Dental consequences of pterygomaxillary dysjunction during fronto-facial monobloc advancement with internal distraction for Crouzon syndrome

Comparison of Internal and External Distraction in Frontofacial Monobloc Advancement: A Three-Dimensional Quantification

BACKGROUND

Crouzon syndrome is characterized by complex craniosynostosis and midfacial hypoplasia. Where frontofacial monobloc advancement (FFMBA) is indicated, the method of distraction used to achieve advancement holds an element of equipoise. This two-center retrospective cohort study quantifies the movements produced by internal or external distraction methods used for FFMBA. Using shape analysis, this study evaluates whether the different distraction forces cause plastic deformity of the frontofacial segment, producing distinct morphologic outcomes.

METHODS

Patients with Crouzon syndrome who underwent FFMBA with internal distraction [Hôpital Necker-Enfants Malades (Paris, France)] or external distraction [Great Ormond Street Hospital for Children (London, United Kingdom)] were compared. Digital Imaging and Communications in Medicine files of preoperative and postoperative computed tomographic scans were converted to three-dimensional bone meshes and skeletal movements were assessed using nonrigid iterative closest point registration. Displacements were visualized using color maps and statistical analysis of the vectors was undertaken.

RESULTS

Fifty-one patients met the strict inclusion criteria. Twenty-five underwent FFMBA with external distraction and 26 with internal distraction. External distraction provides a preferential midfacial advancement, whereas internal distractors produce a more positive movement at the lateral orbital rim. This confers good orbital protection but does not advance the central midface to the same extent. Vector analysis confirmed this to be statistically significant ( P < 0.01).

CONCLUSIONS

Morphologic changes resulting from monobloc surgery differ depending on the distraction technique used. Although the relative merits of internal and external distraction still stand, it may be that external distraction is more suited to addressing the midfacial biconcavity seen in syndromic craniosynostosis.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, III.

Subcranial Midface Advancement in Patients with Syndromic Craniosynostosis

Patients with syndromic craniosynostosis can present with midface hypoplasia, abnormal facial ratios, and obstructive sleep apnea. These symptoms can all be improved with midface advancement, but it is essential to evaluate the specific morphologic characteristics of each patient's bony deficiencies before offering subcranial advancement. Midface hypoplasia in Crouzon syndrome is evenly distributed between the central and lateral midface and reliably corrected with Le Fort III distraction. In contrast, the midface hypoplasia in Apert/Pfeiffer syndromes occurs in both an axial and a sagittal plane, with significantly more nasomaxillary hypoplasia compared with the orbitozygomatic deficiency.

Dental phenotype in Crouzon syndrome: A controlled radiographic study in 22 patients

OBJECTIVE

This retrospective radiographic controlled study investigates the dental phenotype in patients with Crouzon syndrome to determine if differences are observed as suggested by the FGFR2^C342Y/+ Crouzon mouse models, and whether these models could be of interest to study the role of this mutation in tooth development.

DESIGN

We assessed dental phenotype using dedicated linear measurements in 22 children with Crouzon syndrome and compared tooth morphology in both primary and permanent dentitions to an age-matched control group. Descriptive statistics were performed with "Sex" and "Age" as covariates for the permanent tooth models and "Sex" only for the primary tooth models, to take into account potential confounding factors.

RESULTS

We showed that permanent but not primary tooth dimensions were globally reduced in Crouzon syndrome, without microdontia. In permanent dentition, crown height, mesiodistal and faciolingual cervical diameters were reduced by 6.3%, 5.7% and 5.5% respectively (p < 0.05).

CONCLUSION

Our results underline the implication of Fibroblast Growth Factor Receptor 2 (FGFR2) in dental development of humans and contribute to support FGFR2^C342Y/+ Crouzon mouse models as partial replicas of this condition, including in the oral region.

Influence of Monobloc/Le Fort III Surgery on the Developing Posterior Maxillary Dentition and Its Resultant Effect on Orthognathic Surgery

BACKGROUND

Timing of frontofacial surgery for the syndromic craniosynostosis as it relates to various surgical risks has not been adequately studied. The purpose of this study was to investigate posterior dental complications of midface advancement in patients with syndromic craniosynostosis undergoing surgery at different ages and the effects on subsequent orthognathic surgery.

METHODS

A retrospective chart review of patients with syndromic craniosynostosis treated with midface advancement (monobloc or Le Fort III) from 1999 to 2018 was carried out. Patient demographics, records, and imaging studies were reviewed. A subanalysis of those patients who were also treated with orthognathic surgery from 2014 to 2018 with imaging studies available for analysis was also performed.

RESULTS

Thirty-seven patients met the inclusion criteria. Sixty-four percent of the patients had radiographic evidence of maxillary molar dental abnormality. Older age at the time of surgery was significantly associated with a lower odds of sustaining dental injury (OR, 0.55; p = 0.034). The odds of damaging second or third maxillary molars was significantly higher with a younger age at the time of surgery (p = 0.021 and p = 0.034). The odds of sustaining dental injury increased moving posteriorly, showing the risk of abnormal pattern of M3 greater than M2 greater than M1. Advanced age at the time of surgery was significantly associated with decreased odds of dental injury (OR, 0.55; p = 0.034).

CONCLUSIONS

Damage to the developing permanent maxillary molars may affect orthodontic management, mastication, and potentially maxillary development. Delaying frontofacial surgery until development of the permanent maxillary dentition should be considered if other indications do not mandate earlier intervention.

Characteristics of the Sphenoid Bone in Crouzon Syndrome

BACKGROUND

The goal of this study is to analyze the safety of reconstructive surgeries for Crouzon syndrome, and to understand the deformities and complications related to the surgical procedure.

METHODS

Thirty-nine subjects underwent preoperative computed tomographic scans were included (Crouzon, n = 19; controls, n = 20) in this study. Craniofacial cephalometric measurements were analyzed by Materialise software.

RESULTS

The overall average distance from the pterygoid junction to the coronal plane in the patients with Crouzon syndrome was 21.34 mm (standard deviation [SD] 5.13), which was deeper than that in the controls by 35% (P = 0.000).The overall average distances between the left and right foramen ovale and pterion on the sphenoid bone in the subjects were 64.93 mm (SD 7.56) and 67.83 mm (SD 8.57), which were increased by 13% (P = 0.001) and 14% (P = 0.001) compared with those in the controls.The overall distances between the most inferior point of the left and right lateral pterygoid plate and the medial pterygoid plate in the subjects were 51.09 mm (SD 6.68) and 51.51 mm (SD 10.98), which was not statically different from the controls (P = 0.887, P = 0.991, respectively).

CONCLUSIONS

This study characterized the surgically relevant anatomy of the sphenoidal bone. The pterygomaxillary junction is located in the posterior of the skull. Though there are some anatomical differences due to age, it is well known that the cranial cavity of the sphenoid side is likely to be enlarged in Crouzon syndrome, which may contribute to the other complications of the disease.