Endoscopic linear cutting staplers are used in many minimally invasive procedures to staple and divide tissue, including during tissue resection and the construction of some anastomoses.
During firing, staples are driven through compressed tissue and formed against the anvil. The way they form depends on the interaction between the tissue, the selected reload and the stapling system.
Understanding this process helps explain why tissue characteristics, compression, staple height, reload selection and the firing process are important considerations in surgical stapling.
How Do Surgical Staples Form?
In conventional endoscopic linear cutting staplers, staples are held within the cartridge in an open configuration, commonly described as U-shaped.
Before firing, the stapler jaws are positioned around the target tissue and closed. The tissue is compressed between the cartridge and the anvil.
During firing, the staples are driven from the cartridge through the compressed tissue. As the staple legs contact shaped pockets in the anvil, they are guided inward to form the characteristic B-shaped configuration used by many surgical staplers.
At the same time, rows of staples are formed on both sides of the intended transection line while a blade divides the tissue between them. The number, arrangement and dimensions of the staple rows vary between stapling systems.
Because each staple is formed around compressed tissue, the characteristics of the tissue and its interaction with the stapling system can affect the final staple form.
Why Is Staple Line Formation Important?
Individual staples together form the staple line.
For the stapling system to function as intended, the staples need to pass through the tissue and form appropriately against the anvil. The final B-shaped configuration is therefore created during the firing process rather than simply being inserted into the tissue.
Staple formation is one technical component of staple-line integrity. After firing, the staple line is assessed in the context of the procedure.
Staple formation should not, however, be considered in isolation. The condition of the tissue, the surgical technique and other procedural factors may also be relevant to the surgical site.
What Can Affect Staple Formation?
Biological tissues vary in thickness, density and mechanical characteristics, and these properties can also be altered by disease. Inflammation, oedema, fibrosis, scarring or tumour-associated changes may affect how thick or firm tissue is and how it responds to compression. Even within the same organ, tissue characteristics may not be uniform.
These differences matter because staples are formed around tissue while it is compressed between the cartridge and the anvil.
The relationship between the tissue and the stapling system therefore needs to be considered before firing.
Why Does Tissue Compression Matter?
Before staples are formed, tissue is compressed between the stapler jaws.
Compression reduces the thickness of the tissue held between the cartridge and the anvil. Different tissues, however, do not respond to compression in the same way.
A thicker or firmer tissue may behave differently from thinner or more compressible tissue. The amount of tissue within the jaws and the way it responds to compression therefore influence the conditions under which the staples are formed.
This is one reason stapling systems provide different reloads intended for different tissue ranges.
How Is Staple Height Selected?
Stapling systems provide reloads with different staple dimensions and staple heights for different tissue ranges.
Before firing, the surgeon assesses the tissue being stapled and selects a reload appropriate for its thickness and characteristics according to the specifications of the particular stapling system.
Closed staple height generally refers to the specified height of the staple after it has been formed. This needs to be considered in relation to the thickness of the compressed tissue.
If tissue is too thick for the selected reload, it may fall outside the range for which that reload is designed. Likewise, tissue that is too thin may not be appropriate for a reload intended for thicker tissue.
Reload colours, staple heights and recommended tissue ranges are device-specific and should not be assumed to be equivalent between stapling systems.
Some reloads also use different staple heights across the staple rows rather than the same formed height in every row. These configurations form part of the overall cartridge design and vary between stapling platforms.
Staple-Line Formation in the Wider Clinical Context
In gastrointestinal surgery, staple-line formation may form part of an anastomosis.
Anastomotic leakage is an important postoperative complication, but it is multifactorial. Patient characteristics, tissue condition, perfusion, anastomotic tension, disease-related factors and procedural factors may all contribute.
Staple-line formation is therefore one technical consideration within a much broader clinical picture. Appropriate staple formation should not be interpreted as preventing anastomotic leakage, and anastomotic leakage should not be attributed to staple formation alone.
What Happens During Stapler Firing?
Surgical staplers may use either manual or powered mechanisms to drive the firing sequence.
In a manually fired stapler, the surgeon provides the mechanical force required to advance the firing mechanism. In a powered stapler, a motorised system drives the firing sequence.
Staple formation takes place while the stapler advances through tissue held between the jaws. The mechanical resistance encountered during this process may vary along the firing path.
Some powered stapling systems provide visual, audible or electronic information during firing. The type of information available differs between platforms.
Real-Time Firing Curve™ with iREACH IRIS
The iREACH IRIS Powered Stapler incorporates a Real-Time Firing Curve that displays continuous, location-specific firing-force information mapped along the staple line during the firing sequence.
The system also provides visual and audible feedback during key stages of operation.
As the stapler advances through the tissue, the firing curve provides information about the force encountered at different locations along the firing path.
This gives the surgeon additional information about the firing process while it is taking place. It does not directly determine whether staples have formed correctly and does not replace tissue assessment, appropriate reload selection or inspection of the staple line after firing.
Learn more about iREACH IRIS Powered Stapler
Understanding Staple Formation in Surgical Stapling
In endoscopic linear cutting staplers, staple formation involves a sequence of tissue compression, staple deployment and formation against the anvil.
The resulting B-shaped staples form the staple line, but their formation takes place within tissue that can vary considerably in thickness and mechanical characteristics.
Understanding how tissue characteristics, reload selection, staple height and the firing process interact provides useful context for surgical stapling.
Powered stapling systems may also provide information during firing. The iREACH IRIS™ Real-Time Firing Curve™, for example, displays location-specific firing-force information during the firing sequence, providing additional information about the firing process without replacing tissue assessment, reload selection or post-firing inspection of the staple line.
References
U.S. Food and Drug Administration (FDA). Surgical Staplers and Staples for Internal Use – Labeling Recommendations. Guidance addressing surgical stapler use, tissue thickness, staple selection, staple height and staple-line assessment.
Chekan E, Whelan RL. Surgical stapling device–tissue interactions: what surgeons need to know to improve patient outcomes. Medical Devices: Evidence and Research. 2014;7:305–318.
This article is intended for general educational purposes and does not replace individual medical advice, diagnosis or treatment from a qualified healthcare professional.