Are We Underestimating Zygomaticus Variability in Midface Surgery?
Abstract
1. Introduction
1.1. Significance of Zygomatic Muscles in Midface Aesthetics and Expression
1.2. Role as Functional Tension Vectors
1.3. Aim and Scope of This Review
1.4. Clinical Takeaway
2. The Significance of Zygomatic Muscles in Facial Aesthetics
2.1. Role in Contouring the Cheek and Malar Region
2.2. Clinical Takeaway—ZMa and ZMi in Midface Contouring
- Variants of ZMa and ZMi, as classified by Landfald, can significantly influence malar projection and facial symmetry.
- Recognizing these variants preoperatively allows adjustment of surgical and minimally invasive procedures for more predictable outcomes.
3. Procedural Implications of Zygomaticus Major and Minor Variability
3.1. Facelifting Techniques
3.2. Volume Restoration and Fillers
3.3. Thread Lifting Techniques
3.4. Clinical Takeaway—Surgical and Minimally Invasive Planning
- Adapt facelift vectors when ZMa variants (bifid, multibellied, low-insertion) are present.
- Adjust filler planes to account for altered fat compartments or accessory slips.
- Use US guidance to plan thread trajectories and avoid asymmetry.
3.5. Clinical Risks and the Role of Anatomical Mapping
3.6. Key Variant-Related Risks
3.7. Prevention and Mitigation
- Dynamic US—to visualize belly configuration, insertion points, and compartment boundaries in real time.
- Electromyography (EMG)—to assess contraction vectors, asymmetries, and muscle hyperactivity.
3.8. Clinical Takeaway—Risk-Based Planning
- Match each ZMa/ZMi variant with its key procedural risk (e.g., “joker smile” in low-insertion types).
- Use US and EMG mapping before midface interventions to adapt surgical or injection techniques.
- Use dynamic assessment to bridge anatomical imaging with real-time functional behavior.
4. Dynamic Assessment and Preprocedural Planning
4.1. Dynamic Assessment Tools: EMG, Ultrasound, and 3D Analysis
4.2. Patient Assessment Algorithm
4.3. Challenges in Integrating Functional and 3D Data
4.4. Clinical Takeaway —Dynamic Assessment
- Integrate US, EMG, and 3D analysis to map contraction vectors and variant anatomy before planning interventions.
- A multimodal, standardized workflow improves safety, optimizes symmetry, and preserves natural expression.
5. Smile Restoration: Adult and Pediatric Considerations
5.1. Muscle Transfer and Vector Reconstruction
- Gracilis transfer—preferred for its slender morphology, predictable contraction, and ease of microsurgical reinnervation; its oblique pull closely replicates the native ZMa vector [27].
5.2. Pediatric Considerations in Congenital and Syndromic Cases
5.3. Clinical Takeaway—Smile Restoration
- Gracilis transfer best replicates the native ZMa vector; masseter and temporalis require vector adjustment.
- Preoperative US/EMG/3D mapping ensures accurate donor orientation and tension calibration.
- In pediatric cases, early reconstruction should address both anatomy and emotional expressiveness to support psychosocial development.
6. Botulinum Toxin and Mimetic Precision
6.1. Botox in the Treatment of Gummy Smile
6.2. Botox in the Treatment of Smile Asymmetry
6.3. Clinical Takeaway—Botulinum Toxin for Midface Corrections
- Use US/EMG mapping to individualize injection sites and depth.
- Tailor dose and vector to minimize asymmetry or unnatural expression.
- Pay special attention to post-traumatic and post-surgical patients with altered muscle pathways.
7. Personalization of Aesthetic Procedures
7.1. Patient-Specific Mimetic Profile, Smile-Type Classification, and the Dynamic Aesthetics Paradigm
7.2. Clinical Takeaway—Patient-Specific Mimetic Planning
- Classify smile type (horizontal vs. vertical/complex) and key features (gingival display, commissure elevation, symmetry) to guide planning.
- Use multimodal mapping (US, EMG, 3D) to tailor interventions to each patient’s mimetic profile.
- Apply the dynamic aesthetics paradigm to ensure outcomes that are both anatomically sound and emotionally authentic.
8. Dynamic Aesthetics and Smile Perception
Zygomatic Muscles as Structures Influencing Movement Rather Than Just Volume
9. Clinical Practical Recommendation
9.1. Standardized Preoperative Assessment Protocol
- Clinical history and inspection—document facial trauma, prior surgery, and baseline smile symmetry.
- Functional palpation—assess tone, contraction strength, and presence of accessory bands.
- Imaging—combine US for dynamic mapping, EMG for functional assessment, and MRI for deep-structure planning when complex anatomy is suspected.
- Integration—correlate clinical and imaging findings to define anatomical variants.
- Procedural planning—adapt lift vectors, filler planes, botulinum toxin sites, or graft orientation according to variant type.
- Documentation and follow-up—record mapping findings and evaluate outcomes with repeat US/EMG at 1, 3, and 6 months.
9.2. Necessity for Preoperative Imaging
10. Conclusions
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Conflicts of Interest
References
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Variant (Landfald Type) | Primary Risk | Recommended Technique Adaptation |
---|---|---|
Low-insertion ZMa | Lateral overcorrection (“Joker smile”) | Use more vertical lift vector; reduce lateral traction during facelifts |
Bifid ZMa | Asymmetry, visible thread tracks | Adjust facelift/thread vectors to each belly; perform US mapping prior to dissection |
Multibellied ZMa | Uneven filler diffusion, contour defects | Deeper bolus placement; modify injection planes based on compartment boundaries |
Accessory slip ZMi | Perioral disharmony after augmentation | Shift injection depth to subcutaneous plane; adjust filler volume |
Asymmetrical type III/IV ZMa | Oral commissure retraction | Reorient surgical or thread vectors; release tension asymmetrically |
Step | Action | Key Objectives | Tools/Methods |
---|---|---|---|
1 | Clinical history | Identify factors affecting facial anatomy and neuromuscular function | Patient interview, medical records |
2 | Visual inspection | Assess symmetry at rest and in expression | Direct observation, photographic documentation |
3 | Functional palpation | Detect muscle tone, contraction strength, belly configuration, accessory bands | Manual palpation during facial movement |
4 | Imaging | Map anatomical course and functional dynamics | Ultrasound (US), Electromyography (EMG), 3D dynamic analysis |
5 | Classification (Figure 2 panel a–e) | Standardize variant labeling to guide vectors and release paths | Chart annotation linked to Figure 2 |
6 | Integration | Correlate anatomical and functional data | Multimodal data review |
7 | Procedural execution | Apply variant-specific adjustments | Adapt vectors, injection planes, release strategy |
8 | Postoperative follow-up | Validate symmetry and function, detect complications early | Repeat US/EMG, photographic analysis |
Variant\Procedure | Facelift/Midface | Fillers (HA/Fat) | Thread Lifting | BTX |
---|---|---|---|---|
A. ZMa low-insertion (medial–inferior vector) | M(2) • V-adj + RL-mod (limit vertical pull) | H(3) • Plane-Deep + Vol-control (modiolus area) | H(3) • NTZ at modiolus | M(2) • Dose-↓ + BTX-dist (spare ZMa) |
B. ZMa bifid | M(2) • V-adj (more oblique vector) | M(2) • Plane-Deep | M(2) • NTZ over split zone | M(2) • BTX-dist (dominant branch) |
C. ZMa multibellied | M–H(2–3) • RL-mod selectively | M(2) • Plane-Deep | H(3) • NTZ (avoid inter-belly septa) | M(2) • Dose-↓ (avoid mask-smile) |
D. Accessory slip to modiolus/upper lip | M(2) • V-adj (more lateral vector) | H(3) • Plane-Deep + Vol-control | H(3) • NTZ near modiolus | M(2) • BTX-dist (target slip) |
E. ZMi hypertrophy/accessory band | L–M(1–2) • V-adj (keep horizontal component) | M(2) • Plane-SMAS (shallower than ZMa-low) | M(2) • Careful over ZMi | M(2) • Dose-↓ on ZMi (avoid excessive down-pull) |
F. Asymmetry L/R | M(2) • V-adj + RL-mod on dominant side | M(2) • Vol-control (asymmetric) | M(2) • Trajectory asymmetry | M(2) • Dose-asym (balance) |
G. High-insertion ZMa | L(1) • Standard with slight correction | M(2) • Plane-SMAS | M(2) • Safer track (fewer conflicts) | L–M(1–2) • Standard/↓ dose |
H. Zygomaticus–LLS complex variant | M–H(2–3) • RL-mod (control vertical component) | M(2) • Plane-Deep | M(2) • Avoid crossing LLS line | M(2) • BTX-dist (balance ZMa/ZMi/LLS) |
Legend: | L(1) Low risk | M(2) Moderate risk | H(3) High risk |
Donor Muscle | Vector Orientation vs. Native ZMa | Advantages | Limitations | Optimal Use Cases |
---|---|---|---|---|
Gracilis | Oblique pull closely replicates ZMa vector | Slender morphology; predictable contraction; ease of microsurgical reinnervation | Requires microsurgical expertise; donor site morbidity | Gold standard for dynamic smile restoration; best vector match |
Masseter | Predominantly vertical; requires repositioning | Strong elevation; native innervation; reliable performance | Less natural smile mechanics without repositioning | Patients prioritizing strength over vector precision |
Temporalis | Predominantly vertical; requires repositioning | Technically reliable; accessible donor site | Requires extensive re-education; less natural vector | When gracilis or masseter unavailable or contraindicated |
Procedure | Risk Due to Anatomical Variation | Adaptation of Clinical Technique |
---|---|---|
Facelift / Midface Lift | Asymmetry; inappropriate vector tension; ‘joker smile’ deformity | Preoperative mapping of ZMa/ZMi course; modify lifting vectors |
Soft Tissue Augmentation (HA, Fat Grafting) | Uneven filler distribution; asymmetry due to additional bands | US-based mapping; adjust injection planes and volumes |
Thread Lifting | Thread misplacement; insufficient lift from unexpected muscle paths | Preoperative imaging and palpation; individualized thread planning |
Botulinum Toxin Therapy | Incorrect toxin placement; asymmetric smile or incomplete correction | Variant-specific mapping; adjust injection points and dosing |
Smile Reconstruction Surgery | Failure to restore natural smile dynamics | Customized graft placement respecting contraction vectors |
Pediatric Craniofacial Surgery | Long-term deficits due to abnormal muscle topography | Surgical recreation of normal ZMa/ZMi arrangement |
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Landfald, I.C.; Olewnik, Ł. Are We Underestimating Zygomaticus Variability in Midface Surgery? J. Clin. Med. 2025, 14, 7311. https://doi.org/10.3390/jcm14207311
Landfald IC, Olewnik Ł. Are We Underestimating Zygomaticus Variability in Midface Surgery? Journal of Clinical Medicine. 2025; 14(20):7311. https://doi.org/10.3390/jcm14207311
Chicago/Turabian StyleLandfald, Ingrid C., and Łukasz Olewnik. 2025. "Are We Underestimating Zygomaticus Variability in Midface Surgery?" Journal of Clinical Medicine 14, no. 20: 7311. https://doi.org/10.3390/jcm14207311
APA StyleLandfald, I. C., & Olewnik, Ł. (2025). Are We Underestimating Zygomaticus Variability in Midface Surgery? Journal of Clinical Medicine, 14(20), 7311. https://doi.org/10.3390/jcm14207311