Patent Publication Number: US-2022218324-A1

Title: Cervical retractor and method

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. Ser. No. 16/949,144, filed 15 Oct. 2020, the benefit of priority of which is claimed herein and which application is hereby incorporated by reference herein in its entirety. 
    
    
     BACKGROUND 
     Prior cervical retractor blades typically rely on placement of a distal portion or lip of the retractor blade underneath the longitudinal fibers of the longus coli over the transverse processes of the vertebral body to maintain alignment of the retractor. This provides only one point of anatomic fixation (fibers of longus coli) other than the retractor body. Although the retractor blades are ideally positioned on the anterior surface of the respective vertebral bodies&#39; transverse processes, the conformation of the blade is such that it does not actively engage the bony structures. 
     It should also be noted that the fibers of longus coli are elastic and provide little to no fixation to the blade. This lack of fixation, along with the gentle upward slope of the transverse processes, tend to cause the retractor blade to slip from its initial placement by either rotating, slipping, or angling in such a way that the ideal surgical corridor to the vertebral bodies and the associated disc space can be significantly compromised. 
     The elastic nature of the longus coli fixation also means that it is difficult to obtain true midline anterior posterior visualization of the disc space and the associated exiting nerve roots of the vertebral body. The retractor blades are also deficient in that if complete removal of the uncinate processes/uncal vertebral joint is desired, the retractor blades do not provide protection of the vertebral arteries and the exiting nerve roots. 
     SUMMARY 
     A retractor blade includes a shaft having a head portion at a first end and a foot portion at a second end of the shaft. A connector is coupled to the head portion for coupling to a frame. A toe portion extends from the foot portion and has a width and longitudinal curvature configured to at least partially conform to a curvature of a spinal vertebral body and its associated uncinate processes and uncal vertebral joint. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an axial view of a cervical vertebral body representative of cervical  3  through cervical  7  of a human spine. 
         FIG. 2  is a lateral or sagittal view of the cervical spine demonstrating the location of the transverse process 
         FIG. 3  is a coronal view of the cervical spine demonstrating the location of the disc and uncinated process. 
         FIGS. 4A, 4B, and 4C  are top, front elevation, and side elevation views respectively of a medial/lateral blade according to an example embodiment. 
         FIGS. 5A, 5B, and 5C  are top, front elevation, and side elevation views respectively of a cranial/caudal blade according to an example embodiment. 
         FIGS. 6A and 6B  are cross section representations of a portion of spine illustrating a method of using medial/lateral retractor blades according to an example embodiment. 
         FIG. 7  is a side elevation illustrating a portion of a spine with an installed medial/lateral blade according to an example embodiment. 
         FIG. 8  is a perspective view of the spine with medial/lateral blade installed according to an example embodiment. 
         FIGS. 9A, 9B, and 9C  are top, front elevation, and side elevation views respectively of a spine with medial/lateral blade installed according to an example embodiment. 
         FIG. 10  is a perspective view of an example frame having multiple arms for attaching blades according to an example embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration specific embodiments which may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that structural changes may be made without departing from the scope of the present invention. The following description of example embodiments is, therefore, not to be taken in a limited sense, and the scope of the present invention is defined by the appended claims. 
     A surgical corridor is a region of space created by a surgeon running from the surface (skin) to the operative target (vertebral bodies and disc space) that allows for safe retraction of surrounding tissues, optimal visualization of the desired target and associated pathology, and minimal risk of damage to adjacent vital structures. For anterior approaches to the cervical spine, this corridor is perpendicular to the anterior surfaces of the cervical-x and cervical-y vertebral bodies and parallel to the plane of the cervical-x-cervical-y disc space allowing for complete visualization of the target pathology. 
       FIGS. 1, 2, and 3  provide various views of a portion of a human spine, in particular, the cervical spine with labels to provide a reference for the terminology and attachment points for one or more retractor blades described herein. 
       FIG. 1  is an axial view of a cervical vertebral body  100  representative of cervical  3  through cervical  7  of a human spine.  FIG. 1  is labeled with several terms that describe various portions of the cervical vertebral body  100 . Included labeled portions include the following terms: Sulcus for spinal nerve  115 , transverse process  120  (visible in  FIG. 2 ), transverse foramen  125 , superior articular facet  130 , vertebral foramen  135 , bifid spinous process  140 , lamina  145 , lateral mass  150 , and bilateral pedicles  155 . Note that the vertebra foramen  135  is a triangular shaped opening (triangle  135  added for illustration purposes only) formed by the lamina  145 , bilateral pedicles  155 , and body  110 . 
       FIG. 2  is a lateral or sagittal view of the cervical spine  200  demonstrating the location of the transverse process  120  which contains the vertebral artery foramen  125  and vertebral artery (shown in  FIG. 3 ) as well as the location of the uncinate process/uncal vertebral joint  215  and its relationship to the disc space  217  and neuroforamen as illustrated in  FIG. 3 . 
       FIG. 3  is a coronal view of the cervical spine  200  demonstrating the location of the disc  300 , the uncinated process  215 , vertebral artery  310 , and nerve root with various nerves C1-C8. 
     In various embodiments, two different types of surgical retractor blades are used to retract soft tissue of a patient to provide a surgical corridor through anterior skin, subcutaneous tissues, and platysma muscle of the patient while protecting the strap muscles, trachea, esophagus and contents of the carotid sheath. The blades provide access to an anterior portion of the cervical spine. In other words, from the front of the patient to the spine. A medial/lateral blade retracts soft tissue elements in a direction that is perpendicular to the longitudinal axis of the spine with multi-point fixation. A cranial/caudal blade is used to retract soft tissue elements in a direction that is parallel to the longitudinal axis of the spine. 
       FIGS. 4A, 4B, and 4C  are top, front elevation, and side elevation views respectively of a medial/lateral blade  400 . Blade  400  includes a body  410  and a pin  415  attached to a head  420  of the body  410 . Body  410  is a compound planar surface that can be made of various metal, plastic, or ceramic materials and compounds (including fiber or mineral reinforced compounds). The shape and form of the body  410  can be achieved by many fabrication processes including but not limited to machining, forming, casting, molding, etc. The pin  415  in one embodiment is a mostly symmetrical torus shaped feature that can be made of various metal, plastic, or ceramic materials. The shape and form of the pin  415  can be achieved by many fabrication processes including but not limited to machining, casting and molding. The body  410  and pin  415  can be made separately and then joined to make an assembly (mechanical or chemical connection/attachment), or they can be made as a single part of a single material type. 
     Body  410  may be formed of a single piece or multiple pieces that includes regions comprising the head  420  transitioning into a shaft  425  that further transitions into a foot  430 . Each region is configured to perform various functional aspects of providing a surgical corridor. 
     The head  420  includes an upper portion of the body  410 , called a shoulder  435  that extends away from the shaft  425  approximately 20 mm to support the mounting pin  415 . A center of the shoulder  435  is a generally flat planar surface that extends generally 90 degrees from the shaft  425  of the body  410 . The outside edges of the shoulder  435  may be formed with compound curved surfaces shaped to reduce stress concentrations when bearing against body tissues. The shoulder  435  supports the pin which is generally centered on the surface of the shoulder  435 . 
     The pin  415  is shaped such that it allows for the connection of a blade to secondary retractor frame devices such as one shown in a later figure. Such frame devices may be pre-existing and utilize similar connecting pins which are specific to respective frame suppliers. The area of the body  410  where the shoulder  435  transitions to the shaft  425  may be smooth radiused, and without sharp edges or protrusions so as not to hinder access and free motion of surgical tools. 
     The shaft  425  region of the body  410  is a single-curved surface in one embodiment, with common thickness, that is symmetrical along its length. The shaft  425  can vary in length and width according to various use scenarios with common lengths varying between 30 to 70 mm, and widths of approximately 25 mm. In some embodiments, the width may very between 20 and 30 mm. Narrower widths might cause more injury to retracted tissue, while larger widths may also cause injury. 
     In one embodiment, a front surface  440  of the shaft  425  has a transverse concave curvature. A back surface  445  has a transverse convex curvature and is generally of uniform thickness and offset. The back surface  445  engages soft tissue during retraction in use. The cross-section shape of the curvature accelerates (has a shorter radius of curvature) near the sides so as to create a back  445  surface contour that reduces localized stress concentrations when bearing against body tissues. The back surface  445  contour and accelerated curvatures proximate the sides  450  effectively minimize the chances that sharp edges on the sides  450  of the shaft  425  adversely press against or otherwise engage body tissue during retraction of the tissue. 
     The foot  430  on the medial/lateral blade  410  begins as a continuous extension of the surfaces and sides of the shaft  425 . The foot  430  terminates in a toe  455 . Toe  455  maintains the transverse curvature of the shaft  425 , and also longitudinally curves away from the back  445  towards the front  440  of the shaft  425 . Such curvatures are referred to as a symmetrical compound (double-curved) surface curving towards the front  440  concave surface of the shaft  425 . The foot  430  shape provides two functional features. 
     Toe  455  has a radius of curvature R(t)  457  that may be formed to fit over the uncinate process and uncovertebral joint to engage and/or at least partially conform to the uncinate process. In one embodiment, the curvature of the toe is configured to at least partially conform to a curvature of a spinal vertebral body. Example radii of curvature R(t) may vary from 5 to 30 mm. 
     The toe  455  is a narrow semi-elliptical protuberance which is centrally located between the extended shaft  425  sides  450 , and a bridge  465  which consists of two symmetrical, generally linear-shaped edge sections  465  that connect either side of the beginning of the toe  455  with the extended sides  450  of the shaft  425 . The toe  455  has a width, t(w) indicated at  458  that may vary from 4 to 10 mm. A distal end of the toe  455  is rounded in one embodiment. The Toe  455  has edges  470  that are radiused and smooth in one embodiment. An angle  468  of the bridge edge sections  465  relative to a centerline  470  of the front of the body can vary between roughly 60 and 100 degrees. 
     The bridge edge sections  465  may be textured with a plurality of grooves, ridges, serrations, bumps, etc. on distal ends of the bridge sections  465  in order to engage the spine and produce traction and resist sliding along the bone structure against which it rests. In one embodiment, the texture comprises triangular shaped teeth  470 . 
     The toe  455  and bridges  465  function together to produce a secure multipoint stabilizing foundation for the blade  400  with respect to a section of a spine. These anatomical points of bony and elastic fixation include but are not limited to: the curvature of the vertebral body, the anatomy of the lateral aspects of the cervical x-cervical y uncinate processes and uncovertebral joint, the anterior aspects of the cervical x and cervical y transverse processes, and the fibers of the longus coli muscle. The toe  455  of the medial/lateral blade  400  is also designed to protect the vertebral artery and exiting nerve root if complete resection of the uncinate process/uncovertebral joint is desired. 
     The retractor blade  400  does not violate the disc space but is designed to use a combination of bony and soft tissue anatomy to optimize visualization of the disc space. This involves a contoured tip to engage the uncinate process/uncal vertebral joint as well as the teeth on the adjacent areas designed to engage the transverse processes combined with the elastic properties of the longus colli muscles to provide counter fixation. These engagement points provide a triangular type fixation that gives high quality visualization of the disc space and minimizes the movement of the retractor blade, thus providing a stable surgical corridor. The contours also protect the nerve and vertebral artery without incurring direct pressure or retraction of these structures. 
       FIGS. 5A, 5B, and 5C  are top, front elevation, and side elevation views respectively of a cranial/caudal blade  500 . Blade  500  includes a body  510  and a pin  515  attached to a head  520  of the body  510 . 
     Body  510  may be formed of a single piece or multiple pieces that includes regions comprising the head  520  transitioning into a shaft  525  that further transitions into a foot  530 . Each region is configured to perform various functional aspects of providing a surgical corridor. The head  520  and shaft  510  regions may be the same as the head  420  and shaft  410  of blade  400  in some embodiments. The length of the blade  500  may also match or be close to the length of blade  400  during use with a fixture to hold multiple blades in place. Note also that commercially available cranial/caudal blades may be used with blades  400  in some embodiments. 
     The foot  530  region of blade  500  begins as a continuous extension of the surfaces and edges of the shaft  510 . The foot  530  region terminates in a symmetrical double-curved (compound) surface curving towards the convex side, back side  545  of the shaft  510 . The end of the foot  530  region is a smooth concave shape allowing it to slide over the generally convex surfaces of the vertebral body while preventing in pouching of soft tissues such as the esophagus and the omohyoid muscle. An angle (b) indicated at  580  between a centerline of the end of the foot region with a centerline of the shaft  545  region can vary roughly between 90 and 135 degrees. 
     While one or more blades  400  may be placed longitudinally to the spine with the toe  455  engaging the curvature of the vertebral body to provide lateral retraction, blades  500  may be placed perpendicular to the spine over the vertebra bodies to provide superior and inferior retraction of soft tissue to create the surgical corridor. The overall length, width, and depth of the blades  400  and  500  can vary in order to optimize their functionality for specific cervical locations and surgical procedures. 
     Procedural Description: 
       FIGS. 6A and 6B  are cross section representations of a portion of spine illustrating a method of using medial/lateral retractor blades  600  and  605  corresponding to blade  400  and using reference numbers consistent with the prior description of blade  400 . After obtaining access to the anterior cervical spine, the desired cervical x-cervical y disc space (where x is the associated vertebral body  610  located cranial or superior to the disc, cervical  2  through cervical  7  and y is the associated vertebral body (not visible) located caudal or inferior to the disc, cervical  3  through thoracic  1 ) is identified radiographically and marked. The mesial structures (those located opposite the surgeon) consisting of but not limited to the esophagus  615 , trachea  617 , and recurrent laryngeal nerve are gently retracted using temporary retractor devices  620 ,  625 . 
     Longus coli  628  insertions are removed from the bilateral lateral aspects of the cervical x and cervical y vertebral bodies and the bilateral anterior aspects of the associated transverse processes of the cervical x and cervical y vertebral bodies exposing the cervical x-cervical y uncovertebral joint and uncinate processes  635 . Starting with placement of retractor blade  400  opposite the surgeon, the toe of the medial/lateral retractor blade  400  is advanced across the surface of the cervical x-cervical y disc space moving from medial to lateral at approximately a 45 to 75 degree angle crossing over the lateral aspect of the cervical x-cervical y disc space as shown by arrow  640 , finally passing over the uncinate process  635  and uncovertebral joint to rest within the space between the cervical x and cervical y transverse processes, at least partially engaging the lateral aspect of the uncovertebral joint so that the bridges  445  of the foot  430  rest on and engage the associated transverse processes  120  The curvature of the blade need not precisely match the corresponding curvature of the uncinate process. 
     The process is repeated for a second medial/lateral retractor blade  400  that is proximal to the surgeon taking care to protect the contents of the carotid sheath  645 . The retractor blades are then connected to retraction frame arms  650  with tissue further retracted as indicated by arrow  655 . If desired, blades  500  that are parallel to the cervical x-cervical y disc space can be placed and secured to their respective retraction frame arms  650 , not shown. The retraction frame may be of a variety of types and configurations. 
       FIG. 7  is a side elevation illustrating a portion of a spine  700  with an installed blade  400 . The toe  455  passes over the uncinate process  635  and uncovertebral joint to rest within the space between the cervical x  705  and cervical y  710  transverse processes  120 , engaging the lateral aspect of the uncovertebral joint so that the bridges  465  of the foot  430  rest on and engage the associated transverse processes  120 . The toe  455  is thus disposed between adjacent vertebral bodies  705  and  710  to provide a fixation point that does not damage the spine and ensures that the blade  400  stays in retentive contact with the spine  700 . 
       FIG. 8  is a perspective view of the spine  700  with blade  400  installed. Reference numbers are consistent with those used in  FIG. 7 . 
       FIGS. 9A, 9B, and 9C  are top, front elevation, and side elevation views respectively of a spine with blade  400  installed and showing additional detail. Reference numbers are consistent with reference numbers used in previous figures to identify like elements.  FIG. 9A  is situated such that the cranial side is on the left and caudal side on the right.  FIG. 9B  illustrates a sagittal side view, while  FIG. 9C  is a caudal end view. 
       FIG. 10  is a perspective view of an example frame  1000  having multiple arms  1010  for attaching blades  400  and  500  via their respective pins  415  and  515 . The arms may be adjustable in some embodiments to control the size of the surgical opening once blades are placed in retentive contact with desired portions of the spine. 
     Although a few embodiments have been described in detail above, other modifications are possible. Components may be added to or removed from, the described devices. One or more of the described blades may be used with other blades in further embodiments to provide the surgical corridor. Other embodiments may be within the scope of the following claims.