An Apparatus for Testing Devices Used for Determining Protective

Foot Sensation

An Apparatus for Testing Devices Used for Determining Protective

Foot Sensation

U.S. Department of Health and Human Services (HHS)Health Resources and Services Administration (HRSA)

The Bureau of Primary Healthcare (BPHC)

U.S. Department of Health and Human Services (HHS)Health Resources and Services Administration (HRSA)

The Bureau of Primary Healthcare (BPHC)

CAPT James Foto, PE, C.Pedjfoto@hrsa.gov

USPHS Scientific and Training SymposiumEngineer Category Day

Lower Extremity Amputations

> 82,000 / year

- National Diabetes Fact Sheet, CDC, 2003

“The primary objective of neuropathic foot care is to reduce the epidemic occurrences of lower extremity amputations.”

Discussion Points

• Loss of Protective Sensation• Monofilament Research• Automated Filament Tester (AFT)• Testing the AFT

Discussion Points

• Loss of Protective Sensation• Monofilament Research• Automated Filament Tester (AFT)• Testing the AFT

“The whole problem is really one of mechanics, not of medicine. The biological responses of these denervated limbs are qualitatively similar to those of normal limbs. It is the permitted pattern of mechanical stress that is different.”

“The whole problem is really one of mechanics, not of medicine. The biological responses of these denervated limbs are qualitatively similar to those of normal limbs. It is the permitted pattern of mechanical stress that is different.”

Paul W. BrandPaul W. Brand

Causes of Injury Resulting from Mechanical Stress

Causes of Injury Resulting from Mechanical Stress

Acute Trauma• likely cause: nails, glass, accidents

Ischemia• likely cause: tight shoes, foreign

objects in shoes, wrinkles in socks or hosiery

Repetitive Stress• likely cause: normal activities of

daily living such as walking

Acute Trauma• likely cause: nails, glass, accidents

Ischemia• likely cause: tight shoes, foreign

objects in shoes, wrinkles in socks or hosiery

Repetitive Stress• likely cause: normal activities of

daily living such as walking

Loss of Protective Sensation

Loss of Protective Sensation

Discussion Points

• Loss of Protective Sensation• Monofilament Research• Automated Filament Tester (AFT)• Testing the AFT

Monofilament Research• 1890 – Von Frey used varying thickness horse hair• 1960 – Semmes & Weinstein used nylon filament material• 1985 – VonPrince, Werner, Omer, Bell, Brand, Buford• 1986 – Birke & Sims, HD and DM neuropathic feet • 1988 – Bell & Buford, filament repeatability and reliability• 1988 – Holewski et al, extent and progression of neuropathy• 1989 – Mueller et al, interrater and intrarater reliability• 1998 – Birke & Rolfson, Self Administer• 2000 – Booth and Young, bench test w/ load cell• 2004 – Lawrence et al, filament physical properties and wear• 2009 – Feng et al, variation in application methodology

Semmes-Weinstein5.07 (10g) Monofilament

• Designed to buckle at 10g force

π2EI

L2F =

b

(Euler’s Buckling Formula)

Semmes-Weinstein5.07 (10g) Monofilament

• Designed to buckle at 10g force• Standard device for testing LOPS

Semmes-Weinstein5.07 (10g) Monofilament

• Designed to buckle at 10g force• Standard device for testing LOPS• “Feel” / “no feel” binary response

Point of Application

Holewski et al, 1988

Discussion Points

• Loss of Protective Sensation• Monofilament Research• Automated Filament Tester (AFT)• Testing the AFT

Automated Filament Tester

Bench Top Tester Components

• 10 gram Load Cell & Signal Conditioner– AL Design ALD-MEGA-10G– Dataforth 8B38 Isolated Strain Gage SG

• Linear Potentiometer• DAQ Programming Language• Data Acquisition Device• Ball Screw Actuator

Bench Top Tester Components

• 10 gram Load Cell & Signal Conditioner• Linear Potentiometer

– Unimeasure LX-PA-3.8• DAQ Programming Language• Data Acquisition Device• Ball Screw Actuator

Bench Top Tester Components

• 10 gram Load Cell & Signal Conditioner• Linear Potentiometer• DAQ Programming Language

– National Instruments LabVIEW• Data Acquisition Device• Ball Screw Actuator

Bench Top Tester Components

• 10 gram Load Cell & Signal Conditioner• Linear Potentiometer• DAQ Programming Language• Data Acquisition Device

– NI USB-6009 14bit / 48ks/sec Multifxn DAQ• Ball Screw Actuator

Bench Top Tester Components

• 10 gram Load Cell & Signal Conditioner• Linear Potentiometer• DAQ Programming Language• Data Acquisition Device• Ball Screw Actuator

– Hennkwell PK22G2150-062 12v DC Gear Mtr

Labview Programming

Discussion Points

• Loss of Protective Sensation• Monofilament Research• Automated Filament Tester (AFT)• Testing the AFT

Automatic Filament Tester

Output Data

Packaged Filaments

Thank You

CAPTJames Foto, PE, C. PedThe National Hansen’s Disease Programs

1770 Physicians Park DrBaton Rouge, LA 70816

(225) 756-3789jfoto@hrsa.gov