## 3 Results
### U Implant  
Figure 7 plots the difference in fingertip forces for two test configurations (free implant (panel A), glued implant (panel B)) of the U implant along with the suture-based procedure (panel C). The U implant also redistributed forces resulting in lower fingertip forces relative to the baseline. From panels (A) and (B), the U implant did reduce the difference in fingertip forces. However, this is where the U implant's results diverge from the rod implant. The average difference in fingertip forces (computed using Equation (1)) shows that both the free-moving and glued U implant configurations perform worse than short-triangle configuration and about on par with the tall-triangle configuration of the rod implant (see Table 1). Their variation due to tendon tension (computed using Equation (2)) is even worse, performing lower than even the least performing tall-triangle rod implant configuration. In the case of the U implant (panel A), there were a few outliers in fingertip forces that occurred potentially due to controller glitches or spurious stiction in the robotic testbed. These six outliers (out of 200 trials) were omitted for this case when computing the mean fingertip forces but are marked in the figure in the interest of transparency. Finally, we only saw significant differences between the free U implant and the baseline for a small paddle orientation region ([\(-30^{\circ}\), \(-18^{\circ}\)] and [\(27^{\circ}\), \(30^{\circ}\)]). These results do not suggest as much promise of clinical translation for the U implant as the rod implant. Figure 8 depicts the fingertip forces of the index and middle fingers for the three applicable test configurations. Much like with the rod implant, the redistribution is less than perfect, with extensions resulting in larger fingertip forces. Also, increasing tendon tensions generally did increase fingertip forces. The six outliers trials that were omitted when computing the mean fingertip forces are marked in this figure as well. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Configuration** & **Average Difference** & **Variation in Fingertip** & **Paddle Orientations for** \\  & **in Fingertip Forces** & **Force Differences Due to** & **Which Implant** \\  & & **Input Tendon Tension** & **Outperforms Baseline** \\  & _(Lower MAE Is Better)_ & _(Lower MAE Is Better)_ & _(p-Value \(<\) 0.05\%)_ \\ \hline \multicolumn{4}{c}{**Rod implant**} \\ \hline short triangle & \(\downarrow\) 22.54\% (1.35N MAE) & \(\downarrow\) 24.63\% (1.75N MAE) & \([-30^{\circ},-9^{\circ}]\) _and_ \([9^{\circ},30^{\circ}]\) \\ tall triangle & \(\downarrow\) 18.26\% (1.43N MAE) & \(\downarrow\) 19.93\% (1.86N MAE) & \([-30^{\circ},-12^{\circ}]\) _and_ \([9^{\circ},30^{\circ}]\) \\ _glued_ tall triangle & \(\downarrow\) 18.41\% (1.42N MAE) & \(\downarrow\) 20.32\% (1.85N MAE) & \([-30^{\circ},-12^{\circ}]\) _and_ \([9^{\circ},30^{\circ}]\) \\ _baseline_ suture & — (1.75N MAE) & — (2.32N MAE) & — \\ \hline \multicolumn{4}{c}{**U implant**} \\ \hline U implant & \(\downarrow\) 19.54\% (1.28N MAE) & \(\downarrow\) 11.85\% (1.86N MAE) & \([-30^{\circ},-18^{\circ}]\) _and_ \([27^{\circ},30^{\circ}]\) \\ _glued_ U implant & \(\downarrow\) 7.66\% (1.46N MAE) & \(\downarrow\) 11.86\% (1.86N MAE) & \(\underline{\phantom{-}}\) \\ _baseline_ suture & — (1.59N MAE) & — (2.11N MAE) & — \\ \hline \hline \end{tabular}
\end{table} 
Table 1: A performance comparison of all test configurations relative to the suture-based procedure— computed from the data in Figures 5 and 7 using Equations (1) and (2). Figure 7: _Difference between index and middle fingertip forces_ measured at various paddle orientations and tendon tensions with and without the _U implant_: (**A**) U implant configuration; (**B**) glued U implant configuration; and (**C**) baseline suture configuration. The gray background highlights paddle orientations for which fingertip force differences were significantly different compared to the baseline suture configuration.