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- Publisher
- Hindawi Publishing Corporation
- Copyright
- Copyright © 2020 Liying Lin et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
- ISSN
- 1176-2322
- eISSN
- 1754-2103
- DOI
- 10.1155/2020/8858686
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- See Article on Publisher Site
Abstract
Hindawi Applied Bionics and Biomechanics Volume 2020, Article ID 8858686, 11 pages https://doi.org/10.1155/2020/8858686 Research Article 1 2 3 4 3 3 1,5 Liying Lin, Shaowei Jia, Hufei Yang, Ye Li, Shunxin Zhang, Jie Fan, and Li Han School of Medical Imaging, Tianjin Medical University, Tianjin 300203, China Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, School of Biological Science and Medical Engineering, Beihang University, Beijing 100083, China School of Mechanical Engineering, Hebei University of Technology, Tianjin 300130, China Department of Orthopedics, Peking Union Medical College Hospital, PUMC&CAMS, Beijing, China Department of Radiology, Tianjin Medical University General Hospital, Tianjin, China Correspondence should be addressed to Li Han; lhan@tmu.edu.cn Received 1 March 2020; Revised 11 September 2020; Accepted 19 September 2020; Published 19 October 2020 Academic Editor: Mohammad Rahimi-Gorji Copyright © 2020 Liying Lin et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Background. Scoliosis is a three-dimensional (3D) deformity of the spine, which affects the patient’s appearance and may lead to abnormal heart and lung function. The rib cage is a structure composed of ribs, sternum, and costal cartilage, which plays a vital role in stabilising the thoracolumbar spine. This study investigates the influence of the rib cage on the static characteristics of the scoliotic spine. Methods. Two types of 3D finite element (FE) models with or without rib cage (from T1 to S) were established and analysed based on computed tomography (CT) images, to determine the effects of the rib cage on the static characteristics of the scoliotic spine. The FE software, ABAQUS, was used to analyse the static behaviours of scoliotic spine models under a range of loading conditions, including left side bending, right side bending, front tilt, rear supine, and vertical compression. The changes in the von Mises stress (VMS) within the intervertebral discs of spine models with or without rib cage were studied and compared. Results. After including the rib cage, the maximum VMS at the stress concentrations of the normal and scoliotic spine effectively reduced. The VMS in normal intervertebral discs was gentler than that of scoliotic ones. However, the scoliotic spine was more likely to produce large stress concentration in the intervertebral discs of scoliotic segments. Conclusions. Under the common postures, intervertebral discs of scoliotic segments are more susceptible to generate stress concentrations compared with the normal spine. The rib cage could effectively keep the intervertebral discs of scoliotic segments from further injuries. These results are of great significance for the prevention and treatment of the scoliotic spine. 1. Introduction thoracic cavity, and provide stability and share the load of the spine [5–7]. To investigate the role of the rib cage in the stability of the Scoliosis is a deformity of the spine with lateral curvature in spine, scholars have used various methods to study the rela- the coronal plane. This deformity can lead to anatomical changes in the structure of the rib cage, which could, in turn, tionship between them. Previous studies have studied the biomechanics of the rib cage and proved that the rib cage cause changes in the mechanical properties of the spine. The contributes to mechanical stability to the spine [8–11]. Wat- deformity is a biomechanical process, which is part of a kins et al. used experiments on cadaver specimens to study vicious cycle, especially under external loads [1]. Severe sco- the effect of the rib cage on the stability of the normal spine liosis can lead to a “razor-back” appearance, which not only affects the patient’s physical appearance but can also lead to under external load [12]. Gignac et al. used the finite element (FE) method to study the best loading patterns required to abnormal heart and lung function [2–4]. The rib cage is com- correct both the spine and the rib cage scoliotic deformities posed of the sternum, ribs, costal cartilage, and rib joints, [13]. Mannen used cadaver specimens to study the changes which is an important anatomical structure of the thoracic in the mechanical properties of the rib cage of a normal spine spine. It can enhance respiration, protect the organs in the 2 Applied Bionics and Biomechanics (a) (b) (c) (d) Figure 1: Four finite element models are shown: (a) normal spine without rib cage (NS1); (b) normal spine with normal rib cage (NS2); (c) scoliotic spine without rib cage (SS1); (d) scoliotic spine with deformed rib cage (SS2). [14]. Previous studies have lacked the effect of the thoracic were created, including (1) structure of vertebrae composed cage on the spine due to the absence of cadaver samples, but of cortical bone, cancellous bone, and the posterior part of finite element analysis of the spine can compensate for this. the vertebrae; (2) structure of the intervertebral disc com- posed of the annulus fibrosus, nucleus pulposus (which takes In this study, four FE models, including normal spine without rib cage (NS1), normal spine with normal rib cage up one-third of the discs and is located at the posterior end), (NS2), scoliotic spine without rib cage (SS1), and scoliotic and upper and lower endplates; and (3) structure of the rib spine with deformed rib cage (SS2), were selected. Under cage composed of the sternum, ribs, costal cartilage, and rib the conventional postures, such as left side bending, right joints. Four FE models, including NS1, NS2, SS1, and SS2, side bending, front tilt, rear supine, and vertical compression, were developed in the FE software, Abaqus 6.14 (Dassault the effects of the rib cage on the static characteristics of the SIMULIA Inc., France). The upper 12 vertebrae are the tho- scoliotic spine were studied by comparing the von Mises racic vertebrae (T1-T12, from top to bottom), the next 5 are stress (VMS) changes within the intervertebral disc of the lumbar vertebrae (L1~L5, from top to bottom), and the last scoliotic spine. The normal spine was used as the control one is the sacrum, S; all four FE models are shown in Figure 1. group to investigate the protective effect of the rib cage on Figure 1 shows that the normal spine was symmetrical on the intervertebral disc of the scoliotic spine. This study pro- the left and right sides, while the vertebrae of the scoliotic vides a basis for mechanical analysis of thoracoplasty and spine deviated from the midline. There was a right side cur- prevention of scoliosis. vature of the Cobb angle of about 60 at T5~T6 (first side convex) and a left side curvature of the Cobb angle of about at T11~T12 (second side convex). 2. Materials and Methods The four sets of geometric models, as shown in Figure 1, 2.1. Establishment of the Finite Element Model. In this study, were meshed in 3-Matic in the software Mimics 16.0. Each a scoliotic spine and a normal spine were selected as the study edge of the element size was set to about 1 mm, and the mesh subjects. Written informed consent was obtained from all element type used in this research model was C3D4 element. participants of the study. A computed tomography (CT) The quality of the mesh was up to standard qualified in the scanner (64-slice spiral CT, Siemens, Germany) was used at software testing. The FE models of vertebral bodies and inter- the Beijing Union Hospital for imaging of the thoracolumbar vertebral discs are shown in Figure 2. area of the scoliotic spine and the normal spine. The scanning The mesh models were assigned the specific material parameters were a tube voltage of 120 kilovolts (kV), tube cur- properties, as shown in Table 1 [15–18]. rent of 211.20 milliamperes (mAs), interlayer spacing of 0.625 A ligament simulated by a linear tension spring was millimetres (mm), and matrix of 512 × 512 pixels. Each scan added between the vertebrae. According to the human body has a total of 867 transaxial slices obtained in Digital Imaging anatomy, spring was used to simulate human ligament and and Communications in Medicine (DICOM) format. was added to the corresponding position in this study. The The software Mimics 16.0 (Materialise NV, Belgium) was stiffness formula of the spring is as shown in used to construct a basic 3D model of the vertebrae and the rib cage. A smooth 3D model of the vertebrae and rib cage E · A was obtained using Geomagic Studio (Geomagic Inc., USA) k = , ð1Þ software. By performing Boolean calculation, three parts L Applied Bionics and Biomechanics 3 (a) (b) (c) (d) (e) (f) (g) Figure 2: The mesh of vertebral bodies and intervertebral discs are shown: (a) cortical bone; (b) cancellous bone; (c) vertebra; (d) annulus fibrosus; (e) nucleus pulposus; (f) upper and lower endplates; (g) spinal segment. Table 1: The material attributes of various spine structures. -3 Structure Unit type E (MPa) νρ (T·mm ) Cortical bone Tetrahedral unit 12000 0.30 1.7E-9 Cancellous bone Tetrahedral unit 150 0.30 1.1E-9 Posterior part Tetrahedral unit 3500 0.30 1.4E-9 End plate Tetrahedral unit 100 0.40 1.2E-9 Annulus fibrosus Tetrahedral unit 4 0.45 1.05E-9 Nucleus pulposus Tetrahedral unit 1 0.499 1.02E-9 Ribs Tetrahedral unit 5000 0.30 2.0E-9 Intercostal cartilage Tetrahedral unit 480 0.40 2.0E-9 Sternal Tetrahedral unit 10000 0.30 2.0E-9 E: elastic modulus; ν: Poisson’s ratio; ρ: density. Table 2: The structural attributes of the major ligaments in the thoracolumbar sacral spine. Main ligament E (MPa) kL (mm) A (mm ) Anterior longitudinal ligament 7.8 8.74 20 22.4 Posterior longitudinal ligament 10 5.83 12 7.0 Ligamentum flavum 17 15.38 15 14.1 Intertransverse ligaments 10 0.19 32 0.6 Interspinous ligaments 10 10.85 13 14.1 Supraspinous ligament 8.0 2.39 22 10.5 where k is the stiffness of the spring, E is the elastic modulus, At present, the primary means of validating the existing A is the cross-sectional area, and L is the average length. The models of the spine is to compare them with the cadaver material properties of the ligaments are based on published specimen, under the same experiment boundary conditions data, as shown in Table 2 [11, 19]. The supraspinous liga- [20]. To prove the reliability of the proposed FE model, we ment, interspinous ligaments, anterior longitudinal ligament, only chose those parts of the lumbar vertebra model that posterior longitudinal ligament, intertransverse ligaments, were previously studied in the literature. The model pro- and ligamentum flavum in the thoracolumbar segment were posed in this study was validated under physiological load- stimulated. The ligaments between the ribs were not consid- ing modes: (1) compression, (2) anterior and posterior ered due to lack of published data. shear, and (3) the predicted responses were compared 4 Applied Bionics and Biomechanics Table 3: The external load addition in four spinal models [10]. The posture of the spine model The load of the four spinal models Left side bending Add 100 N force from right to left on T1 Right side bending Add 100 N force from left to right on T1 Front tilt Add 100 N force from the back to the front on T1 Rear supine Add 100 N force from the front to the back on T1 Vertical compression Add 100 N force from top to bottom on T1 1.0 1.0 +0.24 0.8 0.8 0.74 0.73 +0.24 0.67 0.63 0.63 0.62 0.61 0.60 0.60 0.57 0.56 0.6 0.6 0.52 0.49 0.47 0.51 0.37 0.4 0.4 0.31 0.28 –0.24 0.2 –0.24 0.2 0.0 0.0 L1 L2 L3 L4 L1 L2 L3 L4 Berkson et al. Berkson et al. Xiang et al. Xiang et al. This study This study (a) (b) 1.0 +0.29 0.8 0.70 0.63 0.60 0.56 0.57 0.6 0.52 0.46 0.39 0.4 0.35 –0.29 0.2 0.0 L1 L2 L3 L4 Berkson et al. Xiang et al. This study (c) Figure 3: Comparison of FE analysis and experimental results: (a) lumbar vertebral deformation under an axial pressure of 400 N; (b) lumbar vertebral deformation under an anterior shear force of 86 N; (c) lumbar vertebral deformation under a posterior shear force of 86 N. against results by Berkson et al. [21] and Xiang et al. [22] 2.2. Static Analysis under similar boundary and loading configurations. The 2.2.1. Selecting Poses for Static Analysis. Given the complexity predicted displacement values at the centre of the superior of human body movement during daily life and travel, the vertebral body (under compression and shear loading) were compared to the aforementioned in vitro experimen- spine movements were simplified to postures such as left side bending, right side bending, front tilt, rear supine, tal results. Axial displacement (mm) Axial displacement (mm) Axial displacement (mm) Applied Bionics and Biomechanics 5 S, von Mises S, von Mises S, von Mises S, von Mises (Avg: 75%) (Avg: 75%) (Avg: 75%) (Avg: 75%) +4.031e+01 +3.033e+01 +5.277e+01 +4.645e+01 +2.000e+01 +1.500e+01 +1.500e+01 +1.500e+01 +1.375e+01 +1.834e+01 +1.375e+01 +1.375e+01 +1.250e+01 +1.667e+01 +1.250e+01 +1.250e+01 +1.125e+01 +1.501e+01 +1.126e+01 +1.125e+01 +1.001e+01 +1.001e+01 +1.334e+01 +1.001e+01 +1.168e+01 +8.759e+00 +8.758e+00 +8.755e+00 +1.001e+01 +7.511e+00 +7.509e+00 +7.506e+00 +6.261e+00 +8.346e+00 +6.263e+00 +6.257e+00 +5.012e+00 +6.682e+00 +5.015e+00 +5.008e+00 +3.764e+00 +5.017e+00 +3.767e+00 +3.759e+00 +2.515e+00 +2.510e+00 +3.352e+00 +2.519e+00 +1.687e+00 +1.271e+00 +1.267e+00 +1.261e+00 +2.246e–02 +2.246e–02 +1.831e–02 +1.161e–02 (a) (b) (c) (d) Figure 4: von Mises stress distribution of discs in four spinal models with left curvature: (a) normal spine without rib cage (NS1); (b) normal spine with normal rib cage (NS2); (c) scoliotic spine without rib cage (SS1); (d) scoliotic spine with deformed rib cage (SS2). and vertical compression. The static analysis of simple pos- mental data. These results align well with the experimental tures of the spine structure can reflect the static characteristics findings of Berkson et al. [21]. Moreover, the vertical dis- of the complex motion of the human body. Therefore, static placements are close to the FE data of Xiang et al. [22]. analyses of four spine models, including NS1, NS2, SS1, and Therefore, the scoliosis model established in the study is val- SS2 were performed in various simple poses. The VMS idation and reliable. changes in the intervertebral disc were compared before and after adding the rib cage at each posture. 3.2. Results of Static Analysis. All the intervertebral discs of the thoracic and lumbar vertebrae T1~S were selected as 2.2.2. Adding Boundary Conditions and Loads. The effect of the research object. The maximum VMS on the interverte- the rib cage on the intervertebral disc of the scoliotic spine bral disc was obtained under various simple postures of the in common postures was analysed. The vertebrae of the spine same load. The change of the equivalent stress of the interver- are connected through the intervertebral disc. The upper and tebral disc in the same posture before and after adding the rib lower endplates of the intervertebral disc connect the annulus cage was studied. fibrosus and the nucleus pulposus. According to the anatom- ical properties of the spine tissue and the common postures 3.2.1. Static Analysis Results of Left and Right Side Bending. in daily life, the tie constraints were used to fix all the existing Under the same external load, the left and right side bending contact surfaces. Also, it was necessary to constrain the six of the spines was simulated, and the equivalent stresses on degrees of freedom on both sides of the sacrum of the four the intervertebral discs of four FE models were studied. The spine models. In order to simulate a simple posture of the VMS distribution cloud diagrams are shown in Figures 4 human body, point-to-surface coupling was created on the and 5. The maximum VMS on the intervertebral disc of the right, left, back, front, and top of the first thoracic vertebra four spine models was measured and plotted as the stress dis- (T1), respectively. An external load was applied to the cou- tribution map of the intervertebral disc of the whole spine, as pling point, and a point mass of 10.5 kilograms (kg) was shown in Figures 6 and 7. added to the upper surface of T1 of the four models to simu- As shown in Figures 4–7, under the same loading con- late the influence of the mass of the head, neck, and upper ditions, the VMS of the intervertebral disc of the normal limbs on the spine model to improve the analysis [3, 23]. spine T1~S showed an increasing trend, and the overall The same loads and boundary conditions were added to the VMS was smaller and more stable than that of the scoli- four spine models in the same posture, as listed in Table 3. otic spine. The VMS of the intervertebral disc of the sco- liotic spine T1~S showed an increasing trend, and the overall VMS was larger than the normal spine. There were 3. Results mutations near the scoliotic segments T4, T8, and T12, 3.1. FE Model Validation. A comparison of the FE model and presenting three distinct peaks. In the normal spine with experimental results is shown in Figure 3. Under an axial the rib cage, the VMS of the intervertebral disc of T1~T12 was slightly reduced, and the VMS of the inter- pressure of 400 Newton (N) and the anterior and posterior shear force of 86 N, the calculated displacements of the vertebral disc of L1~L5 was slightly increased. In the sco- centre of the L1-L4 vertebral surface in the vertical direc- liotic spine with the deformed rib cage, the VMS of the tion fall within the range of the aforementioned experi- intervertebral disc of T1~T12 was significantly reduced, 6 Applied Bionics and Biomechanics 13 13 12 12 11 11 10 10 9 9 8 8 7 7 6 6 5 5 4 4 3 3 2 2 1 1 0 0 SS1 NS1 SS2 NS2 (a) (b) Figure 5: Stress distribution of discs in four spinal models with left curvature: (a) stress distribution of normal spinal intervertebral disc; (b) stress distribution of scoliotic spinal intervertebral disc. NS1, NS2, SS1, and SS2 need to be defined here. S, von Mises S, von Mises S, von Mises S, von Mises (Avg: 75%) (Avg: 75%) (Avg: 75%) (Avg: 75%) +5.440e+01 +4.595e+01 +3.360e+01 +2.855e+01 +1.500e+01 +1.500e+01 +2.000e+01 +1.500e+01 +1.375e+01 +1.375e+01 +1.833e+01 +1.375e+01 +1.250e+01 +1.250e+01 +1.667e+01 +1.250e+01 +1.125e+01 +1.125e+01 +1.500e+01 +1.126e+01 +1.001e+01 +1.000e+01 +1.334e+01 +1.001e+01 +8.758e+00 +8.755e+00 +1.167e+01 +8.759e+00 +7.510e+00 +7.506e+00 +1.001e+01 +7.511e+00 +6.262e+00 +6.256e+00 +8.341e+00 +6.262e+00 +5.013e+00 +5.007e+00 +6.675e+00 +5.014e+00 +3.765e+00 +3.758e+00 +5.010e+00 +3.766e+00 +2.516e+00 +2.509e+00 +3.344e+00 +2.518e+00 +1.268e+00 +1.260e+00 +1.678e+00 +1.269e+00 +1.977e–02 +1.103e–02 +1.288e–02 +2.102e–02 (a) (b) (c) (d) Figure 6: von Mises stress distribution of discs in four spinal models with right curvature: (a) normal spine without rib cage (NS1); (b) normal spine with normal rib cage (NS2); (c) scoliotic spine without rib cage (SS1); (d) scoliotic spine with deformed rib cage (SS2). As shown in Figures 8–11, under the same loading condi- and the VMS of the intervertebral disc of L1~L5 was sig- nificantly increased. tions, the VMS of the intervertebral disc of the normal spine T1~S showed an increasing trend, and the overall VMS was smaller and more stable than that of the scoliotic spine. The 3.2.2. Static Analysis Results of Front Tilt and Rear Supine. VMS of the intervertebral disc of the scoliotic spine T1~S Under the same external load, the front tilt and rear supine showed a normal distribution trend, and the overall VMS were simulated, and the equivalent stresses on the inter- was larger than the normal spine. There was a peak near vertebral disc of four models were studied. The VMS dis- the scoliotic segment T8, gradually decreasing on both sides. tribution cloud diagrams are shown in Figures 8 and 9. In the normal spine with the rib cage, the VMS of the inter- The maximum VMS on the intervertebral disc was mea- vertebral disc of T1~T8 was significantly reduced, and the sured and plotted as the stress distribution map, as shown VMS of the intervertebral disc of L1~L5 was slightly in Figures 10 and 11. increased. In the scoliotic spine with the deformed rib cage, Max von Mises stress (MPa) T1 ~ T2 T2 ~ T3 T3 ~ T4 T4 ~ T5 T5 ~ T6 T6 ~ T7 T7 ~ T8 T8 ~ T9 T9 ~ T10 T10 ~ T11 T11 ~ T12 T12 ~ L1 L1 ~ L2 L2 ~ L3 L3 ~ L4 l4 ~ L5 L5 ~ S Max von Mises stress (MPa) T1 ~ T2 T2 ~ T3 T3 ~ T4 T4 ~ T5 T5 ~ T6 T6 ~ T7 T7 ~ T8 T8 ~ T9 T9 ~ T10 T10 ~ T11 T11 ~ T12 T12 ~ L1 L1 ~ L2 L2 ~ L3 L3 ~ L4 l4 ~ L5 L5 ~ S Applied Bionics and Biomechanics 7 13 13 12 12 11 11 10 10 9 9 8 8 7 7 6 6 5 5 4 4 3 3 2 2 1 1 0 0 NS1 SS1 NS2 SS2 (a) (b) Figure 7: Stress distribution of discs in four spinal models with right curvature: (a) stress distribution of normal spinal intervertebral discs; (b) stress distribution of scoliotic spinal intervertebral discs. NS1, NS2, SS1, and SS2 need to be defined here. S, von Mises S, von Mises S, von Mises S, von Mises (Avg: 75%) (Avg: 75%) (Avg: 75%) (Avg: 75%) +7.831e+01 +7.643e+01 +5.172e+01 +3.976e+01 +1.500e+01 +1.500e+01 +2.000e+01 +1.500e+01 +1.375e+01 +1.375e+01 +1.834e+01 +1.375e+01 +1.250e+01 +1.250e+01 +1.667e+01 +1.250e+01 +1.126e+01 +1.125e+01 +1.501e+01 +1.126e+01 +1.001e+01 +1.000e+01 +1.334e+01 +1.000e+01 +8.759e+00 +8.755e+00 +1.168e+01 +8.761e+00 +7.510e+00 +7.505e+00 +1.001e+01 +7.513e+00 +6.262e+00 +6.256e+00 +8.351e+00 +6.265e+00 +5.014e+00 +5.007e+00 +6.687e+00 +5.017e+00 +3.765e+00 +3.758e+00 +5.022e+00 +3.770e+00 +2.517e+00 +2.509e+00 +3.358e+00 +2.522e+00 +1.269e+00 +1.260e+00 +1.694e+00 +1.274e+00 +2.048e–02 +1.090e–02 +2.995e–02 +2.604e–02 (a) (b) (c) (d) Figure 8: von Mises stress distribution of disc in four spinal models with anterior tilt: (a) normal spine without rib cage (NS1); (b) normal spine with normal rib cage (NS2); (c) scoliotic spine without rib cage (SS1); (d) scoliotic spine with deformed rib cage (SS2). the VMS of the intervertebral disc of T1~T12 was signifi- spine T1~S showed a decreasing trend, and the overall cantly reduced, and the VMS of the intervertebral disc of VMS was smaller and more stable than that of the scoli- L1~L5 was significantly increased. otic spine. The VMS of intervertebral discs of the scoliotic spine T1~S showed a trend of M-type distribution, and 3.2.3. Static Analysis Results of Vertical Compression. Under the overall VMS was large larger than the normal spine. the same external load conditions, the vertical compression There were two peaks near the scoliotic segments T4 and was simulated, and the equivalent stress on the intervertebral T10, gradually decreasing on both sides. In the normal disc of four models was studied. The VMS distribution cloud spine with the rib cage, the VMS of the intervertebral disc diagram is shown in Figure 12. The maximum VMS on the of T1~T8 was significantly reduced, and the VMS of the intervertebral disc was measured and plotted as the stress dis- intervertebral disc of L1~L5 did not change significantly. tribution map, as shown in Figure 13. In the scoliotic spine with the deformed rib cage, the As shown in Figures 11 and 12, under the same loading VMS of the intervertebral disc of T1~T12 was significantly reduced. The scoliotic segments T4 and T10 had the most conditions, the VMS of intervertebral discs of the normal Max von Mises stress (MPa) T1 ~ T2 T2 ~ T3 T3 ~ T4 T4 ~ T5 T5 ~ T6 T6 ~ T7 T7 ~ T8 T8 ~ T9 T9 ~ T10 T10 ~ T11 T11 ~ T12 T12 ~ L1 L1 ~ L2 L2 ~ L3 L3 ~ L4 l4 ~ L5 L5 ~ S Max von Mises stress (MPa) T1 ~ T2 T2 ~ T3 T3 ~ T4 T4 ~ T5 T5 ~ T6 T6 ~ T7 T7 ~ T8 T8 ~ T9 T9 ~ T10 T10 ~ T11 T11 ~ T12 T12 ~ L1 L1 ~ L2 L2 ~ L3 L3 ~ L4 l4 ~ L5 L5 ~ S 8 Applied Bionics and Biomechanics 1 1 0 0 NS1 SS1 NS2 SS2 (a) (b) Figure 9: Stress distribution of disc in four spinal models with anterior tilt: (a) stress distribution of normal spinal intervertebral discs; (b) stress distribution of scoliotic spinal intervertebral discs. NS1, NS2, SS1, and SS2 need to be defined here. S, von Mises S, von Mises S, von Mises S, von Mises (Avg: 75%) (Avg: 75%) (Avg: 75%) (Avg: 75%) +7.643e+01 +7.831e+01 +5.046e+01 +3.831e+01 +1.500e+01 +1.500e+01 +2.000e+01 +1.500e+01 +1.375e+01 +1.375e+01 +1.834e+01 +1.375e+01 +1.250e+01 +1.250e+01 +1.667e+01 +1.250e+01 +1.125e+01 +1.125e+01 +1.501e+01 +1.125e+01 +1.000e+01 +1.334e+01 +1.000e+01 +1.001e+01 +8.758e+00 +8.755e+00 +1.168e+01 +8.754e+00 +7.509e+00 +7.505e+00 +1.001e+01 +7.505e+00 +6.261e+00 +6.256e+00 +8.351e+00 +6.256e+00 +5.012e+00 +5.007e+00 +6.686e+00 +5.007e+00 +3.764e+00 +3.758e+00 +5.022e+00 +3.758e+00 +2.515e+00 +2.509e+00 +3.358e+00 +2.509e+00 +1.267e+00 +1.260e+00 +1.694e+00 +1.259e+00 +1.855e–02 +1.090e–02 +2.970e–02 +1.025e–02 (a) (b) (c) (d) Figure 10: von Mises stress distribution of disc in four spinal models with posterior supine: (a) normal spine without rib cage (NS1); (b) normal spine with normal rib cage (NS2); (c) scoliotic spine without rib cage (SS1); (d) scoliotic spine with deformed rib cage (SS2). significant reductions, and the VMS of the intervertebral Compared with the vertebrae, the intervertebral disc is disc of L1~L5 did not change significantly. more susceptible to deformation and damage under external load [24]. In this study, we compared the VMS of the inter- vertebral discs on T1~S of the thoracolumbar vertebrae of 4. Discussion the scoliotic and normal spine model with and without rib cage. After the rib cage was added to the normal spine, the Scoliosis is a 3D deformity of the spine, which experiences VMS of the intervertebral disc of the thoracic vertebrae gen- asymmetrical loading. Few studies investigated cadaveric erally reduced. The results imply that the rib cage can specimens of the scoliotic spine due to the lack of cadaver increase the stability of the thoracic spine, confirming the specimens, so FEM and FE analyses have been a useful tool conclusions of the previous studies [12, 14]. After the addi- to simulate the cadaver specimens. In this study, four FE tion of rib cage, the stress of intervertebral discs of the normal models were established, and static behaviours of scoliotic spine reduced more evenly, while the stress of the scoliotic spine models (with or without rib cage) were assessed under spine was concentrated on the scoliosis segments, and the the conventional postures. Max von Mises stress (MPa) T1 ~ T2 T2 ~ T3 T3 ~ T4 T4 ~ T5 T5 ~ T6 T6 ~ T7 T7 ~ T8 T8 ~ T9 T9 ~ T10 T10 ~ T11 T11 ~ T12 T12 ~ L1 L1 ~ L2 L2 ~ L3 L3 ~ L4 l4 ~ L5 L5 ~ S Max von Mises stress (MPa) T1 ~ T2 T2 ~ T3 T3 ~ T4 T4 ~ T5 T5 ~ T6 T6 ~ T7 T7 ~ T8 T8 ~ T9 T9 ~ T10 T10 ~ T11 T11 ~ T12 T12 ~ L1 L1 ~ L2 L2 ~ L3 L3 ~ L4 l4 ~ L5 L5 ~ S Applied Bionics and Biomechanics 9 11 11 10 10 9 9 8 8 7 7 6 6 5 5 4 4 3 3 2 2 0 0 NS1 SS1 NS2 SS2 (a) (b) Figure 11: Stress distribution of disc in four spinal models with posterior supine: (a) stress distribution of normal spinal intervertebral discs; (b) stress distribution of scoliotic spinal intervertebral discs. NS1, NS2, SS1, and SS2 need to be defined here. S, von Mises S, von Mises S, von Mises S, von Mises (Avg: 75%) (Avg: 75%) (Avg: 75%) (Avg: 75%) +7.321e+00 +3.931e+00 +1.995e+01 +9.876e+00 +5.000e+00 +2.000e+00 +1.000e+01 +5.000e+00 +4.584e+00 +1.834e+00 +9.167e+00 +4.583e+00 +4.168e+00 +1.667e+00 +8.334e+00 +4.167e+00 +3.751e+00 +1.501e+00 +7.500e+00 +3.750e+00 +3.335e+00 +1.334e+00 +6.667e+00 +3.334e+00 +2.919e+00 +1.168e+00 +5.834e+00 +2.917e+00 +2.503e+00 +1.001e+00 +5.001e+00 +2.501e+00 +2.086e+00 +8.349e–01 +4.168e+00 +2.084e+00 +1.670e+00 +6.684e–01 +3.335e+00 +1.668e+00 +1.254e+00 +5.020e–01 +2.501e+00 +1.251e+00 +8.375e–01 +3.355e–01 +1.668e+00 +8.349e–01 +4.213e–01 +1.691e–01 +8.350e–01 +4.184e–01 +5.022e–03 +2.610e–03 +1.864e–03 +1.864e–03 (a) (b) (c) (d) Figure 12: von Mises stress distribution of disc in four spinal models under vertical compression: (a) normal spine without rib cage (NS1); (b) normal spine with normal rib cage (NS2); (c) scoliotic spine without rib cage (SS1); (d) scoliotic spine with deformed rib cage (SS2). reductions of the stress after the addition of rib cage were also very complicated and requires multiple forces to simulate. concentrated with the scoliosis segments. The result may be Also, muscle tissue near the thorax, spine, and pelvis affect the force and dynamics of the spine. In subsequent studies, explained by the characteristics of the spinal structure of the scoliotic spine. these components need to be included to bring the model and findings closer to reality for clinical research. The research presented in this manuscript has laid a foundation for the further mechanical studies of idiopathic scoliosis. The study has several limitations. The material 5. Conclusions properties of the models are based on generally accepted data. However, the bone material properties may be different Intervertebral discs of scoliotic segments generate stress con- with different individuals, genders, ages, and pathological centrations more commonly compared with normal spine spines. Therefore, the material properties of specific spine under common postures. The rib cage can protect the inter- will be needed to be improved further. Only five postures vertebral discs of scoliotic segments. The rib cage mainly pro- were studied in this study, and each posture was simulated tects different segments in different postures. These results are with one force. In reality, the posture of the human body is of great significance for the prevention and treatment of the Max von Mises stress (MPa) T1 ~ T2 T2 ~ T3 T3 ~ T4 T4 ~ T5 T5 ~ T6 T6 ~ T7 T7 ~ T8 T8 ~ T9 T9 ~ T10 T10 ~ T11 T11 ~ T12 T12 ~ L1 L1 ~ L2 L2 ~ L3 L3 ~ L4 l4 ~ L5 L5 ~ S Max von Mises stress (MPa) T1 ~ T2 T2 ~ T3 T3 ~ T4 T4 ~ T5 T5 ~ T6 T6 ~ T7 T7 ~ T8 T8 ~ T9 T9 ~ T10 T10 ~ T11 T11 ~ T12 T12 ~ L1 L1 ~ L2 L2 ~ L3 L3 ~ L4 l4 ~ L5 L5 ~ S 10 Applied Bionics and Biomechanics NS1 NS2 (a) SS1 SS2 (b) Figure 13: Stress distribution of disc in four spinal models under vertical compression: (a) stress distribution of normal spinal intervertebral discs; (b) stress distribution of scoliotic spinal intervertebral discs. NS1, NS2, SS1, and SS2 need to be defined here. scoliotic spine. This study provides useful references for the Acknowledgments treatments and protection of scoliosis patients and the devel- This work was supported by Tianjin Natural Science Foun- opment of scoliosis medical devices and related products. dation (17JCZDJC32500). Data Availability References The datasets used during the current study are available from the corresponding author on reasonable request. [1] I. A. F. Stokes, “Analysis and simulation of progressive adoles- cent scoliosis by biomechanical growth modulation,” Euro- pean Spine Journal, vol. 16, no. 10, pp. 1621–1628, 2007. Conflicts of Interest [2] F. Pecorelli, V. Grassi, L. Ferrini, and T. Todisco, “Changes in The authors declare that they have no competing interests. respiratory function in disorders of the thoracic cage. With Max von Mises stress (MPa) Max von Mises stress (MPa) T1 ~ T2 T1 ~ T2 T2 ~ T3 T2 ~ T3 T3 ~ T4 T3 ~ T4 T4 ~ T5 T4 ~ T5 T5 ~ T6 T5 ~ T6 T6 ~ T7 T6 ~ T7 T7 ~ T8 T7 ~ T8 T8 ~ T9 T8 ~ T9 T9 ~ T10 T9 ~ T10 T10 ~ T11 T10 ~ T11 T11 ~ T12 T11 ~ T12 T12 ~ L1 T12 ~ L1 L1 ~ L2 L1 ~ L2 L2 ~ L3 L2 ~ L3 L3 ~ L4 L3 ~ L4 l4 ~ L5 l4 ~ L5 L5 ~ S L5 ~ S Applied Bionics and Biomechanics 11 ment method,” Computer-Aided Design, vol. 39, no. 7, special reference to the ventilatory mechanism and the regula- tion in scoliosis,” Italian Journal of Orthopaedics & Trauma- pp. 559–567, 2007. tology, vol. 9, no. 1, pp. 75–89, 1983. [19] Y. Arai, H. E. Takahashi, and H. Suzuki, “Stress analysis of the [3] G. S. Nikolova and Y. E. Toshev, “Estimation of male and lumbar spine using the finite element model,” in Spinal Disor- female body segment parameters of the Bulgarian population ders in Growth and Aging, 1995. using a 16-segmental mathematical model,” Journal of Biome- [20] P. Leborgne, W. Skalli, J. Dubousset, J. Dansereau, R. Zeller, chanics, vol. 40, no. 16, pp. 3700–3707, 2007. and F. Lavaste, Finite element model of scoliotic spine: mechan- [4] C. Lang, R. Wang, Z. Chen et al., “Incidence and risk factors of ical personalization, STUDIES IN HEALTH TECHNOLOGY AND INFORMATICS, 1999. cardiac abnormalities in patients with idiopathic scoliosis,” World Neurosurgery, vol. 125, pp. E824–E828, 2019. [21] M. H. Berkson, A. Nachemson, and A. B. Schultz, “Mechanical [5] C. Liebsch and H.-J. Wilke, “Basic biomechanics of the tho- properties of human lumbar spine motion segments—part II: racic spine and rib cage,” in Biomechanics of the Spine, responses in compression and shear; influence of gross mor- pp. 35–50, Elsevier, 2018. phology,” Journal of Biomechanical Engineering, vol. 101, no. 1, pp. 53–57, [6] D. E. Anderson, E. M. Mannen, R. Tromp et al., “The rib cage reduces intervertebral disc pressures in cadaveric thoracic P. Xiang, C. Du, M. Y. Zhao, S. Tian, L. Z. Wang, and Y. B. Fan, [22] spines by sharing loading under applied dynamic moments,” “Modal analysis of human lumbar spine using finite element Journal of Biomechanics, vol. 70, pp. 262–266, 2018. method,” Journal of Medical Biomechanics, vol. 29, pp. 154– 160, 2014. [7] C. Liebsch, N. Graf, K. Appelt, and H.-J. Wilke, “The rib cage stabilizes the human thoracic spine: an in vitro study using [23] S. T. Takashima, S. P. Singh, K. A. Haderspeck, and A. B. stepwise reduction of rib cage structures,” PLoS One, vol. 12, Schultz, “A model for semi-quantitative studies of muscle no. 6, 2017. actions,” Journal of Biomechanics, vol. 12, no. 12, pp. 929– 939, 1979. [8] L. B. C. Brasiliense, B. C. R. Lazaro, P. M. Reyes, S. Dogan, N. Theodore, and N. R. Crawford, “Biomechanical contribu- [24] B. Frost, S. Camarero-Espinosa, and E. Foster, “Materials for tion of the rib cage to thoracic stability,” Spine, vol. 36, the spine: anatomy, problems, and solutions,” Materials, no. 26, pp. E1686–E1693, 2011. vol. 12, no. 2, p. 253, 2019. [9] J. M. Cormier, Microstructural and mechanical properties of human ribs, Virginia Tech, 1998. [10] I. Oda, K. Abumi, B. W. Cunningham, K. Kaneda, and P. C. McAfee, “An in vitro human cadaveric study investigating the biomechanical properties of the thoracic spine,” Spine, vol. 27, no. 3, pp. E64–E70, 2002. [11] T. Andriacchi, A. Schultz, T. Belytschko, and J. Galante, “A model for studies of mechanical interactions between the human spine and rib cage,” Journal of Biomechanics, vol. 7, no. 6, pp. 497–507, 1974. [12] R. Watkins, R. Watkins, L. Williams et al., “Stability provided by the sternum and rib cage in the thoracic spine,” Spine, vol. 30, no. 11, pp. 1283–1286, 2005. [13] D. Gignac, C.-É. Aubin, J. Dansereau, and H. Labelle, “Optimi- zation method for 3D bracing correction of scoliosis using a finite element model,” European Spine Journal, vol. 9, no. 3, pp. 185–190, 2000. [14] E. M. Mannen, J. T. Anderson, P. M. Arnold, and E. A. Friis, “Mechanical contribution of the rib cage in the human cadav- eric thoracic spine,” Spine, vol. 40, no. 13, pp. E760–E766, [15] Z. Li, M. W. Kindig, J. R. Kerrigan et al., “Rib fractures under anterior-posterior dynamic loads: experimental and finite- element study,” Journal of Biomechanics, vol. 43, no. 2, pp. 228–234, 2010. [16] I. Yamamoto, M. M. Panjabi, T. Crisco, and T. Oxland, “Three-dimensional movements of the whole lumbar spine and lumbosacral joint,” Spine, vol. 14, no. 11, pp. 1256–1260, [17] K. Sairyo, V. K. Goel, A. Masuda et al., “Three-dimensional finite element analysis of the pediatric lumbar spine. Part I: pathomechanism of apophyseal bony ring fracture,” European Spine Journal, vol. 15, no. 6, pp. 923–929, 2006. [18] D. S. Shin, K. Lee, and D. Kim, “Biomechanical study of lum- bar spine with dynamic stabilization device using finite ele-
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Applied Bionics and Biomechanics – Hindawi Publishing Corporation
Published: Oct 19, 2020