When you’re out in the sticks, you want to travel light. This limits the amount of diagnostic supplies you can carry, and generally wilderness medics trend towards carrying supplies that can do multiple jobs. Thus, necessity being the mother of invention, these authors wanted to use an item they already carry in a novel way.
Most of us diagnose fractures with radiography. While x-ray machines may be portable, I’ve yet to see any manufacturers produce an off-road version. Prior studies have shown relatively decent sensitivity and specificity using tuning forks and stethoscopes, by way of listening for a difference in vibratory transmission down the length of the bone. The idea is that a fracture will stop propagation of the waves, or at least reduce them significantly. Then you can compare to the unaffected side and identify an occult fracture.
Since carrying a tuning fork in your pack adds weight without a large amount of utility (maybe you can make a mouth harp out of it at the campfire), the authors tried to find another commonly carried object that could reliably produce a constant vibration. What they came up with was an iPhone 3S using the iVibe app. Not wanting to break the bones of alive patients, they used a cadaver model for the fractures, and a convenience sample of 27 EM residents and 1 EM attending.
Sadly, they weren’t very accurate, with a sensitivity of 73% and specificity of 83%. This is lower than the multiple tuning fork studies, and would probably be even lower in the austere environment, with outside noise, and clothed patients. The authors themselves say this is a pilot study that needs further validation. I would argue that as more people carry ultrasound devices, it will supersede the utility of lower sensitivity testing.
I wouldn’t go out planning on using them for that purpose, but if needed, it is better than nothing. And hey, if it keeps you from calling a helicopter to evacuate someone, or allows you to call one appropriately, then maybe it is worthwhile. At least you’re already carrying the phone and the stethoscope.
Matzek BA, Fivecoat PT, Ritz RB. Novel approach to the diagnosis of fractures in an austere environment using a stethoscope and a cellular phone. Wilderness Environ Med. 2014 Mar;25(1):99-102. [PMID 24393702]
EBM Gone Wild