Anatomy & Physiology

Dimensions and Anatomic Variations of the Orbicularis Oculi Muscle in Nonpreserved, Fresh-Frozen Human Cadavers Bryan R. Costin, M.D.*, Natta Sakolsatayadorn, M.D.*, Stephen A. McNutt, M.D.*, Tal J. Rubinstein, M.D.*, Georgios Trichonas, M.D.*, Karolinne M. Rocha, M.D., Ph.D.*, Jedediah I. McClintic, M.D.*, Lily Huang, M.D.†, Jennifer M. McBride, Ph.D.‡, and Julian D. Perry, M.D.* *Cole Eye Institute, Cleveland Clinic, Cleveland, Ohio; †Case Western Reserve University School of Medicine, Cleveland, Ohio; and ‡Department of Anatomy, Cleveland Clinic Lerner College of Medicine, Cleveland, Ohio, U.S.A.

Purpose: To determine average dimensions of the orbicularis oculi muscle (OOM) from the orbital rim and to investigate polymorphic variations through anatomical dissection of nonpreserved, fresh- frozen human cadavers. Methods: The OOM was exposed using sharp and blunt dissection until its distal borders were identified. A metric ruler was used to measure the superior (S line), inferior (I line), and lateral (L line) dimensions of the OOM from the orbital rim. Data collection included age, gender, and race. Data were analyzed using 2-sample t tests, paired t tests, and mixed effect models. A p-value of ≤0.05 was considered statistically significant. Results: A total of 40 hemifaces of 20 cadavers were dissected. All specimens were Caucasian. Ten specimens were men. Average age was 73.9 years (56–92 years). The overall S line was 1.4 cm (95% confidence interval [CI], 1.23–1.57), the I line was 1.2 cm (95% CI, 1.00–1.36), and the L line was 2.5 cm (95% CI, 2.27–2.68). Men had significantly larger average T, L, and S line values than women (p = 0.003, 0.005, 0.008, respectively). I lines did not differ significantly between genders (p = 0.28). Conclusions: In senescent Caucasians, the OOM extends approximately 1.4 cm superior, 1.2 cm inferior, and 2.5 cm lateral to the orbital rim. The muscle extends significantly further superiorly and laterally in Caucasian men than in women. Knowledge of the extent of the OOM should improve the understanding and the treatment of conditions affecting this region.

texts failed to delineate the extent of the OOM.5–16 The authors sought to determine the average dimensions of the OOM and to investigate polymorphic variations through anatomical dissection of fresh-frozen human cadavers to tailor surgical procedures and neurotoxin delivery better.

METHODS This study was performed using nonpreserved human cadavers registered in the Cleveland Clinic Body Donation Program. Specimens were excluded from this study if previous head and/or neck dissection had been performed or if there was any sign of ocular and periocular trauma including cornea donation. Superficial skin incisions were created along a line located 1 cm lateral and parallel to a line connecting the supraorbital notch (SON) and the infraorbital foramen (IOF) and from the lateral canthus to the superior border of the tragus (Fig. 1). The OOM was exposed using a combination of sharp and blunt dissection until its distal borders were identified and marked with a pin (Fig. 2). A metric ruler was placed along the palpated orbital rim and extended to the pin to measure the superior (S line), inferior (I line), and lateral (L line) dimensions of the OOM from the orbital rim (Fig. 3). The same surgeon (B.R.C.) supervised all dissections and performed all measurements. Medial dissection was not performed. The distance temporally between the lateral orbital rim and the superior border of the tragus was also recorded (T line) as a surrogate for overall head size (Fig. 4). Data collection included age, gender, race, and cause of death.

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T

he orbicularis oculi muscle (OOM) serves a critical protective function for the cornea and represents a central structure in oculoplastic surgery. Despite its importance, very few studies describe the extent or anatomical variations of this protractor muscle.1 A PubMed search in May 2013 using “orbicularis oculi muscle” as the search parameter revealed 1433 titles. A review of these titles showed no reports on the dimensions of the OOM.2–4 Similarly, a recent review of over a half-dozen anatomy Accepted for publication August 30, 2013. The authors have no financial or conflicts of interest to disclose. Presented at the 2013 Annual Meeting of the American Society of Ophthalmic Plastic and Reconstructive Surgeons in New Orleans, Louisiana. Address correspondence and reprint requests to Bryan R. Costin, M.D., Cole Eye Institute, Cleveland Clinic, 9500 Euclid Ave., Cleveland, OH 44195. E-mail: [email protected] DOI: 10.1097/IOP.0000000000000027

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FIG. 1.  External photograph of cadaver No. 3 demonstrates the incision lines for orbicularis oculi muscle dissection.

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Orbicularis Oculi Dimensions

Orbicularis oculi dimensions in Caucasian males and females Right

Male  L line  S line  I line Female  L line  S line  I line

FIG. 2.  External photograph of cadaver No. 3 demonstrates the dissected orbicularis oculi muscle with pins placed for measurement.

Left

N

Mean (SD)

N

Mean (SD)

p

10 10 10

2.6 (0.4) 1.7 (0.4) 1.3 (0.5)

10 10 10

3.0 (0.4) 1.6 (0.4) 1.3 (0.4)

0.017 0.020 0.91

10 10 10

2.1 (0.5) 1.2 (0.4) 1.1 (0.4)

10 10 10

2.2 (0.6) 1.1 (0.3) 1.1 (0.3)

0.26 0.12 0.67

was 1.2 cm (95% CI, 1.00–1.36), and the L line was 2.5 cm (95% CI, 2.27–2.68). About laterality, the right L line was significantly shorter than the left (2.6 cm vs. 3.0 cm, p = 0.017) in men. The right S line was significantly larger than the left (1.7 cm vs. 1.6 cm, p = 0.020). There was no difference between I lines in men (p = 0.91). There was no significant difference between right- and left-sided measurements in women (p = 0.26, 0.12, 0.67). For all T, L, and S lines, men had significantly larger values than women (p = 0.003, 0.005, 0.008, respectively). I lines did not significantly differ between genders (p = 0.28) (Table).

DISCUSSION

FIG. 3. Illustration demonstrates dissection and measurement methodology.

FIG. 4. Illustration shows dimensions of the orbicularis oculi muscle from the orbital rim. Data were analyzed using 2- sample t tests, paired t tests, and mixed effect models. A p-value of 0.05 was considered statistically significant.

RESULTS A total of 40 hemifaces of 20 nonpreserved, fresh-frozen human cadavers were dissected. All specimens were Caucasian. Ten specimens were men. Average age at time of death was 73.9 years (range, 56–92 years), and there was no significant difference between men and women (p = 0.42). The overall S line was 1.4 cm (95% CI, 1.23–1.57), the I line

While the OOM represents a central structure in oculoplastic surgery, few modern studies delineate its extent. Recent studies demonstrate medial variations of the muscle1 and characterize the relationship between the OOM and the levator labii superioris and zygomaticus major muscles.2 These studies offer important clinical implications, such as options to prevent upper lip ptosis after botulinum toxin treatment. A recent dissection study determined the existence of a variant “orbitozygomatic muscle” in Korean adults.3 Lemke17 described vertical lateral OOM fibers consistently occurring distal to the bulk of the orbital OOM but did not quantify the lateral extent of the muscle. However, to the authors’ knowledge, the dimensions of the OOM have not been reported. The authors found that in senescent Caucasians, the OOM extends approximately 1.4 cm superior to the orbital rim, 1.2 cm inferior to the orbital rim, and 2.5 cm lateral to the orbital rim. While men have further extension of the muscle superiorly and laterally, the CIs suggest that the extent of the muscle is relatively constant. Their measurements included all aspects of the muscle laterally, including any vertical lateral fibers. Knowledge of this anatomy should improve surgical and neurotoxin therapy results. Standard neurotoxin patterns for the treatment of blepharospasm and lateral canthal rhytides may be required to extend further laterally to account for the extent of the muscle. Successful orbicularis myectomy for blepharospasm should likely include dissection to the extents found in this study. Similarly, these results suggest that appropriate facial spasm treatment may require neurotoxin injections at least 2.5 cm lateral to the orbital rim. In vivo data during myectomy surgery or nonpreserved cadaver histology studies could verify these results. This study has several limitations. Senescent Caucasian cadavers may not adequately represent the entire population, and racial and age-related polymorphism in the extent of the OOM may exist. Individual cadaver anatomy and preservation state may present dissection challenges. However, the relatively narrow CIs suggest that the dimensions appear constant enough to provide clinical usefulness during surgical and neurotoxin therapy. Further, the nonpreserved and fresh-frozen nature of these

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study specimens obviated the effects of preservatives on native tissue architecture. The difference between right- and left-side results in men suggests sampling error, because any methodological error should have been similar on each side. The power of the sample is limited by the lack of independence between hemiface results of each cadaver. The authors used palpable anatomical landmarks rather than a measured midpoint along the bony orbit to yield more clinically relevant information that the practitioner might use while injecting or operating. They did not perform medial dissection because adherence of tissues in the cadaveric medial canthal region limits accurate gross description. The data regarding the extent of the OOM is reminiscent of the spiral of Tillaux describing rectus muscle insertions and providing valuable reference points during many types of ophthalmic surgical procedures.18,19 In conclusion, this 1.4–1.2–2.5 cm schema should prove valuable during surgical and neurotoxin therapy, and the surgeon should commit knowledge of the average dimensions of the OOM to memory to improve the understanding and the treatment of conditions affecting this region.

REFERENCES 1. Park JT, Youn KH, Lee JG, et al. Medial muscular band of the orbicularis oculi muscle. J Craniofac Surg 2012;23:195–7. 2. Spiegel JH, DeRosa J. The anatomical relationship between the orbicularis oculi muscle and the levator labii superioris and zygomaticus muscle complexes. Plast Reconstr Surg 2005;116:1937–42; discussion 1943–4. 3. Hwang K, Lee DK, Chung IH, et al. Identity of “orbitozygomatic muscle”. J Craniofac Surg 2002;13:202–4. 4. Patrinely JR, Anderson RL. Anatomy of the orbicularis oculi and other facial muscles. Adv Neurol 1988;49:15–23. 5. Drake RL, Vogl W, Mitchell AWM. Gray’s Anatomy for Students. 2nd ed. Philadelphia, PA: Elsevier, 2010:879–80.

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6. Ross LM, Lamperti ED, Taub E. Theime Atlas of Anatomy: Head and Neuroanatomy. Stuttgart, Germany: Theime, 2007:120–3. 7. Rohen JW, Yokochi C, Lütjen-Drecoll E. Color Atlas of Anatomy: A Photographic Study of the Human Body. 7th ed. Philadelphia, PA: Lippincott Williams & Wilkins, 2011:56–63. 8. Jones LT, Reeh MJ, Wirtschafter, JD. Ophthalmic Anatomy: A Manual With Some Clinical Applications. Rochester, MN: American Academy of Ophthalmology and Otolaryngology, 1970:42–5. 9. Beard C, Quickert MH. Anatomy of the Orbit. 2nd ed. Birmingham, AL: Aesculapius Publishing Company, 1977:2–10. 10. Kikkawa DO, Lemke BN. Orbital and eyelid anatomy. In: Dortzbach RK, ed. Ophthalmic Plastic Surgery: Prevention and Management of Complications. New York, NY: Raven Press, 1994:22–3. 11. Bergin DJ. Anatomy of the eyelids, lacrimal system, and orbit. In: McCord CD, Tanenbaum M, Nunery WR, eds. Oculoplastic Surgery. 3rd ed. New York, NY: Raven Press, 1995:67–9. 12. Kikkawa DO, Vasani SN. Ophthalmic facial anatomy. In: Chen WP, ed. Oculoplastic Surgery: The Essentials. New York, NY: Thieme, 2001:1–5. 13. Zide BM. Surgical Anatomy Around the Orbit: The System of Zones. Philadelphia, PA: Lippincott Williams & Wilkins, 2006:37,46. 14. Levine MR. Manual of Oculoplastic Surgery. 4th ed. Thorofare, NJ: Slack Incorporated, 2010:5. 15. Nerad JA. Techniques in Ophthalmic Plastic Surgery: A Personal Tutorial. Philadelphia, PA: Saunders Elsevier, 2010:36–7. 16. Lemke BN, Lucarelli MJ. Anatomy of the ocular adnexa, orbit, and related facial structures. In: Black EH, Nesi FA, Calvano CJ, eds. Smith and Nesi’s Ophthalmic Plastic and Reconstructive Surgery. 3rd ed. New York, NY: Springer, 2012:25–6. 17. Lemke BN, Stasior OG. The anatomy of eyebrow ptosis. Arch Ophthalmol 1982;100:981–6. 18. Tillaux P. Traité d’Anatomie Topographique Avec Applications à la Chirurgie. 6th ed. Paris, France: Asselin et Houzeau, 1890:166–167. 19. Tamburrelli C, Salgarello T, Vaiano AS, et al. Ultrasound of the horizontal rectus muscle insertion sites: implications in preoperative assessment of strabismus. Invest Ophthalmol Vis Sci 2003;44:618–22.

© 2014 The American Society of Ophthalmic Plastic and Reconstructive Surgery, Inc.

Dimensions and anatomic variations of the orbicularis oculi muscle in nonpreserved, fresh-frozen human cadavers.

To determine average dimensions of the orbicularis oculi muscle (OOM) from the orbital rim and to investigate polymorphic variations through anatomica...
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