Correcting Exorbitism by Monobloc Frontofacial Advancement in Crouzon-Pfeiffer Syndrome: An Age-Specific, Time-Related, Controlled Study

Abstract

Background: In FGFR2 craniosynostosis, midfacial hypoplasia features oculo-orbital disproportion and symptomatic exorbitism. Clinical consequences may mandate surgery at a young age to prevent globe subluxation, corneal ulceration, and potential loss of vision. Monobloc osteotomy and distraction osteogenesis (monobloc distraction) seek to correct exorbitism. A report of the age-related impact of monobloc osteotomy and distraction osteogenesis on orbital volume, globe volume, and globe protrusion is presented. Methods: Computed tomographic scan data from 28 Crouzon-Pfeiffer patients were assessed at preoperative, early postoperative, and 1-year follow-up time points. Orbital volumes, globe volumes, and globe protrusions were measured by manual and semiautomatic segmentation techniques, and these were compared to 40 age-matched controls. Results: Crouzon-Pfeiffer syndrome orbital volumes are significantly small, and are significantly overexpanded by distraction to endpoints correcting symptomatic exorbitism. Globe volumes are significantly larger than controls under 5 years, do not independently correlate with globe protrusion, and are unaffected by surgery. Correlation between orbital volume expansion and reduction of globe protrusion is not significant. Age-related variations of postoperative growth potential occur to 1 year postoperatively. The Crouzon-Pfeiffer syndrome FGFR2 orbit exhibits early growth acceleration followed by premature growth arrest at 10 to 14 years. Conclusions: Orbital volume expansion by monobloc osteotomy and distraction osteogenesis is not the sole determinant of reduced globe protrusion. Mean volume relapse of the orbit at 1 year is insignificant across the series. Derived Crouzon-Pfeiffer growth curves suggest that “early functional monobloc” in infants occurs on a background of dynamic orbital growth, which remains programmed to a Crouzon-Pfeiffer FGFR2 phenotype and aligns with the incidence of delayed clinical regression and later secondary surgery. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, IV.

An Unoperated Crouzon Family Treated with Monobloc Distraction: Challenges and Lessons

“…There have also been reports of a 23% relapse rate with use of external distraction for hypoplastic midface, and greater anterior overcorrection of the hypoplastic maxilla is needed in growing children compared to adults, to compensate for a partial relapse and growth deficit. 20 In a study performed by Way et al 21 assessing orbital volumes and globe protrusion in young patients with Crouzon–Pfeiffer syndrome, showed stable orbital volume at 1 year postoperatively with clinical regression back to syndromic form around 12 years of age.…”

Distraction Osteogenesis: Mandible and Maxilla

“…45 However, younger syndromic patients undergoing LeFort or monobloc distraction are more likely to require additional corrective surgery for further advancement and functional improvement. 43 Because of the prevalence of relapse, surgeons frequently overcorrect to account for this morbidity.…”

“…42 Frontofacial advancement with monobloc distraction has served as an invaluable technique for correcting functional deficits in Crouzon and Pfeiffer patients. [41][42][43] Monobloc osteotomy involves separating a segment of both the frontal bone and midface from the rest of the craniofacial skeleton. This procedure begins with bicoronal incisions.…”

“…41 Proptosis is not fully reversed, as other factors such as positioning and shape of the orbit can affect postoperative globe position. 43 Patients who undergo monobloc distraction demonstrate stable outcomes on long-term follow-up, though may require additional anterior maxillary advancement in a staged fashion.…”

Robot-assisted frontofacial correction in very young children with craniofacial dysostosis syndromes: a technical note and early functional outcome

“…3,22 Up to 40% of patients may require some intervention for OSA. 23,24 In the presence of severe airway and ocular issues, midface distraction can be performed early. 25,26 In this scenario, this may be combined with fronto-orbital advancement and remodeling (FOAR), simultaneously or staged.…”