Patent Publication Number: US-2020275960-A1

Title: System and Method for Bone Fixation

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 13/723,902, filed Dec. 21, 2012, which is fully incorporated herein by reference. 
     This application also claims the benefit of U.S. Provisional Application Ser. No. 61/579,318, filed Dec. 22, 2011, which is fully incorporated herein by reference. 
    
    
     FIELD 
     This disclosure relates to biological medical devices and methods, and particularly to biological medical implants and methods for bone fixation. 
     BACKGROUND 
     In many circumstances, it may be desirable to couple two or more bone segments together. For example, a single bone may be damaged in two or more portions and/or two or more adjacent bones may be out of alignment with respect to each other. The joint between two bones may have wear or other problems. In either situation, it may be beneficial to couple and/or secure the bones/bone segments together such that the bones/bone segments are generally anatomically aligned with respect to each other. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Features and advantages of the present invention are set forth by description of embodiments consistent with the present invention, which description should be considered in conjunction with the accompanying drawings wherein: 
         FIG. 1  is a cross-sectional view exploded view of a fixation system consistent with one embodiment of the present disclosure; 
         FIG. 2  is a cross-sectional view of the assembled fixation system of  FIG. 1 ; 
         FIGS. 3-8  illustrate various steps of securing two bones together using a fixation system consistent with the present disclosure; 
         FIGS. 9 a -9 b    illustrate various views of a fixation system consistent with another embodiment of the present disclosure; 
         FIGS. 10 a -10 b    illustrate various views of a fixation system consistent with yet another embodiment of the present disclosure; 
         FIGS. 11 a -11 d    illustrate various views of a fixation system consistent with yet a further embodiment of the present disclosure; 
         FIGS. 12 a -12 d    illustrate various view of a fixation system consistent with yet a further embodiment of the present disclosure; 
         FIG. 13  is a cross-sectional exploded view of another fixation system consistent with the present disclosure; 
         FIG. 14  generally illustrates one embodiment of a fixation system securing two bones in a foot consistent with one embodiment of the present disclosure; and 
         FIG. 15  generally illustrates one embodiment of a fixation system securing two bones in a hand consistent with one embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     By way of summary, one embodiment of the present disclosure may feature a fixation system and method for coupling together two bone or bone segments. The fixation system may include a first and a second fixation element (e.g., but not limited to, a screw) and an interconnect. The first and second fixation elements are coupled to a first and second bone, respectively, and each includes a tapered cavity. The interconnect includes a first and a second tapered protrusion configured to be frictionally received in the tapered cavities of the first and second fixation elements, respectively. Once assembled, the frictional forces between the tapered surfaces form a frictional connection which generally locks the position of the first and second fixation elements together with respect to each other (though the fixation system may also be configured to allow some movements relative to each other). 
     Turning now to  FIGS. 1 and 2 , one embodiment of a fixation system  10  is generally illustrated in an unassembled (i.e., exploded) cross-sectional view (see  FIG. 1 ) and an assembled cross-sectional view (see  FIG. 2 ). The fixation system  10  includes a first and a second fixation element  12 ,  14  as well as an interconnect  16 . As described herein, the fixation system  10  may be used to couple and/or secure to bones and/or bone segments (collectively generally referred to as simply bones for ease of reference) together with respect to each other. The fixation system  10  may therefore be used to arrange or position the bones in a generally anatomically alignment. As used herein, the term “generally anatomically alignment” is intended to mean a positioning of the bones corresponding to the generally accepted medical definition. The term “generally anatomically alignment” may therefore allow for some deviation based on the patient&#39;s overall condition, the skill of the surgeon, and pathology being treated. 
     In the illustrated embodiment, the first fixation element  12  is configured as a screw  18 . According to one embodiment, the screw  18  includes a body portion  20  having one or more external threaded portions  22  configured to threadably engage with a portion of a first bone. The threaded portion  22  may include a self-taping thread. While the first fixation element  12  is shown having an external threaded portion  22 , the body  20  of the first fixation element  12  may alternatively (or in addition) include one or more ribs or protrusions configured to engage the bone to secure the first fixation element  12  to the bone. A portion of the body  20  may have a tapered configuration which decreases from a first end  24  (e.g., a proximal end) to a second end  26  (e.g., a distal end). 
     At least a portion of the body  20  (e.g., but not limited to, the proximal end  24 ) defines a first cavity  28 . The first cavity  28  may include a generally cylindrical region  30  having a tapered inner surface/sidewall  32 . The tapered sidewall  32  decreases in diameter from the opening  34  of the cavity  28  towards the distal end  26 . As described herein, the opening  34  of the cavity  28  is configured to receive a corresponding tapered portion of the interconnect  16  to form a frictional interference connection/coupling as generally illustrated in  FIG. 2 . 
     The proximal end  24  may also include one or more notches  36 . Consistent with the illustrated embodiment, the screw  18  may be rotatably driven, i.e., screwed, into the bone using a driver (not shown for clarity) configured to engage the notches  36  to rotate the screw  18 . Alternatively (or in addition), the first cavity  28  may include a keyed region  38  configured to engage with a corresponding keyed region of the driver to rotate the first fixation element  12  into the bone. 
     The second fixation element  14  is configured to be secured to a second bone and may generally correspond to the first fixation element  12 . For example, the second fixation element  14  may be the same as the first fixation element  12 . Alternatively, the second fixation element  14  may have a different diameter, length, pitch, taper, length of cannulated passage, and/or the like. The dimensions of the first and second fixation elements  12 ,  14  will depend on the intended application and related size of the first and second fixation elements  12 ,  14  dimensions and condition of the first and second bones to be coupled together. For example, the dimensions of the first and second fixation elements  12 ,  14  may be generally about 5 mm in diameter at the proximal outer diameter, tapering down over the 12 mm length of the screw to a 2.5 mm diameter at the distal outer diameter. The interconnect  16  may be approximately 2 mm in diameter and may vary from 6 mm to 13 mm in overall length. 
     The interconnect  16  is configured to couple the first and second fixation elements  12 ,  14 , and therefore the first and second bones. The interconnect  16  includes a first and a second generally cylindrical region  38 ,  40  each having a tapered external surface/sidewall  42 ,  44 , respectively. The tapered sidewalls  42 ,  44  have a taper which generally corresponds to the tapered sidewalls  32  of the first and second fixation elements  12 ,  14 , respectively, to form a frictional or interference fit. In particular, when the interconnect  16  is received within the first and second fixation elements  12 ,  14 , the precision tapered sidewalls  32  of the first and second fixation elements  12 ,  14  abut against the precision tapered sidewalls  42 ,  44  of the interconnect  16  so closely that the friction between the sidewalls  32 ,  42 ,  44  mates the first and second fixation elements  12 ,  14  to the interconnect  16  as generally illustrated in  FIG. 2 . 
     The interconnect  16  may optionally include one or more shoulders, protrusions, or the like  46 . The shoulder  46  extends radially outwardly from the body  48  of the interconnect  16 . According to one embodiment, the shoulder  46  extends circumferentially around the entire perimeter of the body  48 . Alternatively, the shoulder  46  may extend radially outwardly around a portion of the body  48 . The shoulder  46  may separate the first and second sidewalls  42 ,  44  as generally illustrated  FIG. 1  and may limit the distance which the interconnect  16  may be inserted into a cavity  28  of fixation elements  12 ,  14  as generally illustrated in  FIG. 2 . 
     The interconnect  16  may also optionally define one or more internal cavities  49   a ,  49   b . As described herein, the internal cavities  49  may be configured to receive an alignment device to facilitate alignment of an adjacent fixation element (e.g., the second fixation element  14 ). 
     Turning now to  FIGS. 3-8 , one embodiment of a method for coupling a first and a second bone together using a fixation system  10  consistent with at least one embodiment of the present disclosure is generally illustrated. In particular, an end  50  of a first bone  52  may be prepared as generally illustrated in  FIG. 3 . For example, a portion of the end  50  of the bone  52  may be removed to provide additional space for the fixation system  10  and/or to align the bone  52  with respect to the adjacent bones. Optionally, a pilot hole or the like  54  may be formed in the end  50  of the bone  52 . The pilot hole  54  may be formed using a drill and/or a guide wire (not shown). The pilot hole  54  in the bone  52  may be configured to receive a portion of the first fixation element  12 . For example, the pilot hole  54  may be configured to receive the first fixation element  12  and may have a diameter smaller than the outside diameter of the threads  22  of the first fixation element  12  to allow the threads  22  of the first fixation element  12  to engage the bone  52 . 
     After the pilot hole  54  is formed, the first fixation element  12  may be rotatably driven (e.g., screwed) into the bone  52  (for example using a driver) as generally illustrated in  FIG. 4 . Again, it should be noted that the first fixation element  12  may be secured to the bone  52  without a pilot hole  54 . The depth of the first fixation element  12  within the bone  52  may be set by rotating the first fixation element  12  until the first fixation element  12  is in the desired position. By adjusting the depth of the first fixation element  12  within the bone  52 , the fixation system  10  may be used in a wider variety of applications. For example, adjusting the depth of the first fixation element  12  may compensate for different amounts of bone preparation (e.g., removal of bone at the end). 
     After the first fixation element  12  is secured in the first bone  52 , a first tapered sidewall  42  of the interconnect  16  may be co-axially received in the opening  34  of the cavity  28  of the first fixation element  12 , for example, as generally illustrated in  FIGS. 5 and 6 . As seen, the sidewall  42  of the interconnect  16  may be inserted into the cavity  28  of the first fixation element  12  until the shoulder  46  abuts against the proximal end  24  of the first fixation element  12 . Optionally, an alignment device  55  may be used to locate where the second fixation element  14  should be secured to the second bone  56 . For example, the alignment device  55  may include a pin configured to be received in the cavity  49  of the interconnect  16 . The pin  55  may be secured within the cavity  49  and extend beyond the interconnect  16 . The second bone  56  may then be placed into axial alignment with the pin  55 . The pin  55  may include a pointed tip  58  which may pierce and/or mark the location on the second bone  56  where the second fixation element  14  should be secured. 
     Optionally, the pin  55  may be secured into the second bone  56 , and a pilot hole may be formed in the second bone  56  using a cannulated drill bit advanced over the pin  55 . 
     After the location of the second fixation element  14  has been determined, the second fixation element  14  may be rotatably driven (e.g., screwed) into the bone  56  (for example using a driver) as generally illustrated in  FIG. 7 . Again, it should be noted that the second fixation element  14  may be secured to the bone  56  without a pilot hole. The depth of the second fixation element  14  within the bone  56  may be set by rotating the second fixation element  14  until the second fixation element  14  is in the desired position. By adjusting the depth of the second fixation element  14  within the bone  56 , the fixation system  10  may be used in a wider variety of applications. For example, adjusting the depth of the second fixation element  14  may compensate for different amounts of bone preparation (e.g., removal of bone  56  at the end). 
     After the second fixation element  14  has been secured in the second bone  56 , the second tapered sidewall  44  of the interconnect  16  may be co-axially received in the opening  34  of the cavity  28  of the second fixation element  14 , for example, as generally illustrated in  FIG. 8 . As seen, the sidewall  44  of the interconnect  16  may be inserted into the cavity  28  of the second fixation element  14  until the shoulder  46  abuts against the proximal end  24  of the second fixation element  14 . 
     It may be appreciated that the depth of first and second fixation elements  12 ,  14  may be set independent of each other and independent of the interconnect  16 . More specifically, while the depth of the first and second fixation elements  12 ,  14  determines the separation distance between the first and second bones  52 ,  56 , the first and second fixation elements  12 ,  14  and the interconnect  16  are not limited to a specific orientation relative to each other. As such, the separation distance between the first and second bones  52 ,  56  may be infinitely adjustable. 
     It should be appreciated that the various steps in the method described herein do not necessarily have to be performed in any specific order. For example, the first and the second fixation elements  12 ,  14  may be secured in the bones prior to the interconnect  16  being coupled with either of the fixation elements  12 ,  14 . 
     Turning now to  FIGS. 9 a  and 9 b   , an exploded view ( FIG. 9 a   ) and assembled view ( FIG. 9 b   ) of another embodiment of a fixation system  100  is generally illustrated. The fixation system  100  includes a first and a second fixation element  112 ,  114  as well as an interconnect  116 . The first and second fixation elements  112 ,  114  may be similar to any fixation elements described herein. The interconnect  116  includes a first and a second generally cylindrical region  138 ,  140  each having a tapered external surface/sidewall  142 ,  144 , respectively. The tapered sidewalls  142 ,  144  have a taper which generally corresponds to the tapered sidewalls  132  of the first and second fixation elements  112 ,  114 , respectively, to form a frictional or interference fit as generally illustrated in  FIG. 9 b    and as generally described herein. The interconnect  116  of  FIGS. 9 a  and 9 b    does not have a shoulder. 
     With reference to  FIGS. 10 a  and 10 b   , an exploded view ( FIG. 10 a   ) and assembled view ( FIG. 10 b   ) of yet another embodiment of a fixation system  200  is generally illustrated. The fixation system  200  includes a first and a second fixation element  212 ,  214  as well as an interconnect  216 . While the interconnect  216  is illustrated without a shoulder, this is not a limitation of the present disclosure unless specifically claimed as such and the interconnect  216  may include any interconnect described herein. Optionally, the interconnect  216  may include a cannulated passage  217  extending along a longitudinal axis of the interconnect  216  between both ends. At least one of the fixation elements  212 ,  214  includes a cannulated passage  221 . The cannulated passage  221  extends from the proximal end  224  (e.g., from the cavity  228 ) to the distal end  226 . In practice, a guide pin may be inserted into the end of the bone, for example, along the longitudinal axis of the bone. A pilot hole may optionally be formed over a portion of the guide pin, for example using a cannulated drill bit. One or more of the cannulated fixation elements (e.g., cannulated fixation element  240 ) may be advanced over the guide pin such that the guide pin is received within the cannulated passage  221  and the fixation elements  212 ,  214  may be secured into the bone as described herein. Optionally, a cannulated interconnect  216  may also be advanced over the guide pin. 
     Again, while only one fixation element  214  is illustrated with cannulated passage  221 , it should be understood that both fixation elements  212 ,  214  may include a cannulated passage  221 . One advantage of having only one cannulated fixation element  214  is that a guide pin may be inserted into the cavity  228  of the first fixation element  212  and may abut against the distal end  229 . The distal end  229  may therefore prevent the guide pin from moving beyond the first fixation element  212  when the second bone is urged against the guide pin. 
     Alternatively (or in addition), a guide pin may be used which includes a flange extending radially outwardly having a diameter greater than the diameter of the cavity  228 . The flange may be position a distance away from an end of the guide pin such that a portion of the guide pin is received within the cavity  228  of the first fixation element  212  when the flange abuts against the proximal end  224  of the first fixation element. The flange may therefore prevent the guide pin from advancing though the first fixation element  212 , even if the first fixation element  212  is cannulated. 
     Turning now to  FIGS. 11 a -11 d   , various view of another embodiment of a fixation system  300  are generally illustrated. In particular,  FIG. 11 a    is an exploded view,  FIG. 11 b    is an assembled view,  FIG. 11 c    is an exploded cross-sectional view, and  FIG. 11 d    is a cross-sectional assembled view of the fixation system  300 . The fixation system  300  includes a first and a second fixation element  312 ,  314  as well as an interconnect  316 . The first and second fixation elements  312 ,  314  are similar to any of the fixation elements described herein. The interconnect  316  may include tapered surfaces  338 ,  340  which are separated by a flexible region  369 . The tapered surfaces  338 ,  340  are configured to engage with the cavities  328  of the first and second fixation elements  312 ,  314  as described herein. The flexible region  369  is configured to allow the first and second fixation elements to move (e.g., bend) with respect to each other such that the two bones secured together by the fixation system  300  (when assembled) can move. For example, at least a portion of the interconnect  316  (e.g., at least the flexible region  369 ) may include a superelasticity and/or shape memory material such as, but not limited to, nickel titanium alloys nitinol (e.g., an alloy of nickel and titanium). 
     The dimensions of the flexible region  369  may be selected to allow the bending characteristics of the interconnected  316  to be adjusted. For example, the cross-sectional dimensions, shape, and/or length of the flexible region  369  may be adjusted to increase the range of motion (e.g., bending) of the fixation system  300 , the amount of force necessary to bend the fixation system  300 , and/or the direction(s) in which the fixation system may bend. For example,  FIGS. 12 a -12 d    generally illustrates one embodiment of a fixation system  400  including a first and a second fixation element  412 ,  414  and an interconnect  416  having a flexible region  469  configured to allow the fixation system  400  to bend in a generally only one direction (e.g., generally only in a single plane). For example, at least a portion of the flexible region  469  may have a generally rectangular cross-section having a length running along the longitudinal axis of the interconnect  416  and a width and height generally perpendicular thereto. The dimensions of the width or the height may be selected to provide directional movement and stability of the interconnect  416  such that the interconnect  416  will generally only bend in one direct as a result of the forces in which the fixation system  400  will experience in a normal or typical application (e.g., the forces that the fixation system  400  would likely experience when installed in a foot, hand, or the like). 
     While the fixation system  400  is illustrated having a generally rectangular cross-section, this is not a limitation of the present disclosure unless specifically claimed as such. For example, at least a portion of the flexible region  469  may have a generally oval cross-section, one or more longitudinal and/or transverse ribs, grooves, or the like. 
     A benefit of the fixation systems  300 ,  400  is that they may allow for some degree of flexibility when used to couple to adjacent bones which originally were coupled together by way of a joint. In the fixation systems  300 ,  400 , the interconnects  316 ,  416  may have a separation length (i.e., distance between the first and second fixation elements when assembled) which is greater than the separation length of the other embodiments described herein. The larger separation length may facilitate bending of the fixation systems when assembled. The fixation systems may have a diameter of approximately 0.5 to 4 mm, an overall length of between approximately 5 to 20 mm, and may bend up to an angle between 10 degrees to 60 degrees. 
     Turning now to  FIG. 13 , yet another embodiment of a fixation system  500  consistent with the present disclosure is generally illustrated. The fixation system  500  includes a first and a second fixation element  512 ,  514  and an interconnect  516 . At least one of the fixation elements  512 ,  514  includes a generally cylindrical protrusion  598  extending outwardly from the proximal end  524 . The generally cylindrical protrusion  598  has a tapered external surface  599 . The interconnect  516  includes at least one tapered generally cylindrical cavity  528  having a tapered internal surface  530  configured to frictional engage the corresponding tapered external surfaces  599  of protrusions  599  of the corresponding fixation elements  512 ,  514 . While the fixation system  500  is illustrated in which interconnect  516  includes a first and a second tapered generally cylindrical cavity  528  and the interconnect includes a first and a second tapered generally cylindrical protrusion  598 , it should be understood that either of the fixation elements  512 ,  514  may include a tapered cavity as described herein and the corresponding end of the interconnect  516  may have a tapered protrusion as described herein. 
     The fixations systems described herein may be used to couple any two bones. For example, a fixation system  600  consistent herewith may be used to couple two or more bones  602 ,  604  in a foot  606  as generally illustrated in  FIG. 14 . A fixation system  700  consistent herewith may also be used to couple to or more bones  702 ,  704  in a hand  706  as generally illustrated in  FIG. 15 . It should be understood, however, that these are merely illustrative examples and that the fixation systems described herein are not limited to feet  606  and/or hands  706  unless specifically claimed as such. 
     It should be appreciated that various features of the different embodiments described herein may be combined together. For example, the interconnect may be eliminated such that that the two fixation elements may be directly coupled to each other, for example, using a tapered interference connection as described herein. 
     According to one aspect, the present disclosure features a fixation system for coupling a first and a second portion of bone together. The fixation system includes a first fixation element, a second fixation element, and an interconnect. The first fixation element includes an external surface configured to engage the first portion of bone and a first tapered mating surface. The second fixation element includes an external surface configured to engage the second portion of bone and a second tapered mating surface. The interconnect includes a first and a second tapered surface disposed at generally opposite ends. The first and the second tapered surfaces are configured to frictionally engage the first and the second tapered mating surfaces of the first and the second element, respectively, to form frictional interference connections therebetween. 
     According to another aspect, the present disclosure features a fixation system for coupling a first and a second portion of bone together including a first fixation element, a second fixation element, and an interconnect. The first fixation element includes a first body having an external surface configured to engage the first portion of bone. The first body defines a first generally cylindrical protrusion having a tapered external surface. 
     The second fixation element includes a second body having an external surface configured to engage the second portion of bone. The second body defines a second generally cylindrical protrusion having a tapered external surface. The interconnect includes a first and a second tapered generally cylindrical cavity having a tapered internal surface configured to frictionally engage the tapered external surfaces of the first and the second protrusions. 
     According to yet another aspect, the present disclosure features a fixation system for coupling a first and a second portion of bone together including a first fixation element, a second fixation element, and an interconnect. The first fixation element includes a first body having an external surface configured to engage the first portion of bone. The first body defines a first generally cylindrical cavity having a tapered internal surface. The second fixation element includes a second body having an external surface configured to engage the second portion of bone. The second body defines a second generally cylindrical cavity having a tapered internal surface. The interconnect includes a first and a second tapered generally cylindrical protrusion having a tapered external surface configured to frictionally engage the tapered internal surfaces of the first and the second cavities. 
     While the principles of the present disclosure have been described herein, it is to be understood by those skilled in the art that this description is made only by way of example and not as a limitation as to the scope of the invention. The features and aspects described with reference to particular embodiments disclosed herein are susceptible to combination and/or application with various other embodiments described herein. Such combinations and/or applications of such described features and aspects to such other embodiments are contemplated herein. Other embodiments are contemplated within the scope of the present invention in addition to the exemplary embodiments shown and described herein. Modifications and substitutions by one of ordinary skill in the art are considered to be within the scope of the present invention, which is not to be limited except by the following claims. 
     All definitions, as defined and used herein, should be understood to control over dictionary definitions, definitions in documents incorporated by reference, and/or ordinary meanings of the defined terms. 
     The indefinite articles “a” and “an,” as used herein in the specification and in the claims, unless clearly indicated to the contrary, should be understood to mean “at least one.” 
     The phrase “and/or,” as used herein in the specification and in the claims, should be understood to mean “either or both” of the elements so conjoined, i.e., elements that are conjunctively present in some cases and disjunctively present in other cases. Other elements may optionally be present other than the elements specifically identified by the “and/or” clause, whether related or unrelated to those elements specifically identified, unless clearly indicated to the contrary. 
     All references, patents and patent applications and publications that are cited or referred to in this application are incorporated in their entirety herein by reference. 
     While the principles of the present disclosure have been described herein, it is to be understood by those skilled in the art that this description is made only by way of example and not as a limitation as to the scope of the invention. The features and aspects described with reference to particular embodiments disclosed herein are susceptible to combination and/or application with various other embodiments described herein. Such combinations and/or applications of such described features and aspects to such other embodiments are contemplated herein. Other embodiments are contemplated within the scope of the present invention in addition to the exemplary embodiments shown and described herein. Modifications and substitutions by one of ordinary skill in the art are considered to be within the scope of the present invention, which is not to be limited except by the following claims. 
     The terms and expressions which have been employed herein are used as terms of description and not of limitation, and there is no intention, in the use of such terms and expressions, of excluding any equivalents of the features shown and described (or portions thereof), and it is recognized that various modifications are possible within the scope of the claims. Accordingly, the claims are intended to cover all such equivalents. Various features, aspects, and embodiments have been described herein. The features, aspects, and embodiments are susceptible to combination with one another as well as to variation and modification, as will be understood by those having skill in the art. The present disclosure should, therefore, be considered to encompass such combinations, variations, and modifications. 
     Additional disclosure in the format of claims is set forth below: