Although a number authors have published articles suggesting the need to target specific periorbital muscles for desired effect, there remains a great variability in the injection type, location, and dosage.2–4 Moreover, there can be significant variability in muscle anatomy between individuals.5,6 As such, we do not believe that it is critical to target a specific muscle, especially given the diffusion radius of the toxin; rather, the injection should be aimed at restoring balance along the 24-hour clock. For example, if a patient presents with left Mona Lisa (zygomatic) smile because of overactive levator anguli oris and zygomaticus minor, injections are given along the 4- and 5-o’clock positions rather than aiming for the specific muscles (Table 1). Since 2006, the senior author of this article has successfully used the 24-hour clock concept to achieve favorable and predictable outcome in botulinum toxin injection to the lower face and minimize complications.
None of the authors has a financial interest to declare in relation to the content of this article.
Nam Ho Kim, M.D.
Tae Joo Ahn, M.D.
Ro Hyuk Park, M.D.
Kyun Tae Kim, M.D.
Edward Ilho Lee, M.D.
Edward I. Lee Plastic Surgery
1. Janis JE, Rohrich RJThorne CHRhinoplasty.In: Grabb & Smith’s Plastic Surgery20076th edPhiladelphiaLippincott517–532
2. Sucupira E, Abramovitz AA simplified method for smile enhancement: Botulinum toxin injection for gummy smile.Plast Reconstr Surg2012130726–728
3. Suber JS, Dinh TP, Prince MD, Smith PDOnabotulinumtoxinA for the treatment of a “gummy smile”.Aesthet Surg J201434432–437
4. Hwang WS, Hur MS, Hu KS, et alSurface anatomy of the lip elevator muscles for the treatment of gummy smile using botulinum toxin.Angle Orthod20097970–77
5. Kane MAThe effect of botulinum toxin injections on the nasolabial fold.Plast Reconstr Surg200311266S–72S
6. Pessa JE, Zadoo VP, Adrian EK Jr, Yuan CH, Aydelotte J, Garza JRVariability of the midfacial muscles: Analysis of 50 hemifacial cadaver dissections.Plast Reconstr Surg19981021888–1893
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