Could you please settle an argument for me and my wife? She says because I am so fat, the metal plates and screws in my low back won’t set off the airport security alarms. I’m not so sure. This will be my first time through. Should I take precautions and carry my X-rays with me?

Anyone with a joint replacement knows to carry a special letter from the doctor when traveling through airport security. Even with the documentation, travelers with implants can expect delays while security measures are applied. But what about metal implants in the spine? Are they deep enough and/or surrounded by enough body mass to avoid detection?

These questions were explored by a group of researchers in a recent study from England. Both handheld metal detectors and arch way metal detectors were put to the test. Researchers used volunteers carrying metal implants commonly put in the spine as well as patients with metal plates, screws, rods, disc replacements, and/or cages already surgically implanted. Implants varied in size and weight, region (neck, thoracic spine, low back region), and location (anterior, posterior).

All electronic metal devices used were standard ones approved for use in European airports. The volunteers carrying implants walked through the arch way detectors with different combinations of implants (weight, size, location). Some implants were taped to the arms or legs. Others were carried in pockets.

Then 40 patients with spinal implants walked through. Of course, everyone removed all the usual items (cell phones, jewelry, watches, belts, shoes, and so on). Each person in the study (volunteers carrying metal implants and patients implanted with metal devices) was also tested using the handheld wand type of metal detector.

Would it surprise you to know that not one person set off the archway detector? Body fat did not affect the results.Density of the metal did not influence the alarm mechanism either. Volunteers carrying metal could carry up to seven and a half ounces (215 grams) in one location before detection.

The handheld detector was able to pick up most (but not all) spinal implants inside the body. The handheld wand was able to detect even a single screw when the wand was held five centimeters (1.25 inches) away from the body. The ones that were NOT detected were in the front (anterior) portion of the neck. Anything implanted posteriorly (from the back) did set off the alarm on the handheld detector.

The authors concluded that modern handheld metal detectors are sensitive enough to detect most (but not all) metal hardware in the spine. Even when set at maximum sensitivity, the handheld devices did not trigger an alarm for disc replacements or anterior plates and cages. It is possible the position of the implant makes a difference but this will have to be tested further to know for sure.

It is also likely that detection rates are low because the implants are made of titanium (and not iron like weapons and guns). It is also possible that the technology for archway detectors (developed in the late 1970s) needs to be updated for today’s modern devices. Different manufacturers and models of archway metal detectors may also make a difference that should be investigated.

Keep in mind that this study was done in Europe and may not reflect the kind of results you may get moving through airport detection devices in the United States. It is always advised to carry printed documentation (not just X-rays) such as a letter from your physician when traveling. Even with these sources of proof, you will need to allow an extra measure of time when traveling. Equipment, personnel, and the way security procedures are carried out vary from airport to airport so it’s best to be fully prepared.