## 3 Results  
The Rms error of the MIBFT-determined femoral pose parameters ranged from 0.11 to 0.35 mm in translation and 0.18 to 0.47\({}^{\circ}\) in rotation (Table 1). The corresponding ranges of Rms error for tibial poses were 0.18 to 0.26 mm in translations and 0.29 to 0.49\({}^{\circ}\) in rotation (Table 1). The absolute value of the average bias over all trials was less than 0.27 mm in translation and 0.23\({}^{\circ}\) rotation for both the femur and tibia. The corresponding values for the precision were 0.28 mm and 0.46\({}^{\circ}\) (Table 1). The errors in the pose parameters were successively reduced throughout the MIBFT process, in which the initial pose parameters taken from the registered pose in the preceding frame gave averaged absolute errors up to 2 mm in translations and 1.1\({}^{\circ}\) in rotations that were reduced to 0.6 mm and 0.5\({}^{\circ}\), respectively, after 2D/2D template registration. The ultimate averaged absolute errors were down to 0.3 mm and 0.3\({}^{\circ}\) after the 3D/2D image registration (Figure 5). \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Component**} & \multirow{2}{*}{**Error Metric**} & \multicolumn{2}{c}{**Femoral FE**} & \multicolumn{2}{c}{**Tibial FE**} & \multicolumn{2}{c}{**Tibiofemoral FE**} \\ \cline{3-6}  & & **Femur** & **Tibia** & **Femur** & **Tibia** \\ \hline \multirow{2}{*}{\(\mathrm{Tx}\left(\mathrm{mm}\right)\)} & Rms error & 0.28 (0.04) & 0.23 (0.03) & 0.15 (0.03) & 0.18 (0.05) \\  & Bias \(\pm\) precision & \(-\)0.07 \(\pm\) 0.28 & 0.08 \(\pm\) 0.22 & \(-\)0.07 \(\pm\) 0.13 & 0.08 \(\pm\) 0.16 \\ \hline \multirow{2}{*}{\(\mathrm{Ty}\left(\mathrm{mm}\right)\)} & Rms error & 0.35 (0.04) & 0.22 (0.03) & 0.11 (0.01) & 0.20 (0.04) \\  & Bias \(\pm\) precision & 0.27 \(\pm\) 0.23 & 0.12 \(\pm\) 0.18 & 0.02 \(\pm\) 0.10 & 0.13 \(\pm\) 0.15 \\ \hline \multirow{2}{*}{\(\mathrm{Tz}\left(\mathrm{mm}\right)\)} & Rms error & 0.29 (0.05) & 0.26 (0.05) & 0.18 (0.02) & 0.22 (0.04) \\  & Bias \(\pm\) precision & \(-\)0.13 \(\pm\) 0.26 & 0.01 \(\pm\) 0.26 & \(-\)0.04 \(\pm\) 0.17 & 0.00 \(\pm\) 0.22 \\ \hline \multirow{2}{*}{\(\mathrm{\theta}x\left(\mathrm{\SIUnitSymbolDegree}\right)\)} & Rms error & 0.20 (0.06) & 0.30 (0.07) & 0.19 (0.04) & 0.31 (0.13) \\  & Bias \(\pm\) precision & 0.03 \(\pm\) 0.20 & 0.12 \(\pm\) 0.27 & 0.04 \(\pm\) 0.19 & 0.14 \(\pm\) 0.27 \\ \hline \multirow{2}{*}{\(\mathrm{\theta}y\left(\mathrm{\SIUnitSymbolDegree}\right)\)} & Rms error & 0.28 (0.04) & 0.43 (0.05) & 0.47 (0.10) & 0.49 (0.11) \\  & Bias \(\pm\) precision & \(-\)0.03 \(\pm\) 0.28 & 0.09 \(\pm\) 0.42 & \(-\)0.23 \(\pm\) 0.41 & 0.07 \(\pm\) 0.46 \\ \hline \multirow{2}{*}{\(\mathrm{\theta}z\left(\mathrm{\SIUnitSymbolDegree}\right)\)} & Rms error & 0.20 (0.06) & 0.29 (0.05) & 0.18 (0.02) & 0.33 (0.14) \\  & Bias \(\pm\) precision & \(-\)0.03 \(\pm\) 0.19 & 0.02 \(\pm\) 0.29 & 0.03 \(\pm\) 0.18 & 0.01 \(\pm\) 0.33 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Means (standard deviation) of the root-mean-squared errors (Rms errors) of each motion component over all trials for the femur and tibia during isolated femoral and tibial flexion/extension (FE) and tibiofemoral FE. The averaged bias and precision over all trials are also shown. Figure 5: The means and standard deviations of the absolute errors in the six degrees-of-freedom of the femur and tibia throughout the MIBFT. The results corresponding to the initial pose (registered pose in preceding frame), template-registered pose, and final pose are shown in blue, orange, and yellow, respectively.