Patent Publication Number: US-2022233213-A1

Title: Adapter for a surgical access device

Description:
FIELD 
     The present disclosure relates generally to adapters for use with surgical access devices. 
     BACKGROUND 
     This section provides background information related to the present disclosure and is not necessarily prior art. 
     Diagnosis and treatment of conditions affecting the brain are among the most difficult and complex problems that face the medical profession. The brain is a complex and delicate soft multi-component tissue structure that controls bodily functions through a complex neural network connected to the rest of the body through the spinal cord. The brain and spinal cord are contained within and protected by significant bony structures, e.g., the skull and the spine. Given the difficulty of accessing the brain through the hard bony protective skull and the delicate network and complex interactions that form the neural communication network contained within the brain that define the human body&#39;s ability to carry on its functions of speech, sight, hearing, functional mobility, reasoning, emotions, respiration and other metabolic functions, the diagnosis and treatment of brain disorders presents unique challenges not encountered elsewhere in the body. 
     For example, abnormalities such as intracranial cerebral hematomas (ICH), abscesses, Glioblastomas (GB) and metastases (mets) manifest themselves in the intraparenchymal subcortical space (i.e., the white matter) of the brain are particularly challenging to access, let alone treat. The white matter and cortex of the brain contain eloquent communication structures (neural network) which are located in the cortical and subcortical space, called fiber tracts and fascicles. Thus, traditionally, unless the ICH, GB, and/or mets where considered anything but “superficial,” such conditions have been considered inoperable, simply because getting to the abnormality ICH, GB and/or mets are considered just as damaging as letting the condition take its course. Similarly, tissue abnormalities such as tumors, cysts and fibrous membrane growths which manifest within the intraventricular space of the brain are considered challenging to safely access and often inoperable, due to their locations within the brain. 
     To assist in diagnosis and subsequent treatment of brain disorders, clear, accurate imaging of brain tissue through the skull is required. In recent years significant advances have been made in imaging technology, including stereotactic X-ray imaging, Computerized Axial Tomography (CAT), Computerized Tomographic Angiography (CTA), Position Emission Tomography (PET) and Magnetic Resonance Imaging (MRI), Diffusion Tensor Imaging (DTI) and Navigation systems (instrument position tracking systems). These imaging devices and techniques permit the surgeon to observe conditions within the brain in a non-invasive manner without opening the skull, as well as provide a map of critical structures surrounding an area of interest, including structures such as blood vessels, membranes, tumor margins, cranial nerves, including fiber tracts and fascicles. If an abnormality is identified through the use of one or more imaging modalities and/or techniques, it may be necessary or desirable to surgically intervene. 
     Once a course of action has been determined based upon one or more imaging techniques, a surgical treatment may be necessary or desired. To operate surgically within the brain, access must be obtained through the skull and delicate and eloquent brain tissue such as blood vessels, the lymphatic system and nerves overlying and surrounding the abnormality that can be adversely affected by slight disturbances and disruptions. Therefore, great care must be taken in operating on the brain so as not to disturb these eloquent tissues to prevent adverse consequences resulting from an intervention. 
     Traditionally, accessing abnormalities which manifest in deeper spaces within the brain has meant a need for a surgery that creates a disruptive invasive approach. In some instances, in order to obtain access to target tissue, a substantial portion of the skull is removed and entire sections of the overlying brain are retracted to obtain access. For example, surgical brain retractors are used to pull apart or spread delicate brain tissue, which can produce transient and/or permanent deficits. In some instances, a complication known as “retraction injury” may occur due to use of brain retractors. Of course, such techniques are not appropriate for all situations, and not all patients are able to tolerate and recover from such invasive techniques. 
     It is also known to access certain portions of the brain by creating a burr hole craniotomy, but only limited surgical techniques may be performed through such smaller openings. In addition, some techniques have been developed to enter through the nasal passages, opening an access hole through the bone to remove skull-based tumors, for example, in the area of the pituitary. These approaches are referred to as Expanded Endonasal Approaches (EEA). 
     A significant advance in brain surgery is stereotactic surgery involving a stereotactic frame correlated to stereotactic X-ray images and MRI to guide a navigational system probe or other surgical instrument through an opening formed in the skull through brain tissue to a target lesion or other body. A related advance is frameless image guidance, in which an image of the surgical instrument is superimposed on a pre-operative image to demonstrate the location of the instrument to the surgeon and trajectory of further movement of the probe or instrument. 
     It is known to access certain portions of the brain with surgical access systems. An example of a surgical access systems used to access certain portions of the brain may be found in commonly owned co-pending Patent Application No. US 2016/0128722, the contents of which are incorporated by reference in its entirety. A navigation member may be used with an obturator by slidingly engaging with the obturator. 
     One issue with surgical access systems that arises is compatibility a variety of known navigational arrangements and systems. For example, some navigational system probes may be incompatible because they are sized differently, and therefore unable to engage with an existing obturator directly. More specifically, certain navigational system probes may be too wide and therefore unable to be seated within an obturator without alterations being made to the obturator. Alternatively, a navigational system probe may be too narrow and may not be able to be properly seated within an obturator. Additionally, incompatibility may occur due to the material from which the obturator is constructed which can interfere or block the signals produced by the navigational systems, especially those navigational system that utilize electromagnetic signals (an example of which is the AxiEM System manufactured by Medtronic). Notwithstanding the foregoing advances in surgical navigation, there remains a need for improved surgical techniques and apparatuses for operating on brain tissue, including providing multi-compatible navigational systems. 
     SUMMARY 
     This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features. Implementations of the disclosure may include one or more of the following optional features. 
     One aspect of the disclosure provides an adapter for use with a surgical access assembly. The adapter comprises an adapter body and a positioning member. The adapter body is defined by a distal end and a proximal end opposite the distal end. The positioning member extends from the distal end of the adapter body. A channel extends through the adapter body, extending from the proximal end and toward the distal end. 
     In one exemplary arrangement, the adapter body further comprises a locking mechanism to secure a navigation element to the adapter against movement. 
     In one exemplary arrangement, the channel terminates in a closed distal end that defines a seating portion. The distal end tapers inwardly to define the seating portion. A window may be provided to provide visual access to the channel, adjacent the seating portion. 
     In one exemplary arrangement, the adapter body further includes a grip portion disposed adjacent to the proximal end of the adapter body. 
     In one exemplary arrangement, the adapter body includes an engagement section that includes an annular angled surface encircling the proximal end of the positioning member. 
     Another aspect of the disclosure provides an adapter for a surgical access assembly comprising a first adapter casing, a second adapter casing and a mounting piece. The first and second adapter casings are selectively engageable with one another. The first and second adapter casings cooperate to define a channel that is configured to receive a navigation element. The mounting piece is selectively engaged with the first and second adapter casings. 
     In one exemplary arrangement, the first adapter casing includes a first navigation groove defined between a proximal end of the first adapter casing and a distal end of the first adapter casing, and the second adapter casing includes a second navigation groove defined between a proximal end of the second adapter casing and a distal end of the second adapter casing, the first and second navigation grooves collectively define the channel. 
     In one exemplary arrangement, a portion of the mounting piece is disposed within a portion of an inner surface of the first adapter casing and a portion of an inner surface of the second adapter casing to secure the mounting piece to the first and second adapter casings. 
     In one exemplary arrangement, the first adapter casing includes an engagement channel adjacent to the distal end of the first adapter casing, the second adapter casing includes an engagement channel adjacent to the distal end of the second adapter casing, and the mounting piece includes a securing portion that engages with the engagement channel of the first adapter casing and the engagement channel of the second adapter casing. 
     In one exemplary arrangement, an engagement surface of the first adapter casing defines one or more first cooperating members, and wherein an engagement surface of the second adapter casing includes one or more second cooperating members configured to engage with the one or more first cooperating members of the inner surface of the first adapter casing to connect the first and second adapter casings together. 
     In one exemplary arrangement, the mounting piece further includes a window. The window may further include a spring element that is biased inwardly toward the channel. 
     In one exemplary arrangement, the first and second adapter casings are hingedly connected to the mounting portion. 
     Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
    
    
     
       BRIEF DESCRIPTIO OF THE DRAWINGS 
       The drawings described herein are for illustrative purposes only of selected configurations and not all possible implementations, and are not intended to limit the scope of the present disclosure. 
         FIG. 1A  is a perspective view of a portion of an exemplary surgical access assembly assembled with a navigation adapter. 
         FIG. 1B  is a plan view of an obturator for use with an adapter. 
         FIG. 2A  is a front elevational view of the adapter of  FIG. 1 . 
         FIG. 2B  is a side elevational view of the adapter of  FIG. 1 . 
         FIG. 3A  is a cross-section view of the adapter of  FIG. 1  taken along lines  3 A- 3 A of  FIG. 2B , as well as an exploded view of an exemplary navigational element. 
         FIG. 3B  is an enlarged view of area  3 B taken from  FIG. 3A . 
         FIG. 4A  is a top plan view the adapter of  FIG. 1 . 
         FIG. 4B  is a bottom plan view of the adapter of  FIG. 1 . 
         FIG. 5  is a perspective view of an exemplary surgical access assembly assembled with an exemplary navigation adapter. 
         FIG. 6  is a cross-section view of the adapter of  FIG. 5  taken along a center line extending through the adapter. 
         FIG. 7  is an exploded view of the adapter of  FIG. 5 . 
         FIG. 8  is a partially exploded cross-sectional view of a further exemplary navigation adapter and navigational element. 
         FIG. 9  is a side elevational view of the adapter of  FIG. 8 . 
         FIG. 10  is a front cross-sectional view of the adapter and navigational element of  FIG. 8 , assembled. 
         FIG. 11  is a front cross-sectional view of the adapter and navigational element of  FIG. 8  assembled to an obturator. 
         FIG. 12  is an enlarged area  12  taken from area  12  in  FIG. 11 . 
         FIG. 13  is a partial front cross-sectional view of the adapter and navigational element assembled together. 
         FIG. 14  is a front elevational view of the adapter and navigational element of  FIG. 12  assembled to an obturator. 
         FIG. 15  is a perspective view of a further exemplary arrangement of a navigational adapter. 
     
    
    
     Corresponding reference numerals indicate corresponding parts throughout the drawings. 
     DETAILED DESCRIPTION 
     Referring now to the discussion that follows and also to the drawings, illustrative approaches to the disclosed assemblies are shown in detail. Although the drawings represent some possible approaches, the drawings are not necessarily to scale and certain features may be exaggerated, removed, or partially sectioned to better illustrate and explain the present disclosure. Further, the descriptions set forth herein are not intended to be exhaustive or otherwise limit or restrict the claims to the precise forms and configurations shown in the drawings and disclosed in the following detailed description. 
     Described herein is an adapter for a surgical access assembly and various components for use in same. The components disclosed herein provide surgeons with an enhanced ability to minimize trauma to the patient, while providing efficient improved minimally invasive surgical techniques, such as, for example, during intracranial surgical techniques. 
     Referring to  FIG. 1A , a perspective view of a medical access assembly  100  including a navigation adapter  102  mounted to an obturator  104  of a surgical access system is shown. A navigational element  105  is selectively engageable with adapter  102  to be used with obturator  104  of a surgical access system. In use, the obturator  104  is selectively slidably engaged with an outer sheath (not shown) to provide access to an area of interest in a patient. An example of an exemplary surgical access system may be found in commonly owned co-pending Patent Application No. US2016/0128722, the contents of which are incorporated by reference in its entirety. In one exemplary arrangement, the navigational element  105  (best seen in  FIG. 3 ) is defined by a proximal end  107 , a body portion  109  and a distal end  111 . When navigational element  105  is positioned within adapter  102 , the body portion  109  will extend along an axis A-A and beyond an adapter proximal end  106 . By having the proximal end  107  extend proximally from the adapter proximal end  106 , the navigational element  105  is able to selectively connect to a navigation system (not shown). In some implementations, navigational element  105  is a navigation probe having a tapered distal tip  103 . In addition, navigational element  105  may include an annular notch  101 , which may receive a sealing element such as an  0 -ring (not shown). 
     When navigational element  105  is assembled with adapter  104 , body portion  109  extends about axis A-A. As will be discussed in greater detail below, adapter  102  enables navigational element  105  to be used with obturator  104 , even if navigational element  105  is incompatible or unable to operationally engage with obturator  104 . As will be explained in further detail below, an offset X between a proximal end face  113  and a distal tip  115  of the obturator  104  is a known parameter. As the adapter  102  is configured to locate the distal end  111  of the navigational element  105  in the same plane as the proximal end face  113  of the obturator  105 , a navigation system can calculate the location of the distal tip  115  of the obturator  105  by factoring in the known offset X with the location of the distal end  111 . 
     Referring now to  FIGS. 2A-2B , details of the adapter  102  will be described in further detail. Adapter  102  is defined by an adapter body  117  and a positioning member  112 . The adapter body  117  is further defined by proximal end  106  and distal end  108 . In one exemplary arrangement, a handle portion  110  is disposed at the proximal end  106 . The positioning member  112  extends from the distal end  108  of the adapter body  117  and generally along an axis B-B. The positioning member  112  is defined by a length L ( FIG. 2B ) and further includes a tip member  114 . In one exemplary arrangement, the tip member  114  is configured to narrow from a body section  116  of the positioning member  112  to an adapter distal tip  119 . Other tip member  114  configurations are also contemplated such as a rounded distal tip. In some implementations, the adapter body  117  and positioning member  112  are molded together as a unitary body. In other implementations, adapter body  117  and positioning member  112  are in selective engagement with each other. Handle portion  110  may be further defined by grip portions  118  that extends outwardly from axis B-B. In one exemplary arrangement, grip portion  118  is configured to be generally perpendicular to axis B-B. In some implementations, Adapter  102  may further include a locking mechanism  120 , which will be described in more detail below. Though  FIGS. 2A-2B  depict locking mechanism  120  disposed on grip portion  118 , it should be noted that locking mechanism  120  may be disposed anywhere on handle portion  110 . 
     As best seen in  FIG. 2A , adapter body  117  further includes an engagement section  121  disposed distal to handle portion  110 . As best seen in  FIGS. 3A and 3B , engagement section  121  includes an annular angled surface  123  that encircles a proximal end  131  of positioning member  112 . Angled surface  123  is configured to frictionally engage an annular chamfer  125  disposed about a proximal opening  127  formed in a top surface  129  of obturator  104  (see  FIGS. 1A and 3B ). Angled surface  123  is angled inwardly toward a central axis of the positioning member  112 . 
     The handle portion  110  may include an arcuate section  122  disposed between proximal end  106  and engagement section  121 . Arcuate portion  122  may advantageously allow a physician to comfortably hold adapter  102 , reducing physician fatigue and making adapter  102  easier to manipulate in the surgical field. 
     With continued reference to  FIGS. 2-4 , handle portion  110  includes an axial channel  124 . Channel  124  extends from an opening  134  disposed at proximal end  106 , along axis B-B, but terminates proximally of the positioning member  112 . An inwardly extending chamfer  144  may be disposed around opening  134  to assist in directing navigational element  105  within channel  124 . Channel  124  is sized to receive navigational element  105  therewithin. It is contemplated that various adapters  102  may be provided with channels  124  being sized with predetermined diameters that permit known sized navigational elements  105  to be inserted therein. Alternatively, for those arrangements where the diameter of the channel  124  is significantly larger than the diameter of the navigational element  105 , an optional sizing sleeve (not shown) may be provided that has an outside diameter that is receivable within the channel  124 , and has an inside diameter that receives the navigational element  105  snugly. As a further option, navigational member  105  may be provided with the annular notch  101  formed on an outside surface of the body portion  109 , the annular notch  101  receiving an o-ring or a spring clip therein to frictionally retain the navigational element  105  within the channel  124 . 
     Disposed at a distal end  133  of channel  124  is a seating portion  126 . In one exemplary arrangement, seating portion  126  is defined by an annular inwardly directing surface  135 . The inwardly directing surface  135  serves to self-direct and center navigational element  105  when inserted within adapter  102 . Other configurations of seating portion  126  are also contemplated, such as tongue and groove arrangements. 
     Handle portion  110  may also define at least one window  128 . Window  128  allows a user to visually confirm the placement of navigational element  105  ( FIG. 1 ) when disposed within adapter  102 . Windows  128  also serve to reduce the weight of adapter  102 , thereby making adapter  102  easier to manipulate in the surgical field. Reducing the weight of adapter  102  also reduces physician fatigue during a surgical procedure. 
     In the exemplary arrangement, at least one window  128   a  may be disposed adjacent to positioning member  112 , enabling a user to visually confirm that a navigational element  105  is in proper contact with seating portion  126 . As depicted in  FIG. 2A , window  128   a  may be a front-facing window, such that the “front” of the adapter  102  is, with respect to the width of grip portion  118 , being at its widest. Additionally or alternatively, in an exemplary arrangement, a window  128   b  may be positioned adjacent to grip portion  118  to visually confirm that the navigational element  105  is disposed along the axis B-B. As depicted in  FIG. 2B , window  128   b  may be a side-facing window, such that the “side” of the adapter is with respect to the width of grip portion  118  being at its narrowest. Adapter  102  having both a front-facing window  128   a  and a side-facing window  128   b  may be advantageous in allowing a user to ensure proper placement of navigational element  105  ( FIG. 1 ) by viewing navigational element  105  from two different angles. In some implementations, at least a portion of adapter  102  may be made of a transparent material, which also allows a user to visually confirm the placement of navigational element  105  when inside adapter  102 . 
     Referring to  FIG. 3A-4B , in some implementations, locking mechanism  120  of adapter  102  may operatively fix navigational element  105  ( FIG. 3 ) to adapter  102 . More specifically, in one exemplary arrangement, grip portion  118  (or other portion of adapter  102 ) is provided with a receiving aperture  137  that is configured to receive a locking member  139 . In one exemplary arrangement, receiving aperture  137  is threaded. Receiving aperture  137  is in communication with channel  124 . A retaining channel  141  extends generally perpendicular to the receiving aperture  137 . The locking member  139  includes a reduced diameter section  140 . After locking member  139  is at least partially engaged within receiving aperture  137 , a retaining member  143  is positioned within retaining channel  141  so as to be disposed adjacent to the reduced diameter section  140 . In operation, once the retaining member  143  is inserted within the retaining aperture  137 , an actuating member  142  is rotated to move the retaining member  143  toward the channel  124  and into engagement with the navigational element  105 , thereby locking the navigational element  105  within the adapter  102 . The retaining member  143  prevents locking mechanism  120  from being completely disengaged from adapter  102  and entering the surgical field and, particularly, it prevents locking mechanism  120  from contacting exposed body tissue in the surgical field. 
     As shown in  FIG. 3B , obturator  104  may also be provided with a locking mechanism  150  that is similar to locking mechanism  120 . 
     In operation, the navigational element  105  is inserted through opening  134  and into channel  124  until a distal tip  103  engages seating portion  126 . A user may view the navigational element  105  while in the actuator  102  by looking through windows  128 . Once proper positioning is confirmed, if available, locking mechanism  120  is activated to secure navigational element  105  in place within the actuator  102 . 
     Once navigational element  105  is secured to the actuator  102 , the adapter  102  is joined to the obturator  104 . More specifically, the positioning member  112  is inserted within the proximal opening  127  of the obturator  104 . As the positioning member  112  is elongated, a portion of the positioning member  112  will be disposed within the obturator  104 , extending proximally from the top surface of the obturator  104 , as shown in  FIG. 1 . The annular angled surface  123  of the engagement section  121  engages the annular chamfer  125  in a complementary manner. Once positioned, locking mechanism  150  may be actuated to lock the positioning member  112  to the obturator  104 . As discussed above, once so assembled, the seating portion  126  serves to position the distal tip  103  of the navigational element  105  in alignment with the top surface  129  of the obturator  104 . The proximal end  107  of the navigational element  105  is secured to the navigational system. Thus, when the obturator  104  is assembled to the outer sheath of a surgical access assembly, because the offset X between the top surface  129  and the distal tip  115  of the obturator  104  is a known predefined length, the location of the distal tip  115  may be determined while the surgical access assembly is in use, as the distal tip  103  of the navigational element  105  will be known by correlating the offset X with the location of the distal tip  103  of the navigational element  105 . 
     Referring now to  FIGS. 5-7 , a perspective view of a medical access assembly  200  including an alternative adapter  202  mounted to an obturator  104  of a surgical access assembly is shown. Similar to adapter  102 , adapter  202  is configured to selectively engage with obturator  104  of a surgical access system to allow different sized navigational elements  105  to be used with obturator  104 . In one exemplary arrangement, adapter  202  comprises a first adapter casing  204 , a second adapter casing  206 , and a mounting piece  208 . First and second adapter casings  204 ,  206  are each defined by a proximal end  210  and a distal end  212 . In some implementations, at least one of first adapter casing  204 , second adapter casing  206 , and mounting piece  208  may include locking mechanism  120  (best seen in  FIG. 5 ). 
     Referring now to  FIG. 7 , first adapter casing  204  extends partially about an axis D-D and is defined by a proximal end  210   a  and a distal end  212   a.  In one exemplary arrangement, first adapter casing  204  has a generally U-shaped cross-section. First adapter casing  204  includes a navigational channel  214   a  defined between proximal end  210   a  and distal end  212   a  on an inner surface  222   a  of first adapter casing  204 . 
     First adapter casing  204  may include at least one first cooperating member  224  disposed on at least one engaging surface  226   a  of first adapter casing  204 . In one exemplary configuration, the at least one first cooperating member  224  may be configured as a detent and have a thickened end  225 . As depicted in  FIG. 7 , in one exemplary arrangement, the first adapter casing  204  has two first cooperating members  224  disposed adjacent to proximal end  210   a  of first adapter casing  204 , and two first cooperating members  224  disposed adjacent to distal end  212   a  of first adapter casing  204 , disposed on opposite sides of channel  214   a.  It should be noted, however, that the at least one first cooperating member  224  may be located anywhere on the at least one engaging surface  226   a.    
     First adapter casing  204  also includes a mechanism for connecting mounting piece  208  to first adapter casing  204 . In one exemplary arrangement (as depicted in  FIG. 7 ), an engagement channel  228   a  disposed adjacent to distal end  212   a.  Engagement channel  228   a  extends inwardly from inner surface  222   a  of first adapter casing  204 . As will be explained in further detail below, engagement channel  228   a  cooperates with a securing portion  234  of mounting piece  208  to secure mounting piece  208  to first and second adapter casings  204 ,  206 . 
     With continued reference to  FIG. 7 , second adapter casing  206  extends partially about an axis E-E and is defined by a proximal end  210   b  and a distal end  212   b.  In one exemplary configuration, the second adapter casing  206  has a generally U-shaped cross-section. Second adapter casing  206  includes a navigational groove  214   b  defined between proximal end  210   b  and distal end  212   a  on an inner surface  222   b  of second adapter casing  206 . In one exemplary arrangement, second adapter casing  206  is generally a mirror image of first adapter casing  204 . 
     Second adapter casing  206  may include at least one second cooperating member  230  disposed on at least one engaging surface  226   b  of second adapter casing  206 . The at least one second cooperating member  230  may be an indentation configured to permit engagement with a first cooperating member  224  in a complementary manner. In addition, an engagement tab  232  may be disposed within the indentations of second cooperating member  230  adjacent to an edge of the indentation of second cooperating member  230 . With this arrangement, the thickened end of the first cooperating member  224  may snap-fit around the engagement tab  232  to assist in locking the first and second adapter casings  204  and  206  together. As depicted in  FIG. 7 , the second adapter casing  206  has two second cooperating members  230  disposed adjacent to proximal end  210   b  of second adapter casing  206 , and two second cooperating members  230  disposed adjacent to distal end  212   b  of second adapter casing  206 , disposed on either side of the navigation groove  214   b,  generally corresponding to the locations of the first cooperating members  224  of first adapter casing  204   a.  It should be noted, however, that the at least one second cooperating member  230  may be located anywhere on the at least one engaging surface  226   b.    
     It should also be noted that, though  FIG. 7  depicts first adapter casing  204  including four first cooperating members  224 , and second adapter casing  206  including four second cooperating members  230 , first adapter casing  204  may have any number of first cooperating members  224  greater than one, and second adapter casing  206  may have any number of second cooperating members  230  equal to or greater than the number of first cooperating members  224  that first adapter casing  204  has. Furthermore, first adapter casing  204  may have at least one second cooperating member  230  in addition to the at least one first cooperating member  224 . Similarly, second adapter casing  206  may have at least one first cooperating member  224  in addition to the at least one second cooperating member  230 . It should be noted that other engagement mechanisms may be used to secure first adapter casing  204  to second adapter casing  206 . 
     Second adapter casing  206  also includes a mechanism for connecting mounting piece  208  to second adapter casing  204 . In one exemplary arrangement (as depicted in  FIG. 7 ), second adapter casing  204  includes engagement channel  228   b  disposed adjacent to distal end  212   b.  Engagement channel  228   b  extends inwardly from inner surface  222   b  of second adapter casing  206 . As with engagement channel  228   a,  engagement channel  228   b  cooperates with securing portion  234  of mounting piece  208  to secure mounting piece  208  to first and second adapter casings  204 ,  206 . It should be noted that other engagement mechanisms may be used to secure mounting piece  208  to first and second adapter casings  204 ,  206 . 
     With continued reference to  FIG. 7 , mounting piece  208  is defined by a proximal end  218  and a distal end  220 , and extends about an axis E-E. Distal end  220  of mounting piece  208  includes an annular angled surface  233  (best seen in  FIG. 6 ). Angled surface  233  tapers from an outside diameter of the mounting piece  208  toward a positioning member  236  that extends from the distal end  220 . Similar to adapter  102 , angled surface  233  is configured to be complementary to chamfer  125  to seat the mounting piece  208  within obturator  104 . 
     Mounted to a proximal face  235  of the proximal end  218  of mounting piece  208  is the securing portion  234 . Securing portion  234  is configured to engage with engagement channels  228   a,    228   b  of first and second adapter casings  204 ,  206  to form assembled adapter  202  ( FIG. 5 ). Referring to  FIG. 6 , securing portion  234  is defined by a flange member  237  that is spaced from the proximal face  235  such that an annular groove  239  is formed between the flange member  237  and proximal face  235 . The flange member  237  has a diameter that is smaller than a diameter of the mounting piece  208 . 
     A stopper portion  244  may extend outwardly from the flange member  237 . Stopper portion  244  may be received in a complementary key hole (not shown) formed in either of first and second adapter casings  204 ,  206 , within engagement channels  228   a,    228   b,  respectively, to prevent rotation of mounting piece  208  with respect to assembled first and second adapter casings  204 ,  206 . 
     A mounting opening  238  is formed through the securing portion  234 . Mounting opening  238  is in communication with a mounting piece channel  240 . Mounting piece channel  240  may be constructed of a predetermined size to accommodate navigational element  105  ( FIG. 5 ) therein. Mounting piece channel  240  terminates in a closed distal end. Closed distal end may be configured to taper inwardly to define a seating portion  216  that receives the distal tip  103  of navigational element  105 , similar to the seating portion  126  described above in connection with adapter  102 . More specifically, similar to seating portion  126 , seating portion  216  may be annularly angled such that when navigational element  105  contacts seating portion  216 , navigational element  105  is properly seated within adapter  202  so as to be aligned with a top surface of obturator  104 . 
     To assemble adapter  202 , the flange member  237  is inserted within engagement channel  228   a,    228   b,  with the stopper element positioned within a key hole. Simultaneously, the first and second casings  204 ,  206  are brought into engagement with one another such that at least one first cooperating member  224  of first adapter casing  204  engages with the at least one second cooperating member  230  of second adapter casing  206 . This engagement may be a snap-fit arrangement that locks first and second adapter casings  204 ,  206  together in a cooperating manner, thereby trapping the flange member  237  within the first and second casings  204 ,  206 . When first adapter casing  204  is assembled with second adapter casing  206 , navigational channels  214   a,    214   b  combine to form the navigational channel  214  that is in communication with mounting piece channel  240  ( FIG. 6 ) to form a continuous channel. The continuous channel is in communication with proximal opening  127  of obturator, when adapter  202  is assembled to obturator  104 . 
     Once assembled, navigation element  105  may be disposed within combined navigational channel  214 /mounting piece channel  240 , such that the distal tip  103  is directed into seating portion  216 . Once positioned, locking mechanism  120  may be actuated to lock the navigational element  105  within adapter  202 . 
     In some implementations, a window  203   a  may be disposed on at least one of the first and second adapter casings  204 ,  206 . Window  203   a  may extend partially about an axis C-C between proximal end  210  and distal end  212  of assembled first and second adapter casings  204 ,  206 . Alternatively or additionally, a window  203   b  may be disposed on mounting piece  208 , enabling a user to visually confirm that navigational element  105  is in proper contact with seating portion  216  ( FIG. 5 ). In some implementations, Window  203   b  may be offset by  90  degrees from window  203   a.  Similar to window  128 , windows  203   a,    203   b  may allow a user to visually confirm the placement of navigational element  105  when inside adapter  202 . Furthermore, windows  203   a,    203   b  serve to reduce the weight of adapter  202 , thereby making adapter  202  easier to manipulate in the surgical field. Reducing the weight of adapter  202  also reduces physician fatigue during a surgical procedure. Adapter  202  having both windows  203   a,    203   b  may be advantageous in allowing a user to ensure proper placement of navigational element  105  by viewing navigational element  105  from two different angles. In some implementations, at least a portion of at least one of first adapter casing  204 , second adapter casing  206 , and mounting piece  208  may be made of a transparent material, also allowing a user to visually confirm the placement of navigational element  105  when inside adapter  202 . 
     Once assembled, navigational channel  214  may extend along axis C-C and define a first diameter D 1 . Navigational element  105  may also have a second diameter D 2 , which is less than D 1  and allows navigational element  105  to be slidingly received within navigational channel  214 . 
     When navigational element  105  is positioned within adapter  202 , navigational element  105  will extend beyond proximal end  210  of first and second adapter casings  204 ,  206  in a direction away from adapter  202 . This allows navigational element  105  to be connected to a navigational system (not shown) while navigational element  105  is positioned within adapter  202 . Furthermore, when assembled with adapter  202 , navigational element  105  extends beyond distal end proximal end  210  of first and second adapter casings  204 ,  206  and within mounting piece  208 , allowing navigational element  105  to engage seating portion  216 . 
     Once navigational element  105  is secured to the actuator  202 , the adapter  202  is joined to the obturator  104 . More specifically, the positioning member  236  is inserted within the proximal opening  127  of the obturator  104 . As the positioning member  236  is elongated, a portion of the positioning member  236  will be disposed distally within the obturator  104 , spaced from the top surface of the obturator  104 , thereby providing stability of the engagement, as shown in  FIG. 5 . The annular angled surface  233  of the mounting piece  208  engages the annular chamfer  125  of the obturator  104  in a complementary manner. Once positioned, a locking mechanism  150  may be actuated to lock the positioning member  236  to the obturator  104 , as described above. Further, once so assembled, the seating portion  216  serves to position the distal tip  103  of the navigational element  105  in alignment with the top surface  129  of the obturator  104 . The proximal end  107  of the navigational element  105  is secured to the navigational system. Thus, when the obturator  104  is assembled to the outer sheath  104  of a surgical access assembly, because the offset X between the top surface  129  and the distal tip  115  of the obturator  104  is a predefined length, the location of the distal tip  115  may be determined while the surgical access assembly is in use, as the distal tip  103  of the navigational element  105  will be known by correlating the offset X with the location of the distal tip  103  of the navigational element  105 . 
     Referring to  FIGS. 8-12 , a further alternative arrangement of an adapter  302  will be described. Adapter  302  generally includes similar elements as described in connection with adapter  102 , including handle  318 , adapter body  317 , positioning member  312  and seating portion  326 . Like elements from the description of adapter  102  have been given similar reference numbers, increased by  200 . Seating portion  326  is positioned to align with a top surface  129  of obturator  104  such that when a distal tip  319  is nested within seating portion  326 , distal tip  319  is aligned with top surface  129  of obturator  104 , as described above. 
     Much like that described above in connection with adapter  102 , the adapter  302  is configured to selectively receive the navigational element  305 . The navigational element  305  is defined by a proximal end  307 , a body portion  309  and a distal end  311 . The distal end  311  may be configured to taper inwardly from the body portion  309 , terminating in distal tip  319 . Disposed within the distal end  311  is an electromagnetic coil  313 . However, electromagnetic coil  313  is slightly spaced from a distal tip  319  of the navigational element  305 . Thus, as may be seen best in  FIG. 12 , when navigational element  305  is seated within seating portion  326 , electromagnetic coil  313  is disposed slightly above the top surface  129  of obturator  104 . With this arrangement, any interference between the obturator material and signals from the electromagnetic coil  313  of the navigational element  305  may be avoided. 
     Referring to  FIGS. 13-14 , a further alternative arrangement of an adapter  400  is shown. Adapter  400  is similar to adapter  202 . Like elements from the description of adapter  202  have been given similar reference numbers, increased by  200 . While adapter  202  provides for navigational element  105 / 305  to be retained within the channel  214  via the cooperating sizes of the channel  214  and an outside diameter of the navigational element  105 / 305  and/or use of a locking mechanism  120 , as a further alternative, an inside surface of the channel portions  214   a,    214   b  may be formed with a compressible material (examples?) to further frictionally retain the navigational element  105 , thereby relaxing manufacturing tolerances between the channel  214  and the navigational element  105 . 
     As yet a further exemplary arrangement, windows  403   a  may be provided with a spring element  401 . Spring element  401  includes a first end  405  and a free end  407 . The first end  405  is fixed to a proximal end of the window  403   a,  with the free end  405  biased to encroach within the channel  414 . When navigational element  105 / 305  is disposed within the channel  414 , the free end  405  of each spring element  401  will frictionally engage the outside surface of the navigational element  105 / 305 , thereby retaining the navigational element  105 / 305  within the channel  414 . 
     Referring to  FIG. 15 , a further embodiment of a navigation adapter  502  for use with an obturator of a surgical access system. Adapter  502  is similar to adapters  200  and  400 . Like elements from the description of adapter  200  have been given similar reference numbers, increased by  300 . Adapter  502  is defined by first and second adapter casings  504 ,  506 , a mounting piece  508  from which a positioning member  536  extends. 
     The first and second adapter casings  504 ,  506  are each defined by a proximal end  510  and a distal end  512 . In some implementations, at least one of first adapter casing  504 , second adapter casing  506 , and mounting piece  508  may include locking mechanism  120  (best seen in  FIG. 5 ) or may include a spring element  401 . 
     First adapter casing  504  has a generally U-shaped cross-section and includes a navigational groove  514   a  defined between proximal end  510   a  and distal end  512   a  on an inner surface  522   a  of first adapter casing  504 . First adapter casing  504  may include at least one first cooperating member  524  disposed on at least one engaging surface  526   a  of first adapter casing  504 . In one exemplary configuration, the at least one first cooperating member  524  may be configured as a detent and have a thickened end  525 . As depicted in  FIG. 15 , in one exemplary arrangement, the first adapter casing  504  has two first cooperating members  524  disposed generally at the center of the first adapter casing  504 , on either side of the navigation groove  514   a.  However, it is understood that this disclosure is not limited to this arrangement. Moreover, it is understood that additional cooperating members may be provided, similar to the arrangement depicted with respect to first adapter casing  204 . First adapter casing  504  is hingedly connected to mounting piece  508  to first adapter casing  204  by hinge element  505 . 
     Second adapter casing  506  is generally a mirror image of first adapter casing  504  and has a generally U-shaped cross-section and includes a navigational groove  514   b  defined between proximal end  510   b  and distal end  512   b  on an inner surface  522   b  of second adapter casing  506 . Second adapter casing  506  may include at least one second cooperating member  530  disposed on at least one engaging surface  526   b  of second adapter casing  506 . 
     The at least one second cooperating member  530  may be an indentation configured to permit engagement with a first cooperating member  524  in a complementary manner. In addition, an engagement tab  532  may be disposed within the indentations of second cooperating member  530  adjacent to an edge of the indentation of second cooperating member  530 . With this arrangement, the thickened end of the first cooperating member  524  may snap-fit around the engagement tab  532  to assist in locking the first and second adapter casings  504  and  506  together. 
     As depicted in  FIG. 15 , in one exemplary arrangement, the second adapter casing  506  has two second cooperating members  530  disposed generally at the center of the second adapter casing  506 , on either side of the navigation groove  514   b  so as to generally correspond with the locations of the first cooperating members  524 . However, it is understood that this disclosure is not limited to this arrangement. Moreover, it is understood that additional cooperating members may be provided, similar to the arrangement depicted with respect to second adapter casing  506 . Second adapter casing  506  is hingedly connected to mounting piece  508  by hinge element  507 . 
     Mounting piece  508  is defined by a proximal end  518  and a distal end  520 . Distal end  520  of mounting piece  508  includes an annular angled surface (similar to that shown in  FIG. 6 ). The angled surface tapers from an outside diameter of the mounting piece  508  toward a positioning member  536  that extends from the distal end  520 . Similar to adapter  102 , the angled surface is configured to be complementary to chamfer  125  to seat the mounting piece  508  within obturator  104 . 
     A mounting opening  538  is formed through the proximal end  518 . Mounting opening  538  is in communication with a mounting piece channel, similar to mounting piece channel  240 . The mounting piece channel may be constructed of a predetermined size to accommodate navigational element  105  ( FIG. 5 ) therein. The mounting piece channel terminates in a closed distal end and may be configured to taper inwardly to define a seating portion similar to seating portion  216  that receives the distal tip  103  of navigational element  105 . 
     To assemble adapter  502 , the first and second casings  204 ,  206  are pivoted from a non-operational position (as shown in  FIG. 15 ) about the hinge elements  505  and  507  brought into engagement with one another such that at least one first cooperating member  524  of first adapter casing  504  engages with the at least one second cooperating member  530  of second adapter casing  506 . This engagement may be a snap-fit arrangement that locks first and second adapter casings  504 ,  506  together in a cooperating manner. When first adapter casing  504  is assembled with second adapter casing  506 , navigational grooves  514   a,    514   b  combine to form the navigational channel  514  that is in communication with the mounting piece channel, similar to that shown in  FIG. 6  to form a continuous channel. The continuous channel is in communication with proximal opening  127  of obturator, when adapter  502  is assembled to obturator  104 . 
     Once assembled, navigation element  105  may be disposed within combined navigational channel  514 /mounting piece channel, such that the distal tip  103  is directed into the seating portion. Once positioned, a locking mechanism  120  may be actuated to lock the navigational element  105  within adapter  502 , if provided. 
     It will be appreciated that the surgical access system described herein has broad applications. The foregoing embodiments were chosen and described in order to illustrate principles of the apparatuses as well as some practical applications. The preceding description enables others skilled in the art to utilize apparatuses in various embodiments and with various modifications as are suited to the particular use contemplated. In accordance with the provisions of the patent statutes, the principles and modes of operation of this disclosure have been explained and illustrated in exemplary embodiments. 
     It is intended that the scope of the present apparatuses be defined by the following claims. However, it must be understood that this disclosure may be practiced otherwise than is specifically explained and illustrated without departing from its spirit or scope. It should be understood by those skilled in the art that various alternatives to the embodiments described herein may be employed in practicing the claims without departing from the spirit and scope as defined in the following claims. The scope of the disclosure should be determined, not with reference to the above description, but should instead be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. It is anticipated and intended that future developments will occur in the arts discussed herein, and that the disclosed systems will be incorporated into such future examples. Furthermore, all terms used in the claims are intended to be given their broadest reasonable constructions and their ordinary meanings as understood by those skilled in the art unless an explicit indication to the contrary is made herein. In particular, use of the singular articles such as “a,” “the,” “said,” etc. should be read to recite one or more of the indicated elements unless a claim recites an explicit limitation to the contrary. It is intended that the following claims define the scope of the invention and that the apparatus within the scope of these claims and their equivalents be covered thereby. In sum, it should be understood that the invention is capable of modification and variation and is limited only by the following claims.