Patent Publication Number: US-2021169461-A1

Title: Dilation system and method of using the same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 16/266,191, filed on Feb. 4, 2019; which is a continuation of U.S. patent application Ser. No. 15/964,561, filed on Apr. 27, 2018, now U.S. Pat. No. 10,194,895; which is a continuation of U.S. patent application Ser. No. 15/680,433, filed on Aug. 18, 2017, now U.S. Pat. No. 9,974,533; which is a continuation of U.S. patent application Ser. No. 15/202,738, filed on Jul. 6, 2016, now U.S. Pat. No. 9,737,290; which is a continuation of U.S. patent application Ser. No. 12/681,671, filed on Apr. 5, 2010, now U.S. Pat. No. 9,387,009, issued on Jul. 12, 2016; which is a U.S. National Stage Entry of PCT/US08/78927, filed on Oct. 6, 2008; which claims the benefit of U.S. Provisional Application No. 60/977,882, filed on Oct. 5, 2007, entitled “ADJACENT OR LATERAL DILATOR AND METHOD OF USING THE SAME;” the entire contents of each being hereby expressly incorporated by reference herein. 
    
    
     BACKGROUND OF THE INVENTION 
     Generally speaking, sequential dilation systems enable a surgeon to make an initial incision and gradually increase the size of the incision by sequential insertion of increasingly larger dilators. Sequential dilation is preferably able to reduce tissue damage and associated trauma to speed patient recovery time. In addition, dilation is utilized to prepare a surgical path to a surgical site and a stimulator may be utilized with the dilator to direct the dilator along a path that avoids specific areas of the patient&#39;s anatomy, such as neural elements or nerves. 
     SUMMARY OF THE INVENTION 
     A preferred embodiment of the present invention relates generally to minimally invasive surgical procedures and apparatus and, more particularly, to a dilation system and related methods for directional dilation of an incision for use in creating an access opening to a patient&#39;s spine. More specifically, the present invention relates to a dilation system and related methods that are able to laterally access a lumbar region of a patient&#39;s spine through the patient&#39;s psoas muscle. In accordance with one aspect of the present invention, the neural elements or nerves of the psoas muscle are preferably mapped using a stimulating probe, thereby defining a safe zone of passage. The stimulating probe is inserted through the psoas muscle and toward or into the intervertebral disc space. Directional dilators may be used to dilate the psoas muscle to substantially separate tissue on only one side of the stimulating probe. That is, directional, sequential dilators may be inserted to dilate the psoas muscle, for example, on the anterior side of the stimulating probe while substantially leaving the psoas muscle intact on the posterior side of the stimulating probe. Specifically, the directional, sequential dilators may be utilized to directionally dilate tissue away from a neural element or nerve in the patient&#39;s body that is identified by the stimulating probe such that the neural element or nerve is not disturbed or damaged by the dilation process or other surgical procedures that may occur following dilation. 
     Alternatively, the dilation system and method may include a blunt stimulating dilator including at least one channel formed in an outer surface. The channel receives a stimulating probe that is used to map the neural elements or nerves of the psoas muscle and define a safe zone of passage to the patient&#39;s spine. The stimulating dilator is inserted through the psoas muscle and toward or into the intervertebral disc space. A stimulating probe is then inserted into the channel formed in the outer surface of the stimulating dilator in order to verify the neural elements or nerves. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing summary, as well as the following detailed description of the preferred embodiments of the application, will be better understood when read in conjunction with the appended drawings. For the purposes of illustrating the dilation system and methods of the present application, there is shown in the drawings preferred embodiments. It should be understood, however, that the application is not limited to the precise arrangements and instrumentalities shown. In the drawings: 
         FIG. 1  illustrates a side elevational view of a dilation system in accordance with a first preferred embodiment the present invention, which will generally be referred to herein as a directional sequential dilation system; 
         FIG. 2  illustrates a magnified perspective view of the distal end of the directional sequential dilation system shown in  FIG. 1 ; 
         FIG. 2A  illustrates an exploded view of the distal end of the directional sequential dilation system shown in  FIG. 2 ; 
         FIG. 3  illustrates a cross-sectional view of the directional sequential dilation system of  FIG. 1 , taken along line  3 - 3  of  FIG. 1 ; 
         FIG. 4  illustrates a front elevational view of the directional sequential dilation system shown in  FIG. 1  including a schematic representation of a retractor that may be used in connection with the directional sequential dilation system; 
         FIG. 5A  illustrates a side view of a first directional dilator used in connection with the directional sequential dilation system shown in  FIG. 1 ; 
         FIG. 5B  illustrates a front view of the first directional dilator shown in  FIG. 5A ; 
         FIG. 6A  illustrates a side view of a second directional dilator used in connection with the directional sequential dilation system shown in  FIG. 1 ; 
         FIG. 6B  illustrates a front view of the second directional dilator shown in  FIG. 6A ; 
         FIG. 7  illustrates a side elevational view of a dilation system in accordance with a second preferred embodiment of the present invention, which will generally be referred to herein as a blunt stimulating dilation system; 
         FIG. 8  illustrates a top plan view of the blunt stimulating dilation system of  FIG. 7 ; 
         FIG. 9  illustrates a magnified, top perspective view of a proximal end of the blunt stimulating dilation system of  FIG. 7 ; 
         FIG. 10  illustrates a magnified bottom perspective view of a distal end of the blunt stimulating dilation system of  FIG. 7 ; 
         FIG. 11  illustrates a top plan view of a dilation system in accordance with a third preferred embodiment of the present invention, which is also comprised of a blunt stimulating dilation system; and 
         FIG. 12  illustrates a magnified, top perspective view of a proximal end of the blunt stimulating dilation system of  FIG. 11 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Certain terminology is used in the following description for convenience only and is not limiting. The words “right”, “left”, “top” and “bottom” designate directions in the drawings to which reference is made. The words “inwardly” and “outwardly” refer to directions toward and away from, respectively, the geometric center of the directional sequential and blunt stimulating dilation systems and designated parts thereof. The words, “anterior”, “posterior”, “superior”, “inferior” and related words and/or phrases designate preferred positions and orientations in the human body to which reference is made and are not meant to be limiting. The terminology includes the above-listed words, derivatives thereof and words of similar import. 
     Certain exemplary embodiments of the invention will now be described with reference to the drawings. In general, such embodiments relate to dilation systems for accessing a patient&#39;s spinal column and, preferably, for laterally accessing the lumbar region of the patient&#39;s spine. 
     As generally understood by one of ordinary skill in the art, the dilation systems will be described in connection with accessing the spine to perform a surgical procedure, but the dilation systems will find use not only in orthopedic surgery, but in other surgical procedures in which a surgeon wishes to gain access to an internal cavity by cutting the skin and going through the body wall in order to keep the incision spread apart so that surgical instruments can be inserted. For example, the dilation systems may be used for anteriorly or posteriorly accessing the spine, for accessing the thoracic or cervical region of the spine, or for accessing nearly any other part of the body. 
     Referring to  FIG. 4 , generally speaking, during a lateral approach to a patient&#39;s spine  2 , a psoas muscle  4 , which is located on either side of the spine  2 , is preferably separated in order to access the spine  2  and, in particular, an intervertebral disc space  6  or one or more vertebral bodies  8  within a patient&#39;s spinal column. It is desirable to avoid neural elements or nerves  9  of the lumbar plexus that lie within the psoas muscle  4  during such procedures. The anterior third of the psoas muscle  4  is typically considered a safe zone for muscle separation. 
     The neural elements or nerves  9  of the psoas muscle  4  are preferably mapped using a stimulating probe  20 . In this manner, the most posterior neural or nerve free area of the psoas muscle  4  is preferably located and identified. The stimulating probe  20  may then be inserted through the psoas muscle  4  via the most posterior neural or nerve free tissue area or through nearly any other region that is free of neural elements or nerves  9  and toward the spine  2  or into the intervertebral disc space  6  in order to initiate safe tissue separation of the psoas muscle  4 . Directional dilators  30 ,  40  in accordance with the first preferred embodiment of the present invention may be used to dilate the muscle separation. In particular, the directional dilators  30 ,  40  may be used to primarily separate tissue on one side of the stimulating probe  20  (shown as cranial side), preferably on the anterior side of the stimulating probe  20  (e.g., the safe zone as initially identified and marked by the stimulating probe  20 ). That is, by using the directional sequential dilators  30 ,  40 , the tissue on one side of the stimulating probe  20  may be moved while substantially limiting movement of the tissue on the opposite side of the stimulating probe  20 . In comparison, concentric dilators separate the muscle radially and, as such, dilate tissue on both sides of the stimulating probe. This in turn may impinge on neural elements or nerves  9  located outside of the safe zone. 
     Referring to  FIGS. 1-6B , a first preferred embodiment of a dilation system of the present invention is comprised of a directional sequential dilation system  10 . The directional sequential dilation system  10  preferably includes a stimulating probe  20 , a first directional dilator  30  and a second directional dilator  40 . The directional sequential dilation system  10  may include more or less dilators such as, for example, one, three, four, etc. The stimulating probe  20  can be any probe now or hereafter known for transmitting an electrical pulse. The stimulating probe  20  preferably includes a probe tip  20   a  and a longitudinal probe axis  21 . The first directional dilator  30  preferably includes a first longitudinal axis  31 , an outer surface  32 , a proximal end  33 , a distal end  34  and a first bore  35  extending from the proximal end  33  to the distal end  34 . The first directional dilator  30  also preferably includes a first tip  30   a  at the distal end  34  through which the first longitudinal axis  31  extends. The first bore  35  has a first bore axis  36  that extends from a proximal end to a distal end of the first bore  35 . The first longitudinal axis  36  is preferably offset or located a first offset distance A from the first longitudinal axis  31 . The first directional dilator  30  also preferably includes a first channel  38  formed in the outer surface  32  thereof. The first channel  38  is preferably in communication with the first bore  35  along the entire length of the first bore  35 . In use, the first bore  35  and the first channel  38  removably receive the stimulating probe  20  in an assembled configuration (e.g., when the stimulating probe  20  is slidably received within the first bore  35  of the first directional dilator  30 ) so that a surgeon can stimulate the first directional dilator  30 . The probe axis  21  of the stimulating probe  20  is preferably coaxial with the first bore axis  36  of the first directional dilator  30  in the assembled configuration. 
     Similarly, the second directional dilator  40  preferably includes a second longitudinal axis  41 , an outer surface  42 , a proximal end  43 , a distal end  44  and a second bore  45  extending from the proximal end  43  to the distal end  44 . The second bore  45  preferably has a second bore axis  46  that extends from the proximal end  43  to the distal end  44 . The second directional dilator  40  also preferably includes a second tip  40   a  at the distal end  44  through which the second longitudinal axis  41  extends. The second bore axis  46  of the second bore  45  is offset or located a second offset distance B from the second longitudinal axis  41 . The outer surfaces  32 ,  42  of the first and second directional dilators  30 ,  40  are preferably coated to prevent electrical leakage during use, as will be apparent to one having ordinary skill in the art. The second directional dilator  40  also preferably includes a second channel  48  formed in the outer surface  42  thereof that is in communication with the second bore  45 . In use, the second bore  45  and the second channel  48  receive the first directional dilator  30  therein in the assembled configuration (e.g., when the first directional dilator  30  is slidably received within the second bore  45  of the second directional dilator  40 ). The first longitudinal axis  31  of the first directional dilator  30  is preferably coaxial with the second bore axis  46  of the second directional dilator  40  when in the assembled configuration. 
     Because the first and second bore axes  36 ,  46  of the first and second bores  35 ,  45  are offset from the first and second longitudinal axes  31 ,  41  of the first and second directional dilators  30 ,  40 , respectively, inserting the first directional dilator  30  over the stimulating probe  20  and then the second directional dilator  40  over the first directional dilator  30  causes each sequential dilator to “directionally” dilate the opening formed in the patient preferably away from any neural elements, nerves  9  or other anatomic structure on the opposite side of the stimulating probe  20 , as will be described in greater detail below. 
     Moreover, incorporation of the first and second channels  38 ,  48  enables the first and second directional dilators  30 ,  40  to be more closely nested together and thus, substantially eliminate the “cookie cutter” effect that is realized when using multiple concentric dilators of increasing inner bore size. 
     The first directional dilator  30  preferably includes a plurality of first depth indicators  37  located on the outer surface  32  thereof (as best shown in  FIGS. 5A and 5B ). The plurality of first depth indicators  37  extend, on the outer surface  32  of the first directional dilator  30 , generally perpendicular to the first longitudinal axis  31 . The plurality of first depth indicators  37  indicate to the surgeon the various distances between the first tip  30   a  formed at the distal end  34  of the first directional dilator  30  to the respective depth indicator  37  so that, in use, the surgeon can determine how far the first directional dilator  30  has been inserted into the patient. Similarly, as best shown in  FIGS. 6A and 6B , the second directional dilator  40  preferably includes a plurality of second depth indicators  47  located on the outer surface  42  thereof. The plurality of second depth indicators  47  extend, on the outer surface  42  of the second directional dilator  40 , generally perpendicular to the second longitudinal axis  41 . The plurality of second depth indicators  47  indicate to the surgeon the various distances between the second tip  40   a  formed at the distal end  44  of the second directional dilator  40  to the respective depth indicator  47  so that, in use, the surgeon can determine how far the second directional dilator  40  has been inserted into the patient. In the first preferred embodiment, the plurality of first and second depth indicators  37 ,  47  are spaced a distance of eighty millimeters (80 mm) to one hundred fifty millimeters (150 mm) from the first and second tips  30   a,    40   a  in ten millimeter (10 mm) increments. However, the plurality of plurality of first and second depth indicators  37 ,  47  are not limited to these dimensions and may be spaced from the first and second tips  30   a,    40   a  at nearly any distance or spacing that is preferred by a surgeon and is able to show the depth that the first and second directional dilators  30 ,  40  are inserted into the patient. 
     In addition, the first and second directional dilators,  30 ,  40  preferably include first and second grips  39 ,  49 , respectively, located at the proximal ends  32 ,  42  thereof to better enable the surgeon to grip the dilators  30 ,  40  in use. The first and second grips  39 ,  49  may be utilized by the surgeon during insertion, removal, twisting or otherwise manipulating the first and second directional dilators  30 ,  40  during surgery. 
     As best shown in  FIG. 1 , the first directional dilator  30  preferably has a first length Li while the second directional dilator  40  has a second length L 2 . The first length Li is preferably greater than the second length L 2  to facilitate handling and insertion. Similarly, the stimulating probe  20  preferably has a probe length L 3  such that the probe length L 3  is greater than the first length Li and the second length L 2 . The greater first length Li of the first directional dilator  30  permits the proximal end  33  of the first directional dilator  30  to extend further out of the patient in the assembled and operational configurations such that a surgeon may grasp the first grip  39  and remove or otherwise manipulate the first directional dilator  30  even after the second directional dilator  40  is inserted into the patient. In the first preferred embodiment, the first length is two hundred twenty millimeters (220 mm) and the second length is two hundred millimeters (200 mm), but are not so limited and may have nearly any length that permits insertion into the patient with the proximal ends  33 ,  43  extending out of the patient. In addition, the first directional dilator  30  preferably has a first diameter Di and the second directional dilator  40  has a second diameter D 2 , the second diameter D 2  is preferably greater than the first diameter Dl. In the first preferred embodiment, the first diameter Di is approximately seven and seven tenths millimeters (7.7 mm) and the second diameter D 2  is approximately seventeen and one-half millimeters (17.5 mm). However, the first and second diameters Di, D 2  are not so limited and may have nearly any diameter desired by the surgeon for dilating tissue various distances from the stimulating probe  20 . Further, the first and second directional dilators  30 ,  40  are not limited to having a circular cross-section and may have nearly any cross-section and be adapted to shapes that permits directional dilation in a manner that is preferred by a surgeon. For example, the first and second directional dilators  30 ,  40  may have an oval or oblong cross-sectional shape that urges dilation and a surgical working channel even further from a detected nerve  9  than a dilator having a circular cross-section. 
     A method of using the stimulating probe  20  and first and second directional dilators  30 ,  40  will now be described for accessing the patient&#39;s spine  2 . The technique may be particularly desirable for accessing the lumbar region of the spine  2  via a lateral approach, although a similar or the same method may be used in other parts of the patient&#39;s body. 
     Using the stimulating probe  20  and a triggered electromyograph (EMG)  50 , the surgeon preferably maps a safe zone, i.e., a zone generally free of any neural elements or nerves  9 , on the tissue of interest (e.g., psoas muscle  4 ). For example, on the psoas muscle  4 , the anterior third of the psoas muscle  4  is generally considered a safe zone. 
     Once a safe zone is established, anatomical placement is preferably confirmed via intra-operative fluoroscopy. The surgeon inserts the stimulating probe  20  through the psoas muscle  4  toward the patient&#39;s spine  2 . If the surgery is being performed on the intervertebral disc space  6 , the distal end of the stimulating probe  20  may be inserted into the annulus of the desired intervertebral disc space  6 . Preferably, the stimulating probe  20  will be inserted via the most posterior portion of the safe zone. 
     The surgeon can insert or slide the first directional dilator  30  over the stimulating probe  20  so that the first longitudinal axis  31  is located to one side of the stimulating probe  20 , preferably away from a sensed neural element or nerve  9 , through the psoas muscle  4  and into a position proximate the patient&#39;s spine  2 . The surgeon can then insert the second directional dilator  40 , if necessary, to further dilate the tissue proximate the outside surface  32  of the first directional dilator  30  and further away from the sensed neural element or nerve  9 . The surgeon can repeat this process as often as necessary. Finally, if desired, a retractor  60  can be inserted over the second directional dilator  40  to subsequently retract the tissue and to permit removal of the first and second directional dilators  30 ,  40  and the stimulating probe  20 . Alternatively, a working cannula (not shown) may be inserted over the second dilator  40  such that a procedure on the spine  2  may be performed through the working cannula. 
     Additionally, if desired, before inserting the second directional dilator  40 , the stimulating probe  20  can be removed from the first bore  35  and the dilator/probe combination rotated. Thereafter, using the triggered EMG stimulation  50 , the surgeon can verify that the nerve root  9  is located at the expected side of the first directional dilator  30 , preferably opposite the first channel  38 . The stimulating probe  20  is preferably re-inserted into the first bore  35 , before insertion of the second directional dilator  40 . 
     By using the first and second directional dilators  30 ,  40 , as compared to concentric sequential dilators as are generally known to those having skill in the art, the directional sequential dilation system  10  preferably ensures that the access opening is created away from the neural elements or nerves  9  of the psoas muscle  4 , thus avoiding any neural elements or nerves  9  that may, for example, be located on the posterior side of the stimulating probe  20 . 
     Moreover, the directional sequential dilation system  10  also reduces the amount of tissue damage when separating the tissue by minimizing the amount of tissue separation. 
     Alternatively, as shown in  FIGS. 7-10 , a one step blunt stimulating dilator  100  comprising a second preferred embodiment of a dilation system of the present application may be used. The blunt stimulating dilator  100  includes an outer surface  102 , a proximal end  104 , a distal end  106  and a bore  108  extending from the proximal end  104  to the distal end  106 . The proximal end  104  includes an area  110  for attaching a stimulating clip or cord. The distal end  106  includes an exposed, preferably pointed tip  112  for delivering electrical stimulation. The outer surface  102  of the stimulating dilator  100  between the proximal and distal ends  104 ,  106  is preferably coated to prevent electrical leakage. The stimulating dilator  100  also preferably includes a channel  114  formed in the outer surface  102  thereof for receiving a stimulating probe, such as the stimulating probe  20  illustrated in  FIG. 1 . The stimulating probe can be any probe now or hereafter known for transmitting an electrical pulse. 
     The stimulating dilator  100  offers the surgeon the ability to simultaneously stimulate and dilate the psoas muscle  4 . After placing the tip  112  of the stimulating dilator  100  into the disc space, the stimulating probe  20  can be inserted through the channel  114  along the outer surface  102  of the dilator  100  to stimulate the periphery of the dilated tissue. 
     Alternatively, as shown in  FIGS. 11 and 12 , the stimulating dilator  100 ′ comprised of a third preferred embodiment of the present application may include a plurality of channels  114  formed in the outer surface  102  thereof. For example, as shown, the stimulating dilator  100 ′ may include four channels  114   a - d  diametrically spaced on the outer surface  102  of the dilator  100 ′. In this manner, the surgeon can stimulate anterior, posterior, cranially, and caudally to verify the location of the nerve root once the dilator  100 ′ is in place. Although as will be understood by one of ordinary skill in the art, the stimulating dilator  100 ′ may include any number of channels  114  including, for example, two, three, five or more. 
     A method of using the blunt stimulating dilation system will now be described to produce access to the spine  2 , in particular to provide an access opening through the psoas muscle  4  in the lumbar region of the spine  2  via a lateral approach. Although as will be understood by one of ordinary skill in the art, the method may be used in other parts of the body and utilizing alternative approaches. 
     In use, a surgeon inserts, preferably laterally, the blunt stimulating dilator  100 ,  100 ′ into the psoas  4  muscle via, for example, a twisting motion. The surgeon preferably uses a triggered EMG  50  to transmit an electrical pulse into the blunt stimulating dilator  100 ,  100 ′ in order to locate a safe zone in the patient&#39;s psoas muscle  4  by locating nerve roots  9 . Once the location of any nerve root  9  has been confirmed to be posterior to the blunt stimulating dilator  100 ,  100 ′, the surgeon can laterally insert the blunt stimulating dilator  100 ,  100 ′ through the psoas muscle  4  and toward the patient&#39;s spine  2 , preferably into the annulus of the disc space  6 . The surgeon inserts or slides the stimulating probe  20  into the channel  114  formed in the outer surface  102  of the blunt stimulating dilator  100 ,  100 ′. If desired, the surgeon rotates the blunt stimulating dilator  100  with the stimulating probe  20  located in the channel  114  while using the EMG  50  to verify the location of the nerve root  9 . Alternatively, in connection with the four channel blunt stimulating dilator  100 ′, rotation of the blunt stimulating dilator  100  is not required. Rather, the stimulating probe  20  can be independently inserted into each channel  114   a - d  to verify the location of the nerve root  9 . The surgeon can then, if desired, insert a retractor over the stimulating dilator  100 ,  100 ′. 
     While the foregoing description and drawings represent the preferred embodiments of the present invention, it will be understood that various additions, modifications and substitutions may be made therein without departing from the spirit and scope of the present invention as defined in the accompanying claims. In particular, it will be clear to those skilled in the art that the present invention may be embodied in other specific forms, structures, arrangements, proportions, and with other elements, materials, and components, without departing from the spirit or essential characteristics thereof. One skilled in the art will appreciate that the invention may be used with many modifications of structure, arrangement, proportions, materials, and components and otherwise, used in the practice of the invention, which are particularly adapted to specific environments and operative requirements without departing from the principles of the present invention. In addition, features described herein may be used singularly or in combination with other features. The presently disclosed embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims, and not limited to the foregoing description.