Are We Underestimating Zygomaticus Variability in Midface Surgery?

Area of Science:

• Anatomy
• Plastic Surgery
• Medical Imaging

Background:

• The zygomaticus major and minor (ZMa/ZMi) muscles significantly influence smile dynamics and midface contour.
• Morphological variations in ZMa/ZMi, such as bifid or multibellied bellies and accessory slips, are common and can complicate aesthetic and reconstructive procedures.
• These variants can lead to asymmetry, contour irregularities, or undesirable outcomes like a "joker smile" after interventions.

Purpose of the Study:

• To integrate the Landfald classification of ZMa/ZMi variants with a standardized dynamic imaging-based workflow for midface aesthetic and reconstructive procedures.
• To provide a practical protocol for preoperative assessment and procedural planning.
• To enhance safety, predictability, and patient satisfaction in midface interventions.

Main Methods:

• Narrative literature synthesis of anatomical and imaging studies.
• Integration of the Landfald classification for ZMa/ZMi variants.
• Proposal of a standardized dynamic imaging-based workflow including history, dynamic examination, ultrasound (US)/electromyography (EMG) mapping, and optional MRI.
• Review of procedure-specific adaptations for various midface interventions.

Main Results:

• ZMa/ZMi variants, including bifid or multibellied forms, are reported in up to 35% of cadaveric specimens.
• A synthesis of anatomical, biomechanical, and imaging evidence supports the proposed protocol.
• The protocol emphasizes individualized adjustments for surgical vectors, injection planes, and dosing based on patient-specific anatomy and function.

Conclusions:

• Standardizing preoperative dynamic mapping of ZMa/ZMi muscles is essential for improving outcomes in midface procedures.
• Adopting a "patient-specific mimetic profile" enhances safety, predictability, and preserves authentic facial expression.
• The proposed workflow aims to improve patient satisfaction across diverse midface aesthetic and reconstructive interventions.