Abstract

Objectives: To evaluate the incidence and anatomical distribution of misplaced dermal fillers within facial expression muscles using high-frequency ultrasound (HFUS), and to emphasize the value of ultrasound in diagnosis and complication management Introduction: Dermal fillers are widely used for facial rejuvenation and contouring. However, inadvertent injection into facial expression muscles—such as the orbicularis oculi or zygomaticus major—can result in undesirable outcomes, including impaired muscle function, asymmetry, nodules, and prolonged swelling. These complications are often overlooked or misdiagnosed due to limited clinical awareness and insufficient imaging assessment. Materials / method: A cohort of patients previously treated with facial fillers underwent HFUS assessment. The presence, depth, and location of filler material were analyzed, with specific attention to the involvement of key facial expression muscles. All ultrasound evaluations were performed using a high-frequency linear probe with real-time scanning. Results: HFUS identified intramuscular filler placement in several cases, particularly within the orbicularis oculi and zygomaticus major muscles. These findings correlated with reported symptoms such as stiffness, unnatural animation, or localized swelling. HFUS enabled precise localization of misplaced product, supporting safe correction strategies when needed. Conclusion: Misplacement of fillers into facial expression muscles may occur more frequently than anticipated and can lead to both functional and aesthetic complications. High-frequency ultrasound is a powerful tool for detecting such misplacements and should be integrated into routine aesthetic practice. Enhanced anatomical understanding and ultrasound-guided injection techniques are strongly recommended to improve safety, treatment outcomes, and patient satisfaction.