3D planning of ear prosthesis and navigated flapless surgery for craniofacial implants: a pilot study

E5OC5 ePOSTER CLINICAL INNOVATIONS

Background: Several studies used CAD-CAM- guided surgery for craniofacial implants, demonstrating that digital planning of implant insertion and the manufacture of surgical guides improved implant placement to support ear, nose and facial prosthesis. Navigation systems provide important advantages, including reduced costs and time requirements, and the possibility of using flapless surgery.

Aim/Hypothesis: Aim of this pilot study is to describe an innovative navigated flapless surgery for craniofacial implants, prosthetically guided by 3D planning of the ear prosthesis, and to discuss the advantages and disadvantages of the usage of dynamic navigation method.

Materials and Methods: A fully digital computer-assisted method for 3D planning and guided craniofacial implant placement using a dynamic navigation system was devised for the construction of an implant supported ear prosthesis. Laser surface scanning of the face allowed for mapping of the healthy ear onto the defect site, and projection of the volume and position of the final prosthesis. The projected ear volume was superimposed on the skull bone image obtained by cone-beam computed tomography (CBCT), performed with the navigation system marker plate positioned in the patient's mouth. The craniofacial implants were fitted optimally to the ear prosthesis. After system calibration, real-time navigated implant placement based on the virtual planning was performed with minimally invasive flapless surgery under local anesthesia. After 3 months of healing, digital impressions of the implants were made, and the digital manufacturing workflow was completed to manufacture the ear prosthesis.

Results: This pilot study showed that 3D planning of an ear prosthesis, and navigated flapless surgery for craniofacial implants, could be carried out without the need for general anesthesia or per os sedation. The 3D errors in implant entry point and apex position were respectively 3.43 mm and 3.59 mm for implant #1 and 2.87 and 2.83 mm for implant #2, given by the linear distance from the center of the implant base circumferences (entry point and apex level). The angular deviation of the axis of the simulated cylindrical scan abutment was 2.0° for implant #1 and 0.5° for implant #2. The results indicated lower accuracy of the navigated flapless surgery procedure than reported in the literature for the same navigation system when applied for standard oral implants. The proposed digital method facilitated implant positioning during flapless surgery, reducing operation time, patient morbidity, and related costs. This protocol avoids the need for a reference tool fixed in the cranial bone.

Conclusions and Clinical Implications: Within the limitations of this pilot study, the dynamic navigation was viable for allowing flapless surgery and by avoiding the need for general anesthesia. The distance between the reference tools on the system marker plate and those on the handpiece may reduce the ability of the navigation system setting to map the spatial coordinates. Further studies in larger study populations are necessary to validate the findings of this pilot study.

Keywords: flapless surgery, skull malformation, ear prosthesis, navigation, craniofacial implants