Evaluation of the Effect of Hand Size on Forearm Muscle Activity While Using Laparoscopic Instruments.

OBJECTIVE

Percent maximum voluntary contraction (%MVC) provides a normalized assessment of muscle exertion that can be compared between individuals. A higher %MVC during tasks can lead to more rapid muscle fatigue and increased risk of injury. This study evaluates the %MVC of forearm muscles while manipulating four laparoscopic energy devices and compares the differences in muscle activity between surgeons with different hand sizes.

DESIGN

Nonexperimental correlational study.

SETTING

Testing was performed in a simulation lab at Mayo Clinic Arizona.

PARTICIPANTS

Surgeons and surgical trainees that regularly perform robotic/laparoscopic surgery.

INTERVENTIONS: Demographic information, glove size, and grip strength were collected. Four advanced energy devices were assessed. Surface electromyography (sEMG) electrodes were applied to the flexor digitorum superficialis (FDS), extensor carpi ulnaris (ECU), extensor carpi radialis longus (ECR), and extensor pollicis longus (EPL) of the dominant hand. Isometric MVC was performed on each muscle. Participants performed opening, closing, and activation cycles for each instrument. EMG output was filtered and normalized to provide %MVC.

MEASUREMENTS AND MAIN

RESULTS

Twenty-four individuals participated. Fourteen were female. Glove sizes ranged from 5.5 to 8.5, with 6.5 being the most common (n = 8). Glove size analysis was split between small (≤ 6.5) and large (>6.5). When adjusting for training level and instrument used, FDS and ECR displayed statistically significantly higher levels of activation in the small-handed group (p = .0012 and 0.013, respectively). 15% MVC was selected as a cutoff for evaluation due to increased risk of muscle fatigue and injury with sustained use above this threshold. Of the 16 muscle/instrument combinations, 10 showed a mean %MVC of greater than 15% for small hands, with one combination over 15% for large hands.

CONCLUSION

Smaller-handed surgeons demonstrate increased forearm muscle activation when using laparoscopic instruments. Industry partners should consider variations in surgeon hand size when developing instruments to prevent disproportionate risk of injury to surgeons with smaller hands.