Background: Very high pressures are generated at the interface between the
tip of laparoscopic graspers and tissue. The pressure profile suggests that
the high pressure is due to stress concentration at the edge of the jaw. S
tress concentration at an edge can be modified by curving the edge. This st
udy sought to determine the effect of a curved edge on pressures generated
by the jaw of a laparoscopic grasper.
Methods: Pressure generated at the instrument tissue interface was measured
by a thin film pressure transducer. The two instruments that we compared w
ere identical in every respect except the profile of the jaw edge. One was
unmodified; the other had a rounded grasping edge. Load and handle pressure
were constant throughout. Tissue pressures generated by the grasper were r
ecorded as the angle of load was increased from vertical (0 degrees) to 135
degrees.
Results: Localized pressures at the tip of the unmodified instrument reache
d a maximum of 1500 kPa. Pressures at the tip of the curved instrument reac
hed a maximum of 920 kPa under identical conditions.
Conclusion: High pressures generated at the tip of laparoscopic graspers ca
n be reduced by rounding the edge of the jaw.