BACKGROUND Posterior lumbar fusion is a widely accepted surgical technique; however, it has been related to the possibility of paraspinal muscle atrophy after surgery. We investigated 1-year postoperative changes in paraspinal muscle volume using a simple formula applicable to magnetic resonance imaging (MRI) or computed tomography (CT) images. METHODS Patients with degenerative lumbar spinal stenosis who underwent posterior interbody fusion (PLIF) at the L4/5 level in the period from May 2010 to June 2017 were enrolled in this study. Radiologic parameters were measured using MRI or CT images which were taken before surgery and at 1 year after surgery. The volume of the paraspinal muscles was calculated using a simple formula which was derived from the formula for calculating the volume of truncated elliptic cones. RESULTS A total of 40 patients were included; 24 were analyzed using MRI and 16 were analyzed using CT. The mean age of the patients was 59.6 ± 12.1 years and 32 (80.5%) were female. When comparing the preoperative and 1-year-postoperative images, multifidus muscle (MF) reduction was consistently observed in the MRI and CT groups, right and left (p = 0.003, p < 0.001, p = 0.005 and p < 0.001, respectively). In the erector spinae (ES) group, decrease in muscle volume was observed in the right-sided muscles of the CT group (p < 0.001), but no significant change was observed in the MRI group. The psoas muscle showed no significant change after 1 year. Conversely, regression analysis showed a negative correlation between MF muscle volume loss and age in the MRI group (right and left, p = 0.002 and p = 0.015, respectively), that is, the younger the age, the greater loss of muscle mass. CONCLUSION After the posterior lumbar fusion, the volume of the MF muscles was markedly decreased, and the degree of decrease was apparent in the MRI. The volume of the ES muscles, which are located relatively laterally, also tended to decrease at 1 year after surgery.

中文翻译：

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单级后路腰椎融合术后椎旁肌变化：容量分析和文献复习。

背景技术腰椎后路融合术是一种广泛接受的手术技术。然而，这与手术后椎旁肌萎缩的可能性有关。我们使用适用于磁共振成像（MRI）或计算机断层扫描（CT）图像的简单公式，调查了术后1年椎旁肌体积的变化。方法纳入2010年5月至2017年6月以L4 / 5水平进行后路椎体间融合术（PLIF）的退行性腰椎管狭窄症患者。使用MRI或CT图像测量放射学参数，这些图像是在手术前和手术后1年拍摄的。使用简单的公式计算椎旁肌的体积，该公式是从用于计算截头椭圆锥的体积的公式中得出的。结果共纳入40例患者。使用MRI分析24例，使用CT分析16例。患者的平均年龄为59.6±12.1岁，女性为32岁（80.5％）。比较术前和术后1年的图像时，在MRI和CT组中，左右一致观察到多指肌（MF）减少（分别为p = 0.003，p <0.001，p = 0.005和p <0.001） 。在竖脊肌（ES）组中，CT组的右侧肌肉出现肌肉体积减少（p <0.001），而MRI组未观察到明显变化。腰大肌在1年后无明显变化。相反，回归分析显示MRI组中MF肌肉体积减少与年龄之间呈负相关（右和左，分别为p = 0.002和p​​ = 0.015），即，年龄越小，肌肉质量的损失就越大。结论腰椎后路融合术后MF肌肉的体积明显减少，并且在MRI中明显减少。相对侧的ES肌肉的体积在手术后1年也趋于减少。