Lateral rectus pulley concerning the orbital wall. Area of a stereotyped bony insertion.

PURPOSE: To examine the lateral rectus muscle pulley and its bony insertion concerning the orbital rim and periorbita.

DESIGN

Prospective. An observational anatomic study.

METHODS

Study population: Twenty postmortem orbits (10 right, 10 left) of 10 Caucasian cadavers (8 females, 2 males; age range at death, 57-100 years; median age, 79.5 years) fixed by the Thiel method.Intervention: The floor of the temporal fossa was exposed, and a bone window on the lateral wall of the orbit, posterior to the sphenozygomatic suture, was created, keeping the periorbita intact. The lateral canthus and lateral palpebral ligament were isolated and opened, and the eyelids were folded back. The frontozygomatic suture was identified, and the orbital septum opened adjacent to the orbital rim. The conjunctiva was opened at the limbus, and the lateral rectus insertion was isolated. The bone pillar containing the frontozygomatic suture and the insertion of the periorbita and the pulley was isolated and removed en bloc. The lateral rectus muscle was isolated and excised.Main outcome measures: Position of the pulley ring on the lateral rectus muscle belly and its bony attachment area in the lateral wall of the orbit.

RESULTS

The pulley bony attachment was roughly quadrilateral with an approximate area of 90 mm2, 3 mm (mean, range 1-5 mm) posteroinferior to the frontozygomatic suture and 1 mm posterior to the orbital rim. The anterior margin of the pulley sleeve was found at 21.0 mm (median, p25-75 20.0-22.8) from the scleral insertion.

CONCLUSIONS

The lateral rectus pulley is stereotyped in its position in the muscle belly and its bony insertion, coinciding with the point of greatest adhesion of the periorbita to the anterior part of the lateral wall of the orbit.