Abstract:
The invention relates to a device for attaching fixation elements to bone, having a longitudinal member with a channel extending therein adapted for receiving at least one fixation element. A shaft extends within the channel and is positioned coaxially within at least a portion of the longitudinal member and at least a portion of the shaft is retained within the longitudinal member and a distal end of the shaft is configured and adapted to contact at least a portion of the fixation element received within the longitudinal member. A spring is positioned adjacent the shaft for resiliently biasing the shaft in an axial direction and the shaft is moveable with respect to the longitudinal member to drive the fixation element into bone.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    Priority of Provisional Application No. 60/330,977, filed on Nov. 5, 2001 is claimed under 35 U.S.C. §119 and priority of U.S. patent application Ser. No. 09/866,841, filed on May 30, 2001 and PCT Application No. PCT/US02/16656, filed on May 28, 2002 is claimed under 35 U.S.C. §120, the entire contents of which are incorporated by reference. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention relates to a device for the storage and dispensing of osteosynthetic fixation elements, and in particular to a device for attaching fixation elements to bone.  
         BACKGROUND OF INVENTION  
         [0003]    In the surgical treatment of fractures in the maxillofacial area, as well as fractures of the foot and hand, a trend toward preferring ever-smaller implants can clearly be noted. The reason for this is the generally increased understanding of the biomechanical bases of osteosynthesis. In the field of treating maxillofacial fractures, more attention can be paid to the cosmetic results of osteosynthesis, thanks to the miniaturization of implants. In the field of hand surgery, restrictions on movement in the area of the fingers can be avoided. In this regard, smaller osteosynthetic implants in the fingers can be placed under the tendons. In the case of an implant with a large cross-section, the tendons need no longer be extended to their full length.  
           [0004]    The dimensions of some smaller implants (screws, plates and tacks) are in the range of about 0.8 mm to about 2.0 mm. Problems in the area of packaging, storage and manipulation during surgery arise due to this miniaturization. Handling in the operating room, particularly in the maxillofacial area, has proved difficult. Depending on the degree of severity of the fracture or correction, up to 40 bone fixation elements, such as tacks or screws, may be required. These screws must be taken individually by the operating room nurse from a so-called screw rack, checked for length, placed on a screwdriver and given to the surgeon. The surgeon must, in turn, insert them through the osteosynthesis plate into pre-drilled screw holes. During the transfer of the screw and the attempted insertion of the screw, it often falls off the screwdriver, into the wound or onto the operating room floor. The attempt to find a lost screw is often excessively time-consuming, given their dimensions and extends the time spent in surgery. The frequent loss of screws in the operating room, and during packing and sterilization, causes unnecessary costs for the hospital. Thus, it is desirable to have a simple device that can be operated with one hand, thereby freeing the operator&#39;s other hand to align the fixation element or perform other tasks  
           [0005]    An additional problem in dealing with mini-screws arises during their implantation. After the surgeon has selected the osteosynthesis plate proper for the fracture in question, a plate is positioned over the fracture. A hole is then drilled for the screw (0.5-1.5 mm diameter) through one of the plate holes. Commonly, problems arise in controlling the amount of force applied during the insertion of the screw and or tack. For example, if a surgeon is required to insert a screw or tack with manual force, the manula force could be transmitted to the surrounding bone, which could bend thin and/or flexible bone in young patients.  
           [0006]    Also, problems such as surgical gloves tearing or hand pinching can arise if the insertion device has parts that move externally during the firing of the device. Thus, a need exists for an insertion device that minimizes the manual force exertion required and to minimize the gross forces applied to the surrounding bone during insertion.  
         SUMMARY OF INVENTION  
         [0007]    The present invention relates to a device for attaching fixation elements to bone, including a longitudinal member extending along a longitudinal axis from a proximal end to a distal end and having a channel extending therein adapted for receiving at least one fixation element. A shaft extends within the channel and is positioned coaxially within at least a portion of the longitudinal member and at least a portion of the shaft is retained within the longitudinal member and a distal end configured and adapted to contact at least a portion of the fixation element received within the longitudinal member. A spring is positioned adjacent the shaft for resiliently biasing the shaft in an axial direction and the shaft is moveable with respect to the longitudinal member to drive the fixation element into bone. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    [0008]FIG. 1 is a partially transparent elevated view of one embodiment of an insertion device according to the present invention;  
         [0009]    [0009]FIG. 2 is an elevated view of a fixation element for use with the insertion device of FIG. 1;  
         [0010]    FIGS.  3 - 4  illustrate the placement of a fixation element within a pre-drilled hole in bone;  
         [0011]    [0011]FIG. 5 is a partially transparent elevated view of another embodiment of an insertion device;  
         [0012]    [0012]FIG. 6 a partial elevated view of the device of FIG. 5;  
         [0013]    [0013]FIG. 7 is a partially transparent elevated view of another embodiment of an insertion device;  
         [0014]    [0014]FIG. 8 is a cross-sectional view of the embodiment of FIG. 7;  
         [0015]    [0015]FIG. 9 is a partial cross-sectional view of a portion A of the device of FIG. 8;  
         [0016]    [0016]FIG. 10 is an elevated view of another embodiment of an insertion device; and  
         [0017]    FIG. 11  is an elevated view of a cam member of the device of FIG. 10. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0018]    Referring to FIG. 1, a preferred fixation element insertion device  10  according to the present invention generally includes a longitudinal member extending along a longitudinal axis  12  from a proximal end  14  to a distal end  16  and having a channel  18  extending therein. The insertion device is preferably used to drive an osteosynthetic fixation element, such as a resorbable tack, into bone tissue. Channel  18  is configured and dimensioned to receive at least one fixation element for storage, transport, dispensing, and or insertion into bone.  
         [0019]    Referring to FIG. 2, one preferred fixation element compatible with insertion device  10  comprises a tack  20  having a shaft  22  integral with a head  24  at a proximal end thereof. The distal end of shaft  22  has a conical nose  26  to facilitate the insertion of tack  20  into bone tissue. A plurality of circular ribs  28  extend radially from the exterior of shaft  22  to prevent the removal of the tack from the bone tissue after it has been inserted. Head  24  has an outer diameter greater than the diameter of shaft  22  and contacts or rests against the bone or bone plate when the tack is inserted into bone tissue. In the preferred embodiment, the tack is made from a resorbable material so that it remains in the bone tissue temporarily and is absorbed by the body. In alternate embodiments, tack  20  can have numerously different configurations and dimensions. Also, different types of fixation elements altogether can be used with insertion device  10 . For example, biocompatible screws, nails, anchors, rivets, or other similar implants can also be inserted using insertion device  10 .  
         [0020]    Referring again to FIG. 1, insertion device  10  has a handle  30  at the proximal end that is configured to conform to the shape of a person&#39;s hand or palm for easily gripping the device and an applicator extension  32  for holding and dispensing the fixation element. A central channel  70  extends within handle  30  and through extension  32  and is in communication with channel  18  at distal end  16 . Channel  18  generally comprises a socket defined at the distal end  16  and an elongate applicator extension  32  extends between distal end  16  and handle  30 . Extension  32  can be a unitary extension or can include multiple parts. Socket or channel  18  fits about the proximal end of fixation element  20  to hold element  20  in insertion device  10  by an interference or friction fit. In the embodiment of FIG. 1, an individual tack  20  can be held at distal end  16  and head  24  of tack  20  is preferably held within the socket or channel  18  while the shaft  22  of tack  20  projects outside thereof, as shown in FIG. 3. At the distal end of extension  32  is a pronged tip  34  for retaining a fixation element. Pronged tip  34  is generally flexible and when the distal end of extension  32  is pressed, the prongs  34  of sleeve  32  flex around the head of a fixation element to pick up and retain the element. In this way, it is possible to pick up a relatively small fixation element in a simple, single action.  
         [0021]    A shaft member  36  and a firing spring  38  are housed within central channel  40 . Shaft member  36  extends longitudinally within handle  30  and extension  32  and is preferably moveable along axis  12  with respect to handle  30  and extension  32 . Firing spring  38  is positioned at the proximal end of handle  30  and is compressible between a force adjustment dial  39  at proximal end  14  and a proximal end of shaft member  36 , biasing shaft member  36  in the distal direction. Shaft  36  is generally cylindrical and includes a base portion  42  that slidingly engages the interior of channel  40  within handle  30 , a mid-section  44  having a smaller diameter than base portion  42 , and a tip portion  46  having a smaller diameter than mid-section  44 . A first shoulder  43  is positioned at the transition of base portion  42  and mid-section  44  and a second shoulder  45  is positioned at the transition of mid-section  44  and tip portion  46 .  
         [0022]    Shaft  36  is moveable from a loaded position (shown in FIG. 1) to an unloaded position for inserting a fixation element into bone. An activation button  48  extends within channel  40  for activating the movement of shaft  36  from a loaded position to an unloaded position. Button  48  is positioned along a portion of handle  30  and partially extends within channel  40  for engaging shaft  36 . Referring to FIG. 1, when shaft  36  is in the loaded position ledge  49  at the proximal end of button  48  engages second shoulder  45  preventing shaft  36  from moving in the distal direction or to the unloaded position. When button  48  is depressed by an operator, ledge  49  is moved out of engagement with shoulder  45 , thereby permitting shaft  36  to move in the distal direction under the force exerted by firing spring  38  on shaft  36 . As a result, tip portion  46  of shaft  36  is advanced in the distal direction to force fixation element out of extension  32  and shaft  36  is moved to an unloaded position.  
         [0023]    In a preferred embodiment, button  48  is pivotably positioned about a pin  47  and the distal portion of button  48  is biased radially outward by a spring  50  so that ledge  49  at the proximal portion of button  48  is biased inward toward engagement with shoulder  82 . In this regard, a collar  51  is preferably positioned within handle  30  for engaging spring  50  in the radial direction and permitting mid-section  44  of shaft  36  to slide therethrough without engaging spring  51 . When button  48  is depressed, ledge  49  is pivoted radially outward and out of engagement with shoulder. In alternate embodiments, different button assemblies or triggering mechanisms can be used.  
         [0024]    In a preferred embodiment, a thumb slide  52  is positioned along a portion of handle  30  opposite activation button  48  and is moveable in the longitudinal direction for moving shaft  36  from an unloaded to a loaded position. Thumb slide  52  partially extends within channel  40  for engaging shaft  36  and moving shaft  36  in the longitudinal direction. In an unloaded position, shoulder  45  engages an inner ledge  53  of thumb slide  52  and when thumb slide  52  is moved in the proximal direction by an operator, shaft  36  is also retracted. To move shaft  36  to the loaded position, thumb slide  52  is moved in the proximal direction until shoulder  45  slides beyond ledge  49  of button  48  and ledge  49  engages shoulder  45 , thereby locking shaft  36  in the loaded position. This shaft retraction will also compress firing spring  38 . In a preferred embodiment, a spring  54  is housed within handle  30  and biases thumb slide  52  in the distal direction and once shaft  36  is in the loaded position, the thumb slide is released and returns to its resting position. Once shaft  36  is again in the loaded position, another tack can be inserted into the extension  32 .  
         [0025]    Referring to FIGS.  3 - 4 , once the insertion device is loaded, the insertion device can be used to fasten a plate  56  or other device to a bone  57 . In operation, a hole  58  is pre-drilled in the bone tissue at the desired insertion location and the insertion device  10  is placed adjacent the insertion location and the tack is aligned with hole  42 . The activation button  48  is depressed to release shaft  36 , and shaft  36  is driven in the distal direction by the force of firing spring  38  thereby driving tack  20  into the bone tissue. As shown in FIG. 4, once tack  20  is inserted into bone, insertion device  10  is withdrawn from the insertion location and tack  20  is separated from channel  18 . When the insertion device  10  is withdrawn, the forces holding shaft  22  of tack  20  to bone  57  are greater than the forces of the interference fit between head  24  and channel  18  so that head  24  of tack  20  is separated from distal end  16 , leaving tack  20  secured to the bone. The device  10  can then be reloaded by moving the thumb slide in the proximal direction as explained above and inserting slightly smaller external dimensions than the internal dimensions of cover  78  so that the proximal end of sleeve  82  can be inserted into the distal end of cover  78  and sleeve  82  can move in the axial direction with respect to cover  78 . As best seen in FIG. 9, sleeve  82  can include prongs that interlock with ridges on the interior of cover  78  so that when sleeve  82  is inserted into cover  78 , sleeve  82  is not inadvertently removed from cover  78  in the distal direction. In a preferred embodiment, sleeve  82  has prongs  84  that are flexible and are collapsible or bendable into the interior of sleeve  82  so that sleeve  82  can be removed from cover  78  for cleaning, disassembly, or replacement. Prongs  84  are biased radially outwardly so that sleeve  82  can be easily reattached by simply pushing the sleeve into the cover in the proximal direction. The distal end of sleeve  82  preferably has a pronged tip similar to that described previously for retaining a fixation element.  
         [0026]    A central channel  90  extends within handle  72  and through extension  74  and houses a firing spring  91  and a shaft member  92  similar to the embodiment of FIG. 1. Firing spring  91  is biased between force adjustment dial  93  and the proximal end of shaft  92 . Adjustment dial  93  includes a knob  100  with internal threading that engages an externally threaded adjustment slider  102  that is slidably housed within channel  90 . When knob  100  is rotated, adjustment slider  102  slidably moves within channel  90  and compresses or decompresses spring  91  for adjusting the amount of force that is exerted on shaft  92  and consequently the tack during insertion. A pair of knob retaining screws  104  extend radially inward from the exterior of handle  72  and engage a circular groove in knob  100  for retaining knob  100  in the proximal end of handle  72 . A guide screw  106  extends inward from handle  72  and engage a longitudinal groove in adjustment slider  102  to prevent the slider from rotating.  
         [0027]    Shaft  92  extends longitudinally within handle  72  and is generally identical to shaft  36  described above, moving between a loaded and an unloaded position. Shaft  92  includes a base portion  94 , a mid-section  96  having a smaller diameter than base portion  94 , and a tip portion  98  having a smaller diameter than mid-section  96 . A first shoulder  95  is positioned at the transition of base portion  95  and mid-section  96  and a second shoulder  97  is positioned at the transition of mid-section  96  and tip portion  98 . Device  70  includes an activation button  108  similar to button  48  described above for facilitating movement of shaft  92  from the loaded to the unloaded position in the same fashion as described with respect to the embodiment of FIG. 1. To move shaft  92  from the unloaded to the loaded position, holding sleeve  82  and tip portion  98  of shaft  92  is retracted in the proximal direction until shoulder  97  of shaft  92  slides beyond button  108  and the button engages shoulder  97 , thereby locking shaft  92  in the loaded position in a similar fashion to button  48  described above. Also, insertion device  70  preferably has a spring  80  housed within spring cover  78  that biases holding sleeve  82  in the distal direction and once shaft  92  is in the loaded position, the holding sleeve is released and returns to its resting position. In this way, shaft  92  can be easily moved from the unloaded to the loaded position, by depressing device  70  in the distal direction against a solid object, such as a table or a surgeons hand. In all other respects, the method of operation or use of device  70  is similar to the method described above with respect to device  10 .  
         [0028]    Referring to FIGS.  10 - 11 , another embodiment of an insertion device  110  is shown that has yet another alternative loading mechanism. In all other respects, device  110  is similar to device  70  described previously. Insertion device  110  has a cam  112  for moving shaft  92  from the unloaded to the loaded position. In this embodiment, shaft  92  has pins  114  extending outwardly therefrom that engage an internal ramp  116  within cam  112  and when cam  112  is rotated pins  114  slide along ramp  1116  in the proximal direction and thereby move shaft  92  in the proximal direction and shaft  92  is retracted until shoulder  97  of shaft  92  slides beyond button  108  and the button engages shoulder  97 , thereby locking shaft  92  in the loaded position in a similar fashion to button  48  described above. After shaft  92  is locked into the loaded position, cam  112  is rotated to provide clearance for pins  114  to move in the distal direction during the unloading or firing movement of shaft  92 .  
         [0029]    While it is apparent that the illustrative embodiments of the invention herein disclosed fulfill the objectives stated above, it will be appreciated that numerous modifications and other embodiments may be devised by those skilled in the art. Therefore, it will be understood that the appended claims are intended to cover all such modifications and embodiments which come within the spirit and scope of the present invention.