The satisfaction rates with currently available mechanical staplers were low. Japanese surgeons with small hands felt more stress when using the staplers. Ergonometric consideration is necessary in stapler design.

Purpose The satisfaction rating of currently available mechanical staplers for Japanese surgeons with small hands is low. To identify the issue, we examined the relationship of hand dimensions and grip force with the operation force of a mechanical circular stapler. Methods Hand dimensions and grip force were measured in 113 Japanese surgeons (52 men and 61 women). We then evaluated the relationship between grip width and the operation force required to push the lever of the stapler, at three points on the lever, using a digital force gauge. Results The optimal grip width of the dominant hand was 62.5 ± 8.5 mm for men and 55.5 ± 5.9 mm for women (p \ 0.001). The maximum grip force of the dominant hand was 44.2 ± 6.1 kg for men and 29.7 ± 4.5 kg for women (p \ 0.001) and the maximum operation force required to push the lever 7.0, 45.0, and 73.0 mm from the end of the lever was 21.8, 28.6, and 42.4 kg, respectively. Conclusions To our knowledge, this is the first ergonomic study of a surgical stapler to be conducted in Asia. Firing the stapler by gripping the proximal side of the lever is physically impossible for most Japanese women surgeons since the required operation force exceeds the maximum grip force, which probably accounts for the stress perceived by these women.

The laparoscopic stapler is a surgical instrument that automatically creates visceral anastomosis. Although the laparoscopic stapler is widely used, objective ergonomic assessments are lacking. The purpose of this study was to quantitatively assess the force and muscle activities involved during the use of a laparoscopic stapler. The mechanical force needed to create anastomosis in a cattle colon was measured using a tensile tester. Three different loads (150 N, 200 N, and 250 N) were applied individually to compare the anastomosis conditions. The force and muscle activities of the operators of the laparoscopic stapler were also examined. Eleven healthy female subjects (age, 27.4±10.7 years) participated in the study. Force and surface electromyography (EMG) of the flexor digitorum superficialis and flexor digitorum profundus muscles during the use of the laparoscopic stapler were measured and compared to each subjectʼ s maximum grip strength. Approximately 250 N was necessary to operate the laparoscopic stapler appropriately. Although the mean grip strength of the subjects was 27.1±6.8 kg, the mean force applied when they gripped the laparoscopic stapler was 15.1±4.1 kg. Integrated EMG showed no differences between operating the laparoscopic stapler and gripping the hand dynamometer. This study demonstrated that the current design of laparoscopic stapler requires too much force to operate for individuals with small hands and/or low grip strength. In addition, the EMG results indicated that the enormous upper extremity muscular effort is not transmitted efficiently into power to operate the laparoscopic stapler, because of its handle design. Therefore, reconsidering the mechanism of the laparoscopic stapler is crucial to improve the usability of the laparoscopic stapler.