Abstract:
This disclosure is directed to minimally-invasive devices, methods and systems used through small access portals to minimize trauma to structures adjacent the treatment site. The access device includes a guide frame and a cannula support washer movebly coupled to the guide frame. The washer has a cannula port aperture extending therethrough and a surface geometry complementary to the surface geometry of the guide frame. The complementary surface geometries limit movement of the cannula port aperture to arcuate movement along a surface segment of a sphere.

Description:
REFERENCE TO PRIORITY DOCUMENT 
       [0001]    This application claims priority of U.S. Provisional Patent Application Ser. 61/229,179, entitled “Arcuate Surgical Guidance System and Methods” by Marino, et. al., filed Jul. 28, 2009. Priority of the filing date of Jul. 28, 2009 is hereby claimed, and the disclosure of the Provisional Patent Application is hereby incorporated by reference. 
     
    
     BACKGROUND 
       [0002]    Minimally-invasive techniques have been developed that prevent the need for excessive tissue dissection in and around target structures. However the manipulation of percutaneous surgical systems near critical or more delicate structures can cause unwanted damage. 
       SUMMARY 
       [0003]    The subject matter described herein provides many advantages. More details of the devices, systems and methods are set forth in the accompanying drawings and the description below. Other features and advantages will be apparent from the description and drawings. 
         [0004]    The minimally-invasive surgical systems described herein can be used for a variety of interventions within an organ, tissue mass, body cavity, joint or other soft tissue structure or osseous structure minimizing cannula manipulative trauma to structures immediately adjacent thereto. It should be appreciated that the anatomic region within which the system can be used is not limiting. 
         [0005]    In an embodiment, described herein is a guidance system used to prevent manipulative trauma to tissue structures near a target treatment area accessed by a cannula. The guidance system includes an upper guide element having a first opening extending through the upper guide element; a lower guide element coupled to the upper guide element such that a space is formed between the upper and lower guide elements. The lower guide element has a second opening having a shape complementary to the first opening, and the first and second openings align to form an elongate channel. The system also includes an alignment washer having a central port extending through the alignment washer that is accessible via the first opening, the alignment washer slidably disposed within the space between the upper guide element and the lower guide element. The upper guide element, lower guide element and alignment washer each have a geometry that conforms to a segment of a sphere. 
         [0006]    The space can have a width at least as wide as a thickness of the alignment washer. The guidance system can further include a locking element coupled to the upper guide element and lower guide element such that the width of the space between the upper guide element and lower guide element is reduced to fix the orientation of the alignment washer within the space. The guidance system can further include a cannula extending through the central port. The cannula and the alignment washer can be configured to coordinately move within the elongate channel in a variety of axes along the segment of the sphere. A portion of the cannula can extend to the target treatment area. The target treatment area can be distal to a center of the sphere. The portion of the cannula extending distal to the center of the sphere can be configured to undergo distal arcuate movement. A portion of the cannula encircled by the central port can be configured to undergo proximal arcuate movement. The proximal arcuate movement and distal arcuate movement can be complementary. The movement of a portion of the cannula at the center of the sphere can be minimized. 
         [0007]    In an embodiment, disclosed herein is a method of minimally-invasive tissue access including inserting an intracorporeal instrument through a cannula guide device including a guide frame and a cannula support washer moveably coupled within the guide frame and having a cannula port extending through the cannula support washer. The guide frame and the cannula support washer together have a shape that is a surface segment of a sphere. The method also includes telescopically extending the instrument through the cannula port of the cannula support washer until a distal end of the instrument is adjacent an anatomic structure. The method also includes moving a proximal end of the instrument within the cannula port in the cannula support washer within the guide frame along the surface segment of the sphere while the distal end of the instrument pivots about a fixed point at a center of the sphere. 
         [0008]    In another embodiment, disclosed herein is a minimally-invasive tissue access device including a guide frame having a first surface geometry; and a cannula support washer movebly coupled to the guide frame and having a cannula port aperture extending through the washer. The cannula support washer has a second surface geometry complementary to the first surface geometry. The complementary surface geometries of the guide frame and the cannula support washer limit movement of the cannula port aperture to arcuate movement along a surface segment of a sphere. 
         [0009]    The cannula port aperture can be configured to receive a cannula extending through the aperture to a distance from the cannula port aperture that approaches a center of the sphere. Arcuate movement of the cannula support washer within the guide frame can limit movement of the cannula at the center of the sphere to a pivot point and can allow for translation of the cannula along a radial axis of the sphere. The distance can be the radial distance of the sphere between the pivot point of the cannula extending through the cannula port aperture and the cannula support washer aperture. 
         [0010]    Other features and advantages should be apparent from the following description of various embodiments, which illustrate, by way of example, the principles of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    These and other aspects will now be described in detail with reference to the following drawings. Generally speaking the figures are not to scale in absolute terms or comparatively but are intended to be illustrative. Also, relative placement of features and elements may be modified for the purpose of illustrative clarity. 
           [0012]      FIG. 1A  is a simplified sagittal view of a vertebral pair. 
           [0013]      FIG. 1B  is a simplified, transverse plane view of a vertebra. 
           [0014]      FIG. 2A  is a simplified, perspective view of a vertebral pair including an embodiment of a surgical guidance system. 
           [0015]      FIG. 2B  is a perspective view of the surgical guidance system of  FIG. 2A . 
           [0016]      FIG. 3  is a schematic of the surgical guidance system positioned along a surface of a sphere. 
           [0017]      FIG. 4  is a close-up view of the surgical guidance system being actuated along a surface segment of a sphere. 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    In percutaneous surgical procedures in which a small access channel and cannula is placed into or through a specific anatomic region, limited surgical dissection or manipulation can be desirable. As an example, it can be desirable to limit contact with the periannular structures of the lumbar disc, such as exiting spinal nerves within the foramen or the psoas muscle during surgical procedures intended for structures of the distal regions such as within the intervertebral disc space. In order to conduct surgical procedures in these distal regions some degree of manipulation is necessary. 
         [0019]    Described herein are devices, systems and methods for a variety of surgical interventions within an organ, tissue mass, body cavity, joint or other soft tissue structure or osseous structure that minimize cannula manipulative trauma to structures immediately adjacent to the structures being treated. In particular, disclosed herein is an instrument guidance system that constrains an access cannula and associated instrumentation within delicate anatomic regions where minimal manipulation is desired and allows for some distal arcuate movements within the distal surgical field. The instrument guidance system described herein allows for proximal and distal arcuate movements and maintains a fixed pivoting region characterized by minimal movement. 
         [0020]    It should be appreciated that although the present disclosure generally relates to spinal surgery, particularly to minimally-invasive, low-trauma surgical methods and improved access for associated interventions (e.g. disc excision and endplate decortication), the anatomic region within which the system is used can vary and is not limiting. 
         [0021]      FIG. 1A  is a simplified sagittal view of a vertebrae pair  20 ,  21 .  FIG. 1B  is a simplified, transverse plane view of the vertebrae  21  of the vertebrae pair shown in  FIG. 1A . Each vertebra  20 ,  21  includes lamina  12 , transverse processes  14 , a spinous process  16 , central canal  10 , and pedicles  24 . A disc  22  comprised of an annulus and disc nucleus (not shown) is located between the vertebrae pair  20 ,  21 . The spinal cord (not shown) passes through the central canal  10 . Small nerve roots branch off from the spinal cord through spaces or neuroforamen of each vertebra. Due to disc degeneration, expulsion, annulus tears, or other conditions, the spinal cord or other nervous structures can become compressed causing patient discomfort. 
         [0022]    It can be desirable to modify or fix the spatial relationship between the vertebrae pair  20 ,  21  and access the disc space or superior vertebra in order to decompress nerves, for example, to remove herniated or prolapsed discs. For example, access to the disc space  22  or superior vertebra  21  can be achieved via a channel(s) formed percutaneously in an inferior vertebra pedicle  24 , such as one immediately inferior to the disc space or vertebra to be entered. The channel(s) can be used for a number of procedures such as disc resection, excision, endplate decortication, vertebral reduction or compression, delivery of material, pedicle screw fixation, etc. 
         [0023]    In an embodiment as shown in  FIGS. 2A-2B , the instrument guidance system  100  can include a lower guide element  110 , upper guide element  115 , and an alignment washer  120  having a central port  140  through which a cannula  105  can be inserted. The lower guide element  110 , upper guide element  115  and the alignment washer  120  each can have a complementary geometry that conforms to a segment of a sphere. The two guide elements  110 ,  115  can couple together with the alignment washer  120  disposed in a space  135  between them forming an arcuate guide  130  for a cannula  105 . The space  135  between the guide elements  110 ,  115  can be at least as wide as the alignment washer  120  is thick such, that the washer  120  can be manipulated in sliding fashion between the upper and lower guide elements  110 ,  115 . 
         [0024]    Each of the guide elements  110 ,  115  can have an opening such that when the guide elements  110 ,  115  couple together the openings align and an elongate channel  125  extends therethrough. The alignment washer  120  sandwiched between the guide elements  110 ,  115  can span this elongate channel  125  such that at least a portion of the washer  120  remains sandwiched between the guide elements  110 ,  115  regardless of the positioning of the cannula  105  within the elongate channel  125 . As mentioned above, the alignment washer  120  includes a central port  140  through which a cannula  105  can be inserted such that when the cannula  105  extends through the port  140  of the washer  120  it also extends through the elongate channel  125 . The channel  125  allows for the cannula  105  and the washer  120  to coordinately move in a variety of axes along the surface of the sphere. The geometry and size of the openings and thus, the elongate channel  125  can vary. For example, the channel  125  can have a rectangular, square, circular, oblong, arcuate or other geometry. Movement of the cannula  105  within the channel  125  can be limited by the size and shape of the channel  125 . 
         [0025]    As mentioned above, the lower guide element  110 , upper guide element  115  and the alignment washer  120  each can have a complementary geometry that conforms to a segment of a sphere. The combination of these elements provides an overall geometry to the arcuate guide  130  that conforms to that same segment of a sphere. The geometry of the arcuate guide  130  can vary. The arcuate geometry can be for a generally fixed radial distance. Depending on the anatomic location to be treated or accessed, the geometry and dimensions can vary. For example, the guide  130  can have variable geometries and sizes as can the length of the cannula  105  such that the guidance system  100  can correspond with the radial distance from the anticipated guide position to the anatomic structure within which it is desired that the cannula pivot. Multiple arcuate guides  130 , such as a set or kit of guides, with varying radial geometries can be provided for corresponding radial distances. A surgeon can select an appropriate pivot point at a fixed distance from the anticipated location of the arcuate guide  130 . 
         [0026]    The instrument guidance system  100  can also include a locking element (not shown). Once the cannula  105  extending through the central port  140  is properly positioned in a particular axis along the segment of the sphere it can be desirable to fix the orientation of the cannula  105  within the arcuate guide  130 . Similarly, a locking element can be used to fix the cannula  105  to the port  140  through which it passes. The locking element(s) can be of a variety of mechanisms including screws, clamps, friction locks, cam driven locks or other mechanisms as is known in the art. In an embodiment, the locking element clamps the lower and upper guide elements  110 ,  115  such that the space  135  between them is minimized and the washer  120  is fixed in place between the lower and upper guide elements  110 ,  115 . 
         [0027]    Various tools and instruments  150  can be inserted through the cannula  105  and employed via the instrument guidance system  100  to perform procedures. In the example of spinal surgery, it might be desirable to remove disc material, osteophytes or other structures that might be impinging on the nerve root(s), including herniated or prolapsed disc material. Other procedures that can be performed in addition to discectomy, include functional placement devices such as nucleoplasty or arthroplasty devices, endplate “decortication” instruments, annular closure or repair instruments and implants, fusion instrumentation and implants or intervertebral disc arthrodesis devices, fracture reduction devices, bone cyst therapy, intervertebral distraction devices, spacers or cages. Implantation of therapeutic materials such as bone growth materials, nuclear replacement material, bone granules, powdered material, and bone grafting material (autogenous, allogeneic, xenograph, or synthetic) as well as any osteoconductive and/or proliferative material, are also considered herein. More specifically, therapeutic bone growth materials such as osteogenic proteins or growth factors including osteoprogenic factor 1, BMP-7, and bone morphogenetic proteins such as BMP-2. 
         [0028]    As shown in  FIG. 3 , the arcuate guide  130  has a pre-determined radius of curvature R whereby all radii, having radius of curvature R, extending from the arcuate guide  130  will intersect at a common point P, which is the center of an imaginary sphere S. A medical instrument  150  inserted through the cannula  105  disposed anywhere on the arc will dissect with common point P. The arcuate guide  130  is a segment of a sphere and the cannula  105  can be manipulated within this spherical segment by virtue of its movement with the alignment washer  120  within the elongate channel  125 . The target work space (e.g. annulus) can be located at the common point P or just distal to the common point P. 
         [0029]    As shown in  FIG. 4 , a distal arcuate movement (arrow A′) near the target work space can occur that is complementary to the proximal arcuate movement (arrow A) within the arcuate guide  130 . The distal arcuate movement allows for instrumentation  150  inserted through the cannula  105  to be used to perform surgical procedures, such as within the annulus. The common point P of the cannula  105  (and, in turn, any instrumentation  150  inserted through the cannula  105 ) undergoes minimal movement therein preventing tissue damage of the tissues surrounding a structure targeted for treatment. 
         [0030]    The special orientation of the instrument guidance system  100  with respect to the patient can also be adjusted. In an embodiment, the instrument guidance system  100  is attached to an operating table by a table clamp and an adjustable bracing system that is adjustable along a variety of axes. 
         [0031]    While this specification contains many specifics, these should not be construed as limitations on the scope of the claims or of what can be claimed, but rather as descriptions of features specific to particular embodiments. For example, although some of the present disclosure is presented in terms of spinal surgery, this is not intended to be limiting. The devices, systems and methods described herein can be used in a variety of anatomic locations where it would be desirable for cannula manipulation trauma to be minimized. 
         [0032]    Certain features that are described in this specification in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable sub-combination. Moreover, although features can be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination can be directed to a sub-combination or a variation of a sub-combination. Similarly, while operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. 
         [0033]    Although embodiments of various methods and devices are described herein in detail with reference to certain versions, it should be appreciated that other versions, embodiments, methods of use, and combinations thereof are also possible. Therefore the spirit and scope of the appended claims should not be limited to the description of the embodiments contained herein.