Comparison of eight published static finite element models of the intact lumbar spine: predictive power of models improves when combined together.
Finite element (FE) model studies have made important contributions to our understanding of functional biomechanics of the lumbar spine. However, if a model is used to answer clinical and biomechanical questions over a certain population, their inherently large inter-subject variability has to be considered. Current FE model studies, however, generally account only for a single distinct spinal geometry with one set of material properties. This raises questions concerning their predictive power, their range of results and on their agreement with in vitro and in vivo values. Eight well-established FE models of the lumbar spine (L1-5) of different research centers around the globe were subjected to pure and combined loading modes and compared to in vitro and in vivo measurements for intervertebral rotations, disc pressures and facet joint forces. Under pure moment loading, the predicted L1-5 rotations of almost all models fell within the reported in vitro ranges, and their median values differed on average by only 2° for flexion-extension, 1° for lateral bending and 5° for axial rotation. Predicted median facet joint forces and disc pressures were also in good agreement with published median in vitro values. However, the ranges of predictions were larger and exceeded those reported in vitro, especially for the facet joint forces. For all combined loading modes, except for flexion, predicted median segmental intervertebral rotations and disc pressures were in good agreement with measured in vivo values. In light of high inter-subject variability, the generalization of results of a single model to a population remains a concern. This study demonstrated that the pooled median of individual model results, similar to a probabilistic approach, can be used as an improved predictive tool in order to estimate the response of the lumbar spine.
Julius Wolff Institute, Charité-Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, Germany. Electronic address: dreischarf@julius-wolff-institut.de.
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Dreischarf
Julius Wolff Institute, Charité-Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, Germany.
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Zander
Division of Applied Mechanics, Department of Mechanical Engineering, École Polytechnique, Montréal, Quebec, Canada.
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Shirazi-Adl
Orthopaedic Bioengineering Research Laboratory, Colorado State University, USA.
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Puttlitz
Paediatric Spine Research Group, Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, Australia.
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Adam
Department of Physical Therapy and Assistive Technology, National Yang-Ming University, Taipei, Taiwan.
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Chen
Departments of Bioengineering and Orthopaedic Surgery, Colleges of Engineering and Medicine, University of Toledo, USA.
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Goel
Departments of Bioengineering and Orthopaedic Surgery, Colleges of Engineering and Medicine, University of Toledo, USA.
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Kiapour
Department of Mechanical Engineering, Kyung Hee University, Yongin 446-701, Republic of Korea.
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Kim
Orthopaedic Bioengineering Research Laboratory, Colorado State University, USA.
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Labus
Paediatric Spine Research Group, Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, Australia.
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JP
Little
Department of Mechanical Engineering, Kyung Hee University, Yongin 446-701, Republic of Korea.
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Park
Department of Physical Therapy and Assistive Technology, National Yang-Ming University, Taipei, Taiwan.
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Wang
Institute of Orthopaedic Research and Biomechanics, Ulm, Germany.
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Wilke
Julius Wolff Institute, Charité-Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, Germany.
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Rohlmann
Julius Wolff Institute, Charité-Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, Germany; Institute of Orthopaedic Research and Biomechanics, Ulm, Germany.
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Schmidt
D000465:Algorithms; D019245:Compressive Strength; D020342:Finite Element Analysis; D006801:Humans; D008159:Lumbar Vertebrae / Q000033:anatomy & histology / Q000502:physiology*; D008962:Models, Theoretical; D011187:Posture; D011312:Pressure; D011336:Probability; D016059:Range of Motion, Articular / Q000502:physiology; D015203:Reproducibility of Results; D012399:Rotation; D021801:Zygapophyseal Joint / Q000502:physiology
Finite element model; Inter-subject variability; Lumbar spine; Predictive power; Sensitivity; Validation; Verification