Impact of Orbital Rim Osteotomy on Surgical Freedom in Transorbital Endoscopic Approaches: A Cadaveric Study and Novel Methodology.

PURPOSE: Transorbital neuroendoscopic surgery (TONES) is an emerging minimally invasive skull-base approach. The addition of an orbitotomy may increase the size of the surgical corridor, but this measurement has not previously been quantified.

METHODOLOGY: Six fresh-frozen cadaveric specimens (11 orbits) underwent bilateral superior eyelid crease incisions and periorbital dissection to the meningo-orbital band and superior orbital fissure. This was followed by bilateral sphenoidotomy to expose the trigeminal ganglion and temporal dura. A custom surgical probe with an Augmented Reality, University of Cordoba tracker at its base was then positioned with its tip at the foramen ovale, and freedom of instrument articulation was quantified by maneuvering the probe throughout the limits of the exposure. Repeated measurements were taken following lateral (L-TONES) and superolateral (SL-TONES) orbital rim osteotomy.

RESULTS

Both approaches demonstrated statistically significant increases in surgical exposure area when calculated using both convex-hull and simple elliptical area (p < 0.001). SL-TONES achieved the greatest area of 93.78 cm2 (SD, 22.3 cm2), which was 125% greater than standard TONES, which had a mean convex-hull area of 41.6 cm2 (SD: 11.8 cm2). L-TONES provided 70.38 cm2 of exposure when using the convex hull.

CONCLUSIONS

This study presents a novel, inexpensive method of quantifying surgical exposure and demonstrates increased instrument freedom through the successive addition of lateral and superior orbitotomies during TONES dissection.