How do I perform a 10 g (grams) monofilament test?

How to Perform a 10 g Monofilament Test

The 10 g monofilament test should be performed in a quiet, relaxed setting with the patient unable to see where the filament is applied, testing three specific sites on each foot (great toe, third and fifth metatarsal heads) with the monofilament applied perpendicular to the skin until it bends, holding for approximately 2 seconds. 1

Preparation and Equipment

• Use a standardized 10 g (5.07 Semmes-Weinstein) monofilament
• Ensure the testing environment is quiet and relaxed
• Position the patient comfortably with feet supported
• Explain the procedure to the patient

Step-by-Step Testing Procedure

1. Demonstrate the sensation first:

   • Apply the monofilament to the patient's hand, elbow, or forehead so they know what to expect 1

2. Position the patient:

   • Ensure the patient cannot see when or where you are applying the filament 1
   • Have the patient close their eyes during the examination

3. Test the correct sites:

   • Test three specific sites on each foot: 1, 2
     • Great toe (hallux)
     • Third metatarsal head
     • Fifth metatarsal head

4. Apply proper technique:

   • Hold the monofilament perpendicular to the skin surface 1
   • Apply sufficient force to cause the filament to bend or buckle 1
   • Maintain contact for approximately 2 seconds total (approach, skin contact, removal) 1
   • Do not apply over ulcer sites, calluses, scars, or necrotic tissue 1
   • Do not allow the filament to slide across the skin 1
   • Avoid repetitive contact at the same test site 1

5. Ask appropriate questions:

   • Ask the patient if they feel the pressure applied (yes/no) 1
   • Ask where they feel the pressure (left foot/right foot) 1

6. Use proper testing protocol:

   • Apply the monofilament twice at each site 1
   • Include at least one "mock" application where no filament is applied 1
   • This results in three questions per site (two real applications, one mock) 1

7. Interpret results:

   • Protective sensation is present if the patient correctly answers two out of three applications at each site 1
   • Protective sensation is absent with two out of three incorrect answers - the patient is then considered at risk for ulceration 1

Important Considerations

• Monofilament maintenance: Replace monofilaments after testing 10 patients or after 100 compressions, as they lose buckling force with repeated use 2, 3
• Recovery time: Allow monofilaments to recover for 24 hours after extensive use 3
• Quality control: Choose monofilaments from reliable manufacturers, as accuracy varies significantly between brands 3
• Comprehensive assessment: For a complete neuropathy assessment, combine the monofilament test with at least one other neurological test (pinprick, temperature sensation, vibration using 128-Hz tuning fork, or ankle reflexes) 1

Common Pitfalls to Avoid

• Testing over callused areas, which can give false negative results 1, 2
• Applying insufficient pressure that doesn't cause the monofilament to bend 2
• Skipping the mock applications, which help detect false reporting 2
• Using worn-out monofilaments that no longer provide 10 g of pressure 3
• Sliding the monofilament across the skin instead of applying direct pressure 1

By following this standardized approach to monofilament testing, you can effectively screen for loss of protective sensation in patients with diabetes, helping to identify those at risk for foot ulceration and prevent subsequent complications.