Objective

To quantify muscle characteristics (volumes and fat infiltration) and identify their relationship to sagittal malalignment and compensatory mechanism recruitment.

Methods

Female adult spinal deformity patients underwent T1-weighted MRI with a 2-point Dixon protocol from the proximal tibia up to the T12 vertebra. 3D reconstructions of 17 muscles, including extensors and flexors of spine, hip and knee, were obtained. Muscle volume standardized by bone volume and percentage of fat infiltration (Pfat) were calculated. Correlations and regressions were performed.

Results

A total of 22 patients were included. Significant correlations were observed between sagittal alignment and muscle parameters. Fat infiltration of the hip and knee flexors and extensors correlated with larger C7-S1 SVA. Smaller spinal flexor/extensor volumes correlated with greater PI-LL mismatch (r = − 0.45 and − 0.51). Linear regression identified volume of biceps femoris as only predictor for PT (R² = 0.34, p = 0.005) and Pfat of gluteus minimus as only predictor for SVA (R² = 0.45, p = 0.001). Sagittally malaligned patients with larger PT (26.8° vs. 17.2°) had significantly smaller volume and larger Pfat of gluteus medius, gluteus minimus and biceps femoris, but similar values for gluteus maximus, the hip extensor.

Conclusion

This study is the first to quantify the relationship between degeneration of spino-femoral muscles and sagittal malalignment. This pathoanatomical study identifies the close relationship between gluteal, hamstring muscles and PT, SVA, which deepens our understanding of the underlying etiology that contributes to adult spinal deformity.

中文翻译：

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脊髓股骨肌肉影响矢状对齐和代偿性补充：成年脊髓畸形软组织的新外观。

目的

量化肌肉特征（体积和脂肪浸润）并确定其与矢状位错位和代偿机制的关系。

方法

成年女性脊柱畸形患者接受2点Dixon协议的T1加权MRI，从胫骨近端到T12椎骨。获得了17种肌肉的3D重建，包括脊柱，臀部和膝盖的伸肌和屈肌。计算通过骨体积和脂肪浸润百分比（Pfat）标准化的肌肉体积。进行相关和回归。

结果

总共包括22名患者。在矢状面对准和肌肉参数之间观察到显着的相关性。臀部和膝部屈肌和伸肌的脂肪浸润与较大的C7-S1 SVA相关。较小的脊柱屈肌/伸肌体积与更大的PI-LL不匹配相关（r  =-0.45和-0.51）。线性回归确定股二头肌的体积是PT的唯一预测因子​​（R ²  = 0.34，p  = 0.005），臀小肌的Pfat是SVA的唯一预测因子​​（R ²  = 0.45，p = 0.001）。PT较大的矢状畸形患者（26.8°vs. 17.2°）的臀大肌，臀小肌和股二头肌的体积和Pfat明显较小，但是臀大肌即髋伸肌的数值相似。

结论

这项研究是第一个量化脊髓-股骨肌肉变性与矢状位错位之间关系的研究。这项病理解剖学研究确定了臀肌，绳肌与PT，SVA之间的密切关系，从而加深了我们对导致成人脊柱畸形的潜在病因的理解。