INTRODUCTION: Surgeons with smaller hands report increased difficulty using laparoscopic instruments and have been shown to experience increased strain and muscle fatigue. 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 risk of injury. This study evaluates the %MVC of forearm muscles while manipulating laparoscopic energy devices and compares the differences in muscle activity between surgeons with different hand sizes. OBJECTIVE: The objective of this study was to quantify the level of muscle activation required by different hand sizes while using common laparoscopic energy devices, with the goal of providing data for improved, inclusive design of widely used instruments. We hypothesized that smaller-handed surgeons would require higher levels of %MVC when using common laparoscopic instruments when compared to larger-handed surgeons. METHODS: This is a nonexperimental correlational study. Demographic information, glove size, and grip strength were collected. Four laparoscopic advanced energy devices were assessed: Harmonic, Enseal, and two variations of Ligasure. Surface electromyography (sEMG) electrodes were applied to the flexor digitorum superficialis (FDS), extensor carpi ulnaris (ECU), extensor carpi radialis (ECR), and extensor pollicis longus (EPL) of the dominant hand. 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. A cutoff of 15%MVC has historically been used as the level below which prolonged muscle activation could be performed without concern for fatigue and was thus selected as a cutoff point for comparison between groups. RESULTS: Twenty-four individuals participated. Fourteen were female. Glove sizes ranged from 5.5 to 8.5, with 6.5 being most common (n=8). Glove size analysis was split between small (≤6.5) and large (>6.5). Mean %MVC in small-handed participants for FDS, ECU, ECR, and EPL were 21.5, 16.0, 15.75, and 10.73, respectively. In large-handed participants, the same values were 11.42, 14.09, 8.56, and 6.52. When adjusting for training level and instrument used, FDS and ECR displayed significantly higher levels of activation in the small-handed group (P=0.0012 and 0.013, respectively) when evaluated across all instruments. The FDS had the largest difference between hand sizes at 10.8% (95% CI (4.8, 16.8)). Across the 16 combinations of muscle and instrument, 10 showed a mean %MVC greater than 15% for small hands, with only 1 combination over 15% for large hands. In the instruments studied, there does not appear to be an optimal instrument for smaller-handed surgeons in the context of low overall %MVC requirements. CONCLUSIONS: Smaller-handed surgeons demonstrate increased forearm exertion when using laparoscopic instruments. This may increase their risk of injury in comparison to surgeons with larger hands. Future research should seek to further characterize the risk posed to small-handed surgeons. Industry partners should consider variations in surgeon hand size when developing instruments to prevent disproportionate risk of injury to surgeons with smaller hands.Figure 1Table 1Table 2
Olig et al. (Fri,) studied this question.