The reliability of measurements taken from radiographs in the assessment of paediatric flat foot deformity

Background: Radiographic charted values are widely applied in the assessment of paediatric flat foot and as quantitative markers of intervention success. Nearly all literature pertaining to the reliability of these measures relates to the adult foot. In view of the importance placed on these charted values we assessed the inter and intra-rater reliability of 10 key radiographic measures in children aged 7-14 years. Methods: We present the reliability of these measures in terms of intra class correlation and standard error based on repeated measures of 50 radiographs across five independent trained observers. Two new detailed methods are presented for the calculation of lateral and dorso-plantar talo-calcaneal overlap in an attempt to better define the talo-calcaneal inter-relationship. Results: The results demonstrate wide variation of measurement reliability, with some measures being highly reproducible and others showing poor reproducibility. A strong negative correlation between reliability and the number of steps required for the measurement was demonstrated. Consistent with other studies intra-rater reliability tended to be higher than that of inter-rater reliability. Conclusion: In conclusion, we have provided evidence as to which radiographic charted measures may be reliably used in evaluating the paediatric flat foot in children aged 7-14 years, and which measures are not reliable and we advise against their application.