Another inexpensive but very valuable tool in the examination of the diabetic foot for loss of protective sensation is the 128Hz tuning fork. This is a very important but often underutilized examination tool, much like the 10-gm monofilament it is cheap and easy to perform.

In a paper published by Over, et al. they found the 128 Hz tuning fork test to be reproducible and accurate. It was also found to identify severe neuropathy, even in the presence of  a normal result with the 10-g monofilament test. Their conclusion was that the risk of foot ulcers, which is associated with diminished vibratory sensation, can therefore be detected earlier and more accurately with the CTF test.

The technique

1.  Strike the tuning fork against the palm of your hand hard enough that it will vibrate for approximately 40 seconds.
2.  Apply the base of the tuning fork to the patient’s forehead or sternum and ensure that the vibration sensation is understood.
3.  With the patient’s eyes closed, apply the tuning fork to the bony prominence situated at the dorsum of the first toe just proximal to the nail bed. Ask if the vibration sensation is perceived.
4.  Ask the patient to tell you when the vibration stimulus is stopped, and then dampen the tuning fork with your other hand.
5.  One point is assigned for each vibration sensation perceived (vibration “on”). Another point is assigned if the correct timing of dampening of the vibration is perceived (vibration “off ”).
6.  Repeat this procedure again on the same foot until complete

Video demonstration

Quantitative assessment of diabetic peripheral neuropathy with use of the clanging tuning fork test. Endocr Practice 2007 Jan-Feb; 13(1):5-10. Oyer DS, Saxon D, Shah A.