The Pierre Robin Mandible is Hypoplastic and Morphologically Abnormal:

Mandibular morphology and distraction osteogenesis vectors in patients with Robin sequence

The aims of this cohort study were to compare the mandibular morphology between patients with Robin sequence (RS) and controls, and to examine the effects of mandibular distraction osteogenesis (MDO) using different vectors. Measurements of the mandibles of 80 patients with RS and 46 controls aged< 90 days were made using computed tomography. The data were compared among isolated RS patients (n = 58), syndromic RS patients (n = 22), and controls. Patients with RS exhibited significantly shorter ramus and body lengths and larger symphyseal angles than controls (all P < 0.001). Patients with isolated RS had shorter body lengths (P < 0.001), while syndromic patients had shorter ramus and body lengths (both P < 0.001) than controls. Seventy RS patients underwent MDO. Pre-MDO (n = 37) and post-MDO (n = 29) mandibular measurements were compared between patients undergoing MDO with a vertical vector and those undergoing MDO with a horizontal vector. Polysomnography data from part of the cohort highlighted the effectiveness of both vectors. MDO with a horizontal vector conferred 11% and 36% increases in ramus and body length, respectively, while these increases were 34% and 27.5%, respectively, with a vertical vector. MDO with a vertical vector was effective in lengthening ramus and body components and should be considered in the presence of ramus hypoplasia.

Mandibular Distraction Osteogenesis in Robin Sequence Using Three-Dimensional Analysis and Planning

SUMMARY

The optimal management of patients with Robin sequence may include neonatal mandibular distraction osteogenesis, which has been used to achieve excellent functional and aesthetic outcomes in appropriate patients. This article and video vignette depict the treatment of micrognathia and airway obstruction secondary to Robin sequence, demonstrating the planning and surgical approach of the senior author (D.M.S.) using mandibular distraction osteogenesis.

Spatial Analysis of the Temporomandibular Joint and Condyle Following Mandibular Distraction in Robin Sequence

ABSTRACT

To comprehensively assess changes in temporomandibular joint and mandibular condyle morphology in Robin sequence (RS) patients undergoing mandibular distraction osteogenesis (MDO). A retrospective analysis of pediatric patients with RS and functional temporomandibular joints who underwent MDO by a single surgeon was performed. Preoperative and postoperative computed tomography (CT) scans were morphometrically analyzed three-dimensional in 3-matic and Mimics (Materialise). Comparative analysis was performed using Wilcoxon signed-rank tests. Fourteen RS patients were included (28 condyles, 56 CT scans), 78% male and 22% females. The mean age at surgery was 9.4 weeks (range 1.6-46.7 weeks). The average age at initial CT was 5.3 days (range 0-11 days). The mean time interval for CT scan before MDO and after hardware removal were 8.8 ± 6.4 days and 11.2 ± 25.8 days, respectively. Rotatory changes of the condyle revealed a significantly decreased horizontal angle following MDO (-7.55°, 95% confidence interval -11.13° to -3.41°; P < 0.001). Anteroposteriorly, the angle between condylar process and ramus (incline) increased significantly (14.14°, 95% confidence interval 10.71°-19.59°; P < 0.001). Intragroup analysis revealed no difference between left versus right condylar position measurements. The condyle itself increased in size and length and the intercondylion distance increased post-MDO. There were no complications and all patients achieved relief of airway obstruction without tracheostomy. Morphologic and positional changes of the mandibular condyle following MDO in RS patients parallel changes that occur during normal development in non-RS patients. As a result, MDO may facilitate normal condylar morphology and function in RS patients.

Predictors of Respiratory Dysfunction at Diagnosis of Robin Sequence

OBJECTIVES/HYPOTHESIS

Robin sequence (RS) consists of associated micrognathia, glossoptosis, and respiratory dysfunction, with or without cleft palate. Studies on how different patient characteristics impact the severity of respiratory dysfunction are scarce and contradictory; this study investigates how different features affect respiratory obstruction severity at diagnosis of RS in controlled analysis.

STUDY DESIGN

Retrospective cohort study that enrolled 71 RS patients under 90 days old who received care in our institution from 2009 to 2020.

METHODS

The primary outcome, respiratory dysfunction, was categorized into four severity groups and analyzed using a multinomial logistic regression model that considered age, sex, mandible length, cleft palate, syndromic diagnosis, other airway anomalies, and degree of glossoptosis.

RESULTS

Mandible length, syndromic diagnosis, and Yellon grade 3 glossoptosis were related to poorer respiratory outcomes (need for respiratory support). In univariate analysis, for each additional 1 mm of mandible length at diagnosis, a mean reduction of 28% in the risk of needing respiratory support was observed (OR = 0.72; 0.58-0.89); syndromic diagnosis and grade 3 glossoptosis also raised the risk (OR = 6.50; 1.59-26.51 and OR = 12.75; 1.03-157.14, respectively). In multivariate analysis, only mandible length significantly maintained its effects (OR = 0.73; 0.56-0.96), a 27% reduction.

CONCLUSIONS

Mandible length was an independent predictor for more severe respiratory dysfunction in RS patients, with larger mandibles showing protective effects. Syndromic diagnosis and Yellon grade 3 glossoptosis are also likely to be associated with poorer respiratory outcomes, although this was not demonstrated in multivariate analysis.

LEVEL OF EVIDENCE

4 Laryngoscope, 2021.

Loss of Extreme Long-Range Enhancers in Human Neural Crest Drives a Craniofacial Disorder

Non-coding mutations at the far end of a large gene desert surrounding the SOX9 gene result in a human craniofacial disorder called Pierre Robin sequence (PRS). Leveraging a human stem cell differentiation model, we identify two clusters of enhancers within the PRS-associated region that regulate SOX9 expression during a restricted window of facial progenitor development at distances up to 1.45 Mb. Enhancers within the 1.45 Mb cluster exhibit highly synergistic activity that is dependent on the Coordinator motif. Using mouse models, we demonstrate that PRS phenotypic specificity arises from the convergence of two mechanisms: confinement of Sox9 dosage perturbation to developing facial structures through context-specific enhancer activity and heightened sensitivity of the lower jaw to Sox9 expression reduction. Overall, we characterize the longest-range human enhancers involved in congenital malformations, directly demonstrate that PRS is an enhanceropathy, and illustrate how small changes in gene expression can lead to morphological variation.

Is Intensive Care Unit Admission Necessary After Removal of Mandibular Distraction Devices in Infants With Robin Sequence?

OBJECTIVE

Intensive care unit (ICU) care is routinely required after the operation to initiate mandibular distraction osteogenesis (MDO) in infants with Robin sequence (RS). Many patients are also managed in the ICU after subsequent device removal. It is uncertain if ICU care, which is expensive and limited, is necessary after this second operation. The objective of this study was to evaluate the incidence of respiratory events following device removal. We hypothesized that respiratory events would be infrequent and non-ICU inpatient monitoring would be adequate.

DESIGN

This is a retrospective study of patients with RS from 2013 to 2018.

PATIENTS

Patients were included if they had MDO and distractor removal during the first year of life. Patients were excluded if they had a tracheostomy or remained intubated after distractor removal.

MAIN OUTCOME MEASURE

Postoperative respiratory events.

RESULTS

Twenty-five (60% male) patients were included. Mean age and weight at distractor removal were 142 ± 79 days of life and 5.5 ± 1.1 kg. Mean apnea-hypopnea index after completion of distraction was 1.1 ± 1.5 events/hour. Two (8%) patients experienced postoperative respiratory events that required intervention. In 1 (4% of sample) of these, the event was deemed to have benefited from ICU-level care. Two variables were significantly associated with these events: congenital heart disease (P = .020) and concomitant procedure performed during the same operation (P = .020).

CONCLUSIONS

Intensive care unit-level care is rarely needed after distractor removal in infants with RS. Intensive care unit admission should be considered in patients with congenital cardiac disease and when having multiple operations during the same anesthetic.

Short-term condylar and glenoid fossa changes in infants with Pierre Robin sequence undergoing mandibular distraction osteogenesis

The purpose was to evaluate short-term changes in condylar and glenoid fossa morphology in infants with Pierre Robin sequence (PRS) undergoing early (age <4 months) mandibular distraction osteogenesis (MDO) for the management of severe airway obstruction. Computed tomography data from infants with PRS who had MDO were compared to those of age-matched control infants without facial skeletal dysmorphology. Surface/volume, linear, and angular measurements of the condyle and glenoid fossa were obtained and compared between infants with PRS and controls. Eleven infants with PRS met the inclusion criteria. There were five female and six male subjects with a mean age at the time of MDO of 41±32 days. Prior to MDO, PRS mandibles had a smaller condylar articulating surface area and volume than age-matched control mandibles, with a more laterally positioned condylar axis (P≤0.05). Following MDO, there were significant increases in condylar articulating surface area and volume, approaching those of normal controls, with further lateral translation of the condylar axis (P≤0.05). Condyle and glenoid fossa morphology is largely normalized following early MDO in infants with PRS. The condylar axis translates laterally as a result of MDO; this change is not observed with mandibular growth in infants without PRS.

Comparison Between Treacher Collins Syndrome and Pierre Robin Sequence: A Cephalometric Study

OBJECTIVE

The aim of this study was to compare the dentoskeletal pattern of Treacher Collins syndrome (TCS) and nonsyndromic Pierre Robin sequence (PRS).

DESIGN

Retrospective.

SETTING

Single center.

PATIENTS

Eighteen patients diagnosed with TCS (Group TCS) or PRS (Group PRS) in rehabilitation treatment at a single center. Group TCS was composed of 9 patients (4 male, 5 female) with a mean age of 12.9 years (standard deviation = 4.8). Group PRS was composed of 9 patients paired by age and sex with group TCS.

MAIN OUTCOME MEASURE(S)

Cone beam computed tomography-derived cephalometric images taken before the orthodontic or the orthodontic-surgical treatment were analyzed using Dolphin Imaging (Dolphin Imaging 11.0 & Management Solutions). Variables evaluating the cranial base, the maxillary and mandibular skeletal components, maxillomandibular relationship, the vertical components and the dentoalveolar region were measured. Intergroup comparisons were performed using t tests. The significance level considered was 5%.

RESULTS

Intergroup differences in the mandible size and growth pattern were observed. Group TCS showed a smaller mandibular length (Co-Go, Co-Gn) and a higher palatal plane (SN-Palatal Plane) and mandibular plane angles (SN-Go.Gn) compared to group PRS. No differences between TCS and PRS were observed for the sagittal position of the maxilla, maxillomandibular relationship, and dental components.

CONCLUSIONS

Treacher Collins syndrome presented a decreased mandible and a more severe vertical growth pattern compared to PRS.

Quantification of Mandibular Morphology in Pierre Robin Sequence to Optimize Mandibular Distraction Osteogenesis

Background:

Mandibular distraction osteogenesis (MDO) is the primary surgical intervention to treat airway obstruction in Pierre Robin sequence (PRS). Current morphologic studies of PRS mandibles do not translate into providing airway management decisions. We compare mandibles of infants with nonsyndromic PRS to controls characterizing morphological variances relevant to distraction. We also examine how morphologic measurements and airway grades correlate with airway management.

Methods:

Patients with PRS under 2 months old were age and sex matched to controls. Demographic and perioperative data, and Cormack-Lehane airway grades were recorded. Computed tomography scans were used to generate mandibular models. Bilateral condylions, gonions, and the menton were identified. Linear and angular measurements were made. Wilcoxon rank sum and 2-sample t tests were performed.

Results:

Twenty-four patients with PRS and 24 controls were included. Seventeen patients with PRS required MDO. PRS patients had shorter ramus heights (16.7 vs 17.3 mm; P = .346) and mandibular body lengths (35.3 vs 39.3 mm; P < .001), more acute gonial angles (125.3° vs 131.3°; P < .001), and more obtuse intergonial angles (94.2° vs 80.4°; P < .001) compared to controls. No significant differences were found among patients requiring MDO versus conservative management nor among distracted patients with high versus low airway grades.

Conclusion:

Our study examines the largest and youngest PRS population to date regarding management of early airway obstruction with MDO. Our findings indicate that univector mandibular body distraction allows for normalization in nonsyndromic patients with PRS, and airway obstruction management decisions should remain clinical.

A Novel Geometric Morphometric Analytical Method for Classifying Mandibular Morphology in Infants With Isolated Pierre Robin Sequence

PURPOSE

There is a lack of uniformity in the diagnostic criteria and system for the morphologic classification of micrognathia in infants with isolated Pierre Robin sequence (IPRS). Therefore, the aim of this study was to create a morphologic classification system for IPRS-affected mandibles that may guide surgical management and osteotomy design.

PATIENTS AND METHODS

We designed and implemented a retrospective cross-sectional study. The study sample included infants with IPRS. The predictor variables included shape variables of the IPRS-affected mandibles. The outcome of interest was morphologic differences among the IPRS-affected mandibles in the infancy stage. The original coordinate data of the mandibular images were analyzed by a generalized Procrustes analysis and 2-block partial least squares analysis to identify the focal and nonfocal areas in the IPRS-affected mandibles. The original feature points were modified according to the results of 2-block partial least squares analysis. The modified feature points were further analyzed by principal component analysis, K-means cluster analysis, and canonical variate analysis to obtain a morphologic classification of the IPRS-affected mandibles.

RESULTS

One hundred fifty infants with IPRS were enrolled in this study. Principal component analysis showed that the variations among IPRS-affected mandibles were mostly in terms of the shapes of the mandibular ramus, mandibular body, and angle of the mandible. On the basis of the results of K-means cluster analysis and canonical variate analysis, the mandibles in group A3 showed characteristics such as a simply shorter mandibular body. Group B3 was adjusted to show characteristics such as a shorter mandibular body with a more obtuse mandibular angle, whereas group C3 showed characteristics such as a shorter mandibular body with a shorter mandibular ramus.

CONCLUSIONS

Our study confirmed the hypothesis that there are quantifiable morphologic differences among the IPRS-affected mandibles, and it provided a morphologic classification of the IPRS-affected mandibles that will help to promote the clinical diagnosis and treatment.

Dynamical Changes of Mandible and Upper Airway After Mandibular Distraction Osteogenesis in Pierre Robin Sequence

OBJECTIVE

To present the dynamical evaluation of mandible and upper airway size among Chinese infant patients following mandibular distraction osteogenesis in a short-term follow-up and compare predistraction measurements with a normal age- and sex-matched control.

METHODS

All the patients have undergone the computed tomography (CT) scan before mandibular distraction osteogenesis (T0), at the end of the distraction phase (T1), and 3 months after the end of the distraction phase before the distractor removal (T2). A CT analyzing computer software MIMICS was utilized to analyze the anatomic variables of upper airway size and mandible size. All analysis was based on a significance level of 0.05.

RESULTS

Eight patients with Pierre Robin sequence differed mainly in the mandibular body length and the minimum anteroposterior dimension of the retroglossal airway from the control. After mandibular distraction osteogenesis, the mandibular body length and the ramus height both increased significantly, the ramus height also increased after 3 months of consolidation. Only small increase in the airway dimension of the retroglossal area at T2 was observed compared with T1.

CONCLUSION

Mandibular distraction osteogenesis is an effective modality in treating Pierre Robin sequence. Compared with normal control, the main difference may be the length of mandibular body and the area of the retroglossal airway. There may not be an increase in the diameter of airway and the length of mandibular body after 3 months of growth and development in Pierre Robin sequence. Individual surgical plan should be made to gain a better prognosis.

Pierre Robin Sequence: Incidence of Speech-Correcting Surgeries and Fistula Formation

Objective:

Children with Pierre Robin sequence (PRS) and cleft palate have a high rate of velopharyngeal insufficiency (VPI) following primary palatoplasty. Our purpose was to determine the long-term incidence of speech-correcting surgeries (SCSs) and fistula rates in PRS after primary palatoplasty and the influence of possible causal factors.

Design:

A retrospective single-center, observational chart review study.

Participants:

After exclusion, the study cohort comprised 78 nonsyndromic PRS children (48 females) born between 1990 and 2009 and treated at the Cleft Palate and Craniofacial Center of Helsinki University Hospital, Finland. Causal factors included gender, surgeon, age at primary palatoplasty, surgical technique, airway obstruction in infancy, and cleft severity. We analyzed the outcome at age 8 years and at data retrieval, with a median follow-up of 14 years (range: 8-27 years).

Results:

Thirty-four (43.6%) children received SCS by age 8 years, and of the 19 (24.4%) postoperative fistulas, 6 (7.7%) underwent closure. At data retrieval, 37 (47.4%) children had undergone SCS and 8 (10.3%) had a fistula closure. Median age at SCS was 6 years. The results showed no significant association for gender, surgeon, age at primary palatoplasty, surgical technique, cleft severity, or airway obstruction in infancy regarding incidence of SCS, fistulas, or repaired fistulas.

Conclusion:

Pierre Robin sequence in children is associated with a high incidence of SCS and fistula formation, which necessitates accurate clinical follow-up and observation of speech development. The development of VPI in PRS is complex and most likely involving multiple factors.

Neonatal Mandibular Distraction Does Not Increase Inpatient Complications

Objective:

The purpose of this study was to determine whether performing mandibular distraction osteogenesis (MDO) during the neonatal period increased inpatient complications as measured through health-care burden.

Materials and Methods:

This was a retrospective cohort study of the Kids’ Inpatient Database from 2000 to 2011. Infants receiving MDO prior to 12 months of age were included. The primary study predictor was distraction age, classified as either neonatal or non-neonatal. Secondary predictors were patient demographics, hospitalization characteristics, diagnoses, and procedures. The outcomes were the number of procedures performed, postoperative length of stay (pLOS), hospital charges, and the discharge transfer rate. Outcomes were compared between the primary predictors using χ2 and independent 2-sample t tests. Multiple linear and logistic regression models were created using clinically relevant predictors to assess the independent effect of neonatal age on each outcome.

Results:

The study sample contained 102 patients, of who 50 (49.0%) were distracted in the neonatal period. Neonatal MDO patients were more likely to have a cleft palate (86.0% vs 55.8%; P < .001) and present with feeding difficulties (38.0% vs 19.2%; P = .036) that were treated through total parenteral nutrition (26.0% vs 9.6%; P = .030) but otherwise did not have significantly different characteristics compared to non-neonatal patients. The multiple regression models confirmed that neonatal age did not influence any of the study outcomes, although other secondary predictors were found to influence the pLOS, hospital charges, and number of inpatient procedures.

Conclusions:

Neonatal MDO was not associated with increased complications. At experienced centers, neonatal status should not be considered a contraindication to treatment.