Monobloc Advancement

Figure 9.1.  Patient with Apert’s syndrome before (with hypertelorism and midface hypoplasia) and after (with correction by facial bipartition and monobloc distraction with Roman arch, keystone fixation modification). (A) Frontal preoperative view. (B) Frontal postoperative view. (C) Lateral preoperative view. (D) Lateral postoperative view. (E) Lateral view demonstrating preoperative image and postoperative wire mesh midface and forehead volume increase. Panels A–D reprinted with permission from Wolters Kluwer Health (Ref. 12). Copyright © 2008 by the American Society of Plastic Surgeons. Panel E reprinted with permission from Wolters Kluwer Health. (Chan FC, et al. Soft-tissue volumetric changes following monobloc distraction procedure: analysis using digital three-dimensional photogrammetry system [3dMD]. J Craniofac Surg 2013;24:416–420). Copyright © by Mutaz B. Habal, MD.

Ortiz-Monasterio et al. are credited with performing one of the first monobloc procedures.4 The Le Fort III procedure repositioned the midface alone, but the monobloc was unique in advancing the forehead, orbits, and midface as one unit. They reported performing the technique in a series of patients with Crouzon’s syndrome. Among the seven cases they describe, the only complication was partial resorption of the frontal bone. Despite initial enthusiasm for the procedure, the communication of the nasal cavities and ethmoid sinuses with the intracranial space was thought to potentially contribute to serious infectious complications. Several authors questioned whether the risk of infection was too high to warrant its use.5,6 Other anticipated complications were the need for prolonged ventilatory support, leakage of cerebrospinal fluid (CSF), major blood loss, and frontal bone necrosis. Some institutions banned the procedure; however, many surgeons continued to perform the monobloc advancement.

Van der Meulen applied the monobloc technique to the correction of orbital hypertelorism in a patient with a midline craniofacial cleft.7 To correct the Apert’s midface dysplasia and associated orbital hypertelorism, Tessier refined the vertical splitting and reshaping of the monobloc segment, thus correcting the midface deformity in three dimensions in a procedure now known as facial bipartition.8 In 1983, Muhlbauer et al. reported performing monobloc advancement in an infant, but advocated its use only in cases of severe functional impairment.9 Excellent results were reported by Kawamoto for monobloc and facial bipartition in patients with Apert’s and Crouzon’s syndromes.10 However, he noted an exceedingly high complication rate in a subset of patients with ventriculoperitoneal shunts, possibly because the brain failed to fill the extradural space after the advancement.

More recently, it has been shown that gradual advancement by distraction osteogenesis after a monobloc osteotomy lowers the risk of complications.11,12 With the distraction procedure and a delayed advancement (4- to 7-day latency), remucosalization of the nasofrontal area takes place before advancement. In addition, the traditional procedure requires bone grafting and rigid fixation, whereas the monobloc distraction procedure does not.

Table 9.1.  Indications for Monobloc Advancement Surgery.

1.  Midfacial and forehead retrusive deformities

2.  Upper airway obstruction

Obstructive sleep apnea

Tracheostomy dependence

3.  Exorbitism

Ocular keratitis

Corneal ulcers

Globe herniation

Blindness

4.  Intracranial hypertension

9.3  Indications

A monobloc advancement procedure is used in craniofacial dysostosis patients to correct (1) midfacial and forehead retrusive deformities, (2) upper airway obstruction (such as obstructive sleep apnea or tracheostomy dependence), (3) exorbitism (such as ocular keratitis, corneal ulcers, globe herniation, or blindness), and (4) intracranial hypertension (Table 9.1). In addition, a monobloc osteotomy may be used to facilitate a facial bipartition and correct either horizontal or vertical orbital dystopia.

9.4  Advantages and Disadvantages

The monobloc advancement procedure is advantageous because it avoids a second major procedure. In just one operation, both the forehead and midface deformities are corrected and functional improvement may be seen. The main disadvantage to a monobloc advancement is the risk of serious complications (e.g., meningitis, CSF leak, or complete frontal bone loss). In the past, this risk was considered too high for many institutions to advocate its use. The risk of infection may be caused by the large nasofrontal dead space and communication between epidural and ethmoidal sinus tissues left after the acute advancement of the facial–forehead unit. Now that monobloc distraction has been shown to be safer than anacute monobloc advancement, some institutions have been using monobloc distraction as their preferred treatment for craniofacial dysostotic patients with the operative indications listed above.

9.5  Alternative Treatment

There are treatment alternatives for craniofacial dysostosis patients with forehead retrusion and significant midface hypoplasia. Correction may involve either (1) staged procedures with fronto-orbital advancement followed by Le Fort III advancement or (2) a monobloc (one-unit) advancement. Sometimes the initial fronto-orbital advancement procedure performed in infancy maintains its correction so that only midface retrusion remains by midchildhood. In these patients, only Le Fort III advancement is necessary.

The first comparison of the monobloc procedure to the two-stage fronto-orbital advancement with subsequent Le Fort III procedure was reported by Fearon and Whitaker in 1993.13 In their study, 29 patients (30 procedures) who had various craniofacial dysostoses were followed for a mean of 4 years after surgery. About 10 patients had undergone monobloc advancement and 20 patients had undergone the two-stage procedure. All five infectious complications occurred in the monobloc group despite the use of a galeofrontalis flap. The aesthetic result was deemed equivalent between the two groups and was improved if the procedure was done at an older age. Although the monobloc distraction has decreased morbidity, comparison with the staged fronto-orbital advancement with subsequent Le Fort III procedure has not been studied.

9.6  Timing

Patients with craniofacial dysostosis syndromes have cranial vault and midface deformities with common features and similar growth disturbances. Some surgical strategies, including timing and techniques, may thus be generalized for these syndromes. Optimal care, however, should be tailored to each individual diagnosis and each individual patient. The overall goals of the reconstructive surgical plan should be to minimize the number of operations, maximize the results, and achieve a predictable outcome. Typically, a monobloc advancement is necessary in midchildhood, at approximately age 8 to 12 years. At times, functional considerations (e.g., airway obstruction, ocular exposure, or intracranial hypertension) may push a surgeon to operate at a younger age. If the procedure is undertaken at too young an age, less than 8 years, then a subsequent monobloc advancement may be necessary because of growth or relapse. Temporizing therapies, like tarsorrhaphy suturing for ocular exposure or a continuous positive airway pressure mask for obstructive sleep apnea, may help delay a monobloc advancement until an appropriate age.

Recent case reports for severe craniofacial dysostotic patients have shown success with early, infant monobloc distraction using transfacial pins at the time of fronto-orbital advancement.14,15 However, this new methodology has not been studied in detail.

Currently, for those severe cases, infant fronto-orbital advancement with a tracheostomy is most commonly performed in our institution.

9.7  Preoperative Planning

In preparing for a monobloc advancement, a CT with 3-dimensional reconstruction may be used as a “road map.” In addition, we used 3-dimensional photographic imaging for preoperative, postoperative, and follow-up comparison of facial volumetric changes (Figure 9.1

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Apr 14, 2015 | Posted by in Oral and Maxillofacial Surgery | Comments Off on Monobloc Advancement
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