An ergonomic comparison of in-line vs pistol-grip handle configuration in a laparoscopic grasper.

Abstract

Laparoscopic instruments incorporate both in-line and pistol-grip handle configurations, yet it is unclear which design is most advantageous for surgeons, particularly when operating at angles perpendicular to the surgeon's position. We present a detailed electromyographic (EMG) comparison of these handle configurations under different force and angle conditions. Nine general surgeons used a Microsurge grasper with the handle in an in-line (MS-IL) and pistol (MS-PS) configuration, as well as a standard hemostat (HE), to grasp and close two spring-loaded metal plates. The task was performed randomly by each subject with the three instrument configurations at two forces levels (0.7 N, 4.2 N) and at three angles to the surgeons' body (0, 45, and 90 degrees). Surface EMG was measured from the flexor carpi ulnaris (FCU), flexor digitorum profundus (FDP), flexor digitorum superficialis (FDS), extensor carpi ulnaris (ECU), extensor digitorum comunis (EDC), and thenar compartment (TH). The peak root mean squared (RMS) EMG voltage was calculated for each instrument, force, and angle condition. Statistical comparison was carried out by ANOVA. Both laparoscopic handle configurations required significantly higher contractions of all muscle groups compared to the hemostat at the high force level. TH was not affected by laparoscopic handle configuration. MS-IL required higher FCU, ECU, and EDC contractions at 45 degrees compared to MS-PS. However, MS-IL decreased the flexor compartment muscle contractions (FDP, FDS, FCU) at 90 degrees compared to MS-PS. Laparoscopic grasping requires higher forearm and thumb muscle contractions compared to the use of a hemostat. The in-line handle configuration is no better than the pistol configuration except when grasping at 90 degrees to the surgeon, where rotation of the handle and wrist back toward the surgeon significantly decreases forearm flexor compartment muscle contractions.