Surgical stapling procedures have been in practice for over 100 years. Hungarian physician Dr. Humor Hultl is credited as the first surgeon to utilize stapling on a patient. Various stapling devices have been developed over the years, but the basic concept is unchanged and relies heavily on anvils with “precisely shaped pockets” to produce well-formed and secure staples. Typical surgical staples utilize stainless steel and titanium alloys which fire with controlled force sometimes excising and joining tissues simultaneously.
The consistent shape and strength of the stapled tissue depends on the reliable and precisely formed staple shapes when the fired staples strike the anvil pockets. The process of staple formation can be seen in this YouTube video demonstration published by BusinessWire on Covidien’s Tri-Staple (TM) technology device.
Liquidmetal alloys material properties and processes provide a unique combination of advantages for medical stapling anvils applications.
The top 4 advantages Liquidmetal alloys provide are:
- Superior As-Cast Surface Finishes: Liquidmetal As-Cast Surface finishes are excellent and do not require post-molding operation clean-up or polishing like many other processes. Process flaws such as voids, cracks and non-fill conditions that can occur with other technologies are avoided because Liquidmetal alloys are melted and injected while fully liquid and viscous. There are no debinding or sintering steps or casting shell and tree removal requirements as required in MIM (metal injection molding) and investment casting respectively. The surface geometry accurately mimics injection mold surfaces with remarkable precision Anvils made in naturally hard Liquidmetal alloy can provide superior pocket surface finish, which allows titanium staples consistent, uniform, and low-force formation.
- Pocket-to-pocket dimensional accuracy: Liquidmetal alloy’s low solidification shrinkage rate (0.2%) provides outstanding accuracy providing precise pocket-to-pocket alignment. Dimensional control is near equivalent to cold forming or stamping operations to form staple pockets but provides the benefit of no unusual surface conditions that can occur during cold forming stamping operations. Since Liquidmetal injection molding utilizes precise molds Pocket-row straightness is also excellent and pocket-to-pocket location repeatability is outstanding.
- Molded-in Camber for proper alignment to staple cartridge when clamped to tissue: No secondary operations are needed to adjust anvil profile over its length to accommodate the flexural effect of forces applied when clamping on tissue. Liquidmetal alloys have excellent memory when flexural stress is applied, which allows the firing of multiple staple cartridges.
- Lot-to-lot variability limited to mold cavity-to-cavity variability: The molding process is the first and last process that provides the dimensional results. The Liquidmetal molding process does not have multiple process steps that can add multiple sources of variability. Liquidmetal parts do not require any heat treating, tempering or annealing to relieve residual stresses or to achieve final mechanical properties. As a result, there are fewer sources of variation introduced than other manufacturing technologies. The Liquidmetal injection molding process is one-step and achieves the nearest-to-net part achievable in a metal casting process.