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| KOU Bowen,ZHANG Zepei,LIU Jianchao.Biomechanics analysis of the effect of axial loading on the in vivo movement of the lower lumbar spine during flexion and extension in sitting position[J].Chinese Journal of Spine and Spinal Cord,2022,(7):631-638. |
| Biomechanics analysis of the effect of axial loading on the in vivo movement of the lower lumbar spine during flexion and extension in sitting position |
| Received:December 06, 2021 Revised:May 26, 2022 |
| English Keywords:Lumbar spine Intervertebral motion Sitting position In-vivo movement |
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| English Abstract: |
| 【Abstract】 Objectives: To study the the effect of axial loading on the motion characteristics of the lumbar spine during flexion and extension in the sitting position. Methods: Ten subjects were included in the study, five males and five females, aged 31(26, 34) years, with a body mass index(BMI) of 22.5(22.0, 23.4)kg/m2. CT images of the L3－S vertebrae in the supine position were acquired and 3D reconstructed. Transient images of the L3-S1 segments in upright, maximum flexion and extension sitting positions were acquired in dual fluoroscopic imaging system(DFIS). The images were aligned with the 3D model in the Rhinoceros software environment. Relative displacement distances and relative rotation angles of vertebrae from supine to upright sitting position were measured. Range of motion(ROMs) of the vertebrae from maximum flexion to maximum extension in sitting position under physiological conditions and additional axial load(bearing a 10kg special vest) were measured and compared. And the differences in lumbar ROMs from upright sitting to maximum flexion and maximum extension sitting positions were compared. Results: In the physiological sitting position, from supine to upright sitting position, L5 displaced 1.4(0.6, 2.4)mm dorsally relative to S1, and rotated 11.4°(10.2°, 17.9°) in flexion and L3/4 and L4/5 rotated 0.8°(-2.1°, 3.8°) and 4.4°(-1.0°, 8.9°) in the sagittal plane. The rotation magnitudes of L3/4 and L4/5 were with no significant difference from L5/S1(P>0.05). During anterior flexion and posterior extension, the displacement of each segment of L3-S1 in the left-right direction was 2.0(1.6, 2.5)mm, 1.8(1.0, 2.4)mm, and 5.9(3.7, 6.4)mm, respectively; the displacement in the proximal and distal directions was 1.0(0.7, 1.2)mm, 0.7(0.6, 1.3) mm, 3.3(1.7, 4.0)mm, and the displacements of L5/S1 in the left-right and proximal-distal directions were significantly different from those of L3/4 and L4/5(P<0.05); during the movement from neutral sitting to maximum posterior extension sitting, the displacements of each segment of L3-S1 in the left-right direction were 0.7(0.3, 1.4)mm, 0.5(0.3, 0.6)mm, 2.6(1.3, 3.8)mm; the rotation degrees in the sagittal plane were 4.2°(1.1°, 5.6°), 2.2°(1.4°, 3.3°), and 9.5°(4.6°, 12.2°), respectively. Comparing with physiological sitting position, after additional axial loading, the rotation of L5/S1 in the sagittal plane decreased by 1.2° and cranial-caudal direction compressed by 1.5 mm from supine to upright sitting; during flexion and extension, the displacements of L5/S1 reduced by 2.8, 4.1, and 1.3mm at anterior-posterior, left-right, and proximal-distal directions respectively; from upright sitting to maximum extension sitting, the rotation ranges of L5/S1 reduced by 6.1°(P=0.038). Conclusions: Converting from supine to neutral sitting position, the lower lumbar spine tends to be the forward flexion position. There is a greater mobility of L5/S1 in physiological sitting forward flexion and back extension motion. With additional axial loading, L5/S1 mobility decreases. Comparing with L5/S1, the effects on kinematic parameters of additional axial loading on L3/4 and L4/5 during flexion and extension motion in sitting position are less. |
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