I feel there is someting wrong here, a contradiction in terms
aguja trócar con "punta piramidal" con "base cuadrangular cortante"
Needles with a quadrangular base injure the tissues still
more. On the other hand the latter are held more firmly in the needle- holder, and the lance-shaped needles penetrate very readily, even in very firm tissues. The round needles are apt to meet with obstructions, and it is especially difficult to secure them firmly in the needle-holder. Round needles are preferable where little resistance is expected, and hemorrhage from the points of insertion is to be avoided as much as possible.


A trocar, a sharp instrument with a point shaped like a three-sided pyramid, is used to access the inside of blood vessels, bones or body cavities. It's usually inserted within a tube and used primarily for introducing that tube into the body. Because of the puncturing action of the point, the point must be extremely sharp and all three sides must be of uniform size and sharpness.

A photograph of a trocar can be seen here
http://www.incisiontech.com/products/trocars.html



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Note added at 13 hrs (2009-04-01 06:54:23 GMT)
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I believe the sentence is describing this photograph.
Cortante= sharp