Mechanisms of global support and posttraumatic enophthalmos: I. The anatomy of the ligament sling and its relation to intramuscular cone orbital fat.

The mechanisms of posttraumatic enophthalmos were evaluated to determine the interrelation between fat and ligaments in globe support. Anatomic studies demonstrate that the ligaments form an essential "sling" framework for the globe but are alone insufficient to maintain the globe's full forward position. Removal of extramuscular fat in cadavers and in patients undergoing blepharoplasty did not significantly change globe position. Loss of intramuscular cone fat (atrophy or displacement) in cadavers and patients produced enophthalmos. Fat atrophy is not a prominent feature in most patients with posttraumatic enophthalmos. Some loss of intramuscular cone fat from displacement outside the muscle cone is frequently present. The principal mechanism, however, of posttraumatic enophthalmos involves a displacement and change in the shape of orbital soft tissue. Loss of bone and ligament support permits posterior displacement and a reshaping of orbital soft tissue under the influence of gravity and the remodeling forces of fibrous scar contracture. The shape of the retrobulbar orbital contents changes from a modified cone to a sphere, and the globe sinks backward and downward. Given that the volume of orbital soft tissue is constant following trauma, procedures to restore the shape and position of the orbital soft tissue by mobilization and bone reconstruction will correct or significantly improve enophthalmos.