Incarceration of the inferior oblique muscle branch of the oculomotor nerve in patients with orbital floor trapdoor fracture

Abstract

Concomitant incarceration of inferior oblique muscle branch of the oculomotor nerve occurred in 18.6% of patients who had suffered from an orbital floor trapdoor fracture with orbital fat incarceration. Patients with branch incarceration were all under 19 years of age. Branch incarceration resulted in a smaller binocular single vision field, which considerably improved after surgical reduction.

Orbital trapdoor fractures: different clinical profiles between adult and paediatric patients

“…In contrast, bone loses its elasticity in adults,1 and a hinged fractured bone may be only minimally displaced before returning to its initial position 18. As such, only a small amount of orbital tissue may prolapse through the fracture site and into the paranasal sinus 18. Although not significant, this may explain the shorter distance from the fracture site to the tip of the incarcerated orbital tissue in the middle-late adulthood age group compared with other groups.…”

“…As children have highly elastic bones, a hinged fractured bone easily snaps back into its initial position while trapping a considerable amount of orbital tissue 1 18. In contrast, bone loses its elasticity in adults,1 and a hinged fractured bone may be only minimally displaced before returning to its initial position 18. As such, only a small amount of orbital tissue may prolapse through the fracture site and into the paranasal sinus 18.…”

“…Patients with orbital fat incarceration and a BSVF of B1 were closely observed without surgical reduction. The forced duction test was not performed preoperatively because this occasionally causes secondary trauma to orbital soft tissue, including the extraocular muscles, Tenon’s capsule and inferior oblique muscle branch of the oculomotor nerve in patients with orbital trapdoor fractures 18. Surgical reduction was performed under general anaesthesia.…”

Factors influencing surgical outcomes in orbital trapdoor fracture

“…On orbital CT, the orbital fracture site was classified as per the classification in the study conducted by Takahashi et al 3 : horizontally divided into lateral (A1) or medial (A2) to the infraorbital groove/canal, the inferomedial orbital strut (A3), and the medial orbital wall (A4); longitudinally divided into anterior third (S1), middle third (S2), and posterior third (S3). A missing inferior oblique muscle branch of the oculomotor nerve on CT imaging combined with findings of inferior oblique muscle underaction on preoperative Hess chart indicated the presence of incarceration of the inferior oblique muscle branch 11 .…”