A series of 114 bone lengthenings with external fixator, performed in 36 girls and 50 boys with congenital lower limb length discrepancy, was retrospectively analyzed. Bone segment growth rates were measured before lengthening, during the first year after frame removal and finally over long-term follow-up, calculating the ratios of radiological bone length to the number of months between two measurements. Mean follow-up was 4.54 ¡À 0.2 years.
Changes in short- and long-term growth rate distinguished five patterns of bone behavior after lengthening, ranging from growth acceleration to total inhibition.
These five residual growth patterns depended on certain factors causing acceleration or, on the contrary, slowing down of growth: age at the lengthening operation, percentage lengthening, and minimal period between two lengthenings. These criteria help optimize conditions for resumed growth after progressive segmental lengthening, avoiding conditions liable to induce slowing down or inhibition, and providing a planning aid in multi-step lengthening programs.
Level IV. Retrospective study.