## 3 Results
### Pre-Surgical Intramedullary Stress and Strain  
The mean intramedullary stress and strain at the level of maximum compression during flexion was 7.57 \(\pm\) 3.66 kPa and 0.04 \(\pm\) 0.02, respectively. Across subjects, the maximum stress/strain in the cervical spinal cord during flexion was 10.6 \(\pm\) 5.04 kPa  
\begin{table}
\begin{tabular}{c l c c} \hline \hline  & **Measure** & **Mean (SD)** & **n** \\ \hline \multirow{3}{*}{Patient Demographics} & Age & 62.7 (11.6) & 20 \\ \cline{2-4}  & Female sex, n (\%) & 7 (35\%) & 20 \\ \hline \multirow{6}{*}{Preoperative Survey Scores} & Modified Japanese Orthopedic Association & 13.3 (2.08) & 20 \\ \cline{2-4}  & Short Form 36 Physical Component Score & 35.16 (8.979) & 19 \\ \cline{2-4}  & Myelopathy Disability Index & 4.6 (2.8) & 20 \\ \cline{2-4}  & Quick Disabilities of Arm, Shoulder, and Hand & 39.46 (21.9) & 19 \\ \cline{2-4}  & Berg Balance Scale & 48.15 (7.59) & 20 \\ \hline \multirow{6}{*}{GRASSP * Assessments} & Dexterity—right hand & 8.1 (1.2) & 17 \\ \cline{2-4}  & Dexterity—left hand & 8.25 (0.5) & 16 \\ \cline{2-4}  & Dexterity time—right hand (s) & 43.5 (23.0) & 17 \\ \cline{2-4}  & Dexterity time—left hand (s) & 47.2 (21.15) & 16 \\ \cline{2-4}  & Sensation—right hand & 11.4 (1.1) & 18 \\ \cline{2-4}  & Sensation—left hand & 11.4 (1.0) & 18 \\ \hline \multirow{2}{*}{Grip Strength} & Right-hand grip strength (lbs) & 80.6 (33.5) & 20 \\ \cline{2-4}  & Left-hand grip strength (lbs) & 87.1 (39.6) & 20 \\ \hline \multirow{2}{*}{Pinch Grip} & Right pinch grip (lbs) & 9.45 (4.6) & 20 \\ \cline{2-4}  & Left pinch grip (lbs) & 10.0 (4.68) & 20 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Demographics and Functional Scores.  
and 0.05 \(\pm\) 0.02, respectively. The mean intramedullary stress and strain at the level of maximum compression during extension was 5.63 \(\pm\) 2.56 kPa and 0.02 \(\pm\) 0.01, respectively. Across subjects, the maximum stress/strain in the cervical spinal cord during extension was 7.7 \(\pm\) 3.32 kPa and 0.03 \(\pm\) 0.011, respectively (Figure 3). The most common cervical spine level of maximum compression was C5-C6 (40%, n = 8), followed by C6-C7 (25%, n = 5), C4-C5 (20%, n = 4), and C3-C4 (15%, n = 3). In 40% of patients (n = 8), the level of maximum compression coincided with the level of maximum von Mises stress during flexion. The stress and strain during flexion and extension are summarized in Table 2.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**FEM Measurement (Units)** & **Neck Motion** & **Spinal Cord Level** & **Mean (SD)** \\ \cline{3-4}  & \multirow{2}{*}{Flexion} & Maximum Stress & 10.6 (5.04) \\  & & Maximum Compression & 7.6 (3.66) \\ \cline{2-4}  & \multirow{2}{*}{Extension} & Maximum Stress & 7.7 (3.32) \\  & & Maximum Compression & 5.6 (2.56) \\ \hline \hline \end{tabular}
\end{table}
Table 2: Mean Intramedullary stress and strain from patient-specific finite element models (n = 20) during flexion and extension.  
Figure 3: Mean intramedullary von Mises stress (**A**) and principal strain (**B**) during neck flexion and extension from patient-specific finite element models. Mean von Mises stress (**C**) and principal strain (**D**) at each cervical spine level during neck flexion and extension. Error bars represent standard deviations.