Surgical stapling load-ahead test and connection verification

Abstract

The technology relates to a surgical instrument. The surgical instrument may include a shaft assembly comprising a firing rod; a motor coupled to the firing rod and configured to drive the firing rod distally and retract the firing rod proximally; a tool assembly including an end effector; a processor; and memory storing instructions that, when executed by the processor, causes the surgical instrument to perform operations. The operations may include detecting a coupling of the tool assembly to the shaft assembly; based on detecting the coupling of the tool assembly to the shaft assembly, activating the motor to retract the firing rod proximally; monitoring a motor characteristic of the motor during retraction of the firing rod; and based on the monitored motor characteristic crossing a motor-characteristic threshold within a threshold distance, indicating a proper connection of the tool assembly to the shaft assembly.

Description

A0012954W001SURGICAL STAPLING LOAD-AHEAD TEST AND CONNECTION VERIFICATIONCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application No. 63 / 738,622 filed December 24, 2024, entitled “Surgical Stapling Load-Ahead Test and Connection Verification,” which is incorporated herein by reference in its entirety.BACKGROUND

[0002] Surgical devices for treating tissue can be utilized in a variety of treatment procedures, including for closure of tissue or organs (e.g., transection, resection, or anastomoses procedures), for occlusion of organs (e.g., thoracic or abdominal procedures), or for electrosurgically fusing or sealing tissue (e.g., vessel sealing procedures), among others.

[0003] In certain procedures, such as laparoscopic or endoscopic surgical procedures, access to a surgical site is achieved through a small incision or a narrow cannula inserted through a small entrance wound in a patient. In such a case, surgical instruments can include an elongated shaft coupled to an end effector or tool assembly suitable for use in tissue treatment within a limited space. Different portions of these instruments may be disposable and / or replaceable while other portions may be used multiple times. For instance, surgical stapling instruments may include replaceable cartridges and / or reloads while the handle or controller housing is used multiple times. Accordingly, the replaceable cartridges and / or reloads are manually connected to the remainder of the handle or controller housing for use.BRIEF SUMMARY

[0004] This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description section. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended as an aid in determining the scope of the claimed subject matter.

[0005] The technology disclosed herein relates to an automated test that verifies a proper connection of a reload to a shaft assembly of a stapling instrument. The stapling instrument may 126537393.3 JA0012954W001first detect that a reload has been connected to the controller housing of the stapling instrument. Based on the reload being detected, the stapling instrument performs an automated connection test, also referred to as a load-ahead test, to determine whether the reload is properly connected. The connection test causes an electric motor to activate in a direction that retracts the firing rod (e.g., pulls the firing rod proximally). One or more characteristics of the motor (e.g., current drawn by the motor, speed of the motor) are then monitored during retraction of the firing rod to determine whether the reload is properly connected.

[0006] The details of one or more aspects are set forth in the accompanying drawings and description below. Other features and advantages will be apparent from a reading of the following detailed description and a review of the associated drawings. It is to be understood that the following detailed description is explanatory only and is not restrictive of the invention as claimed.BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Various aspects of the disclosure are described herein with reference to the drawings, in which:

[0008] FIG. 1 is a perspective view of an example surgical instrument.

[0009] FIG. 2 is a cross-sectional view of an example surgical instrument.

[0010] FIG. 3 is an enlarged cross-sectional view of a portion of the surgical instrument in FIG.2.

[0011] FIG. 4 depicts a perspective view of a firing rod and knife bar of an example surgical instrument.

[0012] FIG. 5A is a plot of motor current versus distance for a load-ahead test.

[0013] FIG. 5B is a plot of motor speed versus distance for a load-ahead test.

[0014] FIG. 6 depicts an example method for performing a load-ahead test.

[0015] FIG. 7 depicts another example method for performing a load-ahead test.

[0016] FIG. 8 depicts another example method for performing a load-ahead test.

[0017] FIG. 9 depicts another example method for performing a load-ahead test.

[0018] FIG. 10 depicts another example method for performing a load-ahead test.126537393.3 2A0012954W001DETAILED DESCRIPTION

[0019] As briefly described above, some surgical instruments have replaceable or swappable components that are manually attached to the handle and / or controller housing of the surgical instrument. In the example of surgical stapling instruments (e.g., surgical staplers), tool assemblies (also referred to as “reloads”) may be replaced or swapped as they are used. The reloads include a shaft portion as well as an end effector (e.g., stapling cartridge and anvil assembly). The shaft lengths and / or types of end effectors may thus be changed while still using a single handle and / or controller housing. For instance, the clinician may switch reload length, shaft diameter, and / or specialty end effectors, such as buttressed end effectors, curved-tip end effectors, and radial end effectors, among other types. Multiple different reloads may be used during a single procedure. Thus, having the ability to quickly switch from one reload to another becomes beneficial. However, ensuring that the reloads are properly connected prior to use still remains a top priority to help ensure safe procedures.

[0020] For the reload to connect to the remainder of the surgical instrument, tight geometric tolerances are generally held. These tight tolerances, however, potentially allow for the reloads to be misused or misconnected. Currently, a manual clamp test may be performed to help ensure that the reload was properly connected. In the manual clamp test, the end effector must be clamped and released. The user must then visually verify that the knife and / or drive beam of the reload moved proximally and distally. This process often is time consuming (at least in the perspective of active surgery), creates delays in the procedures, and requires visual inspection from a human.

[0021] If the reload is not properly connected, the stapling instrument may be in a state where the stapling instrument is able to drive the knife and / or drive beam forward (e.g., distally), but the instrument cannot retract the knife and / or drive beam (e.g., pull proximally). This improper connection results in the anvil and cartridge being clamped together and effectively locked onto the tissue. This type of improper connection of the reload is referred to as a “load-ahead connection.”

[0022] The technology of this disclosure, among other things, addresses the issues discussed above. For example, the disclosed technology provides for an automated test that verifies a proper connection of the reload with minimal travel distance or time. The stapling instrument may first detect that a reload has been connected to the controller housing of the stapling instrument. Based126537393.3 3A0012954W001on the reload being detected, the stapling instrument performs an automated connection test, also referred to as a load-ahead test herein, to determine whether the reload is properly connected. The connection test causes an electric motor to activate in a direction that retracts the firing rod (e.g., pulls the firing rod proximally). One or more characteristics of the motor (e.g., current drawn by the motor, speed of the motor) are then monitored during retraction of the firing rod to determine whether the reload is properly connected.

[0023] If the firing rod is properly connected to the knife bar of the reload, the firing rod will resist the pulling force from the motor because the knife bar is not configured to move proximally (other than by a negligible amount). The resistance to the retraction force causes a detectable change in the motor characteristics, such as the current drawn by the motor to increase and / or the speed of the motor to decrease. If, however, the firing rod of the reload is not properly connected to the knife bar, the firing rod can be retracted further with little to no resistance. In such cases, the current draw of the motor remains low and / or steady for a longer distance and / or the speed of the motor remains high. As a result, if the motor current increases above a current threshold during the connection test and / or the speed decreases below a speed threshold, the reload is properly connected. If the motor current does not increase above the current threshold and / or the speed does not decrease below the speed threshold (within a threshold distance), then the reload is not properly connected and an error or warning may be issued to the user to reconnect the reload. Other traits (e.g., rate of change) of the motor characteristics may also or alternatively be analyzed to determine whether the reload is properly connected.

[0024] Referring now to FIG. 1 , an example surgical instrument 100 is depicted. In the illustrated example, the surgical instrument 100 is in the form of a handheld surgical stapling instrument or device configured to perform tissue closure procedures, such as anastomoses or transection procedures in some examples. It will be understood that aspects of the disclosure are not so limited and can have general applicability in other surgical instruments, including electrosurgical instruments, ultrasonic surgical instruments, robotic surgical instruments, or network-controllable surgical instruments, in some examples.

[0025] In the example depicted, the surgical instrument 100 includes a handle assembly 110, a shaft assembly 120 extending from the handle assembly 110, and a tool assembly 130 coupled to the shaft assembly 120 as shown. The tool assembly 130 may also be referred to as a reload. The 126537393.3 4A0012954W001handle assembly 110 may also or alternatively be referred to as a controller housing, such as in examples where the surgical instrument is part of a surgical robotics implementation.

[0026] The handle assembly 110 includes a handle portion 112 and a barrel portion 113. The handle portion 112 is illustrated with an activation switch or button 114 for operating the tool assembly 130. The handle portion 112 may also include a movable handle, trigger, or the like.

[0027] The shaft assembly 120 includes an elongated body 122 (e.g., a shaft) extending from a proximal end to a distal end and defines a longitudinal axis. The proximal end of the elongated body 122 may be coupled to the barrel portion 113. The tool assembly 130 is then coupled to the distal end of the elongated body 122. In the non-limiting example shown, the tool assembly 130 includes an end effector 150 and a shaft 132 extending from the end effector 150. The end effector 150 carries a staple cartridge assembly 154 and an anvil assembly 152 for closing or clamping of tissue disposed between the jaw members of the end effector 150. The end effector 150 also includes a knife 156 configured to dissect the tissue after (or during) the stapling of the tissue. The shaft 132 of the tool assembly 130 includes a connection segment 134 on the proximal end of the shaft 132. The connection segment is received in the distal end of the elongated body 122 of the shaft assembly 120.

[0028] In examples, the tool assembly 130 is configured as a single-use or disposable loading unit (DLU). In such a case, the tool assembly 130 is releasably secured to the shaft assembly 120 for disposal upon completion of a surgical procedure (or a portion thereof). Additionally or alternatively, the tool assembly 130 may include one or more electrodes for providing electrosurgical energy, one or more cutting elements for tissue dissection, or the like.

[0029] The example surgical instrument 100 includes a drive assembly for driving operation of the end effector 150 of the tool assembly 130. The drive assembly includes a firing rod 124 extending through the shaft assembly 120 as shown. When the tool assembly 130 is connected to the shaft assembly 120, the distal end of the firing rod 124 is received in the connection segment 134 of the tool assembly 130.

[0030] The drive assembly of the surgical instrument 100 also includes at least one electric motor 119. The electric motor 119 may be a direct-current (DC) motor that is bi-directional. The electric motor 119 is coupled to the firing rod 124 such that activating the electric motor 119 in a first direction causes the firing rod 124 to move distally (e.g., forward), and activating the electric motor126537393.3 5A0012954W001119 in the opposite direction causes the firing rod 124 to move proximally (e.g., backward). Stated another way, movement of the motor 119 in the first direction pushes or drives the firing rod 124 distally, and movement of the motor 119 in a second direction retracts the firing rod 124 proximally. The electric motor 119 may be coupled to the firing rod 124 via one or more gears and / or linkages to translate the rotational motion of the electric motor 119 to the translational movement of the firing rod 124.

[0031] The surgical instrument 100 also includes a controller 116. The controller 116 includes at least one processor 117 and memory 118. The processor 117 may be in the form of a microcontroller, microprocessor, a digital signal processor, an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or the like. The memory 118 may include volatile storage (e.g., random access memory), non-volatile storage (e.g., read-only memory), flash memory, or any combination of such memories. In some examples, the memory 118 may be integrated into a common chip with the processor 117. The memory 118 stores instructions that, when executed by the processor 117, cause the surgical instrument 100 to perform the operations discussed herein. For instance, the memory 118 may store one or more programs that include instructions for performing the operations set forth in FIGs. 6-8. The controller 116 may also include one or more sensors for measuring or detecting various signals, such as the current drawn by the motor 119 and / or motor speed of the motor 119 (e.g., revolutions per minute (RPM)). In some examples, the sensor(s) are integrated into the processor 117 and / or a chip package including the processor 117.

[0032] The surgical instrument 100 may be configured for longitudinal, rotational, and / or articulating motion of the tool assembly 130. In such examples, an articulation mechanism 115 is provided for pivoting or articulating motion of the tool assembly 130 with respect to the longitudinal axis.

[0033] FIG. 2 is a cross-sectional view of a portion of the example surgical instrument 100 with the tool assembly 130 connected to the shaft assembly 120. FIG. 3 is an enlarged cross-sectional view of the portion A indicated in FIG. 2. FIGS. 2-3 are discussed concurrently.

[0034] As can be seen in FIGs. 2-3, the shaft 132 of the tool assembly 130 houses a knife bar 136 (also referred to as a drive bar). The knife bar 136 is coupled, on the distal end, to the knife 156. The proximal end of the knife bar 136 includes a retention segment 133. Distal movement of 126537393.3 6A0012954W001the knife bar 136 advances the knife 156 through the end effector 150 to cut or dissect the tissue. Proximal movement of the knife bar 136 retracts the knife 156 from its distal position after being advanced.

[0035] In some examples, the knife 156 is integrated into a beam (e.g., an I-beam) that also causes the opening and closing of the jaws of the end effector 150. An example of such an integrated knife and I-beam configuration can also be seen in Figure 7 of U.S. Patent Publication No. 2024 / 0341758, assigned to Covidien LP and titled “Handheld Electromechanical Surgical System.” In such examples, as the beam is advanced, the jaws are drawn together to clamp the tissue. The beam advances a sled in front of the beam that pushes staples through the tissue. The trailing I-beam with the knife 156 then cuts the tissue as or after the staples have been formed in the tissue. Thus, in such examples, when the knife 156 is advanced, the tissue is clamped in the jaws. If the knife 156 cannot be retracted, the jaws will remain clamped or locked onto the tissue.

[0036] When the tool assembly 130 is properly coupled to the shaft assembly 120, the firing rod 124 is received into the retention segment 133 of the knife bar 136. The coupling of the tool assembly 130 to the shaft assembly 120 may require the user to insert the connection segment 134 of the tool assembly 130 into the elongated body 122 and then twist the tool assembly 130 to secure the tool assembly 130 to the shaft assembly 120.

[0037] When properly secured, the distal end of the firing rod 124 is positioned within a retention segment 133 of the knife bar 136. When the distal end of the firing rod 124 is positioned within the retention segment 133, flanges 126 of the firing rod 124 are positioned such that proximal movement (e.g., retraction) of the firing rod 124 causes a proximal surface of the flanges 126 to contact a distal surface of protruding fingers 135A-B of the retention segment 133. The protruding fingers 135A-B are diametrically opposed structures extending inwardly toward one another and are separated by a gap. The firing rod 124 extends through the gap and into the retention segment 133.

[0038] FIG. 4 depicts a perspective view of the firing rod 124 and knife bar 136 of the example surgical instrument 100. As can be understood more clearly from FIG. 4, when the tool assembly 130 is connected to the shaft assembly 120, the knife bar 136 may, upon initial connection, be aligned with a narrowed portion 128 of the firing rod 124. Then, as the tool assembly 130 is twisted (e.g., rotated) to secure the tool assembly 130 to the shaft assembly 120, the knife bar 136 rotates 126537393.3 7A0012954W001to a position where the flanges 126 are aligned with the fingers 135A-B of the retention segment 133. As can also be seen in FIG. 4, the knife bar 136 may be formed of multiple laminates or formed sheets of material, such as a metal.

[0039] The narrowed portion 128 of the firing rod 124 may extend from the distal end toward the proximal end by a distance of about 2 mm - 25 mm. The narrowed portion 128 extends through the distal end such that the flanges 126 are formed on opposing sides of the firing rod 124. The flanges 126 protrude outwardly from the narrowed portion 128 such that the flanges 126 can engage the fingers 135A-B when the tool assembly 130 is properly connected to the shaft assembly 120.

[0040] As should be appreciated, several improper connections between the firing rod 124 and the knife bar 136 may be possible. As one improper connection state, the fingers 135A-B may be misaligned with the flanges 126 of the firing rod 124 such that retraction of the firing rod 124 does not cause retraction of the knife bar 136. As another improper connection state, the firing rod 124 may be positioned proximally (e.g., rearwardly) of the knife bar 136 (e.g., positioned proximally of the fingers 135A-B). In this improper connection state, retraction of the firing rod 124 does not cause retraction of the knife bar 136. In both of these improper connection states, however, distal motion of the firing rod 124 will still cause distal motion of the knife bar 136 (e.g., the knife bar 136 can be driven forward). Thus, stapling and cutting of the tissue could occur, but retraction of the knife bar 136 would not be possible, which causes the jaws of the end effector 150 to lock onto the tissue. The connection tests discussed herein are able to detect such improper connection states and prevent firing of the surgical instrument 100 when such improper connection states are detected.

[0041] FIG. 5A is a plot 500 of motor current versus distance for a load-ahead test (e.g., connection test). During the connection test, the firing rod 124 is retracted after a connection of the tool assembly 130 to the shaft assembly 120. If the connection is proper and the firing rod 124 is positioned correctly within the retention segment 133 of the knife bar 136, retraction of the firing rod 124 pulls on the knife bar 136 (e.g., the flanges 126 contact the fingers 135A-B). The knife bar 136 resists the pulling force and the system effectively stretches. This resistance causes the current drawn by the motor 119 to increase. Unlike reaching a full hard stop, however, the current increases gradually (e.g., at less than an instantaneous rate).126537393.3 8A0012954W001

[0042] The plot 500 depicts multiple current signals 502 for multiple different attempted connections of the tool assembly 130 to the shaft assembly 120. The current signals 502 correspond to the current drawn by the motor 119 as the motor 119 is operated in the direction that causes retraction of the firing rod 124. The current is plotted against distance represented in millimeters on the X-axis. The distance is measured in the proximal direction. For instance, the 2 mm distance corresponds to retracting the firing rod 124 by 2 mm (e.g., 2 mm in the proximal direction).

[0043] Two groupings of signals 502 are identified. A pass group 504 are the groupings of signals 502 that result in passing the connection test. A fail group 506 are the groupings of signals 502 that result in failing the connection test. As can be seen from the plot 500, the signals 502 in the pass group 504 all include an increase in current over a short distance, such as less than 2 mm. The signals 502 in the fail group 506, however, do not include such an increase in current. Rather, the increases in current for the signals 502 in the fail group occur at much larger distances and are a sharp increase corresponding to a hard stop encountered by the firing rod 124 as it is being retracted.

[0044] As an example from the pass group 504, an example pass signal 502A is now discussed. For a short distance, the signal 502A remains near a baseline motor-current level 512, which corresponds to the firing rod 124 (and thus the motor 119) encountering minimal resistance. Shortly thereafter, the signal 502A starts to increase steadily from about 0.2 mm to about 1.8 mm. This steady increase in current is the result of the proximal movement of the firing rod 124 pulling on the knife bar 136 and the system stretching in response to the pulling force. During that travel distance, the signal 502A crosses a motor-current threshold 510. The crossing of the motor-current threshold 510, within a threshold distance 514, causes the connection test corresponding to signal 502A to pass.

[0045] As an example from the fail group 506, an example fail signal 502B is now discussed. The fail signal 502B remains at the baseline motor-current level 512 for a much longer distance. This occurs because the firing rod 124 does not engage with the knife bar 136 as the firing rod 124 is being retracted (due to an improper connection). Thus, the firing rod 124 and the motor 119 experience little resistance when retracting the firing rod 124. The fail signal 502B does not increase until a hard stop is reached around 11.5 mm of retraction.126537393.3 9A0012954W001

[0046] The motor-current threshold 510 may be a preset and / or stored value (e.g., static value) and / or may be adjusted dynamically during the connection test. For instance, the motor-current threshold 510 may be between 0.3-0.8 Amps or about 0.5 Amps. The motor-current threshold 510 may also be based on the baseline motor-current level 512. For instance, the motor-current threshold 510 may be based on a multiple of the baseline motor-current level 512. As an example, the motor-current threshold 510 may be between 1.5-4.0 times the baseline motor-current level 512, between 1.5-3.5 times the baseline motor-current level 512, or between 2-4 times the baseline motor-current level 512, among other values.

[0047] The baseline motor-current level 512 may also be a preset and / or stored value (e.g., static value) and / or may be determined or adjusted dynamically during the connection test. For example, as the motor 119 begins operating, the current drawn by the motor 119 may be measured and a baseline motor-current level 512 may be determined from those initial measurements (e g., as an average over multiple measurements). In some examples, the baseline motor-current level 512 may be around 0.2 Amps, but this value may differ based on different motor types.

[0048] The threshold distance 514 may be set and stored based on the configuration of the particular surgical instrument. For instance, based on various tolerances of the shaft assembly 120 and the tool assembly 130 (e.g., between the flanges 126 and the fingers 134A-B), the threshold distance 514 may be set. In some examples, the threshold distance 514 is between 0.1-3.0 mm, 0.5-2.5 mm, 1.0-2.0 mm, 1.5-2.5 mm, or about 2 mm. In some examples, the window for connecting the reload properly is around 0.25 mm. As such, an increase in resistance and current draw should be identified beginning around that distance at the most. In such examples, the threshold distance 514 may be smaller, such as between 0.25-0.5 mm or 0.3-0.8 mm.

[0049] The above examples verify connection of the tool assembly 130 to the shaft assembly 120 based on the motor-current signal 502 crossing the motor-current threshold 510 within the threshold distance 514. Additionally or alternatively, the connection may be verified based on other characteristics of the motor-current signal, such as the rate of change (e.g., slope) of the motor-current signal. As can be seen from the plot 500, the signals 502 in the pass group 504 have a gradual increase over a distance range. The average slopes of the signals 502 between 0.5 mm and 1.0 mm are generally around 0.5 Amps / mm. Thus, analysis of the rate-of-change (e.g., slope) of the motor-current signal 502 may also (or alternatively) indicate a proper (or improper) 126537393.3 10A0012954W001connection. For instance, if the signal 502 has a rate of change within a rate-of-change envelope over a test distance, then the connection test may be passed. The rate-of-change envelope may be defined as 0.2-1.0 Amps / mm in some examples. For example, the lower limit of the rate-of-change envelope may be between 0.1-0.4 Amps / mm and the upper limit of the rate-of-change envelope may be between 0.6-1.5 Amps / mm. In other examples, the rate-of-change envelope may be defined as a function of the baseline motor-current level 512. For instance, the lower limit of the rate-of-change envelope may be between 0.5-2 times the baseline motor-current level 512 per millimeter. The upper limit may be between 3-5 times the baseline motor-current level 512 per millimeter. The test distance may be between 0.2-1.5 mm, 0.4-1.0 mm, or 0.5-0.8 mm. The rate-of-change may be an average rate of change over the analyzed test distance.

[0050] FIG. 5B is a plot 550 of motor speed versus distance for a load-ahead test (e.g., connection test). As discussed herein, during the connection test, the firing rod 124 is retracted after a connection of the tool assembly 130 to the shaft assembly 120. If the connection is proper and the firing rod 124 is positioned correctly within the retention segment 133 of the knife bar 136, retraction of the firing rod 124 pulls on the knife bar 136 (e.g., the flanges 126 contact the fingers 135A-B). The knife bar 136 resists the pulling force and the system effectively stretches. This resistance causes the speed of the motor 119 to decrease. Unlike reaching a full hard stop, however, the motor speed decreases gradually (e.g., at less than an instantaneous rate).

[0051] The plot 550 depicts two motor-speed signals for different attempted connections of the shaft assembly 120 to the shaft assembly 120. The two motor-speed signals include a passing motor-speed signal 552 and a failing motor-speed signal 554. The passing motor-speed signal 552 is for a proper connection of the tool assembly 130 where the connection test is passed. The failing motor-speed signal 554 is for an improper connection of the tool assembly 130 where the connection test is failed. The motor-speed signals correspond to the speed of the motor 119 as the motor 119 is operated in the direction that causes retraction of the firing rod 124. The motor speed is represented in revolutions per minute (RPM) on the Y-axis. The motor speed is plotted against distance, represented in micrometers, on the X-axis. The distance is measured in the proximal direction. For instance, the 2000 pm distance corresponds to retracting the firing rod 124 by 2000 pm (e.g., 2 mm in the proximal direction).126537393.3 11A0012954W001

[0052] As can be seen from the plot 550, the passing motor-speed signal 552 includes a reducing motor speed as the firing rod 124 is retracted and within a fairly short distance. The steady decrease in the motor speed is the result of the proximal movement of the firing rod 124 pulling on the knife bar 136 and the system stretching in response to the pulling force. During the proximal travel distance, the passing motor-speed signal 552 drops below a motor-speed threshold 560. The crossing of the motor-speed threshold 560, within the threshold distance 514, causes the connection test corresponding to passing motor-speed signal 552 to pass.

[0053] For the failing motor-speed signal 554, however, the motor speed does not drop until a much further distance and the reduction in motor speed is much steeper (e.g., the rate of change is high). At the beginning of the failing motor-speed signal 554, during the initial retraction, the motor speed remains at or near a baseline motor speed 562. This is due to the firing rod 124 not engaging the knife and thus not experiencing the additional resistance as the firing rod 124 is retracted. The sharp decrease at the end of the failing motor-speed signal 554 is due to the firing rod 124 reaching a hard stop at a further proximal distance. Because the failing motor-speed signal 554 does not cross the motor-speed threshold 560 within the threshold distance 514, the connection test corresponding to the failing motor-speed signal 554 fails.

[0054] The motor-speed threshold 560 may be a preset and / or stored value (e.g., static value) and / or may be adjusted dynamically during the connection test. For instance, the motor-speed threshold 560 may be between 2000-8000 RPM or about 5000 RPM. The motor-speed threshold 560 may also be based on the baseline motor speed 562. For instance, the motor-speed threshold 560 may be based on a percentage of the baseline motor speed 562. As an example, the motorspeed threshold 560 may be between 10%-70% of the baseline motor speed 562, between 10%-50%, 20%-30%, or 40%-60% of the baseline motor speed 562, among other values.

[0055] The above examples verify the connection of the tool assembly 130 to the shaft assembly 120 based on the motor speed crossing the motor-speed threshold 560 within the threshold distance 514. Additionally or alternatively, the connection may be verified based on other characteristics of the motor-speed threshold 560, such as the rate of change (e.g., slope) of the motor-speed signal. As can be seen from the plot 500, the passing motor-speed signal 552 has a gradual decrease over a distance range. The average slope of the passing motor-speed signal 552 between 0.5 mm and 1.0 mm is generally around 7000 RPM / mm. Thus, analysis of the rate-of-change (e.g., slope) of126537393.3 12A0012954W001the motor-speed signal may also (or alternatively) indicate a proper (or improper) connection. For instance, if the motor-speed signal has a rate of change within a rate-of-change envelope over a test distance, then the connection test may be passed. The rate-of-change envelope may be defined as 5000-9000 RPM / mm in some examples. For example, the lower limit of the rate-of-change envelope may be between 4000-6500 RPM / mm and the upper limit of the rate-of-change envelope may be between 7500-9000 RPM / mm. In other examples, the rate-of-change envelope may be defined as a function of the baseline motor speed 562. For instance, the lower limit of the rate-of-change envelope may be between 30%-70% of the baseline motor speed 562 per millimeter over a test distance. The test distance may be between 0.2-1.5 mm, 0.4-1.0 mm, or 0.5-0.8 mm. The rate-of-change may be an average rate of change over the analyzed test distance.

[0056] FIG. 6 depicts an example method 600 for performing a load-ahead test (e.g., connection test). The method 600 is performed by the surgical instrument 100. For instance, the memory 118 may store instructions for method 600 that are performed by processor 117.

[0057] At operation 602, a coupling of the tool assembly 130 (e.g., reload) to the shaft assembly 120 is detected. The coupling of the tool assembly 130 may be accomplished by detecting a particular electronic component, such as a chip or tag, with in the tool assembly 130. In some examples, the tool assembly 130 may include one or more magnets that are detected when the tool assembly 130 is coupled to the shaft assembly 120. In some examples, detecting the coupling is provided by a mechanical component in the shaft assembly 120 being pushed proximally when the tool assembly 130 is attached. The movement of the mechanical component may be detected (e.g., a switch activated) to indicate the coupling of the tool assembly 130 to the shaft assembly 120.

[0058] Based on detecting that the tool assembly 130 has been coupled to the shaft assembly 120, a connection test is automatically performed. For instance, at operation 604, the motor 119 is activated to retract the firing rod 124 in the proximal direction. At operation 606, the current drawn by the motor 119 is monitored during the retraction of the firing rod 124. Monitoring of the motor-current may be performed with the use of a current sensor that is included in the surgical instrument 100, such as within the controller 116.

[0059] At operation 608, based on the motor current (monitored in operation 606) exceeding a motor-current threshold 510 within a threshold distance 514, an indication of the proper connection of the tool assembly is generated. The motor-current threshold 510 and the threshold distance 514 126537393.3 13A0012954W001may be any of the example motor-current thresholds 510 and / or threshold distances 14 discussed above. The indication may be an audio, visual, and / or haptic output that can be perceived by the clinician using the surgical instrument 100. In other examples, the indication is not explicitly surfaced to the user of the surgical instrument 100. For instance, additionally or alternatively to a surfaced indicator, the connection indication is (or causes) an enablement of functionality of the surgical instrument 100, such as the ability to fire the surgical instrument 100. For instance, the indication of passing the connection test may cause the surgical instrument 100 to enter a firing mode. Without receiving the indication that the connection test has been passed, the surgical instrument 100 may remain in an unenabled mode, which prevents the firing of the surgical instrument 100. In examples, the indication is a stored data value (e.g., a true or 1 indicator) that indicates that the connection test has been passed. In some examples, the indication indicates that the firing rod 124 is not properly loaded in the knife bar 136 and / or load-ahead connection has occurred.

[0060] FIG. 7 depicts another example method 700 for performing a load-ahead test (e.g., connection test). The method 700 is performed by the surgical instrument 100. For instance, the memory 118 may store instructions for method 700 that are performed by processor 117.

[0061] At operation 702, the connection test is initiated in response to detecting the coupling of the tool assembly 130 and / or another input, such as a user selection of an input (e.g., the button 114). At operation 704, the motor 119 is activated to retract the firing rod 124 in the proximal direction. At operation 706, the current drawn by the motor 119 is monitored during retraction of the firing rod 124. Monitoring of the motor-current may be performed with the use of a current sensor that is included in the surgical instrument 100, such as within the controller 116.

[0062] At operation 708, the monitored motor current is compared to a motor-current threshold 510 to determine if the monitored motor current is greater than the motor-current threshold 510. The motor-current threshold 510 may be any of the motor-current thresholds 510 discussed herein.

[0063] If the monitored motor current is greater than the baseline motor-current level 512, the method 700 flows to operation 710. At operation 710, an indication of a proper connection of the tool assembly 130 is generated. The indication of the proper connection may be the same types(s) of indication(s) discussed above in operation 608 of method 600.126537393.3 14A0012954W001

[0064] If, at operation 708, the monitored motor current is not greater than the baseline motorcurrent level 512, the method 700 flows to operation 712. At operation 712, the proximal distance travelled by the firing rod 124 is compared to a threshold distance 514 to determine if the travelled distance is greater than the threshold distance 514. The threshold distance 514 may be any of the threshold distances 514 discussed herein.

[0065] If the travelled distance is not greater than the threshold distance 514, the method 700 returns to operation 708 where operations 708-712 are repeated for subsequent times as the motor 119 continues to retract the firing rod 124 until the motor current exceeds the motor-current threshold 510 or the travelled distance exceeds the threshold distance 514. For instance, operations 708 and 712 may be performed at a first time. If the current is less than the motor-current threshold and the travelled distance is less than the threshold distance, then operations 708 and 712 are performed at a second time after the firing rod has travelled further in the proximal direction.

[0066] If the travelled distance is greater than the threshold distance 514 at operation 712, the method flows to operation 714. At operation 714, an indication of an improper connection of the tool assembly 130 is generated. In some examples, the improper-connection indicator is an audio, visual, and / or haptic output that can be perceived by the clinician using the surgical instrument 100. The improper-connection indicator may provide an indication that the tool assembly 130 is not properly connected. Additionally, the improper-connection indicator may include a data indicator that is stored in the memory 118 of the surgical instrument 100 that indicates the connection test was failed. In examples where the connection test is failed and operation 714 is performed, the surgical instrument 100 may prevent firing the surgical instrument 100 until the tool assembly 130 is reconnected or a different tool assembly 130 is connected and the connection test is passed.

[0067] FIG. 8 depicts another example method 800 for performing a load-ahead test (e.g., connection test). The method 800 is performed by the surgical instrument 100. For instance, the memory 118 may store instructions for method 800 that are performed by processor 117.

[0068] At operation 802, the connection test is initiated in response to detecting the coupling of the tool assembly 130 and / or another input, such as a user selection of an input (e.g., the button 114). At operation 804, the motor 119 is activated to retract the firing rod 124 in the proximal direction. At operation 806, the current drawn by the motor 119 is monitored during retraction of126537393.3 15A0012954W001the firing rod 124 over a test distance. Monitoring of the motor-current may be performed with the use of a current sensorthat is included in the surgical instrument 100, such as within the controller 116. The test distance may be any of the test distances discussed herein.

[0069] At operation 808, the rate of change of the monitored motor current over the test distance is calculated. The calculated rate of change may be determined as an average rate of change over the test distance.

[0070] A determination is then made as to whether the rate of change calculated at operation 808 is within a rate-of-change envelope (e.g., range). This determination may be made by performing operations 810 and 814, which compare the calculated rate of change of the motor current to the lower limit and upper limit of the rate-of-change envelope. The lower limit and the upper limit of the rate-of-change envelope may be any of such limits discussed herein.

[0071] More specifically, at operation 810, the rate of change of the motor current calculated in operation 808 is compared to the lower limit of the rate-of-change envelope to determine if the calculated rate of change is greater than the lower limit of the rate-of-change envelope. If the calculated rate of change is not greater than the lower limit, the method 800 flows to operation 812, where an improper connection of the tool assembly 130 is indicated. Indicating the improper connection in operation 812 may be the same or similar as operation 714 in method 700.

[0072] If the calculated rate of change is greater than the lower limit of the rate-of-change envelope at operation 810, the method 800 flows to operation 814. At operation 814, the rate of change calculated in operation 808 is compared to the upper limit of the rate-of-change envelope to determine if the calculated rate of change is less than the upper limit of the rate-of-change envelope. If the calculated rate of change is not less than the upper limit of the rate-of-change envelope, the method 800 flows to operation 812, where the improper connection is indicated.

[0073] If the calculated rate of change is less than the upper limit of the rate-of-change envelope, the method 800 instead flows to operation 816 where a proper connection of the tool assembly 130 is indicated. Indicating the proper connection at operation 816 may be the same or similar as operation 710 of method 700 or operation 608 of method 600.

[0074] The method 800 may be combined with the method 600 and / or the method 700 to effectively provide for two evaluation criteria for a proper connection. For instance, a proper connection may be found when one of the motor-current threshold is exceeded or when the rate of126537393.3 16A0012954W001change of the motor current is within the rate-of-change envelope. In other examples, a proper connection may be identified only when both the motor-current threshold is exceeded and when the rate of change of the motor current is within the rate-of-change envelope.

[0075] FIG. 9 depicts an example method 900 for performing a load-ahead test (e.g., connection test). The method 900 is performed by the surgical instrument 100. For instance, the memory 118 may store instructions for method 900 that are performed by processor 117. Method 900 is similar to method 600 of FIG. 6, but in method 900 the motor speed characteristics, and respective thresholds, are utilized instead of the current drawn by the motor.

[0076] At operation 902, a coupling of the tool assembly 130 (e.g., reload) to the shaft assembly 120 is detected. The coupling of the tool assembly 130 may be accomplished by detecting a particular electronic component, such as a chip or tag, with in the tool assembly 130. In some examples, the tool assembly 130 may include one or more magnets that are detected when the tool assembly 130 is coupled to the shaft assembly 120. In some examples, detecting the coupling is provided by a mechanical component in the shaft assembly 120 being pushed proximally when the tool assembly 130 is attached. The movement of the mechanical component may be detected (e.g., a switch activated) to indicate the coupling of the tool assembly 130 to the shaft assembly 120.

[0077] Based on detecting that the tool assembly 130 has been coupled to the shaft assembly 120, a connection test is automatically performed. For instance, at operation 904, the motor 119 is activated to retract the firing rod 124 in the proximal direction. At operation 906, the speed of the motor 119 is monitored during retraction of the firing rod 124. Monitoring of the motor speed may be performed with the use of a speed sensor that is included in the surgical instrument 100, such as within the controller 116 or as part of the motor 119 itself.

[0078] At operation 908, based on the motor speed (monitored in operation 906) crossing a motor-speed threshold 560 within a threshold distance 514, an indication of the proper connection of the tool assembly is generated. The motor-speed threshold 560 and the threshold distance 514 may be any of the example motor-speed thresholds 560 and / or threshold distances 514 discussed above. The indications and responses to passing the connection test may be any of the above tests.

[0079] The method 700 of FIG. 7 and method 800 of FIG. 8 may also be performed using the motor speed (and respective motor-speed thresholds) rather than the motor current. These motorspeed methods may be performed alternatively to or in addition to the motor-current126537393.3 17A0012954W001characteristics. For instance, the proper connection may be determined with one or both of the motor current or the motor speed. Accordingly, the methods 600, 700, and / or 800 may generally be performed using motor characteristics and the respective thresholds during the retraction period of the connection tests.

[0080] FIG. 10 depicts another example method 1000 for performing a load-ahead test (e.g., connection test). The method 1000 is performed by the surgical instrument 100. For instance, the memory 118 may store instructions for method 1000 that are performed by processor 117.

[0081] At operation 1002, the connection test is initiated in response to detecting the coupling of the tool assembly 130 and / or another input, such as a user selection of an input (e.g., the button 114). At operation 1004, the motor 119 is activated to retract the firing rod 124 in the proximal direction. At operation 1006, one or more motor characteristics of the motor 119 are monitored during retraction of the firing rod 124. The motor characteristics may include motor current and / or motor speed, among other characteristics. Monitoring of the motor character! stic(s) may be performed with the use of one or more sensors that are included in the surgical instrument 100, such as within the controller 116.

[0082] At operation 1008, the monitored one or more motor characteristics are compared to the respective motor-characteristic threshold(s) to determine if one or more of the threshold(s) have been crossed. For instance, the motor current may be compared to the motor-current threshold to determine if the motor current exceeds the motor-current threshold. As another example, the motor speed may be compared to the motor-speed threshold to determine if the motor speed is below the motor-speed threshold. In some examples, at least two motor characteristics are monitored and compared to their respective thresholds.

[0083] If the one or more monitored characteristics have crossed the respective thresholds, the method 1000 flows to operation 1010. In some examples, multiple or all of the monitored motor characteristics (e.g., both motor speed and motor current) must have crossed their respective thresholds for the method to flow to operation 1010. At operation 1010, an indication of a proper connection of the tool assembly 130 is generated. The indication of the proper connection may be the same types(s) of indication(s) discussed above in operation 608 of method 600.

[0084] If, at operation 1008, the one or more monitored motor characteristics have not crossed the respective threshold(s), the method 1000 flows to operation 1012. At operation 1012, the126537393.3 18A0012954W001proximal distance travelled by the firing rod 124 is compared to a threshold distance to determine if the travelled distance is greater than the threshold distance. The threshold distance may be any of the threshold distances discussed herein.

[0085] If the travelled distance is not greater than the threshold distance, the method 1000 returns to operation 1008 where operations 1008-1012 are repeated for subsequent times as the motor 119 continues to retract the firing rod 124 until the motor characteristic(s) cross the respective threshold(s) or the travelled distance exceeds the threshold distance. For instance, operations 1008 and 1012 may be performed at a first time. If the motor characteristics have not crossed the threshold(s) and the travelled distance is less than the threshold distance, then operations 1008 and 1012 are performed at a second time after the firing rod has travelled further in the proximal direction.

[0086] If the travelled distance is greater than the threshold distance at operation 1012, the method flows to operation 1014. At operation 1014, an indication of an improper connection of the tool assembly 130 is generated. In some examples, the improper-connection indicator is an audio, visual, and / or haptic output that can be perceived by the clinician using the surgical instrument 100. The improper-connection indicator may provide an indication that the tool assembly 130 is not properly connected. Additionally, the improper-connection indicator may include a data indicator that is stored in the memory 118 of the surgical instrument 100 that indicates the connection test was failed. In examples where the connection test is failed and operation 1014 is performed, the surgical instrument 100 may prevent firing the surgical instrument 100 until the tool assembly 130 is reconnected or a different tool assembly 130 is connected and the connection test is passed.

[0087] Those skilled in the art will recognize that the methods and systems of the present disclosure may be implemented in many manners and as such are not to be limited by the foregoing aspects and examples. In other words, functional elements being performed by a single or multiple components, in various combinations of hardware and software or firmware, and individual functions, can be distributed among software applications at either the client or server level or both. In this regard, any number of the features of the different aspects described herein may be combined into single or multiple aspects, and alternate aspects having fewer than or more than all of the features herein described are possible.126537393.3 19A0012954W001

[0088] Functionality may also be, in whole or in part, distributed among multiple components, in manners now known or to become known. Thus, a myriad of software / hardware / fi rmware combinations are possible in achieving the functions, features, interfaces and preferences described herein. In addition, the operations of the methods described herein may be performed in different orders than depicted and / or one or more operations may be performed concurrently.

[0089] Although the disclosure provides specific examples, various modifications and changes can be made without departing from the scope of the disclosure as set forth in the claims below. Accordingly, the specification and figures are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of the present disclosure. Any benefits, advantages, or solutions to problems that are described herein with regard to a specific example are not intended to be construed as a critical, required, or essential feature or element of any or all the claims.

[0090] As should be appreciated from the foregoing, in an aspect, the technology relates to a surgical instrument. The surgical instrument includes a shaft assembly comprising a firing rod; a motor coupled to the firing rod and configured to drive the firing rod distally and retract the firing rod proximally; a tool assembly including an end effector; a processor; and memory storing instructions that, when executed by the processor, cause the surgical instrument to perform operations. The operations include detecting a coupling of the tool assembly to the shaft assembly; based on detecting the coupling of the tool assembly to the shaft assembly, activating the motor to retract the firing rod proximally; monitoring a motor characteristic of the motor during retraction of the firing rod; and based on the monitored motor characteristic crossing a motor-characteristic threshold within a threshold distance, indicating a proper connection of the tool assembly to the shaft assembly.

[0091] In an example, the motor characteristic is at least one of a motor current or a motor speed. In another example, the motor-current threshold is between 1.5-3.5 times a baseline motor current level. In yet another example, the threshold distance is between 0.3-0.8 mm. In still another example, the tool assembly further comprises a knife bar with a retention segment; and a distal end of the firing rod is positioned within the retention segment. In a further example, the retention segment includes protruding fingers that are diametrically opposed structures extending inwardly toward one another and separated by a gap; and the firing rod includes flanges at the distal end, 126537393.3 20A0012954W001wherein the flanges are positioned distally from the protruding fingers of the retention segment. In still yet another example, the operations further include calculating a rate of change of the motor characteristic; and determining that the calculated rate of change is within a rate-of-change envelope, wherein indicating the proper connection is further based on the calculated rate of change being within the rate-of-change envelope.

[0092] In another example, indicating the proper connection of the tool assembly includes generating at least one of an audio, visual, or haptic indicator on the surgical instrument. In yet another example, indicating the proper connection of the tool assembly includes enabling firing of the surgical instrument. In still another example, the surgical instrument is a surgical stapling instrument.

[0093] In another aspect, the technology relates to a surgical instrument that includes a shaft assembly comprising a firing rod; a motor; a tool assembly including an end effector; a processor; and memory storing instructions that, when executed by the processor, cause the surgical instrument to perform operations. The operations include initiating a connection test to verify a proper connection of the tool assembly to the shaft assembly; based on initiating the connection test, activating the motor to retract the firing rod proximally; monitoring a motor characteristic of the motor during retraction of the firing rod; determining that the monitored motor characteristic has not crossed a motor-characteristic threshold; determining that the firing rod has travelled a proximal distance greater than a threshold distance; and based on the monitored motor characteristic not crossing the motor-characteristic threshold and the travelled distance being greater than the threshold distance, indicating an improper connection of the tool assembly to the shaft assembly.

[0094] In an example, the motor characteristic is one of motor speed or motor current. In another example, the threshold distance is between 1.0-2.0 mm. In still another example, the tool assembly further comprises a knife bar with a retention segment; and a distal end of the firing rod is positioned proximally of the retention segment. In a further example, the retention segment includes protruding fingers that are diametrically opposed structures extending inwardly toward one another and separated by a gap; and the firing rod includes flanges at the distal end, wherein the flanges are positioned proximally from the protruding fingers of the retention segment. In yet126537393.3 21A0012954W001another example, indicating the improper connection of the tool assembly includes generating at least one of an audio, visual, or haptic indicator on the surgical instrument.

[0095] In another aspect, the technology is related to a method, implemented by a surgical stapling instrument, for verifying a proper connection of a tool assembly to a shaft assembly of the surgical stapling instrument. The method includes initiating a connection test to verify a proper connection of the tool assembly to the shaft assembly; based on initiating the connection test, activating a motor of the surgical stapling instrument to retract a firing rod of the shaft assembly proximally; monitoring current drawn by the motor during retraction of the firing rod; determining, at a first time, that the monitored current does not exceed a motor-current threshold; determining, at the first time, that the firing rod has travelled a proximal distance less than a threshold distance; determining, at a second time after the firing rod has traveled further in the proximal direction, that the monitored current does exceed the motor-current threshold; determining at the second time, that the firing rod has travelled a proximal distance less than the threshold distance; and based on the motor current exceeding the motor-current threshold and the travelled distance being less than the threshold distance, enabling firing of the surgical stapling instrument.

[0096] In an example, the motor-current threshold is between 1.5-3.5 times a baseline motorcurrent level. In another example, the threshold distance is between 0.5-2.5 mm. In still another example, the method further includes indicating a proper connection of the tool assembly to the shaft assembly by generating at least one of an audio, visual, or haptic indicator on the surgical instrument.

[0097] As used herein, the terms “a” or “an,” as used herein, are defined as one or more than one. Also, the use of introductory phrases such as “at least one” and “one or more” in the claims should not be construed to imply that the introduction of another claim element by the indefinite articles “a” or “an” limits any particular claim containing such introduced claim element to containing only one such element, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an.” The same holds true for the use of definite articles. In addition, “a set” of elements as used herein can refer to any number of elements, including only one element.

[0098] Further, as used herein, the phrase “at least one of element A, element B, or element C” is intended to convey any of element A, element B, element C, elements A and B, elements A and 126537393.3 22A0012954W001C, elements B and C, and elements A, B, and C. In addition, one having skill in the art will understand the degree to which terms such as “about” or “substantially” convey in light of the measurement techniques utilized herein. To the extent such terms may not be clearly defined or understood by one having skill in the art, the term “about” shall mean plus or minus ten percent.

[0099] Unless stated otherwise, terms such as "first" and "second" are used to arbitrarily distinguish between the components such terms describe, and are not intended to indicate relative, temporal, or other prioritization of such components.

[0100] All directional references as may be used herein, e.g., proximal, distal, upper, lower, upward, downward, left, right, lateral, front, back, top, bottom, above, below, vertical, horizontal, clockwise, counterclockwise, etc., are only used for identification purposes to aid the reader's understanding of the present disclosure and do not create limitations, particularly as to the position, orientation, or use of the disclosure. Connection references as may be used herein (e g., attached, coupled, connected, or joined) are to be construed broadly and can include intermediate members between a collection of elements unless otherwise indicated. As such, connection references do not necessarily infer that two elements are directly connected or in fixed relation to one another. Additionally, the drawings of the present disclosure are for purposes of illustration only, and the dimensions, positions, order, or relative sizes of components reflected in the drawings can vary.126537393.3 23

Claims

A0012954W001CLAIMSWhat is claimed is:

1. A surgical instrument, comprising:a shaft assembly comprising a firing rod;a motor coupled to the firing rod and configured to drive the firing rod distally and retract the firing rod proximally;a tool assembly including an end effector;a processor; andmemory storing instructions that, when executed by the processor, cause the surgical instrument to perform operations comprising:detecting a coupling of the tool assembly to the shaft assembly;based on detecting the coupling of the tool assembly to the shaft assembly, activating the motor to retract the firing rod proximally;monitoring a motor characteristic of the motor during retraction of the firing rod; andbased on the monitored motor characteristic crossing a motor-characteristic threshold within a threshold distance, indicating a proper connection of the tool assembly to the shaft assembly.

2. The surgical instrument of claim 1, wherein the motor characteristic is at least one of a motor current or a motor speed.

3. The surgical instrument of claim 1, wherein the motor-characteristic threshold is between 1.5-3.5 times a baseline motor characteristic level.

4. The surgical instrument of claim 1, wherein the threshold distance is between 0.3-0.8 mm.

5. The surgical instrument of claim 1, wherein:126537393.3 24A0012954W001the tool assembly further comprises a knife bar with a retention segment; anda distal end of the firing rod is positioned within the retention segment.

6. The surgical instrument of claim 5, wherein:the retention segment includes protruding fingers that are diametrically opposed structures extending inwardly toward one another and separated by a gap; andthe firing rod includes flanges at the distal end, wherein the flanges are positioned distally from the protruding fingers of the retention segment.

7. The surgical instrument of claim 1, wherein the operations further comprise:calculating a rate of change of the motor characteristic; anddetermining that the calculated rate of change is within a rate-of-change envelope, wherein indicating the proper connection is further based on the calculated rate of change being within the rate-of-change envelope.

8. The surgical instrument of claim 1, wherein indicating the proper connection of the tool assembly includes generating at least one of an audio, visual, or haptic indicator on the surgical instrument.

9. The surgical instrument of claim 1, wherein indicating the proper connection of the tool assembly includes enabling firing of the surgical instrument.

10. The surgical instrument of claim 1, wherein the surgical instrument is a surgical stapling instrument.

11. A surgical instrument, comprising:a shaft assembly comprising a firing rod;a motor;a tool assembly including an end effector;a processor; and126537393.3 25A0012954W001memory storing instructions that, when executed by the processor, cause the surgical instrument to perform operations comprising:initiating a connection test to verify a proper connection of the tool assembly to the shaft assembly;based on initiating the connection test, activating the motor to retract the firing rod proximally;monitoring a motor characteristic of the motor during retraction of the firing rod; determining that the monitored motor characteristic has not crossed a motorcharacteristic threshold;determining that the firing rod has travelled a proximal distance greater than a threshold distance; andbased on the monitored motor characteristic not crossing the motor-characteristic threshold and the travelled distance being greater than the threshold distance, indicating an improper connection of the tool assembly to the shaft assembly.

12. The surgical instrument of claim 11, wherein the motor characteristic is one of motor speed or motor current.

13. The surgical instrument of claim 11, wherein the threshold distance is between 1.0-2.0 mm.

14. The surgical instrument of claim 11, wherein:the tool assembly further comprises a knife bar with a retention segment; anda distal end of the firing rod is positioned proximally of the retention segment.

15. The surgical instrument of claim 14, wherein:the retention segment includes protruding fingers that are diametrically opposed structures extending inwardly toward one another and separated by a gap; andthe firing rod includes flanges at the distal end, wherein the flanges are positioned proximally from the protruding fingers of the retention segment.126537393.3 26A0012954W00116. The surgical instrument of claim 11, wherein indicating the improper connection of the tool assembly includes generating at least one of an audio, visual, or haptic indicator on the surgical instrument.

17. A method, implemented by a surgical stapling instrument, for verifying a proper connection of a tool assembly to a shaft assembly of the surgical stapling instrument, the method comprising:initiating a connection test to verify a proper connection of the tool assembly to the shaft assembly;based on initiating the connection test, activating a motor of the surgical stapling instrument to retract a firing rod of the shaft assembly proximally;monitoring current drawn by the motor during retraction of the firing rod; determining, at a first time, that the monitored current does not exceed a motor-current threshold;determining, at the first time, that the firing rod has travelled a proximal distance less than a threshold distance;determining, at a second time after the firing rod has traveled further in the proximal direction, that the monitored current does exceed the motor-current threshold;determining at the second time, that the firing rod has travelled a proximal distance less than the threshold distance; andbased on the motor current exceeding the motor-current threshold and the travelled distance being less than the threshold distance, enabling firing of the surgical stapling instrument.

18. The method of claim 17, wherein the motor-current threshold is between 1.5-3.5 times a baseline motor-current level.

19. The method of claim 17, wherein the threshold distance is between 0.5-2.5 mm.126537393.3 27A0012954W00120. The method of claim 17, further comprising indicating a proper connection of the tool assembly to the shaft assembly by generating at least one of an audio, visual, or haptic indicator on the surgical instrument.126537393.3 28

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