Abstract:
An instrument that facilitates bending with large degrees of articulation while maintaining ease of manufacturing for medical and surgical applications is discussed.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 61/774,901 (Attorney Docket No. 41663-707.101), filed Mar. 8, 2013, the entire content of which is incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The field of the present application pertains to medical devices. More particularly, the field of the invention pertains to an apparatus, system, and method for performing surgery. 
         [0004]    2. Description of the Related Art 
         [0005]    Robotic surgery has many benefits to improve patient recovery time and allows precise control of medical and surgical application instruments. In robotics, an end effector is the device at the end of a robotic arm, designed to interact with the environment. The exact nature of this device depends on the application of the robot. For example, several examples of end effectors could include a set of forceps, a pair of scissors, a laser, a camera, a cautery tool, a needle, or any other instrument tip that would benefit from being able to be repositioned. 
         [0006]    As previously discussed, which originates from serial robotic manipulators, the end effector means the last link (or end) of the robot. At this endpoint the tools are attached. In a wider sense, an end effector can be seen as the part of a robot that interacts with the work environment. 
         [0007]    Many articulating devices use bending sections comprising many small moving parts for creating an assembly. Typically, the assemblies are difficult to manufacture in smaller geometries since the individual components become difficult to fabricate. 
         [0008]    Another challenge with existing solutions is accommodating the ancillary components for the end effector; which may include pull wire, electrical wires, fluidic lines, and optical fibers. The location of these components within the bending section impacts performance and stability of the bending section. All beams have an imaginary line within the body what will remain the same length when straight or bent, this line is termed the Neutral Axis of the structure. The neutral axis region does not experience any strain or stress. Typically, material that falls on either side of this line will experience strain and will either be extended or compressed. The inside of the bend will compress and the outside of the bend will extend. See  FIG. 1  for an illustration of the neutral axis along with its relationship to the inner and outer bend surfaces. 
         [0009]    For example, if the ancillary components are placed outside of the neutral axis region, they will slide in and out of the bending section if they are able to float relative to the bending section. Otherwise, the components will buckle or stretch due to the axial forces being imposed.  FIG. 2  depicts an illustration of the relationship of components placed away from the components neutral axis. 
         [0010]    Existing solutions for bending sections are created for small articulable instruments that is manufactured from thin walled tube. For example, intricate patterns are cut into the tubing in order to create reliefs that yield a preferential bending direction. However, if a large deflection is required; much of the tubing material will need to be removed in order to allow for such bending. Consequently, a thin walled tube with lots of its material eliminated inevitably loses much of the structure and ability to remain mechanically stable. 
         [0011]    Therefore, it would be advantageous to have a method and apparatus for facilitating the bending of an instrument with large degrees of articulation while maintaining a sufficient amount of stiffness in order to provide stability at the end effector, all while ensuring ease of manufacturing. 
       SUMMARY OF THE INVENTION 
       [0012]    Embodiments described herein are directed to a method, apparatus, and system for bending of an instrument with large degrees of articulation while maintaining ease of manufacturing. 
         [0013]    In other embodiments, methods and apparatus for creating an articulating segment by starting with a solid rod instead of a tube. First, material is removed from the sides of the rod for enabling a bend. In one embodiment, the rod has material removed from the cross section in order to accommodate an actuation wire. 
         [0014]    In other embodiments, the cross section accommodates ancillary components pertaining to the end effector. 
         [0015]    One embodiment provides placing the path of the ancillary components close to the neutral axis of the bending section. Consequently, this reduces interactions between the articulation of the bending section and the ancillary components. Furthermore, resulting in a more predictable bend and end effector behavior. For example and not by way of limitation, removing material from the cross section to accommodate the articulation pull wire and the ancillary components permits manipulation of bending stiffness and the amount of opposing forces it is able to resolve during a medical procedure. 
         [0016]    In one embodiment, the component is manufactured from a superplastic material that will be discussed later, such as, but not limited to Nitinol and other similar materials. The stiffness of the structure was manipulated via the design of the cross sectional profile in order to ensure the structure provides enough stability throughout the complete range of motion. The structure achieves a significant bend by imposing a moment on the structure and will recover to the original position when the moment is removed from the structure. 
         [0017]    This actuation would simply require one pull wire at the tip, which would need to be pulled in order to generate a moment and relaxed to relieve the moment. 
         [0018]    In an alternative embodiment, the component is manufactured from a superplastic material, but the cross section allows a different inner profile by incorporating the relief on the profile, the device lends itself to be manufactured using the wire EDM (Electric Discharge Machining) process without having to initially create a clearance hole. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]      FIG. 1  is a view to facilitate description of a neutral axis; 
           [0020]      FIG. 2  is a view to facilitate description of a neutral axis; 
           [0021]      FIGS. 3A-3D  depict an apparatus for a bending flexure according to a first embodiment of the present invention; 
           [0022]      FIG. 4  is a cross section side view of  FIG. 3 ; 
           [0023]      FIG. 5  is a view of a modeling representation of  FIG. 3  according to a finite element analysis (FEA); 
           [0024]      FIG. 6  is a view depicted an articulated position of the first embodiment depicted in  FIG. 3 ; 
           [0025]      FIG. 7  is an isometric view of an assembly, wherein the flexure subject matter is incorporated into an end effector, according to one embodiment of the present invention; 
           [0026]      FIG. 8  depicts an apparatus for a bending flexure according to a second embodiment of the present invention; 
           [0027]      FIG. 9  is a cross section side view of  FIG. 8 ; and 
           [0028]      FIG. 10  is a cross section side view that depicts bending behavior of  FIG. 9 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0029]    Although certain preferred embodiments and examples are disclosed below, inventive subject matter extends beyond the specifically disclosed embodiments to other alternative embodiments and/or uses, and to modifications and equivalents thereof. Thus, the scope of the claims appended hereto is not limited by any of the particular embodiments described below. For example, in any method or process disclosed herein, the acts or operations of the method or process may be performed in any suitable sequence and are not necessarily limited to any particular disclosed sequence. Various operations may be described as multiple discrete operations in turn, in a manner that may be helpful in understanding certain embodiments; however, the order of description should not be construed to imply that these operations are order dependent. Additionally, the structures, systems, and/or devices described herein may be embodied as integrated components or as separate components. 
         [0030]    For purposes of comparing various embodiments, certain aspects and advantages of these embodiments are described. Not necessarily all such aspects or advantages are achieved by any particular embodiment. Thus, for example, various embodiments may be carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other aspects or advantages as may also be taught or suggested herein. 
         [0031]    The embodiments described herein are directed to an apparatus for a distal bending section of minimally invasive surgical instrument having a large degree of articulation and providing sufficient rigidity to resolve the required forces during remote surgical procedures. Other embodiments provide methods of using the distal bending section and methods for making it. 
         [0032]    One embodiment provides placing the path of the ancillary components close to the neutral axis of the bending section. Consequently, this reduces interactions between the articulation of the bending section and the ancillary components. Furthermore, embodiments of the present invention provide a more predictable bend and end effector behavior. For example and not by way of limitation, removing material from the cross section accommodates the articulation pull wire and the ancillary components, hence, the bending stiffness can be manipulated in order to achieve a desired characteristic. 
         [0033]    In one embodiment, the component is manufactured from a superplastic material. In one embodiment, the material is Nitinol and with superelastic phase at room and/or body temperature. Also, other embodiments include use of any super elastic alloy. In yet another embodiment, the moment of inertia was tuned such that the structure achieves a significant bend by generating a moment on the structure and recovers to the original position when the moment is removed. This actuation would simply require one pull wire at the tip, which would need to be pulled in order to generate a moment and relaxed to relieve the moment. 
         [0034]    In an alternative embodiment, the component is manufactured from a superplastic material, but the cross section allows a different inner profile by incorporating the relief on the profile, the device lends itself to be manufactured using the wire EDM (Electric Discharge Machining) process without having to initially create a clearance hole. 
         [0035]    Referring to  FIG. 3A , finished bending section  300  in accordance to an embodiment of the present invention is depicted.  FIG. 3B  is a longitudinal cross-section through the axis of bending section  300 ,  FIG. 3C  shows an axial cross-section of bending section  300  along line C of  FIG. 3B , and  FIG. 3D  shows an axial cross-section of bending section  300  along line D of  FIG. 3B . 
         [0036]    Referring to  FIG. 3B , material is removed along the top portion of a rod to create void  302 , preferably along the length of the bending section. As discussed below, this void is created to assist in removal of material in the road to create the additional features of this preferred embodiment. Material is also removed from teardrop sections  304 , where adjacent to teardrop section  304  material is left in place forming leaves  306 . A tendon (not shown) extends through void  308  (described below) is attached at the distal end of bending section  300 . When tension is applied to the tendon bending section will bend downward, as shown in the figure, and teardrop voids  304  permit leaves  306  to move inward, and a bend is realized along solid spine  310 . The skilled artisan will appreciate the selection of shapes for the teardrop voids and leaves is a matter of design choice, as well as the amount of material left to form spine  310 . 
         [0037]    Referring now to  FIG. 3C , non-cylindrical channel  312  is formed down the length of the solid rod. Preferably the outer circumference of the rod, and therefore the bending section, has an approximately cylindrical shape, similar to that of a drawn hypotube. Prior art bending sections have material cut from a hypotube, and therefore have a cylindrical inner diameter as well, which results is a uniform sidewall thickness along the length of the prior art bending section. When the outer diameter of the bending section is small, the hypotube walls do not provide sufficient strength and rigidity when large degree articulations are required and where a surgical tool at the distal end requires this rigidity to perform desired procedures. Embodiments of the present invention provide a non cylindrical channel  312  through the bending section, which permits distributing material off-axis (i.e., non-uniform wall thickness) to provide structural rigidity to the bending section, provides a pathway  314  for the tendon off-axis and a pathway  316  proximate to the neutral axis for auxiliary cables (not shown), such as tool actuating or articulating cables. 
         [0038]    One embodiment provides for placing the path of the ancillary components as close to the neutral axis of the bending section. Consequently, this reduces interactions between the articulation of the bending section and the ancillary components. Furthermore, this embodiment provides a more predictable bend and end effector behavior. For example, removing enough material from the cross section to accommodate the articulation pull wire and the ancillary components, hence, the bending stiffness can be manipulated in order to achieve a desired characteristic.  FIG. 4  is a cross section the same as shown in  FIG. 3C . The location of the cross section locations relative to the structure are illustrated in  FIG. 5 . Section c-c demonstrates the cross section of the region  310  that will experience the bend and will contribute to the deflection of the structure. Section d-d demonstrates the region of the structure that provides a chassis  316 , similar to a ribcage, to supports and house the components that are required to articulate the structure and manipulate the end effector. In this Figure, the hatched diagonal sections (referred to as hatched regions) depict a solid cross section. For example, section c-c has a solid cross section on the top portion. In contrast, section d-d has a solid cross section around the entire channel. 
         [0039]    A dashed line near the top of the figure depicts the neutral axis of the apparatus. Also, a dashed arrow depicts the direction of the preferential bending away from the neutral axis in a downward direction. 
         [0040]    Both section views of section c-c and d-d depict a dual oval shaped key opening, or lumen, to accommodate ancillary components (not shown) and an articulation wire (not shown). In some embodiments, the ancillary components could include any or all of the following:
   Pull wires for generating actuation at the end effector;   Fibers for Illumination, laser, vision;   Pneumatics and/or hydraulics;   Electrical wires;   Open lumen for a working channel (open architecture device, end effector is passed through working channel and is interchangeable); and   A telescoping tube that supports the end effector   
 
         [0047]    In one embodiment, the top opening, or lumen, accommodates the ancillary components and the bottom opening accommodates the articulating wire that controls the bending of the apparatus. However, the skilled artisan appreciates different lumen configurations and placements based at least in part on the medical, surgical, or other application of the bending apparatus may be used without deviating from the present invention. 
         [0048]      FIG. 5  is a view of a modeling representation of  FIG. 3  according to a finite element analysis (FEA) which shows the interaction between the articulation wire and the flexure. 
         [0049]      FIG. 6  is a view depicting an articulated position of the the embodiment depicted in  FIGS. 3-4 . This photograph was captured under a microscope and exemplifies the uniform bending of the structure. In one embodiment, the degree of articulation is based at least in part on the amount of reliefs/voids along the length of the structure. In this embodiment, one aspect of the relief also allows the structure a hard stop (a feedback of hitting a barrier) when the leaves come in contact. Consequently, embodiments of the present invention help to prevent over articulation and potential damage to the structure. 
         [0050]      FIG. 7  is an isometric view of an assembly, wherein the flexure subject matter is incorporated into an end effector, according to one embodiment of the claimed subject matter in the present invention; 
         [0051]      FIG. 8  depicts an apparatus for a bending flexure according to another embodiment of the present invention. The skilled artisan will appreciate the shape of non-cylindrical channel  312  can be varied to achieve desired bending and rigidity properties of the bending section. The cross section of the design depicted in  FIG. 8  (shown in  FIG. 9 ), permits the inner profile to break out. By incorporating this relief on the profile, the device lends itself to be manufactured using the wire EDM process without having to initially create a clearance hole 
         [0052]      FIG. 9  is a cross section side view of  FIG. 8 . The two struts  702  on flexure #2 ( FIG. 7 ) tend to bend about the neutral axis, but also slightly into the center of the cross section. This bending characteristic will result in the break out “gap” to start to close as the flexure is articulated, and will eventually close completely during large articulations. 
         [0053]    Also, in this second embodiment, an opening allows for lateral insertion of ancillary components. The concept of having a break out on the inner profile also has a benefit during the assembly process. For example, there is an available gap through the piece, the articulation wire and ancillary components can be inserted laterally instead of axially. This assembly option also allows the flexure to replaced without having to sever the articulation wire. 
         [0054]      FIG. 10  is a cross section side view that depicts bending behavior of the embodiment depicted in  FIG. 8-9 . During operation, the gap will tend to close as the flexure is articulated and will therefore minimize the possibility of having the ancillary components “escape” the inner profile lumens. If the presence of the gap is of concern, the component can still be manufactured with a gap and then “shape set” in order to close the gap before integration into an assembly. 
         [0055]    Elements or components shown with any embodiment herein are exemplary for the specific embodiment and may be used on or in combination with other embodiments disclosed herein. While the invention is susceptible to various modifications and alternative forms, specific examples thereof have been shown in the drawings and are herein described in detail. The invention is not limited, however, to the particular forms or methods disclosed, but to the contrary, covers all modifications, equivalents and alternatives thereof.