Musculoskeletal Modeling of the Lumbar Spine to Explore Functional Interactions between Back Muscle Loads and Intervertebral Disk Multiphysics

Abstract

During daily activities, complex biomechanical interactions influence the biophysical regulation of intervertebral disks (IVDs), and transfers of mechanical loads are largely controlled by the stabilizing action of spine muscles. Muscle and other internal forces cannot be easily measured directly in the lumbar spine. Hence, biomechanical models are important tools for the evaluation of the loads in those tissues involved in low-back disorders. Muscle force estimations in most musculoskeletal models mainly rely, however, on inverse calculations and static optimizations that limit the predictive power of the numerical calculations. In order to contribute to the development of predictive systems, we coupled a predictive muscle model with the passive resistance of the spine tissues, in a L3–S1 musculoskeletal finite element model with osmo-poromechanical IVD descriptions. The model included 46 fascicles of the major back muscles that act on the lower spine. The muscle model interacted with activity-related loads imposed to the osteoligamentous structure, as standing position and night rest were simulated through distributed upper body mass and free IVD swelling, respectively. Calculations led to intradiscal pressure values within ranges of values measured in vivo. Disk swelling led to muscle activation and muscle force distributions that seemed particularly appropriate to counterbalance the anterior body mass effect in standing. Our simulations pointed out a likely existence of a functional balance between stretch-induced muscle activation and IVD multiphysics toward improved mechanical stability of the lumbar spine understanding. This balance suggests that proper night rest contributes to mechanically strengthen the spine during day activity.

Optimization of Three-Level Cervical Hybrid Surgery to Prevent Adjacent Segment Disease: A Finite Element Study

“…As a result, a moment distributed evenly on the cervical segments may be more physiological. Similar concepts involving modeling the paraspinal muscles with multiple attachments were also applied by previous studies in the FE modeling of lumbar spine (Toumanidou and Noailly, 2015).…”

A Systematic Review of Continuum Modeling of Skeletal Muscles: Current Trends, Limitations, and Recommendations

“…Most of the developed laws have been inspired from the Hill-type phenomenological model including passive and active components of the skeletal muscle. It is important to emphasize that the hyperelastic behavior has been included in most of developed models to describe the skeletal muscle passive component [48, 52]. The active component is commonly defined by the relationship between the fiber activation, stretch, and force components.…”

“…One study attempted to measure in vivo data related to contraction amplitude to reduce uncertainty in parameter space and then used it to more accurately reproduce the physical behavior of muscle contraction [59]. Parameter identification was also performed using literature data for the level of stretch-induced fascicle activation [52]. Note that common outcomes of active muscle materials are muscle stress/stretch and strains at fiber and whole muscle levels.…”

“…Despite the complexity in model formulation and evaluation, active muscle modeling has been commonly performed for a large range of muscles including generic muscle tissue [36, 37, 43, 54], brachialis [35], rectus femoris [38, 46], levator ani [40], biceps brachii [23, 39, 55], gastrocnemius [41, 42, 53], tibialis anterior [44, 47, 49–51], biceps femoris longhead [45], soleus [46, 53], ventral interior lateral muscle [48], lumbar spine muscles [52], and facial muscles [22, 26, 56–59]. Geometrical models of skeletal muscles have been reconstructed from medical imaging (CT and MRI) [22, 23, 26, 38, 45, 50, 53–59].…”

Estimation of Trunk Muscle Forces Using a Bio-Inspired Control Strategy Implemented in a Neuro-Osteo-Ligamentous Finite Element Model of the Lumbar Spine

“…To provide more geometrical details, deformable elements, based on fitting a curve on the forces and moments previously obtained by a finite element model of the intervertebral disc, were added to the multi-body model of the lumbar spine; again neglecting the intervertebral joint complexities ( Karajan et al, 2013 , 2014 ; Rupp et al, 2015 ). Moreover, a previous study included active muscle models in a reduced musculoskeletal finite element model of the lumbar spine to explore possible functional relationships between muscle function and intervertebral disc condition ( Toumanidou and Noailly, 2015 ).…”