Ultrasonic criteria of reparative osteogenesis of distraction regeneration of the femur in achondropalzia patients aged 9-12 years with cross-lengthening of the femur and contralateral tibia

Aim: to identify ultrasound criteria for reparative osteogenesis of the distraction regenerate of the femur in patients with achondroplasia, allowing to begin surgical treatment of the contralateral tibia. Materials and methods. The study included patients with achondroplasia aged 9 to 12 years (n = 37), who at the age of 6-7 years underwent the first stage of treatment - lengthening of both tibias. At the second stage of treatment, the femur was lengthened first, and then the contralateral tibia. The period of femur distraction was 63±3 days, the elongation value was 6.5±0.5 cm. Ultrasound scanning (AVISUS Hitachi, Japan) of the bone regenerate was performed 7, 20, 30, 60 days after the beginning of distraction and once a month during the fixation period. Mathematical processing of the results was performed using the variation statistics method, p≤0.05, the reliability of differences was determined by the Wilcoxon W-criterion. Results. To maintain distraction, a "growth zone" of the regenerate is preserved in the middle part of the regenerate, in the form of a weakly mineralized layer with AP=65-85 conventional units. By the end of the distraction period, a narrowing of the echo-positive zone of the regenerate is noted, the amount of connective tissue layer decreases. At the beginning of the fixation period, due to the active mineralization process, the AP of the fragments and the regenerate reached 198±9.0 conventional units and 158±4.5 conventional units, respectively, which indicated the possibility of moderate physical activity on this limb and surgery on the contralateral tibia. Conclusion. Ultrasound criteria for reparative osteogenesis of the distraction regenerate of the femur, allowing for the lengthening of the contralateral tibia in patients with achondroplasia aged 9-12 years are the formation of a characteristic zonal structure of the regenerate throughout the distraction period, the absence of focal formations in all visualized zones of the regenerate, an increase in the AP of the regenerate by the end of the distraction period by 50%, compared with the initial period of treatment, a decrease in the width of the echo-positive zone of the regenerate by the beginning of the fixation period to 45-48% of the achieved lengthening value.