Transection of inferior orbital fissure contents for improved access and visibility in orbital surgery.

BACKGROUND: Selective inferior orbital fissure (IOF) content transection for the purpose of surgical access to the posterior orbital floor is a technique that facilitates visualization of the posterior bony ledges of traumatic orbital floor defects. It also has potential advantages in achieving stable placement of reconstructive materials. Although not new, the surgical technique has not yet been described, and the morbidity of the technique has not been quantified. This article describes the procedure and assesses the morbidity specific to the division of related neural structures. METHODS: The technique and surgical anatomy are described and illustrated with intraoperative photographs. Postoperative assessment of neural structures relevant to the division of IOF contents is performed. These values are compared with the nonoperated side to evaluate the morbidity of the technique. RESULTS: The technique, which is consistently used by the senior author in the repair of orbital floor defects with very small posterior ledges or which extend to and involve the IOF, facilitates better visualization of the posterior ledge and posterolateral ledge in such cases. Surgical outcomes including facial sensation and lacrimal function on the operated side remain within the reference range and are not significantly different when compared with the contralateral nonoperated side. CONCLUSIONS: Selective IOF transection aids in the direct visualization of the posterior bony ledges in the repair of posterior orbital floor defects. It therefore may facilitate the placement of reconstructive materials on bony ledges circumferentially, providing stable reconstruction, potentially reducing implant-related complications without causing increased morbidity.

Effect of tension on nerve regeneration in rat sciatic nerve transection model.

Excessive tension across a nerve repair is known to impair nerve regeneration. However, it is uncertain whether nerve grafting is necessary when end-to-end repair would result in only mild to moderate tension. This study investigated the effect of tension on nerve regeneration. Sciatic nerves of 48 Lewis rats were transected and then repaired primarily after resection of 0-, 3-, 6-, or 9-mm lengths of nerve. Postoperative tension levels were quantified using a tensometer. Robust nerve regeneration was observed at 4 weeks in all except the 9-mm repair group, which showed lower nerve fiber counts, percent neural tissue, and nerve density (P < 0.05) and decreased functional recovery. These data indicate that modest levels of tension are well tolerated, but nerve regeneration drops precipitously once a critical tension threshold is exceeded. This threshold was between 0.39 and 0.56 N in the model studied, corresponding to a nerve defect between 6 mm and 9 mm.