Abstract:
An intramedullary nail has a driving end portion and a non-driving end portion with a longitudinal axis. The non-driving end portion comprises a locking hole arrangement with a sequence of four holes, i.e. spaced from non-driving to driving end a first hole, a second hole, a third hole, and a fourth hole. The first hole and the fourth hole have a corresponding first orientation and the second hole and the third hole have a corresponding second orientation.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a national phase entry under 35 U.S.C. §371 of International Application No. PCT/EP2011/004657 filed Sep. 16, 2011, published on Mar. 21, 2013 as WO 2013/037386, all of which are hereby incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     The invention generally relates to an intramedullary nail. Particularly, the invention relates to a locking hole arrangement provided at a non-driving end portion of an intramedullary nail, wherein this end portion of the nail is adapted to be positioned at a distal end portion of a humerus or a tibia, or at a proximal or at a distal end portion of a femur. 
     In general, the proximal end of the bone is the end of the bone being oriented toward the heart of the human body. The distal end of the bone is the end of the bone being oriented away from the heart of the human body. An intramedullary nail may be a femur nail, a humerus nail or a tibia nail, wherein the intramedullary nail comprises a non-driving end and a driving end. The non-driving end is the end of the nail which firstly enters the intramedullary channel of a bone. Entering the bone from the proximal end of the bone is denoted as antegrade insertion. Entering the bone from the distal end of the bone is denoted as retrograde insertion. Consequently, a nail adapted to be implanted from the proximal end of the tibia may be denoted as antegrade tibia nail, a nail adapted to be implanted from the distal end of the femur may be denoted as retrograde femur nail, a nail adapted to be implanted from the proximal end of the femur may be denoted as antegrade femur nail, and a nail adapted to be implanted from the proximal end of the humerus may be denoted as antegrade humerus nail. 
     As of today, locking of the non-driven end of intramedullary nails is problematic, namely because of the amount of radiation required during the determination of the position and orientation of transverse locking holes formed within the portion of the intramedullary nail when located in a marrow channel of a bone, to be able to insert locking screws through these holes. Furthermore, it is time consuming and ideally requires well-trained and experienced personal. Therefore, it has a significant influence of the overall operation room time required. 
     Currently, the situation is the following: A different locking pattern of the non-driving end portion of an intramedullary nail exists for each one of different nails, e.g. humerus, tibia, femur nails. Locking of the non-driving end portion of an intramedullary nail is performed mostly freehand. 
     U.S. Pat. No. 6,547,791 B1 discloses a tibia nail for retrograde implantation, comprising a tube with a continuous longitudinal bore and including a first anchoring portion with several cross-bores at its non-driving end portion, an adjoining connecting portion, a shank and a second anchoring portion at its driving end portion. The arrangement of the cross-bores permits to fix several fragments at their positions in the region of the tibia plateau, i.e. at the proximal end portion of the tibia. 
     BRIEF SUMMARY OF THE INVENTION 
     It may be seen as a need to make locking of the non-driving end portion of intramedullary nails easier. In general, it is of interest to shorten the operation room time which is beneficial not only for the patient under anaesthesia, but ultimately reduces costs. 
     This is achieved by the subject-matter of each of the independent claims. Further embodiments are described in the respective dependent claims. 
     In general, an intramedullary nail according to the invention comprises a driving end portion and a non-driving end portion with a longitudinal axis. The non-driving end portion comprises a locking hole arrangement with four holes, i.e. a first hole, a second hole, a third hole, and a fourth hole. The four holes are arranged as a sequence from the non-driving end of the intramedullary nail in a direction to the driving end of the nail, with the first hole arranged closer to the non-driving end than the second hole, the second hole arranged closer to the non-driving end than the third hole, and the third hole arranged closer to the non-driving end than the fourth hole. The first hole and the fourth hole have a corresponding first orientation and the second hole and the third hole have a corresponding second orientation. 
     According to an embodiment of the invention, the first orientation is a medio-lateral orientation and the second orientation is an anterior-posterior orientation. The medio-lateral orientation and the anterior-posterior orientation are substantially orthogonal with respect to each other. 
     Due to inaccuracies in determining the respective directions/orientations relative to a human body, orthogonal may include in this context an angle between 80 and 100 degrees. 
     It is noted that the orientation of the first and fourth holes of the locking hole arrangement at the non-driving end portion of the intramedullary nail may also be different to orthogonal relative to the orientation of the second and third holes, as long as this orientation is well defined and, thus, known. For example, the orientation may be 60 degrees or may be 45 degrees. 
     According to an embodiment of the invention, the first, second, third and fourth holes are respectively adapted for receiving a locking screw. 
     Such an arrangement of locking holes may be particularly usable at a non-driving end portion of an antegrade humerus nail, an antegrade tibia nail, an antegrade femur nail as well as a retrograde femur nail. 
     According to another embodiment of the invention, at least one of the first hole, the second hole, the third hole and the fourth hole is orthogonally oriented with respect to the longitudinal axis of the non-driving end portion. 
     It is noted that also an orientation not orthogonally with respect to the longitudinal axis may be provided. It may be, that all holes are inclined in a same way relative to the longitudinal axis, but also that at least one hole is inclined in another way as the other ones. 
     According to another embodiment of the invention, a distance between a centre axis of the first hole and the centre axis of the second hole corresponds to a distance between a centre axis of the third hole and a centre axis of the fourth hole. 
     The distances from a non-driving end of the intramedullary nail to a respective centre axis of a hole may be as follows: 
     A distance from the non-driving end to the centre axis of the first hole may be 4 to 44 mm, preferably 5 mm. 
     A distance from the non-driving end to the centre axis of the second hole may be 9 to 49 mm, preferably 10 mm. 
     A distance from the non-driving end to the centre axis of the third hole may be 24 to 64 mm, preferably 25 mm. 
     A distance from the non-driving end to the centre axis of the fourth hole may be 29 to 69 mm, preferably 30 mm. 
     According to a further embodiment of the invention, the intramedullary nail comprises a fifth hole, wherein a transponder may be arranged in this fifth hole. 
     The fifth hole may have the same orientation as the first hole and the fourth hole, and may be centred between the second hole and the third hole, as well as between the first hole and the fourth hole. The distance from the non-driving end of the intramedullary nail to the fifth hole may be 16.5 to 56.5 mm, preferably 17.5 mm. 
     According to another embodiment of the invention, the five holes are equally spaced from each other. 
     According to a further embodiment of the invention, the transponder may be adapted for generating a signal with a first preferred radiation direction in which the signal has specific symmetry characteristics, allowing the determination of the orientation of the first preferred radiation direction. 
     The signal symmetry characteristics may be the characteristics of a dipole. The first preferred direction may be the axis of the dipole. The dipole signal characteristics may be generated by a coil. 
     Furthermore, the transponder may be adapted for generating a signal being indicative for determining at least one of a spatial position and spatial orientation of the transponder so as to allow determining a respective spatial position and spatial orientation of at least one of the first, second, third and fourth holes, based on a predetermined spatial position and spatial orientation of the respective hole with respect to the transponder. 
     It is noted that the first preferred radiation direction may be aligned with the orientation, i.e. the centre axis of the fifth hole. A second preferred radiation direction may be orthogonal to the first preferred radiation direction. 
     According to yet another embodiment of the invention, at least one of the first hole, the second hole, the third hole, the fourth hole and the fifth hole comprises a thread. By means of the thread, a locking screw and alternatively a transponder may be reliably arranged and fixed within one of the holes. 
     According to another aspect of the invention, a combination of an intramedullary nail, as described above, with a targeting detector is provided, wherein the targeting detector is arranged to detect the signal generating by a transponder at the intramedullary nail. 
     The targeting detector may further be arranged to detect the orientation of the transponder, wherein the detector is adapted for signalling the correspondence of the orientation of at least one of the first hole, the second hole, the third hole and the fourth hole on the one hand, and a targeting orientation on the other hand, based on a predetermined spatial position and a spatial orientation of the respective first hole, second hole, third hole and fourth hole with respect to the transponder. 
     According to one embodiment, the targeting detector may be located at a tool for introducing a locking screw, helping a physician to localize the locking hole in the non-driving end portion of the intramedullary nail during a so-called freehand introduction of a locking screw. 
     On the other hand, the targeting detector may be located at a targeting device having a coupling portion adapted to be coupled to the driving end portion of the intramedullary nail. The targeting device may further comprise a drilling gauge with a drilling axis, for easily introducing a locking screw into a respective locking hole in the non-driving end portion of the intramedullary nail. 
     U.S. Pat. No. 7,686,818 B2, the disclosure of which is incorporated herein by reference, relates to a locking nail and stereotaxic apparatus thereof. Furthermore, US 2008/0170473 A1 the disclosure of which is also incorporated herein by reference, relates to a targeting system. These documents especially provide information concerning exemplary transponders and the use thereof. 
     The aspects defined above and further aspects, features and advantages of the present invention can also be derived from the examples of the embodiments to be described hereinafter and are explained with reference to examples of the embodiments to which the invention is not limited. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will now be detailed by way of an exemplary embodiment with reference to the attached drawings. 
         FIG. 1  illustrates an isometric view of an end portion of an intramedullary nail according to the invention. 
         FIG. 2  is a side view of an intramedullary nail according to the invention. 
         FIG. 3  is a section view of the end portion of the intramedullary nail according to the invention. 
         FIG. 4  is an isometric view of a hole including a thread according to the invention. 
         FIG. 5  is an isometric view of a hole including a transponder according to the invention. 
         FIG. 6  is a side view of a combination of an intramedullary nail and a targeting device. 
     
    
    
     It is noted that the illustration in the drawings is only schematically and not to scale. In different figures, similar elements are provided with the same reference signs. 
     DETAILED DESCRIPTION 
       FIG. 1  is an isometric view of a non-driving end portion  20  of an intramedullary nail  1 . The non-driving end portion  20  includes a longitudinal axis  21 , a non-driving end  22  and a longitudinal bore  23  arranged substantially parallel to the longitudinal axis  21 . The non-driving end  22  is formed as a blunt end of the intramedullary nail  1 . Furthermore, five holes are illustrated in  FIG. 1 . Starting from the non-driving end  22  of the non-driving end portion  20 , the intramedullary nail  1  comprises a first hole  31  with a centre axis  31   a , a second hole  32  with a centre axis  32   a , a fifth hole  35  with a centre axis  35   a , a third hole  33  with a centre axis  33   a , and a fourth hole  34  with a centre axis  34   a . As can be seen, the first hole  31 , the fifth hole  35  and the fourth hole  34  are orientated in a first orientation, and the second hole  32  and the third hole  33  are orientated in a second orientation. 
     Each of the centre axes of the holes is oriented orthogonal to the longitudinal axis  21 . Furthermore, the first hole  31  and the fourth hole  34  are orientated orthogonal to the second hole  32  and the third hole  33 . The fifth hole  35  is arranged in the middle between the first and fourth holes, orientated in the same direction as the first and fourth holes. The fifth hole  35  is adapted for receiving a transponder. Additionally, in  FIG. 1  the directions medio-lateral ML and anterior-posterior AP are illustrated. 
       FIG. 2  is a side view of the intramedullary nail in the medio-lateral direction. As depict in  FIG. 2 , a transponder  50  may be arranged in the fifth hole, in the middle between the first hole  31  and the fourth hole  34 . In this embodiment, the visual part of the transponder has a greater diameter than the respective diameter of the first and fourth holes. 
     Further illustrated in  FIG. 2  are the distances between some of the centre axes of the holes. The distance between the centre axis of the first hole  31  and the centre axis of the fourth hole  34  is indicated as d 1 . The distance between the centre axis of the first hole  31  and the centre axis  32   a  of the second hole  32 , as well as the distance between the centre axis  33   a  of the third hole  33  and the centre axis of the fourth hole  34  is indicated as d 2 , that is, the distance between the centre axes of the first and second holes is equal to that of the third and fourth holes. The distance between the centre axis of the fourth hole  34  and the centre axis of the fifth hole with the transponder  50  is indicated as d 1 /2, that is, the transponder is arranged in the middle between the first and fourth holes. 
     For the sake of completeness, a driving end portion  10  of the intramedullary nails  1  is illustrated in  FIG. 2 . It is noted that the driving end portion  10  may have any shape or size, depending as to whether the intramedullary nail  1  should be used as humerus nail, as tibia nail or as femur nail. 
       FIG. 3  is a section view of the non-driving end portion  20  along the plane A-A of  FIG. 2 . As can be seen in  FIG. 3 , the intramedullary nail  1  has a hollow shaft (due to the longitudinal bore  23 ) with a longitudinal axis  21  at its non-driving end portion  20 . Also in this figure, the first, fourth and fifth hole are illustrated parallel to each other and in a first orientation, within the plane of the figure, and the second and third holes are illustrated parallel to each other and in a second orientation, perpendicular to the plane of the figure. 
       FIG. 4  is an isometric view showing, in detail, one of the holes  31 ,  32 ,  33 ,  34  and  35  of the non-driving end portion of the intramedullary nail  1 . The hole in  FIG. 4  includes a thread  38  and a chamfer  39 . The chamfer  39  may facilitate an introduction of a screw or of a transponder into the hole. 
     It will be understood that the thread  38  may be provided in only one of or at least one of as well as in every one of the holes in the non-driving end portion of the intramedullary nail. As also depict in  FIGS. 1, 2 and 3 , the holes may also comprise only a chamfer  39  and no thread  38 . 
       FIG. 5  is a detailed view of the fifth hole  35  with a transponder  50  located within the fifth hole. Additionally, a first preferred radiation direction  51  of the transponder  50  and a second preferred radiation direction  52  of the transponder  50  are illustrated. The first preferred radiation direction  51  is substantially aligned with the centre axis of the fifth hole  35  and thus with the centre axis of the transponder  50 . The second preferred radiation direction  52  is orientated orthogonal to the first preferred radiation direction  51 . It is noted that the second preferred radiation direction may be within a plane being orthogonal to the first preferred radiation direction. 
       FIG. 6  shows a combination of an intramedullary nail  1  together with a targeting device  100 , wherein the targeting device  100  includes a portion  110  with a coupling portion  112 , wherein the coupling portion  112  may be adapted to be coupled to the driving end portion  10  of the intramedullary nail  1 . Furthermore, the targeting device  100  comprises a portion  120  including at least one drilling gauge  130  with a drilling axis  130   a.    
     The targeting device  100  is dimensioned so that the drilling axis of one of the drilling gauges  130  is aligned with, for example, the centre axis  33   a  of the third hole  33 , and that the drilling axis of another one of the drilling gauges  130  is aligned with the centre axis  32   a  of the second hole  32 . 
     The targeting device  100  may further comprise a targeting detector  150  arranged in a known relation to the holes of the non-driving end portion of the intramedullary nail, so that the targeting detector  150  may receive signals from the transponder  50  to be able to indicate the relative position of the respective drilling gauge relative to one of the holes of the locking hole arrangement in the non-driving end portion  20  of the intramedullary nail  1 . 
     It will be understood, that the targeting device  100  may also be orientated relative to the intramedullary nail so that drilling gauges may be aligned with the first or the fourth hole in the intramedullary nail. 
     While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive. The invention is not limited to the disclosed embodiments. 
     Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practising the claimed invention, from the study of the drawings, the disclosure and the appended claims. In the claims, the word “comprising” does not exclude other elements and indefinite article “a” or “an” does not exclude a plurality. The mere fact that certain measures are recited in mutual different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope. 
     LIST OF REFERENCE SIGNS 
     
         
         
           
               1  intramedullary nail 
               10  driving end portion 
               20  non-driving end portion 
               21  longitudinal axis of non-driving end portion 
               22  non-driven end 
               23  longitudinal bore 
               31  first hole 
               31   a  centre axis of the first hole 
               32  second hole 
               32   a  centre axis of the second hole 
               33  third hole 
               33   a  centre axis of the third hole 
               34  fourth hole 
               34   a  centre axis of the fourth hole 
               35  fifth hole 
               35   a  centre axis of the fifth hole 
               38  thread 
               39  chamfer 
               50  transponder 
               51  first radiation direction 
               52  second radiation direction 
               100  targeting device 
               110  first portion 
               112  coupling portion 
               120  second portion 
               130  drilling gauge 
               130   a  drilling axis 
               150  targeting detector 
             AP anterior-posterior 
             ML medio-lateral 
             d 1 , d 2  distance