One of the easiest and most cost-effective tests to screen for loss of protective sensation is the 10-gm monofilament test. Also known as the Semmes-Weinstein monofilament test (SWM). Studies confirm that loss of pressure sensation using a 10-gm monofilament is highly predictive of future ulceration.

The test is performed with a filament that is intended to bend or buckle when 10-gm of force is applied. Loss of pressure sensation in one or more sites is associated with loss of large fiber nerve function. Ideally at least 4 sites should be tested on each foot, but up to 10 points on the foot are recommened for testing. The figure below demonstrates some of the recommended test sites.

The technique

Start the test by demonstrating the test on a proximal site with the patient responding “yes” or “no” if they recognize the perception of pressure. Then proceed to the recommended sites on the foot. The patient should now have their eyes closed. Apply the monofilament device perpendicular to the skin surface and apply pressure until the monofilament buckles. Continue to hold the pressure for about 1 second and then release. Test each of the 4 recommended sites in a similar manner. When testing try to avoid areas of callus. If areas of callus are present try alternate testing sites, highlighted in light pink, above.

Video demonstration