The lateral orbital tubercle, or Whitnall's tubercle, is found on the zygomatic bone. According to the Basic and Clinical Science Course, it is typically around 11 mm inferior to the frontozygomatic suture (the junction between the frontal bone and zygomatic bone) (1), and sits 4-5 mm posterior to the lateral orbital rim around the midline (2).
Because it serves as an anchor for many structures, it's important to not only know its location, but also everything that attaches to it. Because they all contain the letter L, I remember these structures as the "4 L's":
- Lateral rectus check ligament
- Lockwood suspensory ligament
- Lateral palpebral ligament
- Levator aponeurosis
While I thought this up independently of any outside reference, I think this association is pretty obvious. Since this mnemonic is already on the Internet, I want to make sure I give credit to Dvahal Patel as well (3).
Whitnall's Ligament: Controversy?
Wait, does Whitnall's ligament attach to Whitnall's tubercle? When I first was learning the material, it seemed pretty confusing. The BCSC Section 2 text in Chapter 1 lists Whitnall's ligament as one of the structures that attaches to Whitnall's tubercle, but later on in that same chapter when it describes Whitnall's ligament, the tubercle is not mentioned at all as part of its lateral attachment (instead, the orbital lobe fascia of the lacrimal gland is listed) (1). Several other texts specifically state that Whitnall's ligament does NOT have specific attachments to Whitnall's tubercle (4). Whitnall's original text describing the tubercle doesn't list his eponymous ligament as one of the structures that attaches to it (5). Of course, Wikipedia "definitively" agrees that Whitnall's ligament doesn't attach to Whitnall's tubercle, for what that's worth (6).
Bottom line: Whitnall's ligament does NOT attach to Whitnall's tubercle.
As you can probably guess, many of the anatomical things we have to memorize or learn will be applied in surgery.
- Lateral tarsal strip: In this treatment for lower lid laxity, the lateral tarsal strip is affixed to the periosteum of the lateral orbital wall. Ideally, to preserve anatomical relationships, Whitnall's tubercle serves as the point of reattachment. Other lateral canthal procedures also use this tubercle as a landmark (2).
References and Additional Reading
- Chapter 1: Orbit and Ocular Adnexa. In: Basic and Clinical Science Course, Section 2: Fundamentals and Principles of Ophthalmology, 2010-2011 Edition. American Academy of Ophthalmology.
- Sherman DD, Burkat CN, Lemke BN. Chapter 21: Orbital Anatomy and Its Clinical Applications. In: Tasman W, Jaeger EA. Duane's Ophthalmology on CD-ROM, 2006 Edition. Lippincott Williams & Wilkins. Online.
- Patel D. Whitnall Tubercle Attachment. Ophthalmonics. Website. http://ophthalmonics.blogspot.com/2014/04/whitnall-tubercle-attachment.html
- Subrahamanyam M. Surgical Atlas of Orbital Diseases. Jaypee Brothers Medical Publishers; 2008, 12-13.
- Whitnall SE. On a Tubercle on the Malar Bone, and on the Lateral Attachments of the Tarsal Plates. J Anat Physiol. 1911 Jul; 45: 426-32.
- Superior Transverse Ligament. Wikipedia. Online. https://en.wikipedia.org/wiki/Superior_transverse_ligament.
- Nesi FA, Gladstone G, Black EH, et al., eds. Oculoplastic Surgery Atlas: Eyelid Disorders. Springer; 2002.
Turvey TA, Golden BA. Orbital Anatomy for the Surgeon. Oral Maxillofac Surg Clin North Am. 2012 November; 24(4): 525–536.
- Petruzzelli GJ. Orbit Anatomy. Medscape. Online. http://emedicine.medscape.com/article/835021-overview.