Patent Publication Number: US-2003225405-A1

Title: Fixator with outrigger

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S)  
       [0001] None.  
       BACKGROUND OF THE INVENTION  
       [0002] This invention relates to external bone fixators for setting fractures of the human skeleton. In particular, this invention relates to a modular bone fixator assembly for setting fractures of the distal radius and other bones. This invention improves upon the earlier inventions described in U.S. Pat. Nos. 6,056,748 and 6,283,964, both entitled MODULAR FIXATOR ASSEMBLY, which are incorporated herein by reference.  
       [0003] The prior art is replete with external bone fixator devices which are used for setting various bone fractures. Many external bone fixator devices employ transcutaneous pins (e.g., K-wires), stakes, screws or other types of bone fasteners, which are secured in the bone on opposing sides of the fracture. The pins are then secured to an external splint device. The external splint device may use various articulations to adjust its position relative to the bone fasteners. During the fixation surgery, the bone pieces at the fracture may be realigned by the surgeon. The various articulations in the external splint device may assist the surgeon in realigning the bone pieces. Once the external splint device is secured to the bones and the bone pieces are in the desired alignment positions, the articulations in the fixator are locked in place to maintain the bone alignment for a healing duration.  
       [0004] Some of these external bone fixator devices are especially adapted for repairing fractures of the distal radius. This type of fracture often involves a fracture site close to the distal head of the radius. Fractures of the distal head of the radius are commonly referred to as Colles&#39; fractures. Such fractures may be reduced using bone fasteners set on the distal side of the fracture in the metacarpal bone and bone fasteners set on the proximal side of the fracture in the distal half of the radius.  
       [0005] It has been recognized that it is desirable for the wrist to have a certain degree of mobility during the treatment of wrist fractures. However, prior art fixator devices which employ longitudinal traction applied by proximal and distal pins generally do not allow motion at the wrist without crossing the joint during the period of fracture immobilization.  
       [0006] Accordingly, there is a substantial need for improved external fixator devices. The fixator devices need to be strong, rigid and durable, to withstand any forces or inadvertent blows to which the fracture sight is subjected. The fixator devices must be lightweight, so as to movable by the patient without extreme difficulty. The fixator devices should be reasonable in manufacturing cost and difficulty. The fixator devices should facilitate a wide range of surgical techniques, to permit the surgeon to best adapt to the particular fracture and to provide the best mode of healing.  
       BRIEF SUMMARY OF THE INVENTION  
       [0007] The external fixator of the present invention includes a main body and an outrigger. The main body is attached to a long bone on one side of a fracture, and holds the outrigger so the outrigger is supported over the fracture site. The outrigger is preferably attachable to extend either to the left or to the right of the main body. In one aspect of the invention, a distal body is removeably connectable to the distal end of the main body, and the distal body can be affixed to bone on the opposite side of the fracture to immobilize the joint where the fracture occurs. The distal body is connected to the main body with an adjustable securement section, which provides multiple degrees of adjustment freedom. In another aspect of the invention, the outrigger includes a track for slidably receiving fragment pin supports. Due to various strength and rigidity characteristics of the design, the structure of the fixator can be formed of molded plastic. The fixator facilitates a surgery technique wherein the joint is immobilized for an initial healing duration and then released for a secondary healing duration, with the fragment pins retained in place. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0008]FIG. 1 is a perspective view of a preferred embodiment of the present invention configured for fixation of the right wrist, shown for simplicity without bone pins and without detail on the heads of the set screws.  
     [0009]FIG. 2 is a perspective view showing the fixator of FIG. 1, reconfigured for fixation of the left wrist and shown attached relative to a left wrist skeleton, and also depicted using the alternative outrigger of FIG. 7.  
     [0010]FIG. 3 is an elevational view of the fixator of FIG. 1, shown with set screws and bolts removed from their respective holes  58 ,  60 ,  86 ,  116  and  128 .  
     [0011]FIG. 4 is an opposite elevational view of the fixator of FIG. 1, shown with bolts removed from their respective holes  58 ,  116  and  128 .  
     [0012]FIG. 5 is a bottom (from the proximal) view of the fixator of FIG. 1, shown with bolts removed from their respective holes  58 ,  60  and with a simplified distal end  18 .  
     [0013]FIG. 6 is an end (from the distal) view of the fixator of FIG. 1, shown without the rotatable outer clamp member of the distal body.  
     [0014]FIG. 7 is a perspective view showing an alternative outrigger assembly.  
     [0015] While the above-identified drawing figures set forth preferred embodiments, other embodiments of the present invention are also contemplated, some of which are noted in the discussion. In all cases, this disclosure presents the illustrated embodiments of the present invention by way of representation and not limitation. Numerous other minor modifications and embodiments can be devised by those skilled in the art which fall within the scope and spirit of the principles of this invention.  
    
    
     DETAILED DESCRIPTION  
     [0016] A preferred fixator assembly  10  according to the present invention includes, as primary components, a splint or distractor device  12 , and an outrigger section  14 . The distractor device  12  preferably includes a proximal pin clamp member or main body  16  and a distal pin clamp member or distal body  18 . The distal body  18  is attached to the main body  16  by a securable adjustment segment  20 . The outrigger section  14  includes an outrigger  22  shown holding two fragment pin supports  24 . The outrigger section  14  is attached to the distractor device  12  with an outrigger attachment  26 . The fixator assembly  10  is generally used for repairing fractures of bones, especially fractures of the distal radius  28  as shown in FIG. 2.  
     [0017] The main body  16  is adapted to be fixed to a long bone, which for the preferred embodiment is the distal third of the radius  28 . The main body  16  is thus somewhat elongated to reflect the elongated extent of the distal third of the radius  28 . The main body  16  includes structure for securing it to proximal bone fasteners  30 . In the preferred embodiment, bone fasteners  30  extend through apertures or clamp openings  32  in the main body  16 . The clamp openings  32  extend through the main body  16  transversely relative to the longitudinal axis  34  of the main body  16 . The preferred bone fasteners  30  are 3 mm bone pins or “K-wires”, but many other types of bone fasteners (such as relatively long, thin bone screws, etc.) could equivalently be used. The bone pins  30  described throughout this application may be affixed into the bone (reamed, driven, compression or distraction, etc.) as taught in U.S. Pat. Nos. 6,056,748 and 6,283,964.  
     [0018] During the fixation surgery, the bone pins  30  are preferably inserted through the clamp openings  32  and surgically staked into the distal radius  28 . The bone fasteners  30  may for instance be directed through the main body portion  16  prior to surgical insertion into the radius  28 . Alternatively, the bone pins  30  may be staked into the distal radius  28  and the main body  16  placed over the staked bone pins  30 , but threading the bone pins  30  through the clamp openings  32  prior to/during affixation to the bone aids in aligning the bone pins  30  relative to the radius  28 . Threading the bone pins  30  through the clamp openings  32  prior to/during affixation to the bone also aids in spacing and aligning the bone pins  30  relative to the main body  16 .  
     [0019] Once the bone pins  30  are set in the distal radius  28  and advanced as desired relative to the clamp openings  32  in the main body  16 , the bone pins  30  are secured in place relative to the main body  16 . For instance, the main body  16  maybe positioned relative to the bone pins  30  and the radius  28  such that the main body  16  rests on the soft tissue and skin of the forearm. Alternatively, the surgeon may position the main body  16  spaced a short distance from the tissue of the forearm. The preferred structure to secure the bone pins  30  relative to the main body  16  is with set screws  36  (shown without detail). The set screws  36  are threaded into set screw holes  38  which intersect the clamp openings  32 . Tightening of the set screws  36  will secure the main body  16  relative to the surgically staked bone pins  30 .  
     [0020] The main body  16  can be positioned in either of at least two orientations relative to the long bone (radius  28 ), and the mechanism for securing the main body  16  to the long bone (radius  28 ) preferably accommodates such multiple orientations. For instance, the main body portion  16  of the preferred embodiment includes two pairs of clamp openings ( 32   a  and  32   b ,  32   c  and  32   d ). One pair  32   a ,  32   b  of the clamp openings  32  extend on one side of the longitudinal axis  34  of the main body  16  (i.e., above the longitudinal axis  34  as shown in FIG. 1), and the opposing pair  32   c ,  32   d  of the clamp openings  32  extend on the other side of the longitudinal axis  34  (i.e., below the longitudinal axis  34  as shown in FIG. 1). When positioned for use on the right arm as shown in FIG. 1, the upper set  32   a ,  32   b  of clamp openings  32  will preferably be used, with the lower set  32   c ,  32   d  of clamp openings  32  left vacant. Use of the upper set  32   a ,  32   b  of clamp openings  32  places the main body  16  at an elevation relative to the radius  28  which best positions the main body  16  relative to intended subsequent placement of the distal body  18  and the outrigger  22 , and also minimizes the moments that the weight of the fixator  10  will place on the radius  28  during normal use.  
     [0021] The lower set  32   c ,  32   d  of clamp openings  32  provide some flexibility should the surgeon desire to use the fixator  10  at a higher elevation relative to the radius  28 . However, the primary importance of the lower set  32   c ,  32   d  of clamp openings  32  is to provide flexibility so the main body  16  can be equivalently be used on either right or left arms. As shown in FIG. 2, the main body  16  can be flipped for use with the left arm at the same relative height, simply by utilizing the bone pins  30  through the second (now upper) set  32   c ,  32   d  of clamp openings  32 . The preferred embodiment thus includes four clamp openings  32   a ,  32   b ,  32   c ,  32   d , with only the upper two (which can be either set depending upon left or right orientation) being primarily intended for use. The clamp openings  32   a ,  32   b  are longitudinally spaced about 1½ inches apart, about two inches from the distal end of the main body  16 . This spacing is adequate to support the main body  16  on the radius  28 , while not coming too close to the typical Colles&#39; fracture site in the radial head. If desired, additional bone pin clamp openings may be placed in the main body  16 , to give the surgeon additional flexibility in placement of the bone pins  30 . Similarly, if desired the main body may be made longer, giving the surgeon potential attachment sites into the middle or proximal thirds of the radius  28 . In any orientation, the main body  16  is intended to be affixed such that its longitudinal axis  34  extends roughly parallel to the longitudinal axis of the radius  28 .  
     [0022] The distal pin clamp body  18  of the fixator  10  is used for attachment on the opposite side of the fracture, and serves as a joint fixation body in conjunction with the main body  16  to fix the position of the joint. In the preferred embodiment for use with a Colles&#39; fracture, the distal body  18  is to be secured to a metacarpal and particularly the second metacarpal  40 , thereby setting the wrist and preventing the wrist from flexing during the healing of the Colles&#39; fracture.  
     [0023] Similar to clamp openings  32  of the main body  16 , the distal body  18  also includes transverse clamp openings  42  for transcutaneous bone pins  30  or other bone fasteners. With the distal body  18  of the preferred embodiment, the distal transcutaneous bone pins  30  are surgically set into the second metacarpal  40 . A preferred placement location positions the first metacarpal pin  30  about 5 mm distal to the second metacarpal joint. The distal body  18  is secured relative to the bone pins  30  with set screws  44  (shown in FIGS. 1 and 3 without detail), and thereby positioned such that its longitudinal axis  46  extends roughly parallel to the longitudinal axis of the metacarpal  40 . A spacing between the distal clamp openings  42 /distal bone pins  30  of about one inch is appropriate for attachment into the metacarpal  40 . Because the distal body portion  18  does not support the mass and the concomitant potential moment of the outrigger  22 , a single set of clamp openings  42  are provided which intersect the longitudinal axis  46  of the distal body  18 . If desired however, additional distal clamp openings may be provided to give the surgeon additional options in securing the distal body  18  relative to the second bone  40 .  
     [0024] The distal body  18  is attached to the main body  16  by the secureable adjustment segment  20 . If desired, the distal body  18  can be attached with a universal joint allowing pivotal movement of the distal body  18  to the main body  16 , similar to that taught in U.S. Pat. Nos. 6,056,748 and 6,283,964. For some applications, the distal body  18  may be attached with a simple pin-type hinge, or may even be permanently secured relative to the main body  16 . However, the preferred secureable adjustment segment  20  includes four degrees of adjustable freedom, each separately securable.  
     [0025] As a first degree of freedom, the main body  16  defines a bore  48  which extends axially therein, and an extension rod  50  is received in the bore  48 . The extension rod  50  allows the fixator  10  to be lengthened or shortened as appropriate for the particular size of patient being treated. Any of several mechanisms can be used so the surgeon can control the extension rod  50 . In the preferred embodiment, the extension rod  50  is externally threaded. A thumb screw  52  is attached on the main body  16  such that it is free to rotate. The thumb screw  52  has internal threads which mate with the external threads of the extension rod  50 , such that rotation of the thumb screw  52  advances or retracts the extension rod  50 . The longitudinal position of the extension rod  50  is lockable via a rod set screw  54  (shown without detail in FIG. 3).  
     [0026] Second and third degrees of adjustment freedom are provided by a yoke section  56 , which permits angular adjustment of the distal body  18  relative to the main body  16 . The yoke section  56  is bolted with a horizontal bolt  58  (shown in FIG. 1 without detail) to a distal end of the extension rod  50  and with a vertical bolt  60  (shown in FIG. 1 without detail) to a proximal end of the distal body  18 . Each end of the yoke section  56  includes a peak/valley radially-toothed profile which mates with similarly toothed profiles on the extension rod  50  and distal body  18 . Loosening of the horizontal bolt  58  permits pivoting of the yoke section  56  about a generally horizontal axis  62  defined by the horizontal bolt  58 . Loosening of the vertical bolt  60  permits pivoting of the distal body  18  about a generally vertical axis  64  defined by the vertical bolt  60 . Tightening of the horizontal bolt  58  and the vertical bolt  60  secures the distal body  18  at the desired horizontal and vertical angles relative to the longitudinal axis  34  of the main body  16 . The horizontal and vertical bolts  58 ,  60  preferably include hexagonal recesses to permit tightening and loosening with an allen wrench. Alternatively, a hexagonal head or a head for a flat or Phillips screwdriver, or even thumbscrews may be used.  
     [0027] As a fourth degree of adjustment freedom, the distal body  18  is provided as a central rod  66  (shown in FIG. 6 and in dashed lines in FIG. 5) with a rotatable outer clamp member  68 . A set screw  70  (shown without detail in FIG.  1 ) is provided in a mating threaded hole in the rotatable outer clamp member  68 . With the set screw  70  loosened, the outer clamp member  68  freely rotates relative to the central rod  66 . With the set screw  70  tightened, the outer body  68  is secured to the central rod  66 . Further, the set screw  70  can be fully loosened to permit the outer clamp member  68  to be readily removed from the secureable adjustment segment  20 .  
     [0028] If desired, additional degrees of adjustment freedom may be provided by the securable adjustment segment  20 . For instance, the extension rod  50  and/or bore  48  may be shaped and configured to permit rotation between the main body  16  and the extension rod  50 . The rod set screw  54  could then function to secure the position of the extension rod  50  relative to the main body  16  both longitudinally and rotationally. As another example, the rotatable outer clamp member  68  may be slidable on the central rod  66  to permit extension of the distal body  18 . The set screw  70  would then function to secure the position of the outer clamp member  68  relative to the distal body  18  both longitudinally and rotationally.  
     [0029] One purpose of the adjustment freedom provided by the secureable adjustment segment  20  is to maximize the options available to the surgeon with respect to placement of the bone pins  30  into the second bone (i.e., in the preferred embodiment, into the second metacarpal  40 ). In particular, the fixator  10  can be secured both to the radius  28  and to the second metacarpal  40  with the secureable adjustment segment  20  fully loose, allowing the surgeon ease of motion to stake the bone pins  30  through the fixator  10  and into the bone. A second purpose of the adjustment freedom provided by the secureable adjustment segment  20  is to maximize the options available to the surgeon with respect to the healing orientation of the bones at the fracture site. After the fixator  10  is secured both to the radius  28  and to the second metacarpal  40 , the surgeon can then manipulate the wrist joint to the desired bone healing position, including the appropriate reduction, distraction, palmer flexion and ulnar deviation. The surgeon can perform the desired manipulation of the wrist joint either by applying pressure directly on the wrist joint itself or with the aid of the fixator  10  by properly moving the main body  16  and distal body  18  to thereby manipulate the bones. Once the wrist joint is in the desired bone healing position, the bolts  58 ,  60  and the set screws  44 ,  54 ,  70  are fully tightened so the wrist position is rigidly held by the fixator  10 .  
     [0030] While traditional fixation can be performed with the distractor device  12 , the present invention particularly contemplates use for direct fragment fixation. Direct fragment fixation is performed with the outrigger section  14 . The outrigger  22  is preferably removably attached to the main body  16 . The outrigger  22  may be attached to the main body  16  during surgery, that is, after fixation of the main body  16  to the radius  28  and the distal body  18  to the second metacarpal  40 , and after securement of the securable adjustment segment  20 . By attaching the outrigger  22  to the main body  16  after such fixation and securement, the surgeon has better access to the wrist joint during the fixation and securement steps. Alternatively, the outrigger  22  may be attached to the main body  16  prior to surgery or prior to the fixation and adjustment steps. As an alternative but less flexible embodiment, the outrigger  22  may be permanently secured to the main body  16 .  
     [0031] If desired, the outrigger  22  may be attached to the main body  16  by a mounting member with thumb gear as taught in U.S. Pat. Nos. 6,056,748 and 6,283,964. In the preferred embodiment, however, the outrigger section  14  is attached to the distractor device  12  with a dual sliderail configuration provided by the outrigger attachment  26 . As best shown in FIGS. 5 and 6, the outrigger attachment  26  includes a rail  72  disposed on the main body  16 , a rail  74  disposed on a flange  76  of the outrigger  22 , and a slide plate  78  which operates in conjunction with the two rails  72 ,  74 . As best shown in FIG. 6, the main body rail  72  is provided on a side of the main body  16  toward the fracture site. While the main body rail  72  could extend in any direction, the main body rail  72  in the preferred embodiment extends longitudinally, parallel to the longitudinal axis  34  of the main body  16 . This orientation provides the main body rail  72  while adding the minimal amount of mass and bulk to the main body  16 . The main body rail  72  mates in sliding engagement with a first slide recess  80  provided on the slide plate  78 .  
     [0032] On opposing sides of the main body rail  72 , the slide plate  78  abuts rail plate portions  82  of the main body  16  to provide for maximum vertical stability of the outrigger  22 . The rail plate portions  82  could be co-planar or in parallel planes, but the preferred rail plate portions  82  on the main body  16  extend at angles to each other to better match a generally cylindrical outer profile of the main body  16 .  
     [0033] As best shown in FIG. 5, a second slide recess  84  is provided on the opposite side of the slide plate  78 , facing away from the main body  16 . The second slide recess  84  extends at an angle and preferably perpendicular relative to the first slide recess  80 . The outrigger rail  74  on the flange  76  of the outrigger  22  mates in sliding engagement with the second slide recess  84 . On opposing sides of the outrigger rail  74 , the slide plate  78  abuts the outrigger flange  76  to provide for maximum horizontal stability of the outrigger  22 . The abutment sides of the preferred outrigger flange  76  are co-planar.  
     [0034] For both the outrigger rail  74  and the main body rail  72 , the preferred shape of the rail is a dovetail having a head and a neck which is narrower in cross-section than the head. This shape securely limits movement of the sliding engagements other than in the slide direction, while still being relatively easy to mold. The preferred length of the slide rails  72 ,  74  is about 1½ inches, which has been found sufficient to adequately support the outrigger  22  relative to the main body  16  while still permitting ½ inch or so of adjustability without significant loss of rigidity.  
     [0035] In the preferred outrigger attachment  26 , two distinct modes of separability are available. The main body rail  72  is exposed at its distal end, and the mating recess  80  of the slide plate  78  is exposed at its proximal end. This allows removal of the slide plate  78  from the main body  16  simply by sliding the slide plate  78  fully in the distal direction. Attachment of the slide plate  78  to the main body  16  is performed oppositely, by properly positioning the slide plate  78  relative to the main body  16  and sliding the slide plate  78  in the proximal direction.  
     [0036] The outrigger rail  74  is exposed at its anterior end, and the mating recess  84  of the slide plate  78  is exposed at both its anterior and its dorsal end. This allows removal of the outrigger  22  from the slide plate  78  simply by pulling upward on the outrigger  22 . Because the mating recess  84  of the slide plate  78  is exposed at both ends, the outrigger  22  can be removed in the upward direction regardless of the orientation of the slide plate  78 , that is, regardless of whether the main body  16  is positioned for a right arm with the outrigger  22  extending to the right (FIG. 1) or flipped over and positioned for a left arm with the outrigger  22  extending to the left (FIG. 2). Attachment of the slide plate  78  to the main body  16  is performed oppositely, by properly positioning the outrigger  22  relative to the slide plate  78  and pushing downward.  
     [0037] The two modes of separability give the surgeon flexibility in determining when and how to attach the outrigger  22  to the main body  16 . The slide plate  78  maybe attached to the main body  16  before or after securing the main body  16  to the radius  28 . Similarly, the outrigger  22  may be attached to the slide plate  78  before or after other portions of the surgical procedure. The sliding motion also permits infinite fine position adjustability of the outrigger  22 . In particular, the outrigger  22  should be placed with 1 cm of clearance over the radial articular surface.  
     [0038] Releasable securements are provided for securing the rails  72 ,  74  relative to the their respective slide recesses  80 ,  84 . A first set screw in set screw hole  86 , best shown in FIGS. 1 and 3, is used to set the vertical height of the outrigger  22  relative to the main body  16 . A second set screw in mating set screw hole  88 , best shown in FIGS. 1 and 5, is used to fix the longitudinal extent of the main body  16  relative to the outrigger triangle  22 . Both of these set screws  86 ,  88  are easily accessible to the surgeon from the top of the fixator assembly  10 . A similar set of set screw holes  86 ,  88  is positioned on the other side of the main body  16 , for use when the outrigger  22  is attached to extend to the left over a left arm (FIG. 2).  
     [0039] If desired, the outrigger can be provided as the I-shaped metallic member shaped as taught in U.S. Pat. Nos. 6,056,748 and 6,283,964. In the preferred embodiment, however, the outrigger  22  is provided with a rigid triangular shape projecting generally perpendicular to the outrigger flange  76 , best shown in FIG. 5. The triangular shape is inherently very strong, particularly against deflection from any cantilevered bending stresses placed on the outrigger  22 . The triangular shape generally conforms to the anatomical configuration of the distal radius  28 . In particular, the coronal anatomy of the radius  28  proceeds from the radial styloid backward at an angle of about 102° to 110 ° (depending upon the anatomy of the particular patient) relative to the longitudinal axis of the radius  28 . The triangular shape of the outrigger  22  proceeds back from a distal comer  90  at an angle  92  which should be between about 95° and 118 ° relative to the longitudinal axis  34  of the main body  16 . The angle  92  of the outrigger  22  preferably proceeds at 98° to 115° relative to the longitudinal axis  34  of the main body  16 , more preferably at 102° to 110° (i.e., coinciding with the 12-20° angle of the distal head of the radius  28 ), with a most preferred value being 110°. This angle  92  not only conforms to the anatomical configuration of the distal radius  28 , but also provides an outrigger shape which is inherently strong and well supports the cantilevered stresses placed on it by the fragment fixation pin supports  24 . That is, a proximal leg  94  cooperates with a distal leg  96  to stabilize and strengthen the outrigger  22 . Rigidity is enhanced because the proximal leg  94  and the distal leg  96  are well separated at their attachment to the outrigger flange  76 . The preferred outrigger triangle  22  extends from the flange  76  for nearly three inches, but is still sufficiently long because the triangle  22  is over two inches wide including a nearly one inch attachment to the flange  76 .  
     [0040] The preferred triangular shape only has the distal leg  96  which extends backward at an angle of 110°, with the proximal leg  94  extending forward at an angle of 70°. Only the distal leg  96  is expected to be used for any particular fixation. Of course, when the fixator  10  is used on the opposite arm (from right to left), the direction in which the outrigger  22  faces is reversed (from right to left), and the opposite leg  94  of the triangular shape becomes the more distal of the two legs  94 ,  96 .  
     [0041] The dual slide rail configuration gives two degrees of freedom in placing the outrigger  22  with respect to the main body  16 . If desired, an additional degree of freedom may be provided as depicted in the alternative outrigger  150  of FIG. 7. A securable hinge  152  including a tightening bolt  154  is provided between the base of the triangle  22  and the flange  76 . This securable hinge  152  allows pivoting of the triangle  22  relative to the main body  16 , about a horizontal axis  156  parallel to the longitudinal axis  34  of the main body  16 . The tightening bolt  154  has a head with a slot  158  for a flat head screwdriver. By tightening of the tightening bolt  154 , the rigid securability of the outrigger triangle  22  relative to the main body  16  can be maintained at the position ultimately selected by the surgeon.  
     [0042] The legs  94 ,  96  of the outrigger  22  define tracks having a sliding recess  98 . As best shown in FIGS. 1 and 4, the sliding recess  98  includes opposing lip sections  100 , which assist in supporting and holding the fragment pin supports  24 . The track configuration of the outrigger  22  is inherently strong and rigid while still being relatively lightweight.  
     [0043] The preferred sliding recess  98  has an open end  102 . This open end  102  permits removal of the fragment pin supports  24  from the track  98 . Thus, the surgeon can determine how many fragment pin supports  24  should be lined up in the track  98  for any particular surgery. If desired, the first fragment pin support  24  can be secured in place before the second (or third, etc.) fragment pin support  24  is placed into the track  98 .  
     [0044] The outrigger  22  securely and adjustably locates the fragment pin supports  24 . If desired, the fragment pin supports maybe similar to those described in U.S. Pat. Nos. 6,056,748 and 6,283,964. However, the preferred fragment pin supports  24  shown herein are molded plastic structures. The preferred fragment pin supports  24  provide seven degrees of adjustment freedom in locating the fragment pins  130  into the distal radius  28 .  
     [0045] As a first degree of adjustment freedom and best shown in FIGS. 1 and 4, each fragment pin support  24  includes a knob bolt  104  which rides within the track  98 . The surgeon can select the desired location of each knob bolt  104  in the track  98 . The knob bolt  104  has a head  106  on a threaded shaft section  108 . The head  106  mates with the track  98  including the opposing lip sections  100 , to hold the shaft section  108  rigidly upright with respect to the outrigger  22 . A tightening nut  110  is used on the shaft  108  to releaseably secure the knob bolt  104  at the selected location in the track  98 .  
     [0046] If desired, the head  106  of the knob bolt  104  can be elongated or otherwise have flats which mate with the walls of the track  98 , to more securely hold the knob bolt  104  relative to the outrigger  22 . However, as a second degree of adjustment freedom, the head  106  of the knob bolt  104  is cylindrical without any flats. This allows the surgeon, while the tightening nut is loose, to rotate the knob bolt  104  about the generally vertical axis defined by shaft  108  of the knob bolt  104 , changing the direction in which the fragment pin support  24  extends from the track  98 .  
     [0047] A third degree of adjustment freedom is provided by a pivot arm  112 . The pivot arm  112  includes a fork  114  which mates over the extending end of the knob bolt  104 . The tines of the fork  114  receive a pivot arm bolt  116 , with one of the tines threadingly engaging threads of the pivot arm bolt  116 . Similar to the yoke section  56 , the tines of the fork  114  may have a peak/valley radially-toothed profile which mates with similarly toothed profiles on the projecting end of the knob bolt  104 . Alternatively, the frictional engagement between flat surfaces of the pivot rod fork  114  and the knob bolt  104  may be sufficient to secure the angular position of the knob bolt  104 . Loosening of the pivot arm bolt  116  permits pivoting of the pivot arm  112  about a generally horizontal axis defined by the pivot arm bolt  116 . Tightening of the pivot arm bolt  116  secures the pivot arm  112  to the knob bolt  104  at a desired angle. The preferred pivot arm  112  has a length of less than an inch, just enough to substantially avoid interference between the fragment pin support  24  and the outrigger triangle  22 .  
     [0048] Fourth and fifth degrees of adjustment freedom are provided by a connecting rod  118 . The preferred connecting rod  118  has a cylindrical shaft  120  which slides in a cylindrical hole in the extended end of the pivot arm  112 . The cylindrical shaft  120  allows the connecting rod  118  to be slid upwards and downwards relative to the pivot arm  112 , and also allows the connecting rod  118  to be pivoted about the axis defined by the connecting rod shaft  120 . A set screw  122  (shown without detail in FIG. 6) is threaded into a threaded set screw hole in the exposed end face of the pivot arm  112 . The set screw  122  can be tightened to secure the connecting rod  118  in its desired amount of extension and a desired rotational position relative to the pivot arm  112 . In the preferred embodiment with two fragment pin supports  24 , one of the connecting rods  118  may be longer than the other, such as having lengths of about 1½ inches and 2 inches. The shaft  120  of the connecting rod  118  (which in the preferred embodiment form the thinnest link of the fixator  10 ) must be sufficiently thick to rigidly support the pin holder  124 , such as a diameter of the connecting rod shaft  120  of about ⅕ inch.  
     [0049] A sixth degree of adjustment freedom in the fragment pin support  24  is provided by the pin holder  124 . The pin holder  124  is received between the tines of a fork  126  on the end of the connecting rod  118 . The tines of the connecting rod fork  126  receive a connecting rod bolt  128 , with one of the tines threadingly engaging the connecting rod bolt  128 . Similar to the yoke section  56  and the pivot arm fork  114 , the tines of the connecting rod fork  126  may be flat or may have a peak/valley radially-toothed profile which mates with a similarly toothed profile on the pin holder  124 . Loosening of the connecting rod bolt  128  permits pivoting of the pin holder  124  about a generally horizontal axis defined by the connecting rod bolt  128 . Tightening of the connecting rod bolt  128  secures the pin holder  124  at the desired angular position.  
     [0050] The seventh degree of adjustment freedom is provided by the connection between the fragment pins  130  and the pin holder  124 . The pin holder  124  includes at least one through hole  132  for receiving the fragment pin  130 . A threaded set screw hole intersects the fragment pin through hole  132 , and a threaded set screw  134  (shown in FIG. 1 without detail) is tightenable to secure the fragment pin  130  relative to the pin holder  124 .  
     [0051] Each of the set screws  36 ,  44 ,  54 ,  70 ,  86 ,  88 ,  122 ,  134 , the pivot arm bolt  116  and the connecting rod bolt  128 , all shown in the drawings without detail, preferably include hexagonal recesses to permit tightening and loosening with an alien wrench. Alternatively, a hexagonal head or a head for a flat or Phillips screwdriver, or even thumbscrews may be used.  
     [0052] The fragment pin holders  124  should have sufficient length to adequately support the fragment pins  130 . In the preferred embodiment, the length of the pin holder  124  (and the length of the fragment pin through hole  132 ) is over ½ inch. The preferred surgical technique includes setting the fragment pins  130  through the fragment with the tip of the fragment pin  130  extending into the healthy, intact radius  28 . For the example depicted in FIG. 2, two pins  130  are set beginning in the radial styloid and exiting on the opposite intact radial cortex, and a third pin  130  secures the dorsal fragment from dorsal and distal to volar and proximal, again exiting in the intact portion of the bone  28 . Such pin placement allows the volar tilt of the wrist to be maintained. If necessary because of the condition of the radius  28 , the pin holder  124  sufficiently supports the fragment pin  130  such that the tip of the fragment pin  130  may be driven merely into the fragment, with support sufficient to reduce the fragment being provided by the fragment pin holder  124  without cross-fracture attachment into the radius  28 . The preferred fragment pins  130  are 0.062 inch diameter wires. The wires can be drilled free hand or using the pin holders  124  as templates.  
     [0053] In the preferred embodiment, one of the pin holders  124  includes two fragment pin through holes  132 . The two holes  132  are separated by roughly ½ inch and extend parallel to each other, to support two fragment pins  130  in a generally parallel spaced relationship. The second pin holder  124  includes a single fragment pin through hole  132 .  
     [0054] One of the important advantages of the preferred embodiment is the flexibility it provides the surgeon in the surgical technique used. After the wrist is immobilized with the distractor device  12 , the surgeon may determine where to place fragment pins  130  and how many fragment pins  130  should be used. Wire placement can be varied depending on fracture configuration and/or surgeon&#39;s preference. The fragment pins  130  may be driven into the bone fragments either threaded through the pin holder  124  or even before the fragment pin supports  24  are placed into the outrigger track  98 . After the fragment pins  130  are positioned by the surgeon, the various degrees of adjustment freedom can each be tightened to secure the position of the fragments relative to the outrigger  22 , and via the main body  16  relative to the radius  28 .  
     [0055] Further, movement of the wrist joint during healing is an important part of the healing process. The present invention contemplates fixation of the fragment pins  130  even after the distal body  18  is removed from the second metacarpal  40 . That is, one preferred surgical technique for the present invention involves two separate healing durations. In the first healing duration, the fixator  10  is secured to the distal radius  28 , to the second metacarpal  40 , and to the bone fragments. Once the bone fragments begin to heal, some stress on the joint is beneficial to promote additional healing and faster bone growth. After an initial healing duration when the surgeon is confident that fracture stability exists, a wrist-release surgery is performed, in which the metacarpal pins  30  are removed from the metacarpal  40  and the distal body  18  is removed from the main body  16 . After the wrist release surgery, the patient can attain at least a limited degree of wrist flexation, which improves the secondary healing. The fragment pins  130  still hold the fragments in place to ensure that the wrist is not refractured during this secondary healing. After a secondary healing duration, a third surgery is performed to fully remove the external fixator  10 .  
     [0056] Another important advantage of the preferred embodiment is the range of materials which can be used. The preferred embodiment is designed to handle stresses of the Colles&#39; fracture fixation by using a plastic material. The plastic material used is significantly lighter than metals traditionally used for fixators. The plastic material used, together with the sizes and shapes discussed herein, allows the fixator  10  to be sufficiently rigid without permitting the degree of bending which is inherently possible in most metal fixation structures. The preferred material for the preferred embodiment is a high density plastic, partially glass filled. Because this plastic material is not sufficiently strong to penetrate bone (and for FDA approval reasons), traditional metal bone pins  30  are used, but the remaining parts can all be molded of plastic. In particular, the main body  16 , the distal body  18 , the secureable adjustment segment  20 , the slide plate  78 , the outrigger  22  and the fragment pin supports  24  are all formed of plastic. As a moldable material, manufacture of the fixator  10  can be made less expensive. If desired for cost or thread strength reasons, the set screws  36 ,  44 ,  54 ,  70 ,  86 ,  88 ,  122 ,  134  and bolts  58 ,  60 ,  104 ,  116 ,  128  described herein may be formed as traditional metal structures as well. The preferred material is an ULTEM 1000, 20% glass bead filled plastic, which is an engineered high density poly-ether-imide (PEI) plastic suitable for orthopaedic devices and available from GE Plastics. Other suitable plastic materials might include poly-phenyl-sul-fone (PPSU) (e.g. Amoco Radel R), polysulfone (PSU) (e.g. Amoco Udel P), polyaryletherketone (PAEK) (e.g. BASF Ultrapek), liquid crystal polymer (LCP) (e.g. Vectra); and polyketone (e.g. Amoco Kadel E).  
     [0057] Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention. As one example, while the preferred embodiment has been described as having a “main” body and a “distal” body, for certain applications it maybe desired to heal the joint by having the outrigger  22  supported by the bones distal of the fracture. In the case of a Colles&#39; fracture, this would include attaching the main body  16  to the second metacarpal  40  and attaching the “distal” body to the radius  28 . The relative dimension and sizes of the “main” body and the “distal” body would be adjusted accordingly. Thus a worker skilled in the art will appreciate that the term “distal” is used as a matter of convenience and does not necessarily indicate the orientation of the fixator  10  with respect to the fracture. As another example, while the preferred embodiment is intended for Colles&#39; fractures, the invention could be in many respects equivalently applied to fractures of other long bones, such as the proximal radius, and either proximal or distal ends of the ulna, tibia, fibula, humerus, or femur.