Abstract:
An assembly allowing retraction of soft tissue away from a reference plane; the assembly including at least one retracting element each having a distal end with a formation allowing anchorage of the at least one retracting element. The assembly also includes a proximal end of the at least one retracting element capable of movement through at least one degree of freedom relative to the anchorage.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a divisional of U.S. application Ser. No. 11/660,466, filed Feb. 26, 2009, which is a 371 National Stage Application of PCT/AU2005/001205, filed on Aug. 13, 2005. 
     
    
     BACKGROUND 
       [0002]    The present invention relates to distraction and retraction assemblies. The invention further relates to improved apparatuses for distraction and soft tissue retraction in surgery including, but not limited to, spinal surgery. The invention also provides an assembly which performs the function of retraction optimising mechanical advantage and efficiency in retraction and resisting unwanted pull out of retractors. 
       PRIOR ART 
       [0003]    There are in existence a number of assemblies used in retraction of tissues to facilitate spinal and particularly cervical surgery. The most commonly performed anterior cervical procedure is an intervertebral fusion procedure that typically involve the steps of removing a portion or all of the affected disc material, spreading apart adjacent vertebrae with a distractor, and inserting an implant bone or cage or prosthetic disc into the space previously occupied by the removed disc material. This procedure can be done either from the front of the patient (anterior interbody fusion) or in the lumbar spine from the back (posterior interbody fusion). If done from the front, it is important to reduce the size of the retraction forces applied by the blades of the retractor so that the procedure is as minimally invasive as possible and thus minimally interferes with and minimally traumatizes the organs, tissues and vasculature being displaced to allow access to the vertebral region being treated. Posterior surgery can utilize larger tools since the insertion space is more accommodating and posterior structures requiring retraction i.e. muscles are less sensitive. 
         [0004]    By way of an example of a known device, U.S. Pat. No. 6,017,342 discloses a compression and distraction instrument having two pivotally connected handles. Jaw portions engage objects, such as human bone, for purposes of manouvering. A control screw connects with the handles, through a mechanical advantage arrangement, and the screw pivots the jaw portions for the engagement of the objects. There is an anti-friction connection between the screw and the handles, for accurate and precise movement of the jaws. In one embodiment, the screw is axial of the instrument, and, in the other embodiment, the screw is transverse thereto, both have mechanical advantage. 
         [0005]    In another example of a known distractor U.S. Pat. No. 6,712,825 of Mar. 30, 2004 discloses a spinal disc space distracter for separating adjacent elements, such as vertebrae. The distracter preferably has a scissors-type distracting mechanism, either in a simple scissors or double-acting scissors configuration. The distracter includes blades that are removable from the jaws of the distracter such that different blades may be used depending on the patient and situation with which the distracter is to be used. The jaws include a mating fixture and the blades include a mating portion for removable association with the mating fixture. In accordance with the principles of the invention disclosed, a spinal disc distracter is provided to allow for an implant insertion technique to be performed during distraction of the disc space. The implants are slid into the disc space between the distracter blades, preferably while the blades are in contact with the upper and lower surfaces of the adjacent vertebral bodies. The distracter is formed to be as minimally invasive and atraumatic as possible such that it may readily be used in an anterior or anterolateral approach. 
         [0006]    There are limitations inherent in conventional self retaining retractors used widely in surgery and routinely in anterior spinal surgery. These typically have two blades typically with teeth at one end that are linked by a hinge to scissor type handles. The teeth grip into or under the tissues and apply lateral forces as the handles are compressed by the surgeon to produce the desired exposure. The teeth grip and retract both sides of a wound against each other with equal distribution of retraction force. This means that when retracting two sides with different resistances eg left and right sides of an anterior (front) cervical wound (trachea, larynx, ET tube, oesophagus and thyroid are on one side only) excessive forces and retraction are applied to the easy side in an effort to retract the opposite more resistant side. This is one reason why conventional retractors slip, twist and rise up. Placing the teeth of these retractors under the longus colli muscle (next to the spine) works to an extent and is the standard method by which retractors in the anterior (front) of the neck are secured but it is common for retractors to require repositioning several times during an operation in addition to the difficulty of securing them in the correct place initially. Teeth cannot be made too sharp or too long as they will damage vital structures The second reason they slip is because the retraction forces are coming from the top ie outside the wound at a distance to where they at required at the bottom of the wound. The path of least resistance is up and as the retractor opens even the slight bending tends to produce a vector of force up as the blade follows the path of least resistance out of the wound leading to unwanted displacement of the retractor and therefore compromised retraction. Another reason they slip is that the tissues under retraction stretch reducing their counter force. As self retaining retractors rely on counter force for stability as this is reduced loosening inevitably occurs. 
         [0007]    Repeated adjustment can and does produce unnecessary tissue injury e.g. swallowing problems or hoarseness of voice in perhaps 5-10% of anterior cervical operations. It also wastes time and produces unnecessary bleeding. Persons skilled in the art are aware that one of the most frustrating parts of this type of surgery is positioning and maintaining position of the retractors. Conventional retractors are sometimes weighed down with chains and weights to resist the unwanted upwards rotational forces. 
         [0008]    Some known retractor blades have short spikes for bony fixation that create a point of leverage allowing limited movement of the blade. Other retractor systems allow for fixing a retractor blade to bone within a wound via pins or screws. Some known retractor systems allow rotation of a retractor blade around an axis of rotation attached to a frame that is outside the wound e.g. Synframe™ from Synthes™. 
         [0009]    Hohmans™ and Taylor™ retractors have an integral point that is either hammered into bone or pushed into a position to provide bone fixation and leverage. These are widely used in orthopaedic surgery. A Taylor™ type retractor blade is known which incorporates a tube for a securing pin. Also known are lever type retractors such as a hip retractor system designed by Dr R Barry Sorrells. Also know is a rail system for retractor blades and a blade that has means for fixation to bone with screws. Also known is a hip retractor system designed by a Dr S David Stulberg using only pins that are either drilled or hammered into the bone. Some of these can bend or lever slightly but allow no true rotation. External frames for securing levered retractors are also known. For example an assistant (surgeon) free self-retaining hip surgery retractor designed by Dr S David Stulberg is known. 
         [0010]    If hammered into bone via a short point fixation, then multiple rotations produces loosening and unwanted withdrawal. Where the pins rest on their point as a simple point of leverage but without deep fixation then they are prone to slippage if knocked or an assistant surgeon is not concentrating. Accordingly, a major disadvantage of the prior art is that there are no retraction systems in use that allow free rotation without compromising fixation. 
         [0011]    An anterior cervical system is known whereby retraction blades for cranial and caudal (top and bottom) part of wound are slid over known distraction pins. Additional lateral (side to side) retractors are still required and unconnected. These cranial and caudal blades are loose and can rotate only about the pin, (which is not very useful) and are not adjustable. They provide no lateral retraction parallel to the axis of the spine which is a much greater problem and which is addressed only in the present invention to be described below. 
         [0012]    The Prodisc™ anterior cervical system for cervical disc replacement has distraction screws with distraction arms that slide down over screws. The Prodisc™ uses a screw cap at top that secures the distraction arm, with downward pressure on to the base of the screw. 
       INVENTION 
       [0013]    The present invention in one form provides improvements in distraction and retraction assemblies. The invention further provides an improved apparatus for distraction and soft tissue retraction in surgery, including, but not limited to spinal surgery and which ameliorates the aforesaid disadvantages of the known retractors. The invention also provides an assembly which performs the functions of distraction and retraction optimising mechanical advantage and efficiency in retraction and resisting unwanted pull out of retractors. More particularly, the invention provides an assembly allowing secure anchorage of retractors and also longitudinal and rotational adjustment of the retractors to adjust retraction forces. 
         [0014]    The invention further relates to an assembly which performs the aforesaid retraction functions in conjunction with applied distraction of vertebrae using distraction pins and cooperating sleeves so that mechanical advantage in both distraction and retraction is achieved optimising efficiency in retraction and resisting unwanted pull out of retractors. Although the invention will be described with reference to its surgical applications it will be recognised by persons skilled in the art that the invention has wider applications in retraction alone and in combination retractions and distraction. During a surgical operation retractors are used to facilitate access to tissues. The present invention employs in one form the principle of fixation into bone (either directly or indirectly) to provide a secure anchorage and base for a retractor blade and also a stable axis for rotation of the blade within the wound without the prior art unwanted dislocations. 
         [0015]    The invention improves tissue exposure and surgical site access and minimizes soft tissue injury, bruising etc (due to the more controlled and reduced movements against tissues) whilst allowing variable selective rotation of at least one retractor blade as required during the surgical procedure. The combined features of the ability to adjust retraction pressure and reduce tissue pressure applied by the retractors thus minimizing tissue injury while maintaining stability of the blade distinguishes the present invention from the known prior art. The direct or indirect fixation (anchorage) to bone of a retractor prevents unwanted slippage and avoids the need for readjustment of retractors apart from the selected amount of rotation. The stable axis of rotation from within a surgical wound also imparts a mechanical advantage to retraction pressure reducing operator fatigue. Bone fixation with rotation is achieved in a number of different ways allowing application in numerous anatomical situations. 
         [0016]    In each of the embodiments to be described below including the direct fixation retractor assembly and the indirectly anchored retractor and distraction assemblies there exist the following common features: 
         [0000]    1. A means for fixation to bone
 
2. A connection between the point of fixation and retractor (a link)
 
3. A means for retraction of tissues (a blade)
 
4. A mechanism for variable rotation of retractor blades dictated by direct or indirect fixation of the blade to bone.
 
The fixation to bone, link, blade and means of rotation may be direct retractor engagement or the fixation may be indirect such as that described with reference to  FIG. 20  accomplished by various combinations of components.
 
         [0017]    This invention in all its forms has application whenever bone fixation is available principally in spinal and orthopaedic surgery but also other surgical disciplines. It is, another object of the present invention to provide an improved tissue retraction assembly for retracting wound margins and which provides optimal anchorage of retractor arms, optimal load application to tissue, rotational and longitudinal adjustment and which may be used in conjunction with vertebral distraction pins. 
         [0018]    It is further an object of the present invention to provide an assembly that efficiently and simply manages the insertion of a distractor and retractor. Other objects of the present invention not explicitly stated will be set forth and will be more clearly understood in conjunction with the descriptions of the preferred embodiments disclosed hereafter. 
         [0019]    In its broadest form the present invention comprises an assembly for use in a surgical procedure, including a frame capable of bone distraction and which receives and retains retraction arms for retraction of soft tissue during the surgical procedure; the frame including a first member including a recess which receives a first bone anchor and a second member which cooperates with the first member and receives a second bone anchor; the first member including at least one retaining arm which receives thereon a retractor arm; wherein, the second member is adjustable relative to the first member to allow distraction of bones to which the first and second bone anchors are attached. 
         [0020]    In another broad form the present invention comprises: 
         [0000]    an assembly for combined retraction of wound margins of soft tissue and distraction of vertebrae; the assembly including;
 
a pair of pins anchored in said vertebrae;
 
sleeves concentrically engaging said pins;
 
means to apply a distraction force to said pins via said sleeves;
 
a first side arm having a first end including a recess capable of engaging one said pins and a second end including connection means which releasably receives a first retractor arm via a mating profile;
 
a second side arm having a first end including a recess capable of engaging the other of said pins and a second end including connection means which releasably receives a second retractor arm via a mating profile; wherein said respective connection means each allow rotatable adjustment of each said retractor arms to retract said soft tissue margins.
 
         [0021]    In another broad form the present invention comprises: 
         [0000]    a distraction and retraction assembly for use in a surgical procedure, the assembly including a frame capable of bone distraction and which receives and retains retraction arms for retraction of soft tissue during the surgical procedure; the frame including a first member including a recess which receives a first bone anchor and a second member which co-operates with the first member and receives a second bone anchor; the first member including at least one retaining arm which receives thereon one of said retractor arms; wherein, one of said first and second members when anchored against bone is adjustable relative to the other member thereby inducing distraction of bones to which the first and second bone anchors are attached. 
         [0022]    According to a preferred embodiment, sleeves concentrically engaging said pins; the assembly further comprising means to apply a distraction force to said pins via said sleeves. 
         [0023]    In another broad form the present invention comprises: 
         [0000]    an assembly allowing distraction of adjacent vertebrae and retraction of soft tissue; the assembly comprising; means to apply a distraction load to said vertebrae via anchor pins fixed to each vertebrae; the assembly further including;
 
a first side arm having a first end including a recess capable of engaging a first said pins anchored in a vertebrae, and a second end including connection means which releasably receives a first retractor arm via a mating profile;
 
a second side arm having a first end including a recess capable of engaging a second of said pins and a second end including connection means which releasably receives a second retractor arm via a mating profile; wherein said respective connection means each allow rotatable adjustment of each said retractor arms for adjustment of a retraction force applied to said soft tissue margins.
 
         [0024]    In another broad form the present invention comprises: 
         [0000]    an assembly allowing distraction of at least one vertebrae and retraction of soft tissue; the assembly comprising;
 
means to apply a distraction load to said vertebrae via first and second distraction pins,
 
a first retractor comprising a first side arm having a first end including a recess capable of engaging a first said pins anchored in a vertebrae, and a second end including connection means which releasably receives a first retractor arm via a mating profile;
 
a second retractor having a second side arm having a first end including a recess capable of engaging a second of said pins and a second end including connection means which releasably receives a second retractor arm via a mating profile; wherein said respective connection means each allow rotatable adjustment of each said retractor arms for adjustment of a retraction force applied to said soft tissue margins.
 
         [0025]    In another broadest form the present invention comprises: 
         [0000]    a retraction assembly for retracting soft tissue the assembly comprising;
 
a first set of jaws defining a recess for receiving therein a first pin attached to a first vertebrae and including an arm which receives and retains thereon a first retractor capable of rotation about said arm;
 
a second set of jaws defining a recess for receiving therein a second pin attached to a second vertebrae and including an arm which receives thereon a second retractor capable of rotation about said arm.
 
         [0026]    In another broad form the present invention comprises: 
         [0000]    a retraction assembly comprising
 
a first member including a first arm having a set of jaws defining a recess;
 
a second arm extending from the first member;
 
the second arm having means to receive and releasably retain a first retractor;
 
a second member including a first arm having a set of jaws defining a recess;
 
a second arm extending from the second member;
 
the second arm on said second member having means to receive and releasably retain a second retractor;
 
wherein, when the recess of said first member engages a first pin and the recess of said second member engages a second pin each said first and second retractors, retract wound margins in soft tissue; wherein each said retractors are rotationally adjustable relative to respective said second arms of said first and second members.
 
         [0027]    In another broad form the present invention comprises: 
         [0000]    a distraction and retraction assembly comprising;
 
first and second anchor pins;
 
sleeve members adapted to concentrically engage said pins for transmission of a distraction force on each pin;
 
first and second retraction members; said first retraction member having a first arm having a set of jaws defining a recess which engages one said pins and a second arm extending from the first member;
 
said second arm receiving and retaining a blade capable of retraction of soft tissue;
 
said second retraction member including a first arm having a set of jaws defining a recess engaging a second one of said pins and a second arm extending from the second member; said second arm of said second retraction member comprising a blade capable of retraction of soft tissue;
 
wherein, each said first and second arms engage via mating formations which allow lateral and rotational adjustment of each said first and second retractors.
 
         [0028]    According to a preferred embodiment each said set of jaws are disposed in a common plane and engage the pins anchored in vertebrae. According to one embodiment said jaws are disposed in an orientation which is normal to a longitudinal axis of said first and second arms. According to one embodiment, each said arms include spline formations which engage with corresponding formations on respective first and second retractors. According to a preferred embodiment the spline formations on each said arms provide a mating engagement which allows longitudinal and rotational adjustment of said arms. 
         [0000]    According to a preferred embodiment each said blades include openings which receive and retain a tool adapted for adjustment of the orientation of said blades. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0029]      FIG. 1  shows a perspective view of a retractor assembly capable of concurrent distraction by cooperating anchor pins according to a preferred embodiment. 
           [0030]      FIG. 2  shows a perspective view of a retractor assembly retraction arm anchored to an anchor pin by a joining member. 
           [0031]      FIG. 3  shows an enlarged view of the retractor arm anchor pin of  FIG. 2 . 
           [0032]      FIG. 4  shows an elevation view of the arm anchor pin of  FIG. 3 . 
           [0033]      FIG. 5  shows an elevation view of the arm anchor pin of  FIG. 3 . 
           [0034]      FIG. 6  shows a perspective view of an assembly including an abbreviated retractor arm and joining member including a locating spline assembly according to one embodiment 
           [0035]      FIG. 7  shows the arrangement of  FIG. 6  with retractor arm rotated to an alternative position disposed normally to the plane of the joining member. 
           [0036]      FIG. 8  shows an exploded view of the assembly of  FIG. 6 . 
           [0037]      FIG. 9  shows a retractor arm and joining member assembly according to an alternative embodiment. 
           [0038]      FIG. 10  shows the retractor arm of  FIG. 9  separated from the joining member 
           [0039]      FIG. 11  shows an enlarged view of the joining member of  FIG. 9 . 
           [0040]      FIG. 12  shows a retractor arm and joining member assembly according to an alternative embodiment. 
           [0041]      FIG. 13  shows an enlarged view of the joining member of  FIG. 12 . 
           [0042]      FIG. 14  shows a retractor arm and joining member assembly according to an alternative embodiment. 
           [0043]      FIG. 15  shows an enlarged view of the joining member of  FIG. 14 . 
       
    
    
     DETAILED DESCRIPTION 
       [0044]    The present invention will now be described in more detail according to a preferred embodiment but non limiting embodiment and with reference to the accompanying illustrations. 
         [0045]    Typically according to one method, cervical distraction of vertebrae involves the use of anchor pins temporarily fixed to the vertebrae to be distracted. Generally two anchor pins are used one above and one below a disc or vertebral body of interest. Traditionally in a Caspar system these pins have only been used for distraction purposes via sliding tubes that fit axially over the pins and connect to an associated distraction mechanism. The role of the pin has been expanded to perform one or more of the following roles. The pin acts as x-ray marker to estimate a midline of a spine for cage or prosthetic disc replacement. The known and commonly used Caspar type distracter is then secured to the spine. Distracter tubes that each slide over respective pins and are secured to the pins via a screw applied at a threaded region. This however, does not have snug hex or square fit at a base of the pin but is round and transfers distraction forces along a length of a round pin. This does not provide optimal load transfer to the spinal vertebrae where distraction force is required but rather applies the load at a moment arm distant from the required load application site. The known technique for distraction force application applies a bending and shear force to the pins which must be transferred down the pin to its point of engagement with the vertebrae. A mechanical advantage during distraction is provided the closer the load is applied to the vertebrae due to a reduced moment arm and elimination of a bending moment on the pins so it is desirable to provide an assembly which meets this objective. In that case a shear force is applied at a base of pins to be distracted. 
         [0046]    Throughout the specification a reference to a retractor arm may be taken to be synonymous with side arms, retractor blade and retraction member. A reference to blades will be taken to include a reference to retractors or retractor arms. To fully appreciate the various embodiments of the invention to be described below a summary of the bone fixation methodology and associated apparatuses and assemblies. 
       1. Bone Fixation 
       [0047]    Single Point Bone Fixation 
         [0048]    This is accomplished by screws or short spikes or a spike/screw combination. Spikes are useful where a line of pull is oblique to a line of insertion and where anatomy is unfavorable for screws. Multiples screws or spikes may be used. A portion of the screw or spike may engage and link to other components. This portion is referred to as the anchor. 
         [0049]    Anchor recess shapes which may be used (see figures) include the following non limiting embodiments: 
         [0000]    Mushroom (conical with enlarged point), Cone, dimple, cup for blade,
 
Pedestal, Integral hinge and sidearm for connection to blade, Integral hinge allowing rotation in single plane, Integral small ball and socket with shaft for connection to blade.
 
       2. Means of Rotation 
       [0050]    Anchor incorporates means of rotation anchor with built in shaft for blade attachment that allows rotation in 1 plane only. 
         [0000]    Anchor with built in ball and socket plus shaft for blade fixation that allows rotation in multiple planes.
 
Link blade interface allows rotation either with integral or detachable hinge see  FIGS. 2 , or as in. anterior cx system  FIG. 1 .
 
         [0051]    Linking Components 
         [0052]    The various combinations of component include methods for securing components together, that may permit desired free rotation but may limit movement in other planes likely to produce loosening or fall out. It will be obvious to those skilled in the art that the mechanisms shown limiting unwanted motion are non limiting and that more simple versions of the following components with less stability are envisaged which prevents lift out once rotated. According to one embodiment there are links which lock rotation at the desired point such as the splines on retention members as shown in figure ( FIGS. 1, 6, 7 and 8 . Flathead with recess for locking pin. Once retractor blade rotates to certain angle e.g. 30 degrees recess is exposed allowing pin to be inserted from above down front of the blade. This pin is easily pulled out allowing free rotation of the blade but by insertion prevents blade returning until pin removed. Locking the retractor blade in this fashion means external handles for the blades or weights to pull the blade outwards are avoided. This reduces number of instruments around the operative field, frees or avoids totally the need for an assistant and facilitates x-rays. 
         [0053]    According to one embodiment a retractor blade clicks into position from above which is an alternative to sliding components together but once together resist pull out directly unless slid out sideways. 
         [0054]      FIG. 1  shows a perspective view of a retractor assembly capable of concurrent retraction and distraction by cooperating anchor pins according to a preferred embodiment. Referring to  FIG. 1  there is provided a retraction and distraction assembly  110  comprising retractor arms  111  and  112  terminating respectively in joining members  113  and  114  which engage anchor pin assemblies  115  and  116 . Various shapes of retractor joining member/side arms are possible as required. Retractor arm  111  comprises a first free end portion  117  including a recess  118  and spanning therebetween bridge members  119  and  120 . Bridge members  119  and  120  define spaces  121  and  122  which may attach to an operating tool not shown. The operating tool facilitates rotational movement of retractor arm  111 . Retractor arm  112  comprises a first free end portion  123  including a recess  124  and spanning therebetween bridge members  125  and  126 . Bridge members  125  and  126  define spaces  127  and  128  which may receive an operating tool not shown. As with arm  111 , the operating tool facilitates rotational movement of retractor arm  112  such that arms  111  and  112  cooperate in maintaining retraction of opposing surgical wound margins. Arms  111  and  112  are in use disposed against opposing soft tissue wound margins during surgery to facilitate and maintain adjustable rotational retraction. Arm  111  further comprises blade region  129  which terminates in a formation  130  which defines a recess  131  which receives and retains therein joining arm  132  of joining member  113 . This allows arm  111  to selectively rotate about joining arm  132 . Joining member  113  also comprises a bifurcated portion  133  having two arms which define recess  134  which receives and retains anchorage assembly  115 . Anchorage assembly  115  comprises an anchorage pin  135  having a leading end  136  terminating in a sharp point  137 . Leading end  136  may have thread like screw or pin like to facilitate penetration in bone and a trailing end  138  providing a driving member  138   a  to facilitate bone penetration of point  137 . Pin  135  is housed in guide sleeve  139  which compresses bifurcated portion  133 . Joining member  113  locates between base  138   a  and end  139   a  of sleeve  139 . Anchorage pin  135  which cooperates with sleeve  139  has a leading end  136  terminating in a sharp point  137  to facilitate penetration in bone. Distal end  155  receives a driving member  156  to facilitate compression of sleeve  139   a  against bifurcated portion  133  securing joining member  113 . Pin  135  is housed in guide sleeve  139  which engages bifurcated portion  133 . Guide sleeve  139  has connected thereto an ancillary sleeve  140  which receives in recess  141   a  tool (not shown) to facilitate distraction i.e. separation of anchorage assemblies  116  and  115  along an axis usually but not exclusively parallel to the axes of rotation of arms  111  and  112 . 
         [0055]    Arm  112  further comprises blade region  112   a  which terminates in a formation  142  which defines a recess  143  which receives and retains therein joining arm  144  of joining member  114 . This allows arm  112  to selectively rotate about joining arm  144 . Joining member  114  also comprises a bifurcated portion  145  having two arms which define recess  146  which receives and retains anchorage assembly  116 . Anchorage assembly  116  comprises an anchorage pin  147  having a leading end  148  terminating in a sharp point  149  to facilitate penetration in bone and a trailing end  150  providing a driving member  151  to facilitate compression of sleeve  152  against  145  securing joining member  114 . Pin  147  is housed in guide sleeve  152  which engages bifurcated portion  145 . Guide sleeve  152  has connected thereto an ancillary sleeve  153  which receives in recess  154  a tool (not shown) to facilitate distraction of anchorage assemblies  116  and  115  along an axis parallel to the axes of rotation of arms  111  and  112 . The sleeves  152  and  139  engage onto square portions of respective pins. The bifurcated elements  133  and  145  also engage snugly around square portions of pins  135  and  147 . This connection prevents independent rotation of elements. Combined rotation of all elements is prevented by joining two sleeves and pins together with an external distraction assembly. This distraction assembly (not shown) may join with the assembly as shown via recess  154  and  158  or may be integral as in existing Caspar systems. 
         [0000]    With the above described assembly  110  a surgeon may selectively effect both distraction (of bone) and retraction (of soft tissues). The assembly allows distraction along an axis parallel to the axes of rotation of arms  111  and  112  and selective opposing rotational adjustments of arms  111  and  112  and if required removal of one or other of arms  111  and  112 . 
         [0056]      FIG. 2  shows a perspective view of a part retractor assembly showing retraction arm  160  anchored to an anchor pin  161  by a joining member  162  according to an alternative embodiment. Arm  160  comprises free end portion  163  and blade region  164  which terminates in a formation  165  which defines a recess  166  which receives and retains therein joining arm  167  of joining member  162 . This allows retraction arm  160  to selectively rotate about joining arm  167 . Joining member  162  also comprises a bifurcated portion  168  having two arms which define recess  169  which releasably receives and retains head  170  of anchorage pin  161  terminating in a sharp point  171  to facilitate penetration in bone. Free end portion  163  includes recess  172  which retains bridge members  173  and  174 . Bridge members define openings  176  and  177  which receive an operating tool to facilitate both selective rotation of arm  160  and detachment from either joining member  162  or anchor  161 . 
         [0057]      FIG. 3  shows an enlarged view of the retractor arm anchor pin  161  of  FIG. 2  with corresponding numbering. Head  170  includes recess  180  which receives bifurcated portion  168  of joining member  162 . Bifurcated portion  168  bears on shoulder  181  and locks against underside surface  182  of head  170 . Shoulder  181  is optional and could be removed allowing bifurcated portion  168  of  162  to be positioned securely between  182  and base plate  170   a.    
         [0058]      FIG. 4  shows an elevation view of the arm anchor pin  161  of  FIG. 3  with corresponding numbering. Point  171  may further comprises formations  183  which facilitate bone penetration.  FIG. 5  shows an elevation view of the arm anchor pin  161  of  FIG. 6 . This arrangement of blade secured to anchor pin  161  with mechanism permitting rotation has widespread application in but not limited to orthopaedic and spinal surgery and whenever bone fixation possible. Variations of such devices will be obvious to those skilled in the art. 
         [0059]    Referring to  FIG. 6  there is shown a perspective view of an assembly  260  including abbreviated retractor arm  261  and joining member  262  including locating spline assembly  263  according to one embodiment.  FIG. 6  shows arm  261  at an oblique angle relative to a horizontal plane through joining member  262 .  FIG. 7  shows the arrangement of  FIG. 6  with arm  261  rotated to an alternative position disposed normally to the plane of joining member  262 .  FIG. 8  shows an exploded view of the assembly  260  of  FIG. 6 . Joining member  262  includes a joining shaft  264  terminating in a free end  265  and having a knurled or bevelled surface. Member  262  terminates at its opposite end in a bifurcated member  266  which engages an anchor (not shown) similar to the arrangements previously described. Shaft  264  includes thereon a radial array of splines  267  extending from its circumferential surface  268 . Arm  261  terminates in an enlarged region  269  having a wall  270  which defines a recess  271  adapted to axially receive shaft  264 . Wall  270  has at one end  272  a radial array of elements  273  arranged to align with intermediate spaces between individual splines in spline array  267 . This arrangement allows arm  261  to be selectively released from spline array  267  rotated to alternative positions such as shown in  FIGS. 6 and 7 . This allows a surgeon to selectively position the angle of repose of arm  261  held securely in position by splines  267 . To reposition the angle of arm  261  this is axially released from splines  267 , rotated and then reset. Splines provide a strong resistance to rotational loads applied against the arm  261  during use as a retractor. 
         [0060]    In an alternative embodiment it will be appreciated that position of splines  267  on shaft  268  may be varied to opposite end  265  with a corresponding change of mating profile to other end of recess  271  and in a further embodiment blade could contain splines and the shaft the recesses. Opposite gender spline mating may also be employed. 
         [0061]    The number of splines and teeth angles may be varied according to requirements. In an example of a method of use of the assembly, a surgeon may assemble the combined distracter and retractor assembly of  FIG. 1  according to the following regime. Typically, the assembly may be employed in an anterior approach to the cervical spine. The first step which is based on a known technique involves insertion of pins in vertebrae to be distracted. Preferably there will be two pins  135  and  147  spaced apart which are distracted to allow access to a disc space in the case for instance where a disc is to be replaced. The distracter pins such as those described as in  FIG. 1  are inserted into adjacent vertebrae. The surgeon takes a first retractor arm  111  or  112  whose configuration is selected to accommodate patient anatomy and allows it to directly or indirectly engage a first of said pins causing an associated rod and blade to lie generally parallel to a longitudinal axis of a spine. Arms  111  and  112  are mounted respectively on arms  132  and  144  of joining members  113  and  114 . Sleeves  139  and  152  are positioned over respective pins  135  and  147 . A retractor blade  111  or  112  such as that described with reference to  FIG. 1  is attached if not previously done by sliding respective sleeves ( 130  and  142 ) on the blade along the pivot arm of a joining member  132 ,  144  until mating splines (or other mechanically equivalent engagement) engage. The orientation of the retractor blade is set according to a selected circumferential (rotational) engagement of the respective mating opposed splines. The assembly now formed and shown in  FIG. 1  provides an ability to both distract vertebrae and retract soft tissue as required, the distraction occurring when a distraction force is applied through the sleeves or tubes  139  and  152  which axially engage the pins  136  and  147 . 
         [0062]    The degree of retraction is set by engaging the splines at a predetermined position so as to set the retractor arms  111  and  112  at an angle of repose which keeps soft tissue margins apart as required by the surgeon. If the aforesaid description relates to a right side distracter arm and retractor blade assembly there will be a corresponding left hand side arrangement which is preferably symmetrical about a transverse line through a disc space. If the aforesaid description relates to a left side distracter arm and retractor blade there will be a corresponding right hand side arrangement which is again symmetrical about a transverse line through the disc space. The distraction forces are applied at the base of the pins  136  and  147  to optimise mechanical advantage and to eliminate pin bending loads. This assembly described above allows variable distraction poses and movement without removal of retractors—side retractor arms and blades. 
         [0063]      FIG. 9  shows a retractor arm and joining member assembly  200  according to an alternative embodiment. Assembly  200  comprises a retractor arm  201  and joining member  202  with the retractor arm  201  in a substantially vertical orientation. Arm  201  includes free end portion  203  and blade  204 . End  203  includes bifurcation  205  defining recess  206 . Recess  206  includes bridging members  207  and  208  defining recesses  209  and  210  which receive an operating tool (not shown) which in use facilitates arm rotation for retraction of soft tissues. Blade portion  204  terminates in an enlarged formation  211  defining a recess  212  having a partially cut away wall exposing the interior of recess  212 . This cut away allows insertion and removal of members  202  and  222  plus rotation once centered. Recess  212  receives and retains joining member  202 .  FIG. 10  shows the retractor arm  201  of  FIG. 9  separated from a joining member  202 . 
         [0064]      FIG. 11  shows an enlarged view of the joining member of  FIG. 10 . Joining member  202  is insertable in recess  212  via pivot arm  214 . Pivot arm  214  has preferably intermediate its ends a bridge  215  which terminates in a loop  216  which engages an anchor pin (not shown). Arm  201  may then be rotated through about 30 degrees but it will be appreciated that the wall  217  (see  FIG. 10 ) contains notch  217   a  that allows rotation of bridge  215  to occur limiting rotation as desired of recess  212  can be configured to achieve an alternative degree (more or less) of rotation. 
         [0065]      FIG. 12  shows a retractor arm and joining member assembly  220  according to an alternative embodiment. Assembly  220  comprises a retractor arm  221  and joining member  222  with the retractor arm  221  abbreviated but in a substantially vertical orientation. Blade portion  223  terminates in an enlarged formation  224  defining a recess  225  having a partially cut away wall exposing the interior of recess  225 . 
         [0066]      FIG. 13  shows an enlarged view of the joining member of  FIG. 12 . Recess  225  receives and retains pivot retention arm  226  about which retractor arm  221  is free to rotate. Pivot arm  226  has preferably intermediate its ends a bridge  227  which terminates in an open saddle  228  which engages an anchor pin (not shown). Arm  221  may then be rotated as required about pivot arm  226 . 
         [0067]      FIG. 14  shows a retractor arm and joining member assembly  230  according to an alternative embodiment. Assembly  230  comprises a retractor arm  231  and joining member  232  with the retractor arm  231  abbreviated but in a substantially vertical orientation. Blade portion  233  terminates in an enlarged formation  234  defining a recess  235  having a partially cut away wall exposing the interior of recess  235 .  FIG. 15  shows an enlarged view of the joining member of  FIG. 35 . Recess  235  receives and retains pivot arm  236  about which retractor arm  231  is free to rotate. Pivot arm  236  has preferably at one end a bridge  237  which terminates in an open saddle  238  which engages an anchor pin (not shown). Retractor arm  231  may then be rotated as required about pivot arm  236 . 
         [0068]    According to one aspect of the invention once the retractor blades are inserted they are fixed at or adjacent to a location where a tip of an end of the Retractor blade is required. This is usually deep in the wound and generally involves firm fixation to an adjacent bony surface via a screw, clamp or other gripping device that connects directly to the blade or via an intermediary linkage. 
         [0069]    In most situations this connection with the fixation device will allow rotation of the blade about the point of fixation, either because the point of fixation itself can rotate. This fixation with rotation allows retractor blades to be left in situ throughout a procedure but allowing the surgeon to release the pressure and the retraction forces while working on another area thus reducing the tissue trauma but without having to remove the retractor blade or reposition the retractor blade. Releasing self retaining retractors leads to repeated tissue trauma every time these are reinserted and/or reopened. This system would therefore reduce tissue trauma and save time. It would also mean that the retractor once appropriately inserted can be secured insitu and not become loose or dislodged and require repositioning. The fixation device described in the cervical assembly utilises a pin with a screw thread into the bone and is first embodiment of this principal. 
         [0070]    This components described have multiple applications for the purpose of retraction of tissues. Such assemblies could also act as components in distraction devices alone or be combined with function as base for rotating retractors as illustrated in  FIG. 1 . 
         [0071]    It will be appreciated by those skilled in the art that the utilisation of this principal could be used in numerous other applications adapting to the different anatomy and retraction requirements throughout the spine, musculoskeletal system or wherever bony fixation can be utilised, e.g. the head. It will be further recognised by persons skilled in the art that numerous variations and modifications may be made to the invention without departing from the overall spirit and scope of the invention broadly described herein. Such modifications would allow adaptation of key concepts (which is that retractor blades are fixed at or close to critical point of retraction and may rotate) to provide additional retraction devices for use in anterior or posterior spinal surgery throughout length of spine or in orthopaedics or other surgical disciplines where bony fixation is available.