2022, Vol. 26 ›› Issue (36): 5792-5797

Morphological changes and strain characteristics of lumbar intervertebral disc during sitting in forward flexion

Kou Bowen1, Han Ye1, Hao Yiguang1, Xu Haoxiang1, Wen Wangqiang1, Zhang Zepei2, Lan Jie2, Miao Jun2   

Abstract: BACKGROUND: More activities in daily life involve sitting forward motion; however, the effect of the sitting forward process on lumbar disc deformation and strain characteristics has been less reported.
OBJECTIVE: To analyze the morphological changes of the lumbar disc during sitting forward flexion and the characteristics of strain.
METHODS: Dual fluoroscopic imaging system and computed tomography were used to determine the strain characteristics of the intervertebral discs. L4-5 and L5-S1 levels were studied in 10 asymptomatic subjects (male/female: 5/5, age: 25-35 years, body mass index: 22.4±1.8 kg/m2). The height changes of the disc as a whole, the medial and lateral annulus fibrosus in upright sitting and forward flexion sitting was measured. The ranges of tensile and shear strains in the disc during maximum forward flexion motion were determined in the sitting position.
RESULTS AND CONCLUSION: (1) During sitting and forward flexion, L4-5 and L5-S1 showed similar patterns of change in the medial to lateral height ratios in each region of the annulus fibrosus, with a range of 0-0.1 for L4-5 in forward flexion, but a significant decrease in disc height in L5-S1, with a range of 0.02-0.39. (2) During sitting in forward flexion, L5-S1 was under compressive strain in all regions, especially on the right side, where it was 28.3% more compressed than L4-5 (P=0.011). The shear strain of L5-S1 was greater than that of the superior disc, with a significant increase of 14.8% in the central region compared to L4-5 (P=0.011). (3) It is indicated that forward flexion movement during sitting has a greater effect on the height and strain pattern of all parts of the disc at L5-S1, but less at L4-5. L5-S1 is in compression as a whole during the process, with asymmetric compression on the left and right sides, and with greater shear strain in each region. These characteristics help us to gain a better understanding of degeneration due to altered disc strain and to help postoperative patients achieve a better state of recovery.
Key words: lumbar spine, intervertebral disc deformation, sitting position, forward flexion, morphology, strain