Fibrous dysplasia was a term given by Lichtenstein and Jaffe in 1983 to the benign bone lesion characterized by replacement of normal bone with fibro-osseous connective tissue(Lichtenstein L and Jaffe HL 1942). It could be represented in three forms: monostotic fibrous dysplasia involving only single bone, polystotic fibrous dysplasia involving more than one bone, or fibrous dysplasia (FD) associated with endocrinopathies (McCune-Albright syndrome, Mazabraud syndrome and Jaffe-Lichtenstein syndrome) (Lee et al., 2012) (Deepthi et al., 2016). The term craniofacial dysplasia (CFD) was introduced to describe fibrous dysplasia affecting cranial and facial bones. CFD is not considered as a polystotic FD as other bones elsewhere in the craniofacial complex are free, however it cannot be considered as a pure monostotic FD as it usually affects more than one bone (V. Valentini et al., 2017) (Menon et al., 2013). Thus, CFD can be considered as monofocal FD in which several adjacent bones in single area are affected(Valentino Valentini et al., 2009).

Clinical features of the CFD are represented according to the site of the affected area and the related vital structures. Slow gradual swelling of the affected bone is the first common sign of the CFD. However, a rapidly increased rate of growth may threaten vital structures resulting in more advanced complications as headache, epiphora, hearing loss, blindness, vestibular syndrome, neurosensory disorders, and obstruction of the airway(Couturier et al., 2017).

The management of CFD depends on the patient's age, skeletal maturation, signs, and associated symptoms. In aggressive cases with vital structure involvement, immediate and aggressive procedures should be considered. Whereas in cases of nonaggressive lesions, the general rule is to wait until the lesion becomes quiescent and completes maturity, and then debulking or resection is performed. However, if bony disfigurement can affect the patient's pschycology, then repeated debulking can be done (Lee et al., 2012) (V. Valentini et al., 2017).

The real challenge in treating CFD cases is to reach perfection in esthetics in addition to protection of vital structures, especially when dealing with craniofacial area. Over years the amount of bone removed during debulking and contouring surgeries was determined by the operator's sense and skills, until computer-assisted surgery was widely introduced in the maxillofacial field. The huge advancement of planning software and rapid prototyping technology allowed for virtual planning of surgeries and transferring this plan to the surgical field through patient-specific guides(Ahmed et al., 2020). In this study we aimed to introduce a new computer-guided technique for debulking and contouring the CFD involving the fronto-orbital and fronto-cranial regions using modified patient-specific guides.