Dimensions of the paediatric femur: anatomical limitations of flexible intramedullary nailing

PURPOSE: Although spica casting remains the benchmark for treating diaphyseal femur fractures in preschool children, some authors advocate using flexible intramedullary nails in certain situations. The aim of the current study was to evaluate the anatomic feasibility of flexible nailing in young children. METHODS: Consecutive patients between the ages of zero and ten years with normal femurs who received femur radiographs at a tertiary paediatric hospital over a two-year period were included. Anteroposterior femur radiographs were evaluated for length and isthmus width measurements. Each femur was templated for flexible nail size. The proportions of each age group capable of accommodating two flexible nails up to 4.0 mm in size were determined and compared. RESULTS: A total of 381 full-length femur radiographs were reviewed. There was a strong, direct linear relationship between age and femoral length (R(2) = 0.896) and a moderate correlation between age and femoral isthmus width (R(2) = 0.417). Although the percentage of femurs able to accommodate flexible nails continued to increase with age, this increase did not represent a significant difference when comparing preschool-aged children with older age groups. CONCLUSIONS: Age and femoral length demonstrated a strong, positive correlation while age and isthmus width had weaker correlation. The ability of femurs to accommodate flexible nails increased with age with most children age two years and older able to accommodate two flexible nails of at least 2.5 mm in size. LEVEL OF EVIDENCE: III