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Dag Krohn-Hansen, Bjorn Nicolaissen, Erling Haaskjold, Torstein Meling; On The Anatomy Of The Upper Mid-orbit: The Anatomical Relationships Between The Orbital Septum, The Levator Muscle And The Retroseptal Fat Pad. Invest. Ophthalmol. Vis. Sci. 2012;53(14):4912.
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The purpose with this human cadaver study was to clarify the anatomical rationale for a surgical approach to the levator muscle and the upper mid-orbit structures, in which the orbital septum and the retroseptal fat pad is not harmed during surgery.
Five orbits from three Caucasian cadaver heads fixed in formalin were used for both macro-anatomical dissection studies and the histological examinations. The gross dissections were performed layer by layer. For the sectional anatomy study, midsagital sections of the orbits with the eyelids were performed. This was done with a high-speed saw after the heads were frozen for 72 hours at - 80 degrees Celsius. The orbital sections were thawed and the eyelids and orbits were dissected through, to reveal the anatomical layers at consecutive levels. To define the anatomical layers at microscopic levels, specimens from the sagital sections were stained with H & E, Hematoxylin-Eosin-Safran (HES) and van Gieson. All studies were documented with photographs.
Gross dissections:Our gross dissection studies show a well-defined continuation of the orbital septum, which curves posteriorly from its junction with the levator aponeurosis. The continuation of the orbital septum encloses the fat pad and separates this from the anterior surface of the levator aponeurosis and the levator muscle. Between the orbital septum and the anterior surface of levator, a potential space exists that may be accessed by careful blunt dissection.Sagital sections:From the orbital rim, the orbital septum is directed downwards and split into an anterior-running septal layer and a posterior-running layer. The inner posterior layer curves superiorly to the levator muscle, in the direction of the orbital apex. Superior to the posterior directed orbital septum, the retroseptal fat pad is entirely enclosed and thereby separated from the levator muscle. Microscopic study:The specimens from the posterior-running layer of the orbital septum showed that it consists of dense regular connective tissue. Cross-sectioned bundles of striated muscle were seen just inferior to the septa, representing the levator muscle of palpebra superior.
In summary, we have described that the orbital septum extends posteriorily, encloses the superior orbital fat pad and separates this from the anterior surface of the levator muscle. These findings are the topographic rationale for a potential surgical space in-between the septum and the levator. This space provides a minimal-invasive access corridor for surgery on the levator muscle, for tumour surgery in the upper mid-orbit, and also for surgical replacement of retroseptal fat in the enophthalmic orbit.
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