Sternal wires are small, medical-grade metal sutures used to hold the breastbone (sternum) together after open-heart surgery (sternotomy). These wires remain permanently in the body to allow the bone to heal securely. While these metallic implants rarely trigger the alarms of standard walk-through detectors, the potential for an alarm exists depending on the specific equipment and its operating sensitivity. Understanding the materials and screening technology can help prepare for a smoother experience at checkpoints.
Sternal Wires and the Physics of Detection
Sternal wires seldom set off metal detectors due to their physical properties and low metallic mass. They are typically composed of surgical-grade stainless steel or titanium alloys, chosen for their biocompatibility and low magnetic permeability. Medical-grade stainless steel is often non-ferromagnetic or only weakly magnetic, making it more difficult for electromagnetic detectors to identify compared to highly magnetic (ferrous) metals.
Metal detectors operate based on a sensitivity threshold that must be met to trigger an alarm. Sternal wires are thin and small, meaning their total metallic mass is very low, often falling below the minimum threshold required for detection. The wires are also deeply embedded beneath the skin, muscle, and bone, which further disperses the electromagnetic field signal. Consequently, the combination of non-ferromagnetic material, minimal mass, and deep placement prevents most standard security arches from registering the implant.
Varying Sensitivity of Security Scanning Technologies
The probability of detection changes significantly depending on the type of scanning technology encountered. Walk-through metal detectors typically use Very Low Frequency (VLF) or Pulsed Induction (PI) technology to create a broad electromagnetic field. These devices are designed to detect larger metallic signatures, which is why the low metallic mass of sternal wires usually passes through unnoticed. The high sensitivity required to detect the wires would also cause the detector to alarm for minor items like belt buckles, leading to impractical secondary screening levels.
Handheld wands are more localized and operate at a higher, focused sensitivity than walk-through units. If a walk-through detector does not alarm, a handheld wand passed directly over the chest area during a secondary screening is the device most likely to detect the metal wires. Millimeter-wave scanners (full-body imaging booths) operate differently by bouncing harmless radio waves off the body to detect density and shape anomalies. Since this technology does not primarily rely on detecting metal composition, it is highly unlikely to be triggered by the wires themselves.
Practical Steps for Navigating Security Checkpoints
Proactive communication is the most effective strategy when approaching security checkpoint with a medical implant. Before entering the walk-through metal detector or body scanner, inform the security officer that you have internal sternal wires from a prior surgery. This advance notice helps the staff understand the potential cause if an alarm is triggered and prepares them for the possibility of secondary screening.
Carrying a medical implant card or a brief note from your doctor is a helpful step, even though security agencies often state that such documentation may not be accepted as proof. While these cards can speed up the process by communicating the presence of an implant, security personnel are trained to rely on their own screening procedures. If the metal detector or handheld wand alarms, the standard protocol is a secondary screening, which usually involves a targeted pat-down or a closer wanding of the area. If you are selected for a secondary screening, you have the right to request a private screening with a witness present to ensure comfort and privacy. Security staff are accustomed to screening individuals with medical implants and will proceed with professionalism and discretion to resolve the issue efficiently.