Abstract:
A bone fixation device and method for compressing bone or bone fragments temporarily or permanently using a tension strip to surround the exterior surface of the bone or bone fragments and applying a force to the tension strip wherein the bone or bone fragments are compressed together. Bone or bone fragments are able to heal more quickly when compressed under super natural pressure. The temporary tension strips may be made of bioresorbable polymer and a radiopaque dopent so that the tension strip is visible under fluoroscopic observation.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    U.S. provisional application No. 61/671,703 dated Jul. 14, 2012 and PCT application number PCT/US2013/050480 dated Jul. 15, 2013 the contents of which are hereby incorporated by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates generally to the field of medical devices. In particular, the present invention relates to devices for bone fixation and methods for using the device. 
         [0004]    2. Description of the Related Art 
         [0005]    External fixation is a surgical treatment used to set bone fractures in which a cast would not allow proper alignment of the fracture. In this kind of reduction, holes are drilled into uninjured areas of bones around the fracture and special bolts or wires are screwed into the holes. Outside the body, a rod or a curved piece of metal with special ball-and-socket joints joins the bolts to make a rigid support. The fracture can be set in the proper anatomical configuration by adjusting the ball-and-socket joints. 
         [0006]    Certain difficulties arise with the traditional manner of performing the external fixation; it can be difficult for the surgeon to estimate the necessary amount of tension force correctly. Also, currently available methods of bone fixation are time consuming and often require more than on technician to properly align bone and operate fixation devices simultaneously. 
         [0007]    Alternative bone fixation methods include open reduction internal fixation which involves the implementation of implants to guide the healing process of a bone, as well as the open reduction, or setting, of the bone itself. Open reduction refers to open surgery to set bones, as is necessary for some fractures. Internal fixation refers to fixation of screws and plates, intramedullary bone nails (femur, tibia, humerus) to enable or facilitate healing. Rigid fixation prevents sliding motion across lines of fracture to enable healing and prevent infection. Internal fixation techniques are often used in cases involving serious fractures such as comminuted or displaced fractures or in cases where the bone would otherwise not heal correctly with casting or splinting alone. 
         [0008]    Risks and complications can include bacterial colonization of the bone, infection, stiffness and loss of range of motion, non-union, mal-union, damage to the muscles, nerve damage and palsy, arthritis, tendonitis, chronic pain associated with plates, screws, and pins, compartment syndrome, deformity, audible popping and snapping, and possible future surgeries to remove the hardware. 
       BRIEF SUMMARY OF THE INVENTION 
       [0009]    The disclosed embodiments provide a device and method for bone fixation in a patient. 
         [0010]    In a particular embodiment, a tension strip is wrapped around bone fragments, the amount of tension required to provide compression to bone or bone fragments is adjusted on the tensioning device. Devices used in the field and related to compressing bone fragments are disclosed in U.S. Pat. No. 4,793,385 issued to Dyer, U.S. Pat. No. 5,250,049 issued to Michael, U.S. Pat. No. 6,076,234 issued to Betts, U.S. Pat. No. 6,589, 246, issued to Hack, U.S. Pat. No. 7,641,677 issued to Weiner, U.S. Pat. No. 7,806,895 issued to Weier and U.S. Pat. No. 8,034,076 issued to Criscuolo. Additional US Patent Applications have published including: 20080199824 Hargadon, 20090171357 Justin, 20100274248 Dell, 20100292698 Hulliger, 20100298828 Chico, 20100298829 Schaller, 201000305571 Pratt, 20110034928 Fernandez, and 20110112537 Bernstein. This and all other referenced patents are incorporated herein by reference in their entirety. Furthermore, where a definition or use of a term in a reference, which is incorporated by reference herein, is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply. 
         [0011]    The present invention achieves its objects by providing a device and method that quickly allows access around the bone fragments and a robust device for applying a preset amount of pressure to the bone. 
       OBJECTS OF THE INVENTION 
       [0012]    A bone fixation method comprising a tension strip with a low profile head for receiving a tension strip tail, the tension strip tail placed around a bone with a hollow guide and the hollow guide removed, a tension device (having a long straight body) comprising an engagement portion, a handle portion, and a cutting portion, the engagement portion further comprising a first slot and a second slot, wherein the low profile head is engaged with the tension device at the first slot and the tension strip tail is engaged with the tension device at the second slot, wherein the handle portion is actuated to create a force to move the tension strip tail relative to the low profile head creating tension pressure circumferentially around the bone optionally the cutting portion can be set to cut off excess tension strip tail at a preset pressure setting. 
         [0013]    A tension device that accommodates various widths and thickness of tension strips. 
         [0014]    Tension strips with low profile head and tail portions. 
         [0015]    Bone plate system with a metal or polymeric bar with grooves rather than holes for inexpensive manufacturing methods and adapted to receive tension strips in the groove to that the tension strip does not slide along the axial direction of the bar. 
         [0016]    Tension strip comprised of biodegradable material (commonly available polymers) that can be doped with radiopaque materials such as iodine compounds or metal strips for ease of visualization post procedure with x-ray or fluoroscopic methods. 
         [0017]    Tension strip tail ejection orientation is out of the top of the tension device whereas currently available methods eject cable in the downward direction, often times obstructing technician&#39;s access to the wound site. 
         [0018]    Displacement distance between the engaging head and tension strip exit port, reduce friction and speeds user&#39;s loading and reloading if necessary. 
         [0019]    Preset tension on the tensioning device to automatically set for young bones, adult bones and geriatric bones. The tensioning device can be set to cut automatically when the preset tension is reached. Or the device can be set not to cut automatically. 
         [0000]    Problems with Prior Art 
         [0020]    Current tools for applying tension to fastners have not been ergonomic, often having designs that obscure or make visualization of the fracture difficult. The present invention has an elongate body that is thin so as not to obscure a technician&#39;s vision of the fracture. 
         [0021]    Current tool designs incorporate vertical handles that can inhibit technician access to surgical sites. 
         [0022]    Currently available methods do not incorporate the use of a tension strip guide so that tensioning cannot be performed in short duration sequential order. 
         [0023]    The manners in which the invention achieves its objects and other objects which are inherent in the invention will become more readily apparent when reference is made to the accompanying drawings wherein like numbers indicate corresponding parts throughout. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0024]      FIG. 1  is a cross section view of a bone fracture. 
           [0025]      FIG. 2  is a drawing of a hip implant. 
           [0026]      FIG. 3  is a perspective view of a hip implant that has fractured a femur and metal strips. 
           [0027]      FIG. 4  is a drawing of metal tension strips compressing two bone fragments together. 
           [0028]      FIG. 5  is a top view of a preferred embodiment of a tension strip showing a serrated or textured contact surface. 
           [0029]      FIG. 6  is a side view of a preferred embodiment of a tension strip showing a serrated or textured contact surface. 
           [0030]      FIG. 7  is a perspective cross section of a preferred embodiment of a tension strip engagement head. 
           [0031]      FIG. 8  is a cross section view of a preferred embodiment of a tension strip head. 
           [0032]      FIG. 9  is a cross section view of a preferred embodiment of a tension strip showing a flat contact surface. 
           [0033]      FIG. 10  is a cross section view of a preferred embodiment of a tension strip showing a curved contact surface. 
           [0034]      FIG. 11  is a cross section view of a preferred embodiment of a tension strip showing a smooth contact surface. 
           [0035]      FIG. 12  is a cross section view of a preferred embodiment of a tension strip showing a serrated or textured contact surface. 
           [0036]      FIG. 13  is a side view of a preferred embodiment of a positioning device used for placing tension strips around a bone fragment. 
           [0037]      FIG. 14  is a cross sectional view of a positioning device used for placing tension strips around a bone fragment. 
           [0038]      FIG. 15  is a side view of a positioning device with designated openings. 
           [0039]      FIG. 16  is prior art showing relevant design for commercially available zip tie gun. 
           [0040]      FIG. 17  is prior art showing relevant design for commercially available zip tie gun showing an adjustable pre-set tensioning mechanism. 
           [0041]      FIG. 18  shows a preferred embodiment of a tensioning device. 
           [0042]      FIG. 19  shows a close up view of preferred embodiment of a tensioning device. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0043]      FIG. 1  illustrates a typical bone fracture of a human tibia into two bone fragments.  FIG. 2  illustrates a commercially available hip replacement joint. During a typical hip replacement surgery the technician may use a hammer to push a femoral anchor into the femur bone with great force. It is not uncommon with older patients to have hairline fractures or major fractures occur during the anchoring process in an artificial hip replacement.  FIG. 3  illustrates how prior art metal bands  71  and fasteners  72  could be used in multiple locations to hold fractured bone intact so that an artificial hip implant can be stabilized and bone can heal. 
         [0044]      FIG. 4  illustrates a method of compressing the two bone fragments together with tensioning strips  1 . 
         [0045]      FIGS. 5 and 6  show a tension strip  1  with differentially modified surfaces along the axis. The tension strip  1  comprises a proximal portion  6  that has ribs or texturing for attaching to a tension strip head  10  that further comprises an upper portion  11  and a bottom portion  12 . The tension strip head  10  is attached to a tension strip distal portion  8 . Tension strip  1  has a medial portion  7  disposed between the proximal portion  6  and distal portion  8 . The medial portion  7  is disclosed with various surface modifications to improve friction between the tension strip  1  and bone (see additional  FIGS. 9-12 ). The thickness of the tension strip  1  may also vary as well as the type of texture. 
         [0046]      FIG. 7  illustrates a preferred embodiment of a tension strip head  10 , often referred to as a ratchet in common commercial uses such as an electrician organizing many loose wires into a clean bundle of wires. The top portion  11  of the head  10  is fixed to the tension strip body distal portion  8 . The bottom portion  12  of the head  10  is flexibly attached to the tension strip body distal portion  8 . Either or both the top and bottom portions  11 , 12  of the tension strip head  10  may be textured (such as with ridges) to increase friction and ensure locking with the proximal portion  6  of the tension strip  1 . The proximal portion  6  of the tension strip  1  is folded over and passes between the top and bottom portions  11 , 12  of the tension strip head  10 . As the proximal portion  6  of the tension strip  1  continues to pass through the head  10  ribs on the tension strip surface temporarily displace the bottom portion  12  of the tension strip head  10 . Once the tension strip rib completely clears the ridge on the bottom portion  12  of the tension strip head  10  the bottom portion  12  of the tension strip head  10  returns to its natural unflexed position. In this unflexed position the rib and ridge of the bottom portion  12  of the tension strip head  10  are in frictional contact. Once the proximal portion  6  of the tension strip has passed through the tension strip head  10  a closed loop is formed and the loop cannot be loosened, it can only be tightened.  FIG. 8  shows a close up cross section of a tension strip head  10  with the tension strip proximal portion  6  engaged. 
         [0047]      FIGS. 9 and 10  show a cross section of a medial portion  7  of a tension strip  1 . In particular, in  FIG. 9  the bottom surface  13  has a generally flat profile, the surface could be smooth, have ribs, or otherwise have a textured surface that is complementary to the bottom portion  12  of the tensions strip head  10 .  FIG. 10  illustrates another preferred embodiment wherein the cross section of the tension strip  1  is curved in an arcuate profile. An arcuate profile could increase surface area contact between a tension strip medial portion  7  and bone fragment when compared to a similarly sized tension strip  1  with a flat surface, thus increasing the friction between the tension strip  1  and bone fragment. The more friction between the tensions strip  1  and the bone fragment the less likely that the tension strip  1  can slip in a longitudinal or radial direction. 
         [0048]      FIGS. 11 and 12  show the profile of a medial portion  7  of a tension strip  1 .  FIG. 11  shows a relatively smooth profile to reduce friction with tissue.  FIG. 12  shows textured teeth  14  on the bottom surface  13  of the tension strip  1 . The textured teeth  14  need not cover the entire length of the tension strip  1 , the textured teeth  14  can be preferably tailored to cover a certain bone fragment diameter from 2 millimeter to 10 millimeter for small diameter bones to 10 millimeter to 100 millimeter diameter for larger bones, so called engagement portion since it engages the tension strip head  10 . The bottom surface  13  of the tension strip  1  could have a textured surface for interfacing with the bone fragments and a different surface texture (such as ribs) for engaging the tensions strip head  10 . The proximal portion  6  of the tensions strip  1  can be quite long relative the diameter of the target bone to enable the technician to easily handle the tensions strip  1  and engage the tension strip head  10  into the tensioning device  50 . Thus, the tension strip  1  can have differentially textured bottom surfaces to improve engagement with bone and the tension strip head  10 . 
         [0049]      FIGS. 9 and 10  also illustrate a curved top side  15  of the tension strip  1 . This curved shape can reduce interference with tissue surrounding the bone. Although tension strips  1  could be made of surgical grade metals, in a preferred embodiment the tension strip  1  can be manufactured of a bioresorbable material. Bioresorption rate can be increased by adjusting the surface area to volume ratio of the tension strip profile. Thus, bones that require a longer time to heal could have a thicker cross section or a rectangular cross section. Smaller bones or bones that do not require a long time to heal, i.e. less than six weeks can utilize tension strips  1  with a small cross section or a cross section that promotes quick bioresorption. In a preferred embodiment, a bioresorbable polymer is doped with a radiopaque material to allow patient monitoring via x-ray or fluoroscopic methods. Typical bioresorbable polymers include polylactic and polyglycolic acids, polyetheylene and polydioxanone. Other bioresorbable polymers are well known for different applications such as bioresorbable sutures. Radiopaque dopents are known in the industry, for example compounds containing iodine, barium sulfate and bismuth oxides. Other common biocompatible materials are PEEK polymer. Additionally, the material used for the tension strip  1  must be capable of being manufactured in a sterile environment or capable of post manufacture sterilization, commonly ethylene oxide, autoclave or irradiation. Tension strips must be capable of maintaining a range of pressure from 30-200 psi (207-1379 kPa) because the preferred pressure setting long bones is 100-150 psi (690-1,034 kPa). 
         [0050]    Additionally, the tension strip  1  of a preferred embodiment is low profile and the guide member  22  has a similar low profile that reduces injury to tissue adjacent the bone fragment. The guide member conduit  23  is adapted to receive low profile tension strip  1  and reduce the overall profile of the guide member  22 . 
         [0051]      FIGS. 13 and 14  show an embodiment of a tensioning strip guide member  22 . The guide member  22  is an elongate member, which is generally hook shaped with a conduit  23  for receiving a tensioning strip  1 . A tension strip  1  is inserted into the conduit  23  with the head  10  of the tension strip  1  adjacent the distal opening  25  of the guide member  22 . When a tension strip  1  is placed in this manner, the tension strip head  10  has a profile that is just large enough to match the profile of the guide member  22 . Additionally, the tension strip proximal portion  6  may have a lower profile than the tension strip head  10  and the tension strip proximal portion  6  can fit in the narrow conduit  23  of the tension strip guide member  22 . The distal end  26  of the guide member  22  is inserted through tissue and around a bone fragment. In this embodiment, the low profile tension strip head  10  allows tension strip guide member  22  to pass through tissue without snagging the tissue. This embodiment will reduce trauma to the tissue surrounding the bone. The tension strip guide member  22  is then removed while the technician holds the tension strip head  10  in place. Once the guide member  22  is completely removed the tension strip  1  is in position and the technician can attach the tension strip head  10  to a tensioning device  50  ( FIGS. 16-19 ). The methods of attaching the tension strip  1  to the tension device  50  and actuating the tension device is more fully described below. In an alternative embodiment the conduit  23  of the tension strip guide member  22  is large enough to allow passage of a tension strip head  10  from a proximal opening  24  through a distal opening  25 .  FIG. 14  shows a distal portion  26  that has an angled cut so that it may lead and penetrate tissue with or without a tension strip  1  inserted into the conduit  23 . Contrast  FIG. 15 , the distal opening  125  is blunt and the use of a tension strip  1  would aid in the penetration of tissue. 
         [0052]    Preferred method of placement of a tension strip ( FIG. 15 ):
       1. Technician places tension strip proximal portion  6  into guide member distal opening  125  and pushes tension strip  1  into guide member conduit  123 , the tension strip  1  may optionally protrude out of guide member medial opening  126  or remain in the conduit  123 , the tension strip head  10  is in contact with distal opening  125  and occluding the guide member conduit  123 .   2. The distal opening  125  of the loaded guide member  122  is then placed through the tissue around the bone.   3. Technician then grabs the tension strip head  10 , holds tension strip head  10  in place and removes the guide member  122 .   4. The tension strip  1  is then ready to attach to the tension device  50 .       
 
         [0057]    In this embodiment the guide member  122  would have an extremely low profile, just thick enough to accommodate the thin proximal portion  6  of the tension strip  1 . Also, the low profile head  10  would actually act as an obturator to block the distal opening  125  from snagging tissue. The tension strip guide member  122  can be made of very strong metal such as aluminum or surgical steel so that the guide member  122  is strong enough to push though tissue and maintain the open conduit shape. 
         [0058]    Alternatively, a method utilizes a larger profile guide member  122  and concomitantly larger conduit that could accommodate the tension strip  1  and tension strip head  10 . In such a case the guide member  122  would be placed (with or without a tensions strip loaded) first, then multiple tension strips  1  could be fed through medial opening  126  to distal opening  125  as the guide member  122  is moved along the bone. This method would allow rapid placement of multiple tension strips  1 . 
         [0059]    In an alternative embodiment a tension strip  1  could be pushed through proximal opening  124  to avoid large tissue mass in unusual situations and then positioned to exit medial opening  126  or distal opening  125 . 
         [0060]    The guide member  22 , 122  disclosed in  FIGS. 13-15  have conduits  23 ,  123  respectively, the conduit profile is intended to be complementary to the profile of the tension strip, such that the typical profile is flat thin rectangular shape. Alternatively, the conduit profile could accommodate tension strip  1  profiles as shown in  FIGS. 9-10 . By matching the conduit profile and the tension strip profile the overall profile can be minimized and reduce injury to tissue around the bone. 
         [0061]      FIGS. 16-17  illustrate prior art and a preferred embodiment  FIGS. 18-19 , of a tensioning device  50 . Tensioning devices are know in various industries with various combinations of properties for various field applications. The tensioning device  50  of the present invention comprises a handle  52  that a user holds to control positioning of tensioning device  50 . The tensioning device  50  further comprises a lever  53  that when squeezed towards the handle  52  operates a ratcheting mechanism. The tensioning device  50  further comprises an elongate barrel  60  with a tensioning dial  59  at a proximal end and a blade  56  at a distal end. The distal end of the elongate barrel  60  has an entry channel  57  for receiving a tension strip proximal portion  6 . Once a tension strip  1  is in place around a bone the head  10  is abutted against distal surface  61  of barrel  60  and a user feeds the proximal potion  6  of the tension strip  1  through the head  10  and into entry channel  57 . The user can feed as much excess proximal portion  6  through the entry channel  57  until the proximal portion  6  exits through the top of the elongate barrel  60  via an exit channel  58 . before the user needs to operate the ratcheting mechanism. The ratcheting mechanism has an upper grasper  55  and a lower grasper  56  that are actuated by lever  53  by pivoting about axis  62 .  FIG. 19  shows the upper grasper  55  and lower grasper  56  in the relaxed position (prior to applying pressure to the lever) and  FIG. 18  shows the upper grasper  55  and lower grasper  56  in the actuated position (subsequent to applying pressure to the lever). The disclosed ratcheting mechanism shows that the proximal portion  6  has a textured surface on the top and bottom, alternative designs would only require one side of the proximal portion  6  to have texture and the graspers  55 , 56  are optional such that only one grasper is required to engage and pull a tension strip  1  through exit channel  58 . The ratcheting mechanism allows the operator to maintain very accurate control, while there is virtually no tension applied to the tension strip  1  the ratcheting mechanism can pull ten to thirty millimeters length. As tension in the tension strip  1  builds the user can operate the lever  53  to move advance the tension strip  1  by less than one half millimeter per lever action. 
         [0062]    The elongate barrel  60  further comprises a tension dial  59  at the proximal end and an on/off cutting switch  63 . The tension dial  59  rotates to set the pressure at which tensioning stops. The on/off cutting switch  63  is shown in  FIG. 18  is in the “on” position such that when pressure in the tension strip  1  reaches a predetermined pressure on the tension dial  59  a blade  54  cuts the proximal portion  6  adjacent the head  10 . By placing the blade adjacent the head  10  less than one millimeter of excess material is retained on the tension strip  1 . If the on/off switch  53  is moved to the forward position (not shown) the blade  54  will not automatically cut the tension strip  1 , thus the user can make adjustments to placement of tension strips  1  and gradually add pressure optimally to the fractured bone. 
         [0063]    In this inventive application it is critical that the tension strip  1  be cut as close to the tension strip head  10  as possible to reduce the total amount of material left in the patient as possible. However, there is occasion when the cutting of excess material should be done immediately and occasion to delay cutting the excess material. For example, in applications that require only one tension strip  1  it is time saving to set the tensioning device  50  to automatically cut the excess material. In other applications, for example, in fixing long bones, the tensioning may be done with several tension strips  1  and the user may want to place bone fragments under a slight tension to aid in alignment then come back to the tension strips  1  and increase the tension to a clinically beneficial pressure. By analogy, a mechanic tensions a wheel to an axle by tensioning the bolts in a criss cross fashion. Similarly, a user can adjust the tension on several tension strips  1  then comeback to each tension strip  1  and cut the excess material. So, in a preferred embodiment the functionality to turn on and turn off the automatic cutting function is desirable. 
         [0064]    Another desirable feature of the preferred embodiment is the ability of the user to preselect what force to use to tension the bone fragment. It is well known in the industry that children&#39;s bone fractures depending on the bone age and cause of the fracture may require higher or lower compression to promote healing. Also, normal adult bone compression may be preselected to quickly set the bone. Additional care may be required or a lower compression force used in geriatric patients. 
         [0065]    Another feature that has not been addressed in the prior art is the user ergonomics. In a preferred embodiment,  FIG. 18 , the elongate barrel  60  of the tensioning device  50  is long and narrow to improve user visualization of the target bone. Also, the tension strip  1  is fed through the tension device  50  such that the proximal portion  6  of the tension strip exits the tension strip head  10  channel through the entry channel  57  and out the top of the tensioning device  50  via the exit channel  58 . This allows the user to get close to the bone and not have the tension strip  1  poke down and into the patient body or tissue. Also, due to the close positioning of the tension strip head  10  to the site of removing excess tension strip  1  the overall placement of the tension strip  1  will achieve a low profile. The low profile and reduced excess material will reduce the possibility of tissue damage or a user accidentally snagging excess tension strip. 
         [0066]    It will be understood that various modifications can be made to the various embodiments of the present invention herein disclosed without departing from the spirit and scope thereof. For example, various devices are contemplated as well as various types of construction materials. Also, various modifications may be made in the configuration of the parts and their interaction. Therefore, the above description should not be construed as limiting the invention, but merely as an exemplification of preferred embodiments thereof. Those of skill in the art will envision other modifications within the scope and spirit of the present invention as defined by the claims appended hereto.