Abstract:
A safety trocar is provided in which the cannula is reciprocally mounted to the cannula housing and reciprocates into the cannula housing when a proximally directed force is applied thereto. The piercing tip is maintained in the exposed position by a latching mechanism associated with the obturator shaft, and is automatically withdrawn into the cannula under the force of a spring when the proximal force is removed from the cannula, the cannula thus advancing distally and releasing the latching mechanism. Penetration force is maintained at a minimum, and safe and efficacious trocar entry is facilitated.

Description:
RELATED APPLICATIONS 
     This is a continuation of application Ser. No. 08/352,274 filed Dec. 7,1994, now U.S. Pat. No. 5,486,190, which is a continuation of application Ser. No. 08/176,001 filed Dec. 30, 1993, now abandoned, which is a continuation of application Ser. No. 07/693,582 filed Apr. 30, 1991, now U.S. Pat. No. 5,295,993. This application is also a continuation-in-part of copending application Ser. No. 08/122,612 filed Sep. 15, 1993 now U.S. Pat. No. 6,197,041 which is a continuation of application Ser. No. 07/721,173 filed Jun. 26, 1991, now abandoned. 
    
    
     TECHNICAL FIELD 
     This invention relates to a surgical trocar and more, particularly to a safety trocar in which the sharp cutting tip retracts into the cannula so as to minimize the likelihood of inadvertent injury to viscera and other internal tissue. 
     DESCRIPTION OF THE PRIOR ART 
     Trocars are sharp pointed surgical instruments used to puncture a body cavity. Trocars are generally adapted to be used together with a tubular trocar sleeve or cannula. Once the body cavity has been punctured by the trocar, the sharp trocar is removed from the cannula, thereby leaving the cannula extending into the body cavity. Endoscopic surgical procedures are then performed through the cannula with accessory instrumentation such as laparoscopes, dissectors, graspers, etc. 
     Commercially available safety trocars include a spring-loaded safety shield which is adapted to cover the trocar tip once the body cavity has been entered so as to provide an increased level of protection to internal structures from puncture or laceration. For example, U.S. Pat. No. 4,601,710 to Moll describes a trocar assembly which consists of two subassemblies: a trocar subassembly which includes a sharp-tipped trocar and a spring-loaded tubular safety shield positioned therearound, and a cannula subassembly. 
     When ready for use, the trocar and safety shield of the trocar subassembly are inserted through the cannula. The safety shield is initially in its distal-most position covering the trocar tip. Exertion of pressure against the skin with the trocar causes the shield to be pushed rearwardly against the spring to expose the piercing tip of the trocar. The tip penetrates the skin and underlying tissue with continued pressure. Once the tip has penetrated through the wall and has entered the cavity, the force against the front end of the shield ceases and the shield is automatically moved back to its distally extended position. Viscera and other internal tissue are thus protected from contact with the sharp piercing tip and potential damage therefrom. 
     An article entitled “Needle for the Puncture and Lavage of the Abdominal Cavity” authored by F. S. Subairov discloses a safety device for puncturing the abdominal cavity which consists of a hollow tube, a stylet and a spring. The spring is soldered to the stylet and threaded into the rear of the hollow tube. The distal end of the stylet is exposed from the hollow tube by pressing the stylet toward the tube, thereby compressing the spring. Once the stylet and tube enter a body cavity, the tube is advanced under spring force to cover the distal end of the stylet. A similar device is disclosed in EP 350,291 (see FIGS. 1-4). 
     U.S. Pat. No. 4,535,773 to Yoon suggests several alternative safety trocar designs. In-one embodiment (see FIGS. 22-28), a spring-loaded blunt probe is provided within the trocar shaft, as with conventional Verres needles. The blunt probe is adapted to reciprocally slide through an aperture in the trocar tip such that when the trocar tip enters a body cavity, the blunt probe springs distally forward through the aperture to prevent contact between the trocar tip and body organs. In a second embodiment (see FIGS. 33-36), pressure sensors or transducers are fitted into the trocar blade surfaces and the distal end of the cannula. Sets of electrical leads run through the trocar shaft and communicate with an alarm network in the proximal portion of the device. A further modification is suggested in which the trocar shaft is initially manually extended and maintained in its extended position by a detent which protrudes through a hole in the surrounding tubular structure. The hole aligns with a solenoid socket. When the instrument is fully assembled and the trocar tip is forced through a body wall, the electrical leads running through the trocar shaft send electrical signals to the solenoid which, at the appropriate instant, forces the detent from the hole, allowing the trocar tip to withdraw into the cannula. Additional mechanisms for effecting withdrawal of cutting implements are also known. See, e.g., U.S. Pat. Nos. 4,375,815 to Burns; 3,657,812 to Lee; and 3,030,959 to Grunert. 
     SUMMARY OF THE INVENTION 
     It has now been found that an improved safety trocar may be provided which includes: 
     (a) a cannula assembly comprising a cannula and a cannula housing; 
     (b) a trocar assembly comprising a sharp trocar tip, an obturator shaft, and a trocar housing; 
     (c) means associated with the obturator shaft which releasably maintains the trocar tip in an extended position; 
     (d) means associated with the cannula assembly for releasing the releasable obturator means; and 
     (e) biasing means for retracting the trocar tip from the extended position to a retracted position in response to release of the releasable obturator means. 
     The safety trocar of the present invention is adapted to be armed by the surgeon immediately prior to use. Arming may be accomplished by advancing a button which extends through the trocar housing, by compressing the trocar housing toward the cannula housing, or by like means. Once armed, the trocar tip releasably protrudes beyond the distal end of the cannula. 
     As the surgeon presses the trocar, and more particularly the trocar tip, against the body wall of a patient, an incision into and through the body wall is begun. With continued pressure by the surgeon, the distal end of the cannula comes into contact with the body wall. The initial counterforce exerted by the body wall against the cannula causes a mechanism associated with the cannula to set the obturator shaft (together with the cutting tip) for immediate retraction upon entry of distal end of the the cannula into the body cavity. Thus, removal of the counterforce from the distal end of the cannula, e.g., upon entering the body cavity, results in immediate and automatic withdrawal of the trocar tip into the cannula under the force of a biasing means, e.g., a spring. 
     In a preferred embodiment of the trocar, a latch is associated with the obturator shaft to which the trocar tip is mounted, the latch being biased radially outward and being adapted to engage an internal shelf formed in the cannula when the trocar is armed. The cannula is reciprocally mounted to the cannula housing and biased, e.g., by a compression spring, distally relative to the cannula housing. As the trocar tip enters the body cavity and the body wall exerts force on the distal end of the cannula the cannula reciprocates proximate into the cannula housing. This cannula reciprocation repositions the cannula&#39;s internal shelf relative to the latch such that, upon distal movement of the cannula upon entry into the body cavity, the latch is released from engagement with the internal shelf. A spring which was loaded upon arming the trocar is thus free to immediately retract the trocar tip into the cannula. In a particularly preferred trocar embodiment, abutment means are provided on the exterior of the cannula toward its distal end to facilitate reciprocation thereof through contact with the body wall. 
     The trocar of the invention is also designed to permit manual retraction or disarming of the cutting tip, if so desired. This is accomplished by manually reciprocating the cannula relative to the cannula housing and releasing, thereby disengaging the latch from the internal shelf. The trocar is also typically provided with an indicator which signals the surgeon as to whether the trocar is armed or disarmed. For example, the relative position of the button used to arm the trocar may be calibrated or indexed to communicate the trocar tip position or a window may be provided through which a trocar tip position indicator is visible. 
     The trocar of the present invention provides a safe and efficacious means for gaining access to body cavities to permit minimally-invasive diagnostic and surgical procedures to be accomplished. The trocar is equipped with a reliable mechanism for effectuating immediate, automatic retraction of the cutting tip into the cannula. Penetration force is kept to a minimum through the unique internal mechanism for releasably maintaining the trocar tip in the armed position. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
     FIG. 1 is a side view of a trocar of the present invention in an armed configuration; 
     FIG. 2 is a top view of the trocar assembly of FIG. 1, partially in cross section; 
     FIG. 3 is an exploded view of a spring assembly; 
     FIG. 4 is a front view of a top trocar housing; 
     FIGS. 5 and 6 are plan and side views, respectively, of a spring-retaining plate; 
     FIGS. 7 and 8 are partial side views of the cannula; 
     FIG. 9 is a plan view of a lower cannula housing; 
     FIG. 10 is a sectional side view of the cannula housing of FIG. 9 taken along line  10 - 10 ; 
     FIG. 11 is a bottom view of a trocar housing; 
     FIG. 12 is a side view of a shelf insert; 
     FIG. 13 is a front view of the shelf insert of FIG. 12; 
     FIG. 14 is a side view of a latch; 
     FIG. 15 is a side view of a latch release finger; 
     FIG. 16 is a side view, partially in section, of a portion of a cannula; and 
     FIG. 17 is a side view of a latch subassembly. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIG. 1, trocar  10  is shown in its fully assembled condition with cutting tip  12  extending from cannula  14 . Trocar  10  includes a trocar assembly  16  and a cannula assembly  18 . The longitudinally extending or endoscopic portion of trocar assembly  16  which extends from trocar housing  20  is shielded from view in FIG. 1 by cannula housing  21  and cannula  14 , except for extended cutting tip  12 . A circumferential abutment surface  15  is provided toward the distal end of cannula  14 . 
     Referring now to FIGS. 2 and 3, pyramidal cutting tip  12  is rotatably mounted to obturator shaft  22  at swivel joint  24 . A cylindrical channel  26  is formed in the proximal end of obturator shaft  22 . A tension spring  28  (see FIGS. 1 and 3) is positioned within channel  26  and anchored to obturator shaft  22  at distal extension  30  by pin  32 . An anchor pin  34  which is adapted to mount to rear wall  36  of trocar housing  20  includes an aperture  35  which cooperates with proximal arm  37  to anchor tension spring  28  to trocar housing  20 . 
     A flange  38  is formed at the proximal end of obturator shaft  22  encircling tension spring  28 . Flange  38  forms a half-moon shaped button  40  which slides within slot  42  in the upper face  44  of trocar housing  20 . Movement of button  40  within slot  42  moves obturator shaft  22  and cutting tip  12  relative to trocar housing  20 . Tension spring  28  biases obturator shaft  22  and its accompanying structure proximally, such that flange  38  rests against rear face  46  of slot  42  absent external influences. 
     Referring to FIG. 4, top housing  48  of trocar housing  20  is shown. Top housing  48  includes mounting legs  50  for attachment to a bottom housing  90  (FIG.  11 ). Upper face  44  includes a concave region  52  in the base of which is formed slot  42 . As most clearly seen in FIG. 1, button  40  is sized and dimensioned to conform to and slide within concave region  52  while extending slightly above upper face  44  of trocar housing  20 . The cooperation between concave region  52  and button  40  facilitates unimpeded movement of button  40 , particularly upon retraction of trocar tip  12  as discussed below, without sacrificing convenient thumb access to button  40  for arming of trocar  10  by the surgeon. 
     Turning to cannula assembly  18 , cannula  14  defines a tubular lumen and is reciprocally mounted to cannula housing  21 . Referring to FIGS.  2  and  5 - 8 , a spring-retaining plate  54  is mounted to flange  56  at the proximal end of cannula  14 , e.g., by adhesive or welding, with central aperture  58  in plate  54  aligned with the lumen through cannula  14 . Aperture  58  is sized to accommodate unencumbered passage of obturator shaft  22  and includes oppositely directed extension arms  62 , each arm  62  having an aperture  64 . Apertures  64  receive and frictionally engage cylindrical pins  66 . Aperture extension  60  is formed in one extension arm  62  allowing passage of latch subassembly  147  therethrough, as described below. 
     Referring again to FIG. 2, cannula housing  21  receives spring-retaining plate  54  with cylindrical pins  66  facing proximally. Compression springs  68  are positioned against extension arms  62  and around pins  66 . Pins  66  thus act to position and support springs  68 . Chambers  70  are formed in cannula housing  21  to receive and capture the opposite ends of compression springs  68 . Reciprocation of cannula  14  into cannula housing  21  causes proximal movement of plate  54  which compresses springs  68  within chambers  70 , thereby biasing cannula  14  in the distal direction. 
     Returning to FIGS. 7 and 8, the proximal end of cannula  14  includes two slots  72  and  74 , preferably separated by at least 90°. Alignment slot  72  serves to maintain rotational alignment of cannula  14  with respect to cannula housing  21 . Referring additionally to FIGS. 9 and 10, alignment pin  76  is fixedly secured within aperture  78  in lower cannula housing  80  and, when fully inserted into housing  80 , extends into lumen  82 . In assembling cannula  14  within lower cannula housing  80 , alignment pin  76  is positioned within alignment slot  72 , thereby preventing rotation of cannula  14  yet permitting axial movement of cannula  14  relative to cannula housing  21 . Additionally, inwardly directed orientation pin  84  on proximal housing extension face  86  cooperates with an orientation slot  88  in bottom housing  90  (see FIG. 11) to ensure proper alignment between cannula housing  21  and trocar housing  20 . A gasket  92  and stabilizer plate  96  are positioned within flange  94  in lower cannula housing  80  to provide a gas seal with inserted instrumentation, and to cooperate with an internal flapper valve, as is known in the art. 
     Slot  74  in cannula  14  forms an internal shelf  98  with which latch  100  (see FIG. 14) is adapted to engage. Internal shelf insert  102  (FIGS. 12 and 13) is positioned within cavity  104  in lower cannula housing. Shelf insert  102  comprises angled latching faces  106 , bridging arm  108  and longitudinal slot  110 . Shelf insert  102  is positioned within cavity  104  such that angled latching faces  106  are directed distally and edges  112  are substantially aligned with internal shelf  98  of cannula  14 . Bridging arm  108  abuts outer wall  114  of cavity  104  and is typically secured thereto, e.g., by an adhesive. 
     Latch  100  has a body  116  which forms a latch finger  118  which includes an outer camming face  120  and an inner latching face  122 . Aperture  124  is located in mid-region  117  of body  116  and permits latch  100  to be movably joined to latch release finger  126  (see FIGS.  15  and  17 ). Mid-region  117  is of reduced thickness relative to the remainder of body  116  to accommodate latch release finger  126 . Aperture  128  is formed in the region of body  116  distant from latch finger  118 . 
     Latch release finger  126  includes a substantially triangularly-shaped extension  138  having distal and proximal cam faces  140  and  142 , respectively. Latch release finger  126  also includes an aperture  144  and a spring abutment region  145 . As shown in FIG. 16, latch release finger  126  is movably mounted to latch  100  by means of a pin (not pictured) which passes through apertures  144  and  124  to form a latch subassembly  147 . When release finger  126  is positioned such that extension  138  is directed toward aperture  128 , abutment region  145  extends below latch wall  148 . 
     Latch subassembly  147  is pivotally joined to obturator shaft  22  by a pin (not pictured) which passes through aperture  128  in latch body  116  and aperture  132  in hollow region  130  of shaft  22 . As shown in FIG. 16, a leaf spring  134  is mounted to shelf  136  in hollow region  130 , e.g., by an adhesive. The proximal region  146  of leaf spring  134  biases latch  100  clockwise around aperture  128  and biases release finger  126  counter-clockwise relative to aperture  144 . Hollow region  130  is sized and dimensioned to permit latch subassembly  147  to be fully recessed therewithin (against the bias of leaf spring  134 ). Inasmuch as release finger  126  is restricted in its counter-clockwise rotation by latch finger  118  and/or abutment with wall  119 , and in its clockwise rotation by engagement between spring abutment region  145  and leaf spring  134 , the full range of rotation of release finger  126  is approximately 90°. 
     In use, cutting tip  12  and obturator shaft  22  are introduced through cannula housing  21  and into cannula  14 . When obturator shaft  22  is fully inserted, trocar housing  16  abuts cannula housing  21 . However, cutting tip  21  remains within cannula  14  until trocar  10  is armed by the surgeon. To arm the instrument, the surgeon advances button  40  within channel  42  which distally advances obturator shaft  22  and causes cutting tip  12  to extend beyond cannula  14 . Distal movement of obturator shaft  22  also results in distal movement of latch subassembly  147 . 
     Leaf spring  134  biases latch subassembly  147  outward from hollow region  130 . As obturator shaft  22  moves distally, outwardly biased latch subassembly  147  passes through aperture extension  60  in spring-retaining plate  54 . Outer camming face  120  of latch  100  then contacts flange  56  at the proximal end of cannula  14 , causing counterclockwise rotation of latch subassembly  147  relative to aperture  128  (see FIG.  17 ). This counterclockwise rotation recesses latch subassembly  147  within hollow region  130  against the bias of leaf spring  134 . 
     As cutting tip  12  approaches its fully armed position, latch subassembly  147  comes into alignment with slot  74  in cannula  14 . Outer camming face  120  is thus freed from contact with the inner surface of cannula  14 , and leaf spring  134  causes latch subassembly  147  to rotate clockwise such that latch finger  118  extends radially outward from hollow region  130 . However, latch release finger  126  remains positioned such that extension  138  is directed substantially toward aperture  128 , with abutment region  145  resting against leaf spring  134 . The freeing of camming face  120  from contact with cannula  14  is generally accompanied by an audible click, signalling the surgeon that trocar  10  is armed and further distal movement of button  40  is unnecessary. 
     When the surgeon releases button  40 , tension spring  38  draws obturator shaft  22  proximally until inner latching face  122  of latch  100  engages internal shelf  98  and shelf insert  102 . Latch release finger  126  passes back within cannula  14  proximal of slot  74 , thereby pressing abutment region  145  against the bias of leaf spring  134 . In this fully armed position of FIGS. 1 and 2, cutting tip  12  extends beyond cannula  14  and button  40  is distally located within slot  42 . 
     The surgeon presses armed trocar  10  against the body wall of a patient, thus causing piercing tip  12  to incise the tissue. As cutting tip  12  passes through the body wall, the distal end of cannula  14  is brought into engagement with tissue. The counterforce exerted by the body wall against cannula  14  and abutment surface  15  causes cannula  14  to move proximally against the bias of compression springs  68 . This proximal movement of cannula  14  release latch release finger  126  to enter slot  74 . Latch release finger  126  rotates counterclockwise relative to aperture  144  within longitudinal slot  110  in shelf insert  102 . 
     As the surgeon continues to press trocar  10  against the body wall, piercing tip  12  enters the body cavity. Continued pressure by the surgeon advances cannula  14  into the body cavity as well. As soon as the counterforce of the body wall against the distal end of the cannula  14  and abutment surface  15  is surpassed by the distally-directed force of compression springs  68  against spring-retaining plate  54 , cannula  14  is driven distally relative to cannula housing  18 . As cannula  14  moves distally, internal shelf  98  contacts proximal cam face  142  of latch release finger  126 . Latch release finger  126  is thus driven counterclockwise such that extension  138  abuts latch finger  118  and/or the body of latch release finger  126  abuts wall  119  of latch  100 . In this position, latch release finger  126  prevents engagement between internal shelf  98  and latch finger  118 . 
     As cannula  14  continues to move distally, internal shelf  98  cams latch subassembly  147  counterclockwise relative to aperture  128  against the bias of leaf spring  134 , thus freeing latch finger  118  from engagement with shelf insert  102 . As soon as the tip of latch finger  118  rotates out of engagement with shelf insert  102 , tension spring  28  draws obturator shaft  22  and cutting tip  12  proximally such that cutting tip  12  is positioned within cannula  14 . Button  40  is also drawn proximally within slot  42  and is once again positioned to allow the surgeon to arm trocar  10 , if so desired. 
     If, after arming trocar  10 , the surgeon determines that it is desirable to manually retract cutting tip  12  into cannula  14 , the surgeon simply moves cannula  14  proximally with respect to cannula housing  18  and releases. Cannula  14  will then move distally under the bias of compression springs  68  rotating latch subassembly  147  counterclockwise. Latch finger  118  is thus moved out of engagement with shelf insert  102 , allowing tension spring  28  to withdraw cutting tip  12  into cannula  14 . 
     The position of button  40  within slot  42  provides the surgeon with a visual indication of the position of cutting tip  12  relative to cannula  14 . The audible click associated with the movement of latch  100  during the arming of trocar  10  also provides an aural signal to the surgeon. 
     Many structures may be included toward the distal end of cannula  14  to facilitate the sensing of body wall counterforce to effectuate reciprocation of cannula  14 , abutment surface  15  being but one example. Exemplary structures include radially spaced, outwardly directed protuberances, inflatable means of the type known in the art for fixedly positioning catheters and like devices, and flange means of varying geometries. Such structures may be fixedly secured to cannula  14  or repositionable along the longitudinal axis of cannula based on such factors as patient size and weight. 
     While the above description contains many specific details, these details should not be construed as limitations on the scope of the invention, but merely as examples of preferred embodiments thereof. Those skilled in the art will envision many other possible variations that are within the scope and spirit of the invention as defined by the claims appended hereto.