Congenital fusion of the mandible to the maxilla (syngnathia) is a rare disorder. The first case was reported in 1936 and only a few cases have been reported in the literature since then. This paper reports three new cases of syngnathia. Clinical and radiographic features are presented, as well as surgical management and complications.
Congenital fusion of the jaws is a rare disorder, presenting as fusion of the soft (synechiae) or bone (syngnathia) tissue. Although found in isolated cases, congenital fusion of the jaws is more commonly found in syndromes such as Van der Woude, cleft palate lateral alveolar synechiae syndrome, or in association with other defects and anomalies.
Problems associated with syngnathia include issues with the maintenance and protection of the airway, feeding difficulties and problems with anaesthesia management. Facial growth and development are also compromised. Surgical treatment has been described, but there is no established standard technique. Treatment is individualized, in terms of jaw function and outcome; it may be problematic in complex cases.
The authors report three new cases of congenital syngnathia. Although the patients underwent multiple surgical procedures to release bone fusion, only one case achieved successful release. In the other two patients, fusion recurred, despite surgical treatment.
A 4-month-old female was referred to the authors’ hospital due to an inability to open her mouth since birth. The baby was the second child of parents who were first cousins. Her older brother had no abnormality. On clinical examination, there was bilateral fusion between the mandible and the maxilla and there was mandibular retrognathia ( Fig. 1 A and B ). CT scans showed complete bilateral bone fusion between the mandibular horizontal and ascending rami and the zygomatic complex and maxilla. The temporomandibular joints (TMJs) showed normal morphological features ( Fig. 1 C–F).
The parents reported a previous surgical intervention shortly after birth to open her mouth, resulting in a bilateral mandibular angle fracture. Malunion of this fracture resulted in a10 mm anterior open bite, permitting the mother to breast-feed.
The patient was submitted to general anaesthesia using fibre-optic intubation. During an attempt to perform separation of the fusion, accidental re-fracture of the old angle fractures occurred. The decision was made to use these fractures as temporary pseudo-joints until the infant is older. Postoperative physiotherapy was indicated to maintain mouth opening, to be performed daily. The patient was discharge after 2 weeks. Shortly after discharge, she returned with an inability to open her mouth. The radiographic examination at this time revealed healed fracture lines at the mandibular angles. A second operation was planned. During the attempt to separate, re-fractures at the same fractures occurred. The baby’s parents were informed of the findings and a decision was made to defer the surgery for a few years.
After 7 years, the patient returned for consultation with a history of another five surgeries at different hospitals to correct her problem including distraction osteogenesis. The parents referred to a history of another pregnancy resulting in a boy born with the same congenital problem who died shortly after birth, as well as a fourth child, a normal 1-year-old baby girl.
The patient presented as underweight, with mandibular and midface hypoplasia and speech problems. The clinical and computed tomography (CT) examinations showed fusion of the right side with only 1 cm of interincisal distance, mandibular micrognathia, midface hypoplasia and loss of the left side of the mandibular vertical ramus ( Fig. 2 A–C ). The patient was subjected to surgery for separation of the bone fusion of the mandible using the anatomy of the maxillary and zygomatic bones as a guide for the osteotomy. General anaesthesia was achieved with a blind nasal technique. At the end of the surgery, the mouth opening was 4 cm. On the first postoperative day, the patient had moderate facial oedema and sub-orbital ecchymosis. On the first postoperative day, mouth opening exercises began, which were planned to be performed six times a day. On the third postoperative day, the patient was fully conscious and active and when the resident tried to show the patient how to do her mouth opening exercises, she suddenly became unconscious and exhibited convulsions. Resuscitation manoeuvres were performed on the patient for 2 min. She was transferred to the paediatric ICU immediately where a team tried to resuscitate her for another 20 min before pronouncing her dead. The failure of early intubation in the ICU due to mandibular dysmorphia might have been a difficult factor in life support management, because of her complex airway.
A 3-month-old male, born to consanguineous parents presented with an inability to open his mouth since birth. The prenatal history was uneventful and the child was born by spontaneous vaginal delivery. No records were available of the mother’s obstetric history or the child’s birth. The parents fed the baby through a nasogastric tube. The child was apparently healthy, with no developmental delays or any other anomalies.
The clinical examination revealed fusion between the mandible and maxilla on the right side. CT scans showed fusion of the maxilla and mandible on the right side with normal bilateral TMJs ( Fig. 3 A–C ).
Surgical treatment was performed under general anaesthesia using a fibre-optic endoscope. Using an intraoral approach, a soft tissue incision was made extending to the ramus of the mandible through the area of adhesion from the buccal side. A bone osteotomy using a surgical burr to create the line of separation was completed with osteotomies. Curved osteotomies were used to complete the separation between the posterior maxilla and the horizontal ramus of the mandible. A minimal gap (a few millimetres) was obtained among the fragments due to the presence of the teeth buds. The osteotomy extended posteriorly to complete the separation until free movement of the mandible was obtained. The child was admitted to hospital for 2 weeks for regular mouth opening exercises. His mouth opening at the time of discharge was approximately 25 mm. The patient was reviewed twice weekly for 2 months, and then once a week for 1 month. Over the next few weeks, he exhibited a gradual decrease in mouth opening. Although the parents were instructed to be vigilant about the mouth opening exercises, after 4 months, the mouth opening was 15 mm. Seven months postoperatively, the child returned with inability to open his mouth. A new CT scan revealed complete bone fusion of the mandible and maxilla.
Another surgical intervention was performed through an intraoral approach. A soft tissue incision through the area of fusion was made. An osteotomy was performed at the site of the old osteotomy. Release of the bone fusion was easier and free movement of the mandible was obtained. During an attempt to obtain a wider gap among the fragments to prevent bone refusion, three tooth buds were removed. A buccal mucosal flap was used to cover the bare bone of the mandible. Postoperative physiotherapy was maintained three times daily, and the child was discharged 3 weeks postoperatively with 20 mm mouth opening. After 3 months there was recurrence, with complete bone fusion. After this the patient was lost to follow-up.