The instruments currently used in endoscopic surgery are limited by several
factors, in particular their reduced working space. In order to develop in
struments with manifold degrees of freeedom (DOF), the elementary actions p
erformed by the existing instruments must be defined. Material and methods:
We have broken down into elementary movements the actions performed by the
currently used instruments and analyzed them by measuring the strain on the
instruments and on their working volume. The elementary actions were perfo
rmed in vitro (Pelvitrainer) on an animal model (pig) and also in the cours
e of clinical practice. A total of 6,750 measurements were carried out for
the following actions: grasping, cutting, dissecting, suturing and knotting
. Results: The largest working volumes were measured for the knotting and s
uturing actions (198 degrees in axial rotation and 69 degrees in lateral tr
anslation). The range of the working space was between 8 degrees and 52 deg
rees. Forces exerted on the instrument were between 0.5 and 12 Newton (N).
Forces exerted on the headpoint were between 0.4 and 10.5 N whereas the fri
ction forces were between 0.5 and 1.5N. Comments: By analyzing the elementa
ry actions of endoscopic surgery, we were able to quantify the directions a
nd dimensions of forces sustained by the instruments and were also able to
measure the working volume involved when performing the main actions in end
oscopic surgery. The results obtained provide a basis for the development o
f more sophisticated instruments.