The temporal fossa is surrounded by the skull temporal ridge, the lateral orbital rim, and the zygomatic arch, and is mainly occupied by the temporalis muscle . Consequently, temporalis muscle transfer for reconstructing different maxillofacial defects can result in temporal hollowing, especially when the whole muscle is used . In this study, we used computer-assisted technology to fabricate patient-specific PEEK implants for immediate restoration of temporal fossa after maxillary reconstruction with temporalis muscle flap aiming to facilitate the reconstruction procedure.
Different autogenous and biomaterials have been previously used to reconstruct the temporal area either secondary to augment an exciting deformity and restore the normal contour, or primarily to prevent temporal hollowing and immediately reconstruct the temporalis muscle donor site [7, 10, 12,13,14].
Calvarial onlay grafts have been used to prevent temporal hollowing during pterional craniotomy [14, 15]. The major limitation of this approach was the difficulty in determining the desired graft size, and graft handling during the augmentation procedure . Moreover, this approach is considered extensive in cases where the temporal augmentation is indicated for esthetic reasons after temporalis muscle transfer with no craniotomy. Autologous fat harvested from the abdominal wall has been used by Cervelli et al.  to correct temporal hollowing secondary to temporalis muscle transfer. The result was initially satisfactory; however, a second procedure was indicated for 78 % of the patients, and a third procedure was performed for one patient. Moreover, this approach is applicable only to correct existing temporal hollowing, not to prevent it during the temporalis muscle flap transfer .
Polymethyl methacrylate (PMMA) and Porous high-density polyethylene (PHDPE) are considered as the most used biomaterial for temporal hollowing correction [6, 7, 13, 16,17,18,19,20]. PMMA has been used for orthopedic reconstruction in 1950s. It showed initial questionable clinical results, this urged the manufacturers to improve its biological and mechanical properties. Since then, bone cement has become widely used for orthopedic prostheses [21, 22]. However, PMMA showed satisfactory esthetic results in temporal hollowing reconstruction, it showed more postoperative complications compared to PHDPE implants . PHDPE was developed in the 1970s, became available for clinical implantation since the 1990s. Since then, it has been used for the augmentation and reconstruction of different craniomaxillofacial regions [23, 24]. Aside from PMMA and PHDPE, limited cases are available on other biomaterials for temporal fossa reconstruction such as porcine collagen matrix (Permacol), Mersilene mesh, and titanium implant [8, 9, 14].
In our study, we used PEEK to fabricate the temporal implants. PEEK was first developed in 1978 and used as aircraft and turbine blades. Later in the 1990s, it was used to replace metal implants . It showed to be a strong and thermoplastic material. Its elasticity and energy-absorbing properties are closer to the bone compared to titanium . Nowadays, PEEK is considered the gold standard for patient-specific implants. It showed promising results for the reconstruction of different craniomaxillofacial defects [23, 27,28,29,30,31]. However, its major limitation of the high cost of the compared to PMMA and PHDPE .
Different methods have been used for temporal implants fabrication and adaptation. For PHDPE temporal implants (Medpor implants), the first step was to select an implant of appropriate size. The implant was then carefully carved to the required shape, feathered to ensure that its border is not visible or palpable, and finally placed to fill the fossa [7, 22,23,24]. While, PMMA implants are usually directly molded using cold cure acrylic cement into the required shape and placed over the bare temporal bone after temporalis muscle transfer [6, 13, 17]. Falconer and Phillip  in their study used a prefabricated acrylic prothesis. A wax template for the prothesis was made on a dry skull of average proportions, then the wax was processed in heat-cured acrylic to fabricate the acrylic prothesis. Laloze et al.  in a case report used a preliminary PMMA spacer to shape a Permacol plate which was used for reconstruction. Hatamleh et al.  in another case report used a 3D model of the patient skull to shape a titanium sheet for temporalis contour reconstruction.
In our study, we used patient-specific PEEK temporal implants to immediately restore the temporal fossa contour. Prefabricated patient-specific implants have been proved to reduce the operation time and produce excellent cosmetic results . We used CAS to mimic the temporalis muscle before its transfer and fabricate the implant. The muscle was virtually selected, separated, and refined to construct the virtual implant. Each implant was formed of four parts to accommodate for the PEEK blocks size. The surgical procedure was uneventful and the esthetic result was satisfactory. Different post-operative complications have been reported after temporal reconstruction as seroma, infection, temporal depression, dehiscence, and implant removal . In our study, post-operative clinical follow up was uneventful for all patients except one patient who showed seroma which resolved with serial aspirations. Seroma is the collection of exudative fluid below the flap in large-detachment surgeries. The detachment of large tissue during flap elevation and residual dead space are contributory factors for its formation. Seroma is not a serious of complication but if not drained may evolve to wound dehiscence, implant extrusion, infection, and finally loss of reconstruction .
Our approach seems to avoid adverse events associated with intraoperative molding of PMMA . Moreover, it facilitates the surgical procedures when compared to PHDPE implants. Patient-specific implants eliminate several meticulous steps that are mainly based on the surgeon’s experience as implant selection, adaptation, trimming, and feathering [10, 18, 19]. However, the major limitation of this approach is the relatively high cost of the patient-specific PEEK implants.
Within the limitations of this study, patient-specific PEEK implants represent a promising method for immediate restoration of the temporal fossa after temporalis muscle transfer. However, we recommend the conduction of more investigations and comparative studies for further evaluation of its benefits compared to other implants.