Mandibular growth in infants with Robin sequence treated with the Tübingen palatal plate

This was a retrospective audit in all infants with a diagnosis of RS admitted to our center between 6/2015 and 5/2018. This is a national referral center for RS to which most patients are referred by other hospitals after a trial of prone positioning has failed; only a minority is born in our hospital. Clinical data were extracted from the department’s electronic database.

Following hospital admission, infants are monitored in the neonatal intermediate care unit where the severity of UAO is assessed by a multichannel baseline cardiorespiratory sleep study (polygraphy, PG) [16]. Indication for initiating TPP treatment is a mixed-obstructive apnea index (MOAI) > 3 in this initial sleep study.

Next, a maxillary imprint is taken with a custom-made impression tray using alginate (Tetra-Chrom-Super-Alginat, ISO 1563, Klasse B, Typ I, Kanie-Denta, Herford, Germany). This imprint covers the entire hard palate including the cleft, the alveolar ridges and the vestibule. This procedure takes only a few seconds and is carried out in the neonatal intermediate care unit under cardiorespiratory monitoring without sedation, but in the presence of an experienced neonatologist.

The TPP consists of a palatal part that covers the hard palate and the cleft as well as the alveolar ridges and a velar extension of individual length (approximately 3 cm). The shape of this extension is modeled from dental wax and is then attached dorsally to the plaster cast [20]. After an individual prototype of the plate has been produced, infants undergo fiberoptic nasopharyngoscopy without sedation to assess the type and localization of the UAO. During this endoscopy, which usually takes less than a minute, the tip of the extension descending down to the vallecula epiglottica is checked and is ideally located just above the epiglottis. The angle of the velar extension is responsible for the anterior shifting of the base of the tongue and is adjusted so that it pushes the base of the tongue sufficiently forward to erect the epiglottis, thereby widening the pharyngeal space. If the airway appears endoscopically open, the prototype plate is finished and a strengthening wire incorporated into the extension to safeguard the device against mechanical failure. Plates are held in situ with the help of a fixative cream (Corega Super-Haftcreme; Procter & Gamble, Cincinnati, OH) and by extraoral wire bows secured on the infant’s face using adhesive tape (Steri-Strip and Cavilon-No Sting Barrier Film, Steri-Strip Compound Benzoin Tincture, 3 M Health Care, St. Paul, MN, USA). The TPP is worn continuously and its fit regularly controlled by the nursing staff. The plate is briefly removed once daily to clean the alveolar ridge and inspect it for pressure marks or decubitus. After a few days of treatment with a clinically well-fitting TPP its effectiveness in relieving UAO is assessed by a second sleep study, with the aim of achieving a mixed-obstructive apnea index (MOAI) < 3. If this sleep study still shows a MOAI > 3, the plate is modified.

Treatment in infants also comprises appropriate feeding techniques (finger feeding and Playtex Drop-Ins®, Playtex Products, Edgewell, North Bergen, NY, USA) and an orofacial stimulation therapy according to Castillo-Morales®.

The next sleep study is usually performed approximately 3 months following the initial hospital stay. If the palatal part of the plate has become too small, a new TPP is produced and fitted. In general, new plates become necessary because of maxillary growth, i.e. often after approximately 3–4 months or if a notch appears on the alveolar ridges.

Cardiorespiratory sleep studies were performed using a computerized polysomnographic system (Embla N 7000, MedCare, Reykjavik, Iceland). The study montage comprised the following channels and sensors: chest and abdominal wall movements (respiratory inductive plethysmography, MedCare), nasal pressure and linearized nasal airflow (nasal prongs and built-in pressure transducer, MedCare), pulse oximeter saturation (SpO₂) and pulse waveform (Radical, Masimo Inc., Irvine, USA), electrocardiogram (MedCare), and digital video via an infrared camera (Panasonic; Tokyo, Japan). Recordings commenced in the evening and lasted for at least 8 h. All sleep studies were performed in supine position even prior to fitting the TPP, with children being turned to the prone position or recordings terminated if more than 3 desaturations to < 60% SpO₂ occurred.

Recordings were manually analyzed for the presence of respiratory events as described elsewhere [17, 18, 20]. In brief, total sleep time (TST) was determined from the first to the last 10-min epoch without movement artifact; recordings comprising < 3 h of TST were excluded. Central, mixed and obstructive apneas were identified and a mixed-obstructive apnea index (MOAI) calculated as the sum of mixed and obstructive apneas per hour of TST. Obstructive sleep apnea syndrome (OSAS) was defined as a MOAI > 1.

Desaturation events were defined as a fall in SpO₂ to < 80% (excluding motion-associated events) and expressed as the desaturation index, defined as events per hour of TST (DI80).

One infant had no sleep study performed because he had arrived at our department already with a tracheostomy in place.

The Jaw Index compares the size of upper to that of the lower jaw (Fig. 1). With a small mandible and a clear maxillary overjet, high values are obtained for this index. By using a measuring tape, the maxillary arch was measured from the left to the right tragus via the subnasal point, and the mandibular arch from the left to the right tragus via the pogonion point [8]. The alveolar overjet was determined with a micrometer depth gauge intraorally and defined as the frontodorsal distance between the most anterior points of the upper and lower alveolar arches. The index could usually be measured within < 1 min.

Standard Deviation Scores (SDS) were calulated for weight, length and head circumference

using LMSgrowth (version 2.14; http://​www.​healthforallchil​dren.​com/​?​product=​lmsgrowth). The reference population was the British 1990 growth reference [21] fitted by maximum penalized likelihood.

Descriptive statistics were used to summarize patient characteristics and sleep study results. Results are reported as median and interquartile range (IQR). Sleep parameters and Jaw Index data obtained upon admission, prior to discharge and 3 months later were compared using the Wilcoxon signed rank test; to assess correlations between MOAI and Jaw Index or Maxillary/Mandibular arch ratio the Pearson correlation coefficient was calculated.

Comparisons of SDS values for weight between various time points were performed using the t-test. To account for the impact of intrauterine growth restriction, SDS differences for weight (SDS_discharge − SDS_admission, SDS_{3-month follow-up} − SDS_admission) were calculated to illustrate weight gain. Analyses were performed using GraphPad Prism 7 (GraphPad Software, Inc), and the level of significance was p < 0.05.

The study protocol was approved by the ethics committee of Tuebingen University Hospital (reference number Pr. Nr. 692/2018BO2).

Thirty-one infants with RS were admitted to our department between 6/2015 and 05/2018; in 20 (65%) complete data including the jaw index were available. Median age at admission was 25 (5.5–48.5) days and at the 3-month follow-up 131.5 (111–177) days. Median duration of the initial hospital stay was 17 (13.5–24) days, ranging from 3 to 61 days. Twenty-two infants (71%) had isolated and 9 (29%) syndromic RS. Demographic and clinical characteristics are summarized in Table 1.

Upon admission, 10 (32%) infants needed respiratory support: 5 (16%) were treated with continuous positive airway pressure (CPAP) or high flow nasal cannula, 3 with a pharyngeal tube plus CPAP. One infant was intubated and ventilated on admission and one had been tracheotomized by the referring hospital immediately after birth, but had his tracheostomy closed after 2 weeks of TPP treatment. Median MOAI at admission (excluding the infant with a tracheostomy) was 9.7 (4.8–24.2) and median DI80 was 0.14 (0–1.7; Table 2). Three infants (9.7%) had no OSAS and were only treated with a conventional palatal plate to cover their cleft, all other infants were treated by TPP. No infant needed mechanical ventilation at discharge, but one with syndromic RS did not benefit from TPP treatment and required a tracheostomy. The infant admitted with a tracheostomy had no initial sleep study; four infants did not have a sleep study at discharge (one required a tracheostomy, and three had no OSAS upon admission and were only treated with a conventional palatal plate). All remaining infants had at least two interpretable sleep studies recorded, one prior to and one following treatment. All patients reported in the 3-month follow-up group were treated with a TPP.

There were no serious adverse events like systemic infections or pulmonary aspiration. Predominant side effects were temporary pressure marks/decubitus on the hard or soft palate, which all healed within a few days after manually reshaping the plate.

SDS-scores for weight were similar at admission (− 1.34 (− 1.76 – − 0.57)), discharge (− 1.14 (− 1.79 – − 0.54; p = 0.97)) and at the 3-month follow-up (− 1.50 (− 1.89 – − 0.54; p = 0.68)).

At discharge, 7 infants (23% of n = 31) still received nasogastric tube feedings; this proportion fell to 2 infants with syndromic RS (8% of n = 26) at the 3-month follow-up.

Average value of the Jaw Index at admission was 8.8 (6.3–11.3), compared to 2.1 (2.0–4.0; p < 0.0001) at the 3-month follow up, the latter data in line with reference data on healthy infants obtained previously (Table 3).

Correlation analysis according to Pearson showed no significant correlation between MOAI and Jaw Index, but between the former and the maxillary/mandibular arch ratio (r = 0.58; p = 0.006; Fig. 2). Linear regression showed that an increase in the Maxillary/Mandibulary ratio of 0.1 led to an increase in the MOAI of approximately 20.

There were no differences in sleep study or jaw index results between infants with isolated vs. syndromic RS, but feeding difficulties were more common in the latter (Table 4).