Abstract:
An intraosseous device is disclosed that can be positioned to straddle a bone fracture to stabilize the fracture and provide structural support for the bone and the surrounding areas. The device includes wire assemblies that are deployable on each side of the fracture to anchor the device within the bone. For the device, an elongated tube is formed with a plurality of slots at each tube end. A central member is mounted inside the tube and moveable members are positioned inside the tube, one at each tube end. Wires connect the moveable members to the central member. A rod cooperates with each moveable member and is rotatable to draw each moveable member inwardly toward the central member. This forces each wire to bow and displace a central wire portion through a corresponding slot and into contact with the bone&#39;s inner wall to anchor the device in the bone.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention pertains generally to medical devices for treating, bone injuries and disease. More specifically, the present invention pertains to internal bone fixation devices that are designed to stabilize an injured bone and provide structural support. The present invention is particularly, but not exclusively, useful as a fixation device that is positionable, within a bone, to treat a long bone fracture. 
       BACKGROUND OF THE INVENTION 
       [0002]    The bones of the human skeleton serve many important structural and mechanical purposes. Among them, the bones protect organs, provide a frame to support the body; and function along with muscle and tissue to allow parts of the body to move. Unfortunately, bones are often subject to damage, for example, stress fractures due to high force impacts or bone loss due to osteoporosis or bone cancer. 
         [0003]    Long bones are generally classified as bones that are longer than they are wide. Long bones in the human skeletal system include the femora, tibiae, fibulae, humeri, radii, ulnae, metacarpals, metatarsals, phalanges and the clavicles. Long bones are crucial for skeletal mobility and, due to their size and location on the body, account for the majority of bone fractures. 
         [0004]    Healing of an injured bone involves natural processes. Typically, a fracture treatment regimen consists of restoring the fractured pieces of bone to their natural positions (if necessary), and maintaining those positions while the bone heals. Typically, this process involves aligning the bone portions into suitable positions to facilitate healing and verifying the improved alignment with an X-ray. Once the bone portions are in position to heal, the bone, surrounding tissue and adjacent joints can be stabilized to prevent movement and preserve anatomical alignment. Typically, the stabilization period varies depending on the type of injury. In some cases, only temporary stabilization is required. For example, some injuries may sufficiently heal in about 4-6 weeks. On the other hand, some injuries may require permanent stabilization. 
         [0005]    Apparatus for stabilizing a bone can include plaster or fiberglass casts and metal splints. In addition, surgical nails, screws, plates and wires are often implanted surgically to directly hold the fractured bone together. Also, for some types of long bone fractures, external fixators have been employed. In some cases, permanent stabilization can be achieved by affixing a metal plate or rod directly to the exterior of a fractured bone, for example, using screws to attach the plate or rod to the bone. The plate or rod can then be left permanently implanted within the body to promote healing and add needed structural support to the damaged area. 
         [0006]    In addition to the techniques described above, intramedullary rods have been used to stabilize bone injuries (and thereby promote healing) and add structural support. As the name implies, an intramedullary rod is a metal rod that is forced into the medullary cavity of a bone, typically a long bone, and affixed therein, typically using screws. The screws, however, can be damaging to the bone and can result in mechanical failure and/or biological incompatibility. 
         [0007]    In light of the above, it is an object of the present invention to provide a device that can be implanted into a damaged bone to stabilize the bone and provide structural support for the bone and the surrounding areas. Another object of the present invention is to provide a device that can be positioned within a long bone to straddle a bone fracture with attachment points on each side of the bone fracture. Still another object of the present invention is to provide an intraosseous device positionable to straddle a bone fracture with attachment points that are relatively non-invasive to the bone structure. Yet another object of the present invention is to provide an intraosseous expandable fixation device that is easy to use, is relatively simple to manufacture, and is comparatively cost effective. 
       SUMMARY OF THE INVENTION 
       [0008]    In accordance with the present invention, an intraosseous device that can be implanted inside a fractured bone to stabilize the fracture and provide structural support for the bone and the surrounding areas is provided. More specifically, the intraosseous device can be positioned within a bone to straddle a bone fracture. Once properly positioned inside the bone, wire assemblies contained in the device can be deployed on each side of the fracture to anchor the device within the bone. 
         [0009]    In greater structural detail, the device includes an elongated tube having a tube wall that defines a central tube axis in the direction of tube elongation. At one end of the tube, a proximal tube portion is formed with a plurality of axially aligned slots that extend through the tube wall. At the other end, a distal tube portion is formed with a plurality of axially aligned slots that extend through the tube wall. For example, in one embodiment of the device, four slots are uniformly spaced around the circumference of the tube in both the proximal and distal portions. 
         [0010]    Additionally, for the present invention, a hollow, central member is positioned inside the tube and affixed, to the tube wall between the proximal and distal tube portions. Also positioned inside the tube are a hollow proximal member and a hollow distal member. The proximal member is positioned in the tube adjacent to the proximal tube portion and the distal member is positioned in the tube adjacent to the distal tube portion. Both the proximal member and the distal member are disposed in the tube to allow axial movement of proximal and distal members within the tube. 
         [0011]    To anchor the device to the bone on each side of a bone fracture, the device includes a plurality of proximal wires and a plurality of distal wires. Each proximal wire has a first end that is affixed to the central member and a second end that is affixed to the proximal member. Similarly, each distal wire has a first end that is affixed to the central member and a second end that is affixed to the distal member. Moreover, each proximal wire is aligned with a corresponding slot in the proximal tube portion and each distal wire is aligned with a corresponding slot in the distal tube portion. When the wires are in a relaxed state, they are substantially straight and extend in directions that are substantially parallel to the central tube axis. 
         [0012]    In accordance with the present invention, an actuator rod is provided to move the proximal and distal members within the tube. With this movement, the wires deploy and anchor the device to the bone. In greater structural detail, an actuator rod includes a shaft that is threaded (e.g. with male threads) at a first shaft end and is formed with a head (e.g. bolt head) at a second shaft end. The threaded end of the rod is fed through the hollow proximal and central members to engage a set of threads (e.g. female threads) that are formed in the distal member. The rod is then threaded into the distal member until the rod head abuts the proximal member. At this point, continued rotation of the rod will cause the proximal and distal members to move inwardly toward the central member. This, in turn, will have an effect on the wires. More specifically, each wire will be forced to bow outwardly and displace a central wire portion away from the tube axis and through a corresponding slot formed in the tube. 
         [0013]    In use, the intraosseous device is assembled with the proximal and distal members initially spaced from the central member at respective distances that allow the wires to be in a relaxed state (i.e. substantially straight). Next, the device is positioned within a bone, for example, in the medullary cavity of a long bone, with the proximal tube portion on one side of a bone fracture and the distal tube portion or the other side of the bone fracture. Once the device and bone are properly positioned, the actuator rod is rotated, for example, by inserting a narrow tool into a small opening formed in the bone. As described above, turning the actuator rod causes each wire to bow and extend a central portion of each wire through a corresponding slot. Further rotation of the actuator rod can be performed until each wire contacts and applies a suitable anchoring force against the inner wall of the bone to secure the device in the bone. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    The novel features of this invention, as well as the invention itself, both as to its structure and its operation, will be best understood from the accompanying drawings, taken in conjunction with the accompanying description, in which similar reference characters refer to similar parts, and, in which: 
           [0015]      FIG. 1  is a sectional view showing an intraosseous expandable fixation device positioned to straddle a fracture in a femur bone in accordance with the present invention; 
           [0016]      FIG. 2  is a perspective view of a portion of an intraosseous expandable fixation device shown with the deployable wires in their relaxed, stowed configuration; 
           [0017]      FIG. 3  is a cross sectional view of the intraosseous expandable fixation device portion shown in  FIG. 2  as seen along line  3 - 3  in  FIG. 2 ; 
           [0018]      FIG. 4  is a plan view of an actuator rod; and 
           [0019]      FIG. 5  is a cross sectional view of the intraosseous expandable fixation device including the actuator rod, as seen along line  3 - 3  in  FIG. 2 , and with the wires in their deployed configuration. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0020]    Referring initially to  FIG. 1 , a device  10  is shown operationally positioned in a long bone  12 , which, for illustration purposes, is an adult femur bone  12  which has suffered a fracture  14 . As shown in  FIG. 1 , the device  10  can be positioned within the bone  12  to straddle the bone fracture  14 . Although the device  10  is shown positioned within the medullary cavity  16  of the bone  12 , it is to be appreciated that other positions within the bone  12  may be suitable for employing the device  10  such as location  18  or location  20 . Moreover, in spite of the fact that the device  10  may have certain advantages in treating fractured bones and/or being operationally positioned to straddle a fracture, it is to be appreciated that the device  10  can be useful for other purposes. For example, the device  10  may be used to provide support on one side of a fracture or to provide support in situations where bone loss or bone disease has occurred. 
         [0021]    Referring now to  FIG. 2 , a portion of the device  10  illustrated in  FIG. 1  is shown. As seen there, the portion includes an elongated tube  22  having a tube wall  24  that defines a central tube axis  26  in the direction of tube elongation. It can further be seen that the tube  22  includes a proximal tube portion  28  that is formed with a plurality of axially aligned slots  30   a,b  that extend through the tube wall  24 . The tube  22  also includes a distal tube portion  32  that is formed with a plurality of axially aligned slots  34   a,b  that extend through the tube wall  24 . For the exemplary embodiment shown, four slots are uniformly spaced around the circumference of the tube  22  (i.e. ninety degrees apart) in the proximal portion  28  and four slots are uniformly spaced around the circumference of the tube  22  in the distal portion  32 . Although an embodiment with four slots in each portion is shown and described, it is to be appreciated that more than four slots per portion and as few as one slot per portion may be used. Moreover, the slots do not necessarily need to be uniformly spaced around the circumference of the tube  22  for suitable operation. 
         [0022]    Cross referencing  FIGS. 2 and 3 , it can be seen that, a hollow, central member  36  is positioned inside the tube and affixed to the tube wall  24  via pin  38  between the proximal portion  28  and distal portion  32 . Other attachment means such as adhesive bonding may be used. As shown, the central member  36  can be shaped as a hollow cylinder with an outside diameter that is approximately equal to the inside diameter of the tube  22 . 
         [0023]    Continuing with  FIG. 3 , it can be seen that a hollow proximal member  40  and a hollow distal member  42  are positioned inside the tube  22 . Specifically, the proximal member  40  is positioned in the tube  22  adjacent to the proximal tube portion  28  and the distal member  42  is positioned in the tube  22  adjacent to the distal tube portion  32 . Both the proximal member  40  and the distal member  42  are disposed in the tube  22  to allow axial movement of the proximal member  40  and the distal member  42  within the tube  22 . As shown, the proximal member  40  and the distal member  42  can each have portions shaped as hollow cylinders with an outside diameter that is approximately equal to the inside diameter of the tube  22 . In addition, a key  44  that is formed on the tube wall  24  can ride in a groove  46  that is formed in distal member  42  to prevent rotation of the distal member  42  within the tube  22  while allowing axial movement of the distal member  42 . A similar rotation prevention means (not shown) can be provided to prevent rotation of proximal member  40  (while allowing axial, movement). It can also be seen that the distal member  42  is formed with a set of internal threads  48  (e.g. female threads). 
         [0024]    Continuing with  FIG. 3 , it can be seen that a plurality of proximal wires  50   a ,  50   c  are provided with each proximal wire having a first end that is affixed to the central member  36  and a second end that is affixed to the proximal member  40 . For this purpose, any attachment method known in the pertinent art for attaching a wire to a structure can be used. Also shown, a plurality of distal wires  52   a ,  52   c  are provided with each distal wire having a first end that is affixed to the central member  36  and a second end that is affixed to the distal member  42 .  FIG. 3  shows that each wire  50   a ,  50   c ,  52   a ,  52   c  is aligned with a corresponding slot  30   a ,  30   c ,  34   a ,  34   c , respectively. 
         [0025]      FIG. 4  shows an actuator rod  54  for use with the structure shown in  FIG. 3 . As shown in  FIG. 4 , the actuator rod  54  includes a shaft  56  having a set of external threads  58  (i.e. with male threads) that are formed in the shaft  56  at one end. As detailed further below, the external threads  58  are shaped and sized to achieve successful mating with internal threads  48 , thus, allowing the actuator rod  54  to engage the distal member  42 .  FIG. 4  further shows that the actuator rod  54  includes an abutment head  60 , which as shown in  FIG. 5 , can be formed with a hexagonal shaped recess  62  (other shapes may be used) allowing a complementary tool to fill recess  62  and rotate the actuator rod  54 . 
         [0026]    As best seen in  FIG. 5 , to assemble the device  10 , the threaded end of the rod  54  is fed through the hollow proximal member  40  and central member  36  to engage internal threads  48  formed in the distal member  42 . Once the threads  48 ,  58  are engaged, the rod  54  is rotated until the rod head  60  abuts the proximal member  40 . At this point, the device  10  is assembled and can be implanted into a bone. 
         [0027]    In the assembled configuration and prior to implantation, the wires  50   a ,  50   c ,  52   a ,  52   c  are in their initial, stowed configuration as shown in  FIG. 3 . In this configuration, the proximal member  40  and distal member  42  are spaced from the central member  36  at respective distances that allow the wires  50   a ,  50   c ,  52   a ,  52   c  to be in a relaxed state. As further shown in  FIG. 3 , when the wires  50   a ,  50   c ,  52   a ,  52   c  are in a relaxed state, they are substantially straight and extend in directions that are substantially parallel to the central tube axis  26 . 
         [0028]    With the device  10  assembled and the wires  50   a ,  50   c ,  52   a ,  52   c  in a relaxed state, the device  10  can be positioned within a bone. Comparing  FIGS. 1 and 3 , it can be seen that when the device  10  is properly positioned within a bone  12 , the proximal tube portion  28  is positioned on one side of bone fracture  14  and the distal tube portion  32  is positioned on the other side of bone fracture  14 . Once the device  10  and bone  12  are properly positioned and aligned, the wires  50   a ,  50   c ,  52   a ,  52   c  can be deployed to anchor the device  10  in the bone  12 . 
         [0029]    To deploy the wires  50   a ,  50   c ,  52   a ,  52   c , the actuator rod  54  is rotated, for example, by inserting a narrow tool (not shown) into a small opening formed in the bone  12 . Deployment of the wires  50   a ,  50   c ,  52   a ,  52   c  can best be appreciated by comparing  FIG. 3  (stowed wires) and  FIG. 5  (deployed wires). As shown there, rotation of the actuator rod  54  causes the proximal member  40  and distal member  42  to move inwardly along the axis  26  toward the central member  36 . The effect of this is that the straight line distance between the ends of each wire  50   a ,  50   c ,  52   a ,  52   c  is decreased. As best seen in  FIG. 5 , during rotation of the actuator rod  54 , each wire  50   a ,  50   c ,  52   a ,  52   c  bows outwardly and a central wire portion moves radially from the tube axis  26  and through a corresponding slot  30   a ,  30   c ,  34   a ,  34   c  formed in the tube wall  24 . Rotation of the actuator rod  54  can be continued until each wire  50   a ,  50   c ,  52   a ,  52   c  contacts and applies a suitable anchoring force against the inner wall of the bone  12  to secure the device  10  in the bone  12 . 
         [0030]    For the device  10 , the wires are typically made of a biocompatible material such as a titanium alloy or other biocompatible metal. Additionally, the other components described above are preferably constructed of rigid biocompatible metal such as titanium alloys. 
         [0031]    Those skilled in the pertinent art will appreciate that several variations of the above described embodiments are clearly within the scope of the present invention. For example, an embodiment can be constructed in which the proximal and distal members are stationary and two central members are axially moveable to bow the wires. To achieve movement of the central members, two actuator rods may be used or a single rod having two sets of threads that are spaced apart along the rod shaft (e.g. one left hand threadset and one right hand threadset). In another variation, a different technique known in the art for controllably adjusting the axial spacing of two members (i.e. the proximal and distal, members) may be used. 
         [0032]    While the particular Intraosseous Expandable Fixation Device as herein shown and disclosed in detail is fully capable of obtaining the objects and providing the advantages herein before stated, it is to be understood that it is merely illustrative of the presently preferred embodiments of the invention and that no limitations are intended to the details of construction or design herein shown other than as described in the appended claims.