IntroductionRegenerated bone produced in bone lengthenings and transports makes, from the first days of distraction, a fibrous tissue with a consequent mineralization that develops from the area of the osteotomy fragments to the centre of the bone gap [1]. The regeneration can be normal, cystic or hypertrophic.Radiographs taken during the first 40 days after distraction, in particular in adult patients, show a radiolucent gap that corresponds to the length of distraction obtained with the fixator, without showing signs of bone regeneration. After the first 40 days, the radiograph may show a scarcely radiopaque and badly defined veil of regenerated bone. The ultrasound scan instead offers, from the first days of distraction, a precise outline of the regenerated bone both in its fibrous component and in its parts that show an initial mineralization [2][3][4][5]. In this study, we compared radiographs and ultrasound examinations taken at the same time, and defined the limits between a normal ultrasound scan and a pathological one.

IntroductionNewly formed bone with distractional osteogenesis after bone transport presents morphological characteristics that are different from the contralateral bone segment. These differences are visible upon radiographic examination, which can show increased diameter of the newly formed bone. The information given by radiography (anteroposterior and lateral view) is not however sufficient for precise definition of the morphological characteristics of the regenerated segment and, consequently, is inadequate for assessment of mechanical quality. With reference to several earlier morphological and quantitative studies of regenerated bone after lengthening [1-3], we chose to examine similar properties (thickness of the cortical wall, sectional area of the newly formed medullary canal, density of the regenerated bone fragment in the cortical and medullary components) of corticalized, regenerated bone in order to assess any possible relationships to clinical utility. O R I G I N A L Abstract A morphological analysis using radiography and computed tomography was performed in a total of 17 bone segments following single or double bone transport in 11 and 3 patients, respectively. All bone transports involved the tibia, with the exception of 2 single bone transports, which were femoral. The following parameters were measured: cortical wall thickness, sectional area of the medullary canal, and density of the cortical bone and medullary canal in Hounsfield units (HU). The regenerated segments showed a cortical thickness and density that were less than the contralateral portion, with an enlargement of the medullary canal and an increase in density due to the presence of cancellous bone in the medullary area. Successive controls showed an increase in thickness and density of the cortical bone and a small reduction in the diameter of the medullary canal and its cancellous bone. The variations in the cortical and the medullary canal appeared to be independent of the length of the regenerated segment. In the 3 tibia treated by double bone transport, the anatomical variations in the distal regenerated portion varied less from normal values than the proximal portion of the same segment. In the 2 femurs examined, enlargement of the regenerated section was smaller with respect to cases involving regeneration of the proximal tibia. These differences are presumably dependent on the fact that in the latter case, a more vascularized segment is produced after osteotomy in spongy bone, with respect to those involving the distal tibia or femur. Double transport is preferable due to the reduced treatment times.