Ultrasound evaluation of the tibial graft structure during fixation with the Ilizarov device in patients with achondroplasia

BACKGROUND: Bone regeneration during fixation needs to be evaluated due to clinical measures taken to prevent possible complications, such as evaluation of the correct segment axis, verification of the equality of the extended and contralateral segments (with repeated lengthening), maintenance of fixation rigidity, functional control of the load on the operated limb, and the patient’s motor activity. All of these factors have a direct impact on the structure and maturation of the distraction graft and readiness for device removal. It is relevant to study the proximal graft in bilocal treatment based on the greatest elongation (5.5 [5.0; 6.0] cm) compared to the distal graft. Proximal graft maturation affects the timing of device removal. AIM: The aim was to evaluate the structure of the tibial distraction graft in achondroplasia patients of different ages during the fixation period. MATERIALS AND METHODS: AVISUS Hitachi (Japan) was used for ultrasound scanning with a 7.5 MHz linear sensor. The graft was evaluated using standard programs. The study included achondroplasia patients aged 6–9 years (group I, n = 15) and 10–15 years (group II, n = 15). The study was conducted at 5, 30, 60, and 90 days (with repeated limb lengthening) from the start of the fixation period. In group I of monolocal tibial lengthening, the elongation was 6.5 [6; 7] cm. For bilocal leg lengthening in groups I and II, the proximal graft elongation was 5.5 [5.0; 6.0] cm, and the distal graft elongation was 2.5 [2.0; 3.0] cm. RESULT: In groups I and II, a favorable course of osteogenesis was observed, with typical stages of graft formation. Group II showed slower development of typical structures, resulting in longer fixation times. Therefore, the fixation time was 55 ± 5 days (p ≤ 0.05) in group I and 63 ± 3 days (p ≤ 0.05) in group II (in case of favorable progression). The exception was 1 patient (out of 10 patients with repeated leg lengthening), who developed a hypoechoic cyst-like lesion in the graft midzone during distraction. The time to cortical plate formation increased to 85 ± 5 days (p ≤ 0.05). CONCLUSIONS: Ultrasound evaluation of tibial distraction regeneration during fixation showed that the activity of reparative osteogenesis during this period corresponds to the activity of reparative osteogenesis during distraction. Although it is not possible to fully visualize elongation achieved during fixation due to the formation of echo-dense fragments at the ends of the parent bone, ultrasound scanning allows evaluation of changes in graft filling, vascularization, and graft readiness for removal of the external fixation device.