Abstract:
Described herein are external fixation systems for correcting bone deformities in adjacent bones or fragments thereof. The systems herein include first and second elongate tubes that translate with respect to one another via rotation of an actuation member at an end of one of the rods. At least one housing member is coupled along a length of one of the tubes. The housing member includes at least clamping portion for clamping a portion of a fixation pin therein. When the housing member is in an unlocked state, the clamping portions can move in a variety of directions. When in a locked state, the housing member cannot move with respect to the tube that it is coupled to. The position and orientation of the fixation pin is also set. The locked and unlocked state of the housing member is determined by the positioning of a locking pin coupled to the housing member.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of the filing date of U.S. Provisional Application No. 62/203,174 filed Aug. 10, 2015, the disclosure of which is hereby incorporated by reference herein. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to external fixation systems and methods, and in particular relates to improved fixation pin positioning and orientation using dynamic housing members with clamping portions coupled to a telescoping body. 
       BACKGROUND OF THE INVENTION 
       [0003]    Many different types of bone deformities can be corrected using external fixation systems. Such systems generally use rings, fixation plates, threaded rods or struts for manipulation, angulation, and translation of the deformities of bones. 
         [0004]    Some existing fixation systems on the market have components that are static and do not allow for certain adjustment and/or pivoting. Lack of flexibility in a system may restrict attachment to certain bone areas at certain angles as well as restrict motion of the portion of the body that the external fixation system is being attached to in order to correct. Because of such lack of flexibility, such systems may make it more difficult for the physician to achieve an optimal clinical outcome. 
         [0005]    Mini-rails are external fixation systems known in the art that are used to control distraction and compression during lengthening or deformity correction procedures generally of small bones. The primary use of these systems are in the hand, foot and craniomaxillofacial (“CMF”) regions. Existing mini-rail systems are generally bulky, unnecessarily complex in procedure, and utilize pin configurations that generally flex during correction of bone fragments. 
         [0006]    Further, prior art mini-rails generally consist of exposed threaded rods or “cages” which pin clamps translate on. In other prior art systems, the pin clamps may allow for some polyaxial rotation of the pins that are coupled thereto; however, other degrees of freedom are generally restricted between the pin clamps and the fixation rod that the pin clamp is coupled to. Further, many systems are not configured such that other fixation devices could attach to it unless such other fixation devices are specifically designed to interface with the threaded rod or cage thereof, for example. 
         [0007]    There exists a need for a dynamic mini-rail system that is not bulky and allows surgeons to insert fixation pins, of different diameters, in multiple bone locations and at a wide variety of angles such that ideal bone may be targeted for the best pin purchase. 
       SUMMARY OF THE INVENTION 
       [0008]    The present invention improves upon existing mini-rails by allowing for greater flexibility in fixation pin clamping and placement. The systems and methods described herein are indicated for use in osteotomies, arthrodeses, lengthening cases, fracture fixations, bone reconstruction procedures, revision procedures, non-unions, and delayed unions. 
         [0009]    The systems of the present invention allow a physician to target the best bone possible for ideal pin placement and thread purchase by allowing insertion of fixation pins with different diameters, in multiple bone locations and at a wide variety of angles. The flexibility of the systems of the present invention provide physicians and surgeons the capacity to place pins in the positions they feel are most appropriate. Pairs of fixation pins can be oriented vertically, horizontally, or diagonally with respect to each other. Additionally, the incidence angle of each fixation pin as it is inserted into the bone can be adjusted independently. 
         [0010]    The systems described herein also provide cross platform compatibility by way of a standard 8 mm diameter compression/distraction tube that can easily be coupled to other external fixation devices if desired. Further, the mini-rails of the present invention have a built-in thread such that the mini-rails may be used in other external fixation constructs, such as circular and conventional ex-fix systems, for example. 
         [0011]    The mini-rail systems described herein utilizes a central telescoping tube that can be locked to at a variety of lengths. Housing members including clamping portions are then slid over the tube. The location of each housing member along the tube may be determined independently of each other. 
         [0012]    Each clamping portion can hold two fixation pins of either the same or different diameters (ranging from 2-4 millimeters) through the use of two spring loaded jaws. These two fixation pins can rotate fully and independently about the telescoping tube when the housing members and clamping portions are in an unlocked position. In addition, the spring loaded jaws allow the pin to rotate parallel to the telescoping tube. This bi-axial rotation allows the surgeon to position the pins vertically, horizontally, or diagonally with respect to each other. Tightening of one nut anchors both the pin to the clamping portion and the housing member to the central tube simultaneously. 
         [0013]    A first aspect of the present invention is an external fixation device comprising an external fixation system comprising a first elongate rod, a first housing member and a first locking pin. The first housing member has a fixation pin clamping portion and a rod receiving portion, the fixation pin clamping portion having opposing jaws for receiving and clamping a fixation pin, the rod receiving portion including a longitudinal cavity housing at least a portion of the first elongate rod. The first locking pin is coupled to the fixation pin clamping portion and the rod receiving portion of the first housing member, wherein movement of the first locking pin in a first direction causes the opposing jaws of the fixation pin clamping portion and the rod receiving portion to compress toward one another such that the first housing member is in a locked state and cannot move with respect to the first elongate rod. 
         [0014]    In accordance with one embodiment of the first aspect of the present invention, the first locking pin is at least partially housed within a longitudinal bore defined by both of the fixation pin clamping portion and the rod receiving portion. 
         [0015]    In another embodiment of the first aspect, the longitudinal bore has an axis perpendicular to an axis of the longitudinal cavity of the rod receiving portion. 
         [0016]    In yet another embodiment of the first aspect, the a longitudinal axis is defined between the opposing jaws of the fixation pin clamping portion, the longitudinal axis being perpendicular to the longitudinal bore. 
         [0017]    In still yet another embodiment of the first aspect, the fixation pin clamping portion and the rod receiving portion are rotatably coupled to one another about the axis of the longitudinal bore. Movement of the first locking pin in the first direction causes the fixation pin clamping portion and the rod receiving portion to compress toward one another such that the fixation pin clamping portion and the rod receiving portion cannot move with respect to one another. 
         [0018]    In still yet another embodiment of the first aspect, movement of the first locking pin in a second direction allows the opposing jaws of the fixation pin clamping portion and the rod receiving portion to move away from one another such that the first housing member is in an unlocked state and can move with respect to the first elongate rod. 
         [0019]    In still yet another embodiment of the first aspect, the first locking pin includes an actuator portion and a shaft portion, the shaft portion being located within the longitudinal bore, the actuator portion being rotatable in the first direction. 
         [0020]    In still yet another embodiment of the first aspect, the rod receiving portion includes first and second deflectable legs, the first and second deflectable legs moving toward one another when the first locking pin is moved in the first direction. 
         [0021]    In still yet another embodiment of the first aspect, a second elongate rod has a longitudinal axis coaxial with a longitudinal axis of the first elongate rod when the first and second elongate rods are coupled, and wherein the first and second elongate rods translate with respect to one another along the longitudinal axes thereof. 
         [0022]    In accordance with a second aspect of the present invention, an external fixation device comprises a first elongate rod having a longitudinal axis, a first fixation pin portion having opposing jaws for receiving and clamping a fixation pin, a rod receiving portion rotatably coupled to the first fixation pin clamping portion, the rod receiving portion including a longitudinal cavity housing at least a portion of the first elongate rod, and a first locking pin coupled to the fixation pin clamping portion and the rod receiving portion of the first housing member, wherein movement of the first locking pin in a first direction causes the opposing jaws of the fixation pin clamping portion and the rod receiving portion to compress toward one another such that the first housing member is in a locked state and cannot move with respect to the first elongate rod. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]    A more complete appreciation of the subject matter of the present invention and the various advantages thereof can be realized by reference to the following detailed description in which reference is made to the accompanying drawings in which: 
           [0024]      FIG. 1  is a perspective view of one embodiment of an external fixation system of the present invention. 
           [0025]      FIG. 2A  is a perspective view of a distraction tube of the external fixation system of  FIG. 1 . 
           [0026]      FIG. 2B  is a side view of the distraction tube of  FIG. 2A . 
           [0027]      FIG. 2C  is a cross-section view of the distraction tube of  FIG. 2A  taken along line A-A. 
           [0028]      FIG. 2D  is an exploded perspective view of the distraction tube of  FIG. 2A . 
           [0029]      FIG. 3A  is an exploded perspective view of an embodiment of a housing member of the present invention. 
           [0030]      FIG. 3B  is a front assembled view the housing member of  FIG. 3A . 
           [0031]      FIG. 3C  is a cross-section view of the housing member of  FIG. 3B  taken along line B-B. 
           [0032]      FIG. 4A  is a perspective view of another embodiment of a housing member of the external fixation system of  FIG. 1 . 
           [0033]      FIG. 4B  is a side view of the housing member of  FIG. 4A . 
           [0034]      FIG. 4C  is a front view of the housing member of  FIG. 4A . 
           [0035]      FIG. 5A  is a perspective view of another embodiment of a housing member of the external fixation system of  FIG. 1 . 
           [0036]      FIG. 5B  is a side view of the housing member of  FIG. 5A . 
           [0037]      FIG. 5C  is a front view of the housing member of  FIG. 5A . 
           [0038]      FIG. 6  is a perspective view of another embodiment of an external fixation system of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0039]    In  FIG. 1  there is shown an embodiment of an external fixation system  100  having a distraction tube or telescoping rod  200 , a first housing member  400 , a second housing member  500 , and a plurality of fixation pins  600  coupled to respective clamping portions of the first and second housing members  400 ,  500 . 
         [0040]      FIGS. 2A-2B  are assembled views of distraction tube  200  having an actuation member  240 , a first elongate tube member  260 , a second elongate tube member  280 , a spring clip  294 , a detent  296  and a ball  298 . 
         [0041]    As shown in  FIGS. 2C-2D , actuation member  240  includes an actuation portion  242 , a base portion  244 , an engagement portion  246  and a shaft portion  248 . Actuation portion  242  projects outwardly in a distal direction from a distal end surface  250  of base portion  244 . Engagement portion  246  projects outwardly in a proximal direction from a proximal end surface  252  of base portion  244 . Engagement portion houses at least a portion of detent  296  and ball  298 . Shaft portion  248  projects outwardly in a proximal direction from engagement portion  246 . Actuation portion  242  is preferably configured to be engaged and manipulated by hand or with a tool. In the embodiment shown, actuation portion  242  has four angled flat surfaces  254  in a square configuration with four rounded edges  256  between adjacent surfaces  254 . Engagement portion  246  preferably includes a circumferential recess  257 . Shaft portion  248  includes threads  259  along substantially the entire length thereof. 
         [0042]    First elongate tube member  260  includes a distal end surface  262  and a proximal end surface  264 . First elongate tube member has a bore  268  extending through the proximal and distal end surfaces  262 ,  264  thereof and a protrusion  270  projecting outwardly from an inner surface  272  thereof. A plurality of apertures  274  are located through a circumference of tube member  260 . 
         [0043]    Second elongate tube member  280  includes a distal end surface  282 , a proximal end portion  284 , a tube portion  286  and a shaft portion  288 . Tube portion  286  includes an inner threaded surface  290  and an outer surface  292  having a longitudinal recess  294 . Proximal end portion  284  is shaped in order to couple second elongate tube member to other external fixation constructs, if desired. 
         [0044]    In assembling distraction tube  200 , distal end surface  262  of first elongate tube member  260  preferably mates with proximal end surface  252  of base portion  244  of actuation member  240  with shaft portion  248  of actuation member  240  being housed within bore  268  of first elongate member. Spring clip  294  is at least partially received within circumferential recess  257  of actuation member  240  and a corresponding recess  271  within an inner surface  272  of first elongate tube member  260 . Rotation of actuation member  240  may be calculated by the interaction of detent  296 , ball  298 , and the plurality of apertures  274  in first elongate tube member  260 . Each 90 degree rotation of actuation member  240  either clockwise or counterclockwise amounts to a 1 mm change in length, for example, of distraction tube  200 . 
         [0045]    When actuation member  240  is operatively coupled to first elongate tube member  260 , engagement portion  246  of actuation member  240  engages inner surface  272  of first elongate tube member  260 . Once actuation member  240  and first elongate tube member  260  are coupled, protrusion  270  of first elongate tube member  260  is coupled to longitudinal recess  294  of tube portion  286  at distal end surface  282  of tube portion  286  and slid along longitudinal recess  294  until threaded portion  259  of shaft portion  248  of actuation member  240  comes in contact with inner threaded surface  290  of tube portion  286  of second elongate tube member  280 . Actuation portion  242  is then rotated in a clockwise direction in order to thread shaft portion  248  onto threaded surface  290 . As actuation portion  242  continues to be rotated in a clockwise direction, protrusion  270  continues to ride along longitudinal recess  294  of tube portion  286  in a first direction until proximal end surface  264  lies adjacent a distal end surface  296  of shaft portion  288 . Because protrusion  270  rides along longitudinal recess  294 , first elongate tube member  260  does not rotate with respect to second elongate tube member  280 . Instead, first elongate tube member  260  only translates with respect to second elongate tube  280  along longitudinal axis L 1 . 
         [0046]    If actuation portion  242  is rotated in a counterclockwise direction, protrusion  270  will continue to ride along longitudinal recess  294  of tube portion  286 , but in a second direction along longitudinal axis L 1  such that proximal end surface  264  will be separated from distal end surface  296  of shaft portion  288  a larger linear distance from one another. As long as actuation member  240 , first elongate tube member  260 , and second elongate tube member  280  are coupled to one another, rotation of actuation member  240  in either a clockwise or counterclockwise direction will cause proximal end surface  264  and distal end surface  296  to move closer and further away from one another in a linear direction along longitudinal axis L 1  of external fixation system  100 . 
         [0047]    In another embodiment, tube portion  286  of second elongate tube member  280  has an outer surface  292  that is square shaped and has no longitudinal recess  292  in the outer surface thereof. Also, first elongate tube member  260  has a bore  268  having an inner surface  272  that is square shaped and no protrusion  270  projecting outwardly from the inner surface thereof. In this embodiment, once actuation member  240  and first elongate tube member  260  are coupled, square shaped inner surface  272  of first elongate tube member  260  is coupled to square shaped outer surface  292  of tube portion  286  of the second elongate tube member  280  at distal end surface  282  of tube portion  286  and is slid along the outer surface  292  until threaded portion  259  of shaft portion  248  of actuation member  240  comes in contact with inner threaded surface  290  of tube portion  286  of second elongate tube member  280 . Actuation portion  242  is then rotated in a clockwise direction in order to threaded shaft portion  248  onto threaded surface  290 . 
         [0048]      FIGS. 3A-3C  show a first embodiment of a housing member  300  of an external fixation system. Housing member  300  includes a housing portion  320 , a clamping portion  340 , an actuation portion  360 , and a stopper portion  380 . 
         [0049]    Housing portion  320  includes top and bottom portions  322 ,  326  coupled by way of a curved connector portion  332 . Top and bottom portion  322 ,  326  may be referred to as deflectable legs for their ability to move toward and away from one another through their connection with curved connection portion  332 . Top portion  322  includes a circumferentially grooved superior surface  323 , a substantially planar inferior surface  324  and an aperture  325  extending through surfaces  323 ,  324 . Bottom portion  326  includes substantially planar superior and inferior surfaces  327 ,  328  and a stepped aperture  329  extending through surfaces  327 ,  328 . Stepped aperture  329  has a first aperture portion  330  and a second aperture portion  331 . A longitudinal axis L 2  extends through surfaces  323 ,  324 ,  327 ,  328  of top and bottom portions  322 ,  326 . Curved connector portion  332  has an inner curved surface  334  and an outer curved surface  336 . The coupling of curved connection portion  332  to top and bottom bore portions  322 ,  326  defines an aperture  338  having a longitudinal axis L 3 . 
         [0050]    Clamping portion  340  includes first and second jaw portions  342 ,  348 . First jaw portion  342  has a superior surface  343 , an irregularly shaped inferior surface  344  and an aperture  354  extending through surfaces  343 ,  344 . A chamfer surface  345  and a curved recess surface  346  both extend from superior surface  343  toward inferior surface  344 . Inferior surface  344  includes a substantially planar fixation pin contact surface  347 . Second jaw portion  348  has an irregularly shaped superior surface  349 , a circumferentially grooved inferior surface  350  and an aperture  355  extending through surfaces  349 ,  350 . A chamfer surface  351  extends from inferior surface  350  toward superior surface  349 . Superior surface includes angled first and second fixation pin contact surfaces  352 ,  353 . 
         [0051]    Actuation portion  360  includes a head portion  362 , a shaft portion  364 , a first washer  368 , a spring  372 , and a second washer  376 . Head portion  362  and shaft portion  364  may collectively be referred to as a locking pin. Head portion  362  is configured to be rotated manually or with a tool or driver. Head portion  362  terminates at a planar surface  363 . First washer  368  has superior and inferior surfaces  369 ,  370  and an aperture  371  extending through superior and inferior surfaces  369 ,  370 . Spring  372  has a superior end  373  and an inferior end  374 . Second washer  376  has a spherical head portion  377 , a shaft portion  378  and an aperture  379  extending through the spherical head portion  377  and shaft portion  378 . 
         [0052]    Housing member  300  is first assembled by lining up actuation portion  360 , clamping portion  340 , housing portion  320  and stopper portion  380  along longitudinal axis L 2 . In doing so, apertures  354 ,  355  of first and second jaw portions  342 ,  348  of clamping portion  340  and apertures  325 ,  329  of top and bottom portions  322 ,  326  of housing portion  320  are aligned along longitudinal axis L 2 . First washer  368 , then spring  372 , then second washer  376  are assembled onto shaft portion  364  of actuation portion  360  such that shaft portion  364  extends through apertures in first washer  368 , spring  372  and second washer  376 . Shaft portion  364  is then inserted through the aligned apertures  354 ,  355  of first and second jaw portions  342 ,  348  of clamping portion  340  and apertures  325 ,  329  of top and bottom portions  322 ,  326  of housing portion  320  until a distal end  365  of shaft portion  364  is at least partially located within stepped aperture  329  of bottom portion  326  of housing member  320 . Stopper portion  380  is then at least partially inserted into aperture  329  and coupled to distal end  365  of shaft portion  364 . This coupling may be a compression fit, but is preferably a threaded connection. Threads located on an inner surface  382  of stopper portion  380  engage threads on an outer surface  366  of shaft portion  364 . 
         [0053]    Once the components of housing member  300  are generally assembled as described above, housing member  300  can now be assembled to an elongated rod or distraction tube  200 , for example, of an external fixation system  100  of the present invention. This assembly occurs by inserting an end of an elongate rod or distraction tube  200 , for example, through aperture  338  of housing member  300  such that longitudinal axis L 1  of distraction tube  200  is substantially coaxial with longitudinal axis L 3  of aperture  338 . In order to insert distraction tube  200  into and at least partially through aperture  338 , housing member  300  should be in an unlocked state such that the inferior surface  324  of top portion  322  and superior surface  328  of bottom portion  326  are not in contact with one another and are separated from one another by a substantially planar distance. In this unlocked state, aperture  338  has a neutral or relaxed diameter. Once the housing member  300  is located at a desired position about the length of the distraction tube  200 , actuation portion can be actuated in order to bring the inferior surface  324  of top portion  322  and superior surface  328  of bottom portion  326  into contact with one another while compressing the diameter of aperture  338  such that the position and orientation of housing member  300  with respect to distraction tube  200  is set. In this locked state, a linear distance between the head portion  362  of actuation portion  360  and stopper portion  380  is less than a linear distance between the head portion  362  of actuation portion  360  and stopper portion in the unlocked state. 
         [0054]    In an unlocked state, housing member  300  may rotate about longitudinal axis L 1 . Further, first and second jaw portions  342 ,  348  of clamping portion  340  may rotate with respect to top portion  322  of housing portion  320  about longitudinal axis L 2  which is preferably perpendicular and offset to longitudinal axis L 1 . Jaw portions  342 ,  348  generally correspondingly rotate about longitudinal axis L 2  because of irregularly shaped inferior surface  344  of jaw portion  342  having a corresponding shape to superior surface  349  of jaw portion  348 . Further still, in the unlocked state, jaw portions  342 ,  348  may be distracted away from or compressed toward longitudinal axis L 4  such that the space between surfaces  347  of jaw portion  342  and surfaces  352 ,  353  of jaw portion  348  may be made greater or less depending on the location of the jaw portions  342 ,  348 . 
         [0055]    In clamping a fixation pin  600  such as that shown in  FIG. 1  and  FIG. 3B , for example, fixation pin  600  is inserted into the space between surfaces  347  of jaw portion  342  and surfaces  352 ,  353  of jaw portion  348  at a particular position about the length of fixation pin  600 . As head portion  362  of actuation portion  360  begins to rotate in a clockwise manner about longitudinal axis L 2 , the components of housing member  300  begin to compress toward one another. A user should set the position and orientation of housing member  300  with respect to distraction tube  200 . The jaw portions  342 ,  348  should be rotationally aligned with respect to housing portion  320  in a desired position by engaging the grooves of the circumferentially grooved superior surface  323  with the grooves of the circumferentially grooved inferior surface  350 . As head portion  362  of actuation portion  360  continues to rotate in a clockwise manner, the stopper portion  380  is brought into full engagement within stepped aperture  329  such that a contact portion  384  of stopper portion  380  comes into contact with a ledge portion  337  located at a base of aperture  331  of bottom portion  326  of housing portion  320 . Further rotation of head portion  362  of actuation portion  360  causes the position of fixation pin  600  to be fixed with respect to surfaces  347  of jaw portion  342  and surfaces  352 ,  353  of jaw portion  348 . The housing member is now in a fully locked state such that the location and orientation of fixation pin  600  and housing member  300  with respect to distraction tube  200  is set. 
         [0056]      FIGS. 4A-4C  show an embodiment of a housing member  400  of external fixation system  100  shown in  FIG. 1 . The difference between housing member  300  and housing member  400  is that housing member  400  includes an additional clamping portion, actuation portion and stopper portion. I should be understood that the components of housing member  400  and their interaction with each other is the same as was described with respect to housing member  300 , with like reference numerals referring to like features in the present embodiment. Specifically, housing member  400  includes a housing portion  420 , a first clamping portion  440 , a second clamping portion  440 ′, a first actuation portion  460 , a second actuation portion  460 ′, a first stopper portion  480  and a second stopper portion  480 ′. This embodiment provides a physician, surgeon or any other operating room personnel with additional fixation pin coupling such that a first fixation pin can be coupled to first clamping portion  440  while a second fixation pin can be coupled to second clamping portion  440 ′. Because first and second clamping portions  440 ,  440 ′ are able to be oriented and locked independently of one another, different size fixation pins and different locations and orientations of the fixation pins can be produced using housing member  400 . As shown in  FIG. 1 , for example, housing member  400  allows pin  600  to have a first pin trajectory located in a first clamping portion and another pin to have a second pin trajectory located in a second clamping portion. Each pin shown has a different diameter, wherein pin  600  may be 4 mm in diameter while the second pin may be 2 mm in diameter, for example. Further, housing portion  420 , first clamping portion  440 , first actuation portion  460 , and first stopper portion  480  define a longitudinal axis L 2 ′ while housing portion  420 , second clamping portion  440 ′, second actuation portion  460 ′ and second stopper portion  480 ′ define a longitudinal axis L 2 ″. Longitudinal axes L 2 ′ and L 2 ″ are generally parallel and offset to one another. 
         [0057]      FIGS. 5A-5C  show another embodiment of a housing member  500  of external fixation system  100  shown in  FIG. 1 . The difference between housing member  500  and housing member  400  is that housing member  500  includes first and second groups of clamping portions, actuation portions and stopper portions located in opposite directions of one another. It should be understood that the components of housing member  500  and their interaction with each other is the same as was described with respect to housing member  300 , with like reference numerals referring to like features in the present embodiment. Specifically, housing member  500  includes a housing portion  520 , a first clamping portion  540 , a second clamping portion  540 ′, a first actuation portion  560 , a second actuation portion  560 ′, a first stopper portion  580  and a second stopper portion  580 ′. This embodiment provides a physician, surgeon or any other operating room personnel with variability in set fixation pins about longitudinal axis L 1  of external fixation system  100 . As with housing member  400 , because first and second clamping portions  540 ,  540 ′ are able to be oriented and locked independently of one another, different size fixation pins and different locations and orientations of the fixation pins can be produced suing housing member  500 . Housing portion  520 , first clamping portion  540 , first actuation portion  560 , and first stopper portion  580  define a longitudinal axis L 2 ′″ while housing portion  520 , second clamping portion  540 ′, second actuation portion  560 ′ and second stopper portion  580 ′ define a longitudinal axis L 2 ″″ such that longitudinal axes L 2 ′″ and L 2 ′″ are generally parallel and offset to one another. 
         [0058]    Another embodiment of an external fixation system  100 ′ is shown in  FIG. 6 . External fixation system  100 ′ includes a first distraction tube  200 ′, a second distraction tube  200 ″, first and second housing members  400  and a housing member  500 . Additional flexibility with respect to orienting fixation pins is provided with external fixation system  100 ′ by way of joint  150 . Distraction tube  200 ′ terminates at a first joint end  160  while distraction tube  200 ″ terminates at a second joint end  180 . First joint end interacts with second joint end  180  such that distraction tube  200 ′ can pivot with respect to distraction tube  200 ″ in several directions. Such a construct may be advantageous for use with articulating bones and/or joints. 
         [0059]    Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims.