Prevalence of Bifid Zygomaticus Major Muscle

Facial expression muscles have significant morphological variability, including its size, shape, attachment patterns, and prevalence. The zygomaticus major (ZMj) represents one such important structure involved in facial expressions. The bifid ZMj muscle is a known anatomical variation that clinically presents as a dimple in the cheek; however, its prevalence and variation with ethnicity and geography remains poorly understood. The authors performed the first meta-analysis examine and established the prevalence of bifid ZMj variant across different population groups. From 7 studies identified via electronic databases, the prevalence of bifid ZMj variant was most prominent in the American subgroup 34% (95% CI 22.3%–48%), followed by the Asian subgroup at 27.4% (95% CI 14.3%–46.1%) and European subgroup at 12.3% (95% CI 6.5%–22.1%). Subgroup difference was found to be statistically significant (P = 0.027). The overall prevalence of the bifid ZMj is 22.7% (95% CI 14.3%–34.2%). This contributes to the understanding of various facial muscle morphologies and attachment patterns, which have significant implications in surgical planning and procedures for facial reanimation and recreation of natural patient appearances. Address correspondence and reprint requests to Dr Kevin Phan, MD, BSc, MSc, MPhil, South Western Sydney Clinical School, University of New South Wales (UNSW), Sydney 2170, Australia; E-mail: kphan.vc@gmail.com Received 29 September, 2018 Accepted 27 November, 2018 The authors report no conflicts of interest. © 2019 by Mutaz B. Habal, MD.

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