Ergonomic Aspects of Different Handles for Minimally Invasive Surgery - An Emg Based Study

Abstract

Various studies have been performed to test different instrument handles in minimally invasive surgery (MIS). Although criteria for ergonomic handles have been suggested, to date it remains unresolved which handle design is best suited to various needs. The comparison of electromyogram (EMG) activities in different muscles provides information about the force developed by each muscle and allows to assess its contribution to a functional movement. The aim of the present study was to evaluate different types of handles for a simple grasping maneuver with respect to the force required in the main forearm muscles. Four different types of handles (axial handle, ring handle, shank handle, Hirschberg handle) were tested by 12 volunteers while manipulating a 0.1 N micro switch in a standard arm position. To test the handle with forces used during surgical procedures measurements were repeated with a 2.5 N micro switch. During the test the EMG activity of five forearm muscles was recorded and normalized with respect to the maximum voluntary activity of the respective muscle. The axial handle required significantly more EMG activity than the remaining handles in four of the five muscles tested. Similar results were obtained for both micro switches used but EMG activity increased with the switch force applied. The surgeon requires significantly more EMG activity and thus muscle strength when using the axial handle compared to the remaining handles. With the functional model of the Hirschberg and the ring handle the task can be performed with lower activity.