Abstract:
A minimal incision maximal access system allows for maximum desirable exposure along with maximum access to the operative field utilizing a minimum incision as small as the METRx and Endius systems. Instead of multiple insertions of dilating tubes the design is a streamlined single entry device to avoid repetitive skin surface entry. The system offers the capability to expand to optimum exposure size for the surgery utilizing hinged bi-hemispherical or oval working tubes applied over an introducer obturator which is controllably dilated to slowly separate muscle tissue. Deeper end working and visualization areas with maximum proximal access and work dimensions are provided to makes the operative procedure safer in application and shorten the surgeons&#39;s learning curve because it most closely approximates the ability to use open microdiskectomy techniques. a dual frame system enables full or partial spreading of a working tube set, while an open frame facilitates a four point retraction system.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part application of U.S. patent application Ser. No. 11/165,295 filed Jun. 22, 2005, which is a continuation-in-part of U.S. patent application Ser. No. 11/001,628 filed Nov. 30, 2004 now U.S. Pat. No. 7,173,240, which is a divisional application of U.S. patent application Ser. No. 10/280,624 filed Oct. 25, 2002, now U.S. Pat. No. 6,849,064, the entire contents of each of which are incorporated by reference herein. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to improvements in the field of minimal access lumbar posterior surgery and more particularly to instrumentation which allows for maximal access to the surgical field through the smallest possible incision. Greater access is allowed into the working field while enjoying the reduction of trauma and disturbance to surrounding tissues, which results in a reduced the time necessary to complete the operative procedure, increased safety of the procedure, and increased accuracy by providing an expanded working field. 
     BACKGROUND OF THE INVENTION 
     Microscopic Lumbar Diskectomy techniques were developed and championed by Dr. Robert Williams in the late 1970&#39;s and by Dr. John McCullough in the late 1980&#39;s and 1990&#39;s. For the first time since the advent of Lumbar Disc Surgery by Mixter and Barr in 1934 a method was introduced allowing Lumbar Disc Surgery to be performed through a small incision safely resulting in faster patient recovery and converting a two to five hospital stay procedure virtually to an outpatient procedure. 
     The special retractors developed by Drs. Williams and McCullough however were often difficult to maintain in optimum position and relied on the interspinous and supraspinatus ligaments for a counter fixation point severely stretching the structures. This stretching along with the effects of partial facectomy, diskectomy, removal of the ligamentum flavum and posterior longitudinal ligament contributed to the development of Post Diskectomy Instability. Taylor retractors were also used but were cumbersome, required larger incisions and often injured the facet joints. 
     Dr. William Foley in 1997 introduced a tubular system mated to an endoscope which he labeled a Minimal Endoscopic Diskectomy (MED) system. It featured sequentially dilating the Lumbar Paraspinous Muscles allowing a working channel to be advanced down to the level of operation through which nerve root decompression and Diskectomy Surgery could be performed with a small incision and less muscle trauma. Improvements were made by Dr. Foley in his second generation METRx system. However, there were several disadvantages to the MED and METRx systems. 
     In the MED and METRx systems, the cylindrical working channel considerably restricted visualization and passage of instruments. It also compromised the “angle of approach” necessary for safe usage of the operating instruments. This problem was proportionately aggravated with the long length of the tube. This compromised visualization contributed to the following problems, including nerve injury, dural tear, missed disc fragments, inadequate decompression of the lateral recess, increased epidural bleeding, difficulty controlling epidural bleeding, inadequate visualization of the neuroforamen, and inadequate decompression of neuroforamen. 
     The repetitive introduction of successively larger dilators caused skin abrasion with the potential for carrying superficial skin organisms down to the deeper tissue layers hypothetically increasing the risk of infection. The learning curve for operating in a two dimension endoscopic field proved to be arduous and contributed to the above complications. 
     The attempted use of the METRx system for more complex procedures such as fusion was further hazardous by inherent limitations. 
     Endius in September of 2000 then introduced a similar device which differed by having an expandable foot piece to allow greater coverage of the operative field. However, the enlarged foot piece was unwieldy and difficult to seat properly. Exposure of the angle of approach was also limited by having to operate through a proximal cylindrical tube with its limitations as described before. In comparison to the METRx system the working area was improved but access was again restricted by the smaller proximal cylinder. 
     Both systems offered endoscopic capability but many spine surgeons chose to use an operating microscope or loupes to maintain 3-Dimensional visualization rather than the depth impaired 2-Dimensional endoscopic presentation. Keeping debris off of the endoscopic lens has also proved to be a troubling challenge. 
     SUMMARY OF THE INVENTION 
     The system and method of the invention, hereinafter minimal incision maximal access system, includes a surgical operating system that allows for maximum desirable exposure along with maximum access to the operative field utilizing a minimum incision as small as the METRx and Endius systems. The minimal incision maximal access system disclosed offers advantages over the METRx and Endius systems in several respects. First, instead of multiple insertions of Dilating Tubes the Invention is a streamlined single entry device. This avoids repetitive skin surface entry. Second, the minimal incision maximal access system offers the capability to expand to optimum exposure size for the surgery utilizing hinged bi-hemispherical or oval Working Tubes applied over an introducer Obturator which is controllably dilated to slowly separate muscle tissue. 
     Third, the minimal incision maximal access system maximizes deeper end working and visualization area with maximum proximal access and work dimensions significantly greater than either the METRx or Endius devices and methods. Fourth, the minimal incision maximal access system provides expanded visual and working field to makes the operative procedure safer in application and shorten the surgeons&#39;s learning curve because it most closely approximates the open microdiskectomy techniques. Fifthly, the minimal incision maximal access system has a tapered ended Obturator which allows for tissue spread rather than muscle tissue tear and subsequent necrosis. 
     Sixth, the minimal incision maximal access system controls muscle oozing into the operative field which is controlled by simply opening the tubes further. This also thereby controls the bleeding by pressure to the surrounding tissues. Seventh, in contrast to the cylindrical tube based systems such as the METRx and Endius the minimal incision maximal access system offers a larger working area in proportion to the working depth. For the first time this allows for a minimal access technique to be applied to the large or obese patients. The enlarged footprint of the longer tubes in the minimal incision maximal access system is a major difference from any other minimal access system. 
     An eighth advantage of the minimal incision maximal access system is that ist expandable design allows for excellent exposure for more complex procedures such as fusion and instrumentation including TLIF, PLIF, and TFIF (Transfacet Interbody Fusion), as well as allowing application for anterolateral lumbar disc surgery. The minimal incision maximal access system can also be used for cervical surgery posteriorly (foraminotomy, lateral mass instrumented fusion) as well as anterior cervical diskectomy and fusion. The minimal incision maximal access system can also be used for anterior lumbar interbody fusion be it retroperitoneal, transperitoneal or laparoscopic. 
     A ninth advantage of the minimal incision maximal access system is that the medial oval cutout of the retractors, or sleeve forming the working tube, allows more central docking on the spine which is problematic for other devices. A medialized docking provides access for easier and better and safer dural retraction to address midline pathology. A tenth advantage is had by including an anti-reflective inner surface of the retractor sleeves which eliminates unwanted glare. 
     An eleventh advantage of the minimal incision maximal access system includes the slanted and contoured distal end of the retractor sleeve which allows minimal resistance for entry and advancement to the docking site. A twelfth advantage minimal incision maximal access system is the provision of a variety of retractor tips specific for different surgical procedures. 
     A thirteenth advantage of the minimal incision maximal access system is the provision of oval retractor sleeves for larger access requirements such as pedicle to pedicle exposure and especially in the case where pedicle screw instrumentation is to be applied. This minimizes unnecessary muscle spread by providing a smaller waist profile than a circular system. A fourteenth advantage of the minimal incision maximal access system is that the larger retractor sleeve also features one or two “skirts” to cover the lateral aperture created by the spread of the two retractor sleeves when opened. This prevents soft tissue and muscle ingress into the working cone. The skirts are attached to the working tube either at the hinge or on one of the two halves of the sleeve. 
     A fifteenth advantage of the minimal incision maximal access system is the provision of a modular design in which the retractor sleeves can be quickly removed, changed and reapplied. In this version the proximal port can also be modular and changeable to fit the needs of a specific surgical procedure. A sixteenth advantage of the minimal incision maximal access system is that the retractor sleeves can be made out of metal, ceramic or plastic, can be opaque or translucent, and can have tips of different shapes for different applications. A seventeenth advantage is the provision of snap lock connections of the major parts of the Invention provides for easy assembly and disengagement for cleaning and sterilization purposes. 
     Further, the Obturator is cannulated for carrying a central Guide Pin Passage. It has a Handle component which remains superficial to the skin. The obturator houses an internal hinge device which allows for spread of the two obturator tips. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention, its configuration, construction, and operation will be best further described in the following detailed description, taken in conjunction with the accompanying drawings in which: 
         FIG. 1  is a perspective view of a working tube with an angled upper section and shown in position with respect to an obturator insertable into and workable within the working tube; 
         FIG. 2  is a perspective assembled view illustrating the relative positions of the obturator and working tube; 
         FIG. 3  is a perspective assembled view illustrates the position of the obturator after it has been inserted into the working tube; 
         FIG. 4  is a view taken along line  4 - 4  of  FIG. 2  and looking into the working tube of  FIG. 1 ; 
         FIG. 5  is a sectional view taken along line  5 - 5  of  FIG. 2  and looking into the hinge of working tube of  FIG. 1 , illustrating its hinge connections; 
         FIG. 6  is an side end view of the working tube of  FIGS. 1-5  and illustrating predominantly one of the rigidly connected halves of the invention; 
         FIG. 7  is a side sectional view taken along line  7 - 7  of  FIG. 6  and showing the internal bearing pivot; 
         FIG. 8  is a side sectional view taken along line  8 - 8  of  FIG. 5  and illustrating a option for external bevel for the working tube; 
         FIG. 9  is a side view of the working tube of  FIGS. 1-8  shown with the lower portions in parallel alignment and the upper portions angled with respect to each other; 
         FIG. 10  is a side view of the working tube as seem in  FIG. 9  and shown with the lower portions in an angled relationship and the upper portions in a closer angled relationship with respect to each other; 
         FIG. 11  is a side view of the working tube as seen in  FIGS. 9 and 10  and shown with the lower portions in a maximally angled relationship and the upper portions in parallel alignment signaling maximal spread of the lower portions in bringing the upper portions into parallel alignment; 
         FIG. 12  is a side view of the obturator of  FIG. 1  and seen in an assembled view and emphasizing a through bore seen in dashed line format; 
         FIG. 13  is a side view of the obturator of  FIG. 11  as seen in an assembled view but turned ninety degrees about its axis and emphasizing the through bore; 
         FIG. 14  shows a side view of the obturator  33  of  FIG. 13  with the spreading legs in an angled apart relationship; 
         FIG. 15  is a sectional view taken along line  14 - 14  of  FIG. 12  and gives a sectional view from the same perspective seen in  FIG. 14 ; 
         FIG. 16  is a view of the obturator similar to that seen in  FIG. 15 , but turned ninety degrees along its axis and illustrates the wedge as having a narrower dimension to lend internal stability; 
         FIG. 17  is a closeup view of the external hinge assembly seen in  FIG. 1  and illustrates the optional use of a plug to cover the exposed side of a circular protrusion; 
         FIG. 18  is a view taken along line  18 - 18  of  FIG. 11  and illustrates the use of an optional skirt having flexible members which spread from an initial curled position to a straightened position to better isolate the surgical field; 
         FIG. 19  is a view of the lower tube hemicylindrical portions  65  and  69  in a close relationship illustrating the manner in which the skirts sections within their accommodation slots areas; 
         FIG. 20  is a cross sectional view of the a patient and spine and facilitates illustration of the general sequence of steps taken for many procedures utilizing the minimal incision maximal access system disclosed; 
         FIG. 21  illustrates a fascial incisor over fitting a guide pin and further inserted to cut through external and internal tissue; 
         FIG. 22  illustrates the assembled Working Tube—Obturator being inserted into the area previously occupied by the fascial incisor and advanced to the operative level lamina; 
         FIG. 23  illustrates the obturator  33  being actuated to a spread orientation to which automatically actuates the working tube to a spread orientation; 
         FIG. 24  is a view of the working tube  35  is in place and supported, held or stabilized in the field of view by a telescopy support arm and engagement, the opposite end of the stabilizing structure attached to the operating table; 
         FIG. 25  illustrates further details of the support arm seen in  FIG. 24 , especially the use of a ball joint; 
         FIG. 26  illustrates a side view of the assembly seen in  FIG. 25  is seen with an adjustable clamp operable to hold the working tube open at any position; 
         FIG. 27  is a top view looking down upon the adjustable clamp seen in  FIGS. 25-26  and shows the orientation of the working tube and adjustable clamp in fully closed position; 
         FIG. 28  shows a variation on the obturator seen previously in  FIG. 1  and illustrates the use of handles which are brought together; 
         FIG. 29  illustrates a further variation on the obturator seen previously in  FIG. 1  and illustrates the use of a central ball nut; 
         FIG. 30  is a sectional view taken along line  30 - 30  of  FIG. 29  and illustrates the use of a central support block to support the central threaded surface; 
         FIG. 31  is a top view of a thin, inset hinge utilizable with any of the obturators herein, but particularly obturators of  FIGS. 1 and 29 ; 
         FIG. 32  is a sectional view of the obturator of  FIG. 1  within the working tube of  FIG. 1  with the wedge  51  seen at the bottom of an internal wedge conforming space; 
         FIG. 33  illustrates the obturator seen in  FIG. 32  as returned to its collapsed state. 
         FIG. 34  illustrates a top and schematic view of the use of a remote power control to provide instant control of the working tube using an adjustable restriction on the upper angled hemicylindrical portions of the working tube; 
         FIG. 35  is a view taken along line  35 - 35  of  FIG. 34  and illustrating the method of attachment of the cable or band constriction; 
         FIG. 36  is a mechanically operated version of the nut and bolt constriction band seen in  FIG. 25 ; 
         FIG. 37  is an isolated view of two hemicylindrical tube sections shown joined in a tubular relationship and indicating at least a pair of pivot axes on each hemicylindrical tube section; 
         FIG. 38  is an isolated view of two hemicylindrical tube sections as seen in  FIG. 38  which are angularly displaced apart about a shared first pivot axis on each of the hemicylindrical tube sections; 
         FIG. 39  is an isolated view of two hemicylindrical tube sections as seen in  FIGS. 38 and 39  which are angularly displaced apart about a shared second pivot axis on each of the hemicylindrical tube sections; 
         FIG. 40  is a plan view of a given width supplemental side shield having a width of approximately the separation of the hemicylindrical tube sections as seen in  FIG. 39 ; 
         FIG. 41  is a top view of the supplemental side shield of  FIG. 40 ; 
         FIG. 42  is a pivoting thread support system in which a pair of opposing flank threaded members operate a pivoting support and are connected by a gear mechanism shown in exaggerated format to give single knob separation control; 
         FIG. 43  illustrates a surrounding frame system utilized to provide and enable pivoting and translation; 
         FIG. 44  illustrates a view looking down into the structure of  FIG. 43  shows the overall orientation and further illustrates an optional securing tang; 
         FIG. 45  illustrates a simplified control scheme in which simplicity is emphasized over controllability with less moving parts and expense; 
         FIG. 46  illustrates a further embodiment of a manipulative structure which works well with the structure of  FIG. 45 ; 
         FIG. 47  illustrates another possible realization which combines the control mechanisms of selected portions of  FIGS. 37-46 , combined with other possible options; 
         FIG. 48  illustrates a side view of the side shield seen in  FIG. 47 ; 
         FIG. 49  illustrates one possible configuration for a variable depth guide which is utilizable with any of the devices seen in  FIGS. 37-46  or any other tubular, minimally invasive system; 
         FIG. 50  is a vertical plan view of an expandable frame system which uses detents to set the frame size and which uses an angular distribution system; 
         FIG. 51  is a top view of the system of  FIG. 50  in an expanded position; 
         FIG. 52  is a side view of the system of  FIGS. 50-51 ; 
         FIG. 53  illustrates a top view double pivot hinge fitting and illustrating the gear surfaces; 
         FIG. 54  illustrates the action of the pivot hinge which produces an even angular deflection; 
         FIG. 55  illustrates a top view of a bookwalter device mounted atop a central hinge box seen in  FIG. 53 ; 
         FIG. 56  is a top view of a retractor system employing many of the components seen in  FIGS. 50-52  for applying force from a distance; 
         FIG. 57  is a top view of a hemicylindrical retractor tube extension; 
         FIG. 58  is a side sectional view of the hemicylindrical retractor tube extension of  FIG. 57  attached to the hemicylindrical tube seen in  FIG. 52 ; 
         FIG. 59  is a view looking down into the inside of the hemicylindrical retractor tube extension of  FIGS. 57 and 58 ; and 
         FIG. 60  is a view looking down onto the outside of the hemicylindrical retractor tube extension of  FIGS. 57-59 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The description and operation of the minimal incision maximal access system will be best described with reference to  FIG. 1  and identifying a general system  31 . System  31  includes an obturator  33  and a working tube  35 . The orientation of the obturator  33  is in a slightly displaced from a position of alignment with the working tube  35  for entry into working tube  35  and to provide the initial carefully controlled force for spreading the working tube  35 , as will be shown. 
     Obturator includes an upper control housing  37  and a pair of spreading legs  39  and  41 . The spreading legs  39  and  41  are seen as coming together to form a conical tip and thus have hemi-conical end portions. The spreading legs  39  and  41  over fit the attachment leg portions  43  and  45 , respectively. At the top of the upper control housing  37  a boss  47  surrounds and supports the extension of a control shaft  49 . a knurled thumb knob  50  sits atop the control shaft  49  to facilitate controlled turning of the control shaft  49  to control the degree of spreading of the spreading legs  39  and  41 . Thus spreading can be controlled independently of pressure applied along the length of the obturator  33 . 
     Below the upper control housing  37  is the bottom of the control shaft  49  which operates against a wedge  51 . The wedge  51  operates within a pair of opposing slots  52  in an upper portion  53  of the overfit attachment leg portions  43  and  45 . The lower ends of the overfit attachment leg portions  43  and  45  include insertion tangs  55  which fit within insertion slots  57  of the spreading legs  39  and  41 . The overfit attachment leg portions  43  and  45  are pivotally attached to the upper control housing  37  internally by pivot blocks  59  which fit within access apertures  60 . 
     The working tube  35  has a first lower extending connection tang  61  and a second lower extending connection tang  63 . First lower extending connection tang  61  connects into a slot  64  of a lower tube hemicylindrical portion  65 . The first lower extending connection tang  61  is fixed to an upper angled hemicylindrical portion  67 . The second lower extending connection tang  63  connects into a slot  68  of a lower tube hemicylindrical portion  69 . Second lower extending connection tang  61  is fixed to and an upper angled hemicylindrical portion  71 . The upper angled hemicylindrical portion  67  has a reinforced wear plate  73  for applying upper pressure and force on the upper angled hemicylindrical portions  67  and  71  toward each other to cause the first and second lower extending connection tangs  61  &amp;  63  and their connected lower tube hemicylindrical portions  65  and  69  to be urged away from each other. 
     At the side of the working tube  35  at the transition between the upper angled hemicylindrical portions  67  and  71  and a point just above the first and second lower extending connection tangs  61  &amp;  63  is an external hinge assembly  77 . Hinge assembly  77  may include an optional first guide plate  79  and first circular protrusion  81  attached to upper angled hemicylindrical portions  67 , and a first slotted plate  83  positioned adjacent to first guide plate  79  and having a slot partially surrounding the circular protrusion  81 . 
     Upper angled hemicylindrical portion  71  has a pair of spaced apart facing surfaces facing a matching pair of facing surfaces of the upper angled hemicylindrical portion  67 , of which a dividing line  85  is seen. Upper angled hemicylindrical portions  67  and  71  are be brought together to cause the first and second lower extending connection tangs  61  &amp;  63  and their connected lower tube hemicylindrical portions  65  and  69  to spread apart. 
     In the View of  FIG. 1 , the first and second lower extending connection tangs  61  &amp;  63  are shown in a spread apart relationship. a locking pin  87  is seen which can be used to engage angularly spaced apart apertures in the circular protrusion  81  to provide a detent action to hold the working tube  35  in various degrees of spread. Also seen is a slight exterior bevel  89  on the lower tube hemicylindrical portions  65  and  69 . 
     Note the angled separation of the upper angled hemicylindrical portions  67  and  71  and exposing opposing surfaces  91 . The angle of the opposing surfaces  91  equals the angle of spread of the first and second lower extending connection tangs  61  &amp;  63 . 
     Referring to  FIG. 2 , a perspective assembled view illustrates the relative positions of the obturator  33  and 
     working tube  35  in a position for the obturator  33  to be inserted into the working tube  35  and before any spreading takes place. 
     Referring to  FIG. 3 , a perspective assembled view illustrates the position of the obturator  33  after it has been inserted into the working tube  35  and again before any spreading takes place. Note that the pivot axes of the first and second lower extending connection tangs  61  &amp;  63  are on par with the pivot axes of the insertion tangs  55 . The tip of the obturator  33  extends slightly beyond the bottom most part of the working tube  35  so that the completed assembly can be smoothly urged past muscle and other tissue. 
     Referring to  FIG. 4 , a view taken along line  4 - 4  of  FIG. 1  is a view looking down into the working tube  35 . Other features seen include a wear plate  93  located on the upper angled hemicylindrical portion  71 . In both of the wear plates  73  and  93  a universal port  94  is provided as a bore for insertion of a tool or lever to assist in bringing the upper angled hemicylindrical portions  67  and  71  into a tubular relationship. Further, an identical hinge assembly  77  on the side opposite that seen in  FIG. 1  is shown with the same numbering as the components which were seen in  FIG. 1 . 
     Also seen are a pair of opposing surfaces  95  on upper angled hemicylindrical portion  71  and a pair of opposing surfaces  97  on upper angled hemicylindrical portion  67 . Also seen is a central working aperture  99 . 
     Referring to  FIG. 5 , a view taken along line  5 - 5  of  FIG. 1  is a sectional view looking down into the working tube  35 . The connectivity of the structures seen in  FIG. 4  are emphasized including the connection of circular protrusion  81  to the upper angled hemicylindrical portion  71 , and the connection of first slotted plate  83  to upper angled hemicylindrical portion  67 , and which is indicated by the matching section lines Further, an identical hinge assembly  77  on the side opposite that seen in  FIG. 1  is shown with the same numbering as the components which were seen in  FIG. 1 . 
     Referring to  FIG. 6 , a view of one end of the working tube  35  illustrates predominantly the second angled half portion  63 . Elements seen in  FIGS. 1 and 2  are made more clear in  FIG. 3 . 
     Referring to  FIG. 7 , a side sectional view taken along line  7 - 7  of  FIG. 6  and shows the internal bearing pivot consisting of a slightly greater than hemispherical side bump projection  101  located on upper angled hemicylindrical portion  71 , and a slightly less than hemispherical side circular groove  103  located on upper angled hemicylindrical portion  67 . Also seen is the interconnect slots  64  and  68  as well as the first and second lower extending connection tangs  61  and  63 . In the showing of  FIG. 7  an external bevel  105  is utilized 
     Referring to  FIG. 8 , a side semi-sectional view taken along line  8 - 8  of  FIG. 5  illustrates the integral connectivity of circular protrusion  81  with the upper angled hemicylindrical portion  71 . Seen for the first time in isolation are a pair of pin apertures  107  for engaging the locking pin  87 . 
     Referring to  FIG. 9 , an illustration of a side plan view and in which the lower tube hemicylindrical portions  65  and  69  are in matching straight alignment and forming a lower tube shape, while the upper angled hemicylindrical portions  67  and  71  are angled apart. 
     Referring to  FIG. 10 , a midpoint of movement is illustrates wherein the lower tube hemicylindrical portions  65  and  69  have begun to move apart widening the lower tube shape previously formed into an angled apart opposing hemicylindrical shape, while the upper angled hemicylindrical portions  67  and  71  are brought closer together to have a closer though angled apart an angled apart opposing hemicylindrical shape. 
     Referring to  FIG. 11 , a completed movement, with respect to the view of  FIG. 4  illustrates a state where the lower tube hemicylindrical portions  65  and  69  have moved apart to their maximum extent into a maximally angled apart opposing hemicylindrical shape, while the upper angled hemicylindrical portions  67  and  71  are brought completely together to form an upper tube shape. It is the position of  FIG. 6  which is the ideal working position once the lower tube hemicylindrical portions  65  and  69  are within the body, and provides an expanded working field at the base of the working tube  35 . Surgical work is ideally performed through the upper, abbreviated axial length tube shape formed by the upper angled hemicylindrical portions  67  and  71 . 
     Referring to  FIG. 12 , a side view of the obturator  33  of  FIG. 1  is seen in an assembled view and emphasizing in dashed line format a through bore  111  which extends though the obturator  33  from the knurled knob  50  through to the tip of the pair of spreading legs  39  and  41 . 
     Referring to  FIG. 13 , a side view of the obturator  33  of  FIG. 11  is seen in an assembled view but turned ninety degrees about its axis, and agin emphasizing in dashed line format the through bore  111  which extends though the obturator  33  from the knurled knob  50  through to the tip of the pair of spreading legs  39  and  41 . It is from this position that further actuation will be illustrated. 
     Referring to  FIG. 14 , a side view of the obturator  33  of  FIG. 13  is seen but with the spreading legs  39  and  41  in an angled apart relationship. An optional support  112  is supported by the upper control housing  37  to enable independent support and location of the obturator  33  should it be needed. Once the knurled knob  50  is turned, the wedge  51  seen in  FIG. 1  is driven downward causing the spreading of the spreading legs  39  and  41 . 
     Referring to  FIG. 15 , a sectional view taken along line  14 - 14  of  FIG. 12  gives a sectional view from the same perspective seen in  FIG. 14 . Pivot blocks  59  are seen as having pivot bores  113  which enable the upper portions  53  to pivot with respect to the upper control housing  37  and which enable the downward movement of the wedge  51  to translate into a spreading of the spreading legs  39  and  41 . 
     As can be seen, the knob  50  and control shaft  49  and the wedge  51  have the through bore  111 . In the configuration shown, the control shaft  49  includes a threaded portion  113  which engaged an internally threaded portion  115  of an internal bore  117  of the upper control housing  37 . The boss  47  is shown to be part of a larger insert fitting within a larger fitted bore  119  within the upper control housing  37 . This configuration pushes the wedge  51  downwardly against an internal wedge conforming space  123  to cause the insertion tangs  55  and upper portions  53  to spread apart. The wedge conforming space  123  need not be completely wedge shaped itself, but should ideally have a surface which continuously and evenly in terms of area engages the wedge  51  to give even control. Further, the wedge  51  can be configured to be rotatable with or independently rotationally stable with respect to the control shaft  49 . As can be seen, the through bore  111  continues below the internal wedge conforming space  123  as a pair of hemicylindrical surfaces  125  in the upper portion  53 , as well as a pair of hemicylindrical surfaces  127  in the pair of spreading legs  39  and  41 . 
     Referring to  FIG. 16  a view of obturator  33  similar to that of  FIG. 15 , but turned ninety degrees along its axis is seen. In this view, the wedge  51  is seen as having a narrower dimension to lend internal stability by narrowing the bearing area of the wedge  51  action in opening the pair of spreading legs  39  and  41 . 
     Referring to  FIG. 17 , a closeup view of the external hinge assembly  77  seen in  FIG. 1  illustrates the optional use of a plug  131  to cover the exposed side of the circular protrusion  81 . 
     Referring to  FIG. 18 , a view taken along line  18 - 18  of  FIG. 11  illustrates a view which facilitates the showing of an optional skirt, including a skirt section  133  welded or otherwise attached to lower tube hemicylindrical portion  65 , and a skirt section  133  welded or otherwise attached to lower tube hemicylindrical portion  69 . The skirts sections  133  and  135  are made of thin flexible metal and interfit within a pair of accommodation slots  137  and  139 , respectively. 
     Referring to  FIG. 19 , a view of the lower tube hemicylindrical portions  65  and  69  in a close relationship illustrates the manner in which the skirts sections  133  and  135  fit within the accommodation slots  137  and  139  when the lower tube hemicylindrical portions  65  and  69  are brought together to a circular configuration. 
     Referring to  FIG. 20 , a cross sectional view of the a patient  151  spine  153  is shown for illustration of the general sequence of steps taken for any procedure utilizing the minimal incision maximal access system  31 . There are several procedures utilizable with the minimal incision maximal access system  31 . Only a first procedure will be discussed using illustrative figures. Other procedures will be discussed after minor variations on the minimal incision maximal access system  31  are given below. 
     Procedure I: Diskectomy and Nerve Decompression 
     The patient  151  is placed prone on radiolucent operating table such as a Jackson Table. The patient  151  is then prepared and draped. The operative area is prepared and localized and an imaging device is prepared. A guide pin  155  is insert through the patient&#39;s skin  157 , preferably under fluoroscopic guidance. In the alternative and or in combination, the patient  151  skin can be incised with a scalpel. Other features in  FIG. 20  include the dural sac  159 , and ruptured intervertebral disc  161 . 
     Referring to  FIG. 21 , a fascial incisor  169  over fits the guide pin  155  and is further inserted to cut through external and internal tissue. The fascial incisor  169  is then removed while the guide pin  155  is left in place. Next, using the obturator  33 , the surgeon clears the multifidus attachment with wig-wag motion of the obturator  33  tip end. Next the obturator  33  is actuated to gently spread the multifidus muscle, and then closed. 
     Referring to  FIG. 22 , next the assembled Working Tube  35 —Obturator  33  is inserted into the area previously occupied by the fascial incisor  169  and advanced to the operative level lamina and remove the obturator  33 . As an alternative, and upon having difficulty, the obturator  33  could be initially inserted, followed by an overfit of the working tube  35 . In another possibility, a smaller size of obturator  33  and working tube  35  or combination thereof could be initially utilized, followed by larger sizes of the same obturator  33  and working tube  35 . The assembled Working Tube  35 —Obturator  33  in place is shown in  FIG. 22  with the working ends very near the spine. 
     Referring to  FIG. 23 , the obturator  33  is actuated to a spread orientation, which automatically actuates the working tube  35  to a spread orientation. Spread is had to the desired exposure size. The obturator  33  is thin actuated to a closed or non-spreading position. The obturator and working tube is then again advanced to dock on the spine. The working tube  35  is then fixed to assume an open position either by utilization of the locking pin  87  or other fixation device to cause the working tube  35  to remain open. Then, once the working tube  35  is locked into an open position, the obturator  33  is actuated to a closed or non-spread position and gently removed from the working tube  35 . 
     Referring to  FIG. 24 , the working tube  35  is in place. The working tube  35  may be secured by structure ultimately attached to an operating table. The working tube  35  may be held or stabilized in the field of view by a support  181  which may have an engagement sleeve  183  which fits onto the working tube. As can be seen, the operative field adjacent the spine area is expended even though the incision area is limited. The deeper a given size of working tube  35  is inserted, the smaller its entrance area. After the working tube  35  is stabilized, the surgeon will typically clear the remaining multifidus remnant at the working level and then set up and insert an endoscope or use operating microscope or loupes. The surgeon is now ready to proceed with laminotomy. 
     Referring to  FIG. 25 , further detail on the support  181  and engagement sleeve  183  is shown. A base support  185  may support a ball joint  187 , which may in turn support the support  181 . The support  181  is shown as supporting a variation on the engagement sleeve  183  as a pivot point support engagement end  188  having arm supports  189  and  191 . The arm supports  189  and  191  engage the external pivot structure on the working tube  35  which was shown, for example, in  FIG. 1  to be the external hinge assembly  77 . 
     As a further possibility, the upper angled hemicylindrical portions  67  and  71  are shown as being engaged about their outer periphery by an adjustable clamp  195 . Adjustable clamp  195  includes a band  197  encircling the upper angled hemicylindrical portions  67  and  71 . The ends of band  197  form a pair of opposing plates  199  and are engaged by a nut  201  and bolt  203  assembly. 
     Referring to  FIG. 26 , a side view of the assembly seen in  FIG. 25  is seen with the adjustable clamp  195  operable to hold the working tube  35  open at any position. Referring to  FIG. 27 , a top view looking down upon the adjustable clamp  195  seen in  FIGS. 25-27  shows the orientation of the working tube  35  and adjustable clamp  195  in fully closed position. When used in conjunction with the adjustable clamp  195 , the Reinforced wear plates  73  and  93  are eliminated so as to provide a smooth interface against the exterior of the upper angled hemicylindrical portions  67  and  71 . 
     Referring to  FIG. 28 , a variation on the obturator  33  is seen. An obturator  215  has handles  217  and  219  which operate about a pivot point  221 . A working tube  222  is somewhat simplified but is equivalent to the working tube  35  and is shown as including upper angled hemicylindrical portions  67  and  71 . Handle  219  has a ratchet member  223 , with ratchet teeth  225 , extending from it and a latch  227  pivotally connected about pivot point  229  to handle  217 . 
     Referring to  FIG. 29 , a variation on obturator  33  is seen as an obturator  241  having an upper housing  243 , control shaft  245  having 
     a threaded section  247  and operating through a ball nut  249 . A wedge  251  is extendable down through an operation space made up of a half space  253  in a leg  255  and a half space  257  in a leg  259 . Hinge structures  261  are shown attaching the legs  255  and  259  to the upper housing  243 . A through bore  111  is also seen as extending from the knob  261  through to the bottom of the wedge  251 . An access groove  263  is carried by the leg  259  while An access groove  263  is carried by the leg  259  while an access groove  265  is carried by the leg  255 . 
     Referring to  FIG. 30 , a sectional view taken along line  30 - 30  of  FIG. 29  illustrates the use of a central support block  271  to support the a central threaded surface  273  and the legs  255  and  259 . 
     Referring to  FIG. 31 , a view of a thin, inset hinge  281  utilizable with any of the obturators, but particularly obturators  33  and  241 , is shown. In the case of obturator  33 , by way of example, upper portions  53  accommodate control shaft  49  with its through bore  111 . Inset hinge  281  may be have an inset  283  and secured with machine screws  285 . Inset hinge  281  may be made of a “living hinge” material such as a hard plastic, or it can have its operations base upon control bending of a pre-specified length of steel, since the angle of bend is slight. The connection between the upper portions  53  and the upper control housing  37  may be by any sort of interlocking mechanism, the aforementioned pivot blocks  59  or other mechanism. 
     Referring to  FIG. 32 , a sectional view of the obturator  33  within the working tube  35  is seen. The wedge  51  is seen at the bottom of the internal wedge conforming space  123 . Once the spreading of the working tube  35  is accomplished the working tube  35  is kept open by any of the methods disclosed herein. Also seen is a pivot ball  116  to allow the control shaft  49  to turn with respect to the wedge. The pivot ball will continue to support a central aperture bore  111 . Once the working tube  35  is stabilized in its open position, the obturator  33  is returned to its collapsed state as is shown in  FIG. 33 . 
     Provision of electromechanical power to the operation of the working tube  35  can provide a surgeon an additional degree of instant control. Referring to  FIG. 34 , a top and schematic view of the use of a remote power control to provide instant control of the working tube  25 , similar to the view seen in  FIG. 25  illustrates the use of a remote annular control cable  301  using an internal cable  303  which is closely attached using a guide  305  and which circles the upper angled hemicylindrical portion  67  and  71 , terminating at an end fitting  307 . 
     The annular cable  301  is controlled by a BATTERY MOTOR BOX  311  having a forward and reverse switch  313  (with off or non actuation being the middle position). This enables the surgeon to expand the surgical field as needed and to collapse the surgical field to focus on certain working areas. BATTERY MOTOR BOX  311  is configured with gears to cause the cable  303  to forcibly move axially within the annular cable  301  to transmit mechanical power to the working tube  35 . 
     Referring to  FIG. 35 , a view taken along line  35 - 35  of  FIG. 34  illustrates how the cable  303  is held in place and a closeup of the end termination  307 . 
     Referring to  FIG. 36 , a mechanically operated version of the nut  201  and bolt  203  constriction band seen in  FIG. 25 . The mechanical power linkage can be provided remotely as by a rotating annular cable, but the basic mechanical setup shown illustrates the mechanical principles. On the bolt  203 , a gear head  325  is placed, either by attachment or by the provision of a threaded member and gear head made together. A second gear head  327  is utilized to show the possibility of providing a right angle power take-off in the event that the power connection interferes with the area around the surgical field. A shaft  329  extends from a BATTERY MOTOR BOX  331 . The BATTERY MOTOR BOX  331  has a forward and reverse switch  333 , (with off or non actuation being the middle position). Shaft  329  could be flexible and connected directly into axial alignment with the threaded member of bolt  201  or an integrally formed threaded member. 
     Advantages Over Existing Surgical Techniques 
     In terms of general advantages, there are differences between the minimal incision maximal access system  31 , and its components as described in all of the drawings herein (but which will be referred throughout herein simply as the minimal incision maximal access system  31 , or simply system  31 ) and other devices and procedures.
     1. With regard to the Traditional microdiskectomy technique, the minimal incision maximal access system  31  allows for at least the same, if not better visualization access of the operative field. System  31  offers the same 3-Dimensional work ability or, if preferred, an endoscope can be utilized. System  31  minimizes muscle injury with spread versus extensive cautery dissection. System  31  has clear advantage on the challenging obese and very large patient where the traditional microdiskectomy technique is almost impossible to be applied.   2. With regard to open pedicle screw insertion procedures, system  31  offers muscle approach minimizing muscle devascularization and denervation. The traditional approach had required at least one level proximal and one level distal additional exposure causing extensive muscle injury often leading to “fibrotic” muscle changes resulting in chronic painful and stiff lower back syndrome. System  31  offers the most direct approach to the pedicle entry point selecting the avascular plane between the longissimus and multifidus muscles.   3. With regard to the Sextant Procedure, system  31  offers clear advantage over the Sextant procedure. First, the system  31  offers a procedure which is not a blind pedicle screw technique. System  31  can be applied to larger and more obese patients in which the Sextant procedure cannot be utilized. In this procedure using system  31  oosterolateral fusion can be performed along with insertion of the pedicle screws. The sextant procedure is strictly a tension band stabilization.   

     In general, the components of the minimal incision maximal access system  31  are very simple the hemispherical shapes used for the working tube can be round or oval. A keying system can be had to align the obturator  33  to the working tube  35 . In the case of an oval system, the alignment would be automatic. 
     The minimal incision maximal access system  31  is a modular system with interchangeable parts for both the working tube  35  and the obturator  33 . The guide Pin  155  is of simple construction, as is the fascial incisor  169 . The working tube  35  has a limited number of basic parts, and can be made in the simple, two main piece version of  FIG. 28 , or the multi-piece version of  FIG. 1 , which enables retractor-sleeve substitution. A hinge and stabilization mechanism completes the simplified construction. 
     The obturator  33  is also of simple construction, with upper control housing  37 , pair of spreading legs  39  and  41 , and an internal hinge, whether the pivot blocks  59  or hinge  281  and its ability to support a control shaft  49  having a bore  111  for a guide pin  155 . Guide pin  155  may preferably have a size of from about 0.3 mm to 0.40 mm diameter and 30 cm to 40 cm in length. The fascial incisor may preferably be cannulated for usage with the guide pin  155  and have a width of about 2 mm more than the associated retractor. The overall cutting head length of about 1.2 cm has a shape as indicated in the Figures and has a thickness slightly larger than that of the guide pin  155 . 
     The working tube  35  can have several variations and added details including the simplest shapes as dictated by intended usage. Working tube  35  can have a simple fluted hemi-tube shape or a Slanted box shape. Further, the possibility of a fluted oval shape is dictated when the approach is more angular. The working tube  35  can have an attachment for an endoscope. Working tube  35  can also have a non-symmetric appearance as by having longitudinal cross sectional shape with half of its shape being rounded and one half of its shape being rectangular or box shaped. This could also give rise to a similarly shaped obturator  33 . The working tube  35  should have an anti-reflective inner coating and may be of modular construction. 
     The preferred lower dimensions for the lower tube hemicylindrical portions  65  and  69  include an overall shape which is semi tubular round or oval and having a width of from about 1.6-3.0 cm and a length of from about 4.0-18 cm. Hemicylindrical portions  65  and  69  may have custom cut outs depending upon planned application. 
     The hinge assembly  77  may have male-female post or male-female dial lock design, as well as a hinge housing and a bias (by spring or other mechanism) to keep angular displaceable portions of the working tube  35  closed. a “universal” port provides a point of attachment of an endoscopic or stabilizer bar. 
     The obturator  33  may be any controlled opening device including a circular band or cable, force Plates, or a device attached to hinge assembly  77  or other hinge assembly. 
     All sleeve attachments including the attachable legs  39  and  41 , as well as the lower tube hemicylindrical portions  65  and  69  should be of the friction grip type or snap and lock type or other suitable connection method or structure. 
     Obturator  215  may have squeeze grip scissor style handles  219  and  217  and a controlled dilator. It may utilize an enclosed design with a handle cover having a no-slip surface. It may be attached to the hinge housing of the working tube or separate hinge housing. In fact, it may be of a design to be held in place solely by the working tube  35 . Ideally a cavity will be provided through the center axis to contain the shaft for the dilator mechanism if applicable. 
     The central bore  111  of the obturator  33  may have a diameter of from about 5-10 mm, depending upon the size of the obturator  33  utilized. Obturator  33  should be provided in various widths and length to match working tube. The working tips of the spreading legs  39  and  41  may be changeable according to surgical procedures as described in the operative procedures herein. It may have an inner chamber, or internal wedge conforming space  123  slanted in shape wider proximal and more narrow distal to accommodate the wedge  51 . The internal wedge conforming space  123  can be enclosed with expanding, contracting sleeve. 
     Other Procedures 
     Many other procedures can be facilitated with the use of the inventive minimal incision maximal access system  31  and methods practiced therewith. Procedure I, a diskectomy and nerve decompression procedure was described above with reference to the Figures. Other procedures are as follows: 
     Procedure II: Facet Fusion 
     1. Patient prone on Jackson Table with normal lordosis preserved. This can be increased by placing additional thigh and chest support to increase lumbar lordosis. 
     2. Insert percutaneous special guide pin perpendicular to the floor at a point 1 cm caudal to the Alar-Superior facet notch. 
     3. Apply a flag guide to a first guide pin  155  #1. 
     4. Measure skin to bone depth from the scale on guide pin  155  #1. 
     5. Slide drill guide mechanism on the flag guide to match the skin bone distance. 
     6. Insert guide pin  155  #2 through the drill guide to dock on the superior facet. 
     7. Make a small skin incision for the obturator  33 . 
     8. Working tube  35  should be small oval or round with medial cutout to maximally medialize the working tube  35 . 
     9. Advance the working tube  35  to the L5-S1 joint and dock. 
     10. Drill the guide pin across the joint medial to lateral, rostral to caudal. If in proper position, advance across the joint to engage the ala. 
     11. Drill across the joint with a cannulated drill. 
     12. Check depth flouroscopically and measure. 
     13. Pick appropriate screw length. 
     14. Insert specially designed facet screw and protective bracket, secure tightly. 
     Procedure III: Posterior Lumbar Interbody Fusion (PLIF) 
     1. First half of the procedure similar to microdiskectomy (Procedure I) except for the use of a larger diameter sized working tube  35 . Use a 20-25 mm round or elliptical diameter working tube  35  with a medial cutout to allow docking as close to midline as possible. 
     2. Following diskectomy enlarge the laminotomy to accommodate the tools use for the specific PLIF such as Brantigan cage or Tangent. 
     Procedure IV: Transfacet Interbody Fusion (TFIF) 
     1. Follow the same procedure as the PLIF in terms of selecting and inserting the Working Tube  35 . 
     2. Following the diskectomy, resect the facet joint. 
     3. Approach the posterolateral disc space through the medial ⅔ of the facet joint. Take care not to injure the exiting root above. 
     4. Proceed with Brantigan cage instruments and interbody cages. 
     Procedure V: Pedicle Screw Instrumentation Technique 
     1. Place the patient  151  Prone position on a Jackson Table. 
     2. Guide pin  155  is docked on facet joint angled 30 degree lateral to medial in the plane between the longissimus muscle longitudinally and multifidus muscle medially. 
     3. Make skin incision. 
     4. Fascial incisor introduction. 
     5. Introduce the obturator  33  working tube  35  assembly between the longissimus and multifidus and progressively open the obturator  33  tip ends of the legs  39  and  41 , gradually reaching from the joint above and the joint below. 
     6. Advance the working tube  35  and retract the obturator  33 . 
     7. Use the elliptical Working Tube size 2.5 cm wide and open up to 5 cm. 
     Procedure IV: Anterior Lateral Lumbar Diskectomy Fusion 
     1. Mid lateral decubitus position left side up. Place a “waist roll” to prevent sag of the mid lumbar spine. 
     2. Identify proper level of surgery fluoroscopically. 
     3. Insert a guide pin  155  #1 percutaneously into the superior facet perpendicular to the spine. 
     4. Measure depth skin to joint on the scaled guide pin  155  #1. 
     5. Insert cannulated flag guide over guide pin  155  #1. 
     6. Slide the drill guide to match the depth. 
     7. Insert a guide pin  155  #2 down to the disc space. 
     8. Make skin incision and insert fascial cover. 
     9. Insert the working tube  35  and Obturator  33  combination. 
     10. Progressively dilate the obturator  33 . 
     11. Advance the working tube  35 . 
     12. Perform anterolateral diskectomy and interbody fusion as taught above. 
     13. Use a round or oval shaped retractor or lower tube hemicylindrical portion  65  and  69  as inserts preferably with distal end cutouts in each. 
     Procedure VII: Posterior Cervical Foramenotomy and Lateral Mass Plating 
     1. The patient is placed in a prone position on a Jackson table. 
     2. Fluoroscopic identification of the level of surgery is had. 
     3. Percutaneously insert guide pin  155  with AP and lateral fluoroscopic views. 
     4. Make the initial skin incision. 
     5. Apply the working tube  35  with obturator  33  into the incision. 
     6. Perform slow dilation of the muscle. 
     7. Advance the working tube  35  and collapse and remove the obturator  33 . 
     8. Proceed with surgery. Type of sleeve or lower tube hemicylindrical portion  65  should be round or oval with slanted and to match the slanted lamina. 
     9. For application for Lateral mass plating use an oval working tube  35  for a greater exposure. 
     Procedure VIII: Anterior Cervical Diskectomy Fusion 
     1. Begin with standard anterior cervical diskectomy fusion approach with a incision on the left or right side of the neck. 
     2. Blunt finger dissection is performed between the lateral vascular structures and the medial strap muscle and visceral structures down to the prevertebral fascia. 
     3. Establish the correct level to be operated on fluoroscopically and the guide pin  155  inserted into the disc. 
     4. Apply the working tube  35  and obturator  33  combination and dock at the proper level of the anterior spring. 
     5. Open the working tube  35  and obturator  33 . 
     6. Mobilize longus colli muscle. 
     7. Use special Bent Homen Retractor specifically design to retract the longus colli. 
     8. Proceed with surgery. 
     Procedure IX: Anterior Lumbar Interbody Fusion 
     1. Begin with the standard approach whether it is retroperitoneal, transperitoneal or laparoscopic. 
     2. Apply the special anterior lumbar interbody fusion working tube  35  and obturator  33 . This is a design with a medial lateral opening. It is oval shape and preferably with skirts  133  and  135 . The distal end of the retractor sleeve is slightly flared outward to retract the vessels safely. There is a skirt  133  or  135  applied to the cephalad side and possibly to the caudal side. 
     3. With the vessels and the abdominal contents safely retracted out of harms way, proceed with diskectomy and fusion. 
     One of the aspects emphasized up to this point for the system  31  is structure and circumstance to minimize the upper entry point of the surgery while providing an expanded working area at the distal end of the tube. Structures which achieve this geometry have been shown, and include a flared upper end so that the aperture remains open regardless of the angle of spread. 
     In other applications it is permissible to expand the aperture opening at the top of the working sleeve assembly. Expansion can be for the purposes of introducing further working devices into the working tube, as well as to expand and protect the visual field. For example, further working devices may include implant tools and their held implants, tools to insert plates and screws, and tools to manipulate all of these into their final positions. 
     Visual field protection can be introduced where the surrounding tissue may tend to flow, move or obstruct the surgical working field. Where the bottom-most portions of the spread apart hemicylindrical tube are spread apart, tissue tends to enter the space between the bottom parts of the tube. Additional guarding structure needs to be introduced. 
     a description of the desired articulation of what is hereinafter referred to as a working tube assembly  417 , and including the working tube hemicylindrical portions is begun with respect to  FIG. 37 . The designation of working tube assembly  417  refers to all of the tube structures seen in the earlier  FIGS. 1-36  and as seen in any of the following Figures.  FIG. 37  is an isolated view of two hemicylindrical tube sections shown joined in a tubular relationship and indicating at least a pair of pivot axes on each hemicylindrical tube section. 
     At the top of the structure shown in  FIG. 37  a dashed line indicates an optional fluted structure  419 . Fluted structure is omitted from the drawings for  FIGS. 37-49  in order that the views from the top will not be obscured. The optional fluted opening  419  and is often employed both to maintain the visual field upon opening, as well as to make it easier to add instrumentation into the surgical field. This structure is recommended, as well as all reasonable accommodation to facilitate its use. 
     a first hemicylindrical tube  421  is shown in alignment with a second hemicylindrical tube  423 . Rather than having the upper ends flared out to maintain a circular visual field on a full open position, a clearance notch  425  is provided in first hemicylindrical tube  421 , while a clearance notch  427  is provided in second hemicylindrical tube  423 . 
     The lowermost extent of the clearance notches  425  and  427  coincide with an upper pivot axis  431  of first hemicylindrical tube  421  and upper pivot axis  433  of first hemicylindrical tube  421 . The pivot axes  431  and  433  may include supports either derived from structures going into or out of the first and second hemicylindrical tubes  421  and  423 . In the view of  FIGS. 37-39 , the structures seen facing the viewer are repeated on the opposite side. Thus, pivot axes  431  and  433  are also located on the side opposite that seen in  FIGS. 37-39 . The same is true for all of the numbered structures. In this position, the simultaneous pivoting about the pivot axes  431  and  433  of the first and second hemicylindrical tubes  421  and  423  will not cause interference by portions of the first and second hemicylindrical tubes  421  and  423  which would otherwise interfere. 
     Further, a lower pivot axis  435  is provided below the upper pivot axis  431  of first hemicylindrical tube  421 . Similarly, a lower pivot axis  437  is provided below the upper pivot axis  433  of second hemicylindrical tube  423 . The geometry and pivot points having been identified, double headed arrows illustrate that the pivot points should be able to move toward and away from each other. Ideally, the only limitation should be the interference from the lower ends of the first and second hemicylindrical tubes  421  and  423  with each other. Where the mechanism for moving the first and second hemicylindrical tubes  421  and  423  has maximum independence, secondary considerations of interference are eliminated and only the primary interference between the first and second hemicylindrical tubes  421  and  423  will remain. Where the control mechanism for movement is lesser than that which allows maximum independence, savings can be had in terms of complexity of the mechanism at the expense of the freedom of movement. 
       FIG. 37  illustrates the first and second hemicylindrical tubes  421  and  423  in a closely aligned relationship where the upper pivot axis  431  is closest to the upper pivot axis  433  and where the lower pivot axis  435  is closest to the lower pivot axis  437 . This is the position expected to be used for entry into the body of the patient, especially along with a guide (to be shown) which will be located within and extending below the assembled and parallel linear tube formed by first and second hemicylindrical tubes  421  and  423  to provide a reduced insertion resistance. 
     Ideally, the first and second hemicylindrical tubes  421  and  423  will be inserted as shown in  FIG. 37  and then manipulated to a position shown in  FIG. 38 .  FIG. 38  is an isolated view of two hemicylindrical tube sections as seen in  FIG. 38  which are angularly displaced apart about a shared first pivot axis on each of the hemicylindrical tube sections. The position in  FIG. 38  is characterized by the fact that upper pivot axes  431  and  433  have the same separation as seen in  FIG. 37 , but in which the lower pivot axes  435  and  437  have moved apart. The position seen in  FIG. 38  will be likely achieved just after insertion and in which the internal tissues have been pushed apart. Depending upon the surgical procedure, the first and second hemicylindrical tubes  421  and  423  will be chosen based upon length, so that the lower end will be at the correct height for the tissues to be viewed, manipulated and treated. The action can continue until the lower ends of the first and second hemicylindrical tubes  421  and  423  are sufficiently spaced apart for view and manipulation of the tissues between and adjacent the lower ends. If there is a sufficient viewing opening based upon the original distance of separation of the upper pivot axes  431  and  433 , the procedure may continue through an aperture about the same size of the tube shape seen in  FIG. 37 . 
     Where more of an opening is needed, the first and second hemicylindrical tubes  421  and  423  upper pivot axes  431  and  433  can move more widely apart until a position such as that seen in  FIG. 39  is achieved.  FIG. 39  is an isolated view of the two first and second hemicylindrical tubes  421  and  423  which are angularly displaced apart about a shared second pivot axis on each of the hemicylindrical tube sections. It should be emphasized that the position seen in  FIG. 39  is a position where both the first and second hemicylindrical tubes  421  and  423  are parallel and separated from each other, but this need not be the case. From the position seen in  FIG. 38 , the upper pivot axes  431  and  433  can be moved apart from each other while the lower pivot axes  435  and  437  either remain a constant distance from each other or are brought together. This range of articulation described can be used to physically manipulates the tissues in contact with the first and second hemicylindrical tubes  421  and  423  for any number of reasons, including introduction of further instruments if necessary, as well as to react to changing conditions of tissue at the lower tube. 
     In both  FIGS. 38 and 39  a pair of opposing edges  439  can be utilized to support structures introduced between the first and second hemicylindrical tubes  421  and  423 . Other structures can be used including depressions, apertures and internal projections, such as hooks or latches. An internal structure within the first and second hemicylindrical tubes  421  and  423  would pose little risk of nick to the patient and can be designed to do nothing more than have a minimal interference effect with respect to the visual field. 
     As will be shown, a number of external structures can be employed to achieve the relative separation positions of the upper pivot axes  431  and  433 , as well as the lower pivot axes  435  and  437  that nearly any type of angle can exist on either side of a parallel relationship between the first and second hemicylindrical tubes  421  and  423 , but that most will be in a range of from a parallel relationship to some form of angular relationship seen in  FIG. 38 , where the upper ends at the clearance notches  425  and  427  are closer together than the lower ends distal to the upper pivot axes  431  and  433  and lower pivot axes  435  and  437 . 
     One example of a side shield  441  is seen in  FIG. 40 .  FIG. 40  is a plan view of a given width supplemental side shield  441  having a width of approximately the separation of the hemicylindrical tube sections as seen in  FIG. 39 , while accompanying  FIG. 41  is a top view of the supplemental side shield  441  of  FIG. 40  emphasizing its shape. The side shield  441  can be of any shape, but is shown in a rectangular shape to correspond with the first and second hemicylindrical tubes  421  and  423  in a parallel position as seen in  FIG. 39 . The side shield  441  has a main portion which includes a first side  443  and a pair of lateral engagement portions  445 . The side shield  441  can depend from a number of other structures, but the side shield  441  seen in  FIGS. 40 and 41  utilize an offset surfaces as engagement portions  445 . This geometry, will, absent any interfering structures which are attached to manipulate the first and second hemicylindrical tubes  421  and  423 , enable the side shield  441  to be introduced linearly from the top of first and second hemicylindrical tubes  421  and  423 . The introduction of side shield  441  may be guided somewhat into engagement by the clearance otches  425  and  427 . Much smaller engagement portions  445  could be used to engage the outer edges  439  of the first and second hemicylindrical tubes  421  and  423 , so long as the orientation is so as to protect the surrounding tissues.  FIG. 41  emphasizes the geometry and shows a second side  447 . 
     In the orientation shown, the second side  447  would face toward the inside of the general tube formed in the orientation of  FIG. 39 . If two of the side shields  441  were used, one on either side of the opening seen in  FIG. 39 , the tube shape would be closed on both sides, and an oval viewing area would be formed. It should be emphasized that the side shield  441  can depend from any structure, and not just the opposing edges  439  seen in  FIG. 39 . Structure used to manipulate the first and second hemicylindrical tubes  421  and  423  can be used to both guide and secure any side shield  443 . 
     In terms of a structure to manipulate the first and second hemicylindrical tubes  421  and  423 , it is preferable that the upper pivot axes  431  and  433  may be urged toward and away from each other independently of the urging of the lower pivot axes  435  and  437  toward and away from each other independently. a mechanism which would prevent all manipulations of the first and second hemicylindrical tubes  421  and  423  to a position of binding is desirable, but its complexity may obstruct the surgical field. For example, it would be good to have a mechanism which would prevent upper pivot axes  431  and  433  from moving away from each other while the lower pivot axes  425  and  437  are in their close proximity as depicted in  FIG. 37 . In some cases operator knowledge and skill will probably be required. 
     In terms of supporting the upper pivot axes  431  and  433  and lower pivot axes  425  and  437 , the pivoting and movement may be passive with mechanisms to push or pull directly on the first and second hemicylindrical tubes  421  and  423  or structures which are mechanically attached. As an example of the use of force and movement urging at the pivot points,  FIG. 42  illustrates one such system as a pivoting thread support system  551 . The gearing is shown as unduly expansive to illustrate simply the action, but in reality, several gears may be used. 
     Further, since the a pivoting thread support system  551  is viewed from the top, and as operating the upper pivot axes  431  and  433 , a similar arrangement would be used for the lower pivot axes  425  and  437 . a set of four pivot fittings  553  provide a threaded interior spaced apart from the first and second hemicylindrical tubes  421  and  423 , or fittings supporting the first and second hemicylindrical tubes  421  and  423 . The fittings  553  enable the first and second hemicylindrical tubes  421  and  423  to tilt while keeping the threaded apertures in alignment. 
     A first threaded member  555  has a pair of threaded areas in which the threads are oppose pitched, and a knob  558  for manually turning the thread member  555 . The threads engaging the fitting  553  of first hemicylindrical tube  421  are set to urge first hemicylindrical tube  421  away from second hemicylindrical tube  423 , at the same time that the same turning of the first threaded member engages fitting  553  of first hemicylindrical tube  423  set to urge first hemicylindrical tube  423  away from second hemicylindrical tube  421 . This means that the turning of first threaded member  555  in one direction urges the first and second hemicylindrical tubes  421  and  423  evenly away from each other, and alternatively, the turning of first threaded member  555  in the opposite direction urges the first and second hemicylindrical tubes  421  and  423  evenly toward each other. 
     Likewise, a second threaded member  557  has a pair of threaded areas in which the threads are oppose pitched. The threads engaging the fitting  553  of first hemicylindrical tube  421  are set to urge first hemicylindrical tube  421  away from second hemicylindrical tube  423 , at the same time that the same turning of the first threaded member engages fitting  553  of first hemicylindrical tube  423  set to urge first hemicylindrical tube  423  away from second hemicylindrical tube  421 , but in an oppose orientation than the threads of first threaded member  555 . This means that the turning of second threaded member  557  in the other direction (while the first threaded member  555  is turned in a first direction) urges the first and second hemicylindrical tubes  421  and  423  evenly away from each other. a pair of over sized gears, including a first gear  559  associated with the first threaded member  555 , and a second gear  561  associated with the second threaded member  557  act to cause the first and second threaded members  555  and  557  to move simultaneously and oppositely. a knob  563  is used to manipulate both the first gear  559 , which manipulates the second gear  561 . In a realization in which more gears  559  and  561  are provided, the size of the gears can be reduced and for each intermediate gear, the sense of the threaded members  555  and  557  will change from opposite to same. 
     Referring to  FIG. 43 , a surrounding frame system  571  is seen which is utilized to provide and enable pivoting and translation. A surrounding frame  573  has an open slot  575  which accommodates a pair of pins  577  and  579  which preferably have some tracking along the slot  575  to insure that neither the first hemicylindrical tube  421  nor the second hemicylindrical tube  423  are able to turn within the frame  573 . The opposite side of the frame  573  will have a similar slot  575 . However, where the structures which engage the slot are especially over sized, or where the structural integrity is sufficient, only one slot need be used. The structural dependence on the frame  573  should be such that the two opposing first and second hemicylindrical tubes  421  and  423  will always oppose each other and cannot twist away from each other and can only pivot along their long axis. 
     a turn fitting  581  enables a threaded member  583  to turn while being axially fixed to the first hemicylindrical tube  421 . The threaded member  583  may be threadably engaged to an internal thread  585  at the end of the frame  573 . In this case a knob  587  is used to manually turn the threaded member  583  independently to move the first hemicylindrical tube  421  to the left or to the right. A turn fitting is a structure which holds the end of the threaded member and allows the threaded member  583  to urge the fitting forward or backward while continuing to turn. 
     In the alternative, knob  587  may have an internal thread, and turned with respect to the threaded member  583  draw the threaded member out of the frame  573 . In this case, a spring (as will be shown) could be used to help reverse this operation. Where the knob  587  is internally threaded, the end of the threaded member may be fixed directly to its first hemicylindrical tube  421 . 
     In sum, there are three ways to affect motion, preferably the internal threads  585  enable the threaded member  583  to turn to urge first hemicylindrical tube  421  in both directions with respect to the frame  573 . In the alternative, the threaded member  583  may act only to urge the first hemicylindrical tube  421 , and the tubes  421  and  423  may have another mechanism urging them apart or simply move apart based upon other forces or other structures present. Third, the threaded member  583  may have an end anchored to the first hemicylindrical tube  421  with an internally threaded surface inside knob  587  to enable the knob  587  to be turned to cause the length of threaded member  583  to be withdrawn from the frame  583 . A spring, or other fitting can be used to help reverse the direction of travel. All of the knobs and threaded members shown hereafter have the ability for all three modes of action. 
     Similarly, a turn fitting  591  enables a threaded member  593  to turn while being axially fixed to the second hemicylindrical tube  423 . The threaded member  593  threadably engaged to an internal thread  595  at the end of the frame  573 . a knob  597  is used to manually turn the threaded member  593  independently to move the second hemicylindrical tube  423  to the left or to the right. 
     Similarly, a second surrounding frame  573  has an open slot  575  which accommodates a pair of pins  601  and  603  having expanded heads which fit outside the slot  575  to provide tracking along the slot  575  to further insure that neither the first hemicylindrical tube  421  nor the second hemicylindrical tube  423  are able to turn within either of the frames  573 . 
     a turn fitting  611  enables a threaded member  613  to turn while being axially fixed to the first hemicylindrical tube  421 . The threaded member  613  is threadably engaged to an internal thread  615  at the end of the frame  573 . a knob  617  is used to manually turn the threaded member  613  independently to move the first hemicylindrical tube  421 , at its lower pivot axis  435  at the center of the pin  601 . Similarly, a turn fitting  621  enables a threaded member  623  to turn while being axially fixed to the second hemicylindrical tube  423 . The threaded member  623  threadably engaged to an internal thread  625  at the end of the lower located frame  573 . a knob  627  is used to manually turn the threaded member  623  independently to move the second hemicylindrical tube  423  to the left or to the right at its lower pivot axis  437  at the center of the pin  603 . 
     With the configuration of  FIG. 43 , the position within the upper located frame  573  and separation of the pivot axes  431  and  433  (represented by the pins  577  and  589 ) can be exactly specified. Likewise, the position within the lower located frame  573  and separation of the pivot axes  435  and  437  (represented by the pins  601  and  603 ) can be exactly specified. In typical use, the knobs  617  and  627  and will be activated after insertion to achieve the configuration seen in  FIG. 38 , and then followed by the use of the knobs  587  and  597  to achieve the configuration seen in  FIG. 39 , if necessary. Thereupon the optional side shield  441  may be employed. Where a lesser separation than that seen in  FIG. 39  is used, a narrower side shield  441  may be employed. In a surgical kit, several such shields  441  of different size and shape may be available. 
     Referring to  FIG. 44 , a view looking down into the structure of  FIG. 43  shows the overall orientation and further illustrates an optional securing tang  629  which may be used with either of the upper located or lower located frame  573 , and may be located in any position, or extended in any direction, to better enable the surgeon to stabilize and manipulate any of the assemblies  417 ,  551  and  571  seen. Any structure can be used to help secure the frame  573  and or the first and second hemicylindrical tubes  421  and  423 .  FIG. 44  is an equivalent view through the lower of the frames  573 , including the knobs  617  and  627  as the two frames  573  have equivalent action. Note that having complete control over both the separation, angular relationship, and position of the first and second hemicylindrical tubes  421  and  423  within the frame  573  will enable the surgical practitioner to position the line of sight of the working tube along the frame  573  length and to generally have complete control. 
     Also shown in  FIG. 44  is an optional spring  630  which can be used to bias the force acting upon either of the first and second hemicylindrical tubes  421  and  423 , or it can be used to bias a knob  597  away from the frame  573 . Although shown as an option, the use of a spring  639  may contribute significantly where force is to be had in one direction only, as well as to lock a threaded member such as  593  into a turn fitting by keeping a pulling bias in place. 
     In some cases it may be desired to reduce the number of controls to accomplish certain objectives, such as simplicity, less controllability, less moving parts, inexpense, or the critical need for space about the upper part of any of the assemblies  417 ,  551  and  571 . One example of an arrangement is seen in  FIG. 45 . a frame  631  has an interior having one surface which may generally match one of the first and second hemicylindrical tubes  421  and  423 , and in this case first hemicylindrical tube  421 . The frame  631  may be attached to the first hemicylindrical tube  421  by tack welding or the like, or other means. a single threaded member  633  includes a knob  635 . a structure  637  can be either an engagement turning block to enable the threaded member  633  to both push and pull on the second hemicylindrical tube  423 , or it may simply be a wear block to allow the threaded member  633  to push against it and to protect the second hemicylindrical tube  423  from wear. 
     Because half of the tube assembly of first and second hemicylindrical tubes  421  and  423  is supported by the frame  631 , the second hemicylindrical tube  423  is left to move only slightly and assuming that  FIG. 45  is an upper view and that the pivoting of the second hemicylindrical tube  423  is accomplished at a lower level, especially at the level of lower pivot axis  437 , the frame  631  is left to control second hemicylindrical tube  423  by simply pushing, or by pushing and pulling. Where structure  637  is a turning block, there is a bulbous expansion at the end of threaded member  633  which snaps into structure  637  as a turning block and is free to turn and both push and pull second hemicylindrical tube  423 . The threaded member  633  is threadably engaged into an internal threaded bore  639  within the frame  631 . 
     Referring to  FIG. 46 , one embodiment of a manipulative structure which works well with the structure of  FIG. 45  is shown. The structure shown is a partial section taken at the lower pivot axis level and includes means for pushing and pulling, or pushing alone. Preferably, when used with the structure of  FIG. 45 , it will include pushing and pulling, especially if the structure of  FIG. 45  performs pushing alone. Either of the structures in  FIG. 43  at either the upper or lower pivot axis levels can be substituted for either of the structures shown in  FIGS. 45 and 46  as the structures in  FIG. 43  provide both pushing, pulling, pivoting and level support. 
     Where the structures of  FIG. 45  provides both pushing and pulling, it can be used along with a second structures at the lower pivot axis as any structure which provides both pushing and pulling will also provide some pivoting support. Further, the structure shown in  FIG. 46  is hinged to provide additional pivoting support. The structure of  FIG. 46  can be used at either the upper pivot axes  431  and  433  or the lower pivot axes  435  and  437 . Both the structures of  FIGS. 45 and 46  demonstrate clearly that lesser control structures than are shown in  FIG. 43  can be used to control the first and second hemicylindrical tubes  421  and  423 , along with lesser control inputs, and less control specificity, but also with less moving parts and a lesser mechanical complexity. 
     Referring again to  FIG. 46 , second hemicylindrical tube  423  is seen as tack welded to a reinforcement  651 . The purpose of reinforcement  651  is to provide an expanded thickness of material so that pivoting can occur closer to the edge  439  as is possible. It is further possible to continue the extent of the reinforcement  651  and its pivot point in the direction of first hemicylindrical tube  421  if the other geometries of the other components permit. Reinforcement  651  contains a pair of threaded bores  653 , each of which accommodates one of the threaded screws or bolts  655  shown. The bolts  655  each extend through one end of a “U” shaped fitting  657 , so that the reinforcement  651  and attached second hemicylindrical tube  423  pivots with respect to the fitting  657 . a threaded member  659  engaged an internal threaded bore  671 , and has a knob  673  for ease of manual operation. 
     The threaded member is connected to a turn fitting  675  the first hemicylindrical tubes  421  to be moved toward and away from second hemicylindrical tube  423 . The use of the structure of  FIGS. 45 and 46  may be used together to give the ability to provide control, although not as much control as is seen in  FIG. 43 . Also seen is an 
     Referring to  FIG. 47 , another possible realization is seen, combining the control mechanisms of selected portions of  FIGS. 37-46 , combined with other possible options. An open frame system  691  is seen as having a frame  693  which is either open on at least one side, or which has a side expanded to a distance sufficient to introduce other structures to expand in that direction. Some of the components previously seen include pins  577  and  579  extending through slot  575 . Pins  577  and  579  may have extended vertical and horizontal extent to garner additional stability from the frame  693 , especially where one side is open. 
     Other structures may be used to insure that neither the first hemicylindrical tube  421  nor the second hemicylindrical tube  423  are able to turn within the frame  573 . Also seen are turn fitting  581 , threaded member  583 , knob  587 , turn fitting  591 , threaded member  593 , and knob  597 . The view of  FIG. 47  is from above, and thus the structures most closely correspond to the upper structures seen in  FIG. 43  and in  FIG. 44 . 
     As can be seen in  FIG. 47 , a four point retractor system can be formed with the components and structures of the foregoing Figures. The first and second hemicylindrical tubes  421  and  423  are shown in the open position. On the longer connector arm of the frame  693 , a side shield  695  is supported. The side shield  695  can derive its ability to hold tissue out of the visual field by being locked down onto the frame  693  in the same manner as a wrench fits a bolt head. In this configuration, the side shield can be inserted into the center of the surgical field and then rotated into position and moved down slightly to lock it into place. On the opposite side from side shield  695  is a retractor  697  which has a flat portion entering the surgical field and which is controlled from a point remote with respect to open frame system  691 . An angled portion  699  turns from the flat portion seen entering the surgical field and extends down into the area between the open first and second hemicylindrical tubes  421  and  423 . 
     Also seen are a series of small circular structures  701  about the peripheral upper surface of first and second hemicylindrical tubes  421  and  423 . These structures are at least one of embedded fiber optics and ports for accepting fiber optics. The apertures formed in the metal open at a slight angle to the inside of the first and second hemicylindrical tubes  421  and  423  to direct light into the surgical field without producing a back reflection or other scatter. In cases where the fiber optic is permanently affixed, a light ring section can simply be snapped to or placed on the first and second hemicylindrical tubes  421  and  423 . In cases where the apertures are provided, surgery can continue without fiber optics, or a fiber optics set can be added which can range from an illuminated ring (relying on low angle of incidence and snells law) to direct light through the openings which open to the inside of the first and second hemicylindrical tubes  421  and  423  at a low angle of incidence. Intermediary solutions, such as a light ring having a series of short fiber optic members for insertion into the apertures can be used. To facilitate the use of fiber optics, the hemicylindrical tubes  421  and  423  may be made from a composite material in which the fiber optic components may be present during formation of the tube structures. Other material may be used for tubes  421  and  423 , including materials that either transmit light or have portions which transmit light. 
     As an alternative to the three sided frame  693 , the open portion of the frame could be enclosed by an expandable member  703  which can have any manner of interlock with the three sided frame  693 . One such interlock is illustrated as simply an annular piston dependence where the expandable member  703  includes a smaller tubular insert  705  which fits closely into a matching bore  707  seen in the terminal ends of the three sided frame  693 . The expandable member  703  can be used to lend additional support to the three sided frame  693 , especially forces produced by the threaded members  583  and  593 . The expandable member  703  is also useful to help support the retractor  697  where such provision is made. The main purpose of expandable member  703  is the adjustability to give greater clearance and access. The same adjustability could be had on the side of three sided frame  693  which supports side shield  695 , especially with a more complex mechanism to enable the frame expansion to be locked into place. A locking mechanism for expandable member  703  is not shown so that the drawings may be simplified, but lock ability can be achieved in the same manner as any metal to metal frame construction known in any field of art. 
     Referring to  FIG. 48 , a side view of the side shield  695  is seen. The clearance for locking onto the frame  693  is about the same as the width of the frame  693  so that non rotational fixation can be transmitted along the length of the side shield  695 . 
     Referring to  FIG. 49 , one possible configuration is seen for a variable depth guide  711  which is utilizable with any of the devices seen in  FIGS. 37-46  or any other tubular, minimally invasive system. Variable depth guide  711  has a handle  713  controlling a shaft  715 . Shaft  715  has a through bore  717  which is used to insert a guide line or guide pin to help insert any minimal access system seen in the earlier Figures. 
     a translatable detent ring  719  interacts with a series of detent indentations  721 . The position of the detent ring  719  will correspond to the lengths of the first and second hemicylindrical tubes  421  and  423  with which the variable depth guide  711  is used. Once the practitioner inserts the variable depth guide  711  into any assembly containing a first and second hemicylindrical tubes  421  and  423 , the necessary height can be adjusted so that the tip of the variable depth guide  711  extends just beyond the lower extent of the joined first and second hemicylindrical tubes  421  and  423 . The height is adjusted by forcing the detent ring  719  to the proper detent indentation  721 , and then inserting it into a closely associated first and second hemicylindrical tubes  421  and  423  to form an overall bullet shape for insertion, preferably a guide pin  155 . Once inserted, the variable depth guide  711  is removed. The detent ring  719  carries a frusto-conical surface  723  where it is used with first and second hemicylindrical tubes  421  and  423  having fluted top areas as seen in  FIG. 37  and in previous figures. Any mechanism can be used to achieve a detent action, including an internal pressure ring or a spring loaded bar, or protruding ball bearings. The positional stability of the detent ring can be specified by the spring action of the detent member, and should be sufficiently stable to enable deliberate manual fixation with no inadvertent movement occurring even where significant resistance is encountered. 
     Referring to  FIG. 50  is a vertical plan view looking down upon an expandable frame system  751  which uses detents to set the frame size and which uses an angular distribution system. A frame is used as a support and reference point to manipulate a working tube in much the same way as  FIGS. 37-47 . Expandable frame system  751  enables the user to control the size of the operating theater as needed. Where the task can be accomplished with minimum opening access, such minimum opening is all that needs to be taken. Where greater access is needed, the expandable frame system  751  provides both an expanded work space, and additional surfaces for support of other instrumentation. 
     As before, the retractor blades are seen as a first hemicylindrical tube  753  having an upper flared portion  755  and a second hemicylindrical tube  757  having an upper flared portion  759 . Each of the first and second hemicylindrical tubes  753  and  757  have two points of variable pivoting attachment. 
     Hemicylindrical tube  753  has a pivot bar  781  which may be attached somewhat tangentially to the first hemicylindrical tube  753 , or may include a pair of extensions attached to the outside of the first hemicylindrical tube  753 . Likewise, hemicylindrical tube  757  has a pivot bar  783  which may be also attached somewhat tangentially to the first hemicylindrical tube  753  in the same manner. 
     Pivot bar  781  has circular lands  785  which fit into support fittings  787 . Likewise pivot bar  783  also has circular lands  785  which fit into support fittings  787 . The support fittings  787 , as seen from above, show the lands  785 . In this configuration the lands  785  can be dropped in from above. This is an over-simplified illustration, as some other locking mechanism can be utilized, including ball shape instead of disc shape or other. It would be preferable that the manner of pivoting engagement will firstly enable an ease of assembly and disassembly and secondly provide good stability against dislodgement with respect to any forces experienced when the expandable frame system  751  is in an operational position. 
     Above the point of pivot of the pivot bars  781  and  783 , each of the first and second hemicylindrical tubes  753  and  757  are fitted with a pivot bearing fitting  791 . The pivot bearing fittings  791  can depend from either the first and second hemicylindrical tubes  753  and  757  or their upper flared portions  755  and  759 . The pivot bearing fittings  791  can be hinge type of ball type, or any other type which will enable the upper part of the first and second hemicylindrical tubes  753  and  757  tp be force moved to pivot them with respect to the pivot fittings  781  and  783  in either direction. 
     The pivot bearing fitting  791  is engaged by a cooperating fitting  793  which enables the pivot bearing fitting  791  to pivot with respect to the cooperating fitting  793 . The cooperating fitting  793  is moved with a threaded member  795 , having a thumb control wheel as a tilt screw knob  797 . In the drawings of  FIGS. 50 and 51 , the fittings  791  are located above the pivot bars  781  and  783 , but they need not be. 
     In the embodiments of  FIGS. 50 and 51  the movement of the axes of the pivot bars  783  are affected by the expansion of a frame support including a first lateral member  801  and a second lateral frame member  803 . The ends of firs and second lateral members  801  and  803  are connected to two telescoping frame members  805  and  807 . Telescoping frame member  805  has a central hinge box  811  which is positioned between a first sleeve  813  and a second sleeve  817 . The central frame section pivotally supports a pair of internal spreading bars, including a first spreading bar  821  which extends within first sleeve  813  and a second spreading bar  823  having a ratchet or detent structure (to be described) which extends within second sleeve  817 . 
     Although not shown in  FIGS. 50 and 51 , the spreading bars  821  and  823  will preferably have an internal gear mesh so that both will preferably have an equal angular displacement with respect to the central hinge box  811 . The articulation within the central hinge box  811  will enable the selection of three angular frames of reference with regard to the surface of a patient, namely the angle of first sleeve  813 , the angle of central hinge box  811 , and the angle of second sleeve  817 . Where other objects, such as retractors, light sources etc have to be anchored, three reference angle surfaces are available. 
     The spreading bars  821  and  823  are thus axially fixed with respect to the central hinge box  811 , with the spreading bars  821  and  823  axially slidable within the first and second sleeves  813  and  817 . Many mechanisms can be utilized to fix the position of the spreading bars  821  and  823  within the first and second sleeves  813  and  817 . One such mechanism is show schematically in its most rudimentary form in  FIG. 38  as including a pivot support  825  which supports a lever  827 . The lever  827  operates against a spring  829  and operates an engagement member  831  with respect to detent structures  833  located on the spreading bars  823 . These structures form a first ratchet stop  835 . Operational depression of the lever  827  disengages the detent structures  833  of the spreading bar  823  to slide within the sleeve  817  and releasing the lever  827  enables the spring  829  to act to cause engagement of the engagement member  831 . With this mechanism, or a similar mechanism, the expansion of the expandable frame system  751  can be controlled, with the expansion of the second lateral frame member  803  away from the central hinge box  811 . Similarly the first lateral member  801  is independently movable away from central hinge box  811  with the use of a mechanism similar to the one shown with respect to the pivot support  825 , lever  827 , spreading bar  823  engagement member  831 , and detent structures  833 . 
     The detent structures  833  could be made triangular shaped for sliding in one direction with hold against the other direction. A second mechanism similar to the one shown with respect to the pivot support  825 , lever  827 , spreading bar  823  engagement member  831 , and detent structures  833  is omitted from  FIGS. 50 and 51  for simplicity. Regardless of the structure, the expandable frame system  751  can be exactly positioned. Other assisted mechanisms can be employed, including a threaded member or a pinion or other device which will give the user mechanical advantage in extending the expandable frame system  751 . Further, the fittings illustrated, including pivot bars  781  &amp;  783  with circular lands  785  and slip fitting into support fittings  787 , as well as the pivot bearing fitting  791  and cooperating fitting  793  suggest that the expandable frame system  751  may be added to the operating theater after the first and second hemicylindrical tubes  753  and  757  have been employed into the surgical opening. This will free the surgeon to position the first and second hemicylindrical tubes  753  and  757  without having to handle the supporting frame members. 
     Between the other ends of the first lateral member  801  and second lateral frame member  803  the second telescoping frame member  807  also has a central hinge box  811 . Again, the central hinge box  811  which is positioned between a first sleeve  813  and a second sleeve  817 . The central frame section pivotally supports a pair of internal spreading bars, including the first spreading bar  821  within first sleeve  813  and the second spreading bar  823  which extends within second sleeve  817 . 
     The interfit between the first and second sleeves  813  and  817  and the first and second spreading bars  821  and  823  in both the first and second telescoping frame members  805  and  807  is expected to be of sufficiently tight tolerance so that both of the central hinge box  811  remain directly across from each other. If the latch mechanism supported by the second lateral frame member  803  is released the second lateral frame member  803  should move away from the central frame sections  811 . In other words, one of the central frame sections  811  should not displace to a position other than directly across from each other. 
     The second telescoping frame member  807  could have the same mechanism as the first telescoping frame members  805 , but a slightly different mechanism is shown in order to emphasize the variability which can be employed with respect to the expandable frame system  751 . A retention housing  837  is attached to second sleeve  817  and houses a lock pin  839  and a spring  841  which urges it int the second sleeve  817  where it lockably interfits with the detent structures  833 . These structures may be collectively referred to as a second ratchet stop  843 . The expansion of the expandable frame system  751 , if properly toleranced will enable the right and left sides to be independently controlled in movement toward and away from the away from the central hinge box  811 . The actuation of one release mechanism will enable balanced displacement of its associated first or second lateral members  801  and  803 . 
     Movement of the associated first or second lateral members  801  and  803  by one of the latches shown gives a parallel distance separation of the first hemicylindrical tube  753  with respect to the second hemicylindrical tube  757 , regardless of their respective angular positions (assuming no interference). However, the angularity of the first and second hemicylindrical tube  753  and  757  are set by the movement of the threaded member  795 . As such, the expandable frame system  751  enables independent angularity adjustment for the first and second hemicylindrical tube  753  and  757  and independent parallel separation for the first and second hemicylindrical tube  753  and  757  based upon expansion of the frame. 
     Other features seen in  FIGS. 50 and 51  include a support tang  845  and a pair of manipulation sphere projections as spreader projections  847  to assist in manually manipulating the expandable frame system  751 .  FIG. 51  illustrates a condition in which the expandable frame system  751  is in an expanded orientation, with first lateral member  801  and second lateral frame member  803  equally expanded from central hinge box  811 . Either of the first and second lateral members  801  and  803  could have been extended from the central hinge box  811 . This feature gives the surgeon the flexibility to adjust the positioning of the central hinge box  811 . The central hinge box  811  may also have support structures for other instrumentation, including bores  849  in the central hinge box  811  such as a bookwalter support (to be shown). Bores  849  can be used for locational registry or for threaded attachment. A bookwalter device is especially useful for supporting an additional retractor, in addition to the first and second hemicylindrical tubes  753  and  755 . 
     Referring to  FIG. 52 , a side view of the system of  FIGS. 50-51  illustrates further details. The angle of the incline of the upper flared portions  755  and  759  are illustrated. A scale  851  helps the surgeon to ascertain the depth to which the first and second hemicylindrical tubes  753  and  755  are inserted into the patient (with the additional consideration of any further extension which may be added to the first and second hemicylindrical tubes  753  and  755 ). 
     One possible configuration for the first and second hemicylindrical tubes  753  and  755 , include the use of an upper tube portions along with a lower extension. The scale  851  could also be utilized, in conjunction with the extension to indicate depth. A notch  853  can be used as a reference surface to engage an extension. Another surface can include a raised portion or depressed portion matched to an extension (as will be shown) in each of the first and second hemicylindrical tubes  753  and  755 . 
       FIG. 53  illustrates a double pivot hinge fitting within the central hinge box  811 . A pair of threaded members  861  extend into machined spaces within central hinge box  811  and hold the spreading bars  821  and  823  into a close proximate location such that the complementary gear teeth  863  located on the abutting ends of the spreading bars  821  and  823  intermesh with each other. This arrangement insures that the angular displacement of the spreading bars  821  and  823  with respect to the central hinge box  811  will be equi-angular. This is shown in  FIG. 54  where the angle γ on both sides indicates equi angular displacement. 
     Referring to  FIG. 55 , a top view of the central hinge box  811  illustrates a bookwalter retractor device  871  mounted on the upper surface of the central hinge box  811 . The bookwalter device has a central through bore  873  through which a retractor rail or extension may pass. Typically the retractor extension (not shown) will have a series of detents similar to the detents  833  seen in  FIG. 53 . As the detents emerge from the through bore  873 , they are engaged by a pivoting latch  875  which operates under urging force from a spring  877 . A turnbuckle or other force control structure would enable operation of a gear mechanism to move any type of “east west” retractor blades towards or away from the center. 
     Referring to  FIG. 56 , a plan view is shown of a remote force retraction system employing many of the structures seen in  FIGS. 50-55 , but with a remote force system such as disclosed and shown in U.S. Pat. No. 4,747,394, to Robert S. Watanabe, and incorporated by reference herein. The technique of application of remote force to leave the surgical field open as applied to the expandable frame system  751  is seen as an open minimally invasive expansion system  901 . At the surgical field, many of the components previously seen have the same numbering. 
     A pinion box  903  carries a (removable) key insertable gear  905  seen inside an aperture  907  having teeth  911  which engage a linear gear  913  on a first rack  915 , and which also engage linear gear  917  on a second rack  919 . Rack  915  is fixedly attached to a first main support  921  while rack  919  is fixedly attached to a second main support  923 . As the gear  905  is turned clockwise, the rack  915  freely feeds through an aperture  931  (seen in dashed line format) in second main support  923 , through the pinion box  903  and pushes first support  921  father away from the pinion box  903 . At the same time, the gear  905  pushes the rack  919  freely feeds through an aperture  933  (seen in dashed line format) in first main support  921 , through the pinion box  903  and pushes second support  923  farther away from the pinion box  903 . 
     The result is that two strong support members, namely first support  921  and second support  923  are being forced away from each other remotely, by the turning of the key insertable gear  905 . Note that the areas on either side of the first and second hemicylindrical tubes  753  and  755  are clear to enable other structures to be employed, either unsupported, or independently supported, or possibly supported from structures which support first support  921  and second support  923 . 
     A ratchet latch lever  935  is mounted is mounted to pivot with respect to first support  921  by the action of a spring  937 . The ratchet latch lever  935  is fork shaped to fit around the tip fixed end of rack  914  and to actuate an internal latch  939  which operates within the first support  921  between the first rack  915  and second rack  919 . 
     Also seen is a hinge  941  on first support  921 , and a hinge  943  on second support  923 . The hinges  941  and  943  should preferably have the same angular range and would ideally be from about zero degrees (flat) to about fifteen degrees down with the hinges  941  and  943  rising to form the apex. The hinges  941  and  943  permit the lateral force components to be angularly sloped down, or draped to provide an angled working presentation, and to take up less lateral space in the same plane as the working area. Beyond the hinges  941 , the first support  921  is connected to a first extended support  945  while the second support  923  is connected to second extended support  947 . 
     Both the first and second extended supports  945  and  947  include angular extensions  949  which support the support fittings  787  and other structures previously shown. The first and second extended supports  945  and  947  also support tilt screw knob  797  and manipulation sphere projections as spreader projections  847 . The support details for the first and second hemicylindrical tubes  753  and  755  is essentially the same as was shown for  FIGS. 50 &amp; 51 . 
     In addition, an optional pair of tilt fittings enable the first and second extended supports  945  and  947  to tilt where it may be more advantageous to locate open minimally invasive expansion system  901  over portion of a patient&#39;s body which is angled. A first tilt adjustment fitting  951  can be used to provide tilt to the main extent of first extended support  945 , while a second tilt adjustment fitting  953  can be used to provide tilt to the main extent of second extended support  947 . Typically the first and second tilt adjustment fittings  951  and  953  will be used to set the tilt before an operation begins. As to both of the first and second tilt adjustment fittings  951  and  953 , a support plate  955  is rigidly supported by the portion of the respective first and second extended supports  945  and  947  nearest the hinges  941 . The support plate  955  supports a retention housing  837 . The retention housing includes a lock pin  839  and a spring  841  which urges it through apertures of the support plate  955  and across to a selector plate  957 . As to both of the first and second tilt adjustment fittings  951  and  953 , the selector plate  957  is rigidly supported by the portion of the respective first and second extended supports  945  and  947  on the other side of the respective first and second tilt adjustment fittings  951  and  953 . 
     Although shown in somewhat schematic view, a tilt pin  961  joins portions of first extended support  945  rigidly while enabling the tilting of the portion of the first extended supports  945  on one side of the first tilt adjustment fitting  951  to pivot with respect to the portion of the first extended supports  945  on the other side of the first tilt adjustment fitting  951 . Likewise, a tilt pin  963  joins portions of second extended support  947  rigidly while enabling the tilting of the portion of the second extended supports  947  on one side of the second tilt adjustment fitting  953  to pivot with respect to the portion of the second extended supports  947  on the other side of the second tilt adjustment fitting  953 . In reality, in order to transmit the force rigidity, more complex internal fittings may be utilized. The support plate  955  and selector plate  957  are simple mechanical mechanisms which are located far enough off the axis of pivot to enable selection of a number of angular positions. 
     Other structures can be supported from the both the first and second extended supports  945  and  947 . A pair of slot openings  965  at the far ends of the first and second extended supports  945  and  947  can support additional instrumentation. In addition, the first and second extended supports  945  and  947  include structures  965  which may be apertures or projections or other structures which will enable support to be derived for other retractors. A cross support  971  supports a mechanical housing  973  through which a linear gear  975  can extend. A retractor  976  (which can be of any type) is attached to one end of the linear gear  975 . A hand wheel  977  operates a gear  979  which moves the linear gear  975  through the housing  973 . This assembly is a first cross supported retractor set  981 . A second cross supported retractor set  983  is also shown. This gives the surgical practitioner good control and leverage to operate the “north-south” retractors. 
     An illustration of an extension previously mentioned is illustrated in  FIG. 57  which illustrates a top view of a hemicylindrical extension  991  standing alone. Hemicylindrical extension  991  may have several pair of inwardly directed members  993  (or a single large inwardly directed member  993 ) for engagement against the notches  853  seen in  FIG. 52 . An inwardly directed angled “snap” protrusion  995  springs into a matching opening on either of the first and second hemicylindrical tubes  753  and  755 . The hemicylindrical extension  991  will fit on the outside of the matching first or second hemicylindrical tubes  753  and  755  and the force on the hemicylindrical extension  961  is expected to be inward at its lower extent during spreading. 
     Referring to  FIG. 58 , a side semi-sectional view is shown. A lower portion of first hemicylindrical tube  753  having groove  853 , and a slot  997  is seen in a sectional view. Adjacent the semi section hemicylindrical tube  753  is the hemicylindrical extension  991  in an attached position. The upper end of he notch  853  fixes against up motion, and the slot  997  fixes against down motion when it engaged with inwardly directed angled “snap” protrusion  995 . A stable support relationship is shown. 
     Referring to  FIG. 59 , a view looking down into the inside of the combination of the first hemicylindrical tube  753  and hemicylindrical retractor tube extension  99  of  FIGS. 57 and 58 . It can be seen how the large inwardly directed members  993  wrap around the groove  853  and can be slid upwardly until the inwardly directed angled “snap” protrusion  995  engages. 
     Referring to  FIG. 60 , a view looking down onto the outside of the combination of the first hemicylindrical tube  753  and hemicylindrical retractor tube extension  99  of  FIGS. 57-59  is seen. In addition, the pivot bar  781  with circular lands  785  are also seen below the pivot bearing fitting  791 , for reference. The large inwardly directed member  993  is partially shown in dashed line format. The bottom of the hemicylindrical extension  991  may be of any shape. 
     While the present system has been described in terms of a system of instruments and procedures for facilitating the performance of a microscopic lumbar diskectomy procedure, one skilled in the art will realize that the structure and techniques of the present system can be applied to many appliances including any appliance which utilizes the embodiments of the instrumentation of the system or any process which utilizes the steps of the inventive system. 
     Although the system of the invention has been derived with reference to particular illustrative embodiments thereof, many changes and modifications of the system  31  may become apparent to those skilled in the art without departing from the spirit and scope of the inventive system. Therefore, included within the patent warranted hereon are all such changes and modifications as may reasonably and properly be included within the scope of this contribution to the art.