Abstract:
A method for using a jig to position an implant at an implantation site of a bone. The method includes the following: tapping the implantation site using a tapping device; axially threading the jig into the implantation site using an insertion tool; adjusting the position of the jig at the implantation site as necessary by axially rotating the jig relative to the bone; axially and substantially non-rotationally inserting the implant through the jig whereby the implant contacts a substantially smooth interior surface of the jig to support the implant at the implantation site such that the implant does not substantially contact an interior surface of the bone canal at the implantation site; and securing the implant at the implantation site using bone cement.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     This application is a divisional application of U.S. patent application Ser. No. 10/651,793, filed on Aug. 29, 2003. The disclosure of the above application is incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention generally relates to prosthetic implant positioning devices. In particular, the present invention relates to a positioning jig for properly positioning an implant during shoulder arthroplasty for fractures of the proximal humerus.  
       BACKGROUND OF THE INVENTION  
       [0003]     Fractures of the proximal humerus may occur due to injury or weakened bone. Often, the proximal humerus fractures at different points into multiple fragments, such as the greater tuberosity, the lesser tuberosity, the head, and the shaft. Such fractures may require the replacement of the proximal humerus with an implant. The implant generally consists of a head, neck, and stem.  
         [0004]     To insure that the implant is properly positioned at the proximal humerus, a positioning jig may be used. Conventional positioning jigs typically engage either an exterior or interior portion of the remaining humerus as well as the trial implant and/or the permanent implant. Such positioning jigs permit joint reduction with the trial as well as use of the jig to position the permanent implant in substantially the same position as the trial.  
         [0005]     While current fracture jigs are suitable for their intended uses, they are all subject to improvement. The present invention provides a simplified, easy to use, and efficient fracture jig device, system, and method for positioning both a trial implant and a permanent implant at an injury site.  
       SUMMARY OF THE INVENTION  
       [0006]     The present teachings provide for a method for using a jig to position an implant at an implantation site of a bone. The method includes the following: tapping the implantation site using a tapping device; axially threading the jig into the implantation site using an insertion tool; adjusting the position of the jig at the implantation site as necessary by axially rotating the jig relative to the bone; axially and substantially non-rotationally inserting the implant through the jig whereby the implant contacts a substantially smooth interior surface of the jig to support the implant at the implantation site such that the implant does not substantially contact an interior surface of the bone canal at the implantation site; and securing the implant at the implantation site using bone cement.  
         [0007]     The present teachings further provide for a method for using a jig to position an implant at an implantation site of a bone. The method includes the following: analyzing the implantation site to determine the appropriate size and position of the implant; selecting a trial implant that is substantially the same size as the implant, the trial implant having a trial stem and a trial head; referencing a position of an inferior portion of the trial head against score marks on the trial stem, the trial stem is properly positioned at the implantation site when the score mark corresponding to the inferior portion of the trial head is proximate to a reference surface of the bone; preparing the implantation site using a tapping device having a shank with a control surface operable to engage a control device, a cutting implement having a cutting surface, and an elongated shaft connecting the cutting implement to the shank, the elongated shaft having a series of tick marks that are substantially the same as the score marks on the trial stem, preparation of the implantation site includes driving the tapping device into the implantation site to a depth such that a tick mark corresponding to the score mark referenced against the inferior portion of the trial head is proximate to the reference surface of the bone; positioning a jig at the implantation site using an insertion tool, the insertion tool having a series of reference marks that are substantially the same as the score marks and the tick marks and a head operable to mate with the jig, the jig is positioned at the implantation site to a depth such that a reference mark corresponding to the score mark referenced against the inferior portion of the trial head is proximate to the reference surface of the bone; inserting the trial stem into the jig such that the score mark of the trial stem corresponding to the position of the inferior portion of the trial head is proximate to the reference surface of the bone, thereby positioning the trial stem at an optimum height at the implantation site; adjusting the position of the trial stem as necessary by screwing the jig up or down in the implantation site using the insertion tool; and inserting the implant into the jig and securing the implant in position.  
         [0008]     The present teachings also provide for a method for using a jig to position an implant in an intramedullary canal of a humerus. The method includes the following: tapping the intramedullary canal using a tapping device; axially threading the jig into the intramedullary canal using an insertion tool; substantially centering the implant in the intramedullary canal by axially inserting the implant through both a first end of the jig having a first diameter and a second end of the jig that is opposite to the first end and has a second diameter that is smaller than the first diameter, whereby the implant contacts a substantially smooth inner surface of the jig; adjusting the height of the jig in the intramedullary canal as necessary so that a point on a stem of the implant aligned with an inferior portion of a head of the implant is proximate to an exterior reference surface of the humerus when the implant is seated in the jig; and securing the implant in the intramedullary canal using bone cement.  
         [0009]     Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the embodiments of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]     The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:  
         [0011]      FIG. 1  is a perspective view of a jig illustrated in accordance with an embodiment of the present invention;  
         [0012]      FIG. 1   a  is cross-sectional view of the jig of  FIG. 1  taken along line  2 - 2  of  FIG. 1 ;  
         [0013]      FIG. 2  is a perspective view of a tapping device used to prepare the humerus to receive the jig of  FIG. 1 ;  
         [0014]      FIG. 3  is a perspective view of an insertion device operable to insert the jig of  FIG. 1  within the humerus;  
         [0015]      FIG. 4  is a perspective view of an alternative insertion device operable to insert the jig of  FIG. 1  within the humerus;  
         [0016]      FIG. 5  is a side view of a trial humeral implant;  
         [0017]      FIG. 6  is a side view of the tapping device of  FIG. 1  inserted within a proximal humerus to prepare the humerus for receipt of the jig of  FIG. 1 ;  
         [0018]      FIG. 7  is a side view of the insertion device of  FIG. 3  inserted within the prepared proximal humerus of  FIG. 6  to implant the jig of  FIG. 1  within the humerus;  
         [0019]      FIG. 8  is a side cross-sectional view of the jig of  FIG. 1  seated within the humerus, the jig holding a trial proximal humeral implant within the humerus to permit reduction of the trial joint;  
         [0020]      FIG. 9  is a side cross-sectional view of the jig of  FIG. 1  seated within the humerus, the jig holding a permanent proximal humeral implant in at least substantially the same position as the trial implant of  FIG. 8 ; and  
         [0021]      FIG. 10  is a side cross-sectional view of a jig illustrated in accordance with an alternate embodiment of the present invention, the jig seated within the humerus and holding a permanent proximal humeral implant. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0022]     The following description of the embodiments is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. While the invention is described below as a positioning device, system, and method for a humeral implant, the invention may be used to properly position a variety of different bony and non-bony implants in both human and non-human patients. Further, while the invention is described as a fracture jig, the invention may be used to trial and/or retain an implant regardless of whether a fracture has actually occurred.  
         [0023]     A jig in accordance with an embodiment of the present invention is illustrated in  FIGS. 1 and 1   a  at  10 . As illustrated, the jig  10  generally takes the form of a closed circular sleeve that is a single integral unit. However, the illustration of jig  10  at  FIG. 1  is for demonstrative purposes only as the jig  10  may be an open circular or non-circular sleeve comprised of a single unit or multiple parts. The jig  10  generally includes a first end  12 , a second end  14 , an exterior surface  16 , and an interior surface  18 .  
         [0024]     The second end  14  of the jig  10  includes at least one detail  20 . As illustrated, the detail  20  is a projection that extends from the second end  14 . However, the detail  20  may be a recess within the second end  14  or may be any other suitable engagement surface to permit engagement between the jig  10  and a suitable implantation tool, discussed in detail below. For example, detail  20  does not need to be located at the second end  14  and may be a projection located on the interior surface  18  that engages flutes on the stem of an implant and/or insertion tool.  
         [0025]     The exterior surface  16  optionally includes at least one extension or rib  22 . The ribs  22  project from the exterior surface  16  and extend in a circular, stepwise fashion or in any other manner about the exterior surface  16 . The ribs  22  may be of various shapes and sizes, but are configured for receipt by corresponding depressions at an implantation site. Any other type of retention feature to retain the jig  10  may also be used, such as threads or an annular feature. As illustrated, the ribs  22  do not extend continuously about the exterior surface  16 . However,  FIGS. 1 and 1   a  are for demonstrative purposes only and the ribs  22  may extend about the exterior surface  16  in either a continuous or non-continuous configuration. The ribs  22  may be angled to decrease the force required to implant the jig  10  and/or make the jig  10  self-tapping. In addition to, or in place of, providing angled ribs  22 , the first end  12  and/or the exterior surface  16  may optionally include various other features to make the jig  10  self-tapping.  
         [0026]     With particular reference to  FIG. 1   a , the interior  18  of the jig  10  is open at both the first end  12  and the second end  14  to receive and hold any suitable implant. Alternatively, the jig  10  may be opened at one end to receive the distal most portion of the implant. To better secure the implant within the interior  18 , the interior  18  may be tapered from the second end  14  to the first end  12  with the second end  14  having a greater diameter than the diameter of the first end  12 . The taper of the interior  18  may substantially match the taper of the stem of a typical implant inserted within the interior  18 . Alternatively, any other type of suitable engagement surface may also be employed. For example, interior  18  may include an internal feature that acts as a stop or locating device for receiving an implant.  
         [0027]     The overall size of the jig  10  may vary depending upon the dimensions of the site that it is to be implanted at. Further, the jig  10  may be available in various different lengths and widths. Still further, the diameter of the interior  18  of the jig  10  may also vary, depending upon both the dimensions of the implantation site and the dimensions of the implant to be received by the interior  18 . The diameter of the interior  18  may vary together with, or apart from, changes in the overall size of the jig  10 .  
         [0028]     The jig  10  may be made from a variety of suitable materials. It is preferred that the jig  10  be made from polymethyl-methacrylate. However, any suitable plastic, bone cement, resorbable material, or biocompatible non-resorbable material may be used.  
         [0029]      FIG. 2  illustrates a tapping device at  24 . The tapping device  24  generally comprises a first end  26  having a shank  28 , a second end  30  having a cutting implement  32 , and an elongated shaft  34  that connects the first end  26  to the second end  30 .  
         [0030]     The shank  28  is any typical shank operable to permit control of the tapping device  24  by a suitable instrument, such as a T-handle (not shown). As illustrated, the shank  28  has a recessed control surface  36  for cooperation with, for example, the T-handle and a collar  38  that acts as a stop to prevent the tapping device  24  from drilling to far within the implantation site. The shape and configuration of the shank  28  may vary to permit cooperation with different control instruments, in addition to, or instead of, the T-handle.  
         [0031]     The cutting implement  32  comprises a series of ribs  40  that extend from an outer surface  42 . The ribs  40  extend about the implement  32  in a stepped, spiral orientation. As illustrated, the ribs  40  do not extend around the outer surface  42  in a continuous manner, but are instead interrupted at the same interval in each rib  40 . However, it must be noted that in particular applications the ribs  40  may be configured to extend continuously about the implement  32 . The ribs  40  include leading edges  44  that may be angled to assist in cutting and chipping bone of the implantation area to create threads at the implantation area. It must be noted that this description of the ribs  40  is merely exemplary as the ribs  40  may be of a variety of different design configurations.  
         [0032]     The elongated shaft  34  optionally includes a series of score marks  46 . The score marks  46  are positioned at regular intervals along the shaft  34 . The score marks  46  may include a series of dashes, numbers, letters, or any combination thereof. The score marks  46  may extend the length of the shaft  34  or only a portion of the shaft  34 .  
         [0033]     With reference to  FIG. 3 , an inserter for implanting the jig  10  is illustrated at  48 . The inserter  48  generally comprises a first end  50 , a second end  52  opposite the first end  50 , and an intermediary portion  53  that connects the first end  50  to the second end  52 . The first end  50  has a shank  54  that is substantially similar to the shank  28  of the tapping device  24 . The description of the shank  28  above also applies to the shank  54 , thus making it unnecessary to include a description of the shank  54  here.  
         [0034]     The second end  52  comprises a head  55  defined, in part, by the second end  52  and an upper head region  56 . The head  55  may be of different sizes depending on the size of the jig  10 . The second end  52  is tapered inward, toward an interior of the inserter  48 , at its terminus. The upper head region  56  includes at least one engagement surface  57 . The engagement surface  57  may be an extension as illustrated or may be a recess located within the upper head region  56 .  
         [0035]     The intermediary portion  53  is longer, by approximately 10 mm, than the elongated shaft  34 . The intermediary portion  53  may include a series of score marks  58 . The score marks  58  may be any suitable reference markings, such as numbers or letters. The score marks  58  are positioned at intervals that are at least substantially equal to the score marks  46  of the tapping device  24 . The score marks  58  may extend from the shank  54  to a distance down the intermediary portion  53  substantially equal to a distance that the score marks  46  extend from shank  28 .  
         [0036]      FIG. 4  illustrates an inserter  59  according to a second embodiment. The inserter  59  generally comprises a main body  60 , a first end  62 , and a second end  64  opposite the first end  62 . Extending from the first end  62  is a first handle  66  and a second handle  68 . Both the first handle  66  and the second handle  68  include score marks  69  that are substantially the same as the score marks  58  of inserter  48 . The second end  64  includes a jig engagement detail  70 . The jig engagement detail  70  may be a tab that extends from the second end  64  as illustrated, or may be a recess within the second end  64 . Extending through the main body  60  is an inner region  72 . Generally, the diameter of the inner region  72  is tapered from the first end  62  to the second end  64  and is at least as large as the interior  18  of the jig  10 . The inserter  59  may be of various different sizes depending on the size of the jig  10 .  
         [0037]      FIG. 5  illustrates a trial implant at  74 . While the trial implant  74  is illustrated as a trial humeral implant, the trial implant  74  may be any suitable bony or non-bony implant. The trial humeral  74  is generally comprised of a head  76 , a neck  78 , and a stem  80 . The stem  80  includes a series of score marks  82 . The score marks  82  are generally positioned at uniform intervals along the stem  80  and are typically either letters or numbers. The trial humeral  74  has a vertical reference line A that extends through the stem  80  and at least a portion of the neck  78 . A horizontal reference line B extends from a inferior portion  84  of the head  76 , which is at an opposite end of the head  76  from a superior portion  86 , to one of the score marks  82 .  
         [0038]     The trial humeral  74  may be of various different shapes and sizes depending upon the dimensions of the implantation site. In particular, the head  76  may be of different dimensions, with the particular score mark  82  being referenced by the intersection of reference lines A and B being different depending on the size of the head  76 . For example, if the head  76  is larger than illustrated, the inferior portion  84  will extend further along the stem  80 , thus causing the horizontal reference line B to reference a score mark  82  that is further down the stem  80 .  
         [0039]     With additional reference to  FIGS. 6 through 9  and continued reference to  FIGS. 1 through 5 , the implantation and operation of the jig  10  will now be described in detail. The description details the implantation of the jig  10  within a fractured humerus  88  to position both the trial humeral implant  74  and a permanent humeral implant that replaces a proximal portion of the humerus  88 , including the humeral neck and head (not shown). However, the jig  10  may be implanted in any suitable bony or non-bony surface to position a variety of different implants.  
         [0040]     Before the jig  10  is implanted within the fractured humerus  88 , the fractured humerus  88  is analyzed by a physician, using conventional techniques, to determine what size trial  74 , and specifically what size trial head  76 , is required. Once the proper size is determined, the trial head  76  is secured to the neck  78  and the position of the inferior portion  84  of the head  76  is referenced upon the score marks  82  using the point where horizontal reference line B intersects vertical reference line A. The point where reference lines A and B intersect is carefully noted for further use during the implantation process. The size of the trial  74  chosen also has a bearing on the size of the jig  10  used to support the trial  74  and the permanent implant.  
         [0041]     If the jig  10  is not a self tapping jig, the fractured humerus  88  may be tapped to receive the jig  10 . With reference to  FIG. 6 , to tap the humerus  88 , the tapping device  24  is driven within the intact portion of the fractured humerus  88 . The tapping device  24  is rotated as it is driven so that the ribs  40  create corresponding grooves  90  within the humerus  88 . If the fracture occurs at the medial/inferior intersection of the humeral head and shaft, the tapping device  24  is driven within the humerus  88  until the particular score mark  46  referenced by the intersection of lines A and B on the trial humeral implant  74  is at the surface of the fractured humerus  88 , as illustrated in  FIG. 6 . However, if the fracture is distal to the intersection of the head and shaft, the jig  10  is driven less deeply within the humerus  88 .  
         [0042]     The score marks  46  on the tapping device  24  and the score marks  82  on the trial implant  74  are calibrated such that when the tapping device  24  is driven within the humerus  88  to a depth such that the score mark  46  corresponding to the score mark  82  at the intersection of reference lines A and B of the trial humeral  74  is at the surface of the fractured humerus  88 . The depth of the grooves  90  created by the tapping device  24  are at approximately the proper depth of the jig  10  required to support the trial humeral implant  74 , and a permanent humeral implant, in the proper position. However, since the tapping device  24  is generally longer than the inserter  48 , the grooves  90  will be of an added depth so that the jig  10  may be driven deeper if necessary.  
         [0043]     With reference to  FIG. 7 , after the humerus  88  is tapped, the inserter  48  is used to implant the jig  10  within the humerus  88 . The jig  10  mates with the inserter  48  through cooperation between the engagement surfaces  57  and surfaces between details  20  of the jig  10  when the head  55  is seated within the interior  18  of the jig  10 . The inserter  48  is driven within the tapped humerus  88  to a depth such that the score mark  58  of the inserter  48 , which is equivalent to the score mark  82  of the trial  74  referenced by the intersection of reference lines A and B, is positioned at the surface of the humerus  88 . Driving the inserter  48  to this depth places the jig  10  within the grooves  90  and at an approximate depth to support the trial humeral implant  74  at the correct height.  
         [0044]     Alternatively, the inserter  59  may be used to insert the jig  10  within the humerus  88 . The inserter  59  engages the jig  10  through cooperation between the sleeve engagement detail  70  and surfaces between details  20  of the jig  10 . Using the handles  66  and  68 , the jig  10  is driven within the humerus until the score mark  69  corresponding to the score mark  82  referenced on the trial  74  is positioned at the surface of the humerus  88 . This is done by placing the inserter  59  over the stem  80  of the trial  74  or the stem of a permanent implant  92  ( FIG. 9 ).  
         [0045]     With reference to  FIG. 8 , after the jig  10  is implanted the trial humeral replacement implant  74  is placed within the humerus  88  such that the stem  80  is seated within the interior  18  of the jig  10 . Specifically, the tapered stem  80  is inserted within the tapered interior  18  of the jig  10  until the diameter of the stem  80  becomes the same as or larger than the interior  18  of the jig  10 , thus preventing the implant  74  from being inserted further within the jig  10  and humerus  88 . The jig  10  supports the trial implant  74  within the humerus  88  to create a substantially even cavity between the trial humeral  74  and the humerus  88  to receive bone cement once the permanent implant  92  is in position.  
         [0046]     With the trial humeral  74  supported within the humerus  88  by the jig  10 , the humeral joint is reduced. If the trial humeral  74  is not at the correct height, the inserter  48  may be used to adjust the jig  10  accordingly. If the inserter  59  is used, the inserter  59  may remain secured to the jig  10  during the reduction processes because the trial humeral  74  may be inserted through the inner region  72  of the inserter  59 . The jig  10  may then be adjusted using the inserter  59  without removing the trial  74 .  
         [0047]     With reference to  FIG. 9 , after the trial humeral  74  is properly positioned, it is replaced with the permanent implant  92 . Because the dimensions of the permanent implant  92  are substantially similar to the dimensions of the trial humeral  74 , when the permanent implant  92  is seated within the interior  18  of the jig  10 , it will be in substantially the same position as the trial humeral  74  was. Because the permanent implant  92  is substantially similar to the trial humeral  74 , the permanent implant  92  need not be described in detail. As with the trial implant  74 , support of the permanent implant  92  within the humerus  88  forms a substantially even cement mantle between the permanent implant  92  and the humerus  88  and prevents the permanent implant  92  from contacting the humerus  88 . Before the permanent implant  92  is supported by the jig  10  in proper position, bone cement  94  is introduced within the humerus  88  and later hardens within the mantle formed between the implant  92  and the humerus  88  to affix the implant  92  within the humerus. The permanent implant  92  may be provided with reference marks  96 , which are similar to the marks  82  of the trial  74 , to insure that the permanent implant  92  is in relatively the same position as the trial  74 .  
         [0048]     The above description is meant to encompass various additional embodiments of the present invention. For example, with reference to  FIG. 10 , the interior  18  of the implant  10  may have parallel sidewalls. Further the implant  10  may have a receiving surface  98  operable to receive the trial implant  74  and the permanent implant  92 , as illustrated. The receiving surface  98  may be any suitable surface or detail operable to mate with a corresponding stop surface or detail, such as stop surface  100 , of the trial implant  74  or the permanent implant  92 , as illustrated. In the exemplary embodiment of  FIG. 10 , the receiving surface  98  is a recessed surface of the interior  18  proximate to the second end  14  and the stop surface  100  is a stepped surface of the stem  80 .  
         [0049]     The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.