Abstract:
A system for inserting an implant into a bone comprises a base, a first arm coupled to and extending away from the base in a first direction, a distal end of the first arm configured to removably attach to an implant so that the base is in a desired orientation relative thereto. The system also comprises a second arm extending away from the base in alignment with a target structure of the implant and including a first aiming hole through which the target structure is to be accessed. The system also comprises a protection sleeve and a first aiming hole configured such that, in a first orientation, the protection sleeve is frictionally locked within the first aiming hole and, when rotated therewithin to a second configuration, the protection sleeve is free to move therethrough.

Description:
PRIORITY CLAIM 
       [0001]    The present application claims priority to U.S. Provisional Application Ser. No. 61/251,935 filed on Oct. 15, 2009 to Sean Powell, the entire disclosure of which is incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention is related to the field of bone fixation and, more particularly, related to an aiming arm configured to guide a bone fixation element to a target portion of a bone and subsequently lock the bone fixation element to the bone. 
       BACKGROUND 
       [0003]    The fixation and stabilization of bones in living bodies commonly involves an implant (e.g., an intramedullary nail, etc.) inserted into a target bone. Mechanical aiming instruments are often used to aid in alignment of the implant with or within the target bone. Such an aiming arm generally comprises a protection sleeve inserted through a hole oriented towards the implant to maintain a desired position of the implant relative to the aiming arm and to provide a barrier to protect soft tissue from damage during implantation. Such protection sleeves usually also comprises an opening for the introduction of drills, screws and other instruments or implants therethrough. Presently available aiming arms provide a tensioning mechanism such as a spring, set-screw, or a spring-loaded contact element configured to tension an outer wall of the protection sleeve as it is inserted through the aiming arm. Specifically, these tensioning mechanisms apply a constant frictional force to the protection sleeve for the entire period of insertion through the aiming arm and against the implant or must be selectively engaged or disengaged by an alternate means. 
       SUMMARY OF THE INVENTION 
       [0004]    The present invention is directed to a system for inserting an implant into a bone, comprising a base defining an open central area sized to receive a portion of a patient&#39;s anatomy including a target bone into which an implant is to be inserted and a first arm coupled to the base and extending away therefrom in a first direction, a distal end of the first arm being configured to temporarily mount a proximal end of an implant thereto so that the base is in a desired orientation relative to the implant extending along a desired axis in a second direction opposite the first direction passing through the central area of the base in combination with a second arm separated laterally from the axis so that, when the first arm is in the first target orientation, the second extends away from the base substantially parallel to the axis in alignment with a target structure of an implant coupled to the first arm, the second arm including a first aiming hole through which the target structure is to be accessed and a protection sleeve sized for insertion through the first aiming hole through an intervening portion of soft tissue located adjacent to the bone and to the target structure of an implant coupled to the first arm, one of the protection sleeve and the first aiming hole being configured so that the protection sleeve is frictionally locked in position within the first aiming hole when the protection sleeve is rotated to a first orientation relative to the first aiming hole and, when rotated from the first orientation to a second orientation, the protection sleeve is free to move within the first aiming hole. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]      FIG. 1  shows a perspective view of an exemplary system according to the present invention; 
           [0006]      FIG. 2  shows a zoomed partial cross-sectional view of the system of  FIG. 1  in an unlocked position; 
           [0007]      FIG. 3  shows a second zoomed partial cross-sectional view of the system of  FIG. 1  in a locked position; 
           [0008]      FIG. 4  shows another perspective view of the system of  FIG. 1 ; 
           [0009]      FIG. 5  shows another perspective view of the system of  FIG. 1 ; 
           [0010]      FIG. 6  shows a perspective view of a protection sleeve according to the present invention; 
           [0011]      FIG. 7  shows a perspective view of a second exemplary system according to the present invention; 
           [0012]      FIG. 8  shows a first zoomed partial cross-sectional view of the system of  FIG. 7  in an unlocked position; 
           [0013]      FIG. 9  shows a second zoomed partial cross-sectional view of the system of  FIG. 7  in locked position; 
           [0014]      FIG. 10  shows another perspective view of the system of  FIG. 7 ; and 
           [0015]      FIG. 11  shoes another perspective view of the system of  FIG. 7 . 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    The present invention is directed to a system and method for the fixation of a bone in a living body. Specifically, the present invention is directed to an exemplary protection sleeve configured for non-frictional insertion via a hole extending through an aiming arm. After the protection sleeve has been inserted to a target position relative to an implant (e.g., an intramedullary nail) positioned by the aiming arm, the protection sleeve is rotated to increase a frictional engagement between outer walls thereof with the hole through the aiming arm. Specifically, the protection sleeve is substantially cylindrical except for two flattened diametrically opposing walls extending along a portion of a longitudinal length thereof so that a width of the protection sleeve extending between the flattened walls is smaller than a diameter of outlying portions thereof. The hole formed through the aiming arm comprises leaf spring walls that are radially expandable upon application of a sufficient force thereto. In a first position, the leaf spring walls assume a cross-sectional shape substantially similar to a cross-sectional shape of the protection sleeve with a length between the leaf springs being substantially equivalent to or greater than the width of the portion of the protection sleeve extending between the flattened walls. Upon rotation of the protection sleeve about a longitudinal axis thereof, the increased diameter portions of the protection sleeve come into engagement with the leaf springs applying radially outward force thereto radially expanding the leaf spring walls. Frictional engagement between the leaf spring walls and the increased diameter outer wall of the protection sleeve then helps to maintain a desired position of the protection sleeve relative to the aiming arm. An exemplary embodiment of the present invention thus permits a physician or other user to rotationally lock and unlock the protection sleeve from the aiming arm as needed for the completion of a target bone fixation procedure. As used in this application, the term proximal refers to a direction approaching an end of the system away from a target bone hole for the insertion of a bone implant and the term distal refers to a direction approaching or located within the target bone hole. In an operative configuration, the distal end of the exemplary protection sleeve according to the present invention is inserted into the bone hole and inserted to a target position within the bone. 
         [0017]      FIG. 1  shows a first exemplary system  100  according to the present invention. The system  100  comprises an aiming arm  102 , a protection sleeve  104  and an intramedullary nail  106  configured for insertion into a bone (not shown) in accordance with an exemplary bone fixation procedure. The aiming arm  102  comprises a semi-circular element  108  comprising first, second third, fourth and fifth arms  110 ,  111 ,  112 ,  113 ,  114 , extending distally therefrom. Each of the first, second, third, fourth and fifth arms  110 ,  111 ,  112 ,  113 ,  114  are spaced apart from one another along the semi-circular element  108 , with the first and fifth aims  110 ,  114  located at ends of the semi-circular element  108  substantially diametrically opposed to one another. In an exemplary embodiment, the aiming arm  102  is formed of a radiolucent material (e.g., carbon fiber, plastic or aluminum). The first, second, third, fourth and fifth arms  110 ,  111 ,  112 ,  113 ,  114  extend perpendicular to a plane including the semi-circular element  108  and are substantially parallel to one another. Each of the first and fifth arms  110 ,  114  also comprises a combination hole  116  formed as two substantially circular holes located overlapping one another with the two circular holes open to one another, as those skilled in the art will understand, and a circular hole  118  located adjacent to the combination hole  116 . A slot  120  extends into each of the combination holes  116  from a lateral wall  117  of the corresponding one of the first and fifth arms  110 ,  114  and extends through the combination hole  116  substantially perpendicular to axes of the holes  116 ,  118 . A width of the slot  120  is smaller than the diameters of the circular holes making up the combination hole  116  and the circular hole  118  and a length of the slot  120  along the length of the respective one of the first and fifth arms  110 ,  114  is sufficient to intersect the entire length of the combination hole  116  and circular hole  118  in the same direction. The second, third and fourth arms  111 ,  112 ,  113  each only comprise a single hole  119  and a respective slot  119 ′ configured to receive the protection sleeve  104  therethrough, as will be described in greater detail later on. 
         [0018]    Spring elements  122  housed in each of the slots  120  comprise a first spring member  124  and a second spring member  126 . The spring element  122  is formed of a sufficiently ductile material. The first and second spring members  124 ,  126  are not connected to one another and may optionally be employed alone if, for example, the single hole  119  is used in place of the combination hole  116 . Specifically, the second, third and fourth arms  111 ,  112 ,  113  may comprise a spring element  122  positioned within the single holes  119  configured to apply a radially compressive force to any protection sleeve  104  inserted therethrough. The spring element  122  is held within the slot by one or more pins  123  forming one of a permanent and a removable connection. In an exemplary embodiment, the spring element may be formed of 302 Stainless Steel, 316 Stainless Steel, 17-7PH, Nitinol or Elgiloy®. The first spring member  124  includes a planar element  128  having first and second leaf springs  130  extending into a first circular portion of the combination hole  116 , as shown in the partial cross-sectional views of  FIGS. 2-3 . The leaf springs  130  are biased to a position in which a width of the space therebetween is smaller than a diameter of a non-flattened portion of the protection sleeve  104  but greater than a width of a flattened portion thereof, as will be described in greater detail hereinafter. Similarly, the second spring member  126  is formed with a planar element  132  having a first set of leaf springs  134  extending therefrom into the combination hole  116  in a first direction and a second set of leaf springs  136  extending into the circular hole  118  in a second direction opposite the first direction. Each of the first and second sets of leaf springs  134 ,  136  is sized substantially similarly to the leaf springs  130  with a space formed between each pair of leaf springs being smaller than a diameter of the non-flattened portion of the protection sleeve  104  but greater than a width of the flattened portion thereof. 
         [0019]    The protection sleeve  104  includes an elongated shaft  138  extending from an increased diameter head  142  with an externally scalloped shape, as those skilled in the art will understand, at a proximal end thereof to a distal end  144  having a reduced thickness portion  146 . The reduced thickness portion is substantially cylindrical in shape and comprises a smaller diameter than the shaft  138 , as shown in greater detail in  FIG. 6 . An outer surface of the shaft  138  includes a plurality of generally cylindrical portions and a plurality of flattened portions including flattened sides extending substantially parallel to one another and parallel to a longitudinal axis of the sleeve  104 . Specifically, the protection sleeve  104  in this embodiment comprises two flat surfaces  140  formed on opposing diametrical sides of the shaft  138 , each of the flat surfaces  140  extending along a predetermined length of the shaft, as shown in  FIG. 1 . The distal end  144  of the protection sleeve  104  is formed with a substantially circular cross-section having a diameter smaller than that of the shaft  138  to aid in insertion of the protection sleeve  104  into the bore  148  of the intramedullary nail  106 . A channel  149  extends through the protection sleeve  104  and is open at proximal and distal ends thereof, the channel  149  having a substantially circular cross-section and being dimensioned to permit insertion of a medical instrument or implant therethrough. 
         [0020]    The aiming arm  102  further comprises an insertion handle  150  including a first end extending away from the semi-circular element  108  substantially parallel to and opposite a direction of the arms  110 - 114 . The insertion handle  150  is threadedly connected to a joint  152  and tightened therein via an adjusting knob  153  to lock a position thereof and prevent any movement of the insertion handle  150  relative to the semi-circular element  108 . The insertion handle  150  extends from the joint  152  along a curved path to a second end  156  facing back toward a plane of the semi-circular element  108  and configured to engage a proximal end  158  of the intramedullary nail  106  so that the nail  106 , when attached thereto, extends through the plane of the semi-circular element  108  with the bores  148  thereof aligned with the combination holes  116  and single holes  118  of the first and fifth arms  110 ,  114  or the single holes  119  of the second, third and fourth arms  111 ,  112 ,  113 . Thus the aiming arm  102  and the insertion handle  150  hold the nail  106  in a desired position during insertion to facilitate implantation, as those skilled in the art will understand. 
         [0021]    In accordance with an exemplary method of the present invention, a drill (not shown) is used to drill a first bore opening to the medullary canal of a bone (not shown) so that the intramedullary nail  106  may be inserted therein. The intramedullary nail  106  is then mounted to the second end  156  of the insertion handle  150  prior to insertion thereof into the bone. A user then determines which of the arms  110 - 114  will receive the protection sleeve  104  based on the position of a fracture in the bone or a pending pathological fracture and on the geometry of the nail  106 . In the provided illustration, the first aim  110  is selected to receive the protection sleeve  104 . Thus, the insertion handle  150  and the intramedullary nail  106  are oriented so that, when the intramedullary nail  106  is inserted to a desired position in the first bore (not shown), a drill inserted through the protection sleeve  104  and through the combination hole  116  or the circular hole  118  of the first arm  110  is in alignment with the bore  148  extending through the intramedullary nail  106 . As shown in  FIGS. 1 and 5 , the intramedullary nail  106  comprises a plurality of additional bores  148 ′ extending therethrough at a plurality of angles, each of the bores  148 ′ being substantially perpendicular to a longitudinal axis of the intramedullary nail  106 . Accordingly, a user of the system  100  may select more than one of the arms  110 - 114  to receive the protection sleeve  104  therethrough. Thus, the intramedullary nail  106  may receive any plurality of protection sleeves  104  without deviating from the scope of the present invention. The intramedullary nail  106  is then inserted into the bone and the protection sleeve  104  is inserted into the combination hole  116  in a first configuration with the flat surfaces  140  aligned with the leaf springs  130  so that the protective sleeve  104  slides therepast with a minimal amount of resistance. Once the protection sleeve  104  has been inserted to the target depth in the bore  148 , the protection sleeve  104  is rotated by approximately 90 degrees so that the portions of the shaft  138  having an increased diameter relative to the flat surfaces  140  are in contact with the leaf springs  130  deflecting the leaf springs  130  radially outward against the spring bias and frictionally engaging the leaf springs  130  with the substantially cylindrical portions of the shaft  138  locking the protection sleeve  104  in the desired position. Once the protection sleeve  104  has been locked in this desired position, a drill, screw or other instrument or implant may be inserted through the channel  149  into the bore  148  to drill a transverse second bore at an angle to the first bore (not shown). As those skilled in the art will understand, the second bore extends through a lateral cortex of the bone at a point selected to align with the bore  148  when the nail  106  is in a desired position within the bone. 
         [0022]    In the embodiment discussed above, the protection sleeve  104  is formed with a substantially circular cross-section having two flat surfaces  140  formed on opposing walls thereof. In a first alternate embodiment of the present invention, the shaft  138  may be formed with any cross-sectional shape, including, but not limited to square, hexagonal, octagonal, or another polygon shape so long as the cross-sectional geometry of the sleeve  104  relative to the leaf springs  130  such that, in a first orientation, a reduced diameter or reduced width aspect is presented to the leaf springs  130  and, in a second orientation, a larger diameter or width portion is presented to the leaf springs  130  deflecting the leaf springs  130  radially outward and increasing a resistance to the movement of the protection sleeve  104  relative to the one of the arms  110 - 114  through which it is inserted. The protection sleeve  104  may further comprise any type of recesses and is not limited to the flat surfaces  140 . Specifically, the recesses may be concave, convex, helical or any other shape wherein an outer diameter of the recess is smaller than an outer diameter of the shaft  138 . Furthermore, the protection sleeve  104  may comprise one or any plurality of recesses formed along an outer wall thereof. In yet another embodiment, the recesses may be replaced by features having the same outer diameter as the shaft  138  but which comprise a different material than the shaft  138  such as Nylon or Teflon or may comprise an alternate surface finish (e.g., knurling, grooving or threading) with properties selected to reduce or enhance frictional engagement of portions of the outer surface with the leaf springs  130  relative to the frictional engagement of a surface finish of other portions of the outer surface of the shaft  138 . 
         [0023]    In another embodiment of the present invention, the aiming arm  102  may comprise one or more leaf springs  130 . Furthermore, the leaf springs  130  may be replaced with coil springs, thin flexible mechanical elements (e.g., belleville washers), wave spring, compressible cylinders, wave washers or portions of elastic material (e.g., rubber, plastic). The leaf springs  130  may be intrinsic with the arms  110 - 114  or, in an alternate embodiment, a separate element may be used to enhance contact therewith. The planar element  128  may be permanently affixed to the slot  120  by use of a pin or other mechanical attachment mechanism known in the art or, in an alternate embodiment, may be removable therefrom as needed. 
         [0024]      FIGS. 7-11  depict a system  200  according to another exemplary embodiment of the present invention. The system  200  is formed substantially similarly to the system  100 , with like elements referenced by like reference numerals. The system  200  comprises an aiming arm  202 , a protection sleeve  204  and an intramedullary nail  206  formed substantially similarly to the respective elements of system  100 . A semi-circular element  208  of the aiming arm  202  comprises first, second and third arms  210 ,  212 ,  214  extending distally therefrom and spaced apart from one another. In an exemplary embodiment, the first, second and third arms  210 ,  212 ,  214  extend substantially perpendicularly from a plane housing the aiming arm  202  and are substantially parallel to one another. Similar to the system  100 , each of the first, second and third arms  210 ,  212 ,  214  comprises a combination hole  216  extending laterally therethrough and a circular hole  218  adjacent thereto. Instead of a slot  120  as taught in system  100 , the system  200  comprises a lateral, substantially oval hole  219  and a lateral circular hole  220  extending through a lateral wall  217  thereof. Each of the lateral holes  219 ,  220  have a length corresponding to the length of the combination hole  216  and circular hole  218 , respectively. In an exemplary embodiment, the lateral oval hole  219  and the lateral circular hole  220  are configured and dimensioned so that spring elements  222 ,  224 ,  226  inserted therethrough project into at least a portion of the combination hole  216  and the circular hole  218 , respectively, as will be described in greater detail hereinafter. 
         [0025]    Exemplary spring elements  222 ,  224 ,  226  according to the exemplary embodiment are configured as substantially planar elements formed of a material substantially similar to a material of the spring elements  122  of system  100 . Each of the spring elements  222 ,  224  and  226  is separate from the others and is configured for separate, permanent insertion into one of the lateral holes  219 ,  220 . The spring elements  222 ,  224 ,  226  are held in place within respective ones of the lateral holes  219 ,  220  by a friction fit (e.g., during manufacturing). Each of the spring elements  222 ,  224 ,  226  comprises a first portion  228  and a second portion  230 , the second portion  230  being configured and dimensioned to deflect laterally away from a center of the combination hole  216  or circular hole  218  upon application of a pressure thereto (e.g., by rotation of the protection sleeve  204 ), as described in greater detail with respect to the system  100 . Each of the spring elements  222 ,  224 ,  226  is positioned to project partially into the combination hole  216  and circular hole  218  by a length substantially equivalent to a depth of a cutout formed in the protection sleeve forming the flattened portion  140 , as also described in greater detail earlier. This configuration permits the spring elements to remain substantially unobstructed when the protection sleeve  204  is inserted into the combination hole  216  in the configuration shown in  FIG. 8 . Upon rotation of the protection sleeve  204  to the position shown in  FIG. 9 , a radially expansive force is applied to the spring element  222  causing the second portion  230  to deflect radially outward. 
         [0026]    As shown in  FIGS. 8 and 9 , each of the first, second and third arms  210 ,  212 ,  214  also comprises additional locking holes  232 ,  234 ,  236  adjacent respective ends  211 ,  213 ,  215  thereof. The additional locking holes  232 ,  234 ,  236  may be used to attached extension pieces (not shown) to the system  100 . The ends  211 ,  213 ,  215  also comprise stepped portions  238  having a thickness reduced relative to proximal portions of the arms  210 ,  212 ,  214  to permit attachment to the extension pieces (not shown). 
         [0027]    The exemplary embodiment of system  200  obviates the need for additional arms disposed between the first, second and third arms  210 ,  212 ,  214 , instead replacing these arms with first and second sleeve holes  240 ,  242 . Specifically, the first sleeve hole  240  is provided on a portion of the aiming arm  202  substantially equidistant from the first arm  210  and the second arm  214 . A partially circular extension portion  244  of the aiming arm  202  extends distally from the aiming arm  202  and along a curve having a radius of curvature suited to the dimensions of the sleeve hole  240 , as those skilled in the art will understand. In an exemplary embodiment, the position of the extension portion  244  and the sleeve hole  242  are selected so that a drill sleeve inserted through the sleeve hole  242  is aligned with an opening extending through the intramedullary nail  206 . It is therefore noted that the dimensions of the extension portion  244  may be varied to suit the requirements of a predetermined procedure. Similarly, the sleeve hole  242  positioned between the second and third arms  212 ,  214  may be positioned elsewhere along the aiming arm to conform to the requirements of an intramedullary nail  206  to be used therewith. In the embodiment shown, a portion of the aiming arm  202  housing the sleeve hole  242  is longitudinally offset from the plane housing the aiming arm  202 . It is respectfully submitted that the aiming arm  202  may be formed with any geometry to permit a drill sleeve  204  inserted therethrough to intersect with a target portion of the intramedullary nail  206  without deviating from the spirit and scope of the present invention. 
         [0028]    The system  200  further comprises an insertion handle  250  formed substantially similarly to the insertion handle  150  of the system  100 . Specifically, the insertion handle  250  extends away from the aiming arm  202  along a curved path in a direction substantially opposite a direction of the arms  210 ,  212 ,  214  to an end  252  facing back toward the plane of the aiming arm  202 . A locking portion  254  of the insertion handle  250  is configured for locking engagement with a locking portion  256  of the aiming arm  202 , by, for example, tightening of a threaded knob  258  through each of the locking portions  254 ,  256 . Tightening of the knob  258  locks a position of the insertion handle  250  relative to the aiming arm  202 . The end  252  is configured to engage the proximal end  158  of the intramedullary nail  206  so that the nail  106 , when attached thereto, extends through the plane of the aiming arm  202  with bores  148  thereof aligned with at least one of the combination holes  216 , circular holes  218  or sleeve holes  240 ,  242 . Thus the aiming arm  202  and the insertion handle  250  hold the nail  206  in a desired position during insertion to facilitate implantation. The present invention has been described with respect to intramedullary nails for the fixation of long bones. It is noted however, that the exemplary system of the present invention may also be employed in securing protection sleeves in aiming arms for surgical bone plates or artificial joints. Furthermore, the exemplary system of the present invention may also be used to secure a cylindrical instrument known in the art (e.g., a drill sleeve) into a hollow portion of another cylindrical instrument known in the art (e.g., a protection sleeve). 
         [0029]    Although the present invention has been described with reference to preferred embodiments, it is submitted that various modifications can be made to the exemplary system and method without departing from the spirit and scope of the invention.