  10  and a conventional clamping assembly  12  including the screw member  10 . As shown in  FIG. 1   a , the screw member  10  comprises a head  14 , a cylindrical, non-threaded first portion  16  and a cylindrical, threaded second portion  18 . The length of the first portion  16  along a longitudinal axis  20  of the screw member  10  is denoted  22 . The diameter of the first portion  16  is denoted  24 . The second portion  18  longitudinally extends along a length  26 . The threaded second portion  18  has a minor thread diameter  28  and a major thread diameter  30 . 
       FIG. 1   b  shows the clamping assembly  12  in a closed position. Here, a first section  32  and a second section  34  of a C-shaped clamp can be seen (the entirety of the clamp cannot be seen in  FIG. 1   a  or  1   b ). The first section  32  and the second section  34  each comprises a threaded hole  36 ,  38  each having a minor thread diameter  40  and a major thread diameter  42 . The two threaded holes  36 ,  38  are coaxial and their threads are identical and correspond to the threads  28 ,  30  of the screw member  10 . Consequently, the screw member  10  is adapted to be threadedly engaged with the upper threaded hole  36  as well as with the lower threaded hole  38 . 
     A clearance  44  is established between the first section  32  and the second section  34 . The clearance  44  is somewhat larger than the length  26  of the second portion  18 . 
     In the situation illustrated in  FIG. 1   b , the screw member  10  has been screwed down through the threaded upper hole  36  and screwed into the threaded lower hole  38  until the head  14  longitudinally abuts against a top surface of the first section  32 . Due to the fact that the diameter  24  of the first portion  16  of the screw member  10  is smaller than the minor thread diameter  40  of the threaded upper hole  36 , a clearance  46  is established between the first portion  16  of the screw member  10  and the minor thread diameter  40  of the threaded upper hole  36 . 
       FIG. 1   c  shows the clamping assembly  12  in an open position. As can be seen, the second portion  18  has been disengaged from the threaded lower hole  38 . The screw member is captively held between the first section  32  and the second section  34 . A clearance  48  is established between the lower end of the second portion  18  and a top surface of the second section  34 . In the illustrated situation, one or more surgical cables may be introduced through this clearance  48 . The surgical cables can then be enclosed by the clamping assembly  12  by screwing the screw member  10  back into the threaded lower hole  38  to the closed position as previously described and illustrated in  FIG. 1   b . Furthermore, a clamping force can be generated if desired by screwing the screw member to an extent that the first section  32  and the second section  34  are moved together, wherein the clearance  44  becomes smaller. 
     The above described clamping assembly is bulky and requires a substantial space in a longitudinal direction  50  of the threaded holes  36 ,  38 . In order to overcome this drawback, the nominal clearance  44  may be reduced. This in turn requires the second portion  18  to be at least partly engaged with the threaded upper hole  36  in order for the clamping assembly  12  to adopt the open position. As a consequence, a further drawback appears since the screw member  10  may then unintentionally disengage from the clamping assembly  12  by movements and/or vibrations of the clamping assembly  12 . 
       FIG. 2   a  shows a schematic side view of a screw member  52  according to an embodiment. The screw member  52  comprises a head  54  at its top end, a first portion  56  connected to the head  54  and a threaded second portion  58  at the lower distal end of the screw member  52 . In the present embodiments, the first portion  56  is threaded also and has a major thread diameter  60  and a minor thread diameter  62 . Furthermore, the first portion  56  extends along a distance  64  in a longitudinal direction  66  of the screw member  52 , wherein the second portion  58  is axially spaced apart from the first portion  56  along this longitudinal axis  66 . The second portion  58  has a major thread diameter  68  and a minor thread diameter  70  and extends along a length  72  in the longitudinal direction  66  which may correspond to 1.3 or more thread pitches. The major thread diameter  68  of the second portion  58  is larger than the major thread diameter  60  of the first portion  56 . 
       FIG. 2   b  shows a cross-sectional view of an embodiment of a C-shaped clamp  74  made from a material with elastic properties. A first section  76  and a second section  78  (connected by a flexible side wall of the C that acts as a hinge) constitute integral but opposite parts of the clamp  74 . Between the first section  76  and the second section  78 , a clearance  80  is established. A first hole  82  is arranged through the first section  76 . In this embodiment, the first hole  82  is a threaded through-hole comprising a major thread diameter  84  and a minor thread diameter  86 . 
     Through the second section  78 , a threaded second hole  88  is arranged. In this embodiment, the second hole  88  is concentric with the first hole  82 . As a result, a center axis of the first hole  82  coincides with a center axis  90  of the second hole  88 . The first hole  82  thereby also encloses the center axis  90  of the second hole  88 . The second hole  88  comprises a major thread diameter  92  and a minor thread diameter  94 . The major thread diameter  92  of the second hole  88  is equal to the major thread diameter  84  of the first hole  82 . However, the minor thread diameter  94  of the second hole  88  is smaller than the minor thread diameter  86  of the first hole  82 . The threads of the first hole  82  and the second hole  88  have the same pitch. The threads of the first portion  56  and the second portion  58  of the screw member  52  likewise have the same pitch (which corresponds to the pitch of the threads of the first hole  82  and a second hole  88 ). 
       FIGS. 3   a  to  3   c  show an embodiment of a surgical assembly  96  comprising the screw member  52  and the clamp  74  in three different relative positions between the screw member  52  and the clamp  74 . In these figures, only a limited cross-sectional area of the clamp  74  is illustrated. The screw member  52  is in turn illustrated with a schematic side view on the left hand side and a cross-sectional view on the right hand side. 
       FIG. 3   a  illustrates a closed position of the surgical assembly  96 . From the  FIG. 3  it can be seen that both the major thread diameter  68  of the second portion  58  and the major thread diameter  60  of the first portion  56  of the screw member  52  are larger than the minor thread diameter  94  of the second section  78 . The screw member  52  is threadedly engaged with the threaded second hole  88  by both its threaded second portion  58  and by a part of its threaded first portion  56 . Due to this engagement, the screw member  52  can be longitudinally displaced relative to the clamp  74  by rotation in a direction indicated by arrow  98 . 
     Referring to the first section  76  in  FIG. 3   a , it can further be seen that the major thread diameter  60  of the first portion  56  is freely smaller than the smallest diameter of the first hole  82 . In this case, the major thread diameter  60  of the first portion  56  is smaller than the minor thread diameter  86  of the first hole  82 . The screw member  52  has here been screwed in the second hole  88  until the head  54  abuts in the longitudinal direction  66  against an upper surface of the first section  76 . By screwing the screw member  52  further, the first section  76  and the second section  78  can be pulled closer to each other, thereby reducing the clearance  80 . 
     Referring to  FIG. 3   b , an open position of the surgical assembly  96  is shown. In this illustrated position, the screw member  52  is freely slidable in the longitudinal direction  66 , as indicated by arrow  100 , without needing to be rotated. The slideability is a result of the fact that the major thread diameter  60  of the first portion is smaller than the minor thread diameter  86  of the first hole  82 . 
     The screw member  52  is captively held and slidable between an upper position where the second portion  58  abuts against a lower surface of the first section  76  and a lower position where the second portion  58  abuts against an upper surface of the second section  78 . The position of the screw member  52  in  FIG. 3   b  is somewhat in between the upper and lower position. As can be seen, a clearance  102  is established between the lower end of the second portion  58  of the screw member  52  and the upper surface of the second section  78 . The maximum clearance  102  is accomplished when the screw member  52  is in its upper position. The clearance  102  can then be expressed as the length of the clearance  80  minus the length  72  of the second portion  58  (see  FIGS. 2   a  and  2   b ). 
     In the illustrated open position of  FIG. 3   b , it is highly unlikely that the threaded second portion  58  would unintentionally engage with any of the threaded holes  82 ,  88 . The captively held screw member  52  is therefore prevented from unintentional disengagement from the surgical assembly  96  by vibrations and/or movements of the same. 
       FIG. 3   c  illustrates disengagement of the surgical assembly  96 . As can be seen, the threaded second portion  58  is threadedly engaged with the threaded first hole  82 . Again, the threaded first portion  56  is not engaged with the threaded first hole  82 . From this illustrated position, the screw member  52  can be disengaged from the clamp  74  (or screwed into the open position as illustrated in  FIG. 3   b ) by rotation in the direction of the arrow  98 . 
       FIGS. 4   a  and  4   b  show a system  104  comprising the surgical assembly  96  according to the embodiment and one or more surgical cables  106 .  FIG. 4   a  illustrates the surgical assembly  96  in the open position (see also  FIG. 3   b ). Here, a surgical cable  106  can be introduced through the clearance  102  into a void  108 . The void can be closed by bringing the screw member  52  in the position illustrated in  FIG. 4   b.    
       FIG. 4   b  illustrates the surgical assembly  96  in the closed position (see also  FIG. 3   a ). As can be seen in the figure, the surgical cables  106  are enclosed in the void  108   108  defined by the screw member  52  and the clamp  74 . 
     During surgery, when a surgeon intends to keep together a plurality of surgical cables  106 , these cables  106  can be introduced through the clearance  102  of the surgical assembly  96  and accommodated in the void  108 . The surgeon may then screw the screw member  52  in the position illustrated in  FIG. 4   b  in order to close the surgical assembly  96  and thereby enclose (and, if necessary, clamp) the surgical cables  106  held in the void  108 . When the surgeon later on opens the surgical assembly  96  by unscrewing the screw member  52  into the open position, the surgical cables  106  can be removed and the surgeon does not need to worry about the screw member  52  disengaging from the clamp  74 . 
     Due to the fact that the major thread diameter  60  of the first portion  56  of the screw member  52  interacts with the second hole  88  but not with the first hole  82 , the surgical assembly  96  may be made smaller in size. This is because the clearance  80  of the clamp  74  needs only be larger than the length  72  of the second portion  58  of the screw member  52 . 
     The surgical assembly  96  can be manufactured quite easily. As for the clamp  74 , with a first tap by a drill in one linear relative movement, a temporary “first” hole may be tapped in the first section  26  when also tapping the second hole  88 . Then, with a second tap, the first hole  82  may be tapped by machining the circumference of the temporary “first” hole. For the second tap, a drill with a larger diameter compared to the first tap may be used. In a second step, a thread is cut in at least the second hole  88 . Advantageously, in one linear relative movement (and using a single thread cutting tool) a thread may be cut in the first hole  82  and in the second hole  88 . 
     As for the screw member  52 , in one step a thread cutting tool may be used to cut a thread over the full length of a shaft of the screw member  52 . In a second step, a machine operation may be applied to reduce the major thread diameter in the region of the first portion  56 . These two steps may be performed in any order. 
     While the present disclosure has been described with reference to an exemplary embodiment, it will be appreciated that the present invention is not limited to what has been described above. For example, it will be appreciated that the dimensions of the parts may be varied as needed. Accordingly, it is intended that the present invention may be limited only by the scope of the claims appended hereto. 
     Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims.