Method of transferring rotational motion in an articulating surgical instrument

[0001] This application is a continuation of U.S. patent application Ser. No. 12/244,873, filed on Oct. 3, 2008, the entire disclosure of which is incorporated by reference herein.

[0002] 1. Technical Field

[0003] The present disclosure relates generally to an apparatus for remotely actuating an end effector disposed at a distal end of a surgical instrument. In particular, the apparatus transmits a rotational movement through a shaft of the instrument to maintain a position of the end effector throughout actuation of the end effector.

[0004] 2. Background of Related Art

[0005] Typically in a laparoscopic, an endoscopic, or other minimally invasive surgical procedure, a small incision or puncture is made in a patient's body. A cannula is then inserted into a body cavity through the incision, which provides a passageway for inserting various surgical devices such as scissors, dissectors, retractors, or similar instruments. To facilitate operability through the cannula, instruments adapted for laparoscopic surgery typically include a relatively narrow shaft supporting an end effector at its distal end and a handle at its proximal end. Arranging the shaft of such an instrument through the cannula allows a surgeon to manipulate the proximal handle from outside the body to cause the distal end effector to carry out a surgical procedure at a remote internal surgical site. This type of laparoscopic procedure has proven beneficial over traditional open surgery due to reduced trauma, improved healing and other attendant advantages.

[0006] An articulating laparoscopic or endoscopic instrument may provide a surgeon with a range of operability suitable for a particular surgical procedure. The instrument may be configured such that the end effector may be aligned with an axis of the instrument to facilitate insertion through a cannula, and thereafter, the end effector may be selectively articulated, pivoted or moved off-axis as necessary to appropriately engage tissue. When the end effector of an articulating instrument includes a pair of jaw members for grasping tissue, a force transmission mechanism such as a flexible control wire may be provided to open or close the jaws. For example, the control wire may extend through an outer shaft from the handle to the jaws such that the surgeon may create a tension in the control wire to cause the jaws to move closer to one another. The closure or clamping force generated in the jaws may be directly related to the tension in the control wire applied by the surgeon.

[0007] One type of laparoscopic or endoscopic instrument is intended to generate a significant closure force between jaw members to seal small diameter blood vessels, vascular bundles or any two layers of tissue with the application electrosurgical or RF energy. The two layers may be grasped and clamped together by the jaws of an electrosurgical forceps, and an appropriate amount of electrosurgical energy may be applied through the jaws. In this way, the two layers of tissue may be fused together. The closure forces typically generated by this type of procedure may present difficulties when using a typical control wire to open and close the jaws of an articulating instrument.

[0008] For example, a surgeon's efforts to position the jaws may be frustrated by a tendency for a control wire under tension to realign the jaws with the axis of the instrument after the jaws have been articulated off-axis. Although this tendency may be observed in any type of articulating instrument, the tendency is particularly apparent when the closure forces and necessary tension in the control wire are relatively high, as is common in an electrosurgical sealing instrument. This tendency may be created by the direction of reaction forces through the outer shaft of the instrument.

[0009] The present disclosure describes an endoscopic surgical instrument that transmits rotational movement to an end effector through a shaft of the instrument. The instrument includes an elongated shaft housing defining distal and proximal ends. The distal end of the shaft housing generally defines a distal shaft axis and the proximal end of the shaft housing generally defines a proximal shaft axis. A torsion member extends through the shaft housing and includes distal and proximal ends. The distal end of the torsion member is configured for rotational movement in response to rotational movement of the proximal end of the torsion member. An end effector is coupled to the distal end of the shaft housing. The end effector is moveable between open and closed configurations in response to rotational movement of the distal end of the torsion member. A handle is coupled to the proximal end of the shaft housing, and includes an actuation mechanism functional to selectively induce rotational movement at the proximal end of the torsion member. The torsion member includes a flexible shaft exhibiting a plurality of generally radial slots spaced longitudinally along a length of the flexible shaft.

[0010] The torsion member may be constructed as an elongated tube defining a lumen therethrough. The elongated tube may be constructed of stainless steel. The plurality of slots may include at least two opposed slots having a radial displacement from one another of about 180 degrees, or the plurality of slots may include at least three slots having a radial displacement from one another of about 120 degrees. The shaft housing may be flexible along a length thereof and may be sufficiently rigid to support the end effector in a position when the shaft housing is in a misaligned configuration.

[0011] The end effector may include a pair of opposable jaw members. At least one of the jaw members of the pair of opposable jaw members may be coupled to a source of electrosurgical energy. The end effector may also include an input shaft coupled to the torsion member to receive rotational motion therefrom, and the input shaft may be coupled to a power screw for driving a translation nut longitudinally upon rotational motion in the power screw. The actuation mechanism of the handle may include a nut operatively coupled to a moveable handle such that movement of the movable handle moves the nut longitudinally, and the nut may be coupled to a lead screw such that longitudinal motion of the nut drives rotational motion of the lead screw.

[0012] According to another aspect of the disclosure, the torsion member may include a plurality of substantially rigid segments coupled to one another by universal joints or constant velocity joints.

[0020] Referring initially to FIG. 1, an articulating endoscopic instrument is depicted generally as 10. The instrument 10 includes a handle portion 12 near a proximal end, an end effector 16 near a distal end and an elongated shaft 18 therebetween. Elongated shaft 18 defines a proximal shaft axis “P” substantially aligned with the handle portion 12 and a distal shaft axis “D” substantially aligned with the end effector 16.

[0021] The elongated shaft 18 is flexible such that the proximal shaft axis “P” and the distal shaft axis “D” may be selectively aligned or misaligned as shown. For example, the elongated shaft 18 may be bent in any direction, i.e., in both a horizontal and a vertical plane simultaneously, to assume a compound curve as shown. Other configurations are contemplated for elongated shaft 18, such as hinged or segmented wherein the shaft 18 is constructed from a plurality of substantially rigid members that are nested in series and/or pivotable relative to one another. A degree of rigidity may be maintained by the elongate shaft 18 such that the elongate shaft 18 supports itself to facilitate positioning of the end effector 16 at an anatomical position. Alternatively, a steering and locking mechanism (not shown) may be associated with the end effector 16 such that an operator may position the end effector 16 and lock the orientation of the elongated shaft 18 using a control surface (not shown) on the handle portion 12.

[0022] End effector 16 includes a pair of opposing jaw members 20 and 22. The jaw members 20, 22 are operable from the handle portion 12 to move between an open configuration (see FIG. 2A) to receive tissue, and a closed configuration (see FIG. 2B) to clamp the tissue and impart an appropriate clamping force thereto. When the end effector 16 is in the open configuration, a distal portion of each of the jaw members 20, 22 is spaced from the distal portion of the other of the jaw members 20, 22. In contrast, when the end effector 16 is in the closed configuration, the distal portions of the jaw members 20, 22 are closer together.

[0023] The motion exhibited by end effector 16 may be described as bilateral movement. Both jaw members 20 and 22 are pivotable about a pivot pin 24 such that each jaw member 20, 22 moves relative to distal shaft axis “D” as the end effector 16 is moved between the open and closed configurations. However, unilateral motion is also contemplated wherein an end effector (not shown) includes a stationary jaw that remains fixed relative to distal shaft axis “D” and a moveable jaw that moves relative to distal shaft axis “D” to move the end effector between the open and closed configurations. Further, non-pivotable motion is contemplated. For example, an end effector (not shown) may include jaw members configured for substantially parallel motion.

[0024] End effector 16 is configured for electrosurgical tissue sealing. At least one of the jaw members 20, 22 is connected to a source of electrical energy such that the electrical energy may transmitted through tissue clamped between the jaw members. To form an effective tissue seal, a relatively high clamping force is typically generated to impart a closure pressure on the tissue in the range of from about 3 kg/cm² to about 16 kg/cm². As described in greater detail below, instrument 10 is configured to accommodate pressures in this range such that elongate shaft 18 exhibits no substantial tendency to inadvertently realign the proximal shaft axis “P” and the distal shaft axis “D.” A more complete description of the tissue sealing generally may be found in U.S. Pat. No. 7,367,976 to Lawes et al.

[0025] Handle portion 12 is manipulatable by the surgeon from outside a body cavity to control the movement of the end effector 16 positioned inside the body at a tissue site. For example, the surgeon may separate and approximate a pivoting handle 28 relative to a stationary handle 30 to respectively open and close jaw members 20, 22. Also, a surgeon may adjust an orientation of the jaw members by rotating knob 34. Handle portion 12 accommodates a cable 36 for delivery of an electrosurgical current to the instrument 10.

[0026] Referring now to FIGS. 2A and 2B, end effector 16 is adapted to move between the open configuration depicted in FIG. 2A and the closed configuration depicted in FIG. 2B. This motion of the jaw members 20, 22 is achieved upon the application of a torsion force to end effector 16. Therefore, a control wire placed in tension, which as discussed above may generate reactionary forces in the outer shaft of an instrument and tend to frustrate the articulation of the instrument, is not necessary.

[0027] End effector 16 is adapted to receive the torsion force through input shaft 40 such that input shaft 40 may rotate about an distal shaft axis “D” as indicated by arrows “r.” Input shaft 40 provides connectivity to a suitable external source of rotational motion (e.g. slotted shaft 44 discussed below). Input shaft 40 rotates inside a fixed bearing member 46. Fixed bearing member 46 provides mounting surfaces for direct or indirect fixed coupling to the distal end of elongated shaft 18, which remains stationary relative thereto. In this way, the entire end effector 16 is supported by the instrument 10 and may be caused to articulate relative to the proximal shaft axis “P” (FIG. 1). Fixed bearing member 46 also supports a reactive member 48 on an outer surface thereof. Reactive member 48 extends distally from fixed bearing member 46 and supports pivot pin 24 extending into jaw members 20 and 22. An additional reactive member (not shown) may be supported by fixed bearing member 46 so as to mirror the reactive member 48 shown and provide additional support to pivot pin 24. Reactive member 48 remains stationary relative to fixed bearing member 46 as jaw members 20, 22 pivot open and closed.

[0028] A lead screw or power screw 50 is supported at a distal end of input shaft 40. The power screw 50 is coupled to the input shaft 40 such that both the power screw 50 and the input shaft 40 rotate together. Rotational movement of the power screw 50 drives a translation nut 52 longitudinally along distal shaft axis “D.” For example, rotation of power screw 50 in a first direction advances translation nut 52 from the position depicted in FIG. 2A where the translation nut is disposed at a first distance from the fixed bearing member 46, to the position depicted in FIG. 2B where the translation nut 52 is a second distance from the fixed bearing member 46 that is greater than the first distance. Likewise, rotation of power screw 50 in an opposite direction withdraws translation nut 52 such that translation nut 52 becomes closer to the fixed bearing member 46.

[0029] A force transfer member 54 is supported at a distal end of translation nut 52. Force transfer member 54 may be coupled to translation nut 52 or may be formed integrally therewith such that the force transfer member 54 translates along with the translation nut 52. Force transfer member 54 is formed with a central web 56 having a pair of proximal flanges 58 extending therefrom in opposite directions. An opposed pair of cam pins 60 protrudes laterally from central web 56 into jaw members 20, 22.

[0030] The cam pins 60 work in conjunction with proximal flanges 58 to open and close the jaw members 20, 22. Cam pins 60 engage a pair of cam slots 64 on the jaw members 20, 22 as the cam pins 60 translate distally along with force transfer member 54. Distal translation of cam pins 60 through cam slots 64 cause the jaw members 20, 22 to move from the open configuration of FIG. 2A to a nearly-closed configuration where the cam pins 60 encounter a bend in the cam slots 64. In the nearly-closed configuration, the proximal flanges 58 contact proximal faces of jaw members 20, 22 and a force is transferred from the cam pins 60 to the proximal flanges 130 of the force transfer member 54. Further distal translation of the force transfer member 54 will move the jaws from the nearly-closed configuration to the closed configuration of FIG. 2B.

[0031] In the closed configuration of FIG. 2B, the jaw members 20, 22 may generate a significant clamping force that can be directed at tissue positioned between the jaw members 20, 22. As the proximal flanges 130 press distally against the jaw members 20, 22, the jaw members 20, 22 press distally on the pivot pin 24 coupled to the reactive member 48. An opposite reaction force is realized as a tensile force in the reactive member 48, which links the jaw members to the fixed bearing member 46. Because the reaction force is contained entirely within the end effector 16, this arrangement allows instrument 10 (FIG. 1), to which the end effector 16 is attached, to close jaw members 20, 22 without creating a tendency for distal shaft axis “D” to realign itself with the proximal shaft axis “P.” This functionality is afforded by an instrument 10 equipped to supply rotational motion to the end effector 16.

[0032] Referring now to FIG. 3, instrument 10 is depicted schematically with end effector 16 in the closed configuration. Pivoting handle 28 is approximated to stationary handle 30, and distal portions of jaw members 20, 22 are closer together relative to the open configuration depicted in FIG. 2A. An actuation mechanism 68 receives motion from the pivoting handle to prompt the rotational motion allowing jaw members 20, 22 may be remotely controlled from the handle portion 12.

[0033] Actuation device 68 includes a motion converter 70 housed in handle portion 12. Motion converter 70 converts longitudinal motion supplied by the movement of pivoting handle 28 into rotational motion. To drive the motion converter 70, pivoting handle 28 is coupled to a flexible arm 72, which engages a rounded head portion 74 of a connector 76. Connector 76 is, in turn, coupled to a piston 78. Approximating pivoting handle 28 to stationary handle 30 in the direction of arrow “A” pivots the flexible arm 72 against the rounded head portion 74. The rounded head portion 74 converts the pivotal motion of the pivoting handle 28 into longitudinal motion which drives the connector 76 and piston 78 in a distal direction. Driving the piston 78 in a distal direction drives a nut 80 distally along a lead screw or power screw 82. The power screw 82 is mounted between bearing members 84 such that the power screw 82 rotates about proximal shaft axis “P” as nut 80 is driven longitudinally.

[0034] A torsion member 88 is provided through a shaft housing 90. The shaft housing 90 may be flexible along a length thereof and sufficiently rigid to support the end effector in a position when the flexible shaft is in the misaligned configuration, i.e., when the proximal shaft axis and the distal shaft axis are substantially misaligned. The torsion member 88 is configured to transmit rotational motion from the handle portion 12 to the end effector 16. The torsion member 88 is jointed or flexible to permit shaft 18 to navigate a tortuous path, and exhibits an ability to transmit a rotational displacement along its length. A proximal end of the torsion member 88 is coupled to power screw 82 such that the proximal end of the torsion member 88 rotates with the power screw 82. The distal end of the torsion member 88 is coupled to the input shaft 40 of end effector 16 to supply rotational motion thereto. As described above, rotating input shaft 40 causes the end effector 16 to move to the closed configuration without transferring reactive forces the shaft housing 90 that tend to realign the shaft 18.

[0035] In this manner, approximation of pivoting handle 28 with stationary handle 30 results in the end effector 16 moving to the closed configuration. It follows that separation of pivoting handle 28 from stationary handle 30 results in the end effector 16 moving to the open configuration by the reverse process. The reverse process begins as flexible arm 72 drives the connector 76 in a proximal direction, which, in turn, draws the piston 78 in the proximal direction. This draws nut 80 in the proximal direction, which causes power screw 82 to rotate in the opposite direction than when the nut 80 is driven proximally. This motion in the opposite direction is transmitted through torsion member 88 to the input shaft 40, which causes the end effector 16 to move to the open configuration.

[0036] Referring now to FIG. 4, torsion member 88 comprises an elongate flexible tube having a generally cylindrical wall 92. A lumen 94 extends through the cylindrical wall for the length of the torsion member 88 to facilitate the passage of electrical wires, fluids or other materials through the shaft. 18. The cylindrical wall 92 exhibits a length and thickness that permits the torsion member 88 to transmit torque and rotational movement while remaining flexible to assume the shape imposed upon the shaft 18. Contributing to the flexibility of the shaft is a plurality of slots 96 extending radially through the cylindrical wall 92 to define living hinges 98 opposite the slots 96. Living hinges 98 are portions of the cylindrical wall 92 where the cylindrical wall 92 is weekend in bending to allow the torsion member 88 to pivot, and remains sufficiently strong in torsion to allow the torsion member 88 to transmit radial displacement along its length.

[0037] Slots 96 and corresponding living hinges 94 are spaced longitudinally along the torsion member 88. The number of slots 96 and longitudinal spacing between adjacent slots 96 may be selected according to a bend radius to be achieved by the torsion member 88. Slots 96 are also radially offset with respect to one another to allow the torsion member 88 to bend in a plurality of directions. For example, two opposed slots 96 radially offset by about 180 degrees from one another can allow the torsion member to pivot in two directions in a single plane. Similarly, three slots 96 offset by 120 degree increments can allow the torsion member to bend in multiple planes simultaneously. The radial offset between adjacent slots 96 may be selected accommodate a particular shape to be achieved by the torsion member 88.

[0038] The cylindrical wall 92 is constructed from stainless steel tube to provide a high degree of torque transmission, but other materials may be selected to provide other characteristics. For example, polymers such as nylon or polyethylene may offer greater flexibility and excellent biocompatibility. Alternate shaft geometries are also contemplated. For example, spiral cut notches or braided wire shafts (not shown) may be included for use in a torsion member. Also a solid shaft, i.e., with no central lumen, may be used.

[0039] Referring now to FIG. 5, an alternate embodiment of a surgical instrument is depicted generally as 100. Instrument 100 includes a handle portion 112 and an end effector 116 coupled to one another through an articulating shaft 118. Handle portion 112 and end effector 116 are similar to handle portion 12 and end effector 16 of instrument 10 (see FIG. 3). The handle portion 112 is equipped with a motion converter 120 to convert longitudinal motion generated by movement of handle portion 112 into rotational motion. Similarly, end effector 116 is configured to receive rotational motion to move between open and closed configurations. Unlike instrument 10, rotational motion is transmitted through a shaft housing 122 through a torsion member 124 comprising a plurality of substantially rigid segments.

[0040] Torsion member 124 includes a proximal torsion bar 126 coupled to motion converter 120 at a proximal end and a central torsion bar 128 at a distal end. Likewise, the central torsion bar 128 is coupled to a distal torsion bar 130 opposite the proximal torsion bar 126. The distal torsion bar 130 is coupled to the end effector 116 to provide rotational motion thereto. Each of the torsion bars 126, 128, 130 is elongate and substantially rigid. The torsion bars 126, 128, 130 are each capable of rotation about an independent axis due to their interconnection by joint members 132.

[0041] Joint members 132 may include such mechanisms as a universal joints or constant velocity joints. Universal joints typically consist of a pair of hinges oriented 90 degrees from each other located in close proximity to one another. A constant velocity joint may assume different forms, and is similar to a universal joint as this type of joint is commonly used in shafts that transmit rotational motion through angled pathways.

[0042] Since the torsion member 124 is coupled directly to the end effector 116 and since the torsion force transmitted through torsion member 124 is axial with the torsion member 124, the reactionary forces associated with moving the end effector 116 to the closed configuration are passed back through the torsion member 124 rather than through a shaft housing 132. In this way, the unintentional realignment of shaft 118 may be avoided.

[0043] Although the foregoing disclosure has been described in some detail by way of illustration and example, for purposes of clarity or understanding, it will be obvious that certain changes and modifications may be practiced within the scope of the appended claims.