Bone-Anchored CT Angiography Framework for In Vivo Assessment of Zygomaticus Major Morphology

Background: The zygomaticus major (ZMa) is a key mimetic muscle with reported anatomical variability, but in vivo descriptions based on routinely acquired imaging remain limited. Methods: This retrospective single-centre study evaluated whether clinically indicated head-and-neck CT angiography (CTA) can support a bone-anchored, consensus-based descriptive assessment of ZMa morphology. Seventy-five CTA examinations were analysed bilaterally, yielding 150 hemifaces from 42 males and 33 females. Multiplanar reconstructions were reviewed using skeletal landmarks. Results: ZMa morphology was categorised as Type I (single-bellied), including Type Ia with independent zygomatic origin and Type Ib with proximal fusion with the zygomaticus minor; Type II (double-bellied); or Type III (three-bellied). The ZMa was identifiable in all hemifaces. Type I was observed in 86.7% of hemifaces, including Type Ia in 78.7% and Type Ib in 8.0%; Type II occurred in 12.0% and Type III in 1.3%. Patient-level asymmetry was present in 22.7%. Mean ZMa length was 41.77 ± 6.21 mm, proximal attachment width 5.95 ± 1.36 mm, and distal attachment width 4.39 ± 1.41 mm. These findings suggest that routinely acquired CTA may provide an opportunistic, bone-referenced approach to the descriptive in vivo assessment of visible ZMa morphology and cohort-specific morphometric characteristics. Conclusions: CTA should not be considered a reference-standard modality for facial muscle assessment, and further validation using dedicated soft-tissue imaging and formal reliability testing is required.