Patent Publication Number: US-2023143304-A1

Title: Cutting apparatus

Description:
BACKGROUND 
     A wide variety of surgical assemblies and systems have been developed. Some of these assemblies and systems include instruments used in spinal surgeries. These assemblies and systems are manufactured by any one of a variety of different manufacturing methods and may be used according to any one of a variety of methods. Of the known medical assemblies, systems, and methods, each has certain advantages and disadvantages. 
     Guide tubes can assist in performing surgical procedures on a patient. A robotic or analog mechanical arm can hold a guide tube at a desired location relative to the patient&#39;s anatomy. A surgeon uses the guide tube to guide surgical instruments along a desired trajectory to treat the patient. 
     SUMMARY 
     An example surgical cutting apparatus includes: a housing defining a scalpel guide; a scalpel longer than a length of the housing and having a movement path constrained by the scalpel guide; a handle coupled to a proximal end of the scalpel; and a blade holder at a distal end of the scalpel. 
     Continuing the example surgical cutting apparatus, the scalpel of can be pivotably coupled to the housing. The handle can further include a lock configured to resist the scalpel pivoting in relation to the housing. The lock can include a lock tab. The housing can include a catch. The lock can be slidably disposed within a handle channel of the handle such that the lock tab can selectively fit within the catch to resist the scalpel moving in relation to the housing. The apparatus can be configured such that the scalpel moves relative to the housing when forming an incision. The scalpel can pivot about only a single pivot point or multiple pivot points. The blade holder can be the sole blade holder of the surgical cutting apparatus. The scalpel can be unitary. The handle can be fixed to the scalpel and rotates about the pivot point. The housing can include a housing pivot point. The apparatus can further include a pivot pin extending through the housing pivot point and the scalpel pivot point. The apparatus can include a biaser configured to bias the scalpel into a starting position. The biaser can include at least two springs biasing the scalpel toward parallel with a length of the housing. The apparatus can further include a guide tube of a robot arm. The housing can be disposed within the guide tube. The housing can further include a housing lip disposed at a proximal end of the housing. The housing lip can abut a proximal end of the guide tube, thereby resisting further distal movement of the housing through the guide tube. The housing can include a plurality of grooves extending parallel to the length of the housing. The guide tube can include a detent configured to interact with a groove of the plurality of to resist rotation of the housing within the guide tube. The housing can include a front housing and a back housing coupled together. 
     A second example system includes an arm holding a guide tube having a tube inner diameter and a cutting apparatus. The cutting apparatus includes a housing extending through the guide tube, a scalpel extending through the housing and having a blade disposed at a distal end of the scalpel. The scalpel is pivotably coupled to the housing such that the length of the swing of the distal tip of the blade is greater than the tube inner diameter. 
     Continuing the second example system, the housing can define a scalpel guide, which defines a movement plane in which the scalpel can move. The scalpel guide further constrains an angle of movement of the scalpel. The housing comprises a pivot pin about which the scalpel pivots. 
     An example method includes: inserting a cutting apparatus into a guide tube of a surgical robot such that a blade at a distal end of the cutting apparatus extends distal to a distal end of the guide tube and a handle at a proximal end of the swing scalpel is proximal to a proximal end of the guide tube; after inserting the swing scalpel, unlocking the cutting apparatus; laterally moving the handle in a first direction to a first position such that a tip of the blade reaches a first point by moving in an opposite direction; and laterally moving the handle in a second direction to a second position such that a tip of the blade reaches a second point by moving in an opposite direction. Either or both of the first point and the second point is outside of an inner diameter of the guide tube. 
     The example method can further include rotating the cutting apparatus in the guide tube such that a ball of the guide tube moves from a first groove of the housing of the cutting apparatus to a second groove of the housing of the cutting apparatus. The method can further include forming an incision with the blade such that a skin-level length of the incision is longer than an inner diameter of the guide tube. Forming the incision can include the step of laterally moving the handle in the second direction. Moving the handle to a first position can include overcoming at least one bias force that urges the tip of the blade toward a starting position. Moving the handle to a first position can include pivoting a scalpel arm of the cutting apparatus within a housing of the cutting apparatus. Unlocking the cutting apparatus can include sliding a lock tab from a first position in which a lock tab is disposed within a catch in the housing to a second position in which the lock tab is outside of the catch. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    illustrates a side view of an example cutting apparatus constrained by a guide tube held by an arm. 
         FIG.  2    illustrates a perspective view of the cutting apparatus. 
         FIG.  3    illustrates an exploded view of the cutting apparatus. 
         FIG.  4    illustrates a side view of the cutting apparatus in an unlocked configuration. 
         FIG.  5    illustrates a side view of the cutting apparatus in a locked configuration. 
         FIG.  6    illustrates a cutaway view of the cutting apparatus inserted into the guide tube with the scalpel removed. 
         FIG.  7    illustrates a cutaway view of the cutting apparatus inserted into the guide tube with the scalpel in a starting position. 
         FIG.  8    illustrates the swinging of the scalpel being blocked by the scalpel guide. 
         FIG.  9    illustrates an example method for using the cutting apparatus. 
         FIG.  10    illustrates a partial cutaway view of the cutting apparatus being inserted through the guide tube while the cutting apparatus is in a locked position and the scalpel is in an initial position substantially parallel with the length of the guide tube. 
         FIG.  11    illustrates a partial cutaway view of the cutting apparatus of  FIG.  10    continuing to be inserted and the blade piercing the patient&#39;s tissue. 
         FIG.  12    illustrates a partial cutaway view of the cutting apparatus of  FIG.  11    as its handle is swung from side to side to form an incision. 
         FIG.  13    illustrates a partial cutaway view after the cutting apparatus of  FIG.  12    has been removed and a subsequent instrument provided in its place. 
         FIG.  14    illustrates a partial cutaway view of the cutting apparatus being inserted through the guide tube while the scalpel is swung to one side. 
         FIG.  15    illustrates a partial cutaway view of the cutting apparatus of  FIG.  14    continuing to be inserted and the blade piercing the patient&#39;s tissue. 
         FIG.  16    illustrates a partial cutaway view of the cutting apparatus of  FIG.  15    after its handle was swung to an opposite side to form an incision. 
         FIG.  17    illustrates a partial cutaway view after the cutting apparatus of  FIG.  16    has been removed and a subsequent instrument provided in its place. 
     
    
    
     DETAILED DESCRIPTION 
     An articulating arm holds a guide tube in a desired location proximate a target surgical site of a patient&#39;s anatomy. But forming an incision relative to the target surgical site and guide tube can be difficult. For example, forming an incision prior to positioning the guide tube may require the surgeon to predict or determine where the arm will hold the guide tube, which can lead to errors or somewhat defeat the usefulness of the guide tube. A surgeon may form the incision while the guide tube is in position, but manipulating a traditional scalpel through or around the guide tube can be difficult. The guide tube can be positioned so a user can make a mark or initial incision on the patient&#39;s skin through the guide tube, moved out of the way so a full incision can be formed, and then moved back to continue with the procedure. But such frequent moving can be inefficient. Disclosed examples include a cutting apparatus relevant to improving incision formation through a guide tube. 
     An example of such a cutting apparatus includes a scalpel that pivots about a pivot point within a scalpel housing placed in the guide tube. The cutting apparatus permits dynamic blade movement that reaches beyond the inner circumferential bounds of the distal end of the guide tube to create an incision that is longer than the inner diameter of the guide tube. A handle is coupled to the scalpel and is proximally outside of the housing and guide tube. A cutting blade is coupled to the scalpel and extends distally outside of the housing and the guide tube. The scalpel is locked in a straight position for introduction of the cutting apparatus through a guide tube. After passage through the guide tube, the cutting apparatus is unlocked, which allows for side-to-side swinging of the scalpel in a cutting plane. The side-to-side swinging motion of the scalpel is constrained by a scalpel guide, such as may be defined by the housing. The scalpel is biased toward the center straight position such that the user must overcome the bias force to swing the blade to make an incision. The cutting apparatus can be configured for use through a guide tube of set inner diameter. For instance, the cutting apparatus can be configured to have a close fit with the guide tube such that the cutting apparatus is guided by the guide tube sufficiently well to form an incision suitable for the desired procedure. An example cutting apparatus is shown and described in relation to  FIGS.  1 - 3   . 
       FIG.  1    illustrates a side view of an example cutting apparatus  100  constrained by a guide tube  30  held by an arm  20 .  FIG.  2    illustrates a perspective view of the cutting apparatus  100 .  FIG.  3    illustrates an exploded view of the cutting apparatus  100 . 
     The guide tube  30  can be an end effector or other component held by the arm  20 , such as a robotic or non-robotic articulating arm. The guide tube  30  can be manually or automatically positioned in a desired location relative to a patient, typically close to but not in contact with the patient&#39;s tissue. The arm  20  can resist unwanted movement of the guide tube  30  out of that position. The guide tube  30  can define an inner passage  32  of diameter D 1  through which instruments can be passed and guided. Instruments having a sufficient diameter can pass through and be guided by the guide tube  30 , so as to follow a desired trajectory held by the arm  20 . In some implementations, the guide tube  30  includes a ball  34  or other structure that can interact with one or more detents or grooves of an instrument (e.g., the cutting apparatus  100  or another instrument) to facilitate maintaining a particular rotation of the instrument within the guide tube  30 . 
     In the illustrated example, the cutting apparatus  100  includes a housing  110  through which a scalpel  160  extends. A handle  180  and a blade  10  are coupled to the scalpel  160 . As illustrated in  FIG.  1   , the cutting apparatus  100  can be described relative to X, Y, and Z axes having an origin at the center of the cutting apparatus  100 . As illustrated, the Y axis corresponds to the length of the cutting apparatus  100  and defines a proximal direction (e.g., in a direction toward the end of the cutting apparatus  100  having the handle  180 ) and a distal direction (e.g., toward the end of the cutting apparatus  100  having the blade  10 ). The housing  110  is generally cylindrical and has a circumference defined in the X and Y directions. The cutting apparatus  100  defines a cutting plane in which the scalpel  160  moves the blade  10  and a cutting arc along which the tip of blade  10  moves. The cutting plane need not be perfectly planar and the cutting arc need not be perfectly arcuate. Manufacturing tolerances and user movement may contribute to irregularities in the path of the blade  10 . The cutting plane may be sufficiently planar as to permit a user to form a sufficiently straight incision to perform a surgical procedure. The cutting apparatus  100  can be rotated in the guide tube  30  to angle the cutting plane in a desired direction. 
     The blade  10  can be a cutting blade, such as any of a variety of types of scalpel blades. Example blades  10  can be straight, curved, hooked, crescent-shaped, double sided, other kinds, or combinations thereof. The blade  10  can be configured to couple with a blade holder of the scalpel  160  according to a proprietary or industry standard coupling technique (e.g., ISO 7740:1985, entitled “Instruments for surgery—Scalpels with detachable blades—Fitting dimensions”). Further, while examples are primarily provided in the context of forming an incision, other kinds of surgical tools can be used in addition to or instead of the cutting apparatus  100 . For example, disclosed embodiments can be adapted to be used with laser scalpels, ultrasonic knives, rasps, awls, taps, cutting burrs, rongeurs, scissors, saws, other tissue modification tools, or combinations thereof. Such tools can be guided by the guide tube  30  but still have a degree of movement to permit their use on tissue of the patient. Non-cutting tools can also be used, such as probes. For instance, the blade  10  could be replaced with a working portion of any of such cutting or non-cutting tools and the scalpel  160  and remainder of the cutting apparatus could be modified as needed to accommodate the change. 
     The housing  110  in the illustrated example generally provides an exterior that cooperates with the guide tube  30  and an interior that guides movement of the scalpel  160 . In the illustrated example, the housing  110  is cylindrical in shape with a generally circular cross section. A distal end of the housing  110  can include a bevel to facilitate insertion of the housing  110  into the guide tube  30 . 
     The housing  110  can be divided into a front housing  110   a  and a rear housing  110   b . The divided sections of the housing  110  can be connected via fasteners  152 . In the illustrated example, the fasteners  152  are pins disposed in housing connectors  178  to mate the housings  110   a ,  110   b  together. Example pins have a diameter of 1.5 mm, a length of 8 mm, are constructed from stainless steel, follow ISO 2338, and have an m6 tolerance class. The fasteners  152  can take other forms and alternative techniques may be used to assemble the housing  110 , such as adhesives or welding. 
     The exterior of the housing  110  can be configured to interact with the guide tube  30 . For example, the housing  110  can include a section have a maximum diameter D 2  or width that is less than the internal diameter D 1  of the guide tube  30  so that the portion of the housing  110  can fit within the guide tube. The difference between D 1  and D 2  can be selected to balance ease of insertion of the cutting apparatus  100  into and through the guide tube  30  with the internal diameter D 1  sufficiently constraining movement of the cutting apparatus  100  along the trajectory of the guide tube  30  to be useful. In some examples, the inner passage  32  of the guide tube  30  can be circumferentially bounded such that instruments enter or exit the inner passage  32  only through proximal and distal openings of the guide tube (e.g., the guide tube  30  can lack lateral openings or slots through which instruments can fully or partially pass through the guide tube  30 ). 
     A housing lip  112  can be coupled to or integral with the housing  110 . In the illustrated example, the housing lip  112  is disposed at a proximal end of the housing  110 . The housing lip  112  can be a portion of the housing  110  configured to interact with a proximal portion of the guide tube  30  to resist or prevent further distal movement the cutting apparatus  100  into the guide tube  30 . For example, the housing lip  112  can have an outer diameter or width greater than that of the inner diameter D 2  of the guide tube  30 . As a result, the distal end of the cutting apparatus  100  can be inserted through the guide tube  30  until the housing lip  112  abuts the proximal end of the guide tube  30 , thereby preventing further distal movement of the apparatus  100  relative to the guide tube  30 . 
     The exterior of the housing  110  can define elongate grooves  114 . In the illustrated example, each groove  114  extends along a length of the housing  110 , and the plurality of grooves  114  is disposed circumferentially around the housing  110 . The grooves  114  can receive the one or more balls  34  or other structure of the guide tube  30  to facilitate maintaining a particular rotation of the cutting apparatus  100  about the Y axis, thereby facilitating maintenance of a particular angle of the cutting plane (e.g., relative to the arm  20 ). For example, the one or more balls  34  can fit into one or more of the grooves to form one or more ball-and-detent structures that facilitate (but not necessarily lock) holding the cutting apparatus  100  in a particular angle about the Y axis. 
     The housing  110  can define a catch  126 . The catch  126  can be a portion of the housing  110  in which a lock tab can be received to resist unwanted movement of the scalpel  160 . As described in more detail below, the catch  126  can receive a lock tab of a lock coupled with the handle of the cutting apparatus  100  to resist unwanted movement of the scalpel  160  relative to the housing  110 . 
     The housing  110  can define one or more recesses or breaks  128  that accommodate lateral movement of the scalpel  160  outside of the housing. For example, as illustrated, the proximal and distal ends of the housing  110  include breaks  128  parallel to the cutting plane to that allow for movement of the scalpel without being constrained by the housing  110  at that location. The housing  110  defines proximal and distal breaks  128  that permit the scalpel  160  to have a wider range of motion than would otherwise be permitted by the housing  110 . The breaks  128  can take the form of lateral cutaways in the housing  110  and the scalpel guide  172  into which the scalpel  160  can move. As illustrated, the breaks  128  extend partially, but not entirely, along the length of the housing  110 . In some examples, each break  128  extends approximately 10% along the total length of the housing  110 . In other examples, the breaks  128  extend entirely along the entirety of the housing  110 . 
     Internally, the illustrated housing  110  defines a passage  116  through which the scalpel  160  extends and can move. The housing  110  defines a scalpel guide  172  that constrains movement of the scalpel  160  (e.g., by defining a shape of the passage  116 ). The scalpel guide  172  is one or more structures integral with or coupled to the housing  110 . In the illustrated example, the scalpel guide  172  includes lateral walls that the scalpel  160  abuts if the scalpel  160  is pivoted or otherwise moved sufficiently far in a particular direction. In this manner, the scalpel guide  172  constrains the movement path of the scalpel  160 . In the illustrated example, the scalpel guide  172  is relatively contoured to compliment a shape and position of the scalpel  160  when the scalpel  160  is moved to a furthest desired extend. For example, the scalpel guide  172  can be shaped and disposed such that the scalpel  160  contacts multiple portions of the scalpel guide  172  when movement of the scalpel  160  is halted by the scalpel guide  172 . In other examples, the scalpel guide  172  may not be so contoured. In some examples, the scalpel guide  172  includes one or more pins or other structures that interrupt a motion path of the scalpel  160 . In some examples, the scalpel guide  172  is a track in which the scalpel  160  (or a portion connected thereto) rides. In some examples, the shape, size, or position of the scalpel guide  172  is modifiable by the user so that custom cutting paths can be defined. For instance, a pin can be moved from a first holder to a second holder to change the amount of travel the scalpel  160  has before it contacts the pin. In another example, a user adjusts one or more gears to change a position of the scalpel guide  172 . In a still further example, the scalpel guide  172  is slidable in a track but selectively locked in position by a user adjustable set screw. In yet further examples, the cutting apparatus may not substantially define the scalpel guide  172 . Instead, a range of motion of the scalpel  160  may be limited by the guide tube  30 . 
     The housing  110  can define one or more biaser holders  174  that hold one or more biasers  154 . The biasers  154  can be one or more components of the cutting apparatus  100  that bias the scalpel  160  into or out of a particular position, such as a starting position. In the illustrated example, the particular position is one in which the scalpel  160  is parallel to a length of the housing  110 . In other examples, the biaser  154  can bias the scalpel  160  such that it is pivoted to a particular side of the cutting apparatus  100  (e.g., corresponding to a starting point of an incision). In the illustrated example, the biaser  154  is formed from two springs each having an end seated in a respective biaser holder  174  of the housing  110  and another end interacting (e.g., coupled with) a biaser connection portion  164  of the scalpel  160 . As the scalpel  160  is pivoted in one direction, one of the biasers  154  is lengthened and the other biaser  154  is compressed. The compression and lengthening resists the pivoting and urges the scalpel  160  to return to a position in which the springs are relatively balanced. The biasers  154  can take other forms, such as magnets that interact with one or more magnets disposed at the scalpel  160 . In some examples, in addition to or instead of walls of the scalpel guide  172 , the biaser  154  can constrain the movement of the scalpel  160 . For instance, the biaser  154  may compress or move for a distance, but then become sufficiently incompressible as to resist further movement of a scalpel  160  by a user. Such movement can be customized (e.g., during manufacturing or during use) to set the permitted range of movement. 
     The housing  110  can further include one or more biaser passages  175  through the housing  110  and scalpel guide  172  that permit the insertion of the biasers  154  during a manufacturing or assembly process. The passages  175  can be aligned with a long axis of the biaser holders  174  to aid in insertion of the baiasers  154 . 
     The scalpel  160  is a portion of the cutting apparatus  100  that moves to cut tissue. The scalpel  160  includes an elongate scalpel arm  162  forming the body of the scalpel  160 . The scalpel arm  162  can be a unitary structure having a length greater than a length of the housing  110 . The scalpel  160  can include a biaser connection portion  164 , a pivot point  166 , a proximal connector  167 , and a blade holder  168 . The scalpel  160  can be configured to rotate relative to the housing  110  when forming an incision (e.g., rotate in a direction parallel to a length of the housing  110 ). 
     The biaser connection portion  164  is the portion of the scalpel  160  that interacts with a biaser  154  of the cutting apparatus  100 . For example, the biaser connection portion  164  can be a cutout portion or a recessed portion configured to receive a portion of the biaser  154 . The biaser connection portion  164  can define a shape or include a component configured to couple with the biaser  154 . The biaser connection portion  164  can include a peg or other structure to encourage the biaser  154  stay in appropriate relation to the biaser connection portion  164  (e.g., resist drifting or movement of the biaser  154  away from the biaser connection portion  164 ). In some examples, (e.g., where the biaser  154  is a magnet, the biaser connection portion  164  may be a magnet, a portion holding a magnet, or a magnetic material. 
     The pivot point  166  is a point by which the scalpel  160  is pivotably coupled to the housing  110 . The pivot point  166  can be a portion about which the scalpel  160  rotates relative to the housing  110 . In an example, the pivot point  166  is a fixed point on the scalpel  160 . For example, the housing  110  can include one or more housing pivot points  176  (e.g., each of the front housing  110   a  and the rear housing  110   b  can have a respective housing pivot point  176 ) aligned with the scalpel pivot point  166 . The housing pivot point  176  can be fixed. A pivot pin  150  extends through the one or more housing pivot points  176 . In an example, the pivot pin  150  has a diameter of 1.5 mm, a length of 12 mm, is constructed from stainless steel, follows ISO 2338, and has an m6 tolerance class. In an example, the pivot pin  150  is non-translating (e.g., the pivot pin  150  may rotate, but it does not travel through path, such as a cam channel). In an example, the pivot point  166  is the only pivot point about which the scalpel  160  moves when forming an incision. In an example, the pivot point  166  is the only pivot point about which a component of the apparatus  100  moves when forming an incision. The pivoting relationship between the scalpel  160  and the pivot point  166  can result in the scalpel  160  forming an incision having a variable depth (e.g., is arcuate when viewed perpendicular to the cutting plane). In an example, the pivoting connection (e.g., achieved via the pivot pin  150 ) between the scalpel  160  and the housing  110  can resist the scalpel  160  from moving proximally or distally (e.g., along the Y axis) relative to the housing  110  as well as resist the scalpel from substantially rotating outside of the cutting plane (e.g., resisting rotation of the scalpel  160  about the Y or X axes). In some examples, such restriction of movement may be achieved by the housing  110  itself (e.g., the passage  116  not being sized to substantially permit such movement). In other examples, the pivot pin  166  can be translating, such as following a cam channel defined in one or both of the scalpel  160  and the housing  110 . The pivot point  166  may be one of multiple different pivot points of the cutting apparatus  100  that facilitates cutting action. 
     The blade holder  168  is a portion of the scalpel  160  configured to hold the blade  10 . The blade holder  168  can be a region of the scalpel  160  that is unitary with the scalpel arm  162 . The blade holder  168  can be disposed at a distal region of the scalpel  160 . The blade holder  168  can configured in any of a variety of ways to securely hold the blade  10  for use. The blade holder  168  can secure the blade  10  in an industry standard manner, such as according to BS 2982:1992 (“Specification for Materials and Packaging of Surgical Scalpels with Detachable Blades”) or ISO 7740:1985 (“Instruments for surgery—Scalpels with detachable blades—Fitting dimensions”). An example description of a blade holder  168  and compatible blade  10  is provided at FIGS. 1-4 of U.S. Pat. No. 4,270,416, which is incorporated herein by reference in its entirety for any and all purposes. In an example, the blade holder  168  is the only blade holder of the apparatus  100 . In other examples, the cutting apparatus can include multiple blade holders  168 . In some examples, a single blade holder  168  may be beneficial over multiple blade holders  168  as an incision formed with a single blade may be cleaner (e.g., less ragged) than an incision formed with multiple blades. Further, a single blade may be easier fora user to control than multiple blades. In some examples, the blade holder  168  and the blade  10  are integral or are not configured to be user separable. 
     The proximal connector  167  can be a portion of the scalpel  160  configured to couple with the handle  180 . For example, in the illustrated example, the proximal connector  167  includes two holes into which fasteners  186  can connect to couple the handle  180 . In an example, the fasteners  186  are stainless steel socket head screws having a length of 8 mm and a diameter of 2 mm. 
     The scalpel  160  can lack a portion by which the user directly grasps when forming an incision. The user instead directly grasps the handle  180 , which is coupled with the proximal end of the scalpel  160 . As a result, movement of the handle  180  directly causes movement of the scalpel  160 . Further, the movement of the handle  180  is indirectly constrained by the scalpel guide  172  because the scalpel guide  172  constrains movement of the scalpel  160  and the handle  180  is directly coupled to the scalpel  160 . The connection between the scalpel  160  and the handle  180  results in the handle  180  rotating about the pivot point  166 . The rotation of the handle  180  about the pivot point  166  in the cutting plane causes rotational movement of the scalpel  160  in the cutting plane. 
     The handle  180  is a portion configured to be held by a user&#39;s hand for controlling the scalpel  160 . In an example, the handle  180  is the only portion by which the use grasps the cutting apparatus during use to form an incision. The handle  180  can be configured for grasping based on its size, position, or surface features (e.g., grips or knurling)  100 . In an example, the handle  180  is sized to accommodate grasping by the user. The handle  180  can have a width (or diameter where the handle  180  has a circular cross-section) that is greater than a width of the scalpel  160 , than the inner diameter of the guide tube  30 , than the width of the distal end of the housing  110 , and/or greater than a width of the lip  112 . In an example, the handle  180  is elongate (e.g., longer in the Y direction than it is in the X or Z directions). 
     In the illustrated configuration, the handle  180  defines a longitudinal handle channel  182  and includes a lock ball  184 . Disposed within the handle channel  182  is a lock  120 . The lock  120  is a component configured to resist the scalpel  160  pivoting in relation to the housing  110 . The lock  120  is in a sliding relationship with the handle  180 . The lock  120  is coupled to the handle via a shoulder screw  130  that slides within a lock channel  126 . The lock  120  includes a lock tab  122 . In an example, the lock  120  is slidably disposed within a handle channel  182  of the handle such that the lock tab  122  can selectively fit within the catch  126  to resist the handle  180  moving in relation to the housing  110  (e.g., thereby resisting the scalpel  160  from moving in relation to the housing  110 ). The lock  120  can include at least two lock detents  124  that cooperate with the lock ball  184 . As shown in  FIG.  4   , when the lock ball  184  is engaged with a first lock detent  124 , the engagement retains the lock  120  in an unlocked position, but the engagement can be overcome with sufficient force. To enter the locked position, the lock  120  is slid distally in the handle  180  until the lock tab  122  is disposed within the catch  126  of the housing  110 . The lock tab  122  being disposed within the catch  126  resists movement of the handle  180 , which also resists movement of the scalpel  160  due to the connection between the handle  180  and the scalpel  160 . To enter an unlocked position, the lock  120  is slid proximally until the lock tab  122  leaves the catch  126  of the housing  110 . Sufficient proximal movement can result in the second lock detent  124  being engaged with the lock ball  184 , which can resist the lock  120  falling back into the locked position. As shown in  FIG.  5   , when the lock ball  184  is engaged with a second lock detent  124 , the engagement retains the lock  120  in a locked position, but the engagement can be overcome with sufficient force. With the lock tab  122  no longer constrained by the catch  126 , the handle  180  (and coupled scalpel  160 ) is free to translate laterally (e.g., as a part of the handle  180  rotating about the pivot point  166 ) to cause movement of the blade  10 . 
       FIG.  6    illustrates a cutaway view of the cutting apparatus  100  inserted into the guide tube  30  with the scalpel  160  removed so the scalpel guide  172  can more clearly be viewed. The housing lip  112  rests on the proximal end of the guide tube  30 . 
       FIG.  7    illustrates a cutaway view of the cutting apparatus  100  inserted into the guide tube  30  with the scalpel  160  in a starting position. In this illustrated example, the stating position of the scalpel  160  is one in which the length of the scalpel  160  is perpendicular to the length of the housing  110 . In an example implementation, the forces of the biasers  154  on the scalpel  160  is balanced while in the starting position. 
       FIG.  8    illustrates the swinging of the scalpel  160  being blocked by the scalpel guide  172 . In an example, the angle of rotation of the scalpel  160  permitted by the scalpel guide  172  is ten degrees. In other examples, the angle of rotation can be more or less. 
       FIG.  9    illustrates an example method  900  for using the cutting apparatus  100 . The method  900  can begin with operation  902 . Operation  902  includes positioning a guide tube  30 . The guide tube  30  can be positioned relative to a surgical target site, such as by a patient&#39;s spine when the guide tube  30  is being used for a spinal procedure. In some examples the guide tube  30  is positioned a specific distance away from the patient&#39;s skin to accommodate the cutting apparatus  100  and to allow formation of an incision having a desired depth. The guide tube  30  can be coupled to a robot arm and positioning the guide tube  30  can include the robot arm being manually guided by a user (e.g., the robot arm receives user input that guides the robot arm to a desired position) so that the guide tube  30  is in a desired position. In other examples, the robot arm is programmed to automatically move the guide tube  30  to the desired position. In some examples, the guide tube  30  is held by a non-robotic lockable articulated holding arm  20 . The guide tube  30  can be positioned and then the arm locked in place. Following operation  902 , the flow of the method can move to operation  910 . 
     Operation  910  includes inserting the cutting apparatus  100  into a guide tube  30 . This operation can include inserting the cutting apparatus  100  into the guide tube  30  until the housing lip  112  is in contact with a proximal end of the guide tube  30  such that further advancement of the cutting apparatus  100  is blocked (see, e.g.,  FIG.  6   ), though the cutting apparatus  100  need not be inserted that far. In some examples, the cutting apparatus  100  is inserted into the guide tube  30  in a locked configuration. After or during advancement, the cutting apparatus  100  is unlocked such that the scalpel  160  can rotate about the pivot point  166 . Unlocking the cutting apparatus  100  can include sliding the lock tab  122  from a first position in which a lock tab  122  is disposed within the catch  126  (see, e.g.,  FIG.  4   ) in the housing  110  to a second position in which the lock tab  122  is outside of the catch  126  (see, e.g.,  FIG.  5   ). In some instances, the cutting apparatus  100  is partially inserted while in the locked configuration, then the apparatus  100  is unlocked and the advancement continues. 
     In some examples, operation  910  includes or is related to an operation in which the cutting apparatus  100  is rotated relative to the guide tube. For instance, the cutting apparatus can be rotated in the guide tube  30  such that a ball  34  of the guide tube  30  moves from a first groove  114  of the housing  110  to a second groove  114  of the housing  110 . Following operation  910 , the flow of the method  900  can move to operation  920 . 
     Operation  920  includes forming an incision with the cutting apparatus  100 . The incision can be formed in any of a variety of ways. Generally, a user can form an incision via inserting the blade  10  into the patient&#39;s tissue and moving the handle  180 . For example, the operation  920  can include operation  922 , which includes laterally moving the handle  180  in a first direction to a first position such that a tip of the blade  10  reaches a first point by moving in an opposite direction. Following operation  922 , the flow of the method  900  can move to operation  924 , which includes laterally moving the handle in a second direction to a second position such that a tip of the blade  10  reaches a second point by moving in an opposite direction. The lateral movement of operations  922 , 924  can be caused by rotating the handle  180  about the pivot point  166 . 
     This movement may be resisted by bias forces provided by the one or more biasers  154 . The moving may include overcoming at least one bias force that urges the tip of the blade  10  toward a starting position. In an example, either or both of the first point and the second point is outside of an inner diameter of the guide tube. The moving can include pivoting the scalpel arm  162  of the cutting apparatus  100  within the housing  110  by moving the handle  180 . In some examples, the resulting incision has a skin-level length longer than an inner diameter of the guide tube  30 . In some examples, the movement is halted by the scalpel guide  172  or the user stops the movement before the scalpel guide  172  does. A first example is shown in  FIGS.  10 - 13    and a second example is shown in  FIGS.  14 - 17   . 
       FIG.  10    illustrates the cutting apparatus  100  being inserted through the guide tube  30  while the cutting apparatus  100  is in a locked position and the scalpel  160  is in an initial position substantially parallel with the length of the guide tube  30 . As illustrated, an outer diameter of the housing  110  is sufficiently close to the inner diameter of the guide tube  30  that the guide tube  30  guides the trajectory of the cutting apparatus  100  with sufficiently small margin of error for its use in the surgical procedure. Coupled to the scalpel  160  is a double sided blade  10  (e.g., a # 40  scalpel blade) to facilitate cutting in two directions. The cutting apparatus  100  continues to be inserted and the blade  10  pierces the patient&#39;s tissue as shown in  FIG.  11   . The cutting apparatus  100  is then unlocked and, as shown in  FIG.  12   , the user swings the handle  180  side to side, which causes the blade  10  to move side to side and form an incision. Following formation of the incision, the cutting apparatus  100  is removed. A subsequent instrument  1300  for the procedure (e.g., a dilator as shown in  FIG.  13   ) is then inserted through and guided by the guide tube  30 . The guide tube  30  may be in the same position or a different position between being used to guide the cutting apparatus  100  and being used to guide the subsequent instrument  1300 . 
       FIG.  14    illustrates the cutting apparatus  100  being inserted through the guide tube  30  while the cutting apparatus  100  is in an unlocked position and the scalpel  160  is swung to one side. The cutting apparatus  100  may have been initially inserted into the guide tube  30  while in a locked position and the scalpel  160  being in an initial position and then subsequently unlocked and moved to arrive at the configuration shown in  FIG.  14   . In other implementations, the scalpel being swung to one side is the starting position of the scalpel  160  (e.g., the one or more biasers  154  are configured to resist movement of the scalpel  160  out of this position) and the scalpel  160  may be locked in this position and need be unlocked to leave this position. Coupled to the scalpel  160  is a single sided blade  10 . While swung to one side, the cutting apparatus  100  continues to be advanced through the guide tube  30  and the blade  10  enters the tissue to begin to form the incision as shown in  FIG.  15   . The user then swings the handle toward the opposite side, which causes the blade  10  to form a longer incision and reach the position shown in  FIG.  16   . Following formation of the incision, the cutting apparatus  100  is removed. A subsequent instrument  1300  for the procedure (e.g., a dilator as shown in  FIG.  17   ) is then inserted through and guided by the guide tube  30 . 
     In another example, prior to the blade  10  piercing the patient&#39;s skin, the handle  180  can be moved such that the scalpel  160  pivots to place the blade  10  in a desired starting position. The cutting apparatus  100  is then advanced such that the blade enters the patient&#39;s skin and then the handle is swung in the other direction to form the incision. 
     Although certain embodiments and examples are provided in the foregoing description, the 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 herein. For example, in any method disclosed herein, the operations 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 systems, and/or devices described herein may be embodied as integrated components or as separate components. 
     Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” include plural references unless the context clearly dictates otherwise. Any reference to “or” herein is intended to encompass “and/or” unless otherwise stated.