Department of Orthopedics, Ruijin Hospital, Shanghai Jiaotong University School of Medicine, 197 Ruijin Er Road, Shanghai, 200025, China.
Department of Surgery, Ruijin Hospital, Shanghai Jiaotong University School of Medicine, 197 Ruijin Er Road, Shanghai, 200025, China.
BMC Musculoskelet Disord. 2022 May 30;23(1):509. doi: 10.1186/s12891-022-05466-8.
Low back pain (LBP) is associated with lumbar disc degeneration (LDD) and fatty infiltration of paraspinal muscles. However, there are some controversies about the relationship between LDD and fatty infiltration of paraspinal muscles, and the causation of them is also not clear. Thus, we investigated whether the degree of LDD was associated with fatty infiltration of paraspinal muscles and preliminarily explored the underlying mechanism.
A retrospective study was conducted on 109 patients with chronic LBP. The degree of LDD was assessed by the Pfirrmann classification. Total muscle cross-sectional area, L4 vertebral body endplate area, and fat cross-sectional area at axial T2-weighted MRI were measured. Multifidus and lumbar disc specimens were taken from eight individuals undergoing discectomy for disc herniation. Gene and protein expression levels of TNF were quantified through qPCR assays and ELISA, respectively.
The relative cross-sectional area, total muscle cross-sectional area, and muscle cross-sectional area asymmetry were not related to LDD. Pfirrmann grades correlated strongly with fatty infiltration of the multifidus and moderately with fatty infiltration of the erector spinae and the psoas muscles. Linear regression analysis suggested that Pfirrmann grades were most associated with fatty infiltration of the multifidus. Compared with II-degree degeneration discs (mild-degeneration group), fatty infiltration of the multifidus in IV-degree degeneration discs (severe-degeneration group) significantly increased, accompanied by increased mRNA expression of TNF. Meanwhile, the protein expression levels of TNF (pg/g protein) in discs (16.62 ± 4.33) and multifidus (13.10 ± 2.76) of the severe-degeneration group were higher than those in the mild-degeneration group (disc: 9.75 ± 2.18; multifidus: 7.84 ± 2.43). However, the mRNA expression of TNF in the multifidus was not significantly different between the two groups.
The results suggest that LDD is associated with fatty infiltration of the multifidus. The possible underlying mechanism is that LDD induces fatty infiltration by inflammation. Furthermore, compared with the erector spinae and the psoas muscles, fatty infiltration of the multifidus shows an optimal correlation with LDD, which may contribute to further understanding of LDD pathology.
下腰痛（LBP）与腰椎间盘退变（LDD）和脊柱旁肌肉脂肪浸润有关。然而，LDD 与脊柱旁肌肉脂肪浸润之间的关系存在一些争议，其因果关系也不清楚。因此，我们研究了 LDD 程度是否与脊柱旁肌肉脂肪浸润有关，并初步探讨了其潜在机制。
对 109 例慢性 LBP 患者进行回顾性研究。采用 Pfirrmann 分级评估 LDD 程度。在轴向 T2 加权 MRI 上测量总肌横截面积、L4 椎体终板面积和脂肪横截面积。从 8 例因椎间盘突出行椎间盘切除术的患者中取出多裂肌和腰椎间盘标本。通过 qPCR 检测和 ELISA 分别定量 TNF 的基因和蛋白表达水平。
相对横截面积、总肌横截面积和肌横截面积不对称与 LDD 无关。Pfirrmann 分级与多裂肌和竖脊肌及腰大肌脂肪浸润呈强相关，与竖脊肌脂肪浸润呈中度相关。线性回归分析表明，Pfirrmann 分级与多裂肌脂肪浸润相关性最强。与 II 度退变椎间盘（轻度退变组）相比，IV 度退变椎间盘（重度退变组）的多裂肌脂肪浸润明显增加，同时 TNF 的 mRNA 表达增加。同时，重度退变组椎间盘（16.62±4.33pg/g 蛋白）和多裂肌（13.10±2.76pg/g 蛋白）中 TNF 的蛋白表达水平高于轻度退变组（椎间盘：9.75±2.18pg/g 蛋白；多裂肌：7.84±2.43pg/g 蛋白）。然而，两组多裂肌中 TNF 的 mRNA 表达无显著差异。
结果表明，LDD 与多裂肌脂肪浸润有关。其潜在机制可能是 LDD 通过炎症诱导脂肪浸润。此外，与竖脊肌和腰大肌相比，多裂肌脂肪浸润与 LDD 具有最佳相关性，这可能有助于进一步了解 LDD 病理学。
