Facial Nerve Dysfunction After Mandibular Distraction Osteogenesis in Patients with Robin Sequence: A Systematic Review and Meta-Analysis

Objective Robin Sequence (RS), characterized by micrognathia, glossoptosis, and upper airway obstruction, is an increasingly recognized diagnosis. An effective surgical intervention is mandibular distraction osteogenesis (MDO). This study analyzes published evidence regarding facial nerve dysfunction (FND) associated with MDO. Design and Setting According to PRISMA guidelines, a systematic review was carried out with databases queried in June 2019 using MESH terms, or equivalent terms, as follows: “distraction osteogenesis” and “Robin Sequence”. A review of original Spanish and English articles, were included. Outcome measures included the prevalence of FND; the affected branches; the rate of permanent vs. transient FND; the use of an internal vs. external device; the daily distraction rate; and finally, the overall distraction length. Subsequently, a meta-analysis was conducted to collate results regarding the prevalence of FND and the factors associated with it. Results Of 239 unique studies identified, 19 studies with 729 patients met inclusion criteria; 52 patients developed FND after MDO. A random-effects meta-analysis yielded a pooled prevalence of FND of 6.40%, with moderately heterogeneous studies (I2 = 41%, τ2 = 0.006). Marginal mandibular nerve involvement was most commonly noted. Nine studies reported transient FND, six permanent, one both, and two unspecified. Internal distractors were used in 8 studies and external in 3 and both in 2. Distraction rate was 1.00 to 2.00 mm/day and total distraction length ranged from 13.00 to 22.3 mm. Sample size was the only parameter inversely associated with rate of FND (p = 0.04). Conclusion This analysis of FND associated with MDO for patients with RS demonstrates a lack of consistent documentation. MDO-associated FND does not appear to be uncommon, and permanent dysfunction can occur. This review underscores the importance of thorough documentation to elucidate the mechanism of FND.

An Easy-to-Use Protocol for Segmenting and 3-D Printing Craniofacial CT-Images Using Open-Source Software

Introduction: Stereolithography, also known as 3D printing (3DP), is a versatile and useful technology with many healthcare applications. While 3DP has gained tremendous popularity, it remains a daunting and perceptibly time-consuming process for the inexperienced user, with most turning to commercially printed products. Commercial vendors are expensive. We propose that 3DP is feasible for the inexperienced user with the appropriate knowledge and tools. Methods: A 3DP protocol was created for model design and printing using open-source software and a low-cost desktop printer. It was betatested by 3 inexperienced users. The fidelity of the protocol was then tested in direct comparison to industry models made for 3 patients undergoing mandibular distraction osteogenesis, using standard cephalometric measurements. Results: All inexperienced testers were able to successfully create a 3D model using the easy-to-follow protocol without the use of any other resources. The models were created in a mean time of 170 minutes. All cephalometric measurements on the open-source printed models were equal to within 0.5 to 1.0 mm of the respective industry models. Conclusions: As the 3DP process is simplified and desktop printers and materials become more affordable, we anticipate that its implementation will become more commonplace. We describe a step-by-step, protocol using open-source software and affordable materials to create 3D models.

Treatment of severe mandibular deficiency following TMJ ankyloses by distraction osteogenesis and orthodontic treatment with microimplants

Severe mandibular deficiency caused by temporomandibular joint (TMJ) ankyloses produces functional and aesthetic problems that require complicated long-term treatment. In this case report, we describe the benefits of using microimplant mechanics for controlling the direction of distraction during distraction osteogenesis and for performing the movement of teeth. We also present its remarkable results and long-term stability. A 20-year-old girl presented with a convex profile due to severe mandibular retrognathia after a history of several TMJ surgeries for bilateral TMJ ankyloses. Mandibular distraction osteogenesis (MDO) was performed, and elastics were placed between the microimplants to control the direction of distraction. Subsequently, after retraction of the maxillary anterior teeth and distalisation of the whole mandibular dentition, the facial profile was markedly improved, and good interdigitation was obtained. The six-year follow-up retention and overall stability were satisfactory with good interdigitation and jaw function.

The RNA Methyltransferase METTL3 Promotes Endothelial Progenitor Cell Angiogenesis in Mandibular Distraction Osteogenesis via the PI3K/AKT Pathway

Distraction osteogenesis (DO) is used to treat large bone defects in the field of oral and maxillofacial surgery. Successful DO-mediated bone regeneration is dependent upon angiogenesis, and endothelial progenitor cells (EPCs) are key mediators of angiogenic processes. The N6-methyladenosine (m6A) methyltransferase has been identified as an important regulator of diverse biological processes, but its role in EPC-mediated angiogenesis during DO remains to be clarified. In the present study, we found that the level of m6A modification was significantly elevated during the process of DO and that it was also increased in the context of EPC angiogenesis under hypoxic conditions, which was characterized by increased METTL3 levels. After knocking down METTL3 in EPCs, m6A RNA methylation, proliferation, tube formation, migration, and chicken embryo chorioallantoic membrane (CAM) angiogenic activity were inhibited, whereas the opposite was observed upon the overexpression of METTL3. Mechanistically, METTL3 silencing reduced the levels of VEGF and PI3Kp110 as well as the phosphorylation of AKT, whereas METTL3 overexpression reduced these levels. SC79-mediated AKT phosphorylation was also able to restore the angiogenic capabilities of METTL3-deficient EPCs in vitro and ex vivo. In vivo, METTL3-overexpressing EPCs were additionally transplanted into the DO callus, significantly enhancing bone regeneration as evidenced by improved radiological and histological manifestations in a canine mandibular DO model after consolidation over a 4-week period. Overall, these results indicate that METTL3 accelerates bone regeneration during DO by enhancing EPC angiogenesis via the PI3K/AKT pathway.

Management of Bilateral Temporomandibular Joint Ankylosis and Class 2 Malocclusion in a Patient With Nager Syndrome

Nager syndrome is a rare hereditary syndrome characterized by severe mandibulofacial and pre-axial upper limb anomalies. Patients with Nager syndrome often exhibit syndromic Pierre-Robin sequence secondary to their hypoplastic mandible and require mandibular distraction osteogenesis to prevent dependence on a tracheostomy or gastric tube. This procedure, however, has been associated with temporomandibular joint (TMJ) ankylosis. TMJ ankylosis is a highly debilitating condition that dramatically impairs patients’ function and can result in facial asymmetry in affected children during periods of rapid facial growth. Surgical intervention is warranted in patients who fail physiotherapy; however, there is no gold standard treatment for surgically correcting TMJ ankylosis in patients with Nager syndrome. Herein, we detail the surgical management of TMJ ankylosis and class 2 malocclusion in a patient with Nager syndrome.

The Radiographic “Air Sign” in Neonatal Mandibular Distraction Osteogenesis

Timing of extubation on post-mandibular distraction osteogenesis (MDO) surgery is critical, given that at baseline these infants have difficult airways and failed extubation requires either re-intubation of an already complex airway with a fragile, recently osteotomized mandible, or adjunctive airway measures such as CPAP that may apply unwanted pressure to the surgical site. Thus, the goal is to plan extubation when the risk of failure is minimal. Currently, there is a void in the literature addressing the timing of extubation post-MDO and no objective sign of extubation readiness has been elucidated. This study describes a simple clinical pearl to assist in the evaluation of extubation readiness in these patients. Postoperatively, we obtain weekly radiographs to assess distractor stability and advancement, and to assess for the “Air Sign”. The Air Sign describes a radiolucent space (air) visualized in the oropharynx on lateral radiographs, likely indicating that the tongue based airway obstruction has been relieved by mandibular advancement.