Sample size estimation for growth as an outcome

I would like to know how to calculate sample size for a study that is going to assess growth in height in children and adolescents in routine clinical practice. There will be two groups. Height, height percentile, height standard deviation score (based on population height reference data), height velocity and changes in these variables will be assessed across the study. How a sample size could be estimated? How are we going to do the analysis and interpret the data? Is there a way to control some confounding factors in the analysis? If yes, then how? I searched the literature. None of the articles I found provides a precision-based sample size estimation for this type of study. Thank you so much.

Start with Selecting a sample size for studies with repeated measures | BMC Medical Research Methodology | Full Text

Thank you very much for providing the reference.