Does Patient BMI Affect Ergonomics of Laparoscopic Surgery?

Zhe Liang, BS, Robert Wang, BS, Ahmed M Zihni, MD, MPH, Shuddhadeb Ray, MD, Michael M Awad, MD, PhD. Washington University School of Medicine

INTRODUCTION: The objective of this study was to quantify the ergonomic impact of patient BMI on surgeons’ upper body muscle groups during laparoscopic surgery. Laparoscopic surgery has become the treatment of choice for many common procedures including hernia repairs, bariatric surgeries, and cholecystectomies. However, laparoscopic surgery creates unique ergonomic challenges for the surgeon with the potential to cause pain or injury. Studies have shown that the majority of surgeons who routinely perform laparoscopic procedures experience at least occasional upper body pain or stiffness during surgery, with the neck and back being the most frequent areas of discomfort. Contributors to poor surgeon ergonomics include prolonged operative duration, limited mobility, and poor mechanical efficiency of laparoscopic tools. As obesity rates continue to rise in the United States, we sought to quantify how patient BMI might influence ergonomic stress. We hypothesize that ergonomic stress for the surgeon will be greater for obese patients compared to non-obese patients.

METHODS AND PROCEDURES: We designed a prospective study to measure surgeon upper body muscle activation during laparoscopic surgery. Five attending surgeons experienced in laparoscopic surgery (>500 laparoscopic procedures performed) were recruited to participate, and provided data from a total of 24 laparoscopic surgeries performed over a period of two months (June to July 2014). Using a wireless electromyography (EMG) system, we obtained whole-case EMG traces from each surgeon’s biceps, triceps, deltoid, and trapezius muscles. After normalization to a maximum voltage of contraction (MVC), these EMG tracings were used to calculate average muscle activation for the laparoscopic portions of each procedure. Subjects were also asked to complete the NASA Task Load Index (NTLX) survey following each case as a subjective measure of task difficulty. Student’s T-test was used to compare average muscle activation and NTLX survey scores between patient groups with a BMI greater than 30 with those with a BMI less than 30 (p <0.05 considered statistically significant).

RESULTS: Twenty-four procedures including hernia repairs (n=8), bariatric surgeries (n=6), combination hernia/bariatric (n=6), sigmoid colectomy (n=1), cholecystectomy (n=1), and exploratory removal of an infected mesh (n=1) were analyzed. There were 11 patients with BMI less than 30 and 13 patients with BMI greater than 30. There was no significant difference in average muscle activation during laparoscopic surgery in patients with BMI greater than 30 compared with patients with a BMI less than 30. There was also no significant difference in NTLX when comparing the two groups.

imageCONCLUSIONS: Surprisingly, in our study patient obesity did not appear to affect surgeon ergonomics in laparoscopic procedures. Both muscle activation and perceived task difficulty appear to be independent of patient BMI. Compared to open surgery, the laparoscopic approach may be less affected by patient BMI. This may be due to the additional ergonomic stressors encountered in open surgery, including limited working space, smaller field of view, the added strain of retraction, and suboptimal surgeon posture. Further studies are necessary to confirm this potential ergonomic advantage of laparoscopic surgery over open surgery.

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