The anatomical relationship between the orbicularis oculi muscle and the levator labii superioris and zygomaticus muscle complexes.
OBJECTIVE
The purpose of this study was to define the anatomical relationship between the orbicularis oculi muscle and the levator labii superioris/zygomaticus major.


METHODS
Forty-eight sides of 24 preserved cadaver heads were evaluated. The Frankfort plane, the lateral canthus, and the midpupillary line were marked on each hemiface as landmarks. Four parallel incisions were made perpendicular to the inferior orbital rim and the Frankfort horizontal line. The incisions were midpupillary, lateral canthus, 1 cm lateral to the lateral canthus, and 2 cm lateral to the lateral canthus. Within each incision, measurements were performed that included the depth of the zygomaticus major from the orbicularis oculi (i.e., how superficial is the orbicularis above the zygomaticus complex), the superior to inferior distance between the Frankfort line and the origin of the zygomaticus major, the height of the orbicularis oculi muscle above the levator labii muscle (i.e., how superficial is the orbicularis above the levator in the midpupillary line), and how inferior to the inferior orbital rim is the origin of the levator labii superioris.


RESULTS
The orbicularis oculi muscle was on average 0.5 cm superficial to the zygomaticus major muscle group at 2 cm lateral to the lateral canthus. At this site, the female cadaver zygomaticus muscle depth was approximately 2 mm deeper versus the male cadavers (0.60 cm versus 0.41 cm). On average, the origin of the zygomaticus major was identified 1.40 cm and 1.50 cm inferior to the Frankfort horizontal line at 1 cm lateral to and at the lateral canthus, respectively. Of note, there were 14 instances (15 percent) in which the muscle group was found to be 1 cm or less from the Frankfort horizontal line. At 1 cm lateral to the lateral canthus and at the lateral canthus, the zygomaticus muscle was seen to interdigitate with the orbicularis muscle. On average, the orbicularis oculi muscle lies 0.80 cm superficial to the levator labii muscle complex. The superficial border of the malar eminence also lies at or near the Frankfort line.


CONCLUSIONS
An exact understanding of the location of specific muscle groups can help prevent poor outcomes, such as the lip droop occasionally seen with Botox injections. The Frankfort line may be a more appropriately used landmark for the safe placement of Botox than the commonly used malar eminence.
Spiegel
Jeffrey H
JH
Department of Otolaryngology-Head and Neck Surgery, Boston University School of Medicine, Boston, Massachusetts 02118, USA. jeffrey.spiegel@bmc.org
DeRosa
Jaimie
J
D019274:Botulinum Toxins, Type A / Q000008:administration & dosage; D002610:Cheek; D005152:Facial Muscles / Q000033:anatomy & histology*; D005260:Female; D006801:Humans; D008297:Male; D009465:Neuromuscular Agents / Q000008:administration & dosage; D009801:Oculomotor Muscles / Q000033:anatomy & histology*
D009465:Neuromuscular Agents; D019274:Botulinum Toxins, Type A