Abstract:
A modular fixator assembly capable of allowing motion at the wrist during treatment of wrist fractures. The fixator assembly includes a distractor device, a pin outrigger attached to the distrator device, at least one pin for fixating the fracture fragments, and pin clamping assemblies for attaching the pin to the outrigger. The outrigger conforms to the anatomical configuration of the fractured bone thereby enabling direct fixation of the fracture fragments.

Description:
This application is a divisional of U.S. Pat. application Ser. No. 09/026,791 filed Feb. 20, 1998, now U.S. Pat. No. 6,056,748, the contents of which are herein incorporated by reference. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to external bone fixators for setting fractures of the human skeleton and, in particular, to a modular bone fixator assembly for setting fractures of the distal radius and other bones. 
     BACKGROUND OF THE INVENTION 
     The prior art is replete with external bone fixator devices which are used for setting various bone fractures. Practically all external bone fixator devices employ transcutaneous pins or screws which are secured in the bone on either side of the fracture. The pins are typically attached to an external splint device which adjusts the relative positions of the pins using various articulations. The fixator allows the bone pieces at the fracture to be realigned by a surgeon. Once the bone pieces have been realigned, the articulations in the fixator are locked in place to maintain the bone alignment. 
     Many of these external bone fixator devices are especially adapted for repairing fractures of the distal radius. This type of fracture generally involves a fracture site close to the distal head of the radius. Such fractures are typically reduced using pins set in the metacarpal bone and pins set on the proximal side of the fracture in the distal half of the radius. 
     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 do not allow motion at the wrist without crossing the joint during the period of fracture immobilization. 
     Accordingly, there is a need for an improved fixator device which is capable of allowing motion at the wrist during treatment of fractures of the distal radius and other bones without crossing the affected joint. 
     SUMMARY 
     The present invention is directed to a modular fixator assembly capable of allowing fixation to be confined to the affected bone as well as spanning capabilities thus, allowing motion at the wrist during treatment of fractures of the distal radius and other bones. The fixator assembly comprises a distractor device for providing distracton of a fractured bone, a pin outrigger attached to the distrator device, for enabling fixation of the fracture fragments of the fracture bone, at least one pin for fixating the fracture fragments, and clamping means for attaching the pin to the outrigger. The outrigger conforms to the anatomical configuration of the fractured bone thereby enabling direct fixation of the fracture fragments. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The advantages, nature and various additional features of the invention will appear more fully upon consideration of the illustrative embodiments now to be described in detail in connection with the accompanying drawings. In the drawings: 
     FIG. 1 is a perspective view of the modular fixator assembly of the present invention; 
     FIG. 2A is a partially sectioned, elevational side view of the distractor device shown in FIG. 1; 
     FIG. 2B is an elevational side view from the outrigger side of the distractor device shown in FIG. 1; 
     FIG. 2C is a top plan or dorsal view of the distractor device shown in FIG. 1; 
     FIG. 3A is a top plan or dorsal view of the pin outrigger shown in FIG. 1; 
     FIG. 3B is a cross-sectional view through a segment of the outrigger shown in FIG. 1; 
     FIG. 3C is an elevational distal end view showing the outrigger mounted to the distractor; 
     FIG. 4A is an elevational view of one of the outrigger pins shown in FIG. 1; 
     FIG. 4B is an elevational end view of the screw member of one of the outrigger pins shown in FIG. 1; 
     FIG. 4C is an axial cross-sectional view through the screw member; 
     FIG. 5 is an elevational view of one of the outrigger pin clamp assemblies shown in FIG. 1; 
     FIG. 6A depicts the fixator assembly as used in the modular fixation of a wrist fracture; 
     FIG. 6B depicts the distractor device as used in the direct fixation of the distal radius: 
     FIG. 6C depicts the outrigger as used in the direct fixation of the distal radius using the outrigger pins and the outrigger pin clamp assemblies; 
     FIG. 7 depicts the outrigger pins as used for providing compression between fracture fragments; 
     FIG. 8 is partially sectioned, perspective view of a screw driver adapted for driving the screw member of the outrigger pin; 
     FIG. 9A is an axial cross-sectional view through a hand reamer adapted for use with the outrigger pin; and 
     FIG. 9B is an elevational end view of the hand reamer of FIG.  9 A. 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 is a perspective view of the modular fixator assembly  10  according to an embodiment of the invention. The assembly  10  includes a distractor device  12 , a pin outrigger  14  removably attached to the distractor device  12 , and one or more outrigger pins  18  attached to the outrigger by pin clamp assemblies  16 . The fixator assembly  10  is generally used for repairing fractures of bones, especially fractures of the distal radius. 
     FIG. 2A is an elevational side view, partially in section, of the distractor device  12 . An elongated proximal pin clamp member  20  forms the proximal portion of the distractor device  12 . Proximal transcutaneous pins  22  are adapted to extend through transverse openings or apertures  24  in the proximal pin clamp member  20 . The proximal pins  22  may be secured in place by set screws  26 . The distal end of the proximal pin clamp member  20  includes a closed-ended bore  28  which extends axially therethrough and terminates near the proximal end thereof. The bore  28  receives an externally threaded rod  30 . A thumb screw  31  threadedly attached to the externally threaded rod  30  allows a surgeon to selectively extend or retract the rod  30 . The position of the rod  30  can be locked via a rod set screw  36 . A thumb gear  32 , for distal/proximal adjustment of the pin outrigger  14 , is rotatively disposed within the proximal pin clamp member  20 . The thumb gear  32  extends through an elongated slot  34  defined in the surface of the proximal pin clamp member  20 . 
     A distal pin clamp member  38  forms the distal portion of the distractor device  12 . Distal transcutaneous pins  40  are adapted to extend through transverse openings or apertures  42  in the distal pin clamp member  38 . The distal pins  40  can be secured in place by set screws  44 . A universal joint  46  couples the proximal end of the distal pin clamp member  38  to the distal end of the threaded rod  30 . The universal joint  46  allows universal pivotal movement of the distal pin clamp member  38  relative to the proximal pin clamp member  20 . 
     FIG. 2B is an elevational side view depicting the outrigger side of the distractor device  12 . An undercut, elongated groove  48  extends partially along a side of the proximal pin clamp member  20 . A slidably adjustable outrigger mounting member  50  rides in the groove  48 . The mounting member  50  attaches the outrigger  14  to the proximal pin clamping member  20 . The mounting member  50  includes outwardly extending flanges  52  (shown with broken lines) that are slidably retained in the undercut groove  48 . The mounting member  50  is adapted to be incrementally adjusted in the distal/proximal direction (relative to the proximal pin clamping member  20 ) with the thumb gear  32 . The proximal and distal location of the mounting member  50  may be locked via a set screw  54 . In one embodiment, the groove  48  allows approximately 15 mm of proximal and distal adjustment of the outrigger mounting member  50 . 
     FIG. 2C is a dorsal view of the distractor device  12 . This view shows a pair of I-shaped apertures  56  which extend through the mounting member. The I-shaped apertures  56  receive mounting arms provided on the outrigger  14  as will be explained further on. 
     FIG. 3A is dorsal view of the outrigger  14 . The outrigger  14  includes first and second projecting elements  58 ,  60  which extend from the mounting end  62  of the outrigger  14 . FIG. 3B is a cross-sectional view which shows outer and inner side grooves  64 ,  66  that extend continuously along respective outer  68  and inner side surfaces  68 ,  70  of the outrigger  14 . The grooves  64 ,  66  provide the outrigger with an I-shaped cross-section and enable the, pin clamp assemblies  16  to be slidably mounted to the outrigger  14  as will be explained further on. 
     The first projecting element  58  shown in FIG. 3A, generally conforms to the anatomical configuration of the distal radius. Starting at the mounting end  62 , the first projecting element  58  includes a first generally S-shaped section  72  which extends away from the second projecting element  60 , mimicking the radial styloid. The first section  72  merges with a second generally S-shaped section  74  that extends back toward the second projecting element  60  to conform the element  60  to the coronal anatomy of the distal radius at the level of the wrist joint. The second S-shape section  74  converges with the second projecting  60  element at a generally C-shaped section  76  which corresponds to the level of the distal ulna joint. 
     The second projecting element  60  cooperates with the first projecting element  58  to stabilize and strengthen the outrigger  14 . The second projecting element  60  extends from the C-shaped section  76  toward the mounting end  62 . A jogged section  78  provided in the second projecting element  60  strengthens and stabilizes the element. 
     FIG. 3C is an elevational distal end view of the outrigger  14  mounted to the distractor device  12 . Each projecting member  58 ,  60  has a depending arm  80  (only the first projecting member is visible). Each arm  80  is removably received in a corresponding one of the I-shaped apertures  56  of the mounting member  50 . 
     FIG. 4A is an elevational view of one of the outrigger pins  18 . In the preferred embodiment, each outrigger pin  18  includes a pin member  82  and a tubular screw member  84 . The pin member  82  has an anterior portion  86  and a posterior portion  88 . The anterior portion  86  is circular in cross-section and includes a conventional self-tapping external thread  90 . The posterior portion  88  is adapted to enable a chuck (not shown) to drive the pin member  82  into the bone fragments. This may be accomplish by providing the posterior portion  88  with a square or rectangular cross-section. In other embodiments, only the terminal end  92  of the posterior portion  88  is adapted to be driven by a chuck. In such embodiments the terminal end may be square or rectangular in cross-section and the remainder of the posterior portion can be circular in cross-section. 
     The tubular screw member  84  includes an elongated sleeve  94  and a enlarged head  96  with a frustoconical seating surface  98 . The sleeve  94  includes a tapered lead-in surface  104  which facilitates entrance of the screw member  84  into a drilled bone fragment. 
     FIG. 4C is a cross-sectional view through the screw member  84 . An opened ended bore  100  extends axially through the screw member  84 . The bore  100  includes internal thread  102  that is adapted to engage the external thread  90  on the anterior portion  86  of the pin member  82 . The diameter of the bore is sized to allow the posterior portion  88  of the pin member  82  to pass freely through the screw member  84 . 
     FIG. 4B is an elevational end view of the screw member  84 . The enlarged head  96  includes screw driving means  106  for threading the screw member  84 . In the shown embodiment, the screw driving means  106  is constructed as a socket-like recess. The screw driving means  106  enables the screw member  84  to be driven with a correspondingly adapted screw driver. 
     FIG. 5 is an elevational view of one of the outrigger pin clamp assemblies  16 . Each pin clamp assembly  16  includes a universal joint member  108  having pivotally coupled first and second joint elements  110 ,  112 . The first joint element  110  is adapted for clamping the posterior portion of the pin member via a set screw  114 . The second joint element  112  is coupled to one end of an elongated rod  116 . The other end of the elongated rod  116  is coupled to a swiveling slide member  118  adapted to be slidably attached to the outrigger  14 . The swiveling slide member  118  includes a C-shaped member  120  rotatively coupled to a rod attachment member  122 . The C-shaped member  120  defines a pair of inwardly facing flanges  124  that are adapted to slide and be retained in the outer and inner grooves of the outrigger  14 . The location of the slide member  118  on the outrigger  14  can be fixed with a set screw  126  that extends into the opening of the C-shaped member  120 . The swiveling slide member  118  and the universal joint member  108  enable universal articulated movement of the pin clamp assembly  16 . The pin clamp assembly  16  may be locked into position by locking means associated with each of the swiveling slide and universal joint members  118 ,  108 . The locking means may include set screws or friction bushings. 
     FIG. 6A illustrates the modular fixation of a wrist fracture using the fixator assembly  10 . The distractor device  12  of the fixator assembly  10  provides distraction of the fracture. Distraction of the fracture allows for indirect reduction through ligamentotaxis. When the fracture involves the distal radius, the distal and proximal pins  40 ,  22  of the distractor  12  are respectively placed in the hand metacarpals  128  and the distal ⅓ radius  130 . The distal and proximal pin clamp members  38 ,  20  of the distractor  12  are respectively clamped to the distal and proximal pins  40 ,  22 . Incremental distraction or compression is accomplished by extending or retracting the rod  30  using the thumb screw  31 . The universal joint  46  of the distractor  12  enables the distal pin clamp member  38  to be angularly positioned relative to the proximal pin clamp member  20  to fine tune the position of the hand. 
     Referring still to FIG. 6A, direct fixation of the distal radial fragments  132  is accomplished using the outrigger pins  18  in conjunction with the outrigger pin clamp assemblies  16  and the pin outrigger  14 . As the outrigger  14  extends over the wrist joint, the first projecting element  58  generally follows the profile of the distal radius and distal ulna. This enables the outrigger pins  18 , which are attached to the first projecting element  58  of the outrigger  14  with the outrigger pin clamp assemblies  16 , to be placed obliquely through the distal and proximal radial fragments  132 ,  130  to fixate and stabilize them. The anatomical configuration of the pin outrigger  14  and the universal articulate motion provided by the outrigger pin clamp assemblies  16  will also allow transverse pin placement through the radial styloid. Outrigger pin placement from dorsal and distal to volar and proximal is also possible. Such pin placement allows the volar tilt of the wrist to be maintained. Outrigger pins  18  may also be secured to the second projecting element  60  for further fixation. 
     FIG. 6B illustrates direct fixation of the distal radius using the distractor device  12  without the outrigger pins and the pin outrigger. Such use of the distractor device  12  is possible with certain types of fracture patterns. 
     FIG. 6C illustrates direct fixation of the distal radius using the outrigger pins  18 , the pin outrigger  14 , and the outrigger pin clamp assemblies  16  without the distractor device. This is possible for fracture patterns which do not require distraction or when distraction is no longer required. Such use allows hand motion at the wrist which has been found extremely desirable during the treatment of such fractures. 
     The outrigger pins  18  can also be used alone without the outrigger  14  and pin clamp assemblies  16  with certain other types of fractures. Such use of the pins  18  can be made with or without the distractor device depending upon the nature of the fracture. 
     FIG. 7 illustrates compression of the fracture fragments  134 ,  135  using the outrigger pins  18 . If compression of the fracture fragments  134 ,  135  is desirable, a hand reamer  136  can be used to overdrill the distal bone fragments  134  to open up the hole  138  drilled therein. Compression is provided by driving the screw member  84  of the outrigger pin  18  into the overdrilled hole portion  140  in the distal fragment  134  with a specially adapted screw driver  142 . Continued driving of the screw member  84  pushes the distal fragment  134  toward the proximal fragment  135  which is held in place by the threads  90  of the pin member  82 . 
     FIG. 8 is a perspective view, partially in section, of a screw driver  144  adapted for driving the screw member of the outrigger pin. The screw driver  144  is similar to the one shown in FIG.  7 . The screw driver  144  may include an elongated cylindrical body  146  with a handle  148  disposed at one end and screw member engagement means  150  formed at the other end. An opening  152  (shown with broken lines) extends axially through the body  146  and handle  148  of the screw driver  144 . The opening  152  allows entrance of the pin member so that the screw member engagement means  150  of the screw driver  144  can engage the screw driving means of the screw member. In the shown embodiment the screw member engagement means  150  is hexagonally shaped so that it may be received by screw member heads with hexagonally shaped recesses. However, other shapes are possible depending upon the configuration of the screw member&#39;s screw driving means. 
     FIGS. 9A and 9B depict a hand reamer  154  adapted for use with the outrigger pin assembly. The hand reamer  154  is similar to the one shown in FIG.  7 . The reamer  154  may be a T-shape member having an elongated cylindrical body  156  with a handle  158  disposed at one end and bone cutting means  160  at the other end. An opening  162  extends axially through the reamer  154  to allow entrance of the pin member of the outrigger pin so that the cutting means  160  of the reamer  154  can engage and overdrill the entrance of the hole drilled in the bone fragment. The cutting means  160  may take the form of a plurality of cutting flutes defined on the outer surface of the cylindrical body  156 . 
     It is understood that the above-described embodiments illustrate only a few of the many possible specific embodiments which can represent applications of the principles of the invention. For example, in some embodiments, the outrigger pins can be conventional transcutaneous pins, wires, or screws. In other embodiments, the pin outrigger may have one or more projecting elements conformed to the anatomy of other bones of the skeleton. Hence, numerous modifications and changes can be made by those skilled in the art without departing from the spirit and scope of the invention.