Surgical staples are medical devices used as an alternative to traditional sutures, designed to close incisions or internal wounds quickly and securely. Material selection is governed by two main criteria: mechanical strength and biocompatibility. The material must be robust enough to hold tissue together under tension while remaining inert within the body to prevent rejection or adverse reactions. Staples fall into two primary categories based on their intended use: non-absorbable metals and absorbable synthetic polymers.
Non-Absorbable Materials: Metals Chosen for Strength and Biocompatibility
The majority of non-absorbable surgical staples are made from metals, primarily titanium and surgical-grade stainless steel. Titanium is widely preferred for internal applications due to its exceptional properties as a biomaterial. This metal exhibits a high strength-to-weight ratio, meaning it provides substantial tissue support without adding significant mass.
Titanium also demonstrates superior inertness, resisting chemical reaction with biological tissues and fluids and minimizing inflammation. This resistance is due to a thin, naturally forming oxide layer on the metal’s surface that protects it from corrosion within the body. Furthermore, titanium is non-ferromagnetic, a property that prevents interference with Magnetic Resonance Imaging (MRI) scanners, a significant advantage for patients requiring future diagnostic scans.
Surgical-grade stainless steel, specifically the 316L alloy, is another common material, particularly for external skin staples. The “L” in 316L denotes a low carbon content, which enhances the metal’s corrosion resistance. While stainless steel is highly durable and cost-effective, it may contain trace amounts of nickel. It is used for external skin closure where it will be removed after a brief healing period. These staples provide a strong, immediate closure, distributing tension evenly across the wound edges.
Absorbable Materials: Polymers That Dissolve Over Time
The other major category of surgical staples consists of synthetic polymers that gradually dissolve after their function is complete. These absorbable materials are specifically designed for internal use where a permanent foreign body is undesirable. Common examples include copolymers of polyglycolic acid (PGA) and polylactide (PLA), which are also frequently used in absorbable sutures.
The mechanism by which these polymer staples disappear is called hydrolysis, where water molecules break down the polymer chains. This controlled breakdown occurs slowly over time, allowing the staple to maintain its mechanical strength during the initial healing phase. As the tissue regains its integrity, the polymer material progressively loses mass and strength before being safely metabolized and eliminated by the body.
Absorbable staples eliminate the need for a second procedure to remove internal devices, reducing patient discomfort and surgical risk. For instance, some polylactide-polyglycolide copolymers may be completely absorbed over a period of four to six weeks. This process ensures that no foreign material remains permanently embedded in the tissue once the wound has successfully closed.
Application and Removal: Why Location Dictates Material Choice
The intended location and purpose of the staple determine material selection, dictating whether the device must be removed or dissolve. External staples, typically used to close skin incisions on the torso or scalp, are usually made of stainless steel. These staples are applied quickly and provide excellent wound edge eversion, but they must be manually removed by a healthcare professional once the skin has healed.
Conversely, internal staples are utilized in complex procedures like organ resection or to connect two hollow structures, a process known as anastomosis. In these deep tissue applications, titanium is the preferred non-absorbable choice when permanent closure is required due to its superior biocompatibility and longevity.
Absorbable polymer staples are reserved for internal areas where temporary support is sufficient and long-term foreign material presence could lead to complications. For example, they are sometimes used in cosmetic surgery to close deeper layers beneath the skin or in specific internal anastomoses. The choice between titanium, stainless steel, and a dissolving polymer ultimately depends on balancing the need for immediate strength with the body’s long-term tolerance for a foreign implant.