Monofilaments: The Good, The Bad & The Ugly Dr Michelle Spruce Canadian Federation of Podiatric Medicine Toronto 2008

The Cast: You have to know where to look!

Monofilament Quiz: The Good

Question 1 What percentage of people die within 5 years of having a lower limb amputation?

Monofilament Quiz: The Good Question 2 How many sites should you test per foot? Question 3 Which site would give you the possible earliest detection of altered sensation? ?

The Monofilament Quiz: The Good Question 4 Why is screening for diabetic neuropathy important? 1.Provides valuable research information 2.Significant risk factor for ulceration 3.Linked to increased plantar pressures

Monofilament Quiz: The Good Question 5 How long after diagnosis do people develop peripheral sensory neuropathy?

Monofilament Quiz: The Good Question 6 Diabetes & its complications have increased prevalence in affluent socio-economic groups? TRUE / FALSE

The Bad

10g Monofilament: Current Application Male, Type 2 Diabetes 42 years of age Cholesterol level 8 mmol/l HbA1c of 10% Smoker Works for food company packaging and transporting frozen food Scars on fingers to right hand

Ulceration: Major Predictive Risk Factors Duration of diabetes Neuropathy (VPT, 10g mono, vibration – sensory, motor etc) 2 Peripheral Vascular Disease HbA1c/glycaemic control Deformity History of ulceration Pressure? HbA1c site Boulton A.J.M., Cavanagh P.R., Rayman G., 2006 The Foot in Diabetes, 4 th ed. John Wiley& Sons. Chichester

HbA1c’s An overall appreciation of 30 days control An indicator of glycation, i.e. sugar chains attaching to RBC –So what about the systemic effects Hyperglycaemia positively associated to development of diabetic complications, i.e. neuropathy etc Upper limbs –Coppini DV, Best C. A case of hand ulceration in the diabetic foot clinic--a reminder of hand neuropathy in 'at risk' patients. Diabet Med Sep;17(9):682-3Coppini DV, Best C. Hyperglycaemia effects short term memory Papanikolaou Y, Palmer H, Binns MA, Jenkins DJ, Greenwood CE. Papanikolaou Y, Palmer H, Binns MA, Jenkins DJ, Greenwood CE. Better cognitive performance following a low-glycaemic-index compared with a high-glycaemic-index carbohydrate meal in adults with type 2 diabetes. Diabetologia May;49(5):855-62

So How do I get from high HbA1c’s to neuropathy? Diabetes Mellitus Hyperglycaemia Glycation Accelerated Aging

United Theories HYPERGLYCAEMIA Glycation Oxidative stress vessel occlusion Cell/tissue death NEUROPATHY Stocking & glove Distal - proximal Bounding pulses Warm Unable to detect: 10g Monofilament 128Hz tuning fork Temp differentiation Increased pressure Reduced proprioception ASSESSMENT EDUCATION MONITOR REFER FOOTWEAR PRESSURE REDUCTION DEBRIDEMENT CALLUS

Accelerated Ageing (Oxidative Stress) Theory Up to % of the elderly population (65 – 74) show clinical signs of peripheral neuropathy ? What about ageing diabetic population? Pataky Z, Vischer U. Pataky Z, Vischer U. Diabetic foot disease in the elderly. Diabetes Metab Apr;33 Suppl 1:S56-65.

Glycation - Example Tie the ends of the cotton to the ends of the elastic band Then stretch the elastic band What happens? Should your neurological assessment consider ROM at key joints?

The Ugly

Background: Reliability of 10g Monofilament Previous study: 10g monofilament capable of providing repeatable force for  100 compressions = 24 hr rest period (Booth & Young 2000). Based upon automated force delivery equipment. Tests fibre integrity, it fails to account for the potential non-linearity in human application. What happens real-time dynamic conditions, as would be the case in a busy clinical environment - unknown. No investigations into the inter-reliability and repeatability of the 10g monofilament between multiple users.

Aim: To verify the dynamic effects of multiple testers on 10g monofilament reliability. To determine the mechanical properties of the filament after repeated application of non-linear force.

Subjects 20 male participants recruited from University of Southampton Trained to administer 10g monofilament to protocol as specified by manufacturer (same brand) Training process to allow correct application and familiarisation with test equipment - unrecorded data Equipment 20 new CE approved 10g monofilaments (same brand) Calibrated target for measuring applied force – a modified HVLab tactile Vibrometer (Fig 2) Forces applied to centre of diaphragm were measured by 4 strain gauges bonded to a diaphragm Target for application of 10g monofilament 10-mm square rubber block bonded to centre of the diaphragm Signal linked to computer History of applied forces monitored by experimenter on digital oscilloscope (Fig 5) Protocol Adjustable height of force target for each subject allowing elbow of the preferred hand to be comfortably rested on the desk A new monofilament used for each subject Application paced by audible signal (every 6 seconds) Contact made with target area – filament normal to surface Increase application force until filament bends by approximately 1 cm (Fig 3) Hold bend constant for approximately 1 second then withdraw filament 5 runs performed, each run 10 applications = 50 applications per subject per device Analysis Forces recorded by data acquisition computer Results statistically analysed by SPSS package Subjects 20 male participants recruited from University of Southampton Trained to administer 10g monofilament to protocol as specified by manufacturer (same brand) Training process to allow correct application and familiarisation with test equipment - unrecorded data Equipment 20 new CE approved 10g monofilaments (same brand) Calibrated target for measuring applied force – a modified HVLab tactile Vibrometer (Fig 2) Forces applied to centre of diaphragm were measured by 4 strain gauges bonded to a diaphragm Target for application of 10g monofilament 10-mm square rubber block bonded to centre of the diaphragm Signal linked to computer History of applied forces monitored by experimenter on digital oscilloscope (Fig 5) Protocol Adjustable height of force target for each subject allowing elbow of the preferred hand to be comfortably rested on the desk A new monofilament used for each subject Application paced by audible signal (every 6 seconds) Contact made with target area – filament normal to surface Increase application force until filament bends by approximately 1 cm (Fig 3) Hold bend constant for approximately 1 second then withdraw filament 5 runs performed, each run 10 applications = 50 applications per subject per device Analysis Forces recorded by data acquisition computer Results statistically analysed by SPSS package

Calibrated Target for Measuring Applied Force

Subjects 20 male participants recruited from University of Southampton Trained to administer 10g monofilament to protocol as specified by manufacturer (same brand) Training process to allow correct application and familiarisation with test equipment - unrecorded data Equipment 20 new CE approved 10g monofilaments (same brand) Calibrated target for measuring applied force – a modified HVLab tactile Vibrometer (Fig 2) Forces applied to centre of diaphragm were measured by 4 strain gauges bonded to a diaphragm Target for application of 10g monofilament 10-mm square rubber block bonded to centre of the diaphragm Signal linked to computer History of applied forces monitored by experimenter on digital oscilloscope (Fig 5) Protocol Adjustable height of force target for each subject allowing elbow of the preferred hand to be comfortably rested on the desk A new monofilament used for each subject Application paced by audible signal (every 6 seconds) Contact made with target area – filament normal to surface Increase application force until filament bends by approximately 1 cm (Fig 3) Hold bend constant for approximately 1 second then withdraw filament 5 runs performed, each run 10 applications = 50 applications per subject per device Analysis Forces recorded by data acquisition computer Results statistically analysed by SPSS package Subjects 20 male participants recruited from University of Southampton Trained to administer 10g monofilament to protocol as specified by manufacturer (same brand) Training process to allow correct application and familiarisation with test equipment - unrecorded data Equipment 20 new CE approved 10g monofilaments (same brand) Calibrated target for measuring applied force – a modified HVLab tactile Vibrometer (Fig 2) Forces applied to centre of diaphragm were measured by 4 strain gauges bonded to a diaphragm Target for application of 10g monofilament 10-mm square rubber block bonded to centre of the diaphragm Signal linked to computer History of applied forces monitored by experimenter on digital oscilloscope (Fig 5) Protocol Adjustable height of force target for each subject allowing elbow of the preferred hand to be comfortably rested on the desk A new monofilament used for each subject Application paced by audible signal (every 6 seconds) Contact made with target area – filament normal to surface Increase application force until filament bends by approximately 1 cm (Fig 3) Hold bend constant for approximately 1 second then withdraw filament 5 runs performed, each run 10 applications = 50 applications per subject per device Analysis Forces recorded by data acquisition computer Results statistically analysed by SPSS package

Results – Intra Reliability For each subject peak forces within each run of ten applications (n=50) Means, medians, inter-quartile ranges and total range of the peak forces Significant differences in both mean and median peak force were found between subject runs (p=0.021 and p=0.009) respectively. No significant difference for inter-quartile and total range of peak forces

Mean and Median Peak Force Post hoc analysis revealed highly significant differences in the above modalities on Run 3 and 5 (p=0.013, p=0.03) respectively, in comparison to Run 1.

Time & Force Applied: Oscilloscope SUBJECT ASUBECT B

Results: Inter Reliability Mean Peak Force Between Subjects P=0.001

Conclusions This is the first study to demonstrate that when used by a human, rather than a machine, the 10g monofilament suffers premature mechanical decay at <50% of the recommended number of applications. Similarly, the total range of peak force varies significantly between subjects. Hence, the clinical reliability of the 10g monofilament appears unstable, once the human variable is factored in, requiring a fresh approach to both method and equipment.

Communication!

Falls & Proprioception Studies have shown a link between proprioception and falls H. Mendez et al., 2006 Link between cadence and risk of falls S. Perring & P. Thomas 2007 Loss of sensory input a major risk factor the development of falls … so what about people with diabetes?