## 4 Discussion
most importantly, [PERSON] did not report pressure values specific to the instrumented IVD level, only average values for each motion; therefore, it is unknown if each value included pressure response values for all disc levels. [PERSON]'s values were also not reported with standard deviations, making comparisons of pressure value ranges difficult. As a result, we averaged our IVD level values in an attempt to best compare the data sets. The lowest instrumented IVD level from our feasibility study (i.e., C7/T1) exhibited the most comparable values (in neutral/gentle traction and in extension), while the average of all three IVD level values were most comparable to [PERSON]'s value in flexion. Static cervical intradiscal pressures are not well documented in the literature, and many intra- and interpersonal anatomical differences exist that affect cervical disc properties (e.g., direct correlations between the extent of cervical disc degeneration and IVD pressure response [22; 23; 24]). This phenomenon is well documented in the lumbar spine discs, in which the effects of ageing, including disc degeneration, fibrosis, and/or desiccation, were found to affect/reduce recorded IVD pressures [39; 52; 53]. Similar effects can be anticipated to occur in the cervical spine. The patients included in the [PERSON] study presented with clinical \"complications\", (e.g., cervical spondylic radiculopathy, disc degeneration and/or herniation, neck trauma, etc.). These diagnoses surely affected the reported pressure responses; however, the degree of negative impact was not quantified. Due to the metallic nature of both the pressure sensors and additional instrumentation for 3D motion capture, CT was deemed the most appropriate and safe method of medical imaging for this feasibility study. We maximized the available medical imaging capabilities (i.e., pre-instrumentation CT) and used applicable portions of other MRI-based cervical IVD grading systems (e.g., [PERSON]'s [54], [PERSON]'s [55], [PERSON] [56], and [PERSON]'s [57]) like vertebral endplate changes, narrowing of the disc space/disc height, and the degree of osteophyte formation to \"grade\" the level of degeneration from CT scans. Cervical intervertebral disc grading often involves evaluating morphological changes and degeneration on dissection [58]. In this feasibility study, post-test autopsy was not amenable to the goal \begin{table}
\begin{tabular}{c c c c} \hline
**Level** & **Motion** & **[PERSON] (1999) [24]** & **[PERSON], et al. (2024)** \\ \hline \hline \multirow{4}{*}{C3/C4} & Flexion/Extension & 46.41 & 24.73 +/ – 9.56 \\ \cline{2-4}  & Lateral Bending & 23.21 & 31.09 +/ – 7.39 \\ \cline{2-4}  & Axial Rotation & 36.26 & 20.49 +/ – 3.33 \\ \hline
**Level** & **Motion** & **[PERSON] (1999) [24]** & **[PERSON], et al. (2024)** \\ \hline \multirow{4}{*}{C5/C6} & Flexion/Extension & 33.36 & 15.72 +/ – 10.90 \\ \cline{2-4}  & Lateral Bending & 23.21 & 24.01 +/ – 16.71 \\ \cline{1-1} \cline{2-4}  & Axial Rotation & 24.66 & 30.88 +/ – 19.83 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Comparison of previously established pressure ranges from prior research involving component PMHS without muscle force simulation [24] and the averaged results of this study. Pressure values are expressed in PSI. \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & & **[PERSON], et al. (2024)** & **[PERSON]** \\ \hline
**Motion** & **AVERAGE** & **C3/C4** & **C5/C6** & **C7/T1** & **(1981) [23]** \\ \hline Neutral/Gentle & 42.53 +/ – & 27.31 +/ – & 20.53 +/ – & 79.74 +/ – & 63.58 +/ – \\ \cline{2-4} Traction & 11.83 & 10.08 & 23.01 & 2.40 & 7.40 \\ \hline \multirow{2}{*}{Extension} & 52.05 +/ – & \multirow{2}{*}{9.99 +/ – 4.30} & 10.20 +/ – & 135.96 +/ – & \multirow{2}{*}{-132.28} \\  & 7.68 & & 1.99 & 16.75 & \\ \hline \multirow{2}{*}{Flexion} & 75.47 +/ – & 39.47 +/ – & 21.24 +/ – & 165.71 +/ – & \multirow{2}{*}{-85.34} \\  & 26.38 & 14.82 & 19.80 & 44.53 & \\ \hline \hline \end{tabular}
\end{table}