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Jayaswal D, Kodigudla M, Kelkar A, Goel V, Palepu V. Validation of a patient-specific finite element analysis framework for identification of growing rod-failure regions in early onset scoliosis patients. Spine Deform 2024; 12:941-952. [PMID: 38536653 PMCID: PMC11217039 DOI: 10.1007/s43390-024-00846-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/01/2023] [Accepted: 02/14/2024] [Indexed: 07/03/2024]
Abstract
PURPOSE Growing rods are the gold-standard for treatment of early onset scoliosis (EOS). However, these implanted rods experience frequent fractures, requiring additional surgery. A recent study by the U.S. Food and Drug Administration (FDA) identified four common rod fracture locations. Leveraging this data, Agarwal et al. were able to correlate these fractures to high-stress regions using a novel finite element analysis (FEA) framework for one patient. The current study aims to further validate this framework through FEA modeling extended to multiple patients. METHODS Three patient-specific FEA models were developed to match the pre-operative patient data taken from both registry and biplanar radiographs. The surgical procedure was then simulated to match the post-operative deformity. Body weight and flexion bending (1 Nm) loads were then applied and the output stress data on the rods were analyzed. RESULTS Radiographic data showed fracture locations at the mid-construct, adjacent to the distal and tandem connector across the patients. Stress analysis from the FEA showed these failure locations matched local high-stress regions for all fractures observed. These results qualitatively validate the efficacy of the FEA framework by showing a decent correlation between localized high-stress regions and the actual fracture sites in the patients. CONCLUSIONS This patient-specific, in-silico framework has huge potential to be used as a surgical tool to predict sites prone to fracture in growing rod implants. This prospective information would therefore be vital for surgical planning, besides helping optimize implant design for reducing rod failures.
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Affiliation(s)
- Daksh Jayaswal
- Department of Bioengineering and Orthopaedic Surgery, Engineering Center for Orthopaedic Research Excellence (E-CORE), University of Toledo, 2801 West Bancroft Street, Toledo, OH, 43606, USA
| | - Manoj Kodigudla
- Department of Bioengineering and Orthopaedic Surgery, Engineering Center for Orthopaedic Research Excellence (E-CORE), University of Toledo, 2801 West Bancroft Street, Toledo, OH, 43606, USA
| | - Amey Kelkar
- Department of Bioengineering and Orthopaedic Surgery, Engineering Center for Orthopaedic Research Excellence (E-CORE), University of Toledo, 2801 West Bancroft Street, Toledo, OH, 43606, USA
| | - Vijay Goel
- Department of Bioengineering and Orthopaedic Surgery, Engineering Center for Orthopaedic Research Excellence (E-CORE), University of Toledo, 2801 West Bancroft Street, Toledo, OH, 43606, USA
| | - Vivek Palepu
- Division of Applied Mechanics, Office of Science and Engineering Laboratories, Center for Devices and Radiological Health, U.S. Food and Drug Administration, 10903 New Hampshire Avenue, Building WO 62-2225, Silver Spring, MD, 20993, USA.
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Gruber G, Nicolini LF, Ribeiro M, Lerchl T, Wilke HJ, Jaramillo HE, Senner V, Kirschke JS, Nispel K. Comparative FEM study on intervertebral disc modeling: Holzapfel-Gasser-Ogden vs. structural rebars. Front Bioeng Biotechnol 2024; 12:1391957. [PMID: 38903189 PMCID: PMC11188472 DOI: 10.3389/fbioe.2024.1391957] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2024] [Accepted: 04/29/2024] [Indexed: 06/22/2024] Open
Abstract
Introduction: Numerical modeling of the intervertebral disc (IVD) is challenging due to its complex and heterogeneous structure, requiring careful selection of constitutive models and material properties. A critical aspect of such modeling is the representation of annulus fibers, which significantly impact IVD biomechanics. This study presents a comparative analysis of different methods for fiber reinforcement in the annulus fibrosus of a finite element (FE) model of the human IVD. Methods: We utilized a reconstructed L4-L5 IVD geometry to compare three fiber modeling approaches: the anisotropic Holzapfel-Gasser-Ogden (HGO) model (HGO fiber model) and two sets of structural rebar elements with linear-elastic (linear rebar model) and hyperelastic (nonlinear rebar model) material definitions, respectively. Prior to calibration, we conducted a sensitivity analysis to identify the most important model parameters to be calibrated and improve the efficiency of the calibration. Calibration was performed using a genetic algorithm and in vitro range of motion (RoM) data from a published study with eight specimens tested under four loading scenarios. For validation, intradiscal pressure (IDP) measurements from the same study were used, along with additional RoM data from a separate publication involving five specimens subjected to four different loading conditions. Results: The sensitivity analysis revealed that most parameters, except for the Poisson ratio of the annulus fibers and C01 from the nucleus, significantly affected the RoM and IDP outcomes. Upon calibration, the HGO fiber model demonstrated the highest accuracy (R2 = 0.95), followed by the linear (R2 = 0.89) and nonlinear rebar models (R2 = 0.87). During the validation phase, the HGO fiber model maintained its high accuracy (RoM R2 = 0.85; IDP R2 = 0.87), while the linear and nonlinear rebar models had lower validation scores (RoM R2 = 0.71 and 0.69; IDP R2 = 0.86 and 0.8, respectively). Discussion: The results of the study demonstrate a successful calibration process that established good agreement with experimental data. Based on our findings, the HGO fiber model appears to be a more suitable option for accurate IVD FE modeling considering its higher fidelity in simulation results and computational efficiency.
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Affiliation(s)
- Gabriel Gruber
- Department of Diagnostic and Interventional Neuroradiology, School of Medicine and Health, Klinikum rechts der Isar, Technical University of Munich, Munich, Germany
| | - Luis Fernando Nicolini
- Department of Mechanical Engineering, Federal University of Santa Maria, Av. Santa Maria, Brazil
| | - Marx Ribeiro
- Department for Orthopedics, Trauma and Reconstructive Surgery, University Hospital RWTH Aachen, Aachen, Germany
- Department of Mechanical Engineering, Federal University of Santa Catarina, Florianópolis, Brazil
| | - Tanja Lerchl
- Department of Diagnostic and Interventional Neuroradiology, School of Medicine and Health, Klinikum rechts der Isar, Technical University of Munich, Munich, Germany
- Associate Professorship of Sport Equipment and Sport Materials, School of Engineering and Design, Technical University of Munich, Garching, Germany
| | - Hans-Joachim Wilke
- Institute of Orthopaedic Research and Biomechanics, Trauma Research Centre Ulm, University of Ulm, Ulm, Germany
| | | | - Veit Senner
- Associate Professorship of Sport Equipment and Sport Materials, School of Engineering and Design, Technical University of Munich, Garching, Germany
| | - Jan S. Kirschke
- Department of Diagnostic and Interventional Neuroradiology, School of Medicine and Health, Klinikum rechts der Isar, Technical University of Munich, Munich, Germany
| | - Kati Nispel
- Department of Diagnostic and Interventional Neuroradiology, School of Medicine and Health, Klinikum rechts der Isar, Technical University of Munich, Munich, Germany
- Associate Professorship of Sport Equipment and Sport Materials, School of Engineering and Design, Technical University of Munich, Garching, Germany
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3
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Singh NK, Singh NK, Verma R, Diwan AD. Validation and Estimation of Obesity-Induced Intervertebral Disc Degeneration through Subject-Specific Finite Element Modelling of Functional Spinal Units. Bioengineering (Basel) 2024; 11:344. [PMID: 38671766 PMCID: PMC11048157 DOI: 10.3390/bioengineering11040344] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2024] [Revised: 03/22/2024] [Accepted: 03/25/2024] [Indexed: 04/28/2024] Open
Abstract
(1) Background: Intervertebral disc degeneration has been linked to obesity; its potential mechanical effects on the intervertebral disc remain unknown. This study aimed to develop and validate a patient-specific model of L3-L4 vertebrae and then use the model to estimate the impact of increasing body weight on disc degeneration. (2) Methods: A three-dimensional model of the functional spinal unit of L3-L4 vertebrae and its components were developed and validated. Validation was achieved by comparing the range of motions (RoM) and intradiscal pressures with the previous literature. Subsequently, the validated model was loaded according to the body mass index and estimated stress, deformation, and RoM to assess disc degeneration. (3) Results: During validation, L3-L4 RoM and intradiscal pressures: flexion 5.17° and 1.04 MPa, extension 1.54° and 0.22 MPa, lateral bending 3.36° and 0.54 MPa, axial rotation 1.14° and 0.52 MPa, respectively. When investigating the impact of weight on disc degeneration, escalating from normal weight to obesity reveals an increased RoM, by 3.44% during flexion, 22.7% during extension, 29.71% during lateral bending, and 33.2% during axial rotation, respectively. Also, stress and disc deformation elevated with increasing weight across all RoM. (4) Conclusions: The predicted mechanical responses of the developed model closely matched the validation dataset. The validated model predicts disc degeneration under increased weight and could lay the foundation for future recommendations aimed at identifying predictors of lower back pain due to disc degeneration.
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Affiliation(s)
- Nitesh Kumar Singh
- Computational Biomechanics Lab, Department of Biomedical Engineering, National Institute of Technology, Raipur 492010, India;
| | - Nishant K. Singh
- Computational Biomechanics Lab, Department of Biomedical Engineering, National Institute of Technology, Raipur 492010, India;
| | - Rati Verma
- Biomechanics Lab, School of Biomedical Engineering, Indian Institute of Technology (BHU), Varanasi 221005, India;
| | - Ashish D. Diwan
- Spine Labs & Spine Service, St George & Sutherland Campus, Clinical School of Faculty of Health & Medicine, University of New South Wales, Sydney, NSW 2502, Australia;
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Nicolini LF, Beckmann A, Laubach M, Hildebrand F, Kobbe P, Mello Roesler CRD, Fancello EA, Markert B, Stoffel M. An experimental-numerical method for the calibration of finite element models of the lumbar spine. Med Eng Phys 2022; 107:103854. [DOI: 10.1016/j.medengphy.2022.103854] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2021] [Revised: 05/18/2022] [Accepted: 07/18/2022] [Indexed: 11/27/2022]
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Zhou M, Huff R, Abubakr Y, O'Connell G. Torque- and Muscle-Driven Flexion Induce Disparate Risks of In Vitro Herniation: A Multiscale and Multiphasic Structure-Based Finite Element Study. J Biomech Eng 2022; 144:1133336. [PMID: 35079770 DOI: 10.1115/1.4053402] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2021] [Indexed: 11/08/2022]
Abstract
The intervertebral disc is a complex structure that experiences multiaxial stresses regularly. Disc failure through herniation is a common cause of lower back pain, which causes reduced mobility and debilitating pain, resulting in heavy socioeconomic burdens. Unfortunately, herniation etiology is not well understood, partially due to challenges in replicating herniation in vitro. Previous studies suggest that flexion elevated risks of herniation. Thus, the objective of this study was to use a multiscale and multiphasic finite element model to evaluate the risk of failure under torque- or muscle-driven flexion. Models were developed to represent torque-driven flexion with the instantaneous center of rotation (ICR) located on the disc, and the more physiologically representative muscle-driven flexion with the ICR located anterior of the disc. Model predictions highlighted disparate disc mechanics regarding bulk deformation, stress-bearing mechanisms, and intradiscal stress-strain distributions. Specifically, failure was predicted to initiate at the bone-disc boundary under torque-driven flexion, which may explain why endplate junction failure, instead of herniation, has been the more common failure mode observed in vitro. By contrast, failure was predicted to initiate in the posterolateral annulus fibrosus under muscle-driven flexion, resulting in consistent herniation. Our findings also suggested that muscle-driven flexion combined with axial compression could be sufficient for provoking herniation in vitro and in silico. In conclusion, this study provided a computational framework for designing in vitro testing protocols that can advance the assessment of disc failure behavior and the performance of engineered disc implants.
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Affiliation(s)
- Minhao Zhou
- University of California, Berkeley, Mechanical Engineering Department, 2162 Etcheverry Hall, #1740, Berkeley, CA 94720-1740
| | - ReeceD Huff
- University of California, Berkeley, Mechanical Engineering Department, 2162 Etcheverry Hall, #1740, Berkeley, CA 94720-1740
| | - Yousuf Abubakr
- University of California, Berkeley, Mechanical Engineering Department, 2162 Etcheverry Hall, #1740, Berkeley, CA 94720-1740
| | - Grace O'Connell
- University of California, Berkeley, Mechanical Engineering Department, University of California, San Francisco, Orthopaedic Surgery Department, 2162 Etcheverry Hall, #1740, Berkeley, CA 94720-1740
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Wang W, Zhou C, Guo R, Cha T, Li G. Influence of structural and material property uncertainties on biomechanics of intervertebral discs - Implications for disc tissue engineering. J Mech Behav Biomed Mater 2021; 122:104661. [PMID: 34252706 DOI: 10.1016/j.jmbbm.2021.104661] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2021] [Revised: 05/26/2021] [Accepted: 06/24/2021] [Indexed: 10/21/2022]
Abstract
This study investigated how variations of structural and material properties of human intervertebral discs (IVDs) affect the biomechanical responses of the IVDs under simulated physiological loading conditions using a stochastic finite element (SFE) model. An SFE method, which combined an anatomic FE model of human lumbar L3-4 segment and probabilistic analysis of its structural and material properties, was used to generate a dataset of 500 random disc samples with varying structural and material properties. The sensitivity of the biomechanical responses, including intervertebral displacements/rotations, intradiscal pressures (IDP), fiber stresses and matrix strains of annulus fibrosus (AF), were systematically quantified under various physiological loading conditions, including a 500N compression and 7.5Nm moments in the 3 primary rotations. Significant variations of the IDPs, IVD displacements/rotations, and stress/strain distributions were found using the dataset of 500 ramdom disc samples. Under all the loading conditions, the IDPs were positively correlated with the Poisson's ratio of the NP (r = 0.46 to 0.75, p = 0.004-0.001) and negatively with the Young's modulus of the annulus matrix (r = -0.48 to -0.65, p = 0.003-0.001). The primary intervertebral rotations were significantly affected by the Young's modulus of the annulus matrix (r = -0.44 to -0.71, p = 0.001-0.032) and the orientations of the annular fibers (r = -0.45 to -0.69, p = 0.001-0.029). The heterogeneity of structures and material properties of the IVD had distinct effects on the biomechanical performances of the IVD. These data could help improve our understanding of the intrinsic biomechanics of the IVD and provide references for optimal design of tissue engineered discs by controlling structural and material properties of the disc components.
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Affiliation(s)
- Wei Wang
- Orthopaedic Bioengineering Research Center, Department of Orthopaedic Surgery, Newton-Wellesley Hospital, 159 Wells Avenue, Newton, MA 02459, USA; Department of Orthopaedic Surgery, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA; School of Biological Science and Medical Engineering, Beihang University, Beijing, China
| | - Chaochao Zhou
- Orthopaedic Bioengineering Research Center, Department of Orthopaedic Surgery, Newton-Wellesley Hospital, 159 Wells Avenue, Newton, MA 02459, USA; Department of Orthopaedic Surgery, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
| | - Runsheng Guo
- Orthopaedic Bioengineering Research Center, Department of Orthopaedic Surgery, Newton-Wellesley Hospital, 159 Wells Avenue, Newton, MA 02459, USA; Department of Orthopaedic Surgery, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA; Department of Orthopaedics, The First Affiliated Hospital of Nanchang University, Nanchang, Jiangxi, China
| | - Thomas Cha
- Orthopaedic Bioengineering Research Center, Department of Orthopaedic Surgery, Newton-Wellesley Hospital, 159 Wells Avenue, Newton, MA 02459, USA; Department of Orthopaedic Surgery, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
| | - Guoan Li
- Orthopaedic Bioengineering Research Center, Department of Orthopaedic Surgery, Newton-Wellesley Hospital, 159 Wells Avenue, Newton, MA 02459, USA.
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7
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Agarwal A, Kodigudla M, Kelkar A, Jayaswal D, Goel V, Palepu V. Towards a validated patient-specific computational modeling framework to identify failure regions in traditional growing rods in patients with early onset scoliosis. NORTH AMERICAN SPINE SOCIETY JOURNAL 2021; 5:100043. [PMID: 35141610 PMCID: PMC8820004 DOI: 10.1016/j.xnsj.2020.100043] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/09/2020] [Revised: 12/07/2020] [Accepted: 12/07/2020] [Indexed: 11/24/2022]
Abstract
BACKGROUND While growing rods are an important contribution to early-onset scoliosis treatment, rod fractures are a common complication that require reoperations. A recent retrieval analysis study performed on failed traditional growing rods revealed that there are commonalities among patient characteristics based on the location of rod fracture. However, it remains unknown if these locations correspond to high stress regions in the implanted construct. METHODS A patient-specific finite element scoliotic model was developed to match the pre-operative (pre-op) scoliotic curve of a patient as described in previously published articles, and by using the patient registry information along with biplanar radiographs. A dual stainless-steel traditional growing rod construct was implanted into this scoliotic model and the surgical procedure was simulated to match the post-operative (post-op) scoliotic curve parameters. Muscle stabilization and gravity was simulated through follower load application. Rod distraction magnitudes were chosen based on pre-op to post-op cobb angle correction, and flexion bending load was simulated to identify the high stress regions on the rods. RESULTS The patient-specific finite element model identified two high stress regions on the posterior surface of the rods, one at mid construct and the other adjacent to the distal anchors. This correlated well with the data obtained from the retrieval analysis performed by researchers at U.S. Food and Drug Administration (FDA) which showed the posterior surface of the rod as the fracture initiation site, and the three locations of failure as mid-construct, adjacent to distal anchors, and adjacent to tandem connector. CONCLUSIONS The result of this study confirms that the high stress regions on the growing rods, as identified by the FEA, match the fracture prone sites identified in the retrieval analysis performed at the FDA. This proof-of-concept patient-specific approach can be used to predict sites prone to fracture in growing rods.
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Affiliation(s)
- Aakash Agarwal
- Engineering Center for Orthopaedic Research Excellence (E-CORE), Department of Bioengineering and Orthopaedic Surgery, University of Toledo, 2801 West Bancroft Street, Toledo, OH 43606 USA
| | - Manoj Kodigudla
- Engineering Center for Orthopaedic Research Excellence (E-CORE), Department of Bioengineering and Orthopaedic Surgery, University of Toledo, 2801 West Bancroft Street, Toledo, OH 43606 USA
| | - Amey Kelkar
- Engineering Center for Orthopaedic Research Excellence (E-CORE), Department of Bioengineering and Orthopaedic Surgery, University of Toledo, 2801 West Bancroft Street, Toledo, OH 43606 USA
| | - Daksh Jayaswal
- Engineering Center for Orthopaedic Research Excellence (E-CORE), Department of Bioengineering and Orthopaedic Surgery, University of Toledo, 2801 West Bancroft Street, Toledo, OH 43606 USA
| | - Vijay Goel
- Engineering Center for Orthopaedic Research Excellence (E-CORE), Department of Bioengineering and Orthopaedic Surgery, University of Toledo, 2801 West Bancroft Street, Toledo, OH 43606 USA
| | - Vivek Palepu
- Center for Devices and Radiological Health, Office of Science and Engineering Laboratories, Division of Applied Mechanics, U.S. Food and Drug Administration, Silver Spring, MD 20993 USA
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8
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Galbusera F, Cina A, Panico M, Bassani T. The importance of curve severity, type and instrumentation strategy in the surgical correction of adolescent idiopathic scoliosis: an in silico clinical trial on 64 cases. Sci Rep 2021; 11:1799. [PMID: 33469069 PMCID: PMC7815774 DOI: 10.1038/s41598-021-81319-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2020] [Accepted: 12/18/2020] [Indexed: 11/29/2022] Open
Abstract
Adolescent idiopathic scoliosis is a three-dimensional deformity of the spine which is frequently corrected with the implantation of instrumentation with generally good or excellent clinical results; mechanical post-operative complications such as implant loosening and breakage are however relatively frequent. The rate of complications is associated with a lack of consensus about the surgical decision-making process; choices about the instrumentation length, the anchoring implants and the degree of correction are indeed mostly based on personal views and previous experience of the surgeon. In this work, we performed an in silico clinical trial on a large number of subjects in order to clarify which factors have the highest importance in determining the risk of complications by quantitatively analysing the mechanical stresses and loads in the instrumentation after the correction maneuvers. The results of the simulations highlighted the fundamental role of the curve severity, also in its three-dimensional aspect, and of the instrumentation strategy, whereas the length of the fixation had a lower importance.
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Affiliation(s)
- Fabio Galbusera
- Laboratory of Biological Structures Mechanics, IRCCS Istituto Ortopedico Galeazzi, via Galeazzi 4, 20161, Milan, Italy.
| | - Andrea Cina
- Laboratory of Biological Structures Mechanics, IRCCS Istituto Ortopedico Galeazzi, via Galeazzi 4, 20161, Milan, Italy
| | - Matteo Panico
- Laboratory of Biological Structures Mechanics, IRCCS Istituto Ortopedico Galeazzi, via Galeazzi 4, 20161, Milan, Italy.,Department of Chemistry, Materials and Chemical Engineering "Giulio Natta", Politecnico di Milano, Milan, Italy
| | - Tito Bassani
- Laboratory of Biological Structures Mechanics, IRCCS Istituto Ortopedico Galeazzi, via Galeazzi 4, 20161, Milan, Italy
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Wintrich T, Jonas R, Wilke HJ, Schmitz L, Sander PM. Neck mobility in the Jurassic plesiosaur Cryptoclidus eurymerus: finite element analysis as a new approach to understanding the cervical skeleton in fossil vertebrates. PeerJ 2019; 7:e7658. [PMID: 31720095 PMCID: PMC6842296 DOI: 10.7717/peerj.7658] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2018] [Accepted: 08/11/2019] [Indexed: 11/20/2022] Open
Abstract
The sauropterygian clade Plesiosauria arose in the Late Triassic and survived to the very end of the Cretaceous. Plesiosauria evolved the greatest species diversity of any marine reptile clade, attaining a global distribution. Plesiosauria consist of two clades, Rhomaleosauridae and Neoplesiosauria. Basal Neoplesiosauria have long necks with at least 30 cervicals, but show qualitative osteological evidence for a stiff neck. Here we quantify neck mobility in lateral, ventral, and dorsal directions based on finite element modeling of neck vertebrae from the Middle Jurassic plesiosaur Cryptoclidus eurymerus. We model the mobility in a single motion segment, consisting of two adjacent cervical vertebrae and the joints connecting them. Based on the model with a maximum intervertebral spacing of 3 mm, we find that in Cryptoclidus, the maximum angle of lateral deflection in the motion segment was 2°. The maximum angle of ventral deflection was 5° and of dorsal deflection was 5°. When these values are multiplied by the number of cervical vertebrae, it becomes apparent that neck mobility was limited in all directions. The maximum angle of total lateral deflection in the neck was 67°. The maximum angle of total ventral deflection was 148° and of total dorsal deflection was 157°. This raises the question of the function of such a long, multi-segment but immobile neck. We posit that the long neck served in hydrodynamic and visual camouflage, hiding the bulk of the body from the small but abundant prey, such as schooling fish and squid. Neck immobility may have been advantageous in withstanding strong hydrodynamic forces acting on the neck during predatory strikes.
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Affiliation(s)
- Tanja Wintrich
- Section Paleontology, Institute of Geosciences, University of Bonn, Bonn, Germany.,Institute of Anatomy, University of Bonn, Bonn, Germany
| | - René Jonas
- Institute of Orthopaedic Research and Biomechanics, Universität Ulm, Ulm, Germany
| | | | - Lars Schmitz
- Keck Science Department of the Claremont Colleges, Claremont, CA, USA.,Dinosaur Institute, Natural History Museum of Los Angeles County, Los Angeles, CA, USA
| | - P Martin Sander
- Section Paleontology, Institute of Geosciences, University of Bonn, Bonn, Germany.,Dinosaur Institute, Natural History Museum of Los Angeles County, Los Angeles, CA, USA
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