# Spine, Pelvis and Hip Kinematics--Characterizing the Axial Plane in Healthy and Osteoarthritic Hips
## 2 Materials and Methods
### Motion Analysis  
After the radiographic assessment, all volunteers underwent motion analysis testing in a biomechanics laboratory. They were instructed to warm up for five minutes on a cycle ergometer and then outfitted with 45 reflective markers according to the University of Ottawa motion analysis model (UOMAM) marker set [20]. The participants were initially asked to take a neutral, standing static pose, and then they dynamically performed three trials of seated bend and reach (SBR) and seated maximal trunk rotation (STR) as shown in Figure 2. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Parameters** & **OA** & **Control** & **\(p\)-Value** \\ \hline Participants (n) & 24 & 8 & - \\ Sex (F/M) & 12/12 & 4/4 & - \\ Age (years) & 67 (48–84) & 58 (40–66) & **0.03** \\ Height (m) & 1.68 (1.54–1.85) & 1.69 (1.56–1.88) & 0.79 \\ Weight (kg) & 74 (47–97) & 70 (54–87) & 0.59 \\ BMI (kg/m\({}^{2}\)) & 26 (18–33) & 24 (20–29) & 0.23 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Summary of participants’ demographics, reporting mean (range). \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & **Parameters** & **OA** & **Control** & **\(p\)-Value** \\ \hline \multirow{4}{*}{HOOS} & Symptoms & 39 (5–55) & 99 (90–100) & **<0.001** \\  & Pain & 40 (13–63) & 98 (88–100) & **<0.001** \\  & Activities of Daily Living & 44 (16–69) & 100 (99–100) & **<0.001** \\  & Sports and Recreational Activities & 22 (0–50) & 100 (100–100) & **<0.001** \\  & Quality of Life & 21 (0–50) & 97 (75–100) & **<0.001** \\ \hline \multicolumn{2}{c}{SF-12 physical} & 34 (28–40) & 42 (39–47) & **<0.001** \\ \hline \multicolumn{2}{c}{Oswestry spinal score} & 34 (4–68) & 0 (0–2) & **<0.001** \\ \hline \multicolumn{2}{c}{Oxford hip score} & 21 (9–36) & 48 (46–48) & **<0.001** \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Summary of participants’ patient-reported outcome measures, reporting mean (range). Figure 1: Lateral view of the lumbar spine and pelvis from the standing (**left**) and seated deep flexed forward (**right**). With angles calculated for sacral slope (SS), which is the angle tangent to the S1 endplate and a transverse line; pelvic femoral angle (PFA) defined as an angle based on a line from the center of the S1 endplate to the center of the femoral head and a second line that parallels the diaphysis of the femur; lumbar lordosis (LL) being a line tangent to the S1 endplate relative to a line tangent to the superior L1 endplate. The changes in SS were considered equivalent to the changes in pelvic tilt (PT). Figure 2: (**A**) Lateral view representation of sagittal joint kinematics assessment during SBR: spine flexion, pelvis tilt, and hip flexion. Spine flexion is the angle between the sagittal thorax axis and the sagittal pelvis axis around the fixed transverse axis of the pelvis. Pelvic tilt is measured as the angle in the transverse plane between the projected sagittal pelvic axis and the sagittal laboratory axis. Hip flexion is the angle between the projected sagittal thigh axis and the sagittal pelvic axis. (**B**) Superior view representation of axial joint kinematics assessment during STR: left and right spine rotations, left and right pelvis rotations, and left and right hip rotations. Spine rotation is measured as the angle between the sagittal axis of the thorax and the sagittal axis of the pelvis, around a floating frontal axis. Pelvis rotation is the angle measured between the sagittal axis of the pelvis and the sagittal laboratory axis projected into the pelvis transverse plane. Hip rotation is calculated between the sagittal axis of the thigh and the sagittal axis of the pelvis projected into the plane perpendicular to the long axis of the thigh. The seat height was adjusted according to participants' knee plateau height. Participants initiated the task seated with their hands placed laterally and were instructed to bend their trunk forward and try to touch the ground as far as comfort allowed, as if they were about to tie their shoelaces.