Differences in the performance of commercially available 10-g monofilaments.

Abstract

OBJECTIVE: This independent study was designed to determine the accuracy of 10-g monofilaments manufactured and supplied by popular commercial companies. RESEARCH DESIGN AND METHODS: A total of 160 new 10-g monofilaments (30 Semmes-Weinstein monofilaments [North Coast Medical], 30 Timesco/Sensory Testing Systems monofilaments, 50 Owen Mumford Neuropens, and 50 Bailey Instruments monofilaments) were tested using a calibrated load cell. Each monofilament was subjected to 10 mechanical bucklings of 10 mm while the load cell detected the maximum buckling force. Longevity testing was performed on a subset of the monofilaments by subjecting them to continuous compressions until the buckling force was <9 g. RESULTS: The accuracy of monofilaments to produce a buckling force of 10 g varies among manufacturers. Bailey Instruments and Owen Mumford filaments were the most accurate with 100% buckling within +/-1.0 g of 10 g. Only 70% of the Semmes-Weinstein monofilaments from North Coast Medical buckled within +/-1.0 g of 10 g. A total of 80% of Timesco filaments buckled at <8 g. Longevity tests on Bailey Instruments and Owen Mumford monofilaments demonstrated that 80% continued to buckle within 10% of 10 g after 100 compressions, but only 50% were within this range after 200 compressions. The maximum amount of recovery achieved in any monofilament occurred within 24 h. CONCLUSIONS: Monofilaments made by either Bailey Instruments or Owen Mumford are recommended for use in clinical practice. North Coast Medical monofilaments may operate differently in the U.S. because of different environmental conditions such as differences in humidity. Timesco/Sensory Testing Systems monofilaments were neither accurate enough nor Conformity European marked to recommend their use in the U.K. Longevity and recovery testing suggest that each monofilament will survive usage on approximately 10 patients before needing a recovery time of 24 h before further use.

Evaluation of Cutaneous Spatial Resolution and Pressure Threshold Secondary to Digital Nerve Repair

“…This considerable difference has been studied extensively before, pointing out some general problems inherent in the Semmes-Weinstein monofilament set: (1) the discontinuous scale of the Semmes-Weinstein monofilament test does not allow precise measurement; (2) the problem of measuring a force threshold rather than a pressure threshold; (3) the inability to know the true surface area in contact with the skin at the moment the filament buckles; (4) the variance in manufacturing allowing a 10 percent error in the initial applied force of the filaments; and (5) the fatigue of the nylon with more than 100 uses. 23,[38][39][40][41][42] These circumstances led to the conclusion that normative data are impossible to generate for the Semmes-Weinstein monofilament, thus harshly limiting its intrainstrument and interinstrument comparability. Indeed, the PressureSpecified Sensory Device clearly compensates for most of the mentioned points of criticism: it is measured on a continuous scale (with "open ends"), which even captures extreme values and outliers reliably; whereas the Semmes-Weinstein monofilament test is limited to five grades, potentially neglecting higher or lower values, thus pretending a smaller variance.…”

Diabetic Somatic Neuropathies

“…A final caution on the use of the filaments: Booth and Young (173) identified that filaments manufactured by certain companies do not actually buckle at 10 g of force. Indeed, several tested filaments buckled at Ͻ8 g. Thus, care must be taken when selecting suppliers of filaments.…”

The diabetic foot: from art to science. The 18th Camillo Golgi lecture

“…The 10-g monofilament, used to test pressure perception, is frequently employed to assess diabetic patients' foot ulcer risk status [40]. Although simple to perform, care must be taken to ensure that the filaments used are accurate in delivering a 10-g force when used [41]. Moreover, it has also been suggested that the widespread use of filaments needs to be reappraised as this may not be the most sensitive test [42].…”