US20170007224A1 - Steerable medical device - Google Patents

Abstract

A medical device is provided. The medical device includes an elongated device body having a steerable portion including a plurality of segments. The segments are co-axially mounted over at least one elongated elastic element which is configured for limiting rotation of the segments with respect to each other. The medical device also includes a control wire running alongside the elongated device body and being unrestrained at the steerable portion such that tensioning of the control wire angles the steerable portion from a longitudinal axis of the elongated device body and deflects the control wire away from the steerable portion.

Description

FIELD AND BACKGROUND OF THE INVENTION
• The present invention relates to a steerable medical device and, more particularly, to a medical device which includes unrestrained control wires capable of deflecting away from the steerable portion of the medical device when tensioned.
• Medical devices such as endoscopes and catheters are widely used in minimally invasive surgery for viewing or treating organs, cavities, passageways, and tissues. Generally, such devices include an elongated device body which is designed for delivering and positioning a distally-mounted instrument (e.g. scalpel, grasper or camera/camera lens) within a body cavity, vessel or tissue.
• Since such devices are delivered though a delivery port which is positioned through a small incision made in the tissue wall (e.g. abdominal wall), and are utilized in an anatomically constrained space, it is desirable that the medical device or at least a portion thereof be steerable, or maneuverable inside the body using controls positioned outside the body (at the proximal end of the medical device). Such steering enables an operator to guide the device within the body and accurately position the distally-mounted instrument at an anatomical landmark.
• In order to control deflection of a steerable portion of the device and thus steer the instrument mounted thereon, steerable medical devices typically employ one or more control wires which run the length of the device and terminate at the distal end of the steerable portion or at the distal tip.
• The proximal end of each control wire is connected to the user operated handle; pulling of the wire bends the device body and deflects the steerable portion with relation the pulled wire.
• Numerous examples of steerable devices are known in the art, see for example, U.S. Pat. Nos. 2,498,692; 4,753,223; 6,126,649; 5,873,842; 7,481,793; 6,817,974; 7,682,307 and U.S. Patent Application Publication No. 20090259141.
• Although prior art devices can be effectively steered inside the body, the relatively small diameter of the elongated device body (which is dictated by the diameter of the delivery port), severely limits angle-of-deflection capabilities and increases the pull force required to deflect the steerable device portion.
• As such, it would be highly advantageous to have a steerable medical device having a device body narrow enough for delivery through standard delivery ports and yet capable of providing wide angle steering of the deflectable portion within the body while minimizing the pull force required for such steering.
SUMMARY OF THE INVENTION
• According to one aspect of the present invention there is provided medical device comprising: (a) an elongated device body having a steerable portion including a plurality of segments; (b) optionally, at least one elongated elastic element running through the plurality of segments and being configured for limiting rotation of the segments with respect to each other; and (c) at least one control wire running alongside the elongated device body and being unrestrained at the steerable portion such that tensioning of the at least one control wire angles the steerable portion from a longitudinal axis of the elongated device body and deflects the at least one control wire away from the steerable portion.
• According to further features in preferred embodiments of the invention described below, each of the plurality of segments is configured so as to limit rotation thereof with respect to flanking segments.
• According to still further features in the described preferred embodiments the at least one elongated elastic element has a rectangular cross section.
• According to still further features in the described preferred embodiments the medical further comprises an elastic tubular sheath covering the steerable portion.
• According to still further features in the described preferred embodiments the medical device comprises a plurality of control wires, each being for angling the steerable portion of the elongated device body in a specific direction.
• According to still further features in the described preferred embodiments the plurality of segments are interlinked.
• According to still further features in the described preferred embodiments the medical device further comprises a tissue manipulator attached to a distal end of the elongated device body.
• According to still further features in the described preferred embodiments the tissue manipulator is a grasper, a tissue cutter, or a needle holder.
• According to still further features in the described preferred embodiments the medical device further comprises a rigid sheath covering non-steerable portion of the elongated device body.
• According to still further features in the described preferred embodiments the elongated elastic element is a spring coil.
• According to still further features in the described preferred embodiments rotation between adjacent segments of the plurality of segments is limited by tab-slot engagement between the adjacent segments.
• According to still further features in the described preferred embodiments the control wire is trapped between the device body and the rigid sheath at the non-steerable portion.
• According to still further features in the described preferred embodiments the medical device further comprises at least one retractable lever positioned at a distal end of the steerable portion, the at least one retractable lever being attached to a distal end of the at least one control wire.
• According to another aspect of the present invention there is provided a medical device comprising: (a) an elongated device body having a steerable portion including an elastic shaft; and (b) at least one control wire running alongside the elongated device body and being unrestrained at the steerable portion such that tensioning of the at least one control wire angles the steerable portion from a longitudinal axis of the elongated device body and deflects the at least one control wire away from the steerable portion.
• According to still further features in the described preferred embodiments the at least one control wire is routed through a pair of guide clamps flanking the steerable portion.
• The present invention successfully addresses the shortcomings of the presently known configurations by providing a steerable medical device having a deflectable region being configured capable of angling more than 180 degrees with respect to a longitudinal axis of the device.
• Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods and materials are described below. In case of conflict, the patent specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and not intended to be limiting.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
• The invention is herein described, by way of example only, with reference to the accompanying drawings. With specific reference now to the drawings in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of the preferred embodiments of the present invention only, and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the invention may be embodied in practice.
• In the drawings:
• FIGS. 1a-1hillustrate the present device and the operation of the handle controlling the deflection of the steerable portion(s) and effector end.
• FIG. 2 illustrates the elongated body (fitted with grasper end) and the drive unit components of the device ofFIG. 1.
• FIGS. 3a-billustrate one embodiment of a steerable potion of the present device.
• FIGS. 4a-billustrate another embodiment of a steerable potion of the present device.
• FIGS. 5a-dillustrate one embodiment of a link utilizable for constructing a steerable portion of the present device (FIGS. 5a-c), and a steerable portion constructed from a plurality of links.
• FIG. 6 illustrates a steerable portion with several links removed exposing the spring element fitted within a central core of the links.
• FIGS. 7a-hillustrate an embodiment of the present device that includes a steerable portion fabricated from interconnected disc-shaped links.FIGS. 7a-cillustrate isometric and side views of the device, whileFIGS. 7d-hillustrate the disc-shaped links.
• FIGS. 8a-qillustrate an embodiment of the present device that includes two offset steerable portions deflectable to form, for example, U-shaped (FIG. 8k) and S-shaped (FIG. 8l) articulation configurations.
• FIGS. 9a-billustrate an embodiment of the present device that includes a unitary flexible shaft fitted with guides for routing the control wires.FIG. 9billustrates deflection of the shaft between guides.
• FIGS. 9c-iillustrate another embodiment of the present device that includes a unitary flexible shaft including cutouts for enabling deflection.FIG. 9iillustrates deflection of the shaft between guides.
• FIGS. 9j-killustrate a unitary flexible shaft (FIG. 9k) constructed from disc-like links (FIG. 9j) that are pinned together around a single rotatably-offset pivot point.
• FIGS. 10a-care images of a prototype device tested through various articulation states and deflection angles of the steerable portion.
• FIGS. 11a-billustrate a steerable portion composed of transparent links.
• FIG. 12 is a flowchart diagram describing a design ‘algorithm’ for constructing an articulating region of predetermined properties using the teachings of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
• The present invention is of a medical device and system which can be used in minimally invasive surgery. Specifically, the present invention can be used to provide enhanced steering.
• The principles and operation of the present invention may be better understood with reference to the drawings and accompanying descriptions.
• Before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details set forth in the following description or exemplified by the Examples. The invention is capable of other embodiments or of being practiced or carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein is for the purpose of description and should not be regarded as limiting.
• Steerable medical devices for use in minimally invasive surgery are well known in the art. Such devices typically utilize one or more control wires operable from a proximal end of the device positioned within the body to deflect and thus steer a distal portion of the device positioned within the body. In order to enable the control wire to efficiently deflect the distal portion of the device, the longitudinal axis of the control wire must be offset from the axis of deflection. In general, the greater the offset, the greater deflection that can be achieved with less pulling force applied to the control wire.
• Since the diameter of minimally invasive devices is dictated by the delivery port used to gain access to the intrabody tissues (typically 5, 8 or 10 mm), in existing tools the offset between the control wire and the deflection axis is in fact limited by the diameter of the tool's shaft the diameter of the port and the configuration of the device.
• To overcome this limitation, the present inventor has devised a unique control wire guide configuration which minimizes the overall diameter of the device body and yet provides control wire offset when the steerable portion is angled.
• Thus, according to one aspect of the present invention there is provided a medical device which includes a steerable intrabody portion capable of being steered through a wide range of angles (up to 180 degrees) and patterns such as zigzag or varied diameter curves at one or more points along its length.
• As used herein, the phrase “medical device” refers to any device utilizable in treatment of a subject, preferably a human subject. The medical device of the present invention is preferably used in minimally invasive surgery wherein a steerable distal portion thereof positioned within a body of a subject is controlled from a proximal end positioned outside the body (extra corporeally) via a control mechanism which preferably includes control wires. The medical device can be used for viewing or for manipulating tissues within any body cavity. Examples of medical devices which can benefit from the present invention include an endoscope (e.g. laparoscope or thorascope), a catheter, a needle holder, grasper, Scissors, hook, stapler, retractor and the like.
• The medical device of the present invention includes an elongated device body having a distal portion which is steerable within a body of a subject (also referred to herein as steerable portion), preferably via at least one control wire. As is further described herein, the steerable portion of the device can be deflected in various directions and configurations, e.g. the entire steerable portion can be deflected (arced) towards one direction using a single control wire, or a first segment of the steerable portion can be deflected in one direction while another can be deflected in an opposite direction (zigzag and multi-plane articulation) using two or more control wires.FIGS. 10a-cof the Examples section which follows provides several examples the deflection capabilities of the present device.
• The elongated device body includes one or more control wires disposed along its length. The proximal end of the control wire is attached to control levers which are actuatable by a handle of the medical device or by an electro-mechanical mechanism. The distal end of the control wire is attached to the device body (at a point past the steerable portion). The length of the control wire can be routed within or alongside the device body with the section of wire corresponding to the steerable portion being routed outside the device body such that it can freely move out from the longitudinal axis of the device body (offset) when the steerable portion is angled.
• Enabling the control wire to freely move away from the device body at the steerable portion provides several advantages:
• (i) gradually reduces the force needed to deflect the steerable portion once the steerable portion curves;
• (ii) negates the need for wire guides at the steerable portion (an optionally along the entire device body) thus simplifying construction and reducing friction on the control wires;
• (iii) reduce the friction between the wire and the wire guides;
• (iv) allows to use smaller diameter wires because the force needed to steer the articulation is significantly smaller;
• (v) reduces the means of connecting the wire to the distal end of the articulation because the force needed to steer the articulation is significantly smaller;
• (vi) (iv)+(v) allows to reduce the diameter of the device when linear thus facilitating insertion and removal into body (through, for example, a trocar port);
• (vii) when using the tool manually, all the above a allows the surgeon to operate the tool with much less effort;
• (viii) makes the use of electro-mechanic actuators possible. As it will be described later the significant force reducing allows the use of very small actuators (such as motors) which enables the design of a light weight fully motorized device;
• (ix) The use of very small actuators (such as motors) enables to operate a fully motorized device with small energy consumption; and
• (X) Enabling use of transparent materials in the steerable portion.FIGS. 1-11billustrate several embodiments of the present device which is referred to herein asdevice 10.
• FIG. 1aillustrates a laparoscopic configuration ofdevice10.Device10 includes an elongated device body12 (also referred to herein aselongated body12 or body12) which includes asteerable portion14 fabricated from a series of segments16 (shown inFIGS. 5a-c).
• Device body12 can be 20-40 cm in length and 5-12 mm in diameter.Device body12 can be hollow or solid depending on the use ofdevice10. For example, in cases wheredevice10 is used to steer an endoscopic camera,device body12 can be hollow in order to enable routing of wires or fiber optic cables from a user operable end (handle) to a camera or lens mounted on a distal end of elongated device body. Ahollow device body12 can also be used to route wires for controlling an operation of a tissue manipulator head such as a grasper and/or for accommodating at least one elongated elastic element for providing device body with elastic rigidity (further described hereinbelow).
• Device10 also includes a useroperable interface18 attached to proximal end ofdevice body12 and an effector end20 (e.g. tissue manipulator such as a grasper) attached to a distal end ofdevice body12.Interface18 functions in controlling and setting a orientation and position ofelongated body12, angling ofsteerable portion14 and in operating effector end20 (e.g. opening/closing, rotating and angling a grasper).
• For example, in the configuration shown in Figure la, a user (e.g. surgeon) can press/release handles300 to close and open the jaws of the grasper, rotateinterface18 in order to rotate the grasper jaws, and/ortilt housing400 in order to deflectsteerable portion14. These actions can be done separately or simultaneously.
• Aninterface18 that can be used withdevice10 is further described hereinbelow. Alternatively, thedevice10 can incorporate the interface described in U.S. Provisional Patent Application No. 61/694,865, the contents of which are fully incorporated herein.
• FIG. 2 illustrates routing ofcontrol wires22 fromdrive unit24 to a point distal tosteerable portion14.Drive unit24 can include levers, pulleys and gears for translating hand movements of the user (control movements) to pulling ofcontrol wires22. Such transfer can be mechanical (manual) or motorized. A motorized embodiment ofdrive unit16 is further described in U.S. Provisional Patent Application No.
• 61/872,727.
• In the embodiment shown inFIG. 2,control wires22 are routed within device body12 (e.g. under a sheathcovering device body12 or in the tube) up tosteerable portion14. Atsteerable portion14, control wires22 (one shown) is free fromdevice body12, such that angulation of steerable portion deflectscontrol wire22 away from the longitudinal axis ofdevice body12. Deflection of the control wire away from the longitudinal axis of the device (radially outward) increases the offset between the control wire and the deflection axis of the elongated device body and thus minimizes the pulling force needed to achieve deflection.
• Steerable portion14 (composed of links) is shown in greater detail inFIGS. 3a-4b. InFIGS. 3a-b,control wires22₂22₃are attached todevice body12 at point B and routed intobody12 through point A₂. In between,control wires22₂22₃are free to move away fromdevice body12 and thus deflect away fromdevice body12 when pulled to anglesteerable portion14.FIG. 3aillustrates pulling ofcontrol wires22₂22₃,control wire22₁is not pulled and thus remains flush againstdevice body12. Pulling ofcontrol wires22₂22₃deflects effector end20 (grasper shown) in the plane betweencontrol wires22₂22₃.FIG. 3billustrates simultaneous pulling ofcontrol wires22₂22₃. Both control wires deflect away from device body12 (at steerable portion14) and pulleffector end20 in a plane betweencontrol wires22₂22₃resulting in angling ofeffector end20.
• In the embodiment ofFIGS. 3a-b,control wires22₂22₃and22₁are attached directly todevice body12 at B₁B₂B₃and routed intobody12 through A₁A₂A₃. InFIGS. 4a-b,control wires22 are attached to retractable levers26 at a distal end thereof. Levers26 are disposed withinslots28 indevice body12 whendevice10 is delivered into the body. Levers26 can be spring loaded and sequestered withinslots28 during delivery through a port. Once the region ofdevice body12 containing levers26 exits the port (i.e. is free of the radial constraints imposed by the port inner wall), levers26 can spring out; alternatively, levers26 can fold out whencontrol wires22 are pulled. In any case, once deployed, levers26 deflect the distal ends ofcontrol wires22 away from device body thus increasing leverage ofcontrol wires22 and further reducing the pulling force needed to deflectsteerable portion14. Whendevice body12 is pulled out of the body through a port, levers26 collapse intoslots28 to facilitate removal through the port.
• As is mentioned hereinabove, one embodiments ofdevice body12 or at leaststeerable portion14 is preferably constructed from a series of links.FIGS. 5a-cillustrate one embodiment oflinks30 with assembly oflinks30 intosteerable portion14 illustrated inFIG. 5d.
• Links30 preferably include several arms32 (3 shown) mounted around acentral hub34. As is shown inFIG. 5d, theinter-arm space36 accommodatescontrol wires22, and thus the number of arms32 (preferably 2-12) dictates the number ofcontrol wires22 used indevice10.
• Link30 is preferably fabricated from an alloy or polymer via machining molding or the like.
• Hub34 includes a central circular opening38 (FIG. 5b), while eacharm32 optionally includes an opening39 (FIG. 5a).Opening38 can accommodate an elongated elastic element (e.g. spring coil33 shown inFIG. 6 or an elastic tube) for interlinkinglinks30 and providingdevice body12 with rigidity and elasticity atsteerable portion12.Openings39 can be used to route wires for actuatingeffector end20 or for accommodating elastic rods (as an alternative to one central rod mounted throughopening38.Openings39 can also be used to route electrical wires to operate a motor or a camera or jaws of a grasper or any other sensor or actuator at a point distal tosteerable portion14.Opening38 can also serve as a through lumen for delivering an irrigation tube, optical fibers and the like.
• In order to prevent or limit rotation oflinks30 whencontrol wires22 are pulled, each link includestabs40 andslots42 on opposite faces. Preferably eacharm32 includes atab40 and an opposingslot42 although the length and width can vary betweenarms32 of asingle link30.Tabs40 of alink30 are capable of engagingslots42 of anadjacent link30, thus limiting relative rotation oflinks30.
• The configuration and positioning oftabs40 andslots42 can be selected so as to completely limit rotation, or limit rotation to a specific angle range (5-15 degrees) or a specific direction etc. In any case, the engagement betweentabs40 andslots42 can be reversible thus allowing disengagement therebetween whensteerable portion14 is deflected andlinks30 angle with respect to each other.
• FIGS. 7a-hillustrate another embodiment oflinks30, which can be stacked as shown inFIGS. 7a-cto formsteerable portion14.
• Links30 of this embodiment ofdevice10 are roughly disc-shaped and include acentral opening50, a plurality of circumferential openings52 (FIGS. 7d-g), indents54 (FIGS. 7e, g, h) and depressions56 (FIGS. 7d, f).
• Central opening50 serves for routing one or more wires from the device handle to effectorend20. Such wires are actuated by the handle to control effector end20 (e.g. open, close, rotate grasper).Circumferential openings52 serve forrouting control wires22 for actuating deflection ofsteerable portion14. Indents54 anddepressions56 interconnectadjacent links30 and enable such links to angle with respect to each other. An elastic rod or tube or spring can be positioned throughcentral opening50 to provide elasticity tolinks30.
• FIG. 8aillustrates an embodiment ofdevice10 which includes two independent steerable portions:14 and14′.Device10 includes a device body12 (also referred to herein as shaft12) with a typical diameter of 5-12 mm. The distal end ofdevice body12 is fitted with aneffector end20 which can be, for example, a grasper as shown in this Figure.Steerable portion14′ includes aproximal base link29 which is connected to the distal end ofshaft12, a series oflinks30 and adistal end link31. Distal ends ofcontrol wires22′_1,2,3are connected to link31, while the proximal ends of these wires are connected to a drive unit24 (FIG. 2) which is operated from the handle.
• Control wires22_1,2,3are connected todistal link32 ofsteerable portion14, and are routed throughlink31 and the bodies oflinks30′ to drive unit24 (FIG. 2) which is operated from the handle.
• FIG. 8billustratessteerable portions14 and14′ in greater details. Each ofsteerable portions14 and14′ includes 9 identical links (30 and30′), however, different number of links of different geometry can be used in each steerable portion.Tabs40 and slots42 (described hereinabove with respect toFIG. 5) oflinks30 and30′ are also shown.
• FIG. 8cis a cross sectional view ofsteerable portions14 and14′. Flexible shaft21 (connected to driveunit24 at its proximal end) is positioned throughholes38,37 oflinks29,30′,30,31 and32, the distal end of flexible shaft is connected toeffector20.
• Control wire22′₁passes throughhole28′₁oflink29 andhole36′₁oflink31; distal end ofcontrol wire22′₁is connected to link31 to/inhole36′₁;control wire22′₁is routed out oflinks30′.Control wire22₁passes throughhole27₁oflink29 and throughhole35₁oflinks30′ (shown in detail inFIG. 8d). Atlink31,control wire22¹deflects out through elongated opening34₁oflink31 and runs out oflinks30 to adistal connection point38 atlink32.Control wires22′₂and22′₃are similar in routing and attachment to controlwire22′₁, whilecontrol wires22₂and22₃are similar in routing and attachment ascontrol wire22₁.
• FIG. 8dillustrateslink30′ in detail.Central hole37 accommodatesflexible shaft21 whileholes35 accommodate control wires22_1,2,3(tabs42 andslots40 are also shown).
• FIG. 8eillustrateslink31 in detail.Central hole38 accommodatesflexible shaft21 whileholes36_1,2,3serve as connection points forcontrol wires22′_1,2,3.Elongated openings34_1,2,3route control wires22_1,2,3out oflinks30.
• Deflection ofportions14 and14′ and thus steering and articulation ofshaft12 is effected via pulling forces oncontrol wires22 and22′. If a control wire is close to the center of a steerable portion, such as the case withcontrol wires22 which run throughholes35 insteerable portion14′, then a pulling force on these control wires results in a relatively small deflection, in other words the effect of a pulling force on deflection is in direct relationship to the distance betweencontrol wire22 to a center of asteerable portion14. When acontrol wire22 is connected to a distal end of asteerable portion14 and is free to move through the proximal base, e.g. when threaded throughholes36_1,2,3inlink31, then the effect of a pulling force onsteerable portion14 is enough to deflect it from the longitudinal axis. This effect of the pulling force increases assteerable portion14 deflects sincecontrol wire22 bows outward (radially) and the distance between thecontrol wire22 and center ofsteerable portion14 increases.
• FIG. 8fillustrates a configuration capable of an 80 degree deflection, i.e. effector end20 can assume an angle of 100 degrees with respect to the longitudinal axis ofshaft12. Deflection of proximalsteerable portion14′ is effected by pulling (in a proximal direction) oncontrol wires22′_2,3.
• FIG. 8gis a cross sectional view of the device ofFIG. 8fshowing routing ofcontrol wires22. A prototype constructed in accordance with the configuration ofFIGS. 8f-gis shown inFIG. 10b.
• FIG. 8hillustrates a configuration capable of an 80 degree deflection, i.e. effector end20 can assume an angle of 100 degrees with respect to the longitudinal axis ofshaft12. Deflection of distalsteerable portion14 is effected by pulling (in a proximal direction) oncontrol wire22₁.
• FIG. 8iis a cross sectional view of the device ofFIG. 8hshowing routing ofcontrol wire22₁.Control wire22₁runs throughhole35₁inlinks30′ ofsteerable portion14′ and as such its distance from the center ofsteerable portion14′ is minimal. This small distance, ensures that the pulling forces applied oncontrol wire22_1,2,3will have little or no effect on the deflection ofsteerable portion14′. At the distal end of proximalsteerable portion14′,control wire22₁runs through elongated opening34₁inlink31 and connects to link32 atpoint37₁. This direct connection positions controlwire22₁outward from the center ofsteerable portion14, and therefore increase the moment arm of the pulling force. This enablessteerable portion14′ to deflect (bend) under relatively small pulling forces.
• FIG. 8jillustrates routing ofcontrol wires22₁and22′₁and centralflexible shaft21 and the effect of wire routing on deflection forces. In this Figure, “d” represents 1 unit of distance, in this case, the distance between the center ofhole35₁to the center oflink30′. The following parameters are used for calculations:
• “a”—measurement of the longest arm moment ofcontrol wire22₁from the center point oflink30′. La=1.00d;
• “b”—measurement of the longest arm moment ofcontrol wire22′₁from the center point oflink30′, Lb=2.75d;
• “c”—measurement of the longest arm moment ofcontrol wire22₁from the center point oflink30, Lc=4.00d.
• A force F22₁is applied to controlwire22₁, thus the moment force F22₁applies onportion14′ is:
• 
  Ma=F22₁×La
• 
  Ma=F22₁×1.00d
• The moment the force F22₁applies onportion14 is:
• 
  Mc=F22₁×Le
• 
  Mc=F22₁×4.00d
• The moment applied by onportion14 compared to the moment applied onportion14″ by the same force F22₁is:
• 
  Mc/Ma=F22₁×4.00d/F22₁×1.00d=4
• The above calculations when applied to commercially available devices, illustrate that the present invention can reduce the wire pulling force needed for deflection by at least 25% when compared to such commercially available devices (see Examples section for further detail).
• The bending moment on steerable portion14 (the “target steerable portion”) caused by force (F22₁) applied bycontrol wire22₁is significantly greater than the bending moment onsteerable portion14′ (the “secondary steerable portion”), and as such, a coupling effect between these two steerable portions is minimized.
• Minimizing such coupling enables the use of a simple mechanism, such as hand operated mechanism, to steer the articulation without the need to add a controller to the control wires mechanism.
• When using an electro-mechanical mechanism to pull the control wires then the moments on the secondary portion may be reduced to zero by using a controller that is programmed to apply force oncontrol wire22′₁. The magnitude of this force may be calculated by:
• 
  Ma=Mb(canceling moments)
• 
  Ma=F22₁×La=F22₁×1.00d
• 
  Mb=F22′₁×L=F22′₁×2.35d
• 
  F22₁×La=F22₁×1.00d=F22′₁×L=F22′₁×2.35d
• 
  F22′₁=F22₁×1.00d2.35d
• 
  F22′₁=0.42F22₁
• As calculated the controller will operate the actuator that pullscontrol wire22′₁in a force less than a half of force F22₁(F22′₁=0.42F22₁).
• It will be appreciated that in cases where an electro-mechanical drive unit is used for pulling the control wires, than the control wires routing described above can reduce the energy consumption of the motors controlling the first and second steerable portions.
• The routing principles described hereinabove may be used in any combination to deflect two or more steerable portions and generate any articulation desired. For example,FIG. 8killustrates “U”-shaped articulation witheffector end20 positioned at an angle of 190 degrees. Such articulation is achieved by pullingcontrol wires22′₁and22₂.
• FIG. 8lillustrates an “S”-shaped articulation which can be achieved by pullingcontrol wires22′₁and22₁.
• FIGS. 8m-8pillustrate a device having two steerable portions with deployable arms positioned at a distal end of each steerable portion.Arm39pis hingedly connected to link31 andarm39dis hingedly connected to link33.Arms39pand39dcan swing outward and increase the distance between the end of a control wire connected thereto and the center of the deflectable portion.FIG. 8millustratesarms39pand39din a folded position,FIG. 8nillustratesarms39dand39pin an open position.FIG. 8oillustrates “U”-shaped articulation witharms39dand39pin an open position.FIG. 8pillustrates “S”-shaped articulation witharms39dand39pin an open position.
• FIG. 8qis a cross sectional view of the present device in a “U”-shaped configuration witharms39dand39pin an open position. In thisexample arms39pand39dhave the same dimensions. The moment arm ofcontrol wire22₁attached toarm39dis 5.5d.
• The effect of usingarms39dand39pon the force needed to deflect the steerable portion can be represented by the following calculation:
• Device with no arms:
• 
  Mc=F22₁4.00d
• Device with arms:
• 
  M_armsc=F_arms22₁×5.50d
• 
  M_armsc=Mc
• 
  F22₁×4.00d=F_arms22₁×5.50d
• 
  F_arms22₁=F22₁×4.00d/5.50d
• 
  F_arms22₁=F22₁×4.00d/5.00d
• 
  F_arms22₁=0.73F22₁
• The foregoing describes examples ofdevice10 capable of single plane articulation, however it will be appreciated thatdevice10 having two or more steerable portions can be deflected to form a multi-planar articulated configuration such as that shown inFIGS. 10dor even a complete loop. Such multi-planar articulation can be achieved by actuating control wires which are located at different planes or by for example applying non symmetrical forces on pairs of control wires.
• As is mentioned herein above, any handle and mechanism can be used withdevice10 of the present invention. The construction and operation of one embodiment of a handle utilizable with the present device is illustrated inFIGS. 1b-h.FIGS. 1b-cillustrategrasper head20 andsteerable portion14 which are actuatable via the device handle interface (18) and its internal mechanism. In this embodiment the steerable portion is controlled by 4control wires22.Steerable portion14 is shown deflected in a direction of pulledcontrol wire22₂.
• FIGS. 1d-eand 1gare cross sectional views ofdevice10 showing the mechanism in the handle that enables transfer of interface movements to the control wires.
• Control wires22 (22₁,22₂,22₃,22₄) which are attached to a distal end ofsteerable portion14, are routed via a pair of pulleys. The grasper jaws are actuated viamechanism170, to hole110aat the base of spring110 ofhousing500.Control wires22 are prevented from slipping through spring110 by crimp220. The shape of crimp220 follows the shape of the housing of spring110 to ensure smooth and predictable movement of a compressed spring110 when acontrol wire22 is pushed away from center bybody130.
• Body130 is connected tohousing500 by ball joint bearing.Body130 is located at the center of the mechanism, and may be tilted with respect tohousing500, by forces applied oninterface crown400 by a user.Control wires22surround body130, whenbody130 is in a neutral position eachcontrol wire22 is pressed against the circumferential edge ofbody130 by slot90aofbead90.
• FIG. 1fillustrates the relationship betweenbead90, control wire22 (22₁shown) andbody130 in detail.Bead90 is connected firmly to controlwire22₁and divides controlwire22 into 2 contiguous regions:upper region22_1uandlower region22_1d.Bead90 includes a slot90athat fits into thecircumferential edge130aofbody130.
• FIG. 1h, illustrates in details the control mechanism, shown in a tilted position, withcontrol wire22₁pushed viabead90₁away from center in order to deflectsteerable portion14. The engagement point betweencircumferential edge130aofbody130 andbead90₁, is at the inner side of slot90a. Whilebody130 pushesbead90 away from the center, opposite-positionedbead90₃is released fromcircumferential edge130a.Control wire22₃is connected at a distal end to an opposite side ofcontrol wire22₁. As seen inFIG. 1b, when steerable portion is deflected bycontrol wire22₁, the inner side ofportion14_inis shortened, and the length of14_outat the opposite side ofsteerable portion14 is increased. The length ofwire22₃must increase accordingly. Such length accommodation bycontrol wire22₃is possible by compressing spring110₃.
• The grasper jaws are actuated via a mechanism (FIGS. 1g-h) which is controllable by the surgeon fingers. When handles300 are pressed the arms of mechanism150 elevate piston240 which closes the jaws. If the surgeon releases the force applied tohandles3, springs which are connected to the arms of mechanism150push piston24 back intobody500 and the jaws open.Piston24 is connected to the jaws push/pull mechanism viaflexible shaft17 andtube16.Flexible shaft17 andtube16 are also used to transfer rotation and push-pull movement applied onhousing500.Flexible shaft17 may be bent without changing its length which enable bending ofportion17 in centeringelement19, without resulting an unwanted coupled movement of opening and closing of the jaws i.e. the grasper head and mechanism150 does not move whilesteerable portion14 is bent. The dimension of the inner side ofbody130 is designed not to touchtube160 whenbody130 is tilted to extreme positions.
• Although asteerable portion14 constructed from interconnected links is advantageous in that it enables modular design, asteerable portion14 constructed from a unitary flexible shaft is also envisaged herein.
• A steerable portion constructed from a unitary flexible shaft is advantageous in that it simplifies construction and manufacturability. In addition, such a shaft is better at insulating central electrical wires, used, for example, in diathermia (monopolar or dipolar).
• One example of such an embodiment ofsteerable portion14 is shown inFIGS. 9a-b.
• Steerable portion14 can include one or more steerable portions15 (three shown inFIG. 9a) interposed betweenguides17 attached along a length of aflexible shaft19.Shaft19 can be made of a tube fabricated from any elastic material including stainless steel, nitinol, rubber, silicon and is typically shaped as a solid or hollow cylinder with a diameter of 5-12 mm with wall thickness 0.1-0.5 mm.Steerable segments15 can be 5-30 mm in length and guides17 can be dimensioned to displacecontrol wire22 2-4 mm away fromshaft19. Guides are preferably configured with acentral ring23 for clamping aroundshaft19 and several (e.g. 2-8) circumferentially attached rings25 for routing ofcontrol wires22.
• Elasticity ofshaft19 ensures thatsteerable portion14 orsegment15 deflect when specific control wire orwires22 are pulled and linearize when control wire orwires22 are released.Shaft19 is selected so as to enable elastic deflection of one or moresteerable portions14 by 45 to 180 degrees.
• Another embodiment of a unitarysteerable portion14 is shown inFIGS. 9c-i.
• This embodiment of unitarysteerable portion14 can be 5 mm in diameter (OD) with a central lumen of at least 1.4 mm. Unitarysteerable portion14 is constructed from a polymeric material (e.g. polyamide, polypropylene) that is capable of providing 90 degrees of elastic articulation (repeatedly) under a pulling force of 10 N (looping, spatial articulation) with a bending radius of about 7 mm. When a pulling force is released, an elastic force returnssteerable portion14 to a normal, linear configuration.
• FIG. 9eillustrates asingle unit67 of unitarysteerable portion14 which is designed to allow deflection and yet also stabilizessteerable portion14 when one ormore control wires22 are pulled.
• Eachcontrol wire22 of this configuration of steerable portion14 (threecontrol wires22 shown,22₁,22₂,22₃) controls deflection over an arc of 120 degrees. Such a configuration andcontrol wires22 positioning stabilizessteerable portion14 when all three control wires (22₁,22₂,22₃) are pulled.
• FIG. 9fillustrates a unitarysteerable portion14 constructed from severalcontiguous units67 such as those shown inFIG. 9e.Connector68 functions as a leaf spring-like flexure bar (virtual joint). The extent of Bending ofconnector68 is limited by the geometry of the unit (FIG. 9g). Thus deflection of one unit with respect to another will be equal to:
• $\varepsilon =\frac{2}{3}·\frac{I^2·\sigma }{H·E}$
• wherein H is the thickness ofconnector68, and l is its height. By increasing l and decreasing H each pair of adjacent units become more flexible and less rigid. In such a configuration, the length (L) ofsteerable portion14 is determined by the bend radius desired and can be represented by the following: 2πR/4≅L.
• FIG. 9hillustrates a configuration whereinconnectors68 are offset from each other along a series of 4units67 to enable defection in various directions.FIG. 9iillustrates a configuration ofsteerable portion14 that includes 10contiguous units67 with offsetconnectors68 and a total length of about 11 mm;force70 is applied to the distal end of such a unified steerable body14 (simulatingwire22 pull) to illustrate deflection. When such a force is released,connectors68 elastically returnsteerable portion14 to a linear (normal) configuration.
• In the configuration shown inFIGS. 9e-i,connectors68 having an 1 of 0.5 mm, an H of 0.9 mm and aunit67 with a diameter of 5 mm, will enable asteerable portion14 11 mm in length to deflect 90 degrees under a pulling force of about 10 N.
• FIGS. 9j-killustrate another embodiment of aflexible shaft70 constructed fromunits67. Eachunit67 has a top face and a bottom face each designed for mating with an opposite face of adjacent unit67 (i.e. top to bottom and vice versa). As is shown inFIG. 9j, the bottom face ofunit74 includes twopin engaging elements77. The top face ofunit72 includes asingle element77 for fitting into a space betweenelements77 ofunit74. When mated, apin73 connectselements77 ofunit74 and72 and creates a hinge for allowing articulation. Any number ofunits67 can be pinned together in various orientations (rotational offset of hinge region) to create articulation in one of more directions.
• Table 1 below exemplifies two unitary articulating regions constructed according to the teachings of the present invention.

• TABLE 1
  				Bending
  	Length	Material	Diameter	Radius	Rh	Rt	Pt	Nr
  A
  	14mm	Polyamide		5mm	5 mm	0.4 mm	0.3 mm	1.0 mm	10
  		(pa12)
  B	12 mm	same	8mm	8 mm	0.5 mm	0.5 mm	0.7mm	10
  Rh—vertical height of segment
  Rt—vertical thickness of segment ‘body’
  Pt—vertical height of articulating unit (two segments spaced by ‘hinge’)
  Nr—number of units

• FIG. 12 describes an ‘algorithm’ for selecting material properties and unit dimensions based on size and properties of the articulating region.
• Device10 of the present invention can be used in any minimally invasive procedure as follows. An access site is created in a tissue wall and the shaft ofdevice10 is inserted through the access site and positioned therein usinginterface18. If a trocar is used at the access site,device10 is inserted in a straight configuration. When the effector end of the device is positioned at a target tissue (as ascertained via imaging), the surgeon operates the device throughinterface18 as described hereinabove. Following completion of the procedure, the surgeon withdraws the device from the body and the access site is closed.
• Steerable portion14 (constructed from links or as a unitary body) of the entire shaft ofdevice10 can also be fabricated from a transparent material. Use of a transparent material enables visual inspection of control wires, optical fibers and the like threaded through the device body.
• FIG. 11aillustrates asteerable portion14 constructed from transparent links30 (some of the links were removed for the sake of clarity).Optic fibers62_1,2,3thread through the shaft from the handle tosteerable portion14, throughholes39 oflinks30.FIG. 11bis an image of a prototype constructed with transparent links. The transparent steerable portion enables an operator to seecontrol wires22_2,3and push pullcable21 through the transparent bodies oflinks30.
• An illumination source may be connected to the proximal side ofoptic fibers62_1,2,3at the handle. When illumination is switched on, the transparent articulation radiates light out ofsteerable portion14. The light can be visualized by an operator or an assistant, or may serve as a switch for displaying to the operator data such as CT or MRI data of the patient of tissues near the tip of the tool. The light may also serve to track the position of the tool orsteerable portion14 thereof.
• As used herein the term “about” refers to ±10%.
• Additional objects, advantages, and novel features of the present invention will become apparent to one ordinarily skilled in the art upon examination of the following examples, which are not intended to be limiting.
EXAMPLES
• Reference is now made to the following example, which together with the above descriptions, illustrate the invention in a non limiting fashion.
Force Measurements in Prototype Device
• A test was conducted in order to determine the force needed to deflect a steerable portion of a prototype device by 45° and 90° and to measure the travel length of the wires needed to reach 45° and 90°. Two prototype devices were constructed. The articulation used to test the forces was as describe in details inFIG. 5. Two types of steerable portions were tested, one constructed from 5 mm diameter links and another from 8 mm and 5 mm diameter links. Each steerable portion included 9 links manufactured by a rapid prototype printer.
• Methods
• The shaft of the prototype device was fixed to a table and positioned such that one of the control wires resided on the top side of the shaft. A force measurement device (Shimpo FGN-5b) was attached to this control wire and was fixed to a linear rail. In order to measure forces, the force measurement device was driven away from the shaft until the desired angle of the articulation was measured. The force was recorded and the travel of device was measured.
• Results
• Table 2 below summarizes the test results of two prototypes and a prior art Cambridge articulation unit.
• As is shown by the results presented in this table, the forces needed to deflect the steerable portion of the present invention were 10% and 15% (present device 5 or 8 mm respectively) of the forces needed to deflect a commercial tool (Cambridge Endo).
• Thus, the present device design requires significantly less (6-10 folds less) force by the operator to deflect the steerable portion. This will enable a surgeon to perform surgery using a manual handle without having to apply large forces, thus substantially improving operability and decreasing device-related fatigue. In addition, when used with an electro-mechanical handle, the present device would not require bulky motors and batteries but would rather be fully operable using small motors and battery packs which would considerably lighten the device and enhance maneuverability thereof.
• Another advantage of the present device is shown inFIGS. 10a-cwhich demonstrate the range of articulation and angles of deflection possible with the present device. The present device is capable of 2D and 3D articulation and deflection greater than 180 degrees due to the configuration of the links and in particular the unique routing of cable therein and/or on.
• It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable subcombination.
• Although the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims. All publications, patents and patent applications mentioned in this specification are herein incorporated in their entirety by reference into the specification, to the same extent as if each individual publication, patent or patent application was specifically and individually indicated to be incorporated herein by reference. In addition, citation or identification of any reference in this application shall not be construed as an admission that such reference is available as prior art to the present invention.

Claims (15)

What is claimed is:

1. A medical device comprising:

(a) an elongated device body having a steerable portion including a plurality of segments;

(b) at least one control wire running alongside said elongated device body and being unrestrained at said steerable portion such that tensioning of said at least one control wire angles said steerable portion from a longitudinal axis of said elongated device body and deflects said at least one control wire away from said steerable portion;

and optionally;

(c) at least one elongated elastic element running through said plurality of segments and being configured for limiting rotation of said segments with respect to each other.

2. The medical device ofclaim 1, wherein each of said plurality of segments is configured so as to limit rotation thereof with respect to flanking segments.

3. The medical device ofclaim 1, wherein said at least one elongated elastic element has a rectangular cross section.

4. The medical device ofclaim 1, further comprising an elastic tubular sheath covering said steerable portion.

5. The medical device ofclaim 1, comprising a plurality of control wires, each being for angling said steerable portion of said elongated device body in a specific direction.

6. The medical device ofclaim 2, wherein said plurality of segments are interlinked.

7. The medical device ofclaim 1, further comprising a tissue manipulator attached to a distal end of said elongated device body.

8. The medical device ofclaim 7, wherein said tissue manipulator is a grasper, a tissue cutter, or a needle holder.

9. The medical device ofclaim 1, further comprising a rigid sheath covering non-steerable portion of said elongated device body.

10. The medical device ofclaim 1, wherein said elongated elastic element is a spring coil.

11. The medical device ofclaim 2, wherein rotation between adjacent segments of said plurality of segments is limited by tab-slot engagement between said adjacent segments.

12. The medical device ofclaim 9, wherein said control wire is trapped between said device body and said rigid sheath at said non-steerable portion.

13. The medical device ofclaim 1, further comprising at least one retractable lever positioned at a distal end of said steerable portion, said at least one retractable lever being attached to a distal end of said at least one control wire.

14. A medical device comprising:

(a) an elongated device body having a steerable portion including an elastic shaft; and

(b) at least one control wire running alongside said elongated device body and being unrestrained at said steerable portion such that tensioning of said at least one control wire angles said steerable portion from a longitudinal axis of said elongated device body and deflects said at least one control wire away from said steerable portion.

15. The medical device ofclaim 14, wherein said at least one control wire is routed through a pair of guide clamps flanking said steerable portion.

Images