Fronto-facial monobloc distraction in syndromic craniosynostosis. Three-dimensional evaluation of treatment outcome and facial growth

Abstract

The objectives of this study were to investigate the treatment effect and stability of fronto-facial monobloc distraction osteogenesis. Five consecutive patients who underwent monobloc distraction were included (aged 4.8–18.4 years). Three patients had Crouzon syndrome, one had Apert syndrome, and one had Pfeiffer syndrome. The evaluation included clinical records, serial cephalograms for at least 1-year follow up (average 24.6 months). The treatment and post-treatment changes were measured. The intracranial volume, upper airway volume and globe protrusion were calculated from CT before and after treatment. After distraction, the supraorbital region was advanced 15.3 mm forward, the midface demonstrated forward advancement of 17.7 mm, 22.1 mm and 23.1 mm at orbitale, anterior nasal spine and A point, respectively. The downward movement was 2–3 mm at maxillary level. The intracranial volume increased 11%; the upper airway volume increased 85% on average. Globe protrusion reduced 3.7 mm on average, which was 20% of underlying skeletal movement. Facial growth demonstrated forward remodelling of the supraorbital region, mild downward but no further forward growth of the midface. Monobloc distraction is effective for relieving related symptoms and signs through differential external distraction at different vertical levels of the face.

Syndromic craniosynostosis (SCS) is a rare craniofacial anomaly associated with premature fusion of multiple cranial sutures. The clinical features include brachycephaly, hypertelorism and orbital protosis, hypoplastic maxilla and anterior crossbite . Early surgical intervention is usually indicated to solve the sequelae associated with SCS including increased intracranial pressure (IICP), neurological disorder, corneal exposure keratitis and airway obstruction .

Monobloc fronto-facial advancement is an effective surgical procedure to move the whole midface and forehead forward . The main problems of traditional monobloc advancement are relapse and infection caused by large frontonasal dead space behind the advancement segment . Some patients require secondary surgery to correct the IICP and midface hypoplasia combined with unsatisfactory craniofacial structure. Repeated midface or even monobloc advancement is required due to the limited amount of correction by conventional surgeries .

Distraction osteogenesis (DO) has been widely applied in the craniofacial field since the lengthening of human mandible reported by M c C arthy et al. in 1992 . C hin & T oth attempted to perform intraoperative movement and postoperative distraction at the Le Fort III level; the midface was translated by 20 mm . The Le Fort III DO was then applied to correct the midface hypoplasia of SCS children with either an internal or external device . DO has many advantages over conventional surgery, such as the greater amount of advancement, lower rate of complications and morbidity, less blood loss, less operative time and limited amount of frontal dead space .

The monobloc fronto-facial DO can be performed as either primary or secondary correction of the craniofacial problems associated with SCS . The rigid external distraction (RED-II) system provides better control of the advancement vector of distraction. By using two or three pairs of distraction ports, the distraction force can be delivered at different vertical levels of the face to produce reliable results .

Previous investigations of the treatment effect and facial growth after midface DO in SCS have been mainly related to the Le Fort III level. Evaluation of the three-dimensional (3D) changes in functional space after DO is limited . More detailed evaluation of the progress and changes after DO is required to improve the outcome of treatment. The purpose of this study is to investigate the treatment effect and post-treatment changes of consecutive patients with SCS who underwent fronto-facial monobloc DO treatment.

Materials and methods

This study included consecutive patients who underwent monobloc fronto-facial DO. The five patients ranged in age from 4.8 to 18.4 years (average 9.4 years) at the time of surgery. The diagnoses included three Crouzon, one Apert and one Pfeiffer syndrome ( Table 1 ). All the treatment procedure was performed by the same team, including the plastic surgeon, neurosurgeon and orthodontist.

Table 1
General information about the patients.
Patient Diagnosis Sex Age of DO Appliance retention (day) Cephalometric follow up (months) CT image
1 Pfeiffer M 4.8 150 12 Yes
2 Crouzon F 5.0 147 15 Yes
3 Apert M 8.1 37 56 Yes
4 Crouzon F 12.3 120 17 No
5 Crouzon M 18.4 120 23 No
Average 9.7 114.8 24.6

Bicoronal incisions were made to expose the skull. The orbits and midface were exposed through bilateral infraciliary incision and upper buccal sulcus incisions. The frontal and orbital craniotomies were undertaken in collaboration with a neurosurgeon. The osteotomy of the monobloc and facial partition went through the zygomatic arches, orbital walls, nasal septum, anterior skull base and pterygomaxillary junctions. The whole face and frontal bone were mobilized. The RED-II system (KLS Martin, Jacksonville, FL, USA) was used in all patients, using the cranium as the fixation point. Two pairs of transcutaneous wires were connected to the bilateral supraorbital region and malar eminence with the distraction screws and ports. Maxillary arch advancement was conducted to the extension eyelets of the intraoral appliance with distraction screws. A total of three ports were used to perform the distraction procedure ( Fig. 1 ).

Fig. 1
The monobloc fronto-facial distraction was performed with a rigid external distraction device with three distraction ports.

All the patients were in the hospital intensive care unit for 7 days. The latency period of distraction is 7 days, with a distraction rate of 1–1.5 mm/day. The rhythm of distraction and differential activation amongst three distraction ports were decided by periodic cephalometric valuation, facial appearance and dental occlusion. The consolidation period was prolonged as much as possible. The total appliance retention time is listed in Table 1 ; the average was 115 days.

General information about the patients and their medical history were reviewed and recorded from medical charts, including previous surgery, symptoms and signs before monobloc DO, treatment after DO and post-surgical complications.

Lateral cephalograms were obtained at three time intervals: before treatment (T1); on completion of DO (T2); and at least 1-year follow up (T3). The measurements of T2–T1 indicated treatment changes; T3–T2 indicated post-treatment changes. The cephalometric landmarks were identified and traced. The measurement of the landmark movement was based on an XY coordinate system. The horizontal reference line ‘ X axis’ was defined as 7° below the SN line. The vertical reference line ‘ Y axis’ was defined as the line perpendicular to the X axis through sella. Serial lateral cephalometric films were superimposed at the cranial base near the sella turcica and on the overall shape of the cranium since the anterior part of the cranial base had been lengthened by DO. The XY coordinate system was transferred by the aforementioned superimposition from T1 to T3. Eight landmarks were measured for the distance of the X and Y axes. Measurements to the right of the Y axis or inferior to the X axis indicated a ‘positive’ value ( Fig. 2 ).

Jan 26, 2018 | Posted by in Oral and Maxillofacial Surgery | Comments Off on Fronto-facial monobloc distraction in syndromic craniosynostosis. Three-dimensional evaluation of treatment outcome and facial growth
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