Patent Publication Number: US-11653925-B2

Title: Tissue relaxation monitoring for optimized tissue stapling

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of the filing date of provisional U.S. Application No. 63/028,136, filed on May 21, 2020. 
    
    
     FIELD 
     This disclosure is generally related to powered surgical stapling devices and, more particularly, to powered surgical stapling devices that include software that utilizes strain measurements to optimize stapling and/or cutting of tissue. 
     BACKGROUND 
     Powered surgical stapling devices include a handle assembly, an adapter assembly including a proximal portion supported on the handle assembly, and a tool assembly supported on the distal portion of the adapter assembly. The tool assembly often includes a reload assembly and an anvil assembly moveably positioned relative to the reload assembly to clamp tissue therebetween. The stapling device may also include a strain gauge for measuring characteristics of tissue being clamped and/or stapled, e.g., tissue thickness, tissue compression, etc., and/or parameters related to staple formation or tissue cutting, e.g., cutting force, firing force, etc. Typically, a strain gauge is supported within the adapter assembly and is formed from electronics that can be sterilized or reprocessed to facilitate reuse of the adapter assembly. Such electronics are costly. 
     During a stapling procedure, when clamping tissue many surgeons wait a specified period of time, e.g., fifteen seconds or more, after achieving a predetermined tissue gap between the anvil assembly and the reload assembly. This waiting period provides the clamped tissue with time to relax, e.g., allows fluid to travel out of the clamped tissue into surrounding tissue, and is intended to encourage a less traumatic staple firing. Waiting longer than is necessary for the clamped tissue to achieve an optimum relaxation extends the time of surgery. Conversely, not waiting a sufficient period of time for the tissue to relax can unnecessarily damage the stapled tissue and/or result in staple malformation. 
     Therefore, it would be beneficial to have a device for and method for monitoring tissue relaxation and indicating when optimum tissue relaxation is achieved. 
     SUMMARY 
     A circular stapling device includes a handle assembly including a processor, an adapter assembly operably secured to the handle assembly and including a trocar assembly and a strain gauge assembly, a reload assembly operably secured to the adapter assembly, the reload assembly including a staple cartridge, and an anvil assembly releasably secured to the trocar assembly and moveably positioned relative to the staple cartridge between a spaced position and a clamped position. The processor includes software for determining when tissue clamped between the staple cartridge and the anvil assembly has achieved a predetermined tissue relaxation percent, i.e., when the clamped tissue is determined to have stabilized. 
     In certain aspects of the disclosure, the predetermined tissue relaxation percent is between about 1% and about 0.5%. The strain gauge assembly may include a plurality of strain gauges. The software may be configured to activate an alert when the predetermined tissue relaxation percent is achieved. The software may alert the clinician with an audible, visual, and/or tactile feedback. The software may be configured to initiate a stapling sequence when the predetermined tissue relaxation percent is achieved. The software may be configured to activate an alert after the tissue is clamped for a predetermined time period. The predetermined time may be 15 seconds. The software may be configured to take samples of the clamping force at a predetermined sampling rate. The predetermined sampling rate may be 400 milliseconds. 
     A method of optimizing tissue relaxation during a stapling procedure includes clamping tissue between an anvil assembly and a reload assembly, calculating a tissue relaxation percent of the clamped tissue, and initiating a stapling sequence when the tissue relaxation percent equals or is less than a predetermined tissue relaxation percent. 
     In certain aspects of the disclosure, clamping the tissue includes moving the anvil assembly relative to the reload assembly until a predetermined gap is achieved between the anvil assembly and a staple cartridge of the reload assembly. Calculating the tissue relaxation percent may include using a 6-tap strain gauge history buffer. Initiating the stapling sequence may occur when the measured tissue relaxation percent is between about 0.05% and 1%. Initiating the stapling sequence may occur 15 seconds after clamping tissue is complete. 
     Aspects of the method may further include initiating a cutting sequence. The cutting sequence may be initiated at the completion of the stapling sequence. The cutting sequence may be initiated when the tissue relaxation percent equals or is less than a second predetermined tissue relaxation percent, or after a predetermined time period has elapsed, whichever occurs first. Initiating the cutting sequence may be automatic. Initiating the stapling sequence may occur when the tissue relaxation percent equals or is less than a predetermined tissue relaxation percent, or after predetermined time elapses, whichever occurs first. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       Various aspects and features of the disclosure are described with reference to the drawings wherein like numerals designate identical or corresponding elements in each of the several views, wherein: 
         FIG.  1    is a side perspective view of a surgical stapling device including an adapter assembly having a strain gauge assembly according to aspects of the disclosure; 
         FIG.  2    is a side perspective view of the adapter assembly shown in  FIG.  1    with a trocar assembly and strain gauge assembly shown phantom; 
         FIG.  3    is a side perspective view of a distal portion of the adapter assembly shown in  FIG.  2   , with an outer sleeve removed and a tension gauge support separated from the adapter assembly; 
         FIG.  4    is a side perspective view of the trocar assembly, and a tension gauge housing and tension gauge anchor of the strain gauge assembly, shown in  FIG.  2   ; 
         FIG.  5    is a flow diagram of a stapling sequence according to a method of the disclosure; and 
         FIG.  6    is a flow diagram of a processing step of the stapling sequence in the flow diagram shown in  FIG.  5   . 
     
    
    
     DETAILED DESCRIPTION 
     The devices and methods for optimizing tissue stapling are described in detail with reference to the drawings, in which like reference numerals designate identical or corresponding elements in each of the several views. As used herein the term “distal” refers to that portion of the component farther from the user, while the term “proximal” refers to that portion of the component closer to the user. In addition, the term “clinician” is used generally to refer to medical personnel including doctors, nurses, and support personnel. As used herein, the term “about” means that the numerical value is approximate and small variations would not significantly affect the practice of the disclosed aspects of the disclosure. Where a numerical limitation is used, unless indicated otherwise by the context, “about” means the numerical value can vary by ±10% of the stated value and remain within the scope of the disclosure. 
     The methods of optimizing tissue stapling described below utilize a strain gauge assembly of a circular stapling device to monitor strain gauge data, i.e., clamping force, during a stapling procedure. More particularly, and as will be described in further detail below, software in the stapling device uses strain gauge data to calculate a clamping force and measure the clamping force at a specified sampling rate. From this, a percent change in force between each data sample is calculated. The software then applies a filter by calculating an average percent change over a specified amount of percent change readings. When this average percent change calculated value is equal to or less than a specified tissue relaxation percent, the clinician is encouraged to initiate a firing sequence. If the average percent change value is not equal to or less than the tissue relaxation percent specified value before a predetermined period of time has elapsed, e.g., fifteen seconds (15 s), the clinician is encouraged to initiate the firing sequence after the predetermined period of time has passed. 
       FIG.  1    illustrates a circular stapling device  10  including a handle assembly  12 , an elongate body or adapter assembly  14 , a reload assembly  16  releasably supported on the adapter assembly  14 , and an anvil assembly  18  releasably supported for movement in relation to the reload assembly  16  between an open position ( FIG.  1   ) and a clamped position (not shown). Although the methods for optimizing tissue stapling will be described with reference to a circular stapling device, it is envisioned that the aspects of the disclosure may be modified for use in surgical stapling devices having alternative configurations. 
     The circular stapling device  10  is illustrated as an electrically powered stapling device including an electrically powered handle assembly  12  that may support one or more batteries (not shown). The adapter assembly  14  translates power from the handle assembly  12  to the reload and anvil assemblies  16 ,  18 , respectively, to staple and cut tissue. Examples of electrically powered stapling devices can be found in U.S. Pat. Nos. 9,055,943 and 9,023,014, and U.S. Publication Nos. 2018/0125495 and 2017/0340351. Alternately, it is envisioned that aspects of the disclosure may be incorporated into a stapling device that is configured for use with a robotic system as disclosed in, e.g., U.S. Pat. No. 9,962,159, and does not include a handle assembly. 
     The handle assembly  12  of the circular stapling device  10  includes a stationary grip  12   a  that supports actuation buttons  13  for controlling operation of various functions of the circular stapling device  10 , including, for example, approximation of the reload assembly  16  and anvil assembly  18 , firing of staples from the reload assembly  16 , and cutting or coring of tissue. 
     A processor  20  is disposed within the handle assembly  12  and includes or is operably connected to a memory chip  22 . The memory chip  22  may include one or more of volatile, non-volatile, magnetic, optical, or electrical media, such as read-only memory (ROM), random access memory (RAM), electrically-erasable programmable ROM (EEPROM), non-volatile RAM (NVRAM), or flash memory. The processor  20  may be any suitable processor (e.g., control circuit) adapted to perform the operations, calculations, and/or set of instructions described in the present disclosure including, but not limited to, a hardware processor, a field programmable gate array (FPGA), a digital signal processor (DSP), a central processing unit (CPU), a microprocessor, and combinations thereof. Those skilled in the art will appreciate that the processor may be substituted for by using any logic processor (e.g., control circuit) adapted to execute algorithms, calculations, and/or set of instructions described herein. 
     The adapter assembly  14  includes a proximal portion  14   a  that can be releasably coupled to the handle assembly  12 . The reload assembly  16  includes a proximal portion  16   a  that is releasably coupled to a distal portion  14   b  of the adapter assembly  14 . A staple cartridge  24  is supported on a distal portion  16   b  of the reload assembly  16  and supports a plurality of surgical staples (not shown). A trocar assembly  26  is supported within the distal portion  14   b  of the adapter assembly  14  and extends through the reload assembly  16 . The trocar assembly  26  includes a trocar member  28  for releasably securing and positioning the anvil assembly  18  relative to the reload assembly  16 . 
       FIGS.  2 - 4    illustrate a strain gauge assembly  30  supported within the distal portion  14   b  of the adapter assembly  14  ( FIG.  2   ) and a trocar assembly  40  received through and supported by the strain gauge assembly  30 . The strain gauge assembly  30  is positioned between the trocar assembly  40  and the reload assembly  16 . With the strain gauge data provided by the strain gauge assembly  30 , the clamping force between the staple cartridge  24  of the reload assembly  16  and the anvil assembly  18  can be calculated. The trocar assembly  40  releasably secures the anvil assembly  18  ( FIG.  1   ) to the circular stapling device  10 , and operates to advance and retract the anvil assembly  18  relative to the reload assembly  16 . The software in the handle assembly  12  uses the strain gauge measurements to determine the clamping force over time. As will be described in further detail below, tissue relaxation occurs when the clamping force, i.e., the force on the tissue, stabilizes. 
     The strain gauge assembly  30  includes a tension gauge housing  32 , a tension gauge anchor  34 , and a tension gauge support  36  ( FIG.  3   ). A plurality of strain gauges  38  are supported on an extension portion  32   a  ( FIG.  4   ) of the tension gauge housing  32 . For a detailed description of an exemplary strain gauge assembly, please refer to U.S. patent application Ser. No. 16/809,023, filed Mar. 4, 2020. Although shown as the strain gauge assembly  30 , it is envisioned that the methods of the disclosure may be modified for use with any strain gauge assembly. 
       FIG.  5    illustrates a flow diagram of a stapling procedure for optimizing tissue stapling according to aspects of the disclosure. Initially, tissue to be stapled (not shown) is positioned between an anvil assembly, e.g., the anvil assembly  18  ( FIG.  1   ), and a staple cartridge, e.g., staple cartridge  24  ( FIG.  1   ) of a reload assembly, e.g., reload assembly  16  ( FIG.  1   ). The anvil assembly is then approximated towards the reload assembly to clamp the tissue between the anvil assembly and the staple cartridge of the reload assembly. The anvil assembly is approximated towards the reload assembly until a predetermined clamp gap is achieved between the anvil assembly and the staple cartridge. 
     Strain gauge data provided by a strain gauge assembly, e.g., strain gauge assembly  30  ( FIG.  2   ), is used to calculate a tissue relaxation percent, or more particularly, the percent change in the clamp force between two sample points. Tissue relaxation occurs when the compressed fluid within the clamped tissue has been able to flow into adjacent tissue, i.e., the clamping force stabilizes. Tissue relaxation is determined to have occurred when the tissue relaxation percent equals or is less than a predetermined tissue relaxation percent, typically 0.5-1.0%, or fifteen seconds have elapsed, whichever occurs first. In aspects of the disclosure, the software is configured to alert the clinician, through audio, visual, and/or tactile feedback, when optimum tissue relaxation has occurred and to initiate a stapling sequence. In certain aspects of the disclosure, the stapling procedure may be initiated at any time after the anvil assembly and staple cartridge achieve the clamp gap distance. It is also envisioned that the software may be programmed to automatically initiate the stapling sequence upon either the tissue relaxation percent being achieved, or 15 seconds elapsing. 
     Following the stapling sequence, a tissue cutting or coring sequence is initiated. The cutting sequence may be automatic, or may be manually initiated by the clinician. The cutting sequence may be initiated simultaneously with the stapling sequence, directly following the completion of the stapling sequence, or after a subsequent time period. 
     In certain aspects of the disclosure, tissue relaxation optimization similar to that of the tissue relaxation optimization described above can also be used prior to initiation of the cutting sequence to minimize tissue damage during cutting/coring of the stapled tissue. In this manner, subsequent to completion of the stapling sequence and prior to the initiation of the cutting sequence, the software in the handle assembly calculates a tissue relaxation percent from the strain gauge data provided by the strain gauge assembly. As with the stapling sequence, once the tissue relaxation percent is equal to or less than a predetermined tissue relaxation percent, or a predetermined time period has elapsed, whichever occurs first, the clinician is alerted that the cutting sequence may be initiated. It is envisioned that the cutting sequence may be initiated automatically. 
     In a further attempt to optimize tissue stapling, it is envisioned that the strain gauge assemblies may be used in combination with the software to monitor the clamping forces during tissue clamping. In the event the clamping forces exceed a predetermined threshold, the software can reduce the speed at which the tissue is being clamped, or stop clamping altogether until the clamping force has fallen below the threshold. 
       FIG.  6    is a flow diagram detailing the tissue relaxation optimization procedure. Although shown using a 6-tap strain gauge history buffer, which is updated at a specified sampling rate, it is envisioned that more or less than a 6-tap strain gauge history buffer may be utilized. In one aspect of the disclosure, the sampling rate is 400 milliseconds intervals. 
     After the buffer fills, consecutive strain gauge values are subtracted to calculate the differential change in force and then divided by the previous absolute strain gauge value to determine the percent change in force applied to tissue. This results in five (5) delta percent values which are then averaged. At the next time period, all values in the buffer are shifted down and the new value is placed in the SGFt0 slot. In this manner, only the last five values are used in the calculation. When a new calculation is done, the oldest value is dropped and does not form part of the new calculation. When the averaged delta percent values are less than or equal to a specified tissue relaxation percent, the tissue is determined to be relaxed and the user is encouraged to initiate the firing. As noted above, in certain aspects of the disclosure, at a tissue relaxation percent of between about 0.5% and about 1.0%, tissue is deemed to be sufficiently stabilized, and no further significant change in force is likely. 
     The 6-tap strain gauge history is SGFt5, SGFt4, SGFt3, SGFt2, SGFt1, SGFt0. 
     The delta percentages (DP) are calculated as follows: 
     
       
         
           
             
               
                 
                   
                     DPt 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     4 
                   
                   = 
                     
                   ⁢ 
                   
                     
                       
                         SGFt 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         5 
                       
                       - 
                       
                         SGFt 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         4 
                       
                     
                     
                       SGFt 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       5 
                     
                   
                 
               
             
             
               
                 
                   
                     DPt 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     3 
                   
                   = 
                     
                   ⁢ 
                   
                     
                       
                         SGFt 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         4 
                       
                       - 
                       
                         SGFt 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         3 
                       
                     
                     
                       SGFt 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       4 
                     
                   
                 
               
             
             
               
                 
                   
                     DPt 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     2 
                   
                   = 
                     
                   ⁢ 
                   
                     
                       
                         SGFt 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         3 
                       
                       - 
                       
                         SGFt 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         2 
                       
                     
                     
                       SGFt 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       3 
                     
                   
                 
               
             
             
               
                 
                   
                     DPt 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     1 
                   
                   = 
                     
                   ⁢ 
                   
                     
                       
                         SGFt 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         2 
                       
                       - 
                       
                         SGFt 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         1 
                       
                     
                     
                       SGFt 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       2 
                     
                   
                 
               
             
             
               
                 
                   
                     DPt 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     0 
                   
                   = 
                     
                   ⁢ 
                   
                     
                       
                         SGFt 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         1 
                       
                       - 
                       
                         SGFt 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         0 
                       
                     
                     
                       SGFt 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       1 
                     
                   
                 
               
             
           
         
       
     
     The Percent Reduction (PR) is determined by averaging the Delta Percentages as follows: 
     
       
         
           
             
               PRt 
               ⁢ 
               
                   
               
               ⁢ 
               0 
             
             = 
             
               
                 
                   DPt 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   4 
                 
                 + 
                 
                   DPt 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   3 
                 
                 + 
                 
                   DPt 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   2 
                 
                 + 
                 
                   DPt 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   1 
                 
                 + 
                 
                   DPt 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   0 
                 
               
               5 
             
           
         
       
     
     As noted above, if the predetermined tissue relaxation percent is not detected within 15 seconds, the tissue is determined to be relaxed and the user is encouraged to initiate firing. 
     The above described devices and methods allow clinicians to make a more informed decision about whether clamped tissue has relaxed to a point where the tissue damage is minimized. The software also allows for collection of tissue relaxation data which can be analyzed later to better understand how tissue behaves after clamp and before firing in a real firing. 
     Persons skilled in the art will understand that the devices and methods specifically described herein and illustrated in the accompanying drawings are non-limiting and exemplary. It is envisioned that the elements and features illustrated or described in connection with one aspect of the disclosure may be combined with the elements and features of another without departing from the scope of the disclosure. As well, one skilled in the art will appreciate further features and advantages of the disclosure based on the above-described aspects. Accordingly, the disclosure is not to be limited by what has been particularly shown and described, except as indicated by the appended claims.