Abstract:
A retractor-based access system for performing minimally invasive spine surgery via an anterior approach. The anterior access system and related methods of the present invention involve a plurality of retractor blades under the control of a single retractor handle apparatus.

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
   The present nonprovisional patent application claims benefit of priority under 35 U.S.C. §119(e) from commonly owned and co-pending U.S. Provisional Application Ser. No. 60/648,849, entitled “Surgical Access System and Related Methods,” filed on Jan. 31, 2005, the entire contents of which are hereby expressly incorporated by reference into this disclosure as if set forth fully herein. The present application also incorporates by reference the following co-pending and co-assigned patent applications in their entireties: PCT App. Ser. No. PCT/US02/22247, entitled “System and Methods for Determining Nerve Proximity, Direction, and Pathology During Surgery,” filed on Jul. 11, 2002; PCT App. Ser. No. PCT/US02/30617, entitled “System and Methods for Performing Surgical Procedures and Assessments,” filed on Sep. 25, 2002; PCT App. Ser. No. PCT/US02/35047, entitled “System and Methods for Performing Percutaneous Pedicle Integrity Assessments,” filed on Oct. 30, 2002; and PCT App. Ser. No. PCT/US03/02056, entitled “System and Methods for Determining Nerve Direction to a Surgical Instrument,” filed Jan. 15, 2003 (collectively “NeuroVision PCT Applications”); PCT App. Ser. No. PCT/US2004/031768, entitled “Surgical Access System and Related Methods,” filed on Sep. 27, 2004; and PCT App. Ser. No. PCT/US2005/036454, entitled “Surgical Access System and Related Methods,” filed Oct. 11, 2005 (collectively “Maxcess PCT Applications”). 

   BACKGROUND OF THE INVENTION 
   I. Field of the Invention 
   The present invention relates to accessing a surgical target site in order to perform surgical procedures. 
   II. Discussion of the Prior Art 
   A noteworthy trend in the medical community is the move away from performing surgery via traditional “open” techniques in favor of minimally invasive or minimal access techniques. Open surgical techniques are generally undesirable in that they typically require large incisions and high amounts of tissue displacement to gain access to the surgical target site, which produces concomitantly high amounts of pain, lengthened hospitalization (increasing health care costs), and high morbidity in the patient population. Less-invasive surgical techniques (including so-called “minimal access” and “minimally invasive” techniques) are gaining favor due to the fact that they involve accessing the surgical target site via incisions of substantially smaller size with greatly reduced tissue displacement requirements. This, in turn, reduces the pain, morbidity and cost associated with such procedures. The access systems developed to date, however, fail in various respects to meet all the needs of the surgeon population. The present invention is directed at this need. 
   SUMMARY OF THE INVENTION 
   The present invention accomplishes this goal by providing a retractor-based access system for performing minimally invasive spine surgery via an anterior approach. The anterior access system and related methods of the present invention involve a plurality of retractor blades under the control of a single retractor handle apparatus. 
   According to one broad aspect of the present invention, the access system comprises a tissue retraction assembly capable of being introduced into a distracted region to thereby define and establish an operative corridor. Once established, any of a variety of surgical instruments, devices, or implants may be passed through and/or manipulated within the operative corridor depending upon the given surgical procedure. The tissue retraction assembly may include any number of components capable of performing the necessary retraction. By way of example only, the tissue retraction assembly may include one or more retractor blades extending from a handle assembly. The handle assembly may be manipulated to open the retractor assembly; that is, allowing the retractor blades to separate from one another (simultaneously or sequentially) to create an operative corridor to the surgical target site. 
   The retractor blades may optionally be equipped with a mechanism for transporting or emitting light at or near the surgical target site to aid the surgeon&#39;s ability to visualize the surgical target site, instruments and/or implants during the given surgical procedure. According to one embodiment, this mechanism may comprise, but need not be limited to, coupling one or more light sources to the retractor blades such that the terminal ends are capable of emitting light at or near the surgical target site. According to another embodiment, this mechanism may comprise, but need not be limited to, constructing the retractor blades of suitable material (such as clear polycarbonate) and configuration such that light may be transmitted generally distally through the walls of the retractor blade light to shine light at or near the surgical target site. This may be performed by providing the retractor blades having light-transmission characteristics (such as with clear polycarbonate construction) and transmitting the light almost entirely within the walls of the retractor blade (such as by frosting or otherwise rendering opaque portions of the exterior and/or interior) until it exits a portion along the interior (or medially-facing) surface of the retractor blade to shine at or near the surgical target site. The exit portion may be optimally configured such that the light is directed towards the approximate center of the surgical target site and may be provided along the entire inner periphery of the retractor blade or one or more portions therealong. 
   The retractor blades may also optionally be equipped with one or more electrodes for use in detecting the existence of (and optionally the distance and/or direction to) neural structures such that the operative corridor may be established through (or near) any of a variety of tissues having such neural structures which, if contacted or impinged, may otherwise result in neural impairment for the patient. In this fashion, the access system of the present invention may be used to traverse tissue that would ordinarily be deemed unsafe or undesirable, thereby broadening the number of manners in which a given surgical target site may be accessed. These electrodes are preferably provided for use with a nerve surveillance system such as, by way of example, the “Neurovision PCT Applications” referenced below. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Many advantages of the present invention will be apparent to those skilled in the art with a reading of this specification in conjunction with the attached drawings, wherein like reference numerals are applied to like elements and wherein: 
       FIGS. 1-2  are perspective views of a tissue retraction assembly forming part of a surgical access system according to the present invention; 
       FIG. 3  is a top view of the tissue retraction assembly of  FIGS. 1-2 ; 
       FIG. 4  is a top view of the tissue retraction assembly of  FIG. 1  wherein the retractor blade assemblies have been removed; 
       FIG. 5  is a perspective view of the tissue retraction assembly of  FIG. 4 , in which the half-ring assemblies are illustrated in an exploded view removed from the handle assembly; 
       FIGS. 6-8  are side, perspective, and top views of a retractor blade assembly according to one embodiment of the present invention; 
       FIGS. 9-10  are front and rear views of a retractor blade according to one embodiment of the present invention; 
       FIG. 11  is a perspective view of a base member of a retractor blade holder assembly of the present invention, with the retractor blade and blade extender removed; and 
       FIG. 12  is an exploded perspective view of the base member of  FIG. 11 . 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Illustrative embodiments of the invention are described below. In the interest of clarity, not all features of an actual implementation are described in this specification. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developers&#39; specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure. It is furthermore to be readily understood that, although discussed below primarily within the context of spinal surgery, the surgical access system of the present invention may be employed in any number of anatomical settings to provide access to any number of different surgical target sites throughout the body. The surgical access system disclosed herein boasts a variety of inventive features and components that warrant patent protection, both individually and in combination. 
     FIGS. 1-3  illustrate a tissue retraction assembly  10  forming part of a surgical access system according to one embodiment of the present invention. The tissue retraction assembly  10  includes a plurality of retractor blades  12  coupled to a handle assembly  20  via a plurality of blade holder assemblies  42 . The tissue retraction assembly  10  is shown in a fully retracted or “open” configuration, with the retractor blades  12  positioned a distance from one another so as to form an operative corridor  15  therebetween and extending to a surgical target site (e.g. an annulus of an intervertebral disc). This is accomplished by initially creating a distraction corridor to a surgical target site via any anterior access method well known in the art, such as may be performed via a general or “access” surgeon. Once distracted, the resulting void or distracted region within the patient is of sufficient size to accommodate tissue retraction assembly  10  as described herein. More specifically, the distal ends of the retractor blades  12  are attached to (e.g. introduced into) target vertebrae on either side of an intervertebral space. With the retractor blades  12  so positioned, the proximal ends are attached to the blade holder assemblies  42  while the handle assembly  20  is in a first, “closed” position. At that point, the handle assembly  20  may be operated to move the retractor blades  12  into a second, “open” or “retracted” position to create the operative corridor  15  to the surgical target site (e.g. an intervertebral space). Although shown and described below with regard to a four-bladed configuration, it is to be readily appreciated that the number of retractor blades  12  may be increased or decreased without departing from the scope of the present invention. Moreover, although described and shown herein with reference to a generally anterior approach to a spinal surgical target site, it will be appreciated that the tissue retraction assembly  10  of the present invention may find use in any number of different surgical approaches, including generally posterior, generally postero-lateral, generally lateral and generally antero-lateral. According to a further aspect of the present invention, any or all of the retractor blades  12  may be provided with one or more electrodes  39  (preferably at their distal regions, shown more clearly in  FIGS. 9-10 ) equipped for use with a nerve surveillance system, such as, by way of example, the type shown and described in the NeuroVision PCT Applications (referenced below). 
   In a preferred embodiment, the handle assembly  20  is substantially similar to the type shown and described in commonly owned and currently pending PCT App. Ser. No. PCT/US2004/031768, entitled “Surgical Access System and Related Methods,” filed on Sep. 27, 2004, and U.S. Provisional Pat. App. Ser. No. 60/617,498, entitled “Surgical Access System and Related Methods,” filed Oct. 8, 2004 (collectively “Maxcess Applications”), the entire contents of which are incorporated by reference into the present application as if disclosed herein. The handle assembly  20  may be coupled to any number of mechanisms for rigidly registering the handle assembly  20  in fixed relation to the operative site, such as by way of example only an articulating arm mounted to the operating table. The handle assembly  20  includes first and second arm members  26 ,  28  hingedly coupled via coupling mechanism shown generally at  30 . The distal ends of first and second arm members  26 ,  28  may be equipped with arm extensions  40 ,  41  (shown more clearly in  FIGS. 4-5 ). Arm extensions  40 ,  41  may be formed in any shape desired or required to ensure a suitable operating corridor, including but not limited to a generally curved or arcuate shape. Arm extensions  40 ,  41  may also be configured to couple to the first and second arm members  28 ,  26 , respectively, via any number of suitable manners, including but not limited to providing coupling blocks  45  disposed on the proximal ends of the arm extensions  40 ,  41  with posts  43  extending therefrom for engagement into corresponding recesses  47  formed within the arm members  26 ,  28 . This engagement between the posts  43  and recesses  47  may be augmented via the use of any number of suitable locking features, including but not limited to passing a set screw (not shown) through an aperture  49  in the arm  26 ,  28  such that the set screw (not shown) may be biased into the posts  43  after they have been introduced into the respective recess  47 . 
   A plurality of blade holder assemblies  42  may be slideably attached to arm extensions  40 . Blade holder assemblies  42  each include a base member  44  and a blade extender  46 . Blade extenders  46  are generally elongated in shape and have a medial end dimensioned to slideably engage retractor blades  12 . The retractor blades  12  are each coupled to a medial end of one of blade extenders  46 . Thus, by extension, at least one retractor blade  12  is coupled to the end of the first arm member  26 , and at least one retractor blade  12  is coupled to the end of the second arm member  28 . Through the use of handle extenders  31 ,  33  (e.g., by forcing them towards one another) the arms  26 ,  28  may be simultaneously opened such that the blades  12  coupled to arm extensions  40 ,  41  move away from one another. In a still further aspect of the present invention, the arm extensions  40 ,  41  may be opened up before the retractor blades  12  are coupled thereto. That is, the blade extenders  46  may be manually moved in a generally lateral direction (that is, away from the plane of the distal tip of the blade  12 ) in order to create the operative corridor  15 , at which point the blade extender  46  may be coupled to the blade holder assembly  42  to maintain this position. This may be done by moving the blades  12  sequentially or simultaneously (with at least two blades being moved at the same time). In any event, the dimension and/or shape of the operative corridor  15  may be tailored depending upon the degree to which the arms  26 ,  28  are opened. That is, the operative corridor  15  may be tailored to provide any number of suitable cross-sectional shapes, including but not limited to a generally circular cross-section, a generally ellipsoidal cross-section, and/or an oval cross-section. 
     FIGS. 6-8  illustrate in detail the construction of each blade holder assembly  42  and blade  12  according to a preferred embodiment of the present invention. Blade holder assembly  42  is dimensioned to slideably engage arm extension  40 , and includes a base member  44  and a blade extender  46 . Referring to  FIGS. 11-12 , base member  44  includes a first portion  50 , a second portion  52 , a third portion  54 , pair of clips  56 ,  58 , and a pin member  60 . The first portion  50  may be any geometric shape, including by way of example only generally circular, semi-circular, or generally oval. The first portion  50  includes a first generally planar surface  66 , a second generally planar surface  68 , art aperture  70 , and a semi-cylindrical cutout region  72 . Aperture  66  extends through the width of the first portion  50  and is dimensioned to receive shaft  64  of pin  60 . Semi-cylindrical cutout region  72  is dimensioned to interact with one of arm extensions  40 ,  41 . The second portion  52  may be any geometric shape including by way of example only generally circular, semi-circular, or generally oval, and should have the same general shape as first portion  50 . Second portion  52  includes a first generally planar surface  74 , a second generally planar surface  76 , an aperture  78 , and a semi-cylindrical cutout region  80 . Aperture  78  extends through the width of the second portion  52 , is contiguous with aperture  70 , and is dimensioned to receive shaft  64  of pin  60 . Semi-cylindrical cutout region  80  is dimensioned to interact with one of arm extensions  40 ,  41 . 
   The third portion  54  includes a first generally planar surface  82 , a second surface  84 , a central aperture  86  a pair of first cutout regions  88 ,  90 , and a pair of second cutout regions  92 ,  94 . The third portion  54  may be any geometric shape desired, including by way of example only generally circular, semi-circular, generally oval, generally rectangular, or any combination thereof. Central aperture  86  is generally circular in shape, is contiguous with aperture  78 , and is dimensioned to receive shaft  64  of pin  60 . The first pair of cutout regions  88 ,  90  are located generally on second surface  84 , are generally semi-cylindrical in shape, and are dimensioned to interact with the elongated blade extenders  46 . The second pair of cutout regions  92 ,  94  are generally rectangular in shape, extend substantially the width of third portion  54 , and are dimensioned to receive one of clips  56 ,  58 . The second pair of cutout regions  92 ,  94  are positioned generally perpendicularly to first pair of cutout regions  88 ,  90 , such that cutout region  92  bisects cutout region  88 , and cutout region  94  bisects cutout region  90 . 
   The clips  56 ,  58  may be any shape necessary to removably secure blade extenders  46  to the base member  42 , and are dimensioned to interact with cutout regions  92 ,  94 , respectively. Clips  56 ,  58  include a generally planar surface  96 ,  98 , a semi-cylindrical surface  100 ,  102 , and an aperture  104 ,  106 , respectively. The semi-cylindrical surface  100 ,  102  is dimensioned to interact with the elongated blade extenders  46 , such that the elongated blade extenders  46  are prevented from migrating in a medial or lateral direction. Apertures  104 ,  106  are dimensioned such that they enable clips  56 ,  58  to be secured to the third portion  54 . The pin  60  includes an elongated handle portion  62  and a generally cylindrical shaft  64 . The generally cylindrical shaft  64  is dimensioned to interact with apertures  70 ,  78 ,  86  and traverse the combined widths of the first, second, and third portions  50 ,  52 ,  54 , respectively. Pin  60  functions to secure the first, second, and third portions  50 ,  52 ,  54  to each other, and also to secure blade assembly  42  to one of arm extensions  40 ,  41 . 
   Referring again to  FIGS. 6-8 , blade extender  46  includes a medial portion  108 , a central elongated shaft  110 , and a lateral portion  112 . Medial portion  108  is dimensioned to interact with elongated slot  126  of retractor blade  12 . The medial portion  108  also includes a pivot  114 , which may include any mechanism that allows for changes in the angle defined by the elongated blade extender  46  and the retractor blade  12 . By way of example only, the pivot  114  may comprise a ball-and-socket mechanism. The elongated shaft  110  is dimensioned to interact with the semi-cylindrical surfaces  88 ,  90  of the third portion  54 , and semi-cylindrical surfaces  100 ,  102  of the clips  56 ,  58 . Elongated shaft  110  may include ridges  116  to increase friction to serve as an anti-migration enhancing feature. 
     FIGS. 9-10  illustrate in detail each retractor blade  12  according to a preferred embodiment of the present invention. Retractor blade  12  includes a proximal end  118 , and distal tip  120 , and an elongated portion  122  therebetween. Proximal end  118  includes an elongated slot  126  dimensioned to slideably engage the medial portion  108  of the elongated blade extender  46 . The elongated portion  122  may include a utility clip  124 , which may optionally interact with a light source (not shown) or other mechanism to aid in the procedure. Distal tip  120  may be generally pointed in nature to enable the distal tip  120  to penetrate a vertebral body in order to secure the retractor blades to the bone. Optionally, the retractor blades  12  may be constructed of suitable material and configuration such that light may be transmitted generally distally through the walls of the retractor blades  12  light to shine light at or near the surgical target site. This may be performed by providing the retractor blades  12  having light-transmission characteristics (such as with clear polycarbonate construction) and transmitting the light almost entirely within the walls of the retractor blades  12  (such as by frosting or otherwise rendering opaque portions of the exterior and/or interior) until it exits a portion along the interior (or medially-facing) surface of the retractor blade to shine at or near the surgical target site. The exit portion may be optimally configured such that the light is directed towards the approximate center of the surgical target site and may be provided along the entire inner periphery of the retractor blade  12  or one or more portions therealong. 
   In use, a surgeon may initiate the ALIF procedure by surgical techniques generally known and commonly used in the art. This common procedure includes establishing a small operative corridor by making an incision, clearing the relevant anatomy, and reaching the vertebral body. At this point, a plurality of retractor blades may be inserted such that the distal portions  120  penetrate the targeted vertebral body or bodies in a desired location. Once the retractor blades  12  are inserted in the proper locations, a handle assembly  20  of the present invention may be provided in a “closed” position (preferably rigidly coupled in a fixed relation to the operative site, such as through the use of an articulating arm mounted to the operating table). Before coupling the retractor blades  12  to the handle assembly  20 , the blade assemblies  42  should be positioned in the desired locations along arm extensions  40 ,  41 . When the blade assemblies  42  are properly positioned and secured by tightening pin  60 , the handle assembly  20  may be mated to the retractor blades  12  by inserting medial portions  108  of blade extenders  46  into elongated slots  126 . Once the handle assembly  20  and the retractor blades  12  are sufficiently mated, the operative corridor  15  may be opened by manipulating the handle extenders  31 ,  33  to cause the arms  26 ,  28  to move away from one another. By extension, the plurality of retractor blades  12  also move away from one another, thus expanding the operative corridor  15 . 
   The present invention involves accessing a surgical target site in a fashion less invasive than traditional “open” surgeries. In addition to the features set forth above, the tissue retraction assembly  10  of the present invention may be equipped with one or more electrodes for use in detecting the existence of (and optionally the distance and/or direction to) neural structures associated with the surgical target site or accessing the surgical target site. For example, any or all of the retractor blades  12  may be provided with one or more electrodes  39  (preferably at their distal regions) as shown in  FIGS. 9-10 . These electrodes are preferably provided for use with a nerve surveillance system such as, by way of example, the type shown and described in the following commonly assigned and co-pending applications: PCT App. Ser. No. PCT/US02/22247, entitled “System and Methods for Determining Nerve Proximity, Direction, and Pathology During Surgery,” filed on Jul. 11, 2002; PCT App. Ser. No. PCT/US02/30617, entitled “System and Methods for Performing Surgical Procedures and Assessments,” filed on Sep. 25, 2002; PCT App. Ser. No. PCT/US02/35047, entitled “System and Methods for Performing Percutaneous Pedicle Integrity Assessments,” filed on Oct. 30, 2002; and PCT App. Ser. No. PCT/US03/02056, entitled “System and Methods for Determining Nerve Direction to a Surgical Instrument,” filed Jan. 15, 2003 (collectively “Neurovision PCT Applications”), the entire contents of which are incorporated by reference into the present application as if expressly disclosed herein. Generally speaking, this nerve surveillance system is capable of detecting the existence of (and optionally the distance and/or direction to) neural structures during the distraction and retraction of tissue by detecting the presence of nerves by applying a stimulation signal to such instruments and monitoring the evoked EMG signals from the myotomes associated with the nerves being passed or approached by the retraction system of the present invention. In so doing, the system as a whole (including the surgical access system of the present invention) may be used to form an operative corridor through (or near) any of a variety of tissues having such neural structures, particularly those which, if contacted or impinged, may otherwise result in neural impairment for the patient. In this fashion, the access system of the present invention may be used to traverse tissue that would ordinarily be deemed unsafe or undesirable, thereby broadening the number of manners in which a given surgical target site may be accessed. 
   The surgical access system of the present invention can be used in any of a wide variety of surgical or medical applications, above and beyond the spinal applications discussed herein. Such spinal applications may include any procedure wherein instruments, devices, implants and/or compounds are to be introduced into or adjacent the surgical target site, including but not limited to discectomy, fusion (including PLIF, ALIF, TLIF and any fusion effectuated via a lateral or far-lateral approach and involving, by way of example, the introduction of bone products (such as allograft or autograft) and/or devices having ceramic, metal and/or plastic construction (such as mesh) and/or compounds such as bone morphogenic protein), total disc replacement, etc. . . . ).