Intra- and interrater agreement of pressure pain thresholds in children with orthopedic disorders.

Purpose: Pressure algometry is widely used to obtain measures of mechanical pain sensitivity in adults, both in experimental and clinical pain conditions. Only very few studies describe the use of pressure algometry in children. The purpose of this study was to produce reference values of pressure pain thresholds and to determine the intra- and interrater agreement, in order to introduce pressure algometry as a standardized method for the assessment of pain thresholds in children with orthopedic disorders.

Methods: Pressure pain thresholds were determined at the leg and at the thenar in 50 children aged 4-12 years. All were scheduled for physical examination at the outpatient Orthopedic Clinic at Aarhus University Hospital, Denmark, because of various orthopedic disorders such as clubfoot and Baker's cyst. Pressure pain thresholds were determined by two different raters: 20 children were examined twice by rater 1 (intrarater agreement), and another 20 children were examined by both rater 1 and rater 2 (interrater agreement). An additional ten children were examined once by rater 1 to increase the number of children used to determine the reference values.

Results: The pressure pain threshold was 183.1 kPa (mean, SD: 90.7) at the leg and 179.1 kPa (mean, SD: 97.4 kPa) at the thenar (n = 50). Pressure pain thresholds were similar in boys (n = 27) and girls (n = 23). Also, pressure pain thresholds were not affected by age. Bland-Altman plots showed excellent intrarater agreement and satisfactory interrater agreement.

Conclusion: Pressure algometry has excellent intrarater agreement and satisfactory interrater agreement. Pressure algometry was well-tolerated even by very young children. The method deserves more widespread use both in clinical and experimental settings.