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. 2022 Aug 1:3:931274.
doi: 10.3389/fresc.2022.931274. eCollection 2022.

Computational modeling of posteroanterior lumbar traction by an automated massage bed: predicting intervertebral disc stresses and deformation

Luis Cardoso  1 , Niranjan Khadka  2 , Jacek P Dmochowski  1 , Edson Meneses  1 , Kiwon Lee  3 , Sungjin Kim  3 , Youngsoo Jin  3   4 , Marom Bikson  1
Affiliations

Computational modeling of posteroanterior lumbar traction by an automated massage bed: predicting intervertebral disc stresses and deformation

Luis Cardoso et al. Front Rehabil Sci. .

Abstract

Spinal traction is a physical intervention that provides constant or intermittent stretching axial force to the lumbar vertebrae to gradually distract spinal tissues into better alignment, reduce intervertebral disc (IVD) pressure, and manage lower back pain (LBP). However, such axial traction may change the normal lordotic curvature, and result in unwanted side effects and/or inefficient reduction of the IVD pressure. An alternative to axial traction has been recently tested, consisting of posteroanterior (PA) traction in supine posture, which was recently shown effective to increase the intervertebral space and lordotic angle using MRI. PA traction aims to maintain the lumbar lordosis curvature throughout the spinal traction therapy while reducing the intradiscal pressure. In this study, we developed finite element simulations of mechanical therapy produced by a commercial thermo-mechanical massage bed capable of spinal PA traction. The stress relief produced on the lumbar discs by the posteroanterior traction system was investigated on human subject models with different BMI (normal, overweight, moderate obese and extreme obese BMI cases). We predict typical traction levels lead to significant distraction stresses in the lumbar discs, thus producing a stress relief by reducing the compression stresses normally experienced by these tissues. Also, the stress relief experienced by the lumbar discs was effective in all BMI models, and it was found maximal in the normal BMI model. These results are consistent with prior observations of therapeutic benefits derived from spinal AP traction.

Keywords: automated massage bed; body mass index (BMI); finite element method (FEM); lower back pain; posteroanterior traction; spinal traction; stress relief.

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Conflict of interest statement

The City University of New York holds patents on brain stimulation with MB as inventor. Author MB has equity in Soterix Medical Inc., and also consults, received grants, assigned inventions, and/or serves on the SAB of SafeToddles, Boston Scientific, GlaxoSmithKline, Biovisics, Mecta, Lumenis, Halo Neuroscience, Google-X, i-Lumen, Humm, Allergan Abbvie), Apple. Authors KL, SK, and YJ were employed by Clinical Research Institute, Ceragem Clinical Inc. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. This study received funding from Ceragem Clinical Inc. in the form of a grant to MB, JD, NK, and LC. The funder had the following involvement with the study for providing information about the parameters of the medical device being simulated and providing feedback on simulation results.

Figures

Figure 1
Figure 1
Lower back human model. (A) MRI scan of lower back of a normal BMI subject, (B) Segmentation of tissues; (C) 3D rendering of lumbar discs and spine; (D) Finite element mesh of the lumbar discs and spine.
Figure 2
Figure 2
Mechanical actuator and bed mat layer. Vertical position of actuator rollers at different traction levels. (A) shows resting position of actuator, (B) represents the vertical displacement at traction level 3 (TL3), (C) shows the position of the actuator and bed mat at TL6, (D) is the maximal height reached by the actuator at TL9, corresponding to ~62 mm above resting position.
Figure 3
Figure 3
Actuator and model assembly. (A) shows the stresses and (B) depicts the strains produced by posteroanterior traction produced by the system on the tissues of a normal BMI subject. The front rollers produce the highest deformation on the skin and fatty tissues layer, as well as maximal traction directly under the location of the vertebral bodies L2 to L4.
Figure 4
Figure 4
3D Stress map on different BMI models: normal, overweight, moderate obese and severe obese (column panels) at traction levels 5, 7 and 9 (row panels). The highest stresses occur in the normal BMI model at the highest traction level. The effect of posteroanterior traction is inversely proportional to BMI, and it is evident in all BMI models.
Figure 5
Figure 5
Quantitative co MParison of average stresses on different BMI models: normal, overweight, moderate obese and extreme obese as a function of traction level (TL 1-9) in the lumbar discs. The internal stresses developed in the lumbar discs exhibit a range of variability between 0.075 and 1.7 MPa, depending on the BMI and traction level. The internal stresses in the disc are maximal in the normal BMI model and decrease as the BMI increases.
Figure 6
Figure 6
3D strain maps on different BMI models: normal, overweight, moderate obese and extreme obese (column panels) at traction levels 5, 7 and 9 (row panels). The maximal strains in the intervertebral discs are presented in the normal BMI model at the highest traction level. However, the fat and soft tissues in the moderate and extreme obese models deform the most and shield the intervertebral discs from the strains.
Figure 7
Figure 7
Quantitative co MParison of Strains on different BMI models: normal, overweight, moderate obese and extreme obese as a function of traction level (TL 1-9) in the lumbar discs. The strains developed in the lumbar discs exhibit a range of variability between 0.005 and 0.1, depending on the BMI and traction level. The strains in the disc are maximal in the normal BMI model and decrease as the BMI increases.
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