## 3 Results
### Cadaveric Experiment  
The quad sense device was utilized to record PFJ forces throughout range of motion in both the native PFJ and following a TKR procedure after trial components were placed. In all circumstances, a reproducible pattern of three distinct peaks of recorded PFJ load was generated for each trial. Following a 6 mm preliminary patella cut with a 6 mm neutral shim placed on the sensor, the PFJ load was recorded for this native joint prior to completing TKR cuts and TKR trial component placement. The maximal mean load in Newtons (N) recorded during range of motion in all four native cadaveric knees was measured in each quadrant, with 9.2 N recorded for the medial sensor, 28.8 N in the lateral sensor, 6.4 N in the superior sensor, and 1.0 N in the inferior sensor, respectively (Table 1). A TKR was then performed in all four cadaveric knees. Following TKR instrumentation with trial components placement, PFJ loads in the superior and medial quadrant were observed to significantly decrease with the 6 mm neutral shim in place (Table 2). In Specimen 1 of the right knee, high lateral loads were observed after TKR utilizing graphs generated in real time on the panel PC, and these PFJ loads could be compared visually to the 6 mm native measurement (Figure 9). Dynamic time warping analysis was also performed to compare the native and TKR PFJ loads in Specimen 1, including for the lateral and superior sensors (Figure 10). Using the sequence of shim thickness and angle combinations described in the Section 2 (Figure 5), we performed repeat range of motion trials in order to compare differences in PFJ forces for each quadrant. Changes in the thickness and shim angles significantly altered PFJ loading patterns. We observed that an increase in shim thickness resulted in increased PFJ loading, with statistically significant increases observed in the lateral, superior, and inferior quadrants, as well as statistically significant changes in the medial quadrant (Table 3). Using the angled shims, statistically significant changes in loading to all four sensor quadrants were also observed with changes in shim angle orientation, including utilizing the 6 mm 2.5\({}^{\circ}\) angle shim (Table 4). Furthermore, analyses with multiple comparisons between each of the 6 mm 2.5\({}^{\circ}\) angle shim orientations demonstrated statistically significant differences. In particular, the medial sensor demonstrated statistically significant higher loads when the 6 mm 2.5\({}^{\circ}\) angle shim was placed in a superior orientation (thickest medially) compared to a medial orientation (thickest inferiorly). A similar effect was observed in the superior sensor, where statistically significant higher loads were seen when the 6 mm 2.5\({}^{\circ}\) angle shim was placed in a lateral orientation (thickest superiorly) compared to an inferior orientation (thickest laterally). \begin{table}
\begin{tabular}{l l l l} \hline
**Quadrant** & **Combined Knees** & **Specimen 1** & **Specimen 2** \\ \hline Medical & 9.2 \(\pm\) 11.6 & 0.6 \(\pm\) 0.8 & 17.8 \(\pm\) 10.9 \\ Lateral & 28.8 \(\pm\) 13.0 & 40.6 \(\pm\) 5.0 & 17.0 \(\pm\) 3.9 \\ Superior & 6.4 \(\pm\) 5.6 & 11.5 \(\pm\) 1.7 & 1.3 \(\pm\) 1.4 \\ Inferior & 1.0 \(\pm\) 1.0 & 0.2 \(\pm\) 0.0 & 1.8 \(\pm\) 0.9 \\ \hline \end{tabular}
\end{table} 
Table 1: Baseline mean maximal load measurements (N) and standard deviation recorded in native knees with the 6 mm neutral shim. \begin{table}
\begin{tabular}{l l l l} \hline
**Quadrant** & **Native** & **TKR** & **\(p\)-Value** \\ \hline Medical & 9.2 \(\pm\) 11.6 & 0.6 \(\pm\) 0.6 & 0.021 * \\ Lateral & 28.8 \(\pm\) 13.0 & 38.5 \(\pm\) 26.7 & 0.139 \\ Superior & 6.4 \(\pm\) 5.6 & 3.0 \(\pm\) 2.9 & 0.011 * \\ Inferior & 1.0 \(\pm\) 1.0 & 2.0 \(\pm\) 2.7 & 0.178 \\ \hline \end{tabular} \({}^{*}\)denotes statistical significance.  
\end{table} 
Table 2: Comparison of mean maximal load (N) and standard deviation for all four knees between native trial and TKR trial with the 6 mm neutral shim, compared via paired t-test.