Material combinations and processing methods for surgical instruments

Abstract

Surface preparation of sliding surfaces can enhance wear performance for surgical instruments, such as surgical staplers, that include reusable mechanisms for multiple uses with single-use reloadable cartridges. A combination of surface hardening, surface finishes, and surface coatings can be applied to metal components of surgical instruments to reduce the likelihood of abrasive wear in metal-on-metal sliding engagements. Surface hardening techniques can enable additional manufacturing operations, such as welding, without compromising the strength of the underlying metal substrate. With stainless steel metal substrates, surface hardening or surface hardening techniques can reduce corrosion resistance, so surface coatings can be added to inhibit surface oxidation and provide a barrier against metal-to-metal contact. An additional lubricious coating layer, such as a bone wax coating layer, can enhance wear resistance.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to and the benefit of U.S. Provisional Patent Application No. 63 / 107,321, entitled "Material Combinations and Processing Methods for a Surgical Instrument," filed October 29, 2020, the entire contents of which are incorporated herein by reference.

[0002] FIELD OF THE INVENTION This application relates generally to surgical instruments, and more particularly to material combinations and fabrication methods for sliding components within end effectors of surgical instruments, such as surgical stapling devices. [Background technology]

[0003] Surgical staplers are used to approximate or clamp tissue and to staple the clamped tissue together. Accordingly, surgical staplers have mechanisms for ensuring that the tissue is properly positioned and captured and for driving the staples through the tissue. As a result, this has led to the creation of complex mechanisms, such as multiple triggers and handles, to provide proper stapling of the clamped tissue. These complex mechanisms can result in surgical staplers that are a significant manufacturing burden and a potential source of device failure and confusion for the user. Thus, reliable stapling of clamped tissue without complex mechanisms is desirable. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] U.S. Patent No. 9,668,732 [Patent Document 2] U.S. Patent Application Serial No. 15 / 485,620 [Patent Document 3] U.S. Patent Application Serial No. 15 / 486,227 [Patent Document 4] U.S. Patent Application Serial No. 15 / 486,008 [Patent Document 5] U.S. Patent Application Serial No. 16 / 287,748 Summary of the Invention [Problem to be solved by the invention]

[0005] The surgical stapler may further include replaceable reloadable cartridges so that multiple cartridges can be used with the stapler in a single surgical procedure. The surgical stapler clamping and firing mechanism may include metallic components in sliding contact. Further improvements to the components in sliding contact are desirable to resist wear degradation over multiple firing cycles. [Means for solving the problem]

[0006] In certain embodiments, a surgical stapling instrument is provided herein. The surgical stapling instrument includes an end effector and a firing member. The end effector includes a first jaw and a second jaw pivotally coupled to the first jaw. The firing member is longitudinally slidable relative to the end effector to pivotally move the second jaw relative to the first jaw to actuate the end effector. At least one of the first jaw, the second jaw, and the firing member includes a metal substrate, a dry film surface coating disposed on the metal substrate, and a bone wax layer disposed on the dry film surface.

[0007] In certain embodiments, a surgical stapler is provided herein. The surgical stapler includes an elongated shaft and a jaw assembly. The elongated shaft extends from a proximal end to a distal end. The jaw assembly is positioned at the distal end of the elongated shaft. The jaw assembly includes a cartridge support, an anvil, and a firing member. The cartridge support is configured to receive a reloaded cartridge having a plurality of staples disposed therein. The cartridge support and the anvil are pivotably movable between an open configuration and a closed configuration. The firing member is longitudinally slidable in engagement with the cartridge support and the anvil in the closed configuration to fire the staples. At least one of the anvil, cartridge support, and firing member includes a hard-faced metal substrate, a dry film surface coating disposed on the metal substrate, and a bone wax layer disposed on the dry film surface.

[0008] In certain embodiments, a method of manufacturing a surgical end effector is provided herein. The method includes providing a first jaw member, a second jaw member, and a firing member, each having a metal substrate. The method further includes hardening the metal substrate of at least one of the first jaw member, the second jaw member, and the firing member to a first predetermined hardness. The method further includes applying a dry film coating to the hardened at least one of the first jaw member, the second jaw member, and the firing member. The method further includes applying a bone wax composition to at least one of the first jaw member, the second jaw member, and the firing member. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a perspective view of an embodiment of a surgical stapling device. [Figure 2] 2 is a perspective view of an embodiment of a shaft assembly and a jaw assembly for use with the surgical stapling device of FIG. 1; [Figure 3]2 is a perspective view of an embodiment of a jaw assembly and reload cartridge for use with the surgical stapling device of FIG. 1; [Figure 4] FIG. 4 is a cross-sectional perspective view of the proximal end of the jaw assembly of FIG. 3. [Figure 5] FIG. 4 is a cross-sectional perspective view of the jaw assembly of FIG. 3. [Figure 6] 10 is a graph showing an illustrative force versus progress plot for an exemplary embodiment of the jaw assembly. [Figure 7] 10 is a graph showing an illustrative force versus progress plot for another exemplary embodiment of the jaw assembly. [Figure 8] 10 is a graph showing an illustrative force versus progress plot for another exemplary embodiment of the jaw assembly. [Figure 9A] 1A-1C are schematic diagrams of cross sections of metal substrates for exemplary embodiments of components of a surgical stapler. [Figure 9B] 10 is a schematic diagram of a cross section of a metal substrate for another exemplary embodiment of a component of a surgical stapler. [Figure 10] 10A-10C illustrate an exemplary method for preparing the surfaces of components of a surgical stapler. DETAILED DESCRIPTION OF THE INVENTION

[0010] Referring to Figures 1-2, an embodiment of a surgical stapling device is illustrated. The illustrated embodiment of a surgical stapler 10 comprises an elongate shaft 20, a jaw assembly 30, and a handle assembly 40. Various aspects of the elongate shaft 20 and jaw assembly 30 described herein can be used interchangeably with either a mechanical handle assembly 40 as illustrated or a powered handle assembly 40 including, for example, an electric motor. Furthermore, aspects of the elongate shaft 20 and jaw assembly 30 described herein are contemplated for use with shaft assemblies configured to be operated by a robotic surgical system. Figure 1 illustrates the surgical stapler 10 with the jaw assembly 30 in an open configuration. Figure 2 illustrates a removable, reloadable shaft assembly comprising the elongate shaft 20 and jaw assembly 30 of the surgical stapler 10 with the jaw assembly 30 in an open configuration.

[0011] With continued reference to Figures 1 and 2, the illustrated embodiment of the surgical stapler 10 can be sized and configured for use in laparoscopic surgical procedures. For example, the elongate shaft 20 and jaw assembly 30 can be sized and configured to be introduced into the surgical field through an access port or trocar cannula. In some embodiments, the elongate shaft 20 and jaw assembly 30 can be sized and configured to be inserted through a trocar cannula having a relatively small working channel diameter, such as less than 8 mm. In other embodiments, the elongate shaft 20 and jaw assembly 30 can be sized and configured to be inserted through a trocar cannula having a larger working channel diameter, such as 10 mm, 11 mm, 12 mm, or 15 mm. In other embodiments, it is contemplated that certain aspects of the surgical staplers described herein can be incorporated into a surgical stapling device for use in open surgical procedures.

[0012] With continued reference to FIGS. 1 and 2 , in the illustrated embodiment, a jaw assembly 30 is coupled to the elongate shaft 20 at the distal end 24 of the elongate shaft 20. The jaw assembly 30 includes a first jaw 34 pivotally coupled to a second jaw 32. In the embodiment shown in FIGS. 1-2 , the jaw assembly is articulatably coupled to the elongate shaft such that the jaw assembly can be selectively positioned in an articulated position relative to the central longitudinal axis L. The handle assembly of FIG. 1 includes an articulation knob 190 and an articulation mechanism configured to provide continuously selectable articulation of the jaw assembly of the elongate shaft assembly through an articulation range. In an initial configuration, the second jaw 32 includes a plurality of staples positioned within a reload cartridge 50 positioned therein. That is, the second jaw 32 defines a reload support.

[0013] With continued reference to FIGS. 1 and 2 , in the illustrated embodiment, the jaw assembly 30 can be actuated from an open configuration ( FIG. 1 ) to a closed configuration and then to a stapling configuration by an actuation member or beam that is longitudinally slidable within the elongate shaft. In an initial position, the beam can be positioned at the distal end 24 of the elongate shaft 20. With the beam in the initial position, the first jaw 34 is pivoted away from the second jaw 32 so that the jaw assembly 30 is in the open configuration. The actuation beam engages the first jaw 34 upon translation of the actuation member or beam distally along the longitudinal axis L. Translation of the actuation beam a first distance distal from the initial position can actuate the jaw assembly from the open configuration to the closed configuration. With the jaw assembly 30 in the closed configuration, the actuation beam can be returned proximally a first distance to return the jaw assembly 30 to the open configuration. The distal end of the actuation beam can advance a staple slider configured to deploy staples from the second jaw 32 such that further translation of the distal actuation beam past the first distance deploys a plurality of staples 36 from the second jaw 32.

[0014] 1-3 , in the illustrated embodiment, a handle assembly is coupled to the elongate shaft 20 at its proximal end 22. As shown, the handle assembly 40 has a pistol-grip configuration having a housing defining a fixed handle 42 and a movable handle 44, or trigger, pivotally coupled to the fixed handle 42. In other embodiments, it is contemplated that surgical stapler devices incorporating aspects described herein may have handle assemblies having other configurations, such as a scissors-grip configuration or an in-line configuration. The handle assembly 40 houses an actuation mechanism configured to selectively advance an actuation shaft in response to movement of the movable handle 44 to actuate an actuation beam within the elongate shaft a first distance in an opening-closing stroke, close the jaw assembly from an initial open position a second distance beyond the first distance in a firing stroke that fires staples, and return the actuation beam the second and first distances to an initial position. In certain embodiments, a sliding selector 72 on the handle assembly allows a user to select whether the handle assembly is actuated to actuate the jaw assembly on an open-close stroke or a firing stroke. Various embodiments of handle assemblies and associated actuation mechanisms are disclosed in U.S. Pat. No. 9,668,732, entitled "Surgical Stapler Handle Assembly Having Actuation Mechanism With Longitudinal Rotatable Shaft," and U.S. patent application Ser. No. 15 / 485,620, filed April 12, 2017, entitled "Surgical Stapler Having Articulation Mechanism," both of which are incorporated herein by reference in their entireties.

[0015] Continuing with reference to FIGS. 1-3 , in some embodiments, the surgical stapler 10 can include a plurality of staples positioned within a disposable reload cartridge 50, while the handle assembly 40 and elongated shaft 20 are configured to be reused with multiple staple reload cartridges. In certain embodiments, each reload cartridge 50 can be coupled to a reload cover 150 to shield the tissue-contacting surface and staple pockets of the reload cartridge prior to attachment to the jaw assembly, with the reload cover 150 to be removed before the surgical stapler is introduced to a surgical site. It can be desirable for the handle assembly 40 and elongated shaft 20 to resist performance degradation associated with wear so that the stapler can be reliably operated for multiple clamping and staple firing cycles, each involving a single-use reload cartridge 50. The surgical stapler can include one or more grip and firing lockout mechanisms that can limit the function of the handle assembly to alert the user and enhance patient safety when a reload cartridge is not present in the jaw assembly or when a partially or fully fired reload cartridge is present in the jaw assembly. In certain embodiments, a staple deploying member, such as a translatable sled or slider within the reload cartridge 50, can overcome one or more lockout mechanisms when the staple deploying member is in a proximal position of the jaw assembly, which corresponds to a condition in which an unfired reload cartridge is present within the surgical stapler 10.

[0016] Referring to FIG. 1 , handle assembly 40 includes a coupler 46 at its distal end. Coupler 46 is adapted to engage elongate shaft 20 of surgical stapler 10. Coupler 46 may have a bayonet connection having an outer connector that can removably couple handle assembly 40 to elongate shaft 20 and an inner connector that can removably couple an actuation shaft of handle assembly 42 to an actuation member of elongate shaft 20. That is, surgical stapler 10 may be configured so that handle assembly 40 can be reused with multiple disposable shafts and / or reloadable cartridges during a surgical procedure. In other embodiments, the handle assembly and some portion of the elongate shaft may be reusable, while the remainder of the elongate shaft and jaw assembly are contemplated to define a disposable cartridge. In certain other embodiments, the handle assembly and elongate shaft may be reusable, while the jaw assembly defines a disposable cartridge. In still other embodiments, a jaw insert containing a plurality of staples may define a disposable cartridge, while the remainder of the surgical stapler is reusable.

[0017] As mentioned above, the shaft assemblies, jaw assemblies, and reload cartridges described herein can be used in conjunction with powered stapler handle assemblies or actuators in robotic surgical systems. Various embodiments of powered handle assemblies and associated actuation mechanisms are disclosed in U.S. patent application Ser. No. 15 / 486,227, filed April 12, 2017, entitled "Reload Shaft Assembly for Surgical Stapler," U.S. patent application Ser. No. 15 / 486,008, filed April 12, 2017, entitled "Surgical Stapler Having a Powered Handle," and U.S. patent application Ser. No. 16 / 287,748, filed February 27, 2019, entitled "Surgical Stapler Having a Powered Handle," all of which are incorporated herein by reference in their entireties.

[0018] Referring to FIG. 3 , a perspective view of the jaw assembly of the elongate shaft 20 is shown with the reload cartridge 50 removed from the second jaw 32. As shown, the reload cartridge 50 is removably positionable in a reload support defined by the second jaw 32. In the illustrated embodiment, the reload cartridge 50 includes a plurality of staples disposed therein, each positioned within its own staple pocket formed through the body of the reload cartridge. The top surface of the reload cartridge 50 defines a tissue-contacting surface, which in certain embodiments may be substantially planar. The reload cartridge further includes a blade channel formed therein. As shown, the blade channel extends longitudinally between the rows of staple pockets such that translation of a cutting blade through the blade channel transects tissue between the rows of staples deployed in tissue positioned in the jaws as the staples are fired. The reloading support defined by the second jaw 32 includes a channel sized and configured to removably receive the reloading cartridge 50. For example, in certain embodiments, the channel of the reloading support may include at least one recess 132 sized and configured to receive a corresponding protruding boss on the reloading cartridge 50.

[0019] Referring to Figure 4, an embodiment of a jaw assembly is illustrated. The cross section of the jaw assembly is oriented approximately perpendicular to the longitudinal axis of the jaw assembly at its proximal end, just distal to the distal end 24 of the elongate shaft, to facilitate visibility into certain aspects of the operation of the surgical stapler during closure / tissue clamping and firing operations. In the illustrated embodiment, the surgical stapler comprises an actuation mechanism including a firing member 120 longitudinally translatable within the first and second jaws 34, 32 of the jaw assembly to actuate the jaw assembly from an open configuration to a closed configuration and subsequently fire a plurality of staples from a reload cartridge.

[0020] 4, in certain embodiments, the firing member 120 may include an I-beam profile with an upper flange 126 connected to a lower flange 124 by a vertical blade member 122. The upper flange 126 is translatable within a channel of the first jaw 34, and the lower flange 124 is translatable within a channel of the second jaw 32. The blade member 122 is translatable within the blade channel of the reload cartridge.

[0021] Referring to FIG. 5, certain aspects of an embodiment of a jaw assembly of a surgical stapler are shown. A longitudinal cross-section of the jaw assembly is shown to further illustrate operation of the surgical stapler's actuation mechanism. As shown, the elongated shaft includes an actuation member 128 that is longitudinally slidable therein. The actuation member 128 extends to a distal end to which a firing member 120 is coupled. The reload cartridge 50 includes a translating slider 52 or wedge sled therein that is advanced by distal longitudinal movement of the firing member 120 to fire a plurality of staples from the reload cartridge.

[0022] Continuing to refer to FIG. 5 , the jaw assembly can include an upper channel 136 formed in the first jaw 34. The jaw assembly can further include a lower channel 134 formed in the second jaw 32. In the illustrated embodiment, the upper flange 126 slides within the upper channel 136 of the first jaw 34 and the lower flange 124 slides within the lower channel 134 of the second jaw 32 when the firing member 120 is advanced longitudinally to close the jaw assembly and fire staples from the reload cartridge 50. In the illustrated embodiment, the proximal end of the upper channel 136 includes a ramp such that actuation of the firing member 120 over the ramp pivots the first jaw 34 to the closed configuration. The upper channel 136 further includes a channel distal to the ramp that extends generally parallel to the lower channel 134 when the jaws are in the closed configuration.

[0023] Because it is contemplated that the jaw assembly may be reused with multiple single-use reloaded cartridges 50, the sliding surfaces of firing member 120 and lower and upper channels 134, 136 are desirably configured to minimize performance degradation over multiple use cycles. With tissue clamped between the jaws, the lower surface of upper flange 126 slides against the upper surface of upper channel 136, and the upper surface of lower flange 124 slides against the lower surface of lower channel 134. That is, in certain embodiments, at least these sliding surfaces can be configured to reduce the effects of their frictional engagement. In other embodiments, it may be desirable to configure all of first jaw 34, second jaw 32, and firing member 120 to reduce the effects of their frictional engagement.

[0024] In certain embodiments, the jaw assembly is desirably configured to be reused with at least 10 reloaded cartridges without a significant reduction in performance. In certain embodiments, it may be preferable to configure the jaw assembly to be reused with at least 12 reloaded cartridges without a significant reduction in performance. Furthermore, it may be desirable for the jaw assembly to be configured to be operable with a desired number of reloaded cartridges while the first and second jaws 34, 32 apply an actuation load of at least 80 pounds of compressive force to tissue clamped therebetween. In other embodiments, the jaw assembly is desirably configured to be operable with a desired number of reloaded cartridges with an actuation load of at least 100 pounds of compressive force. In yet other embodiments, the jaw assembly is desirably configured to be operable with a desired number of reloaded cartridges with an actuation load of at least 120 pounds of compressive force. In certain embodiments, the jaw assembly is configured to be operable with a desired number of reloaded cartridges at a desired actuation load with the jaws offset by up to 1 degree from a position where the first jaw 34 is parallel to the second jaw 32 in the closed configuration. In certain embodiments, the jaw assembly is configured to be operable for a desired number of reloaded cartridges at a desired actuation load with the jaws offset by up to 2 degrees from a closed configuration in which the first jaw 34 is parallel to the second jaw 32. During use, misalignment between the jaws can occur during the stapling operation due to deflection of the jaws depending on the thickness or density of the tissue clamped between the jaws.

[0025] Generally, when two surfaces, such as the lower and upper flanges 124, 126 of the firing member and the respective lower and upper channels 134, 136, contact under load and slide relative to each other, frictional forces oppose the movement. The frictional force is proportional to the load but ultimately independent of the contact area. At the microscopic level, each surface is not truly flat but has surface irregularities or asperities. These irregularities create localized contact points across which the contact load is distributed. In such cases, the true contact area is only a small fraction of the apparent nominal area. There are several types of wear that can cause a gradual increase in the coefficient of friction. When asperities first contact, they deform elastically. However, even small loads can generate large contact stresses that, when concentrated in a small area, can cause plastic deformation. The contact points then flatten, forming a joint. Wear generally involves the physical removal of material from a solid object. It can be divided into three categories: abrasive, adhesive, and fatigue. Abrasive wear is a more gradual wear process. This occurs when two surfaces rub against each other, with the harder surface scraping away the softer one. This is often characterized by a rough appearance and may be accompanied by the generation of particulates. Often, some work hardening (cold work) can occur at this stage. Adhesive wear is a more aggressive form of wear that can lead to abrasion, especially in the case of metal-to-metal wear surfaces. At very localized temperatures, the peaks of opposing asperities can deform and move against each other. If the debris is not removed, this type of wear can be further intensified, leading to abrasion due to high frictional forces.

[0026] Referring to Figures 6-8, certain aspects of sliding engagement between two surfaces are shown. Force versus distance plots are shown for an exemplary set of sliding engagement cycles between a pair of exemplary components. Figure 6 shows a force versus distance plot for an exemplary component over several sliding engagement cycles, illustrating abrasive wear and abrasion. Figure 7 shows a force versus distance plot for an exemplary component over several sliding engagement cycles, illustrating multiple cycles of abrasive wear followed by abrasion. Figure 8 shows a force versus distance plot for an exemplary component over several sliding engagement cycles, illustrating moderate abrasive wear.

[0027] Referring to FIG. 6 , an exemplary force versus distance plot is shown for several sliding engagement cycles between exemplary sliding components. The plot illustrates the progression from at least one sliding engagement cycle involving abrasive wear in a first direction 210 and abrasive wear in a second direction 212 to abrasive wear in a first direction 214 and abrasive wear in a second direction 216. As the components move in the first and second directions with abrasive wear, the frictional force between the components is relatively small and relatively constant along the distance of movement. Plot lines above the x-axis represent movement in the first direction (210, 214), while plot lines below the x-axis represent movement in a second direction (212, 216) opposite the first direction. The height (or depth) of the plot lines from the x-axis represents the frictional force required to slide the components. When abrasive wear occurs in the first and second directions 214, 216, the frictional forces become highly irregular and significantly greater than those experienced in the abrasive wear state. Abrasion is highly detrimental to device function because it increases the coefficient of dynamic friction by a factor greater than one, resulting in a significant increase in the force required to actuate the device. In some cases, abrasion can cause the input force required to actuate the device to increase by more than two times the force expected for a single pair of sliding surfaces. That is, surgical stapler embodiments having sliding components that undergo abrasive wear after several sliding engagements may be undesirable for use with multiple reload cartridges because the force required to actuate the actuation mechanism becomes excessive and stresses components within the shaft assembly and handle assembly, making actuation of the handle assembly difficult.

[0028] Referring to FIG. 7 , an exemplary force versus distance plot is shown for several sliding engagement cycles between exemplary sliding components. The plot illustrates the progression from at least several sliding engagement cycles with abrasive wear in a first direction 220 and abrasive wear in a second direction 222 to abrasive wear in a second direction 224. As the components move in the first and second directions with abrasive wear, the plot shows multiple wear cycles in which the frictional force gradually increases until abrasion occurs, while the frictional force between the components is relatively small and relatively constant along the distance of travel. In certain embodiments, components exhibiting such wear characteristics can be used in a surgical stapler, provided that the components remain in an abrasive wear state for at least a sufficient number of wear cycles to allow for the use of a desired number of reloaded cartridges before undergoing abrasive wear.

[0029] Referring to FIG. 8, an exemplary force versus distance plot is shown for several sliding engagement cycles between exemplary sliding components. The plot illustrates repeated actuation over multiple sliding engagement cycles with abrasive wear in a first direction 230 and abrasive wear in a second direction 232 without the components experiencing abrasive wear. As the components move in the first and second directions with abrasive wear, the frictional forces between the components are relatively small and relatively constant along the distance of travel, with minimal increase between cycles. It is desirable to include a jaw assembly for a surgical stapler to have wear characteristics that reduce the likelihood of wear over repeated use with multiple reloaded cartridges.

[0030] In certain embodiments, material selection for components of a surgical stapler that engage in sliding contact, such as the jaw assembly and firing member, can be based on certain priorities. For example, the material selected, as well as the surface preparation coating and its processing, is primarily limited to those that meet biocompatibility standards for use in patient-contacting surgical devices. Furthermore, the selected material desirably can be joined by a welding operation, thereby providing flexibility in the configuration of various aspects of the jaw design, such as by facilitating the use of a two-piece first jaw 34 having a cover or cap welded onto the lower anvil face and forming a channel between the first jaw member. Furthermore, the selected material desirably has sufficient strength and toughness characteristics to withstand repeated staple firing actuations. Furthermore, the selected material may desirably be resistant to oxidation and corrosion. Finally, the selected material desirably can be manufactured by various processes to facilitate manufacturing efficiency, including, for example, a metal injection molding process.

[0031] Various grades of stainless steel can be selected to achieve desired properties. For example, in certain embodiments, grade 17-4 stainless steel can be selected and used for sliding components. In other embodiments, grade 420 stainless steel can be selected and used for sliding components. Grade 420 is a martensitic stainless steel, as opposed to precipitation-hardenable stainless steels such as grade 17-4. Grade 420 stainless steel has a relatively high carbon content compared to grade 17-4 stainless steel. Desirably, grade 420 stainless steel is relatively hardenable compared to low-carbon steels. However, martensitic stainless steels tend to be less weldable than precipitation-hardenable stainless steels because brittle martensite tends to form from rapid cooling of the weld, which can lead to stress-induced cracking. Furthermore, the relatively high carbon content of grade 420 stainless steel can also lead to relatively low corrosion resistance. Grades 17-4 and 420 are each suitable for use in metal injection molding processes.

[0032] In yet another embodiment regarding material selection, grade 13-8 or grade 455 / 465 stainless steel may be selected for use, however, it should be noted that these grades of stainless steel tend to be specialty materials, meaning that these grades of stainless steel may be less desirable in terms of potential cost, availability, and manufacturability concerns.

[0033] Because material selection considerations indicate that a metallic stainless steel material is desirable for use in the jaw assembly and firing member of a surgical stapler, further consideration must be given to preparing these components and engineering their properties to reduce the likelihood of wear that may result from metal-on-metal sliding engagement. Generally, materials with relatively high surface hardness may be more resistant to abrasive wear. Various techniques exist for achieving relatively high surface hardness in metal substrates, such as stainless steel substrates contemplated for use in the sliding components of a surgical stapler. For example, in various embodiments, the surface of a metal substrate for use in sliding contact with reduced wear can be prepared using at least one of diffusion / thermochemical techniques, surface plating techniques, surface coating techniques, and applied energy techniques.

[0034] In diffusion or thermochemical processes, the surface layer of a metal substrate is hardened by adding hardening species such as carbon, nitrogen, or boron, typically at relatively high temperatures. These processes can be referred to as "surface hardening" in that the goal is to produce a relatively hard case or surface layer while maintaining the toughness and ductility of the core. However, typical surface hardening techniques have had undesirable results with stainless steel materials, particularly precipitation-hardened stainless steels, in that they reduce the corrosion resistance of the stainless steel material. Furthermore, in the case of precipitation-hardened stainless steel materials, surface hardening methods involving relatively high temperatures can result in unintended annealing of the material. Furthermore, when a metal substrate is formed using a metal injection molding process, the substrate may have a relatively high degree of porosity. That is, unless there are further modifications to the surface hardening technique to control the depth of the case hardened layer, the depth of the case hardened layer may differ from that of a metal substrate of a similarly hardened material not formed by a metal injection molding process.

[0035] However, certain surface hardening techniques can be used on stainless steel materials with little or no significant undesirable effects. For example, a relatively low-temperature diffusion surface hardening technique commercially known under the trademarks S3P (Specialty Stainless Steel Processes) and KOLSTERISING offered by Bodycote plc. This diffusion technique can surface harden relatively low-carbon stainless steels, such as grade 17-4 stainless steel, with minimal loss of corrosion resistance and minimal impact on the underlying strength and ductility of the metal substrate.

[0036] Another technique for producing hardened layers is through surface modification, which modifies the grain structure of the outer metal substrate through work hardening. For example, shot peening (impacting a substrate with high-velocity shot) or ion implantation (impacting a metal substrate with high-velocity particles) processes can be used to create hardened surface layers. Advantageously, these processes do not affect the surface chemistry, i.e., they do not reduce corrosion resistance. However, if foreign particles are present in the shot (e.g., when the shot media is reused), the foreign particles may become embedded in the metal substrate, potentially resulting in reduced corrosion resistance in localized locations. Furthermore, these surface modification processes can pose manufacturing challenges because only the impacted surface is work hardened, requiring strict control of tooling, shot size, strength, and coverage to facilitate consistent results and reduce the potential for substrate distortion.

[0037] In certain embodiments, surface plating, i.e., introducing a thin layer of a metal compound onto a substrate, can be used to create desirable surface hardness characteristics in surgical stapler sliding components. Examples of types of materials that can be used for surface plating to impart surface hardness include chromium, electroless nickel, diamond-like coatings, and ceramics. Advantageously, depending on the material selected, surface plating can be a dip process that can be performed at the component level with consistent surface characteristics. However, surface plating can affect the weldability of the component because the plating compound will be present in the weld base material, affecting the component's strength. Furthermore, even hard surface plating can be relatively brittle and prone to unwanted cracking and particulation when subjected to high loads at point contacts. In surgical stapler components, in certain instances, the engagement of the firing member flanges into their respective channels can be substantially point contact, especially when there is jaw misalignment or when a large tissue section is clamped between the jaws.

[0038] In certain embodiments, the metal substrate of a sliding component of a surgical stapler can have a face coating applied to it to provide desirable operating characteristics. However, face coatings generally do not adhere to the metal substrate as well as face plating. Furthermore, like face plating, face coatings can particulate under load during use. Thus, it is preferable to use a biocompatible face coating material. Furthermore, if a face coating is applied before welding the material substrates, it can form part of the weld matrix and reduce the strength of the welded component. Therefore, masking the welding location or coating after the welding operation can be selected to minimize the effect of the face coating on the weldability of the substrate.

[0039] Various surface coatings can be applied to metal substrates to improve sliding performance. For example, in certain embodiments, lubricants, such as those commercially available under the trademark KRYTOX from Chemours Company or MOLYKOTE from Dow Corning Corporation, can be applied to the sliding surfaces. In other embodiments, dry film polytetrafluoroethylene (PTFE) coatings can be applied to sliding surfaces to enhance lubrication therebetween. For example, coatings commercially available as Dry Film RA coatings from Donwell Company, Inc. can be applied to sliding components of surgical instruments. PTFE dry film materials may be suitable for use in patient contact applications and can be strategically applied at the component level by spraying or through a dipping process.

[0040] In certain embodiments, sliding performance can be improved by applying bone wax as a surface coating to act as a lubricant between the sliding surfaces. Various bone wax compositions are commercially available, typically comprising primarily beeswax. Bone wax is suitable for use in patient-contact applications because it is traditionally applied to reduce bleeding from bone surfaces during medical procedures. Desirably, bone wax is tacky and retains well on the surface to which it is applied. Furthermore, bone wax generally undergoes minimal particulation even in the case of point-contact engagement between sliding surfaces. However, bone wax can have a relatively low melting transition temperature (which can be approximately 120°F for certain bone wax compositions). This means that the expected temperature ranges for sterilization and shipping must be evaluated to reduce the likelihood of the applied bone wax melting and pooling. Furthermore, because bone wax is typically applied manually to the target surface, uniform application to concave surfaces, such as the jaw assembly channel, may require specialized application tools and procedures.

[0041] Referring to FIG. 9A, a schematic cross-sectional view of a metal substrate surface for use as a sliding surface of a surgical stapling device is shown. As discussed above, in view of various considerations regarding material selection, stainless steel materials are preferred for use in sliding components of surgical stapling devices, such as the firing member and jaw members of a surgical stapler jaw assembly. However, metal-on-metal sliding engagement can subject these materials to unwanted abrasive wear. Therefore, it is desirable to prepare the sliding surface to resist abrasion. In the illustrated embodiment, the component comprises a metal substrate 240 having a first strength and a first hardness. A surface layer 242 of the metal substrate 240 is hardened to a second hardness greater than the first hardness. For example, in certain embodiments, surface hardening is used to produce a surface layer 242 having a depth D at the second hardness. In some embodiments, the surface hardening method uses a diffusion process. In certain embodiments, a low-temperature diffusion surface hardening process is used.

[0042] 9A, in certain embodiments, a first side coating layer 244 can be deposited over the metal substrate 240 and its hardened surface layer 242. For example, in some embodiments, it may be desirable to select the first side coating to inhibit metal-to-metal contact. Additionally, because certain surface hardening methods tend to reduce the corrosion resistance of stainless steel materials, in certain embodiments, it may be desirable for the first side coating layer to provide an antioxidant.

[0043] 9A , in certain embodiments, the surgical stapler component can further include a second face coating layer 246 overlying the first face coating layer 244. The second face coating layer 246 can be selected to reduce wear over multiple sliding engagement cycles. For example, in certain embodiments, a bone wax composition can be disposed over the entire sliding surface to provide sliding lubrication properties over multiple reload cycles. Advantageously, the bone wax composition can improve the sliding of the surgical stapler component at sliding contact, even when increased point contact occurs due to incidental misalignment.

[0044] Continuing with reference to FIG. 9A , another aspect of surface preparation for a sliding component of a surgical stapler is the surface finish. In the case of a sliding surface, it may be undesirable for the surface finish of the sliding component to be either relatively smooth (e.g., less than 25 μin roughness) or have a relatively high roughness (e.g., greater than 75 μin roughness). Very smooth sliding surfaces have a relatively large theoretical contact area and few surface irregularities. That is, these smooth surfaces may tend to facilitate abrasion or cold welding during sliding engagement. In contrast, relatively rough surfaces may result in relatively high frictional forces and particulation as the irregularities bond with each other. A sliding surface having a relatively moderate roughness (e.g., about 25 μin to 75 μin) may desirably experience less abrasion and have a moderate frictional force compared to relatively less rough and relatively rough surfaces. A moderate roughness may also desirably retain a surface coating when the coated surface is in sliding engagement. In certain embodiments, a moderately rough surface having a surface roughness of about 25 μin to 75 μin can be prepared by the tumbling process.

[0045] Referring to Figure 9B, a schematic cross-sectional view of another embodiment of a metal substrate for use as a sliding surface of a surgical stapling device is shown. Similar to the embodiment of the metal substrate shown above with reference to Figure 9A, the illustrated embodiment of the metal substrate comprises a metal substrate core 240, a first coating layer 244, and a second coating layer 246. In certain embodiments, the first coating layer 244 can comprise a dry film, and the second coating layer can comprise a bone wax layer. However, unlike the metal substrate embodiment of Figure 9A, the metal substrate 240 does not include a hardened surface, as shown in Figure 9B.

[0046] In view of the above, there are various embodiments of material selection and surface preparation for achieving desirable sliding performance for the firing member, first jaw, and second jaw without wear over a desired number of firing cycles. In one embodiment, the firing member and jaws of the jaw assembly can comprise grade 17-4 stainless steel material. The 17-4 stainless steel material can be heat treated to the H900 condition (corresponding to a hardness of approximately 45 Rockwell C). The surface layer of the material can be case hardened to a hardness of approximately 70 Rockwell C. For example, in some embodiments, a diffusion process, such as the S3P process available from Bodycote plc, can provide a hardened surface of approximately 65-70 Rockwell C with a case depth of approximately 25-40 microns. The firing member and jaws of the jaw assembly can be tumbled to a moderate surface roughness. For example, the components can have a surface roughness of approximately 25-75 microns. In one embodiment, the components have a surface roughness of approximately 50 microns. A first coating layer of PTFE dry film can be applied. This first coating layer can prevent corrosion on the hardened surface and inhibit metal-to-metal contact. The component can further include a second coating layer of a bone wax composition. Advantageously, this combination of materials and processes results in a jaw assembly and firing member that withstands wear when used repeatedly with multiple single-use reloadable cartridges.

[0047] Other embodiments of the firing member, first jaw, and second jaw of the surgical stapler comprise grade 420 stainless steel material heat treated to a hardness of about 55 Rockwell C. The components can be tumbled to a moderate surface roughness. The components can include a first coating layer of a PTFE dry film and a second coating layer of a bone wax composition.

[0048] Other embodiments of surgical stapler components, including at least one of the firing member, first jaw, and second jaw, comprise grade 17-4 stainless steel. The material is heat-treated to a hardness of approximately 45 Rockwell C. For example, as described above, in certain embodiments, the material can be heat-treated to an H900 condition. No further surface hardening is performed. The components can have a moderately rough surface finish, which can be achieved by a tumbling process. The components can include a first coating layer of PTFE dry film and a second coating layer of a bone wax composition. In certain embodiments, one or more of the firing member, first jaw, and second jaw components can be formed from grade 17-4 stainless steel using a metal injection molding process. Certain metal injection molding processes can result in a metal substrate with relatively high porosity compared to corresponding machined components. Surface hardening techniques for such porous metal injection molded components can produce a relatively deep, but correspondingly relatively brittle, hardened surface layer, which can affect the bulk properties of the surface-hardened component. That is, embodiments of surgical stapler components without a separate surface hardening process may be desirable when the components are formed in a metal injection molding process that can produce a relatively porous metal substrate.

[0049] In the above-described embodiments, the components are prepared so that the face hardness of the jaws and firing member is relatively high and substantially the same (at least about 45 Rockwell C to about 70 Rockwell C). In other embodiments, it is contemplated that the firing member can have a slightly lower face hardness than the jaw members. For example, the firing member can have a face hardness that is up to about 10 Rockwell C less than the face hardness of the jaws.

[0050] Furthermore, while in the above-described embodiments, the surface hardening is provided by diffusion or heat treatment, in other embodiments, it is contemplated that shot peening or another work-hardening technique may be applied to work-harden the surface layer of the metal substrate of the component. This work-hardened surface layer may then be coated with one or more coating layers.

[0051] 10 , a method of preparing a metal substrate for use as a sliding component in a surgical stapler is shown. In certain embodiments, the method can include providing a metal substrate 260. As discussed above, in certain embodiments, the metal substrate can include a stainless steel material, such as grade 17-4 stainless steel or grade 420 stainless steel. In certain embodiments, providing the metal substrate can include metal injection molding the metal substrate component.

[0052] Continuing with reference to FIG. 10 , the method further includes step 262 of hardening the metal substrate to a desired hardness. In certain embodiments, hardening the metal substrate can include heat-treating the metal substrate. For example, in certain embodiments, hardening the metal substrate includes heat-treating the metal substrate to an H900 condition, which corresponds to a hardness of approximately 45 HRC. In various embodiments, hardening the metal substrate can include surface-hardening the metal substrate with a diffusion process. In other embodiments, hardening the metal substrate can include work-hardening a surface layer of the metal substrate, such as by shot peening. In certain embodiments, such as those shown schematically in FIG. 9B , the metal substrate is hardened to a hardness of approximately 45 HRC by heat treatment without further surface hardening. In other embodiments, such as those shown schematically in FIG. 9A , the metal substrate is hardened with a heat treatment process followed by surface hardening, such as by a diffusion process, to achieve a relatively high surface hardness. In some embodiments, the surface layer can be hardened to approximately 45 HRC to 75 HRC. It may be desirable to harden the surface layer to at least approximately 55 HRC. In certain embodiments, the surface layer is hardened to about 70 HRC. In certain embodiments, a metal substrate forming a firing member component for a surgical stapler is surface hardened to a first hardness, and a metal substrate forming a first jaw and a second jaw is surface hardened to a second hardness different from the first hardness. In certain embodiments, the second hardness is within about 10 HRC greater than the first hardness.

[0053] 10 , in certain embodiments, the method further comprises imparting a medium surface finish 264. In certain embodiments, imparting a medium surface finish can include tumbling the component. In certain embodiments, the medium surface finish can include a surface roughness of about 25 μin to 75 μin. In some embodiments, the surface roughness is about 50 μin.

[0054] 10 , in certain embodiments, the method further comprises applying at least one side coating 266. In certain embodiments, applying at least one side coating comprises applying a first side coating and applying a second side coating. In certain embodiments, applying at least one side coating comprises applying a PTFE dry film and applying a bone wax composition.

[0055] While this application discloses certain preferred embodiments and examples, those skilled in the art will recognize that the invention extends beyond the specifically disclosed embodiments to other alternative embodiments and / or uses of the invention and obvious modifications and equivalents thereof. Moreover, various features of these inventions can be used alone or in combination with other features of these inventions other than those expressly described above. Thus, it is intended that the scope of the invention disclosed herein should not be limited by the particular disclosed embodiments described above, but should instead be determined solely by a fair reading of the claims that follow.

Claims

1. A surgical instrument comprising: a first jaw, and a second jaw pivotally coupled to the first jaw; an end effector comprising: a firing member longitudinally slidable relative to the end effector to pivotally move the second jaw relative to the first jaw to actuate the end effector; Equipped with At least one of the first jaw, the second jaw, and the firing member comprises: a metal substrate formed of a metal stainless steel material having a first hardness, the metal stainless steel material of the metal substrate having a surface layer hardened to a surface hardness greater than the first hardness; a dry film surface coating disposed on the surface layer of the metal substrate; and a bone wax layer disposed on the dry film surface. A surgical instrument characterized by:

2. A surgical instrument as described in claim 1, characterized in that the surface layer has the surface hardness to a predetermined depth.

3. 10. The surgical instrument of claim 1, wherein the surface layer is hardened to a surface hardness in the range of about 45 HRC to about 70 HRC.

4. The surgical instrument of claim 1 , wherein the surface layer is formed by a diffusion process.

5. 10. The surgical instrument of claim 1, wherein the metal substrate comprises a grade 17-4 stainless steel material.

6. 6. The surgical instrument of claim 5, wherein the metal substrate is heat treated to H900 conditions.

7. 10. The surgical instrument of claim 1, wherein the metal substrate comprises a grade 420 stainless steel material.

8. 10. The surgical instrument of claim 1, wherein the first jaw, the second jaw, and the firing member each comprise the metal substrate having the first hardness of approximately 45 HRC and the surface hardness in the range of approximately 65-70 HRC.

9. 10. The surgical instrument of claim 1, wherein the metal substrate has a surface finish roughness of between about 25 and 75 microns.

10. The surgical instrument of claim 9, wherein the metal substrate comprises a tumbled surface finish.

11. The surgical instrument of claim 1, comprising a surgical stapler, the surgical stapler comprising: an elongated shaft extending from a proximal end to a distal end; the end effector comprising a jaw assembly at the distal end of the elongate shaft; The jaw assembly includes: a cartridge support defining the second jaw, the cartridge support configured to receive a reloaded cartridge having a plurality of staples disposed therein; and an anvil defining the first jaw, the cartridge support and the anvil being pivotally movable between open and closed configurations; Equipped with the firing member is longitudinally slidable in engagement with the cartridge support and the anvil in the closed configuration to fire staples; 2. The surgical instrument of claim 1.

12. 12. The surgical instrument of claim 11, wherein the metal substrate is case hardened to at least about 55 HRC.

13. 12. The surgical instrument of claim 11, wherein the metal substrate is case hardened using a diffusion process.

14. 12. The surgical instrument of claim 11, wherein the anvil, the cartridge support, and the firing member each comprise a hard-faced metal substrate, a dry film surface coating disposed on the metal substrate, and a layer of bone wax disposed on the dry film surface.

15. A method for manufacturing an end effector for a surgical instrument according to claim 1, comprising: providing the first jaw member, the second jaw member, and the firing member, each comprising the metal substrate; hardening the metal substrate of at least one of the first jaw member, the second jaw member, and the firing member to produce the surface layer having the surface hardness; applying a dry film coating to the cured at least one of the first jaw member, the second jaw member, and the firing member; applying a bone wax composition to at least one of the first jaw member, the second jaw member, and the firing member; A method comprising:

16. 16. The method of claim 15, wherein providing the first jaw member, the second jaw member, and the firing member comprises forming at least one of the first jaw member, the second jaw member, and the firing member from forged metal.

17. 16. The method of claim 15, wherein providing the first jaw member, the second jaw member, and the firing member comprises metal injection molding at least one of the first jaw member, the second jaw member, and the firing member.

18. 16. The method of claim 15, wherein hardening the metal substrate of at least one of the first jaw member, the second jaw member, and the firing member comprises case hardening the metal substrate using a diffusion process.

19. 16. The method of claim 15, wherein hardening the metal substrate of at least one of the first jaw member, the second jaw member, and the firing member comprises hardening the metal substrate using a shot peening process.

20. 16. The method of claim 15, wherein the surface hardness is at least about 55 HRC.

21. 21. The method of claim 20, wherein hardening the metal substrate of at least one of the first jaw member, the second jaw member, and the firing member comprises hardening the metal substrate of all of the first jaw member, the second jaw member, and the firing member to the surface hardness.

22. 21. The method of claim 20, further comprising hardening the metal substrate of another one of the first jaw member, the second jaw member, and the firing member to a second hardness different from the surface hardness.

23. the firing member is hardened to the surface hardness, and the first jaw member and the second jaw member are hardened to the second hardness; the second hardness is less than about 10 HRC greater than the surface hardness; 23. The method of claim 22.

24. 16. The method of claim 15, further comprising tumbling the metal substrate of the at least one of the first jaw member, the second jaw member, and the firing member prior to applying a dry film.

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