Callotasis is a leg lengthening technique using slow distraction of callus which is formed in response to a subperiosteal osteotomy. This technique is now widely used in the orthopedic field to treat leg length discrepancy and short stature. However, little is known about bone modeling during callus elongation. In this study we evaluated the mineralization and modeling process at the site of leg lengthening by dual energy x-ray absorptiometry and radiographical examination using experimental models. The bone mineral content (BMC) reached a maximum when the distraction gap was filled with newly formed bone according to the x-rays, and decreased when medullarization and corticalization began radiographically. After seven weeks, when the BMC became constant bone modeling in the gap was completed. The BMC changes reflect the mineralization and modeling process at the lengthening site.
