Pathway pain sensory evaluation system

PATHWAY Pain & Sensory Evaluation System (Medoc, Israel) with an
intraoral thermode having a round active contact surface (diameter =
6 mm) was used for all thermal tests, which were performed in the sequence:
CDT-WDT-CPT-HPT. For each test, the intraoral thermode was held in place by
the examiner, with a baseline temperature of 32 °C, and temperature
change rate of 1 °C/s for CDT and WDT; for CPT and HPT, the rate of
temperature change from baseline was 1.5 °C/s; the rate of return to
baseline was 8 °C/s. Cut-off temperatures for thermal tests were 0
°C and 54 °C. Participants were instructed to hold a
response unit and press its button once a particular sensation (coolness,
warmth, cold pain, heat pain) was first perceived, ending the trial.
Detection thresholds were calculated as the temperature difference from
baseline; pain thresholds were determined from the absolute temperature
reached. Each test included three measurements; the average of the three
measurements was used as threshold.

Heat thermal stimuli were delivered using a computer-controlled Medoc PATHWAY Pain & Sensory Evaluation System. The position of the thermode was moved between trials to avoid sensitization and/or habituation of cutaneous nociceptors. Heat pain threshold and tolerance were assessed on both the index knee (i.e. the most painful knee) and ipsilateral ventral forearm. Specifically, three sites were assessed across three trials around the joint line of the index knee (i.e., where the femur and tibia meet). The sites were: 1) the medial joint line which was located immediately medial to the patella, 2) the area above the patella which was medially and above the joint line, and 3) the area below the patella which was medially and below the joint line. We used the ascending method of limits with a 16×16mm Advanced Thermal Stimulator (Medoc, Israel). Heat pain threshold was assessed first. For each trial, the thermode would start at a baseline temperature of 32°C and increase at a rate of 0.5°C/second until the participant responded by pressing a button as soon as the sensation “first became painful.” Subsequently, heat pain tolerance was assessed.. Participants were instructed to press the button when they “no longer felt able to tolerate the pain.” For both the heat pain threshold and tolerance procedures, each test was repeated 3 times and the mean temperature was used for analysis.