Differences in the performance of commercially available 10-g monofilaments

This independent study was designed to determine the accuracy of 10-g monofilaments manufactured and supplied by popular commercial companies.

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.

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.

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.