Repeatability and sources of variability in multi-center assessment of segmental foot kinematics in normal adults

Multi-site application of biomechanical models can be a powerful tool as quantitative methods are employed to improve clinical care and to assess larger populations for research purposes. However, the use of such models depends on adequate validation to assure reliability in inter-site measures. We assessed repeatability and sources of variability associated with the assessment of segmental foot kinematics using the Milwaukee Foot Model during multiple testing sessions at two sites. Six healthy ambulators were instrumented and tested during comfortable ambulation; data were analyzed with variance components analysis using a mixed effects linear model. Results indicated that the largest source of variability was inter-subject; measurement error associated with Site and Session fell below 3.5 degrees in over 80% of position measurements and below 2.5 degrees in over 80% of ROM measurements. These findings support the continued use of the segmental foot model at multiple sites for clinical and research purposes.