The shell technique: bilateral fronto-orbital reshaping in trigonocephaly

The shell technique, used in the Pediatric Neurosurgical Department at the Catholic University, Rome, since the 1990s for the correction of trigonocephaly, is associated to a significant reduction in surgical time and intraoperative blood loss as compared to other procedures, while allowing an adequate remodelling of the bifrontal bone by means of multiple radial osteotomies. The technique does not necessitate the creation of a supraorbital bar, as the supraorbital ridges are modified in situ, further reducing the operative blood loss. In spite of reduced surgical time and manipulation, this procedure ensures aesthetic and functional results comparable to more extensive and complex cranial vault reshaping procedures. The main limitation of this technique is related to the surgical timing, as better results are obtained between 3 and 9 months of age, when the skull bone is still ductile to work with, thus allowing it to be remodelled by greenstick fractures. Moreover, in this age group, the cranial defects that result from the enlargement of the frontal bone flap by means of radial cuts and from the anterior displacement of its lateral portions may benefit from the more effective bone regeneration which characterizes younger children as compared to their older counterparts. A small number of cases showing either persistent hypotelorism or temporal depression have been observed in the post-operative period, although these residual deformities probably depend on a more extensive involvement of the cranial base in the synostotic process in these patients than on the procedure itself.