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?

In this study from England, the 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? The handheld detector was able to pick up most (but not all) spinal implants inside 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 handheld wand was able to detect even a single screw when the wand was held five centimeters (1.25 inches) away from the body. 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 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.

More conclusive studies are needed before patients with spinal metal implants are given the green light to travel via airfare without carrying the necessary paperwork. This is one of only a handful of studies on this topic. Results have varied from study to study further demonstrating the need for closer investigation of airport detection of modern spinal implantation.

Reference: Fahad Chinwalla, MRCS, and Michael P. Grevitt, FRCS (Orth). Detection of Modern Spinal Implants by Airport Metal Detectors. In Spine. November 15, 2012. Vol. 37. No. 24. Pp. 2011-2016.