Abstract:
An external bridging/non-bridging bone fixation device including at least a first member and a second member. The first member is implanted substantially permanently on an arm bone during an entire healing process. Whereas the second member is adapted to be substantially temporarily implanted and affixed between the first member and a metacarpal of the associated hand. The second member may be a singular rigid piece or may be formed of several modular pieces affixed together. In particular, the second member may be hinged to allow for an offset or angled implantation. Also, the second member may include a plurality of pieces that are rigidly held together after implantation to allow for high selectivity by a physician. The bridging/non-bridging bone fixation device allows for a bridging adaptation during an initial portion of healing and a non-bridging adaptation during the extended healing process to reduce the possibility of stiffness and plaques due to prolonged periods of immobility.

Description:
FIELD OF THE INVENTION 
     The present invention relates to an external bone fixator and more particularly to an external bone fixator that is selectively a bridging and non-bridging fixator. 
     BACKGROUND OF THE INVENTION 
     It is known in the art that bones should be fixed or aligned in a particular position or orientation after an injury and several different methods are used. One generally known method is to place a cast on the injured area using a material that hardens after application, such as a plaster cast. The use of such a plaster cast, however, generally completely immobilizes the portion of the anatomy about which it is placed. Additionally, such plaster casts are extremely large and bulky and can be rather heavy for a patient who must use the plaster cast. 
     Additional bone fixation devices known in the art include internal fixation plates or external fixators. Attachment devices, such as screws or pins, affix the plate fixators to the bone sections which must be held in place and fixed during the healing process. These internal plates and external fixators are generally of an unitary length and of a fixed construction not allowing any motion of the anatomy to which it is attached while it is in place throughout the entire healing process. 
     Additionally, bone fixation pins and screws, and other internal devices, that are simply lodged into a bone structure may also be used to hold a bone in a fixed position while it is healing. These devices ensure that the bone is held in the proper position during healing without permitting further trauma to the bone. Here again, the internal pins and screws also do not allow movement of the fixed or attached portions of anatomy once inserted. 
     Accordingly, most of these devices create complete immobility in the portion of the anatomy upon which they are placed during the recovery process. This complete immobilization of a portion of anatomy, especially when it is a joint or other moving part, can stiffen and injure the joint due to non-movement. Additionally, adjacent portions of the anatomy are often used to support the part which is healing, thereby immobilizing greater sections of the anatomy. In particular, if an arm or wrist injury occurs and a bone must be fixed during the recovery period, the loss of motion in the joint may increase pain and the possibility of injury after the fixation device has been removed. Therefore, it is desirable to have a fixation device which will allow some movement during a portion of the recovery process, while also ensuring proper immobilization of the body portion under recovery so that corrective healing may occur. 
     SUMMARY OF THE INVENTION 
     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 preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
     The present invention relates to a convertible external bone fixator that converts between a bridging and non-bridging operation. The external bone fixator is made to fix bones relative to each other across a joint and then later allow movement of the joint by removing a first portion of the external bone fixator. The conversion from bridging to non-bridging operation is accomplished without detaching a second portion of the bridging/non-bridging bone fixation device. 
     A first embodiment includes an external bone fixation device for fixing a first bone and a second bone relative to one another in a predetermined orientation. The external bone fixation device includes a first bone fixation member that has a tail portion and a head portion each defining a plurality of bores and extending only along a portion of the length of the first bone. A connector extends from the first bone fixation member. A second bone fixation member has a proximal end and a distal end, wherein the proximal end is selectively affixed to the connector. A first selective attachment device selectively affixes the first bone fixation member to the first bone. A second selective attachment device selectively affixes the second bone fixation member to the second bone. When the first bone fixation member is selectively affixed to the first bone and the second bone fixation member is selectively affixed to both the connector and the second bone the first and second bones are substantially immobile. 
     A second embodiment of the present invention includes an external bone fixation device for fixing an arm bone, a wrist bone, and a metacarpal in a predetermined orientation. The external bone fixation device includes a first rigid bone fixation member, having a proximal tail portion and a distal head portion, defining a plurality of bores through said tail portion and said head portion. A holding mechanism extends from the distal head portion. A second bone fixation member selectively interconnects the holding mechanism and the metacarpal. A first attachment device selectively affixes the first bone fixation member to the arm bone. A second attachment device selectively affixes the second bone fixation member to the metacarpal. When the first bone fixation member is affixed to the arm bone and the second bone fixation member is selectively interconnected between said holding mechanism and the metacarpal, then the metacarpal is substantially immobile. 
     A third embodiment of the present invention includes an external bone fixation device for fixing an arm bone, a wrist bone, or a metacarpal in a predetermined orientation. The external bone fixation device includes a first rigid bone fixation member, having a proximal tail portion and a distal head portion having a side. The proximal tail portion defines a first plurality of bores formed longitudinally along said tail portion. The distal head portion defines a second plurality of bores in an array thereon, wherein at least a portion of the second plurality of bores are displaced laterally from the first plurality of bores. A mounting body extends from the side of the distal head portion. The second bone fixation member has a proximal end and a distal end, wherein a portion of the proximal end is received in said mounting body, and is selectively affixed in the mounting body. A first attachment device affixes the first bone fixation member to the arm bone. A second attachment device selectively affixes the second bone fixation member to the metacarpal. When the first bone fixation member is affixed to the arm bone and the second bone fixation member is selectively affixed to the metacarpal, and the second bone fixation member is selectively affixed in the clamp then the wrist and metacarpal are substantially immobile. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
     FIG. 1 is a perspective view of a bridging/non-bridging external bone fixation device; 
     FIG. 2 a  is a perspective view of the bridging/non-bridging external bone fixation device implanted in the bridging orientation; 
     FIG. 2 b  is a perspective view of the bridging/non-bridging external bone fixation device implanted in the non-bridging orientation; 
     FIG. 3 is a perspective view of a bridging/non-bridging external bone fixation device including a pin clamp according to a second embodiment of the present invention; 
     FIG. 4 is an exploded view of the pin clamp shown in FIG. 3.; and 
     FIG. 5 is a perspective view of a bridging/non-bridging external bone fixation device including a hinged bridging member according to a third embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. 
     With reference to FIG. 1, an external bone fixation device  10  of the present invention includes an arm fixation member  12  and a bridging member  14 . The arm fixation member  12  is similar to that disclosed in commonly assigned U.S. Pat. No. 6,197,027, which is hereby incorporated by reference. The arm fixation member  12  includes a proximal arm or tail portion  16  which defines a plurality of arm bores  18  along its longitudinal axis A. Even though arm bores  18  are formed along the longitudinal axis A of the arm portion  16 , they extend through the arm portion  16 , therefore, the central axes B of the arm bores  18  are perpendicular to the longitudinal axis A of the arm portion  16 . At the distal end of the arm fixation member  12  is a larger block or platter area  20  that defines a plurality of platter bores  24 , each adapted to receive a pin or other fixation device further discussed herein. The platter area  20  has a width greater than the width of the arm portion  16 . Thus, an exterior edge  20   a  of the platter area  20  is laterally offset from the longitudinal axis A of the arm portion  16 . The platter bores  24  cover a substantial area of the platter area  20  and define an array or pattern that extends beyond the longitudinal axis A of the arm portion  16 . Therefore, pins or other fixation devices that are inserted into platter bores  24  may be laterally offset from fixation or attachment devices inserted through arm bores  18 . Nevertheless, the central axis C of the platter bores  24  and the central axis B of the arm bores  18  are substantially parallel to each other. Extending from the exterior edge  20   a  of the platter area  20  is a mounting area or block  26  defining a channel  27 . The mounting block  26  extends from the platter area  20  and is generally integrally formed therewith. It will be understood that the mounting block  26  is laterally offset from the longitudinal axis A of the arm portion  16  since the exterior edge  20   a  of the platter area  20  is also offset. The mounting block  26  acts as a holding mechanism or a clamp and has a top portion  26   a  and a bottom portion  26   b  which are separated from each other except at the ends that meet with the platter area  20 . A screw  28  or other suitable locking device engages threads in the mounting block  26  to adjust the size of the channel  27  so that the mounting block  26  holds bridging member  14  in a pre-determined position. 
     In this first embodiment, the bridging member  14  is a single, long rigid piece which includes a track  30  extending from a medial side of the bridging member  14 . The track  30  is slideably engaged in the channel  27  of the mounting block  26  and held in a pre-determined position. The track  30  is held in the mounting block when the screw  28  is tightened to pull the top portion  26   a  and the bottom portion  26   b  of mounting block  26  together. In this way, the bridging member  14  and the arm fixation member  12  are held in a pre-determined and fixed position. According to the first embodiment, the bridging member  14  and the arm fixation member  12  are held generally parallel to each other although the central longitudinal axis D of the bridging member  14  is laterally offset from the arm portion  16 , due to the size of the platter area  20 . Therefore, the central longitudinal axis D of the bridging member  14  is laterally offset to the central longitudinal axis A of the arm portion  16 , although the bridging member  14  and the arm fixation member  12  are substantially parallel to each other. At the distal end of the bridging member  14  is a metacarpal block  31 . The metacarpal block  31  defines a plurality of metacarpal bores  32  formed transversely there through. Since the metacarpal bores  32  are formed transversely to the bridging member  14 , they have a central axis E substantially perpendicular to the platter bores  24  and the arm bores  18 . Thus, attachment members received in the metacarpal bores  32  would also extend substantially perpendicular to attachment members A received in platter bores  24  or arm bores  18 . As described herein, pins may engage metacarpals through the metacarpal bores  32  to ensure that the metacarpals are held fixed relative to the bridging member  14 . 
     It will also be understood that in an alternative embodiment, the track  30  may extend from the bridging member  14  at a plurality of angles. Such an angled track  30  may be used to account for the uniqueness of a particular patient&#39;s anatomy. If the track  30  is formed at an angle, then the bridging member  14  is held relative to the arm fixation member  12  at an angle. Even when the track  30  is formed at an angle from the bridging member  14 , the central longitudinal axis of the bridging member  14  would still be generally parallel to the central longitudinal axis of the arm fixation member  12 . When the track  30  is formed at an angle, the metacarpal block  31  and the metacarpal bores  32  would have an angle substantially equal to the angle of the track  30 . Therefore, the attachment members that are received in the metacarpal bores  32  would be at an angle other than perpendicular to the attachment members received in platter bores  24  and arm bores  18 . 
     An alternative embodiment includes the track  30  having stops  36  along the track  30  to allow limited movement of the hand during the healing process. The stops  36  may include several different embodiments, but for example may be set screws. The set screws could be inserted through tapped bores in either edge of the track  30  or in tapped bores in the track  30  itself to stop the movement of the bridging member  14  by engaging the top portion  26   a  or the bottom portion  26   b  of the mounting block  26 . In this way, stops  36  may be inserted at some point after implantation of the bridging/non-bridging bone fixation device  10  to allow a limited range of motion without completely removing the bridging member  14 . If stops  36  are included on the track  30 , the bridging member  14  can slide in the mounting block  26  a limited and pre-determined amount of movement of the metacarpal  48  without allowing the unlimited movement of the same by simply removing the bridging member  14 . It will be understood that the stops  36  could be any number of mechanisms such as bumps or raised portions on the track  30 . 
     With particular reference to FIG. 2 a , the bridging/non-bridging bone fixation device  10  of the present invention is shown after implantation onto a human appendage. The bridging/non-bridging bone fixation device  10  is initially implanted in the bridged formation. The bridged formation includes the arm fixation member  12  affixed to an arm bone  39  with at least one attachment device or a pin  40 . The pins  40 , and other pins discussed herein, may be held to the bridging/non-bridging bone fixation device  10  through any conventional means such as a cannulated bolt. Pins  40  are inserted through the arm bores  18  of the arm portion  16  as needed to hold the arm fixation member  12  in place. Additional pins  42  are be placed in the platter bores  24  of the platter area  20  at the proximal end of the arm fixation member  12 . The pins  42  engage the distal end of the arm bone  39  to hold secure the arm fixation member  12 . Pins  40  and  42  are inserted through the arm fixation member  12  substantially parallel to one another. Regardless of whether they are inserted in arm bores  18  or platter bores  24 . Due to the array of the platter bores  24 , however, the pin  42  that is inserted in the platter bores  24  may be inserted laterally offset relative to the pin  40  inserted in arm bore  18 . This will ensure a fixed and substantially solid attachment of the arm fixation member  12  to the arm bone  39 . Furthermore, if the distal end of the arm bone  39  is fractured into more than one piece, additional pins  42  may be inserted in additional platter bores  24  to engage each portion of fractured bone to hold it in place. To complete the bridging orientation, the bridging member  14  is put in place and locked relative to the arm fixation member  12  by clamping the mounting block  26  with screw  28  onto track  30 . Additional pins  46  are inserted through the metacarpal bores  32  of the metacarpal block  31  to hold at least a metacarpal  48 , or a portion of the digits, in a predetermined orientation. The pins  46  in the metacarpal block  31  extend substantially perpendicular to the pins  40  and  42  which are inserted through the arm fixation member  12 . This allows the pins  46  received through the metacarpal bores  32  to engage the metacarpal  48  laterally rather than in line with the pins  40  and  42  which are received in the arm fixation member  12 . This allows for a stable and secure external fixation of the arm bone  39  and the metacarpal  48  relative to each other. Thus, the bridging orientation, shown particularly in FIG. 2 a , is used to lock the arm bone  39 , wrist, and certain metacarpals  48  in a predetermined orientation. 
     During the initial stages of healing, the bridged formation is used to help ensure a completely immobile wrist and hand. After it has been determined that enough initial healing has occurred, so that movement of the digits and wrist may occur safely, then the bridging member  14  may be removed while not disturbing the arm fixation member  12 . As shown particularly in FIG. 2 b , the non-bridging orientation is achieved by removing pins  46  and unlocking mounting block  26  and removing the bridging member  14 . After this occurs, the metacarpal  48  and most of the wrist bones may move freely. Though complete range of motion may not be restored, greater motion is allowed. This is not to say that arm fixation member  12  may not be positioned so as to allow full range of motion of the wrist and digits after removing the bridging member  14 . The arm fixation member  12  is never moved or removed during the non-bridging operation of the non-bridging/bridging bone fixation device  10 . The pins  46  are removed from the metacarpal  48  and then the mounting block  26  is loosened and the bridging member  14  is removed. Therefore, the arm fixation member  12  may be left undisturbed to continue holding the arm bone  39  in a particular orientation. This helps to ensure that stiffness, plaques or other conditions are reduced in the wrist and hand as opposed to locking all of the bones and moving parts of the hand and wrist during the entire healing process. 
     With reference to FIGS. 3 and 4, where like numerals reference like portions discussed in relation to the previous embodiments, a third alternative embodiment includes a modular bridging member  70  that tapers to a round bar at a distal end  72  of the bridging member  70 . The pins  46  that are inserted into the metacarpal  48  are first affixed to a pin clamp  74  which is clamped onto the distal end  72  of the bridging member  70 . The pin clamp  74  is similar to the clamp disclosed in co-pending patent application having a Ser. No. 09/790,770 to Ryan J. Schoenefeld and commonly assigned, which is incorporated herein by reference. With reference to FIG. 4, the pin clamp  74  generally includes a pin retaining portion  76  which has a threaded portion  78  extending therefrom. An internally threaded portion  80  affixes to threaded portion  78 . Held in between internally threaded portion  80  and the threaded portion  78  are two washer portions  82  and a ball joint  84 . The distal end  72  of the bridging member  70  is received through the center portion of the threaded portion  78 , the ball joint  84  and the internally threaded portion  80 . When the internally threaded portion  80  is engaged on the threaded portion  78 , the bail joint  84  is held in a predetermined position. The internal ball joint  84  allows for certain degrees of freedom in the orientation of the pin retaining portion  76  relative to the distal end  72 . Therefore, pins  46  may be orientated relative to the bridging member  70  to allow greater freedom of implanting the pins  46  when implanting the bridging/non-bridging bone fixation device  10  depending upon the particular anatomy or situation of the patient. 
     A fourth alternative embodiment, shown in FIG. 5 where like numerals reference like portions discussed in relation to the previous embodiments, includes a bridging member  100  that is, at least initially, non-rigid. The bridging member  100  includes at least two portions a proximal portion  102  and a distal portion  104  interconnected with a ball joint  106 . The distal end of the proximal portion  102  is a ball socket  108  which receives a ball  110  which extends from the proximal end of the distal portion  104 . The ball socket  108  engages the ball  110  by locking engaging member  108   a  in place with a screw  109 . The ball  110  is received within the ball socket  108  and may rotate in many degrees of freedom and is locked in place with set screw  112  once a proper orientation is gained. It will be understood that any other appropriate device may be used to lock the ball joint  106  in a proper orientation. Metacarpal pins  46  are then received through metacarpal bores  32  to engage a metacarpal  48 . This also allows a physician greater flexibility during the implantation of the bridging/non-bridging bone fixation device  10 . 
     It will also be understood that the alternative embodiment disclosed above may be combined in any number of combinations to achieve the spirit of the present invention while also allowing a great variety options to the physician implanting the bridging/non-bridging bone fixation device  10 . It will also be understood that the bridging/non-bridging bone fixation device  10  may be affixed to the patient in a plurality of ways. Pins  40 ,  42 ,  46  may alternatively, for example, be screws. The pins  40 ,  42 ,  46  may also include threads or ridges that assist in affixing the pin  40 ,  42 ,  46  to the bone structure. Also, the pin  40  may differ from the pin  42  or the pin  46 . Any appropriate device may be used to affix the bridging/non-bridging bone fixation device  10  to the patient. 
     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.