Objective To analyze the anatomical characteristics of the upper airway in Pierre Robin sequence pediatric patients with difficult laryngoscopy using the computed tomography-based three-dimensional reconstruction.Methods Fifty pediatric patients of both sexes with Pierre Robin sequence,aged 10-101 days,weighing 2.0-6.3 kg,of American Society of Anesthesiologists physical status Ⅲ,scheduled for elective mandibular distraction osteogenesis under general anesthesia,were enrolled in this study.Cone beam CT scan was performed to obtain upper airway anatomy information during the natural sleep before operation.Images were imported into medical engineering software MIMICS 17.0 to reconstruct the three-dimensional images of the oral and maxillofacial bones and airways.The related anatomical parameters were measured,including the distance between the alveolar ridge of the upper central incisor and root of the epiglottis (D1),distance between the root of the epiglottis and midpoint of glottis (D2),distance between the bilateral lower edge of the mandible and midpoint of glottis (D3),distance between the alveolar ridge of the lower central incisor and the lower edge of the mandible (D4),length of the mandibular ramus (D5),length of the mandible body (D6),and length of the total mandible (D7),angle between lines D1 and D2 (angle 1),the angle between line D2 and the alveolar ridge of the upper central incisor to the midpoint of glottis (angle 2),the angle between lines D3 and D4 (angle 3),the angle of the point of the upper central incisor alveolar ridge to the trailing edge of the hard palate and then to the root of epiglottis (angle 4),the angle of bilateral mandible (angle 5),the angle of the point of gnathion to the two gonions (angle 6),the airway cross-sectional area at the tip of epiglottis,volume of oral cavity,volume of velopharyngeal cavity,and volume of glossopharyngeal cavity.Fiberoptic bronchoscope-guided endotracheal intubation was performed under topical anesthesia with lidocaine.Propofol,sufentanil and cis-atracurium were intravenously injected to induce anesthesia after successful intubation,and then the pediatric patients were sent to the operating room.Anesthesia was maintained by inhalation of sevoflurane.The exposure of glottis was observed with a laryngoscope.Pediatric patients were divided into difficult laryngoscopy group (group A) and non-difficult laryngoscopy group (group B) according to whether they presented with difficult laryngoscopy (Cormack-Lehane classification Ⅲ or Ⅳ).Results Compared with group B,the airway cross-sectional area at the tip of epiglottis and in the volume of velopharyngeal cavity were decreased (P＜0.05),and no significant change was found in D1,D2,D3,D4,D5,D6,D7,angle 1,angle 2,angle 3,angle 4,angle 5,angle 6,volume of oral cavity or volume of glossopharyngeal cavity in group A (P＞0.05).Conclusion The three-dimensional CT images of the upper airway show characteristic changes in Pierre Robin sequence pediatric patients with difficult laryngoscopy,and the main manifestations are the decrease in the airway section area and in the volume of the palatopharyngeal cavity at the tip of the epiglottis.

Objective:To determine the direction of traction that has the least influence on temporomandibular joint (TMJ) during mandibular distraction osteogenesis(MDO).Methods:(1) The three-dimensional finite element model was established after the mandible data were obtained by cone beam computed tomography (CBCT) scanning, and the validity of the model was verified. (2) Based on the verified three-dimensional finite element model, the distraction osteogenesis of mandible was carried out with six different directions. (3) The effects of different traction directions on disc pressure, osteotomy displacement, temporal bone pressure and condylar pressure were measured.Results:(1)In the thinnest area of the articular disc, the direction of the minimum stress on the upper and lower surfaces of the disc was "along the direction of the mandible, parallel to the surface of the mandible" . (2) Under the same load, the displacement of each osteotomy surface along the traction direction was different, but the difference was not big, and the effect was basically the same. (3) "Along the direction of the mandible, parallel to the surface of the mandible" and "along the direction of the mandible and parallel to the sagittal plane" had less pressure on the temporal bone than other situations, and the two directions of traction were parallel to the mandible. After the force decomposition, the direction of the condyle was the smallest, so the pressure on the condyle was smaller.Conclusions:A satisfactory TMJ model can be obtained by DICOM. The traction force of "along the direction of the mandible body, parallel to the surface of the mandible body" and "along the direction of the mandible body and parallel to the sagittal plane" had the least effect on the TMJ. When designing the traction direction of MDO, we should not only consider the influence of surgery on the shape of jaw and upper respiratory tract, but also weigh in the influence of traction direction on the TMJ, and determine the direction of traction which has the least influence on the TMJ.

Objective:To determine the direction of traction that has the least influence on temporomandibular joint (TMJ) during mandibular distraction osteogenesis(MDO).Methods:(1) The three-dimensional finite element model was established after the mandible data were obtained by cone beam computed tomography (CBCT) scanning, and the validity of the model was verified. (2) Based on the verified three-dimensional finite element model, the distraction osteogenesis of mandible was carried out with six different directions. (3) The effects of different traction directions on disc pressure, osteotomy displacement, temporal bone pressure and condylar pressure were measured.Results:(1)In the thinnest area of the articular disc, the direction of the minimum stress on the upper and lower surfaces of the disc was "along the direction of the mandible, parallel to the surface of the mandible" . (2) Under the same load, the displacement of each osteotomy surface along the traction direction was different, but the difference was not big, and the effect was basically the same. (3) "Along the direction of the mandible, parallel to the surface of the mandible" and "along the direction of the mandible and parallel to the sagittal plane" had less pressure on the temporal bone than other situations, and the two directions of traction were parallel to the mandible. After the force decomposition, the direction of the condyle was the smallest, so the pressure on the condyle was smaller.Conclusions:A satisfactory TMJ model can be obtained by DICOM. The traction force of "along the direction of the mandible body, parallel to the surface of the mandible body" and "along the direction of the mandible body and parallel to the sagittal plane" had the least effect on the TMJ. When designing the traction direction of MDO, we should not only consider the influence of surgery on the shape of jaw and upper respiratory tract, but also weigh in the influence of traction direction on the TMJ, and determine the direction of traction which has the least influence on the TMJ.

MR angiography(MRA)is an important imaging method for non-invasive evaluation on the structure and hemodynamics of portal venous system.With the emergence of new MR sequences and iterations of contrast agents,the applications of portal MRA in children became more and more feasible.The technical research progresses and challenges of portal MRA in children were reviewed in this article.