## 2 Methods
### Anthropometric Relationship between the Surgeon's Hand and the Size of the Handle
To investigate the correspondence between hand size and handle size, we analyzed the anthropometric data for the 135 surgeons who participated in this study, as summarized in Table 1. From the values obtained, we first calculated HLD, PLM, and HBD (Table 4, columns 3 to 5) for each sex and each hand type as defined in [PERSON] et al. (2018), and then, in order to have parameters that are very similar in value for any hand size, calculated the ratios between these three sets of anthropometric values and the optimal median diameter of the handle (Table 4, last three columns). The last two rows of Table 4 give the mean values and standard deviations of these ratios weighted according to the population of each sex and hand type (see Table 2). One observes that, of the three anthropometric ratios, that of PLM (a measure of the inner length of the palm) has the smallest standard deviation (0.0113021). We therefore concluded that this ratio would be the most appropriate to use to relate a surgeon's hand size with the best handle size of a laparoscopic grasper, and hence ultimately the best custom handle design. Figure 4: (a) Hand Length Digitized (58); (b) Hand Length Measured (59); (c) Palm Length Measured (61); (d) Hand Breadth from Digitizer (62); (e) Hand Breadth Measured (63); (f) Crotch 1 Height (69); (g) Crotch 2 Height (70); (h) Crotch 3 Height (71); (i) Crotch 4 Height (72). \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**HSC**} & \multirow{2}{*}{**Sex**} & \multirow{2}{*}{\begin{tabular}{c} **Hand Length** \\ **from Digitizer** \\ **(HLD)** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Palm Length** \\ **Measured** \\ **(PLM)** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Hand Breadth** \\ **from Digitizer** \\ **(HBD)** \\ \end{tabular} } & \multirow{2}{*}{\
\begin{tabular}{c} **\(\O\) Optimum** \\ **Diameter of** \\ **handle D\({}_{\mathbf{M}}\)** \\ \end{tabular} } & \multirow{2}{*}{
\begin{tabular}{c} **Anthropometric Relationship Factor** \\ **handle D\({}_{\mathbf{M}}\)** \\ \end{tabular} } \\ \hline \hline \multicolumn{10}{c}{**Units in mm**} & \multicolumn{1}{c}{} & \multicolumn{1}{c}{} & \multicolumn{1}{c}{} & \multicolumn{1}{c}{} & \multicolumn{1}{c}{} & \multicolumn{1}{c}{} \\ \hline XS & Both sexes & 159.3 & 87.6 & 71.1 & 29.4 & 5.418 & 2.980 & 2.418 \\ \hline \multirow{2}{*}{S} & Male & 174.1 & 97.6 & 79.1 & 32.9 & 5.292 & 2.967 & 2.404 \\  & Female & 170.2 & 94.3 & 72.5 & 31.7 & 5.369 & 2.975 & 2.287 \\ \hline \multirow{2}{*}{M} & Male & 188.8 & 107.8 & 86.5 & 36.4 & 5.187 & 2.962 & 2.376 \\  & Female & 182.1 & 98.2 & 78.9 & 33.1 & 5.502 & 2.967 & 2.384 \\ \hline \multirow{2}{*}{L} & Both sexes & 194.9 & 111.6 & 86.5 & 37.9 & 5.142 & 2.945 & 2.282 \\ \cline{3-8}  & & & & & \(\overline{x}\) & 5.308 & 2.967 & 2.362 \\ \cline{3-8}  & & & & \(\overline{y}\) & 0.1173040 & 0.0113021 & 0.0549504 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Relationships between the Hand Length from Digitizer (HLD), Palm Length Measured (PLM), and Hand Breadth from Digitizer (HBD) dimensions and the optimal median diameters of a laparoscopic surgery handle.