Intra- and interday reliability of the dynamic navicular rise, a new measure for dynamic foot function: A descriptive, cross-sectional laboratory study.

Highlights What is already known • Adult acquired flatfoot is a frequent problem. These patients have an increased risk for pathologies concerning the tibia, the back and posture. • Often used assessments include static and dynamic measures but they do not necessarily reflect foot motion under dynamic conditions. • The lack of reliable parameters in the evaluation of dynamic foot function under load needs a deeper insight in biomechanics of the foot. What this study adds • A new measure, the dynamic Navicular Rise (dNR), is proposed to describe dynamic foot function during stance. • During level walking, the new measure might be seen as new and independent. During stair descent, however, this is not the case. • The results are an example of the limitation and difficulties in interpreting ICCs. Abstract Background The lack of reliable parameters to evaluate dynamic foot function, emphasizes the need for a deeper insight in foot biomechanics. The aims were to investigate the reliability of a new parameter (dynamic navicular rise dNR), and its relationship with the dynamic navicular drop (dND). Methods Twenty healthy participants (mean age 30.2 ± 8.1 years) had to walk on even ground and downstairs. Data of ten trials per task on two measurement days were recorded. The dNR was defined as the difference in millimetres (mm) between the minimum navicular height (NH) during stance and the NH at toe off. To test intra- and interday reliability, Intraclass Correlation Coefficients (ICC 2.1) and repeatability were calculated. To obtain the absolute repeatability (RP) in mm, the equation RP = 1.96 × SD differences was used. Furthermore, the relationship between the dNR and the dND was examined by calculating Pearson (r) or Spearman (r s) correlation coefficients. Results Included participants showed a mean dNR of (12.2 ± 3.7) mm for level walking and (14.8 ± 3.4) mm for stair descent. The ICC 2.1 for the dNR were 0.98 (intraday), 0.91 (interday) for level walking and 0.97 (intraday), 0.94 (interday) for stair descent. The interday repeatability was 3.2 mm (level walking), 2.7 mm (stair descent) respectively. For level walking, r was 0.31 (p = 0.049), and r s = 0.88 (p < 0.001) for stair descent. Conclusions The dNR seems to be highly reliable (ICCs), however, repeatability is unacceptable. For level walking, the dNR might be an independent measure, but not for stair climbing. [ABSTRACT FROM AUTHOR]