Architectural Analysis and Intraoperative Measurements Demonstrate the Unique Design of the Multifidus Muscle for Lumbar Spine Stability
Architectural Analysis and Intraoperative Measurements Demonstrate the Unique Design of the Multifidus Muscle for Lumbar Spine Stability
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DOI：
10.2106/jbjs.g.01311
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发表时间：
2009-01-01
影响因子：
5.3
通讯作者：
Lieber, Richard L.
中科院分区：
文献类型：
--
作者：
Ward, Samuel R.;Kim, Choll W.;Lieber, Richard L.
背景：肌肉不稳定是腰椎损伤和慢性腰痛的重要危险因素。虽然腰椎多裂肌被认为是重要的棘旁肌，但其设计特征尚不完全清楚。本研究的目的是确定人体多裂肌的结构特性、体内肌节长度、活动范围和被动力学特性。我们假设它的结构将以短纤维和大生理横截面积为特征，并且它将在相对较宽的肌节长度范围内工作，但将具有非常坚硬的被动材料特性。方法：将8例尸体标本从T12至骶骨整块切除腰椎。从每个椎体水平分离多裂肌，允许测量质量、肌节长度、归一化纤维长度、生理横截面积和纤维长度与肌肉长度之比。为了确定肌肉的肌节长度操作范围，从脊柱屈曲和伸展位置获得的术中活检标本中测量肌节长度。单个肌纤维的材料特性是通过切除活检标本的被动应力应变试验获得的。结果：平均肌肉质量（及标准误差）为146 +/- 8.7 g，平均肌节长度为2.27 +/- 0.06 μ m，平均归一化纤维长度为5.66 +/- 0.65 cm，平均生理截面积为23.9 +/- 3.0 cm(2)，平均纤维长-肌长比为0.21 +/- 0.03。术中肌节长度测量显示，肌肉的伸展范围为1.98 +/- 0.15 μ m，屈曲范围为2.70 +/- 0.11 μ m。被动力学数据表明，肌肉的材料特性与手臂或腿部的肌肉相当。结论：多裂肌的结构设计（高截面积和低纤维长度与肌肉长度之比）表明多裂肌是一种独特的稳定器，可以产生大的力。此外，多裂肌位于长度-张力曲线的上升部分，当脊柱呈前倾姿势时，使肌肉变得更强壮。
Background: Muscular instability is an important risk factor for lumbar spine injury and chronic low-back pain. Although the lumbar multifidus muscle is considered an important paraspinal muscle, its design features are not completely understood. The purpose of the present study was to determine the architectural properties, in vivo sarcomere length operating range, and passive mechanical properties of the human multifidus muscle. We hypothesized that its architecture would be characterized by short fibers and a large physiological cross-sectional area and that it would operate over a relatively wide range of sarcomere lengths but would have very stiff passive material properties.Methods: The lumbar spines of eight cadaver specimens were excised en bloc from T12 to the sacrum. Multifidus muscles were isolated from each vertebral level, permitting the architectural measurements of mass, sarcomere length, normalized fiber length, physiological cross-sectional area, and fiber length-to-muscle length ratio. To determine the sarcomere length operating range of the muscle, sarcomere lengths were measured from intraoperative biopsy specimens that were obtained with the spine in the flexed and extended positions. The material properties of single muscle fibers were obtained from passive stress-strain tests of excised biopsy specimens.Results: The average muscle mass (and standard error) was 146 +/- 8.7 g, and the average sarcomere length was 2.27 +/- 0.06 mu m, yielding an average normalized fiber length of 5.66 +/- 0.65 cm, an average physiological cross-sectional area of 23.9 +/- 3.0 cm(2), and an average fiber length-to-muscle length ratio of 0.21 +/- 0.03. Intraoperative sarcomere length measurements revealed that the muscle operates from 1.98 +/- 0.15 mu m in extension to 2.70 +/- 0.11 mu m in flexion. Passive mechanical data suggested that the material properties of the muscle are comparable with those of muscles of the arm or leg.Conclusions: The architectural design (a high cross-sectional area and a low fiber length-to-muscle length ratio) demonstrates that the multifidus muscle is uniquely designed as a stabilizer to produce large forces. Furthermore, multifidus sarcomeres are positioned on the ascending portion of the length-tension curve, allowing the muscle to become stronger as the spine assumes a forward-leaning posture.