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The Subzygomatic FossaA Practical Landmark in Identifying the Zygomaticus Major Muscle
Philip J. Miller, MD;
Sarah Smith, MD;
Anil Shah, MD
Arch Facial Plast Surg. 2007;9(4):271-274.
ABSTRACT
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Objective To test the validity of the subzygomatic fossa as a possible landmark in identifying the origin of the zygomaticus major muscle (ZMM).
Methods Twenty-three fresh cadaver facial halves were dissected. Four references points were identified in each cadaver head: the zygomatic arch, the malar eminence, the modiolus, and the ZMM insertion notch. The ZMM insertion notch is a palpable landmark that is typically identified midway between the zygomatic arch and the malar eminience. A straight line was drawn from the ZMM insertion notch to the modiolus. An additional line was drawn from the malar eminence to the modiolus. An incision was made along the each line to the depth of the facial muscles. The presence or absence of the ZMM was recorded, and the location of the ZMM insertion notch was characterized in each cadaver.
Results The ZMM insertion notch was palpated and identified in 23 of 23 facial halves. It was accurate in identifying the course of the ZMM in all 23 facial halves. The line created by the malar eminence to the modiolus was inaccurate in all 23 facial halves.
Conclusion The ZMM insertion notch is a reliable landmark for identification of the ZMM.
INTRODUCTION
The identification of the course of the zygomaticus major muscle (ZMM) plays an important role in facial plastic surgery. First of all, the ZMM serves as an important landmark in deep plane rhytidectomy.1 The facial nerve courses deep to the plane of the ZMM, providing the face-lift surgeon with a reliable guide to dissection into the medial portion of the face.1-2 Also, some surgeons report plication of the ZMM to provide rejuvenation of the aged face.3-4 For patients receiving botulinum toxin type A (Botox) injections for "crow's feet" within the orbicularis oculi, avoidance of the ZMM is critical to prevent the unwanted sequlae of a lip drop.5
The ZMM is responsible for lifting the corners of the mouth, which serves several expressive purposes, including smiling. It is typically a fan-shaped muscle, which may be single headed or bifid in nature.6 The muscle increases in size and thickness in males and in patients with an increasing body mass index.7 Located anterior to the ZMM is the zygomatic cutaneous ligament, or MacGregor's patch.8 Release of this ligament is crucial in providing mobilization of the malar fat pad and rejuvenation of the midface structures. The superficial musculoaponeurotic system layer can be mobilized further and with less tension with release of the zygomatic ligament.2 A backcut of the ZMM itself will also provide improved mobilization of the superficial musculoaponeurotic system layer.4
Deep to the ZMM lies the plexus of the zygomatic branch of the facial nerve. The orbicularis oculi may be partially innervated in certain patients by some nerve branches that lie superficial to the ZMM.9 However, the plexiform innervation of the zygomatic branch of the facial nerve and the vast majority of nerves that lie deep to the ZMM make permanent sequlae unlikely. The ZMM, along with the other upper lip mimetic muscles, inserts at the modiolus.10 The ZMM originates anterior to the zygomatic temporal suture within the subzygomatic fossa11 (Figure 1).
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Figure 1. The zygomaticus major muscle is found by by dropping a vertical line from the lateral border of the orbital rim to the inferior border of the zygoma (adapted from Mendelson12).
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Despite this anatomical description, surgeons have sought complex means of ascertaining the clinical origin of the ZMM (Figures 1, 2, 3, and 4). Mendelson12 described the origin as " a vertical line dropped from the lateral orbital rim to the lower border of the zygoma." Tremolada et al13 described the origin from the malar bone on a line drawn from the lateral canthus to the mandible. Furnas8 reported that the ZMM was located along the zygomatic body, coursing to the modiolus. In a more recent article, Mowlavi and Wilhelmi14 found that the lateral border of the ZMM was 4.4 mm lateral and parallel to an oblique line drawn from the mental protuberance to the notch defined as the most anterior-inferior aspect of the temporal fossa at the junction of the frontal process and the temporal process of the zygoma. Finally, Spiegel and DeRosa5 published an anatomical article in which they describe the origin of the ZMM to be 1.4 cm inferior to the Frankfort horizontal line at 1.0 cm lateral to the lateral canthus.
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Figure 2. The zygomaticus major muscle originates from the malar bone on a line drawn from the lateral canthus to the mandible (adapted from Tremolada et al13).
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Figure 3. The lateral border of the zygomaticus major muscle was found 4.4 mm lateral and parallel to an oblique line drawn from the mental protuberance to the notch defined as the most anterior-inferior aspect of the temporal fossa at the junction of the frontal process and temporal process of the zygoma (adapted from Mowlavi and Wilhelmi14).
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Figure 4. The zygomaticus major muscle originates 1.4 cm inferior to the Frankfort horizontal line at 1.0 cm lateral to the lateral canthus (adapted from Spiegel and DeRosa5).
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While the previous descriptions were fairly accurate in illustrating the course of the ZMM, their overall complexity has prevented them from being universally adopted by facial plastic surgeons. The origin of the ZMM is the subzygomatic fossa, which is located posterior and inferior to the malar eminence and anterior to the zygomatic temporal suture. Despite some contrary reports, the subzygomatic fossa is an easily palpable landmark. The senior author (P.J.M.) has developed a technique for locating the course of the ZMM (Figure 5). By using the palpable subzygomatic fossa itself, the location of the ZMM can be ascertained.
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Figure 5. The subzygomatic fossa is located posterior and inferior to the malar eminence and anterior to the zygomatic temporal suture (adapted from Mowlavi and Wilhelmi14). ZMM indicates zygomaticus major muscle.
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METHODS
Twenty-three fresh cadaver facial halves were dissected. Four reference points were identified in each cadaver head: the zygomatic arch, the malar eminence, the modiolus, and the subzygomatic fossa, which is a palpable landmark that can be identified midway between the zygomatic temporal suture and the malar eminience. A straight line was drawn from the ZMM insertion notch to the modiolus. An additional line was drawn from the malar eminence to the modiolus. An incision was made along the each line to the depth of the facial muscles. The presence or absence of the ZMM was recorded when each of the above landmarks was used (Figure 6). The palpation of the landmarks was performed by a junior resident (S.S.) to ensure that novice surgeons could easily learn to use this technique. The clinical application of the efficacy of the zygomatic notch was applied in 28 consecutive deep-plane rhytidectomies. The zygomatic notch, as well as the modiolus and the proposed location of the ZMM, was identified and marked before the face-lift. A deep-plane rhytidectomy was performed with location of the ZMM using the external landmark as a guide.
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Figure 6. Cadaver demonstrating the zygomatic arch, subzygomatic fossa, and malar emininece marked before dissection. The zygomaticus major muscle can be seen coursing from the subzygomatic fossa to the modiolus.
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RESULTS
The subzygomatic fossa was palpated and identified in 23 of 23 facial halves. The ZMM insertion notch was also accurate in identifying the course of the ZMM in all 23 facial halves. The line created by the malar eminence to the modiolus was inaccurate in all 23 facial halves. Clinically, the location of the subzygomatic fossa correlated well with the location of the ZMM in 58 consecutive rhytidectomy procedures.
COMMENT
We found the subzygomatic fossa to be an easily palpable landmark. Because the subzygomatic fossa is the recognized origin of the ZMM in several textbooks and anatomy books, we chose to use it as the landmark rather than a tangential correlation. We found both the palpability of the subzygomatic fossa and its underlying relationship with the origin of the ZMM to be highly accurate. Molwavi and Wilhelmi14 found the subzygomatic fossa difficult to palpate. However, we found that, by clearly palpating and identifying the zygomatic arch and the malar eminence, the subzygomatic fossa could be easily palpated. As a testament to its ease, a junior resident (S.S.) was able to palpate the fossa in each cadaver case. Landmarks are useful in surgery to provide the surgeon with an appropriate reference to the surrounding structures. A landmark must be accurate and identifiable to be useful. The use of the ZMM as a landmark in deep-plane rhytidectomy has been limited by lengthy descriptions on the origin of this muscle. The subzygomatic fossa simplifies its location and allows ease of identification.
Minimizing complications in such procedures as botulinum toxin injections are crucial to providing optimal patient results. Paralysis of the ZMM has been reported as an inadvertent adverse effect of treating periorbital rhytids.15 Limiting the dilution content of botulinum toxin, experience with injection, and knowledge of the facial anatomy will limit the possibility of this potential sequela occurring. Knowledge of the course of the ZMM will reduce the likelihood of an inadvertent injection.
Extensive knowledge of anatomy is required for safe performance of the deep-plane face-lift, and the ZMM is an important landmark for a safe and effective procedure. We hope that the identification of this landmark muscle will provide improved safety in deep-plane rhytidectomy.
AUTHOR INFORMATION
Correspondence: Anil Shah, MD, New York University, 530 First Ave, Suite 7U, New York, NY 10016 (shaha05{at}med.nyu.edu).
Accepted for Publication: February 6, 2007.
Author Contributions: Study concept and design: Miller, Smith, and Shah. Acquisition of data: Miller and Shah. Analysis and interpretation of data: Miller and Shah. Drafting of the manuscript: Smith and Shah. Critical revision of the manuscript for important intellectual content: Miller and Shah. Statistical analysis: Shah. Administrative, technical, and material support: Smith and Shah. Study supervision: Miller and Shah.
Financial Disclosure: None reported.
Author Affiliations: Division of Facial Plastic Surgery, Department of Otolarygology, New York University School of Medicine, New York, New York.
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