Femoral shaft fracture in children is a frequently encountered problem. Residual leg length discrepancy persisting at skeletal maturity is the most common complication. In this study, a positive correlation was found between the amount of bone fragments overlap and the overgrowth phenomenon. When comparing final leg-length discrepancy with initial fragments overlap, 9.3 mm was found to be the maximal overlap to be tolerated in order to avoid significant leg length discrepancy.
Hariga, H., Mousny, M., & Docquier, P.-L. (2011). Leg length discrepancy following femoral shaft fracture in children: Clinical considerations and recommendations. Acta Orthopaedica Belgica (Bilingual Edition), 77(6), 782-787. https://hdl.handle.net/2078.5/36171 (Original work published 2011)