US20080009797A1 - Trocar system and method of use - Google Patents

Abstract

A trocar system including a cannula and an obturator assembly being at least partially insertable through the cannula. The obturator assembly including a housing, a penetrating tip disposed at a distal end, an elongated shield including a guard extending from a shaft are movable relative to the penetrating tip, and a latch mechanism disposed generally within the housing. The latch mechanism facilitates changing the configuration of the obturator assembly between a fixed-shield orientation, wherein at least a portion of the guard is maintained to extend at least partially distal of the penetrating tip to prevent puncturing of tissue by the penetrating tip, to a non-fixed shield orientation whereby upon application of force to the distal end of the obturator assembly, the guard and penetrating tip are permitted to move relative one another to facilitate puncturing of tissue by the penetrating tip.

Description

BACKGROUND
• 1. Technical Field
• The present disclosure relates to trocar systems for inserting cannulas into patients, and more particularly to modular trocar systems and methods of assembly of trocar systems.
• 2. Background of Related Art
• Minimally invasive procedures are continually increasing in number and variation. Forming a relatively small diameter temporary pathway to the surgical site is the key feature of most minimally invasive surgical procedures. The most common method of providing such a pathway is by inserting a trocar assembly through the skin. In many procedures the trocar is inserted into an insufflated body cavity of a patient. In such procedures, trocar assemblies with seal mechanisms are utilized to provide the necessary pathway to the surgical site while minimizing leakage of insufflation gases through the inserted cannula.
• Trocar assemblies typically include an obturator removably inserted through a cannula assembly. The obturator is assembled with the cannula portion such that the obturator's sharp tip portion extends from a distal end opening of the cannula to facilitate insertion of the cannula through the body wall of the patient. Trocar assemblies are commonly provided with a safety shield of some fashion which protects against unintentional puncturing by the sharpened tip of the obturator. Mechanisms which control the relative movement and locking of the safety shield and the obturator's penetrating tip exist. Such mechanisms can be complex and often require numerous moving parts to accomplish the release and resetting of a the safety shield lock feature so as to permit the obturator's penetrating tip to function only when desired to facilitate insertion of the trocar assembly and placement of the cannula portion thereof.
• A continuing need exists for novel trocar assemblies which provide safety shield latch mechanisms which require fewer component parts while providing increased reliability before, during and after insertion of the trocar assembly in a patient.
SUMMARY
• The present disclosure provides a modular trocar system which overcomes disadvantages associated with previous trocar systems. The presently disclosed modular trocar system satisfies the need for more reliable trocar assemblies while improving manufacturing efficiencies.
• In particular, the present disclosure provides trocar system including a cannula and an obturator assembly being at least partially insertable through the cannula. The obturator assembly including a housing, a penetrating tip disposed at a distal end, an elongated shield including a guard extending from a shaft are movable relative to the penetrating tip, and a latch mechanism disposed generally within the housing. The latch mechanism facilitates changing the configuration of the obturator assembly between a fixed-shield orientation, wherein at least a portion of the guard is maintained to extend at least partially distal of the penetrating tip to prevent puncturing of tissue by the penetrating tip, to a non-fixed shield orientation whereby upon application of force to the distal end of the obturator assembly, the guard and penetrating tip are permitted to move relative one another to facilitate puncturing of tissue by the penetrating tip.
BRIEF DESCRIPTION OF THE DRAWINGS
• Various embodiments are described herein with reference to the drawings, wherein:
• FIG. 1 is a perspective view of one embodiment of the modular trocar system constructed in accordance with the present disclosure;
• FIG. 2 is a perspective view of an obturator assembly constructed in accordance with the present disclosure;
• FIG. 3 is a perspective view with parts separated of the obturator assembly of the embodiment ofFIG. 2;
• FIG. 4 is an enlarged perspective view of a latch mechanism for a safety shield of the obturator assembly of the embodiment ofFIG. 2;
• FIG. 5 is a perspective view of a shield member of the obturator assembly;
• FIG. 6 is a perspective view of a slider member of the latch mechanism;
• FIG. 7 is a perspective view of a knife assembly of the obturator assembly;
• FIG. 8 is an enlarged view of the indicated area of detail inFIG. 7;
• FIG. 9 is a perspective view of the distal end of the knife assembly ofFIG. 7;
• FIG. 10 is a horizontal cross-sectional view taken through the knife assembly ofFIG. 7;
• FIG. 11 is a cross-sectional view taken along section line11-11 ofFIG. 10;
• FIG. 12 is a perspective view illustrating a step of assembling the obturator assembly;
• FIG. 13 is a further step of assembling the obturator assembly;
• FIG. 14 is a perspective view of the inside of a housing cover of the obturator assembly;
• FIG. 15 is a further step in the method of assembling the obturator assembly;
• FIG. 16 is a longitudinal cross-sectional view illustrating the assembled shield member and a shield extension member;
• FIG. 17 is a further step illustrating the assembly of a knife rod with previously assembled components of the obturator assembly;
• FIG. 18 is a cross-sectional view of the proximal end of the components of the obturator assembly illustrated inFIG. 17;
• FIG. 19 is a view similar toFIG. 18, which illustrates securement of the knife rod within the housing cover;
• FIG. 20 is a perspective view illustrating assembly of a guard member with the shield extension member;
• FIG. 20A is a perspective view of the distal end portion of the trocar assembly ofFIG. 1;
• FIG. 20B is a perspective view of an existing trocar assembly design;
• FIG. 21 is a longitudinal cross-sectional view taken through the distal end of the components illustrated inFIG. 20;
• FIG. 22 is a view similar toFIG. 21, showing the guard element attached to the distal end of the shield extension member;
• FIG. 23 is a longitudinal cross-sectional view taken through the obturator assembly;
• FIG. 24 is an enlarged view of the indicated area of detail ofFIG. 23;
• FIG. 25 is a longitudinal cross-sectional view taken through the trocar assembly of the present disclosure;
• FIG. 26 is an enlarged view of the proximal end components ofFIG. 25;
• FIG. 27 is view similar toFIG. 25, which shows insertion of a trocar assembly through the skin of a patient; and
• FIG. 28 is an enlarged view of the proximal end components ofFIG. 27.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
• Referring initially toFIGS. 1 and 2, one embodiment of a modular trocar system in accordance with the present disclosure is designated byreference numeral100 throughout the several views.Modular trocar system100 is particularly adapted for use in minimally invasive surgical procedures such as endoscopic or laparoscopic procedures. Generally,modular trocar system100 includes two principal subassemblies, namely anobturator assembly110 and acannula assembly112. Cannulaassembly112 includes aseal assembly114 and acannula116, as described in detail further herein.
• Except where noted otherwise, the materials utilized in the components of the presently disclosed modular trocar system generally include materials such as either ABS or polycarbonate for housing sections and related components and stainless steel for components that are required to cut tissue. A preferred ABS material is CYCOLAC which is available from General Electric. A preferred polycarbonate material is also available from General Electric under the trademark LEXAN. An alternative polycarbonate material which may be utilized is CALIBRE polycarbonate available from Dow Chemical Company. The polycarbonate materials may be partially glass filled for added strength.
• Referring now toFIGS. 3-9, and initially toFIGS. 3-6,obturator assembly110 includes anobturator housing118 formed fromhousing base119 andcylindrical housing cover120. Once the appropriate components are positioned therewithin (as described below),housing base119 may be attached tocylindrical housing cover120 by engaging mating surfaces, for example byresilient latches122 formed oncover120 interlocking with correspondingly shaped engaging surfaces123 (FIG. 24) formed in thehousing base119. To uniformly connectbase119 and cover120, preferably at least threecorresponding latches122 and engagingsurfaces123 are provided and are spaced evenly around the circumference ofcover120 andhousing base119, respectively.Base119 and cover120 are preferably molded from an ABS material and are preferably configured and dimensioned to functionally cooperate with various sizes of cannulas, e.g., 5-15 mm. Thus,obturator housing118 is adapted to be a modular component for use with a wide range of trocar assemblies.
• When fully assembled,obturator assembly110 includes a safety shield assembly that is movable with respect to a penetrating tip such as, for example,knife blade125. The safety shield assembly includes a shaft formed from an elongatedhollow shield member126 and ashield extension127. Adistal guard member128 is attached to the distal end ofshield extension127. Preferably, all of the safety shield assembly components are molded from a polycarbonate material.Guard member128 is preferably formed as a “dolphin nose” to help minimize the force necessary to penetrate the body. As shown inFIG. 5, the distal section ofelongated shield member126 is provided with a pair of opposing receiving holes148 (only one is visible) to facilitate interaction withshield extension128, as will be described below.Elongated shield member126 also includes a proximal end portion such ascollar130 having a shield position indicator, such asindicator flag132, extending transversely relative toelongated shield member126. Preferablyflag132 is colored to contrast sharply with the surrounding housing components. For example,indicator flag132 may be red if the surrounding housing components are white or light colored. Proximal end portion ofcollar130 includes a bearing surface such asledge134 and a pair ofposts135 formed belowledge134 and extending transversely outwardly.
• Elongated shield member126 is disposed within alongitudinal throughbore136,FIG. 3, formed through cylindricalextended portion138 ofhousing base119 with a distal end surface ofcollar130abutting housing base119 on a proximal face thereof. Cylindricalextended portion138 may be molded as part ofhousing base119 or molded separately and mounted tohousing base119, e.g., by sonic welding. Cylindricalextended portion138 provides transverse support to the shield and obturator components that pass therethrough and preferably includes aninward taper139 at its distal end to facilitate passage through valve/seal assemblies. Abutment between the distal and surface ofcollar130 andhousing base119 limits distal movement ofshield member126 relative thereto.Ledge134 interacts with aslot149 formed in alatch member150 molded as part ofbase119 to assist in the angular orientation ofshield member126 relative tohousing118.
• The safety shield assembly further includes acoil spring140 the distal end of which is seated inshield member126 in an opening formed at the proximal end ofcollar130. Referring temporarily toFIG. 14,housing cover120 preferably includes a distally directed, hollowcylindrical post144 molded to the proximal face thereof. Althoughhollow post144 serves several functions, initially it is noted thatcoil spring140, whichbiases shield member126 toward a distal-most position is positioned around hollowcylindrical post144. Thus,hollow post144 assists in alignment ofcoil spring140, e.g., to prevent kinking thereof. Referring temporarily toFIG. 24, the diameter ofcoil spring140 is preferably selected so thatspring140 fits in a gap region between concentricallydisposed collar130 andhollow post144.
• Housing cover120 is further provided with an open ended slot146 (FIGS. 2 and 14) to slidably receiveposition indicator flag132.Housing cover120 may further be provided with indicia (not shown) positioned adjacent open endedslot146 to provide additional visual indication to the user of the relative positioning of the shield, as is known in the art.
• As noted above, the shield member126 (and therefore the entire shield assembly) is biased in a distal-most position bycoil spring140. A latching mechanism is provided as part ofobturator assembly110 to prevent proximal movement of the shield assembly until such a time asobturator assembly110 is inserted in a cannula assembly, e.g.,cannula assembly112, and the surgeon is prepared to begin trocar entry.
• As best shown inFIGS. 4-6, the latching mechanism includeslatch member150 having twovertical leg portions152 and154 connected by aweb portion155. A pair of biasingposts157,159 extend outwardly, one for each side oflatch member150.Latch member150 is preferably molded as part ofhousing base119 in cantilevered fashion. However, latch150 may be formed as a separate element and secured to base119 by suitable known techniques.
• A release member such asslider156 is distally biased by acoil spring158 which is maintained in axial alignment with a lower end ofslider156 by apost160. The proximal end ofcoil spring158 bears against the inner surface ofhousing cover120 and is maintained in position between apost162 and acylindrical base164 formed in housing cover120 (FIG. 14). The distal biasing ofslider156 causes anarming button166, which extends distally from the distal face ofslider156, to project through an opening formed in the housing base119 (FIG. 24). Compression ofobturator assembly110 relative tocannula assembly112 causesslider156 to translate vertically in a proximal direction as will be described further herein. As shown inFIG. 6,slider156 includes a pair oflegs156a,156bwhich are each connected to abase portion156cand terminate in acrook156d,156econfigured and dimensioned to engageposts157,159 respectively, oflatch150.
• In a preferred embodiment, the components described above, namelyhousing base119,housing cover120, the latching mechanism components,coil spring140, cylindricalextended portion138 andelongated shield member126 constitute a first modular subassembly that may be advantageously manufactured in large quantities and inventoried for use across a wide range of trocar assembly sizes. As noted hereinbelow, other modular subassemblies may be manufactured to different size specifications, e.g., 5 mm, 10 mm, 15 mm, but all would be functionally operable with the first modular subassembly disclosed herein.
• Referring toFIGS. 3 and 7-11, assembly of a second modular subassembly includingknife blade125 will now be addressed in detail.Knife blade125 is preferably fabricated from stainless steel by a suitable process, e.g., by stamping or metal injection molding.
• A proximally extendingelongated portion168 is provided to facilitate attachment ofknife blade125 to aknife rod170. Elongatedproximal portion168 is provided with aslot172 and anotch174. Preferably,knife rod170 is formed by injection molding.Knife blade125 is positioned in the injection mold such that when the rod material is injected into the mold, the material flows around aweb portion176,FIG. 10, which separatesslot172 and notch174. When the material rejoins atslot172, it forms a knit-line178,FIG. 11, and attaches knife blade to the distal end ofknife rod170. Preferably,slot174 is provided with an arcuatedistal terminus180 in the shape of a “cul de sac” to permit the rod material to flow outwardly and fillterminus180.Knife blade125 is further provided with a pair oflateral notches182,184 formed on either side ofweb portion176.Notches182,184 facilitate proper orientation ofknife blade125 in the injection mold prior to formation ofknife rod170. Finally,knife blade125 has a pair of sharpenedcutting edges186,188, which converge to form a sharp penetration point.
• Referring toFIGS. 7, 8,10 and11,knife rod170 has aflexible finger190 formed at a proximal end.Flexible finger190 includes acam surface192 extending outwardly at a proximal end to facilitate assembly ofknife rod170 withhousing cover120, as will be described in greater detail herein.
• Referring now toFIGS. 12-20, a novel method of assembly ofobturator assembly110 is disclosed. As shown inFIG. 12,shield member126 andslider156 are fit intobase119.Shield member126 rides overslider156 causing the slider'slegs156a,156bto ride on top ofposts135 onshield member126.Slider156 fits overguide posts119a,119band119csuch thatbase portion156cis disposed betweenpost119aand posts119b,119c.Further,legs156a,156bare disposed on the outboard sides ofposts119b,119c,respectively.Shield spring140 andslider spring158 are added, as shown inFIG. 13, andhousing cover120 is snapped in place as described above. Referring toFIGS. 15 and 16,shield extension127 is then snapped into place at the distal end ofslider126. In particular,shield extension127 has a clevis formed at a proximal end defining two flexible halves. A pair ofnubs127a,127bsnap fit into receivingholes148 onshield member126.
• Referring toFIGS. 17-19,knife rod170 is slid in through the distal end ofshield extension127, throughshield126, and snapped in place inhousing cover120. As shown inFIGS. 18 and 19, insertion ofknife rod170 into hollowcylindrical post144 ofhousing cover120 causes cam surface to flexfinger190 untilcam surface192 isadjacent recess193 formed inhousing cover120 whereby camming surface entersrecess193 to secureknife rod170 incover120.
• Referring toFIGS. 20-22,guard128 is attached to distal end ofshield extension127. To facilitate attachment,guard128 is provided with a series offlexible fingers128a,128b,128c,128deach having a raised portion formed thereon. The raised portions lock in place in openings such as opening127aformed near the distal end ofshield extension member127. This unique method of assembly is particularly advantageous in that it allows for zero defects on the nose portion ofguard128 which translates into less hang up of the nose portion on tissue upon insertion oftrocar assembly100. For example,FIGS. 20A and 20B illustrate a comparison of the distal end portions of presently disclosedtrocar assembly100 and an existing trocar assembly design. The trocar design shown inFIG. 20B illustrates a circular opening labeled as “A” at the distal end. This opening enables a gap to exist between the knife blade and the opening upon initial insertion of the trocar assembly into a patient, thereby permitting hang-ups of the opening on tissue to occur. The presently disclosedtrocar assembly100 reduces the likelihood of such hang-ups by utilization of the “dolphin nose” design to eliminate the large gaps between the guard element and the knife blade. As an additional feature, eitherguard member128 and/orknife blade125 may be provided with a hydrophillic coating to further reduce the insertion force required to inserttrocar assembly100.
• As shown inFIGS. 20-22, the geometries of and cooperation betweenknife blade125 andguard member128 facilitate ease of insertion ofmodular trocar system100 through a patient's body wall while maintaining surgeon control and, by reason of springbiased guard128, provide an enhanced margin of safety to internal organs. Cuttingsurfaces186,188 are extendable beyond theslot195 formed inguard128. The knife tip portion defines a planar triangular shape. The knife tip portion may initially be generally formed by stamping or metal injection molding and the cutting edges186,188 finely sharpened on both sides ofknife blade125, for example, by machining and/or polishing of the surfaces. Cuttingsurfaces186,188 preferably extend radially outwardly to just within the outer diameter of the cylindrical portion ofguard member128, thereby achieving an incision which approximates the diameter ofguard member128. By incising to the diameter ofguard member128, the force required for insertingmodular trocar system100 through tissue, such as the patient's abdominal wall, is reduced.
• For larger diameter trocar assemblies, each of the components ofobturator assembly110 are the same except a larger sized knife blade and guard member are attached toknife rod170. Also, a larger cannula is attached to the cannula body. This interchangeability of different sized knives and guard members with standard sized components located proximally thereof obviates the need to manufacture and inventory both the components and whole units of non-modular, conventional trocar systems. In particular, the more complex and, therefore, more expensive size-specific elements located in the obturator housing need not be manufactured and inventoried. The manufacturer or distributor need only assemble the appropriate sized knife and guard member with the otherwise standard sized control components as demand dictates.
• Referring now toFIG. 1 in conjunction with and25-28,cannula assembly112 ofmodular trocar system100 includes a molded cylindrical base portion216 having transversely extendinggrip portions218 formed to extend form an annular flange formed at the proximal end of cylindrical base216. A series ofslots222 are formed along the underside or distal side ofgrips218. A similar modular cannula assembly is disclosed in U.S. Pat. No. 5,807,338 to Smith et al., the entire contents of which are hereby incorporated by reference. It is also contemplated, that either cannula base portion216 orcannula116 or both may be formed of transparent or translucent material.
• Slots222 are particularly advantageous in two respects. First, in assemblingcannula assembly112, there are three basic principle components: cylindrical base portion216 having outwardly directing finger grips218, a duckbill valve element224 having aflange226 which is configured and dimensioned to rest onannular flange220 of cylindrical base portion216 and a cannula housing cover portion such asproximal housing element228 which is configured and dimensioned to rest onduck bill flange226 and within the outwardly directed finger grips218. It has been found that by coring out the underside of outwardly extendingfinger grips218 withparallel slots222, molding sinks which had been previously forming on the proximal side of outwardly extendingfingers218 of cylindrical base portion216 were significantly reduced, thereby providing a much more reliable flat surface, as best shown inFIG. 18, against whichduck bill flange226 may rest and against which the upper orproximal housing element228 may be welded.
• This greater cooperation between the two cannula housing elements reduces the force which must be applied as between the two housing elements during the welding process, thereby reducing the likelihood that theduck bill valve224 will be torqued. Torquing of theduck bill valve224 can potentially reduce the sealing function of the element in the absence of a surgical instrument inserted therethrough.
• The second respect in whichslots222 are advantageous is that on the underside of the cylindrical base portion216 is normally the place where the user grips the cannula the cylindrical base portion216. Accordingly, the slots provide an improved gripping surface to the user.
• A further feature ofcannula assembly112 is the provision of adetachable cannula116 which readily connects and disconnects from cylindrical base portion216.Cannula116 is preferably molded with a substantially constant inner and outer diameter. However,cannula116 preferably includes a slightly larger inner diameter at its proximal end, e.g., of 2-3 cms length, to facilitate introduction of instrumentation, and a tapered outer diameter at its distal-most portion, e.g. over the distal-most 2-3 cms of length, the tapered outer diameter being largest at a proximal end thereof and smallest at a distal end thereof. In this way, molding is facilitated while penetration force is minimized by reducing the outer diameter ofcannula116 in the region where tissue first makes contact and by providing a gradual taper to the outside diameter to assist in dilation of tissue as it passes proximally along the outer wall ofcannula116.
• An elastomeric O-ring may be interposed between cylindrical base portion216 andcannula116 to maintain a fluid-type seal betweencannula116 and cylindrical base portion216.Cannula116 is formed of a predetermined diameter so as to form alongitudinal throughbore232 in communication with a passageway formed through cylindrical base portion216 andproximal housing element228.Cannula116 is further provided with anannular flange234 which is particularly sized to be received in the distal end of cylindrical base portion216.Flange234 is preferably a standard size such that cannulas having different sized diameter passageways formed therethrough may be formed with a flange that has the same configuration and dimension asflange234. In this manner, cannulas of varying sized and dimensions may be interchangeably attached to a given cylindrical base portion such as cylindrical base portion216.
• To facilitate the interconnectability ofcannula116 and cylindrical base portion216, a quick connect mechanism is provided which, for example, may be by a series of engageable mating members (not shown) formed oncannula116 proximal offlange234 whichinterconnect cannula116 with cylindrical base portion216 by way of a series of mating indented surfaces (not shown) formed along the inner wall of cylindrical base portion216. The two elements are brought into engagement with each other by inserting the proximal end ofcannula116 into the distal end of cylindrical base portion216 androtating cannula116 clockwise until the mating members engage and lock into the mating surfaces. The two elements may be disengaged by applying a proximally directed force to the cannula toward cylindrical base portion216 androtating cannula116 counterclockwise. This feature is particularly advantageous during manufacture and assembly ofcannula assembly112 in that it facilitates inventory management and manufacturing efficiencies due to the cylindrical base portion216 now being a single component which is able to be utilized across multiple cannula diameter products, the only difference being the cannula which is ultimately secured to the cylindrical base portions at the final stage of manufacture.
• Also provided oncannula assembly112 is aseal assembly240 which generally includes ahousing242 and aseal member244. A similar seal assembly is disclosed in copending PCT Application Serial No. PCT/US98/08970 filed May 1, 1998 by Racenet et al., the entire contents of which are hereby incorporated by reference.
• As another feature,cannula assembly112 may be provided with suture anchoring structure, for example suture anchor holes219 onfinger grips218 or devises221 formed near the proximal end ofcannula116.
• In usage, as shown inFIGS. 25-28,obturator assembly110 is inserted in the proximal end ofcannula assembly112.Obturator assembly110 is pushed intocannula assembly112 until the bottom ofhousing body119 contacts the proximal end ofcannula assembly112. In this manner, armingbutton166 ofslider156 is forced intohousing body119 thereby causingslider156 to rotate such thatlegs156aand156bpush latch150 outwardly so thatweb portion155 is out of axial alignment withledge134, as best shown inFIGS. 25 and 26. Thereafter,trocar assembly100 is inserted through the body wall of the patient,FIG. 27, causing theguard member128 to be urged proximally to revealknife blade125. The proximal movement ofguard member128 andshield member126 connected thereto byshield extension127 causeslegs156a,156bto be rotated back inwardly byposts135. This motion pusheslegs156a,156bupwardly and inwardly away fromlatch150 so thatcrooks156d,156e,respectively, ofslider156 no longer biaslatch150, permittinglatch150 to rest against the outer surface ofledge134. Once theknife blade125 and distal portion ofguard member128 pass through the body wall of the patient, the force ofspring140 causesslider126 to move distally, thereby resettingguard member128 by way ofledge134 once again blocking proximal movement ofguard member128. Onceguard member128 has returned to its distal (guarded) position, it cannot be retracted again until armingbutton166 is permitted to return to its distal position, i.e., by releasing pressure fromobturator assembly110 to allowobturator assembly110 to separate slightly fromcannula assembly112. Once this happens,spring158 pushesslider156 distally to permitlegs156a,156bto re-engageposts157,159 oflatch150.
• It will be understood that various modifications may be made to the embodiments disclosed herein. Therefore, the above description should not be construed as limiting, but merely as exemplifications of preferred embodiments. Those skilled in the art will envision other modifications within the scope and spirit of the present disclosure.

Claims (13)

1. A trocar system which comprises:

a cannula forming an opening longitudinally therethrough and having a proximally facing surface disposed near a proximal end thereof; and

an obturator assembly being at least partially insertable through the cannula and including:

a housing disposed at a proximal end, the housing including a base portion having a distally facing end surface configured and dimensioned to facilitate close proximate positioning thereof with the proximally facing surface of the cannula;

a penetrating tip disposed at a distal end;

an elongated shield including a guard extending from a shaft, the penetrating tip and guard being movable relative one another; and

a latch mechanism disposed generally within the housing, which facilitates changing the configuration of the obturator assembly between a fixed-shield orientation, wherein at least a portion of the guard is maintained to extend at least partially distal of the penetrating tip to prevent puncturing of tissue by the penetrating tip, to a non-fixed shield orientation whereby upon application of force to the distal end of the obturator assembly, the guard and penetrating tip are permitted to move relative one another to facilitate puncturing of tissue by the penetrating tip, the latch mechanism including:

a release member having a button portion and a camming surface; and

a latch operatively associated with the release member, the latch having a blocking surface and a mating surface, the mating surface cooperating with the camming surface of the release member such that upon movement of the release member the camming surface biases the mating surface to move the latch such that the blocking surface permits axial movement of the shield.

2. A trocar system as recited inclaim 1 wherein movement of the release member causes the blocking surface to be displaced out of axial alignment with the shield.

3. A trocar system as recited inclaim 1 wherein the button portion protrudes at least partially through an opening formed in the distally facing end surface of the obturator housing.

4. A trocar system as recited inclaim 1 wherein the latch is biased such that the blocking surface is normally disposed in axial alignment with at least a portion of the shield to prevent axial movement thereof.

5. A trocar system as recited inclaim 2 wherein the blocking surface is disposed proximal of the at least a portion of the shield.

6. A trocar system as recited inclaim 1 wherein the release member is configured and dimensioned such that axial movement of the release member imparts lateral movement of the blocking surface of the latch member.

7. A trocar system as recited inclaim 1 wherein the obturator includes a shaft fixed relative to the housing and the penetrating tip is a flat knife blade secured to the shaft.

8. A trocar system as recited inclaim 1 wherein the shield includes an extended surface which is disposed on the shield such that upon axial movement of the shield, the extended surface biases the actuator member away from the latch to permit the latch to return to its original orientation.

9. A trocar system as recited inclaim 1 wherein the guard is configured and dimensioned to completely enclose the penetrating tip.

10. A trocar system as recited inclaim 1, wherein the shield and guard are separate elements fitted together during assembly of the obturator.

11. A method of inserting a trocar assembly into a patient comprising the steps of:

approximating an obturator assembly with a cannula assembly such that a button portion of a release member is urged proximally and a camming surface of the release member imparts lateral movement of a blocking surface of a latch such that the blocking surface is moved to permit relative movement of the shield and a penetrating tip of the obturator assembly; and

inserting the trocar assembly through the body wall of a patient by pushing the trocar assembly toward the body wall such that a guard of the shield is urged proximally to reveal the penetrating tip and permit passage of the trocar assembly through the body wall.

12. A method of inserting a trocar assembly as recited inclaim 11 wherein lateral movement of the blocking member moves the blocking member out of axial alignment with the shield.

13. A method of inserting a trocar assembly as recited inclaim 11, further including the step of resetting the shield to a fixed orientation distal of the penetrating tip upon passage of the penetrating tip through the body wall and into a cavity of the patient's body, such resetting being facilitated by axial movement of the shield and resilient bias of the latch to a position wherein the blocking surface is axially aligned with at least a portion of the shield.

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