The Prevalence of Neuropathic Pain Pathophysiology Associated With Ankle Fracture

Chronic Pain Grading Scale

Chronic Pain Grading Scale (CPGS) will be used to determine if fracture patients have pain in the chronic phase of injury (6-9 month visit). The pain intensity subscale will be used to categorize participants into those with and without chronic pain. This score is the sum of three questions (current pain, worst pain, average pain over last month), each scored on an 11-point Likert scale with responses ranging from 0-10 for a maximum of 30 points. The participant will be asked to report only on pain related to the site of fracture. Participants scoring 1-30 on the characteristic pain intensity score in the last month at the site of fracture will be classified as having chronic pain related to the fracture. Patients reporting no pain (0) at the site of fracture in the last month will be classified as having no chronic pain.

Douleur Neuropathique (Neuropathic Pain) 4

Douleur Neuropathique (Neuropathic Pain) 4 (DN4). The DN4 is a validated and reliable screening tool for neuropathic pain consisting of 10 items. The first 7 items relate to pain quality (i.e., sensory and pain descriptors) are based on interview with the patient. The last 3 items are based on clinical examination and assess hypoesthesia to touch, and hypoesthesia to prick and brushing. The items of the DN4 are scored based on a yes (1 point)/no (0 points) answer. This leads to a score range of 0-10. The cut-off value for the classification of neuropathic pain is a total score of 4 of 10.72 The DN4 has been used to identify NP in ankle fracture patients.

Assessment of Chronic Regional Pain Syndrome (CRPS)

Assessment of Chronic Regional Pain Syndrome (CRPS). Presence of CRPS will be assessed in study participants beginning at the 6-8 week follow-up visit and all subsequent visits. Assessment of CRPS at earlier timepoints cannot be done rigorously as pain, motor, temperature and other changes comprising in part the CRPS diagnostic criteria can be related to the recent trauma. In addition to the QST procedures, a validated CRPS sign and symptom checklist will be administered by the study coordinator containing items in the 4 symptom and 4 sign categories needed to establish a CRPS diagnosis. For this study the investigators will employ the more rigorous CRPS Research Criteria (all symptom categories positive and 2/4 sign categories).

Central Sensitization measure

Central Sensitization measure: The most common quantitative sensory test used to measure central sensitization in human experimental studies is temporal summation of pain (TS).TS will be administered on the skin proximal to the level of injury and the contralateral uninjured side using a nylon monofilament (Touchtest Sensory Evaluator 6.65) calibrated to bend at 300g of pressure. As in previous studies, participants will rate the perceived pain intensity of a single contact of the monofilament using a 0 to 100 numeric rating scale. Then, participants will provide another pain rating following a series of 10 contacts administered at a rate of 1 contact per second, applied to the body site within an area of 1 cm2. The difference between pain ratings for the single versus multiple contacts reflects temporal summation of mechanical pain. Two trials will be administered.

Mechanical Detection Thresholds

Mechanical detection thresholds will be examined using von Frey monofilaments, with each filament applied three times in ascending sequence until the threshold is detected in at least two of the three trials. Then, the next lower von Frey filament will be applied, and the lowest filament to be detected at least twice will be determined as the mechanical detection threshold.

Pressure pain thresholds

A digital, handheld, clinical grade pressure algometer will be used for the mechanical procedures (AlgoMed, Medoc). The experimenter will apply a slow constant rate of pressure and record the pressure in kilograms when the subject responds. Pressure will be applied using a .5 cm2 probe. Subjects will be instructed to respond when they first feel pain and pressure at threshold will be recorded. Two consecutive measurements at each point with intervals of 20 s will be obtained.