A comparative study of intracranial aneurysm clips: closing and opening forces and physical endurance.

OBJECTIVE: The closing and opening forces of various types of intracranial aneurysm clips were measured, and the physical endurance of the clips was evaluated.
METHODS: Straight, bayonet, angled, fenestrated, and temporary Sugita and Yasargil clips were tested by measuring the forces exerted by the blades as they were opened in wider increments and at various points along their length by a specially designed clip tester. Closing forces after repeated openings, continuous opening, or multiple sterilization procedures also were measured.
RESULTS: The opening forces of Yasargil clips increased linearly and more sharply as the blades were opened wider than those of Sugita clips. Only Sugita clips showed significant differences between the opening and closing forces (hysteresis). Closing forces of all of the tested clips were according to a hyperbolic curve. Straight clips showed a sharper rise in closing forces than those of bayonet, angled, or fenestrated clips. A relatively weak closing force at the tip of Yasargil long clips and a strong closing force at the base of temporary clips were unexpected findings. The closing force decreased by only 3 to 7% after 500 openings and did not decrease after continuous opening for 17 hours or 100 sterilization procedures.
CONCLUSION: Our study showed that the closing forces differed depending not only on the distance of the point of measurement from the clip spring but also on the shapes of the clip blades. Repeated opening or sterilization of the clips did not significantly decrease the closing forces of the aneurysm clips.