[Regeneration formation index--new method of quantitative evaluation of distraction osteogenesis]

One of the most common techniques for limb lengthening is the Ilizarov method. The course of osteogenesis is usually monitored using classic X-ray in this way determining the moment of fixator removal. Classic x-ray evaluation is subjective and therefore errors may easily be encountered. New techniques for objective and quantitative evaluation of radiologic documentation are needed. Computer assisted image analysis offers this possibility.

Aim of this prospective study is to determine a quantitative, measurable method of regenerate description during distraction osteogenesis, based on classic radiography and computer assisted image analysis.

Material consists of 40 patients, in whom long bone lengthening procedures were performed. Altogether 40 lengthening were performed, 16-femur, 20-tibia, 4-humeral. Radiographic data, obtained in standard conditions, were than analyzed digitally. A mathematical bone model was created and later compared with obtained regenerate images. Computer processing lead to determining a new value, called regeneration formation index (RFI). For the model bone, the value is one.

Average femur lengthening was 5.4 cm, tibia lengthening was 5.6 cm, and humeral 8.0 cm. During distraction osteogenesis the RFI, at the end of distraction phase, and the beginning of stabilization phase reached the lowest values, to increase steadily with the progress of osteogenesis, finally at the end of stabilization phase reaching the original values. The pace of RFI increase correlated with the presence of potential complications that require surgical treatment.

Quantitative evaluation of regenerate using the regeneration formation index allows to precisely analyze the course of distraction osteogenesis, particularly to precisely estimate the timing of fixator removal and avoid complications.