title: A curved edge moderates high pressure generated by a laparoscopic grasper.
abstract: 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. Stress concentration at an edge can be modified by curving the edge. This study 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 were 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 recorded as the angle of load was increased from vertical (0 degrees ) to 135 degrees.
  
  
  RESULTS
  Localized pressures at the tip of the unmodified instrument reached a maximum of 1500 kPa. Pressures at the tip of the curved instrument reached a maximum of 920 kPa under identical conditions.
  
  
  CONCLUSIONS
  High pressures generated at the tip of laparoscopic graspers can be reduced by rounding the edge of the jaw.
authors.affiliation: Department of Surgery, University of Sydney, Clinical Sciences Building, Nepean Health, P.O. Box 63, Penrith N.S.W. 2751, Australia.
authors.forename: A J
authors.initials: AJ
authors.lastname: Shakeshaft
authors.forename: J A
authors.initials: JA
authors.lastname: Cartmill
authors.forename: W R
authors.initials: WR
authors.lastname: Walsh
authors.forename: C J
authors.initials: CJ
authors.lastname: Martin
mesh_terms: D010535:Laparoscopy; D011312:Pressure; D013525:Surgical Instruments