The examination of stress shielding in a finite element lumbar spine inclusive of the thoracolumbar fascia

Despite the prevalence of low back pain (LBP) in society, the pathomechanism of LBP continues to elude researchers. LBP patients have demonstrated morphological and material property changes to their lumbar soft tissues, potentially leading to irregular load sharing within the lumbar spine. This study aims to analyze potential stress shielding consequential of augmented soft tissue properties via the comparison of a healthy and LBP finite element models. The models developed in this study include the vertebrae, intervertebral discs and soft tissues from L1-S1. Soft tissue morphology and material properties for the LBP model were augmented to reflect documented clinical findings. Model validation preceded testing and was confirmed through comparison to the available literature. Relative to the healthy model, the LBP model demonstrated an increase in stress by 15.6%, with 99.8% of this stress increase being distributed towards the thoracolumbar fascia. The majority of stress skewed towards the fascia may indicate a potential stress allocation bias whereby the lumbar muscles are unable to receive regular loading, leading to stress shielding. This load allocation bias and subsequent stress shielding may potentially contribute to the progression and pathomechanism of LBP but prospective studies would be required to make that link.

[1]  G. Vanderstraeten,et al.  CT imaging of trunk muscles in chronic low back pain patients and healthy control subjects , 2000, European Spine Journal.

[2]  J. Katz,et al.  Lumbar disc disorders and low-back pain: socioeconomic factors and consequences. , 2006, The Journal of bone and joint surgery. American volume.

[3]  N. Ichihashi,et al.  Association of low back pain with muscle stiffness and muscle mass of the lumbar back muscles, and sagittal spinal alignment in young and middle‐aged medical workers , 2017, Clinical biomechanics.

[4]  E Schneider,et al.  Structure and Function of Vertebral Trabecular Bone , 1997, Spine.

[5]  L. Claes,et al.  New in vivo measurements of pressures in the intervertebral disc in daily life. , 1999, Spine.

[6]  P. Pigeon,et al.  Viscoelastic properties of the human lumbodorsal fascia. , 1993, Journal of biomedical engineering.

[7]  G. Andersson.  Epidemiological features of chronic low-back pain , 1999, The Lancet.

[8]  C. Leboeuf‐Yde,et al.  Low back pain: what is the long-term course? A review of studies of general patient populations , 2003, European Spine Journal.

[9]  O. Gagey,et al.  Magnetic resonance elastography of the lumbar back muscles: A preliminary study , 2018, Clinical anatomy.

[10]  L. Soslowsky,et al.  Supraspinatus Tendons Have Different Mechanical Properties Across Sex. , 2018, Journal of biomechanical engineering.

[11]  A Rohlmann,et al.  Comparison of eight published static finite element models of the intact lumbar spine: predictive power of models improves when combined together. , 2014, Journal of biomechanics.

[12]  Martin Underwood,et al.  Non-specific low back pain , 2012, The Lancet.

[13]  N. Ichihashi,et al.  Effects of the trunk position on muscle stiffness that reflects elongation of the lumbar erector spinae and multifidus muscles: an ultrasonic shear wave elastography study , 2019, European Journal of Applied Physiology.

[14]  Robert Schleip,et al.  Passive muscle stiffness may be influenced by active contractility of intramuscular connective tissue. , 2006, Medical hypotheses.

[15]  M. Deane,et al.  Outcome of low back pain in general practice , 1998, BMJ.

[16]  J Emery,et al.  The challenge of integrating genetic medicine into primary care , 2001, BMJ : British Medical Journal.

[17]  A Rohlmann,et al.  Realistic loading conditions for upper body bending. , 2009, Journal of biomechanics.

[18]  James R. Fox,et al.  Reduced thoracolumbar fascia shear strain in human chronic low back pain , 2011, BMC musculoskeletal disorders.

[19]  T. Keaveny,et al.  Micromechanics of the human vertebral body for forward flexion. , 2012, Journal of biomechanics.

[20]  Mark Driscoll,et al.  Development and validation of a timely and representative finite element human spine model for biomechanical simulations , 2020, Scientific Reports.

[21]  Fong-Chin Su,et al.  Flexion-extension rhythm in the lumbosacral spine. , 1994 .

[22]  M. G. Gelder,et al.  In Reply: BEHAVIOUR THERAPY , 1965 .

[23]  Takuro Tamura,et al.  BodyParts3D: 3D structure database for anatomical concepts , 2008, Nucleic Acids Res..

[24]  J. Cholewicki,et al.  Mechanical stability of the in vivo lumbar spine: implications for injury and chronic low back pain. , 1996, Clinical biomechanics.

[25]  Mark Driscoll,et al.  Investigation of physiological stress shielding within lumbar spinal tissue as a contributor to unilateral low back pain: A finite element study , 2021, Comput. Biol. Medicine.

[26]  Carl-Eric Aubin,et al.  The role of spinal concave–convex biases in the progression of idiopathic scoliosis , 2009, European Spine Journal.

[27]  J. Leong,et al.  The Flexion–Extension Profile of Lumbar Spine in 100 Healthy Volunteers , 2004, Spine.

[28]  M. Driscoll,et al.  The presence of physiological stress shielding in the degenerative cycle of musculoskeletal disorders. , 2011, Journal of bodywork and movement therapies.