Construction of virtual airway model to assist surgical correction of velopharyngeal insufficiency with posterior pharyngeal flap.

OBJECTIVE: Posterior pharyngeal flap (PPF) is one of the most common surgical technique to correct velopharyngeal insufficiency(VPI), during which controlling the sizes of the lateral pharyngeal ports(LPP) is the key to outcomes. One innovative procedure was developed to well control the size of LPP. MATERIALS AND METHODS: 40 patients with repaired cleft palate were collected from June 2022 to August 2023. All patients were diagnosed with VPI, and treated with modified PPF surgery. For each patient, upper airway model was reconstructed, and the virtual airway model of PPF was designed. The nasal valve area was measured as it was considered to be the narrowest part of the upper airway. The upper airway resistances under different sizes of LPP was predicted through computational fluid dynamics analysis. The minimum size of each lateral pharyngeal port without obviously increase of upper airway resistance was calculated through effect of lateral pharyngeal ports' size on upper airway resistance. Postoperative follow-up was 6-18 months, including speech outcome and respiration outcome. Resting soft palate length (RVL), effective working length of soft palate (EWL) and angle of soft palate elevation (AVL) were measured and compared according to the lateral cephalometric radiograph. RESULTS: There was a linear relationship between the threshold value and nasal valve (R = 0.62). Among the forty patients, the average size of nasal valve was 47.81 mm2, the average size of the threshold value of LPP was 31.63mm2. The proportion of velopharyngeal closure competence after surgery was 95 %. Compared with the preoperative measurements, there were significantly increase of RVL, EWL and AVL (P < 0.05). There were significantly difference in the nasal obstruction symptom evaluation score in long-term follow-up compared to short-term follow-up (P < 0.05), and no one needed flap revision. There was no significant difference in nasal respiration and nasal resistance before and after surgery (P > 0.05). CONCLUSION: With the help of computer fluid dynamics analysis, it is possible to predict the threshold size of lateral pharyngeal port without obviously increasing upper airway resistance and reduce the risk of suffering from airway obstruction for patients undergoing PPF surgery.

Potential new method of design for reconstruction of complicated mandibular defects: a virtual deformable mandibular model.

The treatment of complicated mandibular defects, including misshaped and missing bones, is challenging, and the success of reconstruction depends to a large extent on the formulation of a precise surgical plan. There is still no ideal preoperative method of design for reconstruction to deal with large, cross-midline, mandibular, segmental defects. We have built a virtual deformable mandibular model (VDMM) with 3-dimensional animation software. Sixteen handles were set on the model, and these could be easily controlled with a computer mouse to change the morphology of the deformable mandibular model. The computed tomographic (CT) data from 10 normal skulls was used to validate the adjustability of the VDMM. According to the positions of the mandibular fossa of the temporomandibular joint, the maxillary dental arch, and the craniomaxillofacial profile, the model could be adjusted to an ideal contour, which was coordinated with the skull. The VDMM was then adjusted further according to the morphology of the original mandible. A 3-dimensional comparison was made between the model of the deformed mandible and the original mandible. Using 16 control handles, the VDMM could be adjusted to a new outline, which was similar in shape to the original mandible. Within 3mm deviation either way, the absolute mean distribution of deviation between the contour of the deformed model and the original mandible was 92.5%. The VDMM might be useful for preoperative design of reconstruction of complicated mandibular defects.