The following is a summary of “Output force and ratio of laparoscopic graspers: an evaluation of operating room ergonomics,” published in the SEPTEMBER 2023 issue of Obstetrics and Gynecology by Olig, et al.

Laparoscopic surgery is a minimally invasive technique widely used in gynecology. However, it’s associated with surgeon discomfort or injury risks, such as “Laparoscopist’s thumb,” a condition characterized by thenar paresthesia. The disease can be caused by prolonged or excessive grip force using laparoscopic instruments. Despite its recognition, there needs to be more data to guide surgeons in choosing ergonomic instruments that can reduce these risks. For a study, researchers sought to assess the efficiency and ergonomic qualities of commonly used ratcheting laparoscopic graspers by comparing the ratio of applied tissue force to required surgeon input. The evaluation focused on a small-handed surgeon to provide potential metrics for enhancing surgical ergonomics and instrument selection.

Various laparoscopic graspers with different ratcheting mechanisms and tip shapes were assessed, including brands like Snowden-Pencer, Covidien, Aesculap, and Ethicon. A Kocher instrument was used as a comparison for open procedures. Thin-film force sensors (Flexiforce A401) were employed to measure the forces applied. Data were collected and calibrated using an Arduino Uno microcontroller board and MATLAB software. A single-handed, complete closure of each grasper’s ratcheting mechanism was performed three times. The maximum required input force in Newtons was recorded and averaged. The average output force was measured using the varying thickness force sensor with and without LifeLike BioTissue.

The output ratio (the highest output force relative to the required input force) was considered to identify the most ergonomic ratcheting grasper for a small-handed surgeon. The Kocher instrument required an average input force of 33.66 N, with the highest output ratio being 3.46 (112 N output). The Covidien Endo Grasp was the most ergonomic, with an output ratio of 0.96 on the bare force sensor (31.4 N output). The Snowden-Pencer Wavy grasper was the least ergonomic, with an output ratio of 0.06 when applied to the bare force sensor (5.9 N output). In general, the output ratios of these instruments improved as tissue thickness and contact area increased. It was noted that the additional input force provided by the surgeon did not significantly increase the output force for any of the instruments.

Laparoscopic graspers vary in their ability to provide reliable tissue force without requiring excessive input by the surgeon. Output force and output ratio are potential quantitative measures of laparoscopic instrument efficiency and ergonomics. Providing surgeons with such data could help optimize instrument selection, potentially reducing the risk of conditions like “Laparoscopist’s thumb.”

Source: ajog.org/article/S0002-9378(23)00314-9/fulltext