Characterization of labiomandibular movements induced after isolated LeFort I osteotomy in the surgical management of class III malocclusion.

INTRODUCTION: Maxillary surgery alone can be proposed for the surgical management of class III malocclusion, but anticipating outcomes for the labiomental muscle complex is challenging due to the mandibular autorotation phenomenon. The objective of this study was to quantify the mandibular and labiomental movements induced by maxillary osteotomy alone in the management of class III malocclusion according to different clinical and surgical variables. METHODS: The post-operative changes in mandibular and labiomental shapes were studied by geometric morphometry from the pre- and post-operative lateral cephalometric radiograph of 25 patients. The explanatory variables tested were maxillary advancement, maxillary rotation, and divergence. RESULTS: Soft tissues repositioning are different from postoperative mandibular repositioning after maxillary osteotomy. Neuromuscular adjustments of mandible depend on divergence and the maxillary rotation. Labiomental response only depends on divergence. CONCLUSION: The surgical procedure does not have the same bone-related and musculocutaneous effects on patients with the same class III malocclusion. It is therefore essential for surgeons to understand the effects of their procedure on musculocutaneous tissues in order to best anticipate post-operative outcomes.

Craniofacial growth and function in achondroplasia: a multimodal 3D study on 15 patients.

BACKGROUND: Achondroplasia is the most frequent FGFR3-related chondrodysplasia, leading to rhizomelic dwarfism, craniofacial anomalies, stenosis of the foramen magnum, and sleep apnea. Craniofacial growth and its correlation with obstructive sleep apnea syndrome has not been assessed in achondroplasia. In this study, we provide a multimodal analysis of craniofacial growth and anatomo-functional correlations between craniofacial features and the severity of obstructive sleep apnea syndrome. METHODS: A multimodal study was performed based on a paediatric cohort of 15 achondroplasia patients (mean age, 7.8 ± 3.3 years), including clinical and sleep study data, 2D cephalometrics, and 3D geometric morphometry analyses, based on CT-scans (mean age at CT-scan: patients, 4.9 ± 4.9 years; controls, 3.7 ± 4.2 years). RESULTS: Craniofacial phenotype was characterized by maxillo-zygomatic retrusion, deep nasal root, and prominent forehead. 2D cephalometric studies showed constant maxillo-mandibular retrusion, with excessive vertical dimensions of the lower third of the face, and modifications of cranial base angles. All patients with available CT-scan had premature fusion of skull base synchondroses. 3D morphometric analyses showed more severe craniofacial phenotypes associated with increasing patient age, predominantly regarding the midface-with increased maxillary retrusion in older patients-and the skull base-with closure of the spheno-occipital angle. At the mandibular level, both the corpus and ramus showed shape modifications with age, with shortened anteroposterior mandibular length, as well as ramus and condylar region lengths. We report a significant correlation between the severity of maxillo-mandibular retrusion and obstructive sleep apnea syndrome (p < 0.01). CONCLUSIONS: Our study shows more severe craniofacial phenotypes at older ages, with increased maxillomandibular retrusion, and demonstrates a significant anatomo-functional correlation between the severity of midface and mandible craniofacial features and obstructive sleep apnea syndrome.

Chiari malformation type I surgery in children: French multicenter 10-year cohort.

OBJECTIVE: Chiari malformation type I (CM-I) is frequent in children and remains a surgical challenge. Several techniques have been described for posterior fossa decompression. No decision algorithm has been validated, and strategies are highly variable between institutions. The goal of this study was to define therapeutic guidelines that take into consideration patient specificities. METHODS: The authors retrospectively collected data from patients who were < 18 years of age, were diagnosed with CM-I, and were treated surgically between 2008 and 2018 in 8 French pediatric neurosurgical centers. Data on clinical features, morphological parameters, and surgical techniques were collected. Clinical outcomes at 3 and 12 months after surgery were assessed by the Chicago Chiari Outcome Scale. The authors used a hierarchical clustering method to define clusters of patients by considering their anatomical similarities, and then compared outcomes between surgical strategies in each of these clusters. RESULTS: Data from 255 patients were collected. The mean age at surgery was 9.6 ± 5.0 years, syringomyelia was reported in 60.2% of patients, the dura mater was opened in 65.0% of patients, and 17.3% of patients underwent a redo surgery for additional treatment. The mean Chicago Chiari Outcome Scale score was 14.4 ± 1.5 at 3 months (n = 211) and 14.6 ± 1.9 at 12 months (n = 157). The hierarchical clustering method identified three subgroups with potentially distinct mechanisms underlying tonsillar herniation: bony compression, basilar invagination, and foramen magnum obstruction. Each cluster matched with specific outcomes. CONCLUSIONS: This French multicenter retrospective cohort study enabled the identification of three subgroups among pediatric patients who underwent surgery for CM-I, each of which was associated with specific outcomes. This morphological classification of patients might help in understanding the underlying mechanisms and providing personalized treatment.

From micro to macroevolution: drivers of shape variation in an island radiation of Podarcis lizards.

Phenotypictraits have been shown to evolve in response to variation in the environment. However, the evolutionary processes underlying the emergence of phenotypic diversity can typically only be understood at the population level. Consequently, how subtle phenotypic differences at the intraspecific level can give rise to larger-scale changes in performance and ecology remains poorly understood. We here tested for the covariation between ecology, bite force, jaw muscle architecture, and the three-dimensional shape of the cranium and mandible in 16 insular populations of the lizards Podarcis melisellensis and P. sicula. We then compared the patterns observed at the among-population level with those observed at the interspecific level. We found that three-dimensional head shape as well as jaw musculature evolve similarly under similar ecological circumstances. Depending on the type of food consumed or on the level of sexual competition, different muscle groups were more developed and appeared to underlie changes in cranium and mandible shape. Our findings show that the local selective regimes are primary drivers of phenotypic variation resulting in predictable patterns of form and function. Moreover, intraspecific patterns of variation were generally consistent with those at the interspecific level, suggesting that microevolutionary variation may translate into macroevolutionary patterns of ecomorphological diversity.