PURPOSE: A marked native tracheal axial approximation occurs when sheep and canine trachea are replaced with a bioabsorbable scaffold. and this phenomena may be useful in the surgical management of large tracheal defects. The mechanism of this phenomenon is unknown. This study aimed to evaluate tracheal axial approximation phenomenon in mature canine and immature sheep model by CT data analysis.
METHODS: Animals underwent cervical tracheal replacement (5cm) using a bioabsorbable tube and concurrent silicone stenting. Metallic markers were placed on the outside of the trachea to indicate the both proximal and distal ends of the native tracheal rings. Airway and vertebral longitudinal distance parameters were measured by three dimensional CT curvature trace. Airway anatomical positions were represented by horizontal plane of the vertebral body. CT data was compared between 1 week and 3 months in immature sheep models (n=4), 1 week and 9 months in mature canine models (n=4).
RESULTS: Sheep model: tracheal approximation rate of the grafted area was 55% to 71% at three months. Length between cranial edge of C2 vertebral body and caudal edge of C6 body was increased 6.1% to 12.8% (longitudinal growth rate) at 3 months. According to those growth rates total tracheal length between the 1st cartilage ring and distal orifice of the right upper branch was elongated except in one sheep. Canine model: tracheal approximation rate of the grafted area was 57% to 63% at 9 months. There was no longitudinal cervical vertebral growth in all canines. Two of four canines, tracheal length between the 1st cartilage ring and carina were equal at 1week and 9 months. The rest of two animals were shorter at 9 months.
CONCLUSION: Tracheal axial approximation phenomenon was observed in both immature and mature animal model and accounted for by the distal airway moving cranially (carinal shifting) and native tracheal stretching.
CLINICAL IMPLICATIONS: The native tracheal axial shortening phenomenon may serve as a bridge to allow for two-staged end-to-end reconstruction of large tracheal defect using a temporary grafting technique.
DISCLOSURE: Hisashi Tsukada, No Financial Disclosure Information; No Product/Research Disclosure Information