Semmes weinstein monofilament

Mechanical detection thresholds (MDT) were measured using standardized Semmes-Weinstein monofilaments with 20 different diameters (North Coast Medical, Canada). The number of each filament (1.65 to 6.65) corresponds to a logarithmic function of the equivalent forces of 0.008 to 300 g. The filament was applied vertically on the test sites, and pressure was applied slowly until the filament bowed with a total contact time of approximately 1 s. To prevent filament slippage, intra-oral examination sites were dried with gauze before testing [14 (link), 15 (link)].
To detect the mechanical pain threshold (MPT), weighted pinprick stimuli delivered with a custom-made set of seven pinprick stimulators (Aalborg University, Denmark) were used [16 (link)]. Each stimulator had a flat contact surface of 0.2 mm that exerted forces of 8–512 mN. All pinprick tests were made with the stimulator perpendicular to the examination site and in a vertical position with a contact time of 1 s. MDT and MPT were measured using the “method of limits” technique described by Baumgartner [17 (link)]. Five threshold measurements were made, applying a series of ascending and descending stimulus intensities. One threshold value was determined by calculating the geometric mean of these five series.

The animals were acclimatized to the environment for 30 min before behavioral testing, which was conducted blindly.
Thermal pain was evaluated using the IITC Plantar Analgesia Meter (IITC Life Science Inc., USA). Thermal withdrawal latency (TWL) was measured in terms of delayed reflex from the start of radiant heat exposure until hind paw withdrawal. The strength of the heat stimulus was controlled to yield a baseline thermal withdrawal latency of about 15 s in normal and sham-operated rats. Exposure was limited to 20 s, to avoid tissue damage.
Mechanical allodynia was assessed using von Frey filaments (Semmes-Weinstein Monofilaments; North Coast Medical, USA). The paw withdrawal threshold (PWT) was evaluated by steadily controlling the stimulus strength (the "up-and-down" method).

The plantar tactile sensation of the reconstructed leg was assessed with a set of Semmes–Weinstein monofilaments (North Coast Medical, Inc., Morgan Hill, CA, United States) (Figure 1C), which showed good test-retest reliability (ICC = 0.83–0.86) (Collins et al., 2010 (link)). Six monofilaments with different sizes were used in this study: 2.83 (0.07 g), 3.61 (0.4 g), 4.31 (2 g), 4.56 (4 g), 5.07 (10 g), and 6.65 (300 g). Filament size = log10 (10 × force in milligrams). The filaments were applied randomly to the skin (bent 90°) on the bases of the great toe, first and fifth metatarsals, arch, and heel. A randomized null stimulus was added to ensure that participants could not anticipate the application of the filaments. Participants lay supine on the treatment table with their eyes closed and the tester selected filaments from thin to thick until they could perceive the stimulation and respond verbally to the correct location of the test area. The plantar tactile sensation threshold was determined by the thinnest monofilament they could feel (Feng et al., 2009 (link)).

The tactile-pressure threshold of the distal palmar pad of the index finger was evaluated using Semmes–Weinstein monofilaments (North Coast Medical, Morgan Hill, CA, USA). We used 20 types of filaments ranging in weight between 0.004 and 447 g. The esthesiometer pressure in grams for each filament was converted to log₁₀ 0.1 mg, yielding a scale composed of intervals of approximately equal intensity between filaments. Subjects were tested with their eyes closed after receiving clear instructions. The target area was marked on the volar side of the distal phalanx of the dominant index finger. Each filament was pushed into the target area until it bent by approximately 90° for one second. The threshold was recorded as the smallest filament diameter that was perceived in at least 80% of its applications (5 trials). SBF was monitored continuously on the palmar surface of the third finger of the dominant hand using a laser–Doppler flowmeter (ATBF-LC1, Unique Medical, Tokyo, Japan). SBF and the marking signal were simultaneously stored on a computer using an analog–digital converter (UAS-108S, Unique Medical, Tokyo, Japan) at a sampling frequency of 1 kHz and analyzed using computer software (Unique Acquisition 2.11, Unique Medical, Tokyo, Japan).

MDT was measured with the use of standardized Semmes–Weinstein monofilaments with 20 different diameters (North Coast Medical, Canada). The number of each filament (1.65–6.65) corresponds to a logarithmic function of the equivalent forces of 0.008–300 g. To detect the MPT, weighted pinprick stimuli delivered with a custom-made set of seven pinprick stimulators (Aalborg University, Denmark) were used. Each stimulator had a flat contact surface of 0.2 mm that exerted forces of 8–512 mN^{20 (link)}. MDT and MPT were determined by the method of limits, and defined as the geometric mean of 3 series of descending and ascending stimulus intensities^{5 (link)}.