Patent Publication Number: US-2015088267-A1

Title: Bone augment interlocking with bone plate

Description:
PRIORITY 
     This application claims priority to U.S. Provisional Application No. 61/612,701, filed with the United States Patent and Trademark Office on Mar. 19, 2012, the entire contents of which are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to surgical devices, and more particularly, to a bone augment for interlocking with a bone plate. 
     2. Brief Description of the Related Art 
     In the United States, the number of total joint replacements is increasing every year. In 2010, an estimated 500,000 patients received total hip or knee replacements and this does not include those receiving total shoulder, elbow or ankle replacements. The number of total joint replacements will continue to increase as the elderly population grows. Additionally, as engineering improves longevity of prosthetic implants, indications for patients will broaden, driving the age of implantation to younger populations. 
     A bone void can occur in a variety of settings, including fractures requiring total joint replacement as well as high-energy trauma. Prosthetic implants are generally used to treat such fractures. Bone voids occur in areas surrounding prosthetic implants, often resulting from metal or plastic wear, causing an osteolytic reaction leading to bone resorption and loss. The rise in patients requiring prosthetic implantations will result in an increase in infections, mechanical failures and periprosthetic fractures that lead to creation of bone voids. Inserting a prosthetic implant across a bone void can result in an unstable setting. Currently, the options for fixating fractures across bone voids are limited. 
       FIG. 1  illustrates an implant  100  extending from a femur  110  that is to be inserted into a cup area  115  of a hip bone  120 , in the case of a typical hip replacement. However, the hip bone  120  demonstrates an incidence of bone loss, i.e. bone void  130 , such that when the implant  100  is inserted into the cup area  115 , stable fixation will not occur because the implant  100  is not secured to the entire surface of the cup area  115 . 
     SUMMARY OF THE INVENTION 
     According to an embodiment of the present invention a bone augment is provided for filling a void in a bone and providing secure fixation of an implant to the bone. The bone augment includes a sidewall structure having a top surface, a first end and a second end. The sidewall structure rises from a base of the bone augment. The first end of the bone augment is disposed opposite to the second end of the bone augment. An insertion aperture is disposed within the bone augment and extends from the first end of the bone augment to the second end of the bone augment. The bone augment receives a bone plate within the insertion aperture and the bone plate fixes the bone augment within the void. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other objects, features and advantages of certain embodiments of the present invention will be more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  illustrates a diagram of an implant extending from a femur being inserted into a cup area of a hip bone, in a typical hip replacement; 
         FIG. 2  illustrates a perspective view of a bone augment for filling a void in a bone and providing secure fixation of an implant to the bone, according to an embodiment of the present invention; 
         FIG. 3  illustrates a cross-sectional view of a bone plate inserted within a bone augment and affixed to a bone, according to an embodiment of the present invention; 
         FIG. 4  illustrates a top view of a bone plate inserted within a bone augment, according to an embodiment of the present invention; 
         FIG. 5  illustrates a perspective view of a bone augment including screw-receiving protrusions, according to an embodiment of the present invention; 
         FIG. 6  illustrates a front view of a bone augment including a bone augment cap, according to an embodiment of the present invention; and 
         FIG. 7  illustrates a sagittal view of an ilium, acetabulum, pubis, and ischium including a bone plate and a bone augment for treatment of a bone void, according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS OF THE PRESENT INVENTION 
     The following detailed description of embodiments of the invention will be made in reference to the accompanying drawings. In describing the invention, explanation about related functions or constructions known in the art are omitted for the sake of clearness in understanding the concept of the invention to avoid obscuring the invention with unnecessary detail. 
     A bone augment is provided for bone fixation in setting a fracture in native bone, periprosthetic bone loss, or where there is a risk of future bone loss. The bone augment may be utilized to fill a void in any bone. The bone augment provides treatment for filling a void in a bone with concurrent skeletal fixation by interlocking with a bone plate. 
       FIG. 2  illustrates a perspective view of a bone augment for filling a void in a bone and providing secure fixation of an implant to the bone, according to an embodiment of the present invention. Bone augment  200  includes a sidewall structure  210 . The sidewall structure  210  includes a top surface  230 , a first end  250  and a second end  260 . Thus, the top surface  230 , the first end  250  and the second  260  indicate relative locations of the sidewall structure  210 . The sidewall structure  210  rises from a base  220  of the bone augment  200 . According to an embodiment of the present invention, the sidewall structure  210  is configured as a rounded surface arising from the base  220 , the base  220  having a flat surface. For example, the shape of the bone augment  200  may be embodied as a half-sphere. 
     The first end  250  of the bone augment  200  is disposed opposite to the second end  260  of the bone augment  200 . An insertion aperture  240  is disposed within the bone augment  200  and extends from the first end  250  to the second end  260 . The insertion aperture  240  provides an opening in the bone augment  200  that receives a bone plate and allows the bone plate to pass through the bone augment  200 . According to an embodiment of the present invention, the insertion aperture  240  extends through the center of the bone augment  200 , i.e., the insertion aperture  240  remains equidistant to the sidewall structure  210 , the base  220 , and the top surface  230  as the insertion aperture  240  extends through the bone augment  200 . The bone plate fixes the bone augment  200  within a void in a bone, allowing stable fixation of an implant to the bone. 
     According to an embodiment of the present invention, the insertion aperture  240  may extend through the bone augment  200  in a concave or a convex manner with respect to the top surface  230 . Thus, the insertion aperture  240  is centered in the bone augment  200  at the first end  250  and the second  260 , but within the bone augment  200 , the insertion aperture  240  may extend in a curved manner closer to the base  220  when concave and closer to the top surface  230  when convex. Similarly, the insertion aperture  240  can be concave or convex with respect to the sidewall structure  210 . 
     Additionally, where the insertion aperture  240  is concave with respect to the top surface  230 , openings of the insertion aperture  240  may extend through the top surface  230 . In this configuration, the openings of the insertion aperture  240  receive the bone plate perpendicular to a surface of the top surface  230 . 
     Where the insertion aperture  240  is convex with respect to the top surface  220 , openings of the insertion aperture  240  may extend through the base  220 . In this configuration, the openings of the insertion aperture  240  receive the bone plate perpendicular to the surface of the base  220 . 
     The bone augment  200  is constructed of a porous substrate that allows ingrowth of the bone. The porous substrate may be a porous metal specifically designed for medical implantation. For example, the porous substrate may be tantalum, or a tantalum alloy. Use of the tantalum alloy allows for the size and shape of the augment  200  to be adjusted prior to implantation, i.e., the sidewall structure  210  and the base  220  of the augment  200  can be molded to fit the bone void during the surgical procedure. According to an embodiment of the present invention, the top surface  230  is contoured to receive the particular implant in use. 
     The porosity of the porous substrate allows bony ingrowth into the augment  200 , providing increased adherence of the bone to the bone augment  200  and, thus, improved stability for filling the void in the bone. According to an embodiment of the present invention, the augment  200  includes a plurality of pre-formed pores. The pores may be formed in the sidewall structure  210  and the base  220 . 
       FIG. 3  illustrates a cross-sectional view of a bone plate inserted within a bone augment and affixed to a bone, according to an embodiment of the present invention. The sidewall structure  210  includes a first sidewall  300  and a second sidewall  310  extending from the base  220  to meet the top surface  230 . An open channel  320  extends through the top surface  230  from the first end  250  to the second end  260  of the bone augment  200 . The channel  320  provides access to the insertion aperture  240  through the top surface  230  of the bone augment  200 . Thus, the bone plate  330  may be inserted within the insertion aperture  240  through the first end  250  and out of the second end  260  of the bone augment  200 . Alternatively, the bone plate  330  may be inserted within the insertion aperture  240  through the channel  320 . The channel  320  may be wide enough to allow insertion of screws through the bone plate  330 , through the bone augment  200 , and into a bone  340  at varying angles. 
     The bone augment  200  may include pre-drilled screw holes (not shown). The pre-drilled screw holes may be threaded to provide additional locking. The pre-drilled screw holes may be provided with up to  15  degrees of freedom. Thus, the screws may be inserted into the pre-drilled screw holes in any direction, providing a variety of predetermined fixation angles. However, the bone augment  200  does not require pre-drilled screw holes. Specifically, using a multi-point contact threaded screw head and a differential stiffness metal for the screw and the bone plate, such as titanium, or a cobalt-chromium screw with a titanium bone plate, the screws can cut a screw hole tract in the bone augment  200  allowing for variable angle locking that is not predetermined. 
       FIG. 4  illustrates a top view of a bone plate inserted within a bone augment, according to an embodiment of the present invention. Specifically, the augment  200  includes a fastener prong  400  extending from the top surface  230  across the insertion aperture  240 . A length of the fastener prong  400  may be less than a width of the channel  320 , thus leaving the channel  320  open to the insertion aperture  240 . However, according to an embodiment of the present invention, the fastener prong  400  may extend entirely across the insertion aperture  240 , partially enclosing a portion of the top surface  230  of the bone augment  200  around the bone plate  330 . 
     The fastener prong  400  includes a first fastener prong  410  disposed opposite to a second fastener prong  420  on the top surface  230 . The first fastener prong  410  and the second fastener prong  420  extend towards a middle portion of the insertion aperture  240  to a point above and/or below screw insertion openings  430  of the bone plate  330  when the bone plate  330  is inserted within the insertion aperture  240 . The first fastener prong  410  and the second fastener prong  420  secure the bone plate  330  within the insertion aperture  240 . According to an embodiment of the present invention, the bone augment  200  includes additional fastener prongs, i.e., third, fourth, fifth and sixth fastener prongs etc., that secure the bone plate  330  within the insertion aperture  240  along the entire length of the bone augment  200 . 
     The augment  200  includes a plurality of recessed portions  440  in the top surface  230 . The plurality of recessed portions  440  extend across the channel  320  a distance less than a length of the fastener prong  400 . The recessed portions  440  include a first recessed portion  450  and a second recessed portion  460  extending across the insertion aperture  240 . According to an embodiment of the present invention, the first recessed portion  450  and the second recessed portion  460  extend the top surface  230  around the bone plate  330  across the insertion aperture  240  to a point less than the fastener prong  400 . 
       FIG. 4  further illustrates that the bone plate  330  is aligned within the insertion aperture  240  such that the first recessed portion  450  and the second recessed portion  460  allow access to the openings  430  of the bone plate  330 . That is, the first recessed portion  450  and the second recessed portion  460  extend across the insertion aperture  240  to a point where variable-angled insertion of bone screws through the openings  430  remains possible. The first recessed portion  450  and the second recessed portion  460  may extend farther across the insertion aperture  240  when the first recessed portion  450  and the second recessed portion  460  gradually reduce in thickness while extending across the insertion aperture  240 . Thus, according to an embodiment of the present invention, a thickness of the plurality of recessed portions  440  and a thickness of the fastener prong  400  decreases as the plurality of recessed portions  440  and the fastener prong  400  extends across the insertion aperture  240 . Decreasing thickness of the plurality of recessed portions  440  and the fastener prong  400  allows variable angled insertion of bone screws through the bone plate  330  and into the bone augment  200 . The thickness of the plurality of recessed portions  440  and the fastener prong  400  may be thinnest at the middle portion of the insertion aperture  240 . The first fastener prong  410 , the second fastener prong  420 , the first recessed portion  450  and the second recessed portion  460  may similarly gradually reduce in thickness while extending across the insertion aperture  240 . 
     The openings  430  of the bone plate  330  allow insertion of screws, i.e., locking or non-locking elements/fasteners. The screws may be a statically locked element or a variable-angled locked element for securing the bone plate  330  and the bone augment  200  to the bone  340 . The bone plate  330  and the bone augment  200  may be coated by a resorbable or non-resorbable substrate for delivering medication including antibiotics and growth factors. Thus, the bone augment  200  providing a vehicle for local delivery of medication. 
       FIG. 5  illustrates a perspective view of a bone augment including screw-receiving protrusions, according to an embodiment of the present invention. The bone augment  200  includes screw-receiving protrusions  500  that extend from within the insertion aperture  240 . The screw-receiving protrusions  500  rise from a bottom surface of the insertion aperture  240  in a perpendicular manner. The screw-receiving protrusions  500  extend into the openings  430  of the bone plate  330  when the bone plate  330  is inserted into the insertion aperture  240 . Thus, the bone plate  330  is locked into the bone augment  200 , preventing movement of the bone plate  330  while the bone plate  330  is screwed into the bone  340 . 
       FIG. 5  further illustrates the insertion aperture  240  having an expanded opening  510  at the first end  250  of the bone augment  200 . The expanded opening  510  includes a first arcuate surface  520  and a second arcuate surface  530 . The first arcuate surface  520  and the second arcuate surface  530  extend from the insertion aperture  240  to meet the first end  250  of the bone augment  200 . The first arcuate surface  520  includes a first arcuate rim  540  extending along an upper edge of the top surface  230  from the insertion aperture  240  to the first end  250 . The second arcuate surface  530  includes a second arcuate rim  550  extending along the upper edge of the top surface  230  from the insertion aperture  240  to the first end  250 . A width of the expanded opening  510  is greater than a width of the insertion aperture  240 . Accordingly, when a portion of the bone plate  330  is inserted within the insertion aperture  240 , portions of the bone plate  330  outside of the bone augment  200  can be moved laterally with respect to the bone augment  200  in the direction of arrow A. Positioning of the bone plate  330  can therefore be adjusted, allowing proper fixation of the bone plate  330  to the bone  340 . 
       FIG. 6  illustrates a front view of a bone augment including a bone augment cap, according to an embodiment of the present invention. A bone augment cap  600  includes an implant receiving surface  610  and a cap base  620 . The bone augment cap  600  may be constructed of a porous substrate, similar to the bone augment  200 . However, since the bone augment cap  600  is not in contact with the bone  340 , the bone augment cap  600  may be constructed of any material suitable for medical implantation. The implant receiving surface  610  rises from the cap base  620 . The implant receiving surface  610  is provided in a shape that contours to receive a particular implant, thus providing a stable environment for fixation of the implant to the bone  340 . The contour of the implant receiving surface  610  illustrated in  FIG. 6  is provided for illustrative purposes only. That is, the implant receiving surface&#39;s  610  contour may vary depending on the particular implant in use. 
     The bone augment cap  600  further includes a first cap end  622  and a second cap end  624 . The first cap end  622  is disposed opposite to the second cap end  624 . A first cap flange  630  extends from the cap base  620  on the first cap end  622 . A second cap flange  632  extends from the cap base  620  on the second cap end  624 . The first cap flange  630  includes a first bone plate-receiving  aperture  640  and the second cap flange  632  includes a second bone plate-receiving aperture  650 . When the bone augment cap  600  is attached to the bone augment  200  in the direction of arrow B, the cap base  620  rests on the top surface  230  and the first and second bone plate-receiving apertures  640  and  650  overlap with the insertion aperture  240 . Thus, the bone plate  330  is inserted through the first bone plate-receiving aperture  640 , through the bone augment  200  via the insertion aperture  240 , and out through the second bone plate-receiving aperture  650 , locking the bone augment cap  600  to the bone augment  200 . Accordingly, the bone augment cap  600  contacts the top surface  230  and interlocks with the bone augment  200  when the bone plate  330  is inserted within the insertion aperture  240 . 
       FIG. 7  illustrates a sagittal view of an ilium, acetabulum, pubis, and ischium including a bone plate and a bone augment for treatment of a bone void, according to an embodiment of the present invention. The bone plate  330  is fixed to a hip bone  700 . The bone augment  200  fills a bone void  710  in the hip bone  700 . The bone plate  330  attaches the bone augment  200  to the hip bone  700  with bone screws inserted through the bone plate openings  430 . 
       FIG. 7  further illustrates an acetabular component  720 , i.e., a socket portion of a hip replacement, of a total hip arthroplasty revision where a failed total hip arthroplasty resulted in the bone void  710  requiring use of the bone augment  200 . The bone void  710  can also occur as a result of trauma or chronic disease. The acetabular component  720  includes locking tines  730 , which lock-in a polyethylene liner (not shown) over the acetabular component  720 . The acetabular component  720  also includes component screw holes  740  for fixation of locking screws flush with a surface of the hip bone  700 . 
     In the embodiment illustrated in  FIG. 7 , the bone augment  200  is inserted above and behind the acetabular component  720 . Thus, the bone plate  330  locks the bone augment  200  into the bone void  710 , providing a stable base for the acetabular component  720  to be fixed to the hip bone  700 . 
     While the invention has been shown and described with reference to certain embodiments of the present invention thereof, it will be understood by those skilled in the art that various changes in details may be made therein without departing from the spirit and scope of the present invention as defined by the appended claims and equivalents thereof.