Detection of In Vivo Foot and Ankle Implants by Walkthrough Metal Detectors

Abstract

Background: Heightened security concerns have made metal detectors a standard security measure in many locations. While prior studies have investigated the detection rates of various hip and knee implants, none have looked specifically at the detection of foot and ankle implants in an in vivo model. Our goals were to identify which commonly used foot and ankle implants would be detected by walkthrough metal detectors both in vivo and ex vivo. Methods: Over a 7-month period, 153 weightbearing patients with foot and ankle hardware were recruited to walk through a standard airport metal detector at 3 different program settings (buildings, airports, and airports enhanced) with a base sensitivity of 165 (arbitrary units), as currently used by the Transportation Security Administration. The number of implants, location and type, as well as the presence of concomitant hardware outside of the foot and ankle were recorded. To determine the detection rate of common foot and ankle implants ex vivo, different hardware sets were walked through the detector at all 3 program settings. Results: Seventeen patients were found to have detectable hardware at the buildings, airports, and airports enhanced settings. An additional 3 patients had hardware only detected at the airports enhanced setting. All 20 of these patients had concomitant metal implants outside of the foot and ankle from other orthopaedic procedures. All patients with foot and ankle implants alone passed through undetected. Seven hardware sets were detected ex vivo at the airports enhanced setting. Conclusion: Our results indicate that patients with foot and ankle implants alone are unlikely to be detected by walkthrough metal detectors at standard airport settings. When additional hardware is present from orthopaedic procedures outside of the foot and ankle, metal detection rates were higher. We believe that these results are important for surgeons in order to educate patients on how they might be affected when walking through a metal detector such as while traveling. Level of Evidence: Level II, prospective comparative study.