Surgical staples are small medical devices used to close wounds or reconnect internal tissues after an incision or surgery. A common concern for patients is whether these implanted devices are magnetic, which could potentially cause danger during a Magnetic Resonance Imaging (MRI) scan. The vast majority of modern surgical staples are intentionally manufactured from materials that are not strongly attracted to magnetic fields, making them generally safe for use with MRI technology.
Staple Composition and Purpose
Modern surgical staples are primarily composed of medical-grade metals chosen for their high biocompatibility and mechanical properties. Titanium is the most common material used for internal staples, such as those used in gastrointestinal or thoracic surgery, often remaining in the body permanently. This metal is favored because it is lightweight, strong, and highly resistant to corrosion within the body’s environment.
Stainless steel is also utilized, typically for external skin closures where the staples are meant to be removed shortly after the wound has healed. These devices hold tissue edges together securely, providing a quick and consistent closure that can reduce local inflammatory response and minimize the width of the final scar compared to traditional sutures.
Specialized types of staples are used for different surgical applications, such as linear staplers for tissue resection and circular staplers for connecting two hollow organs, known as anastomosis. The materials ensure the staple retains its shape and strength until the wound or connection is healed. Newer developments include biodegradable staples made from materials like magnesium alloys, designed to dissolve harmlessly within the body over time.
Why Surgical Staples Are Not Magnetic
The reason surgical staples are not “magnetic” in the common sense relates to the physics of their constituent materials. Materials are classified based on their interaction with a magnetic field: ferromagnetic, paramagnetic, or diamagnetic. Ferromagnetic materials, like iron and certain steel alloys, are strongly attracted to a magnet, which would be dangerous inside an MRI machine.
Surgical staples are deliberately made from materials that are either diamagnetic or weakly paramagnetic. Titanium, the material most often used for permanent internal staples, is a weakly paramagnetic metal that is not significantly affected by a powerful magnetic field. The specialized stainless steel alloys used for skin staples are often non-ferromagnetic, meaning they do not possess the strong magnetic attraction that would cause movement or heating.
These materials effectively eliminate the risk of the staple being pulled or moved by the strong magnetic fields generated during an MRI. While metal detectors, such as those in airports, may detect the presence of the metal in the staples, this detection is based on the material’s electrical conductivity, not its magnetic properties.
Staples and MRI Safety
The non-ferromagnetic composition of most surgical staples makes them safe for patients undergoing Magnetic Resonance Imaging. Studies conducted with both 1.5 Tesla and 3 Tesla MRI scanners have shown no significant heating or physical displacement of modern stainless steel or titanium staples. Patients with these staples can typically proceed with necessary diagnostic imaging without elevated risk.
The primary interaction between the staples and the MRI is the creation of a “magnetic susceptibility artifact” on the resulting image. This artifact appears as a localized distortion, which can look like a dark or bright area near the metal object. While the staple itself is stable, this image distortion can sometimes obscure the area of interest if the staple is located too close to the tissue the radiologist needs to examine. Medical staff must be informed of the presence of staples so they can confirm the specific material used and ensure the staple’s location does not interfere with the diagnostic quality of the scan.