Now I know that this sounds a bit like witchcraft, but from reading the referenced medical literature, I believe that this can be a viable method of identifying fractures in some situations. If modern medical care is available, I would recommend that you utilize it and not depend on the use of the tuning fork.
I have found two different ways to use the tuning fork to identify broken bones. The first uses a standard stethoscope and a 128 HZ tuning fork. The idea is that you place the tuning fork on the bone distal (farthest away from the suspected break) and the stethoscope on the other side of the suspected break. Strike the tuning fork and place the tip on the bone distal and listen with the stethoscope on the other side. You should hear less or no sound radiating through the bone than through a normal one. With a leg or arm compare the suspected broken one against the unbroken one.
Here is a reference that was published in the Journal of Athletic Training on the results of a test of this method. It was found to be effective. They tested 37 patients with the following results; radiographs confirmed the tuning fork assessment of fracture in 10; 20 true negative results were also confirmed. False-positive results occurred in 5 patients and false-negative results in 2. If this is a method you may consider using in an emergency situation where medical help is not available, I suggest you read the entire test and the procedure that they followed.
The second method is one that has been tested on stress fractures with good success. It is simply to place the tip of the tuning fork directly on th site of the suspected fracture and see if the pain increases. The article VALIDATION OF TUNING FORK TEST IN STRESS FRACTURES AND ITS COMPARISON WITH RADIONUCLIDE BONE SCAN supports the use of this method. I would suggest you read the whole article
There is other information from various sources that supports the use of a tuning fork to diagnose fractures. Enough to convince me to order a tuning fork. They cost well under $10. Now no one diagnostic tool is fool proof, in case of a possible fracture I would suggest that you get the appropriate medical care for your injury. Remember I am not a Doctor and have no real medical training. If in doubt, always get medical help.