Three-dimensional reconstruction of a defect of the frontozygomatic area by custom made Proplast II implant

Abstract

Alloplastic materials are a valid alternative to autologous bone grafts in contour defects of the facial skeleton Biomaterials also reduce donor site morbidity. In addition, alloplastic materials can be contoured exactly as needed. Computed tomography (CT) scan digital data can be computed into three-dimensional data for 1:1 stereolithographic reconstruction of the complete skull or segments as required. The design of an implant for defect reconstruction may even be computed as a mirror image of the unaffected undeformed side. Therefore it is common to perform phantom operations on stereolithographically built models from the patient's head before a complex reconstruction is done. Proplast II has an advantage over other materials, such as hydroxyapatite, titanum, gold, silicone, and polymethylmetacrylate (PMMA), because of the low weight, the fact that the material can be carved with a sharp scalpel, and the possible integration into fibrous and bone tissue. Proplast II is semirigid and can easily be sutured to the bony defect.A 29-year-old male patient presented with a complex bone defect of the frontozygomatic region after a neurosurgical procedure 10 years previously. The skin was soft and mobile, and there was a soft and thin scar above the left orbital rim (Fig. 1). The patient's complaint was of a visible depression over the frontozygomatic suture. Clinical examination showed weakness of the frontalis muscle due to the initial neurosurgical operation. Neurologically, there were no deficits or visual impairment.Production and insertion of implant (Fig. 2) Preoperative investigations included a CT scan with three-dimensional (3-D) reconstruction (Fig. 3). The data were transferred to a laser lithographic molding device. The technique for producing full-scale models is based on laser-curable polymethylmetacrylate (PMMA), which is hardened by laser irradiation (Fig. 4a). Once the skull model was available, the missing part of the frontozygomatic was produced by mirroring the undeformed right area of the frontozygomatic on digital basis. With these data, it was possible to form the missing left part of the frontozygomatic in the model material. This mirrored virtual model was exactly carved to the full size skull model and fixed to the defect with screws (Fig. 4b).This finely adjusted PMMA model was sent to the company which produces custom-made Proplast II implants (Fig. 5) (Genatis, Biofunctional Technology SA, Nyon, Switzerland). Fig. 1Defect of the left frontotemporozygomatic complex in a 29-year-old male patient, due to a neurosurgical procedure 10 years previously

Highly Accurate CAD Tools for Cranial Implants

“…In order to fabricate accurately fitting cranial implants, RP (Rapid Prototype) skull models based on 3D CT data have been used to manually fabricate implants for about a decade. Although clinical reports [1] indicate that these implants show satisfactory results, considerable cost is incurred, and time spent, producing full skull models and carrying out manual fabrication procedures.…”

Computer-aided implant design for the restoration of cranial defects

“…RP (Rapid Prototype) skull models based on 3D CT data have been used to manually fabricate implants for decades 4 . However, many disadvantages are shown by using the implants, including expensive cost, massive time, and complicated procedures 5 . CAD/CAM techniques has been introduced to prefabricate tailored implants for decades which are precisely formed based on the CT data of the patient 6,7 .…”