Trocar with retracting tip and palm actuator mechanism

TROCAR WITH RETRACTING TIP AND PALM ACTUATOR MECHANISM

00021. Field of the Invention

0003This invention relates to surgical instruments, and in particular to an improved trocar for providing com¬ munication with a body cavity. Specifically, it relates to such a trocar having a palm cocking mechanism. 2. Background of the Invention

0004Trocars are very useful surgical instruments that essentially comprise a trocar tube or cannula, which surrounds an obturator having a sharp point or tip on the distal end thereof. The trocar assembly thus described is manually forced by the surgeon with the sharp point or tip serving to pierce the body wall so as to admit the surrounding trocar tube. After the tube is in communication with the body cavity, the obturator is removed and various instruments may be inserted into the cavity through the trocar tube. One such application is to insert an endoscopic instrument for performing endo- scopic surgery within the cavity.

0005A common problem with the simple trocars that were first used is the danger associated with an unprotected piercing tip. First of all, the sharp pointed tip can cause injury to the surgeon and others if it is unpro¬ tected prior to use. After insertion through the body wall, the tip can cause injury to body tissue and organs. In order to solve these and other problems, trocars have been developed that have spring-loaded tubular shields that normally protect and cover the sharp pointed tip until and incident to the trocar tube being thrust through, the body wall tissue. Two such, prior art trocars are shown in U.S. Patent No. 4,601,710 to Moll and U.S. Patent^"No. 4,654,030 to Moll, et al. With the devices of these patents, the surrounding trocar tube is forced in a proximal direction against a biasing spring incident to passing through the body wall tissue so as to expose the pointed tip, which is normally recessed just inside the open distal end of the trocar tube. Once through the body wall, the force on the trocar tube diminishes and it is forced in a distal direction by spring force until it again covers the tip. It thus covers the sharp pointed tip within the body cavity and thereby protects against injury. A locking mechanism may also be provided so that the trocar tube may not be accidentally retracted.

0006A problem with this just-described prior art device is that the trocar tube must move distally against tis- sue resistance in order to cover and protect the tip within the body cavity. Another problem is that a fairly high penetration force is required to cause the blunt trocar tube to move in a proximal direction and uncover the tip until penetration has occurred.

0007Summary and Objects of the Invention .

0008In order to solve the above-described problems, the instant invention provides a trocar wherein an obturator within the trocar tube is movable from a protected posi¬ tion within the tube to an advanced or operative posi- tion in advance of the distal end of the tube. After piercing the body wall and into the cavity, a mechanism in the trocar body reacts to a decrease in force on the tip, and the obturator and attached tip are quickly and automatically withdrawn to a retracted position within the protective trocar tube. Another feature is the provision of a cocking mechanism that is actuable by one hand by means of a palm-operated pushbutton in the rear of the grip housing. By depressing the pushbutton with the palm of the hand, the point is moved forward to be in advance of the trocar tube, and the pushbutton locked in the depressed position. A mechanical advantage is provided wherein the movement of the pushbutton results in about a 2:1 movement of the obturator. Upon penetra¬ tion, the tip moves in a proximal direction for a small "float distance" until it is restrained by the mecha¬ nism. After penetration has been fully completed, the force on the tip decreases and the tip will move dis- tally a short distance, after which a main spring will operate to retract the obturator and thereby the tip. At the end of the retraction, the pushbutton will be unlocked and returned to its normal position extended from the rear of the grip, thus giving a visual indica¬ tion that the trocar is ready for another cycle.

0009Another advantage is that the instant device uses a series of linkages, tracks and springs which are designed to isolate the various motions and forces for purposes of "tuning." For example, a large main spring is used for firing, while a smaller secondary spring is used to oppose the "float distance." In this manner, the springs are tuned to the forces that are needed for their particular function. This also prevents the trocar from "jumping" in the surgeon's hand during point retraction. Still another advantage is the ability to recock the mechanism if it has been fired prematurely, and to do so with ease and with one hand. The palm cock pushbutton facilitates this. Such premature firing can occur due to surgeon technique of hesitation or with¬ drawal. Brief Description of the Drawings

0010Fig. 1 is an exploded top quarter isometric view of the inventive trocar showing its two subassemblies;

0011Fig. 2 is an exploded top quarter isometric view of one of the subassemblies of Fig. 1, namely, the trocar body subassembly;

0012Fig. 3. is a bottom quarter isometric view of the top housing of the trocar body shown in Fig. 2;

0013Fig. 4 is an exploded top quarter isometric view of the other of the subassemblies of Fig. 1, namely, the trocar tube subassembly;

0014Fig. 5 is a top plan cross-sectional view of the inventive trocar in its initial, protected position within the trocar tube; Fig. 6 is a similar view showing the sharp pointed tip of the obturator extended from the trocar tube after depressing the palm cock pushbutton;

0015Fig. 7 is a view of the same with the tip having traveled a small distance back into the trocar tube upon being thrust through a body wall;

0016Fig. 8 is a view of the same with the tip being fully retracted and the palm cock pushbutton returned to its original position;

0017Fig. 9 is a partial, inverted cross-sectional view taken along lines 9-9 in Fig. 1;

0018Fig. 10 is a top plan cross-sectional view of an alternate embodiment wherein the obturator is of reduced diameter to minimize frictional drag from contact with the flapper valve.

0019Detailed Description

0020As shown in Fig. 1, the trocar assembly 10 consists of two basic subassemblies: a trocar tube subassembly 12 and a co-axial trocar body subassembly 14. The two sub- assemblies are designed to be separable from each other as shown. Trocar body subassembly 14 includes a head or grip 16 made up of top and bottom halves 18, 20, respec¬ tively. These top and bottom halves may be made of plastic material such as ABS plastic. The grip 16 is generally rectangular with a rounded rear end wall 22 adapted to fit the palm of the hand of the surgeon. Axially projecting from the rear end wall is a movable pushbutton 24 which will be more fully described here¬ after. Located in the distal end of the grip is a slot 26 which is dimensioned to closely receive a correspond- ingly shaped trocar tube body 28.

0021The slot 26 defines a pair of spaced parallel arms 30, 32 having wings 34, 36 extending laterally there¬ from. Projecting from an aperture 38 in front wall 40 within slot 26 is an elongated obturator 42, which may be conveniently be made of plastic, aluminum or other metal material. A sharp piercing tip or point 44, which may conveniently be made of aluminum or stainless steel material, is fixedly mounted on the distal end thereof. The piercing tip is formed by the intersection of three angled surfaces, two of which are shown at 46, 48. The obturator 42 has a tapered surface which narrows from its distal end 50 to its proximal end to facilitate movement through body tissue. It also has a reduced diameter portion 49 where it enters aperture 38 thereby to facilitate movement through valve body seal 51, as seen in Fig. 5.

0022Returning to Fig. 1, the trocar tube body 28 may be made of plastic material such as ABS plastic. Rounded rear portion 52 of trocar tube body 28 fits within a correspondingly-shaped portion of grip 16. When in this fully engaged position, rounded front walls of the trocar tube body, one of which is shown at 54, will be in register with correspondingly-shaped front walls 56, 58 of grip 16. In this manner, the surgeon can conve- niently grip the trocar by placing a finger on each front wall 56, 58 while holding the rounded rear wall 22 and pushbutton 24 in the palm of the hand.

0023Projecting from the trocar tube body 28 in a distal direction is a tubular trocar tube or cannula 60, which may also be of ABS plastic. The tube 60 has an angled opening 62 and a tapered end portion 64 to facilitate travel through the body wall. A valve lever 65 movable in a recess 66 on the top^" of the trocar tube body 28 permits opening a flapper valve (not shown) , as will be described hereafter.

0024Turning to Fig. 2, the trocar body subassembly will now be described. As seen in this figure, top half 18 and bottom half 20 of grip 16 define a hollow chamber 68 therebetween. The top and bottom halves may be con- veniently held together by fasteners, such as pins 70, press fit into accommodating holes 71 in the top and bottom halves. Pushbutton 24 projects through generally square aperture 72 in the rear end wall 22 of grip 16. Pushbutton 24 includes a rectangular rail 74 on its bot- torn that slides in a correspondingly-shaped track (not shown) in wall '76 of bottom half 20. Travel in the proximal direction is limited by a stop 78 molded into the half 20. A vertical ridge 79 molded in the lateral wall of the pushbutton 24 is biased against the stop 78 by means of a pushbutton coil spring 80. This coil spring is held in place between a projection 82 on push¬ button 66 and a projection 84 on the interior of the bottom half 20.

0025A bifurcated locking member 86 includes a bottom leaf 88 which is normally located in the path of ridge 79 so as to lock the pushbutton in its fully depressed position. Locking member 86 fits within and is retained by elongated groove 90 in a side wall of chamber 68. Located within the chamber 68 is a rotator assembly 92. The rotator assembly consists of upper and lower link members 94, 96. These link members have elongated slots 98, 100 in their proximal ends. Upper link member 94 has depending therefrom at its proximal end an integral cylindrical shaft 102 with a vertical groove 104 there¬ in. Similarly, lower link member 96 has an upwardly directed cylindrical shaft 106 with a tongue 108 dimen¬ sioned to be closely fitted within groove 104. An integral cam 110 on shaft 106 serves to depress leaf 88 at the end of a cycle to permit pushbutton 24 to return to its normal position extended from grip 16. Pin 112 passes through holes 114 and 116 in upper and lower link members 94, 96 respectively. The lower end of pin 112 is restrained in hole 118 in the interior wall 76 of lower half 20. Similarly, and as best seen in Fig. 3, a hole 120 is provided in the inner wall 122 of upper half 18 to accommodate the upper end of pin 112.

0026Returning to Fig. 2 , a cylindrical shaft 124 having a bore 126 therethrough is integrally connected to a middle link member 128. A pin 130 passes through this bore and the ends of pin 130 pass through slots 98, 100 and are movable therein. The lower end of pin 130 is guided by arcuate groove 132 molded within wall 76 of lower half 20. Similarly, and turning to Fig. 3 again, the upper end of pin 130 travels in arcuate groove 134 in upper half 18. Returning to Fig. 2, main torsion spring 136 is wrapped about shaft 106. One free end 138 of the spring is bent at right angles and contacts inte¬ rior side wall 140. The other end 142 is curved and wrapped around shaft 124. Secondary torsion spring 144 has its free ends 146, 148 wrapped around shafts 106 and 124 respectively. A latch 150 is fixed to inner wall 76 by means of screw 152.

0027The rotator assembly 92 is connected to obturator 42 by means of a pin 154 which secures middle link mem¬ ber 128 within slot 156 in the proximal reduced diameter portion 49 of obturator 42. Pivotal movement of the rotator assembly 92 about pin 112 thereby is transmitted to obturator 42 through links 94, 96, shaft 124 and link 128, so as to reciprocate the reduced diameter portion 49 of obturator 42 in aperture 38.

0028Referring to Fig. 5, the trocar assembly 10 is shown in its initial position for storage, transporta¬ tion, and pre-stick clinical handling. In this position and condition, the trocar tip 44 resides within and spaced from the open end 62 of trocar tube 60. Pushbut¬ ton 24, the top portion of which has been cut away for purposes of clarity, extends rearwardly through aperture 72 in grip 16 in a position to be actuated by the palm of the surgeon's hand when the first and second fingers are in position on front walls 56, 58. In order to move the tip 44 to its fully extended or "cocked" position (Fig. 6) , the pushbutton 24 is depressed by the palm in a distal direction. The distal edge 158 of pawl 160 which is fastened to the bottom wall of pushbutton 24 is in a position to contact and move link 96 of rotator assembly 92. Rotator assembly 92 pivots around pin 112 so as to move middle link 128, obturator 42 and tip 44. The pawl 160 rides over a ridge 162 in shaft 106, as best seen in Fig. 9, so that it no longer rests on link 96 when the pushbutton 24 is depressed, enabling the tip 44 to fire even when the pushbutton is depressed. This is because the linkage is free to move into the pushbut¬ ton.

0029As shown in Fig. 6, bottom leaf 88 in locking mem¬ ber 86 springs out to catch ridge 79 and thereby prevent rearward distal movement of the pushbutton 24. The pushbutton is held in this depressed position until a cam 110 integral with link 96 and shaft 106 pushes bottom leaf 88 laterally away from ridge 79. This does not occur until the tip 44 is almost fully retracted. When this happens, pushbutton spring 80 causes the push- button 24 to return to its initial extended position shown in Fig. 5, and the trocar is again ready for use. Continuing with Fig. 6, the trocar obturator 42 is shown fully advanced with tip 44 penetrating a body wall shown in dotted lines. In its fully extended position shown, the tip 44 is located a distance dl of about .1875 inches from open end 62 of trocar tube 60. In this position, pin 130 is at the distal end of slot 98 and on the side edge 164 of latch 150. In this posi¬ tion, the force due to penetration, which may be about 4-10 pounds, is distributed to trocar body subassembly 14 by means of pin 130 contacting the body. For exam¬ ple, force is distributed to body 14 by means of the pin seating in the apex 149 of grove 134. (See: Fig. 3.) Latch 150 prevents pin 130 from entering arcuate groove 132. As shown in Fig. 7, tip 44 moves in a proximal direction so that the distance between the tip and open end 62 falls to a distance d2 of about zero. Thus the tip will have moved proximally a "float distance" of about .1875 inches upon penetration of the body wall. At the same time pin 130 moves to the proximal end of slot 98 against the biasing force of secondary spring 144, which may be about 2 pounds. Pin 130 also moves off the edge 164 of latch 150. As the pin 130 continues to travel along slot 98, the secondary spring 144 is compressed until the pin has traveled the full .1875 inches along the slot. If there is a small change in force at the body wall, the pin 130 will move in the slot and such minor movement will be accommodated by the "float distance" of the slot without premature trigger- ing of the device. The tip 44 will not begin to retract until the force from the body wall is reduced to zero and the pin 130 has traveled back towards the distal end of the slot 98 a portion of the float distance.

0030When pin 130 travels back, it will no longer con- tact edge 164 of latch 150. Rather, it will contact generally perpendicular edge 166 of latch 150, due to the fact that main spring 136 will have moved link 96 laterally. In this position, pin 130 will be restrained from moving laterally by a wall 168. (See: Fig. 3). Secondary spring 144 will then move pin 130 against and compress latch 150 so that pin 130 moves free of the restraining action of wall 168 and into arcuate groove 132. Main spring 136, which may be about 6 pounds of force, will then cause pin 130 to follow the arcuate path of groove 132, as shown in Fig. 8, until it reaches its most proximal position shown in Fig. 5. In doing so, it retracts tip 44 through the linkage mechanism thus described. By having secondary spring 144 at about 2 pounds of force while main spring 136 is about 6 pounds of force, this will allow the tip 44 to be set easily while the stiffer main spring will cause rapid firing. It may be noted that the mechanism does not immediately retract upon reduction of force on the tip. Rather, there must first be a movement of the tip in the distal direction a short distance before this occurs. Again, as bottom link 96 reaches the end of its rotation in the counter-clockwise direction, a cam 110 will depress leaf 88 of locking member 86 so as to release pushbutton 24. Pushbutton 24 will then be moved rearwardly in the proximal direction by the force provided by spring 80 to the fully extended position shown in Fig. 5, so that the trocar body subassembly 14 is ready for another cycle. The return of the pushbut¬ ton to the extended position also gives visual indica¬ tion of this condition. Another visual indicator is provided by a small window 169 in top half 18 of grip 16, as best seen in Fig. 2. When tip 44 is fully advanced, the end of pin 130, which may be painted a highly visible color, appears in window 1-69. When the tip has retracted, pin 130 will no longer be visible in the window. With the pushbutton mechanism thus described, a mechanical advantage will be produced of the order of 2:1. That is, compression of pushbutton 24 its full length of travel of about one-half inch will be trans- lated by the mechanism into about 1 inch travel of the tip 44.

0031After the trocar tube subassembly 12 is in place providing communication within the patient, the trocar body subassembly 14 may be manually removed. As best seen in Fig. 4, within head or grip 16 is a flap valve mechanism generally at 170. The flap valve mechanism includes generally circular seal 51 of deformable mate¬ rial such as rubber, having a circular opening 176 therethrough for admitting the obturator. Seal 51 is mounted within an aperture 178 in the proximal end of housing 16 by means of an annular groove 172. Aperture 176 serves as a port for the entry of instruments and the like during surgery.

0032The flap valve mechanism further includes a generally U-shaped valve 179 mounted along a vertical edge thereof to an integral shaft 180. The shaft 180 is pivotally mounted at opposite ends thereof in holes (not shown) in the grip 16. A circular pad 182, which may be made of plastic material such as Tygon plastic, is fixed to valve 179 by suitable means. A coil spring 184, which is positioned over shaft 180, biases flap valve 178 to normally close off aperture 176 when the obtura¬ tor 42 is removed. In this manner, unwanted foreign matter such as bacteria or the like is prevented from entering aperture 176, and thereby entering the patient, through tube 60.

0033Trocar tube subassembly 12 includes a hollow body or housing 188, having a top portion 190 and a bottom portion 192. A lever 65 may be rotated within fan- shaped recess 66 molded in top portion 190. Lever 65 has a shaft 194 depending therefrom that may be fixed to the upper end of shaft 180 by suitable means. In this manner, rotation of lever 65 will cause valve 178 to be opened against the biasing force of spring 184.

0034In addition, the trocar tube subassembly also includes a conventional one-way check valve which is fixed within an aperture 198 in top portion 190. Valve 196 may be connected to a source of insufflation gas, which may be admitted to the patient cavity through housing 188 and trocar tube 60. Alternatively, a stop- cock valve may be used.

0035In an alternate embodiment shown in Fig. 10, the obturator shank 49 at its distal end is shown to be of reduced diameter from that shown in the previous figures. This reduces the frictional drag on the obturator induced by main seal opening 176 during its movement, which is important to ensure smooth operation of the device. The reduced diameter also increases the angle "A" at which flap valve 178 contacts the obturator shank 49, and thus reduces the spring force (since the spring is less compressed in this position) , thereby reducing the friction which is a function of the force imposed by the valve.

0036It is to be understood that while the invention has been described above in conjunction with the preferred specific embodiments, the description and examples are intended to illustrate and not limit the scope of the invention, which is defined by the scope of the appended claims.