AU2015252096B2 - Surgical access system and related methods - Google Patents

Abstract

A retractor assembly for creating an operative corridor to a spinal target site includes a retractable body and a plurality of retractor blades extending generally perpendicularly to the retractor body. The retractor body is operable to separate the plurality retractor blades relative to each other to retract tissue away from the interior of the retractor blades when the tissue retractor is advanced to the surgical target site and the retractor blades are separated to thereby form an operative corridor to the surgical target site. The retractor body is also operable to splay at least one of the plurality of retractor blades such that a distal end of the retractor blade extends wider than a proximal end of the retractor blade, wherein splaying of the at least one retractor blade is controlled by a gear situated on the retractor body.

Description

2015252096 05 Nov 2015

Surgical Access System and Related Methods

CROSS-REFERENCES TO RELATED APPLICATIONS 2015252096 05 Nov 2015

The present application is a divisional application from Australian Patent Application No. 2011293853, the entire disclosure of which is incorporated herein by reference.

FIELD

Tlris disclosure relates to a surgical retraction system and related instmmentation and methods for accessing a surgical target site for the purpose of performing surgical procedures.

BACKGROUND A noteworthy trend in the medical community is the move away ftom performing surgery via traditional "open" tecliniques in favor of minimally invasive or minimal access techniques. Open surgical techniques are generally undesirable in that they typically require large incisions and high amounts of tissue displacement to gain access to the surgical target site, which produces concomitantly high amounts of pain, lengthened hospitalization (increasing health care costs), and high morbidity in the patient population. Less-invasive surgical techniques (including so-called "minimal access" and "minimally invasive" techniques) are gaining favor due to the fact that they involve accessing the surgical target site via incisions of substantially smaller size with greatly reduced tissue displacement requirements. This, in turn, reduces the pain, morbidity and cost associated with such procedures. On such minimally invasive approach, a lateral transpsoas approach to the spine, developed by NuVasive®, Inc., San Diego, CA (XLIF'() has demonstrated great success in reducing patient morbidity, shortening the length of hospitalization and fast recovery time when it is employed. Improvement ofinstmments and methods employed to the during the lateral access has the potential to further reduce operative time, expand applications for the lateral approach, and increase surgeon adoption of the procedure, all of which will ultimately benefit the patient by provide more opportunity for minimally invasive surgical correction of their ailments. The instruments and methods described herein are designed to address these needs, among others. 2

The discussion, of the background to the invention incl'uded herein including reference to documents, acts, materials, devices, articles and the like is included to explain the context of the present invention. This is not to be taken as an admission or a suggestion that any ofthe material referred to was published, known or part ofthe common general knowledge in Australia or in any other country as at the priority date of any ofthe claims. 2015252096 10Aug2017

Where tire tenus "comprise", "co'mprises", "comprised" or "comprising" are used in this specification (including the claims) they are to be interpreted as specifying the presence ofthe stated features, integers, steps or components, but not precluding the presence of one or more other features, integers, steps or components, or group thereof.

SUMMARY

The present application describes systems and methods for performing surgical procedures on the spine, including (according to a preferred method) creating an operative conddor to the spine via a substantially lateral, trans-psoas approach. The access described herein is accomplished with a surgical access system including a dilation assembly and a retraction assembly. To create the lateral access corridor to the lumbar spine, the patient is positioned on their side and the S'urgical access system is advanced through an incision, into the retroperitoneal space, and then through the psoas muscle until the targeted spinal site (e.g. the disc space between a pair of adjacent vertebral bodies) is reached. The access system may incl'ude a sequential dilation system ofincreasing diameter and a tissue retractor assembly. The sequential dilation assembly is advanced to the target site first and the retractor assembly is then advanced to the target site over the seq'uential dilation system. Nerve monitoring may be performed while advancing each ofthe dilation system and retraction system to the target site to detect the presence of, and thereby avoid, nerves lying in the trans-psoas path to the target site.

Viewed ftom one aspect, the present invention provides a retractor assembly for creating an operative corridor to a spinal surgical target site, the retractor assembly comprising: a retractor body and a plurality of retractor blades extending generally perpendicularly to the retractor body, the retractor body including a first arm having a first longifirdinal axis and a 3 second arm having a second longitudinal axis, a first retractor blade ofthe plurality of retractor blades being rigidly coupled to a distal end ofthe first arm and a second refiactor blade ofthe plurality of retractor blades being rigidly coupled to a distal end ofthe second arm, the first and second arms being movable apart relative to one another to separate tire plurality of retractor blades and retract tissue away ftom the interior ofthe retractor blades to thereby form an operati've corridor to the surgical target site, the first am being coupled to a first lead screw driven rack and pinion gear operable to splay the first retractor blade such that a distal end ofthe first retractor blade extends wider than a proximal end of tire first retractor blade, the first am incl'uding a first static arm portion and a first rotating am portion, the first lead screw driven rack and pinion gear including a first translating rack gear lroused within tire first static arm portion and threadedly engaged about a first lead screw and a first pinion gear engaged with the first translating rack gear and mechanically linked to the first rotating arm potion, wherein the first pinion gear' r'otates about the first longitudinal axis causing the first rotating arm portion and the first retractor blade rigidly coupled to the first rotating arm portion to rotate about the first longifirdinal axis, and wherein the second arm is coupled to a second lead screw driven rack and pinion gear operable to splay the second retractor blade such that a distal end ofthe second retractor blade extends wider than a proximal end ofthe second retractor blade, the second arm including a second static am portion and a second rotating am portion, the second lead screw driven rack and pinion gear including a second translating rack gear housed within the second static arm portion and threadedly engaged about a second lead screw and a second pinion gear engaged with the second translating rack gear and mechanically linked to the second rotating arm potion, wherein the second pinion gear rotates about the second longitudinal axis causing the second rotating arm portion and the second retractor blade rigidly coupled to the second rotating am portion to rotate about the second longitudinal axis. 2015252096 10Aug2017

In some embodiments, the retoactor assembly includes a plurality of retractor blades, three according to a preferred embodiment, and a body. The retractor assembly is then operated to expand the operative corridor to the desired geometry and dimension. The body may include two arms connected to each other by a pivot. Handle extenders may be attached to the arms and squeezed to cause the cephalad-most and caudal most 3a ٠ arms to move away ؛ram each other and away from the posterior blade (which may 2015252096 lOAug preferably be fixed in position) to expand the operative corridor anteriorly (away ftom the nerves posterior to the posterior blade). The cephalad-most and caudal-most blades may also pivot or splay outward ftom a central axis ofinsertion to expand the operative corridor at the surgcal site without increasing the size of the incision. The retractor assembly may exhibit continuous splay such that splay to any angle (within a predetennined range) may be achieved. The continuous splay is achieved through the use ofa gear mechanism coupled to each arm of the reftactor body. The gear mechanism may be a lead screw driven rack and pinion gear. The rack may ftanslate vertically in the retractor body causing he pinion to rotate. The pinion may be connected to one end ofa rotating arm which is coupled at he opposite end to one ofthe reftactor blades to be splayed. Each ofthe two gear mechanisms (one for each arm 3b of the retractor) may operate independently such that the blades can be adjusted independent of each other. 2015252096 05 Nov 2015

According to one example, the posterior most of the blades may be fixed in position relative to the spine prior to operating the retractor to open the blades. This may be accomplished, for example, by attaching an interdiscal shim to the blade and inserting the distal end ofthe shim into the disc space. Alternatively, or in addition, this may be accomplished by connecting an articulating arm between the surgical table (or other suitable mount) and posterior blade (via a translating arm to which the posterior blade is attached). In this manner, the posterior blade will not move posteriorly towards nerve tissue located in the posterior portion ofthe psoas muscle. Instead, the remaining blades and will move away fiom the posterior blade to expand the access corridor. In addition to the interdiscal shim, blade extenders may be coupled to the cephalad and caudal blades. The extenders may have contoured distal ends to match the anatomy at the anterior ofthe vertebral body.

The retractor assembly may be configured to employ a supplemental anterior retractor blade. The supplemental anterior retractor blade provides for selectively increasing the number of retractor blades forming the operative corridor during (or before) use and prevent tissue creep into the operative corridor fiom the anterior border. The ability to selectively increase the number of retractor blades affords additional user control over the size and/or configuration ofthe access corridor, advantageously increasing the versatility ofretractor assembly. The supplemental anterior retractor blade includes a blade and a handle. A connecting device cooperates with the supplemental blade and the cephalad and caudal blades to hold the supplemental retractor blade in position. The supplemental retractor blade may be manipulated to manually retract tissue anteriorly. Thereafter the connecting element may be engaged to the retractor blades to hold the supplemental blade in place.

The posterior (center) blade may be coupled to the nerve monitoring system to conduct nerve monitoring during advancement ofthe retractor assembly and/or during refiaction. According to a first embodiment, the blade may be formed of a conductive material (e.g. aluminum) and coated with an insulative coating. A stimulation signal utilized for the nerve monitoring may then be transmitted through the blade and exit into the body tissue through an 4 uninsulated electrode on the distal end. A special set screw, which connects the retractor blade to the nerve monitoring system may be utilized to prevent current shunting. The set screw includes a nonconductive lower end which contacts the retractor body, while the threaded section that contacts the redactor blade is conductive. According to a second embodiment, the blade may be configured to receive and couple to a disposable electrode. The disposable electrode may be, by way of example, plastic part with a conductive trace deposited along the length of the disposable electrode. An exposed area ofthe conductive trace at a proximal end of the electrode couples with the nerve monitoring system. An exposed area at the distal end ofthe disposable electrode transmits a stimulation signal from the nerve monitoring system to the tissue adjacent the distal end ofthe retractor blade. The disposable electrode may couple to engagement features formed in the posterior blade. The disposable electrode may be sihrated within a channel formed in the blade. The distal end ofthe posterior blade may include a cut-out that exposes the distal end ofthe disposable elecfrode to tissue posterior to the blade. An intradiscal shim for use with the posterior blade/disposable electrode combination may preferably be coated with an insulative coating to prevent current shunting. 2015252096 05 Nov 2015

BRIEF DESCRIPTION OF THE DRAWINGS

Many advantages ofthe present invention will be apparent to those skilled in the art with a reading of this specification in conjunction with the attached drawings, wherein like reference numerals are applied to like elements and wherein:

Fig. 1 is a Fig. 3 is a top-down view depicting the creation of a lateral access corridor formed with a surgical access system via a lateral approach through the side ofthe patient to the target disc space؛

Fig. 2 is a perspective view of one example of a tissue retraction assembly forming part of a surgical access system, shown in a fiilly retracted or "open" position؛

Fig. 3 is a top perspective view ofthe tissue retraction assembly ofFig. 2, shown in a firlly retracted or "open" position؛ 5

Fig. 4 is a top perspective view ofthe tissue retraction assembiy ofFig. 2 shown in a fully ciosed position؛ 2015252096 05 Nov 2015

Fig. 5 is a perspective view ofthe tissue retraction assembly ofFig. 2 shown in a fillly closed position؛

Fig. 6 is a top view ofthe tissue retraction assembly ofFig. 2 shown in a partially open position؛

Fig. 7 is a perspective view ofthe tissue retraction assembly ofFig. 2 shown in a partially open position؛

Figs. 8-9 are perspective views ofthe ftont side and back side, respectively, of an example of a contoured shim forming part of a surgical access system؛

Fig. 10 is an perspective view ofthe contoured shim ofFig. 8 connected to a retractor blade؛

Figs. 11-12 are front perspective and back perspective views, respectively, of one exanrple of a locking shim forming part of a surgical access system؛

Fig. 13 is a top view ofthe locking shim ofFig. 11؛

Fig. 14 is a perspective view of an example of a shim removal tool؛

Fig. 15 is a perspective view ofthe distal portion ofthe shim removal tool ofFig. 14 engaged with the locking shim ofFig. 11؛

Fig. 16 is a perspective view ofthe distal portion ofthe shim removal tool ofFig. 14؛ 6

Fig. 17 is a perspective view ofthe distal portion ofthe shim removal tool ofFig. 15 with the grip extension removed؛ 2015252096 05 Nov 2015

Fig, 18 is a top plan view ofthe arms ofthe tissue rehaction assembly ofFig. 2؛

Fig. 19 is a bottom plan view ofthe arms ofthe tissue retraction assembly ofFig. 2؛

Fig. 20 is a perspective view of an arm member comprising part ofthe tissue retraction assembly ofFig. 2؛

Figs. 21-24 are exploded and perspective views ofa distal pivot member and gear member forming part ofthe arm member ofFig. 20؛

Fig. 25 is a rear perspective view of an anterior retractor blade forming part ofthe tissue retraction system ofFig. 2؛

Fig. 26 is a ftont perspective view ofthe anterior retractor blade ofFig. 2S؛

Fig. 27 is a top perspective view ofthe anterior retractor blade ofFig. 25؛

Fig. 28 is a perspective view ofthe blade assembly portion ofthe tissue retraction system ofFig. 2 with the anterior retractor blade ofFig. 25 attached thereto؛

Fig. 29 is a front perspective view ofthe blade assembly portion ofthe tissue retraction system ofFig. 2 shown in a firlly closed position؛

Fig. 30 is a top perspective view ofthe blade assembly portion ofFig. 29 shown in a partially open position؛

Fig. 31 A is a perspective view ofa setscrew used to attach the posterior retractor blade to the tissue retraction system ofFig. 2؛ 7

Fig, 31 Bis a side cross section view of the set screw ofFig. 31 A couple to the retractor assembly of Fig, 2؛ 2015252096 05 Nov 2015

Fig, 32 is a top perspective view of a posterior translation mechanism forming part of the tissue retraction system Fig, 2, engaged with a wrench and attachment arm؛

Fig, 33 is a bottom perspective view of the posterior translation mechanism ofFig, 32؛ Fig, 34 is a side perspective view of the posterior translation mechanism ofFig. 32؛

Fig, 35 is a perspective view of the wrench ofFig: 32؛

Figs. 36-38 are side views of the attachment arm ofFig. 32؛

Fig. 39 is a top perspective view of the tissue retraction assembly ofFig. 2 engaged with an attachment arm ofFig, 35؛

Figs. 40-41 are side and perspective views, respectively, of an example of a disposable electrode forming part of the tissue retraction system ofFig, 1؛

Figs. 42-43 are perspective views of an example of a retractor blade forming part of the tissue retraction system ofFig, 1 configured to releasably couple with the disposable elechode of Fig, 41؛

Fig, 44 is top perspective view ofthe retractor blade ofFig. 42؛

Figs. 45-46 are perspective views of an assembly comprising the disposable electrode of Fig, 40 coupled to the retractor blade ofFig. 42؛

Figs. 47-48 are perspective views ofthe tissue retraction assembJy of Fig. 2 including the disposable elechode/blade assembly ofFigs. 45؛ 2015252096 05 Nov 2015

Figs. 49-51 illustrate an example ofan insulated locking shim for use with the center blade forming part ofthe tissue retraction system ofFig. 2 to prevent current shunting ftom the center blade when neurophysiologic monitoring is performed ftom the center blade؛

Figs. 52-55 illustrate an example of a shim removal tool for use with the locking shim of Fig. 49؛

Figs. 56 illustrates a second example of a shim removal tool for use with the locking shim - ofFig. 49؛

Fig. 57 is a perspective view ofan example of a nerve monitoring system programmed to perform nerve monitoring before, during and after the creation ofan operative corridor to a surgical target site using the surgical access system ofFig. 2؛

Fig. 58 is a block diagram ofthe nerve monitoring system shown in Fig. 57؛ and Figs. 59-60 are examples of screen displays illustrating exemplary features and information communicated to a user during the use ofthe nerve monitoring system ofFig. 57.

DETAILED DESCRIPTION

Illustrative embodiments ofthe invention are described below. In the interest of clarity, not all feahires ofan achral implementation are described in this specification. It will of course be appreciated that in the development of any such achral embodiment, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which will vary ftom one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for 9 those of ordinary skill in the art having the benefit of this disclosure. It is forthermore to be readily understood that, although discussed below primarily within the context of spinal surgery, the surgical access system of the present invention may be employed in any number of anatomical settings to provide access to any number of different surgical target sites throughout the body. It is also expressly noted that, although shown and described herein largely within the context of a preferred lateral surgery in the lumbar spine, some or all of the components of the access system described may be employed in any number of other spine surgery access approaches. By way of example, in addition to accessing a lumbar disc space (e.g. for firsion, total disc replacement, colectomy, etc...), the surgical access system or some of its components may be used to access the lateral aspect ofthe thoracic spine (e.g. for firsion, total disc replacement, corpectomey, etc...), and foe posterior spine (e.g. for posterior decompression). By way of fijrther example, it is contemplated that the surgical access system or some ofits components may be used to access any ofthe posterior, postero-lateral, anterior, and anterolateral aspects ofthe spine, and maybe employ«! in the lumbar, thoracic and/or cervical spine. 2015252096 05 Nov 2015

The instruments and methods described herein are designed and optimized for creating a lateral access corridor to foe lumbar spine. Accessing the targeted spinal site through foe lateral access corridor avoids a number of disadvantages associated with posterior access (e.g. cutting through back musculafore and possible need to reduce or cut away part ofthe posterior bony structures like lamina, fecets, and spinous process) and anterior access (e.g. use of an access surgeon to move various organs and blood vessels out ofthe way in order to reach the target site). According to one example, the lateral access approacli to the targeted spinal space may be performed according to the methods described in US Patent 7,207,949 entitled “Surgical Access System and Related Methods," and/or US Patent 7,905,840 entitled “Surgical Access System and Related Methods,” the entire contents of which are each inco^orated herein by reference as if set forth herein in their entireties.

With reference to Figs. 1-2, a discussion ofthe lateral access methods is provided in brief detail. With the patient 1 positioned on their side, a surgical access system 6 is advanced through an incision 2, into the retroperitoneal space 3, and then through the psoas muscle 4 until 10 the targeted spinal site (e.g. the disc space 5 between a pair of adjacent vertebral bodies) is reached. The access system 6 may include at least one tissue dilator, and preferably includes a sequential dilation system 7 with an initial dilator 8 and one or more additional dilators 9 of increasing diameter, and a tissue refractor assembly 10. As will be appreciated, the initial dilator 8 is preferably advanced to the target site first, and then each ofthe additional dilators 9 of increasing diameter are advanced in turn over the previous dilator. A k-wire (not shown) may be advanced to the target site and docked in place (for example, by inserting the k-wire into the vertebral disc) prior to, in concurrence with, or after advancing the initial dilator 8 to the target site. With the sequential dilation system 7 positioned adjacent the target site (and optionally docked in place via the k-wire), the refractor assembly 10 is then advanced to the target site over the sequential dilation system 7. 2015252096 05 Nov 2015

According to the embodiment shown, the refractor assembly 10 includes retractor blades 12, 16, 18 and a body 20. According to the preferred method, the refractor assembly 10 is advanced over the dilation system 7 such that the center refractor blade 12 is the posterior most blade. The sequential dilation system 7 is removed and the refractor assembly 10 is operated to expand the operative corridor. That is, the retractor blades 12, 16, and 18 are separated (Fig. 1), providing the lateral access corridor through which instniments and implants may be advance! to the target site. It will be appreciated that any number of procedures may be perfonned on the spine through the lateral access corcidor (e.g. the surgeon may perform a firsion procedure, a total disc replacement, a colectomy, etc...). According to one example, foe posterior blade 12 may be fixed in position relative to the spine prior to opening the refractor blades. This may be accomplished, for example by attaching a shim to the blade (e.g. via a blade frack including dove tail grooves fomed on the interior ofblade) and inserting the distal end ofthe shim into the disc space. Alternatively, or in addition, the posterior blade 12 may be fixed in position by connecting an articulating am between the surgical table (or other suitable mount) and the translating arm associated with the center blade 12). In this manner, the posterior blade 12 will not move posteriorly (towards nerve tissue located in the posterior portion ofthe psoas muscle). Instead, the blades 16 and 18 will move away fiom the posterior blade 12 to expand the access condor. "

Additi.nally, nerve monitoring (including determining nerve proximity and optionally directionality) is preferably perfomied as each component of the access system 6 is advanced through he psoas muscle, protecting the delicate nerve tissue nmning through the psoas, as described in the ‘949 patent and ‘668 application. Monitoring the proximity of nerves not only allows the surgeon to avoid delicate nerves as the access system is advanced to the spine, but by determining the location of the nerves also allows the surgeon to position the posterior blade more posterior (e.g. all the way back to the exiting nerve roots), thus exposing a greater portion of toe target site than would otherwise be safely achievable. 2015252096 05 Nov 2015

With the lateral access corridor formed the target site may be operated on. For example, when performing a ftrsion procedure through the lateal access corridor, the disc space 5 may prepped for insertion of an implant. Preparation of the disc space may include performing an annulotomy, removal of disc material, and abrasion of the endplates, and instruments such as annulotomy knives, pitoitaries, curettes, disc cutters, endplate scrapers may be used. An implant may be inserted into the disc space. Fusion promoting materials may be implanted within foe disc space 5 in and around foe implant. Fixation may be perfomied through foe lateral access condor, or through different approaches.

The retraction assembly described lierein is well suited for creating the lateral access corridor to the lumbar spine as described above. Figs. 2-7 illustrate a tissue retraction assembly 10 foming part of a surgical access system according to the present invention, including a plurality of retractor blades 12, 16, 18 extending from a body 20. By way of example only, the body 20 is provided with a first refractor blade 12, a second retractor blade 16, and a third retractor blade 18. Fig. 2 illusfrates the tissue retraction assembly 10 in a frilly retracted or “open” configuration, with the retractor blades 12, 16, 18 positioned a distance from one another so as to form an operative corridor 15 therebefiveen which extends to a surgical target site (e.g. an annulus of an intervertebral disc). In one exemplary aspect, the blades 16, 18 are capable of being pivoted or rotated relative to foe handle 20, as best appreciated with .combined reference to Figs. 2 & 3. Figs. 4-5 show the tissue refraction assembly 10 in an initial “closed" configuration, with the retractor blades 12, 16, 18 generally abutting one another. Figs. 6-7 show the tissue retraction assembly 10 in a “partially open” configuration. 12

The body 20 may be coupled to any number of mechanisms for rigidly registering the body 20 in fixed relation to the operative site, such as through foe use of an articulating am mounted to the operating table (not showm). The body 20 includes first and second am members 26, 28 hingedly coupled via coupling mechanism shown generally at 30. The second retractor blade 16 is rigidly coupled (generally perpendicularly) to the end of the first arm member 26. 2015252096 05 Nov 2015

The third retractor blade 18 is rigidly coupled (generally perpendicularly) to the end of the second am member 28. The first retractor blade 12 is rigidly coupled (generally perpendicularly to) a translating member 17, which is coupled to the body 20 via a linkage assembly shown generally at 14. The linkage assembly 14 includes a roller member 34 having a pair of manual knob members 36 which, when rotated via manual actuation by a user, causes teefo 35 on the roller member 34 to engage within ratchet-like grooves 37 in the toanslating member 17. Thus, manual operation of the knobs 36 causes the translating member 17 to move relative to the first and second am members 26, 28.

Through the use ofhandle extenders 31,33, foe arms 26,28 maybe simultaneously opened such that the second and foird retractor blades 16, 18 move away from one another. In this fashion, the dimension and/or shape of the operative condor 15 may be tailor^ depending upon the degree to whicli the translating member 17 is manipulated relative to the arms 26, 28. That is, the operative coriidor 15 may be tailored to provide any nmnber of suitable cross-sectional shapes, including but not limited to a generally circular cross-section, a generally ellipsoidal cross-section, a generally triangular cross-section, and/or an oval cross-section. Optional light emitting devices (not shown) may be coupled to one or more of the retractor blades 12, 16, 18 to direct light down the operative corridor 15.

The retractor blades 12,16, 18 may be composed of any rigid matCTial suitable for inttoduction into or aroimd the human body, including but not limits to aluminum, titanium, stainless steel, and/or clear polycarbonate, that would ensure rigidity during tissue disttaction.

The retractor blades 12, 16, 18 maybe optionally coated with a carbon fiber reinforced coating to increase strength and durability. The retractor blades 12,16, 18 may be optionally constructed from partially or wholly radiolucent materials (e.g. aluminum, PEEK, carbon-fiber) to improve 13 the visibility of the surgeon during imaging (e.g. radiographic, MRI, CT, fluoroscope, etc.). Likewise, the retractor body may be composed of any number of rigid materials, particularly including, but not limit«! to aluminum, stainless steel, carbon-fiber, and titanium. According to a preferred embodiment, the retractor blades 12,16, and 18 and body are comprised of stainless steel. The stainless steel has a greater stiffiress than otlier more radiolucent materials (e.g. aluminum) and thus eliminates, or at least reduces, toeing inward (blade flex) of the blades and potential intraoperative breakage, lie the stainless steel does not have the radiolucent characteristics of other materials often used for spinal refractors, the added stiffhess (in addition to the design of the blade rotation gear 79) pennits the body to be constnrcted with less material. Thus cutouts through the body and reduced geometry of the body permit fluoroscopic visibility through the refractor assembly 10 where necessary, without sacrificing the sfrength and stiffoess of the retractor. By way of example only, the cutouts 17a and 17b and indents 17c ofthe translating arm 17 allow optimal visualization of pertinent areas (e.g. posterior border ofthe vertebral bodies in a lateral fluoroscopy image) without sacrificing stiffiiess. The refractor blades 12, 16, 18 may be provided in any number of suitable lengths, depending upon the anatomical environment and surgical approach, such as (for example) the range from 20 mm to 180 mm. Based on this range of sizes, the tissue refraction assembly 10 ofthe present invention is extremely versatile and maybe employed in any of a variety of desired surgical approaches, including but not limited to lateral, posterior, postero-lateral, anterior, and anterolateral, by simply selecting the desired size retractor blades 12, 16, 18 and attaching them to the body 20 as will be described herein. 2015252096 05 Nov 2015

The retractor blades 12, 16, 18 may be equipped with various additional feafores or components. By way of example only, one or more ofthe retractor blades 12, 16, 18 maybe equipped with a shim, such as a contoured extender shim 22 or a locking shim 25 as shown in Figs. 8-13. In a preferred embodiment, the contoured extender shims 22 are suitable for engagement with foe caudal/cephalad refractor blades 16, 18, while the interdiscal locking shim 25 is suitable for engagement with the center blade 12. However, it should be noted that any shim 22, 25 may be used with any blade 12, 16, 18 without departing from the scope ofthe present invention. Refertng to Figs. 8-10, the contoured extender shim 22 extends from refractor blades 16, 18 (as shown on one refractor blade 18 in Fig. 10) to form a protective barter 14 to prevent the ingress or egress of instalments or biological strucfiires (e.g. nerves, vasculafiire, etc.) into or out of the operative corridor 15. By way of example only, the contoured extender shim 22 includes a front face configured to form a portion of the operative corridor and having a generally concave surface 300. The contoured extender shim 22 filrther includes a back surface 302 configured to face the retractor blade 18 and having a generally convex shape. The contoured extender shim 22 filrther has a pair of elongated tab members 304 that are configured to slideably engage elongated slot members 306 that nin the length of the inside surface of foe retractor blade 18. The contour^ extender shim 22 filrther includes a deflectable tab 308 near the proximal end of the contour extender 22. The deflectable tab 308 includes a knob 310 extending away from the deflectable tab 308 on the back side of the contoured extender shim 22. The knob 310 is configured to engage with indentations 312 positioned along the retractor blade 18 to provide for a lock-stop mechanism securing the contoured extender shim 22 in position during use. In this fashion the contoured extender shim 22 is advanced distally along the refractor blade 18 until a desired position has been reach«!. The contoured distal end of the contoured extender shim 22 is shaped to conform to the vertebral body to maximize rontact with the vertebral body, particularly near the anterior drop, and prevent tissue creep into the exposure. For example, the distal end may have a curved surface such that one longitudinal edge of the contoured extender shim 22 is longer than the other longitudinal edge. For example, the geomefry of the distal end 23 allows it to contour to the anterior drop off of the vertebral body as the retractor is opened anteriorly. 2015252096 05 Nov 2015

Refetang to Figs. 11-13, the locking interdiscal shim 25 has a distal tapered region 45 which may be advanced into the disc space for the purpose of distracting the adjacent vertebral bodies (thereby restoring disc height) and/or anchoring the blade 12 relative to foe spine. In similar fashion to the contoured extender-shim 22, the locking interdiscal shim 25 also forms a protective bataer to prevent the ingress or egress of instalments or biological stnictures (e.g. nerves, vasculahire, etc.) into or out of the operative corridor 15. The locking interdiscal shim 25 locks in position on the refractor blade 12 to prevent the shim fiom dislodging and allowing the refractor to move from the targeted location. To lock position on the blade, the shim 25 has a flexible engagement tab 320 wifo a ramped leading edge 49 that allows it to advance down indentations 312 on the inner surface ofthe retractor blade 12. The trailing edge 27 of the 15 engagement tab 320 is squared t. prevent disengagement (thus preventing unwanted back.ut of the shim) ftom the indentation 312 without use of a removal tool 43. The engagement tab 320 also includes a T-shaped removal lip 55 configured to engage a shim removal tool, as described below. The T-shaped lip 55 of the engagement tab 320 allows the removal tool 43 to lift the square lip 27 away from the retractor blade 12 and remove the shim 25. The locking interdiscal shim 25 has a pair of elongated tab members 322 that are configured to slideably engage elongated slot members 306 that run the length ofthe inside surface of the retractor blade 12. 2015252096 05 Nov 2015

The locking interdiscal shim 25 includes a dimple or aperhire 56 located near the proximal end ofthe shim 25 configured for engagement with a shim removal tool, as will be explained in filrther detail below.

Figs. 14-17 illustoate an example of a shim removal tool 43 for extracting the locking interdiscal shim 25 from a retractor blade 12, which in the example provided resembles a Kerrison-style removal tool. By way of example only, removal tool 43 is shown and described herein in conjunction with locking interdiscal shim 25, although it is to be readily appreciated that removal tool 43 may be employed in a similar manner with other locking shims witliout departing from the scope ofthe present invention. The removal tool 43 includes a squeezable handle 46, an elongated region 47 including a stationary arm 330 and a translating ami 332, and a distal end 48. The squeezable handle 46 includes a front handle 46a and back handle 46b. The front handle 46a is pivotably connected to the translating arm 332, while the back handle 46b is immovably connected to the stationary arm 330. The distal end 48 includes a grip extension 334 configure to interact with both the refractor blade 12 and the interdiscal locking shim 25. The grip extension 334 includes a track guide 336 that slideably engages the elongated slot members 306 as describe above in relation the shims 22, 25. The distal end ofthe grip extension 334 includes a pair of arms 338 extending distally from the grip extension 334 in a generally parallel fashion. The anns 338 include a ramped surface 340 sloped such that the thickness ofthe arms 338 at their distal ends is considerably less than the thickness ofthe arms 338 at their proximal ends where they extend from the grip extension 334. The ramped surface 340 may be planar or have a concave curvaftire without departing from the scope ofthe present invention. The distal end ofthe translating am 332 includes a translating plate 342. The translating plate is generally planar and includes a dimple or recess 344 positioned on the lower surface 346 ofthe ' 16 plate 342. The recess 344 is configured to receive a locking ball 348 when the removal tool 43 is in a neutral position (i.e. when the handles 46a, 46b are released). 2015252096 05 Nov 2015

To use the removal tool 43, the distal end 43 including the grip extension 334 is slideably advanced along the retractor blade 12 with the handle 46 in the neutral position until the ramped anns 338 engage the removal lip 55 of the shhn 25. When the handle 46 is in the neutral position, the locking ball 348 retreats into the recess 344 of the translating plate 342 allowing the distal end 48 of the grip extension 334 to engage flush with the shim 25. len he ramped arms 338 engage the removal lip 55 ofthe interdiscal locking shim 25, the lip 55 is deflected outward lifting the engagement tab 320 away fiom the refractor blade 12. Simultaneously, the locking ball becomes positioned in the aperfrre 56 ofthe locking shim 25. Squeezing the front handle 46a causes the translating arm 332 to slideably franslate forward relative to the stationary arm 330. This translates the position ofthe rec٠ess 344 on the translating plate 342 such that the locking ball 348 is prevented from entering flie recess 344. With the locking ball positioned within aperfore 56, the removal tool 43 is now locked to the locking shim 25 such that the shim 25 may be removed by applying a force in a proximal direction relative to the refractor blade 12. Thus, squeezing the removal tool handle 46 locks the distal end 48 to foe interdiscal locking shim 25 while disengaging the the lip 55 ofthe engagement tab 320 from foe indentation.312 of foe refractor blade 12, enabling the user to pull up and remove the shim.

Shim elements 22, 25 may be made from any rigid material suitable for use in the human body, including but not limited to biologically compatible plastic and/or metal (such as aluminum, PEEK, carbon-fibers and titanium). According to one example, the extendCT shims 22 maybe made from plastic and the interdiscal shim 25 may be made of metal. The interdiscal shim 25 may also be coated with an insulative coating (e.g. a parylene coating) to prevent cufrent shunting or density changes from electrodes sifoated at foe distal end ofthe retractor blade 12. Retractor extender shim 22 may have symmetric narrow configurations (FIGS. 8-9), which do not extend laterally from the refractor blade, and/or broad configurations (not shown) that extend laterally from each side ofthe retractor blade, and/or an asymmefric configuration (not shown) whicli extends laterally from one side ofthe retractor blade. The shim elements 22, 25 may be composed of a material that would destruct when autoclaved (such as polymer containing a 17 porti.n ofgJass particles), which may be advantageous in preventing the imauthorized re-use of the retractor extender shim 22 and/or the shim element 25 (which would be provided to the user in a sterile state). 2015252096 05 Nov 2015

Referring now to Figs. 18-24, the mechanisms associated with the ann members 26,28 will be discuss^ in forther detail. Although the inventive features will be discussed in relation to the first aim member 26 only, it should be understood that the second arm member 28 is virttially a minor image of the firet ann member 26 such that feahires shown and described with respect to the first arm member 26 may be present with respect to the second ann member 28 without departing ftom the scope of the present invention. Referring first to Figs. 18-19, the distal region ofthe body 20 is shown in greater detail. Each ann member 26, 28 includes a distal pivot member 70 and a proximal arm portion 71. Referring also to Fig. 20, which shows the first am member 26 in greater detail, the distal pivot member 70 extends distally from the proximal am portion 71 and includes portions ofthe rotating gear mechanism 79 (described in detail below) housed within the proximal arm portion 71. This position ofthe gear mechanism proximal to the retractor blades and operative corridor allows the blades to be splayed without inhibiting visualization ofthe condor during adjustaent. The proximal am portion 71 includes a coupling aperture 72 through which the coupling element 30 passes, a proximal attachment region 74 at which handle extender 31 may be attached, an aperture 76 tlirough which knob 36 passes, and a gear aperture 352 configured to allow passage ofthe upper cap 364 and post head 374 ofthe gear mechanism 79 to allow for accessibility of post head 374 to impart rotation ofthe rettactor blades. The body 20 fiirther includes a restrictor element 97 formed by portions ofthe distal pivot member 70 and the proximal portion 71 working in concert to restrict the degree of allowable angulation for the rettactor blades. At the distal end ofthe distal pivot member 70 is a blade aperture 78 and a screw aperftrre 80. The blade aperture 78 is configured to receive an attachment post ofthe rettactor blade 16, 18 to couple the blade to the body 20. The screw aperttire 80 threadably receives a setscrew 350 for revCTsibly securing the rettactor blade 16, 18 to the body 20. Translating member 17 is shown by way of example only as having a large viewing aperture 17a which fimctions to increase visibility during fluoroscopy. 18

Figs. 2J-24 illustrate and example of the gear mechanism 79 of the distal pivot member 70 in greater detail. The gear mechanism generally comprises a lead screw driven rack and pinion gear including a translating rack (translating gear 360) and a section gear rotating pinion (rotating gear 368). By way of specific exajnple, the gear meclianism 79 includes a tianslating gear 360, an lead screw 362, an upper cap 364, a lower cap 366 and a rotation gear 368. The translating gear 360 includes a central threaded apermre 370 extending therethrough and gear teeth 372 orient^ generally horizontally on tire outside surface. The lead screw 362 includes post head 374, a thread^ region 376, a circumferential ridge 378 positioned between the post head 374 and the threaded region 376, and a ηοη-threaded foot 380. The post head 374 may be configured in any shape desirable to engage a rotation tool to effect rotation of the lead screw, including but not limited to the hexagonal shape shown by way of example only in. Fig. 21. The threaded region 376 is configure to engage with the threaded aperture 370 of the tianslating gear 374. As will be described in detail below, during operation the tianslating gear 360 translates linearly along the threaded region 376 of the lead screw 362. The upper cap 364 has a generally circular cross-section and includes a cential open aperture 382 configured to receive the post head 374 therethrough and circumferential threads 384 configured to threadedly secure the uppCT cap 354 to the ami member 26. The lower cap 366 includes a cential closed aperture 386 configured to receive the foot 380 of the lead screw 362 therein and circumferential threads 388 configured to threadedly secure the lower cap 366 to the first arm member 26. The rotation gear 368 includes at least one horizontal gear tooth 390 extending laterally therefrom and a connector post 392 extending distally tlierefrom. The horizontal gear tooth 390 engages with the gear teetli 372 of the tianslating gear 360. The connector post 392 is received within an aperdire 394 within the distal pivot member 70. A pin 396 is filrther provided to secure the connector post 392 to the distal pivot member 70. 2015252096 05 Nov 2015

In use, a user engages a rotation tool to the post head 374 and rotates in a clockwise direction. This causes the lead screw 376 to rotate. According to one example, the rotation tool may include a torque limiting feahire to prevent loading of the retiactor blades should they become stirck on bone (e.g. osteophjrtes) or features. The lead screw 374 bottoms out in the closed apertiire 386 ofthe lower cap 366. The ridge 378 engages with the lower surface ofAe upper cap 364 ensuring that the lead screw 374 is only able to rotate without any translational 19 movement. Due to the threaded engagement with the translating gear 360, rotation of the lead screw 362 causes the translating gear 360 to translate linearly along he lead screw. Interaction between the gear teeth 372 of the translating gear 360 and the gear teeth 390 ofthe rotating gear 368 cause the rotating gear 368 to rotate. Because the rotation gear 368 is securely fastened to the distal pivot member 70 via the interface between the connector post 392 and aperture 394, this action in turn causes the distal pivot member 70 to pivot. Fig. 24 illustrates the directional movement ofthe various parts. 2015252096 05 Nov 2015

The distal pivot member 70 includes an extension 398 in whicli the apeirtire 394 is located, and a recess 400 extending partially around the outside edge ofthe distal pivot member 70. The recess 400 foims part ofthe restrictor element 97 and is wider than the corresponding extension on the aim 26 that it receives therein. When the distal pivot member 70 rotates, contact between the extension and the wall ofthe recess 400 prevents filrther movement. Thus, the size ofthe recess 400 and/or extension can be set such that blade splay or rotation is contained within a desired range. By way of example only, this range may be beriveen 0 and 20 degrees. However, a larger range of angulation may be possible without departing from the scope ofthe invention, for example range of 0-30 degrees and 0-45 degrees are also contemplated.

Initially, the retractor assembly 10 ofthe present invention is introduced to the surgical target site with the retractor blades 12,16, 18 in a first, folly closed position (shown generally in Figs. 4-5). In this configuration, the refractor blades 16, 18 are oriented in a generally perpendicular configuration. In some instances it may be desirable to pivot either the second refractor blade 16 or the third refractor blade 18 (or both) ourivard in order to increase the volume ofthe operative corridor 15 (by increasing the distal dimension ofthe operative corridor). To accomplish this (with respect to blatle 16), a female hexagonal driver is engaged to the post head 374 offiret arm 26. When the post head 374 is rotated in a clockwise direction, foe blade 16 will pivot in a latCTal (outward) direction. When rotating the post head 374 in a counter-clockwise direction, the blade 16 will pivot a lateral (inward) direction. The blade splay mechanism 79 employed provides for continuous splay (i.e. may be splayed to any angulation from 0 degrees to’ a maximum pennissible angulation). According to the preferred example, a 20 restrictor element 97 prevents angulation above a maximum permissible angle. For example, the maximum permissible angle may be 20 degrees. The restrictor element may also permit the blade from splaying inward past 0 degrees. 2015252096 05 Nov 2015

The blade 18 may be pivoted independently ofblade 16 such that different angles for each blade 16,18 are achieved. Thus, it may be desirable to use blades of differing lengths and still maintain a symmetrical operating condor wherein the distal ends ofblades 16,18 are oriented along the same general plane. Before removing the tissue retraction system 10 from foe operative corridor, the post head 374 should be rotated in a counter-clockwise direction, allowing the retractor blade 16 to reform to their initial alignment (i.e., generally pe^endicular to the handle 20) to focilitate removal. It will be appreciated that the dfrection of rotation could be reversed by simply reversing the thread direction on the acforating screw and translation gear. Furthermore, although the upper cap 364 and Iowct cap 366 have been describe as being secured to the arm 26 via a threaded engagement, any type of engagement is possible, including but not limited to welding, press-fit, and the like.

Referring to Figs. 25-28, a supplemental anterior retractor blade 60 may be provided for optional use with the tissue refoaction assembly 10 described lierein. Supplemental anterior refoactor blade 60 provides for selectively increasing the number of retractor blades fonning the operative corridor during (or before) use. The ability to selectivelj' increase the number of refractor blades affords additional user control over the size and/or configuration ofthe access corcidor, advantageously increasing the versatility of retractor assembly 10. Although supplemental anterior retractor blade 60 is shown and described herein in use with a three-bladed configuration ofthe retractor assembly 10 (thereby comprising a fourth retractor blade as referenced herein), it is to be readily appreciated that foe supplemental anterior retractor blade 60 may be used with a retractor assembly 10 configured with any number of primary refractor blades.

As illustrated in Figs. 25-28, supplemental anterior retractor blade 60 comprises a handle 61, a connecting device 62, a grooved area 64, and a blade 63. The supplemental anterior retractor blade 60 is connected to retractor blades 16, 18. Tire connecting device 62 slidably 21 interlocks with the holding knobs 19 (Figs. 29-30), and the retractor blades 16,18 can move freely (i.e., “open” and "close") while the connecting device 62 remains interlocked with the holding knobs 19. The wi’der end of the holding knobs 19 prevent the connecting device 62 from becoming disconnected. The grooved area 64 of the anterior retractor blade 60 interlocks with the connecting device at the desired depth. The anterior retractor blade may be made from any rigid material suitable for use in the human body, including but not limited to biologically compatible plastic and/or metal (such as aluminum, PEEK, carbon-fibers, stainless steel, and titanium). The anterior retractor blade 60 may be provided in any number of suitable lengths, depending upon the anatomical environment, surgical approach, and length of primary retractor blades 12, 16, 18, such as (by way of example only) the range from 20 mm to 180 mm. 2015252096 05 Nov 2015

With reference to FIG. 2, a prefoned method of using supplemental blade assembly 60 in conjunction with refractor assembly 10 is shown. The retractor assembly 10 is first advanced to the target site (after tissue distraction) and an initial operating corridor is formed according to the methods described above (i.e. moving retractor blades 16, 18 from a “closed” position to a “retracted” position). Once the operating corcidor is created with primary refractor blades 12,16, 18, the supplemental anterior refractor blade 60 may be utilized to expand the operating corridor and/or provide an extra ba^er to prevent ingress ofbody tissue into the corridor. To do so, the connecting device 62 is slidably secured onto the holding knobs 19, and the grooved area 64 then interlocks with the connecting device. This., along with the pressine of the tissue, holds the anterior refractor blade in position. Preferably, when refracting foe tissue, the connecting device 62 is used as a folcrum and the handle 61 is pulled like a lever inward (i.e., towards the refractor assembly 10) and the distal end of the blade will pivot at an outward angle along foe x-axis.

Figs. 32-35 illusfrate an example of a contemplated alternative embodiment to foe franslating arm 17 which could be replace the franslating arm 17 on the retractor assembly 10. The alternative translating arm 91 foms a posterior translation mechanism 90, illusfrate in Figs. 32-35. The posterior translation mechanism 90 permits controlled posterior translation when desired, wifoout the compromising the position of foe refractor body in other directions (i.e., caudal-cephalad alignment). By way of example only, foe posterior translation mechanism 90 allows for foe surgeon to change the position ofthe blade assembly 21 inside of the surgical site 22 without changing the size of the incision. The wrench 93 secures onto the hexagonal locknut 92 at the distal end, which is a female hexagonal shape 94. Turning the wrench handle 95 clockwise loosens the hexagonal locknut 92, which loosens the connection between the center translating arm 91 and the articulating arm attachment 96. This allows the refractor assembly 10 to be posteriorly franslated up to a maximum length of he posterior translation slot (e.g. up to 10 mm in this example) witii respect to the articulating ann attachment 96 by pulling the refractor assembly 10 posteriorly. The hexagonal locknut 92 must be fastened after posterior translation. Thus, ifa surgeon loses alignment during surgery, he or she can realign the refractor assembly 10 posteriorly with ease and safety. 2015252096 05 Nov 2015

Figs. 36-39 illusfrate an example of an articulating arm attachment 100 according to one embodiment of the present invention. The articulating arm attachment 100 includes a quick align feattire for preliminary engagement ofa toothed connector. This feattire provides foe physician with the means to properly and securely align the teeth (i.e., peaks and valleys) of the connector for intersection single handledly. This feattire avoids locking the connectors together before their teeth are properly aligned. This can happen when the teeth become worn and it is more difficult to align the peeks of one connector in the valleys of the other connector.

The quick align articulating ann attacliment 100 comprises a superior tooth«! connector 101, an inferior toothed connector 102, a post 103, and a canted coil ring 104. The canted coil ringl04 rests snugly inside a groove formed in the inferior connector 102. The post 103 screws into and locks onto the inside of the superior connector 101. The post 103 contains a thicker distal end. When connecting toothed connectors 101, 102, the distal end of the post 103 pushes through the canted coil ringl04, which expands to allow the distal end of the post 103 to pass through, and tlien contracts where the post 103 tapers into a groove 107 (Fig. 38). ^en the post 103 is pushed through the canted coil ringl04, and the coil confracts, the Connectore 101, 102 are semi-secured in place. The post 103 is of the proper length that it will only be semi-secured in place when the teeth of the connectors are properly aligned. The connectors 101, 102 can be disconnected (i.e.) pull the post 103 out of the canted coil ringl04) with a moderate effort. By way of example only, to connect the arm attachment 96, the knob 106, which connects to an elongated screw 105, secures the arm attachment to the assembly by screwing the screw 105 into 23 the inferior connector 102, which contains grooves that the screw 105 secures into. While shown for use with an articulating arm and the tootlied connector assembly of the retractor assembly 10, foe quick align connector 100 is suitable for use with any toothed connector assembly. 2015252096 05 Nov 2015

As mention«! above, nerve monitoring may be utiliz«! during advancement and retraction of the refraction assemblyio. According to one example, as picture in Fig. 29, the nerve monitoring component of the refractor system is the center refractor blade 12, which may be made of a conductive material (e.g. aluminum) and coated with a insulative coating to direct stimulation from the nerve monitoring system to the tissue adjacent the distal end. To direct stimulation to foe posterior blade 12, a stimulation clip 550 of foe nei^e monitoring system may be connect«! to the set screw 13 US«1 to couple the posteior blade 12 to the translating arm 17. When a stimulation signal is emitt«! from foe stimulation clip 550 it will travel through foe set screw 13 and into the blade through an uninsulated contact region with foe blade. In order to reduce shunting of current between foe set screw and refractor body 20 a special set screw 760 which is confined to reduce shunting of elecfrical current through foe retractor body, as illustrated in Figs. 31Α and 31Β. The setscrew 760 has a composite (e.g. PEEK) contact surface 762 where the setscrew 760 engages the retractor body, and a metal contact surfact 764 where the setscrew 760 engages the stimulation clip 550. This isolates foe electrical current deliveed to the center blade 12 through a stimulation clip 550 to the refractor blade 12 and prevents shunting of the current through the refractor body. As described above, the blade is generally insulate based on the anodized aluminum construction. The retractor body which has a DSC coating is not insulated. Thus the center blade 12 itself insulates the current from the retractor body at all points of contact except the setsCTew 760. The peek component 762 at the bottom of the setscrew 760 accomplishes this.

According to anofoer example embotliment, picfored in Figs. 40-48 the nerve monitoring components of the tissue refraction assembly includes 2 main components: a disposable electrode 450 and a center (posterior) blade 500, that replaces the center blade 12, designed to couple to the disposable elecfrode 450. A stimulation clip 550 may be used to connect foe disposable electtode to the nerve monitoring system. One potential advantage of the disposable electrode and accompanying center blade is foe increased ability to attain consistent and repeatable nerve 24 monitoring fonctionality throughout the course of a single surgery and from surgery to surgery (since there is no risk of erosion of the insulative coating on the blade which can lead to current shunting). Two potential bamiers to achieving this consistent and repeatable fonctionality are current shunting and reductions in curTent density at the distal end of an electrode which can potentially affect the sensitivity of nerve monitoring equipment as a result of conductive metallic devices in the immediate vicinity of the distal tip of the stimulating electrodes. To combat this potential, a locking intradiscal shim (similar to the shims in Figs. 11-13) with an insulative coating has been developed as a novel solution. By way of the example the insulative coating may be a parylene coating. 2015252096 05 Nov 2015

Figs. 40-48 illustrate an example of one embodiment of the removably couplable disposable electrode 450 and retractor blade 500 for use with the tissue retraction assembly 10 according to the present invention. The disposable electrode 450 assists in the detection of nerves during insertion and positioning of the tissue retraction assembly within the operative corridor and surgical target site, as described above (similar to the electrodes 23). Using a disposable electrode pennits the retractor blade 500 to be sterilize and reused endlessly without the possibility of degradation to the electrode. This in forn ensures that results from nerve monitoring using the electrode are consistent and reduces potentially high costs ofreplacing the entire blade stnictirre if the electiode (or insulating regions surrounding the electrode) degrade.

Figs. 40-41 illustrate one example of a disposable electrode 450 that includes a molded plastic part with a conductive tiace 451 deposited generally along the length of the disposable electrode 450. Preferably, foe disposable electrode 450 is made out of a generally stiff material that can also withstand bending without breaking, such as, for example, PVC. The conductive trace 451 provides a conductive pathway for the delivery of current from a current delivery source (such as a stimulation clip 550) to the distal end of the disposable electrode 450. There are generally two areas along the disposable electiode where the conductive trace 451 is exposed for enabling foe delivery of current to and from the disposable electiode 450. By way of example, foe proximal end of the disposable electiode 450 has a first exposed area 452 which allows a current delivery source to deliver an electric current to the conductive tiace 451. The first exposed area 452 may wrap around the circumference of the proximal end of the disposable 25 electrode 450 to ensure a conductive path between the disposable electrode 450 and a cuiTent delivery device (such as, for example, a stimulation clip 550). The distal end of the disposable electrode 450 has a second exposed area 453 (shown by way of example as a triangular patch) for emission of the electric cuirent from the distal end of foe disposable electrode 450. Other than foe exposed areas 452, 453, the remainder of the conductive trace 451 is insulated with a dielectric roating to prevent current shunting. Any number of conductive materials suiteble for completing the current pathway, such as, for example, silvCT, or copper may be used in the conductive frace 451 witliout departing from the scope of the present invention. 2015252096 05 Nov 2015

The firet exposed area 452 of the disposable electrode may have a generally cylindrical shape for focilitating the connection between the electoode and a nerve monitoring system. For example, as shown in Figs. 47.48, an electrical coupler is shown in foe form ofa plunger clip. Although shown as cylindrical, the connection site for a current delivery device may be any size and shape necessary for making a quality electrical connection wifoout departing from the scope of the present invention. The remainder ofthe body of the disposable electrode 450 may be generally flat with minimal thickness and a variety offeattires for engaging and securing the disposable electrode 450 to a retractor blade 500. For example, wings 455 may extend fiom the sides ofthe disposable electrode 450 for engaging positioning featares within the retractor blade 500, as will be discuss^ in more detail below. Additionally, the distal end ofthe disposable elecfrode 450 may have a ledge 456 for engaging a feafore ofthe retractor blade 500 for fiirther secure positioning ofthe disposable electrode 450 relative to the retractor blade 500, as will also be discussed in more detail below. A single sized disposable electrode 450 is designed to be used with a variety of retractor blade 500 sizes and shapes (for example, refractor blade lengths generally ranging from 20 to 180 mm), but the disposable electrodes may also be available in a variety of shapes and sizes.

Figs. 45-46 illustrate one example assembly ofa disposable elecfrode 450 releasably coupled to refractor blade 500. Preferably, at least the posterior blade is configured to enable the coupling ofa disposable electrode 450. During assembly ofthe disposable elecfrode 450 to the retractor blade 500, the proximal end ofthe disposable elecfrode 450 (more specifically, adjacent the first exposed area 452 end ofthe disposable elecfrode 450) is inserted into generally the distal 26 end of the rettactor blade 500. The wings 455 of the disposable electrode 450 mate with and are constrained by the dovetail grooves 502 which extend longitudinally from the distal end to the proximal end ofthe retractor blade 500. The dovetail grooves 502 provide an insertion guide for the disposable electrode 450 as it is inserted and assists in maintaining proper positioning ofthe disposable electrode 450 while coupled to the retractor blade 500. Additionally, the ledge 456 near the distal end ofthe disposable electrode 450 may engage the cut-out 506 generally near the distal end ofthe retractor blade 500 to firrther assist in securing the positioning ofthe disposable electrode 450 relative to the refractor blade 500. Therefore, the disposable electrode 450 is adapted to the refractor blade 500 so that the second exposed area 453 (shown by way of example as triangular in Figs. 41 and 45) is exposed generally along the outer surface ofthe blade (best shown in Fig. 45). Furthennore, the proximal end ofthe disposable electrode 450 protrudes fiom a machined cavity 504 (best shown in Fig. 44) at the proximal end ofthe refractor blade 500. Depending on the height ofthe blade, the proximal end may be bent or folded so as not to obstruct the surgical corridor, lie the disposable electrode 450 and associated refractor blade 500 have been described herein for use w.ith the refractor assembly 10, particularly for lateral access to the lumbar spine, it is contemplated that the disposable elecfrode refractor blade combination may be usefirl in a variety of surgical procedures (e.g. in a cervical procedure for stimulating the recurcent laryngeal nerve to monitor stahis ofthe nerve during retraction to access the anterior cervical spine). The cut-out 506 may also be usefol as an alignment tool to ensure that the retractor assembly is properly aligned. By way of example, it is generally preferable to have the posterior blade aligned pe^endicular to the disc space such that the cephalad and caudal blades expand directly anterior. Holes (not show) may be provided at the distal end of each ofthe cephalad and caudal blades. The holes will be distinguishable when viewed on a fluoroscopy image if they are not obstnrcted by a radiodense object. When the retractor assembly is properly aligned with the disc space and the refractor blades are in foe closed position, the cut-out 506 is visible in a lateral fluoroscopic image and the holes line up with the cut-out 506 and are also visible. If the holes are not visible, the refractor may need to be realigned. According to another example, a second set of alignment holes may be included (either above or below the first set ofholes) such that the horizontal alignment of foe retractor assembly 10 relative to the spine may also be assessed. 2015252096 05 Nov 2015 27

Fig. 49 is illustrates a locking intradiscal shim 600 designed for use with the center blade 500 and disposable electrode 450, according to an example embodiment. The locking intradiscal shim 600 is similar to the shim 25 of Figs. 10-12 such that a description of all the like elements will not be repeated here. The locking intradiscal shim 600 of Fig. 49 is preferably coated with an insulative parylene coating to mitigate current shunting and changes to current density at the distal tip ofthe disposable electrode. Parylene is the trade name for a variety of chemical vapor deposited poly (p-xylylene) polymers used as moisfore barters and electrical insulators. Among such polymers, Parylene c is maybe particularly suited due to its combination ofbarter properties and manufacturing advantages. The locking intradiscal shim 600 includes a deflectable tab 602 with a lip member 604 that serves as a locking feature. The shim 600 forther includes a cut-out 606 that receives an engagement tab of a removal tool. Figs. 50-51 illustrate the locking intradiscal shim ofFig. 49 coupled to and extending from the distal end ofthe blade 500 with the disposable electrode 450 also coupled to the blade 500. 2015252096 05 Nov 2015

Figs. 52-55 illustrate a shim removal tool 700 according to a second example embodiment. By way of example only, the shim removal tool 700 is shown and described herein in conjunction with the locking intradiscal shim 600 ofFigs. 49 and 50, although it is to be readily appreciated that the shim removal tool may be employed in a similar manner with other locking shims according to the present invention.

The shim removable tool 700 includes a proximal ^p cage 702, a distal engagment region 704,-and an elongated shaft 706 extending therebertveen. The proximal ^ip cage may be generally rectangular in shape and provides a grip for manipulating the tool and also provides a strike surface for impacting the instrument if necessary. The grip cage 702 also surrounds the thumb release 708, which is connected to foe distal region 704 via a spring mechanism 710. The distal region 704 includes a shim fork 712 and a release fork 714. The shim fork 712 includes a guide track 716 that engages the track in the retractor blade (described above). The split ramp 718 at the distal end ofthe shim fork 712 slides along the front oftlie shim 600 and engages behind the lip.member 604, lifting the engagement tab on the back side ofthe removal lip 604 and disengaging the tab from the track guide. This can be done to remove the shim 600 completely from the blade or to simply reposition the shim higher (or lower) along the length of 28 the blade track. As the split ramp 718 fully seats around the removal lip 604, an engagement tab 720 on the shim fork 712 catches in the cutout 606 in the shim 600, locking the shim fork 712 to the shim 600. The release fork 714 may be engaged to remove the engagement tab 720 ofthe shim fork 712 from the shim 600. Depressing the thumb release 708 moves the release fork 714 distally where the split ramp 718 ofthe release fork 714 engages behind the removal lip 722 of the shim fork 712, lifting the engagement tab 720 out ofthe cutout 606 in the shim 600. At the same time, knobs 724 on the release fork 714 push distally on the shim 600 causing the shim fork 712 to slide proximally and disengage from the removal lip 604 ofthe shim 600. 2015252096 05 Nov 2015

Fig. 56 illustrates a shim removal tool 750 according to a third example embodiment.

The shim removal tool 750 works like the shim removal tool 700 ofFig. 52 except that it includes only a shim fork 752 and not a release fork. Thus once the shim fork 752 is engaged the shim must be removed from the blade ttack before the tool can be disengaged. The shim fork 750 works as described with regard to the removal tool 700. The removal tool 750 includes a strike plate 754 for delivering an impaction force to the removal tool. The stake plate 754 includes a threaded hole for connecting additional instruments such as a slap hammer (to aid removal ofthe shim).

As mention«! above, the dilation assembly 7 and retoaction assembly 10 of foe surgical access system 6 may be configured to detect the presence of(and optionally the distance and/or direction to) neural structures during tissue dilation and/or retraction. This is accomplished by employing the following steps: (1) one or more stimulation electrodes are provided on the various dilation and/or retraction components2) ؛) a stimulation source (e.g. voltage or current) is coupled to the stimulation electrodes3) ؛) a stimulation signal is emitted from the stimulation electrodes as the various components are advanced towards or maintained at or near foe surgical target site; and (4) the patient is monitor«! to detennine if the stimulation signal causes muscles associated with nerves or neural structares within the tissue to innervate. If the nerves innervate, this may indicate that neural strucmres may be in close proximity to the distraction and/or retraction components. 29

Neural monitoring may be accomplished via any number of suitable fashions, including but not limited to observing visual twitches in muscle groups associated with the neural structures likely to found in the tissue, as well as any number of monitoring systems, including but not limited to any commercially available “traditional” electromyography (EMG) system (that is, tj^ically operated by a neurophysiologist). Such monitoring may also be carried out via the surgeon-driven EMG monitoring system shown and describe in the ‘949 and ‘840 patents referenced above, as well as PCT Applications PCT/US02/30617 and PCT/US2008/004427, both of which are incoj^orated herein by reference as if set forth entirely herein. In any case (visual monitoring, traditional EMG and/or surgeon-driven EMG monitoring), the access system of the present invention may advantageously be used to traverse tissue that would ordinarily be deemed unsafe or undesirable, thereby broadening the number of manners in which a given surgical target site may be accessed. 2015252096 05 Nov 2015 FIGS. 57-58 illustrate one such monitoring system 170, by way of example only, suitable for use with the surgical access system 6 of the present invention. The monitoring system 170 includes a contiol unit 172, a patient module 174, and an EMG harness 176 and retirm electrode 178 coupled to the patient module 174, and a cable 182 for establishing electrical conununication between the patient module 174 and any number of surgical accessories 196, including the surgical access system of the present invention (retractor assembly 10 ofFIG. 2, dilators 8 and 9 ofFIG. 1, K-wire 42 of Fig. 57). The surgical accessories 196 may forther include, but are not necessarily limited to, devices for perforating pedicle sCTew tests (such as a screw test probe 198), neural pathology monitoring devices (such as a nerve root refractor 200), coupling devices for electronically coupling surgical instraments to foe system 170 (such as electric coupling devices 202, 204 and stimulator driver 206), and pilot hole fonning components (such as a tap member 208, pedicle access probe 210, or other similar device). More specifically, titis electrical communication can be achieve by providing, by way of example only, a hand-held stimulation driver 206 capable of selectively providing a stimulation signal (due to the operation of manually operated buttons on the hand-held stimulation controller 206) to one or more connectors (e.g., coupling devices 202, 204). The coupling devices 202, 204 are suitable to establish electrical communication between the hand-held stimulation controller 206 and (by way of example only) 30 the stimulation electrodes on the κ-wire 42, the dilators 8 and 9, the retractor blades 12, 16, 18, and/or the shim members 22, 25 (collectively “surgical access instruments”). 2015252096 05 Nov 2015

In order to use the monitoring system 170, then, these surgical access instnrments must be connected to at least one of coupling devices 202, 204 (or their equivalent), at which point the user may selectively initiate a stinrulation signal (preferably, a current signal) from the control unit 172 to a particular surgical access instnrments. Stimulating the elecfrode(s) on these surgical access instninrents before, during, and/or after establishing operative corcidor will cause nerves that come into close or relative proximity to the surgical access instalments to depolarize, producing a response in a myotome associated with the innovated nerve.

The control unit 172 includes a touch screen display 190 and a base 192, which collectively contain the essential processing capabilities (software and/or hardware) for controlling the monitoring system 170. The control unit 172 may include an audio unit 168 that emits sounds according to a location of a surgical element with respect to a nerve. The patient module 174 is connected to the control unit 172 via a data cable 194, which establishes the electrical coimections and communications (digital and/or analog) between the control unit 172 and patient module 174. The main fimctions of the control unit 172 include receiving USCT commands via the touch screen displaj, 190, activating stimulation electjodes on the surgical access instruments, processing signal data according to defined algoritiims, displaying received parameters and processed data, and monitoring system statirs and report feult conditions. The touch screen display 190 is preferably equipped with a graphical user interface (GUI) Capable of communicating infoimation to the user and receiving instnictions from the user. The display 190 and/or base 192 may contain patient module interfece circuit (hardware and/or software) that commands the stimulation sources, receives digitized signals and ofoer information from the patient module 174, processes the EMG responses to extract characteristic infomation for each muscle group, and displays the processed data to the operator via the display 190.

In one embodiment, the monitoring system 170 is capable ofdetennining nerve direction relative to one or more oftiie κ-wire 42, the dilators 8 and 9, the retractor blades 12, 16, 18, and/or the shim elements 22, 25 before, during and/or following the creation of an operative 31 corridor to a surgical target site. Monitoring system 170 accomplishes this by having the control unit 172 and patient module 174 cooperate to send electrical stimulation signals to one or more of the stimulation electrodes provided on these instruments. Depending upon the location of the surgical access system 10 within a patient (and more particularly, to any neural structures), the stimulation signals may cause nerves adjacent to or in the general proximity of the surgical access system 10 to depolarize. This causes muscle groups to innervate and generate EMG responses, which can be sensed via the EMG harness 176. The nerve direction feature of the system 170 is based on assessing the evoked response of the various muscle myotomes monitored by the system 170 via the EMG harness 176. 2015252096 05 Nov 2015

By monitoring the myotomes associated with the nerves (via the EMG harness 176 and recording electrode 177) and assessing the resulting EMG responses (via the control unit 172), the surgical access system 10 is capable of detecting the presence of (and optionally the distant and/or direction to) such nerves. This provides the ability to actively negotiate around or past such nerves to safely and reproducibly form the operative corridor to a particular surgical target site, as well as monitor to ensure that no neural structures migrate into contact with the surgical access system 6 after the operative corridor has been establish«!. In spinal surgery, for example, this is particularly advantageous in that the surgical access system 6 maybe particularly suited for establishing an operative corridor to an intervertebral target site in a postero-lateral, trans-psoas fashion so as to avoid the bony posterior elements of foe spinal column.

Figs. 59-60 are exemplary screen displays (to be shown on foe display 190) illustrating one embodiment of the neive direction feature of the monitoring system shown and described with reference to Fig. 57-58. These screen displays are intended to communicate a variety of infonnation to the surgeon in an easy-to-inte^ret fashion. This infonnation may include, but is not necessarily limited to, a display of the fimction 230 (in ftUs case “DIRECTION”), a graphical representation of a patient 231, the myotome levels being monitored 232, the nerve or group associated with a displayed myotome 233, the name of the instrument being used 234 (in this case, a dilator), the size offoe instrament being used 235, the stimulation threshold current 236, a graphical representation of the instrument being used 237 (in this case, a cross-sectional view of a dilator 8 or 9) to provide a reference point ftom which to illustrate relative direction of the 32 instrument to the nerve, the stimulation current being applied to the stimulation electrodes 238, instructions for foe user 239 (in this case, “ADVANCE” and/or “HOLD”), and an arrow 240 indicating the direction ftom the instalment to a nerve. This infomation may be communicated in any number of suitable fashions, including but not limited to the use of visual indicia (such as alpha-numeric characters, light-emitting elements, and/or graphics) and audio conrmunications (such as a speaker element). Although shown with specific reference to a dilating caimula (such as at 234), it is to be readily appreciated that the present invention is deemed to include providing similar infonnation on the display 190 during foe use of any or all oftlie various instalments forming the surgical access system 6 of the present invention, including the dilation assembly 7 (i.e. the K-wire 42 and dilators 8 and 9) and/or the retractor blade 12 or the shim elements 22, 25. 2015252096 05 Nov 2015

As evident from the above discussion and drawings, the present invention accomplishes the goal of gaining access a surgical target site in a fashion less inv.asive than traditional “open” surgeries and, moreover, does so in a manner that provides the ability to access such a surgical target site regardless ofthe neural staichires required to be passed through (or near) in order to establish an operative corridor to the surgical target site. The present invention filrthennore provides the ability to perform neural monitoring in the tissue or regions adjacent the surgical target site during any procedures performed after the operative, cotador has been established.

The surgical access system ofthe present invention can be used in any of a wide variety of surgical or medical applications, above and beyond the spinal applications discuss«! herein.

Such spinal applications may include any procedure wherein instalments, devices, implants and/or compounds are to be introduced into or adjacent the surgical target site, including but not limited to discectomy, fiision (including PLIF, ALIF, TLIF and any fiision effectuated via a lateral or far-lateral approach and involvfog, by way of example, the introduction and/or removal ofbone products (such as allograft or autograft) and/or devices liaving ceramic, metal and/or plastic constniction (such as mesh) and/or compounds such as bone morphogenic piOtein), total disc replacement, etc.

Moreover, the surgical access system ofthe present invention opens the possibility of accessing an increased number of surgical target sites in a “less invasive” fashion by eliminating or greatly reducing the threat of contacting nerves or neural structares while establishing an 33 .perative c٠rrido through or near tissues containing such nerves or neural structures. In so doing, the surgical access system of the present invention represents a significant advancement capable of improving patient care (via reduced pain due to “less-invasive” access and reduced or eliminated risk of neural contact before, during, and after the establishment of the operative corridor) and lowering health care costs (via reduced hospitalization based on “less-invasive" access and increase number of suitable surreal target sites based on neural monitoring). Collectively, these translate into major improvements to the overall standard of care available to the patient population, both domestically and overseas. 2015252096 05 Nov 2015 34

Claims (20)

1. The claims defining the invention are as follows:

   1. A retractor assembly for creating an operative corridor to a spinal surgical target site, the retractor assembly comprising: a retractor body and a plurality of retractor blades extending generally perpendicularly to the retractor body, the retractor body including a first arm having a first longitudinal axis and a second arm having a second longitudinal axis, a first retractor blade of the plurality of retractor blades being rigidly coupled to a distal end of the first arm and a second retractor blade of the plurality of retractor blades being rigidly coupled to a distal end of the second arm, the first and second arms_ being movable apart relative to one another to separate the plurality of retractor blades and retract tissue away from the interior of the retractor blades to thereby form an operative corridor to the surgical target site, the first arm being coupled to a first lead screw driven rack and pinion gear operable to splay the first retractor blade such that a distal end of the first retractor blade extends wider than a proximal end of the first retractor blade, the first arm including a first static arm portion and a first rotating arm portion, the first lead screw driven rack and pinion gear including a first translating rack gear housed within the first static arm portion and threadedly engaged about a first lead screw and a first pinion gear engaged with the first translating rack gear and mechanically linked to the first rotating ami portion, wherein the first pinion gear rotates about the first longitudinal axis causing the first arm portion and the first retractor blade rigidly coupled to the first rotating arm portion to rotate about the first longitudinal axis, and wherein the second arm is coupled to a second lead screw driven rack and pinion gear operable to splay the second retractor blade such that a distal end of the second retractor blade extends wider than a proximal end of the second retractor blade, the second arm including a second static arm portion and a second rotating arm portion, the second lead screw driven rack and pinion gear including a second translating rack gear housed within the second static arm portion and threadedly engaged about a second lead screw and a second pinion gear engaged with the second translating rack gear and mechanically linked to the second rotating arm potion, wherein the second pinion gear rotates about the second longitudinal axis causing the second rotating arm portion and the second retractor blade rigidly coupled to the second rotating arm portion to rotate about the second longitudinal axis.
2. 2. The retractor assembly of claim 1, wherein the first arm includes a restrictor to limit the range of angulation through which the first retractor blade can travel.
3. 3. The retractor assembly of claim 1 or claim 2, wherein the second arm includes a restrictor to limit the range of angulation through which the second retractor blade can travel.
4. 4. The retractor assembly of any one of claims 1 to 3, wherein the range of angulation through which the first and second retractor blades can travel is between 0 and 20 degrees for each of the first and second retractor blades.
5. 5. The retractor assembly of any one of claims 2 to 4, wherein the restrictor comprises an extension of a first width situated at a distal end of the first static arm portion disposed within a recess of a second width greater than the first width situated at a proximal end of the rotating arm portion.
6. 6. The retractor assembly of any one of claims 1 to 5, wherein the first arm and the second arm are coupled to each other about a pivot.
7. 7. The retractor assembly of claim 1 or claim 6, wherein the plurality of retractor blades includes a third retractor blade.
8. 8. The retractor assembly of claim 7, wherein the third retractor blade does not splay.
9. 9. The retractor assembly of claim 8, wherein the retractor assembly includes a third arm and the third retractor blade is rigidly coupled to the third arm.
10. 10. The retractor assembly of claim 9, wherein the third arm is a translating arm that translates relative to the pivot about which the first and second arms are coupled.
11. 11. The retractor assembly of any one of claims 7 to 10, wherein the third retractor blade includes a stimulation electrode.
12. 12. The retractor assembly of claim 11, wherein the stimulation electrode is a disposable electrode and the third retractor blade is an electrode blade configured to couple to receive the disposable electrode.
13. 13. The retractor assembly of claim 12, wherein the electrode blade has an elongate interior slot extending longitudinally therethrough and connected to a distal aperture open to an exterior surface of the electrode blade, and wherein the disposable electrode comprises a nonconductive material having a conductive trace extending the length thereof between a proximal exposed area and a distal exposed area, the disposable electrode is configured to be slideably received within the elongate slot with the distal exposed area aligned with the distal aperture of the electrode blade.
14. 14. The retractor assembly of claim 13, wherein the electrode blade includes a second slot extending longitudinally along the interior surface and configured to slideably receive a blade accessory while the disposable electrode is coupled to the electrode blade.
15. 15. The retractor assembly of claim 14, wherein the blade accessory is an intradiscal shim.
16. 16. The retractor assembly of any one of claims 1 to 15, wherein the retractor assembly includes a supplemental blade assembly attachable to at least two of the plurality of retractor blades.
17. 17. The retractor assembly of claim 16, wherein the supplemental retractor blade assembly includes an elongated supplemental retractor blade and a crossbar connector, the crossbar connector configured to be attached to said at least two retractor blades while engaging the supplemental retractor blade.
18. 18. The retractor assembly of claim 17, wherein the crossbar connector extends from a first end to a second end and has an elongated slot opening in the first end and configured to slideably receive elements of the two retractor blades to slideably attach said crossbar connector to said two retractor blades, the crossbar connector further including a rear face configured to interlock with a series of grooves on the supplemental retractor blade to maintain a desired depth of the supplemental retractor blade relative to the crossbar connector.
19. 19. The retractor assembly of claim 18, wherein the elements slideably receivable within the elongated slot includes a post extending from each of the two retractor blades, each post extending generally perpendicularly relative to said respective retractor blade, the posts being dimensioned to be received in the elongated slot through the opening in the first end, the posts further including enlarged ends that are larger than a height of the slot to prevent disengagement of the crossbar connector from the two blades.
20. 20. The retractor assembly of claim 19, wherein the plurality of retractor blades includes at least three retractor blades, the at least three retractor blades comprising a caudal blade, a cephalad blade, and a center blade, and wherein the crossbar connector engages the caudal blade and the cephalad blade.