Surgical dilator, retractor and mounting pad

A retractor having an elongate body that provides access to a surgical location within a patient. The elongate body is generally ovoid in cross section and includes a plurality of segments that are connected to one another through a plurality of ratcheting mechanisms. The ratcheting mechanisms permit relative movement of the segments with respect to one another when expander dilators are inserted within the retractor. The segments are surrounded and retained by a resilient elastomeric sleeve or bands. The distal end surfaces of the segments include thin edges that are configured to mobilize, dissect, split and retract the terminal tissues in the surgical area. The retractor is used in conjunction with a resilient elastomeric pad that is affixed to the patient and firmly engages the outer surface of the elongate body to thereby anchor the retractor to the patient. A separate anchoring device can be used to connect the retractor to the pad.

FIELD OF THE INVENTION

The present system and method relate to devices and methods for performing percutaneous surgeries, and in particular, to a less invasive access portal for use in orthopedic spinal surgery.

BACKGROUND OF THE INVENTION

Open spinal surgical procedures generally require a relatively long incision, extensive muscle stripping, prolonged retraction of tissues, and increase risk of damage to vascular and nerve tissue. This type of procedure usually necessitates many weeks of post-operative recovery due to the use of long hours under general anesthesia, blood transfusions and the unavoidable trauma caused to the body tissues during the procedures. An open surgical procedure will also result in significant permanent scarring leading to fusion disease.

Surgery performed percutaneously has achieved major improvements over open surgery. The reduction of muscle and tissue dissection significantly reduces post operative recovery, pain, and recovery time. Percutaneous surgery is particularly beneficial for spinal surgery because the surgical area is deep within the body and in locations surrounded by sensitive and critical body tissues. Tube retractors have been developed to provide minimally invasive access to the surgical area. The ability to dilate muscle tissue, as opposed to strip or detach them from the bony anatomy, will reduce the damage and risks normally associated with the open type surgery.

The typical tube retractor technique starts with the identification of the correct entry point, establishing the trajectory from the skin to the pathology to be addressed and the corresponding skin incision. The initial soft tissue dilator is inserted through the incision and forcefully advanced to the objective site. A series of larger dilators are inserted over the initial dilator thereby sequentially increasing the diameter until the final/operative dilator is inserted. Once the operative dilator is in place it must be fixed in order to resist movement that will result from forces imposed by the patient's tissue. Currently, the accepted approach to fixation is a point outside of the patient's anatomy. Typically a rigid arm is attached at one end to the retractor while the opposite end of the arm is attached to a bed rail clamp. Once the retractor is fixed in position, the surgeon begins the operation to address the pathology. Upon completion of the procedure the retractor tube is removed and the skin incision is closed. Because of the reduced morbidity to the patient, the patient's initial recovery time should be less, blood loss should be less, operating room time should be less, anesthesia time should be less, patient stay in the hospital should be less, return to work time should be less and the overall cost of the procedure should be less.

One of the most difficult aspects of the current technique is that the rigid fixation of the retractor is sometimes subject to unintentional or unavoidable movement of the patient during the course of the surgical procedure. Another consistent problem is the inability of the current designs and methods to adequately retract the muscle tissue at the distal end of the retractor, which for all intents and purposes is the most crucial portion of the retractor. Due to the retractors inability to clear the surgical area the surgeon must resort to cutting, cauterizing and removing the final fibers of muscle. This process of physical tissue removal carries with it increased risk of damage to ancillary tissues and nervous tissues, while at the same time increasing morbidity, blood loss and operative time. These difficulties result in high levels of frustration making the technique less likely to be adopted by the majority of surgeons. The current retractors lack the distraction capability at the distal end of the retractor which is where the strongest forces resisting the retractor are present. In addition the current retractor designs do not accommodate the natural anatomical shape of the patient's anatomy where the pathology exists.

DESCRIPTION OF THE PRIOR ART

Retractors for use in percutaneous spinal surgery lack the ability to easily efficiently and clearly access the surgical area. Likewise, they do not have a simple, effective and efficient device to anchor the retractor relative to the patient.

U.S. Pat. No. 5,460,170 discloses an adjustable, expandable retractor suitable for use in small surgical incisions or punctures. The device is able to expand the incision or puncture to one or more enlarged cross-sectional areas and designed to protect the edges of the incision or puncture. The surgical retractor comprises a radially expandable tubular body having a control at the proximal end. Pull wires couple the control to the tubular body such that force applied to the control is transmitted to the tubular body as axially compressive force.

U.S. Pat. No. 3,788,318 discloses an expandable tube, referred to therein as a cannula, is formed by arranging at least one sheet of thin flexible material to form a tube while providing teeth or the like on the interengaging surfaces to permit controlled expansion of the tube by adjusting the surfaces over one another.

U.S. Pat. No. 6,187,000 discloses a cannula with an expandable portion for enabling an increase in the cross-sectional area of the passage at the distal end. The expandable portion of the tube structure, when expanded, has a conical configuration.

U.S. Pat. No. 6,652,553 discloses a surgical tool for use in expanding a cannula and includes a first leg having a first end engageable with an inner surface of the cannula. A second leg is connected with the first leg. The second leg has a second end engageable with the inner surface of the cannula. The first and second ends are movable away from each other to apply a radially outwardly directed force to the inner surface of the cannula and cause expansion of the cannula.

U.S. Pat. No. 7,261,688 discloses a retractor having a working channel formed by a first portion coupled to a second portion. The first and second portions are movable relative to one another from an unexpanded configuration to an expanded configuration to increase the size of the working channel along the length thereof.

U.S. Pat. Nos. 6,524,320 and 7,144,393 disclose a cannula having an expandable portion for enabling an increase in the cross-sectional area of the passage. The expandable portion of the tubular structure has a slot and a guide member disposed in the slot. The guide member is movable from a first end of the slot toward a second end of the slot to enable the cross-sectional area of the passage to increase. The expandable portion has a stop between the first and second ends of the slot engageable with the guide member to retain the guide member in a position relative to the slot and resist movement of the guide member from the position relative to the slot. In the '393 patent, the expandable portion has a contracted condition in which the cross-sectional area of the distal end of the passage has a first cross-sectional area. The expandable portion has an expanded condition in which the distal end of the passage has a second cross-sectional area greater than the first cross-sectional area. The second cross-sectional area is greater than a cross-sectional area of the proximal end of the passage when the expandable portion is in the expanded condition. A retaining mechanism resists movement of the expandable portion from the expanded condition toward the contracted condition during the surgical procedure. The retaining mechanism is released at the conclusion of the surgical procedure to permit movement of the expandable portion from the expanded condition toward the contracted condition for removal of the structure. The expandable sleeve is provided with a lockable means in the expanded position.

U.S. Pat. Nos. 7,179,225 & 7,221,451 disclose a retractor that has an elongate body and an expandable shroud. The elongate body has an outer surface and an inner surface partially defining a passage. The elongate body also has a first longitudinal edge and a second longitudinal edge. The elongate body is capable of having an enlarged configuration when inserted within the patient. In the enlarged configuration the first longitudinal edge is spaced apart from the second longitudinal edge. The expandable shroud is configured to extend from the first longitudinal edge to the second longitudinal edge when the first and second edges are spaced apart. The shroud partially defines the passage. The cross-sectional area of said passage at a first location is greater than the cross-sectional area of the passage at a second location, wherein the first location is distal to the second location. See FIG. 70 in the '225 patent and FIG. 71 for oval and oblong shape.

U.S. Pat. No. 7,223,233 discloses methods and devices for illuminating a surgical space in a patient. A retractor provides a portal or working path for access to a working space location in the patient. The retractor transmits and emits light from a light delivery system to illuminate the working channel and surgical space.

U.S. Publication No. 2006/0041270 discloses an expandable sheath that is insertable into a patient through an incision. Once inserted and advanced to the target surgical site, the sheath can be expanded to an enlarged diameter. The wall of the sheath is fabricated from a tubular structure comprising filamentous elements that extend axially and at least partially circumferentially along the length of the sheath. The tubular filamentous material is drawn or expanded axially to create the small diameter configuration that is inserted into the patient. A standoff attaches the distal end of the tubular filamentous material to the sheath hub by way of radially movable anchors. Additional filamentous tubular material extends out the proximal end of the hub. A compression mechanism forces the additional filamentous tubular material in the distal direction which causes axial compression and radial or diametric dilation of the working length of the sheath, that part of the sheath that extends beyond the proximal end of the hub. Radial dilation is accomplished with no substantial change in sheath working length.

U.S. Publication No. 2006/0200023 discloses systems and methods include an anchor engageable to a vertebra and an extender removably mounted to the anchor. The extender includes an insulating member extending at least partially thereabout to electrically insulate the extender and prevent shunting of electrical signals delivered through the extender to the anchor to structures adjacent the extender. Flexible jacket 26 includes a means for monitoring nerves.

U.S. Publication No. 2008/0234550 discloses a less invasive access port for use in minimally invasive surgery allows for manipulation of the viewing angle into the working site in a transverse plane. According to one exemplary embodiment, the less invasive access port is designed to minimize the need for muscle retraction. Additionally, the less invasive access portal provides sufficient light, irrigation, suction and space for sundrymedical instruments. According to one exemplary embodiment, a less invasive access port device includes a retractor assembly having four retractor blades secured in various positions by pins placed within slots on the retractor blades. A cannula includes integrated interfaces for light, irrigation and suction. A housing forms a collar around a top of the cannula and houses the light, irrigation and suction mechanisms. Instruments and implants may be passed through the cannula and into the working space created by the retractor assembly. Visualization of the working site can be attained under direct vision.

SUMMARY OF THE INVENTION

The present invention is directed to methods and devices for performing percutaneous, minimally invasive spinal surgery. In particular the invention includes a percutaneous tissue retraction device that provides access to the surgical area within the patient. Another aspect of the invention includes a device for anchoring the retractor device directly on the patient without the aid of additional structural elements to affix the retractor to other objects within the operating room such as the operating table.

The current retractor addresses the current problem making its utilization more reproducible, easier to learn and visualize and increases safety while delivering a more consistent result.

The anchoring device includes a pad that is affixed to the patient. Should the patient move slightly, intentionally or unintentionally, the retractor maintains the same tissue retraction and the same trajectory. This provides an accurate and stable portal to the patient's pathology. The pad eliminates the necessity for rigid fixation to a point outside of the field of operation or to an independent immobile point such as a bed rail. The rigid fixation device is metallic and used with conventional metallic split blade retractors that reduce visualization of the approach through the retractor as well as the visualization of the objective site while using operative fluoroscopy.

The anatomical shape of the distal end of the current retractor produces a significantly improved ability to mobilize, dissect, split and retract the terminal tissues of the psoas muscle at the point on the spine where the entry is to be made. Current distal end designs are parallel to the spine and do not comply with the natural shape of the spine.

The ovoid shape of the retractor requires less retraction in two different planes while achieving adequate exposure thereby making the procedure easier and more reproducible.

Likewise, the anatomical shape of the distal end of the dilator when inserted safely and gently, divides/splits the psoas muscle fibers along the longitudinal plane of the spine. The distal end shape of the dilator mobilizes and dissects the muscle fibers more effectively and when subsequently rotated ninety degrees provides a dilator that will safely and gently sweep the terminal fibers in order to enable consistent retraction of the muscle fibers while the retractor is inserted. The final dilator is unique in its ability to create a path for the retractor which complies with the patient's anatomy in a safe, gentle fashion allowing for efficient mobilization of the muscle fibers and maintaining the muscle retraction when inserting the retractor. Current systems use round dilators with flat bottom surfaces. When the retractor is inserted over the final dilator and the dilator is removed, muscle fibers creep under the end of the retractor and the doctor must then use instruments to sweep the fibers out of the way, under the blades or ablate them.

Accordingly, it is an objective of the instant invention to provide a retractor for performing minimally invasive spinal surgery that provides improved access to the surgical area.

It is a further objective of the instant invention to provide a retractor device that the surgeon will find more intuitive to use owing to its construction ease of use.

It is yet another objective of the instant invention to provide a retractor for minimally invasive spinal surgery with an anatomically shaped distal end resulting in a much improved ability to mobilize, dissect, split and retract the terminal tissues of the psoas muscle at the point of the spine where the entry is to be made.

It is a still further objective of the invention to provide a retractor where the walls of the retractor apply an opening force throughout the length of the retractor and provide a more robust retraction.

It is a still further objective of the invention to provide a radiolucent retractor for greater visualization during the surgical procedure.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to methods and devices for performing percutaneoous surgery and in particular spinal surgery. The surgery is performed through a portal or passageway provided by a retractor. The retractor is expandable in situ to thereby increase the size of the surgical area as well as the access thereto. It is particularly constructed to minimize trauma to tissue surrounding the retractor and the surgical area. The retractor can be used with any surgical approach to the spine such as; lateral, postero-lateral and/or antero-lateral, anterior, posterior, posterior mid-line, and in other regions of the body not associated with the spine.

FIG. 1is a top view of retractor1. As shown retractor1is comprised of four discrete segments. As shown, the segments consist of a pair of opposing semi cylindrical members4A and4B as well as a pair of opposing semi elliptical members6A and6B. A ratcheting mechanism8A and8C is located at each of the junctions between opposing semi cylindrical member4B and opposing semi elliptical members6A and6B. Likewise a ratcheting mechanism8B and8D is located at each of the junctions between semi cylindrical segment4A and opposing semi elliptical members6A and6B. The four segments once assembled and surrounded by a silicone sleeve10form a single working unit that is generally elongated and oval shaped in cross section. The sleeve10conforms to the shape of the exterior surfaces of the segments and extends the entire length of the segments from the proximal end, the top portion, to the distal end, bottom portion and exerts a radially directed inward force against segments4A,4B,6A and6B. The assembly thereby forms an elongated ovoid shaped retractor wherein the parallel distraction will occur along the length of the retractor based upon the engagement and disengagement of the teeth placed along the longitudinal axis of the retractor. While shown and described as having four segments the retractor could be formed as two segments each including a semi cylindrical segment and a semi elliptical segment.

The segments4A,4B,6A and6B are formed from plastic or any other suitable radio lucent material. Segments4A and4B each respectively have screw holes12A and12B designed to receive a bone screw for distal fixation of the retractor to a vertebral body. The segments also contain insulated electrical conductors16included in the walls of the segments. The conductors16terminate at the proximal and distal surfaces of the segments with exposed electrical contacts to provide an electrical pathway for nerve monitoring Also included within the segments are internal tracks for mounting fiber optical lights18to provide illumination of the surgical space located at the distal end of the retractor. Each of the segments4A,4B,6A, and6B may contain radio opaque markers24to enable visualization throughout the procedure.

FIG. 2shows a partially exploded top view of the four segments prior to engagement via the ratcheting mechanisms.FIG. 3is an enlarged view of the encircled area ofFIG. 2. As can be seen inFIG. 3semi-circular segments have teeth or grooves20located on the interior surface adjacent both edges of the semi circular segments6A and6B. These teeth or grooves20are located at four separate points along the length of the segments between the proximal and distal end portions as shown inFIG. 5. Alternatively teeth or grooves20can run the entire length of the segments from the distal end portion to the proximal end portion as shown inFIG. 6. As seen from the front view, the lower distal end surface of segments6A and6B form a concave edge26.FIG. 7shows a side view of the external surface of the semi cylindrical segments6A and6B.FIG. 8is a front view of the exterior surface of one of the semi elliptical members4A and4B. As seen from the front view the lower distal end surface of segments4A and4B form a convex edge28. Concave edges26and convex edges28form a tip at the distal end of the retractor1that is anatomical in shape and particularly configured to significantly improve the ability to mobilize, dissect, split and retract the terminal tissues of the psoas muscle at the point on the spine where the entry is to be made.FIG. 9is an exterior surface side view of one of the semi elliptical members4A and4B. One or both of the segments4A and6B contain an insulated electrical conductor16included in the walls of the segments. A tool30, shown inFIGS. 11A and 11Bis used to facilitate a ninety degree rotation of the retractor as will be explained below. The tool30includes a pair of diametrically opposed handles32and34that are each connected to an annular member36. The inner surface38of the annular member36is configured to operatively cooperate with the external surface of sleeve10surrounding the retractor1adjacent the top portion thereof. Semi elliptical segments4A and4B have complimentary teeth or grooves22. Teeth or grooves22are located on the exterior of semi elliptical segments4A and4B adjacent each of the edges of semi elliptical segments4A and4B. Teeth or grooves22extend the entire length of the segments form the proximal to distal end portion as shown inFIG. 9.FIG. 4shows one of the ratcheting mechanisms8A-8D and the inter engagement of teeth20and22as well as sleeve10which exerts a radially directed inward force on each of the retractor segments.

The present system is a patient based retractor that does not require fixation to an articulating arm. The patient based retractor includes a pad40that eliminates the necessity for a rigid fixation to a point outside of the field of operation or to an independent immobile point such as a bed rail. The pad40is applied to the sterilized area on the patient's body41. The physical properties of the material including its size, thickness and composition cause significant friction, or adhesion, between the pad and the sterile site on the patient's skin. By way of example,FIGS. 10A and 10Billustrate the pad40in a deployed position. This can be reinforced with the application of tape and or IOBAN® if necessary. By way of example the pad can be formed from a polyurethane material. While the pad40and retractor1have been shown for use during minimally invasive spinal surgery it should be understood that the anchoring pad40could be used in combination with retractor1or a retractor of any configuration and for other types of surgery as well, such as laparoscopic gal bladder surgery or appendectomy.

The tube retractor technique starts with identifying the correct entry point, and correct trajectory from the skin to the pathology to be addressed. A top view of the incision42is shown inFIG. 10B. The initial soft tissue canulated dilator50of circular cross section, as shown inFIG. 12A, is inserted through the incision and forcefully advanced to the objective site. A series of larger diameter dilators as shown inFIG. 12B,51and52, are inserted over the initial dilator sequentially increasing in diameter until the final operative diameter is inserted. The final operative dilator54is oblong in cross section as is shown inFIGS. 12C through 12F.FIG. 12Cis a front perspective view of the ovoid shaped final dilator.FIG. 12Dis a side view of the bottom or distal end surface56of the final dilator that is convex in shape on both side wall portions.FIG. 12Eis a perspective bottom view of the bottom or distal end surfaces of the final dilator that shows the front and back wall surfaces having bottom edges58that are concave in shape. The two convex surfaces at the lower edge of the side wall portions and the concave edges on the front and back walls form a distal or end surface that is anatomical in shape and particularly configured to significantly improved the ability to mobilize, dissect, split and retract the terminal tissues of the psoas muscle at the point on the spine where the entry is to be made. Once in its proper position the oblong operative dilator54is rotated ninety degrees and then counter rotated back to its original position using the tool30.FIG. 13is a top view of the retractor in position on the patient.FIG. 14Ais a top view of the retractor1in position within the patient's body andFIG. 14B is a side view of the retractor within the patient's body41. As shown inFIGS. 14A and 14Bthe spinal disc60is located between vertebral bodies62and64. As shown, each vertebral body includes a spinous process bone66and a pair of pedicle bones68. Either segment6A or6B can be seen in this view. Once in this position, the retractor1is then rotated ninety degrees using tool30to the position shown inFIG. 15.FIG. 15is a top view of the retractor1in position on the patient after being rotated. The shape of the distal end of the retractor segments provides a significant improvement in the ability to mobilize, dissect, split and retract the terminal tissues of the psoas muscle at the point on the spine where entry is to be made. Current designs are parallel to the spine and do not comply with the natural shape of the spine, thereby allowing the terminal psoas muscle fibers to creep under the retractor and completely undermine the process and in many cases reduces the overall success and intention of the minimally invasive technique. The ninety degree rotation of the retractor1enables the distal portions of the psoas muscle to be mobilized and retracted via the retractor. This action reduces muscle creep thereby reducing the necessity for the surgeon to cut, cauterize and remove muscle fibers to access to the pathology.

Once the retractor1is rotated into final position the final and initial dilators are withdrawn from the patient. At this point, a series of retractor expansion dilators, shown inFIG. 12C, are available for expansion of the retractor1. These expansion dilators are canulated and assist in centering the retractor with the initial k-wire that is already in place. The expansion dilators are 14, 16, 18 and 20 mm in diameter. As progressively larger expansion dilators are inserted within the retractor1, segments4A,4B,6A and6B move relative to one another by virtue of ratcheting mechanisms8A,8B,8C and8D. By way of example, it is contemplated that the distance between segments4A and4B at their mid points can be increased from 14 mm to 18 mm and the distance between segments6A and6B at their mid points can be increased from 18 mm to 22 mm, as shown diagrammatically inFIGS. 17A and 17B. At this point the expansion dilators are removed and the operation can proceed. The retractor is anchored at the near portion by frictional engagement with pad40. In addition the retractor1may be anchored at the distal end portion using bone screws that are inserted through holes12A and12B of the retractor and threaded into the vertebral body. The pad40eliminates the need for a rigid fixation to a point outside the surgical field or to an independent fixed point such as a bed rail. The elimination of these metallic supports that are typically associated with minimally invasive tube or split blade retractors increases the visualization of the approach through the retractor and visualization of the surgical site while using operative fluoroscopy.

The retractor system of the present invention was developed to provide minimally invasive access to a patient's pathology. The ability to dilate muscle tissue, as opposed to the process where the muscle tissue is stripped or detached from the skeletal structure will usually reduce the morbidity associated with the standard invasive technique. The procedure to utilizing the retractor system of the present invention starts with the identification of the correct entry point, the proper trajectory from the skin to the pathology to be addressed as well as the point of incision. After the initial incision has been made through the patient based anchoring pad and into the skin the initial soft tissue dilator is inserted through the incision and forcefully advanced to the objective site. The initial dilator is 6 mm in diameter and round in cross section. Thereafter, a series of progressively larger dilators are inserted over the initial dilator; increasing in diameter until the final operative dilator is inserted. The final operative dilator is oblong in cross section. Once the final operative oblong dilator is in place it is then rotated ninety degrees by tool30and then counter rotated ninety degrees back to its initial position. The retractor1is then placed over the final operative dilator and forcefully advanced to the objective site. Once in position the retractor is then rotated ninety degrees by using a tool30. Thereafter the initial and final dilators are removed. Following removal of the dilators used for initial delivery, a series of expansion dilators, are inserted into the center of the retractor1to expand the open area or portal within the retractor. These expansion dilators are circular in cross section and range in diameter from 14 mm to 20 mm. As the expansion dilators are inserted the ratcheting mechanisms8A,8B,8C, and8D allow relative movement between the adjacent retractor segments by virtue of the disengagement and reengagement of the teeth20and22. The expansion dilator creates a force directed radially outwards thereby causing a shift in the alignment of teeth20and22. Simultaneously resilient sleeve10exerts a radially inward directed force maintaining the teeth20and22in their newly established position.

FIGS. 18A,18B,18C and18D illustrate various views of an alternative embodiment for the oblong final operative dilator. As shown in these views the final operative dilator154includes an upper, proximate, edge156and a lower, distal, edge158. The dilator includes a central passageway160that is generally cylindrical in cross section and extends the entire length of the dilator154from the upper edge156to the lower edge158. The outer surface of the dilator154generally conforms to the inner surface of the retractor and includes a pair of opposing semi elliptical surfaces162A and162B as well as a second pair of opposing semi elliptical surfaces164A and164B which together form a contiguous outer surface of the final operative dilator154. The upper edge surface156is generally planar and formed orthogonally with respect to the outer surface of the retractor. The lower distal edge158is formed from a plurality of thin arcuate surfaces forming a concave shape at the distal end of the dilator. The walls of the distal end portion are tapered to form this series of thin arcuate surfaces. The arcuate surfaces includes a pair of curved surfaces166A and166B proximate the distal ends of semi elliptical surfaces162A and162B. Surfaces166A and166B are connected at a point168located at the most distal end of the dilator. Formed on the lower distal edge surface158adjacent opposing semi elliptical surfaces164A and164B are curved surfaces170and172. Each of the curved surfaces170and172has a first and second ends connected to the curved surfaces166A and166B. The mid point of surfaces170and172being located closer to the upper surface of the final dilator. The lower distal edge158thereby forming an anatomically concave shape at the tip of the dilator. The concave shaped distal end extends over the disc/endplate interface. The concave shape will gently divide the muscle and fiber tissue. The anatomically curved distal tip of the dilator gently separates the final psoas fibers directly attached to the interverbral disc/vertebral body interface along the lateral aspect of the spine. This gentle splitting of the fibers occurs along the same plane as the muscle fibers which ensure a split/separation action. By mobilizing a longer axis of muscle fibers the forces normally associated with larger dilators are applied along a greater surface area of tissue which reduces the forces directly associated with the immediate surrounding tissues and of greater consequence, the neural tissues such as the lumber plexus. Once the fibers have been split along the length of the muscle a gentle rotation of the dilator gently sweeps the terminal fibers attached to the lateral aspect of the intervertebral disc. This enables the tissues to be swept and subsequently maintained outside the working area once the retractor is placed and rotated into its final working position. This action will result in a less disruptive means of exposure thereby reducing the need for cutting or electro-cauterizing the final fibers while providing better visualization of the target area of surgery.

Current dilators and retractors use a cylindrical design with a flat planar surface. They rely on compression of the fibers at the distal aspect of the device to achieve dilation. Typically retractors use compressive forces, sequentially, to distract a parallel opening which increases muscle disruption and potential nerve compression. This arrangement allows for the final fibers to creep under the edges of the retractor and does not allow for sweeping of the final fibers. When the typical retractor is opened with the final fibers still intact within the target area for surgery, they will need to be moved with instruments that makes the process, tedious and increases the risk of neural and vascular structures being unintentionally cut or crushed as the fibers and tissue are cut, torn and/or electro cauterized.

FIGS. 19A,19B,19C,19D and19E illustrate various views of another alternative embodiment for the oblong final operative dilator. As shown in these views the final operative dilator254includes an upper, proximate, edge256and a lower, distal, edge258. The dilator includes a central passageway260that is generally cylindrical in cross section and extends the entire length of the dilator254from the upper edge256to the lower edge258. The outer surface of the dilator254includes a pair of opposing semi elliptical surfaces262A and262B as well as a second pair of opposing semi elliptical surfaces264A and264B which together form a contiguous outer surface of the final operative dilator254. The distal end of dilator254includes concave outer surfaces that extend outwards in a curved fashion from the semi elliptical surfaces262A,262B,264A and264B. Concave surface263A extends radially outward from surface262A. Concave surface263B extends radially outward from surface262B. Concave surface265A extends radially outward from surface264A and concave surface265B extends radially outward from surface and265A. The upper edge surface256is generally planar and formed orthogonally with respect to the outer surface of the dilator. The lower distal edge258is formed from a plurality of thin arcuate surfaces forming a concave shape at the distal end of the dilator. The walls of the distal end portion are tapered to form this series of thin arcuate surfaces. The arcuate surfaces includes a pair of curved surfaces266A and266B proximate the distal ends of semi elliptical surfaces262A and262B. Surfaces266A and266B are connected at a point268located at the most distal end of the dilator. Formed on the lower distal edge surface258adjacent opposing semi elliptical surfaces264A and264B are curved surfaces270and272. Each of the curved surfaces270and272has a first and second ends connected to the curved surfaces266A and266B. The mid point of surfaces270and272being located closer to the upper surface of the final dilator. The lower distal edge258thereby forming an anatomically concave shape at the tip of the dilator. The concave shaped distal end extends over the disc/endplate interface. As final operative dilator254has a distal end that includes concave outer surfaces that extend outwards in a curved fashion from the semi elliptical surfaces262A,262B,264A and264B it will be removed from the incision after its insertion and the aforementioned rotation prior to insertion of the retractor. The configuration of the final operative dilator254will split the psoas muscle in the same manner as described with respect to final operative dilator154.

FIG. 20is a perspective view of an alternative embodiment of the adjustable retractor300. Retractor300is an elongated body that is made up of a plurality of selectively engaging segments. The segments include a first pair of elongated members302A and302B having opposed semi elliptical shaped cross section and a second pair of elongated members304A and304B having opposed semi elliptical shaped cross section. Each segments has a top, or proximate, portion and a bottom, or distal, portion. The length of the elongated members being of a length to span the distance from adjacent the surgical area at the distal end portion to a location external to the patient. The distal end of the retractor300, comprised of the distal ends of elongated members302A,302B,304A and304B, has the correct concave shape to allow for more effective dissection of the terminal tissues at the distal end of the retractor300.

FIG. 21is a top view of the retractor shown inFIG. 20with the retractor in its most compact configuration. As can be seen in this view, elongated members302A and302B have step like teeth306and308that are directed radially inward while elongated members304A and304B have complimentary teeth310and312that are directed radially outward. Teeth306and308on members302A and302B and teeth310and312on members304A and304B generally run the length of the retractor from the proximate to the distal end. The elongated members are retained in a fixed position under the influence of elastomeric bands301that exert a radially directed inward force. Three elastomeric bands are shown inFIG. 20, by way of example, recognizing that more than three or less than three can be used as well. The elastic bands provide the tension necessary to maintain multiple pieces together during initial insertion of the dilator. They also provide the appropriate amount of tension required to allow sequential dilation/opening of the retractor in parallel fashion along the length of the retractor. This aspect of the invention eliminates a problem associated with current retractors wherein the application of dilating force at the proximal end to overcome the physiological forces applied to the human anatomy at the distal end results in a larger opening proximally with little effect and a smaller opening distally. This problem runs counter to the overall objective of minimally invasive proximal openings with minimal disruption of the terminal fibers at the intended surgery target area.

FIG. 22is a top view of the retractor shown inFIG. 20with a retractor dilator expanding the retractor an intermediate expanded configuration. As can be seen in this view, as a first retractor dilator314is inserted into a cavity formed within the assembly of elongated members302A and302B are urged radially apart from one another thereby disengaging the step like teeth on the elongated members. At the same time the first retractor dilator314urges the elongated members310and312radially outward. Upon removal of the first retractor dilator314the retractor300has been reconfigured to an intermediate position as shown inFIG. 23wherein the elongated members310and312have moved radially outward to the next step on elongated members302A and302B. Upon removal of the retractor dilator the elastomeric bands301will again exert a radially directed inward force and maintain engagement of the teeth on the elongated members, as shown inFIG. 23.

FIG. 24is a top view of the retractor ofFIG. 20with a second retractor dilator urging the retractor to the most expanded configuration. The second retractor dilator316is larger than the first retractor dilator314. As the second retractor dilator316is inserted into a cavity formed within the assembly of elongated members, members302A and302B are urged radially apart from one another thereby disengaging the step like teeth on the elongated members. At the same time the second retractor dilator316urges the elongated members310and312radially outward. Upon removal of the second retractor dilator316the retractor300has been reconfigured to a final position as shown inFIG. 24wherein the elongated members310and312have moved radially outward to the next step on elongated members302A and302B. The elastomeric bands301will again exert a radially directed inward force and maintain engagement of the teeth on the elongated members, as shown inFIG. 24.

FIG. 25is a perspective top view the retractor, the patient pad400and a device to anchor the retractor to the patient pad. Patient pad400is similar to pad40, as described above, but further includes a hard ring402, formed from metal or plastic, surrounding the retractor300that has been placed through the pad400. A pair of tabs404extends from the proximal end of the retractor. The material for the tabs404is a more malleable composite of the material used for the retractor. The tabs404include holes or slots406that are configured to receive threaded thumb screws408. Likewise, ring402includes holes and or slots410located around the circumference of the ring402. Thumb screws408are passed through the appropriate apertures406in tabs404and are secured in the appropriate apertures410located on ring402. The tabs can be positioned at the desired location along the ring. Then the thumbscrews are are positioned in the proper apertures and tightened, whereby the tabs will hold the proximal end of the retractor at the desired angle.

FIG. 26is a perspective view an alternative arrangement for anchoring the retractor300to the patient pad400. In this embodiment the retractor300has a pair of radially projecting tabs420that are oriented in diametrically opposed relationship. Patient pad400includes an annular recess or groove422formed either within or recessed on the bottom side of the pad. Located on the upper surface of patient pad400is a pair of diametrically opposed slots424that extend from the upper surface to the groove or recess422. To anchor the retractor, each of the tabs420is brought into alignment with a slot424. After each tab420is positioned within groove422the retractor is rotated with respect to the pad thereby effectively anchoring the retractor300.

FIG. 27is a perspective view of another alternative embodiment to anchor the retractor to the patient pad. In this embodiment tabs440extend from the proximal aspect of the retractor300in diametrically opposed orientation. The tabs440are made from a malleable plastic material. As shown inFIG. 27the tabs fold along the edge of the retractor300and the pad400is placed over the retractor300. The retractor extends through the pad400through a slit formed therein while the tabs are positioned beneath the pad400. The tabs maintain a downward force on the retractor with the constant pressure applied from the patient pad that is in contact with the patient's skin.

FIG. 28is a perspective view of yet another alternative embodiment to anchor the retractor to the patient pad. In this embodiment the proximal aspect of the retractor300includes a series of coarse threads452formed on the exterior surface of the retractor. The patient pad400includes ring454embedded in the upper surface of the patient pad400. The exterior surface of ring454includes thread456configured with the same coarse thread dimension as threads452. An internally threaded annular ring450is used to secure the retractor to the patient pad. The internal threads of annular ring450are sized and configured to threadably engage threads452on the retractor and thread456on the embedded ring454. The retractor is placed through an opening in pad400and the annular ring450is placed over the retractor300. As the ring is tightened it applies a downward force to the retractor's proximal end to maintain the desired depth of the distal tip in the patient's tissue.

FIG. 29is a perspective view of a retractor including a handle to manually stabilize the retractor in the patient. In this embodiment the proximal aspect of the retractor300cooperates with a manual anchoring device that includes an annular member464with a pair of diametrically opposed arms460extending radially outward from annular member464. The bottom surface of annular member464includes an annular groove466. Annular groove466is comprised of a series of semi elliptical segments, configured to mate with the upper surface of the retractor300, and having sufficient width so as to be able to cooperate with the upper peripheral edge of retractor300either in its compact, intermediate or expanded condition. Arms460and annular member464are formed from a rigid material such as a rigid plastic or metal. Each arm includes a gripping element462. As shown, the gripping element is a ball type handle however any other type of handle mechanism such as a vertical post, or “T” or loop configuration would be acceptable. The retractor300would be physically stabilized by an individual grasping and holding either one or both of the gripping elements462in a fixed position. Alternatively, one could use the hand stabilized retractor without the aid of the patient pad400.