Patent Publication Number: US-2023144537-A1

Title: Surgical Drilling System For Determining Bone Breakthrough

Description:
RELATED APPLICATIONS 
     The subject patent application claims priority to and all the benefits of U.S. Provisional Patent Application No. 63/008,060, filed on Apr. 10, 2020, which is hereby incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     Conventional medical and surgical procedures routinely involve the use of surgical tools and instruments which allow surgeons to approach and manipulate surgical sites. By way of non-limiting example, rotary instruments such as handheld drills are commonly utilized in connection with orthopedic procedures to address various musculoskeletal conditions, such as trauma, sports injuries, degenerative diseases, joint reconstruction, and the like. In procedures where handheld drills or similar surgical instruments are employed, rotational torque selectively generated by an actuator (e.g., an electric motor) is used to rotate a releasably-attachable drill bit or other surgical attachments at different speeds. The drill bit may commonly be used to create bore holes for many different purposes, such as to place screws to repair a bone fracture trauma with to hold a fixator in place. 
     While handheld surgical instruments and drill bits are routinely utilized to assist in the performance of a variety of different types of medical and/or surgical procedures, there is a need in the art to continuously improve such drill bits and handheld surgical instruments. 
     SUMMARY 
     The present disclosure relates generally to a surgical drilling system configured for bone drilling. The surgical drilling system is also configured to determine a characteristic of a drilling medium from a characteristic of fluid flow. The surgical drilling system includes a drill chuck configured to be rotated by a motor. The surgical drilling system also includes a surgical drill bit configured to be coupled to the drill chuck. The surgical drill bit includes a shank portion extending distally along a drill bit axis from a proximal end. The shank portion is configured to be coupled to and rotated by the drill chuck. The shank portion has a proximal surface defining a proximal opening. The surgical drill bit also includes a drilling portion for drilling through bone. The drilling portion extends distally along the drill bit axis from the shank portion to a distal end. The drilling portion has a distal cutting region. The distal cutting region includes a rake surface for cutting into a bone while drilling. The distal cutting region also includes a clearance surface for directing bone chips away from the bone during drilling. The distal cutting region also includes a flank surface disposed between the rake surface and the clearance surface. The flank surface defines a distal opening. The flank surface is configured to abut the bone such that the distal opening is occluded by the bone while the rake surface is cutting into the bone. The shank and drilling portions collectively define an inner channel in fluid communication with the proximal and distal openings. The distal opening is configured to be occluded by the bone during drilling to establish fluid pressure within the inner channel. The surgical drilling system also includes a pump configured to transfer fluid from a fluid source into the inner channel of the surgical drill bit through the proximal opening of the surgical drill bit. The surgical drilling system also includes a sensor disposed in fluid communication with the inner channel and configured to generate a signal responsive to a characteristic of the fluid being transferred to the inner channel of the surgical drill bit. The surgical drilling system also includes a controller configured to receive the signal from the sensor and determine a characteristic of the drilling medium at the distal opening of the surgical drill bit based on the signal. 
     Another exemplary configuration provides a surgical drilling system configured for bone drilling. The surgical drilling system is also configured to determine a characteristic of a drilling medium from a characteristic of fluid flow. The surgical drilling system includes a drill chuck configured to be rotated by a motor. The surgical drilling system also includes a surgical drill bit configured to be coupled to the drill chuck. The surgical drill bit includes a shank portion extending distally along a drill bit axis from a proximal end. The shank portion is configured to be coupled to and rotated by the drill chuck. The shank portion has a proximal surface defining a proximal opening. The surgical drill bit also includes a drilling portion for drilling through bone. The drilling portion extends distally along the drill bit axis from the shank portion to a distal end. The drilling portion has a distal cutting region. The distal cutting region includes a rake surface for cutting into a bone while drilling. The distal cutting region also includes a clearance surface for directing bone chips away from the bone during drilling. The distal cutting region also includes a flank surface disposed between the rake surface and the clearance surface. The flank surface defines a distal opening. The flank surface is configured to abut the bone such that the distal opening is occluded by the bone while the rake surface is cutting into the bone. The shank and drilling portions collectively define an inner channel in fluid communication with the proximal and distal openings. The distal opening is configured to be occluded by the bone during drilling to establish fluid pressure within the inner channel. The surgical drilling system also includes a pump configured to transfer fluid from a fluid source into the inner channel of the surgical drill bit through the proximal opening of the surgical drill bit. The surgical drilling system also includes a sensor disposed in fluid communication with the inner channel and configured to generate a signal responsive to a characteristic of the fluid being transferred to the inner channel of the surgical drill bit. The surgical drilling system also includes a controller configured to receive the signal from the sensor and determine a characteristic of the drilling medium at the distal opening of the surgical drill bit based on the signal. 
     Yet another exemplary configuration provides a surgical drilling system configured for bone drilling. The surgical drilling system is also configured to determine a characteristic of a drilling medium from a characteristic of fluid flow. The surgical drilling system includes a drill chuck configured to be rotated by a motor. The surgical drilling system also includes a surgical drill bit extending from a proximal end to a distal end along a drill bit axis. The surgical drill bit is configured to be coupled to the drill chuck and configured to rotate with the drill chuck. The surgical drill bit includes a shank portion adjacent the proximal end of the surgical drill bit. The shank portion is configured to be coupled to and rotated by the drill chuck. The shank portion has a proximal surface defining a proximal opening. The surgical drill bit also includes a drilling portion for drilling through bone. The drilling portion extends distally along the drill bit axis from the shank portion to the distal end of the surgical drill bit. The drilling portion includes a distal cutting region adjacent the distal end of the surgical drill bit for plunging into the bone. The drilling portion also includes a fluted region disposed between the shank portion and the distal cutting region. The fluted region includes a lateral surface defining a lateral opening. The shank and drilling portions collectively define an inner channel in fluid communication with the proximal and lateral openings. The lateral opening is configured to be occluded by the bone during drilling to establish fluid pressure within the inner channel. The surgical drilling system also includes a pump configured to transfer fluid from a fluid source into the inner channel of the surgical drill bit through the proximal opening of the surgical drill bit. The surgical drilling system also includes a sensor disposed in fluid communication with the inner channel and configured to generate a signal responsive to a characteristic of the fluid being transferred to the inner channel of the surgical drill bit. The surgical drilling system also includes a controller configured to receive the signal from the sensor and determine a characteristic of the drilling medium at the lateral opening of the surgical drill bit based on the signal. 
     Another exemplary configuration provides a surgical drilling system configured for bone drilling. The surgical drilling system is also configured to determine a characteristic of a drilling medium from a characteristic of fluid flow. The surgical drilling system includes a drill chuck configured to be rotated by a motor. The surgical drilling system also includes a surgical drill bit for drilling through bone. The surgical drill bit is configured to be coupled to the drill chuck and configured to rotate with the drill chuck. The surgical drill bit extends distally along a drill bit axis from a proximal end to a distal end. The surgical drill bit defines a first inner channel extending distally from the proximal end. The first inner channel has a first geometrical configuration. The first inner channel has a first outlet configured to be occluded during drilling to establish fluid pressure within the first inner channel. The surgical drill bit also includes a second inner channel extending distally from the proximal end. The second inner channel has a second geometrical configuration different from the first geometrical configuration. The second inner channel has a second outlet configured to be occluded during drilling to establish fluid pressure within the second inner channel. The surgical drilling system also includes a pump configured to transfer fluid from a fluid source into the first and second inner channels of the surgical drill bit. The system also includes a sensor disposed in fluid communication with the first and second inner channels. The sensor is configured to generate a first signal responsive to a first characteristic of the fluid being transferred to the first inner channel of the surgical drill bit corresponding to occlusion of the first outlet. The sensor is configured to generate a second signal different from the first signal responsive to a second characteristic of the fluid being transferred to the second inner channel of the surgical drill bit corresponding to occlusion of the second outlet. The surgical drilling system also includes a controller configured to receive the first and second signals from the sensor and determine a characteristic of the drilling medium at the first and second outlets based on the first and second signals. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a perspective view of a surgical drill assembly and a surgical drill bit of a surgical drilling system. 
         FIG.  2    is a schematic view of the surgical drilling system. 
         FIG.  3    is a perspective view of the surgical drill bit. 
         FIG.  4    is a perspective view of a drilling portion of the surgical drill bit. 
         FIG.  5    is an elevation view of a distal cutting region of the drilling portion of the surgical drill bit. 
         FIG.  6    is another perspective view of one configuration of the surgical drill bit with two inner channels extending from a proximal end of the surgical drill bit to a distal end of the surgical drill bit. 
         FIG.  7    is an elevation view of the drilling portion of the surgical drill bit illustrating a taper from the proximal end of the drilling portion to a distal end of the drilling portion. 
         FIG.  8    is a perspective view of another configuration of the surgical drill bit with an inner channel extending along a drill bit axis of the surgical drill bit from the proximal end of the surgical drill bit to a land of a fluted region of the drilling portion of the surgical drill bit. 
         FIG.  9    is a plan view of an exemplary configuration of the surgical drill bit before entering bone or other tissue. 
         FIG.  10    is a plan view of an exemplary configuration of the surgical drill bit with the surgical drill bit having bored through some bone and tissue. 
         FIG.  11    is a plan view of an exemplary configuration of the surgical drill bit with the distal cutting region of the surgical drill bit having bored through the bone and tissue. 
         FIG.  12    is a plan view of an exemplary configuration of the surgical drill bit with the fluted region of the surgical drill bit. 
     
    
    
     DETAILED DESCRIPTION 
       FIG.  1    depicts a perspective view of a surgical drill assembly  32  and a surgical drill bit  34  of a surgical drilling system  30 . The surgical drilling system  30  may be configured for bone drilling. The surgical drill assembly  32  may include a drill chuck  36  and a motor  38  disposed within a housing  40 . The drill chuck  36  is operatively coupled to the motor  38  such that the motor  38  is configured to rotate the drill chuck  36 . The drill chuck  36  is configured to secure the surgical drill bit  34  to the surgical drill assembly  32 . The motor  38  is configured to rotate the drill chuck  36  and the surgical drill bit  34  in unison. It is contemplated that a gear assembly or other form of transmission may be disposed between the motor  38  and the drill chuck  36  to transfer torque from the motor  38  to the drill chuck  36  to rotate the drill chuck  36 . In one configuration, the motor  38  comprises a DC motor. The surgical drill assembly  32  may comprise a battery (not shown) to supply power to the motor  38 . The surgical drill assembly  32  may also comprise a trigger assembly  42  coupled to the housing  40 . The trigger assembly  42  includes a trigger  44  movable relative to the housing  40 . The trigger assembly  42  may be operatively coupled to the motor  38  such that the motor  38  is configured to rotate the drill chuck  36  in response to actuation of the trigger  44 . 
     The surgical drill assembly  32  may also include a fluid coupler  46  configured to be attached to a shank portion  52  of the surgical drill bit  34  to facilitate the transfer of fluid from a fluid source to enter one or more inner channels  82  of the surgical drill bit  34 . The one or more inner channels  82  of the surgical drill bit  34  will be described in greater detail further below. The fluid coupler  46  is configured to prevent leakage of fluid outside the one or more inner channels while fluid is being supplied to the surgical drill bit  34 . The fluid coupler  46  is also configured to dynamically seal the surgical drill bit  34  while the surgical drill bit  34  is being rotated by the drill chuck  36 . 
     The housing  40  of the surgical drill assembly  32  shown in  FIG.  1    comprises a pistol-grip shaped configuration to be held by a user. It is contemplated that the housing  40  may comprise a configuration having another shape to be held by the user. It is also contemplated that the surgical drill assembly  32  may be configured as an end effector for a robotic arm. One such end effector that employs a drill chuck  36  and a fluid coupler  46  is disclosed in U.S. Patent Publication No. 2017/0119421 entitled “End Effector with Liquid Delivery” and filed on Jan. 12, 2017, which is hereby incorporated by reference in its entirety. 
     In  FIG.  1   , the motor  38 , the drill chuck  36 , and the fluid coupler  46  are shown schematically. The motor  38  may be cannulated such that the surgical drill bit  34 , the motor  38 , and the fluid coupler  46  are each arranged along the same axis. In other words, the surgical drill bit  34  may pass through a center of the motor  38  to be coupled to the fluid coupler  46 . In other configurations, the motor  38  may be offset from the axis AX of the surgical drill bit  34  and the fluid coupler. One such configuration is described and illustrated in U.S. Patent Publication No. 2017/0119421. 
     Referring to  FIG.  3   , the surgical drill bit  34  comprises a generally cylindrical body extending along a drill bit axis AX between proximal  48  and distal  50  ends. The surgical drill bit  34  has a shank portion  52  extending distally along the drill bit axis AX from the proximal end  48 . The shank portion  52  is configured to be coupled to and rotated by the drill chuck  36 . A proximal surface  54  of the shank portion  52  defines a proximal opening  56 . In the configuration illustrated in  FIG.  3   , the proximal surface  54  of the shank portion  52  defines two proximal openings  56 . It is contemplated that the proximal surface  54  of the shank portion  52  may define three or more proximal openings  56 . It is also contemplated that the proximal surface  54  of the shank portion  52  may define a single proximal opening  56 . In the configuration illustrated in  FIG.  3   , the proximal opening  56  is defined offset from the drill bit axis AX such that the drill bit axis AX does not pass through the proximal opening  56 . It is contemplated that in other configurations the proximal opening  56  may be defined along the drill bit axis AX such that the drill bit axis AX passes through the proximal opening  56 . 
     The shank portion  52  of the surgical drill bit  34  may comprise a recess  58  for facilitating coupling between the shank portion  52  of the surgical drill bit  34  and the drill chuck  36 . It is contemplated that the shank portion  52  may additionally or alternatively comprise other coupling features such as a tang, a reduced diameter, a hex-head, or another like coupling feature to facilitate coupling between the shank portion  52  of the surgical drill bit  34  and the drill chuck  36 . 
     Referring to  FIGS.  4  and  5    the surgical drill bit  34  includes a drilling portion  60 . The drilling portion is configured to drill through bone. The drilling portion  60  extends distally along the drill bit axis AX from the shank portion  52  to the distal end  50  of the surgical drill bit  34 . The drilling portion  60  comprises a distal cutting region  62  adjacent the distal end  50  of the surgical drill bit  34  and a fluted region  64  disposed between the shank portion  52  of the surgical drill bit  34  and the distal cutting region  62  of the drilling portion  60  of the surgical drill bit  34 . 
     The distal cutting region  62  comprises a rake surface  66  for cutting into bone while drilling. The rake surface  66  illustrated in  FIGS.  4  and  5    is generally planar and generally parallel to the drill bit axis AX. In other configurations, the rake surface  66  may not be parallel to the drill bit axis AX. In still other configurations, the rake surface  66  many not be planar. The distal cutting region  62  may also comprise a clearance surface  68  for directing bone chips away from the bone during drilling. 
     The distal cutting region  62  further comprises a flank surface  70  disposed between the rake surface  66  and the clearance surface  68 . The flank surface  70  may define a distal opening  72 . In the configuration illustrated in  FIGS.  4  and  5   , the flank surface  70  defines two distal openings  72 . It is contemplated that the flank surface  70  may define three or more distal openings  72 . It is also contemplated that the flank surface  70  may define a single distal opening  72 . In the configuration illustrated in  FIGS.  4  and  5   , the distal opening  72  is defined offset from the drill bit axis AX such that the drill bit axis AX does not pass through the distal opening  72 . It is contemplated that in other configurations the distal opening  72  may be defined along the drill bit axis AX such that the drill bit axis AX passes through the distal opening  72 . The flank surface  70  may be configured to abut the bone during drilling such that the distal opening  72  is occluded by the bone while the rake surface  66  is cutting into the bone. 
     As shown in  FIG.  5   , the flank surface  70  may be generally planar and generally perpendicular to the drill bit axis AX. In one configuration, the flank surface  70  may be disposed at an angle θ between zero degrees and fifteen degrees from a reference plane  74  that is perpendicular to the drill bit axis AX. In another configuration, the angle θ between the flank surface  70  and the reference plane  74  may be between zero degrees and ten degrees. 
     In other configurations, the flank surface  70  may be conical or frustoconical. In one such configuration, the angle θ between the flank surface  70  and the reference plane  74  may be between zero degrees and fifteen degrees. In another such configuration, the angle θ between the flank surface  70  and the reference plane  74  between zero degrees and ten degrees. It is contemplated that as the angle between the conical or frustoconical flank surface  70  and the reference plane  74  approaches zero degrees (i.e., the flank surface  70  is parallel to the reference plane  74 ), the conical or frustoconical flank surface  70  approximates a planar surface. 
     In the configuration illustrated in  FIGS.  4  and  5   , the distal cutting region  62  of the drilling portion  60  of the surgical drill bit  34  comprises two rake surfaces  66 , two flank surfaces  70 , and two clearance surfaces  68  arranged circumferentially about the drill bit axis AX. In such a configuration, the flank surfaces  70  and the clearance surfaces  68  are arranged consecutively such that each rake surface  66  and one of the clearance surfaces  68  collectively define a relief  76  where bone fragments or other tissue may accumulate as the rake surface  66  is cutting through bone. In other configurations, the distal cutting region  62  of the drilling portion  60  of the surgical drill bit  34  comprises three or more of each of the rake, flank, and clearance surfaces  66 ,  70 ,  68 . In still other configurations, the distal cutting region  62  of the drilling portion  60  of the surgical drill bit  34  comprises one of each of the rake, flank, and clearance surfaces  66 ,  70 ,  68 . 
     As shown in  FIGS.  3  and  4   , the fluted region  64  of the surgical drill bit  34  may extend proximally toward the shank portion  52  from the distal cutting region  62 . The fluted region  64  may comprise two lands  78  extending between the shank portion  52  and the distal cutting region  62 . The lands  78  may be helically disposed along the fluted region  64  of the drilling portion  60  of the surgical drill bit  34 . The lands  78  define two flutes  80  that likewise helically extend between the shank portion  52  and the distal cutting region  62 . In another configuration, the fluted region  64  may comprise three or more lands  78  extending between the shank portion  52  and the distal cutting region  62  to define three or more flutes  80 . In a further configuration, the fluted region  64  may comprise one land  78  extending between the shank portion  52  and the distal cutting region  62  to define a single flute  80 . In such a configuration, the land  78  may not be distinguishable from the shank portion  52  of the surgical drill bit  34  but for the flute  80 . It is contemplated that the lands  78  and the flutes  80  defined by the lands  78  may not be disposed helically. The lands  78  and the flutes  80  may instead extend linearly along the fluted region  64  of the drilling portion  60  of the surgical drill bit  34 . It is also contemplated that in some configurations, the drilling portion  60  of the surgical drill bit  34  does not include a fluted region  64 . The lands  78  may comprise cutting edges to cut through bone in a lateral direction. 
     Each of the flutes  80  may be in communication with one of the reliefs  76  defined by the clearance surface  68  and the rake surface  66  of the distal cutting region  62  of the drilling portion  60  of the surgical drill bit  34 . In this manner, the bone fragments or other tissue may accumulate in the relief  76  and the clearance surface  68  may direct the bone fragments or other tissue into the flutes  80  of the fluted region  64  to direct the bone fragments or other tissue from the distal cutting region  62  while cutting through bone. In many configurations, the number of flutes  80  are equal to the number of reliefs  76 . 
     As shown in  FIG.  6   , the shank and drilling portions  52 ,  60  of the surgical drill bit  34  collectively define an inner channel  82  in fluid communication with the proximal and distal openings  56 ,  72 . The fluid may be transferred from a fluid source through the fluid coupler  46  of the surgical drill assembly  32  and introduced through the proximal opening  56  of the shank portion  52  of the surgical drill bit  34 . The fluid may then travel through the inner channel  82  and out the distal opening  72 . The distal opening  72  functions as an outlet to permit fluid to exit the surgical drill bit  34  when the distal opening  72  is not occluded. When the distal opening  72  is occluded by bone or tissue, fluid pressure may be established within the inner channel  82  and along the fluid line from the fluid source. In the configuration shown in  FIG.  6   , two inner channels  82  are shown—one for each set of proximal and distal openings  56 ,  72 . It is contemplated that three or more inner channels  82  may be defined in the surgical drill bit  34  for three or more proximal and distal openings  56 ,  72 . It is also contemplated that a single inner channel  82  may be defined in the surgical drill bit  34  for one proximal and distal opening  56 ,  72 . It is further contemplated that the number of inner channels  82  and the number of distal and proximal openings  56 ,  72  may not be equal. For example, the surgical drill bit  34  may define a single proximal opening  56  and two distal openings  72 . An inner channel  82  may extend along the surgical drill bit  34  and eventually split into two paths to be in fluid communication with each distal opening  72 . 
     As shown in  FIG.  7   , the drilling portion  60  of the surgical drill bit  34  may taper toward the drill bit axis AX from the shank portion  52  of the surgical drill bit  34  to the distal end  50  of the surgical drill bit  34 . In other words, the diameter D 2  of the surgical drill bit  34  at the distal end  50  of the surgical drill bit  34  is smaller than the diameter of the surgical drill bit  34  at a proximal end of the drilling portion  60  of the surgical drill bit  34 . In such a configuration, the lands  78  of the fluted region  64  comprise the cutting edges to cut through bone while the surgical drill bit  34  is plunged into bone. 
     As schematically shown in  FIG.  2   , the surgical drilling system  30  may comprise a pump  84  configured to transfer fluid from the fluid source to the fluid coupler of the surgical drill assembly  32  and into the inner channel  82  of the surgical drill bit  34  through the proximal opening  56  of the surgical drill bit  34 . 
     As schematically shown in  FIG.  2   , the surgical drilling system  30  may comprise a sensor  86  disposed in fluid communication with the inner channel  82  of the surgical drill bit  34  and configured to generate a signal responsive to a characteristic of the fluid being transferred to the inner channel  82  of the surgical drill bit  34 . The characteristic of the fluid being transferred to the inner channel  82  of the surgical drill bit  34  may comprises one or more characteristics selected from a fluid velocity, a fluid volumetric flow rate, and a fluid pressure. It is contemplated that the sensor  86  may generate the signal responsive to another characteristics of the fluid being transferred to the inner channel  82  of the surgical drill bit  34 . 
     As schematically shown in  FIG.  2   , the surgical drilling system  30  may comprise a flow regulator  88  such as a control valve disposed in fluid communication with the inner channel  82  of the surgical drill bit  34  to control the flow of fluid from the pump  84  to the inner channel  82  of the surgical drill bit  34 . In other configurations, the pump  84  may be operated to regulate the flow of fluid to the inner channel  82  of the surgical drill bit  34 . It is contemplated that devices other than a control valve may be employed to regulate the flow of fluid being introduced into the inner channel  82  of the surgical drill bit  34 . 
     The surgical drilling system  30  may comprise a controller  90  configured to receive the signal from the sensor  86  and determine a characteristic of the drilling medium at the distal opening  72  of the surgical drill bit  34  based on the signal. The controller  90  may also be configured to generate signals to the pump  84  and the flow regulator  88  to operate the pump  84  and flow regulator  88  in response to signals received from the sensor  86 . The characteristic of the drilling medium at the distal opening  72  of the surgical drill bit  34  may be a presence of tissue or a type of tissue (e.g., cortical bone or cancellous bone). Each type of tissue may have a certain physical characteristic that distinguishes it from another type of tissue. One such physical characteristic is porosity. One type of tissue occluding the distal opening  72  of the surgical drill bit  34  may cause a change in fluid pressure or fluid flow due to its porosity that is different from another type of tissue occluding the distal opening  72  of the surgical drill bit  34 . 
     In one configuration, the controller  90  may receive a signal from the sensor  86  and determine from the signal that the surgical drill bit  34  has broken through a last layer of bone such that the distal cutting region  62  of the drilling portion  60  is no longer cutting bone. The sensor  86  may generate such a signal if there is certain drop in pressure or a certain increase in fluid flow resulting from the distal opening  72  no longer being occluded. In another configuration, the controller  90  may receive a signal from the sensor  86  and determine from the signal a position of the surgical drill bit  34  in the bone. More specifically, the controller  90  may be configured to receive the signal from the sensor  86  and determine that the surgical drill bit  34  has transitioned from a first bone structure to a second bone structure (e.g. cortical bone to cancellous bone). The sensor  86  may be configured to generate one signal responsive to the certain drop in pressure or increase in fluid flow indicating bone breakthrough and another signal responsive to the certain drop in pressure or increase in fluid flow indicating a transition of bone structure. 
     In order to obtain accurate signals of changes in characteristics of the fluid being transferred to the inner channel  82  of the surgical drill bit  34 , it is advantageous to mitigate the leakage of fluid while the surgical drill bit  34  is cutting through bone and the distal opening  72  is occluded. Certain features of the surgical drill bit  34  may be employed to mitigate fluid leakage while the surgical drill bit  34  is cutting through bone. For example, the flank surface  70  of the distal cutting region  62  of the surgical drill bit  34  defining the distal opening  72  ensures the distal opening  72  will be occluded while cutting through bone. It is advantageous for the distal opening  72  to be defined by the flank surface  70  rather than the rake surface  66  or the clearance surface  68 . If the distal opening  72  were defined by the rake surface  66 , bone fragments or tissue may be forced into the inner channel  82  through the distal opening  72 . If the distal opening  72  were defined by the clearance surface  68 , the distal opening  72  would not be occluded by bone during cutting and fluid may leak out and be directed into the flutes  80 . The flank surface  70  being generally planar is another feature that mitigates fluid leakage while the surgical drill bit  34  is cutting through bone. While the surgical drill bit  34  is drilling through bone, the generally planar surface ensures any gaps between the flank surface  70  and the bone are mitigated. The taper of the drilling portion  60  of the surgical drill bit  34  is another feature that mitigates fluid leakage while the surgical drill bit  34  is cutting through bone. The tapered surgical drill bit  34  ensures that the drilling portion  60 , including the fluted region  64 , is always contacting the bone while drilling. 
     After the controller  90  determines there is a breakthrough or a transition of bone structure, the controller  90  may generate one or more signals to the surgical drill assembly  32  to arrest the drill chuck  36  to stop the surgical drill bit  34  from rotating. In configurations where the surgical drilling system  30  includes a robotic arm and an end effector, the controller  90  may be configured to operate the robotic arm to cease movement of the robot arm in addition to arresting the drill chuck  36 . For instance, the robotic arm may have been configured to axially move or “feed” the surgical drill bit  34  along the drill bit axis AX while the surgical drill bit  34  was cutting through bone. When the controller  90  may be configured to stop the robotic arm from continuing to move the surgical drill bit  34  into the bone. 
     In one configuration shown in  FIG.  8   , the controller  90  may be able to determine a breakthrough in a lateral direction relative to the surgical drill bit  34  or a change in bone structure in a lateral direction relative to the surgical drill bit  34 . In such a configuration, an outer lateral surface  92  of one of the lands  78  of the fluted region  64  may define a lateral opening  94 . Fluid may be transferred from the fluid source through the fluid coupler  46  of the surgical drill assembly  32  and introduced through the proximal opening  56  of the shank portion  52  of the surgical drill bit  34 . The fluid may then travel through the inner channel  82  and out the lateral opening  94 . The lateral opening  94  functions as another outlet to permit fluid to exit the surgical drill bit  34  when the lateral opening  94  is not occluded. 
     The outer lateral surface of the lands  78  faces away from the flutes  80  of the fluted region  64 . One of the inner channels  82  may be in fluid communication with one of the proximal openings  56  and the lateral opening  94 . As the outer lateral surface  92  of the lands  78  faces away from the flute  80 , the lateral opening  94  may be occluded by bone while the surgical drill bit  34  is cutting through bone to establish fluid pressure within the inner channel  82 . In one configuration, the distal cutting region  62  of the surgical drill bit  34  is free of any distal openings  72  in fluid communication with any of the inner channels  82  such that the controller  90  determines a breakthrough or change in bone structure in the lateral direction only. 
     In some configurations, the surgical drill bit  34  includes both distal and lateral openings  72 ,  94  with separate inner channels  82  and proximal openings  56  for each of the distal and lateral openings  72 ,  94 . In such a configuration, the inner channel  82  in fluid communication with the distal opening  72  may have a first geometrical configuration and the inner channel  82  in fluid communication with the lateral opening  94  may have a second geometrical configuration different from the first geometrical configuration. The geometrical configurations may be the cross-sectional area of the inner channels. Each of the inner channels  82  may have a different cross-sectional area. The difference in geometrical configurations may result in distinct pressure drops/rises or flow rate gains/losses. The sensor  86  may be configured to generate a first signal responsive to occlusion of the distal opening  72  and a second signal different from the first signal responsive to occlusion of the lateral opening  94 . The controller  90  may be configured to receive the first and second signals from the sensor  86  and determine a breakthrough or change in bone structure responsive to the first and second signals. 
     In  FIGS.  9 - 11   , an exemplary configuration of the surgical drill bit  34  drilling through bone and the distal end  50  of the surgical drill bit  34  transitioning from one tissue type to another for a spinal drilling application. In  FIG.  9   , the surgical drill bit  34  is prepared to enter vertebral bone. The surgical drill bit  34  may be rotated by the drill chuck  36  and motor  38  and the surgical drill bit  34  may be plunged into the vertebral bone to begin cutting the vertebral bone. Shortly before or shortly after the surgical drill bit  34  begins cutting into bone, the pump  84  may draw fluid from the fluid source and force fluid into the inner channel  82  of the surgical drill bit  34 . 
     As the surgical drill bit  34  is cutting through bone, the distal opening  72  is occluded and leakage of the fluid out the distal opening  72  is mitigated. Fluid pressure may be established in the inner channel  82  while the distal opening  72  is occluded. While the surgical drill bit  34  is advanced through the bone and continues cutting the bone to the position shown in  FIG.  10   , the fluid pressure and/or flow rate may fluctuate within an operational range. The deviation of the fluid pressure and/or flow rate within the operational range may not be enough to cause the controller  90  to stop the surgical drill bit  34  from rotating. 
     After the surgical drill bit  34  has broken through an outer layer of a first tissue type, as shown in  FIG.  11   , the sensor  86  may generate a signal to the controller  90  responsive to the fluid pressure and/or flow rate fluctuating outside of the operational range and the controller  90  may determine the surgical drill bit  34  has transitioned to cutting a different type of tissue. The controller  90  may be configured to arrest the drill chuck  36  to stop the surgical drill bit  34  from continuing to cut through bone and/or other tissue. 
     In  FIG.  12   , another exemplary configuration of the surgical drill bit  34  for a spinal drilling application is shown. In this configuration, instead of the distal end  50  of the surgical drill bit  34  transitioning from one type of tissue to another, a lateral or partial breach is shown. In this configuration, the surgical drill bit  34  may have begun drilling in the same manner as described above and with reference to  FIGS.  9  and  10   . However, the trajectory of the surgical drill bit  34  may have been plunged at an incorrect angle or location such that the fluted region  64  may break through the outer layer of the bone before the distal end  50  of the surgical drill bit  34  completely breaks through the outer layer of the bone or transitions from one type of tissue to another. In such an instance when the fluted region  64  of the surgical drill bit  34  breaks through, the lateral opening  94  of the surgical drill bit  34  may cease being occluded and the sensor  86  may generate a signal to the controller  90  responsive to the fluid pressure and/or flow rate fluctuating outside of the operational range and the controller  90  may be configured to arrest the drill chuck  36  to stop the surgical drill bit  34  from continuing to cut through bone and/or other tissue. 
     The foregoing description is merely illustrative in nature and is in no way intended to limit the disclosure, its application, or uses. The broad teachings of the disclosure can be implemented in a variety of forms. Therefore, while this disclosure includes particular configurations, the true scope of the disclosure should not be so limited since other modifications will become apparent upon a study of the drawings, the specification, and the following claims. It should be understood that one or more steps within a method may be executed in different order (or concurrently) without altering the principles of the present disclosure. Further, although each of the configurations is described above as having certain features, any one or more of those features described with respect to any example of the disclosure can be implemented in and/or combined with features of any of the other examples, even if that combination is not explicitly described. In other words, the described examples are not mutually exclusive, and permutations of one or more examples with one another remain within the scope of this disclosure. 
     Spatial and functional relationships between elements (for example, between controllers, circuit elements, semiconductor layers, etc.) are described using various terms, including “connected,” “engaged,” “coupled,” “adjacent,” “next to,” “on top of,” “above,” “below,” and “disposed.” Unless explicitly described as being “direct,” when a relationship between first and second elements is described in the above disclosure, that relationship can be a direct relationship where no other intervening elements are present between the first and second elements, but can also be an indirect relationship where one or more intervening elements are present (either spatially or functionally) between the first and second elements. 
     As used herein, the phrase at least one of A, B, and C should be construed to mean a logical (A OR B OR C), using a non-exclusive logical OR, and should not be construed to mean “at least one of A, at least one of B, and at least one of C.” The term subset does not necessarily require a proper subset. In other words, a first subset of a first set may be coextensive with (equal to) the first set. 
     In this application, including the definitions below, the term “controller  90 ” may be replaced with the term “circuit.” The term “controller  90 ” may refer to, be part of, or include: an Application Specific Integrated Circuit (ASIC); a digital, analog, or mixed analog/digital discrete circuit; a digital, analog, or mixed analog/digital integrated circuit; a combinational logic circuit; a field programmable gate array (FPGA); a processor circuit (shared, dedicated, or group) that executes code; a memory circuit (shared, dedicated, or group) that stores code executed by the processor circuit; other suitable hardware components that provide the described functionality; or a combination of some or all of the above, such as in a system-on-chip. 
     The controller  90  may include one or more interface circuits. In some examples, the interface circuit(s) may implement wired or wireless interfaces that connect to a local area network (LAN) or a wireless personal area network (WPAN). Examples of a LAN are Institute of Electrical and Electronics Engineers (IEEE) Standard 802.11-2016 (also known as the WIFI wireless networking standard) and IEEE Standard 802.3-2015 (also known as the ETHERNET wired networking standard). Examples of a WPAN are the BLUETOOTH wireless networking standard from the Bluetooth Special Interest Group and IEEE Standard 802.15.4. 
     The controller  90  may communicate with other controllers using the interface circuit(s). Although the controller  90  may be depicted in the present disclosure as logically communicating directly with other controllers, in various implementations the controller  90  may actually communicate via a communications system. The communications system includes physical and/or virtual networking equipment such as hubs, switches, routers, and gateways. In some implementations, the communications system connects to or traverses a wide area network (WAN) such as the Internet. For example, the communications system may include multiple LANs connected to each other over the Internet or point-to-point leased lines using technologies including Multiprotocol Label Switching (MPLS) and virtual private networks (VPNs). 
     In various implementations, the functionality of the controller  90  may be distributed among multiple controllers that are connected via the communications system. For example, multiple controllers may implement the same functionality distributed by a load balancing system. In a further example, the functionality of the controller  90  may be split between a server (also known as remote, or cloud) controller and a client (or, user) controller. 
     Some or all hardware features of the controller  90  may be defined using a language for hardware description, such as IEEE Standard 1364-2005 (commonly called “Verilog”) and IEEE Standard 10182-2008 (commonly called “VHDL”). The hardware description language may be used to manufacture and/or program a hardware circuit. In some implementations, some or all features of a controller may be defined by a language, such as IEEE 1666-2005 (commonly called “SystemC”), that encompasses both code, as described below, and hardware description. 
     The term code, as used above, may include software, firmware, and/or microcode, and may refer to programs, routines, functions, classes, data structures, and/or objects. The term shared processor circuit encompasses a single processor circuit that executes some or all code from multiple controllers. The term group processor circuit encompasses a processor circuit that, in combination with additional processor circuits, executes some or all code from one or more controllers. References to multiple processor circuits encompass multiple processor circuits on discrete dies, multiple processor circuits on a single die, multiple cores of a single processor circuit, multiple threads of a single processor circuit, or a combination of the above. The term shared memory circuit encompasses a single memory circuit that stores some or all code from multiple controllers. The term group memory circuit encompasses a memory circuit that, in combination with additional memories, stores some or all code from one or more controllers. 
     The term memory circuit is a subset of the term computer-readable medium. The term computer-readable medium, as used herein, does not encompass transitory electrical or electromagnetic signals propagating through a medium (such as on a carrier wave); the term computer-readable medium may therefore be considered tangible and non-transitory. Non-limiting examples of a non-transitory computer-readable medium are nonvolatile memory circuits (such as a flash memory circuit, an erasable programmable read-only memory circuit, or a mask read-only memory circuit), volatile memory circuits (such as a static random access memory circuit or a dynamic random access memory circuit), magnetic storage media (such as an analog or digital magnetic tape or a hard disk drive), and optical storage media (such as a CD, a DVD, or a Blu-ray Disc). 
     The apparatuses and methods described in this application may be partially or fully implemented by a special purpose computer created by configuring a general purpose computer to execute one or more particular functions embodied in computer programs. The functional blocks and flowchart elements described above serve as software specifications, which can be translated into the computer programs by the routine work of a skilled technician or programmer. 
     The computer programs include processor-executable instructions that are stored on at least one non-transitory computer-readable medium. The computer programs may also include or rely on stored data. The computer programs may encompass a basic input/output system (BIOS) that interacts with hardware of the special purpose computer, device drivers that interact with particular devices of the special purpose computer, one or more operating systems, user applications, background services, background applications, etc. 
     The computer programs may include: (i) descriptive text to be parsed, such as HTML (hypertext markup language), XML (extensible markup language), or JSON (JavaScript Object Notation), (ii) assembly code, (iii) object code generated from source code by a compiler, (iv) source code for execution by an interpreter, (v) source code for compilation and execution by a just-in-time compiler, etc. As examples only, source code may be written using syntax from languages including C, C++, C#, Objective C, Swift, Haskell, Go, SQL, R, Lisp, Java®, Fortran, Perl, Pascal, Curl, OCaml, JavaScript®, HTML5 (Hypertext Markup Language 5th revision), Ada, ASP (Active Server Pages), PHP (PHP: Hypertext Preprocessor), Scala, Eiffel, Smalltalk, Erlang, Ruby, Flash®, Visual Basic®, Lua, MATLAB, SSENSORLINK, and Python®. 
     It will be further appreciated that the terms “include,” “includes,” and “including” have the same meaning as the terms “comprise,” “comprises,” and “comprising.” Moreover, it will be appreciated that terms such as “first,” “second,” “third,” and the like are used herein to differentiate certain structural features and components for the non-limiting, illustrative purposes of clarity and consistency. 
     The invention is intended to be defined in the independent claims, with specific features laid out in the dependent claims, wherein the subject matter of a claim dependent from one independent claim can also be implemented in connection with another independent claim. 
     The present disclosure also comprises the following clauses, with specific features laid out in dependent clauses, that may specifically be implemented as described in greater detail with reference to the configurations and drawings above. 
     CLAUSES 
     I. A surgical drill bit configured for bone drilling and configured to be coupled to a surgical drill assembly that is configured to determine a characteristic of a drilling medium from a characteristic of fluid flow, said surgical drill bit comprising:
         a shank portion extending distally along a drill bit axis from a proximal end, the shank portion configured to be coupled to and rotated by a drill chuck of the surgical drill assembly, and the shank portion having a proximal surface defining a proximal opening; and   a drilling portion for drilling through bone, the drilling portion extending distally along the drill bit axis from the shank portion to a distal end, the drilling portion having a distal cutting region comprising:
           a rake surface for cutting into a bone while drilling,   a clearance surface for directing bone chips away from the bone during drilling, and   a flank surface disposed between the rake surface and the clearance surface, the flank surface defining a distal opening, and the flank surface configured to abut the bone such that the distal opening is occluded by the bone while the rake surface is cutting into the bone;   
           wherein the shank and drilling portions collectively define an inner channel in fluid communication with the proximal and distal openings, and wherein the distal opening is configured to be occluded by the bone during drilling to establish fluid pressure within the inner channel.       

     II. The surgical drill bit of clause I, wherein the flank surface is generally planar. 
     III. The surgical drill bit of clause II, wherein the flank surface is generally perpendicular to the drill bit axis. 
     IV. The surgical drill bit of any one of clauses I to III, wherein the drilling portion further comprises a fluted region extending proximally toward the shank portion from the distal cutting region. 
     V. The surgical drill bit of any one of clauses I to IV, wherein the drilling portion tapers toward the drill bit axis from the shank portion to the distal end. 
     VI. The surgical drill bit of any one of clauses I to V, wherein the distal opening is offset from the drill bit axis. 
     VII. A surgical drilling system configured for bone drilling and configured to determine a characteristic of a drilling medium from a characteristic of fluid flow, said surgical drilling system comprising:
         a drill chuck configured to be rotated by a motor;   a surgical drill bit configured to be coupled to the drill chuck, the surgical drill bit comprising:
           a shank portion extending distally along a drill bit axis from a proximal end, the shank portion configured to be coupled to and rotated by the drill chuck, and the shank portion having a proximal surface defining a proximal opening, and   a drilling portion for drilling through bone, the drilling portion extending distally along the drill bit axis from the shank portion to a distal end, the drilling portion having a distal cutting region comprising:
               a rake surface for cutting into a bone while drilling,   a clearance surface for directing bone chips away from the bone during drilling, and   a flank surface disposed between the rake surface and the clearance surface, the flank surface defining a distal opening, and the flank surface configured to abut the bone such that the distal opening is occluded by the bone while the rake surface is cutting into the bone,   
               wherein the shank and drilling portions collectively define an inner channel in fluid communication with the proximal and distal openings, and wherein the distal opening is configured to be occluded by the bone during drilling to establish fluid pressure within the inner channel;   
           a pump configured to transfer fluid from a fluid source into the inner channel of the surgical drill bit through the proximal opening of the surgical drill bit;   a sensor disposed in fluid communication with the inner channel and configured to generate a signal responsive to a characteristic of the fluid being transferred to the inner channel of the surgical drill bit; and   a controller configured to receive the signal from the sensor and determine a characteristic of the drilling medium at the distal opening of the surgical drill bit based on the signal.       

     VIII. The surgical drilling system of clause VII, wherein the flank surface of the surgical drill bit is generally planar. 
     IX. The surgical drilling system of clause VIII, wherein the flank surface of the surgical drill bit is generally perpendicular to the drill bit axis. 
     X. The surgical drilling system of any one of clauses VII to IX, wherein the drilling portion of the surgical drill bit further comprises a fluted region extending proximally toward the shank portion from the distal cutting region. 
     XI. The surgical drilling system of any one of clauses VII to X, wherein the drilling portion of the surgical drill bit tapers toward the drill bit axis from the shank portion of the surgical drill bit to the distal end of the surgical drill bit. 
     XII. The surgical drilling system of any one of clauses VII to XI, wherein the distal opening of the surgical drill bit is offset from the drill bit axis. 
     XIII. The surgical drilling system of any one of clauses VII to XII, wherein the characteristic of the fluid being transferred to the inner channel of the surgical drill bit comprises one or more characteristics selected from a fluid velocity, a fluid volumetric flow rate, and a fluid pressure. 
     XIV. The surgical drilling system of any one of clauses VII to XIII, wherein the characteristic of the drilling medium at the distal opening of the surgical drill bit comprises one characteristic selected from a tissue presence and a tissue type. 
     XV. The surgical drilling system of any one of clauses VII to XIV, wherein the controller is configured to receive the signal from the sensor and determine a breakthrough event has occurred based on the signal from the sensor. 
     XVI. The surgical drilling system of clause XV, wherein the breakthrough event comprises one event selected from the surgical drill bit breaching through the bone and the surgical drill bit transitioning from a first bone structure to a second bone structure. 
     XVII. The surgical drilling system of any one of clauses XV to XVI, wherein the controller is configured to arrest the drill chuck to stop the surgical drill bit from rotating responsive to the controller determining a breakthrough event has occurred. 
     XVIII. The surgical drilling system of any one of clauses XV to XVII, further comprising a robot arm coupled to the drill chuck and configured to axially move the drill chuck and the surgical drill bit along the drill bit axis, wherein the controller is configured to arrest the robot arm from axially moving responsive to the controller determining a breakthrough event has occurred. 
     XIX. The surgical drilling system of any one of clauses VII to XVIII, wherein the controller is configured to determine a position of the surgical drill bit in the bone based on the signal from the sensor. 
     XX. A surgical drilling system configured for bone drilling and configured to determine a characteristic of a drilling medium from a characteristic of fluid flow, said surgical drilling system comprising:
         a drill chuck configured to be rotated by a motor;   a surgical drill bit extending from a proximal end to a distal end along a drill bit axis, and the surgical drill bit configured to be coupled to the drill chuck and configured to rotate with the drill chuck, and the surgical drill bit comprising:
           a shank portion adjacent the proximal end of the surgical drill bit, the shank portion configured to be coupled to and rotated by the drill chuck, and the shank portion having a proximal surface defining a proximal opening, and   a drilling portion for drilling through bone, the drilling portion extending distally along the drill bit axis from the shank portion to the distal end of the surgical drill bit, the drilling portion comprising:
               a distal cutting region adjacent the distal end of the surgical drill bit for plunging into the bone, and   a fluted region disposed between the shank portion and the distal cutting region, the fluted region comprising a lateral surface defining a lateral opening,   
               wherein the shank and drilling portions collectively define an inner channel in fluid communication with the proximal and lateral openings, and wherein the lateral opening is configured to be occluded by the bone during drilling to establish fluid pressure within the inner channel;   
           a pump configured to transfer fluid from a fluid source into the inner channel of the surgical drill bit through the proximal opening of the surgical drill bit;   a sensor disposed in fluid communication with the inner channel and configured to generate a signal responsive to a characteristic of the fluid being transferred to the inner channel of the surgical drill bit; and   a controller configured to receive the signal from the sensor and determine a characteristic of the drilling medium at the lateral opening of the surgical drill bit based on the signal.       

     XXI. The surgical drilling system of clause XX, wherein the drilling portion of the surgical drill bit tapers toward the drill bit axis from the shank portion of the surgical drill bit to the distal end of the surgical drill bit. 
     XXII. The surgical drilling system of any one of clauses XX to XXI, wherein the characteristic of the fluid being transferred to the inner channel of the surgical drill bit comprises one or more characteristics selected from a fluid velocity, a fluid volumetric flow rate, and a fluid pressure. 
     XXIII The surgical drilling system of any one of clauses XX to XXII, wherein the characteristic of the drilling medium at the lateral opening of the surgical drill bit comprises one characteristic selected from a tissue presence and a tissue type. 
     XXIV. The surgical drilling system of any one of clauses XX to XXIII, wherein the controller is configured to receive the signal from the sensor and determine a breakthrough event has occurred based on the signal from the sensor. 
     XXV. The surgical drilling system of clause XXIV, wherein the breakthrough event comprises one event selected from the surgical drill bit breaching through the bone and the surgical drill bit transitioning from a first bone structure to a second bone structure. 
     XXVI. The surgical drilling system of any one of clauses XXIV to XXV, wherein the controller is configured to arrest the drill chuck to stop the surgical drill bit from rotating responsive to the controller determining a breakthrough event has occurred. 
     XXVII. The surgical drilling system of any one of clauses XXIV to XXVI, further comprising a robot arm coupled to the drill chuck configured to axially move the drill chuck and the surgical drill bit along the drill bit axis, wherein the controller is configured to arrest the robot arm from axially moving responsive to the controller determining a breakthrough event has occurred. 
     XXVIII. The surgical drilling system of any one of clauses XX to XXVI, wherein the controller is configured to determine a position of the surgical drill bit in the bone based on the signal from the sensor. 
     XXIX. The surgical drilling system of any one of clauses XX to XXVIII, wherein the fluted region comprises two lands extending between the shank portion and the distal cutting region, and wherein the two lands define a flute between the two lands. 
     XXX. The surgical drilling system of clause XXIX, wherein one of the two lands comprises the lateral surface that defines the lateral opening, and wherein the lateral surface faces away from the flute. 
     XXXI. The surgical drilling system of any one of clauses XX to XXX, wherein the distal cutting region of the surgical drill bit is free of an opening in fluid communication with the inner channel. 
     XXXII. A surgical drilling system configured for bone drilling and configured to determine a characteristic of a drilling medium from a characteristic of fluid flow, said surgical drilling system comprising:
         a drill chuck configured to be rotated by a motor;   a surgical drill bit for drilling through bone, the surgical drill bit configured to be coupled to the drill chuck and configured to rotate with the drill chuck, and the surgical drill bit extending distally along a drill bit axis from a proximal end to a distal end, and the surgical drill bit defining:
           a first inner channel extending distally from the proximal end, the first inner channel having a first geometrical configuration, and the first inner channel having a first outlet configured to be occluded during drilling to establish fluid pressure within the first inner channel, and   a second inner channel extending distally from the proximal end, the second inner channel having a second geometrical configuration different from the first geometrical configuration, and the second inner channel having a second outlet configured to be occluded during drilling to establish fluid pressure within the second inner channel;   
           a pump configured to transfer fluid from a fluid source into the first and second inner channels of the surgical drill bit;   a sensor disposed in fluid communication with the first and second inner channels and configured to generate a first signal responsive to a first characteristic of the fluid being transferred to the first inner channel of the surgical drill bit corresponding to occlusion of the first outlet, and the sensor configured to generate a second signal different from the first signal responsive to a second characteristic of the fluid being transferred to the second inner channel of the surgical drill bit corresponding to occlusion of the second outlet; and   a controller configured to receive the first and second signals from the sensor and determine a characteristic of the drilling medium at the first and second outlets based on the first and second signals.       

     XXXIII The surgical drilling system of clause XXXII, wherein the first geometrical configuration comprises a first cross-sectional area and the second geometrical configuration comprises a second cross-sectional area different from the first cross-sectional area. 
     XXXIV. The surgical drilling system of any one of clauses XXXII to XXXIII, wherein the surgical drill bit comprises a shank portion adjacent the proximal end of the surgical drill bit, the shank portion configured to be coupled to the drill chuck and configured to rotate with the drill chuck, and wherein the surgical drill bit comprises a drilling portion for drilling through bone, the drilling portion extending distally along the drill bit axis from the shank portion to the distal end of the surgical drill bit, and wherein the drilling portion comprises a distal cutting region adjacent the distal end of the surgical drill bit and a fluted region disposed between the shank portion and the distal cutting region, and wherein the first outlet is defined in the distal cutting region and the second outlet is defined in the fluted region. 
     XXXV. The surgical drilling system of clause XXXIV, wherein the drilling portion of the surgical drill bit tapers toward the drill bit axis from the shank portion of the surgical drill bit to the distal end of the surgical drill bit. 
     XXXVI. The surgical drilling system of any one of clauses XXXII to XXXV, wherein the first and second characteristics of the fluid being transferred to the first and second inner channels of the surgical drill bit comprise one or more characteristics selected from a fluid velocity, a fluid volumetric flow rate, and a fluid pressure. 
     XXXVII. The surgical drilling system of any one of clauses XXXII to XXXVI, wherein the characteristic of the drilling medium at the first and second outlets of the surgical drill bit comprise one characteristic selected from a tissue presence and a tissue type. 
     XXXVIII. The surgical drilling system of any one of clauses XXXII to XXXVII, wherein the controller is configured to receive the first and second signals from the sensor and determine a breakthrough event has occurred based on the first and second signals from the sensor. 
     XXXIX. The surgical drilling system of clause XXXVIII, wherein the breakthrough event comprises one event selected from the surgical drill bit breaching through the bone and the surgical drill bit transitioning from a first bone structure to a second bone structure. 
     XL. The surgical drilling system of any one of clauses XXXVIII to XXXIX, wherein the controller is configured to arrest the drill chuck to stop the surgical drill bit from rotating responsive to the controller determining a breakthrough event has occurred. 
     XLI. The surgical drilling system of any one of clauses XXXVIII to XL, further comprising a robot arm coupled to the drill chuck configured to axially move the drill chuck and the surgical drill bit along the drill bit axis, wherein the controller is configured to arrest the robot arm from axially moving responsive to the controller determining a breakthrough event has occurred. 
     XLII. The surgical drilling system of any one of clauses XXXII to XLI, wherein the controller is configured to determine a position of the surgical drill bit in the bone based on one or both the first and second signals from the sensor.