A short trapezoidal speculum for suprasellar and infrasellar exposure in endonasal transsphenoidal surgery.
OBJECTIVE
A key limitation of the transsphenoidal approach for suprasellar and infrasellar lesions is restricted exposure. Microscope and endoscope-assisted procedures have traditionally used an oval-shaped speculum, the distal end of which restricts superior and inferior visualization. To improve visualization and use of the endoscope, shorter specula, with a trapezoidal distal end, were designed.


METHODS
The new specula have a working length of 60 mm. The proximal 20-mm segment is oval-shaped to conform to the nostril; the middle 20-mm segment has vertically oriented blades; and the distal 20-mm segment transitions to a trapezoidal orientation, with the distal blades angled 15 degrees upward and outward on the suprasellar speculum, or 15 degrees downward and outward on the infrasellar speculum. Both specula have a 5-degree distal outward flare. The upward-angled trapezoidal 60-mm speculum was compared with 70- and 80-mm oval specula in a transsphenoidal clay model. A pen light was projected from the nasal speculum end to a target 100 mm away using a blade opening width of 16 mm. Line drawings were made to quantify the impact of speculum length on the horizontal angle of exposure. The clinical utility of the trapezoidal specula was also assessed.


RESULTS
In the model, the 60-mm upward-angled trapezoidal speculum yielded a surface area illumination of 759 mm, as compared with 579 and 432 mm with the 70-and 80-mm oval specula, an increase in exposure of 31 and 76%, respectively. In the line drawings, the 60-mm speculum provided a horizontal angle of exposure of 30 degrees, as compared with 26 and 23 degrees for the 70- and 80-mm specula, an increase of 17 and 33%, respectively. In patients, provided sufficient mucosa and bone are removed from the posterior nasal cavity, the trapezoidal specula provide an expanded working volume that facilitates endoscopy.


CONCLUSIONS
Short upward- or downward-angled trapezoidal endonasal specula increase parasellar surface area exposure and the horizontal angle of exposure. Initial clinical experience suggests that reducing the speculum length and eliminating the distal curved blades result in greater instrument maneuverability and enhanced visibility for removing parasellar tumors.
Fatemi
Nasrin
N
Division of Neurosurgery, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, California, USA.
Dusick
Joshua R
JR
Malkasian
Dennis
D
McArthur
David L
DL
Emerson
Joshua
J
Schad
Werner
W
Kelly
Daniel F
DF
D004867:Equipment Design; D019544:Equipment Failure Analysis; D006801:Humans; D008866:Microsurgery / Q000295:instrumentation*; D044583:Neuroendoscopy / Q000379:methods*; D019635:Neurosurgical Procedures / Q000295:instrumentation*; D013101:Sphenoid Sinus / Q000601:surgery*