Virtual reconstruction of orbital floor defects using a statistical shape model

• Published in: Journal of anatomy Vol. 240; no. 2; pp. 323 - 329
• Main Authors: Gass, Mathieu, Füßinger, Marc Anton, Metzger, Marc Christian, Schwarz, Steffen, Bähr, Johannes Daniel, Brandenburg, Leonard, Weingart, Julia, Schlager, Stefan
• Format: Journal Article
• Language: English
• Published: England Wiley Subscription Services, Inc 01.02.2022; John Wiley and Sons Inc
• Subjects: Asymmetry; computer‐assisted surgery; Humans; Mathematical models; Medical imaging; Models, Statistical; Orbit - diagnostic imaging; Orbit - surgery; orbital reconstruction; Original Paper; Original Papers; Reconstructive Surgical Procedures; Segmentation; Skull; statistical shape model; Tomography, X-Ray Computed - methods; trauma; trauma; computer-assisted surgery; orbital reconstruction; statistical shape model
• ISSN: 0021-8782; 1469-7580
• DOI: 10.1111/joa.13550

Purpose The current standard in reconstructing defects of the orbital floor, by using the concept of mirroring, is time‐consuming and ignores the natural asymmetry of the skull. By using a statistical shape model (SSM), the reconstruction can be automatized and improved in accuracy. The present study aims to show the possibilities of the virtual reconstruction of artificial defects of the orbital floor using an SSM and its potentials for clinical implementation. Methods Based on 131 unaffected CT scans of the midface, an SSM was created which contained the shape variability of the orbital floor. Nineteen midface CT scans, that were not included in the SSM, were manually segmented to establish ground truth (control group). Then artificial defects of larger and smaller sizes were created and reconstructed using SSM (Group I) and the gold standard of mirroring (Group II). Eventually, a comparison to the surface of the manual segmentation (control group) was performed. Results The proposed method of reconstruction using an SSM leads to more precise reconstruction results, compared with the conventional method of mirroring. Whereas mirroring led to the reconstruction errors of 0.7 mm for small defects and 0.73 mm for large defects, reconstruction using SSM led to deviations of 0.26 mm (small defect) and, respectively, 0.34 mm (large defect). Conclusions The presented approach is an effective and accurate method for reconstructing the orbital floor. In connection with modern computer‐aided design and manufacturing, individual patient‐specific implants could be produced according to SSM‐based reconstructions and could replace current methods using manual bending techniques. By acknowledging the natural asymmetry of the human skull, the SSM‐based approach achieves higher accuracy in reconstructing injured orbits. Reconstruction of orbital floor defects using a statistical shape model (left) and mirroring technique (right). Due to natural asymmetry, the statistical shape model yields more accurate results.