Commentary on: Three-Dimensional Custom-Made Surgical Guides in Facial Feminization Surgery: Prospective Study on Safety and Accuracy

Moving to 3D: Quantifying Virtual Surgical Planning Accuracy Using Geometric Morphometrics and Cephalometrics in Facial Feminization Surgery

Facial feminization surgeries (FFS) aim to feminize facial features in transgender women and include frontal sinus setback, rhinoplasty, and genioplasty. FFS may be performed with virtual surgical planning (VSP) to help generate reproducible and predictable results. However, quantification of changes is challenging because these changes often occur in multiple axes and dimensions that are not easily reduced to a single error metric. The objective of this study was to apply cephalometrics and geometric morphometrics analyses to evaluate shape changes in FFS patients undergoing genioplasty and mandibular contouring. Fourteen patients who underwent genioplasty, mandibular contouring, or both, with a single surgeon and also had matching post-operative followup scans were included. Three-dimensional reconstructions of preoperative, postoperative, and VSP-guided "planned" computed tomography scans of each patient were created using 3D Slicer. Cephalometrics and geometric morphometrics were used to analyze changes. Pairwise 1-tailed t tests showed that postoperative bigonial width values significantly aligned with planned values across individuals. Geometric morphometric analyses, specifically Generalized Procrustes Analysis, demonstrated that the postoperative scans significantly aligned with planned scans in the fixed landmark data set (3-piece genioplasty) and gonial angle semi-landmark data set (mandibular contouring). Among scan sets that did not meet this hypothesis, the final postoperative shape was often between the preoperative and planned shapes, presumably due to post-osteotomy burring that is not captured on VSP. Future work using a greater number of landmarks, such as using statistical shape modeling approaches, may help to evaluate bony changes after FFS  to better integrate changes in bone position with concomitant changes in bony shape.

Applications of three-dimensional surgical planning in facial feminization surgery: A systematic review

BACKGROUND

Despite some reports that have shown an increase in safety, efficiency, and accuracy during feminizing craniofacial procedures utilizing three-dimensional (3D) technology, there are no reports summarizing the available evidence on this matter for facial feminization surgery (FFS). Here, we aimed to systematically review the application of 3D technology on FFS.

METHODS

We conducted a comprehensive search across PubMed, SCOPUS, Ovid MEDLINE®, Web of Science, and ScienceDirect looking for studies reporting the use of 3D surgical planning in the setting of FFS following the PRISMA guidelines. We extracted data on photographic assessment, imaging, surgical application, and surgical technique and outcomes.

RESULTS

This review included 10 studies comprising 1473 transgender female patients and 50 cadaveric cranial specimens. Four studies employed virtual surgical planning (VSP) and the concomitant use of prefabricated cutting guides. One study reported the implementation of 3D VSP using a female skull as a reference. One study used computer-aided design cutting guides and custom plates for FFS. Standardized incorporation of 3D printed models allowed for preoperative planning in three studies. Three studies reported VSP using 3D reconstruction of CT images, but without the use of 3D printing. Three studies used 3D photography with specialized camera technology to enrich clinical documentation and provide a comprehensive facial analysis of soft tissue. Accuracy ranged from 85.7% to 97%. Morbidity ranged from 0% to 12.5%.

CONCLUSION

Based on this data, we believe 3D VSP has promising outcomes in terms of accuracy and low morbidity, encouraging its implementation in FFS. However, further prospective double-arm cohort studies are required.