Transformation in orbital reconstruction

The orbits provide support and protection for several soft-tissue structures associated with vision. A fracture of the orbital walls may affect globe position and vision, and surgical intervention may be indicated to restore the bony anatomy and alleviate sequalae. Reconstruction is challenging due to the orbit’s complex shape and limited overview. Computer-assisted surgery (CAS) minimizes surgical risk and optimizes the reconstruction result. An overview of current CAS approaches and the results of validation studies that show its beneficial effect is provided in the Introduction Part. The aim of this thesis is to improve the current CAS workflow.
The first innovation is the introduction of the Orbital Implant Positioning Frame (OIPF), which provides three-dimensional (3D) assessment of rotation and translation parameters of implant position for postoperative evaluation. The Navigation Chapters describe the OIPF’s use intraoperatively. Real-time, intuitive implant positioning feedback may be provided through the combination of the OIPF, an insertion instrument (TOP) and surgical navigation. This feedback improves implant positioning and reduces operating time. The use of the instrument without navigation also proves to have a beneficial effect on positioning accuracy.
In the Registration Chapters, two novel registration workflows for craniomaxillofacial surgical navigation are introduced: virtual splint registration and registration-free navigation. The accuracy of virtual splint registration proved comparable to bone-anchored fiducial, while invasiveness and radiation exposure were reduced. The results for registration-free navigation are contradictory: it was the most accurate method with electromagnetic tracking, but the least accurate with optical tracking.
The Revision Chapters concern secondary posttraumatic reconstruction with patient-specific implants (PSIs). In a cohort study, design options for PSIs are provided and the clinical results evaluated. Globe position significantly improved and double vision significantly reduced after secondary PSI reconstruction. A novel surgical workflow with the use of PSIs, specifically for secondary orbitozygomatic reconstruction, is described in the final Chapter. This ‘Orbit First’ method allows accurate reconstruction of the orbit independent of the obtained zygoma position.